Zirconia-Zirconia Shear Bond Strength: Influence of Substrate and Cement Compositions

Objectives: Evaluate the bonding ability of two different cement systems applied to different zirconia in term of translucency. A self-adhesive and a dual cure resin cement systems were compared.
Methods: CAD/CAM discs of three different zirconia (Zenostar MO 0 [medium opacity]- T 1 [translucent]- MT 0 [medium translucency], Wieland Dental) were milled and hard sintered in order to obtain two cylinder shapes (12hx12Ømm used as a substrate and 12hx8Ømm to be bonded to the substrate). Both the zirconia bonding surfaces were sandblasted with alumina particles (50µm/2ATM). Two cement were tested in the present study a self-adhesive resin cement (SpeedCEM Plus, Ivoclar Vivadent) and a primer followed by a dual cure resin cement (Monobond Plus/Variolink Esthetic DC, Ivoclar Vivadent). Small cylinders were bonded to the substrate following the manufacturer instructions. After 24h at 37°C storage specimen were subjected to shear bond strength test in a universal testing machine. The substrate was fixed to the machine and shear force was applied to the small cylinder close to the bonding interface. The debonding load, recorded in N, were compared to the bonding surface and Mpa were calculated. Data were statistically analyzed by a 2-Way ANOVA followed by the Tukey test for post-hoc comparison (p<0,05).
Results: No statistically significant difference was found between the three tested zirconia (p=0,780) otherwise Variolink Esthetic DC showed in a statistically significant higher bond strength compared to the SpeedCEM Plus (p=0,001). Inside the groups only Zenostar T 1 showed a significant difference (p=0,005).
Conclusions: The resin cement systems significantly influence the bond strength between zirconia surfaces. The difference of the colored Zenostar T 1 were significantly greater than the differences observed for the not colored groups MO 0 and MT 0 when the primer and dual cure cement was applied. Different zirconia translucencies did not affect the bond strength.