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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 10 (1972), S. 82-90 
    ISSN: 1432-0827
    Keywords: Calcium ; Phosphate ; Precipitation ; Kinetics ; Chemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé La cinétique de la formation et de la transformation des précipités de phosphate de calcium, obtenus en mélangeant de volumes égaux de solutions à 6×10−3 M de calcium total et/ou phosphate total est étudiée à 25°C. Les solutions de phosphate sont préajustées à un pH de 7.4. Les changements de pH et de turbidité des solutions sont suivis simultanément en fonction du temps. Les précipités sont isolés à des intervalles de temps variables et caractérisés par diverses méthodes physico-chimiques. Initialement un précipité avec un rapport molaire Ca/P de 1.5, amorphe aux rayons X et en diffraction électronique, est formé. Le spectre IR indique la présence de PO 4 3− et de HPO 4 2− . Après une période métastable, on observe la précipitation d'un matériel cristallin dans ou sur la phase amorphe. Vingt quatre heures après préparation de l'échantillon les précipités présentent surtout les caractères du phosphate octocalcique.
    Abstract: Zusammenfassung Die Kinetik der Bildung und Transformation von Calciumphosphat-Niederschlägen wurde bei 25°C untersucht. Es wurden dazu gleiche Volumen von Lösungen gemischt, bei einer Konzentration von 6×10−3M totales Calcium und/oder totales Phosphat. Die Phosphatlösungen wurden zuerst auf pH 7,4 eingestellt. Veränderungen des pH und Trübung der Lösungen wurden gleichzeitig als eine Funktion der Zeit aufgezeichnet. Niederschläge wurden in verschiedenen Zeitintervallen isoliert und mit verschiedenen physiko-chemischen Methoden charakterisiert. Am Anfang wurde ein Niederschlag mit einem molaren Ca/P-Verhältnis von 1,5, im Röntgenbild und in der Elektronendiffraktion amorph, gebildet. Infrarotspektren deuteten die Anwesenheit von PO 4 3− - und HPO 4 2− -Ionen an. Nach einer metastabilen Periode erfolgte ein Niederschlag aus kristallinem Material innerhalb oder auf der amorphen Substanz. 24 Std nach der Herstellung der Proben zeigten die Niederschläge in der Hauptsache die Charakteristiken von Octocalciumphosphat.
    Notes: Abstract The kinetics of the formation and transformation of calcium phosphate precipitates obtained by mixing equal volumes of solutions, 6×10−3 M in total calcium and/or total phosphate was investigated at 25°. The phosphate solutions were preadjusted to pH 7.4. Changes of the pH and turbidity of the solutions were followed simultaneously as a function of time. Precipitates were isolated at various time intervals and characterized by different physicochemical methods. Initially a precipitate with a molar Ca/P ratio of 1.5, amorphous to X-ray and electron diffraction was formed. IR spectra indicated the presence of PO 4 3− and HPO 4 2− ions. After a period of metastability, precipitation of a crystalline material within or upon the amorphous matter occurred. Twenty four hours after sample preparation the precipitates showed mainly the characteristics of octacalcium phosphate.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 16 (1974), S. 145-152 
    ISSN: 1432-0827
    Keywords: EHDP ; Bone ; Chemistry ; Serum ; Rabbits
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract The effects of disodium ethane-1-hydroxy-1,1-diphosphonate (EHDP) on bone and serum chemistry were investigated in adult rabbits. EHDP was administered by subcutaneous injection at doses of 0.25, 2.5 and 10 mg/kg body weight/day for of 28 days. Blood samples were obtained weekly from each rabbit and serum levels of total calcium, ionized calcium, inorganic phosphate and alkaline phosphatase were determined. At the end of the treatment period all rabbits were sacrificed and the tibiae removed for chemical analysis and histological evaluation. The effect of EHDP administration on serum chemistry was both dose- and time-related. The highest of the three doses, 10 mg/kg/day, resulted in a time-related decrease in total serum calcium. This dose also caused a rapid but transient reduction in serum ionized calcium. The effect of EHDP on serum inorganic phosphate was biphasic. Administration of 2.5 mg/kg/day resulted in a time-related elevation in this parameter, whereas the 10 mg/kg/day dose resulted in a time-related hypophosphatemic response. There were no significant drug-related changes in tibial fat-free dry weight, ash weight, total calcium or total phosphorus values. However, administration of 2.5 and 10 mg/kg/day EHDP resulted in increased osteoid tissue as measured histologically. These results are compared with data from other EHDP studies, and discussed in relation to the maturity and growth-state of the experimental animals.
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  • 3
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    Springer
    Calcified tissue international 14 (1974), S. 3-14 
    ISSN: 1432-0827
    Keywords: Hydroxyapatite ; Mineral ; Phase ; Chemistry ; Synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Des diagrammes de phase d'équilibre ont été déterminés pour le système CaO-P2O5-H2O en utilisant des techniques de synthèse hydrothermique au cours de variatio nsde température allant de 300–600° et 2 Kb H2O de pression. De l'hydroxyapatite bien cristallisé a été synthétisé et caractérisé. De faibles variations de paramètres de la maille cristalline, liées à la température de synthèse et composition globale du matériel initial, ont été déterminées. Des conditions chimiques précises sont nécessaires pour obtenir de l'apatite, en tant que seule phase solide en équilibre dans la solution. Les résultats de diagramme de phase d'équilibre sont comparés avec ceux obtenus dans des milieux synthétiques.
    Abstract: Zusammenfassung Es wurden Gleichgewichts-Phasendiagramme für das System CaO-P2O5-H2O bestimmt, indem hydrothermale Synthese-Techniken im Temperaturbereich von 300–600° und bei einem Druck von 2 Kb H2O verwendet wurden. Es wurde gut-kristallisiertes Hydroxyapatit erzeugt und charakterisiert. Es wurden geringe Unterschiede in den Parametern der Zelleinheiten festgestellt, welche von der angewandten Temperatur und der Zusammensetzung des Startmaterials abhingen. Es waren genaue chemische Bedingungen nötig, um Apatit als die einzige feste Phase im Gleichgewicht mit der Lösung zu erhalten. Die Resultate der Gleichgewichts-Phasendiagramme werden mit früheren Untersuchungen mit der Synthesetechnik verglichen.
    Notes: Abstract Equilibrium phase diagrams have been determined for the system CaO-P2O5-H2 using hydrothermal synthesis techniques in the temperature range 300–600° and 2 Kb H2O pressure. Well-crystallized hydroxyapatite has been produced and characterized. Small variations in unit cell parameters dependent on temperature of synthesis and bulk composition of the starting materials have been determined. Precise chemical conditions were required to obtain apatite as the only solid phase in equilibrium with solution. Equilibrium phase diagram results are compared with previous synthetic investigations.
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  • 4
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    Springer
    Calcified tissue international 7 (1971), S. 150-162 
    ISSN: 1432-0827
    Keywords: Uranium ; Bone ; Distribution ; Fission ; Chemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Une concentration moyenne de 2.4×10−8 g U/g de cendre a été obtenue à partir de l'os humain normal. La microdistribution de l'uranium dans l'os indique que cet élément est surtout limité à surface de l'endoste et, en particulier, aux surfaces de l'os lamellaire et aux parois des canaux de Havers, ouverts dans l'os corticol. Cette répartition suggère que l'uranium se présente sous une forme chimique impropre à son incorporation dans l'apatite osseux: il ne semble donc pas exister une distribution diffuse significative de l'uranium dans l'os.
    Abstract: Zusammenfassung Eine mittlere Konzentration von 2,4×10−8 g Uran/g Asche wurde in normalen menschlichen Knochen gefunden. Die Feinverteilung von Uran im Knochen zeigt, daß dieses Element hauptsächlich an der endostalen Oberfläche vorkommt, insbesondere an der Oberfläche des trabeculären Knochens und an den Wänden der offenen Haversschen Kanäle im kortikalen Knochen. Diese Verteilung läßt vermuten, daß Uran in einer chemischen Form vorliegt, welche sich für den Einbau in das Knochenapatit nicht eignet. Daraus folgt, daß keine signifikante diffuse Verteilung des Urans innerhalb des Knochens vorliegt.
    Notes: Abstract A mean concentration of 2.4×10−8 g U/g ash has been obtained for normal human bone The microdistribution of uranium in bone indicates that this element is mainly restricted to endosteal surfaces; in particular the surfaces of trabecular bone and the walls of open Haversian canals in cortical bone. This distribution suggests that uranium is present in a chemical form that is not acceptable for incorporation into bone apatite and consequently there does not appear to be a significant diffuse distribution of uranium throughout bone.
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  • 5
    ISSN: 1432-0827
    Keywords: Morphology ; Glycosaminoglycans ; Cartilage ; Chemistry ; Audioradiography ; Healing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Une perte de substance ostéo-cartilagineuse, de taille limitée et identique, est réalisée chez le lapin adulte et la cicatrisation est étudiée histologiquement et par autoradiographie après marquagein vitro au35S-sulfate. Une analyse microchimique est pratiquée pour le contenu et la composition en glycosaminoglycanes. 1. Entre la première semaine et la 4ème et 8ème semaine, un tissu conjonctif non-métachromatique se différencie en un cartilage métachromatique et la quantité de sulfate de chondroitine augmente de façon significative aux dépens des glycoprotéines. 2. Jusqu'à la 4ème semaine, la perte de substance est surtout comblée par de l'os néoformé: après cette période, la région est comblée au delà de la limite de la surface articulaire. 3. Le cartilage hyalin, ressemblant morphologiquement, autoradiographiquement et chimiquement au cartilage articulaire, en ce qui concerne la distribution en glycosaminoglycanes, constitute la surface articulaire de la perte de substance comblée dans un tiers des cas après 8 semaines. Le cartilage hyalin s'observe surtout dans les régions où de l'os néoformé a comblé la cavité médullaire. 4. Dans les deux tiers des cas, après 8 semaines, les surfaces articulaires des zones comblées comportent, non seulement du cartilage, mais aussi du tissu fibreux se formant essentiellement sur les parties latérales et dans les régions, où la cavité médullaire, fliant face, à la surface articulaire, n'a pas été comblée par du tissue osseux. La fraction glycoprotéique augmente par rapport à la fraction chondroitine sulfate. 5. Dans la majorité des cas, après 20 semaines, le cartilage néoformé subit des phénomènes dégénératifs, qui se traduisent par une diminution en chondroitine sulfate.
    Abstract: Zusammenfassung Bei ausgewachsenen Kaninchen wurde ein begrenzter, standardisierter, osteochondraler Defekt hervorgerufen, und das regenerierte Gewebe wurde histologisch und autoradiographisch durch Markierung in vitro mit35S-Sulfat und durch mikrochemische Bestimmung des Gehaltes und der Zusammensetzung der Glykosaminglykane untersucht. Die wichtigsten Befunde waren: 1. Zwischen 1 und 4–8 Wochen veränderte sich nichtmetachromatisches Bindegewebe zu metachromatisch gefärbtem Knorpel, und der Anteil an Chondroitin-Sulfat nahm auf Kosten der Glykoproteine signifikant zu. 2. Bis zu 4 Wochen war der Hauptteil des defekten Gebietes mit neugebildetem Knochen gefüllt; nach dieser Zeit lag dieser Bezirk oberhalb der Verknöcherungsgrenze in Richtung der Gelenkoberfläche. 3. Nach 8 Wochen bestand die Gelenkoberfläche des defekten Gebietes in einem Drittel der Fälle aus hyalinem Knorpel, der morphologisch, autoradiographisch und chemisch dem Gelenkknorpel in Bezug auf die Verteilung von Glykosaminoglykanen glich. Hyaliner Knorpel wurde hauptsächlich an Stellen beobachtet, wo neugebildeter Knochen die Markhöhle geschlossen hatte. 3. Nach 8 Wochen bestand die Gelenkoberfläche des defekten Gebietes in einem Drittel der Fälle aus hyalinem Knorpel, der morphologisch, autoradiographisch und chemisch dem Gelenkknorpel in Bezug auf die Verteilung von Glykosaminoglykanen glich. Hyaliner Knorpel wurde hauptsächlich an Stellen beobachtet, wo neugebildeter Knochen die Markhöhle geschlossen hatte. 4. Nach 8 Wochen bestanden Teile der Gelenkoberfläche des Defektes in zwei Dritteln der Fälle nicht nur aus Knorpel, sondern auch aus fibrösem Gewebe, welches vor allem in den seitlichen Teilen des Defektes und an Stellen vorlag, wo die Markhöhle gegenüber der Gelenkoberfläche nicht mit Knochengewebe verschlossen worden war. Die Glykoproteinfraktion nahm im Vergleich zur Chondroitin-Sulfatfraktion zu. 5. Nach 20 Wochen zeigten sich in den meisten Fällen bei neugebildetem Knorpel degenerative Veränderungen, welche durch eine gewisse Abnahme des Chondroitin-Sulfats wiedergegeben wurden.
    Notes: Abstract A limited, standardized osteochondral defect was created in adult rabbits and the regenerated tissue was examined histologically and autoradiographically after labellingin vitro with35S-sulphate, and microchemically for its content and composition of glycosaminoglycans. The principal findings were: 1. Between 1 week and 4 to 8 weeks, non-metachromatic connective tissue differentiated to metachromatically stained cartilage, and the proportion of the chondroitin sulphate increased significantly at the expense of the glycoproteins. 2. Up to 4 weeks, the major part of the defect area was filled with newly formed bone; after this time, the area lay above the level of the “tidemark”, towards the articular surface. 3. Hyaline cartilage with morphological, autoradiographic and chemical resemblance to the articular cartilage in terms of the distribution of glycosaminoglycans constituted the articular surface of the defect area in one-third of the cases at observation times after 8 weeks. Hyaline cartilage was observed mainly in areas where newly formed bone had closed the medullary cavity. 4. In two-thirds of the cases, after 8 weeks, parts of the articular surface of the defect consisted not only of cartilage but also of fibrous tissue, occurring mainly in the lateral parts of the defect and in areas where the medullary cavity facing the articular surface had not been sealed by bone tissue. The glycoprotein fraction increased relative to the chondroitin sulphate fraction. 5. In most cases after 20 weeks, newly-formed cartilage underwent degenerative changes, which were reflected in some reduction of the chondroitin sulphate.
