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Paul C Dechow - One of the best experts on this subject based on the ideXlab platform.
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material properties of mandibular cortical bone in the american alligator alligator mississippiensis
Bone, 2010Co-Authors: Keith A Metzger, Callum F. Ross, Ruth M Elsey, Uriel Zapata, Qian Wang, Paul C DechowAbstract:article i nfo This study reports the elastic material properties of cortical bone in the Mandible of juvenile Alligator mississippiensis obtained by using an ultrasonic wave technique. The elastic modulus, the shear modulus, and Poisson's ratio were measured on 42 cylindrical Alligator bone specimens obtained from the lingual and facial surfaces of 4 fresh Alligator Mandibles. The data suggest that the elastic properties of alligator mandibular cortical bone are similar to those found in mammals and are orthotropic. The properties most resemble those found in the cortex of mammalian postcranial long bones where the bone is most stiff in one direction and much less stiff in the two remaining orthogonal directions. This is different from cortical bone found in the Mandibles of humans and some monkeys, where the bone has greatest stiffness in one direction, much less stiffness in another direction, and an intermediate amount in the third orthogonal direction. This difference suggests a relationship between levels of orthotropy and bending stress. The comparability of these elastic moduli to those of other vertebrates suggest that the high bone strain magnitudes recorded from the alligator Mandible in vivo are not attributable to a lower stiffness of alligator mandibular bone.
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biomechanical effects of fixed partial denture therapy on strain patterns of the Mandible
Journal of Prosthetic Dentistry, 2006Co-Authors: Junro Yamashita, Qian Wang, Paul C DechowAbstract:Statement of problem The mandibular posterior 3-unit fixed partial denture (FPD) is a conventional prosthodontic therapy and presumably has an effect on the direction and magnitude of occlusal forces and, thus, on the biomechanical environment of the Mandible, which may in turn affect bone structure. However, the impact of FPD therapy on mandibular biomechanics is unknown. Purpose The purpose of this study was to test the hypothesis that 3-unit FPD therapy alters strain patterns in the Mandible during loading. Material and methods Four human cadaver Mandibles missing first molars were bilaterally fixed and artificially loaded on each tooth individually. Surface cortical bone strains were measured with multiple strain gauges during loading of up to 250 N. Next, 3-unit FPDs with a chamfer finish line were fabricated using Type IV gold alloy. Strain measurements were conducted in the same manner to assess differences in strain patterns before and after therapy. Paired-sample tests for metric and angular data were used to assess difference in strain pattern before and after therapies (α=.05). Results When loading was applied on the teeth not involved in FPD therapy, no differences were found before and after FPD placement. When the posterior retainers were loaded, the strain distribution differed ( P =.01); on the buccal cortices, strain levels increased posteriorly but decreased significantly anteriorly. However, these differences were less than 100 μe, and the overall deformation pattern of the Mandible after the FPD therapy was similar to that before FPD therapy. Strain distributions when the pontic was loaded were similar to those when the posterior retainer was loaded. Conclusion Three-unit FPD therapy did not alter the overall deformation pattern of the Mandible during loading.
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variations in cortical material properties throughout the human dentate Mandible
American Journal of Physical Anthropology, 2003Co-Authors: C L Schwartzdabney, Paul C DechowAbstract:Material properties and their variations in individual bone organs are important for understanding bone adaptation and quality at a tissue level, and are essential for accurate mechanical models. Yet material property variations have received little systematic study. Like all other material property studies in individual bone organs, studies of the human Mandible are limited by a low number of both specimens and sampled regions. The aims of this study were to determine: 1) regional variability in mandibular material properties, 2) the effect of this variability on the modeling of mandibular function, and 3) the relationship of this variability to mandibular structure and function. We removed 31 samples on both facial and lingual cortices of 10 fresh adult dentate Mandibles, measured cortical thickness and density, determined the directions of maximum stiffness with a pulse transmission ultrasonic technique, and calculated elastic properties from measured ultrasonic velocities. Results showed that each of these elastic properties in the dentate human Mandible demonstrates unique regional variation. The direction of maximum stiffness was near parallel to the occlusal plane within the corpus. On the facial ramus, the direction of maximum stiffness was more vertically oriented. Several sites in the Mandible did not show a consistent direction of maximum stiffness among specimens, although all specimens exhibited significant orthotropy. Mandibular cortical thickness varied significantly (P < 0.001) between sites, and decreased from 3.7 mm (SD = 0.9) anteriorly to 1.4 mm posteriorly (SD = 0.1). The cortical plate was also significantly thicker (P < 0.003) on the facial side than on the lingual side. Bone was 50-100% stiffer in the longitudinal direction (E(3), 20-30 GPa) than in the circumferential or tangential directions (E(2) or E(1); P < 0.001). The results suggest that material properties and directional variations have an important impact on mandibular mechanics. The accuracy of stresses calculated from strains and average material properties varies regionally, depending on variations in the direction of maximum stiffness and anisotropy. Stresses in some parts of the Mandible can be more accurately calculated than in other regions. Limited evidence suggests that the orientations and anisotropies of cortical elastic properties correspond with features of cortical bone microstructure, although the relationship with functional stresses and strains is not clear.
