title: Disinfection of root canals with photon-initiated photoacoustic streaming.
abstract: BACKGROUND
  This study set out to compare the efficacy of laser-activated and ultrasonically activated root canal disinfection with conventional irrigation, specifically its ability to remove bacterial film formed on root canal walls.
  
  
  METHODS
  Seventy human premolars were shaped to an apical size #20, taper .07, sterilized, and contaminated in situ with oral bacteria for 1 week and incubated for 2 more weeks. Irrigation was done with 6% NaOCl (group 1), NaOCl ultrasonically activated with blunt inserts (group 2), or a pulsed erbium:YAG laser at nonablative settings (group 3) for a total of 60 seconds each. Positive and negative controls were also included. Aerobic bacterial sampling was performed, and the incidence of positive samples after 24 and 48 hours as well as bacterial counts (colony-forming units) were determined. Fixed and demineralized sections 1 mm and 4 mm off the apex were Brown-Brenn stained and assessed for remaining intracanal bacteria/biofilm and dentinal tubule penetration.
  
  
  RESULTS
  All 3 canal disinfection protocols significantly reduced bacterial counts (P < .001). None of the 3 techniques predictably generated negative samples, but laser-activated disinfection was superior to the other 2 techniques in this aspect (P < .05). Histologic sections showed variable remaining bacterial presence in dentinal tubules at the 4-mm level and significantly less bacterial biofilm/necrotic tissue remaining at the 1-mm level after laser-activated irrigation (P < .05).
  
  
  CONCLUSIONS
  Under the conditions of this combined in situ/in vitro study, activated disinfection did not completely remove bacteria from the apical root canal third and infected dentinal tubules. However, the fact that laser activation generated more negative bacterial samples and left less apical bacteria/biofilm than ultrasonic activation warrants further investigation.
authors.affiliation: Department of Endodontics, University of the Pacific, Arthur A. Dugoni School of Dentistry, San Francisco, CA 94115, USA. opeters@pacific.edu
authors.forename: Ove A
authors.initials: OA
authors.lastname: Peters
authors.forename: Sean
authors.initials: S
authors.lastname: Bardsley
authors.forename: Jennifer
authors.initials: J
authors.lastname: Fong
authors.forename: Goldie
authors.initials: G
authors.lastname: Pandher
authors.forename: Enrico
authors.initials: E
authors.lastname: Divito
mesh_terms: D001419:Bacteria / Q000187:drug effects / Q000528:radiation effects; D018441:Biofilms / Q000187:drug effects / Q000528:radiation effects; D015169:Colony Count, Microbial; D003786:Dental Pulp Cavity / Q000382:microbiology*; D004203:Disinfection / Q000295:instrumentation* / Q000379:methods; D006801:Humans; D007834:Lasers; D017319:Photosensitizing Agents / Q000528:radiation effects / Q000627:therapeutic use*; D012388:Root Canal Irrigants / Q000008:administration & dosage* / Q000737:chemistry / Q000528:radiation effects; D016369:Smear Layer; D007507:Therapeutic Irrigation / Q000295:instrumentation*; D014465:Ultrasonics
chemical_list: D017319:Photosensitizing Agents; D012388:Root Canal Irrigants