bluuebunny/crossref_metadata_2025_split huggingface dataset:
Intramedullary fixation of artificial hip joints with bone cement‐precoated implants. I. Interfacial strengths
Authors: Barb W. , Park J. B. , Kenner G. H. , von Recum A. F. 
Published: December 2004

AbstractIn order to minimize the problems associated with implant fixation using acrylic bone cement, a new technique has been investigated. Canine hip prostheses were precoated with self‐curing acrylic bone cement and implanted in random source dogs using the same cement for fixation, a precoated prosthesis on one side and an uncoated (control) on the other. After 1, 3, and 6 months, both femora were excised and sectioned for mechanical assessment of the interfaces among bone, cement, and implant. It was found that the precoated implants had much higher interfacial shear strengths than the uncoated ones (average 14.2 and 6.8 MPa for implant‐cement interface; 2.0 and 1.2 MPa for the cement‐bone interface for all implant periods). The precoated “old” cement and the “new” cement's interfacial shear strength was the strongest with an average of 15.1 MPa for all implant periods. The present results indicate that the precoated hemiarthroplastic implants provide a firmer intramedullary fixation than the traditional, uncoated implants.
Ex vivo shunt testing of hydrogel–silicone rubber composite materials
Authors: Vale Bradley H. , Greer Raymond T. 
Published: December 2004

AbstractHydrogel polymers consisting of HEMA (2‐hydroxyethyl methacrylate) alone or copolymerized with NVP N‐(vinyl pyrrolidone) were incorporated into silicone rubber tubing to produce hydrophilic composite materials. Polymerization methods of the interpenetrating network (IPN) and radiation‐induced type were used to impregnate the silicone rubber substrates. These methods produced materials with varied wettability (contact angle with water ranged from 57° to 95°) but similar texture. The surface morphology as observed in the scanning electron microscope was the same for all the materials. Four types of composite materials and two sizes of silicone rubber control tubing in a total of 19 dogs were used as ex vivo femoral artery‐to‐vein (A–V) shunts and were sampled at 5, 15, 30, 45, and 60 min. Data obtained by using scanning electron microscopy (SEM) were used to determine the type and amount of adhering blood cells at the time intervals described. Large platelet aggregates and/or a variable initial response were found to be predictors of shunt failure (occlusion). Most samples showed only varied levels of platelet adhesion, but other cell types were seen in some samples. The adhesion was found to peak in all cases by 30 min and to reach lower levels by 60 min, suggesting that an initial phase of reaction was complete. The course of platelet adhesion for a 60‐min period is presented.
A comparison of the in vitro cytotoxicity of four restorative materials assessed by changes in enzyme levels in two cell types
Authors: Meryon S. D. , Riches D. W. H. 
Published: December 2004

AbstractA system is described for assessing the toxicity of freshly mixed restorative materials in vitro by measuring changes in the levels of β‐galactosidase and lactic dehydrogenase in both cultured cells and supernatants. The toxic effects of a zinc phosphate and silicate cement, a composite, and zinc oxide/eugenol were studied on two cell types, macrophages and fibroblasts, after 24 h exposure. Zinc oxide/eugenol, Silicap, and zinc phosphate were toxic to macrophages, in that order; Concise appeared to be nontoxic. Only zinc oxide/eugenol exerted significant effects on fibroblasts. Interposing dentine powder between the test cells and the material ameliorated the effects of all materials, possibly by the absorption of toxic components.
Durability of pyrolytic carbon‐containing heart valve prostheses
Authors: Schoen Frederick J. , Titus Jack L. , Lawrie Gerald M. 
Published: December 2004

AbstractTo assess abrasive wear of mechanical valve prostheses containing pyrolytic carbon components, we recovered at necropsy or surgery and analyzed by scanning electron microscopy and surface profilometry eight prostheses. Seven were implanted for 30–85 (mean 50 months). Valves included DeBakey aortic (2), DeBakey mitral (1), Beall mitral (2), Bjork–Shiley aortic (1), Cooley–Cutter mitral (1), and Lillehei–Kaster (L–K) tricuspid (1). All carbon occluders had undetectable wear. Carbon cage struts had a superficial burnish. Metallic struts had insignificant wear marks. In contrast, a Teflon Beall Model 104 valve implanted for 34 days and similarly analyzed had considerable material loss from the cage struts. This study suggests that clinically important abrasive wear will not be a late complication of cardiac valve replacement with pyrolytic carbon prostheses.
The effect of initial temperature on free radical decay in PMMA bone cement
Authors: Turner R. C. , White F. B. , Park J. B. 
Published: December 2004

