title: Clinical antibacterial effectiveness of the self-adjusting file system.
abstract: OBJECTIVE
  To evaluate in vivo the antibacterial effectiveness of the self-adjusting file (SAF) using molecular methods.
  
  
  METHODS
  Root canals from single-rooted teeth with apical periodontitis were instrumented using the SAF system under continuous irrigation with 2.5% NaOCl. DNA extracts from samples taken before and after instrumentation were subjected to quantitative analysis of total bacteria counts and levels of streptococci by quantitative real-time polymerase chain reaction (qPCR). The reverse-capture checkerboard assay was also used to identify 28 bacterial taxa before (S1) and after (S2) SAF instrumentation. SAF was also compared with a conventional hand nickel-titanium instrumentation technique for total bacterial reduction. Data from qPCR were analysed statistically within groups using the Wilcoxon matched pairs test and between groups using the Mann-Whitney U-test and the Fisher's exact test, with significance level set at P < 0.05.
  
  
  RESULTS
  Self-adjusting file significantly reduced the total bacterial counts from a mean number of 1.96 × 10(7) cells to 1.34 × 10(4) cells (P < 0.001). Quantitatively, the 99.9% reduction in total bacterial counts associated with the SAF system was significantly superior to the 95.1% reduction obtained by hand instrumentation (P < 0.001). Qualitatively, SAF resulted in significantly more cases with negative PCR results for bacteria (54.5%) than hand instrumentation (4.5%) (P < 0.001). The SAF system succeeded in significantly reducing the streptococcal levels, but four cases still harboured these bacteria in S2. Checkerboard analysis revealed that not only streptococci but also some anaerobic and even as-yet-uncultivated bacteria may resist the effects of chemomechanical procedures.
  
  
  CONCLUSIONS
  The SAF instrumentation system was highly effective in reducing bacterial populations from infected root canals and performed significantly better than hand instrumentation. However, because half of the samples still had detectable bacteria after preparation with SAF, supplementary disinfection is still required to maximize bacterial elimination.
authors.affiliation: Department of Endodontics and Molecular Microbiology Laboratory, Faculty of Dentistry, Estácio de Sá University, Rio de Janeiro, RJ, Brazil.
authors.forename: M A S
authors.initials: MA
authors.lastname: Neves
authors.forename: I N
authors.initials: IN
authors.lastname: Rôças
authors.forename: J F
authors.initials: JF
authors.lastname: Siqueira
mesh_terms: D058491:Bacterial Load; D003786:Dental Pulp Cavity / Q000382:microbiology*; D005260:Female; D006801:Humans; D008297:Male; D010485:Periapical Periodontitis / Q000382:microbiology* / Q000601:surgery*; D060888:Real-Time Polymerase Chain Reaction; D012388:Root Canal Irrigants / Q000494:pharmacology; D018915:Root Canal Preparation / Q000295:instrumentation*; D012973:Sodium Hypochlorite / Q000494:pharmacology
chemical_list: D012388:Root Canal Irrigants; D012973:Sodium Hypochlorite
keywords: apical periodontitis; bacterial reduction; endodontic treatment; molecular microbiology; self-adjusting file