The effect of a manual instrumentation technique on five types of premolar root canal geometry assessed by microcomputed tomography and three-dimensional reconstruction

<p>Abstract</p> <p>Background</p> <p>Together with diagnosis and treatment planning, a good knowledge of the root canal system and its frequent variations is a necessity for successful root canal therapy. The selection of instrumentation techniques for variants in internal anatomy of teeth has significant effects on the shaping ability and cleaning effectiveness. The aim of this study was to reveal the differences made by including variations in the internal anatomy of premolars into the study protocol for investigation of a single instrumentation technique (hand ProTaper instruments) assessed by microcomputed tomography and three-dimensional reconstruction.</p> <p>Methods</p> <p>Five single-root premolars, whose root canal systems were classified into one of five types, were scanned with micro-CT before and after preparation with a hand ProTaper instrument. Instrumentation characteristics were measured quantitatively in 3-D using a customized application framework based on MeVisLab. Numeric values were obtained for canal surface area, volume, volume changes, percentage of untouched surface, dentin wall thickness, and the thickness of dentin removed. Preparation errors were also evaluated using a color-coded reconstruction.</p> <p>Results</p> <p>Canal volumes and surface areas were increased after instrumentation. Prepared canals of all five types were straightened, with transportation toward the inner aspects of S-shaped or multiple curves. However, a ledge was formed at the apical third curve of the type II canal system and a wide range in the percentage of unchanged canal surfaces (27.4-83.0%) was recorded. The dentin walls were more than 0.3 mm thick except in a 1 mm zone from the apical surface and the hazardous area of the type II canal system after preparation with an F3 instrument.</p> <p>Conclusions</p> <p>The 3-D color-coded images showed different morphological changes in the five types of root canal systems shaped with the same hand instrumentation technique. Premolars are among the most complex teeth for root canal treatment and instrumentation techniques for the root canal systems of premolars should be selected individually depending on the 3-D canal configuration of each tooth. Further study is needed to demonstrate the differences made by including variations in the internal anatomy of teeth into the study protocol of clinical RCT for identifying the best preparation technique.</p

Untersuchungen zur Ertragserhoehung und -stabilisierung bei Krambe durch Massnahmen der Sortenwahl, des Pflanzenbaus und des Pflanzenschutzes Abschlussbericht

SIGLEAvailable from TIB Hannover: F01B827 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Ernaehrung, Landwirtschaft und Forsten, Bonn (Germany)DEGerman

Modellvorhaben Krambe-Anbau 1996-1999 Abschlussbericht

SIGLEAvailable from TIB Hannover: F01B828 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Ernaehrung, Landwirtschaft und Forsten, Bonn (Germany)DEGerman

Erarbeitung von produktionstechnischen Grundlagen fuer den Anbau von Krambe als nachwachsender Rohstoff in Deutschland Abschlussbericht

SIGLEAvailable from TIB Hannover: F99B1478 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Ernaehrung, Landwirtschaft und Forsten, Bonn (Germany)DEGerman

Entwicklung von Verfahren zur Verringerung der Umweltbelastung durch Cadmium bei der Produktion von alkalischen Nickel/Cadmium-Akkumulatoren Abschlussbericht

With 18 refs., 14 tabs., 72 figs.SIGLEAvailable from TIB Hannover: FR 6595 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Freshwater phytoplankton diversity: models, drivers and implications for ecosystem properties

Our understanding on phytoplankton diversity has largely been progressing since the publication of Hutchinson on the paradox of the plankton. In this paper, we summarise some major steps in phytoplankton ecology in the context of mechanisms underlying phytoplankton diversity. Here, we provide a framework for phytoplankton community assembly and an overview of measures on taxonomic and functional diversity. We show how ecological theories on species competition together with modelling approaches and laboratory experiments helped understand species coexistence and maintenance of diversity in phytoplankton. The non-equilibrium nature of phytoplankton and the role of disturbances in shaping diversity are also discussed. Furthermore, we discuss the role of water body size, productivity of habitats and temperature on phytoplankton species richness, and how diversity may affect the functioning of lake ecosystems. At last, we give an insight into molecular tools that have emerged in the last decades and argue how it has broadened our perspective on microbial diversity. Besides historical backgrounds, some critical comments have also been mad