Reactivity kinetics of 52S4 glass in the quaternary system SiO2–CaO–Na2O–P2O5: Influence of the synthesis process: Melting versus sol–gel

A new composition of bioactive glass, in the quaternary system SiO2–CaO–Na2O–P2O5, was synthesized using melting and sol–gel routes. The prepared glass, 52S4: (wt.%) 52% SiO2–30% CaO–14% Na2O–4% P2O5, was soaked in Simulated Body Fluid (SBF) in order to evaluate the kinetic reactivity of this glass versus the synthesis mode. The obtained results have shown that 52S4 is a bioactive glass if it is prepared either by melting or sol–gel methods. The bone-like apatite was formed at the glass surface prepared by sol–gel route after 2 h. However, the formation of this apatite was delayed to 1 day when the glass was prepared by melting method. In addition, this apatite was crystallized, after 30 days soaking in SBF, only if the glass is prepared by melting route. The glass prepared by sol–gel method was more resorbable and leads to silica gel formation up on amorphous apatite layers at any time. So, this silica gel inhibited the crystallization of amorphous apatite.