bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stability of a cyclically loaded hydroxyapatite coating: Effect of substrate material, surface preparation, and testing environment
Authors: Kummer Frederick J. , Jaffe William L. 
Published: May 2005

AbstractCyclic loaing of Ti‐6‐4 and Co‐Cr‐Mo (cast) test samples with grit‐blasted or waffle‐textured surfaces coated with a plasma‐sprayed 50‐μm HA layer was performed in air, Ringer's solution (5% dextrose), 0.9% NaCl (Tris buffer, pH 7.40), and balanced Hank's solution. Maximum interfacial stresses in bending of 40 ksi (280 MPa) and 20 ksi (140 MPa) were utilized, and the speciments tested to 106 cycles at 5 Hz with a MTS servohydraulic machine. Tested samples were examined by optical microscopy to determine coating integrity and thickness and by scanning electron microscopy (electron backscatter mode and EDAX) to determine surface morphology and chemical changes.The following observations were made: (1) Samples cyclically tested in solutions showed a general thinning of the coating, accentuated in the higher‐stressed regions. (2) Samples tested with an equivalent static load in the solutions did not show this centralization. (3) Bare metal interface surfaces were noted on most of the edges of highly stressed central specimen regions, in several entire central regions, and on the upper surfaces of some of the waffled samples. (4) The specimens tested in Ringer's solution (pH 4.70 initially) demonstrated the most dramatic coating deterioration. (5) The coatings on titanium appeared more stable than these on Co‐Cr as tested in all solution environments for both surface types.The HA coating evaluated in this experiment demonstrated increased instability when cyclically loaded in in vitro solutions of lowered pH and depleted cations (Ca2+) at stress levels of 280 MPa. The more physiological solution (Hank's) did not show this increased dissolution at the lower stress level. It is suggested that this type of testing be performed on other HA coatings due to the possible implications for long‐term in vivo coating integrity.
Biocompatibility tests on a novel glass–ceramic system
Authors: Wolfe Leonora A. , Boyde Alan 
Published: May 2005

AbstractThe aim of this study was to look at the bone bonding potential of six formulations of a novel glass‐ceramic system. Cylinders of the ceramics were implanted in rabbit tibiae for 4 and 7 weeks. Histological tests, both quantitative and qualitative, as well as push‐out tests, were carried out during the bonding assessment. Bone growth was quite prolific, even at 4 weeks, as evidenced by growth up to and along the implant surfaces. The interfacial shear strengths compared well with other biomaterials in use as endosseous implants. Therefore it seems pertinent to pursue further long‐term experimentation with this material.
Glass–Ceramic implant in acetabular bone defect: An experimental study
Authors: Yoshii Satoru , Yamamuro Takao , Nakamura Takashi , Oka Masanori , Takagi Haruki , Kotani Seiya 
Published: May 2005

AbstractExtensive acetabular defects produced surgically in 25 dogs were repaired using A ‐ W glass‐ceramic blocks. No dislocation of the femoral head, and no displacement or breakdown of the blocks was seen 1 year after surgery. All dogs were able to run normally shortly after surgery, except for one that limped for a short time. The failure load between the blocks and the bone had increased markedly 2 months after implantation. The failure load/unit area was 33.2 kgw/cm2 1 year after implantation. We conclude that glass‐ceramic supplementation of the acetabulum is successful experimentally, and that this may be a promising method for repair of large acetabular bone defects. © 1992 John Wiley & Sons, Inc.
Osteoconduction of bioceramics in normal and osteopenic rats: Comparison between bioactive and bioinert ceramics
Authors: Iwashita Yasushi , Yamamuro Takao , Kasai Ryuichi , Kitsugi Toshiaki , Nakamura Takashi , Okumura Hideo , Kokubo Tadashi 
Published: May 2005

