Reproducibility and accuracy of linear measurements on dental models derived from cone-beam computed tomography compared with digital dental casts.

INTRODUCTION The aim of this study was to determine the reproducibility and accuracy of linear measurements on 2 types of dental models derived from cone-beam computed tomography (CBCT) scans: CBCT images, and Anatomodels (InVivoDental, San Jose, Calif); these were compared with digital models generated from dental impressions (Digimodels; Orthoproof, Nieuwegein, The Netherlands). The Digimodels were used as the reference standard. METHODS The 3 types of digital models were made from 10 subjects. Four examiners repeated 37 linear tooth and arch measurements 10 times. Paired t tests and the intraclass correlation coefficient were performed to determine the reproducibility and accuracy of the measurements. RESULTS The CBCT images showed significantly smaller intraclass correlation coefficient values and larger duplicate measurement errors compared with the corresponding values for Digimodels and Anatomodels. The average difference between measurements on CBCT images and Digimodels ranged from -0.4 to 1.65 mm, with limits of agreement values up to 1.3 mm for crown-width measurements. The average difference between Anatomodels and Digimodels ranged from -0.42 to 0.84 mm with limits of agreement values up to 1.65 mm. CONCLUSIONS Statistically significant differences between measurements on Digimodels and Anatomodels, and between Digimodels and CBCT images, were found. Although the mean differences might be clinically acceptable, the random errors were relatively large compared with corresponding measurements reported in the literature for both Anatomodels and CBCT images, and might be clinically important. Therefore, with the CBCT settings used in this study, measurements made directly on CBCT images and Anatomodels are not as accurate as measurements on Digimodels.

The effect of nontemporal stimulus size on perceived duration as assessed by the method of reproduction

Perceived duration is assumed to be positively related to nontemporal stimulus magnitude. Most recently, the finding that larger stimuli are perceived to last longer has been challenged to represent a mere decisional bias induced by the use of comparative duration judgments. Therefore, in the present study, the method of temporal reproduction was applied as a psychophysical procedure to quantify perceived duration. Another major goal was to investigate the influence of attention on the effect of visual stimulus size on perceived duration. For this purpose, an additional dual-task paradigm was employed. Our results not only converged with previous findings in demonstrating a functional positive relationship between nontemporal stimulus size and perceived duration, but also showed that the effect of stimulus size on perceived duration was not confined to comparative duration judgments. Furthermore, the effect of stimulus size proved to be independent of attentional resources allocated to stimulus size; nontemporal visual stimulus information does not need to be processed intentionally to influence perceived duration. Finally, the effect of nontemporal stimulus size on perceived duration was effectively modulated by the duration of the target intervals, suggesting a hitherto largely unrecognized role of temporal context for the effect of nontemporal stimulus size to become evident.

Explication as a Method of Conceptual Re-engineering

Taking Carnap’s classic exposition as a starting point, this paper develops a pragmatic account of the method of explication, defends it against a range of challenges and proposes a detailed recipe for the practice of explicating. It is then argued that confusions are involved in characterizing explications as definitions, and in advocating precising definitions as an alternative to explications. Explication is better characterized as conceptual re-engineering for theoretical purposes, in contrast to conceptual re-engineering for other purposes and improving exactness for purely practical reasons. Finally, three limitations which call for further development of the method of explication are discussed.

Accuracy of linear measurements using three imaging modalities: two lateral cephalograms and one 3D model from CBCT data

BACKGROUND The aim of this study was to evaluate the accuracy of linear measurements on three imaging modalities: lateral cephalograms from a cephalometric machine with a 3 m source-to-mid-sagittal-plane distance (SMD), from a machine with 1.5 m SMD and 3D models from cone-beam computed tomography (CBCT) data. METHODS Twenty-one dry human skulls were used. Lateral cephalograms were taken, using two cephalometric devices: one with a 3 m SMD and one with a 1.5 m SMD. CBCT scans were taken by 3D Accuitomo® 170, and 3D surface models were created in Maxilim® software. Thirteen linear measurements were completed twice by two observers with a 4 week interval. Direct physical measurements by a digital calliper were defined as the gold standard. Statistical analysis was performed. RESULTS Nasion-Point A was significantly different from the gold standard in all methods. More statistically significant differences were found on the measurements of the 3 m SMD cephalograms in comparison to the other methods. Intra- and inter-observer agreement based on 3D measurements was slightly better than others. LIMITATIONS Dry human skulls without soft tissues were used. Therefore, the results have to be interpreted with caution, as they do not fully represent clinical conditions. CONCLUSIONS 3D measurements resulted in a better observer agreement. The accuracy of the measurements based on CBCT and 1.5 m SMD cephalogram was better than a 3 m SMD cephalogram. These findings demonstrated the linear measurements accuracy and reliability of 3D measurements based on CBCT data when compared to 2D techniques. Future studies should focus on the implementation of 3D cephalometry in clinical practice.

Selecting Contexts. One Method of Selecting Contexts for Theatre Historiography

In principle, the world and life itself are the contexts of theatrical events. The term context is broad and thus seems hardly usable. It only makes sense to use the term when terminologies and methodologies determine which parts of their contexts are to be incorporated and analysed for which theatrical event. This presentation exemplifies a method which is particularly suitable for sensibly selecting the most important contexts for research in theatre history. The complexity of the representation increases continuously from The Presentation of Self in Everyday Life to Brecht’s “Street Scene” and “Everyday Theatre”, portrayals of rulers in feasts and parades to Hamlet productions by the Royal Shakespeare Company or a Wagner opera in Bayreuth. The different forms of theatre thus constitute a continuum which spans from “everyday theatre” to “art theatre”. The representation of the world in this continuum is sometimes questioned by the means of theatre, for example when Commedia dell’arte takes a critical stance towards the representative theatre of the humanists or when playful devices such as reversal, parody and fragmentation challenge the representative character of productions, which is applied by the Vice character for instance. There is a second component that has an impact on the continuum without a theatrical device: attitude, opinion, norms and bans which originate from society. As excerpts of contexts, they refer to single forms of theatre in the continuum. This results in a complex system of four components which evolves from the panorama between the antipodes “everyday theatre” and “art theatre” as well as both spheres of influence of which only one uses theatrical devices. All components interact in a specific time frame in a specific place in a specific way in each case, which can then be described as the theatricality in this time frame. This presentation will deal with what the concept is capable of doing.