Orthodontic Management of Residual Spaces of Missing Molars: Decision Factors

*Hakima Aghoutan, Sanaa Alami, Amal El Aouame and Farid El Quars*

#### **Abstract**

In the daily practice, the orthodontist may be confronted with particular clinical situations with one or more missing teeth. This can complicate the therapeutic plan and influence the choice of possible extractions imposed by treatment requirements. In case of permanent molar absence, making decision becomes even more delicate. The practitioner must use his/her critical sense and clinical common sense to make the right choice between closing and redeveloping the residual spaces. Its choice must meet the patient's expectations and correct the clinical problem without risking overtreatment, or extending duration care. Several factors guide the therapeutic decision, ranging from the patient's age to economic factors, not to mention the technical complexity, therapeutic predictability, and patient comfort, which determine proper compliance and therefore success. In this chapter, we will focus on these decision-making factors by determining the scientific evidence level in terms of success, survival, and patient-centered outcomes (quality of life and functional efficiency).

**Keywords:** missing permanent molars, first permanent molar, second permanent molar, orthodontic management, decision factors, adult, children, space closure, space reopening, multidisciplinary treatment

#### **1. Introduction**

Orthodontic treatment aims globally to improve dentofacial esthetic and stomatognathic system functions in harmony with the patient's wishes. To achieve these objectives, inter- and intra-arch occlusion is the guiding field of action. Therefore, any orthodontic movement must be carefully considered including in the molar area. Indeed, permanent molars are considered as significant determinants for normal tooth development and facial growth [1, 2]. They play a central role in the mastication of food, in supporting the vertical dimension of the face, and as anchorage teeth against orthodontic forces [3]. Moreover, posterior dental contacts are important to adapt and coordinate growth between the mandible and maxilla and a lack of chewing function in children will disrupt their maxillofacial growth [1, 4]. Hence, every orthodontist must ensure a well-thought-out management of missing molar spaces mostly in children.

The molar missing may be primary, due to the agenesis phenomenon, or secondary to extraction not compensated by prosthetic rehabilitation. It complicates decision-making process, since the orthodontist's first vocation is to balance dentofacial pattern with a better cost-benefit ratio, especially in young patients. What is more, molar absence is generally accompanied with other complicated dental and skeletal problems, which affect treatment planning and outcomes.

Molar agenesis may be an isolated anomaly or associated with particular syndromes. It is an uncommon clinical condition not well documented in the literature. Moreover, it has also been reported that anterior agenesis may depend more on genes while posterior missing might be sporadic [5]. Its prevalence rate has been reported to fluctuate between 0 and 0.05% in the general population for the first permanent molar (FPM) [1] and to revolve around 0.8% for the second permanent molar (SPM) [4]. This phenomenon was reported to be associated with a higher prevalence of other permanent tooth agenesis and advanced tooth agenesis [3]. Consequently, when treating patients with molar agenesis, the orthodontist should consider that observed alterations of craniofacial dimensions might occur beyond the variations associated with age and gender [6].

On the other hand, in case of acquired lack of molars, many factors can be incriminated. Carious lesions, dental hypoplasia including molar-incisor hypomineralization (MIH), and periodontal disease are the major concerns [7, 8]. Several authors have dealt with the best time to extract first permanent molar when this is unavoidable in the young patient. There is only little scientific evidence about the extraction timing in order to minimize unwanted negative effects. In a recent meta-analysis [6], authors suggested that it is when the second permanent molar is at Demirjian stage E. Otherwise, several consequences can occur and if orthodontic need arises, the treatment plan can be complicated or modified to adapt to these modifications, especially in adults.

In this section, we will address the main etiologies and dentoskeletal consequences of molar missing and focus on decision-making factors related to orthodontic management of residual space of one or several missing molars. We will discuss some clinical situations to illustrate this topic.

#### **2. Problem statement**

The consequences of permanent molar extraction and all consequences and treatment considerations have been largely discussed in the literature for the first molar. Second molar is less commonly addressed. Currently, the majority of first permanent molars are extracted because of dental caries [9]. The eruption of the first permanent molar occurs, as its name suggests, around the age of 6 years. Its early eruption, as well as the immaturity of its histological components and its occlusal anatomy (grooves, pits, and fissures), makes it vulnerable to various microbial, periodontal, or structural pathologies, and more prone to possible premature extraction before 15 years [6, 10]. The period between the eruption of the tooth and the definitive maturation of its histological components, especially that of the enamel, is considered to be cario-susceptible.

As said above, permanent molars act as a guide for the permanent teeth since they control the establishment of dental occlusion and participate in the maxillary growth and physiology of the mandibular apparatus. Therefore, loss of permanent molars without any remedy could disturb the developing dentition, generate numerous malocclusions, and affect dental health [6]. It typically leads to occlusal disturbances by pathological migration of neighboring teeth and periodontal lesions as alveolar melting or false periodontal pocket adjacent to the tipped teeth which is induced by bone contour remodeling following the cementoenamel junction [11] (**Figures 1**–**3**).

**195**

**Figure 1.**

*Orthodontic Management of Residual Spaces of Missing Molars: Decision Factors*

discrepancies and prevent the development of malocclusions [10].

These complications are all the more serious, as the period of molar absence on the arch is extended; hence, the importance of the multidisciplinary approach with a large communication between the pediatric dentist and the orthodontist in order to establish the best care and to plan potential extraction, which is useful to correct

For managing this space problem, the orthodontist can adopt two therapeutic strategies including space reopening or space closing. The orthodontist ought to use his/her critical sense and clinical common sense to make the right choice, which must not only take into consideration dental arch length and occlusion [12] but also all the technical and biological specificities of treated case. Space can be reopened for implant insertion, autotransplantation, and prosthetic restoration; while space closing can be undertaken to correct the other associate malocclusions. Either way, his/her choice must meet the patient's expectations and correct the clinical problem

*Case of MIH in a 11-year-old boy, with severe molar damage and loss of 26. We can observe displacement of* 

*second left upper molar: (a and b) lateral occlusion views; (c) occlusal view of maxillary arch.*

*DOI: http://dx.doi.org/10.5772/intechopen.85944*

#### *Orthodontic Management of Residual Spaces of Missing Molars: Decision Factors DOI: http://dx.doi.org/10.5772/intechopen.85944*

These complications are all the more serious, as the period of molar absence on the arch is extended; hence, the importance of the multidisciplinary approach with a large communication between the pediatric dentist and the orthodontist in order to establish the best care and to plan potential extraction, which is useful to correct discrepancies and prevent the development of malocclusions [10].

For managing this space problem, the orthodontist can adopt two therapeutic strategies including space reopening or space closing. The orthodontist ought to use his/her critical sense and clinical common sense to make the right choice, which must not only take into consideration dental arch length and occlusion [12] but also all the technical and biological specificities of treated case. Space can be reopened for implant insertion, autotransplantation, and prosthetic restoration; while space closing can be undertaken to correct the other associate malocclusions. Either way, his/her choice must meet the patient's expectations and correct the clinical problem

**Figure 1.**

*Case of MIH in a 11-year-old boy, with severe molar damage and loss of 26. We can observe displacement of second left upper molar: (a and b) lateral occlusion views; (c) occlusal view of maxillary arch.*

*Human Teeth - Key Skills and Clinical Illustrations*

the variations associated with age and gender [6].

discuss some clinical situations to illustrate this topic.

**2. Problem statement**

The molar missing may be primary, due to the agenesis phenomenon, or secondary to extraction not compensated by prosthetic rehabilitation. It complicates decision-making process, since the orthodontist's first vocation is to balance dentofacial pattern with a better cost-benefit ratio, especially in young patients. What is more, molar absence is generally accompanied with other complicated dental and

Molar agenesis may be an isolated anomaly or associated with particular syndromes. It is an uncommon clinical condition not well documented in the literature. Moreover, it has also been reported that anterior agenesis may depend more on genes while posterior missing might be sporadic [5]. Its prevalence rate has been reported to fluctuate between 0 and 0.05% in the general population for the first permanent molar (FPM) [1] and to revolve around 0.8% for the second permanent molar (SPM) [4]. This phenomenon was reported to be associated with a higher prevalence of other permanent tooth agenesis and advanced tooth agenesis [3]. Consequently, when treating patients with molar agenesis, the orthodontist should consider that observed alterations of craniofacial dimensions might occur beyond

On the other hand, in case of acquired lack of molars, many factors can be incriminated. Carious lesions, dental hypoplasia including molar-incisor hypomineralization (MIH), and periodontal disease are the major concerns [7, 8]. Several authors have dealt with the best time to extract first permanent molar when this is unavoidable in the young patient. There is only little scientific evidence about the extraction timing in order to minimize unwanted negative effects. In a recent meta-analysis [6], authors suggested that it is when the second permanent molar is at Demirjian stage E. Otherwise, several consequences can occur and if orthodontic need arises, the treatment plan can be complicated or modified to adapt to these modifications, especially in adults. In this section, we will address the main etiologies and dentoskeletal consequences of molar missing and focus on decision-making factors related to orthodontic management of residual space of one or several missing molars. We will

The consequences of permanent molar extraction and all consequences and treatment considerations have been largely discussed in the literature for the first molar. Second molar is less commonly addressed. Currently, the majority of first permanent molars are extracted because of dental caries [9]. The eruption of the first permanent molar occurs, as its name suggests, around the age of 6 years. Its early eruption, as well as the immaturity of its histological components and its occlusal anatomy (grooves, pits, and fissures), makes it vulnerable to various microbial, periodontal, or structural pathologies, and more prone to possible premature extraction before 15 years [6, 10]. The period between the eruption of the tooth and the definitive maturation of its histological components, especially that of the enamel, is considered to be cario-susceptible. As said above, permanent molars act as a guide for the permanent teeth since they control the establishment of dental occlusion and participate in the maxillary growth and physiology of the mandibular apparatus. Therefore, loss of permanent molars without any remedy could disturb the developing dentition, generate numerous malocclusions, and affect dental health [6]. It typically leads to occlusal disturbances by pathological migration of neighboring teeth and periodontal lesions as alveolar melting or false periodontal pocket adjacent to the tipped teeth which is induced by bone contour remodeling following the cementoenamel junc-

skeletal problems, which affect treatment planning and outcomes.

**194**

tion [11] (**Figures 1**–**3**).

#### **Figure 2.**

*Orthopantomogram (OPG) of an adult showing the absence of 16 and 26 with version and false periodontal pocket in the mesial side of 17 and 27. We can note the low floor level of the right maxillary sinus, which may complicate orthodontic mesial movement of posterior teeth.*

#### **Figure 3.**

*Case of an adult with multiple molars missing. The over eruption of 17 is due to no-compensated extraction of 47.*

without risking overtreatment, or extending duration care, especially since patients with missing molars often need a compensatory treatment in the opposite arch.

Besides, some authors [11, 13, 14] claim that space closure by molar orthodontic movement is time-consuming and more problematic mainly in the mandibular arch and in atrophic extraction sites exhibiting a reduction in vertical height and a decrease in width of the residual ridge. The orthodontist must avoid teeth tipping, damage of the gingiva and marginal bone. Hence, this decision requires confrontation with the alternative prosthetic treatment especially in old adults who usually show less bone apposition around moved molars into the narrowed space, and poor stability of the closed space, leading in some, if not several, cases to an orthodontic compromise. Nevertheless, fixed appliances can achieve excellent outcomes at different ages following permanent molars' loss particularly with the advent of temporary anchorage devices. Studies have reported that posterior spaces have been closed by protracting posterior teeth, which prevent detrimental effects without reopening of the edentulous spaces or increased pocket depth in the follow-up period [15]. In case of related orthodontic abnormalities, it is necessary to use all or part of the space given by molar extraction to correct the dysmorphy. A golden rule is to determine the anchorage value and location as well as any associated auxiliary devices.

On the other hand, before any prosthetic rehabilitation succeeding space redevelopment, the practitioner has to upright and to parallelize the adjacent teeth in order to gain sufficient space, even apically at the root level [14]. Moreover, in

**197**

in the mandible and maxilla [10].

*Orthodontic Management of Residual Spaces of Missing Molars: Decision Factors*

these cases, wisdom teeth are often removed [16]. Consequently, the orthodontist has always to wonder which of the two options is better: (a) close residual molar space to control the wisdom tooth positioning or (b) remove the third molar and place a prosthesis on the missing molar, which is more expensive. Obviously other biomechanical considerations must be taken into account, to be explained later. On another note, over the years of craniofacial growth, teeth and their supporting tissues are able to adapt to functional demands. Thus, continuous changes are observed after tooth missing, and the orthodontist has to choose optimal treatment for his/her patient taking into account several decision factors. In his literature review [14], Thilander has shown that both closure and space opening alternatives have their advantages as well as disadvantages, but the evidence base is weak, with currently no randomized trials reporting on the outcome of different interventions [9]. More research is needed with relevant clinical follow-up, varying craniofacial morphology, different ages, and large sample. This will be of great value for comprehension of tissue reaction to orthodontic space management and continuous changes of the dentition and its supporting tissues. From then on, treatment choice can be standardized.

The direct consequence of molar extraction is the creation of a 10- to 12-mm diastema. The movements of the neighboring and antagonistic teeth will cause occlusal and periodontal imbalance. It was reported that post-extraction migration occurred in the following ways: over eruption of opposing teeth, horizontal migration of neighboring teeth, space reduced by tipping, dual drift (horizontal and vertical), or complete space closure [6]. In addition to this, authors investigated contour changes of the alveolar processes of posterior extraction sites and demonstrated a reduction in width of the residual alveolar ridge of up to 50% during a 12-month healing period, of which two-thirds of the reduction occurred within the first 3 months of healing in [17]. In case of an extraction on one arch, the opposing tooth can significantly over erupt (**Figures 4** and **5**). In general terms, malocclusions are complicated by the early loss of a first permanent molar without treatment [10]. Moreover, sinus pneumatization was identified after extraction of maxillary posterior teeth. This phenomenon occurs within 4–6 months of healing duration, and is caused by atrophy associated with the replacement of dental socket by nonfunctional bone [18, 19]. The expansion of the sinus was larger following extraction of teeth enveloped by a superiorly curving sinus floor, extraction of several adjacent posterior teeth, and extraction of second molars in comparison with first molars [19]. A systematic review reported that the post-extraction space of first permanent molar was closed mostly by the SPM rather than by the second premolar [6]. For certain authors [20, 21], no significant relation was found between patient Angle's Classification or the timing of FPM extraction based upon SPM development stage and complete spontaneous space closure in both arches, contrary to the usual recommendations indicating that the ideal time for FPM extraction, with fewer undesirable consequences, is when the SPM is at Demirjian stage E (early bifurcation) [6, 9]. For these authors, apart from extraction timing of the FPM, the presence of the third permanent molar, mesioangulation of the SPM in relation to the FPM, and the engagement of second premolar in the bifurcation of the second primary molar are better predictors of spontaneous space closure of the FPM mainly in mandibular arch where closure space is more problematical and leads frequently to mesial tipping and distobuccal rotation of the SPM or angulation and distal movement of the second premolar. This might be due to the differences in the eruption paths of SPM

*DOI: http://dx.doi.org/10.5772/intechopen.85944*

**3. Clinical features**

#### *Orthodontic Management of Residual Spaces of Missing Molars: Decision Factors DOI: http://dx.doi.org/10.5772/intechopen.85944*

these cases, wisdom teeth are often removed [16]. Consequently, the orthodontist has always to wonder which of the two options is better: (a) close residual molar space to control the wisdom tooth positioning or (b) remove the third molar and place a prosthesis on the missing molar, which is more expensive. Obviously other biomechanical considerations must be taken into account, to be explained later.

On another note, over the years of craniofacial growth, teeth and their supporting tissues are able to adapt to functional demands. Thus, continuous changes are observed after tooth missing, and the orthodontist has to choose optimal treatment for his/her patient taking into account several decision factors. In his literature review [14], Thilander has shown that both closure and space opening alternatives have their advantages as well as disadvantages, but the evidence base is weak, with currently no randomized trials reporting on the outcome of different interventions [9]. More research is needed with relevant clinical follow-up, varying craniofacial morphology, different ages, and large sample. This will be of great value for comprehension of tissue reaction to orthodontic space management and continuous changes of the dentition and its supporting tissues. From then on, treatment choice can be standardized.

#### **3. Clinical features**

*Human Teeth - Key Skills and Clinical Illustrations*

*complicate orthodontic mesial movement of posterior teeth.*

**Figure 2.**

**Figure 3.**

without risking overtreatment, or extending duration care, especially since patients with missing molars often need a compensatory treatment in the opposite arch. Besides, some authors [11, 13, 14] claim that space closure by molar orthodontic movement is time-consuming and more problematic mainly in the mandibular arch and in atrophic extraction sites exhibiting a reduction in vertical height and a decrease in width of the residual ridge. The orthodontist must avoid teeth tipping, damage of the gingiva and marginal bone. Hence, this decision requires confrontation with the alternative prosthetic treatment especially in old adults who usually show less bone apposition around moved molars into the narrowed space, and poor stability of the closed space, leading in some, if not several, cases to an orthodontic compromise. Nevertheless, fixed appliances can achieve excellent outcomes at different ages following permanent molars' loss particularly with the advent of temporary anchorage devices. Studies have reported that posterior spaces have been closed by protracting posterior teeth, which prevent detrimental effects without reopening of the edentulous spaces or increased pocket depth in the follow-up period [15]. In case of related orthodontic abnormalities, it is necessary to use all or part of the space given by molar extraction to correct the dysmorphy. A golden rule is to determine the

*Case of an adult with multiple molars missing. The over eruption of 17 is due to no-compensated extraction of 47.*

*Orthopantomogram (OPG) of an adult showing the absence of 16 and 26 with version and false periodontal pocket in the mesial side of 17 and 27. We can note the low floor level of the right maxillary sinus, which may* 

anchorage value and location as well as any associated auxiliary devices.

On the other hand, before any prosthetic rehabilitation succeeding space redevelopment, the practitioner has to upright and to parallelize the adjacent teeth in order to gain sufficient space, even apically at the root level [14]. Moreover, in

**196**

The direct consequence of molar extraction is the creation of a 10- to 12-mm diastema. The movements of the neighboring and antagonistic teeth will cause occlusal and periodontal imbalance. It was reported that post-extraction migration occurred in the following ways: over eruption of opposing teeth, horizontal migration of neighboring teeth, space reduced by tipping, dual drift (horizontal and vertical), or complete space closure [6]. In addition to this, authors investigated contour changes of the alveolar processes of posterior extraction sites and demonstrated a reduction in width of the residual alveolar ridge of up to 50% during a 12-month healing period, of which two-thirds of the reduction occurred within the first 3 months of healing in [17]. In case of an extraction on one arch, the opposing tooth can significantly over erupt (**Figures 4** and **5**). In general terms, malocclusions are complicated by the early loss of a first permanent molar without treatment [10].

Moreover, sinus pneumatization was identified after extraction of maxillary posterior teeth. This phenomenon occurs within 4–6 months of healing duration, and is caused by atrophy associated with the replacement of dental socket by nonfunctional bone [18, 19]. The expansion of the sinus was larger following extraction of teeth enveloped by a superiorly curving sinus floor, extraction of several adjacent posterior teeth, and extraction of second molars in comparison with first molars [19].

A systematic review reported that the post-extraction space of first permanent molar was closed mostly by the SPM rather than by the second premolar [6]. For certain authors [20, 21], no significant relation was found between patient Angle's Classification or the timing of FPM extraction based upon SPM development stage and complete spontaneous space closure in both arches, contrary to the usual recommendations indicating that the ideal time for FPM extraction, with fewer undesirable consequences, is when the SPM is at Demirjian stage E (early bifurcation) [6, 9]. For these authors, apart from extraction timing of the FPM, the presence of the third permanent molar, mesioangulation of the SPM in relation to the FPM, and the engagement of second premolar in the bifurcation of the second primary molar are better predictors of spontaneous space closure of the FPM mainly in mandibular arch where closure space is more problematical and leads frequently to mesial tipping and distobuccal rotation of the SPM or angulation and distal movement of the second premolar. This might be due to the differences in the eruption paths of SPM in the mandible and maxilla [10].

