The Influence of Multiple Firings on Shear-Bond Strength of All-Ceramics

Objectives: All-ceramic restorations have recently gained popularity due to their excellent properties. Clinicans and patients currently attracted to more natural-looking restorations. All-ceramic restorations have the advantages of translucency, biocompatibility, high esthetic, high precision fit and long term success. Multiple firing cycles after the application of several layers of porcelain is usually required to provide higher esthetic results for all-ceramic restorations fabricated with standard layering technique. The aim of this study is to evaluate the effect of the multiple firings and luting agents on the shear bond strength between the lithium disilicate ceramics and luting agents.
Methods: In this study, 120 disc-shaped specimens were fabricated from lithium disilicate-reinforced glass ceramic. All specimens were divided into 12 subgroups (n:10) according to repeated firing procedures (1st, 3rd, 5th, 7th, 9th firings and control group) and type of the luting agent (Variolink N and Rely X Unicem). The specimens were loaded axially in the universal testing machine and the shear bond tests were carried out. Statistical analysis was performed with using one-way ANOVA and Tukey Test (a=.05).
Results: The highest and the lowest shear bond stress values were obtained at 5th and control firing step for group A; 3rd and 1st firing step for group B. But these differences were not statistically significant
Conclusions: The limited data indicated that type of the luting agent have no effect on the shear bond strength between all ceramic and luting agent. Also multiple firings have no effect on the shear bond strength of all ceramic restorations.