Beaver teeth are tough as iron, literally

We drink water with flouride added to help strengthen our teeth.

You've probably been to the dentist and had flouride treatments that taste like bubble gum.

You brush your teeth with toothpaste that has flouride in it, and maybe you even use mouthwash to help strengthen your enamel.

Beavers don't have to do any of that, and they still have strong teeth --- strong enough to chew right through a tree.

Why is that?

Beavers chew through trees, shrubs and branches and then drag those to their dams and lodges. They chew fast and are able to fell an 8-foot tree in only five minutes.

Beavers don't have the most beautiful teeth. In fact, they have dark orange teeth, because their teeth have a different chemical makeup than human teeth. Beaver teeth have thick enamel on the front side that contain iron, keeping the teeth strong. In fact, a study by Northwestern University looked at how humans could improve their teeth using information from beaver teeth.

In addition to being strong, beaver teeth also need to be very sharp to chew through wood, and they need to stay sharp. Think of a knife or an ax. When you use it to chop hard items many times, that sharp blade dulls and needs to be sharpened. Beaver teeth also need to be sharpened as they dull down, but they don't have a knife sharpener. Instead, beaver teeth are self-sharpening.

On the front a beaver tooth is the hard enamel with the iron. The inside of the tooth is softer and wears away as the beaver gnaws, so that leaves a sharp edge of tough enamel. It's like they have a built-in knife sharpener.

However, that constant need to sharpen their teeth means that beavers also need their teeth to keep growing. Human teeth don't grow continuously, because we don't need them to. Beavers are constantly wearing down their teeth, so their teeth are constantly growing.