Effects of additives on the rheological properties and injectability of a calcium phosphate bone substitute material

An injectable calcium phosphate bone substitute material has been prepared by mixing amorphous calcium phosphate (ACP) and dicalcium phosphate dihydrate (DCPD) for use in noninvasive surgery, and the influence of additives, such as disodium hydrogen phosphate, polyethylene glycol (PEG), glycerin, and citric acid, on the rheological properties and injectability of the ACP + DCPD cement system have been studied in this work. Novel approach of thixotropy measurement has been used to characterize the stability of the pastes. The results show that the injectability and the setting time can be augmented by the addition of disodium phosphate solution to the paste but reduced by the addition of PEG 200, glycerin, or citric acid to the paste. This study suggests that the injectability and the setting time of the ACP + DCPD bone substitute material can be balanced, and the injectable calcium phosphate bone substitute material with satisfied fluidity and injectability for clinical operation can be prepared by optimizing the additives and their concentrations, according to different clinical requirements.