Etiological Mechanisms and Genetic/Biological Modulation Related to PTH1R in Primary Failure of Tooth Eruption.

Primary failure of eruption (PFE) is a rare disorder that is characterized by the inability of a molar tooth/teeth to erupt to the occlusal plane or to normally react to orthodontic force. This condition is related to hereditary factors and has been extensively researched over many years. However, the etiological mechanisms of pathogenesis are still not fully understood. Evidence from studies on PFE cases has shown that PFE patients may carry parathyroid hormone 1 receptor (PTH1R) gene mutations, and genetic detection can be used to diagnose PFE at an early stage. PTH1R variants can lead to altered protein structure, impaired protein function, and abnormal biological activities of the cells, which may ultimately impact the behavior of teeth, as observed in PFE. Dental follicle cells play a critical role in tooth eruption and root development and are regulated by parathyroid hormone-related peptide (PTHrP)-PTH1R signaling in their differentiation and other activities. PTHrP-PTH1R signaling also regulates the activity of osteoblasts, osteoclasts and odontoclasts during tooth development and eruption. When interference occurs in the PTHrP-PTH1R signaling pathway, the normal function of dental follicles and bone remodeling are impaired. This review provides an overview of PTH1R variants and their correlation with PFE, and highlights that a disruption of PTHrP-PTH1R signaling impairs the normal process of tooth development and eruption, thus providing insight into the underlying mechanisms related to PTH1R and its role in driving PFE.

Genotype-phenotype analysis of selective failure of tooth eruption-A systematic review.

Tooth eruption is an important and unique biological process during craniofacial development. Both the genetic and environmental factors can interfere with this process. Here we aimed to find the failure pattern of tooth eruption among five genetic diseases. Both systematic review and meta-analysis were used to identify the genotype-phenotype associations of unerupted teeth. The meta-analysis was based on the characteristics of abnormal tooth eruption in 223 patients with the mutations in PTH1R, RUNX2, COL1A1/2, CLCN7, and FAM20A respectively. We found all the patients presented selective failure of tooth eruption (SFTE). Primary failure of eruption patients with PTH1R mutations showed primary or isolated SFTE1 in the first and second molars (59.3% and 52% respectively). RUNX2 related cleidocranial dysplasia usually had SFTE2 in canines and premolars, while COL1A1/2 related osteogenesis imperfecta mostly caused SFTE3 in the maxillary second molars (22.9%). In CLCN7 related osteopetrosis, the second molars and mandibular first molars were the most affected. While FAM20A related enamel renal syndrome most caused SFTE5 in the second molars (86.2%) and maxillary canines. In conclusion, the SFTE was the common characteristics of most genetic diseases with abnormal isolated or syndromic tooth eruption. The selective pattern of unerupted teeth was gene-dependent. Here we recommend SFTE to classify those genetic unerupted teeth and guide for precise molecular diagnosis and treatment.

Primary failure of eruption: Clinical and genetic findings in the mixed dentition.

OBJECTIVE: To test the hypothesis that mutations in the parathyroid hormone 1 receptor ( PTH1R) include effects in both primary and permanent teeth. MATERIALS AND METHODS: DNA was extracted from saliva samples of 29 patients (8 familial and 21 sporadic) who presented with clinical evidence of infraoccluded teeth, and their unaffected relatives (N = 22). Sequencing followed by mutational analysis of the coding regions of PTH1R gene was completed for all individuals (N = 29). RESULTS: Eight of 29 cases revealed a heterozygous pathogenic variant in the PTH1R gene; five of eight variants represented distinct mutations based on comparison with the dbSNP, HGMD, and ESP databases. One mutation (c.1765 T>C p.Trp89Arg) was found to segregate within a family (n = 3). In silico analyses for all variants revealed a putative pathogenic effect. A genotype-phenotype correlation was reported as defined by a functional mutation in PTH1R and corresponding effects on one or more posterior teeth only; unilateral or bilateral involvement, infraoccluded primary teeth. CONCLUSIONS: Novel mutations were reported in the PTH1R gene that included PFE-affected primary molars, thus providing the basis for using a genetic diagnostic tool for early diagnosis leading to proper management.

