BIOACTIVITY OF NA2O-CAO-SIO2 GLASSES

Bioactivities of Na2O-CaO-SiO2 glasses were evaluated by examining the formation of bonelike apatite, which is responsible for their bonding to living bone, on their surfaces in a simulated body fluid, using thin-film X-ray diffraction and Fourier-transform infrared reflection spectroscopy. It was found that glasses in a wide compositional region in the P2O5-free Na2O-CaO-SiO2 system can show bioactivity, as those in the P2O5-containing system, The rate of apatite formation on the surfaces of glasses varied largely with the composition of the glasses. Under a constant SiO2 content of 50 mol%, a glass containing equimole of Na2O and CaO showed the highest rate of the apatite formation. Variation in the rate of apatite formation with the glass composition corresponded well with the rate of increase in the degree of the supersaturation of the simulated body fluid with respect to the apatite due to dissolution of sodium and calcium ions from the glasses. Little difference was observed in the rates of ion dissolution and of apatite formation between P2O5-containing Bioglass 45S5-type and a corresponding P2O5-free Na2O-CaO-SiO2 glass. It is believed that P2O5-free Na2O-CaO-SiO2 glasses also show bioactivity as high as that of Bioglass.