**Figure 4.** *Over eruption of tooth 16 after extraction of tooth 46.*

#### **Figure 5.**

*OPG of the same patient showing the consequences of extraction of tooth 46: over eruption of 16, distal displacement of 45 germ and slight mesial displacement of 47.*

The occlusal and skeletal consequences in the vertical direction after extraction of FPM were much discussed. Some authors noted counterclockwise rotation of the occlusal plane and an improvement in infraclusion [6, 13] but most studies did not notice a significant influence on the vertical dimension [6]. Also, there was no significant effect described on the maxillomandibular relationship in the anteroposterior direction.

Furthermore, it was stated that the FPM and SPM extraction accelerated significantly the development and eruption of the third molars when a posterior space is created [13, 22–24] and led to lingual tipping and retrusion of incisors mostly in lower arch [6]. However, some authors have discussed the effect of various extraction patterns on provision of space both anteriorly and posteriorly within the arch and they highlighted the fact that FPM extraction seems to have less effect on the profile than premolar extraction [13].

Finally, in the aforementioned systematic review, the authors concluded that the published studies have too many weaknesses to draw sufficient evidence. Therefore, further prospective studies are needed to investigate the consequences of FPM extraction and to confirm the ideal time of this extraction.

**199**

treatment [9, 13].

*Orthodontic Management of Residual Spaces of Missing Molars: Decision Factors*

In patients with missing molar, a standard treatment plan does not exist. There are essentially two orthodontic treatment approaches to manage this problem, which are space closure or reopening for prosthetic replacements, and implant or autotransplantation. Several elements guide the therapeutic decision, ranging from the patient's age to economic possibilities, not to mention the technical complexity, therapeutic predictability, and patient comfort, which determine proper compli-

Patients with missing molars often manifest with many underlying skeletal and dental problems and a multidisciplinary approach is recommended and depends on several factors. The amount of crowding, type of malocclusion, facial profile, age of the patient, periodontal conditions, bone volume in alveolar process, vertical or horizontal growth pattern, the number of missing teeth, and the available space should be considered in treatment plan [5]. Moreover, all the consequences that occurred after an old extraction must also be taken into account since they deter-

The main advantage of the space closure resides in the fact that the whole treatment can be finished immediately after completion of orthodontics. When possible, it must be systematically preferred because better longer term outcomes can be achieved without growth-related infraocclusion, blue coloring of the gingiva, or periodontal problems as the tooth has displaced along with its supporting tissues [5]. Additionally, orthodontic space closure will reduce the financial expenses for the patient along with resolving arch crowding or anteroposterior malocclusion. Nevertheless, space closure is one of the most challenging approaches to molar extraction cases [13]. Like any treatment, this procedure presents indications and contraindications that have to be rigorously considered. For example, in hypodivergent patients, the closure of the space cannot be indicated due to the muscular and cortical anchoring, making it difficult or impossible to move the molars horizontally and to reduce the overbite [25]. Likewise, the practice of compensating and balancing the extraction of lost permanent molars along with space closing should be discussed. It aims to preserve occlusal relationships and arch symmetry within the whole dentition. A compensating extraction is the removal of a permanent molar from the opposing quadrant, while a balancing extraction signifies the extraction of a permanent molar from the opposite side of the same dental arch [9]. The long-term prognosis of the remaining permanent molars, the developmental status of the dentition including third molars as well as the underlying malocclusion were the main decision factors for or against balancing and compensating

As regards patient age, this result is of great interest for a young adult or an adolescent by guiding the erupting teeth into a stable occlusion and can be considered a cost-effective alternative to complex restorations that require replacement over the life span [20]. Indeed, despite cessation of statural growth, vertical growth of the face permits continued teeth eruption past puberty and could adversely affect the alignment of teeth after orthodontic therapy. Facial growth in the horizontal plane is ended significantly sooner than growth in the vertical plane predominantly in patients with vertical growth patterns [26]. Accordingly, if an implant is placed before growth and eruption completion, it will become in infraocclusion, as it behaves like ankylosed teeth while the adjacent teeth continue to erupt. The magnitude of the vertical changes after age 20 seems to have little clinical importance [26]. In other words, in case of residual molar space in children, it is largely indicated to choose closure option in order to avoid all restrictions related to the periodontal

*DOI: http://dx.doi.org/10.5772/intechopen.85944*

mine the choice of the biomechanical system.

**4. Treatment choices**

ance and therefore success.

#### **4. Treatment choices**

*Human Teeth - Key Skills and Clinical Illustrations*

*Over eruption of tooth 16 after extraction of tooth 46.*

The occlusal and skeletal consequences in the vertical direction after extraction of FPM were much discussed. Some authors noted counterclockwise rotation of the occlusal plane and an improvement in infraclusion [6, 13] but most studies did not notice a significant influence on the vertical dimension [6]. Also, there was no significant effect described on the maxillomandibular relationship in the anteroposterior direction. Furthermore, it was stated that the FPM and SPM extraction accelerated significantly the development and eruption of the third molars when a posterior space is created [13, 22–24] and led to lingual tipping and retrusion of incisors mostly in lower arch [6]. However, some authors have discussed the effect of various extraction patterns on provision of space both anteriorly and posteriorly within the arch and they highlighted the fact that FPM extraction seems to have less effect on the

*OPG of the same patient showing the consequences of extraction of tooth 46: over eruption of 16, distal* 

Finally, in the aforementioned systematic review, the authors concluded that the published studies have too many weaknesses to draw sufficient evidence. Therefore, further prospective studies are needed to investigate the consequences of FPM

**198**

**Figure 4.**

**Figure 5.**

profile than premolar extraction [13].

*displacement of 45 germ and slight mesial displacement of 47.*

extraction and to confirm the ideal time of this extraction.

In patients with missing molar, a standard treatment plan does not exist. There are essentially two orthodontic treatment approaches to manage this problem, which are space closure or reopening for prosthetic replacements, and implant or autotransplantation. Several elements guide the therapeutic decision, ranging from the patient's age to economic possibilities, not to mention the technical complexity, therapeutic predictability, and patient comfort, which determine proper compliance and therefore success.

Patients with missing molars often manifest with many underlying skeletal and dental problems and a multidisciplinary approach is recommended and depends on several factors. The amount of crowding, type of malocclusion, facial profile, age of the patient, periodontal conditions, bone volume in alveolar process, vertical or horizontal growth pattern, the number of missing teeth, and the available space should be considered in treatment plan [5]. Moreover, all the consequences that occurred after an old extraction must also be taken into account since they determine the choice of the biomechanical system.

The main advantage of the space closure resides in the fact that the whole treatment can be finished immediately after completion of orthodontics. When possible, it must be systematically preferred because better longer term outcomes can be achieved without growth-related infraocclusion, blue coloring of the gingiva, or periodontal problems as the tooth has displaced along with its supporting tissues [5]. Additionally, orthodontic space closure will reduce the financial expenses for the patient along with resolving arch crowding or anteroposterior malocclusion. Nevertheless, space closure is one of the most challenging approaches to molar extraction cases [13]. Like any treatment, this procedure presents indications and contraindications that have to be rigorously considered. For example, in hypodivergent patients, the closure of the space cannot be indicated due to the muscular and cortical anchoring, making it difficult or impossible to move the molars horizontally and to reduce the overbite [25]. Likewise, the practice of compensating and balancing the extraction of lost permanent molars along with space closing should be discussed. It aims to preserve occlusal relationships and arch symmetry within the whole dentition. A compensating extraction is the removal of a permanent molar from the opposing quadrant, while a balancing extraction signifies the extraction of a permanent molar from the opposite side of the same dental arch [9]. The long-term prognosis of the remaining permanent molars, the developmental status of the dentition including third molars as well as the underlying malocclusion were the main decision factors for or against balancing and compensating treatment [9, 13].

As regards patient age, this result is of great interest for a young adult or an adolescent by guiding the erupting teeth into a stable occlusion and can be considered a cost-effective alternative to complex restorations that require replacement over the life span [20]. Indeed, despite cessation of statural growth, vertical growth of the face permits continued teeth eruption past puberty and could adversely affect the alignment of teeth after orthodontic therapy. Facial growth in the horizontal plane is ended significantly sooner than growth in the vertical plane predominantly in patients with vertical growth patterns [26]. Accordingly, if an implant is placed before growth and eruption completion, it will become in infraocclusion, as it behaves like ankylosed teeth while the adjacent teeth continue to erupt. The magnitude of the vertical changes after age 20 seems to have little clinical importance [26].

In other words, in case of residual molar space in children, it is largely indicated to choose closure option in order to avoid all restrictions related to the periodontal

immaturity. In other cases where the extraction space is preserved in growing children, autotransplantation of the tooth is preferable to the implant option [25]. However, other parameters must be studied before deciding treatment plan.

On the other hand, in adults undergoing comprehensive orthodontic therapy, coexisting dental and periodontal problems require multidisciplinary treatment approaches to manage malocclusions often complicated by the migration of adjacent teeth into the extraction sites. Periodontal defects, multiple missing teeth, and atrophic extraction sites make it difficult to close all the extraction spaces, which require remodeling of cortical bone [11]. Also, adults show less bone apposition when moving molars into the narrowed space, poor maintenance of the closed space, and, in some cases, resorption of the second molar roots when moved in place of first molar [11]. Duration of treatment has to be considered and adapted to patient needs. For these reasons, the placement of an implant may be the treatment of choice for adults with missing molars. Be that as it may, this proposition may be in some instances valid for an adult patient whose biological and biomechanical therapeutic specificities must be kept in mind. Precise 3-D control of tooth movement during closure of extraction spaces is very important in meeting treatment goals. Second molar protraction is time-consuming and relatively difficult. Therefore, this treatment option may be justified only when the periodontal health of the protracted second molar is not compromised [24]. Protracting the molars may be advantageous for the patient by increasing alveolar ridge width that had previously been lost in the edentulous space. It should ideally be done before significant vertical bone resorption occurs [27]. In respect of orthodontic force system, bodily movement of molars can be obtained by using temporary skeletal anchorage devices and rational biomechanics [24]. Several authors have reported some useful clinical tips and tricks that surround providing this therapy [11, 13, 15, 27]: a long buccal hook, an uprighting spring, a toe-in bend in the posterior portion of the archwire with constriction, or a balancing lingual force can be used to prevent side effects such as posterior tooth tipping, mesial rotation, and buccal sweep.

Regardless of the chosen option, the fate of wisdom teeth must be assessed. The final success of the treatment depends on its satisfactory positioning [16]. So, it is important to evaluate angulation, eruption space, root developmental stage, and periodontal status of this tooth before deciding to close molar space [27]. Actually, space reopening is indicated when the wisdom tooth is absent.

Furthermore, closure can be difficult, in the maxillary posterior area with sinus proximity, because tooth movement through the maxillary sinus is limited. The increased difficulty of moving teeth in the maxillary sinus is similar to moving a tooth in the atrophic posterior mandibular ridge. In severe cases, the pneumatization can extend completely to the alveolar bone adjacent to the gap. This not only makes it difficult to move teeth through the sinus but also to place an implant without sinus wall lifting surgery [18, 19]. Closing the space should not be chosen as the usual treatment method, as it extends the duration of the treatment without predictable results.

#### **5. Clinical cases**

In this section, we will review some clinical cases with one or more missing molars and will justify our therapeutic choices for each situation.

**201**

**Figure 8.**

**Figure 6.**

**Figure 7.**

*formed adjacent to 37. Tooth 28 is absent.*

*Orthodontic Management of Residual Spaces of Missing Molars: Decision Factors*

*Pretreatment intraoral photographs of a 32-year-old woman with 36 and 46 missing. We can note mesial tipping of 37 associated to a mesiolingual rotation. The space of 36 is more closed than that of 46. (a and c)* 

*Radiographic image of the mesial tipping of teeth 37 and 47, after extraction of lower FPM. Pseudo-pocket was* 

*Intraoral photographs of treatment progress. Extraction site of 36 was closed along with reopening of 46 space.* 

*(a) Frontal occlusion view, (b and c) Buccal occlusion views, (d) Occlusal view of the lower arch.*

*Buccal occlusion views,(b) Frontal occlusion view, (d) Occlusal view of the lower arch.*

*DOI: http://dx.doi.org/10.5772/intechopen.85944*

#### **5.1 Case presentation**

Case no. 1 (**Figures 6–9**).

*Orthodontic Management of Residual Spaces of Missing Molars: Decision Factors DOI: http://dx.doi.org/10.5772/intechopen.85944*

#### **Figure 6.**

*Human Teeth - Key Skills and Clinical Illustrations*

immaturity. In other cases where the extraction space is preserved in growing children, autotransplantation of the tooth is preferable to the implant option [25]. However, other parameters must be studied before deciding treatment plan.

effects such as posterior tooth tipping, mesial rotation, and buccal sweep.

space reopening is indicated when the wisdom tooth is absent.

Regardless of the chosen option, the fate of wisdom teeth must be assessed. The final success of the treatment depends on its satisfactory positioning [16]. So, it is important to evaluate angulation, eruption space, root developmental stage, and periodontal status of this tooth before deciding to close molar space [27]. Actually,

Furthermore, closure can be difficult, in the maxillary posterior area with sinus proximity, because tooth movement through the maxillary sinus is limited. The increased difficulty of moving teeth in the maxillary sinus is similar to moving a tooth in the atrophic posterior mandibular ridge. In severe cases, the pneumatization can extend completely to the alveolar bone adjacent to the gap. This not only makes it difficult to move teeth through the sinus but also to place an implant without sinus wall lifting surgery [18, 19]. Closing the space should not be chosen as the usual treatment method, as it extends the duration of the treatment without

In this section, we will review some clinical cases with one or more missing

molars and will justify our therapeutic choices for each situation.

On the other hand, in adults undergoing comprehensive orthodontic therapy, coexisting dental and periodontal problems require multidisciplinary treatment approaches to manage malocclusions often complicated by the migration of adjacent teeth into the extraction sites. Periodontal defects, multiple missing teeth, and atrophic extraction sites make it difficult to close all the extraction spaces, which require remodeling of cortical bone [11]. Also, adults show less bone apposition when moving molars into the narrowed space, poor maintenance of the closed space, and, in some cases, resorption of the second molar roots when moved in place of first molar [11]. Duration of treatment has to be considered and adapted to patient needs. For these reasons, the placement of an implant may be the treatment of choice for adults with missing molars. Be that as it may, this proposition may be in some instances valid for an adult patient whose biological and biomechanical therapeutic specificities must be kept in mind. Precise 3-D control of tooth movement during closure of extraction spaces is very important in meeting treatment goals. Second molar protraction is time-consuming and relatively difficult. Therefore, this treatment option may be justified only when the periodontal health of the protracted second molar is not compromised [24]. Protracting the molars may be advantageous for the patient by increasing alveolar ridge width that had previously been lost in the edentulous space. It should ideally be done before significant vertical bone resorption occurs [27]. In respect of orthodontic force system, bodily movement of molars can be obtained by using temporary skeletal anchorage devices and rational biomechanics [24]. Several authors have reported some useful clinical tips and tricks that surround providing this therapy [11, 13, 15, 27]: a long buccal hook, an uprighting spring, a toe-in bend in the posterior portion of the archwire with constriction, or a balancing lingual force can be used to prevent side

**200**

predictable results.

**5. Clinical cases**

**5.1 Case presentation**

Case no. 1 (**Figures 6–9**).

*Pretreatment intraoral photographs of a 32-year-old woman with 36 and 46 missing. We can note mesial tipping of 37 associated to a mesiolingual rotation. The space of 36 is more closed than that of 46. (a and c) Buccal occlusion views,(b) Frontal occlusion view, (d) Occlusal view of the lower arch.*

#### **Figure 7.**

*Radiographic image of the mesial tipping of teeth 37 and 47, after extraction of lower FPM. Pseudo-pocket was formed adjacent to 37. Tooth 28 is absent.*

#### **Figure 8.**

*Intraoral photographs of treatment progress. Extraction site of 36 was closed along with reopening of 46 space. (a) Frontal occlusion view, (b and c) Buccal occlusion views, (d) Occlusal view of the lower arch.*

#### **Figure 9.**

*Root correction and mesializing spring used to close left lower space with miniscrew-reinforced anchorage. (a) Buccal left occlusion view, (b) Design and activation of the spring used.*

#### Case no. 2 (**Figures 10–13**).

#### **Figure 10.**

*This case of an adult shows dilapidated 46 with slight over eruption of 16 but not remarkable drifting of 47. (a and c) Buccal occlusion views, (b) Frontal occlusion view, (d) Occlusal view of the lower arch.*

#### **Figure 11.**

*OPG showing difference in molar level at the upper right side. Tooth 46 was unpreservable and enforced extraction was indicated.*

**203**

**Figure 13.**

*prosthesis of 46.*

*Orthodontic Management of Residual Spaces of Missing Molars: Decision Factors*

*Orthodontic treatment was undertaken with the objective to correct the malocclusion while keeping the 46* 

*Posttreatment illustrations. Correction of the dentomaxillary abnormality and prosthetic restoration of missing 46. (a and d) Buccal occlusion views, (b) Frontal occlusion view, (c) Occlusal view of the lower arch, (e) OPG showing the parallelism of the root axes, (f) Occlusal view of the mandibular arch with the provisional* 

*DOI: http://dx.doi.org/10.5772/intechopen.85944*

**Figure 12.**

*space.*

*Orthodontic Management of Residual Spaces of Missing Molars: Decision Factors DOI: http://dx.doi.org/10.5772/intechopen.85944*

#### **Figure 12.**

*Human Teeth - Key Skills and Clinical Illustrations*

Case no. 2 (**Figures 10–13**).

*This case of an adult shows dilapidated 46 with slight over eruption of 16 but not remarkable drifting of 47. (a and c) Buccal occlusion views, (b) Frontal occlusion view, (d) Occlusal view of the lower arch.*

*OPG showing difference in molar level at the upper right side. Tooth 46 was unpreservable and enforced* 

*Root correction and mesializing spring used to close left lower space with miniscrew-reinforced anchorage.* 

*(a) Buccal left occlusion view, (b) Design and activation of the spring used.*

**202**

**Figure 11.**

*extraction was indicated.*

**Figure 10.**

**Figure 9.**

*Orthodontic treatment was undertaken with the objective to correct the malocclusion while keeping the 46 space.*

#### **Figure 13.**

*Posttreatment illustrations. Correction of the dentomaxillary abnormality and prosthetic restoration of missing 46. (a and d) Buccal occlusion views, (b) Frontal occlusion view, (c) Occlusal view of the lower arch, (e) OPG showing the parallelism of the root axes, (f) Occlusal view of the mandibular arch with the provisional prosthesis of 46.*

Case no. 3 (**Figures 14** and **15**).

#### **Figure 14.**

*Case of 47 extraction with large alveolar ridge and no notable migration of opposite and adjacent teeth, except for 48 that slightly drifted mesially. (a and d) Buccal occlusion views, (b) Frontal occlusion view, (c) Occlusal view of the lower arch.*

#### **Figure 15.**

*Lower molar space closure was chosen. After mesializing tooth 48 in place of tooth 47, teeth 46 and 48 have been united to prevent space reopening in waiting for adaptation of periodontal ligament fibers. (a and d) Buccal occlusion views, (b) Frontal occlusion view, (c) Occlusal view of the lower arch.*

**205**

**Figure 17.**

*(d and e) Occlusal views of the upper and lower arches.*

**Figure 16.**

*Orthodontic Management of Residual Spaces of Missing Molars: Decision Factors*

*Case of dentoskeletal class II with absence of 16. We can observe mesial tipping and mesiopalatal rotation of 17. The width of edentulous alveolar ridge was not very narrow. (a) Frontal occlusion view, (b and c) Buccal* 

*Posttreatment intraoral photographs. Remaining space was used to correct dental class II relationship and to mesialize 17 in place of 16. In the left side, first bicuspid was extracted. Extraction of 48 was indicated to compensate upper right molars' mesializing. (a) Frontal occlusion view, (b and c) Buccal occlusion views,* 

*occlusion views, (d and e) Occlusal views of the upper and lower arches.*

*DOI: http://dx.doi.org/10.5772/intechopen.85944*

Case no. 4 (**Figures 16** and **17**).

*Orthodontic Management of Residual Spaces of Missing Molars: Decision Factors DOI: http://dx.doi.org/10.5772/intechopen.85944*

#### Case no. 4 (**Figures 16** and **17**).

#### **Figure 16.**

*Human Teeth - Key Skills and Clinical Illustrations*

Case no. 3 (**Figures 14** and **15**).

