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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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Towle I, Loho T, Salem AS, Berthaume MA, Loch C. Variation in enamel mechanical properties throughout the crown in catarrhine primates. J Hum Evol 2023; 182:103413. [PMID: 37562101 DOI: 10.1016/j.jhevol.2023.103413] [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: 02/10/2022] [Revised: 07/05/2023] [Accepted: 07/08/2023] [Indexed: 08/12/2023]
Abstract
Enamel mechanical properties vary across molar crowns, but the relationship among mechanical properties, tooth function, and phylogeny are not well understood. Fifteen primate lower molars representing fourteen taxa (catarrhine, n = 13; platyrrhine, n = 1) were sectioned in the lingual-buccal plane through the mesial cusps. Gradients of enamel mechanical properties, specifically hardness and elastic modulus, were quantified using nanoindentation from inner (near the enamel-dentine junction), through middle, to outer enamel (near the outer enamel surface) at five positions (buccal lateral, buccal cuspal, occlusal middle, lingual cuspal, lingual lateral). Cuspal positions had higher mechanical property values than lateral positions. Middle enamel had higher mean hardness and elastic modulus values than inner and outer locations in all five crown positions. Functionally, the thicker-enameled buccal cusps of lower molars did not show evidence of increased resistance to failure; instead, lingual cusps-which show higher rates of fracture-had higher average mechanical property values, with no significant differences observed between sides. Preliminary phylogenetic results suggest there is relatively little phylogenetic signal in gradients of mechanical properties through the enamel or across the crown. There appears to be common mechanical property patterns across molar crowns in Catarrhini and potentially among primates more broadly. These results may allow more precise interpretations of dental biomechanics and processes resulting in mechanical failure of enamel in primates, such as wear and fracture.
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Affiliation(s)
- Ian Towle
- Sir John Walsh Research Institute, Faculty of Dentistry, University of Otago, Dunedin 9054, New Zealand.
| | - Thomas Loho
- Faculty of Engineering, The University of Auckland, Auckland 1010, New Zealand
| | - Amira Samir Salem
- Sir John Walsh Research Institute, Faculty of Dentistry, University of Otago, Dunedin 9054, New Zealand
| | - Michael A Berthaume
- Division of Mechanical Engineering and Design, London South Bank University, London SE1 0AA, UK
| | - Carolina Loch
- Sir John Walsh Research Institute, Faculty of Dentistry, University of Otago, Dunedin 9054, New Zealand
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Chai H. On the evolution of the morphology and resilience of molar cusps in fossil hominid teeth. J Mech Behav Biomed Mater 2022; 133:105357. [PMID: 35841750 DOI: 10.1016/j.jmbbm.2022.105357] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2022] [Revised: 06/29/2022] [Accepted: 07/02/2022] [Indexed: 10/17/2022]
Abstract
Teeth play an important role in evolutionary studies due to their good preservation and direct link to diet. The present work makes use of a previously generated database on molar teeth of fossil hominids which consists of cuspal enamel thickness dc, dentin horn angle φ and section width D, all measured on a given histological tooth section. These data are here interpreted with the aid of "fracture stress" QF = PF/D2 and geological age t, where PF is the occlusal force needed to cause cusp failure as determined from dc and φ. QF is virtually a constant in non-hominins ("apes") while monotonically increasing toward present time in hominins. These two trends intersect at t = ts = 4.5 (0.11) mya, a value similar to other divergence estimates. QF was fitted with a function f(t) which is proportional to (dc/D)2. The monotonic variation of QF and in turn dc/D with t contrasts the more complex behavior generally characterizing other physical entities of fossil hominids. The increase in dc/D in hominins promotes tooth resilience and in turn life span. Finally, it is suggested that PF provides an upper bound to the maximum bite force produced by the jaw structure.
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Affiliation(s)
- Herzl Chai
- School of Mechanical Engineering, Tel-Aviv University, Israel.
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4
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Hunter-Schreger Band configuration in human molars reveals more decussation in the lateral enamel of 'functional' cusps than 'guiding' cusps. Arch Oral Biol 2022; 142:105524. [PMID: 36029738 DOI: 10.1016/j.archoralbio.2022.105524] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2022] [Revised: 08/11/2022] [Accepted: 08/15/2022] [Indexed: 11/21/2022]
Abstract
OBJECTIVES Enamel prism decussation, which manifests as Hunter-Schreger Bands (HSB), is considered a mechanism to mitigate crack propagation. During the chewing cycle, the 'functional' cusps that are involved in Phase II crushing and grinding experience more complex patterns of stress than do those that 'guide' the molars into occlusion (Phase I). This study examines HSB configuration in the lateral enamel of human molars to identify potential differences between these cusps as predicted from their functional distinctions. DESIGN Measurements were recorded from scanning electron micrographs of sections through the mesial cusps of unworn permanent molars. For each section, HSB packing density and the relative thickness of decussated enamel were quantified in the cuspal and middle segments of lateral enamel over the guiding and functional cusps. RESULTS No clear trend from first to third molars in HSB configuration was found in either jaw. In maxillary molars, the functional cusp displays higher HSB packing density in the cuspal and middle segments, and relatively thicker decussated enamel in the cuspal segment than does the guiding cusp. In mandibular molars, the functional cusp displays higher HSB packing density in the middle segment than does the guiding cusp, but no difference in relative thickness was found between them. Enamel of mandibular molars shows weaker decussation than maxillary molars. CONCLUSIONS The results suggest that guiding cusps are intrinsically more susceptible to crack propagation than functional cusps in human permanent molars. Structural factors such as enamel decussation should be considered when interpreting enamel chipping patterns in dietary contexts.
