Developmental disturbances associated with agenesis of the permanent maxillary lateral incisor

Agenesis of maxillary lateral incisors: diagnosis and treatment options

Introduction:

There are different possibilities of orthodontic planning for cases with congenital absence of maxillary lateral incisors. This subject divides the opinion of orthodontists and oral rehabilitation clinicians, due to the advantages and disadvantages of each treatment option, which may involve opening spaces for future implants and/or prosthetic restorations, or closing the spaces by positioning the maxillary canines in the place of lateral incisors. The correct diagnosis and careful evaluation of each patient allow to determine the best therapeutic approach. This paper discusses the main topics to be considered when planning these cases.

Objectives:

To evaluate the main aspects related to orthodontic treatment planning in cases of congenital absence of maxillary lateral incisors, to aid the decision-making, with clinical and scientific basis.

Position and Eruption of Permanent Maxillary Canines in Cases of Maxillary Lateral Incisor Agenesis in Mixed Dentition

OBJECTIVE

Assess whether the permanent maxillary canine (MC) has a natural tendency to erupt mesially in children with maxillary lateral incisors agenesis (MLIA), compared to children without agenesis.

STUDY DESIGN

This retrospective, observational, cross-sectional study consisted of children between 5 and 12 years old divided into three groups: the first group with unilateral MLIA, in which an intraindividual analysis was performed, the second group presented bilateral MLIA, and the third group with patients without agenesis. These last two groups were matched for comparison interindividual, being pared by sex and maturation of the MC.

RESULTS

The canine position in the horizontal sector showed a clear mesial positioning of the MC on the agenesis side in individuals with unilateral MLIA (group 1) when compared with the counter lateral side; and in individuals with bilateral MLIA (Group 2) compared with control Individuals without agenesis (group 3). Even with the maintenance of this deciduous tooth in the dental arch, the MC keeps its tendency to mesial eruption.

CONCLUSION

There is a greater tendency for mesial angulation of the maxillary canine in patients with MLIA, regardless of the presence or absence of deciduous lateral incisor.

Three-dimensional evaluation of root dimensions and alveolar ridge width of maxillary lateral incisors in patients with unilateral agenesis

Background

The objective of this retrospective case-control study was to measure the maxillary lateral incisor root dimensions and quantify the labial and palatal bone in patients with unilateral maxillary lateral incisor agenesis (MLIA) after orthodontic treatment and compare them to non-agenesis controls using cone beam computed tomography.

Methods

The labiopalatal and mesiodistal root dimensions, mesiodistal coronal dimensions, and labiopalatal bone and alveolar ridge widths of the maxillary lateral incisor were assessed on posttreatment cone beam computed tomography scans of 15 patients (mean age 16.5 ± 3.4 years, 9 females and 6 males) with maxillary lateral incisor agenesis and 15 gender-matched patients (mean age 16.08 ± 3.23 years) with no dental agenesis or anterior Bolton discrepancy. The Mann-Whitney test was used to distinguish any differences in root width, crown width, or changes in labial or palatal bone width between the two groups.

Results

The median labiopalatal root width was narrower in the MLIA group at the level of the cementoenamel junction (CEJ) to 8 mm apical of the CEJ compared to controls (p ≤ 0.009). The mesiodistal root width was significantly reduced in the MLIA group at the CEJ and at 4 mm apical to the CEJ. The labiopalatal alveolar ridge width was significantly decreased at 2 mm apical to the CEJ in MLIA group. The mesiodistal crown width was significantly smaller in the MLIA group at both the incisal edge and at the crown midpoint. The bone thickness was similar in both groups.

Conclusions

Coronal and root dimensions in patients with MLIA were reduced compared to controls. Alveolar ridge width was also reduced in patients with MLIA, although bone thickness was not different than controls.

Study of alveolar ridge dimensions before and after orthodontic treatment in maxillary lateral incisor agenesis: A pilot study

The objective of this study was to compare the dimensional changes in the alveolar ridge before, at the end of, and one year after orthodontic treatment in cases of Maxillary Lateral Incisor Agenesis and the possibility of using plaster models and panoramic radiographs as substitutes for cone beam-computed tomography.

MATERIAL AND METHODS

A total of 228 measurements were performed on plaster models and panoramic radiographs: before (T1), at the end of (T2), and 1 year after orthodontic treatment (T3). At stage T2, the cone beam-computed tomography was also analyzed. Non-parametric tests were used.

