Effect of Selective Grinding Methods on Fracture Toughness of Monolithic Zirconia with Different Translucency: A FEA Study

Aim: Chairside and laboratory grinding procedures are frequently required to optimize the fit and occlusion of zirconia restorations; however, these adjustments may introduce surface defects, trigger phase transformation, and adversely affect long-term mechanical performance. The influence of clinically relevant grinding parameters on different zirconia generations remains unclear. This study aimed to evaluate the tribomechanical behavior of 3Y-TZP, 4Y-PSZ, and 5Y-PSZ under simulated milling conditions.Materials and Methods: CAD models of mandibular first molar crowns (1.5 mm thickness) were generated and analyzed using finite element analysis with the Explicit Dynamics module in ANSYS Workbench 2022 R2. A 1.0-mm milling bur was modeled as a rigid body, and rotational speeds ranging from 200000 to 400000 RPM were simulated. Zirconia materials were defined as linear isotropic elastic solids. Wet and dry grinding conditions were represented by friction coefficients of 0.15 and 0.45, respectively. Structural reliability was assessed using Weibull statistics.Results: Dry milling significantly increased stress magnitudes (820–960 MPa), resulting in fracture probabilities of up to 77% for 5Y-PSZ. Wet milling substantially reduced stresses (520–620 MPa) across all zirconia types. A rotational speed of 350000 RPM minimized vibrational instability. Conclusion: Wet grinding is critical for preserving the mechanical integrity of high-translucency zirconia. Among the materials tested, 3Y-TZP demonstrated superior resistance under high-stress conditions.