**204**

**Figure 15.**

**Figure 14.**

*view of the lower arch.*

*Lower molar space closure was chosen. After mesializing tooth 48 in place of tooth 47, teeth 46 and 48 have been united to prevent space reopening in waiting for adaptation of periodontal ligament fibers. (a and d)* 

*Case of 47 extraction with large alveolar ridge and no notable migration of opposite and adjacent teeth, except for 48 that slightly drifted mesially. (a and d) Buccal occlusion views, (b) Frontal occlusion view, (c) Occlusal* 

*Buccal occlusion views, (b) Frontal occlusion view, (c) Occlusal view of the lower arch.*

*Case of dentoskeletal class II with absence of 16. We can observe mesial tipping and mesiopalatal rotation of 17. The width of edentulous alveolar ridge was not very narrow. (a) Frontal occlusion view, (b and c) Buccal occlusion views, (d and e) Occlusal views of the upper and lower arches.*

#### **Figure 17.**

*Posttreatment intraoral photographs. Remaining space was used to correct dental class II relationship and to mesialize 17 in place of 16. In the left side, first bicuspid was extracted. Extraction of 48 was indicated to compensate upper right molars' mesializing. (a) Frontal occlusion view, (b and c) Buccal occlusion views, (d and e) Occlusal views of the upper and lower arches.*

#### **5.2 Case discussion**

In all the cases presented above, the molar missing was due to dental decay. Indeed, it is the most common infectious disease worldwide [6]. According to the World Health Organization (WHO), 60–90% of school children have dental caries [6]. The molars are the most affected teeth as they evolve early.

When planning orthodontic treatment with molars missing, the patient age correlated to the amount of residual space, even apically, and the wisdom tooth condition are main decision factors described in the literature [1, 9, 16]. Patient wishes and cooperation must also be taken into account.

Case 1 concerns an adult woman who had chief complaints of upper incisors protrusion and smile asymmetry. She also wanted to resolve the residual mandibular spaces of missing 36 and 46 by the same orthodontic treatment. According to some authors [28], the ideal dimensions for the closure of the lower molars' spaces are 6 mm or less for the mesiodistal space and 7 mm for the buccolingual width. In this clinical case, the 36 space was almost closed. Furthermore, since tooth 28 was absent and tooth 18 was in functional occlusion, the treatment plan consisted of reopening the 46 space and completely closing that of 36. Also, due to mesial tipping of teeth 37, the mesializing movement was performed at the same time as the root correction using a miniscrew-supported spring. Temporary anchorage devices were indeed widely described and reported to be efficient in achieving accurate control of anchorage [15, 29] provided that the orthodontists master their biomechanics well. In case 3, as the space of lost 47 was quite large and the orthodontic abnormality not very complicated, the ideal choice was to maintain 47 space and a prosthetic rehabilitation. However, because of the absence of 18 in addition to a low economic profile of the patient, the residual space of 47 was closed at the expense of treatment duration.

In case 2 of an adult patient, all wisdom teeth have evolved and there was no need to extract to correct the anomaly. Thus, orthodontic treatment was undertaken while keeping the 46 space for a subsequent prosthetic restoration. By contrast, in case 4 that required premolars' extraction, remaining space of tooth 16 was used to mesialize 17 in place of 16 and to correct dental class II relationship with retraction of anterior teeth instead of taking out right first bicuspid.

In summary, in case of orthodontic management of molar absence, whether the residual space is closed or maintained, the control of the orthodontic movement including control of anchorage units and vertical forces as well as axial tipping and rotations is crucial to the success of the chosen therapeutic option [28].

#### **6. Conclusion**

In case of missing molars, orthodontic solutions consist of either closing or opening the space. A careful case assessment must be undertaken before treatment to ensure that the benefits of treatment will outweigh any potential risk of the treatment decided upon.

Space closure remains the best choice if the suitable conditions, notably in children whose prosthetic rehabilitation is still problematic and should be postponed until the growth and eruption process is completed. In adult patients, biological and psychological characteristics must be taken into account to achieve expected outcomes.

The decision-making process depends also on other factors like concomitant malocclusions, third molar development, absence of other teeth, and patient compliance. An orthodontic treatment based on reasoned biomechanic principles will help accomplishment of initial objectives in accordance with patient expectations.

**207**

**Author details**

provided the original work is properly cited.

© 2019 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,

Hakima Aghoutan\*, Sanaa Alami, Amal El Aouame and Farid El Quars

\*Address all correspondence to: hakimaaghoutan.2014@gmail.com

Dentistry, Hassan II University, Casablanca, Morocco

Department of Orthodontics and Dentofacial Orthopedics, Faculty of Medical

*Orthodontic Management of Residual Spaces of Missing Molars: Decision Factors*

The authors declare that they have no conflict of interest.

In the majority of cases, treatment is complicated by all the side effects of the uncompensated absence of molars. Management is sometimes a veritable challenge. Hence, the prevention and early multidisciplinary management are of major

*DOI: http://dx.doi.org/10.5772/intechopen.85944*

importance.

**Conflict of interest**

*Orthodontic Management of Residual Spaces of Missing Molars: Decision Factors DOI: http://dx.doi.org/10.5772/intechopen.85944*

In the majority of cases, treatment is complicated by all the side effects of the uncompensated absence of molars. Management is sometimes a veritable challenge. Hence, the prevention and early multidisciplinary management are of major importance.

#### **Conflict of interest**

*Human Teeth - Key Skills and Clinical Illustrations*

In all the cases presented above, the molar missing was due to dental decay. Indeed, it is the most common infectious disease worldwide [6]. According to the World Health Organization (WHO), 60–90% of school children have dental caries

When planning orthodontic treatment with molars missing, the patient age correlated to the amount of residual space, even apically, and the wisdom tooth condition are main decision factors described in the literature [1, 9, 16]. Patient

Case 1 concerns an adult woman who had chief complaints of upper incisors protrusion and smile asymmetry. She also wanted to resolve the residual mandibular spaces of missing 36 and 46 by the same orthodontic treatment. According to some authors [28], the ideal dimensions for the closure of the lower molars' spaces are 6 mm or less for the mesiodistal space and 7 mm for the buccolingual width. In this clinical case, the 36 space was almost closed. Furthermore, since tooth 28 was absent and tooth 18 was in functional occlusion, the treatment plan consisted of reopening the 46 space and completely closing that of 36. Also, due to mesial tipping of teeth 37, the mesializing movement was performed at the same time as the root correction using a miniscrew-supported spring. Temporary anchorage devices were indeed widely described and reported to be efficient in achieving accurate control of anchorage [15, 29] provided that the orthodontists master their biomechanics well. In case 3, as the space of lost 47 was quite large and the orthodontic abnormality not very complicated, the ideal choice was to maintain 47 space and a prosthetic rehabilitation. However, because of the absence of 18 in addition to a low economic profile of the patient, the residual space of 47 was closed at the expense of treatment duration. In case 2 of an adult patient, all wisdom teeth have evolved and there was no need to extract to correct the anomaly. Thus, orthodontic treatment was undertaken while keeping the 46 space for a subsequent prosthetic restoration. By contrast, in case 4 that required premolars' extraction, remaining space of tooth 16 was used to mesialize 17 in place of 16 and to correct dental class II relationship with retraction

In summary, in case of orthodontic management of molar absence, whether the residual space is closed or maintained, the control of the orthodontic movement including control of anchorage units and vertical forces as well as axial tipping and

In case of missing molars, orthodontic solutions consist of either closing or opening the space. A careful case assessment must be undertaken before treatment to ensure that the benefits of treatment will outweigh any potential risk of the treat-

Space closure remains the best choice if the suitable conditions, notably in children whose prosthetic rehabilitation is still problematic and should be postponed until the growth and eruption process is completed. In adult patients, biological and psychological characteristics must be taken into account to achieve expected

The decision-making process depends also on other factors like concomitant malocclusions, third molar development, absence of other teeth, and patient compliance. An orthodontic treatment based on reasoned biomechanic principles will help accomplishment of initial objectives in accordance with patient expectations.

[6]. The molars are the most affected teeth as they evolve early.

wishes and cooperation must also be taken into account.

of anterior teeth instead of taking out right first bicuspid.

rotations is crucial to the success of the chosen therapeutic option [28].

**5.2 Case discussion**

**206**

outcomes.

**6. Conclusion**

ment decided upon.

The authors declare that they have no conflict of interest.

#### **Author details**

Hakima Aghoutan\*, Sanaa Alami, Amal El Aouame and Farid El Quars Department of Orthodontics and Dentofacial Orthopedics, Faculty of Medical Dentistry, Hassan II University, Casablanca, Morocco

\*Address all correspondence to: hakimaaghoutan.2014@gmail.com

© 2019 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.

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Maxillo-Faciale. 2011;**112**:263-268. DOI: 10.1016/j.stomax.2011.05.003

[23] Baik UB, Kook YA, Bayomec M, Park JU, Park JH. Vertical eruption patterns of impacted mandibular third molars after the mesialization of second molars using miniscrews. The Angle Orthodontist. 2016;**86**:565-570. DOI: 10.2319/061415-399.1

[24] Baik UB, Choi HB, Kim YJ, Lee DY, Sugawara J, Nanda R. Change in alveolar bone level of mandibular second and third molars after second molar protraction into missing first molar or second premolar space. European Journal of Orthodontics. 2019:1-6. DOI: 10.1093/ejo/cjz001

[25] Sayagh M, Maniere-Ezvan A, Vernet C, Muller-Bolla M. Décisions thérapeutiques en présence de premiéres molaires permanentes délabrées chez les sujets jeunes: Enquête descriptive. International Orthodontics. 2012;**10**:318-336. DOI: 10.1016/j. ortho.2012.06.001

[26] Fudalej P, Kokich VG, Leroux B. Determining the cessation of vertical growth of the craniofacial structures to facilitate placement of single-tooth implants. American Journal of Orthodontics and Dentofacial Orthopedics. 2007;**131**:59-67. DOI: 10.1016/j.ajodo.2006.07.022

[27] Baik UB, Kim MR, Yoon KH, Kook YA, Park JH. Orthodontic uprighting of a horizontally impacted third molar and protraction of mandibular second and third molars into the missing first molar space for a patient with posterior crossbites. American Journal of Orthodontics and Dentofacial Orthopedics. 2017;**151**:572-582. DOI: 10.1016/j.ajodo.2016.01.019

[28] Raveli TB, Shintcovsk RL, Knop LAH, Sampaio LP, Raveli DB. Orthodontic replacement of lost permanent molar with neighbor molar:

**208**

*Human Teeth - Key Skills and Clinical Illustrations*

risk factors among 7-9 years old school children in Muradnagar, Ghaziabad. The Open Dentistry Journal. 2018;**12**:714-722. DOI: 10.2174/1745017901814010714

[9] Cobourne MT, Williams A, Harrison M. National clinical guidelines for the extraction of first permanent molars in children. British Dental Journal. 2014;**217**:643-648. DOI: 10.1038/

[10] Eichenberger M, Erb J, Zwahlen M, Schätzle M. The timing of extraction of non-restorable first permanent molars: A systematic review. European Journal of Paediatric Dentistry. 2015;**16**:

[11] Saga AY, Maruo IT, Maruo H, Guariza Filho O, Camargo ES, Tanaka OM. Treatment of an adult with several missing teeth and atrophic old mandibular first molar extraction sites. American Journal of Orthodontics and Dentofacial Orthopedics. 2011;**140**: 869-878. DOI: 10.1016/j.ajodo.2010.06.027

[12] Yüksel S, Üçem T. The effect of tooth agenesis on dentofacial structures. European Journal of Orthodontics. 1997;**19**:71-78. DOI: 10.1093/ejo/19.1.71

[13] Sandy JR, Hons BDS, Atkinson R. For four sixes. American Journal of Orthodontics and Dentofacial Orthopedics. 2000;**117**:418-434. DOI: 10.1177/00220345420210051101

[14] Thilander B. Orthodontic space closure versus implant placement in subjects with missing teeth. Journal of Oral Rehabilitation. 2008;**35**:64-71. DOI: 10.1111/j.1365-2842.2007.01826.x

[15] Baik UB, Chun YS, Jung MH, Sugawara J. Protraction of mandibular second and third molars into missing first molar spaces for a patient with an anterior open bite and anterior spacing. American Journal of Orthodontics and

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[1] Gupta M, Panda S, Mutawwam FA, Kariri FMM. Diagnosis and management of a patient with congenitally missing maxillary first permanent molars: A rare case report. Case Reports in Dentistry. 2016;**2016**: 3-5. DOI: 10.1155/2016/5891705

[2] American Dental Association (ADA).

Tooth eruption—The permanent teeth. Journal of the American Dental Association. 2006;**137**:2006. DOI: 10.14219/JADA.ARCHIVE.2006.0031

[3] Abe R, Endo T, Shimooka S. Maxillary first molar agenesis and other dental anomalies. The Angle Orthodontist. 2010;**80**:1002-1009. DOI:

[4] Bondemark L, Tsiopa J. Prevalence of ectopic eruption, impaction, retention and agenesis of the permanent second molar. The Angle Orthodontist. 2007;**77**:773-778. DOI:

[5] Jamilian A, Darnahal A, Nucci L, D'Apuzzo F, Perillo L. Treatment considerations for missing teeth. In: Kivanç BH, editor. Dental Anatomy. Rijeka: Intech; 2018. pp. 109-120. DOI:

[6] Saber AM, Altoukhi DH, Horaib MF, El-Housseiny AA, Alamoudi NM, Sabbagh HJ. Consequences of early extraction of compromised first permanent molar: A systematic review. BMC Oral Health. 2018;**18**:1-15. DOI:

10.2319/020210-69.1

10.2319/072506-306.1

10.5772/intechopen.69543

10.1186/s12903-018-0516-4

[7] Williams JK, Gowans AJ. Hypomineralised first permanent molars and the orthodontist. European

2003;**4**:129-132

Journal of Paediatric Dentistry.

[8] Rai A, Singh A, Menon I, Singh J, Rai V, Aswal GS. Molar incisor hypomineralization: Prevalence and

**References**

A six-year follow-up. Case Reports in Dentistry. 2017;**2017**:1-9. DOI: 10.1155/2017/4206435

[29] Raveli TB, Raveli DB, De Mathias Almeida KC, Pinto ADS. Molar uprighting: A considerable and safe decision to avoid prosthetic treatment. The Open Dentistry Journal. 2017;**11**:466-475. DOI: 10.2174/1874210601711010466

**211**

**Chapter 13**

**Abstract**

**1. Introduction**

itself, or idiopathic etiology.

such a disturbance.

*and Farid El Quars*

Impacted First and Second

Permanent Molars: Overview

*Sanaa Alami, Hakima Aghoutan, Meriem Bellamine* 

needs of earlier diagnosis, and finally (3) to highlight the treatment options.

**Keywords:** unerupted, impacted teeth, first molars, second molars, permanent molars, retained asymptomatic molars, uprighting molars, orthodontic treatment

the first and second molars, may fail to erupt either as a result of mechanical obstruction, such as the presence of a supernumerary tooth or an odontoma, lack of adequate space in the arch, or because of disruption to the eruptive mechanism

This multifactorial origin disturbance entails various clinical forms. Thereby, a broad range of terms are used so as to illustrate this phenomenon: retention and impaction. In reality, each of these words designates various etiologic factors and involves an accurate diagnostic what leads to the prognosis and the treatment of

This asymptomatic pathology is most of the time a casual discovery and may incite various pathologic conditions of neighboring and opposing teeth, such as caries, periodontitis or roots resorption, and eventually malocclusions. And so, it is

Impaction of a permanent tooth is a relatively common clinical occurrence in the human dentition. It mostly involves the mandibular and maxillary third molars, the maxillary canines or central incisors, and the mandibular second premolars while the first mandibular molars and maxillary second molars are seldom concerned. It deals with an abnormality of position in the wake of the failure of eruption [1]. Raghoebar et al. [2] suggested that teeth of the permanent dentition, of which

Impaction of a permanent tooth is a relatively common clinical occurrence in the human dentition. First mandibular molars and maxillary second molars are rarely impacted with a reported prevalence of 0–2.3% for second molars, 0.02% for the maxillary first molar, and of less than 0.01% for the mandibular first molar. The failures in their eruption mechanism may occur due to an obstacle such as the presence of a supernumerary tooth or an odontoma, lack of adequate space in the arch, an abnormal eruption path, or with idiopathic etiology. It is an asymptomatic pathology which is usually a casual discovery. Early diagnosis and treatment of permanent molars eruption disturbances contributes to optimal outcomes and favorable long-term prognosis by reduction of complication. The purpose of this is chapter is (1) to define prevalence and etiopathogeny of impacted first and second permanent molars, (2) to pinpoint the

#### **Chapter 13**

*Human Teeth - Key Skills and Clinical Illustrations*

A six-year follow-up. Case Reports in Dentistry. 2017;**2017**:1-9. DOI:

[29] Raveli TB, Raveli DB, De Mathias Almeida KC, Pinto ADS. Molar uprighting: A considerable and safe decision to avoid prosthetic treatment. The Open Dentistry Journal. 2017;**11**:466-475. DOI: 10.2174/1874210601711010466

10.1155/2017/4206435

**210**

## Impacted First and Second Permanent Molars: Overview

*Sanaa Alami, Hakima Aghoutan, Meriem Bellamine and Farid El Quars*

#### **Abstract**

Impaction of a permanent tooth is a relatively common clinical occurrence in the human dentition. First mandibular molars and maxillary second molars are rarely impacted with a reported prevalence of 0–2.3% for second molars, 0.02% for the maxillary first molar, and of less than 0.01% for the mandibular first molar. The failures in their eruption mechanism may occur due to an obstacle such as the presence of a supernumerary tooth or an odontoma, lack of adequate space in the arch, an abnormal eruption path, or with idiopathic etiology. It is an asymptomatic pathology which is usually a casual discovery. Early diagnosis and treatment of permanent molars eruption disturbances contributes to optimal outcomes and favorable long-term prognosis by reduction of complication. The purpose of this is chapter is (1) to define prevalence and etiopathogeny of impacted first and second permanent molars, (2) to pinpoint the needs of earlier diagnosis, and finally (3) to highlight the treatment options.

**Keywords:** unerupted, impacted teeth, first molars, second molars, permanent molars, retained asymptomatic molars, uprighting molars, orthodontic treatment

#### **1. Introduction**

Impaction of a permanent tooth is a relatively common clinical occurrence in the human dentition. It mostly involves the mandibular and maxillary third molars, the maxillary canines or central incisors, and the mandibular second premolars while the first mandibular molars and maxillary second molars are seldom concerned. It deals with an abnormality of position in the wake of the failure of eruption [1].

Raghoebar et al. [2] suggested that teeth of the permanent dentition, of which the first and second molars, may fail to erupt either as a result of mechanical obstruction, such as the presence of a supernumerary tooth or an odontoma, lack of adequate space in the arch, or because of disruption to the eruptive mechanism itself, or idiopathic etiology.

This multifactorial origin disturbance entails various clinical forms. Thereby, a broad range of terms are used so as to illustrate this phenomenon: retention and impaction. In reality, each of these words designates various etiologic factors and involves an accurate diagnostic what leads to the prognosis and the treatment of such a disturbance.

This asymptomatic pathology is most of the time a casual discovery and may incite various pathologic conditions of neighboring and opposing teeth, such as caries, periodontitis or roots resorption, and eventually malocclusions. And so, it is an unpredictable situation dentists have to keep up with through the use of proper clinical and radiological assessment [2–5].

Indeed, optimal outcomes can be reached if both of diagnosis and treatment of such a disturbance are early done. However, multiple local factors are involved in the failure of eruption and influence its prognosis and treatment. Among them are inclination axis, stage of the root formation, and the depth of the molar, although their exact roles have not been established and the age of the patient is probably a key factor in the evolution of the cases [1–3].

The treatment options are based on the type of eruptive abnormality and the age of the patient, including observation, orthodontic or surgical approaches and extraction of the unerupted molar. Each approach has its indications, contraindications, advantages, and disadvantages [1, 2].

This chapter copes with an overview of this pathology and aims (1) to recall the mechanisms of normal and disturbed eruption, (2) to define prevalence and etiopathogeny of impacted first and second permanent molars, (3) to shed light on the needs of earlier diagnosis, and ultimately (4) to bring the limelight on the treatment options.