RESULTS

In all 3 stages, there was no statistically significant difference regarding the thickness of the models, the height of the bone in the panoramic radiographs, the space opening and the height of the bone in the panoramic radiographs, or the space opening in the models and the thickness in the same plaster models. However, a statistically significant difference was observed for the width in the panoramic radiograph during all 3 stages. Cone beam-computed tomography did not reveal a statistically significant correlation regarding the height and width of the bone compared with the panoramic radiographs, and the thickness as compared with plaster models.

CONCLUSION

There was no significant variation in thickness, height and width of the bone over time. It was demonstrated that plaster models and panoramic radiographs do not appear to be good substitutes for cone beam-computed tomography for these specific measurements.

A wide mesio-distal gap in sites of congenitally missing maxillary lateral incisors is related to a thin alveolar ridge

OBJECTIVES

To evaluate (i) a possible correlation between the mesio-distal gap width and the alveolar ridge (AR) dimensions in patients missing the maxillary lateral incisor (I2) either due to agenesis or loss and (ii) the possibility of straightforward implant placement based on simulation.

METHODS

The bucco-palatal width, area, and height of the AR at the position of I2, and the mesio-distal gap width between the central incisor and the canine, were assessed in maxillary CT scans of three groups: Patients with (i) agenesis of I2 (T_A ; n = 40); (ii) I2 regularly erupted but extracted (T_L ; n = 24); (iii) I2 regularly erupted and in situ (C; n = 40). Further, the possibility of straightforward placement of an implant 3 or 3.5 mm in diameter ×10 mm in length, with 1 mm distance from the buccal and palatal plate of the alveolar ridge was simulated and compared to the actual treatment delivered.

RESULTS

Bucco-palatal width and area of the AR at I2 and the adjacent teeth was significantly reduced in T_A compared to T_L and C. Further, in T_A , but not T_L , an increasing mesio-distal gap width between the central incisor and canine resulted in a significantly reduced bucco-palatal width of the edentulous AR. This impeded a simulated straightforward implant placement in >50% of the cases in T_A , even with a reduced implant diameter.

CONCLUSIONS

In patients congenitally missing I2, an increased mesio-distal gap width correlates significantly with reduced edentulous AR dimensions. A mesio-distal gap of >6 mm was associated with thin bucco-palatal alveolar ridges, precluding straightforward implant placement in 60-80% of the cases.

Prevalence and distribution of dental anomalies: a comparison between maxillary and mandibular tooth agenesis

INTRODUCTION

The aim of this study was to compare the pattern and prevalence of associated dental anomalies between maxillary and mandibular tooth agenesis (hypodontia).

METHODS

A sample of 3315 dental patients, aged 8.6 to 25.4 years, was surveyed for tooth agenesis (excluding third molars): 106 subjects were diagnosed with maxillary hypodontia (group 1) and 70 with mandibular hypodontia (group 2). Both groups were examined for the following dental anomalies: retained deciduous molars, infraocclusion of deciduous molars, impaction, microdontia of maxillary lateral incisors, supernumerary teeth, transposition, transmigration, and ectopic eruption of the permanent molars. For statistical testing, the chi-square test (P <0.05) was used to compare the occurrences of these anomalies among the groups.

RESULTS

We found that 77.5% of the patients in the mandibular hypodontia group had at least 1 dental anomaly compared with 49.5% in the maxillary hypodontia group (P <0.0001). The only dental anomaly with a significantly increased prevalence in the maxillary hypodontia group compared with the mandibular hypodontia group was microdontia of the maxillary lateral incisors (groups 1, 46.7%; group 2, 12.9%; P <0.0001). On the other hand, the prevalences of retained deciduous molars (group 1, 9.4%; group 2, 60.0%), infraoccluded deciduous molars (group 1, 0.9%; group 2, 7.1%), and impacted teeth (group 1, 22.6%; group 2, 38.6%) were significantly higher in the mandibular hypodontia group. The prevalences of supernumerary teeth, transposition, transmigration, and ectopic eruption of permanent molars were low and not significantly different between the groups.

CONCLUSIONS

Tooth agenesis isolated to the maxilla is frequently associated with microdontia of the maxillary lateral incisors, whereas tooth agenesis isolated to the mandible is frequently associated with retained deciduous molars, infraoccluded deciduous molars, and impacted teeth. The results of this study may provide additional evidence supporting the field-specific genetic control theory for dental development in both jaws.

