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Zirconia has generated tremendous interest in the esthetic materials used for dental restorations. However, using conventional zirconia has some limitations especially in highly esthetically demanding situations, as it lacks the translucency that other ceramic materials possess. This study aimed to evaluate and compare the optical properties (shade, translucency, and opalescence) of three CAD-CAM monolithic multilayer zirconia ceramics (GNX; Ceramill Zolid® Gen-X, ZCP; IPS e.max® ZirCAD, and UPC; Upcera® Esthetic Explore Prime) and one CAD-CAM monolithic multilayer polymer-infiltrated hybrid ceramic (ENM; Vita® Enamic) with a CAD-CAM monolithic lithium disilicate ceramic as control (EMX; IPS e.max® CAD). 200 discs (GNX = 40, ZCP = 40, UPC = 40, ENM = 40, and EMX = 40) were cut, polished, and fully crystallized. Half of the samples for each group were subjected to hydrothermal aging. Descriptive analysis and ANOVA tests were used to compare the groups. Zirconia GNX, ZCP, and UPC groups showed significantly lower optical properties than ENM and EMX groups for both the non-aged and aged samples (p < 0.05). UPC and ENM groups showed a significant decrease in translucency and opalescence after aging (p < 0.05). The optical properties of monolithic multilayer zirconia ceramics were lower than monolithic multilayer polymer-infiltrated hybrid ceramic and lithium disilicate ceramic. Polymer-infiltrated hybrid ceramic was significantly affected by aging.
Almohammed et al. (Thu,) studied this question.