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  • 6
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    Electronic Resource
    Springer
    Calcified tissue international 8 (1971), S. 228-236 
    ISSN: 1432-0827
    Keywords: Skin ; Calcinosis ; Keratin ; Chemistry ; X-ray diffraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Des études histologiques antérieures ont montré que le follicle pileux est particulièrement susceptible de se calcifier, lorsque la peau de rats hypercalcémiques est lésée. Des analyses chimiques et par diffraction aux rayons X du follicule ont confirmé ce résultat. — En se basant sur l'augmentation du calcium et du phosphore, les calcifications débutent dans le tissue folliculaire 6–12 h après une blessure d'intensité moyenne de la peau de rats, ayant reçu du dihydrotachysterol (DHT), et 24–48 h après une blessure similaire chez des rats non injectés. Les diagrammes de diffraction aux rayons X sont diffus. Trois heures après la blessure, on note une augmentation du calcium du tissu folliculaire qui ne semble pas en rapport avec le DHT qui traduit probablement une liaison de calcium plutôt qu'un dépot minéral.
    Abstract: Zusammenfassung Frühere histologische Untersuchungen haben gezeigt, daß der Haarfollikel besonders anfällig für Verkalkungen ist, wenn die Haut von hypercalcämischen Ratten verletzt wird. Dieses Resultat wurde nun durch direkte chemische Bestimmungen und Röntgendiffraktions-analysen von Follikelgewebe bestätigt. Aufgrund der erhöhten Calcium- und Phosphatwerte kann gesagt werden, daß nach einer leichten Quetschung der Haut von Ratten, die mit Dihydrotachysterol (DHT) behandelt wurden, im Haarfollikelgewebe nach 6–12 Std Mineral-ablagerungen stattfanden, wogegen Kontrollratten mit der gleichen leichten Hautverletzung diese Ablagerungen erst nach 24–48 Std zeigten. Röntgendiffraktionsanalysen ergaben ein diffuses Apatit-Muster. Innerhalb 3 Std nach der Verletzung wurde ein Anstieg des Calcium-gehaltes im Follikelgewebe beobachtet, der nicht im Zusammenhang mit der DHT-Behandlung stand, also nicht eine Mineralablagerung, sondern eher eine Bindung von Calcium widerspiegelte.
    Notes: Abstract Previous histological investigations have shown that the hair follicle is particularly susceptible to mineralization when the skin of hypercalcaemic rats is injured. Direct chemical and X-ray diffraction analyses of follicle tissue have now confirmed this finding. As judged by increases in both calcium and phosphorus, mineral deposits began to form in hair follicle tissue 6–12 h after a mild crush injury to the skin of rats dosed with dihydrotachysterol (DHT), and 24–48 h after a similar injury to the skin of non-dosed rats. X-ray diffraction gave a diffuse apatite pattern. Within 3 h of injury there was a rise in the calcium content of follicle tissue which was not related to DHT-dosing and which was probably a reflection of calcium binding rather than mineral deposition.
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  • 7
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    Calcified tissue international 8 (1971), S. 304-319 
    ISSN: 1432-0827
    Keywords: Chemistry ; Calcium ; Phosphate ; Solubility ; Computer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Un programme d'ordinateur a été mis au point pour calculer les activités ioniques du calcium et l'orthophosphate dans un grand nombre de solutions. Dans le cas de solutions synthétiques, les calculs sont vérifiés en comparant les valeurs de pH, obtenues par ordinateur, avec celles observées expérimentalement. Des essais de ce type, avec des solutions possèdant des concentrations de calcium et d'orthophosphate trouvées dans les liquides biologiques et à des valeurs de pH variant de 3.00 à 10.00, indiquent que le programme est adapté pour des applications biologiques. Le programme n'est pas effectif pour des solutions, dans les lesquelles l'ion bromure est la source principale de la force ionique, sans doute, par manque d'équation étendue de Debye-Hückel dans ces circonstances. Aucune formation de complexe de phosphate de sodium n'a été notée à des concentrations biologiques normales.
    Abstract: Zusammenfassung Es wurde ein Computer-Programm ausgearbeitet, um die Ionenaktivitäten von Calcium und Orthophosphat in einer breiten Varietät von Lösungen zu berechnen. Die Berechnungen wurden bei synthetischen Lösungen durch Vergleiche zwischen den auf diese Weise errechneten pH-Werten und den experimentell gefundenen kontrolliert. Diese Art Kontrollen mit Calcium-und Orthophosphatkonzentrationen, wie sie in biologischen Flüssigkeiten gefunden werden, und mit pH-Werten zwischen 3,0 und 10,0 wies darauf hin, daß das Programm für biologische Anwendungen geeignet war. Das Programm konnte nicht benützt werden für solche Lösungen, bei welchen hauptsächlich das Bromidion zur Einstellung der Ionenstärke verwendet wurde, vermutlich weil die erweiterte Debye-Hückel-Gleichung unter diesen Umständen nicht anwendbar ist. Die Bildung eines Natriumphosphat-Komplexes unter normalen biologischen Konzentrationen konnte nicht nachgewiesen werden.
    Notes: Abstract A computer program has been designed to calculate the ionic activities of calcium and orthophosphate in a wide variety of solutions. In the case of synthetic solutions the calculations were checked by comparing the computed pH values with those observed experimentally. Tests of this type with solutions having the concentrations of calcium and orthophosphate found in biological fluids and with pH values ranging from pH 3.0–10.0 indicated that the program was suitable for biological applications. The program was not effective for solutions in which the bromide ion was a principal source of ionic strength probably because of the failure of the extended Debye-Hückel equation under those circumstances. No evidence for the formation of any sodium phosphate complex at normal biological concentrations could be found.
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  • 8
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    Calcified tissue international 10 (1972), S. 171-197 
    ISSN: 1432-0827
    Keywords: Amorphous ; Crystalline ; Calcium phosphate ; Chemistry ; Composition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Des échantillons non lavés de phosphate de calcium amorphe (ACP) contiennent une fraction labile, non remplaçable, riche en phosphate acide avec un rapport Ca/P faible: cette fraction est perdue de façon irréversible au cours du lavage. De l'ACP frais, précipité entre pH 6.6–10.6, varie dans un rapport molaire Ca/P de 1.18 à 1.50 et dans un rapport HPO 4 2− /P total de 33.0% à 10.1%. A pH 7.40, de l'ACP frais a un rapport molaire Ca/P de 1.36±0.02 et contient 22.8 (±2.2)% HPO 4 2− . Les résultats obtenus avec du précipité non lavé ne peuvent s'expliquer par du Ca2+ emprisonné et de l'HPO 4 2− ou du Na+, Cl− et CO 3 2− exogènes. Les phosphates de calcium amorphes constituent une classe de sels ayant des caractères chimiques variables et des propriétés physiques identiques, comparables au verre. Le CaHPO4·xH2O non cristallin peut être un ACP, surtout au cours des phases précoces de formation. A des pH physiologiques, l'ACP se transforme en petits cristaux applatis contenant de fortes quantités de phosphate acide facilement remplaçable. Le fait de laver la couche de surface produit un changement chimique dans les nouveaux cristaux: des cristaux non lavés donnent des diagrammes de diffraction d'apatite peu cristallins, ainsi que des spectres infra-rouges peu nets, intermédiaires entre des apatites et du phosphate octocalcique. Des explications structurales sont proposées et les compositions minérales amorphe/cristalline de l'os et du cartilage sont recalculées.
    Abstract: Zusammenfassung Ungewaschene Proben von amorphem Calciumphosphat (ACP) enthalten eine unersetzliche labile Fraktion, welche reich an saurem Phosphat ist und ein niederes Ca/P-Verhältnis hat und welche während des Waschprozesses unwiderruflich verloren geht. Natives ACP, welches im pH-Bereich 6,6–10,6 ausgefällt wurde, variierte im molaren Ca/P-Verhältnis zwischen 1,18 und 1,50 und in HPO 4 2− /totales P zwischen 33,0 und 10,1%. Bei pH 7,40 hatte natives ACP ein molares Ca/P-Verhältnis von 1,36±0,02 und enthielt 22,8 (±2,2)% HPO 4 2− . Die Werte beim ungewaschenen Niederschlag rühren weder von aus dem Überstand aufgenommenem Ca2+ und HPO2−, noch von außen kommendem Na+, Cl− und CO 3 2− her. Die amorphen Calciumphosphate werden als eine Klasse von Salzen erkannt, welche veränderliche chemische, aber identische glasartige physicochemische Eigenschaften haben. Nicht kristallines CaHPO4·xH2O kann auch ein ACP sein, besonders in den frühen Bildungsstadien. Bei physiologischem pH verwandelt sich ACP in kleine plattenförmige Kristalle, welche große Mengen von leicht ersetzbarem saurem Phosphat enthalten. Das Waschen dieser Oberflächenschicht erzeugte chemische Veränderungen in den resultierenden Kristallen; ungewaschene Kristalle zeigten ein Diffraktionsmuster, das nur schwach demjenigen des kristallinen Aspatites glich, aber ein schlecht aufgelöstes Infrarotspektrum, welches zwischen Apatit und Octocalciumphosphat war. Es werden strukturelle Erklärungen für alle diese Phenomena diskutiert, und revidierte amorph/kristalline Mineralzusammensetzungen von Knochen und Knorpel wurden neu berechnet.
    Notes: Abstract Unwashed samples of amorphous calcium phosphate (ACP) contain an irreplaceable labile fraction, rich in acid phosphate and low in Ca/P ratio, which is irreversibly lost during the washing process. Native ACP precipitated in the pH range 6.6–10.6 varied in Ca/P molar ratio from 1.18 to 1.50 and in HPO 4 2− /total P from 33.0% to 10.1%. At pH 7.40, native ACP had a Ca/P molar ratio of 1.36±0.02 and contained 22.8 (±2.2)% HPO 4 2− . Unwashed precipitate data could not be attributed to either trapped supernatant Ca2+ and HPO 4 2− or extraneous Na+, Cl−, and CO 3 2− . The amorphous calcium phosphates are recognized as a class of salts having variable chemical but identical glass-like, physicochemical properties. Non-crystalline CaHPO4·xH2O may also be an ACP, especially during early formative stages. At physiological pH, ACP transforms to small platy crystals containing large amounts of readily-replaceable acid phosphate. Washing this surface layer produced chemical alterations in the resultant crystals; unwashed crystals had poorly-crystalline apatitic diffraction patterns but exhibited poorly-resolved infrared spectra intermediate between apatite and octacalcium phosphate. Structural explanations for all these phenomena are discussed, and revised bone and cartilage amorphous/crystalline mineral compositions have been re-calculated.
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  • 9
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    Calcified tissue international 8 (1971), S. 197-210 
    ISSN: 1432-0827
    Keywords: Fluorescence ; Calcium ; Collagen ; Chemistry ; Bone ; Dentine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Des composants fluorescents de l'os et la dentine sont séparés des hydrolysats alcalins de leur marice sur des colonnes Sephadex C25 CM d'échange cationique. Les concentrations en fluorescence et le spectre d'excitation (λ max 330 nm) et d'émission (λ max 395 nm) sont les mêmes que ceux observés au niveau des matrices intactes et gélatinisées. Les paramètres de fluorescence ne sont pas altérés par hydrolyse. La filtration sur gel à l'aide de colonnes Sephadex G 10 perment de différencier le matériel isolé en deux composants, ayant la même fluorescence et la même absorption UV. La fluorescence est indépendante de pH de 3.5–9.5. Des études de dialyse et de filtration sur gel de matrices gélatinisées indiquent une association étroite du matériel fluorescent avec les chaines polypeptidiques de collagène.
    Abstract: Zusammenfassung Fluorescierende Bestandteile aus Knochen und Dentin wurden in Sephadex C25 CM Kationen-Austauschersäulen von alkalischen Hydrolysaten ihrer Matrices getrennt. Die Fluorescenzintensitäten sowie die Erregungs- (λ max 330 nm) und Emissions- (λ max 395 nm) Spektren waren dieselben wie bei intakten und gelatinisierten Matrices. Die Fluorescenzparameter wurden durch die Hydrolyse nicht verändert. Eine Gelfiltration über Sephadex-G10-Säulen trennte das isolierte Material in 2 Komponenten auf, welche gleiche Fluorescenz- und UV-Absorptionseigenschaften zeigten. Im pH-Bereich zwischen 3,5 und 9,5 war die Fluorescenz unabhängig vom pH. Dialysierversuche sowie Gelfiltrationsexperimente mitden gelatinisierten Matrices zeigten eine starkgefügte Bindung des fluorescierenden Materials mit den Polypeptidketten des Kollagens.
    Notes: Abstract Fluorescent components in bone and dentine were separated from alkaline hydrolysates of their matrices on Sephadex C25 CM cationic exchange columns. The fluorescence levels, and the excitation (λ max 330 nm) and emission (λ max 395 nm) spectra, were the same as those observed in the intact and gelatinised matrices. The fluorescence parameters were unaltered by the hydrolysis procedure. Gel filtration on Sephadex G. 10 columns further resolved the isolated material into two components with the same fluorescence and UV absorption properties. The fluorescence was independent of pH over the range 3.5–9.5. Dialysis and gel filtration studies on the gelatinised matrices indicated a firmly-bonded association of the fluorescent material with the collagen polypeptide chains.
