1,720,977 research outputs found
Light source influences the conversion degree of dual-curing luting materials
No full textObjectives:
The aim of this study was to evaluate how different light curing sources influence the degree of conversion (DC) of two composite cements used to lute indirect composite restorations of increasing thickness.
Methods:
120 cylindrical onlays (Signum composite – Heraeus - shade A2, 6mm of diameter) of different thickness (2mm, 3mm, 4 mm) were prepared in a custom template. The specimens were divided into three groups (N=40) and luted with different LED light sources (Bluephase C8-Ivoclar Vivadent 800mW/cm2*s for 60s, Bluephase G2-Ivoclar Vivadent 1200 mW/cm2*s for 40 s, Valo-Ultradent, 1000mW/cm2*s for 48s). In each group, 20 inlays were cemented with MultilinkAutomix (Ivoclar-Vivadent), while 20 were cemented with Calibra (Dentsply) interposing the cement between a glass plate and a restoration; the curing tip was shielded so that the light reached the composite material only through the onlay. Each sample was examinated using the Micro-Raman Dilor HR LabRam spectrometer to evaluate the polymer DC. Statistical analysis was carried out using ANOVA test and Tukey's and Fisher's test.
Results:
Multilink Automix DC is significantly higher (p=<0.05) than that of Calibra, regardless of the radiation source used for curing. Bluephase C8 allows to obtain DC values significantly lower (p=<0.05) than those obtained with Valo, while there are no significant differences with Bluephase G2.
1200 mW/cm2*s for 40 s 800mW/cm2*s for 60s 1000mW/cm2*s for 48s
A B A B A B
2 mm 82,2 75,4 85,8 67,8 89 76
3 mm 75,07 70 79,87 61,4 88,4 75
4 mm 71,87 62 75,33 58,4 86,6 66,8
Conclusions:
High radiation power allows a higher degree of conversion in both tested materials. Greater collimation of the light beam allows, even in lamps with medium power, to obtain high DC and a reduced standard deviation
Preoperative diagnosis of a third root canal in first and second maxillary premolars: a challenge for the clinician
No full textAim: The aim of this report was to describe the steps of a diagnostic protocol used to recognise the presence of a third root canal in first and second maxillary premolars at an early stage.
Materials and methods: A total of 43 maxillary first premolars and 51 maxillary second premolars were endodontically treated in a private practice between 1999 and 2004 after having been examined clinically and radiographically.
Results: A third root canal was present in 4 out of the 43 first maxillary premolars (9.3%) and in 1 out of the 51 (1.9%) second maxillary premolars that were endodontically treated. All of the five cases were diagnosed preoperatively. The early interception of an anatomical variant allows the clinician to choose the best operative strategy for a specific tooth in terms of access cavity design, canal shaping and cleaning, filling and post-endodontic restoration.
Conclusions: Radiographic and clinical examinations of maxillary premolars are essential for early diagnosis of the presence of a third root canal. A careful examination of the pulp chamber floor can help to find the orifice of a third root canal intra-operatively
Cleanliness of dentinal walls following post space preparation using magnification
No full textAim: The objective of this study was to assess, by means of a scanning electron microscope (SEM), the cleanliness of canal dentine surfaces after post space preparation with the aid of two different magnification devices, either dental loupes or an operating microscope.
Materials and methods: Twenty extracted single-rooted human teeth (18 canines and 2 premolars) were selected. Root canals were cleaned, shaped using nickel-titanium instruments and filled with gutta-percha. Samples were divided into two groups (n = 10), according to the device used by the operator: A (microscope) and B (loupes). Gutta-percha/sealer fillings were removed using a sequence of low-speed post drills; root canal walls were also cleaned by means of tips for ultrasound and microbrush. SEM images of post spaces were taken, and the presence of both debris and open dentine tubules was evaluated using a three-step scoring system. Mean scores were calculated at three depth levels of post space.
Results: Residual debris was observed in all specimens. Statistically significant differences (P < 0.05) between groups were found at both coronal and apical levels, and better scores for debris and open tubules were obtained by group A.
Conclusions: The use of an operating microscope allowed the authors to achieve superior debridement scores at specific levels (coronal and apical levels) of the post space area, compared with the use of dental loupes
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
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
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
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