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  • Medicine  (428)
  • 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
    Electronic Resource
    Electronic Resource
    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
    Electronic Resource
    Electronic Resource
    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
    Electronic Resource
    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
    Electronic Resource
    Electronic Resource
    Springer
    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
    Electronic Resource
    Electronic Resource
    Springer
    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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    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 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    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) 
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    Keywords: Chemistry ; Polymer and Materials Science
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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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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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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 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    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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    Keywords: Chemistry ; Polymer and Materials Science
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    Journal of Biomedical Materials Research 6 (1972), S. 405-441 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    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 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    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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    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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    Journal of Biomedical Materials Research 6 (1972), S. 395-404 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
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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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    Journal of Biomedical Materials Research 6 (1972), S. 143-144 
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    Keywords: Chemistry ; Polymer and Materials Science
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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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    Journal of Biomedical Materials Research 6 (1972), S. 201-214 
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    Keywords: Chemistry ; Polymer and Materials Science
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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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    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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    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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    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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    Journal of Biomedical Materials Research 6 (1972), S. 15-24 
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    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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  • 38
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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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  • 39
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    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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  • 40
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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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  • 41
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    Journal of Biomedical Materials Research 6 (1972), S. 471-472 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
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  • 42
    ISSN: 0021-9304
    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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  • 43
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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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  • 44
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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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  • 45
    ISSN: 0021-9304
    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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  • 46
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    Journal of Biomedical Materials Research 8 (1974), S. 115-126 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A standardized readily reproducible experimental model has been developed to assess the relative importance of the chemical and physical configuration of sutures as determinants of early infection in contaminated wounds. The chemical structure of the suture appeared to be the most important factor in the development of surgical infection. The incidence of infection in contaminated tissues containing either polypropylene sutures or nylon sutures was lower than the infection rate of tissues subjected to any other nonabsorbable suture. Among the absorbable sutures, polyglycolic acid (PGA) sutures evoked the least inflammatory response. The infection rate of contaminated tissues containing the PGA sutures was not significantly different from the incidence of infection of tissues subjected to the least reactive nonabsorbable sutures. The physical configuration of the suture played a relatively unimportant role in the development of early infection. The infection rate of contaminated tissues containing monofilament nonabsorbable sutures did not differ significantly from the incidence of infection of tissues subjected to multifilament sutures made from the same material. Coating the multifilament suture with either silicone, wax, or Teflon did not alter the incidence of early infection in the contaminated tissue. Finally, the presence of even the least reactive suture in contaminated subdermal tissue potentiated the development of infection.
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  • 47
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    Journal of Biomedical Materials Research 8 (1974), S. 163-173 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Experiments were conducted to further the understanding of tendon reconstructive surgery.A series of 20 dogs was used for replacement of the forepaw extensor carpi radialis tendon (a single tendon only is present in the dog) with active gliding tendon implants. The implants were attached distally and proximally so that new tendon prosthetic designs could be studied as well as new sheath development under gliding conditions.The results, recorded in this paper, show that a “gliding implant” can convert a nonspecific bed of connective tissue or scar into a specific living envelope comparable to a tendon sheath system. This system has been shown to be capable of lubricating and supporting a gliding artificial implant while augmenting normal tendon function. Degrees of active and passive gliding can take place for indefinite periods, providing the mechanical and dynamic capabilities of the new system are understood and controlled. The mature sheath will show a predictable physiologic response to unfavorable stimuli.Further evidence that the new gliding system functions as a physiologic sheath is borne out by the fact that the implant can be replaced in Stage II by a long free tendon graft. The graft is apparently supported in part by fluid nutrition and filmy adhesions between the distal and proximal anastomosis.
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  • 48
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    Journal of Biomedical Materials Research 8 (1974), S. 365-371 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The mandibular staple is an endosseous implant that will permit the attachment of a lower deture in cases of severe alveolar bone atrophy. It is placed through a submental incision and inserted into seven parallel holes drilled into the mandible. A curved bar containing seven pins is inserted in the holes and is place against the inferior border of the mandibular symphysis. The two lateral most pins project into the mouth and the five retentive pins remain completely buried in bone. Two fasteners are screwed down on the threading of the intraoral pins. Later a bridge containing Dalbo attachments is cemented to the fasteners which allow attachment to a lower denture. A series of 25 patients have been completed with 20 successful patients for survival rate of 80%. The longest case has been in for five years and the average case has been in for 3 years. Stainless steel, titanium and ceramic coated titanium has been with apparently equal success. Patient acceptance has been excellent.
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  • 49
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    Journal of Biomedical Materials Research 8 (1974), S. 391-399 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A study sponsored by the National Institute of Dental Research has as its major goal the development of easily fabricated and implantable dental anchors for replacement of missing or extracted teeth. Tissue ingrowth fixes the anchors in the mandibular or maxillary bone where they can serve as a base for future attachment of prefabricated dental caps, bridges, or other dental prostheses. More immediate objectives are to determine the suitability of specific porous titanium and ceramic materials for anchor applications, to develop satisfactory designs and fabrication procedures for producing these devices, and to define material/bone interface bonding characteristics through in vivo studies. The value of the Hanford Miniature Swine as a human analog for dental research is being assessed concurrently.
