Effect of the substitution of La2O3 for CaO on the bioactivity of 2.5CaO.2SiO2 glass.

Glasses of the following composition were prepared: (2.5-x)CaO.x/3La2O3.2SiO2 (0 < or = x < or = 1). Their behavior when soaked in a simulated body fluid (SBF) was studied by means of electron microscopy (EM) equipped with an energy-dispersive system (EDS) for elemental analysis, IR spectroscopy, and x-ray diffraction. All the studied glasses react with SBF by forming a calcium phosphate layer. This layer appears to be increasingly thinner with increasing amounts of La2O3 substituted. The experimental results are in good agreement with mechanisms reported in the literature. Moreover they suggest that lanthanum oxide is retained in the layer below the phosphate. After 6 days of soaking, crystalline hydroxyapatite is formed in the case of La2O3 free glass.