Impact fatigue deformation and residual stress evolution in dental ceramics

Advanced ceramics are widely being used as bio-materials, for example as implants and in reconstructions. The everyday environment of these components often involves corrosive fluids and cyclic fatigue. Restorations such as dental crowns are subject to prolonged cyclic impact fatigue submerged in a primarily warm saline environment. These conditions, in co-ordination with the inherent flaws, favor crack growth and lead to catastrophic failure. One important factor which influences time to failure is the residual stress state. Among ceramic materials used as structural materials, zirconia has a relatively higher fracture toughness and hardness. Synchrotron X-ray micro-diffraction facilitated the determination of residual stresses. Model zirconia base layered composites were subjected to fatigue cycles at loads experienced by a typical dental crown. Sub-micron resolution strain maps containing the deviatoric components were obtained. The distribution of the components of strains as a function of fatigue cycles was observed. These observations, along with the understanding of the residual stresses in zirconia, will assist in developing new components with enhanced strength and damage tolerance resulting in increased lifetime.