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    Journal of Biomedical Materials Research 8 (1974), S. 49-64 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A series of nonporous glasses and glass materials designed with controlled surface ion activities to allow chemical bonding to bone are described. Surface reactivities of these materials in vitro are correlated with biological activities in vivo and in tissue culture. Direct chemical bonding of the materials to bone is demonstrated. The mechanism for development of this bond is through the production of an amorphous ion surface gel on the bioglass. This gel induces osteogenesis by a chemotactic response of osteoblasts.
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  • 51
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    Journal of Biomedical Materials Research 8 (1974), S. 99-113 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: One method of providing an artificial limb for an amputee might be to attach the external prosthesis directly to the skeleton but a major problem is the behavior of the tissues at the point where the prosthesis penetrates the skin surface. Preliminary experiments have been carried out using small flexible implants in porcine skin to study the principles involved. It is confirmed that the epidermis grows down into the dermis around the nonporous materials and the implant-skin junction is unstable and readily becomes infected. It was found that polytetrafluorethylene with pores of 10 μm diameter and hydron sponge with pores of 40 μm diameter became invaded by fibrous tissue and this appeared to prevent the migration of epidermis alongside the implants and a stable ring of epidermal tissue was formed near the skin surface. A review of other situations where epidermal migration is taking place suggests that epidermis is able to migrate through damaged collagenous tissue, possibly with the help of leucocytic enzymes, but that epidermal cell movement is halted when the epidermal sheet is confronted by heathly collagen bundles.
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  • 52
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    Journal of Biomedical Materials Research 8 (1974), S. 145-153 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Polymeric materials are becoming increasingly popular as prosthetic materials in orthopedic surgery. One of these materials, polyethylene, is capable of being fabricated in a porous form suitable for tissue ingrowth. Porous polyethylene appears to be well suited for prosthesis attachment when bonded to its solid form of other prosthetic materials. Extensive bone growth into porous cylindrical specimens implanted in the canine femur has occurred as early as four weeks. Ingrown tissues appear normal and there is minimal inflammatory response. Mechanical strength of the porous material, though not as great as that of the solid material, does appear to be sufficient for certain orthopedic applications. Current research is directed toward determining interfacial strengths and the mechanical properties of the porous polyethylene-bone composite.
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  • 53
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    Journal of Biomedical Materials Research 8 (1974), S. 185-196 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: An investigation was conducted to determine the general physical characteristics of self-curing acrylic resin systems in terms of their potential utilization in total hip arthroplasty.Exothermic temperature, working and setting times were monitored with thermocouples placed in acrylic masses insulated via a Teflon mold. Mechanical strengths were run in an Instron testing machine. The same trends were noted in all systems studied.As thickness or mass increased, the maximum temperature and the setting time increased. As the powder to liquid ratio increased (thereby relatively less liquid), the maximum temperature, set times and dough times decreased, while the working time was essentially unaffected. As the ambient temperature decreased, the maximum temperature decreased while the dough, working and setting times increased.The mechanical strengths of the systems cured at one atmosphere are low compared to high temperature and pressure curing. Flowability of the materials decreases quickly as final set time is approached.Although trends are similar in many self-curing acylic systems minors shifts in complex proprietary compositions can produce a wide span or working and setting times. Because the surgical team controls such parameters as the mass employed, the amount of liquid introduced, and the ambient temperature it is important that they continuously re-evaluate their handling procedures particularly if new acrylic cements would be introduced.
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    Journal of Biomedical Materials Research 8 (1974), S. v 
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    Keywords: Chemistry ; Polymer and Materials Science
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  • 55
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    Journal of Biomedical Materials Research 8 (1974), S. 271-283 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Through a survey of hip replacement arthroplasty the paper establishes the case for objective evaluation of these joints in the patient. It then outlines a simple, non-invasive technique, based on Paul's (1967) locomotion studies, to assess pre- and postoperative functional capability. Preliminary results which establish viability of the procedure are presented.
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    Journal of Biomedical Materials Research 8 (1974), S. 319-328 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A porous titanium alloy called void metal composite (VMC) was investigated for use in knee prosthesis fixation. The interfacial ingrowth fixation of VMC intrameduallary, subchondral, and variable density implants in goat femora was evaluated biomechanically and histologically at six weeks and five months. Biomechanical tests were done under static shear and dynamic, cyclic (fatigue) loading conditions. Readily identifiable bone, strong fixation, and excellent biocompatibility were typical. Some subarticular implants appeared to induce normal hyaline cartilage overgrowth.
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    Journal of Biomedical Materials Research 8 (1974), S. 87-90 
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    Keywords: Chemistry ; Polymer and Materials Science
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  • 58
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    Journal of Biomedical Materials Research 8 (1974), S. 97-117 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A significant variation occurred in the inflammatory response to polyethylene and polyurethane when embedded subcutaneously in experimental animals. This variation apparently is related to the composition of the plastic and adsorption of proteins. The attraction of polymorphonuclear leucocytes by plastics apparently is related to the electrostatic and/or electrokinetic imbalance that occurs at or near the site of implantation.Polyurethane and polyethylene were selected for this study since preliminary observations had shown a variation in inflammatory response when they were embedded subcutaneously in the mouse. From this study it is evident that: (1) variations occurred in the inflammatory reaction in the subcutaneous tissue of mice and rabbits following the embedding of polyethylene and polyurethane; (2) polymorphonuclear leucocytes began to emigrate within hours after these two plastics were implanted, reaching their maximum number within 24 to 48 hr; (3) polymorphonuclear leucocytes usually were absent after the 6th experimental day in mice with polyurethane, but were present for 232 days in mice with polyethylene; (4) polymorphonuclear leucocytes were present in the rabbit for only a few days following subcutaneous implantation of polyethylene and polyurethane; and (5) leucocytes around the implanted polyurethane in the rabbit began to degenerate within 48 hr. The mechanism for this degeneration is not known.
