Decoding the multifaceted signatures and transcriptomic characteristics of stem cells derived from apical papilla and dental pulp of human supernumerary teeth

Supernumerary teeth are advantaged sources for high-quality stem cell preparation from both apical papilla (SCAP-Ss) and dental pulp (DPSCs). However, the deficiency of the systematic and detailed comparison of the biological and transcriptomic characteristics of the aforementioned stem cells largely hinders their application in regenerative medicine. Herein, we collected supernumerary teeth for SCAP-S and DPSC isolation and identification by utilizing multiple biological tests (e.g., growth curve, cell cycle and apoptosis, adipogenic and osteogenic differentiation, and quantitative real-time polymerase chain reaction). Furthermore, we took advantage of transcriptome sequencing and multifaceted bioinformatic analyses to dissect the similarities and diversities between them. In this study, we found that SCAP-Ss and DPSCs showed indistinctive signatures in morphology and immunophenotypes, whereas with diversity in cell vitality and multi-lineage differentiation as well as gene expression profiling and differentially expressed genes-associated gene ontology and signaling pathways. Collectively, our data indicated the diversity of the multifaceted signatures of human supernumerary teeth-derived stem cells both at the cellular and molecular levels, which also supplied new references for SCAP-Ss serving as splendid alternative stem cell sources for regenerative medicine purposes.

Rare Genetic Variants in Human APC Are Implicated in Mesiodens and Isolated Supernumerary Teeth

The activation of Wnt/β-catenin signalling is a prerequisite for odontogenesis. APC, a member of the AXIN-CK1-GSK3β-APC β-catenin destruction complex, functions to modulate Wnt/β-catenin signalling to establish regular teeth number and positions. APC loss-of-function mutations are associated with the over-activation of WNT/β-catenin signalling and subsequent familial adenomatous polyposis (FAP; MIM 175100) with or without multiple supernumerary teeth. The ablation of Apc function in mice also results in the constitutive activation of β-catenin in embryonic mouse epithelium and causes supernumerary tooth formation. The objective of this study was to investigate if genetic variants in the APC gene were associated with supernumerary tooth phenotypes. We clinically, radiographically, and molecularly investigated 120 Thai patients with mesiodentes or isolated supernumerary teeth. Whole exome and Sanger sequencing identified three extremely rare heterozygous variants (c.3374T>C, p.Val1125Ala; c.6127A>G, p.Ile2043Val; and c.8383G>A, p.Ala2795Thr) in APC in four patients with mesiodentes or a supernumerary premolar. An additional patient with mesiodens was compound as heterozygous for two APC variants (c.2740T>G, p.Cys914Gly, and c.5722A>T, p.Asn1908Tyr). Rare variants in APC in our patients are likely to contribute to isolated supernumerary dental phenotypes including isolated mesiodens and an isolated supernumerary tooth.

RUNX2 Nonsense Mutation Associated with Cleidocranial Dysplasia with Unusual Dental Features

Purpose: The purpose of this case report is to describe a RUNX2 nonsense mutation associated with cleidocranial dysplasia (CCD) with unusual dental features. The patient was a 12-year-old Brazilian girl who sought dental care due to over-retention of primary teeth and absence of erupted permanent teeth. Clinical and radiographic examinations revealed multiple impacted permanent teeth, a prominent cingulum of the permanent impacted maxillary incisors and enamel defects (hypoplasia and hypomineralization) in addition to skeletal abnormalities. No supernumerary teeth were present. The diagnostic hypothesis of CCD was raised and the patient was refer- red to the genetic medical service, where the diagnosis was cofirmed. After RUNX2 genetic screening, including polymerase chain reaction and sequencing of both DNA strands, a heterozygous nonsense mutation was identified in exon 2 (c.193 C>T [Q65X]). This article reports unusual dental features in a patient with CCD.

Genetic Pattern, Orthodontic and Surgical Management of Multiple Supplementary Impacted Teeth in a Rare, Cleidocranial Dysplasia Patient: A Case Report

Background: Cleidocranial dysplasia (CCD) is a rare, autosomal dominant skeletal dysplasia with a prevalence of one per million births. The main causes of CCD are mutations in the core-binding factor alpha-1 (CBFA1) or runt-related transcription factor-2 (RUNX2), located at the 6p21 chromosomal region. RUNX2 plays important roles in osteoblast differentiation, chondrocyte proliferation and differentiation, and tooth formation. The disease is characterized by clavicular aplasia or hypoplasia, Wormian bones, delayed closure of cranial suture, brachycephalic head, maxillary deficiency, retention of primary teeth, inclusion of permanent teeth, and multiple supernumerary teeth. Materials and Methods: A 22-year-old girl suffering from cleidocranial dysplasia with short stature, narrow shoulders, craniofacial manifestations (short face, broad forehead, etc.) and dental anomalies (different lower dental elements under eruption, supernumerary and impacted multiple teeth, etc.) was examined at our service (Complex Operative Unit of Odontostomatology of Policlinico of Bari). RX Orthopantomography (OPG) and cone beam computed tomography (CBCT) were requested to better assess the position of the supernumerary teeth and their relationships with others and to evaluate the bone tissue. Results: Under eruption was probably caused by dental interferences with supernumerary teeth; hence, extractions of supernumerary upper canines and lower premolars were performed under general anaesthesia. Surgery outcome was excellent with good tissue healing and improvements in the therapeutic possibilities with future orthodontics. Conclusions: The objective of this article is to give an update about radiological, clinical, and molecular features of CCD and to alert the health team about the importance of establishing an early diagnosis and an appropriate treatment in these patients to prevent impacted teeth complications and to offer them a better quality of life.

