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NEWS

March 2022 ESRFnews

Composite tooth fillings often fail due not to poor dentistry, but to stresses that build up and deform them just after placement. That is the conclusion of researchers at the Charité University in Berlin, Germany, who used the ESRF s ID19 beamline to study damaged teeth as soon as they have been filled.

Performing time-lapse radiography and microtomography enhanced by X-ray phase-contrast, as well as digital image correlation at sub-micrometer resolution, dentist and scientist Paul Zaslansky and colleagues found that within minutes of crystallising in a tooth cavity, a glass polymer filling ceases to relax and begins deforming due to internal stress, as the polymer and glass components interact. The stress can cause the detachment of the root filling or deformation of the tooth cavity walls, and is worst in small cavities, where gaps tend to appear, providing potential sites for infection (Acta Biomater. 140 350). A bigger restoration is going to generate less stresses than a smaller one, which is contrary to what is usually thought, says Zaslansky.

Zaslansky s colleague Kerstin Bitter (pictured left, below), a teacher and practising dentist, says it was deeply impressive, and a bit shocking to see nearly in real time how fillings can delaminate after placement. [Our findings represent] a true paradigm shift, as we, dentists, have always believed that we can fully control how these materials behave.

Don t blame your dentist, say ID19 users

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EBS beamlines gear up

About half of all the flagship and refurbishment beamlines and facilities of the ESRF EBS upgrade programme are ready or near-ready for research. Despite challenges and delays resulting from the COVID-19 pandemic, the ID27 beamline and the high-power laser facility (HPLF) at the ID24 beamline have already welcomed their first users, while the BM18 and ID29 flagship beamlines are beginning to host in-house and friendly users prior to being fully opened. ID27, one of the three EBS

refurbishment beamlines, welcomed its first users in November last year. Dedicated to high-pressure and high- temperature experiments, the beamline will provide significantly higher photon flux density and higher coherence than its predecessor, especially for photon energies above 20 keV the energy range most relevant for diffraction and imaging at extreme conditions. This will enable a new class of nano-X-ray diffraction, X-ray fluorescence and X-ray imaging studies. One month after ID27, the

new HPLF welcomed its first users. Integrated with the ID24 refurbishment beamline, the facility can blast samples with a laser of 50 J energy to induce dynamic compression. It will help tackle the exotic state of warm dense matter found in certain planets, as well as new energy sources, such as internal confinement fusion, and new, super- strong materials. The refurbishment of ID24 itself, to house a branch with a double-crystal monochromator for scanning extended X-ray absorption fine structure spectroscopy, is due to open to users by the start of next year. Meanwhile, the BM18 hutch

tomographically scanned its first complete sample (an entire human brain) in December last year. A brand new flagship beamline dedicated to

phase-contrast tomography, BM18 makes use of the EBS s ultra-coherent X-rays for propagation distances up to 40 m, meaning exceptionally high- detail non-destructive 3D imagery, even on samples up to 2.5 m × 1.5 m in size. Due to material shortages, the large tomographic stage will only be available come the 2023/I period; however, a smaller stage was receiving proposals for the 1 March deadline this year. Every new scan of an organ we do on BM18 during the present commissioning phase becomes the best scan ever, and this tendency should continue for quite some time, says BM18 scientist-in-charge Paul Tafforeau. As this issue went to press, the beamline was welcoming friendly users from the Fraunhofer Institute, as well as Lee Berger of the University of Witwatersrand in Johannesburg, South Africa, bringing fossils of the early human ancestor Australopithecus sediba that was first scanned at the ESRF 12 years ago.

Serial success Another flagship beamline, ID29, is expected to welcome friendly users in June this year. Pioneering the technique of serial synchrotron crystallography, it will overcome the problem of traditional crystallography beamlines in which macromolecules can become damaged before they impart all their structural information. It also allows data collection at room temperature, and can even be used to perform time-resolved experiments. The refurbishment beamline

ID10 for surface science and the flagship beamline ID18 for coherence applications are set for operation in 2024, while the flagship beamline ID03 for hard X-ray diffraction microscopy is expected to become fully operational this time next year.

Every new scan of an organ we do on BM18 during the present commissioning phase becomes the best scan ever, and this tendency should continue for quite some time

Nicolas Sevelin- Radiguet (left) and Raffaella Torchio test out the new high-power laser facility (HPLF).