title: Clinical efficacy of electronic apex locators: systematic review.
abstract: BACKGROUND
  Apical constriction has been proposed as the most appropriate apical limit for the endodontic working length. Despite being the most used, some limitations are attributed to the radiographic method of working length determination. It lacks precision because it is based on the average position of the apical constriction. The electronic apex locators have been presented as an alternative to the odontometry performed by radiography. These devices detect the transition of the pulp to the periodontal tissue, which is anatomically very close to the apical constriction and may perform with improved accuracy.
  
  
  METHODS
  A systematic review was performed to compare the radiographic and electronic methods. Clinical studies that compared both methods were searched for on 7 electronic databases, a manual search was performed on the bibliography of articles collected on the electronic databases, and the authors were contacted to ask for references of more research not detected on the electronic and manual search.
  
  
  RESULTS
  Twenty-one articles were selected. The majority were comparative or evaluation studies, and very few clinical studies comparing both methods are available. Several methodological limitations are present on the collected articles and debated in this review.
  
  
  CONCLUSIONS
  Although the available scientific evidence base is short and at considerable risk of bias, it is still possible to conclude that the apical locator reduces the patient radiation exposure and also that the electronic method may perform better on the working length determination. At least one radiographic control should be performed to detect possible errors of the electronic devices.
authors.affiliation: School of Dental Medicine, Lisbon University, Lisbon, Portugal; Inter PG Endodontics, New York University College of Dentistry, New York, New York; Department of Endodontics, Implantology Institute, Lisbon, Portugal. Electronic address: jnr_martins@yahoo.com.br.
authors.forename: Jorge N R
authors.initials: JN
authors.lastname: Martins
authors.affiliation: School of Dental Medicine, Lisbon University, Lisbon, Portugal; Oral Biology and Biochemistry Group, Biomedical and Oral Sciences Research Unit (FCT Unit 4062), Evidence Based Dentistry Center, Lisbon University, Lisbon, Portugal; Implantology Institute, Lisbon, Portugal.
authors.forename: Duarte
authors.initials: D
authors.lastname: Marques
authors.affiliation: School of Dental Medicine, Lisbon University, Lisbon, Portugal; Oral Biology and Biochemistry Group, Biomedical and Oral Sciences Research Unit (FCT Unit 4062), Evidence Based Dentistry Center, Lisbon University, Lisbon, Portugal; Basic Science and Cranio-Facial Biology, New York University College of Dentistry, New York, New York.
authors.forename: António
authors.initials: A
authors.lastname: Mata
authors.affiliation: School of Dental Medicine, Lisbon University, Lisbon, Portugal; Implantology Institute, Lisbon, Portugal.
authors.forename: João
authors.initials: J
authors.lastname: Caramês
mesh_terms: D003786:Dental Pulp Cavity / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D055615:Electrical Equipment and Supplies / Q000592:standards*; D006801:Humans; D009811:Odontometry / Q000295:instrumentation*; D011859:Radiography; D018915:Root Canal Preparation / Q000295:instrumentation*; D019227:Tooth Apex / Q000033:anatomy & histology* / Q000000981:diagnostic imaging
keywords: Electric impedance; electronics; odontometry; radiography