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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 10 (1972), S. 82-90 
    ISSN: 1432-0827
    Keywords: Calcium ; Phosphate ; Precipitation ; Kinetics ; Chemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé La cinétique de la formation et de la transformation des précipités de phosphate de calcium, obtenus en mélangeant de volumes égaux de solutions à 6×10−3 M de calcium total et/ou phosphate total est étudiée à 25°C. Les solutions de phosphate sont préajustées à un pH de 7.4. Les changements de pH et de turbidité des solutions sont suivis simultanément en fonction du temps. Les précipités sont isolés à des intervalles de temps variables et caractérisés par diverses méthodes physico-chimiques. Initialement un précipité avec un rapport molaire Ca/P de 1.5, amorphe aux rayons X et en diffraction électronique, est formé. Le spectre IR indique la présence de PO 4 3− et de HPO 4 2− . Après une période métastable, on observe la précipitation d'un matériel cristallin dans ou sur la phase amorphe. Vingt quatre heures après préparation de l'échantillon les précipités présentent surtout les caractères du phosphate octocalcique.
    Abstract: Zusammenfassung Die Kinetik der Bildung und Transformation von Calciumphosphat-Niederschlägen wurde bei 25°C untersucht. Es wurden dazu gleiche Volumen von Lösungen gemischt, bei einer Konzentration von 6×10−3M totales Calcium und/oder totales Phosphat. Die Phosphatlösungen wurden zuerst auf pH 7,4 eingestellt. Veränderungen des pH und Trübung der Lösungen wurden gleichzeitig als eine Funktion der Zeit aufgezeichnet. Niederschläge wurden in verschiedenen Zeitintervallen isoliert und mit verschiedenen physiko-chemischen Methoden charakterisiert. Am Anfang wurde ein Niederschlag mit einem molaren Ca/P-Verhältnis von 1,5, im Röntgenbild und in der Elektronendiffraktion amorph, gebildet. Infrarotspektren deuteten die Anwesenheit von PO 4 3− - und HPO 4 2− -Ionen an. Nach einer metastabilen Periode erfolgte ein Niederschlag aus kristallinem Material innerhalb oder auf der amorphen Substanz. 24 Std nach der Herstellung der Proben zeigten die Niederschläge in der Hauptsache die Charakteristiken von Octocalciumphosphat.
    Notes: Abstract The kinetics of the formation and transformation of calcium phosphate precipitates obtained by mixing equal volumes of solutions, 6×10−3 M in total calcium and/or total phosphate was investigated at 25°. The phosphate solutions were preadjusted to pH 7.4. Changes of the pH and turbidity of the solutions were followed simultaneously as a function of time. Precipitates were isolated at various time intervals and characterized by different physicochemical methods. Initially a precipitate with a molar Ca/P ratio of 1.5, amorphous to X-ray and electron diffraction was formed. IR spectra indicated the presence of PO 4 3− and HPO 4 2− ions. After a period of metastability, precipitation of a crystalline material within or upon the amorphous matter occurred. Twenty four hours after sample preparation the precipitates showed mainly the characteristics of octacalcium phosphate.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 16 (1974), S. 145-152 
    ISSN: 1432-0827
    Keywords: EHDP ; Bone ; Chemistry ; Serum ; Rabbits
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract The effects of disodium ethane-1-hydroxy-1,1-diphosphonate (EHDP) on bone and serum chemistry were investigated in adult rabbits. EHDP was administered by subcutaneous injection at doses of 0.25, 2.5 and 10 mg/kg body weight/day for of 28 days. Blood samples were obtained weekly from each rabbit and serum levels of total calcium, ionized calcium, inorganic phosphate and alkaline phosphatase were determined. At the end of the treatment period all rabbits were sacrificed and the tibiae removed for chemical analysis and histological evaluation. The effect of EHDP administration on serum chemistry was both dose- and time-related. The highest of the three doses, 10 mg/kg/day, resulted in a time-related decrease in total serum calcium. This dose also caused a rapid but transient reduction in serum ionized calcium. The effect of EHDP on serum inorganic phosphate was biphasic. Administration of 2.5 mg/kg/day resulted in a time-related elevation in this parameter, whereas the 10 mg/kg/day dose resulted in a time-related hypophosphatemic response. There were no significant drug-related changes in tibial fat-free dry weight, ash weight, total calcium or total phosphorus values. However, administration of 2.5 and 10 mg/kg/day EHDP resulted in increased osteoid tissue as measured histologically. These results are compared with data from other EHDP studies, and discussed in relation to the maturity and growth-state of the experimental animals.
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  • 3
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    Springer
    Calcified tissue international 23 (1977), S. 13-17 
    ISSN: 1432-0827
    Keywords: Dental calculus ; Glycopeptide ; Chemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary A method is described for the isolation and purification of a sulphated glycopeptide from human supragingival calculus. The compound was isolated after using EDTA treatment, 2 M CaCl2 extraction, proteolytic digestion, ethanol precipitation, and finally purified by DEAE cellulose chromatography. It migrated as a single component on cellulose acetate electrophoresis, and chemical and infrared spectral analysis showed the presence of covalently attached sulphate groups. The sulphated glycopeptide was distinguished from being a sulphated glycosaminoglycan.
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  • 4
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    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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  • 5
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    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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  • 6
    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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  • 7
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    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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  • 8
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    Calcified tissue international 8 (1971), S. 304-319 
    ISSN: 1432-0827
    Keywords: Chemistry ; Calcium ; Phosphate ; Solubility ; Computer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Un programme d'ordinateur a été mis au point pour calculer les activités ioniques du calcium et l'orthophosphate dans un grand nombre de solutions. Dans le cas de solutions synthétiques, les calculs sont vérifiés en comparant les valeurs de pH, obtenues par ordinateur, avec celles observées expérimentalement. Des essais de ce type, avec des solutions possèdant des concentrations de calcium et d'orthophosphate trouvées dans les liquides biologiques et à des valeurs de pH variant de 3.00 à 10.00, indiquent que le programme est adapté pour des applications biologiques. Le programme n'est pas effectif pour des solutions, dans les lesquelles l'ion bromure est la source principale de la force ionique, sans doute, par manque d'équation étendue de Debye-Hückel dans ces circonstances. Aucune formation de complexe de phosphate de sodium n'a été notée à des concentrations biologiques normales.
    Abstract: Zusammenfassung Es wurde ein Computer-Programm ausgearbeitet, um die Ionenaktivitäten von Calcium und Orthophosphat in einer breiten Varietät von Lösungen zu berechnen. Die Berechnungen wurden bei synthetischen Lösungen durch Vergleiche zwischen den auf diese Weise errechneten pH-Werten und den experimentell gefundenen kontrolliert. Diese Art Kontrollen mit Calcium-und Orthophosphatkonzentrationen, wie sie in biologischen Flüssigkeiten gefunden werden, und mit pH-Werten zwischen 3,0 und 10,0 wies darauf hin, daß das Programm für biologische Anwendungen geeignet war. Das Programm konnte nicht benützt werden für solche Lösungen, bei welchen hauptsächlich das Bromidion zur Einstellung der Ionenstärke verwendet wurde, vermutlich weil die erweiterte Debye-Hückel-Gleichung unter diesen Umständen nicht anwendbar ist. Die Bildung eines Natriumphosphat-Komplexes unter normalen biologischen Konzentrationen konnte nicht nachgewiesen werden.
    Notes: Abstract A computer program has been designed to calculate the ionic activities of calcium and orthophosphate in a wide variety of solutions. In the case of synthetic solutions the calculations were checked by comparing the computed pH values with those observed experimentally. Tests of this type with solutions having the concentrations of calcium and orthophosphate found in biological fluids and with pH values ranging from pH 3.0–10.0 indicated that the program was suitable for biological applications. The program was not effective for solutions in which the bromide ion was a principal source of ionic strength probably because of the failure of the extended Debye-Hückel equation under those circumstances. No evidence for the formation of any sodium phosphate complex at normal biological concentrations could be found.
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  • 9
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    Calcified tissue international 10 (1972), S. 171-197 
    ISSN: 1432-0827
    Keywords: Amorphous ; Crystalline ; Calcium phosphate ; Chemistry ; Composition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Des échantillons non lavés de phosphate de calcium amorphe (ACP) contiennent une fraction labile, non remplaçable, riche en phosphate acide avec un rapport Ca/P faible: cette fraction est perdue de façon irréversible au cours du lavage. De l'ACP frais, précipité entre pH 6.6–10.6, varie dans un rapport molaire Ca/P de 1.18 à 1.50 et dans un rapport HPO 4 2− /P total de 33.0% à 10.1%. A pH 7.40, de l'ACP frais a un rapport molaire Ca/P de 1.36±0.02 et contient 22.8 (±2.2)% HPO 4 2− . Les résultats obtenus avec du précipité non lavé ne peuvent s'expliquer par du Ca2+ emprisonné et de l'HPO 4 2− ou du Na+, Cl− et CO 3 2− exogènes. Les phosphates de calcium amorphes constituent une classe de sels ayant des caractères chimiques variables et des propriétés physiques identiques, comparables au verre. Le CaHPO4·xH2O non cristallin peut être un ACP, surtout au cours des phases précoces de formation. A des pH physiologiques, l'ACP se transforme en petits cristaux applatis contenant de fortes quantités de phosphate acide facilement remplaçable. Le fait de laver la couche de surface produit un changement chimique dans les nouveaux cristaux: des cristaux non lavés donnent des diagrammes de diffraction d'apatite peu cristallins, ainsi que des spectres infra-rouges peu nets, intermédiaires entre des apatites et du phosphate octocalcique. Des explications structurales sont proposées et les compositions minérales amorphe/cristalline de l'os et du cartilage sont recalculées.
    Abstract: Zusammenfassung Ungewaschene Proben von amorphem Calciumphosphat (ACP) enthalten eine unersetzliche labile Fraktion, welche reich an saurem Phosphat ist und ein niederes Ca/P-Verhältnis hat und welche während des Waschprozesses unwiderruflich verloren geht. Natives ACP, welches im pH-Bereich 6,6–10,6 ausgefällt wurde, variierte im molaren Ca/P-Verhältnis zwischen 1,18 und 1,50 und in HPO 4 2− /totales P zwischen 33,0 und 10,1%. Bei pH 7,40 hatte natives ACP ein molares Ca/P-Verhältnis von 1,36±0,02 und enthielt 22,8 (±2,2)% HPO 4 2− . Die Werte beim ungewaschenen Niederschlag rühren weder von aus dem Überstand aufgenommenem Ca2+ und HPO2−, noch von außen kommendem Na+, Cl− und CO 3 2− her. Die amorphen Calciumphosphate werden als eine Klasse von Salzen erkannt, welche veränderliche chemische, aber identische glasartige physicochemische Eigenschaften haben. Nicht kristallines CaHPO4·xH2O kann auch ein ACP sein, besonders in den frühen Bildungsstadien. Bei physiologischem pH verwandelt sich ACP in kleine plattenförmige Kristalle, welche große Mengen von leicht ersetzbarem saurem Phosphat enthalten. Das Waschen dieser Oberflächenschicht erzeugte chemische Veränderungen in den resultierenden Kristallen; ungewaschene Kristalle zeigten ein Diffraktionsmuster, das nur schwach demjenigen des kristallinen Aspatites glich, aber ein schlecht aufgelöstes Infrarotspektrum, welches zwischen Apatit und Octocalciumphosphat war. Es werden strukturelle Erklärungen für alle diese Phenomena diskutiert, und revidierte amorph/kristalline Mineralzusammensetzungen von Knochen und Knorpel wurden neu berechnet.
