Prologue: Tooth Anatomy and Morphology

*Zühre Akarslan*

#### **1. Introduction**

Knowledge of tooth morphology and anatomy is important in dentistry. Crown morphology is essential in restorative treatment and prosthodontic treatment. External root morphology influences the success of oral surgery, periodontal treatment, orthodontic treatment, and prosthodontic treatment. The knowledge of root canal anatomy is important in endodontics. There can be various root canal configurations affecting the success of root canal treatment [1–3]. The size of teeth crowns, number of roots, and morphology of occlusal surfaces, including cusps, interconnecting depressions, grooves, or pits, may differ among populations and genders [4–9].

There are two sets of teeth during lifetime, the deciduous teeth and the permanent teeth. The deciduous teeth are present in childhood and replaced with the permanent teeth. There are 20 deciduous teeth. Ten of these are located at the maxillae, and 10 of them are located at the mandible. They are consisted of incisors, canines, and molars. There are 32 permanent teeth. Sixteen of these teeth are located in the maxillae, and 16 are located in the mandible. They are consisted of incisors, canines, premolars, and molars. The main difference between the deciduous and permanent dentition is that the permanent dentition has the premolar teeth. There are four premolars in the maxillae and four premolars in the mandible [10].

The permanent incisors are placed in front of the oral cavity. There are total eight incisors, four at the maxillae, and four at the mandible. The function of these teeth is cutting food. Their crowns are flattened and they usually have a single root. The incisors are consisted of the central and lateral teeth. The mandibular central incisor is the smallest tooth in the mouth, but the buccolingual dimension of its root is very large [11–13].

The permanent canines are placed after the lateral incisors. There are two canines in the maxillae and two canines in the mandible. The canines tear and shred food. The canine has a single root and root canal. Its root is longer compared to the incisors [12].

The premolar teeth are located between the canines and the molars. There are four premolars in the maxillae and four premolars in the mandible. The premolars are the transitional teeth. They are only present in the permanent dentition. They guide food from the front of the mouth back to the molars. They can have two or more cusps on their crown [10]. The second maxillary premolar tooth in the maxillae and the first and second premolar tooth in the mandible have one root and root canal. Different from these, the first maxillary premolar tooth has two roots and root canals, one located in the buccal and the other in the palatal area. In some cases there can be extra roots and root canals in these teeth [3].

The permanent molars are located in the posterior region in the oral cavity. The molars are placed after the premolars in the permanent dentition. There are six molars in the maxillae and six molars in the mandible. The functions of these teeth are to crush and grind food. They have multiple cusps on their crown [10]. The root configuration and number differ among these teeth. The maxillary molars usually have three separate roots; mesiobuccal, distobuccal, and palatal. Sometimes there can be one, two, or four roots [14]. On the other hand, the mandibular molars usually have two roots: mesial and distal. However, rarely these teeth can have one or three roots [15].

The teeth may be affected from various anomalies. These anomalies can change the structure, color, shape, and form of the teeth. The anomalies are named as concrescence, fusion, germination, taurodontism, dilaceration, enamel pearls, dens invaginatus, dens in dente, dilated odontoma, dens evaginatus, talon cusp, amelogenesis imperfecta, dentinogenesis imperfecta, osteogenesis imperfecta, dentin dysplasia, regional odontodysplasia, and Turner's hypoplasia. Dentists should have knowledge about these anomalies and the possible complications they can lead during dental treatment [16].

The aim of this book is to provide the readers information about dental morphology, anatomy, and anomalies.

#### **2. Overview of the chapters of this book**

Second chapter: "Tooth Morphology Overview" written by Abeer Alshami, Shatha Alharthi, Munirah bin Shabeeb, and Monika Wahi. The authors start with the nomenclature and continue with tooth numbering systems in this chapter. They give details about the Fédération Dentaire Internationale (FDI) system, tooth morphology and anatomy, and stages of tooth formation. They end the chapter with the hypotheses accepted nowadays about formation of the tooth. The authors provide useful information and rich illustrations for the readers.