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  • 10
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    Calcified tissue international 12 (1973), S. 125-136 
    ISSN: 1432-0827
    Keywords: Mineralization ; Molt ; Isopod ; Chemistry ; Light microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Au cours de la phase inhabituelle de mue d'un isopode d'eau courante,Lirceuts brachyrus, la moitié postérieure de l'exosquelette est éliminée 24 heures avant la moitié antérieure. A ce stade, une reminéralisation se développe dans la partie postérieure alors que la partie antérieure est dans un stade de pré-mue. Le pourcentage de différence en calcium dans les deux moitiés à mi-mue et mue complète est respectivement de 22% (p〈0.01) et 33% (p〈0.01), indiquant une complexation du calcium pendant la mue. La rapidité de la reminéralisation est illustrée par le fait que le contenu minéral total double dans la partie postérieure entre la mi-mue et la mue totale et dans la partie antérieure entre la fin de la mue et un jour après. Le carbonate de calcium, sous forme de calcite, a pu être identifié par diffraction électronique de coupes fines des téguments.
    Abstract: Zusammenfassung Während der ungewöhnlichen Häutungssequenz des Frischwasser-IsopodenLirceus brachyurus (Harger) wird die hintere Hälfte des äußeren Skeletts 24 Std vor der vorderen Hälfte abgestoßen. In der halbgehäuteten Phase erfolgt Remineralisation im hinteren Teil, während der vordere Teil in einem Vorhäutungszustand ist. Der prozentuale Unterschied des Calciums in den zwei Hälften bei Halb- und Vollhäutungszustand ist 22% (p〈0,01) bzw. 33% (p〈0,01), was andeutet, daß Calcium während der Häutung abgesondert wird. Die Geschwindigkeit der Remineralisation erhellt aus der Tatsache, daß sich der Gesamtmineralgehalt im hinteren Teil zwischen Halt- und Vollhäutung, in der vorderen Hälfte jedoch zwischen Endhäutung und einem Tag nach der Häutung verdoppelt. Calciumcarbonat in kristalliner Calcitform wurde mittels Elektronendiffraktion von dünnen Hautschnitten nachgewiesen.
    Notes: Abstract During the unusual molt sequence of the fresh-water isopod,Lirceus brachyrus (Harger), the posterior half of the exoskeleton is shed 24 hours before the anterior half. At the half-molt stage, occurs in the posterior part while the anterior portion is in a pre-molt condition. The percentage difference in calcium in the two halves at half-molt and full-molt is22 (p〈0.01) and33 (p〈0.01) respectively, an indication that calcium is sequestered during The rapidity of remineralization is illustrated by the fact that the total mineral content doubles in the posterior part between half and full molt and in the anterior half between the end of molt and one day after ecdysis. Calcium carbonate in the calcite cystalline form was demonstrated by electron diffraction of thin sections of the integument.
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  • 11
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    Calcified tissue international 13 (1973), S. 259-270 
    ISSN: 1432-0827
    Keywords: Fluorapatite ; Exchange ; Chemistry ; Crystallography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Un échantillon minéral provenant de Burgess, Canada s'est révélé être un speciment exceptionnellement pur de fluoroapatite après analyse chimique et cristallographique. La composition globale de cet échantillon est la suivante: $$(Ca^2 )9.98(Sr^{2 + } ,Na^ + ,K^ + ,Mg^{2 + } )0.02(PO_4^{3 - } )5.98(HCO_3^ - ,CO_3^{2 - } )0.02(F^ - )2$$ . L'axe cristallographique C est de 6.865 A et l'axe a de 9.374 A. Des expériences d'échanges réalisés à l'aide de45Ca,32P et18F indiquent la présence de gros cristallites de surface spécifique de l'ordre de 1 m2/g. Il apparait que l'interprétation physique des processus d'échange ne nécessite pas l'existence de compartiments séparés, avec chacun son propre facteur cinétique, les échanges semblent être simplement liés à un changement exponentiel dans l'énergie libre de la réaction. Pour la réaction suivante: $$(Ca)_5 (PO_4 )_3 OH solide + (F^ - ) \rightleftarrows (Ca)_5 (PO_4 )_3 F solide + (OH^ - )$$ , la constante thermodynamique de 101.26 a été calculée, suggérant que le fluorapatite se forme toujours aux dépens de l'hydroxyapatite dans des conditions physiologiques. Cette transformation se continue en abaissant le pH.
    Abstract: Zusammenfassung Eine Mineralprobe aus Burgess, Kanada, erwies sich nach chemischer und kristallographischer Analyse als außergewöhnlich reines Fluorapatit. Die Gesamtzusammensetzung entspricht: $$(Ca^{2 + } )_{9,98} (Sr^{2 + } ,Na^ + ,K^ + ,Mg^{2 + } )_{0,02} (PO_4^{3 - } )_{5,98} (HCO_3^ - ,CO_3^{2 - } )_{0,02} (F^ - )_2 $$ . Die kristallographische c-Achse wurde bestimmt und ergab 6,865 Å, und die a-Achse ergab 9,374 Å. Austauschwerte, welche durch Anwendung von45Ca,32P und18F erhalten wurden, deuteten auf große Kristalliten mit einer spezifischen Oberfläche von ca. 1 m2/g. Die Befunde deuten darauf hin, daß für die physikalische Erklärung des Austauschvorganges keine separaten Kompartimente mit eigenen kinetischen Faktoren nötig sind, sondern daß der Austausch mit dem exponentiellen Wechsel in der freien Energie der Reaktion in einfacher Beziehung steht. Für die Reaktion $$(Ca)_5 (PO_4 )_3 OH_{in fester Form} + (F^ - ) \rightleftarrows (Ca)_5 (PO_4 )_3 F_{in fester Form} + (OH^ - )$$ wurde als thermodynamische Konstante 101,26 errechnet, was darauf deutet, daß unter physiologischen Bedingungen immer Fluorapatit auf Kosten von Hydroxyapatit entsteht. Diese Umwandlung wird erhöht, wenn das pH erniedrigt wird.
    Notes: Abstract A mineral specimen from Burgess, Canada, proved upon chemical and crystallographic analyses to be an exceptionally pure sample of fluorapatite. The over-all composition corresponds to $$(Ca^{2 + } )_{9.98} (Sr^{2 + } ,Na^ + ,K^ + ,Mg^{2 + } )_{0.02} (PO_4^{3 - } )_{5.98} (HCO_3^ - ,CO_3^{2 - } )_{0.02} (F^ - )_2 $$ . The crystallographic c-axis was determined to be 6.865 Å, and the a-axis 9.374 A. Exchange data obtained by employing45Ca,32P, and18F indicate the presence of large crystallites with a specific surface of the order of 1 m2/g. It is indicated that the physical interpretation of the exchange process does not require the existence of separate departments, each with its own kinetic factor, but that the exchange may be simply related to the exponential change in the free energy of the reaction. For the reaction $$(Ca)_5 (PO_4 )_3 OH_{solid} + (F^ - ) \rightleftarrows (Ca)_5 (PO_4 )_3 F_{solid} + (OH^ - )$$ the thermodynamic constant has been calculated to be 101.26, implying that fluorapatite always will form at the expense of hydroxyapatite under physiologic conditions. This transformation will be furthered by lowering the pH.
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  • 12
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    Journal of Applied Biomaterials 6 (1995), S. 237-242 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Because of the recent trend in total hip arthroplasty to achieve direct contact of the endoprosthesis with cortical bone, comparison of bone apposition from cortical bone and cancellous bone was performed. The response of cortical and cancellous bone to hydroxylapatite was also compared. Implants in cortical bone demonstrated a higher interface shear strength and more bone apposition than those in cancellous bone over all time periods tested. Hydroxylapatite coating increased the interfacial shear and bone apposition in cortical bone at all time periods and in both the 3- and 6-week cancellous bone models. The potential effect of stress shielding (and subsequent bone resorption) by femoral stems ingrown with cortical bone is discussed. © 1995 John Wiley & Sons, Inc.
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    Journal of Applied Biomaterials 6 (1995), S. 249-258 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Ions released from implant surfaces are suspected of playing some role in osteolysis surrounding metal prostheses. To understand how ions may affect osteogenesis, previous work exposed osteogenic cells to metal ions to study acute cytotoxic responses. The purpose of this study was to assess the long-term effects of sublethal ion concentrations on osteogenic cell proliferation and function. Bone marrow stromal cells were harvested from juvenile rats and exposed to solutions of ions associated with Co-Cr-Mo and Ti-6Al-4V implants. Cells were cultured for up to 4 weeks and assayed for total protein, alkaline phosphatase, osteocalcin, and calcium. Other than V+5, none of the ions affected cell proliferation, indicating that the chosen concentrations were sublethal as desired. V+5 elicited delayed gross toxicity not previously observed during acute experiments. At the chosen concentrations, Co+2, Cr+6, Mo+6, and Co-Cr-Mo alloy elicited little effect on cell proliferation and moderate effects on matrix mineralization. Cultures exposed to Ti+4, Al+3, and Ti-6Al-4V alloy also showed no decrease in cell number, but did show near total suppression of osteocalcin secretion and matrix mineralization. These results suggest that ions released from Ti alloy implants may interfere with osteoblastic cell differentiation, contributing to periprosthetic osteolysis by impairing normal osteogenesis. © 1995 John Wiley & Sons, Inc.
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    Journal of Applied Biomaterials 6 (1995), S. 267-282 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Crestal bone loss is observed around various designs of dental implants. A possible cause of this bone loss is related to the stresses acting on periimplant bone. To investigate the relationship between stress state and bone loss, two-dimensional finite element models corresponding to bucco-lingual and mesio-distal sections of canine mandibles with one of two designs of porous-coated dental implants were analyzed. A fully porous-coated design consisting of a solid Ti6A14V core had a porous coating over the entire outer surface of the implant component, while a partially porous-coated design had the porous coating over the apical two-thirds of the implant surface only. Occlusal forces with axial and transverse components were assumed to act on the implant with interface bonding and effective force transfer at all porous coat-bone interfaces and no bonding for the non-porous-coated regions. The results of the analysis indicated that at most implant aspects (buccal, lingual, mesial, and distal), the equivalent stresses in crestal bone adjacent to the coronal-most, non-porous-coated zone of the partially porous-coated implants were lower than around the most coronal region of the fully porous-coated implants. The region of lower stresses around the partially porous-coated implants corresponded to observed areas of crestal bone loss in animal studies, suggesting that crestal bone loss in this case was due to bone disuse atrophy. A number of parameters of the finite element models were varied to determine the effect on the resulting stress fields and, therefore, possible long-term bone remodeling. Based on differences in observed bone structures by histological examination and results of finite element analyses with fully and partially porous-coated implants, an equivalent stress equal to 1.6 MPa was determined to be sufficient to avoid bone loss due to disuse atrophy in the canine mandibular premolar region. © 1995 John Wiley & Sons, Inc.
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  • 15
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    Keywords: Chemistry ; Polymer and Materials Science
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  • 16
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A quantitative method of reporting surface degradation of the ultra-high molecular weight polyethylene (UHMWPE) tibial component from retrieved total knee replacements (TKR) was developed. Specific features include a qualitative assessment expressing the patterns in which the damage was detected as well as a quantitative summary of the observed degradation mechanisms. In addition, a method of measuring lower limb alignment changes with time is described and related to the observed damage patterns. Two case studies are presented. One case illustrated that changes in alignment resulted from factors other than wear. The damage observed on the tibial plateau appeared to occur subsequent to the changes in alignment. The second case illustrated that the wear of the UHMWPE tibial insert lead to the changes in the overall lower limb alignment. The methods described provide additional information regarding TKR failure mechanisms compared to reporting methods currently available. In particular, the collection of temporal alignment data at clinical follow-up visits enhanced the assessment of the retrieved TKR. © 1995 John Wiley & Sons, Inc.
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  • 17
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The purpose of this study was to determine whether small, phagocytosable particles of titanium alloy (Ti) and high-density polyethylene (HDPE) have an adverse effect on bone ingrowth. The bone harvest chamber (BHC) was implanted bilaterally in the proximal tibial metaphysis of six mature rabbits. The BHC has a transverse 1-mm wide pore providing a continuous canal through the chamber for tissue ingrowth. After an initial 6-week period for osseointegration of the BHC, the contents of the canal were harvested repeatedly at 3 weekly intervals. This could be done with the chamber in place, without disturbing its exterior surface or the surrounding bone. The carrier solution, 1% sodium hyaluronate (Healon) was implanted first. In subsequent implantations, Healon was mixed with particles of HDPE or Ti averaging 4.7 ± 2.1 and 3.0 ± 2.6 μm, respectively. The contralateral chamber was left empty and served as a control. The chambers were harvested repeatedly, alternating experimental and control sides. The sections from the control side, and those containing Healon alone demonstrated extensive trabecular bone in a fibrovascular stroma. The sections containing Ti alloy particles were qualitatively and quantitatively similar to the control sections and those containing Healon, except for the presence of small black granules of Ti alloy, dispersed in the fibrovascular stroma or phagocytosed by scattered macrophages. The sections containing HDPE particles were infiltrated and engulfed by mononuclear and multinuclear histiocytic cells in a highly fibrous stroma. The majority of the multinucleated cells present were interpreted as being foreign body giant cells. Less trabecular bone was seen in the HDPE group compared to the other groups. Using the parameters chosen for this experiment, it would appear that small, phagocytosable HDPE particles are more deleterious to net formation of bone compared to particles of Ti alloy. © 1995 John Wiley & Sons, Inc.
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  • 18
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    Journal of Applied Biomaterials 6 (1995), S. 55-64 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: This study deals with a three-point flexure test for the metal-ceramic bond involving geometrically simple specimens (alloy strips partly coated with ceramic) that can be fabricated with reasonable expenditure and sufficient reproducibility. The calculation of the stress distribution in such specimens with the aid of the finite-element method (FEM) is presented. The aim of this numerical analysis is: to investigate the stress distribution in a ceramometallic specimen with dimensions that, in a large number of experiments, have proven to lead to debonding at one end of the ceramic veneer instead of a crack in the middle of the veneer; and to assign a bond strength to the measured critical bending force that takes into account the influence of the Young's modulus of the alloy as well as a possible deviation of the thickness of the metal substrate from the standard value. Bond strength values of a variety of metal-ceramic combinations are demonstrated. These experimental results demonstrate the reproducibility of the test method as well as its sensitivity to diverse parameters. The presented method is proposed as an alternative to another flexure bond test nominated for international standard. In this test ceramometallic strips are bent over a rod to a 90° angle of the specimen ends, subsequently flattened, and the fracture surface visually inspected for adherence of the ceramic to the alloy substrate along the predominant part of the middle third of the specimen. It is clear that such a test can at most deliver qualitative results. © 1995 John Wiley & Sons, Inc.
