bluuebunny/crossref_metadata_2025_split huggingface dataset:
Interactions between segmented polyurethane surfaces and the plasma protein fibrinogen
Authors: Stupp S. I. , Kauffman J. W. , Carr S. H. 
Published: December 2004

AbstractSurfaces of a segmented polyurethane were varied by casting on poly(ethylene terephthalate) (PET) and glass substrates, and were characterized through infrared‐attenuated total‐reflection spectroscopy (ATR). Surfaces cast on glass substrates showed a higher content of polyether segments, whereas those cast on PET contained a higher relative concentration of aromatic segments. Adsorption, and possible conformational changes of fibrinogen, were found to be more substantial on polymer surfaces having a higher content of polyether segments. It is concluded that the relatively good blood compatibility of segmented polyurethanes is partly due to the presence of peptide‐like bonds on aromatic segments.
Properties of heparin–poly (methyl methacrylate) copolymers. II
Authors: Labarre D. , Jozefowicz M. , Boffa M. C. 
Published: December 2004

AbstractA heparin–poly (methyl methacrylate) copolymer in which heparin has been covalently bound was studied. This copolymer showed no release of heparin but presented heparin‐like anticoagulant activity when suspended in plasma. After contact with plasma, the copolymer lost part of its antithrombin activity which could be restored by a high ionic‐strength medium. Because of its solid form, this copolymer offers new possibilities for producing interesting anticoagulant surfaces.
Effect of collagen crosslinking on the rate of resorption of implanted collagen tubing in rabbits
Authors: Chvapil M. , Owen J. A. , Clark D. S. , Koorajian S. , Goodman A. P. 
Published: December 2004

AbstractCollagen tubes were tanned with glutaraldehyde for different periods of time. Some were oxidized with periodate and sterilized with either 60Co (1.5 Mrad) or propylene oxide. The tubes were coated with polyfilamentous polyester fabric, filled with x‐ray contrast material, and implanted subcutaneously in rats and rabbits. Rate of resorption was ascertained by x‐ray procedure of progressive leakage of contrast material.A close relation between tanning time of the collagen fabric‐combined prostheses and rate of their resorption in subcutis was found in both rats and rabbits. In rabbits, however, the implants were resorbed at a significantly faster rate than in rats. No effect of oxidation of collagen on the resorption was observed. Collagen tubes tanned for shorter time periods and sterilized with propylene oxide were more resistant to degradation than those sterilized with irradiation. This difference was absent, however, with material tanned for longer times.The mechanism of resorption of implanted collagen tubes was studied by morphological methods. The role of inflammatory cells in resorption is documented. The paper indicates the advantages as well as limits of the x‐ray method of studying the resorption rate of biodegradable materials.
Skin replacement with bioplast fibrin in ophthalmology
Authors: Tapasztó István , Kerényi Géza 
Published: December 2004

AbstractThe study includes 40 cases of skin replacement performed by an ophthalmologist over a period of 4 years. An absorbable implant material, Bioplast fibrin, was used as a graft following the extirpation of 12 eyelid tumors, the treatment of eight fresh, destructive skin injuries, and the removal of deforming scars around the eyes, in 20 cases. The biocompatible implant provided barrier properties preventing infection or excessive fluid loss. The resorption rate was adjusted to 3–4 weeks. These grafts were gradually replaced by new epithelial tissue growing in from the periphery of the wound edge. The new tissue had the elasticity and cosmetic appearance of surrounding skin. Thus, small periorbital skin tumors can now be removed without the necessity of doing a split thickness skin graft to cover the defect.
Influence of a functional dynamic loading on bone ingrowth into surface pores of orthopedic implants
Authors: Ducheyne P. , De Meester P. , Aernoudt E. , Martens M. , Mulier J. C. 
Published: December 2004