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Desoutter A, Slimani A, Tassery H, Cuisinier F, Sauro S, Salehi H, Panayotov I. Confocal Raman data analysis of tufts and spindles at the human dentin-enamel junction. Arch Oral Biol 2021; 131:105262. [PMID: 34543810 DOI: 10.1016/j.archoralbio.2021.105262] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Revised: 09/07/2021] [Accepted: 09/08/2021] [Indexed: 11/17/2022]
Abstract
OBJECTIVE The aim of this article is to analyze the chemical mapping of tufts and spindles of the human dental enamel using confocal Raman microscopy measuring length, structuration and composition of spindles and tufts. DESIGN we used Raman diffusion, based on the interaction between photons and optic phonons, to reveal chemical bound. Adult molars were selected and longitudinally sectioned. Areas of 120 * 120 μm were scanned near the dentin-enamel junction and grooves. Spectra were collected and phosphate and proteins peak intensities images were reconstructed, related to HPA concentration. Images of Phosphate (PO43-, 960 cm-1) and protein (CH, 2800/3000 cm-1) intensities have been reconstructed. K-mean cluster has been calculated to compare centroid spectra from enamel, dentin and tuft or spindle. RESULTS intensity profile revealed spindles as less mineralized areas than enamel, from 5 to 10 µm large. In the groove of molar, long tufts were found, more than 150 µm. CONCLUSIONS Confocal Raman microscopy is a very interesting tool to characterize chemically secondary structure of enamel. The size of a tuft in the groove allows us make the hypothesis that they could play a role in long term resilience of mechanical stress.
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Affiliation(s)
| | | | - Hervé Tassery
- LBN, Univ Montpellier, Montpellier, France; Université d'Aix-Marseille, Marseille, France
| | | | - Salavatore Sauro
- Dental Biomaterials and Minimally Invasive Dentistry, Department of Dentistry, Cardenal Herrera-CEU University, CEU Universities, C/Santiago Ramón y Cajal, s/n., Alfara del Patriarca, 46115 Valencia, Spain
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The homogenous alternative to biomineralization: Zn- and Mn-rich materials enable sharp organismal "tools" that reduce force requirements. Sci Rep 2021; 11:17481. [PMID: 34471148 PMCID: PMC8410824 DOI: 10.1038/s41598-021-91795-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Accepted: 03/18/2021] [Indexed: 11/09/2022] Open
Abstract
We measured hardness, modulus of elasticity, and, for the first time, loss tangent, energy of fracture, abrasion resistance, and impact resistance of zinc- and manganese-enriched materials from fangs, stings and other "tools" of an ant, spider, scorpion and nereid worm. The mechanical properties of the Zn- and Mn-materials tended to cluster together between plain and biomineralized "tool" materials, with the hardness reaching, and most abrasion resistance values exceeding, those of calcified salmon teeth and crab claws. Atom probe tomography indicated that Zn was distributed homogeneously on a nanometer scale and likely bound as individual atoms to more than ¼ of the protein residues in ant mandibular teeth. This homogeneity appears to enable sharper, more precisely sculpted "tools" than materials with biomineral inclusions do, and also eliminates interfaces with the inclusions that could be susceptible to fracture. Based on contact mechanics and simplified models, we hypothesize that, relative to plain materials, the higher elastic modulus, hardness and abrasion resistance minimize temporary or permanent tool blunting, resulting in a roughly 2/3 reduction in the force, energy, and muscle mass required to initiate puncture of stiff materials, and even greater force reductions when the cumulative effects of abrasion are considered. We suggest that the sharpness-related force reductions lead to significant energy savings, and can also enable organisms, especially smaller ones, to puncture, cut, and grasp objects that would not be accessible with plain or biomineralized "tools".
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Paranthropus robustus tooth chipping patterns do not support regular hard food mastication. J Hum Evol 2021; 158:103044. [PMID: 34303928 DOI: 10.1016/j.jhevol.2021.103044] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2020] [Revised: 06/03/2021] [Accepted: 06/08/2021] [Indexed: 11/22/2022]
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Hogg RT, Elokda A. Quantification of enamel decussation in gracile and robust capuchins (Cebus, Sapajus, Cebidae, Platyrrhini). Am J Primatol 2021; 83:e23246. [PMID: 33638563 DOI: 10.1002/ajp.23246] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Revised: 01/14/2021] [Accepted: 02/13/2021] [Indexed: 11/06/2022]
Abstract
Multiple behavioral and biomechanical analyses have demonstrated that capuchin monkeys (Cebus and Sapajus) are specialized for breaking down hard-object foods as compared to other cebid monkeys. In addition to a complex suite of craniodental adaptations, it has specifically been demonstrated that capuchins possess highly complex dental enamel, with extensive Hunter-Schreger banding and other decussation, that likely serve as an adaptation to resist crack propagation during hard-object feeding. Furthermore, it has been demonstrated that robust capuchins (Sapajus spp., formerly Cebus apella) demonstrate further adaptation for hard-object feeding than other capuchins, routinely breaking down extremely mechanically challenging foods. However, there has been no comparison of dental enamel complexity in robust versus gracile capuchins, to assess whether the dental enamel in Sapajus follows this same pattern of further specialization. Therefore, this study compares dental enamel complexity in images of dental thin sections from a sample of robust versus gracile capuchins using image compression ratio (ICR) analysis. ICR is a variable that correlates with enamel complexity, such that higher ICR values are indicative of increased complexity in the form of enamel decussation. We found no significant difference between robust and gracile capuchins when assessing all teeth in our sample together, however, we did find that robust capuchins have significantly higher ICR values than gracile capuchins for canine teeth, specifically. Our results support prior studies suggesting that robust capuchins are specialized to generate increased masticatory loads with their anterior dentition, specifically, as compared to gracile species.
