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Instruments / Technical Area	Publication Details	Published
I13-2-Diamond Manchester Imaging	Time-lapse in situ 3D imaging analysis of human enamel demineralisation using X-ray synchrotron tomography Cyril Besnard , Ali Marie , Sisini Sasidharan , Robert A. Harper , Shashidhara Marathe , Jonathan Moffat , Richard M. Shelton , Gabriel Landini , Alexander M. Korsunsky Dentistry Journal 11 DOI: 10.3390/dj11050130 Diamond Proposal Number(s): [25756] Open Access Show Abstract ▼ Abstract: Caries is a chronic disease that causes the alteration of the structure of dental tissues by acid dissolution (in enamel, dentine and cementum) and proteolytic degradation (dentine and cementum) and generates an important cost of care. There is a need to visualise and characterise the acid dissolution process on enamel due to its hierarchical structure leading to complex structural modifications. The process starts at the enamel surface and progresses into depth, which necessitates the study of the internal enamel structure. Artificial demineralisation is usually employed to simulate the process experimentally. In the present study, the demineralisation of human enamel was studied using surface analysis carried out with atomic force microscopy as well as 3D internal analysis using synchrotron X-ray tomography during acid exposure with repeated scans to generate a time-lapse visualisation sequence. Two-dimensional analysis from projections and virtual slices and 3D analysis of the enamel mass provided details of tissue changes at the level of the rods and inter-rod substance. In addition to the visualisation of structural modifications, the rate of dissolution was determined, which demonstrated the feasibility and usefulness of these techniques. The temporal analysis of enamel demineralisation is not limited to dissolution and can be applied to other experimental conditions for the analysis of treated enamel or remineralisation.	May 2023
B16-Test Beamline DIAD-Dual Imaging and Diffraction Beamline E01-JEM ARM 200CF E02-JEM ARM 300CF I08-Scanning X-ray Microscopy beamline (SXM) I12-JEEP: Joint Engineering, Environmental and Processing I13-1-Coherence I13-2-Diamond Manchester Imaging I14-Hard X-ray Nanoprobe	Synchrotron X-ray studies of the structural and functional hierarchies in mineralised human dental enamel: a state-of-the-art review Cyril Besnard , Ali Marie , Sisini Sasidharan , Robert A. Harper , Richard M. Shelton , Gabriel Landini , Alexander M. Korsunsky Dentistry Journal 11 DOI: 10.3390/dj11040098 Open Access Show Abstract ▼ Abstract: Hard dental tissues possess a complex hierarchical structure that is particularly evident in enamel, the most mineralised substance in the human body. Its complex and interlinked organisation at the Ångstrom (crystal lattice), nano-, micro-, and macro-scales is the result of evolutionary optimisation for mechanical and functional performance: hardness and stiffness, fracture toughness, thermal, and chemical resistance. Understanding the physical–chemical–structural relationships at each scale requires the application of appropriately sensitive and resolving probes. Synchrotron X-ray techniques offer the possibility to progress significantly beyond the capabilities of conventional laboratory instruments, i.e., X-ray diffractometers, and electron and atomic force microscopes. The last few decades have witnessed the accumulation of results obtained from X-ray scattering (diffraction), spectroscopy (including polarisation analysis), and imaging (including ptychography and tomography). The current article presents a multi-disciplinary review of nearly 40 years of discoveries and advancements, primarily pertaining to the study of enamel and its demineralisation (caries), but also linked to the investigations of other mineralised tissues such as dentine, bone, etc. The modelling approaches informed by these observations are also overviewed. The strategic aim of the present review was to identify and evaluate prospective avenues for analysing dental tissues and developing treatments and prophylaxis for improved dental health.	Apr 2023
