Bio-Medical Materials and Engineering - Volume 7, issue 3

Authors: Valenta, Jaroslav | Hruš, Tomáš | Sochor, Miroslav | Čihák, Radomír | Povýšil, Ctibor | Steidl, Josef

Article Type: Research Article

Abstract: The aim of the present work is to demonstrate of the influence of the adventitia on distribution of residual stresses in the human aorta. The biomaterial increase in media as well as in adventitia in the course of the aorta's growth is formed by an intussusceptive mechanism of growth. In children's aortas, formative elastin lamellae are wavy with high amplitude perpendicular to the aortic surface. In adults' aortas the waves become smoother (stepwise) towards the adventitia. Also introduced is the growth function, which characterizes the biomaterial growth and the interference between the media and adventitial layers. It is possible to …expect an extraordinary variability in the formation of the aortic wall tissue in the course of its growth as a result of metabolic and humoral influences and magnitude of the residual stresses in the course of growth. Show more

Keywords: Residual stress, media, adventitia, connective tissue, hyperplasia, hypertrophy, multilayer vessel, growth function, biological time

DOI: 10.3233/BME-1997-7301

Citation: Bio-Medical Materials and Engineering, vol. 7, no. 3, pp. 159-169, 1997

Authors: Pidaparti, Ramana M. | Liu, Yue | Meiss, Richard A.

Article Type: Research Article

Abstract: The mechanical properties of a contracting smooth muscle can be changed by changing its length. A viscoelastic material model was developed to predict the length-dependent stiffness changes when a constrained muscle is allowed to shorten under a constant external force. Three-dimensional finite element simulations were carried out to estimate the stiffness changes and compared to available experimental data. A good agreement was found indicating that the viscoelastic material model developed gives a valid representation of the length dependent stiffness changes of a smooth muscle. Sensitivity analysis was carried out to determine the relative effects of material constants in the model …on the length dependent stiffness. Show more

Keywords: Smooth muscle, viscoelastic, finite element analysis, stiffness

DOI: 10.3233/BME-1997-7302

Citation: Bio-Medical Materials and Engineering, vol. 7, no. 3, pp. 171-177, 1997

Authors: Tadano, Shigeru | Katagiri, Kazuaki | Umehara, Shinji | Ukai, Takayoshi

Article Type: Research Article

Abstract: This paper presents a constitutive law of the lumbar intervertebral disc to be described mathematically with the finite deformation theory. Mechanical behavior of the cadaveric lumbar disc obtained from continuous cyclic compression-tension tests and continuous cyclic axial torsion tests was formulated by the constitutive equation with a semi-circular shaped model. These equations were formulated with or without taking the nucleus pulposus into account. It was also confirmed that forward-backward bending behavior of the disc could be simulated numerically from these equations.

Keywords: Biomechanics, lumbar intervertebral disc, constitutive equation, cyclic loading, nucleus pulposus

DOI: 10.3233/BME-1997-7303

Citation: Bio-Medical Materials and Engineering, vol. 7, no. 3, pp. 179-191, 1997

Authors: Pidaparti, Ramana M. | Liu, Yue

Article Type: Research Article

Abstract: Stiffness changes due to microdamage in the longitudinal and cross-sectional directions in a dog bone model under different loadings were investigated using three-dimensional finite element analysis. Stiffness changes and severity of both longitudinal and cross-sectional type microcracks were estimated between the damaged and undamaged bone under four-point bending, torsion and tension. Finite element simulation results indicated that longitudinal damage was more severe than cross-sectional damage under axial tension and bending, and the opposite was true for torsional loading. However, for axial tension, the stiffness change due to cross-sectional microcracks remained constant.

Keywords: Microdamage, fatigue, finite element method, bone, simulation

DOI: 10.3233/BME-1997-7304

Citation: Bio-Medical Materials and Engineering, vol. 7, no. 3, pp. 193-203, 1997

Authors: Lewis, Gladius | Kambhampati, Sarma | Roussel, Stephanie

Article Type: Research Article

Abstract: The finite element analysis method and a two-dimensional idealization were used to conduct a parametric study of the effect of the archwire slot (or insert) profile on the stresses in, deformation of, and efficiency of a model of a bonded edge-wise “combination-materials” type of orthodontic bracket. The results are consistent with a priori expectations and are qualitatively the same as those obtained by previous workers who used the two-dimensional photoelasticity stress analysis method. The results thus highlight a possible approach to improving the clinical performance of these brackets.

Keywords: Orthodontic bracket, debonding, finite element analysis, von Mises stress

DOI: 10.3233/BME-1997-7305

Citation: Bio-Medical Materials and Engineering, vol. 7, no. 3, pp. 205-212, 1997

Authors: Cortada, M. | Giner, L. | Costa, S. | Gil, F.J. | Rodríguez, D. | Planell, J.A.

Article Type: Research Article

Abstract: In this work the metallic ion release in oral implants with superstructures of different metals and alloys used in clinical dentistry has been determined. This study has been realized in a saliva environment at 37°C. The measurements of the ion release were carried out by means of the Inductively Coupled Plasma Mass Spectrometry technique. The titanium oral implant coupled with a chromium-nickel alloy releases a high quantity of ions and the implant coupled with the titanium superstructure presents a low value of ion release.

Keywords: Ion release, implants, metals, alloys, corrosion

DOI: 10.3233/BME-1997-7306

Citation: Bio-Medical Materials and Engineering, vol. 7, no. 3, pp. 213-220, 1997