Effect of hydrophobic surface treated fumed silica fillers on a one-bottle etch and rinse model dental adhesive.

The objective of this study was to investigate the effect of hydrophobic surface treatment to fumed silica fillers on the bonding performance of a one-bottle etch and rinse model dental adhesive. In this study, 0.5-5 wt.% of Filler 1 and Filler 2 were loaded into BisGMA/HEMA model dental adhesive. Filler 1 was not treated, while Filler 2 was surface treated with a dimethyl silicone fluid making the silica extremely hydrophobic. The prepared adhesives were characterized through measurements of viscosity, degree of conversion, and water contact angle. SEM was utilized to observe the microstructures at the bonding interface. Micro-tensile bond strength (µTBS) test coupled with fracture surface analysis was carried out to study the mechanical properties. From the experiment, the loadings of Filler 2 is favorable to the improvement of µTBS. The µTBS of experimental adhesive with 1 wt.% Filler 2 increased 42% compared to the model adhesive without filler, and 24% compared to the experimental adhesive with 1 wt.% Filler 1. The effectively penetration of the hydrophobic compositions of the adhesive is considered as the main reason that leads to the increased bond strength, which was proved by the contact angle measurement and SEM observations.