I08-Scanning X-ray Microscopy beamline (SXM) I14-Hard X-ray Nanoprobe	Nanoscale correlative X-ray spectroscopy and ptychography of carious dental enamel Cyril Besnard , Ali Marie , Sisini Sasidharan , Petr Buček , Jessica Walker , Julia E. Parker , Thomas E. J. Moxham , Benedikt Daurer , Burkhard Kaulich , Majid Kazemian , Richard M. Shelton , Gabriel Landini , Alexander M. Korsunsky Materials & Design 375 DOI: 10.1016/j.matdes.2022.111272 Diamond Proposal Number(s): [30684, 31005] Open Access Show Abstract ▼ Abstract: This study reports the characterisation of human dental enamel caries using synchrotron nanoscale correlative ptychography and spectroscopic mapping in combination with scanning electron microscopy. A lamella ̴2.4 µm thick was extracted from a carious enamel region of a tooth using focused ion beam-scanning electron microscopy and transferred to two synchrotron beamlines to perform hard X-ray nano-fluorescence spectroscopy simultaneously with differential phase contrast mapping at a beam size of 50 nm. Soft X-ray ptychography data was then reconstructed with a pixel size of 8 nm. The two dimensional variation in chemistry and structure of carious enamel was revealed at the nanoscale, namely, the organisation of hydroxyapatite nano-crystals within enamel rods was imaged together with the inter-rod region. Correlative use of electron and X-ray scanning microscopies for the same sample allowed visualisation of the connection between structure and composition as presented in a compound image where colour indicates the relative calcium concentration in the sample, as indicated by the calcium Kα fluorescence intensity and grey scale shows the nanostructure. This highlights the importance of advanced correlative imaging to investigate the complex structure-composition relationships in nanomaterials of natural or artificial origin.	Oct 2022
E01-JEM ARM 200CF I13-2-Diamond Manchester Imaging	Hierarchical 2D to 3D micro/nano-histology of human dental caries lesions using light, X-ray and electron microscopy Cyril Besnard , Ali Marie , Petr Buček , Sisini Sasidharan , Robert A. Harper , Shashidhara Marathe , Kaz Wanelik , Gabriel Landini , Richard M. Shelton , Alexander Korsunsky Materials & Design 394 DOI: 10.1016/j.matdes.2022.110829 Diamond Proposal Number(s): [29256, 30666] Open Access Show Abstract ▼ Abstract: Dental caries is a widespread disease that damages teeth by heterogeneous dissolution. Conventional histology identifies different zones within carious lesions by their optical appearance, but fails to quantify the underlying nanoscale structural changes as a function of specific location, impeding better understanding of the demineralisation process. We employ detailed collocative analysis using different imaging modalities, resolutions and fields of view. Focused ion beam-scanning electron microscopy (FIB-SEM) reveals subsurface 3D nanostructure within milled micro-sized volumes, whilst X-ray tomography allows less destructive 3D imaging over large volumes. Correlative combination of these techniques reveals fine detail of enamel rods, inter-rod substance, sheaths, crystallites and voids as a function of location. The degree of enamel demineralisation within the body of the lesion, near its front, and at the surface is visualized in 3D. We thus establish the paradigm of dental 3D nano-histology as an advanced platform for quantitative evaluation of caries-induced structural modification.	Jun 2022
I13-2-Diamond Manchester Imaging	4D microstructural changes in dentinal tubules during acid demineralisation Nathanael Leung , Robert A. Harper , Bin Zhu , Richard M. Shelton , Gabriel Landini , Tan Sui Dental Materials 55 DOI: 10.1016/j.dental.2021.09.002 Diamond Proposal Number(s): [20155] Show Abstract ▼ Abstract: Objective: Dental erosion is a common oral condition caused by chronic exposure to acids from intrinsic/extrinsic sources. Repeated acid exposure can lead to the irreversible loss of dental hard tissues (enamel, dentine, cementum). Dentine can become exposed to acid following severe enamel erosion, crown fracture, or gingival recession. Causing hypersensitivity, poor aesthetics, and potential pulp involvement. Improving treatments that can restore the structural integrity and aesthetics are therefore highly desirable. Such developments require a good understanding of how acid demineralisation progresses where relatively little is known in terms of intertubular dentine (ITD) and peritubular dentine (PTD) microstructure. To obtain further insight, this study proposes a new in vitro method for performing demineralisation studies of dentine. Methods: Advanced high-speed synchrotron X-ray microtomography (SXM), with high spatial (0.325 μm) and temporal (15 min) resolution, was used to conduct the first in vitro, time-resolved 3D (4D) study of the microstructural changes in the ITD and PTD phases of human dentine samples (∼0.8 × 0.8 × 5 mm) during 6 h of continuous acid exposure. Results: Different demineralisation rates of ITD (1.79 μm/min) and PTD (1.94 μm/min) and their progressive width-depth profiles were quantified, which provide insight for understanding the mechanisms of dentine demineralisation. Significance: Insights obtained from morphological characterisations and the demineralisation process of ITD and PTD during acid demineralisation would help understand the demineralisation process and potentially aid in developing new therapeutic dentine treatments. This method enables continuous examination of relatively large volumes of dentine during demineralisation and also demonstrates the potential for studying the remineralisation process of proposed therapeutic dentine treatments.	Sep 2021
