Evolutionary implications of dental anomalies in bats

The gain or loss of anatomical features is an important mechanism of morphological evolution and ecological adaptation. Dental anomalies-the loss or gain of teeth-are widespread and a potential source of craniodental specialization among mammals, yet their macroevolutionary patterns have been rarely explored. We present the first phylogenetic comparative study of dental anomalies across the second largest mammal Order, Chiroptera (bats). We conducted an extensive literature review and surveyed a large sample of museum specimens to analyze the types and prevalence of dental anomalies across bats, and performed phylogenetic comparative analyses to investigate the role of phylogenetic history and dietary specialization on incidence of dental anomalies. We found dental anomalies have a significant phylogenetic signal, suggesting they are not simply the result of idiosyncratic mutations or random developmental disorders, but may have ancestral genetic origins or result from shared developmental pathways among closely related species. The incidence of dental anomalies was not associated with diet categories, suggesting no effect of craniodental specialization on dental anomalies across bats. Our results give insight into the macroevolutionary patterns of dental anomalies in bats, and provide a foundation for investigating new hypotheses underlying the evolution of dental variation and diversity in mammals.

Adjunctive orthodontic therapy for prosthetic rehabilitation in a growing child with Axenfeld-Rieger syndrome: A case report

AIM

The congenital oligodontia impeding the development of the alveolar process resulting in disproportionate jaw growth has been previously reported. This case report describes the interdisciplinary management of an 11-year-old girl with Axenfeld-Rieger syndrome exhibiting oligodontia and maxillary hypoplasia.

METHODS AND RESULTS

An adjunctive orthodontic therapy was performed by taking advantage of bone-anchored maxillary protraction (BAMP) therapy using miniplates and 24-hour traction by intermaxillary Class III elastics. After 6 months of active treatment, the maxilla advanced by approximately 5 mm and upper lip relation improved by 3 mm without any significant changes in vertical relations. All the changes were maintained at 15th-month follow-up. A temporary removable prosthesis was given for immediate esthetics, and the definitive management is discussed.

CONCLUSION

The BAMP therapy can be a befitting alternative in cases exhibiting complex presentation involving skeletal and dentoalveolar components. An appreciable profile improvement without any dentoalveolar side effects can be achieved with BAMP therapy.

X-Linked Hypohidrotic Ectodermal Dysplasia in Crossbred Beef Cattle Due to a Large Deletion in EDA

Simple Summary

Ectodermal dysplasias such as hypohidrotic ectodermal dysplasia (HED), are genetic conditions affecting the development and/or homeostasis of two or more ectodermal derivatives, including hair, teeth, nails, and eccrine glands. In particular, X-linked hypohidrotic ectodermal dysplasia-1 (ECTD1) in humans is characterized by a triad of signs comprising sparse hair, abnormal teeth, and anhidrosis or hypohidrosis. It has been reported in cattle, dogs, mice and rats. Until now, eight pathogenic variants in the bovine ectodysplasin A (EDA) gene causing ECTD1-like disorders have been found. Herein, five affected Red Angus-Simmental bull calves born over a 6-year period (2013–2019) in a single herd in the Western United States are reported showing an ECTD1-like syndrome. Calves were born with severe hypotrichosis and oligodontia. At age 1-week-old two calves died of severe pneumonia. Microscopic findings of the skin revealed small-caliber hair follicles with a mean density in flank skin slightly greater in affected animals than in control animals. Nasolabial, intranasal and tracheobronchial mucosal glands were absent, whereas olfactory glands were unaffected. Whole-genome sequencing (WGS) identified a 53 kb deletion of the X chromosome including parts of the EDA gene as well as the entire AWAT2 gene. The partial deletion of the EDA gene that is known to be associated with forms of ECTD1 is the most likely cause for the reported genodermatosis. Similar rare disorders in livestock are often not diagnosed at the molecular level due to lack of resources, short lifespan of the animals, and concerns for the producers’ reputation.

