1,721,002 research outputs found
In vitro biofilm formation on resin-based composites cured under different surface conditions
No full textObjectives: The interfacial conditions occurring during light-curing procedures of resin-based composites (RBCs) influence their surface properties and therefore the biological behavior of the material. This study aimed to evaluate the influence of different surface curing conditions on in vitro biofilm formation by Streptococcus mutans and mixed oral microflora, in the presence or absence of surface salivary pre-conditioning. Methods: Two nanohybrid RBCs and four interfacial curing conditions (open air, argon, nitrogen and glycerin) were evaluated. Surface roughness (SR), surface elemental composition (energy-dispersive X-ray spectrometry, EDS) and biofilm formation (S. mutans and oral microcosm) were assessed. Surfaces were observed using scanning electron microscopy (SEM). Microbiological tests were performed with and without saliva pre-conditioning of the surfaces. EDS analysis was performed before and after biofilm formation, and biofilm morphology was evaluated using confocal laser scanning microscopy (CLSM). Data were analyzed using multi-way ANOVA and Tukey post-hoc test (p < 0.05). Results: Interfacial curing conditions significantly influenced SR depending on the tested RBC. EDS analysis showed that surface elemental composition was significantly influenced by the interfacial curing condition depending on the tested RBC. Interfacial curing conditions significantly influenced biofilm formation in both microbiological models in the absence of saliva pre-conditioning, depending on the tested RBC, whereas saliva pre-conditioning abrogated these effects. Conclusions: Surface curing conditions significantly impacted biofilm formation in a material-dependent manner, which was abrogated when surfaces were pre-conditioned with saliva. Clinical significance: Curing under glycerin did not improve the microbiological performances of the tested RBCs. These results, needing to be confirmed by in vivo data, have the potential to simplify operative procedures in restorative dentistry
Kinetics of polymerization and contraction stress development in self-adhesive resin cements
No full textObjectives. The aim of the study was to evaluate the contraction stress, microhardness and polymerization kinetics of three self-adhesive cements vs. conventional dual-cure resin cement. Methods. Cements tested were: RelyX Unicem (3M ESPE, St. Paul, MN, USA), MaxCem Elite (Kerr, Orange, CA, USA), Clearfil SA Cement (Kuraray, Tokyo, Japan) and Duolink (Bisco Inc., Schaumburg, IL, USA). Cements were irradiated with a LED-curing unit (bluephase, Ivoclar-Vivadent) for 20 or 40 s and the contraction forces (N) generated during polymerization were continuously recorded for 6 h with a universal testing machine. Polymerization kinetics were monitored using micro-Raman spectroscopy and degree of conversion was calculated. Vickers microhardness was also recorded. All measurements were performed at 10 min and 6 h. Data were statistically analyzed by three-way ANOVA with repeated measures and Tukey's post hoc test (alpha = 0.05). Results. Irrespective of exposure time, stress analysis ranked in the following order: Clearfil SA Cement < MaxCem < RelyXUnicem <= Duolink (p < 0.05). Stress was correlated with microhardness values (p < 0.05). Kinetic curves showed that maximum degree of conversion was attained more quickly than maximum stress after light activation. Significance. The conventional resin-based cement showed higher stress values than the self-adhesive cements. The results were material-dependent and probably correlated to the composition of each material. (C) 2012 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved
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
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