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Affiliation(s)
- Russell T Hogg
- Department of Rehabilitation Sciences, Florida Gulf Coast University, Fort Myers, Florida, USA
| | - Abdallah Elokda
- Department of Biological Sciences, Florida Gulf Coast University, Fort Myers, Florida, USA
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9
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Kucher M, Dannemann M, Modler N, Bernhard MR, Hannig C, Weber MT. Mapping of the Micro-Mechanical Properties of Human Root Dentin by Means of Microindentation. MATERIALS 2021; 14:ma14030505. [PMID: 33494261 PMCID: PMC7864522 DOI: 10.3390/ma14030505] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Revised: 01/18/2021] [Accepted: 01/18/2021] [Indexed: 11/16/2022]
Abstract
The extensive knowledge of root dentin's mechanical properties is necessary for the prediction of microstructural alterations and the teeth's deformations as well as their fracture behavior. Standardized microindentation tests were applied to apical, medial, and cervical root sections of a mandibular human first molar to determine the spatial distribution of the hard tissue's properties (indentation modulus, indentation hardness, Martens hardness, indentation creep). Using an indentation mapping approach, the inhomogeneity of mechanical properties in longitudinal as well as in transversal directions were measured. As a result, the tooth showed strongly inhomogeneous material properties, which depended on the longitudinal and transversal positions. In the transversal cutting planes of the cervical, medial, apical sections, the properties showed a comparable distribution. A statistical evaluation revealed an indentation modulus between 12.2 GPa and 17.8 GPa, indentation hardness between 0.4 GPa and 0.64 GPa and an indentation creep between 8.6% and 10.7%. The established standardized method is a starting point for further investigations concerning the intensive description of the inhomogeneous mechanical properties of human dentin and other types of dentin.
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Affiliation(s)
- Michael Kucher
- Institute of Lightweight Engineering and Polymer Technology (ILK), Technische Universität Dresden, Holbeinstraße 3, 01307 Dresden, Germany; (M.K.); (N.M.)
| | - Martin Dannemann
- Institute of Lightweight Engineering and Polymer Technology (ILK), Technische Universität Dresden, Holbeinstraße 3, 01307 Dresden, Germany; (M.K.); (N.M.)
- Correspondence: ; Tel.: +49-351-463-38134
| | - Niels Modler
- Institute of Lightweight Engineering and Polymer Technology (ILK), Technische Universität Dresden, Holbeinstraße 3, 01307 Dresden, Germany; (M.K.); (N.M.)
| | - Martina Romy Bernhard
- Clinic of Operative and Pediatric Dentistry, Medical Faculty Carl Gustav Carus, Technische Universität Dresden, Fetscherstraße 74, 01307 Dresden, Germany; (M.R.B.); (C.H.); (M.-T.W.)
| | - Christian Hannig
- Clinic of Operative and Pediatric Dentistry, Medical Faculty Carl Gustav Carus, Technische Universität Dresden, Fetscherstraße 74, 01307 Dresden, Germany; (M.R.B.); (C.H.); (M.-T.W.)
| | - Marie-Theres Weber
- Clinic of Operative and Pediatric Dentistry, Medical Faculty Carl Gustav Carus, Technische Universität Dresden, Fetscherstraße 74, 01307 Dresden, Germany; (M.R.B.); (C.H.); (M.-T.W.)
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10
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Chipping and wear patterns in extant primate and fossil hominin molars: 'Functional' cusps are associated with extensive wear but low levels of fracture. J Hum Evol 2020; 151:102923. [PMID: 33360110 DOI: 10.1016/j.jhevol.2020.102923] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2020] [Revised: 11/22/2020] [Accepted: 11/23/2020] [Indexed: 01/01/2023]
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11
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Yi Z, Liao W, Zanolli C, Wang W. A robust alternative to assessing three-dimensional relative enamel thickness for the use in taxonomic assessment. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2020; 174:555-567. [PMID: 33247444 DOI: 10.1002/ajpa.24187] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Revised: 10/18/2020] [Accepted: 11/04/2020] [Indexed: 11/08/2022]
Abstract
OBJECTIVE Three-dimensional relative enamel thickness (3DRET) is important for assessing hypotheses about taxonomy, phylogeny, and dietary reconstruction for primates. However, its weaknesses have not been thoroughly investigated. Here, we analyze its weaknesses and propose an index aiming at better taxonomic discrimination. MATERIALS AND METHODS The dimensionless 3D index, ratio of enamel-thickness to dentine-thickness (3DRED), which is defined as the cubic root of the ratio of 3D average enamel thickness (3DAET) to 3D average dentine thickness (3DADT), is proposed here. To compare 3DRET and 3DRED and their sensitivity to voxel size, a fossil orangutan molar was scanned 14 times with different resolutions ranging from 10 to 50 μm. Enamel thickness analysis was carried out for each resultant digital model. In addition, enamel thickness measurements of 179 mandibular permanent molars (eight genera) were analyzed, followed by investigating the relationship between 3DRET and 3DAET and between 3DRED and 3DAET. RESULTS Regarding sensitivity, 3DRED is more robust than 3DRET. In addition, 3DRET is correlated with 3DAET by linear curve with regression coefficients approximating or larger than 0.8 in most cases, while 3DRED shows less correlation with 3DAET. Furthermore, there are clear separations between different taxa in the bivariate plot of 3DRED against 3DAET, indicative of the taxonomic value of 3DRED. CONCLUSION Under certain conditions, 3DRED promises to be a robust and reliable alternative to 3DRET in taxonomic study.
