Orthograde endodontic retreatment of UR6 with sinus tract

The treatment plan included orthograde endodontic retreatment and follow-up. At presentation, the tooth had a well-adapted mesio-occluso-distal composite restoration, which was preserved. The patient was advised, however, on the need for an indirect restoration after retreatment to reduce the risk of molar fracture. During the first treatment session, the root canal systems were retreated using rotary instruments and ultrasonics to remove residual gutta-percha and sealer. In the mesiobuccal root, three canal orifices were identified: MB1, MB2, and MB3. MB3 merged with MB2 in the coronal third, while MB1 and MB2 merged in the middle third of the root. A sequence of rotary instruments (20/06, 25/06, 30/04) was used for the MB and DB systems, achieving an apical gauging corresponding to…