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BIOTECHNOLOGY (236 journals)                  1 2 | Last

Showing 1 - 200 of 239 Journals sorted alphabetically
3 Biotech     Open Access   (Followers: 8)
Advanced Biomedical Research     Open Access  
Advances in Bioscience and Biotechnology     Open Access   (Followers: 16)
Advances in Genetic Engineering & Biotechnology     Hybrid Journal   (Followers: 7)
Advances in Regenerative Medicine     Open Access   (Followers: 2)
African Journal of Biotechnology     Open Access   (Followers: 6)
Algal Research     Partially Free   (Followers: 11)
American Journal of Biochemistry and Biotechnology     Open Access   (Followers: 67)
American Journal of Bioinformatics Research     Open Access   (Followers: 7)
American Journal of Polymer Science     Open Access   (Followers: 32)
Anadolu University Journal of Science and Technology : C Life Sciences and Biotechnology     Open Access  
Animal Biotechnology     Hybrid Journal   (Followers: 8)
Annales des Sciences Agronomiques     Full-text available via subscription  
Applied Biochemistry and Biotechnology     Hybrid Journal   (Followers: 43)
Applied Biosafety     Hybrid Journal  
Applied Food Biotechnology     Open Access   (Followers: 3)
Applied Microbiology and Biotechnology     Hybrid Journal   (Followers: 64)
Applied Mycology and Biotechnology     Full-text available via subscription   (Followers: 4)
Arthroplasty Today     Open Access   (Followers: 1)
Artificial Cells, Nanomedicine and Biotechnology     Hybrid Journal   (Followers: 1)
Asia Pacific Biotech News     Hybrid Journal   (Followers: 2)
Asian Journal of Biotechnology     Open Access   (Followers: 9)
Asian Pacific Journal of Tropical Biomedicine     Open Access   (Followers: 2)
Australasian Biotechnology     Full-text available via subscription   (Followers: 1)
Banat's Journal of Biotechnology     Open Access  
BBR : Biochemistry and Biotechnology Reports     Open Access   (Followers: 5)
Beitr?ge zur Tabakforschung International/Contributions to Tobacco Research     Open Access   (Followers: 2)
Bio-Algorithms and Med-Systems     Hybrid Journal   (Followers: 2)
Bio-Research     Full-text available via subscription   (Followers: 3)
Bioactive Materials     Open Access   (Followers: 1)
Biocatalysis and Agricultural Biotechnology     Hybrid Journal   (Followers: 4)
Biocybernetics and Biological Engineering     Full-text available via subscription   (Followers: 5)
Bioethics UPdate     Hybrid Journal   (Followers: 1)
Biofuels     Hybrid Journal   (Followers: 11)
Biofuels Engineering     Open Access   (Followers: 1)
Biological & Pharmaceutical Bulletin     Full-text available via subscription   (Followers: 4)
Biological Cybernetics     Hybrid Journal   (Followers: 10)
Biomarkers and Genomic Medicine     Open Access   (Followers: 3)
Biomarkers in Drug Development     Partially Free   (Followers: 1)
Biomaterials Research     Open Access   (Followers: 4)
BioMed Research International     Open Access   (Followers: 4)
Biomédica     Open Access  
Biomedical and Biotechnology Research Journal     Open Access  
Biomedical Engineering Research     Open Access   (Followers: 6)
Biomedical Glasses     Open Access  
Biomedical Reports     Full-text available via subscription  
BioMedicine     Open Access  
Biomedika     Open Access  
Bioprinting     Hybrid Journal   (Followers: 1)
Bioresource Technology Reports     Hybrid Journal   (Followers: 1)
Bioscience, Biotechnology, and Biochemistry     Hybrid Journal   (Followers: 21)
Biosensors Journal     Open Access  
Biosimilars     Open Access   (Followers: 1)
Biosurface and Biotribology     Open Access  
Biotechnic and Histochemistry     Hybrid Journal   (Followers: 1)
BioTechniques : The International Journal of Life Science Methods     Full-text available via subscription   (Followers: 28)
Biotechnologia Acta     Open Access   (Followers: 1)
Biotechnologie, Agronomie, Société et Environnement     Open Access   (Followers: 2)
Biotechnology     Open Access   (Followers: 6)
Biotechnology & Biotechnological Equipment     Open Access   (Followers: 4)
Biotechnology Advances     Hybrid Journal   (Followers: 33)
Biotechnology and Applied Biochemistry     Hybrid Journal   (Followers: 44)
Biotechnology and Bioengineering     Hybrid Journal   (Followers: 153)
Biotechnology and Bioprocess Engineering     Hybrid Journal   (Followers: 5)
Biotechnology and Genetic Engineering Reviews     Hybrid Journal   (Followers: 13)
Biotechnology and Health Sciences     Open Access   (Followers: 1)
Biotechnology and Molecular Biology Reviews     Open Access   (Followers: 2)
Biotechnology Annual Review     Full-text available via subscription   (Followers: 5)
Biotechnology for Biofuels     Open Access   (Followers: 10)
Biotechnology Frontier     Open Access   (Followers: 2)
Biotechnology Journal     Hybrid Journal   (Followers: 16)
Biotechnology Law Report     Hybrid Journal   (Followers: 4)
Biotechnology Letters     Hybrid Journal   (Followers: 34)
Biotechnology Progress     Hybrid Journal   (Followers: 40)
Biotechnology Reports     Open Access  
Biotechnology Research International     Open Access   (Followers: 1)
Biotechnology Techniques     Hybrid Journal   (Followers: 10)
Biotecnología Aplicada     Open Access  
Bioteknologi (Biotechnological Studies)     Open Access  
BIOTIK : Jurnal Ilmiah Biologi Teknologi dan Kependidikan     Open Access  
Biotribology     Hybrid Journal   (Followers: 1)
BMC Biotechnology     Open Access   (Followers: 16)
Cell Biology and Development     Open Access  
Chinese Journal of Agricultural Biotechnology     Full-text available via subscription   (Followers: 4)
Communications in Mathematical Biology and Neuroscience     Open Access  
Computational and Structural Biotechnology Journal     Open Access   (Followers: 2)
Computer Methods and Programs in Biomedicine     Hybrid Journal   (Followers: 8)
Copernican Letters     Open Access   (Followers: 1)
Critical Reviews in Biotechnology     Hybrid Journal   (Followers: 20)
Crop Breeding and Applied Biotechnology     Open Access   (Followers: 3)
Current Bionanotechnology     Hybrid Journal  
Current Biotechnology     Hybrid Journal   (Followers: 4)
Current Opinion in Biomedical Engineering     Hybrid Journal   (Followers: 1)
Current Opinion in Biotechnology     Hybrid Journal   (Followers: 56)
Current Pharmaceutical Biotechnology     Hybrid Journal   (Followers: 9)
Current Research in Bioinformatics     Open Access   (Followers: 12)
Current Trends in Biotechnology and Chemical Research     Open Access   (Followers: 3)
Current trends in Biotechnology and Pharmacy     Open Access   (Followers: 8)
EBioMedicine     Open Access  
Electronic Journal of Biotechnology     Open Access  
Entomologia Generalis     Full-text available via subscription  
Environmental Science : Processes & Impacts     Full-text available via subscription   (Followers: 4)
Experimental Biology and Medicine     Hybrid Journal   (Followers: 3)
Folia Medica Indonesiana     Open Access  
Food Bioscience     Hybrid Journal  
Food Biotechnology     Hybrid Journal   (Followers: 9)
Food Science and Biotechnology     Hybrid Journal   (Followers: 8)
Frontiers in Bioengineering and Biotechnology     Open Access   (Followers: 6)
Frontiers in Systems Biology     Open Access   (Followers: 2)
Fungal Biology and Biotechnology     Open Access   (Followers: 2)
GM Crops and Food: Biotechnology in Agriculture and the Food Chain     Full-text available via subscription   (Followers: 1)
GSTF Journal of BioSciences     Open Access  
HAYATI Journal of Biosciences     Open Access  
Horticulture, Environment, and Biotechnology     Hybrid Journal   (Followers: 11)
IEEE Transactions on Molecular, Biological and Multi-Scale Communications     Hybrid Journal   (Followers: 1)
IET Nanobiotechnology     Hybrid Journal   (Followers: 2)
IIOAB Letters     Open Access  
IN VIVO     Full-text available via subscription   (Followers: 4)
Indian Journal of Biotechnology (IJBT)     Open Access   (Followers: 2)
Indonesia Journal of Biomedical Science     Open Access   (Followers: 2)
Indonesian Journal of Biotechnology     Open Access   (Followers: 1)
Indonesian Journal of Medicine     Open Access  
Industrial Biotechnology     Hybrid Journal   (Followers: 17)
International Biomechanics     Open Access  
International Journal of Bioinformatics Research and Applications     Hybrid Journal   (Followers: 13)
International Journal of Biomechatronics and Biomedical Robotics     Hybrid Journal   (Followers: 4)
International Journal of Biomedical Research     Open Access   (Followers: 2)
International Journal of Biotechnology     Hybrid Journal   (Followers: 5)
International Journal of Biotechnology and Molecular Biology Research     Open Access   (Followers: 3)
International Journal of Biotechnology for Wellness Industries     Partially Free   (Followers: 1)
International Journal of Environment, Agriculture and Biotechnology     Open Access   (Followers: 5)
International Journal of Functional Informatics and Personalised Medicine     Hybrid Journal   (Followers: 4)
International Journal of Medicine and Biomedical Research     Open Access   (Followers: 1)
International Journal of Nanotechnology and Molecular Computation     Full-text available via subscription   (Followers: 3)
International Journal of Radiation Biology     Hybrid Journal   (Followers: 4)
Iranian Journal of Biotechnology     Open Access  
ISABB Journal of Biotechnology and Bioinformatics     Open Access  
Italian Journal of Food Science     Open Access   (Followers: 1)
JMIR Biomedical Engineering     Open Access  
Journal of Biometrics & Biostatistics     Open Access   (Followers: 3)
Journal of Bioterrorism & Biodefense     Open Access   (Followers: 6)
Journal of Petroleum & Environmental Biotechnology     Open Access   (Followers: 1)
Journal of Advanced Therapies and Medical Innovation Sciences     Open Access  
Journal of Advances in Biotechnology     Open Access   (Followers: 5)
Journal Of Agrobiotechnology     Open Access  
Journal of Analytical & Bioanalytical Techniques     Open Access   (Followers: 7)
Journal of Animal Science and Biotechnology     Open Access   (Followers: 4)
Journal of Applied Biomedicine     Open Access   (Followers: 2)
Journal of Applied Biotechnology     Open Access   (Followers: 2)
Journal of Applied Biotechnology Reports     Open Access   (Followers: 2)
Journal of Applied Mathematics & Bioinformatics     Open Access   (Followers: 5)
Journal of Biologically Active Products from Nature     Hybrid Journal   (Followers: 1)
Journal of Biomaterials and Nanobiotechnology     Open Access   (Followers: 6)
Journal of Biomedical Photonics & Engineering     Open Access  
Journal of Biomedical Practitioners     Open Access  
Journal of Bioprocess Engineering and Biorefinery     Full-text available via subscription  
Journal of Bioprocessing & Biotechniques     Open Access  
Journal of Biosecurity Biosafety and Biodefense Law     Hybrid Journal   (Followers: 3)
Journal of Biotechnology     Hybrid Journal   (Followers: 64)
Journal of Biotechnology and Strategic Health Research     Open Access  
Journal of Chemical and Biological Interfaces     Full-text available via subscription   (Followers: 1)
Journal of Chemical Technology & Biotechnology     Hybrid Journal   (Followers: 9)
Journal of Chitin and Chitosan Science     Full-text available via subscription   (Followers: 1)
Journal of Colloid Science and Biotechnology     Full-text available via subscription  
Journal of Commercial Biotechnology     Full-text available via subscription   (Followers: 6)
Journal of Crop Science and Biotechnology     Hybrid Journal   (Followers: 3)
Journal of Essential Oil Research     Hybrid Journal   (Followers: 2)
Journal of Experimental Biology     Full-text available via subscription   (Followers: 25)
Journal of Genetic Engineering and Biotechnology     Open Access   (Followers: 5)
Journal of Ginseng Research     Open Access  
Journal of Industrial Microbiology and Biotechnology     Hybrid Journal   (Followers: 17)
Journal of Integrative Bioinformatics     Open Access  
Journal of Medical Imaging and Health Informatics     Full-text available via subscription  
Journal of Molecular Biology and Biotechnology     Open Access  
Journal of Molecular Microbiology and Biotechnology     Full-text available via subscription   (Followers: 11)
Journal of Nano Education     Full-text available via subscription  
Journal of Nanobiotechnology     Open Access   (Followers: 4)
Journal of Nanofluids     Full-text available via subscription   (Followers: 1)
Journal of Organic and Biomolecular Simulations     Open Access  
Journal of Plant Biochemistry and Biotechnology     Hybrid Journal   (Followers: 4)
Journal of Science and Applications : Biomedicine     Open Access  
Journal of the Mechanical Behavior of Biomedical Materials     Hybrid Journal   (Followers: 12)
Journal of Trace Elements in Medicine and Biology     Hybrid Journal   (Followers: 1)
Journal of Tropical Microbiology and Biotechnology     Full-text available via subscription  
Journal of Yeast and Fungal Research     Open Access   (Followers: 1)
Marine Biotechnology     Hybrid Journal   (Followers: 4)
Meat Technology     Open Access  
Messenger     Full-text available via subscription  
Metabolic Engineering Communications     Open Access   (Followers: 4)
Metalloproteinases In Medicine     Open Access  
Microbial Biotechnology     Open Access   (Followers: 9)
MicroMedicine     Open Access   (Followers: 3)
Molecular and Cellular Biomedical Sciences     Open Access   (Followers: 1)
Molecular Biotechnology     Hybrid Journal   (Followers: 13)
Molecular Genetics and Metabolism Reports     Open Access   (Followers: 3)
Nanobiomedicine     Open Access  
Nanobiotechnology     Hybrid Journal   (Followers: 2)
Nanomaterials and Nanotechnology     Open Access  
Nanomedicine and Nanobiology     Full-text available via subscription  
Nanomedicine Research Journal     Open Access  

        1 2 | Last

Journal Cover
Journal of the Mechanical Behavior of Biomedical Materials
Journal Prestige (SJR): 0.958
Citation Impact (citeScore): 3
Number of Followers: 12  
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 1751-6161
Published by Elsevier Homepage  [3161 journals]
  • A Material Modeling Approach for the Effective Response of Planar Soft
           Tissues for Efficient Computational Simulations
    • Abstract: Publication date: Available online 20 September 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Will Zhang, Rana Zakerzadeh, Wenbo Zhang, Michael S. SacksAbstractOne of the most crucial aspects of biomechanical simulations of physiological systems that seek to predict the outcomes of disease, injury, and surgical interventions is the underlying soft tissue constitutive model. Soft tissue constitutive modeling approaches have become increasingly complex, often utilizing meso- and multi-scale methods for greater predictive capability and linking to the underlying biological mechanisms. However, such modeling approaches are associated with substantial computational costs. One solution is to use effective constitutive models in place of meso- and multi-scale models in numerical simulations but derive their responses by homogenizing the responses of the underlying meso- or multi-scale models. A robust effective constitutive model can thus drastically increase the speed of simulations for a wide range of meso- and multi-scale models. However, there is no consensus on how to develop a single effective constitutive model and optimal methods for parameter estimation for a wide range of soft tissue responses. In the present study, we developed an effective constitutive model which can fully reproduce the response of a wide range of planar soft tissues, along with a method for robust and fast-convergent parameter estimation. We then evaluated our approach and demonstrated its ability to handle materials of widely varying degrees of stiffness and anisotropy. Furthermore, we demonstrated the performance of the meso-structural to effective constitutive model framework in a finite element simulation of a tri-leaflet heart valve, where it demonstrated robust performance. We conclude that the effective constitutive modeling approach has significant potential for improving the computational efficiency and numerical robustness of multi-scale and meso-scale models, facilitating efficient soft tissue simulations in such demanding applications as inverse modeling and growth.
  • On the Observation of Lubrication Mechanisms within Hip Joint
           Replacements. Part I: Hard-on-soft Bearing Pairs
    • Abstract: Publication date: Available online 19 September 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): D. Nečas, M. Vrbka, A. Galandáková, I. Křupka, M. HartlAbstractThe present study describes the lubrication mechanisms within artificial hip joints considering real conformity of rubbing surfaces. Part I is focused on hard-on-soft material combination, introducing the fundamentals of lubrication performance. These pairs have not been explored in terms of in situ observation before. The contact of metal femoral component articulating with transparent polymer acetabular cup was studied using a hip joint simulator. The film formation was evaluated by fluorescent microscopy method. Various model synovial fluids were employed while the key constituents, i.e. albumin, γ-globulin, and hyaluronic acid were fluorescently stained to determine its role in film formation process. Two types of the tests were performed. The first dynamic test aimed on the development of film thickness under constant load during motor driven swinging motion mimicking flexion-extension. Subsequently, a combined test was designed consisting of the three phases; static part with loading/unloading phase (1), pendulum swinging till spontaneous damping of the motion due to friction (2), and static observation under the constant load (3). The results clearly confirmed that the interaction of constituents of synovial fluid plays a dominant role and substantially influences the lubrication conditions. In particular, the main finding coming from the present study is that γ-globulin together with hyaluronic acid form relatively thin stable boundary layer enabling the enhanced adsorption of albumin, thus increasing the lubricant film. Part II of the present study is focused on hard-on-hard pairs while the main differences in film formation process are highlighted among others.