    Notes: Abstract Unwashed samples of amorphous calcium phosphate (ACP) contain an irreplaceable labile fraction, rich in acid phosphate and low in Ca/P ratio, which is irreversibly lost during the washing process. Native ACP precipitated in the pH range 6.6–10.6 varied in Ca/P molar ratio from 1.18 to 1.50 and in HPO 4 2− /total P from 33.0% to 10.1%. At pH 7.40, native ACP had a Ca/P molar ratio of 1.36±0.02 and contained 22.8 (±2.2)% HPO 4 2− . Unwashed precipitate data could not be attributed to either trapped supernatant Ca2+ and HPO 4 2− or extraneous Na+, Cl−, and CO 3 2− . The amorphous calcium phosphates are recognized as a class of salts having variable chemical but identical glass-like, physicochemical properties. Non-crystalline CaHPO4·xH2O may also be an ACP, especially during early formative stages. At physiological pH, ACP transforms to small platy crystals containing large amounts of readily-replaceable acid phosphate. Washing this surface layer produced chemical alterations in the resultant crystals; unwashed crystals had poorly-crystalline apatitic diffraction patterns but exhibited poorly-resolved infrared spectra intermediate between apatite and octacalcium phosphate. Structural explanations for all these phenomena are discussed, and revised bone and cartilage amorphous/crystalline mineral compositions have been re-calculated.
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  • 10
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    Calcified tissue international 23 (1977), S. 39-44 
    ISSN: 1432-0827
    Keywords: Dental cementum ; Collagen ; Protein ; Chemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Cyanogen bromide (CNBr) peptides were prepared of the insoluble collagen of bovine dental cementum. Following chromatographic separation, the peptides were identified by their amino-acid composition. Type I collagen ([α1(I)]2α2) accounted for more than 90% of the organic matrix, while Type III collagen ([α1(III)]3) was present at a level of approximately 5%. Amino-acid analyses revealed that the CNBr peptides from α1(I) and α2 chains of cementum closely resembled the corresponding peptides from calf skin. The only systematic difference was a higher level of hydroxylation of prolyl and lysyl residues of the cementum peptides.
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  • 11
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    Calcified tissue international 23 (1977), S. 87-94 
    ISSN: 1432-0827
    Keywords: Calcium ; Osteoporosis ; Lactation ; Chemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The calcium homeostatic mechanism was challenged in adult female rats by feeding them a calcium-deficient diet containing oxalate, and by subjecting them to pregnancy and lactation. The regimen caused a substantial weight loss, especially in those animals which reared their young well. Severe hypocalcaemia was observed in the lactating rats. Serum-P was slightly elevated. The content of hydroxyproline in serum was considerably elevated, reflecting the degree of calcium deprivation. Serum proteins were least influenced. The calcium depriving regimen reduced the growth of long bones, but did not stop it. The ash content of the bones was considerably reduced, the degree of reduction depended on the degree of calcium deprivation. Ash as percentage of total bone organ was reduced, but not to the same extent as total ash. Analyses of different parts of femur showed that the proximal and distal parts had lost more bone mineral than the diaphyseal shaft. The ash content of cortical bone tissue from the femur was estimated by a volumetric method. No differences were observed between test groups and controls, indicating that no measurable amounts of bone mineral had been removed from the walls of the vascular canals or by osteocytic osteolysis. Planimetric determinations on cross sections from femora disclosed that a great amount of bone had been removed from the endosteal surface of the diaphysis, while the periosteal surface demonstrated reduced bone apposition.
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  • 12
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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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  • 13
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    Calcified tissue international 12 (1973), S. 125-136 
    ISSN: 1432-0827
    Keywords: Mineralization ; Molt ; Isopod ; Chemistry ; Light microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Au cours de la phase inhabituelle de mue d'un isopode d'eau courante,Lirceuts brachyrus, la moitié postérieure de l'exosquelette est éliminée 24 heures avant la moitié antérieure. A ce stade, une reminéralisation se développe dans la partie postérieure alors que la partie antérieure est dans un stade de pré-mue. Le pourcentage de différence en calcium dans les deux moitiés à mi-mue et mue complète est respectivement de 22% (p〈0.01) et 33% (p〈0.01), indiquant une complexation du calcium pendant la mue. La rapidité de la reminéralisation est illustrée par le fait que le contenu minéral total double dans la partie postérieure entre la mi-mue et la mue totale et dans la partie antérieure entre la fin de la mue et un jour après. Le carbonate de calcium, sous forme de calcite, a pu être identifié par diffraction électronique de coupes fines des téguments.
    Abstract: Zusammenfassung Während der ungewöhnlichen Häutungssequenz des Frischwasser-IsopodenLirceus brachyurus (Harger) wird die hintere Hälfte des äußeren Skeletts 24 Std vor der vorderen Hälfte abgestoßen. In der halbgehäuteten Phase erfolgt Remineralisation im hinteren Teil, während der vordere Teil in einem Vorhäutungszustand ist. Der prozentuale Unterschied des Calciums in den zwei Hälften bei Halb- und Vollhäutungszustand ist 22% (p〈0,01) bzw. 33% (p〈0,01), was andeutet, daß Calcium während der Häutung abgesondert wird. Die Geschwindigkeit der Remineralisation erhellt aus der Tatsache, daß sich der Gesamtmineralgehalt im hinteren Teil zwischen Halt- und Vollhäutung, in der vorderen Hälfte jedoch zwischen Endhäutung und einem Tag nach der Häutung verdoppelt. Calciumcarbonat in kristalliner Calcitform wurde mittels Elektronendiffraktion von dünnen Hautschnitten nachgewiesen.
    Notes: Abstract During the unusual molt sequence of the fresh-water isopod,Lirceus brachyrus (Harger), the posterior half of the exoskeleton is shed 24 hours before the anterior half. At the half-molt stage, occurs in the posterior part while the anterior portion is in a pre-molt condition. The percentage difference in calcium in the two halves at half-molt and full-molt is22 (p〈0.01) and33 (p〈0.01) respectively, an indication that calcium is sequestered during The rapidity of remineralization is illustrated by the fact that the total mineral content doubles in the posterior part between half and full molt and in the anterior half between the end of molt and one day after ecdysis. Calcium carbonate in the calcite cystalline form was demonstrated by electron diffraction of thin sections of the integument.
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  • 14
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    Calcified tissue international 13 (1973), S. 259-270 
    ISSN: 1432-0827
    Keywords: Fluorapatite ; Exchange ; Chemistry ; Crystallography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Un échantillon minéral provenant de Burgess, Canada s'est révélé être un speciment exceptionnellement pur de fluoroapatite après analyse chimique et cristallographique. La composition globale de cet échantillon est la suivante: $$(Ca^2 )9.98(Sr^{2 + } ,Na^ + ,K^ + ,Mg^{2 + } )0.02(PO_4^{3 - } )5.98(HCO_3^ - ,CO_3^{2 - } )0.02(F^ - )2$$ . L'axe cristallographique C est de 6.865 A et l'axe a de 9.374 A. Des expériences d'échanges réalisés à l'aide de45Ca,32P et18F indiquent la présence de gros cristallites de surface spécifique de l'ordre de 1 m2/g. Il apparait que l'interprétation physique des processus d'échange ne nécessite pas l'existence de compartiments séparés, avec chacun son propre facteur cinétique, les échanges semblent être simplement liés à un changement exponentiel dans l'énergie libre de la réaction. Pour la réaction suivante: $$(Ca)_5 (PO_4 )_3 OH solide + (F^ - ) \rightleftarrows (Ca)_5 (PO_4 )_3 F solide + (OH^ - )$$ , la constante thermodynamique de 101.26 a été calculée, suggérant que le fluorapatite se forme toujours aux dépens de l'hydroxyapatite dans des conditions physiologiques. Cette transformation se continue en abaissant le pH.
    Abstract: Zusammenfassung Eine Mineralprobe aus Burgess, Kanada, erwies sich nach chemischer und kristallographischer Analyse als außergewöhnlich reines Fluorapatit. Die Gesamtzusammensetzung entspricht: $$(Ca^{2 + } )_{9,98} (Sr^{2 + } ,Na^ + ,K^ + ,Mg^{2 + } )_{0,02} (PO_4^{3 - } )_{5,98} (HCO_3^ - ,CO_3^{2 - } )_{0,02} (F^ - )_2 $$ . Die kristallographische c-Achse wurde bestimmt und ergab 6,865 Å, und die a-Achse ergab 9,374 Å. Austauschwerte, welche durch Anwendung von45Ca,32P und18F erhalten wurden, deuteten auf große Kristalliten mit einer spezifischen Oberfläche von ca. 1 m2/g. Die Befunde deuten darauf hin, daß für die physikalische Erklärung des Austauschvorganges keine separaten Kompartimente mit eigenen kinetischen Faktoren nötig sind, sondern daß der Austausch mit dem exponentiellen Wechsel in der freien Energie der Reaktion in einfacher Beziehung steht. Für die Reaktion $$(Ca)_5 (PO_4 )_3 OH_{in fester Form} + (F^ - ) \rightleftarrows (Ca)_5 (PO_4 )_3 F_{in fester Form} + (OH^ - )$$ wurde als thermodynamische Konstante 101,26 errechnet, was darauf deutet, daß unter physiologischen Bedingungen immer Fluorapatit auf Kosten von Hydroxyapatit entsteht. Diese Umwandlung wird erhöht, wenn das pH erniedrigt wird.
    Notes: Abstract A mineral specimen from Burgess, Canada, proved upon chemical and crystallographic analyses to be an exceptionally pure sample of fluorapatite. The over-all composition corresponds to $$(Ca^{2 + } )_{9.98} (Sr^{2 + } ,Na^ + ,K^ + ,Mg^{2 + } )_{0.02} (PO_4^{3 - } )_{5.98} (HCO_3^ - ,CO_3^{2 - } )_{0.02} (F^ - )_2 $$ . The crystallographic c-axis was determined to be 6.865 Å, and the a-axis 9.374 A. Exchange data obtained by employing45Ca,32P, and18F indicate the presence of large crystallites with a specific surface of the order of 1 m2/g. It is indicated that the physical interpretation of the exchange process does not require the existence of separate departments, each with its own kinetic factor, but that the exchange may be simply related to the exponential change in the free energy of the reaction. For the reaction $$(Ca)_5 (PO_4 )_3 OH_{solid} + (F^ - ) \rightleftarrows (Ca)_5 (PO_4 )_3 F_{solid} + (OH^ - )$$ the thermodynamic constant has been calculated to be 101.26, implying that fluorapatite always will form at the expense of hydroxyapatite under physiologic conditions. This transformation will be furthered by lowering the pH.
