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Force Transmission (force + transmission)

Distribution by Scientific Domains

Medical Sciences	42%
Life Sciences	42%

Selected Abstracts

Force transmission of one- and two-piece morse-taper oral implants: a nonlinear finite element analysis

CLINICAL ORAL IMPLANTS RESEARCH, Issue 4 2004
Murat Cavit Çehreli
Abstract Purpose: To compare force transmission behaviors of one-piece (1-P) and two-piece (2-P) morse-taper oral implants. Material and methods: A three-dimensional finite element model of a morse-taper oral implant and a solid abutment was constructed separately. The implant,abutment complex was embedded in a Ø 1.5 cm × 1.5 cm acrylic resin cylinder. Vertical and oblique forces of 50 N and 100 N were applied on the abutment and solved by two different analyses. First, contact analysis was performed in the implant,abutment complex to evaluate a 2-P implant. Then, the components were bonded with a separation force of 1020 N to analyze a 1-P implant. Results: Von Mises stresses in the implant, principal stresses, and displacements in the resin were the same for both designs under vertical loading. Under oblique loading, principal stresses and displacement values in the resin were the same, but the magnitudes of Von Mises stresses were higher in the 2-P implant. The principal stress distributions around both implants in the acrylic bone were similar under both loading conditions. Conclusion: 2-P implants experience higher mechanical stress under oblique loading. Nevertheless, the 1-P- or 2-P morse-taper nature of an implant is not a decisive factor for the magnitude and distribution of stresses, and displacements in supporting tissues. Résumé Le but de cette étude a été de comparer les comportements de la transmission de la force desimplants buccaux en deux pièces. Un modèle d'éléments finis tridimensionnels d'un implant buccal et d'un pilier solide ont été construits séparément. Le complexe implant/pilier a été enfoui dans un cylindre de résine acrylique d'un diamètre 1,5 × 1,5 cm. Des forces obliques et verticales de 50 et 100 N ont été appliquées sur les piliers et analysées par deux méthodes. D'abord, l'analyse de contraste a été effectuée dans le complexe implant/pilier pour évaluer un implant en deux pièces. Ensuite, les composants ont été reliés avec une force de séparation de 1020N pour analyser un implant en une pièce. Les stress de Von Mises dans l'implant, les principaux stress et les déplacements dans la résine étaient les mêmes pour les deux modèles sous charge verticale. Lorsqu'une charge oblique était appliquée, les stress principaux et les valeurs de déplacements dans la résine étaient semblables mais l'amplitude des stress de Von Mises était plus importante dans l'implant à deux pièces. Les distributions des stress principaux autour des deux implants dans l'os acrylique était semblable sous les deux conditions de charge. Les implants en deux pièces subissent un stress mécanique plus important sous une charge oblique. Cependant, l'implant en une ou deux pièces avec un cône morse n'est pas un facteur décisif sur l'amplitude et la distribution des stress, et les déplacements des tissus de support. Zusammenfassung Ziel: Die Kraftübertragungsverhältnisse von ein- und zweiteiligen oralen Implantaten mit konischem Sitz der Sekundärteile zu untersuchen. Material und Methode: Es wurde je ein separates dreidimensionales Finite Element Modell eines oralen Implantats mit konischem Sitz der Sekundärteile und ein Massivsekundärteil konstruiert. Der Implantat-Sekundärteilkomplex wurde in einem Zylinder aus Acryl mit Durchmesser 1.5cm und Länge 1.5cm eingebettet. Vertikale und schräge Kräfte von 50 N und 100 N wurden auf das Sekundärteil appliziert und durch zwei verschiedene Analysen ausgewertet. Zuerst wurde eine Kontaktanalyse im Implantat-Sekundärteilkomplex zur Auswertung eines zweiteiligen Implantats durchgeführt. Dann wurden die Komponenten mit einer Separationskraft von 1020 N verbunden, um ein einteiliges Implantat zu analysieren. Resultate: Unter vertikaler Belastung waren der Van Mises Stress im Implantat, der generelle Stress und die Displatzierung im Kunststoff für beide Konstruktionen gleich. Unter schräger Belastung waren der generelle Stress und die Displatzierungswerte im Kunststoff die gleichen, jedoch war das Ausmass des von Mises Stress im zweiteiligen Implantat grösser. Die generelle Stressverteilung im Akrylknochen um die Implantate war unter beiden Belastungsbedingungen ähnlich. Schlussfolgerung: Zweiteilige Implantate erleiden grösseren mechanischen Stress unter schräger Belastung. Jedoch ist die ein- oder zweiteilige Konstruktion mit konischem Sitz der Sekundärteile bei Implantaten kein entscheidender Faktor für das Ausmass und die Verteilung des Stresses und für die Displatzierung in den Verankerungsgeweben. Resumen Intención: Comparar los comportamientos de transmisión de fuerzas de implantes orales en cono morse de una o dos piezas. Material y métodos: Se construyeron separadamente un modelo tridimensional de elemento finito de un implante oral de cono morse y un pilar sólido. El complejo implante-pilar se embebió en un cilindro de resina acrílica de , 1.5 cm × 1.5 cm. Se aplicaron fuerzas oblicuas de 50 N y 100 N sobre el pilar y se resolvieron por medio de dos análisis diferentes. Primero, se llevó a cabo un análisis de contacto en el complejo implante-pilar para evaluar un implante de dos piezas. Después, se unieron los componentes con una fuerza de separación de 1020 N para analizar un implante de una sola pieza. Resultados: El estrés de Von Mises, el estrés principal, y el desplazamiento en la resina fueron los mismos para ambos diseños bajo carga vertical. Bajo carga oblicua, los valores de estrés principal y desplazamiento en resina fueron los mismos, pero la magnitud de los estreses de Von Mises fueron mayores en los implantes de dos piezas. Las distribuciones del estrés principal alrededor de ambos implantes in el hueso acrílico fueron similares bajo ambas condiciones de carga. Conclusión: Los implantes de dos piezas experimentan un estrés mecánico mas alto bajo carga oblicua. Sin embargo, la naturaleza de un implante de cono morse de una o dos piezas no es un factor decisivo en la magnitud y distribución de los estreses, y desplazamientos en los tejidos de soporte. [source]

