Glass-ceramics offer great potential both as bioactive and "bioinert" implant materials. The effect of compositional changes on the crystalline phases precipitated and microstructure of enstatite (MgSiO_3) glass-ceramics has been studied. The principle phases precipitated from MgO-SiO_2-Na_2O (MSN) parent glasses were enstatite as the major phase,w ith cristobalite as the secondary phase. Increasing the amount of Na_2O present in the parent glass resulted in an increase in the proportion of cristobalite precipitated. The phase composition was also strongly affected by the additive used, NaF, resulting in proportionally more enstatite than the TiO_2. The additives strongly influenced the microstructure observed. The TiO_2 glasses produced a fine grain size (approx approx 10 mu m) with little residual glass and an acicular fracture surface. The NaF glasses produced large (>100 mu m), spherulitic grains with interstitial porosity. An MTT assay demonstrated that the TiO_2 containing ocmpositions were not cytotoxic.
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