Dental bleaching, also known as tooth whitening, is a common procedure in general dentistry. According to the FDA, whitening restores natural tooth color and bleaching whitens beyond the natural color.

There are many methods available, such as brushing, bleaching strips, bleaching pen, bleaching gel, and laser bleaching. Teeth whitening has become the most requested procedure in cosmetic dentistry today. 

Bleaching methods use carbamide peroxide which reacts with water to form hydrogen peroxide. Carbamide peroxide has about a third of the strength of hydrogen peroxide. This means that a 15% solution of carbamide peroxide is the rough equivalent of a 5% solution of hydrogen peroxide. The peroxide oxidizing agent penetrates the porosities in the rod-like crystal structure of enamel and breaks down stain deposits in the dentin. Power bleaching uses light to accelerate the process of bleaching in a dental office. Another bleaching agent is 6-phthalimido peroxy hexanoic acid (PAP).

Tooth bleaching is not a modern invention. Ancient Romans, for example, used urine and goat milk in an attempt to make and keep their teeth whiter.

At-home

Commercial whitening products intended for home use include gels, chewing gums, rinses, toothpastes, among others. The ADA has published a list of accepted over-the-counter whitening products to help people choose appropriate whitening products. Accepted products have not necessarily been independently tested for efficacy.

Agents

Various chemical and physical agents can be used to whiten teeth. Toothpaste typically has small particles of silica, aluminum oxide, calcium carbonate, or calcium phosphate to grind off stains formed by colored molecules that have absorbed onto the teeth from food. Unlike bleaches, whitening toothpaste does not alter the intrinsic color of teeth.

Bleaching solutions contain peroxide, which bleaches the tooth enamel to change its color. Off-the-shelf products typically rely on a carbamide peroxide solution varying in concentration from 10% to 44%. Bleaching solutions may be applied directly to the teeth, embedded in a plastic strip that is placed on the teeth or use a gel held in place by a mouthguard.

Peroxide based over-the-counter bleaching products have the potential to generate free radicals. Free radicals are known to be capable of reacting with proteins, lipids and nucleic acids, causing cellular damage; because of the potential of hydrogen peroxide to interact with DNA, concerns with carcinogenicity of hydrogen peroxide have been raised, although these concerns so far have not been substantiated through research.