Fabrication and Histological Evaluation of a Fully Interconnected Porous CO 3 Ap Block Formed by Hydrate Expansion of CaO Granules.

Carbonate apatite (CO 3 Ap) fabricated by a dissolution-precipitation reaction from a precursor exhibits excellent osteoconductivity and is readily replaced by bone. In the present study, a fully interconnected porous CO 3 Ap block was fabricated by hydrate expansion and carbonation of CaO granules, and the resulting CaCO 3 was then converted to CO 3 Ap. When CaO granules were exposed to 100% humidity CO 2 in a closed vessel, the CaO granules were hydrated and expanded to form a porous Ca(OH) 2 block. The block was then carbonated to form a porous CaCO 3 block, which was then immersed in a Na 2 HPO 4 solution to convert it to a porous CO 3 Ap block. The resulting CO 3 Ap block possessed a fully interconnected porous structure. Histological analyses 4 and 8 weeks after implantation in rabbits revealed that the porous CO 3 Ap block resulted in more significant material resorption and bone formation than the dense CO 3 Ap block. Therefore, it was concluded that a fully interconnected porous CO 3 Ap block fabricated by the hydrate expansion of CaO granules has potential value as a bone substitute.