Physicochemical Characterization of Resin Composites Containing Calcium Orthophosphate or Bioactive Glass-ceramic and Their Effects on Dentin Remineralization in vitro

Abstract

The objectives of this project are to characterize experimental composites containing different volumetric fractions of bioactive glass ceramic (VCB) or dicalcium phosphate dihydrate (DCPD) in relation to calcium release, degree of conversion, mechanical behavior and optical properties and to evaluate, in vitro, the dentin remineralization achieved with these materials. DCPD particles will be synthesized by co-precipitation, while VCB will be provided by the Glass Research, Education, and Innovation Center, based at the Federal University of São Carlos. The particles will be characterized by scanning electron microscopy, X-ray diffractometry, and laser scattering. Nine composites will be formulated with an organic matrix of BisGMA:TEGDMA combined with DCPD or VCB and silanized barium glass in different proportions: 0/50 (control), 15/35, 25/25, 35/15, and 50/0. The composites will be analyzed for translucency and transmittance (n=10). Additionally, the degree of conversion (n=3) and biaxial flexural strength (n=10) will be evaluated after 24 hours of storage in deionized water. Calcium ion release will be monitored over a period of 28 days (n=3). For the evaluation of dentin remineralization in vitro, artificial lesions (acetic acid, pH 5, 66h) will be created in dentin blocks. The lesion surfaces will receive one of the composites containing only reinforcing glass (negative control), the two materials containing only DCPD or VCB, and two intermediate formulations defined based on the results of other assays. After exposure to SBF (simulated body fluid) for four weeks, remineralization will be evaluated at the interface with the restorative material through attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR, n=5). Recovery of mechanical properties (elastic modulus and hardness) throughout the dentin layer thickness will be assessed via nanoindentation (n=10). Results will be analyzed using ANOVA/Tukey test (alpha: 0.05).