Bio-Medical Materials and Engineering - Volume 12, issue 4

Authors: Kumari, T.V. | Anil Kumar, P.R. | Muraleedharan, C.V. | Bhuvaneshwar, G.S. | Sampeur, Y. | Derangere, F. | Suryanarayanan, R.

Article Type: Research Article

Abstract: Diamond like carbon (DLC) films were deposited on to titanium (Ti) substrates by Plasma Enhanced Chemical Vapour Deposition (PECVD) process. The quality of the films were checked by Raman spectra and nano‐hardness tests. The cytocompatibility of titanium and DLC coated titanium were studied using continuous cell lines of mouse fibroblast cells ( L‐929), Human Osteoblast cells (HOS) and primary human umbilical cord vein endothelial cells (HUVEC). The cellular responses to the materials were assessed both quantitatively and qualitatively. The adhesion and spreading of cells on materials were compared using Ti as a control. Present study indicates an improved cytocompatibility of …DLC coated Ti in comparison to bare Ti. Show more

Keywords: Diamond like carbon, cytotoxicity, fibroblast, osteoblast, endothelial cells, image analysis

Citation: Bio-Medical Materials and Engineering, vol. 12, no. 4, pp. 329-338, 2002

Authors: Assad, Michel | Chernyshov, Alexandr | Leroux, Michel A. | Rivard, Charles‐H.

Article Type: Research Article

Abstract: Porous titanium–nickel (PTN) represents a new biomaterial with orthopedic applications as a long‐term implant. Because of its nickel content, PTN was tested for its potential to stimulate sensitization, irritation, and systemic toxicity reactions after semi‐physiological extraction. In order to do so, an in vivo biocompatibility evaluation was performed following three ISO‐standardized methods using accepted animal models for immunity testing: the classical skin sensitization assay (Buehler patch test) in guinea pigs, the rabbit intracutaneous test, and the systemic injection test in mice. The Buehler patch test in guinea pigs revealed no significant change in skin reactions such as erythema or swelling …between the induction and the challenge period. In the rabbit intracutaneous irritation test, no irritation or sensitization reactions were observed in saline‐extracted PTN samples. Negligible to slight irritation was observed at some of the sites involving PTN samples extracted in cottonseed oil, however the resulting primary irritation index was similar to the one elicited by the blank solution itself. Finally, no toxic symptoms were observed with any of the mice injected with porous titanium–nickel extracts during the acute systemic toxicity test. Based on the above results, porous titanium–nickel is considered to be a non‐sensitizing, non‐irritant, and non‐toxic biomaterial for medical applications. Show more

Keywords: Porous, titanium–nickel, biocompatibility, sensitization testing, irritation testing

Citation: Bio-Medical Materials and Engineering, vol. 12, no. 4, pp. 339-346, 2002

Authors: Ozerdem, Baris

Article Type: Research Article

Abstract: The purpose of total joint arthroplasty is to reduce pain and restore function. Its success depends on the formation of a new bone that stabilizes the prosthesis. The proposed solution for this important problem is to have bio‐coated implant surfaces which are more conductive to bone growth. Additionally, collagen has long been used as a matrix for medical applications, because of its biocompatibility and adaptability. In this study, a test method for measuring the tensile adhesion strength of collagen to titanium alloy and calcium phosphate coated surfaces with different roughness values was developed, in order to evaluate how well the …collagen adheres to the metallic and bio‐coated surfaces. A precision motion system was used to stretch gels that were adherent to the plate surfaces. The tests were done in DMEM solution. The adhesive strength between the collagen gel and plate was significantly higher for calcium phosphate coated surfaces. Adhesive strength was highest in the sample with the highest roughness value. Show more

Keywords: Titanium alloy, calcium phosphate, adhesion, tensile strength, surface roughness

Citation: Bio-Medical Materials and Engineering, vol. 12, no. 4, pp. 347-352, 2002

Authors: Panyayong, W. | Oshida, Y. | Andres, C.J. | Barco, T.M. | Brown, D.T. | Hovijitra, S.

