**Meet the editor**

Dr Farid Bourzgui is a professor of Orthodontics in the School of Dental Medicine at Hassan II University in Casablanca, Morocco. He received his PhD from the School of Dental Medicine at Hassan II University in 1995. He holds various certificates and diplomas: a Certificate of Higher Studies in Group A (major: Technology of Biomaterials used in Dentistry, 1996), a Certificate

of Advanced Studies of group B, (major: Dentofacial Orthopaedics, 1997) from the Faculty of Dental Surgery at University Denis Diderot-Paris VII, France, a diploma of Higher Studies in Biocompatibility of Biomaterials from the Faculty of Medicine and Pharmacy of Casablanca (2002), a Certificate of Clinical Occlusal Odontology from the Faculty of Dentistry Casablanca (2004) and a university degree in Biostatistics and Perceptual Health Measurement from the Faculty of Medicine and Pharmacy of Casablanca in 2011. Farid Bourzgui is a former intern and resident of Casablanca University Hospital, Ibn Rushd in Casablanca. Dr Bourzgui specialises in Orthodontics and received his National Diploma in Dentistry (major: Dentofacial Orthopedics) from the School of Dentistry in Casablanca in 2000. Dr Bourzgui has published a number of articles and book chapters on various aspects of Orthodontics. He has served on the board of the Moroccan Society of Dentistry, and was the President of the Moroccan Society of Dentistry from 2002 to 2004.

## Contents

#### **Preface XIII**

	- **Part 2 Growth and Genetic 123**

#### X Contents

#### **Part 3 Orthodontic Therapy 175**

Chapter 8 **Three-Dimensional Imaging and Software Advances in Orthodontics 177**  Ahmed Ghoneima, Eman Allam, Katherine Kula and L. Jack Windsor

Chapter 9 **The Use of Mini-Implants (Temporary Anchorage Devices) in Resolving Orthodontic Problems 195**  P. Salehi, S. Torkan and S.M.M. Roeinpeikar


#### **Part 4 Temporomandibular Disorder and Orthodontic 325**


#### **Part 5 Orthodontics Risks 401**

VI Contents

**Part 3 Orthodontic Therapy 175** 

Chapter 8 **Three-Dimensional Imaging and** 

and L. Jack Windsor

Chapter 9 **The Use of Mini-Implants** 

**Software Advances in Orthodontics 177**  Ahmed Ghoneima, Eman Allam, Katherine Kula

Farid Bourzgui, Mourad Sebbar, Zouhair Abidine

Stefano Sivolella, Michela Roberto, Paolo Bressan, Eriberto Bressan,

Serena Cernuschi, Francesca Miotti and Mario Berengo

Jeong Hwan Kim, Niloufar Nouri Mahdavie and Carla A. Evans

**in Japanese Unilateral Cleft Lip and Palate Patients 301** Mohammad Khursheed Alam, Takashi S. Kajii and Junichiro Iida

Silvana Regina Perez Orrico, Juliana Álvares Duarte Bonini Campos, Fernanda Oliveira Bello Correa and Carolina Letícia Zilli Vieira

Chapter 12 **Guidelines for "Surgery First" Orthodontic Treatment 265** 

Chapter 13 **Spectrum of Factors Affecting Dental Arch Relationships** 

**Part 4 Temporomandibular Disorder and Orthodontic 325** 

**Temporomandibular Disorders 341**  Ticiana Sidorenko de Oliveira Capote,

Chapter 17 **Dentofacial Aspects of the Changes in** 

Emil Segatto and Angyalka Segatto

Chapter 14 **Occlusion, Orthodontic Treatment and Temporomandibular Disorders: Myths and Scientific Evidences 327** Ephraim Winocur and Alona Emodi-Perlman

Chapter 16 **Temporomandibular Disorders and Orthodontic Treatment – A Review with a Reported Clinical Case 351** Tomislav Badel, Miljenko Marotti and Ivana Savić Pavičin

**Body Posture, Investigation Procedures 377** 

**(Temporary Anchorage Devices) in Resolving Orthodontic Problems 195**  P. Salehi, S. Torkan and S.M.M. Roeinpeikar

Chapter 11 **Uprighting of the Impacted Second Mandibular Molar with Skeletal Anchorage 247**

Chapter 10 **Management of Dental Impaction 219** 

and Zakaria Bentahar

Chapter 15 **Orthodontic Treatment and** 

Chapter 18 **Risks and Complications Associated with Orthodontic Treatment 403**  Cristina Teodora Preoteasa, Ecaterina Ionescu and Elena Preoteasa

#### Chapter 19 **Root Resorption in Orthodontics: An Evidence-Based Approach 429**  Leandro Silva Marques, Paulo Antônio Martins-Júnior, Maria Letícia Ramos-Jorge and Saul Martins Paiva

## Preface

One of the biggest challenges facing practitioners nowadays is offering quality dental care while demonstrating clinical *competence,* and comprehensive and *compassionate* patient *care*. Therefore, training and refreshing of knowledge are absolute necessities that contribute to successful clinical patient care.

The acquisition of new ideas is dependent on reading. As Nietzsche put in his book *Beyond Good and Evil* (1886) "Naturally in order to practice reading as an art, one thing above all is necessary, which nowadays has been thoroughly unlearned, for which one must almost be a cow and at any rate not a "modern man", namely rumination". Such reading should be selective, meeting well-defined objectives, with a critical understanding of the medical and scientific information.

Access to information and the demystification of knowledge are the currency of this century despite the efforts exerted by some retention. Production's "open source" plays and will continue to play a very important role in sharing and disseminating knowledge and expertise. The present book embodies such a state of mind.

The book reflects the ideas of nineteen academic and research experts from different countries. It provides an overview of the state-of-the-art, outlines the experts' knowledge and their efforts to provide readers with quality content explaining new directions and emerging trends in Orthodontics. The book should be of great value to both orthodontic practitioners and to students in orthodontics, who will find learning resources in connection with their fields of study. This will help them to acquire valid knowledge and excellent clinical skills.

Last but not at least, I would like to express my deep gratitude to the editorial team and colleagues who have contributed, one way or another, to the fulfilment of this work.

> **Farid Bourzgui**  Faculty of Dentistry, University of Hassan II Ain Chok Morocco

## **Part 1**

**Epidemiology and Prevention** 

## **Orthodontic Treatment Need: An Epidemiological Approach**

Carlos Bellot-Arcís, José María Montiel-Company and José Manuel Almerich-Silla *Stomatology Department, University of Valencia Spain* 

#### **1. Introduction**

The main aim of orthodontic treatment is to correct malocclusion, in order, whenever possible, to achieve functionally appropriate occlusion and optimum dental and facial aesthetics. To understand what malocclusion is, first we need to define its antonyms, in other words, what is meant by normal occlusion and ideal occlusion. Normal occlusion can be said to be that which meets certain predefined standards.

Edward Hartley Angle (1899) took the first permanent molars as the reference point and established the precise relations between the two dental arches that could be considered "norm-occlusion". "Normal occlusion" was thus defined as a concrete goal that the orthodontist should aim for in order to achieve a structural, functional and aesthetic norm (Canut, 1988). Since Angle's days, normal occlusion and ideal occlusion have been treated as synonyms in orthodontics, giving rise to both semantic and treatment difficulties. Nevertheless, from the statistical point of view the term "normal" implies a certain variation around the mean, while "ideal" implies a concept of perfection as the hypothetical aim (Bravo, 2003).

The occlusal norms that all orthodontists, over many years of professional practice, had borne in mind when deciding their clinical objectives were set out by Andrews (1972) in an article describing the six keys to normal occlusion. He later changed the adjective "normal" occlusion to "optimal" occlusion, arguing that he had used the word "normal" in the sense of optimal or ideal, as was often the case in the 1970s, and that normal occlusion was more correctly called "non-optimal occlusion".

"Orthodontic treatment need" can be defined as the degree to which a person needs orthodontic treatment because of certain features of his or her malocclusion, the functional, dental health or aesthetic impairment it occasions and the negative psychological and social repercussions to which it gives rise.

Throughout the history of orthodontics, there have been authors who have considered that malocclusion can lead to other problems, such as functional problems, temporomandibular dysfunction, and a greater propensity to trauma, caries, or periodontal disease. However, nowadays it is not so evident that these processes or diseases constitute indications for orthodontic treatment. Generally speaking, the psychological and social implications of poor dentofacial aesthetics can be more serious than the biological problems, and in clinical trials, strong correlations have been found between dental aesthetics, treatment need and the severity of the malocclusion (Lewis et al., 1982). Hamdam (2004) concluded that 40% of the patients who underwent orthodontic treatment had been the butt of jokes because of their teeth. However, there was no association between the degree of orthodontic treatment need measured by an objective index (IOTN DHC) and the need perceived by the patients. Kiekens et al. (2006) concluded that what the patients hope for from orthodontic treatment is an improvement in their dentofacial aesthetics and, as a result, greater social acceptance and higher self-esteem. Because of this, in recent decades orthodontists have been increasingly directing their treatments towards improving facial aesthetics.

Strictly speaking, malocclusion is not an illness but an occlusal relationship that lies within the bounds of all the possible occlusal relationships. Deciding the exact point at which a specific malocclusion should be treated remains an open question among orthodontists and the subject of considerable debate in the literature, as owing to its nature, reaching a general consensus is proving really complicated.

The WHO (World Health Organization) defines health as "a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity". Consequently, a person cannot be considered completely healthy if a malocclusion prevents him or her from attaining this state of complete well-being, whether for physical (functional impairment) or psycho-social reasons (serious impairment of self-esteem or dentofacial aesthetics).

Disease does not always entail the absence of well-being, and even when well-being is absent this depends to a large extent on the patient's psychological state and personal and cultural principles and values. While clinical indices are concerned to measure the "disease", a purely biological concept, as objectively as possible, the indices that attempt to measure and determine "health" are very subjective, as health is a more psychological or sociological concept (Bernabé & Flores-Mir, 2006).

It should be emphasized that there is a lack of agreement on what is or is not considered malocclusion, and even greater disagreement when determining the orthodontic treatment need. However, enormous progress in this direction has been made in recent years, with important areas of consensus being reached among the specialists concerning specific situations in which orthodontic treatment should be recommended. The rapid development of indices to measure malocclusion and orthodontic treatment need have unquestionably contributed to these advances.

#### **2. Using indices to measure malocclusion**

#### **2.1 Definition of "index"**

Indices are quantitative assessment tools, employing continuous or numbered scales of malocclusion for epidemiological purposes and for a number of administrative applications.

An orthodontic treatment need index assigns a specific score to each malocclusion feature according to that feature's relative contribution to the overall severity of the malocclusion.

orthodontic treatment. Generally speaking, the psychological and social implications of poor dentofacial aesthetics can be more serious than the biological problems, and in clinical trials, strong correlations have been found between dental aesthetics, treatment need and the severity of the malocclusion (Lewis et al., 1982). Hamdam (2004) concluded that 40% of the patients who underwent orthodontic treatment had been the butt of jokes because of their teeth. However, there was no association between the degree of orthodontic treatment need measured by an objective index (IOTN DHC) and the need perceived by the patients. Kiekens et al. (2006) concluded that what the patients hope for from orthodontic treatment is an improvement in their dentofacial aesthetics and, as a result, greater social acceptance and higher self-esteem. Because of this, in recent decades orthodontists have been increasingly

Strictly speaking, malocclusion is not an illness but an occlusal relationship that lies within the bounds of all the possible occlusal relationships. Deciding the exact point at which a specific malocclusion should be treated remains an open question among orthodontists and the subject of considerable debate in the literature, as owing to its nature, reaching a general

The WHO (World Health Organization) defines health as "a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity". Consequently, a person cannot be considered completely healthy if a malocclusion prevents him or her from attaining this state of complete well-being, whether for physical (functional impairment) or psycho-social reasons (serious impairment of self-esteem or dentofacial

Disease does not always entail the absence of well-being, and even when well-being is absent this depends to a large extent on the patient's psychological state and personal and cultural principles and values. While clinical indices are concerned to measure the "disease", a purely biological concept, as objectively as possible, the indices that attempt to measure and determine "health" are very subjective, as health is a more psychological or

It should be emphasized that there is a lack of agreement on what is or is not considered malocclusion, and even greater disagreement when determining the orthodontic treatment need. However, enormous progress in this direction has been made in recent years, with important areas of consensus being reached among the specialists concerning specific situations in which orthodontic treatment should be recommended. The rapid development of indices to measure malocclusion and orthodontic treatment need have unquestionably

Indices are quantitative assessment tools, employing continuous or numbered scales of malocclusion for epidemiological purposes and for a number of administrative applications. An orthodontic treatment need index assigns a specific score to each malocclusion feature according to that feature's relative contribution to the overall severity of the malocclusion.

directing their treatments towards improving facial aesthetics.

consensus is proving really complicated.

sociological concept (Bernabé & Flores-Mir, 2006).

**2. Using indices to measure malocclusion** 

contributed to these advances.

**2.1 Definition of "index"** 

aesthetics).

Each occlusal feature measured by a particular index is assigned a quantitative value or specific weight based on personal clinical concepts, consensus among specialists, reviews of the literature, social and administrative needs or scientific studies designed specifically for this purpose, hence the great variety of very different indices for recording malocclusion, which can have many uses.

Occlusal indices decide the need for treatment from the point of view of the orthodontist but tend to ignore the patients' own perceptions of their malocclusion and the repercussions it has in their daily lives, not only from a functional point of view but also on their looks, which undoubtedly have an effect on their social relationships. The traditional indices do not give any type of information on how the malocclusion affects the patients' lives from the psychosocial or functional point of view. These aspects seem to have become particularly important in recent years (Kok et al., 2004).

#### **2.2 History, evolution, classification and properties of treatment need indices**

Attempts to classify dentofacial disharmony date back to the beginning of the 19th century, to authors such as Joseph Fox (1776-1816), Christophe François Delabarre (1784-1862), Jean Nicolas Marjolin (1780-1850), Friedrich Christoph Kneisel (1797-1847) or Georg Carabelli (1787-1842). It was not until 1899, however, that Edward Hartley Angle (1855-1930) developed a clear, simple, practical classification that became universally accepted and used. Nonetheless, this index has evident limitations from the epidemiological point of view.

Angle's classification has been followed by many others. That of Lischer (1912) was similar but introduced the terms neutrocclusion (Angle Class I), mesiocclusion (Angle Class III) and distocclusion (Angle Class II). Simon (1922) proposed a classification that sets out the relation between the dental arches by reference to the three anatomical planes, based on different points on the skull. Dewey and Anderson (1942) published a book in which they extended Angle's classification to include five types of Class I malocclusion and three types of Class III malocclusion, known as the Dewey-Anderson Modification. The classification of Ackerman and Proffit (1969) was intended to overcome Angle's main weaknesses; however, it is more of a diagnostic procedure for listing the problems in each case of malocclusion in order to assist the clinician in drawing up a treatment plan.

All the methods described so far are qualitative and serve to describe and classify a patient's malocclusion. However, countries that have health services which offer orthodontic treatment have developed and applied a series of quantitative methods (malocclusion indices) to detect the severity and treatment need of each case, in an attempt to define the priority of some cases over others objectively and thus rationalize their public expenditure.

Tang and Wei (1993) reviewed the literature and summarized the evolution of methods for recording malocclusion in recent decades. They concluded that the trend in both qualitative and quantitative methods has changed, as initially researchers did not define the signs of malocclusion before recording them, chose the variables arbitrarily and recorded the data according to a criterion of all or nothing. This has now changed and a study of the progress in occlusal recording methods shows that they are increasingly accurate, reliable and scientifically-based, and consequently their detection of the problems possesses greater validity.

According to Richmond et al. (1997), an orthodontic index should consist of a numerical scale obtained by considering specific features of the malocclusion, making it possible to determine certain parameters such as treatment need or the severity of malocclusion in an objective way.

In 1966 the World Health Organization (WHO) defined the three characteristics that an index should possess: reliability, validity and validity over time.

There is wide agreement that an orthodontic treatment need index should possess the following characteristics:


Prahl-Andersen (1978) described the features that in his opinion an orthodontic treatment need index should possess. He emphasized that an index should not establish treatment priorities solely on the basis of the severity of the malocclusion and the functional problems that it could entail. It should also assess the degree to which the malocclusion occasions aesthetic impairment. In the medical field, a person's health should be judged on three criteria: objective signs (the orthodontist's diagnosis), subjective symptoms (the patient must recognize the problem) and social sufficiency (social attitudes).

Shaw et al. (1995) highlighted the following uses of the indices:


Throughout the history of orthodontics, indices have been developed to record malocclusions. Abdullah and Rock (2001) considered that most of them must have been developed with the following aims:

accurate, reliable and scientifically-based, and consequently their detection of the

According to Richmond et al. (1997), an orthodontic index should consist of a numerical scale obtained by considering specific features of the malocclusion, making it possible to determine certain parameters such as treatment need or the severity of malocclusion in an

In 1966 the World Health Organization (WHO) defined the three characteristics that an

There is wide agreement that an orthodontic treatment need index should possess the






Prahl-Andersen (1978) described the features that in his opinion an orthodontic treatment need index should possess. He emphasized that an index should not establish treatment priorities solely on the basis of the severity of the malocclusion and the functional problems that it could entail. It should also assess the degree to which the malocclusion occasions aesthetic impairment. In the medical field, a person's health should be judged on three criteria: objective signs (the orthodontist's diagnosis), subjective symptoms (the patient must



Throughout the history of orthodontics, indices have been developed to record malocclusions. Abdullah and Rock (2001) considered that most of them must have been


index should possess: reliability, validity and validity over time.

by the same examiner on different occasions.

serious cases that need to be treated by a specialist.

recognize the problem) and social sufficiency (social attitudes). Shaw et al. (1995) highlighted the following uses of the indices: - Classifying, planning and promoting treatment standards.

problems possesses greater validity.

objective way.

following characteristics:

subjectivity.

need.

benefit from treatment.

discoveries or considerations.


developed with the following aims:


It must not be forgotten that orthodontic treatment need indices, or at least most of them, are designed to determine treatment priority, in other words, to choose the potential patients who will most benefit from orthodontic treatment in a particular health service system.

In Europe, occlusal indices to estimate treatment need have been being used successfully since the end of the 1980s. The indices employed have generally been those developed by european authors but there has been no unanimity as regards which method to employ.

The controversy that surrounds orthodontic treatment need indices is such that in the United States, in 1969 the American Orthodontic Society adopted and recommended the *Salzmann Index* for estimating the treatment needs of the population but withdrew its recommendation in 1985 and currently does not recognize any index as more suitable than any other for this purpose (Parker, 1998).

Many very different indices have been developed to classify and group malocclusions according to severity or level of treatment need.

#### **3. Principal treatment need indices**

The *Malalignment Index* was developed by Van Kirk (1959) because he considered that there was no way of classifying patients objectively according to their tooth or bone malalignment. In this index, each tooth is given a score between 0 and 2 depending on its degree of rotation or displacement compared to the ideal position in the dental arch.

The state of New York started its Dental Rehabilitation Program in 1945 and one of the main problems was to select the patients who would receive orthodontic treatment. As a result, Draker (1960) developed and published *Handicapping Labio-lingual Deviation* (HLD) with the aim of determining orthodontic treatment need. This index assesses 7 criteria (displacement, crowding, overjet, increased overbite, open bite, anterior crossbite and ectopic eruptions) exclusively in the anterior sector, and also takes malformations into account. It can be applied both to models and to examinations of the mouth. When the scores for all the criteria total over 13, the subject is considered to present a physical malocclusion that needs treatment.

The *Treatment Priority Index* (TPI) was developed by Grainger (1967). This index is based on an assessment of ten occlusal features measured in a representative sample of 375 children of 12 years of age, of Anglo-Saxon origin, all without previous orthodontic treatment. The children were examined directly by orthodontic specialists. The patient is considered to need treatment when the scores for the ten occlusal features total over 4.5. A further eleventh feature is only considered in special cases (cleft palate or dysmorphism caused by traumatic injury) in which treatment is a priority. TPI has been used in many studies and although the results have not always been regular, it has proved to give high intra-examiner and inter-examiner reproducibility and reasonably good validity. However, it requires a certain degree of knowledge and experience on the part of the examiner.

Howitt et al. (1967) developed one of the first indices to consider the aesthetic aspects of malocclusion: the *Eastman Esthetic Index* (EEI). In spite of its innovation in measuring the degree of aesthetic impact associated with the malocclusion, it has not achieved such widespread use as other indices.

Salzmann (1967) was one of the first authors to be truly concerned about the patients' own perception of their malocclusion and about the impact and importance of orthodontics, and even of malocclusion, in society. As a result, he published the *Handicapping Malocclusion Assessment Record* (HMAR) index (Salzmann, 1968). The aim was to assess the patients' orthodontic treatment need, classifying the individuals examined according to the level of severity of the problem. This is considered an index with high reproducibility, as it does not use millimetrical measurements but concerns itself with determining functional problems that genuinely constitute an obstacle to the maintenance of oral health and interfere with the patients' proper development owing to their effect on dentofacial aesthetics, mandibular function or speech.

Summers (1971) published the *Occlusal Index* after observing the lack of consensus among orthodontic specialists*.* This index attempts to classify individuals as objectively as possible and presents clearly epidemiological characteristics. It measures nine occlusal features. Its main distinguishing feature is that it takes the patient's age into account.

Bjork et al. (1964) developed a method with clearly defined variables that can be recorded with good inter-examiner agreement. Based on this method, in 1969 a group of scientists from the World Dental Federation (FDI) Commission on Classification and Statistics of Oral Conditions-Measures of Occlusal Traits (COCSTC-MOT) analyzed the problem of determining occlusal status and developing recording systems for epidemiological purposes. The *Method for Measuring Occlusal Traits* was subsequently developed. This was adopted in 1972 by the FDI (1973) and modified by COCSTC-MOT in collaboration with the WHO, giving rise in 1979 to the final version of the "WHO/FDI Basic Method for Recording of Malocclusion", published in the Bulletin of the WHO (1979). The basic aims of this method, which follows clearly defined criteria, are to determine the prevalence of malocclusion and estimate the treatment needs of the population as a basis for planning orthodontic services.

The *Dental Aesthetic Index* (DAI) created by Cons et al. (1986), is unlike other indices in that the authors based it on the public's perception of dental aesthetics. This index has been used very successfully in numerous studies to assess the prevalence of malocclusion and the orthodontic treatment needs of different population groups. It will be discussed in greater detail in the next section.

The *Index of Orthodontic Treatment Need* (IOTN) described by Brook and Shaw (1989) has achieved widespread recognition both nationally and internationally as an objective method

caused by traumatic injury) in which treatment is a priority. TPI has been used in many studies and although the results have not always been regular, it has proved to give high intra-examiner and inter-examiner reproducibility and reasonably good validity. However, it requires a certain degree of knowledge and experience on the part of the

Howitt et al. (1967) developed one of the first indices to consider the aesthetic aspects of malocclusion: the *Eastman Esthetic Index* (EEI). In spite of its innovation in measuring the degree of aesthetic impact associated with the malocclusion, it has not achieved such

Salzmann (1967) was one of the first authors to be truly concerned about the patients' own perception of their malocclusion and about the impact and importance of orthodontics, and even of malocclusion, in society. As a result, he published the *Handicapping Malocclusion Assessment Record* (HMAR) index (Salzmann, 1968). The aim was to assess the patients' orthodontic treatment need, classifying the individuals examined according to the level of severity of the problem. This is considered an index with high reproducibility, as it does not use millimetrical measurements but concerns itself with determining functional problems that genuinely constitute an obstacle to the maintenance of oral health and interfere with the patients' proper development owing to their effect on dentofacial aesthetics, mandibular

Summers (1971) published the *Occlusal Index* after observing the lack of consensus among orthodontic specialists*.* This index attempts to classify individuals as objectively as possible and presents clearly epidemiological characteristics. It measures nine occlusal features. Its

Bjork et al. (1964) developed a method with clearly defined variables that can be recorded with good inter-examiner agreement. Based on this method, in 1969 a group of scientists from the World Dental Federation (FDI) Commission on Classification and Statistics of Oral Conditions-Measures of Occlusal Traits (COCSTC-MOT) analyzed the problem of determining occlusal status and developing recording systems for epidemiological purposes. The *Method for Measuring Occlusal Traits* was subsequently developed. This was adopted in 1972 by the FDI (1973) and modified by COCSTC-MOT in collaboration with the WHO, giving rise in 1979 to the final version of the "WHO/FDI Basic Method for Recording of Malocclusion", published in the Bulletin of the WHO (1979). The basic aims of this method, which follows clearly defined criteria, are to determine the prevalence of malocclusion and estimate the treatment needs of the population as a basis for planning

The *Dental Aesthetic Index* (DAI) created by Cons et al. (1986), is unlike other indices in that the authors based it on the public's perception of dental aesthetics. This index has been used very successfully in numerous studies to assess the prevalence of malocclusion and the orthodontic treatment needs of different population groups. It will be discussed in greater

The *Index of Orthodontic Treatment Need* (IOTN) described by Brook and Shaw (1989) has achieved widespread recognition both nationally and internationally as an objective method

main distinguishing feature is that it takes the patient's age into account.

examiner.

widespread use as other indices.

function or speech.

orthodontic services.

detail in the next section.

for determining treatment need. This index classifies the patients according to both the degree to which the malocclusion affects their stomatognathic system and their aesthetic perception of their own malocclusion, with the aim of identifying which patients would benefit most from orthodontic treatment (Uçüncü & Ertugay, 2001). A more detailed description is given in section 5.

The *Peer Assessment Rating* (PAR) is a more recent index, developed in Europe in 1992 by Richmond et al. (1992). In their article, the authors explained that it would be very helpful for orthodontists to have an index which would enable them to assess the results on completing the treatment. They considered that the indices developed up to that point lacked sufficient reproducibility and validity. The PAR makes it possible to compare the success of orthodontic treatments and also to predict the severity of cases. To develop this rating, 10 orthodontic specialists assessed 200 models and assigned a value to each of the 11 occlusal features they considered indispensable for evaluating the severity of a malocclusion. The total PAR score is the sum of each of the values of the different occlusal features. The success of a treatment is tested by measuring the PAR index before and after treatment and calculating the difference between the scores. The validity of the study was confirmed by another in which 74 dentists examined 272 dental models and assessed their deviation from the ideal on a scale of 1 to 9. They also calculated the PAR score for each of the models. The correlation between the professionals' opinion and the PAR score was r=0.74, showing that this index is a good predictor of subjective clinical assessment. Subsequently, its validity has also been corroborated by other authors (McGorray et al., 1999).

The latest index reported in the literature is the *Index of Complexity, Outcome and Need*  (ICON) developed in 2000 by Daniels and Richmond (2002). Its aim is to bring assessment of need and of the results of orthodontic treatment together in a single index. Its development drew on 97 orthodontists from different countries who gave their subjective opinion of the treatment need, complexity of the treatment and improvement following treatment of 240 initial models and 98 treated models. The criteria employed are the five occlusal features that predicted the expert group's opinion and the IOTN AC (IOTN aesthetic component). Cut-off points were analyzed to determine at what point the index gave an accurate prediction of the specialists' decisions. Good results were obtained for accuracy (85%), sensitivity (85.2%) and specificity (84.4%).

#### **4. Dental Aesthetic Index (DAI)**

Cons et al. (1986) described and explained the Dental Aesthetic Index (DAI). The distinctive feature of the DAI is that it is an orthodontic index which relates the clinical and aesthetic components mathematically to produce a single score. It is based on the SASOC (Social Acceptability Scale of Occlusal Conditions) developed earlier by the same authors (Jenny et al., 1980).

The authors wanted to achieve a different index that would be based on the public's perception of dental aesthetics. This was determined through an evaluation of 200 photographs of different occlusal configurations. The 200 cases were chosen, by a random process, from a larger sample of 1337 study models used in a previous study. The 1337 models represented a population of half a million schoolchildren aged between 15 and 18 years from the state of New York. The 200 photographs employed as stimuli for the assessment of dental aesthetics were chosen through a process that ensured that even the most extreme cases were represented. Approximately 2000 adolescents and adults took part in rating the aesthetics of the 200 photographs, each of which showed the models' occlusion in front and side views. The presence and measurement of 49 occlusal features selected by an international committee as being those it was important to consider when developing an orthodontic index were taken into account for each photograph.

Regression analysis was employed to relate the public's assessment of dental aesthetics to the anatomical measurements of the occlusal features that were present in each photograph. This led to the choice of ten occlusal features as the most important ones to take into account in an orthodontic index, insofar as each of them affected the structures of the mouth and influenced dental aesthetics.

This study provided a statistical basis for establishing the value of the regression coefficients used for the ten occlusal features finally chosen for the regression calculations.

All the variables were adjusted in a linear regression model and a predictive equation called the DAI equation was obtained. In the DAI equation, the score for each of the ten DAI components is multiplied by its respective regression coefficient (weighting), the values are added together and a constant, 13, is added to the total. The result of this operation is the DAI score. The DAI equation is as follows:

(DAI Component X Regression Coefficient) + 13

In the DAI equation the regression coefficients are usually rounded off, making it less precise but easier to apply, especially in epidemiological studies. The actual and rounded regression coefficients and constant are shown in Table 1.

The way to measure the ten DAI components correctly is as follows:


years from the state of New York. The 200 photographs employed as stimuli for the assessment of dental aesthetics were chosen through a process that ensured that even the most extreme cases were represented. Approximately 2000 adolescents and adults took part in rating the aesthetics of the 200 photographs, each of which showed the models' occlusion in front and side views. The presence and measurement of 49 occlusal features selected by an international committee as being those it was important to consider when developing an

Regression analysis was employed to relate the public's assessment of dental aesthetics to the anatomical measurements of the occlusal features that were present in each photograph. This led to the choice of ten occlusal features as the most important ones to take into account in an orthodontic index, insofar as each of them affected the structures of the mouth and

This study provided a statistical basis for establishing the value of the regression coefficients

All the variables were adjusted in a linear regression model and a predictive equation called the DAI equation was obtained. In the DAI equation, the score for each of the ten DAI components is multiplied by its respective regression coefficient (weighting), the values are added together and a constant, 13, is added to the total. The result of this operation is the

In the DAI equation the regression coefficients are usually rounded off, making it less precise but easier to apply, especially in epidemiological studies. The actual and rounded

1. Number of missing visible teeth (incisors, canines, and premolars in the maxillary and mandibular arches). These are only taken into account if they affect the dental aesthetics, so if the space is closed, if eruption of the permanent tooth is expected or if the missing tooth has been replaced by a dental prosthesis, they should not be counted

2. Assessment of crowding in the incisal segments. The aim is to calculate the existing crowding in the upper anterior and lower anterior sextants. The crowding discrepancy is not measured numerically but only as being present or absent. As a result the score will be 0 if there is no crowding, 1 if there is maxillary or mandibular crowding or 2 if

3. Assessment of spacing in the incisal segments. In this case the space between the canines is greater than that required to accommodate the four incisors in a correct alignment. If one or more incisors has a proximal surface without interdental contact, the incisal segment is recorded as spaced. The score will be 0 if there is no spacing, 1 if

there is maxillary or mandibular spacing or 2 if the spacing affects both jaws. 4. Measurement of any midline diastema in millimeters. Diastema is a very important occlusal feature from an aesthetic point of view. The midline diastema is defined as the space in millimeters between the two central permanent maxillary incisors when the

used for the ten occlusal features finally chosen for the regression calculations.

orthodontic index were taken into account for each photograph.

influenced dental aesthetics.

DAI score. The DAI equation is as follows:

as missing visible teeth.

the crowding affects both jaws.

points of contact are in their normal position.

(DAI Component X Regression Coefficient) + 13

regression coefficients and constant are shown in Table 1.

The way to measure the ten DAI components correctly is as follows:



Table 1. Components of the DAI regression equation and their actual and rounded regression coefficients (weights).

Although the DAI was developed for permanent teeth, it can easily be adapted for mixed dentition by simply ignoring missing permanent teeth if these are expected to erupt during the normal time range.

Once the patient's score has been calculated, it can be located on a scale in order to determine its position in relation to the dental aesthetics that are socially most acceptable and least acceptable. The higher the DAI score, the further the occlusal relation is from socially accepted dental aesthetics and the more easily it can be detrimental to the patient.

The DAI has ranges of scores to determine the severity of the malocclusion. A DAI score of 25 or less represents normal occlusion or slight malocclusion. Scores between 26 and 30 indicate moderate malocclusion with questionable treatment need. From 31 to 35, the malocclusion is more serious and treatment is recommended. Scores of 36 or more show severe malocclusion for which treatment is definitely needed.

As mentioned above, although the DAI scale offers these ranges to determine treatment need the scores can be placed on a continuous scale. The continuous scale makes the DAI sufficiently sensitive to differentiate between cases with a greater or lesser need within the same degree of severity. The cutoff points to decide which malocclusions should be treated by the public health services can be modified in view of the available resources.

One of the advantages of the DAI is that it can be obtained in barely 2 minutes, without Xrays, through an oral examination carried out by a trained dental assistant.


Table 2. This hypothetical case illustrates how the DAI is calculated with the rounded coefficients.

The score for the hypothetical case in Table 2 is 41, which would place the patient in the "orthodontic treatment needed" category.

#### **4.1 Validity and reliability of the DAI**

12 Orthodontics – Basic Aspects and Clinical Considerations

Although the DAI was developed for permanent teeth, it can easily be adapted for mixed dentition by simply ignoring missing permanent teeth if these are expected to erupt during

Once the patient's score has been calculated, it can be located on a scale in order to determine its position in relation to the dental aesthetics that are socially most acceptable and least acceptable. The higher the DAI score, the further the occlusal relation is from socially accepted dental aesthetics and the more easily it can be detrimental to the patient. The DAI has ranges of scores to determine the severity of the malocclusion. A DAI score of 25 or less represents normal occlusion or slight malocclusion. Scores between 26 and 30 indicate moderate malocclusion with questionable treatment need. From 31 to 35, the malocclusion is more serious and treatment is recommended. Scores of 36 or more show

As mentioned above, although the DAI scale offers these ranges to determine treatment need the scores can be placed on a continuous scale. The continuous scale makes the DAI sufficiently sensitive to differentiate between cases with a greater or lesser need within the same degree of severity. The cutoff points to decide which malocclusions should be treated

One of the advantages of the DAI is that it can be obtained in barely 2 minutes, without X-

and premolars in the maxillary and mandibular arches). 1 missing tooth x 6 6

4. Measurement of any midline diastema in mm. 0 mm x 3 0 5. Largest anterior irregularity on the maxilla in mm. 3 mm x 1 3 6. Largest anterior irregularity on the mandible in mm. 2 mm x 1 2 7. Measurement of anterior maxillary overjet in mm. 5 mm x 2 10 8. Measurement of anterior mandibular overjet in mm. 0 mm x 4 0 9. Measurement of vertical anterior openbite in mm. 0 mm x 4 0

Constant 13 DAI score 41

Table 2. This hypothetical case illustrates how the DAI is calculated with the rounded

**DAI components Component x R.** 

**weight Total** 

1 segment x 1 1

0 segments x 1 0

2 (full cusp) x 3 6

by the public health services can be modified in view of the available resources.

rays, through an oral examination carried out by a trained dental assistant.

severe malocclusion for which treatment is definitely needed.

1. Number of missing visible teeth (incisors, canines,

2. Assessment of crowding in the incisal segments: 0 = no segments crowded;1 = 1 segment crowded; 2 = 2

3. Assessment of spacing in the incisal segments: 0 = no segments spaced;1 = 1 segment spaced; 2 = 2 segments

10. Assessment of anteroposterior molar relation; largest deviation from normal either left or right, 0 = normal, 1 = 12 cusp either mesial or distal, 2 = 1 full cusp or more

the normal time range.

segments crowded.

either mesial or distal.

coefficients.

spaced.

While developing the DAI and after their studies and subsequent publications, Jenny et al. (1993) considered that one of its characteristics was its high degree of validity.

The authors (Jenny & Cons, 1996) tested the reliability of the DAI when measured by trained assistants and found very high intra-class correlation. Although deep overbites that damage the soft tissues are not scored numerically in the DAI, these and other severe congenital conditions are easily recognized by trained personnel, who can refer such cases to orthodontic specialists.

The same authors found that while the acceptability of particular physical features of faces varied widely between different racial and cultural groups, that of dental characteristics remained far more constant among different cultures. This has made it possible to employ the DAI to assess malocclusions in different regions and countries, where it has shown itself to be a quick, simple, reliable index with a high level of validity.

A comparison of an evaluation of 1337 models by orthodontists with the results of the DAI found 88% agreement (Cons et al., 1986). In a prospective study conducted in Australia it was found that a DAI score that indicated treatment need was a good predictor of future orthodontic treatment (Lobb et al., 1994).

One important aspect of the DAI is that it can be measured by trained dental assistants, and this prior screening of the malocclusion severity levels from which patients can be treated reduces the number of first visits by orthodontists employed in public programs.

Numerous studies have suggested that the DAI can be applied universally without any need for modification or adaptation, allowing it to be used independently of the sample in which the study was conducted (Baca-Garcia et al., 2004).

Also, nowadays, the DAI has been included in the latest WHO oral health survey update (1997). The WHO's recommendation of this method for assessing dentofacial anomalies is a major step in its dissemination as a universal method for evaluating malocclusions.

### **5. IOTN (Index of Orthodontic Treatment Need)**

Peter Brook and William Shaw (1989) developed the Orthodontic Treatment Priority (OTP) index, which they later called the IOTN. It was based on a combination of the SCAN or Standardized Continuum of Aesthetic Need (Evans Shaw, 1987) and the index employed by the Swedish Dental Health Board. The IOTN was subsequently modified by Richmond et al. (1992) and Lunn et al. (1993).

The IOTN consists of two separate components, the aesthetic component (AC) and the dental health component (DHC). It is a method that attempts to determine the degree of malocclusion of a particular patient and that patient's perception of his or her own malocclusion. The novel feature of the IOTN compared to other indices was that it was the first to include a sociopsychological indicator of treatment need.

The two components are analyzed separately and while they cannot be unified to give a single score, they can be combined to classify the patient as needing or not needing orthodontic treatment.

From the start, the authors wanted their index to have two separate components, one to assess the aesthetic impact of the malocclusion and another for the present or potential dental health and functional indications. They also wanted each occlusal feature that contributes to the greater or lesser longevity of the stomatognathic system to be precisely defined, with easily detected and measured levels of severity and cutoff points between them.

Owing to the difficulty in determining the relative contribution of each feature to dental health, the index has to be flexible so that it can be adapted in the light of future research and discoveries.

#### **5.1 The DHC (Dental Health Component) of the IOTN**

The DHC (Dental Health Component) is the clinical or dental health component of the IOTN. It is the result of a modification of the index used by the Swedish Dental Health Board (Linder-Aronson, 1974).

The salient feature of this component of the IOTN is that it classifies patients into five distinct grades with clear cutoff points between each, defined according to the occlusal features of each patient and the contribution of each feature to the longevity of the stomatognathic system. In other words, it classifies the occlusal findings that represent the greatest threat to good oral health and function into different grades. Also, it can be obtained directly from examination of the patient or from study models.

One of the main features of this index is that it is not cumulative: it only takes into account the most severe occlusal feature and classifies the patient directly into the appropriate grade. In the same way, it largely ignores the cumulative effect of less severe occlusal features and, consequently, can undervalue certain malocclusions in some individuals.

The DHC has five grades, from Grade 1 (no need for treatment) to Grade 5 (very great need for treatment).

#### **Index of Orthodontic Treatment Need Dental Health Component (IOTN DHC), (Brook Shaw, 1989).**

#### **Grade 5 (Very great)**


#### **Grade 4 (Great)**



#### **Grade 3 (moderate)**

14 Orthodontics – Basic Aspects and Clinical Considerations

The two components are analyzed separately and while they cannot be unified to give a single score, they can be combined to classify the patient as needing or not needing

From the start, the authors wanted their index to have two separate components, one to assess the aesthetic impact of the malocclusion and another for the present or potential dental health and functional indications. They also wanted each occlusal feature that contributes to the greater or lesser longevity of the stomatognathic system to be precisely defined, with easily

Owing to the difficulty in determining the relative contribution of each feature to dental health, the index has to be flexible so that it can be adapted in the light of future research

The DHC (Dental Health Component) is the clinical or dental health component of the IOTN. It is the result of a modification of the index used by the Swedish Dental Health

The salient feature of this component of the IOTN is that it classifies patients into five distinct grades with clear cutoff points between each, defined according to the occlusal features of each patient and the contribution of each feature to the longevity of the stomatognathic system. In other words, it classifies the occlusal findings that represent the greatest threat to good oral health and function into different grades. Also, it can be

One of the main features of this index is that it is not cumulative: it only takes into account the most severe occlusal feature and classifies the patient directly into the appropriate grade. In the same way, it largely ignores the cumulative effect of less severe occlusal features and,

The DHC has five grades, from Grade 1 (no need for treatment) to Grade 5 (very great need

**Index of Orthodontic Treatment Need Dental Health Component (IOTN DHC), (Brook** 



detected and measured levels of severity and cutoff points between them.

obtained directly from examination of the patient or from study models.

consequently, can undervalue certain malocclusions in some individuals.



quadrant) requiring pre-restorative orthodontics.

**5.1 The DHC (Dental Health Component) of the IOTN** 

orthodontic treatment.

and discoveries.

for treatment).

**Shaw, 1989).** 

**Grade 5 (Very great)** 

pathological cause.

**Grade 4 (Great)** 


Board (Linder-Aronson, 1974).


#### **Grade 2 (little)**


#### **Grade 1 (None)**


Lunn et al. (1993) conducted a study to assess the use of the IOTN. They concluded that this index is a very valid tool for public administration purposes but suggested the need for certain modifications to make it quicker and easier to use.

Their suggestions included reducing the number of IOTN DHC grades to three in order to improve its reliability. These proposals were accepted by the Manchester team that had developed the IOTN.


These modifications make it much easier to determine the treatment need of a population.

Burden et al. (2001) then proposed a further modification specifically for epidemiological studies, reducing the number of grades to two to make the IOTN DHC easier to use and to increase its validity and reliability.


They also decided to use the acronym MOCDO (Missing teeth, Overjet, Crossbites, Displacement of contact points, Overbite) to speed up the process and select the patients that need treatment.

This simplifies training and use. According to this modification, those with the following conditions need treatment:


For the reasons mentioned above this modified IOTN is recommended for epidemiological studies, although it is not useful for administrative purposes because, having only two grades, the patients cannot be classified on a scale of malocclusion severity, so it is more difficult to adjust the resources to the needs.

#### **5.2 The AC (Aesthetic Component) of the IOTN**

Since one of the main reasons for undergoing orthodontic treatment is aesthetic, it was considered that the aesthetic component ought to be represented in a diagnostic tool or an index (Alkhatib et al., 2005) and that the patients' perception of their own malocclusion needed to be taken into account.

The aesthetic component (AC) employs the SCAN Index (Evans Shaw, 1987). It consists of an illustrated scale showing ten grades of dental aesthetics and is employed to determine each patient's aesthetic perception of his or her own malocclusion. To design this index, 1000 intraoral photographs of 12-year-old children were collected and placed in order after a lengthy study (Brook Shaw, 1989). The photographs were rated by six non-dental judges. The result was a scale of ten black and white photographs showing different levels of dental

These modifications make it much easier to determine the treatment need of a population. Burden et al. (2001) then proposed a further modification specifically for epidemiological studies, reducing the number of grades to two to make the IOTN DHC easier to use and to

They also decided to use the acronym MOCDO (Missing teeth, Overjet, Crossbites, Displacement of contact points, Overbite) to speed up the process and select the patients

This simplifies training and use. According to this modification, those with the following





For the reasons mentioned above this modified IOTN is recommended for epidemiological studies, although it is not useful for administrative purposes because, having only two grades, the patients cannot be classified on a scale of malocclusion severity, so it is more

Since one of the main reasons for undergoing orthodontic treatment is aesthetic, it was considered that the aesthetic component ought to be represented in a diagnostic tool or an index (Alkhatib et al., 2005) and that the patients' perception of their own malocclusion

The aesthetic component (AC) employs the SCAN Index (Evans Shaw, 1987). It consists of an illustrated scale showing ten grades of dental aesthetics and is employed to determine each patient's aesthetic perception of his or her own malocclusion. To design this index, 1000 intraoral photographs of 12-year-old children were collected and placed in order after a lengthy study (Brook Shaw, 1989). The photographs were rated by six non-dental judges. The result was a scale of ten black and white photographs showing different levels of dental

less than or equal to 3.5 millimeters with masticatory or speech difficulties.


increase its validity and reliability.

that need treatment.

teeth.

millimeters.

causing gingival or palatal traumatic injury.

difficult to adjust the resources to the needs.

needed to be taken into account.

**5.2 The AC (Aesthetic Component) of the IOTN** 

conditions need treatment:


attractiveness, ranging from photograph 1, the most aesthetic, to number 10, the least aesthetic (Uçüncü Ertugay, 2001).

The patient has to look at his or her mouth in a mirror and identify it with one of the ten photographs in the scale. In this way, each patient's perception of his or her malocclusion can be observed.

To make the IOTN quicker and easier to use and improve its reliability, Lunn et al. (1993) proposed reducing the number of IOTN AC grades from 10 to 3. These proposals were accepted by the Manchester team that had developed the IOTN.


Nowadays, for practical and epidemiological purposes only two grades are considered: patients who identify with photographs 1 to 7 do not need treatment, while those who identify with photographs 8 to 10 do need treatment. It should be pointed out that in most cases, almost no patients identify their own teeth with the great orthodontic treatment need group (photographs 8-10). It is also considered to be no easy task for patients to decide which of the 10 photographs most resemble their own teeth, especially when they are very young.

In practice, the two components of the IOTN are determined separately and an individual is considered to need treatment if the IOTN DHC grade is 4 or 5 or the IOTN AC is in the grades 8-10 group. In either of these two situations the child needs orthodontic treatment for either dental health reasons (DHC) or for exclusively aesthetic reasons (AC). However, according to the modified IOTN developed by Burden et al. (2001), when this is employed in epidemiological studies both components are required, in other words, DHC grades 4-5 and AC grades 8-10.

#### **5.3 Validity and reliability of the IOTN**

When designing and testing the IOTN, Brook and Shaw (1989) observed that the reproducibility of this index was particularly good when measured under suitable conditions, and slightly less good when measured, for example, in schools.

Richmond et al. (1995) confirmed the validity and reliability of the IOTN in a study in which 74 dentists and orthodontists assessed the treatment need of a total of 256 models of orthodontic patients representing all types of malocclusion. The Spearman coefficient for the aesthetic component was 0.84 and that of the dental health component was 0.64.

Brook and Shaw claim good intra- and inter-examiner reproducibility when the IOTN AC is assessed by a dentist. However, according to Holmes (1992), the patients' perception tends to be more optimistic than that of the professionals. Nevertheless, the use of the IOTN AC has been the subject of some controversy in recent years. This is because of the lack of correlation between the dental health component (DHC) and the aesthetic component (AC), as found by Soh and Sandham (2004) in a study of an adult Asian population and by Hassan (2006) in a region of Saudi Arabia. Also, some authors such as Svedström-Oristo et al. (2009) have described certain problems when asking patients, both children and young adults, to identify their mouths with one of the 10 photographs employed as stimuli.

According to Alkhatib et al. (2005), the IOTN is not only valid and reliable but is also sensitive to the needs of patients and accepted both by the patients themselves and by the professionals who employ it. Hamdam (2004) confirmed the validity and reliability of the IOTN. Mandall et al. (2000) and Birkeland et al. (1996) concluded that it is a reproducible and reliable index.

A recent study by Johansson and Follin (2009) showed that the clinical criterion employed by 272 Swedish orthodontists was in good agreement with the results of the IOTN DHC. The main differences were found in IOTN grade 3, as the orthodontists considered most of the malocclusions in this grade to be in need of treatment.

However, O'Brien et al. (1993) found large differences in the choice of the different grades of need in both the DHC and the AC. Turbill et al. (1996) concluded that the IOTN is essentially an epidemiological index that has limitations when assessing the treatment needs of individual patients.

The IOTN is currently employed in the United Kingdom for prioritizing public orthodontic care services. Its reliability and validity have been extensively proved, it is simple and easy to use, and it is also one of the most-often cited indices in the literature.

### **6. The epidemiology of treatment need**

Appropriate assessment and measurement of malocclusions is essential in epidemiological studies in order to ascertain the prevalence and incidence of occlusal alterations among the population. There are certainly many indices and measures for assessing malocclusion, but the DAI and the IOTN are the best known and most widely used owing to their manageability and proven validity.

Tables 3 and 4 show a number of malocclusion prevalence studies conducted since the year of publication of each of these indices up to the present.

On examining the main studies it will be seen that both the DAI and the IOTN have been used to a greater extent in cross-sectional studies with large samples, generally randomly selected, although it will be observed that they meet the requirements for epidemiological or prevalence studies. While the IOTN is used to a greater extent in Europe, The DAI is employed to a similar extent throughout the world, though least in Europe. However, whereas the IOTN is employed more in child/adolescent populations, the DAI is more often employed in adolescent/adult ones.