AbstractRats with experimental osteopenia, which was induced by resecting both ovaries and sciatic nerves (OVX + NX), were used to evaluate osteoconduction of an apatite and wollastonite‐containing glass‐ceramic (designated A‐W.GC) and an alumina ceramic. The bone mineral densities (BMDs) of the femurs were measured by dural energy X‐ray absorptiometry (DEXA) and determination of the ash weight. Twelve weeks after the first operation, when the BMDs in the OVX + NX groups were about 20% less than that in the sham‐treated groups (Sham), the bioceramics were implanted into the proximal tibiae. The bone mineral masses around the implants in the proximal tibiae were evaluated by histological examination of undecalcified specimens and DEXA. Both types of implants in the OVX + NX groups showed less reactive bone than those in the Sham groups. However, a histomorphological study revealed that the direct contact area between bone and implant was larger with bioactive ceramic A‐W.GC than with the bioinert alumina ceramic even under osteopenic conditions while two types of ceramic made no difference on the bone at distance from the implant. The direct contact area with A‐W.GC did not show any difference between the Sham and the osteopenic OVX + NX groups. The bioactive ceramic A‐W.GC appears to have good osteoconductivity solely on its surface even under osteopenic conditions.
The surface treatment of polypropylene molds and its effect on the quality of cast contact lenses
Authors: Lukášk J. , Fenclová T. , Tyráčkková V. , Vacík J. 
Published: May 2005

AbstractAn investigation of the surface by XPS photoelectron spectroscopy has shown that the process of production of cast contact lenses based on poly(2‐hydroxyethyl methacrylateco‐diethyleneglycol methacrylate) is accompanied by mass transfer at the lens‐mold boundary. This phenomenon, which impairs the compatibility of the lens during its application, can be considerably suppressed by employing a suitable surface modification of polypropylene molds. The surface treatment consisting in the oxidation of the mold surface by an AC corona discharge in the oxygen atmosphere increased hydrophilicity of the material, thus facilitating separation of the lens from the mold. The results of the XPS study were also confirmed microscopically by employing the SEM method. © 1992 John Wiley & Sons, Inc.
A versatile alginate droplet generator applicable for microencapsulation of pancreatic islets
Authors: Wolters Gerrit H. J. , Fritschy Wilbert M. , Gerrits Dick , Van Schilfgaarde Reinout 
Published: May 2005

AbstractAlginate beads for immunoisolation of pancreatic islets by microencapsulation should be small, smooth, and spherical in order to ensure that around the islets a strong alginate‐polylysine‐alginate capsule will be formed with optimal biocompatibility and diffusion of nutrients and hormones. However, the preparation of small capsules around islets is difficult. Our newly designed air jet droplet generator allows for variations in the length and diameter of the alginate nozzle and the air jacket and is in this way adaptable to a required bead size. Alginate droplets are converted into rigid beads in a 100 mM CaCl2 solution. Their size depends upon the diameter of the jacket, the air flow rate, and the outer diameter of the nozzle, whereas the production rate depends upon the pressure on the alginate, and on the diameter and the length of the nozzle. When the air flow or the alginate flow surpasses a certain rate, the droplets are fragmented. Thus study describes the mutual relationship of these variables and defines their optimal range for reproducible production of smooth and spherical beads for microencapsulation of islets at an acceptable production rate. © 1992 John Wiley & Sons, Inc.
Strain analysis of flexing blood pump diaphragms
Authors: Kesavan S. K. , Yazdani S. A. 
Published: May 2005

AbstractBlood pumps usually use elastomer diaphragms that undergo repeated small‐strain flexing (deformation). The stresses and strains that develop in the mechanically actuated diaphragms dictate the useful life and fluid‐solid interactions of the diaphragm. A knowledge of these stresses and strains is essential for proper design of the pump's elastomer diaphragm. A nonlinear axisymmetric finite‐element stress‐strain analysis has been carried out on a Hexsyn rubber diaphragm used in a blood pump to illustrate a finite‐element modeling technique. A situation involving the application of an axial deformation load on the diaphragm has been considered. In particular, the strains developed in a blood pump diaphragm during pumping have been quantified to illustrate the analysis technique. © 1992 John Wiley & Sons, Inc.
Preliminary biocompatibility screening of several biodegradable phosphate fiber reinforced polymers
Authors: Andriano Kirk P. , Daniels A. U. , Smutz W. Paul , Wyatt Ronald W. B. , Heller Jorge 
Published: May 2005

