Immersion-induced changes in structure and properties of a TTCP/DCPA/CSH cement

This research was devoted to the investigation of the changes in structure and properties of a tetracalcium phosphate (TTCP)/dicalcium phosphate anhydrous (DCPA)/calcium sulfate hemihydrates (CSH) cement immersed in Hanks’ solution for different periods of time. The cement prepared by mixing TTCP/DCPA/CSH composite cement powder with 0.6 M diammonium hydrogen phosphate ((NH4)2HPO4) setting solution at a liquid/powder (L/P) ratio of 0.28 cm3 g−1 exhibited an average working time and setting time of 6.1 min and 7.1 min, respectively. Experimental results indicated a quick dissolution process of the CSH phase in the solution. After the cement was immersed in Hanks’ solution for 1 day, the TTCP/DCPA-hydroxyapatite (HA) phase transformation had been largely completed and a maximum compressive strength was reached. At this stage, the cement had lost 11% in weight and had a porosity of 26%. After 1 day, the cement gradually decreased its strength, although its weight and porosity level did not change significantly. The long-term pH value of the Hanks’ solution wherein the cement was immersed remained in the range between 6 and 7. The HA phase remained dominant throughout the entire 42 days of immersion. Cytotoxicity test showed that the viability value of the cells incubated with conditioned medium of cement extraction was 88% that of alumina (Al2O3) control and 90% that of blank medium.

• TTCP/DCPA/CSH composite cement exhibited an average working time and setting time of 6.1 min and 7.1 min.
• Experimental results indicated a quick dissolution process of the CSH phase in the solution.
• After the cement was immersed in Hanks’ solution for 1 day, the TTCP/DCPA-hydroxyapatite (HA) phase transformation had been largely completed and a maximum compressive strength was reached.
• At this stage, the cement had lost 11% in weight and had a porosity of 26%.