As noted above, comparison between the different studies is very complicated. The first reason is that they employ different methods and their data collection criteria are sometimes not sufficiently well explained. Examination of the studies shows that they use different indices, so although they measure the same condition (malocclusion prevalence or treatment need), they do not measure it in the same way or consider the same occlusal features. Obviously, also, the different studies were conducted in different populations, with differing sample sizes, ages and geographical origins. For all these reasons, it is posible to make comparisons but prudence is required when drawing conclusions. Epidemiological studies of malocclusion prevalence and orthodontic treatment need in large, representative samples continue to be necessary in order to effect more rigorous comparisons.

According to Alkhatib et al. (2005), the IOTN is not only valid and reliable but is also sensitive to the needs of patients and accepted both by the patients themselves and by the professionals who employ it. Hamdam (2004) confirmed the validity and reliability of the IOTN. Mandall et al. (2000) and Birkeland et al. (1996) concluded that it is a reproducible

A recent study by Johansson and Follin (2009) showed that the clinical criterion employed by 272 Swedish orthodontists was in good agreement with the results of the IOTN DHC. The main differences were found in IOTN grade 3, as the orthodontists considered most of

However, O'Brien et al. (1993) found large differences in the choice of the different grades of need in both the DHC and the AC. Turbill et al. (1996) concluded that the IOTN is essentially an epidemiological index that has limitations when assessing the treatment needs

The IOTN is currently employed in the United Kingdom for prioritizing public orthodontic care services. Its reliability and validity have been extensively proved, it is simple and easy

Appropriate assessment and measurement of malocclusions is essential in epidemiological studies in order to ascertain the prevalence and incidence of occlusal alterations among the population. There are certainly many indices and measures for assessing malocclusion, but the DAI and the IOTN are the best known and most widely used owing to their

Tables 3 and 4 show a number of malocclusion prevalence studies conducted since the year

On examining the main studies it will be seen that both the DAI and the IOTN have been used to a greater extent in cross-sectional studies with large samples, generally randomly selected, although it will be observed that they meet the requirements for epidemiological or prevalence studies. While the IOTN is used to a greater extent in Europe, The DAI is employed to a similar extent throughout the world, though least in Europe. However, whereas the IOTN is employed more in child/adolescent populations, the DAI is more often

As noted above, comparison between the different studies is very complicated. The first reason is that they employ different methods and their data collection criteria are sometimes not sufficiently well explained. Examination of the studies shows that they use different indices, so although they measure the same condition (malocclusion prevalence or treatment need), they do not measure it in the same way or consider the same occlusal features. Obviously, also, the different studies were conducted in different populations, with differing sample sizes, ages and geographical origins. For all these reasons, it is posible to make comparisons but prudence is required when drawing conclusions. Epidemiological studies of malocclusion prevalence and orthodontic treatment need in large, representative

samples continue to be necessary in order to effect more rigorous comparisons.

the malocclusions in this grade to be in need of treatment.

**6. The epidemiology of treatment need** 

of publication of each of these indices up to the present.

manageability and proven validity.

employed in adolescent/adult ones.

to use, and it is also one of the most-often cited indices in the literature.

and reliable index.

of individual patients.



Table 3. Studies of different populations using the IOTN (DHC/AC)


Table 4. Studies of different populations using the DAI

### **7. Conclusions**

20 Orthodontics – Basic Aspects and Clinical Considerations

**Authors (publication year) Country n Age DHC(4-5) AC(8-10)** 

2595 2142 12 15

15-16

1029 176 15-29 18-24

15-16

35% 21%

21.8% 17.1% - -

4.4% 2.4%

**(≥31)** 

30.1% 25.9%

21.2% 16.1%

(2006b) Peru 281 16-25 29.9% 1.8% Hassan (2006) Saudi Arabia 743 17-24 71.6% 16.1% Souames et al. (2006) France 511 9-12 21.3% 7%

Nobile et al. (2007) Italy 1000 11-15 59.5% 3.2% Ngom et al. (2007) Senegal 665 12-13 42.6% 3.3%

(2009) Finland 434 16-25 - 2%

(2010) Algeria 248 12 18.1% 13.7% Hassan and Amin (2010) Saudi Arabia 366 21-25 29.2% -

**Authors (publication year) Country n Age Treatment Need** 

Estioko et al. (1994) Australia 268 12-16 24.1%

Taiwan

Otuyemi et al. (1999) Nigeria 703 12-18 9.2% Johnson et al. (2000) New Zealand 294 10 55.4% Chi et al. (2000) New Zealand 150 10 47% Abdullah and Rock (2001) Malaysia 5112 12-13 24.1% Esa et al. (2001) Malaysia 1519 12-13 24.1% Onyeaso et al. (2003) Nigeria 64 16-45 48.4% Baca-García et al. (2004) Spain 744 14-20 21.1% Onyeaso (2004) Nigeria 136 6-18 50% Onyeaso (2005) Nigeria 577 12-17 22.7% van Wyk and Drummond (2005) South Africa 6142 12 31% Frazão and Narvai (2006) Brazil 13801 12-18 18% Bernabé and Flores-Mir (2006a) Peru 267 16-25 32.6% Marques et al. (2007) Brazil 600 13-15 53.3% Hamamci et al. (2009) Turkey 841 17-26 21.5%

Kingdom

Manzanera et al. (2009) Spain 665 <sup>12</sup>

Table 3. Studies of different populations using the IOTN (DHC/AC)

Manzanera et al. (2010) Spain 655 <sup>12</sup>

Table 4. Studies of different populations using the DAI

Puertes-Fernández et al. (2010) Algeria 248 12 13.2%

Bernabé and Flores-Mir

Svedström-Oristo et al.

Puertes-Fernández et al.

Chestnutt et al. (2006) United

Katoh et al. (1998) Japan

Many very different indices have been developed for classifying malocclusions according to their severity or level of treatment need. Although a certain consensus has been reached on the features that the ideal index should possess, controversy continues over which should be used for this purpose.

Evidently, patients often seek orthodontic treatment but present considerable variations in malocclusion. The wide range of situations between ideal occlusion and very severe malocclusion make it very difficult to establish the precise limits of what should and should not be considered treatment need. Consequently, ascertaining the real malocclusion prevalence and establishing reliable comparisons concerning their frequency in different populations is by no means simple. Also, as there is also no unanimous criterion for deciding what to consider malocclusion, its real frequency cannot be established.

In this chapter we have presented a large number of orthodontic treatment need indices. However, the two indices that are currently most often used for epidemiological studies are the DAI and the IOTN. Hlonga et al. (2004) and Liu et al. (2011) have observed a significant correlation between the two indices. Nevertheless, high correlation does not necessarily imply high agreement (Manzanera et al., 2010). In epidemiological studies this is not a particularly important problem because both are valid methods for determining the orthodontic treatment need of a population, but when they are applied in individual cases, the choice of DAI or IOTN will lead to the appearance of both false negatives and false positives.

Comparison of these two indices finds similarities and differences. Both comprise two components, one anatomical and the other aesthetic, both measure occlusion features proposed by experts and both attempt to identify the individuals with the greatest treatment need in public programs. Although most of the features they measure are identical, each feature is rated differently in the two indices. The advantage of the DAI is that the aesthetic perception is linked to the anatomical assessment through regression analysis to produce a single score, whereas the IOTN has two components that cannot be unified. Also, the DAI offers a continuous scoring system, so it can classify different degrees of malocclusion within each of the pre-established levels. The IOTN cannot establish a continuous order within each grade, so it is more complicated to use for public health programs. In the DAI, unlike the IOTN, the occlusal features examined are different according to whether it is the primary dentition, mixed dentition or permanent dentition that is being measured, and since its design is more suitable for permanent teeth, it leads to the use of more than one epidemiological index.

It would appear, agreeing with some other authors, that DAI is more useful for administrative purposes, in other words, when the budget is limited and the patients must be placed in strict order of severity in order to give priority to those in most need of treatment. This is possible because the DAI scale is continuous, whereas the IOTN makes not distinctions within grades. The IOTN, however, being easily and quickly obtained, is more effective in epidemiological studies, to determine the percentage of the population in need of treatment without establishing priorities.

The great value that society sets on aesthetics nowadays, the importance that patients themselves ascribe to their malocclusions and the extent to which their condition affects their quality of life must not be forgotten. In recent years particular attention has been paid to surveys that attempt to measure the way in which malocclusion affects a person's quality of life; these include studies by De Baets et al. (2011), Liu et al. (2011) and Agou et al. (2011). Such surveys should be employed in decision-making as complementary tools to the different orthodontic treatment need indices.

#### **8. References**


The great value that society sets on aesthetics nowadays, the importance that patients themselves ascribe to their malocclusions and the extent to which their condition affects their quality of life must not be forgotten. In recent years particular attention has been paid to surveys that attempt to measure the way in which malocclusion affects a person's quality of life; these include studies by De Baets et al. (2011), Liu et al. (2011) and Agou et al. (2011). Such surveys should be employed in decision-making as complementary tools to the

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Abu Alhaija, E.S.; Al-Nimri, K.S. Al-Khateeb, S.N. (2004). Orthodontic treatment need and

Ackerman, J.L. Proffit, W.R. (1969). Characteristics of malocclusion: a modern approach to

Agou, S.; Locker, D.; Muirhead, V.; Tompson, B. Streiner, D.L. (2011). Does

Alkhatib, M.N.; Bedi, R.; Foster, C.; Jopanputra, P. Allan, S. (2005). Ethnic variations in orthodontic treatment need in London schoolchildren. *BMC Oral Health*, 27;5:8.

Bernabé, E.; Flores-Mir, C. (2006a). Orthodontic treatment need in Peruvian young adults evaluated through dental aesthetic index. *Angle Orthod*, Vol.76, No.3, pp. 417-421. Bernabé, E. Flores-Mir, C. (2006b). Normative and self-perceived orthodontic treatment

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## **3D Facial Soft Tissue Changes Due to Orthodontic Tooth Movement**

R.A. Al-Sanea1, B. Kusnoto2 and C.A. Evans2

*1Department of Dentistry-Central Region, National Guards Health Affairs 2Department of Orthodontics, University of Illinois at Chicago 1Kingdom of Saudi Arabia 2USA* 

#### **1. Introduction**

28 Orthodontics – Basic Aspects and Clinical Considerations

Van Wyk, P.J. Drummond, R.J. (2005). Orthodontic status and treatment need of 12-year-

WHO (1997). Health Surveys. Basic Methods. Ed. 3 Geneve: World Health Organization.

WHO (1979). Basic method for recording occlusal traits. WHO Bull;57(6):955-61.

pp. 334-336.

old children in South Africa using the Dental Aesthetic Index. *SADJ*; Vol.60, No.8,

Two-dimensional (2D) geometric morphometric analysis is the predominant basis for assessment of changes in facial structures resulting from orthodontic or orthognathic surgical treatment. Linear, angular and proportional 2D measurements of the profile are used to assess changes that take place in the three-dimensional (3D) facial soft tissues. However, these methods give little information about frontal soft tissue changes following treatment. Since patients tend to assess their appearance from frontal and three-quarter profile views, measurement of orthodontic outcomes only in the sagittal view as recorded in 2D lateral cephalograms or profile photographs may not be sufficiently informative. Cone Beam Computerized Tomography (CBCT) as well as 3D surface laser head scans offer better frontal and three-quarter profile data for diagnosis, treatment planning and patient education purposes. However, these 3D methods result in large computer files that require large virtual memory and storage media. Moreover, due to lack of normative 3D databases, the 3D images produced can only provide descriptive rather than geometric data of clinical significance. This chapter outlines the current methods used for morphometric assessment of facial soft tissues and their applications and limitations in the field of orthodontics. A simple and accurate method for the assessment of 3D changes occurring in facial soft tissues due to orthodontic tooth movement is explained. Finally, volumetric changes occurring after orthodontic tooth movement due to soft tissue profile advancement or soft tissue profile retraction are outlined.

#### **2. Two-dimensional morphometrics of facial soft tissues**

#### **2.1 Two-dimensional imaging**

Frontal and lateral photographs and anthropometric measurements along with lateral and frontal cephalometrics are considered the standard records for diagnosis and treatment planning in orthodontic treatment. Two-dimensional geometric morphometrics such as linear, angular and proportional measurements are used to assess changes that take place in facial soft tissues. Research including frontal and lateral photographs has shown that some soft tissue measurements tend to be more reliable than others. In general, frontal measurements are more reliable than lateral ones, and linear measurements are more reliable than angular measurements. Measurements that include subnasale, pogonion, and gnathion tend to be less reliable. Despite the fact that much of the reported evidence in the scientific literature is built around two-dimensional measurements, a substantial amount of information is lacking because:


Fig. 1. Facial folds.

facial soft tissues. Research including frontal and lateral photographs has shown that some soft tissue measurements tend to be more reliable than others. In general, frontal measurements are more reliable than lateral ones, and linear measurements are more reliable than angular measurements. Measurements that include subnasale, pogonion, and gnathion tend to be less reliable. Despite the fact that much of the reported evidence in the scientific literature is built around two-dimensional measurements, a substantial amount of

a. Three-dimensional structures are represented by a set of two-dimensional coordinates. Subject/film/focus geometric relationship could lead to size magnification, distortion,

b. Patients tend to assess their appearance from frontal and three-quarter profile views; measurement of orthodontic outcomes only in the sagittal view as recorded in 2D lateral cephalograms or profile photographs may not be sufficiently informative. An example of that would be surgical orthognathic patients who can relate to malar region changes or mandibular angle and soft tissue chin changes rather than lip profile and

c. For pre-treatment consultation or education sessions, and for discussion purposes, patients tend to describe the soft tissue of the face pointing at vermillion border and philtrum of lips and soft tissue facial folds rather than describing landmarks and linear measurements (Figure 1). The facial folds are skin folds or lines that become accentuated with facial expressions. The most significant factors that contribute to the prominence of the folds are excess skin, skin thinning, excess cheek fat, and ptosis of cheek fat. Many research studies are conducted in the field of plastic and cosmetic surgery on changes that take place in the facial folds with aging and with weight loss or weight gain. Since orthodontic tooth movement contributes to soft tissue profile advancement or retraction, in other words thinning or thickening of soft tissue around the lips as a result of tooth movement, then it would be only practical to borrow these terms for the purpose of patient education and treatment planning in the field of

vertical and horizontal displacement in relation to imaging source.

information is lacking because:

incisor position.

orthodontics.

Fig. 1. Facial folds.

#### **2.2 Two-dimensional morphometric analysis of facial soft tissues**

When superimposing different faces, a limited number of labeled points on each face, e.g., the tip of the nose, corner of the eye and less prominent points on the cheek must be located precisely (Farkas, 1987). Linear and angular measurements between the landmarks provide useful measurements for comparison. The number of reported manually labeled landmarks varies, but usually ranges from 50 to 300 as shown in Figure 2 (O'Toole et al., 1999; Clement & Marks, 2005). Only a correct alignment of all these points allows acceptable comparison between faces, intermediate morphs, a convincing mapping of motion data from the reference or initial treatment image into final treatment image.

Fig. 2. Soft tissue landmarks of the face (Source: Computer-Graphic Facial Reconstruction, Clement & Murray, eds., p. 114, Figure 6.3).

#### **2.3 Facial soft tissue changes in studies utilizing two-dimensional images**

There is controversy in the orthodontic literature regarding the correlation between craniofacial skeletal and soft-tissue profile form (Denis & Speidel, 1987; Bloom, 1961; Burke, 1983; Savara, 1965). For instance, although stereophotogrammetric (Savara, 1965; Burke, 1983; Peck & Peck, 1995), computed tomographic (Marsh & Vannier, 1983; Moss et al., 1987) and cephalometric studies (Riedel, 1950; Tweed, 1944) have indicated soft-tissue profile form is markedly influenced by orthodontic tooth movement and or orthognathic surgery, other studies have suggested the relative independence of the facial soft tissues on the underlying skeletal form (Finnoy et al., 1987; Wisth, 1974).

In an attempt to determine the effects of orthodontic treatment on the soft tissue profile of the lips, several studies were conducted to quantify and to predict the relationship between incisor retraction and lip retraction (Bloom, 1961; Rudee, 1964; Garner, 1974; Roos, 1977; Wisth, 1974; Hershey, 1972). With the exception of one study that found a predictable amount of soft tissue changes in response to incisor retraction (Bloom, 1961) the majority of the studies on both growing and non-growing subjects concluded that the large individual variation prevents the accurate prediction of lip response to incisor retraction in any given person.

Some studies pointed that lip structure seems to have an influence on lip response to incisor retraction. Oliver found that patients with thin lips or a high lip strain displayed a significant correlation between incisor retraction and lip retraction, whereas patients with thick lips or low lip strain displayed no such correlation (Oliver, 1982). In addition, Wisth (1974) found that lip response, as a proportion of incisor retraction, decreased as the amount of incisor retraction increased. This seems to indicate that the lips have some inherent support.

Al-Mesad (1998) studied soft tissue changes in extraction and non-extraction orthodontic patients and found that for the most part, the drape of the upper and lower lips was highly correlated to the changes in both upper and lower incisors. Changes in position of upper and lower incisors were found to influence the final position of upper and lower lips after orthodontic treatment in the total sample for both extraction and non-extraction samples. For every millimeter change in the upper incisor tip in the non-extraction group, approximately 0.2 mm of changes in the upper lip and 0.9 mm in the lower lip occurred. Greater changes were observed in individuals with thin upper and lower lips (0.8 mm changes for the upper lip with only 0.6 mm changes for the lower lip).

Bishara et al. (1995) used standardized facial photographs to compare the soft tissue profile changes in persons with Class II, division 1 malocclusions who were treated with either an extraction or non-extraction treatment modalities. The found that: (1) After treatment the upper and lower lips were retracted significantly more in the extraction group compared with the non-extraction group. These differences persisted into retention; (2) Upper lip length increased more among subjects who were treated without extractions; (3) Upper vermilion height in male subjects and the upper and lower vermilion heights in female subjects increased among subjects who were treated without extractions and decreased among subjects who were treated with four first premolar extractions; (4) Nasolabial angle became significantly more obtuse among the female subjects who were treated with four first premolar extractions (Bishara et al., 1995). Similar findings were noted by Kocadereli (2002). On the other hand, Charles Tweed (1944) firmly stated that non-extraction approach would place the teeth in an unstable position in the basal bone leading to unacceptable relapse afterwards.

Paquette et al. (1992) looked at 'borderline' extraction/non-extraction cases 14.5 years out of retention and found that in the long term, the non-extraction patients had profiles that were 2 mm fuller. A similar study (Luppanapornlarp & Johnston, 1993) looked at carefully

other studies have suggested the relative independence of the facial soft tissues on the

In an attempt to determine the effects of orthodontic treatment on the soft tissue profile of the lips, several studies were conducted to quantify and to predict the relationship between incisor retraction and lip retraction (Bloom, 1961; Rudee, 1964; Garner, 1974; Roos, 1977; Wisth, 1974; Hershey, 1972). With the exception of one study that found a predictable amount of soft tissue changes in response to incisor retraction (Bloom, 1961) the majority of the studies on both growing and non-growing subjects concluded that the large individual variation prevents the accurate prediction of lip response to incisor retraction in any given

Some studies pointed that lip structure seems to have an influence on lip response to incisor retraction. Oliver found that patients with thin lips or a high lip strain displayed a significant correlation between incisor retraction and lip retraction, whereas patients with thick lips or low lip strain displayed no such correlation (Oliver, 1982). In addition, Wisth (1974) found that lip response, as a proportion of incisor retraction, decreased as the amount of incisor retraction increased. This seems to indicate that the lips have some inherent

Al-Mesad (1998) studied soft tissue changes in extraction and non-extraction orthodontic patients and found that for the most part, the drape of the upper and lower lips was highly correlated to the changes in both upper and lower incisors. Changes in position of upper and lower incisors were found to influence the final position of upper and lower lips after orthodontic treatment in the total sample for both extraction and non-extraction samples. For every millimeter change in the upper incisor tip in the non-extraction group, approximately 0.2 mm of changes in the upper lip and 0.9 mm in the lower lip occurred. Greater changes were observed in individuals with thin upper and lower lips (0.8 mm

Bishara et al. (1995) used standardized facial photographs to compare the soft tissue profile changes in persons with Class II, division 1 malocclusions who were treated with either an extraction or non-extraction treatment modalities. The found that: (1) After treatment the upper and lower lips were retracted significantly more in the extraction group compared with the non-extraction group. These differences persisted into retention; (2) Upper lip length increased more among subjects who were treated without extractions; (3) Upper vermilion height in male subjects and the upper and lower vermilion heights in female subjects increased among subjects who were treated without extractions and decreased among subjects who were treated with four first premolar extractions; (4) Nasolabial angle became significantly more obtuse among the female subjects who were treated with four first premolar extractions (Bishara et al., 1995). Similar findings were noted by Kocadereli (2002). On the other hand, Charles Tweed (1944) firmly stated that non-extraction approach would place the teeth in an unstable position in the basal bone leading to unacceptable

Paquette et al. (1992) looked at 'borderline' extraction/non-extraction cases 14.5 years out of retention and found that in the long term, the non-extraction patients had profiles that were 2 mm fuller. A similar study (Luppanapornlarp & Johnston, 1993) looked at carefully

changes for the upper lip with only 0.6 mm changes for the lower lip).

underlying skeletal form (Finnoy et al., 1987; Wisth, 1974).

person.

support.

relapse afterwards.

selected and defined first premolar-extraction cases and non-extraction cases over the same post-retention time frame. The results indicated that the extraction of first premolars tended to flatten the profile by 2-3 mm when compared with non-extraction treatment. Interestingly, the non-extraction patients had the more concave faces post-treatment and this challenges the concept of extractions as part of orthodontic treatment 'dishing the face'. The ability to predict from post-treatment lateral photographs, whether individuals had been treated with or without extractions has been investigated (Boley et al., 1998) The findings indicated a correct response in only 54% of cases - just greater than pure chance.

In a sample of forty adult patients who underwent orthodontic treatment that resulted in either soft tissue profile retraction or soft tissue profile advancement, Al-Sanea, Kusnoto and Evans (Al-Sanea, 2007) studied linear changes occuring in cephalometric soft tissue landmarks: Sn, A, UL, LL, B. Patient selection was based on the following criteria: availability of pre-treatment and post-treatment lateral cephalometric radiographs; availability of acceptable clarity pre-treatment and post-treatment frontal and lateral photographs with lips closed or slightly touching without strain and the patient's head properly oriented in the three planes of space; and absence of facial hair, eye glasses or jewelry. The following criteria were added as part of the study design to minimize undesirable soft tissue facial changes:


In all 2D landmark measurements (Figure 3), a negative soft tissue change was observed in the soft tissue profile retraction group. The opposite was observed in the group that showed advancement of the soft tissue profile. In the profile retraction group, change was the greatest in the upper lip and lower lips (-1.68 and –1.58 mm). Similarly, the most change in the profile advancement group was observed in upper and lower lip and Sn (0.73, 0.85 and 0.86) (Table 1).

In this sample of patients, the overall soft tissue change in the profile retraction group was significantly greater in comparison to the change reported in the profile advancement group in all 2D landmarks (p<0.05). The highest difference in 2D measurements between the two groups was noted in the upper and lower lip (2.40 and 2.42 mms) followed by change at SfB (1.95 mm), followed by change at Sn (1.75 mm) and SfA (1.36 mm). Lack of change at SfA in the soft tissue profile advancement group was the reason why change at SfA was the lowest in comparison to other 2D measurements (Table 2).

Fig. 3. 2D landmarks of soft tissue profile.


#### \* p ≤0.05

Table 1. Means and standard deviations for linear horizontal changes in the soft tissue profile groups.


#### \* p ≤0.05

Table 2. Comparison of 2D measurements of soft tissue profile retraction and advancement groups.

#### **3. Three-dimensional morphometrics of facial soft tissues**

#### **3.1 Three-dimensional facial models**

34 Orthodontics – Basic Aspects and Clinical Considerations

Retraction Group Advancement Group Measurements N Mean ± SD (mm) Measurements N Mean ± SD (mm)

Table 1. Means and standard deviations for linear horizontal changes in the soft tissue

Mean Difference (mm)

> -1.75 -1.36 -2.40 -2.42 -1.95

Table 2. Comparison of 2D measurements of soft tissue profile retraction and advancement

2D-Sn 2D-SfA 2D-UL 2D-LL 2D-SfB

Student


t -value p-value\*

0.001 0.044 0.001 0.004 0.007

Sn A UL LL B

> 0.86 ± 1.65 0.58 ± 1.96 0.73 ± 2.38 0.85 ± 2.63 0.65 ± 2.24


Measurements

2D-Sn 2D-SfA 2D-UL 2D-LL 2D-SfB

Fig. 3. 2D landmarks of soft tissue profile.

2D-Sn 2D-SfA 2D-UL 2D-LL 2D-SfB

\* p ≤0.05

\* p ≤0.05

groups.

profile groups.

The goal of imaging in medicine and dentistry has been to display a patient's anatomic truth. Until now, imaging technology has been largely confined to two dimensions. The development of a 3D digital model of a patient's anatomy would greatly improve our ability to determine different treatment options, to monitor changes over time (the fourth dimension), to predict and display final treatment results, and to measure treatment outcomes more accurately. Lately, computer graphic head modeling has gained wide popularity in the field of plastic and orthognathic surgery for the prediction and simulation of treatment effects. The technique offers great advantages in surgical planning and the prediction of facial deformation. Furthermore, three-dimensional modeling of patient anatomy allows for engineering principles to be applied to such areas as local and general stress analysis of the stomatognathic system, analysis of asymmetry and how it may affect function, TMJ loading and occlusal forces, and reconstruction in oral and maxillofacial surgery. Finally, functional studies on dynamic 3D models will help us to understand the dynamic relationship of the anatomy which orthodontists and maxillofacial surgeons affect everyday in their practices (Quintero et al., 1999; Moss &Linney, 1990; Hatcher & Dial, 1999, Harrell et al., 2002).

#### **3.1.1 Directly acquired three-dimensional facial models**

Three-dimensional facial models "3D Facial Model" can be defined as three-dimensional coordinate data of facial soft tissues (Figure 4). Facial models can be acquired directly in 3D format utilizing computed tomograms (CT), including cone-beam tomography, magnetic resonance imaging (MRI), digital radiography, and digital ultrasound. Those techniques involve the use of ionizing radiation with varying degree, and can produce facial models with surface as well as deep data, depending on degree of segmentation.

Fig. 4. Three-dimensional facial model.

Other direct techniques for producing 3D facial models, that do not involve the use of ionizing radiation, include stereophotogrammetry and simultaneous image capture from more than one camera source. This approach can produce only surface data or a 3D shell of the face." All of the above mentioned allow for the volumetric registration of the hard and or soft tissue of the craniofacial structures and the face with adequate resolution. The end result is a 3D facial model that can be easily viewed on a computer monitor. However, all the techniques generate huge files that require large virtual memory and storage media.

#### **3.1.2 Manually reconstructed three-dimensional facial models**

Facial Models can be reconstructed into 3D format utilizing a variety of 2D or 3D images that are calibrated and merged into a 3D "digital replica" of anatomy. Surface laser scanning can produce multiple 3D images from different angles with a spatial resolution of 0.5 mm (Figure 5). Those images can be manually stitched together, utilizing the scanner software, into a 3D facial model. Similarly, multiple 2D images taken at different views can also be used to construct 3D facial models. In both cases, texture data can be mapped on to the 3D surface which produces a photorealistic 3D model. The main draw back in these settings is that post-processing of the acquired data can significantly alter the dimensions and appearance, particularly with over smoothing. While there have been numerous reports on the use of 3D facial images in evaluation of facial soft tissue changes following orthognathic surgery, these approaches and systems have not been critically validated. The task of validation of these systems for facial imaging is difficult due to the multitude of variables in post-processing and the conditions of image acquisition in the clinic.

Fig. 5. Different surface laser scans before stitching into one 3D head model. (Source: Computer-Graphic Facial Reconstruction, Clement & Murray, eds., p. 234, Figure 12.9).

Furthermore, all systems suffer from potential for patient movement and alterations of facial expression between the multiple views needed to construct a 3D model of the face. Laser-

Other direct techniques for producing 3D facial models, that do not involve the use of ionizing radiation, include stereophotogrammetry and simultaneous image capture from more than one camera source. This approach can produce only surface data or a 3D shell of the face." All of the above mentioned allow for the volumetric registration of the hard and or soft tissue of the craniofacial structures and the face with adequate resolution. The end result is a 3D facial model that can be easily viewed on a computer monitor. However, all the techniques generate huge files that require large virtual memory and storage media.

Facial Models can be reconstructed into 3D format utilizing a variety of 2D or 3D images that are calibrated and merged into a 3D "digital replica" of anatomy. Surface laser scanning can produce multiple 3D images from different angles with a spatial resolution of 0.5 mm (Figure 5). Those images can be manually stitched together, utilizing the scanner software, into a 3D facial model. Similarly, multiple 2D images taken at different views can also be used to construct 3D facial models. In both cases, texture data can be mapped on to the 3D surface which produces a photorealistic 3D model. The main draw back in these settings is that post-processing of the acquired data can significantly alter the dimensions and appearance, particularly with over smoothing. While there have been numerous reports on the use of 3D facial images in evaluation of facial soft tissue changes following orthognathic surgery, these approaches and systems have not been critically validated. The task of validation of these systems for facial imaging is difficult due to the multitude of variables in

**3.1.2 Manually reconstructed three-dimensional facial models** 

post-processing and the conditions of image acquisition in the clinic.

Fig. 5. Different surface laser scans before stitching into one 3D head model. (Source: Computer-Graphic Facial Reconstruction, Clement & Murray, eds., p. 234, Figure 12.9).

Furthermore, all systems suffer from potential for patient movement and alterations of facial expression between the multiple views needed to construct a 3D model of the face. Laserbased systems are a safety concern. While these systems are deemed safe for use with adults, the United State Food and Drug Administration (FDA) has no statement on the safety of laser systems in children, who constitute a majority of the orthodontic and craniofacial treatment group. The light-based imaging systems generally lack the precision of the laser-based systems and suffer from image artifacts due to skin tone, color and reflectance. Additionally, the majority of 3D imaging systems utilize frontal and threequarter facial views to produce a facial model; however this approach does not provide sufficiently accurate representations of the facial profile. The "profile" view generated from these systems is not a true view of the facial profile, as one would have with a camera positioned from the patient's profile. The generated "profile" can be distorted by several millimeters and lack detail of specific features, especially in the lower face and lips. This deficiency is a significant setback because much of our knowledge of growth and development and treatment outcomes is based upon the profile view.

#### **3.1.3 Mathematically reconstructed three-dimensional facial models**

This process involves the use of a framework of anthropometric measurements and texture information that characterize faces in a data set of 3D head scans. Principal Component Analysis (PCA), which is a powerful statistical technique that has found application in fields such as face recognition and image compression where the luxury of graphical representation is not available, can be utilized to analyze patterns of similarities and differences in this data set. After finding patterns in the data, anthropometric measurements and texture information act as geometric constraints for morphing a prototype (i.e., average) 3D facial model. This avarage is then registered on the 2D image and mathematically mapped into a 3D model of the face. A hierarchial algorithm is applied to adjust the model parameters for an optimal 3D reconstruction of the target image. Some imaging software utilize robust mathematical registration and algorithmic methods for the automatic mapping or simulation of faces with varying degree of accuracy depending on the amount of detailed information obtained from the date set. In applying the method to several images of a person, and when more detailed statistics (such as covariance information or exact distributions) are included, the 3D reconstructions can reach almost the quality of laser scans (Blanz & Vetter, 1999). The herarchial modeling technique utilized in software Facegen™ Modeller 3.5 (Singular Inversions, 2009) would serve as a practical, accurate and user friendly interface for the mathematical reconstruction of 3D facial models from readily available 2D images of orthodontic treatments and growth studies.

#### **3.2 Three-dimensional morphometric analysis of facial soft tissue**

Many studies were conducted on the evaluation of facial soft tissues utilizing 3D facial models of orthognathic surgical cases. Regardless whether the facial model was a true capture or a reconstructed one, several factors are impeding our understanding of 3D soft tissue changes in the orthodontic/orthognathic field:


error in 3D facial models. Three-dimensional models require sophisticated registration mathematics for analysis. The combined robust mathematics in the Euclidean Distance Matrix Analysis (EDMA) and Dense Correspondence Algorithm (DCA) serve as reliable registration methods for 3D models. However, further sophisticated mechanisms such as Thin Spline Plate Analysis (TSP) and Finite Element Analysis (FEA) need to be utilized for comparison of 3D changes between pre treatment and post treatment models.

 The 3D images before, during and after processing require computer processers with large virtual memories, not to mention the large storage and back up needed.


Table 3. A comparison between the three different modes of acquisition of 3D facial models.

#### **3.2.1 Three-dimensional methods of registration**

#### **3.2.1.1 Euclidean distance matrix analysis (EDMA)**

In general, the distance between points and in a Euclidean space is given by Weisstein (Weisstein, 1999)

$$d = \left| \mathbf{x} - \mathbf{y} \right| = \sqrt{\sum\_{i=1}^{\mathbf{x}^\circ} \left| \mathbf{x}\_i - y\_i \right|^2}$$

To explain the method of EDMA, let's represent an object by M (K X D) matrix where K is number of landmarks in the object and D is the dimensions, in which these landmarks lie, i.e., a landmark coordinate system (Lele & Richtsmeire, 1991; Lele & Cole, 1995). The form of an object as represented by this collection of landmark coordinates is that characteristic which remains invariant under the group of transformation consisting of rotation (spinning the object on an axis), reflection and translation (moving the object within a given coordinate system). The invariant condition is when the Difference M1, M2 = Diff (M1 R1+1t1, M2 R2+1t2) for any choice of rotation parameters R1, R2 and translation parameters t1, t2. A collection of all K X D matrices that can be obtained by rotation, reflection and translation of M is called an orbit. Under definition of form all matrices in the same orbit represent exactly the same form.

Any object with K landmarks in D dimensions can be represented in an invariant fashion using the vector of distances between all possible pairs of landmarks. This is called the form matrix (Lele & Richtsmeier, 1991). In the Euclidean Distance Matrix Analysis (EDMA) for any two objects with K landmarks, we end up with two form matrices i.e., the vectors of all possible pair wise distances for each one of the objects. One particular description that has been used to outline the difference between these two objects is the vector of the ratios of the corresponding differences, i.e., the form difference matrix (Lele and Richtsmeier, 1991; Lele & Cole, 1995). The important property of this description is that it only depends on the orbits to which the two forms belong, not on the exact locations along these orbits. This overcomes the problem of the lack of the coordinate system for location of change.

#### **3.2.1.2 Finite Element Analysis (FEA)**

38 Orthodontics – Basic Aspects and Clinical Considerations

comparison of 3D changes between pre treatment and post treatment models.

True replica Of surface anatomy. Deep data as well in Cone Beam CT

Radiation exposure in CBCT, light based systems produce image artifacts and potential for patient movement while image capture

**3.2.1 Three-dimensional methods of registration 3.2.1.1 Euclidean distance matrix analysis (EDMA)** 

3D Facial

Pros

Cons

(Weisstein, 1999)

 The 3D images before, during and after processing require computer processers with large virtual memories, not to mention the large storage and back up needed.

Model Acquired Manually reconstructed Mathematically

Table 3. A comparison between the three different modes of acquisition of 3D facial models.

In general, the distance between points and in a Euclidean space is given by Weisstein

'2

*x*

*i d xy x y* 

To explain the method of EDMA, let's represent an object by M (K X D) matrix where K is number of landmarks in the object and D is the dimensions, in which these landmarks lie, i.e., a landmark coordinate system (Lele & Richtsmeire, 1991; Lele & Cole, 1995). The form of an object as represented by this collection of landmark coordinates is that characteristic which remains invariant under the group of transformation consisting of rotation (spinning the object on an axis), reflection and translation (moving the object within a given coordinate system). The invariant condition is when the Difference M1, M2 = Diff (M1 R1+1t1, M2 R2+1t2) for any choice of rotation parameters R1, R2 and translation parameters t1, t2. A collection of all K X D matrices that can be obtained by rotation, reflection and translation of M is called an orbit.

Under definition of form all matrices in the same orbit represent exactly the same form.

1

*i i*

Almost true replica of surface anatomy

Stitching required, over smoothening, computer manipulation, laser use poses safety concerns, potential for patient movement while image capture

reconstructed

Surface anatomy with quality similar to surface laser scans, utilizes readily available 2D images, inexpensive method, user friendly, no radiation or laser use

Not true capture, Computer manipulation required

error in 3D facial models. Three-dimensional models require sophisticated registration mathematics for analysis. The combined robust mathematics in the Euclidean Distance Matrix Analysis (EDMA) and Dense Correspondence Algorithm (DCA) serve as reliable registration methods for 3D models. However, further sophisticated mechanisms such as Thin Spline Plate Analysis (TSP) and Finite Element Analysis (FEA) need to be utilized for

> Three-dimensional face models are described from a mathematical point of view by a huge number of polygons, forming something like a mesh. The nodes of the mesh are the vertices of the polygons. Finite-element scaling analysis can be used to depict clinical changes in terms of allometry (size-related shape-change), and the change in form between an initial configuration and a target configuration can be viewed as a continuous deformation from the initial form, which can be quantified based on major and minor strains (principal strains). If the two strains are equal, the change in form is characterized by a simple increase or decrease in size. However, if one of the principal strains changes in a greater proportion, both size and shape are transformed. The product of the strains indicates a change in size if the result is not equal to 1. For example, a product >1 indicates an increase in size (measured from the base of the mesh of the initial form) equal to the remainder; 1.30 indicates a 30% increase in volume (positive allometry). Similarly, a product of 0.65 indicates a 35% decrease in volume (negative allometry). The products and ratios can be resolved for individual landmarks within the configuration and these can be made linear using a log-linear scale. For ease of interpretation, a pseudocolour-coded scale can be used to provide a graphic display of change in size, as shown in Figure 6 (Singh et al., 2006).

Fig. 6. Finite element analysis pseudocolor scale depecting change in allometry between initial and target 3D facial model.

#### **3.2.1.3 Thin Plate Spline analysis (TPS)**

Suppose that all of the specimen landmarks, in the initial stage, are embedded into a thin, 2D, non-deformed, elastic plate. Due to transformation, landmarks will migrate to other new positions (final stage), so the thin-plate will be distorted, that is, all of the points belonging to the thin-plate will be relocated or dragged by landmark movements. TPS is applied to the comparison of forms as a regression mechanism with the requirement that bending energy or smoothness function is minimized. Applying finite element algorithms, it's possible to define an Area Factor, a Deformation Factor and a Principal Axis Direction for any point in the plate after deformation.

#### **3.2.1.4 Dense Correspondence Algorithm (DCA)**

For three-dimensional morphometric comparisons of pre-treatment and post-treatment head models, comparisons cannot be carried out unless the models are homologous (having equal number of nodes). Based on the closest point algorithm, the post-treatment meshes will utilize the landmarks from the pre-treatment head model as the basic mesh for the dense correspondence procedure when comparing the pre- to post-treatment head model of the same patient. In the closest point algorithm principle, the two models are aligned utilizing the digitized surface landmarks. The new position of the target vertices that lie inbetween the landmarks of the post-treatment model are determined using the Euclidean Distance Matrix Analysis (EDMA) approach. This way the points in the reassembled posttreatment mesh have a one-to-one correspondence with those of the pre-treatment mesh. Finally Thin-Plate Spline analysis is applied. As a result, all of the forms will have the same quantity of nodes, which enables comparison later on (Hutton et al., 2001).

Care should be taken in specifying the greatest distance between homologous landmarks while alignment of the head models. If the distance between a generic landmark of the basic mesh (pre-treatment model) and the surface of any non-basic mesh (post-treatment model) is greater than the parameter specified, then the landmark is definitively discarded.

#### **3.3 Facial soft tissue changes in studies utilizing three-dimensional images**

Ismail and Moss (2002) prospectively compared the 2D and the 3D effects on the face of extraction and non-extraction orthodontic treatment in patients with skeletal Class I patterns. They showed, based on cephalometric values, that the nasolabial angle was larger in the extraction group, while the vermilion boarder of the upper lip was forward in comparison to the extraction group at the end of treatment. Differential geometrics and surface shape analysis showed that for the two treatment modalities in the current study, there was a significant difference in the changes in upper lip thickness. The reduction in upper lip thickness in the extraction group was accompanied by a decrease in exposed vermilion. The converse was true for the non-extraction group, which showed an increase in upper lip thickness in the study. Furthermore, the non-extraction group had more convex cheeks and chins by the end of treatment compared to the extraction group. They also pointed an increased concavity of the labiomental fold region by the end of treatment in the extraction group. Faces in the extraction group became relatively more protrusive with treatment. The surface shape analysis technique showed that the cheeks were flatter in the none-extraction group at the start of treatment, but this reversed with time. In the extraction group, the concavity of the labiomental fold increased, while the non-extraction group showed no change in this area.

Suppose that all of the specimen landmarks, in the initial stage, are embedded into a thin, 2D, non-deformed, elastic plate. Due to transformation, landmarks will migrate to other new positions (final stage), so the thin-plate will be distorted, that is, all of the points belonging to the thin-plate will be relocated or dragged by landmark movements. TPS is applied to the comparison of forms as a regression mechanism with the requirement that bending energy or smoothness function is minimized. Applying finite element algorithms, it's possible to define an Area Factor, a Deformation Factor and a Principal Axis Direction for any point in

For three-dimensional morphometric comparisons of pre-treatment and post-treatment head models, comparisons cannot be carried out unless the models are homologous (having equal number of nodes). Based on the closest point algorithm, the post-treatment meshes will utilize the landmarks from the pre-treatment head model as the basic mesh for the dense correspondence procedure when comparing the pre- to post-treatment head model of the same patient. In the closest point algorithm principle, the two models are aligned utilizing the digitized surface landmarks. The new position of the target vertices that lie inbetween the landmarks of the post-treatment model are determined using the Euclidean Distance Matrix Analysis (EDMA) approach. This way the points in the reassembled posttreatment mesh have a one-to-one correspondence with those of the pre-treatment mesh. Finally Thin-Plate Spline analysis is applied. As a result, all of the forms will have the same

Care should be taken in specifying the greatest distance between homologous landmarks while alignment of the head models. If the distance between a generic landmark of the basic mesh (pre-treatment model) and the surface of any non-basic mesh (post-treatment model)

Ismail and Moss (2002) prospectively compared the 2D and the 3D effects on the face of extraction and non-extraction orthodontic treatment in patients with skeletal Class I patterns. They showed, based on cephalometric values, that the nasolabial angle was larger in the extraction group, while the vermilion boarder of the upper lip was forward in comparison to the extraction group at the end of treatment. Differential geometrics and surface shape analysis showed that for the two treatment modalities in the current study, there was a significant difference in the changes in upper lip thickness. The reduction in upper lip thickness in the extraction group was accompanied by a decrease in exposed vermilion. The converse was true for the non-extraction group, which showed an increase in upper lip thickness in the study. Furthermore, the non-extraction group had more convex cheeks and chins by the end of treatment compared to the extraction group. They also pointed an increased concavity of the labiomental fold region by the end of treatment in the extraction group. Faces in the extraction group became relatively more protrusive with treatment. The surface shape analysis technique showed that the cheeks were flatter in the none-extraction group at the start of treatment, but this reversed with time. In the extraction group, the concavity of the labiomental fold

is greater than the parameter specified, then the landmark is definitively discarded.

**3.3 Facial soft tissue changes in studies utilizing three-dimensional images** 

increased, while the non-extraction group showed no change in this area.

quantity of nodes, which enables comparison later on (Hutton et al., 2001).

**3.2.1.3 Thin Plate Spline analysis (TPS)** 

**3.2.1.4 Dense Correspondence Algorithm (DCA)** 

the plate after deformation.

In a geometric morphometric study on changes in the soft tissue facial profile following orthodontics, Singh et al. (2005) reported a statistically significant difference in the premaxillary region with the non-extraction group being relatively larger in that region by 25%. For the non-extraction group after treatment, localized increases in relative size in the naso-maxillary region size of 25% (p < 0.01) were present. For the extraction group after treatment, a non-significant reduction in relative size of 15% was localized in the putative bicuspid area.

Studies that used FEA to analyze the effect of extraction and non-extraction orthodontic treatment mostly used lateral cephalometrics. Finite elements were constructed using anatomical landmarks in lateral cephalometrics as vertices of the triangular elements and then analysis was carried out as the deformational change needed to produce the final cephalometric radiograph (Lavelle & Carvalho, 1989; Singh et al., 2005). The technique is good as it portrays the change as the amount of strain required to produce the final image. However, the technique utilizes two-dimensional images to portray three-dimensional structures. Therefore, those studies inherit the same limitations associated with studies of two-dimensional data.

Other studies used surface shape analysis to report changes in the face after orthodontic treatment (Ismail & Moss, 2002). They used 3D surface laser scans and compared faces after extraction and non-extraction orthodontic treatment. The experimental design involved description of the shape of the surfaces (i.e., saddle, spherical, dome, ridge, etc). The comparison was carried out mainly to detect how the surface changed in either shape or area. The technique might be useful in terms of comparing three-dimensional data on its own. However, much of our knowledge in growth and development and treatment results are derived from two dimensional landmark measurements of two-dimensional radiographs and photographs.

#### **4. Morphometric analysis of three-dimensional facial models generated utilizing two-dimensional photographs**

Much of our knowledge of treatment outcomes and growth and development of facial soft tissues is based on the frontal and profile photographs of patients. It would be greatly advantagous if these readily available images can be data mined into 3D facial models. A simple and accurate technique for the generation of 3D facial models from sets of 2D readily available pre treatment and post treatment photographs is proposed by Al-Sanea, Kusnoto and Evans (Al-Sanea, 2007).

The pretreatment and post-treatment images for each patient are resized by creating a duplicate layer of the post-treatment image in a contrasting balance, and then adjusting the opacity of the created layer to 60-70%. Later on the post-treatment image layer is overlaid on top of the pretreatment image and its size adjusted until a perfect fit on the eyes is achieved.

Three-dimensional head models were constructed using FaceGen™ Modeller 3.1 and 3.5 (Singular Inversions Inc., Toronto, ON, Canada, 2005 and 2009) from the resized frontal and lateral photographs of the same patients where the 2D cephalometric analysis was carried out. Following the recommendations of the software, 11 surface landmarks were digitized on the frontal photographs and 7 landmarks on the lateral photograph. The surface landmark locations suggested by the software are in accordance with facial soft tissue landmarks definitions outlined by Farkas (1987). After landmark digitization the software computes the average face and the mode of variation in its own dataset based on the age, gender, race, and symmetry information specified to it by the operator. Based on this information the software predicts and produces an average head that can be morphed into the patient's head. During the morphing procedure, the software calculates the texture and geometric information in the image and modifies the 3D model accordingly. The threedimensional image produced is saved in two formats (Facegen: Fg) and (VRML. 97).

A pre-treatment and a post-treatment model were generated for each patient. Computer graphic facial analysis was carried out for those models in each patient using Morphostudio™ 3.02.39 (Orthovisage, New York, NY, 2005). First, twelve surface landmarks are digitized on the face of the model (Figure 7) in order to apply the dense correspondence algorithm. The dense correspondence algorithm transforms vertices in the 3D models into homologous landmarks that are easily compared. For consistency and reliability, the surface landmarks were selected in accordance with the surface landmarks already used to generate the 3D model in Facegen™.

Fig. 7. Landmarks used to generate 3D head model in Facegen™ software as well as apply the dense correspondence algorithm function in Morphostudio™.

The percentage of volume deformation in the post-treatment model (as measured from the base of the mesh of the pretreatment model) was reported through the Finite Element Analysis function of the Morphostudio™ 3.02.39 (Orthovisage, New York, NY, 2005).30 This is represented in the color-coded graphic display in the software (Figure 6). A total of thirtyfour pseudocolor scale measurements were recorded from the surface of the 3D model at different nodes around the lips (Figure 8).

out. Following the recommendations of the software, 11 surface landmarks were digitized on the frontal photographs and 7 landmarks on the lateral photograph. The surface landmark locations suggested by the software are in accordance with facial soft tissue landmarks definitions outlined by Farkas (1987). After landmark digitization the software computes the average face and the mode of variation in its own dataset based on the age, gender, race, and symmetry information specified to it by the operator. Based on this information the software predicts and produces an average head that can be morphed into the patient's head. During the morphing procedure, the software calculates the texture and geometric information in the image and modifies the 3D model accordingly. The three-

dimensional image produced is saved in two formats (Facegen: Fg) and (VRML. 97).

already used to generate the 3D model in Facegen™.

A pre-treatment and a post-treatment model were generated for each patient. Computer graphic facial analysis was carried out for those models in each patient using Morphostudio™ 3.02.39 (Orthovisage, New York, NY, 2005). First, twelve surface landmarks are digitized on the face of the model (Figure 7) in order to apply the dense correspondence algorithm. The dense correspondence algorithm transforms vertices in the 3D models into homologous landmarks that are easily compared. For consistency and reliability, the surface landmarks were selected in accordance with the surface landmarks

Fig. 7. Landmarks used to generate 3D head model in Facegen™ software as well as apply

The percentage of volume deformation in the post-treatment model (as measured from the base of the mesh of the pretreatment model) was reported through the Finite Element Analysis function of the Morphostudio™ 3.02.39 (Orthovisage, New York, NY, 2005).30 This is represented in the color-coded graphic display in the software (Figure 6). A total of thirtyfour pseudocolor scale measurements were recorded from the surface of the 3D model at

the dense correspondence algorithm function in Morphostudio™.

different nodes around the lips (Figure 8).

Fig. 8. Landmark areas where psudocolor scale measurements were recorded.