AbstractThe effect of varying the initial temperature of the components of poly(methyl methacrylate) (PMMA) bone cement has been investigated. Electron paramagnetic resonance (EPR) spectroscopy was used to monitor free radical decay during the curing of the cement. Samples cured in saline at 37°C were found to exhibit first‐order decay kinetics for the polymerization radicals for approximately one week after mixing. This indicates that the decay did not take place by combination or disproportionation and was probably due to a transfer process. Decreasing the temperature of the bone cement components prior to mixing resulted in smaller decay rates, but still with first‐order kinetics. This decrease in decay rate with lower initial temperature may be due to decreased porosity of the cement, possibly due to decreased monomer evaporation. SEM micrographs of the samples were consistent with this change in porosity.
Dissolution of amalgam in saline solution
Authors: Kozono Yoshio , Moore B. K. , Phillips R. W. , Swartz M. L. 
Published: December 2004

AbstractThe experiment was designed to investigate the in vitro corrosion of several modern dental amalgams in saline solution over a six‐month period by measuring changes in the soluble corrosion products. Based on the change of the electrical conductivity of the solution, the dissolution rate seemed to decrease gradually for the first three to four months. Then a rapid increase was observed, indicating a reactivated corrosion process. Larger dissolutions of copper and mercury were observed, especially for the high copper alloys, in these later stages. Zinc and indium, if present, were preferentially released at the earlier stages. Silver and tin could not be detected. Evidence exists that the corrosion of tin results in insoluble deposits of corrosion products.
Corrosion of a new coppergold or copperplatinum intrauterine device
Authors: Gal‐Or L. , Gonen R. , Zilberman A. , Scharf M. 
Published: December 2004

AbstractIt has been shown previously that supplementing plastic intrauterine devices (IUDs) with copper wire enhances the antifertility effect of the device. The use of copper intrauterine contraceptive devices, however, is currently limited to two to three years, mainly because of wire fragmentation, which was observed as early as after eight months of use. In the resulting search for a long‐lasting device, two new systems of duplex wire, with gold and platinum cores electrolytically coated with copper, were devised and studied. Initially, duplex wires and controls were exposed to physiological solution. Copper dissolution rate and corrosion morphology were studied by weight‐loss measurements and optical metallography. Similar systems were then surgically implanted in rat uteri for varying periods of up to 26 weeks. Electron micro‐analysis of corrosion products, in addition to weight‐loss measurements and metallography, was performed. The results showed that a uniform and ductile copper coating is obtainable by electroplating on gold and platinum wires. Rate of copper dissolution is similar to that of solid copper wire. No dissolution of gold and platinum in the controls or coated wires was detected by weight loss, metallography, or atomic absorption measurements. Microanalysis of the deposits and corrosion products on the wires in the uteri environment showed sulfur, chlorine, and calcium, in addition to copper. The results of this study suggest that supplementing IUDs with copper‐coated gold or platinum wires may result in significant prolongation of the life span of the device by preventing uncontrolled loss of copper caused by wire fragmentation.
In vitro retinoid binding and release from a collagen sponge material in a simulated intravaginal environment
Authors: Dorr Robert T. , Surwit Earl A. , Droegemueller William , Alberts David S. , Meyskens Frank L. , Chvapil Milos 
Published: December 2004

