Clinical Management of Missed Root Canals with Dental Operating Microscope

Objectives: To investigate the omission of root canal in endodontic treatment and evaluate the role of dental operating microscope in clinical treatment of missed canals. Methods: 48 teeth suspected of missing root canals were selected for endodontic treatment. Two kinds of preoperative radiographs were taken for each tooth, using straight projection and eccentric projection. The root canal system was explored under dental operating microscope to identify the existence of additional canal. The root canal was then shaped using Ni-Ti rotary instruments Hero 642, cleaned using sodium hypochlorite, and obturated by vertical condensation technique. The efficiency of preparation and obturation was analyzed with radiographs before, during and after operation. Results: Additional canals were verified in 46 teeth. 39.1% of missed canal was identified in maxillary molars, 19.6% both in maxillary premolars and mandibular molars, 13.0% in mandibular premolars and 8.7% in mandibular incisors. With the use of microscope most missed canals were identified and treated well except one calcified canal. There were no transportation, apical blockage, ledge, and instrument fracture in all cases. 43 teeth were filled well, 2 showed slight over-filling, and 1 under-filling. Conclusions: This study underlines the importance of complete knowledge about root canal morphology and possible variations, coupled with full clinical and radiographic examination, and treatment with the use of dental operating microscope, in order to increase the ability of clinicians to treat difficult cases.