Fracture Resistance of Zirconia-Reinforced Lithium Silicate in Single Posterior Implant-Supported Crowns: An In Vitro Study

Abstract

Background/Objectives: Zirconia-reinforced lithium silicate (ZLS) is a glass–ceramic that combines the translucency of lithium disilicate with the enhanced strength provided by dispersed zirconia crystals. Evidence on the mechanical behavior of ZLS implant-supported crowns remains limited. This study evaluated the fracture resistance of posterior monolithic ZLS crowns and analyzed the influence of cement type and artificial aging. Methods: Forty ZLS crowns (Celtra™ Duo) were fabricated, cemented onto straight titanium abutments and assigned to four groups (n = 10) according to cement type (adhesive or self-adhesive) and aging (500,000 cycles at 150 N). Specimens underwent axial load-to-fracture testing using a universal testing machine. Data were analyzed with Student’s t-tests and Kruskal–Wallis tests (α = 0.05). Results: Mean fracture resistance was 1625.46 ± 340.02 N. Although adhesive cement showed higher mean values than self-adhesive cement, no statistically significant differences were found (p = 0.102). Artificial aging also produced no significant reduction in fracture resistance (p = 0.674). All groups exceeded the physiological posterior occlusal forces. Conclusions: Monolithic ZLS crowns cemented onto titanium abutments demonstrated high fracture resistance under axial loading. Within the limitations of this in vitro design, neither cement type nor mechanical aging significantly affected performance. These findings support the mechanical feasibility of ZLS for posterior implant-supported single crowns, although further studies including thermomechanical aging and oblique loading are required.