With Crest Whitestrips Renewal, you can remove up to 20 years of stains from your smile, and all it takes is 30 minutes, twice a day for 10 daysTeeth Whitening - You Have a Choice!All Crest Whitestrips teeth whitening kits have been shown to be safe and effective in extensive clinical and laboratory testing when used as directed. In fact, Crest Whitestrips is the #1 dentist-recommended brand of teeth whitening system in the US.Everyone's teeth are stained for different reasons. Drinking coffee and tea, aging, diet and tobacco use are a few reasons why teeth are not as white as we would like. For this reason, teeth whiten at different rates.If you have more stubborn stains, it may be necessary to use a second box of Crest Whitestrips to achieve your desired whitening results. But no matter your needs, schedule or budget, we have the Crest Whitestrips product that best suits your smile.