Depending who you ask, the practice of adding fluoride to public drinking water is considered one of the top 10 most important public health measures of the 20th century — or it’s poisoning us with every sip. But with inaccurate studies and changing governmental standards, it’s hard to know who’s right in an argument that started over 70 years ago.

The whole thing started as a water-fluoridation experiment in 1945, after evidence surfaced that populations reported fewer cavities in areas with higher levels of naturally occurring fluoride, which leached into water from rocks. Unfortunately, other factors, such as diet and overall health, weren’t considered, leading to a heated debate about whether universal fluoridation was the right way to go.

This practice began during the same time period when asbestos was a prized material for construction and fire retardation, smoking cigarettes gained favor to stay trim, and the pesticide DDT was lauded as chemical magic. But cigarettes, asbestos, and DDT have fallen from grace in the U.S. — while more than 70 percent of the country now has access to fluoridated water.

Purported Benefits

Dr. Ward Johnson, a second-generation dentist in Aspen, Colorado, says the benefits of fluoride on your teeth come when fluoride, which can be present in toothpastes and mouthwashes, gets into tooth enamel, hardening the structure, and thus making your teeth better at resisting cavities.

According to the American Dental Association, fluoridated water lessens the rate of cavities by 25 percent in children and adults. “Even if fluoride ‘only’ delays tooth decay until people are into their 30s,” Johnson says, “it gives people a better chance to keep their teeth and live a healthier life.”

Not even a century ago, it was common for people to go to their graves without a full set of natural teeth — something that the ADA’s conclusions about delayed cavity onset would ostensibly counteract. But Dr. Kathy Thiessen, Director and Senior Scientist at Oak Ridge Center for Risk Analysis and a former fluoride proponent, isn’t so sure the purported benefits of fluoridating water support the practice of deploying it on a national scale.

“There is no continuing evidence to support the benefit, although I’m not sure there ever really was evidence,” according to Thiessen, who says most of the reliable studies done to look at the efficacy of fluoride for preventing tooth decay pre-date 1975. “We do not have good, current studies showing the absence of harm, or a demonstrable benefit that can be proven.”

Causes for Concern

Many fear the potential dental benefits come at the cost of putting populations at an elevated risk of other health issues, such as diabetes, cancer, lower IQs in children, and the bone disease skeletal fluorosis.

But Dr. Howard Pollick, the ADA spokesperson on fluoride, says most fluoride studies have flaws — such as failing to stick with specific scientific criteria or not looking at enough factors — and have been discredited. For example, many of the cited studies regarding diabetes and lower IQs in children were performed in China, where environmental toxins not present in the U.S. played a role in study outcomes.

Still, the U.S. Public Health Service recently lowered the recommended fluoride level to 0.7 milligrams of fluoride per liter of water, down from a 1962-established maximum of 1.2 milligrams per liter. According to Pollick, this new level represents a sweet spot between reducing the incidence of tooth decay and not causing a mottled discoloration in your tooth enamel called dental fluorosis. The fluoridation sounds like it would be a benefit for everyone who wants to have healthy teeth — unless you’re wary about what else it could do down the line.

Freedom of Choice

Johnson says one of the main arguments against the practice of water fluoridation is that it can be seen as medication without warrant or choice. Whether a community augments their water or not, Johnson cautions that it takes years to see changes in dental health.

“Many of the people against fluoridation today are still benefitting from the fluoride exposure they received in their youth,” suggests Johnson. “The proof is in their healthy teeth.”

What to Do

Incomplete studies and advocates on either side of the fluoride fence make it hard to see a clear-cut answer to whether or not fluoride’s taking a toll on your body. But you do have options if you’re not sure about having the mineral in your life. Check with the local water department to find the fluoride levels in your drinking water. Visit the dentist for regular checkups, practice good dental hygiene, and develop a fluoridation plan based upon your dental needs and overall health.

MORE: 10 Ways to Keep Your Teeth Healthy