AbstractThe present status of skeletal fixation of permanent orthopedic implants by poly(methyl methacrylate) (PMMA) is discussed. It is proposed that alternatives to the acrylic cement can improve the skeletal fixation. The present paper is concerned with the fixation method by bone ingrowth into pores of the implant surface.Two different implantation models have been designed to investigate the influence of load bearing upon ingrowth in surface pores of the implant: intramedullary nails as a means of fixation of a femoral pseudarthrosis and hinged knee prostheses. In each animal, implants with identical material characteristics (pore size, density, and thickness of the porous layer) but different loading conditions were used: one implant was “statically” loaded, the other “dynamically.” This procedure allows the evaluation of ingrowth with regard to load bearing only.Two different mean pore sizes, viz., 87 and 110 μm, have been used with the two models. After an 8 week implantation period, bone ingrowth was evident for the statically loaded implants. Calcified tissue ingrowth was, however, not observed in the dynamically loaded implants. The discrepancy in bone ingrowth behavior between the statically and the dynamically loaded implants has been attributed to 1) the gross movement or the micromovement existing at the bone prosthesis interface and 2) the fact that the critical mean pore size for ingrowth with static loading is smaller than the one with dynamic loading.The experimental implantations allow still another conclusion: the results suggest that designs of present clinical prostheses fixed by bone cement cannot be used with the alternative fixation by bone ingrowth unless the deisgn has been changed in a fundamental way. Mechanical factors as well as the phenomenology of bone ingrowth fixation account for this conclusion.
A polymethacrylate–silica composite material for dental implants
Authors: Hodosh M. , Shklar G. , Povar M. 
Published: December 2004

AbstractA study has been carried out on the structure and surface texture of a new dental implant material composed of silica microspheres (3 or 5 wt %) and poly(methyl methacrylate). A recently developed composite material composed of vitreous carbon microballoons and poly(methyl methacrylate) has proven highly successful in clinical use, but the black color presents aesthetic problems at the gingival margin. The new material was developed in order to reproduce the many desirable qualities of the vitreous carbon‐polymethacrylate composite, while omitting the black color. Square wafers (10 mm × 10 mm × 1 mm) were studied, with the surface sandblasted in half of the specimens. Light microscopy revealed an even spacing of spherical configurations throughout the material. Scanning electron microscope studies revealed a finely porous surface with many large craters in the sandblasted specimens.
A total internal‐reflection technique for the examination of protein adsorption
Authors: Watkins Robert W. , Robertson Channing R. 
Published: December 2004

AbstractA Total internal‐reflection fluorescence (TIRF) technique for examining protein adsorption at solid‐liquid interfaces is described. For the representative case of adsorption of bovine γ‐globulin onto silicone rubber, the applicability of the technique to several important aspects of protein adsorption phenomena is demonstrated. Specifically, in addition to the tightly adsorbed protein layer observed herein and previously by many others, the presence of a loosely adsorbed protein layer was also noted under conditions of either static or flowing protein solutions. Taking advantage of the continuous real‐time measurements possible with TIRF, a rate constant for the protein adsorption step during laminar flow was estimated at both 25 and 37°C. These results serve to demonstrate that the TIRF technique represents a significant and versatile new tool for the study of protein adsorption phenomena.
Adsorption of plasma proteins on hydrophobic surfaces. I. Albumin and γ‐globulin
Authors: Bagnall Robert David 
Published: December 2004

AbstractThe adsorption of albumin and γ‐globulin from solution at the liquid/air and liquid/liquid interfaces has been studied by the pendant drop technique as a model for the solid‐liquid system. It is concluded that each protein adsorbs in a constant manner at the air, isooctane, and methylene iodide interfaces at equilibrium (1 hr), and the surface tension components of the protein layer presented to the hydrophobic phase have been found. The range of hydrophobic surfaces for which such constants behavior might be expected has been deduced, and it is shown that most common polymers lie within this range. A new model for protein adsorption is proposed, and the implications for biomaterials are discussed.
Carbon fiber‐reinforced carbon as a potential implant material
Authors: Adams D. , Williams D. F. , Hill J. 
Published: December 2004

