Bio-Medical Materials and Engineering - Volume 11, issue 3

Authors: Li, Shuyu | Hu, Kuanghu | Cai, Nian | Su, Wanfang | Xiong, Haitao | Lou, Zheng | Lin, Tefu | Hu, Yingxiong

Article Type: Research Article

Abstract: Some computer applications for cell characterization in medicine and biology, such as analysis of surface structure of cell wall‐deficient EVC (El Tor Vibrio of Cholera), operate with cell samples taken from very small areas of interest. In order to perform texture characterization in such an application, only a few texture operators can be employed: the operators should be insensitive to noise and image distortion and be reliable in order to estimate texture quality from images. Therefore, we introduce wavelet theory and mathematical morphology to analyse the cellular surface micro‐area image obtained by SEM (Scanning Electron Microscope). In order to describe …the quality of surface structure of cell wall‐deficient EVC, we propose a fully automatic computerized method. The image analysis process is carried out in two steps. In the first, we decompose the given image by dyadic wavelet transform and form an image approximation with higher resolution, by doing so, we perform edge detection of given images efficiently. In the second, we introduce many operations of mathematical morphology to obtain morphological quantitative parameters of surface structure of cell wall‐deficient EVC. The obtained results prove that the method can eliminate noise, detect the edge and extract the feature parameters validly. In this work, we have built automatic analytic software named “EVC.CELL”. Show more

Keywords: EVC, surface structure of cell wall‐deficient form, image processing, automatic analysis, feature extraction

Citation: Bio-Medical Materials and Engineering, vol. 11, no. 3, pp. 159-166, 2001

Authors: Lewis, Gladius | Carroll, Michael

Article Type: Research Article

Abstract: The in vitro quasi‐static tensile and compresssive creep properties of three sets of GUR 1050 ultra‐high‐molecular‐weight polyethylene (UHMWPE) specimens were obtained. These sets were: control (as‐received stock); “low‐gamma” (specimens were crosslinked using γ radiation, with a minimum dose of 5 Mrad); and “high‐gamma” (specimens were crosslinked using γ radiation, with a minimum dose of 15 Mrad). The % crystallinity (%C) and crosslink density (ρx ) of the specimens in the three sets were also obtained. It was found that, in both tension and compression, crosslinking resulted in a significant depreciation in the creep properties, relative to control. The trend in …the creep results is explained in terms of the impact of crosslinking on the polymer's %C and ρx . The present results are in contrast to literature reports that show that crosslinking enhances the wear resistance of the polymer. The implications of the present results, taken together with the aforementioned literature results, are fully discussed vis‐a‐vis the use of crosslinked UHMWPE for fabricating articular components for arthroplasties. Show more

Keywords: Ultra‐high‐molecular‐weight‐polyethylene, crosslinking, creep, crystallinity, crosslink density

Citation: Bio-Medical Materials and Engineering, vol. 11, no. 3, pp. 167-183, 2001

Authors: Nagasawa, S. | Yoshida, T. | Mizoguchi, H. | Ito, M. | Oshida, Y.

Article Type: Research Article

Abstract: A plurality of repeated porcelain‐baking procedures are normally practiced in order to achieve the final adjustment metal–porcelain restorations. By increasing the number of baking cycles, the undesired internal strain would be built‐up, causing the reduction of mechanical properties and deterioration of color characteristics. However the extensive studies on such deterioration have not been done. In this study, effects of numbers (up to 10 times) of repeated baking cycles on baking shrinkage, surface roughness, bend strength, color changes and internal microstructure were investigated when opaque, body and enamel was individually applied or when a triple‐player comprising of these three porcelains was …repeatedly applied. It was concluded that (1) the bend strengths increased by increasing baking cycles, (2) the average surface roughness decreased by increasing number of baking procedures, (3) changes in color characteristics was very small in the Vintage halo porcelain system, and (4) since the pores entrapped in the porcelain remained even by increasing baking cycles, it is recommended to remove the surface pores before forming the next layer when handling the high viscous opaque porcelain. Show more

Keywords: Baking cycles, bend strength, porcelain (opaque, body, enamel), color characteristics, surface roughness

Citation: Bio-Medical Materials and Engineering, vol. 11, no. 3, pp. 185-195, 2001

Authors: Lewandrowski, Kai‐Uwe | Schollmeier, Georg | Ekkemkamp, Axel | Uhthoff, Hans K. | Tomford, William W.

