Aging Time and Temperature Effects on the Structure and Bioactivity of Gel-Derived 45S5 Glass-Ceramics

Porous bioactive glass-ceramics based on the 45S5 Bioglass((R)) composition were fabricated by an acid-catalyzed sol-gel method. The effects of aging time and temperature on the structure and in vitro bioactivity were investigated. Fourier-transform infrared spectroscopy (FTIR) was carried out on the samples to understand the structure and to monitor the formation of hydroxyapatite (HA) after immersion in simulated body fluid (SBF). The bioactivity of gel-derived 45S5 glass-ceramic and amorphous 45S5 Bioglass((R)) was compared. The results showed that an increase in both aging time and temperature can enhance crystallization, whereas bioactivity is reduced with increasing aging time but not significantly influenced by aging temperature. Compared with amorphous 45S5 Bioglass((R)), gel-derived glass-ceramic aged for 3d at 60 degrees C exhibited a more rapid rate of HA formation after immersion for less than 7d. Amorphous 45S5 Bioglass((R)) showed higher HA formation rate after immersion in SBF for more than 7d, whereas the quantity of formed HA on gel-derived 45S5 glass-ceramic was still comparable to that of amorphous 45S5 Bioglass((R)) after immersion for 14d. It is suggested that the lower bioactivity of 45S5 glass-ceramics could be outweighed by the higher surface area and higher content of Si-NBO groups in gel-derived glass-ceramics. The results thus confirm that gel-derived 45S5 glass-ceramic exhibiting bioactivity comparable to that of amorphous 45S5 Bioglass((R)) can be fabricated by sol-gel method under suitable aging conditions.