New Aspects of Tooth Anatomy Revealed by 3D Imaging

Using 3D imaging, a team of French researchers has discovered a structure within the tooth that could explain its incredible strength.

Within the tooth, between the dentin and the enamel, there is a transitional zone—a junction. At the center of this junction are fissures or striations that have been observed in 2D in the past. Until now, scientists had classified them as a secondary structure of the enamel. Today, however, a study published in the journal Archives of Oral Biology shows that these grooves are three-dimensional structures.

During this research, scientists at the Bioengineering and Nanosciences Laboratory in the Department of Dentistry at the University of Montpellier analyzed ten molars extracted from six men and four women, aged 25 to 40. Each tooth was examined using X-ray microtomography, an imaging technique that creates a three-dimensional image from a sample. They then discovered a surprising structure consisting of enamel tufts about ten micrometers thick inside the tooth. These structures have been dubbed “draped tufts” because of their regularly undulating and structured appearance and may explain the teeth’s high resistance.

Enamel is organized into prisms with varying, non-linear trajectories, especially at the dentin-enamel junction. This is what ensures the tooth’s stability. These trajectories are thought to be responsible for the formation of these “draped bushes,” which increase the tooth’s strength.

"It will be interesting to see if this is also found in other hominids."

“The prisms do not travel in a straight line to the enamel surface; they undulate, especially at the beginning, when they are close to the dentin. “We can therefore speculate that these variations, which give rise to an alternation of light and dark bands known as Hunter-Schreger bands, might be the source of the mysterious ‘drapedtufts’structures,” says Alban Desoutter of the Bioengineering and Nanosciences Laboratory at the Faculty of Dentistry in Montpellier, speaking to the magazine *Sciences et Avenir*.”

As *Sciences et Avenir* notes, a study in 2012 had already revealed the presence of these so-called “enamel bushes” in a breed of cow. “We are currently in the midst of our investigation, and we hope to secure time at the Grenoble synchrotron to continue our research. “Our study focused on fragments of adult molars; we’d like to obtain higher-resolution scans—and not just of molars. Next, it will be interesting to see if we can find this in other hominids, such as gorillas or chimpanzees,”explains Alban Desoutter.