AbstractThis article describes preliminary biocompatibility screening of three degradable phosphate fibers containing K+, Ca+2/Na+ and Na+/Ca+2/Al+3 ions in the polymer chain, and of several different degradable polymers reinforced with these fibers. Biodegradable phosphate fibers of calcium–sodium–metaphosphate (CSM) and sodium–calcium–aluminum–polyphosphate (NCAP) were acutely nontoxic in cellular, tissue, and whole animal evaluations, as determined by standard acute toxicity tests. Histological studies of bone implants sites fabricated from composites of copolymers of poly(E‐caprolactone/L‐lactide) and poly(ortho ester) reinforced with either CSM or NCAP fibers showed these composite materials to be nontoxic, with no abnormal inflammatory response. However, histological evaluation of muscle implants sites revealed the appearance of necrotic foci associated with implant sites in 12 of 22 NCAP containing composite specimens (p < 0.05). Results of this preliminary biocompatibility screening suggest CSM fibers may be useful in reinforcing degradable polymers for production of completely biodegradable composites for implant use. © 1993 John Wiley & Sons, Inc.
In vivo behavior of a high performance duplex stainless steel
Authors: Cigada A. , Santis G. De , Gatti A. M. , Roos A. , Zaffe D. 
Published: May 2005

AbstractAn in vivo investigation of a new high molybdenum and nitrogen duplex stainless steel (25Cr7Ni4Mo0.3N) has been performed. Cylindrical pins and specially developed devices, to test in static conditions the in vivo localized corrosion resistance, made of this new duplex steel and of a common austenitic stainless steel were implanted in rabbit's femurs for 6 and 12 months. After sacrifice, SEM observations and EDS microanalyses to detect metallic ion release were carried out on the femur sections surrounding the pins. Morphologic observations with stereoscope and SEM were performed on the metallic surfaces of the special devices in order to detect the presence of localized corrosion. Both ion release and localized corrosion were observed for the specimens made of austentic stainless steel, but not for those made of 25Cr7Ni4Mo0.3N duplex stainless steel. © 1993 John Wiley & Sons, Inc.
Effects of pulsed electromagnetic fields on the foreign body response to particulate debris in a rabbit model
Authors: DoVan T. , Zimmerman M. C. , Bednarz P. , Alexander N. , Deehan M. 
Published: May 2005

AbstractThe effect of pulsed electromagnetic fields (PEMFs) on the foreign body response to particulate debris, similar in morphology and quantity to wear debris present in the tissues around loose total joint prostheses, was investigated using a rabbit model. Cobalt chrome pins were inserted into the femurs along with particulate debris consisting of ultra high molecular weight polyethylene (UHMWPE), polymethylmethacrylate (PMMA), and cobalt chrome (CC). The particles induced a significant cellular response compared to the control animals that did not receive any debris. The application of PEMFs did not increase this foreign body response, nor did it have an effect on the number of resorption cavities, cortical area, or cortical thickness. © 1993 John Wiley & Sons, Inc.
Surface dependent antigens identified by high binding avidity of serum antibodies in a subpopulation of patients with breast prostheses
Authors: Kossovsky Nir , Zeidler Michelle , Chun Grace , Papasian Nora , Nguyen Anhthu , Rajguru Samir , Stassi John , Gelman Andrew , Sponsler Ed 
Published: May 2005

AbstractThere is growing concern in the medical community that silicones, ubiquitous in health care, may exhibit antigenic, immunogenic, and/or adjuvant activity. Sera from women with silicone breast prostheses were assayed by ELISA for humoral immunoreactivity to a variety of common interstitial and cellular components. In decreasing order of frequency, significant IgG avidities were found against silicone surfaces treated with fibronectin–laminin, phospholipids, no treatment, and fibrinogen when compared with sera obtained from healthy, age‐matched, nonimplanted women and a population of nonimplanted women with previously diagnosed autoimmune diseases. Moreover, the sera from approximately 15% of the positive responders were found to react to matrix proteins independent of the siloxane polymer. The data show human antibody production to native macromolecules with antibody avidity being related to molecular conformation. Silicone may function as an adjuvant by inducing changes in the conformation of native molecules. © 1993 John Wiley & Sons, Inc.
Light microscopic identification of submicron polyethylene wear debris
Authors: Guttmann Dan , Schmalzried Thomas P. , Jasty Murali , Harris William H. 
Published: May 2005

