The benefits that motivate widespread fluoridation, kick in at concentrations well below those needed to stain teeth. If I recall the history of it all correctly, the level of fluoride needed to stain teeth basically leaves you with teeth that are all but impervious to run of the mill cavities from plaque buildup. The bugs just don’t have the power to degrade tooth enamel containing fluoride minerals at concentrations that are high enough the staining becomes noticeably brown (im talking about an arbitrary colour grade here so please be generous in interpretation of just what I mean by “brown” if performing additional research to refute me)

So basically while we don’t suffer for lack of fluoride to harden our teeth… the extra fluoride gives us a lot of protection. And yes you can have too much fluoride, but your never going to see that kind of medical pathology unless you somehow get a lot more bioavailable fluoride in you in a short span of time than you could possibly get from drinking multiple litres (or even gallons) of fluoridated water per day, they don’t put enough fluoride in the water to turn teeth brown, and we have ample evidence that fluoride bearing spring water above these concentrations does no harm for long periods of time.

I get being concerned, but we got so much more important things to worry about with regard to environmental chemicals than fluoride. It’s pretty easy to read the history, find out about the kids with the brown but perfect teeth, find the other stories from around the world, the second generation families living healthy on spring water that is/was naturally highly fluoridated, and put it all together yourself without need to take anyone’s word for the fact this actually is a pretty good “one weird trick for perfect teeth”.