1,720,987 research outputs found
Surface roughness of flowable resin composites eroded by acidic and alcoholic drinks
No full textAim: The aim of this study is to evaluate the surface roughness of four flowable resin composites following exposure to acidic and alcoholic drinks.
Materials and Methods: SureFil SDR flow, TetricEvoFlow, Esthet‐X Flow and Amaris Flow HT samples were immersed in artificial saliva, Coca Cola and Chivas Regal Whisky. Each specimen was examined using a Leica DCM 3D microscope: Arithmetical mean height of the surface profiles was measured (Sa).
Results: Kruskal‐Wallis test showed significant differences among various groups (P<0,001). Mann Whitney test was applied and control groups showed significantly lower Sa values than other groups (P=0,008). Coca Cola groups showed highest Sa values (P<0,021). No significant differences (P=0,14) in surface texture were found among the specimens of the different materials. No significant differences were found among TetricEvoFlow, Esthet‐X Flow and Amaris Flow under control conditions nor after Coca Cola application. Under control condition and after Coca Cola application SureFil SDR flow showed significantly higher Sa values. Moreover, after whisky application Amaris Flow showed significantly lower Sa values then the other three groups that showed no significant differences among them.
Conclusions: Acidic and alcoholic drinks eroded the surface roughness of all evaluated flowable resin composites
Decalcifying efficacy of different irrigating solutions: effect of cetrimide addition
No full textThe objective of the present study was to evaluate and com- pare the influence of cetrimide on decalcifying capability of different irrigating solutions. Fifteen maxillary central incisor teeth has been col- lected. The canals were prepared in order to obtain four samples from each root. The specimens were randomly divided into 6 experimental groups (n=10) according to tested irrigating agents. Irrigating agents consisted in different composition of EDTA and citric acid solutions, addicted or not with cetrimide. Each specimen was submitted to three successive 5-min immersions in each solution. After exposures, the concentration of Ca2+ extracted was measured by inductively coupled plasma-atomic emission spectrometry (ICP-AES). Data were analysed by means of Kruskal Wallis and Mann Whitney tests. Significance was predetermined at p < 0.05. For all irrigants, the amounts of Ca2+ extract- ed from root canal dentin samples at 10 minutes were not significantly different from values reported after 15 minutes respectively. Therefore, for all irrigants tested, 10 minutes of application are sufficient to obtain maximum Ca2+ release. Moreover citric acid based agents observed a higher release of Ca2+. The addition of cetrimide did not affect the de- calcifying capability of the EDTA and citric acid solutions
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Ultrastructural analysis of the root canal walls after preparation with two rotary nickel-titanium endodontic instruments
No full textBackground: Root canal preparation may produce a large quantity of smear layer that covers canal walls. Aims: The aim of this study was to evaluate by Scanning Electron Microscope (SEM) the root canal dentine after instrumentation with nickel-titanium rotary files, in order to evaluate the presence/absence of smear layer and the presence/absence of open tubules on the root canal walls at the coronal, middle, and apical third of each sample. Materials and Methods: A total of 20 single-rooted freshly extracted teeth were selected and divided into two groups. For each group, root canals were shaped with Mtwo and Revo-S instruments under irrigation with Sodium hypochlorite and 17% ethylenediaminetetraacetic acid. Specimens were fractured longitudinally and SEM analyzed at standard magnification of ×1000 and ×5000. The presence/absence of smear layer and the presence/absence of open tubules at the coronal, middle, and apical third of each canal were evaluated using a three-step scale for scores. Statistical Analysis Used: Numeric data were analyzed using the Kruskall-Wallis and Mann-Whitney U-Statistical tests and significance was pre-determined at P < 0.05. Results and Conclusions: This study did not reveal differences among the two groups. Mtwo and Revo-S showed no significant difference between them and both presented very low smear layer scores and open tubules scores, with no significant difference among coronal, middle, and apical third. Mtwo and Revo-S rotary instruments seem to be effective in removing smear layer from canal walls
Variations on the Author
Full text link“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
Cyclic fatigue resistance of OneShape, Reciproc, and WaveOne: An in vitro comparative study
No full textAims: The aim of this in vitro study was to evaluate the cyclic fatigue resistance of three single-use nickel–titanium (NiTi) instruments.
Materials and Methods: Forty files each of OneShape (OS), Reciproc R25 (R25), WaveOne Primary (WO) file, and ProTaper (PT) F2 (as control) were tested in four curved artificial canals with different angles and radii of curvature. The number of cycles to fracture (NCF) was determined and the data were compared for differences by using two-way analysis of variance (P < 0.05).
Results: In general, all single-use instruments were more resistant than traditional rotary instrument used as control. R25 showed the highest cyclic fatigue resistance. One Shape and WO files showed similar cyclic fatigue resistance values, higher than PT F2.
Conclusions: Within the limitations of this study, it can be concluded that R25 was the most fatigue resistant. OS rotary instruments seem to have good mechanical resistance, similar to NiTi files developed for reciprocating motion.
Keywords: NiTi; reciprocating motion
Effects of niti rotary and reciprocating instruments on debris and smear layer scores: an SEM evaluation
No full textPurpose: The purpose of the present study was to investigate the cleaning efficacy of 2 different nickel-titanium (NiTi) rotary systems: a new single system reciproc compared with the rotary full sequence Mtwo. the amount of debris and the morphol- ogy of smear layer were the parameters for the evaluation of the cleanliness of root canals. the null hypothesis of the study was that there would be no significant difference in debris scores and smear layer scores between the 2 systems. Methods: Forty single-rooted freshly extracted teeth were selected and divided into 2 groups. For each group, all root canals were shaped with 2 different NiTi instruments (Mtwo and Reciproc) and irrigated with 5.25% NaOCl and 17% ethylene- diaminetetraacetic acid (EDTA) solutions by 3 trained operators. Specimens were fractured longitudinally and prepared for scanning electron microscopy (SEM) analysis at a standard magnification of ×5,000. The presence/absence of smear layer and the presence/absence of debris at the coronal, middle and apical third of each canal were evaluated using two 5-step scales for scores. Numeric data were analyzed using the Kruskal-Wallis and Mann-Whitney U statistical tests, and signifi- cance was set at a P value <0.05. Results: This study revealed significant differences among the various groups. The Mtwo group presented significantly lower smear layer scores than the Reciproc group (P<0.01) in the middle and apical third of the canal. Conclusions: Conventional continuous rotary Ni-Ti instruments associated with 5.25% NaOCl and 17% EDTA solutions seem to be better for obtaining clean dentinal canal walls. reciprocating instruments leave a higher quantity of smear layer which covers dentinal walls and dentinal tubules
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe 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
Full text linkWe 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
- …
