日 磁 歯 誌
J J M ag Dent
ISSN 0918-9629

日本磁気歯科学会雑誌

2022

Volume 31. Number 2

第三十一巻 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 31, Number 2

日本磁気歯科学会
22

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

J J Mag Dent vol. 31

No. 2 2022

The Journal of the Japanese Societyof Magnetic Applications in Dentistry
Volume 31, Number 2

Proceedings of the 21th International Conference
on Magnetic Applications in Dentistry

The Japanese Society of Magnetic Applications in Dentistry

J J Mag Dent vol. 31

No. 2 2022

The 21th International Conference on Magnetic Applications in Dentistry
The 21th International Conference on The Japanese Society of Magnetic Applications in
Dentistry organized by JSMAD was held on the Internet as follows;
Meeting Dates:
Monday, February 21 to Monday, March 7, 2022
Location:
JSMAD web site
http://jsmad.jp/international/21/
General Chair:
Clin. Associate Prof. Tetsuo Ohyama, Nihon University
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. 31

No. 2 2022

Conference Committee
The Japanese Society of Magnetic applications in Dentistry
President of the Japanese Society of Magnetic applications in Dentistry
Dr. Yukyo Takada, Tohoku University
Vice-President of the Japanese Society of Magnetic applications in Dentistry
Dr. Masayuki Hideshima, Tokyo Medical and Dental University
Conference Secretary
Dr. Masatoshi Takahashi, Tohoku 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. Jun Takebe, Aichi-Gakuin 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 Universit
Dr. Motonobu Miyao, Asahi University
Dr. Noriyuki Wakabayashi, Tokyo Medical and Dental University
Dr. Takashi Kaneda, Nihon University

Conference Arrangements Committee
Dr. Shunsuke Minakuchi, Tokyo Medical and Dental Universit
Dr. Masatake Akutagawa, The University of Tokushima
Dr. Shogo Ozawa, Aichi-Gakuin University
Dr. Hisashi Koshino, Health Science University of Hokkaido
Dr. Shuji Ohkawa, Meikai University
Proceeding Committee

J J Mag Dent vol. 31

No. 2 2022

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. Shinya Nakabayashi, Nihon 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) 2022 The Japanese Society of Magnetic Applications in Dentistry
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Visit JSDMD Home Page for updates!
http://www.jsmad.jp/

J J Mag Dent vol. 31

No. 2 2022

The 22th International Conference on Magnetic Applicationsin Dentistry General Information
General Information
The Japanese Society of Magnetic Applications in
Dentistry (President: Yukyo Takada, Tohoku University)
is a scientific association founded in 1991 and is devoted
to furthering the application of magnetism in dentistry.
The 22st International Conference on Magnetic
Applications in Dentistry organized by JSMAD willtake place on the Internet as follows.
Meeting Dates:
March , 2023
Location:
JSMAD web site:
http:/ /jsmad.jp/international/22/
General Chair:Prf. Hideki Aita, Health Science University of Hokkaido
Executive Committee Chair:Dr. Shin Tukagoshi, Health Science University of
Hokkaido
Subjects:
Researches and developments related to dentistry andmagnetism 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
Registration Infomation
Registration:
Send e-mail titled "registration for 22st international
conference" with your Name, University or Institution,
Postal address, Phone, Fax and E-mail address toconference secretariat.
Registration Fees:
No registration fees. Anyone who is interested inmagnetic applications in dentistry can participate in theconference via the Internet. Publishing Charge for
Proceedings:
After the conference, the proceeding will be published.
The publishing charge is 10,000 yen per page. (Nocharge for invited paper.)

Guidelines for Presentation
Deadlines:
Entry: January, 2023
Poster submission: February, 2023
Entry:
Send Title and Abstract within 200 words with yourRegistration.
Paper submission:
Please send papers in Microsoft Word format to theconference secretariat by E-mail. All contents should be
written in English. No multi-byte character, such as
Japanese Kanji, should be contained. A template file canbe obtained from the conference web site. Web
presentations for the conference will be produced by thesecretariat from the paper. The secretariat will not makeany correction of the paper even miss-spelling,grammatical errors etc. Alternative format files are
acceptable. Please contact to the secretariat for moredetailed information.
Discussion:
Discussions will be done using a bulletin board on
JSMAD Web Site via the Internet. The authors should
check the board frequently during the meeting dates. Ifquestions or comments on your presentation are posted,
please answer them as soon as possible.
Notice to Contributors:
Freely-given informed consent from the subjects or
patients must be obtained. Waivers must be obtained forphotographs showing persons.
Note:
Copyright of all posters published on the conference will
be property of the Japanese Society of Magnetic
Applications in Dentistry. Copies of the posters will bemade and transferred to JSMAD web site for continuouspresentation after the meeting dates.
For further information,
send e-mail to conference secretariat.
Conference Secretariat
Dr. Shin Tukagoshi, Health Science University of
Hokkaido

E-mail: jsmad32@ml.hoku-iryo-u.ac.jp

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

J J Mag Dent vol. 31 No. 2 2022

Contents
Session 1
1.

Chair: Hideki Aita (Health Sciences University of Hokkaido)

The study of attractive force occurred in parallel installation of keepers on the coping. -The influence ofthe distance between two keepersM. Yoshida, S. Nakabayashi, H. Yasuda, Y. Nakamura, N. Higuchi, T. Ohyama, and N.
Tsukimura・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・1

2.

Resistance force of magnetic attachments against external lateral displacement
M. Takahashi, G. Togawa, K. Numazaki, M. Kanyi and Y. Takada・・・・・・・・・・・・・・4

Session 2
3.

Chair: Kazuhiro Nagata (The Nippon Dental University)

Long-term follow-up cases of magnetic attachment denture with different prosthetic designs
H. Kumano, Y. Nakamura, H. Nakamura, R. Kanbara, T. Masuda, W. Fujinami, S. Ozawa and J.
Takebe・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・13

4. Denture repair by applying a magnetic attachment after extracting the abutment tooth of a cone crowntelescope: A case report
A.izumida・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・17

Session 3
5.

Chair: Eri Makihara (Kyushu Dental University)

A case report of a removable denture using magnetic attachment and circumferential clasp followed up
for 9 years
M. Sone, D. Matsumoto, N. Koyama, F. Narumi, T. Matsukawa, S. Uchida, K. Takahashi, M. Takagi, Y.
Inoyama, D. Sakamoto, K. Okamoto, and S. Ohkawa・・・・・・・・・・・・・・・・・・・23

6.

