Predicting bite force and cranial biomechanics in the largest fossil rodent using finite element analysis

Josephoartigasia monesi, from the Pliocene of Uruguay, is the largest known fossil rodent, with an estimated body mass of 1000 kg. In this study, finite element analysis was used to estimate the maximum bite force that J. monesi could generate at the incisors and the cheek teeth. Owing to uncertainty in the model inputs, a sensitivity study was conducted in which the muscle forces and orientations were sequentially altered. This enabled conclusions to be drawn on the function of some of the masticatory muscles. It was found that J. monesi had a bite of 1389 N at the incisors, rising to 4165 N at the third molar. Varying muscle forces by 20% and orientations by 10° around the medio‐lateral aspect led to an error in bite force of under 35% at each tooth. Predicted stresses across the skull were only minimally affected by changes to muscle forces and orientations, but revealed a reasonable safety factor in the strength of the skull. These results, combined with previous work, lead us to speculate that J. monesi was behaving in an elephant‐like manner, using its incisors like tusks, and processing tough vegetation with large bite forces at the cheek teeth.     

The ontogeny of maximum bite force in humans

Ontogenetic changes in the human masticatory complex suggest that bite force, a key measure of chewing performance, increases throughout growth and development. Current published bite force values for humans exist for molar and incisal biting, but few studies measure bite forces across all tooth types, or measure bite force potentials in subjects of different ages. In the absence of live data, models of bite force such as the Constrained Lever Model (CLM), are employed to predict bite force at different bite points for adults, but it is unclear whether such a model can accurately predict bite force potentials for juveniles or subadults. This study compares theoretically derived bite forces and live bite force data, and places these within an ontogenetic context in humans. Specifically, we test whether (1) patterns of maximum bite force increase along the tooth row throughout ontogeny, (2) bite force patterns estimated using the CLM match patterns observed from live bite force data, and (3) changes in bite forces along the tooth row and throughout ontogeny are associated with concomitant changes in adductor muscle leverage. Our findings show that maximum bite forces increase throughout ontogeny and change along the tooth row, with the highest forces occurring at the posterior dentition. These findings adhere to the expectations under the CLM and validate the model’s utility in predicting bite force values throughout development. Furthermore, adductor muscle leverage values reflect this pattern, with the greatest leverage values occurring at the posterior dentition throughout ontogeny. The CLM informs our study of mammalian chewing mechanics by providing a model of how morphological changes of the masticatory apparatus during ontogeny affect bite force distribution along the tooth row. Furthermore, the decreased bite force magnitudes observed in juveniles and subadults compared with adults suggest that differences in juvenile and subadult diets may partially be due to differences in bite force production potentials.     

The evolution of bite force in horned lizards: the influence of dietary specialization

Dietary specialization is an important driver of the morphology and performance of the feeding system in many organisms, yet the evolution of phenotypic specialization has only rarely been examined within a species complex. Horned lizards are considered primarily myrmecophagous (ant eating), but variation in diet among the 17 species of horned lizards (Phrynosoma) makes them an ideal group to examine the relationship between dietary specialization and the resultant morphological and functional changes of the feeding system. In this study, we perform a detailed analysis of the jaw adductor musculature and use a biomechanical model validated with in vivo bite force data to examine the evolution of bite force in Phrynosoma. Our model simulations demonstrate that bite force varies predictably with respect to the gape angle and bite position along the tooth row, with maximal bite forces being attained at lower gape angles and at the posterior tooth positions. Maximal bite forces vary considerably among horned lizards, with highly myrmecophagous species exhibiting very low bite forces. In contrast, members of the short‐horned lizard clade are able to bite considerably harder than even closely related dietary generalists. This group appears to be built for performing crushing bites and may represent a divergent morphology adapted for eating hard prey items. The evolutionary loss of processing morphology (teeth, jaw and muscle reduction) and bite force in ant specialists may be a response to the lack of prey processing rather than a functional adaptation per se.     