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Affiliation(s)
- Zhixing Yi
- School of Earth Sciences, China University of Geosciences, Wuhan, China
| | - Wei Liao
- School of Earth Sciences, China University of Geosciences, Wuhan, China.,Anthropology Museum of Guangxi, Nanning, China
| | - Clément Zanolli
- Laboratoire PACEA, UMR 5199 CNRS, Université de Bordeaux, Pessac, France
| | - Wei Wang
- Anthropology Museum of Guangxi, Nanning, China.,Institute of Cultural Heritage, Shandong University, Qingdao, China
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12
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Borrero-Lopez O, Constantino PJ, Bush MB, Lawn BR. On the vital role of enamel prism interfaces and graded properties in human tooth survival. Biol Lett 2020; 16:20200498. [PMID: 32842897 DOI: 10.1098/rsbl.2020.0498] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Teeth of omnivores face a formidable evolutionary challenge: how to protect against fracture and abrasive wear caused by the wide variety of foods they process. It is hypothesized that this challenge is met in part by adaptations in enamel microstructure. The low-crowned teeth of humans and some other omnivorous mammals exhibit multiple fissures running longitudinally along the outer enamel walls, yet remain intact. It is proposed that inter-prism weakness and enamel property gradation act together to avert entry of these fissures into vulnerable inner tooth regions and, at the same time, confer wear resistance at the occlusal surface. A simple indentation experiment is employed to quantify crack paths and energetics in human enamel, and an extended-finite-element model to evaluate longitudinal crack growth histories. Consideration is given as to how tooth microstructure may have played a vital role in human evolution, and by extension to other omnivorous mammals.
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Affiliation(s)
- Oscar Borrero-Lopez
- Departamento de Ingeniería Mecánica, Energética y de los Materiales, Universidad de Extremadura, 06006 Badajoz, Spain
| | - Paul J Constantino
- Department of Biology, Saint Michael's College, Colchester, VT 05439, USA
| | - Mark B Bush
- Department of Mechanical Engineering, University of Western Australia, Crawley, WA 6009, Australia
| | - Brian R Lawn
- Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
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13
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Crofts SB, Smith SM, Anderson PSL. Beyond Description: The Many Facets of Dental Biomechanics. Integr Comp Biol 2020; 60:594-607. [DOI: 10.1093/icb/icaa103] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Synopsis
Teeth lie at the interface between an animal and its environment and, with some exceptions, act as a major component of resource procurement through food acquisition and processing. Therefore, the shape of a tooth is closely tied to the type of food being eaten. This tight relationship is of use to biologists describing the natural history of species and given the high instance of tooth preservation in the fossil record, is especially useful for paleontologists. However, correlating gross tooth morphology to diet is only part of the story, and much more can be learned through the study of dental biomechanics. We can explore the mechanics of how teeth work, how different shapes evolved, and the underlying forces that constrain tooth shape. This review aims to provide an overview of the research on dental biomechanics, in both mammalian and non-mammalian teeth, and to synthesize two main approaches to dental biomechanics to develop an integrative framework for classifying and evaluating dental functional morphology. This framework relates food material properties to the dynamics of food processing, in particular how teeth transfer energy to food items, and how these mechanical considerations may have shaped the evolution of tooth morphology. We also review advances in technology and new techniques that have allowed more in-depth studies of tooth form and function.
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Affiliation(s)
- S B Crofts
- Department of Evolution, Ecology, and Behavior, University of Illinois, 515 Morrill Hall, 505 S. Goodwin Avenue, Urbana, IL 61801, USA
| | - S M Smith
- Field Museum of Natural History, Negaunee Integrative Research Center, 1400 South Lake Shore Drive, Chicago, IL 60605-2496, USA
| | - P S L Anderson
- Department of Evolution, Ecology, and Behavior, University of Illinois, 515 Morrill Hall, 505 S. Goodwin Avenue, Urbana, IL 61801, USA
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14
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Xiao H, Lei L, Peng J, Yang D, Zeng Q, Zheng J, Zhou Z. Research of the role of microstructure in the wear mechanism of canine and bovine enamel. J Mech Behav Biomed Mater 2019; 92:33-39. [PMID: 30654218 DOI: 10.1016/j.jmbbm.2018.12.036] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2018] [Revised: 12/26/2018] [Accepted: 12/27/2018] [Indexed: 10/27/2022]
Abstract
The relationship between the microstructure and tribological behavior of mammalian tooth enamel has not been fully understood. In this paper, the microstructure, mechanical properties, and tribological behavior of canine (carnivore) and bovine (herbivore) enamel are studied using scanning electronic microscopy and nano-indentation/scratch technique, aiming to reveal the contribution of enamel microstructure to its mechanical and tribological properties. Canine enamel has a microstructure of hard keyhole-like rods embedded in soft inter-rod enamel, and its surface exhibits high resistance against both micro-crack initiation and crack-induced delamination during friction and wear process. Bovine enamel with the microstructure consisting of the hydroxyapatite (HAP) nano-fibers in decussation has higher surface hardness and better capabilities of resisting wear and encumbering crack propagation, as compared to canine enamel. In sum, the soft inter-rod enamel in the canine enamel contributes to high load tolerance and then protects enamel surface from brittle damage, while the staggered arrangement of HAP nano-fibers benefits hard bovine enamel in crack propagation resistance and then help resist wear and fatigue. The findings suggest that there exists a self-adaptation in enamel microstructure and tribological performance of mammals with their feeding habits, which will promote and assist the bionic design of high-performance materials.
