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Towle I, Loch C, Oxenham M, Krueger KL, Samir Salem A, de Pinillos MM, Modesto-Mata M, Hlusko LJ. Technical note: Micro-computed tomography calibration using dental tissue for bone mineral research. AMERICAN JOURNAL OF BIOLOGICAL ANTHROPOLOGY 2024; 184:e24952. [PMID: 38775381 DOI: 10.1002/ajpa.24952] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2024] [Revised: 04/13/2024] [Accepted: 04/29/2024] [Indexed: 06/20/2024]
Abstract
Computed tomography (CT) and microcomputed tomography (μCT) require calibration against density phantoms scanned with specimens or during routine internal calibration for assessment of mineral concentration (MC) and density. In clinical studies involving bone, alternative calibration methods using bodily tissues and fluids ("phantomless" calibration) have been suggested. However, such tissues are seldom available in archeological and osteological research. This study investigates the potential of dental tissue as internal reference for calibration of μCT scans, facilitating the analysis of bone MC. We analyzed 70 molars from 24 extant primate species, including eight human teeth, each scanned with density phantoms for calibration. Our findings indicate that sampling specific regions of molars (lateral aspects of the mesial cusps) yields low variation in enamel and dentine MC values, averaging 1.27 g/cm3 (±0.03) for dentine and 2.25 g/cm3 (±0.03) for enamel. No significant differences were observed across molar types or among scanning procedures, including scanner model, resolution, and filters. An ad hoc test on 12 mandibles revealed low variance in MC between the conventional phantom and dental tissue calibration methods; all 36 measurements (low, medium, and high MC for each mandible) were within 0.05 g/cm3 of each other -81% were within 0.03 g/cm3 and 94% within 0.04 g/cm3. Based on these results, we propose a new "phantomless" calibration technique using these mean enamel and dentine MC values. The presented phantomless calibration method could aid in the assessment of bone pathology and enhance the scope of studies investigating bone structure and physical property variations in archeological, osteological, and laboratory-based research.
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Affiliation(s)
- Ian Towle
- Centro Nacional de Investigación sobre la Evolución Humana (CENIEH), Burgos, Spain
- Sir John Walsh Research Institute, Faculty of Dentistry, University of Otago, Dunedin, New Zealand
| | - Carolina Loch
- Sir John Walsh Research Institute, Faculty of Dentistry, University of Otago, Dunedin, New Zealand
| | - Marc Oxenham
- School of Archaeology and Anthropology, Australian National University, Canberra, Australia
- Department of Archaeology, School of Geosciences, University of Aberdeen, Aberdeen, UK
| | - Kristin L Krueger
- Department of Anthropology, Loyola University Chicago, Chicago, IL, USA
| | - Amira Samir Salem
- Sir John Walsh Research Institute, Faculty of Dentistry, University of Otago, Dunedin, New Zealand
| | - Marina Martínez de Pinillos
- Centro Nacional de Investigación sobre la Evolución Humana (CENIEH), Burgos, Spain
- Laboratorio de Evolución Humana (LEH), Universidad de Burgos, Burgos, Spain
| | - Mario Modesto-Mata
- Centro Nacional de Investigación sobre la Evolución Humana (CENIEH), Burgos, Spain
- Universidad Internacional de La Rioja (UNIR), Logroño La Rioja, Spain
| | - Leslea J Hlusko
- Centro Nacional de Investigación sobre la Evolución Humana (CENIEH), Burgos, Spain
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Towle I, Loch C. Variation in enamel prism size in primate molars. Arch Oral Biol 2024; 160:105895. [PMID: 38266424 DOI: 10.1016/j.archoralbio.2024.105895] [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: 11/07/2023] [Revised: 01/10/2024] [Accepted: 01/13/2024] [Indexed: 01/26/2024]
Abstract
OBJECTIVE This study examines whether larger enamel prism diameters accommodate a greater enamel volume from the enamel-dentine junction (EDJ) to the outer-enamel surface (OES) in primate molars, and how prism size relates to enamel thickness and crown location. DESIGN We assessed variation in enamel prism diameter in relation to crown location and enamel thickness in catarrhine lower molars (n = 14 species) and one platyrrhine. Prism diameter and enamel thickness were recorded in four locations (lingual lateral; lingual cuspal; buccal cuspal; buccal lateral), using a buccal-lingual section through the centre of the mesial cusps. Ten prism diameter readings were collected at inner (near the EDJ), outer (near the OES) and middle (between the two locations) enamel for each location. RESULTS Mean prism diameter values for each species were similar (range: 4.06 µm to 5.81 µm). Prism diameter enlarged from inner to outer enamel, suggesting larger prisms help accommodate the increase in enamel volume from the EDJ to the OES. Average prism diameter does not associate with enamel thickness. Instead, cuspal positions had significantly smaller prism diameter at the EDJ than lateral positions, and larger prism sizes at the OES, leading to an overall similar prism diameter mean for all positions (Lingual lateral: 5.11 µm; Lingual cuspal: 5.04 µm; Buccal cuspal: 4.78 µm; Buccal lateral: 4.99 µm). CONCLUSIONS Our study revealed consistent average enamel prism diameters in various crown locations of lower primate molars, potentially contributing to the mechanical integrity and functional optimization of enamel in primates.
