Dentists Discovered the Tooth-Saving Properties of Fluoride by Accident | Smart News | Smithsonian
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Dentists Discovered the Tooth-Saving Properties of Fluoride by Accident

This is the fourth time Portland has voted on fluoride, and it certainly won't be the last

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For the fourth time since 1956, Portland has decided it doesn’t want fluoride in its water. The pro-fluoride side had more money, more support from officials and more diverse backers, but when the votes were tallied, 60 percent of the city voted against adding fluoride to their water.

Fluoride was first added to drinking water in Grand Rapids, Michigan in 1945, just a decade or so after scientists first identified its teeth-saving properties. In 1901, a dentist named Dr. Fredrick McKay moved to Colorado Springs and noticed what the area’s residents called “Colorado brown stain” on patients’ teeth. After years of treating patients, McKay figured that the stain must be coming from the water supply they shared. But he also noticed something interesting. People with the brown stains had less tooth decay.

In 1930, a chemist with the Aluminum Company of American analyzed the well that the spotted-toothed town drank from and found that the water has high concentrations of fluoride—13.7 parts per million, compared to the 1.0 ppm generally found in ground water. Combining McKay’s observations, and the ACA’s findings, dentists started looking into fluoride as a way to protect teeth from decay.

Enter Dr. H. Trendley Dean, who renamed “Colorado brown stain” the more scientific “fluorosis” and did a several year survey to figure out just how much fluorosis there was in the US. What he found was that in 26 states, kids with flourosis also had fewer “dental caries”—a catch-all term for tooth decay. In 1945, Grand Rapids began a study to see whether adding fluoride to the water would have the same effect. In its history of fluoride, the CDC summarizes the preliminary results: “After conducting sequential cross-sectional surveys in these communities over 13-15 years, caries was reduced 50%-70% among children in the communities with fluoridated water.”

These results lead to the United States recommending an optimum water fluoride concentration range of 0.7-1.2ppm, to help people fight tooth decay. The fluoride recommendation came in 1962, and since then about 56 percent of the U.S. population lives in a fluoridated community. About 62 percent of the central water supplies in the country are fluoridated.

But understanding the modern effects of fluoride are a little harder. Several studies have tried to follow up on the effectiveness of fluoride in the water, but since fluoride is now in all sorts of tooth care products it’s hard to separate water fluoride with other sources. Your toothpaste most likely has fluoride in it, and if it doesn’t, your dentist’s toothpaste certainly does. In one literature review, researchers looked at studies on fluoride effectiveness since 1980, and found that the combined effects of fluoride—water delivered or otherwise—prevented about .3 caries per person every year. About on-third of that effect came from fluoride in the water.

A key part of their conclusion was that not only was fluoride effective, but it was important as a public health service for those who don’t have access to regular dental care:

The proportion of the U.S. population comprised of older adults is increasing, most of these persons are likely to be dentate and at risk for dental caries, and many lower-income adults lack access to timely restorative care. Our finding that fluoride is effective among all adults supports the development and implementation of fluoride programs to serve this population.

And in Portland, supporters of fluoride agreed. Not only is Portland the largest U.S. city to reject fluoridation, it’s also a city with one of the highest rates of uninsurance. Their pro-fluoride campaign pointed out that compared to Seattle, a nearby fluoridated community, Portland kids have 40 percent more dental decay.

Anti-flouride Portlanders pointed to a few studies that suggest that fluoride isn’t as safe as the CDC might want you to think. The FDA considers fluoride a contaminant, because it can be toxic at high levels. One oft-cited study found that in China, in places with extremely high fluoride concentrations, the population’s IQ dropped 7 points. The author of that study pointed out that the concentrations of fluoride he looked at in China were three times higher than the amount recommended by the FDA, telling Live Science that his results “do not allow us to make any judgment regarding possible levels of risk at levels of exposure typical for water fluoridation in the U.S.” Another study found a link between fluoride exposure and bone cancer in male children.

Of course, we know now that the anti-fluoride campaign won out, but the debate won’t go away any time soon. This is the fourth time Portland has voted on fluoride, and it certainly won’t be the last.

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About Rose Eveleth
Rose Eveleth

Rose Eveleth is a writer for Smart News and a producer/designer/ science writer/ animator based in Brooklyn. Her work has appeared in the New York Times, Scientific American, Story Collider, TED-Ed and OnEarth.

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