Protective effect of EVA layers under quasi-static loading for veneer-like ceramic discs

This study aimed to evaluate the quasi-static compressive loading of lithium disilicate and hybrid ceramic veneers at two ceramic thicknesses (0.5 mm and 1.0 mm), with and without the interposition of ethylene-vinyl acetate (EVA) plates simulating custom mouthguards. A total of 12 experimental groups were established, combining two ceramic types (lithium disilicate and hybrid ceramic), two ceramic thicknesses (0.5 mm and 1.0 mm), and three EVA plates conditions (no interposition EVA on ceramic - control, EVA with 2.0 mm and EVA 4.0 mm). Ceramic discs were fabricated, cemented onto epoxy resin fiber-reinforced cylinders (G10, dentin analog), and the ceramic/EVA assembly was subjected to compressive loading in a universal testing machine until catastrophic failure occurred. Data were analyzed using three-way ANOVA with Tukey's post hoc test (p < 0.05). Hybrid ceramic showed higher fracture resistance than lithium disilicate (2.886 N vs. 2.314 N; p < 0.001). Ceramic thickness had no significant effect (0.5 mm: 2.551 N; 1.0 mm: 2.649 N; p = 0.098). EVA interposition significantly increased strength (4 mm: 3.074 N > 2 mm: 2.705 N > control: 2.021 N; all p < 0.001). Within its limitations, this study demonstrated that the interposition of EVA plates improved the fracture resistance of the ceramic material under quasi-static loading, especially with 4-mm thickness. Hybrid ceramic exhibited superior quasi-static load-to-fracture resistance compared with lithium disilicate, particularly when combined with EVA plates.