A clinical case of implant overdenture with magnetic attachment using CAD/CAM technology
Suzuki Y，Harada N，Maruo R，Imaizumi N，Muto R，Shimpo H, Kurihara D, Ohkubo
C・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・27

Appendix
How to Write the Proceedings?
for International Conference on Magnetic Applications in Dentistry・・・・・・・・・32

1

The study of attractive force occurred in parallel installation of keepers
on the coping. -The influence of the distance between two keepersM. Yoshida, S. Nakabayashi, H. Yasuda, Y. Nakamura, N. Higuchi, T. Ohyama, and N. Tsukimura
Department of Partial Denture Prosthodontics, Nihon University School of Dentistry

Introduction
In a choice of magnetic keeper, a shape of root is an important factor in deciding the size. Especiallywhen a root cross section is flat, two small size of keepers arranged in parallel are applied to improve
its retention. In the past study of this course, the attractive force of magnetic attachments arranged ina row has been examined, and the study shows that a parallel installation of keepers makes its attractive
force much stronger than a single attachment does. This study shows that how the difference of eachkeepers’ distance affects its attraction.

Objective
This study simulates the case that a root cross section of maxillary first premolar is flat and clarifies
how the distance between the two keepers affects its attractive force as they are arranged in parallel toimprove retention of a denture.

Materials and Methods
Table.1 Details of materials and machine
Materials and Machines
Manufacturer
GIGAUSS
C300
GC
FIXPEED
lot No.180726 GC
Aron alphalot No.8Y27Z TOAGOSEI(an adhesive)
CO.,LTD
Universal
EZ-TestShimadzu
testing machineCorp.
ISO tensile test jig

Abbreviation
C3

EZ-TestExperimental methods
The distance between the each keepers: 0mm,1mm,2mm
From now on they are written as 0mm=0,1mm=1, and 2mm=23different experiment stands are made along with the distance of keepers(Fig.1) (Fig.2)
Data processing methods
The attractive force of C300 was measured 5 times, and a standard value is based on the average. A
theoretical value is 2 times of the standard value. Measurements were held 5 times in eachexperimental method, and an experimental value is based on the average. The obtained experimental
value was statistically processed with statistical analysis software GraphPad Prism, and a significant
level is 5% in both one-way ANOVA and Tukey’s multiple comparison tests.

2

Fig.1 Sample image

Fig.2 Universal testing machine with ISO tensile test jig

Results
The standard value of C300: 265gf
The theoretical value of C300: 530gf (two times of a standard value)
The average value of 0: 462gf The average value of 1: 387gf The average value of 2 :403gf (Table.2)

3

Table.2 The magnetic force of the two parallel installed keepers

Conclusions
The attractive force changes by the difference of the distance between the keepers. In the case ofarranging keepers in contact, compared to the case of arranging them separately, the rate of decline
of its attraction is small against the standard value.

References
1. Nakabayashi. S , Higuchi. N, Nagai. E, Sanada. j, Ootani. K, Ohyama. T, Yasuda. H,
Tsukimura. N. A study of the attractive force of magnetic attachments on keepers mounted inparallel in a coping, J J Mag Dent 28(1):71-75, 2019.

4

Resistance force of magnetic attachments against external lateraldisplacement
M. Takahashi1, G. Togawa1, K. Numazaki2, M. Kanyi3 and Y. Takada1
Division of Dental Biomaterials, Tohoku University Graduate School of Dentistry, JAPANDivision of orthodontics and dentofacial orthopedics, Tohoku University Graduate School of
Dentistry, JAPAN3
Moi Teaching and Referral Hospital, KENYA
1
2

Abstract
The purpose of this study is to demonstrate the resistance force of magnetic attachments against external
forces that displace it laterally along the mating face. The resistance and attractive forces during lateraldisplacement between a magnetic assembly or neodymium magnet and its keeper were measured. The
maximum friction force of the Physio Magnet 5213 magnetic attachment was 1.78 N whereas that ofneodymium keeper was 0.39 N. It was demonstrated that besides frictional force, the magnetic attraction
force contributes towards the overall resistance against external forces that laterally displace the magnetic
assembly from its keeper. The magnetic attachment had a smaller attraction force than the maximum static
friction. Contrastingly, neodymium magnet combined with the same keeper, upon significant displacement,
generated an attraction force that exceeded the maximum static friction force. This is because the magnet’s
open circuit system generated an attraction force that restored the magnet to its keeper. Further
understanding and utilization of this phenomenon, is significant for development of a new magnetic
attachment with a stronger bracing function.

Introduction
Support, retention, and bracing or resistances against lateral forces are the three fundamental aspects
required for stability of dentures during function1). Elements of a denture such as abutments, proximal plate,connectors, occlusal rests, clasps, reciprocators and base plate, contribute towards stability solely or in
combination. Dental magnetic attachments are devices incorporated into the abutments to offer retention
and support with minimal bracing (horizontal stability) 2). These characteristics are absent in other abutment
devices. The use of magnetic attachments eliminates most of the rotational and lateral forces which are
detrimental to the longevity of a tooth’s root3). Use of magnetic attachments also allows for a decrease inabutment teeth loading forces which is an advantage, but a compromise in terms of denture functionality.
However, it is possible to actively increase force generated by bracing components using magnetic
attachments of improved root cap shape or using MT crown2).
Dental magnetic attachments are associated with weak bracing force because only frictional force of themating face provides resistance to external forces acting in the horizontal direction. The magnets attractive
force is not directly involved2). Generally, when force is exerted on an object placed on a horizontal surface
in an attempt to slide it laterally, static friction provides a counter force. Static friction force shows thegreatest magnitude just before the object starts to move. It is termed as the maximum static friction.
Maximum static friction Fs is proportional to the normal force N acting perpendicularly through the object
to the contact surface. The proportionality constant ȝs at that point is called the coefficient of static friction,
whose relationship is represented by the following equation (1).
Fs=ȝsN(1)

When the force applied to move the object becomes greater than Fs, the object starts to slide, and kinetic
friction begins to act on the object instead of static friction. Kinetic friction is a smaller force thanmaximum static friction. It has been proven experimentally that kinetic friction Fk is proportional to normal
force N. The proportionality constant ȝk is called coefficient of kinetic friction, and the following equation(2) describes the relationship.
Fk =ȝkN(2)

The values represented by ȝs and ȝk are constants which are determined by properties of the contact surface,5such as surface roughness, surface energy. The contact surface area and velocity of the moving object haveno direct influence on the constants. The normal force N in most scenarios is the force of gravity acting on
the object. Magnetic attachments possess a very small gravity due to their minute mass. Therefore it is theattractive force of a magnet that predominantly acts as the normal force N. The bracing force of a magnetic
attachment which is its resistance to forces that try to shift the magnetic assembly laterally from its keeper,is majorly dependent on the attractive force. Out of the few studies that investigated the friction force ofmagnetic attachments, only one study reported a magnetic attachment with a friction force of 70~90 g. It isa well-known that dental magnetic attachments are gentle on the roots of the abutment teeth but themechanism needs to be understood well by studying resistance force and its behavior against forces thatcause lateral displacement.

