Journal of the mechanical behavior of biomedical materials
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J Mech Behav Biomed Mater · Mar 2018
Temporal and spatial variations of pressure within intervertebral disc nuclei.
Experimental and computational studies often presume that nuclei pulposi of non-degenerated human lumbar discs function as fluid-filled cavities with single hydrostatic pressures throughout that vary neither with time nor location and orientation. Recent simultaneous measurements of the pressure at multiple locations within disc nuclei have however shown time-dependent and nonhomogeneous pressure distributions. This combined in vitro and in silico study aims to re-examine the temporal and spatial variations of the pressure within disc nuclei with special focus on the effect of tissue hydration. ⋯ With time and as the pore pressure drops, the contribution of the nucleus bulk increases till it reaches equilibrium. The relative share of the annulus bulk in supporting the applied loads markedly increases not only with time but at higher loads and lower hydrations. The hydration state of the disc is hence crucial in the disc pressure distribution and internal response under various static-dynamic loads in vitro and in the replication of in vivo conditions.
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J Mech Behav Biomed Mater · Oct 2017
Fracture strength of lithium disilicate crowns compared to polymer-infiltrated ceramic-network and zirconia reinforced lithium silicate crowns.
The aim of this study was to evaluate the fracture strength of crowns made from current CAD/CAM materials. In addition the influence of crown thickness and chewing simulation on the fracture strength was evaluated. ⋯ All crowns revealed fracture strength above the clinically expected loading forces. Therefore the durability of the tested CAD/CAM materials seems promising also in an occlusal thickness of 1.0mm.
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J Mech Behav Biomed Mater · Oct 2017
ReviewMechanical properties of the abdominal wall and biomaterials utilized for hernia repair.
Abdominal wall hernias are one of the most common and long-standing surgical applications for biomaterials engineering. Yet, despite over 50 years of standard use of hernia repair materials, revision surgery is still required in nearly one third of patients due to hernia recurrence. To date, hernia mesh designs have focused on maximizing tensile strength to prevent structural failure of the implant. ⋯ This is likely dependent on implantation location as the linea alba, rectus sheath, and other tissues of the abdominal wall exhibit different characteristics. Given the number of unknowns yet to be addressed by studies of the human abdominal wall, it is unlikely that any single biomaterial design currently encompasses all of the ideal features identified. More data on the mechanical properties of the abdominal wall will be needed to establish a full set of guidelines for ideal mesh mechanics including strength, compliance, anisotropy, nonlinearity and hysteresis.
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J Mech Behav Biomed Mater · Jan 2017
Characterizing white matter tissue in large strain via asymmetric indentation and inverse finite element modeling.
Characterizing the mechanical properties of white matter is important to understand and model brain development and injury. With embedded aligned axonal fibers, white matter is typically modeled as a transversely isotropic material. However, most studies characterize the white matter tissue using models with a single anisotropic invariant or in a small-strain regime. ⋯ Further, our results suggested that both indentation configurations are needed to estimate the parameters with sufficient accuracy, and that the indenter-sample friction is important. Finally, we also showed that the estimated parameters were consistent with those previously obtained via a trial-and-error forward FE method in the small-strain regime. These findings are useful in modeling and parameterization of white matter, especially under large deformation, and demonstrate the potential of the proposed asymmetric indentation technique to characterize other soft biological tissues with transversely isotropic properties.
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J Mech Behav Biomed Mater · Oct 2016
Experimental validation of DXA-based finite element models for prediction of femoral strength.
Osteoporotic fractures are a major clinical problem and current diagnostic tools have an accuracy of only 50%. The aim of this study was to validate dual energy X-rays absorptiometry (DXA)-based finite element (FE) models to predict femoral strength in two loading configurations. Thirty-six pairs of fresh frozen human proximal femora were scanned with DXA and quantitative computed tomography (QCT). ⋯ In both configurations the DXA-based FE model provided a good 1:1 agreement with the experimental data (CC=0.87 for SIDE and CC=0.86 for STANCE), with proper optimization of the failure criteria. In conclusion we found that the DXA-based FE models are a good predictor of femoral strength as compared with experimental data ex vivo. However, it remains to be investigated whether this novel approach can provide good predictions of the risk of fracture in vivo.