201827

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J J Mag Dent

vol. 27

No. 2 2018

The Journal of the Japanese Societyof Magnetic Applications in Dentistry
Volume 27, Number 2

A
J
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JS D
Proceedings of the 17th International Conference
on Magnetic Applications in Dentistry
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The Japanese Society of Magnetic Applications in Dentistry

JJ Mag Dent vol.27 No.2 2018

JJ Mag Dent vol.27 No.2 2018

JJ Mag Dent vol.27 No.2 2018

JJ Mag Dent vol.27 No.2 2018

J J Mag Dent vol. 27 No. 2 2018

Contents
Session 1
1.

Chair: Masayuki Hideshima (Tokyo Medical and Dental University)

A basic study on accuracy of a Hybrid-resin coping fabricated by CAD/CAM system-Using scanning post and evaluation by μ CTS. Ueda, M. Sone, M. Hamasaka, Y. Okawa, S. Somekawa, D. Matsumoto, K. Takahashi,
F. Narumi, T. Matsukawa, K. Okamoto and S. Ohkawa

2.

Clinical Study about prognosis investigation of abutment teeth and surrounding tissues
using magnetic attachments
T. Masuda, H. Kumano, R. Kanbara, H. Nagai, Y. Nakamura, K. Shoji, Y. Tanaka and J.
TakebeSession 2
3.

Chair: Masatoshi Takahashi (Tohoku University)

A case report of maxillary IARPD using magnetic attachments and anterior milling teeth
A. Tokue, H. Shimpo, D. Kurihara, Y. Suzuki, N. Harada and C. Ohkubo

4.

Marginal bone loss and survival rate of immediately loaded mandibular 2-implant
overdentures retained by magnetic attachments: 3 years follow-up
A. Miyayasu, M. Kanazawa, R. Shimada, M. Iwaki, Y. Sato and S. Minakuchi

Session 3
5.

Chair: Masatake Akutagawa (Tokushima University)

Influence of inclination angle of attractive surface on the attractive force of magnetic
attachment with optimal structural design
H. Kumano, H. Nagai, R. Kanbara, T. Masuda, Y. Nakamura, K. Shoji, Y. Takada, Y.
Tanaka and J. Takebe

6.

Effect of changes in the protocol of fixing a magnetic attachment onto the stage of an ISO
measuring device on retentive forces
M. Takahashi, K. Numazaki, H. Sakatsume, M. Kanyi, K. Sato, K. Sasazaki and Y.
TakadaSession 4
7.

Chair: Shin-ichi Masumi (Kyusyu Dental University)

Working toward the international standardization of dental magnetic attachments- Commission report of the ISO Corresponding Committee in 2017 Y. Takada

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

JJ Mag Dent vol.27 No.2 2018

A basic study on accuracy of a hybrid-resin coping fabricated by
CAD/CAM system -Using scanning post and evaluation by µCTS. UEDA, M. SONE, M. HAMASAKA, Y. OKAWA, S. SOMEKAWA, D.MATSUMOTO, K.
TAKAHASHI, F. NARUMI, T. MATSUKAWA, K. OKAMOTO and S. OHKAWA
Division of Removable Prosthodontics, Department of Restorative and Biomaterials Sciences, Meikai
University School of Dentistry

Abstract
The purpose of this study was to evaluate the fitting accuracy of hybrid resin copings fabricated by thedental CAD/CAM system and manufacturing using a scanning post.
The desktop scanner (Aadva Scan D850,GC) was used in this study, and images were acquired with ascanning post (Scan Posts™,3shape). Designing software (Dental Designer, GC) was employed for creatinga hybrid resin coping design, and a milling machine (Aadva Mill LW-1, GC) was used to fabricate the copingfrom hybrid resin blocks (CERASMART 270,GC) as specimens(n=5). Desktop µCT (SkyScan
1172,SkyScan) was used to measure the marginal and internal fitting accuracy of a hybrid resin coping and
14 measuring points were evolution in this study.
Within limitations, this study suggested that the fitting accuracy of hybrid resin copings fabricated with thisCAD/CAM system using a scanning post was within the clinically acceptable range of 100 ㎛, with the
exception of two points (buccal and lingual margins).

