Incidence of missed canals during endodontic treatment of maxillary first and second molars

Untreated canals are a primary cause of persistent apical periodontitis, and the inability to identify and adequately treat canals has been considered a major cause of failure of root canal therapy in maxillary molars. The purpose of this retrospective study was to use cone beam computed tomography (CBCT) to quantify the number of missed canals in maxillary first and second molars needing endodontic retreatment after treatment by general dentists. A total of 401 CBCT scans of maxillary first and second molars were examined. A total of 214 scan sets (53.37% [95% CI, 48.48%-58.25%]) showed evidence of an untreated canal, with the highest rate (49.38%; n = 198) observed in the second mesiobuccal canal. Imaging revealed that multiple canals were missed in some patients, for a total of 225 missed canals. The examinations showed untreated first mesiobuccal canals in 2.99% of CBCT scan sets (n = 12), untreated distobuccal canals in 2.99% of CBCT scan sets (n = 12), and untreated palatal canals in 0.75% of CBCT scan sets (n = 3). Preoperative CBCT imaging should be considered prior to initial root canal treatment of maxillary molars. When the risks and limitations of CBCT are taken into consideration, the additional information it provides can improve diagnostic accuracy, increase confidence in decision-making, and positively impact treatment planning.