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Affiliation(s)
- Heng Xiao
- Tribology Research Institute, Key Laboratory of Advanced Technologies of Materials, Ministry of Education, Southwest Jiaotong University, Chengdu 610031, China
| | - Lei Lei
- Tribology Research Institute, Key Laboratory of Advanced Technologies of Materials, Ministry of Education, Southwest Jiaotong University, Chengdu 610031, China
| | - Jiapin Peng
- Tribology Research Institute, Key Laboratory of Advanced Technologies of Materials, Ministry of Education, Southwest Jiaotong University, Chengdu 610031, China
| | - Dan Yang
- Tribology Research Institute, Key Laboratory of Advanced Technologies of Materials, Ministry of Education, Southwest Jiaotong University, Chengdu 610031, China
| | - Qihang Zeng
- Tribology Research Institute, Key Laboratory of Advanced Technologies of Materials, Ministry of Education, Southwest Jiaotong University, Chengdu 610031, China
| | - Jing Zheng
- Tribology Research Institute, Key Laboratory of Advanced Technologies of Materials, Ministry of Education, Southwest Jiaotong University, Chengdu 610031, China.
| | - Zhongrong Zhou
- Tribology Research Institute, Key Laboratory of Advanced Technologies of Materials, Ministry of Education, Southwest Jiaotong University, Chengdu 610031, China
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15
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Yilmaz ED, Koldehoff J, Schneider GA. On the systematic documentation of the structural characteristics of bovine enamel: A critic to the protein sheath concept. Dent Mater 2018; 34:1518-1530. [DOI: 10.1016/j.dental.2018.06.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2017] [Revised: 05/24/2018] [Accepted: 06/07/2018] [Indexed: 11/28/2022]
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16
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Zhang Y, Lawn BR. Evaluating dental zirconia. Dent Mater 2018; 35:15-23. [PMID: 30172379 DOI: 10.1016/j.dental.2018.08.291] [Citation(s) in RCA: 53] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Revised: 08/19/2018] [Accepted: 08/21/2018] [Indexed: 10/28/2022]
Abstract
OBJECTIVES To survey simple contact testing protocols for evaluating the mechanical integrity of zirconia dental ceramics. Specifically, to map vital material property variations and to quantify competing damage modes. METHODS Exploratory contact tests are conducted on layer structures representative of zirconia crowns on dentin. RESULTS Sharp-tip micro- and nano-indentations were used to investigate the roles of weak interfaces and residual stresses in veneered zirconia, and to map property variations in graded structures. Tests with blunt sphere indenters on flat specimens were used to identify and quantify various critical damage modes in simulated occlusal loading in veneered and monolithic zirconia. SIGNIFICANCE Contact testing is a powerful tool for elucidating the fracture and deformation modes that control the lifetimes of zirconia dental ceramics. The advocated tests are simple, and provide a sound physical basis for analyzing damage resistance of anatomically-correct crowns and other complex dental prostheses.
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Affiliation(s)
- Yu Zhang
- Department of Biomaterials and Biomimetics, New York University College of Dentistry, New York, NY 10010, USA.