[Tooth eruption disturbances and syndromes]. / Eruptiestoornissen en syndromen.

In the tooth eruption mechanism, various disturbances can appear as a result of gene mutations, a consequence of which can be that tooth eruption does not occur. There are 5 syndromes which involve the complete failure of several or even all teeth to erupt, specifically: cleidocranial dysplasia, Gardner's syndrome, osteopetrosis, mucopolysaccharidosis and GAPO syndrome. Some are very rare and will seldom be encountered in a dental practice, but they show how vulnerable the tooth eruption mechanism is. Dentists are generally the ones who identify a tooth eruption problem in a patient. Since syndromes can be associated with other disorders, additional investigation by a clinical geneticist is always important when a syndrome is suspected.

Establishing the diagnostic criteria for eruption disorders based on genetic and clinical data.

INTRODUCTION: Proper diagnosis and management of eruption disturbances remains challenging but is critical to a functional occlusion. The objective of this study was to establish definitive criteria to differentiate and diagnose eruption disorders, specifically primary failure of eruption (PFE) and ankylosis. METHODS: Sixty-four affected persons were placed into 3 cohorts: PFE diagnosed through confirmed PTH1R mutation (n = 11), PFE diagnosed based on clinical criteria (n = 47), and ankylosis diagnosed based on clinical criteria (n = 6). These groups were assessed to identify clinical features that differentiate PFE and ankylosis. RESULTS: Ninety-three percent of the subjects in the genetic and clinical PFE cohorts combined (n = 58) and 100% in the genetic PFE cohort had at least 1 infraoccluded first permanent molar. Additionally, a novel functional PTH1R mutation, 1092delG, was identified and linked to PFE in the deciduous dentition. CONCLUSIONS: An infraoccluded, supracrestal first molar is a hallmark of PFE, often involving both arches in the permanent or deciduous dentition, and with unilateral or bilateral affection, infraoccluded second premolar or second molar, and multiple affected adjacent teeth. Our results further suggest that PFE and ankylosis might be clinically indistinguishable without knowledge of prior trauma, treatment history, genetic information, or obliteration of the periodontal ligament space.

Triplets with bilateral palatally displaced canines in association with third molar agenesis: an example of biologically related dental anomaly patterns?

This case series shows male triplets with similarly positioned palatally displaced canines and agenesis of third molars. It supports findings reported previously in the literature suggesting a genetic origin for the palatally displaced canine and other dental anomalies which may be biologically related.

Overlap syndrome: a diagnostic dilemma.

We report an interesting case of a young patient who came with a concern for missing teeth and lack of hair on scalp and body. Examination revealed complete absence of teeth, absence of eyebrows, eyelashes and hair over scalp. He was short-statured, had hyperextensible joints and hyperelastic skin, protuberant lips and many other anomalies such that the overall pattern of defects was not recognisable. A wide array of investigations involving the dental and medical faculties were done; however, the final diagnosis could not be reached, since it appeared to involve features of more than one syndrome, thus the name 'overlap syndrome'.

Imaging evalution of the gingival fibromatosis and dental abnormalities syndrome.

OBJECTIVE: The purpose of this study was to evaluate the dentomaxillofacial imaging features of one family affected by the gingival fibromatosis (GF) and dental abnormalities (DA) syndrome. METHODS: Conventional radiographs (periapical and panoramic) and cone beam CT (CBCT) were performed in nine members of this family: four were affected by the syndrome and five were not. RESULTS: The four affected members demonstrated mild generalized GF in association with DA, including hypoplastic amelogenesis imperfecta, intrapulpal calcifications, delay on tooth eruption and pericoronal radiolucencies in unerupted teeth. None of these oral changes were identified in the five unaffected members. All nine members presented alterations in the paranasal sinuses and mucosal thickening of the maxillary sinus was the most common finding. CONCLUSION: Family members not affected by the syndrome showed similar alterations in the paranasal sinuses and CBCT was useful to characterize the dentomaxillofacial features of this new syndrome associating GF and DA.

