The frequency of displacement of a third molar root is low and considered a rare incident. A computer-assisted navigation system is a surgical support system that allows the patient to confirm the surgical site in three dimensions during surgery has recently been introduced to oral and maxillofacial surgery. We used a computer-assisted navigation system to remove a displaced third molar root in the floor of the mouth without complications and report the outline of the procedure and the effectiveness of the computer-assisted navigation system safety.

This was a 56-year-old male who underwent extraction of the mandibular right third molar at a referral clinic. At that time, the proximal root fracture remained in the extraction socket, and the distal root fracture displaced to floor of the mouth. The patient was referred to our hospital immediately after tooth extraction. We extracted the displaced third molar root fracture under general anesthesia using a computer-assisted navigation system to accurately locate the root fracture and performed minimally invasive extraction. The root extraction was performed 18 days after the initial tooth extraction. No lingual nerve exposure was observed during surgery. No sensory abnormalities in the lower lip or tongue were observed postoperatively.

Computer-assisted navigation system is a useful surgical support system that enables oral and maxillofacial surgical procedures and prevents postoperative complications such as lingual nerve palsy safety.