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  • Artikel  (30)
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  • Chemistry  (30)
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  • 1980-1984  (30)
  • 1982  (30)
  • Medizin  (30)
  • 1
    Digitale Medien
    Digitale Medien
    Blood-materials interactions: The minimum interfacial free energy and the optimum polar/apolar ratio hypotheses (1982)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 16 (1982), S. 381-398 
    Details
    ISSN: 0021-9304
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Numerous hypotheses exist to explain observed blood-materials interactions. It is the purpose of this article to test two popular hypotheses, namely, the minimum interfacial free energy hypothesis and the optimum polar/apolar ratio hypothesis. Methacrylate polymers and copolymers were characterized using the captive bubble underwater contact angle method; bulk water content was determined by gravimetric methods; streaming potential measurements were made; and surface roughness and possible particulate contamination were evaluated by reflected light microscopy. In vitro blood tests include whole blood clotting time measurements on polymer-coated tubes; centrifugal force platelet adhesion on polymer-coated coverslips; and a measure of the partial thromboplastin time, Russell's viper venom time (Stypven time), and the prothrombin time of native whole blood exposed to polymer-coated microscope slides. Results suggest that platelet adhesion correlates in the opposite direction of whole blood clotting time and partial thromboplastin time, emphasizing the need for a multiparameter approach to blood-materials testing. Based on these tests the minimum interfacial free energy hypothesis is not supported. In fact, the data suggest the opposite to be true. It is apparent that platelet adhesion can be a misleading indicator of blood compatibility. Neither hypotheses can explain the apparent conflict between the platelet adhesion data and the coagulation time data.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jbm.820160407
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  • 2
    Digitale Medien
    Digitale Medien
    Irradiation crosslinking of the polytetrapeptide of elastin and compounding to dacron to produce a potential prosthetic material with elasticity and strength (1982)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 16 (1982), S. 11-16 
    Details
    ISSN: 0021-9304
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: The poly(tetra peptide), H- (L·Val1-L·Pro2-Gly3-Gly4)n-L·Val-OMe, which is a recurring sequence in tropoelastin the precursor protein of the elastic fiber, has been irradiation crosslinked to produce an elastomeric material with limited strength. When a material such as a Dacron fabric is impregnated by the coacervate phase of the poly(tetra peptide) prior to irradiation crosslinking at 50 Mrad, the crosslinked product exhibits stress-strain curves with good elastomeric properties and high strength. In addition to the stress-strain curves, the material is characterized by scanning electron microscopy.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jbm.820160104
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  • 3
    Digitale Medien
    Digitale Medien
    Effect of pore size on the peel strength of attachment of fibrous tissue to porous-surfaced implants (1982)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 16 (1982), S. 571-584 
    Details
    ISSN: 0021-9304
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Twenty-four rectangular metal plates were fabricated with surface regions in three different pore size ranges (5-20 μm, 20-50 μm, 50-200 μm). The plates were implanted into the dorsal subcutaneous tissue of 12 adult mongrel dogs for periods of 4, 8, 12, and 16 weeks. After animal sacrifice, the fibrous tissue which adhered to the porous-surfaced regions of each plate was mechanically peeled off to give an indication of the strength of tissue attachment. The tissue was examined by both transmitted light and scanning electron microscopy. At each time period, the tissue that contacted the porous regions was found to be collagenized fibroconnective tissue. The mechanical tests indicated an increasing strength of tissue attachment with increasing implantation time and pore size range. The largest pore size range of approximately 50-200 μm produced a mean peel strength of attachment of 27.5 g/mm at the 16-week period.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jbm.820160505
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  • 4
    Digitale Medien
    Digitale Medien
    Enzymatic removal of formalin-fixed tissues from polyester arteries, and its effect on physical properties of fibersAn oral presentationof the resultts of this article was made before the Medical Plastics Division of the Society of Plastic Engineers, 39th Annual Technical Conference, Boston, MA, May 4, 1981. (1982)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 16 (1982), S. 659-668 
    Details
    ISSN: 0021-9304
