Flying by the skin of our teeth

It's been a mystery: how can our teeth withstand such an enormous amount of pressure, over many years, when tooth enamel is only about as strong as glass? A new study by Prof. Herzl Chai of Tel Aviv University's School of Mechanical Engineering and his colleagues at the National Institute of Standards and Technology and George Washington University gives the answer.

The researchers applied varying degrees of mechanical pressure to hundreds of extracted teeth, and studied what occurred on the surface and deep inside them. The study, published in the May 5, 2009, issue of the Proceedings of the National Academy of Sciences, shows that it is the highly-sophisticated structure of our teeth that keeps them in one piece ― and that structure holds promising clues for aerospace engineers as they build the aircraft and space vehicles of the future.

"Teeth are made from an extremely sophisticated composite material which reacts in an extraordinary way under pressure," says Prof. Chai. "Teeth exhibit graded mechanical properties and a cathedral-like geometry, and over time they develop a network of micro-cracks which help diffuse stress. This, and the tooth's built-in ability to heal the micro-cracks over time, prevents it from fracturing into large pieces when we eat hard food, like nuts."

News the aviation industry can bite into

The automotive and aviation industries already use sophisticated materials to prevent break-up on impact. For example, airplane bodies are made from composite materials ― layers of glass or carbon fibers — held together by a brittle matrix.

In teeth, though, fibers aren't arranged in a grid, but are "wavy" in structure. There are hierarchies of fibers and matrices arranged in several layers, unlike the single-thickness layers used in aircrafts. Under mechanical pressure, this architecture presents no clear path for the release of stress. Therefore, "tufts" ― built-in micro cracks ― absorb pressure in unison to prevent splits and major fractures. As Prof. Chai puts it, tooth fractures "have a hard time deciding which way to go," making the tooth more resistant to cracking apart. Harnessing this property could lead to a new generation of much stronger composites for planes.

Prof. Chai, himself an aerospace engineer, suggests that if engineers can incorporate tooth enamel's wavy hierarchy, micro-cracking mechanism, and capacity to heal, lighter and stronger aircraft and space vehicles can be developed. And while creating a self-healing airplane is far in the future, this significant research on the composite structure of teeth can already begin to inspire aerospace engineers — and, of course, dentists.

Creating a super-smile

Dental specialists looking for new ways to engineer that picture-perfect Hollywood smile can use Dr. Chai's basic research to help invent stronger crowns, better able to withstand oral wear-and-tear. "They can create smart materials that mimic the properties found in real teeth," he says.

In natural teeth, there may not be any way to speed up the self-healing ability of tooth enamel, which the Tel Aviv University research found is accomplished by a glue-like substance that fills in micro-cracks over time. But fluoride treatments and healthy brushing habits can help to fill in the tiny cracks and keep teeth strong.

Source: Tel Aviv University (news : web)

   

• VOR - Aug 20, 2009
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  teeth with normal roots are stronger than those with roots removed (root canaled). I think root canals also remove lower enamel etc that weakens that area. ALWAYS get a crown on a root canal, ASAP. If you think your root-canaled tooth is still as stong, you will be sorely disappointed and lose the entire tooth (then need an implant or bridge) when you eventual accidentally bite on a corn kernel or something. I tell you this because it happened to me. I won't make that mistake again. If you think a crown is annoying try an implant, or bridge (which is like 2 crowns on healthy teeth).
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• Birthmark - Aug 21, 2009
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  When will they be able to create artificial teeth for the public? My mother lost her teeth at a young age due to a gluten intolerance, and I don't want it to happen to me, and it would help her and all other people that have lost teeth through accidents, disease, or simply age.
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