摘要:

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 3Msaline atpH 7.4 despite a detection limit of 10−5μg heparin/cm2min. Prolonged partial thromboplastin times of greater than 1200 sec were observed (control: PTT = 120 sec). Preliminaryex vivotesting 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/materia

ISSN:0021-9304    

DOI:10.1002/jbm.820130302

出版商:John Wiley&Sons, Inc.    

年代:1979

数据来源: WILEY

摘要:

AbstractBar‐shaped polymethylmethacrylate test specimens removed from rabbits after implantation for times up to 26 months showed a significant change in fracture stress as determined by three‐point bending in the period between 12 and 26 months. There were no adverse findings in the tissue which developed around the bone‐cement test

ISSN:0021-9304    

DOI:10.1002/jbm.820130303

出版商:John Wiley&Sons, Inc.    

年代:1979

数据来源: WILEY

摘要:

AbstractPolymeric carbons1are 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 p

ISSN:0021-9304    

DOI:10.1002/jbm.820130304

出版商:John Wiley&Sons, Inc.    

年代:1979

数据来源: WILEY

摘要:

AbstractCu‐rich amalgams represent a significant change in amalgam alloy formulation which may result in enhanced performance. Significantly, these systems reduce or eliminate the γ2phase. 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. γ2was found in all systems, but was reduced or eliminated on storage at 37°C at rates which varied from system to system. During γ2elimination, the Cu6Sn5content correspondingly increased, indicating that solid‐state reaction occurs for up to six months in

ISSN:0021-9304    

DOI:10.1002/jbm.820130305

出版商:John Wiley&Sons, Inc.    

年代:1979

数据来源: WILEY

摘要:

AbstractIn the present study the conditions leading to tight binding of human serum albumin to the Amberlite XAD‐7 resin without the use of chemical coupling agents have been defined. Optimal binding (10.97 mm/kg dry XAD‐7) was achieved atpH 5.0 and adsorption conformed to a Langmuir isotherm. Theoretical analysis of the data suggest adsorption of a monolayer of albumin which is suported by the absence of visual surface coating on scanning electron micrographs. Binding of human serum albumin was reduced when two chemical coupling agents, glutaraldehyde and carbodiimide were included in the human serum albumin solution, the elution of adsorbed HSA from the resins under severe flow conditions was reduced, and the amount eluted was minimal in all instan

ISSN:0021-9304    

DOI:10.1002/jbm.820130306

出版商:John Wiley&Sons, Inc.    

年代:1979

数据来源: WILEY

摘要:

Abstract13C NMR spectroscopy has been applied to the analysis of carboxylic poly‐acid cement liquids. Monomer incorporation, composition ratio, sequence statistics, and stereochemical configuration have been considered theoretically, and determined experimentally, from the spectra. Conventionally polymerized poly(acrylic acid) has an approximately random configuration, but other varieties may be synthesized. Two commercial glass‐ionomer cement liquids both contain tartaric acid as a chelating additive but the composition of their poly‐acids are different. Itaconic acid units, distributed randomly, constitute 21% of the repeating units in one of these polyelectro

ISSN:0021-9304    

DOI:10.1002/jbm.820130307

出版商:John Wiley&Sons, Inc.    

年代:1979

数据来源: WILEY

摘要:

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 proce

ISSN:0021-9304    

DOI:10.1002/jbm.820130308

出版商:John Wiley&Sons, Inc.    

年代:1979

数据来源: WILEY

摘要:

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 failur

ISSN:0021-9304    

DOI:10.1002/jbm.820130309

出版商:John Wiley&Sons, Inc.    

年代:1979

数据来源: WILEY

摘要:

AbstractThe role of catheter surface roughness in initiation and propagation of intravascular catheter thrombosis was studied in dogs, utilizing the scanning electron microscope. Catheters were inserted in major arteries and veins for 200 min and the animals then sacrificed. Catheter segments, both with and without associated thrombi, were scrutinized with the scanning electron microscope. No correlation was found between catheter surface roughness and thrombus formation, suggesting that the inherent chemical characteristics of the catheter is most important in the initiation of intravascular catheter thrombus formation.

ISSN:0021-9304    

DOI:10.1002/jbm.820130310

出版商:John Wiley&Sons, Inc.    

年代:1979

数据来源: WILEY

摘要:

AbstractIn this study, specimens of a high‐copper amalgam, prepared at different final Hg contents, were examined in several different experiments. The results showed that as the Hg content is increased, a point is reached beyond which creep and the amount of Sn in γ1exhibit a sudden increase. As the Hg content is increased further, γ2can be detected. These phenomena can be explained by the hypothesis that insufficient Cu is present at higher Hg contents to combine with Sn to form Cu6

ISSN:0021-9304    

DOI:10.1002/jbm.820130311

出版商:John Wiley&Sons, Inc.    

年代:1979

数据来源: WILEY