Study On The Setting Property And Cytotoxicity Of Bone Cement Of Tricalcium Silicate Doped CaF₂

Experimental purposes: Tricalcium silicate（3CaO·SiO2,C₃S）doped CaF₂powders were synthesizedby a co-precipitation method. The paste of bone cement were Prepared by the composited powder as thesolid phase, and the setting property were developed. Cytotoxity of the bone cement in vitro was evaluated.Experimental methods:（1） The content of free CaO（f-CaO）in the C₃S powders was analyzed withthe glycol-ethanol method. The setting time of C₃S bone cement was determined by the GillMorocco（Gilmore） Determination of needle. The dissolution extracts pH value of the paste along soakingtime were detecteded, and the micro-morphology of the paste soaked in the SBF was characterized by SEMand XRD, which commonly described the dynamic change of bone cement in SBF.（2） The L929cellmorphology treated with different paste extracts were observed. Cytotoxity in vitro was evaluated withMTT experimental.Experimental results:（1） Adding CaF₂can effectively reduced the content of f-CaO in the sample. thecontent of CaO without CaF₂in the sample was5.8wt%, and the content of CaO reduced to0.34wt%whenthe content of CaF₂was1.5wt%.（2） With the percentage of CaF₂increasing, the setting time of bonecement increased correspondingly. The C₃S sample without CaF₂initial setting time and final setting timewere92min and149min, while the content of CaF₂was1.5wt%, the initial setting time and final settingtime increased to141min、246min.（3） With the addition of CaF₂, extract’s pH of the paste decreased. Afterimmersion for7d, all the bone cement pH value of soaking liquid closed to neutral.（4） According to theanalysis of XRD and SEM, it can be observed that C-S-H and CDHA formed on the surface of hydratedpaste soaked in SBF.（5） After24h of cell culture, observation of the phenol positive control group byinverted microscope, found that many cells in suspension, almost no living cells, and the cells of negative control group and experimental group were fully stretched, and fusiform or irregular triangles, growth ingood state, the number and the cell morphology did not differ significantly between the negative controlgroup and experiment groups. After120h culture, the experimental group and the negative control groupcells were densely arranged, vigorous growth, two groups of cell gap is significantly reduced.（6） Theresults of cell culture showed that every the experimental group had no cytotoxicity in vitro. Comparedwith the negative control group, the experimental group of doping with1.5wt%CaF₂,which treated with50%concentration of the extract of C₃S bone cement for3d, and50%,75%extracts for5d, indicated therate of cell proliferation had an apparent increation.Experimental conclusion: Pure C₃S could be obtained at1350℃for4h by adding CaF₂from0.6to1.5wt%. With the doping of CaF₂, The hydration of the paste was delayed, and the extract pH of the pastesoaking in SBF decreased. SEM and XRD results indicated that apatite formed on the surface of thematerial after soaking in SBF, which meant the cement being bioactivity. MTT test showed that the bonecement was safe, so it might be taken as a potential bone cement repair alternative material.