The Effect of Thermal and Mechanical Cycling on Shear Bond Strength of Zirconia Core to Porcelain Using Different Surface Treatments

Abstract

Introduction:Cracking and licking are one of the problems of all-ceramic restorations. So far, several ways have been presented to minimize these problems . The aim of this study was to investigate the effect of thermal and mechanical cycles on shear strength of Zirconia bond to Veneer Porcelain under various surface treatments. Materials and Methods: 60 disk zirconia samples were used. Samples were randomly divided into 3 groups. The first group was polished and without additional surface preparation, veneered with porcelain. The other two groups were placed under different surface treatments (with silicon oxide-activated alumina oxide and alumina oxide and primer) and veneered with porcelain. Half of the specimens of each group were placed under the 6000 cycles of heat and 20,000 mechanical load cycles of 50 N for imitation of intraoral conditions. Each sample was then buried with PMMA in the Mounting Jig, so that the interfaces of core and veneer are facing upwards. They were then subjected to shear stress using a Universal testing machine at a speed of 1 mm / min until breaking. The maximum force that led to the breakdown was registered to Newton and then converted to Mpa by appropriate mathematical methods. Results:Comparison of the groups showed that the highest shear bond strength was related to zirconium prepared with aluminum oxide and primer without thermocycling and mechanical cycle and there were no significant difference with cycled group.The lowest shear bond strength was related to polished zirconia with thermocycling and mechanical cycles (p = 0.001) with no significant difference with the same samples without cycling. Conclusion: Preparation with alumina oxide and primer increases the shear bond strength of zirconia bond to porcelain veneer. Thermocycling and friction cycle do not significantly reduce the shear bond strength in all three groups.