MedWorm.com provides a medical RSS filtering service. Over 6000 RSS medical sources are combined and output via different filters. This feed contains the latest items from the 'Journal of the Mechanical Behavior of Biomedical Materials' source. Sun, 14 Mar 2010 16:38:36 +0100 http://www.medworm.com/index.php?rid=3263362&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20142106%26dopt%3DAbstract Authors: Taylor D PMID: 20142106 [PubMed - in process] (Source: Journal of the Mechanical Behavior of Biomedical Materials) Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=3263362 Fri, 12 Feb 2010 05:48:24 +0100 3263362 http://www.medworm.com/index.php?rid=3263361&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20142107%26dopt%3DAbstract Authors: Muthutantri AI, Edirisinghe MJ, Boccaccini AR Porous scaffolds play a key role in tissue engineering (TE) approaches and new processing methods and materials are constantly being developed to cater for the wide range of specifications and requirements. Electrospraying is a relatively new processing method used for producing open-pore scaffolds. In this work, the electrospraying technique was manipulated to make the process more efficient, and the effect of spraying time on the pore size and strut thickness of zirconia scaffolds was explored. Scaffolds of adequate pore size and interconnectivity, with an average compressive strength of approximately 7.5 MPa, by electrospraying for only 10 min are reported. The effect of modifying the sacrificial template on the microstructure a... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=3263361 Fri, 12 Feb 2010 05:48:20 +0100 3263361 http://www.medworm.com/index.php?rid=3263360&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20142108%26dopt%3DAbstract In this study, we presented an estimation method of trabecular permeability by describing the analytical relationship between the volume orientation (VO) fabric tensor, which represents the canalicular orientation, and the permeability tensor. The relationship showed that the trabecular permeability tensor is proportional to the product of the volume fraction of the interstitial fluid and the VO fabric tensor of the canaliculi. We applied the proposed method to a two-dimensional fluorescent image of a trabecular cross section to quantify the canalicular anisotropy and the trabecular permeability tensor. The results indicated that the canaliculi are predominantly oriented in the radial direction of the trabecula, and the permeability depends strongly on the canalicular morphology. PMID:... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=3263360 Fri, 12 Feb 2010 05:48:17 +0100 3263360 http://www.medworm.com/index.php?rid=3263359&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20142109%26dopt%3DAbstract In conclusion, from a mechanical strength viewpoint, we have found that the porous structures produced by the electron beam melting process present a promising rapid manufacturing process for the direct fabrication of customized titanium implants for enabling personalized medicine. PMID: 20142109 [PubMed - as supplied by publisher] (Source: Journal of the Mechanical Behavior of Biomedical Materials) Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=3263359 Fri, 12 Feb 2010 05:48:14 +0100 3263359 http://www.medworm.com/index.php?rid=3263358&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20142110%26dopt%3DAbstract Authors: Anup S, Sivakumar SM, Suraishkumar GK Bone is an ultrafine composite of protein (collagen) and mineral (hydroxyapatite). An analysis to determine the influence of the viscoelasticity of protein on the toughness of bone at the ultrafine scale is conducted by developing a discrete lattice model appropriate for the ultrafine scale called the incremental continuous damage random fuse model (ICDRFM). Collagen viscoelasticity at ultrafine scale is shown to contribute significantly to the toughness of bone. The results obtained are important in the design of biomimetic ultratough artificial composites. PMID: 20142110 [PubMed - as supplied by publisher] (Source: Journal of the Mechanical Behavior of Biomedical Materials) Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=3263358 Fri, 12 Feb 2010 05:48:12 +0100 3263358 http://www.medworm.com/index.php?rid=3263357&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20142111%26dopt%3DAbstract Authors: Miller P, Hu L, Wang J Fundamental to the development and application of biomedical devices is an understanding of the adhesion of cells to substrates. There are many experimental techniques and papers dedicated to the study of cell adhesion. This work aims to elucidate on the cell detachment mechanism in a recently reported cell adhesion measurement experiment by laser-induced stress wave technique. In the experiment the absorption of an Nd:YAG laser pulse generates a stress wave of nanoseconds duration that interacts with and detaches the cell adhered to a Si substrate. Due to the ultra-short timescale involved in the experiment, details of the detachment process were not readily observable. In this work, dynamic finite element method is used to simulate the cell-substrate d... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=3263357 Fri, 12 Feb 2010 05:48:09 +0100 3263357 http://www.medworm.com/index.php?rid=3263356&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20142112%26dopt%3DAbstract In this study, confined compression creep tests were performed on silk hydrogels, over a range of concentrations, to examine the phenomenological behavior of the gels under a physiological loading scenario. Based on the observed behavior, we show that the time-dependent response can be explained by a consolidation mechanism, and modeled using Biot's poroelasticity theory. Two observations are in strong support of this modeling framework, namely, the excellent numerical agreement between increasing load step creep data and the linear Terzaghi theory, and the similar values obtained from numerical simulations and direct measurements of the permeability coefficient. The higher concentration gels (8% and 12% w/v) clearly show a strain-stiffening response to creep loading with increasing loads,... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=3263356 Fri, 12 Feb 2010 05:48:06 +0100 3263356 http://www.medworm.com/index.php?rid=3245666&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20129412%26dopt%3DAbstract Authors: Taylor D PMID: 20129412 [PubMed - in process] (Source: Journal of the Mechanical Behavior of Biomedical Materials) Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=3245666 Mon, 01 Feb 2010 00:00:00 +0100 3245666 http://www.medworm.com/index.php?rid=3245665&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20129413%26dopt%3DAbstract Authors: Ormsby R, McNally T, Mitchell C, Dunne N Polymethyl methacrylate (PMMA) bone cement-multiwalled carbon nanotube (MWCNT) nanocomposites with a weight loading of 0.1% were prepared using 3 different methods of MWCNT incorporation. The mechanical and thermal properties of the resultant nanocomposite cements were characterised in accordance with the international standard for acrylic resin cements. The mechanical properties of the resultant nanocomposite cements were influenced by the type of MWCNT and method of incorporation used. The exothermic polymerisation reaction for the PMMA bone cement was significantly reduced when thermally conductive functionalised MWCNTs were added. This reduction in exotherm translated in a decrease in thermal necrosis index value of the respective n... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=3245665 Mon, 01 Feb 2010 00:00:00 +0100 3245665 http://www.medworm.com/index.php?rid=3245664&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20129414%26dopt%3DAbstract Authors: Little JP, Pearcy MJ, Tevelen G, Evans JH, Pettet G, Adam CJ Analytical and computational models of the intervertebral disc (IVD) are commonly employed to enhance understanding of the biomechanics of the human spine and spinal motion segments. The accuracy of these models in predicting physiological behaviour of the spine is intrinsically reliant on the accuracy of the material constitutive representations employed to represent the spinal tissues. There is a paucity of detailed mechanical data describing the material response of the reinforced-ground matrix in the anulus fibrosus of the IVD. In the present study, the 'reinforced-ground matrix' was defined as the matrix with the collagen fibres embedded but not actively bearing axial load, thus incorporating the contribution of... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=3245664 Mon, 01 Feb 2010 00:00:00 +0100 3245664 http://www.medworm.com/index.php?rid=3245663&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20129415%26dopt%3DAbstract Authors: van Dommelen JA, van der Sande TP, Hrapko M, Peters GW Although many studies on the mechanical properties of brain tissue exist, some controversy concerning the possible differences in mechanical properties of white and gray matter tissues remains. Indentation experiments are conducted on white and gray matter tissues of various regions of the cerebrum and on tissue from the thalamus and the midbrain to study interregional differences. An advantage of indentation, when compared to standard rheological tests as often used for the characterization of brain tissue, is that it is a local test, requiring only a small volume of tissue to be homogeneous. Indentation tests are performed at different speeds and the force relaxation after a step indent is measured as well. White matter ... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=3245663 Mon, 01 Feb 2010 00:00:00 +0100 3245663 http://www.medworm.com/index.php?rid=3245662&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20129416%26dopt%3DAbstract Authors: Prot V, Skallerud B, Sommer G, Holzapfel GA Biomechanical data and related constitutive modelling of the mitral apparatus served as a basis for finite element analyses to better understand the physiology of mitral valves in health and disease. Human anterior and posterior leaflets and chordae tendinae from an elderly heart showing no disease and a hypertrophic obstructive cardiomyopathic heart (HOCM) were mechanically tested by means of uniaxial cyclic extension tests under quasi-static conditions. Experimental data for the leaflets and the chordae tendinae showed highly nonlinear mechanical behaviours and the leaflets were anisotropic. The mitral valve from the HOCM heart exhibited a significantly softer behaviour than the valve from the healthy one. A comparison with porcine... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=3245662 Mon, 01 Feb 2010 00:00:00 +0100 3245662 http://www.medworm.com/index.php?rid=3245661&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20129417%26dopt%3DAbstract Authors: Younesi M, Bahrololoom ME, Fooladfar H Implants made of nickel free austenitic stainless steel can reduce the toxic effect of released nickel ion and compounds from the conventional stainless steels. On the other hand, hydroxyapatite is a ceramic which has been used in orthopaedic applications due to its good osteoconductivity, biocompatibility and bioactivity. However, there is no evidence in the literature up to now on producing composites based on nickel free stainless steel and hydroxyapatite and study of their tribology. The aim of this work was to produce novel biocomposites made up of nickel free stainless steel with hydroxyapatite (prepared by heat treating bone ash) and studying their tribology under various loads in air and in Ringer's physiological solution. Differe... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=3245661 Mon, 01 Feb 2010 00:00:00 +0100 3245661 http://www.medworm.com/index.php?rid=3245650&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20129418%26dopt%3DAbstract Authors: Zhang J, Michalenko MM, Kuhl E, Ovaert TC Indentation tests can be used to characterize the mechanical properties of bone at small load/length scales offering the possibility of utilizing very small test specimens, which can be excised using minimally-invasive procedures. In addition, the need for mechanical property data from bone may be a requirement for fundamental multi-scale experiments, changes in nano- and micro-mechanical properties (e.g., as affected by changes in bone mineral density) due to drug therapies, and/or the development of computational models. Load vs. indentation depth data, however, is more complex than those obtained from typical macro-scale experiments, primarily due to the mixed state of stress, and thus interpretation of the data and extraction of me... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=3245650 Mon, 01 Feb 2010 00:00:00 +0100 3245650 http://www.medworm.com/index.php?rid=3245649&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20129419%26dopt%3DAbstract This study gives a detailed investigation of the microstructure formation of PVA/Gelatin hydrogel in each stage of physical treatments which helps us to explain the role of physical treatments in tuning their physical properties for biomechanical applications. PMID: 20129419 [PubMed - as supplied by publisher] (Source: Journal of the Mechanical Behavior of Biomedical Materials) Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=3245649 Mon, 01 Feb 2010 00:00:00 +0100 3245649 http://www.medworm.com/index.php?rid=3245648&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20129420%26dopt%3DAbstract Authors: Rossmann JS Veins have historically been discussed in qualitative, relative terms: "more compliant" than arteries, subject to "lower pressures". The structural and compositional differences between arteries and veins are directly related to the different functions of these vessels. Veins are often used as grafts to reroute flow from atherosclerotic arteries, and venous elasticity plays a role in the development of conditions such as varicose veins and valvular insufficiency. It is therefore of clinical interest to determine the elastomechanical properties of veins. In the current study, both tensile and vibration testing are used to obtain elastic moduli of bovine veins. Representative stress-strain data are shown, and the mechanical and failure properties reported. Nonlinear ... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=3245648 Mon, 01 Feb 2010 00:00:00 +0100 3245648 http://www.medworm.com/index.php?rid=3245647&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20129421%26dopt%3DAbstract Authors: Hammouda IM The primary aims of this study is to determine the wear and microhardness of composite resin cured with a light emitting diode (LED) and to make a comparison with a conventional halogen light curing unit (VLC LCU). The effect of load on weight loss was also investigated. For the wear tests, composite specimens were prepared in a rectangular mold. Specimens were divided into 5 groups; the first three groups were polymerized with LED LCU for 10, 20, and 40 s. Groups 4 and 5 were polymerized with VLC LCU for 20 and 40 s. Each group was divided into 2 subgroups according to the wearing loads (60 N and 90 N). Weight loss was recorded using a conventional Tribometer (mg). Specimens cured using LED showed greater hardness and less wear compared to conventional VLC-cured s... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=3245647 Mon, 01 Feb 2010 00:00:00 +0100 3245647 http://www.medworm.com/index.php?rid=3245646&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20129422%26dopt%3DAbstract Authors: Landrigan MD, Flatley JC, Turnbull TL, Kruzic JJ, Ferracane JL, Hilton TJ, Roeder RK A new technique using contrast enhanced micro-computed tomography (micro-CT) was developed to improve the ability to detect dentinal cracks in teeth and assess associated risks to oral health. Extracted, whole human molars that exhibited visual evidence of external cracks following extraction and machined, partially fractured elephant dentin specimens were labeled by BaSO(4) precipitation and imaged by micro-CT. Contrast-enhanced micro-CT was demonstrated in vitro to enable non-destructive, 3-D imaging of the presence, morphology and spatial location of dentinal cracks in whole human molars and machined specimens. BaSO(4) staining provided enhanced contrast for the detection of cracks that cou... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=3245646 Mon, 01 Feb 2010 00:00:00 +0100 3245646 http://www.medworm.com/index.php?rid=2955205&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19878896%26dopt%3DAbstract Authors: Taylor D PMID: 19878896 [PubMed - in process] (Source: Journal of the Mechanical Behavior of Biomedical Materials) Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2955205 Tue, 03 Nov 2009 22:46:51 +0100 2955205 http://www.medworm.com/index.php?rid=2955204&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19878897%26dopt%3DAbstract Authors: Bouslama N, Ben Ayed F, Bouaziz J Tricalcium phosphate and synthesized fluorapatite powder were mixed in order to elaborate biphasic composites. The samples were characterized by X-ray diffraction, differential thermal analysis, infrared spectroscopy, scanning electron microscopy and by an analysis using (31)P nuclear magnetic resonance. The sintering of tricalcium phosphate with different percentages of fluorapatite (13.26 wt%; 19.9 wt%; 33.16 wt% and 40 wt%) indicates the evolution of the microstructure, densification and mechanical properties. The Brazilian test was used to measure the rupture strength of the sintered biphasic composites. The mechanical properties increase with the sintering temperature and with the addition of fluorapatite additive. The mechanical resistan... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2955204 Tue, 03 Nov 2009 22:46:48 +0100 2955204 http://www.medworm.com/index.php?rid=2955203&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19878898%26dopt%3DAbstract Authors: Wang Y, Han X, Pan J, Sinka C This paper presents a model for the change in Young's modulus of biodegradable polymers due to hydrolysis cleavage of the polymer chains. The model is based on the entropy spring theory for amorphous polymers. It is assumed that isolated polymer chain cleavage and very short polymer chains do not affect the entropy change in a linear biodegradable polymer during its deformation. It is then possible to relate the Young's modulus to the average molecular weight in a computer simulated hydrolysis process of polymer chain sessions. The experimental data obtained by Tsuji [Tsuji, H., 2002. Autocatalytic hydrolysis of amorphous-made polylactides: Effects of L-lactide content, tacticity, and enantiomeric polymer blending. Polymers 43, 1789-1796] for poly... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2955203 Tue, 03 Nov 2009 22:46:45 +0100 2955203 http://www.medworm.com/index.php?rid=2955202&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19878899%26dopt%3DAbstract Authors: Lievers WB, Waldman SD, Pilkey AK End-constraint is needed when performing tensile and compressive testing of cancellous bone so that frictional and structural end-effects are minimized and the mechanical properties are not underestimated. Since many end-constrained testing techniques are limited to certain sites and species by the large specimen sizes required, reductions in overall specimen length would be advantageous. The following study examines the effect of specimen gauge length and aspect ratio on the elastic tensile testing of cancellous bone from the bovine femoral condyle. Three different nominal gauge lengths (10, 16, 22 mm) were examined at two different diameters (5.1, 10.7 mm) which bound the range typically used for cancellous bone testing. No effect of gauge l... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2955202 Tue, 03 Nov 2009 22:46:42 +0100 2955202 http://www.medworm.com/index.php?rid=2955201&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19878900%26dopt%3DAbstract Authors: Tawara D, Sakamoto J, Murakami H, Kawahara N, Oda J, Tomita K Osteoporosis can lead to bone compressive fractures in the lower lumbar vertebrae. In order to assess the recovery of vertebral strength during drug treatment for osteoporosis, it is necessary not only to measure the bone mass but also to perform patient-specific mechanical analyses, since the strength of osteoporotic vertebrae is strongly dependent on patient-specific factors, such as bone shape and bone density distribution in cancellous bone, which are related to stress distribution in the vertebrae. In the present study, patient-specific general (not voxel) finite element analyses of osteoporotic vertebrae during drug treatment were performed over time. We compared changes in bone density and compressive princip... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2955201 Tue, 03 Nov 2009 22:46:40 +0100 2955201 http://www.medworm.com/index.php?rid=2955200&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19878901%26dopt%3DAbstract In this study, for the fabrication of the abovementioned composite, a versatile process for filling a medical polymer into a porous metallic material has been developed using porous pure titanium (pTi) and polymethylmethacrylate (PMMA). Then, the tensile strength and Young's modulus of pTi filled with PMMA (pTi/PMMA) fabricated using this process are systematically investigated. The tensile strength of pTi can be improved by the PMMA filling. Particularly, the improvement in the tensile strength of pTi pretreated using a silane coupling agent before PMMA filling is greater than that of the non-pretreated pTi because the stress concentration near the pores may be reduced by the improvement in the interfacial adhesiveness between the titanium particles and the PMMA. In contrast, the effect o... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2955200 Tue, 03 Nov 2009 22:46:37 +0100 2955200 http://www.medworm.com/index.php?rid=2955199&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19878902%26dopt%3DAbstract Authors: Kanyanta V, Ivankovic A Mechanical testing and modelling of a material for biomedical applications have to be based on conditions representative of the application of interest. In this work, an ether-based polyurethane elastomer is used to build mock arteries. The aim is to study the behaviour of arteries under pulsatile loading conditions and how that behaviour changes with the development and progression of atherosclerosis. Polyurethane elastomers are widely used as biomaterials, e.g. in tube form for bypasses and catheters. However, their mechanical behaviour has not been extensively characterised. This work establishes the variations in the behaviour of polyurethane elastomer with temperature, humidity and strain rate and also reports planar and equibiaxial tension, relaxa... