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  Subjects -> BIOLOGY (Total: 3193 journals)
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BIOTECHNOLOGY (244 journals)                  1 2 | Last

Showing 1 - 200 of 244 Journals sorted alphabetically
3 Biotech     Open Access   (Followers: 8)
Advanced Biomedical Research     Open Access  
Advances in Bioscience and Biotechnology     Open Access   (Followers: 17)
Advances in Genetic Engineering & Biotechnology     Hybrid Journal   (Followers: 9)
Advances in Regenerative Medicine     Open Access   (Followers: 3)
African Journal of Biotechnology     Open Access   (Followers: 6)
Algal Research     Partially Free   (Followers: 11)
American Journal of Biochemistry and Biotechnology     Open Access   (Followers: 69)
American Journal of Bioinformatics Research     Open Access   (Followers: 7)
American Journal of Polymer Science     Open Access   (Followers: 33)
Amylase     Open Access  
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: 45)
Applied Biosafety     Hybrid Journal  
Applied Food Biotechnology     Open Access   (Followers: 3)
Applied Microbiology and Biotechnology     Hybrid Journal   (Followers: 67)
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: 3)
Bio-Algorithms and Med-Systems     Hybrid Journal   (Followers: 2)
Bio-Research     Full-text available via subscription   (Followers: 4)
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)
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: 8)
Biotechnology & Biotechnological Equipment     Open Access   (Followers: 4)
Biotechnology Advances     Hybrid Journal   (Followers: 34)
Biotechnology and Applied Biochemistry     Hybrid Journal   (Followers: 44)
Biotechnology and Bioengineering     Hybrid Journal   (Followers: 159)
Biotechnology and Bioprocess Engineering     Hybrid Journal   (Followers: 6)
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: 17)
Biotechnology Law Report     Hybrid Journal   (Followers: 4)
Biotechnology Letters     Hybrid Journal   (Followers: 34)
Biotechnology Progress     Hybrid Journal   (Followers: 41)
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: 17)
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: 55)
Current Pharmaceutical Biotechnology     Hybrid Journal   (Followers: 9)
Current Research in Bioinformatics     Open Access   (Followers: 13)
Current Trends in Biotechnology and Chemical Research     Open Access   (Followers: 3)
Current trends in Biotechnology and Pharmacy     Open Access   (Followers: 8)
DNA and RNA Nanotechnology     Open Access  
EBioMedicine     Open Access  
Electronic Journal of Biotechnology     Open Access  
Entomologia Generalis     Full-text available via subscription   (Followers: 1)
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  
Horticultural Biotechnology Research     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)
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: 18)
International Biomechanics     Open Access  
International Journal of Bioinformatics Research and Applications     Hybrid Journal   (Followers: 14)
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: 4)
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 BioScience and Biotechnology     Open Access  
Journal of Biosecurity Biosafety and Biodefense Law     Hybrid Journal   (Followers: 3)
Journal of Biotechnology     Hybrid Journal   (Followers: 63)
Journal of Biotechnology and Strategic Health Research     Open Access   (Followers: 1)
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 Ecobiotechnology     Open Access  
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: 18)
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: 13)
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: 13)
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: 10)
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)

        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: 13  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 1751-6161
Published by Elsevier Homepage  [3155 journals]
  • Influence of contact configuration and lubricating conditions on the
           microtriboactivity of the zirconia-Ti6Al4V pair used in dental
           applications
    • Abstract: Publication date: Available online 13 December 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): A.C. Branco, V. Moreira, J.A. Reis, R. Colaço, C.G. Figueiredo-Pina, A.P. Serro Loosening and fracture of implanted dental crowns is a consequence of relative micromovements between the zirconia abutment and the titanium alloy of the implant, in a biochemical aggressive environment. Thus, it is important to establish the in vitro tribological testing conditions that better mimics such environment. The present work aims to evaluate the effect of ball-on-plate tests configuration on the tribological behavior of ZrO2/Ti6Al4V pair in dry and lubricated conditions, using different lubricants: water, artificial saliva solution and human saliva. Ceramic balls sliding on metallic plates (TiPlate) and metallic balls sliding on ceramic plates (TiBall) were tested and the coefficient of friction (CoF) and wear response was monitored trough nanotribological tests. Open circuit potential was also measured during the tests carried out in saline solution (artificial saliva) to access the tribochemical response. The wear mechanisms were evaluated by scanning electron microscopy and atomic force microscopy analysis. Relevant differences were found between the two configurations, eith and without the presence of human saliva: TiPlate presented always a higher CoF than TiBall, which may have resulted from differences in the degradation and regeneration processes of the titanium passive film during sliding. TiBall demonstrated to be the best choice to reproduce the in vivo conditions, since the metallic surface contacts permanently with zirconia, impairing the titanium repassivation. Regarding the effect of the lubricants, it was observed that human saliva had a protective action of the surfaces, leading to the lowest CoF among the lubricants used (0.19±0.05 for TiBall and 0.35±0.08 for TiPlate) and neglectable wear.Graphical abstractGraphical abstract for this article
       
  • Potential of growth factor incorporated mesoporous bioactive glass for in
           vivo bone regeneration
    • Abstract: Publication date: Available online 12 December 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): V. Lalzawmliana, Akrity Anand, Vinod Kumar, Piyali Das, K. Bavya Devi, Jayanta Mukherjee, Asit Kumar Maji, Biswanath Kundu, Mangal Roy, Samit Kumar Nandi Mesoporous bioactive glass (MBG) has drawn much attention due to its superior surface texture, porosity and bioactive characteristics. Aim of the present study is to synthesize MBG using different surfactants, viz., hexadecyltrimethylamonium(CTAB) (M1), poly-ethylene glycol (PEG) (M2) and pluronic P123 (M3); bioactivity study; and to understand their bone regeneration efficacy in combination with insulin-like growth factors (IGF-1) in animal bone defect model. SBF study revealed the formation of calcium carbonate (CaCO3) and hydroxyapatite (HAp) phase over 14 days. Formation of apatite layer was further confirmed by FTIR, FESEM and EDX analysis. M1 and M2 showed improved crystallinity, while M3 showed slightly decrease in crystalline peak of CaCO3 and enhanced HAp phase. More Ca-P layer formed in M1 and M2 supported the in vivo experiments subsequently. Degree of new bone formation for all MBGs were high, i.e., M1 (80.7 ± 2.9%), M2 (74.4 ± 2.4%) and M3 (70.1 ± 1.9%) compared to BG (66.9 ± 1.8%). In vivo results indicated that the materials were non-toxic, biodegradable, biocompatible, and is suitable as bone replacement materials. Thus, we concluded that growth factor loaded MBG is a promising candidate for bone tissue engineering application.
       
  • Lithium disilicate glass-ceramic Vs translucent zirconia polycrystals
           bonded to distinct substrates: fatigue failure load, number of cycles for
           failure, survival rates, and stress distribution
    • Abstract: Publication date: Available online 12 December 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Gabriel Kalil Rocha Pereira, Priscila Graunke, Angélica Maroli, Camila Pauleski Zucuni, Catina Prochnow, Luiz Felipe Valandro, Ricardo Armini Caldas, Atais Bacchi The present study evaluated the fatigue behavior of monolithic translucent zirconia polycrystals (TZ) and lithium disilicate glass-ceramic (LD) bonded to different substrates. Disc-shaped specimens of ceramic materials TZ and LD were bonded to three substrates with different elastic modulus (E) (fiber-reinforced composite (FRC) - softest material, E = 14.9 GPa; titanium alloy (Ti) – intermediary properties, E = 115 GPa; and zirconia (Yz) - stiffest material, E = 210 GPa). The surfaces were treated and bonded with resin cement (disc-disc set-up). Fatigue testing followed a step-stress approach (initial maximum load= 200 N for 5,000 cycles, incremental step load= 200 N for 10,000 cycles/step). The fatigue failure load and number of cycles until failure were recorded and statistically analyzed. Fractographic and finite element (FEA) analyzes were conducted as well. TZ ceramic depicted higher fatigue failure load, number of cycles until failure, and survival probabilities than LD, irrespective of the substrate. Moreover, TZ and LD presented better fatigue behaviors when bonded to substrates Ti and Yz in comparison to FRC. FEA revealed lower tensile stresses at restorative material when bonded to stiffer substrates. Fractography showed that the fracture origin started at bottom surface of restorative material (except for TZ bonded to Yz, in which crack initiated at load contact point). Translucent zirconia polycrystals present superior mechanical behavior than lithium disilicate glass-ceramic. The substrate type influences the mechanical performance of monolithic dental ceramics (stiffer substrates lead to better fatigue behavior).
       
  • Biomechanical aspects of reinforced implant overdentures: a systematic
           review
    • Abstract: Publication date: Available online 11 December 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Mona Fathy Gibreel, Ahmed Khalifa, Mohamed Mostafa Said, Fatma Mahanna, Nesma El-Amier, Timo O. Närhi, Leila Perea-Lowery, Pekka K. Vallittu PurposeThe purpose of this systematic review was to investigate the effect of the reinforcement on the mechanical behavior of implant overdenture (IOD) bases and its cumulative biological effect on the underlying supporting structures (implants and residual ridge).Material and methodsThe required documents were collected electronically from PubMed and Web of Science databases targeting papers in English with denture base reinforcement for IOD in order to recognize the principal outcomes of reinforcement on the mechanical and biological properties of overdenture. Such biological outcomes as: strains on implants, peri-implant bone loss, residual ridge resorption, and strain on the residual alveolar ridge.ResultsA total of 269 citations were identified. After excluding any repeated articles between databases and the application of exclusion and inclusion criteria, only 13 publications fulfilled the inclusion criteria. Three publications investigated the mechanical properties of fiber and/or metal- reinforced implant overdenture while another 3 articles investigated the effect of metal reinforcement on stress distribution and strains transmitted to the underlying implants. In addition, 3 in vitro studies investigated the effect of metal reinforcement on overdenture base strain and its stresses. Stress distribution to the residual ridge and strain characteristics of the underlying tissues were investigated by 2 in vitro studies. Five clinical studies assisting the clinical and prosthetic maintenance of metal-reinforced IOD were included. Data concerning the denture base fracture, relining, peri-implant bone loss, probing depth, and implant survival rates during the functional period were extracted and considered in order to evaluate the mechanical properties of the denture base, residual ridge resorption and implant preservation rate, respectively.ConclusionThe use of a denture base reinforcement can reduce the fracture incidence of IOD by enhancing its flexural properties and reducing the overdenture base deformation. Strains on the underlying supporting structures of overdenture prosthesis including dental implants and the residual ridge can be decreased and evenly distributed by using a metal reinforcement.
       
  • Mechanical behavior of in vivo degraded second generation resorbable
           magnesium scaffolds (RMS)
    • Abstract: Publication date: Available online 11 December 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Christoph Brandt-Wunderlich, Philipp Ruppelt, Philine Zumstein, Wolfram Schmidt, Daniela Arbeiter, Klaus-Peter Schmitz, Niels Grabow Resorbable magnesium scaffolds are used for the treatment of atherosclerotic coronary vascular disease and furthermore, for vascular restoration therapy. Recently, the first-in-man clinical studies with Magmaris showed promising results regarding the target lesion failure as well as vasomotion properties after 12 and 24 month. The consistency of in vivo degraded magnesium alloys in a cardiovascular environment is qualitatively described in literature, but only little has been disclosed about the actual change in mechanical properties and the behavior of the magnesium alloy degradation products.In the present study, uncoated magnesium scaffolds 3.0 ×20 mm were implanted in coronary arteries of two healthy Goetinnger mini-swine. The scaffolds were explanted to evaluate the mechanical properties of the degraded magnesium scaffolds after 180 days in vivo. Ex vivo sample preparation and test conditions were adapted to a customized compression test setup which was developed to investigate the micro-scale scaffold fragments (width 225 ± 75 µm, thickness 150 µm). As reference bare undegraded magnesium scaffold fragments were tested. Mechanical parameters relating to force as a function of displacement were determined for both sample groups.The undegraded samples showed no fracturing at the maximum applied force of 8 N, whereas the in vivo degraded test samples showed forces of 0.411 ± 0.197 N at the first fracturing and a maximum force of 0.956 ± 0.525 N. The deformation work, calculated as area beneath the force-displacement curve, of the in vivo degraded test samples was reduced by approximately 87–88% compared to the undegraded samples (5.20 mN·mm and 40.79 mN·mm, both at 7.5% deformation).The indication for a complete loss of structural integrity through a reduction of mechanical properties after a certain degradation time increases the chance to restore vascular function and physiological vasomotion in the stented vessel compartment.
       
  • On multiscale boundary conditions in the computational homogenization of
           an RVE of tendon fascicles
    • Abstract: Publication date: Available online 10 December 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Thiago André Carniel, Bruno Klahr, Eduardo Alberto Fancello Present study provides a numerical investigation on multiscale boundary conditions in the computational homogenization of a representative volume element (RVE) of tendon fascicles. A three-dimensional hexagonal-helicoidal finite element RVE composed of two material phases (collagen fibers and cells) and three finite strain viscoelastic models (collagen fibrils, matrix of fibers and cells) compose the multiscale model. Due to the unusual helical geometry of the RVE, the performance of four multiscale boundary conditions is evaluated: the linear boundary displacements model, the minimally constrained model and two mixed boundary conditions allying characteristics of both, linear and minimal models. Numerical results concerning microscopic kinematic fields and macroscopic stress-strain curves point out that one of the mixed models is able to predict the expected multiscale mechanics of the RVE, presenting sound agreement with experimental facts reported in literature, for example: characteristic non-linear shape of the stress-strain curves; macroscopic energy loss by hysteresis; axial rotation of fascicles observed in tensile tests; collagen fibrils are the main load-bearing components of tendons; cells contribute neither to the stiffness nor to the macroscopic energy loss. Moreover, the multiscale model provides important insights on the micromechanics of tendon fascicles, predicting a non-homogeneous and relevant strain localization on cells, even under physiological macroscopic strain amplitudes.
       
  • Magnesium phosphate based cement with improved setting, strength and
           cytocompatibility properties by adding Ca(H2PO4)2·H2O and citric acid
    • Abstract: Publication date: Available online 10 December 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Suchun Yu, Langlang Liu, Chao Xu, Honglian Dai Inorganic phosphate cements have become prevalent as bone filling materials in clinical applications, owing to beneficial properties such as self-setting, biodegradability and osteoconductivity. However, the further development of phosphate cements with higher strength and improved cytocompatibility is expected. In this paper, we reported the preparation of a novel magnesium phosphate based cement (MPBC), which has similar compositions with magnesium phosphate cement (MPC) but Ca(H2PO4)2·H2O and citric acid were additionally added to modulate the performance. The physicochemical and biological properties of MPBC were investigated, the influences of the added Ca(H2PO4)2·H2O and citric acid on the performances of MPBC were analyzed, and the differences of performance between MPBC and MPC were discussed. Experimental results show that the setting time and compressive strength of MPBC were effectively enhanced by the addition of citric acid. In vitro biological degradation indicates that about 15 wt% of MPBC was reduced in 4 weeks. Compared with MPC, MPBC has weaker alkalinity and less dissolution of phosphate, leading to better suitability for cell proliferation and adhesion. These results suggest that as a bone filling material, MPBC shows better performance than MPC in many key indicators and has promising application prospects.
       
  • In vitro and In vivo Comparisons of the Porous Ti6Al4V Alloys Fabricated
           by the Selective Laser Melting Technique and A New Sintering Technique
    • Abstract: Publication date: Available online 10 December 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Ji Li, Zhongli Li, Yueyi Shi, Haoran Wang, Ruiling Li, Jiangping Tu, Gong Jin A new sintering technique using Ti6Al4V powder suspension was performed to prepare porous Ti6Al4V alloy with 75% porosity. Porous Ti6Al4V alloy with the same porosity fabricated by selective laser melting technique was used as the control. The characteristics, mechanical and biological properties of the two types of porous Ti6Al4V alloys were evaluated by mechanical tests, in vitro cell analysis and implantations. Results indicated that both groups showed good biocompatibility and osteogenic ability. However, microstructure and mechanical properties of the sintered porous Ti6Al4V were more similar to the cancellous bone without obvious stress shielding, and the new type of sample may be more effective in achieving early stability after implantation. Therefore, under the study conditions, this new type of porous alloy prospects a good candidate for biomaterials, especially for repairing bone defects and arthroplasty in orthopedics.Graphical abstractGraphical abstract for this article
       
  • Mechanical properties and microstructure of Ti-Mn alloys produced via
           powder metallurgy for biomedical applications
    • Abstract: Publication date: Available online 8 December 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Y. Alshammari, F. Yang, L. Bolzoni Titanium and especially its alloys are highly employed materials in biomedical applications because of their balanced mechanical properties and biocompatibility. Ti-Mn alloys (1, 5, and 10 wt%. Mn) were produced by powder metallurgy as a potential alternative material for biomedical applications. Two sets of samples were produced, one set as-sintered and the other was beta (β) forged. For the as-sintered samples with a content of up to 10 wt% Mn, the tensile strength ranged from 606–1070 MPa. On the other hand, for the β forged alloys the tensile strength ranged from 728–1224 MPa and the maximum value was for Ti-5Mn. Forged Ti-5Mn exhibits a good balance of mechanical properties such as ultimate tensile strength (1224 MPa), elongation (4.6%) and Vickers hardness (415 HV). The purely elastic properties of the Ti-10Mn alloy is attributed to the effects of the omega (ω) phase, the formation of which is due to the high amount of beta stabiliser added to Ti.Graphical abstractGraphical abstract for this article
       
  • Stored potential energy increases and elastic properties alterations are
           produced after restoring dentin with Zn-containing amalgams
    • Abstract: Publication date: Available online 6 December 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Manuel Toledano, Estrella Osorio, Fátima S. Aguilera, Manuel Toledano-Osorio, Modesto T. López-López, Raquel Osorio The aim of this research was to ascertain the mechanical and chemical behavior of sound and caries-affected dentin (CAD), after the placement of Zn-free vs containing amalgam restorations. Peritubular and intertubular dentin were evaluated using, a) nanoindenter in scanning mode; the load and displacement responses were used to perform the nano-Dynamic mechanical analysis and to estimate the complex (E⁎) and storage modulus (E'); b) Raman spectroscopy was used to describe the hierarchical cluster analysis (HCA). Assessments were performed before restoration placement and after restoring, and after 3 months of storage with thermocycling (100,000cy/5 °C and 55 °C). When CAD was treated with Zn-containing restorations, differences between E⁎ and E' at both peritubular and intertubular dentin augmented, with energy concentration and production of implications in the mechanical performance of the restored teeth. E⁎ and E' were very low at intratubular dentin of CAD restored with Zn-containing restorations. The relative presence of minerals, the phosphate crystallinity and the crosslinking of collagen increased their values at both types of dentin (peritubular and intertubular) when CAD was treated with Zn-containing restorations. The nature and secondary structure of collagen improved in CAD treated with Zn-containing amalgams. Different levels of dentin remineralization were revealed by hierarchical cluster analysis.Graphical abstractGraphical abstract for this article
       
  • Strength limits in mesoscaled 3Y-TZP ceramics for micro-surgical
           instruments
    • Abstract: Publication date: Available online 4 December 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): N. Antolino, C. Muhlstein, G. Hayes, J. Adair, R. Bermejo Micro-surgical instruments are a new application for mesoscale ceramics formed using the lost mold-rapid infiltration forming (LM-RIF) process. Instrument strength and reliability are the foremost concerns for this sensitive application. It is hypothesized that increasing grain size can improve the damage tolerance of the parts associated with the transformation toughening in the 3Y-TZP material, while retaining high strength. In this work, mesoscale bend bars (314×22×18 μm) of 3Y-TZP fabricated using the LM-RIF process were heat treated at 1400 °C for 1 h, 8 h, or 16 h, respectively, to obtain samples with different grain sizes. Strength tests were performed under three-point bending and results were evaluated using Weibull statistics. Fractographic and confocal Raman spectroscopic analyses were carried out to interpret the data.Experimental findings showed that the characteristic strength decreased with increasing grain size contrary to the damage tolerance hypothesis. An Orowan-Petch model was recalled to correlate the strength with the flaw size to grain size ratio. At fine grain sizes the strength was controlled by the flaws introduced by the LM-RIF process, whereas at large grain sizes the strength become more grain size controlled. Although larger-grained samples did have a higher propensity to transform, and thus increase toughening, exaggerated grain growth in some of the specimens tested caused an additional flaw population which led to an overall lower strength. Finally, based on the experimental observations and fracture mechanics considerations, we believe that an upper bound of ∼2.5 GPa exists for the strength of mesoscale as-fabricated 3Y-TZP ceramic parts.Graphical abstractGraphical abstract for this article
       
