Diamond is home to an ever-evolving array of beamlines and instruments, allowing scientists from a wide variety of disciplines to collect high-quality, high-resolution data for their groundbreaking research. In materials science, X-ray imaging and tomography experiments can determine the 3D microstructure of samples, while X-ray diffraction techniques offer the phase composition and stress distribution. Most synchrotron beamlines are designed to offer one or the other, with a few that can do both – but not at the same time. Switching between the modes can be complicated and time consuming. Diamond’s Dual Imaging and Diffraction beamline (DIAD) provides both imaging and diffraction capabilities in one instrument. Its novel dual beam design operates with two independent beams meeting at the sample position, one setup for imaging and one for diffraction. By constantly switching between the two modes, DIAD enables in situ and in operando measurements and time-resolved studies. Understanding the complex structure of tooth enamel, the factors involved in its decay and potential strategies for its remineralisation exemplify some outstanding tasks in biomedical materials science that can benefit from the dual beamline approach. In work recently published in Chemical & Biomedical Imaging, a group of researchers from the University of Oxford and the University of Birmingham (led by Professor Alexander Korsunsky) detail a proof-of-concept study that demonstrated how the unique capabilities of DIAD can be used to consider different options for remineralisation and to grade them in terms of how well they work.
Human teeth are a miracle of biological engineering. Their remarkable strength and resilience come from a combination of hard external enamel over an interior of flexible dentine. On the microscopic scale, enamel is built from nanoscale hydroxyapatite (HAp) crystallites, bundled together into micron-scale rods with surrounding inter-rod regions. Delving deeper into the extraordinary structure of teeth provides valuable insights for the development of strong, bio-inspired materials. However, as we’re all aware, teeth aren’t impervious, and can rot away under the onslaught of an acid-provoking modern diet. Unlike those of some other animals (such as rodents), human teeth don’t regenerate. Once they are damaged, we must face the pain of a “drill and fill” repair, or the fitting of synthetic prosthetic replacements.
Project lead Prof Alexander Korsunsky, from the University of Oxford, said:
Teeth are a fascinating example of nature's hierarchical structuring from the nanoscale. Whereas bone and dentine, the inner part of the tooth, remain vascularised and living - meaning constantly renewing, changing, rebuilding, remodelling - enamel is one part of the human body that doesn’t. Nature effectively builds pieces of stone subjected to extreme thermal, chemical and mechanical attack, that can last up to 100 years. In our first major research project we set out to understand the processes involved in dental caries and how they interact with the structure of teeth. Now that another major four-year project has been awarded, we are out to explore what could be done to reverse caries and remineralise enamel.
Prof Korsunsky continued:
It is tremendously important that access to large facilities such as synchrotrons and neutron sources is free at the point of use based on proposals are judged solely on their own merit. Any researcher who – for whatever reason – doesn’t have a current grant can put forward a proposal. If judged good enough, this allows scientists to conduct their experiments, publish the results and develop their ideas. This is how our way forward started with the teeth project. That led us to receiving multi-million EPSRC research grants, with the great benefit of working in close collaboration with Prof Gabriel Landini’s team at Birmingham’s School of Dentistry.
Synchrotron techniques are key to understanding the complex microstructure of tooth enamel. Dr Cyril Besnard (MBLEM, University of Oxford) led several of the team’s experimental studies on Diamond’s different beamlines.
Dr Besnard explained:
As Alexander said, the hierarchical structure of the tooth - from micro to nano – is very interesting to study. The acid produced by bacteria in the mouth demineralises in a complex manner, through preferential demineralisation that leads to the loss of mechanical strength. To develop a remineralisation strategy, we first need to understand the structure of pristine enamel, and then what happens during caries to see where and how the weak points are formed. To extract complete information, we had to combine several techniques going down all the way to the nanoscale, working operando to follow the process and obtain time-resolved information. DIAD is the perfect beamline for these studies, and we were fortunate to have access to it during its commissioning phase. Even though that was during the COVID-19 lockdowns, and we had to work remotely, the beamline team with Dr Hans Deyhle on site carrying out the experimental work, led by Dr Sharif Ahmed, were outstanding in enabling our studies.
The team were able to achieve collocation and correlation between WAXS (wide-angle X-ray scattering), 2D (radiographic), and 3D (tomographic) imaging. X-ray imaging in 2D or 3D modes offers details of the sample microstructure, with X-ray scattering data adding nanoscale and ultrastructural information such as phase and preferred orientation (texture). Diffraction gauge volumes could be visualised within the tomographic data sets, revealing the underlying local information to support the interpretation of the diffraction patterns. Time-dependent WAXS pattern evolution tracked the progression of demineralisation.
Prof Korsunsky said: "Whilst remineralising a tooth we risk creating an unsupported surface that will simply collapse again. It is important to lay good foundations and build from bottom up – we need to visualise what's going as the process is unfolding. However, just seeing density is not enough. It is important for us to know how the crystals that form lay and what their orientation is – we need diffraction for that. We discovered that DIAD's unique capabilities allow us to screen different options and to grade them in terms of how well they work."
To find out more about the DIAD beamline or discuss potential applications, please contact Principal Beamline Scientist Sharif Ahmed: [email protected]
Besnard C et al. The DIAD Approach to Correlative Synchrotron X-ray Imaging and Diffraction Analysis of Human Enamel. Chemical & Biomedical Imaging 2.3 (2024): 222-232. DOI:10.1021/cbmi.3c00122.
Besnard C et al. Synchrotron X-ray Studies of the Structural and Functional Hierarchies in Mineralised Human Dental Enamel: A State-of-the-Art Review. Dentistry Journal 11.4 (2024). DOI:10.3390/dj11040098.
Reinhard C et al. Beamline K11 DIAD: A new instrument for dual imaging and diffraction at Diamond Light Source. Journal of Synchrotron Radiation 28.6 (2021): 1985-1995. DOI:10.1107/S1600577521009875.
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