Introduction

The progress of dental CAD/CAM systems has made it possible to fabricate various clinical applications
including inlays, onlays, crowns, bridges, all-ceramic frameworks, and more dentures in clinical dentistry
and has made possible the creation of highly accurate products. Several reports introduced the fabricationof root canal copings or posts and cores using CAD/CAM1–3); however, they had scanned the acrylic resin
pattern and milled and sintered it onto another material for a root canal coping or post and core instead ofinvesting and casting the pattern into the metal. The technique used the same initial procedures for creatinga metal cast coping or post and core.
Our present study4) introduced a method of fabricating CAD/CAM keeper copings using a scanning post
Scan Posts™,3shape) and revealed no significant difference in the cement space for internal fitting;however, the marginal fitting accuracies were not clear.
The purpose of this study was to evaluate the fitting accuracy of hybrid resin copings fabricated by the
CAD/CAM system with a scanning post.

Materials and Methods

Prepared epoxy resin mandibular canine teeth (338, Nissin) were selected as the abutment teeth for the
copings, and the root canal was recontoured with a drill (ParaPost X Drill, Coltene-Whaledent) to fit the same
form of scan posts and pressed to a depth of 5.0 mm, creating a rotational resistance groove and additional
reduction to gain more clearance (Fig.1).

Fig.1 Abutment tooth form for coping
The copings were made from a hybrid resin block (CERASMART 270, GC). They were designed using

１

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JJ Mag Dent vol.27 No.2 2018

CAD software (Dental Designer, 3Shape) after digitalization of the die was performed using a desktop
scanner (Aadva Scan D850, GC), and they were fabricated by a milling unit (Aadva MILL LW-1, GC) inthisstudy
study(Fig.2).
(Fig.2).The
Thecement
cementspace
spacewaswassetsetbased
basedononour
ourstudy
study(Fig.3).
(Fig.3).
thisFig.2 Work flow of scanning and designing coping

Fig.3 Cement space (㎛)The hardware device used in this study was a desktop μCT scanner (SkyScan 1172, SkyScan) for theevolution of the fitting accuracy of hybrid resin copings. Images were acquired using 104 kV voltage, 100㎂ current, and a 0.5 mm thick aluminum filter. After being scanned, the images were reconstructed in thesoftware (NRecon,thethespace
betweenthe hybrid
resin coping
and the abutment
was measured(NRecon,SkyScan),SkyScan),and
and
space
betweenthe hybrid
resin coping
and the abutment
was
using
the instrument(CTAn, SkyScan).
Measurement
points are points
shownarein Fig.4.
measuredusing the instrument(CTAn, SkyScan).
Measurement
shown in Fig.4.

Fig.4 Measurement points in this study. MB: margin of buccal; ML: margin of lingual; MM:margin of mesial; MD: margin of distal

JJ Mag Dent vol.27 No.2 2018

Results
The mean space between the hybrid resin coping and the abutment of each point is shown in Figs.5 and 6.

Fig.5,6 The mean space between hybrid resin coping and abutment
All points except MB and ML had spaces of less than 100 ㎛ between the hybrid resin coping and theabutment.

Discussion
The fitting accuracy of Point MB and Point ML were inferior to the clinically acceptable range of 100µm.5) This fact could be attributed to the setting of the sprue position in the software. Point MB was
located on the sprue side (Fig.7). This region may be unfavorable for cutting the details of the margin due
to the fact that the milling pathway was inhibited by the sprue. Point ML was located on the opposite sideof the sprue because Point ML was located at the opposite end of a hybrid resin block, and this area wassusceptible to damage during the milling process. The hybrid resin block would be bent in the opposite
direction of the milling load side and would be increased. This fact seems to depend on the characteristicsof the CAD/CAM milling blocks.

Fig.7 Location of point MB and ML after milling

Conclusion
Within the limitations of this study, it was suggested that the fitting accuracy of hybrid resin copings
fabricated with this CAD/CAM system using scan posts was within the clinically acceptable range,
excluding MB and ML.

