title: Evaluation of the maintenance of the apical limit during instrumentation with hybrid equipment in rotary and reciprocating modes.
abstract: BACKGROUND
  The objective of the present study was to evaluate ex vivo the maintenance of the apical limit during instrumentation with the Root ZX (J Morita, Tokyo, Japan) and VDW Gold (VDW GbmH, Munich, Germany) hybrid devices in rotary and reciprocating modes and determine the possible function variations of different preparation levels (0.0 mm and -1.0 mm).
  
  
  METHODS
  Seventy-two human uniradicular mandibular premolars, which had their coronal access performed and their apical foramen (AF) standardized (200 μm) were used. After their randomized division, the root canals were chemically mechanically prepared with #F4 ProTaper (Dentsply Maillefer, Ballaigues, Switzerland) and #R40 Reciproc (VDW GbmH) instruments. At the end of the instrumentation, the last instrument was fixed, and 4.0 mm of the apical portion was worn, permitting the measurement of the distance between the instrument tips and the AF.
  
  
  RESULTS
  The determined precision values of 0.0 and -1.0 mm were 100% and 33.4% (Root), 100% and 41.6% (VDW Gold with rotary movement) and 100% and 33.3% (VDW Gold with reciprocating movement), respectively, with a margin of ±0.5 mm. No statistical differences were found with respect to the comparisons of every level of preparation. However, significant differences were found when comparing the groups with rotary function at the different levels, with a higher precision for the groups that reached the AF.
  
  
  CONCLUSIONS
  It was concluded that both devices, independent of the function used, were more efficient in the maintenance of the apical limit when used until the AF; however, such reliability was compromised when -1.0 mm from the apical limit was established.
authors.affiliation: School of Dentistry of Sobral, Federal University of Ceará, Campus Sobral, Sobral, Ceará, Brazil. Electronic address: bcv@ufc.br.
authors.forename: Bruno Carvalho de
authors.initials: BC
authors.lastname: Vasconcelos
authors.affiliation: School of Dentistry of Sobral, Federal University of Ceará, Campus Sobral, Sobral, Ceará, Brazil.
authors.forename: Luciana Maria Arcanjo
authors.initials: LM
authors.lastname: Frota
authors.affiliation: School of Dentistry of Sobral, Federal University of Ceará, Campus Sobral, Sobral, Ceará, Brazil.
authors.forename: Tamara de Abreu
authors.initials: Tde A
authors.lastname: Souza
authors.affiliation: Brazilian Dental Association, Taguatinga, Federal District, Brazil.
authors.forename: Ricardo Affonso
authors.initials: RA
authors.lastname: Bernardes
authors.affiliation: Departament of Dentistry, Endodontics and Dental Material, Bauru Dental School, University of São Paulo, Bauru, São Paulo, Brazil.
authors.forename: Marco Antonio Hungaro
authors.initials: MA
authors.lastname: Duarte
mesh_terms: D001641:Bicuspid; D004867:Equipment Design; D006801:Humans; D018915:Root Canal Preparation / Q000295:instrumentation*; D019227:Tooth Apex / Q000033:anatomy & histology*
keywords: Electronic foramen locator; root canal preparation; working length determination