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Wan B, Man Z, Li KC, Swain MV, Li Q. On elastoplastic behavior of porous enamel-An indentation and numerical study. Acta Biomater 2024; 183:210-220. [PMID: 38801871 DOI: 10.1016/j.actbio.2024.05.038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2024] [Revised: 05/16/2024] [Accepted: 05/22/2024] [Indexed: 05/29/2024]
Abstract
The micro/nano pores in natural mineralized tissues can, to a certain extent, affect their responses to mechanical loading but are generally ignored in existing indentation analysis. In this study, we first examined the void volume fraction of sound and caries lesion enamels through micro-computed tomography (micro-CT). A Berkovich indentation study was then carried out to characterize the effect of porous microstructure on the mechanical behavior of the human enamels. The indentation tests were also modeled using the nonlinear finite element analysis technique to simulate indentation load-displacement curves, which showed reasonable agreement with the experimental measurements. From the simulation results, the extent of densification in the plastic zone was identified and the corresponding stress and contact pressure evolutions were quantified. Further, a conventional elastic-perfectly plastic material model without considering micropores was also developed to investigate the compaction effect of the porous structure. The simulation results reveal that conventional elastic perfect-plastic constitutive models become less reliable to model the mechanical behavior of carious lesion enamel with increasing loss of mineral content as it underestimates the yield stress and plastic energy dissipation. This study divulges the importance of compaction of porous enamel structure beneath the indented area. Note that understanding the effect of porous microstructures on plastic behavior is vital as the involved inelastic deformation mechanism associated with irreversible processes, such as wear and localized microcracking, has a significant bearing on wear and fatigue behavior of enamel. STATEMENT OF SIGNIFICANCE: Based on micro-CT and nano-indentation characterization, a numerical model was developed aiming to precisely describe the deformation behavior of naturally porous enamel. Inelastic properties and energy dissipation characteristics of porous enamel were investigated in detail. This work demonstrated that the existence of micro-pores in White Spot Lesions (WSLs) contributes to mechanical stability, which can mitigate the reduction in Young's modulus and fracture toughness resulting from loss of mineral components. The knowledge gained from this study can be used to explain the mechanisms related to irreversible processes, such as contact induced cracking and wear, and strengthen understanding of the mechanical behavior of porous mineralized tissues.
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Affiliation(s)
- Boyang Wan
- School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, NSW 2006, Australia
| | - Ziyan Man
- School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, NSW 2006, Australia
| | - Kai Chun Li
- Sir John Walsh Research Institute, University of Otago, Dunedin, New Zealand
| | - Michael V Swain
- School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, NSW 2006, Australia
| | - Qing Li
- School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, NSW 2006, Australia.
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Maliuk A, Marghoub A, Williams CJA, Stanley E, Kéver L, Vickaryous M, Herrel A, Evans SE, Moazen M. Comparative analysis of osteoderms across the lizard body. Anat Rec (Hoboken) 2024. [PMID: 38396371 DOI: 10.1002/ar.25418] [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: 09/21/2023] [Revised: 12/12/2023] [Accepted: 02/11/2024] [Indexed: 02/25/2024]
Abstract
Osteoderms (ODs) are mineralized tissue embedded within the skin and are particularly common in reptiles. They are generally thought to form a protective layer between the soft tissues of the animal and potential external threats, although other functions have been proposed. The aim of this study was to characterize OD variation across the lizard body. Adults of three lizard species were chosen for this study. After whole body CT scanning of each lizard, single ODs were extracted from 10 different anatomical regions, CT scanned, and characterized using sectioning and nanoindentation. Morphological analysis and material characterization revealed considerable diversity in OD structure across the species investigated. The scincid Tiliqua gigas was the only studied species in which ODs had a similar external morphology across the head and body. Greater osteoderm diversity was found in the gerrhosaurid Broadleysaurus major and the scincid Tribolonotus novaeguineae. Dense capping tissue, like that reported for Heloderma, was found in only one of the three species examined, B. major. Osteoderm structure can be surprisingly complex and variable, both among related taxa, and across the body of individual animals. This raises many questions about OD function but also about the genetic and developmental factors controlling OD shape.
