title: Accuracy of an electronic apex locator in the retreatment of teeth obturated with plastic or cross-linked gutta-percha carrier-based materials: an ex vivo study.
abstract: BACKGROUND
  This ex vivo study evaluated the accuracy of the Root ZX electronic apex locator (EAL) (J Morita Corp, Kyoto, Japan) in determining the working length during retreatment of canals sealed with 2 different carrier-based obturating materials (ProTaper Obturator [Dentsply Maillefer, Ballaigues, Switzerland] and GuttaCore [Dentsply Maillefer]) and also evaluated whether they influenced its accuracy differently.
  
  
  METHODS
  Fifty extracted single-rooted human teeth with sound apices were selected for the study. We measured canals with the direct visual technique using a #10 K-file and shaped them with ProTaper Universal instruments (Dentsply Maillefer) up to this predetermined length. After instrumentation, we determined the canal length again using the visual technique (direct length [DL]). This value was considered the "reference point." Specimens were then placed in a tooth holder (Pro-Train; Simit Dental, Mantova, Italy), and the canal length was electronically measured (electronic length 1 [EL1]). Specimens were then obturated with ProTaper Obturators (group 1, n = 25) and GuttaCore (group 2, n = 25). Seven days later, a new electronic length was determined (electronic length 2 [EL2]) during retreatment procedures in the presence of the obturating material. EL1 and EL2 values were compared with DL using the Bland and Altman method. The different influences of the tested materials on the accuracy of the EAL were calculated with repeated measures analysis of variance.
  
  
  RESULTS
  Both EL1 and EL2 values provided a statistically significant overestimation of the actual canal length (DL [P < .05]), with the EL2 values higher from DL. The 2 different materials did not influence the accuracy of the EAL differently (P = .486).
  
  
  CONCLUSIONS
  The measurements obtained with the EAL tested during orthograde retreatments can lead clinicians to overinstrumentation and consequent overfilling of the endodontic space.
authors.affiliation: Department of Restorative Dentistry and Endodontics, University of Rome "Tor Vergata", Rome, Italy. Electronic address: manuele.mancini@tiscali.it.
authors.forename: Manuele
authors.initials: M
authors.lastname: Mancini
authors.affiliation: Department of Restorative Dentistry and Endodontics, University of Rome "Tor Vergata", Rome, Italy.
authors.forename: Pietro
authors.initials: P
authors.lastname: Palopoli
authors.affiliation: Department of Restorative Dentistry and Endodontics, University of Rome "Tor Vergata", Rome, Italy.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Iorio
authors.affiliation: Department of Restorative Dentistry and Endodontics, University of Rome "Tor Vergata", Rome, Italy.
authors.forename: Gabriele
authors.initials: G
authors.lastname: Conte
authors.affiliation: Department of Restorative Dentistry and Endodontics, University of Rome "Tor Vergata", Rome, Italy.
authors.forename: Luigi
authors.initials: L
authors.lastname: Cianconi
mesh_terms: D002138:Calibration; D003432:Cross-Linking Reagents / Q000627:therapeutic use; D003786:Dental Pulp Cavity / Q000033:anatomy & histology*; D055615:Electrical Equipment and Supplies / Q000706:statistics & numerical data*; D006171:Gutta-Percha / Q000627:therapeutic use; D006801:Humans; D008422:Materials Testing; D009811:Odontometry / Q000295:instrumentation* / Q000706:statistics & numerical data; D010969:Plastics / Q000627:therapeutic use; D019233:Retreatment; D012387:Root Canal Filling Materials / Q000627:therapeutic use*; D012389:Root Canal Obturation / Q000379:methods*; D018915:Root Canal Preparation / Q000295:instrumentation* / Q000706:statistics & numerical data; D019227:Tooth Apex / Q000033:anatomy & histology*; D019553:Tooth, Nonvital / Q000473:pathology*
chemical_list: D003432:Cross-Linking Reagents; D010969:Plastics; D012387:Root Canal Filling Materials; D006171:Gutta-Percha
keywords: Electronic apex locator; GuttaCore; ProTaper Obturator; retreatment; working length