#### **2. Normal and disturbed eruption of permanent molars**

Eruption comes down to a process of biological maturation which involves the axial movement of a tooth from the developmental position within the jaw toward the functional position in the occlusal plane [1, 6]. The grounds of this biological mechanism remain unknown even if several hypotheses have already been argued. Amidst these hypotheses, root growth, hydrostatic pressure, and selective bone deposition and resorption are not sufficiently supported by experimental data.

Moreover, there is no denying that the periodontal ligament and the dental follicle provide the required force to generate this tooth eruption. However, although this theory is widely disregarded because eruption also occurs in its absence, it obviously remains the cogent argument. To sum up the foregoing, eruption is a multifactorial process in which the loss of one factor can be successfully offset by another [7].

The eruption of the first and second permanent molars is especially significant for the coordination of facial growth, and for providing sufficient occlusal support for undisturbed mastication [1, 6]. Their eruption differs from that of other permanent teeth in the sense that [2]:


**213**

for impaction.

was about 0.16% [10].

*Impacted First and Second Permanent Molars: Overview DOI: http://dx.doi.org/10.5772/intechopen.86671*

contingent on underlying etiology [8].

disorder eruption should be suspected [3].

mandibular molars and maxillary second molars.

and 0.06% for lower second molars [5].

disturbed eruption of the lower second molar.

respectively [1, 6].

**3. Epidemiology**

bances may vary from delayed eruption to failure of eruption.

Eruption disturbances of teeth are usual and can have a negative sway on the development of the tooth and jaw system. The clinical spectrum of eruption distur-

Failure of eruption, unlike delayed eruption, is considered as the inability of the tooth to emerge in the oral cavity [1]. It may affect one or several teeth, in either the primary or the permanent dentition, and can be partial or complete. In this case, teeth may be totally covered by bone or soft tissue. In every instance, the failure is

Average eruption ages have been established for each dental category; however, there is individual variability in the eruption pattern and dental development. First molars emerge on the mean at 6 years of dental age. Eruption of the permanent second molars occurs, typically, few months after primary second molars, and maxillary primary canines are replaced by their successors at dental age 12 [9]. According to Helm and Seidler, it normal emergence was defined as in the maxilla 12.4 and 11.9 years in the mandible, and 11.9 and 11.4 years for boys and girls,

It is important to consider that 6-month delay in eruption of a permanent mandibular second molar compared with its contralateral counterpart or a 1-year delay in eruption of both molars should indicate a need for further radiographic investigation [9]. When eruption of a permanent tooth is at least 2 years behind schedule,

Impaction of a permanent tooth most commonly involves the mandibular and maxillary third molars that accounts for more than 80% of all impacted teeth. In [9], the following teeth concerned by the impaction are the maxillary canines or central incisors and the mandibular second premolars themselves followed by first

Failure of first and second permanent molars is rare. Their prevalence has only been reported in a few studies. Baccetti [6] found a prevalence rate of 1.7% failure of eruption of both first and second molars. According to Grover [1], for the first permanent molar, it stands for 0.01 and 0.06% in the case of the second one.

Palma et al. [1] and Valmaseda-Castellón et al. [5] found lower second molars to be the most frequently affected, followed by upper second molars. First permanent molar impaction is seldom, with prevalence rates of 0.02% for the maxillary and of less than 0.01% for the mandibular. As regards Grover and Lorton, they found that the prevalence rate of impaction of upper second molars is 0.08% of the population

Likewise, Bondemark and Tsiopa [6] have determined the frequency of anoma-

lies concerning the position and the eruption affecting the second permanent molar. In a point of fact, there is an overall prevalence of eruption disturbances of 2.3% including 1.5%, for ectopic eruption, 0.6% for primary retention, and 0.2%

The findings in South Indian population, with an age range of 15–67 years, brought to the limelight that the prevalence of impacted second mandibular molars

Such rates explain that earlier studies have focused only on the prevalence of

Furthermore, the prevalence of second lower molar seems to be linked to the age of the patient. The results show the frequency higher as patients are younger. Indeed, the prevalence in Sweden was estimated to be around 0.15% for cases

*Impacted First and Second Permanent Molars: Overview DOI: http://dx.doi.org/10.5772/intechopen.86671*

Eruption disturbances of teeth are usual and can have a negative sway on the development of the tooth and jaw system. The clinical spectrum of eruption disturbances may vary from delayed eruption to failure of eruption.

Failure of eruption, unlike delayed eruption, is considered as the inability of the tooth to emerge in the oral cavity [1]. It may affect one or several teeth, in either the primary or the permanent dentition, and can be partial or complete. In this case, teeth may be totally covered by bone or soft tissue. In every instance, the failure is contingent on underlying etiology [8].

Average eruption ages have been established for each dental category; however, there is individual variability in the eruption pattern and dental development. First molars emerge on the mean at 6 years of dental age. Eruption of the permanent second molars occurs, typically, few months after primary second molars, and maxillary primary canines are replaced by their successors at dental age 12 [9]. According to Helm and Seidler, it normal emergence was defined as in the maxilla 12.4 and 11.9 years in the mandible, and 11.9 and 11.4 years for boys and girls, respectively [1, 6].

It is important to consider that 6-month delay in eruption of a permanent mandibular second molar compared with its contralateral counterpart or a 1-year delay in eruption of both molars should indicate a need for further radiographic investigation [9]. When eruption of a permanent tooth is at least 2 years behind schedule, disorder eruption should be suspected [3].

#### **3. Epidemiology**

*Human Teeth - Key Skills and Clinical Illustrations*

clinical and radiological assessment [2–5].

key factor in the evolution of the cases [1–3].

tions, advantages, and disadvantages [1, 2].

permanent teeth in the sense that [2]:

• They do not have preceding primary teeth.

that of the maxillary molars is distally inclined.

tooth have normally been formed.

treatment options.

an unpredictable situation dentists have to keep up with through the use of proper

Indeed, optimal outcomes can be reached if both of diagnosis and treatment of such a disturbance are early done. However, multiple local factors are involved in the failure of eruption and influence its prognosis and treatment. Among them are inclination axis, stage of the root formation, and the depth of the molar, although their exact roles have not been established and the age of the patient is probably a

The treatment options are based on the type of eruptive abnormality and the age of the patient, including observation, orthodontic or surgical approaches and extraction of the unerupted molar. Each approach has its indications, contraindica-

This chapter copes with an overview of this pathology and aims (1) to recall the mechanisms of normal and disturbed eruption, (2) to define prevalence and etiopathogeny of impacted first and second permanent molars, (3) to shed light on the needs of earlier diagnosis, and ultimately (4) to bring the limelight on the

Eruption comes down to a process of biological maturation which involves the axial movement of a tooth from the developmental position within the jaw toward the functional position in the occlusal plane [1, 6]. The grounds of this biological mechanism remain unknown even if several hypotheses have already been argued. Amidst these hypotheses, root growth, hydrostatic pressure, and selective bone deposition and resorption are not sufficiently supported by experimental data. Moreover, there is no denying that the periodontal ligament and the dental follicle provide the required force to generate this tooth eruption. However, although this theory is widely disregarded because eruption also occurs in its absence, it obviously remains the cogent argument. To sum up the foregoing, eruption is a multifactorial process in which the loss of one factor can be successfully offset by another [7]. The eruption of the first and second permanent molars is especially significant for the coordination of facial growth, and for providing sufficient occlusal support for undisturbed mastication [1, 6]. Their eruption differs from that of other

• Their development is sequentially initiated in the tuberosity of the maxilla and at the junction of the ascending and horizontal ramus of the mandible.

• At the beginning, the occlusal surface of the mandibular molars is mesial while

• During growth of the jaws, the crowns gradually move to an upright position.

• Just after emergence, half of the roots of lower first permanent molars and central incisors have been formed while three quarters of the roots of all other

• As a result of the growth of the jaws, the relative position of the first molar shifts anteriorly at the time of the development of the second molar.

**2. Normal and disturbed eruption of permanent molars**

**212**

Impaction of a permanent tooth most commonly involves the mandibular and maxillary third molars that accounts for more than 80% of all impacted teeth. In [9], the following teeth concerned by the impaction are the maxillary canines or central incisors and the mandibular second premolars themselves followed by first mandibular molars and maxillary second molars.

Failure of first and second permanent molars is rare. Their prevalence has only been reported in a few studies. Baccetti [6] found a prevalence rate of 1.7% failure of eruption of both first and second molars. According to Grover [1], for the first permanent molar, it stands for 0.01 and 0.06% in the case of the second one.

Palma et al. [1] and Valmaseda-Castellón et al. [5] found lower second molars to be the most frequently affected, followed by upper second molars. First permanent molar impaction is seldom, with prevalence rates of 0.02% for the maxillary and of less than 0.01% for the mandibular. As regards Grover and Lorton, they found that the prevalence rate of impaction of upper second molars is 0.08% of the population and 0.06% for lower second molars [5].

Likewise, Bondemark and Tsiopa [6] have determined the frequency of anomalies concerning the position and the eruption affecting the second permanent molar. In a point of fact, there is an overall prevalence of eruption disturbances of 2.3% including 1.5%, for ectopic eruption, 0.6% for primary retention, and 0.2% for impaction.

The findings in South Indian population, with an age range of 15–67 years, brought to the limelight that the prevalence of impacted second mandibular molars was about 0.16% [10].

Such rates explain that earlier studies have focused only on the prevalence of disturbed eruption of the lower second molar.

Furthermore, the prevalence of second lower molar seems to be linked to the age of the patient. The results show the frequency higher as patients are younger. Indeed, the prevalence in Sweden was estimated to be around 0.15% for cases

between 10 and 19 years old according to Varpio and Wellfelt, while it accounts for 0.58% for 12-year-old Chinese children according to Davis. Shapira et al. found that the Chinese-American population was representing a higher prevalence (2.3%) of mandibular second molar impaction compared with the Israeli population (1.4%). Likewise, Shiu-yin Cho [9] found higher prevalence of 1% in Chinese schoolchildren.

As regards genders, some studies found a marked prevalence of this abnormality in males [1, 6]. On the contrary, other studies argued that there are more females with impacted lower second molars than males [3, 9, 10]. But in reality, not any significant difference has already been detected [3, 6, 9].

Additionally, the findings of some comparative analysis revealed that the prevalence of eruption has been increasing compared to the previous rates [1, 9, 11]. Evan et al. in their studies aimed to investigate the incidence of lower second molar impaction among two samples of 200 orthodontic patients referred to the Orthodontic Department of Bristol Dental Hospital consecutively in 1976 and 1986. Thereby they concluded in favor of this statement [11].

#### **4. Etiopathogeny**

Numerous local factors are involved in the failure of eruption, and they influence its prognosis and treatment. Teeth of the permanent dentition may fail to erupt either as a result of mechanical obstruction which could be idiopathic or pathological or because of the eruptive mechanism disruption [2]. According to Andreasen et al. [4], three main causes have been involved in the eruption disturbances. These causes include ectopic tooth position, obstacles in the eruption path, and failures in the eruption mechanism.

The failures of the eruption mechanism may occur due to the presence of an obstacle such as a supernumerary tooth or an odontoma, lack of adequate space in the arch, an abnormal eruption path, or an idiopathic etiology.

As a whole, causes of eruption disturbances, particularly failure of tooth eruption, could be categorized into general and local factors. It may depend on syndromic and non-syndromic problems for both kinds of factors [4, 6, 12].


Differential diagnosis for these abnormal eruption patterns was not easy to identify either clinically or radiographically before starting the treatment.

We may conclude that the eruption disturbances of permanent molars may occur due to an impaction, primary retention, or secondary retention [1, 2].

**215**

*Impacted First and Second Permanent Molars: Overview DOI: http://dx.doi.org/10.5772/intechopen.86671*

approach [13].

**Figure 1.**

**4.1 Etiology of impaction**

These terms are used indifferently and often synonymously. The etiology of the three disorders is, however, different as is their diagnosis and treatment

*Panoramic radiograph of a 17-year-old patient with mental and growth retardation. We can note the agenesis of 15, 31, and 48, as well as multiple retentions including 37 inclined distally and overlapped by the germ of 38.*

Impaction is the cessation of the eruption of a tooth. Tooth was deemed to be impacted when its complete eruption to occlusal height was prevented by an

The majority of cases are caused by a clinically or radiographically detectable physical barrier in the eruption path, which is independent of the eruption process. It may be supernumerary teeth and odontogenic tumors or cysts. Impaction may also due to an unusual orientation of the tooth germ [1, 2]. Idiopathic factors was

In most cases, the impaction of maxillary first molars is usually associated with an ectopic eruption path at a mesial angle to the normal path of eruption. It may be the result of failure of the molar to upright from its mesial inclination during eruption [2]. Insufficient space in the dental arches has been also considered as an etiological factor for impaction of second lower molar. It could be explained by the fact that the increase in arch length does not synchronize with the eruption of the second molar, more commonly in the mandible than in the maxilla [1, 11, 12, 14]. The erupting mandibular second premolar and second molar may quite often compete for space in the posterior area of the arch. When this space is inadequate, the earlier erupting

In addition, the developing third molar may also compete for space behind and above the second molar, resulting in its impaction. Its potential involvement in the second lower molar impaction was suggested, due to its altered position caused by dento-alveolar disproportion. As a result, many authors recommended to extract the third molars, as prophylactic measure, to allow for correct eruption of the second molars in teenagers. However, the relationship between impaction of lower second molars and ectopic third molars is often a controversial subject. All the more so, at the usual age of eruption of the second molar, the third molar cannot consti-

Primary retention is synonymous of "unerupted" and "embedded." It is defined as cessation of eruption before gingival emergence, with neither a physical barrier in the eruption path nor being the result of (or and not due to) an abnormal position. The arrest of the eruption process occurs before the crown has penetrated the oral mucosa, and the non-resorbing bone occlusally of a primarily retained molar

second premolar may result in the impaction of the second molar [15].

should be considered as a normal barrier in the eruption path [2, 16].

abnormal contact with another tooth in the same arch [11].

also mentioned as other factor that cause impaction.

tute a barrier in the eruption path [1, 5].

**4.2 Etiology of primary retention**

*Impacted First and Second Permanent Molars: Overview DOI: http://dx.doi.org/10.5772/intechopen.86671*

#### **Figure 1.**

*Human Teeth - Key Skills and Clinical Illustrations*

significant difference has already been detected [3, 6, 9].

Thereby they concluded in favor of this statement [11].

schoolchildren.

**4. Etiopathogeny**

the eruption mechanism.

between 10 and 19 years old according to Varpio and Wellfelt, while it accounts for 0.58% for 12-year-old Chinese children according to Davis. Shapira et al. found that the Chinese-American population was representing a higher prevalence (2.3%) of mandibular second molar impaction compared with the Israeli population (1.4%). Likewise, Shiu-yin Cho [9] found higher prevalence of 1% in Chinese

As regards genders, some studies found a marked prevalence of this abnormality in males [1, 6]. On the contrary, other studies argued that there are more females with impacted lower second molars than males [3, 9, 10]. But in reality, not any

Additionally, the findings of some comparative analysis revealed that the prevalence of eruption has been increasing compared to the previous rates [1, 9, 11]. Evan et al. in their studies aimed to investigate the incidence of lower second molar impaction among two samples of 200 orthodontic patients referred to the Orthodontic Department of Bristol Dental Hospital consecutively in 1976 and 1986.

Numerous local factors are involved in the failure of eruption, and they influence its prognosis and treatment. Teeth of the permanent dentition may fail to erupt either as a result of mechanical obstruction which could be idiopathic or pathological or because of the eruptive mechanism disruption [2]. According to Andreasen et al. [4], three main causes have been involved in the eruption disturbances. These causes include ectopic tooth position, obstacles in the eruption path, and failures in

The failures of the eruption mechanism may occur due to the presence of an obstacle such as a supernumerary tooth or an odontoma, lack of adequate space in

As a whole, causes of eruption disturbances, particularly failure of tooth eruption, could be categorized into general and local factors. It may depend on syndromic and non-syndromic problems for both kinds of factors [4, 6, 12].

• Systemic factors are present in patients with certain syndromes. Usually, multiple teeth are affected. However, eruption failure in the permanent dentition is

• In cases with local eruption disturbance, only one or a few teeth are affected. Local factors related to the failure of eruption include malocclusion disturbances of the deciduous dentition, the position of the adjacent teeth, lack of space in the dental arch, idiopathic factors, supernumerary teeth, odontomas, or cysts.

• Heredity is also mentioned as an etiological factor. Recently, mutations in parathyroid hormone receptor 1 have been identified in several familial cases of primary failure of eruption. Nevertheless, on occasion, the failure of eruption of first and second permanent molars is not associated with any systemic

Differential diagnosis for these abnormal eruption patterns was not easy to

We may conclude that the eruption disturbances of permanent molars may occur due to an impaction, primary retention, or secondary retention [1, 2].

identify either clinically or radiographically before starting the treatment.

the arch, an abnormal eruption path, or an idiopathic etiology.

associated with small number of syndromes [8] (**Figure 1**).

conditions or genetic alterations.

**214**

*Panoramic radiograph of a 17-year-old patient with mental and growth retardation. We can note the agenesis of 15, 31, and 48, as well as multiple retentions including 37 inclined distally and overlapped by the germ of 38.*

These terms are used indifferently and often synonymously. The etiology of the three disorders is, however, different as is their diagnosis and treatment approach [13].

#### **4.1 Etiology of impaction**

Impaction is the cessation of the eruption of a tooth. Tooth was deemed to be impacted when its complete eruption to occlusal height was prevented by an abnormal contact with another tooth in the same arch [11].

The majority of cases are caused by a clinically or radiographically detectable physical barrier in the eruption path, which is independent of the eruption process. It may be supernumerary teeth and odontogenic tumors or cysts. Impaction may also due to an unusual orientation of the tooth germ [1, 2]. Idiopathic factors was also mentioned as other factor that cause impaction.

In most cases, the impaction of maxillary first molars is usually associated with an ectopic eruption path at a mesial angle to the normal path of eruption. It may be the result of failure of the molar to upright from its mesial inclination during eruption [2].

Insufficient space in the dental arches has been also considered as an etiological factor for impaction of second lower molar. It could be explained by the fact that the increase in arch length does not synchronize with the eruption of the second molar, more commonly in the mandible than in the maxilla [1, 11, 12, 14]. The erupting mandibular second premolar and second molar may quite often compete for space in the posterior area of the arch. When this space is inadequate, the earlier erupting second premolar may result in the impaction of the second molar [15].

In addition, the developing third molar may also compete for space behind and above the second molar, resulting in its impaction. Its potential involvement in the second lower molar impaction was suggested, due to its altered position caused by dento-alveolar disproportion. As a result, many authors recommended to extract the third molars, as prophylactic measure, to allow for correct eruption of the second molars in teenagers. However, the relationship between impaction of lower second molars and ectopic third molars is often a controversial subject. All the more so, at the usual age of eruption of the second molar, the third molar cannot constitute a barrier in the eruption path [1, 5].

#### **4.2 Etiology of primary retention**

Primary retention is synonymous of "unerupted" and "embedded." It is defined as cessation of eruption before gingival emergence, with neither a physical barrier in the eruption path nor being the result of (or and not due to) an abnormal position. The arrest of the eruption process occurs before the crown has penetrated the oral mucosa, and the non-resorbing bone occlusally of a primarily retained molar should be considered as a normal barrier in the eruption path [2, 16].

According to Raghoebar [8], primary retention is an isolated condition associated with a localized failure of eruption but no other identifiable local or systemic involvement. It may be caused by a defect in the eruption mechanism and is associated with a disturbance in the resorption of overlying bone. It is not due to an abnormality of the periodontal ligament; but the disturbance in the dental follicle constitutes the main etiological factor that fails to initiate the metabolic events responsible for bone resorption in the eruption trajectory. According to Raghoebar et al. [8], primary retention of permanent teeth is an isolated condition associated with a localized failure of eruption but no other identifiable local or systemic involvement.

#### **4.3 Etiology of secondary retention**

Secondary retention is synonymous of "submerged," "reimpaction," and "reinclusion." It refers to unexplained cessation of eruption after emergence, precisely after a tooth has penetrated the oral mucosa as reported by Raghoebar [8]. This abnormality occurs without the evidence of a physical barrier in the eruption path ectopic position, and it affects less frequently permanent molars than primary molars [2, 13, 16].

The etiology of secondary retention is not well understood. Trauma, infection, disturbed local metabolism, and genetic factors have been suggested as etiological factors. However, ankylosis is probably the main factor in its development. Raghoebar et al. [13] examined 26 secondary retained lower second molars, and they found that all of them had ankylosed areas. However, it is still not clear whether the state of ankyloses was a result of arrested eruption or if it was the primary cause resulting in arrested eruption.

