bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of three formulations of a synthetic foam as models for a range of human cancellous bone types
Authors: Szivek John A. , Thompson Joel D. , Benjamin James B. 
Published: May 2005

AbstractPorous polyurethane foams were prepared from Daro foam components with a range of mechanical properties to simulate human trabecular bone. Ratios of 10.0:5.0, 10.0:7.9, and 10.0:10.0 isocyanate to resin were mixed, cured, and cut into cubes. Properties were determined from uniaxial compression to 50% of the original cube height at a strain rate of 1.2 mm/s. Electron microscopy was used to characterize the foam structure. Average compressive yield stress values, ultimate compressive stresses, and elastic moduli ranged from 4.44 to 2.79, 5.61 to 3.28, and 134.0 to 110.1 MPa, respectively, for the three formulations. The foam materials showed a similar morphology of spherical bubbles, and the average bubble size tended to decrease as the ratio of isocyanate to resin increased even though the bubble size differences were not statistically significant. The results indicate that large blocks of foam can be prepared with consistent mechanical properties simulating a range of trabecular bone properties so that implants can be tested for various patient populations. © 1995 John Wiley & Sons, Inc.
Educational goals for biomaterials science and engineering: Prospective view
Authors: Von Recum Andreas F. , Laberge Martine 
Published: May 2005

AbstractThe research field of biomaterials and surgical implants has matured to a point suggesting that a formal and comprehensive education is now required to handle all professional issues related to biomaterials and implant development. A professional curriculum is proposed for a discipline of biomaterials science and engineering on a graduate level. The curriculum includes the definition of an essential knowledge base and describes two track options for a study period of 3 years. Lists of prerequisites as well as required and suggested courses are presented and discussed. Continuing education courses are presented as examples. A quick vision of the immediate future of the field enforces the need for biomaterials professionals to take the lead in bringing the field into the next century. © 1995 John Wiley & Sons, Inc.
Nucleation and mineralization of organic matrices
Authors: Walton A. G. , Friedman B. A. , Schwartz A. 
Published: May 2005

AbstractFeatures controlling the initiation of matrix calcification have been investigated in a model system. Two major influences which dominate nucleation are the matrix integrity and the location of certain chemical binding sites. It has been shown that chemical chelating groups can, and do, promote calcification under simulated physiological conditions. Organically bound phosphate does not appear to promote nucleation, suggesting that it is chelation of calcium or other cations which is the initial step in tissue calcification. In the sequence of compounds investigated for nucleation catalysis, those possessing at least three chelating groups and a stereopsecific configuration were effective. The mineral phase forming first in association with the organic matrix is a soft non‐apatitic calcium phosphate of Ca/P ratio approximately 1.5. This is the same phase that forms in the absence of organic matrices at physiological pH and is probably the precursor to hydroxyapatite in biological calcification. It is suggested that nucleation catalysts exist both within and outside the collagen fibrillar framework. A possible location of the internal site has been proposed, based on the availability of a capillary channel and chelating ligands, and this postulate is supported by electron microscopic evidence which shows that bone crystals lie within the fibrils, occupying space which terminates in the polar 640 A staining area.
Effect of varying electrolyte concentration on in vitro streaming potentials across canine aortae and carotid arteries
Authors: Srinivasan S. , Burrowes C. B. , Lucas T. , Bauer S. B. , Sawyer P. N. 
Published: May 2005