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  • 19
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    Journal of Applied Biomaterials 6 (1995), S. 87-87 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 20
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
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  • 21
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    Journal of Applied Biomaterials 6 (1995), S. 105-108 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Four different brands of bone cement (Palacos R, Simplex P, Sulfix, CMW 1) were tested for exothermic changes during polymerization at atmospheric pressure and under partial vacuum of 0.2 bar. Palacos R was also mixed at four pressure levels (1.0, 0.2, 0.12, and 0.05 bar). The peak temperature in the bone cement was 46 to 124 °C, depending on the measuring point. There was no difference in peak temperature or duration of temperature increase above 50 °C during the curing of cement whether mixed at atmospheric pressure or under partial vacuum at different pressure levels. © 1995 John Wiley & Sons, Inc.
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  • 22
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    Journal of Applied Biomaterials 6 (1995), S. 99-104 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A major problem in fracture treatment by external fixation is screw loosening, which often results in reduced stability and can lead to prolonged treatment. A load-carrying experiment was conducted to determine whether coating implants with bioactive hyroxyapatite (HA) increases screw stability. Twelve HA-coated ASIF screws with 3 different macroporosities were inserted in 12 sheep that had already been fitted with a 6-pin external fixator for the treatment of a tibial osteotomy. The same number of uncoated polished steel screws served as controls. Although initial stability was not different for HA-coated screws, average removal torque after a 9-week implantation period increased with increasing macroporosity of the HA coating (p 〈.002). Instability of some screws was accompanied by histologic findings of cartilagenous tissue and proliferation of periosteal callus. Near the threads in the tibial cortex and in the shaft area of the screw were seen large numbers of HA particles that had been sheared off during implantation as well as during screw removal because of high contract forces between the HA coating and bone. Particulate debris of HA particles as well as the release of small bone fragments during explantation is likely to be unavoidable since HA adherence to bone is greater than adherence to steel after several weeks of implantation. © 1995 John Wiley & Sons, Inc.
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  • 23
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    Journal of Applied Biomaterials 6 (1995), S. 125-128 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Porous polyurethane foams were prepared from Daro foam components with a range of mechanical properties to simulate human trabecular bone. Ratios of 10.0:5.0, 10.0:7.9, and 10.0:10.0 isocyanate to resin were mixed, cured, and cut into cubes. Properties were determined from uniaxial compression to 50% of the original cube height at a strain rate of 1.2 mm/s. Electron microscopy was used to characterize the foam structure. Average compressive yield stress values, ultimate compressive stresses, and elastic moduli ranged from 4.44 to 2.79, 5.61 to 3.28, and 134.0 to 110.1 MPa, respectively, for the three formulations. The foam materials showed a similar morphology of spherical bubbles, and the average bubble size tended to decrease as the ratio of isocyanate to resin increased even though the bubble size differences were not statistically significant. The results indicate that large blocks of foam can be prepared with consistent mechanical properties simulating a range of trabecular bone properties so that implants can be tested for various patient populations. © 1995 John Wiley & Sons, Inc.
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  • 24
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    Journal of Applied Biomaterials 6 (1995), S. 129-135 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Bioabsorbable films show promise in preventing postoperative interfacial tissue adhesion. Absorbable polymers in film form are generally more sensitive to chemical environments, due to their large surface area to volume ratio. The in vivo environment contains lipids such as cholesterol, triglycerides, and phospholipids, which are known to affect the degradation of permanent and absorbable polymeric biomateials. Preliminary investigations of in vitro lipid exposure of bioabsorbable poly(ortho ester) (POE) films for implant use are described. POE has been studied previously for use in controlled drug delivery and fracture fixation. Six-week in vitro exposure of 65:35 POE films to a cholesterol emulsion (1 g/L) showed no apparent difference in hydrolytic degradation rates of mechanical properties or mass loss compared to deionized water exposed films. Decreases of 28 and 6% in inherent viscosity were observed after 5 weeks for cholesterol and deionized water exposed films, respectively, suggesting cholesterol may have some effect. Further examination of the data, due to sample variation, revealed that clear, uniform films showed only minor changes in mass loss and mechanical properties after 6 weeks in either of the in vitro media. But slightly cloudy films possessing microscopic bubbles showed accelerated degradation in both media, indicating the effect of cholesterol was inconclusive due to sample variation. Control of the microbubble formation process could have utility in controlling hydrolytic degradation of POE films. © 1995 John Wiley & Sons, Inc.
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  • 25
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    Journal of Applied Biomaterials 6 (1995), S. 171-174 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Grit blasting is a common procedure of roughening surfaces to promote physical attachment of porous coatings, but it has been shown to reduce fatigue strength. Shot peening is known to increase fatigue strength by inducing compressive surface stresses; however, it is not known how subsequent grit blasting affects these benefits. This study examines the endurance limits, Se, of ELI grade Ti-6A1-4V specimens under rotating cyclic bending, including polished (control); belted and beaded; belted, beaded, and grit blasted; and belted, beaded, shot peened, and grit blasted. Belting and beading resulted in a slight increase in Se; grit blasting caused a 15% reduction in Se from polished. Fifty percent of this reduction was recovered when shot peening preceded grit blasting, suggesting that residual compressive surface stresses, induced by peening, were not eliminated by the blast process. Roughness averages and RMS values did not correlate with Se trends. SEM results showed classical fatigue fractures, consistent with surface crack initiation. © 1995 John Wiley & Sons, Inc.
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  • 26
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    Journal of Applied Biomaterials 6 (1995), S. 175-183 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Concentrated fibrinogen was prepared from whole blood by cryoprecipitation or chemical precipitation and combined with thrombin to make fibrin glue (FG). Surgical application of FG include control of bleeding, adhesion of tissues, and sealing of tissue defects. The purpose of this study was to compare cryoprecipitation (cryo) of fibrinogen to precipitation using ethanol, ammonium sulfate (AS), and poly(ethylene glycol) (PEG). Our results suggest that AS precipitation is as effective as cryo in yielding fibrin glues with high bond strengths and is more effective than ethanol and PEG precipitation. In addition, the volume of FG per milliliter of plasma is greater after AS precipitation than after a single freeze-thaw cycle. It is concluded that AS is an efficient means for preparing FG from autologous blood. © 1995 John Wiley & Sons, Inc.
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    Journal of Applied Biomaterials 6 (1995), S. 185-190 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Biological materials have been used as prosthetic devices such as heart valves, vascular grafts, and pericardial patches. These biological materials have to be fixed with crosslinking reagents and sterilized subsequently before they can be implanted in humans. Recently, a new crosslinking reagent, epoxy compound, has been used to fix bioprostheses. In this fixation technique, heparin may be ionically bound on the tissue surface. It has been shown that the amount of heparin bound to the tissue surface is proportional to the quantity of protamine impregnated in the biological tissues. However, it is not known if the impregnation of protamine will affect the crosslinking density of the biological tissues. This study was designed to compare the crosslinking densities of the epoxy compound fixed biological tissues with or without heparinization. Fresh porcine aortic valves procured from a slaughter house were first impregnated in various concentrations of protamine sulfate (0, 0.5, 1.0, or 1.5%) for about 30 min. The porcine aortic valves were then crosslinked in a 4% epoxy compound solution (Denacol® EX-313). The porcine samples were taken out at various elapsed fixation periods: 18, 25, 48, 72, 96, and 120 h. Finally, the crosslinked porcine aortic valves were heparinized in a 0.5% sodium heparin solution for about 1 h. The crosslinking densities of the porcine leaflet and the aortic wall of each sample were determined by measuring their shrinkage temperatures. It was revealed that the impregnation of various concentrations of protamine did not seem to significantly alter the shrinkage temperatures of the porcine leaflet and the aortic wall throughout the entire fixation process (p 〉 0.05). This indicated that the impregnation of protamine did not significantly change the crosslinking density of the biological tissues. However, it was found that protamine tended to discolor the tissue and to stiffen the porcine leaflet and the aortic wall. Although the impregnation of protamine did not seem to significantly alter the crosslinking density of the epoxy compound fixed biological tissues, the increase of the stiffness of the heparinized tissues may cause concerns in some clinical applications. © 1995 John Wiley & Sons, Inc.
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  • 28
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    Journal of Applied Biomaterials 6 (1995), S. 209-211 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Reducing the porosity of bone cement substantially strengthens the cement in fatigue. However, concern has been raised that reducing the porosity of the cement would increase the shrinkage of the cement and thus compromise the cement-bone interface. We measured diametral shrinkage of cement mantles prepared with and without centrifugation of the cement. Four cement preparations (centrifuged and uncentrifuged mixed with monomer at either room temperature or 0°C) were used to form cement mantles of four different thicknesses (2, 4, 6, and 8 mm) around a stainless steel rod. We conclude that porosity reduction dramatically increases the fatigue strength of bone cement without substantially changing the diametral dimensions of the polymerized cement when studied in the shape and volume of a cement mantle that would be used for total hip replacement. © 1995 John Wiley & Sons, Inc.
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  • 29
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    Journal of Applied Biomaterials 6 (1995), S. 225-230 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The distal migration of polyethylene wear debris appears to be a major cause of loosening and osteolysis of cementless total hip arthroplasties. The use of modern cementing techniques, circumferential porous or hydroxyapatite (HA) coating has been advocated as a means of preventing access of the particles to the bone-implant interface. The purpose of this study was to compare the ability of different methods of implant fixation to prevent wear debris migration. Three each of smooth, porous-coated, HA-coated, and cemented hemiarthroplasties were implanted in the right hip of 12 dogs. Polyethylene particles were injected into the hip once a month for 4 months and then the femurs were sectioned. The percentage bone ingrowth was 8% for the smooth, 38% for the porous, and 83% for the HA-coated sections. Infiltration of the interface membrane by histiocytes containing polyethylene particles, and endosteal scalloping or osteolysis were found on all sections of the smooth prostheses. No particles or osteolysis were found on any sections of the other three types of prostheses. Capsular and lymph node sections from all dogs revealed histiocytic infiltration with numerous polyethylene particles present. It is concluded that the use of cement, porous, or HA coating prevents or delays access of the polyethylene wear debris to the bone-implant interface. No one of these methods of fixation proved more advantageous in the 5-month limit of this study. © 1995 John Wiley & Sons, Inc.
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  • 30
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Medicine , Technology
    Notes: Thrombosis remains a significant and potentially catastrophic complication of polyethylene terephthalate (Dacron) prosthetic vascular graft implantation. Numerous attempts have been made to create a novel surface that reduces the adverse effects of blood interaction with the material. The purpose of this study was to create reactive groups on Dacron without significantly altering the chemical and physical properties of the biomaterial. These groups would then serve as “anchor sites” for covalent attachment of the blood protein albumin to the surface, thus creating a more biocompatible surface. Denier reduction, an established textile chemistry procedure that creates carboxyl groups on the fiber surface via hydrolysis of the material, was performed at 100°C using sodium hydroxide concentrations of 0.5, 1.0, 2.5, and 5.0% (treated materials referred to as 0.5% hydrolyzed etc.). Tensile strength determination of hydrolyzed materials revealed no statistically significant difference in material strength between control, 0.5, and 1.0% hydrolyzed materials; the 2.5 and 5.0% hydrolyzed materials had significant strength loss as compared to the controls. Significant fiber weight loss occurred in the 1.0, 2.5, and 5.0% hydrolyzed Dacron segments. The 0.5% hydrolyzed material did not have any significant weight loss. Covalent linkage of 125I-albumin to these modified materials using the crosslinker 1-ethyl-3-(3-dimethyl aminopropyl)-carbodiimide hydrochloride (EDC) resulted in the 0.5% hydrolyzed material having the greatest protein binding (330 ng/mg Dacron, 2.4-fold greater than control). Incubation of the 0.5% hydrolyzed material with EDC and various concentrations of 125I-albumin resulted in the 14.80 m̈M solution permitting the greatest binding per milligram Dacron (330 ng/mg Dacron). Scanning electron microscopy, performed blindly, revealed no change in the 0.5% hydrolyzed Dacron as compared to untreated Dacron. The 5.0% hydrolyzed Dacron, however, had noticeable structural damage on the outer periphery of the fiber surface. Observation of the untreated Dacron with nonspecifically bound albumin showed scattered areas of albumin adherent to the fiber surface whereas covalent linkage of albumin to the 0.5% hydrolyzed Dacron via EDC crosslinking showed numerous albumin moieties on each fiber. This study demonstrates that a clinically accepted biomaterial (Dacron) can be chemically modified, without significantly altering the physical and chemical characteristics of the biomaterial, in order to covalently bind albumin to the fiber surface. Thus, these results serve as foundation for creating potential novel biomaterials without significantly altering the properties of the original biomaterial. © 1995 John Wiley & Sons, Inc.
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  • 31
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    Journal of Applied Biomaterials 6 (1995), S. 19-26 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The use of multiple-component systems in orthopedic surgery gives the surgeon increased flexibility in choosing the optimal implant, but introduces the possibility of interfacial corrosion. Such corrosion could limit the longevity of prostheses due either to tissue reactions to corrosion products, or to device failure. The incidence and nature of corrosion of modular total hips was evaluated in a consecutive series of 79 retrieved implants from University Hospitals of Cleveland. Surfaces were examined with stereo- and scanning electron microscopy. Several laboratory studies were undertaken to examine mechanisms that might contribute to the initiation of corrosion. The first set of experiments investigated the effect of head neck extension; the second study looked at the effect of material combinations on fretting corrosion and crevice corrosion. Analysis of retrieved implants demonstrated that fretting corrosion played a major role in the initiation of interface corrosion, and that a correlation existed between corrosion and length of neck extensions. Laboratory studies showed that longer head neck extensions may be more susceptible to fretting corrosion because of an instability at the interface. Short-term mixedmetal corrosion studies demonstrated that the coupling of cobalt and titanium alloys did not render the interface more susceptible to corrosion. It is hypothesized that fretting corrosion contributes to the initiation of modular interface corrosion, and that the problem can be reduced by design changes that increase the stability of the interface. © 1995 John Wiley & Sons, Inc.
