Small, painful sores inside the mouth, on the cheek, inner lip, tongue or gums, are very common. Most are superficial sores called canker sores (aphthous ulcers) that heal on their own. However, some sores may point to a different cause.
What is a canker sore?
A canker sore is a round or oval, painful sore with a white-yellowish centre and a red border. It usually heals without a trace within 7–14 days. It is not contagious.
Common causes of mouth sores
- Mechanical irritation: Biting the cheek, hard brushing, a sharp tooth edge, a broken filling
- Orthodontic appliances: Brackets, wires or the edge of a new aligner can rub against the cheek and tongue
- Stress and tiredness
- Some foods: Acidic or spicy foods can be a trigger for some people
- Vitamin and mineral deficiencies: Low B12, folic acid and iron may be linked to recurring sores
- Hormonal changes
- Some systemic conditions: Recurring and numerous sores can sometimes be a sign of a general illness
Sores during orthodontic treatment
People with new braces often get irritation on the inside of the cheeks and lips in the first weeks; orthodontic wax helps protect these areas. If you wear clear aligners and an aligner edge is digging into your tongue or gums, do not try to cut or file the aligner yourself. We explain what to do on our clear aligner problems and solutions page.
To soothe a canker sore
- Avoid acidic, spicy and hard foods that irritate the sore for a few days.
- Use a soft toothbrush.
- You can rinse your mouth with warm salt water.
- Ask your pharmacist or doctor about gels and mouthwashes from the pharmacy that cover or numb the sore.
When should you see a doctor?
- If a sore lasts more than two weeks
- If a sore does not hurt, feels hard or is growing
- If there are many sores or they come back often
- If you also have a fever, fatigue, joint pain or eye complaints
- If the pain is bad enough to stop you eating and drinking
Mouth sores that do not heal within two weeks must be assessed by a dentist or doctor.
Prevention
- Have sharp tooth edges and broken fillings fixed.
- Pay attention to managing stress and getting regular sleep.
- Eat a balanced diet; with recurring sores, ask your doctor about checking your blood values.
- Toothpastes without sodium lauryl sulphate have been reported to reduce how often sores occur in some people.
