Effect of temperature on the silane coupling agents when bonding core resin to quartz fiber posts.

OBJECTIVES To evaluate the effect of different silane agents and air-drying temperatures on bond strength of translucent quartz fibre posts to composite resin. METHODS The post surface was etched with 10 vol% hydrogen peroxide for 20 min. A two-liquid coupling agent containing 4-methacryolxyethyl trimellitate anhydride (4-META) and gamma-trimethoxysilyil propyl methacrylate (gamma-MPTS) and two pre-hydrolyzed single component silanes containing 3-methacryloxypropyltrimethoxysilane (3-MPS) and glycid-oxi-propyl-trimetil-oxi-silane (GPS), respectively, were used for treating the fiber posts. Two different post-silanization drying temperatures were applied (21 and 38 degrees C). A dual-cure composite resin (Core Paste XP) was selected to build-up the core around posts, obtaining cylindrical specimens that were serially cut in beams and subsequently loaded in tension (muTBS) at a cross-head speed of 1 mm/min until failure. Bond strength data were statistically analyzed by two-way ANOVA and Student-Newman-Keuls tests (alpha=0.05). RESULTS Warm air-drying determined significantly higher bond strengths (p<0.001) for glycid-oxi-propyl-trimetil-oxi-silane (11.6 MPa) and 4-methacryolxyethyl trimellitate anhydride/gamma-trimethoxysilyil propyl methacrylate silane (11.7 MPa). These two systems exhibited lower bond strengths (6.9 and 8.8 MPa, respectively) than 3-methacryloxypropyltrimethoxysilane (11.0 MPa) when dried at 21 degrees C. No statistical differences were recorded for 3-methacryloxypropyltrimethoxysilane when drying at 21 or 38 degrees C. SIGNIFICANCE The composition of the silane coupling agent in terms of acidic content, solvent rate or degree of hydrolysis may influence resin/post bond strength when dried at 21 degrees C. Drying at 38 degrees C most likely facilitates the evaporation of solvents present in the silane agent, resulting in increased bond strength of the composite resin to the fiber post.