What's better than toothpaste, mouthwash, fluoridated water and dental floss combined? Iron, apparently. That's what keeps the large teeth at the front of a beaver's mouth so strong and healthy.
Despite a lifetime's worth of gnawing on massive tree trunks, beavers are essentially immune to tooth decay; and that's because they've got tiny iron-rich nanowires interwoven throughout the enamel core of those outsized incisors.
In studying the composition of beavers' front teeth -- as well as other types of enamel -- researchers were able for the first time reveal the chemical contribution these amorphous internal wires offer.
All enamel is made up of rods or nanowires stacked and woven together. These spaghetti-like structures are mainly composed of hydroxylapatite, a type of calcium apatite. But surrounding these rods or wires is a layer rich in iron and magnesium, a lamination of minerals that help protect the teeth from acid damage. The ionic makeup of this lamination is the key to why beaver teeth are so strong, researchers found.
"A beaver's teeth are chemically different from our teeth, not structurally different," lead study author Derk Joester, a researcher at Northwestern University, explained in a press release.
"We found it is the minority ions -- the ones that provide diversity -- that really make the difference in protection," Joester explained. "In regular enamel, it's magnesium, and in the pigmented enamel of beaver and other rodents, it's iron."
Researchers gained this detailed insight using atom probe tomography. The technique, now common in medical research, involves a microscope-like instrument capable of revealing the cross-sectional atomic structure of a materials inside. The end result, in this case, was high-res imagery of enamel's inner atomic and ionic composition.
"Researchers can look for strategies to harden enamel against acid corrosion -- perhaps using the tougher iron-rich enamel in rodents as a blueprint," Joester wrote in a recent article.
The new study was published this week in the journal Science.