Third chapter: "Root Canal Morphology and Anatomy" written by Esra Güven Pamukçu. This chapter gives the readers beneficial information about root canal anatomy and morphology of maxillary and mandibular incisors, canines, premolars, and molars. A novel tooth morphology classification respecting tooth number, number of roots, and root canal configuration types is presented. A summary of dental anomalies can be found at the end of the chapter.

Fourth chapter: "External and Internal Anatomy of Mandibular Permanent Incisors" written by Mohammed A. Aldawla, Abdulbaset A. Mufadhal, and Ahmed A. Madfa. In this chapter detailed information is given about the external root morphology, the internal root anatomy, and the dental anomalies which can be seen in permanent mandibular incisor teeth. The chapter is written according to a rich literature review which is particularly informative.

Fifth chapter: "External and Internal Anatomy of Maxillary Permanent First Molars" written by Abdulbaset A. Mufadhal, Mohammed A. Aldawla, and Ahmed A. Madfa. This chapter provides the readers useful information about external root morphology, internal root anatomy, variations, and anatomical anomalies of permanent maxillary first molars. The chapter is written according to a rich literature review in an elucidative manner.

Sixth chapter: "Can Orofacial Structures Affect Tooth Morphology?" written by Amanda Valentim, Renata Furlan, Mariana Amaral, and Fernanda Guimarães. This chapter focuses on the role of orofacial forces on the teeth. The authors give information about all factors related in detail. They emphasize the role of the orofacial muscles, oral habits, and hyperfunction of masticator muscles on the occlusion and size and shape of the teeth according to a rich literature review.

**37**

**Author details**

Zühre Akarslan

Gazi University, Ankara, Turkey

Department of Oral and Maxillofacial Radiology, Faculty of Dentistry,

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

\*Address all correspondence to: dtzuhre@yahoo.com

provided the original work is properly cited.

*Prologue: Tooth Anatomy and Morphology DOI: http://dx.doi.org/10.5772/intechopen.89148*

for immediate placement.

information about root morphology of teeth. Evolution and the fabrication procedures and clinical predictability of root-shaped dental implants are explained in the chapter. The readers can benefit from the advantages of the root-shaped implants

Seventh chapter: "Evolution of Dental Implant Shapes and Today's Custom Root Analogue Implants" written by Ayse Sumeyye Akay. The author provides *Prologue: Tooth Anatomy and Morphology DOI: http://dx.doi.org/10.5772/intechopen.89148*

*Human Teeth - Key Skills and Clinical Illustrations*

during dental treatment [16].

phology, anatomy, and anomalies.

**2. Overview of the chapters of this book**

useful information and rich illustrations for the readers.

dental anomalies can be found at the end of the chapter.

literature review which is particularly informative.

size and shape of the teeth according to a rich literature review.

review in an elucidative manner.

in the maxillae and six molars in the mandible. The functions of these teeth are to crush and grind food. They have multiple cusps on their crown [10]. The root configuration and number differ among these teeth. The maxillary molars usually have three separate roots; mesiobuccal, distobuccal, and palatal. Sometimes there can be one, two, or four roots [14]. On the other hand, the mandibular molars usually have two roots: mesial and distal. However, rarely these teeth can have one or three roots [15]. The teeth may be affected from various anomalies. These anomalies can change

the structure, color, shape, and form of the teeth. The anomalies are named as concrescence, fusion, germination, taurodontism, dilaceration, enamel pearls, dens invaginatus, dens in dente, dilated odontoma, dens evaginatus, talon cusp, amelogenesis imperfecta, dentinogenesis imperfecta, osteogenesis imperfecta, dentin dysplasia, regional odontodysplasia, and Turner's hypoplasia. Dentists should have knowledge about these anomalies and the possible complications they can lead

The aim of this book is to provide the readers information about dental mor-

Second chapter: "Tooth Morphology Overview" written by Abeer Alshami, Shatha Alharthi, Munirah bin Shabeeb, and Monika Wahi. The authors start with the nomenclature and continue with tooth numbering systems in this chapter. They give details about the Fédération Dentaire Internationale (FDI) system, tooth morphology and anatomy, and stages of tooth formation. They end the chapter with the hypotheses accepted nowadays about formation of the tooth. The authors provide

