Engineers drill into tooth enamel structure

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Few people enjoy going to the dentist. New research into the nano structure of human tooth enamel could help develop treatments to keep our pearly whites healthier, longer – and lead to less time in the dentist’s chair.
Credit: Peter Macdiarmid / Getty Images

It’s drummed into us from an early age: calcium helps us grow strong, healthy teeth. But magnesium is just as important – and maybe more so, a study into the molecular structure of tooth enamel shows.

A team from the University of Sydney in Australia delved into our chompers’ building blocks and found the contained magnesium-rich nano layers, suggesting the element is particularly important in enamel development.

The work, which could help develop tooth decay treatments and preventive measures, was published in Science Advances.

Aside from brushing teeth and the (hopefully) occasional trip to the dentist, we might not give tooth enamel much thought. But it’s super important – the strong mineralised barrier protects inner layers from plaque and acids produced by microorganisms living in your mouth, for instance.

Despite its value, enamel’s atomic make-up and structure on the nano scale was largely unknown. A study last year into rodent tooth enamel showed it contained magnesium amorphous calcium phosphate.

What about human teeth?

Julie Cairney, Alexandre La Fontaine and colleagues wanted to find out. Their primary research focus was not in dentistry, though – Cairney and La Fontaine are materials engineers and look to improve, among other things, metal strength.

But they realised their extensive experience with microscopy techniques, and linking the microstructure of materials to their properties, could be applied broadly – even to human tissues.

So they got their hands on a healthy adult human molar. It was sliced and subjected to optical microscopy, transmission electron microscopy and atom probe tomography.

Atom probe tomography yields information at an atomic level. Laser light evaporates atoms from a sliver of a tooth sample, which are then collected and their position and identity recorded.

The team discovered enamel comprises tiny crystalline mineral rods woven together – and the space between these rods is packed with amorphous calcium phosphate.

Amorphous calcium phosphate is an organic compound that triggers enamel formation when inorganic ions lodge into its structure. This process is called mineralisation.

Cairney, La Fontaine and their colleagues found the amorphous calcium phosphate regions were rich with magnesium ions, suggesting they are an important factor in enamel formation.

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Magnesium atoms in a needle-shaped sliver of human tooth enamel.
Credit: Tom Hartley / ACMM / The University of Sydney

Knowing how enamel forms in human teeth is a significant step forward in understanding how tooth decay actually occurs – and, of course, finding a way to stop it..

“It [the research] verifies a method that people have proposed to say how enamel forms, which means that in the long-term, now that we know how enamel forms, we might be able to develop methods to grow enamel again which is called remineralisation,” Cairney explains.

“Now the idea would be to take a tooth and dip it into pure fluorine, for example, and then you just go back and look at the difference,” La Fontaine adds.

“Do you see any replenishing of magnesium or fluorine or whatever solution you used in the tooth? Where it is? How it is? How does it work? That’s how basically you come up with treatment.”

The pair is also interested in analysing juvenile and damaged teeth, as they’ve only looked at a healthy adult sample so far.

“We really do think that there are definitely years of work ahead,” La Fontaine says.

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