James M Cook - One of the best experts on this subject based on the ideXlab platform.
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male morphology and dishonest signalling in a fig wasp
Animal Behaviour, 2009Co-Authors: Jamie C Moore, James M Cook, Darren J Obbard, Caroline Reuter, Stuart A WestAbstract:Despite theoretical predictions, dishonest signalling has rarely been observed in aggressive interactions. We present evidence of such signalling in the nonpollinating. g wasp Philotrypesis sp. A ex Ficus rubiginosa. First, morphometric data indicated that an alternative 'atypical' male morph (17.8% of individuals) exists that tends to be larger in body size and has longer Mandibles for a given body size than other 'typical' males. Second, behavioural observations suggested that males use Mandible gape width (which depends on Mandible length) as a cue to assess opponents before fights and retreat without escalating if they are unlikely to win, and, probably because their greater Mandible gape width causes more opponents to retreat without escalating, that atypical males engaged in fewer fights than typical males for a given body size but had higher mating success. Third, atypical males were less likely to win fights than typical males of similar Mandible length relative to opponents. In addition, we found that atypical males incur more injuries (greater receiver-dependent signal costs) than typical males of similar body size relative to rivals. We discuss the implications of our findings for future work on dishonest signalling. (C) 2009 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.
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cryptic male dimorphism and fighting in a fig wasp
Animal Behaviour, 2006Co-Authors: James M Cook, Daniel BeanAbstract:In some nonpollinating fig wasps, male competition for mates often results in serious injury or death. We studied the factors associated with fighting behaviour in an undescribed Philotrypesis fig wasp species. We quantified morphological traits in 440 males and revealed the presence of two discrete, but cryptic, male morphs, termed ‘aggressive’ (A) and ‘passive’ (P). For a given head size, morph A had larger Mandibles. However, the body size distributions of the two morphs overlapped considerably, such that morph designation required calculation of the ratio of Mandible (weapon) size to head size. Importantly, this means that standard analyses for dimorphism do not identify the two morphs correctly. We also sampled 62 pairs of males engaged in escalated fights and compared their size matching with that of randomly chosen pairs of males from the same patch. There was a significantly greater discrepancy in Mandible size in fighting pairs than in randomly chosen pairs of males. Furthermore, our cryptic morph designation revealed the process underlying this pattern, as follows. Although only 22% of males were morph A, 45% of these males were involved in fights. In contrast, 78% of males were morph P, but only 16% of them were involved in fights. The different population frequencies and fighting tendencies of the two morphs combine to ensure that most fights occur between ‘heteromorphic’ pairs and this, in turn, generates the significant jaw size discrepancy recorded between fighting males.
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male mating tactics and lethal combat in the nonpollinating fig wasp sycoscapter australis
Animal Behaviour, 2001Co-Authors: Daniel Bean, James M CookAbstract:Abstract Fatal fights are rare in the majority of animal species but are a common component of mate competition between wingless males of some species of fig-associated wasps. We investigated fatal fighting in Sycoscapter australis, a nonpollinating fig wasp found in the syconia (inflorescences) of the Moreton Bay fig, Ficus macrophylla. Overall, about 25% of males sustained fatal injuries during the mate competition period. Measurement and analysis of 349 males revealed a sevenfold difference in Mandible size between the largest and smallest individuals, as well as evidence for dimorphism in the Mandibles, which showed positive allometry in relation to other body parts. Small and large males did not differ significantly in their injury levels. Mandibles are the main weapons used in fights and injury levels were highest in syconia where males on average had larger Mandibles. Injury levels also increased with the estimated operational sex ratio in a syconium, although this variable explained little of the variation. In contrast to the usual assumptions about wingless male fig wasps, a significant number (17%) of males emerged from their natal syconia. Females emerged at a fairly constant rate over many hours, consistent with contest competition between males for access to matings. In contrast, the more numerous females of the pollinating wasp speciesPleistodontes froggatti showed a strong peak in emergence, consistent with scramble competition between males for access to mates.
Callum F. Ross - One of the best experts on this subject based on the ideXlab platform.
