I don’t doubt the oft-repeated claim that fluoride is good for your teeth. I brush with fluoride toothpaste and wait to spit it out. I don’t rinse.
What happens when you drink or cook with fluoridated water? It seems like it takes a long trip through the stomach and intestines before a small amount, if any, makes it to the teeth. Does some fluoride end up in your heart, liver, brain, etc? What is the point of showering or bathing in fluoridated water? Why wash your clothes in it? Should you use it to water your lawn? Flush the toilet?
That is 0.0000007% fluoride.
The added (or natural) fluoride in drinking water becomes part of your tooth enamel.
Not just by bathing your teeth with fluoride, but also by entering the cells that nourish a healthy tooth.
Fluoride is an enzyme or adjuvant that enhances the production of new tooth enamel, which is how your teeth respond to normal wear and tear and prevent cavities.