  • Quantifying machining outputs of pristine human teeth relevant to dental
           preparation procedures
    • Abstract: Publication date: March 2019Source: Journal of the Mechanical Behavior of Biomedical Materials, Volume 91Author(s): James F. Nowak, Johnson Samuel Minimally-assisted tooth repair (MaTR) systems are envisioned to be capable of substituting for the skill of a dentist. If successfully developed, MaTR systems could enable lower-skilled dental technicians to provide dental care at a fraction of the overall medical cost. This paper explores a key initial step towards the development of such systems by quantifying the machining responses of pristine human teeth relevant to dental preparation procedures. The working hypothesis of the study is that such findings will enable the benchmarking of key process planning and control metrics relevant for the future development of MaTR systems. To this end, pristine human cadaver teeth were cut using a computer-controlled motion platform and dental hand-piece. Relevant cutting responses, such as cutting forces, in-process rotational speed of the dental bur, teeth morphology, and bur wear were captured. The trends in cutting forces show the potential for implementing region-specific process parameters for cutting the enamel and dentin regions of the tooth. A feed-per-tooth value of 0.1 µm at rotational speeds of 8 krpm and 50 krpm is seen to cut both the enamel and dentin regions at cutting forces lower than patient discomfort thresholds identified in literature. Cutting force signals were also successfully mapped against the CT-scan data of the tooth. This mapping indicates a clear identification of the enamel/dentin regions, and a transition region that is dependent on cutting parameters, tooth/tool geometry and tool pose. The trends in the in-process rotational speed of the dental bur indicate that stalling of the dental bur occurs at feed per tooth values greater than 0.25 µm. The evidence of stalling can be detected by both a drop in the cutting force signal and by surface morphology changes on the cut surface of the tooth. MaTR systems should be designed to avoid bur stalling regions by either operating at feed per tooth values ≤ 0.25 µm or by the use of dental spindles with higher torque capacity. Lastly, the type of fit present on the shank of the bur is seen to result in differences in the cutting force signals and wear of the cutting edges (flutes) of the dental bur. In general, a right-angle (RA) fit on the shank of the dental bur results in a larger tool runout leading to uneven loads on the flutes and increased tool wear. The friction grip (FG) fit avoids these problems and may be more suited for MaTR systems.
       
  • First tribological assessment of retrieved Oxinium patellofemoral
           prostheses
    • Abstract: Publication date: February 2019Source: Journal of the Mechanical Behavior of Biomedical Materials, Volume 90Author(s): Shannen Chacko Rajan, Oana Bretcanu, David John Weir, David John Deehan, Thomas Jonathan JoyceGraphical abstractfx1
       
  • The viscoelastic behaviors of several kinds of cancer cells and normal
           cells
    • Abstract: Publication date: Available online 30 November 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Yongfang Xie, Mingling Wang, Min Cheng, Zhiqin Gao, Guohui Wang The purpose of this study was to investigate the viscoelastic behaviors of cancer cells and normal cells using the micropipette aspiration technique combined with the standard linear viscoelastic solid model. The viscoelastic behaviors of pairs of cell lines (human skin cells and human skin cancer cells, human fetal lung fibroblasts and human lung cancer cells, human mammary fibroblasts and human breast cancer cells, and human hepatocyte cells and human hepatocellular carcinoma cells) were tested by the micropipette aspiration technique. The cellular viscoelastic parameters (the instantaneous modulus E0, the equilibrium modulus associated with long term equilibrium E∞, and the apparent viscosity μ) were calculated using a Kelvin standard linear viscoelastic solid model. The present results indicate that the cancer cells were easier to deform, and the viscoelastic parameters (E0, E∞, μ) of the cancer cells were significantly lower than their corresponding normal cells (P
       
  • Full-field analysis of epicardial strain in an in vitro porcine
           heart platform
    • Abstract: Publication date: Available online 30 November 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Paolo Ferraiuoli, Benjamin Kappler, Sjoerd van Tuijl, Marco Stijnen, Bas A.J.M. de Mol, John W. Fenner, Andrew J. Narracott The quantitative assessment of cardiac strain is increasingly performed to provide valuable insights on heart function. Currently, the most frequently used technique in the clinic is ultrasound-based speckle tracking echocardiography (STE). However, verification and validation of this modality are still under investigation and further reference measurements are required to support this activity.The aim of this work was to enable these reference measurements using a dynamic beating heart simulator to ensure reproducible, controlled, and realistic haemodynamic conditions and to validate the reliability of optical-based three-dimensional digital image correlation (3D-DIC) for a dynamic full-field analysis of epicardial strain.Specifically, performance assessment of 3D-DIC was carried out by evaluating the accuracy and repeatability of the strain measurements across multiple cardiac cycles in a single heart and between five hearts. Moreover, the ability of this optical method to differentiate strain variations when different haemodynamic conditions were imposed in the same heart was examined.Strain measurements were successfully accomplished in a region of the lateral left ventricle surface. Results were highly repeatable over heartbeats and across hearts (intraclass correlation coefficient = 0.99), whilst strain magnitude was significantly different between hearts, due to change in anatomy and wall thickness. Within an individual heart, strain variations between different haemodynamic scenarios were greater than the estimated error of the measurement technique.This study demonstrated the feasibility of applying 3D-DIC in a dynamic passive heart simulator. Most importantly, non-contact measurements were obtained at a high spatial resolution (~ 1.5 mm) allowing resolution of local variation of strain on the epicardial surface during ventricular filling. The experimental framework developed in this paper provides detailed measurement of cardiac strains under controlled conditions, as a reference for validation of clinical cardiac strain imaging modalities.Graphical abstractGraphical abstract for this article
       
  • EFFECT OF EPIGALLOCATECHIN-3- GALLATE SOLUTIONS ON BOND DURABILITY AT THE
           ADHESIVE INTERFACE IN CARIES-AFFECTED DENTIN
    • Abstract: Publication date: Available online 30 November 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Melissa Proença Nogueira Fialho, Viviane Hass, Rodrigo Proença Nogueira, Fabiana Mantovani Gomes França, Cecilia Pedroso Turssi, Roberta Tarkany Basting, Flávia Lucisano Botelho Amaral Hydrolytic and enzymatic degradation by matrix metalloproteinases (MMPs) reduces the durability of composite resin restorations on caries-affected dentin (CAD). The use of MMP inhibitors such as epigallocatechin-3-gallate (EGCG) could increase the longevity of the bond to dentin. This study aimed to evaluate the use of EGCG at different aqueous concentrations on the resin-dentin microtensile bond strength (μTBS), fracture pattern and nanoleakage (NL) in immediate (IM) time interval and after 12-months of water storage (1Y) when using a two-step etch-and-rinse adhesive system on CAD. Dentin surfaces of 40 human molars were submitted to a microbiological caries induction protocol and randomized into 5 groups (n = 8) (0.02% EGCG; 0.2% EGCG; 0.5% EGCG; 2% Chlorhexidine [CHX] and no treatment as Control Group - [NT]). After acid etching, the solutions were applied for 60 s followed by application of dental adhesive (Adper Single Bond 2, 3 M ESPE) to CAD surfaces. Subsequently, a resin composite (4 mm) block was built on the dentin. After 24 h, the teeth were sectioned into beam-shaped specimens (cross-sectional area of 1 mm2 and 8-mm high). Half of the specimens were tested in IM and the other half after 1Y. Two samples per tooth were submitted to SEM for NL evaluation. Data were statistically analyzed by two-way ANOVA and Tukey tests (α = 0.05). The results showed that use of EGCG and CHX did not affect μTBS in IM (p> 0.05). After 1Y, there was a reduction in μTBS for all experimental groups (p < 0.05). Adhesive fractures predominated in IM in all groups, except for 0.05% EGCG and NT. After 1Y, there was an increase in these adhesive fractures in all groups. For NL, all agents applied reduced NL in comparison with CT (p < 0.001). CHX showed lower NL (p < 0.001), followed by 0.02% and 0.5% EGCG. NT showed highest NL for both time intervals (p < 0.001). Thus, although the use of EGCG at different concentrations and CHX reduced the NL, they were unable to reduce degradation of μTBS to CAD over time.
       
  • Fabrication of alumina-PSZ composites via spark plasma sintering and their
           mechanical properties
    • Abstract: Publication date: Available online 29 November 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Tomoyuki Fujii, Keiichiro Tohgo, Pandoyo Bayu Putra, Yoshinobu Shimamura Alumina-partially stabilized zirconia (PSZ) composites were fabricated via spark plasma sintering (SPS) technique to produce biocompatible materials with superior mechanical properties. The volume fraction of the composites covered from 100% alumina to 100% PSZ. Their sintering state was examined by optical microscopy, density measurement, and X-ray diffraction, and dense composites without any reaction phases could be fabricated, irrespective of PSZ content. Then, three-point bending tests and hardness tests were conducted. The hardness and elastic modulus agreed with the predictions based on the Voigt model and the Eshelby's equivalent inclusion model combined with the Mori-Tanaka's mean field concept, respectively. While the bending strength of the composites ranged from that of monolithic alumina to that of monolithic PSZ, the fracture toughness of the composites improved as compared with the monoliths of alumina and PSZ. We concluded that the use of alumina and PSZ was effective to fabricate the composites with high mechanical performances.Graphical abstractGraphical abstract for this article
       
  • Bacterial leakage and bending moments of screw-retained,
           composite-veneered PEEK implant crowns
    • Abstract: Publication date: Available online 28 November 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Andreas Wachtel, Tycho Zimmermann, Mona Sütel, Ufuk Adali, Mohamad Abou-Emara, Wolf-Dieter Müller, Sven Mühlemann, Andreas Dominik Schwitalla Due to its elastic modulus close to bone, the high-performance material PEEK (polyetheretherketone) represents an interesting material for implant-supported dental prostheses. Besides a damping effect of masticatory forces, it might have a sealing effect against bacterial leakage of the implant-abutment interface (IAI). So far, PEEK has only been used for provisional implant crowns. Therefore, the aim of the study was the evaluation of the bacterial tightness of screw-retained PEEK crowns on titanium implants with conical IAI during masticatory simulation and subsequent bending moment testing.Ten screw-retained implant crowns in the shape of an upper central incisor consisting of a PEEK crown framework veneered with composite were connected to NobelActive RP titanium implants (4.3 ×11.5 mm, Nobel Biocare AB, Göteborg, Sweden) with a tightening torque of 15 Ncm.Prior to tightening, the interior of the implant was inoculated with a bacterial suspension of Enterococcus faecium. The specimens were overmolded with indicating agar (Kanamycin-Aesculin-Azid-Agar (KAAA), Oxoid Limited, Basingstoke United Kingdom), that turns black in contact with E. faecium. The specimens were subjected to a cyclic masticatory simulation whereby a force of 50 N · cm was applied at an angle of 30° to the implant axis for 1.2 million cycles. Afterwards, the specimens were subjected to a static loading test according to ISO 14801:2007 to determine the bending moment.During masticatory simulation neither a loosening of the implant screws nor any damage to the veneer or the PEEK framework occurred. Furthermore, no bacterial leakage could be observed in any of the specimens. The average maximum bending moment was measured at 352.13 ± 48.96 N∙cm.Regarding masticatory forces, PEEK implant crowns seem to be applicable as definitive implant-supported restorations. Furthermore, the bacterial tightness of the IAI of screw-retained one-piece PEEK implant crowns is advantageous compared to superstructures of conventional materials. Further studies are necessary to substantiate the clinical significance of these findings.
       
  • Influence of nano-hydroxyapatite containing desensitizing toothpastes on
           the sealing ability of dentinal tubules and bonding performance of
           self-etch adhesives
    • Abstract: Publication date: Available online 28 November 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Dandan Pei, Yuchen Meng, Yuncong Li, Jie Liu, Yi Lu ObjectivesTo evaluate the dentinal tubular occlusion of nano-hydroxyapatite (nHAp) containing desensitizing toothpastes and their influence on the resin-dentin bonding performance of two mild self-etch adhesives.Materials and MethodsMid-coronal dentin specimens were prepared from obtained intact human third molars. They were immersed in 1% citric acid for 20 s to expose the dentinal tubules to simulate sensitive teeth and then randomly divided into four groups. The control group received no desensitizing treatment. Experimental groups were treated with two commercial nHAp containing desensitizing toothpastes (Biorepair and Dontodent) and an experimental pure nHAp paste respectively. Each group was further divided into two subgroups and bonded with either G-Bond or Clearfil S3 Bond. The micro-tensile bond strength was tested and failure mode distribution was analyzed. Moreover, the effect of desensitizers on dentinal tubular occlusion was observed by the field-emission scanning electron microscope (FESEM). Resin infiltration of the adhesives labeled by fluorescent Rhodamin B was evaluated under confocal laser scanning microscopy (CLSM).ResultsFESEM revealed that all the desensitizers noticeably occluded the dentinal tubules, and the extents were completer after application for 7 days. The majority of the occlusion still preserved even after acid challenge with cola or adhesive. CLSM demonstrated shorter resin tags were produced in the desensitized groups. When bonding with G-Bond, the pure nHAp group showed comparable bond strength to the control group, while Biorepair and Dontodent treatment decreased the bond strength. For groups bonded with Clearfil S3 Bond, all the desensitizers reduced the bond strengths compared to the control and no significant difference was found among the three groups.ConclusionNano-hydroxyapatite containing desensitizing toothpastes could occlude dentinal tubules effectively with a certain degree of acid resistance, which contributes to the relief of dentin hypersensitivity. While, the application of these nHAp desensitizers comprised the resin infiltration of G-Bond and Clearfil S3 Bond, resulting in decreased bond strengths of the resin-dentin bonding.Graphical abstractGraphical abstract for this article
       
  • Antibiotic Elution and Mechanical Property of TiO2 Nanotubes
           Functionalized PMMA-based Bone Cements
    • Abstract: Publication date: Available online 23 November 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Shou-Cang Shen, Kumaran Letchmanan, Pui Shan Chow, Reginald Beng Hee Tan To overcome the disadvantage of current antibiotic bone cements with low drug elution efficiency, the hollow nanostructured titanium-dioxide (TiO2) nanotubes (TNTs) were formulated with antibiotic loaded bone cement to create nano diffusion networks, enabling enhanced release of antibiotic. By incorporation of TNTs into Poly(methyl methacrylate) (PMMA) based bone cement, more than 50% of loaded antibiotic (such as gentamicin or vancomycin) could be released in two months. As comparison, only about 5% of total drug release was achieved in the absence of TNTs. The mechanical properties of PMMA-based bone cements were well preserved after incorporation of TNTs. Furthermore, the compression strength and bending modules of TNTs formulated antibiotic bone cements could be maintained after the drug release for 70 days or aging in PBS buffer for 3 months. The insoluble TNTs in bone cement is believed to support the mechanical properties after wet aging.
       
  • The Denticulate Ligament – Tensile Characterisation and Finite Element
           Micro-scale Model of the Structure Stabilising Spinal Cord
    • Abstract: Publication date: Available online 20 November 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Katarzyna Polak-Kraśna, Sandra Robak-Nawrocka, Sylwia Szotek, Marcin Czyż, Daniel Gheek, Celina Pezowicz BackgroundDamage to the spinal cord is one of the most debilitating pathologies with considerable health, economic and social impact. Improved prevention, treatment and rehabilitation after spinal cord injury (SCI) requires the complex biomechanics of the spinal cord with all its structural elements and the injury mechanism to be understood. This comprehensive understanding will also allow development of models and tools enabling better diagnosis, surgical treatment with increased safety and efficacy and possible development of regenerative therapies. The denticulate ligaments play an important role in stabilising spinal cord within the spinal canal. They participate in spinal cord movements and play a role in determining the stress distribution during physiological but also traumatic loading. We present detailed tensile characterisation of the denticulate ligaments and a Finite Element micro-scale model of the ligament relating its structure with the distribution of stress under physiological loading.MethodDenticulate ligaments were dissected from cervical spinal levels from 6 porcine cervical specimens with fragments of the pia and dura mater and characterised in terms of their geometry and response to uniaxial tensile loading. The stress-strain characteristics were recorded until rupture of the ligament, ultimate parameters and Young's moduli were determined. The parametric micro-structural Finite Element model was constructed based on literature microscope and histological images of a denticulate ligament as a phenomenological representation of the complex microstructure of a soft tissue. The model was validated against the experimental data.ResultsStress-strain characteristics obtained in tensile test were typical for a soft tissue behaviour. No statistically relevant differences in ultimate strength, strain and Young's moduli were observed between the ligaments harvested from different vertebral levels. Average ultimate tensile stress was 1.26 ± 0.20 MPa at strain 0.51 ± 0.00, rupturing force (1.01 ± 0.21 N) was in agreement with results obtained previously. The Finite Element model accurately predicted the extension-load behaviour of the denticulate ligament in elastic regime. The micro-scale structural representation enabled capturing deformation modes representative of the experimentally observed behaviour.ConclusionsThe presented stress-strain characteristics of the denticulate ligaments add valuable data to the understanding of the biomechanics of the spinal cord and enable development of more accurate models. The developed micro-scale model was capable of capturing biomechanical response of collagenous tissue under tensile loading, it can be applied for the prediction of other soft tissues behaviours. The denticulate ligament model should be included into future spinal cord models to fully represent the complex system's biomechanics and enable development of surgical aid tools to improve patient outcomes and future regenerative therapies.Graphical abstractGraphical abstract for this article
       
  • Characterization of Resilin-like Proteins with Tunable Mechanical
           Properties
    • Abstract: Publication date: Available online 20 November 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Renay S.-C. Su, Emily E. Gill, Yeji Kim, Julie C. Liu Resilin is an elastomeric protein abundant in insect cuticle. Its exceptional properties, which include high resilience and efficient energy storage, motivate its potential use in tissue engineering and drug delivery applications. Our lab has previously developed recombinant proteins based on the resilin-like sequence derived from Anopheles gambiae and demonstrated their promise as a scaffold for cartilage and vascular engineering. In this work, we describe a more thorough investigation of the physical properties of crosslinked resilin-like hydrogels. The resilin-like proteins rapidly form crosslinked hydrogels in physiological conditions. We also show that the mechanical properties of these resilin-like hydrogels can be modulated simply by varying the protein concentration or the stoichiometric ratio of crosslinker to crosslinking sites. Crosslinked resilin-like hydrogels were hydrophilic and had a high water content when swollen. In addition, these hydrogels exhibited moderate resilience values, which were comparable to those of common synthetic rubbers. Cryo-scanning electron microscopy showed that the crosslinked resilin-like hydrogels at 16 wt% featured a honeycomb-like structure. These studies thus demonstrate the potential to use recombinant resilin-like proteins in a wide variety of applications such as tissue engineering and drug delivery due to their tunable physical properties.Graphical abstractGraphical abstract for this article
       
  • A Shear Assay Study of Single Normal/Breast Cancer Cell Deformation and
           Detachment from Poly-Di-Methyl-Siloxane (PDMS) Surfaces
    • Abstract: Publication date: Available online 15 November 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): C.J. Ani, J.D. Obayemi, V.O. Uzonwanne, Y. Danyuo, O.S. Odusanya, J. Hu, K. Malatesta, W.O. Soboyejo This paper presents the results of a combined experimental and analytical/computational study of viscoelastic cell deformation and detachment from poly-di-methyl-siloxane (PDMS) surfaces. Fluid mechanics and fracture mechanics concepts are used to model the detachment of biological cells observed under shear assay conditions. The analytical and computational models are used to compute crack driving forces, which are then related to crack extension during the detachment of normal breast cells and breast cancer cells from PDMS surfaces that are relevant to biomedical implants. The interactions between cells and the extracellular matrix, or the extracellular matrix and the PDMS substrate, are then characterized using force microscopy measurements of the pull-off forces that are used to determine the adhesion energies. Finally, fluorescence microscopy staining of the cytosketelal structures (actin, micro-tubulin and cyto-keratin), transmembrane proteins (vimentin) and the ECM structures (Arginin Glycine Aspartate – RGD) is used to show that the detachment of cells during the shear assay experiments occurs via interfacial cracking between (between the ECM and the cell membranes) with a high incidence of crack bridging by transmembrane vinculin structures that undergo pull-out until they detach from the actin cytoskeletal structure. The implications of the results are discussed for the design of interfaces that are relevant to implantable biomedical devices and normal/cancer tissue.
       
