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  • 1
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Tissue integration in four types of porous implant materials (Interpore 200® or Corallin hydroxyapatite, hydroxyapatite blocks, hydroxyapatite granules and polymethylmethacrylate) was evaluated in vivo. Porous blocks measuring 20 mm × 10 mm × 8 mm were implanted in mandibles and iliac crests of sheep. Bone healing in porous blocks was studied at 2 and 6 months after implantation. The behavior of the material itself was also analyzed. Histological and histomorphometrical analysis revealed bone healing depending upon healing time and material. On the basis of analysis of variance, differences in amounts of bone ingrowth at 2 and 6 months were statistically significant (p = 0.0039 in mandible; p = 0.0351 in iliac crest). The longer the time span, the more mineralized tissues were observed in the specimen. Our data confirmed that hydroxyapatite has osteoconductive capacities. Porous PMMA was found to be biocompatible, but it showed less bonegrowth within the pores. Interpore 200®, which had the highest surface to volume ratio was found to display the highest level of osseointegration and biodegradation. © 2000 Kluwer Academic Publishers
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  • 2
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Sintered microporous cylinders of hydroxyapatite (OHA), tertiary calcium phosphate (β-TCP and rhenanite (CaNaPO4) were implanted in the bone of the forehead of the domestic pig (Sus scrofa). Implants together with the surrounding bone were retrieved after 6 and 12 weeks. X-ray diffraction showed that OHA and β-TCP maintain their crystal structure upon implantation. However, rhenanite is transformed completely into an apatite within 6 weeks. This apatite later incorporates sodium and carbonate. Both β-TCP and rhenanite implants showed some resorption but were otherwise covered with new bone. Electron microprobe analysis showed that the mineral at the interface had a Ca/P ratio characteristic of new bone. At a certain distance from the interface lower Ca/P ratios were found, characteristic of precursor phases of bone mineral. This suggests that the deposition of new bone starts, at least partially, from the surface of the implant. Therefore, β-TCP as well as rhenanite may be called an osteoconductive biomaterial.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 8 (1997), S. 765-770 
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract A two-step chemical treatment followed by immersion in a supersaturated calcification solution (SCS) was found to be a simple way to prepare calcium phosphate (Ca–P) coatings on Ti6Al4V. The Ca–P deposition on the treated metallic surfaces could be accelerated by employing a pre-calcification (Pre-Ca) procedure prior to immersion in SCS. The two-step treatment was performed by etching the metallic plates with a mixture of HCl and H2SO4 followed by ageing in boiling diluted NaOH solution at 140°C. Pre-Ca was carried out by incubating the two-step treated plates in Na2HPO4 solution and then in saturated Ca(OH)2 solution. The formation of a bioactive microporous surface oxide layer on Ti6Al4V by the two-step treatment was most probably responsible for the induction of Ca–P precipitation. The deposition rates and compositions of Ca–P coatings in two different SCSs were investigated by means of scanning electron microscopy, X-ray diffraction and infrared spectrophotometry.
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  • 4
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Polyether–polyester segmented block copolymers (Polyactive®) on the basis of polybutylene terephthalate (PBT) and polyethylene oxide (PEO) were mechanically tested. Tensile strength and modulus of elasticity in compressive and tensile deformation were recorded according to ASTM standards. These tests were done in vitro under dry and wet conditions, and after 3, 9 and 25 wk subcutaneous implantation of these materials in goats. Strength and modulus of elasticity were higher with increased contents of PBT in the copolymers. After water uptake, the polymer displayed a lower strength and stiffness. Disintegration of the materials with 70% PEO content and dumb-bell shape was noted at 3 wk. Disintegration of the cylinders of the same material was seen after 25 wk implantation. Of the materials with 60% PEO content, only four of the five dumb-bells had disintegrated after 25 wk implantation. The in vivo test results of all other implants did not show a clinically relevant decrease of strength and stiffness with time after implantation of the copolymers in the goats. Mechanical behavior of the various copolymers seemed mainly determined by the amount and integrity of the PBT phase.
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  • 5
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract To prevent exposure of artificial tooth root implants, a resorbable root implant may be developed, that in time will resorb in a vertical direction at the same rate as the alveolar ridge does after the loss of the natural teeth. Implants of four calcium phosphates: rhenanite, β-tricalcium phosphate, hydroxylapatite and magnesium-whitlockite were measured duringin vivo resorption and their interactions with the surrounding tissues at experimental periods of 6 weeks and 3 months were investigated. It was shown that a sequence of progressive resorptionin vitro does not correlate with the resorption rates found in thisin vivo experiment.In vivo hydroxylapatite was found to be less resorbable than magnesium-whitlockite and rhenanite less resorbable than β-tricalcium phosphate. Tissue interactions showed that resorption of the calcium phosphates was positively related to the number of osteoclast-like cells and did not completely correlate with the resorption measurements insofar that most rhenanite implants showed a more reactive peri-implant with the largest number of osteoclast-like cells, strongly affecting the implant surface. In contrast, two rhenanite implants showed intimate contact with bone after initial resorption. Because of this divergent reaction with rhenanite, furtherin vivo investigation on this material is proposed.
