Dental Composite Properties’ Designed by Coupling Agent Content

Objective: There is scarce information about the effect of the amount of the silane used over several properties of dental composites. The aim of this study was to determine the influence of the amount of 3-methacryloxypropyl-trimethoxysilane (MTPS) coupling agent on physical and chemical properties of experimental composites. Method: Silica particles (OX50) were treated with 0, 1, 2, 5, 7,5 and 10% MTPS. The silica particles were then mixed with BisGMA/TEGDMA (50/50 wt%) and a photoinitiator system. Degree of conversion (DC) was calculated with FTIR-ATR spectroscopy. Knoop hardness (KH) was characterized with an indenter before and after water storage (4 months, 37^oC). Water sorption and water solubility analyses were adapted from ISO4049. Gloss, roughness (Ra), and color (CIELab) were analyzed before and after toothbrush abrasion (20,000 cycles). Results were analyzed by one or two-way ANOVA/Tukey’s test (p < 0.05). Result: DC was higher for materials formulated with non-treated and 10% treated particles. KH increased with MTPS concentration and was affected by water storage. Water sorption and water solubility presented inverse relationship with the silane content, but only sorption was statistically significant. Gloss did not differ among materials before abrasion. After abrasion, gloss was dependent on the MTPS treatment. The higher was the silane concentration; the lower was roughness after toothbrush abrasion. Color change did not differ among the materials. Conclusion: Materials’ properties might be adjusted according the filler treatment applied. The amount of MTPS coupling agent affected degree of conversion, Knoop hardness, water sorption, gloss and roughness.