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Sources of error in maximum intercuspation from complete dentate full-arch intraoral scans in vitro [Fehlerquellen für die maximale Interkuspidation von Ganzkiefer-Intraoralscans vollbezahnter Kiefer in vitro]
No full textAim: Recording maximum intercuspal position (ICP) is critical for many dental procedures. Digital ICP from intraoral scanners (IOSs) produces variable results. This study investigated the sources of error in recording ICP using an IOS and a recently reported method. Materials and methods: A set of dentate models was scanned three times in a Rexcan DS2 scanner. The models were then scanned six times with a Cerec Omnicam IOS. For each scan, 10 bilateral ‘bite’ scans were performed (n = 6 x 10 bite registrations). Three key points were identified on the first intraoral scan and automatically transplanted onto all subsequent scans. The key point method was validated by using a ‘secondary’ key point transplantation from each scan back to the three laboratory scans, where the location of each point was compared using one-way analysis of variance. Full-arch errors on the intraoral scans were identified by comparing the intermolar key point distances on all intraoral scans against the ‘gold standard’ model scans. Precision of the virtual occlusion was identified by comparing the distance between all upper-lower key point pairs for all intraoral scans using intraclass correlation. Results: Automatic key points were transplanted to model scans with standard deviations (SDs) in location of < 0.003 mm (upper [maxillary]) and < 0.004 mm (lower [mandibular]) arch. The intermolar width of the intraoral scans had a mean error of 0.183 (± 0.061) mm (upper) and 0.017 (± 0.092) mm (lower) arch. Interocclusal key point separation showed poor reliability across groups, but good precision (SD < 0.022 mm) within groups. Conclusion: Automatic key points allowed valid linear distance comparisons across repeated scans. Poor trueness and precision in the full-arch intraoral scans adversely affected interocclusal registrations. Bite scan precision had a less detrimental effect on interocclusal registration
Optimal Use of Physical Centric Relation Records for Digital Workflows
No full textCorrectly articulated dental casts are essential for certain dental treatment. Articulation can be traditional: using a physical articulator; digital: using a physical articulator followed by 3D scanning, or virtual: using 3D scanning and software to articulate scans without initial physical articulation. This study compared the precision of traditional articulation, using physical centric relation records and an articulator and virtually, by digitally aligning scans of the casts and record. Articulated casts and centric relation records were obtained. 12 record pairs were recorded from the articulated casts. Virtual method: all records were scanned, unclamped, in a custom laboratory scanner. The casts were aligned to each scanned record to create virtual articulations. Traditional method: each record was used to physically articulate the casts. Each articulation was recorded using an intraoral scanner. The mean inter-arch separation between three key-points on each cast-pair were used to determine differences in occlusal separation in three anatomical directions, and precision of methods. Traditional articulations: standard deviations in key-point distance never exceeded 0.102mm. The virtual equivalent was 0.059mm. Statistically significant differences (p<0.05) between all anteroposterior separation distances were found between the methods, and in three of six lateral/vertical separations. Virtual articulation was significantly more precise than traditional articulation
Investigating three methods of assessing the clinically relevant trueness of two intraoral scanners
Get PDFAims Intraoral scanners (IOS) are used for a wide range of treatments. Most IOSs produce data appropriate for local work, such as crowns, but evidence suggests that full-arch scans result in more erroneous scans, which may affect the fit of clinical appliances. There are no standardized methods for assessing the quality of IOSs. Though many studies have investigated the accuracy of scanners, one may find the reported values are difficult to interpret in a clinical context. Materials and methods This study investigated the trueness of two IOSs, using three metrics. The clinical value of each metric is discussed. A dentate model was scanned 10 times using two intraoral scanners. Three methods were used to assess the trueness of the scans against a scan produced in a laboratory scanner. Results The mean unsigned distance deviation between a laboratory scan and the Primescan scans was 0.016(±0.006)mm. The mean unsigned distance deviation between the laboratory scan and the Omnicam scans was 0.116(±0.01)mm. The arch width between molars was 55.44mm for the Solutionix scan. The arch width of the Primescan was 55.439(±0.075)mm, while the Omnicam reported 54.672(±0.065)mm. The mean proportion of the Primescan scans deviating beyond 0.1mm when compared against the Solutionix was 0.7(±2.0)%. The equivalent for the Omnicam was 42.1(±2.5)%. Conclusions All methods indicated significantly different results between the scanners. The Primescan produced truer scans than the Omnicam, regardless of measurement method. The intermolar-width and proportion beyond 0.1mm methods may give more clinically relevant insight into the trueness of scan data than current gold-standard methods
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
Full arch precision of six intraoral scanners in vitro
Get PDFPurpose: Intraoral scanners may offer an alternative to traditional impressions. That intraoral scanners produce precise scans is essential. Popular methods used to evaluate precision tend to rely on mean distance deviation between repeated scans. Mean value measurements may underestimate errors resulting in misleading conclusions and clinical decisions. This study investigated the precision of six intraoral scanners using the traditional method of measuring mean error, and a proposed method considering only the most extreme and clinically relevant aspects of a scan. Methods: An edentulous model was scanned five times using six intraoral scanners. The repeated scans were aligned, uniformly trimmed and mean surface deviation measured across all 20 scan combinations within each scanner group. All scan combinations were then measured by arranging scan vertices from greatest to smallest unsigned distance from its compared scan and measuring the median value within the 1% of most greatly deviating points. Traditional mean deviation results and upper-bound deviations were compared. Results: The upper-bound deviation within a scan reported errors up to two times greater than those found when measuring global mean distances. Results revealed clinically relevant errors of more than 0.3 mm in scans produced by the Planmeca and Dentalwings scanners, findings not seen when measuring mean distance error of the complete scan. Conclusions: Upper-bound deviation of a cropped scan may provide a clinically useful metric for scanner precision. The Aadva, 3Shape, CEREC and TDS produced scans potentially appropriate for clinical use while Planmeca and Dentalwings produced deviations greater than 0.3 mm when measuring the upper-bound deviation
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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