日 磁 歯 誌
J J M ag Dent
ISSN 0918-9629

日本磁気歯科学会雑誌

2023

Volume 32. Number 2

第三十二巻 第二号
J J Mag Dent

日本磁気歯科学会雑誌

The Journal of the Japanese Societyof Magnetic Applications in Dentistry
Volume 32, Number 2

日本磁気歯科学会
23

The Japanese Society of Magnetic Applications in Dentistry
日本磁気歯科学会

J J Mag Dent vol. 32 No. 2 2023

The Journal of the Japanese Societyof Magnetic Applications in Dentistry
Volume 32, Number 2

Proceedings of the 22th International Conference
on Magnetic Applications in Dentistry

The Japanese Society of Magnetic Applications in Dentistry

J J Mag Dent vol. 32 No. 2 2023

The 22th International Conference on Magnetic Applications in Dentistry
The 22th International Conference on The Japanese Society of Magnetic Applications in
Dentistry organized by JSMAD was held on the Internet as follows;
Meeting Dates:
Friday, February 24 to Tuesday, March 14, 2023
Location:
JSMAD web site
http://jsmad.jp/international/22/
General Chair:Prof. Hideki Aita, Health Sciences University of Hokkaido
Subjects:
Researches and developments related to dentistry and magnetism such as:•

Magnetic attachments for dentures•

Orthodontic appliances using magnets•

Measurement of jaw movement using magnetic sensors•

Biological effects of magnetic fields•

Dental applications of MRI•OthersJ J Mag Dent vol. 32

No. 2 2023

Conference Committee
The Japanese Society of Magnetic applications in Dentistry
President of the Japanese Society of Magnetic applications in Dentistry
Dr. Masayuki Hideshima, Tokyo Medical and Dental University
Vice-President of the Japanese Society of Magnetic applications in Dentistry
Dr. Jun Takebe, Aichi-Gakuin University
Conference Secretary
Dr. Junichiro Wada, Tokyo Medical and Dental University

Conference Organizing Committee
Dr. Hideki Aita, Health Science University of Hokkaido
Dr. Masatake Akutagawa, The University of Tokushima
Dr. Tetsuo Ichikawa, The University of Tokushima
Dr. Shuji Ohkawa, Meikai University
Dr. Tetsuo Ohyama, Nihon University
Dr. Chikahiro Ohkubo, Tsurumi University
Dr. Hisashi Koshino, Health Science University of Hokkaido
Dr. Mineyo Sone, Meikai University
Dr. Joji Tanaka, Tanaka Dental Clinic
Dr. Fujio Tsuchida, Mami's Dental Office
Dr. Kazuo Nakamura, Sanno Hospital
Dr. Kazuhiro Nagata, The Nippon Dental University
Dr. Yuji Honda, Honda Shika Daiichi Shinryoujo
Dr. Eri Makihara, Kyusyu Dental University
Dr. Shinichi Masumi, Kyusyu Dental University
Dr. Shunsuke Minakuchi, Tokyo Medical and Dental University
Dr. Motonobu Miyao, Asahi University
Dr. Noriyuki Wakabayashi, Tokyo Medical and Dental University
Dr. Takashi Kaneda, Nihon University

31
J J Mag Dent vol. 32

2022
No. 2 2023

Dr. Mineyo Sone, Meikai University
Dr. Hideki Aita, Health Sciences University of Hokkaido
Conference
Arrangements
Dr. Masatake
Akutagawa, Committee
The University of Tokushima
Dr.Dr.
Hirokazu
Kumano,Aichi-gakuin
University
Shunsuke
Minakuchi,
Tokyo Medical
and Dental University
Dr.Dr.
Masatoshi
Takahashi,
TohokuUniversity
Masatake Akutagawa, The University of Tokushima
Dr. Shinya Nakabayashi, Nihon University
Dr. Shogo Ozawa, Aichi-Gakuin University
Dr. Eri Makihara, Kyusyu Dental University
Dr. Hisashi Koshino, Health Science University of Hokkaido

Dr. Manabu Kanazawa, Tokyo Medical and Dental University
Proceeding Committee
Dr. Mineyo Sone, Meikai University
Dr. Hideki Aita, Health Sciences University of Hokkaido
Dr. Masatake Akutagawa, The University of Tokushima
Dr. Hirokazu Kumano, Aichi-gakuin University
Dr. Masatoshi Takahashi, Tohoku University
Dr. Eri Makihara, Kyusyu Dental University

Published by the Japanese Society of Magnetic applications in Dentistryc/oK-Convention Co., Ltd.
Address: 1-24-7-313, Shinjuku Shinjuku-ku, Tokyo, 160-0022, Japan
Copyright (c) 2023 The Japanese Society of Magnetic Applications in Dentistry
All right reserved. No part of this publication may reproduced, stored in a retrieval
system, or transmitted, in any form or by any means, electronic, mechanical,
photocopying, recording, or otherwise, without prior written permission from thepublisher.
B&W:

Ryuwa print
223-5, Fukawa, Kawagoe, Saitama 350-0831 JAPAN

Visit JSDMD Home Page for updates!
http://www.jsmad.jp/

J J Mag Dent vol. 32 No. 2

2023

The 23rd International Conference on Magnetic Applications in Dentistry General Information

General Information
Guidelines for Presentation

The Japanese Society of Magnetic Applications in Dentistry(President: Masayuki Hideshima, Tokyo Medical and Dental

Deadlines:

University) is a scientific association founded in 1991 and is

Entry: January 26, 2024

devoted to furthering the application of magnetism in

Poster submission: February 12, 2024

dentistry. The 23rd International Conference on Magnetic

Entry:

Applications in Dentistry organized by JSMAD will take

Send Title and Abstract within 200 words with yourplace on the Internet as follows.

Registration.