Isolated and Sporadic Human Mesiodens Is Associated with a Synonymous Variant in the ACVR2A Gene

Purpose: The purpose of this study was to use targeted next-generation sequencing (NGS) to identify possible causative genes for isolated and sporadic human mesiodens. Methods: The targeted panel consisted of 101 target genes related to tooth development. NGS of this panel was initially performed on a discovery set (39 cases and 27 controls); association tests were performed after genotyping of nine selected variants in a validation set (57 cases and 56 controls). Results: Among these nine variants, a synonymous variant, ACVR2A (rs1128919) associated with mesiodens was identified. Moreover, in silico analysis was performed and demonstrated the instability of mRNA with the G allele. Conclusions: The formation of isolated and sporadic human mesiodens is associated with a synonymous variation in ACVR2A (rs1128919).

Identification of a novel mutation of RUNX2 in a family with supernumerary teeth and craniofacial dysplasia by whole-exome sequencing: A case report and literature review

RATIONALE

Supernumerary teeth are those that teeth in excess number than the normal count. It is usually associated with genetic syndromes when present in more numbers. Several causal genes, such as APC, NHS, TRPS1, EVC and RUNX2, have been identified. However, etiology of supernumerary teeth remains largely unclear.

PATIENT CONCERNS

A family with the clinical diagnosis of supernumerary teeth, short stature and craniofacial dysplasia was examined.

DIAGNOSES

Molecular genetic analysis found that mutation occurred in the RUNX2 gene. On the basis of this finding and clinical manifestations, the final diagnosis of cleidocranial dysplasia was made.

INTERVENTIONS

Whole exome sequencing (WES) of DNA samples was performed to identify the disease-causing mutation, including the affected child and mother as well as the healthy father.

OUTCOMES

A novel mutation of RUNX2 (c.473C>A; p.A158E) was identified in both patients, but not in normal family member and in-house database containing 3,000 Chinese Han individuals WES. This mutation was further confirmed by Sanger sequencing and predicted to be deleterious by several commonly used algorithms, including SIFT, PPT-2, MutationTaster and Proven. Furthermore, phenotype-genotype correlation analyses of all published 239 cases with different mutations in RUNX2 revealed significant association of supernumerary teeth and facial dysplasia with the Runt domain of the encoded protein.

LESSONS

This is the first WES study to identify genetic cause in Chinese patients with a novel RUNX2 mutation. Our findings expanded the mutation spectrum and clinical features of the disease and facilitated clinic diagnosis and genetic counseling.

Genetic basis of dentigerous cysts associated with supernumerary teeth: A narrative review

In the present study, we sought to: (a) analyze the p53 gene status in dentigerous cysts (DC) associated with supernumerary teeth (ST) in a pair of siblings with ST, of whom one developed a DC; and (b) conduct a narrative review of the literature on ST associated with DC. Blood samples were obtained, and the isolated DNA was used to amplify exons 4-8 of the p53 gene using specific primers, and subsequently sequenced. No mutations were identified in the coding regions of the p53 gene. A review of the literature revealed a prevalence of DC associated with ST to be as high as 13.6%, and that 83% of the case reports performed enucleation of DC and removal of ST. Dentigerous cysts associated with ST in one sibling demonstrated that variations in phenotypes exist, and the absence of mutations cannot eliminate the potential influence of genetic risk factors.

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.

Odontomas and supernumerary teeth: is there a common origin?

The aim of the present work is to analyze all scientific evidence to verify whether similarities supporting a unified explanation for odontomas and supernumerary teeth exist. A literature search was first conducted for epidemiologic studies indexed by PubMed, to verify their worldwide incidence. The analysis of the literature data shows some interesting similarities between odontomas and supernumerary teeth concerning their topographic distribution and pathologic manifestations. There is also some indication of common genetic and immuno-histochemical factors. Although from a nosological point of view, odontomas and supernumeraries are classified as distinct entities, they seem to be the expression of the same pathologic process, either malformative or hamartomatous.

A new phenotypic variant in cleidocranial dysplasia (CCD) associated with mutation c.391C>T of the RUNX2 gene

The RUNX2 gene is a physiological regulatory gene implicated in the development of cleidocranial dysplasia (CCD). A 13-month-old child presented with clinical features of CCD. At the age of 3 years the diagnosis was corroborated by clinical genetic assessment and DNA analysis, revealing a missense mutation p.R131C (c.391C>T) in RUNX2. At the age of 8 years the child was found to have a unique dental phenotype, represented by lack of supernumerary teeth and congenital absence of one tooth. A simple therapeutic approach was adopted, consisting of interceptive orthodontic treatment. The presence of this specific missense mutation in RUNX2, associated with the lack of typical supernumerary teeth may suggest a phenotype-genotype association.

