Enhanced properties of novel zirconia-based osteo-implant systems

Zirconia (ZrO2) ceramic has attracted much attention because of its superior mechanical properties and chemical stability in vivo for medical applications. However, this material has a poor affinity to cells and tissues, which needs to be overcome for bone implant applications. Thus, further research is required to develop a high efficacy ZrO2-based material candidate. Calcium silicate (CaSi)-based materials have gained increasing interest for use as bone graft substitutes because of their high osteogenesis. Efforts have been oriented toward the design of novel ZrO2-based systems where CaSi was added to enhance the osteogenesis of the structural implant ceramics. The effect of CaSi on the phase composition, long-term in vitro degradation, and osteogenesis of the ZrO2-based osteo-implants was evaluated. The experimental results revealed that the CaSi additive did not affect the tetragonal-monoclinic phase transformation of ZrO2. The 5 and 10 wt% CaSi-containing composites had three-point bending strength and biaxial strength values comparable to those of the ZrO2 control, whereas excessive CaSi resulted in the decreased strength. However, the three-point bending strength of 15 and 20 wt% CaSi-containing composites was within the reported bending strength for cortical bone. Interestingly, the bending modulus of the composite implants decreased with the increasing CaSi content. For the in vitro degradation, there were no obvious changes for all osteo-implants with the increasing soaking time, except the slight weight loss (less than 1%) of the 20 wt% CaSi implant. As expected, the higher CaSi implants appreciably enhanced the biological functions of the ZrO2 implant. It is concluded that the CaSi-ZrO2 composite osteo-implants offered a promising alternative to ZrO2 for load-bearing bone implant application.