Fluoride-reinforced 50S8P sol-gel bioactive glass for potential enamel remineralisation

Bioactive glasses (BGs) are widely used in various fields of dentistry, and reinforcing these BGs with fluoride is of particular interest for the remineralisation of dental hard tissue. In this study, fluoride-reinforced 50S8P BGs (BGF and mBGF) were prepared using the sol-gel method at different ageing temperatures. The BGs were manually ground into powder, sieved and characterised using thermogravimetric analysis (TGA) and differential scanning calorimetry ( (TGA-DSC), X-ray diffraction (XRD), X-ray Fluorescence (XRF), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS). The fluoride-reinforced BG (BGF and mBGF) exhibited a greater mass loss based on TGA, whilst DSC analysis showed that the addition of fluoride reduced transition temperature, crystallisation temperature and melting temperature. XRD analysis revealed that fluoride incorporation led to the formation of Na₂Ca₂Si₃O₉and fluorinated phases such as Ca₅(PO₄)₃F, NaCa₂FSiO₄and CaSiO₂F₂. FTIR spectra indicated that fluorine (F) in the composition bonded with Si-O-Si (tetrahedral structure) functional groups. XRF and EDS results confirmed the presence of fluorine in BG and mBGF samples, with a higher fluoride content observed in the mBGF sample. After incubation in simulated body fluid, XRD, FTIR and SEM analyses demonstrated that all three samples (BG, BGF and mBGF) were capable of forming a hydroxyapatite layer. Furthermore, BGF and mBGF exhibited the formation of fluoroapatite, indicating enhanced remineralisation potential. Additionally, these BGs showed non-toxicity at low doses and were biocompatible with SaOS-2 cells based on MTT assay results.