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in vivo bone strain and finite element modeling of the Mandible of alligator mississippiensis
Journal of Anatomy, 2013Co-Authors: Keith A Metzger, Laura B Porro, Jose Iriartediaz, Callum F. RossAbstract:Forces experienced during feeding are thought to strongly influence the morphology of the vertebrate Mandible; in vivo strain data are the most direct evidence for deformation of the Mandible induced by these loading regimes. Although many studies have documented bone strains in the mammalian Mandible, no information is available on strain magnitudes, orientations or patterns in the sauropsid lower jaw during feeding. Furthermore, strain gage experiments record the mechanical response of bone at a few locations, not across the entire Mandible. In this paper, we present bone strain data recorded at various sites on the lower jaw of Alligator mississippiensis during in vivo feeding experiments. These data are used to understand how changes in loading regime associated with changes in bite location are related to changes in strain regime on the working and balancing sides of the Mandible. Our results suggest that the working side Mandible is bent dorsoventrally and twisted about its long-axis during biting, and the balancing side experiences primarily dorsoventral bending. Strain orientations are more variable on the working side than on the balancing side with changes in bite point and between experiments; the balancing side exhibits higher strain magnitudes. In the second part of this paper, we use principal strain orientations and magnitudes recorded in vivo to evaluate a finite element model of the alligator Mandible. Our comparison demonstrates that strain orientations and mandibular deformation predicted by the model closely match in vivo results; however, absolute strain magnitudes are lower in the finite element model.
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free body analysis beam mechanics and finite element modeling of the Mandible of alligator mississippiensis
Journal of Morphology, 2011Co-Authors: Laura B Porro, Fred Anapol, Casey M Holliday, Lupita C Ontiveros, Callum F. RossAbstract:The mechanical behavior of mammalian Mandibles is well-studied, but a comprehensive biomechanical analysis (incorporating detailed muscle architecture, accurate material properties, and three- dimensional mechanical behavior) of an extant archo- saur Mandible has never been carried out. This makes it unclear how closely models of extant and extinct archo- saur Mandibles reflect reality and prevents comparisons of structure-function relationships in mammalian and archosaur Mandibles. We tested hypotheses regarding the mechanical behavior of the Mandible of Alligator mississippiensis by analyzing reaction forces and bend- ing, shear, and torsional stress regimes in six models of varying complexity. Models included free body analysis using basic lever arm mechanics, 2D and 3D beam mod- els, and three high-resolution finite element models of the Alligator Mandible, incorporating, respectively, iso- tropic bone without sutures, anisotropic bone with sutures, and anisotropic bone with sutures and contact between the Mandible and the pterygoid flange. Com- pared with the beam models, the Alligator finite element models exhibited less spatial variability in dorsoventral bending and sagittal shear stress, as well as lower peak values for these stresses, suggesting that Alligator man- dibular morphology is in part designed to reduce these stresses during biting. However, the Alligator models exhibited greater variability in the distribution of medio- lateral and torsional stresses than the beam models. Incorporating anisotropic bone material properties and sutures into the model reduced dorsoventral and torsional stresses within the Mandible, but led to elevated mediolateral stresses. These mediolateral stresses were mitigated by the addition of a pterygoid- mandibular contact, suggesting important contributions from, and trade-offs between, material properties and external constraints in Alligator Mandible design. Our results suggest that beam modeling does not accurately represent the mechanical behavior of the Alligator Mandible, including important performance metrics such as magnitude and orientation of reaction forces, and mediolateral bending and torsional stress distributions. J. Morphol. 272:910-937, 2011. 2011 Wiley-Liss, Inc.
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material properties of mandibular cortical bone in the american alligator alligator mississippiensis
Bone, 2010Co-Authors: Keith A Metzger, Callum F. Ross, Ruth M Elsey, Uriel Zapata, Qian Wang, Paul C DechowAbstract:article i nfo This study reports the elastic material properties of cortical bone in the Mandible of juvenile Alligator mississippiensis obtained by using an ultrasonic wave technique. The elastic modulus, the shear modulus, and Poisson's ratio were measured on 42 cylindrical Alligator bone specimens obtained from the lingual and facial surfaces of 4 fresh Alligator Mandibles. The data suggest that the elastic properties of alligator mandibular cortical bone are similar to those found in mammals and are orthotropic. The properties most resemble those found in the cortex of mammalian postcranial long bones where the bone is most stiff in one direction and much less stiff in the two remaining orthogonal directions. This is different from cortical bone found in the Mandibles of humans and some monkeys, where the bone has greatest stiffness in one direction, much less stiffness in another direction, and an intermediate amount in the third orthogonal direction. This difference suggests a relationship between levels of orthotropy and bending stress. The comparability of these elastic moduli to those of other vertebrates suggest that the high bone strain magnitudes recorded from the alligator Mandible in vivo are not attributable to a lower stiffness of alligator mandibular bone.
Laura B Porro - One of the best experts on this subject based on the ideXlab platform.
