Boron nitride nanosheets modified with zinc oxide nanoparticles as novel fillers of dental resin composite.

OBJECTIVE: The purpose of this study was to synthesize boron nitride nanosheets modified with zinc oxide nanoparticles (BNNSs/ZnO) and incorporate them as a novel inorganic filler to get an antibacterial dental resin composite. METHODS: The BNNSs/ZnO nanocomposites were synthesized via the hydrothermal method and characterized by Field Emission Scanning Electron Microscope (FESEM), Transmission Electron Microscopy (TEM), Energy Dispersive Spectrometer (EDS), X-ray Diffraction (XRD) and Fourier Transform-Infrared (FTIR) Spectroscopy. The BNNSs/ZnO or BNNSs were added into the experimental dental composite with different proportions, respectively. The mechanical and physical properties of the modified dental composite were evaluated. Their antibacterial activities were also assessed by quantitative analysis using Streptococcus mutans (S. mutans). RESULTS: The BNNSs/ZnO nanocomposites were successfully synthesized, and the growth of ZnO nanoparticles (ZnO NPs) on boron nitride nanosheets was confirmed. The flexural strength (FS), flexural modulus (FM) and the compressive strength (CS) of all modified resin composites showed no change compared to the control group. The curing depth, degree of conversion, water absorption and solubility of the modified composites were still within the clinical requirement. The antibacterial rates of the modified composites were significantly increased compared to the control group, which can reach 98 % when 0.5 % BNNSs/ZnO was added. SIGNIFICANCE: The modified dental resin composite with novel BNNSs or BNNSs/ZnO fillers shows significantly high antibacterial activity with suitable physicochemical and mechanical properties.

Dentulous versus edentulous mandibles: CBCT-based morphometric assessment of mandibular canal and alveolar bone.

Background: Precise preoperative knowledge of the mandibular canal (MC) variations and alveolar bone dimensions are vital elements for a successful dental implant. Thus, this study aimed to describe the three-dimensional morphology of the MC and alveolar bone dimensions, followed by a comparison of the variables in edentulous mandibular posterior sides with contralateral dentulous sides among adult Chinese individuals. Such variations were also studied in relation to gender and age. Material and Methods: Cone-beam computed tomography (CBCT) was used for the morphometric analysis of the MC and alveolar bone dimensions in this cross-sectional study that analyzed retrospectively gathered data. Records of 112 individuals (56 males and 56 females) who had one edentulous mandibular posterior side and one dentulous side were included in the analysis. The MC position, length (MCL), and diameter (MCD) along with superior bone height (SBH) and bone width (BW) of the alveolar bone ridge were assessed. Results: The MCD was lower at first (p = 0.016) and second (p = 0.079) molars on the edentulous sides. The SBH, BW1mm, and BW3mm were significantly lower on the edentulous than dentulous sides (p< 0.05). However, there were no significant differences in the MC position or MCL and the incidence of bifid MC for dentulous and edentulous sides. Gender was a significant parameter for MCL, SBH, and BW, while no significant differences were observed in all variables on both sides in relation to age. Conclusions: The position of the MC remains relatively constant regardless of losing teeth or increasing age. However, the MC position and MCL show differences in relation to gender. Alveolar bone dimensions are highly affected by dentate status followed by gender. Therefore, such variations should be considered by surgeons for successful surgical procedures in the posterior mandible. Key words:Mandibular canal, Bifid mandibular canal, edentulous mandible, alveolar bone dimension.