Third chapter: "Root Canal Morphology and Anatomy" written by Esra Güven Pamukçu. This chapter gives the readers beneficial information about root canal anatomy and morphology of maxillary and mandibular incisors, canines, premolars, and molars. A novel tooth morphology classification respecting tooth number, number of roots, and root canal configuration types is presented. A summary of

Fourth chapter: "External and Internal Anatomy of Mandibular Permanent Incisors" written by Mohammed A. Aldawla, Abdulbaset A. Mufadhal, and Ahmed A. Madfa. In this chapter detailed information is given about the external root morphology, the internal root anatomy, and the dental anomalies which can be seen in permanent mandibular incisor teeth. The chapter is written according to a rich

Fifth chapter: "External and Internal Anatomy of Maxillary Permanent First Molars" written by Abdulbaset A. Mufadhal, Mohammed A. Aldawla, and Ahmed A. Madfa. This chapter provides the readers useful information about external root morphology, internal root anatomy, variations, and anatomical anomalies of permanent maxillary first molars. The chapter is written according to a rich literature

Sixth chapter: "Can Orofacial Structures Affect Tooth Morphology?" written by Amanda Valentim, Renata Furlan, Mariana Amaral, and Fernanda Guimarães. This chapter focuses on the role of orofacial forces on the teeth. The authors give information about all factors related in detail. They emphasize the role of the orofacial muscles, oral habits, and hyperfunction of masticator muscles on the occlusion and

Seventh chapter: "Evolution of Dental Implant Shapes and Today's Custom Root Analogue Implants" written by Ayse Sumeyye Akay. The author provides

**36**

information about root morphology of teeth. Evolution and the fabrication procedures and clinical predictability of root-shaped dental implants are explained in the chapter. The readers can benefit from the advantages of the root-shaped implants for immediate placement.

#### **Author details**

Zühre Akarslan Department of Oral and Maxillofacial Radiology, Faculty of Dentistry, Gazi University, Ankara, Turkey

\*Address all correspondence to: dtzuhre@yahoo.com

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

#### **References**

[1] Sanson G. Cutting food in terrestrial carnivores and herbivores. Interface Focus. 2016;**6**:20150109. DOI: 10.1098/ rsfs.2015.0109

[2] Brook AH, Jernvall J, Smith RN, Hughes TE, Townsend GC. The dentition: The outcomes of morphogenesis leading to variations of tooth number, size and shape. Australian Dental Journal. 2014;**59**:131-142. DOI: 10.1111/adj.12160

[3] Mohammadi Z, Shalavi S, Jafarzadeh H. Extra roots and root canals in premolar and molar teeth: Review of an endodontic challenge. The Journal of Contemporary Dental Practice. 2013;**14**:980-986

[4] Felemban NH, Manjunatha BS. Prevalence of the number of cusps and occlusal groove patterns of the mandibular molars in a Saudi Arabian population. Journal of Forensic and Legal Medicine. 2017;**49**:54-58. DOI: 10.1016/j.jflm.2017.05.013

[5] Dholia B, Manjunatha BS. Occlusal morphology of permanent mandibular first and second molars in Gujarati population. Journal of Forensic Dental Sciences. 2015;**7**:137-141. DOI: 10.4103/0975-1475.146368

[6] Mallineni SK, Panampally GK, Chen Y, Tian T. Mandibular talon cusps: A systematic review and data analysis. Journal of Clinical and Experimental Dentistry. 2014;**6**:e408-e413. DOI: 10.4317/jced.51476

[7] Khraisat A, Taha ST, Jung RE, Hattar S, Smadi L, Al-Omari IK, et al. Prevalence, association, and sexual dimorphism of Carabelli's molar and shovel incisor traits amongst Jordanian population. Odonto-Stomatologie Tropicale. 2007;**30**:17-21

[8] Filipovic G, Kanjevac T, Cetenovic B, Ajdukovic Z, Petrovic N. Sexual dimorphism in the dimensions of teeth in Serbian population. Collegium Antropologicum. 2016;**40**:23-28

[9] Martins JNR, Marques D, Francisco H, Caramês J. Gender influence on the number of roots and root canal system configuration in human permanent teeth of a Portuguese subpopulation. Quintessence International. 2018;**49**:103- 111. DOI: 10.3290/j.qi.a39508.