  • On the Observation of Lubrication Mechanisms within Hip Joint
           Replacements. Part II: Hard-on-hard Bearing Pairs
    • Abstract: Publication date: Available online 19 September 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): D. Nečas, M. Vrbka, J. Gallo, I. Křupka, M. HartlAbstractThe present paper represents Part II of the extensive study focused on the lubrication of hip joint replacements. The main goal is to assess the fundamentals of lubrication considering both hard-on-soft (Part I) and hard-on-hard (Part II) bearing pairs. In addition, the effect of individual constituents contained in the model fluid is clarified. For this purpose, multiple model fluids of various composition were employed. In this part of the study, metal-on-glass contact representing hard bearing pairs was observed in situ using pendulum hip joint simulator in combination with thin film colorimetric interferometry method. The designed test consists of initial static loading/unloading phase for the determination of adsorption of molecules on rubbing surfaces. This period is followed by swinging of the pendulum and latest static part under constant load. Three groups of measurements were carried out while fourteen different lubricants were tested. Initially, the experiments were performed with albumin-based model fluid. In that case a substantial positive effect of hyaluronic acid was identified. In contrast, the fluids with γ-globulin as a base constituent showed improved lubrication conditions when phospholipids were added to the solution. Finally, considering the complex fluid, a combined effect of hyaluronic acid and phospholipids caused a better endurance of the lubricant film. The latest part of the paper aims on the comparison of film formation considering hard and soft pairs, highlighting some clear differences. In general, hard pairs exhibit clear decreasing tendency of the film during swinging motion while opposite behaviour was observed for soft pairs.
  • Suitability of developed composite materials for meniscal replacement:
           mechanical, friction and wear evaluation
    • Abstract: Publication date: Available online 18 September 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Adijat Omowumi Inyang, Tamer Abdalrahman, Deon Bezuidenhout, James Bowen, Chistopher Leonard VaughanThe meniscus is a complex and frequently damaged tissue which requires a substitute capable of reproducing similar biomechanical functions. This study aimed at developing a synthetic meniscal substitute that can mimic the function of the native meniscus.Medical grade silicones reinforced with nylon were fabricated using compression moulding and evaluated for mechanical and tribological properties. The optimal properties were obtained with tensile modulus increased considerably from 10.7 ± 2.9 MPa to 114.6 ± 20.9 MPa while compressive modulus was found to reduce from 2.5 ± 0.6 MPa to 0.7 ± 0.3 MPa. Using a tribometer, the coefficient of friction of 0.08 ± 0.02 was measured at the end of the 100,000 cycles.The developed composite could be an auspicious substitute for the native meniscus and the knowledge gained from this study is useful as it enhances the understanding of a potentially suitable material for meniscal implants.Graphical abstractGraphical abstract for this article
  • Corrigendum to “Effect of acidity upon attrition–corrosion of human
           dental enamel” [J. Mech. Behav. Biomed. Mater. 44 (2015) 23–34]
    • Abstract: Publication date: Available online 18 September 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Yun-Qi Wu, Joseph A. Arsecularatne, Mark Hoffman
  • Microstructure analysis and mechanical properties by instrumented
           indentation of Charonia Lampas Lampas shell
    • Abstract: Publication date: Available online 18 September 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): K. BOUFALA, S. OUHENIA, G. LOUIS, D. BETRANCOURT, D. CHICOT, I. BELABBASAbstractScanning electron microscopy, X-ray diffraction and Fourier transformed infrared spectroscopy have been used to characterize the microstructure and instrumented microindentation for the determination of the mechanical properties of Charonia Lampas Lampas shell. Both elastic modulus and hardness are found to be dependent on the texture of the three distinct layers. From the analysis of load-depth curves, the shell exhibits small viscoelastic behavior at low indentation loads and mainly elastoplastic behavior at higher loads. These phenomena were attributed to the influence of the organic matter present in the shell. Both elastic modulus and hardness are found to be load-dependent in each layer in relation to their microstructure and, accordingly, to the anisotropy of the predominant mineral part. At a macroscopic scale, this tendency is explained by using a rule of mixture and jointly by the anisotropy of the aragonite. The Bull and Page model is subsequently applied to the hardness variation in order to compute the macrohardness which is the characteristic hardness number of a material and the hardness parameter related to the indentation size effect. This model describes well the experimental results for the relative higher depths, and deviates for the small depths due to the effect of the viscoelastic behavior which then requires a more appropriate model to describe this phenomenon.
  • Wear and Friction of UHMWPE-on-PEEK OPTIMA™
    • Abstract: Publication date: Available online 17 September 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Raelene M. Cowie, Adam Briscoe, John Fisher, Louise M. JenningsAbstractPEEK-OPTIMA™ is being considered as an alternative bearing material to cobalt chrome in the femoral component of total knee replacement to provide a metal-free implant. The aim of this study was to investigate the influence of lubricant temperature (standard rig running and elevated temperature (~36 °C)) on the wear of a UHMWPE-on-PEEK OPTIMA™ bearing couple using different lubricant protein concentrations (0, 2, 5, 25 and 90% bovine serum) in a simple geometry pin-on-plate configuration. Friction was also investigated under a single temperature condition for different lubricant protein concentrations. The studies were repeated for UHMWPE-on-cobalt chrome in order to compare relationships with temperature (wear only) and lubricant protein concentration (wear and friction).In low lubricant protein concentrations (≤ 5%) there was no influence of temperature on the wear factors of UHMWPE-on-PEEK. With 25% bovine serum, the wear factor of UHMWPE-on-PEEK reduced by half at elevated temperature. When tested in high protein concentration (90% serum), there was no influence of temperature on the wear factor of UHMWPE-on-PEEK. These temperature dependencies were not the same for UHMWPE-on-cobalt chrome.For both material combinations, there was a trend of decreasing friction with increasing protein concentration once protein was present in the lubricant.This study has shown the importance of the selection of appropriate test conditions when investigating the wear and friction of different materials, in order to minimise test artefacts such as polymer transfer, and protein precipitation and deposition.
  • Interrelation among the handling, mechanical, and wear properties of the
           newly developed flowable resin composites
    • Abstract: Publication date: Available online 17 September 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Arisa Imai, Toshiki Takamizawa, Runa Sugimura, Akimasa Tsujimoto, Ryo Ishii, Mami Kawazu, Tatsuro Saito, Masashi MiyazakiAbstractObjectivesThis study investigates the handling, mechanical, and wear properties of the newly developed flowable resin composites and elucidate the interrelations among the tested parameters.MethodsSix flowable and two conventional resin composites are used. Five measurements are performed per resin composite to obtain the average inorganic filler content. Ten specimens per material are used to obtain the flexural strength, flexural modulus, and resilience. For sliding impact wear testing, twelve specimens are prepared. Noncontact profilometer and confocal laser scanning microscopy are used to determine the maximum facet depth and volume loss. Extrusion force and thread formation are used to measure the handling properties of the flowable resin composites. Six measurements are performed per flowable resin composite. Data evaluation is performed using analysis of variance and Tukey's honestly significant difference test at an α-level of 0.05. The correlation between the tested parameters is verified using the Pearson product-moment correlation coefficient.ResultsA subset of flowable resin composites exhibits higher flexural properties and wear resistance as compared to the conventional resin composites. The handling properties of the flowable resin composites are material dependent.ConclusionWhile the resilience parameters exhibit an extremely strong and statistically significant correlation with the wear parameters, the handling properties exhibit no interrelation with the remaining parameters.SignificanceWhile the handling properties of the newly developed flowable resin composites did not correlate with the mechanical and wear properties, some new flowable resin composites have the potential for use in high-stress bearing areas, such as posterior lesions, because of the enhanced mechanical properties and wear resistance.
  • Preparation and in vivo biocompatibility studies of different mesoporous
           bioactive glasses
    • Abstract: Publication date: Available online 17 September 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Akrity Anand, V. Lalzawmliana, Vinod Kumar, Piyali Das, K. Bavya Devi, Asit Kumar Maji, Biswanath Kundu, Mangal Roy, Samit Kumar NandiAbstractA new generation of nanostructured glasses called mesoporous bioactive glasses (MBGs) exhibit superior surface texture, porosity and bioactive characteristics. The present study is carried out to develop and detailed characterize of ternary SiO2-CaO-P2O5 MBG structure, fabricated by three different variations using different surfactants, e.g., hexadecyltrimethylammonium bromide (CTAB), poly-ethylene glycol,(PEG) and Pluronic P123. After thorough physico-chemical characterization, MBG granules were investigated for in vivo bone regeneration in animal bone defect model (rabbit) where standard S53P4 bioactive glass was used as control. All the synthesized MBG powders showed nano-range median particle size of 80–120 nm (MBG-CTAB), 50–70 nm (MBG-PEG and MBG-P123 while their specific surface area as 473.2, 52.2 and 169.3 m2/g respectively. All MBGs showed mesoporous nature corroborating transmission electron microscopy (TEM) observation as well. Bone regeneration property was measured after 45 and 90 days post-implantation at distal epiphysis of rabbit femur by radiography, histology, fluorochrome labeling, micro computed tomography (micro-CT) and vital organ histology. Results from in vivo studies indicated that the MBG materials produce minimal toxicity to the body. Furthermore, the biocompatibility and biodegradability of the implant makes them more suitable for application in bone tissue engineering. Among various implants, MBG fabricated using suitable surfactant (CTAB) shown the best result compared to other implants. Nonetheless, all the materials are suitable for application in bone tissue engineering and have potential for bone regeneration and healing.
  • Mechanical properties, in vitro corrosion resistance and biocompatibility
           of metal injection molded Ti-12Mo alloy for dental applications
    • Abstract: Publication date: December 2018Source: Journal of the Mechanical Behavior of Biomedical Materials, Volume 88Author(s): W. Xu, X. Lu, L.N. Wang, Z.M. Shi, S.M. Lv, M. Qian, X.H. QuA biocompatible Ti-12Mo alloy was fabricated by metal injection moulding (MIM) using non-spherical titanium, molybdenum powders and a purposely designed binder. The density, microstructure and tensile properties were characterized. This was followed by a detailed assessment of its in vitro corrosion and biocompatibility performances, compared with that of two commonly used titanium-based materials extra low interstitial (ELI) Ti-6Al-4V and commercially pure (CP) titanium. The MIM-fabricated Ti-12Mo alloy can achieve a wide range of mechanical properties through controlling sintering process. Specimens sintered at 1400 °C are characterized by fairly uniform near-β microstructure and high relative density of 97.6%, leading to the highest tensile strength of 845.3 ± 21 MPa and elongation of 4.15 ± 0.2% while the highest elastic modulus of 73.2 ± 5.1 GPa. Owing to the formation of protective TiO2-MoO3 passive film, the MIM-fabricated Ti-12Mo alloy exhibits the highest corrosion resistance including the noblest corrosion potential, the lowest corrosion current density and the highest pitting potential in four different electrolytes. The in vitro cytotoxicity test suggests that the MIM-fabricated Ti-12Mo alloy displays no adverse effect on MC3T3-E1 cells with cytotoxicity ranking of 0 grade, which is nearly close to ELI Ti-6Al-4V or CP Ti. These properties together with its easy net-shape manufacturability make Ti-12Mo an attractive new dental implant alloy.Graphical abstractfx1
  • Recent advances in understanding the fatigue and wear behavior of dental
           composites and ceramics
    • Abstract: Publication date: December 2018Source: Journal of the Mechanical Behavior of Biomedical Materials, Volume 88Author(s): Jamie J. Kruzic, Joseph A. Arsecularatne, Carina B. Tanaka, Mark J. Hoffman, Paulo F. CesarDental composite and ceramic restorative materials are designed to closely mimic the aesthetics and function of natural tooth tissue, and their longevity in the oral environment depends to a large degree on their fatigue and wear properties. The purpose of this review is to highlight some recent advances in our understanding of fatigue and wear mechanisms, and how they contribute to restoration failures in the complex oral environment. Overall, fatigue and wear processes are found to be closely related, with wear of dental ceramic occlusal surfaces providing initiation sites for fatigue failures, and subsurface fatigue crack propagation driving key wear mechanisms for composites, ceramics, and enamel. Furthermore, both fatigue and wear of composite restorations may be important in enabling secondary caries formation, which is the leading cause of composite restoration failures. Overall, developing a mechanistic description of fatigue, wear, and secondary caries formation, along with understanding the interconnectivity of all three processes, are together seen as essential keys to successfully using in vitro studies to predict in vivo outcomes and develop improved dental restorative materials.Graphical abstractfx1
  • Effect of Water Concentration on the Shock Response of Polyethylene Glycol
           Diacrylate (PEGDA) Hydrogels: A Molecular Dynamics Study
    • Abstract: Publication date: Available online 15 September 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Ke Luo, Noah Yudewitz, Ghatu Subhash, Douglas E. SpearotAbstractShockwave propagation in poly(ethylene glycol) diacrylate (PEGDA) hydrogels is simulated for the first time using nonequilibrium molecular dynamics simulations. PEGDA hydrogel models are built using the “perfect network” approach such that each crosslink junction is comprised of six chain connections. The influence of PEGDA concentration (20 to 70 wt.%) on shock behavior is investigated for a range of particle velocities (200 to 1000 m/s). In agreement with reported experimental results in the literature on gels with similar densities, shock velocity and pressure in PEGDA hydrogels are found to increase with polymer concentration, within a range bounded by pure water and pure polymer behaviors. Nonlinear relationships are observed for shock pressure and shock front thickness as a function of concentration, and a logarithmic equation is proposed to describe this behavior. In addition, the relationship between pressure and shock front thickness is compared with hydrodynamic theory. Deviation from hydrodynamic predictions is observed at high particle velocities and this deviation is found to be related to viscosity changes. A power-law relationship between strain rate and pressure in PEGDA hydrogels is identified, similar to that of metals. However, a power-law exponent of 1.4 is computed for all gel concentrations, whereas an exponent of 4 is typically reported for metals.
  • Bioinspired silica-infiltrated zirconia bilayers: Strength and interfacial
    • Abstract: Publication date: Available online 14 September 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Dominique Yukie Toyama, Larissa Marcia Martins Alves, Gabriela Freitas Ramos, Tiago Moreira Bastos Campos, Getúlio de Vasconcelos, Alexandre Luiz Souto Borges, Renata Marques de MeloAbstractConventionally veneered zirconia restorations are susceptible to chipping and spalling of the veneering material. The novel translucent zirconias were developed to overcome such issues, although layered zirconia restorations can be re-designed to improve mechanical performance. Thus, the aim of this study was to analyze the strength and structural reliability of zirconia bilayers using conventional (porcelain ceramic under tensile stress) and bioinspired (zirconia under tensile stress) configurations. Sol-gel silica infiltration served as a smooth transition between the zirconia and veneering porcelain. Failure mode and interfacial adhesive mechanism were analyzed using scratch test and interfacial indentation. Bilayered specimens were produced for biaxial flexural testing with Y-TZP and pressed ceramic, which were further divided into four groups (n=30): Conventional (C), Infiltrated conventional (IC), Bioinspired (B) and Infiltrated bioinspired (IB). The results of biaxial flexural strength tests were analyzed by Weibull analysis (95% CI) for determination of the Weibull modulus (m). The infiltration layer was characterized by XRD and SEM, FEG-SEM and EDS. The bioinspired infiltrated group was the most reliable (m=9.59), although the fine damage of veneered conventional (conventional) zirconia demonstrated its superior resistance to scratching and debonding. Therefore, the filling of superficial defects by zirconia silicate demonstrated the need for mechanical retention for better porcelain adhesion.
