The genetic basis of inherited anomalies of the teeth

Orthodontic findings and treatment need in patients with amelogenesis imperfecta: a descriptive analysis

INTRODUCTION

Amelogenesis imperfecta (AI) is a genetically determined, non-syndromic enamel dysplasia that may manifest as hypoplasia, hypomaturation, or hypocalcification and can commonly be classified into four primary groups. In this retrospective analysis, specific orofacial characteristics are described and associated with each of the AI types based on a patient cohort from Witten/Herdecke University, Germany.

METHODS

Data from 19 patients (ten male and nine female, mean age 12.27 ± 4.06 years) with AI who presented at the Department of Orthodontics between July 2011 and December 2023 were analyzed. Baseline skeletal and dental conditions were assessed, including the presence of hypodontia, displacements, and taurodontism. AI was classified into classes I-IV based on phenotype. Treatment needs were evaluated according to the main findings following the German KIG classification, while the radiological enamel situation was determined using panoramic radiographs.

RESULTS

An approximately equal distribution between classes II and III was found and a slight inclination toward a dolichofacial configuration (ΔML-NSL: 5.07 ± 9.23°, ΔML-NL: 4.24 ± 8.04°). Regarding orthodontic findings, disturbance in tooth eruption as well as open bite were the most prevalent issues (both 36.8%, n = 7). The most common AI classes were type I and II, which show an almost even distribution about the skeletal classes in sagittal dimension, while dolichofacial configuration was found most frequently in vertical dimension.

CONCLUSION

Both clinical and radiological orthodontic findings in context with AI are subject to extensive distribution. It seems that no specific orofacial findings can be confirmed in association with AI with regard to the common simple classes I-IV. It may be more appropriate to differentiate the many subtypes according to their genetic aspects to identify possible associated orthodontic findings.

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.

Identification of novel candidate genes associated with non-syndromic tooth agenesis in Mongolian families

OBJECTIVES

This study aimed to identify genetic variants associated with non-syndromic tooth agenesis (TA) in nine families from Mongolia using whole-exome sequencing (WES) and bioinformatics analysis.

MATERIAL AND METHODS

The study enrolled 41 participants, including three inherited and six non-inherited families. WES analysis was performed on 14 saliva samples from individuals with non-syndromic TA. The potential candidate genes were identified through variant filtering and segregation analysis. The filtered variants were then analyzed in silico mutation impact analysis.

RESULTS

WES analysis identified 21 variants associated with TA, and 5 of these variants met all filtering criteria. These variants were located in the exome region of MAST4, ITGA6, PITX2, CACNA1S, and CDON genes. The variant in PITX2 was found in eight participants from inherited and non-inherited families, while the MAST4 variant was identified in 6 participants from inherited families.

CONCLUSIONS

The study identified various genetic variant candidates associated with TA in different family groups, with PITX2 being the most commonly identified. Our findings suggest that MAST4 may also be a novel candidate gene for TA due to its association with the Wnt signaling pathway. Additionally, we found that five candidate genes related to focal adhesion and calcium channel complex were significant and essential in tooth development.

CLINICAL RELEVANCE

Identifying new pathogenic genes associated with TA can improve our understanding of the molecular mechanisms underlying the disease, leading to better diagnosis, prevention, and treatment. Early detection of TA based on biomarkers can improve dental management and facilitate orthodontic and prosthetic treatment.

Association between malocclusions and amelogenesis imperfecta genotype and phenotype: A systematic review

INTRODUCTION

The aim of this systematic review (Prospero CRD42022323188) is to investigate whether an association exists in patients with amelogenesis imperfecta (AI) between occlusal characteristics and genotype on the one hand and enamel structural phenotype on the other.

MATERIAL AND METHODS

Reports up to May 2023 assessing occlusion of individuals with AI were browsed in a systematic search using Medline, Embase, ISI Web of Science, and the grey literature. Randomised control trials, case control studies, and case series specifying both occlusion, assessed by cephalometric or clinical analysis, and genotype or dental phenotype in patients with AI were included without any age limitation. Two authors independently selected the publications and extracted the data in accordance with the PRISMA statement. The risk of bias was assessed with the Critical Appraisal Checklists from the Johanna Briggs Institute.

RESULTS

Twenty-five articles were chosen from the 261 results. Most of the included publications were case series (n=22) and case control studies (n=3). Thirteen studies reported both a genotype (ENAM, FAM83H, FAM20A, DLX3, CNMM4, WDR72) and occlusal diagnostic. The methodological quality of the studies was moderate. All AI phenotypes showed an open bite (OB) rate around 35%, except mixed form. The other malocclusions were not often mentioned. No correlation between occlusal phenotype and genotype or AI phenotype could be identified in patients with AI, as most studies had short occlusal descriptions and small sample sizes.

CONCLUSION

OB malocclusions were more frequently reported in AI. This review highlighted the need for a more accurate description of orofacial features associated with AI, to better clarify the role of amelogenesis genes in the regulation of craniofacial morphogenesis and identify patients requiring orthognathic surgery at an early stage.

FGFR1 variants contributed to families with tooth agenesis

BACKGROUND

Tooth agenesis is a common dental anomaly that can substantially affect both the ability to chew and the esthetic appearance of patients. This study aims to identify possible genetic factors that underlie various forms of tooth agenesis and to investigate the possible molecular mechanisms through which human dental pulp stem cells may play a role in this condition.

RESULTS

Using whole-exome sequencing of a Han Chinese family with non-syndromic tooth agenesis, a rare mutation in FGFR1 (NM_001174063.2: c.103G > A, p.Gly35Arg) was identified as causative and confirmed by Sanger sequencing. Via GeneMatcher, another family with a known variant (NM_001174063.2: c.1859G > A, p.Arg620Gln) was identified and diagnosed with tooth agenesis and a rare genetic disorder with considerable intrafamilial variability. Fgfr1 is enriched in the ectoderm during early embryonic development of mice and showed sustained low expression during normal embryonic development of Xenopus laevis frogs. Functional studies of the highly conserved missense variant c.103G > A showed deleterious effects. FGFR1 (c.103G > A) was overexpressed compared to wildtype and promoted proliferation while inhibiting apoptosis in HEK293 and human dental pulp stem cells. Moreover, the c.103G > A variant was found to suppress the epithelial-mesenchymal transition. The variant could downregulate ID4 expression and deactivate the TGF-beta signaling pathway by promoting the expression of SMAD6 and SMAD7.

