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Besnard C, Marie A, Sasidharan S, Harper RA, Shelton RM, Landini G, Korsunsky AM. Synchrotron X-ray Studies of the Structural and Functional Hierarchies in Mineralised Human Dental Enamel: A State-of-the-Art Review. Dent J (Basel) 2023; 11:98. [PMID: 37185477 PMCID: PMC10137518 DOI: 10.3390/dj11040098] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2023] [Revised: 03/19/2023] [Accepted: 03/28/2023] [Indexed: 05/17/2023] Open
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.
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Affiliation(s)
- Cyril Besnard
- MBLEM, Department of Engineering Science, University of Oxford, Parks Road, Oxford OX1 3PJ, Oxfordshire, UK
| | - Ali Marie
- MBLEM, Department of Engineering Science, University of Oxford, Parks Road, Oxford OX1 3PJ, Oxfordshire, UK
| | - Sisini Sasidharan
- MBLEM, Department of Engineering Science, University of Oxford, Parks Road, Oxford OX1 3PJ, Oxfordshire, UK
| | - Robert A. Harper
- School of Dentistry, University of Birmingham, 5 Mill Pool Way, Edgbaston, Birmingham B5 7EG, West Midlands, UK
| | - Richard M. Shelton
- School of Dentistry, University of Birmingham, 5 Mill Pool Way, Edgbaston, Birmingham B5 7EG, West Midlands, UK
| | - Gabriel Landini
- School of Dentistry, University of Birmingham, 5 Mill Pool Way, Edgbaston, Birmingham B5 7EG, West Midlands, UK
| | - Alexander M. Korsunsky
- MBLEM, Department of Engineering Science, University of Oxford, Parks Road, Oxford OX1 3PJ, Oxfordshire, UK
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Czigány Z, Kis VK. Acquisition and evaluation procedure to improve the accuracy of SAED. Microsc Res Tech 2023; 86:144-156. [PMID: 36069159 PMCID: PMC10087671 DOI: 10.1002/jemt.24229] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2022] [Revised: 07/01/2022] [Accepted: 08/22/2022] [Indexed: 01/21/2023]
Abstract
The achievement of this work is that fine tuning of experimental and evaluation parameters can improve the absolute accuracy and reproducibility of selected area electron diffraction (SAED) to 0.1% without using internal standard. Due to the proposed procedure it was possible to reach a reproducibility better than 0.03% for camera length between sessions by careful control of specimen height and illumination conditions by monitoring lens currents. We applied a calibration specimen composed of nanocrystalline grains free of texture and providing narrow diffraction rings. Refinements of the centre of the diffraction pattern and corrections for elliptic ring distortions allowed for determining the ring diameters with an accuracy of 0.1%. We analyze the effect of different error sources and reason the achieved absolute accuracy of the measurement. Application of the proposed evaluation procedure is inevitable in case of multicomponent nanocomposites or textured materials and/or having close diffraction rings where application of automated procedures is limited. The achieved accuracy of 0.1% without internal standard is approaching that of routine laboratory XRD, and reduction of instrumental broadening due to the elaborated evaluation procedure allows for separation of close reflections, provides more reliable ring width and thus improved input parameters for further nanostructure analysis as demonstrated on dental enamel bioapatite.
