Influence of matrix composition on polymerization stress development of experimental composites

ObjectiveStress development at the tooth/restoration interface is one of the most important reasons for failure of adhesive restorations. The aim of this study was to evaluate the influence of BisGMA/TEGDMA (B/T) and UDMA/TEGDMA (U/T) ratios on polymerization stress (PS) and on the variables related to its development: degree of conversion (DC), polymerization maximum rate (Rpmax), volumetric shrinkage (VS), elastic modulus (E), stress relaxation (SR) and viscosity of experimental composites.MethodComposites were formulated containing B/T or U/T in mol% ratios of 2:8, 3:7, 4:6, 5:5, 6:4, 7:3 and 8:2, and 15 wt% of fumed silica. PS was determined with a universal testing machine. VS was measured with a linometer. E and SR were obtained in three-point bending. DC and Rpmax were determined by real time NIR spectroscopy and viscosity was measured in viscometer. Data were submitted to one-way ANOVA, Tukey test (α = 0.05%) and regression analyses.ResultsPS, VS, E and DC decreased and viscosity and Rpmax increased with base monomer content in both series. PS showed strong correlation with VS, DC and viscosity. PS, VS and DC were higher and viscosity was lower for UDMA-based materials.SignificanceReduced viscosity, kinetics parameters and molecular characteristics led UDMA-based composites to elevated conversion and relatively lower PS at lower TEGDMA contents, compared to B/T composites.