The influence of CaF2 content on the physical properties and apatite formation of bioactive glass coatings for dental implants

This report details the physical properties, bioactivity and biocompatibility of manufactured glasses containing a range of calcium fluoride (CaF₂) concentrations. Compositions were based on the following system: SiO₂, CaO, Na₂O, K₂O, P₂O₅, ZnO and MgO, and in total seven glasses were synthesized using a melt–quench route. The ratio of the base compounds was kept constant, but had increasing CaF₂ concentrations (0.00, 2.44, 4.77, 9.11, 10.33, 11.53 and 13.00 mol%). Glasses were characterized using X-ray diffraction (XRD), differential scanning calorimetry (DSC) and dilatometery. Density was quantified according to Archimedes method and apatite formation tested following immersion in simulated body fluid (SBF) and Tris-buffer solution. Glass coatings were prepared by enamelling technique using 10 mm in diameter pure titanium disks. XRD demonstrates that all glasses are amorphous and that the sintering window, glass transition and softening temperatures decrease with increasing CaF₂ content. In contrast, thermal expansion coefficient and glass density increase with CaF₂ content. After 1 week immersion in SBF and Tris, XRD and Fourier transform infrared (FTIR) spectroscopy showed that the surfaces of all glasses underwent structural changes with evidence of surface apatite formation. Fluoride-electrode analysis indicates that the amount of fluoride released was proportional to the original CaF₂ content. The survival and growth of osteoblasts on the surface of these glasses is consistent with biocompatible characteristics.