Prevalence of maxillary lateral incisor agenesis and associated skeletal characteristics in an orthodontic patient population

Interdisciplinary Management of Bilateral Congenital Lateral Incisor Agenesis

Management of lateral incisor agenesis is a real challenge and needs a strong collaboration between surgical, aesthetic, and orthodontic dentistry. This case report managed upper lateral incisor agenesis with an orthodontic treatment leading to open spaces and placement of cuspids in lateral incisor area to avoid implant placement in maxillary anterior region. Temporary rehabilitation phase, using resin injected tray and removable partial denture, has been placed to maintain mesiodistal dimensions and restore aesthetic during pre-implant analysis and osseointegration. Once osseointegration was fully obtained, keratinized tissue augmentation has been obtained using connective tissue graft. Then, temporary implant fixed crowns allowed soft tissue modeling during interim rehabilitation. Finally, screw-retained permanent crowns were placed to fully restore aesthetic and function. This case goal was to optimize final results and reach patient complete satisfaction using orthodontic treatment combined with implant rehabilitation, and coupled with interdisciplinary management and well-time sequencing treatment.

Genetic and Morphological Variation in Hypodontia of Maxillary Lateral Incisors

(1) Background: Hypodontia has a multifactorial aetiology, in which genetic factors are a major component. Associated with this congenital absence, the formed teeth may show differences in size and shape, which may vary with the specific genetic variants and with the location of the missing teeth. The aims of the present study were to investigate a specific variant of MSX1, derive morphometric tooth measurements in a sample of patients with isolated maxillary lateral incisor agenesis and matched controls, and model the findings. (2) Methods: Genotyping of the MSX1 rs8670 genetic variant and morphometric measurements with a 2D image analysis method were performed for 26 hypodontia patients and 26 matched controls. (3) Results: The risk of upper lateral incisor agenesis was 6.9 times higher when the T allele was present. The morphometric parameters showed significant differences between hypodontia patients and controls and between the unilateral and bilateral agenesis cases. The most affected crown dimension in the hypodontia patients was the bucco-lingual dimension. In crown shape there was significant variation the Carabelli trait in upper first molars. (4) Conclusions: The MSX1 rs8670 variant was associated with variations in morphological outcomes. The new findings for compensatory interactions between the maxillary incisors indicate that epigenetic and environmental factors interact with this genetic variant. A single-level directional complex interactive network model incorporates the variations seen in this study.

Skeletal and dentoalveolar characteristics of maxillary lateral incisor agenesis patients: a comparative cross-sectional study

BACKGROUND

The aim of the study was to evaluate the cephalometric and dentoalveolar characteristics of maxillary lateral incisor agenesis patients, and to compare the findings to a matched control group without tooth agenesis, excluding third molars, from the same population.

METHODS

The pre-orthodontic records of 72 non-growing patients, who were treated at the Orthodontic Department, Faculty of Dentistry, Alexandria University, were used to address the aim of this retrospective study. Patients having unilateral or bilateral maxillary lateral incisor agenesis, with no history of previous orthodontic treatment, congenital craniofacial malformations, facial trauma, or surgeries were divided into two test groups based on the pattern of maxillary lateral incisors agenesis (group I: unilateral (UMLIA), group II: bilateral (BMLIA)). A control group (group III (CTRL)) having a complete set of permanent dentition (excluding third molars), and having no dental anomalies was age-matched with the test groups. Measurements were performed on the pre-orthodontic lateral cephalometric radiographs and the pre-orthodontic digital dental casts. The measured variables were compared between the groups using one-way ANOVA and Kruskal Wallis tests according to the normality of the variable. In case of significant results, both tests were followed by multiple pairwise comparisons using Bonferroni adjusted significance level. Significance level was set at P < 0.05.

RESULTS

BMLIA group showed a smaller SNA angle and maxillary length, a more negative ANB angle and Wits appraisal, and a larger Maxillo-mandibular differential than UMLIA and/or CTRL group. The dental and soft tissue cephalometric measurements did not show any significant differences between the groups. Dentoalveolar cast measurements showed that BMLIA patients presented with significantly smaller maxillary inter-canine width than UMLIA and CTRL patients.

CONCLUSIONS

Cephalometric analysis has shown that subjects with BMLIA have a statistically significant reduced ANB and maxillary length. Tooth eruption may play a role in the development of the maxillary arch.

