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  • Articles  (94)
  • Polymer and Materials Science  (94)
  • 1980-1984  (94)
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  • 1981  (94)
  • Medicine  (94)
  • 1
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 15 (1981) 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
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  • 2
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    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 15 (1981), S. iii 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
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  • 3
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    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 15 (1981), S. ix 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
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  • 4
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    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 15 (1981), S. 9-18 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Physical and antimicrobial properties of a newly developed gelatin based spray-on foam bandage for use on skin wounds have been evaluated. The aqueous foam is sprayed from aerosol containers and effectively covers and washes uneven wound surfaces. The foam dries to form an adherent and stable three-dimensional matrix which diminishes evaporative water losses. The foam possesses antimicrobial activity against gram-positive, gram-negative, and fungal contaminants.
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  • 5
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    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 15 (1981), S. 1-7 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Tubings extruded from one batch of polyvinylchloride resin at five temperatures ranging from 110 to 205°C were tested for thrombogenicity in the saphenous vein and aorta of sheep. There was more thrombus in both the vein and aorta on tubings extruded at lower temperatures. The surface areas of renal infarction were smaller when lower temperature tubings were inserted into the aorta. Scanning electron microscopy showed that lower extrusion temperatures caused greater roughness on the tubings. This greater roughness was confirmed by roughness measurements. It is suggested that the association which has been demonstrated between roughness and thrombus formation might be due to the degree of adhesion of the thrombus to the surface rather than to differences in thrombogenicity.
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  • 6
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    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 15 (1981), S. 19-27 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The tensile strengths of poly(glycolic acid) (PGA) sutures immersed in buffered and unbuffered aqueous media were compared. The media used were an unbuffered physiological saline solution (pH = 5.0) and a phosphate-buffered physiological saline solution (pH = 7.4). PGA samples were immersed for various periods in each medium, and kept at 37 ± 1°C in a constant temperature oven. The tensile strengths of the specimens were tested immediately after removal from the medium. Stress-strain curves of the specimens were expressed in terms of the stress unit “tenacity,” commonly used in the study of fibrous polymers; it is an appropriate unit for materials of fibrous nature. These stress-strain curves were investigated as functions of buffering and duration of immersion. Degradation reduced the tensile strength of PGA more in the buffered saline solution than in the unbuffered. This higher rate of degradation in the buffered solution might be due to the presence of Na2HPO4, which removed the degradation products, shifted the reaction toward increased hydrolosis, and accelerated the loss of tensile strength in the PGA. A continuous decrease in the pH of the unbuffered solution supports this explanation. Tied-chain segments of macromolecules, a theory widely used in the study of mechanical strength of fibrous polymer may be the key to a comprehensive description of the degradation phenomenon of PGA.
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  • 7
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    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 15 (1981), S. 307-317 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Poly(2-hydroxyethyl methacrylate)-(PHEMA) has been prepared by polymerizing in presence of different types of water-soluble additives, at various amounts, which were removed by swelling in water. Mechanical properties of swollen samples have been measured and analyzed by using the classical theory of rubber elasticity. Water permeability measurements were also performed to detect the presence of micropores and to determine the type of water transport. It has been shown that it's possible, using different types and amounts of additives, to obtain a wide range of physical properties of swollen PHEMA as required for various biomedical applications.
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  • 8
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    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 15 (1981), S. 291-305 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The interface of alkali-poor glass ceramic implanted in femora of male Sprague-Dawley rats shows soft tissue, chondroid, osteoid, and bone in connection with the implant. The ultrastructure of the interface with soft tissue mainly exhibits a corrosion process, during which the dissolution of the crystalline phase of the glass ceramic precedes the dissolution of the glassy phase. Macrophages are involved in this process phagocytosing debris of the glassy phase and removing as well as dissolving the remainders of the glass ceramic. Under circumstances not yet fully understood, the corrosion stops, and ground substance like material is deposited, which can be, at least partially, mineralized. After the disappearance of macrophages, chondroblasts, and/or osteoblasts lay down collagen fibrils and ground substance in which matrix vesicles are discernible, representing initial foci of mineralization. Areas with bone connection display collagen fibers and deposits of apatite crystals in close relationship to the bulk glass ceramic as well as small particles mainly derived from the glassy phase of the implant, providing the micromorphological substrate for the shearing and tensile strength of the interface between glass ceramic and bone.
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  • 9
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    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 15 (1981), S. 335-341 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A comparison of 130 grafts done in 101 patients included 47 veins, 25 Johnson & Johnson dialdehyde-starch-tanned collagen prostheses, and 58 NCGT grafts that had been followed for a 40-month period. This study had documented the fact that in spite of frequent poor runoff, a useful result is provided by the NCGT graft apparently due in part to its built-in nonthrombogenic structure providing a cumulative patency of 73%. The patency rate was even superior with venous bypasses. Therefore, we still feel that the autogenous vein provides the most useful bypass conduit available in vascular reconstruction. In situations where a vein could not be used or was not available the NCGT graft offers an equally useful nonthrombogenic surface to maintain prolonged patency. Thus, collagen appropriately modified can provide a useful prosthesis in vascular reconstruction.
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  • 10
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The fate of autologous pericardium when used to replace a tricuspid valve leaflet has been investigated in dogs. Changes have been studied by means of macroscopic, mechanical, histological, scanning electron microscopy, and in vitro culture techniques. In each of nine experiments the valve failed and death occurred within the first 15 post-operative days. Retraction, thickening of the cusp, fibrinous deposition and/or tissue rupture were associated with a decrease of resistance to traction tests, decrease of elasticity and increase of viscosity of the implanted tissue. The early behavior of autologous pericardium was characterized by precocious inflammatory reaction on the valve leaflets, focal disruption of the collagenous structure of the leaflets, absence of fibroblastic cell infiltration as confirmed by in vitro culture of implanted pericardium and the lack of endothelial-like cell surface at the 10th-15th postoperative day.
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  • 11
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    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 15 (1981), S. 343-348 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A silver staining technique was developed to demonstrate microdefects in dental restorative composites. Fine silver particles were preferentially introduced into the damaged region to provide optical contrast between the damaged and the undamaged regions. The amount of silver deposition determined with an electron probe microanalyzer, provided an indication of the extent of damage within the dental composites. Examples to demonstrate this technique were given with one clinically worn dental composite restoration and one in vitro worn composite sample.
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  • 12
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    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 15 (1981), S. 349-361 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Avcothane is a commercially available copolymer of polyether, polyurethane, and polydimethylsiloxane; it is used primarily in aortic balloon pumps. The pumps consist of three segments which are cemented or fused together to form the balloon. The objective of this work is to characterize the surfaces, inside and outside, of the three balloon pump sections. By using x-ray photoelectron spectroscopy (ESCA), ion scattering spectroscopy (ISS), and secondary ion mass spectrometry (SIMS) a detailed analysis of the Avcothane surfaces can be performed and comparisons between various surfaces made. Previous workers have reported ESCA and Auger electron spectroscopy (AES) measurements of Avcothane and comparisons with their results will be presented. SIMS and ISS are useful analytical tools for studying polymeric biomaterials because these techniques are usually more surface sensitive than either ESCA or AES. SIMS and ISS data indicate that a thin fluorine-rich film (probably a fluorocarbon polymer) is present on the Avcothane surface. Signals from the fluorine-rich layer are more intense from the inside of the balloon pump and the intensity generally decreases from top to bottom. The outside sections of the aortic balloon pump also show the presence of fluorine, but the signals are far less intense than from the inside. One possible explanation for the fluorine-rich layer is that a fluorine-containing compound is deposited on the balloon pump during molding and preparation. Another possibility is that the layer is deposited during preparation of the Avcothane itself, but is essentially removed from the outside during sterilization.