Meeting Dates:

Paper submission:

Monday, February 26 to Friday, March 15, 2024

Please send papers in Microsoft Word format to the

Location:

conference secretariat by E-mail. All contents should be

JSMAD web site:

written in English. No multi-byte character, such as Japanese

http://jsmad.jp/international/23/

Kanji, should be contained. A template file can be obtained

General Chair:from the conference web site. Web presentations for the

Associate Prof. Masatake Akutagawa, Tokushima University

conference will be produced by the secretariat from the

Executive Committee Chair:paper. The secretariat will not make any correction of the

Associate Prof. Yuichi Ishida, Tokushima University

paper

Subjects:

Alternative format files are acceptable. Please contact to the

Researches and developments related to dentistry andsecretariat for more detailed information.

magnetism such as:

Discussion:• Magnetic attachments for dentures

Discussions will be done using a bulletin board on JSMAD• Orthodontic appliances using magnets

Web Site via the Internet. The authors should check the• Measurement of jaw movement using magnetic sensors

board frequently during the meeting dates. If questions or• Biological effects of magnetic fields

comments on your presentation are posted, please answer• Dental applications of MRIthem as soon as possible.

• Others

Notice to Contributors:

Registration Informationeven

miss-spelling,grammaticalerrorsetc.

Freely-given informed consent from the subjects or patients

Registration:must be obtained. Waivers must be obtained for photographs

Send e-mail titled "Registration for 23rd international

showing persons.

conference" with your Name, University or Institution,

Note:

Postal address, Phone, Fax and E-mail address to conference

Copyright of all posters published on the conference will besecretariat.

property of the Japanese Society of Magnetic Applications

Registration Fees:in Dentistry. Copies of the posters will be made andNo registration fees. Anyone who is interested in magnetictransferred to JSMAD web site for continuous presentation

applications in dentistry can participate in the conference via

after the meeting dates. For further information. send e-mailthe Internet. Publishing Charge for Proceedings:

to conference secretariat.

After the conference, the proceeding will be published. The

Conference Secretariat

publishing charge is 10,000 yen per page. (No charge forE-mail: iconf2024@jsmad.jp

invited paper.)Tel: +81-886-56-7477

J J Mag Dent vol. 32 No. 2 2023

Contents
Session 1
1.

Chair: Masatoshi TAKAHASHI (Tohoku University Graduate School of Dentistry)

A case report of a removable partial denture using magnetic attachments of different designs on
intermediate missing mandibular molars
M. Sone, D. Matsumoto, M. Numazawa, S. Uchida, Y. Inoyama, D. Sakamoto, K. Okamoto, andM. Fujisawa・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・1

2.

A pilot study on the fitness of a zirconia keeper coping fabricated by CAM system—Applicationof a high-precision scanner
D. Matsumoto, M. Sone, N. Koyama, Y. Taniuchi, K. Aoki, T. Matsukawa, F. Narumi, K. Okamoto,and M. Fujisawa・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・4

Session 2
3.

Chair: Mineyo SONE (Meikai University School of Dentistry)

Report of hands-on seminar on magnetic attachment skills
D. Kurihara, Y. Suzuki, J. Takeyama, H. Shimpo, C.Ohkubo ・・・・・・・・・・・・・・・8

4.

A case report of a removable partial denture with a magnetic attachment on the proximal surface ofabutment teeth
N. Mizokoshi, Y. Suzuki, D. Kurihara, N. Kawamura, C. Ohkubo・・・・・・・・・・・・・13

5.

Retentive force of combined sandwich-type magnetic assemblies
M. Takahashi, G. Togawa, M. Kanyi, K. Ishikawa, and Y. Takada・・・・・・・・・・・・・18

Appendix
How to Write the Proceedings?
for International Conference on Magnetic Applications in Dentistry・・・・・・・・・23

1

A case report of a removable partial denture using magnetic attachmentsof different designs on intermediate missing mandibular molars
M. SONE1, D. MATSUMOTO1, M. NUMAZAWA1, S. UCHIDA1, Y. INOYAMA1, D. SAKAMOTO1,
K. OKAMOTO1, and M FUJISAWA2.
Division of Removable Prosthodontics, Department of Restorative and Biomaterials Sciences, Meikai
University School of Dentistry2
Division of Fixed Prosthodontics, Department of Restorative and Biomaterials Sciences, Meikai
University School of Dentistry1

Abstract
In this presentation, we report a case in which two dentures with different designs of magnetic
attachments were attached to intermediate missing mandibular molars.
The patient, a 59-year-old male, complained of masticatory dysfunction. After the initial preparation, thedistal root of the mandibular right second molar was fitted with a coping magnetic attachment inconsideration of its load-bearing capacity as an abutment tooth, and we decided to fabricate an
extracoronal magnetic attachment using an EC Keeper Tray (GC, Japan) for the mandibular right first andsecond premolars.
The definitive denture had the first molar as a homemade metal tooth and the second molar as a hardresin tooth (SR-Orthosit-PE; Ivoclar-Vivadent AG, Liechtenstein). In addition, GIGAUSS (GC) was used
for a magnetic attachment (the coping type was the D400), and the D600 was applied to the extracoronal
type. One year after the installation of the right denture, in response to the patient's request to use thesame magnetic attachment as the right side, the first and second premolars on the left side were
equipped with similar extra-crown attachments, and the dentures were made of the same material.

Introduction
In the partial denture design, when intermediate missing teeth are on the right and left sides, due to thepatient's need for wearing comfort, we sometimes design two dentures without a major connector. In thispresentation, we report a case in which two dentures with different designs of magnetic attachments wereattached to intermediate missing mandibular molars.

Clinical History
Clinical History: The patient, a 59-year-old male, complained of masticatory dysfunction. He had apartially edentulous maxilla (Kennedy Class ჟ) and a history of arrhythmia. He complained that he wanted

Fig. 1 Intraoral view at the first visit

2

to seat the denture firmly on his right jaw, but he did not want the implant treatment due to his current
systemic history (Fig. 1).
Treatment Procedure: Based on dental X-ray photographs (Fig. 2) and periodontal disease examination(Fig. 3), the distal root of the mandibular right second molar was fitted with a coping type of magnetic
attachment (Fig. 4) in consideration of its load-bearing capacity as an abutment tooth. We decided tofabricate an extracoronal magnetic attachment using an EC Keeper Tray (GC, Japan) for the mandibular
right first and second premolars (Figs. 5 and 6).