Cranial dimensions and forces of biting in the domestic dog

The purpose of this paper is to analyse the effects of cranial size and shape in domestic dogs ( Canis familiaris ) on predicted forces of biting. In addition to continuous size-shape analysis, nine size-shape groups were developed based on three skull shape categories and three skull size categories. Bite forces were predicted from measurements made on dried skulls using two lever models of the skull, as well as simple models derived by regression analysis. Observed bite force values were not available for the database used in this study, so only comparisons between categories and models were undertaken. The effects of shape and size on scaled predicted bite forces were evaluated. Results show that bite force increases as size increases, and this effect was highly significant ( P  < 0.0001). The effect of skull shape on bite force was significant in medium and large dogs ( P  < 0.05). Significant differences were not evident in small dogs. Size × shape interactions were also significant ( P  < 0.05). Bite force predictions by the two lever models were relatively close to each other, whereas the regression models diverged slightly with some negative numbers for very small dogs. The lever models may thus be more robust across a wider range of skull size-shapes. Results obtained here would be useful to the pet food industry for food product development, as well as to paleontologists interested in methods of estimating bite force from dry skulls.     

Feeding biomechanics of the cownose ray,Rhinoptera bonasus,over ontogeny

Growth affects the performance of structure, so the pattern of growth must influence the role of a structure and an organism. Because animal performance is linked to morphological specialization, ontogenetic change in size may influence an organism's biological role. High bite force generation is presumably selected for in durophagous taxa. Therefore, these animals provide an excellent study system for investigating biomechanical consequences of growth on performance. An ontogenetic series of 27 cownose rays (Rhinoptera bonasus) were dissected in order to develop a biomechanical model of the feeding mechanism, which was then compared with bite forces measured from live rays. Mechanical advantage of the feeding apparatus was generally conserved throughout ontogeny, while an increase in the mass and cross‐sectional area of the jaw adductors resulted in allometric gains in bite force generation. Of primary importance to forceful biting in this taxon is the use of a fibrocartilaginous tendon associated with the insertion of the primary jaw adductor division. This tendon may serve to redirect muscle forces anteriorly, transmitting them within the plane of biting. Measured bite forces obtained through electrostimulation of the jaw adductors in live rays were higher than predicted, possibly due to differences in specific tension of actual batoid muscle and that used in the model. Mass‐specific bite forces in these rays are the highest recorded for elasmobranchs. Cownose rays exemplify a species that, through allometric growth of bite performance and morphological novelties, have expanded their ecological performance over ontogeny.     

Cranial myology and bite force performance of Erlikosaurus andrewsi: a novel approach for digital muscle reconstructions

The estimation of bite force and bite performance in fossil and extinct animals is a challenging subject in palaeontology and is highly dependent on the reconstruction of the cranial myology. Furthermore, the morphology and arrangement of the adductor muscles considerably affect feeding processes and mastication and thus also have important dietary and ecological ramifications. However, in the past, the reconstruction of the (cranial) muscles was restricted to the identification of muscle attachment sites or simplified computer models. This study presents a detailed reconstruction of the adductor musculature of the Cretaceous therizinosaur Erlikosaurus andrewsi based on a stepwise and iterative approach. The detailed, three‐dimensional models of the individual muscles allow for more accurate measurements of the muscle properties (length, cross‐section, attachment angle and volume), from which muscle and bite force estimates are calculated. Bite force estimations are found to be the lowest at the tip of the snout (43–65 N) and respectively higher at the first (59–88 N) and last tooth (90–134 N) position. Nevertheless, bite forces are comparatively low for E. andrewsi, both in actual numbers as well as in comparison with other theropod dinosaurs. The results further indicate that the low bite performance was mainly used for leaf‐stripping and plant cropping, rather than active mastication or chewing processes. Muscle and thus bite force in E. andrewsi (and most likely all therizinosaurs) is considerably constrained by the cranial anatomy and declines in derived taxa of this clade. This trend is reflected in the changes of dietary preferences from carnivory to herbivory in therizinosaurs.     