Objective
The purpose of this study was to demonstrate the resistance forces of a magnetic attachment against
lateral displacement. The resistance and attractive forces of magnetic assembly and magnet against its
keeper during lateral displacement were examined.

Materials and Methods
Dental magnetic attachment and magnet
A dental magnetic attachment, Physio Magnet 5213 (magnetic assembly: 5.2 mm in diameter and 1.3
mm in height, with keeper: 5.2 mm in diameter and 0.8 mm in height, Morita) was used in this study. The
set is subsequently referred to as magnetic attachment. A magnet, cylindrical neodymium magnet(Nd-Fe-B: 5.0 mm in diameter and 1.5 mm in height, Trusco) was used. The cylindrical neodymium
magnet was combined with the Physio Magnet keeper. The set is hereinafter referred to as magnet. In orderto have the magnet and keeper in a position whereby their centers match, the magnets diameter must be
smaller than the keepers4). Therefore the magnet selected for use in this study had a slightly smaller
diameter than the keeper's.
Experimental device
The retentive force measuring device used in this study matches the basic description in ISO
13017:20205). It was connected to a digital force gauge (ZPS, Imada). The device was installed in auniversal testing machine (AGS-5kNG, Shimadzu) which controlled the crosshead speed.
Measurement of resistance force of a magnetic attachment or magnet and keeper against
external forces that cause lateral displacement
As shown in the Figure 1, aluminum jigs were fixed with their long axis in a vertical plane. One jig was
fixed to the lower table of the measuring device whereas the other was fixed onto the upper table. A
magnetic assembly and magnet combined with keeper were fixed onto the jigs using cyanoacrylateadhesive with the long axis in a vertical plane as shown in Fig 1. The magnetic assembly or magnet was
pulled upwards so that the mating faces slide against each other at the crosshead speed of 1mm/min, andthe resistance force measured by the force gauge. Recording of measurements was done at a sampling rateof 1 kHz until the magnetic assembly or magnet completely separated from the keeper. After themeasurement, the time values were converted to distance to generate a displacement distance-resistancecurve.

6

Fig. 1Set up of the sample mounted on device to measure resistance forces
Measurement of attractive force during lateral displacement
The measuring device, magnetic attachment and magnet were set up in accordance with the test methodof ISO 130175), and retentive force (attractive force) was measured at crosshead speed of 2 mm/min. The
measurements started when the magnetic assembly or magnet had its center aligned to that of the keeper.
Attractive force measurements were done at intervals of 100 μm horizontal displacement of keeper. The
experiment was run until the magnetic assembly or magnet completely separated from its keeper.

Results
1. Resistance force of magnetic attachment or magnet and keeper against external forcesthat cause lateral displacement along the mating face
The displacement -resistance force curve of the magnetic attachment is shown in Figure 2. The
horizontal axis shows the distance of horizontal shift (displacement) by the magnetic assembly away fromthe keeper whereas the vertical axis shows the resistance force measured. The resistance force just before
the magnetic assembly started to move (maximum static friction force) was 1.78N. Once the assembly
started to move, the force dropped drastically to 1.34 N. Afterwards, the resistance force increased as the
distance approached 0.25 mm, then decreased with increasing distance. The curve had several inflection
points. Beyond 5.2 mm, the resistance dropped to zero.

7
2.0

Resistance (N)

1.5

1.0

0.5

0.0

0.0

1.0

2.0

3.0

4.0

5.0

6.0

displacement distance (mm)Fig. 2 The displacement distance-resistance force curve of the Physio magnetic attachment
The displacement distance-resistance force curve of the neodymium magnet -keeper is shown in Figure 3.
The resistance force just before the initial movement of the magnet (maximum static friction force) was
0.39 N. Afterwards, the force dropped to 0.37 N then showed a transient rise and fall at 0.54 mm. Beyond
that, the force increased monotonically with the increase in distance. As the distance exceeded 4.5 mm, theresistance force decreased to reach zero at 6.4 mm. The decline in resistance force to zero from 5.1 mm
distance point, showed a smooth convex shape.

Resistance (N)

1.0

0.5

0.0

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

displacement distance (mm)Fig. 3The displacement distance-resistance curve of neodymium magnet-keeper

8
2. Horizontal displacement and magnetic attractive force
The relationship between horizontal displacement and the attractive force of magnetic attachment andneodymium magnet are shown in Figure 4 and Figure 5 respectively. In both cases, the attractive forces
decreased with increasing displacement and showed multiple inflections.

12.0

Attractive force (N)

10.0
8.0
6.0
4.0
2.0
0.0

0.0

1.0

2.0
3.0
4.0
Horizontal displacement (mm)

5.0

6.0

Fig. 4The attractive force against horizontal displacement in magnetic attachment

3.5

Attractive force (N)

3.0
2.5
2.0
1.5
1.0
0.5
0.0

0.0

1.0

2.0
3.0
4.0
Horizontal displacement (mm)

5.0

6.0

Fig. 5 The attractive force against horizontal displacement of neodymium magnet and keeper

