Tooth whitening, also known as tooth bleaching, is a common procedure in general dentistry but most especially in the field of cosmetic dentistry. Many people consider white teeth to be an attractive feature of a smile. A child's deciduous teeth are generally whiter than the adult teeth that follow. As a person ages the adult teeth often become darker. This darkening is due to changes in the mineral structure of the tooth, as the enamel becomes less porous. Teeth can also become stained by bacterial pigments, foodstuffs and tobacco.
As white teeth are subconsciously associated with youth, they have become desirable. The procedure to bleach teeth uses oxidising agents such as hydrogen peroxide or carbamide peroxide to lighten the shade of the tooth. The oxidising agent penetrates the porosities in the rod-like crystal structure of enamel and oxidises interprismatic stain deposits; over a period of time, the dentine layer, lying underneath the enamel, is also bleached. Tooth bleaching will generally last from 5 to 7 years, with variations from factors such as cigarette smoking, and tea and coffee consumption.
In most cases, the natural colour of teeth is within a range of light greyish-yellow shades. Teeth naturally darken with age and their appearance can be affected by the accumulation of surface stains acquired from the use of tobacco products and the consumption of certain foods or drinks.
In addition, the perception of the colour of teeth is severely affected by skin tone and make-up. Independent of the real colour of their teeth, people with darker skin or who use dark makeup will look like they have brighter teeth.
Although teeth are not naturally meant to be completely white, people want a brighter smile. Responding to this desire, a wide range of "whitening" options has become available to consumers. These products fall into two main categories: surface whiteners and bleaches.
It should be noted that claims related to tooth whitening are seen as cosmetic in nature. These claims must be accurate, so as not to mislead the public. However, the regulator tolerates some puffery or exaggeration. As a consequence, the results of whitening treatment may not be as convincing as consumers originally expected.