  • Load-bearing capacity under fatigue and survival rates of adhesively
           cemented yttrium-stabilized zirconia polycrystal monolithic simplified
           restorations
    • Abstract: Publication date: Available online 12 November 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Camila Pauleski Zucuni, Andressa Borin Venturini, Catina Prochnow, Gabriel Kalil Rocha Pereira, Luiz Felipe Valandro This study aims to evaluate the fatigue failure load, number of cycles for failure and survival probability of 2nd and 3rd generation yttrium-stabilized zirconia (YSZ) adhesively cemented to a dentin analogue substrate. Disc-shaped specimens (n = 10; Ø = 10 mm; thickness = 1.0 mm) were produced from four 2nd generation YSZs (Lava Plus, 3 M ESPE; Vita In-Ceram YZ-HT, VITA Zahnfabrik; Zirlux FC, IvoclarVivadent; Katana ML-HT, Kuraray) and two 3rd generation YSZs (Katana UTML and Katana STML, Kuraray). Each YSZ disc was adhesively cemented (Multilink Automix System) onto its dentin analogue pair (epoxy resin, Ø = 10 mm; thickness = 2.5 mm). Fatigue tests were conducted through step-stress approach (load ranging from 400 to 2600 N; step-size of 200 N; 20,000 cycles per step, 20 Hz) and the obtained data were analyzed using Kaplan Meier and Mantel-Cox tests. Surface topography and phase transformation (m-, t-, and c-phases) inspections after particle air-abrasion of the YSZs were performed, as well as fractographic analysis of the failed specimens. Second-generation zirconia materials presented higher fatigue failure load, number of cycles for failure, and survival probability than 3rd generation. Similar topographical characteristics of the YSZs could be noted. Phase transformation (t- to m-phase) after YSZ air-abrasion was only observed for 2nd generation materials. All failures started from the surface/sub-surface defects located at the cementation interface. 2nd generation zirconia presented higher load-bearing capacity in cyclic loading than 3rd generation materials.
       
  • Effect of carbon fiber type on monotonic and fatigue properties of
           orthopedic grade PEEK
    • Abstract: Publication date: Available online 3 November 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Noah Bonnheim, Farzana Ansari, Marco Regis, Pierangiola Bracco, Lisa Pruitt Carbon-fiber reinforced (CFR) PEEK implants are used in orthopedic applications ranging from fracture fixation plates to spinal fusion cages. Documented implant failures and increasing volume and variety of CFR PEEK implants warrant a clearer understanding of material behavior under monotonic and cyclic loading. To address this issue, we conducted monotonic and fatigue crack propagation (FCP) experiments on orthopedic grade unfilled PEEK and two formulations of CFR PEEK (PAN- and pitch-based carbon fibers). The effect of annealing on FCP behavior was also studied. Under monotonic loading, fiber type had a statistically significant effect on elastic modulus (12.5 ± 1.3 versus 18.5 ± 2.3 GPa, pitch versus PAN CFR PEEK, AVG ± SD) and on ultimate tensile strength (145 ± 9 versus 192 ± 17 MPa, pitch versus PAN CFR PEEK, AVG ± SD). Fiber type did not have a significant effect on failure strain. Under cyclic loading, PAN CFR PEEK demonstrated an increased resistance to FCP compared with unfilled and pitch CFR PEEK, and this improvement was enhanced following annealing. Pitch CFR PEEK exhibited FCP behavior similar to unfilled PEEK, and neither material was appreciably affected by annealing. The improvements in monotonic and FCP behavior of PAN CFR PEEK is attributed to a compound effect of inherent fiber properties, increased fiber number for an equivalent wt % reinforcement, and fiber aspect ratio. FCP was shown to proceed via cyclic modes during stable crack growth, which transitioned to static modes (more akin to monotonic fracture) at longer crack lengths. The mechanisms of fatigue crack propagation appear similar between carbon-fiber types.
       
  • Surface functionalization of polylactic acid fibers with alendronate
           groups does not improve the mechanical properties of fiber-reinforced
           calcium phosphate cements
    • Abstract: Publication date: Available online 3 November 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Daniela-Geta Petre, Nathan W. Kucko, Anna Abbadessa, Tina Vermonden, Alessandro Polini, Sander C.G. Leeuwenburgh Calcium phosphate cements (CPCs) are frequently used as synthetic bone substitute, but their intrinsic low fracture toughness impedes their application in highly loaded skeletal sites. However, fibers can be used to reduce the brittleness of these CPCs provided that the affinity between the fibers and cement matrix facilitates the transfer of loads from the matrix to the fibers. The aim of the present work was to improve the interface between hydrophobic polylactic acid (PLA) microfibers and hydrophilic CPC. To this end, calcium-binding alendronate groups were conjugated onto the surface of PLA microfibers via different strategies to immobilize a tunable amount of alendronate onto the fiber surface. CPCs reinforced with PLA fibers revealed toughness values which were up to 50-fold higher than unreinforced CPCs. Nevertheless, surface functionalization of PLA microfibers with alendronate groups did not improve the mechanical properties of fiber-reinforced CPCs.
       
  • Mechanical and Surface Chemical Analysis of Retrieved Breast Implants from
           a Single Centre
    • Abstract: Publication date: Available online 2 November 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Louise J Magill, Aleksandra Tanksa, Mohammed Keshtgar, Ashfin Mosahebi, Gavin Jell IntroductionBreast implants are associated with complications such as capsular contracture, implant rupture and leakage often necessitating further corrective surgery. Re-operation rates have been reported to occur in up to 15.4% of primary augmentation patients and up to 27% in primary reconstructions patients within the first three years [1]. The aim of this study was to examine the mechanical and surface chemical properties as well as the fibroblast response of retrieved breast implants in our unit to determine the in vivo changes which occur over time.MethodsEthical approval was obtained. 47 implants were retrieved. Implantation time ranged from 1 month to 388 months (Mean 106.1 months). Tensile strength, elongation, Young's modulus and tear strength properties were measured using Instron 5565 tensiometer on anterior and posterior aspects of the implant. Attenuated total reflectance-fourier transform infra-red spectroscopy (ATR-FTIR), wettability and scanning electron microscopy (SEM) analysis was performed on the shell surfaces. Bicinchoninic acid assay was performed to determine shell protein content. The fibroblast response was determined by seeding HDFa cells on the retrieved implants and cell metabolism measured using Alamar Blue™ assay.ResultsMechanical properties fall with increasing duration of implantation. There were no significant changes in ATR-FTIR spectra between ruptured and intact implants nor significant changes in wettability in implants grouped into 5 year categories. SEM imaging reveals surface degradation changes with increasing duration of implantation.ConclusionsWith increasing duration of implantation, mechanical properties of the breast implants fall. However this was not associated with surface chemical changes as determined by ATR-FTIR and wettability nor protein content of the shells. Thus the reduction in mechanical properties is associated with breast implant failure but further research is required to elucidate the mechanisms.
       
  • Structural Analysis of the Frontal and Parietal Bones of the Human Skull
    • Abstract: Publication date: Available online 1 November 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Stephen L. Alexander, Karin Rafaels, C Allan Gunnarsson, Tusit Weerasooriya Bone specimens were collected from the frontal and parietal bones of 4 adult, human skulls. The microstructure was characterized using micro-tomography (CT) at about 6-μm resolution to map the change of porosity as a function of the depth, P(d), from the inner surface nearest to the brain to the outer surface nearest to the skin. A quantifiable method was developed using the measured P(d) to objectively distinguish between the three layers of the skull: the outer table, diploë, and inner table. The thickness and average porosity of each of the layers were then calculated from the measured porosity distributions, and a Gaussian function was fit to the P(d) curves. Morphological parameters were compared between the two bone types (frontal and parietal), while accounting for skull-to-skull variability. Parietal bones generally had a larger diploë accompanied by a thinner inner table. The arrangement of the porous vesicular structure within the outer table was also obtained with micro-CT scans with longer scan times, using enhanced parameters for higher resolution and lower noise in the images. From these scans, the porous structure of the bone appeared to be randomly arranged in the transverse plane, compared to the porous structure of the human femur, which is aligned in the loading direction.Graphical abstractGraphical abstract for this article
       
  • Forces and moments in cervical spinal column segments in frontal impacts
           using finite element modeling and human cadaver tests
    • Abstract: Publication date: Available online 2 October 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Frank Meyer, John Humm, Yuvaraj Purushothaman, Rémy Willinger, Frank A. Pintar, Narayan Yoganandan Experiments have been conducted using isolated tissues of the spine such as ligaments, functional units, and subaxial cervical spine columns. Forces and or moments under external loading can be obtained at the ends of these isolated/segmented preparations; however, these models require fixations at the end(s). To understand the response of the entire cervical spine without the artificial boundary/end conditions, it is necessary to use the whole body human cadaver in the experimental model. This model can be used to obtain the overall kinematics of the head and neck. The forces and moments at each vertebral level of the cervical column segments cannot be directly obtained using the kinematic and mass property data. The objective of this study was to determine such local loads under simulated frontal impact loading using a validated head-neck finite element model and experiments from whole body human cadaver tests, at velocities ranging from 3.9 to 16 m/s. The specimens were prepared with a nine linear accelerometer package on the head, and a triaxial accelerometer with a triaxial angular rate sensor on T1, and a set of three non-collinear retroreflective targets were secured to the T1 using the accelerometer mount. A similar array of targets was attached to the skull. Head accelerations were computed at the center of gravity of the head using specimen-specific physical properties. Upper and lower neck forces were computed using center of gravity acceleration data. This dataset was used to verify a previously validated finite element model of the head-neck model by inputting the mean T1 accelerations at different velocities. The model was parametrically exercised from 4 to 16 m/s in increments of 3 m/s to determine the forces and moments in the local anatomical system at all spinal levels. Results indicated that, with increasing velocities, the axial loading was found to be level-invariant, while the shear force and moment responses depended on the level. The nonuniform developments of the segmental forces and moments across different spinal levels suggest a shift in instantaneous axis of rotations between the across different spinal levels. Such differential changes between contiguous levels may lead to local spinal instability, resulting in long-term effects such as accelerated degeneration and spondylosis. The study underscored the need to conduct additional research to include effects of posture and geometrical variations that exist between males and females for a more comprehensive understanding of the local load-sharing in frontal impacts.
       
  • In vitro experimental and numerical study on biomechanics and stability of
           a novel adjustable hemipelvic prosthesis
    • Abstract: Publication date: February 2019Source: Journal of the Mechanical Behavior of Biomedical Materials, Volume 90Author(s): Dongxu Liu, Jianfeng Jiang, Yingqi Hua, Zhengdong Cai, Zhongmin Jin, Leiming Gao, Zikai Hua Hemipelvic prostheses are used to reconstruct the damaged pelvis due to bone tumors and traumas. However, biomechanical properties of the reconstructed pelvis remain unclear, causing difficulties to implant development and prediction of surgical outcome. In this study, a novel adjustable hemipelvic prosthesis for the Type 1–3 pelvis resection was used to reconstruct the intact pelvic ring. Two types of Pedicle Screw Rod Systems were proposed to improve the stability of fixation between the prosthesis and the bone. Finite Element models of the reconstructed pelvis were built to analyze the performance of the prosthesis and PSRS. Moreover, an in vitro experimental study was performed to measure the deformation of the human reconstructed pelvis. Numerical results agree well with the experimental data. It was found that displacements and stresses bilaterally transferred more evenly in the reconstructed pelvis enhanced by bilateral Pedicle Screw Rod System. The load-transfer function of the pelvis under double-leg standing stance could be recovered. The bilateral pedicle system has better biomechanical performance than the unilateral pedicle system.Graphical abstractfx1
       
  • Characterization of perfused and sectioned liver tissue in a full
           indentation cycle using a visco-hyperelastic model
    • Abstract: Publication date: February 2019Source: Journal of the Mechanical Behavior of Biomedical Materials, Volume 90Author(s): Ling Li, Ashkan Maccabi, Ahmad Abiri, Yen-Yi Juo, Wenyang Zhang, Yi-Jui Chang, George N. Saddik, Lihua Jin, Warren S. Grundfest, Erik P. Dutson, Jeff D. Eldredge, Peyman Benharash, Robert N. Candler Realistic modeling of biologic material is required for optimizing fidelity in computer-aided surgical training and assistance systems. The modeling of liver tissue has remained challenging due to its nonlinear viscoelastic properties and high hysteresis of the stress-strain relation. While prior studies have described the behavior of liver tissue during the loading status (in elongation, compression, or indentation tests) or unloading status (in stress relaxation or creep tests), a hysteresis curve with both loading and unloading processes was incompletely defined. We seek to use a single material model to characterize the mechanical properties of liver tissue in a full indentation cycle ex vivo perfused and then sectioned. Based on measurements taken from ex-vivo perfused porcine livers, we converted force-displacement curves to stress-strain curves and developed a visco-hyperelastic constitutive model to characterize the liver's mechanical behavior at different locations under various rates of indentation (1, 2, 5, 10, and 20 mm/s). The proposed model is a mixed visco-hyperelastic model with up to 6 coefficients. The normalized root mean square standard deviations of fitted curves are less than 5% and 10% in low (0.3) conditions respectively.
       
  • Optimization of bio-inspired bi-directionally corrugated panel
           impact-resistance structures: Numerical simulation and selective laser
           melting process
    • Abstract: Publication date: Available online 27 November 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Jiankai Yang, Dongdong Gu, Kaijie Lin, Ying Yang, Chenglong Ma The telson (tail plate) of Stomatopoda (mantis shrimp) shows excellent impact resistance properties, and its special structure is an ideal prototype to mimic. In this paper, a series of bi-directionally corrugated panel (DCP) structures inspired by the telson of mantis shrimp was designed. The crush simulation of DCP structures with different structural parameters, namely wavelength (λ) and amplitude (A), was carried out using ANSYS LS-NYNA. In order to verify the simulation results, AlSi10Mg components with DCP structures were fabricated by selective laser melting and the out-of-plane compression tests were conducted to investigate the compression performance. The numerical simulation results indicated that the influence of wavelength of DCP structure on the energy absorption (EA) and specific energy absorption (SEA) capability was greater than that of the amplitude, and the DCP structure with A = 8 mm and λ = 6 mm possessed the best impact resistance performance. The SLM-processed AlSi10Mg components with DCP structures showed high surface quality and good forming accuracy, and the relation between experimental compression behavior and the DCP structure parameter was in good agreement with the numerical results.
       
  • Decellularisation affects the strain rate dependent and dynamic mechanical
           properties of a xenogeneic tendon intended for anterior cruciate ligament
           replacement
    • Abstract: Publication date: Available online 26 November 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Jennifer Helen Edwards, Eileen Ingham, Anthony Herbert Development of new replacement grafts for anterior cruciate ligament (ACL) repair requires mechanical testing to ensure they can provide joint stability following implantation. A decellularised porcine superflexor tendon (pSFT) has been developed previously as an alternative to current reconstruction methods and subjected to biomechanical analysis. The application of varied strain rates to biological tissues is known to alter their biomechanical properties, however the effects of decellularisation on strain rate dependent and dynamic mechanical behaviour of tissues have not been explored. This study utilised tensile testing to investigate the material properties of native and decellularised pSFTs at three different strain rates (1%.s−1, 10%.s−1 and 100%.s−1). In addition, dynamic mechanical analysis (DMA) was used to ascertain the relative contributions of the solid and fluid phase components of the tissues.Ultimate tensile strength was significantly reduced in decellularised compared with native untreated pSFTs but was unaffected by strain rate. In contrast, toe region moduli increased with increasing strain rate for native tissues, but this effect was not observed in decellularised pSFTs. Linear region moduli were unaffected by strain rate, but were significantly reduced in decellularised pSFT compared with native tissue.Following DMA, significant reductions in dynamic modulus, storage modulus and loss modulus were seen in decellularised compared with native pSFT. Interestingly, the damping ability of the tendons was unaffected by decellularisation, suggesting that solid and fluid phases of the tissue were affected equally. These results, alongside previous studies, suggest that decellularisation affects collagen crimp, tissue swelling and collagen fibre sliding. However, despite these findings, the biomechanical properties of decellularised pSFT remain sufficient to act as an off-the-shelf solution for ACL reconstruction.
       
  • How much force is required to perforate a colon during colonoscopy' An
           experimental study
    • Abstract: Publication date: Available online 26 November 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Steve Johnson, Michael Schultz, Mario Scholze, Troy Smith, John Woodfield, Niels Hammer IntroductionColonoscopy is a commonly-performed procedure to diagnose pathology of the large intestine. Perforation of the colon is a rare but feared complication. It is currently unclear how much force is actually required to cause such injury nor how this is altered in certain diseases. Our aim was to analyze the forces required to perforate the colon in experiments using porcine tissues.MethodsUsing 3D printing technology, models of two commercially available colonoscope heads were printed under three configurations: straight (I), 90°- bent (L) and fully bent (U). Samples of porcine colon were assessed with the models and configurations under perpendicular and angular load application and these data compared to the maximum force typically exerted by experienced colonoscopists.ResultsThe force required for perforation was significantly lower for the I compared to the L of the larger colonoscope head configuration under angular loading (14.1 vs. 46.5 N). Similar differences were found for linear stiffness when loaded (I vs. L small when loaded perpendicular: 0.80 vs. 2.41 N/mm; I vs. L large when loaded angled 0.70 vs. 2.06 N/m). The mode and site of failure varied significantly between the scopes, with delamination of the mucosa/submucosa below the sample (96%) for the I, blunt mucosa/submucosa/muscularis failure adjacent to the loading site (77%) for the L, and failure of all colon layers lateral to the loading site (59%) for the U configuration, respectively. Perpendicular and angulated loading resulted in similar load-deformation values. Maximum forces typically exerted by colonoscopists averaged 13.9 to 27.9 N, depending on the colonoscope model and head configuration.DiscussionThe force required for colon perforation varies depending on the type mode of loading and is likely lower than the force an experienced colonoscopist would exert in daily practice. There is a real risk of perforation, especially when the end of the scope is advancing directly into the colonic wall. The given experimental setup allowed to obtain reliable data of the colon in a standardized scenario, forming the basis for further experiments.
       
