My teeth were much whiter after 6 treatments, but afterwards the other 4 didn't do much.
I have never whitened my teeth in my life, so I decided to give it a try.  After the first 6 treatments of Opalescence GO, my teeth were much whiter than before, but the last 4 treatments of the 10 that come in the box didn't make much difference anymore, so if I do it again in the future, I think maybe I'll just do 5 or 6 and save the rest for a later date.  Another thing that I'd like to add, is that in the videos on YouTube show people easily putting the plastic applicator in their mouth and when they took it out the part with the whitening agent would be in their mouth, but for me that didn't work, so I took the part that had the whitening agent out of the plastic applicator and manually put that in my mouth, and that seemed to work good for me.  As a side note, in case you don't read the instructions, when you get the Opalescence Go product, put it in the refrigerator until you want to use it, and then take it out and let it come up to room temperature before actually using it.
Rating: 4 stars