Periapical cyst (radicular cyst)
DESCRIPTION: This is a cyst at the apex of a tooth with a necrotic pulp and is a sequelae of pulpitis. Periapical cysts bear a radiographic resemblance to dental granulomas. About the only substantive difference is the presence of an epithelium lined central cavity in the cyst. The associated tooth is usually asymptomatic. Acute infectious episodes may cause pain. The lesion appears as a sharply circumscribed radiolucent lesion around the apex of the associated tooth. It is often stated to have a thin sclerotic rim at the border but this feature is absent as often as it is present.
ETIOLOGY: This cyst is a direct sequela of inflammation of the pulp that has extended into the adjacent periapical tissues.
TREATMENT: Treatment consists of endodontic therapy or extraction of the associated tooth with curettage of the cyst.
PROGNOSIS: Good
DIFFERENTIAL DIAGNOSIS: Dental granuloma. Lesions such as keratocyst, ossifying fibroma, giant cell granulomas, and the lytic stage of osseous dysplasia may occur at the apex of a tooth and masquerade as a periapical cyst. Several odontogenic tumors may also present in a similar fashion.
COMMENT: A periapical infection with suppuration is correctly called a periapical abscess. An abscess may arise de novo or in a preexisting granuloma or cyst. Drainage of pus provides considerable relief of pain and hastens healing.