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JJ Mag Dent vol.27 No.2 2018

References
1. K. Tsuda, Y. Tanaka, T. Kanazawa, M. Sakane, and K. Kumano: Fabrication of a Keeper Coping by useof the CAD/CAM System, J J Mag Dent, 13(1), 9–17, 2004.
2. N. Bittner, T. Hill, and A. Randi: EVALUATION OF A ONE-PIECE MILLED ZIRCONIA POST AND
CORE WITH DIFFERENT POST-AND-CORE SYSTEMS:AN IN VITRO STUDY, J Prosthet
Dent,103,369-379,2010.
3. M. A. Awad, T. Y. Marghalani:FABRICATION OF A CUSTOM-MADE CERAMIC POST AND CORE
USHING CAD-CAM TECHNOLOGY,J Prosthet Dent,98,161-162,2007.
4. S.Ueda, M. Sone, H.Hamasaka, Y.Okawa, S.Somekawa, M.Masuda, A.Matsui, Y.Toyota, F.Narumi,
T.Matsukawa, K.Okamoto,and S,Ohkawa:A basic study on the accuracy of a zirconia coping
fabricated by the CAD/CAM system -Application for post scanning-,JJ Mag Dent,26 (2),26-29,2017.
5. N. Suto, S. Miura, R. Inagaki, M. Yoda, and K. Kimura: A Basic Study on Fitness of All-ceramic Crown
fabricated by CAD/CAM system, Ann Jpn Prosthodont Soc, 1, 21–28, 2009.

JJ Mag Dent vol.27 No.2 2018

Clinical study about prognosis investigation of abutment
teeth and surrounding tissues using magnetic attachments
T. Masuda,1 H. Kumano,1 R. Kanbara,1 H. Nagai,1 Y. Nakamura,1 K. Shoji,1 W. Fujinami,1Y. Tanaka,2 and J. Takebe1
Department of Removable Prosthodontics, School of Dentistry, Aichi Gakuin University
Aichi Gakuin University

1
2

Abstract
Magnetic attachments are universally recognized for their practical value and are being widelyused as magnetic attachment dentures in clinical dentistry. However, there are still few reports on the
prognostic process of abutment teeth and surrounding tissues when using these magnetic attachments.
Given the expansion of more effective magnetic attachment adaptation, the necessity of objective
prognostic evaluation is very evident. Therefore, in carrying out integrated and objective evaluationof abutment teeth and surrounding tissues when using magnetic attachment, we aimed to analyze theevaluation methods commonly used by collaborating research institutes.
We collected prognostic data according to the standard protocol using common evaluation
manuals and evaluation sheets available in collaborative research institutes.
Although the prognostic evaluation based on the evaluation sheet and protocol was very effective
in considering the adaptation of the magnetic attachment, it unfortunately confirmed that objective
evaluation of abutment teeth and surrounding tissues remains extremely difficult.

Introduction
Magnetic attachments are recognized for their practical value and are being widely used asmagnetic attachment dentures. Although this kind of investigation has previously been reported by
Hoshiai et al.,1,2 there are still few reports on the prognostic process of abutment teeth andsurrounding tissues when using magnetic attachments．Given the expansion of more effective
magnetic attachment adaptation, the need for objective prognostic evaluation from various
viewpoints is very evident.

Objective
The purpose of this study was to compare evaluation methods that have been created incarrying out the integrated and objective evaluation of abutment teeth and surrounding tissues
using magnetic attachments that are common among collaborative research institutes.

Methods of investigation
We collected prognostic data according to the standard protocol using common evaluation
manuals and evaluation sheets available in collaborative research institutes, and we analyzed various
problems of these evaluation methods.
1. The common evaluation sheet
Figure 1 shows the evaluation sheet at the time of setting the magnetic attachment prosthesis. Thiswas created by Nagata, The Nippon Dental University, at the Clinical Evaluation Committee of theJapanese Society of Magnetic Applications in Dentistry.
On the evaluation sheet, patient information, tooth defect type, intraoral photographs, PCR value,
and the subjective evaluation of the patient, abutment tooth, and the state of the residual teeth are
input. As shown in Figure 2, in addition to the evaluation sheet at the time of setting, there is also an

５evaluation sheet when the patient is recalled.
However, when the condition of the abutment teeth is input into the setting time sheet, the state of
the abutment teeth is automatically reflected on the recall sheet. If there is a change, such as "tooth
extraction or loss" in the abutment teeth, it is necessary to make a special effort to correct theabutment tooth information on the recall sheet.
In addition, as a precaution, “the patient identification number can be unique to each university,
but in order to make it possible to refer to the list, the responsible person in each university should
insure that there are no duplicate numbers.” [Note: If this is quoted material, as indicated by thequotation marks, its source should be indicated.]

