Sintering and Etching Condition of ZLS Effects on Bond Strength

Objectives: Purpose of this study was to evaluate the effect of different firing cycles and acid etching condition on resin cement tensile bond strength of zirconia reinforced lithium disilicate system (ZLS) glass ceramics to titanium.
Methods: Square-shaped specimens (N=53) were prepared from CAD/CAM blocks of zirconia reinforced lithium silicate glass ceramics (CeltraDUO, Dentsply) with 12.5 mm x 14 mm rectangular tiles of 2 mm thickness. The specimens were subjected to different firing cycles and etching conditions. They were cemented onto titanium rods (Grade V Ti-alloy, 4.8 mm in diameter, and 1 inch in length) with a resin cement (Theracem, BISCO Dental), and then tested for tensile bond strengths. Least square mean linear regression model was used to analyze the effects on tensile bond strength data using JMP Pro 14, followed by the post hoc Tukey tests and tests (α= 0.05).
Results: The tensile bond strength was significantly affected by etching duration (p<0.001) and firing cycles (p<0.001), but not significantly affected by etchant concentration (p=0.31). The highest load to failure was observed at 30-60 seconds of etching time and the least load to failure was observed at 20 seconds of etching time. In terms of firing cycles, 1 firing cycle provided the highest load to failure in contrast to least load to failure observed with no firing.
Conclusions: Changes in etching time and firing condition of the zirconia reinforced lithium disilicate specimens had a significant effect on the resin cement tensile bond strength. On the other hand etching the specimens under different concentrations of 5 and 9.6% did not differ statistically in terms of resin cement tensile bond strength.