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

Assessment of canal walls after biomechanical preparation of root canals instrumented with protaper universalTM rotary system

OBJECTIVE: The aim of this study was to examine the instrumented walls of root canals prepared with the ProTaper UniversalTM rotary system. MATERIAL AND METHODS: Twenty mesiobuccal canals of human first mandibular molars were divided into 2 groups of 10 specimens each and embedded in a muffle system. The root canals were transversely sectioned 3 mm short of the apex before preparation and remounted in their molds. All root canals were prepared with ProTaper UniversalTM rotary system or with NitiflexTM files. The pre and postoperative images of the apical thirds viewed with a stereoscopic magnifier (X45) were captured digitally for further analysis. Data were analyzed statistically by Fisher's exact test and Chi-square test at 5% significance level. RESULTS: The differences observed between the instrumented and the noninstrumented walls were not statistically significant (p<0.05). CONCLUSIONS: The NitiflexTM files and the ProTaper UniversalTM rotary system failed to instrument all the root canal walls

Fachagentur Nachwachsende Rohstoffe e.V. (FNR). Jahresbericht 1997/98

Im Berichtszeitraumwurden 81 Projekte mit einem Foerdervolumen von 47 Mio. DM durch das BML bewilligt. Der ueberwiegende Anteil der gefoerderten Vorhaben liegt im Bereich der stofflichen Nutzung nachwachsender Rohstoffe (z.B. Erzeugung und Verarbeitung von umweltfreundlichen Biorohstoffen sowie Gewinnung erneuerbarer Energie aus Biomasse). (orig./SR)In the period of report, funding of 81 projects in a total amount of 47 million marks was granted by the federal ministry of science and technology (BMBF). Most of the sponsored projects deal with the harnessing of renewable feedstocks (e.g. production and processing of renewable feedstocks and production of renewable energy sources from biomass).(orig./SR)SIGLEAvailable from TIB Hannover / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Chronology of KSC and KSC Related Events for 2000

This document is intended to serve as a record of Kennedy Space Center (KSC) events and is a reference source for historians and other researchers. Arrangement is by day and month and individual articles are attributed to published sources. Materials were researched and described by the KSC Library Archivist with assistance from KSC Library Librarians for KSC Library Services Contractor InDyne, Inc

Fachagentur Nachwachsende Rohstoffe. Jahresbericht 1996/97

In the period under report, 217 project proposals were examined. During the same period, funding of 87 projects in a total amount of 52.3 million marks was granted by the federal ministry of science and technology (BMBF). This is a distinct increase in the number of funded projects in comparison with the previous period of report. Most of the sponsored projects deal with the harnessing of renewable feedstocks. (orig./SR)Im Bereich der Projektfoerderung wurden im Berichtszeitraum 217 Projektvorschlaege geprueft. Insgesamt wurden in dieser Zeit 87 Projekte mit einem Foerdervolumen von 52,3 Mio. DM durch das BML bewilligt. Damit ist gegenueber dem vorangegangenen Berichtszeitraum eine deutliche Steigerung der Anzahl der bewilligten Vorhaben zu verzeichnen. Der ueberwiegende Anteil der gefoerderten Vorhaben liegt im Bereich der stofflichen Nutzung nachwachsender Rohstoffe. (orig./SR)Available from TIB Hannover / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Ernaehrung, Landwirtschaft und Forsten, Bonn (Germany)DEGerman

Hydrogen from Regenerative Energy Power Sources: pressurised alkaline electrolyser with high efficiency and wide operating range The EU-Project „RESelyser“

The project RESelyser develops high pressure, highly efficient, low cost alkaline water electrolysers that can be integrated with renewable energy power sources (RES) using an advanced membrane concept, highly efficient electrodes and a new cell design. A new separator membrane with internal electrolyte circulation and an adapted design of the cell to improve mass transfer, especially gas evacuation is investigated and demonstrated. Intermittent and varying load operation with RES will be addressed by improved electrode stability and a cell concept for increasing the gas purity of hydrogen and oxygen especially at low power operation. Also the system architecture will be optimized for intermittent operation of the electrolyser. First results will be presented: high performance electrodes with a plasma sprayed coating layer have a surface of more than 30 000 cm2/cm2 electrode area and show high performance and stability. A double layer diaphragm with internal KOH supply improves the gas purity and high current density performance of the cell. The project is supported by the European Union's Seventh Framework Programme (FP7/2007-2013) for the Fuel Cells and Hydrogen Joint Technology Initiative under grant agreement n° [278732

Hydrogen from Regenerative Energy Power Sources: pressurised alkaline electrolyser with high efficiency and wide operating range The Project „RESelyser“

The RESelyser project adresses some of the points to make alkaline electrolysers even more fit to be integrated with fluctuating renewable energy sources Cost reduction Suitable for fast power fluctuations Fast startup, no problems with shutdown Long lifetime High efficiency There is much more potential for improvement of alkaline electrolysers than what can be worked out in one projec