Fatigue of Zirconia - Bioglass Dental Ceramics.

In this work the cyclic fatigue life of 3mol.%Y2O3-stabilized zirconia polycrystalline ceramics, doped with 5%wt 3CaO.P2O5,-SiO2-MgO, has been investigated. Samples with 5 and 10%wt were cold uniaxial pressed (80MPa) and sintered in air at 1200 and 1300 degrees C for 120 minutes. Sintered samples were characterized by X-Ray diffraction and Scanning Electronic Microscopy. Hardness and fracture toughness were determined using Vicker's indentation method, and Modulus of Rupture was determined by four-point bending testing. Furthermore, the cyclic fatigue tests were also realized by four-point bending tests, under frequency of 25 Hz and stress ratio, R, of 0.1, for the best condition. In this condition, highly dense samples were obtained and presented values of hardness, fracture toughness and bending strength of 11.3 +/- 0.1GPa, 6.1 +/- 0.4MPa.m(1/2) and 320 +/- 55MPa, respectively. The increasing of stress level leads to decreasing of the number of cycles and the number of run-out specimens. The stress induced tetragonal-monoclinic (t-m)-ZrO2 transformation, observed by X-Ray diffraction, contributes to the increasing of the fatigue life. Samples 3Y-TZP presents clearly a range of loading conditions where cyclic fatigue can be detected.