Article Type: Research Article

Abstract: Massive cortical bone allografts have been found to incorporate slowly into host bone. They are subject to complications such as nonunion, fatigue fracture and infection. In an attempt to improve osteoinduction in cortical bone allografts, laser perforated and partially demineralized cortical bone allografts were orthotopically transplanted into the sheep tibia. In this model, mid‐shaft tibial bone allografts from out‐bred sheep donor animals were prepared by partial demineralization and drilling of 0.33‐mm diameter holes with a pulsed, 2.94‐μm wavelength Erbium:Yttrium–Aluminum–Garnet laser. Recipient animals of the same out‐bred strain were divided into three groups of eight according to the type of cortical …allograft used: group 1, fresh‐frozen, no treatment; group 2, laser hole grid; and group 3, laser hole grid and partial demineralization. Plain films were taken in two standard views at monthly intervals. Incorporation was evaluated at nine months postoperatively. Longitudinal radiographic data was correlated to a histologic and morphometric evaluation of each bone graft. Computer tomography was used for the latter analysis. Results showed that untreated allografts, although surrounded by a periosteal bone cuff, were poorly incorporated. Partial demineralization lead to excessive resorption of allografts, but little new bone formation. Laser perforation and partial demineralization induced complete incorporation of allografts into the host bone. Based on the results of the radiographic, histologic and morphometric evaluation, the development of laser‐perforated and partially demineralized bone allografts was proposed for clinical use. Show more

Citation: Bio-Medical Materials and Engineering, vol. 11, no. 3, pp. 197-207, 2001

Authors: Lewandrowski, Kai‐Uwe | Schollmeier, Georg | Ekkemkamp, Axel | Uhthoff, Hans K. | Tomford, William W.

Article Type: Research Article

Abstract: Laser perforated and partially demineralized cortical bone allografts were orthotopically transplanted into sheep tibiae. This paper reports results of the mechanical testing of the transplanted bones, which was done at nine months postoperatively. Animals were divided into three groups of eight according to the type of cortical allograft used: group 1, no treatment; group 2, laser hole grid; and group 3, laser hole grid and partial demineralization. Thus, changes in flexural rigidity of 24 transplanted whole tibiae were investigated. Starting in the anterior direction at the tibial tuberosity, the flexural rigidity was determined using a nondestructive 4‐point bending test. The …elliptical distribution of the flexural rigidity was compared to the untreated contralateral control bone of each animal. Mechanical parameters were defined as percentage rates for comparative analysis between groups. Flexural rigidity measurement showed that bones transplanted with untreated allografts were stiffer than contralateral control bones. Partial demineralization of allografts reduced the flexural rigidity of transplanted bones below the level of contralateral control bones. Flexural rigidities of test bones transplanted with laser perforated and partially demineralized allografts were higher than those seen in bones transplanted with partially demineralized allografts. These results were corroborated by the histologic analysis which showed that untreated allografts, although surrounded by a periosteal bone cuff that effectively increased their outer diameter. In contrast, excessive bone resorption was observed in partially demineralized allografts. Laser‐perforated and partially demineralized allografts showed histologic evidence of complete incorporation into the host bone. Based on this mechanical evaluation, it was concluded that processing of cortical bone allografts by the combination of perforation and partial demineralization resulted in improved mechanical strength of the transplanted bones as compared to processing by partial demineralization alone. Show more

Citation: Bio-Medical Materials and Engineering, vol. 11, no. 3, pp. 209-219, 2001

Authors: Nordström, E.G. | Sánchez Muñoz, Orlando L.

Article Type: Research Article

Abstract: The present work deals with fundamental problems around bone bonding mechanism. Different sorts of biomaterials: inert, bioactive and metals are discussed. The importance of surface properties of biomaterials, as, e.g., zeta potential, is of uttermost importance to understand the bonding mechanism.

Keywords: Bone bonding, surface modification, bioactive glass, bio‐ceramics, zeta potential

Citation: Bio-Medical Materials and Engineering, vol. 11, no. 3, pp. 221-231, 2001

Authors: Othman, M.O. | Al‐Nashash, H. | Qassem, W.

Article Type: Research Article

Abstract: ECG analysis of a human body subjected to vertical vibrations of various durations was carried out. Results obtained from a representative subject show that the exposure period has different effects on the P–R time interval of the ECG waves. Vibration increases the Percent Normalized Difference (PND) of the P–R time interval with time till it reaches a steady state value of 29.5. An increase of the exposure duration increases the time constant, while the steady state value remains constant. The PND behavior can be mathematically modeled as a first order system.