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  • 15
    ISSN: 1432-0827
    Keywords: Bacterial amphophile ; Purification ; Chemistry ; Resorption ; Ca influx ; Cyclic AMP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The bone resorptive factor and amphipathic antigen (AcA) previously identified by us in preparations fromActinomyces viscosus have been partially purified, characterized chemically, and compared. They elute at the same location on chromatography with Ac 22. The fatty acid composition of AcA and the bone resorptive factor is the same. Some differences in carbohydrate composition are observed. TheActinomyces factor does not affect calcium influx or cyclic AMP in isolated bone cells. Therefore it is concluded that AcA stimulates resorption either by gaining entrance into bone cells or by way of a yet undetermined second messenger.
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  • 16
    ISSN: 1432-0878
    Keywords: Milk ; Fat globule membrane ; Carbohydrates ; Chemistry ; Ruthenium red ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The fat globules of the cream fractions of human and rat milk were stained with ruthenium red. Under the electron microscope, discrete granules and an amorphous coat of lesser density are seen at the surface of the milk fat globules. Since ruthenium red binds anionic groups selectively, it is probable that the granules containe the greatest concentration of these groups. The cream fraction of rat milk contains hexoses, hexosamines, methylpentoses and sialic acid. Methylpentoses and hexosamines are significantly enriched in the cream fraction. It is concluded that the finding of a surface coat in milk fat globules is in keeping with the Bargmann-Knoop model and suggests a distinct mechanism for carrying certain complex carbohydrates in milk. The role of the negative charges at the outer surface of the membrane coat in maintaining fat globules in suspension and in binding certain cations such as calcium is suggested.
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  • 17
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    Journal of Applied Biomaterials 2 (1991), S. 211-212 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
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  • 18
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    Journal of Applied Biomaterials 2 (1991), S. 213-213 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
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  • 19
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    Journal of Applied Biomaterials 2 (1991) 
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    Keywords: Chemistry ; Polymer and Materials Science
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  • 20
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    Journal of Applied Biomaterials 2 (1991), S. 215-215 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
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    Journal of Applied Biomaterials 2 (1991), S. 217-217 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
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  • 22
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    Journal of Applied Biomaterials 2 (1991), S. 219-229 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: We have developed a bioactive bone cement using CaO—SiO—2—P2O5—CaF2 glass powders and ammonium phosphate solution, and investigaed ist histological and mechanical characteristics in vivo. A bone defect was drilled in the proximal metaphysis of the rat tibia and filled with the bioactive bone cement in paste form or polymethylmethacrylate (PMMA) bone cement in the dough state. The cements were allowed to harden in situ. Histological examinationdemonstrated direct bonding between the new cement and bone by 4 weeks. The bioactive bone cement did not degrade up to 24 weeks postimplantation. The inflammatory reaction to the bioactive bone cement was less intense than the reaction induced by PMMA. Changes in the mechanical properties of the cement in vivo were studied by implanting hardened cylindrical specimens of both types of cement into the hindlimb muscles of ras of rats for 12 weeks. The compressive strength of the bioactive cement increased significantly after implantation, and reached 68 MPa in 1 week and 73 MPa in 4 weeks. These values were comparable to those of PMMA, and were maintained up to 12 weeks after implantation. This bioacive bone cement hadens in situ within a few minutes with negligible rise of temperature and can be easily handled as a paste for filling bone cavities of different shapes. In addition, this cement has good osteoconductive and bone bonding potential and fairly high mechanical strength. Therefore, this new cement could be used both as a bioactive bone cement and bone defect filler.
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  • 23
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    Journal of Applied Biomaterials 2 (1991), S. 241-242 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: It is common experience that carbon fiber braids, which are passed through osseous tunnels, are not incorporated by osteointergration. Rather, they are separated from the boy walls of the tunnels by a granulomatous-cicatrizing interface membrane. In the exceptional case, however, Bony ingrowth into the braid occurs without an intervening soft tissular layer. Bony ingrowth may be contingent on the stability of the carbon fiber braid within the osseous tunnel.
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  • 24
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    Journal of Applied Biomaterials 2 (1991), S. 231-239 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Bioactive glass powders, with a composition of SiO2-CaO-P2O5,have been successfully synthesized via a sol-gel process at considerably loer temperatures than required for conventional melting method. Bioactive glass powders made via conventional methods form an interfacial bond wih none when they are implanted. Bonding is correlated with the formation of a surface hydroxyapatite layer. This study examinded the formation of a hydroxyapatite layer in Tris-buffered solution as a function of SiO2 content of sol-gel derived powders. A FT-IRRS technique was used to monitor the formation of the hydroxyapatite on the surface of the powders. X-ray diffraction analysis and BET were also used to characterize the chemical and physical properties of the sol-gel derived bioactive powders. It was discovered that: (a) the rate of hydroxyapatite formation decreased wih increasing SiO2 content for powders whose SiO2 content was less than 90 mol%; (b) a hydroxyapatite film does not form for the powders whose SiO2 content is more than 90 mol%; (c) the SiO2 limit, beyond which the powders lost their bioactivity, was much higher for bioactive glass powders mad through sol-gel process (90%) than those made by conventional melting methods (60%). These results indicate that it is possible to significantly expand the bioactive composition range through microstructural control made possible by sol-gel processing techniques.
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  • 25
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    Journal of Applied Biomaterials 2 (1991), S. 243-250 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Classically, calcium hydroxide is used as a pulp capping agent in humans to form a dentinal bridge over vital dental pulp tissue. The aim of the present study was to determine whether synthetic hydroxyapatite could be used as a substitute. For this purpose, pulp capping with microsized hydroxyapatite (mean size = 38 nm ± 15 nm) was done under lacal anesthesia in 12 normal premolars, to be extracted for orthodontic purposes form 12 different young patients, having given their informed consent. Clinically, the healing was uneventful in all patients, having given their informed consent. Clinically, the healing was uneventful in all patients. Half of the teeth were extracted at 3 months and the other half at 6 months. The pulps were studied under light microscopy and under scanning and transmission electron microscopy using nondecalcified sections. In all cases, a continuous, well-calcified bridge was observed and no inflammatory cells were present in the residual pulp. In some cases denticles containing some synthetic hydroxyapatite crystals were found in the radicular pulp. The calcified bridge was made up by osteodentine and near the pulp tubular dentine with a layer of predentine and odontoblasts were noted. Odontoblastic processes were lacated in deninal tubules and the intertubular dentine showed interwoven calcified collagen fibrils and hydroxyapatite crystals with a mean length of 0.1 μm along their c axis.
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  • 26
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    Journal of Applied Biomaterials 2 (1991), S. 251-259 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A novel biotechnology is introduced by way of the successful synthesis of nanocrystalline Epstein-Barr virus (EBV) decoys having specific in vivo immunogenie activity. Assembled from ultrafine suface modified tin oxide and purified DNA-free isolated EBV envelope proteins, the decoys consisted of 〉150 nm units whose electophoretic mobilities were similar to whole EBV; whose outer coats were strongly immunoreactive with murine monoclonal anti-EBV antibodies; and which elicited immunospecific niutralizing anti-EBV antibodies in the rabbit. The development of this carier techonology for vaccine preparations is suggested.
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  • 27
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    Journal of Applied Biomaterials 3 (1992), S. 51-57 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A new formulation of acrylic bone cement [methylmethacrylate/n-decylmethacrylate/isobornylmethacrylate (MMA/DMA/IBMA)] developed with the purpose of reducing the biologic adverse effects of bone cements was analyzed by high performance liquid chromatography for residual content of monomers and aromatic amines from the accelerator system [dimethyl-p-toluidine (DMPT), dihydroxypropyl-p-toluidine (DHPPT)] in the cured cement and for concentrations of these constituents in hydrophilic and lipophilic eluates. In comparison with conventional polymethyl-methacrylate acrylics a considerable reduction of both released and residual MMA was experienced, being about 10- to 15-fold. The residual content of the new DMA and IBMA monomers were 0.35% and 0.66%, respectively, in cured cement after 72 h and these could only be detected in the paraffin eluates. The residual content of aromatic amines was considerably reduced with the new cement formulation. No DMPT could be detected and the DHPPT represented a 3- to 4-fold reduction in cured cement and a 8- to 10-fold reduction in eluates. The residual DHPPT content of about 0.07% was found to be practically constant with time. It is concluded that MMA/DMA/IBMA cement cures faster and more completely.
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  • 28
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Recent studies have established that a mechanism of initiation of failure of fixation of cemented femoral components is debonding of the cement-metal interface. Other studies have shown that the torsional forces induced by stair climbing and rising from a chair are very high. Thus, the interface between the femoral prosthesis and the bone cement in total hip arthroplasty (THA) is required to transmit high torsional loads from the metal to the cement in a cyclic shear mode many times per year. These torsional loads likely contribute to the debonding. This study evaluated the efficacy of a thin layer of polymethylmethacrylate (PMMA) precoating in increasing the torsional fatigue strength of the cement-metal interface. Fatigue studies were performed on 15 specimens. Each specimen was tested with and without PMMA precoating. The PMMA precoat significantly and substantially increased the torsional fatigue strength of the cement-metal interface. Thus, PMMA precoating is likely to be a clinical advantage in maintaining the long-term integrity of the cement-prosthesis interface.
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  • 29
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    Journal of Applied Biomaterials 3 (1992), S. 63-71 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
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  • 30
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    Journal of Applied Biomaterials 1 (1990), S. 215-216 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Various x-ray contrast materials, barium sulphate (BaSO4) and zirconium oxide (ZrO2), were tested for their radioactivity by means of a gamma spectrometer. While BaSO4 showed no detectable radiation emission, the ZrO2 materials of various makes showed slight to partially high radioactive emission. From all zirconium oxides, only the pharmaceutic agent OPTIPUR® (MERCK) showed no detectable radioactivity. Taking into account that these x-ray contrast materials remain in the body for decades as components of the bone cement, it would seem prudent to urge cement manufacturers to substitute high purity radiation-free zirconium in place of radioactive zirconium oxide.