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  • 13
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: ABA-type block copolymers composed of 2-hydroxyethyl methacrylate (HEMA), a hydrophilic monomer, and styrene (St), a hydrophobic monomer, were synthesized by the coupling reaction of telechelic oligomers used as prepolymers. These block copolymers may be represented as microphase-separated structures. It is therefore possible to change the balance between hydrophilicity and hydrophobicity in the level of an assembled order of macromolecules. In response to the relative composition of the copolymers, three typical morphological patterns were observed in electron microscopic photographs: dispersed domains of continuous St chains in the region of HEMA chains, alternate HEMA and St lamellae and finally, dispersed phases of continuous HEMA chains in the region of St chains. The effect of the hydrophilic and hydrophobic microdomains of the copolymers on the mode of interaction between polymers and platelets was studied by the microsphere column method. In the case of homopolymers and random copolymers, a significant degree of platelet adhesion and aggregation was observed. However, the degree of platelet adhesion and deformation was suppressed on the surfaces of the block copolymers containing 0.608 and 0.347 mole fractions of HEMA whose microdomains were hydrophilic-hydrophobic lamellae and isolated hydrophilic islands in hydrophobic areas, respectively. These results show that the microphase-separated structures were antithrombogenic and prevented platelet adhesion and deformation. On the basis of the results obtained, the interaction between platelets and polymer surfaces was described in terms of the effect of hydrophilic and hydrophobic microdomains.
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  • 14
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    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 15 (1981), S. 433-435 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
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  • 15
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    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 15 (1981), S. 425-432 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The molecular and macroscopic changes occurring during the polymerization of poly(methyl methacrylate) (PMMA) bone cement have been investigated. Electron paramagnetic resonance (EPR) spectroscopy was used to monitor free-radical generation and this was compared to temperature changes occurring in the cement for various ratios of polymer powder to liquid monomer (P/L ratio) used in the sample preparation. Both the concentration and the characteristic growth time of the free radicals associated with the polymerization of the bone cement depended on the P/L ratio used. Larger P/L ratio resulted in shorter characteristic growth time for the free radicals as well as a shorter time for the occurrence of the peak sample temperature. Smaller P/L ratios gave smaller maximum concentrations of free radicals and larger peak temperatures. These results are explained on the basis of (1) more initiators present at higher P/L ratios resulting in faster polymerization and (2) less initiators and more monomers present at smaller P/L ratios resulting in fewer radicals but more exothermic reactions. The free radicals present in the bone cement due to the manufacturer's sterilization process were found to be proportional to the fraction of powder used in the preparation, indicating negligible monomer loss during sample mixing.
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  • 16
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    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 15 (1981), S. 565-575 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The A.D.A. acute systemic test for type II, class 11 materials defines compliance on the basis of fewer than 50% mortality at 2 weeks. Histopathologic criteria were developed from pilot study data to evaluate the effects of these materials. In this double blind study, the frequency of histopathological changes in lung, liver, small intestine, and kidney were rated at 2 and 5 weeks, for six dental crown and bridge alloys ranging from 44% to 97% (Au, Pt, and Pd). Two positive 360 mg/kg and 1 g/kg of cadmium and two negative, a blank capsule and untreated control groups were used. There was significant difference (chi square test, X2 = 0.95) between the positive and negative controls at 2 and 5 weeks. The lung, liver, kidney showed the highest level of histopathological changes. Significant changes occurred in the four tissues for all alloys at two and five weeks. At five weeks, alloys with a lower noble metal content (44-62%, Au, Pd, and Pt) elicited significant chronic changes, while higher noble metal content (78-97%) showed healing and no significant difference from the negative controls. Applying histopathologic criteria and statistical parameters independent examiners can examine experimental animals and arrive at conclusive and reproducible results.
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  • 17
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    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 15 (1981), S. 605-610 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
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  • 18
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    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 15 (1981), S. 591-603 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Proteolytic enzymes have been employed in an in vitro model to simulate the in vivo degradation of a synthetic poly(amino acid) hydrogel. Trypsin and collagenase had no effect on crosslinked poly(2-hydroxyethyl-L-glutamine) but pronase and papain dissolved the hydrogel. The initial effect of papain was to decrease the effective cross-link density without producing soluble material. This effect was similar to that observed previously in vivo. Analysis of the papain digestion products showed that oligomers of degree of polymerization 4-9 were the chief products. The rate at which oligomers were formed increased with increasing crosslink density. This phenomenon was attributed to hydrophobic effects.
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  • 19
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    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 15 (1981), S. 611-614 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
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  • 20
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    Journal of Biomedical Materials Research 15 (1981), S. 655-661 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Cellulose oxidized with periodate (OC) has been shown to be a biocompatible, biodegradable matrix suitable for immobilization and sustained release of drugs. In the present work, insulin was immobilized on the OC-matrix and the release profile in vivo and in vitro was examined. The hormone is bound to the matrix by Schiff's bond formation and is released by hydrolysis of this bond as well by degradation of the OC-matrix. The release can be sustained over longer periods by reducing the Schiff's base with NaBH4. The insulin depots could be conveniently injected as suspensions and are able to maintain glucose levels in diabetized rabbits at normal values over several days.
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  • 21
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    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 15 (1981), S. 785-785 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
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  • 22
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    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 15 (1981), S. 769-780 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Equipment is described which enables the determination of the creep behavior of small specimens of dental amalgam under tensile stresses. The apparatus has been used to measure the creep strain of both low and high copper dental amalgams at 34°C, in the stress range 9.4 to 38.8 MNm-2, for time periods of up to 24 h. Significant differences were found in the controlling creep mechanisms for the various amalgam types. Conventional amalgam displayed classical steady-state creep. The high copper amalgams, however, were best represented by transient creep equations implying interference to the motion of dislocations by the presence of hardening precipitates.
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  • 23
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    Journal of Biomedical Materials Research 15 (1981), S. 829-833 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A previous study of the effect of final Hg content on the static creep of a single-composition high-Cu amalgam alloy showed a sudden increase or jump in creep at a specific Hg content, and the presence of the Sn—Hg phase (γ2) at final Hg contents subsequent to this creep jump. This observation is consistent with the less-than-optimum clinical performance reported for this alloy. A repetition of these tests conducted on test specimens 3 months and 6 months of age showed the creep jump to shift to higher Hg contents. However, even at 6 months of age, the final Hg content to be expected in clinical restorations was still positioned after the initiation of the creep jump where a small amount of γ2 is known to be present.
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  • 24
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    Journal of Biomedical Materials Research 15 (1981), S. 843-851 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Conventional finishing and polishing techniques used to prepare Vitallium subperiosteal dental implant castings were found to produce low energy surfaces as measured by critical surface tension. Standard metallographic preparation gave slightly higher values. Glow discharge cleaning of both types of polished surface gave much higher critical surface tension values. This suggests the presence of an organic film after surface polishing of the implant which may later affect tissue reaction, in particular attachment, as has been noticed in related animal studies.
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  • 25
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    Journal of Biomedical Materials Research 15 (1981), S. 853-865 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Bone remodeling due to stress-shielding has been studied using a model system consisting of metal-polymer laminated fixation plates securely fixed to canine femurs. The plate stiffness was controlled by varying the ratio of metal facing to polymer core thickness in the laminate design while secure fixation to bone was achieved by providing a porous bone interfacing surface for the ingrowth of bone from the periosteal surface. Observations of laterally and medially placed plates indicated resorption in the area of the periosteal and endosteal bone surfaces respectively, for the higher stiffness composite plates used. The results indicate that plate stiffness greater than approximately 70 GPa (axial) and 6 N m2 (flexural) will result in extensive bone remodeling in the canine femur after a six month implantation period.
