Introduction Intraoral scanners allow direct images of oral situation, with fewer steps than conventional impressions. The purpose of this study was to compare the accuracy of digital impressions, traditional impressions, and digitalization of full-arch gypsum models, to evaluate timing of different methods and finally to study perception of patients about conventional and digital impression techniques. Methods Dental arches of fourteen patients were evaluated by alginate impression, titanium dioxide powder-free intraoral scanning (Trios, 3Shape), and digitalization obtained from gypsum models using the same scanner. Conventional and digital techniques were evaluated through measurements (lower and upper arch anteroposterior length, lower and upper intercanine distance, and lower and upper intermolar distance) with a caliber for analogic models and using a computer software for digital models (Ortho Analyzer, Great Lakes Orthodontics). In addition, chairside and processing times were recorded. Finally, each patient completed a VAS questionnaire to evaluate comfort. Statistical analyses were performed with ANOVA and Tukey tests for accuracy measurements and paired t-test for times and VAS scores. Significance was predetermined at P < 0.05. Results The measurements obtained with intraoral scanning, gypsum models after conventional impression, and digitalized gypsum models were not significantly different. Both chairside and processing times of digital scanning were shorter than the traditional method. VAS reporting patients comfort were significantly higher when evaluating digital impression. Conclusions Intraoral scanners used for orthodontic applications provide useful data in clinical practice, comparable to conventional impression. This technology is more time efficient than traditional impression and comfortable for patients. Further evolution with more accurate and faster scanners could in future replace traditional impression methods.

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A cooperative navigation procedure for a team of autonomous underwater vehicles (AUVs) is described and validated on experimental data. The procedure relies on acoustic communication networking among the AUVs and/or fixed acoustic nodes, and it is suitable as a low-cost solution for team navigation. Embedding the acoustic localization measurements in the communication scheme causes delays and sometimes loss of acoustic data, depending on acoustic propagation conditions. Despite this drawback, the results obtained show that on-board localization estimates have an error of the order of few meters, improving the overall navigation performance and leading the system towards long-term autonomy in terms of operating mission time, without the need of periodic resurfacings dedicated to reset the estimation error. The data were collected during the CommsNet ’13 experiment, led by the NATO Science and Technology Organization Center for Maritime Research and Experimentation (CMRE), and the Breaking The Surface ’14 workshop, organized by the University of Zagreb

Autonomous Underwater Vehicles (AUVs) are increasingly employed in underwater operations within many scientific and industrial tasks (e.g. Oil&Gas operations, exploration and surveillance of archaeological sites, reconnaissance and patrolling for military operations). Autonomous underwater navigation is critical due to lack of access to satellite navigation systems (e.g. the Global Positioning System, GPS) and to the typical low functioning rate of the acoustic underwater localization devices typically used. As a result, an AUV must typically proceed for long time intervals in dead-reckoning, i.e. only relying on the measurements of on-board sensors. In this context, the filtering algorithms used to estimate the state of the AUV play a fundamental role in guaranteeing satisfactory underwater navigation accuracy. In this paper, the authors present a comparison between underwater navigation systems relying on either the Extended Kalman Filter (EKF) or the Unscented Kalman Filter (UKF) for the AUV state estimation. These approaches have been currently tested offline running on the experimental data collected with the Typhoon-class AUVs (TifOne and TifTu) during different missions at sea. Typhoon is an AUV designed by the Department of Industrial Engineering of the University of Florence for exploration and surveillance of underwater archaeological sites in the framework of the THESAURUS project (2011-2013 funded by Tuscan Region) and the European ARROWS project. A performance comparison between the proposed UKF-based navigation system and the standard, EKF-based, system is here presented basing on the experimental data of different missions at sea. In particular the proposed missions are the final demo of the THESAURUS project in Livorno (Italy) in August 2013 and the preliminary tests at sea of the ARROWS project performed during the Breaking the Surface workshop in Biograd na Moru (Croatia) during October 2014. The achieved results are encouraging: the research outcome has shown the effectiveness of both navigation algorithms and the superiority of the UKF