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  • 31
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    Journal of Applied Biomaterials 4 (1993), S. 231-240 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Because of the importance of complement activation in the induced activation of leukocytes in vivo, determination of complement-activating capacity of a candidate biomaterial is an important step in evaluating its biocompatibility. In vitro evaluation can be performed in the presence of human serum by means of techniques described in the literature and reviewed in this paper. Certain physical and chemical parameters involved in complement activation by materials have to be assessed: the chemical composition of the surface, surface area in contact with serum, temperature and duration of contact, and ionic environment with emphasis on divalent ions. Concerning materials evaluation, the adsorption of complement proteins or protein fragments has to be determined in addition to activation. Following screening tests using CH50 determination, activation of both classical and alternative pathways leading to formation of C3 convertases and formation of C5 convertase should be assessed. An example of the determination of the complement-activating capacity of two hydroxylated materials is presented and guidelines for in vitro evaluation are proposed. © 1993 John Wiley & Sons, Inc.
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  • 32
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    Journal of Applied Biomaterials 4 (1993), S. 241-247 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The purpose of this study was to determine the influence of the surgeon's tying techique on knot security using 0 and 2-0 monofilament and multifilament nylon sutures. Using an Instron® Tensile Tester and a portable tensiometer, knot security was achieved with these sutures using four-throw square knots (1=1=1=1). After didactic and psychomotor skill training, medical students were taught to construct the four-throw square knot using either a two-hand tie or an instrument tie. Using the portable tensionmeter, their knot tying techniques were judged to be superior to those used by surgeons. The surgeon's faulty technique can easily be corrected by didactic information and psychomotor skill training. © 1993 John Wiley & Sons, Inc.
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    Journal of Applied Biomaterials 2 (1991), S. 41-48 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: In vitro transmucosal permeation of (14C)-dibutyl phthalate [(14C)DBP], across intact mucosal hamster tissue compared to keratin-stripped mucosal tissue indicated no significant difference (p ≈ 0.069) in (14C)-DBP. However, significantly greater (p 〈 0.022) DBP was found to be concentrated in the keratin-stripped after a period of 6 h. The amount of (14C)-DBP permeating both tissues followed a similar linear increase for next 3 h. However, between 3 and 4 h, the rate of permeation through the untraumatized tissue significantly decreased. This was followed by a rapid linear increase for the next 3 h. In contrast, the cumulative amount of (14C)-DBP permeating the traumatized tissue showed a linear correlation (r = 0.995) over the 6-h period. A theoretical two-layer model was constructed to allow computer simulations of the (14C)-DBP permeation. It was indicated that an average diffusion coefficient for a single DBP molecule through the intact keratin layer would be ∼ 100 times less than through the remaining layer of the model. The model has enabled a possible explanation to be put forward, describing the role of the keratin layer in the permeation of plasticizer mucosal tissue.
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  • 34
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    Journal of Applied Biomaterials 2 (1991), S. 49-54 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Heat generated by tooth reduction and restoration procedures may be harmful to the pulp. Water spray during those procedures aids in maintaining lowered pulpal temperatures. A device that lowers intrapulpal temperatures has been developed and tested in an animal model. The animal's pulp chamber temperatures were lowered to 15.5°C and 12.4°C and maintained at those temperatures for 20 min. Histological examination disclosed no inflammatory reaction to the testing. Therefore, this device may aid in reducing the trauma of dental preparation procedures as well as other effects of lowered temperature on the biology of the dental pulp.
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  • 35
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    Journal of Applied Biomaterials 2 (1991), S. 59-60 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The purpose of my column is to provide readers with current information on biomaterials-related standards produced by both private groups and government agencies, and standards-related activities. Standards are descriptive documents given official status by their producers, and in the case of biomaterials, they are generally intended to provide formalized descriptions of (a) materials used in the construction of medical devices, (b) materials used directly in surgical repairs, (c) test methods to evaluate materials for such applications, and (d) methods for handling or processing such materials.Please consider this column not only a place to obtain biomaterials standards information, but also a place to submit news of biomaterials standards developments in order to get the information before the public. This invitation extends to members of all professional organizations and government agencies in the United States and abroad who are active in standards development and would like specific activities or standards publicized. I will present the information in this column to the extent that allotted space allows.And last, a caveat - since this is a column, it contains both factual information and opinions. I will make every effort to make it clear which is which. Also, as a frame of reference, please note that this column was written and submitted in November 1990.
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  • 36
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    Journal of Applied Biomaterials 2 (1991), S. 67-72 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Poly(vinyl alcohol) (PVA) microspheres impregnated with barium sulphate and methyl iothalamate, having diameters raning from 100 to 1500 μm were prepared by the glutaraldehyde cross-linking of an aqueous dispersion of PVA containing the radiopaques in paraffin oil using dioctyl sulfosuccinate (DOS) as the stabilizing agent and thionyl chloride as the catalyst. while the use of thionyl chloride allowed the formation of spherical, nonaggregatory beads, other catalysts such as magnesium chloride and hydrochloric acid gave rise to an agglomerated product. The radiopaques were found to be firmly trapped inside the microspheres as they did not leach out on prolonged standing in water, on sonication, or on steam sterilization. Microspheres with pores and channels were also made by incorporating a fine powder of methyl methacrylate along with barium sulphate during their preparation and washing out the polymer after the microspheres were formed. The porous nature of such microspheres was confirmed by transmission electron microscopy (TEM). Microspheres containing the radiopaques exhibited hydrophilicity, swelling ability, and compressibility to a significant extent. the radiopaque nature of the microspheres was confirmed by their x-ray images. In vitro tests using heparinized calf blood showed that the microspheres were nonhaemolytic in nature. These microspheres may find application as radiopaque emboli in particulate embolization.
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  • 37
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    Journal of Applied Biomaterials 2 (1991), S. 95-99 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: One-hundred-fifteen retrieved, porous-coated, uncemented patellar knee components of a wide variety of designs were examined for type and amount of tissue ingrowth and for wear and creep of the polyethylene-articulating surface. Examples of well-fixed patellar components of all designs presented regions of bone ingrowth independent of pore size, number of fixation pegs, and the presence or absence of coating on the pegs. Polyethylene breakdown, including delamination, pitting, subsurface cracking, and separation from the metal backing, was common. Comparative analysis indicates that solutions exist and include increasing congruency and polyethylene thickness and eliminating metal fixation buttons.
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  • 38
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    Notes: We have developed a new poly(vinyl alcohol) hydrogel (PVA-H) of increased physical strength through a new manufacturing process. Its mechanical properties have been found to be preferable as a substitute for articular cartilage. To evaluate its biocompatibility as an artificial articular cartilage, a series of in vivo tests within the intraarticular, as well as the intramuscular, environment were conducted. Tissue reactions of cartilage, bone, synovium, and muscle to PVA-H were studied histologically. In the experimental group, in which PVA-H was implanted, inflammatory reactions of all of these tissues were very slight. In the control group, in which ultra-high molecular weight polyethylene (UHMWPE) was implanted, although tissue reactions of bone and muscle were as slight as in the experimental group, those of cartilage and synovium were somewhat more conspicuous. By way of these findings, the better biocompatibility of PVA-H was documented.
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  • 39
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    Notes: New and used polypropylene tailstrings from the Copper 7 (Cu-7) intrauterine device were examined by a combination of analytical techniques. Optical microscopy, scanning acoustic and electron microscopy, x-ray diffraction, energy dispersive x-ray analysis, and chemical etching were employed to elucidate both the surface and interior morphology of new Cu-7 tailstrings. Tailstrings removed from women following varying periods of use were investigated with optical microscopy, scanning and transmission electron microscopy. In addition, a subset of the used tailstrings were cultured to identify the types of microorganisms associated with them. Our findings show that unused Cu-7 tailstrings are in various stages of degradation owing to a combination of factors which include the high-draw ratio employed during manufacturing, the method of packaging, and the use of a particulate colourant. Furthermore, it is evident that used Cu-7 tailstrings undergo major deterioration while in situ because of the unfavorable interactions between the highly drawn polypropylene and the physiological environment. These results indicate that the polypropylene tailstrings as manufactured for use with the Cu-7 IUD fail to meet accepted design criteria for biomedical implants.
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  • 40
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    Journal of Applied Biomaterials 2 (1991), S. 109-113 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Initial rigid fixation is essential for bone ingrowth into a porous-coated prosthesis. In this study, the amount of micromotion between a cut tibial surface and a custom tibial base-plate mounted with various types of screw fixation was measured. Motion transducers were placed at the corners of the baseplate to detect liftoff and subsidence. Central and eccentric loads were then applied. The variables tested included screw number and position, as well as screw length and type of bone purchase.A four-screw peripheral configuration had less micromotion than a three-screw triangulated configuration, and both had less micromotion than a two-screw central condyle configuration. Long screws with cancellous purchase and screws with cortical purchase had less micromotion than short screws with cancellous purchase.These results indicate that important variables which contribute to the initial rigidity of a cementless tibial implant using screw fixation include screw number, configuration, length, and type of bone purchase.
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  • 41
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    Keywords: Chemistry ; Polymer and Materials Science
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    Notes: In this paper we have reviewed the feasibility of using a shock wave lithotripter to loosen the interface between the bone and acrylic bone cement for revision arthroplasty. We have reviewed the physics of shock wave and its applications in medicine, especially its interaction with tissues. The calculations show that the energy is greatly reduced at the interface both in the soft tissue-bone interface and cement-bone interface. On the other hand, a tensile and compressive pressure can be operated at the cement-bone interface that can cause the interface to break if the pressure exceeds the tensile strength of the cement-bone interface.Subsequent papers will deal with in vitro and in vivo application of the shock wave in the treatment of the cement-bone interface in order to weaken it and consequently for easier extraction of bone cement from the intramedullary canal.
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  • 42
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    Journal of Applied Biomaterials 4 (1993), S. 55-60 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Ferromagnetic Ni—Cu alloy wires were characterized in order to obtain well-defined thermoseeds for application in interstitial hyperthermia of prostate cancer. Thermoseeds have been produced which possess Curie points in the therapeutic hyperthermia range, approximately 40 to 50 °C. The effect of thermal treatment and composition on the heating characteristics of the thermoseeds were investigated. The preliminary study shows that the recrystallization is crucial for altering thermoseeds' heating characteristics. Obtaining thermoseeds which behave as desired depends on changes in annealing times and temperatures. One may increase the maximum heating temperature (similar to Curie temperature) by increasing the annealing time and cooling time. Decreasing the lower annealing plateau temperature also increases the maximum seed heating temperature. Higher nickel content compositions did not affect rise time but increased the maximum heating temperature. © 1993 John Wiley & Sons, Inc.
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    Journal of Applied Biomaterials 4 (1993), S. 61-65 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Medicine , Technology
    Notes: The establish criteria for characterizing synthetic sutures, the handling characteristics of silk suture were analyzed. The characteristics that distinguish silk suture from other braided suture materials are its good “knot security” and relatively low “tiedown resistance.” Analytic consideration of knot security suggests that not only superficial friction but also resistance force produced by cross-sectional deformity of braided threads plays an important role in silk's superior performance. Results of a “pullout friction test,” developed to quantitatively evaluate resistance produced by surface friction and cross-sectional deformity suggest that the superiority of silk thread can be explained in terms of high static withdrawal resistance under low loads and relatively low dynamic withdrawal resistance under high loads. © 1993 John Wiley & Sons, Inc.
