3D X-ray imaging unlocks the secrets of the narwhal's spiral tusk

In the Middle Ages, narwhal tusks were believed to possess magical properties and were highly prized by monarchs and nobles. Modern research has revealed that these spiral-shaped tusks are actually elongated canine teeth protruding from a narwhal's mouth, which can reach up to 10 feet in length. Using advanced three-dimensional X-ray imaging, researchers discovered that the tusk's exterior, made of cementum, has a left-handed spiral while its interior, made of dentine, exhibits a right-handed spiral.

This arrangement is believed to help the tusk grow straight, unlike tusks of other animals that curve. The double-spiral structure of the tusk provides superior stability against bending and twisting forces, potentially offering inspiration for designing bioinspired materials.