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Claudin-16 protein (CLDN16) is a component of tight junctions (TJ) with a restrictive distribution so far demonstrated mainly in the kidney. Here, we demonstrate the expression of CLDN16 also in the tooth germ and show that claudin-16 gene (CLDN16) mutations result in amelogenesis imperfecta (AI) in the 5 studied patients with familial hypomagnesemia with hypercalciuria and nephrocalcinosis (FHHNC). To investigate the role of CLDN16 in tooth formation, we studied a murine model of FHHNC and showed that CLDN16 deficiency led to altered secretory ameloblast TJ structure, lowering of extracellular pH in the forming enamel matrix, and abnormal enamel matrix protein processing, resulting in an enamel phenotype closely resembling human AI. This study unravels an association of FHHNC owing to CLDN16 mutations with AI, which is directly related to the loss of function of CLDN16 during amelogenesis. Overall, this study indicates for the first time the importance of a TJ protein in tooth formation and underlines the need to establish a specific dental follow-up for these patients.

BackgroundSince the 2000s, different epidemiological studies focusing on the prevalence or the aetiology of DE in adolescents recognised them as an at-risk population due to their eating behaviours. None was carried out in French adolescents.The primary objective of this study was to assess the prevalence of dental erosion (DE) using the total BEWE score among adolescents in the department of Alpes Maritimes, France. The secondary objectives were to observe changes in prevalence estimates depending on both the cutoffvalue of total BEWE score with different teeth/dental surfaces examined, and to identify the related risk factors.MethodsA cross-sectional study in a multistage random sample of 339 14-yr-old schoolchildren was carried out in 2014. The children completed a self-administered questionnaire concerning diet and oral habits. Caries was assessed with ICDAS-II (International Caries Detection and Assessment System-II) criteria and erosion with BEWE (Basic Erosive Wear Examination) index. The total BEWE score was calculated to assess the DE prevalence with two cutoff values (3 and 1). Data were analysed using descriptive statistics and logistic regression models.ResultsThe 331 children were aged 14.4 ± 0.5 years. The DE prevalence was 39 % using a total BEWE score ≥ 3. With a cutoff total BEWE score of 1 (at least one affected tooth), the prevalence varied from 3.9 to 56.8 % depending on the teeth/surfaces that were used for the analysis. The DE prevalence, assessed with only first molars and maxillary incisors, was about 54 %. The risk factors for DE (total BEWE score ≥ 3) were daily consumption of acidic beverages (OR: 4.0; 95 % CI: 2.1–7.6) and acidic sweets (OR: 3.2; 95 % CI: 1.2–8.0), low socio economic category (OR: 2.4; 95 % CI: 1.1–5.0) and visible dental biofilm (OR: 2.0; 95 % CI: 1.2–3.4).ConclusionDepending on the method chosen, the prevalence varied from 3.9 to 56.8 % among these adolescents. Thus, a consensus on choice of index, teeth to examine and age at assessment is necessary to standardise measurement of DE prevalence.

IntroductionLocal anaesthesia is commonly used in paediatric oral healthcare. Infiltration anaesthesia is the most frequently used, but recent developments in anaesthesia techniques have introduced an alternative: intraosseous anaesthesia. We propose to perform a split-mouth and parallel-arm multicentre randomised controlled trial (RCT) comparing the pain caused by the insertion of the needle for the injection of conventional infiltration anaesthesia, and intraosseous anaesthesia by the computerised QuickSleeper system, in children and adolescents.Methods and analysisInclusion criteria are patients 7–15 years old with at least 2 first permanent molars belonging to the same dental arch (for the split-mouth RCT) or with a first permanent molar (for the parallel-arm RCT) requiring conservative or endodontic treatment limited to pulpotomy. The setting of this study is the Department of Paediatric Dentistry at 3 University dental hospitals in France. The primary outcome measure will be pain reported by the patient on a visual analogue scale concerning the insertion of the needle and the injection/infiltration. Secondary outcomes are latency, need for additional anaesthesia during the treatment and pain felt during the treatment. We will use a computer-generated permuted-block randomisation sequence for allocation to anaesthesia groups. The random sequences will be stratified by centre (and by dental arch for the parallel-arm RCT). Only participants will be blinded to group assignment. Data will be analysed by the intent-to-treat principle. In all, 160 patients will be included (30 in the split-mouth RCT, 130 in the parallel-arm RCT).Ethics and disseminationThis protocol has been approved by the French ethics committee for the protection of people (Comité de Protection des Personnes, Ile de France I) and will be conducted in full accordance with accepted ethical principles. Findings will be reported in scientific publications and at research conferences, and in project summary papers for participants.Trial registration numberClinicalTrials.gov NCT02084433.

The aim of this study was to compare the shear bond strength (SBS) of nine dentine bonding systems (DBS) of different classes to human primary and permanent dentine. Flat dentine occlusal surfaces were produced on human molars (100 primary, 100 permanent) by wet grinding on a 800-grit SiC paper. Nine DBS were applied following the manufacturers' instructions: One total etch multi-step system: Scotchbond Multipurpose Plus (3M/ESPE); Four total etch one-bottle system: Prime &Bond 2.1 (Dentsply), One Step (Bisco), Scotchbond 1 (3M/ESPE), and OptibondSolo Plus (Kerr); Three two-step self-etching primer systems: Clearfil Liner Bond 2 (Kuraray), Clearfil SE Bond (Kuraray), and Prime &Bond NT with NRC (Dentsply); An 'all-in-one' self-etching system: Prompt L-Pop (3M/ESPE). Composite (Z100; 3M/ESPE) cylinders (2 mm diameter, 3 mm high) were polymerized on the treated dentine surfaces and the specimens were stored at 37 degrees C for 24 h prior to testing. Twenty experimental groups were produced and tested. Statistical analysis revealed both a substrate and a bonding system effect. Two adhesive systems (One Step, Prime &Bond NT) had significantly higher bond strengths on permanent than on primary dentine. There was an effect of dentine bonding system on the mode of fracture. Although eight of the 10 DBS tested exhibited higher median SBS values on permanent dentine than on primary dentine, the dependent pairwise comparison identified a significant difference only for two groups. The use of simplified bonding systems does not necessarily result in improved bond strength to primary or to permanent dentine.

Genetic approaches have shown that several genes could modify caries susceptibility; AmelogeninX (AMELX) has been repeatedly designated. Here, we hypothesized that AMELX mutations resulting in discrete changes of enamel microstructure may be found in children with a severe caries phenotype. In parallel, possible AMELX mutations that could explain resistance to caries may be found in caries-free patients. In this study, coding exons of AMELX and exon-intron boundaries were sequenced in 399 individuals with extensive caries (250) or caries-free (149) individuals from nine French hospital groups. No mutation responsible for a direct change of amelogenin function was identified. Seven single-nucleotide polymorphisms (SNPs) were found, 3 presenting a high allele frequency, and 1 being detected for the first time. Three SNPs were located in coding regions, 2 of them being non-synonymous. Both evolutionary and statistical analyses showed that none of these SNPs was associated with caries susceptibility, suggesting that AMELX is not a gene candidate in our studied population.