Since the deformation was expressed over a large area around the lips, point measurements at single nodes were not effective. Multiple measurements had to be recorded at different regions around the lips and averaged together in order to report the average volumetric deformation occurring in that region (Figure 9). Measurements were analyzed to determine changes in the soft tissue of the face following orthodontic treatment that resulted in soft tissue profile retraction or soft tissue profile advancement.

As shown in Figure 8, four lateral measurements were recorded on the same horizontal level of Sn at both the nasolabial fold and the philtrum of the upper lip. These measurements were labeled as upper right and left nasolabial fold (URNL, ULNL) and upper right and left philtrum (URPh, ULPh) respectively. Four lateral measurements were recorded on the same horizontal level of SfA on the nasolabial fold and the philtrum of the upper lip. Those measurements were the middle right and left nasolabial and the middle right and left philtrum (MRNL, MLNL, and MRPh, MLPh respectively). Two lateral measurements were also recorded at the junction of the nasolabial fold and the upper lip (lower right nasolabial and lower left nasolabial- LRNL and LLNL). Three measurements were recorded for the upper lip vermillion boarder in the areas of labiale superius (ls) and crista philtri landmark (cph). Three measurements were recorded on the convex surface of the upper lip, two on each side and one in the middle (RUL, MUL, LUL). The same was for the lower lip, two measurements were recorded on each side of the convex surface and one middle measurement was taken (RLL, MLL, LLL). Three measurements right, left and middle were recorded on the lower lip vermilion border (Rli, Mli, Lli). Two measurements were recorded on the labiomental folds on each side of SfB (RSfB, LSfB). Two measurements (URLLM, ULLLM) were recorded on the lateral labiomental folds and fall at the junction of the lateral labiomental folds and the lower lip. Two other measurements on the lateral labiomental folds were recorded and fell on the same horizontal level of Rli, Mli, Lli (MRLLM, MLLLM). Two measurements (RSfB, LSfB) were recorded on the lateral labiomental folds and fell on the same horizontal level of SfB.

Fig. 9. Averaged 3D measurements.

The percentages of volumetric change were calculated by averaging each five pseudocolor scale measurements on the same horizontal level of each reference landmark. These values were used to report the mean percentage of 3D volumetric change at areas of Sn, SfA, UL, LL, SfB. The averaging procedure for these landmarks is shown in Figure 9.

Furthermore, bilateral measurements at the folds of the face were also averaged. Three bilateral measurements on the right and left nasolabial folds were averaged together denoting change at the nasolabial folds (Right nasolabial fold measurements: URNL, MRNL, LRNL and left nasolabial measurements: ULNL, MLNL, LLNL). All nine measurement enclosed within the philtrum of the upper lip were averaged together (URPh, Sn, ULPh, MRPh, SfA, MLPh, LRPh, Ls, LLPh). Three bilateral vertical measurements on the lateral labiomental folds were averaged together denoting change at the lateral labniomental folds (Right lateral labiomental fold measurements: URLLM, MRLLM, LRLLM and left labiomental fold measurements: ULLLM, MLLLM, LLLLM). These averaged measurements are shown in Figure 10.

Reliability of the FEA method was obtained by recording pseudocolor scale values on different time points for six randomly selected patients and estimating the pair wise correlations among these pseudoscale values. Two-tailed sample Student t-test was calculated to compare the mean measurements in soft tissue profile retraction and soft tissue profile advancement groups at 0.05 level of significance.

Fig. 10. Average measurements at the folds of the face.

The percentages of volumetric deformation of the surface nodes from the base of the pretreatment mesh were calculated by averaging the five pseudocolor scale measurements on the same horizontal level of each reference landmark; leading to the mean percentage of volumetric change at areas of Sn, SfA, UL, LL, SfB. Change was the greatest in upper and lower lip measurements in both profile retraction and profile advancement groups. Change in the profile retraction group was the greatest at the upper lip vermilion border (3D-UV), which was 12.47 %. In the soft tissue profile advancement group however, change was greatest at the vermilion border of the lower lip (7.09%). The greatest difference in 3D measurements between the two groups was noted in the vermilion boarder of the upper lip at 15.71% (Tables 4 and 5).


p ≤0.05

44 Orthodontics – Basic Aspects and Clinical Considerations

The percentages of volumetric change were calculated by averaging each five pseudocolor scale measurements on the same horizontal level of each reference landmark. These values were used to report the mean percentage of 3D volumetric change at areas of Sn, SfA, UL,

Furthermore, bilateral measurements at the folds of the face were also averaged. Three bilateral measurements on the right and left nasolabial folds were averaged together denoting change at the nasolabial folds (Right nasolabial fold measurements: URNL, MRNL, LRNL and left nasolabial measurements: ULNL, MLNL, LLNL). All nine measurement enclosed within the philtrum of the upper lip were averaged together (URPh, Sn, ULPh, MRPh, SfA, MLPh, LRPh, Ls, LLPh). Three bilateral vertical measurements on the lateral labiomental folds were averaged together denoting change at the lateral labniomental folds (Right lateral labiomental fold measurements: URLLM, MRLLM, LRLLM and left labiomental fold measurements: ULLLM, MLLLM, LLLLM). These averaged measurements

Reliability of the FEA method was obtained by recording pseudocolor scale values on different time points for six randomly selected patients and estimating the pair wise correlations among these pseudoscale values. Two-tailed sample Student t-test was calculated to compare the mean measurements in soft tissue profile retraction and soft tissue

LL, SfB. The averaging procedure for these landmarks is shown in Figure 9.

profile advancement groups at 0.05 level of significance.

Fig. 9. Averaged 3D measurements.

are shown in Figure 10.

Table 4. Means and standard deviations for the percentage of volume deformation in the soft tissue profile groups.


\* p ≤0.05

Table 5. Comparison of 3D measurements of soft tissue profile retraction and advancement groups.

Statistically significant differences were found between soft tissue profile retraction and soft tissue profile advancement groups in the percentage of volume deformation at the facial folds regions. The greatest difference between soft tissue profile retraction and soft tissue profile advancement was noted at the Philtrum (Ph) Where the difference was -12.02 and 2.78 respectively while the Lowest difference was at 3D-LLM (-3.36 and 1.71 respectively)

Results are outlined in Table 6.


Table 6. Means and standard deviation for the percentage volume deformation at the facial folds on the soft tissue profile (%).

#### **5. Correlation between two-dimensional and three-dimensional measurements**

Current orthodontic research reports linear 2D or volumetric 3D changes in the facial soft tissues without establishing a relationship between 2D and 3D measurements. Knowing this relationship could enable clinicians to use 2D measurements as a routine tool to determine the behavior of the soft tissue of the face in the three planes of space. This can serve as a useful guide in diagnosis, treatment planning/ prediction and patient communication.

In an attempt to study the relationship between 3D morphologic measurements of soft tissue change following orthodontic treatment and the corresponding two-dimensional change, we (Al-Sanea, Kusnoto and Evans) tested the hypothesis that there is significant correlation between 3D morphologic measurements and 2D morphologic measurements of facial soft tissue change following orthodontic treatment in the same regions of the face in the same patient.

#### **5.1 Correlation measurements between two-dimensional and three-dimensional changes in the soft tissue profile retraction group**

Pearson correlation coefficient was calculated to determine the relationship between twodimensional and three-dimensional measurements in the soft tissue profile retraction group at (0.05) level of significance. No statistically significant correlation existed between twodimensional and three-dimensional measurements. The p values of the correlation ranged between (0.084- 0.661). Table 7 shows the Pearson Correlation values while scatter diagrams are represented in Figure 11-15.


NS: Statistically non significant

46 Orthodontics – Basic Aspects and Clinical Considerations

Table 5. Comparison of 3D measurements of soft tissue profile retraction and advancement

Statistically significant differences were found between soft tissue profile retraction and soft tissue profile advancement groups in the percentage of volume deformation at the facial folds regions. The greatest difference between soft tissue profile retraction and soft tissue profile advancement was noted at the Philtrum (Ph) Where the difference was -12.02 and 2.78 respectively while the Lowest difference was at 3D-LLM (-3.36 and 1.71 respectively)

Groups Retraction Advancement


Measurements N Mean ± SD Mean ± SD

Table 6. Means and standard deviation for the percentage volume deformation at the facial

Current orthodontic research reports linear 2D or volumetric 3D changes in the facial soft tissues without establishing a relationship between 2D and 3D measurements. Knowing this relationship could enable clinicians to use 2D measurements as a routine tool to determine the behavior of the soft tissue of the face in the three planes of space. This can serve as a useful guide in diagnosis, treatment planning/ prediction and patient communication.

In an attempt to study the relationship between 3D morphologic measurements of soft tissue change following orthodontic treatment and the corresponding two-dimensional change, we (Al-Sanea, Kusnoto and Evans) tested the hypothesis that there is significant correlation between 3D morphologic measurements and 2D morphologic measurements of facial soft tissue change following orthodontic treatment in the same regions of the face in

20 20 20

**5. Correlation between two-dimensional and three-dimensional** 

Student


t-value p- value\*

3.82 ± 9.55 2.78 ± 10.82 1.71 ± 11.09

0.000 0.003 0.040 0.045 0.066 0.000 0.001

Difference


Measurements Mean

3D-Sn 3D-SfA 3D-UL 3D-LL 3D-LV 3D-UV 3D-SfB

Results are outlined in Table 6.

3D-NL 3D-Ph 3D-LLM

folds on the soft tissue profile (%).

**measurements** 

the same patient.

\* p ≤0.05

groups.

\*P value is statistically significant at 0.05

Table 7. Correlation measurements between two-dimensional and three dimensional changes in the soft tissue profile retraction group.

Fig. 11. Scatter diagram of correlation between 2D-Sn and 3D-Sn values.

Fig. 12. Scatter diagram of correlation between 2D-SfA and 3D- SfA.

Fig. 13. Scatter diagram of correlation between 2D-UL and 3D- UL.

Fig. 12. Scatter diagram of correlation between 2D-SfA and 3D- SfA.

Fig. 13. Scatter diagram of correlation between 2D-UL and 3D- UL.

Fig. 14. Scatter diagram of correlation between 2D-LL and 3D-LL.

Fig. 15. Scatter diagram of correlation between 2D-SfB and 3D-SfB.

#### **5.2 Correlation measurements between two-dimensional and three dimensional changes in the soft tissue profile advancement group**

Pearson correlation coefficient was calculated to determine the relationship between twodimensional and three-dimensional measurements in the soft tissue profile advancement group at (0.05) level of significance. No statistically significant correlation existed between two-dimensional and three-dimensional measurements except in the upper lip values (2D-UL and 3D-UL) where the p value was 0.033. The p values of the correlation in the rest of the measurements ranged between (0.116-0.917). The Pearson Correlation values and the scatter diagrams are shown in Table 8 and Figures 11-15 respectively.


NS: Statistically non significant

\*P value is statistically significant at 0.05

Table 8. Correlation measurements between two-dimensional and three dimensional changes in the soft tissue profile advancement group.

#### **6. References**


Pearson correlation coefficient was calculated to determine the relationship between twodimensional and three-dimensional measurements in the soft tissue profile advancement group at (0.05) level of significance. No statistically significant correlation existed between two-dimensional and three-dimensional measurements except in the upper lip values (2D-UL and 3D-UL) where the p value was 0.033. The p values of the correlation in the rest of the measurements ranged between (0.116-0.917). The Pearson Correlation values and the

Measurements Number ρ Significance 2D-Sn and 3D- Sn 20 0.363 NS 2D-SfA and 3D-SfA 20 0.025 NS 2D-UL and 3D-UL 20 0.477\* S 2D-LL and 3D-LL 20 0.212 NS 2D-SfB and 3D-SfB 20 -0.207 NS

Table 8. Correlation measurements between two-dimensional and three dimensional

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Al-Mesad, S. (1998). Soft Tissue Changes in White and Black Orthodontic Populations. Master's Thesis A447, University of Illinois at Chicago, Chicago, pp. 1-68. Al-Sanea, R. (2007). Three Dimensional Morphometric Analysis of Facial Soft Tissue

Bishara, S.E.; Cummins, D.M. & Jakobsen, J.R. (1995). A Computer Assisted

Blanz, V. & Vetter, T. (1999). A Morphable Model for the Synthesis of 3D Faces. *SIGGRAPH'* 

Bloom, L.A. (1961). Perioral Profile Changes in Orthodontic Treatment. *American Journal of Orthodontics and Dentofacial Orthopedics*, 47:371, 1961, ISSN 0889-5406 Boley, J.C.; Pontier, J.P.; Smith, S. & Fulbright, M. (1998). Facial Changes in Extraction and

Burke, P. (1983). Stereophotogrammetic Measurement of Change in Soft Tissue Following

Clement, J.G. & Marks, M.K., eds. (2005) Computer-Graphic Facial Reconstruction .

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Non-Extraction Patients. *Angle Orthodontist,* Vol.68, No.6, (December 1998), pp. 539-

Surgery. *British Dental Journal,* Vol.155, No.11, (December 1983), pp. 373-379, ISSN

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**5.2 Correlation measurements between two-dimensional and three dimensional** 

**changes in the soft tissue profile advancement group** 

NS: Statistically non significant

**6. References** 

\*P value is statistically significant at 0.05

546, ISSN 0003-3219

00007-0610

changes in the soft tissue profile advancement group.

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scatter diagrams are shown in Table 8 and Figures 11-15 respectively.


## **Are the Orthodontic Basis Wrong? Revisiting Two of the Keys to Normal Oclusion (Crown Inclination and Crown Angulation) in the Andrews Series**

C. Jiménez-Caro1,2, F. de Carlos1,2, A.A. Suárez1,3, J.A. Vega4 and J. Cobo1,2 *1Instituto Asturiano de Odontología, Oviedo 2Departamento de Cirugía y Especialidades Médico-Quirúrgicas (sección de Odontología), Universidad de Oviedo 3Departamento de Construcción e Ingeniería de la Fabricación (Sección de Ingeniería Mecánica), Universidad de Oviedo 4Departamento de Morfología y Biología Celular, Universidad de Oviedo Spain* 

#### **1. Introduction**

52 Orthodontics – Basic Aspects and Clinical Considerations

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Moss, J.P. & Linney, A.D. (1990). The Prediction of Facial Aesthetics. *The New York State Dental Journal*, Vol.56, No.6, (June-July 1990), pp. 44-46, ISSN 0028-7571 Oliver, B.M. (1982). The Influence of Lip Thickness and Strain on Upper Lip Response to

O'Toole, A.J.; Vetter, T. & Blanz, V. (1999). Three-Dimensional Shape and Two-Dimensional

Paquette, D.E.; Beattie, J.R. & Johnston, L.E. Jr. (1992). A Long-Term Comparison of

Peck, S. & Peck, L. (1995). Selected Aspects of the Art and Science of Facial Esthetics. *Seminars in Orthodontics,* Vol.1, No.1, (June 1995) pp. 105-126, ISSN 1073-8746 Quintero, J.C.; Trosien, A.; Hatcher D. & Kapila S. (1999). Craniofacial Imaging in

Roos, N. (1977). Soft Tissue Changes in Class II Treatment. *American Journal of Orthodontics and Dentofacial Orthopedics,* Vol.72, No.2, (August 1977), pp. 165-175, ISSN 0889-5406 Rudee, D.A. (1964). Proportional Profile Changes Concurrent With Orthodontic Therapy.

Savara, B.S. (1965). Applications of Photogrammetry for Quantitative Study of Tooth and

Singh, G.D.; Maldonado, L. & Thind, B.S. (2004-2005). Changes in the Soft Tissue Facial

Tweed, C. H. (1944). Indications for the Extraction of Teeth in Orthodontic Procedure.

Wisth, P.J. (1974). Soft Tissue Response to Upper Incisor Retraction in Boys. *British Journal of Orthodontics*, Vol.1, No.5, (October 1974), pp. 199–204, ISSN 0301-228X

Weisstein, E.W. (1999). Distance. From: *MathWorld--A Wolfram Web Resource.*

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8756-3150

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http://mathworld.wolfram.com/Distance.html, 1999.

Visualization of the Face and Skull Using Computerized Tomography and Laser Scaling Techniques. *American Journal of Orthodontics and Dentofacial Orthopedics*,

Incisor Retraction. *American Journal of Orthodontics and Dentofacial Orthopedics,* 

Surface Reflectance Contributions to Face Recognition: An Application of Three-Dimensional Morphing. *Vision Research,* Vol.39, No.18, (September 1999), pp. 3145-

Nonextraction and Premolar Extraction Edgewise Therapy in "Borderline" Class II Oatients. *American Journal of Orthodontics and Dentofacial Orthopedics,* Vol.102, No.1,

Orthodontics: Historical Perspective, Current Status, and Future Developments. *Angle Orthodontist*, Vol.69, No.6, (December 1999), pp. 491-506, ISSN 0003-3219 Riedel, R.A. (1950). Esthetics and Its Relation to Orthodontic Therapy. *Angle Orthodontist,*

*American Journal of Orthodontics and Dentofacial Orthopedics,* Vol.50, No.6, (June

Face Morphology. *American Journal of Physical Anthropology*, Vol.23, No.4,

Profile Following Orthodontic Extractions: a Geometric Morphometric Study. *The Functional Orthodontist,* Vol.22, No.1, (Winter 2004-Spring 2005), pp. 34-38, 40, ISSN

*American Journal of Orthodontics and Oral Surgery*, Vol.30, No.8, (August 1944), pp.

In the second half of the last century, Lawrence F. Andrews studied a series of 120 casts, of non-orthodontic subjects with ideal patterns of dental occlusion, and established "*The six keys to normal occlusion*". These were the basis to program the tooth movement directly on the bracket and not in wire bending, and were also the origin of the straight-wire, or preadjusted, appliance of current use in orthodontics. However, until now, the postulates of Andrews never have been contrasted using the scientific method and a proper statistical analysis. Moreover, some orthodontists have the suspect that the criteria of Andrews are not universal and applicable to the whole population since he do not distinguished agedependent changes, ethnical group, sex, or left-right asymmetry. The critical analysis of the Andrews' work is the goal of this Chapter, but we have centered our efforts in the date related to Crown angulation (the mesiodistal "tip") and Crown inclination (labiolingual or buccolingual inclination) which are of capital importance to perform accurately functional and aesthetic orthodontic treatments.

#### **2. Background: Historical context**

The use of the fixed appliance in orthodontic is directly linked to the proposal and guides of Edward H. Angle to move the teeth to the so-called "occlusion line", defined as "*the line, shape and position, must be teeth in balance if there is a normal occlusion*". Angle described in detail the relationships between maxillary and mandible, and maxillary-mandible and teeth, and especially the teeth among them, in order to achieve an ideal occlusion (Angle, 1929b; see the Special Edition of 1981).

These recommendations required the designing of special devices for three-dimensional control of teeth in order to reach the occlusion line and allow teeth to be correctly aligned in both the maxillary and mandible. Furthermore, according to Angle the alignment of the teeth, both crown and root, would result in the expansion of both the maxillary and mandible arches. This was also one of the main objectives to design the Angle's devices. Nevertheless, these postulates are still under discussion (Canut, 2000; Peck, 2008).

In 1887, Angle developed the "E" arch appliance formed by a thick gold wire placed for labial and some stainless steel tape on the first molar adjusted at pressure. This type of arch expanded both maxillary and mandible arches sagittally and transversely, and allowed a movement of simple inclination of the crown through a few ligatures that surrounded the tooth and conformed to the arch.

In the early 20th century with the development of metallurgy emerged the possibility of banding all the teeth and welding devices for the control of rotations. In 1910, Angle introduced the first appliance with individual tooth action and fullbanding, the so-called "pin and tube appliance", which welded small vertical tubes in the bands to introduce a stem attached to the wire. This device facilitated the labiolingual as mesiodistal expansion of the maxillary, and its drawback was the requirement for adjustment and accuracy in addition to the skill by the clinician (Bravo, 2007). Unfortunately one of the problems posed by this device was its inestability (Graber and Vanarsdall, 1994). Later, in 1916, Angle designed a bracket, called "ribbon arch appliance wire-band", containing a rectangular wire fixed by a few pins and placing the wider side on the tooth. This device properly controlled the labiolingual as well as vertical placement of teeth, by facilitating the correction of giroversions. However, it was difficult to place on the cusp and the looseness of the wire in the slot prevented mesiodistal control. Another substantial contribution of Angle was the frontal slot bracket, as opposed to the ribbon arch appliance of vertical opening, which featured great advantages, especially the ease to introduce the wire and the possibility to control the premolars and the adjustment of mesiodistal movement. In 1926 he presented the "bracket 447" with a horizontal slot .022 "x.028" which served to introduce a rectangular wire of the same thickness through the more narrow are, i.e. edgewise. It was made in gold and was called "soft bracket", as it opened easily and distorting (see for a review the Special Edition of Angle's work, 1981).

Over the basis of this model Steiner developed the "bracket 452" (hard bracket), more resistant to deformation which allowed to control teeth movement at the three levels through bends as tip, torque and in-out. This would become the prototype of the contemporary brackets.

Previously to the emergence of the straight wire, Angle already proposed to place the brackets to mesial or distal from the teeth to help to correct teeth rotations (Angle, 1929a), and a posterior angulation of the brackets to get proper root movements (see Meyer and Nelson, 1978). Later, Lewis (1950) joined segments ("arms") linked to the brackets, in contact with the wires for controlling rotations. Thereafter, Holdaway (1952) proposed that the buccal aspect of the brackets could be angulated depending on the degree of severity of the malocclusion. Twenty years later the original idea of Lewis, with some modifications, was adapted by Gottlieb et al. (1972). On the other hand Jarabak and Fizell (1963) minted the well-known phrase "*building treatment into the appliance*" which proposed to incorporate angles within the bracket, and these authors presented at the meeting of the American Association of Orthodontist in 1960 the first bracket model combining crown angulation and crown inclination (Wahl, 2008).

All together the work of all these authors consisted in eliminating bends in the wire to be incorporated into the bracket. All this led to the evolution of the bracket of edgewise to the bracket of straight wire incorporating the information in the slot of the bracket (Figure 1).

Fig. 1. Top line: Scanning electron microscopy of one bracket of standard edgewise appliance from a frontal (A), lateral (B), and oblique (C) view. Bottom line: Scanning electron microscopy of one straight wire bracket from a frontal (D), lateral (E), and oblique (F) view. The absence of information in the slot of the bracket of standard edgewise appliance in comparison with the bracket of the straight-wire appliance can be observed.

#### **2.1 The work of L.F. Andrews**

54 Orthodontics – Basic Aspects and Clinical Considerations

both the maxillary and mandible. Furthermore, according to Angle the alignment of the teeth, both crown and root, would result in the expansion of both the maxillary and mandible arches. This was also one of the main objectives to design the Angle's devices.

In 1887, Angle developed the "E" arch appliance formed by a thick gold wire placed for labial and some stainless steel tape on the first molar adjusted at pressure. This type of arch expanded both maxillary and mandible arches sagittally and transversely, and allowed a movement of simple inclination of the crown through a few ligatures that surrounded the

In the early 20th century with the development of metallurgy emerged the possibility of banding all the teeth and welding devices for the control of rotations. In 1910, Angle introduced the first appliance with individual tooth action and fullbanding, the so-called "pin and tube appliance", which welded small vertical tubes in the bands to introduce a stem attached to the wire. This device facilitated the labiolingual as mesiodistal expansion of the maxillary, and its drawback was the requirement for adjustment and accuracy in addition to the skill by the clinician (Bravo, 2007). Unfortunately one of the problems posed by this device was its inestability (Graber and Vanarsdall, 1994). Later, in 1916, Angle designed a bracket, called "ribbon arch appliance wire-band", containing a rectangular wire fixed by a few pins and placing the wider side on the tooth. This device properly controlled the labiolingual as well as vertical placement of teeth, by facilitating the correction of giroversions. However, it was difficult to place on the cusp and the looseness of the wire in the slot prevented mesiodistal control. Another substantial contribution of Angle was the frontal slot bracket, as opposed to the ribbon arch appliance of vertical opening, which featured great advantages, especially the ease to introduce the wire and the possibility to control the premolars and the adjustment of mesiodistal movement. In 1926 he presented the "bracket 447" with a horizontal slot .022 "x.028" which served to introduce a rectangular wire of the same thickness through the more narrow are, i.e. edgewise. It was made in gold and was called "soft bracket", as it opened easily and distorting (see for a review the Special

Over the basis of this model Steiner developed the "bracket 452" (hard bracket), more resistant to deformation which allowed to control teeth movement at the three levels through bends as tip, torque and in-out. This would become the prototype of the

Previously to the emergence of the straight wire, Angle already proposed to place the brackets to mesial or distal from the teeth to help to correct teeth rotations (Angle, 1929a), and a posterior angulation of the brackets to get proper root movements (see Meyer and Nelson, 1978). Later, Lewis (1950) joined segments ("arms") linked to the brackets, in contact with the wires for controlling rotations. Thereafter, Holdaway (1952) proposed that the buccal aspect of the brackets could be angulated depending on the degree of severity of the malocclusion. Twenty years later the original idea of Lewis, with some modifications, was adapted by Gottlieb et al. (1972). On the other hand Jarabak and Fizell (1963) minted the well-known phrase "*building treatment into the appliance*" which proposed to incorporate angles within the bracket, and these authors presented at the meeting of the American Association of Orthodontist in 1960 the first bracket model combining crown angulation and

Nevertheless, these postulates are still under discussion (Canut, 2000; Peck, 2008).

tooth and conformed to the arch.

Edition of Angle's work, 1981).

crown inclination (Wahl, 2008).

contemporary brackets.

From 1960 Andrews published a series of five studies, which resulted in the development of a new concept for the orthodontic treatment: the straight wire appliance.

The **First study** had as purpose the completion of a thesis for obtaining the certification of the American Board of Orthodontics. It consisted of the static analysis of the occlusion in post-orthodontic treatment casts. He found that there were features common to all them: absence of rotations in the incisors, no cross-bites, and Class I molar relationship of Angle, except in cases of extractions in a single maxillary. However, other parameters were not common at all. He deduced that the optimal positioning of the teeth should sustain in studies of optimal natural dentures (see Andrews, 1989).

In order to perform the **Second study**, Andrews selected 120 casts of non-orthodontic, untreated, patients with supposedly ideal occlusions, from which arose a few assumptions that should determine the occlusal objectives after orthodontic treatment. The compilation of the cases was carried out between 1960 and 1964 with the help of various Orthodontists, among them Brodie (Andrews, 1989). These casts have in common, in addition to lack of orthodontic treatment, a correct teeth alignment and positioning as well as a seemingly an "excellent" occlusion. The concept was, in essence, that if it is know what is right it can identify and quantify what's wrong in a direct and methodical manner. Over the casts Andrews conducted a series of marks: the facial axis (axial) of the clinical crowns, the most prominent portion of incisors, canines and pre-molars, as well as the projection of the medial groove in molars, and the midpoint of the height of each clinical crown.

In the **Third study** he described six characteristics that were always present in the 120 casts. These features would be referred to as "*The six keys to normal occlusion*" and were published in 1972 in the American Journal of Orthodontics (Andrews, 1972). The "Six Keys" would assess the occlusal situation without using measuring instruments, as in the keys II and III (referring to the crown angulation and crown inclination, respectively), Andrews do not use units but simply the positive or negative sign (he used terms such as lightly positive, generally negative, etc). According to Andrews the "Six Keys" are interdependent components of the structural system of optimal occlusion and serve as a basis to assess the occlusion.

They consisted of a series of significant characteristics shared by all of the non-orthodontic normal teeth, and were the following: specific molar relationship (key I), crown angulation (the angulation or mesiodistal "tip" of the long axis of the crown: Key II), crown inclination (the labiolingual or buccolingual inclination of the long axis of the crown: Key III), no rotations (key IV), absence of spaces (key V), and the occlusal plane (key VI). In the own Andrews words "*The six keys to normal occlusion contribute individually and collectively to the total scheme of occlusion and, therefore, are viewed as essential to successful orthodontic treatment*".

The 120 casts analyzed by Andrews showed similarities in values of crown angulation, crown inclination, shape, and size for the different types of teeth. But this was not enough for the design of the new device. Therefore, in a further study attempted to determine the shape, size and position of each tooth in the arch.

For the **Fourth study**, Andrews made new measurements over the 120 casts (see Andrews, 1989). The measurements made in this case were: the determination of the bracket area for each teeth, vertical crown contour, crown angulation, crown inclination, offset of maxillary molars, horizontal crown contour, crown facial prominence and depth of the curve of Spee. So, he doubled the 120 casts and removed the occlusal halves of the crown. On these surfaces he defined a line that joins the portion more vestibular of contact points and the most prominent portions of each clinical crown. He denominated this line as the embrasure line. The values obtained were incorporated into the design of the bracket to eliminate the first order bends. These measurements, except bracket size and curve of Spee, were averaged for each tooth type, and the results served as norms for the design of the new appliance: the straight-wire. After describing outcomes, Andrews concludes that the study reveals essential data on the position (with the exception of the inclination of the incisors), morphology and relative vestibular prominence of each tooth in the arch. The differences in the inclination of the incisors were attributed to disharmonies between the maxillary bones.

The **Fifth**, and final, **study** consisted of comparison of 1156 casts post-treatment in terms of occlusion, with the 120 casts from non-treated subjects with optimal occlusion. This study was focused to the design of a new device able to include the "six keys". The conclusion was that very few of the analyzed casts presented all the "six keys" (Andrews, 1976a). Therefore, he considered necessary the establishment of some premises of treatment, including common objectives, coupled with a new device. The straight wire appliance of Andrews was the first completely pre-adjusted orthodontic appliance. It was designed for the treatment of cases without extraction with one less than 5º ANB, avoiding the need for bends in the wire. As the closure of the spaces after premolar extractions produces undesirable side effects (rotation, inclination), Andrews subsequently introduced different brackets for cases with extractions. Moreover, when designing their brackets, Andrews differentiated between treatments in which the translation of teeth is necessary and that no, the so-called brackets

In the **Third study** he described six characteristics that were always present in the 120 casts. These features would be referred to as "*The six keys to normal occlusion*" and were published in 1972 in the American Journal of Orthodontics (Andrews, 1972). The "Six Keys" would assess the occlusal situation without using measuring instruments, as in the keys II and III (referring to the crown angulation and crown inclination, respectively), Andrews do not use units but simply the positive or negative sign (he used terms such as lightly positive, generally negative, etc). According to Andrews the "Six Keys" are interdependent components of the structural

They consisted of a series of significant characteristics shared by all of the non-orthodontic normal teeth, and were the following: specific molar relationship (key I), crown angulation (the angulation or mesiodistal "tip" of the long axis of the crown: Key II), crown inclination (the labiolingual or buccolingual inclination of the long axis of the crown: Key III), no rotations (key IV), absence of spaces (key V), and the occlusal plane (key VI). In the own Andrews words "*The six keys to normal occlusion contribute individually and collectively to the total scheme of occlusion and, therefore, are viewed as essential to successful orthodontic treatment*". The 120 casts analyzed by Andrews showed similarities in values of crown angulation, crown inclination, shape, and size for the different types of teeth. But this was not enough for the design of the new device. Therefore, in a further study attempted to determine the

For the **Fourth study**, Andrews made new measurements over the 120 casts (see Andrews, 1989). The measurements made in this case were: the determination of the bracket area for each teeth, vertical crown contour, crown angulation, crown inclination, offset of maxillary molars, horizontal crown contour, crown facial prominence and depth of the curve of Spee. So, he doubled the 120 casts and removed the occlusal halves of the crown. On these surfaces he defined a line that joins the portion more vestibular of contact points and the most prominent portions of each clinical crown. He denominated this line as the embrasure line. The values obtained were incorporated into the design of the bracket to eliminate the first order bends. These measurements, except bracket size and curve of Spee, were averaged for each tooth type, and the results served as norms for the design of the new appliance: the straight-wire. After describing outcomes, Andrews concludes that the study reveals essential data on the position (with the exception of the inclination of the incisors), morphology and relative vestibular prominence of each tooth in the arch. The differences in the inclination of the incisors were attributed to disharmonies between the maxillary bones. The **Fifth**, and final, **study** consisted of comparison of 1156 casts post-treatment in terms of occlusion, with the 120 casts from non-treated subjects with optimal occlusion. This study was focused to the design of a new device able to include the "six keys". The conclusion was that very few of the analyzed casts presented all the "six keys" (Andrews, 1976a). Therefore, he considered necessary the establishment of some premises of treatment, including common objectives, coupled with a new device. The straight wire appliance of Andrews was the first completely pre-adjusted orthodontic appliance. It was designed for the treatment of cases without extraction with one less than 5º ANB, avoiding the need for bends in the wire. As the closure of the spaces after premolar extractions produces undesirable side effects (rotation, inclination), Andrews subsequently introduced different brackets for cases with extractions. Moreover, when designing their brackets, Andrews differentiated between treatments in which the translation of teeth is necessary and that no, the so-called brackets

system of optimal occlusion and serve as a basis to assess the occlusion.

shape, size and position of each tooth in the arch.

of translation and standard brackets (Andrews, 1976c, 1989). In a short time the new straight-wire appliance was adopted by the American universities and most of the orthodontists (Andrews, 1976b, 1989). Some year later (Roth, 1976, 1987), designed brackets with information at the three levels, varying the characteristics described by Andrews. He developed the second generation of preprogrammed brackets, increasing the crown inclination in the canines up to 13º to achieve the "best functional occlusion".

The third generation of brackets was developed by McLaughlin, Bennett and Trevisi (MBTTM, McLaughlin et al., 1997; see also McLaughlin and Bennett, 1989). It is based on light forces and sliding mechanics maintaining the advantages of the prescriptions of Andrews and Roth, but eliminating certain limitations.

The introduction of straight-wire appliance in orthodontics led to a great controversy initially, but soon was accepted by all American orthodontic companies since it easily consent to control dental positions with the placement of brackets. Since then, others have developed new appliances, also fully programmed pre-adjusted (see for a review and references Proffit et al., 2008).

#### **3. The Andrew's series: The values for crown angulation and crown inclination revisited**

The first step of our work was to collect the individual values for crown angulation and crown inclination contained in the text and annex from Andrews' book "Straight-Wire, The Concept and Appliance" (Andrews, 1989), confirm that the descriptive statistical are exact, and apply to them a descriptive statistical analysis using the actual current methods.

When we try to validate the Andrews' statistical design the following questions and methodological troubles emerge when analyze the series of 120 casts that are the basis of the Andrews' work:


Therefore, our second step was the verification of the validity of the Andrew's design by contrast of hypothesis. It was carried out a Student t test of paired data to know whether or not there are significant differences in the crown angulation and crown inclination between the right and left hemi-arch with respect of their average values. The null hypothesis was that there are no significant differences in the crown angulation or crown inclination of teeth with respect to the side (p ≥ 0.05) and the study hypothesis was that there are significant differences in the crown angulation or crown inclination of teeth with respect to the side (p ≤ 0.05).

#### **Descriptive statistics in the Andrew's series**

Surprisingly, several errors in the basic descriptive statistics (count, average, standard deviation, minimum and maximum values) were detected for crown angulation but not for crown inclination (Tables 1 and 2). Thus, there is an error between the source (single) data and statistic results appearing in his publication. Moreover, in comparing these basic descriptive statistics with those obtained by us, applying the some probes on the Andrews data, it can be observed again that do not match for crown angulation (Table 1). Thus, there is an error between the source (single) data and statistic results appearing in his publication, and the statistics are no well calculated.


Table 1. **Crown angulation**. Basic descriptive statistics of Andrews' data after revisited by us (black), and after the descriptive statistical study we have carried out (red). Values are expressed in degrees, and the observed differences are highlighted in bold.


Table 2. **Crown inclination**. Basic descriptive statistics of Andrews' data after revisited by us (black), and after the descriptive statistical study we have carried out (red). Values are expressed in degrees, and the observed differences are highlighted in bold.

As Andrews considered the data together then we analyzed if there are differences between left and right teeth. For crown angulation, in comparing the average values of the right side and the left side differences were found to be significant (p<0.05) for all maxillary and mandibular teeth, except for the lower central incisor (Table 3). On the other hand, the comparison of mean averages for crown inclination of the right and left sides significant differences (p<0.05) were found for all upper teeth, except for the canines and first premolars, and for all lower teeth expect for both central and lateral incisors (Table 4).


df: degrees of freedom

58 Orthodontics – Basic Aspects and Clinical Considerations

crown inclination (Tables 1 and 2). Thus, there is an error between the source (single) data and statistic results appearing in his publication. Moreover, in comparing these basic descriptive statistics with those obtained by us, applying the some probes on the Andrews data, it can be observed again that do not match for crown angulation (Table 1). Thus, there is an error between the source (single) data and statistic results appearing in his publication,

**Maxillary Mandible**  Tooth n Range mean±SD n Range mean±SD

1L+1R 240 -3/9 3.59±1.65 240 -4/3 0.53±1.29 1L+1R 240 -3/9 3.59±**1.70** 240 -4/3 0.53±1.29 2L+2R 240 **-2**/15 **8.04**±2.80 240 -5/3 0.38±1.47 2L+2R 240 -26/15 **7.90±3.53** 240 -5/3 0.38±1.48 3L+3R 239 **1**/17 **8.40**±2.97 240 -11/12 2.48±3.28 3L+3R 240 0/17 **8.13±3.21** 240 -11/12 2.48±3.29 4L+4R 240 -2/**12 2.65**±1.69 240 -10/10 1.28±1.90 4L+4R 240 -2/14 **2.90±2.29** 240 -10/10 1.28±1.90 5L+5R 240 0/12 **2.82**±1.52 240 -5/7 1.54±1.35 5L+5R 240 0/12 **2.86±1.54** 240 -5/7 1.54±1.36 6L+6R 240 -7/16 **5.73**±1.90 240 -2/6 2.03±1.14 6L+6R 240 -7/16 **5.69±1.97** 240 -2/6 2.03±1.14 Table 1. **Crown angulation**. Basic descriptive statistics of Andrews' data after revisited by us (black), and after the descriptive statistical study we have carried out (red). Values are

expressed in degrees, and the observed differences are highlighted in bold.

min/max min/max

expressed in degrees, and the observed differences are highlighted in bold.

**Maxillary Mandible** 

Tooth n Range mean±SD n Range mean±SD

1L+1R 240 -7/15 6.11±3.97 240 -17/16 -1.71±5.79 1L+1R 240 -7/15 6.11±3.98 240 -17/16 -1.71±5.80 2L+2R 240 -6/17 4.42±4.38 239 -19/15 -3.24±5.37 2L+2R 240 -6/17 4,42±4.39 240 -19/15 -3.24±5.38 3L+3R 240 -17/10 -7.25±4.21 239 -26/2 -12.73±4.65 3L+3R 240 -17/10 -7.25±4.22 239 -26/2 -12.73±4.66 4L+4R 240 -20/5 -8.47±4.02 240 -35/-1 -18.95±4.96 4L+4R 240 -20/5 -8.47±4.03 239 -35/-1 -18.95±4.97 5L+5R 240 -20/3 -8.78±4.13 240 -45/-8 -23.63±5.58 5L+5R 240 -20/3 -8.78±4.14 240 -45/-8 -23.63±5.60 6L+6R 240 -25/2 -11.53±3.91 240 -55/-9 -30.67±5.90 6L+6R 240 -25/2 -11.53±3.92 240 -55/-9 -30.67±5.91 Table 2. **Crown inclination**. Basic descriptive statistics of Andrews' data after revisited by us (black), and after the descriptive statistical study we have carried out (red). Values are

min/max min/max

and the statistics are no well calculated.

**Andrews data/Our data**

**Andrews data/Our data**

Table 3. **Crown angulation**. Student t test for crown angulation of right vs left arch. Significant differences are highlighted in bold.


df: degrees of freedom

Table 4. **Crown inclination**. Student t test for crown inclination for right vs left arch. Significant differences are highlighted in bold.

These results consent to affirm that significant differences exists between the right and left sides of each arch, for the angulation of crown for all the teeth of the upper arch, and for the majority of the lower arch. Regarding the crown inclination significant differences do not occur in all the maxillary and mandibular teeth but all show any difference.

#### **3.1 Descriptive statistics of separate hemi-arch**

Since significant differences between the right and left hemi-arch were found in the Andrews' series we decided to perform and basic descriptive statistical analysis of both crown angulation and crown inclination in each hemi-arch separately. At a value of the confidence interval 95% the standard deviation shows very high values in some teeth, and the variable dispersion is therefore very broad.

In the upper maxillary the greater homogeneity in crown angulation was found for the central incisor, the second premolar and first molar (Table 5; Fig. 2A). The mandible crown angulation shows a more homogeneous behavior, except for the canine (Table 5; Fig. 2B). The presence of outlier values implies a high variability, and so at a confidence interval 95% wider than would be desirable (Figs. 3A and 3C, and Figs. 3B and 3D).

Fig. 2. Box-plot representation of the maxillary crown angulation (A) and mandibular crown angulation (B) of the data from the Andrews' series.

angulation shows a more homogeneous behavior, except for the canine (Table 5; Fig. 2B). The presence of outlier values implies a high variability, and so at a confidence interval 95%

Fig. 2. Box-plot representation of the maxillary crown angulation (A) and mandibular crown

angulation (B) of the data from the Andrews' series.

wider than would be desirable (Figs. 3A and 3C, and Figs. 3B and 3D).

Fig. 3. Mean values of confidence interval 95% and profiles of the maxillary crown angulation (A,C) and mandibular crown angulation (B,D) of the data from the Andrews' series.


Table 5. **Crown angulation**. Basic descriptive statistics of Andrews' data for hemi-arch after revisited by us. Values are expressed in degrees.

The results for crown inclination are reflected in table 6, and Figures 4A and 4B, which show that the variability of the data is very similar for all teeth. The mandible data presented a top-down performance in terms of average values of the central incisor to the first molar. The study of confidence intervals 95% shows differences between the teeth and the side. In general, the profiles of the subjects were similar for both the maxillary and mandibular teeth (Figs. 5A and 5C, and Figs. 5B and 5D).

confidence interval

Tooth n mean±SD range of

1R upper 120 3.42±1.56 3.06 – 3.62 lower 120 0.44±1.28 0.21 – 0.67 2R upper 120 6.79±2.85 6.04 – 7.54 lower 120 0.54±1.46 0.28 – 0.81 3R upper 119 7.61±2.95 7.07 – 8.16 lower 120 2.87±2.89 2.34 – 3.39 4R upper 120 2.57±2.13 2.19 – 2.96 lower 120 1.52±1.51 1.25 – 1.80 5R upper 120 2.69±1.55 2.40 – 2.98 lower 120 1.81±1.13 1.60 – 2.01 6R upper 120 5.42±2.12 5.01 – 5.82 lower 120 2.27±1.04 2.09 – 2.46

1R upper 120 3.84±1.70 3.53 – 4.15 lower 120 0.61±1.30 0.37 – 0.84 2R upper 120 9.00±2.33 8.58 – 9.42 lower 120 0.54±1.48 0.28 – 0.81 3R upper 120 8.58±3.37 7.97 – 9.20 lower 120 2.87±3.61 2.34 – 3.39 4R upper 120 3.23±2.43 2.80 – 3.67 lower 120 1.52±2.20 1.25 – 1.80 5R upper 120 3.03±1.47 2.77 – 3.30 lower 120 1.81±1.50 1.60 – 2.01 6R upper 120 5.96±1.62 5.66 – 6.25 lower 120 2.27±1.19 2.09 – 2.46

Table 5. **Crown angulation**. Basic descriptive statistics of Andrews' data for hemi-arch after

The results for crown inclination are reflected in table 6, and Figures 4A and 4B, which show that the variability of the data is very similar for all teeth. The mandible data presented a top-down performance in terms of average values of the central incisor to the first molar. The study of confidence intervals 95% shows differences between the teeth and the side. In general, the profiles of the subjects were similar for both the maxillary and mandibular teeth

**Right hemi-arch** 

**Left hemi-arch** 

revisited by us. Values are expressed in degrees.

(Figs. 5A and 5C, and Figs. 5B and 5D).


Table 6. **Crown inclination.** Basic descriptive statistics of Andrews' data for hemi-arch after revisited by us. Values are expressed in degrees.

Fig. 4. Box-plot representation of the maxillary crown inclination (A) and mandibular crown inclination (B) of the data from the Andrews' series.

Fig. 4. Box-plot representation of the maxillary crown inclination (A) and mandibular crown

inclination (B) of the data from the Andrews' series.

Fig. 5. Mean values of confidence interval 95% and profiles of the maxillary crown inclination (A,C) and mandibular crown inclination (B,D) of the data from the Andrews' series.

#### **3.2 Critical comments to the Andrews' work**

After the analysis of the data published by Andrews (1989) in his book *Straight-Wire, The Concept and Appliance* the first thing that draws attention is that the author annex provide data relating to 240 casts instead of 120, which are those said to have studied. This may be due to the fact that the author carried out two measurements by subject (left and right) in each arch, and then globalize the data into a single; but Andrews does not clarify this fact. Is this right? The statistical study we have performed on the Andrews' data shows that there are significant differences between left and right for crown angulation and crown inclination for most of the upper teeth, and form the lower teeth for crown angulation of the lateral incisor to the first molar, and for crown inclination in the canine, premolars and first molar. Therefore, it seems evident that the data from the Andrews study cannot be grouped, and it is necessary to work with each hemi-arch separately and perform the descriptive and comparative analysis for each one of them. From these results the following question arises: it should be necessary use different brackets on left and right side of each patient?

Another surprising finding of our review of the Andrews' data was that the results presented in terms of basic descriptive statistic not always coincide with those from the sources. These errors can be due to erroneous data sheets records or that have been made evil the descriptive analysis.

The Andrews' results are expressed as average values, and the standard deviation was occasionally elevated, thus reflecting a significant dispersion of the sample values. For example, the following measurements for crown angulation (mean±standard deviation, range: minimal-maximal) in the first premolar realize this: upper 2.65°+1.69°, -2.0° to +12°; lower: 2.90°+2.29°, -2º to +14º. The ranges show the enormous variation of values. If in cases of optimal occlusions the crown angulation of this tooth vary between -2° and 12°, take as reference a value of 2.65° in orthodontic appliances does not seems logical.

It would also be desirable that Andrews had studied the type of the data distribution in the sample, and the author seems to assume that the distribution is symmetric, but in the light of the results presented here, it is unlikely to be so. In fact, the normality test indicates that the distribution is not normal in all cases.

The listing of all the individual data of the sample is a sign of honesty by the author, and reflects the statistical methodology of the 1970s. But at the same time it allows us to appreciate their low methodological rigor, in the light of current knowledge when presenting the conclusions as a definitive response to a widely discussed problem. Thus, it is difficult to understand why the orthodontists from around the world have continued to put the brackets using as a reference the average values of the measurements made on 120 casts without rigorous selection criteria. In our casts, as well as in those from other groups (Roth, 1987; Martínez-Asúnsolo and Plasencia, 2004; Zanelato et al., 2004), the findings of Andrews for the crown angulation and inclinations were not confirmed.

Therefore, the Andrews study in terms of design, include the following shortcomings: definition of the characteristics of the sample, the exact criteria of selection of the subjects included in the sample, the absence of a descriptive statistic that analyze the way of the distribution of the data (if distribution is markedly asymmetrical, would be preferable to choose the mean than the average as a measure of central tendency), the type of sampling, and sample size calculation. In the Andrews study the sample size is adequate (240 measurements from 120 casts). Nevertheless, to work with greater precision, for example 0.5 mm, the sample should be higher.

On the other hand, the development of the work of Andrews also suffers from some defects. In this kind of studies it is necessary to assess their reproducibility or reliability, both intraobserver and inter-observed. It is not aware that the Andrews work has been performed by several observers, and therefore it must be we assumed that the measurements were carried out by Andrews himself or by another individual. Still, in any case Andrews should be repeated, at least once more, all measures in the same models and to analyze the reliability between measurements. Also, as quantitative variables, the degree of reliability should have been studied through the appropriate statistical tests: Bradley-Blackwood, correlation coefficient, tor the Student t test for paired samples. The errors we have detected in the Andrews work are surely sufficient to raise necessary a reassessment of the theories of the straight wire. The real debate must be focused on whether the recommendations of Andrews for the crown angulation an inclination may continue to be used for the creation, development and industrialization of orthodontic appliances to serve for the entire population. The tooth size (Agenter et al., 2009; Lee et al., 2011), the place of each teeth in each side hemi-arch, the gender, and the ethnic group (Naranjilla and Rudzki-Janson, 2005) should be considered in the development of future orthodontic appliances.

