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  • 更新日期:2018-09-22
  • Engineering hydrogel viscoelasticity
    J. Mech. Behav. Biomed. Mater. (IF 3.239) Pub Date : 2018-09-21
    Ludovica Cacopardo, Nicole Guazzelli, Roberta Nossa, Giorgio Mattei, Arti Ahluwalia
    更新日期:2018-09-21
  • Fracture toughness of Glass ionomers measured with two different methods
    J. Mech. Behav. Biomed. Mater. (IF 3.239) Pub Date : 2018-09-20
    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<0.05) between methods, however the same trend among materials was observed in both methods. Some materials showed significantly higher values for samples stored in DW and others revealed the same trend but were not significant. Significantly higher (P<0.05) mean fracture toughness values were observed for materials stored for 30 days. Since both fracture toughness test methods revealed the same fracture toughness strength order among materials, either test appears appropriate. GICs maturation led to a difference between 7 and 30-day results. The AS used had a high ionic strength compared to DW, which may have led to increased solubility of GICs and consequently to the reduced fracture toughness values.The results revealed that coating the GIC has a protective effect against storage media.

    更新日期:2018-09-21
  • A Study on the Tubular Composite with Tunable Compression Mechanical Behavior Inspired by wood cell
    J. Mech. Behav. Biomed. Mater. (IF 3.239) Pub Date : 2018-09-20
    Che zhao, Luquan Ren, Zhengyi Song, Linhong Deng, Qingping Liu

    Biological materials have fascinating mechanical properties built up from simple basic material blocks. It is worthwhile to learn how biological materials are constructed, and to apply the knowledge in advanced manufacturing, and to realize new materials by design. In this study, we chose the tubular cell in the soft wood as a biological prototype, and tried to mimic its intelligent construction principle to regulate the compression mechanical behavior through the helical structure. First, by using the multi-material three-dimensional printing technology, we fabricated a series of tubular composites with the helix fibers of a rigid plastic embedded into an elastomeric matrix. Then, through the uniaxial compression tests, we characterized the mechanical behavior of the specimens, having different fiber angle from 0 to 50 deg at constant volume fraction. The results showed that both stiffness and fracture toughness of the printed composite could be regulated effectively by adjusting the fiber angle of the helical structure. Moreover, the helical structure with high fiber angle is able to improve the compression stability of the tubular composite with big lumen. In addition, for the biomimetic composites, the volume fraction of the reinforcements should exceed 40%. Finally, we proposed a new structural design method by combining the reinforcements of different architectures into a double-layered configuration. The intelligent strategy is proven to balance the conflict between the stiffness and toughness of the composites to some extent, and without changing in the building constituents.

    更新日期:2018-09-21
  • On the Observation of Lubrication Mechanisms within Hip Joint Replacements. Part II: Hard-on-hard Bearing Pairs
    J. Mech. Behav. Biomed. Mater. (IF 3.239) Pub Date : 2018-09-19
    D. Nečas, M. Vrbka, J. Gallo, I. Křupka, M. Hartl

    The present paper represents Part II of the extensive study focused on the lubrication of hip joint replacements. The main goal is to assess the fundamentals of lubrication considering both hard-on-soft (Part I) and hard-on-hard (Part II) bearing pairs. In addition, the effect of individual constituents contained in the model fluid is clarified. For this purpose, multiple model fluids of various composition were employed. In this part of the study, metal-on-glass contact representing hard bearing pairs was observed in situ using pendulum hip joint simulator in combination with thin film colorimetric interferometry method. The designed test consists of initial static loading/unloading phase for the determination of adsorption of molecules on rubbing surfaces. This period is followed by swinging of the pendulum and latest static part under constant load. Three groups of measurements were carried out while fourteen different lubricants were tested. Initially, the experiments were performed with albumin-based model fluid. In that case a substantial positive effect of hyaluronic acid was identified. In contrast, the fluids with γ-globulin as a base constituent showed improved lubrication conditions when phospholipids were added to the solution. Finally, considering the complex fluid, a combined effect of hyaluronic acid and phospholipids caused a better endurance of the lubricant film. The latest part of the paper aims on the comparison of film formation considering hard and soft pairs, highlighting some clear differences. In general, hard pairs exhibit clear decreasing tendency of the film during swinging motion while opposite behaviour was observed for soft pairs.

    更新日期:2018-09-20
  • On the Observation of Lubrication Mechanisms within Hip Joint Replacements. Part I: Hard-on-soft Bearing Pairs
    J. Mech. Behav. Biomed. Mater. (IF 3.239) Pub Date : 2018-09-19
    D. Nečas, M. Vrbka, A. Galandáková, I. Křupka, M. Hartl

    The present study describes the lubrication mechanisms within artificial hip joints considering real conformity of rubbing surfaces. Part I is focused on hard-on-soft material combination, introducing the fundamentals of lubrication performance. These pairs have not been explored in terms of in situ observation before. The contact of metal femoral component articulating with transparent polymer acetabular cup was studied using a hip joint simulator. The film formation was evaluated by fluorescent microscopy method. Various model synovial fluids were employed while the key constituents, i.e. albumin, γ-globulin, and hyaluronic acid were fluorescently stained to determine its role in film formation process. Two types of the tests were performed. The first dynamic test aimed on the development of film thickness under constant load during motor driven swinging motion mimicking flexion-extension. Subsequently, a combined test was designed consisting of the three phases; static part with loading/unloading phase (1), pendulum swinging till spontaneous damping of the motion due to friction (2), and static observation under the constant load (3). The results clearly confirmed that the interaction of constituents of synovial fluid plays a dominant role and substantially influences the lubrication conditions. In particular, the main finding coming from the present study is that γ-globulin together with hyaluronic acid form relatively thin stable boundary layer enabling the enhanced adsorption of albumin, thus increasing the lubricant film. Part II of the present study is focused on hard-on-hard pairs while the main differences in film formation process are highlighted among others.

    更新日期:2018-09-20
  • A Material Modeling Approach for the Effective Response of Planar Soft Tissues for Efficient Computational Simulations
    J. Mech. Behav. Biomed. Mater. (IF 3.239) Pub Date : 2018-09-20
    Will Zhang, Rana Zakerzadeh, Wenbo Zhang, Michael S. Sacks

    One of the most crucial aspects of biomechanical simulations of physiological systems that seek to predict the outcomes of disease, injury, and surgical interventions is the underlying soft tissue constitutive model. Soft tissue constitutive modeling approaches have become increasingly complex, often utilizing meso- and multi-scale methods for greater predictive capability and linking to the underlying biological mechanisms. However, such modeling approaches are associated with substantial computational costs. One solution is to use effective constitutive models in place of meso- and multi-scale models in numerical simulations but derive their responses by homogenizing the responses of the underlying meso- or multi-scale models. A robust effective constitutive model can thus drastically increase the speed of simulations for a wide range of meso- and multi-scale models. However, there is no consensus on how to develop a single effective constitutive model and optimal methods for parameter estimation for a wide range of soft tissue responses. In the present study, we developed an effective constitutive model which can fully reproduce the response of a wide range of planar soft tissues, along with a method for robust and fast-convergent parameter estimation. We then evaluated our approach and demonstrated its ability to handle materials of widely varying degrees of stiffness and anisotropy. Furthermore, we demonstrated the performance of the meso-structural to effective constitutive model framework in a finite element simulation of a tri-leaflet heart valve, where it demonstrated robust performance. We conclude that the effective constitutive modeling approach has significant potential for improving the computational efficiency and numerical robustness of multi-scale and meso-scale models, facilitating efficient soft tissue simulations in such demanding applications as inverse modeling and growth.

    更新日期:2018-09-20
  • Microstructure analysis and mechanical properties by instrumented indentation of Charonia Lampas Lampas shell
    J. Mech. Behav. Biomed. Mater. (IF 3.239) Pub Date : 2018-09-18
    K. BOUFALA, S. OUHENIA, G. LOUIS, D. BETRANCOURT, D. CHICOT, I. BELABBAS

    Scanning electron microscopy, X-ray diffraction and Fourier transformed infrared spectroscopy have been used to characterize the microstructure and instrumented microindentation for the determination of the mechanical properties of Charonia Lampas Lampas shell. Both elastic modulus and hardness are found to be dependent on the texture of the three distinct layers. From the analysis of load-depth curves, the shell exhibits small viscoelastic behavior at low indentation loads and mainly elastoplastic behavior at higher loads. These phenomena were attributed to the influence of the organic matter present in the shell. Both elastic modulus and hardness are found to be load-dependent in each layer in relation to their microstructure and, accordingly, to the anisotropy of the predominant mineral part. At a macroscopic scale, this tendency is explained by using a rule of mixture and jointly by the anisotropy of the aragonite. The Bull and Page model is subsequently applied to the hardness variation in order to compute the macrohardness which is the characteristic hardness number of a material and the hardness parameter related to the indentation size effect. This model describes well the experimental results for the relative higher depths, and deviates for the small depths due to the effect of the viscoelastic behavior which then requires a more appropriate model to describe this phenomenon.

