Dental News - Researchers create artificial enamel for airplane construction

Dental Tribune International

Thu. 9. March 2017

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ANN ARBOR, Mich., USA: Unavoidable vibrations, such as those on airplanes, cause objects with rigid structures, including flight computers, beams, chassis and motherboards, to age and crack. These could be designed more like tooth enamel to withstand repeated stresses without damage, according to researchers at the Department of Chemical Engineering at the University of Michigan. They replicated the structure of enamel by sequential growth of zinc oxide nanowire carpets, followed by layer-by-layer deposition of a polymeric matrix around these.

Most absorbing materials are soft and thus not suitable for structural components. The researchers therefore looked to nature for hard materials that are resistant to repeated shocks and vibration. They first investigated teeth, shells and bones from different species, among others. They found that these living structures changed from species to species and over time. However, under an electron microscope, they noticed that tooth enamel had a similar structure whether it came from a walrus, a tyrannosaur or even a human third molar. Through evolution, the structure of tooth enamel has not diversified.

Enamel’s unique features, including its lifetime durability, make it highly resistant to repeated stresses. It is made of micro- and nanoscale ceramic columns interspersed with a soft protein matrix, set into a hard, protective coating. This structure is effective at absorbing vibrations because the stiff columns bend under stress from above, creating substantial friction with the softer polymer surrounding them, lead engineer and Professor of Biomedical Engineering Nicholas Kotov explained.

To recreate the enamel structure, postdoctoral researcher Dr. Bongjun Yeom grew zinc oxide nanowires on a chip, then layered two polymers evenly over the nanowires, baking to cure between coats. It took 40 layers to build up a single micrometer of the enamel-like structure. He then placed another layer of the nanowires with 40 layers of polymer, repeating the whole process up to 20 times.

Using computer modelling, the researchers confirmed that the structure of the synthetic enamel diffused the forces from vibrations through the interaction between the polymer and columns. Synthetic tooth enamel has the properties of natural tooth enamel, but is lighter, more effective and, possibly, less expensive, according to Kotov.

“Artificial enamel is better than solid commercial and experimental materials that are aimed at the same vibration damping,” stated Kotov.

“We expect our findings to apply to all columnar composites and to lead to the development of high-performance load-bearing materials,” the researchers stated. Synthetic enamel would be of good use for environments in which vibrations are inescapable and electronics and structures need to be protected, such as airplanes. However, according to Kotov, automation of the production of the material will be challenging.

The study, titled “Abiotic tooth enamel”, was published online on Mar. 1 in the Nature journal. It was conducted in collaboration with the Michigan Technological University and the Illinois Applied Research Institute.