Static and dynamic in vitro study of a sol-gel glass bioactivity

A comparative study of in vitro bioactivity of a sol-gel glass with composi tion 55% SiO2-41% CaO-4%P2O5 has been carried out by soaking it in a simula ted body fluid (SBF) with and without exchange of this solution. When SBF i s kept constant (static assay) the solution composition changes, increasing the Ca2+ concentration and pH as a function of soaking time while these pa rameters remain nearly constant and very close to human conditions in dynam ic conditions. Glass surface is studied by FTIR, XRD and SEM in order to co mpare the behaviour in the two procedures, revealing that in both cases an apatite-like layer is formed on the glass surface, although there are diffe rences in rate and morphology in this formation. In addition, a study of po rosity was carried out by Hg intrusion pointing out the pore distribution a nd changes in porosity with time for both procedures. A similar behaviour i n mesopore region was detected, while macropores remain nearly constant in static conditions, decreasing from 0.48 to 0.12 mum in just 3 h of soaking in dynamic assay. (C) 2001 Elsevier Science Ltd. All rights reserved.