Intra- and intermuscular variation in human quadriceps femoris architecture assessed in vivo

JOURNAL OF ANATOMY, Issue 3 2006
Anthony J. Blazevich
Abstract Despite the functional importance of the human quadriceps femoris in movements such as running, jumping, lifting and climbing, and the known effects of muscle architecture on muscle function, no research has fully described the complex architecture of this muscle group. We used ultrasound imaging techniques to measure muscle thickness, fascicle angle and fascicle length at multiple regions of the four quadriceps muscles in vivo in 31 recreationally active, but non-strength-trained adult men and women. Our analyses revealed a reasonable similarity in the superficial quadriceps muscles, which is suggestive of functional similarity (at least during the uni-joint knee extension task) given that they act via a common tendon. The deep vastus intermedius (VI) is architecturally dissimilar and therefore probably serves a different function(s). Architecture varies significantly along the length of the superficial muscles, which has implications for the accuracy of models that assume a constant intramuscular architecture. It might also have consequences for the efficiency of intra- and intermuscular force transmission. Our results provide some evidence that subjects with a given architecture of one superficial muscle, relative to the rest of the subject sample, also have a similar architecture in other superficial muscles. However, this is not necessarily true for vastus lateralis (VL), and was not the case for VI. Therefore, the relative architecture of one muscle cannot confidently be used to estimate the relative architecture of another. To confirm this, we calculated a value of whole quadriceps architecture by four different methods. Regardless of the method used, we found that the absolute or relative architecture of one muscle could not be used as an indicator of whole quadriceps architecture, although vastus medialis, possibly in concert with VL and the anterior portion of VI, could be used to provide a useful snapshot. Importantly, our estimates of whole quadriceps architecture show a gender difference in whole quadriceps muscle thickness, and that muscle thickness is positively correlated with fascicle angle whereas fascicle length is negatively, although weakly, correlated with fascicle angle. These results are supportive of the validity of estimates of whole quadriceps architecture. These data are interpreted with respect to their implications for neural control strategies, region-specific adaptations in muscle size in response to training, and gender-dependent differences in the response to exercise training. [source]

