Fatigue behavior of 3%Y2O3-doped ZrO2 ceramics

The objective of this work was to evaluate the cyclic fatigue strength of a commercial pre-sintered tetragonal zirconia ceramics for dental systems, and to determine the main mechanical properties. Samples were sintered in air at 1600 °C for 120 min with heating and cooling rate of 10 °C/min. The sintered specimens were characterized by X-ray diffraction and scanning electron microscopy. Hardness and fracture toughness were determined using the Vicker's indentation method. The strength was determined by four-point bending tests. The cyclic fatigue tests were realized as four-point bending tests within a frequency of 25 Hz and a stress ratio R of 0.1. The Weibull analysis was employed in order to perform failure probability calculations. Sintered specimens presented average values of hardness, fracture toughness and bending strength near to 13.5 GPa, 8 MPa m1/2 and 900 MPa, respectively. The fatigue tests results allow concluding that the fatigue strength limit over 5 × 106 stress cycles is about 550 MPa or around 63% of the static strength of this material. The tetragonal–monoclinic (t–m) zirconia transformation observed by X-ray diffraction of fractured surfaces occurs during cyclic loading and the fracture of specimens. The 3Y-TZP samples clearly present a range of loading conditions where cyclic fatigue can be detected. The fatigue strength limit around 550 MPa is appropriate for application in dental implant parts.