Cause and treatment. Dr. Crabbe gave you an excellent answer. Although the cause is still unknown, we find they often occur with patients under stress where the area more easily ulcerates even with minimal irritation such as from a toothbrush, hard food, etc. There are numerous otc and prescription medications that speed the recovery slightly or alleviate the pain by forming a temporary covering.
Aphthous ulcers. Aphthous ulcers or canker sores are painful ulcerations of the lips, gums, tongue, cheek linings. They can range from pinpoints to large ulcers. They can occur rarely or more than once a month and can take weeks to resolve. The cause of these are unknown but are not infectious. There is no clear predictable treatment that works and other ulcer types like herpes are often confused with them.