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What Is the Hardest Substance in the Human Body?

The hardest substance in the human body is enamel, the protective outer layer of our teeth. Remarkably resilient, enamel shields teeth from daily wear and decay. Its composition of minerals makes it tougher than bone, safeguarding our smiles against the rigors of biting and chewing. Intrigued by how enamel does its job? Discover the science behind this dental defender.

Here's a trivia question that sounds like a riddle: What do you have that's harder than steel yet as brittle as glass? If you think the answer might be on the tip of your tongue, you've nearly got it.

Enamel, the tissue that coats your teeth, is the hardest substance in the human body. It's even tougher than bone. On the Mohs hardness scale, enamel rates a 5, which puts it on or above steel (although only half as hard as the toughest-known substance, diamond). Yet, if you could look closely – like, really closely – at that enamel, you would see that it is not one solid piece but many individual pieces, or rods, grouped together. This arrangement allows your teeth to absorb all kinds of pressure, deflecting the energy downward, rather than trying to sustain it. This design is crucial because if the enamel on your teeth was a solid sheet, it would fracture easily. It's just one more clever trick of nature to chew over.

Tough teeth:

  • According to National Geographic, humans can generate a maximum of 200 pounds per square inch of bite force. That's a lot, but it's nothing compared to a saltwater crocodile's jaws, which can snap shut with a force of 3,700 psi.

  • As tough as enamel is, it can be weakened by everything from a hard toothbrush to acid in foods.

  • Enamel doesn't grow back, and while it can be treated, wear can't be reversed.

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Discussion Comments


Your byline "Clear answers for common questions" does not seem to apply to this article. The author mixes hardness and toughness which are separate properties of a material. Generally toughness decreases as hardness increases.

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    • Although tooth enamel is harder than steel on the Mohs hardness scale, it is also as brittle as glass.
      By: michaeljung
      Although tooth enamel is harder than steel on the Mohs hardness scale, it is also as brittle as glass.