Dental agenesis: genetic and clinical perspectives

Expert consensus on imaging diagnosis and analysis of early correction of childhood malocclusion

Early correction of childhood malocclusion is timely managing morphological, structural, and functional abnormalities at different dentomaxillofacial developmental stages. The selection of appropriate imaging examination and comprehensive radiological diagnosis and analysis play an important role in early correction of childhood malocclusion. This expert consensus is a collaborative effort by multidisciplinary experts in dentistry across the nation based on the current clinical evidence, aiming to provide general guidance on appropriate imaging examination selection, comprehensive and accurate imaging assessment for early orthodontic treatment patients.

The Role of Genetics in Human Oral Health: A Systematic-Narrative Review

Background/Objectives: An individual's genetic makeup influences their organ development, orofacial structures, and overall health. Though many studies have been conducted to determine the inheritance of oral diseases and conditions, there is a lack of comprehensive research classifying these disorders based on the genetic and environmental etiology. Methods: This systematic review aimed to analyze the existing body of literature using the PubMed and Cochrane databases and answer the following question: "What evidence exists supporting the role of genetic factors in oral conditions?" This systematic-narrative review methodically categorizes oral diseases and conditions based on their genetic or environmental linkages. Each classification is rigorously supported by the peer-reviewed articles and evidence strength, affirming the sufficient validity of the identified associations. Results: This study provides an overview of how genetics can influence oral health, from predisposition to susceptibility to various oral diseases, and the impact of genetic alterations on dental and oral conditions. Additionally, this study discusses the importance of understanding the interplay between genetic and environmental factors to improve oral health outcomes. An enhanced understanding of the impact of genetics on oral health will provide a better understanding of the implications of inherited or de novo genetic mutations and their potential interactions with environmental factors. Conclusions: The data collection and analysis indicate 25 oral conditions with strong genetic components and 2 with moderate genetic contributions (fibrous dysplasia and impacted teeth), while 14 oral conditions seem to have weak genetic contributions. Treatment planning that includes genetic testing and counseling as an approach of precision oral healthcare is encouraged to develop appropriate preventative and timely treatment plans to provide the effective management of patients' symptoms.

Association between dental agenesis and facial morphology. A cross-sectional study in France

PURPOSE

Knowing the features of dental evolution and facial morphology, marked by an increase in the prevalence of agenesis and a tendency towards verticalization of the face, the main objective of this cross-sectional observational study was to assess the correlation between the occurrence of agenesis (of 3rd molars or other teeth) and facial morphology in the French population.

METHODS

The study was conducted at the University Hospital of Rennes, France, from June 2022 to October 2022. Patients aged 12-18 years who underwent a global orthodontic assessment were included. Data collected from medical examinations, panoramic, anteroposterior, and lateral x-rays were analyzed for cephalometric and dental features. The association between morphological parameters and agenesis of wisdom teeth or other teeth was assessed by univariate and multivariate analysis.

RESULTS

The study included 259 patients, of whom 89 presented agenesis. Logistic regression analyses identified several morphological parameters associated with agenesis. In the multivariate model, a negative correlation was found between tooth agenesis and FMA (OR = 0.85; p < 0. 001), facial axis (OR = 0.92; p = 0.040), and a positive one with SNB (OR = 1.17; p = 0.023), ANS-Xi-Pm (OR = 1.12; p = 0.013).

CONCLUSION

This study highlights the correlation between agenesis occurrence and specific cephalometric parameters in the French population. The findings suggest that transverse constriction of the maxilla, facial divergence, and anterior projection of the chin symphysis are associated with agenesis. Trial registration number: Opinion n°22.103, dated 06.04.2022.

Removable prosthetic management for tooth agenesis in the pediatric population: A systematic review of case reports and case series

STATEMENT OF PROBLEM

Dental agenesis is a condition in which the absence of teeth causes debilitating problems, primarily in speech, mastication, and esthetics. The optimal removable prosthetic management for the condition is unclear.

PURPOSE

The purpose of this systematic review was to evaluate the spectrum of removable prosthetic techniques with regard to the type of edentulism and to provide clinical guidance for practicing dentists.

MATERIAL AND METHODS

An electronic and manual search was conducted in the PubMed, Scopus, and Google Scholar databases. Publications of case reports and series written in English without data restrictions that reported on removable prosthodontic management of patients with oligodontia, hypodontia, or anodontia were included.

RESULTS

A total of 59 articles comprising 83 case reports were analyzed. In patients with anodontia, the most common treatment option was an acrylic resin complete denture. Hypodontia and oligodontia were commonly managed by using either a partial denture or overdenture. Irreversible hydrocolloid or alginate was the most accepted material for the preliminary impressions and elastomeric materials for definitive impressions. The tooth arrangements were modified to simulate natural dentition and improve esthetics. Modifications of conventional acrylic resin dentures have been proposed for improved denture adaptation. Good retention is essential to the long-term success of prosthetic treatment and may be achieved with a denture reline or with retention clasps. The active growth of the patients means constant maintenance, including denture renewals or repairs, emphasizing the need for long-term follow-up care.

CONCLUSIONS

Prosthodontic rehabilitation at an early age has been shown to significantly impact the overall quality of life for a child with tooth agenesis.

Alveolar morphometry in young adults with and without agenesis of the upper lateral incisor: A retrospective study

INTRODUCTION

We aimed to compare alveolar morphometry in young adults with agenesis of the upper lateral incisor versus the side without agenesis and versus matched controls.

MATERIAL AND METHODS

In this observational retrospective study, cone beam computed tomography scans were obtained of 36 upper hemiarches from young adults aged 15 to 30 years. The hemiarches were distributed into three groups: group 1: 12 upper hemiarches presenting agenesis of the upper lateral incisor; group 2: 12 upper hemiarches from the opposite side without agenesis of the upper lateral incisor (control group 1); and group 3: 12 upper hemiarches without agenesis of the upper lateral incisor matched for age and sex with respect to the affected group (control group 2). A trained and calibrated investigator performed all the alveolar measurements at two different times, including sagittal, coronal and axial slices of each hemiarch. Paired Student's t-tests, Chi-square and repeated measures ANOVA with Bonferroni correction were used, (P<0.05).

RESULTS

Apical mesial evaluation of group 1 (4.22±1.19mm) was significantly lower (P<0.001) than that of groups 2 (6.72±1.17mm) and 3 (7.58±1.67mm). Apical distal evaluation also showed differences (P<0.001) among the three groups, with the dimension being smaller in group 1 with agenesis (4.53±1.14mm), followed by group 2 without agenesis (6.23±1.55mm) and the healthy control group 3 (7.73±1.71mm).

CONCLUSIONS

Lateral incisor agenesis significantly reduces the alveolar dimensions of the affected area. In cases of unilateral agenesis, the unaffected side also shows sequelae, with decreased dimensions compared to cases without agenesis. This condition should be taken into account when making therapeutic decisions regarding rehabilitation with implants or canine replacement.

Does third molar agenesis influence the second lower molar mineralization?

Different studies have established that the mineralization stages of the second mandibular molar can be used in forensic age estimation. Nowadays, the estimate's accuracy is an ethical concern, producing as few false positives (individuals incorrectly classified as older than a determined threshold) and false negatives (individuals incorrectly classified as younger than a determined threshold) as possible. Some have hypothesized that changes in teeth number may influence tooth mineralization, altering the age estimate process. This paper analyzes whether third molar agenesis affects the second mandibular molar mineralization time frame. To do so, 355 orthopantomograms were evaluated for third molar agenesis, and the second mandibular molar mineralization stage was assessed using the Demirjian stages. Student's t-test was used to compare the difference in the mean age at which the various stages of 37 mineralization were reached in the groups with and without third molar agenesis. The level of statistical significance was set at 5%. The results pointed to a delay in second mandibular molar mineralization in the case of agenesis, suggesting the need to consider this when estimating age using dental techniques.

