Purpose: To investigate the effect of ceramic material (lithium disilicate, LDS vs. composition-gradient multilayered zirco-nia 4Y-PSZ and 5-PSZ, Z) and ceramic layer thickness (0.5 mm, 1.0 mm, and 1.5 mm) on fatigue performance and failureload of occlusal veneers on molars.Methods: Seventy-two CAD-CAM-fabricated occlusal veneer restorations (IPS e.max CAD; IPS e.max ZirCAD Prime Es-thetic, Ivoclar Vivadent) were divided into six groups (n=12, LDS-1.5, LDS-1.0, LDS-0.5; Z-1.5, Z-1.0, Z-0.5). Restorations wereadhesively cemented (Variolink Esthetic DC, Ivoclar Vivadent) to dentin-analogue composite dies (Z100, 3M ESPE) andexposed to thermomechanical fatigue (1.2 million cycles, 49 N, 1.6 Hz, 5-55° C). Single-load-to-failure was tested with auniversal testing machine. Data were analyzed using ANOVA with Tukey post-hoc tests and t-tests (P 2683 N (LDS-1.0)>2338 N (LDS-1.5)>1744 N (Z-1.5)>1310 N (Z-0.5)>1198 N (Z-1.0).Conclusions: Ultrathin LDS occlusal veneers outperformed thin and standard thick counterparts, as well as gradientmultilayered zirconia veneers at all thickness levels. Ultrathin gradient multilayered zirconia occlusal veneers were proneto cracks during thermomechanical fatigue. Individual mechanical properties need to be considered when aligning therestoration within the multilayered zirconia blank.Keywords: Ceramics, Occlusal veneer, Ceramic thickness, Fatigue, Computer-aided design
Prott et al. (Thu,) studied this question.