Improvement in biocompatibility of ZrO2–Al2O3 nano-composite by addition of HA

The biocompatibility of zirconia–alumina (ZA) nano-composites in load-bearing applications such as dental/orthopedic implants was significantly enhanced by the addition of bioactive HA. The ZA matrix was composed of nano-composite powder obtained from the Pechini process and had higher flexural strength than conventionally mixed zirconia–alumina composite. Because the ZA nano-composite powder effectively decreased the contact area between HA and zirconia for their reaction during the sintering process, the HA-added ZA nano-composites contained biphasic calcium phosphates (BCP) of HA/TCP and had higher flexural strength than conventionally mixed ZA–HA composite. From the in vitro test with osteoblastic cell-lines, the proliferation and the differentiation (as expressed by the alkaline phosphatase activity) of the cellular response on the HA-added ZA nano-composites gradually increased as the amount of HA added increased. From the mechanical and biological evaluations of the HA-added ZA nano-composites, 30HA (30 vol% HA+70 vol% ZA) was found to be the optimal composition for load-bearing biological applications.