EFFECT OF CRYSTALLIZATION ON APATITE-LAYER FORMATION OF BIOACTIVE GLASS 45S5

The bioactive glass 4555 was crystallized to 8-100 vol% of crystals by thermal treatments from 550-680 degrees C. The microstructure of the glass-ceramics had a very uniform crystal size, ranging from 8 to 20 m u m. Fourier-transform infrared (FTIR) spectroscopy was used to determ ine the rate of hydroxycarbonate apatite (HCA) formation that occurs o n bioactive glass and glass-ceramic implants when exposed to simulated body fluid (SBF) solutions. Crystallization did not inhibit developme nt of a crystalline HCA layer, but the onset time of crystallization i ncreased from 10 h for the parent glass to 22 h for 100% crystallized glass-ceramic. The rate of surface reactions was slower when the perce ntage of crystallization was greater than or equal to 60%. (C) 1996 Jo hn Wiley & Sons, Inc.