How can beaver teeth survive chomping on those trees?

Beavers can chew on huge trees but their teeth don’t break, while humans eat lollies and have to head for the dentist. Now researchers say we can learn from that.

Human teeth are coated in enamel – a complex crystalline substance  which acts as a protective barrier but can become susceptible to degradation from acids in food and drinks.

Enamel is the hardest substance in the human body but is even harder in rodents, which also have an additional outer layer of acid-resistant iron-rich enamel.

New high-resolution images of rodent incisors have revealed tiny pockets of iron-rich materials that give rodent teeth an extra layer of protection. The images also reveal that, unlike previously suggested, the iron-rich material is not responsible for the striking orange to brown colour of many rodents’ incisors. 

The findings, published in a study in the journal ACS Nano, have important implications for human dentistry.

“The functional significance of acid-resistant iron-rich enamel and the understanding of the underlying coloration mechanism in rodent incisors have far-reaching implications for human health, development of potentially groundbreaking dental materials, and restorative dentistry,” the authors write.

Photograph of two specimens of rodent incisors from the skulls of a coypu and beaver
Nano-sized pockets of iron material in rodents’ incisors (coypu on the left and beaver on the right) strengthen and protect the teeth. Credit: Adapted from ACS Nano 2024, DOI: 10.1021/acsnano.4c00578

To investigate the structural and elemental composition of rodent enamel, researchers collected incisors from beavers, coypus, squirrels, marmots, rats, voles, and mice. They took thin slices from different sections of the teeth and imaged them using optical microscopy, 3D focused ion beam tomography and scanning transmission electron microscopy. 

They found the microstructure of the iron-rich enamel contains elongated nanometre-sized pockets, which are filled with small amounts of an iron-containing ferrihydrite-like material. They also found the intense orange-brown colour of rodent incisors comes from a thin surface layer of aromatic amino acids and inorganic minerals.

The authors say that these findings: “…enable the creation of an entirely different class of dental biomaterials with enhanced properties, inspired by the ingenious designs found in nature.”

They suggest adding small amounts of ferrihydrite-like or other colourless biocompatible iron minerals to dental care products could provide protection for human tooth enamel. Additionally, incorporating small amounts of iron hydroxides into synthetic enamel could produce longer-lasting restorations for human teeth.

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