Canker sores, also called aphthous ulcers, are small, painful, round sores with a white or yellow centre and red border that form inside the mouth. They are commonly triggered by minor injury such as a cheek bite or a sharp tooth edge, stress, hormonal changes, certain foods, or toothpastes containing sodium lauryl sulfate. Canker sores are very common, not contagious, and usually heal on their own within 7 to 14 days, but sores lasting longer than two weeks should be examined, which is part of every check-up with the hygiene services team.
Even a tiny canker sore can make eating, talking, and brushing uncomfortable. Many people wonder why they keep getting them, whether they are a sign of something serious, and what actually helps them heal faster. Understanding the triggers is the first step toward fewer flare-ups.
Your dental team can spot patterns in recurring sores and look for causes that are easy to fix. The clinic’s full range of dental services means problems like rough fillings or broken teeth can be repaired quickly.
A chipped tooth or a worn restoration can rub the cheek or tongue repeatedly, creating sores in the same spot. Smoothing the edge or restoring the tooth with a dental crown often stops the problem.
If you are new to the practice, you can learn about the Bolton dental team, or book an appointment if a sore is not healing.
What Is a Canker Sore?
A canker sore is a shallow ulcer in the soft tissue of the mouth, such as the inside of the cheeks and lips, under the tongue, on the soft palate, or at the base of the gums. Unlike cold sores, canker sores are not caused by a virus and are not contagious.
Types of Canker Sores
- Minor: the most common type. Small, oval, and heal within one to two weeks without scarring.
- Major: larger and deeper, can take several weeks to heal and may leave scars.
- Herpetiform: clusters of many tiny sores that may merge. Despite the name, they are not caused by herpes.
Canker Sores vs Cold Sores
| Feature | Canker Sore | Cold Sore |
|---|---|---|
| Location | Inside the mouth | Usually on or around the lips |
| Cause | Injury, stress, triggers, immune factors | Herpes simplex virus |
| Contagious? | No | Yes |
| Appearance | Round ulcer with white or yellow centre | Fluid-filled blisters that crust |
| Healing time | About 1 to 2 weeks | About 1 to 2 weeks |
Are Canker Sores Common, Temporary, or Serious?
- Common: many people get canker sores occasionally.
- Temporary: most heal within two weeks without treatment.
- Needs assessment: sores lasting longer than two weeks, very large sores, frequent recurrences, high fever, or difficulty eating and drinking.
What Causes Canker Sores?
Minor Mouth Injuries
Accidentally biting the cheek, brushing too hard, sharp tooth edges, broken fillings, or poorly fitting dental appliances can damage the tissue and start a sore.
Stress and Lack of Sleep
Many people notice sores during busy, stressful periods.
Hormonal Changes
Some people get sores at certain points in their menstrual cycle.
Foods
Acidic or spicy foods such as citrus, tomatoes, pineapple, and hot peppers can trigger or irritate sores in sensitive people.
Toothpaste Ingredients
Sodium lauryl sulfate, a foaming agent in many toothpastes, is linked to more frequent sores in some people.
Nutritional Deficiencies
Low levels of vitamin B12, iron, folate, or zinc can contribute to recurring sores.
Medical Conditions
Celiac disease, inflammatory bowel disease, and some immune conditions can be associated with frequent mouth ulcers.
How to Heal Canker Sores Faster
- Rinse with warm salt water or a baking soda rinse several times a day.
- Apply an over-the-counter protective gel or paste to cover the sore.
- Use a numbing gel before meals if eating is painful, following the label directions.
- Avoid spicy, acidic, salty, and crunchy foods until healed.
- Switch to a soft toothbrush and brush gently around the sore.
- Try a toothpaste without sodium lauryl sulfate.
- Drink plenty of water and get enough rest.
Safety note: any mouth sore that does not heal within two weeks, bleeds easily, feels hard, or is accompanied by numbness or a lump should be examined promptly by a dentist. Persistent sores need professional assessment to rule out other conditions, including oral cancer.
Professional Treatment Options
- Smoothing sharp teeth or fillings: removes the source of repeated injury.
- Prescription rinses or gels: may reduce pain and inflammation.
- Adjusting appliances: relieves rubbing from retainers, dentures, or guards.
- Referral for blood tests: if deficiencies or medical conditions are suspected.
Foods to Choose and Avoid
| Gentle Choices | Avoid Until Healed |
|---|---|
| Yogurt, milk, smoothies (non-acidic) | Citrus fruits and juices |
| Oatmeal, mashed potatoes, eggs | Spicy foods and hot sauces |
| Soft pasta, soups (not too hot) | Chips, crusty bread, nuts |
| Bananas, melon | Tomatoes, pineapple, vinegar |
How to Prevent Canker Sores From Coming Back
- Use a soft-bristled toothbrush and gentle brushing technique.
- Consider a toothpaste free from sodium lauryl sulfate.
- Have sharp teeth, broken fillings, or rough appliances smoothed or repaired.
- Chew slowly to avoid biting your cheek or tongue.
- Keep a simple food diary to identify personal trigger foods.
- Manage stress through regular sleep, exercise, and relaxation.
- Eat a balanced diet rich in B vitamins, iron, folate, and zinc.
- Wear orthodontic wax over brackets that rub.
Small changes often lead to noticeably fewer sores over time.
