PMC9831808_01
The clinical and radiographic photographs of our case. (A to D) Initial examination. (A) Periapical radiograph demonstrating four roots at tooth 27. (B, C, and D) CBCT transverse section images. (B, C) Radiolucent lesions at the mesial and distal palatal roots of tooth 27. (D) The distal palatal root canal was untreated (arrow). (E, F) Models of affected teeth made from CBCT images. (E) Root canal orifices. (F) Root apex. (G) Intraoperative findings. Untreated distal palatal root canal was found (arrow). (H) Periapical radiograph at the time of gutta-percha point trial. (I) Periapical radiograph after root canal filling of tooth 27. (J, K) One year and four months after root canal filling. (J) Intraoral clinical photograph showing the normal gingiva of tooth 27. (K) Periapical radiograph showing no radiolucent lesion at the tooth 27.
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Periapical radiography revealed an excess root in the distal region (Fig. 1A). Dental cone-beam computed tomography (CBCT) revealed four independent roots: mesial buccal, distal buccal, mesial palatal, and distal palatal, and periapical radiolucent area was observed in the mesial and distal palatal roots (Fig. 1B and C). In addition, the distal palatal root was untreated (Fig. 1D). Prior to treatment, a model of the affected tooth was fabricated using a 3D printer (Fig. 1E and F). Detailed examination under a dental microscope revealed an untreated distal palatal root canal approximately 6 mm distal to the mesial palatal root canal orifice (Fig. 1G). In the first treatment, root canal preparation had been performed using a nickel-titanium rotary file (HyFlex  EDM: 40/04, 50/03; Coltene, Langenau, Germany) as usual, and periapical radiographs of the gutta-percha point trial were taken (Fig. 1H). One week later, at the time of the second treatment, no clinical symptoms were observed, the root canal filling was performed (Fig. 1I). One year and four months after the root canal filling, there were no clinical symptoms (Fig. 1J), and periapical radiography revealed the continuity of the periodontal ligament space (Fig. 1K), indicating a good prognosis.