Apatite formation on the surface of ceravital‐type glass‐ceramic in the body

Abstract

Previous studies on surface structural changes in vitro as well as in vivo of bioactive A-W-type glass-ceramics and Bioglass-type glasses showed that the essential condition for glasses and glassceramics to bond to living bone is formation of a bonelike apatite layer on their surfaces in the body. Gross et al., however, had explained the bone-bonding mechanism of Ceravital-type apatitecontaining glass-ceramic without mentioning formation of the surface apatite layer. In the present study, apatite formation on the surface of one of Ceravitaltype glass-ceramics was investigated in vitro as well as in vivo. An apatitecontaining glass-ceramic of the composition Na₂O 5, CaO 33, SiO₂ 46, Ca(PO₃)₂ 16 wt%, which was named KGS by Gross et al., was soaked in an acellular simulated body fluid which had ion concentrations almost equal to those of the human blood plasma. The same kind of glassceramic was implanted into a rabbit tibia. Thin-film x-ray diffraction, Fourier transform infrared reflection spectroscopy, and scanning electron microscopic observation of the surfaces of the specimens soaked in the simulated body fluid showed that Ceravital-type glass-ceramic also forms a layer of carbonate-containing hydroxyapatite of small crystallites and/or a defective structure on its surface in the fluid. Electron probe x-ray microanalysis of the interface between the glassceramic and the surrounding bone showed that a thin layer rich in Ca and P is present at the interface. These findings indicated that Ceravital-type glassceramics also form the bonelike apatite layer on its surface in the body and bond to living bone through the apatite layer.