Differing therapeutic approaches to cleidocranial dysplasia (CCD)

Cleidocranial dysplasia (CCD) (MIM 119600) is a genetic skeletal disorder characterised by skeletal alterations at numerous bone segments (cranium, clavicles, pelvis) and a typical hyperdontia. It is a hereditary disease of the dominant autosomal type with wide variability of expression. The constant presence of numerous supernumerary teeth poses two orders of problems. On one hand, if these supplementary teeth are impacted, they may constitute a mechanical obstacle to the eruption of normal teeth. If on the contrary they have erupted, they cause aesthetic and functional damage. Surgical therapy is indispensable to restore a correct architecture to the alveolar-dental arches, and it is recommended during childhood to avoid or at least reduce complications in adulthood. Two cases of cleidocranial dysplasia are here reported. The adult patient (Case 1), reached our observation with a poor oral situation, manifested relapsing odontogenic abscesses at several impacted supernumerary teeth. The surgical treatment was complex and invasive, requiring percutaneous access in order to remove a tooth embedded in the mandible and the extraction of almost all residual teeth. This outcome was avoided in the second case, through combined surgical-orthodontic treatment that entailed extraction of the supernumerary teeth and subsequent orthodontic treatment, with restoration of a normal occlusion. In conclusion, management of patients suffering from very rare pathologies should be carefully evaluated in relation to clinical characteristics and possible local and systemic complications. The aim of this study is to illustrate two cases managed in a paradigmatically opposite way. It is paramount for the surgeon to intercept cases of hyperodontia typical of CCD at an early phase. It is possible, through correct surgical-orthodontic treatment, not only to avoid local and general complications, but also to achieve proper occlusion.

Inactivation of IL11 signaling causes craniosynostosis, delayed tooth eruption, and supernumerary teeth

Craniosynostosis and supernumerary teeth most often occur as isolated developmental anomalies, but they are also separately manifested in several malformation syndromes. Here, we describe a human syndrome featuring craniosynostosis, maxillary hypoplasia, delayed tooth eruption, and supernumerary teeth. We performed homozygosity mapping in three unrelated consanguineous Pakistani families and localized the syndrome to a region in chromosome 9. Mutational analysis of candidate genes in the region revealed that all affected children harbored homozygous missense mutations (c.662C>G [p.Pro221Arg], c.734C>G [p.Ser245Cys], or c.886C>T [p.Arg296Trp]) in IL11RA (encoding interleukin 11 receptor, alpha) on chromosome 9p13.3. In addition, a homozygous nonsense mutation, c.475C>T (p.Gln159X), and a homozygous duplication, c.916_924dup (p.Thr306_Ser308dup), were observed in two north European families. In cell-transfection experiments, the p.Arg296Trp mutation rendered the receptor unable to mediate the IL11 signal, indicating that the mutation causes loss of IL11RA function. We also observed disturbed cranial growth and suture activity in the Il11ra null mutant mice, in which reduced size and remodeling of limb bones has been previously described. We conclude that IL11 signaling is essential for the normal development of craniofacial bones and teeth and that its function is to restrict suture fusion and tooth number. The results open up the possibility of modulation of IL11 signaling for the treatment of craniosynostosis.

[Pierre Marie-Sainton cleidocranial dysplasia]

The paper presents a family with hereditary transmitted Marie-Sainton dysplasia affecting the father and his both children. This is a rare syndrome presenting an autosomal pattern of inheritance, characterized by a generalized defect in both membranous and endochondral bone formation resulting in clavicular aplasia, delayed ossification of the fontanelles and the sutures of the skull and prolonged retention of deciduous dentition with delayed eruption of the permanent teeth. The diagnosis is suggested by more or less complete clinical picture and confirmed by multiple radiological explorations (skull, thorax, spinal column, pelvis) and genetical examination. The genetic mutation for cleidocranial dysplasia (CCD) is found on chromosome six and is called CBFA1 (short for core biding factor al or RUNX2) and is the only gene known to be associated with CCD. The normal version of CBFA1 acts to induce osteoblasts which are the type of cells that lay down bone. Although associated psychosocial disorders can occur, the prognosis and life expectancy of this condition are favorable being conditioned however by the complexity of orthodontic procedures which are determinant for these patients life quality.

