bluuebunny/crossref_metadata_2025_split huggingface dataset:
The bone–metal interface following hip nailing
Authors: Cameron H. U. , Fornasier V. L. 
Published: December 2004

AbstractIn order to establish a base line for tissue reaction in relationship to loaded implanted foreign materials that might be used for comparison with new materials, the interface between the trabecular bone in the femoral head and hip nails has been studied in 20 specimens.The interface consists of four distinguishable layers: a cellular layer at the surface, a layer of fibrovascular connective tissue, a layer of collagenous connective tissue and/or fibrocartilage, and a peri‐implant bone plate. Even 10 years after insertion of the nail this interface remained cellularly active, the activity presumably being related to the different modulus of elasticity between the metal and the surrounding trabecular bone.
Mechanical strength of acrylic bone cements impregnated with antibiotics
Authors: Lautenschlager E. P. , Marshall G. W. , Marks K. E. , Schwartz J. , Nelson C. L. 
Published: December 2004

AbstractAdmixing of several antibiotic powders which were insoluble in methyl methacrylate did not decrease the compressive and diametral tensile strengths of two acrylic bone cements when tested after setting for 1 day and after leaching 40 days in water at 37°C. When antibiotics were added as water solutions, the included water resulted in a significant decrease in these bulk mechanical properties.Storage in water for 40 days caused surface irregularities only on specimens of the set antibiotic admixtures. Approximately 0.5% of the admixed dosage of these water‐soluble antibiotics could be leached from the set cements. The observed surface channels, presumably left by the loss of antibiotic, suggest further study of surface‐sensitive mechanical properties may be needed.The bulk mechanical strengths presented here are conclusive only for the particular combinations of antibiotics and cements investigated, and should not be generalized at this time to any or all antibiotic admixtures or other mechanical properties.
Further experimental and clinical experience with aluminum oxide endoprostheses
Authors: Salzer M. , Zweymüller K. , Locke H. , Zeibig A. , Stärk N. , Plenk H. , Punzet G. 
Published: December 2004

AbstractThis paper describes the design principles of a new endoprosthesis made of dense aluminum oxide (Al2O3) and implanted without bone cement. Mechanical tests and animal experiments have proved the sufficient mechanical strength of the bone–prosthesis connection as well as the biocompatibility of the material. So far, 12 tumor patients selected according to strict indication criteria have been operated on. Both the clinical–radiologic and the first histological findings available are encouraging. Special reference is made to the first fully ceramic total hip joint endoprostheses implanted in a human without bone cement.
Interactions of synthetic and natural surfaces with blood in the physiological environment
Authors: Bruck Stephen D. 
Published: December 2004

AbstractEfforts to explain blood compatibility with synthetic and natural surfaces based on a single parameter or a single biological test procedure have either been unsuccessful or led to misleading generalizations. The problem reflects the complex interdependence between material's properties, the composition and properties of blood, and in vivo biorheological conditions. Among the initial events that occur when materials contact blood is the very rapid adsorption of plasma proteins; this process effectively influences the subsequent interactions with the formed blood elements, especially the platelets with the proteinated surfaces.In the case of natural surfaces, when the endothelium is damaged, collagen may become exposed that may cause the activation, adhesion, and aggregation of platelets leading to thrombosis. Current evidence indicates that the platelet‐aggregating ability of collagen depends on its “multimeric” or fibrillar structure, rather than on the activation of the platelet‐bound enzyme system. Under normal conditions, the flowing blood is probably not in direct contact with endothelial cells that line the blood vessel walls, but with an adsorbed layer of plasma proteins. Should a formation of a multilayer of plasma proteins occur following the initial adsorption of a monolayer, this process could be influenced by changes in the solubility of the proteins, especially fibrinogen, the solubility of which is quite low in plasma. The hypothesis is proposed that such changes may be intimately related to the electrical properties of proteins present in the vascular wall and in blood. It is possible that these properties play a much greater role in thrombogenesis and in the problem of blood compatibility than is currently appreciated.Considering synthetic polymers, a number of these have been prepared that exhibit little adverse effects on blood components and, at the same time, retain their physical properties for various periods of time in the physiological environment. These combined biological and physical properties make them useful for various prosthetic and other biomedical applications in surgery and therapy.
Effects of polymer surface molecular structure and force‐field characteristics on blood interfacial phenomena. I
Authors: Nyilas E. , Morton W. A. , Cumming R. D. , Lederman D. M. , Chiu T.‐H. , Bailer R. E. 
Published: December 2004

