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  • 1
    ISSN: 1436-3771
    Keywords: Key words Dentine ; enamel junction ; Odontoblast processes ; Dentinal tubules ; Confocal laser scanning microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The translucency of teeth allows the non-destructive subsurface visualisation of their microstructure by confocal laser scanning microscopy (CLSM) at a level of about 150 μm below the surface. The dentine–enamel junction (DEJ) is accessible only directly adjacent to the cervix of the tooth. Therefore teeth have to be sectioned for studying marginal areas of the dental hard tissue. The potential of the technique for (pseudo) three-dimensional visualisation allows the study of an array of individual confocal images, the interpretation of which is similar to that of macroscopic tomographs (CT-scan, MRI). Additionally, the extended focus mode yields the overlay of individual confocal images in the form of a two-dimensional projection. This mode of operation proved to be particularly suited for the visualisation of odontoblast processes in their whole extension. The three-dimensional junction between enamel and dentine, the branches of the odontoblast processes and their interactions with the DEJ is demonstrable by CLSM without staining or other procedures of sample preparation. The direct microscopic comparison between samples, either fresh or kept in a humid chamber, and Technovit-embedded sample blocks gives evidence that the risk of artefacts by sample storage or by the embedding procedure is minimal. The tomographs limited to subsurface areas of the tissue also exclude mechanical surface artefacts due to grinding or cutting.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Mund-, Kiefer- und Gesichtschirurgie 2 (1998), S. 85-90 
    ISSN: 1434-3940
    Keywords: Schlüsselwörter Strahlenkaries ; In-vitro-Demineralisation ; Konfokale Laser-Scanning-Mikroskopie ; Key words Radiation caries ; In vitro demineralisation ; Confocal laser scanning microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Objective: The volume of literature on radiation-induced caries is still inconsistent as regards the state of the art. Our histotomographic studies have shown direct radiogenic effects on the dentoenamel junction (atrophy of the odontoblast processes). Whether there are direct effects of radiation on dental enamel is not yet known. Material and Method: Sound teeth (group 1, n = 10) were compared either with enamel specimens after high dose in vitro radiation (500– 2500 Gy; group 2; n = 10) and after experimental enoral in situ irradiation (60 Gy; group 3; n = 20), or with teeth from patients after cancer radiotherapy (36 Gy; group 4; n = 20) and with teeth which had obviously decayed due to cancer radiotherapy (60 Gy; group 5; n = 20). Vestibular enamel surfaces of the teeth were exposed to identical in vitro demineralizations (lactic acid gel; pH = 5.0). Each of the samples was prospectively studied histologically by confocal laser scanning microscopy (CLSM) after 90, 180 and 270 min of acid interaction. Data were interpreted micromorphometrically (width of the demineralized area) and micromorphologically. Results: The width of the demineralized area varies between the two in vivo irradiated groups of specimens (group 4: P 〈 0.01; group 5: P 〈 0.001) and the high dose in vitro irradiated teeth (P 〈 0.01) and is significantly different from the sound controls. The histological image of the demineralization in subsurface areas in the teeth of radiotherapy patients is characterized by a total loss of the prismatic structure (homogeneously, amorphous substance). Conclusions: Direct radiogenic effects at the dentoenamel junction have been described earlier. The additional information offered by this study is that there are significant micromorphometric differences in the demineralizing behaviour of irradiated enamel. Obviously, enamel is less resistant to acid attack after irradiation.
    Notes: Fragestellung: Das umfangreiche Schrifttum zur Strahlenkaries zeigt den kontroversen Forschungsstand. Eigene Untersuchungen haben direkt radiogene Veränderungen an der Schmelz-Dentin-Grenze histotomographisch nachweisen können (Atrophie der Odontoblastenfortsätze). Offen ist die Frage nach direkten Strahlenfolgen im Schmelz. Material und Methode: Gesunde Zähne (Gr. 1, n = 10) wurden mit Proben nach hochdosierter In-vitro- (500–2500 Gy, Gr. 2, n = 20) und nach experimentell-enoraler In-situ-Bestrahlung (60 Gy, Gr. 3, n = 20) sowie mit Zähnen von Patienten nach präoperativer Strahlentherapie (36 Gy, Gr. 4, n = 20) und strahlenkariösen Zähnen nach tumortherapeutischer Strahlendosis (60 Gy, Gr. 5, n = 20) verglichen. Im direkten Parallelgruppenvergleich erfolgte eine standardisierte In-vitro-Demineralisierung (Milchsäuregel pH 5,0) an den vestibulären Schmelzoberflächen. Jede Probe wurde prospektiv histologisch durch konfokale Laser-Scanning-Mikroskopie (CLSM) nach 90, 180 und 270 min Entmineralisierung untersucht. Die Auswertung erfolgte mikromorphometrisch (Breite des Demineralisationssaums) und mikromorphologisch. Ergebnisse: Die Breite des Demineralisationssaums unterschied sich sowohl bei beiden in vivo bestrahlten Probengruppen (Gr. 4: p 〈 0,01; Gr. 5: p 〈 0,001) als auch bei den hochdosiert in vitro bestrahlten Zähnen (p 〈 0,01) signifikant von den Befunden der gesunden Kontrollen. Das histologische Bild der Demineralisation an den Zahnoberflächen von Radiotherapiepatienten zeigte dabei einen völligen Verlust der Prismenstruktur (homogen amorphe Substanz). Schlußfolgerungen: Direkte Strahlenfolgen an der Schmelz-Dentin-Grenze wurden in früheren Untersuchungen dargestellt. Zusätzlich konnten jetzt signifikante mikromorphometrische Unterschiede im Demineralisierungsverhalten des bestrahlten Schmelzes gezeigt werden. Offensichtlich ist der Schmelz nach der Bestrahlung für einen Säureangriff weniger resistent.