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  • 1995-1999  (2)
  • 1945-1949
  • 1999  (2)
  • Enossal implants  (1)
  • magnetic suspension balance
  • 1
    ISSN: 1434-3940
    Keywords: Schlüsselwörter Kaufunktionelle Rehabilitation ; Enossale Implantate ; Strahlentherapie ; Prognosefaktoren ; Kaplan-Meier-Analyse ; Key words Rehabilitation of masticatory function ; Enossal implants ; Radiotherapy ; Factors affecting prognosis ; Kaplan-Meier Analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary In comparison to tumor patients not receiving radiotherapy, the rehabilitation of masticatory function after head and neck irradiation is limited due to radiation-induced caries, radioxerostomia, and the risk of osteoradionecrosis. This study focused on implants in the irradiated jaw and on the evaluation of the prognosis and the effect of potential factors on the prognosis. The retrospective study covered 197 implants (47 patients) from 1988 to 1997. The implant prognosis was determined by implant survival statistics (Kaplan-Meier). Losses not related to the implants were censored. In addition, groups were formed according to factors potentially affecting the prognosis. The significance of differences in the groups relative to survival were tested using the log-rank test. Twelve (6.1%) implants from a total of 197 were lost due to peri-implantitis, and eight (4.1%) due to possible biomechanical stress. A total of 52 losses (26.4%) due to death of patients and two (1.0%) due to resection of the jaw were censored; 111 (56.3%) implants remained at recall and the average interval was 33 months. The rates of implant survival (Kaplan-Meier) after 1 and 2 years were 95%, after 3 and 4 years 92%, and after 5 and 6 years 72%. The univariate analysis of group comparisons showed a significantly lower rate of loss after perimplant flap reconstruction (p = 0.036). There was no effect due to the doses of irradiation (p = 0.16), chemotherapy (p = 0.90), or peri-implant osteoplasty (p = 0.84). Although none of the implants inserted before radiotherapy had to be explanted, the implant survival difference in the very heterogeneous groups was not significant (preirradiation, n = 29; postirradiation: n = 156; p = 0.13). According to the literature, the rate of survival of teeth which were sound before radiotherapy (1 year, 75%; 5 years, 45%) was distinctly lower than the survival of enossal implants (1 year, 95%; 5 years, 72%). The high-quality rehabilitation of masticatory function with implant-based protheses is the preferred method of treatment for irradiated tumor patients. In addition, contraindications for enossal implants were ruled out for all studied factors affecting prognosis.
    Notes: Zusammenfassung Einleitung: Die kaufunktionelle Wiederherstellung nach Kopf-Hals-Bestrahlung ist gegenüber anderen Tumorpatienten durch Strahlenkaries, Radioxerostomie und Osteoradionekroserisiko zusätzlich limitiert. Es wurde der Frage der Implantatprognose und potentieller Prognosefaktoren im bestrahlten Kiefer nachgegangen. Material und Methode: Die retrospektive Studie erfaßte von 1988–1997 197 Implantate (47 Patienten). Die Implantatprognose wurde durch Überlebenszeitanalyse (Kaplan-Meier) bestimmt, wobei implantatunabhängige Verluste zensiert wurden. Außerdem erfolgte eine Gruppenbildung nach potentiell die Prognose beeinflussenden Parametern. Grupppenunterschiede in den Überlebensraten wurden mit dem Log-Rank-Test auf Signifikanz geprüft. Ergebnisse: Von 197 Implantaten gingen 12 (6,1%) durch Periimplantitis und 8 (4,1%) durch mögliche biomechanische Überlastung verloren. Zensiert wurden 52 Verluste (26,4%) wegen Versterbens und 2 (1,0%) wegen Kieferresektion. 111 Implantate (56,3%) verblieben im Recall; die gemittelte Nachkontrollphase betrug 33 Monate. Die Überlebensrate (Kaplan-Meier-Analyse) betrug nach 1 und 2 Jahren 95%, nach 3 und 4 Jahren 92% und nach 5 und 6 Jahren 72%. Die univariate Analyse der Gruppenvergleiche zeigte eine lokal signifikant niedrigere Verlustrate nach periimplantärer Weichteilplastik (p = 0,036). Bestrahlungsdosis (p = 0,16), Chemotherapie (p = 0,9) und periimplantäre Osteoplastik (p = 0,84) beeinflußten die Prognose nicht. Obwohl kein vor der Bestrahlung gesetztes Implantat explantiert wurde, war der Unterschied bei sehr inhomogenen Gruppenstärken (prä radiationem: n = 29; post radiationem: n = 156) nicht signifikant (p = 0,13). Schlußfolgerungen: Im Literaturvergleich ist die Überlebensrate prae radiationem gesunder Zähne (1 Jahr: 75%; 5 Jahre: 45%) deutlich schlechter als die Prognose enossaler Implantate (1 Jahr: 95%; 5 Jahre: 72%). Die funktionell hochwertige Restitutio des Kauorgans durch implantatgetragenen Zahnersatz ist damit auch für bestrahlte Tumorpatienten bestätigt. Eine Kontraindikation enossaler Implantation konnte daneben für alle untersuchten zusätzlichen Prognosefaktoren ausgeschlossen werden.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1572-9567
    Keywords: combined viscosity/density measurement ; density ; magnetic suspension balance ; magnetic suspension coupling ; single-sinker densimeter ; viscometer ; viscosity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A new apparatus for measuring the viscosity and density of fluids is presented. The main element of the instrument is an electronically controlled magnetic suspension coupling. For the density measurement (buoyancy principle according to the single-sinker method), this coupling is used for the contactless transfer of the forces acting on a sinker in the measuring cell to an analytical balance. The coupling also serves as a frictionless bearing for a slender rotating cylindrical body which is slowed down due to the viscous drag of the fluid surrounding the cylinder. The viscosity of the fluid can be directly determined from the decay rate of the rotational frequency. The new combined viscometer-densimeter covers a viscosity range of 5 to 150 μPa·s and a density range from 20 to 2000 kg·m−3 at temperatures from 233 to 523 K and pressures up to 30 MPa. Test measurements on the viscosities and densities of nitrogen and carbon dioxide at 253, 293, and 523 K at pressures up to 30 MPa show an estimated total uncertainty of ±0.6 to ±1.0% in viscosity and of ±0.02 to ±0.05% in density.
    Type of Medium: Electronic Resource
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