What it is: In-office whitening treatments, like Zoom! and BriteSmile, use peroxide (the same bleaching agent in drugstore kits). Lip and tongue retractors hold your mouth open, and a wax is painted over your gums, fillings, and any spots the peroxide might irritate. Next, a bleaching gel is applied to the teeth and a blue light activates it for about an hour.
Best for: Those who want instant results and who have sensitive teeth. "Because we cover the areas where the nerves might be exposed, patients are much less likely to experience sensitivity than with other whitening options," says Jeff Golub-Evans, DDS, in New York City, who practices cosmetic dentistry.
Does it work? Yes. It may be slightly uncomfortable to sit in the chair for an hour with your mouth held open, but the procedure can remove about 10 years' worth of staining, says Golub-Evans. As with all whitening treatments, you can't eat or drink anything deeply pigmented, such as berries, soy sauce, red wine, or coffee, for at least 48 hours. "The bleaching agent opens pores in the teeth, which makes them ultra-absorbent to color," says Pia Lieb, DDS, clinical assistant professor at New York University College of Dentistry. Results last a couple of years if you brush and floss regularly.
Cost: $300 to $600.