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  • 26
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    Journal of Biomedical Materials Research 15 (1981), S. 867-878 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Mechanisms of corrosion at the areas of contact between screw heads and plate holes were investigated using electrochemical potential recording techniques. Static crevice corrosion was studied with plates and screws in isotonic and hypertonic saline solutions (0.9 to 7.2% NaCl). Fretting corrosion was studied in vitro with plates screwed to tubular bone analogs which were subjected to cyclic axial loads, and was studied in vivo with plates screwed on the tibia of sheep. Static tests showed that crevice corrosion does not occur in isotonic saline for periods up to one year, but can occur in hypertonic saline solutions. Dynamic loading tests demonstrated immediate potential changes which were related to the magnitude of the applied load, indicating fretting corrosion due to motion between screw head and plate, both in vitro and in vivo. A mechanism for screw-plate relative motion is proposed. It is hypothesized that corrosion seen in clinically retrieved implants due to fretting corrosion which predisposes the contact area to crevice corrosion attack.
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  • 27
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    Journal of Biomedical Materials Research 15 (1981), S. 879-887 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A three-dimensional finite element analysis (FEA) has been used to determine the effect of implant elastic modulus on stresses in tissues around LTI carbon and aluminium oxide dental implants. The finite element model was constructed to represent a baboon mandible containing a blade type dental implant. A three unit fixed bridge was modeled connecting the dental implant to a natural molar. The results of the study indicate that stress levels of approximately a factor of 3 lower in the crestal region can be expected for aluminum oxide implants when compared to the LTI carbon implants. It was also observed that the use of LTI carbon and aluminium oxide dental implants as an abutment in a fixed bridge results in a reduction of stresses in tissues around the natural tooth when compared to normal physiological stress levels.
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  • 28
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Judging biocompatibility of materials with blood includes assessment of hemolysis resulting from flow in contact with those materials. Such hemolysis is influenced in part by the surface roughness and specific hydrodynamic features of the device used. Using a rotating-disk device, with polyethylene disks and human blood, it was shown that roughness under 4 μm has negligible effect and that hemolysis increases sharply for roughness above about 11 μm. Gross roughness (65 μm) causes qualitatively different hemolysis kinetics but not as severe hemolysis as extrapolated from low-roughness data. In the disk geometry, the corner is a key region which generates high hemolysis and thus minor alterations cause hemolytic variations which may tend to obscure materials influences. A series of corner-beveled polycarbonate disks were tested in comparison with the normal square corner and were found always to cause greater hemolysis. Tapering the bevel inward, so the taper angle was on the order of 2°-4°, reduced hemolysis relative to the 45° bevel but still was more hemolytic than the flat disk. Evidence suggests that glassy plastics can be machined with more reproducibility at the corners than plastics above their Tg such as polyethylene. General device design problems regarding hemolysis are discussed.
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  • 29
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    Journal of Biomedical Materials Research 15 (1981), S. 209-230 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The mechanical properties of polyethylene components used in prosthesis are altered after fabrication by the sterilization procedure and by the environmental and mechanical aging which occurs after implantation. To assess the importance and extent of these alterations, ultrahigh molecular weight polyethylenes from two sources, Hercules 1900 and RCH 1000C, were subjected to gamma-ray irradiation and aging in serum and argon environments. Changes induced by these treatments in the structural and mechanical parameters have been determined by a variety of experimental techniques. The effect of irradiation is to introduce crosslinks and to increase the degree of crystallinity resulting in changes in the tensile properties in the direction of higher stiffness and reduced ductility. Aging for six months produced similar changes with subtle differences. The results suggest that the initially low degree of crystallinity which results from the sluggish mobility of the very long chain molecules offers the opportunity for significant changes in the properties during use in the long run.
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  • 30
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    Journal of Biomedical Materials Research 15 (1981), S. 267-277 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: We previously reported the use of polymeric delivery systems capable of sustained release of substances with molecular weights up to 2 × 106. The current study examined the tissue compatibilities of these slow-release agents and of other polymeric materials. To observe in vivo host responses to specific implants, tests were conducted in the rabbit cornea. The cornea as an implant site has several advantages compared to other organs including its clarity, avascularity, sensitivity, and convenient access to view. Corneas were examined using stereomicroscopy and histology. Two polymers suitable for sustained macromolecular release, poly(hydroxyethyl methacrylate), and alcohol-washed ethylene-vinyl acetate copolymer, were noninflammatory. Other polymers considered for sustained macromolecular release, such as polyacrylamide and poly(vinyl pyrrolidone), produced significant inflammation.
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    Journal of Biomedical Materials Research 15 (1981), S. 289-290 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
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  • 32
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    Journal of Biomedical Materials Research 15 (1981), S. 279-288 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Auger electron spectroscopy was used to investigate the relative concentration of the calcium impurity at the external and fracture surfaces of a dense alumina after in vivo exposure for 6, 12, and 23 weeks. The Ca concentration at the external surface initially decreased, reached a minimum at 12 weeks, and increased thereafter. These results were compared with the flexural strength, which decreased nearly linearly from 6 to 23 weeks.
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  • 33
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    Journal of Biomedical Materials Research 15 (1981), S. 383-392 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Rabbit hemolysate-loaded microcapsules having sulfonic acid groups on their surface were prepared and rabbit platelet adhesion onto the sulfonated surface was examined kinetically. Rabbit platelets adhered more markedly onto the surface of a higher charge density than that of a lower one, indicating a trend similar to that found in the case of the surface having carboxyl groups. Moreover, the platelets were found to be stickier in the buffer solution than in the plasma, though the dependence of platelet adhesion in the buffer solution on the magnitude of surface charge of the sulfonated artificial red blood cells was still recognized.
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  • 34
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    Journal of Biomedical Materials Research 15 (1981), S. 363-381 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: We studied the adsorption properties of plasma fibronectin (pFN) on wettable tissue culture (TC) dishes and nonwettable bacteriological (BAC-T) dishes in relationship to its biological activity of promoting fibroblast spreading. The binding of pFN to the dish surfaces was found to be very tight and partially resistant to treatments with 1M NaOH, 2% SDS, 8M urea, or 6M guanidine HCl. Only the combination of trypsin (1 mg/ml) followed by 1M NaOH resulted in complete recovery of surface bound material. The amount of surface bound pFN did not directly correlate with its activity when comparing TC and BAC-T dishes. At low concentrations, more pFN adsorbed onto the surfaces of BAC-T dishes than TC dishes, but the adsorbed material was biologically less active on BAC-T dishes. At high concentrations, pFN adsorbed similarly on both dish surfaces reaching a maximum level of 320 ng/cm2 or 4.4 X 1011 molecules/cm2. The possibility was considered that pFN unfolded into an inactive conformation when adsorbed on BAC-T dishes at a low concentration but that at high concentrations, molecular packing requirements prevented unfolding. Evidence in favor of this hypothesis was the observation that addition of 50 μg/ml of serum albumin simultaneously with low pFN concentrations resulted in adsorption of pFN on BAC-T dishes in an active conformation even though the amount of adsorbed pFN decreased. Competition experiments between pFN and other proteins were carried out, and it was found that pFN has a much higher affinity for BAC-T or TC dish surfaces than albumin or fibrinogen. It was also found that mild heat denaturation of albumin increased its affinity for the surface by an order of magnitude.
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  • 35
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    Journal of Biomedical Materials Research 15 (1981), S. 577-589 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A new hydrogel material has been prepared by crosslinking a hydrophilic, nonionic poly(amino acid), poly(2-hydroxyethyl-L-glutamine). The material properties of the hydrogel can be controlled by variation in the crosslink density, and the swelling ratio was found to be a sensitive and convenient method for measuring the extent of in vivo biodegradation of implanted specimens. Degradation of the material was observed only during the first 2 weeks of subcutaneous implantation in rats, and is attributed to hydrolysis by proteolytic enzymes released during the acute and chronic stages of the normal inflammatory response.