Number of Teeth Is Related to Craniofacial Morphology in Humans

Simple Summary

In modern humans, congenital absence of one or more permanent teeth has a prevalence of 22.6% when considering the third molars and of 6.4% when not. Its high prevalence, in conjunction with evolutionary findings pinpointing to a steady reduction in teeth number, raises the question whether the congenital absence of teeth in modern humans is an evolutionary trend rather than an anomaly. Previous studies have shown that modern humans with less teeth also have smaller faces; however, the association between teeth number and craniofacial morphology remains unclear. Here, we show that less teeth are associated with a flatter profile and a decreased facial height. These findings support the claim of a broader relationship between number of teeth and overall craniofacial development and have evolutionary implications, since face reduction comprises also an evolutionary trend in humans.

Abstract

One of the most common dental anomalies in humans is the congenital absence of teeth, referred to as tooth agenesis. The association of tooth agenesis to craniofacial morphology has been previously investigated but remains unclear. We investigated this association by applying geometric morphometric methods in a large sample of modern humans. In line with previous studies, we report here that a reduced teeth number is linked to a less convex profile, as well as to a shorter face. The effects were similar for males and females; they increased as the severity of the tooth agenesis increased and remained unaltered by the inclusion of third molars and of allometry in the analysis. Furthermore, in cases with tooth agenesis only in the maxilla, there was no detectable effect in mandibular shape, whereas maxillary shape was affected independently of the location of missing teeth. The robustness of the present sample along with the shape analysis and the statistical approach applied, allowed for thorough testing of various contributing factors regarding the presence but also the magnitude of effects. The present findings suggest a relationship between number of teeth and overall craniofacial development and have evolutionary implications.

Prevalence, distribution, and age at clinical detection of missing permanent incisors

OBJECTIVES

To determine the prevalence and distribution of clinically missing permanent incisors, and the age at which they are detected, in school-aged children.

METHODS

A total of 2573 children aged 4-13 underwent oral health screening on at least one occasion between 2001 and 2017. In order to define a threshold age, after which permanent incisor agenesis could be suspected clinically with reasonable certainty, children who had been seen for at least three consecutive years, with any clinically missing permanent incisor were selected (n = 19). The maximum age of detection among these children was chosen as the threshold age. Based on this, a total of 766 children at or above the threshold age were screened for a cross-sectional epidemiological survey. Chi-squared tests were used to compare the prevalence of clinically missing permanent incisors among boys and girls, comparing unilateral versus bilateral, and right- versus left-sided missing teeth.

RESULTS

Roughly 2% of the sample presented with at least one clinically missing maxillary lateral incisor. This was bilateral in half of cases. Clinically missing mandibular incisors were found in 0.5% of children. Finally, the threshold age for clinical suspicion of maxillary lateral incisor agenesis was set at 11.5 years. Agenesis was confirmed in all of the children attending a follow-up radiographic visit.

CONCLUSIONS

Approximately 1 in 50 children present with a clinically missing maxillary lateral incisor. The age at suspicion of maxillary lateral incisor agenesis can sometimes be several years after its expected eruption, perhaps due to significant variation in eruption times.

Morphometric evaluation of cranial base and sella turcica in patients with bilateral agenesis of maxillary lateral incisors

The aim of this paper is to evaluate the dimensions and morphology of cranial base and sella turcica in patients with bilateral agenesis of maxillary lateral incisors (BMLI). This retrospective study was conducted on lateral cephalometric radiographs of 34 female patients with BMLI (17.69 ± 2.96 years) and 34 female patients with complete dentation and skeletal Class 1 relationship serving as a control group (17.22 ± 2.2 years). Basicranial and maxillomandibular variables together with linear dimensions and morphology of sella turcica were evaluated. Differences between groups were analyzed by Student's t test for parametric variables and Mann-Whitney U test for nonparametric variables. Chi-square test followed by post hoc test with Bonferroni correction was used for categoric variables (p < 0.05). When compared to control group, N-S-Se angle was less negative, dimensions between Ba-Se, N-Ba, and N-Ar were larger, and SNA angle was smaller in BMLI group. There were no significant differences between groups regarding the linear dimensions of sella turcica. However, variations in sella turcica morphology were more frequent in BMLI group (n = 17; 50%) when compared to control group (n = 2; 5.8%). The most common morphologic variations in BMLI group were oblique anterior wall (20.6%) and irregularity (notching) in the posterior part of sella turcica (14.7%). The present study showed a statistically significant relationship between the presence of BMLI with some craniofacial parameters and morphological variations of sella turcica. This information may be useful as an additional and early diagnostic tool for BMLI and to highlight the possible links to its development.