### **4. Concluding remarks**

66 Orthodontics – Basic Aspects and Clinical Considerations

comparative analysis for each one of them. From these results the following question arises:

Another surprising finding of our review of the Andrews' data was that the results presented in terms of basic descriptive statistic not always coincide with those from the sources. These errors can be due to erroneous data sheets records or that have been made

The Andrews' results are expressed as average values, and the standard deviation was occasionally elevated, thus reflecting a significant dispersion of the sample values. For example, the following measurements for crown angulation (mean±standard deviation, range: minimal-maximal) in the first premolar realize this: upper 2.65°+1.69°, -2.0° to +12°; lower: 2.90°+2.29°, -2º to +14º. The ranges show the enormous variation of values. If in cases of optimal occlusions the crown angulation of this tooth vary between -2° and 12°, take as

It would also be desirable that Andrews had studied the type of the data distribution in the sample, and the author seems to assume that the distribution is symmetric, but in the light of the results presented here, it is unlikely to be so. In fact, the normality test indicates that

The listing of all the individual data of the sample is a sign of honesty by the author, and reflects the statistical methodology of the 1970s. But at the same time it allows us to appreciate their low methodological rigor, in the light of current knowledge when presenting the conclusions as a definitive response to a widely discussed problem. Thus, it is difficult to understand why the orthodontists from around the world have continued to put the brackets using as a reference the average values of the measurements made on 120 casts without rigorous selection criteria. In our casts, as well as in those from other groups (Roth, 1987; Martínez-Asúnsolo and Plasencia, 2004; Zanelato et al., 2004), the findings of Andrews

Therefore, the Andrews study in terms of design, include the following shortcomings: definition of the characteristics of the sample, the exact criteria of selection of the subjects included in the sample, the absence of a descriptive statistic that analyze the way of the distribution of the data (if distribution is markedly asymmetrical, would be preferable to choose the mean than the average as a measure of central tendency), the type of sampling, and sample size calculation. In the Andrews study the sample size is adequate (240 measurements from 120 casts). Nevertheless, to work with greater precision, for example 0.5

On the other hand, the development of the work of Andrews also suffers from some defects. In this kind of studies it is necessary to assess their reproducibility or reliability, both intraobserver and inter-observed. It is not aware that the Andrews work has been performed by several observers, and therefore it must be we assumed that the measurements were carried out by Andrews himself or by another individual. Still, in any case Andrews should be repeated, at least once more, all measures in the same models and to analyze the reliability between measurements. Also, as quantitative variables, the degree of reliability should have been studied through the appropriate statistical tests: Bradley-Blackwood, correlation coefficient, tor the Student t test for paired samples. The errors we have detected in the

it should be necessary use different brackets on left and right side of each patient?

reference a value of 2.65° in orthodontic appliances does not seems logical.

for the crown angulation and inclinations were not confirmed.

evil the descriptive analysis.

the distribution is not normal in all cases.

mm, the sample should be higher.

While Andrews work is thorough and interesting for its time, it has enough limitations of design or execution to be considered actually as the foundations for the use of an appliance with universal angulation and inclination. Furthermore, we have not found one sufficient material and methodology description in the of Andrews' work to reproduce it accurately. In fact a number of errors in the results of basic descriptive statistics were detected in the Andrews' series. This could be due to errors is the data sheet, or to errors in calculating descriptive statistics.

On the other hand, it cannot be included in a common sample data from measurements obtained from the right and left sides of the maxillary and the mandible as Andrews, given that there are significant differences between the average values of both sides. Therefore it does not seem appropriate to use average angle and tilt values without specifying the side of the arch which belongs to the tooth. Considering the large standard deviations observed in values from the Andrews' series the values of both inclination and angulation cannot be standardized. The variations in the values of angulation and inclination reported by different authors would be sufficient to raise the need for a re-evaluation of the theories of the straight-wire appliance in orthodontics.

#### **5. References**


## **The Importance and Possibilities of Proper Oral Hygiene in Orthodontic Patients**

Melinda Madléna

*Semmelweis University Hungary* 

#### **1. Introduction**

68 Orthodontics – Basic Aspects and Clinical Considerations

Canut JA. 2000. Ortodoncia clínica y terapéutica. 2ª edición. 2000. Barcelona Ed. Masson

Gottlieb EL, Wildman AJ, Lang HM, Lee IF, Struch EC Jr. 1972. The Edgelok bracket. J Clin

Graber TM, Vanarsdall RL Jr. 1994. Orthodontics Currents Principles and Techniques. 2ª

Holdaway RA. 1952. Bracket angulation as applied to the edgewise appliance. Angle Orthod

Jarabak JR, Fizell JA. 1963. Technique and treatment with the light-wire appliance. Sant

Lee SJ, Ahn SJ, Lim WH, Lee S, Lim J, Park HJ. 2011. Variation of the intermaxillary tooth-

McLaughlin RP, Bennett JC. 1989. The transition from standard edgewise to preadjusted

McLaughlin R, Bennett J, Trevisi H. 1997. A clinical review of the MBT orthodontic

Martinez-Asúnsolo P, Plasencia E. 2004. Las 6 llaves de la oclusión de Andrews en 32

Meyer M, Nelson G. 1978. Preajusted edgewise appliances: Theory and practice. Am J

Naranjilla MA, Rudzki-Janson I. 2005. Cephalometric features of lipinos with class I occlusion according to the Munich analysis. Angle Orthod 75:63-68. Peck S. 2008. So what's new? Arch expansion again. Angle Orthod 78:574-575.

Proffitt WR, Fields HW, Sarver DM. 2008. Ortodoncia Contemporánea. 4ª edición. Elsevier

Roth RH. 1976. Five year clinical evaluation of the Andrews straight-wire appliance. J Clin

Wahl N. 2008. Orthodontics in 3 millenia. Chapter 16: Late 20th-century fixed appliances.

Zanelato RC, Grossi AT, Mandetta S. 2004. Individualización de torque para los caninos en

Roth RH. 1987. The straight-wire appliance 17 years later. J Clin Orthod 21:632-642.

aparatos preajustados. Rev Ortodon Dental Press 3:39-55.

modelos con oclusiones ideales no tratadas. Rev Esp Ortod 34:235-244 (Spanish

edición. St. Louis, Missouri. Ed Mosby-YearBook Inc., pp. 627-635.

size relationship in normal occlusion. Eur J Orthod 33:9-14. Lewis PD. 1950. Space closure in extraction cases. Am J Orthod 36: 172-191.

appliance systems. J Clin Orthod 23:142-153.

treatment program. Orthod Perspec 4:3-15.

España 2008 Barcelona (Spanish Edition)

Am J Orthod Dentofacial Orthop 134: 827-830.

S.A., pp. 18-21. (Spanish text)

Orthod 6:613-623.

Louis, Missouri. Mosby.

22:227-236.

text)

Orthod 73:485-498.

Orthod 10:836-850.

The number of orthodontic treatments has been increased nowdays (Silva & Kang, 2001; Thilander et al., 2001; Ciuffolo et al., 2005; Mtaya et al, 2009; Bittencourt & Machado, 2010). The most important motivation for orthodontic treatment is to achieve an improvement in appearance and the fact that in connection with this change some psychological problems could be decreased. These factors are contributed not only to the position but the esthetic appearance of the tooth itself. In some cases orthodontic treatments can attribute to caries preventive intervention, when tooth movements may reduce crowding or other anomalies, thus can contribute to the effectiveness of proper oral hygiene. On the other hand, orthodontic treatments may cause or aggravate plaque accumulation and in this way the development of caries and periodontal diseases which are basically caused by dental plaque. It is suggested that the information about both benefits and risks of orthodontic treatment should be sheared with potential patients.

This chapter explaines the relationships between orthodontic anomalies and orthodontic treatments and dental plaque induced diseases, delineates how to determinate the risk of the orthodontic treatment causing dental caries and periodontal diseases. The third part of this chapter summarizes the possibilities to avoid and reduce these effects using different modern equipments, techniques and adjuvants.

#### **2. Relations between orthodontic anomalies / orthodontic treatment and dental plaque induced diseases**

#### **2.1 Associations of the orthodontic anomalies with dental caries**

It is wellknown for a long time that in some orthodontic cases patients have greater difficulties in maintaining proper oral hygiene (Katz, 1978; Miller & Hobson, 1961). In spite of this, some authors published no correlation between positional anomalies and the caries prevalence. Helm and Petersen (1989a) examined 176 adolescents aged 13-19 years and reexamined them after 20 years in order to detect any relationship between malocclusion and caries, found no association between malocclusion traits and caries prevalence. Other authors published the relationship between the dental caries and the presence of certain malocclusions concerning oral hygiene (e.g. crowding) (Gábris et al., 2006; Nobile et al., 2007; Mtaya et al, 2009). Stahl & Grabowski (2004) reported no positive correlation between prevalence of caries and any malocclusion in primary teeth but in their study significant parallelism in prevalence of malocclusion and caries was found for posterior cross-bite and mandibular overjet in children with mixed dentition.

#### **2.2 Associations of the orthodontic anomalies with periodontal parameters concerning oral hygiene**

The accumulation of plaque can cause gingival redness, bleeding, edema, changes in gingival morphology, reduced tissue adaptation to the teeth, an increase in the flow of gingival crevicular fluid and other clinical signs of inflammation (Figure 1). Maloccluded teeth can be associated with periodontal diseases because of the physically hampered proper oral hygiene.

Fig. 1. Crowded frontal teeth with large amount of plaque.

In case of this anomaly the oral hygiene is harmful, the plaque elimination needs more time and special method. The picture shows a gingivitis as a consequence of the lack of proper oral hygiene.

According to the oral hygiene the most important basic symptom which can show more serious periodontal problems is gingival bleeding on probing (Geiger, 2001). The presence of a positive correlation between malocclusion (e.g. crowding, when the removal of plaque is difficult) and periodontal health has been described by Helm and Petersen (1989b) and Gábris et al. (2006), but on the contrary other studies found no association between amount of plaque or periodontal parameters and malocclusion (including crowding and spacing) (Geiger et al., 1974; Katz, 1978; Buckley, 1980). Other results had been published by Geiger (2001) found the possible associations between certain malocclusions (eg. anterior overjet and overbite, crossbite etc.) and periodontal problems, but these cases probably are not really in connection with oral hygiene.

#### **2.3 Plaque accumulation concerning removable and fixed orthodontic appliances**

The great plaque accumulation on different dental materials has been wellknown for a long time. From these points of view, we also consider removable appliances. In case of removable appliances, the resin base has microporosity. The greater accumulation of plaque

prevalence of caries and any malocclusion in primary teeth but in their study significant parallelism in prevalence of malocclusion and caries was found for posterior cross-bite and

The accumulation of plaque can cause gingival redness, bleeding, edema, changes in gingival morphology, reduced tissue adaptation to the teeth, an increase in the flow of gingival crevicular fluid and other clinical signs of inflammation (Figure 1). Maloccluded teeth can be associated with periodontal diseases because of the physically hampered proper oral hygiene.

In case of this anomaly the oral hygiene is harmful, the plaque elimination needs more time and special method. The picture shows a gingivitis as a consequence of the lack of proper

According to the oral hygiene the most important basic symptom which can show more serious periodontal problems is gingival bleeding on probing (Geiger, 2001). The presence of a positive correlation between malocclusion (e.g. crowding, when the removal of plaque is difficult) and periodontal health has been described by Helm and Petersen (1989b) and Gábris et al. (2006), but on the contrary other studies found no association between amount of plaque or periodontal parameters and malocclusion (including crowding and spacing) (Geiger et al., 1974; Katz, 1978; Buckley, 1980). Other results had been published by Geiger (2001) found the possible associations between certain malocclusions (eg. anterior overjet and overbite, crossbite etc.) and periodontal problems, but these cases probably are not

**2.3 Plaque accumulation concerning removable and fixed orthodontic appliances** 

The great plaque accumulation on different dental materials has been wellknown for a long time. From these points of view, we also consider removable appliances. In case of removable appliances, the resin base has microporosity. The greater accumulation of plaque

**2.2 Associations of the orthodontic anomalies with periodontal parameters** 

mandibular overjet in children with mixed dentition.

Fig. 1. Crowded frontal teeth with large amount of plaque.

really in connection with oral hygiene.

**concerning oral hygiene** 

oral hygiene.

on dental materials than on natural enamel is also wellknown (Skjörland, 1973). This is an increase in microorganisms which can provide an increased risk of carious lesions theoretically. Thus basically the orthodontic treatment with removable appliance causes an additional problem for the oral environment. The surface of the removable appliance will be coated within a short time mainly with streptococci and gram negative and positive rods (Bickel & Geering, 1982). According to the results of Batoni et al. (2001) the use of removable appliances may lead to the creation of new retentive areas and surfaces, which favour the local adherence and growths of streptococcus mutans. However, Schlagenhauf et al. (1989) found that the increase in number of streptococcus mutans was not significant in patients having removable orthodontic appliance comparing to those who weared fixed appliance.

The plaque accumulation is promoted by the physical constituton of different parts of fixed appliance, but there are some other factors having a great importance on plaque accumulation. In the oral cavity all of the tooth surfaces are exposed and rapidly covered by salivary proteins causing different effects (interactions between material, pellicle and bacteria). As a part of fixed appliances, orthodontic bands can cause a gingiva inflammation (Huser et al., 1990). Plaque accumulates particularly beneath bands from which some cement has been washed out adjacent to adhesive retention elements (Gwinnett & Cheen, 1979; Mizrahi, 1982). Plaque is found predominantly cervically to brackets under the arch wires. The scores of different periodontal parameters (Plaque Index, Gingival Bleeding Index) and proportion of spirochetes were found higher for banded molars than for molars with brackets (Boyd & Baumrind, 1992; Freundorfer et al. 1993). The loss of attachment is the highest approximally, particularly in adults, because the margins of band are frequently located subgingivally at approximal sites. In this way band with subgingival margins can promote the higher accumulation of the amount of plaque and contribute to development of gingivitis or periodontitis. In case of periodontitis besides the inflammation of gingiva the loss of connective tissue attachment (wich is irreversible change) also can be seen in the periodontium. In these situations gram negative and anaerobic microrganisms (Porphyromonas gingivalis, Prevotella intermedia, Actinomyces) are disproportionally present along the subgingival band margins (Diamanti-Kpioti et al., 1987) which are frequently associated with further periodontal problems. Beside of this, there is an increased number of spirochetes, mobile rods and fusiform organisms. Gingival hyperplasia may also occure and this complicates the oral hygiene and the dental treatment procedures (Figure 2.)

Fig. 2. Gingival hyperplasia in patient undergoing orthodontic treatment with fixed appliance.

The situation is caused by neglected oral hygiene, which complicate the treatment and oral hygienic procedures.

It has ben published that the elements of fixed orthodontic appliance can change the biologic balance in the oral cavity (Figure 3.).

Fig. 3. Risk of treatment with fixed orthodontic appliances.

Plaque in patients with fixed orthodontic appliance has a lower pH than in non-orthodontic patients (Gwinnett & Cheen, 1979). There is a rapid shift in the composition of the bacterial flora, especially there is an increase in the levels of acidogenic bacteria (streptococcus mutans, lactobacilli), which leads to a decrease in pH. As the pH drop reaches the level of critical value (pH 5.5), the demineralization-remineralization balance is pushed toward mineral loss and demineralization/decalcification.

#### **2.3.1 Decalcification of enamel caused by dental plaque accumulation (white spot lesions) during orthodontic treatment with fixed appliances**

The first clinical evidence of the demineralization is the white spot lesion (WSL), which potentially can become a cavitated carious lesion extending even into the dentin (Featherstone, 2003; Featherstone et al, 2007). White spot lesions are nonfluoridated opacities having a more defined shape and are well differentiated from sorrounding enamel which are often located in the middle of the tooth (Sangamesh & Amitabh, 2011). The WSL has been defined as "subsurface enamel porosity from carious demineralization" presenting itself as a "milky white opacity" when located on smooth surfaces (Nicholson, 2006). Beside of that fact that WSL is a first step to destruction of the teeth, this enamel demineralization associated with fixed orthodontic appliances means an other significant clinical problem for the orthodontists (Ogaard, 1989; Bishara & Ostby, 20008). Because of the plaque

The situation is caused by neglected oral hygiene, which complicate the treatment and oral

It has ben published that the elements of fixed orthodontic appliance can change the biologic

Fixed orthodontic appliances

Plaque accumulation

Plaque in patients with fixed orthodontic appliance has a lower pH than in non-orthodontic patients (Gwinnett & Cheen, 1979). There is a rapid shift in the composition of the bacterial flora, especially there is an increase in the levels of acidogenic bacteria (streptococcus mutans, lactobacilli), which leads to a decrease in pH. As the pH drop reaches the level of critical value (pH 5.5), the demineralization-remineralization balance is pushed toward

**2.3.1 Decalcification of enamel caused by dental plaque accumulation (white spot** 

The first clinical evidence of the demineralization is the white spot lesion (WSL), which potentially can become a cavitated carious lesion extending even into the dentin (Featherstone, 2003; Featherstone et al, 2007). White spot lesions are nonfluoridated opacities having a more defined shape and are well differentiated from sorrounding enamel which are often located in the middle of the tooth (Sangamesh & Amitabh, 2011). The WSL has been defined as "subsurface enamel porosity from carious demineralization" presenting itself as a "milky white opacity" when located on smooth surfaces (Nicholson, 2006). Beside of that fact that WSL is a first step to destruction of the teeth, this enamel demineralization associated with fixed orthodontic appliances means an other significant clinical problem for the orthodontists (Ogaard, 1989; Bishara & Ostby, 20008). Because of the plaque

**Anaerob bacteria**

(Gram negative bacteria Porphyromonas gingivalis Prevotella intermedia Actinomyces species etc.)

**GINGIVITIS, PERODONTITIS**

hygienic procedures.

balance in the oral cavity (Figure 3.).

**Cariogen bacteria** (Streptococcus mutans,

> pH Calcium Phosphate

**DEMINERALIZATION OF THE TOOTH SURFACE**

Fig. 3. Risk of treatment with fixed orthodontic appliances.

**lesions) during orthodontic treatment with fixed appliances** 

mineral loss and demineralization/decalcification.

Lactobacilli)

accumulation on typical places, without proper oral hygiene, during or after the orthodontic treatment demineralization (white spot lesions) can be observed at these above mentioned plaque retention sites and the location of possible carious lesions are changed compared to the situation without orthodontic appliances (Muhler, 1970). The white spot lesions are predominantly appeare on the lower and upper premolars, first molars, maxillary and mandibular lateral inciors and lower canines as a change of tooth structure around the brackets basis or between the brackets/bands and gingival margin in the cervical region and middle third of the teeth, under the orthodontic wires (Ogaard, 2008). The frequency of WSL in orthodontically treated patients were in order lateral incisors, canines, first premolars, 2nd premolars, central incisors (Ogaard, 1989; Chapman et al., 2010). An other previous study showed similar results except those finding that the maxillary central incisors had a greater frequency of WSLs than did the maxillary second premolars (Gorelick et al., 1982). No significant differences were found in WSL incidence and prevalence between the right and left sides of the maxilla and mandible (Gorelick et al., 1982; Ogaard, 1989).

Evaluation of white spot lesions can be performed by macroscopic methods (clinical examination, photographic examination, optical nonfluorescent and fluorescent methods), microscopic methods (orthodontic caries models) and research methods (assessing different preventive agents) (Benson, 2008). The detected prevalence depends on the analytic methods. The highest prevalence of demineralization was detected by quantitative light induced fluorescence method which is much more sensitive than the simple direct visualization (Boersma, 2005). Inspector's unique analysis software is available to determinate the demineralization (Amaechi, 2009). Sound tooth tissue will show up glowing brightly without reflections, demineralised areas generally have a diffuse outline and are darker at the center which distinguishes them from stains and discoloration.

According to the study of Gorelick et al. (1982) the incidence of white spot formation in patients treated with fixed orthodontic appliances was nearly 50% compared to 24% in an untreated control group. In the literature great variations have been published (from 2 - to 97% of the patients) for WSL prevalence associated with orthodontic treatment (Zachrisson and Zachrisson, 1971; Gorelick et al., 1982; Mizrahi, 1982; Artun & Brobakken, 1986; Geiger et al., 1988; Ogaard, 1989; Mitchell, 1992). Although orthodontic patients had significantly more WSLs than non-orthodontic patients but in this stage generally were not registered as caries, requiring restorative treatment (Ogaard et al., 2004). However in some cases, the development of these lesions could be such rapid that it requiers rapid debonding and treatment procedures. It can be occured already within 4 weeks (Ogaard et al., 1988). Carious lesions may appear after debonding in association with bonded retainer also. Earlier studies showed increased caries frequency and higher prevalence of caries and also fillings in persons treated with fixed orthodontic appliances, but most of the further investigations did not confirm this statement which could be in connection with the higher motivation of the patients and the widespread possibility of oral hygiene regimens (Ingerwall, 1962; Zachrisson & Zachrisson, 1971; Hollender & Ronnerman, 1978; Southard et al., 1986; Ogaard, 1989). Muhler (1970) published that the orthodontic treatment without proper oral prophylaxis resulted in an increased incidence of caries which was significantly reduced after an appropriate prophylaxis. According to the study of Zachrisson & Zachrisson (1971) in case of cooperative patients with proper oral hygiene dental caries is a relatively minor problem and the number of new cavities is relatively low but it is contributed by different factors. For example, beside of the individual susceptibility, it has to be considered that generally the patients aged 6-10 years and during an early period of adolescents are in active caries phase, the number of new cavities may increase rapidly during fixed orthodontic treatment in these cases. The publicated incidence and prevalence of WSL can vary by sex. Although Ogaard (1989) found no significant difference between genders, most of the studies published it. According to the study of Zachrisson & Zachrisson (1971), girls had better caries index scores, (and also better periodontal indices) than boys during orthodontic treatment. In spite of these findings, Gorelick et al. (1982) found that females have higher incidence in WSL prevalence, while Boersma (2005) and Al Maaltah et al. (2011) published higher incidence of WSL in male. Chapmen et al. (2010) published a higher incidence of WSLs and also the more severe demineralization in males compared with female patients. It can be in connection with those results of some authors that female patients have been shown to have a greater interest in oral health, they had better oral health and tend to brush and floss their teeth more frequently (Kuusela et al., 1996; Sakki et al., 1998; Ostberg et al., 1999). Chapmen et al. (2010) published that early age at start of fixed appliance treatment, inadequate oral hygiene before the treatment, many treatment appointments with poor oral hygiene were associated with greater incidence and severity of WSLs. Al Maaltah et al. (2011) published that patients with WSLs were significantly younger and more likely to have diseased first molars.

Classification of white spot lesions can be found in a modification of material in publication of Nyvad et al. (1999):

White spot stage 1. Inactive caries (intact surface):

Surface of enamel is white, brown or black. It is glossy with no loss of luster; feels smooth and hard when the tip of the probe is gently moved across the surface. No clinically detectable loss of enamel. Smooth surface lesion typically located away from the gingival margin.

White spot stage 2. Inactive caries (surface discontinuity):

Surface enamel is white, brown or black. It is glossy with no loss of luster; feels smooth and hard when the tip of the probe is gently moved across the surface. Localized surface defects (microcavity) could be found in enamel only. No undermined enamel or softened floor detectable with the explorer.

When on the surface there are cavitated lesion, enamel/dentin cavity easily visible with naked eye, surface cavity feels hard on gentle probing and appears shiney. There is no pulpal involvement.

#### **3. Determination of the risk causing dental caries and periodontal diseases during orthodontic treatment**

It is wellknown that because of the great possibility for the increased plaque accumulation orthodontic patients who are treated with fixed appliance, mainly generally belong to a potentially higher risk group. So a list of risk factors should be recorded for orthodontic patients to identify those persons who need special preventive interventions. Orthodontic treatment may be hazardous for those patients who have no motivaton, no proper supervision or preventive programme. To notice the increased plaque accumulation, it is important for both patients and clinicians to prevent tooth decay, gingival or periodontal problems and tooth discoloration that could compromise the esthetic of smile and well being of the patients. The key for this is represented by dental plaque.

#### **3.1 Identification of dental plaque**

74 Orthodontics – Basic Aspects and Clinical Considerations

and during an early period of adolescents are in active caries phase, the number of new cavities may increase rapidly during fixed orthodontic treatment in these cases. The publicated incidence and prevalence of WSL can vary by sex. Although Ogaard (1989) found no significant difference between genders, most of the studies published it. According to the study of Zachrisson & Zachrisson (1971), girls had better caries index scores, (and also better periodontal indices) than boys during orthodontic treatment. In spite of these findings, Gorelick et al. (1982) found that females have higher incidence in WSL prevalence, while Boersma (2005) and Al Maaltah et al. (2011) published higher incidence of WSL in male. Chapmen et al. (2010) published a higher incidence of WSLs and also the more severe demineralization in males compared with female patients. It can be in connection with those results of some authors that female patients have been shown to have a greater interest in oral health, they had better oral health and tend to brush and floss their teeth more frequently (Kuusela et al., 1996; Sakki et al., 1998; Ostberg et al., 1999). Chapmen et al. (2010) published that early age at start of fixed appliance treatment, inadequate oral hygiene before the treatment, many treatment appointments with poor oral hygiene were associated with greater incidence and severity of WSLs. Al Maaltah et al. (2011) published that patients with WSLs

Classification of white spot lesions can be found in a modification of material in publication

Surface of enamel is white, brown or black. It is glossy with no loss of luster; feels smooth and hard when the tip of the probe is gently moved across the surface. No clinically detectable loss

Surface enamel is white, brown or black. It is glossy with no loss of luster; feels smooth and hard when the tip of the probe is gently moved across the surface. Localized surface defects (microcavity) could be found in enamel only. No undermined enamel or softened floor

When on the surface there are cavitated lesion, enamel/dentin cavity easily visible with naked eye, surface cavity feels hard on gentle probing and appears shiney. There is no

**3. Determination of the risk causing dental caries and periodontal diseases** 

being of the patients. The key for this is represented by dental plaque.

It is wellknown that because of the great possibility for the increased plaque accumulation orthodontic patients who are treated with fixed appliance, mainly generally belong to a potentially higher risk group. So a list of risk factors should be recorded for orthodontic patients to identify those persons who need special preventive interventions. Orthodontic treatment may be hazardous for those patients who have no motivaton, no proper supervision or preventive programme. To notice the increased plaque accumulation, it is important for both patients and clinicians to prevent tooth decay, gingival or periodontal problems and tooth discoloration that could compromise the esthetic of smile and well

of enamel. Smooth surface lesion typically located away from the gingival margin.

were significantly younger and more likely to have diseased first molars.

White spot stage 1. Inactive caries (intact surface):

White spot stage 2. Inactive caries (surface discontinuity):

of Nyvad et al. (1999):

detectable with the explorer.

**during orthodontic treatment** 

pulpal involvement.

Dental plaque is "the soft tenaciosus material found on tooth surfaces which is not readily removed by rinsing with water" (Axelsson, 2000) (Figure 4.).

Fig. 4. Unstained dental plaque on the labial dental surfaces, on the cervical regions of the frontal teeth.

In this patient the consequences of the large amount of plaque (decalcification, gingivitis) are also seen.

In some cases the identification of plaque can be hard with the naked eye because it could have a whitish colour, similarly to the teeth. The plaque amount and localization can be determined by different methods. The simpliest way to scrape the tooth surface with a periodontal probe. Special test tablets containing red or blue dye can be used to stain the plaque. One tablet is chewed thoroughly, moving the mixture of saliva and dye over the teeth and gums for approximately 30 seconds. Then the mouth is rinsed with water and teeth are checked to identify the stained unremoved plaque. The disadvantage of these tablets that may cause a temporary pink or blue color of lips, cheeks, mouth or tongue. (Figure 5.). An other method is using plaque fluorescence. A special fluorescent solution is swirled around the mouth. After that the mouth is rinsed gently with water and the teeth and gums can be checked with an ultraviolet light. The plaque will be coloured in a brillant orange-yellow. This method does not leave stains on other tissues in the mouth.

Fig. 5. The situation after plaque staining with tablets.

The method cause a temporary discoloration on the bucca or the tongue. Matured and fresh plaque can be seen in different colors. More blue plaque coloration means inproper oral hygiene

Some types of plaque staining products can differentiate between the cariogenic and noncariogenic plaque with different colors (Figure 5.). Acid producing ability of a plaque sample and its cariogenic potential can be determined. Non-cariogenic samples turn green or yellow, while cariogenic plaque samples turn red or orange after sucrose challenge from the solution. Some products contain a neutralising solution (e.g. Plaque Indicator Kit from the GC) which can be used for education of the patients, eg. regarding the protective actions of the saliva and a disclosing gel for the demonstration of plaque. The composition of plaque changes in time, which allows pathogenic bacteria to be active on the tooth surface. Using a special disclosing gel, a more than 48 hours old (matured) plaque and a fresh plaque can be seen in two different colours (blue, redish-pink).

The Inspektor QLF-D BiLuminatorTM is a sophisticated device for assessment and monitoring of oral hygiene in the dental surgery. The QLF-D BiLuminator software supports easy acquisition of image pairs and orders them automatically on a visit-patient basis. Plaque and calculus show up brightly red in the QLF –image made by this equipment (Figure 6.). Only those plaque will be seen that has been present for some time (> 1 day).

Fig. 6. White light and QLF image of teeth with orthodontic brackets (publication of the pictures with permission of Inspektor Research System BV, Netherlands).

The BiLuminatorTM can be tremendous help to prevent any damage that may follow the placement of orthodontic brackets. By regularly inspecting teeth it can be ensured that teeth are well cleaned before the brackets are placed and mature plaque will not seen during the orthodontic treatment (Amaechi, 2009).

#### **3.1.1 Measurement of plaque amount**

There are a lot indices for the measurement of plaque amount, among them the index of Silness and Löe (1964) which is very easy to use, is one of the most frequently used in clinical practice. The Plaque Accumulation Rate Index (PFRI) performed by Axelsson (1991), based on the amount of disclosed plaque which is freely accumulated in the 24 hours following professional mechanical tooth cleaning (during which period subjects refrain from all oral hygiene practices. For the PFRI a five point scale was constructed (Figure 7.). There are positive correlations between the scores of PFRI and e.g. gingival bleeding, Plaque Index, level of streptococcus mutans, caries prevalence etc. (Axelsson, 2000).

The method cause a temporary discoloration on the bucca or the tongue. Matured and fresh plaque can be seen in different colors. More blue plaque coloration means inproper oral

Some types of plaque staining products can differentiate between the cariogenic and noncariogenic plaque with different colors (Figure 5.). Acid producing ability of a plaque sample and its cariogenic potential can be determined. Non-cariogenic samples turn green or yellow, while cariogenic plaque samples turn red or orange after sucrose challenge from the solution. Some products contain a neutralising solution (e.g. Plaque Indicator Kit from the GC) which can be used for education of the patients, eg. regarding the protective actions of the saliva and a disclosing gel for the demonstration of plaque. The composition of plaque changes in time, which allows pathogenic bacteria to be active on the tooth surface. Using a special disclosing gel, a more than 48 hours old (matured) plaque and a fresh plaque can be

The Inspektor QLF-D BiLuminatorTM is a sophisticated device for assessment and monitoring of oral hygiene in the dental surgery. The QLF-D BiLuminator software supports easy acquisition of image pairs and orders them automatically on a visit-patient basis. Plaque and calculus show up brightly red in the QLF –image made by this equipment (Figure 6.). Only those plaque will be seen that has been present for some time (> 1 day).

Fig. 6. White light and QLF image of teeth with orthodontic brackets (publication of the

The BiLuminatorTM can be tremendous help to prevent any damage that may follow the placement of orthodontic brackets. By regularly inspecting teeth it can be ensured that teeth are well cleaned before the brackets are placed and mature plaque will not seen during the

There are a lot indices for the measurement of plaque amount, among them the index of Silness and Löe (1964) which is very easy to use, is one of the most frequently used in clinical practice. The Plaque Accumulation Rate Index (PFRI) performed by Axelsson (1991), based on the amount of disclosed plaque which is freely accumulated in the 24 hours following professional mechanical tooth cleaning (during which period subjects refrain from all oral hygiene practices. For the PFRI a five point scale was constructed (Figure 7.). There are positive correlations between the scores of PFRI and e.g. gingival bleeding, Plaque

pictures with permission of Inspektor Research System BV, Netherlands).

Index, level of streptococcus mutans, caries prevalence etc. (Axelsson, 2000).

hygiene

seen in two different colours (blue, redish-pink).

orthodontic treatment (Amaechi, 2009).

**3.1.1 Measurement of plaque amount** 


Fig. 7. The scores of Plaque Formation Rate Index by Axelsson (1991).

#### **3.2 Microbiological and clinical parameters for determination of caries risk**

As caries is a multicausal disease, it is not optimal to examine just one etiological factor for the general prognosis. Caries risk assessment models involve a combination of factors including diet, fluoride exposure, a susceptible host, microflora which all can interplay with a variety of social, cultural and behavioural factors (Featherstone, 2003; Nicolau et al., 2003).

The combination of clinical and microbiological findings increases the sensitivity of caries prognosis to almost 100% (Kneist et al., 1998; Krasse, 1988). New carious lesions will develop if high bacterial counts have been recorded, thus the evaluation of microbiological data is also recommended before the starting of orthodontic treatment, because the caries risk tends to increase dramatically in patients with high bacterial counts after the placement of brackets, due to the difficulties in performing adequate oral hygiene (Kristofferson et al., 1985).

The risk of caries can be determined by other different testing procedures, these are based on determination of quality and quantity of saliva.

#### **3.2.1 Microbiological parameters**

In a regular dental practice the "chairside tests" are very easy to apply for determination of cariogen bacteria and salivary parameters. These tests are available since the begining of 1970s years. Using these products allows semiquantitative evaluation of mutans streptococci in saliva or plaque and lactobacilli in saliva (Larmas, 1975; Jensen & Bratthall, 1989).

Earlier test systems (Dentocult SM, Dentocult LB from Orion Diagnostica, Cariescreen SM from APO Diagnostics, Caries Check SM and Caries Check LB from Hain Diagnostika) needed relatively complicated laboratory working procedures. The newer type of Dentocult tests allows simplier technical work but they work on the same basis.

#### **3.2.1.1 Estimation of mutans streptococci**

The basis of the determination of streptococcus mutans is represented by a basic method of Dentocult SM test could be used for estimation of mutans streptococci. Originally it has been developed by Jensen & Bratthall (1989), but this Dentocult SM (Strip Mutans) is a newer development of the spatula method of Köhler & Bratthall (1979). The test is based on those facts that adhesing of mutans streptococci can be experienced not only to tooth surface but to wooden or plastic spatulas and removable devices also and on the ability of mutans streptococci to grow on hard surfaces and use of a selective broth (high sucrose concentration in combination with bacitracin). The test result shows the risk of caries depending on the level of mutans streptococci CFU (Colony Forming Units/ml) in saliva or in dental plaque, but the result has to be interpreted in relation to the number of the teeth in the mouth (Zickert et al., 1982). An other type of the available simple and accurate chairside test is "Saliva – Check mutans" from the GC, which detects the patients level of streptococcus mutans in 15 minutes only. For this test there is no need for incubator (in contrast with the previously mentioned product) or any other devices. High accuracy is possible as the test strip containes 2 monoclonal antibodies that selectively detect only the streptococcus mutans species, meaning no other bacteria modify the results.

#### **3.2.1.2 Estimation of lactobacilli**

The other organisms that can be associated with caries are lactobacilli. Althoug probably they don't play a primary role in the etiology of caries, lactobacilli can be important from the viewpoint of caries activity (Socransky, 1968). Based on different studies the presence of lactobacilli reflects only high consumption of carbohydrates and therefore it is an indirect test for caries (Klock & Krasse, 1979; Crossner, 1981). On the other hand the test provides information about the activity of existing carious lesions (high levels of lactobacilli show an incresed carious activity which can lead to early treatment of the lesions).

For the estimation of lactobacilli can be used a method of dip slide test (Larmas, 1975). The applied selective lactobacillus agar which supports the grows of the acid forming and acid resistant lactobacilli (mainly Lactobacillus casei). The dip slide has to be placed into the transport tube and incubated for four days at 37 °C (99 °F). Estimation of lactobacilli, similarly to mutans streptococci, can be performed by comparing the result to the chart. For the evaluation the number of the colonies means the relevant information. Because of different incubation times for the various test vials and the short shelf life of the mutans streptococci tests, further efforts have been made for optimize the tests in accordance with the practical viewpoints.

#### **3.2.1.3 CRT bacteria test for combined determination of cariogenic bacteria**

The prognosis for caries risk is more certain in those case when mutans streptococci and lactobacillus tests are combined (Stecksen-Blicks, 1985). CRT Bacteria (Vivadent, Shaan, Lichtenstein) (Figure 8.) is a test which is available for the evaluation of the level both important oral microorganisms by means of selective agars as previously described.

Fig. 8. CRT Bacteria test.

facts that adhesing of mutans streptococci can be experienced not only to tooth surface but to wooden or plastic spatulas and removable devices also and on the ability of mutans streptococci to grow on hard surfaces and use of a selective broth (high sucrose concentration in combination with bacitracin). The test result shows the risk of caries depending on the level of mutans streptococci CFU (Colony Forming Units/ml) in saliva or in dental plaque, but the result has to be interpreted in relation to the number of the teeth in the mouth (Zickert et al., 1982). An other type of the available simple and accurate chairside test is "Saliva – Check mutans" from the GC, which detects the patients level of streptococcus mutans in 15 minutes only. For this test there is no need for incubator (in contrast with the previously mentioned product) or any other devices. High accuracy is possible as the test strip containes 2 monoclonal antibodies that selectively detect only the

The other organisms that can be associated with caries are lactobacilli. Althoug probably they don't play a primary role in the etiology of caries, lactobacilli can be important from the viewpoint of caries activity (Socransky, 1968). Based on different studies the presence of lactobacilli reflects only high consumption of carbohydrates and therefore it is an indirect test for caries (Klock & Krasse, 1979; Crossner, 1981). On the other hand the test provides information about the activity of existing carious lesions (high levels of lactobacilli show an

For the estimation of lactobacilli can be used a method of dip slide test (Larmas, 1975). The applied selective lactobacillus agar which supports the grows of the acid forming and acid resistant lactobacilli (mainly Lactobacillus casei). The dip slide has to be placed into the transport tube and incubated for four days at 37 °C (99 °F). Estimation of lactobacilli, similarly to mutans streptococci, can be performed by comparing the result to the chart. For the evaluation the number of the colonies means the relevant information. Because of different incubation times for the various test vials and the short shelf life of the mutans streptococci tests, further efforts have been made for optimize the tests in accordance with

The prognosis for caries risk is more certain in those case when mutans streptococci and lactobacillus tests are combined (Stecksen-Blicks, 1985). CRT Bacteria (Vivadent, Shaan, Lichtenstein) (Figure 8.) is a test which is available for the evaluation of the level both

streptococcus mutans species, meaning no other bacteria modify the results.

incresed carious activity which can lead to early treatment of the lesions).

**3.2.1.3 CRT bacteria test for combined determination of cariogenic bacteria** 

important oral microorganisms by means of selective agars as previously described.

**3.2.1.2 Estimation of lactobacilli** 

the practical viewpoints.

Fig. 8. CRT Bacteria test.

This test give a possibility for the determining mutans streptococci and lactobacilli at the same time, during the evaluation of caries risk.

Performing the clinical procedures, after two days incubation at 37 ºC (99 ºF) can be detected and evaluated for both mutans streptococci and lactobacilli. Leaving CRT bacteria in the incubator for more than 48 hours for any reason, it will not cause any change in bacterial count. The test sample can be stored in the refrigerator for up to two weeks without any changes.

Evaluation of the CRT bacteria test (with the model chart): higher values than 105 CFU/mL of mutans streptococci in saliva indicate a high risk (Krasse, 1988; Anderson et al., 1993). CRT bacteria test can be applied to check the effectiveness of different antimicrobial treatment of the risk patients. The modification of the above presented procedure gives a possibility for the determination of mutans streptococci not only in saliva but in dental plaque also, but applying this saliva based method, the examination of incubated plaque samples provides only a semiquantitative evaluation of the microorganisms (Kneist et al., 1998). This measure is indicated to monitor the the edges around brackets in orthodontic patients.

The tests are contraindicated after treatment with previous antibiotic treatment (within the previous two weeks) or after the use of antibacterial rinsing solution (the waiting time at least 12 hours).

All tests are very easy to use, can be applied to demonstrate the proper oral hygiene and to check the effects of motivation, generally less expensive than conventional microbiological methods (Newbrun et al., 1984) and do not need specially trained personnel. These are important diagnostic tools for dentists who strive to maintain oral health of their patients.

Presently the trends towards using simple, quick tests which can demonstrate the results clearly (without any other special equipments like e.g. incubator) for the patients in a short time. These tests are based on various methods: e.g. monoclonal antibodies are employed in Saliva Check Mutans from GC, Clinpo TM Cario L-Pop TM from 3M need local measurement of acid production for assessment. This last test was used in a 12 month follow up cohort study to evaluate the association between having a high score on this test and caries occurance in young patients undergoing orthodontic treatment (Chaussain et al., 2010). More studies are needed for the evaluation because of basic method of these tests not yet fully matured in terms of their sensitivity and handling properties.

#### **3.2.2 Assessment of salivary factors**

Salivary factors are in closed connection with caries risk. Determination of salivary enzymes and ions is difficult in the everyday practice, but measurement of salivary flow rate (the volume of saliva during a given period of time) or salivary buffer capacity can be performed relatively easily.

#### **3.2.2.1 Salivary flow rate**

It is wellknown for a long time that in patients with xerostomia the caries rate is increased. So the measurement of this factor must be of interest to evaluate the potentially high risk groups of orthodontic patients. The flow rate can be established easily without any special equipments. The saliva has to be collected in calibrated tube (tube for the lactobacillus test can be used to measure the salivary flow rate as well) (Figure 9.). Secretion rate should be determined for resting saliva and paraffin stimulated saliva. The values for the determination are shown in the Table 1.

Fig. 9. Collecting saliva in a calibrated container.

For determining the risk of caries the dentist should measure the salivary secretation rate.

For the adults stimulated salivary flow rate is less than 0.7 ml/min is considered low, while higher than 1.0 mL/min is considered normal. In case of women the salivary flow rate is generally slightly lower than in men (similarly to the children when compared with the adolescents).


Table 1. Classification of salivary secretion rate for resting and paraffin-stimulated whole saliva (Axelsson, 2000).

The results could be affected by different drug intake (e.g. antihistamines, neuroleptic or antihypertensive agents).

#### **3.2.2.2 Buffer capacity**

Buffering capacity of saliva ensures the pH level and ability for remineralization. The threshold is *under 4* when the process of caries can become faster. For the evaluation can be easily used e.g. Dentobuff strip test also from the Vivadent. A disposable syringe is used to place a single drop paraffin stimulated saliva on a test strip. After about five minutes the color change on the pH indicator strip is compared with the color chart provided. Similar possibility for measuring buffering capacity is Saliva Check Buffer from the GC.

Although it can be important information, the determination of buffer capacity, similarly to the salivary flow rate, has only subordinate role in the reliable identification of patients at high caries risk. The buffer capacity test has greater value in those patients who have exposed root surfaces because exposed dentin is more sensitive to acid than the enamel (Heintze et al, 1999).

#### **3.3 Determination and assessment of the risk of periodontal diseases**

Development and progression of periodontitis basically depends on the interaction of periodontopathogenic bacteria and the host's immune defense system. Science has long sought a diagnostic procedure to predict the risk of periodontitis with determination of the attack and defense mechanisms. For the daily practice, clinical parameters are sufficient to identify patients with potential disease activity. Periodontal diseases are in tight connection with systemic diseases (eg. cardiovascular diseases, diabetes etc.), and there is an evidence that periodontitis associated bacteria or their tissue derived inflammatory mediators are transmitted eg. during pregnancy from mother to child (Genco, 1996; Herzberg & Meyer, 1996; Slavkin, 1997). There are some chairside test which can measure different parameteres associated with periodontitis development. However, it is not clear how these tests could be clinically significant. According to several recently published reviews, none of the available tests is capable identify with at least 80% accuracy those individuals who are at risk for periodontitis (Lang & Bragger, 1991; Jeffcoat et al., 1997). Therefore, clinical evaluation seems to be more useful to carry out periodontal diagnosis and assessment the risk. The dentist has to determine the following points (Heintze et al, 1999):


#### **3.3.1 Clinical measurements**

80 Orthodontics – Basic Aspects and Clinical Considerations

determined for resting saliva and paraffin stimulated saliva. The values for the

For determining the risk of caries the dentist should measure the salivary secretation rate. For the adults stimulated salivary flow rate is less than 0.7 ml/min is considered low, while higher than 1.0 mL/min is considered normal. In case of women the salivary flow rate is generally slightly lower than in men (similarly to the children when compared with the

Secretion rate (ml/min) Very low Low Normal

Resting saliva 0.1 0.1 - 0.25 0.25-0.35 (mean 0.30)

Stimulated saliva 0.7 0.7 - 1 1 – 3 (mean 2)

Table 1. Classification of salivary secretion rate for resting and paraffin-stimulated whole

The results could be affected by different drug intake (e.g. antihistamines, neuroleptic or

Buffering capacity of saliva ensures the pH level and ability for remineralization. The threshold is *under 4* when the process of caries can become faster. For the evaluation can be easily used e.g. Dentobuff strip test also from the Vivadent. A disposable syringe is used to place a single drop paraffin stimulated saliva on a test strip. After about five minutes the color change on the pH indicator strip is compared with the color chart provided. Similar possibility for measuring buffering capacity is Saliva Check Buffer from

determination are shown in the Table 1.

Fig. 9. Collecting saliva in a calibrated container.

adolescents).

saliva (Axelsson, 2000).

antihypertensive agents). **3.2.2.2 Buffer capacity** 

the GC.

Greater plaque accumulation, tendency for bleeding and increased pocket depth have been observed more frequently in orthodontic patients. Therefore, to examine these factors are necessary to determine and monitor a risk of periodontal disease concerning orthodontic treatment.

#### **3.3.1.1 Gingival Bleeding Index**

Gingival Bleeding Index published by Ainamo & Bay (1975) is very simply to use in orthodontic patients. The sulcus is probed carefully on the buccal and lingual surfaces with periodontal probe. It is useful to develop a specific system e.g. to proceed by quadrants. Probing begins on the buccal surface, proceeding from the distal to mesial surfaces, then on the lingual surface from the distal to mesial. Thus each tooth has four points of measurement: buccal, lingual, mesioproximal and distoproximal.

In patient with fixed appliance performing the probing can be more difficult due to bands and other attachments limiting access to the gingival margin (Figure 10.). Still, it is necessary to probe the gingival margin along its entire lengh to get valuable data and to perform adequate preventive interventions.

Fig. 10. Performing clinical measurements for the evaluation of periodontal conditions with a periodontal probe in orthodontic patients.

Although periodontal parameters are very important for the determination of the risk or the exist of periodontal diseases due to orthodontic treatment, sometimes it is difficult to perform because of different parts of the appliance.

#### **3.3.1.2 Loss of attachment**

The gingival sulcus is probed gently with a special periodontal probe. The depth of the gingival sulcus is considered maximally 0.5 mm deep in case of sound gingiva. In some orthodontic cases (mainly in adult patients) the measuring loss of attachment and its documentation are important, but measurement of attachment loss does not correlate with inflammatory activity of a pocket (Lang & Bragger, 1991).

#### **3.3.2 RT-PCR (Reverse Transcription –Polymerase Chain Reaction)**

One of the newest method is the RT-PCR. This is the most sensitive technique for mRNA detection and quantification currently available. It is a fully automated process and exact quantification of anaerob periodontopathogenic bacteria from a small sample of dental plaque. The advantages of this method are high specificity, high sensitivity and objectivity (Dharmaraj, 2011).

In addition to clinical and radiographic parameters and additional data provide information about the groups at higher risk for periodontitis (Fox, 1992). Patients are in higher risk in the following cases:


82 Orthodontics – Basic Aspects and Clinical Considerations

Fig. 10. Performing clinical measurements for the evaluation of periodontal conditions with

Although periodontal parameters are very important for the determination of the risk or the exist of periodontal diseases due to orthodontic treatment, sometimes it is difficult to

The gingival sulcus is probed gently with a special periodontal probe. The depth of the gingival sulcus is considered maximally 0.5 mm deep in case of sound gingiva. In some orthodontic cases (mainly in adult patients) the measuring loss of attachment and its documentation are important, but measurement of attachment loss does not correlate with

One of the newest method is the RT-PCR. This is the most sensitive technique for mRNA detection and quantification currently available. It is a fully automated process and exact quantification of anaerob periodontopathogenic bacteria from a small sample of dental plaque. The advantages of this method are high specificity, high sensitivity and objectivity

a periodontal probe in orthodontic patients.

**3.3.1.2 Loss of attachment** 

(Dharmaraj, 2011).

perform because of different parts of the appliance.

inflammatory activity of a pocket (Lang & Bragger, 1991).

**3.3.2 RT-PCR (Reverse Transcription –Polymerase Chain Reaction)** 


The clinicians must identify susceptible patients and develop strategies to prevent loss of attachment and/or gingival recession. Each patient must be assessed individually for periodontal factors which mean for the patients high risk of developing periodontal disease during orthodontic treatment (Vanarsdall, 2000).

#### **4. Possibilities to avoid or reduce the risk of caries and periodontal diseases concerning orthodontic treatment**

Concerning the orthodontic treatment removable appliances do not cause significant plaque accumulation, while patients with fixed orthodontic appliances have a higher risk for increased plaque formation and with its harmful consequences for demineralization of the teeth and periodontal problems. Most of the lesions occure during fixed orthodontic treatment and appear mainly to be surface demineralization rather than a subsurface lesion. De-and remineralization processes are performed continuously. Sometimes the amount of remineralization can not totally overcome the amount of demineralization (Wilmot, 2008).

Longitudinal studies have shown the beneficial effects of recommendation to perform preventive measures during orthodontic treatment mainly in case of fixed appliances. Applying the possibilities, in these patients there was no clinically significant damage on either hard tissues of the teeth or periodontium (Boyd et al., 1989; Zachrisson & Zachrisson, 1971). Beside of the orthodontists, the general dentists and oral hygienists have a significant role in maintaining proper and effective oral hygiene of the patients undergoing orthodontic treatment with fixed appliances.