Citation: Bio-Medical Materials and Engineering, vol. 11, no. 3, pp. 233-240, 2001

Authors: Dharmastiti, R. | Barton, D.C. | Fisher, J. | Edidin, A. | Kurtz, S.

Article Type: Research Article

Abstract: Unidirectional wear tests of UHMWPE against smooth counterfaces show that molecular chains at the surface of virgin material become oriented parallel to the sliding direction giving low wear rate. It is postulated that under more abrasive conditions and predominantly unidirectional motion as in knee prostheses, it may proof beneficial to provide molecular orientation of the bulk material. Therefore strips of UHMWPE were oriented by die drawing at elevated temperature and the resulting anisotropic material subjected to tensile tests, small punch tests and also unidirectional wear tests both parallel and perpendicular to the draw direction. The tensile tests showed that, in …the parallel direction, the oriented UHMWPE became stiffer and less ductile compared to the virgin UHMWPE. In the perpendicular direction, there were reductions in yield stress, 5% proof stress and energy to failure compared to the virgin material. The small punch test showed that the oriented UHMWPE exhibited apparent hardening when tested in both parallel and perpendicular directions but the mechanical behaviour in the perpendicular direction was comparable to the virgin UHMWPE. The wear tests demonstrated that the oriented UHMWPE did not show any significant improvement of wear resistance for sliding against either isotropically rough or scratched counterfaces. There was no clear dependency between the mechanical properties and wear factors of the oriented UHMWPE. Show more

Keywords: Oriented UHMWPE, wear, die drawing, mechanical properties

Citation: Bio-Medical Materials and Engineering, vol. 11, no. 3, pp. 241-256, 2001

Authors: Xu, Shenzhi | Tomita, Naohide | Ohata, Rie | Yan, Qichang | Ikada, Yoshito

Article Type: Research Article

Abstract: Effects of a static magnetic field were studied on bone formation using an ischemic rat femur model. Metal rods were prepared from magnetized and unmagnetized samariun cobalt to have tapered structure, both with the same geometrical dimension, and were implanted transcortically into the middle diaphysis of 88 rat femurs. Both sides of the rat femoral artery were ligated to create an ischemic bone model, followed by implantation of the tapered rod to the femur. The bone mineral density (BMD) and weight of the femurs were measured at 1st and 3rd week after implantation. The result at the 3rd week …post‐implantation revealed that the BMD and weight of the ischemic bone model rats were significantly reduced, compared with that of non‐operated femur. It was also found that the magnetized group had significantly higher bone weights than the unmagnetized (p<0.05). The BMD of the rats implanted with the magnetized rods were similar to those of the non‐operated (p>0.05). This enhancement of the femural bone formation of the ischemic rat model by the static magnetic field seems to be due to the improved blood circulation of the femur. Show more

Keywords: Static magnetic field, bone mineral density, ischemic model, rat osteoporotic femur

Citation: Bio-Medical Materials and Engineering, vol. 11, no. 3, pp. 257-263, 2001

Authors: Dubois, J.C. | Jardin, C. | Exbrayat, P. | Lissac, M. | Treheux, D.

Article Type: Research Article

Abstract: The influence of sterilization by gamma rays on the structure and the electrical behaviour of sapphire single crystal (α‐Al2 O3 ) was studied successively by thermoluminescence, by cathodoluminescence and by observation of the scanning electron microscope mirror effect. The mirror method allowed us to measure the capacity of an insulating material to trap electrons. The structural analysis of the α‐Al2 O3 showed that there were oxygen vacancies, as well as chromium and titanium impurities. It was possible to demonstrate that these defects, especially the oxygen vacancies, are in a different state after a 30 kilogray irradiation. The valency state …changes of these defects and the presence of trapped charges are accompanied by a deformation of the crystalline lattice which results in a modification of its electrical properties. At room temperature, the irradiated α‐Al2 O3 , unlike non irradiated α‐Al2 O3 , is capable of trapping electrons. It can be concluded that gamma‐ray sterilization modifies the cohesive energy of α‐Al2 O3 , which could lead to mechanical changes (surface charge, friction, wear, fracture strength, …) in this material. Show more

Keywords: Insulating biomaterial, surface charging, cathodoluminescence, scanning electron microscope mirror effect

Citation: Bio-Medical Materials and Engineering, vol. 11, no. 3, pp. 265-273, 2001