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: A method is presented that can be utilized for the removal of formalin-fixed tissues from arterial grafts without. Affecting fiber material properties. Such a method could prove highly useful for studying the changes in the structure and properties of graft fiber as functions of important clinical variables. Information on what actually happens to the arterial graft material in situ with passage of time is greatly lacking in the current graft literature. The method proposed involves treatment of the formalin fixed fiber-tissue complex with an enzymatic preparation containing enzymes derived from the porcine pancreas (pancreatin) in solution with tris(hydroxymethyl) aminomethane buffer at pH 7.6. Studies with two different grafts - a Microknit Dacron Bifurcation from a clinical patient 10¼ years after implantation and stored in formalin for 11 months, and a Sauvage Filamentous Velour of Dacron from an animal 24 h after implantation and stored in formalin for nine months - showed that the treatment was highly effective in completely removing the tissues at concentrations of pancreatin as low as 2.5%. The same treatment given to the virgin yarns of grafts revealed no significant effects on tensile, dimensional, and morphological properties.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jbm.820160513
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  • 5
    Digitale Medien
    Digitale Medien
    A comparison of the in vitro cytotoxicity of four restorative materials assessed by changes in enzyme levels in two cell types (1982)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 16 (1982), S. 519-528 
    Details
    ISSN: 0021-9304
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: A 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.
    Zusätzliches Material: 4 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jbm.820160417
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  • 6
    Digitale Medien
    Digitale Medien
    Reaction of mercury with silver-tin dental amalgam alloy (1982)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 16 (1982), S. 535-547 
    Details
    ISSN: 0021-9304
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Electron diffraction evidence confirming the ordered orthorhombic crystal structure of the γ phase of the silver-tin system has been obtained, and it has been established by optical metallography that an alloy with a composition corresponding to the dental amalgam alloy formula Ag3Sn (i.e., 26.85 wt % Sn) lies outside the single γ phase field and in the duplex (γ + Sn) phase field adjacent to it. Studies of the mechanism of the hardening reaction of single crystals of homogeneous γ phase alloys with mercury were carried out using both scanning and transmission electron microscopy. Mercury attack occurred preferentially along welldefined planes in the single crystals. Using electron channeling and trace analysis techniques these planes of preferential attack were found to be {010} and {011}, and from transmission electron microscopy of thin foils these were shown to be slip bands and deformation twins, respectively. In bicrystals of γ phase material, preferential attack also occurred along grain boundaries. Similar preferential mercury attack, leading to the development of deep planar intrusions into the γ phase material, was observed in an experimental dental amalgam prepared from a lathe-cut homogeneous γ phase amalgam alloy. It is believed that the presence of such features would have important implications for the clinical performance of dental amalgam.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jbm.820160502
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  • 7
    Digitale Medien
    Digitale Medien
    A study of the interface between a fibrous polyurethane arterial prosthesis and natural tissue (1982)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 16 (1982), S. 827-838 
    Details
    ISSN: 0021-9304
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Fibrous polyurethane samples were implanted in subcutaneous tissue, muscle, and as an arterial prosthesis for periods up to six months. The interface between the polymer and living tissue was studied using optical, scanning, and transmission electron microscopy. A good correlation was found between the micromorphology of the polymer-tissue interface observed in three experimental methods used. Ingrowth of tissue occurs by cell penetration into the fibrous network of the polymer implant and eventual encapsulation by connective tissue. Full details of the distribution of collagen and the cell components around the individual polymer fibers and the structure of the connective tissue are given.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jbm.820160608
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  • 8
    Digitale Medien
    Digitale Medien
    Parameters affecting the stress distribution around LTI carbon and aluminum oxide dental implants (1982)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 16 (1982), S. 875-885 
    Details
    ISSN: 0021-9304
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Three-dimensional finite element stress analysis was used to study the effects that implant neck geometry and the tissue properties at the implant-bone interface have on the stress distribution around freestanding blade- and post-type LTI carbon and aluminum oxide dental implants. Implants having neck flares of 13° and 26° were studied. In addition, to simulate fibrous encapsulation of the implant as opposed to a direct bone apposition retention mechanism, a soft tissue interposing layer between implant and bone was also modeled. The results of the study indicate that a reduction in neck flare from 26° to 13° was a positive design change for blade- and post-type LTI carbon implants and blade-type aluminum oxide implant but not for post-type aluminum oxide implant. The results of the study indicate the presence of fibrous tissue surrounding the implants may be indicative of a failing system and may be the result of either hypophysiological stress (aluminum oxide implants) or hyperphysiological stress (LTI carbon implants).