Diversity and function of the fused anuran radioulna

In tetrapods, fusion between elements of the appendicular skeleton is thought to facilitate rapid movements during running, flying, and jumping. Although such fusion is widespread, frogs stand out because adults of all living species exhibit fusion of the zeugopod elements (radius and ulna, tibia and fibula), regardless of jumping ability or locomotor mode. To better understand what drives the maintenance of limb bone fusion in frogs, we use finite element modeling methods to assess the functional consequences of fusion in the anuran radioulna, the forearm bone of frogs that is important to both locomotion and mating behavior (amplexus). Using CT scans of museum specimens, measurement tools, and mesh‐editing software, we evaluated how different degrees of fusion between the radius and ulna affect the von Mises stress and bending resistance of the radioulna in three loading scenarios: landing, amplexus, and long‐axis loading conditions. We find that the semi‐fused state observed in the radioulna exhibits less von Mises stress and more resistance to bending than unfused or completely fused models in all three scenarios. Our results suggest that radioulna morphology is optimized to minimize von Mises stress across different loading regimes while also minimizing volume. We contextualize our findings in an evaluation of the diversity of anuran radioulnae, which reveals unique, permanent pronation of the radioulna in frogs and substantial variation in wall thickness. This work provides new insight into the functional consequences of limb bone fusion in anuran evolution.     

基于有限元分析腓肠肌作用力对足部生物力学的影响

目的探讨不同腓肠肌作用力变化对足跟痛生物力学机制的影响。方法运用Mimics软件对临床计算机断层扫描足部图像进行三维实体模型重建,建立包括骨骼、软组织、韧带及足底筋膜的足部有限元模型。腓肠肌作用在足部上的作用力取人体半体重320 N的40%~90%,每隔5%半体重(即16 N)增加,并计算足底表面压力分布及峰值、足底筋膜应力等。结果足底表面压力分布主要集中在足跟处和跖骨头区域,足底足跟处压力峰值随着腓肠肌作用力的增加而减小,而足底前部压力峰值先减小后增大,在224 N(70%)时达到最小值。足底筋膜的应力随腓肠肌作用力的增加而增加。结论腓肠肌作用力的改变对足底压力及足底筋膜应力产生显著影响。有限元分析有助于对足部疾病病因病理的了解以及对腓肠肌松解术后生物力学结果预测,为治疗提供理论依据。     

Exploring the biomechanics of taurodontism

Taurodontism (i.e. enlarged pulp chamber with concomitant apical displacement of the root bi/trifurcation) is considered a dental anomaly with relatively low incidence in contemporary societies, but it represents a typical trait frequently found in Neandertal teeth. Four hypotheses can be envisioned to explain the high frequency in Neandertals: adaptation to a specific occlusal loading regime (biomechanical advantage), adaptation to a high attrition diet, pleiotropic or genetic drift effects. In this contribution we used finite element analysis (FEA) and advanced loading concepts based on macrowear information to evaluate whether taurodontism supplies some dental biomechanical advantages. Loads were applied to the digital model of the lower right first molar (RM₁) of the Neandertal specimen Le Moustier 1, as well as to the digital models of both a shortened and a hyper-taurodontic version of Le Moustier RM₁. Moreover, we simulated a scenario where an object is held between teeth and pulled in different directions to investigate whether taurodontism might be useful for para-masticatory activities. Our results do not show any meaningful difference among all the simulations, pointing out that taurodontism does not improve the functional biomechanics of the tooth and does not favour para-masticatory pulling activities. Therefore, taurodontism should be considered either an adaptation to a high attrition diet or most likely the result of pleiotropic or genetic drift effects. Finally, our results have important implications for modern dentistry during endodontic treatments, as we observed that filling the pulp chamber with dentine-like material increases tooth stiffness, and ultimately tensile stresses in the crown, thus favouring tooth failure.     

