I've used the Crest White Strips also. They worked really well for me. I first used them @ 5 years ago, before they had the premium ones. I used them for 7 days and had significant results. They did make me teeth VERY sensitive though, so you might want to also invest in some toothpaste for sensitive teeth to use for a few weeks. I used the premium ones last year, and they worked too, but not really any better than the other ones. It was maybe a day or 2 faster.