Cavities are holes, or structural damage, in the teeth.

See also: Early childhood caries

Tooth decay is one of the most common of all disorders, second only to the common cold. It usually occurs in children and young adults but can affect any person. It is a common cause of tooth loss in younger people.

Bacteria are normally present in the mouth. The bacteria convert all foods -- especially sugar and starch -- into acids. Bacteria, acid, food debris, and saliva combine in the mouth to form a sticky substance called plaque that adheres to the teeth. It is most prominent on the back molars, just above the gum line on all teeth, and at the edges of fillings. Plaque that is not removed from the teeth mineralizes into tartar. Plaque and tartar irritate the gums, resulting in gingivitis and ultimately periodontitis.

Plaque begins to build up on teeth within 20 minutes after eating (the time when most bacterial activity occurs). If this plaque is not removed thoroughly and routinely, tooth decay will not only begin, but flourish.

The acids in plaque dissolve the enamel surface of the tooth and create holes in the tooth (cavities). Cavities are usually painless until they grow very large and affect nerves or cause a tooth fracture. If left untreated, a tooth abscess can develop. Untreated tooth decay also destroys the internal structures of the tooth (pulp) and ultimately causes the loss of the tooth.

Carbohydrates (sugars and starches) increase the risk of tooth decay. Sticky foods are more harmful than nonsticky foods because they remain on the surface of the teeth. Frequent snacking increases the time that acids are in contact with the surface of the tooth.