Fig. 2 X-ray photographs at the first visit

Fig. 4 Coping typeof magnetic attachment

Fig. 3 Periodontal disease examination at the first visit

Fig. 5 Extracoronalmagnetic attachment

Fig. 6 EC Keeper Tray

After fixing the coping type of magnetic attachment to the oral cavity, a pick-up impression was taken in
the oral cavity for making a working model, and a framework of the denture was fabricated on it (Fig. 7).
The definitive denture had the first molar as a homemade metal tooth, taking into account the space of the
housing portion of the extracoronal magnetic attachment; the second molar was a hard resin tooth (SROrthosit-PE; Ivoclar-Vivadent AG, Liechtenstein) (Fig. 8). In addition, GIGAUSS (GC) was used for amagnetic attachment (the coping type was the D400), and the D600 was applied to the extracoronalattachment.

Fig. 7 Pick-up impression and denture framework(Right side)

Fig. 8 Definitive denture(Right side)

One year after the installation of the right denture, periodontal disease of the second molar on the left
side of the mandible, which was the abutment of the left bridge, advanced, and the tooth was extracted. In

3response to the patient's request to use the same magnetic attachment as the right side for subsequent defectprostheses, the first and second premolars on the left side of the mandible were equipped with extra-crownattachments similar to the abutment teeth, and the dentures were made of the same material. As a support
function to replace the root attachment on the right side, a mesial rest was added to the third molar on theleft side of the mandible (Figs. 9 and 10).

Fig. 9 Pick-up impression and denture framework(Left side)

Fig. 10 Definitive denture(Left side)

Conclusion
Magnetic attachments can be used as support teeth by reducing the lateral pressure as coping types, even
if the remaining teeth have problems with the crown-to-root ratio due to the absorption of alveolar bone.
In addition, if the crown-to-root ratio is good, it is possible to produce highly stable dentures by having
the abutment teeth carry the retention force and bracing force as an external type of crown (Fig. 11).1,2) In
this case, we applied these advantages and produced a denture. As a result, OHIP-14, which is related to
QOL, was two points from the minimum value. By analyzing the amount of glucose discharge duringgumi-jelly chewing, mandibular movements were quantitatively evaluated to be 188 mg/dl (right side) and
228 mg/dl (left side). We plan to confirm the postoperative course while performing regular maintenancein the future.

Fig. 11 Intraoral view of treatment procedures

References
1.

2.

M. SONE, H. HAMASAKA, Y. OKAWA, S. SOMEKAWA, M. MASUDA, A. MATUI, Y.
TOYOTA, F. OKUTSU, T. MATSUKAWA, K. OKAMOTO and S. OHKAWA: Relationshipbetween denture design and prognosis in removable denture using magnetic attachments. JJ Mag
Dent, 24(1), 68-77, 2015
Y. TANAKA: SHIN JISEI ATATCHIMENTO (New Dental Magnetic Attachment). ISHIYAKUPUBLISHERS INC, Tokyo, 2016.

4$ SLORW VWXG\ RQ WKH ILWQHVV RI D ]LUFRQLD NHHSHU FRSLQJ IDEULFDWHG E\&$0V\VWHP$SSOLFDWLRQRIDKLJKSUHFLVLRQVFDQQHU
'0$76802720621(1.2<$0$<7$1,8&+,.$2.,70$768.$:$
)1$580,.2.$0272DQG0)8-,6$:$ʥ

'LYLVLRQRI5HPRYDEOH3URVWKRGRQWLFV'HSDUWPHQWRI5HVWRUDWLYHDQG%LRPDWHULDOV6FLHQFHV0HLNDL8QLYHUVLW\6FKRRORI'HQWLVWU\ 'LYLVLRQ RI )L[HG 3URVWKRGRQWLFV 'HSDUWPHQW RI 5HVWRUDWLYH DQG%LRPDWHULDOV 6FLHQFHV0HLNDL8QLYHUVLW\6FKRRORI'HQWLVWU\$EVWUDFW,QWKLVVWXG\ZHUHSRUWRQWKHDFFXUDF\RIPDWFKLQJRI]LUFRQLDURRWSODWHVIDEULFDWHGXVLQJDKLJKSUHFLVLRQODERUDWRU\VFDQQHU
7KH DEXWPHQW WRRWK ZDV D SUHIRUPHG URRW SODWHtW\SH HSR[\ DUWLILFLDO WRRWK $
1,66,1 7KHPDQXIDFWXULQJSURFHGXUHLQYROYHVVFDQQLQJWKHZRUNPRGHOXVLQJDODERUDWRU\VFDQQHU (6KDSH PRGHOLQJLWXVLQJGHVLJQVRIWZDUH 'HQWDO6\VWHP6KDSH DQGWKHQFXWWLQJLWZLWKDPLOOLQJPDFKLQH &25L7(&L,PHV,FRUH )LYHVSHFLPHQVZHUHWHVWHGDQG WKH ILWWLQJ DFFXUDF\ RI WKH ]LUFRQLD URRW SODWHVZDV HYDOXDWHG XVLQJWKHFHPHQW UHSOLFDPHWKRG
7KH PHDVXUHPHQWSRLQWVDUHWKH ODELDO PDUJLQ DW SRLQW DWKHODELDOFHUYL[DW SRLQWEWKHODELDOSRVWDWSRLQWFWKHWLSRIWKHSRVWDWSRLQWGWKHOLQJXDOSRVWDWSRLQWHWKHOLQJXDOFHUYL[DWSRLQWIDQGWKHOLQJXDOPDUJLQVHWDVSRLQWJ7KHDYHUDJHJDSVZHUHʸИPDWSRLQWDʸИPDWSRLQWEʸИPDWSRLQWFʸИPDWSRLQWGʸИPDWSRLQWHʸИPDWSRLQWIDQGʸИPDWSRLQWJ
,WZDVVXJJHVWHGWKDWWKH]LUFRQLDURRWSODWHPDQXIDFWXUHGXVLQJDKLJKSUHFLVLRQODERUDWRU\VFDQQHUFRXOGEHDSSOLHGFOLQLFDOO\,QWURGXFWLRQ
7KHSURJUHVV RI GHQWDO &$'&$0 V\VWHPV LQ UHFHQW \HDUVKDV EHHQ UHPDUNDEOH DQG WKHIXUWKHUVLPSOLILFDWLRQRIZRUNIORZDQGLPSURYHPHQWLQWKHFRPSDWLELOLW\RISURVWKHWLFGHYLFHVDUHH[SHFWHG$WWKHWK$QQXDO6FLHQWLILF0HHWLQJZHH[DPLQHGWKHVXLWDELOLW\RID]LUFRQLD
URRWSODWHPDQXIDFWXUHGE\VXSSOHPHQWLQJWKHGHHSSDUWRIWKHPRGHOWKDWZDVGLIILFXOWWR
VFDQXVLQJDVXSSOHPHQWDU\VFDQQLQJSRVWDQGZHUHSRUWHGWKDWLWZDVDFFHSWDEOHIRUFOLQLFDODSSOLFDWLRQ7KLVWLPHZHDWWHPSWHGWRIDEULFDWHD]LUFRQLDURRWSODWHZLWKDVLQJOHV\VWHPXVLQJDGHQWDOVFDQQHUIRUODERUDWRU\XVHZKLFKKDVEHFRPHPRUHVRSKLVWLFDWHGDQGSUHFLVHLQUHFHQW\HDUV
0DWHULDOVDQG0HWKRGV
7KHDEXWPHQWZDVDQHSR[\DUWLILFLDOWRRWK $1,66,1 ZLWKDSRVWSDUWILYHPP5

