Comprehensive analysis of ectopic mandibular third molar: a rare clinical entity revisited

Yaping Wu, Yue Song, Rong Huang, Jiaan Hu, Xiaotong He, Yanling Wang, Guangchao Zhou, Chao Sun, Hongbing Jiang, Jie Cheng, Dongmiao Wang

Ectopic mandibular third molar is a rare clinical entity with incompletely known etiology. Here, we sought to delineate its epidemiological, clinical and radiographic characteristics, and therapy by integrating and analyzing the cases treated in our institution together with previously reported cases. A new definition and classification for ectopic mandibular third molar was proposed based on its anatomic location on panoramic images. Thirty-eight ectopic mandibular third molars in 37 patients and 51 teeth in 49 patients were identified in our disease registry and from literature (1990-2016), respectively. These cases were further categorized and compared according to our classification protocol. The demographic, clinicopathological and radiographic data were collected and analyzed. These ectopic teeth were categorized into four levels, 33 in level I(upper ramus), 32 in level II (middle ramus), 15 in level III (mandibular angle) and 9 in level IV (mandibular body). The common clinical presentations included pain, swelling and limited mouth opening, although sometimes asymptomatic. Most teeth were associated with pathological lesions. Treatments included clinical monitor and surgical removal by intra- or extraoral approach with favorable outcomes. Clinical presentations and treatment options for these teeth were significantly associated with their ectopic locations as we classified. Ectopic mandibular third molars are usually found in patients with middle ages and in upper and middle ramus of mandible. Surgery is preferred to remove these ectopic teeth and associated pathologies when possible.