Surface reactions of bioactive glasses in buffered solutions

In vitro bioactivity of glasses is usually measured in buffered solutions whereby a formation of a hydroxyapatite layer on the surface is taken as an indication of the bioactivity. In this work we compare the layer formation on three glasses in simulated body fluid, Tris buffer solution, sodium phosphate buffered saline and osteoblast medium. Two of the glasses are known bioactive glasses, 45S5 (45 wt.% SiO2) and S53P4 (53 wt.% SiO2), while the third is an experimental composition with a higher silica content (68 wt.% SiO2). Plates of the glasses were immersed in the solutions at 37 °C for different times up to two weeks. The results showed clear differences between the layer developments on the three glasses in the different solutions. The results indicated that the relative order of the reactivity depended on the solution. Thus, results gained in different solutions for different glasses cannot be directly compared.