CONCLUSION

Our research broadens the mutation spectrum associated with tooth agenesis and enhances understanding of the underlying disease mechanisms of this condition.

Esthetic and Functional Rehabilitation of a Child with Complete Anodontia in Primary and Mixed Dentition Stage: A Case Report with 4-year Follow-up

Background

Pediatric dentists face significant challenges when treating a child with anodontia. Early intervention is essential to ensure the normal physiological and psychological development while also promoting normal jaw development.

Case Report

This report describes a 4-year follow-up case of a child with complete anodontia. Prosthetic rehabilitation during the primary and mixed dentition period improved the facial esthetics, self-esteem, speech, and masticatory function of the child.

Conclusion

This case report summarizes the treatment procedure, challenges faced in clinical management and the various prosthetic options with its advantages and disadvantages for a child with anodontia.

How to cite this article

Kaikure MK, Shetty K, Menezes R, et al. Esthetic and Functional Rehabilitation of a Child with Complete Anodontia in Primary and Mixed Dentition Stage: A Case Report with 4-year Follow-up. Int J Clin Pediatr Dent 2023;16(4):649-655.

A comparative retrospective study on the prevalence and therapeutic treatment of dental agenesis between healthy children and children with systemic disease or congenital malformation

BACKGROUND

Dental agenesis (DA) in the permanent dentition is one of the most common dental anomalies, with a prevalence up to 2-10%. Therefore, the aim of this retrospective study was to investigate the prevalence and therapeutic treatment of DA in healthy children (HC) compared to children with systemic disease or congenital malformation (SD/CM).

METHODS

Out of 3407 patients treated at the Department of Paediatric Dentistry of the Justus Liebig University Giessen (Germany) between January 2015 and December 2020, a total of 1067 patients (594 female, 473 male) aged between 4.5 and 18 years were included in this study due to DA. Besides the patients' general medical history and therapeutic treatments, panoramic radiographs were analysed.

RESULTS

In contrast to the HC group with 9.7% DA, the SD/CM group showed a significantly higher prevalence of DA (19.8%; p < 0.05). The latter group was further classified into children with ectodermal dysplasia (4.4%), down syndrome (8.2%), cleft lip and palate (4.4%), intellectual disability/developmental delay (16.4%), and other genetic/organic diseases without intellectual disability (45.9%). Regarding therapeutic treatments, the HC group (59.5%) was significantly more often treated with an orthodontic gap opening compared to the SD/CM group (42.6%; p < 0.05), followed by orthodontic gap closing 36.5% in the HC group and 22.9% in the SD/CM group (p < 0.05), whereas no treatment was predominantly performed in the SD/CM group (37.7%) compared to the HC group (4%; p < 0.05). Furthermore, 50% in the SD/CM group required general anaesthesia for therapeutic treatment (vs. 8.1% in the HC group; p < 0.05).

CONCLUSIONS

Children with SD/CM suffered more often from DA compared to HC that underlines multi- and interdisciplinary treatment of utmost importance. Furthermore, due to intellectual disability, common treatment methods can be complicated by insufficient compliance. This fact underlines the importance of an early attempt to establish the necessary cooperation enabling children with SD/CM to receive therapy.

Effects of Wnt10a and Wnt10b Double Mutations on Tooth Development

WNT molecules are the regulators of various biological functions, including body axis formation, organ development, and cell proliferation and differentiation. WNTs have been extensively studied as causative genes for an array of diseases. WNT10A and WNT10B, which are considered to be genes of the same origin, have been identified as causative genes for tooth deficiency in humans. However, the disrupted mutant of each gene does not show a decrease in teeth number. A negative feedback loop, interacting with several ligands based on a reaction-diffusion mechanism, was proposed to be important for the spatial patterning of tooth formation, and WNT ligands have been considered to play a pivotal role in controlling tooth patterning from mutant phenotypes of LDL receptor-related proteins (LRPs) and WNT co-receptors. The Wnt10a and Wnt10b double-mutants demonstrated severe root or enamel hypoplasia. In Wnt10a^-/- and Wnt10a^+/-;Wnt10b^-/- mice, changes in the feedback loop may collapse the modulation of fusion or split a sequence of tooth formation. However, in the double-knockout mutant, a decrease in the number of teeth was observed, including the upper incisor or third molar in both jaws. These findings suggest that there may be a functional redundancy between Wnt10a and Wnt10b and that the interaction between the two genes functions in conjunction with other ligands to control the spatial patterning and development of teeth.

Genome-wide screening for deubiquitinase subfamily identifies ubiquitin-specific protease 49 as a novel regulator of odontogenesis

Proteins expressed by the paired box gene 9 (PAX9) and Msh Homeobox 1 (MSX1) are intimately involved in tooth development (odontogenesis). The regulation of PAX9 and MSX1 protein turnover by deubiquitinating enzymes (DUBs) plausibly maintain the required levels of PAX9 and MSX1 during odontogenesis. Herein, we used a loss-of-function CRISPR-Cas9-mediated DUB KO library kit to screen for DUBs that regulate PAX9 and MSX1 protein levels. We identify and demonstrate that USP49 interacts with and deubiquitinates PAX9 and MSX1, thereby extending their protein half-lives. On the other hand, the loss of USP49 reduces the levels of PAX9 and MSX1 proteins, which causes transient retardation of odontogenic differentiation in human dental pulp stem cells and delays the differentiation of human pluripotent stem cells into the neural crest cell lineage. USP49 depletion produced several morphological defects during tooth development, such as reduced dentin growth with shrunken enamel space, and abnormal enamel formation including irregular mineralization. In sum, our results suggest that deubiquitination of PAX9 and MSX1 by USP49 stabilizes their protein levels to facilitate successful odontogenesis.

WNT10A variants: following the pattern of inheritance in tooth agenesis and self-reported family history of cancer

OBJECTIVES

The aim of this study was the analysis of WNT10A variants in seven families of probands with various forms of tooth agenesis and self-reported family history of cancer.

MATERIALS AND METHODS

We enrolled 60 young subjects (aged 13 to 17) from the Czech Republic with various forms of tooth agenesis. Dental phenotypes were assessed using Planmeca ProMax 3D (Planmeca Oy, Finland) with Planmeca Romexis software (version 2.9.2) together with oral examinations. After screening PAX9, MSX1, EDA, EDAR, AXIN2 and WNT10A genes on the Illumina MiSeq platform (Illumina, USA), we further analyzed the evolutionarily highly conserved WNT10A gene by capillary sequencing in the seven families.

