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4. The effects of two different patterns on the precision of zirconia all⁃ceramic crowns

Author

ZHANG Juan, LI Dongji⁃ an, JIANG Jie, SITU Yan, ZOU Shuangshuang, and WEN Xingtao

Subjects
Digital impression, 3D scanner, Silicone rubber impression, Marginal adaptation, Proximal con⁃ tact, Occlusal contact, Precision, Medicine
Abstract

Objective The objective of this study was to compare the early clinical effects of zirconia all⁃ceramic crowns using two different impression methods. Zirconia ceramic crowns were produced using digital models based on either a silicone rubber impression perfusion model in vitro or a 3D mouth scanner. Methods A total of 50 patients with a planned restoration of the first permanent molar with zirconia all⁃ceramic crowns after root canal therapy were se⁃ lected and randomly divided into two groups: a digital impression by intraoral 3D scanning group and a digital impres⁃ sion by extraoral scanning after silicone rubber impression group. Zirconia all ⁃ceramic crowns were created by CAD/ CAM in both groups. Marginal adaptation, proximal contact, and occlusal contact were compared between groups. Re⁃ sults There was no significant difference between the two groups in marginal adaptation (P > 0.05). For proximal con⁃ tact and occlusal contact, no significant differences regarding the number of cases for the criteria of level A and level B were found between two groups (P > 0.05), while the misfit value in level B was smaller in the first group than in the second group (P < 0.05). Conclusion Zirconia all ⁃ ceramic crowns with intraoral 3D scanning show excellent early clinical performance.

Published
2018
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6. Flight time minimization of UAV for cooperative data collection in probabilistic LoS channel

Author

Li, Yan, Xu, Shaoyi, Wu, Yunpu, and Li, Dongji

Abstract

This paper investigates the data collection in an unmanned aerial vehicle (UAV)-aided Internet of Things (IoT) network, where a UAV is dispatched to collect data from ground sensors in a practical and accurate probabilistic line-of-sight (LoS) channel. Especially, access points (APs) are introduced to collect data from some sensors in the unlicensed band to improve data collection efficiency. We formulate a mixed-integer non-convex optimization problem to minimize the UAV flight time by jointly designing the UAV 3D trajectory and sensors' scheduling, while ensuring the required amount of data can be collected under the limited UAV energy. To solve this nonconvex problem, we recast the objective problem into a tractable form. Then, the problem is further divided into several sub-problems to solve iteratively, and the successive convex approximation (SCA) scheme is applied to solve each non-convex subproblem. Finally, the bisection search is adopted to speed up the searching for the minimum UAV flight time. Simulation results verify that the UAV flight time can be shortened by the proposed method effectively.

Published
2024
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