Just to add to the other comments, I recommend looking into the "why" fluoride is added to water. I'm currently on the go so I can't provide references, and I'm sorry that it is hard to find due to the prevalence of crazies writing blogs about fluoride, but the general summary is that is was a happy mistake of resource extraction effluent which had more benefit than harm at first, and has now been found to maybe even out instead of being slightly beneficial (depending on your values). The Canadian study linked in a sibling comment addresses that last bit.

Iodine in table salt is probably a better example.