Orthodontic treatment of a non-syndromic patient with congenital agenesis of multiple permanent teeth: a rare case

This article presents the first stage of treatment, respectively the orthodontic management of a non-syndromic, 13-year-old patient, with multiple and asymmetric missing teeth. The difficulty of the case was increased by the association of an impacted premolar and also by the loss, due to extended caries, of three of the first permanent molars. The patient came from a rural area, where access to dental treatment was limited. His parents realized too late that the child had significant damage to his permanent first molars, that he was no longer eating properly and that he had spaces between teeth. The uncertain outcome of endodontic treatment and prosthetic restoration at the level of first permanent molars and the additional costs made the parents decide, together with the dental practitioner, to extract teeth Nos. 16, 36 and 46. Giving the situation, the first phase treatment plan was represented by orthodontic closing of several maxillary spaces and the reduction of edentulous ridge in the mandible, followed by the maintenance of the space for two future implants, each one replacing the first molars in the third and fourth quadrants. Particularly for this growing patient, early intervention to treat and save as much from the permanent teeth as possible, to expose the impacted premolar, to level and align the teeth in order to obtain continuous dental arches and a good occlusion plane, and later to apply space maintainers that will be replaced by prosthetic restorations, represented an enormous step for long-term stability and proper functioning.

The Prevalence of Congenitally Missing Permanent Teeth in a Sample of Orthodontic and Non-Orthodontic Caucasian Patients

BACKGROUND

Hypodontia represents a notable clinical and public health concern.

OBJECTIVE

To assess the prevalence of congenitally missing permanent teeth in a sample of orthodontic/dental patients of Caucasian origin originating from the Greek island of Lesvos.

MATERIALS AND METHODS

Panoramic X-rays from 621 children and adolescents, aged 9 to 16 years (average age 12.5 years), 521 seeking orthodontic care (orthodontic group) and 100 seeking dental care (non-orthodontic group) were examined to identify congenitally missing permanent teeth.

RESULTS

The orthodontic group exhibited a 5.5% prevalence of congenitally missing permanent teeth (2.8% females; 2.7% males), while the non-orthodontic group showed a prevalence of 4% (3% females; 1% males). The descending order of prevalence for missing tooth types was as follows: lower second premolars, upper laterals, lower central incisors, lower canines, upper second premolars, and lower second molars. Among orthodontic patients with missing teeth, 62% presented with an Angle's Class II malocclusion. Hypodontia was most frequently observed in the mandible. No statistically significant differences were observed between the orthodontic and non-orthodontic groups in terms of the percentage of children and types of congenitally missing teeth.

CONCLUSIONS

Congenitally missing teeth were observed in about 4-5% of the studied population with a female predilection. The lower second premolar was the most commonly absent tooth, followed by the maxillary lateral incisors. An Angle's Class II malocclusion was present in the majority of orthodontic patients with hypodontia, mostly in the mandible.

Mandibular Second Premolar Agenesis: A Retrospective Cross-sectional Study from Palestine

Objectives

This retrospective study aimed to determine the prevalence of congenitally missing mandibular second premolars.

Materials and Methods

A total of 1,843 radiographs were collected from five different cities in Palestine. Two experienced dentists independently examined the panoramic radiographs and demographic data (age and gender).

Results

Among the 1,843 radiographs, 1,039 were for females (57.37%) and 804 were for males (43.63%); 13 cases had at least one congenitally mandibular second premolar. The prevalence of congenitally missing mandibular second premolars in the study population was 0.7%. There was no significant association between gender and mandibular second premolar agenesis. Unilateral agenesis was more common than bilateral, and the left side had more cases of congenitally missing mandibular second premolars than the right side.

Conclusions

The prevalence of congenitally missing mandibular second premolars in this study population was 0.7%, within the range reported in other populations.

Compound heterozygous WNT10A missense variations exacerbated the tooth agenesis caused by hypohidrotic ectodermal dysplasia

BACKGROUND

The aim of this study was to analyse the differences in the phenotypes of missing teeth between a pair of brothers with hypohidrotic ectodermal dysplasia (HED) and to investigate the underlying mechanism by comparing the mutated gene loci between the brothers with whole-exome sequencing.

METHODS

The clinical data of the patients and their mother were collected, and genomic DNA was extracted from peripheral blood samples. By Whole-exome sequencing filtered for a minor allele frequency (MAF) ≤0.05 non-synonymous single-nucleotide variations and insertions/deletions variations in genes previously associated with tooth agenesis, and variations considered as potentially pathogenic were assessed by SIFT, Polyphen-2, CADD and ACMG. Sanger sequencing was performed to detect gene variations. The secondary and tertiary structures of the mutated proteins were predicted by PsiPred 4.0 and AlphaFold 2.

RESULTS

Both brothers were clinically diagnosed with HED, but the younger brother had more teeth than the elder brother. An EDA variation (c.878 T > G) was identified in both brothers. Additionally, compound heterozygous variations of WNT10A (c.511C > T and c.637G > A) were identified in the elder brother. Digenic variations in EDA (c.878 T > G) and WNT10A (c.511C > T and c.637G > A) in the same patient have not been reported previously. The secondary structure of the variant WNT10A protein showed changes in the number and position of α-helices and β-folds compared to the wild-type protein. The tertiary structure of the WNT10A variant and molecular simulation docking showed that the site and direction where WNT10A binds to FZD5 was changed.

CONCLUSIONS

Compound heterozygous WNT10A missense variations may exacerbate the number of missing teeth in HED caused by EDA variation.

Oligodontia in the Clinical Spectrum of Syndromes: A Systematic Review

The aim of this systematic review was to describe the clinical and genetic features of syndromes showing oligodontia as a sign. The review was performed according to the PRISMA 2020 checklist guidelines, and the search was conducted using PubMed, Scopus, Lilacs, Web of science, Livivo, and EMBASE and supplemented by a gray literature search on Google Scholar and ProQuest, applying key terms relevant to the research questions. The systematic review identified 47 types of syndromes in 83 studies, and the most common was hypohidrotic ectodermal dysplasia, which was reported in 24 patients in 22 studies. Other common syndromes that reported oligodontia included Axenfeld-Rieger syndrome, Witkop's syndrome, Ellis-van Creveld syndrome, blepharocheilodontic syndrome, and oculofaciocardiodental syndrome. The X-linked mode of inheritance was the most reported (n = 13 studies), followed by the autosomal dominant (n = 13 studies). The review describes the main syndromes that may have oligodontia as a clinical sign and reinforces the need for orodental-facial examining for adequate diagnosis and treatment of the affected patients. Molecular analysis in order to better understand the occurrence of oligodontia is imperative.

Delayed eruption of permanent maxillary first molars among Saudi children: A cross-sectional study

Aim

This retrospective cross-sectional study aimed to determine the prevalence of delayed development and eruption of permanent maxillary first molars (U6) and associated dental anomalies in a sample of Saudi children.

Material and methods

In total, 10,232 panoramic radiographs from 9,672 patients were screened for delayed U6 eruption. Radiographs showing delayed U6 eruption were further examined for associated dental anomalies. The dental age of participants was estimated using The London Atlas of Human Tooth Development and Eruption.

Result

Twenty cases of delayed U6 eruption were found, with a prevalence of 0.2%. Of these patients, 3 and 17 were males and females, respectively; 9 and 11 cases were unilateral and bilateral, respectively. Congenital absence of the adjacent permanent second molar was observed in 8 cases, and the congenital absence of permanent teeth, except the adjacent second permanent molar and third molar, was observed in 6 cases. Peg-shaped lateral incisors were observed in 6 females. No significant associations were observed between delayed U6 eruption and dental anomalies. Overall, the average delayed U6 eruption was 2.3 years for males and 2.8 years for females.

Conclusion

Among a sample of Saudi children, the prevalence of delayed U6 eruption was 1 in 483 (0.2%) and five times higher in females. No significant associations were found between delayed U6 eruption and dental anomalies; however, congenital absence of the adjacent permanent second molar was observed in 40% of cases.

Global Trends and Hotspots in Research on Tooth Agenesis: A 20-Year Bibliometric Analysis

Tooth agenesis, one of the most common developmental defects in humans, not only impairs oral function but can also lead to craniofacial deformities. Bibliometric analysis can reveal significant shifts in research and publishing trends within specific fields. This study aims to provide a comprehensive overview of the research hotspots in tooth agenesis and predict future trends through bibliometric analysis. We searched for English-language publications related to tooth agenesis from 2001 to 2021 on the Web of Science. The publications were limited to original and review articles, and bibliometric parameters such as publication year, country, institution, author, journal, citations, and keywords were extracted and analyzed using VOSviewer, Microsoft Excel 2010, and CiteSpace. A total of 2,287 papers were ultimately selected. The results show that the USA holds a leading position in the field of tooth agenesis research. A total of 9,803 authors participated in these studies, with Alexandre R Vieira from the USA being the most prolific and most cited author. This study indicates that multidisciplinary management has become the consensus first choice for treating dental agenesis. Gene mutations related to tooth agenesis continue to be a research hotspot attracting scholarly attention. Exploring the relationship between tooth agenesis and cancer may be a future research direction. These findings contribute to potential collaborations among experts in future research on the genetic causes of tooth agenesis and tumor development and to assist the scientific community by identifying research gaps in this field.

