bluuebunny/crossref_metadata_2025_split huggingface dataset:
In vitro corrosion testing of titanium surgical implant alloys: An approach to understanding titanium release from implants
Authors: Solar Ronald J. , Pollack Solomon R. , Korostoff Edward 
Published: December 2004

AbstractThe excellent corrosion resistance of titanium and its alloys to physiological chloride solutions is well documented. Occasionally, however, titanium compounds have been found in tissue adjacent to titanium implants. These findings were reported to be unrelated to wear processes, suggesting that either the metal or its passive film was dissolving. The unpredictability of these findings further suggests that preimplantation surface treatments and/or variations in the physiological environment may be factors. To determine a mechanism by which titanium can be released from an implant a study was initiated which employed electrochemical techniques, Auger electron spectroscopy (AES), and replica transmission electron microscopy (RTEM). Specifically, the purpose was to characterize the passive film on titanium and Ti‐6Al‐4V, and to determine if there is dissolution of the film or metal in a static unstressed state. Passive film behavior of commercially pure titanium, Ti‐6Al‐4V and nitrided Ti‐6Al‐4V was studied by anodic polarization and pulse potentiostatic capacitance techniques in Ringer's solution at 37°C with and without physiological additions of several amino acids. Solution Po2, pH, and specimen surface finish were varied to include all probable in vivo conditions. In all tests, potentiostatic anodic polarization of each material yielded potential‐current density curves which showed passivity over the entire experimental range. This range greatly exceeded the oxygen‐reduction reversible electrode potential. No breakdown potentials were observed. The passive current density was not significantly affected by varying the experimental parameters. AES as well as charge and capacitance measurements showed that the electrochemical reaction which occurred was growth of the passive film. The data indicated that the effective electrochemical area of each specimen was less than its geometrical area, and was dependent on both pH and surface finish. The findings of this study showed that, under static conditions, titanium and Ti‐6Al‐4V should withstand exposure to physiological chloride solutions at body temperature indefinitely. Furthermore, the findings are consistent with a model of the implant surface inwhich the naturla air oxide that initially forms on an abraded implant surface is comprised of microscopic oxide needles. It is proposed that (i) the needless canbe broken off or dissolved in vivo, providing the source of the titanium sometimes found in tissue adjacent to an implant, and (ii) use of certain pretreatments may remove the needles prior to surgery, resulting in the more common case in which titanium is nto found in the tissue.
Use of fracture mechanics theory in lifetime predictions for alumina and bioglass‐coated alumina
Authors: Ritter J. E. , Greenspan D. C. , Palmer R. A. , Hench L. L. 
Published: December 2004

AbstractThe fatigue behavior of alumina and bioglass‐coated alumina was determined in air and biological test environments by the dynamic fatigue test technique in which strength is measured as a function of stressing rate. The good correlation found between the test data and fracture mechanics theory indicates that fatigue failure is controlled by the slow crack growth of preexisting flaws and that fracture mechanics theory can be used in making failure predictions for alumina and bioglass‐coated alumina in biological environments. Thus, it is believed that lifetime predictions can be made for ceramic implants on the basis of short‐term test data utilizing fracture mechanics principles.
Heparinized styrene‐butadiene‐styrene elastomers
Authors: Goosen Mattheus F. A. , Sefton Michael V. 
Published: December 2004

AbstractA heparinized high‐strength elastomer has been developed which is potentially useful as a nonthrombogenic vascular prosthesis. A surface hydroxylated styrene‐butadiene‐styrene (SBS) block copolymer with at least 40% extent of reaction after glow‐discharge cleaning was coated with a 20% acetylated polyvinyl alcohol/heparin mixture containing glutaraldehyde and magnesium chloride. After curing at 80°C for 100 min, the polyvinyl alcohol, heparin, and hydroxylated SBS were covalently bound to each other by acetal bridges. The effects of the various substrate and coating parameters were optimized to achieve very strong adhesion between the coating layer and the surface hydroxylated SBS. Heparin was not leached from the surface of the new material using 3M saline at pH 7.4 despite a detection limit of 10−5 μg heparin/cm2 min. Prolonged partial thromboplastin times of greater than 1200 sec were observed (control: PTT = 120 sec). Preliminary ex vivo testing using a simple arteriovenous shunt in the leg of a rabbit showed good thromboresistance. The heparinized SBS shunt chamber remained patent for more than two hours without desorption of heparin. It was concluded that surface hydroxylated SBS heparinized by acetal coupling owed its thromboresistance to the heparin covalently bound to the surface and not to a microenvironment of heparin in solution at the blood/material interface.
The fabrication of artifacts out of glassy carbon and carbon‐fiber‐reinforced carbon for biomedical applications
Authors: Jenkins G. M. , Grigson C. J. 
Published: December 2004

