Tooth bleaching, also known as tooth whitening, 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 decidious teeth are generally whiter than the adult teeth that follow. As a person ages the adult teeth often increase in value — that is to say, they 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, food and tobacco.
A typical course of bleaching can produce dramatic improvements in the cosmetic appearance of most stained teeth. Recently, efforts have been made to accelerate the bleaching process by the use of light. Studies have shown varying results as to the efficacy of light-activated bleaching.