A rapidly-dissolving silica-silver bioactive glass for cariostatic applications

In this study, bioactive glasses were designed for the purposes of reducing the incidence of dental caries and lesion formation by supplying the teeth with therapeutic ions which may support remineralization and provide an antibacterial effect against oral cavity bacteria. Three glasses were synthesised through the melt quench method: Si-Control (SiO2-CaO-P2O5-Na2O), Si-02 and Si-05, where 0.2% and 0.5% Ag2O were substituted, respectively, for SiO2 in the control glass. The glasses were then ground, characterized and dissolved in tris buffer solution (pH=7.30) for 6, 12 and 24 hours, with the pH rise of the solution being recorded (7.48 for Si-Control, and 7.66 for both Si-02 and Si-05 after 24 hours) and the ions that were released into the tris buffer solution quantified. Samples of each glass were subsequently embedded into non-fluoridated toothpaste and samples of the paste were used to brush resin-mounted lamb molars after a 1.0M HCl overnight demineralization challenge. Knoop microhardness measurements were recorded before and after brushing to determine the presence of remineralization on the surface of the teeth (Percent Surface Hardness Loss of 37%, 35% and 34% for Si-Control, Si-02 and Si-05 respectively after 24 hours). Four oral cavity bacterial strains were isolated through swabs of the inner cheek, gums and teeth surfaces of three volunteers, and placed on agar discs. 0.5g of each glass were placed onto the discs and the resultant inhibition zones were measured after 6, 12 and 24 hours. Si-05 consistently performed better than Si-02 on all strains and timeframes, while Si-Control exhibited no antibacterial effect at any time point.