Evaluation of the effect of polishing and glaze techniques on the color, translucency and surface roughness of CAD-CAM all-ceramic materials

The purpose of this study is to evaluate the influence of different surface treatments (Glaze: G and Polishing: P) on the translucency, color stability and surface roughness of LDS (Lithium disilicate), ZLS (Zirconia reinforced lithium silicate) and TrZ (translucent zirconia) materials. 40 specimens (1 mm thickness) discs were prepared from lithium disilicate (IPS e.max CAD), zirconia reinforced lithium silicate (Celtra Duo HT) and translucent zirconia (Cercon HT) materials. Specimens were grinded in order to mimic the chairside-adjustment process for 20 seconds. Two different types of surface treatments were applied to the specimens and the specimens were subjected to 10.000 thermocycles in a coffee solution. Contact profilometer was used to measure the roughness values (Ra: Average Roughness Value, Rz: Maximum Height of Profile), and colorimeter was used to measure color stability and translucency parameters (TP). Color difference data were evaluated with Kruskal Wallis test and Dunnet multiple comparison test. One-way variance analysis (ANOVA) was used to evaluate the roughness data after grinding. Repeated measures ANOVA and Duncan multiple comparison test was used to evaluate the roughness (Ra, Rz) and translucency parameter (TP) data. p<0.05 was considered significant. Only the ZLS-P (Zirconia reinforced Lithiumsilicate-polishing) group's color differences was perceptible but the color differences values of all groups were smaller than the clinically acceptability threshold (<2.23). The highest roughness values (Ra and Rz) were observed in the ZLS material after grinding, followed by LDS and TrZ. ZLS-G (Zirconia reinforced Lithiumsilicate-glaze) and LDS-G (Lithium disilicate-glaze) groups showed the lower mean value Ra than polished groups, which showed no statistically significant difference among them. TrZ-G (Translucent Zirconia-glaze) group showed a significantly higher Ra value compared to TrZ-P (Translucent Zirconia-polishing) group. For all materials, glazing provided lower Rz (Maximum Height of Profile) value, but for TRZ no significant differences were found between the Rz values of glazed and polished surfaces. Before and after coffee thermocycling, LDS presented the highest TP values, followed by ZLS and TrZ. The coffee thermocycling increased the roughness values (Ra and Rz) and decreased the translucency of materials