Bio-Medical Materials and Engineering - Volume 14, issue 3

Authors: Aitchison, G.A. | Johnstone, A.J. | Shepherd, D.E.T. | Watson, M.A.

Article Type: Research Article

Abstract: In recent years there has been a tendency to design and manufacture intramedullary nails from titanium alloy rather than from stainless steel. The aim of this project was to compare the torsional performance of one manufacturers standard stainless steel and titanium alloy tibial intramedullary nails, using their distal locking screw holes and dedicated cross screws to secure each nail distally. A custom built test rig and materials testing machine were used to determine the torsional rigidity of the nails. Theory was used to calculate the torsional rigidity of the central parts of each nail. From the mechanical testing, the mean …torsional rigidity of the titanium alloy nail system was 40.9 N m2 while that of the stainless steel nail system was 34.6 N m2 , for all distal interlocking screw positions tested. Based on theoretical calculations the torsional rigidity of the central part of the nail was 83 N m2 for the stainless steel nail and 66 N m2 for the titanium alloy nail. This study shows the importance of using the distal locking screw holes and dedicated cross screws to secure intramedullary nails during mechanical testing so that clinically relevant results are obtained about the whole nail system and not just the nail. Show more

Keywords: Intramedullary nail, rigidity, tibia, torque, torsion, stiffness

Citation: Bio-Medical Materials and Engineering, vol. 14, no. 3, pp. 235-240, 2004

Authors: Yokobori Jr., A.T. | Ichiki, M. | Ohuchi, H. | Kobayashi, T. | Satoh, T. | Kinoshita, Y.

Article Type: Research Article

Abstract: The proposal of noninvasive diagnostic method of mechanical degradation of vascular wall is clinically useful and it will be correlated with noninvasive diagnostic method of atherosclerosis. Supersonic Doppler effect sensor has been used to measure blood flow velocity as a noninvasive measuring method. However, it is remain problem whether the output from the Doppler effect sensor really detects the pure blood flow velocity. Theoretically, when the Doppler effect sensor is set perpendicular to the blood flow direction, that is, perpendicular to the blood vessel, the output will correspond to the expansion velocity of blood vessel wall, because it detect the …frequency of Doppler shifted supersonic scattered from vascular wall. Previously, on the basis of this concept, using Doppler effect sensor, we showed this method can really detect the deformation velocity of blood vessel wall and it correlates the degradation of elastic property of blood vessel. Furthermore, using this proposed measuring method, atherosclerosis is found to progress correspondingly with the visco‐elastic degradation of vascular wall. In this paper, on the basis of our proposed method, the quantitative noninvasive estimation method of the degradation of vascular wall and the progressive degree of atherosclerosis by unique parameter has been proposed. Using this method, the degradation of vascular wall is correlated to the oxygen metabolic function of blood vessel corresponding to the function of oxygen transportation and progression of atherosclerosis. Furthermore, the organ correlation on the atherosclerosis between lower limb and carotid is investigated by this proposed method. Show more

Keywords: Noninvasive diagnosis, atherosclerosis, quantitative diagnosis, organ correlation, carotid, oxygen metabolic function of blood vessel

Citation: Bio-Medical Materials and Engineering, vol. 14, no. 3, pp. 241-249, 2004

Authors: Torrisi, L. | Visco, A.M. | Campo, N. | Rizzo, D. | Bombara, A.

Article Type: Research Article

Abstract: The significant wear of the UHMWPE bearings of explanted knee prostheses is produced mainly by micrometric debris (“third‐body” wear) that diffuse toward the mobile metal–polymer interface. Here debris is crushed during the movement producing scratches in the metal and in the polymeric surfaces. Mechanical stress and the biological effects change the physical polymeric properties. In order to evaluate the area of UHMWE bearings submitted to high load stresses, in this work physical investigations are performed on the explanted knee prosthesis. Particularly, the roughness profile analysis (RPA) and the micro‐hardness measurements (MHM) resulted suitable for the localisation of the mechanical and …biological wear area. In the stressed zone, surface treatments could be applied in order to improve the mechanical resistance of the polymeric material. Particularly, the ion implantation with heavy ions is proposed to enhance the polymeric wear resistance. The Scanning Electron Microscopy (SEM), Energy Dispersive X‐ray Spectrometry (EDX) and Infrared absorption spectroscopy (FTIR) techniques were also applied and results discussed. Show more

Citation: Bio-Medical Materials and Engineering, vol. 14, no. 3, pp. 251-261, 2004

Authors: Morita, Yusuke | Nakata, Kenichi | Kim, Yoon‐Ho | Sekino, Tohru | Niihara, Koichi | Ikeuchi, Ken