Abstract

X-linked hypohidrotic ectodermal dysplasia-1 (ECTD1) in people results in a spectrum of abnormalities, most importantly hypotrichosis, anodontia/oligodontia, and absent or defective ectodermally derived glands. Five Red Angus-Simmental calves born over a 6-year period demonstrated severe hypotrichosis and were diagnosed as affected with ECTD1-like syndrome. Two died of severe pneumonia within a week of birth. The skin of three affected calves revealed a predominance of histologically unremarkable small-caliber hair follicles. Larger follicles (>50 µm) containing medullated hairs (including guard and tactile hairs) were largely restricted to the muzzle, chin, tail, eyelids, tragus and distal portions of the limbs and tail. The mean histological density of hair follicles in flank skin of two affected calves was slightly greater than that in two unaffected calves. One affected calf was examined postmortem at 10 days of age to better characterize systemic lesions. Nasolabial, intranasal and tracheobronchial mucosal glands were absent, whereas olfactory glands were unaffected. Mandibular incisor teeth were absent. Premolar teeth were unerupted and widely spaced. Other than oligodontia, histological changes in teeth were modest, featuring multifocal disorganization of ameloblasts, new bone formation in dental alveoli, and small aggregates of osteodentin and cementum at the margins of the enamel organ. A 52,780 base pair deletion spanning six out of eight coding exons of EDA and all of AWAT2 was identified. Partial deletion of the EDA gene is the presumed basis for the reported X-chromosomal recessive inherited genodermatosis.

Tooth agenesis: What do we know and is there a connection to cancer?

Like all developmental processes, odontogenesis is highly complex and dynamically regulated, with hundreds of genes co-expressed in reciprocal networks. Tooth agenesis (missing one or more/all teeth) is a common human craniofacial anomaly and may be caused by genetic variations and/or environmental factors. Variants in PAX9, MSX1, AXIN2, EDA, EDAR, and WNT10A genes are associated with tooth agenesis. Currently, variants in ATF1, DUSP10, CASC8, IRF6, KDF1, GREM2, LTBP3, and components and regulators of WNT signaling WNT10B, LRP6, DKK, and KREMEN1 are at the forefront of interest. Due to the interconnectedness of the signaling pathways of carcinogenesis and odontogenesis, tooth agenesis could be a suitable marker for early detection of cancer predisposition. Variants in genes associated with tooth agenesis could serve as prognostic or therapeutic targets in cancer. This review aims to summarize existing knowledge of development and clinical genetics of teeth. Concurrently, the review proposes possible approaches for future research in this area, with particular attention to roles in monitoring, early diagnosis and therapy of tumors associated with defective tooth development.

Functional characterization of ATF1, GREM2 AND WNT10B variants associated with tooth agenesis

OBJECTIVE

To determine the functional effects of ATF1, WNT10B and GREM2 gene variants identified in individuals with tooth agenesis (TA).

SETTINGS AND SAMPLE POPULATION

Stem cells from human exfoliated deciduous teeth (SHED) were used as an in vitro model system to test the effect of TA-associated variants.

MATERIALS AND METHODS

Plasmid constructs containing reference and mutant alleles for ATF1 rs11169552, WNT10B rs833843 and GREM2 rs1414655 variants were transfected into SHED for functional characterization of variants. Allele-specific changes in gene transcription activity, protein expression, cell migration and proliferation, and expression of additional tooth development genes (MSX1, PAX9 and AXIN2) were evaluated. Data analyses were performed using Student's t-test. P-values ≤ .05 were considered statistically significant.

RESULTS

Mutant variants resulted in significantly decreased transcriptional activity of respective genes (P < 0.05), although no changes in protein localization were noted. Expression of MSX1 was significantly decreased in ATF1- and GREM2-mutant cells, whereas PAX9 or AXIN2 mRNA expression was not significantly altered. Mutant WNT10B had no significant effect on the expression of additional TA genes. ATF1- and GREM2-mutant cells presented increased cell migration. Cell proliferation was also affected with all three mutant alleles.

CONCLUSIONS

Our results demonstrate that ATF1, WNT10B and GREM2 mutant alleles have modulatory effects on gene/protein function that may contribute to TA.