The Response of Cranial Biomechanical Finite Element Models to Variations in Mesh Density

Finite element (FE) models provide discrete solutions to continuous problems. Therefore, to arrive at the correct solution, it is vital to ensure that FE models contain a sufficient number of elements to fully resolve all the detail encountered in a continuum structure. Mesh convergence testing is the process of comparing successively finer meshes to identify the point of diminishing returns; where increasing resolution has marginal effects on results and further detail would become costly and unnecessary. Historically, convergence has not been considered in most CT‐based biomechanical reconstructions involving complex geometries like the skull, as generating such models has been prohibitively time‐consuming. To assess how mesh convergence influences results, 18 increasingly refined CT‐based models of a domestic pig skull were compared to identify the point of convergence for strain and displacement, using both linear and quadratic tetrahedral elements. Not all regions of the skull converged at the same rate, and unexpectedly, areas of high strain converged faster than low‐strain regions. Linear models were slightly stiffer than their quadratic counterparts, but did not converge less rapidly. As expected, insufficiently dense models underestimated strain and displacement, and failed to resolve strain “hot‐spots” notable in contour plots. In addition to quantitative differences, visual assessments of such plots often inform conclusions drawn in many comparative studies, highlighting that mesh convergence should be performed on all finite element models before further analysis takes place. Anat Rec, 2011. © 2011 Wiley‐Liss, Inc.     

Functional anatomy and feeding biomechanics of a giant Upper Jurassic pliosaur (Reptilia: Sauropterygia) from Weymouth Bay,Dorset, UK

Pliosaurs were among the largest predators in Mesozoic seas, and yet their functional anatomy and feeding biomechanics are poorly understood. A new, well‐preserved pliosaur from the Kimmeridgian of Weymouth Bay (UK) revealed cranial adaptations related to feeding. Digital modelling of computed tomography scans allowed reconstruction of missing, distorted regions of the skull and of the adductor musculature, which indicated high bite forces. Size‐corrected beam theory modelling showed that the snout was poorly optimised against bending and torsional stresses compared with other aquatic and terrestrial predators, suggesting that pliosaurs did not twist or shake their prey during feeding and that seizing was better performed with post‐symphyseal bites. Finite element analysis identified biting‐induced stress patterns in both the rostrum and lower jaws, highlighting weak areas in the rostral maxillary‐premaxillary contact and the caudal mandibular symphysis. A comparatively weak skull coupled with musculature that was able to produce high forces, is explained as a trade‐off between agility, hydrodynamics and strength. In the Kimmeridgian ecosystem, we conclude that Late Jurassic pliosaurs were generalist predators at the top of the food chain, able to prey on reptiles and fishes up to half their own length.     

原子力显微镜在细胞与生物大分子超微结构和力学研究中的应用

作为微纳米科学理论与技术迅猛发展的代表,原子力显微镜(atomic force microscopy,AFM)在其25年的发展过程中极大地推进了生物学在微纳米尺度上的拓展,为微纳米生物学的诞生与发展提供了重要技术手段。本文在介绍AFM基本原理和检测模式的基础上,结合作者在该领域的研究成果和工作经验,从生物结构与形态学研究、表面物化性质表征、生物大分子的力学操纵三方面综述了AFM在细胞与生物大分子超微结构与生物力学特性研究中的具体应用,并重点探讨了AFM在细胞与生物大分子科学研究中亟待改进和解决的科学与技术问题,提出了一些探讨性的见解和建议。     

Masticatory muscle architectural correlates of dietary diversity in Canidae,Ursidae, and across the order Carnivora

Carnivorans represent extreme ecomorphological diversity, encompassing remarkable variation in form, habitat, and diet. The relationship between the masticatory musculature and dietary ecology has been explored in a number of carnivoran lineages, including felids and the superfamily Musteloidea. In this study, we present novel architectural data on two additional carnivoran families—Ursidae and Canidae—and supplement these previous studies with additional felid, musteloid, herpestid, hyaenid, and viverrid taxa (a total of 53 species across 10 families). Gross dissection data were collected following a standardized protocol—sharp dissection followed by chemical digestion. Summed jaw adductor forces were also transformed into bite force estimates (BF) using osteologically calculated leverages. All data were linearized, log-transformed, and size-adjusted using two proxies for each taxon—body mass (BM) and cranial geometric mean—to assess relative scaling trends. These architectural data were then analyzed in the context of dietary ecology to examine the impact of dietary size (DS) and dietary mechanical properties (DMP). Muscle mass, physiological cross-sectional area, and BF scaled with isometry or positive allometry in all cases, whereas fascicle lengths (FLs) scaled with isometry or negative allometry. With respect to diet, BM-adjusted FLs were strongly correlated with DS in musteloids, but not in any other lineage. The relationship between size-adjusted BF and DMP was also significant within musteloids, and across the sample as a whole, but not within other individual lineages. This interfamilial trend may reflect the increased morphological and dietary diversity of musteloids relative to other carnivoran groups.     

