Effect of various additives on microstructure, mechanical properties, and in vitro bioactivity of sodium oxide-calcium oxide-silica-phosphorus pentoxide glass–ceramics

• MgO makes glass network tighter and reduces glass–ceramic bioactivity.
• TiO2 makes the network more integrated and has no significant effect on bioactivity.
• CaF2 decreases the integrity of glass network and promotes glass crystallization.
• CaF2 improves the bioactivity and crystallization which does not inhibit bioactivity.
• The doping ions in glass significantly improve the mechanical properties.

The partial substitution of MgO, TiO2, or CaF2 for CaO in the Na2OCaOSiO2P2O5 (45S5) system was conducted by the sol–gel method and a comparative study on structural, mechanical properties, and bioactivity of the glasses was reported. Based on thermogravimetric and differential thermal analysis, the gels were sintered with a suitable heat treatment procedure. The glass–ceramic properties were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and so on, and the bioactivity of the glass–ceramic was evaluated by in vitro assays in simulated body fluid (SBF). Results indicate that with the partial substitution of MgO, TiO2, CaF2 for CaO in glass composition, the mechanical properties of the glass–ceramics have been significantly improved. Furthermore, CaF2 promotes glass crystallization and the crystallization does not inhibit the glass–ceramic bioactivity. All samples possess bioactivity; however, the bioactivity of these glass–ceramics is quite different. Compared with 45S5, the introduction of MgO decreases the ability of apatite induction. The addition of TiO2 does not significantly improve the bioactivity, and the replacement of CaO by CaF2 shows a higher bioactivity.

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