AbstractKnowledge of the characteristics of the blood–intima interface is important because it leads to information concerning (a) the normal antithrombotic mechanism (b) nature of interreactions between blood and intima (c) testing and selection of vascular wall substitutes which are antithrombotic and inhibit clotting. A technique for obtaining the electrical interfacial characteristics of blood vessel walls is by measuring streaming potentials. Experiments described in the present work are extensions of original in vivo streaming potential measurements. In vitro streaming potentials were measured across fresh canine aortae and carotid arteries using Krebs saline serum substitute, logarithmically varying both internal and external electrolyte concentrations. Positive streaming potentials were measured indicating that the blood vessel wall is negatively charged. Streaming potentials increased linearly with increasing flow rate, decreased with increasing internal electrolyte concentration, decreased with increasing external electrolyte concentration, and reversed, becoming positive, with aging of exteriorized artery. Thus the electrical characteristics of the blood vessel wall are dependent on an ionic balance between the blood vessel wall, flowing blood stream, and external environment. The information demonstrates the importance of electrochemical and physicochemical phenomena in the structure and function of the vascular interface and helps explain in vivo conditions conducive to or inhibitory of intravascular thrombosis.
Metallurgical analyses of failed orthopedic implants
Authors: Cahoon J. R. , Paxton H. W. 
Published: May 2005

AbstractSeveral metallic orthopedic implants which failed in service and for which the medical histories are known are comprehensively examined using metallographic techniques and electron microprobe analyses to determine the causes of failure. The results indicate that fatigue is a major cause of failure and that, in all probability, the fatigue is initiated by poor design or poor material.
Utilization of polyelectrolyte complexes in biology and medicine
Authors: Markley Lita L. , Bixler Harris J. , Cross Robert A. 
Published: May 2005

AbstractPolyelectrolyte complexes are ionic hydrogels formed by the coreaction of two oppositely charged, strongly ionized polyelectrolytes. While insoluble in simple solvents and infusible, these polymers can be fabricated into membranes, fibers, and other shaped articles by casting from ternary solvents. Homogeneous membranes are optically clear, amorphous structures in which the equilibrium gel water content can be controllably varied from ca. 30–90%. The net ion‐exchange capacity of the membrane can be varied from zero to ca. 2.0 meq/g, either cationic or anionic. Homogeneous membranes are characterized by unusually high water and gas permeabilities and permeabilities to water and soluble solutes which can be controlled by adjustment of gel water content and ion‐exchange capacity. Anisotropic membranes can also be prepared which are high flux molecular ultrafilters for solutes as small as sucrose. The anisotropic membranes have found widespread use in biology for fractionation, concentration, and purification of biopolymers. Homogeneous membranes show promise as analogues for biological membranes. A number of applications are being evaluated in medicine and surgery. These include: vascular grafts, antithrom‐bogenic coatings for plastic prostheses, contact lenses, corneal implants, and surgical adhesives. In addition, polyelectrolyte complex membranes are showing considerable promise for artificial kidneys and blood oxygenators.
Implant testing of polymerizing materials
Authors: Roydhouse Richard H. 
Published: May 2005

AbstractAn implant test, in which 0.3–0.5 g of solidifying or polymerizing material was injected into the belly wall of rats, was used to compare the tissue reactions to four materials. A histological survey was made of the tissue reactions to stainless steel pins, zinc oxide–eugenol mixtures, cold‐cure acrylic resin, silicate dental cement, and to a polymer–filler system (dental restorative). The irritant effects of the implant on the fibrous encapsulation about these foreign bodies were used to assess the toxicity of the material. Implanted stainless steel pins acted as a control for comparison. Zinc oxide–eugenol and silicate cement produced necrosis when injected in the mixed but unset state; the irritation continued for 30 days after implantation and was sufficient to impede fibrous encapsulation. Fibrous encapsulation about injections of cold cure acrylic resin and an experimental composite of polymer and filler occurred 5 days after similar encapsulation about implanted stainless steel implants. The inclusion of a relatively inert filler decreased the initial reaction to a monomer–catalyst mixture.
The determination of tear energy of extensible materials of dental interest
Authors: Webber Richard L. , Ryge Gunnar 
Published: May 2005

AbstractThe clinical performance of somatoprosthetic materials and some elastic impression materials has been related to their resistance to tearing. In most instances, the test method used has been tear strength determinations, many of which are notoriously sensitive to variations in specimen geometry. It has been shown that the energy per unit area of new torn surface is independent of specimen geometry. Two relatively simple equations were found to determine the probable range of energies involved in tearing standardized trouser‐shaped specimens regardless of the elastic properties of the materials tested. The energies so obtained for three highly extensible materials were found to be relatively independent of specimen geometry within the unstretched limits specified by ASTM test No. D 1938–62T. It is, therefore, concluded that a modification of Greensmith's trousers method for determining tear energy can be conveniently applied to extensible materials of dental interest.
Influence of acid‐treated Ag3Sn on the tensile strength and fracture of dental amalgam
Authors: Young F. A. , Wilsdorf H. G. F. 
Published: May 2005

