Preparation and characterisation of zirconia/hydroxyapatite bioactive composites as potential dental implants

In dental implants, zirconia is well-known as a crown material due to its excellent acid and base resistances and appearance close to natural teeth. In addition, its extraordinary mechanical properties render zirconia to be a potential candidate as an implant component of a whole implanted tooth, if its biocompatibility can be improved to promote adhesion to natural hard tissues. This study aims to enhance the bioactivity of zirconia with the aim of improving its integration with gum bone. Hydroxyapatite is the major component of natural bone and is thus selected as the modifier to improve the bioactivity of zirconia. A series of zirconia/hydroxyapatite composites with varied compositions were prepared under different conditions in order to find the optimal composites for the target application. Various analytical technologies and mechanical tests are employed to characterise the structure and properties of resultant composites. Results show that the component ratio and sintering temperature have a significant influence on the composite properties. An increase in hydroxyapatite component tends to enhance bioactivity but decline mechanical strength. Composites containing 10 wt% of hydroxyapatite maintain sufficient mechanical strength under the optimal sintering conditions whilst possessing excellent bioactivity, demonstrating that hydroxyapatite-modified zirconia has the potential as dental implant materials. Sintering results suggest that mechanical strength is obtained at 1400 °C for 2 h for the composite containing 10 wt% of hydroxyapatite.