Effect of Primers and Resins on the Shear Bond Strength of Resin Composite to Zirconia

Objective. To evaluate the effects of various surface conditioning methods and agents. Methods. The intaglio zirconia substrates were air particle abraded with Al2O3 (Ø 50 μm) for 10 s. An air pressure of 450 kPa and a nozzle distance of 10 mm were used. Surface conditioning by groups: A = silane coupling agent  + organophosphate adhesive; B = organophosphate primer + silane coupling agent + organophosphate adhesive; C = organophosphate primer; D = methacrylate adhesive; E = thiophosphate primer + methacrylate adhesive. Composite stubs were bonded to substrates and photo-polymerized. The specimens were thermocycled 8000 times 55±1∘C and 5±1∘C and kept in distilled water for 14 d. The shear bond strengths were measured with a universal testing machine. Results. Shear bond strengths (MPa ± SD): Group A 25.8±6.7, Group B 26.5±8.6, Group C 16.7±8.5, Group D 2.6±0.7, and Group E 4.2±1.2. ANOVA: significant differences among groups (P<.05). Groups A and B: mainly cohesive fractures, Group C: mixed or adhesive fractures, Groups D and E: adhesive fractures. Conclusions. A value of 10–13 MPa is the minimum acceptable shear bond strength. Groups A, B, and C exceeded this limit, Groups D and E could not achieve the limit.published_or_final_versio