Teeth Reveal the Source of Their Strength

Human teeth have such a remarkable strength, that dentists never cease to be amazed at how even a tooth covered in cracks can still hold together, without breaking apart. They know that the enamel, which constitutes the outer layer of the teeth, is a very strong, yet brittle material, and so they couldn't explain thus far how it was that teeth simply didn't break to pieces, and lasted a lifetime. A scientific paper, published in the April 13th issue of the journal Proceedings of the National Academy of Sciences, finally reveals the source of teeth's strength.

National Institute of Standards and Technology (NIST) expert Brian Lawn told LiveScience that the thing keeping teeth together was their microscopic, “basket-weave”-like structure, which gives enamel the ability to stop cracks from spreading. In other words, even if cracks do appear, they cannot extend beyond the area they have first affected. Naturally, when people bite on, or get hit by a very strong object, the enamel will shatter completely, but, if they use their teeth within “normal parameters,” they could last a lifetime.

During their experiments, the members of the NIST team tested teeth coming from humans, sea otters, as well as other animals, and pressured them with a metal rod, a sort of worst-case scenario for these species. They found that the cracks did not propagate too much on account of the structure of the enamel, which allowed cracks to form, but prevented them from spreading. The research was financed with money from the George Washington University Research Endowment Fund.

The find could have significant applications in dentistry, especially in designing and constructing artificial teeth. Bad ones are currently covered with crowns, made of materials that look nothing like the structure of a natural tooth. This makes these prosthetics more or less useless and subject the patient to the risk of having one breaking down in their mouth at any time. Lawn has now started working on a new class of materials, to replace the ones currently in use for creating fake teeth.

In addition to immediate applications, the discovery could also provide anthropologists with clues as to what the first hominids ate, as well as what their diet consisted of. These experts could also piece together an evolutionary time line, detailing how teeth got increasingly complex and better adapted to the foods we ate over the millennia.