Strength and toughness are two structural properties that tend to be mutually exclusive. Strong materials are usually brittle while tough ones are usually weak. But materials scientist Robert Ritchie of the Lawrence Berkeley National Laboratory says that teeth combine both properties surprisingly well.

"If the whole tooth were made of enamel it would break very quickly. So there’s an underlying tougher layer called dentin. And we looked at how cracks which form in the enamel never make it to the dentin because they get blunted out. And that’s how armor works. You need a hard layer to stop a bullet for example but if it was all made of that it would just shatter so you have got to have something underneath to absorb the energy. It is not as hard but it’s tougher."

That’s how teeth are able to withstand strong bite forces and millions of mastication cycles without shattering.