Nonsurgical Treatment of Class III Malocclusion with Both Anterior and Posterior Crossbites Combined with Impacted and Congenitally Missed Teeth

Class III malocclusions present a great challenge for many orthodontists, especially if malocclusions are found in adult patients and alongside other dental problems. This case report shows an adult patient with a skeletal class III anterior crossbite, a unilateral posterior crossbite on the right side, a congenital absence of both lateral incisors and retained deciduous teeth, and shift in the lower midline. The upper retained deciduous teeth and lower premolars were extracted. Leveling and alignment were initiated. Build-up composite resin placed on the first molars allowed for bite opening. The crossbites were corrected by using sequentially larger archwires combined with class III elastics until both the anterior and posterior crossbites were corrected. The impacted upper right canine was exposed using the closed eruption technique and leveled into the position of the upper lateral incisor. Miniscrews were utilized to close the residual spaces. Both canines were reshaped to simulate the upper lateral incisors. At the end of the treatment, good esthetic and functional results were obtained. In conclusion, orthodontic camouflage can be a viable option for treating patients with multiple skeletal and dental problems.

Relationships between skeletal morphology and patterns of bilateral agenesis of third molars in Japanese orthodontic patients

The aim of this study was to reveal the correlations between bilateral agenesis of third molars (M3s) and skeletal morphology in Japanese male and female orthodontic patients. Sixty patients (30 males, 30 females), with bilateral agenesis of maxillary M3s and without agenesis of mandibular M3s (group U), and 60 patients (30 males, 30 females), with bilateral agenesis of mandibular M3s and without agenesis of maxillary M3s (group L), were selected as agenesis groups. Additionally, 60 patients (30 males, 30 females) with all four M3s were selected as the control group (group C). Patients in these three groups had no agenesis of teeth other than M3s. Lateral cephalograms of each patient were used to evaluate skeletal morphology of the maxilla and mandible. Two-way analysis of variance was used for statistical comparisons. Groups U and L had significantly smaller maxillary length and area than group C. Group U exhibited a significantly smaller lower facial height than group C. Males showed significantly larger maxillary length; total mandibular and mandibular body length; mandibular ramus height; SNB angle; maxillary area; and mandibular symphysis, corpus and ramus areas than females. Females had significantly larger lower facial height, gonial angle and ANB angle than males. Smaller maxillary length and area and lower facial height should be considered in planning orthodontic treatment for patients with bilateral agenesis of maxillary and mandibular M3s.

Association between craniofacial morphological patterns and tooth agenesis-related genes

Background

The aim of the present study was to assess if genetic polymorphisms in tooth agenesis (TA)-related genes are associated with craniofacial morphological patterns.

Methods

This cross-sectional, multi-center, genetic study evaluated 594 orthodontic Brazilians patients. The presence or absence of TA was determined by analysis of panoramic radiography. The patients were classified according to their skeletal malocclusion and facial growth pattern by means of digital cephalometric analysis. Genomic DNA was extracted from squamous epithelial cells of buccal mucosa and genetic polymorphisms in MSX1 (rs1042484), PAX9 (rs8004560), TGF-α (rs2902345), FGF3 (rs1893047), FGF10 (rs900379), and FGF13 (rs12838463, rs5931572, and rs5974804) were genotyped by polymerase chain reaction using TaqMan chemistry and end-point analysis.

Results

Genotypes (p = 0.038) and allele (p = 0.037) distributions for the FGF3 rs1893047 were significantly different according to the skeletal malocclusion. Carrying at least one G allele increased in more than two times the chance of presenting skeletal class III malocclusion (OR = 2.21, CI 95% = 1.14–4.32; p = 0.017). There was no association between another skeletal craniofacial pattern and some polymorphism assessed in the present study.

Conclusion

Our results suggest that the genetic polymorphism rs1893047 in FGF3 might contribute to variations in the craniofacial sagittal pattern.

Association between sella turcica bridging and congenitally missing maxillary lateral incisors

Background/purpose

Sella turcica bridging (STB) and its association with dental anomalies has been investigated and reported in literature. This is the first study that exclusively compared STB among the orthodontic patients with congenital missing maxillary lateral incisors (CMMLI) and individuals with complete dentition.

Materials and methods

The retrospective study has recruited 49 patients with CMMLI (13 males and 36 females aged between 12 and 43 years) and 49 patients with complete dentition. Sella dimensions and association of STB with CMMLI were evaluated and the results were analysed using descriptive and inferential statistics.

Results

The comparison of mean diameter, length, and depth of sella between groups showed reduction in length among the CMMLI (p = 0.04). CMMLI group has shown a significant higher (p < 0.05) number of subjects (69.4%) with calcification when compared to control group (46.9%). The odds of having sella's bridging in patients with CMMLI were 2.5 times greater than patients with full set of teeth. Age showed a significant (p < 0.001) positive correlation with sella's width only in CMMLI.