Figure 1: The evaluation sheet
Figure 2: The evaluation sheet at recall
at the time of setting
magnetic attachment
prosthesis
2. The subjects of the magnetic attachment prognostic investigation
These are the subjects of the magnetic attachment prognostic investigation:
・Patients who visited Aichi Gakuin University Hospital, Department of Prosthodontics, from 2013
to 2017・Patients for whom prostheses were made using magnetic attachments
・Patients who are currently in recall
3. Applicable research subjects
There were 39 suitable research subjects; among these 39, the following conditions and total
numbers of incidence were observed: (1) total magnetic attachment dentures—50, and (2) total
abutment teeth—84. Of the 50 dentures, 15 were complete overdentures (including two implant
overdentures), and 35 were partial dentures including 6 nonmetal clasp dentures. Figure 3 shows theclassification of the magnetic attachment dentures.

Figure 3: The classification of magnetic attachment dentures

JJ Mag Dent vol.27 No.2 2018

Results of the investigation
1. The classification of abutment teeth by tooth typeFigure 4 shows the results of the classification of the abutment teeth to be investigated by toothtype. It was found that the magnetic attachment was best adapted to both the maxillary andmandibular canine of the 84 abutment teeth we investigated. Conversely, there was little tendency
to adapt to the mandibular central incisor and mandibular molar.

Figure 4: The classification of abutment teeth by tooth type2. The number of teeth lost
The number of lost abutment teeth to which the magnetic attachment was applied during thefive-year investigation period is shown in Figure 5. The total number of lost teeth was 13. Of these,nine were via tooth extraction and four via teeth keeper detachment. Regarding these abutment teeth,
statistics do not include continuing recalls after recreating the magnetic attachment.

Figure 5: The number of abutment teeth lost during the five-year investigation period
3. The 5-year survival rate
The five-year survival rate of the abutment teeth to which the magnetic attachments were appliedin this investigation was about 85%.
In a previous prognostic investigation by Hoshiai et al.,1 the exact same five-year survival rate wasabout 95%, and the 10-year survival rate was reported to be 88%. A trend very similar to the results
obtained in this investigation was seen. Table 1 shows the comparison of the five-year survival rateof the abutment teeth between this investigation and the previous investigation of Hoshiai et al.
Results of the survival rate based on tooth type resulted in a high survival rate of canines andpremolars and a low survival rate of anterior teeth and molars. However, the survival rate of molars
was high when limited to complete dentures.

７８

JJ Mag Dent vol.27 No.2 2018

Table 1: Comparison of the five-year survival rate of abutments teeth

Discussion
In this study, a prognostic investigation into magnetic attachments was conducted using
common evaluation methodology used by collaborative research institutes. The following
observations were made:Despite the fact that investigating the loss of abutment teeth is considered to be one of the moststable and simple evaluation methods in the prognostic investigation of magnetic attachments, it
was discovered through this investigation that evaluations regarding detachment, resetting, andremaking of the keeper; evaluation of the periodontal pocket; and evaluation regarding the
subjective factors of patients were complicated and difficult.
Furthermore, a prognostic evaluation based on the evaluation sheet and protocol was very
effective in considering the adaptation of the magnetic attachment; unfortunately, it confirmed thatthe objective evaluation of abutment teeth and surrounding tissues remains extremely difficult. In
the future, we would like to further study the relevance of the evaluation items at the time of data
analysis.

References
1.
K. Hoshiai，Y. Tanaka，N. Hasegawa, et al.: Longitudinal study on metal plate dentureswith magnetic attachments, J J Mag Dent, 13(1), 1–8, 2004.
2.
K. Hoshiai, R. Ito, M. Miwata, et al.: Investigation on longitudinal survival rates ofmagnetic attachments—its relation to the probing depth of abutments, J J Mag Dent, 20(1), 68–75,
2011.

A case report of maxillary IARPD using magnetic attachments andanterior milling teeth
A. Tokue,1 H. Shimpo,1 D. Kurihara,1 Y. Suzuki,1 N. Harada,2 and C. Ohkubo1
1
Department of Removable Prosthodontics, Tsurumi University School of Dental Medicine
2
Dental Technician Training Institute, Tsurumi University School of Dental Medicine

