A 21-year-old Caucasian male patient was referred for endodontic treatment of his maxillary left first molar. The tooth was periodically percussion sensitive, but not sensitive to temperature. Radiographic examination (Fig. 5) revealed the presence of a deep amalgam restoration in close proximity to the pulp chamber. There was no evidence of root canal preparation or filling. According to the patient, the last treatment on this tooth was completed at the age of 13 years. The root structure was not clearly demonstrated on the radiograph. After removal of the coronal amalgam, a cotton pellet was found in the pulp chamber as well as an orange-brown paste on the pulp chamber floor. The pulp chamber was cleaned ultrasonically and rinsed with a 2.5% sodium hypochlorite solution. The pulp chamber floor was then explored to locate the canal orifices, which had not been opened. One mesial orifice was found, as well as a broad distal C-shaped orifice with two canals separated by an isthmus (Fig. 6). A second mesiobuccal canal was not found, even though magnification was used.
Figure 5. Case 2: preoperative periapical radiograph of the maxillary left first molar.
Figure 6. Case 2: access opening - one orifice in the mesiobuccal root and a semilunar opening connecting the palatal with the distobuccal canal can be seen.
The canal lengths were determined electronically with the AFA Apexfinder (EIE Analytic Technology, Orange, CA, USA). The two canals in the C-shape appeared to join in the apical third. The clinical conclusion was that the palatal and distobuccal canals merged in a C-shaped single canal and that there was only a small isthmus separating the orifices. The root canals were then instrumented in a conventional manner and obturated by means of hybrid guttapercha condensation, as in case 1, and AH-26 sealer (Fig. 7).
Figure 7. Case 2: radiograph of the obturated canal system.
Figure 8. Case 2: radiograph of the contralateral first molar, with normal root anatomy.
The radiographic examination of the contralateral first molar revealed a normal root anatomy and the presence of three roots (Fig. 8).