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This is Scientific American's 60-second Science, I'm Christopher Intagliata.

Of all the stuff you can buy on eBay — here's a new one: human teeth. "I think I probably averaged maybe $5 a tooth." Kelly Keenan, a biochemist at Stockton University in New Jersey¹. Keenan chased down the chompers to investigate what whitening strips do to a tooth's chemical composition. So she stuck the teeth in styrofoam, applied² the whitening strips per manufacturer instructions, and added some artificial saliva³: a liquid mixture at the pH and with salts you'd find in regular spit.

Treatments complete, she extracted proteins from the teeth. And found that the more rounds of whitening the teeth experienced, the fewer proteins she could recover — because hydrogen peroxide in the whitening strips was snipping⁴ chemical bonds. "The bigger picture is that hydrogen peroxide can penetrate⁵ the enamel⁶ and dentin and it can cause your proteins to break down. And smaller pieces are removed from those proteins."

She and her undergraduate students presented on that research at the 2019 Experimental Biology meeting in Orlando. Now this is just a preliminary study. And the pulp⁷ of your teeth can replenish⁸ proteins in the dentin, though not the enamel — so it's unclear whether these effects would cause permanent damage in real, living teeth. One thing's for sure: supplies of teeth for experiments seem to be plentiful⁹.

I think I bought a set of 15. And the person's like, let me know if you need more. This person also claimed the teeth were from his mouth, which, you don't have that many more to go!

Thanks for listening for Scientific American — 60-Second Science. I'm Christopher Intagliata.