Dilemmas pertaining to three canals in the mesiobuccal root of a maxillary second molar: a case report
A 36-year-old female came to the department with the chief complaint of dull spontaneous pain in the upper left posterior tooth for the previous 2 weeks. She reported a fractured restoration on the same tooth few months back. On examination, an open cavity with a dislodged restoration and exposed mesiobuccal pulp horn was seen with respect to the maxillary left second molar. An intraoral radiograph revealed the presence of radiolucency encroaching on the pulp horn with an apparently normal periapex. Thermal sensitivity tests elicited a lingering pain in the patient. Based on the clinical and radiographic findings, a diagnosis of irreversible pulpitis was formulated.\nSubsequent to anesthesia and rubber dam isolation, access cavity preparation was initiated and the mesiobuccal, distobuccal, and palatal canals were located. Anticipating the presence of extra canals, further exploration was carried out deliberately and two sticky points were located. This led to finding of two additional canals in the mesiobuccal root on the line connecting the mesiobuccal and palatal canal orifice (). Magnifying loupes (2.5X, ST250, STAC Dental Instruments Inc., Brampton, Canada), a DG 16 endodontic explorer, and sodium hypochlorite were the adjuncts used to locate the canals. After locating the orifices, an attempt was made to understand the internal anatomy of the mesiobuccal root using K files and intraoral periapical radiographs. While negotiating the canals individually in the mesiobuccal root, there was no hindrance in the movement of the #10 K file in any of the three canals. However, simultaneous insertion posed obstruction in the vertical movement of the files in the 2 extra canals. The above finding raised an element of doubt regarding the configuration of the canals. Intraoral periapical radiographs were taken from three different horizontal angulations (). However, all of the radiographs suffered from overlapping of the endodontic files radiopacity. Only a mesially angulated radiograph revealed limited information on where files associated with the second and third mesiobuccal canals were seen to be meeting in the middle third of the root approximately and continue to merge with the file in first mesiobuccal canal (). To avoid any missed canals, and for better understanding of the tooth's internal anatomy, a MDCT (Brilliance CT 64-channel, Philips Healthcare, Andover, MA, USA) scan was suggested because cone-beam computed tomography (CBCT) was not available in the set up or in the vicinity. The interpretation regarding the number of separate orifices and canals present in the coronal third or at the orifice level was inconsistent with the clinical or radiographic findings. In contrast to the 3 orifices and canals, clinically and radiographically, MDCT revealed only 1 large canal (). In the middle and apical third, 2 canals and 1 canal respectively could be distinguished in both radiographic and MDCT images ().\nThe configuration of the canals in the mesiobuccal root was perceived to be 3-2-1 () after correlating and computing the clinical, radiographic, and MDCT scan findings. Three separate coronal orifices extending apically to three separate canals were identified as mesiobuccal (MB), middle mesiobuccal (m-MB), and palatal mesiobuccal (p-MB) based on their anatomic positions. The m-MB and p-MB merged into one canal at a distance of approximately 5 mm from the orifice level. Following this, the canal joined the MB canal at a distance of approximately 9 mm from the orifice level. Finally, the canal ended with a single apical foramen at the apex. The distances mentioned above were calculated using the thickness of each slice of the MDCT scan images, which was 0.7 mm obtained using DentaScan software (GE Healthcare, Milwaukee, WI, USA). After understanding the anatomy of the mesiobuccal root and confirming the absence of extra canals in other roots, the treatment proceeded. The biomechanical preparation of MB, distobuccal, and palatal canals was completed using ProTaper NiTi rotary files (Dentsply Maillefer, Ballaigues, Switzerland). m-MB and p-MB canals were prepared with K-files using the step-back technique. Following one week of intracanal medication with calcium hydroxide, the canals were obturated using the cold lateral compaction technique ().