Unstable cracking (chipping) of veneering porcelain on all-ceramic dental crowns and fixed partial dentures

The central argument of this study is that residual stresses developed during the preparation of all-ceramic crowns and fixed partial dentures coupled with contact-induced cracking are the origin of the excessive chipping observed in clinical applications. The aim of this paper is to provide a simple basic analysis of the causes of residual stress development in ceramics and identify the key thermo-mechanical parameters responsible for these stresses and the resultant contact-induced failure. For simplicity, a bilayer planar geometry is considered. The key outcomes are the critical role of thermo-elastic properties and the thickness of the structures. The approach is then used to evaluate the propensity for unstable cracking of a range of crown structures, including substructures of a range of ceramics, and to show that two specific combinations are most prone to this behaviour, namely porcelain fused to glass ceramics and zirconia substrates. In addition, a simple approach for the minimization of the likelihood for such behaviour and chipping is proposed. Crown Copyright (c) 2009 Published by Elsevier Ltd. on behalf of Acta Materialia Inc. All rights reserved.