Researchers find shark teeth made of natural fluoride

Jul 27, 2012 by Bob Yirka report

( -- German researchers studying shark teeth have found at least two species that have fluorinated calcium phosphate - mineral fluoroapatite, as a main component, one of the main ingredients in toothpaste, which partly explains why sharks don’t ever get cavities. The researchers looked at Isurus oxyrinchus and Galeocerdo cuvier (mako and tiger sharks) and found, as they explain in their paper published in the Journal of Structural Biology, after very close examination, that the outer coating of the shark teeth contained one hundred percent fluoride.

To gain a better understanding of how manage to keep their in such pristine condition, the team looked at two species that eat in very different ways. Mako sharks rip off flesh when feeding as opposed to tiger sharks who use their teeth to slice neatly through their meal. Under close observation using regular and scanning electron microscopes, the team was able to determine the exact makeup of the ingredients of the shark’s teeth. Besides the hard crystal enamel structure that makes up the outside of the teeth, they found an inner organic dentin made of proteins which was more elastic, similar to that of . They note also the well known fact that sharks are able to replace teeth that are lost many times throughout their life cycle. The result they say, is a nearly perfect design, allowing sharks to rely on their teeth to keep them fed.

Teeth coated with fluoroapatites are known to be less water soluble than hydroxyapatite which is what humans and most other mammals have coating their teeth, which should help teeth that have them remain more stable in underwater environments and thus less prone to attacks by various bacteria which can lead to decay.

The researchers also conducted hardness tests, and found that despite the being made of a naturally harder mineral, they were not harder than human teeth; this because the crystal structure of human teeth has a pattern arrangement more suited to hardness. They noted that teeth in general tend to have such dual structures to keep them from shattering when encountering hard objects.

Explore further: Male monkey filmed caring for dying mate (w/ Video)

More information: Structure, composition, and mechanical properties of shark teeth, Journal of Structural Biology, Volume 178, Issue 3, June 2012, Pages 290–299.

The teeth of two different shark species (Isurus oxyrinchus and Galeocerdo cuvier) and a geological fluoroapatite single crystal were structurally and chemically characterized. In contrast to dentin, enameloid showed sharp diffraction peaks which indicated a high crystallinity of the enameloid. The lattice parameters of enameloid were close to those of the geological fluoroapatite single crystal. The inorganic part of shark teeth consisted of fluoroapatite with a fluoride content in the enameloid of 3.1 wt.%, i.e., close to the fluoride content of the geological fluoroapatite single crystal (3.64 wt.%). Scanning electron micrographs showed that the crystals in enameloid were highly ordered with a special topological orientation (perpendicular towards the outside surface and parallel towards the center). By thermogravimetry, water, organic matrix, and biomineral in dentin and enameloid of both shark species were determined. Dentin had a higher content of water, organic matrix, and carbonate than enameloid but contained less fluoride. Nanoindentation and Vicker’s microhardness tests showed that the enameloid of the shark teeth was approximately six times harder than the dentin. The hardness of shark teeth and human teeth was comparable, both for dentin and enamel/enameloid. In contrast, the geological fluoroapatite single crystal was much harder than both kinds of teeth due to the absence of an organic matrix. In summary, the different biological functions of the shark teeth (“tearing” for Isurus and “cutting” for Galeocerdo) are controlled by the different geometry and not by the chemical or crystallographic composition.

via Discovery

Related Stories

Stem cells grow fully functional new teeth

Jul 13, 2011

(Medical Xpress) -- Researchers from Japan recently published a paper in PLoS One describing their successful growth and transplantation of new teeth created from the stem cells of mice.

Mole rat dental structure similar to a shark

Oct 11, 2011

( -- Sharks are capable of continually growing new teeth. As the teeth age, they fall out and new ones move forward similar to that of a tooth conveyor belt. Humans, and most mammals, on the other ...

Recommended for you

Male monkey filmed caring for dying mate (w/ Video)

Apr 18, 2014

( —The incident was captured by Dr Bruna Bezerra and colleagues in the Atlantic Forest in the Northeast of Brazil.  Dr Bezerra is a Research Associate at the University of Bristol and a Professor ...

Orchid named after UC Riverside researcher

Apr 17, 2014

One day about eight years ago, Katia Silvera, a postdoctoral scholar at the University of California, Riverside, and her father were on a field trip in a mountainous area in central Panama when they stumbled ...

In sex-reversed cave insects, females have the penises

Apr 17, 2014

Researchers reporting in the Cell Press journal Current Biology on April 17 have discovered little-known cave insects with rather novel sex lives. The Brazilian insects, which represent four distinct but re ...

Fear of the cuckoo mafia

Apr 17, 2014

If a restaurant owner fails to pay the protection money demanded of him, he can expect his premises to be trashed. Warnings like these are seldom required, however, as fear of the consequences is enough to ...

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

1 / 5 (1) Jul 28, 2012
Non of the fishes that have teeth ever have cavities, not just sharks. I would guess that flushing perpetually with water (as they are, living and breathing with water!) is conducive to keep the teeth from bacterias ever establishing a foothold.

More news stories

Biologists help solve fungi mysteries

( —A new genetic analysis revealing the previously unknown biodiversity and distribution of thousands of fungi in North America might also reveal a previously underappreciated contributor to climate ...

Making graphene in your kitchen

Graphene has been touted as a wonder material—the world's thinnest substance, but super-strong. Now scientists say it is so easy to make you could produce some in your kitchen.