Biocompatibility of Hydroxyapatite-Alumina and Hydroxyapatite-Zirconia Composites including Commercial Inert Glass (CIG) as a Ternary Component

Hydroxyapatite (HA), chemical formula Ca10(PO4)6(OH)2, is a very popular bioceramic for orthopedic and dental applications. Although HA has excellent biocompatibility, its inferior mechanical properties make it unsuitable for load-bearing implant applications. Therefore,HA should be strengthened by a secondary phase to produce a composite that possesses robust mechanical properties. The aim of this study was to compare the microstructural and mechanical properties and biocompatibility of HA-Al2O3 and HA-ZrO2 composites with the addition of 5 and 10wt% commercial inert glass (CIG) independently and to determine from the studied composites the onewith themost suitable composition for biomedical applications. The powders were pressed and then, the pellets were sintered between 1000 – 1300 °C for four hours. The thermodynamic analyses of the sampleswere performed bymeans ofDTA followed by the thermodynamic analysis program FactSage. Microstructural characterizations were carried out using SEM + EDS and XRD, while hardness and compression tests were performed to measure the mechanical properties. The results showedthat thecompressive strengthandthemicrohardnessofHA-Al2O3 composites increasedwithrisingCIG content and increasing sintering temperature. On the other hand, forHA-ZrO2 composites, increasingCIG content caused an elevation inhardness andadecrease in compressive strengthvalues at 1300 °C.Thebiocompatibility tests (in vitro and in vivo) were performed on those composites that possessed the highest physical andmechanical properties. In conclusion, the optimumCIG contentwas determined to improve themechanical properties and biocompatibility of the composites. The mechanical properties and biocompatibility of HA-Al2O3 composites have been found to be lower than those ofHA-ZrO2 composites. In this study, the ideal compositewas selected asHA-ZrO25wt% (HZC5) sintered at 1200 °C.