The properties of calcium phosphate cement consisting of α tricalcium phosphate ( α TCP) and tetracalcium phosphate (TTCP) have been investigated by using a cement liquid that contained citric acid with concentration of 0.05?mol/L or higher. The relationship between the setting time of the system cement and the concentration of citric acid solution shows concave type curve. When solution concentration was 0.2?mol/L, the setting time was 8 min, which was the shortest. While the relationship between 24?h compressive strength of the cement and the citric acid concentration shows convex type curve. When solution concentration was 0.2?mol/L, the compressive strength was 39.0?MPa, which was the highest. Afterwards, the microstructure of the hardening product was observed by SEM, the effect of citric acid on the exothermic rate of hydrate reaction was studied by microcalorimeter, and the crushed specimens were subjected to X ray diffraction. The results verified that the low citric acid concentration can accelerate the hydrate reaction rate of the α TCP/TTCP system. However, the high citric acid concentration inhibited hydroxyapatite formation and retarded the rate of hydrate reaction of the α TCP/TTCP cement.
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