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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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Vertebrate Taphonomy and Diagenesis: Implications of Structural and Compositional Alterations of Phosphate Biominerals. MINERALS 2022. [DOI: 10.3390/min12020180] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Biominerals are recorders of evolution and palaeoenvironments. Predation is one of the most frequent modes leading to the concentration of small vertebrates in fossil assemblages. Consumption by predators produces damages on bones and teeth from prey species, and one of the greatest challenges to taphonomists is differentiating original biological and secondary, geologically altered attributes of fossils. Excellent morphological preservation is often used to assume that the structure and composition of fossils are not modified. Nevertheless, during predation and fossilization, both the physical structure and chemical composition of enamel, dentine and bone are altered, the degree and extent of which varies from site to site, depending on the nature of the burial environment. A relationship between the surficial alterations and the compositional changes which take place during fossilization has yet to be established. Herein, I present a review of old and recent taphonomic studies that collectively reveal the wide diversity of microstructural and chemical changes that typically take place during fossilization of vertebrate remains, including common taphonomic biases and the challenges inherent to reconstructing the history of vertebrate fossil assemblages.
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Bras W, Myles DAA, Felici R. When x-rays alter the course of your experiments. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 33:423002. [PMID: 34298526 DOI: 10.1088/1361-648x/ac1767] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2021] [Accepted: 07/23/2021] [Indexed: 06/13/2023]
Abstract
The continuing increase in the brilliance of synchrotron radiation beamlines allows for many new and exciting experiments that were impossible before the present generation of synchrotron radiation sources came on line. However, the exposure to such intense beams also tests the limits of what samples can endure. Whilst the effects of radiation induced damage in a static experiment often can easily be recognized by changes in the diffraction or spectroscopy curves, the influence of radiation on chemical or physical processes, where one expects curves to change, is less often recognized and can be misinterpreted as a 'real' result instead of as a 'radiation influenced result'. This is especially a concern in time-resolved materials science experiments using techniques as powder diffraction, small angle scattering and x-ray absorption spectroscopy. Here, the effects of radiation (5-50 keV) on some time-resolved processes in different types of materials and in different physical states are discussed. We show that such effects are not limited to soft matter and biology but rather can be found across the whole spectrum of materials research, over a large range of radiation doses and is not limited to very high brilliance beamlines.
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Affiliation(s)
- Wim Bras
- Chemical Sciences Division, Oak Ridge National Laboratory, One Bethel Valley Road, Oak Ridge TN 37831, United States of America
| | - Dean A A Myles
- Neutron Scattering Division, Oak Ridge National Laboratory, One Bethel Valley Road, Oak Ridge TN 37831, United States of America
| | - Roberto Felici
- CNR-SPIN, Area della ricerca di Tor Vergata, via del Fosso del Cavaliere 100, 00133 Roma, Italy
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Effect of X-ray irradiation on ancient DNA in sub-fossil bones - Guidelines for safe X-ray imaging. Sci Rep 2016; 6:32969. [PMID: 27615365 PMCID: PMC5018823 DOI: 10.1038/srep32969] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2016] [Accepted: 08/15/2016] [Indexed: 11/25/2022] Open
Abstract
Sub-fossilised remains may still contain highly degraded ancient DNA (aDNA) useful for palaeogenetic investigations. Whether X-ray computed [micro-] tomography ([μ]CT) imaging of these fossils may further damage aDNA remains debated. Although the effect of X-ray on DNA in living organisms is well documented, its impact on aDNA molecules is unexplored. Here we investigate the effects of synchrotron X-ray irradiation on aDNA from Pleistocene bones. A clear correlation appears between decreasing aDNA quantities and accumulating X-ray dose-levels above 2000 Gray (Gy). We further find that strong X-ray irradiation reduces the amount of nucleotide misincorporations at the aDNA molecule ends. No representative effect can be detected for doses below 200 Gy. Dosimetry shows that conventional μCT usually does not reach the risky dose level, while classical synchrotron imaging can degrade aDNA significantly. Optimised synchrotron protocols and simple rules introduced here are sufficient to ensure that fossils can be scanned without impairing future aDNA studies.