Phenotypic and Genotypic Features of Thai Patients With Nonsyndromic Tooth Agenesis and WNT10A Variants

Tooth agenesis is one of the most common orodental anomalies that demonstrate phenotypic and genotypic heterogeneity with a prevalence of 2.5%–7%. Mutations in WNT10A have been proposed to be the most common cause of nonsyndromic tooth agenesis (NSTA). The aim of this study was to characterize the dental features and genetic variants of NSTA in a Thai population. We recruited 13 unrelated patients with NSTA who attended the Faculty of Dentistry, Chulalongkorn University, Thailand, from 2017 to 2019. All 13 underwent whole exome sequencing that identified likely pathogenic genetic variants, all in WNT10A, in five patients. All five patients had second premolar agenesis, while three also had absent or peg-shaped upper lateral incisors. Patient 1 possessed a novel heterozygous duplication, c.916_918dupAAC (p.Asn306dup) in WNT10A. Patients 2 and 3 harbored a heterozygous and homozygous c.637G > A (p.Gly213Ser) in WNT10A, respectively. Patients 4 possessed a heterozygous c.511C > T (p.Arg171Cys) in WNT10A. Patient 5 harbored a homozygous c.511C > T (p.Arg171Cys) in WNT10A and a novel heterozygous c.413A > T (p.Asn138Ile) in EDARADD, suggesting digenic inheritance. We recruited another 18 family members of these five patients. Out of 23 participants, homozygous WNT10A variants were identified in 2 patients and heterozygous variants in 17 individuals. Both homozygous patients had NSTA. Eight out of 17 heterozygous individuals (8/17) had NSTA or a peg-shaped lateral incisor, indicating a 47% penetrance of the heterozygous variants or 53% (10/19) penetrance of either homozygous or heterozygous variants in WNT10A. The frequencies of the c.511C > T in our in-house 1,876 Thai exome database, Asian populations, and non-Asian populations were 0.016, 0.005–0.033, and 0.001, respectively; while those of the c.637G > A were 0.016, 0.004–0.029, and 0.000, respectively. In conclusion, our study reports two novel variants with one each in WNT10A and EDARADD, expanding the genotypic spectra of NSTA. Second premolar agenesis is a common phenotype in affected individuals with variants in WNT10A; however, its penetrance is incomplete. Lastly, the different frequencies of WNT10A variants, c.511C > T and c.637G > A, in diverse populations might contribute to the prevalence range of NSTA between continents.

Functional Effects of WNT10A Rare Variants Associated with Tooth Agenesis

Mutations in WNT10A have frequently been reported as etiologic for tooth agenesis (TA). However, the effects of WNT10A variation on gene/protein function and contribution to TA phenotypes remain poorly understood. Here, we performed bioinformatic and functional characterization analysis of WNT10A variants. In silico prediction of variant function was performed with VIPUR for all WNT10A missense variants reported in the Exome Aggregation Consortium database. Functional characterization experiments were then performed for selected WNT10A variants previously associated with TA. Expression vectors for wild-type and mutant WNT10A were made and transfected into stem cells from human exfoliated deciduous teeth (SHED) for evaluation of gene/protein function, WNT signaling activity, and effects on expression of relevant genes. While 75% of WNT10A variants were predicted neutral, most of the TA-associated variants received deleterious scores by potentially destabilizing or preventing the disulfide bond formation required for proper protein function. WNT signaling was significantly decreased with 8 of 13 variants tested, whereas wild-type-like activity was retained with 4 of 13 variants. WNT10A-mutant cells (T357I, R360C, and R379C mutants) showed reduced or impaired binding affinity to FZD5, suggesting a potential mechanism for the decreased WNT signaling. Mutant cells also had decreased WNT10A protein expression in comparison to wild-type cells. mRNA expression of PAX9, MSX1, AXIN2, and RUNX2 (known tooth development genes) was perturbed in mutant cells and quite significantly for PAX9 and RUNX2. Transcriptome analysis of wild-type and T357I-mutant cells identified 36 differentially expressed genes (26 downregulated, 10 upregulated) involved in skeletal system development and morphogenesis and pattern specification. WNT10A variants deemed pathogenic for TA likely affect protein folding and/or stabilization, leading to decreased WNT signaling and concomitant dysregulated expression of relevant genes. These findings may allow for improved interpretation of TA phenotypes upon clinical diagnosis while providing important insights toward the development of future tooth replacement therapies.