AbstractA carbon fiber‐reinforced carbon is being evaluated as a promising implant material. In a unidirectional composite, high strengths (1200 MN/m2 longitudinal flexural strength) and high modulus (140 GN/m2 flexural modulus) may be obtained with an interlaminar shear strength of 18 MN/m2. Alternatively, layers of fibers may be laid in two directions to give more isotopic properties. The compatibility of the material with bone has been studied by implanting specimens in holes drilled in rat femora. For a period of up to 8 weeks, a thin layer of fibrous tissue bridged the gap between bone and implant; but this tissue mineralizes and by 10 weeks, bone can be observed adjacent to the implant, giving firm fixation. Potential applications include endosseous dental implants where a greater strength in the neck than that provided by unreinforced carbon would be advantageous.
“Floating‐socket” total shoulder replacement: Anatomical, biomechanical, and surgical rationale
Authors: Buechel Frederick F. , Pappas Michael J. , DePalma Anthony F. 
Published: December 2004

AbstractA prosthesis based on a new concept of gleno‐humeral motion has been developed and clinically tested for the past 2 years. The “floating‐socket” total shoulder replacement contains a nondislocatable, dual spherical bearing system consisting of a small sphere within a larger sphere with their centers offset to provide the physiologic “floating fulcrum” for mechanically advantageous motion. This geometric configuration allows a prosthetic range of motion in excess of anatomical limits to allow soft tissue structures to limit motion rather than mechanical impingement. The device is constructed from Co‐Cr‐Mo alloy and RCH‐1000 polyethylene such that no metal‐metal contact can occur.Experimental results in a 112‐lb adult male chimpanzee and six clinical cases have revealed superior fixation strength of both glenoid and humeral components, as well as functional adaptation of the prosthesis without fracture of fixturing bone or prosthetic dislocation.
Development of adhesive pit and fissure sealants using a MMA resin initiated by a tri‐n‐butyl borane derivative
Authors: Nakabayashi Nobuo , Masuhara Eiichi , Mochida Ei , Ohmori Ikuo 
Published: December 2004

AbstractA new adhesive fissure sealant, which consists of a solution of 3% 2‐hydroxy‐3‐β‐naphthoxypropyl methacrylate in methyl methacrylate (MMA), poly‐MMA powder and an oxidized tri‐n‐butyl borane, a polymerization initiator, was developed. Tensile bond strength between an acid‐etched bovine enamel and a poly‐MMA bar joined by this sealant was 60 kg/cm2, and the value did not decrease much after 30 days immersion in water at 37°C. Penetration of fuchsin into the sealant–enamel interface during a percolation test was not observed. SEM observation showed no voids between the enamel and the cured sealant.
Platelet–foreign surface interactions: Release of granule constituents from adherent platelets
Authors: Whicher S. J. , Brash J. L. 
Published: December 2004

AbstractThe interaction of suspensions of washed pig platelets with nine artificial surfaces (glass, polystyrene, three segmented polyurethanes, and surfaces formed by coating glass with albumin, fibrinogen, γ‐globulin, and collagen) is reported. Platelet adhesion and release from adherent platelets were measured via labeling with 51Cr and 14C‐serot onin. The apparatus was a couette flow device allowing observation of surface‐platelet effects uncomplicated by transport or flow effects. Using a two‐level factorial design the effects of albumin, fibrinogen, red cells, and platelet count on adhesion and release were estimated for each surface.Comparison of the various surfaces showed that collagen and γ‐globulin are the most reactive (mean adhesion, 34 platelets/1000 μm2, mean release 50% of granule contents). The other surfaces showed lower levels of release (∼25%), indistinguishable one from another. The adhesion levels of two hydrophilic polyurethanes and albumin were low, while those of the remaining surfaces were moderate.The effect of albumin was to reduce adhesion for the “moderate” group of surfaces. Fibrinogen increased adhesion to nonprotein surfaces and decreased release for collagen and γ‐globulin surfaces. High platelet count increased adhesion to fibrinogen, γ‐globulin, and collagen surfaces. Red cells increased adhesion to all surfaces and increased release for collagen and γ‐globulin.
Evaluation of a precipitation hardened wrought cobalt‐nickel‐chromium‐titanium alloy for surgical implants
Authors: Cahoon J. R. , Hill Liliane D. 
Published: December 2004

