Fracture Modelling for Porcelain/Zirconia Ceramic Prosthesis

Objectives: The aim of this study was to investigate the fracture behaviours of porcelain veneered to a zirconia core ceramic material structures and dental prostheses such as crown and fixed partial denture (FPD). Methods: A numerical approach was developed to evaluate the two dimensional ceramic models and dental restorations under a controlled cooling rate from high temperature (approximate 900°C) to room temperature (25°C). The extended finite element method (X-FEM) has emerged as a powerful numerical procedure for simulating crack initiation and propagation. In the material sample case, two design scenarios are considered with cracking in the porcelain/zirconia bi-layered material systems with thickness ratios of 2:1 and 1:1 respectively, which is induced by the thermal residual stress during fabrication. In the prosthesis case, the crack in three, four and six-unit bi-material dental bridges are considered under multi-loading cases. Results: The findings showed that the factors affecting the fracture behaviours included geometry of models, thickness of structures, cooling rates and mismatches of temperature-dependent material properties. Unlike the existing studies with prescriptions of initial cracks, the XFEM model presented herein will predict the progressive damage in the material and prosthetic structures. This will then be followed by automatic crack insertion and subsequent crack growth from a continuum to discrete manner. The fracture patterns exhibits a good agreement with the experimental data and clinical observation. Conclusions: Since the numerical results correlates well to the clinical and laboratory observations, the XFEM model of crack initiation and propagation could predict the likelihood for fracture. It is therefore of significant potential to the development of optimal dental prostheses.