RESULTS

All the detected variants were heterozygous or compound heterozygous with various levels of phenotypic expression. The most severe phenotype (oligodontia) was found in a proband who was compound heterozygous for the previously identified WNT10A variant p.Phe228Ile and a newly discovered c.748G > A variant (p.Gly250Arg) of WNT10A. The newly identified variant causes substitution of hydrophobic glycine for hydrophilic arginine.

CONCLUSIONS

We suggest that the amino acid changes in otherwise highly conserved sequences significantly affect the dental phenotype. No relationship between the presence of WNT10A variants and a risk of cancer has been found.

CLINICAL RELEVANCE

Screening of PAX9, MSX1, EDA, EDAR, AXIN2 and WNT10A genes in hope to elucidate the pattern of inheritance in families.

Oral Alterations in Heritable Epidermolysis Bullosa: A Clinical Study and Literature Review

Epidermolysis bullosa (EB) is a group of skin disorders with skin fragility characterized by blistering from minimal mechanical trauma with rupture at the dermoepidermal junction. There are four major classical heritable EB types, due to mutations in as many as 20 distinct genes: EB simplex (EBS), junctional EB (JEB), dystrophic EB (DEB), and Kindler EB (KEB). This study is aimed at reporting case series on patients (N = 8; males, n = 5 and females, n = 3, age range 12-68 years) affected by EB and performs a review of the literature on this topic. This group of disorders can affect oral soft and hard tissues in various ways, resulting in various effects including enamel hypoplasia, dental caries, microstomia, ankyloglossia, oral blistering, and ulcerations early-onset periodontal disease. From the sample results, it can be concluded that the clinical manifestation of EB patients is highly variable and very different in prognosis. Oral health deeply influences the quality of life of EB patients. Dental management is essential to prevent the aggravation of soft tissue damage and tooth loss and to improve the quality of life through prosthetic and restorative therapies. Dentists should consider the oral alterations of EB subtypes to perform a personalized approach to the patients' needs in a preventive and therapeutic point of view.

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.

Multivariate GWAS of Structural Dental Anomalies and Dental Caries in a Multi-Ethnic Cohort

Odontogenesis is a complex process, where disruption can result in dental anomalies and/or increase the risk of developing dental caries. Based on previous studies, certain dental anomalies tend to co-occur in patients, suggesting that these traits may share common genetic and etiological components. The main goal of this study was to implement a multivariate genome-wide association study approach to identify genetic variants shared between correlated structural dental anomalies and dental caries. Our cohort (N = 3,579) was derived from the Pittsburgh Orofacial Clefts Study, where multiple dental traits were assessed in both the unaffected relatives of orofacial cleft (OFC) cases (n = 2,187) and unaffected controls (n = 1,392). We identified four multivariate patterns of correlated traits in this data: tooth agenesis, impaction, and rotation (AIR); enamel hypoplasia, displacement, and rotation (HDR); displacement, rotation, and mamelon (DRM); and dental caries, tooth agenesis and enamel hypoplasia (CAH). We analyzed each of these four models using genome-wide multivariate tests of association. No genome-wide statistically significant results were found, but we identified multiple suggestive association signals (P < 10-5) near genes with known biological roles during tooth development, including ADAMTS9 and PRICKLE2 associated with AIR; GLIS3, WDR72, and ROR2 associated with HDR and DRM; ROBO2 associated with DRM; BMP7 associated with HDR; and ROBO1, SMAD2, and MSX2 associated with CAH. This is the first study to investigate genetic associations for multivariate patterns of correlated dental anomalies and dental caries. Further studies are needed to replicate these results in independent cohorts.

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.

Ghrelin hormone might have a potential role in amelogenesis

AIMS

Amelogenesis imperfecta and generalised enamel hypoplasia are developmental dental anomalies that affect dental enamel. While amelogenesis imperfecta results from various gene mutations, the exact underlying mechanisms of the etiopathogenesis of both remain unclear. This study aims to evaluate Ghrelin hormone levels in children with generalised enamel hypoplasia to establish whether Ghrelin might have a potential role in enamel hypoplasia's etiology. The second purpose is to determine the correlations among the blood levels of Ghrelin, growth hormone (GH), insulin-like growth factor-1 (IGF-1), bone alkaline phosphatase (BALP) and osteocalcin (OC) that are vital in dental development.

MATERIAL AND METHODS

Study was designed with two study groups, AI (hypoplastic amelogenesis imperfecta) (n = 15; mean-age 10.36 ± 1.90) and GEH (idiopathic generalised enamel hypoplasia) (n = 15; mean-age 10.42 ± 1.84), and a healthy control (n = 15; mean-age 10.39 ± 1.91) group. After fasting for 10-12 hours, simultaneous blood samples were collected; then, after centrifugation, serum and plasma were stored at -80°C until the day of analysis. Total Ghrelin levels of plasma and serum levels of GH, IGF-1, BALP and OC were measured using commercial ELISA kits.

RESULTS

Ghrelin levels of AI and GEH groups were significantly lower (P < .01) than the control group.

CONCLUSION

This is the first study to reveal the decreased levels of Ghrelin in plasma of children with generalised enamel hypoplasia, suggesting a potential role for Ghrelin in amelogenesis. In order to determine its function in enamel formation, further studies should be carried out. The result of the present study suggests that paediatricians refer children with abnormal Ghrelin levels to a paediatric dentist to contribute to appropriate prophylactic and therapeutic interventions. Generalised enamel hypoplasia may also indicate possible abnormalities in Ghrelin levels for paediatricians. Therefore, paediatricians' knowledge about the clinical appearance of generalised enamel hypoplasia should be increased.

Radiographic Diagnosis of Systemic Diseases Manifested in Jaws

Radiographic changes of the oral and maxillofacial hard tissues can be an indication of an underlying systemic disease. In this article, the range of individual disease entities that have both systemic and dental manifestations are reviewed. Images for many conditions are provided to illustrate the radiographic changes. A summary of the most common jaw affected, radiographic and pathognomonic findings, and management aspects is listed in a table format within this article for quick reference.

Ancient anomalies: Twinned and supernumerary incisors in a medieval Nubian

During the analysis of a skeletal assemblage from a medieval cemetery in Nubia (c. AD 500-1550), a young adult female with abnormally developed maxillary incisors was discovered. The possible causes of the two dental anomalies found in this individual and their archaeological context are discussed. The remains are from a medieval assemblage from the Fourth Cataract region of Nubia, which forms part of the Nubian collection curated at the British Museum. The left central incisor has a twinned crown with two root canals, and a supernumerary tooth is present on the right side between the central incisor and lateral incisors. Although two different dental anomalies are present, the bilateral expression suggests that the same biological mechanism could be responsible.

