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

Abstract

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 a 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 3-acryloxypropyltrimethoxysilane, 3 glycidoxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, styrylethyltrimethoxysilane, and 3-isocyanatopropyltriethoxysilane, which had been prepared in 95% ethanol (pH 4.5). A ready-to-use 3-methacryloxypropyltrimethoxysilane (RelyX™ Ceramic Primer) was used as the control. One resincomposite cement (RelyX™ Unicem) stub was bonded to each silicatized and silanized zirconia specimen. Half of the specimen groups were dry-tested and half were thermo-cycled at 6000 cycles between 5 °C and 55 °C, with a constant dwelling time of 30 s. The shear bond strengths of the cement stubs bonded to zirconia were 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 The highest shear bond strength was obtained for 3-acryloxypropyltrimethoxysilane in dry storage, 11.7 MPa (SD, 2.3 MPa) and after thermo-cycling 17.6 (4.1) MPa for glycidoxypropyltrimethoxysilane. The lowest shear bond strength values were obtained with control silane: in dry storage, 4.5 (1.3) MPa, after thermo-cycling 6.5 (2.6) MPa. Thermo-cycling increased the bond strengths significantly (ANOVA, p < 0.001) and differently for each 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.