Thanks to Infuenster, I had the privilege to try out the Colgate toothbrush with the built in whitening pen. I have now tried it for about 4 days and this is my take on it! When I first got it I was pretty impressed with it. The toothbrush made my teeth feel really clean and I love that. The whitening gel seemed sticky but really didn't bother me. I am a big coffee drinker and my teeth are pretty yellow. I think I can notice a difference but not to sure. I can say that my teeth do feel different in a good way.
I think that the gel may have some kind of peroxide in it because I feel a little foamy when I use it. I will continue to use it and see what happens.