April 20, 2002 | David F. Coppedge

Teeth Resist Cracking

51; Here’s a story to share with your dentist.  You can crack a tooth, but it takes a lot of force.  This should be surprising, since tooth enamel is as brittle as glass.  The way the enamel develops, researchers found, absorbs excess energy and gives your teeth an extraordinary crack resistance.
    “Human enamel is brittle,” begins an article on Science Daily.  “Like glass, it cracks easily; but unlike glass, enamel is able to contain cracks and remain intact for most individuals’ lifetimes.
    Researchers at George Washington University found, surprisingly, a function for mistakes (or what might be mistakenly thought of as mistakes).  During tooth development, tiny imperfections called tufts form.  The tufts allow cracks to develop from the inside, not the surface, where they might otherwise form sites for decay.  “Acting together like a forest of small flaws, tufts suppress the growth of these cracks by distributing the stress amongst themselves.”  They found even more functions for these slight imperfections:

“This is the first time that enigmatic developmental features, such as enamel tufts, have been shown to have any significance in tooth function” said GW researcher Paul Constantino.  “Crack growth is also hampered by the ‘basket weave’ microstructure of enamel, and by a ‘self-healing’ process whereby organic material fills cracks extended from the tufts, which themselves also become closed by organic matter.  This type of infilling bonds the opposing crack walls, which increases the amount of force required to extend the crack later on.”

So it appears that the tooth is engineered to grow even stronger against cracking over time.  The team found strong resemblances between the teeth of sea otters and humans in these self-healing characteristics.

Did this article mention evolution?  Yes! — but not in the way you might be expecting.  No just-so story here.  Get this: “This research evolved as part of an interdisciplinary collaboration between anthropologists from The George Washington University and physical scientists from the National Institute of Standards and Technology in Gaithersburg, Md.  The team studied tooth enamel in humans and also sea otters, mammals with teeth showing remarkable resemblances to those of humans.”  That’s intelligent design, folks!  It was guided by human curiosity and following the evidence where it leads.  This is bound to cause some tooth grinding in the halls of the NCSE.

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Categories: Amazing Facts, Human Body

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