Abstract

The patient was a 51-year-old female with a partially edentulous maxillary jaw (six anterior teeth
remained, Kennedy classification I, Eichner classification B4). Her chief complaints were difficulties
of mastication using existing denture and bad aesthetic due to metal clasps on the anterior teeth.
Prosthetic rehabilitation was planned using an implant-assisted removable partial denture (IARPD)
with magnetic attachments and milling crowns on the anterior remaining teeth.
Two implants (GENESiO Plus, GC, Japan) were placed in the regions of #14 and #24, andmagnetic attachments (GIGAUSS D400, GC) were set on custom abutments using adhesive cement(Super-Bond, Sun Medical, Japan). Porcelain fused to metal crowns with milling on their lingualsides was placed on the six remaining anterior teeth. IARPD with a Co-Cr framework was delivered
after the vertical dimension was heightened.
Sufficient retention and stability could be provided by the combination of milling crowns andmagnetic attachments, and satisfactory aesthetic and function could be achieved using the IARPD.

Introduction
From an aesthetic perspective, patients are distinguished by metal clasps on their anterior teeth. In
this case, an implant-assisted removable partial denture (IARPD)1,2 with magnetic attachments3 andmilling crowns on the remaining anterior teeth was fabricated for aesthetic reasons.

Patient characteristics
The patient was a 51-year-old female with a partially edentulous maxillary jaw, including dentalroot fractures #16, #15, and #24 (Figs. 1, 2). A maxillary acrylic partial denture had been worn forfive years. Her chief complaints were mastication difficulties using the existing denture and badaesthetic due to metal clasps on the anterior teeth (six anterior teeth remained, Kennedy
classification I, Eichner classification B4). She had no significant medical history.

Fig. 1 Intraoral photograph at the first visit

Fig. 2 Panorama radiograph at the first visit

Treatment progresses
2014/ June
September
2015/ FebruaryFirst visits are made.
Teeth #16, #15, and #24 are extracted.
Two implants (GENESiO Plus, GC, Japan) were placed in the regions of #14
and #24 with socket rifting.

May

Second-stage surgery for the implants is undergone.

November

The vertical dimension is increased using a treatment denture.

2016/ July

Functional Bite Impression (FBI)4 is made.

2017/ January

Porcelain fused to metal crowns with milling on their lingual sides was placedon the six remaining anterior teeth. An IARPD with Co-Cr framework wasdelivered.

February,

Magnetic attachments (GIGAUSS D400, GC) were set on the custom abutments
using adhesive cement (Super-Bond, Sun Medical, Japan).

Fig. 3 Magnetic attachments (GIGAUSS D400, GC) were set on the custom abutments
using adhesive cement (Super-Bond, Sun Medical, Japan).

Functional Bite Impression (FBI)

A

B

E

F

C

D

Fig. 4 FBI tray (Fig. A) was fabricated and tried in the oral cavity (Fig. B). Using auto-polymerized resin (pattern resin,GC) on the occlusal surface, the functionally generated path was recorded (Fig. C). The definitive impression (Exafine,GC) was made under occlusal pressure after the border molding, and the anatomical morphologies of the opposite teeth
were recorded with white silicone impression material (Fit Checker, GC).

Delivered prosthetic appliances

a

b

d

c

Fig. 5 View of the mucosal surface of a metal-based denture (Fig. a). Fabricated porcelain fused to metalcrowns with milling on their lingual sides and an IARPD with a Co-Cr framework (Fig. b). Intraoral
photograph when wearing prosthesis (Figs. c, d).

Fig. 6 Panorama
postoperative visit

radiograph

at

the

Discussion
Sufficient retention and stability could be provided by the combination of milling crowns andmagnetic attachments, and satisfactory aesthetic and function could be achieved using the IARPD.

References
1.
C. Ohkubo: Effect of implant support on distal extension removable partial dentures: invitro assessment, J Oral Rehabili, 34(1), 52–56, 2007.
C. Ohkubo: Effect of implant support on distal-extension removable partial dentures: in2.
vivo assessment, Int J Oral Maxillofac Implants, 23(6), 1095–1101, 2008.
3.
Y. Suzuki, K. Kono, H. Shimpo, et al.: Clinical evaluation of implant-supported
removable partial dentures with a stress-breaking attachment, Implant Dent, 26(4), 516–523,
2017.
4.
S. Shimizu, Y. Sato, M. Shirai, et al.: Occlusion accuracy of restorations and removablepartial dentures fabricated using the impression under occlusal force with FGP, J Oral Sci, in
Press.