#### **4.1 Patients with removable appliances**

Although removable orthodontic appliances do not increases alone the absolute level of pathogenic microorganisms, but frequently provide more retention places for bacterial deposits (Figure 11.). In these cases the aim of oral hygienic procedures is the elimination of plaque from the appliance to prevent reinfection of the cleaned teeth. It is very difficult to keep the removable appliance totally free of plaque. Different cleaning methods are recommended mainly for home care. The orthodontist can suggest to clean with toothbrush and toothpaste (or soap) under running water or to clean the appliance in water bath containig a cleanser tablet. Both of them show some disadvantages: the combination of toothbrush-toothpaste cleaning is effective only on the easily accessable surfaces (Diedrich, 1989), while the use of self acting cleansing tablet allows just 2-3% of total deposits remaining on the appliances (Rabe et al., 1986). The antibacterial effectiveness of these tablet cleansers is doubtful and they can lead to obvious corrosion of the metal solder connections (Rabe et al.,1986). One more possibility for cleaning the removable appliances can be an ultrasonic bath, which is an expensive method and is not affordable for all patients wearing removable orthodontic appliances.

Fig. 11. Removable appliance with many retention sites and bacterial deposits.

In case of removable appliance it is necessary to clean the appliance to prevent reinfection of the cleaned teeth.

In the literature different materials are mentioned for reducing the level of pathogenic bacteria in the mouth. E.g. application of SRD (Slow Release Dosage) of chlorhexidine on the tooth surface showed a plaque reducing effect (Friedman et al., 1985), but other material with the same ingredient (e.g. Cervitec varnish) can be used effectively. Cervitec can successfully reduce cariogenic bacteria like mutans streptococci on different tooth surfaces, and promote the plaque reducing effect in the mouth (Huizinga et al., 1990; Petersson et al., 1991; Twetman & Petersson, 1997; Madléna et al., 2000). Slow release fluoride devices also can be used in case of high risk patients with removable appliances, although these products are preferred for patients treated with fixed appliances. Using slow fluoride release containing polymethyl metacrylate (Orthocryl Plus) ensures continuous low concentration of fluoride in saliva for more months which provides an optimal circumstance for the remineralization of initial carious lesions (Miethke & Newesely, 1988; Alacam et al., 1996). In case of patients using removable appliance to perform all dental and gingival treatment should be offered before the begining of the treatment.

#### **4.2 Patients with fixed appliances**

84 Orthodontics – Basic Aspects and Clinical Considerations

1989), while the use of self acting cleansing tablet allows just 2-3% of total deposits remaining on the appliances (Rabe et al., 1986). The antibacterial effectiveness of these tablet cleansers is doubtful and they can lead to obvious corrosion of the metal solder connections (Rabe et al.,1986). One more possibility for cleaning the removable appliances can be an ultrasonic bath, which is an expensive method and is not affordable for all patients wearing

Fig. 11. Removable appliance with many retention sites and bacterial deposits.

In case of removable appliance it is necessary to clean the appliance to prevent reinfection of

In the literature different materials are mentioned for reducing the level of pathogenic bacteria in the mouth. E.g. application of SRD (Slow Release Dosage) of chlorhexidine on the tooth surface showed a plaque reducing effect (Friedman et al., 1985), but other material with the same ingredient (e.g. Cervitec varnish) can be used effectively. Cervitec can successfully reduce cariogenic bacteria like mutans streptococci on different tooth surfaces, and promote the plaque reducing effect in the mouth (Huizinga et al., 1990; Petersson et al., 1991; Twetman & Petersson, 1997; Madléna et al., 2000). Slow release fluoride devices also can be used in case of high risk patients with removable appliances, although these products are preferred for patients treated with fixed appliances. Using slow fluoride release containing polymethyl metacrylate (Orthocryl Plus) ensures continuous low concentration of fluoride in saliva for more months which provides an optimal circumstance for the remineralization of initial carious lesions (Miethke & Newesely, 1988; Alacam et al., 1996). In case of patients using removable appliance to perform all dental and gingival treatment should be offered before the begining of the

removable orthodontic appliances.

the cleaned teeth.

treatment.

For the proper effects preventive actions and interventions should begin as early as possible, long before the active orthodontic therapy both in removable and fixed applience cases, but especially important for patients with fixed appliances.

There are three main categories should be considered concerning the preventive program for orthodontic patients: preventive actions and interventions *before, during and after* the active orthodontic treatment (Table 2.).


Table 2. Preventive viewpoints before, during and after the active orthodontic treatment with fixed orthodontic appliance (Lundström et al., 1980; Hotz, 1982).

In all patients but especially in case of fixed appliance it is very important that all general dental and periodontal treatment should be completed *before* orthodontic treatment. It is compulsory to consult with the general dentist or any specialist to gain a statement that the patient is ready for orthodontic treatment. To prepare a written inform consent including the necessity of improved oral hygiene is also necessary before begining of the treatment. The oral condition has also to be recorded on the patient's chart and demonstrated with clinical photos.

Concerning the treatment, bonding of molars is better and ensures better possibilities to remove the plaque than banding, especially in adults. For the same reason it is suggested to use single arch wires, if the case allows and to remove excess composite around brackets (mainly from the gingival third). Theoretically use of fluoride containing orthodontic adhesives are preferable during orthodontic treatment and in case of fixed retainer. In vitro studies glass ionomer cements have demonstrated a more sustained fluoride release and evidence that these cements may reduce decalcification (Vorhies et al., 1998; Chung et al., 1999; Millett et al., 1999). At the same time, according to a systematic review, glass ionomer cement could be more effective than composite resin in preventing white spot formation, but still the scientific evidence is weak. The authors conclude that fluoride releasing bonding material for bonding brackets showed almost no demineralization-inhibiting effect (Derks et al., 2004).

Because of the limitation of successful bonding with glass ionomer adhesives, further investigations are needed for the recommendations on the usage of fluoride containing adhesives during fixed orthodontic treatment (Rogers et al., 2010). Uysal et al. (2011) conclude that using antibacterial monomer containing adhesive for bonding orthodontic brackets successfully inhibited caries incidence in vivo, the cariostatic effect was localized around the brackets and proved to be significant after 30 days.

Lingual appliances can cause extra difficulties in performing proper oral hygiene. The longer the treatment time with fixed appliance, the more time needed to maintain oral health in such a non-ideal circumstance. It is preferable to minimize the length of treatment with either conventionally or lingually placed fixed orthodontic appliance (e.g. by early corrections of skeletal and alignment problems in the mixed dentition with removable appliances). In addition a light cure sealant containing fluoride should also be advisable to be applied on the entire free surface, which can also be reapplied during the treatment (Frazier et al., 1996). Fluoride containing elastomeric chains also may reduce the degree of decalcification (Banks et al., 2000).

#### **4.2.1 Motivation of the patients and oral hygienic training; control of oral hyiene**

*Before* the orthodontic treatment it is very important to inform the patients about the importance of the improved oral hygiene concerning orthodontic treatment with fixed appliance and to explain the causes of caries and periodontal disease. The dentist can use any gingival indices and disclosure of the plaque for the patient to be motivated. The patients need proper information about the preventive possibilities concerning fixed orthodontic appliance after its application. It could be very useful to check the oral hygiene throught the complete orthodontic therapy. Beside of the use of fluoride containing toothpaste and brushing with conventional brushes also during the treatment at least twice a day, additional methods could be suggested helping to improve oral hygiene. Recording and documentation of the improvement in oral hygiene in the patient's chart is also necessary. Although motivation and oral hygiene training represent the most important points before the orthodontic treatment, it can be repeated as frequently as it is needed not only before but during the active orthodontic treatment as well. *After finishing the orthodontic treatment* the orthodontist also has to advice the patients to maintain proper oral hygienic habits.

#### **4.2.2 Oral hygienic training methods**

It is a possibility and a responsibility of the orthodontists to involve their patients in a systemic program for the prevention of caries and periodontal diseases focusing on mechanical removal of plaque and elimination of pathogen microorganisms. Because of tooth cleaning is much more difficult in patients undergoing orthodontic therapy with fixed appliance, patients and orthodontists/dentists or specially trained personnel require much efforts and time to show the possibilities of proper oral hygiene. Ask the patients to demonstrate the efficiency of brushing at each regular visit until they have mastered the technique.

The patients can use both hand or electric tooth brushes with short head, soft and rounded bristle end, but they can apply special orthodontic brushes (eg. when middle row of bristles is shorter than the outer row) and have to ask other special equipments also (eg. floss, interdental brushes, etc.) (Figure 12.). The patients may be instructed in the modified Bass technique. It is also important to let the toothbrush air-dried for 24 hours between uses. Tooth cleaning requires at least 10 minutes for patients. Approximal surfaces could be cleaned properly with dental floss. Interdental brushes and Superfloss must be used for the proper oral hygiene not only on the approximal surfaces but the tooth surfaces around the bracket and band margins as well (Heintze et al., 1999; Boyd, 2001).

Fig. 12. Special brushes for orthodontic patients.

During the orthodontic treatment with fixed appliance it is necessary to suggest special equipments for the proper oral hygiene and to check the effectiveness of them.

#### **4.2.3 Control of oral hygiene**

86 Orthodontics – Basic Aspects and Clinical Considerations

bonding material for bonding brackets showed almost no demineralization-inhibiting effect

Because of the limitation of successful bonding with glass ionomer adhesives, further investigations are needed for the recommendations on the usage of fluoride containing adhesives during fixed orthodontic treatment (Rogers et al., 2010). Uysal et al. (2011) conclude that using antibacterial monomer containing adhesive for bonding orthodontic brackets successfully inhibited caries incidence in vivo, the cariostatic effect was localized

Lingual appliances can cause extra difficulties in performing proper oral hygiene. The longer the treatment time with fixed appliance, the more time needed to maintain oral health in such a non-ideal circumstance. It is preferable to minimize the length of treatment with either conventionally or lingually placed fixed orthodontic appliance (e.g. by early corrections of skeletal and alignment problems in the mixed dentition with removable appliances). In addition a light cure sealant containing fluoride should also be advisable to be applied on the entire free surface, which can also be reapplied during the treatment (Frazier et al., 1996). Fluoride containing elastomeric chains also may reduce the degree of

**4.2.1 Motivation of the patients and oral hygienic training; control of oral hyiene** 

*Before* the orthodontic treatment it is very important to inform the patients about the importance of the improved oral hygiene concerning orthodontic treatment with fixed appliance and to explain the causes of caries and periodontal disease. The dentist can use any gingival indices and disclosure of the plaque for the patient to be motivated. The patients need proper information about the preventive possibilities concerning fixed orthodontic appliance after its application. It could be very useful to check the oral hygiene throught the complete orthodontic therapy. Beside of the use of fluoride containing toothpaste and brushing with conventional brushes also during the treatment at least twice a day, additional methods could be suggested helping to improve oral hygiene. Recording and documentation of the improvement in oral hygiene in the patient's chart is also necessary. Although motivation and oral hygiene training represent the most important points before the orthodontic treatment, it can be repeated as frequently as it is needed not only before but during the active orthodontic treatment as well. *After finishing the orthodontic treatment* the orthodontist also has to advice the patients to maintain proper

It is a possibility and a responsibility of the orthodontists to involve their patients in a systemic program for the prevention of caries and periodontal diseases focusing on mechanical removal of plaque and elimination of pathogen microorganisms. Because of tooth cleaning is much more difficult in patients undergoing orthodontic therapy with fixed appliance, patients and orthodontists/dentists or specially trained personnel require much efforts and time to show the possibilities of proper oral hygiene. Ask the patients to demonstrate the efficiency of brushing at each regular visit until they have mastered the

around the brackets and proved to be significant after 30 days.

(Derks et al., 2004).

decalcification (Banks et al., 2000).

oral hygienic habits.

technique.

**4.2.2 Oral hygienic training methods** 

*During the active treatment* patients should evaluate their teeth (and appliances) and determine these are whether clean or not. Regular recall examinations are necessary but the intervals between the recall examinations depend on the initial conditions. At the recall examinations during both the active treatment phase and the retention period regularly should perform the determination of caries risk (mutans streptococci and lactobacilli counts) and the evaluation of the condition of gingiva.

*During the retention phase*, removable retainers mean lower risk because these appliances allow an easier tooth cleaning procedure. The attached fixed retainers represent plaque retentive sites in the mouth, although these appliances are believed not to lead to initial carious lesions or periodontal problems if properly fabricated (Artun, 1984; Gorelick et al., 1982). Further advantage of removable devices is that they could be used as carriers of medicaments to provide more intensive prophylaxis.

#### **4.2.4 Dietary counselling**

Sugar is not a single causative factor of dental caries but it can appear as an important external modifying risk factor in this process. Due to this reason the dental personnel have to ask the patients about their nutritional habits, optimally using a questionnaire. It is very important to know the average frequency of intake of any types of the cariogenic foods (Axelsson, 1999).

The dietary control is in close connection with microbiologic evaluations. As high salivary levels of lactobacilli indicate a high sugar intake and a low pH in the oral cavity, the lactobacillus test is useful for the objective supplement to the dietary questionnaire (Axelsson, 1999). Sugar intake can be assessed eg. from a 24 hour recall questionnaire. For caries prevention and control the following dietary recommendations should be performed for the patients according to Axelsson (1999):


#### **4.2.5 Professional tooth cleaning**

Professional tooth cleaning represents a basic method and means professional removal of all deposits from the teeth by dentist, dental hygienist or specially trained nurses. For the proximal surfaces dental floss must be used (and fissures must be sealed if indicated). Calculus (mineralized plaque) can be removed with manual or ultrasonic scalers, after it the teeth should be polished. A complete professional tooth cleaning should be performed before the active orthodontic treatment and at the appointments of control examinations.

#### **4.2.6 Use of fluorides**

A correlation between reduced caries prevalence and natural fluoride content of drinking water was published firstly by Dean (1938). Saliva usually contains a low amount of fluoride (Twetman et al., 1999). The importance of fluoridation is basic to maintain the health of teeth, particularly in the prevention of caries and remineralization of incipient carious lesions. A report published by the WHO (1994) and a review article by Rolla et al. (1991) state that the use of fluoridated tooth paste had led to a significant decrease in the incidence of caries in the industrialized countries. The ability of fluoride to retard or prevent the development of dental caries appears to involve several mechanisms including a reduction in the acid solubility of enamel, promotion of enamel remineralization, inhibition of glucose uptake and utilization by acidogenic bacteria. Demineralization refers to the loss of minerals (mainly calcium and phosphate ions) from the tooth structure due to the acidic and cariogenic challenge. Fluoride can help to prevent the mineral loss. When the pH drops below approximately 5.5, calcium ions are dissolved from the enamel and bond with fluoride ions forming a calcium fluoride (CaF2) layer (Rolla & Saxegaard, 1990). CaF2 is insoluble in the saliva and remains on the teeth for months (Dijkman et al., 1983). The CaF2 layer functions as a pH controlled fluoride reservoir and is the most important supplier of free fluoride ions during the cariogen challenge (Fischer et al., 1995). Fluoride uptake and release of the enamel are strongly dependent on the duration of contact with the fluoridated agent (Ten Cate & Arends, 1980; Chen et al., 1985). With an appropriate fluoride formulation, incipient lesions could be reduced in size or even be repaired (Tranaeus et al., 2001).

Research suggests that topical fluorides might also decrease decalcification during orthodontic treatment (Geiger et al., 1988; Shannon & West, 1979; Benson et al., 2004; Derks et al., 2004; Chadwick et al., 2005; Sudjalim et al, 2006). Daily use of fluoride toothpaste, in combination with specific oral hygienic instructions, is recommended as the basis of caries and periodontal prophylaxis programme. Although fluoride concentration in different products may vary, below 0.1% in a dentifrice is not recommended for orthodontic patients (Ogaard et al., 2004). There are a number of locally applicable agents to improve maintain proper oral hygiene. The most important aim with the fluoridated dental care products first of all to strengthen of enamel against to caries, enhance the remineralization, protection against demineralization and improve or ensure gingival health. Beside of the toothpaste, fluoridated agents are included in different forms of gels, mouthrinses, varnishes and other products.

Topical fluoride may be applied by professional personnel in dental office or by patients at home. Using other local fluoridaton's method, a balance should be maintain between the prevention of dental caries and minimising the risk of dental mottling (Oulis et al., 2009). Generally, dentifrice alone is ineffective in preventing development of lesions (O'Reilly & Featherstone, 1987).

#### **4.2.6.1 Fluoride rinses**

88 Orthodontics – Basic Aspects and Clinical Considerations

The dietary control is in close connection with microbiologic evaluations. As high salivary levels of lactobacilli indicate a high sugar intake and a low pH in the oral cavity, the lactobacillus test is useful for the objective supplement to the dietary questionnaire (Axelsson, 1999). Sugar intake can be assessed eg. from a 24 hour recall questionnaire. For caries prevention and control the following dietary recommendations should be performed

1. The first meal of the day (breakfast), should be a balanced composition of dairy products, grains and fruit eg. yogurt and muesli, fresh fruit and vegetables. It is not the same as the commercial continental breakfast containing mainly fat, sugar and water which causes rapid swings in blood sugar levels stimulating a high frequency of sugar

3. Sticky, sugar containing products should be eliminated. Sugarless sweets containing

4. In each meal, fiber rich products that stimulate chewing and salivary flow should be

5. Selected individuals with extremely high risk of development of caries should clean all surfaces just before each meal, to limit the drop in pH during and immediately after the

Professional tooth cleaning represents a basic method and means professional removal of all deposits from the teeth by dentist, dental hygienist or specially trained nurses. For the proximal surfaces dental floss must be used (and fissures must be sealed if indicated). Calculus (mineralized plaque) can be removed with manual or ultrasonic scalers, after it the teeth should be polished. A complete professional tooth cleaning should be performed before the active orthodontic treatment and at the appointments of control examinations.

A correlation between reduced caries prevalence and natural fluoride content of drinking water was published firstly by Dean (1938). Saliva usually contains a low amount of fluoride (Twetman et al., 1999). The importance of fluoridation is basic to maintain the health of teeth, particularly in the prevention of caries and remineralization of incipient carious lesions. A report published by the WHO (1994) and a review article by Rolla et al. (1991) state that the use of fluoridated tooth paste had led to a significant decrease in the incidence of caries in the industrialized countries. The ability of fluoride to retard or prevent the development of dental caries appears to involve several mechanisms including a reduction in the acid solubility of enamel, promotion of enamel remineralization, inhibition of glucose uptake and utilization by acidogenic bacteria. Demineralization refers to the loss of minerals (mainly calcium and phosphate ions) from the tooth structure due to the acidic and cariogenic challenge. Fluoride can help to prevent the mineral loss. When the pH drops below approximately 5.5, calcium ions are dissolved from the enamel and bond with fluoride ions forming a calcium fluoride (CaF2) layer (Rolla & Saxegaard, 1990). CaF2 is

2. The total number of meals, including all, should be limited to about four.

sugar substitutes (xylitol, sorbitol, aspartam etc.) should be used.

for the patients according to Axelsson (1999):

intake all day.

included.

**4.2.6 Use of fluorides** 

**4.2.5 Professional tooth cleaning** 

meal.

Relevant studies have shown that daily use of fluoride rinse during the orthodontic treatment can reduce the incidence of initial carious lesions. At the same time, relatively few of orthodontic patients rinsed daily with fluoride containing mouthrinses (Geiger et al., 1988).

It has been published that caries reduction with different mouthrinses was estimated 25-30 % (Geiger et al., 1988; Newbrun, 1992). Rinses generally contain 0.025 to 0.05 % sodium fluoride, 0.025 % amine fluoride, 0.01 % zinc fluoride or 0.025 % APF (Acidulated Phosphate Fluoride), but more highly concentrated solutions are recommended for patients with increased risk (Zachrisson, 1975). Patients in high caries risk such as orthodontic patients should use a daily rinse of eg. 0.05% sodium fluoride at home (Petersson, 1993). Fluoride containing mouthrinse can be used at a time that is different to any tooth brushing for an additive effect to fluoride toothpaste (Oulis et al., 2009) or after the toothbrushing to complete the fluoride intake.

#### **4.2.6.2 Fluoride gels**

Fluoride containing gels can be used on patients yearly or half-yearly in dental office or can be used regularly by the patient, at home. The application of fluoride gels can reduce the occurance of caries by 21-30 % (Marinho et al., 2002; Marthaler, 1988).

#### **4.2.6.3 Fluor protector gel**

The Fluor Protector Gel (Vivadent, Shaan, Liechtenstein) contains calcium (Ca), phosphate and 1450 ppm fluoride (F) forming a CaF2 layer and a direct incorporation of Ca, fluoride and phosphate ions into the tooth enamel. CaF2 preferably deposits on demineralized surfaces and this layer is additionally stabilised by phosphate ions (Rolla and Saxegaard, 1990), which are also contained in Fluor Protector Gel. If the pH falls into the acidic range, the calcium fluoride layer releases Ca and phosphate ions which are released into the saliva and form a depot. It will work against demineralization or can contribute to the formation of fluoro-apatite or fluoro-hydroxyl-apatite. This replacement of hydroxy ion by a fluoride ion in the hydroxy apatite ensures the tooth enamel with higher resistance to pH drops (Fischer et al., 1995).

The Fluor Protector Gel can either used by the dentist in the dental surgery or by the patients at home, in different ways. It can be used in place of toothpaste to brush the teeth, or in the evening, after cleaning the teeth with toothpaste, when Fluor Protector Gel can be additionally applied with the toothbrush. It is suggested for cleaning interdental spaces of natural dentition or fixed dental restorations etc.. It also can be used with a tray filled with gel inserting it once or twice daily, and leaving it in place for 10 minutes every occasion.

It is especially recommended in high risk patients undergoing orthodontic treatment with fixed appliances.

#### **4.2.6.4 Stannous fluoride gel**

Since the late 1970s, 0.4% stannous fluoride (SnF2) gels have been widely used as therapeutic agents for number of common oral diseases and conditions, and promoted as the preferred preventive and treatment products (Hastreiter, 1989; Paraskevas & van der Weiden, 2006). It contains more than 90% available stannous ion (Sn2+) which is useful againts either plaque accumulation or gingivitis.

#### **4.2.6.5 Halitosis tooth and tongue gel, Amine fluoride gel (see below)**

#### **4.2.6.6 Amine fluoride/ amine and stannous fluoride containing products**

The use of amine fluorides in dentistry was recommended firstly by Mühlemann et al. (1957). The beneficial effects of them are well known as protective agents against mainly caries and dental plaque accumulation (Schmid, 1983; Öhrn & Sanz, 2009). These products were used in the form of dentifrices, gels and fluids in various caries preventive programs and suggested as alternatives or adjunctives for systemic fluoridation. Clinical studies with amine fluorides can be divided into trials with dentifrice only, with gel only or combined use of these products similarly to the use of mouthrinse and/or toothpaste. Fluoride containing gels are recommended annually or semiannually in the dental office. By the patients' home use, it is suggested to brush once a week, after a regular toothbrusing. Gels contain high concentration of different types of fluorides. Gels containing amine fluoride (in 12 500 ppm concentration) (Elmex gel, Gaba Int. Ltd., Switzerland) are used mostly in Europe. The active ingredients of the clinically tested relatively new product (Halitosis tooth and tongue gel) (Gaba Int. Ltd., Switzerland) (Figure 13.) are amine fluoride/ stannous fluoride and zinc lactate). This gel protects against caries, cleans the teeth and tongue (by

The Fluor Protector Gel (Vivadent, Shaan, Liechtenstein) contains calcium (Ca), phosphate and 1450 ppm fluoride (F) forming a CaF2 layer and a direct incorporation of Ca, fluoride and phosphate ions into the tooth enamel. CaF2 preferably deposits on demineralized surfaces and this layer is additionally stabilised by phosphate ions (Rolla and Saxegaard, 1990), which are also contained in Fluor Protector Gel. If the pH falls into the acidic range, the calcium fluoride layer releases Ca and phosphate ions which are released into the saliva and form a depot. It will work against demineralization or can contribute to the formation of fluoro-apatite or fluoro-hydroxyl-apatite. This replacement of hydroxy ion by a fluoride ion in the hydroxy apatite ensures the tooth enamel with higher resistance to pH drops (Fischer

The Fluor Protector Gel can either used by the dentist in the dental surgery or by the patients at home, in different ways. It can be used in place of toothpaste to brush the teeth, or in the evening, after cleaning the teeth with toothpaste, when Fluor Protector Gel can be additionally applied with the toothbrush. It is suggested for cleaning interdental spaces of natural dentition or fixed dental restorations etc.. It also can be used with a tray filled with gel inserting it once or twice daily, and leaving it in place for 10 minutes every

It is especially recommended in high risk patients undergoing orthodontic treatment with

Since the late 1970s, 0.4% stannous fluoride (SnF2) gels have been widely used as therapeutic agents for number of common oral diseases and conditions, and promoted as the preferred preventive and treatment products (Hastreiter, 1989; Paraskevas & van der Weiden, 2006). It contains more than 90% available stannous ion (Sn2+) which is useful againts either plaque

The use of amine fluorides in dentistry was recommended firstly by Mühlemann et al. (1957). The beneficial effects of them are well known as protective agents against mainly caries and dental plaque accumulation (Schmid, 1983; Öhrn & Sanz, 2009). These products were used in the form of dentifrices, gels and fluids in various caries preventive programs and suggested as alternatives or adjunctives for systemic fluoridation. Clinical studies with amine fluorides can be divided into trials with dentifrice only, with gel only or combined use of these products similarly to the use of mouthrinse and/or toothpaste. Fluoride containing gels are recommended annually or semiannually in the dental office. By the patients' home use, it is suggested to brush once a week, after a regular toothbrusing. Gels contain high concentration of different types of fluorides. Gels containing amine fluoride (in 12 500 ppm concentration) (Elmex gel, Gaba Int. Ltd., Switzerland) are used mostly in Europe. The active ingredients of the clinically tested relatively new product (Halitosis tooth and tongue gel) (Gaba Int. Ltd., Switzerland) (Figure 13.) are amine fluoride/ stannous fluoride and zinc lactate). This gel protects against caries, cleans the teeth and tongue (by

**4.2.6.5 Halitosis tooth and tongue gel, Amine fluoride gel (see below) 4.2.6.6 Amine fluoride/ amine and stannous fluoride containing products** 

**4.2.6.3 Fluor protector gel** 

et al., 1995).

occasion.

fixed appliances.

**4.2.6.4 Stannous fluoride gel** 

accumulation or gingivitis.

helping a special tongue cleaner) and even neutralizes odour-active compounds in the oral cavity. It is offered for adults and childrens above the age of 12 years. It is also very useful for orthodontic patients with fixed orthodontic appliances because of these appliances can cause oral malodour (Babacan et al., 2011). This product is available in the form as mouthrinse with 250 ppm fluoride content.

Fig. 13. Halitosis tooth and tongue gel and a tongue scraper.

This product is very useful for the patients undergoing orthodontic treatment.

Clinical trials with amine fluoride toothpaste, performed between 1968 and 1995 with a duration of 2.5-7 years, has reported reduction in mean DMFT/DMFS of between 7.1 and 35 % (Marthaler, 1968; 1974; Patz & Naujoks, 1970; Ringelberg et al., 1979; Cahen et al., 1982; Leous et al.,1995). Studies with amine fluoride gel between 1970 and 1989 with a duration of 1.5-7 years reported caries reductions of 31 - 53 % (Marthaler et al., 1970; Shern et al., 1976; Franke et al., 1977; Obersztyn & Kolwinski, 1984; Szőke & Kozma, 1989). In a 7-year clinical study using a combination of amine fluoride products a 43% reduction in DMFS mean values was found (Künzel et al., 1977). Madléna et al. (2002) published significant reduction in DMFS value (38 % including white spot lesions) and 34 % (not including white spot lesions) and a significant reduction in Plaque Index values with the combined use of amine fluoride containing toothpaste and gel in a high risk groups of adolescents. Márton et al. (2008) published beneficial effects of amine fluoride products.

The effects of Sn2F or AmF/Sn2F containing products on plaque accumulation were examined by many investigators (Øgaard et al., 1980; Bánóczy et al., 1989; Zimmermann et al., 1993; Mengel et al., 1996; Madléna et al., 2004; Gerardu et al., 2007). Madléna et al. (2009) proved the beneficial effects of amine fluoride /stannous fluoride containing products on periodontal parameters in patients treated with fixed orthodontic appliances. However, during a short term (four week-) examination period, there was no found significant difference between the groups using amine fluoride containing toothpaste only and the other group with combined use of toothpaste and mouthrinse containing the same ingredient. Although, at the same time numbers of streptococcus mutans and lactobacilli were reduced and level of periopathogen microorganisms also showed a very impressive decrease after even a four weeks use (Madléna et al., 2009; Nagy et al, 2010).

#### **4.2.6.7 Fluoride varnishes**

The development of fluoride varnishes started after the study of Mellberg et al. (1966). These authors found that considerable amounts of fluoride were released from enamel within the first 24 hours following the topical application of acidulated fluoride phosphate preparations. APF (Acidulated Phosphate Fluoride) increases the uptake of fluoride into the enamel because of its low pH. It is used mostly in the US. Schmid (1964) presented a topical fluoride method using a varnish with a high fluoride concentration. It was the Duraphat (Colgate Oral Pharmaceutical Inc., Canton, USA) which had the ability to adhere to tooth surfaces in the presence of saliva. Duraphat varnish consists of a natural resin (colophonium base with 5 % sodium fluoride (2.23 % F- ) dissolved in ethanol. It hardens the enamel in contact with saliva producing a temporary cover over the enamel. The patient is instructed to refrain from brushing for four hours after application (Retief et al, 1985; Staley 2008). The varnish also leaves calcium fluoride on the surface of the enamel in a CaF2-like material that is less soluble and most likely leaches away from the surface through the pellicle (Dijkman & Arends, 1988). The other similar varnish system (Fluor protector) (Vivadent, Shaan, Liechtenstein) was introduced by Arends and Schuthof in 1975. Fluor protector contains 0.1 % F- as difluorosilane dissolved in ethyl acetate and isoalylpropionate solution which has acidic properties. It is advisable that the patients avoid rinsing after application. Eating or brushing the teeth should also be avoided at least 45 minutes after the treatment. The differences can be found between the two varnishes are important in solvent, fluoride concentration, consistency, hardening time, colour, scent and taste. The varnishes coat the tooth surfaces as a thin layer that hardens a few minutes after application. The cost benefit ratio of fluoride varnishes is better then that of gels, and these products ensure the elimination the problem of compliance, as they are applied professionally (two to four times per year).

Beside of the above mentioned two types of fluoride varnish there are some other products. Duraflor (DenTrek, registered trademark of OMNI™ Preventive Care) is a 5 % NaF varnish containing xylitol and a bubble gum flavouring. Cavity shield contains 5% NaF in a neutral resin. The fluoride content is reported more uniform than that of Duraphat (Shen & Autio-Gold, 2002). The unit dose can be mixed easily and applied to teeth (Chu & Lo, 2006). Bifluorid 12 (Oceanwealth Horizon , (Voco), Düsseldorf, Germany) contains both NaF (2.7% F) and CaF2 (2.9 % F). This combination of fluoride allows more fluoride deposit on the surface of demineralized enamel than NaF varnish alone (Attin et al., 1995).

Clinical studies showed beneficial effects of fluoride varnishes on caries reduction in both permanent and deciduous dentitions (Marinho, 2004). In the permanent dentition it was ranged from 20-70% compared to untreated controls (Petersson, 1975; de Bruyn & Arends, 1987), although it is very important to consider that clinical results are strongly influenced by different factors ( e.g. caries prevalence, frequency of application of the varnish, caries risk etc.). Fluoride varnishes should be considered for use as a preventive adjunctive method to reduce demineralization adjacent to orthodontic brackets, especially in patients exhibiting pure compliance in oral hygiene and home fluoride use (Todd et al., 1999).

Advantages of fluoride varnishes are multiple: prolonged contact time acting as a slow release reservoir; these could be applied simply, quickly, easily; there is no need for widespread professional prophylaxis before the application of varnish because this procedure does not mean any additional effect, varnishes are safe, for even very young children. (Chu & Lo, 2006). Both parents and dentists prefer fluoride varnishes to fluoride gels (Warren et al., 2000). One disadvantage of Duraphat is its poor esthetic effect (a yellow film of varnish remains on the teeth for several hours after application) (Warren et al., 2000).

In a conclusion: there is moderate information is available on remineralization effectiveness of fluoride varnishes, but based on some investigations these could be offered for potential remineralization of the enamel (Castellano & Donly, 2004; Ogaard et al., 1984, 1996).

#### **4.2.6.8 Slow release fluoride devices**

92 Orthodontics – Basic Aspects and Clinical Considerations

first 24 hours following the topical application of acidulated fluoride phosphate preparations. APF (Acidulated Phosphate Fluoride) increases the uptake of fluoride into the enamel because of its low pH. It is used mostly in the US. Schmid (1964) presented a topical fluoride method using a varnish with a high fluoride concentration. It was the Duraphat (Colgate Oral Pharmaceutical Inc., Canton, USA) which had the ability to adhere to tooth surfaces in the presence of saliva. Duraphat varnish consists of a natural resin (colophonium

contact with saliva producing a temporary cover over the enamel. The patient is instructed to refrain from brushing for four hours after application (Retief et al, 1985; Staley 2008). The varnish also leaves calcium fluoride on the surface of the enamel in a CaF2-like material that is less soluble and most likely leaches away from the surface through the pellicle (Dijkman & Arends, 1988). The other similar varnish system (Fluor protector) (Vivadent, Shaan, Liechtenstein) was introduced by Arends and Schuthof in 1975. Fluor protector contains 0.1 % F- as difluorosilane dissolved in ethyl acetate and isoalylpropionate solution which has acidic properties. It is advisable that the patients avoid rinsing after application. Eating or brushing the teeth should also be avoided at least 45 minutes after the treatment. The differences can be found between the two varnishes are important in solvent, fluoride concentration, consistency, hardening time, colour, scent and taste. The varnishes coat the tooth surfaces as a thin layer that hardens a few minutes after application. The cost benefit ratio of fluoride varnishes is better then that of gels, and these products ensure the elimination the problem of compliance, as they are applied

Beside of the above mentioned two types of fluoride varnish there are some other products. Duraflor (DenTrek, registered trademark of OMNI™ Preventive Care) is a 5 % NaF varnish containing xylitol and a bubble gum flavouring. Cavity shield contains 5% NaF in a neutral resin. The fluoride content is reported more uniform than that of Duraphat (Shen & Autio-Gold, 2002). The unit dose can be mixed easily and applied to teeth (Chu & Lo, 2006). Bifluorid 12 (Oceanwealth Horizon , (Voco), Düsseldorf, Germany) contains both NaF (2.7% F) and CaF2 (2.9 % F). This combination of fluoride allows more fluoride deposit on the surface of demineralized enamel than NaF varnish

Clinical studies showed beneficial effects of fluoride varnishes on caries reduction in both permanent and deciduous dentitions (Marinho, 2004). In the permanent dentition it was ranged from 20-70% compared to untreated controls (Petersson, 1975; de Bruyn & Arends, 1987), although it is very important to consider that clinical results are strongly influenced by different factors ( e.g. caries prevalence, frequency of application of the varnish, caries risk etc.). Fluoride varnishes should be considered for use as a preventive adjunctive method to reduce demineralization adjacent to orthodontic brackets, especially in patients

exhibiting pure compliance in oral hygiene and home fluoride use (Todd et al., 1999).

Advantages of fluoride varnishes are multiple: prolonged contact time acting as a slow release reservoir; these could be applied simply, quickly, easily; there is no need for widespread professional prophylaxis before the application of varnish because this procedure does not mean any additional effect, varnishes are safe, for even very young children. (Chu & Lo, 2006). Both parents and dentists prefer fluoride varnishes to fluoride

) dissolved in ethanol. It hardens the enamel in

base with 5 % sodium fluoride (2.23 % F-

professionally (two to four times per year).

alone (Attin et al., 1995).

Considering that intraoral levels of fluoride play a key role in the dynamics of dental caries, it has been suggested that the use of controlled and sustained delivery systems can be considered as a means of controlling dental caries incidence in high risk individuals (Mirth, 1980).

In a review of Pessan et al. (2008) there are three types of devices: Copolymer membrane device, Glass device, Hydroxyapatite Eudragit RS100 diffusion controlled F system. The third one is the newest type of slow release device, which consists of a mixture of hydroxyapatite, NaF and Eudragit RS100; it contains 18 mg NaF and intended to release 0.15 mg F/day. It was demonstrated that the use of this device is able to significantly increase salivary and urinary F concentration for at least 1 month (Altinova et al., 2005). These devices are effective in raising intraoral F concentrations at levels able to reduce enamel solubility, resulting in caries protective effect. The use of slow relesase devices have been shown to have a very favourable benefit regarding cost-effecitiveness ratios (Toumba, 1996). Slow release devices can show a high anticaries effect for patients in high caries risk (Featherstone, 2006). Beside of this, such a device would overcome compliance problems also. It may not eliminate all carious lesions, but would lead to dramatic reduction and in combination with antibacterial treatments could indeed eliminate caries in high risk individuals (Pessan et al., 2008).

#### **4.2.7 Oral health care products for chemical plaque control**

#### **4.2.7.1 Chlorhexidine (CHX) containing products**

Among chemical plaque control agents chlorhexidine digluconate has proven to be the most effective and safe. It seems to be the most important antimicrobial ingredient in dental products, which is available in forms of rinse, gel and varnish. Inspite of the side effects, experienced first of all with the mouthrinse, using of these products is considered as the best possibility to treat gingivitis.

#### *4.2.7.1.1 Chlorhexidine mouthrinses*

These types of clorhexidine containing products [(e.g. Corsodyl mouthrinses (GlaxoSmithKline, Brentford, UK)] are the most frequently used form in dentistry for patients with gingivitis and periodontitis and before or after surgical procedures. Professionally chlorhexidine solution could be used for irrigation the inflammed pockets. Anderson et al. (1997) published that use of CHX mouthrinse in addition to regular oral hygiene was effective in reducing plaque and gingivitis in adolescents undergoing orthodontic treatment. Ready to use 0.1 or 0.2 % mouthrinses are available. Löe et al. (1972) published that twice daily rinsing with an 0.2% CHX solution reduced the total bacterial count in saliva by 85-90%. In practice, it is offered for twice-daily use for a limited, 6 week term because of the side effects of this agent. These are the discoloration of the teeth, fillings and tongue, taste disturbances (hot and bitter) in the mouth. It can leave an unpleasant aftertaste and repeated use lead to an impaired sense of taste and desquamations.

Based on the available reviews, chlorhexidine rinses have not been highly effective in preventing caries or at least the clinical data are not convincing (Autio-Gold, 2008). Due to the current lack of long term clinical evidence for caries prevention and reported side effect, CHX rinses should not really be recommended for caries prevention. However, the use of gels, and varnishes should also be studied further on to have evidence-based recommendations for their clinical role in caries prevention (Autio-Gold, 2008).

#### *4.2.7.1.2 Chlorhexidine gels*

Treatment with gel seems to be more effective than treatment with mouthrinse because the gel adheres to the tooth surface for longer period. Emilson (1981) published that CHX containing gel inhibited the plaque formation on tooth surfaces, effected on Gram positive and Gram negative bacteria such as mutans streptococci. CHX containing gel (e.g. Corsodyl with 1% CHX) (GlaxoSmithKline, Brentford, UK) similarly to other gels can be applied with toothbrush or in a custom made tray. The use of tray is better because the gel can attach the tooth surface without dilution and it is not distributed on the mucosa. The CHX gel ensures significant reduction in mutans streptococci, at the same time the patient has no unpleasent sense of taste. The time tested ingredient CHX reduces the growth of harmful bacteria and yeast. So there are less plaque formed on the teeth or appliances and the inflammation of gum tissues subsides.

Because of the beneficial effects, CHX containing gel suggested to use with a special soft tray. This therapy delivered by a tray which is offered for only older children, adolescents or adults who are able to apply the gel and tray safety, otherwise the gel should be used with toothbrush or with cotton roll.

Clinical studies defined the caries inhibiting effect of CHX (Zickert et al., 1982). It was also published that the effect of CHX gel is increased with combined use of fluoride gel (Ostela & Tenovuo, 1990; Meurman, 1988). In addition to the antibacterial CHX (0.11%), Cervitec gel (Vivadent, Schaan, Liechtenstein) containing fluoride (900 ppm) which promotes remineralization and protects the teeth from caries. At the same time it is an effective antimicrobial product. Cervitec gel can be used with interdental brushes, with toothbrush, tray or it can be applied directly on the gum.

#### *4.2.7.1.3 Chlorhexidine varnishes*

During the past decade, varnishes for local delivery of antimicrobial agents have been developed and investigated in vitro and in vivo. The inhibitory effect of CHX on mutans streptococci or new carious lesions was confirmed with fixed orthodontic appliances (Lundström and Krasse, 1987; Madléna et al., 2000; Derks et al., 2004) (Figure 14.).

orthodontic treatment. Ready to use 0.1 or 0.2 % mouthrinses are available. Löe et al. (1972) published that twice daily rinsing with an 0.2% CHX solution reduced the total bacterial count in saliva by 85-90%. In practice, it is offered for twice-daily use for a limited, 6 week term because of the side effects of this agent. These are the discoloration of the teeth, fillings and tongue, taste disturbances (hot and bitter) in the mouth. It can leave an unpleasant aftertaste and repeated use lead to an impaired sense of taste and

Based on the available reviews, chlorhexidine rinses have not been highly effective in preventing caries or at least the clinical data are not convincing (Autio-Gold, 2008). Due to the current lack of long term clinical evidence for caries prevention and reported side effect, CHX rinses should not really be recommended for caries prevention. However, the use of gels, and varnishes should also be studied further on to have evidence-based

Treatment with gel seems to be more effective than treatment with mouthrinse because the gel adheres to the tooth surface for longer period. Emilson (1981) published that CHX containing gel inhibited the plaque formation on tooth surfaces, effected on Gram positive and Gram negative bacteria such as mutans streptococci. CHX containing gel (e.g. Corsodyl with 1% CHX) (GlaxoSmithKline, Brentford, UK) similarly to other gels can be applied with toothbrush or in a custom made tray. The use of tray is better because the gel can attach the tooth surface without dilution and it is not distributed on the mucosa. The CHX gel ensures significant reduction in mutans streptococci, at the same time the patient has no unpleasent sense of taste. The time tested ingredient CHX reduces the growth of harmful bacteria and yeast. So there are less plaque formed on the teeth or appliances and the inflammation of

Because of the beneficial effects, CHX containing gel suggested to use with a special soft tray. This therapy delivered by a tray which is offered for only older children, adolescents or adults who are able to apply the gel and tray safety, otherwise the gel should be used with

Clinical studies defined the caries inhibiting effect of CHX (Zickert et al., 1982). It was also published that the effect of CHX gel is increased with combined use of fluoride gel (Ostela & Tenovuo, 1990; Meurman, 1988). In addition to the antibacterial CHX (0.11%), Cervitec gel (Vivadent, Schaan, Liechtenstein) containing fluoride (900 ppm) which promotes remineralization and protects the teeth from caries. At the same time it is an effective antimicrobial product. Cervitec gel can be used with interdental brushes, with toothbrush,

During the past decade, varnishes for local delivery of antimicrobial agents have been developed and investigated in vitro and in vivo. The inhibitory effect of CHX on mutans streptococci or new carious lesions was confirmed with fixed orthodontic appliances

(Lundström and Krasse, 1987; Madléna et al., 2000; Derks et al., 2004) (Figure 14.).

recommendations for their clinical role in caries prevention (Autio-Gold, 2008).

desquamations.

*4.2.7.1.2 Chlorhexidine gels* 

gum tissues subsides.

toothbrush or with cotton roll.

*4.2.7.1.3 Chlorhexidine varnishes* 

tray or it can be applied directly on the gum.

Fig. 14. The effect of chlorhexidine containing varnish (Cervitec) on newly developed carious lesions during orthodontic treatment (\*p<0.05)

The number of the new carious lesions was significantly lower in the quadrants treated with Cervitec than in the quadrants treated with placebo (\*p<0.05).( Madléna et al., 2000).

It has been concluded by a review that the most persistent reduction of mutans streptococci have been achived by chlorhexidine varnishes followed by gels and lastly mouthrinses (Autio-Gold, 2008). Cervitec plus is a newer, now available member of the "Cervitec family" (Vivadent, Shaan, Liechtenstein) containing chlorhexidine and thymol). Comparing three varnish systems (Chlorzoin, containing CHX 10% (Knowell Therapeutic Technologies, owned company Toronto, Canada), EC 40, containing CHX 40% (Biodent BV, Nijmegen, The Netherlands), Cervitec Plus, containing CHX 1%), a single application of a highly concentrated varnish (EC 40), is sufficient even with reduced contact time, whereas repeated applications and longer retention time required for varnishes with lower chlorhexidine concentration (Chlorzoin and Cervitec). All of the three varnish systems had a similar effect on mutans streptococci in the oral flora. However, none of these varnishes could maintain a significant suppression of mutans streptococci for a period of up to 6 months (repeated application is required for the effectiveness). Concerning the chlorhexidine containing varnishes there may be noticed some advers effects, similarly to other chlorhexidine containing products: staining of teeth and tongue, or taste disturbancies associated with accidental contact of CHX varnish with oral mucosa (Matthijs & Adriaens, 2002).

The most sensitive bacteria to chlorhexidine-thymol varnish (Cervitec plus) are Porphyromonas gingivalis and Aggregatibacter Actynomycetemcomitans. Therefore, chlorhexidine varnishes may be promising for the prevention of periodontal disease or as an adjunct to periodontal therapy (Petersson et al. 1992; Matthijs & Adriaens, 2002). Twetman and Petersson (1997) reported that a combined treatment with a chlorhexidine – thymol and a fluoride varnish resulted in a longer inhibiting effect on interdental plaque samples, than chlorhexidine-thymol varnish alone. The use of dental varnishes with antimicrobial properties might have potential benefits for patients with chronic gingival inflammation (Matthijs & Adriaens, 2002).

#### **4.2.7.2 Other products**

#### *4.2.7.2.1 Essential oils containing products - Listerine (Johnson & Johnson, Maidenhead, UK)*

Active ingredients of this oral rinse are essential oils (eucalyptol, thymol, menthol) for bactericid effect, contains methyl salicylate (against analgesia and inflammation) and alcohol (in which the active ingredients are diluted). It should be used as a rinse twice daily for 1 minute. As it does not contain any fluoride or its fluoride concentration is very low (in the newer products), has no effect on caries, but it has an antigingivitis effect According to a systematic review published by Van Leeuwen et al. (2011), in long term use, the standardized formulation of essential-oil mouthwas appeared to be a reliable alternative to chlorhexidine mouthwash with respect to parameters of gingival inflammation. Listerine toothpaste is not established as effective product against gingivitis (Boyd, 2001).

#### *4.2.7.2.2 Triclosan-containing products - (Colgate total) (Colgate Palmolive Co. USA)*

It is also an antigingivitis agent including good taste and supragingival calculus control (Volpe et al., 1996). Triclosan is available only in toothpaste (Colgate total) (Colgate Palmolive Co. USA), has an antibacterial effect and is often combined with zinc to increase the antiplaque effect. Thus, it may give potential benefits for orthodontic patients as a supplement to fluoride dentifrice during orthodontic treatment.

#### *4.2.7.2.3 Hyaluronic acid containing products (Gengigel) (Ricefarma, Milano, Italy)*

Hyaluronic acid is naturally occures as physiological constituent of connective tissue (especially in gingival mucosa). It ensures antioedematous and tissue repair functions, helps to perform an antiinflammatoric effect, so can be helpful during the orthodontic treatment with fixed appliances. The lack of hyaluronic acid is responsible for the continuation of the inflammatory condition. In these cases application of hyaluronic acid provides periodontal tissue with accelerated repair functions by preventing the deficiency of natural gingival hyaluronic acid and enhancing its effects.

The hyaluronic acid containing Gengigel can be available in forms gel, rinse and spray. Pistorius et al. (2002) published positive effects of Gengigel spray: this product ensured significant improvements in gingival parameters in case of gingivitis, after 7 days application. All Gengigel products are suggested to use in case of gingivitis, gingival bleeding, gingival pockets (also gingival recession, abrasion and other tissue trauma etc.), after the correct oral hygiene three to five times a day (after main meals) for 3-4 weeks, continuing until the symptomes have disappeared. Side effect has not been experienced with these products.

#### *4.2.7.2.4 Antibiotics*

Use of oral or systemic antibiotic therapy is indicated to eliminate specific pathogenic organisms. However, antibiotic therapy can never replace the mechanical removal of subgingival deposits and it should be only a supplemental, supportive therapy, similarly to the treatment of serious periodontal diseases, but this indication belongs to an experienced periodontist and should not be administrated routinly by an orthodontist.

