i picked up some pills at the pharmacist the other day which you break in your mouth and it spreads a red dye over parts of the teeth which still have plaque on them- thus tells you which parts you are not brushing properly.
are these safe to take?

I may be dating myslef here but these have been available for at least 30-40 years as far as I know - usually they are given to young children when they are just learning how to brush properly. I remember using them when I was quite young. Unless they have changed the ingredients significantly I would assume they are safe - they are probably primarily made of a food dye that sticks to plaque due to it being "sticky" in and of itself.

cheers- id never heard of em!