AbstractA dilute HCl wash of Ag3Sn powder results in a dental amalgam exhibiting 20% higher tensile strength. It was found that the fracture propagation paths in treated and untreated specimens were different.The support of the National Institute of Dental Research under Grant No. DE‐30233 and Program Project DE‐02111 is gratefully acknowledged.
Antithrombogenic cellulose film
Authors: Britton R. A. , Merrill E. W. , Gilliand E. R. , Salzman E. W. , Austen W. G. , Kemp D. S. 
Published: May 2005

AbstractA careful solvent‐exchange procedure followed by liquid‐phase reaction of ethyleneimine with cellulose film in a nonpolar solvent provides an effective method of uniformly aminoethylating cellulose. The protonated aminoethyl groups on the cellulose can then ionically bind heparin, a blood anticoagulant. Heparinized aminoethylated cellulose tubing at low levels of aminoethylation (ca. 0.2–0.3% nitrogen) exhibited excellent antithrombogenic properties as well as excellent mechanical strength properties. The in vitro tests demonstrated indefinitely long whole‐blood clotting times with normal thrombin times. In the in vivo experiments, the heparinized aminoethylated cellulose tubing provided extended patency when implanted intravascularly in the regions of low blood flow rate (infra renal inferior vena cava of dogs). A principal use of this film is in the artificial kidney.
Fiber metal composites in the fixation of skeletal prosthesis
Authors: Galante Jorge , Rostoker William 
Published: May 2005

AbstractTo serve as a component of a load‐bearing skeletal prosthesis, a porous material should offer the following attributes: (1) pore channels over 100μ in diameter; (2) continuity of pore channels; (3) matrix material inert and compatible with animal tissues; (4) manufacturable as thick coatings or thin‐walled complex surface assemblies; (5) manufacturable to precision dimensions; (6) large compliance comparable to bone; (7) crack resistance, particularly under impact.A porous composite was manufactured by molding and sintering short metal fibers, which fulfilled all of these requirements. The composite was manufactured both with titanium and Vitallium fibers.Experimental implants were performed in dogs and rabbits indicating peripheral bone formation around the implant at 2 weeks and penetration from 3 weeks on. Shear strength values at the prosthesis‐bone interface were in the range of 20 kg/cm2 3 weeks after implantation.Femoral prostheses implanted in dogs revealed fixation by bone formation and maintenance by bone ingrowth up to 1 yr following implantation.Massive incorporation with bone of skeletal segmental replacements for the baboon's femur were seen up to 3 months following implantation.Practical problems that can be encountered with the use of porous fiber metal composites for prosthesis fixation relate to: (1) the possibility of long‐term corrosion occurring in an implant with a very large surface area; (2) technical problems with implantation requiring intimate contact between the fiber metal surface and the bone and (3) the difficulties in removing an implant which has failed for mechanical reasons requiring that a device manufactured using fiber metal composites for fixation be absolutely failure free from a mechanical viewpoint.
Biomechanical investigations of bone‐porous carbon and porous metal interfaces
Authors: Nilles J. L. , Lapitsky M. 
Published: May 2005

