BackgroundOrodental diseases include several clinically and genetically heterogeneous disorders that can present in isolation or as part of a genetic syndrome. Due to the vast number of genes implicated in these disorders, establishing a molecular diagnosis can be challenging. We aimed to develop a targeted next-generation sequencing (NGS) assay to diagnose mutations and potentially identify novel genes mutated in this group of disorders.MethodsWe designed an NGS gene panel that targets 585 known and candidate genes in orodental disease. We screened a cohort of 101 unrelated patients without a molecular diagnosis referred to the Reference Centre for Oro-Dental Manifestations of Rare Diseases, Strasbourg, France, for a variety of orodental disorders including isolated and syndromic amelogenesis imperfecta (AI), isolated and syndromic selective tooth agenesis (STHAG), isolated and syndromic dentinogenesis imperfecta, isolated dentin dysplasia, otodental dysplasia and primary failure of tooth eruption.ResultsWe discovered 21 novel pathogenic variants and identified the causative mutation in 39 unrelated patients in known genes (overall diagnostic rate: 39%). Among the largest subcohorts of patients with isolated AI (50 unrelated patients) and isolated STHAG (21 unrelated patients), we had a definitive diagnosis in 14 (27%) and 15 cases (71%), respectively. Surprisingly, COL17A1 mutations accounted for the majority of autosomal-dominant AI cases.ConclusionsWe have developed a novel targeted NGS assay for the efficient molecular diagnosis of a wide variety of orodental diseases. Furthermore, our panel will contribute to better understanding the contribution of these genes to orodental disease.Trial registration numbersNCT01746121 and NCT02397824.

Regenerative dental pulp strategies require the identification of precursors able to differentiate into odontoblast-like cells that secrete reparative dentin after injury. Pericytes have the ability to give rise to osteoblasts, chondrocytes, and adipocytes, a feature that has led to the suggestion that odontoblast-like cells could derive from these perivascular cells. In order to gain new insights into this hypothesis, we investigated the effects of dexamethasone (Dex), a synthetic glucocorticoid employed to induce osteogenic differentiation in vitro, in a previously reported model of human dental pulp cultures containing pericytes as identified by their expression of smooth muscle actin (SMA) and their specific ultrastructural morphology. Our data indicated that Dex (10(-8) M) significantly inhibited cell proliferation and markedly reduced the proportion of SMA-positive cells. Conversely, Dex strongly stimulated alkaline phosphatase (ALP) activity and induced the expression of the transcript encoding the major odontoblastic marker, dentin sialophosphoprotein. Nevertheless, parathyroid hormone/parathyroid hormone-related peptide receptor, core-binding factor a1/osf 2, osteonectin, and lipoprotein lipase mRNA levels were not modified by Dex treatment. Dex also increased the proportion of cells expressing STRO-1, a marker of multipotential mesenchymal progenitor cells. These observations indicate that glucocorticoids regulate the commitment of progenitors derived from dental pulp cells to form odontoblast-like cells, while reducing the proportion of SMA-positive cells. These results provide new perspectives in deciphering the cellular and molecular mechanisms leading to reparative dentinogenesis.

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In vitro approaches have extensively been developed to study reparative dentinogenesis. While dental pulp is a source of unidentified progenitors able to differentiate into odontoblast-like cells, we investigated the effect of two media; MEM (1.8mM Ca and 1mM Pi) and RPMI 1640 (0.8mM Ca and 5mM Pi) on the behaviour of human dental pulp cells. Our data indicate that MEM significantly increased cell proliferation and markedly enhanced the proportion of α-smooth muscle actin positive cells, which represent a putative source of progenitors able to give rise to odontoblast-like cells. In addition, MEM strongly stimulated alkaline phosphatase activity and was found to induce expression of transcripts encoding dentin sialophosphoprotein, an odontoblastic marker, without affecting that of parathyroid hormone/parathyroid hormone related protein-receptor and osteonectin. In conclusion, these observations demonstrate that not only proliferation but also differentiation into odontoblast-like cells was induced by rich calcium and poor phosphate medium (MEM) as compared to RPMI 1640. This study provides important data for the determination of the optimal culture conditions allowing odontoblast-like differentiation in human pulp cell culture.

The aim of the present work was to characterize the odontoblastic proliferation, differentiation, and matrix mineralization in culture of the recently established M2H4 rat cell line. Proliferation was assessed by cell counts, differentiation by RT-PCR analysis, and mineralization by alizarin red staining, atomic absorption spectrometry, and FTIR microspectroscopy. The results showed that M2H4 cell behavior closely mimics in vivo odontoblast differentiation, with, in particular, temporally regulated expression of DMP-1 and DSPP. Moreover, the mineral phase formed by M2H4 cells was similar to that in dentin from rat incisors. Finally, because in mice, transforming growth factor (TGF)-beta1 over-expression in vivo leads to an hypomineralization similar to that observed in dentinogenesis imperfecta type II, effects of TGF-beta1 on mineralization in M2H4 cell culture were studied. Treatment with TGF-beta1 dramatically reduced mineralization, whereas positive control treatment with bone morphogenetic protein-4 enhanced it, suggesting that M2H4 cell line is a promising tool to explore the mineralization mechanisms in physiopathologic conditions.