    更新日期:2018-09-19
  • Interrelation among the handling, mechanical, and wear properties of the newly developed flowable resin composites
    J. Mech. Behav. Biomed. Mater. (IF 3.239) Pub Date : 2018-09-17
    Arisa Imai, Toshiki Takamizawa, Runa Sugimura, Akimasa Tsujimoto, Ryo Ishii, Mami Kawazu, Tatsuro Saito, Masashi Miyazaki

    ObjectivesThis study investigates the handling, mechanical, and wear properties of the newly developed flowable resin composites and elucidate the interrelations among the tested parameters.MethodsSix flowable and two conventional resin composites are used. Five measurements are performed per resin composite to obtain the average inorganic filler content. Ten specimens per material are used to obtain the flexural strength, flexural modulus, and resilience. For sliding impact wear testing, twelve specimens are prepared. Noncontact profilometer and confocal laser scanning microscopy are used to determine the maximum facet depth and volume loss. Extrusion force and thread formation are used to measure the handling properties of the flowable resin composites. Six measurements are performed per flowable resin composite. Data evaluation is performed using analysis of variance and Tukey's honestly significant difference test at an α-level of 0.05. The correlation between the tested parameters is verified using the Pearson product-moment correlation coefficient.ResultsA subset of flowable resin composites exhibits higher flexural properties and wear resistance as compared to the conventional resin composites. The handling properties of the flowable resin composites are material dependent.ConclusionWhile the resilience parameters exhibit an extremely strong and statistically significant correlation with the wear parameters, the handling properties exhibit no interrelation with the remaining parameters.SignificanceWhile the handling properties of the newly developed flowable resin composites did not correlate with the mechanical and wear properties, some new flowable resin composites have the potential for use in high-stress bearing areas, such as posterior lesions, because of the enhanced mechanical properties and wear resistance.

    更新日期:2018-09-18
  • Wear and Friction of UHMWPE-on-PEEK OPTIMA™
    J. Mech. Behav. Biomed. Mater. (IF 3.239) Pub Date : 2018-09-17
    Raelene M. Cowie, Adam Briscoe, John Fisher, Louise M. Jennings

    PEEK-OPTIMA™ is being considered as an alternative bearing material to cobalt chrome in the femoral component of total knee replacement to provide a metal-free implant. The aim of this study was to investigate the influence of lubricant temperature (standard rig running and elevated temperature (~36 °C)) on the wear of a UHMWPE-on-PEEK OPTIMA™ bearing couple using different lubricant protein concentrations (0, 2, 5, 25 and 90% bovine serum) in a simple geometry pin-on-plate configuration. Friction was also investigated under a single temperature condition for different lubricant protein concentrations. The studies were repeated for UHMWPE-on-cobalt chrome in order to compare relationships with temperature (wear only) and lubricant protein concentration (wear and friction).In low lubricant protein concentrations (≤ 5%) there was no influence of temperature on the wear factors of UHMWPE-on-PEEK. With 25% bovine serum, the wear factor of UHMWPE-on-PEEK reduced by half at elevated temperature. When tested in high protein concentration (90% serum), there was no influence of temperature on the wear factor of UHMWPE-on-PEEK. These temperature dependencies were not the same for UHMWPE-on-cobalt chrome.For both material combinations, there was a trend of decreasing friction with increasing protein concentration once protein was present in the lubricant.This study has shown the importance of the selection of appropriate test conditions when investigating the wear and friction of different materials, in order to minimise test artefacts such as polymer transfer, and protein precipitation and deposition.

    更新日期:2018-09-18
  • Preparation and in vivo biocompatibility studies of different mesoporous bioactive glasses
    J. Mech. Behav. Biomed. Mater. (IF 3.239) Pub Date : 2018-09-17
    Akrity Anand, V. Lalzawmliana, Vinod Kumar, Piyali Das, K. Bavya Devi, Asit Kumar Maji, Biswanath Kundu, Mangal Roy, Samit Kumar Nandi

    A new generation of nanostructured glasses called mesoporous bioactive glasses (MBGs) exhibit superior surface texture, porosity and bioactive characteristics. The present study is carried out to develop and detailed characterize of ternary SiO2-CaO-P2O5 MBG structure, fabricated by three different variations using different surfactants, e.g., hexadecyltrimethylammonium bromide (CTAB), poly-ethylene glycol,(PEG) and Pluronic P123. After thorough physico-chemical characterization, MBG granules were investigated for in vivo bone regeneration in animal bone defect model (rabbit) where standard S53P4 bioactive glass was used as control. All the synthesized MBG powders showed nano-range median particle size of 80–120 nm (MBG-CTAB), 50–70 nm (MBG-PEG and MBG-P123 while their specific surface area as 473.2, 52.2 and 169.3 m2/g respectively. All MBGs showed mesoporous nature corroborating transmission electron microscopy (TEM) observation as well. Bone regeneration property was measured after 45 and 90 days post-implantation at distal epiphysis of rabbit femur by radiography, histology, fluorochrome labeling, micro computed tomography (micro-CT) and vital organ histology. Results from in vivo studies indicated that the MBG materials produce minimal toxicity to the body. Furthermore, the biocompatibility and biodegradability of the implant makes them more suitable for application in bone tissue engineering. Among various implants, MBG fabricated using suitable surfactant (CTAB) shown the best result compared to other implants. Nonetheless, all the materials are suitable for application in bone tissue engineering and have potential for bone regeneration and healing.

    更新日期:2018-09-18
  • Suitability of developed composite materials for meniscal replacement: mechanical, friction and wear evaluation
    J. Mech. Behav. Biomed. Mater. (IF 3.239) Pub Date : 2018-09-18
    Adijat Omowumi Inyang, Tamer Abdalrahman, Deon Bezuidenhout, James Bowen, Chistopher Leonard Vaughan
    更新日期:2018-09-18
  • Bioinspired silica-infiltrated zirconia bilayers: Strength and interfacial bonding
    J. Mech. Behav. Biomed. Mater. (IF 3.239) Pub Date : 2018-09-14
    Dominique Yukie Toyama, Larissa Marcia Martins Alves, Gabriela Freitas Ramos, Tiago Moreira Bastos Campos, Getúlio de Vasconcelos, Alexandre Luiz Souto Borges, Renata Marques de Melo

    Conventionally veneered zirconia restorations are susceptible to chipping and spalling of the veneering material. The novel translucent zirconias were developed to overcome such issues, although layered zirconia restorations can be re-designed to improve mechanical performance. Thus, the aim of this study was to analyze the strength and structural reliability of zirconia bilayers using conventional (porcelain ceramic under tensile stress) and bioinspired (zirconia under tensile stress) configurations. Sol-gel silica infiltration served as a smooth transition between the zirconia and veneering porcelain. Failure mode and interfacial adhesive mechanism were analyzed using scratch test and interfacial indentation. Bilayered specimens were produced for biaxial flexural testing with Y-TZP and pressed ceramic, which were further divided into four groups (n=30): Conventional (C), Infiltrated conventional (IC), Bioinspired (B) and Infiltrated bioinspired (IB). The results of biaxial flexural strength tests were analyzed by Weibull analysis (95% CI) for determination of the Weibull modulus (m). The infiltration layer was characterized by XRD and SEM, FEG-SEM and EDS. The bioinspired infiltrated group was the most reliable (m=9.59), although the fine damage of veneered conventional (conventional) zirconia demonstrated its superior resistance to scratching and debonding. Therefore, the filling of superficial defects by zirconia silicate demonstrated the need for mechanical retention for better porcelain adhesion.

    更新日期:2018-09-15
  • Effect of Water Concentration on the Shock Response of Polyethylene Glycol Diacrylate (PEGDA) Hydrogels: A Molecular Dynamics Study
    J. Mech. Behav. Biomed. Mater. (IF 3.239) Pub Date : 2018-09-15
    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.

    更新日期:2018-09-15
  • Human plasma gels: their preparation and rheological characterization for cell culture applications in tissue engineering
    J. Mech. Behav. Biomed. Mater. (IF 3.239) Pub Date : 2018-09-13
    Lucía Barreda, Ismael Marcet, Sara Llames, Marta Pevida, Eva García-Pérez, Álvaro Meana, Manuel Rendueles, Mario Díaz

    Tissue engineering is one of the fields of clinical medicine that has forged ahead in recent years, especially because of its role as a potential alternative to organ transplantation. The main aim of this study has been the development of biocompatible materials to form extracellular matrix (ECM) structures in order to provide the necessary conditions for the settlement, proliferation and differentiation of dermal cells such as fibroblasts. To this end, human plasma gels were synthesized with the addition of increasing concentrations of transglutaminase (TGase), which catalyses the formation of covalent bonds between Lys and Glu residues. These materials were structurally characterized using rheology and texturometry and were found to have good structural resistance and elasticity for fibroblast culture. A remarkable improvement in the mechanical properties of the human plasma gels was detected when the two highest TGase concentrations were tested, which may be interpreted as an increase in the number of covalent and non-covalent bonds formed between the plasma protein chains. Furthermore, a human fibroblast primary culture was seeded on human plasma scaffolds and satisfactorily proliferated at 37 °C. This was verified in the images obtained by optical microscopy (OM) and by scanning electron microscopy (SEM), which confirmed that the structure of this type of material is suitable for the growth and proliferation of dermal fibroblasts.

