The anecdote I have is that one of my grand daughter's teeth are worse than my other grand children and grand nieces and nephews. She used RO water more than the others when she was younger, and her dentist reinforced the idea that RO water was unfriendly to early tooth health, apparently due to reduced fluoridation. I'm not suggesting that is worse than forever chemicals.
The things I've read about fluoridation make it sound like fluoride applied to the surfaces of the teeth (eg via brushing) has the most benefit. I have to wonder if your grand daughter was also using a non-fluoride toothpaste.
I’m dubious. Millions of people in the country are on wells and don’t use any fluoride, also fluoride isn’t present in every municipal drinking water supply.
