1,720,957 research outputs found
Trueness and precision of 5 intraoral scanners in the impressions of single and multiple implants: a comparative in vitro study
No full textBackgroundUntil now, a few studies have addressed the accuracy of intraoral scanners (IOSs) in implantology. Hence, the aim of this in vitro study was to assess the accuracy of 5 different IOSs in the impressions of single and multiple implants, and to compare them.MethodsPlaster models were prepared, representative of a partially edentulous maxilla (PEM) to be restored with a single crown (SC) and a partial prosthesis (PP), and a totally edentulous maxilla (TEM) to be restored with a full-arch (FA). These models were scanned with a desktop scanner, to capture reference models (RMs), and with 5 IOSs (CS 3600 (R), Trios3 (R), Omnicam (R), DWIO (R), Emerald (R)); 10 scans were taken for each model, using each IOS. All IOS datasets were loaded into a reverse-engineering software where they were superimposed on the corresponding RMs, to evaluate trueness, and superimposed on each other within groups, to determine precision. A statistical analysis was performed.ResultsIn the SC, CS 3600 (R) had the best trueness (15.20.8m), followed by Trios3 (R) (22.3 +/- 0.5m), DWIO (R) (27.8 +/- 3.2m), Omnicam (R) (28.4 +/- 4.5m), Emerald (R) (43.1 +/- 11.5m). In the PP, CS 3600 (R) had the best trueness (23 +/- 1.1m), followed by Trios3 (R) (28.5 +/- 0.5m), Omnicam (R) (38.1 +/- 8.8m), Emerald (R) (49.3 +/- 5.5m), DWIO (R) (49.8 +/- 5m). In the FA, CS 3600 (R) had the best trueness (44.9 +/- 8.9m), followed by Trios3 (R) (46.3 +/- 4.9m), Emerald (R) (66.3 +/- 5.6m), Omnicam (R) (70.4 +/- 11.9m), DWIO (R) (92.1 +/- 24.1m). Significant differences were found between the IOSs; a significant difference in trueness was found between the contexts (SC vs. PP vs. FA). In the SC, CS 3600 (R) had the best precision (11.3 +/- 1.1m), followed by Trios3 (R) (15.2 +/- 0.8m), DWIO (R) (27.1 +/- 10.7m), Omnicam (R) (30.6 +/- 3.3m), Emerald (R) (32.8 +/- 10.7m). In the PP, CS 3600 (R) had the best precision (17 +/- 2.3m), followed by Trios3 (R) (21 +/- 1.9m), Emerald (R) (29.9 +/- 8.9m), DWIO (R) (34.8 +/- 10.8m), Omnicam (R) (43.2 +/- 9.4m). In the FA, Trios3 (R) had the best precision (35.6 +/- 3.4m), followed by CS 3600 (R) (35.7 +/- 4.3m), Emerald (R) (61.5 +/- 18.1m), Omnicam (R) (89.3 +/- 14m), DWIO (R) (111 +/- 24.8m). Significant differences were found between the IOSs; a significant difference in precision was found between the contexts (SC vs. PP vs. FA).Conclusions The IOSs showed significant differences between them, both in trueness and in precision. The mathematical error increased in the transition from SC to PP up to FA, both in trueness than in precision
Accuracy of 6 Desktop 3D Printers in Dentistry: A Comparative In Vitro Study
No full textPURPOSE: To compare the accuracy of 6 desktop 3D printers in dentistry. METHODS: A parallelepiped (PP) with known geometry and holes of different diameters was designed and printed with 6 desktop 3D printers (Sheraprint 40®; Solflex 350®; Form 2®; MoonRay D75®; Vida HD®; XFAB 2000®). For each printer, 9 PPs were printed with proprietary materials; these PPs were not cured and underwent dimensional analysis by optical microscopy and precision probing. A file representative of a dentate model (DM) was also printed with the aforementioned printers. For each printer, 3 DMs were printed with the proprietary materials. These DMs were cured and after 1 month, scanned with a desktop scanner and superimposed on the virtual reference model, to investigate trueness. RESULTS: Dimensional analysis by optical microscopy and precision probing highlighted the reliability of the 3D printed models; errors were compatible with clinical use. However, both linear and diameter measurements revealed statistically significant differences between the machines. The trueness of the DMs 1 month after printing was low, suggesting that they underwent dimensional contraction over time, albeit with differences between the printers. CONCLUSIONS: The 3D printed models showed acceptable accuracy, although statistically significant differences were found among them
Trueness and precision of 3D-printed versus milled monolithic zirconia crowns: An in vitro study
Get PDFPurpose: To compare the trueness and precision of 3D-printed versus milled monolithic zirconia crowns (MZCs). Methods: A model of a maxilla with a prepared premolar was scanned with an industrial scanner (ATOSQ (R), Gom) and an MZC was designed in computer-assisted-design (CAD) software (DentalCad (R), Exocad). From that standard tessellation language (STL) file, 10 MZCs (test) were 3D-printed with a Lithography-based Ceramic Manufacturing (LCM) printer (CerafabS65 (R), Lithoz) and 10 MZCs (control) were milled using a 5-axis machine (DWX-52D (R), DGShape). All MZCs were sintered and scanned with the aforementioned scanner. The surface data of each sample (overall crown, marginal area, occlusal surface) were superimposed to the original CAD file (ControlX (R), Geomagic) to evaluate trueness: (90-10)/2, absolute average (ABS AVG) and root mean square (RMS) values were obtained for test and control groups (MathLab (R), Mathworks) and used for analysis. Finally, the clinical precision (marginal adaptation, interproximal contacts) of test and control MZCs was investigated on a split-cast model printed (Solflex350 (R), Voco) from the CAD project, and compared. Results: The milled MZCs had a significantly higher trueness than the 3D-printed ones, overall [(90-10)/2 printed 37.8 pm vs milled 21.2 pm; ABS AVG printed 27.2 pm vs milled 15.1 pm; RMS printed 33.2 pm vs milled 20.5 pm; p = 0.0000051, at the margins [(90-10)/2 printed 25.6 pm vs milled 12.4 pm; ABS AVG printed 17.8 pm vs milled 9.4 pm; RMS printed 22.8 pm vs milled 15.6 pm; p= 0.0000111 and at the occlusal level [(90-10)/2 printed 50.4 pm vs milled 21.9 pm; ABS AVG printed 29.6 pm vs milled 14.7 pm; RMS printed 38.9 pm vs milled 22.5 pm; p = 0.0000051. However, with regard to precision, both test and control groups scored highly, with no significant difference either in the quality of interproximal contact points (p = 0.355) or marginal closure (p = 0.355). Conclusions: Milled MZCs had a statistically higher trueness than 3D-printed ones; all crowns, however, showed high precision, compatible with the clinical use. Clinical significance: Although milled MZCs remain more accurate than 3D-printed ones, the LCM technique seems able to guarantee the production of clinically precise zirconia crowns
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
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