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Hegedűs M, Kis VK, Rózsa N, Kovács Z. A novel image processing procedure for the quantitative evaluation of dental enamel prism arrangement. Microsc Res Tech 2024; 87:808-817. [PMID: 38093599 DOI: 10.1002/jemt.24473] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2023] [Accepted: 11/27/2023] [Indexed: 03/02/2024]
Abstract
Enamel prism is the main microstructural unit of mammalian enamel which composed of hundreds of bioapatite nanocrystals. Prism structure plays a key role in the excellent mechanical performance of dental enamel during millions of chewing cycles without significant remodeling. Thus, quantitative understanding of prism architecture is of utmost importance for biomechanical materials design. To characterize enamel prism orientation quantitatively, a novel image processing method has been developed. Our method is based on scanning electron microscopy images of etched enamel surface and consists of an ellipse fitting procedure, which provides a numerical approximation of prism shape and orientation in the studied cross section. The obtained analytical data allow to construct color coded orientation maps, which provide quick and useful insight into the microstructure of enamel. Besides striking visualization, orientation maps allow to extract and plot the rich information on the azimuthal and inclination angles of the prisms as function of location. Numerical data on prism arrangement can be analyzed using statistical tools over large areas, which paves the way towards quantifying comparative investigation of prism arrangement either in dentistry research or evolution biology. The application of the method is demonstrated for a distal-mesial cross-section of sound human tooth enamel. HIGHLIGHTS: Scanning electron microscopy images of etched enamel surface are analyzed using ellipse fitting. Geometrical parameters of the fitted ellipses provide numerical data of thousands of prisms. Prism arrangement is visualized on color coded orientation maps and analyzed using statistical tools.
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Affiliation(s)
- Máté Hegedűs
- Department of Materials Physics, Eötvös Loránd University, Budapest, Hungary
| | - Viktória K Kis
- HUN-REN Centre for Energy Research, Budapest, Hungary
- Department of Mineralogy, Eötvös Loránd University, Budapest, Hungary
| | - Noémi Rózsa
- Faculty of Dentistry, Department of Pedodontics and Orthodontics, Semmelweis University, Budapest, Hungary
| | - Zsolt Kovács
- Department of Materials Physics, Eötvös Loránd University, Budapest, Hungary
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Guatelli-Steinberg D, Renteria C, Grimm JR, Maeret Carpenter I, Arola DD, McGraw WS. How mangabey molar form differs under routine vs. fallback hard-object feeding regimes. PeerJ 2023; 11:e16534. [PMID: 38099313 PMCID: PMC10720418 DOI: 10.7717/peerj.16534] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2023] [Accepted: 11/07/2023] [Indexed: 12/17/2023] Open
Abstract
Background Components of diet known as fallback foods are argued to be critical in shaping primate dental anatomy. Such foods of low(er) nutritional quality are often non-preferred, mechanically challenging resources that species resort to during ecological crunch periods. An oft-cited example of the importance of dietary fallbacks in shaping primate anatomy is the grey-cheeked mangabey Lophocebus albigena. This species relies upon hard seeds only when softer, preferred resources are not available, a fact which has been linked to its thick dental enamel. Another mangabey species with thick enamel, the sooty mangabey Cercocebus atys, processes a mechanically challenging food year-round. That the two mangabey species are both thickly-enameled suggests that both fallback and routine consumption of hard foods are associated with the same anatomical feature, complicating interpretations of thick enamel in the fossil record. We anticipated that aspects of enamel other than its thickness might differ between Cercocebus atys and Lophocebus albigena. We hypothesized that to function adequately under a dietary regime of routine hard-object feeding, the molars of Cercocebus atys would be more fracture and wear resistant than those of Lophocebus albigena. Methods Here we investigated critical fracture loads, nanomechanical properties of enamel, and enamel decussation in Cercocebus atys and Lophocebus albigena. Molars of Cercopithecus, a genus not associated with hard-object feeding, were included for comparison. Critical loads were estimated using measurements from 2D µCT slices of upper and lower molars. Nanomechanical properties (by nanoindentation) and decussation of enamel prisms (by SEM-imaging) in trigon basins of one upper second molar per taxon were compared. Results Protocone and protoconid critical fracture loads were significantly greater in Cercocebus atys than Lophocebus albigena and greater in both than in Cercopithecus. Elastic modulus, hardness, and elasticity index in most regions of the crown were greater in Cercocebus atys than in the other two taxa, with the greatest difference in the outer enamel. All taxa had decussated enamel, but that of Cercocebus atys uniquely exhibited a bundle of transversely oriented prisms cervical to the radial enamel. Quantitative comparison of in-plane and out-of-plane prism angles suggests that decussation in trigon basin enamel is more complex in Cercocebus atys than it is in either Lophocebus albigena or Cercopithecus cephus. These findings suggest that Cercocebus atys molars are more fracture and wear resistant than those of Lophocebus albigena and Cercopithecus. Recognition of these differences between Cercocebus atys and Lophocebus albigena molars sharpens our understanding of associations between hard-object feeding and dental anatomy under conditions of routine vs. fallback hard-object feeding and provides a basis for dietary inference in fossil primates, including hominins.
