Abstract: Objective　 To identify the clinical and radiographic characteristics as well as surgical removal method of ectopic mandibular third molar (EMTM) and its associated disease. Methods Clinical cases involving mandibular third molars treated from January 2012 to December 2017 in the Affiliated Stomatological Hospital, Nanjing Medical University were identified. All data regarding the ectopic mandibular third molars diagnosed by panoramic radiography or cone-beam CT were collected and analyzed to reveal the clinical manifestation, radiographic features, associated pathology and therapeutic strategy. Results A total number of 47 EMTMs in 46 patients meeting the inclusion criteria were included. They were frequently identified in coronoid, ramus, mandibular angle and body. Local swelling, pain and limited mouth opening were typical clinical symptoms. The occurrence of local swelling was associated with anatomic sites of ectopic teeth(P<0.05). 89.37% of EMTMs were accompanied with dentigerous cyst or tumor. Most cases were treated by intraoral approach to extract the EMTM and remove the simultaneous disease, and there were fewer postoperative complications. Conclusions: EMTM is a relatively rare disease entity and usually accompanied with odontogenic swelling or tumorous lesion. Its clinical diagnosis is mainly based on radiographic findings and the overall prognosis after operative treatment is favorable.

Key words: mandibular third molar, ectopic tooth, CBCT, diagnosis, treatment