Effects of Sr/F-bioactive glass nanoparticles on pH, elemental release, dentin remineralisation, and cytotoxicity of 1.1% NaF toothpaste

Objective: This study examined the effect of Sr/F-bioactive glass nanoparticles (Sr/F-BAG) concentration on 1.1% NaF toothpaste. The effects of additives on pH, fluoride and elemental release, dentin remineralisation, and cytotoxicity were determined. Materials and methods: Sr/F-BAG particles were incorporated into 1.1% NaF toothpaste (0, 1, 2, and 4 wt%). F release and pH upon immersion in deionised water were determined using a fluoride-specific electrode and pH meter (n = 8). Elemental release was analysed using Inductively Coupled Plasma Optical Emission Spectroscopy (n = 3). Dentin remineralisation (mineral-to-collagen ratio) after application of experimental toothpaste was compared using Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR, n = 9). Cytotoxicity was assessed using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay (n = 3). Colgate PreviDent 5000 Plus toothpaste (PV) was used as a commercial comparison. Results: The addition of 0 to 4 wt% Sr/F-BAG linearly increased pH and F release of the 1.1% NaF toothpaste. Each 1 wt% increase in Sr/F-BAG concentration, raised pH by 0.3 and fluoride release by 457 ppm. The additives also enhanced the release of Ca, P, and Sr from the experimental toothpaste. At high concentration of Sr/F-BAG (4 wt%), the pH of the experimental toothpaste was comparable to PV (p > 0.05) but with significantly higher fluoride release (p < 0.05). However, PV demonstrated a significantly higher increase in mineral-to-collagen ratio compared to the experimental materials. The dentin surface treated with PV also showed more evident mineral precipitation. Furthermore, the experimental toothpaste containing 4 wt% Sr/F-BAG demonstrated higher cell viability (90%) than PV (56%). Conclusion: The addition of Sr/F-BAG enhanced the release of F, Ca, P, Sr, and increased the pH of the toothpaste. However, the experimental toothpaste with added bioactive glass up to 4 wt% did not demonstrate superior remineralising effects compared to commercial 1.1% NaF toothpaste. In addition, the incorporation of Sr/F-BAG promoted the cytocompatibility of the experimental toothpaste.