Your teeth are made up of an inner dentin layer and a hard outer enamel layer, which protects the teeth. When you put stuff in your mouth -- food, cigarette smoke, coffee, etc. -- another layer gradually forms on top of the enamel layer. Basically, the foreign material accumulates to form a pellicle film over the enamel layer and stains the teeth.

A dentist can clean away this film, through aggressive scaling and chemical treatments. Even brushing your teeth can knock out some of it -- brushing with the abrasive toothpaste cleans the tooth in the same sort of way scrubbing with an abrasive pad cleans a dish. "Whitening toothpastes" are designed to work even harder on this layer. The problem is, as this pellicle layer sits on your teeth for years and years, the foreign material gets into the enamel. Simply put, enamel is porous, which means staining agents can work their way down into the tooth, where you can't simply scour them away. The deeper stains are basically harmless, but many people find them unattractive.

This is where true tooth whiteners come in. Basically, the whiteners use bleaching chemicals to get into the pores of the tooth enamel and set off a chemical reaction (specifically, an oxidation reaction) that breaks apart the staining compounds. Most tooth whiteners use one of two chemical agents: carbamide peroxide or hydrogen peroxide and when used in the mouth will enter the porous enamel layer and helps remove the stains.

Home Bleaching Trays

To begin the at-home procedure, the dentist takes impressions (molds) of your mouth, and then has soft, custom mouth trays made. To administer the treatment, you put a thin ribbon of the gel into the tray and wear it for two hours during the day, or while sleeping. This treatment can be done until you have reached your desired whiteness.

Over a decade of research has proven bleaching and other whitening methods to be both safe and effective. Several products in the market today have shown no adverse effects on teeth or gums in substantial clinical and laboratory testing. Be sure to look for clinically proven products, follow directions and consult with your dentist.