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Affiliation(s)
- Zsolt Czigány
- Institute of Technical Physics and Materials Science, Centre for Energy Research, Budapest, Hungary
| | - Viktória Kovács Kis
- Institute of Technical Physics and Materials Science, Centre for Energy Research, Budapest, Hungary
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Free R, DeRocher K, Cooley V, Xu R, Stock SR, Joester D. Mesoscale structural gradients in human tooth enamel. Proc Natl Acad Sci U S A 2022; 119:e2211285119. [PMID: 36534796 PMCID: PMC9907129 DOI: 10.1073/pnas.2211285119] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Accepted: 10/30/2022] [Indexed: 12/24/2022] Open
Abstract
The outstanding mechanical and chemical properties of dental enamel emerge from its complex hierarchical architecture. An accurate, detailed multiscale model of the structure and composition of enamel is important for understanding lesion formation in tooth decay (dental caries), enamel development (amelogenesis) and associated pathologies (e.g., amelogenesis imperfecta or molar hypomineralization), and minimally invasive dentistry. Although features at length scales smaller than 100 nm (individual crystallites) and greater than 50 µm (multiple rods) are well understood, competing field of view and sampling considerations have hindered exploration of mesoscale features, i.e., at the level of single enamel rods and the interrod enamel (1 to 10 µm). Here, we combine synchrotron X-ray diffraction at submicrometer resolution, analysis of crystallite orientation distribution, and unsupervised machine learning to show that crystallographic parameters differ between rod head and rod tail/interrod enamel. This variation strongly suggests that crystallites in different microarchitectural domains also differ in their composition. Thus, we use a dilute linear model to predict the concentrations of minority ions in hydroxylapatite (Mg2+ and CO32-/Na+) that plausibly explain the observed lattice parameter variations. While differences within samples are highly significant and of similar magnitude, absolute values and the sign of the effect for some crystallographic parameters show interindividual variation that warrants further investigation. By revealing additional complexity at the rod/interrod level of human enamel and leaving open the possibility of modulation across larger length scales, these results inform future investigations into mechanisms governing amelogenesis and introduce another feature to consider when modeling the mechanical and chemical performance of enamel.
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Affiliation(s)
- Robert Free
- Department of Materials Science and Engineering, Northwestern University, Evanston, IL60208
| | - Karen DeRocher
- Department of Materials Science and Engineering, Northwestern University, Evanston, IL60208
| | - Victoria Cooley
- Department of Materials Science and Engineering, Northwestern University, Evanston, IL60208
| | - Ruqing Xu
- Argonne National Lab, Advanced Photon Source, Lemont, IL60439
| | - Stuart R. Stock
- Department of Cell and Developmental Biology, Feinberg School of Medicine, Northwestern University, Chicago, IL60611
- Northwestern University, Simpson Querrey Institute, Chicago, IL60611
| | - Derk Joester
- Department of Materials Science and Engineering, Northwestern University, Evanston, IL60208
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Hiraishi N, Gondo T, Shimada Y, Hill R, Hayashi F. Crystallographic and Physicochemical Analysis of Bovine and Human Teeth Using X-ray Diffraction and Solid-State Nuclear Magnetic Resonance. J Funct Biomater 2022; 13:jfb13040254. [PMID: 36412897 PMCID: PMC9680385 DOI: 10.3390/jfb13040254] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2022] [Revised: 11/14/2022] [Accepted: 11/16/2022] [Indexed: 11/22/2022] Open
Abstract
Dental research often uses bovine teeth as a substitute for human teeth. The aim of this study was to evaluate differences in the crystalline nanostructures of enamel and dentin between bovine and human teeth, using X-ray diffraction (XRD) and solid-state nuclear magnetic resonance (NMR). The crystallite size (crystallinity) and microstrains were analyzed using XRD with the Rietveld refinement technique and the Halder-Wagner method. The 31P and 1H NMR chemical environments were analyzed by two-dimensional (2D) 1H-31P heteronuclear-correlation (HETCOR) magic-angle spinning (MAS) NMR spectroscopy. Enamel had a greater crystallite size and fewer microstrains than dentin for both bovine and human teeth. When compared between the species, the bovine apatite had a smaller crystallite size with more microstrains than the human apatite for both dentin and enamel. The 2D HETCOR spectra demonstrated that a water-rich layer and inorganic HPO4- ions were abundant in dentin; meanwhile, the hydroxyl group in the lattice site was more dominant in enamel. A greater intensity of the hydroxyl group was detected in human than in bovine for both dentin and enamel. For 31P projections, bovine dentin and bovine enamel have wider linewidths than human dentin and human enamel, respectively. There are differences in the crystallite profile between human and bovine. The results of dental research should be interpreted with caution when bovine teeth are substituted for human teeth.
