Method: Ten Zirconia discs (Lava Zirconia) were treated as follows: (1) No treatment (control), (2) Sandblasting with 110 µm aluminum-oxide (Al2O3) particles; (3) Tribochemical silica coating using 30 µm Al2O3 particles modified by silica. Resin composite discs (3mm x 3mm, Filtek Supreme, 3M ESPE) were bonded to zirconia using: (1) RelyX Unicem (3M ESPE); (2) SpeedCem (Ivoclar Vivadent). After 24h bonded specimens were loaded in a shear-test set up until failure. Data were analyzed using three-way analysis of variance (ANOVA) and Tukey’s tests for multiple comparisons (p < 0.001). Failure mode was recorded and the interfacial morphology of debonded specimens was observed using a stereomicroscope.
Result: Bond strength of SpeedCem cement to zirconia was significantly higher than that of RelyX Unicem, regardless of the surface treatment (α=0.05). Sandblasting and tribochemical silica coating surface treatments showed no significant difference, regardless of the luting cement used or the use of silane coupling agent. The use of Silane significantly increased the shear bond strength values when surface was treated.
Conclusion: The pre-surface treatment (sandblasting and silica coating) and the application of a small inorganic filler size MDP-containing cement/silane increased the shear bond strength between zirconium oxide ceramic and the resin composite. The MDP-containing luting cement (SpeedCem)/Silane (Monobond Plus) is recommended to bond zirconia ceramics and surface treatments are necessary.