Mechanical interaction of cell with extracellular environment affects its function. The mechanisms by which mechanical stimuli are sensed and transduced into biochemical responses are still not well understood. Considering this, two finite element (FE) bendo-tensegrity models of a cell in different states are proposed with the aim to characterize cell deformation under different mechanical loading conditions: a suspended cell model elucidating the global response of cell in tensile test simulation and an adherent cell model explicating its local response in atomic force microscopy (AFM) indentation simulation. The force-elongation curve obtained from tensile test simulation lies within the range of experimentally obtained characteristics of smooth muscle cells (SMCs) and illustrates a nonlinear increase in reaction force with cell stretching. The force-indentation curves obtained from indentation simulations lie within the range of experimentally obtained curves of embryonic stem cells (ESCs) and exhibit the influence of indentation site on the overall reaction force of cell. Simulation results have demonstrated that actin filaments (AFs) and microtubules (MTs) play a crucial role in the cell stiffness during stretching, whereas actin cortex (AC) along with actin bundles (ABs) and MTs are essential for the cell rigidity during indentation. The proposed models quantify the mechanical contribution of individual cytoskeletal components to cell mechanics and the deformation of nucleus under different mechanical loading conditions. These results can aid in better understanding of structure-function relationships in living cells.

• MeSH
• analýza metodou konečných prvků * MeSH
• biologické modely * MeSH
• biomechanika MeSH
• cytoskelet metabolismus   MeSH
• eukaryotické buňky cytologie   metabolismus   MeSH
• mechanické jevy * MeSH
• mikrofilamenta metabolismus   MeSH
• mikrotubuly metabolismus   MeSH
• pevnost v tahu MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

BACKGROUND: The aim of this paper was to design a finite element model for a hinged PROSPON oncological knee endoprosthesis and to verify the model by comparison with ankle flexion angle using knee-bending experimental data obtained previously. METHOD: Visible Human Project CT scans were used to create a general lower extremity bones model and to compose a 3D CAD knee joint model to which muscles and ligaments were added. Into the assembly the designed finite element PROSPON prosthesis model was integrated and an analysis focused on the PEEK-OPTIMA hinge pin bushing stress state was carried out. To confirm the stress state analysis results, contact pressure was investigated. The analysis was performed in the knee-bending position within 15.4-69.4° hip joint flexion range. RESULTS: The results showed that the maximum stress achieved during the analysis (46.6 MPa) did not exceed the yield strength of the material (90 MPa); the condition of plastic stability was therefore met. The stress state analysis results were confirmed by the distribution of contact pressure during knee-bending. CONCLUSION: The applicability of our designed finite element model for the real implant behaviour prediction was proven on the basis of good correlation of the analytical and experimental ankle flexion angle data.

• Klíčová slova
• Endoprosthesis, Finite element method, Finite element model, Knee joint, Knee-bending, Oncological implant,
• MeSH
• algoritmy MeSH
• analýza metodou konečných prvků MeSH
• analýza selhání vybavení MeSH
• biologické modely * MeSH
• design s pomocí počítače MeSH
• kolenní kloub patofyziologie   MeSH
• kosterní svaly patofyziologie   MeSH
• lidé MeSH
• mechanický stres MeSH
• modul pružnosti MeSH
• nádory kostí patofyziologie   chirurgie   MeSH
• pevnost v tahu MeSH
• pevnost v tlaku MeSH
• počítačová simulace MeSH
• protetické vybavení metody   MeSH
• protézy - design MeSH
• protézy kolene * MeSH
• šlachy patofyziologie   MeSH
• software MeSH
• svalová kontrakce MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• validační studie MeSH

A three-dimensional finite element model of a vascular smooth muscle cell is based on models published recently; it comprehends elements representing cell membrane, cytoplasm and nucleus, and a complex tensegrity structure representing the cytoskeleton. In contrast to previous models of eucaryotic cells, this tensegrity structure consists of several parts. Its external and internal parts number 30 struts, 60 cables each, and their nodes are interconnected by 30 radial members; these parts represent cortical, nuclear and deep cytoskeletons, respectively. This arrangement enables us to simulate load transmission from the extracellular space to the nucleus or centrosome via membrane receptors (focal adhesions); the ability of the model was tested by simulation of some mechanical tests with isolated vascular smooth muscle cells. Although material properties of components defined on the basis of the mechanical tests are ambiguous, modelling of different types of tests has shown the ability of the model to simulate substantial global features of cell behaviour, e.g. "action at a distance effect" or the global load-deformation response of the cell under various types of loading. Based on computational simulations, the authors offer a hypothesis explaining the scatter of experimental results of indentation tests.

