Antibacterial Effects of Silver Fluoride and Difluorosilane-based Varnish on Streptococcus mutans

The purpose of this study is to evaluate the antibacterial effects of two liquid fluoride materials on Streptococcus mutans (S. mutans). Riva star aqua™ (SDI, Bayswater, Australia), which consists of silver fluoride (AgF, step 1) and potassium iodide (KI, step 2), and Fluor protector® (FP; Ivoclar Vivadent, Liechtenstein) were used for experimental groups. Experimental groups were divided into 4 groups : AgF, KI, AgF + KI and FP. For the positive control (PC) group, ampicillin was used, and the negative control group (NC) did not receive any additional treatment. Each group was divided into 30 and 50 µL groups by volume of liquid and applied to flat-coated S. mutans. The diameter of the zone of inhibition was measured. The PC and AgF groups showed larger diameters than other materials (p < 0.05), and the AgF group showed no significant difference from the PC group in the 50 µL group (p > 0.05). The FP group showed larger diameters than the AgF + KI group in the 30 µL (p = 0.009). The KI group did not show significant difference from the NC group (p > 0.05). AgF is comparable to ampicillin in antibacterial effects on S. mutans, and better than FP.