A Three-Dimensional Finite Element Analysis to Evaluate and Compare Stress Levels and Distribution Patterns in Lithium Disilicate and Zirconia Crowns.

Objective: This article aims to assess and compare the patterns of stress distribution and the biomechanical responses of monolithic zirconia and monolithic lithium disilicate crowns of different occlusal thicknesses using three-dimensional (3D) finite element analysis (FEA). Materials and Methods: A 3D FEA model of a mandibular first molar with all supporting structures was constructed. Eight models were developed to simulate clinically recommended preparation thicknesses for each material, including monolithic zirconia ( Results: Across all thicknesses, zirconia crowns developed higher peak internal VM stress (maximum: 456.8 MPa) but transferred less tensile stress to the underlying dentin (maximum: S ≈ 127 MPa) than lithium disilicate crowns, which transferred greater stress to the dentin (maximum: S ≈ 145.7 MPa). For both materials, non-axial loads (45 and 90 degrees) generated markedly higher stress concentrations (maximum: VM ≈ 457 MPa) than vertical loads (maximum: VM ≈ 278 MPa). Stress distribution within the lithium disilicate crown became visibly more homogeneous with increasing occlusal thickness. Conclusion: Within the limitations of this in silico model, monolithic zirconia exhibited a stress-shielding pattern in which more stress was retained within the crown and less was transmitted to the dentin, whereas lithium disilicate transmitted comparatively more stress to the dentin. Non-axial loading produced the highest stress peaks for both materials in this simulation. Because each material was modeled at the occlusal thickness clinically recommended for it, direct material-versus-material superiority cannot be inferred from these results, and clinical extrapolation should be made with caution.