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Affiliation(s)
- Noriko Hiraishi
- Department of Cariology and Operative Dentistry, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo 113-8549, Japan
- Correspondence:
| | - Tadamu Gondo
- Department of Cariology and Operative Dentistry, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo 113-8549, Japan
| | - Yasushi Shimada
- Department of Cariology and Operative Dentistry, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo 113-8549, Japan
| | - Robert Hill
- Dental Physical Sciences Unit, Institute of Dentistry, Queen Mary University of London, London E1 4NS, UK
| | - Fumiaki Hayashi
- NMR Operation Team, Laboratory for Advanced NMR Application and Development, RIKEN Center for Biosystems Dynamics Research, Yokohama 230-0045, Japan
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Diez-García S, Sánchez-Martín MJ, Amigo JM, Valiente M. Combination of Two Synchrotron Radiation-Based Techniques and Chemometrics to Study an Enhanced Natural Remineralization of Enamel. Anal Chem 2022; 94:5359-5366. [PMID: 35319204 PMCID: PMC8988122 DOI: 10.1021/acs.analchem.1c05498] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
![]()
The limitations to
assess dental enamel remineralization have been
overcome by a methodology resulting from the appropriate combination
of synchrotron radiation-based techniques on both, infrared microspectroscopy
and micro X-ray diffraction, with the help of specific data mining.
Since amelogenin plays a key role in modulating the mineralization
of tooth enamel, we propose a controlled ion release for fluorapatite
structural ions (Ca2+, PO43–, and F–, also including Zn2+) by using
weak acid and weak base ion-exchange resins in the presence of amelogenin
to remineralize the surface of etched teeth. This combination provides
the necessary ions for enamel remineralization and a guide for crystal
growth due to the protein. Remineralized tooth samples were analyzed
by applying the indicated methodology. The synchrotron data were treated
using principal component analysis and multivariate curve resolution
to analyze the mineral layer formed in the presence and absence of
amelogenin. The remineralizing treatment created a fluorapatite layer
free of carbonate impurities and with a similar orientation to that
of the natural enamel thanks to amelogenin contribution.
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Affiliation(s)
- Sandra Diez-García
- GTS Research Group, Department of Chemistry, Faculty of Science, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain
| | - María-Jesús Sánchez-Martín
- GTS Research Group, Department of Chemistry, Faculty of Science, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain
| | - José Manuel Amigo
- Ikerbasque, Basque Foundation for Science, María Díaz de Haro, 48013 Bilbao, Spain.,Department of Analytical Chemistry, University of the Basque Country UPV/EHU, P.O. Box 644, 15 48080 Bilbao, Basque Country, Spain
| | - Manuel Valiente
- GTS Research Group, Department of Chemistry, Faculty of Science, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain
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Dean MC, Le Cabec A, Van Malderen SJ, Garrevoet J. Synchrotron X-ray fluorescence imaging of strontium incorporated into the enamel and dentine of wild-shot orangutan canine teeth. Arch Oral Biol 2020; 119:104879. [DOI: 10.1016/j.archoralbio.2020.104879] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Revised: 07/10/2020] [Accepted: 08/10/2020] [Indexed: 10/23/2022]
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Free R, DeRocher K, Xu R, Joester D, Stock SR. A method for mapping submicron-scale crystallographic order/disorder applied to human tooth enamel. POWDER DIFFRACTION 2020; 35:117-123. [PMID: 34219911 PMCID: PMC8248910 DOI: 10.1017/s0885715620000251] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Tooth enamel, the outermost layer of human teeth, is a complex, hierarchically structured biocomposite. The details of this structure are important in multiple human health contexts, from understanding the progression of dental caries (tooth decay) to understanding the process of amelogenesis and related developmental defects. Enamel is composed primarily of long, nanoscale crystallites of hydroxyapatite that are bundled by the thousands to form micron-scale rods. Studies with transmission electron microscopy show the relationships between small groups of crystallites and X-ray diffraction characterize averages over many rods, but the direct measurement of variations in local crystallographic structure across and between enamel rods has been missing. Here, we describe a synchrotron X-ray-based experimental approach and a novel analysis method developed to address this gap in knowledge. A ~500-nm-wide beam of monochromatic X-rays in conjunction with a sample section only 1 μm in thickness enables 2D diffraction patterns to be collected from small well-separated volumes within the enamel microstructure but still probes enough crystallites (~300 per pattern) to extract population-level statistics on crystallographic features like lattice parameter, crystallite size, and orientation distributions. Furthermore, the development of a quantitative metric to characterize relative order and disorder based on the azimuthal autocorrelation of diffracted intensity enables these crystallographic measurements to be correlated with their location within the enamel microstructure (e.g., between rod and interrod regions). These methods represent a step forward in the characterization of human enamel and will elucidate the variation of the crystallographic structure across and between enamel rods for the first time.
