How they work: A dentist coats teeth with a hydrogen peroxide solution, then shines a blue light to speed whitening. “You can buy at-home versions of these lights, but they often cost as much as a professional treatment and won’t work as well,” says Bill Dorfman, a cosmetic dentist and the author of Billion Dollar Smile.
The whitening effect: Five to eight shades. Lasts 6 to 12 months.
Good to know: Take an anti-inflammatory (such as Advil) an hour before treatment to prevent discomfort. In the 48 hours following a treatment, the enamel is highly susceptible to staining. Temporarily avoid dark foods and drinks, like coffee, berries, and red wine.
Average cost: $200 to $800 a treatment. (Shown: Philips Zoom WhiteSpeed lamp, which takes less than an hour.)