    更新日期:2018-09-14
  • Elastic Properties Measurement of Human Enamel Based on Resonant Ultrasound Spectroscopy
    J. Mech. Behav. Biomed. Mater. (IF 3.239) Pub Date : 2018-09-12
    Haijun Niu, Fan Fan, Rui Wang, Qiang Zhang, Fei Shen, Pengling Ren, Tao Liu, Yubo Fan, Pascal Laugier

    ObjectivesTo investigate the elastic properties of human enamel using resonant ultrasound spectroscopy (RUS).MethodsSix rectangular parallelepiped specimens were prepared from six human third molars. For all specimens, the theoretical resonant frequencies were calculated using the Rayleigh-Ritz method, knowing the specimen mass density and dimensions, and using a priori stiffness constants. The experimental resonant frequencies were measured and extracted by RUS. Then, the optimal stiffness constants were retrieved by adjustment of the theoretical resonant frequencies to the measured ones based on the Levenberg-Marquardt method. The engineering elastic moduli, including Young’s moduli, shear moduli, and Poisson’s ratios, were also calculated based on the optimal stiffness constants.ResultsThe five independent stiffness constants C11, C12, C13, C33, and C44 were 90.2 ± 6.65 GPa, 34.7 ± 6.90 GPa, 29.5 ± 4.82 GPa, 83.5 ± 8.93 GPa, and 37.0 ± 10.9 GPa, respectively. Young’s moduli E11 and E33, shear moduli G13 and G12, and Possion’s ratios υ12 and υ13 were 71.7 ± 7.34 GPa, 69.2 ± 7.32 GPa, 37.0 ± 10.9 GPa, 28.1 ± 4.35 GPa, 0.303 ± 0.098, and 0.248 ± 0.060, respectively.SignificanceElastic properties are critical for developing dental materials and designing dental prostheses. The RUS method may provide more precise measurement of elastic properties of dental materials.

    更新日期:2018-09-13
  • Novel adhesives for distal radius fixation: A biomechanical analysis
    J. Mech. Behav. Biomed. Mater. (IF 3.239) Pub Date : 2018-09-12
    Cina Mehrvar, Paul Kuzyk, Jamshied Shamlou, Oleg Safir, Paul Zalzal, Adel Alhalawani, Mark R. Towler, Marcello Papini

    Wrist fractures can be difficult to treat due to advanced age of the patient, medical co-morbidities, and comminution of the bone. This study examines the effectiveness of two injectable glass polyalkenoate cements (GPCs), derived from two different glasses (A and B), as minimally invasive treatments for distal radius fractures. Twenty-seven fresh cadaveric radial pairs were tested either in compressive fatigue or to quasi-static compressive failure. The radii tested to failure had one pair fixated with a GPC while the other was left intact. The radii tested under fatigue had one pair fixated with a GPC and the other with a volar locking plate. A wedge osteotomy was used to simulate a severely comminuted fracture. When loaded to failure, the radii fixated with a GPC made from glass A or B were found to be, respectively, at least 57% and 62% as strong as their intact biological pair (95% Confidence Interval, Lower). Using a paired t-test, the radii fixated with either adhesive were found to be significantly stiffer than their biological pairs fixated with a volar locking plate for all cycles of fatigue loading. The adhesives under investigation demonstrate promise as treatment for distal radius fractures. In vivo investigations are warranted to determine the effect that the adhesives have on the bone remodelling process.

    更新日期:2018-09-13
  • 更新日期:2018-09-11
  • 更新日期:2018-09-10
  • The effect of pleural fluid layers on lung surface wave speed measurement: experimental and numerical studies on a sponge lung phantom
    J. Mech. Behav. Biomed. Mater. (IF 3.239) Pub Date : 2018-09-06
    Boran Zhou, Xiaoming Zhang

    Pleural effusion manifests as compression of pleural fluid on the lung parenchyma contributing to hypoxemia. Medical procedures such as drainage of plural fluid releases this compression and increases oxygenation. However, the effect of pleural effusion on the elasticity of lung parenchyma is unknown. By using lung ultrasound surface wave elastography (LUSWE) and finite element method (FEM), the effect of pleural effusion on the elasticity of superficial lung parenchyma in terms of surface wave speed measurement was evaluated in a sponge phantom study. Different thicknesses of ultrasound transmission gel used to simulated pleural fluid were inserted into a condom, which was placed between the sponge and standoff pad. A mechanical shaker was used to generate vibration on the sponge phantom at different frequencies ranging from 100 to 300 Hz while the ultrasound transducer was used to capture the motion for measurement of surface wave speed of the sponge. FEM was conducted based on the experimental setup and numerically assessed the influence of pleural effusion on the surface wave speed of the sponge. We found from FEM experiments that the influence of thickness of ultrasound transmission gel was statistically insignificant on the surface wave speed of the sponge at 100 and 150 Hz.

    更新日期:2018-09-07
  • Use of experimental-resin-based materials doped with carboxymethyl chitosan and calcium phosphate microfillers to induce biomimetic remineralization of caries-affected dentin
    J. Mech. Behav. Biomed. Mater. (IF 3.239) Pub Date : 2018-09-07
    Zihua Huang, Yipin Qi, Kai Zhang, Lisha Gu, Jiaxin Guo, Ruoxun Wang, Sui Mai

    This study investigated carboxymethyl chitosan (CMC)-induced biomimetic mineralization of collagen fibrils, with the aim of synthesizing experimental resins doped with CMC and calcium phosphate microfillers to remineralize artificial caries-affected dentin (ACAD) and enhance resin–dentin bonding durability. A size exclusion test provided evidence for the rejection of CMC (Mw 150 kDa) by collagen fibrils. Transmission electron microscopy and selected area electron diffraction conducted on reconstituted two-dimensional collagen showed typical deposition of needle-like hydroxyapatite crystals within collagen fibrils through CMC-induced biomimetic mineralization. The Vickers hardness test revealed significant improvement (P < 0.001) of the hardness of ACAD treated with CMC-containing experimental resins. Confocal laser scanning microscopy showed reduced dentin permeability and defect sites after biomimetic mineralization. On microtensile bond strength testing, the CMC-remineralized ACAD had better bonding with resin than ACAD and traditionally remineralized ACAD in both self-etch and etch-and-rinse bonding modes (P < 0.001). In conclusion, CMC is efficient in directing the biomimetic mineralization of collagen fibrils. The experimental resins containing CMC can induce dentin biomimetic remineralization and improve the bonding performance of ACAD.

    更新日期:2018-09-07
  • Effect of organic/inorganic nanoparticles on performance of polyurethane nanocomposites for potential wound dressing applications
    J. Mech. Behav. Biomed. Mater. (IF 3.239) Pub Date : 2018-09-04
    Arman Jafari, Shadi Hassanajili, Mohammad Bagher Karimi, Amir Emami, Farnaz Ghaffari, Negar Azarpira
    更新日期:2018-09-05
  • Magic angles and fibre stretch in arterial tissue: insights from the linear theory
    J. Mech. Behav. Biomed. Mater. (IF 3.239) Pub Date : 2018-09-05
    C.O. Horgan, J.G. Murphy

    This work is motivated by the current widespread interest in modelling the mechanical response of arterial tissue. A widely used approach within the context of anisotropic nonlinear elasticity is to use an orthotropic incompressible hyperelasticity model which, in general, involves a strain-energy density that depends on seven independent invariants. The complexity of such an approach in its full generality is daunting and so a number of simplifications have been introduced in the literature to facilitate analytical tractability. An extremely popular model of this type is where the strain energy involves only three invariants. While such models and their generalisations have been remarkably successful in capturing the main features of the mechanical response of arterial tissue, it is generally acknowledged that such simplified models must also have some drawbacks. In particular, it is intuitively clear that the correlation of such models with experiment will suffer limitations due to the restricted number of invariants considered. Our purpose here is to use the linearised theory for infinitesimal deformations to provide some guidelines for the development of a more robust nonlinear theory. The linearised theory for incompressible orthotropic materials is developed and involves six independent elastic constants. The general stress-strain law is inverted to provide an expression for the fibre stretch in terms of the stress. We examine the linearised response for simple tension in two mutually perpendicular directions corresponding to the axial and circumferential directions in the artery, obtaining an explicit expression for the fibre stretch in terms of the applied tension, fibre angle and linear elastic constants. The focus is then on determining the range of fibre orientation angles that ensure that the fibres are in tension in these simple tension tests. It is shown that the fibre stretch is positive for both simple tension tests if and only if the fibre angle is restricted to lie between two special angles called generalised magic angles. For the special case where the strain-energy function for the nonlinear model depends only on the three invariants I1,I4,I6, it is shown that the corresponding linearised model, called the standard linear model (SLM), depends on three elastic constants and the fibre stretch is positive only in the small range of fibre angles between the classic magic angles 35.26° and 54.74°. However, when the two additional invariants I5,I7 are included in the nonlinear strain energy so that the corresponding linear model involves four elastic constants, it is shown that the domain of fibre angle for which the stretch is positive is much larger and that the fibre stretch is monotonic with respect to the fibre angle in this range.