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  • 6
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: To gain more information on the in vivo behaviour of rhenanite (CaNaPO4), particles of this material and of hydroxylapatite were mixed with gelatin or saline and inserted in tooth sockets of beagle dogs for periods of 3 and 6 months. Rhenanite appeared to transform into an apatite containing carbonate, sodium and magnesium. Resorption of both calcium phosphate particles was not observed histologically and was not shown histomorphometrically. Calcium phosphates were not found in lymph node tissue. The presence of particles in the sockets gave rise to new bone formation. Histomorphometry demonstrated that statistically significant more bone deposition occurred on rhenanite particles than on hydroxylapatite particles. Also gelatin, meant as a spacer, contributed to new bone formation.
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  • 7
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Glutaraldehyde (GA) crosslinking (fixation) of collageneous tissues is a widely used method for the preparation of implantible tissues to be used as biomaterials. In an attempt to optimize the fixation process, experiments were carried out with two types of collagen (native collagen membrane and synthetic collagen sheet) to study the effect on crosslinking of temperature, GA concentration and fixation time. Secondly, stimulation of GA diffusion was studied and finally, a procedure of low T-presoaking followed by brief exposure to high temperatures was investigated. As a measure of the degree of crosslinking the shrinkage temperature (T s) was determined. Temperature (20°C or 45°C), concentration (0.1% or 1.0%) or fixation time (4 or 24 h) were found to be positively correlated with the T s of the collagen sheets. Whereas untanned collagen exhibits a T s of around 60°C, short-term (1 or 5 min), high-temperature (50°C) fixation with a 0.1% GA solution caused the shrinkage temperature to increase to 72°C and 85.1°C, respectively. Fixation with 0.01% GA for 5 min at 50°C appeared equally effective as 1 min with 0.1% GA (T s=70°C). Microwave irradiation showed to be slightly more effective in enhancing the crosslinking process compared with conventional heating. Surprisingly, at any combination of temperature, concentration and fixation periods of 4 h or 24 h, an increased T s towards the central regions of the collagen was observed. Soaking the samples at 20°C (1 h) or at 0°C (3 h) with subsequent short-time heating to 45°C caused an almost equal rise in T s throughout the collagen samples and is therefore recommended for preparing implantable tissues.
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  • 8
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: This study reports in vitro biocompatibility screening of different kinds of silane-treated hydroxyapatite (HA) powders, for use as modified filler in resorbable composite. The silane coupling agents investigated were all methoxysilanes, with either vinyl (VS), or methacryloxy (MPS), or primary amine (AMMO), or secondary amine (TRIAMO), or diamine (DAS) functionality. Evaluation of cell adhesion on the different silanized HA surfaces, indirect agar-overlay test and direct contact test on extracts showed the acute toxicity of all five free silane agents, the innocuity of strongly adsorbed silane molecules on HA surfaces and the dose-dependent toxicity of leachable silanol molecules.
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  • 9
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: A method was developed to improve the interfacial bonding between hydroxyapatite and a biodegradable copolymer PolyactiveTM 70/30. Hydroxyapatite was first surface modified by the polyelectrolytes polyacrylic acid or poly(ethylene-co-maleic acid) in aqueous solutions. Subsequently the surface-modified hydroxyapatite was used as filler in composites with PolyactiveTM 70/30. The strength, elongation at break and elastic modulus of the composite in aqueous environment were significantly improved by this method. Based on these experimental results, it is believed that the interface improvement is due to hydrogen bonding and/or dipole interactions formed between polyelectrolyte molecules and polyethylene glycol segments in the polymer matrix. Due to the introduction of interfacial bonding by using such method, a new biodegradable bone-bonding composite can be made.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 7 (1996), S. 359-361 
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Composite films made of poly L/D copolymer and hydroxylapatite (HA) as filler material were made in two different volume percentages. As references pure copolymer films and composite films with magnesium oxide (MgO) were prepared to serve as strongly basic model filler material. All these materials were immersed in phosphate buffered saline to study the effect of filler materials on the degradation rate of the copolymer. Filled films showed less molecular weight decrease than the unfilled films, while lactate release was higher for the filled films than for the unfilled films. This effect implies that the filler materials influence the degradation mechanism by preventing the occurrence of the autocatalytic effect of the acidic endgroups, resulting from hydrolysis of the polymer chains. The polymer chains at the surface of the material are less protected by the filler materials, which causes a more rapid degradation of these chains and a higher lactate release. At the same time composites seem to show an erosion type of degradation rather than bulk degradation in unfilled materials.
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