What makes your teeth so tough?

You may take them for granted, but your teeth are a marvel. They break up all your food over the course of your life, while being strong enough to withstand breakage themselves. And they’re formed using only the raw materials from the food they grind down in the first place. What’s behind their impressive strength?

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Teeth rely on an ingenious structure that makes them both hard and tough. Hardness can be thought of as the ability to resist a crack from starting, while toughness is what stops the crack from spreading.

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Very few materials have both properties. For instance, glass is hard but not tough while leather is tough but not hard. Teeth manage both by having two layers: a hard external cap of enamel, made up almost entirely of a calcium phosphate, and beneath it, a tougher layer of dentin, partly formed from organic fibers that make it flexible.

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Today, the ability to consume diverse forms of food enables mammals to survive in habitats ranging from mountain peaks and ocean depths to rainforests and deserts. So the success of our biological class is due in no small measure to the remarkable strength and adaptability of the humble mammalian molar.

From the TED-Ed Lesson How did teeth evolve? – Peter S. Ungar

Animation by Cabong Studios