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  • 36
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    Journal of Biomedical Materials Research 15 (1981), S. 731-747 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Total hip prostheses combining cobalt and titanium alloys in direct physical contact are currently being used. The purpose of this paper was to investigate the possibility of an accelerated corrosion occurring due to the coupling of these alloys. Electrochemical corrosion studies based on mixed potential and protection potential theories were used to study the in vitro effects of coupling the titanium and cobalt alloys. Verification of these studies was made by direct coupling experiments. Macroscopic examination of surface features of four retrieved total hip prostheses ranging from 0-6 years implantation were conducted. The electrochemical studies predicted coupled corrosion potentials of -0.22 V and low coupled corrosion rates of 0.02 μA/cm2. Direct coupling experiments verified these results. Cobalt-titanium interfaces on the implants were macroscopically examined, and no instances of extensive corrosion were found. Overall, the in vitro corrosion studies and the examination of retrieved prostheses predicted no exaggerated in vivo corrosion due to the coupling of these cobalt and titanium alloys.
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  • 37
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    Notes: A study was undertaken to evaluate the ion-beam texturing of aluminum oxide as a means of providing a surface which will produce a biological prosthetic attachment. A wafflelike pattern of surface contours 150 × 75 × 35 μm deep was produced on cylindrical dental implants. The textured surfaces were compared to the as received surfaces in adult mongrel dogs. Implants were inserted into surgically modified healed extraction sites and were left in place for six months. Post-sacrifice mechanical testing was used to quantify the displacement response of the implants.The clinical, radiographic and mechanical testing evaluations did not reveal any statistically significant differences in the performance of the dental implants. However, it was observed that anatomical site and mandibular geometry with respect to implant size play a significant role in affecting implant retention.
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    Journal of Biomedical Materials Research 15 (1981), S. 781-784 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
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    Journal of Biomedical Materials Research 15 (1981) 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Journal of Biomedical Materials Research 15 (1981), S. 805-817 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Evidence for the lack of toxicity of various bioglass formulations has been deduced from studies carried out, both in vivo and in vitro, in several different centers. Recent studies of the authors, described here, include testing of solid bioglass implants in the soft tissues of rats and rabbits for time periods of up to eight weeks. Two new techniques are described for the toxicological testing of particulate biomaterials. These tests, which involve rat peritoneal macrophages in culture and a mouse pulmonary biomaterial embolus model, indicate the biocompatibility of bioglass powders. Thus, the surface activity so critical in bone adhesion is without toxic effect in nonosseous tissues in contact with solid bioglass implants. Should wear occur and produce particulate bioglass, the material should be eliminated without consequence.
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    Journal of Biomedical Materials Research 15 (1981), S. 787-793 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: Retention times (Rt) for acrylates, methacrylates, and vinyl monomers were measured with two different columns (C18 Corasil and C8 LiChrosorb) using reverse-phase HPLC in order to obtain their partition coefficients between 1-octanol and water (log P). The log P values of test compounds were determined from the regression curves between RT and log P values of a number of standards using C8 LiChrosorb. The log P values obtained in this manner agreed closely with the log P values observed in previous studies. However, the peaks of these compounds were not sharp and some compounds were eluted for more than 10 min. Thus, the measurement of accurate Rt values is tedious. C18 Corasil was therefore used for this experiment in a mobile phase (methanol : water = 85 : 15). The Rt of some methacrylates with P values over 4 were delayed due to the hydrophobic interaction between these compounds and the C18 packing material. However, in the measurable region of the log P values (about -1 to +4), log P correlated linearly with log Rt following two different regression curves: one for aliphatic and aromatic compounds with the functional groups (r = 0.92), and the other for compounds without these groups (r = 0.99). It is concluded that log P values of methacrylates widely used in dentistry can be determined easily and accurately by HPLC.
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    Journal of Biomedical Materials Research 15 (1981), S. 819-827 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Notes: Addition of chlorosulfonyl isocyanate to C=C bonds in cis-1,4-polyisoprene and reaction of the adduct with NaOH resulted in the formation of a water-soluble polyelectrolyte with N-sulfate and carboxylate groups. The polyelectrolyte showed anticoagulant activity and it was found, just as with heparin, that the activity was related to molecular weight and N-sulfate content.
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    Journal of Biomedical Materials Research 15 (1981), S. 835-841 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The work hardening characteristics of several casting alloys were determined from true stress-true strain data. A regression technique was used to fit the data to linear or nonlinear mathematical expressions. Manipulation of the expressions made it possible to calculate the work necessary to deform the alloys. Several nonprecious alloys proved to be as easy to cold form as a conventional, high gold containing alloy.
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    Journal of Biomedical Materials Research 15 (1981), S. 97-102 
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    Keywords: Chemistry ; Polymer and Materials Science
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  • 45
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    Journal of Biomedical Materials Research 15 (1981), S. 83-96 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Analytical and experimental studies were performed to examine some characteristics of poly(methyl methacrylate) bone cement in the context of total hip replacement. Proceeding from fundamental principles of balance of energy and heat conduction, three simulation models of total hip replacement, using the finite-element method of numerical analysis, were used to predict the temperature response in the femoral prosthesis, cement, cancellous bone, and bone-cement interface. When cement collars are a centimeter or less in thickness, the models predict little likelihood of permanent bone thermal necrosis. In addition, laboratory experimental results indicate that peak temperatures attained in Simplex-P and Palacos-R cement specimens are nearly identical and that adding 0.5 and 1.0 g of the antibiotic gentamicin to Palacos-R has negligible influence on peak temperature. Experimental results also indicate that cooling cement specimens to 8°C extends the set time, which in turn could significantly increase the likelihood of stemcement loosening during surgery.
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  • 46
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    Notes: The physiochemical properties of a hydrogel used as a scleral buckling implant for retinal detachment surgery are described. The new material was prepared by simultaneous polymerization and crosslinking of 2-hydroxyethyl acrylate with methyl acrylate and ethylene diacrylate, in the presence of an inert diluent, ethylene glycol. At equilibrium swelling, the hydrogen absorbed 17% water and had a durometer hardness (DH) of 15 (Shore Durometer A-2). A unique property of this material was its swelling hysteresis; when the gel swollen in 70% ethanol was placed in water, it retained a high level of hydration (75% water) and softness (DH 8), and most of its elasticity and strength as well. Then the swelling decreased very slowly so that the implant reached its ultimate size at equilibrium swelling in ca. 1 year. This property is especially useful in the scleral buckling procedure, in which a soft implant indents the sclera over the detached retina until reattachment is achieved. In addition to this advantage, this hydrogel is more elastic and stronger than available hydrogels of similar softness.
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  • 47
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    Journal of Biomedical Materials Research 15 (1981), S. 527-542 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Fracture toughness and modulus of rupture tests have been carried out on three aluminas, which differed in composition and microstructure, in a variety of environments (air, deionized water, albumen/salt solution, Ringer's solution, and fresh human plasma). Generally tests in liquid environments were found to result in a reduction in the asmeasured critical stress intensity factor and the modulus of rupture, as compared with the values appertaining to air. However, estimates of the stress for a 50-year, 99.9% survival probability were encouraging; for high-purity, small-grain-size alumina a value of 112 MN/m2 was calculated, which is considerably greater than the estimated maximum tensile stress in a femoral sphere.
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    Journal of Biomedical Materials Research 15 (1981), S. 543-551 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: Eight acrylic bone cement products were examined according to the methods set out in three published performance standards, viz., Australian Standard 2265 Part 1, 1979, ASTM specification F451-76, and the ISO specification 5833/1, 1979. In addition, chemical analyses were carried out by GC, NMR, and IR spectroscopy as well as refractive index measurement, all to establish the main constituent of the products. All the products compiled to the physical, compositional, and sterility requirements of AS 2265. However, all but one sample failed to comply with the solubility requirements of ASTM F451-76. Also, none of the samples compiled with the doughing time requirements of ISO 5833/1. On further analysis, the results suggest that the water solubility and sorption requirements of ASTM F451-76 are restrictive and that the ISO doughing time test methodology requires modification. Various degrees of noncompliance to the requirement of all three specifications were noted on the labeling and in the information content of product inserts. Two additional clauses on mixing tools and radiopacity have been suggested for incorporation into the above standards.