Illegal tusk harvest and the decline of tusk size in the African elephant

Harvesting of wild populations can cause the evolution of morphological, behavioral, and life history traits that may compromise natural or sexual selection. Despite the vulnerability of large mammals to rapid population decline from harvesting, the evolutionary effects of harvesting on mega‐fauna have received limited attention. In elephants, illegal ivory harvesting disproportionately affects older age classes and males because they carry large tusks, but its' effects on tusk size for age or tusk size for stature are less understood. We tested whether severe historical elephant harvests eliminated large tuskers among survivors and whether elephants born thereafter had smaller tusks. Adjusting for the influence of shoulder height – a metric strongly correlated with body size and age and often used as a proxy for age – we compared tusk size for elephants sampled in 1966–1968, prior to severe ivory harvesting in the late 1970s and early 1980s, with tusk size of survivors and elephants born during population recovery in the mid‐1990s. In a regional population, tusk length declined by ˜21% in male and by ˜27% in female elephants born during population recovery, while tusk length declined by 22% in males and 37% in females among survivors. Tusk circumference at lip declined by 5% in males but not in females born during population recovery, whereas tusk circumference reduced by 8% in male and by 11% in female survivors. In a single subpopulation, mean tusk length at mean basal tusk circumference declined by 12.4% in males and 21% in females. Tusk size varied between elephant social groups. Tusk homogeneity within social groups and the often high genetic similarity within social groups suggest that tusk size may be heritable. Our findings support a hypothesis of selection of large tuskers by poachers as a driver of the decline in tusk size for age proxy and contemporary tusk evolution in African elephants.

Esthetic Assessment of the Effect of Gingival Exposure in the Smile of Patients with Unilateral and Bilateral Maxillary Incisor Agenesis

PURPOSE

The aim of this study was to determine the dental esthetic perception of the smile of patients with maxillary lateral incisor agenesis (MLIA); the perceptions were examined pre- and post-treatment. Esthetic determinations were made with regard to the gingival exposure in the patients' smile by orthodontists, general dentists, and laypersons.

MATERIALS AND METHODS

Three hundred eighty one people (80 orthodontists, 181 general dentists, 120 laypersons) rated the attractiveness of the smile in four cases before and after treatment, comprising two cases with unilateral MLIA and contralateral microdontia and two with bilateral MLIA. For each case, the buccal photograph was adjusted using a computer to apply standard lips to create high, medium, and low smiles. A numeric scale was used to measure the esthetic rating perceived by the judges. The resulting arithmetic means were compared using an ANOVA test, a linear trend, and a Student's t-test, applying a significance level of p < 0.05. The predictive capability of the variables, unilateral, or bilateral MLIA, symmetry of the treatment, gingival exposure of the smile, group, and gender were assessed using a multivariable linear regression model.

RESULTS

In the pre- and post-treatment cases, medium smile photographs received higher scores than the same cases with high or low smiles, with significant differences between them. In all cases, orthodontists were the least-tolerant evaluation group (assigning lowest scores), followed by general dentists. In a predictive linear regression model, bilateral MLIA was the more predictive variable in pretreatment cases. The gingival exposure of the smile was a predictive variable in post-treatment cases only.

CONCLUSION

The medium-height smile was considered to be more attractive. In all cases, orthodontists gave the lowest scores, followed by general dentists. Laypersons and male evaluators gave the highest scores. Symmetrical treatments scored higher than asymmetrical treatments. The gingival exposure had a significant influence on the esthetic perception of smiles in post-treatment cases.

Palatally impacted maxillary canine with congenitally missing lateral incisors and midline diastema

Multiple treatment options are available for patients who have impacted canines in addition to congenitally missing lateral incisors. This article describes the treatment of a 13-year-old postpubertal girl with bilaterally impacted permanent maxillary canines, missing lateral incisors, retained deciduous canines, and a midline diastema. The orthodontic treatment plan included extraction of the deciduous canines. A lingual and labial approach (1-couple force system) was used to move the permanent canines into the arch. Through a collaborative team effort, including an orthodontist and a periodontist, the outcome was excellent esthetically and functionally.