Stages of a Canker Sore
| Stage | What You Notice | Typical Timing |
|---|---|---|
| Early | Tingling or burning in one spot | One to two days before the sore appears |
| Ulcer forms | Round sore with a white or yellow centre and red border | Days one to three |
| Most painful | Pain peaks, especially when eating | Days two to four |
| Healing | Pain eases, sore shrinks | Days five to ten |
| Resolved | Tissue looks normal again | Within about two weeks |
Canker Sores in Children
Children can get canker sores too, often after biting their cheek, a fall, or brushing too hard. Offer soft, cool foods, encourage gentle brushing, and avoid acidic juices until healing. Seek advice if your child has many sores at once, a high fever, refuses to drink, or the sores last longer than two weeks, as other conditions such as viral infections can look similar.
Myths About Canker Sores
- Myth: “Canker sores are contagious.” Fact: they are not caused by a virus and cannot spread to others.
- Myth: “They mean poor hygiene.” Fact: canker sores occur even in people with excellent oral care.
- Myth: “Putting salt directly on the sore heals it.” Fact: this can be very painful. A diluted salt water rinse is gentler and effective.
- Myth: “Dental visits are not needed for mouth sores.” Fact: dentists examine all soft tissues and can identify sores that need further care.
Real Patient Scenarios
The Sharp Filling
A patient kept getting sores on the same side of the tongue. A rough edge on an old filling was smoothed and later replaced, and the sores stopped.
The Stressful Season
Another patient noticed sores during exam periods. Switching to an SLS-free toothpaste and managing stress reduced flare-ups.
The Persistent Ulcer
A third patient had a sore that had not healed after three weeks. Prompt assessment and referral provided answers and appropriate care.
When a Mouth Sore Is Not a Canker Sore
Several other conditions can cause sores or patches in the mouth, and some need different treatment:
- Cold sores: blisters caused by the herpes simplex virus, usually on the lips.
- Oral thrush: white patches that can be wiped away, caused by yeast, common in denture wearers or after antibiotics.
- Denture sores: pressure areas from a poorly fitting denture.
- Burns: from very hot food or drinks, usually on the palate.
- Lichen planus: lacy white patches or sore areas linked to the immune system.
- Persistent ulcers or patches: red or white areas that do not heal need professional evaluation.
A dentist can examine the sore, ask about your history, and recommend the right next step, whether that is simple care at home, an adjustment, or referral to a specialist.
Oral Cancer Screening During Checkups
During routine visits, your dentist checks your lips, cheeks, tongue, gums, palate, and throat for any unusual changes. Early detection of persistent sores or patches makes a significant difference to outcomes. Tell your dentist if you smoke, drink alcohol frequently, or have noticed any changes in your mouth.
Common Mistakes to Avoid
- Poking or picking at the sore.
- Using strong alcohol-based mouthwash, which can sting and irritate.
- Ignoring sores that keep returning in the same spot.
- Waiting more than two weeks before having a non-healing sore checked.
Easing Pain While You Eat
Eating with a canker sore is often the hardest part. Let hot foods cool before eating, cut food into small pieces, chew on the opposite side, and use a straw for cold drinks so they bypass the sore. Applying a protective paste or numbing gel shortly before meals, as directed, can make eating noticeably more comfortable. Rinse with water after meals to remove food particles that could irritate the sore.
Why Licensed Professionals Matter
Most mouth sores are harmless, but a trained eye is needed to tell them apart from conditions that need further care. In Ontario, dentists must be registered with the Royal College of Dental Surgeons of Ontario (RCDSO), which ensures safe, ethical standards. Routine checkups include a careful look at all soft tissues in the mouth.
Caring for Your Whole Mouth in Bolton
Bolton Park Dentistry is a trusted family Dental Clinic in Bolton offering comprehensive care in a calm, welcoming environment designed to ease anxiety. The clinic welcomes new patients, provides same-day appointments when available for urgent needs, and offers sedation options for patients with dental anxiety, making it a dependable Emergency Dental Clinic in Bolton as well as a place for routine care.
Services include hygiene and preventive care, amalgam-free and bonded fillings, crowns, bridges, extractions, root canal therapy, implant restoration, porcelain veneers, teeth whitening, athletic sports guards, TMJ/TMD therapy, non-surgical gum therapy, and free consultations for implants and braces. Families across Bolton and surrounding communities choose it as their Family Dentist in Bolton, and many visit for a Cosmetic Dentist in Bolton or the Best Teeth Whitening Bolton has to offer. Call 647-496-2336, email reception@boltonparkdentistry.com, visit boltonparkdentistry.com, or stop by 14 Parr Blvd Unit 5, Bolton, Ontario L7E 4H1. Many patients describe it as the Best Dental Clinic in Bolton, a friendly Dental Office in Bolton, and home to a Top Dentist in Bolton, and every Dentist in Bolton on the team is registered with the RCDSO.
Frequently Asked Questions
How long do canker sores last?
Minor canker sores usually heal within 7 to 14 days. Larger sores can take several weeks.
Are canker sores contagious?
No. They cannot be passed to other people through kissing or sharing utensils.
Why do I keep getting canker sores?
Common reasons include mouth injuries, stress, certain foods, toothpaste ingredients, and nutritional or medical factors.
When should I see a dentist about a mouth sore?
If it lasts longer than two weeks, is very large, keeps returning, or comes with fever or difficulty eating.
Can braces or appliances cause canker sores?
Yes. Rubbing from brackets, wires, or appliances can cause sores. Orthodontic wax or an adjustment helps.
Conclusion
Canker sores are common, non-contagious mouth ulcers triggered by injury, stress, foods, and other factors.
Most heal within two weeks with gentle care and simple remedies.
Sores that last longer or keep returning should be examined by your dental team.