#### **4.3 Remineralization – Treatment of white spot lesions after removal of fixed appliance**

#### **4.3.1 Fluorides**

96 Orthodontics – Basic Aspects and Clinical Considerations

Active ingredients of this oral rinse are essential oils (eucalyptol, thymol, menthol) for bactericid effect, contains methyl salicylate (against analgesia and inflammation) and alcohol (in which the active ingredients are diluted). It should be used as a rinse twice daily for 1 minute. As it does not contain any fluoride or its fluoride concentration is very low (in the newer products), has no effect on caries, but it has an antigingivitis effect According to a systematic review published by Van Leeuwen et al. (2011), in long term use, the standardized formulation of essential-oil mouthwas appeared to be a reliable alternative to chlorhexidine mouthwash with respect to parameters of gingival inflammation. Listerine toothpaste is not established as effective product against

It is also an antigingivitis agent including good taste and supragingival calculus control (Volpe et al., 1996). Triclosan is available only in toothpaste (Colgate total) (Colgate Palmolive Co. USA), has an antibacterial effect and is often combined with zinc to increase the antiplaque effect. Thus, it may give potential benefits for orthodontic patients as a

Hyaluronic acid is naturally occures as physiological constituent of connective tissue (especially in gingival mucosa). It ensures antioedematous and tissue repair functions, helps to perform an antiinflammatoric effect, so can be helpful during the orthodontic treatment with fixed appliances. The lack of hyaluronic acid is responsible for the continuation of the inflammatory condition. In these cases application of hyaluronic acid provides periodontal tissue with accelerated repair functions by preventing the deficiency of natural gingival

The hyaluronic acid containing Gengigel can be available in forms gel, rinse and spray. Pistorius et al. (2002) published positive effects of Gengigel spray: this product ensured significant improvements in gingival parameters in case of gingivitis, after 7 days application. All Gengigel products are suggested to use in case of gingivitis, gingival bleeding, gingival pockets (also gingival recession, abrasion and other tissue trauma etc.), after the correct oral hygiene three to five times a day (after main meals) for 3-4 weeks, continuing until the symptomes have disappeared. Side effect has not been experienced

Use of oral or systemic antibiotic therapy is indicated to eliminate specific pathogenic organisms. However, antibiotic therapy can never replace the mechanical removal of subgingival deposits and it should be only a supplemental, supportive therapy, similarly to the treatment of serious periodontal diseases, but this indication belongs to an experienced

periodontist and should not be administrated routinly by an orthodontist.

*4.2.7.2.1 Essential oils containing products - Listerine (Johnson & Johnson, Maidenhead, UK)* 

*4.2.7.2.2 Triclosan-containing products - (Colgate total) (Colgate Palmolive Co. USA)* 

*4.2.7.2.3 Hyaluronic acid containing products (Gengigel) (Ricefarma, Milano, Italy)* 

supplement to fluoride dentifrice during orthodontic treatment.

hyaluronic acid and enhancing its effects.

with these products. *4.2.7.2.4 Antibiotics* 

**4.2.7.2 Other products** 

gingivitis (Boyd, 2001).

Fluoride increses the initial rate of remineralization of early enamel lesions and slow down the progress of carious process by reacting with the minerals present in the surface of the lesion. Enamel can be remineralized with meticulous toothbrushing twice per day, with fluoridated dentifrice. Additional fluoride application can further enhance the remineralization process. This would include eg. fluoridated dentifrice with higher dose, fluoride rinses, topical fluoride gels, fluoride varnishes and professionally applied topical fluoride such as 2% sodium fluoride, 8% stannous fluoride and 1.23% acidulated phosphate fluoride (Donly & Sasa, 2008). At the same time it was published that when high doses of fluoride are used locally (mainly during the first few weeks after completed the orthodontic treatment), the arrested lesion stays the same size and frequently becomes unsightly and stained with organic debris which is esthetically not optimal on the labial surfaces (Ogaard et al., 2004; Willmot, 2008). To avoid arresting the lesion and obtunding the surface layer several authors recommended low dose fluoride applications to enhance subsurface remineralization It was published that 50 ppm fluoride mouthrinse had a higher efficiency for remineralization than control solution for regular mouthrinse containing 250 ppm (Linton, 1996; Lagerwij et al., 1997). In spite of these observations, Wilmot (2004) did not confirm the therapeutic effect of low fluoride (50 ppm) products and concluded that postorthodontic white spot lesions (WSL) reduced in size during the 6 months by approximately half of the original size, but there was no clinical advantage of using the low fluoride formulation of mouthrinse/toothpaste in this process comparing to those of using fluoride free products as a control. The mean size of the lesions reduced with time in both groups. A therapeutic effect (less than 30%) was non significant. Beside of the labial surfaces application of concentrated fluoride was suggested to prevent the progresson of the lesions. It has been also suggested that acid etching of fluoride treated lesions could facilitate remineralization of the lesions by oral fluids (Hicks et al., 1984).

#### **4.3.2 Use of Casein Phosphopeptide-Amorphus Calcium Phosphate (CPP-ACP)**

Enamel can also be remineralized with Casein Phosphopeptide-Amorphus Calcium Phosphate preparations. CPP-ACP is capable to be absorbed through the enamel surface and could affect the carious process (Reynolds, 1987) CPP-ACP system (the trade name is RecaldentTM) which allows freely available calcium and phosphate ions to attach to enamel and reform into calcium phosphate crystals. The free calcium and phosphate ions released from the CPP-ACP and deposit into the enamel rods. The available types of these products: water based mousse, topical creme (these are the most frequently used forms) mouthrinses, sugarfree lozenges and chewing gum (which is not suggested for orthodontic patients).

As CPP-ACP is derived from milk casein, should not be used in patient with protein and or hydroxybenzoates allergy. Studies of the effects of CPP-ACP show a dose related increase in enamel remineralization (Sudjalim et al., 2006). These products have beneficial effects in reducing area of demineralized lesions after 4 weeks (Bröchner et al., 2011).

Using the mousse (GC Tooth Mousse) to treat post-orthodontic lesions, a thermoplastic retainer needs in which a pea sized amount of CPP-ACP mousse has been spread evenly. After proper oral hygiene the patient places the mousse at night and wears the retainer throughout sleep. Flavouring helps to stimulate saliva flow rate which helps to rinse bacteria and food residues from the teeth and enhances the effectiveness of CPP ACP in the mouth.

The GC MI Paste Plus is a water based topical creme containing Recaldent TM CPP-ACP and fluoride (900 ppm). It can be used on teeth at home when the patient apply the products with a tray (Figure 15.), similarly to the mousse or without a tray simply with clean finger or cotton tipped applicator and let it work for 3-5 minutes.

Fig. 15. Use of MI Paste Plus with a tray.

This material containing CPP ACP and fluoride can help in remineralization process e.g. after finishing the orthodontic treatment with fixed appliance

#### **4.3.3 Microabrasion**

Enamel microabrasion abrades the enamel surface, leaving a highly polished surface with Ca phosphate packed into the interprismatic enamel surface space. This highly polished enamel surface can then be bleached.

This method has been widely used for the removal of superficial non-carious enamel defects for which it can be use for example performing 18% hydrochloric acid and pumice technique (Welbury & Shaw, 1990; Rodd & Davidson, 1997). This method seems to be an effective treatment approach for cosmetic improvement of long-standing postorthodontic demineralized enamel lesions (Welbury & Carter, 1993; Croll & Bullock, 1994). Studies demonstrate that although microabrasion removes small amounts of the enamel surface, the new polished surface is less susceptible to bacterial colonization and demineralization than natural non abraded enamel (Segura et al., 1997 a,b).

Following the microabrasion technique, a 4 minute 2% sodium fluoride treatment is recommended. If the microbrasion technique could not ensure optimal esthetics and some whitened enamel is still remain, vital tooth bleaching can be considered (Donly & Sasa, 2008).

### **5. Conclusion**

98 Orthodontics – Basic Aspects and Clinical Considerations

After proper oral hygiene the patient places the mousse at night and wears the retainer throughout sleep. Flavouring helps to stimulate saliva flow rate which helps to rinse bacteria and food residues from the teeth and enhances the effectiveness of CPP ACP in the

The GC MI Paste Plus is a water based topical creme containing Recaldent TM CPP-ACP and fluoride (900 ppm). It can be used on teeth at home when the patient apply the products with a tray (Figure 15.), similarly to the mousse or without a tray simply with clean finger or

This material containing CPP ACP and fluoride can help in remineralization process e.g.

Enamel microabrasion abrades the enamel surface, leaving a highly polished surface with Ca phosphate packed into the interprismatic enamel surface space. This highly polished

This method has been widely used for the removal of superficial non-carious enamel defects for which it can be use for example performing 18% hydrochloric acid and pumice technique (Welbury & Shaw, 1990; Rodd & Davidson, 1997). This method seems to be an effective treatment approach for cosmetic improvement of long-standing postorthodontic demineralized enamel lesions (Welbury & Carter, 1993; Croll & Bullock, 1994). Studies demonstrate that although microabrasion removes small amounts of the enamel surface, the new polished surface is less susceptible to bacterial colonization and demineralization than

cotton tipped applicator and let it work for 3-5 minutes.

Fig. 15. Use of MI Paste Plus with a tray.

enamel surface can then be bleached.

natural non abraded enamel (Segura et al., 1997 a,b).

**4.3.3 Microabrasion** 

after finishing the orthodontic treatment with fixed appliance

mouth.

The number of orthodontic treatments among them the frequency of treatments with fixed appliances is increasing nowadays. In some cases orthodontic treatments mean caries preventive interventions when tooth movements may reliese crowding or other anomalies thus can contribute the effectiveness of proper oral hygiene. On the other hand these treatments may have causative effect on plaque induced oral diseases. For these patients effective preventive oral health care is needed and orthodontists have to be responsible for helping to keep proper oral hygiene in their patients.

The risk of caries can be determined by different tests (e.g. SM, LB chairside tests) or assessment of some salivary factors. Measurement of plaque has been found also very useful to determinate the risk of caries. The severity of periodontal diseases and the risk for these diseases can be determined by clinical measurements. Bleeding on probing remained the most certain clinical sign of periodontal inflammations. Chairside tests are available to measure different parameters associated with periodontitis, but presently there is no such a particular parameter or method predicting the possibility of periodontitis.

For prevention of caries and periodontal diseases clinicians should instruct the patients effectively to be able to perform proper oral hygiene. Regular removal of plaque and calculus at critical places can help a lot. Regular recalls, well constructed programs of regular professional oral hygiene can give great help for at-risk patients.

Beside of dietary counselling, to reduce cariogenic bacteria, use of professional and home care measures and techniques (cleaning instruments, fluoridated paste, restorative methods, application of fluoride and chlorhexidine containig materials, plaque disclosing products, special toothbrushes and other equipments etc.) could provide help.

Because of the increasing number of patients in need of orthodontic appliances, this chapter is important and useful not only for orthodontists, but general dentists or periodontists and dental students as well.

### **6. Acknowledgements**

The author is greatfully acknowledge the review of the chapter by professor Gábor Nagy and excellent technical assistance of Ágnes Siki to find all necessary data of the references.

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## **Other Applications of Photo Catalyst in Dental Treatments in Diverse Fields**

Seung-Ho Ohk1 and Hyeon-Shik Hwang2

*1Department of Oral Microbiology, 2Department of Orthodontics and Dental Science Research Institute, Chonnam National University Korea* 

#### **1. Introduction**

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children highly infected with the bacterium streptococcus-mutans, *Arch Oral Biol* 

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brackets: an in-vivo study, *Am J Orthod Dentofac Orthop* 139(5): 650-656. Vanarsdall, R. J.(2000). Periodontal/orthodontic interrelationships, In: *Orthodontics: Current* 

varnishes, *Acta Odontol Scand* 57(5): 263-266.

(Third edition), ISBN 0-8151-9363-7, St Louis, USA

A systematic review, *J Periodontol* 82(2): 174-194.

vitro study, *Am J Orthod Dentofac Orthop* 114(6): 668-674.

pigmentation from enamel, *Dent Update* 17(4): 161-163.

*and Fluoride Use*, WHO, Genf: 1-37. ISBN: 92-4-120846-5

orthodontic treatment, *Scand J Dent Res* 79(6): 394-401.

fixed appliances, *Scand J Dent Res* 79(3): 183-192.

concepts, *Angle Orthod* 45(1): 72-81.

*Dent Res* 59(6): 1065-1066.

27(10): 861-868.

351.

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S14.

181-185.

219.

and separate gland secretions after topical treatment with three different fluoride

monomer-containing adhesive on enamel demineralization around orthodontic

*principles and techniques* Graber, T. M. & Vanarsdall, R. .J. (Eds.), 801-838. Mosby Inc,

to chlorhexidine with respect to plaque and parameters of gingival inflammation:

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adjacent to orthodontic brackets bonded with hybrid glass ionomer cements: An in

technique in the treatment of post-orthodontic decalcification, *Br J Orthod* 20(3):

Photocatalysts do not make the light faster. The term 'photocatalyst' represents chemical substances that act as a catalyst when exposed to light. For several decades numerous studies have been published about photocatalyst in water treatment process and air pollution control. Among several photocatalysts, TiO2 has been considered as the most useful and harmless substance. With the illumination of UV-A light, TiO2 photocatalysts decompose organic compounds through oxidation, with hydroxyl radicals (HO) being produced by the oxidation of water. Various methods have been introduced for the surface modification of orthodontic treatment devices. Among them, Sol-gel dip-coating, CVD and PE-CVD methods were applied to coat photocatalytic TiO2 on the surface of orthodontic wires and brackets. The antibacterial activities of the surface-modified orthodontic wires and brackets were demonstrated on *Streptococcus mutans* and *Porphyromonas gingivalis*. Viable cell counts with dilution-agar plate method and spectrophotometry were carried out to evaluate the antibacterial effect of photocatalytic TiO2. Besides the photocatalytic degradation of organic compounds, there are several unique characteristics of photocatalytic TiO2 were reported. In virtue of those characteristics it can be used in various ways such as preventing air contamination, antifog glasses and anti-bacterial paints. Sometimes many useful points are considered as handicaps in other point of view and vice versa. For example, to show photocatalytic activity for the TiO2, usually it needs illumination with wavelength of less than 380. However, this drawback could be, in turn, used as a useful tool to control the release of hydroxyl radical from water since there is not much of UV-A in normal sun light.

The definition of photocatalysts and basic mechanism of photocatalytic activity will be described in this chapter.

Application and evaluation methods of photocatalyst, antibacterial efficiency on oral pathogens and safety of photocatalyst will be mentioned also. With the advantage of photocatalytic TiO2, safety, versatile applications and other important remarkable characteristics of photocatalytic TiO2 will be described in this section.

#### **2. What is photocatalyst?**

#### **2.1 Photochemical reaction**

Does the 'photocatalyst' catalyze photo-reaction or catalyze reactions with the exposure of light? Literally, both of the meanings are correct. However, the later will be explained in this chapter.The term 'photocatalyst' represents chemical substance that act as a catalyst when exposed to light. 'Photocatalytic reaction' again can be classified as one of photo-reactions. The most popular example of photo-reaction is a photographic film. Although digital imaging technique is popular these days, one of the most excellent inventions was the development of photography. In a traditional way of taking photo, a target image was exposed to a roll of film installed in the dark space of camera. This photographic film is a sheet of plastic paper such as polyester, nitrocellulose or cellulose acetate coated with a light-sensitive silver bromide emulsion. When the emulsion is exposed to sufficient light, bromide ion (Br-) produces brom-atom and electron (e-). This electron, in turns, binds to silver ion (Ag+) to make metallic silver, which blocks light and appears as the black part of film negative.

> Br- + [light] Br + e-Ag+ + e- Ag

In 1972, Honda and Fujishima have reported electrochemical decomposition of water (Fujishima & Honda, 1972). They have found that when platinum and titanium dioxide (TiO2) were connected as cathode and anode, respectively, water is decomposed with a illumination of xenon lamp to make hydrogen and oxygen molecules (Fig.1 ).

Fig. 1. Decomposition of water with photocatalytic TiO2.

2H2O + [Light, < 400 nm] + TiO2 2H + O2

This is a coupled reaction of reduction (4H+ 2H2) and oxidation (4OH- O2 + 2H2O) with four molecules of water (4H2O, 4H+ + 4OH- ) producing hydrogen and oxygen molecules. Titanium dioxide can absorb light energy of below 400 nm and emits electrons to catalyze the decomposition of water.

#### **2.2 Photocatalytic TiO2**

112 Orthodontics – Basic Aspects and Clinical Considerations

Does the 'photocatalyst' catalyze photo-reaction or catalyze reactions with the exposure of light? Literally, both of the meanings are correct. However, the later will be explained in this chapter.The term 'photocatalyst' represents chemical substance that act as a catalyst when exposed to light. 'Photocatalytic reaction' again can be classified as one of photo-reactions. The most popular example of photo-reaction is a photographic film. Although digital imaging technique is popular these days, one of the most excellent inventions was the development of photography. In a traditional way of taking photo, a target image was exposed to a roll of film installed in the dark space of camera. This photographic film is a sheet of plastic paper such as polyester, nitrocellulose or cellulose acetate coated with a light-sensitive silver bromide emulsion. When the emulsion is exposed to sufficient light,

silver ion (Ag+) to make metallic silver, which blocks light and appears as the black part of

+ [light] Br + e-

Ag+ + e- Ag In 1972, Honda and Fujishima have reported electrochemical decomposition of water (Fujishima & Honda, 1972). They have found that when platinum and titanium dioxide (TiO2) were connected as cathode and anode, respectively, water is decomposed with a

2H2O + [Light, < 400 nm] + TiO2 2H + O2 This is a coupled reaction of reduction (4H+ 2H2) and oxidation (4OH- O2 + 2H2O) with four molecules of water (4H2O, 4H+ + 4OH-) producing hydrogen and oxygen molecules.

). This electron, in turns, binds to

) produces brom-atom and electron (e-

Br-

illumination of xenon lamp to make hydrogen and oxygen molecules (Fig.1 ).

Fig. 1. Decomposition of water with photocatalytic TiO2.

**2. What is photocatalyst? 2.1 Photochemical reaction** 

bromide ion (Br-

film negative.

Several substances have been known to have photocatalytic activities such as ZnO, Nb2O5, WO3, SnO2, ZrO2, CdS, ZnS, CdSe, and GaP. One of the most important reason that titanium dioxide is widely used is that it is chemically stable in most of acid, base and organic solvents. In the contrary, ZnO has similar energy band and high photocatalytic activity. However, when it is illuminated with light in aqueous solution, it can be easily dissolved in water as a Zn+ ion. It also can be easily melt with sulfuric acid or nitric acid. Therefore, ZnO cannot be used separately.

#### **3. Surface modification of orthodontic treatment devices**

#### **3.1 Anodic oxidation**

When metal or silicon plates are immersed in an appropriate electrolyte a fine and rigid thin oxidized film will form on the surfaces plates. Anodic oxidation of aluminum is commonly introduced for their (semi-) transparent, anti-corrosion characteristics. The film composed by anodic oxidation usually shows stable conductivity. Neutral or acidic electrolytes are commonly used for aluminum, but there are not many options for other metals. Several dental implants have used anodic oxidation method for the surface modification to enhance their bone integration efficiency (Schupbach *et al.*, 2005).

#### **3.2 Sol-gel dip-coating method**

Dip-coating method is the oldest and most commonly used technique in deposition of thin film. Jenaer Glaswerk Schott & Gen are the first who have filed a patent with dip-coating technique for silica film in 1939. Sol-gel coatings, on the other hand, are being studied and applied in a diverse way such as protective coatings, passivation layers, ferroelectrics, sensors and membranes. The sol-gel dip-coating method uses inorganic precursors in aqueous or organic solvents. Those precursors are hydrolyzed and condensed to form polymers. Solid substrates are usually taken out of coating bath vertically at a constant speed. While taken out of the bath, the substrate entrains the liquid. Along with the evaporation of the solvent, wedge shaped film is formed on the surface of substrate. A lot of researchers have used sol-gel dip-coating method to study the application of the photocatalytic TiO2 (Dongare *et al.*, 2003; Lee *et al.*, 2004; Zainal *et al.*, 2005).

#### **3.3 CVD (Chemical vapor deposition) and PE-CVD (Plasma enhanced-CVD) method**

Chemical vapor deposition method is the most widely used technique in semiconductor industries. It can form thin films from different precursors onto a substrate. In a CVD technique, a substrate is exposed to multiple volatile precursors with an inert gaseous carrier at high temperature and pressure. Those volatile precursors react or decompose on the surface of desired substrates, which form a thin film. Since CVD is one of the most well studied, and set up techniques, it is good for mass production.

Plasma enhanced CVD (PE-CVD) is a more progressed and important technique in VLSI (Very-large-scale integration) and TFT (Thin film transistor) manufacturing. The most important advantage of PE-CVD is low process temperature, which enables lower the manufacturer's budget. It uses plasma energy instead of heat energy for the reaction between precursors and substrates. Due to the wide range of applications of photocatalytic TiO2, much of studies have been reported with CVD and PE-CVD technique for the application (Giavaresi *et al.*, 2003; Gluszek *et al.*, 1997; Gonzalez-Elipe *et al.*, 2004; Mills *et al.*, 2002).

### **4. Antibiotic effect of photocatalytic TiO2**

After Fujishima and Honda (Fujishima & Honda, 1972) reported the photolytic effect of TiO2 in 1972, a series of efforts have been carried out to apply in various ways. Among them Matsunaga *et al*. have first reported photocatalytic TiO2 has antibacterial effect on *Lactobacillus acidophilus, Saccharomyces cerevisiae* and *Escherichia coli* (Matsunaga *et al.*, 1985). Since hydroxyl radical (HO•) became of interest in decomposing organic compounds, it is no wonder to try antibacterial effect on various microorganisms. It was well documented that chemical oxidation with hydroxyl radical has a high activity in degradation of organic compounds (Ireland & Valinieks, 1992). Accordingly, antibacterial effect of photocatalytic TiO2 that could efficiently produce hydroxyl radical in aqueous solution with illumination of light was demonstrated. Major microorganisms that have tested with photocatalytic TiO2 were listed in Table 1.

According to the early report presented by Ireland *et al*. *Escherichia coli* showed rapid cell death in a mixture with the anatase crystalline form of titanium dioxide (Ireland *et al.*, 1993). Cho *et al*. also explained correlation between HO• radicals and the rate of *E. coli* inactivation which indicates that the HO• radical is the primary oxidant species responsible for inactivating *E. coli* in the UV/TiO2 process (Cho *et al.*, 2004). Effort to clarify the antibacterial effect of titanium plate by surface modifications has been also reported. Yoshinari *et al*. tried to modify the surface of titanium plate by ion implantation (Ca+, N+, and F+), oxidation (anode oxidation, titania spraying), ion plating (TiN, alumina), and ion beam mixing (Ag, Sn, Zn, Pt) with Ar+ (Yoshinari *et al.*, 2001). Among them they have reported that F+ implanted specimens significantly inhibited the growth of both *Porphyromonas gingivalis* and *Actinobacillus actinomycetemcomitans*. However, this antibacterial effect might be caused by the formation of a metal fluoride complex on the surfaces.

Since orthodontic wires and brackets provide a sufficient habitat for oral infectious microorganisms, orthodontic patients might have a higher risk of contracting other dental diseases (Balenseifen & Madonia, 1970; Sakamaki & Bahn, 1968; Scheie *et al.*, 1984). Therefore, as well as the orthodontic patients, clinicians should pay attention to reduce the chances for oral microorganisms to adhere to the surfaces of teeth and orthodontic wires. Chun *et al*. have tried to apply photocatalytic TiO2 to orthodontic wires (Chun *et al.*, 2007). They used sol-gel dip coating method to modify the surfaces of wires. Special device for efficient illumination of UV-light to TiO2-coated orthodontic wires using quartz cylinder was designed and used for the adhesion assay (Fig. 2). Since *Streptococcus mutans* that causes dental caries can easily adhere to tooth surface or orthodontic devices attached to tooth surfaces anti-adhesion effect of photocatalytic TiO2 was monitored. Modified surface of wires showed effectively reduced adhesion of bacterial cells. Surface modification with

Plasma enhanced CVD (PE-CVD) is a more progressed and important technique in VLSI (Very-large-scale integration) and TFT (Thin film transistor) manufacturing. The most important advantage of PE-CVD is low process temperature, which enables lower the manufacturer's budget. It uses plasma energy instead of heat energy for the reaction between precursors and substrates. Due to the wide range of applications of photocatalytic TiO2, much of studies have been reported with CVD and PE-CVD technique for the application (Giavaresi *et al.*, 2003; Gluszek *et al.*, 1997; Gonzalez-Elipe *et al.*, 2004; Mills *et al.*,

After Fujishima and Honda (Fujishima & Honda, 1972) reported the photolytic effect of TiO2 in 1972, a series of efforts have been carried out to apply in various ways. Among them Matsunaga *et al*. have first reported photocatalytic TiO2 has antibacterial effect on *Lactobacillus acidophilus, Saccharomyces cerevisiae* and *Escherichia coli* (Matsunaga *et al.*, 1985). Since hydroxyl radical (HO•) became of interest in decomposing organic compounds, it is no wonder to try antibacterial effect on various microorganisms. It was well documented that chemical oxidation with hydroxyl radical has a high activity in degradation of organic compounds (Ireland & Valinieks, 1992). Accordingly, antibacterial effect of photocatalytic TiO2 that could efficiently produce hydroxyl radical in aqueous solution with illumination of light was demonstrated. Major microorganisms that have tested with photocatalytic TiO2

According to the early report presented by Ireland *et al*. *Escherichia coli* showed rapid cell death in a mixture with the anatase crystalline form of titanium dioxide (Ireland *et al.*, 1993). Cho *et al*. also explained correlation between HO• radicals and the rate of *E. coli* inactivation which indicates that the HO• radical is the primary oxidant species responsible for inactivating *E. coli* in the UV/TiO2 process (Cho *et al.*, 2004). Effort to clarify the antibacterial effect of titanium plate by surface modifications has been also reported. Yoshinari *et al*. tried to modify the surface of titanium plate by ion implantation (Ca+, N+, and F+), oxidation (anode oxidation, titania spraying), ion plating (TiN, alumina), and ion beam mixing (Ag, Sn, Zn, Pt) with Ar+ (Yoshinari *et al.*, 2001). Among them they have reported that F+ implanted specimens significantly inhibited the growth of both *Porphyromonas gingivalis* and *Actinobacillus actinomycetemcomitans*. However, this antibacterial effect might be caused by

Since orthodontic wires and brackets provide a sufficient habitat for oral infectious microorganisms, orthodontic patients might have a higher risk of contracting other dental diseases (Balenseifen & Madonia, 1970; Sakamaki & Bahn, 1968; Scheie *et al.*, 1984). Therefore, as well as the orthodontic patients, clinicians should pay attention to reduce the chances for oral microorganisms to adhere to the surfaces of teeth and orthodontic wires. Chun *et al*. have tried to apply photocatalytic TiO2 to orthodontic wires (Chun *et al.*, 2007). They used sol-gel dip coating method to modify the surfaces of wires. Special device for efficient illumination of UV-light to TiO2-coated orthodontic wires using quartz cylinder was designed and used for the adhesion assay (Fig. 2). Since *Streptococcus mutans* that causes dental caries can easily adhere to tooth surface or orthodontic devices attached to tooth surfaces anti-adhesion effect of photocatalytic TiO2 was monitored. Modified surface of wires showed effectively reduced adhesion of bacterial cells. Surface modification with

2002).

were listed in Table 1.

**4. Antibiotic effect of photocatalytic TiO2** 

the formation of a metal fluoride complex on the surfaces.

photocatalytic TiO2 enabled orthodontic wires to have effective anti-adherent characteristics. Using Scanning electron microscope damaged bacterial cell surfaces could be observed when treated with TiO2. Similar effect was observed in *Porphyromonas gingivalis*, which is known as one of the major pathogen of periodontitis.


Table 1. Major microorganisms that have positive results with photocatalytic TiO2.

Other than antibacterial effect, the efficacies of TiO2 on viruses and prion have also demonstrated. Sang *et al*. have tested rotavirus, astrovirus, and feline calcivirus (FCV) to verify the inactivation effect of TiO2 with irradiation of visible light (Sang *et al.*, 2007). According to the report, light activated TiO2 could partially degrade dsRNA of the rotavirus particles. They have found that activated TiO2 with illumination of light in aqueous solution produces a significant amount of reactive oxygen species such as superoxide anions (O2 -) and hydroxyl radicals (•OH) after activation for 8, 16, and 24 hrs. Destruction of nucleic acid was also confirmed by Ashikaga *et al*. (Ashikaga *et al.*, 2000). Those reactive oxygen species affect not only nucleotides but also other organic compounds such as peptides or proteins. With this special features, Paspaltsis *et al.* have examined the photocatalytic TiO2 to prion protein, which is known to cause transmissible spongiform encephalopathy (TSB) (Paspaltsis *et al.*, 2006). Inoculation of prion protein (PrPSC) with a TiO2/H2O2 treatment to Syrian hamsters showed higher survival rate than control group and retarded presentation of clinical symptom for 50 days later. Since prion is strongly resistant to commonly used conventional decontamination methods, they have presented photocatalytic TiO2 as a potential disinfecting agent for liquid waste and TSE infectious agent.

Fig. 2. Apparatus for the assay of anti-adhesion effect of TiO2-coated orthodontic wire.

#### **5. Other applications of photo catalyst in dental treatments**

We are unconsciously in contact with diverse form of titanium dioxide these days. It is now commonly used in making papers, fabrics, toothpastes and wall paints. Photocatalytic TiO2 has a broad spectrum of applications in virtue of its almighty capability of degrading almost every organic compounds. It has been realized that TiO2 can absorb energy from light (usually UV light) and react with water molecules to produce reactive oxygen species.

One of the main focuses of applying photocatalytic TiO2 was decontamination of polluted environments such as air cleaning system, decomposition of waste water. At the beginning of studies on the photocatalytic TiO2, it was mainly applied to degrade highly toxic dyes from textile industries (Muneer *et al.*, 1997; Saquib & Muneer, 2003). However, its scope has been gradually expanded to various areas such as herbicides (Singh *et al.*, 2003) or pesticides (Daneshvar *et al.*, 2004) and other industrial waste water (Makino *et al.*, 2007).

Several companies producing ceramic tiles are using TiO2 on the very surface of their products which is so-called self-cleaning tiles. Due to the ability to decompose organic molecules, these self-cleaning tiles can disinfect contamination of their surfaces by themselves only if there's a little portion of moisture and enough sun light. It might be very useful in hospitals, public restrooms, and household bathrooms. This unique advantage can be expanded to trivial devices used in most of clinics such as forceps, spatulas, scissors, and any rigid ceramic or metal surfaces to reduce the opportunity of cross infection.

Another useful aspect of TiO2 is the hydrophilic property. Coating with photocatalytic TiO2 layer on rigid ceramic or metal surfaces provides super-hydrophilic property that might dramatically reduce contact angle. Ohdaira *et al*. in Department of General Surgery, Jichi Medical Universitym Japan have designed special laparoscope that has antifogging effect (Ohdaira *et al.*, 2007). This property also can be applied to dental mirrors, bathroom mirrors, and car windows to impose antifogging characteristics.

### **6. Limitations and drawbacks of photocatalytic TiO2**

Even though photocatalytic TiO2 has various utilities and potentials, still it has some limitations and drawbacks. It still needs improvements in reaction rate, broad spectrum of light source, specificity (or wide range of target) and stability. Several limitations and expected solutions are listed in Table 2. However, many of these are not solved yet.


Table 2. Several limitations of photocatalytic TiO2.

#### **6.1 Surface area**

116 Orthodontics – Basic Aspects and Clinical Considerations

of clinical symptom for 50 days later. Since prion is strongly resistant to commonly used conventional decontamination methods, they have presented photocatalytic TiO2 as a

Fig. 2. Apparatus for the assay of anti-adhesion effect of TiO2-coated orthodontic wire.

We are unconsciously in contact with diverse form of titanium dioxide these days. It is now commonly used in making papers, fabrics, toothpastes and wall paints. Photocatalytic TiO2 has a broad spectrum of applications in virtue of its almighty capability of degrading almost every organic compounds. It has been realized that TiO2 can absorb energy from light (usually UV light) and react with water molecules to

One of the main focuses of applying photocatalytic TiO2 was decontamination of polluted environments such as air cleaning system, decomposition of waste water. At the beginning of studies on the photocatalytic TiO2, it was mainly applied to degrade highly toxic dyes from textile industries (Muneer *et al.*, 1997; Saquib & Muneer, 2003). However, its scope has been gradually expanded to various areas such as herbicides (Singh *et al.*, 2003) or pesticides

Several companies producing ceramic tiles are using TiO2 on the very surface of their products which is so-called self-cleaning tiles. Due to the ability to decompose organic

(Daneshvar *et al.*, 2004) and other industrial waste water (Makino *et al.*, 2007).

**5. Other applications of photo catalyst in dental treatments** 

produce reactive oxygen species.

potential disinfecting agent for liquid waste and TSE infectious agent.

Since photocatalytic reaction occurs at the solid surface of TiO2, it is very easy to separate substrates or products from photocatalyst. However substrates should be in contact with photocatalyst, which causes relatively low reaction rate and less homogeneity compared to other reactions such as gas-gas, or liquid-gas reactions. The first way to manage this problem is to increase surface area of the catalysts and the way to increase surface area is to reduce the particle sizes. Some solid catalysts are used in a unique three dimensional structure such as 'honey comb structure' to increase surface area. However it is not suitable for the photocatalytic TiO2 because it needs illumination of UV or day light to activate. Therefore making round shaped particles and reduction in size may be the only way to increase surface area. Average diameter of commonly used TiO2 ranges from 20 nm to 0.5 μm. Ultrafine particles of even below 10 nm of diameter are now developed and used in some fields. The average surface area of some ultrafine particle is reduced down to 7 nm which has about 300 m2/g of surface area. Photocatalytic activity of this particle is 2 – 4 times higher than the particle that has 50 m2/g of surface area. The activity did not increase as much as the surface area because ultrafine particles usually can aggregate each other. But there is no reason not to use ultrafine particles if it shows higher activity even though increasing fold of activity is not high as that of surface area.

#### **6.2 Crystalline forms**

Titanium dioxide forms three kinds of crystals: those are rutile, anatase, and brookite (Fig. 3). It is usually said that anatase crystal has higher photocatalytic activity than others. Depending on the crystalline type, binding structure of T-O and characteristics of crystal surface varies of course. However, the reason is unclear until now. Anatase crystal of TiO2 can be formed between 400 – 500 Ԩ and transformed to rutile at more than 900 Ԩ.

Fig. 3. Anatase and rutile forms of crystalline TiO2.

#### **6.3 Light sources**

118 Orthodontics – Basic Aspects and Clinical Considerations

structure such as 'honey comb structure' to increase surface area. However it is not suitable for the photocatalytic TiO2 because it needs illumination of UV or day light to activate. Therefore making round shaped particles and reduction in size may be the only way to increase surface area. Average diameter of commonly used TiO2 ranges from 20 nm to 0.5 μm. Ultrafine particles of even below 10 nm of diameter are now developed and used in some fields. The average surface area of some ultrafine particle is reduced down to 7 nm which has about 300 m2/g of surface area. Photocatalytic activity of this particle is 2 – 4 times higher than the particle that has 50 m2/g of surface area. The activity did not increase as much as the surface area because ultrafine particles usually can aggregate each other. But there is no reason not to use ultrafine particles if it shows higher activity even though

Titanium dioxide forms three kinds of crystals: those are rutile, anatase, and brookite (Fig. 3). It is usually said that anatase crystal has higher photocatalytic activity than others. Depending on the crystalline type, binding structure of T-O and characteristics of crystal surface varies of course. However, the reason is unclear until now. Anatase crystal of TiO2

can be formed between 400 – 500 Ԩ and transformed to rutile at more than 900 Ԩ.

increasing fold of activity is not high as that of surface area.

Fig. 3. Anatase and rutile forms of crystalline TiO2.

**6.2 Crystalline forms** 

As the term 'photo-' represents, illumination of light is essential for the photocatalytic TiO2 to get catalytic activity. It is the most important limitation in designing reactors with photocatalytic TiO2. Even worse is the fact that most of photocatalytic TiO2 can only utilize UV rather than visible light. It may not be a drawback of TiO2, if any devices or reactors use natural sun light as a light source. However, in the view point of energy efficiency, if the reactor can utilize only a part of natural sun light and cannot utilize visible light, energy efficiency of the reactor will be less than 5% at most. Some of physical or chemical changes of titanium dioxide should be necessary to absorb and utilize visible light. Otherwise, photocatalytic TiO2 can utilize visible light by mixing a small amount of other inorganic substances such as chromic oxide (Cr2O3, VI). However, in this case, reduced photocatalytic activity should be expected.

Limitation of light source may not always be a drawback of photocatalytic TiO2. Since it produces hydroxyl radicals in aqueous solution and hydroxyl radical can decompose most of organic compounds, prolonged release of hydroxyl radical might be harmful in living organisms such as human. In case of antibacterial orthodontic wire described in section 3, it was coated with photocatalytic TiO2 for its additional feature. The fact that releases of hydroxyl radicals from the photocatalytic TiO2 for decomposition of bacterial cell wall compartments may imply a negative supposition. Hydroxyl radicals may also act on normal oral epithelial cells. In this case, the limitation of TiO2 could, in turn, be a simple solution for the problem. The fact that relatively low intensity of UV light in normal day light is an advantage in this case. Since, photocatalytic activity of TiO2 is usually activated by UV light, it can be regulated by manually controlling the illumination time and period in dental clinics.

#### **7. Conclusion**

When Fujishima and Honda reported the remarkable characteristics of titanium dioxide in 1972, few people have noticed the potentials of this white powder. Combined with the powerful effect of reactive oxygen species it became an almost almighty substance that can be used in environmental cleanup industries, personal hygiene products and even food industries. Not many substances have been interested in such diverse fields. However, there are still some drawbacks to overcome in the application of photocatalytic TiO2. That means it is still worthy of challenge in the field of photocatalysis research.

#### **8. References**


Chun, M. J., Shim, E., Kho, E. H., Park, K. J., Jung, J., Kim, J. M., Kim, B., Lee, K. H., Cho, D.

Daneshvar, N., Hejazi, M. J., Rangarangy, B. & Khataee, A. R. (2004) Photocatalytic

Dongare, M. K., Sonawane, R. S. & Hegde, S. G. (2003) Preparation of titanium(IV) oxide thin film photocatalyst by sol-gel dip coating. *Mater Chem Phys,* 77, 744-750. Elsaka, S. E., Hamouda, I. M. & Swain, M. V. (2011) Titanium dioxide nanoparticles addition

Fujishima, A. & Honda, K. (1972) Electrochemical photolysis of water at a semiconductor

Gerrity, D., Ryu, H., Crittenden, J. & Abbaszadegan, M. (2008) Photocatalytic inactivation of

Giavaresi, G., Giardino, R., Ambrosio, L., Battiston, G., Gerbasi, R., Fini, M., Rimondini, L. &

Gluszek, J., Masalski, J., Furman, P. & Nitsch, K. (1997) Structural and electrochemical examinations of PACVD TiO2 films in Ringer solution. *Biomaterials,* 18, 789-794. Gonzalez-Elipe, A. R., Gracia, F. & Holgado, J. P. (2004) Photoefficiency and optical,

Ireland, J. C. & Valinieks, J. (1992) Rapid measurement of aqueous hydroxyl radical concentrations in steady-state HO flux systems. *Chemosphere,* 25, 383-396. Ireland, J. C., Klostermann, P., Rice, E. W. & Clark, R. M. (1993) Inactivation of *Escherichia* 

Kuhn, K. P., Chaberny, I. F., Massholder, K., Stickler, M., Benz, V. W., Sonntag, H. G. &

Lee, J. M., Kim, M. S. & Kim, B. W. (2004) Photodegradation of bisphenol-A with TiO2

Liga, M. V., Bryant, E. L., Colvin, V. L. & Li, Q. (2011) Virus inactivation by silver doped

Makino, T., Matsumoto, K., Ebara, T., Mine, T., Ohtsuka, T. & Mizuguchi, J. (2007) Complete

titanium dioxide and UVA light. *Chemosphere,* 53, 71-77.

antibacterial properties. *The Angle orthodontist,* 77, 483-488.

*contaminants, and agricultural wastes,* 39, 285-296.

*International journal of artificial organs,* 26, 774-780.

properties. *Journal of dentistry,* 39, 589-598.

electrode. *Nature,* 238, 37-38.

*engineering,* 43, 1261-1270.

*Langmuir,* 20, 1688-1697.

*microbiology,* 59, 1668-1670.

3605-3613.

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L., Bai, D. H., Lee, S. I., Hwang, H. S., and Ohk, S. H. (2007) Surface modification of orthodontic wires with photocatalytic titanium oxide for its antiadherent and

degradation of an organophosphorus pesticide phosalone in aqueous suspensions of titanium dioxide. *Journal of environmental science and health Part B, Pesticides, food* 

to a conventional glass-ionomer restorative: Influence on physical and antibacterial

viruses using titanium dioxide nanoparticles and low-pressure UV light. *Journal of environmental science and health Part A, Toxic/hazardous substances & environmental* 

Torricelli, P. (2003) In vitro biocompatibility of titanium oxide for prosthetic devices nanostructured by low pressure metal-organic chemical vapor deposition. *The* 

microstructural, and structural properties of TiO2 thin films used as photoanodes.

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immobilized on the glass tubes including the UV light lamps. *Water research,* 38,

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**Part 2** 

**Growth and Genetic** 

122 Orthodontics – Basic Aspects and Clinical Considerations

Yoshinari, M., Oda, Y., Kato, T. & Okuda, K. (2001) Influence of surface modifications to titanium on antibacterial activity in vitro. *Biomaterials,* 22, 2043-2048. Zainal, Z., Lee, C. Y., Hussein, M. Z., Kassim, A. & Yusof, N. A. (2005) Electrochemical-

operational parameters. *Journal of hazardous materials,* 118, 197-203.

assisted photodegradation of dye on TiO2 thin films: investigation on the effect of

## **Genetic Factors Affecting Facial Growth**

James K. Hartsfield Jr.1, Lorri Ann Morford1 and Liliana M. Otero1,2

*1University of Kentucky 2Pontificia Universidad Javeriana 1USA 2Colombia* 

#### **1. Introduction**

Malocclusion is the manifestation of complex genetic and environmental interactions on the development of the oral-facial region. Historically, orthodontists have been interested in genetics as a means to better understand why a patient has a particular occlusion, and to determine the best course of treatment for the malocclusion. The application of genetic information in treatment, however, has been hampered by several factors including: 1) the presumption that heritability studies have some clinical relevance to the individual patient, which they do not (Harris, 2008); 2) the presumption that whatever genetic factors may have contributed to the occlusion will also affect how the patient responds to treatment, which they may not; and 3) a lack of understanding to the extent at which genetic factors may interact with environmental factors (such as those created during orthodontic and dentofacial orthopedic treatments) to influence single gene (Mendelian) traits versus "Complex" traits which are more frequently observed in the clinic. (Hartsfield, 2011)

While it is essential to consider genetic factors when diagnosing the underlying cause for virtually all oral-facial anomalies and developmental variations, the importance of how genetic factors will affect the outcome of treatment is often not appreciated. Understanding the etiology of a malocclusion is important, e.g., if the patient is a thumb sucker, then that habit must stop. But in terms of etiology, the factors that influenced a malocclusion to develop may not be the same ones that will influence how the patient responds to treatment of that malocclusion. In addition, the patient's developmental stage during treatment is typically a later stage then when the basis of the malocclusion first formed. Although an environmental modification may alter the development of the phenotype at a particular moment, gross structural morphology, already present, may not change readily unless the environmental modification is sufficient to alter preexisting structure.(Buschang & Hinton, 2005) As every orthodontist knows, the ability of the practitioner to affect a change is dependent both on the time of intervention (treatment) and the patient's stage of development.

Knowing whether the cause of the problem is genetic has been cited as a factor in eventual outcome; that is, if the problem is genetic, then orthodontists may be limited in what they can do (or change), because of an intrinsic "predestination." This is a misapplication of genetics to clinical practice since most malocclusions we treat appear to not be the result of a single dominant (Mendelian) gene.(Mossey, 1999b) There are inappropriate uses of heritability estimates in the literature as a proxy for evaluating whether a malocclusion or some anatomic morphology is "genetic." This however has no relevance to the question. Regardless of the heritability estimate, there is not a yes or no answer. Heritability estimates only apply to the group that was studied and the environmental factors that they were exposed to up to that time. They do not necessarily apply to an individual at the time of the study, and are not predictive for an individual or the group in the future.(Harris, 2008) How genetic factors will influence the response to environmental factors, including treatment, and the long-term stability of its outcome as determined by genetic linkage or association studies, should be the greatest concern for the clinician as they are the only way leading to a better understanding of the genetic background of the individual patient in terms of their malocclusion and response to treatment.(Hartsfield, 2008) It is of critical importance in clinical practice to understand how genetic factors and their interaction with environmental factors may affect facial growth. The aim of this chapter is to review what is known about the genetic factors that affect facial growth with an emphasis on human studies involving malocclusion.

#### **2. Genome, genotype, phenotype, modes of inheritance and epigenetics**

An individual's **genome** is defined as the genetic information inherited from both of their parents. The information encoded in a patient's genome can influence growth and development when the coded information is converted into the form of **protein** (and/or regulatory molecules such as microRNAs (miRNAs)). This information is encoded by ~3.2 billion nucleotide base pairs (bps), comprised of adenine (A), thymine (T) , cytosine (C) and guanine (G) residues, that are organized into sequences on 23 pairs of chromosomes. Each individual has 22 pairs of **autosomal chromosomes** (chromosomes that exhibit the same copy number in both males and females) and 1 pair of **sex chromosomes** (XX or XY). One chromosome of each pair is inherited from the individual's mother and the other pair from their father. Collectively this genetic information is often referred to as a person's DNA or genetic code. Amazingly, the genetic sequences of all humans appear to be ~99.9% identical, and hence it is a mere 0.1% of the sequence information which codes for our individual differences.

It is estimated that the human genome is comprised of 25,000 genes (accounting for only ~2% of the entire genome), with the average gene length being ~3,000 bps of information. A **gene** is a specific sequence of information that provides the instructions for making a unique protein or set of related proteins. The location or "address" for any gene within a genome is called its **locus** (plural loci: i.e., referring to the physical location of more than one gene). A determination of the actual DNA code (A, T, C or G) for a specific location within a person's genome describes their **genotype** for that location. Since there is natural variation in the sequence of DNA, a specific gene at a locus can still vary among individuals and homologous chromosomes in the same individual. These different forms of the "same" gene are called **alleles**. When the alleles on homologous chromosome pairs are the same, they are said to be **homozygous**. When the alleles on homologous chromosome pairs are different, they are said to be **heterozygous**. The **mode of inheritance** describes how the genetic information is passed down one generation to the next.

Within a single individual, the majority of cells in the body will contain a complete copy of the genome the individual inherited from their parents. Only a small number of specialized

heritability estimates in the literature as a proxy for evaluating whether a malocclusion or some anatomic morphology is "genetic." This however has no relevance to the question. Regardless of the heritability estimate, there is not a yes or no answer. Heritability estimates only apply to the group that was studied and the environmental factors that they were exposed to up to that time. They do not necessarily apply to an individual at the time of the study, and are not predictive for an individual or the group in the future.(Harris, 2008) How genetic factors will influence the response to environmental factors, including treatment, and the long-term stability of its outcome as determined by genetic linkage or association studies, should be the greatest concern for the clinician as they are the only way leading to a better understanding of the genetic background of the individual patient in terms of their malocclusion and response to treatment.(Hartsfield, 2008) It is of critical importance in clinical practice to understand how genetic factors and their interaction with environmental factors may affect facial growth. The aim of this chapter is to review what is known about the genetic factors that affect facial growth with an emphasis on human studies involving

**2. Genome, genotype, phenotype, modes of inheritance and epigenetics** 

An individual's **genome** is defined as the genetic information inherited from both of their parents. The information encoded in a patient's genome can influence growth and development when the coded information is converted into the form of **protein** (and/or regulatory molecules such as microRNAs (miRNAs)). This information is encoded by ~3.2 billion nucleotide base pairs (bps), comprised of adenine (A), thymine (T) , cytosine (C) and guanine (G) residues, that are organized into sequences on 23 pairs of chromosomes. Each individual has 22 pairs of **autosomal chromosomes** (chromosomes that exhibit the same copy number in both males and females) and 1 pair of **sex chromosomes** (XX or XY). One chromosome of each pair is inherited from the individual's mother and the other pair from their father. Collectively this genetic information is often referred to as a person's DNA or genetic code. Amazingly, the genetic sequences of all humans appear to be ~99.9% identical, and hence it is a mere 0.1% of the sequence information which codes for our individual

It is estimated that the human genome is comprised of 25,000 genes (accounting for only ~2% of the entire genome), with the average gene length being ~3,000 bps of information. A **gene** is a specific sequence of information that provides the instructions for making a unique protein or set of related proteins. The location or "address" for any gene within a genome is called its **locus** (plural loci: i.e., referring to the physical location of more than one gene). A determination of the actual DNA code (A, T, C or G) for a specific location within a person's genome describes their **genotype** for that location. Since there is natural variation in the sequence of DNA, a specific gene at a locus can still vary among individuals and homologous chromosomes in the same individual. These different forms of the "same" gene are called **alleles**. When the alleles on homologous chromosome pairs are the same, they are said to be **homozygous**. When the alleles on homologous chromosome pairs are different, they are said to be **heterozygous**. The **mode of inheritance** describes how the genetic

Within a single individual, the majority of cells in the body will contain a complete copy of the genome the individual inherited from their parents. Only a small number of specialized

information is passed down one generation to the next.

malocclusion.

differences.

cell types (e.g. mature erythrocytes, mature T- and B-cells of the immune system, sperm, and egg cells) eliminate a portion of inherited DNA to facilitate the cell's ability to perform a specialized function. Aside from these specialized cell types, most cells within an individual's body become (or differentiate into) a particular kind of cell (e.g. a muscle, nerve, or skin cell, etc…) or become part of a larger tissue or organ based upon the pattern of genes that are turned "on" or "off" within each cell. The process of turning a gene "on" is referred to as "gene expression" and most forms of gene expression lead to the production a protein or set of related proteins. Hence, a well differentiated cell like an osteoblast, does not become an osteoblast due to the presence of unique DNA codes found only is osteoblast cells or due to the loss of non-osteoblast related genetic information. An osteoblast becomes an osteoblast due to the genes and related proteins (or regulatory molecules) being expressed within the cell combined with the influence of any environmental factors that can alter these expression pattern(s).

