Effect of Different Liner Techniques and Argon Plasma Treatment of Zirconia Base on the Adhesion and Color Change of Veneering Ceramic

Abstract

This in vitro study aimed to investigate the bond strength and discoloration between the zirconia framework and veneer ceramic applied after liner and argon plasma treatment with two different techniques. A total of 200 zirconium substructures of 12 mm length, 10 mm width, and 0.7 mm thickness were divided into five subgroups for the application of different thicknesses of liner: C (no liner application), L1 (0.1 mm), L2 (0.2 mm), L3 (0.1 mm + 0.1 mm) and LA (0.1 mm + 0.1 mm + argon plasma). The zirconia substructures were fabricated by two different techniques (A: layering, B: press-on). The specimens of the three subgroups Control, Group L3, and Group LA were tested for color difference. Color parameters were measured using a spectrophotometer before and after thermal cycling, and differences (CIEDE 2000 [Delta E-00]) were calculated. The shear bond strength was applied to all subgroups using a universal testing machine. The data were analyzed statistically using the Shapiro-Wilk, Levene, and Kruskal-Wallis tests. The interface and fractured surfaces of the specimens were also evaluated by scanning electron microscopy (SEM). Significant differences were found between the groups (p < 0.05) in terms of shear bond strength and color differences (p < 0.001). Group LA showed significantly higher bond strength and color stability than the other groups (p < 0.001). The results of the study demonstrated that the application of liner and argon plasma between the upper and lower structures of all-ceramic systems significantly affects the bond strength and final colour of the restorations.