Journal of the American Ceramic Society, Vol.87, No.12, 2195-2200, 2004
Chemical processing of CaHPO(4)(.)2H(2)O: Its conversion to hydroxyapatite
The aim of this paper is to develop. a robust chemical process to synthesize Na- and K-doped brushite (DCPD: dicalcium phosphate dihydrate, CaHPO(4)(.)2H(2)O), a potential starting material for bone substitutes. The powders were synthesized by using sodium phosphate and potassium phosphate and aqueous solutions containing calcium chloride at room temperature, followed by drying at 37degreesC. DCPD powders thus formed were found to contain 460 ppm K and 945 ppm Na. On calcination in air, these powders readily transformed into monetite (DCPA: dicalcium phosphate anhydrous, CaHPO4) first, and then into Ca2P2O7 (calcium pyrophosphate). Na- and K-doped DCPD powders were shown to completely transform, in less than I week, into poorly crystalline carbonated apatite on immersion in an acellular simulated/synthetic body fluid (SBF) solution at 37degreesC. The Tris (i.e., tris(hydroxymethyl)aminomethane) buffered SBF solution used in this study had a carbonate ion concentration of 27 mM equal to that of human plasma. DCPD powders of this study displayed a notable apatite-inducing ability. This finding suggests the use of these DCPD powders as the starting materials for potential bone substitutes, which can be easily manufactured in aqueous solutions friendly to living tissues, at temperatures between room temperature and 37degreesC.