Detect special structure in human tooth enamel

Enamel looks like bone, but it is not really living tissue. The outer layer of the tooth encapsulates and protects the other tissue inside the tooth, formed when we were young, and once the tooth is developed, it is incapable of self-repair or natural regrowth.

Fortunately, the process of creating tooth enamel produces a substance that is very durable, even . more than steel. New research shows an unprecedented mechanism that helps with its exceptional resilience.

"We apply enormous pressure on tooth enamel every time we chew, hundreds of times a day," says physiologist Pupa Gilbert from the University of Wisconsin-Madison.

The structure of special human enamel.

The answer lies in what researchers call the "hidden structure" of tooth enamel , which is the infinite arrangement of nanocrystals that make up our outer teeth.

These tiny crystals are made from a type of calcium apatite called hydroxyapatite . The same mineral is found in the teeth of other organisms and the crystals are actually very small, less than a thousandth of a human hair thick.

"Prior to this study, we had no method to examine the structure of tooth enamel. But with a technique that I had previously invented, called polarization dependent image contrast mapping (PIC). ) , you can measure and display colors in the direction of the individual nanocrystals and see millions of them at the same time , ' says Gilbert.

The new method makes the architecture of complex biological samples instantly visible to the naked eye, and in doing so, reveals something scientists have never seen before.

Using PIC mapping on human teeth, the researchers observed that hydroxyapatite nanocrystals were not oriented in the way the researchers had previously assumed.

In tooth enamel, the crystals are bundled into forms called rods and alternating , but the team has found a gradual change in direction between the unexpectedly adjacent nanocrystals, with determination. The direction of deviation is between 1 and 30 degrees in adjacent crystals.

"We believe that the misalignment of adjacent enamel nanocrystals provides a hardening mechanism. If all the crystals are in the same direction, a horizontal crack may propagate across the crystal interfaces," he said. while if the crystals are in the wrong direction, the cracks mainly propagate along the crystal interfaces, ' the researchers said.

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