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Instruments / Technical Area	Publication Details	Published
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	In situ monitoring and analysis of enamel demineralisation using synchrotron X-ray scattering Tan Sui , Enrico Salvati , Robert A. Harper , Hongjia Zhang , Richard M. Shelton , Gabriel Landini , Alexander M. Korsunsky Acta Biomaterialia DOI: 10.1016/j.actbio.2018.07.027 Diamond Proposal Number(s): [15981] Show Abstract ▼ Abstract: Dental caries is one of the most common chronic diseases that affect human teeth. It often initiates in enamel, undermining its mechanical function and structural integrity. Little is known about the enamel demineralisation process caused by dental caries in terms of the microstructural changes and crystallography of the inorganic mineral phase. To improve the understanding of the carious lesion formation process and to help identify efficient treatments, the evolution of the microstructure at the nano-scale in an artificially induced enamel erosion region was probed using advanced synchrotron small-angle and wide-angle X-ray scattering (SAXS and WAXS). This is the first in vitro and time-resolved investigation of enamel demineralisation using synchrotron X-ray techniques which allows in situ quantification of the microstructure evolution over time in a simulated carious lesion. The analysis revealed that alongside the reduction of mineral volume, a heterogeneous evolution of hydroxyapatite (HAp) crystallites (in terms of size, preferred orientation and degree of alignment) could be observed. It was also found that the rate and direction of dissolution depends on the crystallographic orientation. Based on these findings, a novel conceptual view of the process is put forward that describes the key structural parameters in establishing high fidelity ultrastructure-based numerical models for the simulation of the enamel demineralisation process.	Jul 2018

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