  • Selective Laser Melting processed Ti6Al4V lattices with graded porosities
           for dental applications
    • Abstract: Publication date: Available online 29 August 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Zena J Wally, Abdul M Haque, Antonio Feteira, Frederik Claeyssens, Russell Goodall, Gwendolen C ReillyDental implants need to support good osseointegration into the surrounding bone for full functionality. Interconnected porous structures have a lower stiffness and larger surface area compared with bulk structures, and therefore are likely to enable better bone-implant fixation. In addition, grading of the porosity may enable large pores for ingrowth on the periphery of an implant and a denser core to maintain mechanical properties. However, given the small diameter of dental implants it is very challenging to achieve gradations in porosity. This paper investigates the use of Selective Laser Melting (SLM) to produce a range of titanium structures with regular and graded porosity using various CAD models. This includes a novel ‘Spider Web’ design and lattices built on a diamond unit cell. Well-formed interconnecting porous structures were successfully developed in a one-step process. Mechanical testing indicated that the compression stiffness of the samples was within the range for cancellous bone tissue. Characterization by scanning electron microscopy (SEM) and X-ray micro-computed tomography (μCT) indicated the designed porosities were well-replicated. The structures supported bone cell growth and deposition of bone extracellular matrix.Graphical abstractGraphical abstract for this article
  • Nondestructive characterization of bone tissue scaffolds for clinical
    • Abstract: Publication date: Available online 25 August 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Ali Entezari, Zhongpu Zhang, Andrian Sue, Guangyong Sun, Xintao Huo, Che-Cheng Chang, Shiwei Zhou, Michael V Swain, Qing LiObjectivesThis study aimed to develop a simple and efficient numerical modelling approach for characterizing strain and total strain energy in bone scaffolds implanted in patient-specific anatomical sites.Materials and methodsA simplified homogenization technique was developed to substitute a detailed scaffold model with the same size and equivalent orthotropic material properties. The effectiveness of the proposed modelling approach was compared with two other common homogenization methods based on periodic boundary conditions and the Hills-energy theorem. Moreover, experimental digital image correlation (DIC) measurements of full-field surface strain were conducted to validate the numerical results.ResultsThe newly proposed simplified homogenization approach allowed for fairly accurate prediction of strain and total strain energy in tissue scaffolds implanted in a large femur mid-shaft bone defect subjected to in-vivo loading condition. The maximum discrepancy between the total strain energy obtained from the simplified homogenization approach and the one obtained from detailed porous scaffolds was 8.8%. Moreover, the proposed modelling technique could significantly reduce the computational cost (by about 300 times) required for simulating an in-vivo bone scaffolding scenario as the required degrees of freedom (DoF) was reduced from about 26 million for a detailed porous scaffold to only 90,000 for the homogenized solid counterpart in the analysis.ConclusionsThe simplified homogenization approach has been validated by correlation with the experimental DIC measurements. It is fairly efficient and comparable with some other common homogenization techniques in terms of accuracy. The proposed method is implicating to different clinical applications, such as the optimal selection of patient-specific fixation plates and screw system.Graphical abstractGraphical abstract for this article
  • Microstructural evolution and mechanical properties of a friction-stir
           processed Ti-hydroxyapatite (HA) nanocomposite
    • Abstract: Publication date: Available online 22 August 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): R. Rahmati, F. KhodabakhshiAbstractIn this research, a new metal matrix nanocomposite with enhanced capability for biomedical applications was fabricated by incorporation of nano-sized hydroxyapatite (HA) particles within the titanium substrate using multi-pass friction-stir processing (FSP). These n-HA particles were dispersed effectively within the titanium matrix. Titanium metal-matrix was processed without introducing the HA nanoparticles, as well, for the aim of comparison. The results showed the formation of different regions with various microstructural features and mechanical property across the processed materials. A thin layer with ultra-fine grain structure and indentation hardness value of up to ~400 HV was formed on the surface after FSP modification of coarse-grained titanium substrate. This was due to severe shear deformation induced by the rotating shoulder as well as the surface absorption of N and O elements from the atmosphere inside the layer. Incorporation of nanoparticles and subsequent grain structural refinement owing to operative dynamic recrystallization mechanisms leads to a maximum hardness improvement of up to ~250 HV in the lower regions (as compared to the average hardness value of base metal ~150 HV). The FSP modified pure titanium exhibited a good combination of strength and ductility by refining the grain structure with a well-developed dimple-like structure on the fracture surface. For the nanocomposite specimen, the trend of the tensile property was found deteriorative showing the impaired features on the fracture surface. This is attributed to the complex structure of HA compound and low quality of interfacial bonding between the nanoparticles and titanium matrix.
  • On the effect of labour durations using an anisotropic
           visco-hyperelastic-damage approach to simulate vaginal deliveries
    • Abstract: Publication date: Available online 11 August 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): M.C.P. Vila Pouca, J.P.S. Ferreira, D.A. Oliveira, M.P.L. Parente, Teresa Mascarenhas, R.M. Natal JorgeInjuries sustained by the pelvic floor muscles during childbirth are one of the major risk factors for the development of pelvic floor dysfunctions. The ability to predict the loss of the tissue integrity and the most affected regions prior to the childbirth would represent a compelling difference in choosing the appropriate management of labour.Previous biomechanical studies, using the finite element method, were able to simulate a vaginal delivery and analyse the mechanical effects on the pelvic floor muscles during the passage of the foetus. Complementing these studies, the aim of this work is to improve the characterization of the pelvic floor muscles, by using an anisotropic visco-hyperelastic constitutive model, including a continuum mechanics damage model. Viscoelasticity is a key feature to obtain more realistic results since biological tissues present relaxation effects that allow larger deformations without damage. This work analyses the reaction forces and the loss of tissue integrity sustained by the pelvic floor and evaluates the effects of different durations of labour. A delaying pushing technique of rest and descend is also studied in this work.The results obtained showed that the reaction forces vary with the duration of labour, with higher force levels associated with higher stretch rates. The pubovisceral muscle is the most affected of the levator ani, presenting an affected region of approximately 30%. The relaxation properties of the tissue contribute to diminish the damage levels, supporting the theory of delayed pushing applied in the second stage of labour.Graphical Graphical abstract for this article
  • Influence of magnesium particles and Pluronic F127 on compressive strength
           and cytocompatibility of nanocomposite injectable and moldable beads for
           bone regeneration
    • Abstract: Publication date: December 2018Source: Journal of the Mechanical Behavior of Biomedical Materials, Volume 88Author(s): Govindaraj Perumal, Boopalan Ramasamy, A. Maya Nandkumar, Mukesh DobleA novel one-step preparation of magnesium particles and Pluronic F127 incorporated with calcium sulfate hemihydrate (CSH) and nano-hydroxyapatite (nHA) ready to use injectable or moldable beads was developed for bone tissue regeneration applications. The nanocomposite showed setting time less than 15 min, very good injectability (75–85%) and good mechanical strength (52–80 MPa). Samples immersed in SBF showed controlled degradation (40–45% reduction in weight) in 28 days. The nanocomposite bone graft was cytocompatible against MG63 osteosarcoma cells and increased the osteogenic gene expression by 2–3 folds. These results indicate that it can be a potential defect filling biomaterial for bone tissue regeneration at the fracture site.Graphical abstractfx1
  • Human plasma gels: their preparation and rheological characterization for
           cell culture applications in tissue engineering
    • Abstract: Publication date: Available online 13 September 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Lucía Barreda, Ismael Marcet, Sara Llames, Marta Pevida, Eva García-Pérez, Álvaro Meana, Manuel Rendueles, Mario DíazAbstractTissue engineering is one of the fields of clinical medicine that has forged ahead in recent years, especially because of its role as a potential alternative to organ transplantation. The main aim of this study has been the development of biocompatible materials to form extracellular matrix (ECM) structures in order to provide the necessary conditions for the settlement, proliferation and differentiation of dermal cells such as fibroblasts. To this end, human plasma gels were synthesized with the addition of increasing concentrations of transglutaminase (TGase), which catalyses the formation of covalent bonds between Lys and Glu residues. These materials were structurally characterized using rheology and texturometry and were found to have good structural resistance and elasticity for fibroblast culture. A remarkable improvement in the mechanical properties of the human plasma gels was detected when the two highest TGase concentrations were tested, which may be interpreted as an increase in the number of covalent and non-covalent bonds formed between the plasma protein chains. Furthermore, a human fibroblast primary culture was seeded on human plasma scaffolds and satisfactorily proliferated at 37 °C. This was verified in the images obtained by optical microscopy (OM) and by scanning electron microscopy (SEM), which confirmed that the structure of this type of material is suitable for the growth and proliferation of dermal fibroblasts.
  • Elastic Properties Measurement of Human Enamel Based on Resonant
           Ultrasound Spectroscopy
    • Abstract: Publication date: Available online 12 September 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Haijun Niu, Fan Fan, Rui Wang, Qiang Zhang, Fei Shen, Pengling Ren, Tao Liu, Yubo Fan, Pascal LaugierAbstractObjectivesTo investigate the elastic properties of human enamel using resonant ultrasound spectroscopy (RUS).MethodsSix rectangular parallelepiped specimens were prepared from six human third molars. For all specimens, the theoretical resonant frequencies were calculated using the Rayleigh-Ritz method, knowing the specimen mass density and dimensions, and using a priori stiffness constants. The experimental resonant frequencies were measured and extracted by RUS. Then, the optimal stiffness constants were retrieved by adjustment of the theoretical resonant frequencies to the measured ones based on the Levenberg-Marquardt method. The engineering elastic moduli, including Young’s moduli, shear moduli, and Poisson’s ratios, were also calculated based on the optimal stiffness constants.ResultsThe five independent stiffness constants C11, C12, C13, C33, and C44 were 90.2 ± 6.65 GPa, 34.7 ± 6.90 GPa, 29.5 ± 4.82 GPa, 83.5 ± 8.93 GPa, and 37.0 ± 10.9 GPa, respectively. Young’s moduli E11 and E33, shear moduli G13 and G12, and Possion’s ratios υ12 and υ13 were 71.7 ± 7.34 GPa, 69.2 ± 7.32 GPa, 37.0 ± 10.9 GPa, 28.1 ± 4.35 GPa, 0.303 ± 0.098, and 0.248 ± 0.060, respectively.SignificanceElastic properties are critical for developing dental materials and designing dental prostheses. The RUS method may provide more precise measurement of elastic properties of dental materials.
  • Novel adhesives for distal radius fixation: A biomechanical analysis
    • Abstract: Publication date: Available online 12 September 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Cina Mehrvar, Paul Kuzyk, Jamshied Shamlou, Oleg Safir, Paul Zalzal, Adel Alhalawani, Mark R. Towler, Marcello PapiniAbstractWrist fractures can be difficult to treat due to advanced age of the patient, medical co-morbidities, and comminution of the bone. This study examines the effectiveness of two injectable glass polyalkenoate cements (GPCs), derived from two different glasses (A and B), as minimally invasive treatments for distal radius fractures. Twenty-seven fresh cadaveric radial pairs were tested either in compressive fatigue or to quasi-static compressive failure. The radii tested to failure had one pair fixated with a GPC while the other was left intact. The radii tested under fatigue had one pair fixated with a GPC and the other with a volar locking plate. A wedge osteotomy was used to simulate a severely comminuted fracture. When loaded to failure, the radii fixated with a GPC made from glass A or B were found to be, respectively, at least 57% and 62% as strong as their intact biological pair (95% Confidence Interval, Lower). Using a paired t-test, the radii fixated with either adhesive were found to be significantly stiffer than their biological pairs fixated with a volar locking plate for all cycles of fatigue loading. The adhesives under investigation demonstrate promise as treatment for distal radius fractures. In vivo investigations are warranted to determine the effect that the adhesives have on the bone remodelling process.
  • The failure of polypropylene surgical mesh in vivo
    • Abstract: Publication date: December 2018Source: Journal of the Mechanical Behavior of Biomedical Materials, Volume 88Author(s): David TaylorAbstractSurgical mesh materials made from fibres of polypropylene (PP) have been widely used for over fifty years. However in recent times the use of these materials has been called into question for certain surgical operations, known as “pelvic organ” or “transvaginal” procedures. This article reviews the current state of knowledge and uses some simple biomechanics analysis in order to make recommendations for future work. My conclusion is that the failure rate of PP mesh in pelvic organ products is unacceptably high whilst being much lower when it is used for hernia repair. The precise mechanical environment is difficult to quantify but a tentative conclusion is that failure by purely mechanical mechanisms (fatigue and creep) is unlikely. There is some evidence for environmental degradation (i.e. stress-corrosion) but this is highly contested in the literature. On balance my conclusion is that stress-corrosion failure is the most likely explanation but currently no experimental results exist to prove conclusively that this failure mechanism occurs in vivo. Further work is needed, especially the analysis of explanted material, to resolve this urgent problem.
  • Compressive Properties and Constitutive Modeling of Different Regions of
           8-week-old Pediatric Porcine Brain under Large Strain and Wide Strain
    • Abstract: Publication date: Available online 10 September 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Zhigang Li, Haifeng Yang, Guangliang Wang, Xiaoqiang Han, Shaopeng ZhangPorcine head is often used as a human surrogate in traumatic head injury research. Extensive research on mechanical properties of adult human / porcine brain tissues has been performed previously; however, very limited data is available for children, which is particular important for modelling the pediatric traumatic brain injury (TBI). In this study, uniaxial compression tests at strain rates of 0.01/s, 1/s and 50/s up to 50% strain were performed for the corona radiata, corpus callosum, thalamus, cortex, cerebellum and brainstem of 8-week-old piglets. No significant difference in tissue strength was found among the cerebrum regions of cortex, thalamus, corona radiata and corpus callosum. The average stress of cerebellum was approximate 21% and 15% higher than that of cerebrum at a strain of 0.25 and 0.5, respectively, but it did not reach statistical significant level than most of the cerebrum regions. Brainstem was the stiffest among these 6 regions, and it was significant stiffer than most regions of cerebrum, with average stress of about 28% and 40% higher at a strain of 0.25 and 0.5, respectively. The strengths of all these three regions showed significant strain-rate dependent characteristics, with the strain rate increasing from 0.01/s to 50/s, the average stress of cerebrum, cerebellum and brainstem increased to approximate 4.6, 6.3 and 6.3 times, respectively at a strain of 0.25; and increased to approximate 1.9, 2.6, and 2.5 times, respectively at a strain of 0.5. One-term Ogden model was used to fit the experimental data to obtain the material parameters and numerical simulation was performed on the compression of cerebrum specimen. Results show that the constitutive model and the calibrated parameters can well represent the compressive behavior of the brain tissue at different strain rates. The results of this study are useful for developing biofidelic pediatric brain FE models and further predict the brain injuries under impact conditions.Graphical abstractGraphical abstract for this article
  • Multi-material Ti6Al4V & PEEK cellular structures produced by Selective
           Laser Melting and Hot Pressing: a tribocorrosion study targeting
           orthopedic applications
    • Abstract: Publication date: Available online 10 September 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): F. Bartolomeu, M. Buciumeanu, M.M. Costa, N. Alves, M. Gasik, F.S. Silva, G. MirandaTi6Al4V-alloy is commonly used in dental and orthopedic applications where tribochemical reactions occur at material/bone interface. These reactions are one of the main concerns regarding Ti6Al4V implants due to the generation of wear particles, linked to the release of metallic ions in toxic concentration which occurs when TiO2 passive film is destroyed by means of wear and corrosion simultaneously. In the present study, a multi-material Ti6Al4V-PEEK cellular structure is proposed. Selective Laser Melting technique was used to produce Ti6Al4V dense and cellular structured specimens, whilst Hot-Pressing technique was employed to obtain multi-material Ti6Al4V-PEEK structures. This study investigates the tribocorrosion behavior of these materials under reciprocating sliding, comparing them with commercial forged Ti6Al4V. Open-circuit-potential was measured before, during and after sliding while dynamic coefficient of friction was assessed during sliding. The results showed an improved wear resistance and a lower tendency to corrosion for the multi-material Ti6Al4V-PEEK specimens when compared to dense and cellular structures mono-material specimens. This multi-material solution gathering Ti6Al4V and PEEK, besides being able to withstand the loads occurring after implantation on dental and orthopedic applications, is a promising alternative to fully dense metals once it enhances the tribocorrosion performance.Graphical abstractGraphical abstract for this article
  • Use of experimental-resin-based materials doped with carboxymethyl
           chitosan and calcium phosphate microfillers to induce biomimetic
           remineralization of caries-affected dentin
    • Abstract: Publication date: Available online 7 September 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Zihua Huang, Yipin Qi, Kai Zhang, Lisha Gu, Jiaxin Guo, Ruoxun Wang, Sui MaiAbstractThis study investigated carboxymethyl chitosan (CMC)-induced biomimetic mineralization of collagen fibrils, with the aim of synthesizing experimental resins doped with CMC and calcium phosphate microfillers to remineralize artificial caries-affected dentin (ACAD) and enhance resin–dentin bonding durability. A size exclusion test provided evidence for the rejection of CMC (Mw 150 kDa) by collagen fibrils. Transmission electron microscopy and selected area electron diffraction conducted on reconstituted two-dimensional collagen showed typical deposition of needle-like hydroxyapatite crystals within collagen fibrils through CMC-induced biomimetic mineralization. The Vickers hardness test revealed significant improvement (P < 0.001) of the hardness of ACAD treated with CMC-containing experimental resins. Confocal laser scanning microscopy showed reduced dentin permeability and defect sites after biomimetic mineralization. On microtensile bond strength testing, the CMC-remineralized ACAD had better bonding with resin than ACAD and traditionally remineralized ACAD in both self-etch and etch-and-rinse bonding modes (P < 0.001). In conclusion, CMC is efficient in directing the biomimetic mineralization of collagen fibrils. The experimental resins containing CMC can induce dentin biomimetic remineralization and improve the bonding performance of ACAD.