| | - Brian R Lawn
- Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
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17
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Constantino PJ, Borrero‐Lopez O, Lawn BR. Mechanisms of tooth damage and
Paranthropus
dietary reconstruction. BIOSURFACE AND BIOTRIBOLOGY 2018. [DOI: 10.1049/bsbt.2018.0017] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Affiliation(s)
| | - Oscar Borrero‐Lopez
- Departamento de Ingeniería Mecánica, Energética y de los MaterialesUniversidad de Extremadura06006BadajozSpain
| | - Brian R. Lawn
- Materials Measurement LaboratoryNational Institute of Standards and TechnologyGaithersburgMD20899USA
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18
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Scott JE, Campbell RM, Baj LM, Burns MC, Price MS, Sykes JD, Vinyard CJ. Dietary signals in the premolar dentition of primates. J Hum Evol 2018; 121:221-234. [DOI: 10.1016/j.jhevol.2018.04.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2015] [Revised: 04/12/2018] [Accepted: 04/16/2018] [Indexed: 10/16/2022]
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19
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Püschel TA, Marcé-Nogué J, Kaiser TM, Brocklehurst RJ, Sellers WI. Analyzing the sclerocarpy adaptations of the Pitheciidae mandible. Am J Primatol 2018; 80:e22759. [PMID: 29664191 DOI: 10.1002/ajp.22759] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2016] [Revised: 02/28/2018] [Accepted: 03/30/2018] [Indexed: 11/09/2022]
Abstract
Primates are interpreted to be ancestrally adapted to frugivory, although some modern groups show clear adaptations to other diets. Among them, pitheciids stand out for specifically predating seeds. This dietary specialization is known as sclerocarpy and refers to the extraction of seeds from surrounding hard tissues using the anterior dentition followed by the mastication of seeds by the molars. It has been proposed that Callicebus-Pithecia-Chiropotes-Cacajao represent a morphocline of increasingly specialized anatomical traits for sclerocarpic foraging. This study addresses whether there is a sclerocarpic specialization gradient in the mandibular morphology of pitheciids. Finite element analysis (FEA) was used to simulate two biting scenarios and the obtained stress values were compared between different pitheciids. Geometric morphometrics (GM) were used to display the morphological variation of this group. No support was found for the morphocline hypothesis from a biomechanical viewpoint since all pitheciins showed similar stress values and on average Chiropotes rather than Cacajao exhibited the strongest mandible. From a morphological perspective, it was found that there is indeed relative "robusticity" continuum in the pitheciid mandible for some aspects of shape as expected for the morphocline hypothesis, but this gradient could be related to other factors rather than sclerocarpic specialization. The present results are expected to contribute to a better insight regarding the ecomorphological relationship between mandibular morphology and mechanical performance among pitheciids.
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Affiliation(s)
- Thomas A Püschel
- School of Earth and Environmental Sciences, University of Mancheste, Manchester, United Kingdom
| | - Jordi Marcé-Nogué
- Center of Natural History (CeNak), Universität Hamburg, Hamburg, Germany.,Institut Català de Paleontologia M. Crusafont, Universitat Autònoma de Barcelona, Cerdanyola del Vallès, Barcelona, Spain
| | - Thomas M Kaiser
- Center of Natural History (CeNak), Universität Hamburg, Hamburg, Germany
| | - Robert J Brocklehurst
- School of Earth and Environmental Sciences, University of Mancheste, Manchester, United Kingdom
| | - William I Sellers
- School of Earth and Environmental Sciences, University of Mancheste, Manchester, United Kingdom
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20
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21
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Nikolaus A, Currey JD, Lindtner T, Fleck C, Zaslansky P. Importance of the variable periodontal ligament geometry for whole tooth mechanical function: A validated numerical study. J Mech Behav Biomed Mater 2017; 67:61-73. [DOI: 10.1016/j.jmbbm.2016.11.020] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2016] [Revised: 11/01/2016] [Accepted: 11/24/2016] [Indexed: 11/27/2022]
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22
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Zaslansky P, Currey JD, Fleck C. Learning from evolutionary optimisation: what are toughening mechanisms good for in dentine, a nonrepairing bone tissue? BIOINSPIRATION & BIOMIMETICS 2016; 11:051003. [PMID: 27615450 DOI: 10.1088/1748-3190/11/5/051003] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The main mass of material found in teeth is dentine, a bone-like tissue, riddled with micron-sized tubules and devoid of living cells. It provides support to the outer wear-resistant layer of enamel, and exhibits toughening mechanisms which contribute to crack resistance. And yet unlike most bone tissues, dentine does not remodel and consequently any accumulated damage does not 'self repair'. Because damage containment followed by tissue replacement is a prime reason for the crack-arresting microstructures found in most bones, the occurrence of toughening mechanisms without the biological capability to repair is puzzling. Here we consider the notion that dentine might be overdesigned for strength, because it has to compensate for the lack of cell-mediated healing mechanisms. Based on our own and on literature-reported observations, including quasistatic and fatigue properties, dentine design principles are discussed in light of the functional conditions under which teeth evolved. We conclude that dentine is only slightly overdesigned for everyday cyclic loading because usual mastication stresses may come close to its endurance strength. The in-built toughening mechanisms constitute an evolutionary benefit because they prevent catastrophic failure during rare overload events, which was probably very advantageous in our hunter gatherer ancestor times. From a bio-inspired perspective, understanding the extent of evolutionary overdesign might be useful for optimising biomimetic structures used for load bearing.
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Affiliation(s)
- Paul Zaslansky
- Julius-Wolff-Institute Charité Berlin Föhrerstr. 15 D-13353 Berlin, Germany
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23
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Glowacka H, McFarlin SC, Catlett KK, Mudakikwa A, Bromage TG, Cranfield MR, Stoinski TS, Schwartz GT. Age-related changes in molar topography and shearing crest length in a wild population of mountain Gorillas from Volcanoes National Park, Rwanda. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2016; 160:3-15. [PMID: 26853974 DOI: 10.1002/ajpa.22943] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2015] [Revised: 12/26/2015] [Accepted: 01/01/2016] [Indexed: 11/12/2022]
Abstract
OBJECTIVES Great ape teeth must remain functional over long lifespans. The molars of the most folivorous apes, the mountain gorillas, must maintain shearing function for 40+ years while the animals consume large quantities of mechanically challenging foods. While other folivorous primates experience dental senescence, which compromises their occlusal surfaces and affects their reproductive success as they age, it is unknown whether dental senescence also occurs in mountain gorillas. In this article, we quantified and evaluated how mountain gorilla molars change throughout their long lifespans. MATERIALS AND METHODS We collected high-resolution replicas of M(1)s (n = 15), M(2)s (n = 13), and M(3)s (n = 11) from a cross-sectional sample of wild mountain gorilla skeletons from the Virunga Volcanoes, ranging in age from 4 to 43 years. We employed dental topographic analyses to track how aspects of occlusal slope, angularity, relief index, and orientation patch count rotated change with age. In addition, we measured the relative length of shearing crests in two- and three-dimensions. RESULTS Occlusal topography was found to decrease, while 2D relative shearing crest length increased, and 3D relative crest lengths were maintained with age. DISCUSSION Our findings indicate that shearing function is maintained throughout the long lifetimes of mountain gorillas. Unlike the dental senescence experienced by other folivorous primates, mountain gorillas do not appear to possess senesced molars despite their long lifetimes, mechanically challenging diets, and decreases in occlusal topography with age.
