Optimization of a calcium orthophosphate cement formulation occurring in the combination of monocalcium phosphate monohydrate with calcium oxide

In a previous study it has been found that mixtures of monocalcium phosphate monohydrate MCPM and calcium oxide CaO set upon mixing with water. In this study it was found that the optimum composition for such a mixture is a Ca/P molar ratio of 1.35±0.02. The milling procedure for preparation of the powder of this cement was also optimized. the optimum water/powder ratio appeared to be 0.53±0.01. Amounts of precipitated hydroxyapatite up to 7% by weight increased the compressive strength and the diametral tensile strength of the cement. The maximum values found for these properties were 6 and 1.6 MPa, respectively. Finally, it was found that the cement obtained its maximum strength within 5 h but this diminished upon further soaking in Ringer's solution at 37°C until after 10 weeks of soaking the strength was decreased to 62% of the maximum value.