Retrieval of a Displaced Mandibular Tooth Fragment From the Floor of the Mouth Using a Combined Navigation System and Endoscope: A Case Report.

BACKGROUND If a tooth fragment is displaced into the floor of the mouth during mandibular third molar extraction, surgical retrieval can be challenging because the fragment cannot be directly visualized in the operative field. Several studies have described the use of navigation systems or endoscopic techniques individually. However, to the best of our knowledge, no reports have described their combined use for this condition. CASE REPORT A 37-year-old man underwent extraction of a left mandibular third molar at a dental clinic in May 2021, during which a root fragment was displaced into the floor of the mouth. An attempt to retrieve the fragment under general anesthesia at another hospital was unsuccessful, and the patient was subsequently referred to our department. Because direct retrieval was considered technically difficult, surgical retrieval was performed by using a combination of electromagnetic navigation and endoscopic guidance. The fragment was successfully removed via an intraoral approach with minimal surgical invasion. Postoperatively, the wound healed uneventfully and no lingual nerve injury was observed. CONCLUSIONS Electromagnetic navigation systems provide real-time spatial localization based on preoperative imaging, and are particularly useful when the target is difficult to palpate or directly visualize. Endoscopic guidance provides enhanced illumination and direct visualization within confined anatomical spaces, thereby facilitating minimally invasive surgery. In the present case, the combined use of electromagnetic navigation and endoscopic guidance can facilitate accurate intraoperative localization and minimally invasive retrieval of a displaced mandibular root fragment on the floor of the mouth.