Amelogenesis imperfecta (AI) designates a group of genetic diseases characterized by a large range of enamel disorders causing important social and health problems. These defects can result from mutations in enamel matrix proteins or protease encoding genes. A range of mutations in the enamel cleavage enzyme matrix metalloproteinase-20 gene (MMP20) produce enamel defects of varying severity. To address how various alterations produce a range of AI phenotypes, we performed a targeted analysis to find MMP20 mutations in French patients diagnosed with non-syndromic AI. Genomic DNA was isolated from saliva and MMP20 exons and exon-intron boundaries sequenced. We identified several homozygous or heterozygous mutations, putatively involved in the AI phenotypes. To validate missense mutations and predict sensitive positions in the MMP20 sequence, we evolutionarily compared 75 sequences extracted from the public databases using the Datamonkey webserver. These sequences were representative of mammalian lineages, covering more than 150 million years of evolution. This analysis allowed us to find 324 sensitive positions (out of the 483 MMP20 residues), pinpoint functionally important domains, and build an evolutionary chart of important conserved MMP20 regions. This is an efficient tool to identify new- and previously-identified mutations. We thus identified six functional MMP20 mutations in unrelated families, finding two novel mutated sites. The genotypes and phenotypes of these six mutations are described and compared. To date, 13 MMP20 mutations causing AI have been reported, making these genotypes and associated hypomature enamel phenotypes the most frequent in AI.

Background Guidelines in pediatric restorative dentistry recommend the use of preformed pediatric stainless steel crowns (SSCs) in cases of severe tooth decay of at least two surfaces. This clinically effective and safe restorative option is frequently refused by parents for esthetic reasons; they prefer conventional restorations using esthetic filling materials (composites, glass ionomer) if lesion severity limited to two surfaces permits. Recently, manufacturers have proposed esthetic preformed pediatric zirconia crowns (ZCs) but these have been assessed in only two randomized clinical trials (RCT) with follow-ups of 6 and 12 months. Only one of these RCTs was carried out on primary molars to test ZCs (NuSmile ZR) without a groove in its inner surface. The primary objective of this proposed RCT is to assess the effectiveness of ZCs compared with SSCs. Our hypothesis is that the effectiveness of ZCs will be equivalent to that of SSCs. Methods In this split-mouth, 2-year RCT, pairs of primary molars in 101 child participants will be randomized and restored with SSCs (ESPE, 3M) and ZCs (EZCrowns, Sprig Oral Health Technologies) characterized by grooves on their inner surface. Primary molars will first be allocated to SSCs, and 1 to 2 weeks later the other primary molar of the same pair will be restored by ZC. The primary outcome is the success defined by the “absence of major clinical and radiographic failure” (e.g., pain, pulp infection, dental abscess or periradicular pathology visible on radiographs). The secondary outcomes include the retention and fracture rates, the gingival condition, the wear of the antagonist of the treated teeth, as well as both parental and child satisfaction. Discussion This study will investigate two types of preformed pediatric crowns for the management of severe decay on primary molars. The results may help practitioners choose the better therapeutic option and to explain to parents the advantages and disadvantages of these two therapies. Trial registration NCT03296709 . Registered on  27 September 2017. Electronic supplementary material The online version of this article (10.1186/s13063-019-3559-1) contains supplementary material, which is available to authorized users.

Loss-of-function mutations of RUNX2 are responsible for cleidocranial dysplasia, an autosomal dominant disorder characterized by delayed closure of cranial sutures, aplastic or hypoplastic clavicles, moderate short stature and supernumerary teeth. By contrast, an increased gene dosage is expected for duplication of the entire RUNX2 sequence and thus, a phenotype different from cleidocranial dysplasia. To date, two cousins with a duplication including the entire RUNX2 sequence in addition to MIR586, CLIC5 and the 5' half of SUPT3H have been reported. These patients presented with metopic synostosis and hypodontia. Here, we report on a family with an affected mother and three affected children. The four patients carried a 285 kb duplication identified by array comparative genomic hybridization. The duplication includes the entire sequence of RUNX2 and the 5' half of SUPT3H. We confirmed the duplication by real-time quantitative PCR in the four patients. Two children presented with the association of metopic craniosynostosis and oligo/hypodontia previously described, confirming the phenotype caused by RUNX2 duplication. Interestingly, the mother and one child had isolated hypodontia without craniosynostosis, broadening the phenotype observed in patients with such duplications.