Pericoronitis
Infection of the gum flap over a partly erupted wisdom tooth. The gum is red, swollen and tender, there may be a bad taste, and chewing forces the opposing tooth onto the flap. This is the most frequent wisdom tooth emergency.
Wimpole Street opens 1 October 2026. For a dental emergency today, call South Kensington 020 7183 2362 (open 7 days) or St Paul's 020 7183 3709 (Mon–Fri).
South Kensington
Open seven days a week
St Paul's, City of London
Open Monday to Friday
Emergency dentistry · Wimpole Street, Marylebone
Wisdom tooth emergency: infection, swelling and difficulty opening
Wisdom teeth cause trouble because they arrive late into a jaw that has run out of room. A tooth that is half through the gum leaves a flap where food and bacteria collect, and the resulting infection, pericoronitis, can turn a dull ache at the back of the mouth into a swollen face and a jaw that will barely open within a couple of days. Not every episode needs the tooth removed on the spot, but every one needs assessing. Wimpole Street opens on 1 October 2026; until then, the same team handles wisdom tooth emergencies at South Kensington and St Paul’s.
Before you are seen
Right now: what to do
- 01
Rinse frequently with warm salt water, aiming the water at the back of the mouth. A chlorhexidine mouthwash from a pharmacy is a useful alternative for a few days.
- 02
Clean under the gum flap gently with a soft brush or a single-tuft brush. It is uncomfortable, but trapped food is what feeds the infection.
- 03
Take a painkiller as directed on the pack; ibuprofen is often more effective for this kind of inflammatory pain if it is suitable for you.
- 04
Eat soft food and avoid chewing on the affected side. Sharp or crumbly foods lodge under the flap.
- 05
If the opposing upper tooth is biting on the swollen gum, note it: sometimes smoothing or removing that upper tooth is part of the fix.
- 06
Do not apply heat to the face or place aspirin on the gum. A cool compress on the cheek is preferable if there is swelling.
Take any painkiller only as directed on the pack, never place aspirin against the gum, and ask a pharmacist if you already take other medicines.
Diagnosis
What's likely causing it
Decay in the wisdom tooth or its neighbour
Wisdom teeth are hard to clean and often decay quietly. Worse, a tilted wisdom tooth traps plaque against the back of the second molar and can cause decay there, threatening a far more valuable tooth.
Abscess
Untreated pericoronitis or deep decay can progress to a collection of pus in the bone or soft tissue, with spreading swelling and, sometimes, difficulty opening.
Impaction pressure
A wisdom tooth wedged against the tooth in front produces a deep, aching pressure and occasional sharp pain, particularly in the late teens and twenties as the tooth attempts to erupt.
Cyst around an unerupted tooth
Rarely, the sac around a buried wisdom tooth enlarges into a cyst that hollows the jaw. Usually painless until infected, it shows up on an X-ray as a dark area around the crown.
Cheek trauma
An upper wisdom tooth erupting outwards can bite the cheek repeatedly, producing an ulcer that feels like a toothache from the inside.
At the clinic
How the emergency visit runs
- Step 1
Assess and triage
We measure how far you can open, check for swelling in the neck and floor of the mouth and take your temperature before examining the tooth.
- Step 2
X-ray
A digital image, or a panoramic OPG where needed, shows the angle of the tooth, its roots, the nerve position and any decay or cyst.
- Step 3
Settle the infection
The area is numbed and the flap irrigated to flush out debris. A dressing may be placed. Antibiotics are added if there is spreading swelling or fever.
- Step 4
Decide about the tooth
A first episode is often settled and monitored. Repeated infections, decay or damage to the neighbouring molar lead to a recommendation for extraction.
- Step 5
Extraction or referral
Straightforward wisdom teeth are removed here once the infection has calmed. Deeply impacted teeth near the nerve may be referred to an oral surgeon.
