Quantcast
ZME Science
  • CoronavirusNEW
  • News
  • Environment
    • Climate
    • Animals
    • Renewable Energy
    • Eco tips
    • Environmental Issues
    • Green Living
  • Health
    • Alternative Medicine
    • Anatomy
    • Diseases
    • Genetics
    • Mind & Brain
    • Nutrition
  • Future
  • Space
  • Feature
    • Feature Post
    • Art
    • Great Pics
    • Design
    • Fossil Friday
    • AstroPicture
    • GeoPicture
    • Did you know?
    • Offbeat
  • More
    • About
    • The Team
    • Advertise
    • Contribute
    • Our stance on climate change
    • Privacy Policy
    • Contact
No Result
View All Result
ZME Science

No Result
View All Result
ZME Science
No Result
View All Result
Home Science Biology

Nanoscale look at tooth enamel reveals its ‘mis-orientation’ that makes it so strong

Chomp!

Alexandru Micu by Alexandru Micu
September 30, 2019
in Biology, News, Science

A first-of-its-kind look at the nanostructure of tooth enamel helps uncover the secret of the hardest substance in the human body.

PIC mapping of tooth enamel, with colors representing degrees of nanocrystal mis-orientation.
Image credits Pupa Gilbert.

While the enamel on our teeth looks pretty much like bone, it’s not actually living tissue (while bones are). Enamel grows while teeth are developing to encase all the other material in our teeth and provides protection. Once the teeth are fully developed, they lose the ability to repair or grow new enamel. It’s not so bad, though: enamel is incredibly tough and harder, pound for zpound, than steel.

The skin of our teeth

“We apply huge pressure on tooth enamel every time we chew, hundreds of times a day,” says biophysicist Pupa Gilbert from the University of Wisconsin-Madison. “Tooth enamel is unique in that it has to last our entire lifetime. How does it prevent catastrophic failure?”

The new study reports it all comes down to enamel’s “hidden structure”. The outer layer of our teeth, they explain, is constructed out of a complex weave of hydroxyapatite nanocrystals. Hydroxyapatite is a phosphate mineral from the apatite family that contains calcium and makes up to 70% of our bones by weight.

ADVERTISEMENT

In tooth enamel, hydroxyapatite takes the shape of crystals one-thousandth the thickness of human hair. They’re so small, the team explains, that nobody has been able to get a proper look at them until now.

“Prior to this study, we just didn’t have the methods to look at the structure of enamel,” Gilbert says. “But with a technique that I previously invented, called polarisation-dependent imaging contrast (PIC) mapping, you can measure and visualise in colour the orientation of individual nanocrystals and see many millions of them at once.”

Using the PIC technique on human tooth enamel, the team spotted that the hydroxyapatite nanocrystals were not oriented in as we had previously assumed. Instead, they’re bundled up into ‘rods’ and ‘interrods’. The team further describes a gradual change in the orientation between adjacent nanocrystals that was similarly unexpected. Differences in orientation between adjacent crystals ranged between 1 and 30 degrees, they report.

Get more science news like this...

Join the ZME newsletter for amazing science news, features, and exclusive scoops. More than 40,000 subscribers can't be wrong.

   

“We propose that mis-orientation of adjacent enamel nanocrystals provides a toughening mechanism,” the study reads. “If all crystals are co-oriented, a transverse crack can propagate across crystal interfaces, whereas if the crystals are mis-oriented a crack primarily propagates along the crystal interfaces.”

While testing their hypothesis in real life would be very difficult, computer modeling of the enamel’s structure and its behavior supports the team’s view. These models showed that cracks could spread through enamel’s crystal structure through pressure and how, also revealing that cracks propagated more quickly through perfectly-aligned crystal networks. The researchers therefore believe that the angles of mis-orientation they found in enamel is the best at deflecting cracks, selected for over the course of millions of years of natural evolution.

ADVERTISEMENT

“Crack deflection is a well-established toughening [mechanism], we therefore conclude that in enamel the observed mis-orientations play a key mechanical role: they increase the toughness of enamel at the nanoscale, which is fundamentally important to withstand the powerful masticatory forces, approaching 1,000 newtons, repeated thousands of times per day.”

The paper “The hidden structure of human enamel” has been published in the journal Nature Communications.

Alexandru Micu

Alexandru Micu

Stunningly charming pun connoisseur, I have been fascinated by the world around me since I first laid eyes on it. Always curious, I'm just having a little fun with some very serious science.

Follow ZME on social media

ADVERTISEMENT
ADVERTISEMENT
ADVERTISEMENT
ADVERTISEMENT
  • Coronavirus
  • News
  • Environment
  • Health
  • Future
  • Space
  • Feature
  • More

© 2007-2019 ZME Science - Not exactly rocket science. All Rights Reserved.

No Result
View All Result
  • Coronavirus
  • News
  • Environment
    • Climate
    • Animals
    • Renewable Energy
    • Eco tips
    • Environmental Issues
    • Green Living
  • Health
    • Alternative Medicine
    • Anatomy
    • Diseases
    • Genetics
    • Mind & Brain
    • Nutrition
  • Future
  • Space
  • Feature
    • Feature Post
    • Art
    • Great Pics
    • Design
    • Fossil Friday
    • AstroPicture
    • GeoPicture
    • Did you know?
    • Offbeat
  • More
    • About
    • The Team
    • Advertise
    • Contribute
    • Our stance on climate change
    • Privacy Policy
    • Contact

© 2007-2019 ZME Science - Not exactly rocket science. All Rights Reserved.