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Affiliation(s)
- Anastasiia Maliuk
- Department of Mechanical Engineering, University College London, London, UK
- Department of Zoology, National Museum of Natural History, NAS of Ukraine, Kyiv, Ukraine
| | - Arsalan Marghoub
- Department of Mechanical Engineering, University College London, London, UK
| | - Catherine J A Williams
- Department of Biomedical Sciences, University of Guelph, Guelph, Ontario, Canada
- Department of Biology, Aarhus University, Aarhus, Denmark
- Department of Animal and Veterinary Sciences, Aarhus University, Tjele, Denmark
| | - Edward Stanley
- Department of Natural History, Florida Museum of Natural History, Gainesville, Florida, USA
| | - Loïc Kéver
- Département Adaptations du Vivant, UMR7179 CNRS/MNHN, Paris, France
| | - Matthew Vickaryous
- Department of Biomedical Sciences, University of Guelph, Guelph, Ontario, Canada
| | - Anthony Herrel
- Département Adaptations du Vivant, UMR7179 CNRS/MNHN, Paris, France
- Department of Biology, Evolutionary Morphology of Vertebrates, Ghent University, Ghent, Belgium
- Department of Biology, University of Antwerp, Wilrijk, Belgium
- Naturhistorisches Museum Bern, Bern, Switzerland
| | - Susan E Evans
- Department of Cell and Developmental Biology, University College London, London, UK
| | - Mehran Moazen
- Department of Mechanical Engineering, University College London, London, UK
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Marghoub A, Kéver L, Williams CJA, Abzhanov A, Vickaryous M, Herrel A, Evans SE, Moazen M. The role of cranial osteoderms on the mechanics of the skull in scincid lizards. Anat Rec (Hoboken) 2023; 306:2415-2424. [PMID: 36748783 DOI: 10.1002/ar.25168] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2022] [Revised: 01/04/2023] [Accepted: 01/04/2023] [Indexed: 02/08/2023]
Abstract
Osteoderms (ODs) are calcified organs formed directly within the skin of most major extant tetrapod lineages. Lizards possibly show the greatest diversity in ODs morphology and distribution. ODs are commonly hypothesized to function as a defensive armor. Here we tested the hypothesis that cranial osteoderms also contribute to the mechanics of the skull during biting. A series of in vivo experiments were carried out on three specimens of Tiliqua gigas. Animals were induced to bite a force plate while a single cranial OD was strain gauged. A finite element (FE) model of a related species, Tiliqua scincoides, was developed and used to estimate the level of strain across the same OD as instrumented in the in vivo experiments. FE results were compared to the in vivo data and the FE model was modified to test two hypothetical scenarios in which all ODs were (i) removed from, and (ii) fused to, the skull. In vivo data demonstrated that the ODs were carrying load during biting. The hypothetical FE models showed that when cranial ODs were fused to the skull, the overall strain across the skull arising from biting was reduced. Removing the ODs showed an opposite effect. In summary, our findings suggest that cranial ODs contribute to the mechanics of the skull, even when they are loosely attached.
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Affiliation(s)
- Arsalan Marghoub
- Department of Mechanical Engineering, University College London, London, UK
| | - Loïc Kéver
- Département Adaptations du Vivant, Bâtiment, UMR 7179 MECADEV C.N.R.S/M.N.H.N, d'Anatomie Comparée, Paris, France
| | - Catherine J A Williams
- Department of Biology, Aarhus University, Aarhus C, Denmark
- Department of Biomedical Sciences, University of Guelph, Guelph, Ontario, Canada
| | - Arkhat Abzhanov
- Department of Life Sciences, Faculty of Natural Sciences, Imperial College London, Silkwood Park Campus, Berkshire, UK
| | - Matthew Vickaryous
- Department of Biomedical Sciences, University of Guelph, Guelph, Ontario, Canada
| | - Anthony Herrel
- Département Adaptations du Vivant, Bâtiment, UMR 7179 MECADEV C.N.R.S/M.N.H.N, d'Anatomie Comparée, Paris, France
| | - Susan E Evans
- Centre for Integrative Anatomy, Department of Cell and Developmental Biology, University College London, London, UK
| | - Mehran Moazen
- Department of Mechanical Engineering, University College London, London, UK
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Cherepanov GO, Gordeev DA, Melnikov DA, Ananjeva NB. Osteoderm Development during the Regeneration Process in Eurylepis taeniolata Blyth, 1854 (Scincidae, Sauria, Squamata). J Dev Biol 2023; 11:22. [PMID: 37367476 DOI: 10.3390/jdb11020022] [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: 04/05/2023] [Revised: 05/17/2023] [Accepted: 05/19/2023] [Indexed: 06/28/2023] Open
Abstract
Osteoderms are bony structures that develop within the dermal layer of the skin in vertebrates and are very often found in different lizard families. Lizard osteoderms are diverse in topography, morphology, and microstructure. Of particular interest are the compound osteoderms of skinks, which are a complex of several bone elements known as osteodermites. We present new data on the development and regeneration of compound osteoderms based on the results of a histological and Computed Microtomography (micro-CT) study of a scincid lizard: Eurylepis taeniolata. The specimens studied are stored in the herpetological collections of the Saint-Petersburg State University and Zoological Institute of the Russian Academy of Sciences located in St. Petersburg, Russia. The topography of osteoderms in the integuments of the original tail area and its regenerated part was studied. A comparative histological description of the original and regenerated osteoderms of Eurylepis taeniolata is presented for the first time. The first description of the development of compound osteoderm microstructure in the process of caudal regeneration is also presented.
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Affiliation(s)
- Gennady O Cherepanov
- Department of Vertebrate Zoology, Faculty of Biology, Saint Petersburg State University, 199034 St. Petersburg, Russia
| | - Dmitry A Gordeev
- Department of Biology and Bioengineering, Institute of Natural Sciences, Volgograd State University, 400062 Volgograd, Russia
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