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  • 32
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    Journal of Applied Biomaterials 6 (1995), S. 35-41 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: In ligament replacement cases where the artificial ligament has worn and partially or totally ruptured, the released wear particles have been associated with a chronic synovitis that inhibits integration of the ligament and contributes to the ultimate failure of the device. In this study, the biological response to ligament wear particles from nine different artificial ligaments was quantitatively evaluated in vivo. Wear particles, the majority of which were 〈7 μm, were generated in vitro. These particles were injected into rabbit knee joints, and the biological response as well as the systemic migration of the particles were evaluated histologically after 4 weeks. The extent of the inflammatory reaction to the ligament wear particles was found to be significantly (p 〈 0.05) influenced by the type of material implanted. No particles were found in the regional lymph nodes or in the spleen, liver, kidney, or lung. © 1995 John Wiley & Sons, Inc.
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  • 33
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    Journal of Applied Biomaterials 6 (1995), S. 43-53 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Two experimental methods for restoring flexor tendon sheath integrity and preventing adhesions around traumatized flexor tendons utilizing artificial tendon sheaths made of either hydroxyapatite (HAp) or alumina were studied in a flexor tendon-trauma model and compared to a standard tendon sheath repair and a control. Eighty toes were divided equally into a control group, a sheath repair group, an HAp group, and an alumina group. Profundus tendons in zone II were divided and repaired after sublimis excision in all groups. In the sheath repair group, the flexor sheath was also repaired after suturing the tendon. In artificial sheath groups, sheaths made of HAp and alumina were placed over the repair sites to protect them from the surrounding tissues. In the control group, after repairing the tendon, the flexor sheath was excised and no artificial sheaths were used. Each toe was immobilized in a plaster cast for 3 weeks. After three weeks, the plaster cast was removed followed by the removal of the sheaths in the artificial sheath groups through a small incision in the skin in zone II. Active mobilization was encouraged in each group. Postoperative adhesions were examined at 3, 6, 9, and 12 week intervals by using light microscopic techniques. To further explore the effects of artificial sheaths on tendon healing, transmission electron microscopy was done for the HAp and alumina groups at 3, 6, and 12 week intervals. Results demonstrated decreased severity of postoperative adhesions in the HAp as well as in the alumina groups in comparison with the sheath repair and controls. A space resembling the fibro-osseous canal was formed around the tendon after removing the sheaths. This space remained patent until 12 weeks, 9 weeks after removing the sheaths, and a newly formed tendon sheath-like structure lined by synovial cells and with a peritenon-like structure over the tendon surface was observed. In the sheath repair and control groups, the severity of adhesions was decreased with the passage of time, to some extent due to unrestricted mobility. However, a newly formed tendon sheath or peritenon-like structure was not observed. Electron microscopic studies confirmed good healing at the suture in the HAp and alumina groups with no evidence of necrosis. These results are qualitative in nature as no statistical tests were performed. From these results we conclude that if the tendon is separated from the surrounding granulation tissue by a barrier with good biocompatibility, the tendon can heal with fewer adhesions. Artificial sheaths may be used to reduce adhesions in severe injuries of the hand where postoperative immobilization is necessary due to fractures, vascular, or nerve injuries. © 1995 John Wiley & Sons, Inc.
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  • 34
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    Journal of Applied Biomaterials 6 (1995), S. 65-68 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A natural poly(hydroxybutyrate-co-9% hydroxyvalerate) copolyester was processed into a three-dimensional porous foam structure by salt leaching/solvent casting with previously sieved sodium chloride salts. Laboratory-built P(HB-9% HV) foams and commercial collagen sponges were cut into small rectangular specimens, sterilized, and prewetted using ethanol, rinsed with Dulbecco's minimum essential medium + 10% serum culture media, and seeded with fibroblasts isolated from canine anterior cruciate ligaments. The fibroblast cultures into such porous substrates were performed from 0 to 35 days by incubation (5% CO2) at 37°C. It demonstrated that the P(HB-HV) sustained a cell proliferation rate similar to that observed in collagen sponges, up to at least 35 days, with a maximal cell density on the day 28 in culture. On the other hand, the P(HB-HV) materials kept their structural integrity during the culture period while the collagen foams contracted greatly. Further, the total protein production after 4 weeks in culture was found to be twice as high (190 ± 10%) in the P(HB-9% HV) foam than in the collagen foam. Porous P(HB-HV) materials appear to be adequate polymeric substrates for cell cultures. However, further evaluations are still required to confirm such preliminary results. © 1995 John Wiley & Sons, Inc.
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  • 35
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    Journal of Applied Biomaterials 6 (1995), S. 69-74 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Neodymium-iron-boron magnets are being increasingly used in orthodontic and orthopedic appliances. The purpose of this study was to investigate the in vitro cytotoxicity of these new “super” magnets. A modified agar overlay technique was performed using both L929 mouse fibroblasts and adult human oral mucosal fibroblasts. The neodyium-iron-boron magnets were tested in the following forms: uncoated magnetized, uncoated demagnetized, parylene coated demagnetized, and parylene coated magnetized. Results revealed that uncoated magnetized, uncoated demagnetized, and parylene coated magnetized were cytotoxic to both L929 mouse fibroblasts and human oral mucosal fibroblasts. However the parylene coated demagnetized neodymium magnets were only cytotoxic to the human mucosal fibroblasts. This study supports the hypothesis that these are cytotoxic effects of possibly corrosion products and of magnetism. The specific toxic effects of parylene were not examined in this present study. Statistical analysis (Mann-Whitney U-test, p = 0.014) suggested that, in this experiment, the human oral mucosal fibroblasts were more sensitive to the effects of these rare earth magnets. With the evidence of a biological effect, the use of implanted magnets must at present be limited until the safety can be assured. © 1995 John Wiley & Sons, Inc.
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    Journal of Applied Biomaterials 6 (1995) 
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    Keywords: Chemistry ; Polymer and Materials Science
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  • 37
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    Journal of Applied Biomaterials 6 (1995), S. 75-83 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A new bone cement was developed with the purpose of reducing the adverse biological effects during cementation of implants. This bone cement is characterized by lower exotherm, low release of monomer, low residual content of monomer, and retained physical properties. The essential innovation was substitution of half of the methylmethacrylate (MMA) in the monomer with long chain, high molecular weight, less volatile, and less soluble methacrylates (n-decylmethacrylate, isobornyl-methacrylate), as well as alteration of the accelerator system to a mix of dihydroxypropyl-p-toluidine and N,N-dimethyl-p-toluidine. The powder contains butyl-methacrylate-MMA copolymers. These measures lower the glass-transition temperature, and permit more complete mixing in an integrated package, mixing, and delivery system consisting of a vacuum packed, double chamber pouch. The porosity was reduced to about 2% and the largest voids measured 0.1 mm. The polymerization exotherm was reduced to 58 °C. The compressive strength was 82 MPa, the four-point bending strength 55 MPa, the flexural modulus 2.24 GPa, the tensile strength 32 MPa, and the shear strength 36 MPa. The fracture toughness was 0.89 MPa √cm. These mechanical properties together with the fatigue life were on level with manually mixed, conventional PMMA bone cements. © 1995 John Wiley & Sons, Inc.
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  • 38
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    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Medicine , Technology
    Notes: A Synthetic composite bone graft material, composed of fibrillar collagen, hydroxyapatite, and tricalcium phosphate, was evaluated in canine femoral shaft defects and compared to ungrafted defects and defects grafted with autogenous bone. The results of mechanical testing of the grafted femora in torsion at 1 year postoperatively were previously reported. This report details the histological and microscopic features of the graft sites. The results of this study suggest that the healing of the graft site is not yet complete at 1 year and that healing may be more complete in defects that received the synthetic graft as compared to ungrafted sites and autogenous bone graft. The bone tissue appears to respond to the graft particles as if they were bone particles. © 1995 John Wiley & Sons, Inc.
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  • 39
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    Journal of Applied Biomaterials 6 (1995), S. 109-116 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The effects of metal ions released from orthopedic implants on nearby bone cells remain largely unknown. The purpose of this study was to examine the acute toxicity of metal ions on osteogenic cells derived from bone marrow. Bone marrow stromalcells were cultured with metal ions found in commonly used orthopedic implants, that is, Ti-6Al-4V, Co-Cr-Mo, and 316L stainless steel. Solutions of individual ions and combinations representing the alloy composition were prepared from atomic absorption standards and added to the cultures to give concentrations ranging from 50 ppb to 5o ppm. After a 48-h period of exposure to ions, the bone marrow cultures were examined for effects of cytotoxicity by measuring total cell number, total cell protein, and mitochondrial activity. Cr6+ was grossly cytotoxic; Co2+, Mo6+, Fe3+, and Ni2+ were moderately cytotoxic; and Ti4+, Al3+, V5+, and Mn2+ were minimally toxic, as determined by the assays used. Ion solutions representing Co-Cr-Mo and 316L stainless steel were moderately toxic; solutions representing Ti-6Al-4V were toxic at only the highest concentrations used. The observed cytotoxicity was time-dependent, with irreversible toxic effects being initiated following as short as a 3- to 6-hour exposure. These results show that metal ions associated with Co-Cr-Mo and 316L stainless steel are toxic to osteogenic cells at concentrations approximating those measured in the fibrous membrane encapsulating orthopedic implants. © 1995 John Wiley & Sons, Inc.
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  • 40
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    Journal of Applied Biomaterials 6 (1995), S. 117-123 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The main function of the intervertebral disc is to transmit and attenuate compressive and torsional forces, and stabilize the intervertebral joint. Unfortunately, the disc may be displaced or damaged due to trauma or disease causing the nucleus to herniate and protrude into the vertebral canal or intervertebral foramen. Pressure on the spinal nerve may cause pain or paralysis in the area of its distribution. At present, the surgical procedures used to alleviate this condition include disc excision, and/or spinal fusion. A more desirable situation would involve removing the nucleus pulposus and part or all of the annulus fibrosis and implanting a suitable biofunctional equivalent. Such a prostheis should attenuate stresses and prevent abnormal stress at adjacent intervertebral joints. Maintenance of normal disc height would prevent impingement of the posterior facet joints and facet joint syndrome. In a previous companion paper (J. Applied Biomat. 5:125-132; 1994), the mechanical behavior of disc prostheses manufactured from fiber reinforced, elastomeric thermoset resins were examined. In order to develop devices which were more practical from a manufacturing standpoint and extremely reproducible, the fiber reinforced thermoset resins were replaced by multi-durometer thermoplastic elastomeric materials. In the present paper, the mechanical properties of thermoplastic multicomponent desings have been investigated. © 1995 John Wiley & Sons, Inc.
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  • 41
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    Journal of Applied Biomaterials 6 (1995), S. 137-144 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The research field of biomaterials and surgical implants has matured to a point suggesting that a formal and comprehensive education is now required to handle all professional issues related to biomaterials and implant development. A professional curriculum is proposed for a discipline of biomaterials science and engineering on a graduate level. The curriculum includes the definition of an essential knowledge base and describes two track options for a study period of 3 years. Lists of prerequisites as well as required and suggested courses are presented and discussed. Continuing education courses are presented as examples. A quick vision of the immediate future of the field enforces the need for biomaterials professionals to take the lead in bringing the field into the next century. © 1995 John Wiley & Sons, Inc.
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    Journal of Applied Biomaterials 6 (1995) 
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    Keywords: Chemistry ; Polymer and Materials Science
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  • 43
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    Journal of Applied Biomaterials 6 (1995), S. 167-169 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A novel drug delivery system for osteomyelitis was developed using porous hydroxyaptite blocks (HA-b) loaded with antibodies by centrifugation. In the study, 10 mm3 HA-b was placed in a container and mixed with antibiotic solution; the antibiotic was then loaded into the pores of the HA-b by centrifuging at 1500 rpm for 15 min. Slow release of HA-b in both moist form and dried form (by heating at 160°C) was tested after loading with the antibiotic arbekacin sulfate (ABK), 1-N-(S)-4 amino-2-hydroxybutyryl dibekacin. To estimate the concentration of antibiotic, both forms of HA-b were placed in 3 mL of phosphate buffered saline (PBS), which was replaced every 48 h. In both groups, which were loaded with 70 mg ABK per one block of HA (concn 0.5 μg/mL) which is sufficiently high to control most pathogens, was maintained for 21 exchanges of PBS (after 42 days). Minimum inhibitory concentration for methicillin-resistant Staphylococcus aureus (MRSA), 3.13 μg/mL, was maintained until nine exchanges took place (after 18 days). The centrifugation method is wsimple, and driked ABK produced by heating loaded HA-b is particularly useful in clinical applications for osteomyelitis. © 1995 John Wiley & Sons, Inc.
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  • 44
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    Journal of Applied Biomaterials 6 (1995), S. 191-197 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: In this study, reinforced poly(L-lactic acid) (PLLA) fibers made by a dry-spinning/hot-drawing process were evaluated for use as a suture. The initial tensile strength of the PLLA fibers was lower than the initial tensile strength of the commercially available sutures: PDS, VicrylTM, silk, and Ethilon™. However, after 12 weeks immersion in a phosphate saline buffer at 37°C, PDS sutures have lower tensile strength than PLLA sutures and the tensile strength of Vicryl™ was unmeasurable because of fragmentation. Initially, PLLA fibers distinegrated into fibrils during degradation triggering an inflammatory response comparable to degradable multifilament sutures. However, the intensity of the inflammatory response against the PLLA fibers decreased and after 80 weeks implantation in the muscle layer of the abdominal wall of rats it was comparable to the one against Ethilon™. The inflammatory response against Ethilon™, which is considered to be nondegradable, increased in the same period, probably due to the change in shape. In practice, the handling characteristics of PLLA sutures are superior to the monofilament sutures like PDS and EthilonTM and comparable with the multifilament sutures like VicrylTM and silk. The knot security, but this remains to be investigated. It is concluded that dry-spun/hot-drawn (reinforced) PLLA fibers have the potential for use as long-term degradable suture material. © 1995 John Wiley & Sons, Inc.