GHHSDVUHFRPPHQGHGE\WKLVVRFLHW\$VIRUWKHPDQXIDFWXULQJSURFHGXUHDIWHUWDNLQJDQ
LPSUHVVLRQDFFRUGLQJWRWKHVWDQGDUGPHWKRGDZRUNLQJPRGHOZDVPDGHLWZDVVFDQQHGXVLQJDGHQWDOVFDQQHUIRUODERUDWRU\XVH (6KDSH DQGLWZDVWKHQVFDQQHGXVLQJGHVLJQVRIWZDUH 'HQWDO6\VWHP6KDSH $IWHUPRGHOLQJZHFXWLWRXWXVLQJDPLOOLQJPDFKLQH)LJVDQG 7KHFHPHQWVSDFHZDVWKHVSHFLILHGYDOXHRIWKHVRIWZDUHDQGWKHQXPEHU
RIWHVWVDPSOHVZDVILYH

)LJ6FDQQHGPRGHODQGGHVLJQHGNHHSHUFRSLQJ)LJ )DEULFDWHG]LUFRQLDNHHSHUFRSLQJ
7KHILWWLQJDFFXUDF\ZDVHYDOXDWHGXVLQJWKHFHPHQWUHSOLFDPHWKRGZKLFKTXDQWLILHVWKH
JDSEHWZHHQWKHPRGHODQGWKHURRWSODWHEDVHGRQWKHWKLFNQHVVRIWKHVLOLFRQHUXEEHUFRDWLQJ )LJ ,QDGGLWLRQWKHJDSGLVWDQFH ZDVPHDVXUHGE\FDSWXULQJDGLJLWDOLPDJHRIWKHFXWVXUIDFHRIWKHVLOLFRQHUXEEHUWRJHWKHUZLWKDVFDOHXVHGDVDUHIHUHQFHDQGPHDVXULQJ
LWRQD3&,QDGGLWLRQVHYHQPHDVXUHPHQWSRLQWVZHUHVHWDVVKRZQLQ)LJ

)LJ)DEULFDWLRQSURFHGXUHRIVSHFLPHQV &HPHQWUHSOLFDWHFKQLTXH

6







)LJ0HDVXULQJSRLQWVDODELDOPDUJLQEODELDOFHUYLFDOFODELDOFHQWHURISRVWGWLSRIWKH
SRVWHOLQJXDOFHQWHURISRVWIOLQJXDOFHUYLFDOJOLQJXDOPDUJLQ
5HVXOWV

7KHDYHUDJHJDSVDUH ʸИPDWSRLQWDʸИPDWSRLQWEʸ
ИPDWSRLQWFʸИPDWSRLQWGʸИPDWSRLQWHʸИP DWSRLQWIDQGʸИPDWWKHJSRLQW )LJ 0HDVXUHPHQWSRLQWVDEFHIDQGJVKRZHGJRRGFRPSDWLELOLW\DVFRPSDUHGZLWKWKHDOORZDEOHUDQJHRIFRPSDWLELOLW\IRU
&$'&$0SURVWKHVHVUHSRUWHGE\6XWRHWDOͿ ZKLFKLVИP

)LJ$YHUDJHJDSYROXPH&RQFOXVLRQ
7KHUHDVRQFRPSDWLELOLW\ZDVJHQHUDOO\JRRGZDVWKRXJKWWREHWKHLQIOXHQFHRIVPRRWKDQG

KLJKO\DFFXUDWHPRGHOLQJRIWKHPRGHOGXHWRWKHLPSURYHGPHDVXUHPHQWDFFXUDF\RIWKH
FDPHUDDQGWKHFRUUHVSRQGLQJVRIWZDUH,QDGGLWLRQWKHUHDVRQWKHYDOXHRISRLQWGGLGQRW

7

PHHWWKHVWDQGDUGZDVFRQVLGHUHGWREHWKDWWKHVHWWLQJYDOXHRIWKHFHPHQWVSDFHZDVKLJKDVFRPSDUHGWRWKRVHRIRWKHUSRLQWVDQGWKDWVFDQQLQJDQGPLOOLQJZHUHVRPHZKDWGLIILFXOWGXHWRWKHPRUSKRORJ\  ,QWKHIXWXUHZHSODQWRYHULI\WKHILWWLQJDFFXUDF\ZLWKDSRVWOHQJWKRIPPRUPRUHDQG
DOVRWRLQYHVWLJDWHZKHWKHULWLVSRVVLEOHWRVHWWKHDQWLURWDWLRQJURRYHDQGWKHNHHSHUKRXVLQJ
5HIHUHQFHV 16XWR60LXUD5,QDJDNL<.DQHWD0<RGDDQG..LPXUD$%DVLF6WXG\RQ
)LWQHVVRI$OOFHUDPLF&URZQ)DEULFDWHGE\&$'&$06\VWHP$QQ-SQ3URVWKRGRQW
6RFt




8

Report of a hands-on seminar on magnetic attachment skills
D. Kurihara, Y. Suzuki, J. Takeyama, H. Shimpo, C. Ohkubo
Department of Removable Prosthodontics, Tsurumi University School of Dental Medicine

Introduction
Unlike conventional mechanical force-application mechanisms, magnetic attachments use magnetic
force and have many advantages, such as their small size, simple shape, and their use of a less harmful
lateral force. For clinical success with magnetic attachments, accurate positioning of the magnetic
assembly on the keeper and its connection are very important, as inadequate attachment causes a gap
between the contact surface and a significant reduction in retentive force. In order to acquire theneeded skills, a hands-on seminar titled “Learning Magnetic Attachments—Laboratory and Clinical
Procedures” was held at the 131st Annual Meeting of the Japanese Society of Prosthetic Dentistry incooperation with the Japan Society of Magnetic Applications in Dentistry. In this paper, we will reporton this seminar.

