Load-Bearing Capacity of Lithium Silicate Derivates Applied as Ultra-Thin Occlusal Veneers on Molars

Purpose: This study aimed to evaluate the load-bearing capacity of three different millable lithium silicate derivatives compared with lithium disilicate ceramic when used as ultra-thin occlusal veneers on eroded molars. The null hypothesis stated that there would be no significant differences in load-bearing capacity (Fmax). Material and Methods: Four groups were tested: three groups with lithium silicate derivatives—“Celt” (Celtra, Dentsply Sirona, Bensheim, Germany), “Vita” (Vita Suprinity PC, Vita Zahnfabrik, Bad Säckingen, Germany), and “Nice” (n!ce, Straumann, Basel, Switzerland)—and a control group with lithium disilicate ceramic, “Emax” (IPS e.max CAD, Ivoclar Vivadent) (n = 20 per group). Extracted molars (n = 80) were prepared to simulate erosion and restored with occlusal veneers designed and milled by using CAD/CAM technology. After thermo-mechanical aging, the specimens were subjected to static load testing until fracture. Failure types were recorded and analyzed. Statistical evaluation included the Wilcoxon rank-sum test for group comparisons and Weibull distribution modeling to assess fracture probabilities. Results: Thermo-mechanical aging caused restoration debonding in three specimens from the “Nice” and “Celt” groups, resulting in fatigue resistance of 100% for “Emax” and “Vita”, 90% for “Celt”, and 95% for “Nice”. The mean Fmax values ranged from 892 N to 2087 N, with the “Vita” group demonstrating the highest values. Significant differences in stress values were observed among groups (p < 0.05). Cohesive failure was the most frequent failure mode. Conclusions: All tested lithium silicate derivatives demonstrated high load-bearing capacity and are suitable for ultra-thin occlusal veneers on eroded molars. Cohesive failures dominated, indicating reliable material performance and stable bonding under load.