Title Enhanced resin-composite bonding to zirconia framework after pretreatment with selected silane monomers

Objective. To evaluate the effect of five experimental silane monomer primers in vitro on the shear bond strength of a phosphate ester resin-composite cement bonded to silicatized zirconia framework. Methods. A total of 144 planar zirconia (Procera AllZircon) specimens were subjected to tribochemical silica-treatment, randomly divided into 12 sub-groups (n=12), and silanized with 1.0% (v/v) activated solutions of 3acryloxypropyltrimethoxysilane, 3 glycidoxypropyltrimethoxysilane, 3methacryloxypropyltrimethoxysilane, styrylethyltrimethoxysilane, and 3isocyanatopropyltriethoxysilane, which had been prepared in 95% ethanol (pH 4.5). A ready-to-use 3-methacryloxypropyltrimethoxysilane (RelyXTM Ceramic Primer) was used as the control. One resin-composite cement (RelyXTM Unicem) stub was bonded to silicatized and silanized zirconia using polyethylene molds. Half of the specimen groups were dry-tested (without aging) and half were thermo-cycled at 6000 cycles between 5 oC and 55 oC, with a constant dwelling time of 30 s. The shear bond strength of the cement stubs bonded to zirconia was measured using a universal testing machine using a constant cross-head speed of 1 mm/min. The silane primer activation was evaluated using Fourier-transform infrared spectroscopy. Results. In dry conditions, the highest shear bond strength was 11.7 (SD 2.3) MPa, obtained with 3-acryloxypropyltrimethoxysilane and after thermo-cycling 17.6 (4.1) MPa, both. Thermo-cycling increased the bond strengths significantly (ANOVA, p<0.001) and varied with the type of silane (ANOVA, p<0.001). Significance. Silanization with five experimental silane primers in vitro produced significantly greater shear bond strengths than the ready-to-use control silane.