Interesting. I never thought about using activated charcoal for cleaning your teeth but it actually makes sense if you think about it.
You can even use activated charcoal as first aid when someone consumes poisonous stuff because the charcoal can bind the toxic molecules before your body absorbs them.
Another tip for white teeth from my mother: use coconut oil.
have you tried oil pulling with coconut oil?
Not long enough, but I know people who tried it and they mostly said it's working.