Marginal bone loss and survival rate of immediately loaded
mandibular two-implant overdentures retained by magnetic
attachments: a three-year follow-up
A. Miyayasu,1 M. Kanazawa,1 R. Shimada,1 M. Iwaki,2 Y. Sato,1 S. Minakuchi1
Gerodontology and Oral Rehabilitation, Tokyo Medical and Dental University

1

General Dentistry, Tokyo Medical and Dental University

2

Abstract
Purpose: The aim of this study was to compare marginal bone loss and survival rate, between
immediately and conventionally loaded mandibular two-implant overdentures retained by magnetic
attachments.
Method: Nineteen participants with edentulous mandibles were randomly assigned into either an
immediate loading group or conventional loading group. Each participant received two implants in
the interforaminal region with flapless surgery. In the immediate group, each implant was connected
keepers and loaded with mandibular overdentures on the same day of implant placement. In theconventional group, the implants were connected to healing abutments. The healing abutments were
replaced with keepers and loaded with overdentures. The marginal bone loss was measured at
immediate, 6-month, 1-year, 2-year and 3-year after implant placement using digital X-rays. To
compare the marginal bone loss of two groups, Mann-Whitney U test was performed. To compare thesurvival rate of two groups, log-rank test was performed.
Result & Discussion: There is no significantly difference between marginal bone loss at every
evaluation time. One patient in the conventional group withdrew 1 month after implants placement
because of implant failure. Therefore the 3-year accumulate survival rate is 100% and 89% for
immediate group and conventional group respectively, and there is no significantly difference
between the groups.
Introduction
Several recent studies have shown that implant-supported overdentures (IODs) provide adequate denturestability and retention, improve patient quality of life (QoL), and lead to higher denture satisfaction, including better
function, speech, and comfort.1 The McGill consensus suggested that a two-implant overdenture (2-IOD) should
become the first treatment choice for the edentulous mandible.2 Immediate loading of IOD treatment has been
attempted to shorten the healing period and to allow earlier use of dentures than with conventional loading.
Objective
The aim of this study was to compare marginal bone loss and survival rate of immediately andconventionally loaded mandibular two-implant overdentures retained by magnetic attachments.

Materials and Methods
5DQGRPDOORFDWLRQ

Figure 1 shows the clinicalprocedures of this trial. This study was arandomized unblinded parallel-group trial&RQYHQWLRQDO JURXS,PPHGLDWH JURXS

5HFHLYHGDQHZPDQGLEXODUFRPSOHWHGHQWXUHUHOLQHG

thatcompared

immediately

loadedmandibular 2-IODs retained by magnetic
attachments with conventionally loaded
mandibular 2-IODs. Participants withcompletely edentulous mandibles and any

3ODQQLQJ

opposing maxillary remaining teeth wererecruited and randomly assigned equally to,PSODQW LQVHUWLRQ VXUJHU\
Set magnetic
attachments

Set healing abutments
and relieve denture

two groups: the immediate loading group(immediate group) and the conventionalloading group (conventional group).
Each participant received two implants in
the interforaminal region with flaplesssurgery. In the immediate group, each

$IWHUPRQWK
Set magnetic
attachments

implant was connected to each keeper andloaded with mandibular overdentures on
the same day as implant placement. In theconventional group, the implants were

2EVHUYDWLRQ)LJ&OLQLFDO SURFHGXUHVconnected to healing abutments. The inneraspects of the denture base around thehealing abutments were relieved. Threemonthsabutments were replaced with keepers and loaded with overdentures.

after

surgery,

thehealingDigital X-rays were taken immediately and at six months, one year, two years, and three years after
implant placement. Marginal bone loss was measured by the difference in the marginal bone level immediately after
the implant placement and in each observation period. To compare the marginal bone loss of the two groups, a MannWhitney U test was performed. To compare the survival rate of two groups, a log-rank test was performed todetermine the three-year accumulated survival rate.
The study protocol was approved by the Ethics
Committee at Tokyo Medical and Dental University (Number:693) and registered with the UMIN Center (UMIN-CTR Clinical
Trial, Universal Trial Number: UMIN000009889).

Results
Participants were randomly allocated into the immediate group(n = 10) or the conventional group (n = 9). One
patient in the conventional group withdrew one
month after implant placement because of
implant failure.
Figure 4 shows the marginal bone loss results.
The three-year marginal bone loss medians are
1.17 mm for the immediate group and 1.43 mm
for the conventional group. At every evaluation
time, there was no significant difference inmarginal bone loss. One patient in theconventional group withdrew one month after
implant placement because of implant failure.
Therefore, the three-year accumulated survival
rates are 100% and 89% for the immediategroup and the conventional group, respectively(Fig. 5), and there is no significant difference
between the groups.

