Ceramics provide excellent chemical durability, wear resistance, biocompatibility and respect for the environment. One of the most important properties to be considered in fully ceramic dental implants is the cyclic fatigue due to cyclic mechanical stress to which the implants are overwhelmed during mastication processes which can induce thousands of stress cycles per day in a restoration, thereby significant display subcritical crack growth and so can reduce the resistance of ceramic components, over time. In this work, the prediction of fatigue life cycle of ZrO2-Al2O3 composite was investigated. A powder mixture containing 80% ZrO2 and 20% Al2O3 was compacted and sintered at 1600 °C. The sintered samples were characterized by X-ray diffraction and scanning electron microscopy. Hardness, toughness and bending strength were determined and the results used in determining the parameters of fatigue. The fatigue tests were performed on device 4 point bending under 25 Hz frequency and stress ratio of 0.1. An increased level of stress has led to reduction of lifetime under fatigue. Based on parameters determined by the mechanical tests and fatigue, and using Weibull statistic associated with models for determining growth subcritical fault, the rate of crack propagation in composite is determined and related to phase transformation mechanism and residual stress between the phases. The components subject to cyclic loading exhibited subcritical crack propagation at stress levels significantly lower than KIC. Despite this susceptibility to subcritical crack growth, calculations based on the parameters of fatigue and the applied voltages indicate that the composite structures with components ZrO2-Al2O3 can exhibit lifetime greater than 20 years, if the diameter of the structural member is suitably designed.
ceramic; ZrO2-Al2O3 composite; mechanical properties; fatigue
