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

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

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

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

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

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

Large mandibular continuity defects pose a significant challenge in oral maxillofacial surgery. One solution to this problem is to use computer-guided surgical planning and additive manufacturing technology to produce patient-specific reconstruction plates. However, when designing customized plates, it is important to assess potential biomechanical responses that may vary substantially depending on the size and geometry of the defect. The aim of this study was to assess the design of two customized plates using finite element method (FEM). These plates were designed for the reconstruction of the lower left mandibles of two ameloblastoma cases (patient 1/plate 1 and patient 2/plate 2) with large bone resections differing in both geometry and size. Simulations revealed maximum von Mises stresses of 63 MPa and 108 MPa in plates 1 and 2, and 65 MPa and 190 MPa in the fixation screws of patients 1 and 2. The equivalent strain induced in the bone at the screw-bone interface reached maximum values of 2739 micro-strain for patient 1 and 19,575 micro-strain for patient 2. The results demonstrate the influence of design on the stresses induced in the plate and screw bodies. Of particular note, however, are the differences in the induced strains. Unphysiologically high strains in bone adjacent to screws can cause micro-damage leading to bone resorption. This can adversely affect the anchoring capabilities of the screws. Thus, while custom plates offer optimal anatomical fit, attention should be paid to the expected physiological forces on the plates and the induced stresses and strains in the plate-screw-bone assembly.

• Klíčová slova
• Finite element analysis, Mandible reconstruction, Maxillofacial surgery, Rapid prototyping, Reconstruction plate,
• MeSH
• analýza metodou konečných prvků MeSH
• dospělí MeSH
• interní fixátory MeSH
• kostní destičky MeSH
• kostní šrouby * MeSH
• lidé středního věku MeSH
• lidé MeSH
• mandibula anatomie a histologie   chirurgie   MeSH
• mechanický stres * MeSH
• počítačová rentgenová tomografie metody   MeSH
• počítačová simulace MeSH
• počítačové zpracování obrazu metody   MeSH
• software MeSH
• tlak MeSH
• zákroky plastické chirurgie metody   MeSH
• Check Tag
• dospělí MeSH
• lidé středního věku MeSH
• lidé MeSH
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

STATEMENT OF PROBLEM: Masticatory forces acting on dental implants can result in undesirable stress in adjacent bone, which in turn can cause bone defects and the eventual failure of implants. PURPOSE: A mathematical simulation of stress distribution around implants was used to determine which length and diameter of implants would be best to dissipate stress. MATERIAL AND METHODS: Computations of stress arising in the implant bed were made with finite element analysis, using 3-dimensional computer models. The models simulated implants placed in vertical positions in the molar region of the mandible. A model simulating an implant with a diameter of 3.6 mm and lengths of 8 mm, 10 mm, 12 mm, 14 mm, 16 mm, 17 mm, and 18 mm was developed to investigate the influence of the length factor. The influence of different diameters was modeled using implants with a length of 12 mm and diameters of 2.9 mm, 3.6 mm, 4.2 mm, 5.0 mm, 5.5 mm, 6.0 mm, and 6.5 mm. The masticatory load was simulated using an average masticatory force in a natural direction, oblique to the occlusal plane. Values of von Mises equivalent stress at the implant-bone interface were computed using the finite element analysis for all variations. Values for the 3 most stressed elements of each variation were averaged and expressed in percent of values computed for reference (100%), which was the stress magnitude for the implant with a length of 12 mm and diameter of 3.6 mm. RESULTS: Maximum stress areas were located around the implant neck. The decrease in stress was the greatest (31.5%) for implants with a diameter ranging from of 3.6 mm to 4.2 mm. Further stress reduction for the 5.0-mm implant was only 16.4%. An increase in the implant length also led to a decrease in the maximum von Mises equivalent stress values; the influence of implant length, however, was not as pronounced as that of implant diameter. CONCLUSIONS: Within the limitations of this study, an increase in the implant diameter decreased the maximum von Mises equivalent stress around the implant neck more than an increase in the implant length, as a result of a more favorable distribution of the simulated masticatory forces applied in this study.

