By Catherine Paddock PhD

Using nanoscale technology, researchers have, for the first time, produced detailed 3-D maps of the composition and structure of mature human tooth enamel. The maps show the position of atoms critical to the process of tooth decay.

The team of material and structure engineers and dentists – from the University of Sydney in Australia – produced the 3-D maps using a relatively new microscopy technique called atom probe tomography.

The researchers describe their work in a paper published in the journal Science Advances and suggest it should help improve oral hygiene and to prevent caries or tooth decay.

According to the World Health Organisation (WHO), 60-90 percent of schoolchildren and nearly 100 percent of adults worldwide have dental cavities, which occur via the progressive dissolution of dental enamel.

Human dental enamel is the hardest tissue in the body. It protects teeth from the wear and tear of daily grinding and chewing as well as from chemical attack.

Scientists have already established that the mechanical strength and resistance to fatigue of dental enamel comes from its complex hierarchical structure of periodically arranged bundles of hydroxyapatite (HAP) nanowires.

Fast facts about tooth decayThe new study gives detailed information about important trace ions in the tough structure of tooth enamel.

  • Rates of tooth decay have fallen significantly in the United States over the last 40 years, except in young children, where they have recently started rising again
  • 42 percent of U.S. children aged 2-11 have decay in their primary teeth
  • 92 percent of U.S. adults aged 20-64 have had tooth decay in their permanent teeth; 26 percent have untreated decay.

The new study gives detailed information about important trace ions in the tough structure of tooth enamel.

Senior author Julie Cairney, materials and structures engineer and professor in Sydney’s Faculty of Engineering and Information Technologies, says:

“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.”

One of the team’s key findings surrounds the magnesium-rich regions between the hydroxyapatite nanorods that make up the structure of tooth enamel.

Prof. Cairney says this is the first direct evidence that an amorphous magnesium-rich calcium phosphate phase plays an essential role in governing the behavior of teeth. Such a phase has been proposed before, but without evidence.

One of the study’s lead researchers, Dr. Alexandre La Fontaine of Sydney’s Australian Centre for Microscopy and Microanalysis, says:

“The mapping has the potential for new treatments designed around protecting against the dissolution of this specific amorphous phase.”

Another important discovery was that the team could also see “nanoscale clumps” of organic material in the 3-D structure.

The presence of organic clumps suggests proteins and peptides occur in disparate patterns throughout the enamel, rather than all along the nanorod interfaces, as was previously thought.