In Vitro Assessment of Anti-Bacterial and Anti-Biofilm Effects of Nanosilver Solution on Dental Plaque Microorganisms

Nanosilver particles have the potential to serve as bactericidal agent because of the antimicrobial influences of silver ion. This in vitro study aimed to evaluate the antimicrobial and antibiofilm properties of nanosilver against two dental plaque microorganisms, namely Streptococcus mutans (Sm) and Aggregatibacter actinomycetemcomitans (Aa).

Initially, growth inhibition zone test was performed in brain heart infusion agar medium using Cup-plate method. Subsequently, microdilution method was utilized to determine the Minimal Inhibitory Concentrations (MIC) and Minimal Bactericidal Concentrations (MBC). Furthermore, the kinetics of bacterial death was assessed by the Time-Kill Test in different time points (i.e., 30, 60, and 120 sec, as well as 5 min). In addition, the effect of these microorganisms was investigated on the formation of the bacterial biofilms using the tissue Culture Plate Method (TCP).

The results of the t-test indicated that chlorhexidine (120 μg/ml) and nanosilver (200 μg/ml) had the same antimicrobial effect on S m, whereas chlorhexidine was more effective against Aa (P<0.0001). The MIC and MBC of silver nanoparticles were 3.90 and 3.90 μg/ml for Sm and 6.5 and 13.01 μg/ml for Aa. The kinetics of bacterial death evaluation demonstrated that in both tested bacteria, the antimicrobial agents were able to reduce microorganism populations regarding 6 algorithmic cycles significantly after 30 sec of the contact with the antibacterial agent. The t-test statistical analysis showed no significant difference between nanosilver and chlorhexidine groups regarding the biofilm decreasing percentage for Sm and Aa (P>0.05).

Nanosilver had rapid and significant antibacterial effects against dental plaque microorganisms. It is also very effective in inhibiting biofilm formation in two bacterial species in in vitro condition.