Phenotypic heterogeneity of non-syndromic supernumerary teeth: genetic study

BACKGROUND

Numerical dental anomalies, through their phenotypic diversity and etiological complexity, represent a very topical chapter in dental practice. In Romania, there is no recent complex genetic study, regarding supernumerary teeth (ST), as a whole.

PATIENTS, MATERIALS AND METHODS

In this research, through the specific genetic study of the phenotypic variability of ST, completed with clinical examinations and paraclinical investigations, to which statistical determinations were added, we performed a complex genetic-clinical and statistical analysis of ST, within a representative group, consisting of 574 patients, who came for specialized dental treatment, between 01/01/2018-05/30/2019, at the private dental offices (Lucky Dental), in Bucharest, Romania.

RESULTS

Following this study, it was possible to characterize the phenotypic variability of ST, to analyze the pattern of abnormality genetic transmission in the families of investigated patients, to identify people at risk, and specify the therapeutic conduct of choice, specific to each case.

CONCLUSIONS

We consider this paper to be of interest for medical practice by bringing new, recent data on the current prevalence of non-syndromic ST, their clinical phenotypes, and the specifics of their genetic determinism in the studied population group.

Dentine disorders and adhesive treatments: A systematic review

OBJECTIVES

A better understanding of the microstructure and mechanical properties of enamel and dentine may enable practitioners to apply the current adhesive dentistry protocols to clinical cases involving dentine disorders (dentinogenesis imperfecta or dentine dysplasia).

DATA/SOURCES

Publications (up to June 2020) investigating the microstructure of dentine disorders were browsed in a systematic search using the PubMed/Medline, Embase and Cochrane Library electronic databases. Two authors independently selected the studies, extracted the data in accordance with the PRISMA statement, and assessed the risk of bias with the Critical Appraisal Checklist. A Mann-Whitney U test was computed to compare tissues damage related to the two dentine disorders of interest.

STUDY SELECTION

From an initial total of 642 studies, only 37 (n = 164 teeth) were included in the present analysis, among which 18 investigating enamel (n = 70 teeth), 15 the dentine-enamel junction (n = 62 teeth), and 35 dentine (n = 156 teeth). Dentine is damaged in cases of dentinogenesis imperfecta and osteogenesis imperfecta (p = 2.55E-21 and p = 3.99E-21, respectively). These studies highlight a reduction in mineral density, hardness, modulus of elasticity and abnormal microstructure in dentine disorders. The majority of studies report an altered dentine-enamel junction in dentinogenesis imperfecta and in osteogenesis imperfecta (p = 6.26E-09 and p = 0.001, respectively). Interestingly, enamel is also affected in cases of dentinogenesis imperfecta (p = 0.0013), unlike to osteogenesis imperfecta (p = 0.056).

CONCLUSIONS

Taking into account all these observations, only a few clinical principles may be favoured in the case of adhesive cementation: (i) to preserve the residual enamel to enhance bonding, (ii) to sandblast the tooth surfaces to increase roughness, (iii) to choose a universal adhesive and reinforce enamel and dentine by means of infiltrant resins. As these recommendations are mostly based on in vitro studies, future in vivo studies should be conducted to confirm these hypotheses.

Relationship between upper lateral incisors anomalies and palatal displaced canine: a case-control retrospective study

BACKGROUND

An observational case-control study was designed to retrospectively assess the association among sex, skeletal and dental variables and the and the palatal maxillary canine impaction.

METHODS

The STROBE guidelines were followed. The records of 2195 subjects were analyzed. The data records of subjects with palatally displaced canine (PDC) were compared with the data of randomly selected subjects without PDC. Descriptive statistics, logistic regression model and χ2 test were used.

RESULTS

One hundred and one subjects presented at least one PDC; 106 subjects without PDC were randomly selected. From the logistic model, it was found that only gender and persistence of the deciduous canine were significantly associated with PDC. The Chi-square test showed a correlation between the presence of upper lateral incisor anomalies and PDC, otherwise, considering the unilateral impaction, there was no statistically significant difference in the relationship between canine impaction and the presence of the lateral incisor anomalies, on the same or opposite side of the impaction.

CONCLUSIONS

The female sex and the persistence of maxillary deciduous canines are associated with PDC. The anomalies of the lateral incisor do not seem to play a mechanistic role, but could rather represent a genetic variable of the canine eruption disorder.

Dental disorders in sows from Swedish commercial herds

Knowledge on dental disorders in commercial sows is limited although such conditions may have important animal welfare implications. In a pilot study, the dental and periodontal health of 58 sows (Landrace*Yorkshire-crosses) from 8 Swedish commercial pig herds, slaughtered at one abattoir, were investigated. The oral cavity was inspected and abnormalities were recorded on a dental chart modified for pigs. Dental abnormalities, absence of teeth, supernumerary teeth, tooth fractures, signs of caries, and malalignment were recorded. The study revealed that 19% of the sows had supernumerary teeth and 59% of the sows missed at least one tooth. Periodontitis, calculus and malalignment were observed in 33%, 45% and 17%, respectively. Tooth wear was very common both in incisors (total 83%) and in premolars/molars (total 84%). One or more tooth fractures (between 1 and 6 per sow) was found in 41%. Signs of caries was found in 9%. In order to assess oral health, three indices were used: calculus index (CI), periodontal index (PDI) and tooth wear index (TWI). Severe periodontitis, tooth wear in incisors and tooth wear in premolars/molars were found in 7%, 34% and 35%, respectively. With respect to animal welfare, the etiology and the effects of the disorders on health, stress and pain need to be investigated.

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.

Root Dimensions in Patients with Mild Hypodontia and a Control Group

Objectives  The aim of this study was to compare root dimensions (length and mesiodistal widths) between subjects with mild hypodontia and an age- and sex-matched control group.

Materials and Methods  Root dimension measurements of all permanent teeth excluding third molars were made on standardly taken orthopantomograms of 50 individuals (25 hypodontia and 25 controls) attending the University of Sharjah Dental Hospital. The length and two mesiodistal widths were measured for each fully formed root. The length of the root was measured digitally by drawing a line from the midpoint and bisecting the mesiodistal cemento-enamel junction (CEJ) of the tooth and extended to its apex. The mesiodistal widths of each root were measured at the cervical region and at half way of and perpendicular to the length of the root.

