title: Characteristics of bony changes and tooth displacement in the mandibular cystic lesion involving the impacted third molar.
abstract: OBJECTIVE
  The purpose of this retrospective study is to find the differentiating characteristics of cystic and cystic-appearing lesions that involve the impacted mandibular third molar by analyzing panoramic radiographs and computed tomography images, and to aid the preoperative diagnosis.
  
  
  METHODS
  Eighty-one patients who had a mandibular cystic or cystic-appearing lesion that involved impacted mandibular third molar and underwent cyst enucleation were included in the study. The preoperative panoramic radiograph and computed tomography findings were analyzed in accordance to the histopathologic type.
  
  
  RESULTS
  Most of the cystic lesions containing the mandibular third molar were diagnosed as a dentigerous cyst (77.8%). The occurrence of mesio-distal displacement of the third molar was more frequent in the odontogenic keratocyst (71.4%) and in the ameloblastoma (85.7%) than in the dentigerous cyst (19.1%). Downward displacement was primarily observed in each group. Odontogenic keratocyst and ameloblastoma showed more aggressive growth pattern with higher rate of bony discontinuity and cortical bone expansion than in dentigerous cyst.
  
  
  CONCLUSIONS
  When evaluating mandibular cystic lesions involving the impacted mandibular third molar, dentigerous cyst should first be suspected. However, when the third molar displacement and cortical bone absorption are observed, then odontogenic keratocyst or ameloblastoma should be considered.
authors.affiliation: Department of Oral and Maxillofacial Surgery, Gangnam Severance Hospital, Yonsei University College of Dentistry, Seoul, Korea.
authors.forename: Jin-Hyeok
authors.initials: JH
authors.lastname: Lee
authors.affiliation: Department of Oral and Maxillofacial Surgery, Gangnam Severance Hospital, Yonsei University College of Dentistry, Seoul, Korea.
authors.forename: Sung-Min
authors.initials: SM
authors.lastname: Kim
authors.affiliation: Department of Oral and Maxillofacial Surgery, Yongin Severance Hospital, Yonsei University College of Dentistry, Seoul, Korea.
authors.forename: Hak-Jin
authors.initials: HJ
authors.lastname: Kim
authors.affiliation: Department of Oral and Maxillofacial Radiology, Yongin Severance Hospital, Yonsei University College of Dentistry, Seoul, Korea.
authors.forename: Kug-Jin
authors.initials: KJ
authors.lastname: Jeon
authors.affiliation: Department of Oral and Maxillofacial Surgery, Gangnam Severance Hospital, Yonsei University College of Dentistry, Seoul, Korea.
authors.forename: Kwang-Ho
authors.initials: KH
authors.lastname: Park
authors.affiliation: Department of Oral and Maxillofacial Surgery, Gangnam Severance Hospital, Yonsei University College of Dentistry, Seoul, Korea.
authors.forename: Jong-Ki
authors.initials: JK
authors.lastname: Huh
keywords: Ameloblastoma; Dentigerous cyst; Mandible; Odontogenic cysts; Third molar