    更新日期:2018-09-05
  • Effect of graphene on setting and mechanical behaviour of tricalcium phosphate bioactive cements
    J. Mech. Behav. Biomed. Mater. (IF 3.239) Pub Date : 2018-09-05
    Carmen Baudín, Teresa Benet, Pilar Pena

    The potential reinforcing effect of graphene on calcium phosphate cements (CPCs)-based for injectable bone substitutes and scaffolds is presented. The influence of graphene (0–3.84 vol.%) on the microstructural development during setting and the resultant mechanical properties of CPCs constituted by α+β-tricalcium phosphate is analysed. Optimum setting conditions were established using uniaxial compression strength of CPC and composites with pristine and functionalized graphene and liquid/solid ratios (L/S = 0.5–0.6 mL/g) that allowed the mixing and spatulation of the powders. Tensile strength of optimised materials has been determined using the Diametric Compression of Discs Test (DCDT). X-ray diffraction, Raman spectroscopy and FE-SEM-EDS on fracture surfaces were used to investigate phase composition and morphological changes in set specimens. Strengthening occurs for functionalized graphene additions up to 1.96 vol.% due to different toughening mechanisms. Crack deflection, bridging and branching by graphene and, finally, the pull-out of the unbroken graphene sheets have been identified. Interlayer sliding between the graphene before pulling-out is an additional toughening process. Main effect of graphene on strength is the increase of reliability.

    更新日期:2018-09-05
  • Braided bioresorbable cardiovascular stents mechanically reinforced by axial runners
    J. Mech. Behav. Biomed. Mater. (IF 3.239) Pub Date : 2018-09-05
    Fan Zhao, Wen Xue, Fujun Wang, Jing Sun, Jing Lin, Laijun Liu, Kun Sun, Lu Wang

    Polymeric bioresorbable stents (BRSs) can eliminate the long-term stent restenosis by degrading after vascular remolding and have been recommended for the congenital heart disease treatment. However, the mechanical weakness remains one of main inferiorities of their applications. So, the aim of this study was to develop mechanically reinforced bioresorbable stents (MRBSs) based on poly(p-dioxanone) (PPDO) monofilaments and braiding technology. Axial runners were introduced and MRBSs showed greatly higher compression force and relatively lower viscous performance, as well as longer mechanical stability during degradation, compared with controls. Besides, stent compression behaviors were analyzed experimentally and numerically to investigate their deformation mechanisms. The results showed increased contacting points and friction force among yarns in MRBSs. Also, the skeleton formed in MRBSs attributed to higher yarn bending degree, strain energy and better structure stability during compression. Combined with the non-linear PPDO material stress-strain ratio and thermodynamic theory, yarn based stent compression modes were discussed. In addition, the autocatalysis and nonrandom chain scission degradation behaviors of MRBSs were revealed.

    更新日期:2018-09-05
  • Precision of different fatigue methods for predicting glass-ceramic failure
    J. Mech. Behav. Biomed. Mater. (IF 3.239) Pub Date : 2018-09-05
    Rodrigo Ottoni, Jason A. Griggs, Pedro H. Corazza, Álvaro Della Bona, Márcia Borba

    This study aimed to characterize the fatigue behavior using two fatigue methods, boundary and staircase, and to predict the probability of failure (Pf) of zirconia-reinforced lithium silicate glass-ceramic (ZLS). Bar-shaped specimens of ZLS (18×4×1.2 mm) were fabricated. Thirty specimens were subjected to a three-point flexural strength test using a universal testing machine with 0.5 mm/min crosshead speed, in 37 °C distilled water. Flexural strength data were analyzed with Weibull statistics. Eighty-six bars were subjected to cyclic fatigue using boundary and staircase methods. Fatigue tests were performed in a pneumatic cycling machine (2 Hz, 37° C distilled water) for 10³ and 104 cycles. Fatigue data were analyzed using an inverse power law relationship and log normal-lifetime distribution. Fracture toughness (KIc) was determined using V-notched specimens (18×4×3 mm) and the short beam toughness method (n=7). Vickers hardness (VH) was evaluated (4.9 N, 20 s). Fractographic and EDS analyses were also performed. ZLS showed a characteristic strength of 197 MPa, Weibull modulus of 4, VH of 6.67 GPa and KIc of 1.93 MPa.m1/2. After 103 cycles, for both methods, there was a degradation of 78% of the initial strength. There was no significant degradation when the number of cycles increased from 103 to 104. Both methods resulted in similar Pf and precision at 40 MPa (~50% Pf). Yet, staircase shows good accuracy and precision in predicting the stress amplitude for a Pfnear 50%; while boundary is also effective for Pflower than 50%. The fatigue methods evaluated show similar accuracy and precision for predicting the Pf of a glass-ceramic when simulations were made in the range of stress levels and lifetimes used in the fatigue tests.

    更新日期:2018-09-05
  • 更新日期:2018-09-05
  • Effects of Compression on Orientation of Ligands in Fluorescent Complexes between Hydroxyapatite with Amino Acids and their Optical Properties
    J. Mech. Behav. Biomed. Mater. (IF 3.239) Pub Date : 2018-09-05
    Sarita MORAKUL, Yuichi OTSUKA, Andaradhi NARARYA, Motohiro TAGAYA, Satoshi MOTOZUKA, Kiyoshi OHNUMA, Yukio MIYASHITA, Yoshiharu MUTOH

    This study aims to reveal the effects of pressure during cold isostatic pressing (CIP) on the microstructure and optical properties of fluorescent HAp complexes. Although the microsturucture-dependent properties of fluorescent HAp complexes have been reported to improve the antibacterial properties of photocatalyst coating layers, the mechanism behind the changes in the fluorescence properties of highly compressed HAp complexes has not yet been unveiled. CIP was successfully used to fabricate fluorescent HAp – amino acid complexes, and their fluorescence intensities increased with increasing fabrication pressure. Peak wavelength of fluorescence emitted by the HAp – amino acid complexes exhibited yellow to red shift. Although the thickness of the amino acid layer was saturated in higher pressure cases, the concentration of amino acids increased proportionally with pressure, which suggests changes in the packing structures of the ligands in the HAp– amino acid complexes. Polarized Raman spectroscopy measurements clearly detected ligands normally arranged to the HAp layer under high pressure fabrication conditions, which can provide the tightly packed ligand structure in the HAp– amino acid complexes. These tightly packed ligand structure in the HAp– amino acid complexes could emit stronger fluorescence owing to the increased density of complexations. This newly found pressure dependency in the optical properties of HAp–amino acid complexes is beneficial for developing biocompatible fluorescence materials or enhancement agents for antibacterial coating layers.

    更新日期:2018-09-05
  • Mechanical and Structural Analysis of the Pulmonary Valve in Congenital Heart Defects: A Presentation of Two Case Studies
    J. Mech. Behav. Biomed. Mater. (IF 3.239) Pub Date : 2018-08-31
    Fatiesa Sulejmani, Anastassia Pokutta-Paskaleva, Olga Salazar, Mohsen Karimi, Wei Sun

    ObjectiveCongenital Heart Disease (CHD) is the leading cause of pediatric mortality, with many cases affecting the right ventricular outflow tract (RVOT) or pulmonary valve (PV). Understanding the mechanics of the disease condition can provide insight into development of durable repair techniques and bioengineered replacement devices. This work presents a mechanical and structural analysis of the pulmonary valve of two pediatric cases.MethodsTwo PV tissues were excised as part of the operative procedure. One PV was obtained from a 9-month-old with Noonan syndrome (Patient 1) and the other from a 6-month-old with tricuspid atresia (Patient 2). The leaflets were subjected to planar biaxial tensile testing and second harmonic generation (SHG) imaging for mechanical and structural evaluation.Results and DiscussionPatient 1 exhibited a more anisotropic mechanical response than Patient 2, with sample stiffness on par with that of adult PV tissue. Additionally, both samples showed radial and circumferential alignment of collagen fibers on the ventricularis and fibrosa sides of the leaflets, respectively. Collagen fibers on the fibrosa side were also more crimped than on the ventricularis side.

