A cyst is a sac or pouch that forms under the skin or in bone. The cyst can be empty or contain fluid. A cyst is not cancerous. A cyst is lined with a kind of tissue called epithelium. This type of tissue normally is found in surface layers, such as the skin and the lining of the mouth. Cysts may form when epithelium cells move into deeper body layers and begin to multiply.

Oral cysts are found in the head or neck. They can be in the jawbone, or in soft tissues such as the salivary glands, skin or inside the mouth. There are many types of cysts. Sometimes a cyst in the jawbone is lined with epithelium that normally forms teeth. This is called an odontogenic cyst. This type of jaw cyst can grow large enough to move teeth and cause problems with the bite (the way teeth come together). A large odontogenic cyst also can weaken the jaw because the cyst replaces the hard bone tissue. This makes the jaw more likely to break. The jaw can become inflamed, infected and painful.

One type of odontogenic cyst, called an odontogenic keratocyst, tends to grow very fast. It is difficult to treat and comes back more often than other types of cysts. People with an inherited condition called basal cell nevus syndrome can form this type of cyst.

The most common cyst found in the mouth is the apical periodontal cyst. It develops as a result of an infection in the tooth pulp, or nerve. This infection typically is caused by decay. A dentigerous cyst forms at the crown of a tooth that has not yet come into the mouth. This type of cyst can cause roots of already erupted teeth in the area to resorb (dissolve).

Usually, the cyst is removed by surgery. An oral surgeon usually does this procedure under local anesthesia. If the cyst is infected, antibiotics may be given. The outlook is excellent because cysts can be removed by surgery. However, some cysts return. People who have had a cyst removed should be checked from time to time by a dentist.