Bioactive glasses have been used for many years as bone graft substitutes, to fill defects and augment bone structures. These materials are commercialized in the form of powder, granules, putty, and paste. Research activities have been conducted on 3D bioactive glass porous structures to provide structural support during bone ingrowth. Recent studies have shown that these materials might react with humidity and atmospheric CO2 and form carbonates. The kinetics of carbonate formation as well as their impact on powder properties (dissolution, sintering) are, however, not well documented.
This study presents the evolution of 45S5 powders (24.5Na2O-24.5CaO-6P2O5-45SiO2 wt%) after accelerated aging treatments (90%relative humidity, 5%CO2, 37°C). The results clearly show that 45S5 powder reacts with the atmosphere and forms various carbonates (CaCO3, Na2CO3 and NaHCO3) on the surface. The amount and variety of carbonates present on the powder evolves with time. Some of these carbonates quickly dissolve when immersed in water, thus affecting the pH of the solution. The carbonate species and adsorbed humidity affect the sintering process, even if they are decomposed during sintering and leave no residues. Thus it is important to control and monitor the aging process of bioactive glass. This may be done by controlling the atmosphere during processing, handling and storage of the material.