COMPOSITIONAL DEPENDENCE OF BIOACTIVITY OF GLASSES IN THE SYSTEM CAO-SIO2-AL2O3 - ITS INVITRO EVALUATION

In order to investigate fundamentally the effect of Al2O3 on the bioactivity of glasses and glass-ceramics, the compositional dependence of bioactivity of glasses in the system CaO-SiO2-Al2O3 was studied in vitro. It is already known that the essential condition for glasses and glass-ceramics to bond to living bone is the formation of an apatite layer on their surfaces in the body, and that the surface apatite layer can be reproduced even in an acellular simulated body fluid which has almost equal ion concentrations to those of the human blood plasma. In the present study, bioactivity of the glasses was evaluated by examining apatite formation on their surfaces in the simulated body fluid with thin-film X-ray diffraction, Fourier transform infrared reflection spectroscopy and scanning electron microscopic observation. Only CaO-SiO2-Al2O3 glasses containing Al2O3 less than 1.5 mol% formed the surface apatite as well as Al2O3-free CaO-SiO2 glasses, but CaO-SiO2-Al2O3 containing Al2O3 more than 1.7 mol% did not form it as well as an SiO2-free CaO-Al2O3 glass. This indicates that only a small amount of addition of Al2O3 to glass compositions suppresses the bioactivity of glasses and glass-ceramics by suppressing apatite formation on their surfaces in the body.