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    Journal of Biomedical Materials Research 8 (1974), S. 185-188 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Keywords: Chemistry ; Polymer and Materials Science
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: Two types of dense Al2O3 ceramics (99.6% purity, 96% purity) were tested in the following fields of interest.1Wear resistibility using a pin and disk method under distilled water and human synovial fluid. Both types showed minimal initial corpuscular wear.2Biocompatibility of ceramic wear particles in mice and rats after injection by different ways. The crystal material is permanently deposited in macrophages, after transport via lymphpatic and blood vessels also in the RES without chronic inflammatory and progressive fibrotic response.3Under moderate stress conditions ceramic plates are fixed firmly by new bone formation within 2-3 months according to tetracycline label studies of bone growth in rats.4A new ceramic total hip prosthesis with two different socket designs for cement free fixation in bone is proposed and used in sheep experiments. The results of a 4 month experiment is presented showing firm fixation of the prosthesis under full stress conditions.
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    Journal of Biomedical Materials Research 8 (1974), S. 85-97 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A study of the tissue compatibility of aluminum oxide implants under different stress conditions in rabbits was performed over four- and eight-week implantation periods. The specific objectives were to examine endosteal bone ingrowth into aluminum oxide coneshaped plugs in amputated tibiae, while additional pellet-shaped implants in the tibiae and femora of rabbits with amputated and nonamputated limbs were studied to determine: (1) if the degree of loading placed on the amputated limb was sufficient to promote bone activity, (2) the degree of inertness and/or toxicity of the aluminum oxide implants, and (3) a possible cause of bone spurs.The results of the radiographic, histologic and microradiographic analyses of the in vivo implants demonstrated that there was little mineralized bone ingrowth into the coneshaped aluminum oxide implants in the amputated tibiae. The study also showed that the aluminum oxide pellet implants in the tibiae and femora of the nonamputated limbs demonstrated excellent mineralized bone ingrowth into surface and internal pores. By comparing these results with the incomplete ingrowth into corresponding pellet implants in the tibiae and femora of amputated limbs, it was determined that a lack of weight bearing and damage to the musculature and vascularity following amputation were interfering with the normal bone activity and therefore bone ingrowth.Angiographs and radiographs of the amputated tibiae demonstrated that bone spurs were present and that they originated at the site of the periosteal damage. Their cause was believed to be associated with an increase in the vascularity of the adjacent tissues.
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    Journal of Biomedical Materials Research 8 (1974), S. 137-144 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Ceramic materials for permanent implantation in osseous tissue, called osteoceramics, were based on an equimolar mixture of Ca3(PO4)2 and MgAl2O4. Tooth roots with dense regions and with regions of controlled porosity for tissue ingrowth were made from the material. They were implanted submucosally in the mandible and maxilla of dogs. Tissue response was aceptable and strong attachment occurred. Thin sections are presented showing the interface of the alveolar bone and the prosthesis.
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    Journal of Biomedical Materials Research 8 (1974), S. 155-162 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Clinical studies will permit only small sections of tendon sheaths to be removed for biopsy at restricted levels as the sheaths were to be used for tendon grafting. In active gliding programs, biopsy has been limited to small sheath sections in immediate relation to the distal or proximal anastomosis where gliding motion may be induced or minimal. In the passive gliding programs, biopsy has been limited to the most proximal segments where considerable folding of the sheath occurs or cul-de-sac buckling of the implant may produce irritation.As these were the only practical clinical sources of sheath sections for biopsy and study, the authors felt that a comparison study of sheath development in animals would broaden our understanding in humans. With this objective in mind, three canine laboratory studies were carried out where, for pure purposes of investigation, entire sheath sections were removed at designated time intervals for study.The flexible implants were well accepted, affording the opportunity to observe development of early sheaths in a controlled connective tissue environment, free from the stress of joint motion.The semi-rigid implants showed equal acceptance in side-by-side tissue level of the same dog as the flexible implant. This influenced changes in artificial tendon development from extrusion to the more exacting mold fabrication. It seemed evident that the degree of increase in stiffness of the new artificial tendons to gain a superior surface for gliding and increased strength would not change tissue acceptance providing flexibility was maintained.The cellular response in this study did not seem to represent a foreign body phenomena but an orderly acceptance of the soft tissue environment to the smooth surface of the inert implant.It is concluded that this study confirmed in animals the clinical findings of Mayer, Bunnell, Milgram, and Carroll.The consistent orderly development of the new sheaths formed in response to the static implants is impressive. The authors believe the appearance of these histologic sections are likely correlations with the development of new sheaths around the Hunter Tendon Prosthesis during the three-four week postoperative period when the hand is resting in a functional dressing.
