A Water Setting Tetracalcium Phosphate- Dicalcium Phosphate Dihydrate Cement
Elena F. Burguera, F Guitian, Laurence C. Chow
This paper reports the development of a calcium phosphate cement, comprising tetracalcium phosphate (TTCP) and dicalcium phosphate dihydrate (DCPD), that hardens in 14 min with water as the liquid or 6 min with a 0.25 mol/L sodium phosphate as the liquid without the need of using seeds as a setting accelerator. It was postulated that reduction in porosity would increase cement strength. Thus, the effects of applied pressure during the initial stages of the cement setting reaction, with either water or the phosphate solutions as liquid, on cement strength and porosity were studied. The cement powder comprised an equimolar mixture of TTCP (median particle size 17mm) and DCPD (median particle size 1.7mm). Compressive strength (CS) values of samples prepared with distilled water were (mean standard deviation; n = 6) 47.6 2.4 MPa, 50.7 4.2 MPa and 52.9 4.7 MPa at applied pressures of 5 MPa, 15 MPa and 25 MPa, respectively. When phosphate solution was used instead, the CS values obtained were 41.5 2.3 MPa, 37.9 1.7 MPa and 38.1 2.3 MPa at the same pressure levels. Statistical analysis of the results showed that pressure produced an improvement in CS when water was used as the setting liquid but not when the phosphate solution as the setting liquid. Compared to previously reported TTCP-DCPD cements, the greater CS values and shorter setting times together with a simplified formulation should make the present TTCP DCPD cement a useful material as bone substitute for clinical applications.