AbstractA simple, yet specific, means to identify submicron polyethylene (PE) particles in routine histologic sections would be practically useful. We have previously reported a very fine, diffuse, birefringence (when viewed under polarized light) in the cytoplasm of phagocytic cells from around total hip replacements (THRs) with a PE acetabular bearing and proposed that this finding was caused by multiple submocron PE particles. In order to determine the specificity of this light microscopie finding, we have analyzed a wide range of specimens (N = 27), characterized by a foreign‐body inflammatory response to both biologic and prosthetic material, that do not contain PE. In no case was there any suggestion of the diffuse cytoplasmic birefringence that is characteristic of specimens from THRs with a PE acetabular bearing surface. This study indicates that, within the range of orthopedic implant materials and designs currently in use, this diffuse birefringence is a specific finding and it represents a simple, practical, and useful method for ligh microscopic identification of submicron PE. © 1993 John Wiley & Sons, Inc.
Porous polyurethane tubes as vascular graft
Authors: Fujimoto Keiji , Minato Masao , Miyamoto Susumu , Kaneko Takaaki , Kikuchi Haruhiko , Sakai Kazuhiko , Okada Masao , Ikada Yoshito 
Published: May 2005

AbstractA vascular graft with the inner diameter of about 3 mm was prepared from segmented poly (ether urethane) with an extrusion technique. To make the wall of the vascular grafts porous, NaCl salts were added to the polyurethane solution to be extruded and removed with water extraction after evaporating the solvent in the extruded tube. The wall was reinforced with elastic fiber to prevent dilation. The compliance of the vascular graft measured with the method of Hayashi et al. ranged from 0.2 to 0.3% mmHg−1. The initial Young's modulus was close to that of canine carotic artery, to which the porous polyurethane graft 4‐cm long was anastomosed. Vascular grafts were occluded within 2 weeks after implantation, when their pore size was 0, 1.7, or 4.4 m̈m, whereas those with the pore size of 5.5, 7.4, and 30 m̈m were patent for longer than 4 weeks. When the vascular graft with the pore size of 30 m̈m was implanted for 6 months, the luminal surface was covered with neointima, but the endothelium‐like cells appearing in the middle of the intima of the vascular graft were immature and sometimes had a very big nucleus. In addition, spindle‐shaped, modified smooth muscle cells were noticed in the deep layer of the neointima, especially in the tissue where anastomotic intimal hyperplasia occurred. © 1993 John Wiley & Sons, Inc.
Effects of metallic debris on adult bovine articular chondrocyte metabolism in vitro
Authors: Maloney William J. , Castro Frank , Schurman David J. , Smith R. Lane 
Published: May 2005

AbstractThe purpose of this study was to examine the effects of particles, derived from metals commonly used in joint prostheses, on chondrocyte proliferation, metabolism, and morphology in vitro. Chondrocyte viability was influenced by the type and concentration of metal particle added. Cobalt was toxic to chondrocytes at all particle concentrations (0.83–0.000083%, v/v), whereas the chromium, titanium and titanium‐aluminum particles only effected chondrocyte viability at high concentrations. The metabolic response of chondrocytes to particulate debris as assessed by caseinase, collagenase, and hexosaminidase activities were variable at low concentrations but were always reduced at high concentrations (0.83% v/v). Prostaglandin E2 levels in the medium showed a steady increase when particle load increased, except in the medium of chondrocytes exposed to titanium‐aluminum. Scanning electron microscopy of chondrocytes exposed to titanium showed ruffled cell borders and frequent membrane blebbings. This was in contrast to chondrocytes exposed to cobalt, where the crenated appearance indicated cell death, and titanium‐aluminum, where the cells appeared quiescent. These findings show that metal particles alter chondrocyte viability and metabolism and suggest that particulate debris may influence the integrity and stability of articular cartilage following hemiarthroplasty. © 1994 John Wiley & Sons, Inc.
Effects of intermittent micromotion versus polymer particles on tissue ingrowth: Experiment using a micromotion chamber implanted in rabbits
Authors: Goodman Stuart , Aspenberg Per , Song Yong , Regula Donald , Doshi Amol , Lidgren Lars 
Published: May 2005

