In the future there will be no more dentists Friday, 30 September 2016

Tooth decay affects almost 100 per cent of adults worldwide. But new use of microscopic technologies could be the first step in stopping the degeneration of enamel and other organic tissue.

Two engineers from the University of Sydney are using a technique called atom probe tomography (APT) to map the chemical structure of the enamel of human teeth.

The technology allows three-dimensional visualization and chemical analysis at the atomic scale and can generate a deeper scientific understanding of what causes enamel to decay, says Professor Julie Cairney, Material and Structures Engineer in the Faculty of Engineering and Information Technologies.

“Dental professionals have known that certain trace ions are important in the tough structure of tooth enamel but until now it had been impossible to map the ions in detail,” says Cairney.

“The structure of human tooth enamel is extremely intricate and while we have known that magnesium, carbonate and fluoride ions influence enamel properties, scientists have never been able to capture its structure at a high enough resolution or definition.”

Cairney believes that the most exciting part isn’t the data itself, but the possibilities it entertains.

“If we understand how decay occurs and if we understand how teeth can potentially grow new enamel then there’s the potential for really amazing treatments in dentistry,” says Cairney.

“We haven’t done that, but we’ve given some information that might be able to help with that.”

Mapping the enamel

APT allowed the researchers to examine the chemical and atomic makeup of the tooth better than other technologies available, says Dr Alexandre La Fontaine, Post Doctoral Researcher in the School of Aerospace, Mechanical and Mechatronic Engineering at the University of Sydney.

“So basically this is the only machine that can give you a three dimensional image of atoms into a template,” says La Fontaine. “A classic transmission electron microscope would only give you a two dimensional projection. So it’s actually quite important. It’s the ultimate characterisation tool.”

But APT isn’t a new technology, having been used in the metal industry for years, and now by tech companies like IBM, who have used it to understand and utilise high performance semiconductors to degrees unachievable with previous technologies.

However, it’s only recently that the technology has been used to map organic tissue, and this is the first instance of it being used on humans.

“The first enamel model that was created using atom probe tomography was a rodent tooth, and that was three or for years ago,” says La Fontaine. “And that’s why we started our project on human dental enamel.”

This is the first attempt to atomically map a human tooth, and the most extensive collection of data from the atomic mapping of any tooth previously.

“The rodent tooth is usually used as a model for the human tooth but what we did was we needed to verify. So we’ve seen things very similar to the rodent tooth but we have been able to map much more of the enamel compared to what they published,” says La Fontaine.

“We were able to look at 400 to 500 million atoms, so it gave us much better statistics of what is happening in the enamel.”

Preventing bone degeneration

Understanding the chemical activity within enamel could lead to a solution for the problem of tooth decay, says Julie Cairney.

“At the moment we looked at healthy enamel, so we’re quite interested in looking if we can get microstructural information from teeth that have started to decay,” says Cairney.

Once they can understand whether it is the magnesium that dissolves in the decay process they will be on the way to reversing the demineralisation that occurs.

“If you could potentially block the acidic attack, for example, into the very core of the enamel, that would be brilliant. And then would come potentially remineralisation,” says La Fontaine.

“We want to actually verify how enamel properly dissolves and how to repair it.”

But teeth are just the start. Given the funding, there is a strong possibility that the technology could also be used to help prevent bone degeneration, says La Fontaine.

“We will apply for funding to study bone and cartilage,” says La Fontaine.

Tooth and bone are both made of calcium based chemicals called apatites. Hydroxyapatite is a type of phosphate apatite that also forms more than half of the chemical makeup of bone.

“Bone and cartilage is actually very similar to enamel chemically, It’s a type of hydroxyapatite, it’s an apatite. So yes, our plan is to do that, definitely.”

The applications of APT are extensive, so don’t be surprised if you begin hear more about its use in other areas as well.

“Just watch this space,” says La Fontaine. “Because more and more, you will see results from atom probes in various areas of science.”

[Image: This image shows the findings from the project. Magnesium-rich intergranular layers in the enamel. The needle form of the image demonstrates the shape the samples need to be cut into in order to be able to ionize the atoms individually.]