Statistical Analysis  Two sample t -tests were used to compare root dimension measurements between the hypodontia and control groups.

Results  There were no significant differences between genders with regard to root length or widths measurements, and therefore genders were combined for further analysis. Patients with hypodontia have significantly shorter root lengths than controls for the upper central incisors, upper canines, first premolars, and lower first molars ( p < 0.05). Similarly, root width at the midpoint of the root was found to be less in hypodontia group than that in controls for the upper central incisors, lower first premolars, upper first molars, and all second premolars ( p < 0.05). Similar pattern of differences was found with regard to the root width at the cervical region ( p < 0.05).

Conclusions  Patients with hypodontia have shorter and narrower roots of the whole permanent dentition except the upper lateral incisors, lower incisors, lower canines, and all second molars when compared with controls. In effect, this may affect the orthodontic treatment planning and implant placement.

X-ray microanalysis of dentine in primary teeth diagnosed Dentinogenesis Imperfecta type II

Aim

To analyse the elemental composition of dentine in primary teeth from children diagnosed with Dentinogenesis Imperfecta type II (DI) and from normal sound primary teeth using X-ray microanalysis.

Materials and methods

X-ray microanalysis of the elements C, O, Na, Mg, P, Cl, K and Ca were performed in the dentine of five normal primary teeth and in seven primary teeth diagnosed DI. The analysis was made in a low magnification in 10 points from the enamel-dentine junction/root surface toward the pulp. The data was also evaluated with an inductive analysis.

Results

Lower values for C were found in DI-dentine compared with normal dentine. Na had significantly higher values in DI-dentine while Mg had significantly lower values. The inductive analysis revealed that Na and Mg were the most important elements for discriminating DI-dentine from normal dentine.

Conclusions

Dentine in primary teeth from patients diagnosed with Dentinogenesis Imperfecta type II analysed with XRMA have lower values of C and Mg and higher values of O and Na compared with normal primary dentine.

Electronic supplementary material

The online version of this article (10.1007/s40368-018-0392-2) contains supplementary material, which is available to authorized users.

Etching Patterns of Sodium Hypochlorite Pretreated Hypocalcified Amelogenesis Imperfecta Primary Molars: SEM Study

Aim: To investigate the etching patterns of hypocalcified amelogenesis imperfecta (AI) in primary molars pretreated with 5.25% NaOCl prior to phosphoric acid application using scanning electron microscopy (SEM). Study design: Ten hypocalcified AI primary molars were collected, sectioned longitudinally into 2 parts and allocated into two groups of ten specimens each. The enamel surface in the first group (control group) was etched using 37% phosphoric acid gel for 15 seconds; while in the second group (study group), it was pretreated using 5.25 sodium hypochlorite(NaOCl) for 60 seconds prior to acid etching. Each specimen was examined at 16 different sites, and evaluated for the etching pattern (types I, II, and III) distribution using SEM. A total of 320 microphotographs at 1,500 magnification were obtained using Auto-Cad 2007 software. Results: The etching pattern with phosphoric acid was not uniform with predominance of type III etching (65.63%), while the pretreated enamel surfaces showed a significant increase in type I and II(82.5%) etching patterns (P<0.001). Conclusion: Treatment of primary teeth affected by hypocalcified AI using 5.25% NaOCl prior to phosphoric acid etching significantly improves the etching pattern which is required for good resin bonding.

Homozygous Recessive Versican Missense Variation Is Associated With Early Teeth Loss in a Pakistani Family

Only a few genes involved in teeth development and morphology are known to be responsible for tooth abnormalities in Mendelian-inherited diseases. We studied an inbred family of Pakistani origin in which two first-cousin born brothers are affected by early tooth loss with peculiar teeth abnormalities characterized by the absence of cementum formation. Whole exome sequencing revealed a H2665L homozygous sequence variant in the VCAN gene. Dominant splicing mutations in VCAN are known to cause Wagner syndrome or vitreoretinopathy. We explored teeth morphology in these two patients, while versican expression was assessed by western blot analysis. Early signs of vitreoretinopathy were found in the elder brother while the parents were completely negative. Our findings suggest that the homozygous recessive H2665L missense sequence variant impairs the normal morphology of the teeth roots via loss of cementum synthesis, and is also associated with early onset, recessive, Wagner syndrome, thus expanding both the phenotype mutation scenario and the inheritance mode of VCAN mutations.

Dental radiographic findings in 18 individuals with SATB2-associated syndrome

OBJECTIVE

To characterize the radiographic dental phenotype of individuals with SATB2-associated syndrome (SAS).

MATERIALS AND METHODS

Participants were evaluated by a multidisciplinary team during a concurrent clinic conducted during the 1st international SAS family meeting held in 2017 at a single institution. Whenever possible, panoramic and/or periapical radiographs were obtained in clinic or previously obtained and provided by the caregiver.

RESULTS

Of the 37 individuals evaluated, 18 (12 males, median age 8.5 years) underwent radiographic examination. Dental radiographs revealed anomalies in all individuals starting at 2 years of age. The most consistent finding was delayed development of the mandibular second bicuspids (83%) with other common radiographic findings including delayed development of the roots of the permanent teeth (78%), severely rotated (56%) or malformed teeth (44%), and taurodontism (44%).

CONCLUSIONS

Dental anomalies are fully penetrant and can be documented radiographically in all individuals with SAS.

CLINICAL RELEVANCE

Dental radiographic findings of delayed second premolar development and delayed development of permanent root formation, especially concurrent with findings of taurodontism and malformed teeth, support a clinical suspicion for SAS and should help differentiate SAS from other neurodevelopmental syndromes.

Axin2 overexpression promotes the early epithelial disintegration and fusion of facial prominences during avian lip development

The epithelial disintegration and the mesenchymal bridging are critical steps in the fusion of facial prominences during the upper lip development. These processes of epithelial-mesenchymal transition and programmed cell death are mainly influenced by Wnt signals. Axis inhibition protein2 (Axin2), a major component of the Wnt pathway, has been reported to be involved in lip development and cleft pathogenesis. We wanted to study the involvement of Axin2 in the lip development, especially during the epithelial disintegration of facial prominences. Our results show that Axin2 was expressed mainly in the epithelium of facial prominences and decreased when the prominences were about to contact each other between Hamburger-Hamilton stages 27 and 28 of chicken embryos. The epithelial integrity was destructed or kept intact by the local gain or loss of Axin2 expression, resulting in morphological changes in the facial processes and their skeletal derivatives including the maxilla, nasal, premaxilla bone, and their junctions without cleft formation. These changes were related to expression changes in nuclear β-catenin, pGSK3β, Slug, Smad3, E-cadherin, and p63. All these data indicate that Axin2 participates in the regulation of epithelial integrity and fusion by promoting epithelial disassociation, basement membrane breakdown, and seam loss during the fusion of facial prominences in lip development.

