Review (4/5): Just keep your mouth over the sink
It's true what the negative reviewers say: that this product can be messy..but after a couple of month's use I can say if you just keep your mouth over the sink when you brush with it and it's not a problem - the black stuff stays in the sink and you just rinse it down the drain. It's not like it stains or anything. Otherwise, I love the way it makes my teeth feel and it has brightened them. I am loath to use the otc chemical whiteners and this stuff is all natural and non-toxic, so count me in. I use it once a day in addition to my daily oral regimen and I will continue to do so.