title: Evaluation of periapical radiographs in the recognition of C-shaped mandibular second molars.
abstract: OBJECTIVE
  The purpose of this study was to evaluate in a blind trial the efficacy of radiographs to recognize C-shaped mandibular second molars and to determine the incidence of this entity amongst second mandibular molars treated in the Department of Endodontology at the School of Dentistry of the University of Thessaloniki during a seven-year period (1989 - 95).
  
  
  METHODS
  A total of 480 clinical records of root treated mandibular second molars were reviewed. The preoperative, working length, and final radiograph of each tooth alone and in combination were examined in groups as follows: group 1 (preoperative radiographs only), group 2 (working length radiographs), group 3 (final radiographs), group 4 (preoperative and working length radiographs), group 5 (preoperative and final radiographs) and group 6 (all three radiographs). The efficacy of each combination to identify the C-shaped cases was evaluated based on the interpretation of three experienced dentists looking simultaneously at each case. Films were examined on a viewer using a magnifying glass and allowing a two-week interval between groups. Results were compared with the clinical diagnoses stated on the patients' records (group 7).
  
  
  RESULTS
  The review of clinical records revealed that 4.58% of second molars had C-shaped canals. Radiographic interpretation was overall more effective when based on film combinations (groups, 4, 5, and 6) than on single radiographs. Amongst the latter, working length radiographs were more helpful than the preoperative and final ones. Preoperative radiographs were the least effective in diagnosing C-shaped cases.
  
  
  CONCLUSIONS
  Simultaneous interpretation of preoperative, working length and post-treatment radiographs is important when attempting to diagnose a C-shaped configuration.
authors.affiliation: Department of Endodontology, Dental School, Aristotelian University, Thessaloniki, Greece. lyroudia@zeus.csd.auth.gr
authors.forename: T
authors.initials: T
authors.lastname: Lambrianidis
authors.forename: K
authors.initials: K
authors.lastname: Lyroudia
authors.forename: O
authors.initials: O
authors.lastname: Pandelidou
authors.forename: A
authors.initials: A
authors.lastname: Nicolaou
mesh_terms: D003786:Dental Pulp Cavity / Q000033:anatomy & histology* / Q000000981:diagnostic imaging*; D006801:Humans; D008334:Mandible; D008963:Molar / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D011861:Radiography, Dental; D015203:Reproducibility of Results; D014092:Tooth Root / Q000033:anatomy & histology / Q000000981:diagnostic imaging*