Objective
In the seminar, a 40-minute lecture on the characteristics of magnetic attachments and how toproceed with treatment, their application, design, treatment procedures, and possible problems wasgiven. After the lecture, 50 minutes was provided to practice using a simulation model and overdenture
and to train in the clinical procedure of fixing the magnetic assembly to the denture base using
autopolymerized resin.
Lecture1. Explanation of points to note when placing magnetic attachments(1) Causes of significant decrease in retention
Failures in the attachment procedures include misalignment of the magnetic assembly, namely, airgaps due to the intrusion of the resin onto the keeper surface or polymerization shrinkage.
As for the misalignment of the magnetic assembly and the keeper, it has been reported that theattractive force decreased by about 1/3 when an air gap of 0.1 mm was vertically created and by about
2/3 when the magnetic assembly was horizontally displacedbyp
y 0.5 mm ((Figs.
g 1, 2))1) .

Fig. 1 Effect of vertical gaps
between the magnetic assembly
and the keeper on attraction force1)

Fig. 2 Effect of horizontal deisplacementof the magnetic assembly on the keeper
on the attractive force1)(2) Polymerization shrinkage of autopolymerized resins(i) As the amount of autopolymerized resin used when fixing the magnetic assembly was increased,shrinkage of the autopolymerized resins also increased, and the air gap grew.

9(ii) The brush-on technique showed lower polymerization shrinkage and better dimensional accuracy
as compared to the mixing technique (Fig. 3)2).
(iii) The brush-on technique can control the amount of resin on the inner surface of the denture baseby the placement of a spillway. The results include the prevention of misfitting dentures and denturesthat are difficult to remove due to resin that has penetrated into the undercut around the keeper coping(Fig. 4).
(iv) Holding the denture until the resin is polymerized and the timing of denture removal are also
important.

Fig. 3 Polymerization shrinkage of
autopolymerized resin using thebrush-on and mixing techniques2)

Fig. 4 Spillway provided to thedenture base(3) Placement of the magnetic assmbly
The magnetic assmbly should be placed after the denture is settled, considering the minimum
shrinkage of the autopolymerized resin.
2. Movie explaining the clinical procedure of magnetic attachments (Fig. 5)

Fig. 5 Clinical procedure for applying a magnetic attachment

10

Practice
Placement of magnetic attachments (magnetic assembly) (Figs. 6-9)

Fig. 6 Jaw model of a partially edentulous mandible with left and right remaining canines,
overdenture, and magnetic attachments (Physio Magnet, Kedika Corporation) used in theseminar.

Fig. 7 A space for magnetic attachments was created on the denture. The denture was placedon the jaw model, and a spillway was provided.

Fig. 8 After applying vaseline to the keeper coping and the residual ridge, the magnetic
assembly was placed on the keeper. Using the brush-on technique, the magnetic assembly
was fixed with autopolymerized resin using light pressure.

Fig. 9 After the resin was polymerized, thedenture was removed and polished.

Results
The seminar was held twice, with a total of 40 participants (23 males and 17 females) divided into twogroups of 20. There were 33 university and 7 non-university participants. Difficulties such as thedetachment of the magnetic assembly and lack of retentive force were observed during the fixing
procedures.
The results of the post-seminar questionnaire are shown in Figs. 10-12.

11

Fig. 11 Work place of participants

Fig. 10 Work years of participants

Fig. 12 Evaluation of the seminar

Discussion
Not using metal primers and the premature removal of the denture from the simulation model during
the polymerization of the resin were considered to be reasons for the detachment. Insufficient retentive
force may be due to misalignment of the magnetic assembly, namely, an air gap caused by the intrusionof the resin onto the keeper surface.

Conclusion
From a post-seminar questionnaire, most of participants learned well the clinical and laboratory
procedures for magnetic attachments and were satisfied with the seminar.

References
1) Ai M, Shiau YY. New magnetic applications in clinical dentistry. Quintessence Publishing Company,
Tokyo, 2004, 28–50.
2) Hanatani S, Shibuya N, Muraishi E, et al. Dimensional accuracy of autopolymerized resin applied
using the brush-on technique. Int Chin J Dent. 2009; 9 (1): 9–13.

12

Acknowledgments
We would like to thank the Morita Corporation, the Kedika Corporation, and the Kikutani
Corporation for their support of this seminar, as well as the teacing staff in our department for theircooperation in organizing the seminar.

13

A case report of a removable partial denture with magnetic attachmentson the proximal surfaces of abutment teeth
N. Mizokoshi,1 Y. Suzuki,1 D. Kurihara,1 N. Kawamura,2 C. Ohkubo1
1
2

Department of Oral Rehabilitation and Prosthodontics，Tsurumi University School of Dental Medicine
Dental Technician Training Institute, Tsurumi University School of Dental Medicine

Introduction
Overdentures with magnetic attachments are a prosthetic approach that can restore masticatory ability
and provide a highly aesthetic appearance, but they are difficult to apply to vital teeth. We will report acase of a removable partial denture (RPD) with magnetic attachments applied to the proximal surfacesof the abutment teeth to minimize invasion of the tooth structure.

Case report1.

Patient Information

The patient is an 80-year-old female with remaining mandible teeth #48, #42〜#34, and #38. She wassuffering from mastication difficulty and poor aesthetics due to metal clasps on the anterior teeth, andshe requested the least invasive prosthetic treatment. Radiographic findings showed #24 root fracture.

Fig. 1 Panoramic radiograph at the first examination

Fig. 2 Intraoral photograph at the first examination

Fig. 3 Placement of existing removable partial denture

14

2.