All these factors present something of a diagnostic challenge to the clinician. It is important to distinguish between these three phenomena in order to understand the clinical features and to choose an adequate treatment.

#### **5. Diagnostic approach**

The failure of eruption is an asymptomatic pathology. That means that it is usually a casual discovery and its diagnosis is generally made late. It may incite various pathologic conditions on the permanent dentition such as caries, periodontitis, pericoronitis, and risk of root resorption of adjacent teeth as well as the situations leading to the loss of permanent teeth, incomplete development of the alveolar process, shortening of the facial height, and occlusal disturbances. Thus, it is suggested that these abnormalities should be diagnosed and treated at an early age [3, 5].

Indeed, prompt diagnosis is essential in order to improve prognosis and to palliate the consequences of the failure of eruption of permanent molars. It involves full medical history, and it appropriates clinical and radiographic examinations which are sufficient to distinguish clearly between impaction, primary, and secondary retention [1, 2, 17]. As eruption time may vary between individuals, an appropriate follow-up of children with mixed dentition is required at 6-month intervals to manage their eruption pattern and dental development, especially in cases of posterior crowding and when molar retention is suspected [9].

#### **5.1 Clinical analysis**

This is a crucial step in the management of these abnormalities. It is important to raise the civil age, which must be correlated with dental age in order to claim a

**217**

sis' diagnosis [3].

*related to secondary retention.*

**Figure 2.**

**Figure 3.**

**5.2 Radiographic analysis**

*Impacted First and Second Permanent Molars: Overview DOI: http://dx.doi.org/10.5772/intechopen.86671*

primary, or secondary retention.

possible eruption delay. A child is considered to be late toothed when the dental and civil ages differ by more than 2 years from the average values for permanent teeth. In addition, it is imperative to note on questioning a history of trauma or infection as well as a possible notion of heredity, emphasizing a family history of eruption failure or ankylosis affecting at least one primary tooth [8]. This facilitates the identification of the clinical form of the abnormality according to possible etiological factors. The clinical examination cannot claim to make a reliable diagnosis of dental impaction or retention. Only radiographic analysis will make it possible to conclude this and above all to decide between the three clinical forms, namely, impaction,

Some signs, although rare, could be characteristic of particularly secondary dental retention. Indeed, clinically secondary retention is usually suspected on the one hand when a molar is in infra-occlusion at an age when the tooth would normally be in occlusion (**Figures 2** and **3**) This is because the adjacent teeth continue to erupt but the growth of the alveolar process in the affected area stops. On the other hand,

the involvement of ankylosis might be detected with the percussion test [3].

*Intraoral photographs showing arrested eruption of the tooth 16 after gingival rupture associated with an* 

*infraocclusion in this side and growth cessation of the alveolar process.*

However, particular attention should be focused on the number of teeth with delayed eruption, referring to the contralateral tooth. A 6-month delay in eruption of a permanent mandibular second molar compared with its contralateral or a 1-year delay in eruption of both molars should justify suspicion of molar retention

*The orthopantomogram revealed the absence of a physical obstacle and a vertical position of the tooth 16* 

The involvement of ankylosis might be detected with the percussion test and radiographic evidence of the periodontal ligament obliteration. The scanner or the cone beam computed tomography are the only tools which may identify the ankylo-

Unerupted molar is often detected in a routine panoramic radiograph during pedodontic or orthodontic evaluation and treatment planning. But, it is usually not

and should indicate a need for further radiographic investigation [9].

#### *Impacted First and Second Permanent Molars: Overview DOI: http://dx.doi.org/10.5772/intechopen.86671*

possible eruption delay. A child is considered to be late toothed when the dental and civil ages differ by more than 2 years from the average values for permanent teeth.

In addition, it is imperative to note on questioning a history of trauma or infection as well as a possible notion of heredity, emphasizing a family history of eruption failure or ankylosis affecting at least one primary tooth [8]. This facilitates the identification of the clinical form of the abnormality according to possible etiological factors.

The clinical examination cannot claim to make a reliable diagnosis of dental impaction or retention. Only radiographic analysis will make it possible to conclude this and above all to decide between the three clinical forms, namely, impaction, primary, or secondary retention.

Some signs, although rare, could be characteristic of particularly secondary dental retention. Indeed, clinically secondary retention is usually suspected on the one hand when a molar is in infra-occlusion at an age when the tooth would normally be in occlusion (**Figures 2** and **3**) This is because the adjacent teeth continue to erupt but the growth of the alveolar process in the affected area stops. On the other hand, the involvement of ankylosis might be detected with the percussion test [3].

#### **Figure 2.**

*Human Teeth - Key Skills and Clinical Illustrations*

**4.3 Etiology of secondary retention**

primary cause resulting in arrested eruption.

clinical features and to choose an adequate treatment.

crowding and when molar retention is suspected [9].

involvement.

molars [2, 13, 16].

**5. Diagnostic approach**

According to Raghoebar [8], primary retention is an isolated condition associated with a localized failure of eruption but no other identifiable local or systemic involvement. It may be caused by a defect in the eruption mechanism and is associated with a disturbance in the resorption of overlying bone. It is not due to an abnormality of the periodontal ligament; but the disturbance in the dental follicle constitutes the main etiological factor that fails to initiate the metabolic events responsible for bone resorption in the eruption trajectory. According to Raghoebar et al. [8], primary retention of permanent teeth is an isolated condition associated with a localized failure of eruption but no other identifiable local or systemic

Secondary retention is synonymous of "submerged," "reimpaction," and "reinclusion." It refers to unexplained cessation of eruption after emergence, precisely after a tooth has penetrated the oral mucosa as reported by Raghoebar [8]. This abnormality occurs without the evidence of a physical barrier in the eruption path ectopic position, and it affects less frequently permanent molars than primary

The etiology of secondary retention is not well understood. Trauma, infection, disturbed local metabolism, and genetic factors have been suggested as etiological factors. However, ankylosis is probably the main factor in its development. Raghoebar et al. [13] examined 26 secondary retained lower second molars, and they found that all of them had ankylosed areas. However, it is still not clear whether the state of ankyloses was a result of arrested eruption or if it was the

All these factors present something of a diagnostic challenge to the clinician. It is important to distinguish between these three phenomena in order to understand the

The failure of eruption is an asymptomatic pathology. That means that it is usually a casual discovery and its diagnosis is generally made late. It may incite various pathologic conditions on the permanent dentition such as caries, periodontitis, pericoronitis, and risk of root resorption of adjacent teeth as well as the situations leading to the loss of permanent teeth, incomplete development of the alveolar process, shortening of the facial height, and occlusal disturbances. Thus, it is suggested that these abnormalities should be diagnosed and treated at an early age [3, 5].

Indeed, prompt diagnosis is essential in order to improve prognosis and to palliate the consequences of the failure of eruption of permanent molars. It involves full medical history, and it appropriates clinical and radiographic examinations which are sufficient to distinguish clearly between impaction, primary, and secondary retention [1, 2, 17]. As eruption time may vary between individuals, an appropriate follow-up of children with mixed dentition is required at 6-month intervals to manage their eruption pattern and dental development, especially in cases of posterior

This is a crucial step in the management of these abnormalities. It is important to raise the civil age, which must be correlated with dental age in order to claim a

**216**

**5.1 Clinical analysis**

*Intraoral photographs showing arrested eruption of the tooth 16 after gingival rupture associated with an infraocclusion in this side and growth cessation of the alveolar process.*

#### **Figure 3.**

*The orthopantomogram revealed the absence of a physical obstacle and a vertical position of the tooth 16 related to secondary retention.*

However, particular attention should be focused on the number of teeth with delayed eruption, referring to the contralateral tooth. A 6-month delay in eruption of a permanent mandibular second molar compared with its contralateral or a 1-year delay in eruption of both molars should justify suspicion of molar retention and should indicate a need for further radiographic investigation [9].

The involvement of ankylosis might be detected with the percussion test and radiographic evidence of the periodontal ligament obliteration. The scanner or the cone beam computed tomography are the only tools which may identify the ankylosis' diagnosis [3].

#### **5.2 Radiographic analysis**

Unerupted molar is often detected in a routine panoramic radiograph during pedodontic or orthodontic evaluation and treatment planning. But, it is usually not the main reason for referral to the orthodontist. Early detection and treatment is imperative to avoid possible complications and to eliminate the need for advanced orthodontic and surgical treatment [15].

The radiological examination must first conclude that the germs of unerupted molars are present. Also, as reported by Vedtofte [12, 18], it should also focus on registration of dental abnormalities in tooth retained and dentition in general such as:


Vedtofte and Andreasen [18] found a high prevalence of dens invagination and taurodontic in second lower molars with arrested eruption (**Figure 4**). They suggested that there was an association between morphological deviations and periodontal membrane malfunction, the latter causing eruption disturbances. Root dilacerations were also observed in arrested eruption upper and lower molars but they are not related to a particularly deep bony position of the molar. It could explain the association between root abnormalities and eruptive disorders in permanent molars [12].

In addition, some measurements must be recorded on the orthopantomogram as the angulation of impacted tooth and depth of retention. The inclination axis of the molars is measured from tracing long axis of unerupted teeth and adjacent teeth, perpendicular to the tangent to the tips of the cusps. The angle between these lines is measured for each side of the jaw in order to conclude an average value [9, 11, 12] (**Figure 5**).

The degree of non-eruption could be evaluated radiographically in millimeters of bone, from the alveolar ridge to the central fossa of the unerupted molar or vertical distance between distal marginal ridge of the first molar and mesial marginal ridge of the impacted second molar [1, 3] (**Figure 6**).

Because permanent teeth may fail to erupt either as a result of mechanical obstruction or disruption to the eruptive mechanism itself [2], both clinical and radiographical diagnosis approach should conclude in an impaction, primary, or secondary retention on the basis of the various etiological factors, which are as follows:


#### *5.2.1 Radiological characteristics of impaction*

The orthopantomograph reveals, in this specific case, odontogenic cysts, odontoma, supernumerary teeth, or signs of insufficient space in the posterior side

**219**

**Figure 6.**

**Figure 5.**

**Figure 4.**

with lower second molar.

*to the mesial marginal ridge of the impacted second molar.*

of dental arch as malposition of the tooth germs of the third molars overlapping

*Readapted from [3]. Registration of impacted teeth depth from distal marginal ridge of the first molar (DM1)* 

*Readapted from [11, 12]. Registration of angulation of impacted teeth from the angle between long axis of first and second lower molars. Angle greater than 40° means mesial inclination. Angle between 40 and −20° means* 

*Panoramic radiograph of a 13-year-old patient showing a delayed eruption of first and second permanent molars with intrapulpal calcifications and taurodontism of the first lower permanent molars and second lower* 

The great majority of mandibular second molar impaction was associated with a degree of mesial angulation which could be radiographically seen as an oblique

*Impacted First and Second Permanent Molars: Overview DOI: http://dx.doi.org/10.5772/intechopen.86671*

*premolars. We also note the reinclusions of the second temporary molars.*

*vertical position. Angle less than −20° means distal inclination.*

*Impacted First and Second Permanent Molars: Overview DOI: http://dx.doi.org/10.5772/intechopen.86671*

#### **Figure 4.**

*Human Teeth - Key Skills and Clinical Illustrations*

orthodontic and surgical treatment [15].

• Root deflection dilacerations

case of impacted second molar)

ridge of the impacted second molar [1, 3] (**Figure 6**).

• Taurodontism

• Invagination

permanent molars [12].

(**Figure 5**).

follows:

molar impaction;

• The root growth stage;

*5.2.1 Radiological characteristics of impaction*

such as:

the main reason for referral to the orthodontist. Early detection and treatment is imperative to avoid possible complications and to eliminate the need for advanced

The radiological examination must first conclude that the germs of unerupted molars are present. Also, as reported by Vedtofte [12, 18], it should also focus on registration of dental abnormalities in tooth retained and dentition in general

• Resorption or tooth decay in adjacent primary or permanent teeth (primary molar or second premolar in case of impacted first molars, and first molar in

Vedtofte and Andreasen [18] found a high prevalence of dens invagination and taurodontic in second lower molars with arrested eruption (**Figure 4**). They suggested that there was an association between morphological deviations and periodontal membrane malfunction, the latter causing eruption disturbances. Root dilacerations were also observed in arrested eruption upper and lower molars but they are not related to a particularly deep bony position of the molar. It could explain the association between root abnormalities and eruptive disorders in

In addition, some measurements must be recorded on the orthopantomogram as the angulation of impacted tooth and depth of retention. The inclination axis of the molars is measured from tracing long axis of unerupted teeth and adjacent teeth, perpendicular to the tangent to the tips of the cusps. The angle between these lines is measured for each side of the jaw in order to conclude an average value [9, 11, 12]

The degree of non-eruption could be evaluated radiographically in millimeters of bone, from the alveolar ridge to the central fossa of the unerupted molar or vertical distance between distal marginal ridge of the first molar and mesial marginal

Because permanent teeth may fail to erupt either as a result of mechanical obstruction or disruption to the eruptive mechanism itself [2], both clinical and radiographical diagnosis approach should conclude in an impaction, primary, or secondary retention on the basis of the various etiological factors, which are as

• The detection of mechanical obstruction and posterior crowding typical of

The orthopantomograph reveals, in this specific case, odontogenic cysts, odontoma, supernumerary teeth, or signs of insufficient space in the posterior side

• The signs of ankylosis characteristic of secondary retention.

**218**

*Panoramic radiograph of a 13-year-old patient showing a delayed eruption of first and second permanent molars with intrapulpal calcifications and taurodontism of the first lower permanent molars and second lower premolars. We also note the reinclusions of the second temporary molars.*

#### **Figure 5.**

*Readapted from [11, 12]. Registration of angulation of impacted teeth from the angle between long axis of first and second lower molars. Angle greater than 40° means mesial inclination. Angle between 40 and −20° means vertical position. Angle less than −20° means distal inclination.*

#### **Figure 6.**

*Readapted from [3]. Registration of impacted teeth depth from distal marginal ridge of the first molar (DM1) to the mesial marginal ridge of the impacted second molar.*

of dental arch as malposition of the tooth germs of the third molars overlapping with lower second molar.

The great majority of mandibular second molar impaction was associated with a degree of mesial angulation which could be radiographically seen as an oblique

or even horizontal position of the tooth. A very rare case of an inverted impacted second molar where its crown was directed toward the lower border of the mandible was reported [15].

Nevertheless, when the first molar is affected, the radiographs show a mesial inclination and atypical resorption of the distal surface of the adjacent primary second molar. The main sign is the long axis which is not parallel to the normal eruption path [2].

#### *5.2.2 Radiological characteristics of primary retention*

Because the arrest of the eruption process occurs before the crown has penetrated the oral mucosa, the crown is often covered by bone and mucosa. Thus, the non-resorbing bone occlusally should be considered as a normal barrier in the eruption path [2, 16].

Primary retention is defined as an incomplete tooth eruption despite the presence of a clear eruption pathway. Radiographically, the molar is normally oriented in its eruption path, and roots are deeply situated and sometimes completely formed. The growth of roots has occurred apically due to bone resorption around the radicular portion [4, 16].

A follow-up of at least 6 months is necessary to detect radiographically whether the tooth is showing any eruptive movement or not, in order to make a differential diagnosis between primary and secondary retention.

#### *5.2.3 Radiological characteristics of secondary retention*

Ankylosis was suggested to be the main etiological factor in secondary retained permanent teeth. Histological study conducted by Raghoebar compared 26 secondarily retained molars removed in children group (mean age = 16.2 ± 3.9 years), with six normally erupted molars which were removed for orthodontic or prosthetic reasons [13]. The author found areas of ankylosis along the roots of all secondary retained molars located at the bifurcation and interradicular root surface in 81% of the cases.

Thus, it is difficult to specify the diagnosis of such disturbance only from orthopantomographs. Intraoral periapical radiographs allows to identify a periodontal obliteration and hypercementosis. The computed tomography scan represents supplemental examination to bring a definitive diagnosis of ankylosis [3].

Another factor in favor with the diagnosis of secondary retention is tooth position. Wellfelt maintains that ankylosis is often suspected in vertically positioned teeth (**Figures 7** and **8**).

#### **Figure 7.**

*Intraoral photographs (A) before treatment and (B) 2 years after orthodontic and surgical treatment, showing arrested eruption of 37 after gingival rupture, with no movement of this tooth related to secondary retention.*

**221**

• Age.

*Impacted First and Second Permanent Molars: Overview DOI: http://dx.doi.org/10.5772/intechopen.86671*

and secondary retention, tooth is rather vertical.

*Post-treatment panoramic radiograph revealed vertical position of retained tooth.*

choose a suitable treatment [2, 8].

factor in the evolution of the case.

variables could be mentioned [1, 3]:

• Degree of non- eruption,

• Stage of root formation,

thus in secondary retention.

• Dental inclination,

**6.1 Decision-making factors of treatment**

**6. Treatment**

**Figure 8.**

Finally, primary and secondary retention could be differentiated considering the stage during which the molar stops the eruption process [2]. In addition, the mesial angulation of the molars is characteristic of the impaction, whereas in the primary

The diagnosis characteristics of eruption disorders are different but the treatment approaches are identical in some cases. Primary and secondary retention of permanent molars reflects disturbances in a particular stage of the eruptive process, while impaction is due to a physical barrier or an abnormal tooth position and thus not directly related to a particular eruptive stage. It is important to distinguish between these three phenomena in order to understand the clinical features and to

Multiple local factors are involved in the failure of eruption and influence its prognosis and treatment. We cite lack of space in the arch, dental anatomy, inclination axis, stage of the root formation, and the depth of the molar. Although their exact roles have not been yet established. The age of the patient is probably a key

Several entities are an indicator of retention's severity and could influence the prognosis and treatment protocol of unerupted permanent molars. The following

The inclination axis of the molars has certainly an impact on clinical treatment results [1]. Wellfelt [1] reported that the mesioangular inclination was most successfully treated because the ankylosis is often suspected in vertically positioned teeth,

*Impacted First and Second Permanent Molars: Overview DOI: http://dx.doi.org/10.5772/intechopen.86671*

**Figure 8.** *Post-treatment panoramic radiograph revealed vertical position of retained tooth.*

Finally, primary and secondary retention could be differentiated considering the stage during which the molar stops the eruption process [2]. In addition, the mesial angulation of the molars is characteristic of the impaction, whereas in the primary and secondary retention, tooth is rather vertical.

## **6. Treatment**

*Human Teeth - Key Skills and Clinical Illustrations*

*5.2.2 Radiological characteristics of primary retention*

diagnosis between primary and secondary retention.

*5.2.3 Radiological characteristics of secondary retention*

dible was reported [15].

eruption path [2].

eruption path [2, 16].

the radicular portion [4, 16].

teeth (**Figures 7** and **8**).

or even horizontal position of the tooth. A very rare case of an inverted impacted second molar where its crown was directed toward the lower border of the man-

Nevertheless, when the first molar is affected, the radiographs show a mesial inclination and atypical resorption of the distal surface of the adjacent primary second molar. The main sign is the long axis which is not parallel to the normal

Because the arrest of the eruption process occurs before the crown has penetrated the oral mucosa, the crown is often covered by bone and mucosa. Thus, the non-resorbing bone occlusally should be considered as a normal barrier in the

Primary retention is defined as an incomplete tooth eruption despite the presence of a clear eruption pathway. Radiographically, the molar is normally oriented in its eruption path, and roots are deeply situated and sometimes completely formed. The growth of roots has occurred apically due to bone resorption around

A follow-up of at least 6 months is necessary to detect radiographically whether the tooth is showing any eruptive movement or not, in order to make a differential

Ankylosis was suggested to be the main etiological factor in secondary retained permanent teeth. Histological study conducted by Raghoebar compared 26 secondarily retained molars removed in children group (mean age = 16.2 ± 3.9 years), with six normally erupted molars which were removed for orthodontic or prosthetic reasons [13]. The author found areas of ankylosis along the roots of all secondary retained molars located at the bifurcation and interradicular root surface in 81% of the cases. Thus, it is difficult to specify the diagnosis of such disturbance only from orthopantomographs. Intraoral periapical radiographs allows to identify a periodontal obliteration and hypercementosis. The computed tomography scan represents supplemental examination to bring a definitive diagnosis of ankylosis [3].