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jbm.820160612
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  • 9
    Digitale Medien
    Digitale Medien
    Susceptibility of surgical cobalt-base alloy to pitting corrosion (1982)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 16 (1982), S. 799-810 
    Details
    ISSN: 0021-9304
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: The objective of this investigation was to evaluate the in vitro and in vivo susceptibilities of a surgical cobalt-chromium-molybdenum alloy to localized corrosion. In vitro cyclic anodic polarization curves were generated for the cobalt alloy under various surface and electrolyte conditions. Surfaces of the test specimens were examined before and after each polarization experiment. In vivo analyses involved macroscopic and microscopic examinations of cobalt alloy surfaces on retrieved total hip prostheses. The electrolyte selected for the in vitro polarization study was 0.9% saline at a pH of 7.00 ± 0.05 and temperature of 37 ± 1°C in both aerated and deaerated conditions. Surface conditions for the cobalt alloys included nonpassivated and passivated treatments. Hysteresis behavior was exhibited by the passivated alloy but not by the nonpassivated alloy. According to the protection potential theory, hysteresis behavior indicates a material should be susceptible to pitting corrosion. Therefore, based on polarization curves and theory, the results of the present study indicated the cobalt alloy was susceptible to pitting corrosion when in the passivated condition but not when in the nonpassivated condition. Examination of the surfaces before and after each polarization curve revealed no evidence of pitting corrosion. Also, the examination of nonwear cobalt surfaces of total hip prostheses with implantation times up to 6 years revealed no features uniquely identified as the result of pitting corrosion. Therefore, it was hypothesized that certain conditions inherent in the electrochemical phase of this study had caused the development of hysteresis behavior for the passivated alloy, and this hysteresis behavior should not be associated with pitting corrosion as is normally taken to be the case by application of the protection potential theory. Instead, it is postulated that the hysteresis behavior exhibited by the passivated alloy is due to processes involving a breakdown of the pre-established passive film followed by a repassivation characteristic of the saline electrolyte.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jbm.820160606
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  • 10
    Digitale Medien
    Digitale Medien
    Microleakage of conventional and microfilled composite restorative resins (1982)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 16 (1982), S. 901-910 
    Details
    ISSN: 0021-9304
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Microfilled composite resins have been introduced in clinical dentistry because of the difficulty in finishing conventional composite resins satisfactorily. Owing to the difference in coefficients of thermal expansion of the two resin systems, the objective of this in vitro study was to evaluate microleakage of a conventional and a microfilled composite resin. Class V cavities with butt cavosurface margins were prepared in the middle third of the facial surfaces of the crowns of 80 noncarious human premolar teeth; they were acid etched within the preparations only. Forty preparations were restored with Concise composite and forty with Silar microfilled resin. Ten teeth from each group were subjected to cyclic temperature changes between 5 and 55°C for 1000, 2500, or 5000 cycles, respectively, and ten teeth from each group were not cycled (controls). After suitable preparation, the teeth were immersed in 45Ca solution for 18 h and contact radiographs were prepared. Microleakage was scored 0-3 at both the cervical and occulusal margins of the restorations. Microleakage was significantly greater at the cervical margins than at the occlusal margins. Differences within occlusal and cervical microleakages among the two resins were not significant.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jbm.820160614
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