  • The effect of pleural fluid layers on lung surface wave speed measurement:
           experimental and numerical studies on a sponge lung phantom
    • Abstract: Publication date: Available online 6 September 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Boran Zhou, Xiaoming ZhangAbstractPleural effusion manifests as compression of pleural fluid on the lung parenchyma contributing to hypoxemia. Medical procedures such as drainage of plural fluid releases this compression and increases oxygenation. However, the effect of pleural effusion on the elasticity of lung parenchyma is unknown. By using lung ultrasound surface wave elastography (LUSWE) and finite element method (FEM), the effect of pleural effusion on the elasticity of superficial lung parenchyma in terms of surface wave speed measurement was evaluated in a sponge phantom study. Different thicknesses of ultrasound transmission gel used to simulated pleural fluid were inserted into a condom, which was placed between the sponge and standoff pad. A mechanical shaker was used to generate vibration on the sponge phantom at different frequencies ranging from 100 to 300 Hz while the ultrasound transducer was used to capture the motion for measurement of surface wave speed of the sponge. FEM was conducted based on the experimental setup and numerically assessed the influence of pleural effusion on the surface wave speed of the sponge. We found from FEM experiments that the influence of thickness of ultrasound transmission gel was statistically insignificant on the surface wave speed of the sponge at 100 and 150 Hz.
  • Precision of different fatigue methods for predicting glass-ceramic
    • Abstract: Publication date: Available online 5 September 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Rodrigo Ottoni, Jason A. Griggs, Pedro H. Corazza, Álvaro Della Bona, Márcia BorbaAbstractThis study aimed to characterize the fatigue behavior using two fatigue methods, boundary and staircase, and to predict the probability of failure (Pf) of zirconia-reinforced lithium silicate glass-ceramic (ZLS). Bar-shaped specimens of ZLS (18×4×1.2 mm) were fabricated. Thirty specimens were subjected to a three-point flexural strength test using a universal testing machine with 0.5 mm/min crosshead speed, in 37 °C distilled water. Flexural strength data were analyzed with Weibull statistics. Eighty-six bars were subjected to cyclic fatigue using boundary and staircase methods. Fatigue tests were performed in a pneumatic cycling machine (2 Hz, 37° C distilled water) for 10³ and 104 cycles. Fatigue data were analyzed using an inverse power law relationship and log normal-lifetime distribution. Fracture toughness (KIc) was determined using V-notched specimens (18×4×3 mm) and the short beam toughness method (n=7). Vickers hardness (VH) was evaluated (4.9 N, 20 s). Fractographic and EDS analyses were also performed. ZLS showed a characteristic strength of 197 MPa, Weibull modulus of 4, VH of 6.67 GPa and KIc of 1.93 MPa.m1/2. After 103 cycles, for both methods, there was a degradation of 78% of the initial strength. There was no significant degradation when the number of cycles increased from 103 to 104. Both methods resulted in similar Pf and precision at 40 MPa (~50% Pf). Yet, staircase shows good accuracy and precision in predicting the stress amplitude for a Pfnear 50%; while boundary is also effective for Pflower than 50%. The fatigue methods evaluated show similar accuracy and precision for predicting the Pf of a glass-ceramic when simulations were made in the range of stress levels and lifetimes used in the fatigue tests.
  • Braided bioresorbable cardiovascular stents mechanically reinforced by
           axial runners
    • Abstract: Publication date: Available online 5 September 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Fan Zhao, Wen Xue, Fujun Wang, Jing Sun, Jing Lin, Laijun Liu, Kun Sun, Lu WangAbstractPolymeric bioresorbable stents (BRSs) can eliminate the long-term stent restenosis by degrading after vascular remolding and have been recommended for the congenital heart disease treatment. However, the mechanical weakness remains one of main inferiorities of their applications. So, the aim of this study was to develop mechanically reinforced bioresorbable stents (MRBSs) based on poly(p-dioxanone) (PPDO) monofilaments and braiding technology. Axial runners were introduced and MRBSs showed greatly higher compression force and relatively lower viscous performance, as well as longer mechanical stability during degradation, compared with controls. Besides, stent compression behaviors were analyzed experimentally and numerically to investigate their deformation mechanisms. The results showed increased contacting points and friction force among yarns in MRBSs. Also, the skeleton formed in MRBSs attributed to higher yarn bending degree, strain energy and better structure stability during compression. Combined with the non-linear PPDO material stress-strain ratio and thermodynamic theory, yarn based stent compression modes were discussed. In addition, the autocatalysis and nonrandom chain scission degradation behaviors of MRBSs were revealed.
  • Effects of Compression on Orientation of Ligands in Fluorescent Complexes
           between Hydroxyapatite with Amino Acids and their Optical Properties
    • Abstract: Publication date: Available online 5 September 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Sarita MORAKUL, Yuichi OTSUKA, Andaradhi NARARYA, Motohiro TAGAYA, Satoshi MOTOZUKA, Kiyoshi OHNUMA, Yukio MIYASHITA, Yoshiharu MUTOHAbstractThis study aims to reveal the effects of pressure during cold isostatic pressing (CIP) on the microstructure and optical properties of fluorescent HAp complexes. Although the microsturucture-dependent properties of fluorescent HAp complexes have been reported to improve the antibacterial properties of photocatalyst coating layers, the mechanism behind the changes in the fluorescence properties of highly compressed HAp complexes has not yet been unveiled. CIP was successfully used to fabricate fluorescent HAp – amino acid complexes, and their fluorescence intensities increased with increasing fabrication pressure. Peak wavelength of fluorescence emitted by the HAp – amino acid complexes exhibited yellow to red shift. Although the thickness of the amino acid layer was saturated in higher pressure cases, the concentration of amino acids increased proportionally with pressure, which suggests changes in the packing structures of the ligands in the HAp– amino acid complexes. Polarized Raman spectroscopy measurements clearly detected ligands normally arranged to the HAp layer under high pressure fabrication conditions, which can provide the tightly packed ligand structure in the HAp– amino acid complexes. These tightly packed ligand structure in the HAp– amino acid complexes could emit stronger fluorescence owing to the increased density of complexations. This newly found pressure dependency in the optical properties of HAp–amino acid complexes is beneficial for developing biocompatible fluorescence materials or enhancement agents for antibacterial coating layers.
  • Optimizing the deformation behavior of stent with nonuniform Poisson's
           ratio distribution for curved artery
    • Abstract: Publication date: Available online 5 September 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Yafeng Han, Wenfeng LuStent implantation at a highly curved artery has always been a challenge, considering the relatively high chance of in-stent restenosis (ISR) caused by severe straightening effect and high strain energy over the vessel wall. In this paper, a novel optimization based design method was proposed to manipulate the deformation behavior of the common ring-and-link stent. By changing the location of the connection point between rings and links, traditional ring-and-link structure was modified to achiever tunable Poisson's ratio (PR). With the nonuniform cellular structure design method proposed in a previous study, PR distribution of the stent structure was optimized to achieve the desired curvature. As a result, the obtained stent structure with nonuniform PR could perfectly fit into the curved artery after expansion, without causing any obvious vessel straightening. To validate the proposed method, two different vessel models were introduced. Firstly, a short vessel with a constant curvature was set as the design objective, and both numerical and experimental tests were conducted. Further, a patient-specific vessel was applied. Both test results showed that optimized stents would cause much smaller vessel straightening. Moreover, vessels stented by the optimized structures had much lower stress concentration and strain energy. All those properties will decrease the possibility of ISR significantly.Graphic abstractGraphical abstract for this article
  • Effect of graphene on setting and mechanical behaviour of tricalcium
           phosphate bioactive cements
    • Abstract: Publication date: Available online 5 September 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Carmen Baudín, Teresa Benet, Pilar PenaAbstractThe potential reinforcing effect of graphene on calcium phosphate cements (CPCs)-based for injectable bone substitutes and scaffolds is presented. The influence of graphene (0–3.84 vol.%) on the microstructural development during setting and the resultant mechanical properties of CPCs constituted by α+β-tricalcium phosphate is analysed. Optimum setting conditions were established using uniaxial compression strength of CPC and composites with pristine and functionalized graphene and liquid/solid ratios (L/S = 0.5–0.6 mL/g) that allowed the mixing and spatulation of the powders. Tensile strength of optimised materials has been determined using the Diametric Compression of Discs Test (DCDT). X-ray diffraction, Raman spectroscopy and FE-SEM-EDS on fracture surfaces were used to investigate phase composition and morphological changes in set specimens. Strengthening occurs for functionalized graphene additions up to 1.96 vol.% due to different toughening mechanisms. Crack deflection, bridging and branching by graphene and, finally, the pull-out of the unbroken graphene sheets have been identified. Interlayer sliding between the graphene before pulling-out is an additional toughening process. Main effect of graphene on strength is the increase of reliability.
  • Magic angles and fibre stretch in arterial tissue: insights from the
           linear theory
    • Abstract: Publication date: Available online 5 September 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): C.O. Horgan, J.G. MurphyAbstractThis work is motivated by the current widespread interest in modelling the mechanical response of arterial tissue. A widely used approach within the context of anisotropic nonlinear elasticity is to use an orthotropic incompressible hyperelasticity model which, in general, involves a strain-energy density that depends on seven independent invariants. The complexity of such an approach in its full generality is daunting and so a number of simplifications have been introduced in the literature to facilitate analytical tractability. An extremely popular model of this type is where the strain energy involves only three invariants. While such models and their generalisations have been remarkably successful in capturing the main features of the mechanical response of arterial tissue, it is generally acknowledged that such simplified models must also have some drawbacks. In particular, it is intuitively clear that the correlation of such models with experiment will suffer limitations due to the restricted number of invariants considered. Our purpose here is to use the linearised theory for infinitesimal deformations to provide some guidelines for the development of a more robust nonlinear theory. The linearised theory for incompressible orthotropic materials is developed and involves six independent elastic constants. The general stress-strain law is inverted to provide an expression for the fibre stretch in terms of the stress. We examine the linearised response for simple tension in two mutually perpendicular directions corresponding to the axial and circumferential directions in the artery, obtaining an explicit expression for the fibre stretch in terms of the applied tension, fibre angle and linear elastic constants. The focus is then on determining the range of fibre orientation angles that ensure that the fibres are in tension in these simple tension tests. It is shown that the fibre stretch is positive for both simple tension tests if and only if the fibre angle is restricted to lie between two special angles called generalised magic angles. For the special case where the strain-energy function for the nonlinear model depends only on the three invariants I1,I4,I6, it is shown that the corresponding linearised model, called the standard linear model (SLM), depends on three elastic constants and the fibre stretch is positive only in the small range of fibre angles between the classic magic angles 35.26° and 54.74°. However, when the two additional invariants I5,I7 are included in the nonlinear strain energy so that the corresponding linear model involves four elastic constants, it is shown that the domain of fibre angle for which the stretch is positive is much larger and that the fibre stretch is monotonic with respect to the fibre angle in this range.
  • Effect of organic/inorganic nanoparticles on performance of polyurethane
           nanocomposites for potential wound dressing applications
    • Abstract: Publication date: Available online 4 September 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Arman Jafari, Shadi Hassanajili, Mohammad Bagher Karimi, Amir Emami, Farnaz Ghaffari, Negar AzarpiraThis study focuses on the evaluation and modification of polyurethane (PU) membranes containing organic and inorganic nanoparticles for potential use as a wound dressing. For the purpose of PU nanocomposite preparation, chitosan (CS) was converted into nanoparticles by the ionic-gelation method to improve its blending capability with the PU matrix. These CS nanoparticles (nano-CS) were obtained as a hyrdophilic organic filler with different contents and were utilized along with inorganic titanium dioxide (TiO2) nanoparticles in the nanocomposite membrane preparation. The membranes were prepared using phase inversion technique and their microstructure was controlled by manipulating the solvent non-solvent exchange rate. Obtained results demonstrate that addition of polymer solvent to nonsolvent induced a microstructure alteration from finger-like to sponge-like, which is more suitable for fluid uptake and consequently more useful for wound dressing applications. Similar results were obtained by introduction of nanoparticles to membranes. Due to the polar nature of nanoparticles and their effects on PU structure, prepared membranes showed 71.5% improve in swelling when compared to neat PU. Moreover, the reinforcement effect of nanoparticles caused an 18.94% increase in ultimate tensile strength in comparison with bare PU film, while elongation at break was not affected considerably. In addition, prepared PU nanocomposite films showed suitable antibacterial activity of 69% against Staphylococcus aureus and did not show any toxicity to human fibroblast cells. Based on these results, simultaneous use of TiO2 and chitosan nanoparticles can improve both physical and antibacterial properties of PU as an ideal wound dressing.Graphical abstractGraphical abstract for this article
  • The role of water in the initial sliding of nacreous tablets: findings
           from the torsional fracture of dry and hydrated nacre
    • Abstract: Publication date: Available online 31 August 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Saleh Alghamdi, Fen Du, Jie Yang, Ting TanNacre exhibits remarkable mechanical properties resulting from its hierarchical brick-and-mortar structures. By using pure shear stresses of torsion, we demonstrate how nacre resists the initial tablet sliding by tuning its nanoscale toughening mechanisms in dry and hydrated conditions. In hydrated nacre, hydrogen bonds between water molecules and organic matrices provide temporal paths for stress redistributions, through which the shear resistance is gradually transferred from mineral bridges to contacted nanoasperities. In the subsequent sliding, dynamical interactions between nacreous tablets enable substantial plasticity before the catastrophic failure of hydrated nacre. Our findings should help pursuing further insights into the interfacial behavior of natural and artificial laminated nanomaterials under different conditions.Graphical abstractGraphical abstract for this article
  • Influence of primers on the properties of the adhesive interface between
           resin composite luting cement and fiber-reinforced composite
    • Abstract: Publication date: Available online 31 August 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Aftab A. Khan, Abdulaziz A. Al-Kheraif, Badreldin A. Mohamed, Leila Perea-Lowery, Eija Säilynoja, Pekka K. VallittuAbstractObjectivesThe purpose of this study was to characterize the adhesive interface formed due to the dissolving capability of 4 primer systems into pre-polymerized semi-interpenetrating polymer network (semi-IPN)-based fiber-reinforced composite (FRC) and luting cement.Materials and methodsSemi-IPN FRC (everStick C&B, StickTech) prepregs stored for various durations (at 4 °C; 1, 1.5, and 3 years) were used to fabricate the specimens. FRC specimens (n=10) were light-cured and treated with primers before adhering a luting cement onto them. Each age group was divided into four subgroups according to the primer used: no priming, a dimethacrylate adhesive primer, universal primer, and primer intended for composite surfaces. The degree of monomer conversion (DC%) of the luting cement; nanohardness, elastic modulus and structural information of the luting cement–FRC adhesive interface were measured.ResultsAccording to analysis of variance (P≤0.05), no statistical difference was observed in the DC% among the tested groups. However, both universal and composite primers showed increased nanohardness in 1- and 1.5-year-aged groups. The highest nanohardness (0.55 ± 0.21 GPa) and elastic modulus (14.27 ± 5.19 GPa) were observed in specimens of 1-year-aged FRC primed with the application of universal primer. Raman spectroscopy and scanning electron microscopy examination confirmed the presence of poly(methyl methacrylate) at the interface when the FRC prepregs were aged for 3 years before use.ConclusionBoth primers improved diffusion of monomers of composite luting cement into the polymerized semi-IPN polymer structure and possible covalent binding with pendant methacrylate groups in the polymer matrix of FRC. The diffusing capability of universal and composite primers might increase the opportunity to form solid adhesive interface bonding between the FRC and composite luting cement.
  • Mechanical and Structural Analysis of the Pulmonary Valve in Congenital
           Heart Defects: A Presentation of Two Case Studies
    • Abstract: Publication date: Available online 31 August 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Fatiesa Sulejmani, Anastassia Pokutta-Paskaleva, Olga Salazar, Mohsen Karimi, Wei SunAbstractObjectiveCongenital Heart Disease (CHD) is the leading cause of pediatric mortality, with many cases affecting the right ventricular outflow tract (RVOT) or pulmonary valve (PV). Understanding the mechanics of the disease condition can provide insight into development of durable repair techniques and bioengineered replacement devices. This work presents a mechanical and structural analysis of the pulmonary valve of two pediatric cases.MethodsTwo PV tissues were excised as part of the operative procedure. One PV was obtained from a 9-month-old with Noonan syndrome (Patient 1) and the other from a 6-month-old with tricuspid atresia (Patient 2). The leaflets were subjected to planar biaxial tensile testing and second harmonic generation (SHG) imaging for mechanical and structural evaluation.Results and DiscussionPatient 1 exhibited a more anisotropic mechanical response than Patient 2, with sample stiffness on par with that of adult PV tissue. Additionally, both samples showed radial and circumferential alignment of collagen fibers on the ventricularis and fibrosa sides of the leaflets, respectively. Collagen fibers on the fibrosa side were also more crimped than on the ventricularis side.
