abstracts4-1-e

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Current Status of Researches on Biomagnetism

Kazuhiko Atsumi

President, Suzuka University of Medical Science and Technology

The researches on biomagnetism which was promoted by development of SQUID are divided into the two fields : measurements on biomagnetic signals (medical diagnosis) and biological effects of magnetism on living bodies (medical treatment).

The researches o biomagnetic measurements are divided into the four areas as follows,

1) MEG, MCG, MMG, MGG etc.

2) MPG

3) Electromagnetic flowmetry etc.

4) Magnetic resonance measurements

On the other hands, the researches on biological effects of magnetism were performed on cells, tissues, organs and living bodies ; fishes, birds, mammals and humans and the theories of effects and the guidelines of safety were proposed.

Keywords : biomagnetism, magneto cardiogram, magneto encephalogram, biological effect of magnetism, guideline of safety on magnetic radiation

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Estimation of Corrosion Resistance for SUS430 Stainless Steels made from High Purity Fe regarding Dental Magnetic Materials

Yukyo Takada and Osamu Okuno

Department of Dental Materials Science, School of Dentistry, Tohoku University

Corrosion resistance and saturation magnetic flux densities were measured in several commercial ferritic stainless steels to find composition of the stainless steels with magnetic property and corrosion resistance enough to use for dental magnetic materials. Those two properties showed contradiction regarding amount of Fe and Cr contained in the stainless steels. Since the corrosion resistance of commercial SUS430 stainless steels were slightly inferior to that of SUS316L and SUS304 stainless steels, they might be limits to be used for dental magnetic materials. Accordingly SUS430 stainless steels made from high purity Fe were investigated in this study because high purity Fe had succeeded in improving the corrosion resistance of ferritic stainless steels. Elution test in 0.9mass% NaCl solution revealed that these SUS430 stainless steels had corrosion resistance to compare with SUS316L stainless steels as biomaterial. Therefore they would be useful for dental magnetic materials in spite of requiring complicated and delicate technique for use.

Keywords : ferritic stainless steel, corrosion resistance, elution test, saturation magnetic flux density, anodic polarization

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Morphological Analysis of the Magnetic Attachment "MAGFIT^®" and Various Resin Teeth

Masayuki Kobayashi, Hitoshi Aizawa, Yoshinori Matsuoka, Yoshiro Kagawa, Kazumoto Hoshiai, Tomohiko Ishigami, Yoshinobu Tanaka, Kenji Hiranuma, Michio Okada^*, Shirou Tanaka and Yasuyuki Sano

The First Department of Prosthodontics, School of Dentistry, Aichi-Gakuin University
^*Department of Dental Laboratory, University Hospital, School of Dentistry, Aichi-Gakuin University

The purpose of this paper is to investigate the outer shape and inner construction of composite resin artificial teeth which are commercially available and are generally popular at the moment and compare them with the size of the magnetic attachment, "Magfit".

Various types and sizes of composite resin artificial teeth were cross sectioned and the contour of the magnetic assembly of the Magfit was superimposed on them.

The results may be summarized as follow :

1) The size of all of the artificial molar teeth are suitable for the magnetic attachment, "Magfit".

2) The size of all of the artificial premolar teeth are inadequate for installation of the magnetic attachment without sacrificing the PMMA layer, located beneath the outer composite layer, by grinding the inside of the teeth to make space for the attachment. This PMMA layer is indispensable in combining the artificial tooth to the denture base.

3) The magnetic attachment can not be installed in the most of artificial incisor teeth. They cross the contour line and project to the outside of the teeth. This is more critical especially on the palatal or lingual side.

4) Magnetic attachments should be reduced in size, or specifically designed artificial teeth will be needed for exclusive use with magnetic attachments.

Keywords : magnetic attachment, artificial tooth, contour, composite resin artificial tooth

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Investigation of Foreign-made Dental Magnetic Attachments

Kazumi Noguchi, Hiroshi Mizutani^* and Minoru Ai^*

Magnetic and Electronic Materials Research Laboratory, Hitachi Metals, Ltd.
^*The First Department of Prosthodontics, Faculty of Dentistry, Tokyo Medical and Dental University

The technical trend of the foreign-made magnetic attachments were reviewed.

The results are summarized as follows ;

1. Magnetic attractive forces are in the range from 320gf to 880gf.

2. The magnetic circuit design is categorized into three types. They are cup york type, sandwich type, and the corrosion proof cap type.

3. Some samples are larger size than the domestic ones. The seals of some magnetic assemblies are not tight enough.

4. All samples are assembled with Nd-Fe-B magnet.

5. All magnetic assemblies have a retention design such as V shape groove, cross hatch pattern type and side wings, which improve the settle of assemblies from a denture.

Keywords : magnetic attachment, attractive force, rare earth magnets, magnetic application

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