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    Journal of Biomedical Materials Research 15 (1981), S. 913-922 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A quantitative tissue culture method is described for toxicity testing of biomaterials. The material to be evaluated, or in the case of insoluble materials - an extract of the material, is incubated on a monolayer of fibroblasts in 24 well culture plates. The activity of the fibroblasts is ascertained by measuring the rate of mitosis (3H-thymidine incorporation), the synthesis of glycosaminoglycans (35SO4= incorporation) or production of total protein (3H-tryptophan incorporation). By proper choice of label, the effect of the biomaterial on cellular proliferation or production of macromolecules or both may be assessed. Materials with a cytotoxic effect cause inhibition of incorporation of radioactive label in the above assays. The cell monolayers can also be inspected microscopically for evidence of cytotoxicity. The method is quantitative, simple, reproducible, rapid, and suitable for screening of a large number of samples.
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    Journal of Biomedical Materials Research 15 (1981), S. 943-943 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Journal of Biomedical Materials Research 15 (1981), S. 29-36 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Medicine , Technology
    Notes: The addition of drugs to the cold cured acrylics has been demonstrated to variably affect their mechanical properties. This study investigated the effects, to the mechanical properties of a cold cured denture base material, of the addition of drugs and water. Chlorhexidine acetate was incorporated into the denture reline material at 10% w/w in the polymer phase of the material. Specimens also contained 10, 20, or 30% water w/w in the monomer phase of the material with or without the drug. The hardness of the specimens decreased with the addition of water to drug containing or drug-free specimens. Furthermore, there was a significant reduction in the modulus of elasticity of the material with the addition of drugs and water or water alone, which was progressive as the amount of water increased. The load at fracture was similarly reduced as the water incorporation increased. The results demonstrated the considerable effects drug and water incorporation had upon the material. However, this would not negate the use of the material in the oral cavity in the reline or rebase situation employing existing prostheses. Moreover, the reduction in material strength may have the advantage of progressive loss of material with a resulting improved release pattern of the contained drug.
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  • 52
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    Notes: The effect of in vivo electrical stimulation on the interfacial strength between porous titanium implants and cortical bone was studied in mongrel dogs. The interfacial shear strength of the stimulated implants was consistently greater than that of controls. No difference could be observed in the quality of bone ingrowth. The data suggest that the rate and quantity of bone ingrowth were enhanced by electrical stimulation.
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    Journal of Biomedical Materials Research 15 (1981), S. 47-59 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A recently developed dynamic mechanical analysis technique was utilized to determine the setting rates of dental amalgams. Via a compound parallel beam apparatus the dynamic mechanical properties of five amalgam materials were continuously measured at 37°C within ca. 7 min after the start of trituration. Over a 15 hr period results showed that the modulus of elasticity (Ea) increased from 1.2 × 1010 Pa to 6.5 × 1010 Pa - the latter generally approaching those values reported via ultrasonic techniques. Moduli results via compression tests on microspecimens (3 × 2 × 1 mm) paralleled previous reliable literature data, nominally yielding values for Ea of 2-3 × 1010 Pa. The extent of Ea scatter from both inter- and intrapreparer experiments appeared similar, although superior technique generally could be recognized by a systematic shift of the mean results to higher Ea's. In addition to modulus studies both compressive strengths (σmax) and their corresponding strains (∊) were measured on microspecimens at a strain rate (∊) of 0.031 min-1, with a significant increase being noted in σmax for the one material tested at over an order of magnitude increase in ∊.
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    Journal of Biomedical Materials Research 15 (1981), S. 61-71 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The physical and chemical properties of echinoderm skeleton are reviewed. A method is described for preparing cell-free, sterile echinoderm skeletal plates (ossicles) which were used as porous substrates for cell cultures. Ossicles of the starfish Pisaster ochraceus were evaluated as substrates for the culture of three mammalian cell lines. Each line grew vigorously on ossicles, and fibroblasts quickly infiltrated their porous microstructure. Echinoderm skeletal plates provide a simple, convenient alternative to coverslips and porous membranes for SEM or correlated SEM/TEM studies of cell behavior. More importantly, the preliminary evidence for biocompatibility presented suggests that native echinoderm skeleton has potential use as a biomaterial and, because of its microstructure and relative solubility; deserves evaluation as a kind of biodegradable ceramic.
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    Journal of Biomedical Materials Research 15 (1981), S. 73-82 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The interfacial shear properties of bone tissue growth into porous coated Ti-6A1-4V femoral implants have been examined as a function of the pore size of the porous surface. Three particle size range powders (297 μm, 420-500 μm, 595-707 μm) were used to fabricate cylindrical implants which were inserted into the femoral medullary canal of dogs for 6 months. Push-out tests on the removed femurs are reported and reveal: (i) that those implants residing in cortical bone exhibited significantly higher shear properties than the equivalent implants in cancellous bone and (ii) that the interfacial shear strength and stiffness decreased with increasing pore diameter within the range 175-325 μm. The extent of bone ingrowth into the surface of the implants was measured using quantitative optical microscopic techniques. This indicated that the percentage of bone which had grown into the surface was inversely proportional to the square root of the pore size and that further the shear properties of the interface were proportional to the extent of bone in-growth.
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    Journal of Biomedical Materials Research 15 (1981), S. 111-113 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Journal of Biomedical Materials Research 15 (1981), S. 115-115 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Journal of Biomedical Materials Research 15 (1981) 
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  • 59
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    Notes: The suitability of barium titanate (BaTiO3) ceramic for direct substitution of hard tissues was evaluated using both electrically stimulated (piezoelectric) and inactive (nonpolarized) test implants. Textured cylindrical specimens, half of them made piezoelectric by polarization in a high electric field, were implanted into the cortex of the midshaft region of the femora of dogs for various periods of time. Interfacial healing and biocompatibility of the implant material were studied using mechanical, microradiographical, and histological techniques. Our results indicate that barium titanate ceramic shows a very high degree of biocompatibility as evidenced by the absence of inflammatory or foreign body reactions at the implant-tissue interface. Furthermore, the material and its surface porosity allowed a high degree of bone ingrowth as evidenced by microradiography and a high degree of interfacial tensile strength. No difference was found between the piezoelectric and the electrically neutral implant-tissue interfaces. Possible reasons for this are discussed. The excellent mechanical properties of barium titanate, its superior biocompatibility, and the ability of bone to form a strong mechanical interfacial bond with it, makes this material a new candidate for further tests for hard tissue replacement.
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    Journal of Biomedical Materials Research 15 (1981), S. 137-145 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: Fatigue tests conducted both in air and synthetic physiological solution show that the fatigue strength of surgical stainless steel in synthetic physiological solution is about 10% lower than the strength in air for a given endurance level. It is proposed that surgical stainless steel which is normally passive in physiological solution suffers corrosion fatigue because of susceptibility to crevice corrosion which occurs at extrusions and intrusions (crevices) on the surface thereby shortening the crack initiation time and the fatigue life.
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    Journal of Biomedical Materials Research 15 (1981), S. 117-135 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The age-hardening and tensile properties were determined for seven 10-14 kt. gold alloys, a conventional type II, and a sterling silver alloy. For the low-gold alloys the heat hardening curves indicated that the maximum aging effects were attained after 30 min at 400°C. From tensile tests on either wire or dumbbell specimen configurations, Young's modulus (E), proportional limit (P.L.), ultimate tensile strength (U.T.S.), and elongation to break were measured for alloys in both the solution annealed (S) and the hardened (H) state. These stress-strain data not only confirmed previous correlations noted for conventional gold alloys between either E, P.L., or U.T.S. and hardness and between U.T.S. and P.L., but also varied systematically with the Au/Cu ratios in the (H) state. Under identical heat treatment and tensile testing conditions, comparison of the manufacturers' cast samples with this laboratory's specimens showed that, while the E, P.L., and U.T.S. differed somewhat, the greatest change occurred in the elongation to break. Here after measuring the porosity of the different specimen configurations and analyzing the log10 elongation with VHN, the conclusion was clear: Specimen geometry markedly influenced the physical properties. On this basis the proposed dumbbell geometry is advocated over the wire specimen configuration currently cited in ADA Specification No. 5.