[10] Yavuzyılmaz H. Diş Morfolojisi ve Anatomisi. [Tooth Morphology and Anatomy]. 6th ed. Beşevler Ankara Türkiye: Gazi Kitapevi; 2013. pp. 27-191

[11] Ozaki T, Satake T, Kanazama E. Morphological significance of root length variability in comparison with other crown dimensions. The Journal of Nihon University School of Dentistry. 1987;**29**:233-240

[12] Yamanaka A, Iwai H, Uemura M, Goto T. Patterning of mammalian heterodont dentition within the upper and lower jaws. Evololution and Development. 2015;**17**:127-138. DOI: 10.1111/ede.12116

[13] McGowan S. Characteristics of teeth: A review of size, shape, composition, and appearance of maxillary anterior teeth. The Compendium of Continuing Education in Dentistry. 2016;**37**:164-171

[14] Alrahabi M, Sohail Zafar M. Evaluation of root canal morphology of maxillary molars using cone beam computed tomography. Pakistan Journal of Medical Sciences. 2015;**31**:426-430. DOI: 10.12669/pjms.312.6753

[15] Akpınar KE, Ay S, Er K, Köşger HH. Türk toplumunda alt molar dişlerin kök ve kanal sayıları [The number of roots and canals in mandibular molars of a Turkish sub-population]. Ondokuz Mayis Universitesi Dis Hekimliği Fakültesi Dergisi. 2004;**5**:123-127

**39**

*Prologue: Tooth Anatomy and Morphology DOI: http://dx.doi.org/10.5772/intechopen.89148*

[16] Lam EWN. Dental anomalies. In: White SC, Pharoah MJ, editors. Oral Radiology Principles and Interpretation. 6th ed. St. Louis, Missouri: Mosby,

Elsevier; 2009. pp. 295-323

*Prologue: Tooth Anatomy and Morphology DOI: http://dx.doi.org/10.5772/intechopen.89148*

[16] Lam EWN. Dental anomalies. In: White SC, Pharoah MJ, editors. Oral Radiology Principles and Interpretation. 6th ed. St. Louis, Missouri: Mosby, Elsevier; 2009. pp. 295-323

**38**

*Human Teeth - Key Skills and Clinical Illustrations*

[1] Sanson G. Cutting food in terrestrial carnivores and herbivores. Interface Focus. 2016;**6**:20150109. DOI: 10.1098/

Sexual dimorphism in the dimensions of teeth in Serbian population. Collegium Antropologicum. 2016;**40**:23-28

[9] Martins JNR, Marques D, Francisco H, Caramês J. Gender influence on the number of roots and root canal system configuration in human permanent teeth of a Portuguese subpopulation. Quintessence International. 2018;**49**:103-

111. DOI: 10.3290/j.qi.a39508.

[10] Yavuzyılmaz H. Diş Morfolojisi ve Anatomisi. [Tooth Morphology and Anatomy]. 6th ed. Beşevler Ankara Türkiye: Gazi Kitapevi; 2013. pp. 27-191

[11] Ozaki T, Satake T, Kanazama E. Morphological significance of root length variability in comparison with other crown dimensions. The Journal of Nihon University School of Dentistry.

[12] Yamanaka A, Iwai H, Uemura M, Goto T. Patterning of mammalian heterodont dentition within the upper and lower jaws. Evololution and Development. 2015;**17**:127-138. DOI:

[13] McGowan S. Characteristics of teeth: A review of size, shape, composition, and appearance of maxillary anterior teeth. The Compendium of Continuing Education in Dentistry. 2016;**37**:164-171

[14] Alrahabi M, Sohail Zafar M. Evaluation of root canal morphology of maxillary molars using cone beam computed tomography. Pakistan Journal of Medical Sciences. 2015;**31**:426-430.

