The C-shaped mandibular second molar: incidence and other considerations. Members of the Arizona Endodontic Association.

Although its most common configuration is two roots and three canals, the mandibular second molar may have many different combinations. Cooke and Cox were the first to describe a single-rooted mandibular second molar with a continuous slit connecting some or all of the canals. If sectioned horizontally through the main portion of the root, this slit had the shape of the letter "C." Other papers were written and lectures were presented on this and similar entities, but its frequency and significance have remained the object of speculation because large numbers of these teeth have not been categorized. By combining the efforts of an endodontic study club, 811 endodontically treated mandibular second molars were evaluated. Sixty-two of these (7.6%) were identified as C-shapes. Other aspects of this configuration were also investigated.