  • Visco-Elasto-Plastic modeling of small intestinal submucosa (SIS) for
           application as a vascular graft
    • Abstract: Publication date: Available online 31 August 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Paolo Sánchez Puccini, Juan Carlos Briceño TrianaIn developing new tissue engineered for vascular grafts, the mechanical properties of the material and its evolution once implanted are of utmost importance because they determine the regeneration of the vessel and the blood flow through the conduit. In fact, compliance mismatch is considered the main determinant of graft failure. In this research, we analyze the dynamic properties of the small intestinal submucosa (SIS), and propose and validate a constitutive model to fit the material's behavior. A uniaxial creep and recovery test was performed on SIS tubes to find the constitutive parameters. The model was composed by an elastic element in series with two Kelvin-Voigt solid elements and a plastic slider. The first elastic component was defined using Mooney-Rivlin strain energy function, while the plastic component was defined using a third-degree polynomial function of the plastic stress. The viscoelastic behavior was defined using the creep compliance formulation for the Kelvin-Voigt model. The parameters for the plastic and non-linear elastic elements followed a normal distribution, while the spring and dashpot constants of the visco-elastic element had a linear dependence on the load applied. The constitutive model was then used to simulate the SIS under the geometrical and pressure conditions found in native vessels for 1000 cycles at a frequency of 60 cycles per minute. From the cases simulated, performance curve charts were obtained in terms of the compliance of the material. These curve charts can be used as a predictive tool of the graft's behavior based on its geometry.Graphical abstractGraphical abstract for this article
  • The effect of 3D-printed Ti6Al4V scaffolds with various macropore
           structures on osteointegration and osteogenesis: a biomechanical
    • Abstract: Publication date: Available online 31 August 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Han Wang, Kexin Su, Leizheng Su, Panpan Liang, Ping Ji, Chao WangAbstractA properly designed porous scaffold can accelerate the osseointegration process, and the use of computer-aided design (CAD) and additive manufacturing (AM) techniques has the potential to improve the traditional porous scaffold approach. In this study, we evaluate the effect of porous Ti6Al4V (Ti) with different pore structures on osteointegration and osteogenesis. Porous Ti scaffolds with different pore structures based on four commercially available implants were designed and manufactured by CAD and selective laser melting (SLM). Micro-CT showed that SLM was able to produce Ti scaffolds with different pore structures. The mechanical properties evaluated by finite element analysis and compression tests indicated that the four porous scaffolds in our study were mechanically adapted, despite their different mechanical properties. Then, we used 3D-printed porous discs to culture human bone marrow mesenchymal stem cells (hBMMSCs), the main seed cells of bone tissue engineering. The results showed no significant difference among the four groups in cell morphology, viability and proliferation. In addition, four groups showed a comparable mineralization ability even though Ti-g had a higher alkaline phosphatase activity (ALP). In vivo tests in a rabbit model showed that all four groups were suitable for new bone ingrowth and integration. These findings indicate that the four different pore structures in the Ti scaffolds provided good osteointegration and osteogenesis.
  • Design of a Surrogate for Evaluation of Methods to Predict Bone Bending
    • Abstract: Publication date: Available online 30 August 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Caitlyn J. Collins, Matt Boyer, Thomas Crenshawm, Heidi-Lynn PloegAbstractThe high incidence of osteoporosis and related fractures demands for the use and development of methods capable of detecting changes in bone mechanical properties. The most common clinical and laboratory methods used to detect changes in bone mechanical properties, such as stiffness, strength, or flexural rigidity, include: mechanical testing, medical imaging, medical image-based analytical calculations, and medical image-based finite element analysis. However, the innate complexity of bone makes validation of the results from each method difficult. The current study presents the design, fabrication, and functional testing of a bi-material and computed tomography scan compatible bone-surrogate which provides consistent reproducible mechanical properties for methodological evaluation of experimental, analytical, and computational bone bending stiffness prediction methods.
  • Biphasic Analysis of Rat Brain Slices Under Creep Indentation Shows
           Nonlinear Tension-Compression Behavior
    • Abstract: Publication date: Available online 30 August 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Ruizhi Wang, Malisa SarntinoranontAbstractBiphasic theory can provide a mechanistic description of deformation and transport phenomena in soft tissues, and has been used to model surgery and drug delivery in the brain for decades. Knowledge of corresponding mechanical properties of the brain is needed to accurately predict tissue deformation and flow transport in these applications. Previously in our group, creep indentation tests were conducted for multiple anatomical regions in acute rat brain tissue slices. In the current study, a biphasic finite element model of creep indentation was developed with which to compare these data. Considering the soft tissue structure of brain, the solid matrix was assumed to be composed of a neo-Hookean ground matrix reinforced by continuously distributed fibers that exhibits tension-compression nonlinearity during deformation. By fixing Poisson's ratio of the ground matrix, Young's modulus, fiber modulus and hydraulic permeability were estimated. Hydraulic permeability was found to be nearly independent of the properties of the solid matrix. Estimated modulus (40 Pa ~1.1 kPa for the ground matrix, 3.2~18.2 kPa for fibers) and hydraulic permeability (1.2~5.5×10-13m4/N s) fell within an acceptable range compared with those in previous studies. Instantaneous indentation depth was dominated by tension provided by fibers, while the tissue response at equilibrium was sensitive to Poisson's ratio. Results of sensitivity analysis also point to the necessity of considering tension-compression nonlinearity in the solid phase when the biphasic material undergoes large creep deformation.
  • Effect of pore geometry on the fatigue properties and cell affinity of
           porous titanium scaffolds fabricated by selective laser melting
    • Abstract: Publication date: Available online 30 August 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Danlei Zhao, Yutian Huang, Yong Ao, Changjun Han, Qian Wang, Yan Li, Jie Liu, Qingsong Wei, Zhen ZhangPorous titanium scaffolds with different unit cell type (tetrahedron and octahedron) and pore size (500 μm and 1000 μm) were fabricated by selective laser melting (SLM), and the effects of unit cell type and pore size on their fatigue properties and cell affinity were studied. The fatigue properties were performed by static and dynamic mechanical testing, while the cell affinity was evaluated in vitro with mouse osteoblast cells. It was found that octahedron scaffolds exhibited superior static mechanical properties, longer fatigue lives and higher fatigue strength in comparison to those of tetrahedron ones. As expected, scaffolds with 1000 μm pore resulted in lower compressive properties and shorter fatigue lives compared to those with 500 μm pore. The differences were analyzed based on the unit cell structure, porosity, and manufacturing imperfections. Scanning electron microscopy (SEM) and immunofluorescence showed that cells spread better on octahedron scaffolds than those on tetrahedron ones. Meanwhile, the scaffolds with 1000 μm pore were more suitable for cell attachment and growth within the same unit cell owing to higher porosity. The comparison of different pore geometry on the mechanical and biological property provided further insight into designing an optimal porous scaffold.Graphical abstractGraphical abstract for this article
  • Origin of low Young modulus of multicomponent, biomedical Ti alloys -
           seeking optimal elastic properties through a first principles
    • Abstract: Publication date: Available online 30 August 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): P. Kwasniak, J.S. Wróbel, H. GarbaczAbstractMulticomponent, biomedical β-Ti alloys offer ultra-low Young modulus values that are related to a unique and poorly understood reduction of C44 and C’ elastic constants in comparison with binary systems. The elastic properties of such materials are difficult to control due to the large variations occurring even for a small change in chemical composition, which cannot be explained using existing theories. In this article, we investigate the above issues through systematic ab initio elastic constants calculations for a series of binary, ternary and quaternary Ti alloys. Special attention is paid to examining the reliability of the methodology adopted and to clarifying the atomic scale mechanisms that affect the mechanical properties of the systems analysed. It was found that the lower boundary of the polycrystalline Young modulus of Ti-Nb-base β phase is close to 50 GPa, and strongly depends on two specific electronic hybridisations related to niobium and simple metals addition that control C44 and C’. Based on the relationship established between electronic structure and mechanical properties, we propose several quaternary alloys whose directional Young modulus values are equal or similar to that of human bones. Some electronic-based guidelines for designing new multicomponent β-Ti alloys are also formulated.
  • A three-dimensional micromechanical model of brain white matter with
           histology-informed probabilistic distribution of axonal fibers
    • Abstract: Publication date: Available online 30 August 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Seyed Abdolmajid Yousefsani, Farzam Farahmand, Amir ShamlooAbstractThis paper presents a three-dimensional micromechanical model of brain white matter tissue as a transversely isotropic soft composite described by the generalized Ogden hyperelastic model. The embedded element technique, with corrected stiffness redundancy in large deformations, was used for the embedment of a histology-informed probabilistic distribution of the axonal fibers in the extracellular matrix. The model was linked to a multi-objective, multi-parametric optimization algorithm, using the response surface methodology, for characterization of material properties of the axonal fibers and extracellular matrix in an inverse finite element analysis. The optimum hyperelastic characteristics of the tissue constituents, obtained based on the axonal and transverse direction test results of the corona radiata tissue samples, indicated that the axonal fibers were almost thirteen times stiffer than the extracellular matrix under large deformations. Simulation of the same tissue under a different loading condition, as well as that of another white matter tissue, i.e., the corpus callosum, in the axonal and transverse directions, using the optimized hyperelastic characteristics revealed tissue responses very close to those of the experiments. The results of the model at the sub-tissue level indicated that the stress concentrations were considerably large around the small axons, which might contribute into the brain injury.
  • Femoral entheseal shape and attachment angle as potential risk factors for
           anterior cruciate ligament injury
    • Abstract: Publication date: Available online 30 August 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Callan M. Luetkemeyer, Benjamin C. Marchi, James A. Ashton-Miller, Ellen M. ArrudaAbstractAlthough non-contact human ACL tears are a common knee injury, little is known about why they usually fail near the femoral enthesis. Recent histological studies have identified a range of characteristic femoral enthesis tidemark profiles and ligament attachment angles. We tested the effect of the tidemark profile and attachment angle on the distribution of strain across the enthesis, under a ligament stretch of 1.1. We employed a 2D analytical model followed by 3D finite element models using three constitutive forms and solved with ABAQUS/Standard. The results show that the maximum equivalent strain was located in the most distal region of the ACL femoral enthesis. It is noteworthy that this strain was markedly increased by a concave (with respect to bone) entheseal profile in that region as well as by a smaller attachment angle, both of which are features more commonly found in females. Although the magnitude of the maximum equivalent strain predicted was not consistent among the constitutive models used, it did not affect the relationship observed between entheseal shape and maximum equivalent strain. We conclude that a concave tidemark profile and acute attachment angle at the femoral ACL enthesis increase the risk for ACL failure, and that failure is most likely to begin in the most distal region of that enthesis.
  • Atomic force microscopy measurements probing the mechanical properties of
           single collagen fibrils under the influence of UV light in situ
    • Abstract: Publication date: Available online 30 August 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Marcus Schulze, Melanie Rogge, Robert W. StarkCollagen plays a decisive role as a functional substrate in tissue engineering. In particular, the rigidity of the collagen influences the behaviour of the attached cells. Thus, modification and controlled adjustment of collagen's characteristics are essential. To this end, controlled exposure to ultraviolet (UV) light is a promising process because it can be temporally and spatially well defined. In this study, we investigated the effect of UV exposure on surface supported single collagen fibrils in situ. This procedure allowed for a direct comparison between the untreated and modified states of type I collagen. Atomic force microscopy was used to map the mechanical properties. Exposure to UV light was used to influence the mechanical properties of the fibrils in varied liquid environments (deionized water and phosphate-buffered saline (PBS)). The results led to the assumption that combined UV/thermal treatment in deionized water continuously lowers the elastic modulus. In contrast, experiments performed in PBS-based solutions in combination with UV-B and UV-C light or thermal treatment up to 45 °C suggested an increase in the modulus within the first 30 to 40 minutes that subsequently decreased again. Thus, the wavelength, exposure, temperature, and chemical environment are relevant parameters that need to be controlled when modifying collagen using UV light.Graphical abstractGraphical abstract for this article
  • Synthesis and characterization of bio-compatible shape memory polymers
           with potential applications to endovascular embolization of intracranial
    • Abstract: Publication date: Available online 29 August 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Robert Kunkel, Devin Laurence, Jingyu Wang, Donnie Robinson, Joshua Scherrer, Yi Wu, Bradley N. Bohnstedt, Aichi Chien, Yingtao Liu, Chung-Hao LeeIntracranial aneurysms (ICAs) are focal dilations in the brain's arteries. When left untreated, ICAs can grow to the point of rupture, accounting for 50–80% of subarachnoid hemorrhage cases. Current treatments include surgical clipping and endovascular coil embolization to block circulation into the aneurysmal space for preventing aneurysm rupture. As for endovascular embolization, patients could experience aneurysm recurrence due to an incomplete coil filling or compaction over time. The use of shape memory polymers (SMPs) in place of conventional platinum coils could provide more control and predictability for mitigating these complications. This study was focused on characterization of an aliphatic urethane-based SMP to evaluate its potential as a novel biomaterial for endovascular embolization. Twelve compositions of the SMP were synthesized and their thermomechanical properties together with the shape recovery behavior were comprehensively investigated. Our results showed that the SMPs experienced a significant decrease in storage and loss moduli as heated above their glass transition temperatures (32.3°C-83.2 °C), and that all SMPs were thermally stable up to 265 °C. Moreover, the SMPs exhibited both composition-dependent stress relaxation and a decrease in elastic modulus during cyclic loading. The shape recovery time was less than 11 seconds for all SMP compositions, which is sufficiently short for shape changing during embolization procedures. Several candidate compositions were identified, which possess a glass transition temperature above body temperature (37 °C) and below the threshold of causing tissue damage (45 °C). They also exhibit high material strength and low stress relaxation behavior, suggesting their potential applicability to endovascular embolization of ICAs.Graphical abstractGraphical abstract for this article
  • Breast implant surface texture impacts host tissue response
    • Abstract: Publication date: Available online 28 August 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Michael Atlan, Gina Nuti, Hongpeng Wang, Sherri Decker, TracyAnn PerryBackgroundSurface texture of a breast implant influences tissue response and ultimately device performance. Characterizing differences among available surface textures is important for predicting and optimizing performance.MethodsScanning electron microscopy (SEM) and X-ray computed tomography (CT)-imaging were used to characterize the topography and surface area of 12 unique breast implant surface textures from seven different manufacturers. Samples of these surface textures were implanted in rats, and tissue response was analyzed histologically. In separate experiments, the force required to separate host tissue from the implant surface texture was used as a measure of tissue adherence.ResultsSEM imaging of the top and cross section of the implant shells showed that the textures differed qualitatively in evenness of the surface, presence of pores, size and openness of the pores, and the depth of texturing. X-ray CT imaging reflected these differences, with the texture surface area of the anterior of the shells ranging from 85 to 551 mm2, which was 8% to 602% greater than that of a flat surface. General similarities based on the physical structure of the surfaces were noted among groups of textures. In the rat models, with increasing surface texture complexity, there was increased capsule disorganization, tissue ingrowth, and tissue adherence.ConclusionsSurface area and topography of breast implant textures are important factors contributing to tissue ingrowth and adherence. Based on surface area characteristics and measurements, it is possible to group the textures into four classifications: smooth/nanotexture (80–100 mm2), microtexture (100–200 mm2), macrotexture (200–300 mm2), and macrotexture-plus (>300 mm2).Graphical abstractGraphical abstract for this article
  • Discrimination between HCV29 and T24 by controlled proliferation of cells
           co-cultured on substrates with different elasticity
    • Abstract: Publication date: Available online 28 August 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): J. Raczkowska, S. Prauzner-BechcickiIn this work the impact of substrate elasticity on the proliferation of two cell lines, a non-malignant transitional epithelium HCV-29 and a bladder transitional cell carcinoma T24 cultured individually and in co-culture was analyzed. A significantly stronger, highly cell-dependent impact of mechanical properties on cellular behavior was shown for cells co-cultured from the mixture. A more effective proliferation process observed for T24 cells was analyzed quantitatively for asymmetric HCV29:T24 mixtures co-cultured on soft substrate. The obtained results suggests that the proliferation of T24 cells is even 4 times more effective as compared to HCV29 cells and confirm strong invasiveness of metastatic T24 cells. The high adaptiveness of T24 cells to adverse environmental conditions enables easy and accurate discrimination between not isolated healthy and cancer cells.Graphical abstractGraphical abstract for this article
  • Jointly modified mechanical properties and accelerated hydrolytic
           degradation of PLA by interface reinforcement of PLA-WF
    • Abstract: Publication date: Available online 28 August 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Wan Lu, Zhang YanhuaPolylactic acid (PLA), one of the most likely green and environmentally friendly materials, is an alternative to petroleum-based plastic. It still remains a challenge to increase the degradation rate and decrease the cost of PLA without compromised mechanical properties. Low cost PLA/wood flour (WF) composite was elaborately designed and fabricated with improved interface compatibility through the introducing of polymethyl methacrylate (PMMA). The result indicated that compared with that of neat PLA, the tensile strength and bending strength of PLA/WF/PMMA (8:2) (80 wt% of the PLA, 20 wt% of WF and PMMA (8:2)) were increase by 4.60% and 26.54% respectively. Through the hydrolysis experiments combined with the SEM analysis, the main reason for the improvement of the mechanical properties of composite materials was that PMMA makes continuous three-phase composition, and interface compatibility of PLA and WF with overly different polarity was modified. Meanwhile, the hydrolysis rate of PLA/WF/PMMA was much faster than that of PLA. Finally, there was a more significant discovery that the addition of PMMA changed material degradation mechanism, and it was why to efficiently accelerate the degradation rate of the material. This will provide a new inspiration for PLA degradation research, and a fresh perspective is to be given other materials.Graphical abstractGraphical abstract for this article
  • Effect of the cushioning running shoes in ground contact time of phases of
    • Abstract: Publication date: Available online 25 August 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Andrea Roca-Dols, Marta Elena Losa-Iglesias, Rubén Sánchez-Gómez, Ricardo Becerro-de-Bengoa-Vallejo, Daniel López-López, David Rodríguez-Sanz, Eva María Martínez Jiménez, César Calvo-LoboAbstractThe main objective of this research was to know how five different cushioning shoes may interfere in ground contact times of each gait phase of walking and running in contrast with barefoot condition. Thirty healthy sport recreational male runners participated in this study. They played over a treadmill wearing minimalist, Boost®, Ethyl-vinyl-acetate (EVA), Air® chamber and pronation-control cushioning shoes technologies and under barefoot condition, recording the last 30 seconds of walking and running at 5.17 km/h and 9 km/h respectively, while ground contact time duration of each phase of gait was recorded with circular standard pressure sensors located on plantar feet. During walking, the heel contact phase was the station that increased significantly ground contact times wearing all sole cushioning shoes (p
  • The Relationship between Thiol-acrylate Photopolymerization Kinetics and
           Hydrogel Mechanics: An Improved Model Incorporating Photobleaching and
           Thiol-Michael Addition
    • Abstract: Publication date: Available online 24 August 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Hongyuan Zhu, Xiaoxiao Yang, Guy M. Genin, Tian Jian Lu, Feng Xu, Min LinAbstractBiocompatible hydrogels with defined mechanical properties are critical to tissue engineering and regenerative medicine. Thiol-acrylate photopolymerized hydrogels have attracted special interest for their degradability and cytocompatibility, and for their tunable mechanical properties through controlling factors that affect reaction kinetics (e.g., photopolymerization, stoichiometry, temperature, and solvent choice). In this study, we hypothesized that the mechanical property of these hydrogels can be tuned by photoinitiators via photobleaching and by thiol-Michael addition reactions. To test this hypothesis, a multiscale mathematical model incorporating both photobleaching and thiol-Michael addition reactions was developed and validated. After validating the model, the effects of thiol concentration, light intensity, and pH values on hydrogel mechanics were investigated. Results revealed that hydrogel stiffness (i) was maximized at a light intensity-specific optimal concentration of thiol groups; (ii) increased with decreasing pH when synthesis occurred at low light intensity; and (iii) increased with decreasing light intensity when synthesis occurred at fixed precursor composition. The multiscale model revealed that the latter was due to higher initiation efficiency at lower light intensity. More broadly, the model provides a framework for predicting mechanical properties of hydrogels based upon the controllable kinetics of thiol-acrylate photopolymerization.
