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. Tue, 07 Feb 2012 10:08:07 +0100 http://www.medworm.com/index.php?rid=5659650&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%3D22301168%26dopt%3DAbstract Authors: Tolidis K, Papadogiannis D, Papadogiannis Y, Gerasimou P Abstract Various types of indirect restorations are available for dental treatment and resin cements are commonly used as a luting medium. The aim of this study was to evaluate the mechanical properties of contemporary resin luting agents under different testing conditions and temperatures. The materials tested were Choice 2 (CH), Clearfil Esthetic Cement (EC), Resicem (RC) and RelyX Unicem (RX). Each material was examined after 24 h of storage at 21 °C dry and wet at 21, 37 and 50 °C under dynamic and static testing and parameters such as shear and flexural modulus, loss tangent, dynamic viscosity and Poisson's ratio were calculated. The resin cements were also subjected to creep testing under different constan... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5659650 Wed, 01 Feb 2012 05:00:00 +0100 5659650 http://www.medworm.com/index.php?rid=5659649&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%3D22301169%26dopt%3DAbstract Authors: Balla VK, Bhat A, Bose S, Bandyopadhyay A Abstract The purpose of this first generation investigation is to evaluate fabrication, in vitro cytotoxicity, cell-material interactions and tribological performance of TiN particle reinforced Ti6Al4V composite coatings for potential wear resistant load bearing implant applications. The microstructural analysis of the composites was performed using scanning electron microscope and phase analysis was done with X-ray diffraction. In vitro cell-material interactions, using human fetal osteoblast cell line, have been assessed on these composite coatings and compared with Ti6Al4V alloy control samples. The tribological performance of the coatings were evaluated, in simulated body fluids, up to 1000 m sliding distance under 10 N normal... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5659649 Wed, 01 Feb 2012 05:00:00 +0100 5659649 http://www.medworm.com/index.php?rid=5659648&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%3D22301170%26dopt%3DAbstract In this study, we performed a multi-axial mechanical test and histological analysis to characterize the mechanical and structural properties of the aged human, porcine and ovine CS tissues. The results showed that the aged human CS tissues exhibited much stiffer and highly anisotropic behaviors compared to the porcine and ovine. Both of the porcine and ovine CS vessel walls were thicker and mainly composed of striated muscle fibers (SMF), whereas the thinner aged human CS had higher collagen, less SMF, and more fragmented elastin fibers, which are possibly due to aging effects. We also observed that the anatomical features of porcine CS vessel might be not suitable for PTMA deployment. These differences between animal and human models raise questions for the validity of using animal models... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5659648 Wed, 01 Feb 2012 05:00:00 +0100 5659648 http://www.medworm.com/index.php?rid=5659647&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%3D22301171%26dopt%3DAbstract Authors: Myant C, Underwood R, Fan J, Cann PM Abstract Lubricant films were measured for a series of bovine serum and protein containing (albumin, globulin) saline solutions for CoCrMo femoral component sliding against a glass disc. Central film thickness was measured by optical interferometry as a function of time (constant mean speed: 0 and 10 mm/s) and variable mean speed (0-50 mm/s). The effect of load (5-20 N) on film thickness was also studied. The development of the wear scar on the CoCrMo surface was monitored by measuring the width of the contact zone during the film thickness tests. The results showed film thickness increased with time for both the static and sliding tests. Films formed in the static, loaded test were typically in the range of 3-40 nm. The globulin co... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5659647 Wed, 01 Feb 2012 05:00:00 +0100 5659647 http://www.medworm.com/index.php?rid=5659646&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%3D22301172%26dopt%3DAbstract Authors: Kefalas V, Eftaxiopoulos DA Abstract Experimental study of bovine cancellous bone up to compaction under uniaxial compression and up to fracture under tension, has been pursued in this article. Compression experiments have revealed the known three stages of the constitutive response, namely the initial increasing and softening branches at moderate strains, the plateau region at large strains and the hardening part at very large strains under compaction. Tension tests have quantified the increasing and softening branches of the stress-strain curve up to fracture. Subsequently, a constitutive mechanical model, for the simulation of the experimental findings up to very large strains (75% engineering strain under compression), is proposed. The model is based on the statistical... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5659646 Wed, 01 Feb 2012 05:00:00 +0100 5659646 http://www.medworm.com/index.php?rid=5659645&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%3D22301173%26dopt%3DAbstract Authors: González S, Pellicer E, Fornell J, Blanquer A, Barrios L, Ibáñez E, Solsona P, Suriñach S, Baró MD, Nogués C, Sort J Abstract The influence of partial substitution of Mg by Pd on the microstructure, mechanical properties and corrosion behaviour of Mg(72-x)Zn(23)Ca(5)Pd(x) (x=0, 2 and 6 at.%) alloys, synthesized by copper mould casting, is investigated. While the Mg(72)Zn(23)Ca(5) alloy is mainly amorphous, the addition of Pd decreases the glass-forming ability, thus favouring the formation of crystalline phases. From a mechanical viewpoint, the hardness increases with the addition of Pd, from 2.71 GPa for x=0 to 3.9 GPa for x=6, mainly due to the formation of high-strength phases. In turn, the wear resistance is maximized for an intermediate Pd content (i.e., Mg(7... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5659645 Wed, 01 Feb 2012 05:00:00 +0100 5659645 http://www.medworm.com/index.php?rid=5659644&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%3D22301174%26dopt%3DAbstract This study may provide gel scientists new ideas in designing and fabricating hydrogels with well-defined microstructures and unique mechanical and swelling properties. PMID: 22301174 [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=5659644 Wed, 01 Feb 2012 05:00:00 +0100 5659644 http://www.medworm.com/index.php?rid=5659643&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%3D22301175%26dopt%3DAbstract In this study, we reported a possible role of triplet repeats of aspartate-serine-serine (3DSS) peptides in promoting mineral deposition onto human enamel from free ions. Human enamel specimens were acid demineralized, exposed briefly to 3DSS peptide solution, and then immersed in artificial saliva. At various stages of treatments, nanomechanical behaviors, surface morphology, surface roughness and the sorts of deposited minerals were characterized by nanoindentation, scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray diffraction (XRD), respectively. The results indicated that treatment with 3DSS peptide promoted the uniform deposition of apatites with small crystalline size, in terms of prohibiting deformation, which resulted in a smaller average surface roughness... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5659643 Wed, 01 Feb 2012 05:00:00 +0100 5659643 http://www.medworm.com/index.php?rid=5659642&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%3D22301176%26dopt%3DAbstract Authors: Widjaja LK, Kong JF, Chattopadhyay S, Lipik VT, Liow SS, Abadie MJ, Venkatraman SS Abstract A series of triblock copolymers comprising end block of PLLA modified with PCL, and random copolymer of PCL and PTMC as soft segment were synthesized. DSC data show that PCL disrupted the crystallinity of PLLA, making the hard block to be completely amorphous when the PCL content is 50%. Correspondingly, the addition of PCL into PLLA block enhances the elongation of the triblock considerably. With regards to the elasticity, however, creep test results show that adding PCL to PLLA block seems to reduce the "equilibrium" recovery, while cyclic test results shows that the instantaneous recovery increased significantly with more PCL inside PLLA block. It was also observed that the degra... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5659642 Wed, 01 Feb 2012 05:00:00 +0100 5659642 http://www.medworm.com/index.php?rid=5659641&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%3D22301177%26dopt%3DAbstract Authors: Byeli AV, Kukareko VA, Kononov AG Abstract Titanium and zirconium alloys are considered to be promising materials for orthopaedics because of their biocompatibility with tissues. Their main drawbacks for application as implants have generally been considered to be insufficient levels of mechanical and tribological properties. In this research the influence of equal channel angular pressing and nitrogen ion implantation on the structure and properties of Ti and Zr alloys has been investigated to ensure the optimum combination of the bulk material and surface layer properties. The data obtained showed that equal channel angular pressing and nitrogen ion implantation can be efficiently used to improve bulk and surface properties of Ti and Zr based implants. PMID: 22301177... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5659641 Wed, 01 Feb 2012 05:00:00 +0100 5659641 http://www.medworm.com/index.php?rid=5659640&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%3D22301178%26dopt%3DAbstract Authors: May-Pat A, Herrera-Kao W, Cauich-Rodríguez JV, Cervantes-Uc JM, Flores-Gallardo SG Abstract In this work, the effect of the incorporation of comonomers containing amine groups on the mechanical and fracture properties of acrylic bone cements was studied. Cements were prepared with either diethyl amino ethyl acrylate (DEAEA), dimethyl amino ethyl methacrylate (DMAEM) or diethyl amino ethyl methacrylate (DEAEM) as comonomer in the liquid phase. It was found that strength and modulus decreased with increasing comonomer content in the bending and compressive tests. It was also observed that fracture toughness (K(IC)) and the critical strain energy release rate (G(IC)) increase with increasing comonomer concentration and are significantly higher compared to the control formula... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5659640 Wed, 01 Feb 2012 05:00:00 +0100 5659640 http://www.medworm.com/index.php?rid=5659639&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%3D22301179%26dopt%3DAbstract Authors: Damiens R, Rhee H, Hwang Y, Park SJ, Hammi Y, Lim H, Horstemeyer MF Abstract The turtle's shell acts as a protective armor for the animal. By analyzing a turtle shell via finite element analysis, one can obtain the strength and stiffness attributes to help design man-made armor. As such, finite element analysis was performed on a Terrapene carolina box turtle shell. Experimental data from compression tests were generated to provide insight into the scute through-thickness behavior of the turtle shell. Three regimes can be classified in terms of constitutive modeling: linear elastic, perfectly inelastic, and densification regions, where hardening occurs. For each regime, we developed a model that comprises elasticity and densification theory for porous materials and obtaine... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5659639 Wed, 01 Feb 2012 05:00:00 +0100 5659639 http://www.medworm.com/index.php?rid=5659638&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%3D22301180%26dopt%3DAbstract Authors: Gil FJ, Espinar E, Llamas JM, Manero JM, Ginebra MP Abstract Reuse of NiTi orthodontic wires has become increasingly common in dental clinics. For sterilization and recovery of the original superelastic properties of the wires, a heat treatment is usually performed between 500 and 600 °C. The aim of this study was to analyze the effect of these thermal treatments on the mechanical behavior and the microstructure of NiTi archwires of different compositions. A reduction of the Ni content was observed in the matrix of the thermally treated archwires, due to the formation of Ti(3)Ni(4) precipitates. The nickel-rich precipitates were observed and characterized by Transmission Electron Microscopy (TEM) and electron diffraction. They were found to alter the mechanical propertie... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5659638 Wed, 01 Feb 2012 05:00:00 +0100 5659638 http://www.medworm.com/index.php?rid=5659637&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%3D22301181%26dopt%3DAbstract Authors: Zhang Y, Allahkarami M, Hanan JC Abstract Residual stress plays a critical role in failure of ceramic dental crowns. The magnitude and distribution of residual stress in the crown system are largely unknown. Determining the residual stress quantitatively is challenging since the crown has such complex contours and shapes. This work explored the feasibility and validity of measuring residual stress of zirconia and porcelain in ceramic crowns by nanoindentation. Nanoindentation tests were performed on the cross-section of a crown for both porcelain and zirconia along four critical locations: the thickest, thinnest and medium porcelain thicknesses. Zirconia and porcelain pieces, chipped off from the crown and annealed at 400 °C, were used as reference samples. The residual ... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5659637 Wed, 01 Feb 2012 05:00:00 +0100 5659637 http://www.medworm.com/index.php?rid=5659636&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%3D22301182%26dopt%3DAbstract Authors: Barnes D, Johnson S, Snell R, Best S Abstract Bioactive coatings are applied to components of modern orthopædic implants to improve the host tissue response to the implants. Such coatings cannot be applied to polymeric implants by high-temperature techniques, because the use of high temperatures may critically degrade the polymer substrate. Regardless of the coating technique that is used, the coating must be sufficiently well adhered to the underlying substrate to provide any practical benefit. This paper investigates the use of scratch testing to measure the adhesion strength of calcium phosphate (CaP) coatings that were applied to a poly(carbonate urethane) (PCU) substrate by an aqueous process at temperatures of 19, 28, 37, and 50 °C. This work represents the first t... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5659636 Wed, 01 Feb 2012 05:00:00 +0100 5659636 http://www.medworm.com/index.php?rid=5659635&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%3D22301183%26dopt%3DAbstract Authors: Taylor D, O'Mara N, Ryan E, Takaza M, Simms C Abstract Fracture toughness is important for any material, but to date there have been few investigations of this mechanical property in soft mammalian tissues. This paper presents new data on porcine muscle tissue and a detailed analysis of all previous work. The conclusion is that, in most cases, fracture toughness has not in fact been measured for these tissues. Reanalysis of the previous work shows that failure of the test specimens generally occurred at the material's ultimate strength, implying that no information about toughness can be obtained from the results. This finding applied to work on cartilage, artificial neocartilage, muscle and the TMJ disc. Our own data, which was also found to be invalid, gave measured frac... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5659635 Wed, 01 Feb 2012 05:00:00 +0100 5659635 http://www.medworm.com/index.php?rid=5659634&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%3D22301184%26dopt%3DAbstract Authors: Yang L, van der Werf KO, Dijkstra PJ, Feijen J, Bennink ML Abstract The mechanical properties of individual collagen fibrils of approximately 200 nm in diameter were determined using a slightly adapted AFM system. Single collagen fibrils immersed in PBS buffer were attached between an AFM cantilever and a glass surface to perform tensile tests at different strain rates and stress relaxation measurements. The stress-strain behavior of collagen fibrils immersed in PBS buffer comprises a toe region up to a stress of 5 MPa, followed by the heel and linear region at higher stresses. Hysteresis and strain-rate dependent stress-strain behavior of collagen fibrils were observed, which suggest that single collagen fibrils have viscoelastic properties. The stress relaxation process ... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5659634 Wed, 01 Feb 2012 05:00:00 +0100 5659634 http://www.medworm.com/index.php?rid=5659633&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%3D22301185%26dopt%3DAbstract Authors: Kerl J, Parittotokkaporn T, Frasson L, Oldfield M, Rodriguez Y Baena F, Beyrau F Abstract A laser based technique for planar time-resolved measurements of tissue deformation in transparent biomedical materials with high spatial resolution is developed. The approach is based on monitoring the displacement of micrometer particles previously embedded into a semi-transparent sample as it is deformed by some form of external loading. The particles are illuminated in a plane inside the tissue material by a thin laser light sheet, and the pattern is continuously recorded by a digital camera. Image analysis yields the locally and temporally resolved sample deformation in the measurement plane without the need for any in situ measurement hardware. The applicability of the method fo... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5659633 Wed, 01 Feb 2012 05:00:00 +0100 5659633 http://www.medworm.com/index.php?rid=5659632&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%3D22301186%26dopt%3DAbstract Authors: Chatelin S, Vappou J, Roth S, Raul JS, Willinger R Abstract The characterization of brain tissue mechanical properties is of crucial importance in the development of realistic numerical models of the human head. While the mechanical behavior of the adult brain has been extensively investigated in several studies, there is a considerable paucity of data concerning the influence of age on mechanical properties of the brain. Therefore, the implementation of child and infant head models often involves restrictive assumptions like properties scaling from adult or animal data. The present study presents a step towards the investigation of the effects of age on viscoelastic properties of human brain tissue from a first set of dynamic oscillatory shear experiments. Tests were also... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5659632 Wed, 01 Feb 2012 05:00:00 +0100 5659632 http://www.medworm.com/index.php?rid=5659629&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%3D22301187%26dopt%3DAbstract Authors: Khan F, Yeakle C, Gomaa S Abstract Enhancements to the service life and performance of orthopedic implants used in total knee and hip replacement procedures can be achieved through optimization of design and the development of superior biocompatible polymeric materials. The introduction of a new or modified polymer must, naturally, be preceded by a rigorous testing program. This paper presents the assessment of the mechanical properties of a new filled grade of ultra high molecular weight polyethylene (UHMWPE) designated AOX(TM) and developed by DePuy Orthopaedics Inc. The deformation behavior was investigated through a series of tensile and compressive tests including strain rate sensitivity, creep, relaxation, and recovery. The polymer was found to exhibit rate-reversal ... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5659629 Wed, 01 Feb 2012 05:00:00 +0100 5659629 http://www.medworm.com/index.php?rid=5659626&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%3D22301188%26dopt%3DAbstract Authors: Birdi G, Bridson RH, Smith AM, Mohd Bohari SP, Grover LM Abstract Biopolymers such as alginates have been widely researched for clinical use. Their clinical application, however, have been limited due to their unpredictable and often rapid degradation rates. Here we show that the degradation of an alginate hydrogel can be tailored through the addition of orthosilicic acid (OSA). On immersion in aqueous media a negligible quantity of orthosilicic acid was released from the gel matrix. The presence of the OSA within the gel was shown to significantly slow degradation of the alginate hydrogel when immersed in a potent calcium chelator (EDTA) when compared with the control group. Sample degradation was associated with a significant calcium release from the non-modified gel; ho... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5659626 Wed, 01 Feb 2012 05:00:00 +0100 5659626 http://www.medworm.com/index.php?rid=5440839&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%3D22100074%26dopt%3DAbstract Authors: Bhatia A, Albazzaz M, Espinoza Orías AA, Inoue N, Miller LM, Acerbo A, George A, Sumner DR Abstract Dentin matrix protein-1 (DMP1) is a key regulator of biomineralization. Here, we examine changes in structural, geometric, and material properties of cortical bone in a transgenic mouse model overexpressing DMP1. Micro-computed tomography and three-point bending were performed on 90 femora of wild type and transgenic mice at 1, 2, 4, and 6 months. Fourier transform infrared imaging was performed at 2 months. We found that the transgenic femurs were longer (p<0.01), more robust in cross-section (p<0.05), stronger (p<0.05), but had less post-yield strain and displacement (p<0.01), and higher tissue mineral density (p<0.01) than the wild type femurs at 1 and 2 m... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440839 Fri, 25 Nov 2011 03:28:52 +0100 5440839 http://www.medworm.com/index.php?rid=5440838&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%3D22100075%26dopt%3DAbstract Authors: Liu B, Dui G, Zhu Y Abstract This paper is concerned on the phase transformation mechanism of porous Shape Memory Alloys (SMAs). A unit-cell model is adopted to establish the constitutive relation for porous SMAs, the stress distributions, the phase distributions and the martensitic volume fractions for the model are then derived under both pure hydrostatic stress and uniaxial compression. Further, an example for the uniaxial response under compression for a porous Ni-Ti SMA material considering hydrostatic stress is supplied. Good agreement between the theoretical prediction of the proposed model and published experimental data is observed. PMID: 22100075 [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=5440838 Fri, 25 Nov 2011 03:28:43 +0100 5440838 http://www.medworm.com/index.php?rid=5440837&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%3D22100076%26dopt%3DAbstract Authors: He G, Liu P, Tan Q Abstract A kind of porous metal-entangled titanium wire material has been investigated in terms of the pore structure (size and distribution), the strength, the elastic modulus, and the mechanical behavior under uniaxial tensile loading. Its functions and potentials for surgical application have been explained. In particular, its advantages over competitors (e.g., conventional porous titanium) have been reviewed. In the study, a group of entangled titanium wire materials with non-woven structure were fabricated by using 12-180 MPa forming pressure, which have porosity in a range of 48%-82%. The pores in the materials are irregular in shape, which have a nearly half-normal distribution in size range. The yield strength, ultimate tensile strength, and ela... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440837 Fri, 25 Nov 2011 03:28:34 +0100 5440837 http://www.medworm.com/index.php?rid=5440836&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%3D22100077%26dopt%3DAbstract Authors: Keten S, Chou CC, van Duin AC, Buehler MJ Abstract Disulfide bonds are important chemical cross-links that control the elasticity of fibrous protein materials such as hair, feather, wool and gluten in breadmaking dough. Here we present a novel computational approach using the first-principles-based ReaxFF reactive force field and demonstrate that this approach can be used to show that the fracture strength of disulfide bonds is decreased under the presence of reducing agents, due to a loss of cross-link stability controlled by the chemical microenvironment. Simulations in explicit solvents and dithiothreitol (DTT) indicate an intermediate step involving weakened elongated bonds, illustrating the tunability of the elasticity, rupture mechanism and strength of proteins. We p... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440836 Fri, 25 Nov 2011 03:28:26 +0100 5440836 http://www.medworm.com/index.php?rid=5440835&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%3D22100078%26dopt%3DAbstract In this study, an anisotropic brain injury criterion is developed that is able to describe the effects of the oriented microstructure based on micromechanical simulations. The effects of both the main axonal direction and of local deviations from this direction are accounted for. With the anisotropic criterion for brain injury, computational head models will be able to account for aspects of diffuse axonal injury at the cellular level and can therefore more reliably predict injury. PMID: 22100078 [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=5440835 Fri, 25 Nov 2011 03:28:17 +0100 5440835 http://www.medworm.com/index.php?rid=5440834&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%3D22100079%26dopt%3DAbstract This study evaluated the effect of microwave irradiation and water storage on the viscoelastic properties of two denture base resins (Lucitone 550-L and Vipi Wave-VW) and two reline resins (Kooliner-K and Tokuyama Rebase Fast II-TR II). Eight specimens (40×10×3.3 mm) of each material were evaluated by dynamic mechanical thermal analysis (DMTA) after processing, water storage for 7 days (WS), one (MW1) and 7 cycles of microwave irradiation (MW7). For each specimen, DMTA runs were carried out within different temperature intervals. Values of storage modulus (E(')) and loss tangent (tan δ) at 37 °C were obtained from the first and last runs. From the last run, values of E(') at the glass transition temperature (Tg) and maximum tan δ were also recorded. Data were analyzed by a 2-way ANO... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440834 Fri, 25 Nov 2011 03:28:07 +0100 5440834 http://www.medworm.com/index.php?rid=5440833&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%3D22100080%26dopt%3DAbstract Authors: Brown CP, Houle MA, Chen M, Price AJ, Légaré F, Gill HS Abstract With increasing interest in treating osteoarthritis at its earliest stages, it has become important to understand the mechanisms by which the disease progresses across a joint. Here, second harmonic generation (SHG) microscopy, coupled with a two-dimensional spring-mass network model, was used to image and investigate the collagen meshwork architecture at the cartilage surface surrounding osteoarthritic lesions. We found that minor weakening of the collagen meshwork leads to the bundling of fibrils at the surface under normal loading. This bundling appears to be an irreversible step in the degradation process, as the stress concentrations drive the progression of damage, forming larger bundles and cracks th... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440833 Fri, 25 Nov 2011 03:27:58 +0100 5440833 http://www.medworm.com/index.php?rid=5440832&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%3D22100081%26dopt%3DAbstract Authors: Deymier-Black AC, Almer JD, Stock SR, Dunand DC Abstract Various methods are used to investigate the variability in elastic properties across a population of deciduous bovine incisor root dentin samples spanning different animals, incisor types, and locations within teeth. First, measurements of elastic strains by high-energy synchrotron X-ray scattering during compressive loading of dentin specimens provided the effective modulus-the ratio of applied stress to elastic phase strain-for the two main phases of dentin (hydroxyapatite crystals and mineralized collagen fibrils), shedding light on load transfer operating at the nanoscale between collagen and mineral phases. Second, Young's moduli were measured at the macroscale by ultrasonic time-of-flight measurements. Third, t... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440832 Fri, 25 Nov 2011 03:27:49 +0100 5440832 http://www.medworm.com/index.php?rid=5440831&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%3D22100082%26dopt%3DAbstract In this study, atomic force microscopy was used to measure the nanoindentation hardness and surface topography of the uncross-linked and cross-linked chitosan films. Elastic modulus was then calculated from the nanoindentation results. The effective elastic modulus was determined by microhardness with some modifications to previous theories. The microhardness of the chitosan films were measured using Vicker's hardness meter under three different loads. Our results show that the microhardness and elastic modulus for cross-linked chitosan films are higher than the uncross-linked films. However, the cross-linked chitosan films show increased brittleness when compared to uncross-linked films. By increasing the load magnitude, the microhardness increases for both uncross-linked and cross-linked... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440831 Fri, 25 Nov 2011 03:27:40 +0100 5440831 http://www.medworm.com/index.php?rid=5440830&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%3D22100083%26dopt%3DAbstract Authors: Magnenet V, Schiavi-Tritz J, Huselstein C, Rahouadj R Abstract Constitutive equations accounting for the coupling between chemical and mechanical phenomena are developed for the Ca(2+) alginate gel from the framework of thermodynamics of irreversible processes with internal variables. The development of the model is based on the Gibbs-Duhem relation and kinetic relations acting on generalized non-equilibrium forces. The constitutive equations are then compared to mechanical data obtained from uniaxial compressive tests at different velocities. A good agreement is observed between model and data. Furthermore, the model is able to predict the evolution of the mechanical response when the initial quantity of crosslinked Ca(2+) ions varies. PMID: 22100083 [PubMed - in proc... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440830 Fri, 25 Nov 2011 03:27:30 +0100 5440830 http://www.medworm.com/index.php?rid=5440829&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%3D22100084%26dopt%3DAbstract Authors: Hassan MA, Hamdi M, Noma A Abstract The mechanical behavior of the heart muscle tissues is the central problem in finite element simulation of the heart contraction, excitation propagation and development of an artificial heart. Nonlinear elastic and viscoelastic passive material properties of the left ventricular papillary muscle of a guinea pig heart were determined based on in-vitro precise uniaxial and relaxation tests. The nonlinear elastic behavior was modeled by a hypoelastic model and different hyperelastic strain energy functions such as Ogden and Mooney-Rivlin. Nonlinear least square fitting and constrained optimization were conducted under MATLAB and MSC.MARC in order to obtain the model material parameters. The experimental tensile data was used to get the nonl... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440829 Fri, 25 Nov 2011 03:27:21 +0100 5440829 http://www.medworm.com/index.php?rid=5440828&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%3D22100085%26dopt%3DAbstract Conclusions. The addition of 17 vol% of Al(2)O(3)/GdAlO(3) longitudinal fibers to porcelain/glass infiltrated alumina bilayers significantly improved its flexural strength. 10 vol% or 17 vol% of fibers inclusion increased the flexural strength for all groups. PMID: 22100085 [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=5440828 Fri, 25 Nov 2011 03:27:10 +0100 5440828 http://www.medworm.com/index.php?rid=5440827&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%3D22100086%26dopt%3DAbstract Authors: Sommer G, Holzapfel GA Abstract Human arteries with non-atherosclerotic intimal thickening consist of three distinct layers: adventitia, media and intima. From a series of axial extension and inflation tests on intact and layer-dissected human carotid arteries (adventitia and media-intima composite), a 3D structurally-based strain-energy function (SEF) is calibrated, and a set of five material parameters is identified which is not yet available in the literature. The zero-stress states of the artery tubes investigated are considered in the calibration process, and the related kinematics for the finite deformation of the individual continuum are described in detail. The SEF employed is capable of describing the different mechanical properties of the intact and layer-dissect... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440827 Fri, 25 Nov 2011 03:27:00 +0100 5440827 http://www.medworm.com/index.php?rid=5440826&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%3D22100087%26dopt%3DAbstract Authors: Zivic F, Babic M, Grujovic N, Mitrovic S, Favaro G, Caunii M Abstract Deformation behavior of polymethyl methacrylate (PMMA) bone cement is explored using microindentation. Two types of PMMA bone cement were prepared. Vacuum treated samples were subjected to the degassing of the material under vacuum of 270 mbar for 35 s, followed by the second degassing under vacuum of 255 mbar for 35 s. Air-cured samples were left in ambient air to cool down and harden. All samples were left to age for 6 months before the test. The samples were then subjected to the indentation fatigue test mode, using sharp Vickers indenter. First, loading segment rise time was varied in order to establish time-dependent behavior of the samples. Experimental data showed that viscous part of the deformat... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440826 Fri, 25 Nov 2011 03:26:50 +0100 5440826 http://www.medworm.com/index.php?rid=5440825&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%3D22100088%26dopt%3DAbstract In this study, we have investigated the influence of location and orientation on the deformation characteristics of 56 samples of excised human skin. Uniaxial tensile tests were carried out at a strain rate of 0.012 s(-1) on skin from the back. Digital Image Correlation was used for 2D strain measurement and a histological examination of the dermis was also performed. The mean ultimate tensile strength (UTS) was 21.6±8.4 MPa, the mean failure strain 54%±17%, the mean initial slope 1.18±0.88 MPa, the mean elastic modulus 83.3±34.9 MPa and the mean strain energy was 3.6±1.6 MJ/m(3). A multivariate analysis of variance has shown that these mechanical properties of skin are dependent upon the orientation of the Langer lines (P<0.0001-P=0.046). The location of specimens on the back... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440825 Fri, 25 Nov 2011 03:26:39 +0100 5440825 http://www.medworm.com/index.php?rid=5440824&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%3D22100089%26dopt%3DAbstract Authors: Jimenez-Palomar I, Shipov A, Shahar R, Barber AH Abstract The mechanical properties of rat bone at micron length scales have been evaluated as a function of environmental conditions using an in situ atomic force microscope (AFM) setup while observing using scanning electron microscopy (SEM). Focused ion beam fabricated rat bone cantilever samples were tested in both low and high vacuum conditions in the SEM as well as wet in air using the AFM to measure their elastic modulus. The elastic modulus of rat bone at micron length scales is shown to be independent of the environmental testing conditions and indicates water is bound to bone material even under relatively high vacuum conditions. Our work therefore shows how in situ mechanical testing of bone while observing using h... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440824 Fri, 25 Nov 2011 03:26:29 +0100 5440824 http://www.medworm.com/index.php?rid=5440823&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%3D22100090%26dopt%3DAbstract The objective of this study was to develop a nanoscratch technique that can be used to measure the in situ toughness of bone at micro/nanostructural levels. Among the currently possible techniques, the surface scratch test may be conducted on very small regions, thus exhibiting a potential in determining the in situ failure behavior of materials. To adapt such a technique for assessing bone toughness at the micro/nanostructural levels and for limited stocks in small animal bone models (e.g. zebra finish and mice), a simple but reasonably accurate mechanistic model for the nanoscratch test was developed in this study. This model was based on the assumption that the removal energy of the tissue required during the nanoscratch test is the manifestation of the in situ toughness and the shear f... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440823 Fri, 25 Nov 2011 03:26:20 +0100 5440823 http://www.medworm.com/index.php?rid=5440822&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%3D22100091%26dopt%3DAbstract Authors: Grant CA, Phillips MA, Thomson NH Abstract Low frequency (0.1-2 Hz) dynamic mechanical analysis on individual type I collagen fibrils has been carried out using atomic force microscopy (AFM). Both the elastic (static) and viscous (dynamic) responses are correlated to the characteristic axial banding, gap and overlap regions. The elastic modulus (∼5 GPa) on the overlap region, where the density of tropocollagen is highest, is 160% that of the gap region. The amount of dissipation on each region is frequency dependent, with the gap region dissipating most energy at the lowest frequencies (0.1 Hz) and crossing over with the overlap region at ∼0.75 Hz. This may reflect an ability of collagen fibrils to absorb energy over a range of frequencies using more than one mecha... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440822 Fri, 25 Nov 2011 03:26:11 +0100 5440822 http://www.medworm.com/index.php?rid=5440821&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%3D22100092%26dopt%3DAbstract In this study, we investigated the effectiveness of a chitosan fiber reinforcement approach to enhancing the mechanical properties of chitosan scaffolds. Chitosan fibers were fabricated using a solution extrusion and neutralization method and incorporated into porous chitosan scaffolds. The effects of fiber/scaffold mass ratio, fiber mechanical properties and fiber length on scaffold mechanical properties were studied. The results showed that incorporating fibers improved scaffold strength and stiffness in proportion to the fiber/scaffold mass ratio. A fiber-reinforced, heart valve scaffold achieved leaflet tensile strength values of 220±17 kPa, comparable to the radial values of human pulmonary valve leaflets. Additionally, the effects of 2 mm fibers were found to be up to threefold gr... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440821 Fri, 25 Nov 2011 03:26:02 +0100 5440821 http://www.medworm.com/index.php?rid=5440820&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%3D22100093%26dopt%3DAbstract Authors: Rubitschek F, Niendorf T, Karaman I, Maier HJ Abstract The present study reports on the corrosion fatigue behavior of ultrafine-grained (UFG) Niobium 2 wt-% Zirconium (NbZr) alloy in simulated body fluid (SBF). The alloy was processed using multipass equal channel angular processing at room temperature, resulting in a favorable combination of high strength and ductility along with superior biocompatibility and excellent corrosion resistance. Electrochemical measurements revealed stable passive behavior in SBF saline solutions, similar to conventional Ti-6Al-4V alloy. High-cycle fatigue tests showed no alteration in the crack initiation behavior due to the SBF environment, and an absence of pitting and corrosion products. More severe test conditions were obtained in the fat... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440820 Fri, 25 Nov 2011 03:25:53 +0100 5440820 http://www.medworm.com/index.php?rid=5440819&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%3D22100094%26dopt%3DAbstract The objective of this study is to identify the significance of the fibre-matrix interaction in the human annulus fibrosus by careful investigation of the experimental data, the theoretical constitutive models, and the numerical simulation results in the literature. Based on the experimental results from biaxial and uniaxial tests, it is shown that the mechanical behaviour of the matrix can be well simulated by an incompressible neo-Hookean type model, but the effective stiffness of the matrix depends on fibre stretch ratio, which can only be explained by fibre-matrix interaction. Furthermore, we find that this interaction takes place anisotropically between the matrix and the fibres distributed in different proportions in different directions. The dependence of the tangent stiffness of the... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440819 Fri, 25 Nov 2011 03:25:44 +0100 5440819 http://www.medworm.com/index.php?rid=5440818&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%3D22100095%26dopt%3DAbstract In conclusion, this study showed that three mechanically significant structural features of cartilage are important: (1) the strain limiting surface layer; (2) the micro-level boundaries in its zonally differentiated structure, and (3) the extent of fibrillar interconnectivity. Degeneration degrades or destroys the articular surface and 'destructures' the fibrillar network such that the latter functions less effectively as a proteoglycan entrapment system. PMID: 22100095 [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=5440818 Fri, 25 Nov 2011 03:25:34 +0100 5440818 http://www.medworm.com/index.php?rid=5440817&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%3D22100096%26dopt%3DAbstract Authors: Natali AN, Fontanella CG, Carniel EL Abstract The present paper pertains to the definition of a numerical model of the calcaneal fat pad region, considering a structure composed of adipose and connective tissues organized in fibrous septae and adipose chambers. The mechanical response is strongly influenced by the structural conformation, as the dimension of adipose chambers, the thickness of connective septae walls and the mechanical properties of the different soft tissues. In order to define the constitutive formulation of adipose tissues, experimental data from pig specimens are considered, according to the functional similarity, while the mechanical response of connective tissue septae is assumed with regard to the mechanical behaviour that characterize ligaments. Dif... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440817 Fri, 25 Nov 2011 03:25:25 +0100 5440817 http://www.medworm.com/index.php?rid=5440816&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%3D22100097%26dopt%3DAbstract Authors: Ding L, Davidchack RL, Pan J Abstract This paper presents a molecular dynamics study on the change in Young's modulus of semi-crystalline polymers during degradation by chain scissions, which is relevant to the study of mechanical properties of biodegrading polymers. Using a simple polymer model whose structural and mechanical properties are similar to that of a commonly used biodegrading polymer poly(glycolic acid), we combine molecular dynamics and Monte Carlo to model a system of two polymer crystals separated by an amorphous region between them. The polymer chains in the amorphous region are cut randomly to mimic hydrolysis chain scissions. In a series of virtual tensile tests, the systems with various numbers of chain scissions are subjected to a unidirectional deform... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440816 Fri, 25 Nov 2011 03:25:17 +0100 5440816 http://www.medworm.com/index.php?rid=5440815&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%3D22100098%26dopt%3DAbstract Authors: Halgrin J, Chaari F, Markiewicz E Abstract The present paper focuses on the mechanical behavior analysis of bones at mesoscopic scale, paying a special attention to the trabecular bone and the bone marrow filling the porosities. Uni-axial quasi-static compression tests under unconfined conditions have been performed to identify the mechanical behavior of 46 trabecular bone samples. The bone marrow for 22 samples has been preserved to analyze the fluid flow effects on the crushing response. Although deformation patterns do not differ significantly, the average crush behavior of the trabecular bone shows an unexpected decrease of the mechanical properties when the marrow is kept in the sample (26% for the elastic modulus (E(a)), 38% for the maximum compressive stress (σ(max... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440815 Fri, 25 Nov 2011 03:25:07 +0100 5440815 http://www.medworm.com/index.php?rid=5440814&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%3D22100099%26dopt%3DAbstract Authors: McNamara IR, Rayment A, Brooks R, Best S, Rushton N Abstract Impaction bone grafting using morcellised allograft can successfully restore bone stock in revision surgery. However, concerns exist regarding supply of bone and transmission of infection. Bone-graft extenders, such as tricalcium phosphate (TCP) and hydroxyapatite (HA), are used to minimise the use of donor bone. However, concerns exist around a reported increased risk of femoral fracture during impaction bone grafting with a 1:1 mixture of TCP/HA and morcellised bone graft (MBG) during impaction grafting in human cadaveric femora. Using a sawbones model, it was evaluated whether there was increased femoral cortical strain with a HA:MBG mixture during impaction grafting compared to MBG impacted at the same and a ... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440814 Fri, 25 Nov 2011 03:24:58 +0100 5440814 http://www.medworm.com/index.php?rid=5440813&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%3D22100100%26dopt%3DAbstract Authors: Keown AJ, Bush MB, Ford C, Lee JJ, Constantino PJ, Lawn BR Abstract An experimental simulation study is made to determine the effects of occlusal wear on the capacity of teeth to resist fracture. Tests are carried out on model dome structures, using glass shells to represent enamel and epoxy filler to represent dentin. The top of the domes are ground and polished to produce flat surfaces of prescribed depths relative to shell thickness. The worn surfaces are then loaded axially with a hard sphere, or a hard or soft flat indenter, to represent extremes of food contacts. The loads required to drive longitudinal cracks around the side walls of the enamel to failure are measured as a function of relative wear depth. It is shown that increased wear can inhibit or enhance load-b... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440813 Fri, 25 Nov 2011 03:24:49 +0100 5440813 http://www.medworm.com/index.php?rid=5440812&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%3D22100101%26dopt%3DAbstract Authors: Hernández-Gascón B, Peña E, Pascual G, Rodríguez M, Bellón JM, Calvo B Abstract Routine hernia repair surgery involves the implant of synthetic mesh. However, this type of procedure may give rise to pain and bowel incarceration and strangulation, causing considerable patient disability. The purpose of this study was to compare the long-term behaviour of three commercial meshes used to repair the partially herniated abdomen in New Zealand White rabbits: the heavyweight (HW) mesh, Surgipro(®) and lightweight (LW) mesh, Optilene(®), both made of polypropylene (PP), and a mediumweight (MW) mesh, Infinit(®), made of polytetrafluoroethylene (PTFE). The implanted meshes were mechanical and histological assessed at 14, 90 and 180 days post-implant. This behaviour was comp... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440812 Fri, 25 Nov 2011 03:24:39 +0100 5440812 http://www.medworm.com/index.php?rid=5440811&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%3D22100102%26dopt%3DAbstract In conclusion, A-SG was more flexible than Z-SG according to FEA. A-SG may decrease the incidence of complications in the setting of tortuous aorto-iliac aneurysms. Our numerical model could be used to assess flexibility of further manufactured as well as newly designed SGs. PMID: 22100102 [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=5440811 Fri, 25 Nov 2011 03:24:30 +0100 5440811 http://www.medworm.com/index.php?rid=5440810&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%3D22100103%26dopt%3DAbstract Authors: Dickey BT, Tyndyk MA, Doman DA, Boyd D Abstract There exists clinical evidence of fractures in adjacent vertebrae subsequent to vertebral augmentation procedures, such as vertebroplasty (VP) and kyphoplasty (KP). A potential contributory factor to such fractures may be the excessive mismatch of mechanical properties between contemporary bone cements (i.e. polymethyl methacrylate (PMMA) and bisphenol-a-glycidyl dimethacrylate (BIS-GMA)) and bone. Aluminum-free glass polyalkenoate cements (GPCs) present an interesting alternative to conventional bone cements. GPCs adhere to the philosophy that implant materials should have mechanical characteristics similar to those of the bone, and also offer chemical adhesion and intrinsic bioactivity. However, their influence on the loadi... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440810 Fri, 25 Nov 2011 03:24:21 +0100 5440810 http://www.medworm.com/index.php?rid=5440809&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%3D22100104%26dopt%3DAbstract Conclusion: This modelling helps by providing a 'scaling factor' through which the between studies variability associated with computational methods differences is minimised. This is especially important where researchers or clinicians require values which are consistent in the context of establishing the 'true' tendon mechanical properties to inform models or materials based on the biological properties of the human tendon. PMID: 22100104 [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=5440809 Fri, 25 Nov 2011 03:24:12 +0100 5440809 http://www.medworm.com/index.php?rid=5440898&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%3D22098858%26dopt%3DAbstract Authors: Simms C, Screen H, Evans S PMID: 22098858 [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=5440898 Tue, 01 Nov 2011 04:00:00 +0100 5440898 http://www.medworm.com/index.php?rid=5440897&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%3D22098859%26dopt%3DAbstract Authors: Brunon A, Bruyère-Garnier K, Coret M Abstract This paper aims at describing an inflation test protocol on a human liver capsule using stereo-correlation. The biaxial tension created by the inflation test is comparable to the type of loading the capsule would be subjected to during a liver compression. Confocal microscopy associated to an anti-collagen coloration reveals that the tissue is isotropic at the meso-scale. Stereo-correlation provides the strain field of the capsule during the test. It emphasizes the boundary condition effects on the strain field. The measurement of the shape of the capsule is used to determine the parameters of two hyperelastic (polynomial and exponential) homogeneous models. The ultimate first principal strain before failure is measured locall... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440897 Tue, 01 Nov 2011 04:00:00 +0100 5440897 http://www.medworm.com/index.php?rid=5440896&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%3D22098860%26dopt%3DAbstract Authors: Volokh KY Abstract The arterial wall is a composite where the preferred orientation of collagen fibers induces anisotropy. Though the hyperelastic theories of fiber-reinforced composites reached a high level of sophistication and showed a reasonable correspondence with the available experimental data they are short of the failure description. Following the tradition of strength of materials the failure criteria are usually separated from stress analysis. In the present work we incorporate a failure description in the hyperelastic models of soft anisotropic materials by introducing energy limiters in the strain energy functions. The limiters provide the saturation value for the strain energy which indicates the maximum energy that can be stored and dissipated by an infinite... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440896 Tue, 01 Nov 2011 04:00:00 +0100 5440896 http://www.medworm.com/index.php?rid=5440895&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%3D22098861%26dopt%3DAbstract Authors: Hodis S, Zamir M Abstract Under the dynamic conditions of pulsatile flow, the forces exerted by the fluid on the vessel wall create considerable displacements and stresses within the thickness of the vessel wall. We review a series of analytical options for exploring the dynamics of the vessel wall, specifically displacements and stresses within the depth of the vessel wall, under a range of conditions including the degree of external tethering and the mechanical consistency of the wall material. It is shown that one of the most important effects of tethering is that of drastically restricting radial displacements of and within the vessel wall. This restriction in turn places limits on the length and speed of the propagating wave. Specifically, the wave speed is significan... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440895 Tue, 01 Nov 2011 04:00:00 +0100 5440895 http://www.medworm.com/index.php?rid=5440894&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%3D22098862%26dopt%3DAbstract This study attempts to characterise the time-dependent behaviour of the AV at different strain and load increments, and to gain insight into the contribution of the microstructure to this behaviour. Uniaxial incremental stress-relaxation and creep experiments were undertaken, and the experimental data analysed with a generalised Maxwell model, to determine the characteristic time-dependent parameters. Results showed that the time dependent response of the tissue differed with the loading direction, and also with the level of applied load or strain, in both stress-relaxation and creep phenomena. Both phenomena were consistently more pronounced in the radial loading direction. Fitting of the Maxwell model highlighted that the time dependent modes required to model the data also varied in dif... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440894 Tue, 01 Nov 2011 04:00:00 +0100 5440894 http://www.medworm.com/index.php?rid=5440893&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%3D22098863%26dopt%3DAbstract The objective of this study, therefore, was to investigate the effects of tissue orientation and enzymatic degradation of glycosaminoglycan (GAG) and elastin on AF shear mechanical properties. Significant anisotropy was found: the circumferential shear modulus, G(θz), was an order of magnitude greater than the radial shear modulus, G(rθ). In the circumferential direction, prestrain significantly increased the shear modulus, suggesting an important role for collagen fiber stretch in shear properties for this orientation. While not significant and highly variable, ChABC treatment to remove GAG increased the circumferential shear modulus compared to PBS control (p=0.15). Together with the established literature for tensile loading of fiber-reinforced GAG-rich tissues, the trends for changes... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440893 Tue, 01 Nov 2011 04:00:00 +0100 5440893 http://www.medworm.com/index.php?rid=5440892&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%3D22098864%26dopt%3DAbstract Authors: Masen MA Abstract This work focuses on the friction in contacts where the human finger pad is one of the interacting surfaces. This 'tactile friction' requires a full understanding of the contact mechanics and the behaviour of human skin. The coefficient of friction cannot be considered as a property of the skin alone, but depends on the entire tribo-system. In this work, frictional forces were measured using a commercially available load cell. Parameters such as the hydration of the skin, the normal load on the contact and the roughness of the contacting surfaces were varied, whilst keeping the other parameters constant. The tests were performed under controlled environmental conditions. The total friction force is a combination of forces related to adhesion and to deform... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440892 Tue, 01 Nov 2011 04:00:00 +0100 5440892 http://www.medworm.com/index.php?rid=5440891&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%3D22098865%26dopt%3DAbstract Authors: Driscoll TP, Nerurkar NL, Jacobs NT, Elliott DM, Mauck RL Abstract Fibrocartilages, including the knee meniscus and the annulus fibrosus (AF) of the intervertebral disc, play critical mechanical roles in load transmission across joints and their function is dependent upon well-defined structural hierarchies, organization, and composition. All, however, are compromised in the pathologic transformations associated with tissue degeneration. Tissue engineering strategies that address these key features, for example, aligned nanofibrous scaffolds seeded with mesenchymal stem cells (MSCs), represent a promising approach for the regeneration of these fibrous structures. While such engineered constructs can replicate native tissue structure and uniaxial tensile properties, the mul... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440891 Tue, 01 Nov 2011 04:00:00 +0100 5440891 http://www.medworm.com/index.php?rid=5440890&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%3D22098866%26dopt%3DAbstract Authors: Limbert G Abstract Characterising and modelling the mechanical behaviour of biological soft tissues is an essential step in the development of predictive computational models to assist research for a wide range of applications in medicine, biology, tissue engineering, pharmaceutics, consumer goods, cosmetics, transport or military. It is therefore critical to develop constitutive models that can capture particular rheological mechanisms operating at specific length scales so that these models are adapted for their intended applications. Here, a novel mesoscopically-based decoupled invariant-based continuum constitutive framework for transversely isotropic and orthotropic biological soft tissues is developed. A notable feature of the formulation is the full decoupling of sh... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440890 Tue, 01 Nov 2011 04:00:00 +0100 5440890 http://www.medworm.com/index.php?rid=5440889&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%3D22098867%26dopt%3DAbstract Authors: Canal C, Ginebra MP Abstract Calcium phosphate cements (CPC) consist of one or more calcium orthophosphate powders, which upon mixing with water or an aqueous solution, form a paste that is able to set and harden after being implanted within the body. Different issues remain still to be improved in CPC, such as their mechanical properties to more closely mimic those of natural bone, or their macroporosity to favour osteointegration of the artificial grafts. To this end, blends of CPC with polymer and ceramic fibres in different forms have been investigated. The present work aims at providing an overview of the different approaches taken and identifying the most significant achievements in the field of fibre-reinforced calcium phosphate cements for clinical applications, wi... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440889 Tue, 01 Nov 2011 04:00:00 +0100 5440889 http://www.medworm.com/index.php?rid=5440888&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%3D22098868%26dopt%3DAbstract We report on the in vivo histological and mechanical performance of titanium dental implants with a new surface treatment (2Step) consisting of an initial grit-blasting process to produce a micro-rough surface, followed by a combined chemical and thermal treatment that produces a potentially bioactive surface, i.e., that can form an apatitic layer when exposed to biomimetic conditions in vitro. Our aim was to assess the short- and mid-term bone regenerative potential and mechanical retention of 2Step implants in mandible and maxilla of minipigs and compare them with micro-rough grit-blasted, micro-rough acid-etched, and smooth as-machined titanium implants. The percent of bone-to-implant contact after 2, 4, 6, and 10 weeks of implantation as well as the mechanical retention after 4, and 6 ... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440888 Tue, 01 Nov 2011 04:00:00 +0100 5440888 http://www.medworm.com/index.php?rid=5440887&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%3D22098869%26dopt%3DAbstract Authors: Vernerey FJ, Farsad M Abstract Biological tissues are very particular types of materials that have the ability to change their structure, properties and chemistry in response to external cues. Contractile cells, i.e. fibroblasts, are key players of tissue adaptivity as they are capable of reorganizing their surrounding extra-cellular matrix (ECM) by contracting and generating mechanical forces. This contractile behavior is attributed to the development of a stress-fiber (SF) network within the cell's cytoskeleton, a process that is known to be highly dependent of the nature of the mechanical environment (such as ECM stiffness or the presence of stress and strain). To describe these processes in a consistent manner, the present paper introduces a mutiphasic formulation (flu... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440887 Tue, 01 Nov 2011 04:00:00 +0100 5440887 http://www.medworm.com/index.php?rid=5440886&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%3D22098870%26dopt%3DAbstract In this study, the fabrication and properties of a synthetic keratoprosthesis skirt for use in osteo-odonto-keratoprosthesis (OOKP) surgery are discussed. In the search for a new material concept, bioactive glass and polymethyl methacrylate (PMMA)-based composites were prepared. Three different bioactive glasses (i.e. 45S5, S53P4 and 1-98) and one slowly resorbing glass, FL107, with two different forms (i.e. particles and porous glass structures) were employed in the fabrication of specimens. In in vitro studies, the dissolution behaviour in simulated aqueous humour, compressive properties, and pore formation of the composites were investigated. According to the results, FL107 dissolved very slowly (2.4% of the initial glass content in three weeks); thus, the pore formation of the FL107 co... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440886 Tue, 01 Nov 2011 04:00:00 +0100 5440886 http://www.medworm.com/index.php?rid=5440885&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%3D22098871%26dopt%3DAbstract Authors: Fornell J, Van Steenberge N, Varea A, Rossinyol E, Pellicer E, Suriñach S, Baró MD, Sort J Abstract The effects of annealing treatments on the microstructure, elastic/mechanical properties, wear resistance and corrosion behavior of rod-shaped Ti(40)Zr(10)Cu(38)Pd(12) bulk glassy alloys, synthesized by copper mold casting, are investigated. Formation of ultrafine crystals embedded in an amorphous matrix is observed for intermediate annealing temperatures, whereas a fully crystalline microstructure develops after heating to sufficiently high temperatures. The glassy alloy exhibits large hardness, relatively low Young's modulus, good wear resistance and excellent corrosion behavior. Nanoindentation measurements reveal that the sample annealed in the supercooled liquid regio... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440885 Tue, 01 Nov 2011 04:00:00 +0100 5440885 http://www.medworm.com/index.php?rid=5440884&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%3D22098872%26dopt%3DAbstract This study shows that it is possible to significantly improve metal-porcelain bond strength by applying an overpressure during porcelain firing. PMID: 22098872 [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=5440884 Tue, 01 Nov 2011 04:00:00 +0100 5440884 http://www.medworm.com/index.php?rid=5440883&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%3D22098873%26dopt%3DAbstract Authors: Bellini C, Glass P, Sitti M, Di Martino ES Abstract Capsule endoscopes are pill-size devices provided with a camera that capture images of the small intestine from inside the body after being ingested by a patient. The interaction between intestinal tissue and capsule endoscopes needs to be investigated to optimize capsule design while preventing tissue damage. To that purpose, a constitutive model that can reliably predict the mechanical response of the intestinal tissue under complex mechanical loading is required. This paper describes the development and numerical validation of a phenomenological constitutive model for the porcine duodenum, jejunum and ileum. Parameters characterizing the mechanical behavior of the material were estimated from planar biaxial test data, ... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440883 Tue, 01 Nov 2011 04:00:00 +0100 5440883 http://www.medworm.com/index.php?rid=5440882&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%3D22098874%26dopt%3DAbstract Authors: Van Houten EE, Peters A, Chase JG Abstract Results from the application of a novel nonlinear hybrid reconstruction algorithm within a Digital Image Elasto-Tomography (DIET) system are presented. A hybrid reconstruction algorithm was optimized to solve for the elasticity distribution of two heterogeneous silicone phantoms using a shape-based parameterization. The hybrid algorithm achieved comparable performance to Combinatorial Optimization methods with significantly less computational expense. The specificity of three-parameter reconstruction was confirmed by successful reconstruction of a homogeneous silicone phantom, indicating the potential suitability of the DIET system for application to inclusion imaging in elastography. PMID: 22098874 [PubMed - in process] (Sour... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440882 Tue, 01 Nov 2011 04:00:00 +0100 5440882 http://www.medworm.com/index.php?rid=5440881&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%3D22098875%26dopt%3DAbstract Authors: Topoliński T, Cichański A, Mazurkiewicz A, Nowicki K Abstract This paper presents the results of a study of 61 trabecular bone samples exposed to a cyclic (1 Hz) compression load. The load was increased stepwise. Characteristic patterns of the hysteresis loop for the middle cycles of successive steps of load and for respective steps of load are presented. Characteristic patterns of secant modulus were also determined. The fatigue life results recorded were compared with the indices of bone architecture determined using micro-CT. Using Pearson's correlation, the best relationship between fatigue life and bone volume ratio (BV/TV) and the maximum load for which there was also reported a maximal value secant stiffness were identified. Based on these findings, it was determi... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440881 Tue, 01 Nov 2011 04:00:00 +0100 5440881 http://www.medworm.com/index.php?rid=5440880&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%3D22098876%26dopt%3DAbstract Authors: Pereira FA, Morais JJ, Dourado N, de Moura MF, Dias MI Abstract Fracture energy release rate under mode II loading of bovine cortical bone is determined using a miniaturized testing device of the end loaded split test. The energy release rate is evaluated by means of a data reduction scheme based on specimen compliance, beam theory and crack equivalent concept. Experimental tests were carried out to evaluate the Resistance curve which provides a successful method to characterize fracture behavior of quasi-brittle materials like bone. A numerical analysis including a cohesive damage model was used to validate the procedure. It was demonstrated that the end loaded split test and proposed data reduction scheme provide a valuable solution for mode II fracture characterization ... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440880 Tue, 01 Nov 2011 04:00:00 +0100 5440880 http://www.medworm.com/index.php?rid=5440879&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%3D22098877%26dopt%3DAbstract Authors: Singhal A, Deymier-Black AC, Almer JD, Dunand DC Abstract Bone X-ray irradiation occurs during medical treatments, sterilization of allografts, space travel and in vitro studies. High doses are known to affect the post-yield properties of bone, but their effect on the bone elastic properties is unclear. The effect of such doses on the mineral-organic interface has also not been adequately addressed. Here, the evolution of elastic properties and residual strains with increasing synchrotron X-ray dose (5-3880 kGy) is examined on bovine cortical bone. It is found that these doses affect neither the degree of nanometer-level load transfer between the hydroxyapatite (HAP) platelets and the collagen up to stresses of -60 MPa nor the microscopic modulus of collagen fibrils (both ... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440879 Tue, 01 Nov 2011 04:00:00 +0100 5440879 http://www.medworm.com/index.php?rid=5440878&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%3D22098878%26dopt%3DAbstract This study compared the progression of microdamage leading to fracture and the related local strains during this process in trabecular and cortical bone tissue. Unmachined single bovine trabeculae and similarly-sized cortical bovine bone samples were mechanically tested in three-point bending and concomitantly imaged to assess local strains using a digital image correlation technique. The bone whitening effect was used to detect microdamage formation and propagation. This study found that cortical bone tissue exhibits significantly lower maximum strains (trabecular 36.6%±14% vs. cortical 22.9%±7.4%) and less accumulated damage (trabecular 16100±8800 pix/mm(2) vs. cortical 8000±3400 pix/mm(2)) at failure. However, no difference was detected for the maximum local strain at whitening on... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440878 Tue, 01 Nov 2011 04:00:00 +0100 5440878 http://www.medworm.com/index.php?rid=5440877&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%3D22098879%26dopt%3DAbstract Authors: Nganga S, Ylä-Soininmäki A, Lassila LV, Vallittu PK Abstract Glass-fibre-reinforced composites (FRCs) are under current investigation to serve as durable bone substitute materials in load-bearing orthopaedic implants and bone implants in the head and neck area. The present form of biocompatible FRCs consist of non-woven E-glass-fibre tissues impregnated with varying amounts of a non-resorbable photopolymerisable bifunctional polymer resin with equal portions of both bis-phenyl-A-glycidyl dimethacrylate (BisGMA) and triethyleneglycol dimethacrylate (TEGDMA). FRCs with a total porosity of 10-70 vol% were prepared, more than 90 vol% of which being functional (open pores), and the rest closed. The pore sizes were greater than 100 μm. In the present study, the push-out test... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440877 Tue, 01 Nov 2011 04:00:00 +0100 5440877 http://www.medworm.com/index.php?rid=5440876&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%3D22098880%26dopt%3DAbstract In conclusion, the good compliance, enhanced stretchability, stable mechanical behavior over an extended period, and reduced degradation rates make the 3-5 wt% composites promising candidates for application in soft tissue engineering. PMID: 22098880 [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=5440876 Tue, 01 Nov 2011 04:00:00 +0100 5440876 http://www.medworm.com/index.php?rid=5440875&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%3D22098881%26dopt%3DAbstract Authors: El Halabi F, Rodriguez JF, Rebolledo L, Hurtós E, Doblaré M Abstract Cranial implants have experienced a significant evolution in the last decade in different aspects such as materials, method of fixation, and the structure. In addition, patient-specific cranial implants have recently been started to be developed. To achieve this objective, efficient mechanical characterization and numerical modeling of the implant are required to guarantee its functionality on each patient as well as to facilitate further developments. In this work, mechanical characterization and numerical models have been performed for patient-specific Polyaryletherketone (PEEK) scaffold cranial implants. Mechanical characterization has been performed at the scaffold and the whole implant levels under... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440875 Tue, 01 Nov 2011 04:00:00 +0100 5440875 http://www.medworm.com/index.php?rid=5440874&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%3D22098882%26dopt%3DAbstract Authors: Assidi M, Dos Reis F, Ganghoffer JF Abstract The goal of this manuscript is to set up a novel methodology for the calculation of the effective mechanical properties of biological membranes viewed as repetitive networks of elastic filaments, based on the discrete asymptotic homogenization method. We will show that for some lattice configurations, flexional effects due to internal structure mechanisms at the unit cell scale lead to additional flexional effects at the continuum scale, accounted for by an internal length associated to a micropolar behavior. Thereby, a systematic methodology is established, allowing the prediction of the overall mechanical properties of biological membranes for a given network topology, as closed form expressions of the geometrical and mechanic... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440874 Tue, 01 Nov 2011 04:00:00 +0100 5440874 http://www.medworm.com/index.php?rid=5440873&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%3D22098883%26dopt%3DAbstract Conclusions: The molecular weight of the PMMA beads of multiphase denture base polymers considerably influences their flexural properties and formation of IPN layer between the matrix polymer and the PMMA beads. PMID: 22098883 [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=5440873 Tue, 01 Nov 2011 04:00:00 +0100 5440873 http://www.medworm.com/index.php?rid=5440872&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%3D22098884%26dopt%3DAbstract Authors: Lucchini R, Carnelli D, Ponzoni M, Bertarelli E, Gastaldi D, Vena P Abstract The aim of this paper is to show that damage mechanisms can account for the response of lamellar bone to nanoindentation tests, with particular regards to the decrease of indentation stiffness with increasing penetration depth and to the loss of contact stiffness during the unloading phase of the test. For this purpose, indentation experiments on bovine cortical bone samples along axial and transverse directions have been carried out at five penetration depths from 50 to 450 nm; furthermore, a continuum damage model has been implemented into finite element analyses, which are able to simulate indentation experiments. Experiments along the axial direction have shown a decrease of about 20% of the i... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440872 Tue, 01 Nov 2011 04:00:00 +0100 5440872 http://www.medworm.com/index.php?rid=5440871&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%3D22098885%26dopt%3DAbstract Authors: Sun F, Hao YL, Nowak S, Gloriant T, Laheurte P, Prima F Abstract A flash-thermal treatment technique has been developed very recently to improve both the critical stress to induce the martensitic transformation (MT) and the recoverable deformation of the metastable β type titanium alloys. In this paper, this strategy is applied to both Ti-26Nb and Ti-20Nb-6Zr (at.%) alloys. Since both alloys have identical martensite start (Ms) temperature, it makes possible to investigate the effect of Zr on mechanical properties after the flash-thermal treatment. It is clearly shown that a flash treatment of 360 s at 873 K on heavily cold-rolled samples results in good balance between the tensile strength, the ductility and the recoverable strains. Such contribution is more significan... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440871 Tue, 01 Nov 2011 04:00:00 +0100 5440871 http://www.medworm.com/index.php?rid=5440870&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%3D22098886%26dopt%3DAbstract Authors: Faria AC, Rodrigues RC, Claro AP, de Mattos Mda G, Ribeiro RF Abstract The present study evaluated microstructure, microhardness and wear resistance of experimental titanium alloys containing zirconium and tantalum. Alloys were melted in arc melting furnace according to the following compositions: Ti-5Zr, Ti-5Ta and Ti-5Ta-5Zr (%wt). Hemispheres and disks were obtained from wax patterns that were invested and cast by plasma. Microstructures were evaluated using optical microscopy and X-ray diffraction (XRD) analysis and also Vickers microhardness was measured. Hemispherical samples and disks were used for 2-body wear tests, performed by repeated grinding of the samples. Wear resistance was assessed as height loss after 40,000 cycles. The data were compared using ANOVA and ... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440870 Tue, 01 Nov 2011 04:00:00 +0100 5440870 http://www.medworm.com/index.php?rid=5440869&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%3D22098887%26dopt%3DAbstract Authors: Prendergast PJ, Galibarov PE, Lowery C, Lennon AB Abstract Computational modelling is becoming ever more important for obtaining regulatory approval for new medical devices. An accepted approach is to infer performance in a population from an analysis conducted for an idealised or 'average' patient; we present here a method for predicting the performance of an orthopaedic implant when released into a population-effectively simulating a clinical trial. Specifically we hypothesise that an analysis based on a method for predicting the performance in a population will lead to different conclusions than an analysis based on an idealised or 'average' patient. To test this hypothesis we use a finite element model of an intramedullary implant in a bone whose size and remodelling a... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440869 Tue, 01 Nov 2011 04:00:00 +0100 5440869 http://www.medworm.com/index.php?rid=5440868&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%3D22098888%26dopt%3DAbstract This study focuses on the basic understanding of surface mechanical behavior of burnished biodegradable MgCa0.8 (wt%) alloy. The effects of burnishing parameters, i.e., pressure, feed, speed, number of path, and burnishing pattern on surface integrity factors such as surface topography, roughness, microhardness, microstructure, and residual stresses are investigated. The burnished surfaces are shinier and smoother than the as-machined ones. The MgCa alloy can be safely burnished at suitable burnishing conditions since no cracks are produced at the surface and in the subsurface. The microstructure including grain size does not show a noticeable change after burnishing. The machined surfaces are harder than the burnished ones down to the deep subsurface (∼200 μm) as opposed to the shallo... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440868 Tue, 01 Nov 2011 04:00:00 +0100 5440868 http://www.medworm.com/index.php?rid=5440867&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%3D22098889%26dopt%3DAbstract Authors: Chatelin S, Deck C, Renard F, Kremer S, Heinrich C, Armspach JP, Willinger R Abstract In the case of head trauma, elongation of axons is thought to result in brain damage and to lead to Diffuse Axonal Injuries (DAI). Mechanical parameters have been previously proposed as DAI metric. Typically, brain injury parameters are expressed in terms of pressure, shearing stresses or invariants of the strain tensor. Addressing axonal deformation within the brain during head impact can improve our understanding of DAI mechanisms. A new technique based on directional measurements of water diffusion in soft tissue using Magnetic Resonance Imaging (MRI), called Diffusion Tensor Imaging (DTI), provides information on axonal orientation within the brain. The present study aims at coupling ... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440867 Tue, 01 Nov 2011 04:00:00 +0100 5440867 http://www.medworm.com/index.php?rid=5440866&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%3D22098890%26dopt%3DAbstract Authors: Trexler MM, Lennon AM, Wickwire AC, Harrigan TP, Luong QT, Graham JL, Maisano AJ, Roberts JC, Merkle AC Abstract Modeling human body response to dynamic loading events and developing biofidelic human surrogate systems require accurate material properties over a range of loading rates for various human organ tissues. This work describes a technique for measuring the shear properties of soft biomaterials at high rates of strain (100-1000 s(-1)) using a modified split Hopkinson pressure bar (SHPB). Establishing a uniform state of stress in the sample is a fundamental requirement for this type of high-rate testing. Input pulse shaping was utilized to tailor and control the ramping of the incident loading pulse such that a uniform stress state could be maintained within the sp... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440866 Tue, 01 Nov 2011 04:00:00 +0100 5440866 http://www.medworm.com/index.php?rid=5440865&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%3D22098891%26dopt%3DAbstract Authors: Claramunt R, García Páez JM, Alvarez L, Spottorno J, Ros A, Casado MC Abstract The medium-term fatigue behaviour of calf pericardium (similar to the one used to manufacture cardiac bioprostheses valve leaflets) has been studied. 96 samples were tested under fatigue subjecting them to biaxial stress at 1 Hz frequency for 5000 cycles, in 4 series of 24 samples, at several supra-physiological mean pressures and pressure amplitudes. Short-term damage parameters such as the accumulated energy consumption in 10 cycles (E(10)) and medium-term ones after 5000 cycles like total energy consumption (E(t)) and maximum displacement of the membrane (D(t)) have been evaluated. E(10) showed exponential growing tendency with pressure and linear tendency with pressure amplitude when only... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440865 Tue, 01 Nov 2011 04:00:00 +0100 5440865 http://www.medworm.com/index.php?rid=5440864&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%3D22098892%26dopt%3DAbstract In conclusion, if tested under conditions which should better reproduce the in-vivo behaviour, mobile UKPs did not show a worse wear behaviour than fixed components in terms of weight losses, although UHMWPE changes at the molecular scale could be detrimental. PMID: 22098892 [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=5440864 Tue, 01 Nov 2011 04:00:00 +0100 5440864 http://www.medworm.com/index.php?rid=5440863&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%3D22098893%26dopt%3DAbstract Authors: Rouhi G Abstract In this paper, for the first time, a tri-phasic model of bone resorption using a mixture with chemical reactions is proposed. Three constituents (matrix, fluid, and cells) are considered. Conservation equations and entropy inequality are provided. The dependent variables in the constitutive equations, such as the rate of resorption, are assumed to be a function of temperature, deformation gradient, and the extent of the chemical reactions. Using constitutive equations in the second law of thermodynamics, a criterion for the thermodynamic equilibrium state is obtained which contains a bio-chemo-mechanical affinity. Using the proposed model, one can find a theoretical explanation for some clinically observed behavior of bone, for instance for the greater rat... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440863 Tue, 01 Nov 2011 04:00:00 +0100 5440863 http://www.medworm.com/index.php?rid=5440862&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%3D22098894%26dopt%3DAbstract Authors: Stráský J, Janeček M, Harcuba P, Bukovina M, Wagner L Abstract Three different microstructures-equiaxed, bi-modal and coarse lamellar-are prepared from Ti-6Al-4V alloy. Electric discharge machining (EDM) with a high peak current (29 A) is performed in order to impose surface roughness and modify the chemical composition of the surface. Detailed scanning electron microscopy (SEM) investigation revealed a martensitic surface layer and subsurface heat affected zone (HAZ). EDX measurements showed carbon enriched remnants of the EDM process on the material surface. Rotating bending fatigue tests are undertaken for EDM processed samples for all three microstructures and also for electropolished-benchmark-samples. The fatigue performance is found to be rather poor and not par... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440862 Tue, 01 Nov 2011 04:00:00 +0100 5440862 http://www.medworm.com/index.php?rid=5440861&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%3D22098895%26dopt%3DAbstract Authors: Ionescu AM, Alaminos M, Cardona Jde L, García-López Durán Jde D, González-Andrades M, Ghinea R, Campos A, Hita E, Pérez Mdel M Abstract In this work, the rheological properties of the biomaterial fibrin with different agarose concentrations, used for the generation of a bioengineered human corneal stroma by tissue engineering, before and after using a nanostructuring technique, were analyzed. The transparency of these artificial human stromas was also investigated. The temporal evaluation of the properties of these biomaterials is essential for the design of functional biological human corneal replacements. The nanostructuring technique used for the generation of nanostructured corneal constructs (NCCs) had a major influence on the rheological properties of the fibrin... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440861 Tue, 01 Nov 2011 04:00:00 +0100 5440861 http://www.medworm.com/index.php?rid=5440860&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%3D22098896%26dopt%3DAbstract Authors: Coelho PG, Granato R, Marin C, Teixeira HS, Suzuki M, Valverde GB, Janal MN, Lilin T, Bonfante EA Abstract Implant surface characterization and biomechanical testing were made to evaluate the effect of different surface treatments along with different implant bulk configurations expressed as biomechanical fixation at early implantation times. Three implant surfaces, namely bioactive ceramic electrodeposition (ED), alumina-blasted/acid etched (AB/AE), and resorbable blasting media (RBM) were fabricated in three implant macrogeometries (cylindrical, small chamber, and large chamber). All combinations between surface and bulk configurations were placed in the radii of beagle dogs (n=18), which were euthanized 14 and 40 days after surgery (n=9 animals per time in vivo). The im... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440860 Tue, 01 Nov 2011 04:00:00 +0100 5440860 http://www.medworm.com/index.php?rid=5440859&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%3D22098897%26dopt%3DAbstract This study evaluates the influences of 8DSS peptide and ionic concentrations of simulated body fluid on remineralization behaviors. The polished enamel specimens were acid-demineralized, exposed briefly to 8DSS peptide solution, and then immersed into simulated body fluid (SBF) that favors mineral deposition. At various stages of treatment, nanohardness and elastic modulus were determined by nanoindentation. The results show that the nanomechanical properties of the acid-demineralized enamel were greatly improved as increasing the ionic concentrations of SBF due to the acceleration of mineral deposition. Additionally, the demineralized enamel, treated with 8DSS peptide and immersed into SBF ×2 solution, possesses the highest values of nanohardness and elastic modulus resulting from the co... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440859 Tue, 01 Nov 2011 04:00:00 +0100 5440859 http://www.medworm.com/index.php?rid=5440858&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%3D22098898%26dopt%3DAbstract Authors: Chandra A, Ryu JJ, Karra P, Shrotriya P, Tvergaard V, Gaisser M, Weik T Abstract Stress dependent electrochemical dissolution is identified as one of the key mechanisms governing surface degradation in fretting and crevice corrosion of biomedical implants. The present study focuses on delineating the roles of mechanical stress and chemical conditions on the life expectancy of modular hip implants. First, material removal on a stressed surface of Ti6Al4V subjected to single asperity contact is investigated experimentally to identify the influence of contact load, in-plane stress and chemical environment on mean wear rates. A range of known stress levels are applied to the specimen while its surface is mechanically stimulated in different non-reactive to oxidizing aqueous en... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440858 Tue, 01 Nov 2011 04:00:00 +0100 5440858 http://www.medworm.com/index.php?rid=5440857&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%3D22098899%26dopt%3DAbstract This study investigates rupture causes by analysing the mechanical properties of failed and intact implants in the recent generation of silicon gel breast implants. The main scope is to assess whether mechanical weakness of the shells should be considered as a major cause of breast implant rupture or, on the contrary, the prosthesis shell damage is likely due to other random factors. Some tests were performed on the shells of a wide number of explanted prostheses, to evaluate the mechanical properties as a function of prostheses status at explantation (intact/ruptured) and variable degree of swelling. A weakening of the shell mechanical properties, so as a significant difference in the ultimate strength and stiffness of intact versus ruptured prostheses, was found. This attenuation of the ... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440857 Tue, 01 Nov 2011 04:00:00 +0100 5440857 http://www.medworm.com/index.php?rid=5440856&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%3D22098900%26dopt%3DAbstract This study investigated the relationship between the various deformation-induced products and the mechanical properties-including Young's modulus, microstructure, and tensile properties-of Ti-30Zr-(5,6,7)mass%Mo alloys subjected to solution treatment (ST) and cold-rolling (CR). After ST, each alloy is composed of a β phase and a small amount of athermally formed ω phase, and exhibits a low Young's modulus. During CR, deformation-induced phase transformation occurs in all the alloys. The change in Young's modulus due to CR is highly dependent on the types of deformation-induced products. The decrease in Young's modulus due to CR is related to the deformation-induced α(') phase transformation accompanying with the disappearance of athermal ω phase, and the increase in Young's modulus is ... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440856 Tue, 01 Nov 2011 04:00:00 +0100 5440856 http://www.medworm.com/index.php?rid=5440855&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%3D22098901%26dopt%3DAbstract Authors: Ipek Nakaş G, Dericioglu AF, Bor S Abstract While the wide range of applications of TiNi alloys makes them highly appealing due to their shape memory and superelasticity properties, the production of TiNi in the porous form further enlarges their application fields. Porous TiNi alloys have been studied extensively for biomedical applications since their elastic modulus is similar to that of bone. Accordingly, TiNi foams have been widely characterized in terms of their various mechanical properties; however, their fatigue properties have not been well studied, even though this is of vital importance in structural applications such as medical implants. In the scope of this study, TiNi foams processed from prealloyed powders by the magnesium space holder technique were mecha... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440855 Tue, 01 Nov 2011 04:00:00 +0100 5440855 http://www.medworm.com/index.php?rid=5440854&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%3D22098902%26dopt%3DAbstract Authors: Abraham AC, Edwards CR, Odegard GM, Donahue TL Abstract Imaging of meniscal tissue reveals an extracellular matrix comprised of collagen fibrils arranged in circumferential bundles and radially aligned tie fibers, implicating structural material anisotropy. Biochemical analyses demonstrate regional disparities of proteoglycan content throughout the meniscal body, a constituent known to affect the shearing response of fibrocartilagenous tissue. Despite this phenomenological evidence and previous mechanical testing implicating otherwise, the meniscus if often modeled as a homogeneous, transversely isotropic material with little regard for regional specificity and material properties. The aim of this investigation was to determine if shear stress response homogeneity and dire... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440854 Tue, 01 Nov 2011 04:00:00 +0100 5440854 http://www.medworm.com/index.php?rid=5440853&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%3D22098903%26dopt%3DAbstract Authors: Dirks JH, Dürr V Abstract The antenna of the Indian stick insect Carausius morosus is a highly specialized near-range sensory probe used to actively sample tactile cues about location, distance or shape of external objects in real time. The length of the antenna's flagellum is 100 times the diameter at the base, making it a very delicate and slender structure. Like the rest of the insect body, it is covered by a protective exoskeletal cuticle, making it stiff enough to allow controlled, active, exploratory movements and hard enough to resist damage and wear. At the same time, it is highly flexible in response to contact forces, and returns rapidly to its straight posture without oscillations upon release of contact force. Which mechanical adaptations allow stick insects t... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440853 Tue, 01 Nov 2011 04:00:00 +0100 5440853 http://www.medworm.com/index.php?rid=5440852&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%3D22098904%26dopt%3DAbstract Authors: Ahmed R, Faisal NH, Paradowska AM, Fitzpatrick ME, Khor KA Abstract The failure of an orthopaedic implant can be initiated by residual strain inherent to the hydroxyapatite coating (HAC). Knowledge of the through-thickness residual strain profile in the thermally sprayed hydroxyapatite coating/substrate system is therefore important in the development of a new generation of orthopaedic implants. As the coating microstructure is complex, non-destructive characterization of residual strain, e.g. using neutron diffraction, provides a useful measure of through thickness strain profile without altering the stress field. This first detailed study using a neutron diffraction technique, non-destructively evaluates the through thickness strain measurement in nanostructured hydroxya... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440852 Tue, 01 Nov 2011 04:00:00 +0100 5440852 http://www.medworm.com/index.php?rid=5440851&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%3D22098905%26dopt%3DAbstract Authors: Shepherd TN, Zhang J, Ovaert TC, Roeder RK, Niebur GL Abstract Nanoindentation has become a standard method for measuring mechanical properties of bone, especially within microstructural units such as individual osteons or trabeculae. The use of nanoindentation to measure elastic properties has been thoroughly studied and validated. However, it is also possible to assess time dependent properties of bone by nanoindentation. The goal of this study was to compare time dependent mechanical properties of bone measured at the macroscopic level with those measured by nanoindentation. Twelve samples were prepared from the posterior distal femoral cortex of young cows. Initially, dogbone samples were prepared and subjected to torsional stress relaxation in a saline bath at 37 °C... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440851 Tue, 01 Nov 2011 04:00:00 +0100 5440851 http://www.medworm.com/index.php?rid=5440850&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%3D22098906%26dopt%3DAbstract Authors: Curran DJ, Fleming TJ, Towler MR, Hampshire S Abstract The effects of ion substitution in hydroxyapatite (HA) on crystal structure and lattice stability is investigated in the green state and post sintering. The effects of ion incorporation on the biaxial flexural strength and hardness are also investigated. Sintering is carried out at 1200 °C using comparative conventional and microwave regimes. Post sintering, the effects of ion incorporation manifest as an increase in the lattice d-spacings and a reduction of the crystallite size. Some HA decomposition occurs with β-TCP stabilisation in conventional sintering (CS), but this phase is destabilised during microwave sintering (MS), generating α-TCP. Conventional sintering (CS) allows higher densification in the undoped ... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440850 Tue, 01 Nov 2011 04:00:00 +0100 5440850 http://www.medworm.com/index.php?rid=5440849&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%3D22098907%26dopt%3DAbstract Authors: Wang X, Chen Y, Xu L, Xiao S, Kong F, Woo KD Abstract A β-type Ti-based composite, Ti-35Nb-2.5Sn-15-hydroxyapatite (HA), has been synthesized by mechanical alloying and powder metallurgy. The effects of milling time on microstructure, mechanical properties and biocompatibility of the sintered composites were investigated by scanning electronic microscopy (SEM), X-ray diffraction (XRD), microhardness tests, compression tests and cells culture. The results revealed when milling time increased, the homogeneity and relative density of the sintered composite increased, but the finished sintering temperature decreased. The compression Young's modulus of sintered composite from 12 h milled powders was about 22 GPa and its compression strength was 877 MPa. The cell culture res... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440849 Tue, 01 Nov 2011 04:00:00 +0100 5440849 http://www.medworm.com/index.php?rid=5440848&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%3D22098908%26dopt%3DAbstract In conclusion, blending bone marrow with acrylic bone cement seems to be a promising method to increase the compliance of PMMA cement for use in cancellous bone augmentation in osteoporotic patients due to its modified mechanical properties, lower polymerization temperature and elevated initial viscosity. PMID: 22098908 [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=5440848 Tue, 01 Nov 2011 04:00:00 +0100 5440848 http://www.medworm.com/index.php?rid=5440847&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%3D22098909%26dopt%3DAbstract Authors: Alonso Gil R, Igual Muñoz A Abstract The corrosion and tribocorrosion behavior of an as-cast high carbon CoCrMo alloy immersed in phosphate buffered solution (PBS) and phosphate buffered solution with bovine serum albumin (PBS+BSA) have been analyzed by electrochemical techniques and surface microscopy. After the electrochemical characterization of the alloy in both solutions, the sample was studied tribo-electrochemically (by open circuit potential, OCP measurements, potentiodynamic curves and potentiostatic tests) in a ball-on-disk tribometer rotating in different sliding velocities. The influence of solution chemistry, sliding velocity and applied potential on the corrosion and tribocorrosion behavior of the CoCrMo alloy has been studied. Anodic current density increas... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440847 Tue, 01 Nov 2011 04:00:00 +0100 5440847 http://www.medworm.com/index.php?rid=5440846&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%3D22098910%26dopt%3DAbstract Authors: Robinson HJ, Markaki AE, Collier CA, Clyne TW Abstract The adhesion of bovine chondrocytes and human osteoblasts to three titania-based coatings, formed by plasma electrolytic oxidation (PEO), was compared to that on uncoated Ti-6Al-4V substrates, and some comparisons were also made with plasma sprayed hydroxyapatite (HA) coatings. This was done using a centrifuge, with accelerations of up to 160,000 g, so as to induce buoyancy forces that created normal or shear stresses at the interface. It is shown that, on all surfaces, it was easier to remove cells under normal loading than under shear loading. Cell adhesion to the PEO coatings was stronger than that on Ti-6Al-4V and similar to that on HA. Cell proliferation rates were relatively high on one of the PEO coatings, whic... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440846 Tue, 01 Nov 2011 04:00:00 +0100 5440846 http://www.medworm.com/index.php?rid=5440845&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%3D22098911%26dopt%3DAbstract The objective of this study is a detailed identification of the anisotropic elastic properties of the secondary osteon in the lamella plane. Additionally, the principal material orientation with respect to the osteon is assessed. Therefore a new nanoindentation method was developed which allows the measurement of indentation data in three distinct planes on a single osteon. All investigated osteons appeared to be anisotropic with a preferred stiffness alignment along the axial direction with a small average helical winding around the osteon axis. The mean degree of anisotropy was 1.75 ± 0.36 and the mean helix angle was 10.3(°)±0.8°. These findings oppose two well established views of compact bone microstructure: first, the generally clear axial stiffness orientation contradicts a re... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440845 Tue, 01 Nov 2011 04:00:00 +0100 5440845 http://www.medworm.com/index.php?rid=5440844&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%3D22098912%26dopt%3DAbstract This study was designed to propose the regression model capable of estimating the prestrain of the human abdominal aorta. The length of the abdominal aorta before, l, and after excision from the body, L, the diameter, heart weight, thickness of left ventricle and degree of atherosclerosis were collected in autopsies of 156 male cadavers of known age. Longitudinal prestrain was quantified by means of the stretch ratio λ=l/L. Statistical analysis revealed significant dependence between age, prestrain, diameter and atherosclerosis, which were best fitted to the power law equation. Longitudinal prestretch reduced with age significantly; λ(mean)=1.30±0.07 for age <30 (n=29), whereas λ(mean)=1.06±0.03 for age >59 (n=31) with p-value <0.0001. Raw data gave linear correlation coeffic... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440844 Tue, 01 Nov 2011 04:00:00 +0100 5440844 http://www.medworm.com/index.php?rid=5440843&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%3D22098913%26dopt%3DAbstract In conclusion, the results still suggest a preference for fresh cadaveric spine specimens for quantitative biomechanical in-vitro testing, because they provide the best physiological conditions. However, for preliminary tests, which may only be used for orientation, embalmed specimens using the Thiel fixation method might serve as an alternative. Compared to formalin-fixated specimens which become approximately 5 times stiffer and completely lose their non-linear load-deformation-characteristic, as found in a previous study; the Thiel fixation maintains the non-linear load-deformation-characteristic but increases the range of motion. PMID: 22098913 [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=5440843 Tue, 01 Nov 2011 04:00:00 +0100 5440843 http://www.medworm.com/index.php?rid=5440842&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%3D22098914%26dopt%3DAbstract The objective of this study was to examine the effects of cavity configuration on the polymerization shrinkage and stress of light-cured composite restorations by combining local strain measurement and a finite element analysis (FEA). Dental mesio-occluso-distal cavities of various widths and depths (each for 2 vs. 4 mm), representing different configuration factors, were prepared on extracted molars. The displacements of the bonded tooth cusps and cavity floors, caused by polymerization shrinkage of composite restorations, were assessed utilizing a digital-image-correlation (DIC) technique. The cervical marginal microleakage was investigated by examining the resin replicas of these restorations under SEM. The local material properties of the polymerized composite along the curing depth we... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440842 Tue, 01 Nov 2011 04:00:00 +0100 5440842 http://www.medworm.com/index.php?rid=5440841&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%3D22098915%26dopt%3DAbstract In this study microstructural and nano-mechanical properties of a bioceramic bone scaffold were investigated as a function of the sintering temperature in the range of 950-1150 °C, through the use of scanning electron microscopy (SEM), X-ray diffraction (XRD) and nanoindentation testing. Although the samples presented the same crystallographic phase, an increase in sintering temperature resulted in increased grain size, density and crystallite size. The intrinsic mechanical properties were measured by nanoindentation testing and analyzed with the Oliver-Pharr method. The nanoindentation tests consisted of a series of fourteen partial unload tests (n=14 per treatment) of twelve steps ranging from 1 to 12 mN. Statistically significant increases in hardness and elastic modulus were measur... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440841 Tue, 01 Nov 2011 04:00:00 +0100 5440841 http://www.medworm.com/index.php?rid=5440840&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%3D22098916%26dopt%3DAbstract Authors: Hidaka K, Moine L, Collin G, Labarre D, Louis Grossiord J, Huang N, Osuga K, Wada S, Laurent A Abstract The present study investigates the mechanical properties of three embolization microspheres (E-ms): tris-acryl gelatin microspheres (TG-ms), acrylamido polyvinyl alcohol microspheres (APVA-ms), and polyphosphazene-coated polymethylmethacrylate microspheres (PP-PMMA-ms). Compression and relaxation tests were performed on monolayers of particles and their Young's moduli and relaxation half times (RHTs) were determined. The elasticity of E-ms was evaluated by applying Hertz theory with the assumptions of incompressibility and a Poisson's ratio of 0.5. The Young's moduli of TG-ms, APVA-ms, and PP-PMMA-ms were 39.6 ± 5.05 kPa, 18.8±4.00 kPa, and 13.6±1.98 kPa, respect... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5440840 Tue, 01 Nov 2011 04:00:00 +0100 5440840 http://www.medworm.com/index.php?rid=5105609&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%3D21783101%26dopt%3DAbstract Authors: Taylor D PMID: 21783101 [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=5105609 Mon, 08 Aug 2011 11:00:02 +0100 5105609 http://www.medworm.com/index.php?rid=5105608&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%3D21783102%26dopt%3DAbstract Authors: Wang X, Han C, Hu X, Sun H, You C, Gao C, Haiyang Y Knitting is an ancient and yet, a fresh technique. It has a history of no less than 1,000 years. The development of tissue engineering and regenerative medicine provides a new role for knitting. Several meshes knitted from synthetic or biological materials have been designed and applied, either alone, to strengthen materials for the patching of soft tissues, or in combination with other kinds of biomaterials, such as collagen and fibroin, to repair or replace damaged tissues/organs. In the latter case, studies have demonstrated that knitted mesh scaffolds (KMSs) possess excellent mechanical properties and can promote more effective tissue repair, ligament/tendon/cartilage regeneration, pipe-like-organ reconstruction, etc. In ... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5105608 Mon, 08 Aug 2011 10:59:51 +0100 5105608 http://www.medworm.com/index.php?rid=5105607&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%3D21783103%26dopt%3DAbstract The objectives of this study were to quantify and model the axial creep and recovery responses of nondegenerate and degenerate human lumbar discs. Two experiments were performed. First, a slow compressive ramp was applied to 2000 N, unloaded to allow recovery for up to 24 h, and re-applied. The linear-region stiffness and disc height were within 5% of the initial condition for recovery times greater than 8 h. In the second experiment, a 1000 N creep load was applied for four hours, unloaded recovery monitored for 24 h, and the creep load repeated. A viscoelastic model comprised of a "fast" and "slow" exponential response was used to describe the creep and recovery, where the fast response is associated with flow in the nucleus pulposus (NP) and endplate, while the slow response is associat... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5105607 Mon, 08 Aug 2011 10:59:36 +0100 5105607 http://www.medworm.com/index.php?rid=5105606&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%3D21783104%26dopt%3DAbstract Authors: Luo Q, Nakade R, Dong X, Rong Q, Wang X The interactions between mineral and collagen phases in the ultrastructural level play an important role in determining the mechanical properties of bone tissue. Three types of mineral-collagen interaction (i.e., ionic interactions, hydrogen/van der Waals bonds, and van der Waals/viscous shear in opening/sliding mode, respectively) have been simulated in this study, using cohesive zone-modeling techniques. Considering the inhomogeneity of bone, a probabilistic failure analysis approach has been also employed to account for the effect of mineral-collagen interfacial behavior on microdamage accumulation in lamellar bone tissues. The results of this study suggested that different interfacial behaviors cause different types of microdamage ac... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5105606 Mon, 08 Aug 2011 10:59:25 +0100 5105606 http://www.medworm.com/index.php?rid=5105605&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%3D21783105%26dopt%3DAbstract Authors: Panjwani B, Satyanarayana N, Sinha SK Ultra-high molecular weight polyethylene (UHMWPE) thin film was coated onto Ti6Al4V alloy specimens using dip coating method. Tribological performance of this coating (thickness of 19.6±2.0 μm) was evaluated using 4 mm diameter Si(3)N(4) ball counterface in a ball-on-disk tribometer. Tests were carried out for different normal loads (0.5, 1.0, 2.0 and 4.0 N) and rotational speeds of the disk (200 and 400 rpm). UHMWPE coating formed in this study exhibits high hydrophobicity with water contact angle of 135.5±3.3° and meets the requirements of cytotoxicity test using the ISO 10993-5 elution method. This coating shows low coefficient of friction (0.15) and high wear durability (>96,000 cycles) for the tested conditions. PFPE overcoat ... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5105605 Mon, 08 Aug 2011 10:59:12 +0100 5105605 http://www.medworm.com/index.php?rid=5105604&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%3D21783106%26dopt%3DAbstract Authors: Chen PY, McKittrick J A method to completely demineralize and deproteinize bone was used to investigate the mechanical properties of either the mineral or protein phase in cancellous bone and compared to an untreated one. Compression tests on cancellous bovine femur and elk antler (Cervus elaphus canadensis) were performed on demineralized, deproteinized, and untreated samples in an air-dry condition. Results showed that the elastic modulus and compressive strength of the demineralized (protein only) and deproteinized (mineral only) samples were far lower than that of the untreated ones, indicating a strong synergetic effect between the two phases. Experimental data showed that the demineralized, deproteinized, and untreated samples can be modeled as cellular solids, with the ... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5105604 Mon, 08 Aug 2011 10:58:56 +0100 5105604 http://www.medworm.com/index.php?rid=5105603&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%3D21783107%26dopt%3DAbstract Authors: Liu Q, Subhash G, Moore DF A new approach for characterization of agarose gel permeability under compression at different loading velocities is proposed. Uniaxial compression tests on thin agarose gel specimens in a rigid porous confinement cell immersed in a water bath are undertaken. The equilibrium response of the gel, which is assumed to be achieved under extremely low-loading velocity (of the order of tens nanometers per second) is considered to be the response of the hydrated gel scaffold. The water exudation behavior from the agarose gel was extracted from the load-displacement response under various loading velocities by subtracting the equilibrium response. It was found that the pressure on water in the gel is not a linear function of loading velocity or volume flow r... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5105603 Mon, 08 Aug 2011 10:58:46 +0100 5105603 http://www.medworm.com/index.php?rid=5105602&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%3D21783108%26dopt%3DAbstract Authors: An B, Liu Y, Arola D, Zhang D In this investigation, the crack propagation mechanisms contributing to the toughness of cortical bone were studied using a combination of experimental and numerical approaches. Compact tension (CT) specimens were prepared from bovine cortical bones to achieve crack propagation in the longitudinal and transverse directions. Stable crack extension experiments were conducted to distinguish the crack growth resistance curves, and virtual multidimensional internal bond (VMIB) modeling was adopted to simulate the fracture responses. Results from experiments indicated that cortical bone exhibited rising resistance curves (R-curves) for crack extension parallel and perpendicular to the bone axis; the transverse fracture toughness was significantly larger... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5105602 Mon, 08 Aug 2011 10:58:37 +0100 5105602 http://www.medworm.com/index.php?rid=5105601&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%3D21783109%26dopt%3DAbstract Authors: Takahashi Y, Zhu W, Sugano N, Pezzotti G We have visualized at the nanometer scale the topological, chemical and mechanical characteristics of long-term in vivo exposed bearing surfaces of femoral heads made of monolithic alumina. Four self-mated alumina retrievals were studied, which were exposed in the human body for relatively long periods of time ranging between 7.7 and 10.7 yrs. Besides conventional morphological features, monitored by atomic force microscopy, the topographic distributions of point defects and lattice strain on the surface of the heads were systematically probed by collecting high spatially and spectrally resolved cathodoluminescence spectra from zones of different wear severity. Three types of optically active point-defect site could be detected: (i) oxy... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5105601 Mon, 08 Aug 2011 10:58:14 +0100 5105601 http://www.medworm.com/index.php?rid=5105600&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%3D21783110%26dopt%3DAbstract We report failure analysis of sternal wires in two cases in which a perichronal fixation technique was used to close the sternotomy. Various characteristics of the retrieved wires were compared to those of unused wires of the same grade and same manufacturer and with surgical wire specifications. In both cases, wire fracture was un-branched and transgranular and proceeded by a high cycle fatigue process, apparently in the absence of corrosion. However, stress anlysis indicates that the effective stress produced during strong coughing is lower than the yield strength. Our findings suggest that in order to reduce the risk for sternal dehiscence, the diameter of the wire used should be increased. PMID: 21783110 [PubMed - in process] (Source: Journal of the Mechanical Behavior of Biomedica... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5105600 Mon, 08 Aug 2011 10:58:00 +0100 5105600 http://www.medworm.com/index.php?rid=5105599&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%3D21783111%26dopt%3DAbstract Authors: Menéndez-Proupin E, Cervantes-Rodríguez S, Osorio-Pulgar R, Franco-Cisterna M, Camacho-Montes H, Fuentes ME Hydroxyapatite (HAP) and fluorapatite (FAP) are essential components of dental enamel and bone. In this paper, we report a computational study of the elastic properties of HAP and FAP using ab initio and force field techniques. We have obtained the HAP and FAP elastic stiffness constants in hexagonal symmetry by fitting the Hooke law for both the energy-strain and stress-strain relations. Our ab initio HAP stiffness constants differ from the results of previous calculations, but follow similar trends. The HAP and FAP stiffness constants calculated with the ab initio method are very similar, although FAP is slightly stiffer than HAP in the hexagonal plane, and more comp... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5105599 Mon, 08 Aug 2011 10:57:51 +0100 5105599 http://www.medworm.com/index.php?rid=5105598&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%3D21783112%26dopt%3DAbstract Authors: Ural A, Zioupos P, Buchanan D, Vashishth D Evaluating the mechanical response of bone under high loading rates is crucial to understanding fractures in traumatic accidents or falls. In the current study, a computational approach based on cohesive finite element modeling was employed to evaluate the effect of strain rate on fracture toughness of human cortical bone. Two-dimensional compact tension specimen models were simulated to evaluate the change in initiation and propagation fracture toughness with increasing strain rate (range: 0.08-18 s(-1)). In addition, the effect of porosity in combination with strain rate was assessed using three-dimensional models of micro-computed tomography-based compact tension specimens. The simulation results showed that bone's resistance agai... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5105598 Mon, 08 Aug 2011 10:57:43 +0100 5105598 http://www.medworm.com/index.php?rid=5105597&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%3D21783113%26dopt%3DAbstract This study evaluated the tradeoffs amongst fatigue crack propagation resistance, wear resistance, and oxidative stability in a wide variety of clinically-relevant cross-linked ultra-high molecular weight polyethylene. Highly cross-linked re-melted materials showed good oxidation and wear performance, but diminished fatigue crack propagation resistance. Highly cross-linked annealed materials showed good wear and fatigue performance, but poor oxidation resistance. Moderately cross-linked re-melted materials showed good oxidation resistance, but moderate wear and fatigue resistance. Increasing radiation dose increased wear resistance but decreased fatigue crack propagation resistance. Annealing reduced fatigue resistance less than re-melting, but left materials susceptible to oxidation. This ... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5105597 Mon, 08 Aug 2011 10:57:35 +0100 5105597 http://www.medworm.com/index.php?rid=5105596&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%3D21783114%26dopt%3DAbstract Authors: Ge X, Leng Y, Ren F, Lu X Fluoridated hydroxyapatite (FHA) coatings exhibit great potential for applications on implants which require good bioactivity and high antibacterial activity. This work is a comparative study of chemical stability, adhesive strength and zeta potential of a nanothick (about 200 nm) FHA coating which is densely and uniformly deposited on a titanium substrate electrochemically. The chemical stability of the nanothick coatings was evaluated using a dissolution test in a simulated physiological solution. The dissolution tests indicate that the fluorine-containing calcium phosphate (CaP) coating with an appropriate heat treatment is chemically stable in a physiological environment, even more so than its HA counterpart. The adhesive strength of FHA coatings ... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5105596 Mon, 08 Aug 2011 10:57:26 +0100 5105596 http://www.medworm.com/index.php?rid=5105595&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%3D21783115%26dopt%3DAbstract This study provides the rationale for evaluating such effects and clinical guidelines for occlusal design are proposed. PMID: 21783115 [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=5105595 Mon, 08 Aug 2011 10:56:58 +0100 5105595 http://www.medworm.com/index.php?rid=5105594&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%3D21783116%26dopt%3DAbstract In this study, the uniaxial volume averaged stress-strain behavior was extracted from the FEA to help calibrate inelastic constitutive equations. PMID: 21783116 [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=5105594 Mon, 08 Aug 2011 10:56:49 +0100 5105594 http://www.medworm.com/index.php?rid=5105593&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%3D21783117%26dopt%3DAbstract Authors: Wilberforce SI, Finlayson CE, Best SM, Cameron RE The enhanced biological and degradation properties of bioresorbable polymer matrix nanocomposites intended for use in orthopaedic applications have been demonstrated recently. However, at the moment there are only limited reports addressing their mechanical properties under physiological conditions, which is of central importance to the successful design of these nanocomposites. Here, we show that at room temperature in dry conditions, the incorporation of α-tricalcium phosphate nanoparticles into a matrix of poly(D,L-lactide-co-glycolide) increases the compressive strength and modulus. The values at room temperature obtained for nanocomposites compounded by a modified solvent evaporation method via attrition milling in aceton... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5105593 Mon, 08 Aug 2011 10:56:40 +0100 5105593 http://www.medworm.com/index.php?rid=5105592&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%3D21783118%26dopt%3DAbstract Authors: Xi J, Lamata P, Lee J, Moireau P, Chapelle D, Smith N Parameter estimation from non-invasive measurements is a crucial step in patient-specific cardiac modeling. It also has the potential to provide significant assistance in the clinical diagnosis of cardiac diseases through the quantification of myocardial material heterogeneity. In this paper, we formulate a novel Reduced-order Unscented Kalman Filter (rUKF) applied to the left ventricular (LV) nonlinear mechanical model based on cubic-Hermite finite elements. Material parameters in the widely-employed transversely isotropic Guccione's constitutive law are successfully identified for both homogeneous and heterogeneous cases. We conclude that the four parameters in Guccione's law can be uniquely and correctly determined in-si... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5105592 Mon, 08 Aug 2011 10:56:31 +0100 5105592 http://www.medworm.com/index.php?rid=5105591&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%3D21783119%26dopt%3DAbstract In this study, we compared four hyperelastic constitutive models fitted to uniaxial and biaxial tension, confined compression, and shear experiments from the literature. Models were either directly based on Spencer's formulation for a fiber-reinforced composite material with two equivalent fiber families or represented the annulus as two transversely isotropic materials. Each model was composed of additive strain energy terms that represent specific constituents of the annulus fibrosus (proteoglycan matrix, collagen fibers, and collagen crosslinks). Additionally, we investigated the effect of restricting the fibers such that they supported tensile loads only. Best fit coefficients for these models were calculated both including and excluding shear data from the regression. All of the model... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5105591 Mon, 08 Aug 2011 10:56:22 +0100 5105591 http://www.medworm.com/index.php?rid=5105590&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%3D21783120%26dopt%3DAbstract Authors: Hadj Henni A, Schmitt C, Tremblay MÉ, Hamdine M, Heuzey MC, Carreau P, Cloutier G With the emergence of new biomaterials and elastography imaging techniques, there is a need for innovative instruments dedicated to viscoelasticity measurements. In this work, we introduce a novel hyper-frequency viscoelastic spectroscopy (HFVS) technique dedicated to characterize soft media subjected to mid-to-very-high frequency stress ranges (or, equivalently, to probe short-to-very-short relaxation times). HFVS, which has been implemented in an analytical instrument performing non-contact measurements in less than 1 s between 10 and 1000 Hz, is a suitable tool to study viscoelasticity for bio-applications. In this context, HFVS has been compared to classical oscillatory rheometry on several... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5105590 Mon, 08 Aug 2011 10:56:15 +0100 5105590 http://www.medworm.com/index.php?rid=5105589&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%3D21783121%26dopt%3DAbstract Authors: Sedaghatizadeh N, Atefi G, Fardad AA, Barari A, Soleimani S, Khani S In this investigation, semiempirical and numerical studies of blood flow in a viscoelastic artery were performed using the Cosserat continuum model. The large-amplitude oscillatory shear deformation model was used to quantify the nonlinear viscoelastic response of blood flow. The finite difference method was used to solve the governing equations, and the particle swarm optimization algorithm was utilized to identify the non-Newtonian coefficients (k(υ) and γ(υ)). The numerical results agreed well with previous experimental results. PMID: 21783121 [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=5105589 Mon, 08 Aug 2011 10:56:05 +0100 5105589 http://www.medworm.com/index.php?rid=5105588&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%3D21783122%26dopt%3DAbstract Authors: Majumdar P, Singh SB, Chakraborty M The suitability of heat treated Ti-13Zr-13Nb (TZN) alloy for biomedical load bearing applications has been investigated. Depending upon the heat treatment conditions, the microstructure of TZN alloy mainly consists of α, β or α" martensite phases. In general, for all the deformation and solution treatment temperatures the variation of the hardness and tensile strength with cooling rate is similar. The elastic modulus of TZN alloy decreases with an increase in cooling rate from the solution treatment temperature. Relatively fine α+β microstructure increases the hardness and tensile strength. The presence of martensite and/or retained β in the microstructure decreases the hardness and elastic modulus and increases the ductility substanti... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5105588 Mon, 08 Aug 2011 10:55:55 +0100 5105588 http://www.medworm.com/index.php?rid=5105587&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%3D21783123%26dopt%3DAbstract Authors: Lin YS, Wei CT, Olevsky EA, Meyers MA The Arapaima gigas scales play an important role in protecting this large Amazon basin fish against predators such as the piranha. They have a laminate composite structure composed of an external mineralized layer and internal lamellae with thickness of 50-60 μm each and composed of collagen fibers with ∼1 μm diameter. The alignment of collagen fibers is consistent in each individual layer but varies from layer to layer, forming a non-orthogonal plywood structure, known as Bouligand stacking. X-ray diffraction revealed that the external surface of the scale contains calcium-deficient hydroxyapatite. EDS results confirm that the percentage of calcium is higher in the external layer. The micro-indentation hardness of the external layer... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5105587 Mon, 08 Aug 2011 10:55:48 +0100 5105587 http://www.medworm.com/index.php?rid=5105586&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%3D21783124%26dopt%3DAbstract In this study the change in the mechanical properties of three biopolymer hydrogels alginate, low methoxy pectin and gellan gum have been assessed in cell culture conditions. Samples of the gels were prepared encapsulating rat bone marrow stromal cells which were then cultured in osteogenic media. Acellular samples were also prepared and incubated in standard cell culture media. The rheological properties of the gels were measured over a culture period of 28 days and it was found that the gels degraded at very different rates. The degradation occurred most rapidly in the order alginate > Low methoxy pectin > gellan gum. The ability of each hydrogel to support differentiation of bone marrow stromal cells to osteoblasts was also verified by evidence of mineral deposits in all three of ... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5105586 Mon, 08 Aug 2011 10:55:41 +0100 5105586 http://www.medworm.com/index.php?rid=5105585&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%3D21783125%26dopt%3DAbstract Authors: Tsamis A, Bothe W, Kvitting JP, Swanson JC, Miller DC, Kuhl E Progressive alterations in cardiac wall strains are a classic hallmark of chronic heart failure. Accordingly, the objectives of this study are to establish a baseline characterization of cardiac strains throughout the cardiac cycle, to quantify temporal, regional, and transmural variations of active fiber contraction, and to identify pathways of mechanical activation in the healthy beating heart. To this end, we insert two sets of twelve radiopaque beads into the heart muscle of nine sheep; one in the anterior-basal and one in the lateral-equatorial left ventricular wall. During three consecutive heartbeats, we record the bead coordinates via biplane videofluoroscopy. From the resulting four-dimensional data sets, w... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5105585 Mon, 08 Aug 2011 10:55:33 +0100 5105585 http://www.medworm.com/index.php?rid=5105584&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%3D21783126%26dopt%3DAbstract Authors: Libertiaux V, Pascon F, Cescotto S For decades, incompressibility has been a major assumption in the mechanical study of brain tissue. This assumption is based on the hydrated nature of the biological tissues and the incompressibility of fluids. In this paper, an experimental validation of this assumption using digital image correlation is presented. Unconfined compression tests, relaxation tests and cyclic tests were performed on cylindrical samples of swine brains at loading rates suitable for neurosurgical applications. Digital image correlation was used to evaluate the evolution of the volume ratio throughout the tests. The preparation of the samples is described and it is demonstrated that it causes no statistically significant change of their mechanical properties. The r... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5105584 Mon, 08 Aug 2011 10:55:25 +0100 5105584 http://www.medworm.com/index.php?rid=5105583&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%3D21783127%26dopt%3DAbstract Authors: Lin DJ, Ju CP, Huang SH, Tien YC, Yin HS, Chen WC, Chern Lin JH The purpose of this study was to evaluate the osteointegration of a titanium (Ti) implant with the calcium phosphate cement (CPC) and autograft prostheses by pull-out test and histological examination. Stems of sixty Ti cylinders were bilaterally inserted into femoral medullary canals in 30 rabbits at the 1st, 4th, 12th, 26th and 70th postoperative weeks. The bone autograft and CPC were filled into the pre-trimmed bone marrow cavity with a polymethyl methacrylate retarder in the distal end, and then a Ti cylinder was inserted into femurs. The CPC group was significantly (p<0.05) associated with a larger pull-out force at 4th (37%) and 12th (62%) weeks compared to the autograft group. The bone area and the bone-... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5105583 Mon, 08 Aug 2011 10:55:18 +0100 5105583 http://www.medworm.com/index.php?rid=5105582&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%3D21783128%26dopt%3DAbstract In conclusion, alginate can mimic the viscoelastic properties of the NP and preserve the biosynthetic phenotype of NP cells but certain limitations like long-term stability still have to be addressed. PMID: 21783128 [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=5105582 Mon, 08 Aug 2011 10:55:10 +0100 5105582 http://www.medworm.com/index.php?rid=5105580&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%3D21783129%26dopt%3DAbstract Authors: Nakai M, Niinomi M, Ishii D Porous titanium (pTi) can possess a low Young's modulus equal to that of human bone, depending on its porosity. However, the mechanical strength of pTi deteriorates greatly with increasing porosity. On the other hand, certain medical polymers exhibit biofunctionalities, which are not possessed intrinsically by metallic materials. Therefore, a biodegradable medical polymer, poly-L-lactic acid (PLLA), was used to fill in the pTi pores using a modified in-situ polymerization technique. The mechanical and biodegradable properties of pTi filled with PLLA (pTi/PLLA) as fabricated by this technique and the effects of the PLLA filling were evaluated in this study. The pTi pores are almost completely filled with PLLA by the developed process (i.e., technique... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5105580 Mon, 08 Aug 2011 10:55:01 +0100 5105580 http://www.medworm.com/index.php?rid=5105579&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%3D21783130%26dopt%3DAbstract Authors: Killion JA, Geever LM, Devine DM, Kennedy JE, Higginbotham CL Poly(ethylene glycol) hydrogels are currently under investigation as possible scaffold materials for bone regeneration. The main purpose of this research was to analyse the mechanical properties and thermal behaviour of novel photopolymerised poly(ethylene glycol) dimethacrylate (PEGDMA) based hydrogels. The effect of varying macromolecular monomer concentration, molecular weight and water content on the properties of the resultant hydrogel was apparent. For example, rheological findings showed that storage modulus (G') of the hydrogels could be tailored to a range between approximately 14,000 and 70,000 Pa by manipulating both of the aforementioned criteria. Equally striking variations in mechanical performance wer... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5105579 Mon, 08 Aug 2011 10:54:54 +0100 5105579 http://www.medworm.com/index.php?rid=5105578&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%3D21783131%26dopt%3DAbstract Authors: Jiang S, Liu S, Feng W PVA has been proposed as a promising biomaterial suitable for tissue mimicking, vascular cell culturing and vascular implanting. In this research, a kind of transparent PVA hydrogel has been investigated in order to mimic the creatural soft tissue deformation during mini-invasive surgery with needle intervention, such as brachytherapy. Three kinds of samples with the same composition of 3 g PVA, 17 g de-ionized water, 80 g dimethyl-sulfoxide but different freeze/thaw cycles have been prepared. In order to investigate the structure and properties of polyvinyl alcohol hydrogel, micro-structure, mechanical property and deformation measurement have been conducted. As the SEM image comparison results show, with the increase of freeze/thaw cycles, PVA hydrogel... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5105578 Mon, 08 Aug 2011 10:54:46 +0100 5105578 http://www.medworm.com/index.php?rid=5105577&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%3D21783132%26dopt%3DAbstract Authors: Galbusera F, Schmidt H, Noailly J, Malandrino A, Lacroix D, Wilke HJ, Shirazi-Adl A Osmotic phenomena influence the intervertebral disc biomechanics. Their simulation is challenging and can be undertaken at different levels of complexity. Four distinct approaches to simulate the osmotic behaviour of the intervertebral disc (a fixed boundary pore pressure model, a fixed osmotic pressure gradient model in the whole disc or only in the nucleus pulposus, and a swelling model with strain-dependent osmotic pressure) were analysed. Predictions were compared using a 3D poroelastic finite element model of a L4-L5 spinal unit under three different loading conditions: free swelling for 8 h and two daily loading cycles: (i) 200 N compression for 8 h followed by 500 N compression for 16 ... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5105577 Mon, 08 Aug 2011 10:54:38 +0100 5105577 http://www.medworm.com/index.php?rid=5105576&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%3D21783133%26dopt%3DAbstract Authors: Avanzini A Ultra High Molecular Weight Polyethylene (UHMWPE) is a polymeric material employed in critical biomedical applications. Knowledge of its mechanical behavior is essential in order to obtain accurate prediction of stresses and deformations in real components, in particular when cyclic loading is considered. In the present research the effects of alternating and pulsating cyclic strain on the mechanical response of UHMWPE were studied by means of an experimental procedure based on tests carried out in strain control at different mean cyclic strain levels. During the tests the temperature increase due to hysteretic heating was controlled by means of a compressed air cooling apparatus specifically devised. By taking advantage of the possibility to control and stabilize t... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5105576 Mon, 08 Aug 2011 10:54:28 +0100 5105576 http://www.medworm.com/index.php?rid=5105575&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%3D21783134%26dopt%3DAbstract In conclusion, this study demonstrates that the application of long-term hydrostatic pressure can be used to improve the functional properties of cartilaginous tissues engineered using bone marrow derived MSCs by enhancing collagen and GAG accumulation. The response to such loading however is donor dependent, which has implications for the clinical utilisation of such a stimulus when engineering cartilaginous grafts using autologous MSCs. PMID: 21783134 [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=5105575 Mon, 08 Aug 2011 10:54:20 +0100 5105575 http://www.medworm.com/index.php?rid=5105574&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%3D21783135%26dopt%3DAbstract Authors: Zhang XF, O'Shea H, Kehoe S, Boyd D The use of nerve guidance conduits to repair peripheral nerve discontinuities has attracted much attention from the biomaterials community, with many resorbable and non-resorbable materials in clinical use. However, a material with ideal biocompatibility, sufficient mechanical properties (to match that of the regenerating nerve) coupled with a suitable degradation rate, has yet to be realized. Recently, potential solutions (composite nerve guidance conduits) which support the emerging philosophy of allowing synthetic materials to establish key interactions with cells in ways that encourage self-repair (i.e. ionic mediators of repair such as those observed in hard tissue regeneration) have been proposed in the literature; such composites comp... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5105574 Mon, 08 Aug 2011 10:54:11 +0100 5105574 http://www.medworm.com/index.php?rid=5105573&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%3D21783136%26dopt%3DAbstract This study was conducted to investigate the suitability of the small punch test for characterizing polyetheretherketone (PEEK) polymeric biomaterials for changes in material grade, crystallinity, and molding process. The small punch test reproducibly characterized the mechanical behavior of PEEK and was able to distinguish differences induced by molding process alterations and annealing. Peak load was most sensitive to changes in crystallinity, grade, molding process, and increased with increasing crystallinity, but decreased with the addition of image contrast materials. The ultimate displacement was negatively correlated with crystallinity. Molding process conditions had the greatest influence on metrics of the small punch test, when compared with the effects of annealing and the additio... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5105573 Mon, 08 Aug 2011 10:54:00 +0100 5105573 http://www.medworm.com/index.php?rid=5105572&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%3D21783137%26dopt%3DAbstract Authors: Paakinaho K, Heino H, Väisänen J, Törmälä P, Kellomäki M The hydrolytic degradation of oriented poly(L-lactide-co-glycolide) 85L/15G (PLGA 85/15) sample materials with various amounts of lactide monomer was monitored in vitro at 37 °C. The materials were manufactured from medical grade PLGA 85/15 by a two-step melt extrusion-die drawing process. Results showed that the hydrolytic degradation rate depended highly on the lactide monomer content, which in turn influenced the retention of mechanical properties, mass loss, crystallinity, and dimensional stability. Even small quantities of lactide monomer (0.05-0.20 wt%) affected especially the retention of mechanical properties, which started to decline rapidly upon the inherent viscosity reaching 0.6-0.8 dl/g due to hydrol... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5105572 Mon, 08 Aug 2011 10:53:48 +0100 5105572 http://www.medworm.com/index.php?rid=5105571&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%3D21783138%26dopt%3DAbstract Authors: Deubener J, Höland M, Höland W, Janakiraman N, Rheinberger VM The critical stress intensity factor, also known as the crack tip toughness K(tip), was determined for three base glasses, which are used in the manufacture of glass-ceramics. The glasses included the base glass for a lithium disilicate glass-ceramic, the base glass for a fluoroapatite glass-ceramic and the base glass for a leucite glass-ceramic. These glass-ceramic are extensively used in the form of biomaterials in restorative dental medicine. The crack tip toughness was established by using crack opening displacement profiles under experimental conditions. The crack was produced by Vickers indentation. The crack tip toughness parameters determined for the three glass-ceramics differed quite significantly. The c... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5105571 Mon, 08 Aug 2011 10:53:33 +0100 5105571 http://www.medworm.com/index.php?rid=5105570&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%3D21783139%26dopt%3DAbstract Authors: Böl M, Weikert R, Weichert C This work deals with the development and implementation of an electromechanical skeletal muscle model. To this end, a recently published hyperelastic constitutive muscle model with transversely isotropic characteristics, see Ehret et al. (2011), has been weakly coupled with Ohm's law describing the electric current. In contrast to the traditional way of active muscle modelling, this model is rooted on a non-additive decomposition of the active and passive components. The performance of the proposed modelling approach is demonstrated by the use of three-dimensional illustrative boundary-value problems that include electromechanical analysis on tissue strips. Further, simulations on the biceps brachii muscle document the applicability of the model ... Journal of the Mechanical Behavior of Biomedical Materials journals http://www.medworm.com/rss/comments.php?id=5105570 Mon, 08 Aug 2011 10:53:14 +0100 5105570