    更新日期:2018-09-01
  • The effect of 3D-printed Ti6Al4V scaffolds with various macropore structures on osteointegration and osteogenesis: a biomechanical evaluation
    J. Mech. Behav. Biomed. Mater. (IF 3.239) Pub Date : 2018-08-31
    Han Wang, Kexin Su, Leizheng Su, Panpan Liang, Ping Ji, Chao Wang

    A properly designed porous scaffold can accelerate the osseointegration process, and the use of computer-aided design (CAD) and additive manufacturing (AM) techniques has the potential to improve the traditional porous scaffold approach. In this study, we evaluate the effect of porous Ti6Al4V (Ti) with different pore structures on osteointegration and osteogenesis. Porous Ti scaffolds with different pore structures based on four commercially available implants were designed and manufactured by CAD and selective laser melting (SLM). Micro-CT showed that SLM was able to produce Ti scaffolds with different pore structures. The mechanical properties evaluated by finite element analysis and compression tests indicated that the four porous scaffolds in our study were mechanically adapted, despite their different mechanical properties. Then, we used 3D-printed porous discs to culture human bone marrow mesenchymal stem cells (hBMMSCs), the main seed cells of bone tissue engineering. The results showed no significant difference among the four groups in cell morphology, viability and proliferation. In addition, four groups showed a comparable mineralization ability even though Ti-g had a higher alkaline phosphatase activity (ALP). In vivo tests in a rabbit model showed that all four groups were suitable for new bone ingrowth and integration. These findings indicate that the four different pore structures in the Ti scaffolds provided good osteointegration and osteogenesis.

    更新日期:2018-09-01
  • Influence of primers on the properties of the adhesive interface between resin composite luting cement and fiber-reinforced composite
    J. Mech. Behav. Biomed. Mater. (IF 3.239) Pub Date : 2018-08-31
    Aftab A. Khan, Abdulaziz A. Al-Kheraif, Badreldin A. Mohamed, Leila Perea-Lowery, Eija Säilynoja, Pekka K. Vallittu

    ObjectivesThe purpose of this study was to characterize the adhesive interface formed due to the dissolving capability of 4 primer systems into pre-polymerized semi-interpenetrating polymer network (semi-IPN)-based fiber-reinforced composite (FRC) and luting cement.Materials and methodsSemi-IPN FRC (everStick C&B, StickTech) prepregs stored for various durations (at 4 °C; 1, 1.5, and 3 years) were used to fabricate the specimens. FRC specimens (n=10) were light-cured and treated with primers before adhering a luting cement onto them. Each age group was divided into four subgroups according to the primer used: no priming, a dimethacrylate adhesive primer, universal primer, and primer intended for composite surfaces. The degree of monomer conversion (DC%) of the luting cement; nanohardness, elastic modulus and structural information of the luting cement–FRC adhesive interface were measured.ResultsAccording to analysis of variance (P≤0.05), no statistical difference was observed in the DC% among the tested groups. However, both universal and composite primers showed increased nanohardness in 1- and 1.5-year-aged groups. The highest nanohardness (0.55 ± 0.21 GPa) and elastic modulus (14.27 ± 5.19 GPa) were observed in specimens of 1-year-aged FRC primed with the application of universal primer. Raman spectroscopy and scanning electron microscopy examination confirmed the presence of poly(methyl methacrylate) at the interface when the FRC prepregs were aged for 3 years before use.ConclusionBoth primers improved diffusion of monomers of composite luting cement into the polymerized semi-IPN polymer structure and possible covalent binding with pendant methacrylate groups in the polymer matrix of FRC. The diffusing capability of universal and composite primers might increase the opportunity to form solid adhesive interface bonding between the FRC and composite luting cement.

    更新日期:2018-09-01
  • 更新日期:2018-09-01
  • Effect of pore geometry on the fatigue properties and cell affinity of porous titanium scaffolds fabricated by selective laser melting
    J. Mech. Behav. Biomed. Mater. (IF 3.239) Pub Date : 2018-08-30
    Danlei Zhao, Yutian Huang, Yong Ao, Changjun Han, Qian Wang, Yan Li, Jie Liu, Qingsong Wei, Zhen Zhang
    更新日期:2018-08-31
  • Origin of low Young modulus of multicomponent, biomedical Ti alloys - seeking optimal elastic properties through a first principles investigation
    J. Mech. Behav. Biomed. Mater. (IF 3.239) Pub Date : 2018-08-30
    P. Kwasniak, J.S. Wróbel, H. Garbacz

    Multicomponent, biomedical β-Ti alloys offer ultra-low Young modulus values that are related to a unique and poorly understood reduction of C44 and C’ elastic constants in comparison with binary systems. The elastic properties of such materials are difficult to control due to the large variations occurring even for a small change in chemical composition, which cannot be explained using existing theories. In this article, we investigate the above issues through systematic ab initio elastic constants calculations for a series of binary, ternary and quaternary Ti alloys. Special attention is paid to examining the reliability of the methodology adopted and to clarifying the atomic scale mechanisms that affect the mechanical properties of the systems analysed. It was found that the lower boundary of the polycrystalline Young modulus of Ti-Nb-base β phase is close to 50 GPa, and strongly depends on two specific electronic hybridisations related to niobium and simple metals addition that control C44 and C’. Based on the relationship established between electronic structure and mechanical properties, we propose several quaternary alloys whose directional <100> Young modulus values are equal or similar to that of human bones. Some electronic-based guidelines for designing new multicomponent β-Ti alloys are also formulated.

    更新日期:2018-08-31
  • Design of a Surrogate for Evaluation of Methods to Predict Bone Bending Stiffness
    J. Mech. Behav. Biomed. Mater. (IF 3.239) Pub Date : 2018-08-30
    Caitlyn J. Collins, Matt Boyer, Thomas Crenshawm, Heidi-Lynn Ploeg

    The high incidence of osteoporosis and related fractures demands for the use and development of methods capable of detecting changes in bone mechanical properties. The most common clinical and laboratory methods used to detect changes in bone mechanical properties, such as stiffness, strength, or flexural rigidity, include: mechanical testing, medical imaging, medical image-based analytical calculations, and medical image-based finite element analysis. However, the innate complexity of bone makes validation of the results from each method difficult. The current study presents the design, fabrication, and functional testing of a bi-material and computed tomography scan compatible bone-surrogate which provides consistent reproducible mechanical properties for methodological evaluation of experimental, analytical, and computational bone bending stiffness prediction methods.

    更新日期:2018-08-31
  • Biphasic Analysis of Rat Brain Slices Under Creep Indentation Shows Nonlinear Tension-Compression Behavior
    J. Mech. Behav. Biomed. Mater. (IF 3.239) Pub Date : 2018-08-30
    Ruizhi Wang, Malisa Sarntinoranont

    Biphasic theory can provide a mechanistic description of deformation and transport phenomena in soft tissues, and has been used to model surgery and drug delivery in the brain for decades. Knowledge of corresponding mechanical properties of the brain is needed to accurately predict tissue deformation and flow transport in these applications. Previously in our group, creep indentation tests were conducted for multiple anatomical regions in acute rat brain tissue slices. In the current study, a biphasic finite element model of creep indentation was developed with which to compare these data. Considering the soft tissue structure of brain, the solid matrix was assumed to be composed of a neo-Hookean ground matrix reinforced by continuously distributed fibers that exhibits tension-compression nonlinearity during deformation. By fixing Poisson's ratio of the ground matrix, Young's modulus, fiber modulus and hydraulic permeability were estimated. Hydraulic permeability was found to be nearly independent of the properties of the solid matrix. Estimated modulus (40 Pa ~1.1 kPa for the ground matrix, 3.2~18.2 kPa for fibers) and hydraulic permeability (1.2~5.5×10-13m4/N s) fell within an acceptable range compared with those in previous studies. Instantaneous indentation depth was dominated by tension provided by fibers, while the tissue response at equilibrium was sensitive to Poisson's ratio. Results of sensitivity analysis also point to the necessity of considering tension-compression nonlinearity in the solid phase when the biphasic material undergoes large creep deformation.

    更新日期:2018-08-31
  • Visco-Elasto-Plastic modeling of small intestinal submucosa (SIS) for application as a vascular graft
    J. Mech. Behav. Biomed. Mater. (IF 3.239) Pub Date : 2018-08-31
    Paolo Sánchez Puccini, Juan Carlos Briceño Triana
    更新日期:2018-08-31
  • 更新日期:2018-08-30
  • Femoral entheseal shape and attachment angle as potential risk factors for anterior cruciate ligament injury
    J. Mech. Behav. Biomed. Mater. (IF 3.239) Pub Date : 2018-08-30
    Callan M. Luetkemeyer, Benjamin C. Marchi, James A. Ashton-Miller, Ellen M. Arruda

    Although non-contact human ACL tears are a common knee injury, little is known about why they usually fail near the femoral enthesis. Recent histological studies have identified a range of characteristic femoral enthesis tidemark profiles and ligament attachment angles. We tested the effect of the tidemark profile and attachment angle on the distribution of strain across the enthesis, under a ligament stretch of 1.1. We employed a 2D analytical model followed by 3D finite element models using three constitutive forms and solved with ABAQUS/Standard. The results show that the maximum equivalent strain was located in the most distal region of the ACL femoral enthesis. It is noteworthy that this strain was markedly increased by a concave (with respect to bone) entheseal profile in that region as well as by a smaller attachment angle, both of which are features more commonly found in females. Although the magnitude of the maximum equivalent strain predicted was not consistent among the constitutive models used, it did not affect the relationship observed between entheseal shape and maximum equivalent strain. We conclude that a concave tidemark profile and acute attachment angle at the femoral ACL enthesis increase the risk for ACL failure, and that failure is most likely to begin in the most distal region of that enthesis.