Another factor in favor with the diagnosis of secondary retention is tooth position. Wellfelt maintains that ankylosis is often suspected in vertically positioned

*Intraoral photographs (A) before treatment and (B) 2 years after orthodontic and surgical treatment, showing arrested eruption of 37 after gingival rupture, with no movement of this tooth related to secondary retention.*

**220**

**Figure 7.**

The diagnosis characteristics of eruption disorders are different but the treatment approaches are identical in some cases. Primary and secondary retention of permanent molars reflects disturbances in a particular stage of the eruptive process, while impaction is due to a physical barrier or an abnormal tooth position and thus not directly related to a particular eruptive stage. It is important to distinguish between these three phenomena in order to understand the clinical features and to choose a suitable treatment [2, 8].

#### **6.1 Decision-making factors of treatment**

Multiple local factors are involved in the failure of eruption and influence its prognosis and treatment. We cite lack of space in the arch, dental anatomy, inclination axis, stage of the root formation, and the depth of the molar. Although their exact roles have not been yet established. The age of the patient is probably a key factor in the evolution of the case.

Several entities are an indicator of retention's severity and could influence the prognosis and treatment protocol of unerupted permanent molars. The following variables could be mentioned [1, 3]:


The inclination axis of the molars has certainly an impact on clinical treatment results [1]. Wellfelt [1] reported that the mesioangular inclination was most successfully treated because the ankylosis is often suspected in vertically positioned teeth, thus in secondary retention.

The degree of non-eruption or depth of the impaction seems to be a less decisive factor in the evolution than the stage of root formation. In fact, it was reported that when roots of the unerupted tooth are completely formed, the chances of successful treatment decrease [1]. Furthermore, Fu et al. found, in their study conducted on a Taiwanese population, that the impacted depth was highly and positively correlated with the initial uprighting period [3].

This could explain that patient's age is considered as a key factor in the prognosis of this disorder. Most pediatric population studies show that resulting malocclusions and abnormalities in adjacent and opposing teeth are frequent and start at very early ages. [5] Furthermore, we have mentioned that the age affects certainly the initial uprighting period, but it has a small impact on the performance and outcomes of the technique. Thus, these teeth malposition should be diagnosed and treated at an early age. Fu et al. suggested that there was a statistically significant relationship between poor evolution of the unerupted molar and the following factors: age over 14 and root formation of the unerupted molar in its last stages [3].

Finally, both diagnosis and treatment planning should be placed into the perspective of the patient's age, the stage of eruption, as well as of factors like the patient's needs and self-image [2]. Even if the disturbances do not occur frequently, it is important to develop an early diagnosis in order to start the treatment at the optimal time, between 11 and 14 years, when root formation is incomplete [3, 6].

#### **6.2 Treatment modalities**

Eruption disturbances may manifest clinically and radiographically as impaction, primary retention, or secondary retention. The treatment protocol for its management is based on the type of eruptive abnormality and the age of the patient. Treatment options include observation, surgical exposure or repositioning, orthodontic uprighting, and extraction of the unerupted molar. Each modality has its indications, contra-indications, advantages, and disadvantages.

Generally, as stated by Andreasen [8], the active orthodontic and/or surgical treatment is indicated in cases of impacted ectopic erupting teeth and primary retention. However, a primary observation period seems to be required before any intervention to confirm diagnosis through a radiographical follow-up. Spontaneous eruption into normal occlusion could occur in rare cases. Abstention is recommended in cases of secondary retention due to ankylosis, or deeply impacted lower second molars. Extraction may be the norm in case of failure of teeth repositioning.

Due to low frequency of impacted first molars, numerous studies and case reports are available regarding the clinical management of second molar disturbed eruption. All approaches and techniques can also be applied to unerupted first molars despite their low incidence.

#### *6.2.1 Observation*

Kavadia and others underline the importance of tight control of impacted lower second molars. They suggest that active treatment should only be considered after an observation period of at least 12 months exclude the possibility of self-correction [9].

So when the identified etiology is an obstacle, the early removal of the barrier usually allows the molar to erupt spontaneously.

Furthermore, abnormal position of the germ of a third molar may form a barrier causing impaction of the second molar. The recommended treatment is removal of the third molar at the age of 11–14 years in combination with a thorough follow-up of the eruption of the second molar [2]. In other cases, some clinicians advocate removal of the second molar allowing eruption of the third molar at its position [14].

**223**

*Impacted First and Second Permanent Molars: Overview DOI: http://dx.doi.org/10.5772/intechopen.86671*

which may include [9]:

mesially

• Orthodontic uprighting

• Surgical repositioning

the extraction site.

*6.2.2 Orthodontic uprighting*

is contraindicated [2, 15].

roots have a poor prognosis [2].

• Conventional appliances

• Distalization segment wire

deeply impacted teeth.

*6.2.2.1 Conventional appliances*

have been also reported [4].

• Temporary skeletal anchorage.

is required [13]. Numerous methods can be considered:

the teeth and allowing "self-correction" and eruption [15].

Once the chance of self-correction has been ruled out, dentists should discuss with patients and parents the various treatment options for the impacted molars,

• Extraction of the impacted second molar to allow the third molar to drive

Generally, as stated by Andreasen [8], the active orthodontic treatment is indicated in cases of impacted ectopic erupting teeth and primary retention. Orthodontic approach is important to provide a good occlusion and to reduce the risk of caries and periodontal disease and can be performed with or without extraction of the adjacent third molar. However, in cases of extreme horizontal impaction or widely diverging roots, orthodontic uprighting of permanent molars

The optimal moment for uprighting is when two-thirds of the roots have been formed, between 11 and 14 years old for second molar. Molars with fully formed

Beyond age, orthodontic modalities are depending of mesial tipping and depth of concerned teeth. So, when orthodontics is indicated, an efficient mechanics plan

All of these methods, however, have limitations, especially in the approach of

When a second molar is slightly mesially angulated with a sufficient emerging area, several devices have been suggested in the literature to correct simply this malposition such as separating elastic or brass ligature wire between tipped teeth and neighboring one. These artifices operate as a spring, relieving contact between

Interarch vertical elastics and a removable appliance with an uprighting spring

The correction of this abnormality can also be done simply by including the impacted molar in the orthodontic treatment from the first stage of alignment and leveling of the orthodontic treatment. A tube is then bonded to the vestibular surface of the molar, which will be engaged in the continuous arch. Alignment and distalization will be ensured by superelastic arches and a push coil spring

• Extraction of the impacted second molar and transplant of the third molar into

Once the chance of self-correction has been ruled out, dentists should discuss with patients and parents the various treatment options for the impacted molars, which may include [9]:

• Orthodontic uprighting

*Human Teeth - Key Skills and Clinical Illustrations*

with the initial uprighting period [3].

**6.2 Treatment modalities**

molars despite their low incidence.

usually allows the molar to erupt spontaneously.

*6.2.1 Observation*

The degree of non-eruption or depth of the impaction seems to be a less decisive factor in the evolution than the stage of root formation. In fact, it was reported that when roots of the unerupted tooth are completely formed, the chances of successful treatment decrease [1]. Furthermore, Fu et al. found, in their study conducted on a Taiwanese population, that the impacted depth was highly and positively correlated

This could explain that patient's age is considered as a key factor in the prognosis of this disorder. Most pediatric population studies show that resulting malocclusions and abnormalities in adjacent and opposing teeth are frequent and start at very early ages. [5] Furthermore, we have mentioned that the age affects certainly the initial uprighting period, but it has a small impact on the performance and outcomes of the technique. Thus, these teeth malposition should be diagnosed and treated at an early age. Fu et al. suggested that there was a statistically significant relationship between poor evolution of the unerupted molar and the following factors: age over 14 and root formation of the unerupted molar in its last stages [3]. Finally, both diagnosis and treatment planning should be placed into the perspective of the patient's age, the stage of eruption, as well as of factors like the patient's needs and self-image [2]. Even if the disturbances do not occur frequently, it is important to develop an early diagnosis in order to start the treatment at the optimal time, between 11 and 14 years, when root formation is incomplete [3, 6].

Eruption disturbances may manifest clinically and radiographically as impaction, primary retention, or secondary retention. The treatment protocol for its management is based on the type of eruptive abnormality and the age of the patient. Treatment options include observation, surgical exposure or repositioning, orthodontic uprighting, and extraction of the unerupted molar. Each modality has

Generally, as stated by Andreasen [8], the active orthodontic and/or surgical treatment is indicated in cases of impacted ectopic erupting teeth and primary retention. However, a primary observation period seems to be required before any intervention to confirm diagnosis through a radiographical follow-up. Spontaneous eruption into normal occlusion could occur in rare cases. Abstention is recommended in cases of secondary retention due to ankylosis, or deeply impacted lower second molars. Extraction may be the norm in case of failure of teeth repositioning. Due to low frequency of impacted first molars, numerous studies and case reports are available regarding the clinical management of second molar disturbed eruption. All approaches and techniques can also be applied to unerupted first

Kavadia and others underline the importance of tight control of impacted lower second molars. They suggest that active treatment should only be considered after an observation period of at least 12 months exclude the possibility of self-correction [9]. So when the identified etiology is an obstacle, the early removal of the barrier

Furthermore, abnormal position of the germ of a third molar may form a barrier causing impaction of the second molar. The recommended treatment is removal of the third molar at the age of 11–14 years in combination with a thorough follow-up of the eruption of the second molar [2]. In other cases, some clinicians advocate removal of the second molar allowing eruption of the third molar at its position [14].

its indications, contra-indications, advantages, and disadvantages.

**222**


#### *6.2.2 Orthodontic uprighting*

Generally, as stated by Andreasen [8], the active orthodontic treatment is indicated in cases of impacted ectopic erupting teeth and primary retention. Orthodontic approach is important to provide a good occlusion and to reduce the risk of caries and periodontal disease and can be performed with or without extraction of the adjacent third molar. However, in cases of extreme horizontal impaction or widely diverging roots, orthodontic uprighting of permanent molars is contraindicated [2, 15].

The optimal moment for uprighting is when two-thirds of the roots have been formed, between 11 and 14 years old for second molar. Molars with fully formed roots have a poor prognosis [2].

Beyond age, orthodontic modalities are depending of mesial tipping and depth of concerned teeth. So, when orthodontics is indicated, an efficient mechanics plan is required [13]. Numerous methods can be considered:


All of these methods, however, have limitations, especially in the approach of deeply impacted teeth.

#### *6.2.2.1 Conventional appliances*

When a second molar is slightly mesially angulated with a sufficient emerging area, several devices have been suggested in the literature to correct simply this malposition such as separating elastic or brass ligature wire between tipped teeth and neighboring one. These artifices operate as a spring, relieving contact between the teeth and allowing "self-correction" and eruption [15].

Interarch vertical elastics and a removable appliance with an uprighting spring have been also reported [4].

The correction of this abnormality can also be done simply by including the impacted molar in the orthodontic treatment from the first stage of alignment and leveling of the orthodontic treatment. A tube is then bonded to the vestibular surface of the molar, which will be engaged in the continuous arch. Alignment and distalization will be ensured by superelastic arches and a push coil spring

(**Figure 9**). A variant of the same device can be proposed; the superelastic wire used for alignment and leveling of the teeth is curved distally of impacted molar which is engaged in the tube and bended on mesial (**Figure 10**).

Such methods might require considerable treatment time with the risk of extending the overall duration of orthodontic treatment. Indeed, since the arch sections cannot change, the leveling of the dental arches is delayed. This widely justifies the use of fixed auxiliaries as an efficient alternative.

#### *6.2.2.2 Distalization segment wire/auxiliary spring fixed*

A button, mini tube, or eyelet button is usually bonded on the visible area of the tooth. An auxiliary segment is constructed of flexible wire nickel titanium, copper Ni Ti, or titanium molybdenum alloy (TMA) with loop. This cantilever is generally placed after leveling of the dental arch, which is then used as stabile unity for distalization of impacted tooth. In fact, molar uprighting requires good anchorage control, and subsequently, a full-arch fixed appliance is necessary to protect from undesirable tooth movements [19]. Continuous 0.019 × 0.025 stainless steel wire from first molar to second premolar or first molar is recommended as an anchorage unit.

Then, NiTi wire can be used to upright the tooth. Finally, the tube is bonded to introduce the tooth into the conventional wire to complete leveling and finish treatment [14, 15, 20].

Various patterns have been revealed in the literature, from the simplest to the most complex, taking advantage of the elastic properties of wire alloys.

The 0.016 × 0.022 Ni-Ti or 0.016 × 0.025 Cu Ni-Ti may be used to distalize angulated molar. The segment wire is inserted between the retained molar and the neighboring tooth on the arch. Due to its superelasticity, the wire is curved and then bonded to the occlusal face of the adjacent tooth. A moment of force is generated resulting in move of the molar to the distal (**Figures 11** and **12**).

**Figure 9.** *Association of superelastic wire and coil spring between first and second lower molars.*

#### **Figure 10.**

*Continuous superelastic wire curved in distal of second lower molar then introduced into the tube to achieve its distalization.*

**225**

**Figure 13.**

*the impacted tooth.*

*Impacted First and Second Permanent Molars: Overview DOI: http://dx.doi.org/10.5772/intechopen.86671*

(**Figure 13**).

molar.

**Figure 11.**

**Figure 12.**

Like Fu et al. [4], the same sections of Ni-Ti or copper Ni-Ti can be used to upright orthodontically the mandibular second molar. The sectional wire is here ligated on the continuous wire that served to align and level the dental arch

In other retrospective study, Fu et al. [3] described the pole arm appliance as an effective treatment modality and success predictable for impacted second lower

*0.016 × 0.022 Ni-Ti or 0.016 × 0.025 Cu Ni-Ti sectional wire, placed between first and second retained molars, is* 

*Right quadrant of a panoramic radiograph illustrating the placement of the 0.016 × 0.022 Ni-Ti sectional wire* 

*0.016 × 0.022 Ni-Ti or 0.016 × 0.025 Cu Ni-Ti sectional wire, ligated to stainless steel continuous arch wire and then introduced between second premolars and impacted first molar, produces a sufficient moment to distalize* 

*occlusally curved and bonded on occlusal face of first molar aligned on the arch.*

*between first molar (46) and lower retained second molar (47).*

*Impacted First and Second Permanent Molars: Overview DOI: http://dx.doi.org/10.5772/intechopen.86671*

Like Fu et al. [4], the same sections of Ni-Ti or copper Ni-Ti can be used to upright orthodontically the mandibular second molar. The sectional wire is here ligated on the continuous wire that served to align and level the dental arch (**Figure 13**).

In other retrospective study, Fu et al. [3] described the pole arm appliance as an effective treatment modality and success predictable for impacted second lower molar.

#### **Figure 11.**

*Human Teeth - Key Skills and Clinical Illustrations*

engaged in the tube and bended on mesial (**Figure 10**).

*6.2.2.2 Distalization segment wire/auxiliary spring fixed*

justifies the use of fixed auxiliaries as an efficient alternative.

(**Figure 9**). A variant of the same device can be proposed; the superelastic wire used for alignment and leveling of the teeth is curved distally of impacted molar which is

A button, mini tube, or eyelet button is usually bonded on the visible area of the tooth. An auxiliary segment is constructed of flexible wire nickel titanium, copper Ni Ti, or titanium molybdenum alloy (TMA) with loop. This cantilever is generally placed after leveling of the dental arch, which is then used as stabile unity for distalization of impacted tooth. In fact, molar uprighting requires good anchorage control, and subsequently, a full-arch fixed appliance is necessary to protect from undesirable tooth movements [19]. Continuous 0.019 × 0.025 stainless steel wire from first molar to second premolar or first molar is recommended as an anchorage

Then, NiTi wire can be used to upright the tooth. Finally, the tube is bonded to introduce the tooth into the conventional wire to complete leveling and finish

Various patterns have been revealed in the literature, from the simplest to the

The 0.016 × 0.022 Ni-Ti or 0.016 × 0.025 Cu Ni-Ti may be used to distalize angulated molar. The segment wire is inserted between the retained molar and the neighboring tooth on the arch. Due to its superelasticity, the wire is curved and then bonded to the occlusal face of the adjacent tooth. A moment of force is generated

*Continuous superelastic wire curved in distal of second lower molar then introduced into the tube to achieve its* 

most complex, taking advantage of the elastic properties of wire alloys.

resulting in move of the molar to the distal (**Figures 11** and **12**).

*Association of superelastic wire and coil spring between first and second lower molars.*

Such methods might require considerable treatment time with the risk of extending the overall duration of orthodontic treatment. Indeed, since the arch sections cannot change, the leveling of the dental arches is delayed. This widely

**224**

**Figure 10.**

**Figure 9.**

*distalization.*

unit.

treatment [14, 15, 20].

*0.016 × 0.022 Ni-Ti or 0.016 × 0.025 Cu Ni-Ti sectional wire, placed between first and second retained molars, is occlusally curved and bonded on occlusal face of first molar aligned on the arch.*

#### **Figure 12.**

*Right quadrant of a panoramic radiograph illustrating the placement of the 0.016 × 0.022 Ni-Ti sectional wire between first molar (46) and lower retained second molar (47).*

#### **Figure 13.**

*0.016 × 0.022 Ni-Ti or 0.016 × 0.025 Cu Ni-Ti sectional wire, ligated to stainless steel continuous arch wire and then introduced between second premolars and impacted first molar, produces a sufficient moment to distalize the impacted tooth.*

The pole arm is constructed of 0.016 × 0.022 inch titanium molybdenum alloy (TMA) wire (**Figure 14**). The distal part is inserted from lingual side under the contact point, between first molar and second angulated molar, then it is pushed buccally. The uprighting spring is curved to the mesial dental arch and ligated to the anchor wire. Finally, the lingual extremity is fixed with composite resin on the occlusal surface of the first molar (**Figure 15**). The reactivation of the pole arm is recommended every 6 weeks, simply by lifting the buccal arm occlusally.

Majourau et al. [14] proposed 0.017 × 0.025 TMA "cemented springs" whose distal part is supported by a stainless steel button bonded to disto-occlusal surface of the retained molar. The auxiliary wire is inserted from the distal of the first molar auxiliary tube. Then, it is curved to give it the configuration of loop. The spring is activated through a combination of the gingival loop form and open coil inserted between a loop and the auxiliary molar tube (**Figure 16**).

All the appliances aforementioned have the advantage of avoiding early bonding of impacted molars as well as the need of surgical exposure of sufficient surface for the bonding.

Then, when the impacted second molar had been uprighted to some degree, a tube can be bonded to it for further alignment.

TMA uprighting spring, with or without helical loop is needed to finish distal displacement of molar and to produce eruptive force to bring teeth into occlusion with their upper opponents.

Majourau [14] reports using 0.017 × 0.025 TMA cantilever spring, which is engaged in the second molar tube and hooked distally to the canine. The intrusive

**Figure 14.**

*The pole arm uprighting spring of 0.016 × 0.022 TMA is used. The lingual extremity is bonded on occlusal surface of adjacent tooth; then, the arm is introduced from lingual under contact point. The buccal part is curved and ligated to anchor continuous arch wire (readapted from [3]).*

#### **Figure 15.**

*The activation of pole arm uprighting spring is ensured by a plicature leading the mesial arm occlusally (readapted from [3]).*

**227**

extrusion (**Figure 18**).

**Figure 16.**

**Figure 17.**

*6.2.2.3 Temporary skeletal anchorage*

*Impacted First and Second Permanent Molars: Overview DOI: http://dx.doi.org/10.5772/intechopen.86671*

*molar is used as an anchorage unit (readapted from [14]).*

force was negligible since a continuous stiff stainless steel wire consolidated the

*Illustrative diagram of 0.017 × 0.025 TMA sectional wire associated with open coil to upright impacted the second lower molar. TMA spring is bent around the button, then configured as loop, and finally inserted from distal in accessory tube of the first molar. Continuous 0.019 × 0.025 stainless steel wire from first molar to first* 

Many others suggested the use of tip back cantilever of 0.017 × 0.025 TMA wire with loop [15, 21, 22]. It is a long cantilever which gives a high moment-to-force ratio and produces effects on the tooth in three planes, mainly in the mesiodistal direction and the vertical direction providing both distal crown tipping and molar

*Illustration of eruptive force produced by TMA cantilever spring without loop. This sectional wire is required to* 

Orthodontic treatment methods, with continuous or segment wire, for molar uprighting have some disadvantages, including extrusion of the target molar, unwanted reciprocal movement of the anchorage units, need for bulky appliances, and longer treatment time. The development of orthodontic miniscrew implants

Skeletal anchorages have some advantages in that they reduce the side effects formerly associated with dental anchorage and provide vertical and distal traction

lower arch from first molar to first molar (**Figure 17**).

