Methods: Commercially pure titanium (CP-Ti) and zirconia ceramics (Zirconia) were assessed. For each substrate, 80 disks were randomly divided into five groups and primed with no (control) or with one of four agents: Clearfil Ceramic Primer (CCP), Clearfil Photo Bond (CPB), Clearfil Photo Bond with Clearfil Porcelain Bond Activator (CPB + Activator), and Estenia Opaque Primer (EOP). The specimens were then bonded with a gingiva-colored indirect composite (Ceramage Concentrate GUM-D) on the substrates. Shear bond strengths were measured before and after 20,000 thermocycles. Data were analyzed using the Steel-Dwass test for multiple comparisons, and Mann-Whitney U-test (p = 0.05).
Results: For CP-Ti, mean pre-/post-thermocycling shear bond strength varied from 12.2/10.3 to 32.8/23.1 MPa. For Zirconia, mean pre-/post-thermocycling bond strength ranged from 7.3/4.9 to 29.1/12.1 MPa. Shear bond strengths of all groups were significantly reduced with thermocycling (p < 0.001). For CP-Ti and Zirconia, CPB and CPB + Activator group exhibited significantly higher bond strengths (p < 0.05) than the other groups at 0 and 20,000 thermocycles. No significant differences were found between EOP and CCP groups or between CPB and CPB + Activator groups for the CP-Ti and Zirconia at 20,000 thermocycles.
Conclusions: Shear bond strength of a gingiva-colored indirect composite to commercially pure titanium and zirconia ceramics is decreased with the application of thermocycling. Application of a hydrophobic phosphate monomer and polymerization initiator can be effective for durable bond strength of titanium or zirconia ceramics. The use of silane would not enhance the bond strength of the gingiva-colored indirect composite to titanium and zirconia ceramics.