Article Type: Research Article

Abstract: Acrylic resins have been used in many different applications in dentistry, especially in the fabrication of provisional fixed partial dentures. Ideally, a provisional crown and bridge material should be easy to handle and should protect teeth against physical, chemical, and thermal injuries. Some of the problems associated with this use are related to the material's poor mechanical properties. It has been demonstrated that acrylic resin can be strengthened through the addition of structural component of different size distributed in the acrylic matrix, thus forming a composite structure. The purpose of this study was to investigate the addition effects of …mixtures of titania (titanium dioxide, TiO2 ) powder and zirconia (zirconium dioxide, ZrO2 ) powder being incorporated with pre‐polymerized beads mixed in monomer liquid, on some mechanical and physical properties of PMMA resin. The pre‐polymerized powder poly(methyl methacrylate) resin was admixed with titania and zirconia powder. A mixing ratio was controlled by volume % of 0, 1.0, 2.0, and 3.0 (samples with 0 v/o served as control groups). For using mixture of titania and zirconia, total amount of the mixture was controlled by volume % of 1.0, 2.0, and 3.0, in which titania and zirconia were mixed at the ratio 1 :1, 1 :2 and 2 :1. Prior to mechanical tests, all rectangular‐shaped samples (25 mm × 2 mm × 5 mm) were stored in 37°C distilled water for 7 days after polishing all six sides of samples. Samples were then subjected to the three‐point bending flexion test to evaluate the bending strength as well as the modulus of elasticity. Weight gain and exothermic reaction survey were investigated as well. All data were collected and analyzed with one‐way analysis of variance (ANOVA) and Sidak method (p=0.05). It was found that the addition of particles generally decreased the water absorbed by the composite system. Only 1 percent by volume concentration of 1 :1 ratio and 2 percent by volume concentration of 1 :2 and 2 :1 ratios had significantly higher strength than control group. There was significantly higher toughness (in terms of energy‐to‐break) for 1 percent by volume concentration of 1 :1 ratio and 2 percent by volume concentration of 2 :1 ratio than control group. There was no significant difference between control group and all percent by volume combinations in modulus of elasticity. In addition, there was no significant variations of exothermic reaction. Show more

Keywords: Composite resin, provisional restorations, polymethylmethacrylate resin, titania, zirconia, mechanical properties

Citation: Bio-Medical Materials and Engineering, vol. 12, no. 4, pp. 353-366, 2002

Authors: Cheng, Cheng‐Kung | Chen, Chen‐Sheng | Liu, Chien‐Lin

Article Type: Research Article

Abstract: The anterior lumbar interbody fusion is the common procedure in the management of the degenerated disc in the lumbar spine, but the biomechanical behavior of the fused segment would be changed because of the implantation of bone graft at the different locations. To investigate the biomechanical alteration, the study applied the finite element model to undergo the stress analysis. A three‐dimensional finite element model of the lumbar spine was established, and modified to the three fusion models consisted of the bone graft at the anterior site, the middle site and the posterior site, respectively. The 12 N m flexion and …the 10 N m torsion with pre‐load 150 N were imposed on the L1 vertebral body. The results of the finite element model indicated that placing bone graft at anterior site could effectively resist flexion moment, and decreased the tensile force of the posterior ligaments about 15% above. Placing bone graft at posterior site could resist torsional moment, and also led to none of contact force of the facet joint in the fused segment. However, wherever the bone grafts were placed, stress slightly increased on the disc adjacent to interbody fusion about 5% below. Show more

Keywords: Finite element analysis, lumbar spine, bone graft

Citation: Bio-Medical Materials and Engineering, vol. 12, no. 4, pp. 367-374, 2002

Authors: Karov, J. | Sinclair, A. | Hinberg, I.

Article Type: Research Article

Abstract: The repassivation of Ortron90, a high chromium stainless steel alloy, was studied to assess the effect of passive layer removal on corrosion levels. Cathodic dissolution of the passive layer followed by potentiostatic experiments within the passive region were employed to study the repassivation process. The scratch method, carried out for comparison purposes, yielded current densities similar to those obtained by cathodic dissolution. The detailed analysis of the slopes of plots of log I/log t indicated that the repassivation did not follow any of the existing growth models. It also suggested that the slope depended on the extent of repassivation and reached …a minimum when three to five monolayers of oxide were completed. The virtual potentiodynamic plots suggested the presence of some form of protective layer within 5–10 seconds and the change in open circuit potential vs time indicated that the passive layer present after 10 seconds of repassivation continued to evolve for about 1000 to 1500 seconds possibly representing a transition between two different forms such as oxide and a oxyhydroxides. Estimation of the effect of localized removal of passive layer on the corrosion indicated a dramatic increase in local corrosion density. These results show that a fast repassivation rate is an important requirement for biocompatibility of alloys used to manufacture dental and orthopaedic devices. Show more

Citation: Bio-Medical Materials and Engineering, vol. 12, no. 4, pp. 375-386, 2002

Authors: Hoffmann, M. | Gonzalez‐Mora, V. | Chiesa, R. | Cigada, A. | Stroosnijder, M.F.

