Fluoride analysis triggers renewed debate over what levels are safe for kids Most communities in the U.S. add fluoride to the tap water. It has been common practice for nearly 80 years to protect against tooth decay and cavities, and it's considered a major achievement in public health. The Centers for Disease Control and Prevention says research shows that community water fluoridation reduces cavities by around 25%. It has also long drawn opponents who have raised concerns about the practice,...