  • Characterization of low-shrinkage dental composites containing
           methacrylethyl-polyhedral oligomeric silsesquioxane (ME-POSS)
    • Abstract: Publication date: February 2019Source: Journal of the Mechanical Behavior of Biomedical Materials, Volume 90Author(s): Talita Angelina Tavares Canellas, Aline de Almeida Neves, Ingrid Kimberly Bezerra dos Santos, Amanda Ramos Pereira de Rezende, Carlos Eduardo Fellows, Eduardo Moreira da Silva The aim of this study was to characterize low-shrinkage dental composites containing methacrylethyl-polyhedral oligomeric silsesquioxane (ME-POSS). Four experimental composites were manufactured, two of which contained organic matrixes of BisGMA-TEGDMA (70/30 wt% - BGC) and BisEMA-TEGDMA (80/20 wt% - BEC). The two other experimental composites replaced BisGMA and BisEMA with 25 wt% of ME-POSS (BGP and BEP). The composites also contained 70 wt% of 0.7 µm silanized BaBSi particles. The following properties were evaluated: Degree of conversion (DC%), volumetric polymerization shrinkage (VS%), polymerization shrinkage stress (Pss), flexural strength (FS), Flexural modulus (FM), hardness (KHN), water sorption (Wsp), water solubility (Wsl), diffusion coefficient (D), and wear. The DC% was not influenced by the presence of ME-POSS, with BEC (75.6%) and BEP (74.8%) presenting higher DC% than BGC (60.6%) and BGP (55.6%). The ME-POSS-containing composites (BGP and BEP) presented significantly lower VS% and Pss. The FS ranged from 92.7 to 142.0 MPa and the FM from 3.6 to 10.3 GPa. ME-POSS did not influence the KHN. BEC and BEP presented lower Wsp and Wsl when compared to BGC and BGP. D ranged from 1.0 × 10−6 to 7.4 × 10−6 cm2 m−1. Incorporation of ME-POSS significantly decreased the wear for both binary matrices (p 
       
  • An interface damage model that captures crack propagation at the
           microscale in cortical bone using XFEM
    • Abstract: Publication date: February 2019Source: Journal of the Mechanical Behavior of Biomedical Materials, Volume 90Author(s): Anna Gustafsson, Hanifeh Khayyeri, Mathias Wallin, Hanna Isaksson Reliable tools for fracture risk assessment are necessary to handle the challenge with an aging population and the increasing occurrence of bone fractures. As it is currently difficult to measure local damage parameters experimentally, computational models could be used to provide insight into how cortical bone microstructure and material properties contribute to the fracture resistance. In this study, a model for crack propagation in 2D at the microscale in cortical bone was developed using the extended finite element method (XFEM). By combining the maximum principal strain criterion with an additional interface damage formulation in the cement line, the model could capture crack deflections at the osteon boundaries as observed in experiments. The model was used to analyze how the Haversian canal and the interface strength of the cement line affected the crack trajectory in models depicting osteons with three different orientations in 2D. Weak cement line interfaces were found to reorient the propagating cracks while models with strong interfaces predicted crack trajectories that penetrated the cement line and propagated through the osteons. The presented model is a promising tool that could be used to analyze how local, age-related material changes influence the crack trajectory and fracture resistance in cortical bone.Graphical abstractfx1
       
  • Optimization method for the determination of Mooney-Rivlin material
           coefficients of the human breasts in-vivo using static and dynamic finite
           element models
    • Abstract: Publication date: Available online 22 November 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Yue Sun, Lihua Chen, Kit-lun Yick, Winnie Yu, Newman Lau, Wanzhong Jiao It has been a long-standing problem in the engineering design of bra for optimal support and shaping due to the difficulty of quantifying the hyper-elastic properties of human breasts. The objective of this study is to determine an optimal approach to obtain the non-linear properties of breast soft tissues and the corresponding deformations during motions. The Mooney-Rivlin material parameters of the breasts in-vivo were verified through an optimization process that involved iteratively changing the material coefficients with the integration of static and dynamic finite element models. Theoretical equations of a rigid-flexible coupled system during the motion of forward-leaning were established with gravitational, centrifugal and Coriolis forces to simulate the dynamic deformation of the flexible breasts. The resultant, optimally generated, coefficients of the Mooney-Rivlin hyperelastic material type for the breast were found. This new set of breast material coefficients was verified by finite element analysis of the breast deformation during forward-leaning and running movement. The method proposed in this study provides an effective way to determine the breast properties for predicting breast deformation and analysis of the bra-breast contact mechanism and thus, improving the design of bras.
       
  • Fretting damage of Ni-rich ultrafine grained NiTi superelastic wires
    • Abstract: Publication date: Available online 20 November 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): S.R. Soria, C.E. Callisaya, H. Soul, S. Claramonte, A. Yawny The effects of fretting on Ni-rich ultra-fine grained NiTi superelastic wires have been characterized. Fretting tests have been performed using wire on wire in 90° cross-cylinder configuration until 105 cycles in air at 25 °C. Constant displacement amplitude of 50 µm and normal loads of 10, 20 and 50 N were considered. For a normal load of 10 N, the tribosystem performed in Gross Slip Regime and the predominance of wear damage was observed. Mixed Fretting Regime was instead observed for normal loads of 20 N and 50 N. In these cases, the predominant damage mechanism was crack formation with the cracks oriented normal to the displacement direction. Occurrence of martensitic transformation in the contact region was inferred from the particular shape of the fretting loops. Due to their possible impact on biocompatibility, the debris detached from the tribosystem during the different experiments were collected and characterized by TEM. They consisted in agglomerations of nano-crystalline TiO2 (rutile) and NiO oxide particles sized between 10 and 20 nm.Graphical abstractGraphical abstract for this article
       
  • Functional polyhedral oligomeric silsesquioxane reinforced poly(lactic
           acid) nanocomposites for biomedical applications
    • Abstract: Publication date: Available online 19 November 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Lin Huang, Jianwang Tan, Wenqiang Li, Lin Zhou, Zhibin Liu, Binghong Luo, Lu Lu, Changren Zhou Polyhedral oligomeric silsesquioxane reinforced poly (L-lactic acid) nanocomposites (PLLA/POSS) were prepared to overcome the insufficient mechanical properties of PLLA. In order to improve the compatibility between the nanofillers and matrix, PLLA chains were grafted onto the POSS nanoparticles via microwave-assisted ring opening polymerization (ROP). Herein, a series of interface-modified polyhedral oligomeric silsesquioxane (POSS-(PLLA)32) nanoparticles with various PLLA tail lengths were synthesized and the influence of the structure and additional amount of POSS nanoparticles on the properties of PLLA based nanocomposites were studied. POSS nanoparticles exhibit effective nucleation activity and lead to a significant improvement in the mechanical strength, thermal stability and biocompatibility of the resulting nanocomposites. The addition of 6 wt% POSS-(PLLA)32 600 shows the optimal mechanical properties owing to has the longest PLLA tail length on POSS core, which possesses the optimal interfacial compatibility between POSS nanoparticles and PLLA. The Young's modulus improved by 57% and the tensile strength increased by 26.5% compared with neat PLLA. Moreover, the introduction of POSS nanoparticles lead to a porous fiber structure when processed by electrospinning and the nanofibrous scaffold effectively promoted cells adhesion and spreading. These results demonstrate the potential applications of the PLLA/POSS nanocomposites in tissue engineering and regenerative medicine.Graphical abstractGraphical abstract for this article
       
  • Linear viscoelastic and microstructural properties of native male human
           skin and in vitro 3D reconstructed skin models
    • Abstract: Publication date: Available online 17 November 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Deepika Malhotra, Sharadwata Pan, Lars Rüther, Thomas B. Goudoulas, Gerrit Schlippe, Werner Voss, Natalie Germann The study reports first ever account of measurements of linear viscoelastic moduli under small amplitude oscillatory shear deformations, for commercially available juvenile and aged in vitro 3D reconstructed skin models. The results were compared with those of native male whole human and dermis-only foreskin samples, catering to a wide age group from 0.5 to 68 years, including samples from a 23-year-old male abdomen. In the strain sweep tests, the dermis of the juvenile/young age group assumed a higher intrinsic elastic modulus than the whole skin. A reverse qualitative trend was noted for the adult/aged age group. Confirmed by the histological examination of the stained cross-sections, this is attributed to the nascent epidermal differentiation and the high fiber density of dermal collagen. The oscillation frequency sweeps exposed a greater dependence of the elasticity on the frequency for the native male dermis foreskin samples as compared to the whole skins, irrespective of age. This is anticipated since the extremely structured epidermis confers higher resistance to the whole skins towards intracycle deformations compared to the dermis, thereby storing smaller elastic energy. The 3D skin models examined in this work exhibited a broader linear viscoelastic region, a larger viscoelasticity, and much higher dynamic moduli, compared to the native skin. The rheological trends are a significant addition to the literature and may be used as a reference for the design of next generation of scaffolds.Graphical abstractGraphical abstract for this article
       
  • EVALUATION OF THE SINTERING TEMPERATURE ON THE MECHANICAL BEHAVIOR OF
           β-TRICALCIUM PHOSPHATE/CALCIUM SILICATE SCAFFOLDS OBTAINED BY GELCASTING
           METHOD
    • Abstract: Publication date: Available online 17 November 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Lilian de Siqueira, Cynthia Guimarães de Paula, Rubia Figueredo Gouveia, Mariana Motisuke, Eliandra de Sousa Trichês Scaffolds have been studied during the last decades as an alternative method to repair tissues. They are porous structures that act as a substrate for cellular growth, proliferation and differentiation. In this study, scaffolds of β-tricalcium phosphate with calcium silicate fibers were prepared by gel casting method in order to be characterized and validated as a better choice for bone tissue treatment. Gel-casting led to scaffolds with high porosity (84%) and pores sizes varying from 160 to 500 µm, which is an important factor for the neovascularization of the growing tissue. Biocompatible and bioactive calcium silicate fibers, which can be successfully produced by molten salt method, were added into the scaffolds as a manner to improve its mechanical resistance and bioactivity. The addition of 5 wt.% of calcium silicate fibers associated with a higher sintering temperature (1300 °C) increased by 64.6% the compressive strength of the scaffold and it has also led to the formation of a dense and uniform apatite layer after biomineralization assessment.Graphical abstractGraphical abstract for this article
       
  • Development of graphene oxide/calcium phosphate coating by pulse
           electrodeposition on anodized titanium: biocorrosion and mechanical
           behavior
    • Abstract: Publication date: Available online 16 November 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Leila Fathyunes, Jafar Khalil-Allafi, Maryam Moosavifar In this work, graphene oxide (GO) reinforcement was used to improve the strength and fracture toughness of the calcium phosphate (CaP) coating applied on the anodized titanium using pulse electrodeposition. The results showed that the CaP coating consisted of mixed phases of octa-calcium phosphate (OCP), dicalcium phosphate dehydrate (DCPD) and hydroxyapatite (HAp); however, compositing of this coating with GO caused deposition of the pure HAp phase. Moreover, the nanohardness and elastic modulus for the CaP-GO coating increased over 52% and 41%, respectively, as compared to those measured for the GO-free coating. An improvement of about 16% in the adhesion strength of the CaP coating composited with GO to the anodized titanium was also arisen from improving integrity, crystallinity and decreasing the elastic modulus mismatch of this coating with titanium substrate. Finally, uniformity in the microstructure and more biostability of the CaP-GO coating led to its better protection against the corrosion of anodized titanium.
       
  • Edge chipping resistance of ceramics bonded to a dentine analogue
    • Abstract: Publication date: Available online 12 November 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Cristiano Taufer, Alvaro Della Bona ObjectiveTo evaluate the edge chip resistance (ReA) of two CAD/CAM monolithic ceramics (GC- IPS e.max CAD and YZ- Zenostar Zr Translucent) bonded to a dentine analogue substrate (G10- NEMA G10).MethodsPlate-shaped specimens were prepared from GC and YZ ceramics and were either bonded (B) to G10 or attached (NB) to a universal testing machine for edge chipping test. Samples from all groups (GC-B, GC-NB, YZ-B and YZ-NB) were indented (n = 25) at different edge distances (d= 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6 mm) to produce chips. Force (F, in N) and d values were recorded and ReA (in N/mm) were calculated. Data were statistically analyzed using Pearson´s correlation, Student t, ANOVA and Tukey tests (α=0.05).ResultsA strong correlation (R≥ 0.98) was found between F and d values for all groups. ReA values increased with increasing d, irrespective of ceramic type (GC and YZ) or fixation method (B and NB). Significant differences (p0.05) at greater d (0.5 and 0.6 mm), meaning, bonding (B) to G10 protected both materials against chipping close to the edge.ConclusionsThe larger the distance from the occlusal contact to the restoration edge, the greater the chance to avoid ceramic chipping in monolithic restorations. For d ≤ 0.3 mm, such F vs d relation is less critical for edge resistance of YZ and for resin bonded monolithic ceramics.
       
  • Enhanced corrosion resistance and bonding strength of Mg substituted
           β-tricalcium phosphate/Mg(OH)2 composite coating on magnesium alloys via
           one-step hydrothermal method
    • Abstract: Publication date: Available online 12 November 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Yishu Lin, Shu Cai, Song Jiang, Dongli Xie, Rui Ling, Jiayue Sun, Jieling Wei, Kaier Shen, Guohua Xu To overcome the defect of high degradation rate of magnesium (Mg), bioactive coatings with compact structure, sufficient bonding strength and enhanced corrosion resistance are essential for Mg-based biodegradable implants. In this study, a dense Mg-substituted β-tricalcium phosphate and magnesium hydroxide (β-TCMP/Mg(OH)2) composite coating was prepared on AZ31 alloy via one-step hydrothermal method. The influences of hydrothermal temperature on its composition, microstructure of the surface and interface, bonding strength and corrosion behavior were evaluated. The results showed that the compact composite coating synthesized at 140 °C not only possessed a crack-free bilayered structure with an adequate bonding strength (more than 20.88 ± 1.60 MPa), but also got an extreme high impedance (1197.003 ± 152.817 kΩ·cm2) so that significantly enhanced the corrosion resistance and inhibited the formation of pitting corrosion. Furthermore, the in vitro immersion test suggested that the composite coating slower the initial degradation rate of Mg alloys and enhanced its surface bioactivity to some extent.Graphical abstractGraphical abstract for this article
       
  • Controlled mercerization of bacterial cellulose provides tunability of
           modulus and ductility over two orders of magnitude
    • Abstract: Publication date: Available online 6 November 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Mousa Younesi, Xinyu Wu, Ozan Akkus Effects of mercerization process on plant-based cellulose is well studied in the literature whereas the effects of mercerization on mechanical properties of bacterial cellulose is not investigated. In this work bacterial cellulose (BC) was mercerized in NaOH solution with different molar concentrations of 0, 1.50, 1.75, 2.00, 2.13, 2.25, 5.00, 7.00 and 10.00 M. The BC samples shrunk substantially with increasing NaOH concentration. At the same concentration, NaOH treatment resulted in significantly larger shrinkage than KOH treatment. Mercerization of BC samples in 7 M NaOH resulted in an order of magnitude increase in elongation from 5.4 ± 1.6% to 50.8 ± 5.7% along with about 30-fold reduction in Young's modulus. Mercerized samples in 4 M NaOH had maximum toughness among all groups at a value of 64.0 ± 15.8 MJ•m−3. Changes in BC crystalline structure from cellulose I to cellulose II were characterized and confirmed semiquantitatively by using X-ray diffraction (XRD) and Raman spectroscopy. Results of this work demonstrated mercerization as a method to tune the mechanical properties of BC precisely. Mercerized BC as a biocompatible material with tunable mechanical properties shows potential to be utilized in tissue engineering and regenerative medicine in the future.
       
  • Mechanical behaviour of extremely tough TZP bioceramics
    • Abstract: Publication date: Available online 3 November 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Frank Kern, Helen Reveron, Jérôme Chevalier, Rainer Gadow Tetragonal Zirconia Polycrystals (TZP) is attractive for structural biomedical applications because of their excellent mechanical properties at room-temperature, which include high strength, fracture toughness and wear resistance. In this work, zirconia stabilized with Y or Yb or Yb+Nd, all containing 0.5 vol.% Al2O3, were prepared by hot-pressing (HP) at 50–60 MPa and sintered at 1300–1350 °C for 1 h. Microstructural features, phase composition and mechanical properties were investigated. The strength was measured by 4-point bending (4P-B), piston-on-three-balls (P-3B) and three-balls-on-three-balls (3B-3B) biaxial methods. Toughness was determined by indentation strength in bending (ISB). Vickers hardness (Hv) and the Young modulus (E) were also estimated. Preliminary aging behaviour (LTD) was also here considered.Measured biaxial strength was significantly higher (until 1.83 times) than the uniaxial one because of the tetragonal to monoclinic (t-m) zirconia phase transformation which is strongly influenced by the loading configuration. The variation of the strength with the testing method is attributed to the compressive stresses generated by the phase transformation which is particularly favoured under P-3B tests and also to the calculation of the stresses from elastic theories. LTD preliminary tests showed excellent aging resistance of 3Yb-0.5 A ceramics.
       
  • * &rft.title=Journal+of+the+Mechanical+Behavior+of+Biomedical+Materials&rft.issn=1751-6161&rft.date=&rft.volume=">Effect of tribochemical silica coating or multipurpose products on bonding
           performance of a CAD/CAM resin-based material *
    • Abstract: Publication date: Available online 2 November 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Xinyi Wu, Haifeng Xie, Hongliang Meng, Lu Yang, Bingzhuo Chen, Ying Chen, Chen Chen ObjectivesNanocomposite ceramics have been widely used in clinical practice; however, a standard, recommended bonding protocol has not been determined yet. The present study aimed to evaluate application of tribochemical silica coating or multipurpose products on bonding performance of a CAD/CAM resin-based material (known as nanocomposite ceramic).Materials and MethodsNanocomposite ceramic specimens were fabricated and assigned into 11 groups to build bonded specimens (n=15) according to surface treatments (none; air particle abrasion with 50-μm alumina followed by application of a silane coupling agent or a universal adhesive; tribochemical silica coating followed by application of a silane coupling agent or a universal adhesive) and resin luting cements (conventional resin cement, RelyX Veneer; self-adhesive resin cement RelyX Unicem) used. Micro-shear bond strength (μ-SBS) was measured after 24-h water storage or ageing with 10,000 thermocycles plus additional 90-d water storage. Surface roughness after alumina air abrasion and tribochemical silica coating were determined using a profilometer. Surface morphology and element variation were observed by using a scanning electron microscope (SEM)/energy dispersion spectrum (EDS). X-ray photoelectron spectroscopy (XPS) was used to characterize nanocomposite ceramic powders conditioned with silane coupling agent or the universal adhesive used in the μ-SBS test. The nanocomposite ceramic plates received alumina air abrasion, tribochemical silica coating, or without, were determined using X-ray diffraction (XRD).ResultsNanocomposite ceramic treated with alumina air abrasion achieved the highest surface roughness, followed by those treated with tribochemical silica coating. Newly formed Si-O-Si bonds on the nanocomposite ceramic surface were detected by XPS after treatment with silane coupling agent or universal adhesive, and a Zr-O-P bond was detected after treating with universal adhesive. μ-SBS was significantly affected by bond strategies and ageing. Ageing by thermocycling and water storage significantly decreased μ-SBS. μ-SBS values derived by use of a universal adhesive or self-adhesive resin cement alone were no lower than the values derived by use of a silane coupling agent alone. Pre-silanization further enhanced the bonding improvement of universal adhesive or self-adhesive resin cement. However, tribochemical silica coating failed to provide higher μ-SBS compared with alumina air abrasion. XRD detected no monoclinic zirconia phase after alumina air abrasion or tribochemical silica coating, suggesting that these two roughening methods did not lead to phase transformation of zirconia fillers.ConclusionsCombination of presilanization and universal adhesives improve resin bonding of nanocomposite ceramics. Tribochemical silica coating is not superior to alumina air abrasion for pretreated nanocomposite ceramics.Graphical abstractGraphical abstract for this article
       
  • The effect of different preconditioning protocols on repeatability of
           bovine ACL stress-relaxation response in tension
    • Abstract: Publication date: Available online 2 November 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Mohammadhossein Ebrahimi, Ali Mohammadi, Aapo Ristaniemi, Lauri Stenroth, Rami K. Korhonen Mechanical characterization of soft tissues such as ligaments remains challenging. There is variability in the measured material parameters of ligaments, most of which is related to natural tissue variability, but some of it can be a result of using different testing protocols. Generally preconditioning (cyclic loading-unloading) is performed prior to actual tests to reduce the experimental variability. Commonly, preconditioning protocols for ligaments with a small strain level and 10 sinusoidal loading-unloading cycles are used. The effect of preconditioning and its parameters including strain level, number of cycles and number of preconditioning repetitions on the repeatability of tensile stress-relaxation tests are poorly known for knee ligaments. In the present study, forty-eight dumbbell-shaped bovine anterior cruciate ligament (ACL) samples were used to evaluate the repeatability of stress-relaxation response. Different preconditioning protocols with 2% and 6% strain levels and 1, 5 or 10 preconditioning repetitions were applied. After preconditioning, one-step stress-relaxation test was carried out twice with an hour resting period in between the tests. The equilibrium stress showed no systematic bias when only one preconditioning repetition was applied (2.0±3.1% difference and p>0.05 between repeated tests). Systematic bias in the peak-to-equilibrium stress ratio was not observed when higher strain level and number of repetitions were used (0.5±1.6% difference and p>0.05 between repeated tests). In conclusion, the commonly used preconditioning protocol is capable of producing repeatable equilibrium stress levels of bovine ACLs from stress-relaxation tests in tension. However, if repeatable peak-to-equilibrium stress ratio is desirable, higher strain and number of preconditioning repetitions are recommended.
       
