title: Centering and transportation: in vitro evaluation of continuous and reciprocating systems in curved root canals.
abstract: BACKGROUND
  One of the goals of endodontic therapy is the shaping and cleaning of the root canal system. In recent years, there has been multiple systems instrumentation, and changes in their dynamics are central to maintain the original shape of the canal after preparation.
  
  
  OBJECTIVE
  The aim of this study was to evaluate centering and transportation in curved root canals after using ProTaper(®) and MTwo(®) in continuous rotation, Reciproc(®) in reciprocating motion, and a step-down manual instrumentation technique.
  
  
  METHODS
  Mesiobuccal roots of human extracted the first and second maxillary molars were selected and the canals (n = 60) were divided into four groups according to the preparation techniques: PT-ProTaper(®); MT-MTwo(®); RE-Reciproc(®); MI-manual instrumentation.
  
  
  METHODS
  The final apical diameter was standardized to a size 25. Centering and transportation were evaluated by cone-beam computed tomography and Adobe Photoshop 8.0 software.
  
  
  METHODS
  The data were statistically analyzed by ANOVA and Tukey post hoc.
  
  
  RESULTS
  Results of transportation showed no statistical differences (P > 0.05) between groups, and significantly, difference (P < 0.05) between ProTaper(®) and Reciproc(®) was found when evaluating centering ability in the apical third.
  
  
  CONCLUSIONS
  We concluded that there were no differences in transportation between the evaluated systems for the preparation of curved root canals with an apical instrumentation diameter of #25. For centering ability, in the apical third, ProTaper(®) presented worst behavior when compared to Reciproc(®).
authors.affiliation: Department of Endodontics, School of Dentistry, University of Republic, Montevideo, Uruguay.
authors.forename: Beatriz Vilas
authors.initials: BV
authors.lastname: Navós
authors.affiliation: Department of Conservative Dentistry, School of Dentistry, Federal University of Rio Grande do Sul, Porto Alegre, RS, Brazil.
authors.forename: Carolina Bender
authors.initials: CB
authors.lastname: Hoppe
authors.affiliation: Department of Conservative Dentistry, School of Dentistry, Federal University of Rio Grande do Sul, Porto Alegre, RS, Brazil.
authors.forename: Leticia Boldrin
authors.initials: LB
authors.lastname: Mestieri
authors.affiliation: Department of Conservative Dentistry, School of Dentistry, Federal University of Rio Grande do Sul, Porto Alegre, RS, Brazil.
authors.forename: Daiana Elizabeth
authors.initials: DE
authors.lastname: Böttcher
authors.affiliation: Department of Conservative Dentistry, School of Dentistry, Federal University of Rio Grande do Sul, Porto Alegre, RS, Brazil.
authors.forename: Marcus Vinicius Reis
authors.initials: MV
authors.lastname: Só
authors.affiliation: Department of Conservative Dentistry, School of Dentistry, Federal University of Rio Grande do Sul, Porto Alegre, RS, Brazil.
authors.forename: Fabiana Soares
authors.initials: FS
authors.lastname: Grecca
keywords: Cone-beam computed tomography; endodontics; nickel-titanium alloy; root canal preparation