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Affiliation(s)
- Debbie Guatelli-Steinberg
- Department of Anthropology, The Ohio State University, Columbus, OH, United States of America
- School of Anthropology and Conservation, University of Kent, Canterbury, Kent, United Kingdom
| | - Cameron Renteria
- Department of Materials Science and Engineering, University of Washington, Seattle, WA, United States of America
- Department of Oral Health Sciences, School of Dentistry, University of Washington, Seattle, WA, United States of America
| | - Jack R. Grimm
- Department of Materials Science and Engineering, University of Washington, Seattle, WA, United States of America
| | - Izabela Maeret Carpenter
- Department of Materials Science and Engineering, University of Washington, Seattle, WA, United States of America
| | - Dwayne D. Arola
- Department of Materials Science and Engineering, University of Washington, Seattle, WA, United States of America
- Department of Oral Health Sciences, School of Dentistry, University of Washington, Seattle, WA, United States of America
- Department of Mechanical Engineering, University of Washington, Seattle, WA, United States of America
- Department of Restorative Dentistry, School of Dentistry, University of Washington, Seattle, WA, United States of America
| | - W. Scott McGraw
- Department of Anthropology, The Ohio State University, Columbus, OH, United States of America
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Byron C, Reed D, Iriarte-Diaz J, Wang Q, Strait D, Laird MF, Ross CF. Sagittal suture strain in capuchin monkeys (Sapajus and Cebus) during feeding. AMERICAN JOURNAL OF BIOLOGICAL ANTHROPOLOGY 2023; 180:633-654. [PMID: 36790169 DOI: 10.1002/ajpa.24701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2022] [Revised: 12/13/2022] [Accepted: 01/16/2023] [Indexed: 05/26/2023]
Abstract
OBJECTIVES Morphological variation in cranial sutures is used to infer aspects of primate feeding behavior, including diet, but strain regimes across sutures are not well documented. Our aim is to test hypotheses about sagittal suture morphology, strain regime, feeding behavior, and muscle activity relationships in robust Sapajus and gracile Cebus capuchin primates. MATERIALS AND METHODS Morphometrics of sinuosity in three regions of the sagittal suture were compared among museum specimens of Sapajus and Cebus, as well as in robust and gracile lab specimens. In vivo strains and bilateral electromyographic (EMG) activity were recorded from these regions in the temporalis muscles of capuchin primates while they fed on mechanically-varying foods. RESULTS Sapajus and the anterior suture region exhibited greater sinuosity than Cebus and posterior regions. In vivo data reveal minor differences in strain regime between robust and gracile phenotypes but show higher strain magnitudes in the middle suture region and higher tensile strains anteriorly. After gage location, feeding behavior has the most consistent and strongest impact on strain regime in the sagittal suture. Strain in the anterior suture has a high tension to compression ratio compared to the posterior region, especially during forceful biting in the robust Sapajus-like individual. DISCUSSION Sagittal suture complexity in robust capuchins likely reflects feeding behaviors associated with mechanically challenging foods. Sutural strain regimes in other anthropoid primates may also be affected by activity in feeding muscles.
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Affiliation(s)
- Craig Byron
- Department of Biology, Mercer University, Macon, Georgia, USA
| | - David Reed
- Department of Oral Biology, University of Illinois, Chicago, Illinois, USA
| | - Jose Iriarte-Diaz
- Department of Biology, University of the South, Sewanee, Tennessee, USA
| | - Qian Wang
- Department of Biomedical Sciences, Texas A&M University College of Dentistry, Dallas, Texas, USA
| | - David Strait
- Department of Anthropology, Washington University in St. Louis, St. Louis, Missouri, USA
- Palaeo-Research Institute, University of Johannesburg, Johannesburg, South Africa
| | - Myra F Laird
- Department of Basic and Translational Sciences, School of Dental Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Callum F Ross
- Department of Organismal Biology and Anatomy, University of Chicago, Chicago, Illinois, USA
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