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 (Ca ₃SiO₅, 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 C ₃S doped with 0, 1, 2 and 3 wt% CaF₂ were about 88, 102, 168 and 136 νm, 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.