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

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.

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 30s. 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 1mm/min. The silane primer activation was evaluated using Fourier-transform infrared spectroscopy.

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).

Silanization with five experimental silane primers in vitro produced significantly greater shear bond strengths than the ready-to-use control silane.