AbstractThe mechanical strengths of four types of ingrown porous carbon and two types of porous metal bone implants were correlated with the type of osseous ingrowth into the porous interfaces. Intracortical cylinders were implanted into canine long bones and examined at 3, 6, and 12 weeks. Histological techniques were used to study bone ingrowth. Tetracycline labelling and electron microprobe analysis were used to characterize the degree of mineralization of the ingrowth. Shear strengths of bone‐porous material interfaces were measured on cylinders forced out in compression. Histology revealed readily identifiable bone in most porous specimens. Mineralization was found to various depths in all porous specimens. After ingrowth, the porous metals, possessing appreciable inherent strength, displayed interfacial shear strengths from one‐third to two‐thirds that of cortical bone. The very porous carbon lattices, possessing little inherent strength, developed interfacial strength after ingrowth approaching that of the ingrowing cortical bone. The less open, more rigid porous carbon implants developed smaller interfacial strengths, averaging between one‐eighth and one‐half that of the ingrowing cortical bone.
Glassy carbon: A potential dental implant material
Authors: Hucke E. E. , Fuys R. A. , Craig R. G. 
Published: May 2005

AbstractThe carbonization of certain polymers under carefully controlled conditions yields glassy carbon bodies which may have potential application in the dental profession. Considerable evidence is now available for the good compatibility of a variety of carbonaceous materials with tissue and bone. Many carbons remain relatively inert in the human environment compared to metals and polymers. Disordered carbons with strengths exceeding that of graphite are commercially available with elastic modulus in the same range as that reported for bone(∼3 × 106 psi). The object of this study was to determine mechanical properties and characterize the structure of a new porous glassy carbon material.Compressive and tensile strength data were obtained for carbon samples with a wide range of pore structures. A scanning electron microscope and a mercury porosimeter were used to observe variations in pore structures. The porous materials tested exhibited compressive strength values up to 48,000 psi and ultimate tensile strength values up to 7,500 psi. Sonic modulus values from 1 to 4.6 × 106 psi have been measured. Some carbon samples had interconnected porosity exceeding 50% and median pore diameters greater than 50 μ. Material with an interconnected mean pore size as small as 46 Å has also been produced. Preliminary animal implant studies are in progress.
Orthopedic implants—a clinical and metallurgical analysis
Authors: Weinstein A. , Amstutz H. , Pavon G. , Franceschini V. 
Published: May 2005

AbstractA study of metallic implants consecutively removed from 133 patients at the Hospital for Special Surgery during a 2‐year period was conducted to evaluate their performance. They had been implanted for 2 weeks to over fifteen years. The implants studied consisted of prostheses and internal fixation devices used for open reduction of fractures or immobilization of osteotomies. The implants had been fabricated from either stainless steel or cobalt‐chromium alloys.Case histories and roentgenograms were reviewed. A detailed inspection of each implant was performed including failure analysis when required. Crevice or fretting corrosion was noted on all but one stainless steel implant of the plate and screw type, and to a lesser extent with the cobalt‐chromium alloy implants. Extreme wear was noted on contact areas of articulating prosthetic components made of cobalt chromium alloy. Complete mechanical failures of internal fixation devices were attributable to fatigue, design deficiencies or misuse of the implant. These findings are discussed in light of the clinical results.
The measurement and effects of friction and wear in artificial hip joints
Authors: Walker P. S. , Salvati E. 
Published: May 2005

AbstractThe two systems for artificial hip joints in use at present are metal‐on‐metal and metal‐on‐plastic. There are many variables affecting friction and wear, which include diameter, sphericity, relative geometry of the components, and surface roughness. Tests in a simulating machine incorporated cyclic load and motion. Frictional torque of metal‐on‐plastic joints increased with diameter; Charnley 22 mm diameter producing lowest friction. For metal‐on‐metal the contact situation produced variable results, but friction was higher than for the plastic joints. Reciprocating friction machine tests suggested that high molecular weight polyethylene and AP4 polyester gave low friction and wear. Vitallium gave at least three times the friction of the plastic using γ‐globulin solution as lubricant; but wear appeared to be much less.
Biological activity and histocompatibility of dense Al2 O3/MgO ceramic implants in rats
Authors: Griss Peter , von Andrian‐Werburg Hans , Krempien Burghard , Heimke Gunther 
Published: May 2005

