The apatite formation ability of CaF2 doping tricalcium silicates in simulated body fluid

The purpose of this study was to investigate the effects of CaF2 on the apatite formation ability of tricalcium silicates (Ca3SiO5, C3S) and the mechanism of apatite formation on C3S pastes. Different amounts of CaF2 (0, 1, 2 and 3 wt%) were mixed in the raw materials during the synthesis process of C3S. The apatite formation ability of the CaF2 doping C3S was examined by soaking the one-day setting pastes in simulated body fluid (SBF). The fluoride concentrations, pH values, structural and morphological variations of the pastes were examined during soaking in SBF. With the addition of CaF2, the initial crystalline apatite formation time of the pastes was decreased from three days to one day. After soaking for seven days, the thicknesses of apatite layers depositing on the surface of C3S doped with 0, 1, 2 and 3 wt% CaF2 were about 88, 102, 168 and 136 mu m, respectively. C3S doped with 2 wt% CaF2 showed the better ability to induce the formation of apatite. Furthermore, the mechanism of the apatite formation of the CaF2 doping C3S pastes may be attributed to the formation and stability of F-substituted apatite determined by x-ray photoelectron spectroscopy (XPS) at the early age. The results indicated that CaF2 doping C3S has better in vitro bioactivity, and may be used to prepare novel bone cement.