Discussion

9
1. Resistance force of magnetic attachment against external forces that cause lateraldisplacement along the mating faceIn this study, the mating face of the magnetic attachment was fixed onto the measuring device with thelong axis parallel to the vertical plane so that only the attractive force of the magnet affects the normal
force which in turn relates to friction force. The maximum static friction was determined from theresistance displacement curve. Normal force N is the attractive force at zero displacement. The coefficientof static friction was calculated using equation (1). The kinetic friction which is active soon after themagnetic assembly or magnet starts to move, was derived from the resistance displacement curve. The
coefficient of kinetic friction was calculated using equation (2). The calculated coefficients of static friction
and of kinetic friction for the magnetic attachment 5213 were equal to 0.17 and 0.13 respectively. The
values reinforced a well-known concept of, coefficient of static friction being greater that of kinetic friction.
Ishihata et al. in a previous study3) reported that the frictional force of a magnetic attachment was about 1/3
its attractive force. The coefficient of friction in that study was about 0.33. The large difference between thetwo studies is that the material of the magnetic attachments used was different. The magnetic attachment in
Ishihata et al.'s study was made of stainless steel and experimental magnetic alloy E6), while the magnetic
attachment used in this study was made of magnetic stainless steel. The coefficient of friction exhibited bya pair of contacting surfaces is highly dependent on the different material deformation characteristics andthe surface roughness.
Friction force is proportional to the normal force but independent of the contact surface area (Amontons'law). Therefore, kinetic friction force was calculated at different positions of displacement using Equation(2), after acquisition of coefficient of kinetic friction and data on attractive forces at different positions. The
results are shown in Figure 6 alongside the resistance force. If kinetic friction is the only force that resists
the external forces responsible for lateral displacement of magnetic attachments, then the two sets of values
would be identical and the two curves superimposed onto each other. However, in this case, the resistanceforce was larger than the kinetic friction force calculated. This implies that the resistance force measured
includes laterally attraction force related to the magnetic attachments. The magnetic assembly creates amagnetic circuit on the mating face when in contact with the keeper which generates a strong attractive
force. Even when the magnetic assembly has been displaced until it is no longer in contact with the keeper,a small attraction force towards the keeper persists. The small attraction force attempts to restore themagnetic assembly back in contact with the keeper. Therefore, the measured resistance force is the sum of
kinetic friction force acting along the mating face and the attraction force due to the magnetic fields.

2.0
Kinetic friction force
Resistance force

Force (N)

1.5

1.0

0.5

0.0

0.0

1.0

2.0

3.0

4.0

5.0

6.0

Horizontal displacement (mm)Fig. 6 Kinetic friction force and resistance force corresponding to different positions of horizontal
displacement of magnetic attachment
The difference between the resistance force and the kinetic friction force was calculated to obtain the10attraction force of the magnetic attachments in each position. Using the coefficient of static friction andattractive force values at each position, the maximum static friction force exerted at each position of lateraldisplacement was obtained using formula (1). The results are shown in the Figure 7. As demonstrated on
this figure, the attraction force that attempts to restore the magnetic assembly into congruence with thekeeper is generally smaller than the maximum static friction force. Therefore, the attraction force does not
automatically get an already displaced magnetic attachment back to its original position with keeper ormove further.

2.0
Magnetic attraction force
Maximum static friction force

Force (N)

1.5

1.0

0.5

0.0

0.0

1.0

2.0
3.0
4.0
5.0
6.0
Horizontal displacement (mm)Fig. 7 Magnetic attraction force and maximum static friction force at each displaced position of magnetic
attachment
2. Resistance force of neodymium magnet against forces that cause lateral displacement
along the mating face
The coefficients of static and kinetic friction while using neodymium magnet were determined in asimilar manner to that of magnetic attachment. The attained coefficients of static and kinetic friction were0.12 and 0.11. Coefficient of static friction was larger than that of kinetic friction. Kinetic friction force ateach position of lateral displacement was calculated in a manner similar to that of magnetic attachment.
The data of kinetic force along with the resistance force are represented in a graph shown as in figure 8.
Similar to the case of magnetic attachment, the resistance force was larger than the kinetic friction. This isbecause the attraction force between magnet and keeper even in their displaced condition is incorporated
into the measured resistance force. The measured resistance force is the sum of the kinetic friction force at
the mating face and the attraction force due to the magnetic force. Since neodymium magnets arecharacterized by open magnetic circuit, the magnetic fields from the bottom side (opposite to mating face)of the magnet and the exposed surface of the keeper generate an attraction force. This attraction force pulls
the magnet back towards the fixed keeper. Contrary to the case of the magnetic attachment in which theresistance force quickly dropped to zero when the magnetic assembly completely separated from the keeper,
the attraction force in this case persisted even after the separation point (distance of 5.1 mm). The abovefinding is a feature of open magnetic circuit, whose magnetic force after separation is inversely
proportional to the square of the distance (inverse square law) causing the magnetic force to decrease
slowly in a convex shape. On the other hand, the Physio magnetic attachment used in this study has aclosed magnetic circuit in which the two poles close to each other undergo little magnetic flux leaks
causing quick decay of magnetic force.

11
1.0
Kinetic friction force

Force (N)Resistance force

0.5

0.0

0.0

1.0

2.0
3.0
4.0
5.0
Horizontal displacement (mm)

6.0

7.0

Fig. 8Kinetic friction force and resistance force corresponding to positions of lateral displacement of theneodymium magnet
The neodymium magnet’s laterally attraction force and the maximum static friction force at each positionof lateral displacement were determined in the same method as the magnetic attachment. The results areshown in the Figure 9. Unlike the magnetic attachment scenario, the magnets attraction force exceeded the
maximum static friction force when the magnet was displaced significantly by more than 2.5 mm. The
resultant force can restore the magnet to coincide with its keeper. The restoring force generated in themagnet combination used in this study was small, but it may be possible to increase it through use ofcertain selective combination of magnets. Although magnetic attachments are gentle on the tooth root, they
act as weak bracing components. Clinical application of the restoring forces, would simplify alignment of
the keeper to magnetic assembly. It may also be possible to develop a new magnetic attachment withenhanced bracing function using the information on the phenomenon of restoring forces.

1.0
Magnetic attraction force

Force (N)Maximum static friction force

0.5

0.0

0.0

1.0

2.0
3.0
4.0
5.0
6.0
Horizontal displacement (mm)Fig. 9 Magnetic attraction force and maximum static friction at each position of the neodymium magnet

12Conclusion
The maximum friction force of the Physio Magnet 5213 recorded was 1.78 N. It was clearly
demonstrated that besides frictional force, magnetic attraction force also influences the overall resistanceforce that stops displacement and restores a magnetic assembly to its keeper.

Acknowledgments
The authors greatly acknowledge KEDC Co., Ltd. for providing the Physio Magnet 5213.

