Mechanical properties and cytotoxicity of 3Y-TZP bioceramics reinforced with Al2O3 particles

The influence of Al2O3 addition and sintering parameters on the mechanical properties and cytotoxicity of tetragonal ZrO2–3 mol% Y2O3 ceramics was evaluated. Samples containing 0, 10, 20 and 30 wt.% of Al2O3 particles were prepared by cold uniaxial pressing (80 MPa) and sintered in air at 1500, 1550 and 1600 °C for 120 min. The effects of the sintering conditions on the microstructure were analyzed by X-ray diffraction analysis and scanning electron microscopy. Hardness and fracture toughness were determined by the Vickers indentation method and the mechanical resistance by four-point bending tests. As a preliminary biological evaluation, “in vitro” cytotoxicity tests were realized to determine the cytotoxic level of the ZrO2–Al2O3 composites, using the neutral red uptake method with NCTC clones L929 from the American Type Culture Collection (ATCC) bank. Fully dense ceramic materials were obtained with a hardness ranging between 1340 HV and 1585 HV, depending on the amount of Al2O3 in the ZrO2 matrix. On the other hand, no significant influence of the Al2O3 addition on fracture toughness was observed, exhibiting values near 8 MPa m1/2 for all compositions and sintering conditions studied. The non-cytotoxic behavior, the elevated fracture toughness, the good bending strength (σf = 690 MPa) and the elevated Weibull's modulus (m = 11) exhibited by the material, show that these ceramic composites are highly suitable biomaterials for dental implant applications.