Medically Approved

Are you getting too much (or not enough) fluoride? 

Girl brushing her teeth next to dad

This natural mineral helps protect teeth from cavities and decay. But getting the right amount is key. Learn more about its risks, benefits and whether a fluoride prescription is right for you.  

Brierley Horton, RDN

By Brierley Horton, RDN

To keep teeth in tip-top shape, oral health experts say that brushing alone isn’t enough. That goes for kids — and adults. One treatment they often recommend is fluoride.  

This natural mineral helps prevent the second most common disease in the world: tooth decay. And it’s been added to toothpastes, mouth rinses and public drinking water. But its use, especially in tap water, has been steeped in controversy. 

So how exactly does fluoride work? Is it safe? And who should consider having fluoride treatments? Below, we answer these questions and more. 

(Have you grabbed your free Optum Perks prescription discount card yet? It could save you up to 80% at the pharmacy. Here’s how it works.) 

How fluoride helps prevent cavities 

Let’s first look at how cavities form. When you eat or drink something sugary or starchy, the bacteria in your mouth also have a feast. They turn those carbohydrates into acids. And that acid mixes with food and your saliva to form plaque. It’s a sticky substance that coats your teeth. 

If the plaque sticks around, it can dissolve tooth enamel. And this creates cavities, or holes. (These are the dangers of gum disease.) 

But if you drink, rinse or brush with fluoride, it helps prevent this damage. First, the mineral becomes part of your tooth’s structure. This makes the tooth more resistant to the bacteria’s acid. Second, it helps correct existing damage. And third, it prevents bacteria from making the acid in the first place. 

Sodium fluoride is one of the most common forms of fluoride. It’s the form that’s added to some drinking water, toothpastes and mouthwashes. 

“We consume many foods and beverages that demineralize our teeth,” says W. Adrian Lovell III, DMD. He’s the owner of Lovell Pediatric Dentistry in Birmingham, Alabama. “Fluoride can help reverse these effects and strengthen and protect our teeth,” he adds. 

Recommended reading: Your toolkit for fighting gum disease. 

Why was fluoride added to drinking water? 

Well, lots of kids had lots of tooth decay. According to the American Academy of Pediatric Dentistry (AAPD), 90% of American teens in the 1960s had a cavity in at least 1 permanent tooth. Adding fluoride to public water was seen as a cost-effective way to help curb cavities. It was also fair. If parents couldn’t afford dental treatments, their children would still benefit. 

In 1945, Grand Rapids, Michigan, became the first city to raise fluoride levels in drinking water. It worked. And soon, more and more cities followed suit. 

By the early 2000s, the number of U.S. teens with cavities dropped to 60%. Along with fluoride toothpastes and rinses, water-supplied fluoride has helped turn the tide on tooth decay. 

But is all this fluoride safe? 

Since fluoride came on the scene, people have worried about its health effects. And not all cities have raised their water’s fluoride levels.   

That said, all the evidence points to its safety. Experts around the world have done large studies to make sure. Fluoride hasn’t been shown to affect children’s health. And it’s effective in protecting teeth. In fact, a review of more than 70 studies found that the more kids used fluoride toothpastes, the lower their risk of cavities. 

At very high doses, though, fluoride can be toxic. But this kind of exposure is rare, according to the National Institutes of Health. “A child would have to eat a large amount of toothpaste before they start having any negative effects,” says Dr. Lovell. 

Talk with your dentist about how much fluoride is right for you and your family. They’re trained to assess fluoride exposure, says Dr. Lovell. And they can suggest age-appropriate levels of fluoride. 

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How to make sure kids (and adults) get the right amount of fluoride 

For most people, using fluoride toothpaste is enough to prevent cavities (unless their dentist says otherwise). 

For kids under 3, the AAPD recommends putting just a smear of toothpaste on their brush. For those 3 to 6, they suggest using no more than a pea-sized amount. Dr. Lovell also suggests supervising their twice-a-day brushing when you can. 

And everyone can benefit from the “spit don’t rinse” technique. Rinsing can wash away the fluoride left behind by brushing. 

Why would someone be prescribed a fluoride rinse, gel or supplement? 

They could be at a high risk for cavities. Or maybe their drinking water doesn’t have extra fluoride in it. Only some public water systems have fluoride. Well water doesn’t. 

Fluoride prescriptions should be given based on your risk and how much fluoride you take in, says Dr. Lovell. “It never hurts to ask if it’s something you should consider.” 

These special rinses and gels are meant to be used regularly at home. Always follow your doctor’s directions to make sure you get the most benefit. 

What about fluoride supplements? They were popular in the 1970s and ’80s. But oral health experts now know that lower doses of fluoride applied more often is the better approach.   

Recommended reading: 7 reasons your mouth is always dry (and what to do about it). 

What about fluoride treatments at the dentist’s office? 

“These treatments have a higher concentration of fluoride,” says Dr. Lovell. They create a protective layer on the surface of your teeth. “When that coating is exposed to acid, it releases fluoride,” he explains. This helps repair enamel and reduce plaque. 

Some adults can benefit from fluoride treatments. But they’re more common in kids. “Children are very dynamic,” explains Dr. Lovell. They’re losing teeth and getting new ones. And thorough brushing can be hit or miss (not for lack of trying, though). These treatments can give their teeth extra protection while they move through these stages. 

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Additional sources
Background on cavities: Cleveland Clinic 
Current guidelines around fluoride use in children: American Academy of Pediatric Dentistry 
Negative effects of fluoride: National Institutes of Health