*achieve impacted molar repositioning in correct occlusion (readapted from [14]).*

provided solutions to most of these problems [19].

*Impacted First and Second Permanent Molars: Overview DOI: http://dx.doi.org/10.5772/intechopen.86671*

#### **Figure 16.**

*Human Teeth - Key Skills and Clinical Illustrations*

The pole arm is constructed of 0.016 × 0.022 inch titanium molybdenum alloy (TMA) wire (**Figure 14**). The distal part is inserted from lingual side under the contact point, between first molar and second angulated molar, then it is pushed buccally. The uprighting spring is curved to the mesial dental arch and ligated to the anchor wire. Finally, the lingual extremity is fixed with composite resin on the occlusal surface of the first molar (**Figure 15**). The reactivation of the pole arm is

Majourau et al. [14] proposed 0.017 × 0.025 TMA "cemented springs" whose distal part is supported by a stainless steel button bonded to disto-occlusal surface of the retained molar. The auxiliary wire is inserted from the distal of the first molar auxiliary tube. Then, it is curved to give it the configuration of loop. The spring is activated through a combination of the gingival loop form and open coil inserted

All the appliances aforementioned have the advantage of avoiding early bonding of impacted molars as well as the need of surgical exposure of sufficient surface for

Then, when the impacted second molar had been uprighted to some degree, a

TMA uprighting spring, with or without helical loop is needed to finish distal displacement of molar and to produce eruptive force to bring teeth into occlusion

Majourau [14] reports using 0.017 × 0.025 TMA cantilever spring, which is engaged in the second molar tube and hooked distally to the canine. The intrusive

*The pole arm uprighting spring of 0.016 × 0.022 TMA is used. The lingual extremity is bonded on occlusal surface of adjacent tooth; then, the arm is introduced from lingual under contact point. The buccal part is* 

*The activation of pole arm uprighting spring is ensured by a plicature leading the mesial arm occlusally* 

*curved and ligated to anchor continuous arch wire (readapted from [3]).*

recommended every 6 weeks, simply by lifting the buccal arm occlusally.

between a loop and the auxiliary molar tube (**Figure 16**).

tube can be bonded to it for further alignment.

the bonding.

**Figure 14.**

with their upper opponents.

**226**

**Figure 15.**

*(readapted from [3]).*

*Illustrative diagram of 0.017 × 0.025 TMA sectional wire associated with open coil to upright impacted the second lower molar. TMA spring is bent around the button, then configured as loop, and finally inserted from distal in accessory tube of the first molar. Continuous 0.019 × 0.025 stainless steel wire from first molar to first molar is used as an anchorage unit (readapted from [14]).*

#### **Figure 17.**

*Illustration of eruptive force produced by TMA cantilever spring without loop. This sectional wire is required to achieve impacted molar repositioning in correct occlusion (readapted from [14]).*

force was negligible since a continuous stiff stainless steel wire consolidated the lower arch from first molar to first molar (**Figure 17**).

Many others suggested the use of tip back cantilever of 0.017 × 0.025 TMA wire with loop [15, 21, 22]. It is a long cantilever which gives a high moment-to-force ratio and produces effects on the tooth in three planes, mainly in the mesiodistal direction and the vertical direction providing both distal crown tipping and molar extrusion (**Figure 18**).

#### *6.2.2.3 Temporary skeletal anchorage*

Orthodontic treatment methods, with continuous or segment wire, for molar uprighting have some disadvantages, including extrusion of the target molar, unwanted reciprocal movement of the anchorage units, need for bulky appliances, and longer treatment time. The development of orthodontic miniscrew implants provided solutions to most of these problems [19].

Skeletal anchorages have some advantages in that they reduce the side effects formerly associated with dental anchorage and provide vertical and distal traction forces simultaneously with proper line of action and moment. It is also beneficial for obtaining [19] [23] Thus, orthodontic miniscrews have a major impact on reducing the overall treatment time unlike conventional treatment.

Moreover, they simplify the design of orthodontic devices. All the abovementioned devices can be used in combination with it to avoid the need for dental anchoring. Depending on the situation, the skeletal anchor can be used directly; the minivis serves as a docking point for the sectional wire with direct application of an appropriate force system. Lee et al. suggest uprighting second molar into two steps, using an open coil spring and a stainless steel uprighting spring (**Figures 19** and **20**) [19].

Conventional orthodontic methods are often the best alternative to extraction or surgically repositioning of the first and second permanent molars. It produces certainly excellent outcomes, but could not be successfully predicted or may be contraindicated for horizontally position, deeply impaction or molars with gross displacement [9, 15, 19]. In such challenging cases, a combination of surgical and orthodontic treatment is appropriate [2, 4].

#### *6.2.3 Surgical approaches*

Surgical approaches of unerupted permanent molars included surgical exposure for orthodontic uprighting and traction into their correct position in the arch, as well as challenging treatment options of surgical repositioning. It consists essentially of uprighting and repositioning of the impacted molar, eventually including extraction of the third molar [15] [20]. Posterior available space should be analyzed

#### **Figure 18.**

*Diagram of tip back cantilever: It is a long uprighting spring of 0.017 × 0.025 TMA. The activation force is directed to the occlusal (readapted from [15, 21, 22]).*

#### **Figure 19.**

*Miniscrews used as direct anchor with segmental wire and coil spring to distalize and extrude the second lower molar. In the first step (A), the distalization is ensured by 0.016 stainless steel wire and open coil spring. In the second step (B), tip back moment is delivered from 0.016 × 0.022 in. Stainless steel wire spring to upright impacted molar (from Lee et al., readapted from [19]).*

**229**

*Impacted First and Second Permanent Molars: Overview DOI: http://dx.doi.org/10.5772/intechopen.86671*

process for a favorable outcome [19].

following by orthodontic traction or luxation.

treatment, with a success rate of 70%.

*6.2.3.1.1 Surgical exposure and orthodontic traction*

ful treatment in both jaws.

anesthesia. He proposed to (**Figure 21**):

molar follicle

Magnusson et al. in their study found that [24]:

*6.2.3.1 Surgical exposure*

**Figure 20.**

before planning orthodontic and surgical traction, to prevent periodontal risks. Removal of the third molar often completes this procedure, and more rarely, the second molar when the first one is impacted. Undoubtedly, analysis of anatomic location, desired eruption path, and available space should proceed the uprighting

*Miniscrews used as indirect anchor to reinforce dental stabile unit then with tip back cantilever to extrude it.*

In cases of horizontally or deeply impaction, orthodontics alone cannot straighten the molar because of the limited access. A surgical exposure is required

• Surgical exposure was the most successful treatment and the best choice of

• The success rate was 50% when surgical exposure was combined with extrac-

• Surgical exposure of the second molar, with or without extraction of the third molar and/or luxation of the second molar, seems to result in the most success-

It consists of exposure and uncovering the crown, followed by bonding an orthodontic attachment. Temporary skeletal anchorage is the appropriate and efficient

Kim [23] suggested the use of 1.3–1.2 mm × 8 mm mini screws in the retromolar

Chang [25] reported a simple, effective, and expedient mechanics for managing horizontally and deeply impaction of second lower molar in only 4 months. 2 × 14 mm stainless steel bone screw is positioned superiorly in ramus under local

• First, remove all obstructions to eruption, as ectopic position of the third

area following extraction of the third molar. Traction is initiated on the day of

tion of the third molar and/or luxation of the second molar.

means to upright and tract the tooth in its ideal position [15, 23].

surgery with elastic threads that were replaced every 4 weeks.

*Human Teeth - Key Skills and Clinical Illustrations*

orthodontic treatment is appropriate [2, 4].

*directed to the occlusal (readapted from [15, 21, 22]).*

*impacted molar (from Lee et al., readapted from [19]).*

*6.2.3 Surgical approaches*

forces simultaneously with proper line of action and moment. It is also beneficial for obtaining [19] [23] Thus, orthodontic miniscrews have a major impact on reduc-

devices can be used in combination with it to avoid the need for dental anchoring. Depending on the situation, the skeletal anchor can be used directly; the minivis serves as a docking point for the sectional wire with direct application of an appropriate force system. Lee et al. suggest uprighting second molar into two steps, using an open coil

Moreover, they simplify the design of orthodontic devices. All the abovementioned

Conventional orthodontic methods are often the best alternative to extraction or surgically repositioning of the first and second permanent molars. It produces certainly excellent outcomes, but could not be successfully predicted or may be contraindicated for horizontally position, deeply impaction or molars with gross displacement [9, 15, 19]. In such challenging cases, a combination of surgical and

Surgical approaches of unerupted permanent molars included surgical exposure for orthodontic uprighting and traction into their correct position in the arch, as well as challenging treatment options of surgical repositioning. It consists essentially of uprighting and repositioning of the impacted molar, eventually including extraction of the third molar [15] [20]. Posterior available space should be analyzed

*Diagram of tip back cantilever: It is a long uprighting spring of 0.017 × 0.025 TMA. The activation force is* 

*Miniscrews used as direct anchor with segmental wire and coil spring to distalize and extrude the second lower molar. In the first step (A), the distalization is ensured by 0.016 stainless steel wire and open coil spring. In the second step (B), tip back moment is delivered from 0.016 × 0.022 in. Stainless steel wire spring to upright* 

ing the overall treatment time unlike conventional treatment.

spring and a stainless steel uprighting spring (**Figures 19** and **20**) [19].

**228**

**Figure 19.**

**Figure 18.**

**Figure 20.** *Miniscrews used as indirect anchor to reinforce dental stabile unit then with tip back cantilever to extrude it.*

before planning orthodontic and surgical traction, to prevent periodontal risks. Removal of the third molar often completes this procedure, and more rarely, the second molar when the first one is impacted. Undoubtedly, analysis of anatomic location, desired eruption path, and available space should proceed the uprighting process for a favorable outcome [19].

#### *6.2.3.1 Surgical exposure*

In cases of horizontally or deeply impaction, orthodontics alone cannot straighten the molar because of the limited access. A surgical exposure is required following by orthodontic traction or luxation.

Magnusson et al. in their study found that [24]:


#### *6.2.3.1.1 Surgical exposure and orthodontic traction*

It consists of exposure and uncovering the crown, followed by bonding an orthodontic attachment. Temporary skeletal anchorage is the appropriate and efficient means to upright and tract the tooth in its ideal position [15, 23].

Kim [23] suggested the use of 1.3–1.2 mm × 8 mm mini screws in the retromolar area following extraction of the third molar. Traction is initiated on the day of surgery with elastic threads that were replaced every 4 weeks.

Chang [25] reported a simple, effective, and expedient mechanics for managing horizontally and deeply impaction of second lower molar in only 4 months. 2 × 14 mm stainless steel bone screw is positioned superiorly in ramus under local anesthesia. He proposed to (**Figure 21**):

• First, remove all obstructions to eruption, as ectopic position of the third molar follicle

#### **Figure 21.**

*Illustration of surgical exposure and traction of second lower molar through bone screw. The button is bonded to the accessible surface (A) and then moved if necessary (B) so as to obtain a sufficient amplitude of traction on the minivis. 2 × 14 mm stainless steel bone screw is inserted into the ascending ramus, and power chain is connected between attachment and screw (readapted from [25]).*


#### *6.2.3.1.2 Surgical exposure and luxation*

Luxation is an effective technique with good long-term prognosis. Such approach finds its major indication in favorable impacted molars before complete apical root edification. Indeed, it has been reported that molars luxated prior to complete root formation erupted spontaneously and continued their normal root development.

The potential risks of luxation include pulpal devitalization and root fracture, although a prophylactic endodontic treatment of the luxated molar is not recommended.

During the 1916s, luxation has been described to be used successfully in ankylosed permanent molars that are typical of secondary retention, although luxation seems to promote new areas of ankylosis rather than breaking bony connections [2].

The prognosis seems to be better than that of dental transplant because the tooth is not removed from its socket and the apical blood vessels are not damaged.

#### *6.2.3.2 Surgical repositioning*

It is a simple technique which produces fast results; it seems to be the most convenient procedure when patient compliance is minimal, when impacted teeth have limited access or failed to respond to orthodontics methods, or for angle of inclination of less than 75° [9, 15, 26]. Nevertheless, there is a risk of pulp necrosis, root resorption, and ankylosis [9].

Several authors suggested that this procedure usually lead to predictable successful results if root formation is not completed, usually between the ages of 11 and 14. According to Botton [17], if surgery is performed too soon, then the tooth may be unstable and may shift from its position. If performed too late, then there is risk of root fracture and possible disruption of blood supply leading to pulpal necrosis [17] [24].

**231**

*Impacted First and Second Permanent Molars: Overview DOI: http://dx.doi.org/10.5772/intechopen.86671*

cause external root resorption.

positioned second molar.

molars.

stabilization.

**7. Extraction**

position [2, 15].

in two different approaches as follows:

the delayed eruption of third molar [24].

tooth from migrating bucally or lingually [17, 26].

weeks.

Removal of the third adjacent molar is often necessary to make surgical uprighting easier. In addition to that, surgically tipped molar should be stabilized for few

Boyton et al. [17] Kravitz et al. [26] describe the stages of surgical uprighting of second lower molar. After intrasulcular incision from the distobuccal line angle of the first molar to posteriorly the external oblique ridge, a full-thickness mucoperiosteal flap is raised to expose the second and third molars if it is present. Then, distal and buccal bone of molar is removed to expose the cement-enamel junction avoiding any contact with the cementum and periodontal ligament fibers that may

The surgeon uses steady and gentle force with straight elevator to elevate the tooth distally and prevent root fracture. Sometimes, the surgeon removes additional distal bone to perform the molar uprighting. When the occlusal surface of impacted molar is approximately level with the occlusal plane, the patient is instructed to bite down gently to ensure that the molar is just below the occlusal plane to prevent occlusal trauma. The site should be irrigated with copious amounts of normal saline and then closed with sutures. The attached gingiva should be kept intact and positioned appropriately to ensure a healthy periodontal environment for the newly

Some recommended bonding a tube to the molar as soon as it is repositioned. For others, an intact lingual and buccal plate or a periodontal dressing prevents the

According to Boyton, no additional autogenous bone or bone substitutes are needed to stabilize the tooth. Other authors [27] advocate the use of absorbable gelatin sponge or autogenous alveolar bone to stabilize the repositioned second

An immediate postoperative Panorex is recommended. The follow-up includes a 1-week postoperative appointment and then another appointment in 6 months for a repeated Panorex. Orthodontic treatment should begin 1–2 weeks after surgery, with a mandibular arch-wire extended through the second-molar bracket for

Surgical extraction of unerupted permanent molar is indicated when exposure, luxation, and orthodontics treatment fail, in the presence of a pathological process, or when prognosis is poor because of fully formed roots or extremely unfavorable

Extraction as an alternative procedure of retention treatment can be considered

• Extraction of retained or impacted second molar with the intention of replacing it with the third molar. The third molar drift mesially when it is at low Nolla stage from 5 to 8. Nevertheless, success of this treatment depends on the eruption path of the third molar which could be unpredictable [5, 9, 15]. Magnusson et al., in their study evaluating the outcome after treatment and without treatment of retained second molars, found that treatment with removal impacted molar replaced with the third molar was the least successful both in the maxilla and mandible. They reported that few molars that did erupt were all malpositioned with a risk for elongation of the antagonist because of

*Human Teeth - Key Skills and Clinical Illustrations*

• Expose surgically and luxate the lower second molars to rule out an eventual ankylosis. The covered bone is removed down to the level of the cementoe-

*Illustration of surgical exposure and traction of second lower molar through bone screw. The button is bonded to the accessible surface (A) and then moved if necessary (B) so as to obtain a sufficient amplitude of traction on the minivis. 2 × 14 mm stainless steel bone screw is inserted into the ascending ramus, and power chain is* 

• Bond button or eyelet on distal surface and then connect elastic chain from attachment to bone screw before closing soft tissue with interrupted sutures to

Luxation is an effective technique with good long-term prognosis. Such approach finds its major indication in favorable impacted molars before complete apical root edification. Indeed, it has been reported that molars luxated prior to complete root formation erupted spontaneously and continued their normal root

The potential risks of luxation include pulpal devitalization and root fracture, although a prophylactic endodontic treatment of the luxated molar is not

is not removed from its socket and the apical blood vessels are not damaged.

It is a simple technique which produces fast results; it seems to be the most convenient procedure when patient compliance is minimal, when impacted teeth have limited access or failed to respond to orthodontics methods, or for angle of inclination of less than 75° [9, 15, 26]. Nevertheless, there is a risk of pulp necrosis,

Several authors suggested that this procedure usually lead to predictable successful results if root formation is not completed, usually between the ages of 11 and 14. According to Botton [17], if surgery is performed too soon, then the tooth may be unstable and may shift from its position. If performed too late, then there is risk of root fracture and possible disruption of blood supply leading to pulpal necrosis [17] [24].

During the 1916s, luxation has been described to be used successfully in ankylosed permanent molars that are typical of secondary retention, although luxation seems to promote new areas of ankylosis rather than breaking bony connections [2]. The prognosis seems to be better than that of dental transplant because the tooth

namel junction for optimal molar uprighting.

*connected between attachment and screw (readapted from [25]).*

control blending.

development.

**Figure 21.**

recommended.

*6.2.3.2 Surgical repositioning*

root resorption, and ankylosis [9].

*6.2.3.1.2 Surgical exposure and luxation*

**230**

Removal of the third adjacent molar is often necessary to make surgical uprighting easier. In addition to that, surgically tipped molar should be stabilized for few weeks.

Boyton et al. [17] Kravitz et al. [26] describe the stages of surgical uprighting of second lower molar. After intrasulcular incision from the distobuccal line angle of the first molar to posteriorly the external oblique ridge, a full-thickness mucoperiosteal flap is raised to expose the second and third molars if it is present. Then, distal and buccal bone of molar is removed to expose the cement-enamel junction avoiding any contact with the cementum and periodontal ligament fibers that may cause external root resorption.

The surgeon uses steady and gentle force with straight elevator to elevate the tooth distally and prevent root fracture. Sometimes, the surgeon removes additional distal bone to perform the molar uprighting. When the occlusal surface of impacted molar is approximately level with the occlusal plane, the patient is instructed to bite down gently to ensure that the molar is just below the occlusal plane to prevent occlusal trauma. The site should be irrigated with copious amounts of normal saline and then closed with sutures. The attached gingiva should be kept intact and positioned appropriately to ensure a healthy periodontal environment for the newly positioned second molar.

Some recommended bonding a tube to the molar as soon as it is repositioned. For others, an intact lingual and buccal plate or a periodontal dressing prevents the tooth from migrating bucally or lingually [17, 26].

According to Boyton, no additional autogenous bone or bone substitutes are needed to stabilize the tooth. Other authors [27] advocate the use of absorbable gelatin sponge or autogenous alveolar bone to stabilize the repositioned second molars.

An immediate postoperative Panorex is recommended. The follow-up includes a 1-week postoperative appointment and then another appointment in 6 months for a repeated Panorex. Orthodontic treatment should begin 1–2 weeks after surgery, with a mandibular arch-wire extended through the second-molar bracket for stabilization.

#### **7. Extraction**

Surgical extraction of unerupted permanent molar is indicated when exposure, luxation, and orthodontics treatment fail, in the presence of a pathological process, or when prognosis is poor because of fully formed roots or extremely unfavorable position [2, 15].

Extraction as an alternative procedure of retention treatment can be considered in two different approaches as follows:

• Extraction of retained or impacted second molar with the intention of replacing it with the third molar. The third molar drift mesially when it is at low Nolla stage from 5 to 8. Nevertheless, success of this treatment depends on the eruption path of the third molar which could be unpredictable [5, 9, 15]. Magnusson et al., in their study evaluating the outcome after treatment and without treatment of retained second molars, found that treatment with removal impacted molar replaced with the third molar was the least successful both in the maxilla and mandible. They reported that few molars that did erupt were all malpositioned with a risk for elongation of the antagonist because of the delayed eruption of third molar [24].


