PMC8012114_01
Preoperative radiograph. The intraoral periapical radiograph showed radiolucency at the root apex and overextended gutta-percha through a perforation in the apical part of one of the three roots of the maxillary left first molar.
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After radiographic examination, the tooth showed radiolucency related to the mesiobuccal root and overextended gutta-percha through a perforation in the apical part of the distobuccal root (Figure 1).
The maxillary left first molar after removal of the gutta-percha from the three canals.
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The rubber dam was applied and caries excavation using a size 3 mm in diameter round diamond bur, and the access cavity was edited using the conic steel bur endo-Z (Dentsply Maillefer, Ballaigues, Switzerland) at high-speed underwater spray; Reciproc  blue (R25/0.08 mm) (VDW GmbH, Munich, Germany) was used for the removal of the gutta-percha and three hand H-files (Dentsply Maillefer, Ballaigues, Switzerland) for the removal of the overextended gutta-percha in the distobuccal root (Figure 2).
Preoperative CBCT images. The axial view of CBCT showed the apical perforation site (black arrows) at the distobuccal root (a). The sagittal view of CBCT showed the apical perforation site of the tooth apex.
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Cavit  temporary filling material (3M ESPE, Seefeld, Germany) was then placed, and the rubber dam was removed, and the patient was asked to take cone-beam computed tomography (CBCT) to determine the location and size of the apical perforation (Figures 3(a) and 3(b)).
Intraoral periapical radiograph for the treatment procedure of maxillary left first molar. Working length was determined (a). Placement of MTA to repair the perforation site at the distobuccal root (b). Matching cone for the three canals after cleaning and shaping was done (c).
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Corp., Kyoto, Japan), then radiographic X-ray for the final working length was taken (Figure 4(a)), and also, cleaning and shaping were done using Vortex blue (#40/0.04 mm) (Dentsply Sirona, Charlotte, Tulsa Dental, Tulsa, OK, USA) was placed in the apical third of the canal (Figure 4(b)), and a small size gutta-percha was placed in the main canal to prevent closure, the temporary filing was applied, and the patient was dismissed to allow the setting of MTA material. The third visit followed the same anesthesia and rubber dam isolation as explained previously, removal of the temporary filling and irrigation using 15 mL of 3% NaOCl activated with the EndoVac  irrigation system (Vista Dental, Racine, WI, USA) for 5 minutes in each canal and using a 30-gauge side vented irrigating needle (Max-I-Probe, Dentsply Maillefer, Ballaigues, Switzerland). Corp., New York, USA) and master cones were fitted (Figure 4(c)). Cold single cone technique (hydraulic condensation technique) with (#30/0.06) matching gutta-percha cones and bioceramic sealer were used as an obturation method.
Postoperative intraoral radiographs. Intraoral periapical radiograph of the maxillary left first molar after root canal retreatment (a). Intraoral bitewing radiograph of the maxillary left first molar after root canal retreatment (b).
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The tooth was restored using dental glass ionomer filling material (GC FUJI IX GP) (GC Corporation, Tokyo, Japan), the bite was checked, and postoperative radiographs were taken (Figures 5(a) and 5(b)).
Postoperative intraoral periapical radiograph of the maxillary left first molar after a one-year follow-up period of retreatment: the radiolucent region of the tooth was healing.
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The 1-year follow-up revealed periapical tissue healing at the root apex of the upper left first molar (#26) (Figure 6).