Introduction

For as long as I can remember, I have bought into the gospel of fluoride believing that my teeth would surely rot out of my head without its protection. So it felt a little illicit, recently, when I bought a box of fluoride-free German kids’ toothpaste for my daughter. This toothpaste came in blue, understated packaging no cartoon characters or candy flavors which I associated with German practicality. Instead, it contained an anticavity ingredient called hydroxyapatite, vouched for by several dental researchers I interviewed for this story. Could it be, I wondered as I clicked “Buy,” that toothpaste doesn’t need to contain fluoride after all?

The scientific case for hydroxyapatite toothpaste is relatively simple: Composed of calcium and phosphate, hydroxyapatite is a mineral that comprises our bones and teeth. This enamel, the outer layer of tooth structure, is normally about 96 percent hydroxyapatite. Back in the 1970s, NASA researchers patented an idea for repairing teeth with a hydroxyapatite precursor; nothing came of it at that time, but a Japanese company acquired the patent and finally developed a popular toothpaste called Apagard. Hydroxyapatite toothpaste was approved in Japan back in 1993 for the prevention of cavities. It’s also approved in Canada and supported by the Canadian Dental Association. It’s sold in Europe, where the European Commission has deemed the ingredient safe in toothpaste.

Fluoride, though, remains the reigning monarch in the United States. You probably won’t see toothpaste containing hydroxyapatite at your corner drugstore. A few boutique hydroxyapatite-based brands have cropped up, but unless they get FDA approval, they can’t market themselves for cavity prevention. The American Dental Association, meanwhile, gives its Seal of Acceptance only to toothpastes that contain fluoride.

Fluoride

Fluoride does work remarkably well: It gets incorporated into the enamel structure of the tooth itself, forming some sort of mineral crystal that is far more resistant to cavity-causing acid than the tooth’s natural material, says Bernhard Ganss, a scientist at the University of Toronto’s Faculty of Dentistry. “​The dogma in dentistry has always been: Fluoride is a good thing.”.

The thing with fluoride is that, in very large quantities, it becomes a bad thing. If one ingests too much, fluorosis results, in which the teeth get mottled in mild cases or structurally weak in serious conditions. This can also happen to bones. More controversially, high levels of fluoride in drinking water—higher than the level recommended in the U.S., but lower than the current EPA limit—have been linked to lower IQ in children. Toothpaste typically contains more than 1,000 times as much fluoride as is recommended in drinking water. Of course, we use much less toothpaste than water, and it’s not meant to be swallowed, but young children do not spit out toothpaste reliably.

Hydroxyapatite

Hydroxyapatite could be a way to sidestep the fluoride controversy. It offers the anticavity benefits of fluoride without the risks. Bennett Amaechi, a professor in the department of comprehensive dentistry at the University of Texas Health Science Center at San Antonio, told me he now recommends it to concerned parents looking for an alternative to fluoride. Indeed, he has partnered with toothpaste manufacturers to research ​​​hydroxyapatite, but Felicitas Bidlack said the same thing about its utility. Bidlack is not a dentist, but she is a researcher into tooth enamel, and was suggested to me by the American Dental Association, which one could hardly accuse of being anti-fluoride. Yet for kids under 2 still learning not to swallow toothpaste, she would probably opt for hydroxyapatite. “That’s what I would do as a mother,” she told me.   Fluoride toothpaste is in a bit of catch-22, Bidlack added. Candy flavors, bright colors, glitter—what’s not to like with toothpaste for kids when it comes to brushing teeth? But if too tempting, they may just end up eating it. “If you give them fluoride with this nice-tasting goop that they’re putting into their mouths, there is definitely a potential for incidental ingestion,” says Ganss, who has co-authored papers on hydroxyapatite with scientists from the German company Dr. Wolff Group, which makes toothpaste. He went even further: For toddlers, “I would actually really stand up and say no fluoride, period.”

These conversations have been really clarifying for me. I’ve gotten so much mixed information about fluoride and its place in my 1-year-old’s life. Toothpaste marketed to kids under 2 in the United States doesn’t contain fluoride. According to the American Academy of Pediatrics—whose advice our pediatrician repeated—we’re supposed to start fluoride toothpaste as soon as their first tooth erupts, but only a rice-size smear would limit the exposure to fluoride. So is fluoride good or not? Is it safe or not? Wouldn’t it be nice not to deal with fluoride at all?

Hydroxyapatite doesn’t have the long history of fluoride, but so far, the evidence looks good: In clinical trials involving kids or adults and tracking them for six months to a year and a half—largely funded by toothpaste manufacturers—hydroxyapatite and fluoride have come out about equally protective against cavities. The hydroxyapatite is not chemically as resistant to cavity-causing acid as the mineral formed by fluoride, says Ganss, but daily brushing might replenish hydroxyapatite frequently enough that real-world protection is similar. There are some other perks of the mineral, too: In studies, hydroxyapatite has helped reduce tooth sensitivity and the amount of bacteria stuck to teeth. The one thing it can’t do is settle the controversy over adding fluoride to drinking water, which is done as a public-health measure in most parts of the U.S. to prevent tooth decay. Hydroxyapatite can’t be put into drinking water, because it doesn’t dissolve at a neutral pH. “The tap water would be milky,” Ganss says. “It would probably clog all your pipes within a few days or so.”

The scientists I spoke to felt fluoride was good for something—treatments and toothpaste, say, for adults who know not to swallow too much. Amaechi still brushes with the Colgate he’s used all his life, as he sees no reason for him, as an adult, to change his habits. But he does recommend hydroxyapatite in specific situations—for example, patients with dry mouth, he says, may particularly benefit from this formulation.

Conclusion

Of course, age 2 isn’t some magic threshold at which the calculus regarding toothpaste in small children suddenly changes. Canada, in fact, advises holding off on fluoride for most kids until age 3; fluoride-free options for kids are now spreading in the US, even without FDA approval of hydroxyapatite. This German children’s toothpaste only came in boring white mint, whereas in the U.S. there were a variety of different brands already selling much more interesting flavors, like orange creamsicle and birthday cake.