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    Journal of Applied Biomaterials 4 (1993), S. 73-75 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: There has been an increase in the use of primary reference material as a standard for identifying the cellular response to biomaterials. One such material is NHLBI-DTB polydimethylsiloxane (PDMS). The PDMS was developed for blood contacting studies and is composed of PDMS backed on one side with mylar. The results of implantation studies of two different publications are discussed in light of the different materials and different surface topographies of each of the materials. The appropriateness of in vivo studies using this reference material is questioned. © 1993 John Wiley & Sons, Inc.
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  • 45
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    Journal of Applied Biomaterials 2 (1991) 
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    Keywords: Chemistry ; Polymer and Materials Science
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  • 46
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    Journal of Applied Biomaterials 2 (1991), S. 141-142 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The purpose of my column is to provide readers with current information on biomaterials-related standards produced by both private groups and government agencies, and also on standards-related activities. Standards are descriptive documents given official status by their producers, and in the case of biomaterials, they are generally intended to provide formalized descriptions of (a) materials used in the construction of medical devices, (b) materials used directly in surgical repairs, (c) test methods to evaluate materials for such applications, and (d) methods for handling or processing such materials.Please consider this column not only a place to obtain biomaterials standards information, but also a place to submit news of biomaterials standards developments in order to get the information before the public. This invitation extends to members of all professional organizations and government agencies in the United States and abroad who are active in standards development and would like specific activities or standards publicized. I will present the information in this column to the extent that allotted space allows.And last, a caveat-since this is a column, it contains both factual information and opinions. I will make every effort to make it clear which is which. Also, as a frame of reference, please note that this column was written and submitted in March 1991.
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    Journal of Applied Biomaterials 2 (1991), S. 147-152 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Ultrastructural properties of precipitated apatites were characterized before and after sintering at 900 and 1250 °C using high resolution transmission electron microscopy. The apatite crystals were oriented with respect to the electron beam so that the crystals could be examined in relation to the high resolution images of the (001) and (100) planes. The ultrastructural properties were found to be affected by sintering temperature. Numerous lattice defects, including atomic vacancies, dislocations and two types of grain boundaries were observed. In addition, a new type of three-dimensional lattice defect was frequently observed in the apatites sintered at 900 °C. This type of lattice defect has the character of a hexagonal parallelipiped void, probably resulting from an aggregation of atomic vacancies. Calcium phosphate ceramics (hydroxyapatite and tricalcium phosphate) prepared by precipitation and subsequent sintering to temperatures above 1100 °C are presently used as bone grafts. The amount and kind of defects such as those observed in this study have significant implications on the extent of the degradation of these materials in vivo.
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  • 48
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    Journal of Applied Biomaterials 2 (1991), S. 153-159 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Glass plates of the chemical composition: CaO (29.0), SiO2 (31.0), Fe2O3 (40.0), B2O3 (3.0), P2O5 (3.0) in weight ratio were heated to 1050 °C at a rate of 5 °C/min and then cooled to laboratory temperature. The resulting glass-ceramic containing magnetite and wollastonite crystals showed high-saturation magnetization. The bonding ability of this new glass-ceramic to bone tissue was evaluated using rabbit tibiae, and compared with glass of the same composition. This glass-ceramic formed a Ca, P-rich layer on its surface and bonded tightly with bone within 8 weeks of implantation. However, the glass did not form this Ca, P-rich layer, nor had it bonded with bone at 25 weeks. The bone-heating ability of this glass-ceramic was investigated by applying a max. 300-Oe, 100-kHz magnetic field. The granules of the glass-ceramic filled in the rabbit tibiae heated the whole surrounding bone to more than 42 °C and maintained this temperature for 30 min. Bioactive ceramics reinforce the mechanical strength of bone tissue. Furthermore, this heat-generating bioactive glass-ceramic can be used for hyperthermic treatment of bone tumors.
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    Journal of Applied Biomaterials 2 (1991), S. 161-170 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: In order to apply the extracorporeal shock wave lithotripter (ECWSL) technique to the loosening of the bone-cement interface for the extraction of the cement during revision arthroplasty it is essential to know the dose-response characteristics. The present study shows that the number of shocks needed to break the interface between a 2- and 6-mm-thick bovine femoral bone and bone cement is similar to the fatigue behavior of a material, that is, Log(N) = C(kV) + D, where N is the number of shock impulses, kV is the power setting of the lithotripter machine in kilovolts, and C and D are constants. Iso-pressure distribution of the traveling shock wave front through a simulated bone in a Plexiglass® tube using Fuji® pressure film showed quantitative pressure contours from which one can understand the effective area of shock wave and its distribution. The most effective area of the shock wave was about 1.5 cm in diameter at 23 and 25 kV with pressure at least 7.0 MPa which is more than sufficient to break the bone-cement interface in tension.
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    Journal of Applied Biomaterials 4 (1993), S. 341-346 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A testing method was developed to evaluate the mechanical properties of a fibrin adhesive in an effort to correlate mechanical strength to fibrinogen content. Autologous fibrin adhesives with varying fibrinogen content were loaded to failure in shear using a mechanical testing machine. The method developed was capable of distinguishing a mechanical strength difference among the three fibrin sample lots used in the study. A number of parameters were evident that could lead to testing variability. The development of a more sophisticated component delivery system would greatly reduce the variability of these parameters and thus, the product reliability. Ultimately, the information gathered from the current and future studies will form a type of quality control standard to directly correlate the percentage of fibrinogen in a particular sample to its adhesive performance. © 1993 John Wiley & Sons, Inc.
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    Journal of Applied Biomaterials 4 (1993), S. 359-361 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Journal of Applied Biomaterials 4 (1993), S. 113-113 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Journal of Applied Biomaterials 4 (1993), S. 114-114 
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    Journal of Applied Biomaterials 4 (1993), S. 115-115 
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    Journal of Applied Biomaterials 4 (1993) 
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    Journal of Applied Biomaterials 4 (1993), S. 363-363 
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  • 57
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    Journal of Applied Biomaterials 5 (1994) 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Journal of Applied Biomaterials 4 (1993), S. 365-365 
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    Journal of Applied Biomaterials 5 (1994), S. 9-16 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Medicine , Technology
    Notes: Eight patients with failure of metal-backed patellar components were studied for evidence of intraarticular and systemic metal deposition. Seven of the eight patients had failure of a titanium-based patellar component that then articulated with a cobaltchromium femoral component. One patient had articulation of a cobalt-chromium patellar component against a cobalt-chromium femoral component. All components failed by the same pattern of failure. Wearing of the ultra high molecular weight polyethylene was followed by displacement of the polyethylene and then metal-to-metal contact of the components.Methods for analysis of the debris included light and electron microscopy of synovial tissue and electron dispersive x-ray analysis (EDAX) of tissue. Graphite furnace atomic absorption spectroscopy (GFAAS) was done on synovial fluid and synovial tissue as well as urine and blood specimens taken at various times from implantation to patellar revision.Massive deposition of metallic debris within the knee joint was documented both histologically and by GFAAS. Titanium levels reached as high as 2776 ppm (mg/L) in the synovial fluid and as high as 917 mg/g of synovial tissue. Elevation of all the pertinent metals was seen in the tissue and body fluids. Titanium and aluminum levels were the highest. Titanium levels in the serum generally were highest near the time of implant failure. Other metal elevations were variable and could not be related to the time of failure. Synovial fluid levels of all metals and serum levels of titanium are reflective of intraarticular generation of metallic debris.This study demonstrates that in situations of failure of a device, massive intraarticular debris generation occurs and systemic transport will occur. To date no systemic consequences can be attributed to the deposition of debris and follow-up urine and blood specimens suggest that debridement and revision of the failed device results in lowering of the ion levels. © 1994 John Wiley & Sons, Inc.
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    Journal of Applied Biomaterials 5 (1994), S. 1-7 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Microthane foam, a poly(ester)urethane, used as a covering of some breast implants (Meme or Replicon by Surgitek) degrades readily in phosphate buffer pH 7.4 producing multiple unknown products in addition to 2,4 and 2,6 toluenediamine (TDA). The cumulative weight loss of the foam in buffer was 1.5% at 1 week and 2% at 2 weeks. Multiple peak molecular weights from 105 to 665 000 were found in the aqueous foam extracts following 2 weeks of incubation at 37°C using size exclusion chromatography (SEC). TDA was measured in the foam buffer extracts by high pressure liquid chromatography (HPLC) and confirmed by gas chromatography/mass spectroscopy (GC/MS). The total cumulative levels of 2,4 TDA and 2,6 TDA measured were 3 ± 0.65 μg/g of foam and 1.13 ± 0.19 μg/g of foam following 36 days of incubation at 37 °C. Higher amounts, 8.96 μg/g of 2,4 TDA and 3.3 μg/g of 2,6 TDA, were obtained at 50 °C. The cumulative release of TDA in aqueous extracts was found to correlate linearly with time suggesting a slow but continuous production of TDA under neutral conditions. However, less than 0.2 μg/g of TDA was detected as residual TDA in the methylene chloride extracts following up to 60 days at 37 °C. PU foam extracted with methylene chloride under similar conditions showed higher foam weight loss, 4.4 and 5% at 1 and 2 weeks, respectively. The results presented in this study provide further evidence that Microthane undergoes hydrolysis under neutral conditions in aqueous solutions producing TDA and other unknown low molecular weight components and oligomers. © 1994 John Wiley & Sons, Inc.
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    Notes: Polyurethane films that contained various amounts of zinc diethyldithiocarbamate (ZDEC) and zinc dibutyldithiocarbamate (ZDBC) were prepared as standard reference materials (SRM). Using three cell lines of V79, L929, and Balb/3T3 cells, the cytotoxicity of the dithiocarbamates and the SRM films were compared by agar diffusion assay, filter diffusion assay, neutral red assay, cell growth assay, and colony assay. Among these in vitro cytotoxicity tests, colony assay was found to be the most sensitive method for detecting the cytotoxicity. The cytotoxic potentials of extracts from SRM films correlated well with the concentrations of ZDEC or ZDBC involved in SRM. When various rubber materials including SRM and surgical rubber latex materials were tested, cytotoxic potentials of these extracts were also correlated with the inflammatory tissue capsule thickness in short-term implantation tests. On the basis of these results, the SRM is judged to be useful for validating test sensitivity, and comparing the correlation between in vitro and in vivo responses. © 1993 John Wiley & Sons, Inc.