A Comparative Analysis of Tooth Size Discrepancy between Male and Female Subjects Presenting with a Class I Malocclusion

OBJECTIVES

To evaluate the tooth size discrepancy and Bolton's ratios between male and female subjects with a Class I malocclusion.

MATERIALS AND METHODS

The digital e-models of 100 male and 100 female 12-year-old southern Chinese children with a Class I malocclusion were selected. The mesiodistal widths from permanent first molar to the contralateral side first molar of the upper and lower dentitions were measured. Differences between the tooth size discrepancy, together with the anterior and overall Bolton's ratios between male and female subjects, were assessed using a two-sample t-test. A paired t-test was used to determine differences between antimetric pairs of teeth within the same arch.

RESULTS

Females had statistically significant smaller teeth than males (P < 0.05) except the upper left and lower left lateral incisor and lower left and right central incisors. The mean values of anterior Bolton's ratios for males and females were 77.04 and 77.03, respectively (P > 0.05), while the mean values of overall Bolton's ratios of male and female are 90.48 and 90.65, respectively (P < 0.05). The clinical significant differences (Cohen's d > 0.2) for contralateral tooth size were shown on the maxillary canines, lateral incisors, and central incisors of males; and mandibular canines and lateral incisors of females.

CONCLUSIONS

Southern Chinese females presenting with Class I malocclusions have smaller mesiodistal tooth dimensions compared to males. Both males and females presented several tooth size asymmetries. There are no statistical differences in anterior and overall Bolton's ratios between the genders.

A review on non-syndromic tooth agenesis associated with PAX9 mutations

Tooth agenesis in the reduction of tooth number which includes hypodontia, oligodontia and anodontia is caused by disturbances and gene mutations that occur during odontogenesis. To date, several genetic mutations that unlock the causes of non-syndromic tooth agenesis are being discovered; these have been associated with certain illnesses because tooth development involves the interaction of several genes for tooth epithelium and mesenchyme odontogenesis. Mutation of candidate genes PAX9 and MSX1 have been identified as the main causes of hypodontia and oligodontia; meanwhile, AXIN2 mutation is associated with anodontia. Previous study using animal models reported that PAX9-deficient knockout mice exhibit missing molars due to an arrest of tooth development at the bud stage. PAX9 frameshift, missense and nonsense mutations are reported to be responsible; however, the most severe condition showed by the phenotype is caused by haploinsufficiency. This suggests that PAX9 is dosage-sensitive. Understanding the mechanism of genetic mutations will benefit clinicians and human geneticists in future alternative treatment investigations.

Maxillary lateral incisor agenesis; a retrospective cross-sectional study

Objective

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

Methods

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

Results

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

Conclusion

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

Homeobox genes and tooth development: Understanding the biological pathways and applications in regenerative dental science

OBJECTIVES

Homeobox genes are a group of conserved class of transcription factors that function as key regulators during the embryonic developmental processes. They act as master regulator for developmental genes, which involves coordinated actions of various auto and cross-regulatory mechanisms. In this review, we summarize the expression pattern of homeobox genes in relation to the tooth development and various signaling pathways or molecules contributing to the specific actions of these genes in the regulation of odontogenesis.

MATERIALS AND METHODS

An electronic search was undertaken using combination of keywords e.g. Homeobox genes, tooth development, dental diseases, stem cells, induced pluripotent stem cells, gene control region was used as search terms in PubMed and Web of Science and relevant full text articles and abstract were retrieved that were written in English. A manual hand search in text books were also carried out. Articles related to homeobox genes in dentistry and tissue engineering and regenerative medicine of odontogenesis were selected.

RESULTS

The possible perspective of stem cells technology in odontogenesis and subsequent analysis of gene correction pertaining to dental disorders through the possibility of induced pluripotent stem cells technology is also inferred.

CONCLUSIONS

We demonstrate the promising role of tissue engineering and regenerative medicine on odontogenesis, which can generate a new ray of hope in the field of dental science.

Prevalence of Dental Anomalies in Odisha Population: A Panoramic Radiographic Study

AIM

The aim of this study was to evaluate the prevalence of dental anomalies (DAs) in Odisha population using panoramic radiographs.

MATERIALS AND METHODS

In this study, 1,080 panoramic radiographs were evaluated for DAs. Dental records were reviewed for diagnostic confirmation. Anomalies related to the shape, size, position of teeth, and number of roots (supernumerary roots) were evaluated.

RESULTS

The study results showed the prevalence of DAs to be 35.27%. The most prevalent was dilaceration, which was seen in 46.71% cases followed by peg laterals in 20.99%.

CONCLUSION

Dental anomalies were present in more than one-third of the study group, which was mostly related to shape of the teeth. Early diagnosis of these DAs helps in avoiding complications.

CLINICAL SIGNIFICANCE

Identification of DAs requires proper examination and thereby subsequent correct diagnosis. These anomalies can pose complications in normal functioning of orofacial complex. The knowledge of the prevalence of such anomalies aids dental practitioners for a proper treatment plan.

Maternal Smoking during Pregnancy Is Associated with Offspring Hypodontia

Little is known about environmental risk factors for hypodontia. The objective of this study was to investigate the association between hypodontia and common environmental risk factors, such as maternal smoking and alcohol and caffeine consumption during pregnancy. Eighty-nine hypodontia cases with 1 or more missing permanent lateral incisors and/or 1 or more missing premolars were enrolled in this clinic-based case-control study. Some 253 controls with no missing teeth were frequency matched to cases by age and sex. Hypodontia was diagnosed using panoramic radiographs. Sociodemographic data were collected from both the participants and their mothers, with maternal self-reported active and passive smoking, as well as alcohol and caffeine consumption during pregnancy, assessed by a questionnaire. Odds ratios (ORs) and their 95% confidence intervals (CIs) were calculated with logistic regression to assess the strength of association between risk factors and hypodontia. OR estimates were then adjusted for possible confounders, such as maternal age at delivery, sex and gestational age of the child, and household socioeconomic background. Significant associations were found between hypodontia and maternal cigarette use during pregnancy, as well as the number of cigarettes smoked per day. The consumption of 10 or more cigarettes per day during pregnancy was associated with greater odds of having a child with hypodontia (adjusted OR, 4.18; 95% CI, 1.48-11.80; P = 0.007). Observed associations between hypodontia, second-hand smoke, and alcohol and caffeine consumption were not statistically significant. Maternal smoking during pregnancy is associated with hypodontia. Larger samples and prospective observational study designs, however, are needed to investigate this association further.

