[ashke]

So it's like owning a set of china... for your teeth?

The practice of teeth whitening began in the Middle Ages. Teeth would be filed down by a barber-surgeon and then soaked in a concentrated solution of nitric acid. Although the procedure did work to make teeth white, it also destroyed the tooth enamel and led to major tooth decay.

Today’s dentists use whitening techniques that involve gels, strips and pastes to make teeth their whitest. Tooth discoloration is caused by colored molecules such as tannins and polyphenols, found in red wine, coffee and tea, which become absorbed by the tooth enamel’s surface.

Cigarettes, blueberries and other foods that contain dark pigments can also discolor your tooth enamel. Some of the staining can be removed by brushing, but over time the compounds can seep into the enamel.

Other causes of tooth discoloration are aging and certain antibiotics in childhood. Teeth gradually turn more yellow as we age, and the antibiotic tetracycline can turn children’s teeth gray if taken during early childhood.

Toothpastes depend on abrasive substances including silica, aluminum oxide, calcium phosphates and calcium carbonate to remove stains.

However, to remove stains that are below the surface, a whitening agent containing hydrogen peroxide will likely be needed. The use of peroxide as a teeth whitener was discovered in the early 1970s when scientists using the substance as an oral antiseptic found that it also brightened teeth.

Hydrogen peroxide forms radical intermediates--extremely unstable and destructive molecules--that break down into water and oxygen. The radical intermediates react with the pigments that stain teeth and destroy much of the double-bond network that gives the pigments their color, according to researchers.

If whiteners don’t work on your teeth, as often happens, tooth veneers are another option. Veneers are thin coverings made of porcelain that are bonded to your teeth. Though they won’t stain, they are not as long lasting as real teeth.

-- from http://www.mercola.com/2003/mar/12/teeth_whiteners.htm