title: Investigation of apex locators and related morphological factors.
abstract: BACKGROUND
  The purpose of this study was to investigate the ability of three electronic apex locators (EALs) to detect the minor foramen and morphological influencing factors relative to working length determination.
  
  
  METHODS
  Three hundred fifty-six extracted teeth were decoronated, and the coronal portion of the canal was flared. The distance between the major foramen and the file tips (DMFF) was determined by different EALs. The relationship between the DMFFs determined by the EAL and the morphological features of the root apex was analyzed by linear regression analysis.
  
  
  RESULTS
  The average DMFFs were 0.261 mm, 0.376 mm, and 0.383 mm for the Root ZX (J. Morita, Kyoto, Japan), Raypex 5 (VDW, Munich, Germany), and Elements Apex Locator (SybronEndo, Anaheim, CA), respectively. The file tips determined by EALs were much closer to the major foramen in teeth with a "lateral major foramen" (p < 0.001). The area and diameters of the minor foramen were significantly related to the variation of the DMFFs determined by EALs.
  
  
  CONCLUSIONS
  When the "minor foramen" reading was given, the file tip connected to the Root ZX was much closer to the major foramen than the other two EALs. The minor foramen's morphology and the major foramen's location were both important influencing factors on the performance of EALs.
authors.affiliation: State Key Laboratory Breeding Base of Basic Science of Stomatology (Hubei-MOST) and Key Laboratory of Oral Biomedicine Ministry of Education, School and Hospital of Stomatology, Wuhan University, Wuhan 430079, China.
authors.forename: Jiangfeng
authors.initials: J
authors.lastname: Ding
authors.forename: James L
authors.initials: JL
authors.lastname: Gutmann
authors.forename: Bing
authors.initials: B
authors.lastname: Fan
authors.forename: Yao
authors.initials: Y
authors.lastname: Lu
authors.forename: Hao
authors.initials: H
authors.lastname: Chen
mesh_terms: D003786:Dental Pulp Cavity / Q000033:anatomy & histology*; D004581:Electronics / Q000295:instrumentation / Q000706:statistics & numerical data; D004867:Equipment Design; D006801:Humans; D008422:Materials Testing; D009811:Odontometry / Q000295:instrumentation* / Q000706:statistics & numerical data; D018915:Root Canal Preparation / Q000295:instrumentation; D019227:Tooth Apex / Q000033:anatomy & histology*