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Hennig C, Thomas CDL, Clement JG, Cooper DML. Does 3D orientation account for variation in osteon morphology assessed by 2D histology? J Anat 2015; 227:497-505. [PMID: 26249538 DOI: 10.1111/joa.12357] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/22/2015] [Indexed: 12/01/2022] Open
Abstract
The primary microstructural unit of cortical bone, the secondary osteon or Haversian system, is widely assumed to have a cylindrical shape. It is generally accepted that osteons are roughly circular in cross-section and deviations from circularity have been attributed to deviations from longitudinal orientation. To our knowledge this idealized geometric relationship, which assumes osteons are perfect cylinders, has not been rigorously explored. As such, we sought to explore two research questions: (i) Does the orientation of osteons in 3D explain variation in shapes visualized in 2D? (ii) Can differences in osteon 3D orientation explain previously reported age-related differences observed in their 2D cross-sectional shape (e.g. more circular shape and decreased area with age)? To address these questions we utilized a combination of 2D histology to identify osteon shape and superimposed micro-computed tomography data to assess osteon orientation in 3D based upon the osteonal canal. Shape was assessed by the inverse of Aspect Ratio (On.AspR(-1), based on a fitted ellipse) - which ranged from 0 (infinitely elongated shape) to 1 (perfectly circular). A sample (n = 27) of human female anterior femoral cortical bone samples from across the human lifespan (20-87 years) were included in the analysis, which involved 1418 osteons. The overall mean measure of On.AspR(-1) was 0.703 (1.42 Aspect Ratio). Mean osteon orientation was 79.1° (90° being longitudinal). While we anticipated a positive relation between orientation and On.AspR(-1), we found the opposite - a weak negative correlation (with more oblique 3D osteon alignment, the 2D shape became more circular as reflected by increased On.AspR(-1)). When analysis of covariance was performed with age and orientation as covariates, the negative relation with orientation was replaced by a significant relation with age alone. This relation with age accounted for 41% of the variation of On.AspR(-1). The results revealed that osteons, on average, are not circular in cross-section and that 3D orientation cannot account for deviation from circular shape. Osteons thus are strictly speaking not cylinders, as they tend to have elliptical cross-sections. We observed that osteons did become less elliptical in cross-section with age independent of orientation - suggesting this is a real change in morphology.
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Plomp KA, Viðarsdóttir US, Weston DA, Dobney K, Collard M. The ancestral shape hypothesis: an evolutionary explanation for the occurrence of intervertebral disc herniation in humans. BMC Evol Biol 2015; 15:68. [PMID: 25927934 PMCID: PMC4410577 DOI: 10.1186/s12862-015-0336-y] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2014] [Accepted: 03/19/2015] [Indexed: 12/19/2022] Open
Abstract
Background Recent studies suggest there is a relationship between intervertebral disc herniation and vertebral shape. The nature of this relationship is unclear, however. Humans are more commonly afflicted with spinal disease than are non-human primates and one suggested explanation for this is the stress placed on the spine by bipedalism. With this in mind, we carried out a study of human, chimpanzee, and orangutan vertebrae to examine the links between vertebral shape, locomotion, and Schmorl’s nodes, which are bony indicators of vertical intervertebral disc herniation. We tested the hypothesis that vertical disc herniation preferentially affects individuals with vertebrae that are towards the ancestral end of the range of shape variation within Homo sapiens and therefore are less well adapted for bipedalism. Results The study employed geometric morphometric techniques. Two-dimensional landmarks were used to capture the shapes of the superior aspect of the body and posterior elements of the last thoracic and first lumbar vertebrae of chimpanzees, orangutans, and humans with and without Schmorl’s nodes. These data were subjected to multivariate statistical analyses. Canonical Variates Analysis indicated that the last thoracic and first lumbar vertebrae of healthy humans, chimpanzees, and orangutans can be distinguished from each other (p<0.028), but vertebrae of pathological humans and chimpanzees cannot (p>0.4590). The Procrustes distance between pathological humans and chimpanzees was found to be smaller than the one between pathological and healthy humans. This was the case for both vertebrae. Pair-wise MANOVAs of Principal Component scores for both the thoracic and lumbar vertebrae found significant differences between all pairs of taxa (p<0.029), except pathological humans vs chimpanzees (p>0.367). Together, these results suggest that human vertebrae with Schmorl’s nodes are closer in shape to chimpanzee vertebrae than are healthy human vertebrae. Conclusions The results support the hypothesis that intervertebral disc herniation preferentially affects individuals with vertebrae that are towards the ancestral end of the range of shape variation within H. sapiens and therefore are less well adapted for bipedalism. This finding not only has clinical implications but also illustrates the benefits of bringing the tools of evolutionary biology to bear on problems in medicine and public health. Electronic supplementary material The online version of this article (doi:10.1186/s12862-015-0336-y) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Kimberly A Plomp
- Human Evolutionary Studies Program and Department of Archaeology, Simon Fraser University, Burnaby, BC, Canada.