  • Mechanical and biological performance of axially loaded novel
           bio-nanocomposite sandwich plate-type implant coated by biological polymer
           thin film
    • Abstract: Publication date: Available online 24 August 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): S. Sahmani, S. Saber-Samandari, M. Shahali, H. Joneidi Yekta, F. Aghadavoudi, AH. Montazeran, M.M. Aghdam, A. KhandanAbstractPost-surgical infection is one of the essential problems in bone scaffolds that is usually treated with antibiotics. This issue may be related to the poor blood supply for bone tissue due to high concentrations of drug. In the current study, the effect of zinc oxide (ZnO) nanoparticles on the antibacterial behavior of the nanocrystalline hydroxyapatite (n-HA) scaffolds coated by gelatin-ibuprofen (GN-IBO) is evaluated. To this end, the bio-nanocomposite scaffolds are fabricated via the space holder technique and then characterized with the aid of X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The compressive strength, fracture toughness, porosity, elastic modulus as the mechanical properties, and the apatite formation, biodegradation, drug release and wettability beside the roughness as the biological properties are predicted. The obtained experimental results indicate that the bio-nanocomposite scaffolds containing 10 wt% ZnO has suitable mechanical and biological properties. After that, an analytical model is developed to predict the nonlinear instability and vibration responses of an axially loaded sandwich plate-type implants made of the fabricated n-HA-ZnO bio-nanocomposites coated by GN-IBO thin film corresponding to various weight fractions of ZnO nanoparticles. It is found that ZnO peaks in the positions of 2θ are equal to 31.6°, 33.6°, 34°, 46.4°, and 62°, which represent the crystalline characteristics. Also, it is revealed that through addition of ZnO nanoparticles, the hardness and elastic modulus as well as the bone formation and biodegradation rate of the bio-nanocomposite scaffold enhance, while its drug release in the phosphate buffer solution detected with UV spectrum reduces. It is found that by increasing the ZnO weight fraction, the critical axial buckling load of the sandwich bio-nanocomposite implant enhances, and it buckles at lower axial shortening. However, it is seen that for higher value of wt% ZnO, its influence on the critical buckling load decreases.
  • The Determining Role of Nanoscale Mechanical Twinning on Cellular
           Functions of Nanostructured Materials
    • Abstract: Publication date: Available online 24 August 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): K.C. Nune, I. Montes, V.S.Y. Injeti, M.C. Somani, R.D.K. MisraAbstractConsidering that micromotions generated at the bone-implant interface under physiological loading introduce mechanical strain on the tissue and surface of the implant and that strain can be introduced during processing of the biomedical device, we elucidate here the interplay between mechanically-induced nanoscale twinning in austenitic stainless steel on osteoblast functions. Mechanically-induced nanoscale twinning significantly impacted cell attachment, cell-substrate interactions, proliferation, and subsequent synthesis of prominent proteins (fibronectin, actin, and vinculin). Twinning was beneficial in favorably modulating cellular activity and contributed to small differences in hydrophilicity and nanoscale roughness in relation to the untwinned surface.
  • Fatigue behavior and surface characterization of a Y-TZP after laboratory
           grinding and regeneration firing
    • Abstract: Publication date: Available online 23 August 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Gabriela Scatimburgo Polli, Gabriel Rodrigues Hatanaka, Filipe de Oliveira Abi-Rached, Márcio de Souza Góes, José Mauricio dos Santos Nunes ReisAbstractThis study evaluated the effect of grinding and regeneration firing on the flexural fatigue limit and surface characterization of LavaTM Y-TZP ceramic. Forty bar-shaped specimens with 20×4.0×1.2 mm constituted the as-sintered group (AS = control group), and 80 specimens with 20×4.0×1.5 mm were ground with cylindrical laboratory stone under water-cooling (WG) or in a dry condition (G) to reach 1.2 mm in thickness. Half of specimens were submitted to regeneration firing (1000 ºC, 30 min), forming the groups AS/R, WG/R and G/R. Fatigue limit (500,000 cycles, 10 Hz) was determined by staircase method in a 4-point flexural fixture. Data were analyzed by 2-way ANOVA and Tukey HSD tests (α=.05). The surface topography (n=3) and fracture area (n=3) were evaluated by SEM. Samples were also analyzed by Rietveld refinement from X-ray diffraction data. ANOVA revealed significant differences (PAS>G (P
  • Effects of Artificial Aging and Progression of Cracks on Thin Occlusal
           Veneers Using SD-OCT
    • Abstract: Publication date: Available online 23 August 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Christine Yazigi, Hartmut Schneider, Mohamed Sad Chaar, Claudia Rüger, Rainer Haak, Matthias KernAbstractObjectivesThe purpose of this study was to evaluate the effects of artificial aging on thin glass-ceramic occlusal premolar veneers, adhesively bonded to dentin, by examining the changes caused by artificial aging using spectral domain optical coherence tomography (SD-OCT). In addition, the development of cracks in the ceramic veneers and their possible influence on the behavior of the ceramic restorations were examined.MethodsIn total, 48 extracted sound upper premolars were prepared in the dentin for occlusal veneers milled from lithium disilicate ceramic blocks (IPS e.max CAD, Ivoclar Vivadent, Liechtenstein). All restorations were adhesively bonded using resin cement (Variolink Esthetic DC, Ivoclar Vivadent). Specimens were 3-dimensionally and 2-dimensionally imaged by SD-OCT (Telesto II, Thorlabs GmbH, Germany), then subjected to thermal-dynamic loading in a chewing simulator with 1,200,000 cycles at a load of 10 kg. Specimens were 2D and 3D imaged again after the artificial aging. Finally, they were subjected to quasi-static loading using a universal testing machine until failure occurred and later examined microscopically to assess the mode of failure. ANOVA test was performed for statistical analysis of data and Tukey’s post-hoc test was used to compare the groups at 5% significance level. Chi-Square Test and Fischer’s Exact Test of Independence were conducted to test the association between nominal variables.ResultsNo changes or irregularities were observed in the cement layer or tooth substrate after the aging process. However, wear of the ceramic was noticed at the surface of contact with the antagonist during the test. The development of cracks was detected in 23% of the specimens. Cracks did not affect the fracture strength (p>0.05) but influenced the mode of failure (p≤0.001).SignificanceOptical coherence tomography allows an easy and non-invasive method to internally scan teeth and restorations. Development of cracks in the ceramic did not affect the fracture strength of the restorations but might lead to a more catastrophic type of failure.
  • Replication and Bioactivation of Ti-based Alloy Scaffold Macroscopically
           Identical to Cancellous Bone from Polymeric Template with TiNbZr Powders
    • Abstract: Publication date: Available online 23 August 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Xi Rao, Jihan Yang, Jing li, Xue Feng, Zilin Chen, Yidie Yuan, Binglian Yong, Chenglin Chu, Xiaodong Tan, Qunliang SongAbstractIn the present work, a new type of porous Ti-based alloy scaffold with high porosity (about 75%) and interconnected pores in the range of 300~1000 μm was fabricated by polymeric foam replication method with TiNbZr powders. This porous scaffold, which is consisted with major β phase Ti and minor α Ti phase, exhibits a compressive strength of 14.9 MPa and an elastic modulus of 0.21 GPa, resembling the mechanical properties of nature human cancellous bone (σ=10~50 MPa, E=0.01~3.0 GPa). To improve its osteogenic potential, a bioactive nanostructural titanate network coating was applied to the scaffold surface using hydrothermal treatment. The bone-like apatite inducing ability of the treated scaffold was systemically assessed using SBF immersion during 3~28 days. The nanostructural titanate network coated on porous TiNbZr scaffold is favorable for apatite nucleation and subsequent growth due to the hydrolysis of titanate. The results suggest that highly porous TiNbZr scaffolds with an appropriate bioactive coating, which was fabricated in this study, could be potentially used for bone tissue engineering application.
  • Effect of Setting Atmosphere on Apatite Cement Resorption: An In Vitro and
           In Vivo Study
    • Abstract: Publication date: Available online 23 August 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Arief Cahyanto, Kanji Tsuru, Kunio IshikawaAbstractObjectivesThe aim of this present study was to investigate the effect of setting atmosphere on replacement of apatite cement with new bone both in vitro and in vivo.Material and methodsApatite cement consisting of an equimolar mixture of tetracalcium phosphate and anhydrous dicalcium phosphate was mixed with distilled water and allowed to set at 37 °C and 100% relative humidity under 0%, 5%, and 100% CO2 atmospheres. X-Ray diffraction and Fourier Transform Infrared Spectroscopy were employed to confirm the carbonate apatite formation. Micro-CT and histological evaluation was made at 1 and 6 month(s) using twelve 10-week-old specific-pathogen-free male Wistar rats.ResultsB-type carbonate apatite was found when the apatite cement was set under 100% CO2 and 5% CO2. More carbonate apatite was formed in the case of 100% CO2 when compared with 5% CO2, and none was formed under 0% CO2. Interestingly, unreacted tetracalcium phosphate was significant when apatite cement was set under 0% CO2, indicating the formation of Ca-deficient hydroxyapatite. When a bone defect of rat tibia was reconstructed in these conditions of apatite cement and sintered hydroxyapatite, replacement of the apatite cement was confirmed 6 months after implantation, whereas no replacement was observed in the case of sintered hydroxyapatite. The amount of replacement of apatite cement with bone was greater, on the order of 100% CO2 and 5% CO2, followed by 0% CO2.ConclusionThe results obtained in the present study demonstrated that setting atmosphere clearly plays an important role in the replacement of set apatite cement with bone.
  • Scalable novel PVDF based nanocomposite foam for direct blood contact and
           cardiac patch applications
    • Abstract: Publication date: Available online 22 August 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Ratnakar Arumugam, Raj Kumar Chinnadurai, Bala Nehru Subramaniam, Bhuvaneshwar Devaraj, Veni Subramanium, Srinadhu Endu Sekhar, Satyanarayana NallaniAbstractScalable novel beta phase polyvinylidene fluoride - poly(methyl methacrylate) (PVDF-PMMA) polymer blend based nanocomposite foam with hydroxyapatite (HAp) and titanium dioxide (TiO2) as nanofillers (β-PVDF-PMMA/HAp/TiO2) (β-PPHT-f), was prepared by using salt etching assisted solution casting method. The prepared β-PPHT-f nanocomposite material was characterized using XRD, FT-IR, SEM-EDS. The XRD and FTIR results confirmed the formation of β phase of β-PPHT-f. The SEM and EDS results confirmed the formation of high porous structured closed cell type morphology of β-PPHT-f. It also, confirmed the uniform distribution of Ti, Ca, P, N and O, in β-PPHT-f. Contact angle measurements performed using sessile drop method with water and EDTA treated blood (EDTA blood) as probe liquids revealed that β-PPHT-f is hydrophilic with contact angle of 48.2° as well as hemophilic with contact angle of 13.7°. Porosity, fluid absorption and retention investigation by gravimetric analysis revealed that β-PPHT-f was 89.2% porous and can absorb and retain 139.15% and 87.05% of water and blood, respectively. The hemolysis assay performed as per ASTM F756 procedure revealed that β-PPHT-f is non hemolytic. Also, the Leishman stained blood smears prepared from whole blood incubated with β-PPHT-f for 3, 4, 5 and 6 hours at 37 ° C revealed that the blood cells were not affected by β-PPHT-f, its surface morphology and elemental composition. H9c2 cell line studies on a transparent film prepared using β-PPHT-f revealed that the elemental composition of the nanocomposite favored H9c2 cell adhesion and differentiation. All the characterization results indicate that the newly developed scalable novel β-PPHT-f is hemocompatible and cardiomyocyte compatible, suggesting it as a useful material for direct blood contact and cardiac patch applications.
  • Experimental reconstruction of an abdominal wall defect with electrospun
           polycaprolactone-ureidopyrimidinone mesh conserves compliance yet may have
           insufficient strength
    • Abstract: Publication date: Available online 21 August 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Lucie Hympanova, Marina Gabriela Monteiro Carvalho Mori da Cunha, Rita Rynkevic, Radoslaw A. Wach, Alicja K. Olejnik, Patricia Y.W. Dankers, Boris Arts, Tristan Mes, Anton W. Bosman, Maarten Albersen, Jan DeprestAbstractPurposeElectrospun meshes mimic the extracellular matrix, which may improve their integration. We aimed to compare polycaprolactone (PCL) modified with ureidopyrimidinone (UPy) electrospun meshes with ultra-lightweight polypropylene (PP; Restorelle) reference textile meshes for in vivo compliance. We chose UPy-PCL because we have shown it does not compromise biomechanical properties of native tissue, and because it potentially can be bioactivated.MethodsWe performed ex vivo biomechanical cyclic loading in wet conditions and in vivo overlay of full-thickness abdominal wall defects in rats and rabbits. Animals were sacrificed at 7, 42 and 54 days (rats; n=6/group) and 30 and 90 days (rabbits; n=3/group). Outcomes were herniation, mesh degradation and mesh dimensions, explant compliance and histology. High failure rates prompted us to provide additional material strength by increasing fiber diameter and mesh thickness, which was further tested in rabbits as a biomechanically more challenging model.ResultsCompliance was tested in animals without herniation. In both species, UPy-PCL-explants were as compliant as native tissue. In rats, PP-explants were stiffer. Contraction was similar in UPy-PCL and PP-explants. However, UPy-PCL-meshes macroscopically degraded from 30 days onwards, coinciding with herniation in up to half of animals. Increased fiber and mesh thickness did not improve outcome. Degradation of UPy-PCL is associated with an abundance of foreign body giant cells until UPy-PCL disappears.ConclusionAbdominal wall reconstruction with electrospun UPy-PCL meshes failed in 50%. Degradation coincided with a transient vigorous foreign body reaction. Non-failing UPy-PCL-explants were as compliant as native tissue. Despite that, the high failure rate forces us to explore electrospun meshes based on other polymers.