    更新日期:2018-08-30
  • A three-dimensional micromechanical model of brain white matter with histology-informed probabilistic distribution of axonal fibers
    J. Mech. Behav. Biomed. Mater. (IF 3.239) Pub Date : 2018-08-30
    Seyed Abdolmajid Yousefsani, Farzam Farahmand, Amir Shamloo

    This paper presents a three-dimensional micromechanical model of brain white matter tissue as a transversely isotropic soft composite described by the generalized Ogden hyperelastic model. The embedded element technique, with corrected stiffness redundancy in large deformations, was used for the embedment of a histology-informed probabilistic distribution of the axonal fibers in the extracellular matrix. The model was linked to a multi-objective, multi-parametric optimization algorithm, using the response surface methodology, for characterization of material properties of the axonal fibers and extracellular matrix in an inverse finite element analysis. The optimum hyperelastic characteristics of the tissue constituents, obtained based on the axonal and transverse direction test results of the corona radiata tissue samples, indicated that the axonal fibers were almost thirteen times stiffer than the extracellular matrix under large deformations. Simulation of the same tissue under a different loading condition, as well as that of another white matter tissue, i.e., the corpus callosum, in the axonal and transverse directions, using the optimized hyperelastic characteristics revealed tissue responses very close to those of the experiments. The results of the model at the sub-tissue level indicated that the stress concentrations were considerably large around the small axons, which might contribute into the brain injury.

    更新日期:2018-08-30
  • Selective Laser Melting processed Ti6Al4V lattices with graded porosities for dental applications
    J. Mech. Behav. Biomed. Mater. (IF 3.239) Pub Date : 2018-08-29
    Zena J Wally, Abdul M Haque, Antonio Feteira, Frederik Claeyssens, Russell Goodall, Gwendolen C Reilly
    更新日期:2018-08-30
  • Synthesis and characterization of bio-compatible shape memory polymers with potential applications to endovascular embolization of intracranial aneurysms
    J. Mech. Behav. Biomed. Mater. (IF 3.239) Pub Date : 2018-08-29
    Robert Kunkel, Devin Laurence, Jingyu Wang, Donnie Robinson, Joshua Scherrer, Yi Wu, Bradley N. Bohnstedt, Aichi Chien, Yingtao Liu, Chung-Hao Lee
    更新日期:2018-08-29
  • 更新日期:2018-08-29
  • 更新日期:2018-08-29
  • Breast implant surface texture impacts host tissue response
    J. Mech. Behav. Biomed. Mater. (IF 3.239) Pub Date : 2018-08-28
    Michael Atlan, Gina Nuti, Hongpeng Wang, Sherri Decker, TracyAnn Perry
    更新日期:2018-08-29
  • 更新日期:2018-08-29
  • Mechanical and biological performance of axially loaded novel bio-nanocomposite sandwich plate-type implant coated by biological polymer thin film
    J. Mech. Behav. Biomed. Mater. (IF 3.239) Pub Date : 2018-08-24
    S. Sahmani, S. Saber-Samandari, M. Shahali, H. Joneidi Yekta, F. Aghadavoudi, AH. Montazeran, M.M. Aghdam, A. Khandan

    Post-surgical infection is one of the essential problems in bone scaffolds that is usually treated with antibiotics. This issue may be related to the poor blood supply for bone tissue due to high concentrations of drug. In the current study, the effect of zinc oxide (ZnO) nanoparticles on the antibacterial behavior of the nanocrystalline hydroxyapatite (n-HA) scaffolds coated by gelatin-ibuprofen (GN-IBO) is evaluated. To this end, the bio-nanocomposite scaffolds are fabricated via the space holder technique and then characterized with the aid of X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The compressive strength, fracture toughness, porosity, elastic modulus as the mechanical properties, and the apatite formation, biodegradation, drug release and wettability beside the roughness as the biological properties are predicted. The obtained experimental results indicate that the bio-nanocomposite scaffolds containing 10 wt% ZnO has suitable mechanical and biological properties. After that, an analytical model is developed to predict the nonlinear instability and vibration responses of an axially loaded sandwich plate-type implants made of the fabricated n-HA-ZnO bio-nanocomposites coated by GN-IBO thin film corresponding to various weight fractions of ZnO nanoparticles. It is found that ZnO peaks in the positions of 2θ are equal to 31.6 ° , 33.6 ° , 34 ° , 46.4 ° , and 62 ° , which represent the crystalline characteristics. Also, it is revealed that through addition of ZnO nanoparticles, the hardness and elastic modulus as well as the bone formation and biodegradation rate of the bio-nanocomposite scaffold enhance, while its drug release in the phosphate buffer solution detected with UV spectrum reduces. It is found that by increasing the ZnO weight fraction, the critical axial buckling load of the sandwich bio-nanocomposite implant enhances, and it buckles at lower axial shortening. However, it is seen that for higher value of wt% ZnO, its influence on the critical buckling load decreases.

    更新日期:2018-08-26
  • The Relationship between Thiol-acrylate Photopolymerization Kinetics and Hydrogel Mechanics: An Improved Model Incorporating Photobleaching and Thiol-Michael Addition
    J. Mech. Behav. Biomed. Mater. (IF 3.239) Pub Date : 2018-08-24
    Hongyuan Zhu, Xiaoxiao Yang, Guy M. Genin, Tian Jian Lu, Feng Xu, Min Lin

    Biocompatible hydrogels with defined mechanical properties are critical to tissue engineering and regenerative medicine. Thiol-acrylate photopolymerized hydrogels have attracted special interest for their degradability and cytocompatibility, and for their tunable mechanical properties through controlling factors that affect reaction kinetics (e.g., photopolymerization, stoichiometry, temperature, and solvent choice). In this study, we hypothesized that the mechanical property of these hydrogels can be tuned by photoinitiators via photobleaching and by thiol-Michael addition reactions. To test this hypothesis, a multiscale mathematical model incorporating both photobleaching and thiol-Michael addition reactions was developed and validated. After validating the model, the effects of thiol concentration, light intensity, and pH values on hydrogel mechanics were investigated. Results revealed that hydrogel stiffness (i) was maximized at a light intensity-specific optimal concentration of thiol groups; (ii) increased with decreasing pH when synthesis occurred at low light intensity; and (iii) increased with decreasing light intensity when synthesis occurred at fixed precursor composition. The multiscale model revealed that the latter was due to higher initiation efficiency at lower light intensity. More broadly, the model provides a framework for predicting mechanical properties of hydrogels based upon the controllable kinetics of thiol-acrylate photopolymerization.

    更新日期:2018-08-26
  • Effect of the cushioning running shoes in ground contact time of phases of gait
    J. Mech. Behav. Biomed. Mater. (IF 3.239) Pub Date : 2018-08-25
    Andrea Roca-Dols, Marta Elena Losa-Iglesias, Rubén Sánchez-Gómez, Ricardo Becerro-de-Bengoa-Vallejo, Daniel López-López, David Rodríguez-Sanz, Eva María Martínez Jiménez, César Calvo-Lobo

    The main objective of this research was to know how five different cushioning shoes may interfere in ground contact times of each gait phase of walking and running in contrast with barefoot condition. Thirty healthy sport recreational male runners participated in this study. They played over a treadmill wearing minimalist, Boost®, Ethyl-vinyl-acetate (EVA), Air® chamber and pronation-control cushioning shoes technologies and under barefoot condition, recording the last 30 seconds of walking and running at 5.17 km/h and 9 km/h respectively, while ground contact time duration of each phase of gait was recorded with circular standard pressure sensors located on plantar feet. During walking, the heel contact phase was the station that increased significantly ground contact times wearing all sole cushioning shoes (p<0.001), excepting no sole shoes (minimalist), versus barefoot condition, being Air® chamber the model that showed the highest times of contact floor versus barefoot (0.28±0.08ms and 0.23±0.12ms vs 0.12±0.07ms and 0.18±0.07ms in heel contact during midstance phases, respectively). During running, propulsion phase was the station that showed the highest spent times on ground contact with the floor under all shoe conditions, even with minimalist, being again Air® chamber the model with higher significant times in two of three phases versus barefoot (0.11±0.04ms and 0.16±0.11ms vs 0.09±0.03ms and 0.10±0.02ms in midstance and propulsion phases respectively). Air chamber® was the model too with the most switch ratio to forefoot strike pattern (0.07±0.10ms to 0.16±0.11 from heel contact to propulsion phase, respectively). In conclusion, a ground contact times increase using all cushioning running shoes compared with barefoot condition was shown in both walking and running test.