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Discussion
Elsyad et al. concluded that immediately loaded two implants supporting a ball-retained mandibular
overdenture are associated with more marginal bone resorption as compared with conventionally loaded implants
after three years.3 On the other hand, in this study, significant difference in marginal bone loss was not observed.
This might be because, with regard to retention mechanisms, magnetic attachments appear to reduce lateral force
on implants.
Conclusion
Although the tendency to have more marginal bone loss could be observed in the immediately loaded
group, there are no significant differences between the two groups in either marginal bone loss or survival rate.

References
1. J.M. Thomason, G. Heydecke, J.S. Feine, J.S. Ellis: How do patients perceive the benefit of reconstructive
dentistry with regard to oral health-related quality of life and patient satisfaction? A systematic review. Clin
Oral Implants Res, 18, 168–188, 2007.
 J.S. Feine, G.E. Carlsson, M.A. Awad, et al.: The McGill consensus statement on overdentures. Mandibular
two-implant overdentures as first choice standard of care for edentulous patients. Montreal, Quebec, May
24–25, 2002. Int J Oral Maxillofac Implants, 17, 601–602, 2002. 
3. M.A. Elsyad, Y.F. Al-Mahdy, M.M. Fouad: Marginal bone loss adjacent to conventional and immediateloaded two implants supporting a ball-retained mandibular overdenture: a 3-year randomized clinical trial.
Clin Oral Implants Res, 23, 496–503, 2012.
JJ Mag Dent vol.27 No.2 2018

Influence of the inclination angle of attractive surfaces on the attractive
force of a magnetic attachment with an optimal structural design
H. Kumano,1 H. Nagai,1 R. Kanbara,1 T. Masuda,1 Y. Nakamura,1 K. Shoji,1 N. Hasegawa,1 Y. Takada,2Y. Tanaka,3 and J. Takebe1
Department of Removable Prosthodontics, School of Dentistry, Aichi Gakuin University

1

Division of Dental Biomaterials, Tohoku University Graduate School of Dentistry

2

Aichi Gakuin University

3

Abstract
We analyzed and investigated the influence of the inclination angle of attractive surfaces on the attractive
force of a magnetic attachment with an optimal structure design by using a three-dimensional finite element
method. Two types of analysis models were constructed: a basic model and an optimal model with an
optimal structural design. The analysis considered the attractive force when the magnetic assembly and thekeeper were in contact with each other and the inclination and the detachment with the one end of thekeeper as a fulcrum. There were 21 different inclination angles of the attractive surface, ranging from 0 to
20 in one-degree increments. The keeper was observed with regard to an increase in the inclination angle of
the attractive surface and the related decrease in the magnetic flux density inside the magnet assembly
using both the basic and optimal models. In both the basic and optimal models, the attractive force
decreased in inverse proportion to the inclination angle of the attractive surface. The results of this analysis
suggest that the magnetic attachment with the optimal structural design is strongly influenced by the
inclination angle of the attractive surface.

Introduction
Magnetic attachments have continued to improve. Various magnetic circuits have been designed so that amagnetic attachment of minimal size can exert a higher attractive force. A magnetic attachment consists ofa magnet assembly and a keeper. A magnet in the magnetic assembly is encapsulated by magnetic andnonmagnetic materials. Magnetic flux can penetrate a magnetic body but cannot penetrate a nonmagnetic
material. Magnetic flux is the magnetic line of forces. It penetrates magnetic materials and forms a closed
magnetic circuit that exerts attractive force when a magnetic assembly and a keeper come into contact.
Until now, to further improve the attractive force of a magnetic attachment, the following methods havebeen used: (1) changing the magnetic circuit of magnetic attachment structure, (2) analyzing the attractive
force, and (3) using a three-dimensional finite element method.1 Using these methods, the central portion of
the keeper and magnet set of nonmagnetic material is applied to the optimal structure, confirming that there
was an improvement in the attractive force of the magnetic attachment.2

Objective

17

18

JJ Mag Dent vol.27 No.2 2018

A three-dimensional finite element method was used to analyze the influence of attractive surface
inclination on the attractive force of a magnetic attachment with an optimal structural design.