Mitochondrial displacements in response to nanomechanical forces

JOURNAL OF MOLECULAR RECOGNITION, Issue 1 2008
Yaron R. Silberberg
Abstract Mechanical stress affects and regulates many aspects of the cell, including morphology, growth, differentiation, gene expression and apoptosis. In this study we show how mechanical stress perturbs the intracellular structures of the cell and induces mechanical responses. In order to correlate mechanical perturbations to cellular responses, we used a combined fluorescence-atomic force microscope (AFM) to produce well defined nanomechanical perturbations of 10,nN while simultaneously tracking the real-time motion of fluorescently labelled mitochondria in live cells. The spatial displacement of the organelles in response to applied loads demonstrates the highly dynamic mechanical response of mitochondria in fibroblast cells. The average displacement of all mitochondrial structures analysed showed an increase of ,40%, post-perturbation (,160,nm in comparison to basal displacements of ,110,nm). These results show that local forces can produce organelle displacements at locations far from the initial point of contact (up to ,40,µm). In order to examine the role of the cytoskeleton in force transmission and its effect on mitochondrial displacements, both the actin and microtubule cytoskeleton were disrupted using Cytochalasin D and Nocodazole, respectively. Our results show that there is no significant change in mitochondrial displacement following indentation after such treatments. These results demonstrate the role of the cytoskeleton in force transmission through the cell and on mitochondrial displacements. In addition, it is suggested that care must be taken when performing mechanical experiments on living cells with the AFM, as these local mechanical perturbations may have significant structural and even biochemical effects on the cell. Copyright © 2008 John Wiley & Sons, Ltd. [source]

The musculotendinous system of an anguilliform swimmer: Muscles, myosepta, dermis, and their interconnections in Anguilla rostrata

JOURNAL OF MORPHOLOGY, Issue 1 2008
Nicole Danos
Abstract Eel locomotion is considered typical of the anguilliform swimming mode of elongate fishes and has received substantial attention from various perspectives such as swimming kinematics, hydrodynamics, muscle physiology, and computational modeling. In contrast to the extensive knowledge of swimming mechanics, there is limited knowledge of the internal body morphology, including the body components that contribute to this function. In this study, we conduct a morphological analysis of the collagenous connective tissue system, i.e., the myosepta and skin, and of the red muscle fibers that sustain steady swimming, focusing on the interconnections between these systems, such as the muscle-tendon and myosepta-skin connections. Our aim is twofold: (1) to identify the morphological features that distinguish this anguilliform swimmer from subcarangiform and carangiform swimmers, and (2) to reveal possible pathways of muscular force transmission by the connective tissue in eels. To detect gradual morphological changes along the trunk we investigated anterior (0.4L), midbody (0.6L), and posterior body positions (0.75L) using microdissections, histology, and three-dimensional reconstructions. We find that eel myosepta have a mediolaterally oriented tendon in each the epaxial and hypaxial regions (epineural or epipleural tendon) and two longitudinally oriented tendons (myorhabdoid and lateral). The latter two are relatively short (4.5,5% of body length) and remain uniform along a rostrocaudal gradient. The skin and its connections were additionally analyzed using scanning electron microscopy (SEM). The stratum compactum of the dermis consists of ,30 layers of highly ordered collagen fibers of alternating caudodorsal and caudoventral direction, with fiber angles of 60.51 ± 7.05° (n = 30) and 57.58 ± 6.92° (n = 30), respectively. Myosepta insert into the collagenous dermis via fiber bundles that pass through the loose connective tissue of the stratum spongiosum of the dermis and either weave into the layers of the stratum compactum (weaving fiber bundles) or traverse the stratum compactum (transverse fiber bundles). These fiber bundles are evenly distributed along the insertion line of the myoseptum. Red muscles insert into lateral and myorhabdoid myoseptal tendons but not into the horizontal septum or dermis. Thus, red muscle forces might be distributed along these tendons but will only be delivered indirectly into the dermis and horizontal septum. The myosepta-dermis connections, however, appear to be too slack for efficient force transmission and collagenous connections between the myosepta and the horizontal septum are at obtuse angles, a morphology that appears inadequate for efficient force transmission. Though the main modes of undulatory locomotion (anguilliform, subcarangiform, and carangiform) have recently been shown to be very similar with respect to their midline kinematics, we are able to distinguish two morphological classes with respect to the shape and tendon architecture of myosepta. Eels are similar to subcarangiform swimmers (e.g., trout) but are substantially different from carangiform swimmers (e.g., mackerel). This information, in addition to data from kinematic and hydrodynamic studies of swimming, shows that features other than midline kinematics (e.g., wake patterns, muscle activation patterns, and morphology) might be better for describing the different swimming modes of fishes. J. Morphol., 2008. © 2007 Wiley-Liss, Inc. [source]