Hypodontia: An Update on Its Etiology, Classification, and Clinical Management

Hypodontia, or tooth agenesis, is the most prevalent craniofacial malformation in humans. It may occur as part of a recognised genetic syndrome or as a nonsyndromic isolated trait. Excluding third molars, the reported prevalence of hypodontia ranges from 1.6 to 6.9%, depending on the population studied. Most affected individuals lack only one or two teeth, with permanent second premolars and upper lateral incisors the most likely to be missing. Both environmental and genetic factors are involved in the aetiology of hypodontia, with the latter playing a more significant role. Hypodontia individuals often present a significant clinical challenge for orthodontists because, in a number of cases, the treatment time is prolonged and the treatment outcome may be compromised. Hence, the identification of genetic and environmental factors may be particularly useful in the early prediction of this condition and the development of prevention strategies and novel treatments in the future.

Genetic Disorders of Dental Development: Tales from the Bony Crypt

PURPOSE OF REVIEW

The ebb and flow of genetic influence relative to the understanding of craniofacial and dental disorders has evolved into a tacit acceptance of the current genetic paradigm. This review explores the science behind craniofacial and dental disorders through the lens of recent past and current findings and using tooth agenesis as a model of advances in craniofacial genetics.

RECENT FINDINGS

Contemporary studies of craniofacial biology takes advantage of the technological resources stemming from the genomic and post-genomic eras. Emerging data highlights the role of key genes and the epigenetic landscape controlling these genes, in causing dentofacial abnormalities. We also report here a novel Glu78FS MSX1 mutation in one family segregating an autosomal dominant form of severe tooth agenesis as an illustration of an evolving theme, i.e., different mutations in the same gene can result in a spectrum of dentofacial phenotypic severity. The future of clinical therapeutics will benefit from advances in genetics and molecular biology that refine the genotype-phenotype correlation. Indeed, the past century suggests a continued convergence of genetic science in the practice of clinical dentistry.

Carriers with functional null mutations in LAMA3 have localized enamel abnormalities due to haploinsufficiency

The hereditary blistering disease junctional epidermolysis bullosa (JEB) is always accompanied by structural enamel abnormalities of primary and secondary dentition, characterized as amelogenesis imperfecta. Autosomal recessive mutations in LAMA3, LAMB3 and LAMC2 encoding the heterotrimer laminin 332 (LM-332) are among the genes causing JEB. While examining pedigrees of JEB patients with LAMA3 mutations, we observed that heterozygous carriers of functional null mutations displayed subtle enamel pitting in the absence of skin fragility or other JEB symptoms. Here, we report two new LAMA3 functional null mutations: nonsense c.2377C>T p.(Arg793Ter) and splice-site c.4684+1G>A mutation in heterozygous carriers exhibiting enamel pitting. Both parents had offspring affected with JEB and displayed subtle enamel pitting of secondary dentition without any sign of skin blistering. The reported enamel abnormality in LAMA3 mutation carriers could be attributed to a half dose effect of the laminin α3 chain (haploinsufficiency).

DNA methylation is critical for tooth agenesis: implications for sporadic non-syndromic anodontia and hypodontia

Hypodontia is caused by interactions among genetic, epigenetic, and environmental factors during tooth development, but the actual mechanism is unknown. DNA methylation now appears to play a significant role in abnormal developments, flawed phenotypes, and acquired diseases. Methylated DNA immunoprecipitation (MeDIP) has been developed as a new method of scanning large-scale DNA-methylation profiles within particular regions or in the entire genome. Here, we performed a genome-wide scan of paired DNA samples obtained from 4 patients lacking two mandibular incisors and 4 healthy controls with normal dentition. We scanned another female with non-syndromic anodontia and her younger brother with the same gene mutations of the PAX9,MSX1,AXIN2 and EDA, but without developmental abnormalities in the dentition. Results showed significant differences in the methylation level of the whole genome between the hypodontia and the normal groups. Nine genes were spotted, some of which have not been associated with dental development; these genes were related mainly to the development of cartilage, bone, teeth, and neural transduction, which implied a potential gene cascade network in hypodontia at the methylation level. This pilot study reveals the critical role of DNA methylation in hypodontia and might provide insights into developmental biology and the pathobiology of acquired diseases.

Prenatal ultrasound and postmortem histologic evaluation of tooth germs: an observational, transversal study

Introduction

Hypodontia is the most frequent developmental anomaly of the orofacial complex, and its detection in prenatal ultrasound may indicate the presence of congenital malformations, genetic syndromes and chromosomal abnormalities.

To date, only a few studies have evaluated the histological relationship of human tooth germs identified by two-dimensional (2D) ultrasonography. In order to analyze whether two-dimensional ultrasonography of tooth germs may be successfully used for identifying genetic syndromes, prenatal ultrasound images of fetal tooth germs obtained from a Portuguese population sample were compared with histological images obtained from fetal autopsies.

Methods

Observational, descriptive, transversal study. The study protocol followed the ethical principles outlined by the Helsinki Declaration and was approved by the Ethics Committee of the School of Dental Medicine, University of Porto (FMDUP, Porto, Portugal) and of the Centro Hospitalar de Vila Nova de Gaia/Espinho (CHVNG/EPE, Porto, Portugal) as well as by the CGC Genetics Embryofetal Pathology Laboratory. Eighty-five fetuses examined by prenatal ultrasound screening from May 2011 to August 2012 had an indication for autopsy following spontaneous fetal death or medical termination of pregnancy. Of the 85 fetuses, 37 (43.5%) were randomly selected for tooth germ evaluation by routine histopathological analysis. Fetuses who were up to 30 weeks of gestation, and whose histological pieces were not representative of all maxillary tooth germs was excluded. Twenty four fetus between the 13^th and 30^th weeks of gestation fulfilled the parameters to autopsy.

Results

Twenty four fetuses were submitted to histological evaluation and were determined the exact number, morphology, and mineralization of their tooth germs. All tooth germs were identifiable with ultrasonography as early as the 13^th week of gestation. Of the fetuses autopsied, 41.7% had hypodontia (29.1% maxillary hypodontia and 20.9% mandibular hypodontia).

