August 1, 2006

An international team of researchers have finally got their teeth into making artificial dental enamel. Their work, published in the journal Advanced Materials, could lead to new tough coatings for engineering applications as well as the possibility of a natural fix for broken or rotten teeth that avoids heavy metal fillings.

Researchers have chewed over how to make novel materials that mimic some of the best physical and chemical properties of natural compounds for many years. Among such natural materials is dental enamel, which is not only smooth, but very hard, making it a potential coating for engineering components in which wear and tear are a normally serious problem.

Dental enamel is the outermost layer of the teeth and is the hardest mineralized tissue in the human body. It is composed mainly of millions of microscopic crystals of the mineral hydroxyapatite. These tiny hexagonal rods pack together to form a structure known as the enamel prism. The tight packing of these units makes all the difference between "al dente" and a slurp by protecting the living tooth within and making it hard enough to bite through most foods.

Cells, known as ameloblasts, build the dental enamel from mineral salts and enamel proteins. However, once the enamel layer is complete, the ameloblast cells die, leaving behind an essentially dead coating on each tooth. If you damage the enamel, there are no quick fix cells to carry out a repair and regenerate it.

Brian Clarkson of the University of Michigan and colleagues in Poland have now taken a bite out of nature's recipe book and used the so-called hydrothermal method to make artificial dental enamel. The hydrothermal approach has been used to make other materials before and is analogous to using a pressure cooker. The ingredients are crystallized from water under high pressure so that it is well above its boiling point. This is the first time hydrothermal chemistry has been used to create artificial dental enamel.

Under the microscope, Clarkson's synthetic dental enamel has a very similar crystal structure to natural enamel. The new synthetic material is also almost as tough as natural enamel and supports the growth of living cells. As such it might one day be used to grow artificial teeth, something that anyone who suffers daily ritual of dunking their false teeth in sterilizing solution at bed time might welcome.

"This work demonstrates the potential of applying nanotechnology to the direct creation of biomaterials with a specific biological architecture, in this case, human enamel," Clarkson says. "We are now working on producing thicker apatite films and blocks of this synthetic enamel to be used as veneer coverings for unsightly teeth and caps (crowns) for teeth which are heavily filled and/or broken down."