Strips

"Whitening strips are very thin polyethylene strips that are coated with a peroxide-based whitening gel, which should be applied twice a day for two weeks," Smigel says. "The strips are applied to upper and lower teeth twice a day for 30 minutes per application. This process continues for two weeks." Some newer versions require less of a time commitment and can be used in as little as two hours.

"The strips provide a consistent application of the whitening agent and dentists have found that the strips have produced noticeably whiter results," Smigel says. "Results are seen in a few days, and final results are sustained for about four months.

"The disadvantage with whitening strips is that they are one-size-fits-all and fit best on the upper front 6-8 teeth. If your teeth are even and fairly average in size, you should not have a problem," Smigel says. "However, if teeth are larger than normal or uneven, the strip will whiten teeth unevenly since it can only lighten the area that it covers." Another downside: increased tooth sensitivity is common among users of whitening strips.

Crest 3D White Whitestrips Intensive Professional Effects, $50.99, available at Drugstore.com.