Article Type: Research Article

Abstract: While only alumina is applied to all‐ceramic joint prostheses at present, a stronger ceramic is required to prevent fracture and chipping due to impingement and stress concentration. Zirconia could be a potential substitute for alumina because it has high strength and fracture toughness. However, the wear of zirconia/zirconia combination is too high for clinical use. Although some investigations on composite ceramics revealed that mixing of different ceramics was able to improve the mechanical properties of ceramics, there are few reports about wear properties of composite ceramics for joint prosthesis. Since acetabular cup and femoral head of artificial hip joint are …finished precisely, they indicate high geometric conformity. Therefore, wear test under flat contact was carried out with an end‐face wear testing apparatus for four kinds of ceramics: alumina monolith, zirconia monolith, alumina‐based composite ceramic, and zirconia based composite ceramic. Mean contact pressure was 10 MPa and sliding velocity was 40 mm/s. The wear test continued for 72 hours and total sliding distance was 10 km. After the test, the wear factor was calculated. Worn surfaces were observed with a scanning electron micrograph (SEM). The results of this wear test show that the wear factors of the both composite ceramics are similarly low and their mechanical properties are much better than those of the alumina monolith and the zirconia monolith. According to these results, it is predicted that joint prostheses of the composite ceramics are safer against break down and have longer lifetime compared with alumina/alumina joint prostheses. Show more

Keywords: Artificial joint, flat contact, composite ceramics, alumina, zirconia

Citation: Bio-Medical Materials and Engineering, vol. 14, no. 3, pp. 263-270, 2004

Authors: Tsui, C.P. | Tang, C.Y. | Leung, C.P. | Cheng, K.W. | Ng, Y.F. | Chow, D.H.K. | Li, C.K.

Article Type: Research Article

Abstract: An active finite element model was developed to predict the mechanical behaviors of skeletal muscle–tendon complex during isometric, shortening and lengthening contraction. The active finite element was created through incorporation of a user‐defined material property into ABAQUS finite element code. The active finite element is controlled by a motor element that is activated by a mathematical function. The nonlinear passive behavior of the muscle was defined by the viscoelastic elements and can be easily altered to other properties by using other elements in the material library without the need of re‐defining the constitutive relation of the muscle. The isometric force–length …relationship, force–strain relations of the muscle–tendon complex during both shortening and lengthening contraction and muscle relaxation response were predicted using the proposed finite element model. The predicted results were found to be in good agreement with available experimental data. In addition, the stress distribution in the muscle–tendon complex during isometric, shortening and lengthening contractions was simulated. The location of the maximum stress may provide useful information for studying muscle damage and fatigue in the future. Show more

Keywords: Active finite element, skeletal muscle, shortening contraction, lengthening contraction, isometric contraction

Citation: Bio-Medical Materials and Engineering, vol. 14, no. 3, pp. 271-279, 2004

Authors: Dupont‐Gillain, C.C. | Alaerts, J.A. | Dewez, J.L. | Rouxhet, P.G.

Article Type: Research Article

Abstract: Three patterned systems aiming at the control of mammalian cell behavior are presented. The determinant feature common to these systems is the spatial distribution of extracellular matrix (ECM) proteins (mainly collagen) on polymer substrates. This distribution differs from one system to another with respect to the scale at which it is affected, from the supracellular to the supramolecular scale, and with respect to the way it is produced. In the first system, the surface of polystyrene was oxidized selectively to form micrometer‐scale patterns, using photolithography. Adsorption of ECM proteins in presence of a competitor was enhanced on the oxidized domains, …allowing selective cell adhesion to be achieved. In the second system, electron beam lithography was used to engrave grooves (depth and width ∼1 μm) on a poly(methyl methacrylate) (PMMA) substratum. No modification of the surface chemistry associated to the created topography could be detected. Cell orientation along the grooves was only observed when collagen was preadsorbed on the substratum. In the third system, collagen adsorbed on PMMA was dried in conditions ensuring the formation of a nanometer‐scale pattern. Cell adhesion was enhanced on such patterned collagen layers compared to smooth collagen layers. Show more

Keywords: Cell–material interaction, cell adhesion, extracellular matrix protein, collagen, XPS, AFM

Citation: Bio-Medical Materials and Engineering, vol. 14, no. 3, pp. 281-291, 2004

Authors: Peerapattana, Jomjai | Otsuka, Kuniko | Otsuka, Makoto

Article Type: Research Article

Abstract: This study aimed to prepare a colon drug delivery system using dry‐coated time‐controlled disintegration wax matrix tablets. Indomethacin was used as a model drug. Behenic acid and lactose were used as coating materials. The effects of lactose content and pH of the dissolution medium on drug release were investigated. The porosity and the tortuosity of the surface matrix layer were calculated. Four formulations of wax matrices containing different percentages of lactose in the surface layer, i.e. 70, 65, 60 and 55, were prepared. The lag times of indomethacin release from the matrices in 0.05 M phosphate buffer pH 7.4 were …50, 162, 294 and 539 minutes for formulations containing 70, 65, 60 and 55% lactose, respectively. The release of drug from formulations containing lactose in the range of 60–70% in different media, i.e. 0.05 M phosphate buffer pH 7.4, 0.05 M alkaline borate buffer pH 8.5 and in the case of pH changed media from pH 1.3 to pH 7.4, was not different (p=0.1). This implies that the different environment in the gastro‐intestinal tract will not affect the release of this delivery device. The required lag time period can be met by varying the amount of lactose. Show more

Keywords: Wax matrix tablet, colon drug delivery, co‐grinding, sustained drug release, time‐controlled disintegration tablet

Citation: Bio-Medical Materials and Engineering, vol. 14, no. 3, pp. 293-301, 2004

Authors: Yeni, Yener N. | Dong, X. Neil | Fyhrie, David P. | Les, Clifford M.