Cleft Palate Patient With Conductive Hearing Loss Due to Stapes Fixation

Congenital stapes fixation is characterized by congenital conductive hearing loss that is not progressive. This rare disease may be accompanied by additional middle ear anomalies. However, the occurrence of congenital stapes fixation with cleft palate and oligodontia was described by Gorlin et al. in 1973, and no further cases have been reported in the literature. Congenital stapes fixation was detected after the exploratory tympanotomy operation performed on a 15-year-old male patient admitted to our clinic with hearing loss, more prominent on the left. The patient also had a previous operation due to cleft lip and had congenital deficiencies in the upper and lower teeth. We present the second case report in the literature which we think belongs to this syndrome, which is defined as cleft palate, stapes fixation, and oligodontia syndrome by Gorlin et al. Laryngoscope, 131:E1279-E1281, 2021.

Aetiological Evaluation of Oligodontia in a Three-Generation Family

PURPOSE

The aim of this study was to assess the genetic evaluation of a three-generation consanguineous family with isolated oligodontia.

MATERIALS AND METHODS

A 16-year-old male patient who had been referred for orthodontic treatment due to the presence of oligodontia, and his family members who presented several missing teeth had been enrolled in the study. Clinical and radiological assessments and genetic analysis including whole-exome sequencing were performed.

RESULTS

Genetic evaluations revealed both homozygous and heterozygous mutations (c.T682A:p.F228I) in the WNT10A gene of six affected members of the family. Higher frequency of agenesis of mandibular second molar was found in homozygous relative to heterozygous WNT10A mutations.

CONCLUSION

The present findings have provided evidence for a known variant in the WNT10A gene in a three-generation consanguineous family with isolated oligodontia, while the results confirmed that cases with homozygous mutation revealed clinical heterogeneity.

Autotransplatation of immature third molars as substitutes for congenitally missing second premolars: an alternative solution in a young patient with oligodontia

Auto transplantation of immature donor teeth can be a strategic therapeutic solution in young patients. It is preferable to choose this approach instead of prosthetic restorations because it offers a unique and definitive solution. Orthodontic space closure is not always deemed desirable, especially in non-extraction cases (53,54). Successful auto transplantations allow alveolar growth through eruption of donor teeth together with the adjacent dentition when skeletal and dental development is not yet completed. Auto transplantation of third molars is less well-recognised and less documented. The available literature shows promising success rates. Immature donor teeth are reportedly associated with better outcomes than mature donor teeth. Aim of this case report was to analyse the short-term outcomes of auto transplantation of immature maxillary third molars to replace the missing mandibular second premolars in a 17-year-old healthy female with oligodontia. The surgical procedure was performed as a single step. Left and right lower second deciduous molars (7.5-8.5), close to exfoliation, were extracted. Donor upper third molars with developing root were extracted as a traumatically as possible and immediately placed into the surgically modified recipient sites. They were stabilized by a sectional wire. One year after surgery, the survival of both transplanted teeth was achieved. They showed periodontal health, normal mobility and continuation of root development during the follow-up period. The upper left third molar responded to all success criteria, no signs of ankylosis, root resorption (infection or inflammatory), and pulp necrosis. The upper right third molar had long-standing evidence of not progressive cervical external inflammatory root resorption without any clinical signs. Further research is needed to determine their long-term survival and success rates.

