Distorted Patterns of Dentinogenesis and Eruption in Msx2 Null Mutants: Involvement of Sost/Sclerostin.

The muscle segment homeogenes Msx1 and Msx2 play a major role in tooth and bone formation. Periodontal osteoclast impairment also occurs in Msx2 null mutant mice, which is restored by overexpression of the receptor activator of NF-κB targeted in osteoclast lineage. Here, we investigated the role of Msx2 in dentinogenesis. Experiments were performed on Msx2(-/-) mice and the MDPC-23 odontoblastic cell line. After Msx2 gene silencing, real-time quantitative RT-PCR data showed significant overexpression of Runx2, Bglap, Dspp, and Alpl. Of three inhibitors of Wnt/ß-catenin signaling (Dkk1, SostDc1, and Sost/Sclerostin), only Sost was expressed in postnatal teeth and overexpressed in Msx2(-/-) tooth samples. Initial crown dentin formation-primary dentinogenesis-occurred fairly normally in Msx2(-/-) teeth, albeit with distorted cusp patterns. Later stages of tooth development were characterized by a deviation from secondary toward tertiary dentinogenesis with osteodentin formation and impaired dentin deposition leading to limited root elongation. In Msx2(-/-)/receptor activator of NF-κB-transgenic double mutants, the dentin phenotype, notably in the roots, was rescued and sclerostin levels were normalized. These data suggest that Msx2 may act indirectly on dentinogenesis by controlling osteoclast activity and the signaling network related to eruption, supporting and further extending the concept that Msx2 controls formation of mineralized tissues by inhibition of the Wnt/ß-catenin pathway; Sost in dentin and Dkk1 in bone, as previously demonstrated.

The causes of failure and the longevity of direct coronal restorations: A survey among dental surgeons of the town of Abidjan, Côte d'Ivoire.

OBJECTIVE: This study aimed to itemize the causes for the failure of direct coronal restorations (DCRs) according to the practitioners of Côte d'Ivoire in order to provide recommendations for good practice. MATERIALS AND METHODS: A descriptive, self-reporting, prospective survey was carried out among 109 dental surgeons (DSs) in the town of Abidjan based on 587 randomly selected practitioners supplied by the National Board of the Order. RESULTS: The results show that 98.10% of the surveyed DSs had previously encountered cases of failure. Fracturing of the restoration, which is the basis for the hiatus, is the main cause of failure according to 51.40% of the surveyed practitioners, followed by pain "under the restoration" cited by 26.20% of them. Failure occurs within 6 months (30.85% of those surveyed), after 5 years (9.6% of those surveyed) for restorations with composite or glass ionomer cement (GIC), while for DCRs with amalgam, failure occurs within 6 months (28.70%), after 5 years (16%) and beyond 10 years (3.20%). CONCLUSION: The practitioners often encountered failures of DCRs, with fracture of the restoration as the cause. Dental amalgam appears to have a greater longevity than adhesive restorations. Faced with a failure, they more often opted for a replacement of the DCRs rather than a repair.

Direct technique premolar coronal restorations: From metallic material to "complete adhesive restoration".

INTRODUCTION: The choice of restorative materials has for a long time been determined by the tooth position. Thus, premolar restoration depended on the practitioner's clinical assessment and practical experience in regard to the material to be handled. AIM: The objective of this study was to assess, in the students' practice, the change in the choice of materials used for premolars restoration. MATERIALS AND METHODS: This was a retrospective study based on the available care records in the department of conservative dentistry and endodontics of a dental school. Variables analyzed included the year of restoration, the type of material, the premolar position in the arch, and the coronal restoration site (occlusal, proximal, and cervical). Data collected were processed with the SPSS software version 22 (SPSS Inc., Chicago, IL, USA; 2013). The statistical significance threshold was set at 5% for Pearson's Chi-square test. RESULTS: Between 1994 and 2017, 1738 restored premolars were identified. Over the years, amalgam restorations declined from 99.2% in 1994 to 1.3% in 2017, contrary to composite whose frequency increased from 0.6% to 88.6%. Maxillary premolars were exclusively restored with composite in 2017 when amalgam was still, somewhat, used for mandibular premolars. CONCLUSION: The reversal in the choice of materials in favor of composites reflects the global trend. This seems to be related to the current awareness of the prohibition, among others, of medical devices containing mercury.