Non-syndromic multiple supernumerary teeth in a family unit with a normal karyotype: case report

Introduction. Hyperdontia is an odontostomatologic anomaly characterized by an excess in tooth number. It seems to occur more often in patients with hereditary factors concerning this anomaly: this case represents a rare form of hyperdontia, with bilateral multiple supernumerary teeth, with evident penetrance of the phenotype in the family unit engaged in the present study. The karyotype determination excludes a pathogenesis on chromosomal basis.Case report. A 30 years old patient came to our observation with five impacted teeth (1.8, 2.8, 3.8, 4.7 and 4.8), as well as with the presence of an impacted supernumerary tooth (distomolar 4.9). The patient was suggested to allow us to perform a radiologic screening to his two sisters aged 17 and 13 years.The X-ray photography showed that the elder sister had nine impacted teeth; these were 1.8 - 1.9 - 2.8 - 2.9 - 2.10 - 3.8 - 3.9 - 4.8 - 4.9; while the youngest sister had four impacted teeth, that is 1.8 - 1.9 - 2.8 - 2.9.Conclusions. The value of the present case report can be used as a paradigm for the assessment of the hereditary factors predisposing the onset of hyperdontia, and for the consequent management by oral surgeon of family units in which the odontostomatologic anomaly was detected without any syndromic forms.

Identical unerupted maxillary incisors in monozygotic twins

Mesiodens is the most common type of supernumerary tooth found in the premaxilla. It might be discovered by the orthodontist by chance on a radiograph or as the cause of an unerupted maxillary central incisor. The genetic transmission of supernumerary and impacted teeth is poorly understood. The occurrence of identical unerupted maxillary central incisors and mesiodentes in monozygotic twins suggests that genetic factors might influence the etiology of this problem. In this case report, we discuss the treatment of unerupted maxillary permanent incisors caused by mesiodentes in monozygotic twins.

Controlling the number of tooth rows

The organization and renewal capacity of teeth vary greatly among vertebrates. Mammals have only one row of teeth that are renewed at most once, whereas many nonmammalian species have multirowed dentitions and show remarkable capacity to replace their teeth throughout life. Although knowledge on the genetic basis of tooth morphogenesis has increased exponentially over the past 20 years, little is known about the molecular mechanisms controlling sequential initiation of multiple tooth rows or restricting tooth development to one row in mammals. Mouse genetics has revealed a pivotal role for the transcription factor Osr2 in this process. Loss of Osr2 caused expansion of the expression domain of Bmp4, a well-known activator of tooth development, leading to the induction of supernumerary teeth in a manner resembling the initiation of a second tooth row in nonmammalian species.

[Occurrence of supernumerary upper incisor teeth in Pax6-/- mouse fetuses]

OBJECTIVE

To investigate the occurrence of supernumerary upper incisor teeth in Pax6-/- mouse fetuses and to provide a model to explore the role of Pax6 in the upper incisor development and the mechanism of supernumerary teeth involving Pax6.

METHODS

Twenty Pax6-/- mouse fetuses of strain DEBA were isolated on E18.5 (embryonic day). The fetuses were sectioned serially in coronal plane and stained with haematoxylin and erosion, then the presence of supernumerary teeth in the upper anterior area was examined histologically, and also the number, morphology and structure of lower incisor germs and the first and second molar germs in the maxilla and mandible were observed histologically. Eighteen E18.5 mouse fetuses of strain DEBA with Pax6+/+ genotype were used as control.

RESULTS

Of the 20 Pax6-/- fetuses examined, four possessed a single supernumerary tooth in the upper incisors' region. No supernumerary upper incisor teeth were observed in any of the 18 Pax6+/+ fetuses examined. In the regions of lower incisors and the first and second molars of the maxilla and mandible, no significant difference was observed between Pax6-/- and Pax6+/+ fetuses regarding the number, morphology and structure of tooth germs.

CONCLUSIONS

The results suggest that Pax6 played an important role in the development of upper incisor teeth in mice.

Unraveling the molecular mechanisms that lead to supernumerary teeth in mice and men: current concepts and novel approaches

Supernumerary teeth are defined as those that are present in excess of the normal complement of human dentition and represent a unique developmental anomaly of patterning and morphogenesis. Despite the wealth of information generated from studies on normal tooth development, the genetic etiology and molecular mechanisms that lead to congenital deviations in tooth number are poorly understood. For developmental biologists, the phenomenon of supernumerary teeth raises interesting questions about the development and fate of the dental lamina. For cell and molecular biologists, the anomaly of supernumerary teeth inspires several questions about the actions and interactions of transcription factors and growth factors that coordinate morphogenesis, cell survival and programmed cell death. For human geneticists, the condition as it presents itself in either syndromic or non-syndromic forms offers an opportunity to discover mutations in known or novel genes. For clinicians faced with treating the dental complications that arise from the presence of supernumerary teeth, knowledge about the basic mechanisms involved is essential. The purpose of this manuscript is to review current knowledge about how supernumerary teeth form, the molecular insights gained through studies on mice that are deficient in certain tooth signaling molecules and the questions that require further research in the field.

Rudiment incisors survive and erupt as supernumerary teeth as a result of USAG-1 abrogation

The term "supernumerary teeth" describes production of more than the normal number of teeth in the primary or permanent dentitions. Their aetiology is not understood. Uterine sensitization associated gene-1 (USAG-1) is a BMP antagonist that plays important roles in the local regulation of BMP signaling by binding and neutralizing BMP activities, and also serves as a modulator of Wnt signaling. We report here that USAG-1 deficient mice have supernumerary teeth. The supernumerary maxillary incisor appears to form as a result of the successive development of the rudimentary upper incisor tooth. We confirmed that the USAG-1 expression is localized to the epithelium and mesenchyme of the rudimentary maxillary incisor tooth organ formation. USAG-1 abrogation rescued apoptotic elimination of odontogenic mesenchymal cells. Based upon these results, we conclude that USAG-1 controls the number of teeth in the maxillary incisor region by regulating apoptosis.