Identification of potential key variants in mandibular premolar hypodontia through whole-exome sequencing

Determining genotype-phenotype correlations in patients with hypodontia is important for understanding disease pathogenesis, although only a few studies have elucidated it. We aimed to identify genetic variants linked to non-syndromic bilateral mandibular second premolar hypodontia in a Korean population for the first time by specifying the phenotype of hypodontia. Twenty unrelated individuals with non-syndromic bilateral mandibular second premolar hypodontia were enrolled for whole-exome sequencing. Using a tooth agenesis gene set panel consisting of 112 genes based on literature, potential candidate variants were screened through variant filtering and prioritization. We identified 13 candidate variants in 12 genes, including a stop-gain variant (c.4750C>T) in LAMA3. Through the functional enrichment analysis of the prioritized genes, several terms related to tooth development were enriched in a protein-protein interaction network of candidate genes for mandibular premolar hypodontia. The hypodontia group also had approximately 2-fold as many mutated variants in all four genes related to these key terms, which are CDH1, ITGB4, LAMA3, LAMB3, as those in the 100 healthy control group individuals. The relationship between enriched terms and pathways and mandibular premolar hypodontia was also investigated. In addition, we identified some known oligodontia variants in patients with hypodontia, strengthening the possibility of synergistic effects in other genes. This genetic investigation may be a worthwhile preliminary attempt to reveal the pathogenesis of tooth agenesis and sets a background for future studies.

Odontoma and other congenital dental anomalies: Implications for forensic identification

Forensic odontology plays a crucial role in establishing the identity in mass disasters and criminal cases with high accuracy. Dental anomalies and features help in such situations. Congenital and developmental dental anomalies can be easily documented to establish distinctive and individualistic characteristics of an individual. The location, number of teeth involved, and the type of anomaly vary between individuals. Similarly, dental malformations also assist greatly in the identification process. Many types of dental anomalies have been studied in the past for their individualistic characteristics in forensic examinations. One such dental anomaly is odontoma, which is a benign odontogenic malformation. This malformation may also help in the identification of the deceased, when recorded and examined accurately. An odontome is a malformed teeth-like structures consisting of enamel, dentin, and pulpal tissue, formed due to the growth of completely differentiated epithelial and mesenchymal cells. If antemortem (AM) dental records incorporate information regarding odontomes and other dental anomalies, including in radiographs, orthopantomograms or microradiographs, positive identification may be established by comparison of these records with postmortem (PM) records. In the present communication, a rare case of compound composite odontoma in the anterior mandible with multiple denticles has been discussed with a brief overview of congenital and developmental dental anomalies. The authors emphasize the importance of such rare dental anomalies and malformations which may be used for identifying the deceased in mass disasters and forensic identification.

Association of congenitally missing teeth with adult temporomandibular disorders in the urban health checkup population

BACKGROUND

Congenitally missing tooth is the most common dental abnormality which leaves spaces in the arch, leads to numerous forms of malocclusion due to the Bolton index discrepancy and is even associated with abnormal craniofacial morphology. Even though the roles of malocclusion and tooth loss in temporomandibular disorders (TMD) development remain controversial, basic researches have found some common molecules are involved in osteoarthritis and dental agenesis. However, the association of congenitally missing teeth with TMD is unknown. We hence investigated the association of congenitally missing teeth with TMD.

METHODS

A cross-sectional analysis of 586 control participants (male: 287, female: 299, 38.33 ± 11.65 years) and 583 participants with non-third molar congenitally missing teeth (male: 238, female: 345, 39.13 ± 11.67 years) who consecutively received routine dental and TMD checkup according to Diagnostic Criteria for Temporomandibular Disorders Axis I in Health Management Center, Xiangya Hospital was performed. Logistic regression analysis was used to study the association of congenitally missing teeth with TMD.

RESULTS

The congenitally missing teeth group included 581 hypodontia and 2 oligodontia participants. The congenitally missing anterior teeth participants, the congenitally missing posterior teeth participants and participants with both congenitally missing anterior and posterior teeth accounted for 88.34%, 8.40% and 3.26% of the congenitally missing teeth group respectively. Congenitally missing teeth group had greater ratios of females and orthodontic history. Participants with congenitally missing teeth had a significantly higher prevalence of overall TMD (67.24%) in comparison to control participants (45.90%). After adjusting age, gender, presence of congenitally missing teeth, number of congenitally missing teeth, number of non-congenitally missing teeth, number of dental quadrants with missing teeth, visible third molar and orthodontic history, the variables of age, gender, presence of congenitally missing teeth and number of dental quadrants with missing teeth were significant for overall TMD. Multivariable logistic regression analysis showed congenitally missing tooth was significantly related with overall TMD [odds ratio (OR):1.689(1.080-2.642), P = 0.022], intra-articular TMD [OR: 1.711(1.103-2.656), P = 0.017] and pain-related TMD [OR: 3.093(1.321-7.239), P = 0.009].

CONCLUSION

Congenitally missing tooth is a risk factor for TMD. When treating the congenitally missing teeth population, TMJ evaluation and multidisciplinary strategies are necessary.

Maxillary lateral incisor agenesis is associated with maxillary form: a geometric morphometric analysis

BACKGROUND AND OBJECTIVE

Agenesis of the maxillary lateral incisor occurs in up to 4% of all individuals and requires multidisciplinary treatment. Its developmental origins, however, are not fully understood. Earlier studies documented genetic factors contributing to agenesis but also an association with craniofacial morphology. In this study, we assessed the association between maxillary morphology and lateral incisor agenesis by a geometric morphometric approach to disentangle the roles of developmental plasticity and genetic factors.

MATERIALS AND METHODS

We quantified the maxillary alveolar ridge by 19 two-dimensional landmarks on cross-sectional images of 101 computed tomography scans. We compared the shape and size of the alveolar ridge across patients with unilateral or bilateral agenesis of maxillary lateral incisors and patients with extracted or in situ incisors.

RESULTS

The maxillary alveolar ridge was clearly narrower in patients with agenesis or an extracted incisor compared to the control group, whereas the contralateral side of the unilateral agenesis had an intermediate width. Despite massive individual variation, the ventral curvature of the alveolar ridge was, on average, more pronounced in the bilateral agenesis group compared to unilateral agenesis and tooth extraction.

CONCLUSIONS

This suggests that pleiotropic genetic and epigenetic factors influence both tooth development and cranial growth, but an inappropriately sized or shaped alveolar process may also inhibit normal formation or development of the tooth bud, thus leading to dental agenesis.

CLINICAL RELEVANCE

Our results indicate that bilateral agenesis of the lateral incisor tends to be associated with a higher need of bone augmentation prior to implant placement than unilateral agenesis.

A Rare Incidence of Nonsyndromic Mandibular Incisor Agenesis in a Three-generation Family: Case Report and Literature Review

Hypodontia is an inherited condition involving the absence of one to six teeth. The permanent dentition is the most frequently affected; however, it may also affect the primary dentition. A congenitally missing tooth (CMT) is the most common dental abnormality, with the missing mandibular second premolar, maxillary lateral incisor, maxillary second premolar, and mandibular central incisor accounting for 90% of CMT in hypodontia studies. The etiology of CMT has been attributed to environmental and genetic contributing factors, with the latter having a strong influence. It may occur in isolation or in association with syndromes. Congenitally missing mandibular incisor is more common in the Asian population and females. Depending on the number and location of missing teeth, hypodontia may be a considerable issue for the clinician since it may impact occlusal balance, mastication, speech, and esthetics and often requires a multidisciplinary approach. Missing mandibular incisors are of particular interest to orthodontists because of the possibility of mandibular retrognathism, the potential for the development of malocclusion, and difficulty in achieving a balanced occlusion. This case report describes the skeletal and dental features of a nonsyndromic familial occurrence of missing mandibular incisors in three generations. A comprehensive literature search was also performed to review the familial cases with missing mandibular incisors.