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2955199 Tue, 03 Nov 2009 22:46:34 +0100 2955199 http://www.medworm.com/index.php?rid=2955198&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19878903%26dopt%3DAbstract The objective of this study was to investigate this interaction and to determine what effect it has on the ultimate strength of the whole bone. This objective was achieved by compression testing rapid prototype (RP) models of cylindrical trabecular bone cores, with and without an integral surrounding shell and incorporating increasing levels of artificially induced bone loss. Corresponding finite element (FE) models were generated and the load sharing of the shell and trabecular core was analysed under linear elastic loading conditions. The results of the physical RP model tests and corresponding FE analyses indicated that there was a reinforcing effect between the cortical shell and the trabecular core for all models tested and that the reinforcing effect became relatively more important ... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2955198 Tue, 03 Nov 2009 22:46:31 +0100 2955198 http://www.medworm.com/index.php?rid=2955197&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19878904%26dopt%3DAbstract In this study, novel bioactive glass-ceramic powders exhibiting different nominal calcium-mica to fluorapatite ratios were used as fillers for light-cured dental composites. Wear tests on the resulting samples were undertaken using a micro-tribometer with a linear reciprocating ball-on-flat geometry using lubrication from artificial saliva. The surfaces of the worn composites were then evaluated using optical microscopy. In order to enhance matrix bonding, the surfaces of the different particulates were treated using hydrofluoric acid to provide a porous surface and the resulting surface morphology was evaluated using scanning electron microscopy. Although in the case of the samples containing low fluorapatite contents (20 wt%; A2), surface etching enhanced the wear resistance of the compo... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2955197 Tue, 03 Nov 2009 22:46:28 +0100 2955197 http://www.medworm.com/index.php?rid=2955196&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19878905%26dopt%3DAbstract Authors: Ito D, Tanaka E, Yamamoto S The purpose of this study is to develop a constitutive model of skeletal muscle that describes material anisotropy, viscoelasticity and damage of muscle tissue. A free energy function is described as the sum of volumetric elastic, isochoric elastic and isochoric viscoelastic parts. The isochoric elastic part is divided into two types of shear response and the response in the fiber direction. To represent the dependence of the mechanical properties on muscle activity, we incorporate a contractile element into the model. The viscoelasticity of muscle is modeled as a three-dimensional model constructed by extending the one-dimensional generalized Maxwell model. Based on the framework of continuum damage mechanics, the anisotropic damage of muscle tissu... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2955196 Tue, 03 Nov 2009 22:46:25 +0100 2955196 http://www.medworm.com/index.php?rid=2955195&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19878906%26dopt%3DAbstract Authors: Lewis G, Li Y Four variants of poly (methyl methacrylate) (PMMA) bone cement were used, the difference being in the method used to sterilize the powder (three different dosages of gamma irradiation and ethylene oxide gas) and, hence, in the molecular weight of the powder. For each cement powder, the number-average molecular weight and weight-average molecular weight (and, hence, the polydispersity index, PDI) were determined using gel permeation chromatography. For each of the cured cements, the fatigue lives (N(f)) of specimens, at loads corresponding to stresses (S) of +/-10.0 MPa, +/-12.5 MPa, +/-15.0 MPa, and +/-20.0 MPa, were determined using the protocol detailed in ASTM F2118-03. Hence, the values of the three Weibull parameters were determined for each cement set-S com... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2955195 Tue, 03 Nov 2009 22:46:22 +0100 2955195 http://www.medworm.com/index.php?rid=2955194&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19878907%26dopt%3DAbstract Authors: Buyanov AL, Gofman IV, Revel'skaya LG, Khripunov AK, Tkachenko AA Bacterial cellulose-polyacrylamide (BC-PAAm) composite hydrogels are prepared by synthesis of PAAm networks inside the BC matrices. The behavior of these gels and of the ionic ones obtained via partial hydrolysis of BC-PAAm gels is studied under swelling and compressive deformation conditions. The dependences of the hydrogels' properties on the BC matrix preparation conditions, gel synthesis conditions and the BC content in the hydrogel compositions are studied. Two types of BC gel pellicle are used in the hydrogel synthesis, namely matrix pellicles subjected to pre-pressing (samples of series A) and those not subjected to any mechanical actions before synthesis (series B samples) containing about 99% water. The... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2955194 Tue, 03 Nov 2009 22:46:19 +0100 2955194 http://www.medworm.com/index.php?rid=2955193&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19878908%26dopt%3DAbstract In conclusion, the present work provides direct evidence of viscoelastic behavior at the single fibril level, which has not been previously measured. PMID: 19878908 [PubMed - in process] (Source: Journal of the Mechanical Behavior of Biomedical Materials) Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2955193 Tue, 03 Nov 2009 22:46:17 +0100 2955193 http://www.medworm.com/index.php?rid=2955192&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19878909%26dopt%3DAbstract We present definitive evidence for crack growth from internal defects called 'tufts' in human enamel. Transverse slices (normal to the tooth axis) sawn from extracted human teeth are embedded in a polycarbonate sandwich configuration and tested in simple flexural loading. The evolution of ensuing cracks across the enamel sections is viewed in situ by a video camera. The observations unequivocally identify tufts as sources of internal tooth fracture. In sufficiently thin slices the enamel becomes translucent, allowing for through-thickness observations of the crack topography. Crack segments that appear to be disjointed on a section surface link up into a contiguous primary crack below the surface, suggesting some crack resistance by 'bridging' behind the advancing crack tip. The role of th... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2955192 Tue, 03 Nov 2009 22:46:14 +0100 2955192 http://www.medworm.com/index.php?rid=2955191&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19878910%26dopt%3DAbstract Authors: Kirchner HO, Neukirch S We use the existing data of force-extension experiments on F-actin molecules tied into knots to compute a value of 0.15 for the static friction coefficient for contact between different parts of the same molecule with itself. This estimate for protein-protein friction is relevant for the stabilization of the 273 known proteins with knots, one percent of the structures deposited in the Protein Data Bank. PMID: 19878910 [PubMed - in process] (Source: Journal of the Mechanical Behavior of Biomedical Materials) Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2955191 Tue, 03 Nov 2009 22:46:11 +0100 2955191 http://www.medworm.com/index.php?rid=2955190&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19878911%26dopt%3DAbstract Authors: Morrow DA, Haut Donahue TL, Odegard GM, Kaufman KR Of the plethora of work performed analyzing skeletal muscle tissue, relatively little has been done in the examination of its passive material properties. Previous studies of the passive properties of skeletal muscle have been primarily performed along the longitudinal material direction. In order to ensure the accuracy of the predictions of computational models of skeletal muscles, a better understanding of the tensile three-dimensional material properties of muscle tissue is necessary. To that end, the purpose of this study was to collect a comprehensive set of tensile stress-strain data from skeletal muscle tissue. Load-deformation data was collected from eighteen extensor digitorum longus muscles, dissected free of aponeur... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2955190 Tue, 03 Nov 2009 22:46:08 +0100 2955190 http://www.medworm.com/index.php?rid=2955189&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19878912%26dopt%3DAbstract Authors: Simmons WN, Cocks FH, Zhong P, Preminger G A novel composite kidney stone phantom has been developed. This stone phantom is producible with mechanical properties mimicking the range of tensile fracture strength and acoustic properties of human kidney stones and is an inorganic/organic composite material, as are natural kidney stones. Diametral compression testing was used to measure tensile fracture strength, which determines the acoustic comminution behavior of kidney stones. Ultrasound transmission tests were made to characterize the acoustic properties of these stone phantoms. Both the tensile fracture strength (controllable from 1 to approximately 5 MPa) and acoustic properties (C(L) = 2700-4400 m/s and C(T)=1600-2300m/s) of these composite phantom stones match those of a ... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2955189 Tue, 03 Nov 2009 22:46:05 +0100 2955189 http://www.medworm.com/index.php?rid=2752758&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19716100%26dopt%3DAbstract Authors: Roeder RK PMID: 19716100 [PubMed - in process] (Source: Journal of the Mechanical Behavior of Biomedical Materials) Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2752758 Wed, 02 Sep 2009 03:06:28 +0100 2752758 http://www.medworm.com/index.php?rid=2752757&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19716101%26dopt%3DAbstract Authors: Crawford GA, Chawla N, Houston JE Titanium dioxide (TiO(2)) coatings exhibit desirable properties as biocompatible coatings. In this paper we report on mechanical properties and deformation behavior of (TiO(2)) nanotubes grown on pure titanium substrates through anodic oxidation. Characterization of the as-processed coatings was conducted using scanning electron microscopy (SEM). Nanoindentation, using Interfacial Force Microscopy (IFM), was employed to probe the Young's modulus of the nanotubes. Using the IFM technique, the modulus of the nanotube coating may be measured with minimal contribution from the underlying Ti substrate. The modulus of the (TiO(2)) nanotube coating was estimated at 4-8 GPa. This technique was also used to study the inelastic deformation behavior of t... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2752757 Wed, 02 Sep 2009 03:06:25 +0100 2752757 http://www.medworm.com/index.php?rid=2752756&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19716102%26dopt%3DAbstract Authors: Thomas BH, Craig Fryman J, Liu K, Mason J A new class of hydrogels combining both hydrophilic and hydrophobic structures are presented. Hydrogels have been investigated as cartilage replacement materials due to the high water content potentially leading to low friction, low wear, and rubbery or pliable nature similar to native cartilage. Unfortunately, many of these hydrogels lack the required shear, tear, and creep strength necessary to be used as cartilage replacement materials. The new hydrogels presented here utilize hydrophobic domains to reinforce the structure and provide higher tear, shear, and creep strengths versus traditional hydrogels without sacrificing water content, low friction and pliability. The mechanical properties of some of these gels are reported, and it... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2752756 Wed, 02 Sep 2009 03:06:22 +0100 2752756 http://www.medworm.com/index.php?rid=2752755&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19716103%26dopt%3DAbstract Authors: Niu X, Rahbar N, Farias S, Soboyejo W This paper combines experiments, simulations and analytical modeling that are inspired by the stress reductions associated with the functionally graded structures of the dentin-enamel-junctions (DEJs) in natural teeth. Unlike conventional crown structures in which ceramic crowns are bonded to the bottom layer with an adhesive layer, real teeth do not have a distinct "adhesive layer" between the enamel and the dentin layers. Instead, there is a graded transition from enamel to dentin within a approximately 10 to 100 microm thick regime that is called the Dentin Enamel Junction (DEJ). In this paper, a micro-scale, bio-inspired functionally graded structure is used to bond the top ceramic layer (zirconia) to a dentin-like ceramic-filled polym... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2752755 Wed, 02 Sep 2009 03:06:19 +0100 2752755 http://www.medworm.com/index.php?rid=2752754&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19716104%26dopt%3DAbstract Authors: Jhon MH, Chrzan DC The mechanical properties of structural biomaterials are determined by features at many length scales. One example is the presence of an organic adhesive in nacre. The organic material contains biopolymers with discrete domains that may unfold as the polymer is extended. A statistical model for the mechanical response of a single biopolymer with these characteristics is introduced and studied. The response to tensile strain under displacement-controlled and load-controlled conditions is examined. Under the assumption of irreversible unfolding, analytical expressions for the load at first unfolding were derived, and a transition in behavior was observed for fast and slow loading. For titin, under displacement controlled extension, this transition occurs at ab... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2752754 Wed, 02 Sep 2009 03:06:16 +0100 2752754 http://www.medworm.com/index.php?rid=2752753&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19716105%26dopt%3DAbstract Authors: Lin AY, Meyers MA The shear strength of the interface between tiles of aragonite in the nacre of red abalone Haliotis rufescens was investigated through mechanical tensile and shear tests. Dog-bone shaped samples were used to determine the tensile strength of nacre when loaded parallel to the plane of growth; the mean strength was 65 MPa. Shear tests were conducted on a special fixture with a shear gap of 200 microm, approximately 100 microm narrower than the spacing between mesolayers. The shear strength is found to be 36.9+/-15.8 MPa with an average maximum shear strain of 0.3. Assuming the majority of failure occurs through tile pull-out and not through tile fracture, the tensile strength can be converted into a shear strength of 50.9 MPa. Three mechanisms of failure at the... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2752753 Wed, 02 Sep 2009 03:06:13 +0100 2752753 http://www.medworm.com/index.php?rid=2752752&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19716106%26dopt%3DAbstract Authors: Nyman JS, Leng H, Neil Dong X, Wang X The hierarchical arrangement of collagen and mineral into bone tissue presumably maximizes fracture resistance with respect to the predominant strain mode in bone. Thus, the ability of cortical bone to dissipate energy may differ between compression and tension for the same anatomical site. To test this notion, we subjected bone specimens from the anterior quadrant of human cadaveric tibiae to a progressive loading scheme in either uniaxial tension or uniaxial compression. One tension (dog-bone shape) and one compression specimen (cylindrical shape) were collected each from tibiae of nine middle aged male donors. At each cycle of loading-dwell-unloading-dwell-reloading, we calculated maximum stress, permanent strain, modulus, stress relaxa... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2752752 Wed, 02 Sep 2009 03:06:11 +0100 2752752 http://www.medworm.com/index.php?rid=2752751&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19716107%26dopt%3DAbstract Authors: Baker KC, Bellair R, Manitiu M, Herkowitz HN, Kannan RM Current bone graft substitute materials do not address the complex architectural and biomechanical requirements to achieve a successful spinal fusion. The development of porous, structural constructs for use in spinal fusion surgeries is thus an area of intense interest. Numerous techniques have been introduced to fabricate porous resorbable polymer constructs. However, these techniques have been associated with the use of potentially harmful organic solvents, and resulted in materials with less than optimal properties. Supercritical carbon dioxide (scCO(2)) processing appears to be a promising technique for producing reinforced biodegradable foams. The structure, mechanical properties and water uptake capacity of PDLGA c... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2752751 Wed, 02 Sep 2009 03:06:07 +0100 2752751 http://www.medworm.com/index.php?rid=2752750&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19716108%26dopt%3DAbstract Authors: Converse GL, Conrad TL, Roeder RK The apparent mechanical properties of hydroxyapatite (HA) whisker reinforced polyetherketoneketone (PEKK) scaffolds were evaluated in unconfined, uniaxial compression to investigate the effects of the porosity (75%, 82.5% and 90%), HA content (0, 20 and 40 vol%) and mold temperature (350, 365 and 375 ( composite function)C). Increased porosity resulted in a non-linear decrease in the elastic modulus and yield strength for both reinforced and unreinforced PEKK scaffolds, as expected. The increase in elastic modulus and yield strength with increased relative density followed a power-law, similar to trabecular bone and other open-cell foams. HA whisker reinforcement generally resulted in an increased elastic modulus from 0 to 20 vol% HA and a sub... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2752750 Wed, 02 Sep 2009 03:06:05 +0100 2752750 http://www.medworm.com/index.php?rid=2640537&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19627836%26dopt%3DAbstract Authors: Oyen M, Taylor D PMID: 19627836 [PubMed - in process] (Source: Journal of the Mechanical Behavior of Biomedical Materials) Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2640537 Mon, 27 Jul 2009 06:59:17 +0100 2640537 http://www.medworm.com/index.php?rid=2640536&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19627837%26dopt%3DAbstract Authors: Kaufman JD, Klapperich CM The accuracy of mechanical properties from depth-sensing indentation, or nanoindentation, depends on the accuracy of the displacement measurement used to calculate these properties. Here, current nanoindentation techniques and analysis methods for accurate displacement measurements are reviewed. First, the ability of a commercial instrument to sense the surface of soft materials is examined. Second, methods of sample surface detection are reviewed. Finally, a case of overestimation of the elastic modulus of a compliant material using nanoindentation with incorrect displacement values is presented. PMID: 19627837 [PubMed - in process] (Source: Journal of the Mechanical Behavior of Biomedical Materials) Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2640536 Mon, 27 Jul 2009 06:59:15 +0100 2640536 http://www.medworm.com/index.php?rid=2640535&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19627838%26dopt%3DAbstract Authors: Mencík J, He LH, Swain MV Load response of viscoelastic-plastic materials depends on the load magnitude and history, and can be described by rheological models consisting of springs and dashpots. The parameters in these models can be obtained by instrumented indentation. Time-dependent properties are determined best from the time course of indenter displacement under constant load, but one must consider also the initial loading history. For characterization of instantaneous elastic and plastic response, fast loading and unloading are necessary. The paper summarizes the formulae for indentation into elastic-plastic and viscoelastic-plastic materials, and proposes a procedure for testing and data evaluation. Its application is illustrated on the indentation of human enamel.... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2640535 Mon, 27 Jul 2009 06:59:13 +0100 2640535 http://www.medworm.com/index.php?rid=2640534&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19627839%26dopt%3DAbstract Authors: Gupta S, Lin J, Ashby P, Pruitt L Nanoindentation has shown promise as a mechanical characterization tool for orthopaedic biomaterials since it can probe the properties of small, heterogeneous, irregularly shaped tissue volumes in physiological environments. However, the majority of nanoindentation analyses have been limited to the determination of linear elastic and viscoelastic properties. Since biomaterials possess complex nonlinear, hydrated, time-dependent constitutive behavior, the objective of the present study is to explore the ability of nanoindentation to determine physiologically relevant material properties using a fibril reinforced poroelastic (FRPE) model. A further goal is to ascertain the sensitivity of nanoindentation load-displacement curves to different FRPE... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2640534 Mon, 27 Jul 2009 06:59:11 +0100 2640534 http://www.medworm.com/index.php?rid=2640533&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19627840%26dopt%3DAbstract The objective of this study was to use nanoindentation to investigate the transition from meniscal attachment into underlying subchondral bone through uncalcified and calcified fibrocartilage. Nanoindentation tests were performed on both the anterior and posterior meniscal insertions to measure the instantaneous elastic modulus and elastic modulus at infinite time. The elastic moduli were found to increase in a bi-linear fashion from the external ligamentous attachment to the subchondral bone. The elastic moduli for the anterior attachments were consistently larger than those for the matching posterior attachments at similar indentation locations. These results show that there is a gradient of stiffness from the superficial zones of the insertion close to the ligamentous attachment into th... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2640533 Mon, 27 Jul 2009 06:59:08 +0100 2640533 http://www.medworm.com/index.php?rid=2640532&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19627841%26dopt%3DAbstract Authors: Kavukcuoglu NB, Patterson-Buckendahl P, Mann AB In healthy bone there is a balance between bone resorption and formation. When an imbalance occurs there is an overall loss of bone mass leading to an increased risk of fracture. The deterioration is typically accompanied by changes in the non-collagenous proteins in the bone. Osteocalcin (OC) is the most abundant noncollageneous bone matrix protein and it is believed to play a role in bone formation and resorption. Nanoindentation and Raman microspectroscopy have been used to correlate the mechanical and chemical properties of cortical bone from femora of OC -/- (osteocalcin deficient) mice and their wild-type controls (OC +/+). There are significant intra-bone variations in mechanics and crystallinity especially in the mid-cort... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2640532 Mon, 27 Jul 2009 06:59:06 +0100 2640532 http://www.medworm.com/index.php?rid=2640531&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19627842%26dopt%3DAbstract This study was aimed at investigating the application of an inverse finite element analysis technique to identify material parameters of polymer gels via nanoindentation creep testing, optimization, and finite element simulation. Nanoindentation experiments were conducted using a rigid circular flat punch, and then simulated using the commercial software ABAQUS. The optimization (error minimization) procedure was integrated in the parameter determination process using a Matlab shell program, which makes this approach readily adaptable to other test geometries and material models. The finite element results compare well with a derived analytical viscoelastic solution for a rigid circular flat punch on a Kelvin-Voigt half-space. PMID: 19627842 [PubMed - in process] (Source: Journal of th... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2640531 Mon, 27 Jul 2009 06:59:04 +0100 2640531 http://www.medworm.com/index.php?rid=2640530&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19627843%26dopt%3DAbstract The objective of this study was to apply deformation partitioning to explore the role of hydration, tissue type, and degree of mineralization in bone and calcified cartilage. Wet, ethanol-dehydrated, and PMMA-embedded equine cortical bone samples and PMMA-embedded human femoral head tissues were analyzed for contributions of elastic, plastic and viscous deformation to the overall nanoindentation response at each site. While the alteration of hydration state had little effect on any measure of deformation, unembedded tissues demonstrated significantly greater measures of resistance to plastic deformation than PMMA-embedded tissues. The PMMA appeared to mechanically stabilize the tissues and prevent extensive permanent deformation within the bone material. Increasing mineral volume fraction ... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2640530 Mon, 27 Jul 2009 06:59:02 +0100 2640530 http://www.medworm.com/index.php?rid=2640529&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19627844%26dopt%3DAbstract Authors: Chan YL, Ngan AH, King NM In this paper, the usefulness of the specimen shaping ability of focused ion beam (FIB) milling in the micrometer scale and the high force resolution of the nanoindentation technique are demonstrated on human primary teeth. Micro-cantilevers, with a triangular cross-section <5 microm in width and 10 microm in length, were produced within 50 microm of the dentin-enamel junction (DEJ) using FIB milling, and were point-loaded at their free ends at 20 microN/s until failure using a nanoindenter. The elastic modulus and flexural strength of such micro-samples of human enamel, and their variation with respect to prism orientation, were studied and compared to data from bulk enamel measured using nanoindentation and three-point bend tests. The elastic mod... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2640529 Mon, 27 Jul 2009 06:58:59 +0100 2640529 http://www.medworm.com/index.php?rid=2640528&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19627845%26dopt%3DAbstract Authors: Kruzic JJ, Kim DK, Koester KJ, Ritchie RO Indentation techniques for assessing fracture toughness are attractive due to the simplicity and expediency of experiments, and because they potentially allow the characterization of both local and bulk fracture properties. Unfortunately, rarely have such techniques been proven to give accurate fracture toughness values. This is a concern, as such techniques are seeing increasing usage in the study of biomaterials and biological hard tissues. Four available indentation techniques are considered in the present article: the Vickers indentation fracture (VIF) test, the cube corner indentation fracture (CCIF) test, the Vickers crack opening displacement (VCOD) test and the interface indentation fracture (IIF) test. Each technique is discus... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2640528 Mon, 27 Jul 2009 06:58:56 +0100 2640528 http://www.medworm.com/index.php?rid=2640527&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19627846%26dopt%3DAbstract Authors: Oyen ML, Cook RF Mechanical properties of biological materials are increasingly explored via nanoindentation testing. This paper reviews the modes of deformation found during indentation: elastic, plastic, viscous and fracture. A scheme is provided for ascertaining which deformation modes are active during a particular indentation test based on the load-displacement trace. Two behavior maps for indentation are presented, one in the viscous-elastic-plastic space, concerning homogeneous deformation, and one in the plastic versus brittle space, concerning the transition to fracture behavior when the threshold for cracking is exceeded. Best-practice methods for characterizing materials are presented based on which deformation modes are active; the discussion includes both nanoinde... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2640527 Mon, 27 Jul 2009 06:58:54 +0100 2640527 http://www.medworm.com/index.php?rid=2640526&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19627847%26dopt%3DAbstract Authors: Lee TC, Taylor D PMID: 19627847 [PubMed - in process] (Source: Journal of the Mechanical Behavior of Biomedical Materials) Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2640526 Mon, 27 Jul 2009 06:58:52 +0100 2640526 http://www.medworm.com/index.php?rid=2640525&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19627848%26dopt%3DAbstract This article provides an extensive review on the issues of mandibular and maxillary bone remodeling as a result of dental implantation. Following the success of remodeling-driven orthopedic design from the long bone community, substantial clinical/experimental data of implantation have been driving the development of corresponding remodeling laws and algorithms to various dental settings, of which it is believed to contain potential to significantly impact on futuristic dental implant design. In this paper, the published remodeling data is analyzed and different biomechanical remodeling stimuli are assessed. The established relationships between bone density and corresponding mechanical properties are outlined and a range of potential methods of predicting the mandible and maxilla remodeli... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2640525 Mon, 27 Jul 2009 06:58:50 +0100 2640525 http://www.medworm.com/index.php?rid=2640524&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19627849%26dopt%3DAbstract Authors: Sobieraj MC, Rimnac CM Ultra high molecular weight polyethylene (UHMWPE) is a semicrystalline polymer that has been used for over four decades as a bearing surface in total joint replacements. The mechanical properties and wear properties of UHMWPE are of interest with respect to the in vivo performance of UHMWPE joint replacement components. The mechanical properties of the polymer are dependent on both its crystalline and amorphous phases. Altering either phase (i.e., changing overall crystallinity, crystalline morphology, or crosslinking the amorphous phase) can affect the mechanical behavior of the material. There is also evidence that the morphology of UHMWPE, and, hence, its mechanical properties evolve with loading. UHMWPE has also been shown to be susceptible to oxidat... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2640524 Mon, 27 Jul 2009 06:58:46 +0100 2640524 http://www.medworm.com/index.php?rid=2640523&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19627850%26dopt%3DAbstract Authors: Rakngarm A, Mutoh Y The surface of commercially pure Ti (cp-Ti) substrate was grit-blasted with Al(2)O(3) powders and then wet-blasted with HAp/Ti mixed powders at room temperature. Then plasma spraying with Ti powders or HAp/Ti mixed powders on the blasted surface was carried out to form a bond coat layer, denoted as T50 and T100 bond coat for the former and HT100 bond coat for the later. The HAp top coat was subsequently sprayed with 100 mum thickness. The XRD patterns showed that the as-sprayed HT100 bond coat layer was mainly composed of HAp with minor components of Ti and TiO(2). EDS analysis also showed there co-existed HAp and Ti without reaction in the HT100 bond coat layer. Some cracks were observed in the bond coat and the top coat layers after compression-compressio... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2640523 Mon, 27 Jul 2009 06:58:44 +0100 2640523 http://www.medworm.com/index.php?rid=2640522&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19627851%26dopt%3DAbstract Authors: Zhu Y, Dui G In this paper, an equivalent three-phase micromechanical model of composite with an elasto- plastic matrix and shape memory alloy (SMA) reinforcement is developed. Compared with the traditional two-phase method, the interaction among the austenitic phase, the martensite phase and the matrix phase is considered. During applications of the model, the predicted curve shows good agreement with the experimental result. Most attention is given to the effect of fiber shape on the overall response of the composite and the residual stress. It is helpful to design an intelligent composite. PMID: 19627851 [PubMed - in process] (Source: Journal of the Mechanical Behavior of Biomedical Materials) Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2640522 Mon, 27 Jul 2009 06:58:41 +0100 2640522 http://www.medworm.com/index.php?rid=2640521&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19627852%26dopt%3DAbstract Authors: Mullins LP, Bruzzi MS, McHugh PE In this work, the post-yield behaviour of cortical bone is investigated using finite element modelling, nanoindentation and atomic force microscopy. Based on recent investigations, it is proposed that, since pressure dependent deformation mechanisms may contribute to yielding in bone, constitutive models attempting to capture its post-yield behaviour should also incorporate pressure dependence. Nanoindentation testing is performed using a spheroconical indenter tip, and subsequent atomic force microscopy at the indented site shows that bone does not exhibit surface pile-up. By simulating the nanoindentation test, it is found that a Mises based constitutive law cannot simultaneously capture the deformations and load-displacement curve produced d... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2640521 Mon, 27 Jul 2009 06:58:38 +0100 2640521 http://www.medworm.com/index.php?rid=2640520&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19627853%26dopt%3DAbstract In conclusion, the reinforcement of the porcelain with continuous fibers resulted in an efficient mechanism to increase its mechanical properties; however the addition of milled fibers had no significant effect on the material because the porcelain was not able to wet the ceramic particles during the firing cycle. PMID: 19627853 [PubMed - in process] (Source: Journal of the Mechanical Behavior of Biomedical Materials) Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2640520 Mon, 27 Jul 2009 06:58:36 +0100 2640520 http://www.medworm.com/index.php?rid=2640519&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19627854%26dopt%3DAbstract Authors: Yan J, Taskonak B, Mecholsky JJ Dentin, the mineralized tissue forming the bulk of the tooth, serves as an energy-absorbing cushion for the hard, wear-resistant enamel and protects the inner soft tissues. Several studies used fracture mechanics methods to study the fracture toughness of dentin. However, all of them utilized precracks and cannot be used to estimate the intrinsic critical flaw size of dentin. We applied quantitative fractography to study the fracture pattern and fracture toughness of human dentin. Sixteen specimens were prepared from the coronal dentin and fractured in three-point flexure. Fracture surfaces were examined using a scanning electron microscope and the fracture toughness was calculated using a fracture mechanics equation. It was found that human den... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2640519 Mon, 27 Jul 2009 06:58:34 +0100 2640519 http://www.medworm.com/index.php?rid=2640518&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19627855%26dopt%3DAbstract Authors: Lyons JG, Geever LM, Nugent MJ, Kennedy JE, Higginbotham CL Numerous authors have reported on hydrogel technologies providing products suitable for applications in biomedical, personal care as well as in nano-sensor applications. Hydrogels fabricated from single polymers have been extensively investigated. However, in many cases a single polymer alone cannot meet divergent demands in terms of both properties and performance. In this work, hydrogels were prepared by physically blending the natural polymer agar with polyvinyl alcohol in varying ratios to produce a new biosynthetic polymer applicable for a variety of purposes. Hydrogen bonding was observed to take place between the polyvinyl alcohol and the agar molecules in the composite materials leading to changes in the therm... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2640518 Mon, 27 Jul 2009 06:58:31 +0100 2640518 http://www.medworm.com/index.php?rid=2640517&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19627856%26dopt%3DAbstract Authors: Chen X, Brodland GW To address the fundamental question, "How is the thickness of an embryonic epithelium determined?" equations of force equilibrium are derived and used to construct a theory applicable to embryonic epithelia and other labile monolayers, including confluent cultured cells. Under typical physiological conditions, the underlying mathematical relationships can be reworked into one simple algebraic equation. The theory shows that sheet thickness is determined by mechanical interactions between microfilaments, microtubules, cell adhesion systems and in-plane loading. It also explains the perplexing negative in-plane Poisson's ratio observed in some uniaxial tensile tests of embryonic epithelia. Thickness anomalies can affect phenotype, and the equations make it po... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2640517 Mon, 27 Jul 2009 06:58:29 +0100 2640517 http://www.medworm.com/index.php?rid=2640516&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19627857%26dopt%3DAbstract Authors: Shah MB, Ferracane JL, Kruzic JJ The fracture properties and micromechanisms of fracture for two commercial dental composites, one microhybrid (FiltekZ250) and one nanofill (FiltekSupreme Plus), were studied by measuring fracture resistance curves (R-curves) using pre-cracked compact-tension specimens and by conducting both unnotched and double notched four point beam bending experiments. Four point bending experiments showed about 20% higher mean flexural strength of the microhybrid composite compared to the nanofill. Rising fracture resistance was observed over approximately 1 mm of crack extension for both composites, and higher overall fracture resistance was observed for the microhybrid composite. Such fracture behavior was attributed to crack deflection and crack bridgin... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2640516 Mon, 27 Jul 2009 06:58:27 +0100 2640516 http://www.medworm.com/index.php?rid=2640515&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19627858%26dopt%3DAbstract The objective of this study was to determine the influence of agarose concentration, the cooling rate during gelation, the thermal history following gelation and the cell seeding density on the initial mechanical properties of agarose hydrogels. The average ramp modulus of 2% agarose gel in tension was 24.9 kPa (+/-1.7, n=10), compared with 55.6 kPa (+/-0.5, n=10) in compression. The average tensile equilibrium modulus was 39.7 kPa (+/-5.7, n=6), significantly higher than the compressive equilibrium modulus of 14.2 kPa (+/-1.6, n=10). The equilibrium and dynamic compressive modulus of agarose hydrogels were observed to reduce if maintained at 37 ( composite function)C following gelation compared with samples maintained at room temperature. Depending on the methodology used to encapsulate c... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2640515 Mon, 27 Jul 2009 06:58:25 +0100 2640515 http://www.medworm.com/index.php?rid=2640514&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19627859%26dopt%3DAbstract Authors: Grytz R, Meschke G A microstructurally oriented constitutive formulation for the hyperelastic response of crimped collagen fibrils existing in soft connective tissues is proposed. The model is based on observations that collagen fibrils embedded in a soft matrix crimp into a smooth three-dimensional pattern when unloaded. Following ideas presented by Beskos and Jenkins [Beskos, D., Jenkins, J., 1975. A mechanical model for mammalian tendon. ASME Journal of Applied Mechanics 42, 755-758] and Freed and Doehring [Freed, A., Doehring, T., 2005. Elastic model for crimped collagen fibrils. Journal of Biomechanical Engineering 127, 587-593] the collagen fibril crimp is approximated by a cylindrical helix to represent the constitutive behavior of the hierarchical organized substructur... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2640514 Mon, 27 Jul 2009 06:58:21 +0100 2640514 http://www.medworm.com/index.php?rid=2640513&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19627860%26dopt%3DAbstract Authors: Jalili K, Abbasi F, Oskoee SS, Alinejad Z A limitation in the use of hydrophilic polymers as implantable devices is their inherently poor mechanical strength. Using interpenetrating polymer networks (IPNs) consisting of both hydrophilic and hydrophobic networks is an effective method of strengthening these polymers. In this work, a series of poly(dimethyl siloxane) (PDMS)/poly(acrylic acid) (PAAc) sequential IPNs were synthesized and their properties, including swelling, morphology, and mechanical strength, were investigated. A reinforcing effect of the addition of PAAc to PDMS was observed at a concentration of 20 wt%, where this component had a bimodal size distribution. All of the IPNs exhibited rubbery behavior in the swollen state. Phase inversion in the IPNs occurred at ... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2640513 Mon, 27 Jul 2009 06:58:18 +0100 2640513 http://www.medworm.com/index.php?rid=2640512&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19627861%26dopt%3DAbstract This study examines the non-linear elastic response of PVA cryogel under uniaxial tension and investigates how processing parameters such as the concentration, the number of thermal cycles, and the thawing rate affect this response. The relationship between the coefficients of the material model and the processing parameters was interpolated to find the set of parameters that would best approximate the elastic response of healthy porcine coronary arteries under uniaxial tension. PMID: 19627861 [PubMed - in process] (Source: Journal of the Mechanical Behavior of Biomedical Materials) Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2640512 Mon, 27 Jul 2009 06:58:15 +0100 2640512 http://www.medworm.com/index.php?rid=2640511&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19627862%26dopt%3DAbstract Authors: Nazari A, Bajaj D, Zhang D, Romberg E, Arola D An evaluation of the crack growth resistance of human coronal dentin was performed on tissue obtained from patients between ages 18 and 83. Stable crack extension was achieved over clinically relevant lengths (0< or = a < or =1mm) under Mode I quasi-static loading and perpendicular to the nominal tubule direction. Results distinguished that human dentin exhibits an increase in crack growth resistance with extension (i.e. rising R-curve) and that there is a significant reduction in both the initiation (K(o)) and plateau (K(p)) components of toughness with patient age. In the young dentin (18< or =age< or =35) there was a 25% increase in the crack growth resistance from the onset of extension (K(o)=1.34 MPa m(0.5)) to th... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2640511 Mon, 27 Jul 2009 06:58:13 +0100 2640511 http://www.medworm.com/index.php?rid=2640510&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19627863%26dopt%3DAbstract Authors: Cordell JM, Vogl ML, Wagoner Johnson AJ While recognized as a promising bone substitute material, hydroxyapatite (HA) has had limited use in clinical settings because of its inherent brittle behavior. It is well established that macropores ( approximately 100 microm) in a HA implant, or scaffold, are required for bone ingrowth, but recent research has shown that ingrowth is enhanced when scaffolds also contain microporosity. HA is sensitive to synthesis and processing parameters and therefore characterization for specific applications is necessary for transition to the clinic. To that end, the mechanical behavior of bulk microporous HA and HA scaffolds with multi-scale porosity (macropores between rods in the range of 250-350 microm and micropores within the rods with average ... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2640510 Mon, 27 Jul 2009 06:58:11 +0100 2640510 http://www.medworm.com/index.php?rid=2640509&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19627864%26dopt%3DAbstract Authors: Creel JA, Stover SM, Martin RB, Fyhrie DP, Hazelwood SJ, Gibeling JC The compliance technique has been used to monitor crack length during fracture and fatigue testing of materials. Difficulties arise when this technique is applied to anisotropic biological materials such as bone. In this tutorial, two different methods of analyzing compliance calibration data are described: the standard ASTM method and a new approach developed by the authors specifically for anisotropic materials. An example is given showing how data from equine cortical bone can be analyzed. In this example, calibration tests were conducted on thirty-six three point bend specimens machined from the mid-diaphysis of six pairs of equine third metacarpal bones. Cracks were propagated in three orientations with ... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2640509 Mon, 27 Jul 2009 06:58:05 +0100 2640509 http://www.medworm.com/index.php?rid=2640547&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19627826%26dopt%3DAbstract Authors: Raeisi Najafi A, Arshi AR, Saffar KP, Eslami MR, Fariborz S, Moeinzadeh MH Microcracks formed in bone are due to fatigue and cyclic loading. This formation is associated with a reduction of bone resistance to fracture. However, the significance of the parameters that govern microcrack behavior is not yet fully explored. A two-dimensional micromechanical fiber-ceramic matrix composite material model of the osteonal cortical bone is presented in this paper. The solution for the edge dislocations as Green's function, is adopted to formulate a system of singular integral equations for the general microcracks in vicinity of the osteon. The effects of microstructural morphology and heterogeneity of the bone upon the fracture behavior is investigated by computing the Stress Intensity... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2640547 Tue, 30 Jun 2009 23:00:00 +0100 2640547 http://www.medworm.com/index.php?rid=2640546&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19627827%26dopt%3DAbstract Authors: Gefen A, Shalom R, Elad D, Mandel Y Keratoconus is a non-inflammatory disease characterized by irregular thinning and gradual bulging of the cornea, which results in distortion of the corneal surface that causes blurred vision. We conducted three-dimensional finite element (FE) simulations to analyze the biomechanical factors contributing to the distorted shape of a keratoconic cornea. We assumed orthotropic linear elastic tissue mechanical properties, and simulated localized tissue thinning (reduction from 0.5 mm to 0.35 or 0.2 mm). We analyzed tissue deformations, stresses and theoretical dioptric power maps predicted by the models, for intraocular pressure (IOP) of 10, 15 20 and 25 mmHg. The analyses revealed that three factors affect the shape distortion of keratoconic cor... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2640546 Tue, 30 Jun 2009 23:00:00 +0100 2640546 http://www.medworm.com/index.php?rid=2640545&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19627828%26dopt%3DAbstract Authors: Sultana T, Georgiev GL, Baird RJ, Auner GW, Newaz G, Patwa R, Herfurth HJ Biomedical devices and implants require precision joining for hermetic sealing which can be achieved with low power lasers. The effect of two different thin metal film coating methods was studied in transmission laser micro-joints of titanium-coated glass and polyimide. The coating methods were cathodic arc physical vapor deposition (CA-PVD) and electron beam evaporation (EB-PVD). Titanium-coated glass joined to polyimide film can have neural electrode application. The improvement of the joint quality will be essential for robust performance of the device. Low power fiber laser (wave length = 1100 nm) was used for transmission laser micro-joining of thin titanium (Ti) film (approximately 200 nm) coated P... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2640545 Tue, 30 Jun 2009 23:00:00 +0100 2640545 http://www.medworm.com/index.php?rid=2640544&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19627829%26dopt%3DAbstract Authors: Karami G, Grundman N, Abolfathi N, Naik A, Ziejewski M A finite element based micromechanical model has been developed for analyzing and characterizing the microstructural as well as homogenized mechanical response of brain tissue under large deformation. The model takes well-organized soft tissue as a fiber-reinforced composite with nonlinear and anisotropic behavior assumption for the fiber as well as the matrix of composite matter. The procedure provides a link between the macroscopic scale and microscopic scale as brain tissue undergoes deformation. It can be used to better understand how macroscopic stresses are transferred to the microstructure or cellular structure of the brain. A repeating unit cell (RUC) is created to stand as a representative volume element (RVE) of ... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2640544 Tue, 30 Jun 2009 23:00:00 +0100 2640544 http://www.medworm.com/index.php?rid=2640543&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19627830%26dopt%3DAbstract Authors: Espinoza Orías AA, Deuerling JM, Landrigan MD, Renaud JE, Roeder RK Experimental investigations for anatomic variation in the magnitude and anisotropy of elastic constants in human femoral cortical bone tissue have typically focused on a limited number of convenient sites near the mid-diaphysis. However, the proximal and distal ends of the diaphysis are more clinically relevant to common orthopaedic procedures and interesting mechanobiology. Therefore, the objective of this study was to measure anatomic variation in the elastic anisotropy and inhomogeneity of human cortical bone tissue along the entire length (15%-85% of the total femur length), and around the periphery (anterior, medial, posterior and lateral quadrants) of the femoral diaphysis, using ultrasonic wave pro... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2640543 Tue, 30 Jun 2009 23:00:00 +0100 2640543 http://www.medworm.com/index.php?rid=2640542&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19627831%26dopt%3DAbstract Authors: Smith TJ, Kennedy JE, Higginbotham CL The current study involves the development of a hydrogel carrier for a H(2)O(2) delivery system. In this work poly (vinyl alcohol) (PVA) and poly (acrylic acid) (PAA) based hydrogels were prepared, and their mechanical and physical properties examined. The novel aspect of this research is the differing functionality created by varying the concentration of H(2)O(2). The mechanical and thermal properties were determined by parallel plate rheometry and modulated differential scanning calorimetry (MDSC) respectively. The results indicated that the hydrogels containing H(2)O(2) are significantly weaker than those synthesised using water alone at test temperatures of 30 and 45 degrees C. MDSC analysis suggested that thermal transitions occur at ... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2640542 Tue, 30 Jun 2009 23:00:00 +0100 2640542 http://www.medworm.com/index.php?rid=2640541&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19627832%26dopt%3DAbstract This study describes a novel system for acquiring the 3D strain field in soft tissue at sub-millimeter spatial resolution during negative pressure wound therapy (NPWT). Recent research in advanced wound treatment modalities theorizes that microdeformations induced by the application of sub-atmospheric (negative) pressure through V.A.C. GranuFoam Dressing, a reticulated open-cell polyurethane foam (ROCF), is instrumental in regulating the mechanobiology of granulation tissue formation [Saxena, V., Hwang, C.W., Huang, S., Eichbaum, Q., Ingber, D., Orgill, D.P., 2004. Vacuum-assisted closure: Microdeformations of wounds and cell proliferation. Plast. Reconstr. Surg. 114, 1086-1096]. While the clinical response is unequivocal, measurement of deformations at the wound-dressing interface has not... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2640541 Tue, 30 Jun 2009 23:00:00 +0100 2640541 http://www.medworm.com/index.php?rid=2640540&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19627833%26dopt%3DAbstract In this study, we use these results to describe the strain energy function for arterial elastin, with dependence on a reduced subclass of invariants, as W=W(I(1),I(4)). We use previously published equations for this dependence [Humphrey, J.D., Strumpf, R.K., Yin, F.C.P., 1990a. Determination of a constitutive relation for passive myocardium: I. A new functional form. J. Biomech. Eng. 112, 333-339], in combination with a theoretical guided Rivlin-Saunders framework [Rivlin, R.S., Saunders, D.W., 1951. Large elastic deformations of isotropic materials VII. Experiments on the deformation of rubber. Phil. Trans. R. Soc. A 243, 251-288] and biaxial mechanical experiments, to obtain the form of this dependence. Using mechanical equivalence of elastin in the circumferential and longitudinal direc... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2640540 Tue, 30 Jun 2009 23:00:00 +0100 2640540 http://www.medworm.com/index.php?rid=2640539&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19627834%26dopt%3DAbstract Authors: Boukallel M, Girot M, Régnier S This paper deals with the development of an open design platform for characterization of mechanical cellular behavior. The resulting setup combines Scanning Probe Microscopy (SPM) techniques and advanced robotic approaches in order to carry out both prolonged observations and spatial measurements on biological samples. Visual and force feedback is controlled to achieve automatic data acquisition and to monitor process when high skills are required. The issue of the spring constant calibration is addressed using an accurate dynamic vibration approach. Experimentation on the mechanical cell characterization under in vitro conditions on human adherent Epithelial Hela cells demonstrates the viability and effectiveness of the proposed setup. Fin... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2640539 Tue, 30 Jun 2009 23:00:00 +0100 2640539 http://www.medworm.com/index.php?rid=2640538&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19627835%26dopt%3DAbstract Authors: Little JP, Tevelen G, Adam CJ, Evans JH, Pearcy MJ Biological tissues are subjected to complex loading states in vivo and in order to define constitutive equations that effectively simulate their mechanical behaviour under these loads, it is necessary to obtain data on the tissue's response to multiaxial loading. Single axis and shear testing of biological tissues is often carried out, but biaxial testing is less common. We sought to design and commission a biaxial compression testing device, capable of obtaining repeatable data for biological samples. The apparatus comprised a sealed stainless steel pressure vessel specifically designed such that a state of hydrostatic compression could be created on the test specimen while simultaneously unloading the sample along one axis w... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2640538 Tue, 30 Jun 2009 23:00:00 +0100 2640538 http://www.medworm.com/index.php?rid=2640558&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19627815%26dopt%3DAbstract Authors: Taylor D PMID: 19627815 [PubMed - in process] (Source: Journal of the Mechanical Behavior of Biomedical Materials) Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2640558 Tue, 31 Mar 2009 23:00:00 +0100 2640558 http://www.medworm.com/index.php?rid=2640557&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19627816%26dopt%3DAbstract Authors: Gautieri A, Buehler MJ, Redaelli A Collagen is an important structural protein in vertebrates and is responsible for the integrity of many tissues like bone, teeth, cartilage and tendon. The mechanical properties of these tissues are primarily determined by their hierarchical arrangement and the role of the collagen matrix in their structures. Here we report a series of Steered Molecular Dynamics (SMD) simulations in explicit solvent, used to elucidate the influence of the pulling rate on the Young's modulus of individual tropocollagen molecules. We stretch a collagen peptide model sequence [(Gly-Pro-Hyp)(10)](3) with pulling rates ranging from 0.01 to 100 m/s, reaching much smaller deformation rates than reported in earlier SMD studies. Our results clearly demonstrate a stron... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2640557 Tue, 31 Mar 2009 23:00:00 +0100 2640557 http://www.medworm.com/index.php?rid=2640556&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19627817%26dopt%3DAbstract Authors: Al-Munajjed AA, O'Brien FJ Lyophilised collagen scaffolds have shown enormous potential in tissue engineering in a number of areas due to their excellent biological performance. However, they are limited for use in bone tissue engineering due to poor mechanical properties. This paper discusses the development of a calcium-phosphate coating for collagen scaffolds in order to improve their mechanical properties for bone tissue engineering. Pure collagen scaffolds produced in a lyophilization process were coated by immersing them in sodium ammonium hydrogen phosphate (NaNH(4)HPO(4)) followed by calcium chloride (CaCl(2)). The optimal immersing sequence, duration, as well as the optimal solution concentration which facilitated improved mechanical properties of the scaffolds was in... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2640556 Tue, 31 Mar 2009 23:00:00 +0100 2640556 http://www.medworm.com/index.php?rid=2640555&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19627818%26dopt%3DAbstract Authors: Sprio S, Tampieri A, Celotti G, Landi E This work deals with the preparation of bioactive ceramic composites to be employed for the development of load-bearing bone substitutes, made of hydroxyapatite (Ca(10)(PO(4))(6)(OH)(2), HA) and bioactive dicalcium silicate (Ca(2)SiO(4), C(2)S) as a reinforcing phase. The composite materials were prepared by Fast Hot-Pressing (FHP), which allowed the rapid sintering of monolithic ceramics at temperatures up to 1500 degrees C, well above the commonly adopted temperatures for the consolidation of hydroxyapatite (1200-1300 degrees C). The purpose was to achieve the grain coalescence of both HA and the strengthening phase, so that to obtain a homogeneous ceramic material characterized by controlled phase composition and improved mechanical s... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2640555 Tue, 31 Mar 2009 23:00:00 +0100 2640555 http://www.medworm.com/index.php?rid=2640554&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19627819%26dopt%3DAbstract Authors: Guitar A, Vigna G, Luppo MI Thermohydrogen processing (THP), a technique in which hydrogen is used as a temporary alloying element, can refine the microstructure and improve the final mechanical properties of the Ti-6 Al-4V alloy. THP allows microstructural modification of titanium alloys near net shape such as biomaterial components obtained by powder metallurgy and castings, since it does not require mechanical working. Two THP, called THP-A and THP-B, have been evaluated in samples of Ti-6Al-4V with a coarse and lamellar microstructure typical of castings and powder metallurgy. The THP-A is based in the eutectoid decomposition of the beta(H) phase to alpha phase and hydride phase. The THP-B is based in the isothermal decomposition of alpha('') martensite phase, obtained by ... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2640554 Tue, 31 Mar 2009 23:00:00 +0100 2640554 http://www.medworm.com/index.php?rid=2640553&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19627820%26dopt%3DAbstract Authors: Cosmi F, Steimberg N, Dreossi D, Mazzoleni G Skeletal abnormalities reported in humans and laboratory animals after spaceflight, include cancellous osteopenia, decreased cortical and cancellous bone formation, aberrant matrix ultrastructure, decreased mineralization and reduced bone strength. Although considerable effort has been made up to now to understand the skeletal effects of spaceflight, in order to estimate health risk, our knowledge in this area is still largely incomplete. It is widely accepted that the mechanical strength of cancellous bone is related not only to the mineral content, but also to the trabecular micro-architecture arrangement. Three-dimensional numerical analysis of bone volumes has been shown to be an important tool in this field. The Cell Method, a ... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2640553 Tue, 31 Mar 2009 23:00:00 +0100 2640553 http://www.medworm.com/index.php?rid=2640552&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19627821%26dopt%3DAbstract Authors: Deguchi S, Fukamachi H, Hashimoto K, Iio K, Tsujioka K Previous studies on the intracellular force balance that forms the adherent cell structure have paid much attention to the mechanical behavior of cells seen in the horizontal project plane. By contrast, there are only few quantitative considerations on that in the vertical plane. Particularly, the contribution of the nucleus to the bearing of the vertical cell structure remains unclear. Here, we investigated the determinant of the vertical cell morphology from experimental and numerical approaches. The effect of cytoskeleton-affecting agents on the vascular endothelial cell height, as a measure of the vertical force balance, was examined by atomic force microscope indentation, demonstrating that actin depolymerization caus... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2640552 Tue, 31 Mar 2009 23:00:00 +0100 2640552 http://www.medworm.com/index.php?rid=2640551&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19627822%26dopt%3DAbstract Authors: Pourzal R, Theissmann R, Williams S, Gleising B, Fisher J, Fischer A Metal-on-metal hip arthroplasties undergo distinct release of toxic metal particles and ions. Thus, it is necessary to minimize this. In order to evaluate the wear behaviour of metal-on-metal hip replacements it is essential to understand the micro-structural changes in the sub-surface region. Previous studies revealed that cobalt chromium metal-on-metal implants are able to alter their mechanical behaviour by adjusting the microstructure to load. The reason for this is the so-called mechanical mixing. This means that a nano-crystal layer is formed by rotating clusters of atoms that incorporate denatured proteins from the interfacial medium. This is followed by a layer of rhombic shaped nano-crystals in betwe... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2640551 Tue, 31 Mar 2009 23:00:00 +0100 2640551 http://www.medworm.com/index.php?rid=2640550&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19627823%26dopt%3DAbstract We present constitutive model selection and parameter estimation for perfused porcine liver in indentation, and demonstrate that a quasilinear viscoelastic model with shear modulus relaxation offers good model-experiment agreement in terms of indenter displacement (0.19 mm RMS error) and tissue displacement field (0.97 mm RMS error). PMID: 19627823 [PubMed - in process] (Source: Journal of the Mechanical Behavior of Biomedical Materials) Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2640550 Tue, 31 Mar 2009 23:00:00 +0100 2640550 http://www.medworm.com/index.php?rid=2640549&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19627824%26dopt%3DAbstract In this study, we examined the effects of varying collagen concentration and crosslink density on the biological, structural and mechanical properties of collagen-GAG scaffolds for bone tissue engineering. Three different collagen contents (0.25%, 0.5% and 1% collagen) and two different dehydrothermal (DHT) crosslinking processes [1] 105 degrees C for 24 h and [2] 150 degrees C for 48 h were investigated. These scaffolds were assessed for (1) pore size, (2) permeability (3) compressive strength and (4) cell viability. The largest pore size, permeability rate, compressive modulus, cell number and cell metabolic activity was all found to occur on the 1% collagen scaffold due to its increased collagen composition and the DHT treatment at 150 degrees C was found to significantly improve the me... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2640549 Tue, 31 Mar 2009 23:00:00 +0100 2640549 http://www.medworm.com/index.php?rid=2640548&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19627825%26dopt%3DAbstract Authors: Weiss S, Meissner A, Fischer A Coronary heart disease has become the most common source for death in western industrial countries. Since 1986, a metal vessel scaffold (stent) is inserted to prevent the vessel wall from collapsing [Puel, J., Joffre, F., Rousseau, H., Guermonprez, B., Lancelin, B., Valeix, B., Imbert, G., Bounhoure, J.P, 1987. Endo-prothéses coronariennes autoexpansives dans la Préevention des resténoses apés angioplastie transluminale. Archives des Maladies du Coeur et des Vaisseaux, 1311--1312]. Most of these coronary stents are made from CrNiMo-steel (AISI 316L). Due to its austenitic structure, the material shows strength and ductility combined with corrosion resistance and a satisfactory biocompatibility. However, recent studies indicate... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2640548 Tue, 31 Mar 2009 23:00:00 +0100 2640548 http://www.medworm.com/index.php?rid=2084700&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19122858%26dopt%3DAbstract Authors: Zhang K, Siegmund T, Chan RW The human voice is produced by flow-induced self-sustained oscillation of the vocal fold lamina propria. The mechanical properties of vocal fold tissues are important for understanding phonation, including the time-dependent and transient changes in fundamental frequency (F(0)). Cyclic uniaxial tensile tests were conducted on a group of specimens of the vocal fold lamina propria, including the superficial layer (vocal fold cover) (5 male, 5 female) and the deeper layers (vocal ligament) (6 male, 6 female). Results showed that the vocal fold lamina propria, like many other soft tissues, exhibits both elastic and viscous behavior. Specifically, the transient mechanical responses of cyclic stress relaxation and creep were observed. A three-network con... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=2084700 Thu, 01 Jan 2009 05:00:00 +0100 2084700 http://www.medworm.com/index.php?rid=1557712&cid=s_37220_173_f&fid=37220&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18443659%26dopt%3DAbstract This study demonstrates new methods for the non-destructive and three-dimensional detection of fatigue microdamage accumulation in cortical bone in vitro, which may be useful to gain further understanding into the role of microdamage in bone fragility. PMID: 18443659 [PubMed - as supplied by publisher] (Source: Journal of the Mechanical Behavior of Biomedical Materials) Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=1557712 Tue, 01 Jan 2008 05:00:00 +0100 1557712