Use Crest 3D White 2 Hour Express Whitestrips for visibly whiter teeth in just 2 hours. For a little time commitment, you'll see noticeable results. And you only need to use ONE treatment to get results that last three months. This package includes four separate treatments, enough to keep your teeth white for an entire year. Crest 2 Hour Whitestrips use the Advanced Seal, no-slip technology that allows you to talk, drink water and go about your day while you whiten with no sticky mess. They're also enamel safe and use the same effective whitening ingredient that dentists use.