The visible or measurable characteristics of an individual is their **phenotype**. A phenotype is determined based on the combination of: (1) the inherited genetic information being expressed by cells within the individual (e.g., the individual's genotype); (2) the environment in which the proteins (or regulatory molecules) are being expressed; and (3) any genotype-environment interactions that could influence protein (or regulatory molecule) expression or function. In contrast, a **trait** is a particular aspect or characteristic of the overall phenotype. An **inherited trait** is one that has the ability to be transferred from one generation to the next generation. A **syndrome** is a combination of traits that occur together in non random pattern that is different from the usual pattern.(Hartsfield & Bixler, 2011)

When the information in a single gene locus is essentially responsible for the development of a trait or syndrome, this trait or syndrome is said to be *monogenic*. If the gene locus is located on one of 22 autosomal chromosome pairs (chromosomes other than the X or Y sex chromosomes), and only one copy of a specific gene allele on the autosomal pair is sufficient to lead to the production of the trait or syndrome, then the individual is typically heterozygous for that allele and the effect on the inheritance pattern of the trait or syndrome is **autosomal dominant**. If the production of the trait or syndrome does not occur when only one copy of a particular allele is present at the locus on a paired set of autosomes, but does occur when two copies of that particular allele are present at the locus of a paired set of autosomes, then the inheritance pattern of the trait or syndrome is **autosomal recessive**. In this situation the "recessive" alleles are said to be homozygous.(Mossey, 1999a) This may be the case by having a common ancestor (inbreeding) in which the alleles are presumed to be identical, or by the random combination of alleles that although may not be of identical DNA sequence, still are operationally recessive.

The following are characteristic for **autosomal dominant inheritance**: (1) the trait or syndrome occurs in successive generations; (2) when an individual has the gene allele that results in the trait or syndrome, each child of theirs has a 50% chance of inheriting that gene allele; (3) males and females are equally likely to have the trait or syndrome; and (4) parents who do not have the trait or syndrome have offspring who do not have the trait or syndrome (see figure 1). However, there are notable caveats to these characteristics. Just because an individual has the "dominant" gene allele that would usually lead to the development of some particular trait or syndrome, such as Class III malocclusion, Treacher Collins syndrome or Crouzon syndrome (a common craniosynostosis condition), the appearance of the trait or syndrome may "skip a generation" in what is called **nonpenetrance** in the individual, or incomplete penetrance in a group of individuals who have the genotype but don't manifest the trait or syndrome.(Cruz et al., 2008; Everett et al., 1999; Hennekam et al., 2010) In addition, traits and syndromes with autosomal dominant inheritance typically have **varying degrees of severity** in individuals who show any evidence of the condition, which is termed **variable expressivity** of the phenotype. Thus analyzing the genome/genotype of even traits or syndromes with autosomal dominant may not "precisely" predict the phenotype, but certainly can often indicate there will be a major effect on growth and development to some degree. Variable expressivity also may apply to the pleiotropic effect of a particular genotype: that is the expression of a gene resulting in seemingly disparate traits in an individual. Thus even dominant traits that are said to be due to a change in a single gene can be influenced by the proteins from other genes and environmental factors (see figure 2).

Fig. 1. Autosomal dominant Inheritance.

Fig. 2. Interaction of Genetic and Environmental Factors on an "Monogenic Dominant" Trait.

Collins syndrome or Crouzon syndrome (a common craniosynostosis condition), the appearance of the trait or syndrome may "skip a generation" in what is called **nonpenetrance** in the individual, or incomplete penetrance in a group of individuals who have the genotype but don't manifest the trait or syndrome.(Cruz et al., 2008; Everett et al., 1999; Hennekam et al., 2010) In addition, traits and syndromes with autosomal dominant inheritance typically have **varying degrees of severity** in individuals who show any evidence of the condition, which is termed **variable expressivity** of the phenotype. Thus analyzing the genome/genotype of even traits or syndromes with autosomal dominant may not "precisely" predict the phenotype, but certainly can often indicate there will be a major effect on growth and development to some degree. Variable expressivity also may apply to the pleiotropic effect of a particular genotype: that is the expression of a gene resulting in seemingly disparate traits in an individual. Thus even dominant traits that are said to be due to a change in a single gene can be influenced by the proteins from other genes and

Fig. 2. Interaction of Genetic and Environmental Factors on an "Monogenic Dominant"

environmental factors (see figure 2).

Fig. 1. Autosomal dominant Inheritance.

Trait.

In **autosomal recessive inheritance** the transmission of the pedigree is typically horizontal (present only in siblings, see figure 3). Parents of a child with a trait or syndrome that has an autosomal recessive mode of inheritance are typically heterozygous ("carriers"). The heterozygous parents would then have a 25% of each child of theirs having the autosomal recessive trait or syndrome.

Fig. 3. Autosomal recessive inheritance.

For X linked traits, recessive genes on the one male X chromosome express themselves phenotypically as if they were dominant genes because a male usually only has one X chromosome (hemizygous). In this case the males with the genotype are affected in the pedigree, although in some cases the females can be affected as well. Females who are heterozygous for the gene associated with the X linked recessive phenotype may show some expression of the phenotype. This is because most of the genes on one of the X chromosomes in each cell of a female normally will be inactivated by a process called **lyonization (or X chromosome inactivation)**. Early in fetal development (at approximately the 16-cell morula stage), each cell of the developing female fetus inactivates almost all the genes on one of her two X chromosomes, and all cells that develop from that cell will show the inactivation of the same X chromosome. Depending on the ratio of cells with the X chromosome that has the recessive gene on it versus the X chromosome that does not have the recessive gene, the female may show some variable manifestation of the condition.

Most traits do not adhere to patterns of Mendelian inheritance. These traits are referred to as complex or common diseases and traits, and reflect their complex interaction between genes from more than one locus and environmental factors. Polygenic traits infer the effect of multiple genes on the phenotype, but can be affected by environmental factors also (see figure 4). The distinction between polygenic traits and multifactorial traits (both are traits influenced by environmental and multiple genetic factors) has been made for some multifactorial traits that are discrete (dichotomous) and that occur in an individual once a developmental threshold of genetic and environmental factors to produce the phenotype has been reached.

Fig. 4. Interaction of Genetic and Environmental Factors on a Complex Trait.

Epigenetics is the study of acquired and heritable changes in gene function that occur without a change in the DNA sequence. Environmental factors can influence epigenetic mechanisms such as DNA modification (i.e., methylation), histone modification (e.g., lysine and arginine methylation, acetylation, ubiquitination, phosphorylation, sumoylation, ADP ribosylation, deamination and proline isomerization)), and post-transcriptional silencing by RNA interference (microRNA, miRNA). All of these processes can result in gene activation and inactivation.(Lambert & Herceg, 2011) Epigenetic mechanisms can mediate the effect of the environment (e.g., dietary, hormonal and respiratory factors) on the human genome by controlling the transcriptional activity of specific genes, at specific points in time in specific organs.(Gabory et al., 2009; Schwartz, 2010) Malocclusion is a trait than can be greatly influenced by environmental factors. Corrucini suggested that the rapid increase in malocclusion in indigenous Australian people was produced by dietary factors concurrent with industrialization, and emphasized the importance of environmental influences on occlusal variation and the variability of apparent genetic determinants with respect to the environment or population in which they are measured.(Corruccini, 1984, 1990; Corruccini et al., 1990) Likewise Kawala et al. after studying the concordance of malocclusion in twins showed the distribution of within-pair malocclusions depended upon the gender of the individuals, and supported the impact of environmental factors.(Kawala et al., 2007)

In the consideration of environmental effects upon the development of malocclusion, it should not be forgotten that one's genome may influence the response to environmental factors. This is supported by the differences in shape of the mandibular condyles being "slightly greater" among four different inbred strains of mice on a hard diet than on a soft

Fig. 4. Interaction of Genetic and Environmental Factors on a Complex Trait.

factors.(Kawala et al., 2007)

Epigenetics is the study of acquired and heritable changes in gene function that occur without a change in the DNA sequence. Environmental factors can influence epigenetic mechanisms such as DNA modification (i.e., methylation), histone modification (e.g., lysine and arginine methylation, acetylation, ubiquitination, phosphorylation, sumoylation, ADP ribosylation, deamination and proline isomerization)), and post-transcriptional silencing by RNA interference (microRNA, miRNA). All of these processes can result in gene activation and inactivation.(Lambert & Herceg, 2011) Epigenetic mechanisms can mediate the effect of the environment (e.g., dietary, hormonal and respiratory factors) on the human genome by controlling the transcriptional activity of specific genes, at specific points in time in specific organs.(Gabory et al., 2009; Schwartz, 2010) Malocclusion is a trait than can be greatly influenced by environmental factors. Corrucini suggested that the rapid increase in malocclusion in indigenous Australian people was produced by dietary factors concurrent with industrialization, and emphasized the importance of environmental influences on occlusal variation and the variability of apparent genetic determinants with respect to the environment or population in which they are measured.(Corruccini, 1984, 1990; Corruccini et al., 1990) Likewise Kawala et al. after studying the concordance of malocclusion in twins showed the distribution of within-pair malocclusions depended upon the gender of the individuals, and supported the impact of environmental

In the consideration of environmental effects upon the development of malocclusion, it should not be forgotten that one's genome may influence the response to environmental factors. This is supported by the differences in shape of the mandibular condyles being "slightly greater" among four different inbred strains of mice on a hard diet than on a soft diet for six weeks. When the environment changed sufficiently, the response was different among animals with different genotypes that were not different before the environmental change.(Lavelle, 1983) Siblings may often have similar malocclusions not just because of common genetic or environmental factors, but also because of their shared genetic factors affecting how they respond to the shared environmental factors.(King et al., 1993) However, none of these studies on the effect of environmental factors were focused on epigenetic modifications as a result of environmental factors influencing malocclusion. As the exploration of epigenetics continues throughout biology and medicine, it may also be an interesting area to explore in facial growth.

#### **3. Heritability and malocclusion**

Most problems in orthodontics (or any outcome of growth), unless acquired by trauma, are not strictly the result of only genetic or only environmental factors. The ideal occlusion condition shows a proportional growth between the cranial base, the maxilla and the mandible; and involves the harmonious relation between skeletal bases and soft tissues (perioral musculature, lips and tongue).(Mossey, 1999b) The general morphology of craniofacial bones and teeth are largely genetically determined, although clearly variation is partly attributable to environmental factors.(Corruccini et al., 1990; Harris, 2008; Klingenberg et al., 2004; Kraus & Lufkin, 2006; Thesleff, 2006; Townsend et al., 2003) Genetic mechanisms predominate during embryonic craniofacial morphogenesis and in the etiology of many craniofacial abnormalities, therefore genetic factors must be considered in the etiology of malocclusion. However environment is also thought to influence dentofacial morphology postnatally, particularly during facial growth. In response to the presumption of the genome being the predetermining force for facial development and by inference skeletal malocclusion, the Functional Matrix Hypothesis by Moss theorized the primary role of function in craniofacial growth and development. Still, Moss did conclude that both genomic and environmental/epigenetic factors are necessary causes, that neither alone is a sufficient cause and that only the two interacting together furnish both the necessary and sufficient cause(s) of growth and development.(Moss, 1997b, 1997a)

One method employed to estimate this relative contribution of genetic and environmental factors is by calculating the heritability of a trait. Heritability in the broad since (*H2*) includes all additive, interactive and other types of genetic and environmental influences. This is impossible to derive, since all the factors and how they interact is not known. Therefore heritability estimates in the literature are in the narrow sense (*h2*), and represent the proportion of the total phenotypic variance in a sample that is contributed by additive genetic variance. However, the estimated ratio of genetic variation does not take into account gene-gene or gene-environment interaction.(Hartsfield, 2011) Numerous studies have examined how genetic variation contributes to either or both occlusal and skeletal variation among family members. It is difficult to estimate the influence of environmental (treatment) factors in craniofacial growth because the heritability studies of occlusion are typically based on twins and siblings who did not receive orthodontic treatment. Twin pairs and other groups of siblings containing one or more treated patients (with moderate to severe malocclusion) may have been excluded from most studies. Moreover the twin studies have not included extensive analysis of the parents, nor familial, and nutritional habits; and usually have not compared the twin group with a control group to ascertain environmental covariance (similarity due to twins and other siblings being in a common environment). Therefore, estimates of genetic and environmental contributions may have been affected by lack of accounting for a common environmental effect(Corruccini & Potter, 1980) and ascertainment bias.(King et al., 1993)

The cause of most skeletal- and dentoalveolar based malocclusions is essentially multifactorial in the sense that many diverse causes converge to produce the observed outcome.(King et al., 1993) Numerous studies have examined how genetic variation contributes to either or both occlusal and skeletal variation among family members.(Arya et al., 1973; Boraas et al., 1988; Byard et al., 1985; Cassidy et al., 1998; Chung & Niswander, 1975; Corruccini et al., 1986; Devor, 1987; Fernex et al., 1967; Gass et al., 2003; Harris et al., 1973; Harris et al., 1975; Harris & Smith, 1980; Harris & Johnson, 1991; Hauspie et al., 1985; Horowitz et al., 1960; Hunter et al., 1970; Johannsdottir et al., 2005; King et al., 1993; Kraus et al., 1959; Litton et al., 1970; Lobb, 1987; Lundstrom & McWilliam, 1987; Manfredi et al., 1997; Nakata et al., 1973; Nikolova, 1996; Proffit, 1986; Saunders et al., 1980; Susanne & Sharma, 1978; Watnick, 1972) In most studies (particularly those that try to account for bias from the effect of shared environmental factors, unequal means, and unequal variances in monozygotic and dizygotic twin samples),(Harris & Potter, 1997) variations in cephalometric skeletal dimensions are associated in general with a moderate to high degree of genetic variation, whereas in general, variation of occlusal relationships has little or no association with genetic variation.(Harris, 2008)

Although the heritability estimates are low, most of the studies that looked at occlusal traits found that genetic variation is positively correlated with phenotypic variation for arch width and arch length more than for overjet, overbite, and molar relationship. Still, arch size and shape are associated more with environmental variation than with genetic variation.(Cassidy et al., 1998) Because many occlusal variables reflect the combined variations of tooth position and basal and alveolar bone development, these variables (e.g., overjet, overbite, and molar relationship) cannot be less variable than the supporting structures. They will vary because of their own variation in position and those of the basilar structures.(Harris & Johnson, 1991) Heritability studies must be supplemented and to some degree superseded by studies linking or associating specific traits with variation in genetic markers such as single nucleotide polymorphisms (SNPs), variable number of tandem repeats, or other types of specific DNA variation.

For example, SNPs in the *EDA* gene and the gene for its receptor *XEDAR*, were found to be associated with dental crowding greater than 5 mm in a Hong Kong Chinese Class I malocclusion sample. It was thought that this may at least be due in part to variation in tooth size as the gene product of EDA is involved in tooth development, and mutations in EDA cause X-linked Hypohydrotic Ectodermal Dysplasia.(Ting et al., 2011) A possible affect on tooth size is consistent with the findings that in skeletal Class I crowding cases tooth size variation may more often play a role than skeletal growth.(Bernabe & Flores-Mir, 2006; Hashim & Al-Ghamdi, 2005; Poosti & Jalali, 2007; Ting et al., 2011) Although these genes are located on the X chromosome, the associations remained after adjustment for sex. This type of investigation is thought to help get around the problem of confounding environmental factors, although an increased analysis of epigenetic markers may show this is not that simple. Still these studies are the only way in which possible predictive data will be collected and tested.

covariance (similarity due to twins and other siblings being in a common environment). Therefore, estimates of genetic and environmental contributions may have been affected by lack of accounting for a common environmental effect(Corruccini & Potter, 1980) and

The cause of most skeletal- and dentoalveolar based malocclusions is essentially multifactorial in the sense that many diverse causes converge to produce the observed outcome.(King et al., 1993) Numerous studies have examined how genetic variation contributes to either or both occlusal and skeletal variation among family members.(Arya et al., 1973; Boraas et al., 1988; Byard et al., 1985; Cassidy et al., 1998; Chung & Niswander, 1975; Corruccini et al., 1986; Devor, 1987; Fernex et al., 1967; Gass et al., 2003; Harris et al., 1973; Harris et al., 1975; Harris & Smith, 1980; Harris & Johnson, 1991; Hauspie et al., 1985; Horowitz et al., 1960; Hunter et al., 1970; Johannsdottir et al., 2005; King et al., 1993; Kraus et al., 1959; Litton et al., 1970; Lobb, 1987; Lundstrom & McWilliam, 1987; Manfredi et al., 1997; Nakata et al., 1973; Nikolova, 1996; Proffit, 1986; Saunders et al., 1980; Susanne & Sharma, 1978; Watnick, 1972) In most studies (particularly those that try to account for bias from the effect of shared environmental factors, unequal means, and unequal variances in monozygotic and dizygotic twin samples),(Harris & Potter, 1997) variations in cephalometric skeletal dimensions are associated in general with a moderate to high degree of genetic variation, whereas in general, variation of occlusal relationships has little or no

Although the heritability estimates are low, most of the studies that looked at occlusal traits found that genetic variation is positively correlated with phenotypic variation for arch width and arch length more than for overjet, overbite, and molar relationship. Still, arch size and shape are associated more with environmental variation than with genetic variation.(Cassidy et al., 1998) Because many occlusal variables reflect the combined variations of tooth position and basal and alveolar bone development, these variables (e.g., overjet, overbite, and molar relationship) cannot be less variable than the supporting structures. They will vary because of their own variation in position and those of the basilar structures.(Harris & Johnson, 1991) Heritability studies must be supplemented and to some degree superseded by studies linking or associating specific traits with variation in genetic markers such as single nucleotide polymorphisms (SNPs), variable number of tandem

For example, SNPs in the *EDA* gene and the gene for its receptor *XEDAR*, were found to be associated with dental crowding greater than 5 mm in a Hong Kong Chinese Class I malocclusion sample. It was thought that this may at least be due in part to variation in tooth size as the gene product of EDA is involved in tooth development, and mutations in EDA cause X-linked Hypohydrotic Ectodermal Dysplasia.(Ting et al., 2011) A possible affect on tooth size is consistent with the findings that in skeletal Class I crowding cases tooth size variation may more often play a role than skeletal growth.(Bernabe & Flores-Mir, 2006; Hashim & Al-Ghamdi, 2005; Poosti & Jalali, 2007; Ting et al., 2011) Although these genes are located on the X chromosome, the associations remained after adjustment for sex. This type of investigation is thought to help get around the problem of confounding environmental factors, although an increased analysis of epigenetic markers may show this is not that simple. Still these studies are the only way in which possible predictive data will be

ascertainment bias.(King et al., 1993)

association with genetic variation.(Harris, 2008)

repeats, or other types of specific DNA variation.

collected and tested.

#### **4. Use of family data to predict growth**

Siblings have been noted as often showing similar types of malocclusion. Examination of parents and older siblings has been suggested as a way to gain information regarding the treatment need for a child, including early treatment of malocclusion.(Harris & Kowalski, 1976; Litton et al., 1970; Niswander, 1975; Saunders et al., 1980) Niswander noted that the frequency of malocclusion is decreased among siblings of index cases with normal occlusion, whereas the siblings of index cases with malocclusion tend to have the same type of malocclusion more often. (Niswander, 1975) There are high correlation coefficient values between parents and their offspring for Class II and Class III malocclusions.(Nakasima et al., 1982) It has been shown that the craniofacial skeletal patterns of children with Class II (division 1) malocclusions are familial (i.e., occur more often in multiple members of some families), and that a high resemblance to the skeletal patterns occurs in their siblings with normal occlusion.(Harris et al., 1975) Although this was ascribed to the Class II (division 1) being "heritable," common environmental factors were not taken into account. From this it was concluded that the genetic basis for this resemblance is probably polygenic, and family skeletal patterns were used as predictors for the treatment prognosis of the child with a Class II malocclusion, although it was acknowledged that the current morphology of the patient is the primary source of information about future growth.(Harris & Kowalski, 1976)

Each child receives half of his or her genes from each parent, but not likely the same combination of genes as a sibling unless the children are monozygotic twins. When looking at parents with a differing skeletal morphology, knowing which of the genes in what combination from each parent is present in the child is difficult until the child's phenotype matures under the continuing influence of environmental factors. When considering polygenic traits, the highest phenotypic correlation that can be expected based on genes in common by inheritance from one parent to a child, or between siblings, is 0.5. Because the child's phenotype is likely to be influenced by the interaction of genes from both parents, the "mid-parent" value may increase the correlation with their children to 0.7 because of the regression to the mean of parental dimensions in their children. Squaring the correlation between the two variables derives the amount of variation predicted for one variable in correlation with another variable. Therefore, at best, using mid-parent values, only 49% of the variability of any facial dimension in a child can be predicted by consideration of the average of the same dimension in the parents. Only 25% of the variability of any facial dimension in a child can be predicted, at best, by considering the same dimension in a sibling or one parent. Because varying effects of environmental factors interact with the multiple genetic factors, the usual correlation for facial dimensions between parents and their children is about 30%, yielding even less predictive power.(Hunter, 1990)

In most patients, the mode of inheritance for the craniofacial skeleton is polygenic (complex). However, in some families (e.g., with a relatively prognathic mandible compared with the maxilla), the mode of inheritance is not polygenic. Future research may investigate the genetic factors that do not fit a polygenic mode that may be present in some families. Identification of those factors will increase the ability to predict the likelihood of a particular resulting morphology. Unfortunately, orthodontists do not have sufficient information to make accurate predictions about the development of occlusion simply by studying the frequency of its occurrence in parents or even siblings. Admittedly, family patterns of resemblance are frequently obvious, and observed family tendencies should not be ignored. Nonetheless, predictions must be made cautiously because genetic and environmental factors and their interaction are unknown and difficult to evaluate and predict with precision.(Hartsfield, 2011)

#### **5. Genetic markers associated with variations in growth of complex etiology**

#### **5.1 Growth hormone receptor**

Growth hormone is an important factor in craniofacial and skeletal growth. A variant in the growth hormone receptor and its gene (*GHR*), when there is a proline amino acid instead of threonine at the 561st residue in the protein, is referred to as the *GHR* P56IT allele. Of a normal Japanese sample of 50 men and 50 women, those who did not have the *GHR* P56IT allele had a significantly greater mandibular ramus length (condylion-gonion) than did those with the *GHR* P56IT allele. The average mandibular ramus height in those with the *GHR* P56IT allele was 4.65 mm shorter than the average for those without the *GHR* P56IT allele. This significant correlation between the *GHR* P56IT allele and shorter mandibular ramus height was confirmed in an additional 80 women.(Yamaguchi et al., 2001) Interestingly, the association was with the mandibular ramus height but not mandibular body length, maxillary length, or anterior cranial base length. This suggests a site-, area-, or region-specific effect. The study concluded that the *GHR* P56IT allele may be associated with mandibular height growth and can be a genetic marker for it. Still, whether the effect is directly on the mandible or some other nearby tissue or on another matrix is not clear. It has been suggested that *GHR* variants P561T and C422F are associated with mandibular ramus height in Japanese population and that the SNPs of the *GHR* gene associated with differences in mandibular ramus height in the Japanese are likely to be different in other ethnic groups. (Tomoyasu et al., 2009)

This is supported by the finding that although there is a possible association between the *GHR* polymorphisms P561T, C422F and "haplotype 4" in a Korean population, there was not significant association between these markers and mandibular height in African-Americans, European-Americans, and Hispanics.(Kang et al., 2009) This group suggested that this finding might partly explain the differing craniofacial morphology among different ethnicities. Analysis of the possible association between the P561T variant in the *GHR* gene and mandibular growth during early childhood did not find a difference between mandibular protrusion and normal occlusion. (Sasaki et al., 2009) To see what effect different diets would have on individuals with and without the *GHR* P56IT allele would be interesting as a means of looking at genetic and environmental factor interaction. Undoubtedly many other genes that may influence craniofacial structure, including ramus height, could be identified, and their variation could be studied along with different environmental factors (e.g., orthodontic treatment) and the resulting phenotype.

#### **5.2 Growth differences during puberty**

Increased accuracy in the estimation of pubertal facial growth would be of great benefit prior to the utilization of different therapeutic modalities including orthodontics, orthopedic growth modification and surgery. Research and discussion about facial growth and treatment in the literature have focused either on the timing of the greatest amount of facial growth, particularly for the mandible(Gu & McNamara, 2007; Hunter et al., 2007; Verma et

Nonetheless, predictions must be made cautiously because genetic and environmental factors and their interaction are unknown and difficult to evaluate and predict with

**5. Genetic markers associated with variations in growth of complex etiology** 

Growth hormone is an important factor in craniofacial and skeletal growth. A variant in the growth hormone receptor and its gene (*GHR*), when there is a proline amino acid instead of threonine at the 561st residue in the protein, is referred to as the *GHR* P56IT allele. Of a normal Japanese sample of 50 men and 50 women, those who did not have the *GHR* P56IT allele had a significantly greater mandibular ramus length (condylion-gonion) than did those with the *GHR* P56IT allele. The average mandibular ramus height in those with the *GHR* P56IT allele was 4.65 mm shorter than the average for those without the *GHR* P56IT allele. This significant correlation between the *GHR* P56IT allele and shorter mandibular ramus height was confirmed in an additional 80 women.(Yamaguchi et al., 2001) Interestingly, the association was with the mandibular ramus height but not mandibular body length, maxillary length, or anterior cranial base length. This suggests a site-, area-, or region-specific effect. The study concluded that the *GHR* P56IT allele may be associated with mandibular height growth and can be a genetic marker for it. Still, whether the effect is directly on the mandible or some other nearby tissue or on another matrix is not clear. It has been suggested that *GHR* variants P561T and C422F are associated with mandibular ramus height in Japanese population and that the SNPs of the *GHR* gene associated with differences in mandibular ramus height in the Japanese are likely to be different in other

This is supported by the finding that although there is a possible association between the *GHR* polymorphisms P561T, C422F and "haplotype 4" in a Korean population, there was not significant association between these markers and mandibular height in African-Americans, European-Americans, and Hispanics.(Kang et al., 2009) This group suggested that this finding might partly explain the differing craniofacial morphology among different ethnicities. Analysis of the possible association between the P561T variant in the *GHR* gene and mandibular growth during early childhood did not find a difference between mandibular protrusion and normal occlusion. (Sasaki et al., 2009) To see what effect different diets would have on individuals with and without the *GHR* P56IT allele would be interesting as a means of looking at genetic and environmental factor interaction. Undoubtedly many other genes that may influence craniofacial structure, including ramus height, could be identified, and their variation could be studied along with different

environmental factors (e.g., orthodontic treatment) and the resulting phenotype.

Increased accuracy in the estimation of pubertal facial growth would be of great benefit prior to the utilization of different therapeutic modalities including orthodontics, orthopedic growth modification and surgery. Research and discussion about facial growth and treatment in the literature have focused either on the timing of the greatest amount of facial growth, particularly for the mandible(Gu & McNamara, 2007; Hunter et al., 2007; Verma et

precision.(Hartsfield, 2011)

**5.1 Growth hormone receptor** 

ethnic groups. (Tomoyasu et al., 2009)

**5.2 Growth differences during puberty** 

al., 2009); or the estimated extent of facial growth to be attained.(Chvatal et al., 2005; Turchetta et al., 2007) As useful as average facial growth predictions based upon expected growth curves may be, more valid prediction must incorporate and account for the variation associated with individual genetic factors, particularly those that are highly pertinent to the pubertal growth spurt. The pubertal growth spurt response is mediated by the combination of sex steroids, growth hormone, insulin-like growth factor (IGF-I) and other endocrine, paracrine and autocrine factors. Testosterone and estradiol in mice have a direct, sex-specific stimulatory activity on male and female derived chondroprogenitor cell proliferation. Testosterone stimulated growth and local production of IGF-I and IGF-I-R in chondrocyte cell layers of an isolated organ culture of mice mandibular condyle.(Maor et al., 1999) Investigation into the effects of neonatal surgical castration and prepubertal chemical castration on craniofacial growth in rats showed that craniofacial growth was related to testosterone concentration. Administration of low doses of testosterone in boys with delayed puberty not only accelerates their statural growth rate, but their craniofacial growth rate as well.(Verdonck et al., 1998; Verdonck et al., 1999)

Ovariectomized and orchiectomized mice that sex hormone levels influenced condylar morphogenesis changed the internal structure of the mandibular condyle.(Fujita et al., 2001) It has been suggested that the suppression of sex hormone secretion in the growth phase might inhibit craniofacial growth and result in poor craniofacial development, particularly nasomaxillary bone and mandible, in new born and pubertal rats.(Fujita et al., 2004; Fujita et al., 2006) It has been demonstrated using administration of sex hormone specific receptor antagonists that growth of the mandible and femur is induced in response to the stimulation of the estrogen receptor beta (ERβ) in chondrocytes before and during early puberty in mice. In late and after puberty, the growth is induced by the stimulation of estrogen receptor alpha (ERα) in male and female mice. From this it was proposed that a screen of sex hormones could be used as an indicator of bone maturity to accurately predict the beginning and end of growth in orthodontic treatment.

*CYP19A1* is the gene that encodes aromatase. This enzyme catalyzes the rate limiting step in estrogen biosynthesis by converting androgens. In order to best diagnose and treat the child or adolescent patient, the orthodontist needs to know as much as possible about the patient's growth potential. As useful as predictions based upon expected growth models starting from early in the patient's life may be, prediction must incorporate and account for the variation associated with individual genetic factors, especially those that are highly pertinent to the pubertal growth spurt.

Estrogens are a group of hormones involved in growth and development.(Honjo et al., 1992) Estrogen stimulates chondrogenesis, promotes the progressive closure of the epiphyseal growth plate, has an anabolic effect on the osteoblast and an apoptotic effect on the osteoclast, and increases bone mineral acquisition in axial and appendicular bone during adolescence and into the third decade.(Grumbach, 2000) Aromatase (also known as estrogen synthetase) is a key cytochrome P450 enzyme involved in estrogen biosynthesis.(Bulun et al., 2003) This steroidogenic enzyme catalyzes the final step of estrogen biosynthesis by converting testosterone and androstenedione to estradiol and estrone, respectively.(Guo et al., 2006) Regulation of this gene's transcription is critical for the testosterone/estrogen (T/E) ratio in the body since aromatase plays an important role in the conversion of androgens to estrogens. Some studies have shown that the T/E ratio is critical in the development of sex-indexed facial characteristics such as the growth of cheekbones, the mandible and chin, the prominence of eyebrow ridges and the lengthening of the lower face. (Schaefer et al., 2005; Schaefer et al., 2006)

The difference in the average sagittal jaw growth between the two groups of Caucasian males with different *CYP19A1* alleles with the greatest differences in growth per year was just over 1.5 mm per year during treatment for the maxilla, and 2.5 mm per year for the mandible. (Hartsfield Jr. et al., 2010) There was no statistical difference for the particular *CYP19A1* alleles in females. This is particularly impressive since at the beginning of treatment there was no significant difference among the males based upon the *CYP19A1*  genotype. The significant difference only expressed itself over the time of treatment during the cervical vertebral stage associated with increased growth velocity.(Hartsfield et al., 2010) Interestingly the same result was found in a group of Chinese males and females, strongly suggesting that this variation in the *CYP19A1* gene may be a multi-ethnic marker for sagittal facial growth. (He et al., 2011) Although the difference in average annual sagittal mandibular and maxillary growth based upon this *CYP19A1* genotype were significant, as one factor in a complex trait (sagittal jaw growth), they account for only part of the variation seen, and therefore by itself has little predictive power. Further investigation of this and other genetic factors, their interactions with each other and with environmental factors will help to explain what has up to now been an unknown component of individual variations in facial growth.

#### **5.3 Class II division 2 (Class II/2) malocclusion**

There is evidence that Class II division 2, and particularly Class III malocclusions, can have a strong genetic component. The Class II division 2 (II/2) malocclusion is a relatively rare type of malocclusion, representing between 2.3% and 5% of all malocclusions in the western white population.(Ast et al., 1965; Mills, 1966) In one study 100% of 20 monozygotic (MZ) twin pairs were concordant for II/2 malocclusion, while only 10.7% of 28 dizygotic (DZ) twin pairs demonstrated concordance for the Class II/2 malocclusion. (Markovic, 1992) These findings suggest the effect of common genetic or environmental factors; however, the much lower concordance for DZ twins would suggest that multiple genetic factors rather than a single gene contribute to the risk for Class II/2. This was reinforced by Ruf et al. concluding that the etiology of Class II/2 malocclusion was unclear, with neither form nor function the sole controlling factor.(Ruf & Pancherz, 1999)

From a developmental viewpoint it is interesting that there is a strong association of Class II/2 malocclusion with dental developmental anomalies, more so than for other Angle malocclusion classes.(Basdra et al., 2001) Excluding 3rd molars, agenesis of other teeth was at least three times more common in Class II/2 subjects than in the general population. In addition, there were a significantly greater number of dental developmental anomalies present in Class II/2 subjects as compared to the general population. They found 56.6% of Class II/2 patients exhibited developmental tooth anomalies including hypodontia as compared to as many as 35% of the general population having agenesis of one or more third molar.(Basdra et al., 2000) In addition Peck et al. showed a statistically significant reduction in permanent maxillary incisor mesial-distal width associated with Class II/2.(Peck et al., 1998)

development of sex-indexed facial characteristics such as the growth of cheekbones, the mandible and chin, the prominence of eyebrow ridges and the lengthening of the lower face.

The difference in the average sagittal jaw growth between the two groups of Caucasian males with different *CYP19A1* alleles with the greatest differences in growth per year was just over 1.5 mm per year during treatment for the maxilla, and 2.5 mm per year for the mandible. (Hartsfield Jr. et al., 2010) There was no statistical difference for the particular *CYP19A1* alleles in females. This is particularly impressive since at the beginning of treatment there was no significant difference among the males based upon the *CYP19A1*  genotype. The significant difference only expressed itself over the time of treatment during the cervical vertebral stage associated with increased growth velocity.(Hartsfield et al., 2010) Interestingly the same result was found in a group of Chinese males and females, strongly suggesting that this variation in the *CYP19A1* gene may be a multi-ethnic marker for sagittal facial growth. (He et al., 2011) Although the difference in average annual sagittal mandibular and maxillary growth based upon this *CYP19A1* genotype were significant, as one factor in a complex trait (sagittal jaw growth), they account for only part of the variation seen, and therefore by itself has little predictive power. Further investigation of this and other genetic factors, their interactions with each other and with environmental factors will help to explain what has up to now been an unknown component of individual variations in

There is evidence that Class II division 2, and particularly Class III malocclusions, can have a strong genetic component. The Class II division 2 (II/2) malocclusion is a relatively rare type of malocclusion, representing between 2.3% and 5% of all malocclusions in the western white population.(Ast et al., 1965; Mills, 1966) In one study 100% of 20 monozygotic (MZ) twin pairs were concordant for II/2 malocclusion, while only 10.7% of 28 dizygotic (DZ) twin pairs demonstrated concordance for the Class II/2 malocclusion. (Markovic, 1992) These findings suggest the effect of common genetic or environmental factors; however, the much lower concordance for DZ twins would suggest that multiple genetic factors rather than a single gene contribute to the risk for Class II/2. This was reinforced by Ruf et al. concluding that the etiology of Class II/2 malocclusion was unclear, with neither form nor

From a developmental viewpoint it is interesting that there is a strong association of Class II/2 malocclusion with dental developmental anomalies, more so than for other Angle malocclusion classes.(Basdra et al., 2001) Excluding 3rd molars, agenesis of other teeth was at least three times more common in Class II/2 subjects than in the general population. In addition, there were a significantly greater number of dental developmental anomalies present in Class II/2 subjects as compared to the general population. They found 56.6% of Class II/2 patients exhibited developmental tooth anomalies including hypodontia as compared to as many as 35% of the general population having agenesis of one or more third molar.(Basdra et al., 2000) In addition Peck et al. showed a statistically significant reduction in permanent maxillary incisor

(Schaefer et al., 2005; Schaefer et al., 2006)

**5.3 Class II division 2 (Class II/2) malocclusion** 

function the sole controlling factor.(Ruf & Pancherz, 1999)

mesial-distal width associated with Class II/2.(Peck et al., 1998)

facial growth.

Further evidence for a polygenic complex etiology for Class II/2 was found in a study of 68 subjects (67 self reported as white and 1 white/African-American who was a child of one of the 18 probands). (Morrison, 2008) A proband is the affected individual through whom a family is first seen or studied for a genetic trait, syndrome or disorder. In this study, researchers included 50 reported first-degree relatives of each proband, with a minimum of 2 first-degree relatives of each proband. The findings showed a marked increase in the number of females affected with Class II/2 in both the probands and their first-degree relatives than affected males. Of the 36 first-degree relatives whose occlusion was analyzed, 6 (16.7%) were found to be Class II/2. The relative risk (RR) of first-degree relatives to have a Class II/2 was found to be 3.3 – 7.3. The confidence interval (CI) was 1.1-10.3 if the RR was 3.3 and 1.7-31.6 if the RR was 7.3.

Agenesis of one or more permanent teeth (excluding 3rd molars) was found in 2 (11.1%) of the 18 probands and 7 (14.0%) of the 50 first-degree relatives. Agenesis of one or more 3rd molars was found in 4 (22.2%) of the 18 probands and 12 (24.0%) of the 50 first-degree relatives. Agenesis of one or both permanent maxillary incisors was found in none of the 18 probands and 2 (4.0%) of the 50 first-degree relatives. One or more small teeth (excluding 3rd molars) were found in 4 (22.2%) of the 18 probands and 15 (30.0%) of the 50 first-degree relatives. Small maxillary permanent incisors were found in none of the 18 probands and 4 (8.0%) of the 50 first-degree relatives. Agenesis of one or more permanent teeth in combination with the presence of one or more small permanent teeth was found in 2 (11.1%) of the 18 probands and 7 (14.0%) of the 50 first-degree relatives. Of the 36 first-degree relatives evaluated for malocclusion, 6 (16.67%) were found to be Class II/2. The RR for first-degree relatives of the probands to have a Class II/2 malocclusion was 3.3 – 7.35.(Morrison, 2008)

These results indicate that first-degree relatives of Class II/2 probands have a significantly increased risk of having a Class II/2 malocclusion as compared with individuals from the general population. Were Class II/2 malocclusion to be the result of variation in a single gene, acting in either a dominant or recessive fashion, the relative risk would be expected to be much higher. Rather, the modest, albeit significant increase in risk appears consistent with results from previous studies, which suggest a multifactorial etiology for Class II/2 malocclusion.

The question could be raised as to whether or not anomalous maxillary lateral incisors are associated with the Class II/2 malocclusion phenotype, and therefore share common etiological factors. Basdra et al. showed that 13.9% of Class II/2 subjects had agenesis of maxillary lateral incisors and 7.5% had peg-shaped or small maxillary lateral incisors. In contrast, Morrison found none of the probands had agenesis of or small maxillary lateral incisors, although first-degree relatives of the Class II/2 probands showed similar frequencies of hypodontia and microdontia of other teeth as the II/2 probands. However, the frequencies of these dental anomalies in the probands and first degree relatives were not significantly greater than those in the general population.(Morrison, 2008) Thus it is unclear if Class II/2 probands and their first-degree relatives are at an increased risk of developing hypodontia and/or microdontia. Investigations of a larger sample of Class II/2 subjects and relatives to address that question and possible common etiological factors, including genes associated with tooth development and hypodontia, are needed.

A start on this was made when DNA markers (single nucleotide polymorphisms, also referred to as SNPs) in two genes associated with dental development and or hypodontia, *MSX1*, *PAX9*, *AXIN2*. *RUNX2* and *RUNX3* were investigated in 94 Class II/2 Caucasian subjects (31 with hypodontia) compared to 89 non-Class II/2 Caucasian subjects without hypodontia. (Morford et al., 2010b; Morford et al., 2010a) A borderline-association of all Class II/2 subjects with the *PAX9* SNP (rs8004560) was identified (p=0.06). A borderline-association of the same rs8004560 *PAX9* SNP was also identified for subjects with Class II/2 with hypodontia of any permanent tooth, excluding third-molars, when compared to non-Class II/2 without hypodontia (p=0.08) but not when compared to Class II/2 without hypodontia (p=0.46). No associations of Class II/2 with the *PAX9* rs1955734, *MSX1* rs3821949, *RUNX2* (rs1406846), *RUNX3* (rs6672420), or *AXIN2* (rs7591, rs2240308) genotypes were identified. There was a significant association (p=0.0286) for Class II/2 subjects (with or without hypodontia) and the *RUNX2* rs6930053 SNP. However, there was no association of *RUNX2* rs6930053 for subjects with Class II/2 that had hypodontia of any permanent tooth, including third-molars, when compared to Class II/2 subjects without hypodontia (p=0.3858). This suggests a mild impact of *PAX9* (or a locus in linkage-disequilibrium with it) on the development of Class II/2 with hypodontia, and that *RUNX2* (or genetic loci in linkage-disequilibrium with *RUNX2*) plays a role in Class II/2 development but not in the occasionally-associated hypodontia. These findings and other DNA markers should be investigated in a larger Caucasian and other ethnic groups.(Malinowski, 1983; Strohmayer, 1937; Suzuki, 1961)

#### **5.4 Class III malocclusion**

Although all Angle occlusion types a Class III malocclusion were initially only based on the sagittal relationship of the permanent first molars, it has generally been recognized that this dental relationship is often observed with a corresponding skeletal relationship as well. Thus, the Class III malocclusion is a complex disorder characterized by a combination of dental and skeletal features that characteristically result in the appearance of a prominent lower jaw. Often referred to as mandibular prognathism (taken from the Greek pro =forward and gnathos =jaw), skeletal aspects of this disorder can be a result of pure mandibular prognathism, maxillary hypoplasia/retrognathism, or a combination of the two. These phenotypic variations create a significant heterogeneity among Class III subjects that can vary according to sex and ethnicity, and account for some of the difficulty encountered when investigating the condition.(Singh, 1999) The familial nature of mandibular prognathism was first reported by Strohmayer (1937) as noted by Wolff et al (1993) in their analysis of the pedigree of the Hapsburg family.(Wolff et al., 1993)

The highest prevalence of Class III malocclusion is observed in East Asian populations such as Korean, Chinese, and Japanese (8%-40%).(Allwright, 1964; Ishii et al., 2002) By comparison, African populations exhibit a reduced prevalence rate (3-8%) compared to Asian samples(Emrich et al., 1965; Garner & Butt, 1985), as do individuals of European or European-American (Caucasian) decent (reports varying between 0.48%-9.5%, with most in the 3-5% range)(Davidov et al., 1961; Emrich et al., 1965; Goose et al., 1957; Helm, 1968; Horowitz, 1970; Ingervall, 1974; Laine & Hausen, 1983; Luffingham & Campbell, 1974; Massler & Frankel, 1951; Solow & Helm, 1968; Tipton & Rinchuse, 1991) While the prevalence in a sample of Native American Chippewa Indian children is relatively low (2.6- 3.1%),(Grewe et al., 1968) North American Eskimos in Labrador, Canada have a class III prevalence of approximately 16%.(Zammit et al., 1995) (Zammit, Hans, et al. 1995)

A start on this was made when DNA markers (single nucleotide polymorphisms, also referred to as SNPs) in two genes associated with dental development and or hypodontia, *MSX1*, *PAX9*, *AXIN2*. *RUNX2* and *RUNX3* were investigated in 94 Class II/2 Caucasian subjects (31 with hypodontia) compared to 89 non-Class II/2 Caucasian subjects without hypodontia. (Morford et al., 2010b; Morford et al., 2010a) A borderline-association of all Class II/2 subjects with the *PAX9* SNP (rs8004560) was identified (p=0.06). A borderline-association of the same rs8004560 *PAX9* SNP was also identified for subjects with Class II/2 with hypodontia of any permanent tooth, excluding third-molars, when compared to non-Class II/2 without hypodontia (p=0.08) but not when compared to Class II/2 without hypodontia (p=0.46). No associations of Class II/2 with the *PAX9* rs1955734, *MSX1* rs3821949, *RUNX2* (rs1406846), *RUNX3* (rs6672420), or *AXIN2* (rs7591, rs2240308) genotypes were identified. There was a significant association (p=0.0286) for Class II/2 subjects (with or without hypodontia) and the *RUNX2* rs6930053 SNP. However, there was no association of *RUNX2* rs6930053 for subjects with Class II/2 that had hypodontia of any permanent tooth, including third-molars, when compared to Class II/2 subjects without hypodontia (p=0.3858). This suggests a mild impact of *PAX9* (or a locus in linkage-disequilibrium with it) on the development of Class II/2 with hypodontia, and that *RUNX2* (or genetic loci in linkage-disequilibrium with *RUNX2*) plays a role in Class II/2 development but not in the occasionally-associated hypodontia. These findings and other DNA markers should be investigated in a larger Caucasian and other

Although all Angle occlusion types a Class III malocclusion were initially only based on the sagittal relationship of the permanent first molars, it has generally been recognized that this dental relationship is often observed with a corresponding skeletal relationship as well. Thus, the Class III malocclusion is a complex disorder characterized by a combination of dental and skeletal features that characteristically result in the appearance of a prominent lower jaw. Often referred to as mandibular prognathism (taken from the Greek pro =forward and gnathos =jaw), skeletal aspects of this disorder can be a result of pure mandibular prognathism, maxillary hypoplasia/retrognathism, or a combination of the two. These phenotypic variations create a significant heterogeneity among Class III subjects that can vary according to sex and ethnicity, and account for some of the difficulty encountered when investigating the condition.(Singh, 1999) The familial nature of mandibular prognathism was first reported by Strohmayer (1937) as noted by Wolff et al (1993) in their

The highest prevalence of Class III malocclusion is observed in East Asian populations such as Korean, Chinese, and Japanese (8%-40%).(Allwright, 1964; Ishii et al., 2002) By comparison, African populations exhibit a reduced prevalence rate (3-8%) compared to Asian samples(Emrich et al., 1965; Garner & Butt, 1985), as do individuals of European or European-American (Caucasian) decent (reports varying between 0.48%-9.5%, with most in the 3-5% range)(Davidov et al., 1961; Emrich et al., 1965; Goose et al., 1957; Helm, 1968; Horowitz, 1970; Ingervall, 1974; Laine & Hausen, 1983; Luffingham & Campbell, 1974; Massler & Frankel, 1951; Solow & Helm, 1968; Tipton & Rinchuse, 1991) While the prevalence in a sample of Native American Chippewa Indian children is relatively low (2.6- 3.1%),(Grewe et al., 1968) North American Eskimos in Labrador, Canada have a class III

prevalence of approximately 16%.(Zammit et al., 1995) (Zammit, Hans, et al. 1995)

ethnic groups.(Malinowski, 1983; Strohmayer, 1937; Suzuki, 1961)

analysis of the pedigree of the Hapsburg family.(Wolff et al., 1993)

**5.4 Class III malocclusion** 

Populations in South America are often a mixture of Caucasian/European, African and Amerindian decent. While the percentage of children in Bogotá, Colombia with Class III has been reported as 3.7%, Brazilian children exhibited a frequency between 4 -10%.(Grando et al., 2008; Martins Mda & Lima, 2009; Thilander et al., 2001) In areas of the Middle East, the prevalence of class III also displays variation with the highest prevalence in Egypt at 10.6%,(El-Mangoury & Mostafa, 1990) followed by 7.8% in Iran,(Borzabadi-Farahani et al., 2009) and 5.1% in Lebanon.(Saleh, 1999)

Several studies have suggested the existence of multiple patterns or sub-phenotypes of the Class III malocclusion based on anatomical appearance. For example, Ellis and McNamara reported considerable variation among class III patients. The most common combination of variables was a retrusive maxilla, protrusive maxillary incisors, retrusive mandibular incisors, a protrusive mandible, and a long lower facial height.(Ellis & McNamara, 1984) Although they did not find significant sex differences, Baccetti et al. showed a significant degree of sexual dimorphism in craniofacial features in subjects with class III malocclusion.(Baccetti et al., 2005) The female Class III subjects presented smaller linear dimensions in the maxilla, mandible, and anterior facial heights when compared with male subjects. The increase in mandibular growth was three times greater in males with class III than in subjects with normal occlusion.(Baccetti et al., 2007) Martone and colleagues suggested that craniofacial growth generates several head form types resulting in anatomic sub-groupings of Classes III.(Martone et al., 1992) Mackay et al (1992) identified five Class III subgroups, all of which exhibited mandibular prognathism.(Mackay et al., 1992) English children with Class III malocclusions divided into groups (normal anteroposterior positioned mandibles and protruded mandibles) according to their SNB angle were found to have significant differences in both groups relating to sagittal position of the maxilla and mandibular rotation.(Hashim & Sarhan, 1993)

Bui et al (2006) found five clusters representing distinct subphenotypes of class III malocclusion. The groupings of variables reflected anteroposterior and vertical dimensions rather than specific craniofacial structures, suggesting that different genes are involved in controlling dimension versus structure. The five subgroupings or "Prototype Clusters" were described as follows: (1) prognathic mandible with long face, (2) maxillary deficiency with decreased vertical dimension (low angle), (3) maxillary deficiency with increased vertical dimension (high angle), (4) mild prognathic mandible with normal vertical dimension, and (5) a combination of prognathic mandible and maxillary deficiency with normal vertical dimension.(Bui et al., 2006) Further studies of the variation of the subtypes of the Class III phenotype within families should facilitate increased understanding of the genetic and nongenetic factors involved.

