title: Methodological considerations in the determination of working length.
abstract: OBJECTIVE
  The aim of this study was to evaluate the diagnostic efficacy of an electronic system for the determination of working length, in comparison with two radiological methods (conventional film and digital radiography).
  
  
  METHODS
  The study sample consisted of 28 root canals belonging to 20 human mandibular teeth. A comparison was made between the working length measurements obtained by two radiological methods (conventional film and digital radiography) and an apex locator, using as gold standard the observation of the file position within the root following selective grinding of the root tissue.
  
  
  RESULTS
  The electronic method was satisfactory in 67.8% of cases, versus 50.6% and 61.4% for the conventional and digital radiological methods. respectively. No statistically significant differences occurred between the techniques according to the chi-squared and Kruskal-Wallis nonparametric tests.
  
  
  CONCLUSIONS
  None of the techniques was totally satisfactory in establishing the true working length. There were no differences between the techniques investigated.
authors.affiliation: Department of Stomatology, Valencia University Medical and Dental School, Spain. forneruv.es
authors.forename: M A
authors.initials: MA
authors.lastname: Martínez-Lozano
authors.forename: L
authors.initials: L
authors.lastname: Forner-Navarro
authors.forename: J L
authors.initials: JL
authors.lastname: Sánchez-Cortés
authors.forename: C
authors.initials: C
authors.lastname: Llena-Puy
mesh_terms: D000704:Analysis of Variance; D003786:Dental Pulp Cavity / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D017097:Electric Impedance; D006801:Humans; D008334:Mandible; D009811:Odontometry / Q000379:methods*; D011861:Radiography, Dental / Q000379:methods; D015203:Reproducibility of Results; D018709:Statistics, Nonparametric; D019227:Tooth Apex / Q000033:anatomy & histology* / Q000000981:diagnostic imaging