摘要:

AbstractA series of poly(α‐amino acid)s with controlled chemical variations were investigated in order to assess the effect of different chemical moieties upon arterial thrombosis. The gross implant surface properties ranged from hydrophobic to hydrophilic, ionic and nonionic. The materials were tested by implantation within canine femoral and carotid arteries. Results were compared with the response to the polyurethane Biomer.The changes in implant surface chemistry elicited a range of response that varied from intense thrombosis and rapid vessel occlusion to minimal thrombosis and endothelialization. The results showed that no simple relationship exists between a gross surface property, such as hydrophobicity, and the degree of thrombosis resistance. Some hydropobic and hydrophilic materials were found to have good thrombosis were shown to play and hydrophilic materials were found to have good thrombosis were shown to play an important role in both initial thrombosis and endothelialization. The major difference between materials that progressed to to rapid vessel occlusion and materials that remained patent was the degree of direct leukocyte adherence and spreading on the implant surface prior to extensive platelet aggregation (<30 min). It was consistent for both hydrophobic and hydrophilic materials that the lack of direct leukocyte adherence to the implant surface was associated with intense thrombosis and rapid vessel occlusion. Conversely, the presence of numerous leukocytes directly adherent to either hydrophobic or hydrophilic surfaces appeared to have a moderating effect upon thrombosis and vessels with these implants remained patent. In instances when thrombosis was nonocclusive, the surfaces of the thrombi became endothelialized, primarily through the transformation of mononuclear leukocytes into endothelial cells. This article includes a hypothetical model representing the sequence of events and alternative pathways occurring at the blood‐material interface, with special attention given to the involvement of leukocytes in arterial thromb

ISSN:0021-9304    

DOI:10.1002/jbm.820130402

出版商:John Wiley&Sons, Inc.    

年代:1979

数据来源: WILEY

摘要:

AbstractA high‐strength, high‐ductility, austenitic stainless steel has been evaluated for use in surgical implants by performingin vivotests 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 thein vivotests 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 fromin vitrostudies. 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 anin vitrot

ISSN:0021-9304    

DOI:10.1002/jbm.820130403

出版商:John Wiley&Sons, Inc.    

年代:1979

数据来源: WILEY

摘要:

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 a

ISSN:0021-9304    

DOI:10.1002/jbm.820130404

出版商:John Wiley&Sons, Inc.    

年代:1979

数据来源: WILEY

摘要:

AbstractThe adsorption of albumin, γ‐globulin, and fibrinogen was measured on threeex vivopolymeric shunt surfaces [polyvinyl chloride (PVC), Silastic, and segmented polyether urethane (Biomer)] exposed to flowing heparinized, canine bloodin vivo. Small amounts of radiolabeled proteins were infused into anesthetized mongrel dogs and the deposition of radioactivity on the walls of femoral arteriovenous shunts was followed with time for two hours following initial blood‐polymer contact.Previously, transientin vivoplatelet and fibrin deposition onto PVC, Silastic, and Biomer was measured by a similar technique in the absence of anticoagulant. A time‐dependent phase of thrombus deposition followed by thromboembolism was observed on the PVC and Silasticshunt surfaces but not on the Biomer surface. In the studies reported here on PVC and Silastic, fibrinogen adsorption was found to predominate initially, though it subsequently desorbed somewhat and was replaced by albumin and γ‐globulin. On Biomer, the adsorption of all three proteins increased with time following initial blood contact and fibrinogen was less prominent initially. The PVC surface was found to become passivated with respect to further thrombogenesis after 60‐min exposure to flowing blood, at which time a higher fraction of albumin was present on the surface compared to that at earlier blood contact times. These results indicate that rearrangement of adsorbed protein species occurs with time on polymer surfaces exposed to flowing bloodin vivo. Early and predominant fibrinogen adsorption appears to be an important factor in the thrombogenic and embolic events observed on the PVC and Silastic shunt surf

ISSN:0021-9304    

DOI:10.1002/jbm.820130405

出版商:John Wiley&Sons, Inc.    

年代:1979

数据来源: WILEY

摘要:

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 ad

ISSN:0021-9304    

DOI:10.1002/jbm.820130406

出版商:John Wiley&Sons, Inc.    

年代:1979

数据来源: WILEY

摘要:

AbstractA study has been carried out on the coupling of proteins onto crosslinked poly(vinylalcohol) hydrogel membranes and ethylene‐vinyl alcohol copolymer(EVA) films pre‐viously grafted with oxidized starches having many pendant aldehyde groups. The coupling reaction of proteins is based on the Schiff's base formation between the amino groups of proteins and the aldehyde groups of the oxidized starches which have been grafted onto the substrate membrane or film through acetalization of the aldehyde of starch with hydroxyl groups of the substrate polymers. The grafting of oxidized starches onto the EVA films seems to be restricted to the film surface, since no detectable change is observed in the weight and the attenuated total reflection infrared spectrum of the grafted films. The amount of grafted protein, determined by the ninhydrin method, reveals that, at least, plasma proteins such as serum albumin and fibrinogen are grafted to the film surface in a monomolecular layer without undergoing a marked denaturation. The α‐amylase grafted onto the EVA film showed a distinct enzymatic activity in hydrolysis of amylose and starch, but the activity was very low compared with that of the ungrafted, soluble α

ISSN:0021-9304    

DOI:10.1002/jbm.820130407

出版商:John Wiley&Sons, Inc.    

年代:1979

数据来源: WILEY

摘要:

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 s

ISSN:0021-9304    

DOI:10.1002/jbm.820130408

出版商:John Wiley&Sons, Inc.    

年代:1979

数据来源: WILEY

摘要:

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 ofMacaca 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 otherwi

ISSN:0021-9304    

DOI:10.1002/jbm.820130409

出版商:John Wiley&Sons, Inc.    

年代:1979

数据来源: WILEY

摘要:

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, thein vitroeffect 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

ISSN:0021-9304    

DOI:10.1002/jbm.820130410

出版商:John Wiley&Sons, Inc.    

年代:1979

数据来源: WILEY

摘要:

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.

ISSN:0021-9304    

DOI:10.1002/jbm.820130411

出版商:John Wiley&Sons, Inc.    

年代:1979

数据来源: WILEY