AbstractPolymeric carbons1 are produced by the carbonization of a wide range of organic polymeric systems. We have concentrated on the fabrication of two types of polymeric carbons, glassy carbon and carbon‐fiber‐reinforced carbon (CFRC), both involving phenolic resin precursors. We describe herein the technology which enables us to make dental implants and heart valves out of glassy carbon. We also show how carbon‐fiber‐reinforced carbon can be made in the form of rods and plates for orthopedic use and molded before firing to produce complex, rigid, individually sculptured shapes suitable for maxillofacial bone replacement. The mechanical properties will be discussed in relation to the structure of these various forms of polymeric carbon.The main purpose of the work is to show that the technology of polymeric‐carbon manufacture is essentially simple and the manufacturing process is readily carried out in laboratories which have already been equipped to fabricate standard dental prostheses.
Time‐Dependent phase changes in Cu‐rich amalgams
Authors: Marshall Sally J. , Marshall Grayson W. 
Published: December 2004

AbstractCu‐rich amalgams represent a significant change in amalgam alloy formulation which may result in enhanced performance. Significantly, these systems reduce or eliminate the γ2 phase. This work studied the phase changes which occurred from one hour to six months in 13 commercial amalgams by x‐ray diffraction. This included 9 two‐particle or blend systems and 4 single‐particle systems. γ2 was found in all systems, but was reduced or eliminated on storage at 37°C at rates which varied from system to system. During γ2 elimination, the Cu6Sn5 content correspondingly increased, indicating that solid‐state reaction occurs for up to six months in some systems.
The influence of grain size on the fatigue behavior of annealed 316 LVM stainless steel
Authors: Clemens D. , Galante J. , Rostoker W. 
Published: December 2004

AbstractExperimental tests demonstrate that there is a sharp drop in resistance to fatigue fracture when the grain size is increased from 75 to 150 μm. This is at least a partial explanation for fatigue fractures of the stems of total hip‐joint prostheses reported in the literature. It is also shown that plastic strains associated with fatigue stressing increase with increasing grain size so that loosening of the bone cement embedment may also be part of the premature failure process.
Bending properties of wire‐reinforced bone cement for applications in spinal fixation
Authors: Saha Subrata , Kraay Matthew J. 
Published: December 2004

AbstractPMMA beam specimens were tested in four‐point bending to determine if the bending strength of acrylic bone cement, as used in posterior spinal fusion, could be improved by metal‐wire reinforcement. The result showed that the load‐carrying capacities of 1‐ and 0.5‐mm diam stainless‐steel‐wire‐reinforced PMMA specimens in bending were significantly higher than similar unreinforced normal PMMA samples. On an average, steel reinforcement comprising approximately 1% of the cross‐sectional area of the PMMA specimens caused a 15% increase in bending strength. Even after the cement fractured, the reinforcing wires still sustained an appreciable amount of bending moment, thus preventing catastrophic failure of cement alone.
A comparative study of poly(glycolic acid) and catgut as suture materials. Histomorphology and mechanical properties
Authors: Pavan Andrea , Bosio Maurizio , Longo Tito 
Published: December 2004

