Solution effects on the surface reactions of a bioactive glass.

The in vitro surface reactions of a 45S5 bioactive glass in three simulated body fluids (SBF) are analyzed using Fourier transform infrared (FTIR) spectroscopy. Five reaction stages are observed. Calcium and phosphate ions in SBF accelerate to a small extent the repolymerization of silica (Stage 3) and formation of an amorphous calcium-phosphate (a-CP) layer (Stage 4) on the glass surface. The a-CaP layer is crystallized to form hydroxy-carbonate apatite (HCAp) (Stage 5) more rapidly in the Ca- and P-containing SBF solutions (in 90 min rather than 120 min). However, Mg ions in SBF slow down formation of the a-CaP layer and greatly retard crystallization of HCAp on the glass surface.