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    Journal of Applied Biomaterials 6 (1995), S. 203-208 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Journal of Applied Biomaterials 6 (1995), S. 223-223 
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    Keywords: Chemistry ; Polymer and Materials Science
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  • 47
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    Journal of Applied Biomaterials 6 (1995), S. 213-218 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The occlusion and stability of five synthetic plugs used to restrict the femoral canal prior to cemented arthroplasty was assessed. A model was employed consisting of a hollow wooden dowel to simulate the canal, with adapters fixed to both ends to accommodate cement insertion and pressurization, and to produce a closed distal cavity. Three different canal diameters within the range accommodated by the plug selected were employed to assess insertion force, distal pressure during both insertion and pressurization of acrylic cement, and plug migration and leakage for each device. There was a wide variation among plugs in the magnitudes of the force and distal pressure upon plug insertion. During cement pressurization, cement leakage and/or plug migration was noted in all trials, and either of these events resulted in pressure rises in the distal cavity. Most notably, differences of only 0.5 mm in the diameter of the canal resulted in marked changes in the occlusion and stability achieved. It is concluded that for the range of canal sizes anticipated intraoperatively, these synthetic plugs appear deficient to varying extents in their ability to occlude or remain stable in the intramedullary canal. © 1995 John Wiley & Sons, Inc.
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  • 48
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
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    Notes: The purpose of this study was to compare hydroxyapatite (HA)-coated titanium (Ti) and HA-coated cobalt-chrome (CoCr) implants in the distal femur of the rabbit by evaluating bone apposition and interfacial shear strength. Bilateral cylindrical implants with a plasma sprayed 50-m̈m thick HA coating were press-fit into the metaphyseal cancellous bone of the lateral femoral condyles in a transverse fashion, and the animals were sacrificed at 2, 4, and 8 weeks postimplantation. Mechanical strength of the interface between HA and bone was measured using the pushout method. For histologic analysis, the fractional linear extent of bone apposition was quantitated. No differences were found in the interfacial shear strength between the Ti and CoCr at any time period. The amount of bone apposition increased significantly at each time interval for both substrate metals, but there were no significant differences between the two substrates at any of the time periods studied. The HA-coated CoCr implants performed in a similar manner to the HA-coated Ti implants, both mechanically and histologically, suggesting that HA-coated CoCr implants deserve further study as a viable alternative to Ti for the biological fixation of total joint components in orthopaedic surgery. © 1995 John Wiley & Sons, Inc.
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  • 49
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    Journal of Applied Biomaterials 6 (1995), S. 243-248 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Historically, pyrolytic carbon has been a material for cardiovascular applications, but it has several properties suited for orthopedic uses as well. Pyrolytic carbon has an elastic modulus similar to bone and is highly fatigue resistant, but has not been used in orthopedics because of poor fixation to bone. Plasma sprayed hydroxylapatite (HA) has significantly improved the bonding of bone to titanium alloy implants. The effect of plasma-sprayed HA on pyrolytic carbon implants was investigated in this study. Cylindrical samples were implanted through a single cortex in Beagle femurs. The animals were sacrificed after 8 weeks, and a mechanical push-out test was performed on the implants immediately after explantation. Samples were microradiographed, stained for histology, and examined histomorphometrically. Interface strength for each type of implant was calculated. Pyrolytic carbon showed almost no attachment strength with an average strength value of 1.59 MPa. HA-coated pyrolytic carbon (8.71 MPa) yielded the same interfacial strength as HA-coated titanium (8.71 MPa). Histology revealed that bone was in direct apposition to all implants, both HA coated and noncoated. Failures occurred between the core material and the coating, or within the coating, but not at the bone/HA interface. Histomorphometry results confirmed that the two types of HA-coated implants had more bone apposition than the uncoated pyrolytic carbon implants. It was concluded that a plasma sprayed HA coating significantly improves the bone fixation of pyrolytic carbon. © 1995 John Wiley & Sons, Inc.
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  • 50
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    Keywords: Chemistry ; Polymer and Materials Science
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    Notes: Heparin oligosaccharides with different anticoagulant activities were prepared and immobilized onto pyrolytic carbon coated graphite (PC) heart valve materials commonly used in mechanical heart valve prostheses. Prior to immobilization, PC surfaces were modified by radio-frequency plasma polymerized N-vinyl-2-pyrrolidone (PPNVP) thin films (∼ 100 nm) and derivatized to provide surface hydroxyl groups. Cleaved, low affinity heparin (C-heparin) with factor Xa inhibition activity of 107 to 130 IU/mg, was prepared by partial deaminative cleavage of commercial crude heparin, and high-affinity heparin (HA-heparin) with factor Xa inhibition activity of 550 to 1000 IU/mg was prepared by fractionation of C-heparin using agarose-ATIII affinity chromatography. C-heparin and HA-heparin were immobilized to surface modified PC by reductive amination. Anticoagulant activity of the heparin immobilized surfaces was determined by chromogenic assay for the inhibition of factor Xa. Highest surface anticoagulant activity was measured on C-heparin immobilized surfaces (64.0 ± 7.3 mIU/cm2) compared with HA-heparin immobilized surfaces (27.2 ± 12.2 mIU/cm2), suggesting higher binding of C-heparin than HA-heparin on the modified PC surfaces. Immobilized surfaces were evaluated under dynamic flow conditions, by subjecting samples to shear stress of up to 206 dyn/cm2 in the presence of 5% albumin solution or human plasma. Anticoagulant activity of the immobilized heparin was retained, although reduced, and the modified surfaces showed evidence for protein resistance. © 1995 John Wiley & Sons, Inc.
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    Journal of Applied Biomaterials 6 (1995), S. 283-288 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The effect of sodium fluoride on the polarization resistance of titanium was investigated. Titanium plates were exposed to sodium chloride solutions with increasing fluoride concentrations. This was done at pH 7 and 4 at 37°C. The polarization resistance technique was chosen because it is the only electrochemical corrosion test procedure that allows sequential measurements of the same specimen and provides a quantitative basis to estimate corrosion currents unlike measurements of the potential. The results showed a large decrease in polarization resistance with increasing fluoride concentration at pH 4. The polarization resistance at pH 7 remained constant after a slight decrease at a very high value, even with a high fluoride concentration. The results clearly confirm that titanium is attacked by fluoride in an acidic environment. The clinical implications are that fluoride rinses or fluoride gels must have a neutral pH if there is a titanium containing device in the oral environment despite the less prophylactic effectiveness. © 1995 John Wiley & Sons, Inc.
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    Journal of Applied Biomaterials 6 (1995), S. 303-304 
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    Keywords: Chemistry ; Polymer and Materials Science
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  • 53
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    Journal of Applied Biomaterials 6 (1995), S. 1-7 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Surgical implants need to be free from contaminants before implantation. The effectiveness of a presently used Clemson bioengineering cleaning (CBC) protocol was evaluated for cleaning three different biomaterials (titanium, aluminum oxide, and polyethylene terephthalate, PET) contaminated with three different contaminants (calcium chloride, zinc chloride, and hexadecane). Radiolabeled tracer analysis (RTA), with the use of liquid scintillation, was used as the surface analytical technique to quantitatively determine the removed from the biomaterial surface. On average, the ultrasonic cleaning step removed 99.96% of all three contaminants from both titanium and aluminum oxide. The CBC protocol did not sufficiently clean PET fabric contaminated with hexadecane leaving 11.76% of the contaminant after the ultrasonic step. With the use of isopropyl alcohol in series with 1% Liquinox, the ultrasonic step cleaned the fabric soiled with hexadecane within 30 min, removing 99.85% of the hexadecane initially on the surface. RTA proved to be an excellent method of quantifying surface contamination on implant materials, and for assessing the effectiveness of cleaning protocols in question. © 1995 John Wiley & Sons, Inc.
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    Journal of Applied Biomaterials 6 (1995) 
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    Keywords: Chemistry ; Polymer and Materials Science
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  • 58
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    Notes: In research animals, the immune adjuvant activity of silicone in eliciting antibodies to associated protein antigens is now well established. In humans, the immune adjuvant activity of silicone remains controversial. Clusters of data from various research groups are beginning to define the boundary conditions for future large epidemiological studies. In that spirit, this manuscript reports pilot clinical data from a serological study conducted 3 years ago and reported previously in this journal. Sera from a self-selected symptomatic population of patients with breast implants were assayed for elevated concentrations of antibodies showing binding avidity to silicone surface associated antigens [anti-SSAA(x)]. In that study of 249 patients, two distinct statistically significant subgroups were identified on the basis of the serological assay alone: patients without any elevated anti-SSAA(x) (negative) and patients with elevated anti-SSAA(x) (positive) (p 〈 0.001). In this study, a clinical survey returned by 226 of those patients was correlated with the previously acquired serological findings. The 11 most common clinical complaints reported by the 199 anti-SSAA(x) negative patients and by the 27 anti-SSAA(x) positive were compared and their frequencies analyzed. The 199 anti-SSAA(x) negative patients, as a group, showed a lower frequency of a variety of signs and symptoms compared to the 27 anti-SSAA(x) positive patients. Statistically significant differences were seen in three of the symptoms: fever, foot pain, and sleep disturbance (p 〈 0.05). In addition, the syndrome of fever in the absence of local chest pain was a significantly associated with anti-SSAA(x) positivity (p 〈 0.001). © 1995 John Wiley & Sons, Inc.
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    Journal of Applied Biomaterials 6 (1995), S. 161-165 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: We performed a histomorphological and morphometric analysis of the effects of short daily periods of micromotion and phagocytosable particles of high density polyethylene (PE) on bone ingrowth into a 1 × 1 × 5 mm canal within a titanium chamber in rabbits. The micromotion chamber (MC) was implanted in the tibia of nine mature New Zealand white rabbits. After osseointegration and first harvest of tissue, 40 micromotions (amplitude = 0.5 mm) were applied daily at a rate of 1 Hz for a 3-week period. The tissue within the chamber was then harvested. For the second treatment, PE particles (108/mL) were placed within the canal. The tissue in the chamber was harvested 3 weeks later. The next treatment was a 3-week rest period, in which neither micromotion nor particles were utilized; a harvest followed. The final treatment combined PE particles and micromotion, followed by a harvest 3 weeks later. Sections from control harvests contained extensive trabecular bone arranged longitudinally throughout the canal in a fibrovascular stroma. Micromotion produced longitudinally oriented fibrous tissue within the chamber. PE particles were associated with macrophages, surrounding and engulfing the birefringent particles. The combination of particles and micromotion produced a fibrous stroma laden with macrophages. PE particles and micromotion, alone or together, produced a similar effect in inhibiting bone ingrowth, compared to nonmoved chambers without particles. In this short-term experiment, no additive or potentiating effect of these two stimuli could be demonstrated. © 1995 John Wiley & Sons, Inc.
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    Journal of Applied Biomaterials 6 (1995), S. 199-202 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The biological effects of the corrosion products of neodymium iron boron (Nd2Fe14B) magnets are largely unknown. The aim of this study was to identify the types of corrosion product and to evaluate the effect of the corrosion products (CP) of Nd2Fe14B magnets on the proliferation of human oral mucosal fibroblasts. Uncoated Nd2Fe14B magnets were stored in saline at 37°C for 6 months and the corrosion products collected. 100 μL of a cell suspension (human oral mucosal fibroblasts [4 × 104 cell/mL]) was aliquoted into 72 wells of a 96-well plate, the remaining plates receiving culture medium only. After 12 h incubation at 37°C, each well then received 100 μL of either (A) culture medium, (B) 100% CP, (C) 50%, or (D) 0% CP. The plates were reincubated at 37°C for a further 48, 96 or 144 h. Fibroblast proliferation was assessed using the methylene blue uptake/elution technique. The compounds in the corrosion product were examined using quantitative X-ray analysis. Statistical analysis (ANOVA, Bonferroni's test 0.05, SAS v 6.04), showed that at each time point, the cell numbers in groups B, C. and D were significantly lower than group A. Within groups B, C, and D no significant differences were found, despite the suggestion of a dose response effect. Fibroblast proliferation in the presence of corrosion products was significantly lower than with culture medium. Fibroblast proliferation did occur in the presence of 0, 50, and 100% CP. The actual corrosion products appeared to be salts of iron but 3.2% (±0.6) of neodymium chloride (NDCl3) was found. © 1995 John Wiley & Sons, Inc.
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    Journal of Applied Biomaterials 6 (1995), S. 219-221 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Journal of Applied Biomaterials 6 (1995) 
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    Journal of Biomedical Materials Research 5 (1971), S. 135-148 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Hollow fibers have been produced and evaluated for use as membrane oxygenators in an artificial heart device. Gas permeable capillaries now commercially available are unsuitable for this use because of: (1) low percent open cross-sectional area, (2) large internal diameter, and (3) high cost. A number of polymers were initially selected for evaluation because of their reported high gas permeabilities. Those selected include a number of rubbers of various compositions, certain poly-α-olefins and an experimental thermoplastic silicone rubber copolymer. These materials were first evaluated as flat membranes (films) for their gas permeabilities and also for ease of preparation in hollow fiber form. Hollow fibers were prepared from the most promising of those studied, poly-4-methylpentene-1 and the thermoplastic polydimethylsiloxane copolymer. Fibers, ranging in the size from 30 to 300 μ ID, were spun with open cross-sectional areas of 40-65%. Oxygen and carbon dioxide permeabilities measured on these fibers were compared to that of SilasticDow Corning medical grade poly (dimethylsiloxane). rubber membranes. These permeabilities range from 1/20 that of Silastic rubber for unmodified poly-4-methylpentene-1 to 2/3 for the thermoplastic silicone copolymer. Modification of poly-4-methylpentene-1 has made it possible to increase it's permeability by tenfold, while still maintaining physical properties necessary to spin and fabricate this material.
