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What is a Peri-Apical Cyst?

A peri-apical (radicular) cyst is the most common tooth-derived cyst.

A cyst is a sac-like structure (in this case) derived from tooth-related tissues. It can be gas-filled, gel-filled or blood-filled but normally it is not pus-filled (that is, it is not normally/initially infected).

What are the signs & symptoms?

Whilst small, the cyst is often not noticed. When larger though, teeth can become mobile. Cysts can become infected and this can be when it is first noticed by either dentist or patient.

Photo of an excised peri-apical cyst (tooth already removed)

What are the causes of Peri-Apical Cysts?

The usual cause is a tooth that becomes infected with the result that the tooth dies.

Toxins from the dead tooth-pulp exit the end of the tooth, leading to inflammation of the surrounding tissues. This inflammation stimulates the cells found in the tooth-supporting structures, resulting in the formation of a peri-apical granuloma that may be infected or sterile.

Eventually, the granuloma becomes a cyst.

These are not usually clinically detectable when small but are most often discovered as incidental findings on X-rays.

How are they treated?

Several treatment options exist for such cysts.

Many cysts resolve with endodontic therapy (‘root canal treatment’) of the involved tooth. Those lesions should be monitored radiographically to ensure such resolution.

Cysts that fail to resolve with such therapy should be surgically removed and checked under a microscopic analysis. This is often accompanied by an ‘apicectomy’ of the tooth involved. This entails shaving off the end of the tooth and sealing, preventing the recurrence of the cyst (in theory).