  • Gating and Inactivation of Mechanosensitive Channels of Small Conductance:
           A Continuum Mechanics Study
    • Abstract: Publication date: Available online 2 November 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Liangliang Zhu, Qiang Cui, Hang Xiao, Xiangbiao Liao, Xi Chen Mechanosensitive channels of small conductance (MscS) in Escherichia coli (E. coli) serve as a paradigm for understanding the gating behaviors of the MscS family of ion channels. In this work, we develop a continuum mechanics framework to explore the conformational states of MscS during the gating transition. A complete gating transition trajectory from the closed to the open state along with partially open intermediates is obtained, and the open structure is close to the available structural model from crystallographic studies. The computational efficiency of the modeling framework makes it possible to explore the roles of various structural elements (e.g., loops that connect transmembrane helices) and specific interactions in the gating transition. It is observed that removing either the Asp62-Arg131 salt bridge or the Phe68-Leu111 non-polar interaction leads to essentially non-conducting structures even with a membrane tension close to the lysis limit. The loop connecting TM2 (the second transmembrane helix) and TM3 is found to be essential for force transmission during gating, while the loop connecting TM1 and TM2 does not make any major contribution. Based on the different structural evolutions observed when the TM3 kink is treated as a loop or a helical segment, we propose that the helical propensity of the kink plays a central role in inactivation; i.e., under prolonged sub-threshold membrane tension, transition of the initially flexible loop to a helical segment in TM3 may lead to MscS inactivation. Finally, the gating transition of MscS under different transmembrane voltages is explored and found to be essentially voltage independent. Collectively, results from the current continuum mechanics analysis provide further insights into the gating transition of MscS at structural and physical levels, and specific predictions are proposed for further experimental investigations.Graphical abstractGraphical abstract for this article
       
  • Designed for Resistance to Puncture: The Dynamic Response of Fish Scales
    • Abstract: Publication date: Available online 2 November 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): S. Ghods, S. Murcia, E.A. Ossa, D. Arola Natural dermal armors are serving as a source of inspiration in the pursuit of “next-generation” structural materials. Although the dynamic strain response of these materials is arguably the most relevant to their performance as armors, limited work has been performed in this area. Here, uniaxial tension and transverse puncture tests were performed on specimens obtained from the scales of Asian carp over strain rates spanning seven decades, from 10−4 to 103 s−1. The importance of anatomical variations was explored by comparing the performance of scales from the head, middle and tail regions. In both loading orientations, the scales exhibited a significant increase in the resistance to failure with loading rate. The rate sensitivity was substantially higher for transverse loading than for in-plane tension, with average strain rate sensitivity exponents for measures of the toughness of 0.35 and 0.08, respectively. Spatial variations in the properties were largest in the puncture responses, and scales from the head region exhibited the greatest resistance to puncture overall. The results suggest that the layered microstructure of fish scales is most effective at resisting puncture, rather than in-plane tension, and its effectiveness increases with rate of loading. X-ray microCT showed that delamination of plies in the internal elasmodine and stretching of the fibrils were key mechanisms of energy dissipation in response to puncture loading. Understanding contributions from the microstructure to this behavior could guide the development of flexible engineered laminates for penetration resistance and other related applications.
       
  • Mechanical performance of conical implant-abutment connections under
           different cyclic loading conditions
    • Abstract: Publication date: Available online 1 November 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Kuang-Ta Yao, Hung-Chan Kao, Cheng-Kung Cheng, Hsu-Wei Fang, Chang-Hung Huang, Ming-Lun Hsu ObjectivesConical implant-abutment connections are popular for its anti-bending performance; on the other hand, the torsional and axial forces also play important roles in occlusion. However, so far there were scarce studies on their effects on connection stability. Therefore, this study seeks to investigate the mechanical performance of conical connections under different cyclic loading conditions.Methods15 conical implant-abutment assembles (Cowell Medi, Busan, South Korea) were divided into 3 groups according to different cyclic loadings. In group BTA, the loading condition of the posterior occlusion was simulated (20~200 N, 30° off-axis and 4 mm eccentric to implant axis), generating a bending moment, a torsional moment, and an axial loading. In group BT, a bending moment and a torsional moment of the posterior occlusion were applied (10~100 N, 90° off-axis and 4 mm eccentric to implant axis). In group B, only a bending moment was applied (10~100 N, 90° off-axis and through implant axis). The fatigue testing machine ran at 10 Hz until failure, or to the upper limit of 106 cycles. The fatigue cycles and failure modes were recorded. Besides, the value of the torque loss of the abutment screw, the difference between initial torque and post-load reverse torque, was calculated. The data were statistically analyzed. Morphologies of the abutment conical surface were examined by scanning electron microscopy.ResultsIn group B and BTA, all samples passed the test (106 cycles). While, in group BT, all abutments generated rotation within 140 cycles, showing significant differences compared to the other two groups (p
       
  • Tuning strain-induced γ-to-ε martensitic transformation of biomedical
           Co–Cr–Mo alloys by introducing parent phase lattice defects
    • Abstract: Publication date: Available online 1 November 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Kenta Yamanaka, Manami Mori, Shigeo Sato, Shinki Tsubaki, Kozue Satoh, Masayoshi Kumagai, Muneyuki Imafuku, Takahisa Shobu, Akihiko Chiba In this study, we examined the effect of pre-existing dislocation structures in a face-centered cubic γ-phase on strain-induced martensitic transformation (SIMT) to produce a hexagonal close-packed ε-phase in a hot-rolled biomedical Co–Cr–Mo alloy. The as-rolled microstructure was characterized by numerous dislocations as well as stacking faults and deformation twins. SIMT occurred just after macroscopic yielding in tensile deformation. Using synchrotron X-ray diffraction line-profile analysis, we successfully captured the nucleation of ε-martensite during tensile deformation in terms of structural evolution in the surrounding γ-matrix: many dislocations that were introduced into the γ-matrix during the hot-rolling process were consumed to produce ε-martensite, together with strong interactions between dislocations in the γ-matrix. As a result, the SIMT behavior during tensile deformation was accelerated through the consumption of these lattice defects, and the nucleation sites for the SIMT ε-phase transformed into intergranular regions upon hot rolling. Consequently, the hot-rolled Co–Cr–Mo alloy simultaneously exhibited an enhanced strain hardening and a high yield strength. The results of this study suggest the possibility of a novel approach for controlling the γ → ε SIMT behavior, and ultimately, the performance of the alloy in service by manipulating the initial dislocation structures.Graphical Graphical abstract for this article
       
  • The Mechanical Response of Commercially Available Bone Simulants for
           Quasi-Static and Dynamic Loading
    • Abstract: Publication date: Available online 30 October 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): A.D. Brown, J.B. Walters, Y.X. Zhang, M. Saadatfar, J.P. Escobedo-Diaz, P.J. Hazell Bone is a complex hierarchal structured material with varying porosity and mechanical properties. In particular, human cranial bone is essentially a natural composite consisting of low porosity outer and inner tables and a cancellous interior, or diploë. Experimental studies of biomechanically accurate cranial bone analogues are of high importance for biomechanical, forensics, and clinical researchers, which could improve the understanding and prevention of traumatic injury. Many reported studies use commercially available bone surrogates to draw biomechanical and forensics conclusions; however, their mechanical properties are not tabulated over a range of strain rates. This study elucidates the mechanical viability of three leading commercially available bone surrogates, i.e. Synbone, Sawbone, and Bonesim, over a large range of strain rates (10−3 to 103 s−1). Quasi-static compression testing was conducted using a universal testing machine and a Split-Hopkinson Pressure bar system equipped with high-speed video was used to determine the dynamic mechanical behavior of these materials. Micro-computed X-ray tomography (XRT) were performed on each material to investigate their pore structures and distributions. All materials exhibited strain rate dependent strength behavior, particularly at high loading rates (≥103 s−1). The Young's modulus was found to increase with strain rate from 10−3 to 10−1 s−1 for transversely and longitudinally loaded surrogate materials except for Synbone and the higher density Bonesim. The higher density Bonesim was determined to be the most suitable cranial bone simulant tested based on a combination of transverse Young's Modulus (1500 MPa), yield strength (19 MPa), ultimate strength (49 MPa), and ultimate strain (17%). These materials show limited promise for applications where the measured elastic properties and strengths are of interest.
       
  • Do endodontic retreatment techniques influence the fracture strength of
           endodontically treated teeth' A systematic review and meta-analysis
    • Abstract: Publication date: Available online 26 October 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Ricardo Schestatsky, Gustavo Dartora, Rodrigo Felberg, Aloísio Oro Spazzin, Rafael Sarkis-Onofre, Ataís Bacchi, Gabriel Kalil Rocha Pereira One of the major concerns about endodontically retreated teeth (ERT) is undoubtedly its loss of remnant structure, which could lead to consequently greater fracture risk. Therefore, the objective of this systematic review is to assess the influence of endodontic retreatment on the fracture strength of the dental tooth remnant. In vitro studies assessing the influence of mechanical retreatment on the mechanical properties (static or under fatigue) of restored teeth were searched in PubMed and SCOPUS databases. Three independent reviewers screened titles/abstracts of articles and the full-text of potentially eligible studies. The risk of bias was independently assessed by one researcher and verified by another two. Comparison between the mean load to fracture of teeth after endodontic treatment and after endodontic retreatment were estimated using pairwise random effects meta-analysis to calculate pooled mean differences. Three studies were included for the systematic review and 2 for the meta-analysis. The pooled effect indicated a statistical difference (Mean difference: −121.03 95%CI: −183.02, −59.05) between conditions favoring the endodontically treated teeth. However, the low number of studies combined with their heterogeneity made it difficult to prove such phenomenon. ERT might present lower fracture strength than endodontically treated teeth. However, more coherent laboratory tests may provide better evidence and quantitative parameters on how much reliability can be attributed to an endodontic retreatment, in addition to which technique can provide more predictable results in this conservative approach.
       
  • Dynamics of a capsule flowing in a tube under pulsatile flow
    • Abstract: Publication date: Available online 25 October 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Jorge Maestre, Jordi Pallares, Ildefonso Cuesta, Michael A. Scott We analyze numerically the behavior of a deformable micro-capsule confined in a pipe under a pulsatile flow. The capsule moves and is deformed by the action of a pulsatile flow inside the tube with a non-null mean velocity. This configuration can be found in the nature and in many bioengineering systems where artificial capsules are driven by micro-pumps through micro-channels. The capsule is considered as a thin hyperelastic membrane, which encloses an internal fluid. As it has been demonstrated in the literature, this model represents a wide range of artificial capsules, for example, the alginate-based capsules, typically used in bioengineering applications. A hybrid isogeometric finite element method and boundary element method based on a T-spline discretization and formulated in the time domain is used to solve the mechanical and hydrodynamical equations. The influence of the relative rigidity of the membrane, frequency and amplitude of the pulsatile flow is studied. Results show that the behavior of the capsule differs from steady flows and it depends strongly on the frequency of the flow and mechanical characteristic of the capsule.
       
  • Effect of light-curing protocols on the mechanical behavior of bulk-fill
           resin composites
    • Abstract: Publication date: Available online 25 October 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): João Felipe Besegato, Eduardo Inocente Jussiani, Avacir Casanova Andrello, Ricardo Vignoto Fernandes, Fabio Martins Salomão, Bruno Luiz Santana Vicentin, Cássia Cilene Dezan-Garbelini, Márcio Grama Hoeppner ObjectiveTo investigate the effect of two light-curing protocols on mechanical behavior of three bulk-fill resin composites (BFRC) considering their optical properties.MethodsOne increment of 4 mm thickness of the bulk-fill resin composites Opus Bulk Fill, Tetric N-Ceram and Filtek Bulk Fill Flow were submitted to two different light-curing protocols: Sp - irradiance of 1000 mW/cm2 (20 s); Xp - irradiance of 3200 mW/cm2 (6 s). To assess the influence on the mechanical behavior it was studied polymerization shrinkage by X-ray microtomography (n = 3), Vickers hardness (n = 10) at the top and bottom surfaces of the samples, irradiance reaching the bottom surface (n = 3) and absorbance spectrum during the light-curing time interval (n = 3). Data were analyzed by two-way ANOVA test for parametric data and Kruskal Wallis test, followed by Wilcoxon or Mann-Whitney U post-test, for non-parametric data.ResultsAll BFRCs contracted when light-cured, with greater contraction for Xp. Filltek Bulk Fill Flow showed highest polymerization shrinkage, for both Sp and Xp. All BFRCs showed minor hardness values on the bottom surface, with greater reduction for Xp. All BFRCs exhibited a decrease in irradiance at 4mm depth. A decrease in absorbance intensity throughout the light-cure was observed, except for Opus Bulk Fill.ConclusionsRegardless BFRCs composition, the light-curing protocol with lower irradiance and longer exposure time results in lower polymerization shrinkage and higher hardness. The higher irradiance in a shorter time interval compromises the mechanical behavior of the resin composites, which may result in undesirable clinical outcomes.
       
  • Dentin pretreatment with 45S5 and niobophosphate bioactive glass: Effects
           on pH, antibacterial, mechanical properties of the interface and
           microtensile bond strength
    • Abstract: Publication date: Available online 25 October 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): José Bauer, Allana Silva e Silva, Edilausson Moreno Carvalho, Paulo Vitor Campos Ferreira, Ceci Nunes Carvalho, Adriana Pigozzo Manso, Ricardo Marins de Carvalho ObjectivesThe aim of the study was to evaluate the effect of bioactive glass (45S5 and NbG) suspensions on bond strength (µTBS), hardness, modulus of elasticity, pH and antibacterial activity of the resin-dentin interfaces after 3 months.MethodsGroups with different concentrations (5% and 20%) of two types of glass (45S5 and NbG), and a control group (distilled water) were studied. Twenty-five extracted human third molars were etched with phosphoric acid. The means of the two-way ANOVA and Holm-Sidak tests (α=5%). The antimicrobial activity data were analyzed by the Kruskal-Wallis test (α=5%).ResultsThe interactions were significant among groups for µTBS (p=0.033). Significant reductions in µTBS were observed after 3 months storage in PBS for the Control and 5% NbG Groups. Suspensions with 5% and 20% 45S5 glass and 20% NbG resulted in stable µTBS values and increased hardness after 3 months. Both 20% suspensions (45S5 and NbG) increased the elastic modulus. A significant greater reduction in bacterial growth was observed with the use of 20% 45S5.ConclusionRewetting dentin with the suspension of 20% 45S5 glass prevented the reduction in bond strength; increased hardness; modulus of elasticity of the resin-dentin interface, and demonstrated antibacterial activity against Streptococcus mutans.
       
  • Fluid load support does not explain tribological performance of PVA
           hydrogels
    • Abstract: Publication date: Available online 21 October 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Elze Porte, Philippa Cann, Marc Masen The application of hydrogels as articular cartilage (AC) repair or replacement materials is limited by poor tribological behaviour, as it does not match that of native AC. In cartilage, the pressurisation of the interstitial fluid is thought to be crucial for the low friction as the load is shared between the solid and liquid phase of the material. This fluid load support theory is also often applied to hydrogels. However, this theory has not been validated as no experimental evidence directly relates the pressurisation of the interstitial fluid to the frictional response of hydrogels. This lack of understanding about the governing tribological mechanisms in hydrogels limits their optimised design. Therefore, this paper aims to provide a direct measure for fluid load support in hydrogels under physiologically relevant sliding conditions. A photoelastic method was developed to simultaneously measure the load on the solid phase of the hydrogel and its friction coefficient and thus directly relate friction and fluid load support. The results showed a clear distinction in frictional behaviour between the different test conditions, but results from photoelastic images and stress-relaxation experiments indicated that fluid load support is an unlikely explanation for the frictional response of the hydrogels. A more appropriate explanation, we hypothesized, is a non-replenished lubricant mechanism. This work has important implications for the tribology of cartilage and hydrogels as it shows that the existing theories do not adequately describe the tribological behaviour of hydrogels. The developed insights can be used to optimise the tribological performance of hydrogels as articular cartilage implants.Graphical Graphical abstract for this article
       
  • A novel micro-grooved collagen substrate for inducing vascular smooth
           muscle differentiation through cell tissue arrangement and nucleus
           remodeling
    • Abstract: Publication date: Available online 21 October 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Kazuaki Nagayama, Keiichi Uchida, Akiko Sato Vascular smooth muscle cells (SMCs) actively remodel arterial walls through biomechanical signals and dedifferentiate from the contractile to the synthetic state under pathological conditions. It is important to determine the differentiation mechanism of SMCs to understand their pathophysiology in disease. Previously, we found that the F-actin cytoskeleton in dedifferentiated SMCs on dishes was firmly connected to the nucleus, and that internal mechanical signals in SMCs are transmitted directly to the nucleus, indicating that nuclear-cytoskeletal interactions could be associated with SMC differentiation. However, mechanical environments in vivo are quite different from those of cultured cells: SMCs in vivo show an elongated shape and form a tissue that aligns with the circumferential direction of the walls. Thus, in the present study, we established a simple technique to fabricate a novel micro-grooved native collagen substrate that mimics the elongated cell shapes and alignment observed in vivo. The substrates had “wavy wrinkle” grooves with a width of ~5 µm and a Young's modulus of ~500 kPa, which were quite similar to those of the elastic lamina in vascular tissues. Using confocal microscopy image-based analysis, and nano-indentation imaging with atomic force microscopy, we found that SMCs on the micro-grooved collagen formed significant cell tissue arrangement, and changed their nuclear morphology to a “slim ellipsoid” in response to the force-reduction caused by F-actin remodeling, which consequently improved SMC differentiation. These findings indicated that this type of intracellular force-reduction around the nucleus has a crucial effect on SMC differentiation. Our micro-grooved collagen substrate is a powerful tool to investigate the mechanism of vascular SMC mechanotransduction.Graphical abstractGraphical abstract for this article
       
  • Unravelling the viscoelastic, buffer-like mechanical behavior of tendons:
           A numerical quantitative study at the fibril-fiber scale
    • Abstract: Publication date: Available online 19 October 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Nikolaos Karathanasopoulos, Georgios Arampatzis, J-Francois Ganghoffer We investigate the capacity of tendons to bear substantial loads by exploiting their hierarchical structure and the viscous nature of their subunits. We model and analyze two successive tendon scales: the fibril and fiber subunits. We present a novel method for bridging intra-scale experimental observations by combining a homogenization analysis technique with a Bayesian inference method. This allows us to infer elastic and viscoelastic moduli at the embedded fibril scale that are mechanically compatible with the experimental data observed at the fiber scale. We identify the rather narrow range of moduli values at the fibrillar scale that can reproduce the mechanical behavior of the fiber, while we quantify the viscoelastic contribution of the embedding, non-collagenous matrix substance. The computed viscoelastic moduli suggest that a great part of the stress relaxation capacity of tendons needs to be attributed to the embedding matrix substance of its inner components, classifying it as a primal load relaxation constituent.
       
