eine in vitro-Untersuchung

Zielsetzung: Kiefermodelle können mit Modellscannern, intraoralen Scannern und mittlerweile auch digitalen Volumentomographie (DVT)-Geräten digitalisiert werden. Das Ziel dieser Studie war es, die Genauigkeit der verschiedenen direkten und indirekten Digitalisierungsverfahren anhand von drei klinisch relevanten Strecken zu vergleichen. Methode: Ein als Patient dienendes Studienmodell wurde dreidimensional gedruckt und mittels Doppelmischtechnik abgeformt. Die Abformung wurde mit Gips ausgegossen. An beiden Modellen wurden die Masterwerte für die Zahnbogenlänge, die Intermolarenweite und die Intercaninenweite, mit einem Koordinatenmessgerät (Zeiss O-Inspect 422) gemessen. Anschließend wurde das gedruckte Modell mit sechs Intraoralscannern gescannt. Das Gipsmodell wurde mit elf Modellscannern und fünf DVT-Geräten gescannt. Pro Gerät wurden 37 Scans angefertigt. Die resultierenden Stereolithografie-Daten wurden exportiert und mit einer speziellen Messsoftware (ConvinceTM Premium 2012 (3Shape)) linear vermessen. Alle Messungen wurden mit den Masterwerten des entsprechenden Modelles verglichen. Ergebnisse: Die Genauigkeitsmessungen ergaben signifikante Unterschiede zwischen den Digitalisierungsverfahren sowie den Gerätegruppen. Die höchsten Genauigkeiten erzielten die Modellscanner und einzelne DVT-Geräte. Weitere DVT-Geräte zeigten eine etwa vierfach höhere mittlere Abweichung. Die Intraoralscanner wiesen sowohl bei der mittleren Abweichung als auch der Standardabweichung etwa vierfach höhere Werte auf als die Modellscanner. Schlussfolgerung: Einige DVT-Geräte eignen sich zur Digitalisierung von Gipsmodellen und weisen klinisch eine sehr gute Genauigkeit auf, sodass Praxen die mit DVT-Geräten ausgestattet sind Gipsmodelle digitalisieren könnten ohne zusätzliche Geräte zu benötigen.Objective: Dental models can be digitized with model scanners, intraoral scanners and recently also by cone-beam computed tomography. The aim of this study is to investigate the accuracy of various direct and indirect digitization procedures using three clinically relevant distances. Method: A study model serving as a patient was printed three-dimensionally and molded using a double mix technique. The impression was casted with plaster. The master values for the length of the archlength, the intermolar width and the intercanine width were measured on both models using a coordinate measuring device (Zeiss OInspect 422). The printed model was then scanned with six intraoral scanners. The plaster model was scanned with eleven model scanners and five CBCT devices. 37 scans were taken per device. The resulting stereolithography data were exported and measured linearly using special measuring software (Convince ™ Premium 2012 (3Shape)). All measurements were compared with the master values of the respective model. Results: The accuracy measurements showed significant differences between the digitization methods and the device groups. The highest accuracy was achieved using model scanners and some CBCT devices. Other CBCT devices showed a four times higher mean deviation. The intraoral scanners showed about four times higher values for both the mean deviation and the standard deviation than the model scanners. Conclusion: Some CBCT devices are suitable for the digitization of plaster models and show very good clinical accuracy. Dental offices equipped with CBCT devices could digitize plaster casts without the need for additional devices

Comparison on students’ motivation in learning music between China and Hong Kong / Debbie Mitchelle Robben

The purpose of this study was to explore whether there are comparisons between two countries, namely China and Hong Kong, on students and parents' perception towards learning music and the factors that affect students' motivation in learning music. Secondary data was used where articles, journals, books, and previous related researches became the source of information for this study. Findings suggest that students and parents' perception towards learning music between these two countries is more or less the same and the factors that affect students' motivation in learning music are generally the same and show not much of a difference

