Objective: In this study, we evaluated the effect of two silane coupling agents and their blends with a cross-linker silane on the bond strength of a dimethacrylate-based resin composite cement to surface-conditioned zirconia.
Material and methods: A total of 40 planar zirconia specimens were used for 8 test groups. After alumina particle abrasion, followed by tribochemical silica-coating, the specimens were randomly assigned to four silanizations: with 1.0 vol% 3-methacryloyloxypropyltrimethoxysilane or 1.0 vol% 3-mercaptopropyltrimethoxysilane or their blends with 1.0 vol% 1,2-bis-(triethoxysilyl)ethane (all in ethanol/water). The resin composite (RelyX ARC, 3M ESPE) stubs (n=10/group) were light-polymerized onto zirconia specimens. Four test groups were tested without water storage and 4 thermo-cycled at 6000 cycles (5+/-1 degrees C to 55+/-1 degrees C), with a dwelling time of 30 s. The shear bond strength of the cement stubs to zirconia was measured using a universal testing machine at a constant cross-head speed of 1 mm/min. Scanning electron microscopy was employed for imaging the zirconia surface after conditioning and testing. Failure mode was evaluated visually. A surface chemical analysis was carried out with the EDXA system.
Results: The highest shear bond strength was 21.9+/-8.7 MPa, obtained with a blend of 3-mercaptopropyltrimethoxysilane and 1,2-bis-(triethoxysilyl)ethane (dry storage), and 16.0+/-1.5 MPa, with 3-methacryloyloxypropyltrimethoxysilane (thermo-cycled). Thermo-cycling decreased the bond strengths significantly (ANOVA, p<0.01), and the silanes differed significantly (p<0.005). Some specimens suffered from spontaneous debonding during thermo-cycling.
Conclusions: The luting cement adhesion might be promoted to silica-coated zirconia with 1.0 vol% 3-methacryloyloxypropyltrimethoxysilane and with a blend of 1.0 vol% 3-mercaptopropyltrimethoxysilane and 1.0 vol% 1,2-bis-(triethoxysilyl)ethane.