Dental abscess symptoms: which stay in the tooth, and which are an emergency?

A periapical abscess starts inside the tooth. A deep cavity, a crack or a blow lets bacteria reach the living tissue in the centre of the tooth (the pulp); MouthHealthy, the ADA's patient site, writes that this route can end in the death of the pulp, and that when pus collects in the jawbone at the root tip it is called an abscess. MSD Manuals defines the abscess the same way: a collection of pus at the tip of a tooth root, usually formed by an infection spreading from the tooth into the surrounding tissue. An abscess arising from the gum itself, from a deep gum pocket, is a separate picture; we cover it on our page on gum swelling and abscesses.

The first symptom is usually pain, and its character gives it away. MedlinePlus describes the main symptom as severe, continuous toothache that does not stop; MSD adds that the pain gets worse when chewing. With ordinary sensitivity, a cold sip causes a brief twinge that passes at once. With an abscess, the pain comes on by itself, lasts a long time and sharpens when pressure is put on the tooth. The tooth may feel as though it touches before the others when you close, because the inflammation at the root tip is thought to push the tooth slightly up in its socket.

The NHS list of symptoms goes beyond pain: redness in the mouth or face and jaw, sensitivity to hot or cold food and drink in the affected area, a bad taste in the mouth, difficulty opening the mouth and chewing, swelling in the face or jaw, swollen glands on either side of the neck, and a high temperature. MedlinePlus adds a bitter taste, bad breath and a swelling on the gum that looks like a pimple; it clearly marks swelling in the jaw as a very serious symptom.

That small bump on the gum is an exit route the abscess has opened for itself (a fistula). When the pus builds up pressure in the bone, it breaks through the thinnest point and reaches the gum; the bump fills, bursts, leaves a salty or foul taste and after a while fills again. Because the pus drains out, the pain often eases. This does not mean the infection is over; as long as the source tooth stays as it is, the channel stays open too. MedlinePlus specifically says to see a dentist if you notice a bump or pimple on your gum.

Sometimes the same exit route opens not into the mouth but onto the skin of the face. A spot on the chin, along the jawline or on the cheek that looks like a pimple or a small sore, heals and then starts draining again, is the typical appearance. A review of dental skin fistulas covering 42 publications reports that these lesions are often mistaken for a skin infection, a cyst or a tumour, that patients see a dermatologist, a GP or a surgeon before reaching a dentist, and that the median delay in diagnosis is 12 months. A series of four cases from Korea likewise shows that dental complaints are often very slight, and that all the fistulas closed once the source tooth was treated.

Feeling which tooth is causing the symptom is not as easy as it seems. In a study in India of 114 patients with pulp and root tip inflammation in a lower first molar, when the teeth were tapped lightly (a percussion test), 57% of the healthy teeth next to the diseased tooth also responded with pain; for the matching healthy teeth on the opposite side the rate was 10.5%, and the more severe the spontaneous pain, the more common this misleading tenderness was. So trying to find the culprit by looking in a mirror and touching your teeth can lead you to the wrong tooth. The right tooth is found by reading a cold test, a percussion test and an X-ray together.

The real danger of an abscess lies not in the tooth but around it. MSD Manuals writes that the infection can spread to the jaw, the floor of the mouth or the cheek area, and that infections spreading in a way that affects the airway can be serious and life-threatening. In a study at Jena University Hospital in Germany of 997 inpatients treated surgically over 12 years, systemic complications were seen in 3.8%; the infection having spread to more than one tissue space was independently and strongly associated with this risk (odds ratio 5.5, with a wide confidence interval of 2.4 to 12.7), and older age, COPD (chronic obstructive pulmonary disease) and chronic alcohol dependence were also risk factors.

In a sample of 2,530 people who went to emergency departments in the United States in 2022 with a diagnosis of dental infection, the rate of severe complications was 9.8%: infection around the eye socket (orbital cellulitis) 3.1%, rapidly spreading death of soft tissue (necrotising fasciitis) 2.8%, and brain abscess 1.2%. 69% of these people were admitted to hospital. These figures reflect a group that had reached A&E, and was therefore already severe; they do not mean that every abscess seen by a dentist in time runs this course. But they show clearly why swelling spreading to the eye and neck counts as an emergency.

