Effect of physical and chemical characteristics on the washout resistance of calcium sulfate pellets

The washout resistance of bone substitute in body fluid is essential for its medical application. In the present study, the effect of physical and chemical characteristics of calcium sulfate pellets on the washout resistance is investigated. Special attention is paid to the effect of crystalline structure. A calcium sulfate hemihydrate powder was used as the starting material, then heated to a temperature up to 1225 °C. Using a synchrotron X-ray diffractometer, the phase evolution from hemihydrate to anhydrite is characterized. The washout resistance of hemihydrate is very poor under the attack of a large amount of simulated body fluid (SBF). The anhydrite can be categorized into III, II and I; the resistance of anhydrite III is also poor. Nevertheless, the anhydrite II shows an excellent resistance to washout. Furthermore, the preosteoblast MC3T3-E1 cells can attach and proliferate on the surface of anhydrite II pellet. The washout resistance of anhydrite I is poor for the formation of microcracks.