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    Journal of Biomedical Materials Research 8 (1974), S. 197-207 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Poly-α-amino acids have been investigated for possible use in a wide variety of biomedical applications. These range from dialysis membranes to artificial skin substitutes to degradable sutures. The large number of available α-amino acids potentially provides an extremely large number of poly-α-amino acids. The majority of materials investigated to date are copolymers composed of two components, one of which usually provides the desired property for the given application.This paper deals with the further examination of a series of γ-benzyl-L-glutamate-L-leucine copolymers. Evidence is provided on the effect of these copolymers on the biological environment as determined by implantation in rats up to 200 days. In vitro tests were also performed and the effect of these tests on the stress-strain properties of one of the copolymers is presented.Preliminary evidence on biodegradable copolymer films is also included. These materials have free γ-carboxyl groups on the glutamate components.
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  • 66
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    Journal of Biomedical Materials Research 8 (1974), S. 427-434 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Following the classification of tissues according to their “dominant” and “interactive” components the paper surveys their load-deformation behavior, highlighting in particular the significance of time dependence. This leads to a discussion of the implant/tissue interaction in which the complexity that could be created by varying load and deformation time rates at the interface is explored.
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  • 67
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    Keywords: Chemistry ; Polymer and Materials Science
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    Notes: The compatibility of implanted ceramic materials with autogenous bone, and the subsequently noted influence of the ceramic on the rate of new bone formation, were investigated to evaluate such materials for use in orthopedic implants. Three ceramic materials, aluminium oxide (Al2O3), zirconium oxide (ZrO2), and calcium aluminate (yCaO · xAl2O3) were tested. These were placed in the femurs of rhesus monkeys for periods of 50, 100, and 350 days. Definite compatability between the autogenous bone and the materials was exhibited for the implant time periods evaluated. No toxicogenic activity was noted in any of the biochemical, biomedical, and ceramographic evolutions. An added benefit resulted from the calcium aluminate composition, which was fabricated as a two-phase oxide material to make it slightly soluble in the body fluids. In the 50- and 100- day implants, the bone penetrated the ceramic for distances up to 100 μ while the ceramic dissolved and the pores enlarged. In addition, the mineralization in the area of the calcium aluminate was greater than that found around the other ceramics. Radiographs over the entire 350-day implant period confirmed the increased callus formation around all of the materials with no signs of rejection evident in the surrounding osseous or soft tissues. After 350 days the entire pore area of the calcium aluminate ceramic was infiltrated with a columnar substance which on the basis of scanning electron microscope procedures was considered to be mineralized osteoid.
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    Journal of Biomedical Materials Research 5 (1971), S. 53-62 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A series of DL-methionine/L-leucine copolymers was prepared from the coresponding N-carboxy-anhydrides. The copolymers formed clear flexible films having low water vapor transmission rates. Peroxide oxidation of the pendant methyl-theioethyl groups to methyl-sulfinoethyl groups enhanced the hydrophilic properties of the membranes, and the water vapor transmission rates rapidly increased with an increase in the number of pendant methyl-sulfinoethyl groups. Increasing the leucine content of the membranes produced a 13-fold increase in the carbon dioxide permeability and a 6-fold increase in oxygen permeability, whereas, an increase in the methionine content doubled the carbon dioxide-oxygen separation factor.Synthetic poly (α-amino acids) are very similar to naturally occurring proteins with respect to composition and conformation. Because of these similarities, they are being considered in aerosol spray bandages, synthetic skin applications and as coatings for plastic prostheses. The unusual permeability characteristics of the DL-methionine/L-leucine copolymers make them interesting membranes for possible use in artificial kidney machines and blood oxygenators.
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    Journal of Biomedical Materials Research 5 (1971), S. 63-79 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The flexural tests on 37 whole equine metacarpus bones are described and the results are given in terms of fundamental material properties as a function of age. The moduli of elasticity, rupture, and failure increase then decrease with increasing age. The rupture and failure deformations decrease with age. The stiffness and fragility indices increase with age. Averaging the data for all ages, the modulus of rupture was 35 ksi, the deflection at rupture was 0.22 inches, and the modulus of elasticity was 1.7 × 10 psi. The flexural rupture strength is about twice the uniaxial compression strength and about five times greater than the torsional strength for whole bone tests. The moduli of elasticity are about the same for flexure and uniaxial compression, and about five times greater than the torsional modulus of rigidity for whole equine bone.
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    Journal of Biomedical Materials Research 5 (1971) 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
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  • 71
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    Notes: A porous ceramic, in the form of small discs, has been implanted into the upper tibiae of adult mongrel dogs in survival experiments. A similar sized disc of a metal (vitallium, titanium, or stainless steel) was also implanted, for comparison, into each tibia. The tissue specimens were studied by microangiography and correlated histology. At the 4-month, and longer, intervals, the specimens were sectioned with the ceramic disc in situ. Injected capillaries were then observed to have penetrated the ceramic.The metals became surrounded by a shell of new-bone, lined by a fibrous membrane of varying thickness. The ceramic implants, on the other hand, appeared to have remained inert within the cancellous area of the tibiae, not surrounded by either a membrane or an osseous shell.Implications of these findings were discussed and further experiments, some of which are in progress, were proposed.
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  • 72
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    Notes: The management of severe flexor tendon injuries of the hand has been dramatically improved by tendon sheath reconstruction with an artificial tendon, followed by conventional tendon grafting. The purpose of this study was to investigate the nature of neosheath formation.In 25 chickens, the flexor tendons and sheaths in a toe were excised and replaced with a United States Army artificial tendon. An artificial tendon was also placed in the back, and four weeks later, tendons and surrounding tissue as well as normal tendon sheaths were excised and submitted for light, transmission electron microscopy and scanning electron microscopy.In all instances, neosheaths formed around the silastic coated artificial tendon. The neosheaths formed in the foot and back were similar to normal sheath, having the same cellular and fibrous composition. Reconstruction of the normal anatomy with an artificial tendon explains why this surgical technique gives superior results to other less physiologic procedures in patients with severe hand injuries.
