Let's take a deep breath and take a deeper look at the recent research published by Harvard University warning about the association of fluoride in drinking water and lower IQ levels in children. The study focused on two Chinese villages where fluoride occurs naturally in the water. One village had an extremely high level (2.47 mg/L) which is almost four times the amount currently recommended in the United States (0.7-1.2 mg/L.) The authors of the Harvard report recommend further study before they make a definitive conclusion.
What should you do in the meantime? If you are, nonetheless concerned, I would recommend taking some action. First get the fluoride level tested in your own water. Hopefully, it will not exceed the current recommended level that is between .7-1.2 mg/L . Also, you can opt to take a topical approach with fluoride, having your child use a daily fluoride rinse that is swooshed and spit. This would not be appropriate for younger children who cannot mechanically do this because they may swallow the rinse. I also recommend using a fluoride tooth paste. This will definitely help with cavity prevention. Don't forget the flossing, though!
The other action that you can take as a parent to ensure your child's dental health is to eliminate soda and sugary candy. You may also be interested to know that the body recognizes anything made with white flour as a sugar. Therefore, all of us should brush after eating snacks such as crackers, pretzels, etc. since the crumbs can become lodged in the tooth surfaces and cause decay.
Caveat: A recent study published by the American Journal of Public Health reported no adverse correlation between fluoride and IQ after studying 1000 patients from birth until the age of thirty eight.