The Work of Toothpaste
Toothpaste has two functions—cosmetic and hygienic. It improves one's appearance by removing stains from teeth. The hygienic function of toothpaste helps prevent tooth decay by removing food particles and plaque from teeth and delivering other decay preventing substances such as fluoride. Plaque is a sticky substance that forms on teeth. It is made up primarily of common oral bacteria and products of those bacteria. Plaque also contains some saliva and components that dissolve from food onto the teeth. If plaque is not removed, the bacteria digest the sugar in foods and beverages to form a family of acids that slowly erode a tooth's enamel (hard outer coating).
A major purpose of brushing is to prevent plaque from turning into tartar. Tartar, also called calculus, is a hard mineral substance that is chemically similar to tooth enamel. It forms along the gum line when calcium salts in saliva collect on the teeth along with dead bacteria in plaque. Tartar above the gum line does not hurt the teeth, but because it quickly absorbs stains and turns brown, it is a cosmetic problem. Tartar below the gum line can cause gingivitis (inflamed gums), which may lead to periodontitis (loss of bone that supports teeth) and eventually loss of teeth.
All toothpastes are mixtures of an abrasive, a detergent, a thickener, a humectant (moisturizer), water, and other ingredients such as flavoring agents, coloring, and sweeteners. Most toothpastes also contain a fluoride compound that helps prevent tooth decay. Some toothpastes contain compounds that fight tartar formation.
Other toothpastes contain desensitizing agents to reduce the sensitivity of tooth surfaces below the gum line. This sensitivity can develop if the gums recede or are worn away by brushing too hard with an extra firm toothbrush. Some toothpastes also contain a bleaching agent that may make teeth look whiter.