Inherited dental anomalies: a review and prospects for the future role of clinicians

Inherited dental anomalies such as hypodontia, supernumerary teeth, enamel defects, and diastema are evident in large segments of most populations. Although treatment options for many of these conditions are ever improving, much remains to be understood about their etiology and pathophysiology. In this review, the authors hope to enthuse dental professionals into aiding the human geneticist by collaborating in studies seeking the underlying genetic cause of dental anomalies and referring patients presenting these conditions to the human geneticist.

Autosomal dominant inherence of multiple supernumerary teeth

The case is presented of 16 supernumerary teeth in an 11-year-old Chinese female patient with congenital cardiopathy. It was found that the patient's mother had the same clinical manifestation. A detailed investigation into the family history was carried out. Though the etiology of this dental anomaly remains unclear, genetics as a key factor in the development of supernumerary teeth is highlighted.

[Genetic studies of a Chilean family with three different dental anomalies]

BACKGROUND

Congenital dental anomalies can affect up to 25% of the population.

AIM

To report the genetic study of a family with dental anomalies.

MATERIAL AND METHODS

We studied a Chilean family presenting with three independent dental phenotypes: third molar agenesis, supernumerary teeth, and dentinal dysplasia type I. We searched for mutations in candidate genes proposed for tooth agenesis and supernumerary teeth: IRF6, FGFR1, MSX1, MSX2, PAX9, PRDM16 and TGFA. We also studied DSPP as a candidate gene for dentinal dysplasia type I.

RESULTS

We did not find mutations in FGFR1, MSX2, PAX9, PRDM16, or TGFA. We found a MSX1 mutation (G16D) in both affected and unaffected family members. Also, we found a genetic variation not described before in IRF6 in the dentinal dysplasia type I case.

CONCLUSIONS

Further investigation is necessary to evaluate if these variants are functional in nature. Finally, we are reporting a mutation in DSPP in an asymptomatic 2-year-old child, which illustrates the ethical pitfalls of interpreting molecular data for genetic counseling of young and/or asymtomatic individuals.

Familial occurrence of nonsyndromal multiple supernumerary teeth. A rare condition

The occurrence of multiple supernumerary teeth is a rare phenomenon and is often found in association with syndromes such as cleidocranial dysplasia, Gardners syndrome, or cleft lip and palate. Only a few examples of nonsyndromal multiple supernumerary teeth have been reported in the literature. There is a predilection for the mandible and in the premolar area followed by the molar and anterior regions. This article reports the presence of nonsyndromal multiple supernumerary teeth involving both jaws in children and in their mothers. The clinical and radiographic appearance of the anomalies and treatment modalities are discussed.

Non-syndromic multiple supernumerary teeth transmitted as an autosomal dominant trait

Supernumerary teeth are common in the general population and occur more frequently in-patients with family history of such teeth. Multiple supernumerary teeth are associated with cleidocranial dyplasia and Gardner syndrome. However it is rare to find multiple supernumeraries in individuals with no other associated disease or syndrome. We describe the occurrence of multiple supernumerary teeth in a family occurring as a non-syndromal trait. The autosomal dominant transmission of non-syndromal multiple supernumerary teeth is new.

[Oral and maxillofacial manifestations of familial adenomatosis polyposis. Gardner's syndrome]

Patients suffering from familial adenomatosis polyposis develop multiple pre-malignant gastrointestinal polyps and are at high risk of developing colon cancer. In addition extra-intestinal manifestations are observed frequently. The combination of extra-intestinal manifestations and familial adenomatosis polyposis is named Gardner's syndrome. An early diagnosis of this disease is important because it could mean a better prognosis for the patient. This review describes the oral and maxillofacial symptoms of FAP, and its potential implications for dental treatment.

Epigenetic influences may explain dental differences in monozygotic twin pairs

BACKGROUND

Comparisons between monozygotic (MZ) co-twins have tended to focus on the similarities between their dentitions rather than differences. The aim of this study was to determine the prevalence of discordant expression for simple hypodontia and supernumerary teeth in MZ twin pairs and to explain how phenotypic differences might occur despite their similar genotypes.

METHODS

Records of 278 pairs of MZ twins, including dental casts and radiographs, were examined and the prevalences of discordant expression for missing upper lateral incisors (ULI) or second premolars (PM2), and of mesiodentes, were determined. Zygosities were confirmed by comparisons of blood markers and DNA.

RESULTS

There was evidence of at least one missing ULI or PM2 in 24 of the 278 MZ pairs (8.6 per cent), with 21 of these 24 pairs (87.5 per cent) showing discordant expression. Nine of the 278 MZ pairs (3.2 per cent) displayed evidence of mesiodentes, with eight of these nine pairs (88.9 per cent) being discordant.