  • Influence of nanocellulose on mechanics and morphology of polyvinyl
           alcohol xerogels
    • Abstract: Publication date: Available online 19 October 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): R. Pramanik, B. Ganivada, Farsa Ram, Kadhiravan Shanmuganathan, A. Arockiarajan Xerogels are porous networks of crosslinked polymers that are useful for biomedical applications such as drug delivery, scaffold engineering, tissue regeneration, cell culture and wound dressing. However, inferior mechanical properties curtail their applications to a considerable extent. Nanocellulose fibers and crystals are often added into the polymer matrix to improve their mechanical strength. Here, nanocellulose in the mass ratios of 7%, 13% and 18% are loaded into polyvinyl alcohol (PVA) matrix followed by thermo-morpho-mechanical characterization. With increase in nanocellulose content, thermal degradation occurs at a lower temperature. It is observed that addition of higher quantity of nanocellulose crystals leads to the formation of weak cellulose-rich regions causing xerogel rupture. This is predominantly observed for xerogel loaded with 18% nanocellulose crystals. Similarly, addition of higher quantity of nanocellulose fibers increase brittleness of the xerogels causing fracture. This is predominantly observed for xerogel loaded with 18% nanocellulose fibers. Creep strain and stress relaxation is observed to decrease with addition of nanocellulose loading owing to molecular chain restriction and polymer chain immobility.Graphical abstractGraphical abstract for this article
       
  • Multiscale Modeling for the Heterogeneous Strength of Biodegradable
           Polyesters
    • Abstract: Publication date: Available online 19 October 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Taohong Zhang, Geyu Jin, Xiaoxiao Han, Yue Gao, Qingfeng Zeng, Binbin Hou, Dezheng Zhang A heterogeneous method of coupled multiscale strength model is presented in this paper for calculating the strength of medical polyesters such as polylactide (PLA), polyglycolide (PGA) and their copolymers during degradation by bulk erosion. The macroscopic device is discretized into an array of mesoscopic cells. A polymer chain is assumed to stay in one cell. With the polymer chain scission, it is found that the molecular weight, chain recrystallization induced by polymer chain scissions, and the cavities formation due to polymer cell collapse play different roles in the composition of mechanical strength of the polymer. Therefore, three types of strength phases were proposed to display the heterogeneous strength structures and to represent different strength contribution to polymers, which are amorphous phase, crystallinity phase and strength vacancy phase, respectively. The strength of the amorphous phase is related to the molecular weight; strength of the crystallinity phase is related to molecular weight and degree of crystallization; and the strength vacancy phase has negligible strength. The vacancy strength phase includes not only the cells with cavity status but also those with an amorphous status, but a molecular weight value below a threshold molecular weight. This heterogeneous strength model is coupled with micro chain scission, chain recrystallization and a macro oligomer diffusion equation to form a multiscale strength model which can simulate the strength phase evolution, cells status evolution, molecular weight, degree of crystallinity, weight loss and device strength during degradation. Different example cases are used to verify this model. The results demonstrate a good fit to experimental data.
       
  • Strontium doped hydroxyapatite from Mercenaria clam shells: Synthesis,
           mechanical and bioactivity study
    • Abstract: Publication date: Available online 17 October 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Anindya Pal, Purnendu Nasker, Sudeep Paul, Amit Roy Choudhury, Arijit Sinha, Mitun Das Synthesis of strontium-doped hydroxyapatite from Mercenaria clam shells has been carried out by hydrothermal method. The doping of bioceramic, processed from biogenic resources is mostly unexplored. The objective is to understand the effect of strontium (Sr) incorporation on phase stability, sintering behaviour, mechanical properties and cytotoxicity of hydroxyapatite (HAp) derived from clam shells. The different molar concentrations of Sr, varies from 10, 30, 50, 70% of Ca, were substituted into the HAp. The synthesized powders were sintered at 1200 °C in air. The as synthesized powders and sintered specimens were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and high resolution transmission electron microscopy. The crystallite size and cell parameters of sintered specimens were analyzed from XRD. The XRD of hydrothermally synthesized powders mostly matched with HAp with slight shifting due to Sr doping. However, some distinct Sr based compounds were also observed where Sr substitution is more that 50% of Ca. The XRD of sintered specimen showed increasing β-tricalcium phosphate (β-TCP) phase with Sr substitution. The sintered density of solid samples gradually increased from 3.04 g/cc to 3.50 g/cc and surface energy decreased with increasing Sr substitution. Similarly, microhardness, fracture toughness and nanohardness of solid samples found to be enhanced with Sr substitution. The elastic modulus gradually increased from 130 to 137 GPa for HAp and Sr substituted HAp (70% of Ca). The in vitro cytotoxicity of sintered specimen against mouse osteoblast cell line showed that all the samples were nontoxic. However cell proliferation found low for the solid samples containing more than 50% Sr substitution.Graphical Graphical abstract for this article
       
  • Shock absorbing ability in healthy and damaged cartilage-bone under
           high-rate compression
    • Abstract: Publication date: Available online 16 October 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Shaktivesh, Fatemeh Malekipour, Peter V.S. Lee Articular cartilage is a soft tissue that distributes the loads in joints and transfers the compressive load to the underlying bone. At high rate and magnitudes of mechanical loading, cartilage and subchondral bone together are susceptible to damage. In addition, any disruption to the cartilage's structure, caused by injury, trauma or disorder such as osteoarthritis (OA), can alter the mechanism of load transfer from the cartilage to the underlying bone. Changes in the cartilage structure can also alter the ability of cartilage-bone to absorb and dissipate the impact energy. To investigate the effects of cartilage degradation on cartilage-bone shock absorption ability, the top 50% of the cartilage thickness was removed (modified cartilage) to mimic the cartilage thickness reduction in Grade III cartilage lesion and the remaining cartilage-bone unit (modified cartilage-bone) was compressed at high-rate (4% strain at 5 Hz). High-speed camera and microscope were used to capture microscopic deformation, and digital image correlation technique (DIC) employed to quantify the deformation of cartilage and bone. The mechanical properties (i.e. stiffness, strain, absorbed and dissipated energies) of cartilage and bone were calculated before and after the removal of the top 50% of the cartilage thickness, consisting of both the superficial tangential zone (STZ) and part of the middle zone of the cartilage. The results showed a significant degradation in the mechanical properties of the cartilage-bone unit after the removal of the top 50% cartilage thickness. The stiffness of the modified cartilage reduced significantly (by ~39%) and energy absorption in underlying bone increased by 32%, which can make the bone more vulnerable to damage in the modified cartilage-bone unit. In addition, the energy dissipation in the modified cartilage-bone unit was also increased by approximately 14%. These changes in mechanical properties suggest a crucial role of the STZ and middle zone (within the top 50% cartilage thickness) in protecting the underlying bone from the severe compressive impact loading. Results also indicated that under physiological contact stress of 7 MPa, strain in damaged cartilage was increased by 3.22% without affecting the mechanical behaviour of the underlying bone.
       
  • Matrix stiffness regulates Epithelial-Mesenchymal Transition via
           cytoskeletal remodeling and MRTF-A translocation in osteosarcoma cells
    • Abstract: Publication date: Available online 16 October 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Jun Dai, Liang Qin, Yan Chen, Huan Wang, Guanlin Lin, Xiao Li, Hui Liao, Huang Fang Matrix stiffness is known to alter cellular behaviors in various biological contexts. Previous investigations have shown that epithelial–mesenchymal transition (EMT) promotes the progression and invasion of tumor. Mechanical signaling is identified as a regulator of EMT. However, the molecular mechanisms underlying the influence exerted by matrix stiffness on EMT in osteosarcoma remains largely unknown. Using polyacrylamide hydrogel model, we investigate the effects of matrix stiffness on EMT and migration in osteosarcoma. Our data indicates that high matrix stiffness regulates cell morphology and promotes EMT and migration in osteosarcoma MG63 cell line in vitro. Notably, matrix stiffness promotes polymerization of actin and nuclear accumulation of myocardin-related transcription factor A (MRTF-A). Furthermore, inhibiting MRTF-A by CCG 203971 significantly reduces EMT and migration on rigid gels. These data suggest that matrix stiffness of the tumor microenvironment actively regulate osteosarcoma EMT and migration through cytoskeletal remodeling and translocation of MRTF-A, which may contribute to cancer progression.Graphical abstractGraphical abstract for this article
       
  • A combination of the finite element analysis and experimental indentation
           via the cornea
    • Abstract: Publication date: Available online 16 October 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Alireza Karimi, Reza Razaghi, Toshihiro Sera, Susumu Kudo The purpose of this study was to perform a set of experimental indentation test to certify our proposed eye model enables to have a better deformation assessment for the eye globe under the indentation load compared to other eye models. To do that, twenty-four enucleated human globes were removed from the cadavers. A screw at 5 different loading rates indented to the eye globes and the resulting macroscopic force-displacement as a result of the deformation in the apex of the cornea was measured. The experimental results revealed significantly higher stiffness, elastic modulus, and maximum force for the globe at higher loading rates (50 and 100 mm/min) (n = 4 globes, p
       
  • Implant-to-bone force transmission: a pilot study for in vivo strain gauge
           measurement technique
    • Abstract: Publication date: Available online 15 October 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Fabio Cozzolino, Davide Apicella, Guixue Wang, Antonio Apicella, Roberto Sorrentino The experimental determination of local bone deformations due to implant loading would allow for a better understanding of the biomechanical behavior of the bone-implant-prosthesis system as well as the influence of uneven force distribution on the onset of implant complications. The present study aimed at describing an innovative in vivo strain gauge measurement technique to evaluate implant-to-bone force transmission, assessing whether and how oral implants can transfer occlusal forces through maxillary bones.In vivo force measurements were performed in the maxillary premolar region of a male patient who had previously received a successful osseointegrated titanium implant. Three linear mini-strain gauges were bonded onto three different buccal cortical bone locations (i.e. coronal, middle, apical) and connected to strain measuring hardware and software. A customized screw-retained abutment was manufactured to allow for vertical and horizontal loading tests.As to the vertical load test, the patient was instructed to bite on a load cell applying his maximum occlusal force for 20 seconds and then recovering for 10 seconds to restore the bone unstrained state; the test was repeated 20 times consecutively. As regards the horizontal load test, the implant was subjected to a total of 20 load applications with force intensities of 5 and 10kg. During the tests, the recorded signals were plotted in real time on a graph as a function of time by means of a strain analysis software.The described strain gauge measurement technique proved to be effective in recording the forces transmitted from osseointegrated implants to the cortical bone. Horizontal loads caused higher deformations of cortical bone than vertical biting forces; in both situations, the deformation induced by the force transferred from the implant to the bone progressively decreased from the coronal to the apical third of the alveolar ridge. At approximately 9 mm from the implant neck, the effect of occlusal force transmission through osseointegrated titanium implants was negligible if compared to the apical region.
       
  • Is short term intraoperative application of disinfectants harmful to
           breast implants in breast reconstruction' An experimental study and
           literature survey
    • Abstract: Publication date: Available online 15 October 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Marweh Schmitz, Dirk W. Schubert, Joachim Kaschta, Jonas Daenicke, Bastian L. Walter, Raymund E. Horch ObjectivesBacterial contamination of breast implants and biofilm formation has been discussed as a major reason for implant loss and capsular contraction. Intra- and perioperative treatment of breast implants with disinfectants to prevent bacterial contamination has been frequently reported. Given the increasing awareness of concerns about product liability the question of whether short-time irrigation of implants with antimicrobial substances during the operative procedure would potentially alter the integrity of the implant shell has attracted legal and medical interest. In this study we therefore investigated whether irrigating breast implants with antimicrobials commonly used in clinical practice with a clinically relevant application time would affect the physical integrity of the implant shell.Materials and MethodsSamples, which were previously punched from the shell of explanted standard silicone gel filled breast implants in a defined way, were exposed to different disinfectant solutions for two minutes. Multiple defined specimens from 5 different explants from 4 different producers (including PIP) were tested. The testing included tensile strength and disruption tests.ResultsIn our prospective test series we could not find a significant influence of a single distinct disinfectant on silicone shell implant surfaces.ConclusionDespite the potential legal implications that might be considered when a surgeon manipulates an implant with disinfectants intraoperatively, we find it worthwhile to state that from a material and surgical standpoint there is no evidence that short-time treatment of alloplastic materials would be detrimental to the physical properties of the implant shell.
       
  • Diffusion of charged and uncharged contrast agents in equine mandibular
           condylar cartilage is not affected by an increased level of sugar-induced
           collagen crosslinking
    • Abstract: Publication date: Available online 14 October 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Fereshteh Mirahmadi, Jan Harm Koolstra, Sepanta Fazaeli, Frank Lobbezoo, G. Harry van Lenthe, Jessica Snabel, Reinout Stoop, Vincent Everts Nutrition of articular cartilage relies mainly on diffusion and convection of solutes through the interstitial fluid due to the lack of blood vessels. The diffusion is controlled by two factors: steric hindrance and electrostatic interactions between the solutes and the matrix components. Aging comes with changes in the cartilage structure and composition, which can influence the diffusion. In this study, we treated fibrocartilage of mandibular condyle with ribose to induce an aging-like effect by accumulating collagen crosslinks. The effect of steric hindrance or electrostatic forces on the diffusion was analyzed using either charged (Hexabrix) or uncharged (Visipaque) contrast agents. Osteochondral plugs from young equine mandibular condyles were treated with 500 mM ribose for 7 days. The effect of crosslinking on mechanical properties was then evaluated via dynamic indentation. Thereafter, the samples were exposed to contrast agents and imaged using contrast-enhanced computed tomography (CECT) at 18 different time points up to 48 h to measure their diffusion. Normalized concentration of contrast agents in the cartilage and contrast agent diffusion flux, as well as the content of crosslink level (pentosidine), water, collagen, and glycosaminoglycan (GAG) were determined. Ribose treatment significantly increased the pentosidine level (from 0.01 to 7.6 mmol/mol collagen), which resulted in an increase in tissue stiffness (~1.5 fold). Interestingly, the normalized concentration and diffusion flux did not change after the induction of an increased level of pentosidine either for Hexabrix or Visipaque. The results of this study strongly suggest that sugar-induced collagen crosslinking in TMJ condylar cartilage does not affect the diffusion properties.Graphical abstractGraphical abstract for this article
       
  • Effects of changes in the structural parameters of bionic straw sandwich
           concrete beetle elytron plates on their mechanical and thermal insulation
           properties
    • Abstract: Publication date: Available online 3 October 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Zhijie Zhang, Jinxiang Chen, M.A. Elbashiry Elsafi, Zhensheng Guo, Xindi Yu To develop new, environmentally friendly prefabricated building materials, the effects of individual changes in structural parameters on the mechanical and thermal insulation properties of straw sandwich concrete beetle elytron plates (SCBEPs), i.e., sandwich plates with trabeculae constituting the core layer structure, were analyzed by ABAQUS. In addition, based on the analysis results, the structural parameters were preliminarily optimized. The results revealed the following. 1) The bearing capacity of a SCBEP is mainly controlled by deformation (i.e., the maximum deflection). The two most influencing factors on the deflection are the panel thickness T and the trabecular radius R. In contrast, although the panel area is very large, the influence of changing the panel thickness on the thermal insulation performance ranks only third. This demonstrates that the thermal bridge effect of the concrete trabeculae and edges is the primary limitation on further improvements to the thermal insulation performance of SCBEPs. 2) Based on the effects of individual changes in structural parameters on the performance of SCBEPs and their actual processing and application requirements, the structural parameters of a SCBEP with optimized mechanical properties and thermal insulation properties are determined. 3) Compared with aerated concrete wallboards, the optimized SCBEP has a higher rigidity, more compacted surface and better durability. Compared with straw concrete wallboards, the optimized SCBEP has a higher straw content and better thermal insulation performance. Thus, it provides a new avenue for the development of a new, lightweight wallboard.
       
  • Degradation in vitro and in vivo of β-TCP/MCPM-based premixed calcium
           phosphate cement
    • Abstract: Publication date: Available online 3 October 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Yao Shu, Yu Zhou, Pengwei Ma, Chunge Li, Cheng Ge, Ying Wang, Qihong Li, Kaitao Yu, Rongjian Lu, Xuan Zou, Yuji Yin, Junjie Li Premixed calcium phosphate cements (CPCs) have been developed to shorten the surgical time of conventional CPCs. However, there is lack of investigation on degradation behavior of premixed CPCs in vitro and in vivo. In this study, the premixed CPCs are prepared by mixing glycerol or polyethylene glycol (PEG) with the CPC power (β-tricalcium phosphate (β-TCP) and monocalcium phosphate monohydrate (MCPM)), and their degradation performances including the microstructure, chemical composition and mechanical properties are systematically evaluated both in vitro and in vivo (subcutaneous implantations in rabbits). When the premixed CPCs aged in PBS or FBS, results show weight loss of the specimens, decreased pH value and increased calcium ion concentration of aging media. Meanwhile, the setting products convert from dicalcium phosphate dihydrate (DCPD) to dicalcium phosphate anhydrous (DCPA), and no hydroxyapatite deposit. The specimen size and the molecular weight of non-aqueous solvent can modulate the setting product of premixed CPCs. For the larger specimens, DCPA is the main setting product, for the smaller ones, the composite contained DCPD and DCPA. With the decrease of the molecular weight of the non-aqueous solvent PEG, the setting product change from both DCPD and DCPA to DCPA due to the quicker exchange rate of PEG with water. After a period of subcutaneous implantation, the surface of the grafts obviously disintegrated with the formation of porous structures, but their internal morphology do not obviously change.
       
  • In-vitro performance of CAD/CAM crowns with insufficient preparation
           design
    • Abstract: Publication date: Available online 3 October 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Martin Rosentritt, Verena Preis, Michael Behr, Stephanie Krifka PurposeTo compare the debonding and fracture force of different CAD/CAM composite crowns with respect to the influence of water storage (0d vs. 90d/37 °C) and types of cementation (adhesive vs. self-adhesive).MethodsExtracted human molars were prepared with a worst-case preparation scenario providing a nonretentive design (height ~4 mm; angle ~15°) and reduced fitting (250 µm). After digitalization, 72 crowns (n=8 per group; circular wall thickness 1.5 mm / occlusal thickness ~2.5 mm) were milled from the composites (CS, LU), one experimental composite (EX), a resin-infiltrated ceramic (VE), and a feldspar ceramic reference (VM). The crowns were adhesively bonded (Scotchbond Universal + Rely X Ultimate, 3 M), and two groups (EX, VE) were additionally cemented with a self-adhesive cement (RelyX Unicem, 3 M). After 90-d water storage, thermal cycling and mechanical loading (TCML) were performed. Restorations, which failed during storage or TCML, were analyzed using scanning electron microscopy, and surviving restorations were loaded to fracture. To evaluate storage effects, two materials (EX, LU) were investigated without water storage.ResultsCS (7×) and LU (2×) exhibited debonding during 90-d storage. LU (5×) debonded during TCML. Cement remained on the inner sides of the crowns in all cases. EX and VE survived storage and TCML without failure or debonding. Two specimens of VM exhibited cracks after TCML. Fracture forces varied between 720 N and 2155 N. Solely the results between VE and VM were not significantly different (p=0.204). Debonding effects due to water storage were material dependent. Fracture forces in tendency (p>0.117) were higher for self-adhesive cementation.ConclusionsDebonding and stability of CAD/CAM crowns were material dependent. Water storage affected debonding, and cementation marginally influenced performance and fracture force.
       