  • Load-Bearing Capacity of Lithium Disilicate and Ultra-Translucent
    • Abstract: Publication date: Available online 21 August 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Jing Yan, Marina R. Kaizer, Yu ZhangObjectiveThe aim of this study was to evaluate the load-bearing capacity of monolithic lithium disilicate (LiDi - IPS e.max CAD) and novel ultra-translucent zirconia restorative systems of various compositions: 5Y-PSZ (5 mol% yttria-partially-stabilized zirconia) and 4Y-PSZ (4 mol% yttria-partially-stabilized zirconia); relative to a 3Y-TZP (3 mol% yttria-stabilized zirconia) control.Materials and methodsExperiments were carried out with 10 disc specimens (Ø12×1 mm) per ceramic material. The zirconia intaglio surface (as machined) was sandblasted (50 µm Al2O3 at 2 bar), while LiDi was etched with 5% HF for 20 s. The ceramic discs were then adhesively bonded onto a dentin-like substrate (G10, a high-pressure fiberglass material) using Multilink Automix cement and Monobond Plus primer, producing a ceramic/cement/dentin-like substrate trilayer structure. The bonded specimens were stored in water for 3 days at 37 °C prior to a Hertzian indentation flexural radial fracture test. The plate-on-foundation theory was used to validate the load-bearing capacity of the trilayer systems based on the flexural tensile stress at the ceramic intaglio (cementation) surface—a cause for bulk fracture of ceramic onlays.ResultsThe experiment data showed that, when bonded to and supported by a dentin-like substrate, the load-bearing capacity of LiDi (872 N) is superior to the 5Y-PSZ (715 N) and can even reach that of 4Y-PSZ (864 N), while 3Y-TZP still holds the highest load-bearing capacity (1195 N). Theoretical analyses agree with experimental observations. The translucency of 5Y-PSZ approaches that of LiDi, which are superior to both 4Y-PSZ and 3Y-TZP.ConclusionsWhen adhesively bonded to and supported by dentin, lithium disilicate exhibits similar load-bearing properties to 4Y-PSZ but much better than 5Y-PSZ.Graphical abstractGraphical abstract for this article
  • Carbon dots intensified poly (ethylene glycol)/chitosan/sodium
           glycerophosphate hydrogel as artificial synovium tissue with slow-release
    • Abstract: Publication date: Available online 21 August 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Hailin Lu, Leifeng Lv, Jun Ma, Wenrui Ban, Shanshan Ren, Guangneng Dong, Jianhui Li, Xiaoqian DangThe ultra-high molecular weight polyethylene (UHMWPE) and metal artificial joint pair is limited by wear debris and short service life. Here we report the development of a hydrogel which exhibits lubricant release to intensify the lubrication effect of artificial joints.This study adopted an injectable method to prepare carbon dots/poly (ethylene glycol)/chitosan/sodium glycerophosphate (CDs/PEG/CS/GP) composite hydrogel, and the carbon dots were used to intensify the rheological and mechanical properties. In addition, the composite hydrogel had slow-release properties, and the release solution contained CDs, PEG and GP has excellent lubrication effect. At last, the MTT assay, LIVE/DEAD staining, H&E staining results and safety evaluation in BALC/c mice proved that the hydrogels had good biocompatibilility and were safety for application in vivo.Graphical abstractCDs, PEG and GP have hydroxyls and they would crosslink with each other via hydrogen bond effect.Graphical abstract for this article
  • Effect of compliant layers within piezoelectric composites on power
    • Abstract: Publication date: Available online 21 August 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): E.D. Krech, E.S. Cadel, R.M. Barrett, E.A. FriisAbstractFor patients that use tobacco or have diabetes, bone healing after orthopedic procedures is challenging. Direct current electrical stimulation has shown success clinically to significantly improve bone healing in these difficult-to-fuse populations. Energy harvesting with piezoelectric material has gained popularity in the last decade, but is challenging at low frequencies due to material properties that limit total power generation at these frequencies. Stacked generators have been used to increase power generation at lower voltage levels but have not been widely explored as a load-bearing biomaterial to provide DC stimulation. To match structural compliance levels and increase efficiency of power generation at low frequencies, the effect of compliant layers between piezoelectric discs was investigated. Compliant Layer Adaptive Composite Stacks (CLACS) were manufactured using five PZT discs connected electrically in parallel and stacked mechanically in series with a layer of low modulus epoxy between each disc. The stacks were encapsulated, keeping PZT and overall volume constant. Each stack was electromechanically tested by varying load, frequency, and resistance. As compliant layer thickness increased, power generation increased significantly across all loads, frequencies, and resistances measured. As expected, increase in frequency significantly increased power output for all groups. Similarly, an increase applied peak-to-peak mechanical load also significantly increased power output. The novel use of CLACS for power generation under load and frequencies experienced by typical orthopedic implants could provide an effective method to harvest energy and provide power without the use of a battery in multiple low frequency applications.
  • Nonstoichiometric wollastonite bioceramic scaffolds with core-shell pore
           struts and adjustable mechanical and biodegradable properties
    • Abstract: Publication date: Available online 21 August 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Zhouwen Jin, Ronghuan Wu, Jianhua Shen, Xianyan Yang, Miaoda Shen, Wangqiong Xu, Rong Huang, Lei Zhang, Guojing Yang, Changyou Gao, Zhongru Gou, Sanzhong XuAbstractControllable mechanical strength and biodegradation of bioceramic scaffolds is a great challenge to treat the load-bearing bone defects. Herein a new strategy has been developed to fabricate porous bioceramic scaffolds with adjustable component distributions based on varying the core-shell-structured nozzles in three-dimensional (3D) direct ink writing platform. The porous bioceramic scaffolds composed of different nonstoichiometic calcium silicate (nCSi) with 0%, 4% or 10% of magnesium-substituting-calcium ratio (CSi, CSi-Mg4, CSi-Mg10) was fabricated. Beyond the mechanically mixed composite scaffolds, varying the different nCSi slurries through the coaxially aligned bilayer nozzle makes it easy to create core-shell bilayer bioceramic filaments and better control of the different nCSi distribution in pore strut after sintering. It was evident that the magnesium substitution in CSi contributed to the increase of compressive strength for the single-phasic scaffolds from 11.2 MPa (CSi), to 39.4 MPa (CSi-Mg4) and 80 MPa (CSi-Mg10). The nCSi distribution in pore struts in the series of core-shell-strut scaffolds could significantly adjust the strength [e.g. CSi@CSi-Mg10 (58.9 MPa) vs CSi-Mg10@CSi (30.4 MPa)] and biodegradation ratio in Tris buffer for a long time stage (6 weeks). These findings demonstrate that the nCSi components with different distributions in core or shell layer of pore struts lead to tunable strength and biodegradation inside their interconnected macropore architectures of the scaffolds. It is possibly helpful to develop new bioactive scaffolds for time-dependent tailoring mechanical and biological performances to significantly enhance bone regeneration and repair applications, especially in some load-bearing bone defects.
  • Ratcheting behavior of UHMWPE reinforced by carbon nanofibers (CNF) and
           hydroxyapatite (HA): experiment and simulation
    • Abstract: Publication date: Available online 21 August 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Jianhai Wang, Hong Gao, Lilan Gao, Yun Cui, Zhengyuan SongAbstractUniaxial tensile tests were performed to investigate the mechanical properties of the ultra-high molecular weight polyethylene (UHMWPE) with different modification conditions. It was found that the different modification conditions have great influence on the mechanical properties of the UHMWPE. Subsequently, the uniaxial ratcheting behaviors of the UHMWPE/CNF and UHMWPE/HA composite materials were observed under the stress-controlled cyclic tensile condition at room temperature. The dependence of uniaxial ratcheting of composite materials on the mean stress, stress amplitude, stress rate and nano-material content was investigated. The results show that the ratcheting strain and its rate of the two composite materials increase as the mean stress and stress amplitude increase, however, the ratcheting strain and its rate decrease with the increase of the stress rate and nano-material content. Furthermore, it is found that the ratcheting strain of the UHMWPE/HA composite material is more remarkable than that of the UHMWPE/CNF composite material. A new viscoplastic constitutive model is proposed to describe the ratcheting behavior of the UHMWPE composite materials. In this model, a new viscosity function and modified kinematic hardening law were employed. Comparison of simulation and experimental results shows that the simulations are in good agreement with the experimental results.
  • Effects of multiple firings on mechanical properties and resin bonding of
           lithium disilicate glass-ceramic
    • Abstract: Publication date: Available online 21 August 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Hongliang Meng, Haifeng Xie, Lu Yang, Bingzhuo Chen, Ying Chen, Huaiqin Zhang, Chen ChenObjectivesThis study aimed to evaluate the effects of different firing cycles on surface hardness, fracture toughness, and roughness of lithium disilicate glass-ceramic, as well as their bond strength to resin.Materials and MethodsA total of 320 polished lithium disilicate glass-ceramic plates were assigned to four main groups (n=60) to receive one, two, three, or four firing cycles, respectively. Ceramic plates of the four groups were conditioned with HF acid followed by silanization. The pre-treated ceramic plates were cemented with composite resin cylinders using conventional or self-adhesive resin cements to build bonded specimens, and submitted to shear-bond-strength (SBS) testing after water storage for 24 h or 3 mo at 37 °C. The ceramic received different firing cycles after polishing or HF etching was observed using a scanning electron microscope, and their surface roughnesses were determined by a profilometer. The surface Vickers hardness, fracture toughness, and related Weibull analysis results of the polished ceramics after undergoing different firing-cycle times were compared.ResultsOne sintering significantly increased fracture toughness of lithium disilicate glass-ceramic; however, multiple firing cycles failed to increase it further. Weibull analysis revealed a significant difference in terms of structural reliability among the specimens receiving 0–4 firing cycles. Specimens that received no firing cycle showed the highest surface hardness. Multiple firing cycles had no significant influence on the surface Vickers hardness and surface roughness. HF etching increased surface roughness, and the roughened surface improved the resin SBS of lithium disilicate glass-ceramic. Multiple firing cycles had no significant effect on surface roughness. Furthermore, multiple firing cycles and 3-mo water storage had no significant effect on the SBS.ConclusionsThe mechanical properties of lithium disilicate glass-ceramics would be partially affected by multiple firing cycles, while their resin bonding would not be.Graphical abstractGraphical abstract for this article
  • Effect of hydroxyapatite fillers on the mechanical properties and
           osteogenesis capacity of bio-based polyurethane composite scaffolds
    • Abstract: Publication date: Available online 21 August 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Jingjing Du, Yi Zuo, Lili Lin, Di Huang, Lulu Niu, Yan Wei, Kaiqun Wang, Qiaoxia Lin, Qin Zou, Yubao LiAbstractA newly designed hydroxyapatite-polyurethane (HA-PU) composite scaffold was prepared by polymerizing glyceride of castor oil (GCO) with isophorone diisocyanate (IPDI) and HA as fillers. The aim of this study was to determine the effect of HA fillers on the mechanical properties and osteogenesis capacity of the composite scaffolds. The physical and biological properties of the scaffold were evaluated by SEM observation, mechanical testing, cell culture and animal experiments. The results showed that HA fillers enhanced the mechanical properties of PU composite scaffolds such as compressive strength and elastic modulus. The mechanical properties of the scaffolds were seen to increase with increase in HA loading. The compressive strength of composite scaffold with 0 wt%, 20 wt%, 40 wt% of HA was 0.6 ± 0.1 MPa, 2.1 ± 0.1 MPa, and 4.6 ± 0.3 MPa, respectively. In vitro biodegradation studies of scaffolds were carried out. The results showed that all of the scaffolds were susceptible to cholesterol esterase (CE) -catalyzed degradation. HA-PU composite scaffolds exhibited a high affinity to osteoblastic cells and were good template for cell growth and proliferation. When implanted in bone defects of rats, PU scaffolds incorporated HA were biocompatible with the tissue host and had no immune rejection. Moreover, the higher the loading of HA in the composite scaffold, the better chances of osteogenesis. It confirmed that the prepared HA-PU composite scaffolds can be promising candidate for bone repair and bone tissue engineering.
  • Comparative study of the wear of the pair human teeth/Vita Enamic® vs
           commonly used dental ceramics through chewing simulation
    • Abstract: Publication date: Available online 20 August 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): F. Santos, A. Branco, M. Polido, A.P. Serro, C.G. Figueiredo-PinaCeramic based prosthetic materials have been used in dental restorations due to their excellent aesthetic and biocompatibility. However, due to concerns related to their mechanical properties and abrasive action against natural teeth, a proper selection of these materials is crucial to preserve the occlusal interactions and prevent abnormal dental wear. The aim of this work is to compare the wear performance of Vita Enamic®, a polymer infiltrated ceramic (PIC), with that of other three commercial ceramic based dental materials - Zirconia, Leucite and Zirconia Veneered - when tested against natural teeth. The crystalline structure, wettability, topography and hardness of the prosthetic materials were characterized before wear testing. Chewing simulator experiments (360,000 cycles, load 49 N) against dental human cusps were carried out using artificial saliva as lubricant. The wear of both teeth and prosthetic materials was quantified and the involved wear mechanisms were analyzed by scanning electron microscopy. The results showed that Zirconia presented the most suitable tribological behavior, since it led to the lowest wear on both occlusal surfaces. The prosthetic material presenting the highest wear was Vita Enamic®. Regarding the cusps’ wear, the highest values were found for both Leucite and Zirconia Veneered. Polishing wear was the main wear mechanism in Zirconia system (prosthetic material and opposing enamel), while in the remaining ones was fragile fracture associated with abrasive wear. No direct relation could be stablished between wettability, initial roughness and hardness of the prosthetic materials and the wear of the tribological systems. Contrarily, microstructure and toughness revealed to be critical parameters.Graphical abstractGraphical abstract for this article
  • Collective cell polarization and alignment on curved surfaces
    • Abstract: Publication date: Available online 18 August 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Chenglin Liu, Jiayi Xu, Shijie He, Wanjun Zhang, Huiqi Li, Bo Huo, Baohua JiAbstractCurvature as an important topological parameter of 3D extra-cellular matrix has drawn growing attention in recent years. But the underlying mechanism that curvature influences cell behaviors has remained unknown. In this study, we seeded cells on semi-cylindrical and hemispheric surfaces and tested cell alignment and polarization. We found that the surface curvature has profound effect on cell behaviors. With the decrease of diameter of the cylinder/sphere (i.e. increase of curvature), the cells would more preferentially align and polarize with large aspect ratio in the axial/peripheral direction. And the behaviors of the alignment and polarization were position-dependent. For example, at the end of the cylinder, the cells preferred to align circumferentially; while in the interior region, the cells preferred to align in the axial direction. We showed that the cell polarization and alignment were closely correlated with the in-plane stresses in cell layer. That is, the cell polarization and alignment were controlled by the maximum shear stress, which drove cells to align and polarize along the maximum principal stress. The curvature could influence the magnitude of the maximum shear stress and thus regulate cell behaviors. This study provided important insights into the mechanisms of surface curvature influencing cell behaviors in tissue morphogenesis. In addition, our theory of the stress dependent cellular polarity provides a generalized interpretation of the curvature and edge effects which might be extended to understand other steric effects in cell behaviors.
  • Effect of SR-microCT radiation on the mechanical integrity of trabecular
           bone using in situ mechanical testing and digital volume correlation
    • Abstract: Publication date: Available online 16 August 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Marta Peña Fernández, Silvia Cipiccia, Enrico Dall’Ara, Andrew J Bodey, Rachna Parwani, Martino Pani, Gordon W Blunn, Asa H Barber, Gianluca TozziThe use of synchrotron radiation micro-computed tomography (SR-microCT) is becoming increasingly popular for studying the relationship between microstructure and bone mechanics subjected to in situ mechanical testing. However, it is well known that the effect of SR X-ray radiation can considerably alter the mechanical properties of bone tissue. Digital volume correlation (DVC) has been extensively used to compute full-field strain distributions in bone specimens subjected to step-wise mechanical loading, but tissue damage from sequential SR-microCT scans has not been previously addressed. Therefore, the aim of this study is to examine the influence of SR irradiation-induced microdamage on the apparent elastic properties of trabecular bone using DVC applied to in situ SR-microCT tomograms obtained with different exposure times. Results showed how DVC was able to identify high local strain levels (>10,000 µε) corresponding to visible microcracks at high irradiation doses (~230 kGy), despite the apparent elastic properties remained unaltered. Microcracks were not detected and bone plasticity was preserved for low irradiation doses (~33 kGy), although image quality and consequently, DVC performance were reduced. DVC results suggested some local deterioration of tissue that might have resulted from mechanical strain concentration further enhanced by some level of local irradiation even for low accumulated dose.Graphical abstractGraphical abstract for this article
  • Mechanical characterization of arteries affected by fetal growth
           restriction in guinea pigs (Cavia porcellus)
    • Abstract: Publication date: Available online 14 August 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Daniel Cañas, Claudio García-Herrera, Emilio A. Herrera, Diego Celentano, Bernardo J. KrauseAbstractFetal growth restriction (FGR) is a perinatal condition associated with a low birth weight that results mainly from maternal and placental constrains. Newborns affected by this condition are more likely to develop in the long term cardiovascular diseases whose origins would be in an altered vascular structure and function defined during fetal development. Thus, this study presents the modeling and numerical simulation of systemic vessels from guinea pig fetuses affected by FGR. We aimed to characterize the biomechanical properties of the arterial wall of FGR-derived the aorta, carotid, and femoral arteries by performing ring tensile and ring opening tests and, based on these data, to simulate the biomechanical behavior of FGR vessels under physiological conditions. The material parameters were first obtained from the experimental data of the ring tensile test. Then, the residual stresses were determined from the ring opening test and taken as initial stresses in the simulation of the ring tensile test. These two coupled steps are iteratively considered in a nonlinear least-squares algorithm to obtain the final material parameters. Then, the stress distribution changes along the arterial wall under physiological pressure were quantified using the adjusted material parameters. Overall, the obtained results provide a realistic approximation of the residual stresses and the changes in the mechanical behavior under physiological conditions.
