Dental Abscess – A Problem “Boiled” Down

This article will give you a “boiled” down version of the problem of an abscess in the mouth; it’s causes, symptoms and treatment.  Included are tips on what you can do at home to relieve any pain.


What is an Abscess?

An abscess is a common dental problem. Such infections can come from a variety of sources, even though it is usually only on the gum that they appear. For example, an infection arising from a diseased tooth will appear on the gum that lies over that tooth.

Like all abscesses, the cause is generally a bacterial infection.

Abscess on gum above a front tooth.

An abscess on gum above a front tooth.

Common sources of dental abscesses are:

  • Tooth decay. This is teeming full of bacteria. If this bacteria gets into the dental pulp, it can spread to cause infection inside and at the root of the tooth. This is known as a periapical abscess, and can travel out to the gum that lies over the root (see photo). Pulp death can also result from dental treatment on a diseased tooth. Read more on decay here.
  • In severe gum disease (periodontal disease), abscesses can form in the gaps that occur between the teeth and gums. These gaps around the teeth and under the gum-line are hard to clean, and are full of the microbes that cause the periodontitis. We discuss periodontal abscess here.
  • Pericoronitis from impacted wisdom teeth, is an inflammation of the gum overlying a wisdom tooth. The area between the wisdom tooth and it’s overlying gum flap is a perfect space for bacteria to proliferate in the mouth.
  • Foreign objects, such as food debris lodging in the mouth, causing a gingival abscess.

This summary picture shows the chief causes: 1. decay/nerve damage and 2. gum infection

Graphic showing the causes of a dental abscess

In general, an abscess is a collection of pus. This forms when the body is trying to fight off an infection. The pus contains the bacteria, as well as cells and fluids from the body’s immune system. The body will try to drain pus away but when it cannot, it collects to form an abscess. Toothache results when there is a build-up of pressure from the fluid, this pressure will fire off the nerve endings that lead us to feel pain.

There are many medical conditions that can diminish the immune system and put one at increased risk of such conditions. Patients with diabetes mellitus or HIV infection are examples of those who may be immuno-suppressed. Likewise some people are on medication that lower the immune system’s effectiveness, e.g. transplant patients or those receiving treatment for cancer.



Abscesses can be classified as either:

  • Acute. The infection is ‘new’ and has come up quickly. Read about the symptoms below.
  • Chronic. It has been present for some time.  Typically the symptoms are less severe here, often as the body’s immune system is, to an extent, dealing with the infection.

Acute abscesses are potentially very dangerous if they are allowed to spread.  Therefore they should be treated immediately.




The symptoms of an acute infection might include:

  • Throbbing pain, which is often severe.  The pain persists; it does not come and go.
  • Pain may be worse at night, often when one puts their head down.
  • Pain on chewing/biting down in the area.
  • Painful lump on the gum around the tooth – this is typically red and very tender.
  • The tooth may become mobile as the swelling gets larger.
  • If the swelling is severe, you may feel generally unwell, with a fever and swollen glands.

A chronic abscess is usually less bothersome.  The infection may drain through a little pimple (sinus) on the gum. As the pus is draining away, and not building up, the symptoms (if any) are less severe.  There may be a bad smell or taste coming from your mouth.

Note that a chronic abscess can become severe and acute at any time.


Typical scenario: At first, an abscess may cause a toothache, which can be severe. The tooth’s nerve also can become infected. If the infection burrows through to the gum via a channel called a ‘fistula‘, it can form a visible swelling/bump/’pimple’ (boil). Once the boil breaks open, the pain often gets much better. However, dental treatment is still needed even if the pain clears – the initial problem will still be there!

If the gum abscess does not drain, the infection can spread to other areas of the head and neck. In this case, it can (rarely) become life-threatening.



Your dentist will usually be able to tell where the problem is coming from by:

  • Examining the area for any swelling.
    "Image of a dental xray showing a large abscess on a front tooth"

    A dental X-ray showing a large front tooth abscess (the dark circle)

  • Feeling the area for any tenderness.
  • Tapping the tooth and testing the nerve to check if it is healthy or not.
  • Taking dental X-rays of the area. Sometimes X-rays will not pick up an infection if it is small and has only arisen (it may take a few days for changes to be visible).



A short note here on treatment: The steps involved to treat pain include first draining the infection and possibly taking antibiotics. Further treatment will then be needed to clear the source of the problem and prevent recurrence. This may be root canal, extraction or periodontal treatment.

For more information, see the following page on tooth abscess treatment.


Final Words

If you have symptoms of an infection or abscess in your mouth, attend the dentist as soon as possible dentist. Even if the problem has cleared up, it is always important to get final treatment finished, otherwise it will recur – Often at the most inconvenient of times!!!


Prevention of abscesses is achieved by following general dental care advice and regularly attending the dentist for check-ups.

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