Strong teeth for beavers are a must (you try cutting down a tree with your incisors!), but how do they keep those chompers healthy and tough without access to fluoride or a toothbrush? A new study out of Northwestern University reports that beavers have natural protection against tooth decay built into the chemical structure of their teeth.
Researchers found that beaver teeth have a high concentration of iron in them. In addition to causing the teeth to be a reddish-brown color, the iron also makes the enamel harder and more resistant to acid erosion, even more than teeth treated with fluoride.
The research team studied the enamel of rabbits, mice, rats and beavers, as rodent enamel is surprisingly similar to human enamel. In a series of experiments, they subjected the teeth to acid and took before and after images. While layers of hydroxylapatite “nanowires” make up the core structure of enamel, lead author of the study Professor Derk Joester, discovered that the enamel’s acid resistance was actually controlled by the iron- and magnesium-rich material surrounding the nanowires. These minerals are the ones that support the enamel’s acid resistance and structural properties. With this discovery, Joester and his team are the first to decipher the exact composition and structure of enamel.
“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, a professor of materials science and engineering at 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.”
In addition to providing a breakthrough in detailing enamel’s composition and structure, the research could have major implications for preventing and treating tooth decay in humans.
“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.”