  It is proposed in this study to observe the influence of P2O5 on the
formation of the apatite-like layer in a bioactive glass via a complete PIXE
characterization. A glass in the SiO2-CaO-P2O5 ternary system was elaborated by
sol-gel processing. Glass samples were soaked in biological fluids for periods
up to 10 days. The surface changes were characterized using Particle Induced
X-ray Emission (PIXE) associated to Rutherford Backscattering Spectroscopy
(RBS), which are efficient methods for multielemental analysis. Elemental maps
of major and trace elements were obtained at a micrometer scale and revealed
the bone bonding ability of the material. The formation of a calcium
phosphate-rich layer containing magnesium occurs after a few days of
interaction. We demonstrate that the presence of phosphorus in the material has
an impact on the development and the formation rate of the bone-like apatite
layer. Indeed, the Ca/P atomic ratio at the glass/biological fluids interface
is closer to the nominal value of pure apatite compared to P2O5 free glasses.
It would permit, in vivo, an improved chemical bond between the biomaterials
and bone.
