Abstract
A hardening material was developed by mixing tetracalcium phosphate [Ca4(PO4)2O] powder with citric acid [C6H8O7] - malonic acid [C3H4O4] solution. When mixed at a powder to liquid ratio (P/L) of 1.3 (g/g), this paste hardened within 3-4 minutes with its surface pH rapidly increasing to the neutral range. The strength of the hardening material was sufficient for dental and/or bone cement at P/L=1.3 and above. No apatite was detected in the hardening material by X-ray powder diffraction, however in distilled water its crystal structure was partially converted to apatite. This conversion was more rapid in phosphate buffer solution (pH=8.0); it occurred within one day, and the crystal structure of products was similar to bone apatite. The hardening material was slightly soluble (ca.2wt%) in distilled water. However the residue, which was amorphous, was also converted to apatite in phosphate buffer solution (pH=8.0). These results suggest the usefulness of this hardening material as a basic material of bioactive dental and bone cement.
