Evaluating Fracture Resistance of Implant-Supported Crowns Using Lithium Disilicate vs. Zirconia Restorations

Background: Implant-supported crowns are required to withstand larger occlusal forces, especially in posterior areas. Restorative ceramics, such as lithium disilicate and monolithic zirconia, are popular; however, their mechanical properties differ greatly. The objective of this study was to compare the fracture and fatigue resistance between lithium disilicate and zirconia crowns in simulated oral conditions. Methods: A randomized controlled in vitro study was conducted between January and May 2025 at the Department of Prosthodontics. 120 implant-supported crowns were prepared and randomly divided into two equal groups. Group A included lithium disilicate crowns, and Group B monolithic zirconia crowns. All the crowns were cemented with standardized titanium abutments and were subjected to thermocycling (5,000 cycles) and mechanical loading (100,000 cycles at 100 N). A universal testing machine was used to measure fracture strength and fatigue performance. Statistical analysis, mainly using SPSS version 26.0, included independent t-tests and chi-square tests. Statistical significance was at p < 0.05. Results: The fracture resistance was significantly higher in Group B (zirconia; 1835 ± 225 N) compared to Group A (lithium disilicate; 1325 ± 195 N), p < 0.001. Group B crowns had a 54 (90%) survival rate compared to a 29 (48.3%) survival rate for Group A under fatigue loading, thereby suggesting improved long-term mechanical durability. Conclusion: In implant-supported restorations, the fracture resistance of monolithic zirconia crowns was much higher compared to lithium disilicate. Due to strong masticatory forces, zirconia might be the choice in posterior sections. More clinical trials are needed to confirm the long-term results.