Conclusion

Patients with CMMLI tend to have an increased frequency of STB, and decreased sella turcica length.

Canine substitution of congenitally missing maxillary lateral incisors in Class I and Class III malocclusions by using skeletal anchorage

INTRODUCTION

This prospective cohort study aimed to evaluate canine substitution supported by skeletal anchorage as a viable treatment protocol for patients with maxillary lateral incisor agenesis (MLIA) and skeletal Class I or Class III.

METHODS

Patients (n = 30) who met the following criteria were recruited: (1) bilateral MLIA or unilateral MLIA with a riziform contralateral incisor with a planned extraction; (2) skeletal Class I or Class III; and (3) dentoalveolar discrepancy in the mandible <5 mm. The archwire sequence routine was administered, combined with a rapid palatal expander, temporary intraoral skeletal anchorage device, and intermaxillary traction with Class III elastics. The results of the cephalometric analyses, peer assessment rating indexes, and the patient's smile self-evaluation using the visual analog scale were compared between initial and final treatments.

RESULTS

This study indicated that closing the space in patients with Class I or Class III malocclusion by using temporary intraoral skeletal anchorage devices in the mandible, along with Class III elastics, yielded satisfactory outcomes. Proper occlusion was established by mesialization of the maxillary teeth and correction of the intermaxillary discrepancy, thereby yielding beneficial and significant cephalometric changes after the treatment. The soft tissue profile was maintained when it was harmonious before the treatment and improved posttreatment in patients in whom the profile was initially inharmonious. All occlusions improved, as evidenced by the peer assessment rating index. Smile esthetics were also enhanced after orthodontic treatment for all patients.

CONCLUSIONS

Canine substitution may be safely offered to patients with Class I and Class III skeletal pattern and MLIA.

New perspective for evaluation of tooth widths in patients with missing or peg-shaped maxillary lateral incisors: Quadrant analysis

INTRODUCTION

Missing or peg-shaped maxillary lateral incisors can affect the mesiodistal dimensions of the dentition.

METHODS

The pretreatment casts of patients with bilateral (BMLI, n = 35) or unilateral (UMLI, n = 29) missing maxillary lateral incisors or bilateral peg-shaped maxillary lateral incisors (BPLI, n = 16) were evaluated. The mesiodistal widths of all permanent teeth except the second and third molars were measured, and the sums of total and quadrant tooth widths were calculated. The results were compared with a control group (n = 32) with normal maxillary lateral incisors. A quadrant analysis was performed by comparing the quadrants with lateral incisor agenesis, peg-shaped lateral incisors, and normal lateral incisors with each other. Statistical analysis was performed by 1-way analysis of variance followed by Tukey and Tamhane tests.

RESULTS

In the BMLI and BPLI groups, significant reductions in individual tooth widths and total tooth widths were seen. The size discrepancies were the greatest in the maxillary central incisors and decreased gradually from the incisors to the molars. Compared with the control group, the tooth-size discrepancy was more pronounced in the BPLI group followed by the BMLI and UMLI groups. Due to the variability in clinical presentations of the UMLI group, the association with the reduction of the tooth sizes was not significant. But the quadrant analysis showed that in quadrants with a missing or peg-shaped lateral incisor, the teeth were significantly narrower than in quadrants with normal incisors; this indicates the importance of the contralateral side in unilaterally affected patients during analysis.

CONCLUSIONS

Bilateral missing or peg-shaped maxillary lateral incisors were significantly associated with reduction of individual mesiodistal tooth widths as well as their total and quadrant sums. Patients with a unilaterally missing lateral incisor should be analyzed individually with quadrant analysis, since the variability in the contralateral side would affect the traditional analysis results.

Maxillary lateral incisor agenesis; a retrospective cross-sectional study

Objective

This study aims to estimate the prevalence of congenitally missing lateral incisors in a sample of 2662 dental patients in Palestine.

Methods

A total of 2662 digital panoramic radiographs were retrospectively examined for the presence of congenitally missing permanent lateral incisors. The radiographs were obtained from the archival records of patients attending a local dental center at the city of Nablus in Palestine.

Results

The prevalence of missing lateral incisors among the examined population (n = 2662) was found to be 1.91%. Unilateral agenesis accounted for 66.6% of the total cases that showed at least one missing lateral incisor. Around 79% of the unilateral cases were on the left side while 21% were on the right side. Bilateral agenesis accounted for 33.3% of 34 cases that had at least one congenitally missing permanent maxillary lateral incisor.

Conclusion

The prevalence of missing maxillary lateral incisors in this study population was 1.91%) which was within the range reported in different populations.