A cyst is a sac or pouch that contain fluid and lined with a kind of tissue called epithelium. A cyst is non-cancerous lesion. Oral cysts can be found in the jawbone, or in soft tissues such as the salivary glands, skin or inside the mouth.
Sometimes a cyst in the jawbone is lined with epithelium that normally forms teeth, called an odontogenic cyst. This type of jaw cyst can grow large enough to move teeth causing problems with the bite and can weaken the jaw because it replaces the hard bone tissue. The jaw can become inflamed, infected and painful. The most common cyst found in the mouth is the apical periodontal cyst, which develops as a result of an infection in the tooth pulp, or nerve.
An impacted tooth that is not removed can also form a cyst that develops from the dental follicle; this type of cyst is called a dentigerous cyst. Dental cysts can grow into large lesions because they apply pressure over the bone causing bone resorption. A small odontogenic jaw cyst may be painless, it can be seen on an X-ray as a dark area in the bone. When an odontogenic cyst becomes large and infected, it may be painful.