Structure and function of the septum nasi and the underlying tension chord in crocodylians

A long rostrum has distinct advantages for prey capture in an aquatic or semi‐aquatic environment but at the same time poses severe problems concerning stability during biting. We here investigate the role of the septum nasi of brevirostrine crocodilians for load‐absorption during mastication. Histologically, both the septum nasi and the septum interorbitale consist of hyaline cartilage and therefore mainly resist compression. However, we identified a strand of tissue extending longitudinally below the septum nasi that is characterized by a high content of collagenous and elastic fibers and could therefore resist tensile stresses. This strand of tissue is connected with the m. pterygoideus anterior. Two‐dimensional finite element modeling shows that minimization of bending in the crocodilian skull can only be achieved if tensile stresses are counteracted by a strand of tissue. We propose that the newly identified strand of tissue acts as an active tension chord necessary for stabilizing the long rostrum of crocodilians during biting by transforming the high bending stress of the rostrum into moderate compressive stress.     

The mechanical function of the periodontal ligament in the macaque mandible: a validation and sensitivity study using finite element analysis

Whilst the periodontal ligament (PDL) acts as an attachment tissue between bone and tooth, hypotheses regarding the role of the PDL as a hydrodynamic damping mechanism during intraoral food processing have highlighted its potential importance in finite element (FE) analysis. Although experimental and constitutive models have correlated the mechanical function of the PDL tissue with its anisotropic, heterogeneous, viscoelastic and non‐linear elastic nature, in many FE simulations the PDL is either present or absent, and when present is variably modelled. In addition, the small space the PDL occupies and the inability to visualize the PDL tissue using μCT scans poses issues during FE model construction and so protocols for the PDL thickness also vary. In this paper we initially test and validate the sensitivity of an FE model of a macaque mandible to variations in the Young’s modulus and the thickness of the PDL tissue. We then tested the validity of the FE models by carrying out experimental strain measurements on the same mandible in the laboratory using laser speckle interferometry. These strain measurements matched the FE predictions very closely, providing confidence that material properties and PDL thickness were suitably defined. The FE strain results across the mandible are generally insensitive to the absence and variably modelled PDL tissue. Differences are only found in the alveolar region adjacent to the socket of the loaded tooth. The results indicate that the effect of the PDL on strain distribution and/or absorption is restricted locally to the alveolar bone surrounding the teeth and does not affect other regions of the mandible.     

Anatomical variability of the frontal sinuses and their application in forensic identification

The uniqueness of anatomical structures and their variations provides the basis for forensic identification of unknown deceased persons. Similar to fingerprints, each frontal sinus is so distinctive and unique that the chances of two individuals having the same morphology of the frontal sinuses is extremely remote. Radiographs, especially the occipitomental view commonly used in the assessment of paranasal pathology, provide excellent records of these sinuses. The case illustrated here is an application of the frontal sinus identification of a victim in a mass disaster. Clin. Anat. 12:16–19, 1999. © 1999 Wiley‐Liss, Inc.     

