title: Effect of X-ray beam angulation and intraradicular contrast medium on radiographic interpretation of lower first molar root canal anatomy.
abstract: OBJECTIVE
  To compare evaluator radiographic interpretation of noncontrasted and contrasted root canal anatomy on radiographs taken at a 0 or 30 degrees mesial angle to the orthoradial orientation.
  
  
  METHODS
  Pulp tissue was removed from 20 mandibular first molar teeth using NaOCl irrigation and hand files. Standardized radiographs at 0 and 30 degrees angulation were obtained of each tooth positioned in a dried mandible. Contrast medium (iohexol) was injected passively into the canals and a second pair of corresponding radiographs was obtained. A third pair of radiographs was taken after infusing canals under vacuum with contrast medium. Using set criteria, three evaluators assessed the canal anatomy of the mesial root on radiographs: (i) the number of visible canals, (ii) whether the canal(s) was visible along the entire length of the root, (iii) the location of the canal terminus in relation to the radiographic apex, (iv) configuration of canal(s), (v) level of multiple canals merging and (vi) the presence of lateral canals. The teeth were then cleared for visual assessment. The data were compared using logistic regression and the intra- and interevaluator reliability assessed with the Kappa test.
  
  
  RESULTS
  Noncontrasted 0 degrees images were significantly better (P < 0.05) than noncontrasted 30 degrees images for detecting the number of visible canals, whether the canal(s) was visible along the entire length of the root, the location of the canal terminus in relation to the radiographic apex and level of multiple canals merging. The 0 degrees images contrasted by vacuum or passive injection were significantly better (P < 0.05) than 30 degrees images only for assessing whether the canal(s) was visible along the entire length of the root, whilst the 0 degrees image contrasted by passive injection was also better (P < 0.05) at assessing the location of the canal terminus in relation to the radiographic apex. At 30 degrees, contrast medium passively or vacuum introduced improved (P < 0.05) the detection of the number of visible canals, whether the canal(s) was visible along the entire length of the root and configuration of canal(s), whilst vacuum also improved (P < 0.05) the location of the canal terminus in relation to the radiographic apex. Overall, there was no significant difference (P > 0.05) between images contrasted by passive injection or vacuum.
  
  
  CONCLUSIONS
  Under the conditions of this study, conventional radiographs taken at a 0 degrees orientation provided more information than 30 degrees radiographs. Contrast medium improved radiographic interpretation of canal anatomy, especially when used with 30 degrees radiographs.
authors.affiliation: Department of Oral Rehabilitation, University of Otago, Dunedin, New Zealand.
authors.forename: H J
authors.initials: HJ
authors.lastname: Naoum
authors.forename: R M
authors.initials: RM
authors.lastname: Love
authors.forename: N P
authors.initials: NP
authors.lastname: Chandler
authors.forename: P
authors.initials: P
authors.lastname: Herbison
mesh_terms: D003287:Contrast Media; D003786:Dental Pulp Cavity / Q000033:anatomy & histology* / Q000000981:diagnostic imaging*; D006801:Humans; D007472:Iohexol; D016015:Logistic Models; D008334:Mandible; D008963:Molar / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D015588:Observer Variation; D011861:Radiography, Dental / Q000295:instrumentation / Q000379:methods*; D014092:Tooth Root / Q000033:anatomy & histology / Q000000981:diagnostic imaging
chemical_list: D003287:Contrast Media; D007472:Iohexol