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  • 62
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    Journal of Biomedical Materials Research 15 (1981), S. 147-157 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Model synthetic tendons consisting of 20 vol % of texturized poly(ethylene terephthalate) fibers and of the water-swollen poly(2-hydroxyethyl methacrylate) matrix have the tensile modulus E = 1.5 ± 0.1 GPa, strength and strain-at-break σb = 85 ± 10 MPa and ∊b = 0.08 ± 0.02. The force required for breaking tendons with the diameters 2, 3, 4 mm is, respectively, 300, 500, and 960 N. By these properties model synthetic tendons closely imitate the properties of natural tendons. Long-term (100 min) and repeated short-term (30 times 1 min) creep shows that on loading model tendons lose some 10% of their stiffness, but that the whole deformation is reversible. The shape of the compliance vs. time dependence of synthetic tendons closely resembles the dependence determined for the parent fiber. The stiffness and strength of a tendon are given by those of the fiber bundle used; by varying fiber volume fraction, it is possible to adjust the required mechanical properties of tendons.
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    Journal of Biomedical Materials Research 15 (1981), S. 183-189 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Homopolymers of the hydrogel poly(2-hydroxyethyl methacrylate) are produced with no observable bubbles trapped in the lattice by performing the free radical initiated polymerization reaction under pressure (700 kPa). Implantable hydrogel structures of intricate and exact geometry, such as nipples for ureteral anastomoses in the prosthetic urinary bladder, can be made using this technique.
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  • 64
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    Journal of Biomedical Materials Research 15 (1981), S. 159-182 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Loosening is a major cause of failure in total arthroplasties. The efficacy of the fixation systems depends not only on the bulk properties of the components but also on the interfaces through which they interact. This study was initiated to examine the implant/bone-cement interface for four of the most commonly used implant materials, Co—Cr—Mo, Ti—6Al-4V, 316SSLVM and ultrahigh molecular weight polyethylene (UHMWPE). The surface preparation, specimen design, joining, and testing techniques were studied and then standardized in a manner which accurately represents current clinical procedures. The interfaces were tested for both their quasistatic and fatigue properties. Finite-element and fracture toughness analyses of the quasistatic shear specimens were performed in order to provide results of an absolute nature which could be subsequently compared to bulk material properties of bone cement. The interfaces were tested “dry” (i.e., at room temperature and 50% R.H.) and in physiological saline at 37°C. The interfaces demonstrated both fracture toughness and fatigue properties far inferior to those of bone cement. A predominantly interfacial type failure was observed using SEM fractography. The ultimate compressive strength (U.C.S.) of bone cement was measured after prolonged exposure to saline at 37°C and showed no decrease in U.C.S. suggesting that the reasons for the interface strength reductions were interfacial rather than bulk in nature. The “wetting'” ability of bone cement was measured using contact angles at various cure times on the four implant materials. These measurements showed that intimate interfacial contact is impossible with current clinical methods. This study indicates that failure of the implant/bonecement interface is likely only a short period after implantation and therefore may be a major contributor to implant loosening.
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  • 65
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    Notes: Analysis of the anodic polarization and alternate immersion test response of 16 precious metal alloys with compositions similar to those of commercial dental golds indicate that alloys containing high (Ag + Cu) contents are likely to be more corrosion and tarnish prone. It also appears that the alloys containing high precious metals contents (Au, Pt, and Pd) are characterized by immunity or anodic film protection over a range of anodic overpotentials, indicating superior corrosion resistance.
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  • 66
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    Journal of Biomedical Materials Research 15 (1981), S. 203-208 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Samples of low viscosity poly(methyl methacrylate) (PMMA), graphite reinforced PMMA, and graphite reinforced low viscosity PMMA were evaluated for their compression strength and fracture toughness. These results were compared with two currently used plain PMMA bone cements. There were no statistically significant differences in compression strength between the five cements. Graphite reinforcement of plain cement produced a 32% increase in fracture toughness over plain cement. Graphite reinforcement of low viscosity cement also produced a significant increase in toughness (31%) over low viscosity cement with fiber reinforcement. However, low viscosity cement demonstrated significantly less fracture toughness than plain PMMA.
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    Journal of Biomedical Materials Research 15 (1981), S. 231-245 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A semiempirical epitaxial model has been derived which correlates and interrelates the surface free energy, ultrastructural morphology, surface charge, surface chemistry, and surface molecular motions of a model triblock copolymer to thrombogenesis. This paper addresses the aspect of: (1) ultrastructure order versus disorder, (2) primary and secondary molecular motions, (3) surface and side chain chemistry, (4) thrombogenesis, and (5) the derived epitaxial model based on the above observations. This model can be extrapolated to include and predict the relative thrombogenic responses of various crystalline and semicrystalline polymeric substrates, i.e., aliphatic polyolefins, polyurethanes, and polypeptides.
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  • 68
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A new technique has been employed for producing Model 11 Biomer bladders with integrally textured blood-contacting surfaces. For the past year, we have been routinely fabricating integrally textured polymeric surfaces from negative-replica silicone molds, which are a high-fidelity facsimile of conventionally flocked bladders. The objectives of this investigation are threefold: (1) To develop a blood-contacting surface that promotes the formation of a stable pseudoneointimal lining; (2) to investigate means of accelerating replacement of initial fibrin coagulum by a collagenous lining; and (3) to characterize the resultant pseudoneointimal lining biochemically, histologically, and ultrastructurally. Systematic in vivo studies were undertaken to evaluate the new surface in terms of its ability to form a thin, stable, biologic lining. Control experiments were carried out to compare results with previous experience utilizing polyester fibril flocked surfaces. Additional studies were conducted to define the effects of cell seeding of integrally textured surfaces. A total of 16 experiments have been conducted to date; eight bladders were seeded with allogeneic fetal cells prior to implantation and eight bladders were unseeded, to serve as controls. In vivo trials of seeded surfaces have resulted in the formation of strong, cellular, and highly collagenous linings, with collagen contents varying between 31% and 65%. These linings contain viable cells and thus exhibit high cellular activity, as evidenced by postexplant cell culture techniques. This indicates that a living, viable pseudoneointima has been generated. On the other hand, control (nonseeded) linings do not produce significant amounts of collagen in their linings.
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    Journal of Biomedical Materials Research 15 (1981) 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Journal of Biomedical Materials Research 15 (1981), S. 403-423 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The adsorption of proteins affects cellular interactions with foreign surfaces and thus plays an important role in determining the biocompatibility of implants. Previous studies have indicated differences in the affinity of various proteins for a given polymer, and differences in the affinity of fibrinogen for a series of polymers varying in hydrophilicity. These studies suggest that differences in the composition of the protein layer adsorbed to polymers from plasma might exist. To examine this hypothesis, the proteins adsorbed from plasma to a series of polymers varying in hydrophilicity were analyzed with the iodogram technique. Copolymers of hydroxyethyl methacrylate and ethyl methacrylate made by the radiation grafting technique were exposed to plasma for 0.5 or 150 min. The adsorbed proteins were iodinated, eluted with SDS, and separated with polyacrylamide gel electrophoresis. Fibrinogen, immunoglobulin G, hemoglobin, and a peak tentatively ascribed to prothrombin were the major proteins detected. Very little iodine was incorporated into adsorbed albumin, even though it was shown to be present by a separate experiment using dye binding. The fraction of total radioactivity associated with each of nine proteins was found to vary markedly and systematically among the surfaces. The distribution of radioactivity into the proteins was very different on 0.5 and 150-min plasma exposed polymers. The results reflect both compositional differences in the adsorbed protein layer on the polymers and differences in the accessibility of proteins to the labeling reagent in the adsorbed state. Differences in the organization of the adsorbed protein layer may play a key role in determining whether cell surface receptors can come in contact with the specific plasma protein able to further stimulate the cell.