• MeSH
• analýza metodou konečných prvků MeSH
• biologické modely * MeSH
• buněčný převod mechanických signálů fyziologie   MeSH
• cytoskelet MeSH
• lidé MeSH
• mechanický stres MeSH
• myocyty hladké svaloviny chemie   cytologie   fyziologie   MeSH
• počítačová simulace MeSH
• svaly hladké cévní chemie   cytologie   fyziologie   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

This study investigated the effect of implant thickness and material on deformation and stress distribution within different components of cranial implant assemblies. Using the finite element method, two cranial implants, differing in size and shape, and thicknesses (1, 2, 3 and 4 mm, respectively), were simulated under three loading scenarios. The implant assembly model included the detailed geometries of the mini-plates and micro-screws and was simulated using a sub-modeling approach. Statistical assessments based on the Design of Experiment methodology and on multiple regression analysis revealed that peak stresses in the components are influenced primarily by implant thickness, while the effect of implant material is secondary. On the contrary, the implant deflection is influenced predominantly by implant material followed by implant thickness. The highest values of deformation under a 50 N load were observed in the thinnest (1 mm) Polymethyl Methacrylate implant (Small defect: 0.296 mm; Large defect: 0.390 mm). The thinnest Polymethyl Methacrylate and Polyether Ether Ketone implants also generated stresses in the implants that can potentially breach the materials' yield limit. In terms of stress distribution, the change of implant thickness had a more significant impact on the implant performance than the change of Young's modulus of the implant material. The results indicated that the stresses are concentrated in the locations of fixation; therefore, the detailed models of mini-plates and micro-screws implemented in the finite element simulation provided a better insight into the mechanical performance of the implant-skull system.

• Klíčová slova
• 3D printing, Cranioplasty, Finite element method, Mechanical properties, Skull implant,
• MeSH
• analýza metodou konečných prvků * MeSH
• experimentální implantáty * MeSH
• lebka * MeSH
• lidé MeSH
• mechanický stres * MeSH
• počítačová simulace * MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Biomechanical models based on the finite element method have already shown their potential in the simulation of the mechanical behaviour of cells. For instance, development of atherosclerosis is accelerated by damage of the endothelium, a monolayer of endothelial cells on the inner surface of arteries. Finite element models enable us to investigate mechanical factors not only at the level of the arterial wall but also at the level of individual cells. To achieve this, several finite element models of endothelial cells with different shapes are presented in this paper. Implementing the recently proposed bendotensegrity concept, these models consider the flexural behaviour of microtubules and incorporate also waviness of intermediate filaments. The suspended and adherent cell models are validated by comparison of their simulated force-deformation curves with experiments from the literature. The flat and dome cell models, mimicking natural cell shapes inside the endothelial layer, are then used to simulate their response in compression and shear which represent typical loads in a vascular wall. The models enable us to analyse the role of individual cytoskeletal components in the mechanical responses, as well as to quantify the nucleus deformation which is hypothesized to be the quantity decisive for mechanotransduction.

• MeSH
• analýza metodou konečných prvků MeSH
• buněčný převod mechanických signálů * MeSH
• endoteliální buňky metabolismus   MeSH
• lidé MeSH
• mikrotubuly MeSH
• modely kardiovaskulární * MeSH
• počítačová simulace * MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH

• MeSH
• analýza metodou konečných prvků * MeSH
• anatomické modely MeSH
• kolenní kloub anatomie a histologie   fyziologie   MeSH
• lidé MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Osseointegration is paramount for the longevity of dental implants and is significantly influenced by biomechanical stimuli. The aim of the present study was to assess the micro-strain and displacement induced by loaded dental implants at different stages of osseointegration using finite element analysis (FEA). Computational models of two mandible segments with different trabecular densities were constructed using microCT data. Three different implant loading directions and two osseointegration stages were considered in the stress-strain analysis of the bone-implant assembly. The bony segments were analyzed using two approaches. The first approach was based on Mechanostat strain intervals and the second approach was based on tensile/compression yield strains. The results of this study revealed that bone surrounding dental implants is critically strained in cases when only a partial osseointegration is present and when an implant is loaded by buccolingual forces. In such cases, implants also encounter high stresses. Displacements of partially-osseointegrated implant are significantly larger than those of fully-osseointegrated implants. It can be concluded that the partial osseointegration is a potential risk in terms of implant longevity.

• Klíčová slova
• Dental implants, Micro finite element analysis, Osseointegration, Strain intensity, Stress intensity,
• MeSH
• analýza metodou konečných prvků MeSH
• analýza zatížení zubů metody   MeSH
• biologické modely * MeSH
• biomechanika MeSH
• lidé MeSH
• mandibula fyziologie   MeSH
• mechanický stres MeSH
• osteointegrace fyziologie   MeSH
• počítačové zpracování signálu MeSH
• rentgenová mikrotomografie MeSH
• zubní implantáty * MeSH
• Check Tag
• lidé MeSH
• mužské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• zubní implantáty * MeSH

This study aimed to introduce a procedure for determining the bilinear elastic moduli (E1 and E2) of the periodontal ligament for a mathematical tooth model to analyse stress in the mandible. The bone and tooth morphology were scanned from a dry skull and an extracted intact tooth, respectively, and reconstructed in a three-dimensional finite element model. The model showed good agreement with previously reported in vivo premolar movement when an E1 for the first phase tooth movement of 0.05 MPa and an E2 for the second phase of 8.0 MPa with ε(12) of 0.075 were adopted. The mandible model analysis indicated that a remarkably high maximum compressive stress in the cervical cortical bone and the tensile stress in areas of masticatory muscle attachment were found. Future stress analyses using a jaw model may follow the process of determination of bilinear moduli to enhance accurate simulation with less calculation time.