How to cite this article

Selvaraj M, Sennimalai K, Samrit VD, et al. A Rare Incidence of Nonsyndromic Mandibular Incisor Agenesis in a Three-generation Family: Case Report and Literature Review. Int J Clin Pediatr Dent 2023;16(2):388-395.

Advances in tooth agenesis and tooth regeneration

The lack of treatment options for congenital (0.1%) and partial (10%) tooth anomalies highlights the need to develop innovative strategies. Over two decades of dedicated research have led to breakthroughs in the treatment of congenital and acquired tooth loss. We revealed that by inactivating USAG-1, congenital tooth agenesis can be successfully ameliorated during early tooth development and that the inactivation promotes late-stage tooth morphogenesis in double knockout mice. Furthermore, Anti- USAG-1 antibody treatment in mice is effective in tooth regeneration and can be a breakthrough in treating tooth anomalies in humans. With approximately 0.1% of the population suffering from congenital tooth agenesis and 10% of children worldwide suffering from partial tooth loss, early diagnosis will improve outcomes and the quality of life of patients. Understanding the role of pathogenic USAG-1 variants, their interacting gene partners, and their protein functions will help develop critical biomarkers. Advances in next-generation sequencing, mass spectrometry, and imaging technologies will assist in developing companion and predictive biomarkers to help identify patients who will benefit from tooth regeneration.

An in vitro and computational validation of a novel loss-of-functional mutation in PAX9 associated with non-syndromic tooth agenesis

Congenital tooth agenesis (CTA) is one of the most common craniofacial anomalies. Its frequency varies among different population depending upon the genetic heterogeneity. CTA could be of familial or sporadic and syndromic or non-syndromic. Five major genes are found to be associated with non-syndromic CTA, namely PAX9, MSX1, EDA1, AXIN2, and WNT10A. Very few studies have been carried out so far on CTA on this Indian population making this study unique and important. This study was initiated to identify potential pathogenic variant associated with congenital tooth agenesis in an India family with molar tooth agenesis. CTA was investigated and a novel c.336C > G variation was identified in the exon 3 of PAX9, leading to substitution of evolutionary conserved Cys with Trp at 112th amino acid position located at the functionally significant DNA-binding paired domain region. Functional analysis revealed that p.Cys112Trp mutation did not prevent the nuclear localization although mutant protein had higher cytoplasmic retention. EMSA using e5 probe revealed that mutant protein was unable to bind with the paired-domain-binding site. Subsequently, GST pull-down assay revealed lower binding activity of the mutant protein with its known interactor MSX1. These in vitro results were consistent with the computational results. The in vitro and computational observations altogether suggest that c.336C > G (p.Cys112Trp) variation leads to loss of function of PAX9 leading to CTA in this family.

Non-syndromic hypodontia of maxillary lateral incisors and its association with other dental anomalies

BACKGROUND

Tooth agenesis (TA) is the developmental absence of one or more teeth and is the most common craniofacial disorder in humans. Maxillary lateral incisor agenesis (MLIA) is a specific subtype of TA and can have esthetic, functional, and psychosocial implications for patients. The aim of this study was to evaluate the prevalence of MLIA amongst patients with non-syndromic tooth agenesis, as well as its association with other dental anomalies.

MATERIALS AND METHODS

The dental records of 240 patients with non-syndromic congenitally missing teeth treated at the University of Alabama at Birmingham Department of Orthodontics were reviewed. Dolphin Imaging software was used to identify missing teeth, microdonts, peg laterals, impactions, and transpositions. Data were analyzed using chi-square or Fisher's exact test. All the tests were two-sided at the significance level of 0.05 (SAS 9.4).

RESULTS

In the patient cohort, MLIA prevalence was 37.5% (second most common) and no gender or ethnic differences were identified. We also observed the bilaterally missing lateral incisors more frequently than the unilateral presentation (p = 0.0006). Additionally, 62.5% of patients with unilateral MLIA displayed a contralateral tooth that was a peg (p = 0.0001); however, no association was found with other microdonts. Furthermore, of the 90 patients missing at least one maxillary lateral incisor, 42.2% were missing another tooth type and 10% of MLIA patients also had an impacted tooth (mainly maxillary canines). However, these were not statistically significant. Finally, no transposed teeth were found in our patients.

CONCLUSIONS

This study found that maxillary lateral incisors were the second most frequently missing teeth. When clinicians diagnose congenital absence of a maxillary lateral incisor, the patient should be evaluated for other missing teeth, peg lateral incisors, or potential impactions, especially maxillary canines.

Morphological Diversity of Permanent Maxillary Lateral Incisors and Their Impact on Aesthetics and Function in Orthodontically Treated Patients

The aim of this study was to determine the frequency of different crown shapes and associated dental anomalies of the permanent maxillary lateral incisor (PMLI) and their impact on aesthetics and occlusion (function) in orthodontically treated patients. Materials and Methods: The records of 372 subjects, which consisting of study casts, panoramic radiographs and anamnestic data, were investigated for crown shape and associated dental anomalies of PMLI and potential dental treatment to achieve satisfactory aesthetics and function. Descriptive statistics, including means, standard deviations and percentages for the observed variables, were calculated. Data were analyzed using the chi-square test. p-Values < 0.05 were considered as statistically significant. Results: The results showed that the most common crown shapes of PMLI were trapezoidal-shaped (59.8%), followed by central incisor-shaped (26.7%), canine-shaped (11.2%) and peg-shaped (2.3%), without statistically significant difference between genders. Developmental anomalies were found in 86 (11.6%) PMLI. All subjects with developmental anomalies were included in orthodontic treatment, and 91.2% of them need interdisciplinary treatment to achieve satisfactory aesthetics and function. Conclusions: The morphological diversity and developmental anomalies of the PMLI may affect aesthetics and function and should be considered in treatment planning.

Prevalence of Dental Anomalies in Taiwanese Children with Cleft Lip and Cleft Palate

The aim of this study was to investigate the prevalence of tooth agenesis, tooth malformation, and eruption patterns of upper canines/first premolars in Taiwanese children. A total of 132 cleft lip and cleft palate (CLCP) patients (82 boys and 50 girls) underwent alveolar bone grafting (ABG) between 2012 and 2022. The patients' dental records and X-ray images were inspected. We examined dental anomalies, including congenital missing teeth, microdontia, and transposition from the upper canines to the upper first premolars in these CLCP patients. Additionally, we investigated the mean ABG operation age (9.27 ± 0.76 years) of our patient; 40.9% of them received pre-ABG orthodontic treatment at 8.72 ± 0.70 years. Among the 132 cleft subjects, the prevalence of tooth agenesis is 73.5% (97/132). The most frequently missing teeth are the maxillary lateral incisors (right side: 46.2%; left side: 47.0%). In this study, microdontia are found in all the upper incisors, of which the highest percentage (18.9%) is observed in the upper left lateral incisors. The prevalence of upper canine and first premolar transposition is 10.6%. The pattern of tooth agenesis and microdontia of the upper lateral incisors shows a strong correlation with the cleft sites of these CLCP patients in our study. These results may support the idea that the patterns of dental anomalies in CLCP patients are region-specific.

Prevalence of dental anomalies in different facial patterns and malocclusions in an Iranian population

Objective

This study aimed to evaluate the prevalence and association of dental anomalies with different types of malocclusions and facial patterns.

Methods

In this cross-sectional study, the records of patients referred to the Orthodontics Department at 12-20 years of age were collected. The patients were classified into four types of malocclusion: Cl I, Cl II div 1, Cl II div 2, and Cl III, and three types of facial patterns: normal, long, and short. Fifteen dental anomalies were searched within the documents. The statistical analysis of data was performed with chi-squared and Fisher's exact test.

Results

Among 602 patients evaluated in this study, 28.6% were males, and 71.4% were females. The prevalence of Cl I, Cl II div1, Cl II div 2, and Cl III was 58.3%, 28.7%, 5.5%, and 7.5%, respectively. The normal facial pattern was most prevalent (47.2%), followed by the long facial pattern (41.4%) and short facial pattern (11.5%); 60.7% of the study population had at least one dental anomaly. Dilaceration was the most common anomaly (27.7%), followed by impaction (21.8%) and hypodontia (18.9%). Most dental anomalies were found in females, Cl II malocclusion, and long face samples. A statistically significant association was found between transposition and male gender (P = 0.006) and between short roots and Cl II malocclusion (P = 0.047). No significant association was found between dental anomalies and facial patterns.