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    Journal of Biomedical Materials Research 8 (1974), S. 219-226 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The biomaterials engineer of today has an extremely limited choice of approved metallic implant alloys with which to conduct his studies. There is essentially no incentive for larger companies to initiate basic research in the biomaterials field. New alloys which would have the best chance of developing as biomaterials would be “spin-off” alloys from somewhat related industries and currently in production. MP35N is just such a spin-off alloy with a background of years of in-vitro testing and use in corrosive environments. When compared to the desired implant material requirements, the material properties required of MP35N for present applications readily indicate its potential use as a biomaterial.It is a castable alloy which exhibits good as-cast ductility. In the wrought condition, yield strength levels from 60,000 to over 310,000 psi are possible with accompanying good ductility characteristics. Excellent stress corrosion cracking resistance and improved fatigue strength over present cast implant material are also characteristic of MP35N. Results, to date, from in-vivo tests indicate tissue compatibility of MP35N at least comparable to HS-21 (Vitallium).Possible medical applications for MP35N would include hip and knee joints, bone plates, heart pacer electrodes, suture wire and clips, and Endosseous blade implants.
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    Journal of Biomedical Materials Research 8 (1974), S. 285-288 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The bone-implant interface and the accompanying difficulties with fixation continue to be a major area of research activity. Biological fixation would appear to be the ideal method of fixation. Press-fit metal implants may be part of a larger answer that may include sintering, coatings, or both.
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    Journal of Biomedical Materials Research 18 (1984) 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Journal of Biomedical Materials Research 18 (1984), S. v 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Journal of Biomedical Materials Research 18 (1984), S. 413-425 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A complete study of the static and dynamic strength of complete maxillary dentures was undertaken. First, the denture base material was investigated in its various forms from the point of view of tension, creep, relaxation, fatigue, and the effect of a corrosive environment. Complete dentures were tested under static compression, and the distribution of stresses along the midline of the upper dentures was determined by means of strain rosettes and by reciprocating compression, the determination of their fatigue strength. The results were found to conform with experience as far as lifetime of complete dentures is concerned.
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    Journal of Biomedical Materials Research 18 (1984), S. 435-462 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Notes: Many authors have examined the mechanical properties of bone cement and the various factors that affect its mechanical behavior. This article presents a comprehensive survey on the reported mechanical properties of bone cement. Variables that influence the mechanical properties, such as handling characteristics, strain rate, loading modes, additives, porosity, blood inclusion, in vivo environment, temperature, etc. have also been reviewed. The importance of specifying these variables in reporting test results on the mechanical properties of bone cement is pointed out. Previous attempts to improve the mechanical properties of bone cement are also summarized. Future research areas important for fully characterizing the physical properties of PMMA are also suggested.
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    Journal of Biomedical Materials Research 18 (1984), S. 137-146 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: Randomly cross-linked copolymers of 2-hydroxyethyl-methacrylate (HEMA) and methyl-methacrylate (MMA) have been prepared and studied in the dry and swollen state. Tensile and indentation tests indicate that by changing the composition of copolymers, it is possible to obtain materials with a wide range of mechanical properties and corresponding glass transition temperatures. Water diffusion coefficients in sorption and desorption experiments have been calculated and compared.
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    Notes: Although dogs have been used widely to study the healing of large caliber synthetic grafts, hypercoagulability probably makes the dog a poor model for studies of small caliber vascular prostheses. The baboon's coagulation system is similar to man's, but large caliber baboon grafts were reported to endothelialize rapidly. In this study the healing pattern of 4mm internal diameter Dacron carotid interpositon grafts in baboons was determined using specimens harvested at time points between 2 weeks and 18 months post-implantation and examined with light and scanning electron microscopy. The luminal surface of baboon grafts in the acute healing phase (〈1 month) was comparable to that reported in the literature for dogs. Baboon grafts did not completely endothelialize until 10-12 weeks post-implantation. For work with small caliber vascular protheses, the dog appears to have no advantage over the baboon as an animal model on the basis of graft healing.
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    Journal of Biomedical Materials Research 18 (1984) 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Journal of Biomedical Materials Research 18 (1984), S. 395-401 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The macrophage plays a pivotal role in both wound healing and cellular response to implants, including percutaneous devices. Within twenty-four hours macrophages were found in close contact with the implant surface. Eventually fibroplasts and connective tissue proliferate, and finally the implant will be encapsulated. The presence of macrophages is essential for the activation of collagen synthesis by fibroplasts. Implant shape and surface can profoundly affect macrophage behavior. At rough implant surfaces macrophages with giant cells are present for many months with the possibility of chronic granulomatous reactions. Superior tissue compatibility should be associated with smooth, well contoured implants with no acute angles.