  • A Structure-Based Constitutive Model of Arterial Tissue Considering
           Individual Natural Configurations of Elastin and Collagen
    • Abstract: Publication date: Available online 2 October 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Alexander Rachev, Tarek Shazly The study proposes a novel theoretical-experimental approach for structure-based constitutive modeling of the passive mechanical properties of arterial tissue. The major novelty is accounting for the existence of individual natural configurations of elastin and collagen and their mechanical interaction in terms of the constituents' individual prestretches in the tissue natural state. The structure-based modeling of collagen allows accounting for effects of change in constituents' prestretch in terms of the change in feasible microstructural parameters, such as range of collagen recruitment stretch, mode of collagen mass fraction intensity function, and fiber directions. The results from an illustrative example for a porcine renal artery show that the model is robust and can adequately describe pressure-radius response and the stress-stretch relationship. The predictive capability of the model is tested in simulations of an isolated change in collagen prestretch and of elastin degradation in an artery kept at constant length. We expect this model to advance understanding about arterial rheology and serve as a useful tool for interpreting experimental data and solving boundary value problems relevant to vascular physiology at normal and pathological states.
       
  • Assessment of elastic coefficients of child cortical bone using resonant
           ultrasound spectroscopy
    • Abstract: Publication date: Available online 2 October 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Marie Semaan, Pierric Mora, Simon Bernard, Franck Launay, Cédric Payan, Philippe Lasaygues, Martine Pithioux, Cécile Baron The assessment of the anisotropic elastic properties of non-pathological child cortical bone remains a challenge for the biomechanical engineering community and an important clinical issue. Resonant ultrasound spectroscopy (RUS) can be used to determine bone stiffness coefficients from the mechanical resonances of bone specimens. Here, a RUS protocol was used on 7 fibula specimens from children (mean age 14±3 years) to estimate the whole elastic stiffness tensor of non-pathological child cortical bone considered as orthotropic. Despite a small number of sample, results are consistent with this hypothesis, even if a trend towards transverse isotropy is discussed. Indeed, the average values of the 9 independent stiffness coefficients obtained in this study for child bone are: C11 = 16.73±0.19 GPa, C22 = 16.19±0.12 GPa, C33 = 24.47±0.30 GPa, C44 = 4.14±0.08 GPa, C55 = 4.16±0.07 GPa, C66 = 3.13±0.05 GPa, C12 = 10.14±0.20 GPa, C13 = 10.67±0.27 GPa, C23 = 10.25±0.14 GPa.
       
  • Damping and mechanical behavior of metal-ceramic composites applied to
           novel dental restorative systems
    • Abstract: Publication date: Available online 1 October 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): S. Madeira, M. Gasik, Júlio C.M. Souza, F.S. Silva, Bruno Henriques Conversely to natural teeth, where periodontal ligament (PDL) and pulp works as a damper reducing the effect of the stress on surrounding structures, when natural teeth is lost and replaced or restored the biting forces are directly transmitted to the bone or affect the integrity of the adjacent bottom layers. In this study, damping capacity and dynamic Young's modulus of CoCrMo-porcelain composites for dental restorations were evaluated. Dynamic Young's modulus and damping capacity of materials were assessed by dynamic mechanical analyzes (DMA) at 1 and 10 Hz frequencies, over a temperature ranging (18–60 °C). Results show that by reinforcing dental porcelain with metallic particles, producing ceramic matrix composites (CMCs) with 20 vol.% and 40 vol.% of metallic particles, the damping capacity and dynamic Young's modulus are improved. A decrease on both properties of the metal matrix composites (MMCs) with increasing ceramic particles content (from 20 vol.% to 40 vol.% of ceramic phase) was observed for all the studied frequencies and temperatures. While damping capacity is strongly dependent on frequency, no significant difference in dynamic Young's modulus was found.Results show that besides the yet reported advantages of the bio-inspired functionally graded restorations over traditional bilaminate ones, traduced by improved veneer to substrate adhesion and by the enhanced thermal and mechanical stress distribution, these restorations can also display improved behavior as regard to a damping capacity, which may have a positive impact in the long-term performance of implant – supported prosthesis.Graphical abstractGraphical abstract for this article
       
  • Effects of Knee Simulator Control Method and Radiation Dose on UHMWPE Wear
           Rate, and Relationship between Wear Rate and Clinical Revision Rate in
           National Joint Registry
    • Abstract: Publication date: Available online 1 October 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Yoshimitsu Okazaki, Minako Hosoba, Syuichi Miura, Tadashi Mochizuki The wear rate of five types of cruciate-retaining artificial knee joint ultrahigh-molecular-weight polyethylene (UHMWPE) inserts was examined using two custom-made knee joint simulators satisfying ISO 14243-1 (load control) and ISO 14243-3 (displacement control). The wear rate of knee joints composed of a UHMWPE insert and a Co-Cr-Mo alloy or oxidized zirconium femoral component linearly increased with increasing number of wear cycles, and the volumetric wear rate per million cycles was approximately 6–18 mm3/Mc. The wear rate was the lowest in the highly crosslinked knee joint irradiated at 90 kGy (Scorpio) among the five UHMWPE inserts. The extent of oxidation in UHMWPE after a knee simulator test of up to 5×106 cycles was small. The load-controlled wear rates measured in this work were close to the displacement-controlled wear rates reported in the literature. The effect of the control method on the wear rate was small for Nexgen and Scorpio knee joints. However, it was larger for the PFC Sigma knee joint having a high curvature of the surface. The wear rate of various knee joints made of highly crosslinked UHMWPE (XLPE) markedly decreased when they were subjected to a radiation dose of 40 kGy or more. The 10-year cumulative percentage revision rate since the primary operation slightly decreased with decreasing volumetric knee simulator wear rate for conventional UHMWPE (CPE) and XLPE knee joint inserts. The XLPE knee joint was shown to exhibit reduced in vivo wear and lower rates of revision for total knee replacement. On the other hand, Nexgen and PFC Sigma (both CPE) knee joints showed the lowest revision rate in the AOA and NJR national joint replacement registries. The volumetric wear rates of 3 mm3/Mc for XLPE and 15 mm3/Mc for CPE knee joint inserts are recommended as a goal for the development of new knee joints.
       
  • Ultra-thin occlusal veneers bonded to enamel and made of ceramic or hybrid
           materials exhibit load-bearing capacities not different from conventional
           restorations
    • Abstract: Publication date: Available online 27 September 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Alexis Ioannidis, Sven Mühlemann, Mutlu Özcan, Jürg Hüsler, Christoph H.F. Hämmerle, Goran I. Benic ObjectivesThe objective of this study was to test whether or not the load-bearing capacity of occlusal veneers bonded to enamel and made of ceramic or hybrid materials does differ from those of porcelain-fused-to-metal or lithium disilicate glass ceramic crowns.Material and methodsIn 80 human molars occlusal enamel was removed without extending into the dentin in order to mimic substance defects caused by attrition. The restorations were digitally designed at a standardized thickness of either 0.5 mm or 1.0 mm. For each thickness, 4 test groups were formed each including a different restorative material: “0.5-ZIR”: 0.5 mm thick zirconia (Vita YZ HT); “1.0-ZIR”: 1.0 mm thick zirconia (Vita YZ HT); “0.5-LDC”: 0.5 mm thick lithium disilicate ceramic (IPS e.max Press); “1.0-LDC”: 1.0 mm thick lithium disilicate ceramic (IPS e.max Press); “0.5-HYC”: 0.5 mm thick PICN (Vita Enamic); “1.0-HYC”: 1.0 mm thick PICN (Vita Enamic); “0.5-COC”: 0.5 mm thick tooth shaded resin composite (Lava Ultimate) and “1.0-COC”: 1.0 mm thick tooth shaded resin composite (Lava ultimate). Each group consists of 10 specimens. Two additional groups of 10 specimens each were used as controls and exhibited conventional crown preparations. In one group the crowns were made of lithium-disilicate ceramic (“CLD”: IPS e.max CAD) and the other group consisted of porcelain-fused to metal crowns (“PFM”). All restorations were cemented onto the prepared teeth following the manufacturer's instruction of the corresponding luting cement. Subsequently, they were thermo-mechanically aged and then loaded until fracture. Load-bearing capacities (Fmax) between the groups were compared applying the Kruskal-Wallis test (p < 0.05) and pairwise group comparisons using the Dunn's method.ResultsMedian values (and quartiles) for the load-bearing capacity amounted to (Fmax) 2’407 (1’670; 2’490) N for the CLD group and to 2’033 (1’869; 2’445) N for the PFM group. For the 0.5 mm thick restorations Fmax reached the highest median value in group 0.5-HYC 2’390 (1’355; 2’490) N, followed by 0.5-COC 2’200 (1’217; 2’492) N and 0.5-LDC 1’692 (1’324; 2’355) N. No results were obtained for group 0.5-ZIR due to the impracticability to fabricate ultra-thin specimens. The distribution of the values for the 1.0 mm thick restorations was 2’489 (2’426; 2’491) N for 1.0-COC, 2’299 (2’156; 2’490) N for 1.0-ZIR, 2’124 (1’245; 2’491) N for 1.0-HYC, and 1’537 (1’245; 1’783) N for 1.0-LDC. The differences of the medians between the test and the control groups did not reach statistical significance for the 0.5 mm thick specimens (KW: p = 0.6952 and p = 0.6986). Within the groups exhibiting 1.0 mm thickness, however, significant different medians were found: 1.0-LDC < 1.0-ZIR and 1.0-LDC < 1.0-COC (KW: p < 0.0209).ConclusionsRegarding their maximum load-bearing capacity, minimally invasive occlusal veneers made of ceramic and hybrid materials can be applied to correct occlusal tooth wear and thus replace conventional crown restorations.Graphical abstractGraphical abstract for this article
       
  • Investigation on the orientation dependence of elastic response in Gyroid
           cellular structures
    • Abstract: Publication date: Available online 27 September 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Lei Yang, Chunze Yan, Haiyang Fan, Zhaoqing Li, Chao Cai, Peng Chen, Yusheng Shi, Shoufeng Yang Materials used for hard tissue replacement should match the elastic properties of human bone tissue. Therefore, cellular structures are more favourable for the use of implants than solid materials for their custom-designed mechanical properties. The superimposed load from various directions in vivo makes uniaxial compression testing insufficient for describing the mechanical responses. In this paper, the rotational symmetry of Gyroid cellular structure (GCS) was discussed. An approach using structural simplification and analytical solution was presented to investigate the relationship between Young's modulus and volume fraction, as well as the orientation dependence of the mechanical responses for GCS loaded in various orientations. It is concluded that the analytical solution is reasonable for a low volume fraction, through the comparison between analytical results, finite element (FE) and experimental data. Gained polar diagrams illustrate the anisotropic property of GCS and also confirm the superiority for their stable mechanical responses of diverse loading directions.Graphical abstractGraphical abstract for this article
       
  • The performance of sol-gel silica coated Y-TZP for veneered and monolithic
           dental restorations
    • Abstract: Publication date: Available online 27 September 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Ana Flávia Nunes Reis, Gabriela Freitas Ramos, Tiago Moreira Bastos Campos, Pedro Henrique Condé Oliveira Prado, Getúlio Vasconcelos, Alexandre Luiz Souto Borges, Renata Marques de Melo ObjectivesThe purpose of the study was to characterize the microstructure, constituents, and mechanical properties of mono and bilayered zirconia specimens infiltrated with silica by the sol gel method.Methods180 zirconia discs (14-mm diameter) were divided in 3 groups (n=60) according to thickness (1.2, 0.5 mm) and further divided in two groups (n=30) according to treatment (infiltrated or not). Disk thickness was 1.2 mm for the control samples. Veneering feldspathic porcelain had two thicknesses (0.5 mm and 1 mm) at the tops of the zirconia discs. All groups were subjected to the biaxial flexural test in an aqueous medium. Weibull analysis was performed for determination of the Weibull modulus (m) and characteristic strength (σ0). The specimens were characterized by SEM and EDS and XRD. Hardness and elastic modulus were measured by nano-indentation and pulse-echo methods, respectively. Fracture toughness was determined by the nano-indentation technique. A scratch test was used for evaluation of the adhesion between the zirconia and porcelain.ResultsThere was less variability (higher Weibull modulus) in the infiltrated monolithic specimens; biaxial flexural strength was not statistically higher in the veneered infiltrated specimens and was decreased for the 1-mm veneered infiltrated group. The difractograms showed formation of ZrSiO4 crystal phase. Hardness also increased in the infiltrated monolithic zirconia, whereas fracture toughness decreased. Adhesion between zirconia and porcelain was superior in the non-infiltrated monolithic specimens.ConclusionsInfiltration increased the structural homogeneity and hardness of the monolithic zirconia, but it reduced fracture toughness, and the adhesion to porcelain.Clinical significanceWithin the limitations of the present study, it is possible to recommend the infiltration of silica gel in zirconia only for monolithic restorations.Graphical abstractGraphical abstract for this article
       
  • Design and models of helical needle geometries for core biopsies
    • Abstract: Publication date: Available online 26 September 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Marco Giovannini, Jian Cao, Kornel Ehmann Biopsy needles are standard medical devices for extracting biological tissue with the purpose of diagnosing a specific anomaly such as cancerous masses, or lumps. The outcome of these procedures greatly relies on the quality of the samples which, in turn, depends on the forces acting on the needle during its insertion. In this scenario, the design of the needle tip plays a fundamental role in determining the cutting forces. Yet, since the dawn of modern medicine, only a few studies have proposed novel needle tip configurations. In this study, the geometry of biopsy needles is investigated, and helical cutting edges characterized by a three-dimensional (3D) profile are conceived. Mathematical models were formulated to compute the cutting angles and the tissue fracture forces. The proposed methodology is general and can be applied to any 3D needle cutting edge geometry. The utility of the helical geometry was demonstrated on a 14-gauge hollow needle which is generally used during breast biopsies. Experimental insertions were performed at different cutting speeds on phantom tissue. The results show that helical needles generate lower cutting forces than commercial needles and recommendations are formulated for the selection of their cutting parameters. The outcome of this investigation is applicable to biopsy examinations in which a hollow needle is adopted to acquire soft tissue samples.
       
  • Collagen Fibre Orientation and Dispersion Govern Ultimate Tensile
           Strength, Stiffness and the Fatigue Performance of Bovine Pericardium
    • Abstract: Publication date: Available online 26 September 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): A. Whelan, J. Duffy, R.T. Gaul, D. O’Reilly, D.R. Nolan, P. Gunning, C. Lally, B. Murphy The durability of bovine pericardium leaflets employed in bioprosthetic heart valves (BHVs) can significantly limit the longevity of heart valve prostheses. Collagen fibres are the dominant load bearing component of bovine pericardium, however fibre architecture within leaflet geometries is not explicitly controlled in the manufacture of commercial devices. Thus, the purpose of this study was to ascertain the influence of pre-determined collagen fibre orientation and dispersion on the mechanical performance of bovine pericardium.Three tissue groups were tested in uniaxial tension: cross-fibre tissue (XD); highly dispersed fibre-orientations (HD); or preferred-fibre tissue (PD). Both the XD and PD tissue were tested under cyclic loading at 1.5 Hz and a stress range of 2.7 MPa.The results of the static tensile experiments illustrated that collagen fibre orientation and degree of alignment significantly influenced the material's response. Whereby, there was a statistically significant decrease in material properties between the XD groups and both the PD and HD groups for ultimate tensile strength and stiffness (p
       
  • PMMA/Double-Modified Organoclay Nanocomposites as Fillers for Denture Base
           Materials with Improved Mechanical Properties
    • Abstract: Publication date: Available online 26 September 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Fateme Shakeri, Azizollah Nodehi, Mohammad Atai The aim of this study was to investigate the effect of double-modified organoclay on mechanical properties of polymethylmethacrylate (PMMA) denture base resins. An organoclay was further modified via a silanization process using 3-trimethoxysilylpropyl methacrylate (MPS) as a reactive silane coupling agent. X-ray diffraction patterns (XRD), thermogravimetric analysis (TGA), and Fourier-transform infrared spectroscopy (FTIR) confirmed the presence of MPS in the resulting double-modified nanoclay structure. Surface tension of the original and double-modified nanoclays, were determined using contact angle measurements. Results showed that double-modified nanoclay has more organophilic nature due to silanization of the clay edges. Free radical suspension polymerization of methylmethacrylate monomers in the presence of different amounts of double-modified organoclay was performed and PMMA/clay nanocomposites were obtained. Results of dynamic mechanical thermal analysis (DMTA) showed increased storage modulus and glass transition temperature for the resulting nanocomposites with respect to neat PMMA. Higher improvements in storage modulus and glass transition temperature were obtained for nanocomposites containing 0.25 and 0.5 wt% of double-modified nanoclay. TEM observations of the nanocomposite containing 0.5 wt% of double-modified nanoclay showed prevailing exfoliated morphology. Aforementioned nanocomposites with higher mechanical properties were incorporated into a denture base formulation and their mechanical properties were studied using static flexural and fracture toughness tests. According to the results, both reinforced samples showed increased flexural strength, flexural modulus and fracture toughness in comparison to the neat matrix. The average improvements in flexural strength, flexural modulus and fracture toughness were about 30%, 65.8% and 32%, respectively.Scanning electron microscopy (SEM) images of the fracture surface of the resin matrices subjected to static tests showed brittle and ductile surface fracture for neat and reinforced denture base specimens, respectively.
       
  • Anisotropic Freeze-Cast Collagen Scaffolds for Tissue Regeneration: How
           Processing Conditions Affect Structure and Properties in the Dry and Fully
           Hydrated States
    • Abstract: Publication date: Available online 25 September 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Prajan Divakar, Kaiyang Yin, Ulrike G.K. Wegst Few systematic structure–property-processing correlations for directionally freeze-cast biopolymer scaffolds are reported. Such correlations are critical to enable scaffold design with attractive structural and mechanical cues in vivo. This study focuses on freeze-cast collagen scaffolds with three different applied cooling rates (10, 1, and 0.1 °C/min) and two freezing directions (longitudinal and radial). A semi-automated approach for structural characterization of fully hydrated scaffolds by confocal microscopy is developed to facilitate an objective quantification and comparison of structural features. Additionally, scanning electron microscopy, and compression testing are performed longitudinally and transversely. Structural and mechanical properties are determined on dry and fully hydrated scaffolds. Longitudinally-frozen scaffold have aligned and regular pores while those in radially-frozen ones exhibit greater variations in pore geometry and alignment. Lamellar spacing, pore area, and cell wall thickness increase with decreasing cooling rate: in longitudinally-frozen scaffolds from 25 µm to 83.5 µm, 814 µm2 to 8,452 µm2, and 4.21 µm to 10.4 µm, and in radially-frozen ones, from 69 µm to 116 µm, 7,679 µm2 to 25,670 µm2, and 6.18 µm to 13.6 µm, respectively. Both longitudinally- and radially-frozen scaffolds possess higher mechanical property values, when loaded parallel rather than perpendicular to the ice-crystal growth direction. Modulus and yield strength range from 779-4,700 kPa and 38–137 kPa, respectively, as a function of cooling rate and freezing direction. Collated, the correlations obtained in this study enable the custom-design of freeze-cast collagen scaffolds, which are ideally suited for a large variety of tissue regeneration applications.Graphical Graphical abstract for this article
       
  • Extraordinary Mechanical Performance in Disentangled UHMWPE Films
           Processed by Compression Molding
    • Abstract: Publication date: Available online 25 September 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Ana E. Ferreira, M. Rosário Ribeiro, Henri Cramail, João P. Lourenço, Vicente Lorenzo, Ernesto Pérez, Maria L. Cerrada An approach to obtain disentangled ultra-high molecular weight polyethylene (UHMWPE) films is proposed using a common compression molding. For that, disentangled UHMWPE nascent powders from reactor are processed at temperatures lower than the main melting peak and at high pressure. Then, disentangled UHMWPE films obtained from homogeneous polymerization powders and from those that incorporate SBA-15 mesoporous silica can be easily achieved by this simple methodology. These disentangled UHMWPE based materials show very high crystallinity and, consequently, outstanding elastic modulus and hardness, both further increasing by presence of mesoporous SBA-15 in the hybrids.Graphical Graphical abstract for this article
       
  • Modeling of Osteoprobe Indentation on Bone
    • Abstract: Publication date: Available online 25 September 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Ashraf Idkaidek, Iwona Jasiuk Osteoprobe (ActiveLife, Santa Barbara, CA) is a novel handheld microindentation instrument designed to test bone in vivo by measuring a Bone Material Strength index (BMSi). In this paper, the Osteoprobe indentation on a cortical bone is modeled computationally to gain insights into the physical interpretation of the BMSi output. The analysis is conducted using an axisymmetric finite element model with an isotropic viscoelastic-plastic constitutive law with continuum damage. The computational model is validated by comparing it with experimental data from the literature. Experimental factors (indenter tip radius and friction coefficient between the indenter and the bone) and four mechanical properties of bone (Young's modulus, compressive yield stress, and damage and viscosity constants) are varied to study their influence on the BMSi.We find that varying the friction coefficient can proportionally change the BMSi up to 3%. The indenter tip radius is proportional to the BMSi, with the more pronounced proportional relation when it is greater than 30 μm. Young's modulus has a proportional relation with the BMSi, where decreasing it by 73% reduces the BMSi by 41%. The damage constant has an inversely proportional relation to the BMSi, where increasing it from 0.5 to 0.96 reduces the BMSi by 29%. The compressive yield stress and the viscosity constant have a close proportional relation to the BMSi, where increasing the compressive yield stress from 50 MPa to 200 MPa increases the Osteoprobe BMSi by 21%.In summary, the friction coefficient and the indenter tip radius (when smaller than 30 μm) have a small effect on BMSi. Young's modulus and damage have stronger relations with the BMSi than compressive yield stress and viscosity constant. This fundamental study provides new insights into the BMSi measurement and serves as a basis for further computational and experimental investigations on the Osteoprobe technique. Such research is needed to facilitate the embrace of this technique by the clinical community.
       
