title: Time-dependent antibacterial effects of the self-adjusting file used with two sodium hypochlorite concentrations.
abstract: BACKGROUND
  This in vitro study evaluated the time-dependent ability of the self-adjusting file (SAF) used with either of two NaOCl concentrations to reduce bacterial populations in long oval root canals.
  
  
  METHODS
  Oval-shaped canals from extracted teeth were infected with Enterococcus faecalis for 30 days and subjected to preparation with the SAF system using continuous irrigation with either 2.5% NaOCl (n = 11) or 6% NaOCl (n = 11). Bacteriological samples were taken before preparation (baseline) and after 2, 4, and 6 minutes of SAF operation.
  
  
  RESULTS
  Intragroup quantitative analyses revealed that the SAF operating for 2, 4, or 6 minutes yielded a highly significant bacterial reduction when compared with counts at baseline (P < .001) irrespective of the NaOCl concentration. No significant differences were found for intragroup analyses comparing the three time periods (P > .05). Likewise, intergroup quantitative analysis showed no significant difference for the SAF with 2.5% NaOCl or 6% NaOCl during 2, 4, or 6 minutes (P > .05). The incidence of positive cultures in the 2.5% NaOCl group was 6 of 11, 5 of 11, and 2 of 11 after 2, 4, and 6 minutes, respectively. Corresponding figures in the 6% NaOCl group were 4 of 11, 2 of 11, and 1 of 11. When all samples were gathered together, overall findings revealed that using the SAF for 6 minutes significantly reduced both the bacterial counts (P = .02) and the incidence of positive cultures (P = .04) when compared with 2 minutes.
  
  
  CONCLUSIONS
  Findings revealed that the SAF promoted a significant reduction in bacterial populations even after only 2 minutes regardless of the NaOCl concentration. The most impressive results were obtained after a 6-minute operation.
authors.affiliation: Department of Endodontics, Faculty of Dentistry, Estácio de Sá University, Rio de Janeiro, Rio de Janeiro, Brazil.
authors.forename: Flávio R F
authors.initials: FR
authors.lastname: Alves
authors.forename: Bernardo M
authors.initials: BM
authors.lastname: Almeida
authors.forename: Mônica A S
authors.initials: MA
authors.lastname: Neves
authors.forename: Isabela N
authors.initials: IN
authors.lastname: Rôças
authors.forename: José F
authors.initials: JF
authors.lastname: Siqueira
mesh_terms: D015169:Colony Count, Microbial; D003762:Dental Instruments; D003786:Dental Pulp Cavity / Q000382:microbiology*; D013293:Enterococcus faecalis / Q000187:drug effects*; D004867:Equipment Design; D006801:Humans; D012388:Root Canal Irrigants / Q000008:administration & dosage / Q000494:pharmacology*; D018915:Root Canal Preparation / Q000295:instrumentation* / Q000379:methods*; D012973:Sodium Hypochlorite / Q000008:administration & dosage / Q000494:pharmacology; D007507:Therapeutic Irrigation / Q000379:methods
chemical_list: D012388:Root Canal Irrigants; D012973:Sodium Hypochlorite