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Affiliation(s)
- Halszka Glowacka
- Institute of Human Origins, School of Human Evolution and Social Change, Arizona State University, Tempe, AZ
| | - Shannon C McFarlin
- Department of Anthropology and Center for the Advanced Study of Human Paleobiology, the George Washington University, DC.,Division of Mammals, National Museum of Natural History, Smithsonian Institution, DC
| | - Kierstin K Catlett
- Institute of Human Origins, School of Human Evolution and Social Change, Arizona State University, Tempe, AZ
| | | | - Timothy G Bromage
- Department of Biomaterials and Biomimetics, New York University College of Dentistry, NY.,Department of Basic Science and Craniofacial Biology, New York University College of Dentistry, NY
| | | | | | - Gary T Schwartz
- Institute of Human Origins, School of Human Evolution and Social Change, Arizona State University, Tempe, AZ
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24
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Constantino PJ, Borrero‐Lopez O, Pajares A, Lawn BR. Simulation of enamel wear for reconstruction of diet and feeding behavior in fossil animals: A micromechanics approach. Bioessays 2015; 38:89-99. [DOI: 10.1002/bies.201500094] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
| | - Oscar Borrero‐Lopez
- Departamento de Ingeniería MecánicaEnergética y de los MaterialesUniversidad de ExtremaduraBadajozSpain
| | - Antonia Pajares
- Departamento de Ingeniería MecánicaEnergética y de los MaterialesUniversidad de ExtremaduraBadajozSpain
| | - Brian R. Lawn
- Materials Measurement LaboratoryNational Institute of Standards and TechnologyGaithersburgMDUSA
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25
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Ziscovici C, Lucas PW, Constantino PJ, Bromage TG, van Casteren A. Sea otter dental enamel is highly resistant to chipping due to its microstructure. Biol Lett 2015; 10:20140484. [PMID: 25319817 DOI: 10.1098/rsbl.2014.0484] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Dental enamel is prone to damage by chipping with large hard objects at forces that depend on chip size and enamel toughness. Experiments on modern human teeth have suggested that some ante-mortem chips on fossil hominin enamel were produced by bite forces near physiological maxima. Here, we show that equivalent chips in sea otter enamel require even higher forces than human enamel. Increased fracture resistance correlates with more intense enamel prism decussation, often seen also in some fossil hominins. It is possible therefore that enamel chips in such hominins may have formed at even greater forces than currently envisaged.
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Affiliation(s)
- Charles Ziscovici
- Department of Anthropology, Center for the Advanced Study of Human Paleobiology, George Washington University, Washington, DC 20052, USA
| | - Peter W Lucas
- Department of Bioclinical Sciences, Faculty of Dentistry, Kuwait University, PO BOX 24923, Safat 13110, Kuwait
| | - Paul J Constantino
- Department of Biology, Saint Michael's College, Colchester, VT 05439, USA
| | - Timothy G Bromage
- Department of Biomaterials and Biomimetics, New York University College of Dentistry, 345 East 24th Street, New York, NY 10010, USA Department of Basic Science and Craniofacial Biology, New York University College of Dentistry, 345 East 24th Street, New York, NY 10010, USA
| | - Adam van Casteren
- Department of Bioclinical Sciences, Faculty of Dentistry, Kuwait University, PO BOX 24923, Safat 13110, Kuwait Max Planck Weizmann Center for Integrative Archaeology and Anthropology, Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, Leipzig 04103, Germany
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26
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McGraw WS, Vick AE, Daegling DJ. Dietary variation and food hardness in sooty mangabeys (Cercocebus atys): Implications for fallback foods and dental adaptation. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2014; 154:413-23. [DOI: 10.1002/ajpa.22525] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2014] [Accepted: 04/21/2014] [Indexed: 11/11/2022]
Affiliation(s)
- W. Scott McGraw
- Department of Anthropology; The Ohio State University; Columbus OH 43210-1106
| | - Anna E. Vick
- Department of Social and Behavioral Sciences; Santa Fe College; Gainesville FL 32606
| | - David J. Daegling
- Department of Anthropology; University of Florida; Gainesville FL 32611-7305
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27
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O'Brien S, Keown AJ, Constantino P, Xie Z, Bush MB. Revealing the structural and mechanical characteristics of ovine teeth. J Mech Behav Biomed Mater 2014; 30:176-85. [DOI: 10.1016/j.jmbbm.2013.11.006] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2013] [Revised: 11/10/2013] [Accepted: 11/12/2013] [Indexed: 10/26/2022]
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28
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Romero A, Ramírez-Rozzi FV, De Juan J, Pérez-Pérez A. Diet-related buccal dental microwear patterns in Central African Pygmy foragers and Bantu-speaking farmer and pastoralist populations. PLoS One 2013; 8:e84804. [PMID: 24367696 PMCID: PMC3868657 DOI: 10.1371/journal.pone.0084804] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2013] [Accepted: 11/19/2013] [Indexed: 12/03/2022] Open
Abstract
