New veneering ceramics have been developed with adapted physical properties for high-strength ceramic core materials to fabricate esthetic, functional, and strong all-ceramic restorations. Objectives: To evaluate and compare bond strength of three veneering ceramics to zirconium-oxide ceramic core material. Methods: Three specifically developed veneering ceramics were fired in cylinders to flat Lava zirconium-oxide ceramic core (LavaCore) specimens (total n=90, n=30/grp) with the following combinations: LavaCeram/LavaCore(LAV); Cerabien ZR/LavaCore(CER); GC Initial/LavaCore(GCI). Veneering ceramic VitaOmega (VIO) was fired to metal-alloy (Stability) as a control (n=30). Subgroups (n=15) were stored for 3d (saline) or stored and thermocycled (TC:10,000cycles) to evaluate thermal effects. Shear bond strength was tested with Instron (model 4411) at 1mm/min. Two-way ANOVA was performed with GLM procedure and Summary statistics with MEANS procedure in SAS (α=0.05). Tukey's HSD was used as the means separation procedure. Results: Mean bond strength [MPa] was significantly different (p<0.001) between all materials (CER>GCI>LAV>VIO) with CER 18.1±0.6; CER-TC 20.3±0.7; GCI 16.7±0.7; GCI-TC 17.5±0.6; LAV 14.3±0.6; LAV-TC 14.8±0.8; VIO 8.0±0.6; VIO-TC 6.1±0.5. F-test for the Thermocyling variable indicated no statistical difference (p=0.4011). Significant interaction between materials and thermocycling (p=0.0326) necessitated testing for the effect of thermocycling for each material separately. Thermocycling had a significant effect for CER (p=0.0246), but no effect for VIO (p=0.0581), GCI (p=0.4023) or LAV (p=0.6265). Conclusions: The three veneering materials revealed significantly different shear bond strength values to zirconium-oxide ceramic core material. However, all ceramic-ceramic combinations were significantly stronger than the metal-ceramic control. Thermocycling caused significantly higher bond strength values for one group, but had no significant effect on all other groups. Supported by 3M ESPE.