LEF1 haploinsufficiency causes ectodermal dysplasia

Ectodermal dysplasias are a family of genodermatoses commonly associated with variants in the ectodysplasin/NF-κB or the Wnt/β-catenin pathways. Both pathways are involved in signal transduction from ectoderm to mesenchyme during the development of ectoderm-derived structures. Wnt/β-catenin pathway requires the lymphoid enhancer-binding factor 1 (LEF1), a nuclear mediator, to activate target gene expression. In mice, targeted inactivation of the LEF1 gene results in a complete block of development of multiple ectodermal appendages. We report two unrelated patients with 4q25 de novo deletion encompassing LEF1, associated with severe oligodontia of primary and permanent dentition, hypotrichosis and hypohidrosis compatible with hypohidrotic ectodermal dysplasia. Taurodontism and a particular alveolar bone defect were also observed in both patients. So far, no pathogenic variants or variations involving the LEF1 gene have been reported in human. We provide further evidence for LEF1 haploinsufficiency role in ectodermal dysplasia and delineate its clinical phenotype.

Hypodontia - not only an orthodontic problem

BACKGROUND

The meta-analysis of the data collected in the years 1939-1993 clearly shows an increasing incidence of hypodontia. The disorder is characterized by a congenital absence of deciduous or permanent teeth. It is a significant esthetical and functional problem, which may negatively affect the patient's psychosocial development.

OBJECTIVES

The aim of the study was to determine the scale of hypodontia using a sample of Polish orthodontic patients.

MATERIAL AND METHODS

The orthopantomograms and medical records of 674 patients aged 6-15 years (376 girls and 298 boys) were analyzed in order to identify dental agenesis. Deciduous and wisdom teeth were excluded from the study. Data regarding gender, the location of the disorder as well as the number and type of missing buds was recorded.

RESULTS

Hypodontia was found in 11.6% of the subjects (7.6% girls and 4% boys), more often in the mandible (44.9%) than in the maxilla (28.2%) or in both jaws (26.9%), and these differences were statistically significant (p = 0.096). The occurrence rates of uniand bilateral hypodontia were similar: 51.3% and 48.7%, respectively. The incidence of left-sided hypodontia (37.2%) significantly prevailed over rightsided hypodontia (14.1%) (p < 0.01). Tooth 35 was the most frequently missing one (13.5%).

CONCLUSIONS

The large discrepancy in hypodontia prevalence indicates that geographical differences and varying sample sizes greatly affect the results of studies. The literature lacks comprehensive studies regarding hypodontia in Poland. More studies with similar sample sizes and selection criteria need to be carried out. Through an early detection of hypodontia, it is possible to plan comprehensive, interdisciplinary treatment. Regardless of the discrepancies in the literature as to the exact location of the problem, hypodontia affects over 10% of the population of patients treated orthodontically, which justifies the need to study this issue.

Interdisciplinary Approach to Treat Patients With Tooth Agenesis: A Case Report

INTRODUCTION

Tooth agenesis is a type of dental anomaly in which individuals are missing teeth due to developmental failure as a result of genetic or environmental factors. With approximately one fourth of the population missing ≥1 third molar, tooth agenesis is considered a common dental anomaly. However, the severity of tooth agenesis can range from a missing single tooth to multiple teeth. When suffering from severe tooth agenesis, the patient's health and social relationships are often affected.

CASE PRESENTATION

The patient in this report congenitally lost 11 teeth and suffered from compromised esthetics and impaired chewing function. In such a severe tooth agenesis case, interdisciplinary treatments involving orthodontics, periodontics, and prosthodontics were engaged to reconstruct the ideal biology, function, and esthetics for the patient. With an interdisciplinary approach, the periodontist played an important role in the rehabilitation of the edentulous regions with implants in combination with various hard and soft tissue augmentation procedures. In addition, the patient with severe tooth agenesis presented with additional dental anomalies. The periodontist, therefore, had to collaborate with other specialists to provide early detection and intervention to avoid future complications, such as the management of infraoccluded ankylosed deciduous molars and aberrant frenum. The patient at the end of treatment had a good occlusion with improved function and esthetics.

CONCLUSION

This case report describes the interdisciplinary treatment approach used and points out the role of periodontists in the treatment of a patient with severe tooth agenesis.

