How they work: The most precise and thorough over-the-counter option, each ampoule (tube) is filled with a 6.5 percent–concentration hydrogen peroxide gel solution. Squeeze the gel onto the attached brush, then paint it on your teeth.
The whitening effect: Up to five shades, when used twice daily for one to two weeks. Lasts 6 to 12 months.
Good to know: To keep the gel in place and to ensure that it reaches the enamel, not just the plaque on top, blot your teeth with a tissue before you apply.
Average cost: $45 to $144 a kit. (Shown: GLO Science GLO Solo Teeth Whitening, $45 for a two-week supply, sephora.com.)