Pygmy hunter-gatherers from Central Africa have shared a network of socioeconomic interactions with non-Pygmy Bantu speakers since agropastoral lifestyle spread across sub-Saharan Africa. Ethnographic studies have reported that their diets differ in consumption of both animal proteins and starch grains. Hunted meat and gathered plant foods, especially underground storage organs (USOs), are dietary staples for pygmies. However, scarce information exists about forager–farmer interaction and the agricultural products used by pygmies. Since the effects of dietary preferences on teeth in modern and past pygmies remain unknown, we explored dietary history through quantitative analysis of buccal microwear on cheek teeth in well-documented Baka pygmies. We then determined if microwear patterns differ among other Pygmy groups (Aka, Mbuti, and Babongo) and between Bantu-speaking farmer and pastoralist populations from past centuries. The buccal dental microwear patterns of Pygmy hunter-gatherers and non-Pygmy Bantu pastoralists show lower scratch densities, indicative of diets more intensively based on nonabrasive foodstuffs, compared with Bantu farmers, who consume larger amounts of grit from stoneground foods. The Baka pygmies showed microwear patterns similar to those of ancient Aka and Mbuti, suggesting that the mechanical properties of their preferred diets have not significantly changed through time. In contrast, Babongo pygmies showed scratch densities and lengths similar to those of the farmers, consistent with sociocultural contacts and genetic factors. Our findings support that buccal microwear patterns predict dietary habits independent of ecological conditions and reflect the abrasive properties of preferred or fallback foods such as USOs, which may have contributed to the dietary specializations of ancient human populations.
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Affiliation(s)
- Alejandro Romero
- Universidad de Alicante, Departamento de Biotecnología, Alicante, Spain
| | - Fernando V. Ramírez-Rozzi
- Centre National de la Recherche Scientifique, Unité Propre de Recherche “Dynamique de l’Évolution Humaine,” Paris, France
| | - Joaquín De Juan
- Universidad de Alicante, Departamento de Biotecnología, Alicante, Spain
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29
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Lawn BR, Bush MB, Barani A, Constantino PJ, Wroe S. Inferring biological evolution from fracture patterns in teeth. J Theor Biol 2013; 338:59-65. [DOI: 10.1016/j.jtbi.2013.08.029] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Revised: 08/21/2013] [Accepted: 08/27/2013] [Indexed: 10/26/2022]
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30
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Zaslansky P, Maerten A, Fratzl P. Apatite alignment and orientation at the Ångstrom and nanometer length scales shed light on the adaptation of dentine to whole tooth mechanical function. BIOINSPIRED BIOMIMETIC AND NANOBIOMATERIALS 2013. [DOI: 10.1680/bbn.13.00007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
Human teeth are capped by a highly mineralized enamel layer that rests on a bone-like material termed dentine. Dentine is composed mainly of collagen and carbonated apatite known to form the biological composite of all types of bone by combining into mineralized collagen fibrils. The apatite mineral is found both within and also encasing the fibrils, but in dentine, particularly in the crown, mineral is also found in regions where there is no collagen, forming peritubular dentine cuffs that surround narrow channels that perforate and render dentine porous. The authors hypothesize that regional variations in the mineral spatial configuration may reflect local adaptation to functional needs of whole teeth. The 3D orientation of the micron-sized tubules and the associated clusters of peritubular mineral vary on the length scale of millimeters. The orientation and degree of coalignment of the nanometer-sized mineral platelets in dentine exhibit marked changes at the same length scale, matching predicted load-trajectories in loaded teeth. However, wide-angle X-ray diffraction mapping shows that there is almost no preferred orientation of the 002 reflection (and hence the c-axis of apatite). The authors thus propose that the orientation of the peritubular and intertubular mineral compensate for localized preferred orientations, to create an overall average, randomly oriented mineral configuration.
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Affiliation(s)
- P. Zaslansky
- Julius Wolff Institute and Berlin-Brandenburg Center for Regenerative Therapies, CharitÉ – UniversitÄtsmedizin, Berlin, Germany
| | - A. Maerten
- Materials Engineering, Technische UniversitÄt, Berlin, Germany
| | - P. Fratzl
- Department of Biomaterials, Max-Planck-Institute of Colloids and Interfaces, Potsdam, Germany
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31
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Lawn BR, Chai H, Barani A, Bush MB. Transverse fracture of canine teeth. J Biomech 2013; 46:1561-7. [DOI: 10.1016/j.jbiomech.2013.03.018] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2012] [Revised: 02/19/2013] [Accepted: 03/16/2013] [Indexed: 11/26/2022]
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32
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Effect of property gradients on enamel fracture in human molar teeth. J Mech Behav Biomed Mater 2012; 15:121-30. [DOI: 10.1016/j.jmbbm.2012.06.014] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2012] [Revised: 06/19/2012] [Accepted: 06/23/2012] [Indexed: 11/23/2022]
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