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    Journal of Biomedical Materials Research 18 (1984), S. 427-434 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Notes: A Ni-45 wt % Ti (Ni-50 at % Ti) alloy was cast into molds of magnesia and silica investments by use of a dental argon-arc pressure casting machine with a copper crucible. The castings exhibited shape memory properties. The shape recovery process was sharper in the specimens cast in magnesia investment molds than in those cast in silica (phosphate-bonded) investment molds. The latter casting had a hard region of the periphery, suggesting that shape recovery process may be affected by reaction of molten metal with silica. Furthermore, the alloy possessed the adequate mechanical properties for consideration as crown-and-bridge prostheses.
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  • 84
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    Notes: The release of corrosion products by implants has become a matter of concern. Using a microsphere model, the release of chromium, cobalt, and nickel, secondary to implantation of various surface area exposures of F-75, a cast cobalt-chromium alloy, was studied over a 30 day period in the rat. Dose related elevations were observed in the serum concentration of chromium and cobalt but not of nickel, with the maxima being achieved at 3 days after metal implantation followed by declines in concentration. The chromium elevation, approximately twelvefold for a surface area to body weight (SA/BW) ratio of 300 x is similar to that previously reported in patients receiving total hip replacement arthoplasties. However, the cobalt elevation, twentyfold for a SA/BW ratio of 300 x, has not been previously observed. These serum concentration changes are as yet unexplained, but are probably not due to fibrous capsule maturation or alloy repassivation.
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    Journal of Biomedical Materials Research 18 (1984), S. 547-559 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: An in situ immunoradiometric assay was devised to quantitate human fibrinogen deposited on hemodialysis membrane, Cuprophane, from in vitro exposure to fibrinogen solution and from ex vivo extracorporally clinical use. The method requires a monospecific 125I-labeled antifibrinogen-IgG purified by DEAE chromatography and immunoadsorption. The labeled antifibrinogen IgG was shown to react specifically with fibrinogen adsorbed and immobilized (by glutaraldehyde) on Cuprophane. Other plasma proteins such as human albumin, IgG, or α-thrombin, adsorbed singly or coadsorbed with fibrinogen on the surface did not seem to affect the fibrinogen-antifibrinogen reaction. The presence of blood cells such as platelets and granulocytes with fibrinogen on Cuprophane reduced only slightly the uptake of 125I-antifibrinogen-IgG. The examination of fibrinogen-fibrin deposition on clinically used Cuprophane by this technique and by autoradiography of the same material following 125I-antifibrinogen-IgG conjugation indicated that the deposition of fibrinogen was heavy and heterogeneous. We concluded that this in situ method may be useful to monitor fibrinogen-fibrin deposition and adsorption of other plasma proteins that occur under in vitro, ex vivo, and in vivo conditions.
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    Journal of Biomedical Materials Research 18 (1984), S. 601-607 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: This study was undertaken to examine the effectiveness of a commercially available n-butyl-2-cyanoacrylate (Histoacryl blueTri-Hawk International, 1570 Barré, Montréal, H4L 4M6 Quebec.) as a local treatment for cutaneous ulcers. Two ulcers, approximately 0.5 cm2 each, were made on the backs of 30 hamsters. The right side was covered with a thin film of tissue adhesive, while the left side was left untreated as a control. Animals were sacrificed at various times post-operatively, the tissue excised, processed, and examined with the light microscope. Results showed that cyanoacrylate decreased the inflammatory exudate early in the experiment, and epithelial migration occurred slightly earlier in experimental tissue. Scab formation was absent in experimental sites until the layer of adhesive was lost. After 2 days, healing was comparable in both experimental and control, and the sites were indistinguishable histologically at day 5.
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    Journal of Biomedical Materials Research 18 (1984) 
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    Journal of Biomedical Materials Research 18 (1984), S. 895-909 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: An alternative to the usual technique of preclotting porous textile vascular prostheses prior to surgical implantation is to render them impermeable to blood by impregnation with a cross-linked albumin filler matrix. This material subsequently becomes the foundation for cellular development. The compatibility of such impregnated fabrics with newly formed endothelial cells has been evaluated by an in vitro organotypic culture method. This technique enables the characterization and numeration of cells that develop on blood contact surfaces and enables determination of their rate of development. Woven, knitted, and velour fabrics were evaluated folllowing coating with albumin and either storage in Tyrode solution or 40% ethanol or desiccation by critical point drying. Preclotted cardiovascular repair fabrics prepared according to conventional surgical protocol served as controls. The identification of the newly formed cells was confirmed histologically. The most extensive and rapid cellular development was observed on the woven fabric and is believed may have resulted from the smoother surface topography of this substrate. Good cellular development was noted particularly on fabrics which had been stored in Tyrode solution. Ethanol had a deleterious effect on the apparent compatibility.
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    Journal of Biomedical Materials Research 18 (1984), S. 695-705 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Human prothrombin in Tyrode's solution, in mock plasma (albumin, fibrinogen, and IgG mixture), and in citrated plasma adsorbs to Cuprophane, polyvinylchloride, and polyacrylonitrile surfaces. The adsorption of prothrombin is maximal in Tyrode's solution and minimal in plasma. The surface concentrations of prothrombin are highest on polyacrylonitrile, second on polyvinylchloride, and lowest on Cuprophane at all prothrombin concentrations tested in the bulk solution. Qualitative tests show that prothrombin adsorbed to polyvinylchloride can be activated by Taipan snake venom to generate thrombin that clots fibrinogen. However, more quantitative tests indicate that only part of the adsorbed prothrombin on all three materials can be activated to form thrombin exhibiting amidolytic activity. The partial reactivity of adsorbed prothrombin is further confirmed by release of 125I-peptide from surface bound 125I-prothrombin after treatment with Australian Taipan snake venom. Prothrombin bound to Cuprophane seems to promote granulocyte adhesion, but has no effect on platelet adhesion.
