J Korean Assoc Oral Maxillofac Surg.  2014 Oct;40(5):225-232. 10.5125/jkaoms.2014.40.5.225.

Characteristics of bony changes and tooth displacement in the mandibular cystic lesion involving the impacted third molar

• Lee JH
• Kim SM
• Kim HJ
• Jeon KJ
• Park KH
• Huh JK

• KMID: 2005452
• DOI: http://doi.org/10.5125/jkaoms.2014.40.5.225

Abstract

OBJECTIVES
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.
MATERIALS AND 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.
CONCLUSION
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.

Keyword

Third molar; Dentigerous cyst; Odontogenic cysts; Ameloblastoma; Mandible

MeSH Terms

Absorption
Ameloblastoma
Dentigerous Cyst
Diagnosis
Humans
Mandible
Molar, Third*
Odontogenic Cysts
Retrospective Studies
Tooth*

Figure

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  Fig. 1 Tooth displacement patterns on panoramic radiographs. Any position that did not deviate from the described standard was considered normal. A. a: Occlusal plane of the mesial teeth. b: The line parallel to (a), extending to the root tips of the second molar. c: The line perpendicular to (a) and tangent to the height of the distal contour of the second molar. d: The line parallel to (c) and located behind the length of the mesio-buccal width of the second molar. B. Downward displacement. C. Backward displacement. D. Back-upward displacement.

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  Fig. 2 Tooth displacement patterns on computed tomography imaging. A. No displacement. B. Lingual displacement. C. Buccal displacement.

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  Fig. 3 Growth patterns of the lesion on displayed panoramic radiographs. A. Back-upward (arrow). B. Downward (arrow). C. Down-forward (arrow). D. Down-forward and back-upward (arrow).

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  Fig. 4 Growth patterns of the lesion shown on computed tomography imaging. A. Buccal (asterisk). B. Bucco-lingual. C. Lingual (asterisk).

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