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Affiliation(s)
- R. Free
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois, USA
| | - K. DeRocher
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois, USA
| | - R. Xu
- Argonne National Lab, Advanced Photon Source, Lemont, Illinois 34ID-E, USA
| | - D. Joester
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois, USA
| | - S. R. Stock
- Northwestern University, Feinberg School of Medicine, Chicago, Illinois, USA
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Koldehoff J, Swain MV, Schneider GA. The geometrical structure of interfaces in dental enamel: A FIB-STEM investigation. Acta Biomater 2020; 104:17-27. [PMID: 31917293 DOI: 10.1016/j.actbio.2019.12.040] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2019] [Revised: 12/20/2019] [Accepted: 12/31/2019] [Indexed: 11/26/2022]
Abstract
In this study a high resolution structural analysis revealed that enamel prisms are surrounded by an interface that is discontinuous with frequent mineral to mineral contact separated by gaps. This contact manifests either by crystallites bridging the boundary between prismatic and interprismatic enamel or continuous crystallites curving and bridging the interprismatic enamel to the prisms. The geometrical resolution of this TEM investigation of the interfaces is ≤2 nm as a basis for micromechanical models. Within this resolution, contrary to existing structural descriptions of dental enamel structure in materials science literature, here the crystallites themselves are shown to be either in direct contact with each other, sometimes even fusing together, or are separated by gaps. Image analysis revealed that on average only 57 ± 15% of the interface consists of points of no contact between crystallites. This work reveals structural features of dental enamel that contribute important understanding to both the architecture and mechanical properties of this biological material. A new structural model is proposed and the implications for the mechanical properties of dental enamel are discussed. STATEMENT OF SIGNIFICANCE: In this study a high resolution structural analysis, employing focused ion beam and transmission electron microscopy revealed that enamel prisms are surrounded by interfaces that are discontinuous with frequent mineral to mineral contact separated by gaps. Although the interfaces in enamel have been investigated previously, existing studies are lacking in detail considering the geometry and morphology of the interfaces. We think that this result is of great importance when it comes to the understanding of the mechanical properties. In our opinion the concept of soft sheaths is no longer feasible. The resulting observations are included in a new structural model which provides new qualitative insights into the mechanical behavior. Existing analytical models were applied to simulate the new geometrical structure.
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Bikondoa O, Bouchenoire L, Brown SD, Thompson PBJ, Wermeille D, Lucas CA, Cooper MJ, Hase TPA. XMaS @ the ESRF. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2019; 377:20180237. [PMID: 31030656 PMCID: PMC6501888 DOI: 10.1098/rsta.2018.0237] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 02/27/2019] [Indexed: 05/27/2023]
Abstract
This paper describes the motivation for the design and construction of a beamline at the European Synchrotron Radiation Facility (ESRF) for the use of UK material scientists. Although originally focused on the study of magnetic materials, the beamline has been running for 20 years and currently supports a very broad range of science as evidenced by the research topics highlighted in this article. We describe how the beamline will adapt to align with the ESRF's upgrade to a diffraction limited storage ring. This article is part of the theme issue 'Fifty years of synchrotron science: achievements and opportunities'.