CONCLUSION

Our findings show that differences in the expression of missing or extra teeth occur often between MZ co-twins whose genetic make-up predisposes them to simple hypodontia or mesiodentes. We postulate that minor variations in epigenetic events during odontogenesis may account for these distinct differences.

[Anomalies of the skull in cleidocranial dysplasia]

BACKGROUND

The description of the otorhinolaryngeal and craniofacial anomalies in patients with cleidocranial dysplasia.

METHODS

For this study, 26 patients with cleidocranial dysplasia were examined after their medical history had been recorded. The main focus was placed on otorhinolaryngological and orthodontic findings.

RESULTS

The portion of spontaneous mutations in our patient population was 46.1%. All patients exhibited otorhinolaryngological and craniofacial anomalies. While single ENT-anomalies were expressed in 76.9%-92.3% of the patients, the craniofacial findings were distributed over 84.6%-92.3%.

CONCLUSION

The expression of this rare disorder is variable and its symptomatology not always distinct. Otorhinolaryngological and craniofacial anomalies are often apparent. Appropriate treatment can significantly contribute to an improvement in the patient's quality of life. In cases of ambiguous findings, we recommend consultation with an experienced clinician as well as genetic counselling.

Five mandibular incisors: an autosomal recessive trait?

A fifth mandibular incisor is a eumorphic supernumerary tooth and has rarely been described in the medical literature. We report here a large Lebanese consanguineous family where four individuals displayed five incisors in the anterior mandible. Such familial observation has not been previously described. The possibility of an autosomal recessive inheritance for this nonsyndromic trait is discussed.

Supernumerary teeth "mesiodens". Case report

The supernumerary tooth is an anomaly of dental eruption that is not rare to find in the clinical practice. Among the supernumerary teeth the "mesiodens" is most frequent. The mesiodens is found in the region of the superior central incisors and it can be the cause of many complications. The aim of this work is the description of a rare symptomatic case of mesiodens and the diagnostic and therapeutic strategies to adopt when this dental anomaly occurs. In particular the authors suggest making radiographic examinations only in the family of patients with dental anomalies of number, thinking that the incidence of such anomalies is too low to justify mass radiographic examinations.

Familial occurence of mesiodens--a case report

Molariform supernumerary teeth in the maxillary central incisor area are uncommon. This article reports the presence of a molariform mesiodens in daughter and a conical mesiodens in father. Detailed investigation into family history of patients with mesiodens is needed. Though the etiology of this dental anomaly remains unclear, genetics as a key factor in the development of supernumerary teeth is highlighted.

Further studies of a model for the etiology of anomalies of tooth number and size in humans

A multifactorial model based on an underlying continuous distribution of tooth size, with thresholds determining hypodontia and supernumeraries, has been proposed [1]. Our aim is to investigate this model by comparing tooth morphology of affected patients and their first degree relatives with normal controls. An image analysis system [2] was used to measure teeth on study models of controls, patients with hypodontia of varying degrees and location, first-degree relatives of hypodontia index cases, and patients with supernumerary teeth in the maxillary incisor region. Mesio-distal crown size in hypodontia patients was smaller than controls, and this difference was significant for all tooth types. There was a general pattern: the more severe the hypodontia, the smaller the size of the tooth formed. Patients with supernumerary teeth had permanent maxillary central and lateral incisors and canines that were significantly larger in mesio-distal width than controls. The maxillary central incisors also differed in taper in supernumerary patients compared to controls. Hypodontia prevalence was higher in first-degree relatives (22%) of hypodontia index cases than in the general population (4.4%), and unaffected relatives had smaller teeth than controls. Thus, there were generalized and localized effects within the dentition, and these findings are compatible with the statistical expectations of the proposed multifactorial model.

Non-syndrome multiple supernumerary teeth in Nigerians

The present study was carried out to ascertain frequency of multiple supernumerary teeth not associated with syndrome in Nigerians. A total of 13 patients comprising of 10 males (76.92%) and 3 female (23.07%) representing 0.098% of the study population had multiple supernumerary teeth. Multiple supernumerary teeth without any associated systemic diseases or syndrome are rare as reported by BLUMENTHAL (3) RUHLMAN and NEELY (17), KANTOR et al. (10) is not the case in this study. The maxillary region has the highest frequency of occurrence with 12 times (66.67%) followed by the mandibular premolar region with 4 times (22.22%) while maxillary premolar and mandibular anterior region shared (5.55%) respectively. The conical and tuberculate types of supernumerary teeth were found in the midline region, while the supplemental supernumerary teeth were more in the mandibular premolar region with 12 (70.58%) follow by maxillary midline 4 (23.52%) and the lower incisor region 1 (5.88%) which is in consonant with WINTER and BROOK (2), STAFNE (19) NAZIF, FUTALO ZULLO (15). The role of genetics in the aetiology of multiple supernumerary teeth as found in this study, the occurrence of supernumerary teeth on two brothers and a daughter to one of the affected brothers, tends, to suggest an autosomal dominant mode of inheritance and the challenges to management by the orthodontists are discussed.

