Characterisation, by the PIXE method, of trace elements during physicochemical reactions at the periphery of bioactive glass pastilles in contact with biological fluids

The prerequisite for bioactive glasses to bond to living bone is the formation of biologically active apatites on their surface in the body. Reactions and bioactivity mechanisms between bioactive glasses and bone depend on the glass composition. We study a glass in the SiO2-Na2O-CaO-P2O5-K2O-Al2O3-MgO system. To characterise physicochemical reactions at the materials periphery, we immersed the glass pastilles into biological fluids for periods of 5, 10, and 20 days. The surface changes were studied at the micrometer scale by a Particle Induced X-ray Emission ( PIXE) method associated with Rutherford Backscattering Spectroscopy (RBS). After 20 days of immersion, elemental maps showed the formation of a calcium-phosphate layer at the surface of the glass pastilles. The thickness of this layer was around 15 mu m. Thanks to the PIXE method, we demonstrated the presence of traces of Mg in this layer. The glass doped with MgO leads to the formation of an apatite which incorporates magnesium. Formation of this Ca-P-Mg layer represents the bioactive properties of the studied glass. This biologically active layer improves the properties of the glass and will permit a chemical bond between the ceramic and bone.