Article Type: Research Article

Abstract: A strong positive correlation between the apparent ultimate strength and stiffness of bone tissue that can be expressed by a unified relationship has been observed for cortical bone in tension and low‐density cancellous bone in compression. For practical purposes, the existence of a relationship between strength and stiffness is significant in that bone stiffness can be measured in vivo using non‐invasive methods. It is generally accepted that bone strength is greater in compression than in tension whereas there is no substantial evidence that bone stiffness in compression is different from that in tension. This might suggest that compressive strength …would relate to the stiffness, if at all, in a way that is different from tensile strength. In order to examine similarities and differences in the way strength is associated with stiffness between modes of loading and tissue type, we tested equine cortical bone and bovine cancellous bone in compression and examined these data together with previously reported data from compression testing of human cancellous bone as well as tensile testing of cortical bone from various sources. We have found for cortical bone that (i) the sensitivity of strength to stiffness is the same for tension and compression (p>0.75, ANCOVA), and (ii) the difference between the magnitudes of compressive and tensile strength for cortical bone is the result of an additive, rather than a multiplicative factor (52.1 MPa after adjusting to 1 microstrain/s, p<0.0001, ANOVA). High‐density bovine tibial cancellous bone, on the other hand, has a steeper slope for its compressive strength–stiffness relationship than that for cortical bone and human cancellous bone, resulting in a transitional relationship between compressive strength and stiffness for a range of bone types and densities. Based on the current results and previous work, it is suggested that the offset strength in the compressive strength–stiffness relationship may be a direct manifestation of the difference between the compressive and tensile strengths of the bone material that constitutes the building blocks of the bone structure. Deviation of high‐density cancellous bone compressive behavior from the other bone types and densities is attributed to stress distribution differences between the bone types. Show more

Keywords: Bone, strength–stiffness relationship, modulus, structure–function, adaptation

Citation: Bio-Medical Materials and Engineering, vol. 14, no. 3, pp. 303-310, 2004

Authors: Litonjua, Luis A. | Andreana, Sebastiano | Patra, Abani K. | Cohen, Robert E.

Article Type: Research Article

Abstract: Wedged‐shaped lesions at the cemento‐enamel junction of teeth have been attributed primarily to biomechanical loading forces that cause flexure and failure of enamel and dentin. This theory, termed abfraction, remains controversial. This review examined studies on mechanical properties of enamel and dentin and studies on bite forces and mastication as background information. Abfraction is based principally on a few early finite element analysis and photoelastic models showing stress concentration at the dental cervical area without actually showing enamel and dentin fracture. However, a review of more recent dental stress analyses has been contradictory. Particularly, analyses of the periodontal ligament and …alveolar bone, not modeled in previous studies, have shown that those structures may dissipate occlusal loading forces from the cervical areas. In addition, some models may not fully represent intricate dental anatomy and complex occlusal function. Therefore, the key basis of the abfraction theory may be flawed. Show more

Keywords: Abfraction, dental stress analysis, tooth cervix, bite force, dental enamel, dentin, finite element analysis, photoelastic model, abrasion, erosion

Citation: Bio-Medical Materials and Engineering, vol. 14, no. 3, pp. 311-321, 2004

Authors: Grosgogeat, B. | Boinet, M. | Dalard, F. | Lissac, M.

Article Type: Research Article

Abstract: Objectives: The aim of this study was to compare the electrochemical behaviour of two materials used in oral implantology. Methods: The resistance to corrosion of Ti grade 2 and the alloy Ti–6Al–4V was studied in an artificial saliva solution. It has been observed that the passivation of titanium by an oxidised layer can be shown both by cyclic voltametry and by electrochemical impedance spectroscopy. Moreover, this latter technique, rarely used in odontology, opens up interesting perspectives, enabling a more quantitative approach to the resistance of the passive layer to be adopted. Results: Also, the impedance data recorded for Ti grade …2 and the alloy Ti–6Al–4V, in the artificial saliva solution were shown that Ti grade 2 has a higher resistance to corrosion and a thicker oxide layer than the alloy Ti–6Al–4V. Significance: The fact that the electrochemical properties of Ti–6Al–4V are lower than that titanium's ones indicate than a release of ions aluminum and or vanadium ions in the body can occur. This is why we recommend to the dental practitioners to preferably use titanium in implantology. Show more

Keywords: Corrosion, biocompatibility, titanium, artificial saliva, electrochemical impedance spectroscopy

Citation: Bio-Medical Materials and Engineering, vol. 14, no. 3, pp. 323-331, 2004