Bioactivity of CaO·SiO₂-based glasses:in vitro evaluation

Abstract

In order to fundamentally study compositional dependence of bioactivity of glasses, both the surface structural changes of P₂O₅-free CaO · SiO₂ glass due to exposure to a simulated body fluid and the effects of adding a third component, such as Na₂O, MgO, B₂O₃, Fe₂O₃, P₂O₅ and CaF₂, were investigated. An acellular aqueous solution which had almost equal ion concentrations to those of the human blood plasma was used as the simulated body fluid. The surface structure changes were examined by electronprobe X-ray microanalysis, thin-film X-ray diffraction (XRD) and Fourier transform infrared (FTIR) reflection spectroscopy. It was found that even P₂O₅-free CaO · SiO₂ glass forms an apatite layer on its surface in the simulated body fluid, and that the rate of formation of the surface apatite layer is increased with the addition of Na₂O and P₂O₅ while it decreased with the addition of MgO, B₂O₃, CaF₂ and Fe₂O₃. This indicates that even P₂O₅-free CaO · SiO₂ glass can bond to living bone, forming the surface apatite layer in the body and that its bioactivity is increased with the addition of Na₂O and P₂O₅ while it is decreased with MgO, B₂O₃, CaF₂ and Fe₂O₃. It is speculated that a glass of the composition CaO · SiO₂ 100, Fe₂O₃ 3 in weight ratio does not bond to living bone.