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 9 (1952), S. 581-585 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 16 (1990), S. 331-334 
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The hydrogen concentration profiles of electrochromic multilayer systems produced by evaporation have been determined by means of nuclear reaction analysis. The H content of individual oxidic materials was found to be larger than for single films, especially for SiO2. The time-dependent H uptake under various ambient conditions was investigated. Systems produced by ion plating were also profiled for hydrogen.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 65 (1993), S. 1116-1117 
    ISSN: 0009-286X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 68 (1996), S. 1100-1101 
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 70 (1998), S. 1198-1199 
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 14 (1979), S. 244-253 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The very complex isomerization patterns of methoxy and carbomethoxy substituted cycloalkanes (3- to 7-membered rings) have been investigated using collisional activation, metastable ion characteristics and field ionization kinetics. The extent of isomerization depends on both the ring size and the substituent. Irrespective of the electronic properties of the substituent, ring opening involves exclusively the C-1—C-2 bond whereby linear alkene radical cations are formed. In the case of OCH3- and COOCH3 substituents the position of the resulting double bond (terminal or α,β-unsaturated) is determined more by the ring size of the precursor molecules and less by the electronic properties of the substituents. Contrary to these findings alklyl substituted cycloalkanes (3- to 5-membered rings) rearrange exclusively to terminal alkene radical cations. The barrier for double bond isomerization seems to be substantially influenced by substituents.
    Notes: Unter Benutzung mehrerer Techniken, wie Stoßaktivierung, Charakteristik metastabiler Ionen und Feldionisationskinetik, wird das äußerst komplexe Isomerisierungsverhalten von methoxy- und caarbomethoxysubstituierten Cycloalkanen (drei-bis siebengliedrege Ringe) analysiert. Das Ausmaß der Isomerisierung hängt sowohl von der Ringgröße als auch vom Substituenten ab, während die Ringöffnung unabhängig von den elektronischen Eigenschaften der Substituenten immer die C-1—C-2-Bindung betrifft. Hierbei werden ausschließlich lineare Alken-Radikalkationen erzeugt. Bei OCH3- und COOCH3-Substituenten wird die Lage der resultierenden Doppelbindung terminal oder α,β-ungesättigt hauptsächlich durch die Ringgröße des Cycloalkan-Molekülions und weniger durch den Substituenten beeinfluß. Alkylsubstituierte Cycloalkane (drei- bis fünfgliedrige Ringe) lagern sich allerdings nur zu terminalen Alken-Radikalkationen um. Die Barriere der Doppelbindungswanderung scheint vom Substituenten abhängig zsu sein.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Chalcogenide Glasses with Organic Components. V. The Reactivity in the Glass-forming Systems Selenium, Arsenic, Bromine, 4,4′-Bis(selenenylbromido)azobenzene and Selenium, Arsenic, Iodine, 4,4′-Bis(diiodarsa)biphenyleneSe—As—Br glasses and 4,4′-bis(selenenylbromido)azobenzene react in the solid state. In this case arsenic is an acceptor for bromine, and azobenzene groups will be linked via poly-selenide groups with the glass matrix. The reaction is proved by DTA. At elevated temperatures, the selenium-carbon bond will be replaced by a carbon-bromine link yielding 4,4′-dibromazobenzene. Solid 4,4′-bis(diiodarsa)biphenylene shows a similar reaction with Se—As—I above TG. The pyrolysis takes place at higher temperatures.
    Notes: Gläser des Systems Se—As—Br reagieren im festen Zustand mit 4,4′-Bis-(selenenylbromido)azobenzol. Dabei wirkt Arsen als Bromakzeptor, und die Azobenzolgruppen werden über Polyselenidgruppen mit der Glasmatrix verknüpft. Die Reaktion wurde differentialthermoanalytisch verfolgt. Bei höheren Temperaturen werden die Selen-Kohlenstoff-Bindungen durch Brom-Kohlenstoff-Bindungen ersetzt. 4,4′-Dibromazobenzol kann durch Sublimation isoliert werden. Festes 4,4′-Bis(dijodarsa)biphenyl reagiert in analoger Weise mit unterkühlten Selen-Arsen-Jod-Schmelzen.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 29 (1995), S. 337-337 
    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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