U.S. researchers say the trick sea urchins use to keep their teeth razor-sharp could lead to tools for humans that never need sharpening or honing.

Sea urchins can use their teeth to eat into stone, creating pockets where they can hide from predators and protect themselves from crashing waves. Researchers at the University of Wisconsin-Madison say despite constant scraping and grinding into rock, urchin teeth never get dull, a university release said Wednesday.

The secret is in the structure of sea urchin teeth, made up of calcite crystals arranged crosswise in layers separated by organic materials that are not as sturdy as the crystals.

"The organic layers are the weak links in the chain," Gilbert says. "There are breaking points at predetermined locations built into the teeth."

As each layer breaks away, a fresh, sharp layer of calcite crystal is exposed in an ongoing process.

"Now that we know how it works, the knowledge could be used to develop methods to fabricate tools that could actually sharpen themselves with use," she says.

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