What signs and symptoms distinguish canker sores from other types of mouth ulcers?

Dentists usually distinguish canker sores (recurrent minor aphthous ulcers) from other mouth ulcers by way of taking a history from their patient, discussing their symptoms and by way of visual inspection. Typically there is no medical testing (i.e., biopsy or culturing) that is used to diagnose canker sores.

The hallmark characteristics of canker sores are their appearance, location, and the fact that they are recurrent. Additionally, the tissues surrounding a canker sore lesion will appear healthy and the patient will have no distinguishing systemic features (such as a fever or malaise).

Where do canker sores form?

Canker sores only form on the "loose" tissues of the mouth (those areas where the skin is not tightly bound to the underlying bone). These types of tissues include the skin covering the inside of the lips and cheeks, the floor of the mouth, the underside of the tongue, the soft palate, and the tonsillar areas. Dentists refer to the skin in these areas as the "nonkeratinized" tissues of the mouth.

What do canker sore mouth ulcers look like?

A canker sore's earliest stage will be characterized by the formation of a reddish area on the skin in one of the locations described above. Possibly this area will be slightly elevated and it will often produce a tingling sensation. This initial lesion will subsequently degenerate into an ulcer taking the following classic form:

A shallow individual ulcer that is round or oval in shape. The ulcer will usually be no more than a 1/4 inch in diameter. The center of the ulcer will be covered with a loosely attached white or grayish membrane. The edges of the ulcer will be regular (not jagged) and surrounded by a reddish halo. The tissue adjacent to the canker sore will be healthy in appearance. Canker sores usually are painful. It is common that the presence of a canker sore will interfere with eating or will cause a person to want to limit their oral movements.

Other characteristics used to diagnose aphthous ulcers.

• Canker sores can usually be expected to heal within 4 to 14 days. Usually this healing is uneventful and with no residual scarring.
• Once a person has initially experienced an outbreak of canker sores the probability of recurrence is high, although the rate of recurrence is quite variable. A rate of one outbreak every 1 to 3 months would be considered typical (encompassing 50% of those who get canker sores). 30% of people who suffer from outbreaks of these lesions deal with their presence on a monthly basis.
• A person's first canker sores typically appear between the ages of 10 and 20 years and then decrease in frequency and severity as the person ages.
• Some studies have suggested that women are more likely to experience canker sores than men (but not all studies have confirmed this fact).
• It's been estimated that roughly 20% of the general population experiences canker sores.
• There is no evidence to suggest that canker sores are contagious.
• The potential to experience canker sores appears to be unrelated to race. The occurrence of these lesions does seem to be more common in people who live in North America as opposed to those who live on other continents.

Canker sore variations.

• Outbreaks of multiple canker sores can and do occur (in contrast to the classic single ulcer form). Usually the total number of canker sores that will form at one time will be six or fewer. If multiple canker sores do develop they tend to be widely distributed throughout the person's mouth (as opposed to being clustered together).
• If two canker sores exist in close proximity to each other they can coalesce into a single larger and irregularly shaped mouth ulcer (as opposed to the classic round or oval shaped lesion).
• The number of outbreaks of canker sores a person experiences can vary greatly. Most persons will have only a few episodes a year while, at the other extreme, others will have nearly continuous outbreaks and will never be free of mouth ulcers for an extended period of time.
• Canker sores are smallish shallow mouth ulcers. There is another form of aphthous ulcer, termed "major aphthae," that is characterized by a large deep ulceration. The healing of this type of aphthous ulcer will often be prolonged and can result in scarring.