Evaluation of periapical radiographs in the recognition of C-shaped mandibular second molars

Aim 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 deter mine the incidence of this entity amongst second mandibular molars treated in the Department of Endodontology at the School of Dentistry of the Univer sity of Thessaloniki during a seven-year period (1989-95). Methodology A total of 480 clinical records of root treated mandibular seco nd molars were reviewed. The preoperative, working length, and final radiog raph of each tooth alone and in combination were examined in groups as foll ows: group 1 (preoperative radiographs only), group 2 (working length radio graphs), group 3 (final radiographs), group 4 (preoperative and working len gth 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 experience d dentists looking simultaneously at each case. Films were examined on a vi ewer using a magnifying glass and allowing a two-week interval between grou ps. Results were compared with the clinical diagnoses stated on the patients' r ecords (group 7). Results The review of clinical records revealed that 4.58 % of second molars had C-shaped canals. Radiographic interpretation was ove rall more effective when based on film combinations (groups 4. 5, and 6) th an on single radiographs. Amongst the latter, working length radiographs we re more helpful than the preoperative and final ones. Preoperative radiogra phs 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-sh aped configuration.