Effect of X-ray beam angulation and intraradicular contrast medium on radiographic interpretation of lower first molar root canal anatomy

AIMS: 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. METHODOLOGY: 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) 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.