Distributed crack analysis of ceramic inlays.

In all-ceramic restorations, crack formation and propagation phenomena are of major concern, since they may result in intra-oral fracture. The objective of this study was calculation of damage in porcelain MOD inlays by utilization of a finite-element (FE) implementation of the distributed crack theory. "Damage" is defined as the parameter that describes the local decrease of stiffness caused by microdefects. In the simulated MOD ceramic inlay, the crack initiation starts at the internal occlusal surface near the pulpo-axial line angle. This initiation is invisible from the external surface and cannot be detected by the clinician. The crack initiation at the internal surface started as soon as 55-60% of the loading needed for complete fracture was reached. The use of FE techniques for calculation of the fracture in loaded ceramic inlays offers prospects for further detailed study of the crack behavior, including three-dimensional modeling and cyclic loading situations.