Fusion of the permanent maxillary right incisor to a supernumerary tooth in association with a gemination of permanent maxillary left central incisor: a dental, genetic and dermatoglyphic study

The relationship between fusion of the permanent maxillary right central incisor to a supernumerary tooth in association with gemination of permanent maxillary left central incisor and dermatoglyphics were investigated.

Congenital tooth anomalies and malocclusions: a genetic link?

The aim of the present study was to investigate putative relationships between different malocclusions such as Class III and Class II division 1, and congenital tooth anomalies. Two-hundred Class III and 215 Class II division 1 patients were examined for the presence of any of the following congenital tooth anomalies: maxillary incisor hypodontia, maxillary canine impaction, transpositions, supernumerary teeth, and tooth agenesis. Their occurrence rates were then calculated as a percentage of the total sample and were compared for statistical differences. The results revealed no statistical difference (P > 0.05) in the occurrence rates of upper lateral incisor agenesis, peg-shaped laterals, impacted canines, or supernumerary teeth between the Class III and the Class II division 1 malocclusions. When the occurrence rate of all congenital tooth anomalies was compared between the two malocclusions, Class III subjects showed significantly higher rates (P < 0.05). Comparison with published surveys on general populations showed similar occurrence rates. It can be concluded that subjects with Class III and Class II division 1 malocclusions show patterns of congenital tooth anomalies similar to those observed in the general population. Congenital tooth anomalies may represent another criterion for the study of malocclusion, with respect to their origin and development.

Similar locations of impacted and supernumerary teeth in monozygotic twins: a report of 2 cases

In this article, the cases of monozygotic twin brothers with similar developmental dental anomalies have been presented. Localization of impacted and supernumerary teeth and synchronous appearance of analogous ailments (leading to third tonsil removal and removal of supernumerary teeth from the anterior maxilla) are discussed. The boys' mother had also been treated for supernumerary teeth during childhood.

Retention of permanent incisors by mesiodens: a family affair

The term mesiodens refers to a supernumerary tooth that is present in the midline of the maxilla between the two central incisors. One or two mesiodentes may be present. We present a rare case of two sisters, in both of whom a pair of mesiodentes caused the retention of permanent incisors. They were referred to our hospital with asymptomatic delayed eruption of upper incisors. This article is written to point out genetic factors as the possible origin of supernumerary teeth.

Orthodontic, genetic, and periodontal considerations in the treatment of impacted maxillary central incisors: A study of twins

Treatment of twins each with one impacted maxillary central incisor and a mesiodens is described. Treatment included rapid expansion, extraction of the mesiodens, surgical exposure of the impacted central incisor, and its forced eruption. The impacted incisor was brought into functional position in one patient but was lost in the other because of insufficient root length and high mobility. Orthodontic, genetic, and periodontal considerations of these 2 cases are evaluated.

Inverted impaction of a mesiodens: a case report

Dental, radiological, dermatoglyphic and genetic findings of a patient showing inverted impaction of a mesiodens are presented. It is probable that the inversion of the mesiodens was caused by contact of the incisal edge of the crown of the mesiodens by the apex of the root of the erupting right maxillary central incisor tooth.

Taurodontism in association with supernumerary teeth

The dental, radiological, genetic and dermatoglyphic findings of an additional patient with taurodontism in association with supernumerary teeth were presented and the findings of the patient were compared with those in the literature.

A rare case of hereditary multiple impacted normal and supernumerary teeth

An eight-year-old girl residing in Bangalore presented with a complaint of retained primary maxillary and mandibular incisors. Radiographic examination of the case revealed multiple impacted permanent succedaneous teeth with deficient resorption of primary teeth and multiple impacted supernumerary teeth. Family history revealed that the mother also exhibited multiple impacted supernumerary teeth. Based on the clinical presentation, radiographic examination and histopathological studies, this paper discusses the differential diagnosis and management of such a case.

Multiple supernumerary teeth in two brothers: a case report

Supernumerary teeth (hyperdontia) are relatively common in the general population and occur more frequently in patients with a family history of such teeth. Supernumerary teeth have been reported in many genetic syndromes, but multiple supernumerary teeth occurring as an isolated non-syndromic trait are rare. This article describes a rare non-syndromic variety of multiple impacted supernumerary teeth in two brothers.

A controlled study of associated dental anomalies

The purpose of this study was to reveal patterns of association among seven types of dental anomalies (aplasia of second premolars, small size of maxillary lateral incisors, infraocclusion of primary molars, enamel hypoplasia, ectopic eruption of first molars, supernumerary teeth, and palatal displacement of maxillary canines) in an untreated orthodontic population, ages 7 to 14. The prevalence of associated tooth anomalies in seven groups of 100 subjects selected according to one primarily diagnosed dental anomaly was compared with the prevalence of the examined dental anomalies in a control group of 1,000 subjects. Significant reciprocal associations (p < 0.005) were found among five of the anomalies (aplasia of second premolars, small size of maxillary lateral incisors, infraocclusion of primary molars, enamel hypoplasia, and palatal displacement of maxillary canines), suggesting a common genetic origin for these conditions. Supernumerary teeth appeared to be a separate etiological entity with respect to all other examined tooth anomalies. The existence of associations between different tooth anomalies is clinically relevant, as the early diagnosis of one anomaly may indicate an increased risk for others.