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    Journal of Biomedical Materials Research 18 (1984), S. 727-736 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: Bovine pericardial tissue and tissue-derived bioprosthesis fixed in glutaraldehyde and stored in either glutaraldehyde or formaldehyde can induce cytotoxic reactions even after prolonged washing due to the slow leaching of the chemicals used for crosslinking and sterilizing. Sequential rinsing for up to 60 min was still not sufficient to eliminate cytotoxic effects. On the other hand, satisfactory results were obtained when cardiac valves made from glutaraldehyde fixed pericardium were stored in a solution containing 0.02% of propyl-hydroxy-benzoate and 0.18% methyl-hydroxy-benzoate. The valves stored in this solution and rinsed three times for 1 min in normal saline showed few signs of residual cytotoxicity. Rinsing in a solution containing glycine was partially effective in neutralizing the cytotoxic effect, and this or similar approaches offer good possibilities. The use of Chang cells grown in culture provides an excellent quantitative assay for the assessment of residual cytotoxicity and for evaluating the host response to different methods of fixation, storage, and rinsing of tissue derived bioprosthesis.
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    Journal of Biomedical Materials Research 18 (1984), S. 771-779 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Few in vitro systems for testing dental restorative materials have taken into account the protection afforded by the residual dentine in vivo. In turn opinions differ as to whether an increase in residual dentine thickness increases this protection. In this study an increase in the depth of dentine powder beneath zinc oxide eugenol (ZOE) reduced its toxicity, while this was not the case with the glass ionomer cement. Compaction of the powder had no effect, suggesting that protection was due to binding of the toxicant to the dentine rather than it acting as a physical barrier. Protein was shown to be very important in moderating the cytotoxicity of ZOE. These results suggest that in vivo the irritancy of some materials may be related to the depth of residual dentine but not others. The effect of exposure period and volume of these materials on their cytotoxicity was also investigated. Increasing the volume of ZOE while retaining the same surface area increased the toxicity of ZOE, while with the glass ionomer it had no effect.
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    Journal of Biomedical Materials Research 18 (1984), S. 881-894 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The macromolecular properties of 17 virgin commercial arterial prostheses and a series of explanted prostheses, both manufactured from poly(ethylene terephthalate) (PET) yarns, have been studied by gel permeation chromatography (GPC) and by differential scanning calorimetry (DSC). Only small differences were found between the average molecular weights and the degree of crystallinity of the unused reference grafts. A broadening of the DSC curves was observed for the prostheses containing texturized yarns compared with those made solely from flat, untexturized yarns. This broadening may be due to greater heterogeneity of the crystal sizes caused by the texturizing process and to the use of two or more different yarns with dissimilar thermal histories in the same prosthesis. Average molecular weights of the explant series were significantly lower than those of the corresponding reference grafts but almost time independent. The polydispersity index and the degree of crystallinity of the explants remained constant as a function of time. These results are discussed in regard to others available in the literature.
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  • 93
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A cage implant system was utilized to quantitatively and qualitatively characterize in vivo leukocyte interactions with cast Biomer. Scanning electron microscopy (SEM) in conjunction with cytochemical staining procedures were used to investigate the cellular events at the leukocyte/Biomer interface as well as in the inflammatory exudate over a 21-day implantation period. SEM was used to characterize leukocyte morphology on the Biomer surface and the cytochemical stains were used to differentially count leukocytes and to demonstrate intracellular alkaline and acid phosphatase activity. The results showed that the population density of leukocytes on the Biomer surface diminished with implantation time. The population density of multinucleated foreign body giant cells remained constant with time, while the numbers of nuclei per giant cell increased. The differential analysis revealed that macrophages preferentially adhered to the Biomer surface compared to other leukocytes in the exudate. The phagocytic capability of all adherent leukocytes, including giant cells, decreased with time and this corresponded to changes in leukocyte morphology observed with SEM.
    Additional Material: 10 Ill.
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  • 94
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    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 18 (1984), S. 1017-1030 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Bioreactive-glass-coated hip prostheses were implanted in dogs for periods of time ranging from 3 to 17 months. The prostheses were tailor-made for each animal through the use of standard radiographs. However, such a procedure does not necessarily yield a close apposition between the glass layer and bone. As a result, the initial stability of the component can be lost before bone bonding is established. Secondary to this phenomenon, the micromotion can lead to a continuous disruption of the top film on the glass despite the evidence of various reaction layers on the glass surface.
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  • 95
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    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 18 (1984), S. 961-968 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Polyurethanes are finding increasing utilization in biomedical applications. Recently, the reported finding of methylene dianiline (4,4′-diaminodiphenylmethane, MDA) in the aqueous extracts of autoclaved 4,4′-diphenylmethane diisocyanatebased polyurethanes promoted our investigation of the origin and extent of extractable methylene dianiline in polyurethanes. A high-pressure liquid chromatography procedure using precolumn derivatization is utilized to selectively monitor the appearance of this diamine in the aqueous extracts of polyurethanes subjected to water immersion, heat aging, and various sterilization techniques. No MDA was found in the aqueous extracts of the treated polyurethane except for the case of prolonged steam autoclaving. The appearance of 3-5 ppb MDA in the extract under these conditions is attributed to hydrolysis of the polymer. The stability of the polyurethanes under most conditions renders these materials useful in biomedical applications.
