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Abscess, gum boil, periostitis

An abscess is a limited area of pus formed as a result of a bacterial infection. The body's immune system reacts to the infection, and sends white blood cells to the area to try to get rid of the bacteria. Pus is a mixture of live and dead white blood cells, enzymes and parts of destroyed cells and tissues. When there is no way for pus to drain, it forms an abscess.

Abscesses can form in almost every part of the body. In the mouth, abscesses form in gum tissue or in the roots of teeth and in the surrounding areas of the tooth. They can be caused by trauma (food or debris embedded deep in the gum), by bacteria that enters through a cavity and gets into the dental pulp, or from a deep periodontal pocket. People with a lowered resistance to infection are at increased risk of developing an abscess. At first, the abscess may cause a toothache, which can be severe. The tooth's nerve can become infected and the infection can burrow through to the gum, forming a visible boil that can rupture in the mouth. Once the abscess ruptures, the pain often decreases significantly, but dental treatment is still necessary. If the abscess does not drain, the infection can spread to other areas of the head and neck and can become life threatening.


The main symptom is persistent, throbbing pain. At first, the tooth will be sensitive to heat and pressure while chewing. Later, you may develop a fever. Swollen lymph nodes under the jaw or in the neck can be tender and you may feel pain in the sinus area. If the abscess ruptures, a sudden rush of foul-smelling and foul-tasting fluid will spill into the mouth.


Usually, your dentist can diagnose a tooth abscess by examining your mouth. He or she may push on the swollen area of the gum and do a pulp test on the affected tooth to see if it is still alive. A pulp test can involve:

  • Gentle tapping (percussion) on the tooth
  • Temperature testing
  • Using an electric tester on the tooth

Your dentist also may take an X-ray to look for bone erosion around the tip of the tooth's root.


Saving an abscessed tooth begins with draining the infection, which usually relieves pain and removes much of the infection. Root canal treatment may be necessary and should be started as soon as possible to remove diseased tissue.

If the abscess involves gum tissue, your dentist may suggest that you rinse with warm salt water (1/8 of a teaspoon of salt in 8 ounces of water) a few times a day for several days. You may be prescribed antibiotics to help make sure the infection has been eliminated.

If you have a toothache or notice evidence of an abscess on your gum, visit your dentist. Even if the abscess drains and the pain decreases, a visit to the dentist for complete treatment is crucial.