Jaw cysts are cavities that form inside the jaw bones and are usually caused by an infected tooth or form automatically (e.g. around an impacted wisdom tooth). They contain liquid and are lined with a thin membrane. They are benign lesions. However, when they are left untreated for long, cysts grow in size, destroying the surrounding bone. When they get infected they cause pain and swelling.
When the cause of the problem is an infected tooth, the first step to treatment is root canal treatment, which sometimes completely cures the cyst. In other cases, when the cyst has expanded over a larger area, or affects multiple teeth, the treatment consists of surgical excision.