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  • 96
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The binding of metal ions from salts and from corrosion products of 316 LVM stainless steel and MP-35 to blood cells and serum proteins was studied in vitro. In the first series of experiments, metal salts were added to whole blood and then the blood separated into red cells, white cells, and serum. Nickel from nickel chloride or corrosion products of stainless steel bound in very small quantities to blood cells. Cobalt from cobalt chloride bound to both red cells and white cells. Chromium from chromic chloride (Cr3+) bound to cells in very small quantities whereas chromium from potassium dichromate (Cr6+) and corrosion products showed very high to binding to red cells and some binding to white cells. In a second series of experiments the blood was separated into its components and then the metal salts were added and the binding pattern was identical. In a third series of experiments serum which had interacted with the metal salts or corrosion products was separated into its components by isolectric focusing on polyacrylamide gels. Almost all of the metal, whatever the source, was detected in the albumin region of the gels indicating strong binding to albumin. These studies on the cell and protein binding of the metals help to explain the dissemination of corrosion products from the site of the implant and subsequent systemic responses by some individuals.
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  • 97
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: In an attempt to find an alternative procedure to the preclotting of porous textile vascular prostheses, the feasibility of an albumin coating and ethanol preservation technique has been evaluated by implanting albuminated polyester prostheses as substitutes in the thoracic aorta of dogs. Nine different grafts representing woven, knitted, and velour constructions were implanted for periods ranging from 4 h to 6 months. At the sacrifice, the grafts were excized for measurement of the thrombogenicity of the flow surface, for pathological examination by light microscopy and SEM, and for quantifying the changes in the textile structure during implantation. Also the kidneys were removed and examined for infarcts caused by trapped circulating emboli. The healing characteristics of the nine different grafts proved similar and followed the same sequence of events as preclotted control grafts. The albumin coating and ethanol preservation resulted in a somewhat slower rate of healing. Yet, given sufficient time, a more completely healed graft was achieved as evidenced by the presence of endothelial-like cells throughout the length of the graft. In addition, the albumin is believed to reinforce the textile structure by reducing the tendency to stretch and dilate in vivo.
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  • 98
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    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 18 (1984), S. 1115-1124 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: For intravascular implantation, a biofunctional surface seems to retard surface thrombosis upon synthetic materials. Prostaglandins, like PGI2, PGE1, and PGD2, etc., are believed to stimulate membrane-bound adenyl cyclase and thereby raise intracellular levels of c-AMP within platelets, which inhibit platelet adhesion and aggregation. A new procedure is suggested for the immobilization of prostaglandin E1 on an albuminated polymer matrix, through glutaraldehyde coupling. Materials thus prepared show dramatic antiplatelet effects, with regard to platelet adhesion, when compared with albumin-immobilized surfaces. The affinity of various modified surfaces toward platelet adhesion is studied, using washed platelets suspended in Tyrode's solution. Octane contact angle studies are used to develop an understanding of the varied nature of bound substrates at equilibrium on polymer surfaces. These are studied at the solid/liquid interface, which is closest to in vivo conditions. The plasma recalcification time demonstrates the anticoagulant properties of various surfaces. A possible role of PGE1 in reducing platelet activity in the presence and absence of vitamin C is discussed. This technique may be used in the development of nonthrombogenic surfaces on existing biomedical polymers. Simultaneous pharmaceutical modification of the blood with vitamin C may enhance the blood compatibility of the surface.
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  • 99
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    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 5 (1971), S. 59-74 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Excellent in vivo thromboresistance has been obtained for FEP Teflon and for a polyether urethane prepared with electronegative surfaces using the electret effect. In vitro tissue culture studies have shown a marked improvement in tissue compatibility for negatively electrified Teflon. Studies on other materials, including Hypalon rubber, sulfonate cross-linked Hypalon and Kel F have shown a moderate improvement in blood compatibility. These in vitro and in vivo experiments will be described. Surface physical properties of these electrified materials, including water contact angle and charge, have been measured. Correlations between surface physical measurements and blood compatibility data will be presented.
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  • 100
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    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 5 (1971), S. 105-127 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Flexible and rigid epoxy and urethane polymers containing heparin chemically and uniformly incorporated throughout and/or ionically complexed to quaternized amine grops were prepared and shown to have excellent thromboresistance in vitro and in vivo. These heparin-modified polymers were implanted into the vena cava of dogs and successfully passed multiple acute (2 hr) and chronic (2 week) exposure periods. It was also demonstrated that the chemically coupled heparinized epoxies had no measurable adverse effects on blood cells, platelets, or plasma proteins, and that the heparin was not extractable. Significantly, epoxies containing polyoxypropylene/polyoxyethylene glycol (an additive which had no thrombus-inhibiting properties of its own) also exhibited excellent thromboresistance when characterized in vivo in dogs. The applicability of these various materials for the fabrication of circulatory assist device components was demonstrated. The effect of polymer polarity, surface charge, and conductivity were investigated with indeterminate results and unmodified commercial polymers uniformly exhibited poor clotting characteristics. In vitro clot-inhibiting characteristics were shown to be a sufficient, but not necessary, condition for indicating in vivo thromboresistant activity in polymer systems.
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