The genetic factors appear to be heterogeneous, with monogenic (usually autosomal dominant with incomplete penetrance and variable expressivity) influences in some families and multifactorial (polygenic complex) influences in others.(Cruz et al., 2008; Downs, 1927 ; El-Gheriani et al., 2003; Krauss et al., 1959; Litton et al., 1970; Niswander, 1975; Stiles & Luke, 1953; Strohmayer, 1937; Thompson & Winter, 1988; Wolff et al., 1993) This contributes to the variety of anatomical changes in the cranial base, maxilla, and mandible that may be associated with "mandibular prognathism" or a Class III malocclusion.(Bui et al., 2006; Singh, 1999) The prevalence of Class III malocclusion varies among races and can show different anatomic characteristics between races.(Ishii et al., 2002) Considering this heterogeneity, and possible epistasis (the interaction between or among gene products on their expression) and even epigenetics, it is not surprising that genetic linkage and candidate gene studies to date have indicated the possible location of genetic loci influencing this trait in several chromosomal locations (see figure 5).(Falcão-Alencar et al., 2010; Frazier-Bowers et al., 2009; Jang et al., 2010; Li et al., 2010; Li et al., 2011; Tassopoulou-Fishell et al., 2011; Xue et al., 2010; Yamaguchi et al., 2005)

Fig. 5. Chromosome location of markers linked or associated with Class III malocclusion in humans.

#### **6. Personalized orthdontics**

In summary, "Personalized Medicine" is a new buzz phrase, based initially upon pharmacogenetics and now exploding as genome-wide association and pathway studies are undertaken. The understanding of the combination and interaction of genetic and environmental (including treatment) factors (nature and nurture together) that influence the growth treatment response of our patients is fundamental to the evidence based practice of orthodontics. Conclusions from retrospective studies must be evaluated by prospective testing to truly evaluate their value in practice. Genome-wide association studies, metabolic pathway analysis and candidate gene studies are necessary to further the evidence base for the practice of orthodontics to determine what the best treatment plan is for each patient in the era of truly personalized orthodontics.(Hartsfield, 2008)

#### **7. References**

Allwright, W.C. (1964). A survey of handicapping dentofacial anomalies among Chinese in Hong Kong. *Int Dent J,* Vol. 14, No. 1964), pp. 505-519,

heterogeneity, and possible epistasis (the interaction between or among gene products on their expression) and even epigenetics, it is not surprising that genetic linkage and candidate gene studies to date have indicated the possible location of genetic loci influencing this trait in several chromosomal locations (see figure 5).(Falcão-Alencar et al., 2010; Frazier-Bowers et al., 2009; Jang et al., 2010; Li et al., 2010; Li et al., 2011; Tassopoulou-Fishell et al., 2011; Xue

Fig. 5. Chromosome location of markers linked or associated with Class III malocclusion in

In summary, "Personalized Medicine" is a new buzz phrase, based initially upon pharmacogenetics and now exploding as genome-wide association and pathway studies are undertaken. The understanding of the combination and interaction of genetic and environmental (including treatment) factors (nature and nurture together) that influence the growth treatment response of our patients is fundamental to the evidence based practice of orthodontics. Conclusions from retrospective studies must be evaluated by prospective testing to truly evaluate their value in practice. Genome-wide association studies, metabolic pathway analysis and candidate gene studies are necessary to further the evidence base for the practice of orthodontics to determine what the best treatment plan is for each patient in

Allwright, W.C. (1964). A survey of handicapping dentofacial anomalies among Chinese in

et al., 2010; Yamaguchi et al., 2005)

humans.

**7. References** 

**6. Personalized orthdontics** 

the era of truly personalized orthodontics.(Hartsfield, 2008)

Hong Kong. *Int Dent J,* Vol. 14, No. 1964), pp. 505-519,


Cassidy, K.M., Harris, E.F., Tolley, E.A. & Keim, R.G. (1998). Genetic influence on dental

Chung, C.S. & Niswander, J.D. (1975). Genetic and epidemiologic studies of oral

Chvatal, B.A., Behrents, R.G., Ceen, R.F. & Buschang, P.H. (2005). Development and testing

Corruccini, R.S. & Potter, R.H. (1980). Genetic analysis of occlusal variation in twins.

Corruccini, R.S. (1984). An epidemiologic transition in dental occlusion in world

Corruccini, R.S., Sharma, K. & Potter, R.H. (1986). Comparative genetic variance and

Corruccini, R.S. (1990). Australian aboriginal tooth succession, interproximal attrition, and

Corruccini, R.S., Townsend, G.C., Richards, L.C. & Brown, T. (1990). Genetic and

Cruz, R.M., Krieger, H., Ferreira, R., Mah, J., Hartsfield, J., Jr. & Oliveira, S. (2008). Major

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## **A Simplified Method to Determine the Potential Growth in Orthodontics Patients**

Gladia Toledo Mayarí

*School of Dentistry/ Havana Medical University Cuba* 

#### **1. Introduction**

152 Orthodontics – Basic Aspects and Clinical Considerations

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> The current Orthodontics worries is about the early correction of malocclusion, giving importance to the harmonization of the bone bases in connection with the discrepancy and positioning of the teeth, that can be corrected in any time of life, for what is of great importance is to know the biggest peak of growth (Peluffo, 2001; Quirós 2000).

> The maturation stages can have a considerable influence in the diagnosis, the goals of the treatment, the planning and the eventual result of the orthodontic treatment (Madhu et al., 2003; Toledo 2004).

> The clinical decisions with regards to the use of the extraoral force, functional appliances, the treatment without extractions and the orthognatic surgeon is based on the considerations of the growth, for this reason, the prediction of the quantity of active growth, mainly in the craniofacial complex, are useful to the orthodontists (Toledo, 2004).

> The orthodontic diagnosis has a group of stages in those that have multiple evaluation factors which are used in the study of the malocclusions. In general evaluation of a patient, it is important to consider the general physical development and the potential growth (Quirós 2000).

> The pubertal growth spurt of is an advantageous period in the orthodontic treatment and it should be kept in mind in connection with the planning of the treatment. One of the objectives of the orthodontic treatment during the adolescence, in the cases with skeletal discrepancies is to take advantage of the changes of growth of the patient. (Fiani, 1998; Padrós & Creus, 2002).

> In the adolescent, the phase of somatic maturity can influence in the selection of the appliances, the course of the treatment and the retention after the therapy (Geran et al. 2006). Because of this the study and the knowledge of the maturation stage and the phase of growth of the patient, is very important for making more efficient therapy. Authors like Nanda (Nanda, 1955), Björk and Helm (Björk & Helm, 1967), and Hägg and Taranger (Hägg & Taranger, 1980a, 1980b, 1982) established that the pattern of growth and facial development is similar to that of the general skeletal growth, and that the maximum peak of pubertal growth of the craniofacial structures occurs between 6 and 8 months after the maximum peak of pubertal growth in the stature.

Due to the wide individual variation, the chronological age cannot be used in the evaluation of the pubertal growth (Fiani, 1998), for that reason is appealed to determine the biological age. It is calculated starting from the bone, dental, morphological and sexual ages (Ceglia, 2005).

The study of the bone maturation is the surest and reliable method to evaluate the biological age of the individuals and to fix the physiologic maturity (Gutiérrez Muñiz et al. 2006).

In spite of the difficulties that outline the different existent methods (quality of the X-ray, minimum modifications of the projection, variability intra and inter observant, errors in the reading of the online systems, population in which the method is based, etc.) the evaluation of the bone maturation is indispensable in the clinical practice, since it is a parameter of great importance in the study of the alterations of the growth (Paesano et al, 1998).

The hand, the wrist and the distal epiphysis of the radius and the ulna present a great number of secondary centers of ossification on the whole, and they can reproduce in a single X-ray. For this reason, they are often chosen as study centers when it is sought to determine the state of skeletal maturation, although other centers of ossification of secondary epiphysis can be used, such as, the elbow and the tarsal bones (Cha, 2003).

Todd, in 1937, was the first author that mentioned the term "determinant of the maturity", when referring to the gradual changes that occur on the growth of the cartilage during the trial of coalition of the epiphysis with the diaphysis and that they can be determined by studying radiographic plaques (Quirós Álvarez, 2006). Years later Greulich and Pyle called them indicators of maturity and in 1959 they established the norms of skeletal age to value the bone maturation of the complete hand (Greulich & Pyle, 1959). As the different epiphyses don't often mature at the same time, discrepancies that are resolved with subjective trials which subtract precision to the method arise (Tanner et al. 1983).

Tanner and Whitehouse (Tanner et al. 1983), develop the method Tanner - Whitehouse 2 (TW2) to evaluate the bone development, through X-rays of the lefts hand and wrist, which has had great acceptance for their precision, being used at the present time in numerous countries (Izaguirre de Espinoza et al. 2003; Jiménez Hernández et al., 1986; Ortega et al., 2006).

In 1979, the professor Jordan (Jordan, 1979) publishes the results of the Study of Physical Growth in Cuba, where it uses the method TW2 in the determination of the bone maturation. Later on, in 1987 a group of investigators of the Department of Growth and Human Development determine the patterns of the Cuban population's bone maturation for sex and race through the method TW2 (Jiménez JM et al., 1987). This method is one of those that is used in Cuba in the evaluation of the bone maturation (Abreu Suárez et al., 1995).

Some authors have looked in the X-rays of the hand specific indicators of the spurt of pubertal growth (Fishman, 1982). Björk and Helm (Björk & Helm, 1967) and Gupta (Gupta, 1995) point out as a reliable indicator of the installation of the puberty, the beginning of the ossification of the sesamoid bone. Toledo (Toledo, 2004) and Rakosi and Jonas (Rakosi & Jonas, 1992) affirm that the appearance of the hook of the hamate bone is also a good indicator of the installation of the puberty.

Due to the wide individual variation, the chronological age cannot be used in the evaluation of the pubertal growth (Fiani, 1998), for that reason is appealed to determine the biological age. It is calculated starting from the bone, dental, morphological and

The study of the bone maturation is the surest and reliable method to evaluate the biological age of the individuals and to fix the physiologic maturity (Gutiérrez Muñiz et al. 2006).

In spite of the difficulties that outline the different existent methods (quality of the X-ray, minimum modifications of the projection, variability intra and inter observant, errors in the reading of the online systems, population in which the method is based, etc.) the evaluation of the bone maturation is indispensable in the clinical practice, since it is a parameter of great importance in the study of the alterations of the growth (Paesano

The hand, the wrist and the distal epiphysis of the radius and the ulna present a great number of secondary centers of ossification on the whole, and they can reproduce in a single X-ray. For this reason, they are often chosen as study centers when it is sought to determine the state of skeletal maturation, although other centers of ossification of secondary epiphysis

Todd, in 1937, was the first author that mentioned the term "determinant of the maturity", when referring to the gradual changes that occur on the growth of the cartilage during the trial of coalition of the epiphysis with the diaphysis and that they can be determined by studying radiographic plaques (Quirós Álvarez, 2006). Years later Greulich and Pyle called them indicators of maturity and in 1959 they established the norms of skeletal age to value the bone maturation of the complete hand (Greulich & Pyle, 1959). As the different epiphyses don't often mature at the same time, discrepancies that are resolved with

Tanner and Whitehouse (Tanner et al. 1983), develop the method Tanner - Whitehouse 2 (TW2) to evaluate the bone development, through X-rays of the lefts hand and wrist, which has had great acceptance for their precision, being used at the present time in numerous countries (Izaguirre de Espinoza et al. 2003; Jiménez Hernández et al., 1986; Ortega

In 1979, the professor Jordan (Jordan, 1979) publishes the results of the Study of Physical Growth in Cuba, where it uses the method TW2 in the determination of the bone maturation. Later on, in 1987 a group of investigators of the Department of Growth and Human Development determine the patterns of the Cuban population's bone maturation for sex and race through the method TW2 (Jiménez JM et al., 1987). This method is one of those that is used in Cuba in the evaluation of the bone maturation (Abreu Suárez et al., 1995).

Some authors have looked in the X-rays of the hand specific indicators of the spurt of pubertal growth (Fishman, 1982). Björk and Helm (Björk & Helm, 1967) and Gupta (Gupta, 1995) point out as a reliable indicator of the installation of the puberty, the beginning of the ossification of the sesamoid bone. Toledo (Toledo, 2004) and Rakosi and Jonas (Rakosi & Jonas, 1992) affirm that the appearance of the hook of the hamate bone is also a good

subjective trials which subtract precision to the method arise (Tanner et al. 1983).

can be used, such as, the elbow and the tarsal bones (Cha, 2003).

sexual ages (Ceglia, 2005).

et al, 1998).

et al., 2006).

indicator of the installation of the puberty.

In Maxillary Orthopedics one of the most utilized methods in the evaluation of the growth potential has been the one of Grave and Brown (Rakosi & Jonas, 1992; Tedaldi et al., 2007) that it divides the process of maturation of the bones of the hand in nine stages, between the 9th and the 17th year of age. The ossification characteristics are detected to the level of the phalanges, bones of the carpus and radius, and the stages of growth of the fingers are valued according to the relationship between the epiphysis and the diaphysis (Fiani, 1998). The evaluation of the Grave and Brown's method is recommended by Ortiz et al. (Ortiz et al., 2007), Spinelli Casanova et al. (Spinelli Casanova et al, 2006) and Pancherz and Hägg (Pancherz & Hägg, 1985) before the therapeutic interceptive in Orthodontics patients, to choose the ideal treatment according to the stages of bone maturation that the patient presents, diminishing this way the time in the use of the appliances and making them more effective. Previous to the realization of this investigation (Toledo Mayarí & Otaño Lugo, 2010a, 2010b, 2010c), was not reported in Cuba the use of Grave and Brown's method.

The inconvenience that presents the evaluation of the bone maturation through the hand in orthodontics patients , is the use of an additional X-ray for the patient, besides that this is not carried out with the dental X-ray machine, being necessary to remit the patient to a radiology service.

The current tendency in Orthodontics is to reduce the number of X-rays to the strictly necessary ones (Bujaldón Daza et al., 1998), for that indexes of skeletal maturation have been developed with the profiles of the bodies of the cervical vertebras that generally appear in the lateral teleradiography of skull used for the orthodontist diagnostic (Ortiz et al., 2007), being discharges correlations in the evaluations of the bone age between the cervical vertebras and the bones of the hand (Edilmar et al., 2005; Gandini et al., 2006; Hassel & Farman, 1995; San Roman et al., 2002; Uysal et al., 2006).

Also with the objective of substituting the X-ray of the hand that constitutes an additional exhibition to radiations in the patients of Orthodontics, Leite et al. (Leite et al., 1987), analyze the first three fingers, which include in the lateral teleradiography of skull and they don't find significant differences between the analysis of the bone maturation of the total hand and that of the three fingers. Shigemi Goto et al. (Shigemi Goto et al., 1996) and Rossi et al. (Rossi et al., 1999), analyze the changes at level of the first finger, in the distal phalanx and in the proximal respectively, finding that the evaluations at level of the phalanges constitute a quick and useful clinical method, to evaluate the growth potential in patient of Orthodontics. Madhu et al. (Madhu et al., 2003) and Ozer et al.((Ozer et al., 2006) use the stages of maturation of the middle phalange of the third finger, visualized in an X-ray of 41x31mm., taken with a machine of dental X rays conventional, where they find out that the evaluation of the stages of maturation of the middle phalanx of the third finger, constitutes an alternative method that can be used to determine the bone maturation, of the children in growth. Previous to the realization of this investigation, was not reports that in Cuba the patient's growth potential was evaluated through the middle phalange of the third finger, that which motivated us to determine the stages of maturation of that phalange and to identify the concordance between these and the stages of skeletal maturation, whereas clause that of existing concordance among the same ones, we will have a simplified method, for the determination of the growth potential, without the necessity of using an X-ray of the hand and an additional X-rays machine.

Problem of Investigation:

Whereas clause that in Orthodontics the evaluation of the growth potential has influence in the diagnosis, the treatment plan, the results and the prognostic of the treatment, and that the evaluation of the bone maturation through the X-ray of the hand, that is the anatomical area that is used in the evaluation of the bone maturation in Cuba, constitutes an additional X-ray for the tributary patients of orthodontist treatment, it would be necessary to respond:

What is the bone age of our patients?

What stages of skeletal maturation and of maturation of the middle phalange of the third finger they do present the same ones?

What is the relationship between the bone age and the chronological age, the stages of skeletal maturation and the stages of maturation of the middle phalange of the third finger in our patients?

What concordance does it exist among the methods to determine the growth potential in patient of Orthodontics?

The formulation of these questions forms the bases of a hypothesis that can be defined as it continues:

Considering that the growth potential constitutes the grade of growth becomes for the individual between the state in the moment of the exam and the definitive ceasing of this. In the determination of this potential, inside the diagnosis in Orthodontics, you can substitute the radiographic of the hand, being clinically useful the analysis of the bone maturation through the middle phalange of the third finger.

To give answers to the questions and the hypothesis, the following objectives were formulated:

General objective: To propose a simplified method to determine the growth potential in Orthodontics patient.

Specific objectives:


#### **2. Background**

In this epigraph are approached theoretical aspects of great importance in the specialty of Orthodontics that were considered in this investigation, due to the great majority of the children that go to the clinic and they are tributary of orthodontic treatment, they are in periods of growth and development, reason why when ignoring their biological age, we could incur in errors when outlining a diagnosis, prognostic and treatment plan.

Whereas clause that in Orthodontics the evaluation of the growth potential has influence in the diagnosis, the treatment plan, the results and the prognostic of the treatment, and that the evaluation of the bone maturation through the X-ray of the hand, that is the anatomical area that is used in the evaluation of the bone maturation in Cuba, constitutes an additional X-ray for the tributary patients of orthodontist treatment, it would be necessary to respond:

What stages of skeletal maturation and of maturation of the middle phalange of the third

What is the relationship between the bone age and the chronological age, the stages of skeletal maturation and the stages of maturation of the middle phalange of the third finger

What concordance does it exist among the methods to determine the growth potential in

The formulation of these questions forms the bases of a hypothesis that can be defined as it

Considering that the growth potential constitutes the grade of growth becomes for the individual between the state in the moment of the exam and the definitive ceasing of this. In the determination of this potential, inside the diagnosis in Orthodontics, you can substitute the radiographic of the hand, being clinically useful the analysis of the bone maturation

To give answers to the questions and the hypothesis, the following objectives were

General objective: To propose a simplified method to determine the growth potential in

1. To determine according to sex and chronological age: the bone age, the stages of skeletal maturation and the stages of maturation of the middle phalange of the third

2. To identify the relationship between the bone age and: the chronological age, the stages of skeletal maturation and the stages of maturation of the middle phalange of the third

In this epigraph are approached theoretical aspects of great importance in the specialty of Orthodontics that were considered in this investigation, due to the great majority of the children that go to the clinic and they are tributary of orthodontic treatment, they are in periods of growth and development, reason why when ignoring their biological age, we

could incur in errors when outlining a diagnosis, prognostic and treatment plan.

Problem of Investigation:

in our patients?

continues:

formulated:

Orthodontics patient. Specific objectives:

finger.

finger.

**2. Background** 

patient of Orthodontics?

What is the bone age of our patients?

finger they do present the same ones?

through the middle phalange of the third finger.

3. To identify the concordance between the studied methods.

The terms of growth and development are used to indicate the series of changes of volume, forms and weight that suffers the organism from the fecundation until the mature age (Cannut Brusola, 1988; J. Mayoral & G. Mayoral, 1990).

The growth in an individual's active development, is a continuous phenomenon that begins in the moment of the conception and it culminates at the end of the puberty, period during which reaches the maturity in their physical, psycho-social and reproductive aspects. Both processes have characteristic communes to all the individuals of the same species, what makes them predictable, however, they present wide differences between the subjects, given by the pattern's of growth individual character and development. This typical pattern emerges on one hand of the interaction of genetic and environmental factors that establish the growth potential and for other, the magnitude that this potential is expressed (Proffit, 1994).

The chronological age, that constitutes the time lapsed from the birth until the moment of the exam (Proffit, 1994), it doesn't always allow to value the development and the patient's somatic maturation, for that is appear to determine the biological maturity (Fiani, 1998).

According to Gutiérrez Muñiz et al. (Gutiérrez Muñiz et al., 2006) "the concept of biological maturity is defined as the successive transformations through the time, from the conception until the adulthood, existing two applicable fundamental methods at the present time for its evaluation: the bone age and the dental age".

The bone age is established determining radiograph of the number and size of the centers of ossification epiphysis, which should be compared with the existent norms for each age and sex (Recalde Cortes et al. 1997; Tanner et al., 1983). Each bone begins with a primary center of ossification that will grow progressively at the same time that is remodeled being able to acquire an or more epiphysis and finally it will acquire the mature form with the coalition from the epiphysis to the body of the bone. The sequence for each bone is the same as for the events that will happen in it, taking place independently late to the grade or advance with regard to the chronological age (Cattani, 2003; Fiani, 1998; Proffit, 1994).

The potential growth constitutes the grade of growth becomes for the individual between the state in the moment of the exam and the definitive ceasing of this (Proffit, 1994). It is given by the existent relationship between the bone age and the chronological age: to smaller bone age for a certain chronological age the individual's growth potential will be bigger, that is to say, the grade late of the bone age in connection with the chronological age reflects theoretically the years of growth residual extra or, that is the same thing, the years of growth that he has left before the closing of the epiphysis (Cattani, 2003; Proffit, 1994).

Theoretically, any part of the body can be used to determine the bone age, but in practice the hand and the wrist, are the most used, because they possess a great number of bones and epiphyses in development what allows the pursuit of the changes that happen through the years of the growth (Freitas et al. 2004; Jordan, 1979). They are also the most convenient areas to value the bone maturation, to be far from the gonads and to need less radiation (Jordán et al. 1987; Recalde Cortes et al. 1997).

The methods that are used to evaluate the growth potential of the left hand are: the TW2 that determines the bone age according to the maturation stages of each one of the bones; and the Grave and Brown that divides the process of maturation of the bones in nine stages of skeletal maturation. These two methods have disadvantage for the Orthodontics patients because the use of an additional X-ray, which is not carried out in the dental X rays machine, being necessary the patient's remission.

The current tendency in Orthodontics in the evaluation of the bone maturation is to reduce the number of X-rays to the strictly necessary ones (Bujaldón Daza et al., 1998), for that investigators exist as: Hassel and Farman (Hassel & Farman, 1995) that they try to develop some indexes of skeletal maturation with the profiles of the bodies of the cervical vertebras that appear in the lateral teleradiography of skull used for the orthodontist diagnostic. The advantages of using the cervical vertebras, it is centered in the reduction of radiographies to those that are subjected to the patients and for the easiness of consenting to the same ones (Ortiz et al., 2007).

Also in patient of Orthodontics with the objective of doing without of the X-ray of the hand that constitutes an additional exhibition to radiations, and it implies the use of a machine of rays X that is not used in a conventional way in Dentistry; the evaluation of the bone maturation has been used and of the growth potential through the development of the phalanges, that also has the purpose of simplifying the estimate, since alone the changes are analyzed at level of some phalanges, according to the relationship between the epiphysis and the diaphysis (Madhu et al., 2003).

Inside the diagnosis in Orthodontics, it is very important the evaluation of the growth potential, since most of the patients that require orthodontist treatment, are in a period of active growth, and with the treatment it can modify the facial growth, well be braking it, accelerating it or forward a normal vector (Tedaldi et al, 2007). According to Proffit (Proffit, 1994) it is not possible to modify a growth that is not taking place, and if a functional apparatus is placed on a patient that is not growing, the obtained result will be almost totally a dental mobilization.

The children with maxillary discrepancies usually benefit from the application of techniques to modify the growth. Since the bones of the face, and in particular the maxillary ones, suffer spontaneous changes during the different phases of growth, before establishing a treatment to correct skeletal malocclusions, it is necessary to know the opportune moment to begin the same one, according to the growth potential that the patient presents, to make more efficient our therapy (Tedaldi et al., 2007, Proffit, 1994).

The guiding principle is that growth can only be modified when it is occurring (Proffit, 1994), there is the importance of knowing the growth potential that the patient presents, when we carry out the diagnosis of the skeletal problems. Keeping in mind these aspects motivates ourselves to determine in the same sample three appraisal methods of the growth potential (Method TW2, Serious method and Brown, and determination of the stages of maturation of the half phalange of the third finger), with the objective of to propose a simplified method to determine the growth potential in patient of Orthodontics.

#### **3. Methodological design**

A cross-sectional technological innovation research was conducted in the period of January 2004 to April 2007, in the Clinic of Orthodontics of Havana School of Dentistry, in a sample of 150 patients between 8 and 16 years of age. A sampling was used by quotas according to sex and age, being divided in two groups, 75 for each sex. The patients were selected with previous condition to present good state of general health; to have measures of weight and height, that were between 10 and 90 percentile, of the Cuban Score of Weight for Height (Gutiérrez Muñiz et al., 2006); absence of chronic illnesses; absence of oligodontias; absences of congenital malformations; that they didn't have treatment corrective of the spinal column ; the need for the characteristics of their malocclusion, the realization of a lateral teleradiography of skull to complete their diagnosis; and to have signed the informed consent in writing.

#### **3.1 Variables**

158 Orthodontics – Basic Aspects and Clinical Considerations

of skeletal maturation. These two methods have disadvantage for the Orthodontics patients because the use of an additional X-ray, which is not carried out in the dental X rays machine,

The current tendency in Orthodontics in the evaluation of the bone maturation is to reduce the number of X-rays to the strictly necessary ones (Bujaldón Daza et al., 1998), for that investigators exist as: Hassel and Farman (Hassel & Farman, 1995) that they try to develop some indexes of skeletal maturation with the profiles of the bodies of the cervical vertebras that appear in the lateral teleradiography of skull used for the orthodontist diagnostic. The advantages of using the cervical vertebras, it is centered in the reduction of radiographies to those that are subjected to the patients and for the easiness of

Also in patient of Orthodontics with the objective of doing without of the X-ray of the hand that constitutes an additional exhibition to radiations, and it implies the use of a machine of rays X that is not used in a conventional way in Dentistry; the evaluation of the bone maturation has been used and of the growth potential through the development of the phalanges, that also has the purpose of simplifying the estimate, since alone the changes are analyzed at level of some phalanges, according to the relationship between the epiphysis

Inside the diagnosis in Orthodontics, it is very important the evaluation of the growth potential, since most of the patients that require orthodontist treatment, are in a period of active growth, and with the treatment it can modify the facial growth, well be braking it, accelerating it or forward a normal vector (Tedaldi et al, 2007). According to Proffit (Proffit, 1994) it is not possible to modify a growth that is not taking place, and if a functional apparatus is placed on a patient that is not growing, the obtained result will be almost

The children with maxillary discrepancies usually benefit from the application of techniques to modify the growth. Since the bones of the face, and in particular the maxillary ones, suffer spontaneous changes during the different phases of growth, before establishing a treatment to correct skeletal malocclusions, it is necessary to know the opportune moment to begin the same one, according to the growth potential that the patient presents, to make more efficient

The guiding principle is that growth can only be modified when it is occurring (Proffit, 1994), there is the importance of knowing the growth potential that the patient presents, when we carry out the diagnosis of the skeletal problems. Keeping in mind these aspects motivates ourselves to determine in the same sample three appraisal methods of the growth potential (Method TW2, Serious method and Brown, and determination of the stages of maturation of the half phalange of the third finger), with the objective of to propose a

A cross-sectional technological innovation research was conducted in the period of January 2004 to April 2007, in the Clinic of Orthodontics of Havana School of Dentistry, in a sample of 150 patients between 8 and 16 years of age. A sampling was used by quotas

simplified method to determine the growth potential in patient of Orthodontics.

being necessary the patient's remission.

consenting to the same ones (Ortiz et al., 2007).

and the diaphysis (Madhu et al., 2003).

our therapy (Tedaldi et al., 2007, Proffit, 1994).

totally a dental mobilization.

**3. Methodological design** 

Were studied the variables: chronological age, bone age (TW2), sex, stages of skeletal maturation and stages of maturation of the middle phalanx of the third finger.

Chronological age: Was considered the decimal age (Jordán, 1979): For the calculation, we subtracted the boy's date of birth and the date of the exam. The numeral was provided by the last two digits of the year and the decimal fraction was looked for in the table of decimal age.

Bone age (TW2): Was calculated in dependence of the sum of the punctuation of each stage for Radius, Ulna and Fingers, according to the patterns of the Cuban population's bone maturation, for the method TW2 (Jiménez et al., 1987).

Sex: Female and male.

Stages of skeletal maturation: Was classified according to Grave and Brown's method in stages of the 1 at 9.

Stages of maturation of the middle phalanx of the third finger: Was classified according to the relationship among the epiphysis and the diaphysis in one of the following stages (Toledo, 2004):


#### **3.2 Ethical aspects**

With all the patients that participated in the investigation and their parents, an interview was conducted before the beginning of that, where they were explained on what it consisted with the study, frequency, evaluation type and the radiological protection measures that would be taken for not damaging the patient's health. If they agreed, the patients and their parents should sign the informed consent, approving their holding in the study.

#### **3.3 Technical and procedures of obtaining the information**

#### **3.3.1 For the determination of: The bone age and the stages of skeletal maturation**

Firstly you proceeded to each observer's training in the appraisal methods of the studied maturation. The information was picked up and analyzed by two residents and two specialists of Orthodontics, each resident and each specialist determined in the same sample, one of the two methods of study of the maturation analyzed in this investigation (method TW2 and method of Grave and Brown).

To each patient was made the clinical history of Orthodontics and was realized an radiographic of the left hand (Fig. 1) where they were determined: the bone age for the method TW2 (Jiménez et al, 1987) and the stages of skeletal maturation for the method of Grave and Brown (Tedaldi et al. 2007).

Fig. 1. Radiographic of the left hand.

The radiographic of the left hand was realized with the same regulations that the utilized ones in the National Study of Growth and Human Development in Cuba, carried out by Jordan (Jordán, 1979).

Each radiographic of the left hand was evaluated by the resident and the specialist in a first observation and in three weeks later in a second observation; that is to say a total of four times to calculate the variability inter and intra observant. The cases where discrepancy existed they were studied again to obtain the final results.

#### **3.3.2 To determine the stages of skeletal maturation of the middle phalanx of the third finger of the left hand**

In a paper of size Letter (21,59 cm. x 27,94 cm.), at a distance of 10 cm. of the superior margin and 10 cm. of the left margin, the contour of a film dental standard, Kodak marks, of 41x31 mm. was traced, and it was clipped by the traced area, being an opening in the paper with the dimensions of the dental film.

The paper was placed on the X-rays of the left hand of the 150 studied patients, it was made coincide the opening of the paper on the union between the middle phalanx and the proximal phalanx of the third finger and it was placed on a fixed negatoscope (Fig. 2).

specialists of Orthodontics, each resident and each specialist determined in the same sample, one of the two methods of study of the maturation analyzed in this investigation

To each patient was made the clinical history of Orthodontics and was realized an radiographic of the left hand (Fig. 1) where they were determined: the bone age for the method TW2 (Jiménez et al, 1987) and the stages of skeletal maturation for the method of

The radiographic of the left hand was realized with the same regulations that the utilized ones in the National Study of Growth and Human Development in Cuba, carried out by

Each radiographic of the left hand was evaluated by the resident and the specialist in a first observation and in three weeks later in a second observation; that is to say a total of four times to calculate the variability inter and intra observant. The cases where discrepancy

**3.3.2 To determine the stages of skeletal maturation of the middle phalanx of the third** 

In a paper of size Letter (21,59 cm. x 27,94 cm.), at a distance of 10 cm. of the superior margin and 10 cm. of the left margin, the contour of a film dental standard, Kodak marks, of 41x31 mm. was traced, and it was clipped by the traced area, being an opening in the paper with

The paper was placed on the X-rays of the left hand of the 150 studied patients, it was made coincide the opening of the paper on the union between the middle phalanx and the proximal phalanx of the third finger and it was placed on a fixed negatoscope (Fig. 2).

(method TW2 and method of Grave and Brown).

Grave and Brown (Tedaldi et al. 2007).

Fig. 1. Radiographic of the left hand.

existed they were studied again to obtain the final results.

Jordan (Jordán, 1979).

**finger of the left hand** 

the dimensions of the dental film.

Fig. 2. Placement of the prepared paper on the union between the middle phalanx and the proximal phalanx of the third finger, in the radiographic of the left hand.

The analysis of the radiographic was carried out using a compass to measure the bone size in the middle phalanx and the maturation stage was classified with A to E, according to the classification proposed by Toledo (Toledo, 2004). With this procedure it was possible to locate each patient evaluated in a stage of maturation of the middle phalanx of the third finger, the same one was carried out by the main investigator and a specialist in Orthodontics, member of the investigation team, in two different opportunities to calculate the variability intra and inter observant.

#### **3.4 Technical and procedures of elaboration and analysis**

The information was stored in a data base automated in the system Excel, of the package Office 2003 on Windows XP professional and for the prosecution of the results the statistical packages SPSS version 11.5 and STATISTICA version 6.1 were used.

To calculate the variability intra and inter observant in the studied methods, the coefficient Kappa was applied (Begole, 2003).

The percentage was used for the qualitative variables and for the quantitative variables the arithmetic mean like measure summary and the standard deviation like variation measure (Bayarre et al. 2005).

You prove statistics employees: The association grade was calculated among the quantitative variables by means of the lineal correlation coefficient of Pearson (Begole, 2003) and the association grade among the variables in ordinal scales by means of the correlation coefficient of ranges of Spearman (Begole, 2003). To calculate the concordance among the results obtained in the studied methods, the coefficient Kappa was applied (Begole, 2003).

In all the used statistical tests, the used level of significance was of 0.05.

The results were presented in tables designed to the effect.

#### **4. Results**

In this epigraph the main results are presented, it contains the analysis of 6 tables.

The analysis of the variability intra and inter observant, their agreement was evaluated regarding the methods studied by means of an index Kappa. With relationship to the variability intra observant, that is to say, the level of discrepancy with regard to the valuations of oneself after three weeks, discrepancies didn't exist, in the three valued methods, being the agreement of 1,000 in the 150 cases, in each one of the methods. With relationship to the variability inter observant, that is to say, the level of discrepancy with regard to the valuations among the two observants, discrepancies didn't exist among these, being the agreement of 1,000 in the 150 cases, for these three methods.

#### **4.1 Determination according to sex and chronological age of: The bone age, the stages of skeletal maturation and the stages of maturation of the middle phalanx of the third finger**

#### **4.2 Identification of the relationship among the bone age and: The chronological age, the stages of skeletal maturation and the stages of maturation of the middle phalanx of the third finger**

Table 1 shows the arithmetic mean and the standard deviation of the chronological age and the bone age, calculated by the method TW2, according to groups of ages in the feminine sex, were found that in the groups of ages that were between the 8,00 and the 12,99 years and of 15.00 to 16.99 years, the bone age was bigger than the chronological one, being smaller in the remaining groups of ages. The coefficient of lineal correlation of Pearson among the bone age (TW2) and the chronological one presented a value of 0,977; that which signifies a very strong positive correlation, highly significant (p <0,010).


r= 0,977 p = 0,000 n =75

r (lineal correlation coefficient of Pearson among bone age (TW2) and chronological age).

Table 1. Arithmetic mean (X) and standard deviation (DE) of chronological age and bone age (TW2) by groups of age in females.

Table 2 shows the arithmetic mean and the standard deviation of the chronological age and the bone age calculated by the method TW2 according to groups of ages in the masculine sex, it was found that in the groups of ages that were between 8,00 and 12,99 years, the bone age was smaller than the chronological one, being bigger starting from 13,00 years. The coefficient of lineal correlation of Pearson among the bone age (TW2) and the chronological one presented a value of 0,983; that which signifies a very strong positive correlation, highly significant (p <0,010).


r = 0,983 p = 0,000 n =75

162 Orthodontics – Basic Aspects and Clinical Considerations

The analysis of the variability intra and inter observant, their agreement was evaluated regarding the methods studied by means of an index Kappa. With relationship to the variability intra observant, that is to say, the level of discrepancy with regard to the valuations of oneself after three weeks, discrepancies didn't exist, in the three valued methods, being the agreement of 1,000 in the 150 cases, in each one of the methods. With relationship to the variability inter observant, that is to say, the level of discrepancy with regard to the valuations among the two observants, discrepancies didn't exist among these,

In this epigraph the main results are presented, it contains the analysis of 6 tables.

**4.1 Determination according to sex and chronological age of: The bone age, the stages of skeletal maturation and the stages of maturation of the middle phalanx of** 

**4.2 Identification of the relationship among the bone age and: The chronological age, the stages of skeletal maturation and the stages of maturation of the middle phalanx** 

Table 1 shows the arithmetic mean and the standard deviation of the chronological age and the bone age, calculated by the method TW2, according to groups of ages in the feminine sex, were found that in the groups of ages that were between the 8,00 and the 12,99 years and of 15.00 to 16.99 years, the bone age was bigger than the chronological one, being smaller in the remaining groups of ages. The coefficient of lineal correlation of Pearson among the bone age (TW2) and the chronological one presented a value of 0,977; that which

> 8,00-8,99 8,38 0,33 8,72 1,22 9,00-9,99 9,87 0,17 10,55 0,47 10,00-10,99 10,53 0,33 10,58 0,98 11,00-11,99 11,58 0,24 12,36 0,47 12,00-12,99 12,75 0,20 13,32 0,89 13,00-13,99 13,42 0,28 12,57 0,73 14,00-14,99 14,86 0,01 14,78 0,46 15,00-16,99 15,19 0,14 15,20 0,70

Chronological age Bone age (TW2)

X1 DE1 X2 DE2

being the agreement of 1,000 in the 150 cases, for these three methods.

signifies a very strong positive correlation, highly significant (p <0,010).

r (lineal correlation coefficient of Pearson among bone age (TW2) and chronological age).

Table 1. Arithmetic mean (X) and standard deviation (DE) of chronological age and bone

Group of Ages

**4. Results** 

**the third finger** 

**of the third finger** 

r= 0,977 p = 0,000 n =75

age (TW2) by groups of age in females.

r (lineal correlation coefficient of Pearson among bone age (TW2) and chronological age).

Table 2. Arithmetic mean (X) and standard deviation (DE) of chronological age and bone age (TW2) by groups of age in males.

Table 3 shows the arithmetic mean and the standard deviation of the chronological age and the bone age (TW2) according to stages of skeletal maturation and sex, it was found that in each maturation stage, the averages of the chronological age were smaller in the feminine sex than in the masculine one. With relationship to the bone age calculated by the method TW2, in the feminine sex the averages of the same one went superior to those of the chronological age, in all the studied stages, however, in the masculine sex the bone age overcame the chronological one in the stages 4, 5, 6 and 8. The stages 4 and 5 are those of more clinical significance, belonged together with the chronological ages of 11,35 and 11,77 years in the feminine sex and 13,76 and 13,82 years in the masculine one and with the bone ages of 11,78 and 12,34 years in the feminine sex and of 14,20 and 14,57 years in the masculine one. It was observed that the females were earlier in their maturation stages than the males and that the stages advanced as it increased the chronological age and the bone age of the patients, in both sexes. The coefficient of correlation of ranges of Spearman among the bone age (TW2) and the stages of skeletal maturation presented a value of 0,855 in the feminine sex and 0,903 in the masculine one, both sexes showed a positive correlation, very significant (p <0,010). In the studied sample they were not patient in the stage 9.


Sex Female rho= 0,855 p = 0,000 n =75

Sex Male rho= 0,903 p = 0,000 n =75

rho (Correlation coefficient of Spearman among bone age (TW2) and stages of skeletal maturation.

Table 3. Arithmetic mean (X) and standard deviation (DE) of chronological age and bone age (TW2) by stages of skeletal maturation and sex.

Table 4 shows arithmetic mean and the standard deviation of the chronological age and the bone age (TW2) according to stages of maturation of the middle phalanx of the third finger and sex, it was found that in all the maturation stages the averages of the chronological age were smaller in the feminine sex than in the masculine one. In feminine sex the bone age overcame the chronological one in all the stages and in the masculine one in the stages B, C and E. The stage C (cap stage), it happened that 11,77 year-old chronological age and the bone one of 12,34 years, with a standard deviation of 1,18 and 0,99 years respectively in the females, while in the males, went to the 13,82 years and 14,57 years, with a standard deviation of 1,13 and 0,72 years respectively. It was observed that the females were earlier in their maturation stages than the males. The coefficient of correlation of ranges of Spearman among the bone age (TW2) and the stages of maturation of the middle phalanx of the third finger presented a value of 0,888 in the feminine sex and 0,921 in the masculine one, both sexes showed a positive correlation, very significant (p <0,010).


Sex Female rho= 0,888 p = 0,000 n =75

Sex Male rho= 0,921 p = 0,000 n =75

rho (Correlation coefficient of Spearman among bone age (TW2) and stages of maturation of the middle phalanx of the third finger

Table 4. Arithmetic mean (X) and standard deviation (DE) of chronological age and bone age (TW2) by stages of maturation of the middle phalanx of the third finger and sex.

#### **4.3 Identification of concordance between the studied methods**

164 Orthodontics – Basic Aspects and Clinical Considerations

rho (Correlation coefficient of Spearman among bone age (TW2) and stages of skeletal maturation. Table 3. Arithmetic mean (X) and standard deviation (DE) of chronological age and bone

Table 4 shows arithmetic mean and the standard deviation of the chronological age and the bone age (TW2) according to stages of maturation of the middle phalanx of the third finger and sex, it was found that in all the maturation stages the averages of the chronological age were smaller in the feminine sex than in the masculine one. In feminine sex the bone age overcame the chronological one in all the stages and in the masculine one in the stages B, C and E. The stage C (cap stage), it happened that 11,77 year-old chronological age and the bone one of 12,34 years, with a standard deviation of 1,18 and 0,99 years respectively in the females, while in the males, went to the 13,82 years and 14,57 years, with a standard deviation of 1,13 and 0,72 years respectively. It was observed that the females were earlier in their maturation stages than the males. The coefficient of correlation of ranges of Spearman among the bone age (TW2) and the stages of maturation of the middle phalanx of the third finger presented a value of 0,888 in the feminine sex and 0,921 in the masculine one, both

> Chronological age Bone age (TW2) Female Male Female Male X1 DE1 X1 DE1 X2 DE2 X2 DE2

A 8,59 0,66 11,38 1,34 8,97 1,25 10,66 1,11 B 11.55 1.4 13.06 0.71 11.52 0.92 13.25 0.92 C 11,77 1,18 13,82 1,13 12,34 0,99 14,57 0,72 D 13.83 1.23 15.93 0.86 13.59 1.17 15.7 0.63 E 14.24 0.98 16.25 0.23 14.45 1.03 16.56 0.28

rho (Correlation coefficient of Spearman among bone age (TW2) and stages of maturation of the middle

Table 4. Arithmetic mean (X) and standard deviation (DE) of chronological age and bone age (TW2) by stages of maturation of the middle phalanx of the third finger and sex.

1 8,59 0,66 11,38 1,34 8,97 1,25 10,66 1,11 2 10,06 0,54 11,61 0,87 10,25 0,71 10,50 1,20 3 11,63 1,35 11,71 0,65 11,82 0,84 10,50 0,89 4 11,35 1,71 13,76 0,80 11,78 1,18 14,20 0,14 5 11,77 1,18 13,82 1,13 12,34 0,99 14,57 0,72 6 13,34 0,97 14,96 0,97 13,77 0,79 15,46 0,54 7 15,31 0,17 16,35 0,48 15,45 0,07 16,08 0,62 8 14,24 0,98 16,25 0,23 14,45 1,03 16,56 0,28

Chronological age Bone age (TW2) Female Male Female Male X1 DE1 X1 DE1 X2 DE2 X2 DE2

Stages of skeletal maturation

Sex Female rho= 0,855 p = 0,000 n =75 Sex Male rho= 0,903 p = 0,000 n =75

Stages of maturation of the middle phalanx of the third finger

Sex Female rho= 0,888 p = 0,000 n =75 Sex Male rho= 0,921 p = 0,000 n =75

phalanx of the third finger

age (TW2) by stages of skeletal maturation and sex.

sexes showed a positive correlation, very significant (p <0,010).

Table 5 shows the percentages of females according to the stages of skeletal maturation and stages of maturation of the middle phalanx of the third finger, it was found that in the stage of skeletal maturation 1, 100,00% was in the stage A of maturation of the middle phalanx of the third finger; in the stages 2, 3 and 4, 100% was in the stage B of the phalanx; in the stage 5, 100% was in the C; in the 6 and the 7, 100,00% was in the stage D and in the stage 8, 100,00% was in the stage E of the phalanx. The coefficient of concordance Kappa between the stages of skeletal maturation and the stages of maturation of the middle phalanx of the third finger, presented a value of 1,000 that which evidenced a perfect concordance, very significant (p <0.010).


Coefficient Kappa = 1,000 p=0,000 n=75

Table 5. Percentage of females according to stages of skeletal maturation and stages of maturation of the middle phalanx of the third finger.

Table 6 shows the percentages of males according to the stages of skeletal maturation and stages of maturation of the middle phalanx of the third finger, it was found that in the stage of skeletal maturation 1, 100,00% was in the stage A of maturation of the middle phalanx of the third finger; in the stages 2, 3 and 4, 100% was in the stage B of the phalanx; in the stage 5, 100% was in the C; in the 6 the biggest percent was in the D (75,00); in the 7, 100,00% was in the stage D and in the stage 8, 100,00% was in the stage E of the phalanx. The coefficient of concordance Kappa between the stages of skeletal maturation and the stages of maturation of the middle phalanx of the third finger, presented a value of 0,964; that which evidenced a high concordance, very significant (p <0.010).


Coefficient Kappa = 0,964 p=0,000 n=75

Table 6. Percentage of males according to stages of skeletal maturation and stages of maturation of the middle phalanx of the third finger.

#### **5. Discussion**

In this epigraph, one discussed the most important results and they were compared with the results of other investigations, with foundations starting from the revised bibliography.

With relationship to the variability intra and inter observant results were completely coincident in the three studied methods. The author considers that the results are due to the previous training of the investigators in each one of the studied evaluation methods.

With relationship to the variability intra observant and inter observant in the analysis of the stage of maturation of the middle phalanx of the third finger, coincidence existed among the four carried out observations. The author considers that the results are due to the simplification of this method, since in the same alone the changes are analyzed at level of a single phalanx.

In the studied sample, the bone age of the patients, calculated through the method TW2, didn't coincide with the chronological age. These results coincide with those of Malavé and Rojas (Malavé & Rojas, 2000) whom they outlined that, the chronological age is not a good indicator of the level of an individual's bone maturation.

In the three methods of study of the analyzed maturation, it was found that the females matured before the males of their same age. These results coincide with studies carried out for Grave and Townsend (Grave & Townsend, 2003), Demirjian et al. (Demirjian et al, 1985) and Liversidge and Speechly (Liversidge & Speechly, 2001), who they find that, the females mature more early than the males, that which is important to consider in the general evaluation of the orthodontist patient.

1 15 15 100,00 - - - - - - - - 2 11 - - 11 100,00 - - - - - - 3 12 - - 12 100,00 - - - - - - 4 2 - - 2 100,00 - - - - - - 5 20 - - - - 20 100,00 - - - - 6 8 - - - - 2 25,00 6 75,00 - - 7 5 - - - - - - 5 100,00 - - 8 2 - - - - - - - - 2 100,00

Table 6. Percentage of males according to stages of skeletal maturation and stages of

In this epigraph, one discussed the most important results and they were compared with the results of other investigations, with foundations starting from the revised bibliography.

With relationship to the variability intra and inter observant results were completely coincident in the three studied methods. The author considers that the results are due to the

With relationship to the variability intra observant and inter observant in the analysis of the stage of maturation of the middle phalanx of the third finger, coincidence existed among the four carried out observations. The author considers that the results are due to the simplification of this method, since in the same alone the changes are analyzed at level of a

In the studied sample, the bone age of the patients, calculated through the method TW2, didn't coincide with the chronological age. These results coincide with those of Malavé and Rojas (Malavé & Rojas, 2000) whom they outlined that, the chronological age is not a good

In the three methods of study of the analyzed maturation, it was found that the females matured before the males of their same age. These results coincide with studies carried out for Grave and Townsend (Grave & Townsend, 2003), Demirjian et al. (Demirjian et al, 1985) and Liversidge and Speechly (Liversidge & Speechly, 2001), who they find that, the females mature more early than the males, that which is important to consider in the general

previous training of the investigators in each one of the studied evaluation methods.

Stages of maturation of the middle phalanx of the third finger

A B C D E
