Bioactivities of a SiO2-CaO-ZrO2 glass in simulated body fluid and human parotid saliva

A glass in the system wollastonite-zirconia, with a nominal composition of: 43.5 wt% SiO2 -43.5 wt% CaO -13wt% ZrO2. was obtained. This was soaked in two different solutions: simulated body fluid (SBF) and parotid human saliva (PHS), in order to compare its behaviour in a natural high protein content (PHS) medium and in an acellular protein-free solution (SBF). The SBF solution contained the same inorganic salts as in the human blood plasma, while the PHS contained both inorganic salts and various proteins. Both immersion systems were maintained for one month at 37degreesC. The results have shown that the glass does not show any in vitro bioactivity when is soaked in SBF. However, a hydroxyapatite-like (HA-like) layer is formed on its surface when immersed in PHS. The interfacial reactions product was examined by Scanning Electron Microscopy (SEM), fitted with Energy-Dispersive X-say Spectroscopy (EDS). Additionally, changes in ionic concentrations in both systems and pH right at the interface glass/surrounding fluid were also determined. The results confirm that to establish the potential bioactivity in vitro of a material, the physiological medium must be properly selected.