Repair of additional teeth to existing denture

The existing RPD could not be used because the metal crowns (#24, #25) were detached. After #24
was extracted due to root fracture, the maxillary existing RPD was repaired with additional resin teeth(Fig. 4).

Fig. 4 Existing maxillary RPD after repair with additional resin teeth
3.
3.1

Treatment plans
Delivery of maxillary titanium RPD with magnetic attachment with cast metal
copingA magnetic attachment with a cast metal coping was placed on the root of #25 where the Cr had
become detached with the core. A titanium RPD with a half clasp on #23 and a cast clasp on #14〜#16
was fabricated (Figs. 5–7).

Fig. 5 #25 Tooth preparation, impression taking, placed magnetic attachment with coping

Fig. 6 Difinitive impression of the maxilla

Fig. 7 Definitive maxillary titanium RPD

15

3.2

Magnetic attachments placed on the proximal surfaces of the abutment teeth in
the mandible

To avoid a non-aesthetic metal clasp on the anterior teeth, the keepers were fixed to the proximal
surfaces of the abutment teeth (#34 and #42) using composite resin. A keeper fixation part was
fabricated on the working model using optical transparency composite resin (Fig. 8).

Fig. 8 Fabrication of composite resin parts for keeper fixation
3.3

Abutment teeth preparation using a preparation guide

Figure 9 shows the retentive forces when the magnetic attachments were applied to the proximal
surfaces of the teeth with various angles of both keepers. The preparation guide was made on the modelin advance, pre-treatment of the abutment tooth were performed for forming surfaces (Fig. 10).

Fig. 9 Retentive forces when the magnetic attachments were applied to theproximal surfaces of the teeth with various angles of both keepers1

16

Fig. 10 Preparation of the abutment teeth using a preparation guide
3.4

Keepers were attached to the proximal surfaces

Two keepers were attached to the proximal surfaces of #34 and #42 using composite resin (Fig. 11).

Fig. 11 Keepers attached with composite resin
3.5

Fabrication of a mandibular RPD framework

The mandibular denture framework was conventionally fabricated with a lingual plate. A cap clasp
and a ring clasp were placed on #48 and #38, respectively (Fig. 12).

Fig. 12 The completed RPD framework
3.6

Completed definitive mandibular RPD (Figs. 13–14)

Fig. 13 Occlusal view of the definitive RPD

17Fig. 14 Magnetic assemblies were placed in the proximal plates of the RPD.
3.7

Delivery of the definitive mandiblar RPD (Figs. 15–16)

Fig. 15 Intraoral view of definitive maxillary and mandiblar RPDs

Fig. 16 Assessment of previous and definitive dentures by VAS

Discussion/conclusion
Magnetic attachments were applied to the proximal surfaces of the anterior teeth to improve theaesthetics with a minimally invasive treatment. The patient was fully satisfied with the aesthetics andthe assurance of adequate retentive force.

References1.

Miyama Y, Yamaguchi M, Mizuno Y, Tsuchida F, Takishin N, Abe M, and Hosoi T. Studies on theretentive force of the magnetic attachment applied on the proximal surface, part 1. J Jpn Soc M
Applications in Dentistry. 2008; 17(1): 30–35.

18

Retentive force of combined sandwich-type magnetic assemblies
M. Takahashi1, G. Togawa1, M. Kanyi2, K. Ishikawa1, 3 Y. Takada1
Division of Dental Biomaterials, Tohoku University Graduate School of Dentistry, JAPANMoi Teaching and Referral Hospital, KENYA
3
Tohoku University Hospital, JAPAN
1
2

Abstract
Dental magnetic attachments are mostly paired combinations of magnetic assembly and keeper or twomagnets. A combination of two magnetic assemblies is rare. In this study, we investigated retentive force
characteristics of a set of two sandwich-type magnetic assemblies. Mating surfaces of two oval-shaped
magnetic assemblies (Magfit EX600W) were placed in contact with different polarities facing each other.
The pair was mounted on a measuring device and retentive force experiments conducted as specified in ISO
13017. The measurements were done with the two magnetic assemblies aligned and when one magnetic
assembly was displaced along the long axis then short axis direction. The retentive force of a pair of magnetic
assemblies was higher than that of magnetic assembly combined with keeper. There was a decline in retentive
force measured upon separation of mating faces. It was more gradual in the case of two magnetic assemblies
compared to assembly and keeper. Displacement along the minor axis, caused a decline in retentive force
which was more in a pair of magnetic assembly compared to a magnetic assembly paired with keeper.
Furthermore, a pair of combined magnetic assemblies generated a large restoring force against displacement.
It was established advantageous to combine two magnetic assemblies.

Introduction
Dental magnetic attachments are often used as retentive elements in partial and complete dentures. They
can also be utilized in implant overdentures such as 2-IOD and 4-IOD. From 2021, the Japanese insurance
system committed to cater for cost of dental magnetic supported appliances1). Its usage is therefore expected
to rise in future. Magnetic attachments manufactured in Japan are predominantly a combination of magnetic
assembly and keeper. A magnetic assembly exhibits closed magnetic circuit which is characterized by highretentive force despite its small size. Leakage of magnetic field associated with the closed circuit is minimal.
On the other hand, products made in other countries utilize both closed and open magnetic circuit typemagnets. To overcome poor corrosion resistance of rare–earth magnets, magnets used in dentistry are covered
with stainless steel or titanium2). A magnet is simple and easy to manufacture compared to magnetic assembly.
However, its open magnetic circuit feature is associated with high leakage of magnetic field, and low retentive
force relative to its size. In order to compensate for the weak retentive force of magnet-keeper combination,
it may be beneficial to combine two magnets. In practice, there are three possible combinations of dental
magnetic attachments: magnetic assembly to keeper, magnet to keeper, and magnet to magnet.
The magnet to magnet combination exhibits a retentive force greater than that of magnet-keeper
combination. It is therefore postulated that two magnetic assemblies combined would also yield higher
retentive force than magnetic assembly to keeper. However, there is no research on retentive force whencombining two magnetic assemblies.
The two types of magnetic assemblies for application as dental magnetic attachments which exist are cupyoke and sandwich type3). It is difficult to combine two cup-yoke type of magnetic assemblies because thecontact mating faces are of similar polarity causing repulsion (Fig. 1). Sandwich types are easy to combine
due to the attraction force exhibited by the unlike poles which make up mating faces (Fig. 2). This study
explored the possibility and characteristics of a new combination that involves two sandwich-types ofmagnetic assemblies.

