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Drilling teeth and filling them with metals may soon be considered a 20th-century barbarism, a throwback to the time when dentists were barbers.
For 20 years, scientists at USC’s Center for Craniofacial Molecular Biology have been analyzing tooth enamel — the hardest substance found in vertebrates — with the goal of one day replacing gold and silver fillings with a man-made material identical or similar to the organic stuff.
Recently, School of Dentistry research professor A.G. Fincham and his colleagues identified the tiny spheres that regulate the formation and organization of tooth enamel. Called nanospheres, these minuscule structures control tooth enamel’s crystalline growth.
Crystalline? Yep. “Essentially, your teeth are made of rock,” says Fincham.
CCMB researchers first saw the spheres in 1994. “Magnified, they looked like tiny ping-pong balls among the long ribbons of crystal,” Fincham says. Under a more powerful atomic-force microscope, the spheres were seen to be uniformly 18 to 20 nanometers in diameter (roughly 1/500th the size of a red blood cell).
The CCMB team had used nano-spheres four years ago as an ingredient in cloning a synthetic version of mouse amelogenin, a naturally occurring tooth-specific protein. Researchers can now
produce this protein in quantity.
“The structure of the amelogenin enamel protein is virtually the same in all vertebrates — from wallabies to humans — suggesting it has a very specialized function,” Fincham says. “That function is to spontaneously self-assemble into a matrix with nanospheres.”
Currently, CCMB researchers are growing a special tooth enamel crystal within synthetic matrices. The crystals grow only on their end faces, building a scaffold on which mature enamel can eventually form. Once enzymes break down the amelogenin proteins, the crystals start to grow on all faces. They thicken, clump together and create mature enamel.
For now, the crystals grown in the lab are about 100 times smaller than
the crystals nature makes. They grow haphazardly, and the resulting material is considerably weaker than natural enamel.
“We can’t make enamel yet, but we can see how nature does it,” Fincham says.
Entrepreneurs, take note: there’s more at stake here than nice teeth. “The same principles that nature uses to make enamel might also be applied to create novel synthetic materials,” Fincham says.
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