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    Journal of Biomedical Materials Research 5 (1971), S. 41-47 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Advanced forms of elemental carbon were identified as potential implantable prosthetic materials and a study was conducted to determine specific applications. A survey of the carbon industry established material sources and specifications on available types of material. Specimen materials were supplied to several research organizations for in-vivo evaluation and produced acceptable results. Specific designs have been generated for a broad range of implantable prosthetics and prototypes have been provided for preliminary evaluation. The feasibilty of an organic mechanical attachment between cortical bone tissues and elemental carbon has been successfully demonstrated.
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    Journal of Biomedical Materials Research 5 (1971), S. 69-89 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The success of material implants in the vascular system has been limited by the fact that the intial events of blood coagulation on foreign material surfaces are not understood. Many materials have been evaluated in the search for a suitable implant material in this system. Recent success of porous ceramic materials in bone-ceramic compatibility studies stimulated the feeling that these materials should be tested in other body tissues such as the blood.Ceramic disks of Al2O3 and TiO2 were evaluated using a contact angle measurement technique to determine the characteristics of these material surfaces before and after exposure to a blood environment. This technique involved measuring the contact angle of sessile drops of various liquids on these surfaces with a microscope fitted with a goniometer eyepiece. By plotting these contact angles according to the procedure of Zisman, the characteristics of the surfaces could be evaluated.The clean ceramic disks were found to be extremely wettable even after exposure to a physiological saline environment. On exposure of these disks to a blood environment, it was observed that some type of film was adsorbed from the blood onto the ceramic surface during the initial minutes of exposure. This film had wetting characteristics consistent with layers of fibrinogen.
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    Journal of Biomedical Materials Research 5 (1971), S. 143-159 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The skeletal attachment of a limb prosthesis approaches two specific and separate problems in tissue reaction to prosthetic materials: Skeletal fixation and trancutaneous interface.The skeletal fixation problem must be looked upon as a method to distribute the stress concentration of prosthetic material in such a manner so that living tissue is not embarrassed by prolonged excessive pressures. One must consider the functional mechanical stresses separate from the toxicological reaction of living tissues to prosthetic materials. Our current experience identifies the fact that vitreous carbon is extremely benign from the standpoint of living tissue reaction. Moreover, when placed in the configuration of irregular surfaces, it apparently encourages bone growth contiguous with the material. To this point, however, the reaction of living material to broad surfaces contiguous with vitreous carbon has not placed under concentration of functional stresses. Porous ceramic to this date has not supplied an appropriate answer to this problem.Transcutaneous perforation is available in the clinical sense only when a method can be presented which requires no specific hygiene and dressing. No drainage at all must be the rule at a transcutaneous perforation. Vitreous carbon in our experience so far has made contiguous epithealization feasible down the neck of a skin perforation. Four millimeters, from our experience, seems to be an appropriate location of epithelial downgrowth before transition into non epithealized connective tissue is available. The use of fixation skirts is felt to be necessary to provide stable, transcutaneous perforation.This paper presents evidence of the favorable tissue reaction both from a skeletal and cutaneous standpoint to vitreous carbon materials. A specific design for the successful skeletal fixation limb prosthesis is as yet not currently available and must await further clinical experience with human skin reaction to transcutaneous devices.
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    Journal of Biomedical Materials Research 5 (1971), S. 231-249 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A study has been made of the ceramic-epoxy composite “Cerosium.” Experiments were conducted to evaluate the tissue reaction to such material and the extent of bonding established between ceramic and the tissues in which it was implanted. It was found that this material was well tolerated by the body and obtained definite fixation within the tissues when implanted into both bone and tendon. This occurred, however, not by the active infiltration of tissue but by fibrous encapsulation and it is recommended that for more meaningful stabilization, material of larger pore size is required.When Cerosium was implanted into the knee joints of rabbits, it was found to be unsuitable for intra-articular use because of the abrasive effect on the opposing cartilage and bone surfaces and the susceptibility of the material itself to abrasive wear. Furthermore, a full mechanical evaluation of standard specimens of Cerosium showed it to be degraded within the body due to a breakdown of the impregnating polymer.Ceramic-epoxy composites require a strong matrix and a totally stable impregnating material. While mechanically suited to replacing weight bearing surfaces, a smooth surface glaze is essential to avoid abrasive effects upon the opposing bone surface. Further investigation is required before these materials can be fully accepted into the armamentarium of the implant surgeon.
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    Journal of Biomedical Materials Research 6 (1972), S. 281-296 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: For many years man has engendered the idea of replacing lost or unserviceable teeth with natural or artificial substitutes has, however, only recently been shown to offer a viable alternative to externally attached prostheses. Ceramics were selected which have demonstrated compatibility with long bones and optimization of the ceramic properties was undertaken. Implants were made in the jawbones of adult dogs. Both tooth root replicas and crown-root combinations were employed. Anchorage of the implants was found to range from stable attachment to rapid exfoliation. The calcium aluminates were found to possess barely adequate mechanical strengths.This research suggests that these ceramics can function as effective tooth roots if the proper designs and surgical techniques are employed. Sufficient evidence of tissue compatibility has been amassed to warrant further study.
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    Journal of Biomedical Materials Research 6 (1972), S. 333-343 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: Metals and polymers have received considerable attention with respect to their potential use in human implantation. Serious study of the ceramics for this purpose has only recently begun. Materials for implantation in any body site must meet certain requirements. Each class of material has been found to have some highly desirable properties as well as some undesirable characteristics. Materials for use in dental implantation, particularly for the replacement of individual teeth, are subjected to environmental factors not generally existent in other implantation sites. Preliminary studies of the ceramics have suggested that, from the physiologic standpoint, they may be the best implantable substitute for hard tissues (bones and teeth) yet achieved. There are, however, many questions remaining to be answered concerning the selection of the most suitable material, its fabrication, and the reaction of tissues to it. These questions should serve to indicate future areas of exploration.
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    Notes: Ceramic and ceramic composite materials and devices were developed for specific maxillofacial applications. These applications included: (1) Replacement of hard tissue voids in low stress areas with a phosphate-bonded alumina-foamed ceramic and a calcium aluminate-bonded alumina foam; (2) development of porous ceramic-coated metallic devices for stabilization of mandibles with avulsed segments; (3) development of implantable ceramic tooth roots onto which more or less conventional crowns may be mounted.Efforts to date have been rewarding. Using the rhesus monkey for all experimental implant work, incorporation of porous ceramic foam prostheses to eliminate maxillary defects has been accomplished. Also, we have succeeded in stabilizing the mandible where segments of from 3 to 8 mm were removed. Bridging of the gap with new bone occurred within 6 weeks resulting in a total regeneration of the resected area with restoration of normal mandibular function. Finally, implantable tooth roots were developed. Three different surface treatment techniques have been used on a basic high-density alumina core. The first is a high-density matt finish which can only permit a fibrous tissue attachment or bony approximation but no ingrowth. The second is a porous alumina coating intended to permit bone ingrowth. The third is a rough surface consisting of particles of alumina sintered to the surface to maximize the bone/ceramic interface shear strength potential. Implantations of both anterior and posterior tooth roots with all three surface configurations have been successful for periods of up to six months.
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    Journal of Biomedical Materials Research 6 (1972), S. 3-14 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: In vitro transmission rates of benzocaine were measured to determine the feasibility of augmenting the permeability of silicone rubber implants by introduction of co-permeant plasticizers into the systems. It was shown that permeation can be enhanced or inhibited depending on the co-permeant used, including increased mass transfer of methylene blue, previously reported to be a non-permeant. Factors influencing such potentiation or diminution are thought to be solubility relationships among all components present, diffusivity, molecular volumes and mobilities of the co-permeants, hydrogen bonding capabilities, and potential for internal segmental motion of polymeric plasticizers.
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    Notes: Hypoeutectic alloys of the Au-Co system were studied for use in dental castings. Microhardness and tensile data were determined for annealed and aged alloys of compositions from 0.5 to 10 at. % Co in Au. Maxima for this alloy of HK 119, elongation 23% in 10 mm, yield strength of 185 MN/m2 (0.2% offset) and tensile strength of 257 MN/m2 occurred following aging at 350°C for 15 min. The system is considered promising for use as a dental casting gold alloy.
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    Journal of Biomedical Materials Research 6 (1972), S. 105-113 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Notes: Nine samples of plastic, including PVC stabilized with various amounts of organotins, silicone rubber, PTFE, polyethylene, polypropylene, and a U.S.P. negative control high density polyethylene, were implanted in rat gluteal muscle. Frozen sections were cut in a cryostat microtome and treated for enzyme histochemical reactions. These included succinic dehydrogenase, acid phosphatase, aminopeptidase and adenosine triphosphatase. The results illustrate that enzyme histochemical data can be of value in supplementing other methods in the evaluation of polymers for tissue compatibility.
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    Journal of Biomedical Materials Research 6 (1972), S. 405-441 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Notes: Porcelain inlays coupled by a silane treatment to composite resins which were used as cementing media and in turn retained by an undercut were evaluated as to their marginal integrity and retention against conventionally restored teeth. These included restorations in teeth with undercuts of resins, composites, and porcelain inlays cemented with zinc oxyphosphate cements.The evaluations were determined by isotope penetration during thermal cycling (180 cycles from 12 to 50°C), scanning electron microscopy of sectioned restorations, and mechanical pull tests.The results showed improved retentive qualities and markedly improved resistance to marginal penetration. Improved adaptation of the composite to the tooth surface was produced by the mechanical action of seating the porcelain inlay.
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    Journal of Biomedical Materials Research 6 (1972), S. 193-199 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: Silicone rubber implants removed from patients undergoing revision arthroplasty were examined for breakage and cracks and analyzed for lipid content. No relationship was observed between lipids extracted from the implants and the implantation time. Neither was the absorption of lipids and the incidence of breakage of the implants found to be related. Various factors contributing to the possible failure and breakage of the joint implants are discussed.
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  • 78
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    Journal of Biomedical Materials Research 6 (1972), S. 297-310 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The criteria for an ideally successful tooth implant should inlcude: (1) stable physiologic retension, (2) non-toxicity, (3) durability and sound function in the oral cavity, (4) non-carcinogenicity, and (5) esthetic satisfaction.Many complex factors such as the anatomic site itself (the tooth socket), proper healing of the periodontium, viability of the periodontal membrane in tooth reimplants, the oral microbial flora, the general health of the implant recipient, non-traumatic occulsion, physical and chemical properties of artificial implant material, and adequate stabilization influence the success of a tooth implant.Initial results demonstrate that ceramic (calcium aluminate) tooth implants with a 50 to 75-μ porosity appear to more promisingly meet the criteria for successful artificial tooth implantation than implants fabricated from plastic (polymethylmethacrylate), which produced osteomyelitis in 5/21 jaw block specimens in baboons with complete lack of true periodontal attachment between alveolar bone of the implant socket and the plastic tooth implant, shown microscopically and ultramicroscopically.
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  • 79
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    Journal of Biomedical Materials Research 6 (1972), S. 395-404 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 80
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    Journal of Biomedical Materials Research 6 (1972), S. 49-58 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Two methods are described for evaluating the thromboresistance of materials available as tubing. In the first method lengths of the tubing containing canine blood were incubated at 37°C, opened at timed intervals and examined for clots. For all materials tested, mean clotting times ranged from 5.2 min for glass to 〉 300 min for silicone rubber treated with GBH, TDMAC-heparin or TDMAN-heparin. For most materials, in vitro clotting times ranged from 20 to 60 min. Further testing in vitro indicated that heparin was more firmly bound to silicone rubber as TDMAC-heparin than as GBH. In the second method, short segments of tubing were surgically placed within the femoral veins of anesthetized dogs, examined for patency after 2 hr, removed and examined for thrombi. None of the materials tested appeared completely thromboresistant by the 2 hr in vitro method. Tubes of glass or unheparinized materials were usually completely occluded at the end of the test; silicone rubber treated with TDMAC-heparin apperared relatively thromboresistant. Results of in vitro and in vivo testing were generally in good agreement and were consistent with the known thromboresistant properties of materials.
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  • 81
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    Journal of Biomedical Materials Research 6 (1972), S. 143-144 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 82
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    Journal of Biomedical Materials Research 6 (1972), S. 115-141 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The surfaces of many plastics and other materials of interest in the fabrication of implants can be made nonthrombogenic by treating them with an inorganic heparin complex (IHC) system consisting essentially of a soluble metal salt, a solvent, and heparin. During complexing, the metal salt polymerizes at the same time it is trapped in the collapsing matrix of the surface; the entrapped inorganic polymer then reacts with heparin, probably by chelation. Treatment with an IHC system is not known to alter the mechanical or physical properties of the treated material. If desired, the surface can be made radiopaque by incorporating bismuth chloride or other contrast salts during complexing. After treatment, the surface can be autoclaved or sterilized with ethylene oxide. Materials that have been made nonthrombogenic by the IHC system include Silastic, polyurethane, cellulose acetobutyrate, polymethylmethacrylate, nylon, polyethylene, polypropylene, polyethylene-vinyl acetate, polystyrene, natural rubber, and polyvinyl chloride.
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  • 83
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    Journal of Biomedical Materials Research 6 (1972), S. 201-214 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
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  • 84
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    Journal of Biomedical Materials Research 6 (1972), S. 185-192 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Abrasion and performance of artificial heart valves are related to geometrical configuration, blood flow dynamics, manufacturing techniques, and interaction of materials. Incidence of thromboembolism, valve insufficiency, and shortened longevity are critically dependent upon these factors. The effect of construction parameters on valve performance is discussed in general terms and illustrated from in vivo experience with a specific low-profile design.
