Note how the people promoting fluoride never explain to their readers the form being used in our water systems, conveniently they call it the layman's term "fluoride" like I have, when they don't want their readers to know its form being added to the water is Hexafluorosilicic Acid.
Any amount of hazardous material, is damaging to the cells. That's why many scientists have stated that "Fluoride is not safe in any amount" because it's accumulating, so toxic that the body has a difficult time removing it. It clings to calcium, which our bones are partially made of. Fluoride displaces magnesium in the bones of humans and animals, which then causes the bones to be more brittle.