Bioactive Glasses Based on SiO2-CaO-Na2O-P2O5-ZrO2 System: Effects of ZrO2 on the Glass Structure, Solubility and Mineral Precipitation in Simulated Body Fluid

Zirconia (ZrO2) containing bioactive glasses (BG’s) have been synthesized to determine their influence on the structure of a 0.56SiO2–0.15Na2O-0.25CaO-0.04P2O5 glass and the resulting solubility within a hydrated environment. In this study, the SiO2 content was directly substituted with 0.04 ZrO4 (Mol. Fr.) and structural analysis of the Control and Zr-Glasses was conducted using X-ray Photoelectron Spectroscopy (XPS) and Magic Angle Spinning-Nuclear Magnetic Resonance (MAS-NMR). These techniques indicate that the overall network connectivity (NC) of the glass increases with ZrO2/SiO2 substitution, suggesting that ZrO2 acts predominantly as a network former in the glass structure. The ion release profiles of the glasses incubated in de-ionized water from 1 to 1000 h showed decreased dissolution rates for the Zr-containing glasses. The in vitro bioactivity of glasses tested in Simulated Body Fluid (SBF) showed calcium phosphate (CaP) formation on the surface of all glasses after 100–1000 h incubation; however, the Zr-glass experienced delayed CaP precipitation compared to the Zr-free Control.