AbstractThe “quality” of poly(glycolic acid) as an absorbable suture material was investigated in comparison with catgut. Tissue reactions to poly(glycolic acid) and plain catgut were examined histomorphologically at different time intervals after implantation in rats, and compared. Four mechanical properties were also examined as relevant quality factors: elastic stiffness, tensile strength, toughness, and percent elongation at rupture of the suture material per se (unknotted). The variation of these properties in poly (glycolic acid) implants was followed since their insertion in the tissues. Histological behavior and mechanical properties appear to be more closely correlated in the case of poly(glycolic acid) than in the case of catgut, as a consequence of a greater regularity of tissue reaction towards the synthetic material. Both tissue reaction and tensile properties variation are independent of size in the case of the braided poly(glycolic acid) sutures examined. Elastic stiffness and tensile strength decrease steadily in time; toughness and ultimate elongation display an increase up to a maximum within one day since implantation, and then decrease.
In vivo evaluation of a high‐strength, high‐ductility stainless steel for use in surgical implants
Authors: Syrett Barry C. , Davis Edward E. 
Published: December 2004

AbstractA high‐strength, high‐ductility, austenitic stainless steel has been evaluated for use in surgical implants by performing in vivo tests in rats, rabbits, dogs, and rhesus monkeys. This stainless steel, a TRIP (TRansformation Induced Plasticity) steel containing about 4% Mo, was compared with two alloys in current clinical use: Type 316L stainless steel and cast Vitallium. Compared with the other two alloys, cast Vitallium generally had higher resistance to corrosion and superior biocompatibility in all animals. The tests in rats and dogs indicated that the corrosion resistances of the TRIP steel and the Type 316L stainless steel were similar and that the tissue reactions caused by these alloys were also similar. However, in rhesus monkeys, the TRIP steel was shown to be susceptible to stress‐corrosion cracking and much more susceptible to crevice corrosion than Type 316L stainless steel. Limited tests in rabbits supported the observation that the TRIP steel is susceptible to stress‐corrosion cracking. These inconsistencies in the in vivo tests underline the need for a reevaluation of the popular test techniques and of the animals commonly chosen for assessing the suitability of candidate implant materials. The “worst case” results from the rhesus monkey tests were entirely consistent with previous results obtained from in vitro studies. However, further work must be performed before the behavior of metals in humans, rhesus monkeys, or any other animal, can be predicted with confidence from an in vitro test program.
The effects of radiation sterilization on the properties of ultrahigh molecular weight polyethylene
Authors: Nusbaum H. J. , Rose R. M. 
Published: December 2004

AbstractThe effects of radiation sterilization on ultrahigh molecular weight polyethylene were explored by freeze fractures, electron spin resonance, absorption of aqueous media, density measurements, small‐angle and wide‐angle x‐ray scatter, differential scanning calorimetry, infrared and ultraviolet‐visible spectrometry, static and dynamic mechanical properties measurements, mechanical fatigue measurements, and standard environmental stress cracking measurements. The rate of fluid absorption increased significantly due to the appearance of carbonyl groups. As the fluids were absorbed, density increased and small‐angle x‐ray scatter (SAXS) intensity diminished slightly, as expected. Small changes in mechanical properties (e.g., tensile properties and dynamic spectrum) were always consistent with the cross‐linking which occurs after irradiation; the only significant mechanical deterioration was in the fatigue properties. The nonspherulitic, inhibited crystallinity which characterized this material and which is responsible for its excellent static resistance to environmental stress cracking was not at all changed.
Durability of the bond between bone and various 2‐cyanoacrylates in an aqueous environment
Authors: Brauer G. M. , Kumpula J. W. , Termini D. J. , Davidson K. M. 
Published: December 2004

AbstractThe durability of the bond strength developed between 2‐cyanoacrylate esters and bone has been determined by aging specimens in water. One‐day bond strength of the isobutyl and isomeric amyl 2‐cyanoacrylates varied from 6.2 to 7.2 MPa. The strength of the bond decreased on storage or on thermocycling in water. Hydrolytic stability increased with increasing length of the alkyl ester group. After a six‐month storage in water the various amyl 2‐cyanoacrylates retained from 70% to 73% of their one‐day bond strength. Pretreatment of the bone surface prior to application of the adhesive did not prove beneficial. The cured 2‐cyanoacrylate can be removed from the substrate surface by appropriate solvents. Thus, it is not bonded covalently to bone. The bond strength, especially of the isobutyl and amyl 2‐cyanoacrylates to bone in an aqueous environment, appears to be superior to other adhesives. Provided these monomers are biocompatible, they may be useful clinically where an intermediate‐term adhesion is desired.
Tissue response to surface‐treated tantalum implants: Preliminary observations in primates
Authors: Meenaghan Michael A. , Natiella Joseph R. , Moresi John L. , Flynn Harry E. , Wirth John E. , Baier Robert E. 
Published: December 2004

