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  • 1
    Electronic Resource
    Electronic Resource
    Effect of glass bioactivity on new bone development induced by demineralized bone matrix in a rat extraskeletal site (1994)
    Springer
    Archives of orthopaedic and trauma surgery 113 (1994), S. 210-214 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF00441834
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  • 2
    Electronic Resource
    Electronic Resource
    Glass-ceramic-coated titanium hip endoprosthesis (1995)
    Springer
    Archives of orthopaedic and trauma surgery 114 (1995), S. 119-122 
    Details
    ISSN: 1434-3916
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Titanium alloy hip endoprostheses coated with a bioactive glass ceramic (BGC) were followed in rabbits. All test endoprostheses remained stable, and image analysis showed an average of 78% bonding of the BGC-coated implants to bone at 52 weeks. The uncoated Ti-alloy controls demonstrated an average of 37% bone coverage after 52 weeks. By scanning electron microscopy the thickness of the BGC reaction layer was found to stabilize at 60 μm after bioactive bone bonding. The results indicate that the BGC coating must be thicker than the reaction layer to prevent detachment from the core metal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00422839
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  • 3
    Electronic Resource
    Electronic Resource
    Glass transition temperature of glasses in the SiO2-Na2O-CaO-P2O5-Al2O3-B2O3 system (1992)
    Springer
    Journal of materials science 3 (1992), S. 326-328 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract A total of 24 glasses in or near the bioactive region in the system SiO2-Na2O-CaO-P2O5-Al2O3-B2O3 were studied. By differential thermal analysis their glass transition temperatures,T g, were determined. On basis of an experimental plan for 16 glasses, two phenomenological equations describing the relationship betweenT g and glass composition were developed. The equations describeT g within the compositional ranges: SiO2, 38.0–65.5 Na2O, 15.0–30.0; CaO, 10.0–25.0; P2O5, 0–8.0; B2O3, 0–3.0; Al2O3, 0–3.0 wt%. The glass transition temperature shows a linear dependence of the Na2O content. The higher the Na2O content, the lower theT g. Compositional alterations not including Na2O influencesT g little in comparison with changes in the Na2O content.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00705363
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  • 4
    Electronic Resource
    Electronic Resource
    Evaluation of the acceptance of glass in bone (1992)
    Springer
    Journal of materials science 3 (1992), S. 145-150 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Six glasses in the SiO2-Na2O-CaO-P2O5-Al2O3-B2O3-system were implanted in rabbit tibia. The bone-implant interfaces were studied by scanning electron microscopy (SEM) and in a push-out test. In SEM it seems possible to distinguish between physical contact and chemical bonding between glass and bone. The measured push-out strength is about 0.5 MPa if no bone contact exists. If physical contact exists the push-out strength is 2–3 MPa. The push-out strength of titanium falls within these limits. Glasses, which on basis of the SEM study are concluded to chemically bond to bone, show push-out strengths of 16–23 MPa. Two non-bonding glasses are compared. One possesses only a silica-rich surface, whereas the other possesses a calcium phosphate-rich surface. Both develop a close contact with bone, but neither bonds chemically. There is no significant difference in their push-out strengths, which are comparable to that of titanium. Even if a calcium phosphate-rich layer forms at the glass surface, bonding may be reduced if Al2O3 is included in the glass composition. Further, a phosphate-free bioactive glass is compared with two phosphate-containing bioactive glasses. The phosphate-free glass bonds by incorporating phosphate from the body fluid into its surface. Push-out data indicate that this glass is not as firmly attached to bone as the phosphate-containing ones. The calcium phosphate layer formed is non-uniform, which might explain the lower bonding strength.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00705283
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  • 5
    Electronic Resource
    Electronic Resource
    In vivo behaviour of glasses in the SiO2-Na2O-CaO-P2O5-Al2O3-B2O3 system (1990)
    Springer
    Journal of materials science 1 (1990), S. 219-227 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF00701080
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  • 6
    Electronic Resource
    Electronic Resource
    Bioactive glass and glass-ceramic-coated hip endoprosthesis: experimental study in rabbit (1995)
    Springer
    Journal of materials science 6 (1995), S. 14-18 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00121240
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  • 7
    Electronic Resource
    Electronic Resource
    Bioactive double glass coatings for Co-Cr-Mo alloy (1995)
    Springer
    Journal of materials science 6 (1995), S. 242-247 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00146863
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  • 8
    Electronic Resource
    Electronic Resource
    The stability of hydroxyapatite in an optimized bioactive glass matrix at sintering temperatures (1991)
    Springer
    Journal of materials science 2 (1991), S. 133-137 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract The stability of sintered hydroxylapatite particles was studied in glass matrices of the system SiO2-CaO-P2O5-Na2O-Al2O3-B2O3 at sintering temperatures between 700 and 1000 °C. The results from X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectroscopy (EDX) analysis, transmission electron microscopy (TEM) and electron diffraction showed that above 700 °C the Na+ ions diffuse into the hydroxylapatite particles which then transform into rhenanite. The glass matrix undergoes crystallization yielding wollastonite crystals and a silica rich matrix.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00692970
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  • 9
    Electronic Resource
    Electronic Resource
    Calcium phosphate formation at the surface of bioactive glass in vitro (1991)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 25 (1991), S. 1019-1030 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The calcium phosphate formation at the surface of bioactive glass was studied in vitro. Glass rods and grains were immersed in different aqueous solutions and studied by means of scanning electron microscopy and energy dispersive x-ray analysis. Surface morphological changes and weight loss of corroded grains were monitored. In-depth compositional profiles were determined for rods immersed in the different solutions. The solutions used were tris-buffer (trishydroxy-methylaminomethane + HCl), tris-buffer prepared using citric acid (trishydroxy-methylaminomethane + C6H8O7·H2O), and a simulated body fluid, SBF, containing inorganic ions close in concentration to those in human blood plasma. It was found that the calcium phosphate formation at the surface of bioactive glass in vitro proceeds in two stages. When immersing the glass in tris or in SBF a Ca,P-rich surface layer forms. This accumulation takes place within the silica structure. Later, apatite crystals forming spherulites appear on the surface. The Ca/P-ratio of initially formed calcium phosphate was found to be about unity. It is proposed that this is due to bonding of phosphate to a silica gel. The surface is stabilized, i.e., leaching is retarded, by the rapid Ca,P-accumulation within the silica structure before apatite crystals are observed on the surface. It is proposed that the initially formed calcium phosphate is amorphous and that the crystallization is initiated within the silica gel. The crystallizing surface provides nucleation sites for extensive apatite formation on the glass surface. In the presence of citrate no Ca,P-accumulation occur at the glass surface, but soluble Ca-citrate complexes form. By comparing the weight loss during corrosion in tris with that in the calcium and phosphate containing SBF, it is possible to establish whether the glass can induce apatite formation at its surface or not.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820250808
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  • 10
    Electronic Resource
    Electronic Resource
    Dissolution, leaching, and Al2O3 enrichment at the surface of bioactive glasses studied by solution analysis (1993)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 27 (1993), S. 941-948 
    Details
    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
    URL: http://dx.doi.org/10.1002/jbm.820270713
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