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  • 85
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Glass ceramic implants containing 45% SiO2 with a Ca/P ration of 5 become firmly fixed to bone when placed in a cortical defect of an intact rat femur. The addition of fluoride ions to the implant prevents this fixation. The most significant difference between the two compositions is in their solubilites. The presence of high local concentractions of Ca and PO4 ions at the interface of the soluble non-fluoride containing implant, could account for the deposition of bone at its surface.It is not felt from these studies, however, that this model will be usable as a mass screening tecunique for evaluating materials variables. It is felt that other less laborous in vitro systems need to be devised.
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  • 86
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    Journal of Biomedical Materials Research 6 (1972), S. 147-154 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The thermal properties of dental materials are important in certain aspects of tooth repair and the restoration of dental function. This is especially true for polymeric dental materials, for which low thermal conductivity is often considered an important asset. This paper contains a report on the surprisingly large effect that pressure (well with in the range encountered on the biting surfaces of teeth) can have on heat transfer in polymers that are widely used in dentistry. A sandwich type pressure-conductivity cell has been used to measure the thermal conductivity K of polystyrene, polymethyl methacrylate, polyethyl methacrylate, and poly-n-butyl methacrylate. The measurements span the range -50 to 50°C and pressures up to 2000 bar. For the polymers mentioned (and many others) K at a given temperature increases as pressure is increased. Initial increases in pressure to several hundred bars may typically increase the over-all heat transfer coefficient by a factor of two or more. At higher pressures, the relative slope (dK/dp)/K is typically about 10% per kilobar. Some comments are made about the thermal contact coefficient and the thermal diffusivity which are of more direct interest to dentists than K itself.
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  • 87
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    Keywords: Chemistry ; Polymer and Materials Science
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  • 88
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    Keywords: Chemistry ; Polymer and Materials Science
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    Notes: The pressure dependence of the elastic constants of various halides, hard tissues and synthetic apatites have been examined in the 0- to 50-kilobar range using a solid media, pressure apparatus coupled with an ultrasonic interferometer. The samples includ: hydroxy-, fluor-, and chlor-apatite, NaCl, CaF2, mollusc shell (aragonite), ivory, dentin and enamel, and fish, bovine, and human bones. High pressures were used in order to assess the effects of porosity in aggregate samples and to make measurements on specimens of ideal density. Computer analysis of the measured longitudinal and shear ultrasonic velocities yields the pressure dependence of the bulk, shear, and Young's moduli and Poisson's ratio. Atmospheric pressure values at ideal density are obtained by back extrapolation from the high pressure measurements.
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  • 89
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    Journal of Biomedical Materials Research 6 (1972) 
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    Keywords: Chemistry ; Polymer and Materials Science
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  • 90
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    Journal of Biomedical Materials Research 6 (1972), S. 15-24 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Heat vulcanized silicone elastomer (Silastic-Dow) has been in clinical use as a prosthetic replacement material for over a decade. When subjected to operating stress in body fluids, as in cardiac poppet-valves, failure has occurred. Fractures of silastic finger-joint prosthesis have also been experienced.Chemical and fractographic analyses of such failed finger-joint prostheses raise the suspiciaon of failure. Severe discoloration of the implant at the point of maximal stress concentration, the presence of significant amounts of triglyceride and cholesterol on the fractured prostheses, and the pattern of fracture markings indicate that fracture was due to a combination of chemical surface deterioration and stress concentration.Study of the method of surgical insertion of these prostheses suggests failure to completely excise the volar plate and other palmar joint structures could create a step off and sufficiently increase the stress in the bending element of the device to cause fracture. In vitro cyclic testing at 37°C in serum failed to cause fracture of these devices after 10 million cycles, but did produce gradual discoloration of the entire prosthesis which began and was most noticeable at the point of bending. Although the prostheses adsorb lipid, which may produce surface deterioration, it is anticipated that properly inserted, the service life of these devices should be more than adequate for full clinical application.
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  • 91
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    Journal of Biomedical Materials Research 6 (1972), S. 97-127 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A family of materials referred to as Avcothane elastomers has been developed. These materials have displayed a considerable degree of blood compatibility both in vitro and in vivo, althous they do not contain any added anticoagulant and are not equipped with any suface charges in any manner.A member of this family the Avcothane-51 elastomer, has rortinely delivered Lee-White clotting times whose mean is close to 60 min. Long-term aortic implantations of tubular prostheses made from this elastomer did not induce any pathological effects in swine. Results obtained in canine vena caval implantations and replacement appear to be consistent with the nonthrombogenic properties observed in vitro. This elastomer was utilized as the blood contact surface of the AERL Circular Assist Device which did not induce any significant intraluminal or intravascular thrombosis in acute implantations. An experimental model of a Left Heart Bypass Pump employing Avcothane-51 surfaces throughout was tested in completely nonanticoagulated dogs for bypass periods ranging from 2 to 24 hr. Hematologic studies performed during these bypass periods indicated no prohibitive changes in blood composition. In the form of tri-segmented Intra-Aortic Balloon Pumps, the elastomer was chronically implanted in swine. The combined effects of the material and pumping of this device did not cause any significant thromboembolic or hemolytic effects which demonstrated its safe applicability to human implantations.
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  • 92
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    Keywords: Chemistry ; Polymer and Materials Science
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    Notes: As of this date, tri-segmented intra-aortic balloons made from Avcothane-51 elastomer were applied in the counterpulsation treatment of about 80 cardiac patients. The combined effects induced by the implanted elastomer and the hemodynamics of pumping are analyzed by means of hematologic changes observed in a set of 28 patients who were treated at the Massachusetts General Hospital for an average period of about 4 days, and represent a widely diversified group in terms of their clinical conditions. In no case were, any significant adverse hematologic effects induced by this assist device whether the hosts had been anticoagulated or not heparinized at all. While platelet levels were somewhat affected by the assist device, the particular conditions of the patient appear to have an effect of at least, equal magnitude. In addition to platelet levels steadily decreasing with pumping time, changes in platelet levels similar to the pattern of “platelet tide” occurred with about equal frequency. Monitored in terms of erythrocyte counts and plasma hemoglobin levels, no significant degree of hemolysis could be detected. Leukocyte counts in patients having above-normal levels at the beginning of pumping returned to normal while in other cases there were no significant changes. Fibrinogen, one of the plasma proteins most sensitive to foreign surfaces, showed levels increasing from subnormal to normal as a function of pumping time. The overall in vivo performance of Avcothane-51 balloons appers to be consistent with the state of the surfaces of recovered devices, showing only the presence of occasional adherent platelets upon examination by scanning electron microscopy.
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  • 93
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    Journal of Biomedical Materials Research 6 (1972), S. 347-374 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: In this investigation, ceramics were studied to determine their role as rigid, abrasive implants in soft, living tissue. Discs and tubes of three ceramics, CaO·Al2O3, CaO·TiO2, and CaO·ZrO2, were introduced as porous and non-porous structures into muscle and connective tissue sites in rabbits. The animals were observed grossly to determine the duration of redness and swelling following surgery, and samples were retrieved at 1 week, 3 months, 6 months, and 9 months after implantation. A mild, acute inflammatory response immediately followed the implantation of all three materials in both the porous and non-porous forms. Histological sections of the ceramics and surrounding tissue, cut and stained for light microscopy, demonstrated the absence of inflammatory cells and revealed the normal morphology and organization of the cells present around all types of implants tested. Tissue around discs of porous ceramics healed faster and exhibited thinner fibrous encapsulations than with impervious discs of the same material. Healthy fibrous connective tissue with an ample blood supply occupied those implants with pores of 45-100 mμ, and even more rapidly filled the samples with a 100- to 150-μ pore size. The tissue ingrowth and tight adherence to the porous samples was believed responsible for the more moderate response to porous implants. No adverse responses of any kind were observed, except in a very few, atypical specimens.
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    Journal of Biomedical Materials Research 6 (1972), S. 471-472 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 95
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The cobalt-based alloy containing approximately 30% chromium and 5% molybdenum is widely used for the fabrication of internal fixation appliances. This alloy exhibits superior corrosion resistance in the presence of body fluid because of a durable and rapidly formed surface layer of chromium oxide. Although biocompatible, clinical use of this alloy appears to have been complicated by relatively great adhesion of tissue and bone to the metal. The adhesion engenders considerable difficulty when removal of an applicance should become necessary.It was hypothezied that this adhesion derives from the ceullular growth proceeding within the microporosity of the metal surface; the growth proceeds efficiently because of relatively low levels of cytotoxic metal ions released at the metal surface. In order to limit adhesion, polytetrafluoroethylene polymer (PTFE) was used to virtually eliminate surface microporosity and to substantially reduce metal surface free energy.1 One of the efficient techniques was to lap the metal surface with a solid piece of PTFE.A series of eighteen 12- to 22-kg dogs were used to evaluate the above thesis. Control and treated cobalt alloy plates and screws were used to fix induced longbone fractures in the same animal. Also, five animals received implants on decorticated iliac crests. The histological data for control (untreated) plates showed that in nine of the eleven experiments bone was demonstrated closely adjacent to the surface of the appliance. However, in seven of these cases fibrous tissue was also present to a substantial degree. The presence of bone correlated with generally increased difficulty in removal of the plate. On the other hand, the results with treated implants showed that in ten of eleven cases the appliances were grossly encapsulated with fibrous tissue and were relatively easy to remove.
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  • 96
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    Journal of Biomedical Materials Research 6 (1972), S. 489-498 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: In previous studies from our laboratories, it was shown that metals and alloys which register negative potentials in blood vs. the normal hydrogen electrode (NHE) tend to be antithrombogenic, while those with positive potentials are invariably thrombogenic. Of the metals, only the corrodible ones fall in the first group and the noble ones in the second. Blood compatible metals appear to be essential for some types of medical devices. This paper deals with a novel approach of maintaining an implanted metallic prostheses at a negative potential. A copper vascular prostheses in a dog was made the cathode in a polarizing circuit, which in addition consists of a smal mercury battery, a resistor and an auxiliary electrode. Such experiments were conducted in three animals, and the potentials ranged from -60 to -160 mV/NHE. The three dogs were sacrificed after 6, 8, and 14 days and the tubes were examined. All tubes were free of thrombus deposits; minimal junctional thrombi were found. Two copper tubes with no polarizing circuit and registering positive potentials were occluded after 8 and 14 days, respectively. Histologic and electron-microscopic studies of the thrombus deposits in tubes at spontaneous potentials and of the junctional thrombus deposits in the tube at negative potentials showed similar structures. The present experiments further confirm the view that the potential across the conductive material-blood interface is a more basic parameter than the chemical nature of the surface in determining its blood-compatible characteristic.
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  • 97
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    Journal of Biomedical Materials Research 6 (1972), S. 533-543 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: An ideal material for an artifical urinary bladder has not yet been designed. In order to study the effects of long-term exposure of urine to velour-lined Silastic silicone rubber, seven 80% cystectomized sheep had their natural bladders replaced with a Dacron velour-lined, Silastic prosthesis. Animals were sacrificed 1 week, 3, 6, 9, and 18 months postimplantation of their prosthesis.While the luminal surface of the prosthesis one week after implantation had small isolated patches of epithelium on it none of the remaining animals had any evidence of tissue growth on this surface. No stones or calcifications were found on the luminal surface of the prostheis in any of the animals except the 18-month survivor who had microscopic evidence of early calcification.The convex (serosal) surface of all the artifical bladders was covered with a thick connective tissue layer. At 9 months a muscle layer was seen in this tissue and it was clear the prosthesis was acting as a scaffold around which regeneration of the natural bladder was taking place. At 18 months after implantation regeneration of the natural bladder was complete and the prosthesis remained as a functionless, crumpled, hard foreign body in the lumin of the new bladder.It appears that velour-lined Silastic silicone rubber though not ideal may be an effective artificial bladder material as long as it remains functional.
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  • 98
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The preparation of block polymer surface-active agents derived solely from propylene oxide and ethylene oxide is described. The physical properties of a nonionic surfactant of 12,500 molecular weight, Pluronic F-127, are presented. The toxicity data of the polymeric series is reviewed. The preparation of cold aqueous solutions of the F-127 solution, to which silver salts and other medicaments are then added, is described. By raising the temperature, these fluid liquids are then converted to strong “ringing” gels or viscous ointments which are suitable for application to a burn wound or abraded skin area. The factors involved in altering the yield strength of the gel are presented.
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  • 99
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    Journal of Biomedical Materials Research 7 (1973), S. 353-367 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The transport of urea and other biologically interesting solutes in aqueous solution across poly(2-hydroxyethyl methacrylate) (p-HEMA) hydrogel membranes has been studied. The results show that p-HEMA membranes have a high permeability to urea due to a strong interaction between the polymer and urea, and, in addition, they are consistent with a pore flow model in which solute transport takes place through water-filled regions essentially unaffected by the surrounding polymer matrix. The results indicate that such p-HEMA membranes might be suitable for hemodialysis applications.
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    Journal of Biomedical Materials Research 7 (1973), S. 405-418 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: This work represents a preliminary study of one case history of a silicone heart valve. The laboratory techniques employed have proven useful in characterizing the polymer before and after implantation. Before any model explaining ball variance can be proposed it must be determined whether the polymer loses its integrity because specific constituents in the body fluids interact with primary valence bonds in the polymer chains, or if the fluids simply cause swelling and plasticization of the crosslinked system and the damage is the result of mechanical work on the weaker polymer system. Detailed kinetic and thermodynamic studies are underway to answer these questions.The work summarized in this paper refers to the evaluation of only one specimen and should not be taken to mean that every silicone ball from a heart valve prosthesis will show this variance. The incidence of functionally variant silicone balls as reported to one manufacturer represents approximately 1.5% of the aortic and less than 0.05% of the mitral prostheses which have been supplied by this manufacturer. A small percent of valves of this type have the potential of becoming functionally variant and this is one failure mode which should be considered in the implantation of silicone ball valves.
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