References
1. S. Yamashita, Correspondence to the force applied to the partial denture. In: M. Ai and Y. Igarashi,
editor, Standard Partial Denture Prosthodontics, pp 43-57, Gakkenshoin Ltd., Tokyo, 2016.
2. Y. Tanaka, New dental magnetic attachment, pp 44-57, Ishiyaku Publishers, Inc, Tokyo, 2016.
3. N. Ishihata, H. Mizutani and M. Ai: Application of ferromagnetic alloy for prosthodontics Part 5.
Application of magnetic attachment for prosthetically hopeless teeth, J JpnProsthodont Soc, 31(6),1445-1453, 1987.
4. M. Takahashi, K. Numazaki, H. Yamaguchi and Y. Takada:A study of the usage of open circuit magnets
as dental magnetic attachments with reference to retentive force, J J Mag Dent, 27(1), 61-62, 2018.
5. ISO 13017:2020. Dentistry—Magnetic attachments.
6. H. Mizutani, N. Ishihata, M. Ai, H. Harada, O. Okuno, I. Miuraand M. Kojima: Application offerromagnetic alloy for prosthodontics Part 1. Accuracy of casting, J JpnProsthodont Soc, 25(4),687-694, 1981.

13

Paper submission
Long-term follow-up cases of magnetic attachment denture withdifferent prosthetic designs
H. Kumano, Y. Nakamura, H. Nakamura, R. Kanbara, T. Masuda, W. Fujinami, S. Ozawa and
J. Takebe.
Department of Removable Prosthodontics, School of Dentistry, Aichi Gakuin University

Introduction
The magnetic attachments can be small and powerful attractive force by using a neodymium magnet
which is one of rare earth magnets. This system can be used as abutment teeth by decreasing the lateralforce even if crow-root ratio is poor. Therefore, the clinical efficacies of a magnetic attachment havebeen widely demonstrated1,2). The most important advantage of the magnetic attachment is that it canbe used in the root cap type or MT (Magno telescopic) crown type according to the clinical conditionsof the abutment tooth. As a result, it is possible to preserve abutment teeth with maximized support
ability by using either type of them, which is considered to have great clinical advantage. This report
is a case study of partial denture prosthesis designed with magnetic attachments of the MT (Magnotelescopic) crown type for the maxilla and the root cap type for the mandible, which are followed ingood condition for a long time.

Summary of the case
Patient is a 71-year-old woman. The chiefcomplaint was to look better, worry about the bite,and not be able to bite things.
Medical history was hypothyroidism. Historyof present illness was stained teeth, misalignmentof the bite, difficulty in biting, and pain in TMJ.
After splint treatment at the previous doctor, theTMJ problem was improved. However, in May
2007, the patient requested mastication and
Fig.1 Intraoral views and mandibular removableaesthetic treatment and thus consulted thepartial denture at the time of initial examination
department.
In the present illness, many restorations set on
the remaining teeth in the maxilla and gingival recession at themargin was observed. In the mandible, as well as in the maxilla,
all remaining teeth except for the residual root were set withrestorations. 35 of the intermediate defect was set with the fixed
partial denture incorporating a bar-type retainer.45 was a residualroot and 46,47 was distal extension missing. The facing ofrestorations that had been set was discolored. Mandibular tours
was found on the lingual of the mandible. In addition, when theFig.2 Panoramic radiographs
removable partial denture was set, it was observed the bite raisingat the time of initial(Fig.1).
examination
From panoramic radiographs at the time of initial examination,
radiolucency at the apex was observed in 25, 27 and 36, and poor root canal filling was observed in
16 and 26. Poor crown-root ratio was observed in the mandibular anterior teeth region. In addition,
incompatibility of the restorations in the maxillary and mandibular molars was observed (Fig.2).

14

Based on the above findings, it was diagnosed as masticatory disorder due to mandibular molar
defect and esthetic disorder due to discoloration of the facing of the maxillary and mandibular fixed
partial dentures.

Treatment and progress
Using the occlusal vertical dimension of the old denture as areference, the study cast was mounted on a semi adjustable
articulator and examined. The presence of the vomiting reflex was
found in the maxilla during the taking of preliminary impression.
Imaging examination using panoramic radiographs showed apoor crown-root ratio in the remaining mandibular teeth. Then, it
Fig.3 The design of thewas decided to remove all prosthesis for remaining teeth of thedefinitive prosthesis
mandible and to make treatment denture of overdenture type.
Before making the treatment denture, we had to remove themandibular torus that was thought to cause pain when wearing thedenture. Next, the poor prosthesis for the remaining mandibular
teeth were removed and treatment denture was set. The maxilla,
as well as the mandible, were also set with a provisional bridge
after the poor prosthesis were removed. While adjusting theinterim prosthesis set on the maxilla and mandible, re-root canaltreatment was performed for 15,16,26,27,36,45. 36 of the distalroot was treated with hemi section because of poor prognosis.
Fig.4 Panoramic radiographs
After re-root canal treatment, the definitive prosthesis wasof the inner crown of the MT
designed (Fig.3). The design of the definitive prosthesis for thecrown and root cap withmaxilla was a removable dental prosthesis with MT (Magnokeeper (2011.8)
telescopic) crown type using magnetic attachments for theretainer, because the clinical condition of the abutment teeth wasgood. The reason for making it a removabledental prosthesis was to consider how to deal
with 13 defects and the vomiting reflex. In themandible, considering the clinical condition of
the abutment teeth and the crown-root ratio, theoverdenture was made with a root cap withkeeper as the retainer.
After taking precise impression of the maxillary
and mandibular abutment teeth, the inner crownof the MT crown and the root cap with keeper
were made. After making the inner crown of theMT crown in the maxilla, pickup impression was
taken and the outer crown of the MT crown was
made. Then, according to the conventional
Fig.5 Intraoral view of the definitive prosthesis
method, the maxillary and maxillary definitiveand placement (2011.8)
prosthesis was made (Fig.4,5). In the maxilla, themagnet assembly was set at the time of placement of the definitive prosthesis. In the mandible, onemonth after the definitive prosthesis was set in place, a magnetic assembly was set on the abutment
tooth after checking that there was no pain in the mandibular residual mucous membrane. The fit ofthe definitive prosthesis was good, and the patient was satisfied both functionally and aesthetically.
After that, it was recalled once every three months.
However, one year and three months after the definitive prosthesis was set in place, mobility of teeth
45 and 36, which were of uncertain prognosis, increased. Therefore, it was diagnosed that it wasdifficult to preserve them, and the teeth were extracted. After healing of the extraction socket, metal
plate denture with the two-piece artificial resin tooth was made to improve the rigidity of the denture

15

and to maintain the stable occlusal relationship(Fig.6). To obtain an occlusal surface in harmony
with jaw movement, the two-piece artificial resin
tooth was used for about two months. Then, theocclusal surface was replaced with lithium
disilicate glass ceramics.
After the metal plate denture was set in themandible, it was recalled regularly every six
months. The purpose of the recall is to manage
Fig.6 Intraoral view and the prosthesis forthe periodontal disease of the remaining teeth
maxilla and mandible (2013.7)
and to check and adjust the occlusal changes ofthe denture and remaining teeth. At present, thedentures and remaining teeth are in good condition (Fig.7,8,9,10).

