SOLUTION EFFECTS ON THE SURFACE-REACTIONS OF 3 BIOACTIVE GLASS COMPOSITIONS

The in vitro five-stage surface reactions of two bioactive glass compo sitions, 45S5 and 52S4.6, and one bioinert glass, 60S3.8, exposed to t hree simulated body fluids (SBF) were analyzed using Fourier Transform infrared Spectroscopy (FTIR). There was Little effect of SBF composit ion on ion exchange, silica hydrolysis, and silica polymerization (sta ges 1-3) of glass with silica content up to 52 wt%. However, calcium a nd phosphate ions in SBF accelerated the formation of an amorphous cal cium-phosphate (a-CP) layer (stage 4), and crystallization (stage 5) o f the hydroxycarbonate apatite (HCAp) layer. The magnesium ions had a retardation effect on the kinetics of stages 4 and 5, but little effec t on stages 1-3. In SBF solutions which contained calcium and phosphat e ions an amorphous calcium-phosphate (a-CaP) layer formed on even a 6 0S3.8 glass which was not bioactive in vivo. However, the a-CaP layer did not crystallize to form HCAp. Thus, there is a significant contrib ution from the ions present in the SBF solutions to the HCAP formation and crystallization of HCAp on bioactive glasses. Also, silanol repol ymerization is necessary for rapid crystallization of HCAp. (C) 1993 J ohn Wiley and Sons, Inc.