Carbonated hydroxyapatite as bone substitute

B-carbonateapatite (CHA) powder was synthesized starting from calcium nitrate tetrahydrate, diammonium hydrogen phosphate and sodium hydrogen carbonate. The powder was fully characterized in terms of phase purity, stoichiometry, morphology, specific surface area and particle size distribution. The thermal stability of the powder in air and CO2 atmosphere also was evaluated by thermal analysis. Electroacoustic analysis of the water based suspension of the CHA powder was used to determine the stability of the slurry. Porous bodies of CHA were prepared by impregnation of cellulose sponges with a proper slurry of the powder and optimizing the subsequent sintering. The fired samples were characterized in terms of phase purity and carbonate content, microstructure and pore size distribution. The compressive strength also was evaluated, resulting in 6.0 „b 0.5 MPa. First results of in vivo tests on New Zealand White rabbits showed good biocompatibility and osteointegration of the CHA implant, with higher osteoconductive properties and earlier bioresorption, compared to HA samples, used as control.