title: Treatment of root canal biofilms of Enterococcus faecalis with ozone gas and passive ultrasound activation.
abstract: BACKGROUND
  Biofilms of resistant species such as Enterococcus faecalis pose a major challenge in the treatment of root canals with established periapical disease. This study examined the effects of gaseous ozone delivered into saline on biofilms of E. faecalis in root canals of extracted teeth with and without the use of passive ultrasonic agitation.
  
  
  METHODS
  Biofilms of E. faecalis were established over 14 days in 70 single roots that had undergone biomechanical preparation followed by gamma irradiation. The presence and purity of biofilms were confirmed using scanning electron microscopy and culture. Biofilms were treated with saline (negative control), 1% sodium hypochlorite for 120 seconds (positive control), ozone (140 ppm ozone in air at 2 L/min delivered into saline using a cannula for 120 seconds), saline with passive ultrasonic activation (70 kHz and 200 mW/cm(2) applied to an ISO 15 file held passively within the canal, for 120 seconds), and ozone followed immediately by ultrasonic agitation. After treatment, samples were taken from the biofilm and serially diluted for plate counting.
  
  
  RESULTS
  Analysis revealed that 1% sodium hypochlorite was the most effective disinfecting agent followed by ozone combined with ultrasonic agitation, ozone alone, and finally ultrasonic alone.
  
  
  CONCLUSIONS
  Although none of the treatment regimes were able to reliably render canals sterile under the conditions used, ozone gas delivered into irrigating fluids in the root canal may be useful as an adjunct for endodontic disinfection.
authors.affiliation: School of Dentistry, The University of Queensland, Brisbane, Queensland, Australia.
authors.forename: Peter D
authors.initials: PD
authors.lastname: Case
authors.forename: Philip S
authors.initials: PS
authors.lastname: Bird
authors.forename: William A
authors.initials: WA
authors.lastname: Kahler
authors.forename: Roy
authors.initials: R
authors.lastname: George
authors.forename: Laurence J
authors.initials: LJ
authors.lastname: Walsh
mesh_terms: D058491:Bacterial Load / Q000187:drug effects; D001431:Bacteriological Techniques; D018441:Biofilms / Q000187:drug effects*; D019551:Dental Disinfectants / Q000494:pharmacology; D003786:Dental Pulp Cavity / Q000382:microbiology*; D013293:Enterococcus faecalis / Q000187:drug effects*; D006801:Humans; D008422:Materials Testing; D050296:Microbial Viability / Q000187:drug effects; D008855:Microscopy, Electron, Scanning; D016877:Oxidants / Q000494:pharmacology*; D010126:Ozone / Q000494:pharmacology*; D012388:Root Canal Irrigants / Q000494:pharmacology; D012973:Sodium Hypochlorite / Q000494:pharmacology; D013997:Time Factors; D014465:Ultrasonics / Q000295:instrumentation
chemical_list: D019551:Dental Disinfectants; D016877:Oxidants; D012388:Root Canal Irrigants; D010126:Ozone; D012973:Sodium Hypochlorite