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Translucency of monolithic ceramics and the effect of surface condition on their flexural strength and enamel wear
No full textPLEASE NOTE: This work is protected by copyright. Downloading is restricted to the BU community: please log in with a valid BU account to access and click Download. If you are the author of this work and would like to make it publicly available, please contact [email protected] (DScD) --Boston University, Goldman School of Dental Medicine, 2013 (Department of Restorative Sciences and Biomaterials).Includes bibliographic references: leaves 195-204.Objectives: New block materials have been developed to fabricate full-contour restorations. Typically, zirconia and lithium disilicate (IPS e.max CAD) are s milled to full contoured restorations and then subjected to various grinding and polishing procedures in the dentist hand to improve the fit. Various finishing procedures may affect physical and mechanical properties of the material. The purposes of this study are (1) to evaluate the wear resistance and the abrasiveness of zirconia and lithium disilicate with different surface finish against dental enamel, (2) to evaluate the flexural strength of zirconia and lithium disilicate restorative materials subjected to various finishing procedures and (2) to compare the translucency of three different brands of zirconia.
Materials and methods:
(1) 190 ceramic specimens (3 x5 x12 mm) - 10 from each group: IPS e.max CAD polished, glazed, ground and repolished, BruxZir polished, glazed, ground and repolished, Zirlux polished, glazed, ground and repolished, Zenostar polished, glazed, ground and repolished, Vita Mark II polished, Ceramco 3 polished and Unipack Prismatic porcelain polished were subjected to 600,000 strokes of enamel wear in a wear machine under a constant 400g load. Enamel specimens were prepared from sound, caries-free, extracted teeth. Measuring height and weight loss and then calculating volume loss determined the amount of enamel wear. The amount of ceramic wear was determined by measuring weight loss and calculating volume loss. Before and after 60,000, 120,000 and 600,000 strokes of wear testing; surface roughness was measured for each ceramic specimen using a portable surface roughness tester.
(2) 150 bars (2 x 4 x 20 mm) of IPS e.max CAD, BruxZir, old Zirlux, new Zirlux and Zenostar were randomly divided into 15 groups of 10 specimens each. Experimental groups are polished (Buehler Ecomet 250 polisher, 45, 15, 6, 1 micron diamond grit), ground (coarse grit diamond bur grinding) and repolished (medium and fine grit diamond bur finishing and Dialite diamond-impregnated polishers). A 3-point-bending test, span 1 5 mm, was used to measure the flexural strength of materials using an Instron machine at a crosshead speed of 0.5 mm/min with a 10 kN load cell. The surfaces of few random specimens were examined in the SEM.
(3) Spectrophotometer coIor i5 was used to measure the translucency of O.5 mm thick specimens: 30 BruxZir, 30 Zenostar and 30 Zirlux. All data was transferred to an excel sheet and translucency parameter was calculated.
Statistical analysis was conducted using t-test, one-way and two-way ANOVA and Bonferroni’s post hoc test at p = 0.05 1evel of significance.
Results:
(1) Statistical analysis revealed a significantly less enamel abrasion and greater wear resistance for the Zirconia materials than any other group. The most abrasive materials are Ceramco 3 and Unipack prismatic porcelain. Vita Mark II and IPS e.max CAD exhibit an intermediate position. Glazing and coarse grinding significantly increase the abrasiveness of Zirconia to enamel while only glazing increases the abrasiveness of IPS e.max CAD. On the ceramic level, only glazed zirconia exhibited volume loss by enamel wear.
(2) Two-Way ANOVA demonstrated significant difference in flexural strength between the test groups (p[less than] 0.05). IPS e.maX CAD demonstrated lower flexural strength than any Zirconia material tested. Surface finish did not alter the flexural strength of IPS e.max CAD. The new Zirlux flexural strength was also Iower than the old Zirlux, BruxZir and Zenostar which did not differ significantly. Bonferroni’s post hoc multiple comparison tests demonstrated that coarse grinding significantly lower the flexural strength of the zirconia materials while finishing and repolishing raise it back to its starting level except in Zenostar where repolishing cause further reduction in the flexural strength.
(3) Translucency testing demonstrated significant difference between the different brands of zirconia in the study: BruxZir is slightly less translucent than Zirlux and Zenostar.
Conclusions: Despite the limitations of this study, less wear of antagonist teeth was shown with Zirconia than with feldspathic porcelain. Polishing of zirconia full-contoured restoration is recommended for the best results in term of wear behavior and flexural strength
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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