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Studies for a Magnetic Measurement System for Mandibular Movement Using Neural Networks

Masatake Akutagawa, Yohsuke Kinouchi*

School of Medical Sciences, The University of Tokushima
*Faculty of Engineering, The University of Tokushima

A measurement system for the position and orientation of mandible using a permanent magnet, magnetic sensors and an artificial neural network technique is described. The problem in estimation the magnet position and direction is an inverse problem. Typical methods such as iterative calculations or calibration matching involve intensive calculations. Proposed system makes use of the neural network's ability to realize any function within a short processing time. Computer simulations are used for evaluating measurement accuracy. From the results, we obtained an average error of 7 µm for position and 0.004 degree for angular orientation. These estimation accuracies are satisfactory enough to measure a boundary movement, conditions of occlusion and kinetic characteristics.

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The Study on Influence of Different Setting Angles and Direction of Magnetic Attachments to Retentive Force of Complete Overdenture (Part I)

Yimin Zhao, Taizo Sugimoto*, Kenji Hiranuma*, Yoshinobu Tanaka*

Department of Prosthodontics, College of Stomatology, Fourth Military Medical University, China
*The First Department of Prosthodontics, School of Dentistry, Aichi-Gakuin University

The aim of this research is to evaluate the influence of different setting angles and setting directions of magnetic attachments to retentive force of complete overdenture and explore the possibility to utilize the influence to improve the retention of complete overdenture.
4 keepers of Magfit EX magnetic attachment were setted on the position of bilateral canines and second molars of a standardedentulous mandibular model in different inclined angles and in horizontal, lingual, buccal, mesial and distal inclined directions respectively. A imitated overdenture base with 4 magnetic attachment was made on the model with light cured resin. The strongest retentive force of every overdentures was measured and recorded under vertical (90°) and forward inclined (60°) unloading directions in speed of 1mm/min , 200mm/min respectively. Some interesting results have been obtained from the research, which will be useful for the clinical work.

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Clinical Observations of Dental Magnetic Attachments

Hiroshi Mizutani, Masato Kotake, Kazuo Nakamura and Minoru Ai

The 1st Department of Prosthodontics, Tokyo Medical and Dental University

More than 10 years have passed since dental magnetic attachments were applied to clinical use. As they utilize magnetic attractive force in place of friction, it is said that their retentive force is numerical and durable. However, it is not clear whether the problems of corrosion, wear and/or decreasing retentive force are occurred under the condition of oral cavity. 50 patients(17 men and 33 women, ave.68.7 years) directly treated by the presenters were used in this study. The period after insertion of magnetic dentures extended from 0.5. to 6.5 years. The investigated items were (1) the corrosion, wear and retentive force of magnetic attachments and (2) the mobility, depth of pocket and alveolar bone height of abutment teeth. The results were as follows;

1)Regarding the magnetic attachments
(1) Cases with corrosion were not found.
(2) In 3 teeth out of 75 abutment teeth color changes of the attachments were found.
(3) On 5.5 year attachments, only slight scratches were found.

2)Regarding the abutment teeth
(1) Many cases with decreasing the depth of pockets and the tooth mobility were found during this period.
(2) Cases with remarkable decreasing alveolar bone were not found.

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Magnetic Attachment of Cap Shape (MACS) for Implant

Jyoji Tanaka, Kazumasa Hoshino, Hiroshi Mizutani*

Clinical Implant Society of Japan, MACS Implant Center
*Tokyo Medical and Dental University

Magnets can retain objects with their magnetic force, and have various characteristics that are different from conventional mechanical retainers. They are attracting close attention as improved denture retainers. Furthermore, several problems such as adverse effects during magnetic resonance imaging and deterioration of the keeper (prepared by casting and treated with acids) remain. To resolve these problems and to expand the advantages and use of the magnets, we are developing a new magnet system called a magnetic attachment Magnetic Attachments of a Cap Shape (MACS). This reports on clinical cases which apply the MACS to the implant treatment mainly.

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