A study of beavers' tooth enamel could lead to new breakthroughs in oral hygiene for humans.

Beavers are known for their super-strong teeth, and scientists discovered that their chompers have decay-fighting iron built into the chemical structure, Washington University in St. Louis reported.

"This work is an excellent example of the structural-chemical novelty that we are still discovering in natural, biomineralized materials, such as tooth and bone," said Jill D. Pasteris​, a professor of earth and planetary sciences at the university.

This iron-enriched enamel was found to be harder and more resistant to acid damage than most seen in the natural world. These findings could lead to a better understanding of human tooth decay and lead to improved fluoride treatments.

According to the study, the beaver enamel contains "layers of well-ordered, carbonated hydroxylapatite 'nanowires'" at their core surrounded by material containing small amounts of an amorphous solid rich in iron and magnesium; the solid works to control the acid resistance and mechanical properties of the enamel. This study is the first to show the exact composition and structure of this type of enamel.

"The unstructured material, which makes up only a small fraction of enamel, likely plays a role in tooth decay," said researcher Derk Joester, lead author of the study and associate professor of materials science and engineering in Northwestern University's McCormick School of Engineering and Applied Science. "We found it is the minority ions - the ones that provide diversity - that really make the difference in protection. In regular enamel, it's magnesium, and in the pigmented enamel of beaver and other rodents, it's iron."

To make their findings the researchers used powerful atom-probe tomography and other techniques to look at rabbit, mouse, rat and beaver enamel.

"A beaver's teeth are chemically different from our teeth, not structurally different," Joester said. "Biology has shown us a way to improve on our enamel. The strategy of what we call 'grain boundary engineering' - focusing on the area surrounding the nanowires - lights the way in which we could improve our current treatment with fluoride."

The findings were published in a recent edition of the journal Nature.