Carbonate apatite artificial bone

Bone apatite is not hydroxyapatite (HAp), it is carbonate apatite (CO(3)Ap), which contains 6–9 mass% carbonate in an apatitic structure. The CO(3)Ap block cannot be fabricated by sintering because of its thermal decomposition at the sintering temperature. Chemically pure (100%) CO(3)Ap artificial bone was recently fabricated through a dissolution–precipitation reaction in an aqueous solution using a precursor, such as a calcium carbonate block. In this paper, methods of fabricating CO(3)Ap artificial bone are reviewed along with their clinical and animal results. CO(3)Ap artificial bone is resorbed by osteoclasts and upregulates the differentiation of osteoblasts. As a result, CO(3)Ap demonstrates much higher osteoconductivity than HAp and is replaced by new bone via bone remodeling. Granular-type CO(3)Ap artificial bone was approved for clinical use in Japan in 2017. Honeycomb-type CO(3)Ap artificial bone is fabricated using an extruder and a CaCO(3) honeycomb block as a precursor. Honeycomb CO(3)Ap artificial bone allows vertical bone augmentation. A CO(3)Ap-coated titanium plate has also been fabricated using a CaCO(3)-coated titanium plate as a precursor. The adhesive strength is as high as 76.8 MPa, with excellent tissue response and high osteoconductivity.