AbstractTo quantify the effects of major surface structural factors influencing interfacial reactions induced by polymers in native blood, model surfaces of solvent‐cast films of two analogous poly (ether urethanes) and three homologous polyamides (nylon 4, 6/6, and 12) were exposed ex vivo to canine blood under the well‐defined hemodynamic conditions of the Stagnation Point Flow Experiment. The selected surfaces allow for incremental changes in properties and were characterized by their “Composite Surface Free Energy Function,” γ′s, which describes the surface force field as the sum of the mean dispersion (\documentclass{article}\pagestyle{empty}\begin{document}$ \bar \gamma $\end{document}sd) and polar (\documentclass{article}\pagestyle{empty}\begin{document}$ \bar \gamma $\end{document}sp) contributions and is computed from wettability spectra obtained with ultrapure diagnostic liquids. Blood interfacial effects were measured by the shear‐limited diameter of the white cell circle formed around the stagnation point, the flow parameter at which symmetric aggregation occurred, and the surface‐number density of platelets, [Ps], remaining adherent under fixed conditions. At identical flows, within each group of polymers, both the WBC‐circle diameter and [Ps] scale with \documentclass{article}\pagestyle{empty}\begin{document}$ \bar \gamma $\end{document}sp/γ′s, implying that (1) only the magnitude but not the interaction mechanism varies as a function of incremental structural and surface changes, (2) the primary determinant of surface‐induced effects is the polar force contribution, and (3) the magnitude of γ′s is secondary if \documentclass{article}\pagestyle{empty}\begin{document}$ \bar \gamma $\end{document}sd/γ′s is sufficiently great.
On the fate of methyl methacrylate in blood
Authors: Rijke A. M. , Johnson R. A. , Oser E. R. 
Published: December 2004

AbstractThe fate of methyl methacrylate in fresh human blood was investigated in vitro by using gas chromatography. It was found that methyl methacrylate is present in cells in concentrations twice as large as in plasma, but it disappears exponentially with time at a rate that is at least 10 times faster than that in cells. The rate constant in cells is very small or even zero. The half‐life of methyl methacrylate in whole blood is 3 hr at 20°C. Gas chromatography is a convenient method for the rapid determination of methyl methacrylate levels in blood.
Inhibition and enhancement of platelet aggregation by collagen derivatives
Authors: Kay W. W. , Kurylo E. , Chong G. , Bharadwaj B. 
Published: December 2004

AbstractRat tail tendon tropocollagen rapidly caused the aggregation of blood platelets coincident with collagen multimerization. Several long‐chain alkyl derivatives of collagen, however, were completely unable to induce platelet aggregation even at unusually high concentrations. These collagen derivatives varied in their polymerization properties, and the polymerization of tropocollagen derivatives was shown not necessarily to be a prerequisite for platelet aggregation. These collagen derivatives may enhance the antithrombogenic properties of collagenbased prostheses. A short‐chain derivative, collagen‐glycine ethyl ester, profoundly enhanced platelet aggregation in the absence of any measurable polymerization. This derivative may be useful as a growth‐promoting burn dressing.
Membrane permeability for inorganic phosphate ion
Authors: Moise O. , Sideman S. , Hoffer E. , Rousseau I. , Better O. S. 
Published: December 2004

AbstractThe need for a more efficient removal of inorganic phosphate ions from the blood of uremic patients has led to the quest for blood‐compatible semipermeable membranes with a high permeability for phosphate ions. Commercial hemodialysis membranes, various hydrogel‐type membranes and a number of collodionbased charged membranes were compared. Positively charged collodion membranes were found most promising for future application in hemodialysis or hemoperfusion systems.
A study of the corrosion of dental amalgam using the ring‐disk electrode
Authors: Gal‐Or Leah , Bruckenstein Stanley , Carter J. M. 
Published: December 2004

