The antimicrobial sensitivity of Streptococcus mutans and Streptococcus sangius to colloidal solutions of different nanoparticles applied as mouthwashes

Abstract

Background: Metal nanoparticles have been recently applied in dentistry because of their

antibacterial properties. This study aimed to evaluate antibacterial effects of colloidal solutions

containing zinc oxide (ZnO), copper oxide (CuO), titanium dioxide (TiO2) and silver (Ag)

nanoparticles on Streptococcus mutans and Streptococcus sangius and compare the results with those

of chlorhexidine and sodium fl uoride mouthrinses.

Materials and Methods: After adding nanoparticles to a water-based solution, six groups were

prepared. Groups I to IV included colloidal solutions containing nanoZnO, nanoCuO, nanoTiO2 and

nanoAg, respectively. Groups V and VI consisted of 2.0% sodium fl uoride and 0.2% chlorhexidine

mouthwashes, respectively as controls. We used serial dilution method to fi nd minimum inhibitory

concentrations (MICs) and with subcultures obtained minimum bactericidal concentrations (MBCs)

of the solutions against S. mutans and S. sangius. The data were analyzed by analysis of variance and

Duncan test and P < 0.05 was considered as signifi cant.

Results: The sodium fl uoride mouthrinse did not show any antibacterial effect. The nanoTiO2-

containing solution had the lowest MIC against both microorganisms and also displayed the lowest

MBC against S. mutans (P < 0.05). The colloidal solutions containing nanoTiO2 and nanoZnO showed

the lowest MBC against S. sangius (P < 0.05). On the other hand, chlorhexidine showed the highest

MIC and MBC against both streptococci (P < 0.05).

Conclusion: The nanoTiO2-containing mouthwash proved to be an effective antimicrobial

agent and thus it can be considered as an alternative to chlorhexidine or sodium fluoride

mouthrinses in the oral cavity provided the lack of cytotoxic and genotoxic effects on biologic

tissues.

Key Words: Mouthrinse, nanoparticle, Streptococcus mutans, Streptococcus sangius