  • Monitoring cementless femoral stem insertion by impact analyses: an in
           vitro study
    • Abstract: Publication date: Available online 10 August 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Antoine Tijou, Giuseppe Rosi, Romain Vayron, Hugues Albini Lomami, Philippe Hernigou, Charles-Henri Flouzat-Lachaniette, Guillaume HaïatThe primary stability of the femoral stem (FS) implant determines the surgical success of cementless hip arthroplasty. During the insertion, a compromise must be found for the number and energy of impacts that should be sufficiently large to obtain an adapted primary stability of the FS and not too high to decrease fracture risk. The aim of this study is to determine whether a hammer instrumented with a force sensor can be used to monitor the insertion of FS.Cementless FS of different sizes were impacted in four artificial femurs with an instrumented hammer, leading to 72 configurations. The impact number when the surgeon empirically felt that the FS was fully inserted was noted Nsurg. The insertion depth E was assessed using video motion tracking and the impact number Nvid corresponding to the end of the insertion was estimated. For each impact, two indicators noted I and D were determined based on the analysis of the variation of the force as a function of time.The pull-out force F was significantly correlated with the indicator I (R² =0.67). The variation of D was analyzed using a threshold to determine an impact number Nd, which is shown to be closely related to Nsurg and Nvid, with an average difference of around 0.2. This approach allows to determine i) the moment when the surgeon should stop the impaction procedure in order to obtain an optimal insertion of the FS and ii) the FS implant primary stability. This study paves the way towards the development of a decision support system to assist the surgeon in hip arthroplasty.Graphical abstractGraphical abstract for this article
  • Double-network gels with dynamic bonds under multi-cycle deformation
    • Abstract: Publication date: Available online 10 August 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): A.D. Drozdov, J. deClaville ChristiansenApplication of double-network (DN) gels with dynamic bonds as implants for repair of damaged and degenerate cartilage tissue and their use as synthetic non-degradable scaffolds for growth, proliferation and differentiation of stem cells requires understanding of the mechanical behavior of these materials under cyclic deformation. A constitutive model is developed for the viscoelastic and viscoplastic responses of DN gels with covalent and non-covalent junctions under multi-cycle loading. Viscoelasticity is treated as breakage and reformation of temporary junctions driven by thermal fluctuations. Viscoplasticity is thought of as sliding of permanent junctions with respect to their initial positions in the polymer network. Adjustable parameters in the governing equations are found by fitting observations in tensile loading–unloading tests with various maximum strains and multi-cycle tests with monotonically increasing maximum elongation ratios per cycle on two DN gels with physical junctions formed due to hydrogen bonds and ionic complexation. Numerical analysis demonstrates the ability of the model not only to describe observations correctly, but also to predict the mechanical response in multi-cycle tests with sophisticated deformation programs. Quantitative and qualitative effects of metal-coordination bonds on the mechanical behavior of supramolecular gels are revealed by simulation.Graphical abstractGraphical abstract for this article
  • 3D laser scanning in conjunction with surface texturing to evaluate shift
           and reduction of the tibiofemoral contact area after meniscectomy
    • Abstract: Publication date: Available online 9 August 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Roberto De Santis, Antonio Gloria, Stefano Viglione, Saverio Maietta, Francesco Nappi, Luigi Ambrosio, Dante RoncaMeniscectomy significantly change the kinematics of the knee joint by reducing the contact area between femoral condyles and the tibial plateau, but the shift in the contact area has been poorly described. The aim of our investigation was to measure the shift of the tibiofemoral contact area occurring after meniscectomy.We used laser scans combined to surface texturing for measuring the 3D position and area of the femoral and tibial surfaces involved in the joint. In particular, natural condyles (porcine model) were analysed and the reverse engineering approach was used for the interpretation of the results from compression tests and local force measurements in conjunction with staining techniques.The results suggested that laser scans combined to surface texturing may be considered as a powerful tool to investigate the stained contours of the contact area. Beside the largely documented reduction of contact area and local pressure increase, a shift of the centroid of the contact area toward the intercondylar notch was measured after meniscectomy.As a consequence of the contact area shift and pressure increase, cartilage degeneration close to the intercondylar notch may occur.Graphical abstractGraphical abstract for this article
  • A method for investigating the cellular response to cyclic tension or
           compression in three-dimensional culture
    • Abstract: Publication date: Available online 8 August 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Babak Sarrafpour, Philip Boughton, Ramin M. Farahani, Stephen C Cox, Gareth Denyer, Elizabeth Kelly, Hans ZoellnerWe have an interest in the cellular response to mechanical stimuli, and here describe an in-vitro method to examine the response of cells cultured in a three-dimensional matrix to mechanical compressive and tensile stress. Synthetic aliphatic polyester scaffolds coated with 45S5 bioactive glass were seeded with human dental follicular cells (HDFC), and attached to well inserts and magnetic endplates in six well palates. Scaffolds were subjected to either cyclic 10% tensile deformation, or 8% compression, at 1 Hz and 2 Hz respectively for 6, 24 or 48 hours, by uniaxial motion of magnetically-coupled endplates. It was possible to isolate high quality mRNA from cells in these scaffolds, as demonstrated by high RNA integrity numbers scores, and ability to perform meaningful cRNA microarray analysis, in which 669 and 727 genes were consistently upregulated, and 662 and 518 genes down regulated at all times studied under tensile and compressive loading conditions respectively. MetaCore analysis revealed the most regulated gene ontogenies under both loading conditions to be for: cytoskeletal remodelling; cell adhesion-chemokines and adhesion; cytoskeleton remodelling-TGF WNT and cytoskeletal remodeling pathways. We believe the method here described will be of value for analysis of the cellular response to cyclic loading.Graphical abstractGraphical abstract for this article
  • Load-Sharing Biomechanics at the Thoracolumbar Junction under Dynamic
           Loadings Are Modified by Anatomical Features in Adolescent and Pediatric
           vs Adult Functional Spinal Units
    • Abstract: Publication date: Available online 8 August 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Tanvir Mustafy, Pierre-Jean Arnoux, Aurélie Benoit, Rohan-Jean Bianco, Carl-Eric Aubin, Isabelle VillemureGraphical abstractGraphical abstract for this article
  • Effect of primer-cement systems with different functional phosphate
           monomers on the adhesion of zirconia to dentin
    • Abstract: Publication date: Available online 7 August 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Dayanne Monielle Duarte Moura, Ana Beatriz do Nascimento Januário, Arthur Magno Medeiros de Araújo, Amanda Maria de Oliveira Dal Piva, Mutlu Özcan, Marco Antonio Bottino, Rodrigo Othávio Assunção SouzaAbstractPurposeThe objective of this study was to evaluate the effect of primer-cement systems with different functional phosphate monomers on the adhesion of zirconia to dentin with and without aging protocols.Materials and MethodsBovine teeth (N=180) were embedded in acrylic resin after sectioning their roots with with their coronal parts exposed. The buccal surface of each tooth was polished with silicon carbide papers (#200, 400, 600) until dentin exposure. Sintered zirconia cylinders (N=180) (Ø: 3.4 mm; height: 4 mm) (Vita In-Ceram 2000) were prepared and distributed into 18 groups (n=10 per group) considering the following factors: “Cementation System” (Panavia F - PAN; RelyX Ultimate - ULT, Multilink N - MULT) and “aging” (water storage in distilled water at 37 °C for 24 h (control, C); 30 days (30D); 6 months (6 M) and thermocycling for 5000 (5TC), 10000 (10TC) and 20000 (20TC) thermal cycles (5–55 °C; dwell time: 30 s)”. Zirconia and dentin cementation surfaces were conditioned according to the recommendations of the manufacturers of each resin cement. The cylinders were adhesively cemented to the dentin surfaces and the specimens were submitted to the aging protocols. After aging, the specimens were subjected to shear bond strength test (SBS) (1 mm/min) in a Universal Testing Machine and failure types were analyzed. The data (MPa) were statistically using Kruskal-Wallis followed by the Dunn test (α=5%). The degree of conversion (DC) rates of the cementing systems were also measured.ResultsWhile without aging (24 h) no significant difference was found between the cement systems (p>0.05), after 30D (4.3–5.4), the highest decrease in all groups were observed after 5TC (1.5–2.3) (p
  • A New Model of Passive Muscle Tissue Integrating Collagen Fibers:
           Consequences for Muscle Behavior Analysis
    • Abstract: Publication date: Available online 1 August 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Ali-Akbar Karkhaneh Yousefi, Mohammad Ali Nazari, Pascal Perrier, Masoud Shariat Panahi, Yohan PayanAbstractMechanical properties of muscle tissue are crucial in biomechanical modeling of the human body. Muscle tissue is a combination of Muscle Fibers (MFs) and connective tissue including collagen and elastin fibers. There are a lot of passive muscle models in the literature but most of them do not consider any distinction between Collagen Fibers (CFs) and MFs, or at least do not consider the mechanical effects of the CFs on the Three-Dimensional (3-D) behavior of tissue. As a consequence, unfortunately, they cannot describe the observed stress-stretch behavior in tissue in which the reinforced direction is not parallel to the MF direction. In this research, a new passive muscle model is presented, in which the CFs are separately considered in the formulation: they are distributed along the MFs in a cross-shaped arrangement. Thanks to this new architecture, a mechanical reinforced direction can be proposed, in addition to the muscle main fiber direction.The passive biomechanical properties of the genioglossus muscle of a bovine tongue have been measured under uniaxial tensile tests. To characterize the 3-D response of the tissue, tests have been performed in different directions with respect to the MF direction. Moreover, a Constitutive Law (CL) has been proposed for modeling this behavior. In addition to our measurements on the bovine genioglossus muscle, results published in the literature on experimental data from the longissimus dorsi of pigs and the chicken pectoralis muscle were used to appraise the applicability of the proposed model. It is demonstrated that the proposed passive muscle model provides an accurate description of the fiber-oriented nature of muscle tissue. Also, it has been shown that using Finite Element Analysis (FEA) it might be possible to predict the angle θ between CFs and MF.
  • Investigation of inner mechanism of anisotropic mechanical property of
           antler bone
    • Abstract: Publication date: Available online 1 August 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Zhongqi Fang, Bin Chen, Shiyun Lin, Wei Ye, Hang Xiao, Xi ChenAbstractBones have different functions and various applications depending on the roles they play in different mammal bodies. The internal relationships between the functions and microstructures of bones need further expounding to understand their specific mechanical properties. In this study, the relationships between the mechanical properties and microstructures of the compact bone of antler (called as antler bone for short) along its three different orientations are investigated. First, the bending mechanical properties of the specimens of the antler bone along its three different orientations are tested with material-testing machine, followed by the observations of the crack-extending routes and the fracture surfaces of the three different orientations with a scanning electron microscope (SEM). The results of the tests reveal that the antler bone possesses anisotropic mechanical property. Namely, the mechanical properties of the antler bone are closely related to its orientations. Concretely, the fracture strength, elastic modulus and work-of-fracture along the transversal orientation of the bone are remarkably larger than those of the longitudinal and radial orientations. The results of the observation of the SEM show that there are different crack-extending routes and fracture-surface characteristics along the three different fracture orientations of the bone. Specifically, there are crack deflections and crack twists along the transversal fracture orientation, crack bridging along the longitudinal fracture orientation and crack rounding of osteons along the radial fracture orientation. Based on the tested and observed results, the fractal models of the crack-extending routes along the three different fracture orientations are presented. The fractal dimensions and critical crack extension forces along the three different fracture directions are calculated based on the fractal models. Further, the box-counting method is adopted to verify the correctness of the models. It is indicated that the fractal dimension and fracture energy of the transversal orientation are obviously larger than those of the longitudinal and radial orientations, which are in accordance with the experimental results.
  • Biomechanical properties and microstructure of neonatal porcine ventricles
    • Abstract: Publication date: Available online 29 July 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Faizan Ahmad, R. Prabhu, Jun Liao, Shwe Soe, Michael D. Jones, Jonathan Miller, Parker Berthelson, Daniel Enge, Katherine M. Copeland, Samar Shaabeth, Richard Johnston, Ian Maconochie, Peter S. TheobaldNeonatal heart disorders represent a major clinical challenge, with congenital heart disease alone affecting 36,000 new-borns annually within the European Union. Surgical intervention to restore normal function includes the implantation of synthetic and biological materials; however, a lack of experimental data describing the mechanical behaviour of neonatal cardiac tissue is likely to contribute to the relatively poor short- and long-term outcome of these implants. This study focused on characterising the mechanical behaviour of neonatal cardiac tissue using a porcine model, to enhance the understanding of how this differs to the equivalent mature tissue. The biomechanical properties of neonatal porcine cardiac tissue were characterised by uniaxial tensile, biaxial tensile, and simple shear loading modes, using samples collected from the anterior and posterior walls of the right and left ventricles. Histological images were prepared using Masson’s trichrome staining, to enable assessment of the microstructure and correlation with tissue behaviour. The mechanical tests demonstrated that the neonatal cardiac tissue is non–linear, anisotropic, viscoelastic and heterogeneous. Our data provide a baseline describing the biomechanical behaviour of immature porcine cardiac tissue. Comparison with published data also indicated that the neonatal porcine cardiac tissue exhibits one-half the stiffness of mature porcine tissue in uniaxial extension testing, one-third in biaxial extension testing, and one-fourth stiffness in simple shear testing; hence, it provides an indication as to the relative change in characteristics associated with tissue maturation. These data may prove valuable to researchers investigating neonatal cardiac mechanics.Graphical abstractGraphical abstract for this article
  • Synthesis of Bone Implant Substitutes using Organic Additive Based
           Zirconia Nanoparticles and their Biodegradation Study
    • Abstract: Publication date: Available online 25 July 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): M. Bashir, S. Riaz, Z.N. Kayani, S. NaseemZirconia, a hard-ceramic, is potential material for bone and dental implants. However, the problem limiting its application is inertness. This problem can be minimized using body compatible and non-toxic organic additives. Organic additives-based zirconia (OZ) nanoparticles are synthesized using sol–gel method. Zirconium oxychloride is used as precursor and water as solvent. OZ nanoparticles are calcined in temperature range of 100–1000 °C. Transition from mixed zirconia phases to amorphous behavior is observed at 300 °C. Phase-pure tetragonal ZrO2 (t-ZrO2) along with reduced crystallite size ~12.7 nm is observed at 500 °C. Mixed phases, started to appear at 800 °C, exhibit increased monoclinic to tetragonal ratio at 900–1000 °C. SEM images show OZ nanoparticles with ~50 nm diameter at 500 °C. Nanoparticles with ~50 nm and ~70–75 nm diameter along with nanowires (~8 nm) are observed at 600–700 °C. FTIR band at 500 cm−1 along with shoulder at 580 cm−1 and Raman band at 148 cm−1 confirm the presence of t-ZrO2 at 500–600 °C. High value of hardness, ~15 GPa, and dielectric constant (~55–68) suitable for bio-application, is observed for OZ nanoparticles calcined at 500 °C. Optimized t-ZrO2 is immersed in stimulated body fluid for 1, 2, 4, 8, 13, 20 and 26 weeks. Small degradation in weight and hardness is observed even after 26 weeks of immersion.Graphical abstractGraphical abstract for this article
  • How important is sample alignment in planar biaxial testing of anisotropic
           soft biological tissues' A finite element study
    • Abstract: Publication date: Available online 18 July 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Heleen Fehervary, Julie Vastmans, Jos Vander Sloten, Nele FamaeyAbstractFinite element models of biomedical applications increasingly use anisotropic hyperelastic material formulations. Appropriate material parameters are essential for a reliable outcome of these simulations, which is why planar biaxial testing of soft biological tissues is gaining importance. However, much is still to be learned regarding the ideal methodology for performing this type of test and the subsequent parameter fitting procedure.This paper focuses on the effect of an unknown sample orientation or a mistake in the sample orientation in a planar biaxial test using rakes. To this end, finite element simulations were conducted with various degrees of misalignment. Variations to the test method and subsequent fitting procedures are compared and evaluated.For a perfectly aligned sample and for a slightly misaligned sample, the parameters of the Gasser-Ogden-Holzapfel model can be found to a reasonable accuracy using a planar biaxial test with rakes and a parameter fitting procedure that takes into account the boundary conditions. However, after a certain threshold of misalignment, reliable parameters can no longer be found. The level of this threshold seems to be material dependent.For a sample with unknown sample orientation, material parameters could theoretically be obtained by increasing the degrees of freedom along which test data is obtained, e.g. by adding the data of a rail shear test. However, in the situation and the material model studied here, the inhomogeneous boundary conditions of the test set-ups render it impossible to obtain the correct parameters, even when using the parameter fitting method that takes into account boundary conditions.To conclude, it is always important to carefully track the sample orientation during harvesting and preparation and to minimize the misalignment during mounting. For transversely isotropic samples with an unknown orientation, we advise against parameter fitting based on a planar biaxial test, even when combined with a rail shear test.
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Heriot-Watt University
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