2015.2

2019.22017.32021.6

Fig.8 Panoramic radiographs ofthe current condition (2021.12)

Fig.7 Periodontal conditions

Fig.9 Intraoral view of the prosthesis formaxilla and mandible and placement (2017.6)

Fig.10 Intraoral view of the prosthesis formaxilla and mandible and placement (2021.6)

Conclusions
This time, MT (Magno telescopic) crown type was selected for the retainer in the maxilla, where
the clinical conditions of the abutment teeth were relatively good. Since the clinical conditions of theabutment teeth were poor, a root cap type was selected for the retainer in the mandible. Finally, thepartial denture prosthesis was designed using different methods of magnetic attachments in the maxilla
and mandible.
The most important advantage of the magnetic attachment is that it can be used in the root cap typeor MT crown type according to the clinical conditions of the abutment tooth. As a result, it is possible
to preserve abutment teeth with maximized support ability by using either type of them, which isconsidered to have great clinical advantage. Therefore, it is considered that this case had a good long-16

term, functional and aesthetic follow-up. The maintenance of the dentures and remaining teeth will be
continued with the main purpose of checking and adjusting the occlusal changes.

References
1. Tanaka Y. New Magnetic Attachment –New Prosthetic Treatment using magnets-.1st Ed. Tokyo:
Ishiyaku Publishers Inc; 2016.
2.Tanaka Y, Nakamura Y, Hoshiai K. General remarks concerning magnetic attachments in dentistry.
Proc Japan Acad; 78(5): 97-105,2002.

17

Denture repair by applying a magnetic attachment after extracting theabutment tooth of a cone crown telescope: A case report
A.Izumida
Department of Comprehensive Dentistry, Tohoku University Hospital

Abstract
In this case report, a denture was repaired by applying a magnetic attachment after extracting theabutment tooth of a cone crown telescope. The patient was a 76-year-old female. She wore a denturewith a cone crown telescope for three missing teeth: the left central incisor, the lateral incisor, and thecanine. The second premolar on the left side of the maxilla, one of the abutment teeth, was extracted
due to root fracture. Subsequently, a full metal crown with an extracoronal magnetic attachment wasaffixed to the maxillary left first molar behind the defect. Denture repair was performed by adding amagnetic attachment to the inner surface of the outer crown of the second premolar on the left side of
the maxilla to match the keeper of the extracoronal magnetic attachment. The patient was satisfied
with using the repaired denture. In addition, by adopting an extra-crown attachment, it was possible
to reduce the burden on the abutment tooth.

Introduction
 In recent years, dental magnetic attachments have become easier to handle in general clinicalpractice due to their miniaturization, retentive force, improved corrosion resistance, and the fact thatthey can also be applied to extracoronal magnetic attachments. Another advantage is that, with a little
ingenuity, there are various ways to use them.
 In this case, one of the abutment teeth of the removable partial denture was extracted. The full metalcrown of the existing tooth at the extraction site was made into a full metal crown equipped with an
extracoronal magnetic attachment, and the denture was repaired by affixing a magnetic attachment to
the inner surface of the denture so as to fit the keeper.

Outline of the case
The condition of the prosthetic device in the oral cavity at this patient's first visit was shown in theprevious report, 1) but the basics are given below.
The patient was a 77-year-old female. On June 12, 2020, she came to the hospital complaining ofupper left pain during occlusion. Intraoral views and the denture are shown in Figure 1. As a general
medical history, the patient was being treated for hypertension.

18

Her current dental history is as follows. In December 2000, inner crowns of the cone crowntelescope on the maxillary right central incisor, left first premolar, and left second premolar were
produced for three tooth defects. A removable partial denture equipped with outer crowns conforming
to those inner crowns was then set. In November 2014, the inner crown of the maxillary right central
incisor, one of the abutment teeth, was removed for root canal treatment due to acute apicalperiodontitis. In July 2015, after endodontic treatment, the maxillary right central incisor was repairedby fitting a magnotelescopic crown (MT crown) with a magnetic attachment to fit the existing outercrown.
The current disease is as follows. The second premolar on the left side of the maxilla, which was
the focus of the main complaint, had occlusal pain for about 3 weeks; additionally, red swelling wasobserved in the buccal gingiva, the tooth mobility was second grade, and the periodontal pocket depth
was 9 mm at the deepest point. A dental photograph of the second premolar on the left side of themaxilla is shown in Figure 2. A root fracture extending to the apex was found, and the tooth was judged
to be unsavable, so it was extracted on June 30.

19

Clinical procedure
In planning the prosthetic treatment, the following factors were considered: The denture had beenused for a long time, but the fit of the denture was good, and the patient could use the denture
comfortably. Therefore, the prosthetic treatment plan after tooth extraction was shown as follows andwas accepted by the patient:(1) Fabricate a provisional crown with an extracoronal attachment after removing the full metalcrown of the maxillary left first molar.
(2) Produce a full metal crown with an extracoronal magnetic attachment keeper after the residual
ridge being stable.
(3) Mount the magnetic assembly on the inner surface of the outer crown of the second premolar
on the left side of the maxilla.
(4) Maintain and recall.
Treatments were performed as follows.
A provisional crown with extracoronal attachment to the maxillary left first molar was made by
applying a bent ready-made rest wire to the outside of the crown. The extracoronal attachment was
fitted to the inner surface of the outer crown of the second premolar on the left side of the maxilla(Fig.3).

20

Working casts without the denture (Fig.4ձ) and with the denture (Fig.4ղ) were prepared for the
production of a full metal crown with the extracoronal attachment. In this case, since it was used on
the inner surface of the outer crown of the second premolar on the left side of the maxilla, GIGAUSSC400® (GC, Japan) was used as the magnetic attachment, and the extracoronal attachment was
manufactured by the keeper bonding method.
The crown morphology was waxed up in consideration of the following points (Fig.4ճ). The mesial
surface was adapted to the distal surface of the second premolar on the left side of the maxilla of themodel with denture. The part of the extracoronal attachment in contact with the mucosal surface wasfitted with a dentureless model. For the pedestal to which the keeper of the extracoronal attachment isaffixed, a model with denture was used, and wax-up was performed on the model in which the occlusal
surface was ground, leaving the axial surface of the second premolar on the left side of the maxilla.
The wax pattern was buried and cast according to the conventional method, and then the cast bodywas adjusted and polished (Fig.4մ).