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    Journal of Applied Biomaterials 5 (1994), S. 17-21 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Ultra high molecular weight polyethylene (UHMWPE), used in total joint replacement implants, undergoes oxidative degradation due to gamma radiation sterilization and to exposure to oxidizing agents in the body environment. UHMWPE components also experience large stresses both on and near the articulating surface. It is hypothesized that there is a causal relationship between chemical degradation and mechanical loading of UHMWPE joint components. This report describes the development of an in vitro test to examine the combined effects of chemical environment and cyclic loading history on the chemical, physical, and mechanical properties of UHMWPE. The test apparatus consists of modular load trains, in which strings of UHMWPE test specimens can be subjected to cyclic tensile and compression load ranges, while being exposed to either control or degrading environments. Following cyclic loading for specified time intervals, the specimens can be statically loaded to determine the effect of cyclic loading and environment on the monotonic tensile and compressive stress-strain behavior of UHMWPE. To determine the appropriate control and degrading environments, gamma radiation sterilized UHMWPE specimens were maintained (unloaded) for up to 6 months in aqueous environments of distilled water and three concentrations of hydrogen peroxide (0.01, 0.1, and 1.0%) in distilled water at 37°C. Specimens were evaluated with depth from the surface for changes in density. Infrared spectroscopy (IR) analysis was conducted on selected surface sections. No significant changes in density or surface IR spectra occurred for specimens in distilled water as compared with the UHMWPE in the initial radiation sterilized condition. Specimens exposed to hydrogen peroxide solutions demonstrated changes in density and IR spectra consistent with oxidative degradation and comparable to the changes previously observed on retrieved UHMWPE components. Based on these results, distilled water was selected for the control environment. A 0.5% hydrogen peroxide solution was selected for the test environment, to produce moderate changes at a rate compatible with the maximum 12-month time period of the experiment. © 1994 John Wiley & Sons, Inc.
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    Journal of Applied Biomaterials 5 (1994), S. 39-45 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Neonatal rat calvaria osteoblasts were cultured on hydroxyapatite (as received or relatively-rough surface and mechanically polished to a 0.3-m̈m finish) and on glass (reference material) in Dulbecco's Modified Eagle Medium supplemented with 10% fetal bovine serum, 50 μg/mL ascorbic acid, and 10 mM β-glycerophosphate under standard, sterile, cell-culture conditions for 1, 3, 7, 14 and 21 days. At the end of the prescribed time periods, the cells were fixed and embedded in resin before removing the material substrates by exposure to acid solutions. Transmission electron microscopic examination of stained, ultrathin sections of the biological structures revealed osteoblast monolayers at 1 day of culture but multilayered cell structures at later time periods (14 and 21 days). The osteoblasts exhibited continuous contact and intimate apposition on polished hydroxyapatite and on glass; in contrast, osteoblasts on as received or rough hydroxyapatite made contact with discrete high points, spanned low regions of the material surface, and did not conform to all substrate contours. An electron dense layer (composed of mucopolysaccharides and proteins) was observed on all substrates tested after 7 days of culture. Collagen fibrils were seen interspersed among the osteoblasts as early as 3 days of culture; at later culture times, (i.e., 21 days) mineralized loci were observed in the extracellular matrix. © 1994 John Wiley & Sons, Inc.
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  • 64
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The aim of this study is the in vitro evaluation of the functional modifications of human endothelial cells in the presence of Dacron® impregnated with resorbable proteins. For this purpose, human endothelial cells isolated from the umbilical vein have been put in contact for 48 h with knitted Dacron® impregnated with collagen or gelatin and with nonimpregnated knitted Dacron® and double velour Dacron®. As control, endothelial cells cultured in the absence of material were used. After the contact time, cell counts were performed. In addition, the concentrations of two proteins synthesized by endothelium, tissue plasminogen activator (t-PA) and plasminogen activator inhibitor 1 (PAI-1), were evaluated on the supernatants. In the cultures in contact with Dacron® impregnated with collagen or gelatin and in those in contact with knitted Dacron®, we have observed a smaller cell growth than that observed in cultures without materials. The synthesis of t-PA showed some significant variations between the control cultures and those in contact with the materials. PAI-1 production was significantly reduced in the cultures in contact with gelatin impregnated Dacron® and with knitted Dacron®. Double velour Dacron® caused no significant variation in any of the examined parameters. © 1994 John Wiley & Sons, Inc.
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    Journal of Applied Biomaterials 5 (1994), S. 191-193 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Tissue specimens retrieved from four regions adjacent to hip implants during revision surgery were subjected to a novel treatment to make possible the quantitative separation of residual metal particulates and metal reaction products (metal ions and metal-protein complexes). The tissues were exposed to sodium hypochlorite solution that degraded and solubilized them, liberating metal reaction products and leaving behind metal wear particles, which were separated by centrifugation. Atomic absorption spectrophotometry was used to analyze the concentrations of the separated metal ions and wear particles. Co ion concentrations were 0.05 to 0.9 mM, Cr ion concentrations were 0.04 to 2.1 mM, and Ti ion concentrations were 0.30 to 0.60 mM. The weight of Co metal particles was 0.1 to 4.9 mg/100 mg tissue, of Cr metal particles 0.07 to 2.2 mg/100 mg tissue, and of Ti particles 0.09 to 5.2 mg/100 mg tissue; one black tissue sample contained 3333 mg Ti/100 mg tissue. No correlation was found between the concentrations of these two entities in the samples examined, probably due to the complex and varied processes creating them. The procedures discussed here will result in data that can help elucidate the separate contributions of metal reaction products and metal particulates to implant loosening. © 1994 John Wiley & Sons, Inc.
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    Journal of Applied Biomaterials 5 (1994), S. 195-201 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Modular hip prostheses are increasing in variety and utilization. Component stability, high endurance limit, and minimal particulate debris generation are critical for long-term clinical success. The purpose of this study was to characterize the fatigue response and evaluate the in vitro potential for component motion and wear of the S-ROMTM, a Ti-6Al-4V hip prosthesis with a modular design based on a Morse taper connection. A fatigue jig was desiged to simulate fixation of the device at the sleeve-bone interface only with distal support mainly against the lateral endosteal cortex. Two series of tests were performed in air at room temperature: one with direct vertical loading (to produce high bending moments in the coronal plane) and one with a compound loading angle directed at 15° out-of-plane (to include torsional physiological loads). Applied loads using a servohydraulic test machine ranged from 5 × BW (body weight) to 9 × BW (1 × BW = 73 kg, ≈ 160 lb) at 10 Hz on an Instron apparatus. No mechanical failures were observed on the 11-mm size stems below 6 × BW for in-plane vertical loading, and at or below 7 × BW for out-of-plane loading. Using displacement monitoring with a sensitivity of 35 μm, no measurable slippage or relative motion was detected between the stem and sleeve when they were properly assembled. Examination of the contact areas with scanning electron microscopy revealed random surface modification (an indication of fretting or burnishing) with occasional evidence of transfer of material between stem and sleeve. At loads under 7 × BW there was no visual evidence of loose wear debris in the presence of gross stability. Overall, the extent of surface change or wear was relatively small in all components tested at physiological load levels. © 1994 John Wiley & Sons, Inc.
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    Journal of Applied Biomaterials 5 (1994) 
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    Keywords: Chemistry ; Polymer and Materials Science
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  • 68
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: Effects of compliance mismatch at end-to-end artery/graft anastomoses on the distributions of wall stresses and compliance were studied using the finite element method. The canine common carotid artery (CCA), and expanded polytetrafluoro-ethylene (EPTFE) thin-walled graft, and a newly developed polyurethane graft (HS-2) were used as the models for the host artery, stiff graft, and compliant graft, respectively. Mechanical properties of CCA and HS-2 were determined from a pressure-diameter test, those of EPTFE graft were obtained by tensile test. Nonlinear elasticity of CCA and HS-2 was incorporated by iterating a linear FEM analysis: elastic moduli of the vessel walls were changed every 5 mmHg. The results showed that, in the case of the artery/EPTFE anastomosis in which the diameters of the artery and the graft were matched at 0 mmHg, regions of high tensile and shear stresses appeared in the graft near the anastomosis at the intraluminal pressure of 100 mmHg. The stress concentrations were remarkable, even if the diameters were matched at 100 mmHg and the pressure was varied within a physiological range (60-140 mmHg). Moreover, a hypercompliant zone appeared in the arterial wall near the anastomosis in this case. On the other hand, neither high stress concentrations nor hypercompliant zone appeared near the artery/HS-2 anastomosis. Because the mechanical complications at the compliance-mismatched anastomosis might finally result in graft failure and occlusion, it is important to match the compliance of graft to that of natural arteries, particularly to improve the patency of small-calibered arterial grafts. © 1994 John Wiley & Sons, Inc.
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    Journal of Applied Biomaterials 5 (1994), S. 99-101 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
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  • 70
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Hyaluronic acid (HA) and hydroxypropylmethylcellulose (HPMC) in buffered saline are “viscoelastics” used in ophthalmic surgery to prevent mechanical damage to delicate eye structures and to form a protective coating over corneal endothelium.HA is a high molecular weight polysaccharide that exhibits decreasing viscosity at increased shear rates. HPMC is a cellulose derivative that exhibits low surface tension. This study examines the physical properties of HA and HPMC solutions and attempts to correlate these properties with the ability of those macromolecules to coat and protect ocular structures.Results presented in this article suggest mixtures of HA and HPMC exhibit low surface tension and ease of aspiration characteristics that are desired in viscoelastic materials. For this reason a blend of these two macromoleculars offers handling advantages over each of these individual macromolecules. © 1994 John Wiley & Sons, Inc.
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    Journal of Applied Biomaterials 5 (1994), S. 109-115 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The purpose of this study was to examine the effects of particles, derived from metals commonly used in joint prostheses, on chondrocyte proliferation, metabolism, and morphology in vitro. Chondrocyte viability was influenced by the type and concentration of metal particle added. Cobalt was toxic to chondrocytes at all particle concentrations (0.83-0.000083%, v/v), whereas the chromium, titanium and titanium-aluminum particles only effected chondrocyte viability at high concentrations. The metabolic response of chondrocytes to particulate debris as assessed by caseinase, collagenase, and hexosaminidase activities were variable at low concentrations but were always reduced at high concentrations (0.83% v/v). Prostaglandin E2 levels in the medium showed a steady increase when particle load increased, except in the medium of chondrocytes exposed to titanium-aluminum. Scanning electron microscopy of chondrocytes exposed to titanium showed ruffled cell borders and frequent membrane blebbings. This was in contrast to chondrocytes exposed to cobalt, where the crenated appearance indicated cell death, and titanium-aluminum, where the cells appeared quiescent. These findings show that metal particles alter chondrocyte viability and metabolism and suggest that particulate debris may influence the integrity and stability of articular cartilage following hemiarthroplasty. © 1994 John Wiley & Sons, Inc.
