Controlling degradation in calcium phosphate cements

Calcium phosphate based cements can be moulded to irregular contours often encountered in medicine. Brushite cements are more soluble than hydroxyapatite (HA) in physiological conditions and as such can be more rapidly resorbed. The metastable nature of brushite means that it converts to HA following immersion in physiological conditions. This phase change reduces the resorption rate, resulting in long term stability. In this study, macropores were incorporated into brushite cement to accelerate degradation, preventing hydrolysis and long term stability. The incorporation of beads into the cement had no effect on the composition of the cement. By varying the proportion of beads in the cement, it was possible to control degradation and prevent the formation of HA within the cement. Interestingly, in the macroporous cement, after 14 days of aging, the only crystalline component was beta-tricalcium phosphate, suggesting that an amorphous binding phase was formed following brushite dissolution; this phase may maintain the integrity of the cement.