In vivo evaluation of chelate-Setting cement fabricated from hydroxyapatite including bone minerals using a rabbit's tibia model

Hydroxyapatite (HAp) is one of components of bone and teeth, and has an osteoconductivity. Thus, the HAp has been used as biomaterials for bone graftings. We have succeeded in development of the novel chelate-setting calcium-phosphate cement (CPC) using pure HAp particles surface-modified with inositol phosphate (IP6). While, biological apatite presented in bone and teeth of mammals contains various ions: Na₊, K₊, Mg₂₊, C1_-", F" and C0_32-", in addition to Ca₂₊ and P0₄ ions. In this work, in order to create the chelate-setting CPC with enhanced osteoconductivity, the above-mentioned biological apatite powder (hereafter, bone HAp), instead of pure HAp, was used as a starting powder for fabrication of the chelate-setting cement. The biocompatibility of the resulting chelate-setting bone HAp cement (hereafter, IP6-bone HAp cement) was examined using a rabbit's tibia model. When the living reaction to hard tissue was histologically examined after 4 weeks implantation, we could observe that newly-formed bone directly bonded to the surface of the specimen. The newly-formed bone was also present around the cement specimen. The amounts of newly-formed bone around IP6-bone HAp cement was about 1.5 times those around IP6-pure HAp cement without bone minerals. The above findings demonstrate that the present IP6-bone HAp cements are one of the promising candidates as novel CPC with enhanced osteoconductivity.