Conclusions

This results indicate that prenatal ultrasound is a reliable method for detecting of hypodontia an early gestational ages. Further studies with larger samples are needed to confirm these results.

Further evidence for causal FAM20A mutations and first case of amelogenesis imperfecta and gingival hyperplasia syndrome in Morocco: a case report

Background

Amelogenesis imperfecta represents a group of developmental conditions, clinically and genetically heterogeneous, that affect the structure and clinical appearance of enamel. Amelogenesis imperfecta occurred as an isolated trait or as part of a genetic syndrome. Recently, disease-causing mutations in the FAM20A gene were identified, in families with an autosomal recessive syndrome associating amelogenesis imperfecta and gingival fibromatosis.

Case presentation

We report, the first description of a Moroccan patient with amelogenesis imperfecta and gingival fibromatosis, in whom we performed Sanger sequencing of the entire coding sequence of FAM20A and identified a homozygous mutation in the FAM20A gene (c.34_35delCT), already reported in a family with this syndrome.

Conclusion

Our finding confirms that the mutations of FAM20A gene are causative for amelogenesis imperfecta and gingival fibromatosis and underlines the recurrent character of the c.34_35delCT in two different ethnic groups.

Axis inhibition protein 2 polymorphisms may be a risk factor for families with isolated oligodontia

The objective of the present study was to search for Msh homeobox 1 (MSX1), paired box gene 9 (PAX9), ectodysplasin‑A (EDA) and axis inhibition protein 2 (AXIN2) variants in a family with isolated oligodontia and analyse the pathogenesis of mutations that result in oligodontia phenotypes. Members of a single family (but of different descent) with oligodontia and unrelated healthy controls were enrolled in our study. Genomic DNA was isolated from blood samples. Mutation analysis was performed by amplifying MSX1, PAX9, EDA and AXIN2 exons as well as their exon‑intron boundaries and sequencing the products. DNA sequencing of the AXIN2 gene revealed three mutations in the two patients with oligodontia: a homozygotic silent mutation c.1365A>G (p.Pro455=) in exon 3, two c.956+16A>G mutations (II‑1: homozygosis; III‑1: heterozygosis) and c.1200+71A>G (homozygosis) in the intron, which possibly contributed to structural and functional changes in proteins. The heterozygotic mutations c.1365A>G and c.1200+71A>G were identified in the proband's mother (II‑2). No mutations were detected in the MSX1, PAX9 and EDA genes of oligodontia patients. The findings suggest that the c.956+16A>G, c.1365A>G and c.1200+71A>G mutations of AXIN2 may be responsible for the oligodontia phenotype in this family, but these findings require further study.

Amelogenin gene influence on enamel defects of cleft lip and palate patients

The aim of this study was to investigate the occurrence of mutations in the amelogenin gene (AMELX) in patients with cleft lip and palate (CLP) and enamel defects (ED). A total of 165 patients were divided into four groups: with CLP and ED (n=46), with CLP and without ED (n = 34), without CLP and with ED (n = 34), and without CLP or ED (n = 51). Genomic DNA was extracted from saliva followed by conducting a Polymerase Chain Reaction and direct DNA sequencing of exons 2 through 7 of AMELX. Mutations were found in 30% (n = 14), 35% (n = 12), 11% (n = 4) and 13% (n = 7) of the subjects from groups 1, 2, 3 and 4, respectively. Thirty seven mutations were detected and distributed throughout exons 2 (1 mutation - 2.7%), 6 (30 mutations - 81.08%) and 7 (6 mutations - 16.22%) of AMELX. No mutations were found in exons 3, 4 or 5. Of the 30 mutations found in exon 6, 43.34% (n = 13), 23.33% (n = 7), 13.33% (n = 4) and 20% (n = 6) were found in groups 1, 2, 3 and 4, respectively. c.261 C > T (rs2106416), a silent mutation, was detected in 26 subjects, and found more significantly (p = 0.003) in patients with CLP (groups 1 and 2 - 23.75%), compared with those without CLP (groups 3 and 4 - 8.23%). In the groups without ED, this silent mutation was also found more significantly (p = 0.032) among subjects with CLP (17.65% in group 2), compared with those without CLP (7.8% in group 4). In conclusion, this study suggested that AMELX may be a candidate gene for cleft lip and palate.

An unusual double supernumerary maxillary mesiodens in a Middle Iron Age skeleton from South Uist, Western Isles, Scotland

OBJECTIVE

Bilaterally occurring and fully erupted mesiodens occur infrequently in the modern population and have been little documented from past populations. This research presents an unusual case of a double maxillary mesiodens in the permanent dentition occurring in skeletal remains dating to the Middle Iron Age (250-410 AD) from South Uist, Western Isles of Scotland.

METHODS

Osteological analysis of an adult male included the inventory of teeth present/absent and analysis of dental pathologies (caries, calculus, periodontal disease, ante-mortem tooth loss, periapical abscesses), developmental defects and orthodontic anomalies (enamel hypoplastic defects, malposition, rotation, crowding, agenesis and supernumerary teeth).

RESULTS

An unusual expression of double, fully erupted, mesiodens in the anterior permanent maxillary dentition representing supernumerary central incisors exists. The complete eruption had contributed to anterior displacement of one central incisor alveolar socket similar to documented modern clinical cases. Shallow sockets also implied an associated stunted development of the original central maxillary incisor roots. Occlusal enamel wear indicated the mesiodens had been abraded during mastication.

CONCLUSION

Current clinical data suggest there is a much higher tendency for single mesiodens to exist rather than double and examples often fail to fully erupt into the dentition. This relative rarity may account for the few previous reports of this dental anomaly from past human remains and especially of this date. The fully erupted double example from South Uist contributes to the known evidence for orthodontic anomalies in the past.

Stress response pathways in ameloblasts: implications for amelogenesis and dental fluorosis

Human enamel development of the permanent teeth takes place during childhood and stresses encountered during this period can have lasting effects on the appearance and structural integrity of the enamel. One of the most common examples of this is the development of dental fluorosis after childhood exposure to excess fluoride, an elemental agent used to increase enamel hardness and prevent dental caries. Currently the molecular mechanism responsible for dental fluorosis remains unknown; however, recent work suggests dental fluorosis may be the result of activated stress response pathways in ameloblasts during the development of permanent teeth. Using fluorosis as an example, the role of stress response pathways during enamel maturation is discussed.