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in vivo bone strain and finite element modeling of the Mandible of alligator mississippiensis
Journal of Anatomy, 2013Co-Authors: Keith A Metzger, Laura B Porro, Jose Iriartediaz, Callum F. RossAbstract:Forces experienced during feeding are thought to strongly influence the morphology of the vertebrate Mandible; in vivo strain data are the most direct evidence for deformation of the Mandible induced by these loading regimes. Although many studies have documented bone strains in the mammalian Mandible, no information is available on strain magnitudes, orientations or patterns in the sauropsid lower jaw during feeding. Furthermore, strain gage experiments record the mechanical response of bone at a few locations, not across the entire Mandible. In this paper, we present bone strain data recorded at various sites on the lower jaw of Alligator mississippiensis during in vivo feeding experiments. These data are used to understand how changes in loading regime associated with changes in bite location are related to changes in strain regime on the working and balancing sides of the Mandible. Our results suggest that the working side Mandible is bent dorsoventrally and twisted about its long-axis during biting, and the balancing side experiences primarily dorsoventral bending. Strain orientations are more variable on the working side than on the balancing side with changes in bite point and between experiments; the balancing side exhibits higher strain magnitudes. In the second part of this paper, we use principal strain orientations and magnitudes recorded in vivo to evaluate a finite element model of the alligator Mandible. Our comparison demonstrates that strain orientations and mandibular deformation predicted by the model closely match in vivo results; however, absolute strain magnitudes are lower in the finite element model.
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free body analysis beam mechanics and finite element modeling of the Mandible of alligator mississippiensis
Journal of Morphology, 2011Co-Authors: Laura B Porro, Fred Anapol, Casey M Holliday, Lupita C Ontiveros, Callum F. RossAbstract:The mechanical behavior of mammalian Mandibles is well-studied, but a comprehensive biomechanical analysis (incorporating detailed muscle architecture, accurate material properties, and three- dimensional mechanical behavior) of an extant archo- saur Mandible has never been carried out. This makes it unclear how closely models of extant and extinct archo- saur Mandibles reflect reality and prevents comparisons of structure-function relationships in mammalian and archosaur Mandibles. We tested hypotheses regarding the mechanical behavior of the Mandible of Alligator mississippiensis by analyzing reaction forces and bend- ing, shear, and torsional stress regimes in six models of varying complexity. Models included free body analysis using basic lever arm mechanics, 2D and 3D beam mod- els, and three high-resolution finite element models of the Alligator Mandible, incorporating, respectively, iso- tropic bone without sutures, anisotropic bone with sutures, and anisotropic bone with sutures and contact between the Mandible and the pterygoid flange. Com- pared with the beam models, the Alligator finite element models exhibited less spatial variability in dorsoventral bending and sagittal shear stress, as well as lower peak values for these stresses, suggesting that Alligator man- dibular morphology is in part designed to reduce these stresses during biting. However, the Alligator models exhibited greater variability in the distribution of medio- lateral and torsional stresses than the beam models. Incorporating anisotropic bone material properties and sutures into the model reduced dorsoventral and torsional stresses within the Mandible, but led to elevated mediolateral stresses. These mediolateral stresses were mitigated by the addition of a pterygoid- mandibular contact, suggesting important contributions from, and trade-offs between, material properties and external constraints in Alligator Mandible design. Our results suggest that beam modeling does not accurately represent the mechanical behavior of the Alligator Mandible, including important performance metrics such as magnitude and orientation of reaction forces, and mediolateral bending and torsional stress distributions. J. Morphol. 272:910-937, 2011. 2011 Wiley-Liss, Inc.
Uriel Zapata - One of the best experts on this subject based on the ideXlab platform.
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material properties of mandibular cortical bone in the american alligator alligator mississippiensis
Bone, 2010Co-Authors: Keith A Metzger, Callum F. Ross, Ruth M Elsey, Uriel Zapata, Qian Wang, Paul C DechowAbstract:article i nfo This study reports the elastic material properties of cortical bone in the Mandible of juvenile Alligator mississippiensis obtained by using an ultrasonic wave technique. The elastic modulus, the shear modulus, and Poisson's ratio were measured on 42 cylindrical Alligator bone specimens obtained from the lingual and facial surfaces of 4 fresh Alligator Mandibles. The data suggest that the elastic properties of alligator mandibular cortical bone are similar to those found in mammals and are orthotropic. The properties most resemble those found in the cortex of mammalian postcranial long bones where the bone is most stiff in one direction and much less stiff in the two remaining orthogonal directions. This is different from cortical bone found in the Mandibles of humans and some monkeys, where the bone has greatest stiffness in one direction, much less stiffness in another direction, and an intermediate amount in the third orthogonal direction. This difference suggests a relationship between levels of orthotropy and bending stress. The comparability of these elastic moduli to those of other vertebrates suggest that the high bone strain magnitudes recorded from the alligator Mandible in vivo are not attributable to a lower stiffness of alligator mandibular bone.
