A swollen, throbbing lump on the gum can come from two quite different places. It may be an infection in the gum pocket beside a tooth, or an infection that started inside the tooth and has tracked out through the root. From the outside they can look almost the same, but the treatment for one does not fix the other, so working out the source is the first thing a dentist does.
Either way, a dental abscess is an infection that needs to be seen promptly, and a few warning signs mean it needs care the same day.
Same pus, different starting points
An abscess is a collection of pus where the body has walled off a bacterial infection. In the mouth, the pressure of that pus is what causes the throbbing.
A gum abscess, also called a periodontal abscess, forms in the tissues that support the tooth, usually inside a deep pocket between the gum and the root. A tooth abscess, also called a periapical abscess, begins in the pulp, the nerve and blood vessels inside the tooth, and collects at the tip of the root in the jawbone.
How a gum abscess develops
Most gum abscesses happen in people with gum disease, where deep pockets let bacteria and debris collect. A review by Herrera D and colleagues in the Journal of Clinical Periodontology (2000) described the periodontal abscess as one of the more common dental emergencies, particularly in people with untreated gum disease. They can also flare during or after gum treatment. In people without gum disease, something wedged under the gum, such as a popcorn husk or a fragment of a toothpick, is a common trigger.
A gum abscess often shows up as a smooth, shiny, tender swelling close to the gum line. The tooth may feel loose or sore to bite on. Because the problem is outside the tooth, the nerve inside is often still healthy.
How a tooth abscess develops
A tooth abscess starts when bacteria get into the pulp, usually through deep decay, a cracked tooth, a leaking filling or an old injury. The pulp becomes inflamed and eventually dies, and infection spreads out of the root tip into the bone.
Many people notice toothache first, sometimes severe and throbbing, sometimes worse at night or when lying down. The tooth may become very tender to bite on and can feel slightly high. Swelling may follow, and a small pimple on the gum can appear if the infection finds a way to drain. Some tooth abscesses cause surprisingly little pain, particularly once the nerve has died, and are only found on an X-ray.
How a dentist tells them apart
You do not need to work out which kind you have before you book. The dentist will look at where the swelling sits and measure the gum pocket around the tooth. A cold test helps show whether the nerve inside is alive, and an X-ray shows whether there is infection at the root tip, bone loss along the side of the root, or both. Sometimes a gum problem and a tooth problem are present together, which is one reason testing matters.
As a rough guide, a deep pocket next to a tooth that still responds to cold points towards a gum abscess. A tooth that no longer responds, with a dark area at the root tip on the X-ray, points towards a tooth abscess.
Treatment depends on the source
Whichever type it is, the first step is usually to release the pus and relieve the pressure.
For a gum abscess, that means draining and cleaning out the pocket, often with the root surface cleaned under local anaesthetic. Treating the underlying gum disease afterwards, sometimes with a course of deep cleaning, helps stop it coming back. If the tooth has lost a lot of support, removing it may be the better option.
For a tooth abscess, the infected pulp has to be dealt with. That means root canal treatment to clean and seal the inside of the tooth, or removing the tooth if it cannot be saved.
Antibiotics are sometimes added when infection is spreading or you are unwell, but they do not remove the source. Herrera and colleagues noted that the role of antibiotics in gum abscesses is debated. Without the dental treatment, the abscess is likely to return.
Signs that need same-day care
Most abscesses are urgent rather than life-threatening, and should be seen within a day or so. Get help straight away, through a dentist or a hospital emergency department, if you have:
- swelling spreading across the face, under the jaw or down the neck
- a fever or you feel generally unwell
- trouble swallowing, opening your mouth or breathing
- swelling near the eye
These can mean the infection is spreading into deeper tissues. Our guide on what to do in a dental emergency covers the first steps.
Until you are seen
Over-the-counter pain relief taken as directed on the pack, and warm salt-water rinses, can ease discomfort. Avoid chewing on that side. Do not put aspirin against the gum, as it can burn the tissue, and do not try to squeeze or pierce the swelling.
Common questions
The swelling burst and the pain eased. Do I still need to go?
Yes. Drainage relieves pressure, but the cause is still there, and the abscess usually comes back if it is not treated.
Can I just take antibiotics?
Antibiotics alone do not fix a gum pocket or an infected tooth. They may be prescribed alongside treatment in some cases, but the dental treatment still needs to happen.
Can a tooth with a gum abscess be saved?
Often, if there is enough bone support left and the gum disease can be controlled. Your dentist will discuss the outlook once the infection has settled.
If you have a painful swelling, our general dentists in Melrose Park can assess it and talk you through the options. New patient offers are on our current deals page.
Dental infections can occasionally become serious. If you have spreading swelling, fever, or difficulty breathing or swallowing, seek urgent medical care.
