Effect of silver diamine fluoride on nicotine-induced Streptococcus mutans biofilm

Silver diamine fluoride (SDF) reagent is used to prevent and arrest caries lesions. However, the mechanism of its action is not fully reported. The antimicrobial effect of SDF was determined on an established nicotine-induced Streptococcus mutans biofilm by measuring colony-forming units (CFUs), different application times, and extracellular polysaccharide (EPS) synthesis.

S mutans biofilm was established with and without 2 mg/mL of nicotine in tryptic soy broth supplemented with sucrose. Nicotine and nonnicotine-induced biofilm groups were treated with 38% SDF for 1 minute. Non-SDF-treated groups were used as a control. The biofilm was plated on blood agar plates, and CFUs were determined. In addition, different SDF application times (30 seconds and 1, 2, and 3 minutes) were tested. For EPS production, S mutans were incubated with and without nicotine in tryptic soy broth supplemented with sucrose. SDF groups were treated with SDF for 1 minute. A phenol-sulfuric acid assay was used to measure the total carbohydrate produced.

There was a significant effect of SDF on reducing CFUs for both nicotine and nonnicotine groups. The different application times of SDF reduced CFUs for all tested groups. EPS production was significantly reduced with the SDF application.

The use of SDF with different application times disrupted established S mutans biofilms. In addition, EPS production was reduced by the application of SDF. This confirms the ability of a shorter SDF treatment time to be effective and suggests a possible mechanism of action for the inhibition of caries development.