title: Comparison of two rotary systems in root canal preparation regarding disinfection.
abstract: BACKGROUND
  The aim of the present study was to determine the disinfection of preparations carried out by using the Protaper or MTwo system in canals infected with Enterococcus faecalis.
  
  
  METHODS
  Twenty-eight distobuccal canals of upper molars were used, in which the canals were sterilized after being enlarged to #20 file and then contaminated with an inoculation of a culture of E. faecalis. After the incubation period, bacterial samples were collected and were seeded on plates for analysis of colony-forming units (CFU)/mL. The teeth were divided into 2 groups according to the rotary system used for instrumentation; 2 noninstrumented teeth served as the control group. Then bacterial samples were collected and were seeded on plates for analysis of CFU/mL again. The data obtained were evaluated by the Wilcoxon and Mann-Whitney U tests.
  
  
  RESULTS
  Bacterial reduction was 81.94% and 84.29%, respectively, in ProTaper and Mtwo systems, and there was no statistically significant difference (P > .05).
  
  
  CONCLUSIONS
  Both systems, ProTaper and Mtwo, reduced the amount of bacteria in the mechanical disinfection of the root canal system, demonstrating that they are suitable for this purpose.
authors.affiliation: Department of Restorative Dentistry, School of Dentistry, University of São Paulo, São Paulo, SP, Brazil. professormachado@hotmail.com
authors.forename: Manoel Eduardo de Lima
authors.initials: ME
authors.lastname: Machado
authors.forename: Luiz Antônio Bichels
authors.initials: LA
authors.lastname: Sapia
authors.forename: Silvana
authors.initials: S
authors.lastname: Cai
authors.forename: Guilherme Henrique Rosa
authors.initials: GH
authors.lastname: Martins
authors.forename: Cleber Keiti
authors.initials: CK
authors.lastname: Nabeshima
mesh_terms: D015169:Colony Count, Microbial; D003786:Dental Pulp Cavity / Q000382:microbiology*; D004203:Disinfection / Q000379:methods*; D013293:Enterococcus faecalis / Q000254:growth & development; D004867:Equipment Design; D006801:Humans; D008422:Materials Testing; D008963:Molar / Q000382:microbiology; D018915:Root Canal Preparation / Q000295:instrumentation / Q000379:methods*; D012399:Rotation