Fabrication of low-crystalline carbonate apatite foam bone replacement based on phase transformation of calcite foam

Abstract

Carbonate apatite (CO3Ap) foam may be an ideal bone substitute as it is sidelined to cancellous bone with respect to its chemical composition and structure. However, CO3Ap foam fabricated using α-tricalcium phosphate foam showed limited mechanical strength. In the present study, feasibility of the fabrication of calcite which could be a precursor of CO3Ap was studied. Calcite foam was successfully fabricated by the so-called "ceramic foam" method using calcium hydroxide coated polyurethane foam under CO2+O2 atmosphere. Then the calcite foam was immersed in Na2HPO4 aqueous solution for phase transformation based on dissolutionprecipitation reaction. When CaO-free calcite foam was immersed in Na2HPO4 solution, low-crystalline CO3Ap foam with 93-96% porosity and fully interconnected porous structure was fabricated. The compressive strength of the foam was 25.6±6 kPa. In light of these results, we concluded that the properties of the precursor foam were key factors for the fabrication of CO3Ap foams.