Here is an excerpt:
Fluoride
If you still believe fluoride in your drinking water prevents cavities and helps build strong teeth, you’ve fallen for a cleverly devised mass-deception.. As this recent study done on children in India shows, fluoride is anything but a cavity fighter. fluoride is a well-known toxin that actually leads to an increased risk of cavities and can cause a wide range of health problems, including weakening your immune system and accelerating aging due to cellular damage.
https://www.mercola.com/article/water.htm