Tray bleaching

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Tray Bleaching
What it is: The dentist makes a mold of your teeth to create thin plastic trays that fit like mouth guards. You fill the trays with bleaching gel and wear them for three days, an hour a day, every three months. Steven Fox, DDS, a New York City dentist who has done extensive research in the field of remineralizing teeth, recommends tray bleaching for a few days every two to three months as a good way to maintain the results of an in-office bleaching treatment.

Best for: Maintenance after an in-office whitening treatment.

Does it work? Yes. Because the trays are made specifically to fit your mouth, the peroxide spreads evenly on teeth. But beware of overbleaching: Peroxide can dissolve the calcium in tooth enamel (the outer layer), which exposes the nerves, resulting in sensitivity. Calcium depletion can also cause decay, says Fox. Though teeth can be remineralized with a paste or a fluoride treatment, you shouldn't wear the trays more than four to six times per year.

Cost: $400 to $800.