Conclusion

Significant associations were reported between transposition and male gender and between short roots and Cl II malocclusion. In our population, dilaceration was the most common dental anomaly.

Novel LRP6 Mutations Causing Non-Syndromic Oligodontia

The process of tooth formation is a series of reciprocal interactions between the ectoderm and mesoderm, and it is believed that many genetic factors are involved in this complex process. More than a dozen genes have been identified in non-syndromic tooth agenesis; however, the genetic etiology underlying tooth agenesis is not fully understood yet. In this study, we identified two novel LRP6 mutations in two non-syndromic oligodontia families. Both probands had 16 and 17 missing teeth in their permanent dentition. Mutational analysis identified a de novo frameshift mutation by a 1-bp insertion in exon 9 (NM_002336.2: c.1870dupA, p.(Met624Asnfs*29)) and a splicing donor site mutation in intron 8 (c.1762+2T>C). An in vitro splicing assay confirmed the deletion of exon 8, and the deletion would result in a frameshift. Due to the premature termination codons introduced by the frameshift, both mutant transcripts would be degraded by nonsense-mediated mRNA decay, resulting in haploinsufficiency.

Tooth agenesis in German orthodontic patients with non-syndromic craniofacial disorder: a retrospective evaluation of panoramic radiographs

Objectives

The study objective was to evaluate the tooth agenesis in German orthodontic patients with non-syndromic cleft lip and/or palate and Robin sequence compared to a control group without craniofacial disorder.

Materials/methods

A total of 108 panoramic radiographs were examined using the binary system of Tooth Agenesis Code (TAC) (excluding the third molar). Patients were divided into the craniofacial disorder group 1 (n = 43) and the healthy control group 2 (n = 65). Parameters such as skeletal class malformation, sex, localization of the cleft, craniofacial disorder, and interobserver reliability were assessed.

Results

Permanent tooth agenesis was observed in 44% of group 1 and 14% in group 2 with a statistically significant higher prevalence (p = 0.00162 (χ²)). Fourteen different TAC patterns were observed in group 1, ten of these occurring only once in separate patients. The distribution of the TAC codes in group 2 showed nine different possibilities of TAC code patterns; seven TACs were unique. In group 1, the most frequently absent teeth were the maxillary lateral incisor of the left side (30%); in group 2, the second premolar of the lower jaw on the right side (9%). Male patients with craniofacial disorder showed a higher percentage of tooth agenesis than female.

Conclusion

The data presented here shows a statistically significant higher prevalence of tooth agenesis in German patients with non-syndromic craniofacial disorder.

Clinical relevance

Radiographic evaluation enables the diagnosis of tooth agenesis. Recognizing early on the higher prevalence of tooth agenesis in patients exhibiting a craniofacial disorder is an important issue when developing long-term and comprehensive interdisciplinary treatment.

Does Sex, Skeletal Class and Mandibular Asymmetry Affect Tooth Length and Asymmetry in Tooth Length?

Introduction: The aim of our cross-sectional study is to determine whether there is a link between sex, skeletal class and mandibular asymmetry in orthodontic patients, with tooth length and asymmetry in tooth length on contralateral sides of the mandible. Methods: As the source for relevant data to answer this question, 3D cone-beam tomography (CBCT) images of a total of 95 future orthodontic patients were retrospectively selected from private practice records and were analyzed. The CBCT images were part of routine orthodontic diagnosis. Patients were divided into three groups (Class I, Class III with asymmetry and Class III without asymmetry) based on skeletal variables assessed on orthodontic cephalometric images and frontal photos of the face. Three null hypotheses were developed, and a series of statistical tests was performed in order to support or reject them. Results: We have established that there exists a sexual dimorphism in some of the teeth’s lengths in our sample. Furthermore, we failed to find a link between mandibular asymmetry and asymmetry in tooth length. We have also found a link between skeletal class and tooth length differences in some of the analyzed measurements. Conclusions: Computational models used to design orthodontic appliances and to plan orthodontic treatment should be more individualized to consider a patient’s sex and skeletal class.

The Human Genetics of Dental Anomalies

The development of tooth is a highly complex procedure and mastered by specific genetic programs. Genetic alterations, environmental factors, and developmental timing can disturb the execution of these programs, and result in various dental anomalies like hypodontia/oligodontia, and supernumerary teeth, which are commonly seen in our clinical practice. Advances in molecular research enabled the identification of various genes involved in the pathogenesis of dental anomalies. In the near future, it will help provide a more accurate diagnosis and biological-based treatment for these anomalies. In this article, we present the molecular phenomenon of tooth development and the genetics of various dental anomalies.

Patent highlights August-September 2021

A snapshot of noteworthy recent developments in the patent literature of relevance to pharmaceutical and medical research and development.

Nonmalignant Features Associated with Inherited Colorectal Cancer Syndromes-Clues for Diagnosis

Simple Summary

Familiarity with nonmalignant features and comorbidities of cancer predisposition syndromes may raise awareness and assist clinicians in the diagnosis and interpretation of molecular test results. Genetic predisposition to colorectal cancer (CRC) should be suspected mainly in young patients, in patients with significant family histories, multiple polyps, mismatch repair-deficient tumors, and in association with malignant or nonmalignant comorbidities. The aim of this review is to describe the main nonmalignant comorbidities associated with selected CRC predisposition syndromes that may serve as valuable diagnostic clues for clinicians and genetic professionals.

Abstract

Genetic diagnosis of affected individuals and predictive testing of their at-risk relatives, combined with intensive cancer surveillance, has an enormous cancer-preventive potential in these families. A lack of awareness may be part of the reason why the underlying germline cause remains unexplained in a large proportion of patients with CRC. Various extracolonic features, mainly dermatologic, ophthalmic, dental, endocrine, vascular, and reproductive manifestations occur in many of the cancer predisposition syndromes associated with CRC and polyposis. Some are mediated via the WNT, TGF-β, or mTOR pathways. However the pathogenesis of most features is still obscure. Here we review the extracolonic features of the main syndromes, the existing information regarding their prevalence, and the pathways involved in their pathogenesis. This knowledge could be useful for care managers from different professional disciplines, and used to raise awareness, enable diagnosis, and assist in the process of genetic testing and interpretation.

The First Report of a Missense Variant in RFX2 Causing Non-Syndromic Tooth Agenesis in a Consanguineous Pakistani Family

Background: The syndromic and non-syndromic congenital missing teeth phenotype is termed tooth agenesis. Since tooth agenesis is a heterogeneous disorder hence, the patients show diverse absent teeth phenotypes. Thus identifying novel genes involved in the morphogenesis of ectodermal appendages, including teeth, paves the way for establishing signaling pathways.

Methods and Results: We have recruited an autosomal recessive non-syndromic tooth agenesis family with two affected members. The exome sequencing technology identified a novel missense sequence variant c.1421T &gt; C; p.(Ile474Thr) in a regulatory factor X (RFX) family member (RFX2, OMIM: 142,765). During the data analysis eight rare variants on various chromosomal locations were identified, but the co-segregation analysis using Sanger sequencing confirmed the segregation of only two variants RFX2: c.1421T &gt; C; p.(Ile474Thr), DOHH: c.109C &gt; G; p.(Pro37Ala) lying in a common 7.1 MB region of homozygosity on chromosome 19p13.3. Furthermore, the online protein prediction algorithms and protein modeling analysis verified the RFX2 variant as a damaging genetic alteration and ACMG pathogenicity criteria classified it as likely pathogenic. On the other hand, the DOHH variant showed benign outcomes.

Conclusion:RFX2 regulates the Hedgehog and fibroblast growth factor signaling pathways, which are involved in the epithelial and mesenchymal interactions during tooth development. Prior animal model studies have confirmed the expression of rfx2 at a developmental stage governing mouth formation. Moreover, its regulatory role and close association with ciliary and non-ciliary genes causing various dental malformations makes it a potential candidate gene for tooth agenesis phenotype. Further studies will contribute to exploring the direct role of RFX2 in human tooth development.