With the pictures in the first list, you need to see a dentist the same day, or at the first opportunity; an abscess is never something to wait out at home. If any of the signs in the second list is present, do not wait for an appointment.

The examination is ordered to establish first whether the infection has spread, then which tooth is the source, and finally whether the tooth can be saved.

1. 1

   Signs of spread first

   Temperature, swelling in the face and neck, swelling of the eyelid, how far the mouth opens, swallowing and the voice are asked about and checked. If any of the signs on the NHS emergency list is present, treatment is planned in hospital rather than in the dental chair; if needed, advanced imaging establishes which tissue spaces the infection has spread to.

2. 2

   The history of the pain

   You are asked when the pain started, whether it comes on by itself, whether it wakes you at night, whether it gets worse when you bite, and whether it has suddenly eased in the last few days. Pain that suddenly eases may show that the pus has found a way out or that the nerve has died completely; neither is recovery.

3. 3

   Testing the teeth

   The suspect tooth and its neighbours are tapped lightly, a cold test checks whether the nerve is alive, and the gum is checked for a bump or a deep pocket. MedlinePlus writes that tapping an abscessed tooth causes pain; but because healthy neighbouring teeth are known to respond to tapping with pain quite often too, the decision is not left to a single test.

4. 4

   An X-ray and, if needed, a CBCT scan

   The dentist looks for a dark area at the root tip, a fractured root or bone loss around an old root filling. If there is a fistula, a thin tracer can be placed in it and an X-ray taken to show which tooth the channel leads to; for skin fistulas, reviews give this method or a cone beam CT (CBCT) scan as the investigation of choice.

5. 5

   Draining the pus

   The NHS describes the first step of treatment as draining the pus. This is done under local anaesthetic, either by opening a channel through the tooth or by making a small cut in the swelling, and because the pressure drops, the pain often eases quickly.

6. 6

   Removing the source

   If the tooth can be saved, root canal treatment is done; if it cannot, it is extracted. MSD Manuals writes that removing the diseased pulp and draining the pus matter more than antibiotics.

They all share the same logic: the pus is drained and the source is removed. Which one is chosen depends on how much healthy tooth tissue is left and the state of the root.

The points below are decisions that lead to an abscess growing or to the wrong tooth being treated.

The course below is for the usual situation in which a periapical abscess is drained by a dentist and the source is treated. The plan of the clinician treating you takes priority.

1. Straight after drainage

   Once the pus is drained and the pressure drops, the throbbing often eases markedly. The NHS writes that painkillers may be recommended for a few days after treatment, and that antibiotics are sometimes given as well.

2. The first few days

   The swelling in the face should get smaller day by day, not bigger. During this period, as the NHS recommends, soft food, a soft toothbrush and avoiding very hot or very cold things make it easier.

3. If there is a fistula

   The exit route in the gum or skin closes once the source tooth has been treated. Any mark left on the skin fades over time; if it does not close, the treated tooth or the source should be reviewed.

4. Over months

   Whether the bone loss at the root tip is filling in is followed with check-up X-rays. In the skin fistula cases too, healing was confirmed by X-rays showing bone re-forming at the root tip.

We do not give a single figure, because of two abscesses with the same name, one ends with root canal treatment in a single session and the other with drainage in hospital. These are the items that determine the scope:

Whether the infection has spread

An abscess confined to the root tip is treated by a dentist; infection that has spread into the deep tissue spaces is treated in hospital.

Whether the tooth can be saved

Root canal treatment with a filling or crown on top, and extraction, are entirely different items of work.

Whether the tooth has had root canal treatment before

Redoing root canal treatment or root tip surgery can involve more work than a first root canal treatment.

The need for imaging

Most abscesses become clear with an examination and an X-ray; a CBCT scan may be needed for a skin fistula or an unclear source.