AbstractFour in vitro preparations were constructed to simulate the intravaginal release of two retinoids, all‐trans‐retinoic acid (t‐RA) and 13‐cis‐retinoic acid (c‐RA), from a 0.7% collagen sponge diaphragm insert. Four t‐RA concentrations, 0.019, 0.05, 0.1, and 0.15% in methanol were added to the sponge. The release into an artificial vaginal fluid was monitored serially over 72 h by serial analysis for t‐RA and c‐RA using high‐pressure liquid chromatography. In each preparation, retinoid release was immediate and noncontinuous. At 37°C, the retinoids were stable for at least 48 h. Trans‐retinoic acid was the predominant retinoid recovered. Only trace amounts of the cis‐isomer were released. Peak t‐RA levels were 20 μM after 0.01%, 60–80 μM after 0.05%, 100–200 μM after 0.1%, and 320 μM after 0.15%. When the vaginal fluid bath was changed after 5 h, no further significant retinoid release occurred. There was significant loss of up to 70% of the applied t‐RA into the collagen sponge. The retinoid binding was concentration dependent (higher binding with higher concentrations) and was maximal only after 24 h of co‐incubation. The discontinuous release of t‐RA and the high degree of binding to collagen would seem to preclude use of the diaphragm insert as a vaginal drug delivery system, at least for retinoids.
Crystallinity, solubility, and dissolution rate behavior of fluoridated CO3 apatites
Authors: Okazaki Masayuki , Takahashi Junzo , Kimura Hiroshi , Aoba Takaaki 
Published: December 2004

AbstractTo study the effect of fluoride on the physicochemical properties of carbonate‐containing apatites, two series of fluoridated CO3 apatites with various fluoride contents were synthesized at 80°C and pH 7.4. The a‐axis dimensions of these apatites decreased with the increase of both fluoride and carbonate contents. The crystallinity of the apatites showed similar patterns of variation with the degree of fluoridation irrespective of carbonate content. These patterns appear analogous to the complex pattern of the fluoridated hydroxyapatites previously reported. In contrast to this unexpected crystallinity phenomena, the apparent solubility of fluoridated CO3 apatites in acetate buffer solutions at pH 4.0 and 6.0 and 37°C decreased monotonically with increasing degree of fluoridation and approached that of fluoridated hydroxyapatites at high fluoride content. Dissolution rate of fluoridated CO3 apatite pellets at pH 4.0 also showed a simple decrease with increasing degree of fluoridation and was extremely sensitive to acid at low fluoride content.
Mechanical properties of the fibrous tissue found at the bone‐cement interface following total joint replacement
Authors: Hori R. Y. , Lewis J. L. 
Published: December 2004

AbstractA long‐term problem associated with total joint replacements is the formation of a fibrous tissue at the bone‐cement interface which may compromise the fixation of the prosthesis. In this study, harvestable amounts of interfacial fibrous tissue were generated using a prosthetic replacement of the canine stifle joint as an animal model. The collected tissues were examined histologically and by uniaxial, unconfined compression tests. The fibrous tissue had a matlike structure. The heavy collagen fibers were distributed at random in sheets and the sheets themselves were layered to form a mat. Such a structure may be able to resist compressive stresses normal to the plane of the mat but is probably not well suited to resist shearing stresses. The fibrous tissue proved to be a very compliant, deformable material and to undergo very large strains with load. The stress‐strain curve for the tissue was nonlinear and was characterized by large deformations at low loads. But with increasing loads, the material became stiffer, and at high loads, the stress‐strain curve became linear with a short‐term tangent modulus of 1.9 MPa at a stress level of 0.5 MPa and a compressive strain level of 50%. With regard to total joint replacement systems which consist of an outer bone shell followed by a thin layer of fibrous tissue, a mantle of PMMA cement and a central core of metal or UHMW polyethylene, the fibrous tissue is substantially more yielding and deformable than the other elements of the structure and may have a significant effect on the structural behavior of the system.
Effect of a cement‐bone composite layer and prosthesis geometry on stresses in a prosthetically resurfaced tibia
Authors: Shrivastava S. C. , Ahmed A. M. , Shirazi‐Adl A. , Burke D. L. 
Published: December 2004