AbstractA Co‐Ni‐Cr‐Ti precipitation hardening alloy is evaluated for use as a surgical implant alloy. Static and fatigue strength studies indicate that the alloy is equivalent, or superior to, present implant alloys. In vitro and in vivo corrosion studies indicate that the material has good general corrosion resistance but may be susceptible to crevice corrosion. However, there appear to be no inherent difficulties in using precipitation hardened alloys for surgical implants and therefore it may be possible to develop a new class of materials possessing ultra‐high strength and excellent corrosion resistance for use in surgical implant applications.
Evaluation of couple/crevice corrosion by prosthetic alloys under in vivo conditions
Authors: Rostoker W. , Galante J. O. , Lereim P. 
Published: December 2004

AbstractAlloys of cast Co‐Cr‐Mo, wrought Co‐Cr‐W, wrought Co‐Ni‐Cr‐Mo (MP35N), Ti‐6% Al‐4% V, and graphite were incorporated in specimens which simulated both a couple and a crevice corrosion condition. These specimens were implanted in a dog for 30 months. Post‐sacrifice examination showed no substantial evidence of corrosion activity on the surfaces of the metals except for a tarnish film on the titanium alloy specimens. The presence of the tarnish film is taken as some evidence of corrosion activity and this correlated with a thicker average fibrous membrane, cellular activity in and near the fibrous membrane, and some increased vascularity. These must be regarded as preliminary observations.
Ferrographic analysis of wear particles in arthroplastic joints
Authors: Mears D. C. , Hanley E. N. , Rutkowski R. , Westcott V. C. 
Published: December 2004

AbstractAnalysis of aspirated synovial fluid appears to be a useful method for the study of the rates, mechanisms, and biological responses to wear in surgical joint replacements. Ferrography, an industrial technique of magnetic separation of particulate matter from samples of lubricating solutions, allows separation of wear debris from synovial fluid. Bichromatic microscopy and SEM X‐ray analysis permit identification of metallic particles from arthroplastic joints. Polarized light microscopy characterizes and differentiates polyethylene and polymethacrylate debris. The number and morphology of the wear particles in synovial specimens from arthroplastic joints correlate with the rate and the mechanisms of wear, as confirmed by examination of the implant and the adjacent synovial tissue.
Reaction of vaginal tissue of rabbits to inserted sponges made of various materials
Authors: Chvapil M. , Chvapil T. A. , Owen J. A. , Kantor M. , Ulreich J. B. , Eskelson C. 
Published: December 2004

AbstractSponges of the same size made of collagen (CS), polyurethane (PU), polyvinylalcohol (PVA) and acetylcellulose (AC) were inserted for 10 days in the vaginas of 22 rabbits. Light and scanning electron microscopy of the vaginal wall and its mucosal lining showed signs of cytotoxicity only with PU and AC while CS and PVA picture did not differ from sham controls. In order to explain the reasons for the toxic effects, all sponges were extracted into aqueous or organic solvent media and analyzed by gas liquid chromatography. Only several minute peaks in organic solvents were found. Extracts of all sponges tested for cytotoxicity in fibroblast cultures showed significant inhibition of H3–thymidine uptake. Nevertheless, extract of collagen sponge was significantly less cytotoxic than the extracts of all other sponges.
Arterio‐venous shunt with percutaneous leads in calves for long‐term in vivo testing of blood‐contact materials
Authors: Grosse‐Siestrup C. , Krautzberger W. , Bücherl E. S. 
Published: December 2004

