Objectives: The aim of this study was to evaluate the feasibility of regulation of NaF release from bis-GMA/TEGDMA resin using gamma-methacryloxypropyltrimethoxysilane (gamma-MPTS).
Methods: NaF powder was treated with gamma-MPTS to form a polysiloxane layer on its surface. The morphology and the composition of the NaF powder treated with gamma-MPTS were evaluated using scanning electron microscopy, infrared spectroscopy, contact angle measurement and X-ray photoelectron spectroscopy. Bis-GMA/TEGDMA resin containing 50 wt% NaF powder was prepared as a model resin and immersed in distilled water at 37 degrees 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 gamma-MPTS delivered polysiloxane. A larger amount of fluoride was released at the initial stage from the resin containing NaF treated with no gamma-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 gamma-MPTS.
Significance: We found that gamma-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.