Bio-Medical Materials and Engineering - Volume 8, issue 5-6

Authors: Yokobori, A. Toshimitsu | , ,

Article Type: Research Article

Abstract: In our earlier studies, we considered osteogenesis to be a nucleation mechanism accompanied by preliminary diffusion and showed the optimum mechanical conditions for promoting this ionic diffusion. In this study, we performed an analysis of the nucleation mechanism of hydroxyapatite (HA) in areas with a high concentration of transported Ca and PO4 ions in the pore region along the collagen alignment. We derived the equation of the HA nucleation rate as a function of hydrostatic tensile stress, \sigma _{\rm P} and surface energy change (\gamma -\lambda ) , where \gamma is the surface …energy of the HA particle and \lambda is the decreasing factor of \gamma during HA nucleation. \lambda is thus related to the effect of chemical and electric stimulations. Finally, we formulated a unified equation of the nucleation rate of HA, which consists of ionic diffussion and HA nucleation processes. Show more

Keywords: Osteogenesis, nucleation, diffusion, hydroxyapatite, mineralization

Citation: Bio-Medical Materials and Engineering, vol. 8, no. 5-6, pp. 253-257, 1998

Authors: Lewis, Gladius

Article Type: Research Article

Abstract: In this second part of the series of reviews, attention focuses on analytical and numerical methods that have been used to estimate the magnitude of the contact stress in: models of articular joints; models of total joint replacements, without and with the associated joint; or models of simple physical systems that are deemed to have relevance to conditions at articular surfaces in arthroplasties. Three main recommendations emerge from this review. First, analytical methods should be avoided. Second, for numerical studies, the nonlinear contact finite element method should be used. Third, more work is needed in many areas, an example of …which is the effect of the method of sterilization of tibial inserts on the estimated contact stress at the tibiofemoral interface in knee implants. Show more

Keywords: Contact stress, Hertzian theory, elasticity solutions, finite element method, boundary element method, joint replacements

Citation: Bio-Medical Materials and Engineering, vol. 8, no. 5-6, pp. 259-278, 1998

Authors: Airaudo, Charles B. | Gayte‐Sorbier, André | Bianchi, Christine

Article Type: Research Article

Abstract: The stability of two antidepressant drugs, clomipramine and viloxazine hydrochlorides, was studied as was their possible sorption on Stedim 6^{\hbox{\psyrf\char210}} , a new multilayer polyethylene‐lined film, which was considered comparatively to polyvinyl chloride (PVC) and glass surfaces. Appropriate amounts of the drugs were added to 500 ml of 5% dextrose and 0.9% sodium chloride solutions in Stedim 6^{\hbox{\psyrf\char210}} and PVC bags, and in glass flasks, in order to obtain the concentrations currently used in clinical practice. All the containers were stored at room temperature in daylight for 72 hours. Samples were taken at various times and …evaluated for remaining drug concentrations by UV spectrometry. The two drugs appeared stable under the given conditions. No concentration decrease was observed in glass flasks. Viloxazine hydrochloride showed an excellent compatibility with the PVC bags, but a slight concentration decrease (about 6–7% in 72 hours) was observed for clomipramine hydrochloride, depending on the contact duration. The compatibility of the two drugs with the new material Stedim 6^{\hbox{\psyrf\char210}} was found to be perfect. The behavioral differences observed between the two drugs with regard to PVC are explained in terms of differences of lipophilicity of the drugs. Those observed for a given drug with regard to the two materials are due to the crystalline structure of polyethylene and the amorphous one of PVC. Show more

Keywords: Stedim 6^{\hbox{\psyr\char210}}, PVC, clomipramine, viloxazine, sorption

Citation: Bio-Medical Materials and Engineering, vol. 8, no. 5-6, pp. 279-283, 1998

Authors: Lewis, Gladius | Nyman, Jeffry S. | Trieu, Hai H.

Article Type: Research Article

Abstract: In light of the time‐intensive nature of using real‐time shelf‐aged specimens in research into property changes of ultra‐high‐molecular‐weight polyethylene (UHMWPE), accelerated thermal diffusion oxidative aging (usually referred to as accelerated aging) is frequently resorted to. A number of such aging protocols have been reported in the literature, with various claims for their producing changes in the properties of the polymer being the same as or similar to those seen in real‐time shelf‐aged samples. The thrust of the present work is the presentation of a methodology for examining such claims. The methodology is applied to six properties (% crystallinity, melting temperature, …oxidation index, ultimate tensile strength, ultimate tensile elongation, and tensile toughness) of 4150HP UHMWPE grade, sterilized using six different methods, prior to and following the use of a specific accelerated aging protocol (oxygen gas at 70^\circ C and 507 kPa pressure; 14 d.). These six properties have been identified in the literature as being strongly correlated with the clinical wear of UHMWPE articular components. It is shown that the claim for the protocol used in the present work (in terms of the simulated equivalent shelf aging time) is plausible. It needs to be emphasized, however, that this conclusion is tentative given the paucity of the relevant literature results that are currently available and which are vital to the application of the methodology. Show more

Keywords: Ultra‐high‐molecular‐weight polyethylene (UHMWPE), sterilization methods, wear, accelerated aging

Citation: Bio-Medical Materials and Engineering, vol. 8, no. 5-6, pp. 285-298, 1998

