Zirconia-hydroxyapatite composite material with micro porous structure

Objectives: Titanium plates and apatite blocks are commonly used for restoring large osseous defects in dental and orthopedic surgery. However, several cases of allergies against titanium have been recently reported. Also, sintered apatite block does not possess sufficient mechanical strength. In this study, we attempted to fabricate a composite material that has mechanical properties similar to biocortical bone and high bioaffinity by compounding hydroxyapatite (HAp) with the base material zirconia (ZrO₂), which possesses high mechanical properties and low toxicity toward living organisms. Methods: After mixing the raw material powders at several different ZrO ₂/HAp mixing ratios, the material was compressed in a metal mold (8 mm in diameter) at 5 MPa. Subsequently, it was sintered for 5 h at 1500 °C to obtain the ZrO₂/HAp composite. The mechanical property and biocompatibility of materials were investigated. Furthermore, osteoconductivity of materials was investigated by animal studies. Results: A composite material with a minute porous structure was successfully created using ZrO ₂/HAp powders, having different particle sizes, as the starting material. The material also showed high protein adsorption and a favorable cellular affinity. When the mixing ratio was ZrO₂/HAp = 70/30, the strength was equal to cortical bone. Furthermore, in vivo experiments confirmed its high osteoconductivity. Significance: The composite material had strength similar to biocortical bones with high cell and tissue affinities by compounding ZrO₂ and HAp. The ZrO₂/HAp composite material having micro porous structure would be a promising bone restorative material.