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    Journal of Applied Biomaterials 3 (1992), S. 167-176 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Thrombogenicity was assessed by measuring the amount of 111In-platelets and 125I-fibrinogen deposited on the inner luminal surface of six polyurethanes for up to 60 min of blood contact in a canine ex-vivo shunt model. Commerical and laboratory synthesized polymers were examined. Two of the commercially synthesized polyurethanes (Biostable PURs) do not contain ether linkages in the polymer backbone and have previously shown resistance to oxidative and hydrolytic degradation. Static contact angle measurements, dynamic contact angle measurements, and ESCA were used to characterize the surfaces of these polyurethanes. The effectiveness of an acetone extraction used to remove extrusion waxes from Pellethane 2363-80A was similarly studied. Both Pellethane 2363-80A and the ether-free materials had relatively nonthrombogenic surfaces, as indicated by low platelet and fibrinogen deposition, making them potentially good candidates for biomedical applications.
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    Journal of Applied Biomaterials 3 (1992), S. 183-190 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: An expanded polytetrafluoroethylene (PTFE) prosthesis used to reconstruct the posterior cruciate ligament in a 37-year-old Caucasian male was retrieved and histologically examined in this study. Backscattered electron (BSE) microscopy, utilized to observe the mineralized tissue ingrowth into the retrieved specimen, revealed an absence of bony ingrowth within the graft. Light microscopy demonstrated an exuberant foreign body giant cell response surrounding and invading the substance of the graft, and also revealed evidence of graft degradation. These observations indicate that PTFE may not be as favorable a material for reconstruction of ligamentous tissues as previously reported.
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    Journal of Applied Biomaterials 3 (1992), S. 177-182 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The effects of thermoforming on the instantaneous flexural properties and structure of thermoplastic fiber-reinforced composite (FRC) wires were studied to determine the preferred temperature range for clinical forming. Five different formulations of FRC wires were heated to clinically relevant thermoforming temperatures in a special mold that was designed to maintain their shape. In addition, one formulation was also heated without the restraining effect of the mold. Flexural properties were determined. A temperature above the Tg is necessary to allow sufficient softening and avoidance of distortion in shape during clinical forming. However, higher temperatures will result in significant structural disintegration of the wires with consequent decrease in flexural modulus. Thus, for every material, there is a heating range or “working range” where the material can be properly formed with minimal changes in the physical properties. This was primarily related to the Tg of the matrix used.
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    Journal of Applied Biomaterials 3 (1992), S. 191-195 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Preliminary experiments suggest pretreatment of absorbable crystalline, calcium-sodium-metaphosphate (CSM) microfibers with trimethoxy-based silane coupling agents yields a polysiloxane film barrier which protects the fiber surface from early dissolution due to water. Compared to thermoplastic poly(L-lactic acid) (PLLA) composites reinforced with untreated fibers, PLLA composites reinforced with a variety of silane pretreated microfibers showed increased mechanical properties, suggesting improved adhesion was achieved at the fiber/matrix interface. Unfortunately, the silane pretreated CSM/PLLA composite showed no increase in wet strength retention after short-term in vitro exposure. This may be due to plasticization from water entering the composite at areas of incomplete fiber wetting by the highly viscous molten PLLA. However, when a nonabsorbable, low viscosity unsaturated polyester thermoset resin was reinforced with methacryloxy-silane pretreated CSM microfibers, there was no decrease in flexural strength and less than a 10% decrease in flexural modulus after 7 days exposure to 7.4 pH Tris-buffered saline at 37°C.
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    Journal of Applied Biomaterials 3 (1992), S. 207-210 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Higher chained alkyl cyanoacrylates have potential to function efficiently as space filling, hydrophobic, viscoelastic, biocompatible, and rapidly polymerizing bone adhesives. Hence they may be useful in applications where a void has to be filled, such as replacement of the intervertebral disc. To assess their applicability as space filling material in such an pplication, three alkyl cyanoacrylates; methoxyethyl cyanoacrylate, isobutyl cyanoacrylate, and isoamyl cyanoacrylate have been evaluated in this study. The bonding strength of these cyanoacrylates to bone in a space filling situation have been measured. The results indicate the bond strength of isoamyl cyanoacrylate (0.13 MPa) to be significantly (p 〈 0.05) lower compared with methoxyethyl cyanoacrylate (0.33 MPa) and isobutyl cyanoacrylate (0.37 MPa). There was no significant difference in the bond strengths of isobutyl cyanoacrylate and methoxyethyl cyanoacrylate.
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    Journal of Applied Biomaterials 3 (1992), S. 217-224 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The aim of this study was to look at the bone bonding potential of six formulations of a novel glass-ceramic system. Cylinders of the ceramics were implanted in rabbit tibiae for 4 and 7 weeks. Histological tests, both quantitative and qualitative, as well as push-out tests, were carried out during the bonding assessment. Bone growth was quite prolific, even at 4 weeks, as evidenced by growth up to and along the implant surfaces. The interfacial shear strengths compared well with other biomaterials in use as endosseous implants. Therefore it seems pertinent to pursue further long-term experimentation with this material.
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    Journal of Applied Biomaterials 3 (1992), S. 197-206 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Bioabsorbable polymer/inorganic phosphate fiber composites are prone to rapid degradation due to water sensitivity of the interface between the degradable polymer and the degradable fiber. This article describes successful fabrication and laboratory evaluation of a candidate bioabsorbable composite implant material with mechanical properties similar to bone. The composite studied was poly(ortho ester) reinforced with randomly-oriented, crystalline microfibers of calcium-sodium-metaphosphate. The component materials showed no acute cytotoxicity as determined by tissue culture agar overlay. Treating the microfibers with a diamine-silane coupling agent improved mechanical properties and slowed degradation in saline, but strength still decreased 50% in 1 week. When the composite material was then coated with a layer of matrix polymer alone it retained 70% of its strength and 70% of its stiffness after 4 weeks exposure to 7.4 pH Tris-buffered saline at body temperature. The marked improvement with the coating can be attributed to the hydrophobicity of poly(ortho esters).
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    Journal of Applied Biomaterials 3 (1992), S. 211-215 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Cyclic loaing of Ti-6-4 and Co-Cr-Mo (cast) test samples with grit-blasted or waffle-textured surfaces coated with a plasma-sprayed 50-μm HA layer was performed in air, Ringer's solution (5% dextrose), 0.9% NaCl (Tris buffer, pH 7.40), and balanced Hank's solution. Maximum interfacial stresses in bending of 40 ksi (280 MPa) and 20 ksi (140 MPa) were utilized, and the speciments tested to 106 cycles at 5 Hz with a MTS servohydraulic machine. Tested samples were examined by optical microscopy to determine coating integrity and thickness and by scanning electron microscopy (electron backscatter mode and EDAX) to determine surface morphology and chemical changes.The following observations were made: (1) Samples cyclically tested in solutions showed a general thinning of the coating, accentuated in the higher-stressed regions. (2) Samples tested with an equivalent static load in the solutions did not show this centralization. (3) Bare metal interface surfaces were noted on most of the edges of highly stressed central specimen regions, in several entire central regions, and on the upper surfaces of some of the waffled samples. (4) The specimens tested in Ringer's solution (pH 4.70 initially) demonstrated the most dramatic coating deterioration. (5) The coatings on titanium appeared more stable than these on Co-Cr as tested in all solution environments for both surface types.The HA coating evaluated in this experiment demonstrated increased instability when cyclically loaded in in vitro solutions of lowered pH and depleted cations (Ca2+) at stress levels of 280 MPa. The more physiological solution (Hank's) did not show this increased dissolution at the lower stress level. It is suggested that this type of testing be performed on other HA coatings due to the possible implications for long-term in vivo coating integrity.
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    Journal of Applied Biomaterials 3 (1992), S. 237-238 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Journal of Applied Biomaterials 3 (1992), S. 239-242 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Journal of Applied Biomaterials 3 (1992), S. 231-236 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Biomaterials is emerging as an identifiable intellectual field of study. There are necessary preparatory studies to equip individuals to work within the field at various levels. The formal and informal instructional requirements are considered within the context of the academic program of the Department of Bioengineering at Clemson University, one of the first US university programs to focus on instruction and research in biomaterials.
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    Journal of Applied Biomaterials 3 (1992), S. 225-230 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 84
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    Journal of Applied Biomaterials 6 (1995), S. 237-242 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Because of the recent trend in total hip arthroplasty to achieve direct contact of the endoprosthesis with cortical bone, comparison of bone apposition from cortical bone and cancellous bone was performed. The response of cortical and cancellous bone to hydroxylapatite was also compared. Implants in cortical bone demonstrated a higher interface shear strength and more bone apposition than those in cancellous bone over all time periods tested. Hydroxylapatite coating increased the interfacial shear and bone apposition in cortical bone at all time periods and in both the 3- and 6-week cancellous bone models. The potential effect of stress shielding (and subsequent bone resorption) by femoral stems ingrown with cortical bone is discussed. © 1995 John Wiley & Sons, Inc.
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    Journal of Applied Biomaterials 6 (1995), S. 249-258 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Ions released from implant surfaces are suspected of playing some role in osteolysis surrounding metal prostheses. To understand how ions may affect osteogenesis, previous work exposed osteogenic cells to metal ions to study acute cytotoxic responses. The purpose of this study was to assess the long-term effects of sublethal ion concentrations on osteogenic cell proliferation and function. Bone marrow stromal cells were harvested from juvenile rats and exposed to solutions of ions associated with Co-Cr-Mo and Ti-6Al-4V implants. Cells were cultured for up to 4 weeks and assayed for total protein, alkaline phosphatase, osteocalcin, and calcium. Other than V+5, none of the ions affected cell proliferation, indicating that the chosen concentrations were sublethal as desired. V+5 elicited delayed gross toxicity not previously observed during acute experiments. At the chosen concentrations, Co+2, Cr+6, Mo+6, and Co-Cr-Mo alloy elicited little effect on cell proliferation and moderate effects on matrix mineralization. Cultures exposed to Ti+4, Al+3, and Ti-6Al-4V alloy also showed no decrease in cell number, but did show near total suppression of osteocalcin secretion and matrix mineralization. These results suggest that ions released from Ti alloy implants may interfere with osteoblastic cell differentiation, contributing to periprosthetic osteolysis by impairing normal osteogenesis. © 1995 John Wiley & Sons, Inc.
