Periapical cysts, also known as radicular cysts, are the most frequent cystic lesion related to teeth (see mandibular lesions) and result from infection of the tooth.
On imaging, they generally present as round or pear-shaped, unilocular, lucent lesions in the periapical region, measuring <1 cm.
These are typically seen in middle to older age (3rd to 6th decades) 2.
Periapical cysts result from infection of the tooth, which spreads to the apex and into the adjacent bone. This leads to apical periodontitis, granuloma formation and eventual cyst formation. These cysts are therefore centered on the apex of the tooth and tend to be small, most <1 cm. There is also unsurprisingly usually overt evidence of caries.
Plain radiograph and CT
Most radicular cysts appear as round or pear-shaped, unilocular, lucent lesions in the periapical region 3. They are usually <1 cm in diameter and are bordered by a thin rim of cortical bone. The associated tooth usually has a deep restoration or large carious lesion. Caries will appear as erosion of the enamel/crown of the associated tooth.
MRI is not the first-line imaging modality but periapical cysts would appear as a non-enhancing lesion at the apex of a tooth. These cysts typically return low T1 signal and high T2 signal.
- inflammation involves tooth root apex
- periapical granuloma
- lesion around the crown of unerupted/impacted tooth
- keratocystic odontogenic tumour
Lucent lesions of the jaw
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- 3. Scholl RJ, Kellett HM, Neumann DP et-al. Cysts and cystic lesions of the mandible: clinical and radiologic-histopathologic review. Radiographics. 19 (5): 1107-24. Radiographics (full text) - Pubmed citation
- 4. Pasler FA, Visser H. Pocket Atlas of Dental Radiology. Thieme Medical Pub. (2007) ISBN:1588903354. Read it at Google Books - Find it at Amazon
- 5. Scheinfeld MH, Shifteh K, Avery LL et-al. Teeth: what radiologists should know. Radiographics. 2012;32 (7): 1927-44. Radiographics (full text) - doi:10.1148/rg.327125717 - Pubmed citation