Compositional dependence on the in vitro bioactivity of invert or conventional bioglasses in the Si-Ca-Na-P system

The bioactivity of 34 invert or conventional glasses in the P-free and P-containing Si-Ca-Na system was evaluated by examining the in vitro Hydroxy Carbonate Apatite (HCA) formation time. The silica content in the glasses varies between 39.48 and 55 mol %. The surfaces of glasses after soaking in simulated body fluid at 37 degrees C were analyzed by Fourier transform infraRed spectroscopy and scanning electron microscopy coupled with energy dispersive spectroscopy. To understand the HCA formation mechanism, the modification of the glass surface structure was studied. The aim was to understand, in the Si-Ca-Na-P system, the function of each constituent on glass reactivity. It was noted that the bioactivity of Si-Ca-Na-P glasses depends on the P ratio. One of the P-free glasses is as bioactive as the Hench's Bioglass noted 45S5, because it needs 12 h to develop HCA as for Hench's one. In the quaternary system, some of the P-rich and Na, Si-poor glasses are more bioactive than 45S5 (6-10 h to obtain HCA). Two phosphorus effects were observed: the repolymerization of the silicate network and the formation of phosphate-modifier cation complexes.