• MeSH
• analýza metodou konečných prvků * MeSH
• biologické modely MeSH
• lidé MeSH
• mandibula patofyziologie   MeSH
• mechanický stres MeSH
• moláry MeSH
• počítačová simulace MeSH
• povrchové vlastnosti MeSH
• processus alveolaris patofyziologie   MeSH
• regresní analýza MeSH
• síla skusu MeSH
• zubní implantáty * MeSH
• zubní lůžko patofyziologie   MeSH
• zubní protéza - design * MeSH
• zuby-sanace - selhání MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• zubní implantáty * MeSH

Dental implant failure is mainly the consequence of bone loss at peri-implant area. It usually begins in crestal bone. Due to this gradual loss, implants cannot withstand functional force without bone overload, which promotes complementary loss. As a result, implant lifetime is significantly decreased. To estimate implant success prognosis, taking into account 0.2 mm annual bone loss for successful implantation, ultimate occlusal forces for the range of commercial cylindrical implants were determined and changes of the force value for each implant due to gradual bone loss were studied. For this purpose, finite element method was applied and von Mises stresses in implant-bone interface under 118.2 N functional occlusal load were calculated. Geometrical models of mandible segment, which corresponded to Type II bone (Lekholm & Zarb classification), were generated from computed tomography images. The models were analyzed both for completely and partially osseointegrated implants (bone loss simulation). The ultimate value of occlusal load, which generated 100 MPa von Mises stresses in the critical point of adjacent bone, was calculated for each implant. To estimate longevity of implants, ultimate occlusal loads were correlated with an experimentally measured 275 N occlusal load (Mericske-Stern & Zarb). These findings generally provide prediction of dental implants success.

• Klíčová slova
• bone loss, implant dentistry, osseointegration, finite element,
• MeSH
• analýza metodou konečných prvků * MeSH
• analýza zatížení zubů MeSH
• časové faktory MeSH
• lidé MeSH
• mandibula patologie   MeSH
• mechanický stres MeSH
• osteointegrace MeSH
• síla skusu MeSH
• zatížení muskuloskeletálního systému MeSH
• zobrazování trojrozměrné MeSH
• zubní implantáty * MeSH
• zubní protéza - design MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• zubní implantáty * MeSH

The finite element analysis (FEA) has been identified as a useful tool for the stress and strain behaviour determination in lower limb prosthetics. The residual limb and prosthetic socket interface was the main subject of interest in previous studies. This paper focuses on the finite element analysis for the evaluation of structural behaviour of the Sure-flex™ prosthetic foot and other load-bearing components. A prosthetic socket was not included in the FEA. An approach for the finite element modelling including foot analysis, reverse engineering and material property testing was used. The foot analysis incorporated ground reaction forces measurement, motion analysis and strain gauge analysis. For the material model determination, non-destructive laboratory testing and its FE simulation was used. A new, realistic way of load application is presented along with a detailed investigation of stress distribution in the load-bearing components of the prosthesis. A novel approach for numerical and experimental agreement determination was introduced. This showed differences in the strain on the pylon between the experimental and the numerical model within 30% for the anteroposterior bending and up to 25% for the compression. The highest von Mises stresses were found on the foot-pylon connecting component at toe off. Peak stress of 216MPa occurred on the posterior adjusting screw and maximum stress of 156MPa was found at the neck of the male pyramid.

• MeSH
• amputovaní * MeSH
• analýza metodou konečných prvků * MeSH
• dospělí MeSH
• lidé MeSH
• mechanický stres MeSH
• protézy - design MeSH
• protézy a implantáty * MeSH
• tibie * MeSH
• zatížení muskuloskeletálního systému MeSH
• Check Tag
• dospělí MeSH
• lidé MeSH
• mužské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH