Examination of the whole mouth
We look at the ulcer itself, the surrounding tissue, the teeth and any appliance that could be responsible, and check the rest of the lining, the tongue and the neck as part of a routine screen.
About this treatmentDental condition · Wimpole Street, Marylebone
Mouth ulcers: why they appear, how to settle them, and the one rule about timing
A mouth ulcer is a small break in the lining of the mouth, usually round or oval, with a pale yellow or grey centre and a red rim. It stings when you eat anything salty, sharp or hot, and then, in the great majority of cases, it heals on its own in a week to ten days without leaving a mark. Most adults get them from time to time. Some get them in crops every few weeks for years, a pattern known as recurrent aphthous ulceration, which is uncomfortable but not dangerous. Others get a single ulcer where a sharp tooth, a filling edge or a denture rubs, and it goes as soon as the cause is smoothed. Our interest as dentists is twofold: finding and removing anything in the mouth that is causing or prolonging ulcers, and making sure the rare ulcer that is not an ulcer at all is picked up early. The rule we ask every patient to remember is simple. Any sore or patch that has not healed after three weeks should be looked at, whatever it feels like.
Recognising it
How it usually feels
A round or oval sore with a pale centre and red edge
The classic minor ulcer, usually under a centimetre, on the inside of the lip, cheek or under the tongue.
Stinging with salty, acidic or spicy food
Exposed nerve endings in the lining react to anything irritant.
A tingling or burning spot a day before the ulcer shows
Common in recurrent ulcers; some patients learn to treat at this stage.
Several small ulcers at once
Clusters point towards the recurrent aphthous pattern rather than trauma.
An ulcer always in the same place beside a tooth or denture
Strongly suggests a mechanical cause that can be removed.
A sore that is painless, firm or has lasted more than three weeks
Not typical of a simple ulcer and the reason for the three-week rule.
Behind the symptoms
What's going on
- 01
Rubbing and minor injury
Biting the cheek, a toothbrush slip, a rough edge on a broken tooth or filling, an orthodontic bracket or a denture flange that digs in. Trauma ulcers appear exactly where the injury happened and heal quickly once the cause is dealt with.
- 02
Recurrent aphthous ulceration
The commonest cause of repeated ulcers, often starting in the teenage years and running in families. The lining reacts to triggers such as stress, tiredness, hormonal changes, certain foods and minor trauma. The mechanism is immune rather than infectious, so the ulcers cannot be passed on.
- 03
Nutritional deficiencies
Low iron, vitamin B12 or folate can present as new or worsening ulcers, particularly in adults who did not have them before. A blood test through your GP is worthwhile when ulcers have recently become frequent.
- 04
Medical conditions and medicines
Inflammatory bowel disease, coeliac disease, Behçet’s disease and some viral infections cause mouth ulcers, and drugs such as nicorandil and certain anti-inflammatories can too. Ulcers alongside gut symptoms, genital ulcers, eye inflammation or skin rashes need a medical rather than a dental opinion.
- 05
Oral cancer
Uncommon, but it is the reason a non-healing sore is never ignored. Early lesions can look like a harmless ulcer or a white or red patch, and are often painless. Smoking, heavy drinking and age raise the risk. Caught early, treatment is far simpler, which is why we examine the whole mouth at every check-up.
Before your appointment
What you can do today
- Rinse with warm salt water or a chlorhexidine mouthwash two or three times a day to keep the ulcer clean while it heals.
- A pharmacy gel or paste containing a local anaesthetic or a protective barrier can take the edge off eating.
- Switch to a toothpaste without sodium lauryl sulphate for a few weeks and see whether the frequency changes.
- Avoid the foods that sting until the ulcer has closed; sharp crisps, citrus and vinegar are the usual offenders.
- If a tooth or denture edge is catching, cover it with orthodontic wax until it can be smoothed.
- Note the date each ulcer appears so that you can tell us how long it has been present with confidence.
These are holding measures, not a substitute for an examination. Use any pain relief exactly as directed on the pack and check with a pharmacist if you take other medicines.
In the chair
How we treat it at Wimpole Street
Removing the cause
A sharp cusp or filling edge is polished smooth in minutes; a denture flange is eased; a broken tooth is rebuilt. Trauma ulcers should then heal within a fortnight.
About this treatmentPrescription rinses and pastes
For recurrent ulcers, a steroid mouthwash or paste used at the first tingle shortens each episode and reduces pain. Anaesthetic rinses help with eating during a bad crop.
About this treatmentDenture adjustment or reline
A denture that rubs repeatedly is relieved at the sore spot or relined so that it seats evenly, since a persistently rubbing denture can produce an overgrowth of tissue as well as ulcers.
About this treatmentReferral when it is needed
An ulcer or patch that has not healed at three weeks, or has features that concern us, is referred promptly to an oral medicine or maxillofacial clinic for assessment and, if required, a biopsy.
About this treatmentFees
Costs to expect
A consultation at Wimpole Street to assess an ulcer, including a full soft-tissue examination, is expected to be £95. Smoothing a sharp edge that is causing an ulcer is usually done in the same appointment and included in the fee; replacing a broken filling that is responsible is from £185.
Prescription mouthwashes and pastes are charged at the pharmacy. Denture adjustments are quoted at the visit, and a reline is priced from the denture fee schedule once we have assessed the fit. Referral for a suspicious lesion is made without charge to you beyond the assessment visit, and we write to your GP without delay.
Figures are indicative prices for Wimpole Street and are confirmed in a written plan once a dentist has examined you. Fees match our South Kensington and St Paul's clinics.
Don't wait if
When to see a dentist
- A sore or patch anywhere in your mouth has been present for three weeks or longer.
- An ulcer is getting bigger rather than smaller, or feels firm or raised.
- A red or white area has appeared and is not going away.
- You have ulcers that keep returning in the same place beside a tooth or denture.
- Ulcers have become frequent recently and you also feel tired or run down.
- You have ulcers together with gut symptoms, skin rashes or eye inflammation.
FAQ
Common questions
The common recurrent type is not; it is an immune reaction in the lining, not an infection, so kissing and sharing cutlery carry no risk. Cold sores on the lip are caused by a virus and are contagious, but they are blisters that crust over rather than open ulcers inside the mouth.
Stress and lack of sleep are among the most consistently reported triggers for recurrent aphthous ulcers, probably through their effect on the immune system. Hormonal shifts around menstruation have a similar effect for some women. Reducing the triggers you can control, and treating early with a prescribed paste, tends to lessen both frequency and severity.
Almost all ulcers are benign and heal within two weeks. The features we look for are a sore that has persisted beyond three weeks, one that is painless or firm, a patch that is red, white or speckled, or unexplained numbness or a lump. If any of those apply, have it checked promptly; the point is not alarm but early assessment, which makes treatment far simpler if it is ever needed.
Yes. Dentists can prescribe steroid mouthwashes and pastes, anaesthetic and antiseptic rinses, and can advise on toothpaste changes. If we suspect a deficiency or an underlying medical condition, we will ask your GP to arrange blood tests and, where appropriate, refer you to oral medicine.
Marylebone, W1
Wimpole Street opens 1 October 2026
Leave your details and we will be in touch when the Marylebone diary opens. If the problem cannot wait, the same clinicians are already seeing patients in South Kensington and at St Paul's.
Related conditions
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
