Fabrication of porous calcite using chopped nylon fiber and its evaluation using rats

Fabrication and Histological Evaluation of a Fully Interconnected Porous CO3Ap Block Formed by Hydrate Expansion of CaO Granules

Carbonate apatite (CO₃Ap) 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 CO₃Ap block was fabricated by hydrate expansion and carbonation of CaO granules, and the resulting CaCO₃ was then converted to CO₃Ap. When CaO granules were exposed to 100% humidity CO₂ 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 CaCO₃ block, which was then immersed in a Na₂HPO₄ solution to convert it to a porous CO₃Ap block. The resulting CO₃Ap block possessed a fully interconnected porous structure. Histological analyses 4 and 8 weeks after implantation in rabbits revealed that the porous CO₃Ap block resulted in more significant material resorption and bone formation than the dense CO₃Ap block. Therefore, it was concluded that a fully interconnected porous CO₃Ap block fabricated by the hydrate expansion of CaO granules has potential value as a bone substitute.

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

Carbonate apatite (CO₃ Ap) 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 CO₃ Ap 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 CO₃ Ap. Porous CO₃ Ap 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 CO₃ Ap granules, the largest amount of mature bone was seen to be formed inside the pores of CO₃ Ap (120) [porous CO₃ Ap granules made using 120-μm microfiber] followed by CO₃ Ap (50) and CO₃ Ap (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 CO₃ Ap (120). It is concluded, therefore, that the optimal pore size of the CO₃ Ap is that of CO₃ Ap (120), which is 85 μm.

Fabrication of calcite blocks from gypsum blocks by compositional transformation based on dissolution-precipitation reactions in sodium carbonate solution

Calcium carbonate (CaCO₃) has been used as a bone substitute, and is a precursor for carbonate apatite, which is also a promising bone substitute. However, limited studies have been reported on the fabrication of artificial calcite blocks. In the present study, cylindrical calcite blocks (ϕ6×3mm) were fabricated by compositional transformation based on dissolution-precipitation reactions using different calcium sulfate blocks as a precursor. In the dissolution-precipitation reactions, both CaSO₄·2H₂O and CaSO₄ transformed into calcite, a polymorph of CaCO₃, while maintaining their macroscopic structure when immersed in 1mol/L Na₂CO₃ solution at 80°C for 1week. The diametral tensile strengths of the calcite blocks formed using CaSO₄·2H₂O and CaSO₄ were 1.0±0.3 and 2.3±0.7MPa, respectively. The fabrication of calcite blocks using CaSO₄·2H₂O and CaSO₄ proposed in this investigation may be a useful method to produce calcite blocks because of the self-setting ability and high temperature stability of gypsum precursors.