Transmission Electron Microscopic Observation of Glass-Ceramic A-W and Apatite Layer Formed on Its Surface in a Simulated Body Fluid

In the interior of glass-ceramic A-W, both the apatite and β-wollastonite were homogeneously dispersed in a glassy matrix, taking a form of rice grain 50 nm in width and 100 nm in length. The apatite layer formed on the glass-ceramic in the simulated body fluid consisted of fine needle-like apatite crystals about 10 nm in thickness and 100 nm in length, which are elongated along c-axis and randomly oriented. The apatite crystals in the surface layer were in direct contact with those within the glassceramic without intervention of such silica gel layer as observed for Bioglass®-type glasses. No crystallographic relation was observed between them. The apatite crystals in the surface layer were calciumdeficient, and contained small amounts of Mg and Si.