Influence of neck rotation and neck lateroflexion on mandibular equilibrium

JOURNAL OF ORAL REHABILITATION, Issue 5 2010
H. J. SCHINDLER
Summary, Neuromuscular interaction between neck and jaw muscles has been reported in several studies. However, the influence of experimentally modified posture of the neck on jaw muscle activity during isometric biting was not investigated so far. The aim of the present study was to test by the aid of simultaneous electromyographic and intraoral bite force measurements whether neck rotation and lateroflexion, in contrast to a straightforward neck position, change the isometric cocontraction patterns of masticatory muscles under identical submaximum bite forces of 50,200 N. Electric muscle activity of all masticatory muscles and changes of the reduction point (RP) of the resultant bite force vectors were examined. An anteroposterior displacement of the RPs could be observed for the rotated and lateroflexed neck position in comparison with the straightforward position. On the other hand, the results revealed no significant differences between bilateral muscle activation under the different test conditions. These findings suggest a force transmission between the neck and the masticatory system, but no essential activity changes in the masticatory muscles under short time posture modification of the neck. [source]

Properties of the two neuromuscular compartments in a split bipennate muscle

JOURNAL OF ORTHOPAEDIC RESEARCH, Issue 6 2004
Barry P. Pereira
Abstract Bipennate muscles may be split along their distal aponeurosis, dividing each into two compartments. These sub-muscle units may be used in tendon transfers. This paper presents the contractile properties of the two sub-units of the flexor carpi ulnaris in a macaca fascicularis, after it was split by up to 80% of its length. The sub-muscle units were electrically stimulated and found to have independent isometric contraction, with minimal contraction recorded from the non-stimulated sub-unit. Also, the sum of the forces measured from each unit when stimulated individually, was found to be greater than the force of the whole muscle, given the same isometric conditions. The distal aponeurosis which is common allows force transmission between the compartments. Splitting the muscle along this distal aponeurosis alters this function and the force capacity of the muscle, providing a new potential for using the sub-units as grafts for tendon transfers. © 2004 Orthopaedic Research Society. Published y Elsevier Ltd. All rights reserved. [source]

Postcontraction changes of muscle architecture in human quadriceps muscle

MUSCLE AND NERVE, Issue 4 2004
Konrad Mahlfeld MD
Abstract Maximal voluntary contraction changes the mechanical properties of skeletal muscle. Using ultrasound, we investigated whether these changes are reflected by changes in muscle architecture in the vastus lateralis muscle of 8 healthy volunteers. The mean pennation angle during the time interval from 3 to 6 min after maximal voluntary contraction (late postcontraction state) was 14.4 ± 1.11° (mean ± SEM) and differed significantly from the precontraction state (16.2 ± 1.39°), but the pennation angle in the early postcontraction state did not change statistically from the precontraction angle. Thus, postcontraction changes of the muscle,tendon interface appeared for 6 min after a maximal contraction, which may be important for biomechanical optimization of force transmission in vivo. Muscle Nerve 29: 597,600, 2004 [source]