Evaluation of the Bond Strength between Zirconia Core and Veneering

Objective: To determine whether the bond strength of veneering porcelain to a zirconia core in bilayered ceramics was similar to that of the Co-Cr metal ceramic control.Methods: Five groups of ten specimens each were fabricated,whose dimensions were 15 mm in length and 8 mm in diameter at the core,and 2 mm in thickness and 8 mm in diameter for the veneer.The groups were GR.1(control group): Co-Cr alloy/IPS d.SIGN(Ivoclar),GR.2: IPS e.maxZirCad/ IPS e.maxZirPress(Ivoclar),GR.3: IPS e.maxZirCad/IPS e.maxCeram(Ivoclar),GR.4: Lava Frame(3M ESPE)/ Lava Ceram(3M ESPE) and GR.5: Lava Frame(3M ESPE)/IPS e.maxCeram(Ivoclar).A shear strength test was used in all samples with a universal testing machine.The chosen crosshead speed was of 0.50 mm/min.The obtained results were analyzed by SPSS 18.0,using a one way analysis of variance test(ANOVA) and LSD multiple comparisons test to determine whether significant differences existed between the groups(P0.05).Results: GR.1: 13.87 MPa,GR.2: 13.10 MPa,GR.3: 10.97 MPa,GR.4: 12.72Mpa and GR.5: 4.77 Mpa.Conclusion: The bond strength of zirconia core and veneering porcelain was similar to the Co-Cr metal ceramic control.The pressed technique of veneering porcelain on zirconia cores showed the higher results than the layers technique.The lowest results were for the group using porcelains from different manufacturers.