DOI: 10.12669/pjms.312.6753

[15] Akpınar KE, Ay S, Er K, Köşger HH. Türk toplumunda alt molar dişlerin kök ve kanal sayıları [The number of roots and canals in mandibular molars of a Turkish sub-population]. Ondokuz Mayis Universitesi Dis Hekimliği Fakültesi Dergisi. 2004;**5**:123-127

1987;**29**:233-240

10.1111/ede.12116

[2] Brook AH, Jernvall J, Smith RN, Hughes TE, Townsend GC. The dentition: The outcomes of morphogenesis leading to variations of tooth number, size and shape. Australian Dental Journal. 2014;**59**:131-142. DOI: 10.1111/adj.12160

[3] Mohammadi Z, Shalavi S,

Jafarzadeh H. Extra roots and root canals in premolar and molar teeth: Review of an endodontic challenge. The Journal of Contemporary Dental Practice.

[4] Felemban NH, Manjunatha BS. Prevalence of the number of cusps and occlusal groove patterns of the mandibular molars in a Saudi Arabian population. Journal of Forensic and Legal Medicine. 2017;**49**:54-58. DOI:

[5] Dholia B, Manjunatha BS. Occlusal morphology of permanent mandibular first and second molars in Gujarati population. Journal of Forensic Dental Sciences. 2015;**7**:137-141. DOI:

10.1016/j.jflm.2017.05.013

10.4103/0975-1475.146368

10.4317/jced.51476

Tropicale. 2007;**30**:17-21

[8] Filipovic G, Kanjevac T,

Cetenovic B, Ajdukovic Z, Petrovic N.

[6] Mallineni SK, Panampally GK, Chen Y, Tian T. Mandibular talon cusps: A systematic review and data analysis. Journal of Clinical and Experimental Dentistry. 2014;**6**:e408-e413. DOI:

[7] Khraisat A, Taha ST, Jung RE, Hattar S, Smadi L, Al-Omari IK, et al. Prevalence, association, and sexual dimorphism of Carabelli's molar and shovel incisor traits amongst Jordanian population. Odonto-Stomatologie

rsfs.2015.0109

**References**

2013;**14**:980-986

**41**

**Chapter 4**

**Abstract**

*and Ahmed A. Madfa*

External and Internal Anatomy of

Mandibular Permanent Incisors

A clear understanding of dental root anatomy, external and internal, is an essential prerequisite to all dental procedures. In periodontology, the external root morphology has been proven to have a clinical significance in the predisposing factors of periodontal diseases. Orthodontic literature shows the importance of radicular anatomy in orthodontic mechanics through the concept of anchorage. The significance of internal root anatomy has been emphasized by studies demonstrating that variations in canal geometry before cleaning, shaping, and obturation procedures had a greater effect on the outcome than the techniques themselves. The mandibular central incisor is the smallest tooth in the mouth, but the buccolingual dimension of its root is very large. This tooth is usually single-rooted; however, the root canal system of this group is unpredictable. The incidence of two canals has been reported as low as 0.3% and as high as 45.3%. The wide range of variation reported in literature regarding the prevalence of a second canal has been related to methodological and racial differences. This chapter will summarize the morphological aspects of the root canal anatomy published in the literature of the anterior mandibular teeth. This will provide precious knowledge regarding root canal

*Mohammed A. Aldawla, Abdulbaset A. Mufadhal*

morphology and its variation among populations.

**1. External root morphology**

**Keywords:** morphology, mandibular incisors, variation, root canal

The mandibular central and lateral incisors have a single conical root. The root dimensions of both incisors vary corresponding to the crown. They are narrow in mesiodistal dimension and wide in labiolingual dimension and taper uniformly on both proximal sides from the CEJ to the apex. The apical end may curve slightly to the distal. Longitudinal root depressions can be seen in both incisors from the mesial and distal views. Multiple comparisons revealed that, among all permanent teeth, mandibular central incisor has the shortest root. Furthermore, in contrary to maxillary incisors, the root of mandibular lateral incisor is longer than that of mandibular central incisor [1]. It has been reported that the average lengths of mandibular central incisor and lateral incisor roots are 12.6 mm (7.7–17.9) and 13.5 (9.4–18.1), respectively [2]. Kim et al. [3] measured the mandibular incisor root lengths using CBCT in Korean population and found that no significant differences

#### **Chapter 4**
