title: Reduction in Enteroccocus faecalis counts - a comparison between rotary and reciprocating systems.
abstract: OBJECTIVE
  To compare the chemomechanical reduction and regrowth of Enterococcus faecalis between rotary and reciprocating systems in root canal preparation.
  
  
  METHODS
  Seventy-six single-rooted human mandibular premolars were selected and standardized to 15 mm in length. Root canals were enlarged up to a size 25 K-file and irrigated with distilled water and then were infected with E. faecalis for 4 weeks. The specimens were divided into 3 groups (n = 24) for instrumentation with Mtwo, Twisted File and WaveOne. Each group was further divided into two subgroups (n = 12) according to the irrigant used: distilled water or 5.25% sodium hypochlorite (NaOCl). Before and after rotary preparation, microbiological samples were collected using three sterilized paper points, and efficacy was expressed as reduction in percentage. The proportion of grown samples for 60 days was evaluated using nonparametric Kaplan-Meier survival analysis. Differences amongst groups were tested using the log-rank test at a significance level of 0.05.
  
  
  RESULTS
  In the main root canal, the percentage reduction in the distilled water and 5.25% NaOCl groups ranged from 95.9% to 100%, with no significant differences amongst the three systems (P > 0.05). The bacterial regrowth in NaOCl groups revealed that Mtwo had the lowest number of samples regrown at 60 days, giving statistically significant differences with respect to Twisted File (P = 0.029) and WaveOne (P = 0.005).
  
  
  CONCLUSIONS
  Reciprocating and rotary systems resulted in similar percentage reduction in E. faecalis when using either distilled water or 5.25% NaOCl solution. Over time, the Mtwo system was more effective regarding disinfection.
authors: Department of Stomatology, School of Dentistry, University of Granada, Granada, Spain.
authors: C M
authors: CM
authors: Ferrer-Luque
authors: I
authors: I
authors: Bejarano
authors: M
authors: M
authors: Ruiz-Linares
authors: P
authors: P
authors: Baca
mesh_terms: D058491:Bacterial Load; D001641:Bicuspid; D018441:Biofilms / Q000254:growth & development; D003786:Dental Pulp Cavity / Q000382:microbiology*; D013293:Enterococcus faecalis / Q000254:growth & development*; D006801:Humans; D066298:In Vitro Techniques; 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: Enterococcus faecalis; Mtwo; Twisted File; WaveOne; biofilms; regrowth