21

 The full metal crown with an extracoronal attachment was set in the oral cavity. At the next visit, amagnetic attachment was fitted to the inner surface of the outer crown of the second premolar on theleft side of the maxilla (Fig.5).

22Discussion
In this case, by extracting the second premolar on the left side of the maxilla, the Kennedy
classification is type 1 of Class III, and the Eichner classification is B-1. Including the maxillary rightsecond molar that had already been missing, 5 teeth were missing. Since there was no defect in themandible, the number of teeth decreased from 24 to 23, and the number of occlusal supports decreased
from 10 to 9. In Miyachi's occlusal triangle, the area changed from the first area to the second.2)
However, the patient had 9 occlusal supports and 23 teeth, had no tooth loss for the past 21 years, andshe had more teeth and occlusal supports than other people of her generation. As a result of considering
these factors, it was judged that the minimum prosthetic treatment was possible in this case.
Regarding the maxillary left first molar, the periodontium was generally good, and the pocket depth
was about 3 mm, although the margins of the full metal crown were incompatible.
The patient was using the denture well and strongly hoped to continue using it. Therefore, she wasrelatively reluctant to make new dentures. In this case, the purpose of prosthetic treatment was to use
the existing denture as much as possible while not placing an excessive burden on the abutment teeth.
When she was presented a treatment plan using a full metal crown with an extracoronal attachment,
she gave her consent to the treatment plan. 3)

Conclusions
As a prosthetic treatment after tooth extraction, the existing full metal crown of the existing tooth
was remade into a full metal crown with an extracoronal attachment. The existing denture was repairedby setting a magnetic attachment on the inner surface of the outer crown of the denture to fit the keeper.
By using the existing denture, we enabled the patient to use the repaired denture without discomfort
and with high satisfaction. In addition, the use of a magnetic attachment could reduce the burden on
the abutment teeth.

References
1) A. Izumida. Denture repair with the application of a magnetic attachment to the inner crown of atelescopic crown: A three-year follow-up case. J J Mag Dent 2019;28:9–13.
2) T. Miyachi. Clinical evaluation and risk analysis for partially edentulous arch —Imbalance of thenumber of teeth between maxilla and mandible as a risk factor—. Ann Jpn Prosthodont Soc
2013;5:21–27.
3) T. Ohyama, T. Ishigami, S. Sakaguchi, E. Nagai, K. Ohtani, T. Fujimoto, Y. Katakura, M.
Takamura, and A. Magima. The extracoronal magnetic attachment using ready-made patterns. J J
Mag Dent 2006;15:28–32.

23

A case report of a removable denture using magnetic attachment andcircumferential clasp followed up for 9 years
M. Sone, D. Matsumoto, N. Koyama, F. Narumi, T. Matsukawa, S. Uchida, K. Takahashi, M. Takagi, Y.
Inoyama, D. Sakamoto, K. Okamoto, and S. Ohkawa
Division of Removable Prosthodontics, Department of Restorative and Biomaterials Sciences, Meikai
University School of Dentistry

Abstract
To reconstruct a harmonious craniofacial system, it is essential to maintain an appropriate occlusal
vertical dimension (OVD). This clinical report describes the prognosis of a magnetic attachment denturethat improved an immediate denture to maintain an appropriate OVD and the optimum mandibular
position. As a definitive prosthesis, a removable maxillary overlay denture was fabricated that included a
coping type of magnetic attachment, copings, and circumferential clasps.
Nine years after the denture setting, the definitive prosthesis has been used without serious problems,
and the magnetic attachment has no clinically significant loss of retention.

Introduction
To reconstruct a harmonious craniofacial system, it is essential to maintain an appropriate occlusal
vertical dimension(OVD). This clinical report describes the prognosis of a magnetic attachment denturethat improved an immediate denture to maintain an appropriate OVD and the optimum mandibular
position.

Clinical History
The patient, a 63-year-old female, complained of masticatory dysfunction. The patient had received amaxillary fixed bridge from tooth #3 to tooth #11 in 1989; however, the restoration failed, having amarginal discrepancy and damage by caries (Fig.1). We did not diagnose infraocclusion by analysis of the
OVD. Finally, we suggested fabricating a removable maxillary overlay denture with a coping type ofmagnetic attachment as a definitive prosthesis byy use of an immediate denture to maintain the optimum

Fig.1 Intraoral view at the initial examination

24

mandibular position, which the patient found acceptable.

Treatment Procedure
As the first therapy, the incompatible fixed bridge in a marginal portion was removed, and tooth #3 wasextracted. Then an immediate maxillary denture was set on a portion of the missing teeth. With theimmediate denture, the patient obtained an adequate occlusal relationship and maintained the optimum
mandibular position (Fig.2).

Fig.2 Intraoral view with immediate denture
As a definitive prosthesis, the reinforcement structure of the framework for preventing denture base
fracture was made to cover about three quarters of the circumference of the magnetic attachment, andprotrusion of the labial side was avoided (Fig.3). GIGAUSS C600® (GC, Japan), the magnetic attachment
in this case report, was applied to tooth #6. The keeper of the magnetic attachment and magnetic assembly
were fixed with adhesive resin cement (Multilink® Automix, Ivoclar Vivadent, Liechtenstein) (Fig.4).

Fig.3 Reinforcement structure of framework

Fig.4 Keeper of the magnetic attachment

A removable maxillary overlay denture was fabricated and included a coping type of magnetic attachment,

Fig.5 Removable maxillary overlay denture

25

circumferential clasps (wire type), and a horseshoe plate as the major connector. This denture wasfabricated with the existing occlusal height and the optimum mandibular position (Fig.5). Figure 6 is an
intraoral view of the definitive prosthesis.

