Review (2/5): it's fun to see your mouth full of black foam -- ...
I don't see much if any change, certainly no startling results. I even wonder if it just grays the enamel a bit, toning down the original yellowish cast. I'm going to keep using it until the jar is empty; will update if anything changes. (On the upside, it's fun to see your mouth full of black foam -- and to smile broadly at your husband with horror-movie mouth.)