AbstractIn six calves an extracorporeal arteriovenous shunt in combination with a successful type of percutaneous lead has been implanted. Flow chambers with various test materials can be inserted. Preliminary results show that this shunt can be used for long term tests for evaluation of blood contact material and studies about thrombus formation in an ex vivo setting as well as for permanent blood access for the purpose of various measurements, drug application and for hemodialysis.
A correlation between abrasion resistance and other properties of some acrylic resins used in dentistry
Authors: Harrison A. , Huggett R. , Handley R. W. 
Published: December 2004

AbstractThis investigation studies the relationship of hardness, elastic modulus and scratch width as dependent variables to the abrasion resistance of twenty‐three dental acrylic resins. The multiple correlation R, when all three variables are used as predictors, is 0.727. Because of the significant intercorrelations between the variables themselves a stepwise multiple regression analysis showed hardness as a redundant variable. Abrasive wear can be estimated from the following equation

The deletion of scratch width does not appreciably reduce the standard deviation of the estimate:

The method of curing the specimens conformed to the respective manufacturers' instructions. Abrasion and scratch tests were performed using methods developed by the authors and previously described in the literature, whereas the hardness and elastic modulus results were devised from standard test procedures.Further research is currently in progress to improve the predictive power of abrasion resistance with additional new variables.
Investigations with bioactivated polymethylmethacrylates
Authors: Hennig W. , Blencke B. A. , Brömer H. , Deutscher K. K. , Gross A. , Ege W. 
Published: December 2004

AbstractCompound bone cement on a PMMA base with an additive of bioactive glass ceramic particles in different portions and different particle sizes are tested in animal experiments. The tissue reactions to extracorporal polymerized specimens and to in situ polymerized specimens are observed. The experiments with an implantation period up to six months demonstrate a tight bonding between the newly formed osseous tissue and the glass ceramic particles at the interface. The inflammatory reactions in the vicinity of the implant are small. It is the objective of the investigations to improve the adherance of the bone cement at the interface to achieve a more durable anchorage of bone cement in the tissue.
Implant site infection rates with porous and dense materials
Authors: Merritt Katharine , Shafer Judith W. , Brown Stanley A. 
Published: December 2004

AbstractThe infection rate of implant sites bearing porous and dense implants was studied in mice. In the first model (acute infection) the mice were injected with Staphylococcus aureus subcutaneously at the implant site at the time of implantation. In the second (chronic) model the implants were left in place for four weeks for encapsulation or invasion to occur and then the organisms were inoculated. In the acute model the infection rate with the porous materials was greater. In the chronic model after tissue invasion the infection rate with the dense materials was greater. This supports the hypothesis that microorganisms can evade host defense mechanisms if they enter the pores of the implant before tissue invasion, but that once the implant is invaded with host tissue the bacteria are less apt to establish infection.
ESCA studies of surface chemical composition of segmented polyurethanes
Authors: Paik Sung C. S. , Hu C. B. 
Published: December 2004

AbstractSurface chemical analysis of two commercially available polyurethanes, i.e., Avcothane and Biomer was carried out by electron spectroscopy for chemical analysis (ESCA). The depth which is subject to analysis is in the range of 50–100 Å. The variables studied in this study are the difference in exposure to air or to the mold substrate during the solvent casting process. Model compounds such as a pure polydimethylsiloxane, polyether soft segment and hard segment copolymer were used to identify and assign various ESCA peaks. The air facing surface of Avcothane which is the blood contacting surface is found to be covered mostly with polydimethylsiloxane polymer, with a small amount of polyether soft segment mixed with silicone. Therefore, the hard segment of the polyurethanes is hidden beneath the blood contact surface in Avcothane. In Biomer films, the air facing surface contains a greater concentration of polyether soft segment than the substrate surface. These results are consistent with our previous results obtained by Fourier transform IR internal reflection studies and Auger electron spectroscopy.