Section 8. Mouth and Dental Disorders

Chapter 112. Mouth Sores

Topics: Introduction | Canker Sores | Oral Herpes Simplex | Other Mouth Sores

Canker Sores

Canker sores (aphthous ulcers) are small, painful sores inside the mouth.

Canker sores are very common. The cause is unknown, but stress seems to play a role--for example, a college student may get canker sores during final exam week. A canker sore appears as a round white spot with a red border. The sore almost always forms on soft, loose tissue on the inside of the lip or cheek; on the tongue, the floor of the mouth, or soft palate; or in the throat. Small canker sores (less than ½ inch in diameter) often appear in clusters of two or three; generally, they disappear by themselves within 10 days and do not leave scars. Larger canker sores are less common; they are irregularly shaped, can take many weeks to heal, and frequently leave scars. People with AIDS often have large canker sores that persist for weeks.

Many people who get canker sores get them repeatedly--often several times a year.

Symptoms and Diagnosis

The main symptom of a canker sore is pain--far more than would be expected from something so small. The pain, which lasts 4 to 7 days, worsens if the tongue or food rubs the sore or if hot or spicy foods are eaten. Severe canker sores can cause fever, swollen lymph nodes in the neck, and a generally run-down feeling.

A doctor or dentist identifies a canker sore by its appearance and the pain it causes.

Treatment

Treatment consists of relieving the pain until the sore heals by itself. An anesthetic such as dyclonine or lidocaine may be used as a mouth rinse. However, because these mouth rinses numb the mouth and throat and thus may make swallowing difficult, children using them should be watched to ensure that they do not choke on their food. Lidocaine in a thicker preparation (viscous lidocaine) can also be swabbed directly on the canker sore. A protective coating gel of carboxymethylcellulose, often combined with a corticosteroid (such as triamcinolone or betamethasone), may be applied to protect the sore and temporarily relieve pain by reducing inflammation.

If a person has many canker sores, a doctor or dentist may prescribe a tetracycline mouth rinse. People who have repeated outbreaks of canker sores may start using the tetracycline mouth rinse as soon as they feel a sore developing. Another treatment option, applying silver nitrate directly to the canker sore, destroys the nerves under the sore to relieve pain.

Finally, for the most severe cases, a corticosteroid may be prescribed as a dexamethasone mouth rinse or, rarely, as prednisone tablets taken by mouth. However, before prescribing a corticosteroid, a doctor ensures that the person does not also have oral herpes simplex infection, which can be further spread by corticosteroids. Corticosteroid rinses and tablets are absorbed into the body more than are corticosteroids given in gel form, so the side effects may be a concern (see Section 5, Chapter 67).