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  • Electronic Resource  (15)
  • 1
    Electronic Resource
    Electronic Resource
    Development of a force controlled periodontal probing instrument (1979)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of periodontal research 14 (1979), S. 0 
    Details
    ISSN: 1600-0765
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1600-0765.1979.tb00222.x
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  • 2
    Electronic Resource
    Electronic Resource
    The effect of processing temperature and time on the structure and fracture characteristics of self-reinforced composite poly(methyl methacrylate) (1999)
    Springer
    Journal of materials science 10 (1999), S. 503-512 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract A novel material, self-reinforced composite poly(methyl methacrylate) (SRC-PMMA) has been previously developed in this laboratory. It consists of high-strength PMMA fibers embedded in a matrix of PMMA derived from the fibers. As a composite material, uniaxial SRC-PMMA has been shown to have greatly improved flexural, tensile, fracture toughness and fatigue properties when compared to unreinforced PMMA. Previous work examined one empirically defined processing condition. This work systematically examines the effect of processing time and temperature on the thermal properties, fracture toughness and fracture morphology of SRC-PMMA produced by a hot compaction method. Differential scanning calorimetry (DSC) shows that composites containing high amounts of retained molecular orientation exhibit both endothermic and exothermic peaks which depend on processing times and temperatures. An exothermic release of energy just above Tg is related to the release of retained molecular orientation in the composites. This release of energy decreases linearly with increasing processing temperature or time for the range investigated. Fracture toughness results show a maximum fracture toughness of 3.18 MPa m1/2 for samples processed for 65 min at 128°C. Optimal structure and fracture toughness are obtained in composites which have maximum interfiber bonding and minimal loss of molecular orientation. Composite fracture mechanisms are highly dependent on processing. Low processing times and temperatures result in more interfiber/matrix fracture, while higher processing times and temperatures result in higher ductility and more transfiber fracture. Excessive processing times result in brittle failure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008909311523
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  • 3
    Electronic Resource
    Electronic Resource
    Prediction of service lifetime and performance of a prosthetic thermoplastic (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 58 (1995), S. 1661-1668 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The service lifetime and performance for a prosthetic and orthotic thermoplastic, SubortholenTM, was measured using correlations between artificial and natural weathering degradation data of (1) the accumulated carbonyl compound concentration at the polymer surface, (2) changes in thickness of the surface reaction zone, and (3) changes in hardness and tensile properties. An empirical, mathematical relationship between artificial and natural weathering exposures is presented. Results show that the hardness degradation is a useful parameter to estimate the different stages in clinical performance of Subortholen. Corroborating hardness, tensile properties, and weathering exposure time, the service lifetime for Subortholen was determined to be 4-6 years. This finding indicates that the correlation between artificial and natural weathering degradation may provide an effective way to calculate the most appropriate time to replace a worn prosthetic or orthotic device before the device passes into a dangerous stage. © 1995 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1995.070581001
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  • 4
    Electronic Resource
    Electronic Resource
    Deformation processing of PMMA into high-strength fibers (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 44 (1992), S. 1321-1330 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Poly(methyl methacrylate) was drawn into fibers by melt extrusion followed immediately by a transient temperature drawing process. By varying five processing variables, fibers ranging from 0.635 mm to 25 μm in diameter were produced. Heat-induced relaxation of the aligned structure was used to determine the draw ratio of the resultant fibers and therefore the degree of polymer chain alignment imposed by the deformation process. The resulting changes in length and diameter were measured and it was found that draw ratios of 5-20 had been achieved under the varying processing conditions. It was also observed that fiber diameter immediately after drawing is a good predictor of the degree of orientation present in the fiber irrespective of the processing conditions. To test the effect molecular orientation has on material properties, fibers with varying degrees of orientation were tested in tension. As expected, increasing alignment resulted in increasing tensile strength. The maximum observed true ultimate tensile strength was 225 ± 53 MPa and was seen in fibers with a draw ratio equal to 18.7 ± 4.5. Fibers with a lower degree of alignment, while not as strong in tension, exhibited significantly increased ductility. True strains of as high as 25% were observed.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1992.070440802
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  • 5
    Electronic Resource
    Electronic Resource
    Degree of polymerization of acrylic bone cement (1975)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 9 (1975), S. 27-34 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Self-curing poweder-liquid admixed acrylic systems are used for internal fixation of total hip and total knee prostheses. Gel permeation chromatography revealed that the polymer chain length distributions of set cements were basically unaffected by their curing pressures. However, a decrease of approximately 11% in porosity coupled with a measured increase in mechanical strengths could be induced through the use of high curing pressures well beyond those attainable by the surgeon in the current arthroplasties. The conclusion of the investigation was that, to improve such cements, attention should be focused on elimination of porosity rather than attempting to produce higher degrees of polymerization.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820090104