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.

Primary failure of eruption (PFE)--clinical and molecular genetics analysis.

BACKGROUND: The term "primary failure of eruption" (PFE) refers to the complete or partial failure of a primary non-ankylosed tooth to erupt due to a disturbance of the eruption mechanism. Up to now, the molecular basis for this failure was unknown. PATIENTS AND METHODS: Four families were studied in whom at least two members were affected by non-syndromic PFE as part of a clinical and molecular genetics study. Radiological diagnostics (OPTs) were carried out in all patients and their unaffected relatives (control group). The genetic analysis included a genomewide linkage analysis followed by direct DNA sequencing of positional candidate genes. RESULTS: Starting from the index patients, we were able to reconstruct pedigrees over two and/or three generations in the families that indicated an autosomal-dominant mode of inheritance of non-syndromic PFE. Fifteen patients were diagnosed with PFE. Gender distribution was nearly equal (7 female, 8 male). Molecular genetic analysis of the PTHR1 gene revealed three distinct heterozygous mutations (c.1050-3C>G; c.543+1G>A; c.463G>T). Unaffected persons exhibited no mutations. CONCLUSIONS: Knowledge of the genetic causes of non-syndromic PFE can now be used for the differential diagnosis of eruption failure. It permits affected family members to be identified early and may lead to new treatment possibilities in the long term. The genetically-verified diagnosis of "primary failure of eruption" can protect patients and orthodontists from years of futile treatment, because orthodontic treatment alone does not lead to success. Moreover, it has a negative influence on unaffected teeth and areas of the jaw.

The role of periodontal ligament cells in delayed tooth eruption in patients with cleidocranial dysostosis.

OBJECTIVE: The clinical appearance of patients with cleidocranial dysplasia (CCD), which is caused by mutations in the RUNX2 gene, is characterized by anomalies of the clavicles, thorax, spine, pelvis and extremities and by disturbances of the skull and tooth development. Of orthodontic relevance are multiple supernumerary teeth associated with delayed tooth eruption. The present investigation is based on the hypothesis that an altered phenotypic expression of periodontal ligament (PDL) cells from CCD patients and a reduced ability of those cells to support the differentiation of bone-resorbing osteoclasts might contribute to delayed tooth eruption. MATERIALS AND METHODS: To test this hypothesis, PDL cells from healthy donors and from two patients with clinically and molecular biologically diagnosed CCD were characterized for the basal and induced mRNA expression of osteoblast marker genes. The physiological relevance of the findings for the differentiation of osteoclasts was examined in an osteoclast assay, as well as in a co-culture model of PDL cells and osteoclast precursors. RESULTS: Both CCD patients displayed missense mutations of the RUNX2 gene. The in vitro experiments revealed an unaltered expression of RUNX2 mRNA, however especially in CCD patient 2 there was a reduced basal expression of mRNA for the key regulatory gene for bone remodeling RANKL. Furthermore, compared to the control cells from healthy donors, these factors were less inducible by stimulation of the cultures with 1alpha,25(OH)(2)D(3). In the osteoclast assays as well as in the co-culture experiments, PDL cells from the CCD patients showed a reduced capacity to induce the differentiation of active osteoclasts. CONCLUSIONS: These data indicate that PDL cells from CCD patients express a less distinctive osteoblastic phenotype resulting in an impaired ability to support osteoclastogenesis which might, in part, account for the delayed tooth eruption that can be observed clinically.

Cleidocranial dysplasia: a family report.