Orthodontic Considerations in Restorative Management of Hypodontia Patients With Endosseous Implants

The use of implant-supported restorations in patients with hypodontia remains challenging and requires a multistage treatment that begins in late mixed dentition and continues into late adolescence. The aim of this article is to review the role of orthodontics in endosseous implant rehabilitation of patients with hypodontia. The MEDLINE, Web of Science, Scopus, Cochrane databases, and necessary scientific textbooks were searched for relevant studies and reviews, and as far as possible, they were only included if they had been cited at least once in the literature. Dental implants are susceptible to overloading as the periodontal ligament is absent and the proprioceptive nerve endings are either lacking or very limited. Patients with hypodontia may present with skeletal features such as short and retrognathic maxilla, prognathic mandible, and shorter lower anterior facial height, and they sometimes need orthognathic correction as part of their overall treatment. Dental problems vary and include bimaxillary retroclination of incisors, spacing, centerline discrepancies, microdontia, hypoplastic enamels, ankylosis of the retained primary teeth, overeruptions, and volume deficiencies of alveolar ridges. The challenges mentioned, as well as bone volume deficiencies, compromise the successful placement of implants. Orthodontic strategies and techniques, such as uprighting mechanics, extrusion/intrusion, delayed space opening, and orthodontic implant site-switching, can be used to create, preserve, or augment the implant site. After orthodontic site development, the final planned position of the teeth should be maintained with a rigid bonded retainer; overlooking this stage may compromise the implant site and require orthodontic retreatment.

Tooth agenesis in a Portuguese population

OBJECTIVE

The aim of this retrospective study was to evaluate the prevalence and pattern of hypodontia in the permanent dentition, including and excluding third molars, in a Portuguese sample.

PATIENTS AND METHODS

The study group comprised 2888 patients, observed between 2005 and 2009 at the Dentistry Clinic of the Instituto Superior de Ciências de Saúde-Norte (ISCSN, Portugal). The patients were examined for evidence of hypodontia and presence or absence of deciduous teeth in those presenting agenesis. The age range varied from 7 to 21 years. In order to study the absence of the third molar, subjects under 14 years were excluded. Statistical analysis was performed using SPSS(®).

RESULTS

Excluding third molars, the prevalence of tooth agenesis was 6.1% for the Portuguese population. Tooth agenesis was found more frequently in females than in males, although this difference was not statistically significant (P>.05). The most commonly missing tooth was the mandibular second premolar, followed by maxillary lateral incisor, and maxillary second premolar. There was a significantly higher prevalence of missing third molars in the agenesis group than in the non-agenesis group. There was a correlation between second premolar and upper lateral agenesis with presence of their corresponding deciduous teeth.

CONCLUSIONS

The prevalence of tooth agenesis was found to be 6.1% for this Portuguese population and there was a correlation between agenesis and presence of deciduous teeth and between agenesis and missing third molars.

Craniofacial repercussions in maxillary lateral incisors agenesis

OBJECTIVES

Assessment of the influence of maxillary lateral incisor agenesis (MLIA) on the facial morphogenesis.

METHODS

Evaluation of the skeletal dimensions of the upper maxilla and its incisor region. Analysis was performed among three groups: individuals with MLIA, its relatives and the normal population. Among these a comparison between adults and growing individuals was performed.

RESULTS

MLIA may interfere with the maxillary length and the anterosuperior facial height, negatively conditioning on its potential growth. MLIA was not correlated with changes of the palatine plane inclination, maxillary height nor with adjustment of the anterior nasal spine dimensions related to the Frankfurt plan or to the posterior nasal spine-Frankfurt plan during the observed development stage; the backward angle of the incisors in children with bilateral agenesis of lateral incisors appear to have been corrected in adulthood.

CONCLUSIONS

MLIA is associated with an upper maxilla shortening, and appear to interfere significantly with the anterior facial height, reducing its potential size.

Dental repercussions of maxillary lateral incisor agenesis

The aim of this study was to assess the influence of maxillary lateral incisor agenesis (MLIA) on the position of other teeth in the dental arch. The sample consisted of 147 individuals (66 males and 81 females) divided into two age groups: a growth phase group (A) comprising 43 individuals (18 males and 25 females, ages ranging from 9 to 16 years) and an adult group (B) (with females older than 14 and males older than 18 years) comprising 104 individuals (48 males and 56 females, ages ranging from 15 to 45 years). Within these groups, the individuals were then divided into three subsets: group 1 with MLIA, group 2 relatives of group 1 but without MLIA, and group 3 individuals from the general population (without agenesis and unrelated). Clinical evaluation of the maxillary dental midline and of the antero-posterior relationship between the upper and lower arches at the first permanent molars and canines was performed. Variables were compared by a chi-square test. There was a significant (P < 0.05) clinical association between the presence of MLIA (more often unilateral) and the deviation of the maxillary dental midline. MLIA was associated with a Class II malocclusion; this was more frequent on the same side as the agenesis.