Opalescence PF 35% Teeth Whitening 8 Pack

I have used the 20% several times before with excellent results. With the 20%, you have to leave the trays in much longer. However, you will achieve the same whitening effect with either product. The 35% is MUCH stronger. Should you forget to take the 35% trays out on time (even ten minutes too long), you will regret it. Tooth and gum sensitivy will be quite noticable. With the the 20% solution, should you forget to take the trays out on time (even an hour or two), the resultant tooth and gum sensitivity will be far less. The 35% solution is a great produt, just keep your eye on the clock and follow the directions.

As always, great shipping and prices with Amazon. I checked several sites, and Amazon had the best overall offer.