AbstractSamples of capacitor grade tantalum were surface‐treated by a variety of methods. These surface treatments allowed testing of the same basic material which was millfinished, metallurgically polished, electrochemically oxidized, sintered with a porous surface, and glow‐discharged. Surface characterization was accomplished by contact angle measurements, Scanning Electron Microscopy, energy‐dispensed x‐ray analysis, and internal reflection spectroscopy. Subsequent to characterization, the material was surgically implanted in the subperiosteal region of the mandible, the buccal mucosa, and the subcutaneous paravertebral region of the back of Macaca speciosa (stumptail monkey). The tissue reaction at intervals of up to three weeks was evaluated morphologically and ultrastructurally. Significant differences in tissue response were noted at the interfaces with glow‐discharge‐treated versus lower surface energy samples. Adjacent to the glow‐discharge‐treated implants, two distinct tissue zones were identified. Zone #1, nearest the implant, exhibited an increased cellularity. This consisted of 4–5 layers of highly active mesenchymal cells or fibroblast‐like cells with spindle‐shaped nuclei and prominent cytoplasmic features. At various foci along the interface, hyperchromatic nuclear forms were noted to project into the space left by removal of the implant. These observations, coupled with a predominance of intercellular ground‐substance material and less collagen at the interface, may indicate some form of bioadhesion. The deeper Zone #2 was 2–3 times as thick and consisted of typical fibroblastic cells with a lamellar configuration, bordered by an occasional delicate‐lined space. Independent of implantation site or surface texture, all other implants showed occasional multinucleated giant cells and a decrease in the cellular character of Zone #1. Both zones were reduced in thickness and composed of more mature fibroblasts. Some specimens exhibited intracytoplasmic vacuolization. It may be concluded, therefore, that surface‐free energy of the implanted specimens played a significant role in inducing differential tissue response to otherwise similar pure metal samples.
Influence of methyl methacrylate on quantitative gel diffusion assay of immunoglobulins
Authors: Petty William 
Published: December 2004

AbstractInfection is not a common problem following implant surgery using the bone cement, polymethyl methacrylate. When infection occurs, its often disastrous results makes for major complications. Many methods have been used in an attempt to reduce bacterial contamination at the time of implant surgery, but little attention has been given to the problem of possible effects of implant materials on the immune mechanisms of the host. In the experiments reported here, the in vitro effect of methyl methacrylate monomer on human immunoglobulins was determined using a quantitative gel diffusion technique. When methyl methacrylate monomer was added to serum samples containing immunoglobulin, it caused no statistically significant change in the immunoglobulin concentration of immunoglobulin‐G, immunoglobulin‐A, or immunoglobulin‐M. It is possible that methyl methacrylate could affect other types of antigen antibody reactions which may be important in resisting infection, but the evidence reported here indicates that in low concentrations, methyl methacrylate monomer does not affect the normal reactivity of immunoglobulins of the G, M, or A class.
Release characteristics of dibucaine dispersed in konjac gels
Authors: Nakano Masahiro , Takikawa Kaori , Arita Takaichi 
Published: December 2004

AbstractA possible use of konjac gel for sustained release of drugs was examined in a monolithic system containing dibucaine. Dibucaine was dispersed in the gel which was prepared by gelation of the konjac flour in a borax solution at 60°. The cumulative amount of the drug released plotted against the square root of time was linear in the monolithic system. This relationship was in agreement with that expected from the theoretical equation for planar configuration. The mechanism of the release of the drug from the gel may be considered to be a leaching of the drug by the permeating fluid. The release profile from dried konjac gel was similar to that from undried gel, but that from unwarmed gel showed a deviation from linearity although sustained release was similarly obtained.
In vitro and in vivo evaluations of dacron velour and knit prostheses
Authors: Sawyer P. N. , Stanczewski B. , Hoskin G. P. , Sophie Z. , Stillman R. M. , Turner R. J. , Hoffman H. L. 
Published: December 2004

