This is going to be unsupported by links and will not be technical enough to please many people, but that does not matter in the long run. This is something that you can see for yourself.
Ask everyone you know how many cavities they have. Then ask them if they grew up drinking well-water or city-water.
You will find that most people with zero cavities grew up drinking well-water. The more cavities they have, the more likely they are to have grown up drinking fluoridated water.
As for me, 0 cavities and grew up with well-water. You now have your first test result. Mark it down and begin asking others.