Congenitally missing second permanent molars in non‑syndromic patients (Review)

Hypodontia (tooth agenesis) is regarded as the most common congenital dental anomaly. The present review discusses the epidemiological characteristics of congenitally missing second permanent molars (CMSPMs) within a systematic review of the literature. The review was based on Pubmed library associated with the search of various scientific databases or academic resources, improved by hand search of reference lists. The terms ‘hypodontia’ or ‘anodontia’ in combination with ‘prevalence’ or ‘epidemiology’ were searched in the data sources for studies published between January 2001 and December 2020. Abstracts of non-English papers were also analyzed. The inclusion criteria were as follows: i) Study provided precise data about CMSPMs, even if no second permanent molar was reportedly missing; ii) the number of CMSPMs distributed by jaw was provided and iii) studies on subjects >3 years were used. The exclusion criteria were as follows: i) Studies on patients with history of trauma of the maxilla or the mandible, any type of syndrome affecting bone metabolism, metabolic disorders, previous extraction or tooth loss due to dental caries, cleft lip and palate; ii) studies performed on cohorts of patients with hypodontia and iii) studies reporting data including third molars, except for those that presented sufficient data to perform correct calculations. A total of 79 studies were selected, accumulating a population of 281,968 people, with an average sample size of 3,524.60±11,255.25. The prevalence of CMSPMs (IpHSPM) was 2.79±3.16% among all missing teeth (1.03±1.59% for upper CMSPMs and 1.76±2.32% for lower CMSPMs; P=0.011). There were no significant differences (P=0.250) in IpHSPM between men (1.59±1.52%) and women (2.13±1.67%). However, significant differences were recorded between continents. Furthermore, lower CMSPMs were found more frequently in orthodontic samples (P=0.033). The prevalence of CMSPMs is low compared with the overall prevalence of CM teeth. Despite the rarity of these anomalies, early detection is important to enable practitioners to plan and start treatment at the best time for optimal results.

Prevalence and Pattern of Non-syndromic Hypodontia among Adolescents in Southern Part of India

Background

Non-syndromic hypodontia is the most common developmental dental anomaly, but there is a paucity of literature on its prevalence and severity in the Indian population.

Aim and objectives

To estimate the prevalence of non-syndromic hypodontia among adolescent schoolchildren in the southern part of India.

Settings and design

This cross-sectional study was conducted in 20 schools from two states of southern India, named—Andhra Pradesh and Telangana. A total of 5,458 children in the age-group 13 to 15 years were selected.

Materials and methods

Clinical examination was carried out to check the absence of a permanent tooth and was confirmed by radiographic findings. The inclusion criterion was children with all the permanent teeth erupted (except third molars) and exclusion criteria were teeth missing due to reasons other than congenital agenesis. A Chi-square test was applied to check the significance.

Results

The total prevalence of hypodontia in the study sample was 1.4%. Girls displayed a higher prevalence value (1.9%) than boys (1.1%). Maxillary lateral incisor was the most commonly congenitally missing tooth, followed by mandibular incisors and mandibular second premolar. Overall, hypodontia with a predominance of unilateral pattern and a predilection for the left side was observed.

Conclusion

The most common missing permanent tooth (except third molars) was the maxillary lateral incisor. Hypodontia was more prevalent in females and had a predominance of unilateral patterns with a predilection toward the left side.

How to cite this article

Manasa Devi TL, Dutta B, Dwijendra KS, et al. Prevalence and Pattern of Non-syndromic Hypodontia among Adolescents in Southern Part of India. Int J Clin Pediatr Dent 2021;14(4):492–496.

Research algorithm for the detection of genetic patterns and phenotypic variety of non-syndromic dental agenesis

Introduction: Dental agenesis (DA), brings together the anodontia, oligodontia, hypodontia, characterized by a deficit in the development of a variable number of teeth. The objectives of the study were to illustrate the phenotypic variability of non-syndromic DA, to identify cases of DA with hereditary genetic transmission, and establish the mode of DA genetic pattern in these cases, together with the determination of DA prevalence in the population group study. Patients, Materials and Methods: The cross-sectional observational study was performed on a mixed population group, consisting of 861 Caucasian patients, between January 2018–December 2019. The clinical evaluation protocol of patients with DA, used to illustrate their phenotype, included the following stages: oral examination, photographic examination, and radiological examination. The evaluation protocol specific to the family genetic study of patients with DA, involved the following three stages: family survey, construction of the family tree and analysis of the pedigree structure. Results: The prevalence of DA in the population group was 2.78%. Regarding the phenotype, DA mainly affected the upper arch (50% of cases); bilateral DA had a significantly increased incidence (83.33% of cases) compared to unilateral form; in most cases (75%), a patient lacked one to two teeth, the lack of two teeth being the most common form (83.33% of cases); the upper lateral incisors were the teeth most frequently involved in DA (31.11% of the total missing teeth). Regarding the family genetic study, hereditary DA with autosomal dominant inheritance was present in 37.50% of cases. In the other cases (62.50%), isolated, sporadic forms of DA were registered, suggesting a spontaneous de novo mutation or a disorder of odontogenesis of a non-genetic nature. Conclusions: We consider that this study is of interest for current scientific research with applicability in dental medicine, by bringing actual information on the prevalence of non-syndromic DA in South-East Romania, the variety of phenotypic spectrum of DA for this geographic area, and the role of heredity in the DA genetic determinism in the studied population.

Role of Maternal Infections and Inflammatory Responses on Craniofacial Development

Pregnancy is a tightly regulated immunological state. Mild environmental perturbations can affect the developing fetus significantly. Infections can elicit severe immunological cascades in the mother's body as well as the developing fetus. Maternal infections and resulting inflammatory responses can mediate epigenetic changes in the fetal genome, depending on the developmental stage. The craniofacial development begins at the early stages of embryogenesis. In this review, we will discuss the immunology of pregnancy and its responsive mechanisms on maternal infections. Further, we will also discuss the epigenetic effects of pathogens, their metabolites and resulting inflammatory responses on the fetus with a special focus on craniofacial development. Understanding the pathophysiological mechanisms of infections and dysregulated inflammatory responses during prenatal development could provide better insights into the origins of craniofacial birth defects.

Use of a Modified Nance Appliance for Esthetic Rehabilitation of a Child Patient with Rare Nonfamilial and Nonsyndromic Oligodontia

Congenital absence of more than 6 teeth except the third molar is known as oligodontia. It can affect both primary and permanent dentitions. The affected individuals usually demonstrate esthetic, functional, and psychological concerns. The present case report is about a 4-year-old female patient with multiple missing (both primary and permanent) teeth with esthetic and social problems. On extraoral examination, the patient demonstrated upper lip relapse due to missing anterior teeth. On physical examination, no other abnormality was detected in relation to the hair, appendages, or presence of a cleft. On intraoral and radiographic examination, 21 teeth were missing, which included both the primary and the permanent tooth buds. To encourage a positive behavioral change, it was decided to carry out prosthetic intervention using a modified fixed Nance appliance and acrylic teeth. After the replacement of the missing teeth, a marked improvement in the profile and esthetics was seen.

Gastrointestinal symptoms in patients with isolated oligodontia and a Wnt gene mutation

OBJECTIVE

Since Wnt signaling plays an important role in both tooth agenesis and altered intestine homeostasis, the aim was to compare gastrointestinal symptoms in patients with isolated oligodontia caused by a Wnt pathway gene mutation and controls.

METHODS

A case-control study was designed to compare self-reported gastrointestinal symptoms among patients with isolated oligodontia, caused by a Wnt signaling gene mutation, and fully dentate controls. The Gastrointestinal Symptom Rating Scale (GSRS) was used to assess gastrointestinal symptoms. Prevalence and severity of gastrointestinal symptoms among patients and age- and gender-matched controls were evaluated.

RESULTS

Twenty patients with isolated oligodontia and a pathogenic variant in the wnt pathway genes WNT10A, LRP6, or PAX9 participated. The prevalence of gastrointestinal symptoms was higher in the oligodontia patients compared to their controls (Χ² (1) = 87.33, p = .008). Mean GSRS total scores (p = .011) and domain scores for "abdominal pain" (p = .022), "reflux" (p = .003) and constipation (p = .030) were higher for these oligodontia patients compared to their controls.

CONCLUSION

Gastrointestinal symptoms are more prevalent and more severe in patients with isolated oligodontia and a deficiency in a Wnt pathway-related gene, when compared to controls without tooth agenesis.