Oral Health-Related Quality of Life in Dutch Children Diagnosed with Oligodontia. A Cross-Sectional Study

There is need to get insight into condition-specific oral health-related quality of life in Dutch children with oligodontia. Between October 2014 and March 2017, 11–17-year-old oligodontia patients were approached to join a study assessing the impact of oligodontia on condition-specific oral health-related quality of life (OHrQoL). The patients received a condition-specific OHrQoL questionnaire prior to the start of orthodontic treatment. Non-oligodontia children in the same age group, but also requiring orthodontic treatment, were approached to serve as a control. The Fisher’s Exact Test was used for comparison purposes with the control group because of the small group sizes. Furthermore, subgroup analyses were performed for gender, age, number of congenitally missing teeth, tooth agenesis in the aesthetic region, orthodontic classification and microdontia via independent t-tests. p-values of <0.05 were considered statistically significant. Twenty-eight oligodontia patients and 23 controls agreed to participate. The oligodontia patients’ scores were comparable to the controls except for the items about dental appearance and treatment complexity. The impact of oligodontia on OHrQoL in youngsters is limited and mainly concerns dental appearance and the complexity of the treatment.

Concurrent manifestation of oligodontia and thrombocytopenia caused by a contiguous gene deletion in 12p13.2: A three-generation clinical report

BACKGROUND

Wnt and Wnt-associated pathways play an important role in the genetic etiology of oligodontia, a severe form of tooth agenesis. Loss-of-function mutations in LRP6 , encoding a transmembrane cell-surface protein that functions as a coreceptor in the canonical Wnt/b-catenin signaling cascade, also contribute to genetic oligodontia.

METHODS AND RESULTS

We describe a three-generation family with hereditary thrombocytopenia and oligodontia. Genome wide array analysis was performed. The array results from the index patient revealed an interstitial loss of 150 kb in 8p23.1 (chr8:6,270,299-6,422,558; hg19) encompassing MCPH1 and ANGPT2 and an interstitial loss of 290 kb in 12p13.2 (chr12:12,005,720-12,295,290; hg19) encompassing ETV6, BCL2L14 and LRP6.

CONCLUSION

This case report shows a three-generation family with hereditary thrombocytopenia and oligodontia with a heterozygous 290 kb novel contiguous gene deletion in band p13.2 of chromosome 12, encompassing LRP6 and ETV6. In this report we discuss the clinical relevance of the deletion of both genes and illustrate the importance of thorough examination of oligodontia patients. Comprising not only the oral status but also the medical history of the patients and their relatives.

Hypodontia, Oligodontia and Anodontia in West Virginia Appalachia

Purpose: Children in West Virginia have a high prevalence of missing permanent teeth when compared to children in the rest of the nation. The purpose of this study is to determine the prevalence of permanent tooth hypodontia/oligodontia/anodontia in West Virginia children and to compare the prevalence by sex.Methods: Five hundred panoramic radiographs of West Virginia children, ages 6-11 years, were examined for missing permanent tooth buds/permanent teeth. Data analyses included frequency determinations, Chi square analyses, and logistic regression.Results: Sixty children (12.0%, n=500) had at least one missing permanent tooth bud/permanent tooth. There were 15.5% of females and 8.8% of males who had at least one missing permanent tooth bud/permanent tooth. In adjusted logistic regression on at least one missing permanent tooth bud/permanent tooth, females had an adjusted odds ratio of 2.11 [95% Confidence Interval: 1.18, 3.75; p = .011] compared with males. Other variables in the analysis failed to reach significance.Conclusion: In this sample of West Virginia children, females were more likely to have at least one missing permanent tooth bud/permanent tooth compared to males. Early recognition and treatment planning for dental care is needed for children with hypodontia/oligodontia/anodontia.

X-Linked Hypohidrotic Ectodermal Dysplasia-General Features and Dental Abnormalities in Affected Dogs Compared With Human Dental Abnormalities

X-linked hypohidrotic ectodermal dysplasia (XLHED) is a genetic disorder characterized by abnormalities in ectodermal derivatives such as sweat glands, hair, and teeth. In animals, the highest number of cases has been reported in dogs, which show characteristic congenital alopecia and develop abnormalities in the shape and number of teeth. Although the clinical phenotype of the affected individuals is typical, this disorder remains almost unknown in veterinary clinical practice. With the aim of making it better known, we gathered in this review the main clinical and genetic aspects of XLHED, placing emphasis on dental abnormalities.

