Antibacterial Effect of Gold Nanoparticles Coated Dental Floss Against Cariogenic Bacteria

Abstract

Background: Carious lesions can occur on the proximal surfaces of the posterior teeth. Streptococcus mutans and Streptococcus sobrinus, are the main acidogenic bacteria that are commonly associated to dental caries. Interproximal cleaning is an important form of oral self-care habits, considering such areas of the dentition are easily affected by caries. Accordingly, dental floss has been used as an additional tool to enhance the quality of the cleaning process. It is reasonable that dental flossing should reduce interproximal caries risk because it is capable of removing parts of the interproximal plaque. The aim of this study was to evaluate the antibacterial activity of gold nanoparticle (AuNPs), when coated on unwaxed dental floss. Methods: Streptococcus mutans and Streptococcus sobrinus were cultured in Brain Heart Infusion (BHI) agar. Broth microdilution method was used to determine the minimum inhibitory concentrations (MICs) and the minimum bactericidal concentrations (MBCs) of the AuNPs with subcultures so obtained. Then, the bacteria were grown and spread on blood agar on which identical lengths (20mm) of unwaxed dental floss coated with gold nanoparticles (AuNPs) at concentration of 0.05, 0.1, and 0.5 mg/mL were placed. Control included untreated unwaxed dental floss and unwaxed dental floss with 0.2% Chlorhexidine (CHX). Five randomized sites of the inhibition zones were measured in millimeters in each concentration per floss. Means ± S.D. of the inhibition zones were calculated. Results: The MIC and MBC of AuNPs against S. sobrinus and S. mutans were 0.5 μg/mL and 1.0 μg/mL, respectively. The results indicated that gold nanoparticles (AuNPs) coated unwaxed dental floss, placed on blood agar with S. mutans and S. sobrinus demonstrated significant inhibition of bacterial growth. Gold nanoparticles (AuNPs) coated unwaxed dental floss at 0.05, 0.1, 0.5 mg/mL resulted in zones of inhibition ranging from 2.93 ± 0.30 mm to 4.71 ± 0.32 mm for S. sobrinus and 2.95 ± 1.73 mm to 5.18 ± 0.61 mm for S. mutans, respectively. Conclusion: In vitro study demonstrated that the AuNPs-coated unwaxed dental floss had antibacterial activities against cariogenic bacteria.