Fabrication of solid and hollow carbonate apatite microspheres as bone substitutes using calcite microspheres as a precursor

Spherical carbonate apatite (CO ₃Ap) microspheres approximately 1 mm in diameter were fabricated by granulation of calcium hydroxide around a core followed by carbonation and phosphatization through dissolution-precipitation reaction. CO ₃Ap microspheres with high uniformity could not be achieved without using a core. Solid CO ₃Ap microspheres were obtained using a calcite core whereas hollow CO ₃Ap microspheres were obtained using a NaCl core. The obtained microsphere was identified as B-type CO ₃Ap by Fourier transform infrared analysis and the carbonate content was approximately 7-8 wt% regardless of the type of core used for sample preparation. The mechanical strength of both the solid and hollow CO ₃Ap microspheres was sufficient for practical use as a bone substitute.