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    Journal of Applied Biomaterials 6 (1995), S. 267-282 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Crestal bone loss is observed around various designs of dental implants. A possible cause of this bone loss is related to the stresses acting on periimplant bone. To investigate the relationship between stress state and bone loss, two-dimensional finite element models corresponding to bucco-lingual and mesio-distal sections of canine mandibles with one of two designs of porous-coated dental implants were analyzed. A fully porous-coated design consisting of a solid Ti6A14V core had a porous coating over the entire outer surface of the implant component, while a partially porous-coated design had the porous coating over the apical two-thirds of the implant surface only. Occlusal forces with axial and transverse components were assumed to act on the implant with interface bonding and effective force transfer at all porous coat-bone interfaces and no bonding for the non-porous-coated regions. The results of the analysis indicated that at most implant aspects (buccal, lingual, mesial, and distal), the equivalent stresses in crestal bone adjacent to the coronal-most, non-porous-coated zone of the partially porous-coated implants were lower than around the most coronal region of the fully porous-coated implants. The region of lower stresses around the partially porous-coated implants corresponded to observed areas of crestal bone loss in animal studies, suggesting that crestal bone loss in this case was due to bone disuse atrophy. A number of parameters of the finite element models were varied to determine the effect on the resulting stress fields and, therefore, possible long-term bone remodeling. Based on differences in observed bone structures by histological examination and results of finite element analyses with fully and partially porous-coated implants, an equivalent stress equal to 1.6 MPa was determined to be sufficient to avoid bone loss due to disuse atrophy in the canine mandibular premolar region. © 1995 John Wiley & Sons, Inc.
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  • 87
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
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  • 88
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    Journal of Applied Biomaterials 3 (1992), S. 287-303 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: To prevent wound dehydration and bacterial penetration, a wound dressing should be occlusive, but on the other hand it should also be permeable for wound exudate to prevent bullae formation. To meet these requirements a new type of polyurethane wound dressing which consists of a microporous top layer (pore size 〈 0.7 μm) supported by a sublayer with a highly porous sponge-like structure containing micropores (pore size 〈10 μm) as well as macropores (pore size: 50-100 μm) was designed. The pores of both layers are interconnected and form a continuous structure in the membrane. Membranes according to this design were prepared either by means of a two-step or by means of a one-step casting process. Both fabrication methods are based on phase inversion techniques. Asymmetric polyurethane Biomer® membranes prepared by the two-step casting process were tested in vivo as full thickness skin substitutes using guinea pigs. Neither wound dehydration nor infections were observed while the drainage capacity of the wound dressing was effective in preventing bullae formation. Furthermore the wound dressing remained firmly adhered to the wound surface during the whole process of wound healing. In contrast to all other commercial wound dressings currently available the polyurethane wound dressing applied on excised clean wounds did not need to be replaced during healing but could be left on the wound until full regeneration of the skin had taken place after which it was spontaneously repelled. © 1992 John Wiley & Sons, Inc.
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  • 89
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    Journal of Applied Biomaterials 3 (1992), S. 305-311 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Blood pumps usually use elastomer diaphragms that undergo repeated small-strain flexing (deformation). The stresses and strains that develop in the mechanically actuated diaphragms dictate the useful life and fluid-solid interactions of the diaphragm. A knowledge of these stresses and strains is essential for proper design of the pump's elastomer diaphragm. A nonlinear axisymmetric finite-element stress-strain analysis has been carried out on a Hexsyn rubber diaphragm used in a blood pump to illustrate a finite-element modeling technique. A situation involving the application of an axial deformation load on the diaphragm has been considered. In particular, the strains developed in a blood pump diaphragm during pumping have been quantified to illustrate the analysis technique. © 1992 John Wiley & Sons, Inc.
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  • 90
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    Journal of Applied Biomaterials 2 (1991), S. 209-210 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The purpose of my column is to provide readers with current information on biomaterials related standards produced by both private groups and government agencies, and also on standards-related activities. Standards are descriptive documents given official status by their producers, and in the case of biomaterials, they are generally intended to provide formalized descriptions, of (a) materials used in the construction of medical devices, (b) materials used directly in surgical repairs, (c) test methods to evaluate materials for such applications, and (d) methods for handling or processing such materials.Please consider this column not only a place to obtain biomaterials standards information, but also a place to submit news of biomaterials standards developments in order to get the information before the public. This invitation extends to members of all professional organizations and government agencies in the United States and abroad who are active in standards development and would like specific activities or standards publicized. I will present the information in this column to the extent that allotted space allows.At last, a caveat-since this is a column, it contains both factual information and opinions. I will make every effort to make it clear which is which. Also, as a frame of reference, please note that this column was written and submitted in June 1991.
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  • 91
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    Journal of Applied Biomaterials 2 (1991), S. 281-283 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The patent literature can be a morass of confusion. It is complicated by legalese, often uncommunicative titles, and difficult, as well as cryptic, categorization. To kiip current with the broad arena of patents on biomaterials and medical devices is much more difficult than keeping current with the scientific literature of the international journals.It is the goal of my column to provide readers with techniques and tools to better utilize this rich source of scientific information. Also, I intend to provide focused surveys of recent patents in specific areas relating to biomaterials and medical devices. Finally, I will try to include discussion of what constitures patentable material and educate those of us who are new to patent literature and new to the requirements of applying for patents for our discoveries.I appeal to the readership to submit requests for specific areas to be addressed in this column. The interaction will enrich us all.
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  • 92
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    Journal of Applied Biomaterials 2 (1991), S. 285-287 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
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  • 93
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    Journal of Applied Biomaterials 3 (1992) 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
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  • 94
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    Journal of Applied Biomaterials 3 (1992), S. 17-22 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Poly(etherurethane) (PEU) and poly(etherurethaneurea) (Biomer®) films with and without antioxidant stabilizers were subcutaneously implanted into dogs and rats for up to 10 weeks. It was found that the molecular weight of the PEU films decreased over the 10-week period, while the Biomer® films increased in molecular weight. The presence of the stabilizers resulted in less severe changes in molecular weight. Surface cracking was most pronounced on both the stabilized and nonstabilized PEU films. Stress did not have to be applied to induce the surface cracking.
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  • 95
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    Journal of Applied Biomaterials 3 (1992), S. 9-15 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: An improved affinity support and an immunoadsorbent suitable for extracorporeal perfusion of whole blood (or plasma) are reported. The affinity support consists of calcined diatomite-type silica particles to which a synthetic oligosaccharide hapten, viz. Atrisaccharide representing human blood group A, with a linking spacer-arm is chemically attached. The immunoadsorbent thus obtained is surface-modified with a polymer coating. The modified immunoadsorbent is not hemolytic and shows no loss of biological activity in reducing antibody titers in vitro. An important feature of the improved immunoadsorbent is that the polymer coating providesa better surface resistance and therefore stability to the affinity support to prevent the release of potentially harmful fines. The usefulness of a physically stable support as an affinity adsorbent for the selective removal of specific antibodies or unwanted substances directly from the blood circulation by extracorporeal immunoadsorption has profound medical significance because this would provide an efficient but safe and practical alternative to therapeutic intervention using plasma exchange or plasma perfusion, both of which require plasmapheresis.
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  • 96
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A neonatal incubator has been custom modified to enable measurement of initial platelet retention on biomaterials in vitro under clinically relevant hemodynamic conditions. To calibrate this device, platelet retention on several materials having microconduit geometry (0.7-1.0 mm i.d.) has been measured after perfusion with citrated whole blood (containing 111 Indium-labelled platelets) at a shear rate of 312 s-1, 37°C, and 80 cm H2O transmural pressure. The relative reactivity of these materials toward platelets was: glass 〈 Fibrinogen(Fg)-coatedglass 〈 Fg-coated polyethylene 〈 polyethylene ∼ = Expanded polytetrafluoroethylene. Interindividual variation is relatively large (coefficient of variation = 35.5 ± 9.3%), but comparison to intraindividual controls reduces the variability to 14.8 ± 10.3%, a level which is suitable for economical testing of platelet retention to biomaterials in the presence or absence of drugs. This approach may have particular value in the study of the mechanism of platelet interactions with artificial microvascular grafts under perfusion conditions which are relevant to the first moments of flow, when initial platelet deposition occurs.
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  • 97
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    Journal of Applied Biomaterials 3 (1992), S. 23-28 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The present investigation describes the formulation and the in vivo efficacy of prolonged controlled-release chitosan matrices, containing the novel anticalcification agents adipoyland suberoylbisphosphonate (AdBP and SuBP). Chitosan matrices were prepared by the solvent-cast method and the role of several factors such as polymer molecular weight (MW), crosslinking, and drug load concentration, on the release rate profile have been examined. Crosslinking of chitosan films retarded degradation rate of the polymer but not the release rate of the embedded drug. Chitosan's MW and drug load concentration did not affect drug release rate. The release kinetics of the bisacylphosphonates were characterized by initial burst-effect and pseudo zero-order kinetics in the following release phase. AdBP/chitosan matrices (co-implanted subdermally in rats with the calcifiable bioprosthetic heart valve tissue) significantly inhibited tissue calcification after 15 and 30 days implantation (66.4 and 108.6 μg/mg Ca++ in comparison to 2.7 and 3.6 μg/mg Ca++, untreated and treated groups, respectively). No side effects were noted.
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  • 98
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    Journal of Applied Biomaterials 3 (1992), S. 39-44 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Radio-frequency air plasma treatments of Ti-6-4 and Co-Cr implants increased surface wettability but concurrently increased ionic release. In vitro tissue culture experiments demonstrated no enhancement of cell growth and enrichment. Short-term rabbit tibial implants also showed no difference between treated and untreated implants.
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  • 99
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Quantitative methods of evaluating ingrowth into porous coated implants have traditionally involved destructive mechanical testing. In this study, it was hypothesized that the response to a vibrational stimulus could estimate the shear strength at the bone-implant interface as measured by pushout. A derived model predicts that the square of the frequency at resonance is linearly related to this interfacial strength. It was further hypothesized that the level of vibration required for a meaningful response would not be destructive. This study was done using nonloaded, porous coated cylindrical implants which were press fit in the distal femora of dogs. Femora were harvested at 2, 4, and 6 weeks postimplantation. The implants were sectioned into 4-mm slices and then evaluated by vibration, pushout, and light microscopy. Vibrational response analysis was conducted with broad band random excitation using Fast Fourier transform signal analysis. Pushout values were obtained using a materials testing machine. The resulting correlation was statistically significant (F = 201, r2 = 0.90, p 〈 10-6). Light microscopic evaluation of vibrated samples showed no difference at the bone-implant interface when compared to controls.
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  • 100
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    Journal of Applied Biomaterials 1 (1990), S. 321-327 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: An aqueous humor draining device, with size comparable to that of the Krupin tube, was constructed by using poly-HEMA material. Deposits were found on the surface of poly-HEMA when contacted in vitro with the aqueous humor of the rabbit's eye. A fibrous structure, probably composed of proteins and other macromolecules, developed on poly-HEMA surface in 15 days after the draining device was implanted into the rabbit's eye. The draining device was still in function 250 days after its implantation. SEM analysis of the retrieved poly-HEMA draining device indicated that the poly-HEMA tube opening was not blocked by any substance. These results suggest that poly-HEMA could be used as a biomaterial for construction of the aqueous humor draining device to relieve the intraocular pressure of glaucoma patients. Its long-term application awaits further investigation.
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