新型脑脊液引流分离装置的设计及分析

目的 在现有临床引流装置基础上,对患者端引流管与引流袋端引流管连接处设计两种新型结构,对比两种结构并验证其是否满足临床使用的设计需求。方法 结构1采用电磁驱动方式进行吸合,结构2采用永磁体磁化方式进行吸合,并建立静态电磁场有限元模型。比较两种结构在施加不同电流作用下的受力情况,分析其磁力线分布及磁感应强度,设计模拟实验并进行初步实验研究。结果 结构1、2在吸合状态下,闭合端面处最大磁感应强度均出现在两铁芯接触位置。结构1吸力可通过电流调节,在通1 A电流时,闭合端面处最大磁感应强度为0.76 T,实验测得电磁力为6.08 N,结构2实验测得磁力为6.68 N,均小于8 N 缝合线张力。结构2通过给驱动线圈供电产生反向磁场实现装置分离。结论 当电流为1 A时,结构1可以满足磁吸力要求;当结构2的电流达到1.8 A时,可以实现装置分离。两种结构设计均满足临床设计需求,结构2在使用过程中更具备安全性。同时,有限元分析及实验测试验证了结构的可行性。     

Skull Mechanics and the Evolutionary Patterns of the Otic Notch Closure in Capitosaurs (Amphibia: Temnospondyli)

Capitosaurs were among the largest amphibians that have ever lived. Their members displayed an amphibious lifestyle. We provide new information on functional morphology data, using finite element analysis (FEA) which has palaeoecological implications for the group. Our analyses included 17 taxa using (2D) plate models to test four loading cases (bilateral, unilateral and lateral bitings and skull raising system simulation). Our results demonstrates that, when feeding, capitosaurs concentrated the stress at the circumorbital region of the capitosaur skull and cranial sutures probably played a key role in dissipating and absorbing the stress generated during biting. Basal members (as Wetlugasaurus) were probably less specialized forms, while during Middle‐ and Late Triassic the group radiated into different ecomorphotypes with closed otic notch forms (as Cyclotosaurus) resulting in the strongest skulls during biting. Previous interpretations discussed a trend from an open to closed otic notch associated with lateral repositioning of the tabular horns, but the analysis of the skull‐raising system reveals that taxa exhibiting posteriorly directed tabular horns display similar results during skull raising to those of closed otic notch taxa. Our results suggest that various constraints besides otic notch morphology, such as the elongation of the tabular horns, snout length, skull width and position, and size of the orbits affect the function of the skull. On the light of our results, capitosaur skull showed a trend to reduce the stresses and deformation during biting. Capitosaurs could be considered crocodilian analogues as they were top‐level predators in fluvial and brackish Triassic ecosystems. Anat Rec, , 2012. © 2012 Wiley Periodicals, Inc.     

以有限元法仿真分析闭合式上颌窦提升的黏膜形变

背景：如何避免闭合式上颌窦提升种植治疗中医源性上颌窦黏膜穿孔等并发症成为近年研究的热点。 目的：以有限元法比较闭合式上颌窦提升种植治疗中不同上颌窦黏膜厚度对黏膜穿孔的影响。 方法：在ANSYS有限元分析软件的SHELL63单元中分别建立0.3,0.5,0.8 mm厚度上颌窦黏膜与4.2 mm直径种植体的有限元模型,模拟闭合式上颌窦提升手术抬高黏膜,根据大变形非线性理论计算3种厚度上颌窦黏膜中心Von Mises最大应力值,并进行统计学分析。 结果与结论：通过对3种厚度上颌窦黏膜提升1-5 mm的形变与应力分析,发现上颌窦黏膜高变形区发生在黏膜顶端中心,在黏膜提升1-4 mm时,最大应变值曲线变化温和,在大于4 mm高度后曲线斜率明显增加;在上颌窦黏膜提升5 mm之内,0.3,0.5,0.8 mm 3种厚度黏膜中心最大Von Mises应力值差异无显著性意义(P > 0.05)。提示上颌窦黏膜提升高度大于4 mm之后,黏膜弹性拉伸大幅增加,增大了穿孔的概率;对于上颌窦黏膜厚度为0.3-0.8 mm需要进行闭合式上颌窦提升治疗的患者,其所面对的黏膜穿孔风险是无差别的;而上颌窦黏膜厚度小于0.3 mm的患者,要更加慎重地选择上颌窦提升方案以防止黏膜穿孔的发生。 中国组织工程研究杂志出版内容重点：组织构建;骨细胞;软骨细胞;细胞培养;成纤维细胞;血管内皮细胞;骨质疏松;组织工程全文链接：