Authors: Khang, Gilson | Jeon, Ju Hyoung | Lee, Jin Whan | Lee, Hai Bang

Article Type: Research Article

Abstract: Surface treatment as gold sputter‐deposited treatment onto various polymeric surfaces has been investigated to improve the cell‐, tissue‐ and blood‐compatibility. Surface treated samples were characterized by measurement of contact angle goniometer and electron spectroscopy for chemical analysis (ESCA). The contact angles on the gold‐coated polymeric surfaces decreased from 95\!\sim\! 65^{\circ} to around 50^\circ , i.e., increased hydrophilicity due to incorporation of gold thin layer. From the results of ESCA analysis of the modified polymeric surfaces, surface modification by the gold‐sputter method was successfully performed. Morphology of the adhered platelets on the gold‐coated polymeric surfaces showed lesser …activating than control, and the number of adhered platelets surface modified samples decreased with decreasing water contact angle. Fibroblast cell adhesion and growth on the gold‐coated polymeric surfaces were more active than those of control. It seems that surface wettability and surface chemistry of gold play important roles for platelet adhesion and cell adhesion, spreading and growth. Show more

Keywords: Gold‐deposition, wettability, biocompatibility, fibroblast, platelets, adhesions

Citation: Bio-Medical Materials and Engineering, vol. 8, no. 5-6, pp. 299-309, 1998

Authors: Yoshikawa, Takafumi | Ohgushi, Hajime | Uemura, Toshimasa | Nakajima, Hiroshi | Ichijima, Kunio | Tamai, Susumu | Tateisi, Tetsuya

Article Type: Research Article

Abstract: From four patients (mean age, 60 years; range 51–76 years), 3 ml of bone marrow was collected from the ilium. The marrow was cultured to concentrate and expand the marrow mesenchymal cells on a culture dish. The cultured cells were then subcultured either on another culture dish or in porous areas of hydroxyapatite ceramics in the presence of dexamethasone and \beta ‐glycerophosphate (osteogenic medium). The subcultured tissues on the dishes were analyzed by scanning electron microscopy (SEM), and subcultured tissues in the ceramics were implanted intraperitoneally into athymic nude mice. Vigorous growth of spindle‐shaped cells and a marked …formation of bone matrix beneath the cell layers was observed on the subculture dishes by SEM. The intraperitoneally implanted ceramics with cultured tissues revealed thick layer of lamellar bone together with active osteoblasts lining in many pore areas of the ceramics after 2 months. The in vitro bone formation on the culture dishes and in vivo bone formation in porous ceramics were detected in all cases. These results indicate that we can assemble an in vitro bone/ceramic construct, and due to the porous framework of the ceramic, the construct has osteogenic potential similar to that of autologous cancellous bone. A significant benefit of this method is that the construct can be made with only a small amount of aspirated marrow cells from aged patients with little host morbidity. Show more

Keywords: Human marrow cell, osteogenesis, tissue engineering, hydroxyapatite, dexamethasone

Citation: Bio-Medical Materials and Engineering, vol. 8, no. 5-6, pp. 311-320, 1998

Authors: Kotha, S.P. | Walsh, W.R. | Pan, Y. | Guzelsu, N.

Article Type: Research Article

Abstract: The effect of fluoride ions on the mechanical properties of bone tissue in tension was investigated with an in vitro model. Structurally effective Bone Mineral Content (BMC) of bovine bone tissue was changed by fluoride ion treatment. First, bovine cortical bone specimens were treated with a detergent solution in order to increase the diffusion rates of the treatment ions across the samples. After the initial treatment, different ion solutions were used to treat the tension samples (fluoride, sodium and chloride). Ionic strength and pH were varied. Experimental results showed that the sodium chloride solutions of different ionic strengths, at physiological …and high pH, do not affect the mechanical properties of bone tissue in tension. However, uniform fluoride treatment across the samples reduced the mechanical strength of bone tissue by converting small amounts of bone mineral to mostly calcium fluoride. This action reduces the structurally effective BMC and also possibly effects the interface bonding between the bone mineral and the organic matrix of the bone tissue. Show more

Keywords: Bone tissue, composite behavior, bone mineral content (BMC), mechanical properties, fluoride ions, mineral phase, organic phase, interfacial bonding

Citation: Bio-Medical Materials and Engineering, vol. 8, no. 5-6, pp. 321-334, 1998

Authors: Gil, F.J. | Solano, E. | Campos, A. | Boccio, F. | Sáez, I. | Alfonso, M.V. | Planell, J.A.

Article Type: Research Article

Abstract: The lack of low friction coefficient for the NiTi superelastic archwires makes difficult the optimal use of these materials in orthodontic applications. In this study, the decrease of this friction coefficient has been achieved by means of nitrogen diffusion heat treatments. The titanium nitride coating has been characterised by means of optical and scanning electron microscopy. Transformation temperatures, critical stresses, hardness and friction coefficient have been determined. Besides, the metallic ion release studies showed that the titanium nitride coating prevents biodegradation.

Keywords: NiTi, superelasticity, nitrogen diffusion, shape memory, friction

Citation: Bio-Medical Materials and Engineering, vol. 8, no. 5-6, pp. 335-342, 1998

Authors: Yang, Cheng‐Hong

Article Type: Research Article

Abstract: In this paper, we applied variable degree, variable step size LMS algorithm to adaptive Morse code recognition for persons with impaired hand coordination and dexterity. The automatic recognition of Morse code by the disabled is difficult because they cannot maintain a stable typing rate. Therefore, a suitable adaptive automatic recognition method is needed. In this adaptive Morse code recognition method, three processes are involved: character separation, character recognition, and adaptive processing. Statistical analyses demonstrated that the proposed method resulted in a better recognition rate compared to alternative methods from the literature.

Keywords: Morse code, adaptive signal processing, LMS, Friedman test, multiple comparison test

Citation: Bio-Medical Materials and Engineering, vol. 8, no. 5-6, pp. 343-352, 1998

Article Type: Other

Citation: Bio-Medical Materials and Engineering, vol. 8, no. 5-6, pp. 353-355, 1998