What Are Aphthous Ulcers?
Aphthous ulcers are the most common type of mouth ulcer. They present as small, round or oval sores, typically white or yellowish in colour with a surrounding red border. They form on the non-keratinised soft tissues of the mouth — areas such as the inner cheeks, inner lips, underside of the tongue, and the floor of the mouth.
Unlike cold sores, which are caused by the herpes simplex virus and typically appear on or around the lips, aphthous ulcers are not caused by a viral infection and are not contagious. They can occur as single sores or in small clusters, and while they can be uncomfortable — particularly when eating, drinking, or speaking — they are almost always benign.
Most aphthous ulcers are classified as minor and heal without scarring. Less commonly, major aphthous ulcers may develop, which are larger, deeper, and may take several weeks to resolve. Understanding the possible causes can help identify whether dental factors are contributing to their development.
Common Causes of Mouth Ulcers
Mouth ulcers can be triggered by a variety of factors. In many cases, the cause is straightforward — such as accidental trauma to the soft tissue. Dental irritation is a common local cause that can often be addressed through professional assessment.
Minor Trauma
Accidentally biting the inside of the cheek, lip, or tongue is one of the most common triggers. Trauma from sharp foods, vigorous tooth brushing, or dental procedures can also contribute.
Sharp or Rough Tooth Edges
A chipped, fractured, or worn tooth can create a sharp edge that repeatedly irritates the adjacent soft tissue, leading to ulcers that recur in the same location.
Ill-Fitting Restorations
Overhanging fillings, rough crown margins, or deteriorating restorations can cause ongoing friction against the cheek, lip, or tongue, provoking ulcer formation.
Orthodontic Appliances
Fixed braces, retainers, and other orthodontic devices can rub against the soft tissues of the mouth, particularly during the initial adjustment period or following wire changes.
Stress and Fatigue
Periods of emotional stress, anxiety, or physical fatigue are commonly associated with aphthous ulcer outbreaks, though the precise mechanism is not fully understood.
Nutritional Factors
Deficiencies in certain nutrients — including iron, vitamin B12, and folate — have been associated with an increased tendency to develop mouth ulcers in some individuals.
When a Dental Cause Should Be Considered
When mouth ulcers recur in the same location or persist longer than expected, a local dental cause should be considered. Sharp or rough surfaces within the mouth can create a point of repeated irritation that prevents healing or triggers new ulcers in the same area. Identifying and correcting the source may help reduce the frequency of recurrence.
Fractured or Sharp Tooth
A broken or chipped tooth can leave a rough or sharp edge that catches on the cheek, lip, or tongue with each movement, causing repeated tissue damage and ulcer formation in the same area.
Overhanging Fillings
When a filling extends beyond the natural contour of the tooth, it can create a ledge that traps food and irritates the adjacent gum or cheek tissue, contributing to chronic ulceration.
Broken Restorations
A crown, bridge, or filling that has fractured or partially dislodged may expose rough surfaces or sharp margins that repeatedly traumatise the surrounding soft tissue.
Braces or Orthodontic Appliances
Brackets, wires, and removable aligners can create pressure points or friction against the inner cheeks, lips, and tongue, particularly after adjustments or when components shift.
Symptoms That Require Professional Review
While most mouth ulcers are harmless and self-limiting, certain patterns warrant professional assessment. The following signs suggest that a dental or medical review may be beneficial:
Ulcers Lasting More Than Two Weeks
Most aphthous ulcers heal within one to two weeks. An ulcer that persists beyond this timeframe should be assessed to exclude other causes and ensure appropriate management.
Frequent Recurrence
If ulcers recur regularly — particularly in the same location — this may suggest a local dental cause such as a sharp edge or rough restoration that could be addressed.
Increasing Size
An ulcer that grows rather than gradually healing warrants professional review. While most enlarging ulcers remain benign, assessment helps confirm the nature of the lesion.
Associated Swelling or Pain
Significant swelling, persistent pain, or difficulty eating or speaking alongside an ulcer may indicate a secondary issue that benefits from professional evaluation.
These signs do not necessarily indicate a serious condition, but professional assessment helps confirm the nature of the ulcer and ensures appropriate care is provided.
Professional Dental Assessment
A dental assessment for recurrent or persistent mouth ulcers involves a careful examination of the teeth, gums, restorations, and soft tissues of the mouth. Your dentist will look for potential sources of irritation — such as sharp tooth edges, overhanging fillings, or rough restoration margins — that may be contributing to ulcer formation.
The overall condition of the oral tissues will also be evaluated, including the health of the gums and the standard of oral hygiene. In some cases, your dentist may enquire about your general health, diet, and any medications you are taking, as these factors can occasionally be relevant.
If no dental cause is identified and the ulcer persists or raises any clinical concern, your dentist may recommend referral to a medical practitioner or specialist for further investigation. This collaborative approach ensures that all potential contributing factors are considered.
Professional Management Options
Management of mouth ulcers depends on the identified cause. Where dental irritation is contributing, addressing the source aims to remove local contributing factors and may help reduce the frequency of recurrence. Your dentist will recommend the most appropriate approach:
Smoothing Sharp Tooth Edges
If a sharp or rough tooth surface is identified as the source of irritation, your dentist can carefully smooth the edge to remove the point of contact. This straightforward procedure may help reduce the recurrence of ulcers in the affected area.
Adjusting Restorations
Overhanging or rough fillings, crowns, or other restorations can be adjusted, reshaped, or replaced to improve the contour and reduce friction against the soft tissue.
Orthodontic Appliance Review
If braces or other appliances are contributing to ulcer formation, your orthodontist can review the fit, adjust components, and advise on protective measures such as orthodontic wax.
Monitoring Healing
In cases where no specific dental cause is identified, your dentist may recommend monitoring the ulcer over a defined period. A follow-up appointment can be arranged to confirm healing.
Referral for Further Investigation
If ulcers persist despite addressing dental factors, or if there is any clinical concern about the nature of the lesion, referral to a specialist or medical practitioner may be recommended for further evaluation.
Professional Assessment for Recurrent Mouth Ulcers
Persistent or recurring mouth ulcers should be evaluated to identify whether dental irritation, sharp tooth surfaces, or other local factors are contributing. A professional examination can confirm the cause and guide appropriate management to help reduce irritation and support healing.
Our dental team provides general dentistry assessments and restorative care to identify and address dental sources of irritation. Where edge smoothing or repair is needed, composite bonding may be used to restore a smooth, comfortable tooth surface. If you are experiencing significant pain or discomfort, our emergency dental assessment service is also available.
Assessment for mouth ulcers and potential dental irritation is available at our London clinics. You can attend our South Kensington dental clinic or our City of London clinic near St Paul's for a professional dental review.
Can Mouth Ulcers Be Prevented?
While it is not always possible to prevent mouth ulcers entirely — particularly those triggered by stress or other systemic factors — certain measures can help reduce the frequency and severity of outbreaks.
- Take care when eating hard, sharp, or crunchy foods that may scratch or injure the inside of the mouth
- Use a soft-bristled toothbrush and gentle brushing technique to minimise trauma to the gums and soft tissues
- Have any sharp, rough, or broken tooth edges assessed by your dentist so they can be smoothed or repaired
- If you wear braces or a dental appliance, use orthodontic wax on any areas causing friction and report persistent irritation to your orthodontist
- Attend regular dental check-ups so that deteriorating fillings, rough restorations, or other potential sources of irritation can be identified early
- Consider lifestyle measures to manage stress, as periods of heightened stress are commonly associated with ulcer outbreaks
