When Should You See a Dentist?

Canker sores are very common and they are not contagious. These irritating little sores will normally go away on their own in about one to two weeks.
Even though treatment is usually not necessary for a canker sore, you should see a dentist if one or more of the following occur:
The canker sores persist more than two weeks
The canker sore is unusually large (more than one centimeter in diameter)
A persistent high fever accompanies the sores.
The pain from the canker sore is unbearable
You experience difficulty drinking with the sores
A dentist can easily diagnose and recognize the type of sore in your mouth based on where it is located and how it looks.

What is a Canker Sore?

Many people often wonder exactly what are canker sores?
Canker sores, also known as Aphthous Ulcers, are small lesions that occur inside the mouth, and are not contagious.


One to two days before appearing, a burning or tingling sensation may be present in the area of the mouth where the lesion is developing. Rarely, a fever might present itself when developing a canker sore.
Canker sores appear inside the mouth as round or oval sores typically with a red border and yellow or white center. Canker sores typically develop:
On the top surface of the tongue and the tip of the tongue
Underneath the tongue, on the floor of the mouth
The inside of the cheek and lip
On the gum tissue
Canker sores do not develop on the external surfaces of the lips and are not to be confused with cold sores.

Types of Canker Sores

Canker sores may be classified as:
Minor – Although painful, minor canker sores are often fully healed within two weeks after onset. The size of a minor canker sore varies, but typically stays under 1/3 inch to 1/2 inch.
Major – Canker sores that appear larger that 1/3 inch to 1/2 inch, last longer than two weeks, and appear to have irregular margins — oddly shaped — may be classified as major. Rarely, this type of canker sore may leave behind a scar. Common in immunosuppressed patients.
Herpetiform Canker Sores – A cluster of several tiny lesions that appear to form one larger sore. This type of canker sore may last from one week to one month.

Canker sores may become painful, especially when eating, drinking, and talking.
The cause of canker sore development varies from person to person, with an exact cause unknown.
Treatments for canker sores also vary depending on the suspected cause.
It is recommended that you seek treatment from your dentist if you have recurrent canker sores and/or canker sores that do not heal after 14 days.
Also Known As:
Aphthous Ulcers
Common Misspellings:
Kanker sores

What Causes Canker Sores?

Canker sores are very painful sores found inside the mouth that often appear out of nowhere, leaving suffers asking: What causes canker sores?

Answer: We know what canker sores are, but the exact cause is still unknown. Women statistically suffer from canker sores more often than men. Canker sores are typically seen in people between the ages of 10 and 40, although they have been known to show up at any age.

There is reason to believe that certain types of bacteria and/or viruses are responsible for the painful mouth sores. Canker sores are not contagious and are not related to the herpes simplex virus, also known as cold sores.

Canker sores are caused by:

  • Injuries to the mouth, as seen frequently by contact sports players. Accidentally biting the inside of the cheek or lip may also result in a canker sore
  • Temperature hot food or drink may cause a canker sore in the area of the mouth that was essentially burnt by the offending substance
  • Spicy and/or acidic foods often produce a canker sore as a response to the irritation these spices and acids create in the mouth
  • The use of chewing (smokeless) tobacco will often cause a canker sore to develop in the area of the mouth where the tobacco is held, due to the irritating chemicals found in the addictive product
  • Poor-fitting, complete or partial dentures may cause canker sores in the area of the mouth where the denture may rubbing on the tissue. The development of a canker sore is often one of the first signs that indicate the need for a denture reline or adjustment by your dentist or denturist
  • Orthodontic brackets, bands, and various other orthodontic attachments will often cause canker sores to develop in area of the mouth where there is constant friction on the oral tissues. This is common when orthodontic treatment first begins and may occur after each subsequent adjustments, throughout each stage of treatment
  • Allergies to metals such as nickel may become evident in the mouth of a person wearing orthodontic devices necessary to move the teeth. Canker sores may begin to appear adjacent to the metal attachments. This is often referred to as contact dermatitis.
  • Broken teeth are often sharp and may rub on the oral tissues to produce painful canker sores. Broken restorations may also cause a similar effect on the oral tissues
  • Emotional stress has been identified as a possible trigger that may cause the development of canker sores
  • Bacteria responsible for peptic ulcers known as Helicobacter pylori, has been linked to canker sore occurrence
  • Vitamin deficiencies, specifically vitamin B12, foliate (folic acid), and iron, may trigger canker sore development
  • Hormonal changes, notably during menstruation, pregnancy, and menopause, have been linked to canker sores
  • Canker sores often run in families. Genetics may be a factor for many canker sore sufferers
  • Allergic reactions and sensitivities to certain foods may cause a canker sore to develop. Allergic reaction to certain types of bacteria found in the mouth may also result in this type of mouth ulcer
  • Celiac disease sufferers may experience canker sores. Gluten may be associated with the development of canker sores in those with celiac disease
  • Information associated with inflammatory bowel disease (IBD) often will list canker sores as a complication associated with Crohn’s disease and ulcerative colitis
  • Mouth sores are a common occurrence observed in immunosuppressed patients, such as those with HIV/AIDS
  • Behcet’s Disease, a rare autoimmune disease that damages the body’s blood vessels notes mouth sores, more specifically canker sores, as a one of the four most common symptoms of the disease
  • Sodium lauryl sulfate is a common ingredient in toothpaste and had been associated with the development of canker sores

Treatment is generally not necessary for most canker sores as they tend to heal quickly on their own. If canker sores persist for longer than 2 weeks, see the dentist.

See your dentist immediately if canker sores:

  • Become unusually larger than normal
  • Are extremely painful, interfering with eating, drinking, and talking
  • Begin to appear more frequently than normal
  • Do not heal after 14 days
  • Are accompanied by a high fever
  • Appear to become infected