| | | | - Darlene A Weston
- Department of Anthropology, University of British Columbia, Vancouver, BC, Canada. .,Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany.
| | - Keith Dobney
- Department of Archaeology, University of Aberdeen, Aberdeen, UK.
| | - Mark Collard
- Human Evolutionary Studies Program and Department of Archaeology, Simon Fraser University, Burnaby, BC, Canada. .,Department of Archaeology, University of Aberdeen, Aberdeen, UK.
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Le Cabec A, Tang N, Tafforeau P. Accessing developmental information of fossil hominin teeth using new synchrotron microtomography-based visualization techniques of dental surfaces and interfaces. PLoS One 2015; 10:e0123019. [PMID: 25901602 PMCID: PMC4406681 DOI: 10.1371/journal.pone.0123019] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2014] [Accepted: 02/26/2015] [Indexed: 12/02/2022] Open
Abstract
Quantification of dental long-period growth lines (Retzius lines in enamel and Andresen lines in dentine) and matching of stress patterns (internal accentuated lines and hypoplasias) are used in determining crown formation time and age at death in juvenile fossil hominins. They yield the chronology employed for inferences of life history. Synchrotron virtual histology has been demonstrated as a non-destructive alternative to conventional invasive approaches. Nevertheless, fossil teeth are sometimes poorly preserved or physically inaccessible, preventing observation of the external expression of incremental lines (perikymata and periradicular bands). Here we present a new approach combining synchrotron virtual histology and high quality three-dimensional rendering of dental surfaces and internal interfaces. We illustrate this approach with seventeen permanent fossil hominin teeth. The outer enamel surface and enamel-dentine junction (EDJ) were segmented by capturing the phase contrast fringes at the structural interfaces. Three-dimensional models were rendered with Phong’s algorithm, and a combination of directional colored lights to enhance surface topography and the pattern of subtle variations in tissue density. The process reveals perikymata and linear enamel hypoplasias on the entire crown surface, including unerupted teeth. Using this method, highly detailed stress patterns at the EDJ allow precise matching of teeth within an individual’s dentition when virtual histology is not sufficient. We highlight that taphonomical altered enamel can in particular cases yield artificial subdivisions of perikymata when imaged using X-ray microtomography with insufficient resolution. This may complicate assessments of developmental time, although this can be circumvented by a careful analysis of external and internal structures in parallel. We further present new crown formation times for two unerupted canines from South African Australopiths, which were found to form over a rather surprisingly long time (> 4.5 years). This approach provides tools for maximizing the recovery of developmental information in teeth, especially in the most difficult cases.
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Affiliation(s)
- Adeline Le Cabec
- ESRF—The European Synchrotron, 71, avenue des Martyrs, CS 40220, F-38043 Grenoble, Cédex 9, France
- Department of Human Evolutionary Biology, Harvard University, Cambridge, MA, 02138, United States of America
- Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, D-04103, Leipzig, Germany
- * E-mail: (PT); (ALC)
| | - Nancy Tang
- Department of Human Evolutionary Biology, Harvard University, Cambridge, MA, 02138, United States of America
- Department of Preventive Medicine, Exposure Biology Laboratory, Icahn School of Medicine at Mount Sinai, New York, New York, United States of America
| | - Paul Tafforeau
- ESRF—The European Synchrotron, 71, avenue des Martyrs, CS 40220, F-38043 Grenoble, Cédex 9, France
- * E-mail: (PT); (ALC)
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9
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Weber GW. Virtual Anthropology. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2014; 156 Suppl 59:22-42. [DOI: 10.1002/ajpa.22658] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Gerhard W. Weber
- Department of Anthropology; University of Vienna; A-1090 Vienna Austria
- Core Facility for Micro-Computed Tomography; University of Vienna; A-1090 Vienna Austria
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