There is arguably no animal better known for its teeth than the beaver. The famed dam builders don’t brush or floss, they don’t visit the dentist and they don’t drink fluoridated water but their teeth remain strong.

According to researchers at Northwestern University, this is because of iron, built into the chemical structure of their teeth. According to the researchers this makes their teeth harder and more resistant to acid than regular enamels, even those treated with fluoride.

Enamel is made of layers of hydroxyapatite, or “nanowires”. However, the researchers discovered that the material surrounding these nanowire contains materials such as iron and magnesium and these control the acid resistance and mechanical properties of the enamel.

The team behind this research, led by Derk Joester, is the first to show that this amorphous or unstructured phase in enamel exists and the first to show its composition and structure.

“We have made a really big step forward in understanding the composition and structure of enamel — the tooth’s protective outer layer — at the smallest length scales,” said Joester in a statement.

Joester is the lead author of the study and an associate professor of materials science and engineering in the McCormick School of Engineering and Applied Science.

“The unstructured material, which makes up only a small fraction of enamel, likely plays a role in tooth decay. 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,” he continued.

While tooth decay is frequently not taken as seriously as other health problems, it is one of the most common chronic diseases and a serious public health issue. According to the American Dental Association, $111 billion per year is spend on dental services in the U.S. alone. That number, obviously, does not include those who fail to visit the dentist for financial or other reasons. According to the World Health Organization, nearly all adults and 60 to 90 percent of children suffer from tooth decay at some point.

For their research, the team conducted a series of experiments on rabbit, mouse and beaver enamel. Using atom-probe tomography and other techniques to map the structure, they found the amorphous structures surrounding the nanowire.

Next they subjected the teeth to acid and took before and after pictures of the results. They found that the periphery of the nowness dissolved, but not the nanowire.

The team then identified the biomaterials, such as iron and magnesium, to determine how they contribute to the resistance of the enamel to acid dissolution. In particular, they were interested in the pigmented enamel of the beaver’s powerful incisors. They found that these teeth in particular, showed an improvement over fluoride teated enamel.

“A beaver’s teeth are chemically different from our teeth, not structurally different. 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,” said Joester.

The research appears in the February 13 edition of the journal Science and a related paper appears in Frontiers in Physiology.