Tooth agenesis: part 2. Orthodontic treatment and prosthetic possibilities

Dental agenesis has a great clinical significance due to its frequency during daily practice and the therapeutic problems that can arise from it. This paper will explore all the aspects to consider in order creating a proper multidisciplinary treatment plan: in particular, orthodontic, prosthetic and implantologic therapeutic alternatives are described for the rehabilitation of the different areas of the dental arches. In fact, dental agenesis is a problem that often requires the intervention of specialists from the different fields of dentistry and its treatment must meet aesthetics needs, stomatognathic function and patient satisfaction.

Tooth agenesis: part 1. Incidence and diagnosis in orthodontics

Dental agenesis has a great clinical significance due to its frequency during daily practice and the therapeutic problems that can arise from it. This paper will explore the incidence of dental agenesis, its diagnosis and how this anomaly affects the teeth differently. The second subsequent paper will look at its treatment and management.

Occlusal Rehabilitation in a Patient with Oligodontia and Microdontia using Implants and Full-Ceramic Restorations: A Clinical Report

Oligodontia is the agenesis of six or more permanent teeth, excluding the third molars. Multidisciplinary dental treatments should be performed sequentially due to the restoration requirements for good oral function, aesthetics and self-confidence of patients. In this study, we report a case using dental implants and full-ceramic prostheses to restore the absent and malformed teeth in a patient with agenesis of 18 permanent teeth and with some primary teeth retained. The dental sequential treatments began when she was 16 years old, and she wore removable partial dentures for 4 years with unsatisfying restoration outcome. When she became an adult, dental implants and full-ceramic prostheses were used to restore the absent and malformed teeth. Finally, the patient was very satisfied with the functional and aesthetic outcomes of the prosthetic treatment.

Novel mutations identified in patients with tooth agenesis by whole-exome sequencing

OBJECTIVES

To identify potentially pathogenic mutations for tooth agenesis by whole-exome sequencing.

SUBJECTS AND METHODS

Ten Chinese families including five families with ectodermal dysplasia (syndromic tooth agenesis) and five families with selective tooth agenesis were included. Whole-exome sequencing was performed using genomic DNA. Potentially pathogenic mutations were identified after data filtering and screening. The pathogenicity of novel variants was investigated by segregation analysis, in silico analysis, and functional studies.

RESULTS

One novel mutation (c.441_442insACTCT) and three reported mutations (c.252delT, c.463C>T, and c.1013C>T) in EDA were identified in families with ectodermal dysplasia. The novel EDA mutation was co-segregated with phenotype. A functional study revealed that NF-κB activation was compromised by the identified mutations. The secretion of active EDA was also compromised detection by western blotting. Novel Wnt10A mutations (c.521T>C and c.653T>G) and EVC2 mutation (c.1472C>T) were identified in families with selective tooth agenesis. The Wnt10A c.521T>C mutation and the EVC2 c.1472C>T mutation were considered as pathogenic for affecting highly conserved amino acids, co-segregated with phenotype and predicted to be disease-causing by SIFT and PolyPhen2. Moreover, several reported mutations in PAX9, Wnt10A, and FGFR3 were also detected.

CONCLUSIONS

Our study expanded our knowledge on tooth agenesis spectrum by identifying novel variants.

Genetic analysis: Wnt and other pathways in nonsyndromic tooth agenesis

Tooth agenesis (TA) is one of the most common developmental anomalies that affects the number of teeth. An extensive analysis of publicly accessible databases revealed 15 causative genes responsible for nonsyndromic TA, along with their signaling pathways in Wnt/β-catenin, TGF-β/BMP, and Eda/Edar/NF-κB. However, genotype-phenotype correlation analysis showed that most of the causal genes are also responsible for syndromic TA or other conditions. In a total of 198 different mutations of the 15 genes responsible for nonsyndromic TA, 182 mutations (91.9%) are derived from seven genes (AXIN2, EDA, LRP6, MSX1, PAX9, WNT10A, and WNT10B) compared with the remaining 16 mutations (8.1%) identified in the remaining eight genes (BMP4, DKK1, EDAR, EDARADD, GREM2, KREMEN1, LTBP3, and SMOC2). Furthermore, specificity analysis in terms of the ratio of nonsyndromic TA mutations versus syndromic mutations in each of the aforementioned seven genes showed a 98.2% specificity rate in PAX9, 58.9% in WNT10A, 56.6% in MSX1, 41.2% in WNT10B, 31.4% in LRP6, 23.8% in AXIN2%, and 8.4% in EDA. These findings underscore an important role of the Wnt and Wnt-associated pathways in the genetic etiology of this heterozygous disease and shed new lights on the discovery of novel molecular mechanisms associated with tooth agenesis.