  • Fracture toughness of Glass ionomers measured with two different methods
    • Abstract: Publication date: Available online 20 September 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Negin Alvanforoush, Rebecca Wong, Michael Burrow, Joseph Palamara Glass Ionomer Cements (GICs) are brittle materials with low fracture toughness and strength. Therefore, understanding the fracture toughness is an important parameter to know, due to GICs being promoted for load-bearing restorations. Also, little is known about the effects of artificial saliva (AS) on fracture toughness of GICs. This project aimed to study the effects of storage and compare two different fracture toughness test methods, namely: Compact-Tension test and 4-point bending test. Samples were made from a Zinc-reinforced-GIC (ChemFil), High viscosity bulk-fill-GIC (HV) with and without LC-coating (EQUIA), Resin-Modified GIC (RM-GIC) (Riva-LC), HV-RMGIC (Riva-HV-LC) and flowable bulk-fill Giomer (Beautifil-Bulk Flowable) using a custom-made mould. Specimens were stored in either AS or distilled-water (DW) for 7 or 30 days. After storage, specimens were tested for fracture toughness. Results were analysed with Analysis of variance (ANOVA), Mann-Whitney and Weibull statistics. ANOVA showed a significant difference (P
       
  • 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. Spearot Shockwave 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.
       
  • 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 Reilly Dental 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
       
  • A comparison of selected physico-chemical properties of calcium alginate
           fibers produced using two different types of sodium alginate
    • Abstract: Publication date: Available online 13 October 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Rhoda Au Yeung, Ross A. Kennedy Sodium alginate is a non-toxic natural polysaccharide found in marine brown algae. It is able to form solid gels by the action of poly-valent cations (commonly calcium but not magnesium) which cross-link the polysaccharide chains at the guluronic acid groups. Alginate-based products are popular in many industries, including food production and in pharmaceutical and biomedical applications. It is utilized in manufacture of wound-care products due to its biocompatibility and gel forming capabilities upon the absorption of wound exudate.Considering the potential influence of the alginate composition on the properties of the resultant fibers, two sodium alginate powders were selected based on their contrasting compositions. The GHB alginate was high in guluronic acid whereas the LKX alginate was high in mannuronic acid. The sodium alginate solutions (4% w/w) were extruded into a calcium chloride (3% w/v) bath to produce calcium alginate fibers. The fibers were dried at 22°C and 32% relative humidity for 72 hours. Selected properties of the blank (unloaded) fibers were analysed: diameter measurements by optical microscopy, mechanical strength using a universal testing machine, morphology by scanning electron microscopy, and calcium content by inductively coupled plasma atomic emission spectroscopy. One of the key aims of this work was to evaluate the variability of these properties along moderately large lengths of fiber and to determine the difference (if any) between replicate lengths of fibers.This study showed that the alginate type influenced selected properties of the resultant fibers. The mean diameter and calcium content of the GHB fibers were 232µm and 2.79µmoles/mg respectively, whereas the LKX fibers were about 10% thicker and had 2.58µmoles/mg calcium ion content. The fibers of each alginate could be distinguished visually based on gross differences as well as differences in their microstructure. Mechanical testing of the fibers produced stress-strain plots displaying largely non-elastic behaviour. There was no statistically significant (p
       
  • Shear thinning/self-healing hydrogel based on natural polymers with
           secondary photocrosslinking for biomedical applications
    • Abstract: Publication date: Available online 12 October 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Esmat Jalalvandi, Amin Shavandi Injectable hydrogel systems are useful in many biomedical applications, including drug or cell delivery carriers and scaffolds. Here, we describe the design and characterization of a shear thinning hydrogel that undergoes a disassembly when shear forces are applied during injection and is self-healing once the shear forces are removed. This hydrogel is based on a cyclodextrin modified alginate, and a methacrylated gelatin which initially forms through a weak guest-host interaction between hydrophobic cyclodextrin cavities and the aromatic residue of gelatin. Methacrylated gelatin possesses photocrosslinkable functionalities which can go through a light-initiated polymerization to create secondary crosslinking sites and further crosslink the matrix. The shear thinning and self-healing behavior of these gels monitored in low and high strain range, viscosity of the hydrogels components and gelation kitenitc were studied. The rheological analyses showed the formation of shear thinning gels which were furthere stabilized by visible light exposure. The cytotoxicity of the hydrogels towards human mesenchymal stem cells were assessed and the rate of mass loss over a week period was studied.
       
  • Bioactive Ti + Mg composites fabricated by powder metallurgy: the relation
           between the microstructure and mechanical properties
    • Abstract: Publication date: Available online 12 October 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Martin Balog, Ahmed Mohamed Hassan Ibrahim, Peter Krizik, Oto Bajana, Alena Klimova, Amir Catic, Zdravko Schauperl Metallic implant materials are biomaterials that have experienced major development over the last fifty years, yet some demands posed to them have not been addressed. For the osseointegration process and the outcome of endosseous implantation, it is crucial to reduce the stress shielding effect and achieve sufficient biocompatibility. Powder metallurgy (PM) was utilized in this study to fabricate a new type of titanium (Ti) + magnesium (Mg) bioactive composite to enable stress-shielding reduction and obtain better biocompatibility compared with that of the traditional Ti and Ti alloys used for dental implants. Such composites are produced by well-known cost-effective and widely used PM methods, which eliminate the need for complex and costly Ti casting used in traditional implant production. The relation between the microstructure and mechanical properties of as-extruded Ti + (0 − 24) vol.% Mg composites was investigated with respect to the Mg content. The microstructure of the composites consisted of a biodegradable Mg component in the form of filaments, elongated along the direction of extrusion, which were embedded within a permanent, bioinert Ti matrix. As the Mg content was increased, the discrete filaments became interconnected with each other and formed a continuous Mg network. Young's modulus (E) of the composites was reduced to 81 GPa, while other tensile mechanical properties were maintained at the values required for a dental implant material. The corrosion behavior of the Ti + Mg composites was studied during immersion in a Hank's balanced salt solution (HBSS) for up to 21 days. The elution of Mg pores formed at former Mg sites led to a further decrease of E to 74 GPa. The studied compositions showed that a new Ti + Mg metallic composite should be promising for load-bearing applications in endosseous dental implants in the future.
       
  • Finite element analysis comparing WaveOne, WaveOne Gold, Reciproc and
           Reciproc Blue responses with bending and torsion tests
    • Abstract: Publication date: Available online 12 October 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): María Prados-Privado, Rosa Rojo, Carlos Ivorra, Juan Carlos Prados-Frutos To evaluate the bending and torsional properties of four nickel-titanium endodontic files, we simulated and compared WaveOne® primary size 25 with 0.07 taper, WaveOne Gold® primary size 25 with 0.07 taper, Reciproc® primary size 25 with 0.08 taper, and Reciproc Blue® primary size 25 with 0.08 taper. Three-dimensional models were created using computer-aided design software and numerically analyzed in ANSYS® Workbench. Boundary conditions for the numerical analyses were based on the ISO 3630-1 specifications. The highest stress levels were recorded for WaveOne® and Reciproc®. Numerical results of the bending test showed that WaveOne Gold® is 86% more flexible than WaveOne® with a deflection of 3 mm. Reciproc Blue® was 42.31% more flexible than Reciproc® file with a deflection of 3 mm. The WaveOne® instrument withstood the highest stress under the torsion test, followed by Reciproc®, then Reciproc Blue® files. The stress under torsion in the WaveOne® and WaveOne Gold® files is reduced in a 51%. Regarding Reciproc® and Reciproc Blue® files, the stress under torsional moments remains very similar. Our results exposed a considerable difference in terms of stress tolerance between WaveOne® and WaveOne Gold®. However, Reciproc® files demonstrated a similar stress distribution. The results obtained through finite element analysis suggest that thermal treatment of files might improve their flexibility, increasing resistance during the preparation of highly curved canals. Also, the values obtained regarding the improvement of flexibility were in accordance with the manufacturer claims.
       
  • Nanomechanical characterization of time-dependent deformation/recovery on
           human dentin caused by radiation-induced glycation
    • Abstract: Publication date: Available online 12 October 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Takuma Tobe, Yo Shibata, Ayako Mochizuki, Naofumi Shimomura, Jun Zhou, Wurihan, Reina Tanaka, Sachiko Ikeda, Zhongpu Zhang, Qing Li, Tomio Inoue, Takashi Miyazaki An increase in non-enzymatic collagen matrix cross-links, such as advanced glycation end-products (AGEs), is known to be a major complication in human mineralized tissues, often causing abnormal fractures. However, degradation of mechanical properties in relation to AGEs has not been fully elucidated at the material level. Here, we report nanoscale time-dependent deformation and dimensional recovery of human tooth dentin that has undergone glycation induced by x-ray irradiation. The reduction in enzymatic collagen cross-linking and the increased level of AGEs with concomitant growth of disordered collagen matrix diminished creep deformation recovery in the lower mineralized target region. However, the elevated AGEs level alone did not cause a reduction in time-dependent deformation and its recovery in the higher mineralized target region. In addition to the elevated AGEs level, the degradation of the mechanical properties of mineralized tissues should be assessed with care in respect to multiple parameters in the collagen matrix at the molecular level.Graphical abstractX-ray irradiation of human tooth dentin causes the matrix deterioration, including reduction in enzymatic collagen cross-linking with concomitant growth of AGEs and disordered collagen matrix.Graphical abstract for this article
       
  • Simulation of 3D Nanomanipulation for rough spherical elastic and
           viscoelastic particles in a liquid medium; experimentally determination of
           cell's roughness parameters and Hamaker constant's correction
    • Abstract: Publication date: Available online 12 October 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): M.H. Korayem, S. Shahali, Z. Rastegar Due to the softness and vulnerability of biological cells, in manipulation operations, it is not possible to insert excessive force to move these cells. Also, cells in their living environment face with many dynamic factors; therefore, in order to prevent their destruction and death, consideration the environmental conditions, the theoretical studies that underlie the laboratory research should be closer to the actual results. So, in this article by simultaneous consideration of cell's viscoelasticity and asperities on its surface, as well as the correction of the viscoelastic constant in the liquid medium, the effects of the number of asperities on the contact area between cell and substrate on the manipulation process are investigated and by considering different mediums effects, cell's roughness and developed Hamaker for viscoelastic state, more accurate results of simulations are obtained. On the other hand, atomic force microscopy is also a powerful and multifunctional imaging device that provides observation and manipulation of biological samples, including single-cells, in a liquid medium. Consequently, in this study, using this device, the topography of the benign breast cancer cell is carried out in a liquid medium in contact mode. To correct the viscoelastic Hamaker constant, results are obtained using the Gwyddion software for extracting the roughness radius and the particle's height distribution function. In addition, simulation of the 3D manipulation for elastic and viscoelastic spherical bioactive particles in both air and liquid mediums is done applying particle's roughness with elastic and viscoelastic Hamaker constants. Results indicate that in the liquid medium due to changes in the adhesion force as well as the presence of drag force and surface tension, the critical force is reduced compared to air medium, and the effect of particle's roughness on the critical force and time is related to the number of asperities on the contact surface. Also, results are in good agreement with results of applying the particle's folding coefficient in the manipulation. In the second phase of the manipulation, the change trend in the manipulation force varies in different operating conditions.
       
  • Development of a Validated Glenoid Trabecular Density-Modulus Relationship
    • Abstract: Publication date: Available online 12 October 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Nikolas K. Knowles, G. Daniel G. Langohr, Mohammadreza Faieghi, Andrew Nelson, Louis M. Ferreira Incorporating subject-specific mechanical properties derived from clinical-resolution computed tomography data increases the accuracy of finite element models. Site-specific relationships between density and modulus are required due to variations in trabecular architecture and tissue density by anatomic location. Equations have been developed for many anatomic locations and have been shown to have excellent statistical agreement with empirical results; however, a shoulder-specific density-modulus relationship does not currently exist. This study used micro-finite element cores of glenoid trabecular bone and co-registered quantitative computed tomography finite element models to develop a validated glenoid trabecular density-modulus relationship. Micro finite element model tissue density was considered as either homogeneous or heterogeneous, scaled by CT-intensity. When heterogeneous tissue density was considered, near absolute statistical agreement was predicted in the co-registered QCT-derived finite element models. The validated relationships have also been adapted for use in whole bone scapular models and have the potential to dramatically increase the accuracy of clinical-resolution CT-derived shoulder finite element studies.
       
  • Porous decellularized trachea scaffold prepared by a laser micropore
           technique
    • Abstract: Publication date: Available online 11 October 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): Yongjun Zhang, Yong Xu, Yanqun Liu, Dan Li, Zongqi Yin, Yingying Huo, Gening Jiang, Yong Yang, Zongxin Wang, Yaqiang Li, Fangjia Lu, Yi Liu, Liang Duan, Guangdong Zhou Rapid development of tissue engineering technology provides new methods for tracheal cartilage regeneration. However, the current lack of an ideal scaffold makes engineering of trachea cartilage tissue into a three-dimensional (3-D) tubular structure a great challenge. Although a decellularized trachea matrix (DTM) has become a recognized scaffold for trachea cartilage regeneration, it is difficult for cells to detach from or penetrate the matrix because of its non-porous structure. To tackle these problems, a laser micropore technique (LMT) was applied in the current study to enhance trachea sample porosity, and facilitate decellularizing treatment and cell ingrowth. Furthermore, after optimizing LMT and decellularizing treatment parameters, LMT-treated DTM (LDTM) retained its natural tubular structure with only minor extracellular matrix damage. Moreover, compared with DTM, the current study showed that LDTM significantly improved the adherence rate of cells with perfect cell biocompatibility. Moreover, the optimal implantation cell density for chondrogenesis with LDTM was determined to be 1×108 cells/ml. Collectively, the results suggest that the novel LDTM is an ideal scaffold for trachea tissue engineering.Graphical abstractGraphical abstract for this article
       
  • Cortical bone properties in the Brtl/+ mouse model of Osteogenesis
           imperfecta as evidenced by acoustic transmission microscopy
    • Abstract: Publication date: Available online 11 October 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): S. Blouin, N. Fratzl-Zelman, A. Roschger, W.A. Cabral, K. Klaushofer, J.C. Marini, P. Fratzl, P. Roschger Higher skeletal fragility has been established for the Brtl/+ mouse model of osteogenesis imperfecta at the whole bone level, but previous investigations of mechanical properties at the bone material level were inconclusive. Bone material was analyzed separately at endosteal (ER) and periosteal regions (PR) on transverse femoral midshaft sections for 2-month old mice (wild-type n=6; Brtl/+ n=6). Quantitative backscattered electron imaging revealed that the mass density computed from mineral density maps was higher in PR than in ER for both wild-type (+2.1%, p
       
  • Crack Initiation and Growth in a Special Quasi-sandwich Crossed-lamellar
           Structure in Cymbiola nobilis Seashell
    • Abstract: Publication date: Available online 10 October 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): H.M. Ji, X.W. Li, D.L. Chen Sandwich structure consisting of three crossed-lamellar layers (inner, middle and outer) is one of the most common structures found in mollusk shells, and is normally arranged in a 0°/90°/0° or 90°/0°/90° mode. However, the Cymbiola nobilis seashell in the present study is observed to exhibit a unique quasi-sandwich structure, where the inner and middle layers have an ~15° rotation in comparison with those of typical sandwich structures, resulting in a 15°/75°/0° or 75°/15°/90° mode. This has been identified as the weak/tough/weak and tough/weak/tough modes, and the sample arranged in the 15°/75°/0° mode with a tough layer in the middle has a higher strength than that arranged in the 75°/15°/90° mode with a weak layer in the middle. The fracture resistances of these two types of structural arrangements depend mainly on crack propagation. The interfaces between the macrolayers can effectively arrest the crack propagation especially when the tough layer is positioned in the middle (15°/75°/0° mode), hence increasing the strength and toughness of materials. Salient toughening mechanisms involving crack deflection together with zig-zag crack propagation paths as well as the fiber pull-out of second-order lamellae are identified. Moreover, triangular fracture paths with a convex morphology are observed to form due to the concurrent occurrence of fiber fracturing and channel cracking in single 1st-order lamellae. These findings shed light on the superb crack propagation resistance of the unique quasi-sandwich structure in the C. nobilis shell, thus paving the way for the development of bio-inspired advanced structural materials.
       
  • Effect of collagen packing and moisture content on leather stiffness
    • Abstract: Publication date: Available online 5 October 2018Source: Journal of the Mechanical Behavior of Biomedical MaterialsAuthor(s): S.J.R. Kelly, R. Weinkamer, L. Bertinetti, R.L. Edmonds, K.H. Sizeland, H.C. Wells, P. Fratzl, R.G. Haverkamp Applications for skin derived collagen materials, such as leather and acellular dermal matrices, usually require both strength and flexibility. In general, both the tensile modulus (which has an impact on flexibility) and strength are known to increase with fiber alignment, in the tensile direction, for practically all collagen-based tissues. The structural basis for flexibility in leather was investigated and the moisture content was varied. Small angle X-ray scattering was used to determine collagen fibril orientation, elongation and lateral intermolecular spacing in leather conditioned by different controlled humidity environments. Flexibility was measured by a three point bending test. Leather was prepared by tanning under biaxial loading to create leather with increased fibril alignment and thus strength, but this treatment also increased the stiffness. As collagen aligns, it not only strengthens the material but it also stiffens because tensile loading is then applied along the covalent chain of the collagen molecules, rather than at an angle to it. Here it has been shown that with higher moisture content greater flexibility of the material develops as water absorption inside collagen fibrils produces a larger lateral spacing between collagen molecules. It is suggested that water provides a lubricating effect in collagen fibrils, enabling greater freedom of movement and therefore greater flexibility. When collagen molecules align in the strain direction during tanning, leather stiffens not only by the fiber alignment itself but also because collagen molecules pack closer together, reducing the ability of the molecules to move relative to each other.Graphical abstractGraphical abstract for this article
       
 
 
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