    更新日期:2018-08-26
  • Nondestructive characterization of bone tissue scaffolds for clinical scenarios
    J. Mech. Behav. Biomed. Mater. (IF 3.239) Pub Date : 2018-08-25
    Ali Entezari, Zhongpu Zhang, Andrian Sue, Guangyong Sun, Xintao Huo, Che-Cheng Chang, Shiwei Zhou, Michael V Swain, Qing Li
    更新日期:2018-08-26
  • The Determining Role of Nanoscale Mechanical Twinning on Cellular Functions of Nanostructured Materials
    J. Mech. Behav. Biomed. Mater. (IF 3.239) Pub Date : 2018-08-24
    K.C. Nune, I. Montes, V.S.Y. Injeti, M.C. Somani, R.D.K. Misra

    Considering that micromotions generated at the bone-implant interface under physiological loading introduce mechanical strain on the tissue and surface of the implant and that strain can be introduced during processing of the biomedical device, we elucidate here the interplay between mechanically-induced nanoscale twinning in austenitic stainless steel on osteoblast functions. Mechanically-induced nanoscale twinning significantly impacted cell attachment, cell-substrate interactions, proliferation, and subsequent synthesis of prominent proteins (fibronectin, actin, and vinculin). Twinning was beneficial in favorably modulating cellular activity and contributed to small differences in hydrophilicity and nanoscale roughness in relation to the untwinned surface.

    更新日期:2018-08-24
  • Replication and Bioactivation of Ti-based Alloy Scaffold Macroscopically Identical to Cancellous Bone from Polymeric Template with TiNbZr Powders
    J. Mech. Behav. Biomed. Mater. (IF 3.239) Pub Date : 2018-08-23
    Xi Rao, Jihan Yang, Jing li, Xue Feng, Zilin Chen, Yidie Yuan, Binglian Yong, Chenglin Chu, Xiaodong Tan, Qunliang Song

    In the present work, a new type of porous Ti-based alloy scaffold with high porosity (about 75%) and interconnected pores in the range of 300~1000 μm was fabricated by polymeric foam replication method with TiNbZr powders. This porous scaffold, which is consisted with major β phase Ti and minor α Ti phase, exhibits a compressive strength of 14.9 MPa and an elastic modulus of 0.21 GPa, resembling the mechanical properties of nature human cancellous bone (σ=10~50 MPa, E=0.01~3.0 GPa). To improve its osteogenic potential, a bioactive nanostructural titanate network coating was applied to the scaffold surface using hydrothermal treatment. The bone-like apatite inducing ability of the treated scaffold was systemically assessed using SBF immersion during 3~28 days. The nanostructural titanate network coated on porous TiNbZr scaffold is favorable for apatite nucleation and subsequent growth due to the hydrolysis of titanate. The results suggest that highly porous TiNbZr scaffolds with an appropriate bioactive coating, which was fabricated in this study, could be potentially used for bone tissue engineering application.

    更新日期:2018-08-23
  • Effects of Artificial Aging and Progression of Cracks on Thin Occlusal Veneers Using SD-OCT
    J. Mech. Behav. Biomed. Mater. (IF 3.239) Pub Date : 2018-08-23
    Christine Yazigi, Hartmut Schneider, Mohamed Sad Chaar, Claudia Rüger, Rainer Haak, Matthias Kern

    ObjectivesThe purpose of this study was to evaluate the effects of artificial aging on thin glass-ceramic occlusal premolar veneers, adhesively bonded to dentin, by examining the changes caused by artificial aging using spectral domain optical coherence tomography (SD-OCT). In addition, the development of cracks in the ceramic veneers and their possible influence on the behavior of the ceramic restorations were examined.MethodsIn total, 48 extracted sound upper premolars were prepared in the dentin for occlusal veneers milled from lithium disilicate ceramic blocks (IPS e.max CAD, Ivoclar Vivadent, Liechtenstein). All restorations were adhesively bonded using resin cement (Variolink Esthetic DC, Ivoclar Vivadent). Specimens were 3-dimensionally and 2-dimensionally imaged by SD-OCT (Telesto II, Thorlabs GmbH, Germany), then subjected to thermal-dynamic loading in a chewing simulator with 1,200,000 cycles at a load of 10 kg. Specimens were 2D and 3D imaged again after the artificial aging. Finally, they were subjected to quasi-static loading using a universal testing machine until failure occurred and later examined microscopically to assess the mode of failure. ANOVA test was performed for statistical analysis of data and Tukey’s post-hoc test was used to compare the groups at 5% significance level. Chi-Square Test and Fischer’s Exact Test of Independence were conducted to test the association between nominal variables.ResultsNo changes or irregularities were observed in the cement layer or tooth substrate after the aging process. However, wear of the ceramic was noticed at the surface of contact with the antagonist during the test. The development of cracks was detected in 23% of the specimens. Cracks did not affect the fracture strength (p>0.05) but influenced the mode of failure (p≤0.001).SignificanceOptical coherence tomography allows an easy and non-invasive method to internally scan teeth and restorations. Development of cracks in the ceramic did not affect the fracture strength of the restorations but might lead to a more catastrophic type of failure.

    更新日期:2018-08-23
  • Fatigue behavior and surface characterization of a Y-TZP after laboratory grinding and regeneration firing
    J. Mech. Behav. Biomed. Mater. (IF 3.239) Pub Date : 2018-08-23
    Gabriela Scatimburgo Polli, Gabriel Rodrigues Hatanaka, Filipe de Oliveira Abi-Rached, Márcio de Souza Góes, José Mauricio dos Santos Nunes Reis

    This study evaluated the effect of grinding and regeneration firing on the flexural fatigue limit and surface characterization of LavaTM Y-TZP ceramic. Forty bar-shaped specimens with 20×4.0×1.2 mm constituted the as-sintered group (AS = control group), and 80 specimens with 20×4.0×1.5 mm were ground with cylindrical laboratory stone under water-cooling (WG) or in a dry condition (G) to reach 1.2 mm in thickness. Half of specimens were submitted to regeneration firing (1000 ºC, 30 min), forming the groups AS/R, WG/R and G/R. Fatigue limit (500,000 cycles, 10 Hz) was determined by staircase method in a 4-point flexural fixture. Data were analyzed by 2-way ANOVA and Tukey HSD tests (α=.05). The surface topography (n=3) and fracture area (n=3) were evaluated by SEM. Samples were also analyzed by Rietveld refinement from X-ray diffraction data. ANOVA revealed significant differences (P<.001) for grinding protocol, regeneration firing and their interaction. In the groups not submitted to regeneration firing, the mean flexural fatigue limit of WG was higher (P<.05) than that of G and AS, with no statistical difference between each other (P>.05). After regeneration firing the inequality WG>AS>G (P<.05) was observed. The regeneration firing increased the fatigue limit of AS group and decreased those of G and WG groups (P<.05). Grinding protocols created evident grooves on zirconia surface. Failures initiated on tensile side of all specimens. The percentages (wt%) of monoclinic phase before cyclic loading were: AS (7.4), AS/R (6.5), G (2.8), G/R (0.0), WG (4.4), WG/R (0.0); and after cyclic loading: AS (8.6), AS/R (1.2), G (2.4), G/R (5.7), WG (6.3), WG/R (0.0). Wet grinding did not compromise the fatigue limit of zirconia, increasing its mechanical strength. Regeneration firing reduced the fatigue limit of ground samples, despite reducing the amount of monoclinic phase in all experimental conditions.

    更新日期:2018-08-23
  • Effect of Setting Atmosphere on Apatite Cement Resorption: An In Vitro and In Vivo Study
    J. Mech. Behav. Biomed. Mater. (IF 3.239) Pub Date : 2018-08-23
    Arief Cahyanto, Kanji Tsuru, Kunio Ishikawa

    Objectives The aim of this present study was to investigate the effect of setting atmosphere on replacement of apatite cement with new bone both in vitro and in vivo. Material and methods Apatite cement consisting of an equimolar mixture of tetracalcium phosphate and anhydrous dicalcium phosphate was mixed with distilled water and allowed to set at 37 °C and 100% relative humidity under 0%, 5%, and 100% CO2 atmospheres. X-Ray diffraction and Fourier Transform Infrared Spectroscopy were employed to confirm the carbonate apatite formation. Micro-CT and histological evaluation was made at 1 and 6 month(s) using twelve 10-week-old specific-pathogen-free male Wistar rats. Results B-type carbonate apatite was found when the apatite cement was set under 100% CO2 and 5% CO2. More carbonate apatite was formed in the case of 100% CO2 when compared with 5% CO2, and none was formed under 0% CO2. Interestingly, unreacted tetracalcium phosphate was significant when apatite cement was set under 0% CO2, indicating the formation of Ca-deficient hydroxyapatite. When a bone defect of rat tibia was reconstructed in these conditions of apatite cement and sintered hydroxyapatite, replacement of the apatite cement was confirmed 6 months after implantation, whereas no replacement was observed in the case of sintered hydroxyapatite. The amount of replacement of apatite cement with bone was greater, on the order of 100% CO2 and 5% CO2, followed by 0% CO2. Conclusion The results obtained in the present study demonstrated that setting atmosphere clearly plays an important role in the replacement of set apatite cement with bone.