Fig.6 Intraoral view with definitive prostheses

Outcome of Treatment
Presently, 9 years and 7 months have passed since the definitive prosthesis was set (Fig.7). Maintenance
was initially performed every month, but since the prognosis was good, it has been changed to every 3 to
4 months after the first year. In addition to PMTC, maintenance included cleaning and cleaning guidanceby various cleaning tools such as Taft brushes, disinfection around the branch teeth by chlorhexidinehydrochloride, and the application of plaque dye in the oral cavity and denture every 6 months. At thattime, TBI was always performed for #6 (Fig.8). After about 8 years, there was no problem with #6, but
secondary caries was observed in #10. There may have been an effect that the maintenance interval became
a little longer due to the situation of COVID-19, but it is also possible that too much attention was focused
only on cleaning the coping type of magnetic attachment (#6) (Fig.9). In this case, many fulcrum lines
could be set because the front, back, left, and right of the abutment teeth could be arranged. In addition,
molar abutment teeth with crown morphology have an excellent bracing function as compared to abutment
teeth with crown morphology in the form of the root surface, and it seems that the burden of the coping
type of magnetic attachment for #6 was reduced (Fig.10).

Fig. 7 Intraoral view with definitive
prosthesis at 9 years after treatment

Fig.8 Maintenance

26

Fig.9 Intraoral view with definitive
prosthesis at 8 years after treatment

Fig.10 The fulcrum line

Conclusions
A magnetic attachment could be provided as a useful retentive appliance for alleviating patientcomplaints regarding aesthetics and function. It is difficult to maintain an ideal combination of aesthetics
and functionality because the design of a final prosthesis is complex. Therefore, continuous follow-up isnecessary with occlusal adjustment and relining of the denture base to prevent any reduction of the OVD.

27

A clinical case of implant overdenture with magnetic
attachment using CAD/CAM technology
Suzuki Y̏䠈Harada N̐䠈Maruo Ȑ䠈Imaizumi N̏䠈Muto Ȑ䠈Shimpo H̏, Kurihara D̏,
Ohkubo C̏Dept of Removable Prosthodontics䠈Tsurumi University School of Dental Medicine

̏2

Dental Technician Training Institute, Tsurumi University School of Dental Medicine

Abstract
࠙Objectiveࠚ
In recent years, digital dentistry based on computer-aided design and computer-aided
manufacturing (CAD/CAM) has become increasingly popular, and the workflow for the
fabrication of removable dentures has changed dramatically. This case was used
CAD/CAM technology for maxillary conventional overdenture and mandibular implant
overdenture (IOD) with magnetic attachments.
࠙Methodࠚ
CAD/CAM dentures were fabricated using DENTCA system (DENTCA Inc., Mitsui
Chemical Inc.). On the initial visit, exclusive plastic trays (DENTCA tray, DENTCA Inc.)
were used for making definitive impression, determination of vertical dimension, andrecording of the centric relation with gothic-arch tracing. On the second visit, 3D printed
try-in dentures were placed in the patient’s mouth, occlusion, retention, stability, andesthetics were checked and corrected. On the final visit, CAD/CAM dentures weredelivered in the patient’s mouth.
࠙Results, Discussionࠚ
Maxillary conventional overdenture and mandibular IOD with magnetic attachments canbe fabricated using CAD/CAM technology for high strength and accuracy prosthesis.
Introduction
Computer-aided design and computer-aided manufacturing (CAD/CAM) technology has been applied
to removable denture fabrication. CAD/CAM dentures can be fabricated with high precision by
reducing because polymerization distortion is eliminated. This case was used CAD/CAM technology
for maxillary conventional overdenture and mandibular implant overdenture (IOD) with magnetic
attachments.

Patient’s characteristics
The patient was a 65-years old female with partially edentulous maxillary jaw including dental root
fractures #23 and #26 and fully edentulous mandibular jaw including dental implant fractures #47 (Fig.
1, 2). Maxillary and mandibular acrylic partial denture was worn for five years. Her chief complaints
were unstable and difficulties of mastication using existing dentures. There was no significant medical
history.

28

Fig. 1 Intraoral photograph at the first visit

Treatment progresses

2017/ February
April 
July 

࣭First visits
࣭Extraction of #23, #26 teeth, and remove of #47 implant.
࣭Two implants (Magfit MIP fixture, PLATON, Japan) were placed in the regionsof # 33 and # 43
November ࣭Definitive impressions of both maxilla and mandibular jaws were made and themaxillomandibular relationship was recorded.
࣭3D printed try-in dentures were placed in the patient’s mouth, occlusion,
retention, stability, and esthetics were checked.
࣭CAD/CAM dentures were delivered to the patient’s mouth.
࣭ Magnetic attachments (Magfit MIP, PLATON, Japan) were set on the
CAD/CAM denture.

Implant placement
Fig. 2 Shema of Mini implant and magnetic attachment
Mini dental implant has been applied as a convenient
treatment option for edentulous patients in cases where
standard-sized Implants cannot be placed for economical
and/or anatomical reasons

Magfit MIP㸦PLATON㸧Fig. 3 Two mini implants were placed at canine regions.

Fig. 4 Magnetic attachment keepers(Magfit MIP flat keeper, PLATON)
were set on the implants.

29

 CAD/CAM dentures were fabricated using DENTCA system

a: Use hard flow polyvinyl siloxane impression material for first impression

b: Apply medium flow polyvinyl siloxane for wash impression. Seatand border mold to capture anatomical landmarks.
Fig. 5 a,b Definitive impressions of both the maxilla and mandible were made with a double impression
technique using polyvinyl siloxane impression materials (Exafine, hard and medium flow types; GC
Corp) with custom trays (DENTCA tray, Size M; DENTCA Inc).

Fig. 6 Both impressions were sectioned and separated anteroposteriorly

30

Fig. 7 Gothic arch was traced, and the maxillomandibular relationship was registered using theanterior portions of the impressions.

Fig. 8 Virtual teeth were automatically arranged according to average positions of anatomical
landmark using a digital design system (PreForm v1.9.1 CAD software; DENTCA Inc). 3D printed
try-in dentures were placed in the patient’s mouth, occlusion, retention, stability, and esthetics werechecked and corrected.

Fig. 9 Maxillary and mandibular complete dentures was milled from acrylic resin block andcommercially available denture teeth were bonded with resin adhesive.

31

Fig. 10 Panorama radiograph at the postoperative visit

Results and Discussion
Maxillary conventional overdenture and mandibular IOD with magnetic attachments can be fabricatedusing CAD/CAM technology for high strength and accuracy prosthesis. Sufficient retention andstability could be provided by the magnetic attachments, and satisfactory aesthetic and function could
be achieved using the DENTCA system.

32

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

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日本磁気歯科学会雑誌
第三十一巻 第二号
J J Mag Dent

日本磁気歯科学会

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