Brush kids’ teeth with just a little fluoride toothpaste


Use a smear (left) of fluoridated toothpaste on your baby’s teeth as soon as they erupt, and a pea-sized dollop (right) between ages 3 to 6, say new recommendations from the American Dental Association.

Courtesy of the American Dental Association

When Baby V began sprouting teeth, I hopped online to figure out how to handle the new sharp, white residents of her mouth. I quickly found my answer. I’m supposed to use a pea-sized amount of non-fluoridated toothpaste until Baby V turns 2, and then switch to fluoridated toothpaste. No, wait. I’m supposed to gently wipe the teeth and gums with a wet piece of cloth. Actually, no. I’m supposed to brush, but just with water. Thank you, Internet, for clearing that up.

Since my failed fact-finding mission, I’ve settled on brushing Baby V’s teeth in the morning and night with a little bit of fluoride-free toothpaste. But as I hear more horror stories of toddlers with teeth so decayed that they have to be anesthetized to have their cavities filled, I began to worry. Maybe we need to bring a little more cavity-busting fluoride into our tooth-brushing regimen.

That sounded like a sensible plan, until I started pulling research papers that say that ingesting fluoride while teeth are still growing in the gums can lead to white, chalky streaks on teeth, a condition called fluorosis. In higher amounts, fluoride can cause bone problems. Caught between a mouth full of rotten teeth on one side and a disfiguring disorder on the other, what’s a parent to do?

You could try ignoring the problem, which worked for me until last week, when the American Dental Association (ADA) helpfully released new guidelines (paywalled, but read a press release here) on how to care for young children’s teeth. Based on a review of the science led by J. Tim Wright, a pediatric dentist at the University of North Carolina School of Dentistry in Chapel Hill, the ADA now recommends that children’s teeth should be brushed with a smear of fluoride toothpaste as soon as they appear. The new recommendations also change the advice for older kids: Children should keep using a smear — not the pea-sized amount previously recommended — until their third birthday. Children between ages 3 and 6 should use a pea-sized amount of fluoride toothpaste.

Fluoride works to prevent cavities by rebuilding teeth. Highly reactive fluoride sticks to molecules in the tooth that become exposed when bacteria-produced acid attacks the teeth. Fluoride molecules latch on to the tooth and beckon other minerals such as calcium and phosphate in a process called remineralization.

Fluoride’s main anticavity superpowers come from topical application to the tooth surface — exactly the situation when fluoridated toothpaste is used. When fluoride is ingested, the levels of the entire body are raised. The resulting fluoride-rich saliva bathes the teeth and allows remineralization.

Scientists know this process works in adults. There aren’t good studies on fluoride cavity prevention in young children, but presumably, fluoride has a similar protective effect, Wright says. “There are always gaps in our knowledge,” Wright says. But there’s enough evidence out there to convince him the new guidelines will help prevent cavities and fluorosis, too, he says.

The ideal fluoride level that prevents cavities but has no ill effects is about 0.05 milligrams per kilogram of body weight per day. (That limit is probably debatable, especially for small children, but that’s another post.) In the updated guidelines, the ADA calculates kids’ probable exposure to fluoride from toothpaste: Assuming that an average-sized 2-year-old brushes her teeth twice a day and swallows the toothpaste, a smear of toothpaste (about the size of a single grain of rice) would result in 0.013 milligrams of fluoride per kilogram of weight per day. But a pea-sized dollop would lead to 0.033 milligrams per kilogram. That’s approaching the level at which fluorosis might become a concern, Wright says.

Since studies have shown that risk of fluorosis for some permanent teeth peaks around age 2, it makes sense to use just a smear of fluoridated toothpaste for children between ages 2 and 3, especially since fluoride comes from sources other than toothpaste. My city’s water is spiked with fluoride to reach levels of 0.7 parts per million. (In case you were wondering, Brita filters don’t get rid of fluoride.) In such small amounts, “you’re going to have to drink a boatload of water” to get enough fluoride to cause fluorosis, Wright says. Likewise for food: Fish, particularly canned fish that contains bones, and tea both can have high levels of fluoride, but those aren’t usually large parts of a young kid’s diet.

Perhaps a bigger concern: Parents should be careful about using too much fluoridated toothpaste — a pretty common habit, studies have found. “People tend to think a little is good, more is better,” Wright says.

Not so. For little kids who can’t spit toothpaste out yet, parents can wipe the excess toothpaste off their teeth after brushing. (But not with water, says Wright. A water rinse washes away some of fluoride’s benefits.)

The new recommendations might not be ideal for people who drink well water with unusually high fluoride levels. But most young kids in the United States ought to be using a little smear of fluoride toothpaste, Wright says.

The long and short of it: Although there aren’t good data showing that small amounts of fluoride toothpaste prevent cavities in little kids, it probably helps more than it hurts. So I’ve got my partial, best-guess answer. Tonight, I’ll buy some fluoride toothpaste and use a smear on Baby V. But just a little. 

Laura Sanders is the neuroscience writer. She holds a Ph.D. in molecular biology from the University of Southern California.

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