Objective
The aim of this study was to explore possibility of combining two sandwich-type magnetic assemblies andinvestigate the retentive force characteristics. A combination of magnetic assembly and keeper, which forms
the ordinary magnetic attachment, was used for comparison.

19

S

N

N

S

N
S
S
N
Fig. 1 Combination of cup-yoke typeof magnetic assemblies

Fig. 2 Combination of sandwich typeof magnetic assemblies

Materials and Methods
1. Dental magnetic attachment
Oval sandwich-type dental magnetic attachments (MAGFITEX600W, 3.8 mm major axis and 2.8 mm
minor axis length, Aichi steel Corp.) were used in this study. The magnetic assembly was either combinedwith a keeper or another magnetic assembly. The mating faces were placed in contact with different polarities
across each other (Fig. 2). Magnetic keeper was paired up with magnetic assembly to represent the ordinary
magnetic attachment.
2. Procedure of retentive force measurement
The retentive force measuring device used in this study matches the description in ISO 13017:20203). The
device was connected to a digital force gauge (ZPS, Imada) and retentive force measured at crosshead speedof 2 mm/min. recording was done at a sampling rate of 1 kHz. Applying the known time and speed values,
distance was calculated then a retentive force curve generated. The experiment begins when the magnetic
assembly has its center aligned to that of keeper or second magnetic assembly. The measurements were done
at intervals of 100 μm horizontal displacement, along the major and minor axis direction, of keeper or second
magnetic assembly. The measurement is terminated when the magnetic assembly completely separates fromits keeper or second magnetic assembly.

Results and Discussion
1. Retentive force of aligned magnetic attachments
The retentive force of a magnetic assembly paired with keeper or second magnetic assembly was 5.26 N
and 6.45 N, respectively. Therefore use of a second magnetic assembly instead of keeper raised the retentive
force by 1.23 times. This is attributed to the shorter distance between the magnetic poles of two magnetic
assemblies (Fig. 3b) compared to magnetic assembly and its keeper (Fig. 3a). Additionally, the volume of themagnet is doubled, and the energy of the magnet increased causing an enhanced effect. However, due tosaturation of the cup yoke’s magnetic flux density, the retentive force is not doubled. Magnets whose design
involves closed magnetic circuit are characterized by small size and relatively large retentive force. The force
can be further enhanced through combination of two magnetic assemblies.

(a)

(b)

Fig. 3 Schematic diagram of magnetic flux flow in the magnetic attachments (a) combination of magnetic
assembly and keeper, (b) a pair of magnetic assemblies

20
2. Decline of retentive force upon complete separation of mating face
Retentive force curves for the two set up combinations are shown in Fig. 4. The displacement position ata time when the mating faces separate is denoted as 0 mm. For both scenarios, the retentive force values
decreased with increasing distance which corresponds to displacement of the magnetic assembly away fromkeeper or second assembly. However, the rate of decline was moderate when two magnetic assemblies werepaired up compared to the one with keeper. Although magnetic flux volume emitted from the assembly yokes
is same, magnetic field lines are concentrated more towards the second magnetic assembly yoke than thosethat flow solely within the first assembly as shown in Fig 5. A combination of two magnetic assemblies offers
a wider range of influence on the attractive force and is stable against air gap.
10.0

two magnetic
assemblies

Force (N)8.0magnetic assemblyand keeper

6.0
4.0
2.0
0.0

-1

0

1
2
3
Distance (mm)Fig. 4 Retentive force curve

4

(a)

(b)

Fig. 5 Images of magnetic flux flow after separationof mating faces. (a) magnetic assembly and keeper
combination, (b) pair of magnetic assemblies

Retentive force (N)3. Changes in retentive force against lateral displacement
Fig. 6 shows the change in retentive force when the second magnetic assembly was shifted in the major
axis direction. The retentive force decreased gradually with increasing displacement. The loss in retentive
force was linear at a displacement of 1.2 to 2.5 mm. This pattern was similar to that of the combination of
the magnetic assembly and the keeper4). The retentive force is therefore dependent on the contact surface
area between the two magnetic assemblies upon displacement along the major axis direction.

7.0
6.0
5.0
4.0
3.0
2.0
1.0
0.0

0.0
1.0
2.0
3.0
4.0
Horizontal displacement (mm)Fig. 6 Retentive force against displacement along major axis direction
Fig. 7 shows the changes in retentive force when displacement occurs along the minor axis direction. The
retentive force decreased sharply upon displacement to reach 0 N at 1.5mm. Further displacement generated
negative values which imply a repulsion of magnetic assemblies. This phenomenon was not observed in themagnetic assembly and keeper set up4).
As illustrated in Fig. 3, congruently matched magnetic assemblies have unlike poles in contact thereby
producing an attractive force. Displacement along the minor axis direction, as shown in Fig. 8, creates varying
scenarios in which some parts of magnetic assemblies are in attraction whereas others are in repulsion. The

21

Retentive force (N)resultant force acting in a direction perpendicular to the mating face is measured and represents the retentive
force. At the initial stages of displacement, the attractive force exceeds the repulsive force. At about 1.5 mm
displacement, the two forces are equal resulting into 0 N retentive force. Further displacement yields a higher
repulsive force compared to attractive force.

7.0
6.0
5.0
4.0
3.0
2.0
1.0
0.0
-1.0

0.0
1.0
2.0
3.0
Horizontal displacement (mm)Fig.7 Retentive force against displacement along minor axis direction

S

S

S

N

N

S

attractive repulsive
force > force

NN

N

attractive repulsive
force = force

N

S

S

attractive repulsive
force < force

Fig.8 Images of forces between two magnetic assemblies in response to displacement along the minor
axis direction
Besides the attractive and repulsive forces explained above; there also exists (lateral) forces that act in a
direction parallel to the mating faces. Fig 9 demonstrates how attraction and repulsion forces act in a manner
similar to closed and open coil springs respectively. A VOLJKWGLVSODFHPHQW DĺE) is accompanied by restoring
force which acts like springs taking the set up back to the RULJLQDOSRVLWLRQ EĺD  Therefore, combining two
magnetic assemblies yields a "restoring force" which counters the effect of minor lateral displacement.