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    Journal of Biomedical Materials Research 15 (1981), S. 441-445 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Journal of Biomedical Materials Research 15 (1981), S. 437-440 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Journal of Biomedical Materials Research 15 (1981), S. 447-447 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Journal of Biomedical Materials Research 15 (1981), S. 449-463 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The permanent set of a range of elastomeric impression materials, used in dentistry, was investigated as a function of the materials′ age and the duration and level of the deformation. The permanent set appears to be primarily controlled by the rate of polymerization at the time of deformation. However, stress relaxation experiments revealed that, for condensation silicone and in particular polysulfide elastomers, bond interchange reactions produce additional permanent set. The rate of recovery of the elastomers from deformation was very rapid and was consistent with the influence of entanglements in the network.
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    Journal of Biomedical Materials Research 15 (1981), S. 465-477 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The objective of this work was to determine whether there is a significant difference in composition between the air facing and mold facing sides of Biomer and to see if the mold itself affects the polymer surface. A detailed analysis of Biomer was undertaken using x-ray photoelectron spectroscopy (ESCA), secondary ion mass spectroscopy (SIMS), and low energy ion scattering spectroscopy (ISS). Previous workers have used FTIR and ESCA to study Biomer and comparisons with their results will be discussed. Because of the increase in surface sensitivity SIMS and ISS can be valuable tools for studying polymeric materials. SIMS has been used to identify the structure of the Biomer air and mold facing surfaces from both glass and nickel molds. ESCA and ISS have indicated the presence of a silicon contaminant on the air and mold facing surfaces and SIMS has shown that the form of the silicon contaminant is probably a polysiloxane.
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    Journal of Biomedical Materials Research 15 (1981), S. 479-488 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Fretting corrosion of stainless-steel round hole plates and spherical head screws was studied using a simulator that produced a rocking motion of the heads in the plate holes. Experiments were run for 7 days, with the simulator producing 1 oscillation/s for 16 h/day. Fretting corrosion was studied in 0.9% NaCl and in a 10% solution of fetal calf serum in saline. The results showed a tenfold decrease in fretting corrosion when the serum was added to the saline. Measurements of the weight of the two screws and two-hole plate showed those in saline lost 2.9 mg as compared to 0.3 for those in 10% serum. The concentration of nickel in the saline solutions was 12.4 μg/mL compared with 0.85 in serum. Visual examination of the solutions and implants revealed that those in saline had a significant amount of corrosion products while those tested in 10% serum were bright and shiny. Recordings of electrical potentials demonstrated that the addition of serum to saline significantly reduced the change in potential from rest to fretting condition.
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  • 78
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    Notes: In the oral environment, dental restorative materials are exposed to temperatures ranging from 10° to 50°C. Since the properties of many polymeric materials are sensitive to temperature of this magnitude, it is important to define the effects of service temperature on the mechanical properties of polymer matrix dental composites. Six commercial composites were tested in compression at 11 temperatures, ranging from 2° to 80°C. The volume fraction of filler particles in the materials is either 0.45 or 0.55, and they contain a range of particle sizes and particle compositions. The tests show that ultimate strength decreases linearly with increasing temperature. Strength is higher for the lower volume fraction material and is decreased by the presence of a small percentage of very large particles. Elastic modulus and yield strength decrease sigmoidally with increasing temperature and depend only on particle volume fraction. In the clinically significant temperature range, ultimate strength decreases 14%, the decrease in elastic modulus is either 6 or 11%, and the yield strength decreases 45%. The data show that the temperature conditions of the oral environment can significantly affect the mechanical properties of composite dental restorative materials.
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    Journal of Biomedical Materials Research 15 (1981), S. 511-525 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Medical grade silicone rubber samples were immersed in distilled water and in pseudo-extracellular fluid (PECF) at 37.5°C for up to four months. Periodically, the storage modulus and log decrement of the samples were measured on a torsion pendulum. Up to 20% increases in storage modulus and about 40% decreases in log decrement were found over the four months independent of sample surface area. Similar trends were seen in both distilled water and in PECF. Higher (59°C) storage temperatures accelerated the changes. Small amounts of moisture uptake were detected. However, the presence of water in the samples did not cause the change in mechanical properties.
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    Journal of Biomedical Materials Research 15 (1981), S. 553-563 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: With a view to developing biomaterials for semipermanent substitution, we have studied a composite material constituted with collagen and a synthetic polymer which possesses high tissue compatibility. This collagen - synthetic polymer composite was applied as a support for immobilization of enzymes for the purpose of providing a material surface with biological function. The enzymes, urokinase and trypsin, were successfully bound to the collagen membrane layer which had been activated by acyl azide formation of its carboxyl groups. The enzyme-bearing composite material showed excellent catalytic activity toward a protein substrate as well as a low-molecular-weight synthetic substrate. The immobilized urokinase was characterized enzymatically and compared with native urokinase. The apparent affinity of immobilized urokinase for the substrate was slightly decreased, but its intrinsic kinetic properties were not significantly affected. No decrease in its esterase activity was observed both on repeated use and on long-term storage, and its fibrinolytic activity was stable on heat or disinfection treatment. When this urokinase-bearing composite material was applied into rabbit blood vessels, its in vivo fibrinolytic activity was maintained. Thus, enzyme - collagen - synthetic polymer composites may find wide application for biomaterials and artificial organs as functional biomaterials.
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    Journal of Biomedical Materials Research 15 (1981), S. I 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Journal of Biomedical Materials Research 15 (1981), S. 663-672 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Filler-free silicones are believed to be more blood-compatible than those containing fillers. An ultrapure silica-free room temperature vulcanizing silicone system was prepared and characterized using a swelling experiment, an infrared spectrometer, an x-ray spectrometer, a scanning electron microscope and neutron activation analysis. The polymer was found to be suitable for medical applications needing an extremely smooth surface.
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    Journal of Biomedical Materials Research 15 (1981), S. 619-653 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A 12-channel wear screening device was used to compare the wear properties of a variety of prosthetic joint materials. Two types of tests were run: (1) Ultrahigh molecular weight (UHMW) polyethylene bearing against metal or ceramic counterfaces and (2) various polymers bearing against 316 stainless steel as a standard counterface. Wear was quantified by weighing the polymer specimens, with presoaking and control-soak specimens used to minimize the error due to fluid absorption. The specimens were lubricated with bovine blood serum. Friction and polyethylene wear was very low with each of the metals (316 stainless steel, cobalt-chrome alloy, multiphase alloy, and titanium 6-4 alloy) such that the differences in wear rate would not be significant in terms of choosing a material for clinical application. However, titanium 6-4 alloy was found to be especially susceptible to abrasive wear by particles of acrylic cement. Nitrided titanium 6-4 counterfaces were impervious to acrylic abrasion. Polyethylene wear against highly polished, fully dense ceramics (Sialon, Alumina, Macor, and pyrolytic graphite) was as low as that with the metal counterfaces. Wear increased slightly with increasing ceramic surface roughness. The coefficient of friction of polyethylene against pyrolytic graphite was two to three times higher than with the metals or other ceramics. All of the alternate polymers underwent more wear than UHMW polyethylene. Teflon and polyester, two polymers that have proven unsuccessful in prior clinical use, had wear rates 1600 and 830 times greater than polyethylene, respectively, an indication that the laboratory wear test provided a quantitative prediction of the behavior of the materials in vivo. However, it was difficult to assess the clinical significance of the less extreme wear rates since the ability of the tissues encapsulating a prosthesis to accomodate wear debris is not known on a quantitative basis.
