Fluoridation of public water supplies has been going on in Connecticut since today’s 50-year-olds were cutting their baby teeth.

In that half-century, dentists and public health officials have made up their minds that fluoride clearly prevents tooth decay.

While the evidence has shown fluoride is good preventive medicine, it is also good medical and dental practice to use the lowest effective dose of any medicine, and that is the intent of a law recently signed by the governor and taking effect Oct. 1.

The new act, based on the recommendation of the state Department of Public Health, amends an older law to require that the amount of fluoride added to the public water supply be in line with federal standards issued in 2015. The U.S. Public Health Service developed those standards after a scientific study that took into account the fluoride in most toothpastes and other ways people eat and drink it naturally, such as grape juice and broccoli.

The law requires that water companies serving 20,000 or more customers add fluoride in amounts that vary by no more than 0.15 milligram from the federal standard of 0.7 milligrams per liter. That nearly halves the previous allowable amount. It also leaves out people using private wells, which should be tested for naturally occurring fluoride so users can make informed decisions about whether to add fluoride to their diet.

Preventing tooth decay, which is one of the most common and neglected childhood diseases, is why the American Dental Association campaigns for fluoridation. Physicians also prescribe fluoride to treat osteoporosis, rheumatoid arthritis and Crohn’s disease.

Fluoride in the water supply has always had its critics. Skepticism is good, and certainly the news about unsafe drinking water in Flint, Michigan and elsewhere has reminded people that you are what you drink. But fluoride has had time to prove itself as safe and effective. Public Act 16-4 recognizes that.