A novel EDAR missense mutation identified by whole-exome sequencing with non-syndromic tooth agenesis in a Chinese family

Background

Causative variants in genes of the EDA/EDAR/NF‐κB pathway, such as EDA and EDARADD, have been widely identified in patients with non‐syndromic tooth agenesis (NSTA). However, few cases of NSTA are due to ectodysplasin‐A receptor (EDAR) variants. In this study, we investigated NSTA‐associated variants in Chinese families.

Methods

Peripheral blood samples were collected from the family members of 24 individuals with NSTA for DNA extraction. The coding region of the EDA gene of the 24 probands was amplified by PCR and sequenced to investigate new variants. Whole‐exome sequencing and Sanger sequencing were then performed for probands without EDA variants detected by PCR.

Results

A novel missense variant EDAR c.338G>A (p.(Cys113Tyr)) was identified in one family. In addition, three known EDA variants (c.865C>T, c.866G>A, and c.1013C>T) were identified in three families. Genotype–phenotype correlation analysis of EDAR gene mutation showed that NSTA patients were most likely to lose the maxillary lateral incisors and the maxillary central incisors were the least affected. The phenotype of mutations at codon 289 of EDA in NSTA affected patients was characterized by lateral incisors loss, rarely affecting the maxillary first molars.

Conclusion

A novel EDAR missense variant c.338G>A (p.(Cys113Tyr)) was identified in a family with NSTA, extending the mutation spectrum of the EDAR gene. Genotype–phenotype correlation analyses of EDAR and EDA mutations could help to improve disease status prediction in NSTA families.

Radiographic Diagnosis in the Pediatric Dental Patient

This article emphasizes the selection criteria for radiographic acquisition in children due to the greater sensitivity of children for radiation compared with adults. Diagnosis of common pediatric dental conditions, including dental caries, periodontitis, dental anomalies, cysts, tumors, and traumatic dental conditions, are discussed with relevant clinical scenarios.

Genetics of Dentofacial and Orthodontic Abnormalities

The development of craniofacial complex and dental structures is a complex and delicate process guided by specific genetic mechanisms. Genetic and environmental factors can influence the execution of these mechanisms and result in abnormalities. An insight into the mechanisms and genes involved in the development of orofacial and dental structures has gradually gained by pedigree analysis of families and twin studies as well as experimental studies on vertebrate models. The development of novel treatment techniques depends on in-depth knowledge of the various molecular or cellular processes and genes involved in the development of the orofacial complex. This review article focuses on the role of genes in the development of nonsyndromic orofacial, dentofacial variations, malocclusions, excluding cleft lip palate, and the advancements in the field of molecular genetics and its application to obtain better treatment outcomes.

Are developmentally missing teeth a predictive risk marker of malignant diseases in non-syndromic individuals? A systematic review

Background:

Different genes and loci that are associated with non-syndromic developmental tooth agenesis (TA) have the same causation pathway in the development of tumours including breast cancer (BC), epithelial ovarian cancer (EOC), colorectal cancer (CRC) and lung cancer (LC).

Objectives:

To assess the link between TA and the development of cancer.

Search sources:

This registered review included a comprehensive search of electronic databases (Cochrane Central Register of Controlled Trials [CENTRAL], LILACS, Scopus, Web of Science and Medline via Ovid) until 1 April 2020, supplemented by manual, grey literature and reference lists search. There was no restriction in term of date of publication, gender, race or type of hypodontia.

Data selection:

The primary outcome was the relationship between TA and cancer. The secondary outcome was to identify the genetic correlation between TA and cancer.

Data extraction:

Study selection, data extraction and risk of bias assessment were performed independently and induplicate by two reviewers, with disputes resolved by a third reviewer.

Results:

Eight studies with a moderate-high risk of bias were included in the final review, with a total of 5821 participants. Due to the heterogeneity among the included studies, the data were presented narratively. Limited studies reported a high prevalence of EOC (19.2%–20%) and CRC (82%–100%) in individuals with TA (depending on the study) compared to those without TA (3% for EOC and 0% for CRC). While others reported a weak correlation between EOC and CRC and TA ( P > 0.05). Weak evidence suggested a strong correlation between breast, cervical uterine and prostate cancers and TA ( P < 0.05).

Conclusions:

Though low-quality evidence suggests a link between TA and cancer, it was not possible to verify that TA can hold a predictive value as a marker for cancers. Further research is needed to confirm the association.

Registration:

PROSPERO (CRD42020139751).

Prevalence of congenitally missing upper lateral incisors in an orthodontic adolescent population

OBJECTIVE

To determine the frequency of congenitally missing maxillary lateral incisors (LIs) and to find out its variability in relation to gender.

MATERIALS AND METHODS

A retrospective study was carried out between January 2017 and December 2017. Orthopantomographs (OPGs) and lateral cephalographs record search of all orthodontic adolescent patients aged 12 to 18 years were taken from the archival records of the department. Orthopantomographs helped to diagnose the presence of unilateral/bilateral maxillary lateral incisors while the ANB angle was calculated from the lateral cephalographs to divide the subjects into various skeletal malocclusions.

STATISTICAL ANALYSIS USED

The statistical analysis was done using the Statistical Package for Social Sciences (SPSS version 17.0). The frequencies were compared with the help of the Chi-square test. P <0.05 was considered statistically significant.

RESULTS

The frequency of missing upper laterals among the male patients was 0.9%, however, 2.8% of the female patients were having missing maxillary lateral incisors. Based on gender, 62.16% had a bilateral expression of missing upper laterals, 16.21% had left unilateral expression, and 21.62% had right unilateral expression. Furthermore, skeletal class I malocclusion had a prevalence of 54.16% of bilateral missing lateral incisors in upper arch as compared to 40% of left unilateral expression and 37.5% of right unilateral expression whereas in skeletal class II malocclusion, the prevalence of right unilateral expression was 37.5% as compared to bilateral expression which was 33.33%. The left unilateral expression in skeletal class II malocclusion was found to be only 20%. The highest prevalence of missing laterals in skeletal class III malocclusion was left unilateral expression which was around 40%. The prevalence of right unilateral expression was 25% whereas the bilateral absence of upper laterals in skeletal class III malocclusion was 12.5%.

CONCLUSION

The prevalence rate for congenitally missing upper lateral incisors in the orthodontic adolescent population aged 12 to 18 years was found to be 3.77% in the present study while females were found to have a greater percentage of agenesis of the upper lateral incisors (2.8%) as compared to the males (0.9%).

Dental Age, Agenesis, and Morphology in Patients With Operated Single-Suture Craniosynostoses

OBJECTIVE

The aim of this study was to evaluate the dental age, agenesis, and morphology of children with surgically operated single-suture craniosynostoses from orthopantomographs.

DESIGN

A single-centered cross-sectional observational archival study.

PATIENTS

A sample of 196 Finnish patients with single-suture craniosynostosis without additional birth defects or syndromes (excluding Muenke syndrome) was included in this study.

MAIN OUTCOME MEASURES

Dental age was assessed using the method developed by Demirjian et al. and modified by Nyström et al. for the Finnish population. Methods described by Tulensalo et al. and Oehlers et al. were used to study taurodontism and dens invaginatus, respectively.

RESULTS

The study sample of 149 patients was divided into 3 groups: patients with sagittal synostosis (n = 103), coronal synostosis (n = 25), and metopic synostosis (n = 21). Orthopantomographs taken on average at ages 8.20 to 8.33 were used. The dental ages in different groups were on average 0.37, 0.60, and 0.66 years ahead of normative values, for sagittal, coronal, and metopic groups, respectively. Tooth agenesis, taurodontism, and invaginated teeth were found in all groups with invaginations having a high prevalence. Peg-shaped upper lateral incisors and one geminated lower lateral incisor were also found.

CONCLUSIONS

These descriptive data may help improve dental care in patients with single-suture craniosynostosis.

Prevalence of congenitally missing second premolar teeth in the Dravidian population

Introduction

In the practice of dentistry, one of the most common dental anomalies encountered is the congenitally missing teeth (CMT) with dierent prevalence in each region. CMT are those that fail to erupt in the oral cavity and remain invisible in radiographs. The aim of this study was to evaluate the prevalence of congenitally missing second premolar teeth in the Dravidian population that can be used in forensic research.