AbstractThe rotating ring‐disk electrode technique has been applied to the study of anodic dissolution of dental amalgam in a simulated saline solution.The electroactive domains of the silver, tin, and mercury couples (the main constituents of the amalgam) were determined from current–potential curves obtained at a rotating gold‐disk electrode in solutions containing salts of the respective metals. Subsequently, anodic currents were applied to a rotating amalgam‐disk electrode and the soluble products produced were identified using a concentric gold ring electrode, i.e., using the rotating gold‐ring, amalgam‐disk electrode. Species generated at the amalgam disk are transferred to the gold ring by convective diffusion. Tin ions were found to be the only soluble species generated at the amalgam disk. No evidence for dissolution of other components was found. The selective dissolution of tin from the amalgam is also consistant with potential shifts observed in repetitive current‐potential curves of an amalgam disk.This study provides a direct proof for the selective dissolution of tin during corrosion of dental amalgam in an in vitro environment.
Biocompatibility testing of polymers: In vivo implantation studies
Authors: Gourlay Stuart J. , Rice Robert M. , Hegyeli Andrew F. , Wade Clarence W. R. , Dillon James G. , Jaffe Howard , Kulkarni R. K. 
Published: December 2004

AbstractAn in vivo method is described for screening polymeric materials for biocompatibility. The test is based on grading acute and subacute tissue reactions at 7 and 28 days, respectively, following implantation in rats. The method is reproducible and reliable. It is designed to provide uniform test criteria for biocompatibility assessment in the early phases of the development of surgical implant materials.
Surface finish of dental composite restorative materials
Authors: Tolley L. G. , O'Brien W. J. , Dennison J. B. 
Published: December 2004

AbstractFive composite filling materials were finished using six finishing procedures currently in clinical use. The average roughness produced by each procedure was measured by means of a Surfanalyzer with four replications for each procedure on each of the five materials. Statistical analysis indicated that finishing with silicon carbide disks produced the smoothest surfaces. Acceptable surfaces were obtained with stones or with burs. Use of an alumina paste after a green stone‐white Arkansas sequence did not produce a significant improvement.Two processes of filler particle abrasion were distinguished by means of electron microscopy: wear and shear. Fracture striations indicated particle shear.The roughest surfaces were produced by the use of a diamond instrument which is contraindicated. Acceptable finishing procedures for the composite materials tested include silicon carbide disks for accessible areas or 12 fluted finishing burs for more inaccessible areas.
Strength of a dense alumina ceramic after aging in vitro
Authors: Krainess F. E. , Knapp W. J. 
Published: December 2004

AbstractRods of dense alumina ceramic were aged in Ringer's solution for time periods up to 12 weeks, with half of the rods being aged while mechanically stressed. Pyrex‐type glass rods were similarly tested for comparison purposes. No reduction in flexural strength was observed in dense alumina rods after aging, providing no permeation of the solution into the ceramic occurred. However, a marked reduction in flexural strength was experienced by alumina rods, nominally dense and nonporous, into which some permeation of the saline solution was observed after aging; the largest reduction in strength occurred in such rods aged while mechanically stressed. The results indicate the importance and advantage of using densely sintered alumina ceramics as implants for optimum structural performance over an extended time period.
Tissue reaction to ceramic implant material
Authors: Harms J. , Mäusle E. 
Published: December 2004

AbstractThe biocompatibility of alumina ceramic was tested by means of macrophage cultures, intraperitoneal (i.p.) and intramuscular (i.m.) application of powdered particles in rats, and by implantation of solid samples in the paravertebral muscles and the condylus of femur. No acute cytotoxicity was found in macrophage cultures. The i.p. and i.m. application of powdered particles in the beginning showed a granulocytic reaction, later followed by a histiocytic reaction. Also, the morphological changes in the organs of reticulo histiocytic system (RHS) are shown. In the solid sample implantation, the fibrogenetic stimulus is measured by morphological analysis of the connective tissue membrane around the sample. The importance of the individual cell observation by transmission‐electron microscope (TEM) examination is evidenced. The experimental results are compared to the environmental reaction of smaller animal‐adapted prostheses and prostheses having been implanted in human patients. Good biocompatibility is confirmed by these investigations; also regarding central position of the macrophages, the environmental reaction due to implant material is shown.
In vitro evaluation of hemolytic and cell culture toxicity potential of residual ethylene oxide in selected medical materials
Authors: Jones Alan B. 
Published: December 2004

