title: Synergistic antimicrobial action of chlorhexidine and ozone in endodontic treatment.
abstract: OBJECTIVE
  The aim of this study was to determine whether irrigation with sodium hypochlorite, chlorhexidine, and ozone gas, alone or in combination, were effective against Enterococcus faecalis and Candida albicans; these are microorganisms frequently isolated from teeth with periapical lesions resistant to endodontic treatment.
  
  
  METHODS
  220 single root teeth, recently extracted, were inoculated with Candida albicans and Enterococcus faecalis. The formulations tested were sodium hypochlorite at 1, 3, and 5% chlorhexidine at 0.2% and 2% and ozone gas applied for different periods of time. The combination of sodium hypochlorite at 5% and chlorhexidine at 2%, with gaseous ozone, were also assessed. For the most active treatments the mechanism of action was assessed through flow cytometry.
  
  
  RESULTS
  Sodium hypochlorite, chlorhexidine, and gaseous ozone alone were ineffective in completely eliminating the microorganisms. The association of chlorhexidine at 2% followed by ozone gas for 24 seconds promoted the complete elimination of Candida albicans and Enterococcus faecalis. Flow cytometry shows that ozone and chlorhexidine act differently, which could explain its synergic activity.
  
  
  CONCLUSIONS
  This new disinfection protocol, combining irrigation with chlorhexidine at 2% and ozone gas for 24 seconds, may be advantageous when treating infected root canals.
authors: Department of Endodontics, Catholic University of Portugal, Campus Viseu, Estrada da Circunvalação, 3504-505 Viseu, Portugal.
authors: Rita
authors: 0000-0002-8497-2186
authors: R
authors: Noites
authors: Department of Microbiology, Faculty of Medicine, Alameda Professor Hernâni Monteiro, 4200-319 Porto, Portugal.
authors: Cidália
authors: C
authors: Pina-Vaz
authors: Department of Microbiology, Faculty of Medicine, Alameda Professor Hernâni Monteiro, 4200-319 Porto, Portugal.
authors: Rita
authors: R
authors: Rocha
authors: Department of Endodontics, Faculty of Dentistry, Rua Dr. Manuel Pereira da Silva, 4200-393 Porto, Portugal.
authors: Manuel Fontes
authors: MF
authors: Carvalho
authors: Department of Microbiology, Faculty of Medicine, Alameda Professor Hernâni Monteiro, 4200-319 Porto, Portugal.
authors: Acácio
authors: A
authors: Gonçalves
authors: Department of Endodontics, Faculty of Dentistry, Rua Dr. Manuel Pereira da Silva, 4200-393 Porto, Portugal.
authors: Irene
authors: 0000-0002-5885-0724
authors: I
authors: Pina-Vaz
mesh_terms: D000890:Anti-Infective Agents / Q000494:pharmacology*; D002176:Candida albicans / Q000187:drug effects; D002710:Chlorhexidine / Q000494:pharmacology*; D004357:Drug Synergism; D004708:Endodontics; D013293:Enterococcus faecalis / Q000187:drug effects; D005434:Flow Cytometry; D006801:Humans; D008826:Microbial Sensitivity Tests; D010126:Ozone / Q000494:pharmacology*; D012390:Root Canal Therapy; D012973:Sodium Hypochlorite / Q000494:pharmacology
chemical_list: D000890:Anti-Infective Agents; D010126:Ozone; D012973:Sodium Hypochlorite; D002710:Chlorhexidine