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Affiliation(s)
- Ian Towle
- Sir John Walsh Research Institute, Faculty of Dentistry, University of Otago, Dunedin 9054, New Zealand; Centro Nacional de Investigación sobre la Evolución Humana (CENIEH), Paseo Sierra de Atapuerca 3, 09002 Burgos, Spain.
| | - Carolina Loch
- Sir John Walsh Research Institute, Faculty of Dentistry, University of Otago, Dunedin 9054, New Zealand
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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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Towle I, Salem AS, Veneziano A, Loch C. Variation in enamel and dentine mineral concentration and density in primate molars. Arch Oral Biol 2023; 153:105752. [PMID: 37385050 DOI: 10.1016/j.archoralbio.2023.105752] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2023] [Revised: 05/24/2023] [Accepted: 06/15/2023] [Indexed: 07/01/2023]
Abstract
OBJECTIVE Variation in enamel and dentine mineral concentration and total effective density can be reliably collected using Micro-CT scans. Both variables are suggested to reflect mechanical properties such as hardness and elastic modulus in dental tissues, meaning Micro-CT methods allow relative composition and mechanical properties to be collected non-destructively. DESIGN 16 lower molars from 16 Catarrhine primates were Micro-CT scanned alongside hydroxyapatite phantoms using standardized settings and methods to calculate mineral concentration and total effective density. Mineral concentration, total effective density and thickness of dentine and enamel were calculated for four cusps, representing each 'corner' of the tooth and four lateral crown positions (i.e., mesial, buccal, lingual and distal). RESULTS The results show mean mineral concentration and total effective density values were higher in areas of thicker enamel, while the opposite was observed for dentine. Buccal positions had significantly higher mineral concentration and total effective density values than lingual areas. Cuspal positions had higher mean values than lateral enamel, for both dentine (mineral concentration cuspal: 1.26 g/cm3; lateral: 1.20 g/cm3) and enamel (mineral concentration cuspal: 2.31 g/cm3; lateral: 2.25 g/cm3). Mesial enamel had significantly lower values than other locations. CONCLUSIONS These common patterns across Catarrhine taxa may be linked to functional adaptations related to optimization of mastication and tooth protection. Variation in mineral concentration and total effective density may also be associated with wear and fracture patterns, and can be used as baseline information to investigate the effect of diet, pathological changes and aging on teeth through time.
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Affiliation(s)
- Ian Towle
- Sir John Walsh Research Institute, Faculty of Dentistry, University of Otago, Dunedin 9054, New Zealand.