    更新日期:2018-08-23
  • Microstructural evolution and mechanical properties of a friction-stir processed Ti-hydroxyapatite (HA) nanocomposite
    J. Mech. Behav. Biomed. Mater. (IF 3.239) Pub Date : 2018-08-22
    R. Rahmati, F. Khodabakhshi

    In this research, a new metal matrix nanocomposite with enhanced capability for biomedical applications was fabricated by incorporation of nano-sized hydroxyapatite (HA) particles within the titanium substrate using multi-pass friction-stir processing (FSP). These n-HA particles were dispersed effectively within the titanium matrix. Titanium metal-matrix was processed without introducing the HA nanoparticles, as well, for the aim of comparison. The results showed the formation of different regions with various microstructural features and mechanical property across the processed materials. A thin layer with ultra-fine grain structure and indentation hardness value of up to ~400 HV was formed on the surface after FSP modification of coarse-grained titanium substrate. This was due to severe shear deformation induced by the rotating shoulder as well as the surface absorption of N and O elements from the atmosphere inside the layer. Incorporation of nanoparticles and subsequent grain structural refinement owing to operative dynamic recrystallization mechanisms leads to a maximum hardness improvement of up to ~250 HV in the lower regions (as compared to the average hardness value of base metal ~150 HV). The FSP modified pure titanium exhibited a good combination of strength and ductility by refining the grain structure with a well-developed dimple-like structure on the fracture surface. For the nanocomposite specimen, the trend of the tensile property was found deteriorative showing the impaired features on the fracture surface. This is attributed to the complex structure of HA compound and low quality of interfacial bonding between the nanoparticles and titanium matrix.

    更新日期:2018-08-22
  • Scalable novel PVDF based nanocomposite foam for direct blood contact and cardiac patch applications
    J. Mech. Behav. Biomed. Mater. (IF 3.239) Pub Date : 2018-08-22
    Ratnakar Arumugam, Raj Kumar Chinnadurai, Bala Nehru Subramaniam, Bhuvaneshwar Devaraj, Veni Subramanium, Srinadhu Endu Sekhar, Satyanarayana Nallani

    Scalable novel beta phase polyvinylidene fluoride - poly(methyl methacrylate) (PVDF-PMMA) polymer blend based nanocomposite foam with hydroxyapatite (HAp) and titanium dioxide (TiO2) as nanofillers (β-PVDF-PMMA/HAp/TiO2) (β-PPHT-f), was prepared by using salt etching assisted solution casting method. The prepared β-PPHT-f nanocomposite material was characterized using XRD, FT-IR, SEM-EDS. The XRD and FTIR results confirmed the formation of β phase of β-PPHT-f. The SEM and EDS results confirmed the formation of high porous structured closed cell type morphology of β-PPHT-f. It also, confirmed the uniform distribution of Ti, Ca, P, N and O, in β-PPHT-f. Contact angle measurements performed using sessile drop method with water and EDTA treated blood (EDTA blood) as probe liquids revealed that β-PPHT-f is hydrophilic with contact angle of 48.2° as well as hemophilic with contact angle of 13.7°. Porosity, fluid absorption and retention investigation by gravimetric analysis revealed that β-PPHT-f was 89.2% porous and can absorb and retain 139.15% and 87.05% of water and blood, respectively. The hemolysis assay performed as per ASTM F756 procedure revealed that β-PPHT-f is non hemolytic. Also, the Leishman stained blood smears prepared from whole blood incubated with β-PPHT-f for 3, 4, 5 and 6 hours at 37 ° C revealed that the blood cells were not affected by β-PPHT-f, its surface morphology and elemental composition. H9c2 cell line studies on a transparent film prepared using β-PPHT-f revealed that the elemental composition of the nanocomposite favored H9c2 cell adhesion and differentiation. All the characterization results indicate that the newly developed scalable novel β-PPHT-f is hemocompatible and cardiomyocyte compatible, suggesting it as a useful material for direct blood contact and cardiac patch applications.

    更新日期:2018-08-22
  • Effects of multiple firings on mechanical properties and resin bonding of lithium disilicate glass-ceramic
    J. Mech. Behav. Biomed. Mater. (IF 3.239) Pub Date : 2018-08-21
    Hongliang Meng, Haifeng Xie, Lu Yang, Bingzhuo Chen, Ying Chen, Huaiqin Zhang, Chen Chen
    更新日期:2018-08-21
  • Ratcheting behavior of UHMWPE reinforced by carbon nanofibers (CNF) and hydroxyapatite (HA): experiment and simulation
    J. Mech. Behav. Biomed. Mater. (IF 3.239) Pub Date : 2018-08-21
    Jianhai Wang, Hong Gao, Lilan Gao, Yun Cui, Zhengyuan Song

    Uniaxial tensile tests were performed to investigate the mechanical properties of the ultra-high molecular weight polyethylene (UHMWPE) with different modification conditions. It was found that the different modification conditions have great influence on the mechanical properties of the UHMWPE. Subsequently, the uniaxial ratcheting behaviors of the UHMWPE/CNF and UHMWPE/HA composite materials were observed under the stress-controlled cyclic tensile condition at room temperature. The dependence of uniaxial ratcheting of composite materials on the mean stress, stress amplitude, stress rate and nano-material content was investigated. The results show that the ratcheting strain and its rate of the two composite materials increase as the mean stress and stress amplitude increase, however, the ratcheting strain and its rate decrease with the increase of the stress rate and nano-material content. Furthermore, it is found that the ratcheting strain of the UHMWPE/HA composite material is more remarkable than that of the UHMWPE/CNF composite material. A new viscoplastic constitutive model is proposed to describe the ratcheting behavior of the UHMWPE composite materials. In this model, a new viscosity function and modified kinematic hardening law were employed. Comparison of simulation and experimental results shows that the simulations are in good agreement with the experimental results.

    更新日期:2018-08-21
  • Nonstoichiometric wollastonite bioceramic scaffolds with core-shell pore struts and adjustable mechanical and biodegradable properties
    J. Mech. Behav. Biomed. Mater. (IF 3.239) Pub Date : 2018-08-21
    Zhouwen Jin, Ronghuan Wu, Jianhua Shen, Xianyan Yang, Miaoda Shen, Wangqiong Xu, Rong Huang, Lei Zhang, Guojing Yang, Changyou Gao, Zhongru Gou, Sanzhong Xu

    Controllable mechanical strength and biodegradation of bioceramic scaffolds is a great challenge to treat the load-bearing bone defects. Herein a new strategy has been developed to fabricate porous bioceramic scaffolds with adjustable component distributions based on varying the core-shell-structured nozzles in three-dimensional (3D) direct ink writing platform. The porous bioceramic scaffolds composed of different nonstoichiometic calcium silicate (nCSi) with 0%, 4% or 10% of magnesium-substituting-calcium ratio (CSi, CSi-Mg4, CSi-Mg10) was fabricated. Beyond the mechanically mixed composite scaffolds, varying the different nCSi slurries through the coaxially aligned bilayer nozzle makes it easy to create core-shell bilayer bioceramic filaments and better control of the different nCSi distribution in pore strut after sintering. It was evident that the magnesium substitution in CSi contributed to the increase of compressive strength for the single-phasic scaffolds from 11.2 MPa (CSi), to 39.4 MPa (CSi-Mg4) and 80 MPa (CSi-Mg10). The nCSi distribution in pore struts in the series of core-shell-strut scaffolds could significantly adjust the strength [e.g. CSi@CSi-Mg10 (58.9 MPa) vs CSi-Mg10@CSi (30.4 MPa)] and biodegradation ratio in Tris buffer for a long time stage (6 weeks). These findings demonstrate that the nCSi components with different distributions in core or shell layer of pore struts lead to tunable strength and biodegradation inside their interconnected macropore architectures of the scaffolds. It is possibly helpful to develop new bioactive scaffolds for time-dependent tailoring mechanical and biological performances to significantly enhance bone regeneration and repair applications, especially in some load-bearing bone defects.

    更新日期:2018-08-21
Some contents have been Reproduced with permission of the American Chemical Society.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
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