Objective: To analyze the radiographic features of ameloblastoma (AM), odontogenic keratocyst (OKC) and dentigerous cyst (DC) occurring around the impacted third molars in the mandible and provide useful information for differential diagnosis of these lesions.
Methods: Patients with complete clinical data, pathological diagnosis and spiral CT or cone-beam CT images of AM, OKC or DC occurring around the impacted mandibular third molars were collected. Imaging characteristics including location, internal density, cortex expansion, root resorption and types of impacted teeth were analyzed.
Results: A total of 142 patients were collected, including 90 males and 52 females. Among them, 45 were OKC, 24 were AM, and 73 were DC. Among the 45 OKCs, 23 cases (51%) were located in the ramus of the mandible, mixed density were seen in 16 cases (36%). Among the 24 AMs, 18 cases (75%) were located in the ramus of the mandible, 13 cases (54%) were with buccal expansion, and 14 cases (58%) presented root resorption of teeth involved in the lesions. Among the 73 DCs, 61 cases (84%) were located around the crowns of impacted third molars, 51 cases (70%) with no significant expansion, and inverted impaction were shown in 42 cases (58%).
Conclusion: DCs were common in the lesions collected in this study, and their positions mostly were around the crown of the third molars and most of the impacted teeth were inverted. OKCs and AMs mostly occurred in the ramus of the mandible. Among them, OKC was more common in women, and mixed density could be observed in some OKC cases. Cortex expansion and the root resorption were more common in AMs.
 

impacted mandibular third molar,odontogenic keratocyst,ameloblastoma,dentigerous cyst