Numerical Modelling of Fracture Behaviours of Dental Restorations

Abstract

Ceramics have been increasingly becoming the prevalent materials of choice for such major prosthetic restoration as crowns and bridges. Their performance has been under much scrutiny as the key factors involved are investigated and identified for ensuring clinical success. However, long-term function in the oral cavity (mastication), and such problems as manufacturing defects, bruxism, or an impact accident, can lead to porcelain fracture. This has become a major barrier limiting more extensive exploitation of ceramic materials to fully replace metals in major dental restorative procedures such as multi-unit fixed partial dentures (FPDs), where tensile stresses may be substantial. This thesis aims to apply the eXtended Finite Element Method (XFEM) to prediction of crack initiation and propagation in all-ceramic dental prostheses. XFEM analyses were conducted to not only help quantify stress concentration and distribution, but also inherently accommodate the failure criteria from a fracture mechanics perspective. The modelling validation was performed by comparing the XFEM simulation with the in-vitro experiments. Fractographic analysis has also been introduced to define the cause of failures, as well as to identify the role of residual stresses, and pre-existing flaws on the longevity of dental restorations. Through the eight research projects conducted in this thesis, including thermal induced fracture of core-veneered ceramic structures, fracture behaviours of inlay and onlay FPDs, XFEM based topology optimization of all-ceramic structures, and fracture simulations of caries restorations and crowns, XFEM has been demonstrated to be an effective tool for analysing the fracture behaviours and optimising ceramic prostheses for enhancing longevity of various restorations. The outcomes generated in this thesis provided dentists and dental technicians with fundamental understanding in the fracture mechanics for a range of all-ceramic dental prostheses, thereby obtaining clinical guide for enhancing the fracture strength of the structure.