S

N

N

N

S

S

S
N

(a)           (b)Fig. 9 Schematic drawing to illustrate spring effect of repulsion and attraction forces (a) well aligned, (b)slight displacement

22
4. Clinical application of combined magnetic assemblies
Dental magnetic attachment set up that involves two magnetic assemblies provides salient features whichhave meaningful applications in dentistry especially complete dentures. The spring like action by restoring
force acts as a guide in proper alignment of magnetic attachments. It eases the procedure of incorporating
magnetic assembly into denture. Higher retentive forces associated with magnetic assemblies compared tokeeper of the same size offers improved denture stability. Erroneous inclusion of air gap has minimal effectas the consequent decrease in retentive force is gradual. The restoring force further promotes denture stability
as minor denture displacement during function is automatically corrected. Major displacement of themagnetic attachment against abutment tooth in a horizontal direction triggers the repulsion forces which aid
in removal of denture from the oral cavity. The concept of combining two magnetic assemblies isadvantageous compared to use of assembly and keeper in terms of retentive force and stability.

Conclusion
The retentive force of a pair of magnetic assemblies was higher than that of magnetic assembly combinedwith keeper. The decline in retentive force was more gradual for the set up involving two magnetic assemblies
compared to assembly and keeper. A pair of combined magnetic assemblies generates a restoring andrepulsive force upon small and large displacements along the minor axis, respectively. It was establishedadvantageous to combine two magnetic assemblies.

Acknowledgments
The authors greatly acknowledge Aichi steel Corp. for providing the MAGFIT EX600W.

References
1. C. Ohkubo: Appropriate procedures and viewpoints for magnetic attachments, J J Mag Dent, 31(1), 1-6,
2022.
2. Y. Takada, M. Takahashi, Y. Kinouchi, Y. Nakamura, Y. Tanaka, H. Sato, A. Izumida and T. Tenkumo:
Materials and internal structures of foreign-made dental magnetic attachments, J J Mag Dent, 22(1), 96102, 2013.
3. ISO 13017:2020. Dentistry—Magnetic attachments.M. Takahashi, H. Yamaguchi and Y. Takada: Change
in retentive force with a horizontal shift of oval-shaped dental magnetic attachments, J J Mag Dent, 28(1),48-55, 2019.
4. M. Takahashi, H. Yamaguchi and Y. Takada: Change in retentive force with a horizontal shift of ovalshaped dental magnetic attachments, J J Mag Dent, 28(1), 48-55, 2019.

23

25 mm
25 mm

How to Write the proceedings
TiTle including No. : Times New Roman 14pt Bold

0.5 line
0.5 line

One line
0.5 line

Name (Initial. Family name) : Times New Roman 11 pt, (indent of a 0.5 line above and under this line)
ex. Y. Takada, N. Takahashi1 and O. Okuno2
Affiliation: Times New Roman 11 pt, ex. Division of Dental Biomaterials, Graduate School of dentistry,
A
Tohoku University
1
Depatrtment of Magnet Science, School of Dentistry, Inaka College
2
Laboratry of Magnet, Institute of Sendai
0.5pt line (Black)
Abstract: Times New Roman bold 11 pt. Type
Abstract should be 10.5 point type (fonts such as Times New Roman (for body text) and Arial(for Headlines)
are easy to read)
0.5pt line (Black)

Manuscript Basics

One line

0.5 line
The proceedings book will be printed directly from the manuscript provided by the author. The conference
secretariat staff does not edit or proofread manuscripts, so all material should be concise and error free. The
entire paper must be legible.
The components of a paper are (in order of appearance)
Introduction
Objective
Materials and Methods
Results or (Results and discussion)
Discussion
Conclusion
Acknowledgements
References

Manuscripts Should

One line

0.5 line
be in a one-column format
be 10.5 point type (fonts such as Times New Roman (for body text) and Arial(for Headlines) are easy
to read)•be single-spaced•
be justified within the column•
be written by the standard format of MS Word 2003 (number of characters and lines in a page)
Authors should use the page size of A4 format (210 mm × 297 mm). Four spaces (half size English
character) should be inserted in the head of first line between paragraphs.

••

Main Headings
•
•
•
•
•
•
•

bold 12 pt. Type12 pts. (1 line space) before and 6 pts. (0.5 line space) after
upper- and lower-case
NO underline (underscore)
NO italic
one line of space above and below, except when the heading is at the top of a column
left justified

Subheadings•
be bold 10.5 pt. type (font: Arial)
25 mm

25 mm

24
•
•
•
•
•
•
•
•
•
•

upper and lowercase
NO underline (underscore)
NO italic
indented and on-line with the rest of the paragraph (no extra space above and below)
Secondary Subheadings
italic 10.5 pt. type (font: Arial)
upper and lowercase
NO underline (underscore)
NO bold
indented and on-line with the rest of the paragraph (no extra space above and below)

Margins•••

Top 25 mm
Bottom 25 mm
Left and right 25 mm

Figures and Tables
All figures and tables should be imported directly into the document and will be printed along with thetext. Figures and tables will NOT be reduced or enlarged by the conference secretariat staff. All figures andtables will be printed in black and white, so do not refer to colors within text to describe graph lines orparticular areas of photos.
However, if you will demand the PDF file of your manuscript, you may use colors because the PDF filerefer to colors. Note, however, that you should use colors which can be distinguished even when they are
printed in black and white.
All figures and tables should be numbered consecutively and placed in numerical order within the
manuscript. For each figure, a caption should be placed directly below the figure, and should include thefigure number and caption text.

References
Literature references should be listed at the end of the paper in the same order that they appear in thetext, and in accordance with the following examples.
1. Journal article (example): Y. Takada, N. Takahashi and O. Okuno: Electrochemical behavior and released
2.

ions of the stainless steels used for dental magnetic attachments, J J Mag Dent, 16(2), 49-52, 2007.

Book (example): R. Kunin, On Exchanging Resins, pp 88, Robert E. Kreiger Publishing Company, New
York, 1972.