The Mediating Effect of NPD-Activities and NPD-Performance on the Relationship between Market Orientation and Organizational Performance

Empirical research has demonstrated that a market orientation has in general a positive effect on organizational performance. The potential benefits of a market orientation have, however, not been realized because academics and practitioners do not yet understand the modus operandi that transform market orientation into superior organizational performance. Recent research has demonstrated that the proficiency in new product development (NPD) activities might be the key in the conversion of market orientation into superior NPD-performance, and hence, organizational performance. This study is designed to test a set of hypotheses related to the interrelationships among market orientation, the proficiency in NPD-activities, NPD-performance, and organizational performance. The results from a sample of 126 manufacturing firms in the Netherlands present evidence for the mediating role of the proficiency in several NPD-activities and NPD-performance in the relationship between market orientation and organizational performance. The fact that this mediating role has been found thus provides a better understanding of how market-oriented behaviors are transformed into superior value for customers.performance evaluation;innovation;statistical analysis;market orientation;studies

Optical evidence for adsorption of charged inverse micelles in a Stern layer

Understanding the properties and behavior of nonpolar liquids containing surfactant and colloidal particles is essential for applications such as electrophoretic ink displays and liquid toner printing. Charged inverse micelles, formed from aggregated surfactant molecules, and their effect on the electrophoretic motion of colloidal particles have been investigated in quite some detail over the past years. However, the interactions of charged inverse micelles at the electrode interfaces are still not well understood. In some surfactant systems the charged inverse micelles bounce off the electrodes, while in other systems they are quickly adsorbed to the electrodes upon contact. In this work a fluorocarbon solvent doped with a fluorosurfactant is investigated in which the adsorption of charged inverse micelles to the electrode occurs slowly, leading to long-term charging phenomena. We propose a physical model and an equivalent electrical model based on adsorption and desorption of inverse micelles into a Stern layer with finite thickness. We compare two limiting cases of this model: the 'adsorption/desorption' limit and the 'Stern layer adsorption' limit. Both limits are compatible with electrical measurements. The 'Stern layer adsorption' limit additionally explains the optical measurements, because these measurements indicate that the diffuse double layer vanishes over time when a polarizing voltage step is applied. The obtained value for the Stern layer thickness and the proportionality between the charging time constant and the surfactant concentration are also compatible with the 'Stern layer adsorption' limit

Ultrasonography of the painful hip in childhood

There are many diseases in childhood that affect the hip joint. Some diseases are systemic in origin and initially may present themselves as hip disorders, such as rheumatoid arthritis. other diseases are localized specifically in the hip joint, such as transient synovitis and Perthes' disease, mostly unilateral. Neoplastic or infectious diseases around the hip joint may also manifest themselves as a painful hip. If both hips are affected the differential diagnosis should include skeletal dysplasias (multiple epiphyseal dysplasia) and metabolic diseases (hypothyroidism, Gaucher's disease, mucopolysaccharidoses and mucolipidoses)

pH sensor properties of electrochemically grown iridium oxide

The open-circuit potential of an electrochemically grown iridium oxide film is measured and shows a pH sensitivity between −60 and −80 mV/pH. This sensitivity is found to depend on the state of oxidation of the iridium oxide film; for a higher state of oxidation (or more of the oxide in the high valence state), the sensitivity is also higher. This high sensitivity can be explained on the basis of the extra proton release as a result of the acidic character of the porous hydrous oxyhydroxide, in combination with the redox behaviour.\ud \ud The response time to a pH step is measured and is found to depend mainly on the thickness of the oxide; it varies from 40 ms to 0.35 s due to the porous nature of the film.\ud \ud Drift measurements show that an iridium oxide film in reduced state is slowly oxidized by dissolved oxygen, whereas a pre-oxidized film in a pH = 4.01 buffer solution in contact with air shows a long-term drift of <0.3 mV/h