Fabrication and characterization of remineralizing dental composites containing hydroxyapatite nanoparticles.

The aim of this study was to fabricate and characterize dental composites containing hydroxyapatite nanoparticles (HApNPs). Four dental composites were produced from the same organic matrix (70 wt% Bis-GMA and 30 wt% TEGDMA), with partial replacement of BaBSi particles (65 wt%) by HApNPs in the following concentrations (wt%): E0 (0) - control, E10 (10), E20 (20) and E30 (30). Ca2+ and PO43- release was evaluated in solutions with different pHs (4, 5.5, and 7) using atomic emission spectroscopy with microwave-induced nitrogen plasma while the enamel remineralization potential was evaluated in caries-like enamel lesions induced by S. mutans biofilm using micro-CT. The following properties were characterized: degree of conversion (DC%), microhardness (KHN), flexural strength (FS), elastic modulus (EM) and translucency (TP). The higher the HApNPs content, the higher the Ca2+ and PO43- release. The ions release was influenced by pH (4 > 5.5 > 7) (p < 0.05). All composites loaded with HApNPs were able to remineralize the enamel (E30 = E20 > E10) (p < 0.05). Contrarily, E0 was not able of recovering the enamel mineral loss. E0 and E10 presented highest DC%, while E20 and E30 showed similar and lowest DC%. KHN and FS were decreased with the addition of HApNPs, while EM was not influenced by the incorporation of HApNPs. E10 presented statistically similar TP to E0, while this property decreased for E20 and E30 (p < 0.05). Incorporation of HApNPs into dental composites promoted enamel remineralization, mainly at potentially cariogenic pH (= 4), while maintained their overall performance in terms of physicomechanical properties.

Does the Misfit Volume of Prosthetic Crowns Differ Before and After Ceramic Application? An In Vitro Radiographic Microtomography Analysis.

PURPOSE: To estimate the misfit volume of zirconia vs metal-ceramic crowns. MATERIALS AND METHODS: Five specimens were fabricated from zirconia and five from nichrome (metal-ceramic). Microcomputed tomography techniques were used to obtain volumetric reconstructions of misfit volume before and after ceramic application. RESULTS: The mean misfit volume for metal-ceramic crowns was 8.80 mm3, and for zirconia crowns was 6.76 mm3 (P = .003, 95% confidence interval [CI] 0.714 to 3.358). Misfit volume also did not differ significantly before and after ceramic application (metal-ceramic, P = .375, 95% CI 0.513 to 1.363; zirconia, P = .253, 95% CI 0.257 to 0.977). CONCLUSION: Zirconia crowns had a smaller mean misfit volume than metal-ceramic crowns. The change in misfit volume after ceramic application was minimal and unlikely to be of clinical relevance.

The Influence of Dentin Age and the Presence of Cracks in Removal of the Root Filling Material.

INTRODUCTION: This study evaluated the removal of the filling material during endodontic retreatment considering the presence of cracks and the dentin age. METHODS AND MATERIALS: A total of 20 freshly extracted single-rooted teeth were categorized into the following two groups according to the age of the patients: Group Young (Y; aged 18-30 years) and Group Old (O; aged ≥60 years). Each tooth specimen was scanned by microcomputed tomography (micro-CT) subsequently after endodontic retreatment with the Reciproc instruments (REC). The images were analyzed for differences in the volume of dentin cracks and the presence of the filling material in the middle and apical thirds of the teeth among the groups, according to the dentin age. RESULTS: The micro-CT images showed that after retreatment, there were more cracks in the old root dentin than those in the young root dentin, although the difference was not statistically significant (P>0.05). The greatest reduction in the filling material was achieved when the old root dentin with cracks was retreated when compared with that of the young root dentin with cracks, but the difference was not statistically significant (P>0.05). CONCLUSION: The dentinal age and the presence of cracks were not found to be relevant factors for the removal of the filling material.