AbstractA comparative study of stress distributions in the component materials of a number of models of a prosthetically resurfaced tibia is presented. Although the geometry is idealized to be axisymmetric, the loadings for which the finite element analyses are performed are considered to be nonaxisymmetric, simulating more realistically the loading conditions in vivo. The different models are chosen with the view of determining the influence of changes in the prosthesis design on the induced stress distribution in the component materials. The changes considered are in the thickness of the cement and the cement‐bone composite layers, and in the shape of the prosthesis. Experimentally measured values of strains are compared with the analytically predicted values to check the validity of the assumptions used in the finite element modeling. The comparison of induced stresses in the different materials reveals the desirability, from a mechanical behavior point of view, of introducing a cement‐bone composite layer and using a prosthesis with domed subsurface in the fixation system. It is shown that for a model incorporating these features, considerable reduction of stresses in the cement, in its bulk and at its interface with the prosthesis plate, is achieved. The reduced stresses can be expected to have beneficial effects on the long‐term behavior of the cement and its interfaces in the fixation system.
Detecting margin leakage of dental composite restorations
Authors: Wu W. , Cobb E. , Dermann K. , Rupp N. W. 
Published: December 2004

AbstractThe degree of microleakage between a restoration and the cavity wall is difficult to quantify objectively. A silver‐staining method is used and compared to the radioisotope method with results that indicate a superior definition and more accurate evaluation of microleakage. In addition to the accuracy, two advantages are presented: (1) scoring of the leakage can be refined and divided into more precise numbers, and (2) teeth can be observed directly in a microscope without resorting to the indirect interpretation of film or photograph.
Preliminary report on the osteogenic potential of a biodegradable copolymer of polyactide (PLA) and polyglycolide (PGA)
Authors: Hollinger Jeffrey O. 
Published: December 2004

AbstractA biodegradable copolymer of 50 polylactide:50 polyglycolide was prepared for implantation into experimentally created osseous defects in the tibias of 25 rats. Similarly prepared defects were made in the humeri of the same rats and these defects did not receive copolymer implants. Upon sacrifice, both the implant treated and untreated sites of the experimentally produced osseous defects were evaluated by gross appearance and by histomorphometric examination using a Zeiss Videoplan Image Analysis System with Osteoplan (version 4.1). The animals were evaluated in groups of five at 7, 14, 21, 28, and 42 days. When compared with bony defects that were not treated with the biocompatible, biodegradable copolymer implant, the implant sites displayed an accelerated rate of healing at 7, 14, 21, and 28 days (p < 0.001). A similar healing response rate, however, was observed at 42 days (p < 0.25–0.1). No adverse host tissue responses were observed histologically.
The incidence and significance of rub marks on the stem of removed total hip replacements
Authors: Dobbs H. S. , Robertson J. L. M. 
Published: December 2004

AbstractThis article presents data on the incidence of rub marks (burnishing) on the stems of 180 removed total hip replacement femoral components most of which were McKees and Stanmores. The incidence varied with the reason for removal. It was low for assorted removals excluding fractured stem removals, higher for “loose stem” removals, and highest for fractured stem removals. For “loose stem” removals, it appeared to increase with implantation time. For fractured stem removals it appeared to increase with the time elapsed between fracture and removal. On not‐fractured removal, rub marks appeared to indicate that the component had been loose, but on fractured stem removals they appeared to indicate only that the component had been loose after fracture.
Surface modification and evaluation of some commonly used catheter materials. I. Surface properties
Authors: Triolo Philip M. , Andrade Joseph D. 
Published: December 2004

AbstractDouble catheter systems consisting of a stiff outer catheter and a flexible, buoyant, flow‐directed, inner catheter which is often balloon‐tipped have been employed with increasing frequency recently in both therapeutic and diagnostic procedures. Their use, however, has been restricted because of the excessive friction generated between the two catheters. In an attempt to decrease friction between polymers commonly used as catheter materials, oxidation of polyethylene, fluorinated ethylene‐propylene copolymer, poly(vinyl chloride), silicone rubber, and polystyrene surfaces was induced by exposing the polymers to radio frequency glow discharge (RFGD) in a helium environment. All polymers were surface characterized utilizing x‐ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and contact angle measurements before and after oxidation. This article describes the materials and methods used to fabricate and characterize the polymer surfaces and the results of the characterization. The results indicate that increases in oxygen concentration at the surface of the polymers and decreases in air‐water contact angles occur with increased RFGD exposure time. Plateau values were usually obtained after 5–30 s exposure time, yet no apparent changes in surface topography were noted by scanning electron microscopy. The hydrophilic surfaces produced were stable for up to three months storage time in air.
Surface modification and characterization of some commonly used catheter materials. II. Friction characterization
Authors: Triolo Philip M. , Andrade Joseph D. 
Published: December 2004

