Evaluation of surface treatments on shear bond strength between zirconia and veneer ceramic: Before and after thermal cyclic

Objective: The purpose of this study, to investigate the effect of different surface treatments applied before and after sintering and thermal cycling application on the bond strength between zirconia and veneering porcelain. In the study, it is also aimed to evaluate the effect of the surface transformation and post-sintering phase transformation amount and surface roughness between zirconia core and veneering porcelain. Method: 220 pre-sintered zirconia core specimens (7 mm diameter and 3 mm height) prepared in CAD/CAM and half of the specimens were sintered, and 2 groups were divided, with and without thermal cycling. Then zirconia specimens were divided into 5 subgroups according to different surface treatments before and after sintering and surface treatments were applied. SEM, AFM and XRD analyzes were then performed on random specimens from each group. Zirconia specimens were veneered with veneering porcelain (5 mm diameter and 3 mm height).5000 thermal cycles were applied to the specimens in the thermal cycle group. The shear bond strength was tested using a universal testing machine. Results: Statistical analysis of surface treatments was performed by Kruskal Wallis Variance Analysis and Mann Whitney U test. There was no statistically difference in control, sandblasting, 3W-8 Hz, 3W-15 Hz and 3W-20 Hz groups (p> 0.05).It was found that the application of surface treatment before sintering generally increased the bonding strength, but it was not statistically significant (p> 0.05).It was also found that the thermal cycling treatment decreased the bonding but there was no statistical significance except for 20 Hz group (p <0.02) before sintering (p> 0.05). Surface treatments before and after sintering provided t → m transformation in zirconia, but post sintering, it was seen that the m phase values decreased. Conclusions: According to the results of the study, surface treatments before sintering were found to be higher than those after sintering. It has also been observed that thermal cycling practices have reduced the bond strength values.