A 10-year-old girl presented with a chief complaint of many unerupted teeth. Complete clinical and radiological examination of this patient confirmed the diagnosis of cleidocranial dysplasia (CCD). Her father also presented similar features with a lesser clinical severity. CCD is an autosomal-dominant heritable skeletal disease caused by heterozygous mutations in the osteoblast-specific transcription factor RUNX2 gene. Failure of tooth eruption is probably mainly due to this mutated gene in CCD patients. Interdisciplinary treatment approach is obligatory for rehabilitation of these patients. In confirmed cases, genetic counseling for family planning should certainly be advised.

Malposition of unerupted mandibular second premolar in children with palatally displaced canines.

OBJECTIVE: To test the hypotheses that (1) the distal angulation of unerupted mandibular premolar (MnP2) is significantly greater in children with palatally displaced canines (PDC) than in those in a control sample; and (2) delayed tooth formation is significantly more frequent in children with both malposed MnP2 and PDC than in children with PDC only. MATERIALS AND METHODS: We examined retrospectively panoramic radiographs from 43 patients with PDC who had no previous orthodontics. A control sample consisted of age- and sex-matched patients. The distal angle formed between the long axis of MnP2 and the tangent to the inferior border was measured. Dental age was evaluated using the Koch classification. RESULTS: A significant difference was observed between the mean inclination of the right side MnP2 in the PDC group (75.4 degrees) and that of the control group (85.8 degrees). This difference was highly statistically significant (P < .0001). The same evaluation was carried out for the left side, with similar results. The average dental age was found to be delayed in patients who showed both abnormalities (malposed MnP2 and PDC) compared with patients who showed the PDC anomaly only. CONCLUSION: Both hypotheses are retained. Statistically, PDC and MnP2 malposition are significantly associated suggesting a common genetic etiology, despite taking place on opposite jaws. While the presence of PDC or MnP2 anomaly has been associated with a delay in tooth formation, we find the presence of both anomalies to show a more profound delay. Our findings suggest a delay in tooth formation as a possible common genetic mechanism for these 2 malposition anomalies.

Case reports of a new syndrome associating gingival fibromatosis and dental abnormalities in a consanguineous family.

BACKGROUND: Gingival fibromatosis (GF) is characterized by fibrotic enlargement of the gingiva that can be inherited as an isolated trait (named hereditary gingival fibromatosis) or as a component of a syndrome. This article reports one kindred affected by a syndrome characterized by GF associated with dental abnormalities (DA) including generalized thin hypoplastic amelogenesis imperfecta (AI). METHODS: To characterize the pattern of inheritance and the clinical features, 70 family members were examined. Hematoxylin and eosin staining, immunohistochemistry, and scanning electronic microscopy (SEM) were performed to identify the alterations on gingiva, teeth, and dental follicles. RESULTS: Examination of the family pedigree demonstrated multiple consanguineous first-cousin marriages and an autosomal recessive trait of inheritance. Four members demonstrated mild GF in association with DA, including generalized thin hypoplastic AI, intrapulpal calcifications, delay of tooth eruption, and pericoronal radiolucencies involving unerupted teeth. One of those four patients also had mental retardation (MR). MR as an isolated feature was observed in six members, whereas isolated GF was found in one individual. A combination of gingivectomy and gingivoplasty followed by regular dental procedures were performed in these patients. Histologic examination of the gingival enlargement revealed a dense connective tissue containing myofibroblasts, islands of odontogenic epithelium, and calcified psammomatous deposits, which resembled cementicle-like structures by SEM. Pericoronal lesions also showed calcified psammomatous deposits in association with islands of odontogenic epithelium. Enamel ultrastructure analysis revealed normal surface alternating with irregular and porous areas. CONCLUSION: To the best of our knowledge, these cases represent a new syndrome within the spectrum of those including GF.

A familial case of popliteal pterygium syndrome.