#### **8. Conclusion**

The eruption failure of first and second permanent molars is rare and asymptomatic. This disturbance is often detected in a routine panoramic radiograph during pedodontic or orthodontic evaluation and represents a real diagnostic and therapeutic challenge for the practitioner.

Considering the main etiological factors, three clinical forms can be distinguished: impaction, primary, and secondary retention. Therefore, it is crucial to diagnose this abnormality early for an optimal treatment time and outcomes, as well as reduction of dental and periodontal complications.

Its management is considered difficult and unpredictable, and there is no clear standard solution. Despite observation, abstention, or extraction of unerupted permanent molars, several orthodontic and surgical methods for uprighting impacted molars was reported. All of the methods have specific indications, advantages, and disadvantages depending of clinical form, retention depth, stage of root formation, and age of patient.

If the prognosis of orthodontic and/or surgery repositioning of impacted and primary retained molars is favorable, the treatment of secondary retention seems to depend on the age of the patient and the extent of infraocclusion and malocclusion.

The major treatment concern of secondarily retained molars is that these molars cannot be moved orthodontically due to an abnormal periodontal ligament. By contrast, orthodontics or combined surgical-orthodontic approach is a major modality in treatment of impacted teeth as these molars often have an abnormal position in the eruption path. Primarily retained molars can also be moved orthodontically, but this is often not necessary because of the normal position in the eruption tract.

#### **Acknowledgements**

The authors would like to express their gratitude to all the specialists in the orthodontics and pedodontics department at the Ibn Rochd University Hospital of Casablanca for their kind contribution to the work. Their special thanks go especially to Dr. N. Falah, Z. El Jalil, S. El Kaki, A. Moutawakil, and L. Bouchghel.

**233**

**Author details**

\*, Hakima Aghoutan1

Hassan II University of Casablanca, Morocco

provided the original work is properly cited.

\*Address all correspondence to: sanalami1@yahoo.fr

, Meriem Bellamine2

© 2019 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,

1 Faculty of Dental Medicine, Department of Dento-facial Orthopedic,

2 Department of Orthodontics, Casablanca Hospital center, Morocco

and Farid El Quars1

Sanaa Alami1

*Impacted First and Second Permanent Molars: Overview DOI: http://dx.doi.org/10.5772/intechopen.86671*

#### **Conflict of interest**

The authors declare that they have no conflict of interest.

*Impacted First and Second Permanent Molars: Overview DOI: http://dx.doi.org/10.5772/intechopen.86671*

*Human Teeth - Key Skills and Clinical Illustrations*

distal surface of adjacent teeth [24].

therapeutic challenge for the practitioner.

well as reduction of dental and periodontal complications.

[9, 15, 24].

**8. Conclusion**

and age of patient.

**Acknowledgements**

**Conflict of interest**

malocclusion.

• Extraction of the impacted second molar followed by immediate transplantation of retained molar or third molar into the extraction site. It is technically demanding and carries a risk of pulp necrosis, root resorption, and ankylosis

• Both transplantation and surgical repositioning were suggested as invasive techniques because of the deeply impacted positions with high risk of neurovascular damage, mandibular fracture, or the deep infrabony defect on the

The eruption failure of first and second permanent molars is rare and asymptomatic. This disturbance is often detected in a routine panoramic radiograph during pedodontic or orthodontic evaluation and represents a real diagnostic and

Considering the main etiological factors, three clinical forms can be distinguished: impaction, primary, and secondary retention. Therefore, it is crucial to diagnose this abnormality early for an optimal treatment time and outcomes, as

Its management is considered difficult and unpredictable, and there is no clear standard solution. Despite observation, abstention, or extraction of unerupted permanent molars, several orthodontic and surgical methods for uprighting impacted molars was reported. All of the methods have specific indications, advantages, and disadvantages depending of clinical form, retention depth, stage of root formation,

If the prognosis of orthodontic and/or surgery repositioning of impacted and primary retained molars is favorable, the treatment of secondary retention seems to depend on the age of the patient and the extent of infraocclusion and

The major treatment concern of secondarily retained molars is that these molars cannot be moved orthodontically due to an abnormal periodontal ligament. By contrast, orthodontics or combined surgical-orthodontic approach is a major modality in treatment of impacted teeth as these molars often have an abnormal position in the eruption path. Primarily retained molars can also be moved orthodontically, but this is often not necessary because of the normal position in the eruption tract.

The authors would like to express their gratitude to all the specialists in the orthodontics and pedodontics department at the Ibn Rochd University Hospital of Casablanca for their kind contribution to the work. Their special thanks go especially to Dr. N. Falah, Z. El Jalil, S. El Kaki, A. Moutawakil, and L. Bouchghel.

The authors declare that they have no conflict of interest.

**232**

## **Author details**

Sanaa Alami1 \*, Hakima Aghoutan1 , Meriem Bellamine2 and Farid El Quars1

1 Faculty of Dental Medicine, Department of Dento-facial Orthopedic, Hassan II University of Casablanca, Morocco

2 Department of Orthodontics, Casablanca Hospital center, Morocco

\*Address all correspondence to: sanalami1@yahoo.fr

© 2019 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] Palma C, Coelho A, González Y, Cahuana A. Failure of eruption of first and second permanent molars. Journal of Clinical Pediatric Dentistry. 2015;**27**:239-245. DOI: 10.17796/ jcpd.27.3.dm4v13441p161928

[2] Raghoebar GM, Boering G, Vissink A, Stegenga B. Eruption disturbances of permanent molars: A review. Journal of Oral Pathology and Medicine. 1991;**20**:159-166. DOI: 10.1111/j.1600- 0714.1991.tb00913.x

[3] Fu PS, Wang JC, Wu YM, Huang TK, Chen WC, Tseng YC, et al. Impacted mandibular second molars. A retrospective study of prevalence and treatment outcome. The Angle Orthodontist. 2012;**82**:670-675. DOI: 10.2319/102111-656.1

[4] Fu PS, Wang JC, Chen CH, Huang TK, Tseng CH, Hung CC. Management of unilaterally deep impacted first, second, and third mandibular molars. The Angle Orthodontist. 2012;**82**:565-571. DOI: 10.2319/062411-409.1

[5] Valmaseda-Castellón E, De-la-Rosa-Gay C, Gay-Escoda C. Eruption disturbances of the first and second permanent molars: Results of treatment in 43 cases. American Journal of Orthodontics and Dentofacial Orthopedics. 1999;**116**:651-658. DOI: 10.1016/S0889-5406(99)70200-3

[6] Bondemark L, Tsiopa J. Prevalence of ectopic eruption, impaction, retention and agenesis of the permanent second molar. The Angle Orthodontist. 2007;**77**:773-778. DOI: 10.2319/072506-306.1

[7] Cassetta M, Altieri F, di Mambro A, Galluccio G, Barbato E. Impaction of permanent mandibular second molar: A retrospective study. Medicina

Oral, Patología Oral y Cirugía Bucal. 2013;**18**:564-568. DOI: 10.4317/ medoral.18869

[8] Ahmad S, Bister D, Cobourne MT. The clinical features and aetiological basis of primary eruption failure. European Journal of Orthodontics. 2006;**28**:535-540. DOI: 10.1093/ejo/ cjl033

[9] Cho SY, Ki Y, Chu V, Chan J. Impaction of permanent mandibular second molars in ethnic Chinese school children. Journal of the Canadian Dental Association. 2008;**74**(6):521. Available from: www.cda-adc.ca/jcda/ vol-74/issue-6/521.html

[10] Srinivasan MR, Poorni S, Venkatesh A, Vasanthi B. Prevalence of impacted permanent mandibular second molars in south Indian population: A cross-sectional study. Indian Journal of Dental Research. 2016;**27**:540-543. DOI: 10.4103/0970-9290.195645

[11] Evans R. Incidence of lower second permanent molar impaction. British Journal of Orthodontics. 2014;**15**:199- 203. DOI: 10.1179/bjo.15.3.199

[12] Cassetta M, Altieri F, Calasso S. Etiological factors in second mandibular molar impaction. Journal of Clinical and Experimental Dentistry. 2014;**6**:150- 154. DOI: 10.4317/jced.51382

[13] Raghoebar GM, Boering G, Jansen H, Vissink A. Secondary retention of permanent molars: A histologic study. 1989;**18**:427-431. DOI: 10.1111/j.1600- 0714.1989.tb01338.x

[14] Majourau A, Norton LA. Uprighting impacted second molars with segmented springs. American Journal of Orthodontics and Dentofacial Orthopedics. 1995;**107**:235-238. DOI: 10.1016/S0889-5406(95)70137-0

**235**

*Impacted First and Second Permanent Molars: Overview DOI: http://dx.doi.org/10.5772/intechopen.86671*

> [23] Kim K-J, Park JH, Kim M-J, Jang H-I, Chae J-M. Posterior available space for uprighting horizontally impacted mandibular second molars using orthodontic microimplant anchorage. Journal of Clinical Pediatric

Dentistry. 2018;**43**:56-63. DOI: 10.17796/1053-4625-43.1.11

[24] Magnusson C, Kjellberg H. Impaction and retention of second molars: Diagnosis, treatment and outcome. The Angle Orthodontist. 2008; **79**:422-427. DOI: 10.2319/0003-3219 (2009)079[0422:iarosm]2.0.co;2

[25] Lin S-Y, Chang C, Roberts WE. Simple mechanics to upright horizontally impacted molars with ramus screws. Orthodontic Journal of Nepal. 2016;**5**:42-47. DOI: 10.3126/ojn.

[26] Kravitz ND. Surgical uprighting of lower second molars. Journal of Clinical Orthodontics. 2016;**50**(1):33-40. Available from: www.jco-online.com

[27] Johnson JV, Quirk GP. Surgical repositioning of impacted mandibular second molar teeth. American Journal of Orthodontics and Dentofacial Orthopedics. 1987;**91**:242-251. DOI: 10.1016/0889-5406(87)90454-9

v5i2.15231

[15] Shpack N, Finkelstein T, Lai YH, Kuftinec MM, Vardimon A, Shapira Y. Mandibular permanent second molar impaction treatment options and outcome. Open Journal of Dentistry and Oral Medicine. 2013;**1**:9-14. DOI:

[16] Hanisch M, Hanisch L, Kleinheinz J, Jung S. Primary failure of eruption (PFE): A systematic review. Head and Face Medicine. 2018;**14**:2-9. DOI:

10.13189/ojdom.2013.010103

10.1186/s13005-018-0163-7

10.1093/ejo/21.1.31

10.1186/s40510-017-0200-2

[20] Yordanova G. Treatment of impacted lower left second molar and over erupted upper second molar. Journal of Dental Health, Oral Disorders and Therapy. 2018;**9**:106-108. DOI: 10.15406/jdhodt.2018.09.00338

[21] Sawicka M, Racka-pilszak B, Rosnowska-Mazurkiewicz A. Uprighting partially impacted permanent second molars. The Angle Orthodontist. 2007;**77**:148-154. DOI:

[22] Shapira Y, Borell G, Nahlieli O, Kuftinek MM. Uprighrting mesialy impacted mandibular permanent second molars. The Angle Orthodontist.

10.2319/010206-461

1998;**68**:173-178

[17] Boynton T, Lieblich SE. Surgical uprighting of second molars. Atlas of the Oral and Maxillofacial Surgery Clinics of North America. 2013;**21**: 235-237. DOI: 10.1016/j.cxom.2013.05.001

[18] Vedtofte H, Andreasen JO, Kjær I. Arrested eruption of the permanent lower second molar. European Journal of Orthodontics. 1999;**21**:31-40. DOI:

[19] Magkavali-Trikka P, Emmanouilidis G, Papadopoulos MA. Mandibular molar uprighting using orthodontic miniscrew implants: A systematic review. Progress in Orthodontics. 2018;**19**:1-12. DOI:

*Impacted First and Second Permanent Molars: Overview DOI: http://dx.doi.org/10.5772/intechopen.86671*

[15] Shpack N, Finkelstein T, Lai YH, Kuftinec MM, Vardimon A, Shapira Y. Mandibular permanent second molar impaction treatment options and outcome. Open Journal of Dentistry and Oral Medicine. 2013;**1**:9-14. DOI: 10.13189/ojdom.2013.010103

[16] Hanisch M, Hanisch L, Kleinheinz J, Jung S. Primary failure of eruption (PFE): A systematic review. Head and Face Medicine. 2018;**14**:2-9. DOI: 10.1186/s13005-018-0163-7

[17] Boynton T, Lieblich SE. Surgical uprighting of second molars. Atlas of the Oral and Maxillofacial Surgery Clinics of North America. 2013;**21**: 235-237. DOI: 10.1016/j.cxom.2013.05.001

[18] Vedtofte H, Andreasen JO, Kjær I. Arrested eruption of the permanent lower second molar. European Journal of Orthodontics. 1999;**21**:31-40. DOI: 10.1093/ejo/21.1.31

[19] Magkavali-Trikka P, Emmanouilidis G, Papadopoulos MA. Mandibular molar uprighting using orthodontic miniscrew implants: A systematic review. Progress in Orthodontics. 2018;**19**:1-12. DOI: 10.1186/s40510-017-0200-2

[20] Yordanova G. Treatment of impacted lower left second molar and over erupted upper second molar. Journal of Dental Health, Oral Disorders and Therapy. 2018;**9**:106-108. DOI: 10.15406/jdhodt.2018.09.00338

[21] Sawicka M, Racka-pilszak B, Rosnowska-Mazurkiewicz A. Uprighting partially impacted permanent second molars. The Angle Orthodontist. 2007;**77**:148-154. DOI: 10.2319/010206-461

[22] Shapira Y, Borell G, Nahlieli O, Kuftinek MM. Uprighrting mesialy impacted mandibular permanent second molars. The Angle Orthodontist. 1998;**68**:173-178

[23] Kim K-J, Park JH, Kim M-J, Jang H-I, Chae J-M. Posterior available space for uprighting horizontally impacted mandibular second molars using orthodontic microimplant anchorage. Journal of Clinical Pediatric Dentistry. 2018;**43**:56-63. DOI: 10.17796/1053-4625-43.1.11

[24] Magnusson C, Kjellberg H. Impaction and retention of second molars: Diagnosis, treatment and outcome. The Angle Orthodontist. 2008; **79**:422-427. DOI: 10.2319/0003-3219 (2009)079[0422:iarosm]2.0.co;2

[25] Lin S-Y, Chang C, Roberts WE. Simple mechanics to upright horizontally impacted molars with ramus screws. Orthodontic Journal of Nepal. 2016;**5**:42-47. DOI: 10.3126/ojn. v5i2.15231

[26] Kravitz ND. Surgical uprighting of lower second molars. Journal of Clinical Orthodontics. 2016;**50**(1):33-40. Available from: www.jco-online.com

[27] Johnson JV, Quirk GP. Surgical repositioning of impacted mandibular second molar teeth. American Journal of Orthodontics and Dentofacial Orthopedics. 1987;**91**:242-251. DOI: 10.1016/0889-5406(87)90454-9

**234**

*Human Teeth - Key Skills and Clinical Illustrations*

Oral, Patología Oral y Cirugía Bucal. 2013;**18**:564-568. DOI: 10.4317/

[8] Ahmad S, Bister D, Cobourne MT. The clinical features and aetiological basis of primary eruption failure. European Journal of Orthodontics. 2006;**28**:535-540. DOI: 10.1093/ejo/

[9] Cho SY, Ki Y, Chu V, Chan J. Impaction of permanent mandibular second molars in ethnic Chinese school children. Journal of the Canadian Dental Association. 2008;**74**(6):521. Available from: www.cda-adc.ca/jcda/

vol-74/issue-6/521.html

[10] Srinivasan MR, Poorni S,

10.4103/0970-9290.195645

203. DOI: 10.1179/bjo.15.3.199

154. DOI: 10.4317/jced.51382

0714.1989.tb01338.x

[13] Raghoebar GM, Boering G,

impacted second molars with

Jansen H, Vissink A. Secondary retention of permanent molars: A histologic study. 1989;**18**:427-431. DOI: 10.1111/j.1600-

[14] Majourau A, Norton LA. Uprighting

segmented springs. American Journal of Orthodontics and Dentofacial Orthopedics. 1995;**107**:235-238. DOI: 10.1016/S0889-5406(95)70137-0

[12] Cassetta M, Altieri F, Calasso S. Etiological factors in second mandibular molar impaction. Journal of Clinical and Experimental Dentistry. 2014;**6**:150-

Venkatesh A, Vasanthi B. Prevalence of impacted permanent mandibular second molars in south Indian population: A cross-sectional study. Indian Journal of Dental Research. 2016;**27**:540-543. DOI:

[11] Evans R. Incidence of lower second permanent molar impaction. British Journal of Orthodontics. 2014;**15**:199-

medoral.18869

cjl033

[1] Palma C, Coelho A, González Y, Cahuana A. Failure of eruption of first and second permanent molars. Journal

[2] Raghoebar GM, Boering G, Vissink A, Stegenga B. Eruption disturbances of permanent molars: A review. Journal of Oral Pathology and Medicine. 1991;**20**:159-166. DOI: 10.1111/j.1600-

[3] Fu PS, Wang JC, Wu YM, Huang TK, Chen WC, Tseng YC, et al. Impacted mandibular second molars. A retrospective study of prevalence and treatment outcome. The Angle Orthodontist. 2012;**82**:670-675. DOI:

of Clinical Pediatric Dentistry. 2015;**27**:239-245. DOI: 10.17796/ jcpd.27.3.dm4v13441p161928

0714.1991.tb00913.x

**References**

10.2319/102111-656.1

10.2319/062411-409.1

10.2319/072506-306.1

[4] Fu PS, Wang JC, Chen CH, Huang TK, Tseng CH, Hung CC. Management of unilaterally deep impacted first, second, and third mandibular molars. The Angle Orthodontist. 2012;**82**:565-571. DOI:

[5] Valmaseda-Castellón E, De-la-Rosa-Gay C, Gay-Escoda C. Eruption disturbances of the first and second permanent molars: Results of treatment

in 43 cases. American Journal of Orthodontics and Dentofacial Orthopedics. 1999;**116**:651-658. DOI: 10.1016/S0889-5406(99)70200-3

[6] Bondemark L, Tsiopa J. Prevalence of ectopic eruption, impaction, retention and agenesis of the permanent second molar. The Angle Orthodontist. 2007;**77**:773-778. DOI:

[7] Cassetta M, Altieri F, di Mambro A, Galluccio G, Barbato E. Impaction of permanent mandibular second molar: A retrospective study. Medicina

**237**

**Chapter 14**

**Abstract**

root replacement.

**1. Introduction**

Evolution of Dental Implant

Analogue Implants

*Ayse Sumeyye Akay*

Shapes and Today's Custom Root

Native tooth has a unique design to serve perfect stomatognathic function and esthetics which could never be replaced with another material or apparatus if it is lost. Over the past few decades, screw-type endosseous implants have been considered to be as the gold standard for the rehabilitation of edentulism owing to the similarity with the anatomical root shape and location inside the alveolar bone. They have been widely investigated so as to find out the ideal characteristics. Further researches have focused on the cervical region of the dental implant because the maximum stress is pronounced around the implant neck. The ideal characteristics indicate that a wide implant neck for better stress distribution, and a large surface area with a minimal thread geometry for a better long term crestal bone stability. Along with the growing clinical knowledge and digital technology, an innovative and noteworthy approach for implant dentistry, custom root analogue implant (RAI), has evolved. With the computer aided design and manufacturing (CAD/CAM) methods, original and optimized characteristics could be transferred to the custom dental implants just as performing an original

**Keywords:** dental implant, custom root-shaped implant, anatomically shaped

Natural teeth have unique design which serve complex stomatognathic functions and fulfill distinctive biomechanical needs. The anatomy of the natural tooth eventuates after a complex biological process which is moderated by epithelialmesenchymal collaboration [1]. The morphological features in each type of tooth are variable, and several classifications have been proposed to define the diversity of root forms and potential anomalies regarding the number and shape of the roots [2–5]. Basically, the natural root has conical shape with a smaller width towards to the apex and often with longitudinal grooves. The root of the maxillary central incisors is wider mesiodistally in vestibular part, and both maxillary and mandibular canines have wider and longer root forms in order to compensate the lateral and oblique forces whereas maxillary lateral and mandibular incisors present a modest shape. Premolars generally have single root with a slight curve at the apex except from the maxillary first premolar which has probably two roots at vestibular and

implant, root analogue implant, CAD/CAM, digital dentistry

#### **Chapter 14**