Materials and Methods

In this retrospective study, a total of 4600 panoramic radiographs of Dravidian children (2580 girls and 2020 boys) with an age group of 9-17 years were viewed for congenitally missing second premolar teeth.

Results

The total number of congenitally missing second premolars was 80 (1.73%). The prevalence was seen more in girls (60%) than boys (40%). Mandibular second premolar was the most commonly missing teeth. Bilateral agenesis (66%) was more prevalent than the unilateral agenesis (34%).

Conclusion

The prevalence of congenitally missing second premolar teeth in the Dravidian population was 1.02%. The study of CMT is important in performing dental treatments and also in the field of forensic research as it can provide knowledge on the diversities among populations.

Prediction of agenesis of the maxillary second premolar based on the developmental stages of the maxillary canine, first premolar, and second molar

OBJECTIVE

This study aimed to suggest criteria for the early diagnosis of agenesis of the maxillary second premolars (U5) based on the developmental stages of the maxillary canines (U3), first premolars (U4), and second molars (U7).

DESIGN

Overall, 303 control patients and 72 patients with agenesis who met the inclusion criteria were analyzed among 5136 patients aged 5-11 years for whom panoramic radiographs were obtained at Seoul National University Dental Hospital from June 2008 to December 2009. All developmental stages of U3, U4, U5, and U7 in both groups were evaluated and categorized into the stages proposed by Demirjian et al. To confirm the delayed dental development in the agenesis group, the Wilcoxon rank sum test was used. For verifying the tooth with the most similar developmental pattern to U5, the Kendall tau Rank Correlation and Bootstrap methods were used. Moreover, survival analysis and leave-one-out-cross-validation were performed to identify the earliest developmental stages of U3, U4, and U7 at which agenesis of U5 can be confirmed.

RESULTS

The developmental stage of U4 in the agenesis group was significantly delayed compared with that in the control group at ages 5-10. All of the stages of U3, U4, and U7 showed high correlation coefficients with U5.

CONCLUSION

U5 agenesis can be confirmed with high prediction accuracy when at least two of the three conditions are satisfied: U3, U4, and U7 in Demirjian stages E, D, and C, respectively.

Variations in AXIN2 predict risk and prognosis of colorectal cancer

Objective

Colorectal cancer (CRC) and hypodontia are frequent and different diseases with common genes are involved in their etiology. The objective of this study was to identify the association between AXIN2 rs2240308 with hypodontia and CRC.

Patients and methods

This study consisted of 50 individuals with hypodontia, 50 individuals with CRC, and 155 healthy individuals from Colombia. SNP genotyping assays of rs2240308 were performed and family history of cancer in individuals with hypodontia was documented. In silico analysis was implemented to define the genomic profile of the AXIN2 gene associated with CRC. Multivariate analysis, chi square, odd ratio tests, and R software were used for statistical analysis.

Results

AXIN2 rs2240308 showed association with CRC (OR = 5.4 CI: 2.7–10.4; p < 0.001) and with other familial cancer in individuals with hypodontia (p < 0.005 OR = 1.75, 95% CI: 1.22–6.91). In silico analysis showed that variations in AXIN2 found in CRC patients, were more frequently in earlier stages of tumor and patients who carry variations in the AXIN2 gene have a worse prognosis (p < 0.05). The association between AXIN2 rs2240308 with hypodontia was not significant.

Conclusions

These results suggest that AXIN2 rs2240308 polymorphism is associated with CRC and AXIN2 could be a risk marker for predisposition and prognosis of CRC.

The role of accelerated dental development on the occurrence of aberrant dental traits that indicate malocclusion

BACKGROUND

Timing of dental development might help orthodontists to optimize initiation of treatment and to prevent and intercept dental misalignment. This study examines the association between timing of dental development and aberrant dental traits such as crowding, impaction, and hypodontia.

METHODS

This study was performed using 4446 ten-year-old children from a multiethnic birth cohort, the Generation R Study. Dental development was defined using the Demirjian method. Crowding, impaction, and hypodontia were ascertained from 2D and 3D pictures and radiographs. We built three series of logistic regression models to test the associations of dental age with crowding, impaction, and hypodontia. Similar models were built to investigate the associations of the developmental stages of each left mandibular tooth with crowding, impaction, and hypodontia.

RESULTS

Inverse associations were found between every 1-year increase in dental age and the presence of crowding [odds ratio (OR) = 0.84, 95% confidence interval (CI): 0.79, 0.89], impaction of teeth (OR = 0.66, 95% CI: 0.52, 0.84), and hypodontia (OR = 0.52, 95% CI: 0.47, 0.56). Lower developmental stages of the second premolar were associated with the presence of crowding (OR = 0.90, 95% CI: 0.83, 0.98). Lower developmental stages of the second premolar (OR = 0.88, 95% CI: 0.79, 0.98), first molar (OR = 0.76, 95% CI: 0.65, 0.90), and the second molar (OR = 0.83, 95% CI: 0.73, 0.94) were associated with the presence of tooth impaction. Lower developmental stages of all mandibular teeth except the central incisor were associated with hypodontia (P < 0.05).

CONCLUSION

Accelerated dental development is associated with lower occurrence of crowding, impaction, and hypodontia.

Non-syndromic occurrence of true generalized microdontia with hypodontia: A case report

RATIONAL

Dental abnormalities can occur at any stage of tooth development. Of these abnormalities, true generalized microdontia is a rare condition in which all teeth are smaller than normal, while hypodontia is defined as the absence of 1 to 5 teeth. As far as we are aware, no article has reported a case of the non-syndromic occurrence of true generalized microdontia with hypodontia.

PATIENT CONCERNS

A 9-year-old girl who had no systemic diseases presented with congenital absence of maxillary lateral incisors bilaterally and small teeth involving the whole dentition.

DIAGNOSES

Based on intraoral examinations and panoramic radiograph, the patient was diagnosed with the simultaneous occurrence of true generalized microdontia, hypodontia, and a variation of maxillary 1st molar with a single root and single canal. Also, the patient had premature loss of mandibular molars and canines, periapical periodontitis in the mandible left 1st primary molar and deep caries in mandible left secondary primary molar.

INTERVENTIONS

A removable appliance to hold space for early loss of mandibular molars and canines was made at the present stage. The mandible left 1st primary molar had periapical periodontitis and the affected tooth was extracted. Furthermore, the distal surface of the mandible left 2nd primary molar was filled with complex resin materials. A multi-disciplinary therapy plan was carefully designed including orthodontics, dental implants and esthetic restoration in the future.

OUTCOMES

The patient complied well with instructions for wearing the removable space maintainer, which helps prevent mesial migration of the permanent 1st molars, at the current stage. The therapeutic efficiency on periapical periodontitis and caries lesions was also good.

LESSONS

The non-syndromic presence of true generalized microdontia is extremely rare. A personalized treatment plan with multi-disciplinary considerations should be given for these patients. The pathogenesis remains unclear but may be related to genetic as well as environmental factors. More studies are urgently needed to explore the pathogenesis and treatment options for the future.

Retained Primary Molars and Related Reasons in Umm Al-Qura University, Makkah: A Retrospective Study

Background:

Retention of primary molars beyond the expected time of exfoliation is uncommon; this condition is known as persistence. A retained primary tooth, with the crown in good condition, roots, and supporting alveolar bone can serve adults for many years.

Objective:

To determine the prevalence of retained primary molars and investigate the reasons for their persistence in Umm Al-Qura University.

Methods:

Overall, 500 extra-oral panoramic radiographs were assessed to investigate whether primary molars persisted beyond the expected exfoliation period. Dental records were also reviewed to investigate the possible reasons for persistence. The collected data were tabulated and statistically analyzed, with P < .05 considered significant.

Results:

Seventy-six retained primary molars were identified (39 in females and 37 in males) in 500 panoramic radiographs (from 260 females and 240 males). Agenesis of the permanent successor tooth was the most frequently encountered reason for the retention of primary molars (19%). The second most frequent reason was ectopic deviation of the path of eruption of the successor (11%). The third most common reason was impaction of the successor (10%).

Conclusion:

The incidence of retained primary molars in the investigated population was 15.2%. The most common reason for the persistence of primary molars was agenesis of the permanent successor, followed by ectopic eruption and impaction of the successor teeth. These data highlight the need for education and awareness of dentists and patients to preserve the primary tooth when there is no permanent successor present and support an appropriate treatment plan for each case.