AbstractThree types of dense alumina oxide ceramic (Al2O3) 99.7%, MgO 0.3%; density more than 3.9 g/cm3 differing only in their average grain size (5–15μ) and stainless steel (V4A) plates were implanted into the left femur of male Wistar rats 6 months old. Light and scanning electron microscopic techniques were used to investigate tissue reaction and the ceramic surface. Both ceramic and stainless steel plates were surrounded by a soft tissue layer that differed greatly depending on the implant type in respect to the fiber/cell ratio. While the body tended to enclose the metal plate with a small more or less avascular tissue mostly composed of fibers and some inactive fibrocytes, around the ceramic implants a highly cellulated soft tissue of mesenchyme character developed with signs of osteoblast and chondrocyte metaplasia. Adjacent to this mesenchyme a dense cuff of newly formed woven bone arose, showing numerous active osteocytes. Both metaplastic tendency of the newly formed messenchyme and osteocyte activity in the surrounding bone did not decrease remarkably towards the end of the experiment (70 weeks after operation), while the tissue around metal implants reached a steady relatively reactive state 12–24 weeks after operation. Intimate ceramic surface‐mesenchyme contacts without foreign body reactions supported the idea that alumina oxide ceramic tends to be incorporated into the body's physiological environment while metals are “excluded” by fibrous tissue layers of low biological activity. Corrosion on the ceramic surface was not detectable.
Platelet adhesion onto microcapsule membranes with different degrees of sulfonation
Authors: Muramatsu Nobuhiro , Kondo Tamotsu 
Published: May 2005

AbstractMicrocapsules having different numbers of sulfonic acid groups on their surfaces were prepared by the interfacial polycondensation method. Platelets adhered to these capsules, and the rate and degree of platelet adhesion were found to be remarkable on those microcapsules that had high surface charge compared to those with low surface charge. This trend was strengthened by the coating of the capsules with plasma, while the electrophoretic mobilities of the plasma‐coated capsules showed a considerable reduction and no appreciable difference between the respective mobilities could be observed. This trend suggest that the adsorption of plasma components on microcapsules, and not their surface negative charge, affected platelet adhesiveness directly. In connection with the glycosyl transferase hypothesis, the adsorption pattern and its effect on platelet adhesion of albumin, γ‐globulin, and fibrinogen were examined. The protein adsorption pattern varied depending on both the type of protein and the magnitude of negative charge on the microcapsule surface, but its effect on platelet adhesion was not fully consistent with the glycosyl transferase hypothesis. It was concluded from the findings that the surface negative charge of the capsules strongly affected the composition, molecular orientation, and/or configuration of the adsorbed plasma components, which probably induced the differences in platelet adhesiveness depending on the magnitude of surface negative charge of the microcapsules.
Polyester prostheses as substitutes in the thoracic aorta of dogs. I. Evaluation of commercial prostheses
Authors: Guidoin R. , Gosselin C. , Martin L. , Marois M. , Laroche F. , King M. , Gunasekera K. , Domurado D. , Sigot‐Luizard M. F. , Blais P. 
Published: May 2005

AbstractUsing canine models, a representative selection of polyester or Dacron vascular prostheses, including woven, knitted, and velour types, were evaluated for their relative healing characteristics and for their structural changes during implantation. Following residence periods ranging from 4 h to 6 months at the site of the thoracic aorta, the dogs were sacrified, and the grafts were excized for measurement of the thrombogenicity of the flow surface and for pathological examination by light microscopy and SEM. The kidneys were also removed and examined for infarcts caused by any trapped circulating emboli. The extent of healing, the presence of embolizing nuclei, and the thrombogenicity and morphology of the lumen surface were also assessed. The healing characteristics of each type of device proved similar. Velour fabrics exhibited more extensive encapsulation, but frequently their internal capsules failed to incorporate all the fibers. In all cases, cellular development on the lumen was limited to areas contiguous to the anastomoses. The initial porosity of the devices as measured by water permeability did not appear to influence the healing sequence to a significant extent. The grafts did exhibit differences in structural stability depending on whether they were of a knitted or woven construction. We suggest that users consider these different mechanical and structural properties when making their choice of a graft. Despite these differences, we believe that the healing process is far more host dependent than graft dependent.