Popliteal pterygium syndrome (PPS) is a rare malformation disorder characterized by autosomal dominant inheritance, highly variable expressivity and incomplete penetrance. The disorder is caused by the mutation of the IRF6 gene and the respective protein, which belongs to a family of nine transcription factors and is involved in the differentiation and proliferation of keratinocytes. Mutations in the IRF6 gene give rise to popliteal pterygium syndrome, Van Der Woude syndrome and nonsyndromic orofacial clefts. The anomalies from which affected patients suffer can be subdivided into alterations of the orofacial region, the musculoskeletal system and the genitals. Diagnosis is difficult, as is differential diagnosis, due to the variability of the manifestations. Prenatal diagnosis is possible by means of sequence analysis of the IRF6 gene in DNA extracted from the chorionic villus or amniotic fluid, or by means of intrauterine ultrasound. The prognosis is generally good, with normal mental development and the possibility to correct most of the alterations through targeted surgery. The case presented in this study involves two patients: a father and daughter who suffer from PPS, of whom the former was not diagnosed at birth. The two patients have undergone numerous operations over the years on various parts of the body and sequence analysis of the IRF6 gene, which revealed the presence of a mutation in the target site.

Dental and facial bone abnormalities in pyknodysostosis: CT findings.

Pyknodysostosis is an autosomal-recessive disorder of osteoclast dysfunction causing osteosclerosis, with associated maxillofacial anomalies. Multidetector CT with multiplanar and 3D reconstruction illustrated the pathologic findings in this case. Abnormalities included multiple retained deciduous teeth, unerupted teeth with associated follicles, an irregularly expanded alveolus and body of the mandible, and an obtuse mandibular angle. Volume-rendered imaging better delineated the irregular dentition, with crowding and retention of deciduous teeth.

The clinical features and aetiological basis of primary eruption failure.

Primary failure of eruption (PFE) is a poorly understood condition associated with tooth eruption failure. This investigation systematically reviews the literature, evaluates clinical features and associations with PFE, and describes five further cases. Publications were selected and identified as describing PFE when there was no identifiable aetiological factor contributing to eruption failure and no evidence of successful orthodontic extrusion of the affected tooth or teeth. A data abstraction form recorded the following additional information; subject age, gender, general health status, and teeth present. Eighteen publications were sourced that detailed at least one case of PFE in a manner conforming to the selection criteria; these papers included a total of 35 individual cases, to which five previously unreported subjects were added. Within the whole sample of 40 cases, a total of 24 (60 per cent) were females and 16 (40 per cent) males. First and second molar teeth were most commonly affected; incisors, canines, and premolars were also involved, but with a reduced individual frequency. There was no significant difference in incidence between the maxilla and mandible, or between left and right sides. A family history of eruption failure was found in almost 50 per cent of the sample, with eruption failure or ankylosis affecting at least one primary tooth, also a common finding. Within the 40 cases, hypodontia was present at levels higher than population norms. PFE appears to be a condition that predominantly affects the molar dentition. The increased frequency of hypodontia in affected individuals and common findings of a family history regarding tooth eruption problems suggests a significant genetic component to the aetiology of this rare condition.

Osteoglophonic dysplasia: dental and orthodontic implications.

AIMS AND OBJECTIVES: Documentation of dental and orthodontic implications of osteoglophonic dysplasia (OGD). SETTINGS AND PARTICIPANTS: Case report describing oral and dental manifestations of a female with OGD, aged 39 years, who was first documented three decades ago. RESULTS: This rare genetic disorder manifests with gross stunting of stature, associated with severe craniofacial malformation and multiple unerupted teeth. Radiographically, multiple lucent lesions were present in the tubular bones and mandible as well as several impacted teeth. CONCLUSION: We concluded that prosthetic dental replacement in this patient would be difficult because of the distorted jaw relationship and large alveolar ridges. Equally, craniofacial reconstruction might be compromised by obstruction of the nasal airways, difficulty in intubation and postoperative respiratory problems.