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  • 6
    Electronic Resource
    Electronic Resource
    Mechanical properties of bone cements containing large doses of antibiotic powders (1976)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 10 (1976), S. 929-938 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The addition of up to 10 g gentamicin sulfate antibiotic powder to 60 g units of Simplex-P acrylic bone cement caused gradual, proportional decreases in the bulk mechanical properties of compressive and diametral tensile stengths. Water leaching of the antibiotic from the cement did not significantly decrease these strengths.Scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDS) showed the antibiotic to reside in the acrylic matrix as discrete particles not usually associated with internal porosity. The surface-sensitive flexural strength of a proprietary bone cement was lowered immediately by small quantities of antibiotic powder, and continued to decrease as doses of up to 10 g/unit were admixed. Water leaching caused channeling as the antibiotic was removed from the surface, but it did not create further changes in flexural strength.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820100610
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  • 7
    Electronic Resource
    Electronic Resource
    Monomer release from methacrylate bone cements during simulated in vivo polymerizationThis investigation was supported in part by USPHS General Research Support Grant No. RR05689-03. (1979)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 13 (1979), S. 135-147 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The release of monomer from methylmethacrylate bone cements was studied during immersion in an aqueous environment intended to simulate in vivo polymerization of the material. Monomer release from disk-shaped specimens into an aqueous environment was assayed by gas chromatography. The simulated intracorporal polymerization was carried out under a variety of conditions intended to encompass possible clinical variables. The majority of monomer release occurred within the first 15 min of immersion. Under conditions generally recommended for commercial cements the release into aqueous media was always less than 3% of the total monomer weight. Clinically feasible options of delaying the time from onset of mixing of the cement to insertion into the host resulted in only a 0.7 wt % difference in the amount of released monomer. Measurements for a variety of monomer/powder ratios demonstrated a minimum in the amount of released monomer at a ratio of about 0.4 ml/g. In terms of unit area covered, thin specimens released less monomer than thick specimens.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820130114
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  • 8
    Electronic Resource
    Electronic Resource
    Anodic polarization of porous fiber metals (1974)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 8 (1974), S. 189-191 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820080208
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  • 9
    Electronic Resource
    Electronic Resource
    The influences of electrical potential and surface finish on the fatigue life of surgical implant materials (1975)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 9 (1975), S. 611-621 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The influence of both imposed anodic potential in Ringer's solution and surface finish on the fatigue lives of annealed 316 type stainless steel and annealed pure titanium were measured and statistically compared to fatigue data run in air. The applied potentials in simulated extracellular fluid approximated conditions existing within the body while also producing the types of surface defects actually found on removed long time implants within the time interval of the accelerated R. R. Moore fatigue tests. Differentiating tests were run at single levels of applied cyclic stress well above the endurance limits.In Ringer's solution, the fatigue life of the 316 stainless steel decreased with increasing applied potential, and at +500 mV was significantly shorter than when run in air. At each condition, the 316 stainless steel was independent of initial surface finish. In contrast, the fatigue life of titanium improved rapidly with increasingly fine surface finishes. Furthermore, compared to air, the application of +500 mV in Ringer's solution improved the life of the rough surface finished material and markedly increased the number of cycles to failure for the electropolished specimens.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820090607
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  • 10
    Electronic Resource
    Electronic Resource
    The creep compliance of dental amalgam in the stress range of 20-80 MPa (1982)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 16 (1982), S. 599-608 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The continuous compressive creep curves of four distinct types of one-week-old dental amalgam were monitored for one day on a specially designed mini-specimen creep apparatus. Creep conditions included three different applied constant stress levels (20, 40, and 80 MPa), and temperatures ranging from 0°C to 60°C. To compensate for changing dimensions at high creep strains, the data was converted to terms of compressive creep compliance. For all types of dental amalgam, compressive creep increased both with increased applied stress and with increased test temperature. The two high copper systems evaluated appear to approach a steady-state creep condition up to the highest temperatures tested, but the two conventional amalgams appear to change their creep exponent precipitously at temperatures above 45°C.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820160507
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