Bioactive cement which can set in a few minutes and bond to living bone is obtained by mixing CaO-SiO2-P2O5-CaF2 glass powders with ammonium phosphate solution. The mechanical strength of the cement has been investigated as a function of phosphate ion concentration and pH of the ammonium phosphate solution and powder to liquid ratio. A glass powder with a composition CaO 47.1, SiO2 35.8, P2O5 17.1, CaF2 0.75 in mass ratio was mixed with ammonium phosphate solution, placed in 100% humidity at 37°C for 1h and immersed into a simulated body fluid (SBF). The compressive strengths of the cements soaked in SBF for 23h increased with increase in phosphate ion concentration and pH of the ammonium phosphate solution and in powder to liquid ratio. It has been found that the cements using ammonium phosphate solution with pH 7.4 and phosphate ion concentration of 3.7M give the highest compressive strength of 58MPa. It has been indicated that for the fixed ratio of powder to liquid, the compressive strength of the cement soaked in SBF increases with increasing amount of the hydroxyapatite layer formed at the intergranular spaces in the glass powders.