| | - Amira Samir Salem
- Sir John Walsh Research Institute, Faculty of Dentistry, University of Otago, Dunedin 9054, New Zealand
| | - Alessio Veneziano
- Department of Mechanical Engineering, Universitat Rovira i Virgili, Tarragona, Spain
| | - Carolina Loch
- Sir John Walsh Research Institute, Faculty of Dentistry, University of Otago, Dunedin 9054, New Zealand
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Faber J, Hinrichsen J, Greiner A, Reiter N, Budday S. Tissue-Scale Biomechanical Testing of Brain Tissue for the Calibration of Nonlinear Material Models. Curr Protoc 2022; 2:e381. [PMID: 35384412 DOI: 10.1002/cpz1.381] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Revised: 01/14/2022] [Indexed: 06/14/2023]
Abstract
Brain tissue is one of the most complex and softest tissues in the human body. Due to its ultrasoft and biphasic nature, it is difficult to control the deformation state during biomechanical testing and to quantify the highly nonlinear, time-dependent tissue response. In numerous experimental studies that have investigated the mechanical properties of brain tissue over the last decades, stiffness values have varied significantly. One reason for the observed discrepancies is the lack of standardized testing protocols and corresponding data analyses. The tissue properties have been tested on different length and time scales depending on the testing technique, and the corresponding data have been analyzed based on simplifying assumptions. In this review, we highlight the advantage of using nonlinear continuum mechanics based modeling and finite element simulations to carefully design experimental setups and protocols as well as to comprehensively analyze the corresponding experimental data. We review testing techniques and protocols that have been used to calibrate material model parameters and discuss artifacts that might falsify the measured properties. The aim of this work is to provide standardized procedures to reliably quantify the mechanical properties of brain tissue and to more accurately calibrate appropriate constitutive models for computational simulations of brain development, injury and disease. Computational models can not only be used to predictively understand brain tissue behavior, but can also serve as valuable tools to assist diagnosis and treatment of diseases or to plan neurosurgical procedures. © 2022 The Authors. Current Protocols published by Wiley Periodicals LLC.
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Affiliation(s)
- Jessica Faber
- Friedrich-Alexander-Universität Erlangen-Nürnberg, Institute of Applied Mechanics, Egerlandstraße 5, 91058 Erlangen, Germany
| | - Jan Hinrichsen
- Friedrich-Alexander-Universität Erlangen-Nürnberg, Institute of Applied Mechanics, Egerlandstraße 5, 91058 Erlangen, Germany
| | - Alexander Greiner
- Friedrich-Alexander-Universität Erlangen-Nürnberg, Institute of Applied Mechanics, Egerlandstraße 5, 91058 Erlangen, Germany
| | - Nina Reiter
- Friedrich-Alexander-Universität Erlangen-Nürnberg, Institute of Applied Mechanics, Egerlandstraße 5, 91058 Erlangen, Germany
| | - Silvia Budday
- Friedrich-Alexander-Universität Erlangen-Nürnberg, Institute of Applied Mechanics, Egerlandstraße 5, 91058 Erlangen, Germany
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Mechanical food properties and dental topography differentiate three populations of Lemur catta in southwest Madagascar. J Hum Evol 2016; 98:66-75. [DOI: 10.1016/j.jhevol.2015.09.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2014] [Revised: 03/26/2015] [Accepted: 09/10/2015] [Indexed: 11/22/2022]
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Lucas PW, Philip SM, Al-Qeoud D, Al-Draihim N, Saji S, van Casteren A. Structure and scale of the mechanics of mammalian dental enamel viewed from an evolutionary perspective. Evol Dev 2015; 18:54-61. [DOI: 10.1111/ede.12169] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- Peter W. Lucas
- Department of Bioclinical Sciences; Faculty of Dentistry; Kuwait University; Jabriya, Kuwait, P.O. Box 24923 Safat 13110 Kuwait
| | - Swapna M. Philip
- Department of Bioclinical Sciences; Faculty of Dentistry; Kuwait University; Jabriya, Kuwait, P.O. Box 24923 Safat 13110 Kuwait
| | - Dareen Al-Qeoud
- Department of Bioclinical Sciences; Faculty of Dentistry; Kuwait University; Jabriya, Kuwait, P.O. Box 24923 Safat 13110 Kuwait
| | - Nuha Al-Draihim
- Department of Bioclinical Sciences; Faculty of Dentistry; Kuwait University; Jabriya, Kuwait, P.O. Box 24923 Safat 13110 Kuwait
| | - Sreeja Saji
- Department of Bioclinical Sciences; Faculty of Dentistry; Kuwait University; Jabriya, Kuwait, P.O. Box 24923 Safat 13110 Kuwait
| | - Adam van Casteren
- Max Planck Weizmann Center for Integrative Archaeology and Anthropology; Max Planck Institute for Evolutionary Anthropology; Deutscher Platz 6 D-04103 Leipzig Germany
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Kappeler PM, Fichtel C. Eco-evo-devo of the lemur syndrome: did adaptive behavioral plasticity get canalized in a large primate radiation? Front Zool 2015; 12 Suppl 1:S15. [PMID: 26816515 PMCID: PMC4722368 DOI: 10.1186/1742-9994-12-s1-s15] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
BACKGROUND Comprehensive explanations of behavioral adaptations rarely invoke all levels famously admonished by Niko Tinbergen. The role of developmental processes and plasticity, in particular, has often been neglected. In this paper, we combine ecological, physiological and developmental perspectives in developing a hypothesis to account for the evolution of 'the lemur syndrome', a combination of reduced sexual dimorphism, even adult sex ratios, female dominance and mild genital masculinization characterizing group-living species in two families of Malagasy primates. RESULTS We review the different components of the lemur syndrome and compare it with similar adaptations reported for other mammals. We find support for the assertion that the lemur syndrome represents a unique set of integrated behavioral, demographic and morphological traits. We combine existing hypotheses about underlying adaptive function and proximate causation by adding a potential developmental mechanism linking maternal stress and filial masculinization, and outline an evolutionary scenario for its canalization. CONCLUSIONS We propose a new hypothesis linking ecological, physiological, developmental and evolutionary processes to adumbrate a comprehensive explanation for the evolution of the lemur syndrome, whose assumptions and predictions can guide diverse future research on lemurs. This hypothesis should also encourage students of other behavioral phenomena to consider the potential role of developmental plasticity in evolutionary innovation.
