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  • 1
    ISSN: 1434-3916
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of two kinds of bioactive glass and two kinds of phosphate-free glass on new bone development induced by dernineralized bone matrix (DBM) were studied in the rat abdominal muscle pouch model. After 8 weeks' implantation histomorphometric analysis revealed that the amount of new bone in DBM combined with bioactive glass was comparable to DBM without bioactive glass. DBM grafts combined with phosphate-free glass showed significantly less new bone formation. Scanning electron microscopic examination confirmed that new bone bonded to the surface of bioactive glass. The release of ions from the glass seemed to slow down after new bone had bonded to it. Exclusion of phosphate from a bioactive glass resulted in loss of ability to develop the Ca,P-rich surface layer needed for bone bonding. contains BMP and other growth factors capable of inducing bone formation when implanted in various sites in laboratory animals [17–19]. Bioactive glasses have several beneficial properties as a bone substitute. The crystal chemistry of the surface formed in in vivo apatite contributes to a high bone bonding rate [6, 8], and the rate of reactivity can be controlled by choice of glass composition [2]. In addition, bonding of glass to soft tissues has been reported [7, 20]. We have previously reported formation of new bone directly on bioactive glass, induced by DBM in rat muscle tissue [13]. In the present study, the effects of four different glasses on new bone formation in DBM were studied in an extraskeletal site.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Sixteen glasses in the SiO2-Na2O-CaO-P2O5-Al2O3-B2O3 system were studied. The glasses were implanted in rabbit tibia. According to theirin vivo behaviour, they were divided into five groups. A phenomenological equation for thein vivo behaviour was developed. The solubility of the glasses was determinedin vitro as weight loss in Tris buffer solution. The tissue response is discussed in relation to the glass composition and the solubility. For bone-bonding glasses calcium phosphate formation takes place within a silica-gel at the glass surface. The gel must be sufficiently hydrated and flexible to allow calcium phosphate to build up. The results suggest that alumina can inhibit bone bonding by retarding the formation rate of a silica-rich layer, by stabilizing the silica structure enough to prevent calcium phosphate build-up within the layer, or by either disturbance of the bone mineralization or bone incompatibility of an alumina-containing calcium- and phosphorus-rich surface layer. The mechanism responsible for the lack of bone adherence is determined by the glass composition. Up to about 1.5 wt % Al2O3 can be included in the glass without destroying the bioactivity.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 1 (1990), S. 182-184 
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract A hydroxyapatite slurry was prepared by stirring into water a stoichiometric mixture of tricalcium phosphate and calcium hydroxide until the solid content was 50 wt%. Samples were then prepared by slip casting, drying and firing in vacuum at 1000 to 1300° C for 1 h. The fired samples were crushed and soaked in ordinary mineral water for up to 2 months and examined by differential thermal analysis and thermogravimetry, infrared spectroscopy, X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray analysis, and direct-current plasma emission spectroscopy. One phosphate ion was found to be replaced by carbonate and practically all hydroxide by water, regardless of heat treatment. The infrared spectra showed a close resemblance to that obtained from natural bone.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Co−Cr−Mo endoprostheses with a dual bioactive glass (BG) coating and titanium implants coated with a bioactive glass-ceramic (BGC) were studied under lead-bearing conditions in the rabbit hip. The dual BG coating contained an inner layer of high durability and an outer bioactive layer. Each type of coating improved the stabilization of prosthesis during the experiment period of 8 weeks compared to non-coated control implants. EDXA analysis confirmed the ability of BG and BGC coatings to bond chemically to bone. The BGC coating on titanium alloy proved superior to the dual BG coating on Co−Cr−Mo prosthesis with regard to bone formation on the surface of the implant. The bioactive top layer of the dual BG coating showed resorption, especially in the areas without direct bone contact. This is explained by partial crystallization of the glass during firing. Thermal discrepancy between BGC coating and titanium core caused cracking of the coating, which remains a major obstacle to its use as a bioactive coating.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 6 (1995), S. 242-247 
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Glass compositions for double coatings for a Co-Cr-Mo alloy were developed. The glass compositions were chosen to fulfil such requirements as matching thermal expansion, low glass transition temperature and moderate solubility. For the ground coat a fairly high durability is required, whereas the cover coat must be bioactive, i.e. become attached to living bone by a chemical bond. Two compositions of each type were developed by computer-aided optimization. The glasses were chosen in the Na2O−CaO−B2O3−Al2O3−SiO2−P2O5 system. The bioactivity was tested in vitro by immersion in a simulated body fluid. The double coatings on Co−Cr−Mo alloy released hexavalent chromium into the solution as detected by yellow colouration and spectrophotometry. This colouration was strong at the margin between coated and uncoated metal and may be explained by oxidation of trivalent chromium of the alloy in the presence of glass. The released chromium did not have any notable effect on the calcium phosphate formation. After replensihing the solution no coloration was observed. This suggests that the chromate is easily dissolved and that it may be possible to wash it out prior to implantation.
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  • 6
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 27 (1993), S. 941-948 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Five glass compositions in or near the bioactive region in the system SiO2—Na2O—CaO—P2O5—Al2O3 were studied in vitro by immersion in Tris buffer. The Si concentration can be taken as a measure of the amount of dissolved glass, whereas the Na concentration can be used to estimate the thickness of the Si-rich (Si gel) layer. Upon immersing a bioactive glass into Tris buffer, a surface layer of a few micrometer thickness is dissolved during the first 8 h. During the first few hours of immersion, the rate of dissolution of the glass network is equal to or exceeds that of the growth of the Si-rich layer. If the glass contains Al2O3, most of the aluminum that would be released due to dissolution of the silica network is enriched in the Si-rich surface layer that forms due to leaching. Al2O3 is not only bonded by the Si gel but also interferes with formation of culcium phosphate. © 1993 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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