I13-2-Diamond Manchester Imaging	3D analysis of enamel demineralisation in human dental caries using high-resolution, large field of view synchrotron X-ray micro-computed tomography Cyril Besnard , Robert A. Harper , Thomas E. J. Moxham , Jonathan D. James , Malte Storm , Enrico Salvati , Gabriel Landini , Richard M. Shelton , Alexander M. Korsunsky Materials Today Communications 392 DOI: 10.1016/j.mtcomm.2021.102418 Diamond Proposal Number(s): [20479] Open Access Show Abstract ▼ Abstract: We report major advances in the analysis of synchrotron 3D datasets acquired from human healthy and carious dental enamel. Synchrotron tomographic data for three human carious samples and a non-carious reference tooth sample were collected with the voxel size of 325 nm for a total volume of 815.4 × 815.4 × 685.4 μm3. The results were compared with conventional X-ray tomography, optical microscopy, and focused ion beam-scanning electron microscopy. Clear contrast was seen within demineralised enamel due to reduced mineral content using synchrotron tomography in comparison with conventional tomography. The features were found to correspond with the rod and inter-rod structures within prismatic enamel. 2D and 3D image segmentation allowed statistical quantification of important structural characteristics (such as the aspect ratio and the cross-sectional area of voids, as well as the demineralised volume fraction as a function of lesion depth). Whilst overall carious enamel predominantly displayed Type 1 etching pattern (preferential demineralisation of enamel rods), a transition between Type 2 (preferential inter-rod demineralisation) and Type 1 was identified within the same lesion for the first time. This study does not intend to give extensive results on the different lesions studied, but to illustrate a new method and its potential application.	May 2021
B16-Test Beamline	Analysis of in vitro demineralised human enamel using multi-scale correlative optical, scanning electron microscopy and high-resolution synchrotron wide-angle X-ray scattering Cyril Besnard , Robert A. Harper , Enrico Salvati , Thomas E. J. Moxham , Leon Romano Brandt , Gabriel Landini , Richard M. Shelton , Alexander M. Korsunsky Materials & Design DOI: 10.1016/j.matdes.2021.109739 Diamond Proposal Number(s): [19192] Open Access Show Abstract ▼ Abstract: Enamel caries is a highly prevalent disease that involves demineralisation of the enamel structure. In this study, we report the analysis of artificially demineralised human enamel slices etched using lactic acid (2 % v/v) in comparison with healthy enamel using correlative techniques of optical and electron microscopy, as well as scanning diffraction. Demineralisation of the enamel was characterised within the micron to sub-micron scale. The structure of the healthy enamel was investigated using focused ion beam - scanning electron microscopy (FIB-SEM) and compared with an etched sample to reveal structural differences. Additional chemical analysis using energy-dispersive X-ray spectroscopy (EDS) was performed and a decrease in the Ca/P atomic % ratio was found in etched samples in comparison with healthy enamel, suggesting more loss of calcium compared with phosphorus. Synchrotron wide-angle X-ray scattering (WAXS) was performed on the samples to reveal the differences in the diffraction patterns before and after etching in terms of lattice structure and preferred orientation (texture). Texture maps were extracted from diffraction analysis at 500 nm spatial resolution. These maps were correlated with the dimension of the enamel structure. The multi-scale correlative approach provided insights into the demineralisation-induced enamel structure alteration at a resolution approaching 500 nm.	Apr 2021
