Digital 3D-Printed Surgical Guide for Removal of a Separated Instrument at the Maxillary Sinus Floor and Apical Microsurgery

This case report describes a maxillary first molar with chronic apical periodontitis (CAP) and a separated endodontic instrument migrated to the maxillary sinus floor, which was successfully managed with digital guide-assisted endodontic microsurgery. A 20-year-old female patient presented with long-standing occlusal pain and discomfort in the left maxillary first molar. Clinical examination revealed a temporary restoration, tenderness to percussion, and no gingival swelling. During root canal treatment, the mesiobuccal (MB2) canal was found to be calcified and non-negotiable, and a small segment of a nickel-titanium instrument was separated and extruded beyond the apex. Periapical radiography and cone-beam computed tomography showed the separated nickel-titanium instrument exiting the MB root apex into the periapical region adjacent to the maxillary sinus floor. A diagnosis of CAP was established. Given the inaccessible MB2 canal and the separated instrument located outside the apex, conventional endodontic retreatment was not feasible. Accordingly, a digital surgical guide was designed to precisely localize the separated fragment, followed by apical microsurgery including apicoectomy, cyst debridement, instrument retrieval, retrograde preparation, and iRoot BP filling. At the 2-year follow-up, the periapical radiolucency had nearly disappeared, maxillary sinus floor mucosal thickening was significantly relieved, and the affected tooth maintained normal function after crown restoration. This is the first reported case, to our knowledge, in which a digital 3D-printed surgical guide-assisted microsurgery successfully removed a separated instrument beneath the maxillary sinus floor and preserved the tooth without sinus complications.