The failure loads of all-ceramic crowns are influenced not only by the theoretical strengths of the component materials but also by prosthesis geometry and size and location of flaws, so there is a need for a study that will compare the fracture resistance of such systems using a clinically relevant but simple and reproducible geometry. Objective: The research aim was to compare the in vitro fracture resistance and origin of failure of simulated first molar crowns fabricated using three all-ceramic systems, IPS Empress® 2, Procera® AllCeram, and In-Ceram® Zirconia. Methods: Twenty axisymmetric crowns of each system were fabricated to the same final thickness. The center of the occlusal surface on each of 15 specimens per system was axially loaded to fracture in a universal testing machine, and the maximum load was recorded. Fractured surfaces were examined using optical and electron microscopy to determine the most prevalent origin of failure in each system. Five crowns per system were sectioned, and thickness of the cement, core material, and veneer porcelain layers were measured along the axis of symmetry, 3 mm from the axis, and 1 mm below the die cusp. Results: The mean failure loads were: 825 ± 376 N (IPS Empress® 2), 876 ± 292 N (Procera® All-Ceram), and 1019 ± 268 N (In-Ceram® Zirconia). One-way ANOVA showed no statistically significant differences among the three systems (p = 0.23, b = 0.70). The origin of failure was most commonly found at the interface between ceramic core and veneer porcelain for all systems. Two-way MANOVA showed a significant interactive effect of system and location on both cement thickness and core thickness (p < 0.001). Conclusion: There was no significant difference in fracture resistance or failure origin between the all-ceramic systems studied for this application. This study was supported by Baylor Research Funds.

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