title: Incidence of Dentinal Defects on the External Apical Root Surface after Instrumentation with WaveOne Reciprocating Files at Different Working Lengths.
abstract: BACKGROUND
  The aim of this in vitro study was to identify the formation of dentinal defects on the external apical root surface of teeth instrumented at different working lengths by using WaveOne reciprocating files.
  
  
  METHODS
  Sixty human single-rooted mandibular premolars were divided into 3 groups (n = 20) according to the file used for instrumentation: WaveOne Small (WOS), premolars presenting mechanical resistance to the penetration of #10 K-file 1 mm short of the apical foramen; WaveOne Primary (WOP), this limit easily reached with #10 K-file; and WaveOne Large (WOL), this limit easily reached with #20 K-file or higher. A closed system and a muffle were created to allow alternating sessions of root canal instrumentation and image acquisition. The teeth were further divided according to 3 different working lengths: 1 mm short of the apical foramen, flush with the apical foramen, and 1 mm beyond the apical foramen. Micrographs of the external apical root surface of each specimen at baseline and after instrumentation up to each working length were examined for the presence of dentinal defects. Inter-examiner agreement was evaluated by using Pearson correlation test, and the Kruskal-Wallis test was used to analyze intragroup and intergroup differences (P < .05).
  
  
  RESULTS
  Inter-examiner agreement was high in all experimental groups (r = 1.0000, r = 0.8885, and r = 0.7867 for WOS, WOP, and WOL, respectively). There was no significant difference in the number of teeth with dentinal defects in the intergroup (P = .8119) or intragroup analyses (P = .9309, .8648, and .4772 for WOS, WOP, and WOL, respectively).
  
  
  CONCLUSIONS
  Instrumentation with different WaveOne files up to different working lengths was not associated with the formation of dentinal defects.
authors.affiliation: Department of Endodontics, Dental Research Center, São Leopoldo Mandic University, Campinas, SP, Brazil. Electronic address: bitencourtmar@hotmail.com.br.
authors.forename: Marcela
authors.initials: M
authors.lastname: de Arruda Bitencourt
authors.affiliation: Department of Endodontics, Dental Research Center, São Leopoldo Mandic University, Campinas, SP, Brazil.
authors.forename: Daniel Guimarães
authors.initials: DG
authors.lastname: Pedro Rocha
authors.affiliation: Department of Endodontics, Dental Research Center, São Leopoldo Mandic University, Campinas, SP, Brazil.
authors.forename: Carlos Eduardo
authors.initials: CE
authors.lastname: da Silveira Bueno
mesh_terms: D001641:Bicuspid / Q000473:pathology* / Q000601:surgery; D003762:Dental Instruments; D003804:Dentin; D004867:Equipment Design; D006801:Humans; D066298:In Vitro Techniques; D015994:Incidence; D008334:Mandible; D008422:Materials Testing; D018915:Root Canal Preparation / Q000295:instrumentation*; D019227:Tooth Apex / Q000473:pathology* / Q000601:surgery
keywords: Dentinal defects; WaveOne file; root canal preparation