AbstractBoth micromotion and particulate debris have been implicated in the process of aseptic loosening of joint arthroplasties and the failure of bone ingrowth into porous coated prostheses. In the present study, we compare the histological and histomorphometric results of tissue ingrowth into titanium chambers in the presence of interfacial micromotion versus phagocytosable particles of two polymers used in orthopedic surgery. The micromotion chamber, having a 1 × 1 × 5 mm transverse canal for tissue ingrowth was implanted into the proximal right tibia of five mature male New Zealand white rabbits. In the first series, the chambers were manipulated at 40 cycles per day (cpd) at 1 Hz, using an amplitude of 0.5 mm. The tissue within the chamber was harvested after 3 weeks. In the following series, fabricated particles of bone cement or highdensity polyethylene (HDPE) were mixed with the carrier, 1% sodium hyaluronate (Healon) to obtain a concentration of 108 particles/mL; this solution was implanted in the canal of the chamber but micromotion was not instituted. Histological sections from control, nonmoved chambers, or those implanted with the carrier Healon alone contained extensive trabecular and woven bone embedded in a fibrovascular stroma. The application of 40 cpd resulted in less formation of bone and more fibrous tissue within the chamber. The sections containing particles of bone cement were infiltrated by numerous foamy, mononuclear, and multinuclear histiocytes. HDPE particles were associated with more fibrosis and a less aggressive foreign body response compared to cement particles. Chambers manipulated at 40 cpd and those containing cement or HDPE particles contained less bone compared to nonmoved chambers or those containing Healon alone. Despite evoking different histological reactions, the presence of micromotion or polymer particles appears to inhibit the formation of bone in this experimental model. © 1994 John Wiley & Sons, Inc.
Corrosion and cell culture evaluations of nickel‐chromium dental casting alloys
Authors: Bumgardner J. D. , Lucas L. C. 
Published: May 2005

AbstractIn this study, the corrosion and surface properties of four commercially available nickel‐chromium dental casting alloys, were evaluated using electrochemical corrosion testing and Auger electron microscopy. The corrosion tests were conducted under cell culture conditions of 5% CO2 humidified atmosphere at 37°C in minimum essential medium (MEM) balanced salt solution, 95% MEM–5% FBS (fetal bovine serum) cell culture media, and in 95% MEM–5% FBS media after cold solution sterilization of test samples. The results of the surface and corrosion analyses were correlated to cytotoxicity and metal ion release from the alloys using agarose overlay and direct contact cell culture tests. The surface and electrochemical corrosion analyses demonstrated that the non‐beryllium containing alloys were more resistant to accelerated corrosion processes as compared to the beryllium‐containing alloys. All alloys demonstrated decreased corrosion rates in cell culture solutions after cold solution sterilization treatment. The corrosion products released from the nickel‐based alloys failed to alter the cellular morphology and viability of human gingival fibroblasts, however they did cause reductions in cellular proliferation. The potential for accelerated corrosion and the exposure of local and systemic tissues to elevated levels of corrosion products raises concerns over the biocompatibility of these alloys. © 1994 John Wiley & Sons, Inc.
Inhibition of in vitro calcium phosphate precipitation in presence of polyurethane via surface modification and drug delivery
Authors: Chandy Thomas , Kumar B. Ajith , Sharma Chandra P. 
Published: May 2005

AbstractBiomaterial associated calcification is the principal cause of the clinical failure of bioprosthetic implants. The present investigation describes the mineralization of polymeric substrate in an extracirculatory environment and the possible methods of prevention. Calcification was examined on various polyurethane films (and bioprosthetic tissue) incubated in metastable solutions of calcium phosphate and the role of polymer casting and precipitation was evaluated. The formulation and the in vitro efficacy of prolonged controlled‐release chitosan matrices, containing the novel anticalcification agents, such as Fe+++ or protamine sulfate (PS), were also attempted. The in vitro release profiles of PS from chitosan beads was performed in a rotating shaker (100 rpm) in 0.1 M phosphate buffer (pH 7.4) and was monitored spectrophotometrically. The amount and percentage of drug release were much higher initially, which was controlled with the incorporation of egg phosphatidyl choline (EPC). The PS loaded chitosan beads (coincubated in calcium phosphate solution with the calcifiable polyurethane films) significantly inhibited biomaterial calcification (about 40–50% inhibition). Surface modification of polyurethanes with Fe+++ or PS also inhibited the calcification profile of the material. These findings suggest the possibility of a combination therapy for prevention of biomaterial associated calcification via surface modifications in conjunction with long‐term controlled release of the anticalcifying drugs. © 1994 John Wiley & Sons, Inc.