The types of mouth ulcers are diverse, with a multitude of associated causes including: physical abrasion, acidic fruit, infection, other medical conditions, medications, and cancerous and nonspecific processes. Once formed, the ulcer may be maintained by inflammation and/or secondary infection.
The most common cause of ulcers is trauma to the mouth. A sharp edge of a tooth, accidental biting, sharp, abrasive, or excessively salty food, hot drinks, poorly fitting dentures, dental braces or trauma from a toothbrush may injure the mucosal lining of the mouth resulting in an ulcer. These ulcers usually heal at a moderate speed if the source of the injury is removed (for example, if poorly fitting dentures are removed or replaced).
Repeat episodes of mouth ulcers can be indicative of an immunodeficiency, signaling low levels of immunoglobulin in the oral mucous membranes.