Assessment of the antimicrobial effect of fluoride varnish containing nanosilver and conventional fluoride varnish on oral streptococci: an in-vitro study

Abstract

Background/aim Oral streptococci are commonly found in the human oral cavity and are considered the foremost cariogenic pathogens in tooth decay. The aim of this study was to assess the antimicrobial effect of fluoride varnish containing nanosilver particles with different concentrations and conventional fluoride varnish on oral streptococci. Materials and methods Streptococcus mutans (ATCC 25175) and Streptococcus salivarius (ATCC 13419) were grown in nutrient agar medium with 5% blood agar in the bacteriological laboratory. Then both strains were further cultured on Mueller–Hinton agar media separately; three different concentrations of nanosilver fluoride (Nsf) varnish (432, 216, and 108 µg/ml) were prepared and applied on the Mueller–Hinton plates. Conventional fluoride varnish was included as the control sample. The plates were further incubated anaerobically for 24 h at 37°C in the incubator. The antimicrobial effect of different varnishes was assessed by measuring the diameter of inhabitation zones in millimeters by a ruler. Statistical analysis was performed using analysis of variance test, followed by Tukey’s post-hoc test. Results The Nsf varnish showed antimicrobial effect against S. mutans, where the mean value of inhibition zone size (mm) was increased by increasing the concentration of Nsf. For S. salivarius, the mean value of inhibition zone (mm) was gradually decreased by increasing concentration of Nsf. Conventional fluoride varnish showed no inhibition zones in both bacterial strains. Conclusion Nsf varnish had better antibacterial effect than conventional fluoride varnish against both S. mutans and S. salivarius.