Different strategies for treating intracanal fractured instruments in a single tooth: A case report.

A fractured instrument (FI) in the root canal is a common complication during root canal therapy. Under current medical conditions, instrument separation cannot be completely avoided because of the complex morphology of root canals and the limited surgical field and operating space of the surgeon. FIs, especially those broken in the apical third of the canal, render it difficult to completely remove infection in the root canal, where the residual infection can easily develop into reinfection. The removal of FIs is therefore the preferred option for the majority of clinicians in such cases. However, root canal preparation instruments are frequently fractured during treatment because of the complex root canal morphology, such as curvature or severe calcification, which further increases the difficulty of instrument removal. In the present case, a 41-year-old female patient complained of worsening pain in the left maxillary first molar for 3 days. This patient had been treated at another hospital 2 years earlier, but the discomfort persisted after treatment. Preoperative periapical radiography revealed suspected FIs at the apical third of the mesiobuccal (MB) root and the middle third of the distal buccal (DB) root, underfilling of the palatal (P) root canal and large hypodense areas surrounding the periapical region of all roots. Next, the micro-ultrasound technique was used to remove the FI in the DB canal; a bypass through the second MB canal (MB2) was created to fill the apical stop of the MB root and the P canal was retreated. The therapeutic effect of the bypass technique was assessed by comparing bypass treatment and removal treatment for endodontic FIs. The 9-month and 27-month follow-ups revealed that the periapical inflammation surrounding the DB root treated after removal of the FI and the MB root treated by bypass was significantly controlled compared with that before the operation. In addition, the present report reviewed the research progress in bypass and removal techniques, focusing on the difficulties and key points of successful root canal therapy.