The role of MgO on thermal properties, structure and bioactivity of bioactive glass coating for dental implants

The successful application of bioactive glasses as a coating for titanium implants to improve osseointegration is dependent on achieving a thermal expansion coefficient (TEC) match between the two phases. Many studies have indicated that magnesium affects the thermal and structural properties of a glass. However, its effect on bioactivity of bioactive glasses is still under debate. In this study, we characterize the effect of magnesium on the thermal properties, structure and bioactivity of glasses containing MgO. Seven glasses with different MgO concentrations have been synthesized by melt-derived technique. All these glasses contain SiO2, CaO, MgO, ZnO, Na2O, K2O and P2O5 and have been characterized by X-ray diffraction (XRD), differential scanning calirometry (DSC) and dilatometry. Additionally, the oxygen density and bulk density have been investigated. The bioactivity of the MgO glass series was evaluated in simulated body fluid (SBF) and Tris-buffer solution. The results indicate that magnesium suppresses crystallization and decreases TEC, glass transition temperature (Tg) and softening (Ts) temperature. Oxygen density increases proportionally with MgO content; whereas glass density decreases. After different time points, XRD and Fourier transform infra-red spectroscopy (FTIR) show that magnesium does not inhibit the apatite forming ability of the glasses, but retards the time of apatite deposition. The glass coatings of this series exhibit clear clinical application for use as a functional barrier: osteoblastic attachment and growth was poor, however, fibroblastic biocompatibility was good.