Familial occurrence of mesiodentes with unusual findings: case reports

Supernumerary teeth are common and can occur throughout the oral cavity. Molariform supernumerary teeth in the maxillary central incisor area have rarely been reported. This article reports the presence of mesiodentes in two siblings, one of whom exhibited an unusual molariform mesiodens. The clinical and radiographic appearance of the anomalies and treatment modalities are discussed.

Supernumerary premolar teeth in siblings

The familial nature of supernumerary teeth is discussed in this paper and illustrated with a report showing the development of supernumeraries in siblings. The orthodontic treatment and possible sequelae to the development of supernumerary teeth in the premolar region is highlighted.

Genetic background effects on dental and other craniofacial abnormalities in homozygous small eye (Pax6Sey/Pax6Sey) mice

Small eye (Pax6Sey) is a semi-dominant mutation affecting development of the eyes, brain and nasal structures. The mutant phenotype arises from defects within the Pax6 gene and several mutant alleles have been identified. A previous study reported that Pax6Sey/Pax6Sey homozygotes, in a random-bred stock, had a median cartilaginous rod-like structure in the nasal region and 80% had supernumerary upper incisor teeth. In this study we show that supernumerary upper incisor teeth and a previously unreported nasal capsule-derived cartilaginous 'spur' occur in compound heterozygous Pax6Sey-Neu/Pax6Sey and homozygous Pax6Sey/Pax6Sey fetuses from several strains of mice. The frequencies of the abnormal phenotypes were not related to allele type but showed variable penetrance, which was dependent on genetic background. The median nasal cartilaginous rod-like structure was present in all homozygous small eye fetuses. The Pax6Sey/Pax6Sey homozygote may provide insight into the complex gene interactions involved in eye, nasal and craniofacial morphogenesis.

Mesiodentes: incidence, morphology, etiology

There are many publications in the literature focusing on clinical, radiological and surgical aspects of the treatment of mesiodentes. However, the etiology of this dental anomaly remains widely unclear. The purpose of this study was to evaluate etiologic factors for mesiodentes in a collective comprising 30 patients with a total of 45 mesiodentes. Thirty-one percent of the patients showed a familial disposition, pointing to inheritance as a key factor in the development of mesiodentes. Our results further support the hypothesis of related etiologic factors for several dental and craniofacial anomalies, such as hyperdontia, hypodontia and cleft lip and palate. Finally, we report the gemination of a deciduous incisor on the same side as a mesiodens. We also found differences in the mesiodistal width of central incisors depending on unilateral or bilateral occurrence of mesiodentes. Both these findings support the dichotomy theory of the split in the tooth bud inducing the development of mesiodentes, a theory we favor over that of local hyperactivity of the dental lamina.

Dental findings in parents of children with cleft lip and palate

The incidence of dental abnormalities in the cleft lip and palate population has been reported to be much higher than in the normal population. The role of genes in the production of a cleft lip and palate, and dental anomalies is thought to be complex, with autosomal dominant, recessive, and x-linked genes all playing a role. Noncleft parents can carry some of the cleft lip and palate genes, which produce clinically subtle manifestations in their facial skeleton. The purpose of this study was to look for evidence of increased dental anomalies in the non-cleft parents of cleft lip and palate children. The dentitions of the parents of 60 children with different types of cleft lip and palate were examined prospectively to see whether or not they exhibited features found more readily in the cleft lip and palate rather than did the normal population. Their dentitions were studied to record the following dental features: congenitally missing teeth, supernumerary teeth, or morphologic changes of the crowns of the permanent teeth. The number and position of any frenal attachments were also recorded. The results of this study did not show any differences in incidence of dental anomalies from the noncleft population. There was no evidence to support the hypothesis that congenital absence of lateral incisors is a microform of cleft lip and palate. Further, these results also failed to reveal any consistent pattern in the number and position of frenal attachments.

Severe dental aberrations in familial steroid dehydrogenase deficiency: a new association

Severe numerical dental aberrations are rare, and are most often seen as a part of certain syndromes. We here report on a Saudi Arabian family where first-cousin marriages have caused numerical and structural dental abnormalities linked to autosomal recessively inherited liver diseases. The two latest affected children in this family have had their liver defect successfully treated with fat-soluble vitamins and chenodeoxycholic acid, enabling us to study their dental development. One boy exhibits 11 supernumerary teeth, a general hypomineralisation and enamel hypoplasia, while an affected cousin successfully diagnosed at an early age, so far, only suffers from structural enamel defects. The children are otherwise healthy. There is no resemblance to any known syndromes. We suggest that the supernumerary teeth and the liver disease are caused by the same genetic defect, and represent a new association. The hypomineralisation, however, is most likely to result from vitamin deficiency secondary to malabsorption during the first years of life, before successful treatment was instituted.