AbstractDacron velour and knit prostheses were compared with respect to long‐term patency when used as canine aortic implants. These grafts were rated, according to the average numerical value of six equally weighted criteria, in decreasing order of performance: velour I, velour II, circular knit III, velour IV, circular knit V, warp‐knit VI, warp‐knit VII and VIII, warp‐knit IX and warp‐knit X. In general, compacting and crimping methods using halogenated hydrocarbons produced the least successful grafts. Grafts of identical brand but compacted and crimped by different methods exhibited different patencies. No true healing of any of the grafts was observed. Layered deposits of inner fibrous capsule were formed at rates and thicknesses c a acteristic for each type of graft employed. A functioning Dacron femoral‐popliteal bypass removed from a human after 9 months exhibited inner and outer fibrous capsules similar to those from canine implants.
In vitro heterogeneous degradation of poly(n‐alkyl α‐cyanoacrylates)
Authors: Vezin W. R. , Florence A. T. 
Published: December 2004

AbstractMethods by which in vitro heterogeneous phase degradation rates of the poly(n‐alkyl α‐cyanoacrylates) have been directly obtained are described. The data indicate that the rates of degradation in aqueous buffer solutions depend not only upon pH of the medium and length of the monomer alkyl side chain, but also critically upon polymer particle specific surface, particle size, polymer molecular weight, and molecular weight distribution. A modification of the currently held theory of degradation of these polymers is required, and postulated.
The influence of design parameters on calcar stresses following femoral head arthroplasty
Authors: Cook S. D. , Klawitter J. J. , Weinstein A. M. 
Published: December 2004

AbstractA two‐dimensional finite element model (FEM) was used to investigate the effect of various prosthesis design parameters on stresses along the proximal medial aspect of the femur. Strain calculations were compared to reported experimentally measured strains for an intact femur and femur containing a prosthesis in an effort to verify the FEM results. The results of the study indicated that stress levels in the medical aspect of the femur approaching those of the intact femur are possible with a device having an elastic modulus similar to bone. It was found that acrylic bone cement had little effect on stress profiles in the medial aspect when compared to stresses for devices utilizing a direct bone to implant attachment mechanism. It was also found that reduction in implant stem length and elastic modulus of tissue present at the prosthesisbone interface could be used to increase stresses in the medial aspect; however, their effects were not as dramatic as reducing the elastic modulus of the stem material.
Oxygen permeability of carbon‐surfaced microporous membranes
Authors: Borovetz Harvey S. , Mateer David D. , Hardesty Robert L. , Haubold Axel D. 
Published: December 2004

AbstractA study was conducted to measure the permeability to oxygen (PmO2) of microporous membranes coated with ultra‐low‐temperature isotropic (ULTI) carbon. Carbon‐surfaced membranes were fabricated by application of a thin complete layer (0.7 to 1.7 microns thick) of ULTI carbon onto one surface of a microporous substrate. Based upon the average values of 27 measurements in a diffusion cell, a mean reduction in PmO2 of only 10% results following the treatment of the microporous substrate with ULTI carbon. The values for PmO2 are not dependent upon the thickness of the carbon film over the range of film thickness of 0.7 to 1.7 microns. When coupled with the known antithrombotic characteristics of ULTI carbon, an oxygenator incorporating carbon‐surfaced microporous membranes has the potential for use in clinical extracorporeal membrane oxygenation (ECMO).
Time‐temperature behavior for creep of dental amalgam
Authors: Greener E. H. , Szurgot K. , Lautenschlager E. P. 
Published: December 2004

AbstractFrom 0 to 24 hours at an initial static stress of 34.5 MPa and in the temperature range of 0 to 60°C, the creep behavior of four different one‐week‐old dental amalgams was monitored in a recently developed minispecimen creep apparatus. In most instances the behavior could not be described by a linear relationship. Therefore, the usefulness of calculating creep rate based upon only two times, i.e., 1 and 4 hours, must be questioned. On the other hand, the observed creep kinetics were found to follow accepted nonlinear models of dislocation/obstacles interactions which may be thermally activated.