Dissolution kinetics physico-chemical reacyions at bioactive glass/bone interface studied by STEM-EDXS
Résumé
Bioactive glass coatings are interesting to develop direct bond between prostheses and bone. But, the high solubility of these materials limits their application. Addition of alumina can be used to control their solubility, but may inhibit the bonding mechanisms. In this work, we study a bioactive glass in the SiO2-Na2O-CaO-P2O5-K2O-Al2O3-MgO system. After delays of implantation from 2 to 12 months, the bioactive glass/bone interface is characterised by Energy Dispersive X-ray spectroscopy coupled to Scanning Transmission Electron Microscopy. Bioactive glass dissolution can be decomposed in three steps with selective leaching. Results show that at 2 months after implantation, the bioactive glass is composed with Al, Si, Ca and P. Alumina addition increases the coating stability without inhibiting bonding process. Complex physico-chemical reactions take place at the glass periphery. The coating bonded to bone through a Ca-P rich layer on top of a Si rich layer. These phenomena are associated to bioactivity property, which occurs up to 6 months. At this period, the dissolution of the apatite layer occurs. After 12 months, the bioactive glass is composed with silicon