Fabrication of porous carbonate apatite granules using microfiber and its histological evaluations in rabbit calvarial bone defects

Carbonate apatite (CO₃Ap) granules are known to show good osteoconductivity and replaced to new bone. On the other hand, it is well known that a porous structure allows bone tissue to penetrate its pores, and the optimal pore size for bone ingrowth is dependent on the composition and structure of the scaffold material. Therefore, the aim of this study was to fabricate various porous CO₃Ap granules through a two-step dissolution–precipitation reaction using CaSO₄ as a precursor and 30-, 50-, 120-, and 205-μm diameter microfibers as porogen and to find the optimal pore size of CO₃Ap. Porous CO₃Ap granules were successfully fabricated with pore size 8.2–18.7% smaller than the size of the original fiber porogen. Two weeks after the reconstruction of rabbit calvarial bone defects using porous CO₃Ap granules, the largest amount of mature bone was seen to be formed inside the pores of CO₃Ap (120) [porous CO₃Ap granules made using 120-μm microfiber] followed by CO₃Ap (50) and CO₃Ap (30). At 4 and 8 weeks, no statistically significant difference was observed based on the pore size, even though largest amount of mature bone was formed in case of CO₃Ap (120). It is concluded, therefore, that the optimal pore size of the CO₃Ap is that of CO₃Ap (120), which is 85 μm.