AbstractThe hemolytic potential of pure ethylene oxide in solution was evaluated as a function of initial ethylene oxide concentration in three test systems, diluted whole blood in isotonic saline, erythrocytes washed and resuspended in isotonic saline, and erythrocytes washed and resuspended in isotonic phosphate buffer. Concentrations of 2 mg/ml (2000 ppm) were necessary before cell lysis was observed in either of the isotonic saline systems. This value increased to 10 mg/ml (10,000 ppm) in the isotonic buffer system. Efforts have been made to correlate the hemolysis and cell culture toxicity of residual ethylene oxide in five medical materials to the toxicity of pure ethylene oxide. Only materials exhibiting a low order of inherent toxicity showed any correlation. In poly(vinyl chloride) tubing containing 1.8 and 2.1 mg ethylene oxide per gram of materials, a small amount of toxicity was seen in the cell culture system but toxicity was absent in the hemolysis test.
Mechanical properties of antibacterial silicone rubber for hydrocephalus shunts
Authors: Van Noort R. , Bayston R. 
Published: December 2004

AbstractIn an effort to find a solution to the serious problem of bacterial colonization of cerebrospinal‐fluid shunting devices, room‐temperature and heat‐vulcanizing silicone rubbers were impregnated with gentamicin sulphate. The effects on the mechanical properties of the two rubbers were studied. Results show that the tensile strength and extensibility of the room‐temperature‐vulcanizing silicone rubber reduced with increasing concentration of the drug. For the heat‐vulcanizing silicone rubber, the tensile strength was also found to decrease with increasing drug content. The extensibility after an initial reduction at low concentrations was found to increase at drug concentrations in excess of 10 mg/g. Nevertheless, the changes in mechanical properties measured are considered not to be so great as to preclude the application of drug‐impregnated silicone rubbers to cerebrospinal‐fluid shunting devices.
Influence of cold working on fatigue behavior of stainless steels used for prothesis: Application to the study of wires with small sections
Authors: Coquillet B. , Vincent L. , Guiraldenq P. 
Published: December 2004

AbstractOrthodontists mainly use stainless austenitic wires with a wide range of ultimate tensile strength. To characterize the dynamical behavior of these wires, the authors have perfected machines to test materials with their original surface roughness without any prior machining of surfaces. Fatigue limits are discussed through mechanical and structural properties of the austenitic steels, with special attention given to cold working. Typical features of fracture, and particularly of the first cracks, are shown by means of scanning electron microscopy.
Platelet interaction with synthetic copolypeptide films
Authors: Solomon D. D. , Cowan D. H. , Anderson J. M. , Walton A. G. 
Published: December 2004

AbstractKinetic and equilibrium studies of blood platelet binding to copolypeptide films show that attachment and serotonin release are not dependent upon the composition of the copolypeptide. Data may be explained by postulating that platelets frequently collide elastically with the surface but leave behind material that modifies subsequent behavior. Similarly, material released from platelets adsorbs at the interface and the extent of attachment and serotonin release are modified and controlled by these adsorbed species. Basically, if the platelet is exposed to a clean surface, its collision with the surface leads to activation and release. In the presence of inert protein, the collision is cushioned by the protein and platelets do not attach or release to any extent. Finally, if protein (or other entities) released from the platelet provide attachment sites, than attachment occurs without release. It is postulated that the behavior of platelets at surfaces is controlled by these interrelated processes.
Trituration and creep
Authors: Rehberg H. J. , Gramberg U. 
Published: December 2004

AbstractGreep values of amalgam have been thought to be typical and nearly equal to their order of magnitude, depending on composition and particle shape. Recently it has been shown that trituration time may cause changes in creep magnitudes. The type of mixer and its frequency have contributed additional variabilities. These variations could not be related consistently to changes in creep values. Increases in condensation pressure did contribute to more predictable and constant values found with different mixing times.
Performance analysis of total hip prostheses: Some particular metallurgical observations
Authors: Ducheyne Paul , De Meester Paul , Aernoudt Etienne 
Published: December 2004

