title: 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 fluoride mouthrinses.
  
  
  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 fluoride and 0.2% chlorhexidine mouthwashes, respectively as controls. We used serial dilution method to find 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 significant.
  
  
  RESULTS
  The sodium fluoride 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).
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Orthodontics, Dental Research Center, Faculty of Dentistry, Mashhad University of Medical Sciences, Mashhad, Iran.
authors.forename: Farzaneh
authors.initials: F
authors.lastname: Ahrari
authors.affiliation: Department of Orthodontics, Dental Research Center, Faculty of Dentistry, Mashhad University of Medical Sciences, Mashhad, Iran.
authors.forename: Neda
authors.initials: N
authors.lastname: Eslami
authors.affiliation: Department of Medicinal Chemistry, Faculty of Farmacy, Mashhad University of Medical Sciences, Mashhad, Iran.
authors.forename: Omid
authors.initials: O
authors.lastname: Rajabi
authors.affiliation: Department of Microbiology, School of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran.
authors.forename: Kiarash
authors.initials: K
authors.lastname: Ghazvini
authors.affiliation: Dentist, Private Practice, Mashhad, Iran.
authors.forename: Sahar
authors.initials: S
authors.lastname: Barati
keywords: Mouthrinse; Streptococcus mutans; Streptococcus sangius; nanoparticle