Compositional dependence of bioactivity of glasses in the system CaO-SiO2-P2O5. Its in Vitro evaluation

Abstract

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. The apatite layer can be reproduced on their surfaces even in an acellular simulated body fluid which has ion concentrations almost equal to those of the human blood plasma. In the present study, in order to investigate the compositional dependence of bioactivity of glasses fundamentally, the apatite formation on the surfaces of glasses in the system CaO-SiO2-P2O5 was examined in the simulated body fluid. Thin-film X-ray diffraction, Fourier transform infrared reflection spectroscopy and scanning electron microscopic observation were used for detecting the apatite formation. It was found that CaO-SiO2 glasses free form P2O5 as well as those containing small amounts of P2O5 form the apatite layer on their surfaces, whereas CaO-P2O5 glasses free from SiO2 as well as those containing SiO2 do not form it. This indicates that bioactive glasses and glass-ceramics are obtained in compositions based on CaO-SiO2 rather than CaO-P2O5, contrary to the general view. These results were interpreted in terms of ions dissolved from glasses.