Fees
Emergency fees
Wisdom tooth fees are graded by how much surgery is involved, which the X-ray tells us before we start. Removal is generally scheduled a few days after the emergency visit, once swelling has subsided and you can open comfortably.
| Item | Fee |
|---|---|
Emergency assessment New-patient rate (usual fee £95). | £30 |
Digital X-ray or OPG Small image £20; panoramic OPG up to £100. | £20–£100 |
Irrigation and dressing of the flap Settles pericoronitis at the first visit. | from £95 |
Simple wisdom tooth extraction Fully erupted tooth, no bone removal. | from £250 |
Surgical wisdom tooth extraction Gum lifted and some bone removed. | from £450 |
Complex or impacted extraction Deeply buried or unfavourably angled teeth. | from £850 |
Prescription Antibiotics where infection has spread. | private prescription |
Indicative prices for Wimpole Street, identical to our South Kensington and St Paul's clinics. Whatever is recommended is set out in writing, with the cost, before any treatment starts.
Once you are home
Afterwards
- After irrigation, keep rinsing with salt water or chlorhexidine three times a day and clean the flap after every meal. The gum should be noticeably better within 48 hours.
- If the tooth has been removed, bite on the gauze for 30 minutes, avoid rinsing for the first day, and then start gentle warm salt water rinses from day two.
- Expect swelling to peak around day two or three after an extraction, then subside. A cold pack in the first 24 hours helps.
- Do not smoke, drink through a straw or do heavy exercise for 48 hours after an extraction; all three raise the risk of a painful dry socket.
- Tingling or numbness of the lip or tongue lasting more than a day after an extraction should be reported so it can be monitored.
- If an episode of pericoronitis has been settled rather than the tooth removed, book a review; a second infection usually tips the balance towards extraction.
FAQ
Questions patients ask
Sometimes, if the tooth is straightforward and there is little swelling. More often the infection is settled first, because anaesthetic works less well in acutely inflamed tissue and healing is more predictable once the swelling has gone. Extraction then follows within days.
No. A single mild episode of pericoronitis in a tooth that is still erupting may never recur once the tooth is fully through. Removal is recommended for repeated infections, decay, damage to the neighbouring tooth, cysts or a tooth that cannot erupt properly.
Inflammation around a lower wisdom tooth spreads into the chewing muscles beside it, causing them to go into protective spasm. Opening improves as the infection settles, but if it is getting rapidly worse it is a red flag for spreading infection and needs urgent attention.
Antibiotics help when infection has spread into the face, but pericoronitis is driven by debris under the gum flap, and that has to be cleaned out. Antibiotics alone tend to give a week or two of relief before the problem returns.
The nerve supplying the lower lip and chin runs close to the roots of some lower wisdom teeth. The X-ray shows this relationship, and where the risk is significant we discuss it fully and may refer you to an oral surgeon or arrange a 3D scan first.
South Kensington on 020 7183 2362 sees emergencies seven days a week, including Sundays. St Paul’s on 020 7183 3709 covers Monday to Friday. The same dentists and fees apply.
Also on this site
Other emergencies we treat
Marylebone, W1
Emergency care at Wimpole Street from 1 October 2026
Register your interest and we will contact you as the Marylebone diary opens. Anything that hurts today should go to South Kensington or St Paul's, where the same clinicians keep emergency slots each day.
Opening 1 October 2026
Wimpole Street is not yet seeing patients. Until then, please book or call our South Kensington clinic on 020 7183 2362 or our St Paul's clinic on 020 7183 3709. Questions about the new clinic: wimpolestreet@md.co.uk.
Until we open
Need an appointment before 1 October 2026?
The same clinical team already works from two other Medical & Dental clinics. Book at either one now and, if you prefer, move your ongoing care to Wimpole Street once the doors open.
South Kensington
- 20 Old Brompton Road, London SW7 3DL
- Open seven days a week
- 020 7183 2362
St Paul's, City of London
- 5 Ave Maria Lane, London EC4M 7AQ
- Open Monday to Friday
- 020 7183 3709
