Regulation of NaF release from bis-GMA/TEGDMA resin using γ-methacryloxypropyltrimethoxysilane

Objectives: The aim of this study was to evaluate the feasibility of regulation of NaF release from bis-GMA/TEGDMA resin using γ- methacryloxypropyltrimethoxysilane (γ-MPTS). Methods: NaF powder was treated with γ-MPTS to form a polysiloxane layer on its surface. The morphology and the composition of the NaF powder treated with γ-MPTS were evaluated using scanning electron microscopy, infrared spectroscopy, contact angle measurement and X-ray photoelectron spectroscopy. Bis-GMA/TEGDMA resin containing 50wt% NaF powder was prepared as a model resin and immersed in distilled water at 37°C, and the amount of fluoride released from the resin was measured using a fluoride electrode. The mechanical strength in terms of diametral tensile strength before and after fluoride release was also measured, and statistically analyzed using one-way factorial ANOVA and Fisher's PLSD method. Results: NaF powder was covered with hydrophobic γ-MPTS delivered polysiloxane. A larger amount of fluoride was released at the initial stage from the resin containing NaF treated with no γ-MPTS. However, fluoride release terminated in a relatively shorter period. In contrast, we observed a smaller amount of fluoride released for a longer period from the resin containing NaF treated with γ-MPTS. Significance: We found that γ-MPTS treatment is useful for the regulation of NaF release from bis-GMA/TEGDMA resin. The mechanism of slow NaF release may be the formation of a hydrophobic polysiloxane layer on the surface of NaF powder and resulting slow water diffusion to NaF powder.