Prosthetic rehabilitation of patients with hypohidrotic ectodermal dysplasia: A systematic review

Hypohidrotic ectodermal dysplasia (HED) comprises a large group of inherited disorders of ectodermal structures, characterised by hypo- or anhidrosis, hypotrichosis and hypo- or oligo- or anodontia. We aimed to systematically assess the spectrum of prosthodontic approaches with regard to the patients' age and to provide clinical implications for practicing dentists. An electronic and manual search was conducted in four databases (Medline, LIVIVO, Cochrane Library, Web of Science Core Collection). Publications of multiple study designs written in English or German without data restrictions, reporting on prosthodontic treatment of patients diagnosed with HED and afflicted with oligo- or anodontia, were included. In total, 75 articles on 146 patients were analysed according to the patients' age. In children aged 2-17 years, removable full or partial (over)dentures represented standard treatment. In the mandible, implant-supported removable dentures on two interforaminal implants presented an alternative, already in young childhood. In cases with more than six teeth per jaw, also fixed (resin) bridges were used, frequently after orthodontic treatment. In adults, fixed or removable reconstructions with the help of up to eight implants per jaw, usually placed after bone augmentation procedures, were standard. Ten case reports/series with long-term follow-up illustrated the need for consistent maintenance including denture renewals. Prosthodontic rehabilitation should start in early childhood and needs to be revised in accordance with the patients' growth. Treatment should be carried out by a multidisciplinary team addressing variable demands in different age groups.

Rare and Common Variants Conferring Risk of Tooth Agenesis

We present association results from a large genome-wide association study of tooth agenesis (TA) as well as selective TA, including 1,944 subjects with congenitally missing teeth, excluding third molars, and 338,554 controls, all of European ancestry. We also tested the association of previously identified risk variants, for timing of tooth eruption and orofacial clefts, with TA. We report associations between TA and 9 novel risk variants. Five of these variants associate with selective TA, including a variant conferring risk of orofacial clefts. These results contribute to a deeper understanding of the genetic architecture of tooth development and disease. The few variants previously associated with TA were uncovered through candidate gene studies guided by mouse knockouts. Knowing the etiology and clinical features of TA is important for planning oral rehabilitation that often involves an interdisciplinary approach.

Genetic study of non-syndromic tooth agenesis through the screening of paired box 9, msh homeobox 1, axin 2, and Wnt family member 10A genes: a case-series

Non-syndromic tooth agenesis (NSTA) is the most common developmental anomaly in humans. Several studies have been conducted on dental agenesis and numerous genes have been identified. However, the pathogenic mechanisms responsible for NSTA are not clearly understood. We studied a group of 28 patients with sporadic NSTA and nine patients with a family history of tooth agenesis. We focused on four genes - paired box 9 (PAX9), Wnt family member 10A (WNT10A), msh homeobox 1 (MSX1), and axin 2 (AXIN2) - using direct Sanger sequencing of the exons and intron-exon boundaries. The most prevalent variants identified in PAX9 and AXIN2 genes were analyzed using the chi-square test. The sequencing results revealed a number of variants in the AXIN2 gene, including one novel missense mutation in one patient with agenesis of a single second premolar. We also identified one variant in the AXIN2 gene as being a putative risk factor for tooth agenesis. Only one missense mutation was identified in the WNT10A gene and this mutation was found in two patients. Interestingly, WNT10A is reported as the most prevalent gene mutated in the European population with NSTA.