I13-2-Diamond Manchester Imaging	Finite element modelling and experimental validation of enamel demineralisation at the rod level Enrico Salvati , Cyril Besnard , Robert A. Harper , Thomas Moxham , Richard M. Shelton , Gabriel Landini , Alexander M. Korsunsky Journal Of Advanced Research DOI: 10.1016/j.jare.2020.08.018 Open Access Show Abstract ▼ Abstract: In the past years, a significant amount of effort has been directed at the observation and characterisation of caries using experimental techniques. Nevertheless, relatively little progress has been made in numerical modelling of the underlying demineralisation process. The present study is the first attempt to provide a simplified calculation framework for simulating the demineralisation process at the length scale of enamel rods and its validation by comparing the data with statistical analysis of synchrotron X-ray CT results. The local orientation of the hydroxyapatite crystals is accounted to solve a time-dependent reaction-diffusion equation, in which H ions diffuse and demineralise the enamel. insights into the pH level of the etchant solution and origin of different etching morphology were obtained by simulating these processes through the newly developed model. The implications of this study itself pave the way for simulations of enamel demineralisation within different complex scenarios and higher length scales. Indeed, the framework proposed can incorporate the presence of chemical species other than H ions and their diffusion and reaction leading to dissolution and re-precipitation of hydroxyapatite. It is the authors’ hope and aspiration that ultimately this work will help identify new ways of controlling and preventing caries.	Sep 2020
I12-JEEP: Joint Engineering, Environmental and Processing	Crack tip stress field analysis of crack surface contact and opening during in situ wedge loading of human enamel Enrico Salvati , Cyril Besnard , Robert A. Harper , Thomas Moxham , Richard Shelton , Gabriel Landini , Alexander M. Korsunsky Key Engineering Materials 827, 85 - 91 DOI: 10.4028/www.scientific.net/KEM.827.85 Diamond Proposal Number(s): [20540] Show Abstract ▼ Abstract: Shallow cracks are often observed in dental enamel, however do not normally lead to deep fractures. Previous work has highlighted the toughening mechanisms that operate in enamel during crack propagation, but very little is known about the deformation and stress fields arising around the propagating cracks during realistic loading conditions. This work aims to elucidate how the stresses are distributed within human dental enamel when a pre-existing crack is subjected to opening and surface contact with in situ indentation. We present a synchrotron-based in situ analysis coupled with a linear elastic finite element method simulation. The experimental reconstructed stress fields identified a prominent residual stress within the enamel, accompanied by a visible pattern that appeared clearly associated with its underlying microstructure. The numerical modelling of the stress field and discerning of surface contact and crack opening caused by the indentation was subsequently possible, even if in this study the influence of the anisotropy induced by the presence of features at a smaller scale was neglected. The implications of these findings and directions for future research are discussed.	Dec 2019
B16-Test Beamline	Structure-function correlative microscopy of peritubular and intertubular dentine Tan Sui , Jiří Dluhoš , Tao Li , Kaiyang Zeng , Adrian Cernescu , Gabriel Landini , Alexander Korsunsky Materials 11 DOI: 10.3390/ma11091493 Diamond Proposal Number(s): [11831, 21312] Open Access Show Abstract ▼ Abstract: Peritubular dentine (PTD) and intertubular dentine (ITD) were investigated by 3D correlative Focused Ion Beam (FIB)-Scanning Electron Microscopy (SEM)-Energy Dispersive Spectroscopy (EDS) tomography, tapping mode Atomic Force Microscopy (AFM) and scattering-type Scanning Near-Field Optical Microscopy (s-SNOM) mapping. The brighter appearance of PTD in 3D SEM-Backscattered-Electron (BSE) imaging mode and the corresponding higher grey value indicate a greater mineral concentration in PTD (~160) compared to ITD (~152). However, the 3D FIB-SEM-EDS reconstruction and high resolution, quantitative 2D map of the Ca/P ratio (~1.8) fail to distinguish between PTD and ITD. This has been further confirmed using nanoscale 2D AFM map, which clearly visualised biopolymers and hydroxyapatite (HAp) crystallites with larger mean crystallite size in ITD (32 ± 8 nm) than that in PTD (22 ± 3 nm). Correlative microscopy reveals that the principal difference between PTD and ITD arises primarily from the nanoscale packing density of the crystallites bonded together by thin biopolymer, with moderate contribution from the chemical composition difference. The structural difference results in the mechanical properties variation that is described by the parabolic stiffness-volume fraction correlation function introduced here. The obtained results benefit a microstructure-based mechano-chemical model to simulate the chemical etching process that can occur in human dental caries and some of its treatments.	Aug 2018

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