Kanji Tsuru
Introduction of Interconnected Macro Pores into Carbonate Apatite Bone Substitute: Bridging granules with brushite
Kanji Tsuru and Kunio Ishikawa
Department of Biomaterials, Faculty of Dental Science, Kyushu University
Carbonate apatite (CO3Ap) bone substitute has attracted attention because it can be replaced to new bone due to the resorption by osteoclasts, followed by the deposition of bone mineral by osteoblasts [1]. At present, clinical trial using CO3Ap granules is being conducted, whereas introduction of interconnected macro pores into CO3Ap bone substitute is studied in parallel in order to enhance the rate of its bone replacement.
Piling and bridging of CO3Ap granules are one of methods to fabricate interconnected porous CO3Ap bone substitute, for example, hexagonal closest packing structure has interconnected porous structure consisting of intergranular space. For the bridging of CO3Ap granules, setting mechanism of brushite forming cement could be applied. Briefly, when CO3Ap granules were reacted with acidic calcium phosphate solution, the most thermodynamically stable brushite under acidic condition were precipitated on the granular surface and interlocked each other to obtain the bridging of CO3Ap granules. The obtained CO3Ap granules bridged with brushite were immersed in sodium carbonate solution to transform from brushite to CO3Ap.
In vivo study indicated that the interconnected porous CO3Ap showed higher resorbability than the CO3Ap without macro pores. The interconnected porous CO3Ap thus fabricated is expected to be useful as an artificial bone substitute because of its interconnected porous structure and chemical composition.
[1] K. Ishikawa, Bone substitute fabrication based on dissolution-precipitation reaction, Mater. 3 (2010) 1138-1155.