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Affiliation(s)
- Oier Bikondoa
- XMaS Beamline, European Synchrotron Radiation Facility, 71 Avenue des Martyrs, Grenoble 38043, France
- Department of Physics, University of Warwick, Coventry CV4 7AL, UK
| | - Laurence Bouchenoire
- XMaS Beamline, European Synchrotron Radiation Facility, 71 Avenue des Martyrs, Grenoble 38043, France
- Department of Physics, University of Liverpool, Liverpool L69 7ZE, UK
| | - Simon D. Brown
- XMaS Beamline, European Synchrotron Radiation Facility, 71 Avenue des Martyrs, Grenoble 38043, France
- Department of Physics, University of Liverpool, Liverpool L69 7ZE, UK
| | - Paul B. J. Thompson
- XMaS Beamline, European Synchrotron Radiation Facility, 71 Avenue des Martyrs, Grenoble 38043, France
- Department of Physics, University of Liverpool, Liverpool L69 7ZE, UK
| | - Didier Wermeille
- XMaS Beamline, European Synchrotron Radiation Facility, 71 Avenue des Martyrs, Grenoble 38043, France
- Department of Physics, University of Liverpool, Liverpool L69 7ZE, UK
| | - Chris A. Lucas
- Department of Physics, University of Liverpool, Liverpool L69 7ZE, UK
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Dean MC, Spiers KM, Garrevoet J, Le Cabec A. Synchrotron X-ray fluorescence mapping of Ca, Sr and Zn at the neonatal line in human deciduous teeth reflects changing perinatal physiology. Arch Oral Biol 2019; 104:90-102. [PMID: 31176148 DOI: 10.1016/j.archoralbio.2019.05.024] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2019] [Revised: 05/06/2019] [Accepted: 05/21/2019] [Indexed: 12/21/2022]
Abstract
OBJECTIVES Our first objective was to review the evidence describing the appearance and microstructure of the neonatal line in human deciduous teeth and to link this with known changes in neonatal physiology occurring at and around birth. A second objective was to explore ways to improve identification of the neonatal line by mapping the pre- and postnatal distribution of Ca, Sr and Zn in deciduous cuspal enamel and superimposing these maps onto transmitted light micrographs that included a clear true section of the neonatal line. MATERIALS AND METHODS We used synchrotron X-ray fluorescence to map elemental distributions in pre- and postnatal enamel and dentine. Two deciduous canines and 5 deciduous molars were scanned with an X-ray beam monochromatised to 17.0 keV at either 10.0, 2.5 or 1.0 μm resolution and 10 ms integration time. RESULTS Calcium maps distinguished enamel and dentine but did not clearly demarcate tissues formed pre- or postnatally. Strontium maps reflected presumed pre- and postnatal maternal serum levels and what are likely to be diet-dependent regions of Sr enrichment or depletion. Prenatal Zn maps, particularly for dentine, mirror elevated levels in the fetus and in colostrum during the first few days of life. CONCLUSIONS The neonatal line, enamel dentine junction and surface enamel were all Zn-rich. Within the neonatal line Zn may be associated with increased crystallinity but also with caries resistance, both of which have been reported previously. Elemental mapping may improve the identification of ambiguous NNLs and so be useful in forensic and archaeological studies.
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Affiliation(s)
- M Christopher Dean
- Department of Cell and Developmental Biology, University College London, Gower Street, London WC1E 6BT, UK; Department of Earth Sciences, Centre for Human Evolution Research, Natural History Museum, Cromwell Road, London SW7 5BD, UK.
| | - Kathryn M Spiers
- Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, 22607 Hamburg, Germany
| | - Jan Garrevoet
- Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, 22607 Hamburg, Germany
| | - Adeline Le Cabec
- Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, D-04103 Leipzig, Germany
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