The technician told me I would not have any tooth sensitivity, but in fact, my teeth hurt so badly I decided to go out and buy some of the toothpaste made for sensitivity, which I had never used before. It worked very well and I just wished I had been warned so I would have had it on hand and wouldn't have suffered needlessly. Also, the whitening is barely noticable. It's almost no different at all. Not worth the money, even with the Groupon price.