Article Type: Research Article

Abstract: A novel pin‐on‐disk type wear tester is described allowing a rapid screening of different types of polyethylene under both unidirectional and multidirectional sliding motion. The wear of four polyethylene materials sliding against a roughened CoCrMo alloy was evaluated: a non‐irradiated UHMWPE, a UHMWPE irradiated with a dose of 25 kGy in air, and two types of crosslinked UHMWPE (100 kGy, air), which were subjected to a stabilization heat treatment in nitrogen at 155°C for 72 hours (XLPE I) and in water at 130°C for 72 hours (XLPE II), respectively. Under multidirectional sliding conditions both types of XLPE exhibited significantly …less wear with respect to the 25 kGy irradiated UHMWPE and the non‐irradiated UHMWPE, even under the rough counterface conditions applied. Under unidirectional sliding motion both types of XLPE exhibited the highest wear of all materials tested, because the orientation hardening effect acting under linear lubricated condition is less pronounced for crosslinked polyethylene. Show more

Citation: Bio-Medical Materials and Engineering, vol. 12, no. 4, pp. 387-395, 2002

Authors: Crampon, M.‐A. | Brailovski, V. | Sawan, M. | Trochu, F.

Article Type: Research Article

Abstract: In this paper, a new nerve cuff electrode with shape memory alloy armature is presented. The proposed electrode is dedicated either to peripheral nerve stimulation or recording and its manufacturing does not require any expensive or complex technique. Shape Memory Alloy (SMA) armature ensures the complete and firm closing of the electrode, so that the complexity of the installation procedure is considerably reduced. A preliminary analysis of the electrode mechanical behavior prior, during and after installation has been done through numerical simulations and in vitro testing. It was proved theoretically and experimentally that the SMA electrode closes completely with an …appropriate few second delay after its installation. No external fixation such as sutures is needed to secure permanent electrode‐nerve contact. Furthermore, theoretical analysis has shown that the design of SMA electrode can be adapted for safe close‐fitting installation, thanks to the device partial opening in case of nerve swelling. Show more

Keywords: Implantable electrodes, nerve cuffs, shape memory alloys, electrostimulation

Citation: Bio-Medical Materials and Engineering, vol. 12, no. 4, pp. 397-410, 2002

Authors: Zaki, M. | Saad, F. | Al‐Ebiary, M.N.

Article Type: Research Article

Abstract: The present work aims to elucidate the influence of neck‐stem angle inclination on the principal normal and shear stress distributions and values along the interfaces of the stem/cement and bone/cement in a cemented Charnley curved back femoral component. The same stresses were also examined for the intact bone that was considered as a reference for the obtained results. The interface is considered the weakest link in the structure and its endurance limit to failure is much less than the limit of the adjacent materials. Interface loading is by far the influential aspect governing the induced interface stresses in femoral total …hip replacement. Therefore, higher values and nonuniform distribution of stresses at the interface may lead to loosening and crack initiation and propagation that usually precede the stem fracture. Show more

Keywords: Stem neck angle, principal stresses, finite element, standard Charnley stem, artificial hip joint

Citation: Bio-Medical Materials and Engineering, vol. 12, no. 4, pp. 411-421, 2002

Authors: Lewandrowski, Kai‐Uwe | Bondre, Shrikar P. | Shea, Marie | Untch, Christopher M. | Hayes, Wilson C. | Hile, David D. | Wise, Donald L. | Trantolo, Debra J.

Article Type: Research Article

Abstract: The aim of this study was to evaluate biomechanically the healing of an osteochondral fragment created in the distal sheep femur in response to fixation with a resorbable composite screw made of polylactide and hydroxylapatite. Pure poly(L‐lactide) screws were used for comparison. At follow‐up times of 4 or 8 weeks, specimens were examined with standard radiography, biomechanics, and histology. The intact contralateral femur served as a control. Only minimal signs of polymer degradation were seen in the histologic specimens. At 8 weeks, most osteotomies had healed completely and there was no difference in compressive strength and elastic modulus of cylindrical …cores between the two types of biodegradable implants used. The width of the repair tissue at the tissue‐implant interface was 250±50 μm representing a clear transition zone of newly formed trabecular bone separating the implant from the surrounding plexiform bone. We conclude that relatively large polylactide implants, blended with hydroxyapatite, are capable of fixing an osteochondral fragment in an animal model. Biomechanical data assessing the quality of the bone formed at the osteotomy sites were found to be equivalent when compared to the control poly(L‐lactide) implants of similar design and size. In addition, hydroxylapatite composite implants showed benign tissue responses and good implant osteointegration. Results suggest that hydroxylapatite composite screw implants can be used for similar indications as pure poly(L‐lactide) implants in current clinical use. Show more

Keywords: Bioresorbable screw, hydroxyapatite, osteotomy healing, implant osteointegration

Citation: Bio-Medical Materials and Engineering, vol. 12, no. 4, pp. 423-438, 2002