Patient-friendly definition from the DentistsDirectory.org dental glossary.
Gum recession occurs when the gingival margin — the edge of the gum tissue where it meets the tooth — gradually migrates downward (on lower teeth) or upward (on upper teeth), exposing the root surface beneath. Once gum tissue has receded, it does not grow back on its own. The exposed root surface is more vulnerable to both sensitivity and decay than enamel-covered tooth structure, and significant recession can eventually compromise the stability of the tooth.
Recession has several causes that can occur alone or in combination. Aggressive tooth brushing — scrubbing with too much force or using a stiff-bristled brush — is one of the most common causes, gradually wearing away the delicate gum margin. Gum disease (periodontitis) destroys the connective tissue and bone that support the gum, causing it to recede as part of the disease process. Grinding and clenching (bruxism) places lateral forces on the teeth that can contribute to gum loss. Thin gum tissue (thin biotype) is more susceptible to recession than thicker tissue, which is partly genetically determined. Orthodontic tooth movement outside the bone envelope can also cause recession in some cases.
Mild recession with no sensitivity or function concerns may only require monitoring and addressing the cause (such as brushing technique correction). More significant recession, especially where the root surface is sensitive, aesthetically noticeable, or at risk of further progression, can be treated with a gum graft — a surgical procedure performed by a periodontist in which donor gum tissue (from the patient's own palate or a tissue bank) is placed to cover the exposed root and rebuild the gum margin. Results are highly predictable and can both resolve sensitivity and stop further recession.