• MeSH
• analýza metodou konečných prvků * MeSH
• biologické modely MeSH
• biomechanika MeSH
• hrot zubního kořene anatomie a histologie   MeSH
• lidé MeSH
• mandibula anatomie a histologie   fyziologie   MeSH
• mechanický stres MeSH
• modul pružnosti MeSH
• musculus masseter anatomie a histologie   fyziologie   MeSH
• musculus pterygoideus anatomie a histologie   fyziologie   MeSH
• musculus temporalis anatomie a histologie   fyziologie   MeSH
• odontometrie MeSH
• periodontální vaz fyziologie   MeSH
• počítačová simulace * MeSH
• počítačové zpracování obrazu metody   MeSH
• pohyb MeSH
• premolár anatomie a histologie   fyziologie   MeSH
• processus alveolaris anatomie a histologie   fyziologie   MeSH
• síla skusu MeSH
• zobrazování trojrozměrné metody   MeSH
• zubní kořen anatomie a histologie   MeSH
• zubní korunka (anatomie) anatomie a histologie   MeSH
• zubní lůžko anatomie a histologie   fyziologie   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

INTRODUCTION AND HYPOTHESIS: Objective of this study was to develop an MRI-based finite element model and simulate a childbirth considering the fetal head position in a persistent occiput posterior position. METHODS: The model involves the pelvis, fetal head and soft tissues including the levator ani and obturator muscles simulated by the hyperelastic nonlinear Ogden material model. The uniaxial test was measured using pig samples of the levator to determine the material constants. Vaginal deliveries considering two positions of the fetal head were simulated: persistent occiput posterior position and uncomplicated occiput anterior position. The von Mises stress distribution was analyzed. RESULTS: The material constants of the hyperelastic Ogden model were measured for the samples of pig levator ani. The mean values of Ogden parameters were calculated as: μ1 = 8.2 ± 8.9 GPa; μ2 = 21.6 ± 17.3 GPa; α1 = 0.1803 ± 0.1299; α2 = 15.112 ± 3.1704. The results show the significant increase of the von Mises stress in the levator muscle for the case of a persistent occiput posterior position. For the optimal head position, the maximum stress was found in the anteromedial levator portion at station +8 (mean: 44.53 MPa). For the persistent occiput posterior position, the maximum was detected in the distal posteromedial levator portion at station +6 (mean: 120.28 MPa). CONCLUSIONS: The fetal head position during vaginal delivery significantly affects the stress distribution in the levator muscle. Considering the persistent occiput posterior position, the stress increases evenly 3.6 times compared with the optimal head position.

• Klíčová slova
• FEM modeling, Levator ani muscle trauma, Ogden material model, Persistent occiput posterior position, Vaginal delivery,
• MeSH
• analýza metodou konečných prvků MeSH
• naléhání plodu * MeSH
• pánevní dno diagnostické zobrazování   MeSH
• plod * MeSH
• prasata MeSH
• těhotenství MeSH
• vedení porodu MeSH
• zvířata MeSH
• Check Tag
• těhotenství MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH

Dental implant dimensions, and bone quality and quantity play a key role in early osseointegration and long-term prognosis in posterior edentulous maxilla. Treatment with short implants, preferably in a bicortical manner, is an accepted modality; however, short implants have limitations leading to increased stress concentrations in alveolar bone, potential overload and implant failure. Implant models of 3.3, 4.1, 4.8 and 5.4 mm diameter and 4.5, 5.5, 6.5, 7.5 and 8.5 mm length were placed in posterior maxilla 3-D models with corresponding residual bone heights. Bone-implant assemblies were analyzed in finite element software ANSYS 15. All materials were assumed to be linearly elastic and isotropic. 118.2 N oblique loading was applied to investigate stress distributions in bone tissues. The concept of ultimate functional load (UFL) was selected as a criterion to compare load-carrying capacity of implants and to evaluate the influence of available bone height and implant dimensions on load-carrying capacity. For all implants, UFL was calculated by limiting von Mises stresses in cortical or cancellous bone with bone strength (100 MPa for cortical and 2 MPa for cancellous bone). Implant load-carrying capacity depends on diameter and available bone height. Wide implants have higher load-carrying capacity than narrow implants. Short implants with proper diameter and length avoid bone overstress, even in Type IV bone.

• Klíčová slova
• Finite element analysis, Posterior maxilla, Short implant,
• MeSH
• analýza metodou konečných prvků * MeSH
• lidé MeSH
• maxila * fyziologie   MeSH
• osteointegrace MeSH
• testování materiálů * MeSH
• zatížení muskuloskeletálního systému MeSH
• zubní implantáty * MeSH
• zubní protéza - design MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• zubní implantáty * MeSH