Can a sea mollusk's teeth aid in design of materials

The first study using an atomic-scale imaging tool to look at the chemical structure of a sea creature’s tooth has important implications for human dentistry including the potential for creating better, stronger materials for tooth replacement and for treating flouritis.

Two researchers at Northwestern University, who released their results in January, used atom-probe tomography to study the teeth of a tiny sea creature, an Eastern beaded chiton. They created a three-dimensional map identifying the location and identity of millions of atoms that make up the tiny creature’s teeth.

The sea mollusk has teeth that are similar to human teeth in significant ways. Both have a hard outer layer, like enamel, and a soft core.

“The general structure of the tooth is reminiscent of human teeth,” said Dirk Joester, who was lead author of the paper and is the Morris E. Fine junior professor in material and manufacturing at the McCormick School of Engineering and Applied Materials.

The chiton’s outer layer is composed of magnetite, a tough iron oxide that gives the teeth a black sheen. The marine creature feeds on algae that grow on rocks and, in a manner comparable to a conveyor-belt, it creates a new row of teeth every day to replace older, worn teeth that are moved out of the way.

The ability to see new and mature teeth made the chiton an ideal subject to study.

“You can go back in time and see the (older) teeth,” said Joester. “Each row is less mineralized. It gives us a picture of the entire development of the teeth.”   

Joester, along with Lyle Gordon, a doctoral student in his lab, were able to locate organic fibers hidden in the magnetite. The map revealed the first direct proof that carbon-based fibers, each between 5 and 10 nanometers in diameter, also contain either sodium or magnesium ions. The team also was the first to demonstrate proof of the location, size and chemical composition of the organic fibers inside the mineral.

Joester said being able to understand the architecture of teeth on a nanoscale, and how inorganic and organic materials interface, will lead to the creation of more resilient tooth replacement materials. Those materials will combine the best properties of organic and inorganic materials.

“If you can understand biological materials than you can reverse engineer a solution,” he said.

He also said it may allow for better treatment of an increasing problem, flouritis.

“Flouritis is really on the rise, but it’s poorly understood,” he said. “We’ll be able to better understand how fluoride moves around the teeth and see it at a much higher resolution.”

Other applications include the tracking of cancer and osteoporosis drugs in the bone.

Joester said he is currently is using atomic-scale imaging tools to study the teeth of rats and pigs and expects to have results in about a year.