Expert Q&A: How fluoride helps kids and its unique history in Michigan

Fluoride is an important component of children’s oral health in the United States.

Many kids in this country get fluoride from their drinking water, their toothpaste and the occasional treatment in the dentist’s office.

What is fluoride, though, and why does it support healthy teeth?

Sarah Clark, M.P.H., research scientist in the Department of Pediatrics at Michigan Medicine and co-director of the University of Michigan Health C.S. Mott Children's Hospital National Poll on Children's Health, answers these and other questions.

Why is fluoride important to kids’ oral health?
Clark: Fluoride is a mineral, and when it intersects with the teeth, it remineralizes the enamel and makes it stronger.

That prevents cavities, because that stronger tooth is more resistant to the decay that comes about when the bacteria in your mouth combines with sugar and forms an acid that then attacks the teeth.

So, fluoride helps make the tooth stronger. And it prevents the growth of those cavity-causing bacteria.

How did fluoride become a part of children’s oral health?
Clark: Scientists have been studying the connection between fluoride and oral health in kids for over 100 years. And they kind of stumbled on it accidentally.

Fluoride naturally occurs in water.

In most instances, it occurs at levels that are too low to really get that protective effect against cavities.

But in some communities, the fluoride level in the water is naturally higher.

The way they discovered those areas was that the kids had what's called fluorosis— discoloration from too much fluoride; it can look like brown spots or white streaks on the teeth.

But the surprising thing was that the kids with fluorosis had fewer cavities!

The fluoride was protecting their teeth.

That prompted scientists to work on figuring out the amount of fluoride that would be effective in preventing cavities, but not so much that it causes fluorosis.

And they’ve continued that work over the years.

There was a recalibrating of the target amount in 2015 by the public health officials in the country, reducing the target to 0.7 parts per million as the best level.

From those discoveries, how did public health experts determine how much fluoride kids need?
Clark: In general, we want kids to have fluoride protection throughout the day and especially at nighttime.

Tooth decay happens when sugary particles on or between the teeth combine with bacteria in the mouth to form acid that attacks the tooth enamel; during the day, our saliva washes some of those sugary particles away—but at night, we have less saliva to do that job.

So how can kids get fluoride at different times in the day?

One common way is to have kids brush with fluoridated toothpaste in the morning and at bedtime.

Only a small amount is needed (about the size of a pea), and kids should spit out the toothpaste rather than swallow.

Another common way is drinking fluoridated water, which gives a coating of protection while washing away those sugary particles on the teeth.

It can be tricky to figure out how much fluoridated water a child actually consumes; it’s not something most parents keep track of.

And remember, bottled water typically is not fluoridated.

In addition, the dentist might apply a fluoride varnish, foam, or gel after they clean the child’s teeth, to give a good coating of protection.

So there’s not one answer—it’s a combination of the water the child drinks, the toothpaste the child uses, and whatever fluoride the dentist applies.

It’s really important that families work with their dentists to figure out what that individual kid needs.

And most importantly, fluoride is not magic! Kids still need to brush and floss to prevent tooth decay.

How does water fluoridation work in Michigan?
Clark: The individual communities really decide what they want to do with their water supply.

Each community can make that decision about whether to fluoridate that water—and here in Michigan, most of them do. But in some areas, the natural level of fluoride in the water supply is high enough that additional fluoridation is not needed.

But importantly, the Michigan Department of Environment, Great Lakes, and Energy works with the water authorities of each community that does fluoridation.

What they do is testing and technical assistance to help communities get as close to that target of 0.7 parts per million.

And importantly, they have a regular testing program, so that community members can see how well they’re doing.

Grand Rapids was actually the first city in the world to fluoridate its water, in 1945.

For the research study, Grand Rapids and Muskegon were the pair—Muskegon was the control community that didn’t receive the fluoride.

The results were so positive, they actually stopped the research study early.

They didn't feel it was ethical to withhold community water fluoridation from Muskegon because what they saw in Grand Rapids was so positive.

Some places that once fluoridated their water have chosen to remove it, such as Calgary, Alberta. How were kids affected in those places?
Clark: Calgary was a great natural experiment.

The voters chose to discontinue a community water fluoridation program.

Then after it was discontinued, researchers examined the teeth of 7- and 8-year-olds.

Then they compared those results with kids in Edmonton, where the fluoridation hadn’t been discontinued.

And what they found out was that the kids in Calgary had significantly more dental decay than the kids in Edmonton, and that gap got worse as time went by and they were further away from having fluoridation.

It’s clear that fluoridation helps.

The question you're looking at if you remove fluoridation from your community water supply is: Do you feel confident that kids have another way to make up what you just removed, so kids are not at greater risk of dental decay?

A recent review in JAMA Pediatrics discussed the relationship between fluoride exposure and children’s IQ scores. What did it find? And has this review changed perceptions of water fluoridation?
Clark: It’s important and good to reevaluate public health recommendations periodically to make sure they’re still achieving their goals and are not having negative effects.

Before 2015, officials had a recommended target of 0.7-1.2 parts per million.

Then in 2015, they brought it down to 0.7.

The JAMA Pediatrics article is a meta-analysis—not a new research project, but rather a synthesis of fluoride-related research from around the world.

These studies were done in different countries with different water quality and with different methods.

No study is perfect—some are less perfect than others.

The authors chose the studies they thought were most relevant and had good methodology; when they synthesized the results, they concluded that there is an association between fluoridated water and lower IQ scores.

Before you go, “We’ve got to get the fluoride out of the water,” I think it’s important to consider to some of the critiques of the JAMA Pediatrics article.

The biggest critique is that the meta-analysis didn’t examine the connection between fluoridated water and IQ at the currently recommended levels of fluoridation—the levels were much higher.

So, it’s like comparing apples to oranges.

A second thing is the water quality of the communities involved in some of the studies; if the water supply contains higher amounts of lead or other heavy metals, that could affect IQ.

Finally, the critiques point out that if you look at the individual studies included in the meta-analysis, there’s a lot of variation in their results—some with an association and some without.

So the upshot, for me, is that it’s good to ask the question, but I’m less convinced that this meta-analysis should prompt an immediate policy change—or cause people to immediately decide we shouldn’t do any water fluoridation.

First, we need more data that reflects the current target level of 0.7 ppm, so we’re understanding the real-world association.

Then once those data are available, it would be important to bring together a diverse group of stakeholders—people who may have differing views about water fluoridation, but who pledge to work together to review the data and think through the need for changes in recommendations.

How would you sum up the overall importance of fluoride to children’s oral health?
Clark: I really like this explanation a colleague in the Michigan Department of Health and Human Services gave: “Fluoride in toothpaste, fluoride in water, and fluoride treatments at the dentists all work in different ways to keep teeth healthy, much like seatbelts and airbags work together to keep you and your family safe.”