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Affiliation(s)
- Peter M Kappeler
- Behavioral Ecology and Sociobiology Unit, German Primate Center, Kellnerweg 4, 37077 Göttingen, Germany
| | - Claudia Fichtel
- Behavioral Ecology and Sociobiology Unit, German Primate Center, Kellnerweg 4, 37077 Göttingen, Germany
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Abstract
A review is presented of the mechanical damage suffered by tooth crowns. This has been the subject of much recent research, resulting in a need to revise some of the thinking about the mechanisms involved. Damage is classified here by scale into macro-, meso- and microfracture. The focus is on the outer enamel coat because this is the contact tissue and where most fractures start. Enamel properties appear to be tailored to maximize hardness, but also to prevent fracture. The latter is achieved by the deployment of developmental flaws called enamel tufts. Macrofractures usually appear to initiate as extensions of tufts on the undersurface of the enamel adjacent to the enamel-dentine junction and extend from there into the enamel. Cracks that pass from the tooth surface tend to be deflected by an enamel region of high toughness; if they find the surface again, a chip (mesofracture) is produced. The real protection of the enamel-dentine junction here is the layer of decussating inner enamel. Finally, a novel analysis of mechanical wear (microfracture) suggests that the local toughness of the enamel is very important to its ability to resist tissue loss. Enamel and dentine have contrasting behaviours. Seen on a large scale, dentine is isotropic (behaving similarly in all directions) while enamel is anisotropic, but vice versa on a very small scale. These patterns have implications for anyone studying the fracture behaviour of teeth.
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Affiliation(s)
- Peter W. Lucas
- Department of Bioclinical Sciences, Faculty of Dentistry, Kuwait University, Jabriya, Kuwait
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Boyer DM, Winchester J, Kay RF. The effect of differences in methodology among some recent applications of shearing quotients. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2014; 156:166-78. [PMID: 25256698 DOI: 10.1002/ajpa.22619] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2014] [Accepted: 09/08/2014] [Indexed: 11/08/2022]
Abstract
A shearing quotient (SQ) is a way of quantitatively representing the Phase I shearing edges on a molar tooth. Ordinary or phylogenetic least squares regression is fit to data on log molar length (independent variable) and log sum of measured shearing crests (dependent variable). The derived linear equation is used to generate an 'expected' shearing crest length from molar length of included individuals or taxa. Following conversion of all variables to real space, the expected value is subtracted from the observed value for each individual or taxon. The result is then divided by the expected value and multiplied by 100. SQs have long been the metric of choice for assessing dietary adaptations in fossil primates. Not all studies using SQ have used the same tooth position or crests, nor have all computed regression equations using the same approach. Here we focus on re-analyzing the data of one recent study to investigate the magnitude of effects of variation in 1) shearing crest inclusion, and 2) details of the regression setup. We assess the significance of these effects by the degree to which they improve or degrade the association between computed SQs and diet categories. Though altering regression parameters for SQ calculation has a visible effect on plots, numerous iterations of statistical analyses vary surprisingly little in the success of the resulting variables for assigning taxa to dietary preference. This is promising for the comparability of patterns (if not casewise values) in SQ between studies. We suggest that differences in apparent dietary fidelity of recent studies are attributable principally to tooth position examined.
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Affiliation(s)
- Doug M Boyer
- Department of Evolutionary Anthropology, Duke University, Durham, NC, 27708
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