AbstractMetallurgical observations of phenomena which influence the clinically successful performance of permanent implants and implant materials are reported. The effect of casting voids in cast cobalt chromium femoral stems of total hip replacements is discussed first. Pitting corrosion occurred in a retrieved stainless‐steel implant type AISI 316 containing 2.7% Mo. The fractographic pattern of this device retrieved for fatigue failure shows typical characteristics of corrosion‐enhanced fatigue.
Synthesis of a fine neurological electrode by plasma polymerization processing
Authors: Cannon J. G. , Dillon R. O. , Bunshah R. F. , Crandall P. H. , Dymond A. M. 
Published: December 2004

AbstractThis research is part of a continuing program for the development of a coaxial depth electrode for research and diagnostic studies of neurological diseases. The requirements for this electrode include (1) strength and resistance to buckling sufficient to ensure self‐forced penetration of brain tissue to a depth of 6 cm; (2) biocompatibility of the materials employed; (3) resistance to brittle fracture; and (4) a total diameter of less than 200 μm to minimize tissue damage. Earlier synthesis efforts using chemical vapor deposition techniques have been successful, although the process yield was 40% and an outer insulating layer had yet to be deposited. Plasma polymerization processes have been employed to realize an increase in the yield and provide an outer insulating layer. The starting material is W‐26 at.% Re wire, nominally 125 μm in diameter. Hexamethyldisilazane (CH3)3SiNHSi(CH3)3 is used to deposit the insulating layers. The paper describes factors influencing the choice of materials, deposition techniques, and properties of electrodes.
The flow properties of dental cements
Authors: Wilson Alan D. , Lewis Brian G. 
Published: December 2004

AbstractThe flow properties of several major types of dental cements were investigated using slow compressive strength and creep techniques. Considerable differences were found in their behavior. Whereas the phosphate‐bonded and glass‐ionomer cements exhibited brittle fracture, the other cements tended to distort to a greater or lesser extent under load. All cements showed some creep under load but the extent of this varied considerably: the creep of phosphate‐bonded cements being very small and that of the eugenol and related cements considerable.
The interaction of plasma proteins with polymers. I. Relationship between polymer surface energy and protein adsorption/desorption
Authors: Baszkin Adam , Lyman Donald J. 
Published: December 2004

AbstractAdsorption of bovine albumin, γ‐globulin and fibrinogen from phosphate buffer solution (pH = 7.5) onto several polymer films was studied using the radioiodinated proteins (125I). The kinetics of desorption of the proteinated polymer films in bovine plasma was determined. Contact angle measurements on these same polymers allowed the calculation of dispersive (W) and polar (Ip) components of the polymer‐protein solution system. Results from these measurements show that the nondispersive‐dispersive force balance at the polymer‐protein solution interface, expressed by the Ip/W ratio, is an important factor for binding of proteins on polymer surfaces. The purity of fibrinogen and the cleaning procedures for the polymer surfaces influence the absolute values of proteins adsorbed on polymer surfaces.
Prevention of platelet adhesion to porous surfaces
Authors: Predecki Paul , Life L. , Newman M. M. 
Published: December 2004

AbstractPorous samples of cellulose diacetate/nitrate CAN (millipore filter), polycarbonate PC (nuclepore filter), cellulose diacetate CA, and polydimethyl siloxane SR of various pore sizes were immersed in stirred heparinzied human blood while being perfused with lactated Ringer's solution at variours rates. Control samples were exposed to the blood in the absence of perfusion. The control tests showed that CAN and PC adhered platelets rapidly to plateau levels of 1–5 × 106/cm2 in ∼ 4 min, while CA and SR remained platelet‐free. The critical perfusion rate, v to prevent adhesion of platelets (and all formed elements) to the CAN and PC was ∼0.1 cc/min cm2 at a shear rate of ∼620 sec−1 independent of pore size tested. v increased slightly with stirring rate. A simplified diffusion‐convection model was used to qualitatively account for the effects observed.