The clinical success of laminate veneer restorations largely relies on the mechanical properties of the materials used. With the rise of ultra-translucent multilayered zirconia, it is crucial to evaluate the impact of facial thickness and yttria content on fracture resistance. This study aimed to computationally assess and compare the fracture resistance of zirconia veneers with varying facial thicknesses and yttria levels using Finite Element Analysis (FEA). A standardized 3D model of a maxillary central incisor featuring a butt-joint incisal design was created using ANSYS R18.1. Veneers with thicknesses of 0.75 and 1.00 mm were modeled using 3Y-YZP and 5Y-YZP zirconia. Supporting structures, such as the periodontal ligament and bone, were simulated. Occlusal forces of 15 N at 90° (protrusive) and 50 N at 60° (oblique) were applied to the palatal surface, and the stress distributions were analyzed using the von Mises criteria. Mesh convergence was verified, and the material properties were considered to be isotropic and elastic. The highest von Mises stress was 687.4 MPa in 5Y-YZP veneers at 0.75 mm thickness under oblique loading, while 3Y-YZP veneers showed significantly lower stress (407.2 MPa). Under a 50 N oblique load, 3Y-YZP with a thickness of 1.00 mm had a strength of 418.3 MPa compared to 561.3 MPa at 0.75 mm (25.5% reduction), while 5Y-YZP decreased from 687.4 MPa to 601.7 MPa (12.5% reduction). Overall, the 3Y-YZP veneers consistently exhibited superior mechanical performance compared to the 5Y-YZP veneers under all loading scenarios. This FEA-based simulation emphasizes the importance of selecting the appropriate zirconia type and veneer thickness based on load conditions. The 3Y-YZP is preferable for high-stress cases such as bruxism, and 5Y-YZP is preferable for aesthetic areas with adequate thickness.
Khandelwal et al. (Mon,) studied this question.