In Search of Pearly Whites



Given the option, most of us would prefer to have a dazzling smile. Drugstore shelves are stacked with tooth-whitening products: it's hard to find a toothpaste without a "whitening" promise on the box. Here are some facts about prettying up tooth enamel.

What's the chemical used to bleach teeth?
In home bleaching kits or the dentist's office, it's usually a peroxide compound. This penetrates tooth enamel and breaks apart the compounds staining the teeth. Toothpastes usually contain nonbleaching abrasive agents that remove stains by polishing but don't alter the color of enamel. Some pastes now also contain a small amount of peroxide.

Do the whitening toothpastes work?
Not very well, since the chemicals are in contact with your teeth for only a short time. They are also diluted with saliva and water in the normal course of brushing. It would take a long time for the effect (if any) to become noticeable.

What about home kits?
Most produce only modest improvements. You can apply peroxide to your teeth in many ways: whitening strips, gels, pens, and traditional tray-based systems. The peroxide-coated strips are thin, almost invisible. You use them twice a day for 30 minutes during a two-week period. If you are using a gel, you apply it to your teeth with a small brush twice a day for two weeks. The whitening pen is similar. The tray-based systems come with a mouth-guard that you place over your teeth while applying the chemical. You can buy one through your dentist, as well as at the drugstore. All these measures will whiten enamel somewhat. They can also irritate your gums.

What about the dentist?
A dentist will use a stronger solution of peroxide and sometimes a laser or a special light to hasten tooth whitening. And the mouth-guard will be customized, rather than one-size-fits-all, as in the home kit. A dentist should be able to protect your gums from irritation more effectively than you could at home. It's probably the safest and most effective way to bleach. But the cost could run around $500.

What about crowns and fillings and other restorations?
Whiteners don't work on crowns and restorations. If you whiten your natural teeth, any restorations you have may stand out more.

Does the effect last?
The gleam will start to fade within a month, especially if you drink coffee, tea, or red wine--or eat other foods that stain teeth. And if you smoke, your teeth will quickly discolor.

Are there risks? Who should avoid bleaching?
Bleaching can temporarily increase tooth sensitivity; peroxide can irritate the gums. There's preliminary evidence that the strength of tooth enamel might be impaired by repeated bleaching. People with very sensitive teeth and those with periodontal disease, worn enamel, or deep cavities should not bleach.