I have sensitive teeth, so when I started receiving samples of this from the dentist, I thought I'd give it a shot. And you know what? It made my teeth even more sensitive than they already were. The pain was unbearable and I couldn't figure out what the deal was. I stopped using this and after a few days the extreme sensitivity diminished. I thought it was a fluke, but after reading many reviews online I saw that a lot of other people had the same experience and I did with the product. I keep receiving this in sample for from the dentist every 6 months, but even free you can't get me to use it again.