AbstractThe effects of the modification of polystyrene (PS), polyethylene (PE), poly(vinyl chloride) (PVC), silicone rubber (SR), and fluorinated ethylene propylene (FEP) copolymer by radio frequency glow discharge in a helium environment were presented in part I. The hydrated polymer surfaces were characterized by XPS, SEM, visual microscopy, and by contact angle measurements. In general, exposure of the polymers to RFGD produced an oxidized hydrophilic surface, yet the roughness of the surface was unaltered by the relatively mild plasma conditions used. In this article, the frictional behavior of oxidized and unoxidized SR, PE, and FEP in distilled water, isotonic saline, and blood plasma environments is examined experimentally. The results are discussed in relation to the properties generally believed to affect frictional phenomena and to the surface properties as determined in part I. Results indicate that RFGD‐treated SR generates less friction than untreated SR when dragged across all untreated and treated polymer surfaces, whether the medium is distilled water or an isotonic saline solution. Friction is consistently lower in a blood plasma medium between all surfaces investigated, most probably because of the presence of adsorbed proteins at the polymer interfaces.
Isobutyl 2‐cyanoacrylate as an osseous adhesive in the repair of osteochondral fractures
Authors: Harper Marion C. , Ralston Michael 
Published: December 2004

AbstractAn in vivo evaluation of isobuty 2‐cyanoacrylate as an osseous adhesive was done in an effort to answer two questions: Used in limited amounts, can this monomer maintain the reduction of an unstable intra‐articular osteochondral fracture while allowing for fracture healing around the sites of adhesive placement? Used in limited amounts, in this monomer toxic to adjacent viable bone? Osteochondral fractures were created in 32 dog knees. In 16 knees, the fracture reduction was secured with three small drops of adhesive placed around the periphery of the fracture surface. In 16 control knees no adhesive was used. Eighty‐one percent of the fractures in the adhesive‐treated group united compared to 56% of the control group. Although the difference in number of fractures that healed in the two groups is not definitely statistically significant and no conclusion was drawn as to effectiveness of the adhesive, osseous healing was noted to proceed around the sites of adhesive placement and the monomer appeared nontoxic to adjacent bone.
Ultrastructural observations of cells at the interface of a biodegradable polymer: Polyglactin 910
Authors: Matlaga Barbara F. , Salthouse Thomas N. 
Published: December 2004

AbstractTransmission electron microscopy was used to study the ultrastructure of cells at the interface with an implanted biodegradable polymer, Polyglactin 910. Various stages of implantation were observed from 1 day to 63 days, when absorption of the polymer was essentially complete. Events occurring at the interface include initial adhesion of macrophages on the implant surface; phagocytosis of wound debris; and subsequent erosion, invasion, and phagocytosis of the polymer by macrophages and giant cells. A vascular perfusion technique for fixation of the polymer sites implanted in soft tissue is also described.
A novel process for the manufacturing of porous grafts: Process description and product evaluation
Authors: Leidner Jacob , Wong Edward W. C. , MacGregor David C. , Wilson Gregory J. 
Published: December 2004

AbstractA novel process has been developed for the manufacture of porous vascular grafts from solutions or melts of polymers. It allows the manufacture of grafts with controllable porosity, pore size, and mechanical properties. In this process, the polymer melt or polymer solution is extruded through fine orifices; the fibers are then fibers are then stretched and wound on a rotating mandril. Fiber‐fiber bonding takes place, resulting in the formation of stable porous tubes. The effects of the process variables on the physical properties of the resulting graft have been studied and preliminary in vivo evaluation in dogs has demonstrated graft patency with a thin, stable neointima in both small (4 mm) and large (10 mm) caliber configurations.