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  • 86
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    Keywords: Chemistry ; Polymer and Materials Science
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    Notes: Plasma protein adsorption is an important initial event in the response of tissue to foreign materials. Little is known about the way in which the chemical properties of materials influence the nature of the adsorbed layer and thus the later cellular responses. In this study, the amounts of fibrinogen, immunoglobulin G, albumin, and hemoglobin adsorbed from plasma to a series of HEMA-EMA random copolymers varying in hydrophilicity was measured. The adsorption of each protein varied in a characteristic way with copolymer composition probably reflecting a different affinity of the proteins for the various copolymers. A complex variation in the composition of the adsorbed protein layer on polymers varying in hydrophilicity was thus evident. Surface enrichment of the proteins, calculated as the ratio of the surface and bulk fraction of each protein, also varied with copolymer composition, and indicated substantial differences in the composition of the surface and bulk phases. Surface area variations among the copolymers, preferential adsorption of 125I proteins, and the possibility of structural degradation of 125I proteins in plasma were investigated but did not appear to influence the adsorption results. The ability of polymers to fractionate plasma proteins and concentrate them at their surface is concluded to be a key factor in the complex processes which determine the compatibility of polymers in vivo.
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    Journal of Biomedical Materials Research 15 (1981), S. 719-730 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: To study the mechanical behavior of a commercially available UHMWPE reinforced with carbon fibers, measurements of contact area, contact pressure and time-dependent deformation were made on tibial components from a contemporary total knee replacement loaded to physiological levels. For comparison, similar measurements were performed on identical components manufactured from plain UHMWPE. Contact area and pressure results reflected the increased stiffness of the carbon-UHMWPE material, with smaller contact areas and generally higher contact pressures versus the plain UHMWPE at the same load. Stresses in both materials under the contact area approached or exceeded the yield stresses for the materials when the physiological load was high or the radius of the femoral component indenter decreased (similar to flexion of the knee). Time-dependent deformation over a 24 h period was reduced significantly in the carbon-UHMWPE components for a high physiological load.
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    Journal of Biomedical Materials Research 15 (1981), S. 697-718 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Blood compatibility has been studied for hydrophilic polymers such as poly(vinyl alcohol) (PVA), its derivative, and polyethylene grafted with water-soluble monomers. The surfaces in contact with electrolyte solutions have been characterized by measuring the zeta potentials. The study of plasma protein adsorption on these polymers has revealed that bovine serum albumin as well as bovine serum fibrinogen adsorbs to a lesser extent as the hydrophilicity of the polymers increases. Platelet deposition and fibrin formation, examined using platelet-rich plasma, have been found to take place less significantly on PVA as well as sodium acrylate- and acrylamide-grafted polyethylene than on nongrafted and acrylic acid-grafted polyethylene. Ex vivo experiments with canine whole blood have shown that formation of thrombus on PVA is less than on siliconized glass but increases upon heat treatment which reduces the hydrophilicity. When PVA tubes of about 1 mm diameter are anastomosed to the carotid artery of rat, the patency rate is found to depend strongly on the anastomotic technique. From the results on the zeta potential and the experiments in vitro and ex vivo it can be concluded that the material having a surface from which solvated, neutral chains are extended into the outer aqueous phase may exhibit excellent resistance to thrombus formation.
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    Journal of Biomedical Materials Research 15 (1981), S. 757-768 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The development of linear elastic fracture mechanics has been traced briefly, with emphasis on the approach based on stress intensity. Factors affecting fracture toughness include the effects of the environment, but little about these is known at present. Fracture behavior in two-phase acrylic systems has also been reviewed. In the light of this, SEN specimens of heatcured denture-base PMMA were saturated in a range of liquids and extended to failure at chewing speed. Crack initiation toughnesses and critical flaw sizes were thus determined. The effects of the chemical environment on the relationship between these two parameters showed that vegetable oil had increased the notch sensitivity of the resin, while 4% ethanol and soap solution increased the plasticization of the crack tip beyond that in water alone. Although the behavior at the crack tip was similar for all the other aqueous media, the craze resistance of the resin could be altered by the chemical nature of the liquid; this might explain in part the behavioral strengths of the un-notched material.
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  • 91
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 15 (1981), S. 795-804 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Tensile strength of poly(glycolic acid) suture (PGA) of size 2-0 was examined as a function of three pH levels, 5.25,7.44, and 10.09 of the buffer. Cord and yarn grip was used to eliminate grip-induced failure of breaking strength tests. It was found that Dexon sutures degraded significantly faster in pH = 10.09 buffer than the other two lower pH buffers. There was no significant difference in degradation rate at pH = 5.25 and 7.44. At 7 days, PGA sutures lost almost half of its original tensile strength at pH = 10.09, while the same sutures still remained more than 95% of their original breaking strength at buffers of pH = 5.25 and 7.44. After 21 days, no trace of sutures could be detected in the buffer of pH = 10.09 while about 20% strength still remained in the buffers of pH = 7.44 and 5.25. Cage effect in the crystalline phase and pH dependent hydrogen bonding were introduced to explain the difference in degradation phenomenon of PGA at buffers of various pH.
    Additional Material: 3 Ill.
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  • 92
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 15 (1981), S. 903-911 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Fine ultrastructures of the cross sections of membranes, which are derived from chitosan and utilizable as artificial kidney, are examined by scanning electron microscopy (SEM). Three types of unique ultrastructure of the membrane cross sections are present: N-acylchitosan membranes [N-acetyl (1), N-propionyl (2), N-butyryl (3), N-pentanoyl (4), N-hexanoyl (5), N-octanoyl (6), and N-benzoyl (7)], N-benzylidenechitosan membranes (8) and chitosan membranes (9). The vertical cross sections of membranes 1-7 consist of orderly arranged layers that are formed by an assembly of particle units of fibrils. Neither fibrils nor layers are present and a smooth surface is characteristic of the cross sections of (8). On the other hand, the particle units of fibrils are absent and a nappy rough surface is characteristic of the cross sections of (9). N-Acetylation of (9) affords the particle units of fibrils that are disorderly oriented. Low- and middle-molecular compounds (MW 〈 2000) pass through small pores among these fibrils present in orderly arranged layers of the membranes. Properties of these N-acylchitosan membranes well meet the requirements of artificial kidney membranes.
    Additional Material: 2 Ill.
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  • 93
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 15 (1981), S. 889-902 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Numerous studies have been carried out on drug-polymer sustained release systems designed for implantation. The majority of these efforts have been directed toward determining the in-vitro rate of drug release from specific systems or drug polymer combinations and the in-vivo studies have attempted to utilize analysis of the blood serum and excretory products as a measure of the release rate and behavior. To gain a better understanding of the influence of the local tissue environment and implant site on release behavior, we have investigated the release behavior of a gentamicin-silicone rubber system implanted in canines. Particular attention has been directed toward investigating the role that the fibrous capsule which eventually surrounds the implant plays in determining the rate and pattern of drug release. The drug burst effect was decreased by the use of a drug-free silicone rubber membrane on the gentamicin-silicone rod implant. Analysis for gentamicin in the tissue adjacent to the implant for periods up to four weeks indicated that the release rate was retarded by the development of the fibrous capsule. The temporal and spatial variations in gentamicin levels in the tissue surrounding the rod implants were determined. In addition, the influence of implant coating and gentamicin loading level in the implant on local tissue concentrations with time were also investigated. These studies provide evidence that the fibrous capsule surrounding a drug-polymer sustained release implant may influence the release behavior of the drug in an avantageous or disadvantageous manner depending upon the desired function of the sustained release system.
    Additional Material: 6 Ill.
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  • 94
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    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 15 (1981), S. 941-941 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Type of Medium: Electronic Resource
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