Materials and Methods
1. Analysis model
The magnetic assembly was 3.6 mm in diameter and 1.3 mm in height; a magnet inside the magnetic
assembly was round and was 2.6 mm in diameter and 0.5 mm in height. The ring was 0.2 mm wide and 0.2
mm high. The disk yoke had a diameter of 2.2 mm and a height of 0.2 mm. The keeper was round andsharp; it had a diameter of 3.6 mm and a height of 0.7 mm.Considering the models had line symmetry, half of a model is shown as a basic model (Fig. 1), and theother half is shown as an optimal model (Fig. 2). The structural design of the optimal model is the same asthat of the basic model but also has nonmagnetic material inserted into the magnetic attachment.
The analysis range was 3.0 mm around a magnetic assembly and a keeper. Marc Mentat 2010
(Multi-Purpose Finite Element Pre and Post Processor, MSC) was used for model construction, and μ-MF
(electromagnetic field analysis system, μ-TEC) analysis software was used. The element was athree-dimensional pentahedron and hexahedron element type. The element count was 107,604, and thenodal point count was 112,468.

Fig.1 Basic model
2. Analysis condition
The components of the magnet were

Fig. 1 Basic model
Table 1 Analysis conditions

Nd-Fe-B (neodymium, ferrum, boron),and its magnetic properties were
calculated based on the thermal propertyof GIGAUSS D 600 and values provided
by the manufacturer.3 The component of
the disk yoke and the keeper was themeasurement of the magnetic properties
of SUSXM27, and the B-H curve of themagnetic properties was calculated by the approximation formula (Table 1).4

3. Analysis items
From the condition where the magnet
assembly and the keeper were in contact witheach other in the optimal model, the attractive
force when inclined and detached from one
end of the keeper as a fulcrum was analyzed.
The attractive surface had 21 different
inclination angles ranging from 0 to 20 in
one-degree increments. In addition, the same
analysis item was used in the basic modelFig. 3 Analysis items(Fig. 3).
Results of the analysis were evaluated as the magnetic flux density vs. the attractive force.

Results
1. Magnetic flux density distribution
Representative magnetic flux density distribution (Figs. 4, 5).

Fig. 4 Magnetic flux density distribution(Basic model)

Fig. 5 Magnetic flux density distribution(Optimal model)

In both the basic and optimal models, concurrent with an increase in the inclination angle of the attractive
surface, we observed a decrease in the magnetic flux density inside the magnet assembly, the keeper, andthe magnetic flux density in the disk yoke on the right side of the magnet assembly. In addition, an increasein magnetic field leakage at the top of the keeper of the attractive surface was observed with the increase of
the inclination angle of the attractive surface in both the basic model and the optimal model. When
comparing the basic and optimal models, inclination angles of 0, 1, and 5 degrees of the attractive surface
showed an increase in the magnetic flux density at the shield disk of the magnet assembly in the optimalmodel. However, at 7 and 10 degrees, this increase in magnetic flux density was not observed.

2. Attractive force
A graph of the analysis of theattractive force results is shown(Fig. 6). Attractive forces in boththe basic and optimal models
decreased in inverse proportion to
the inclination angle of attractive
surfaces. The inclination angles of
attractive surfaces up to 5 degrees
were greater in the optimal model
than in the basic model; thus, it
was confirmed that the attractive force is large.

Fig. 6 Attractive force

When the inclination angle of an attractive surface was 6 degrees or more, it was confirmed that theattractive force was almost the same for both the basic and optimal models.
The reduction rate of the attractive force in the inclination angle of an attractive surface of 6 degrees was
about 44% in the basic model and about 58% in the optimal.

Discussion
1．Efficiency of the finite element method
It is difficult to measure and observe details of the behavior of attractive and repelling forces created by amagnet. This is because the magnetic field has a gradient in all directions; therefore, a simple calculation
formula cannot be established. The finite element method allows the visualization and simulation of theinner behavior of the magnetic circuit by adding various conditions. Searching for optimal magnetic
circuits using the finite element method is considered time-efficient and cost-effective.
2．Efficiency of the analysis model
Magnets have a magnetic field distribution in space defined as a “leaky magnetic field.” In other words, it
has a magnetic field around the magnetic attachment. Therefore, the accuracy of the analysis results will be
increased if the analysis range of the magnetic structure of the magnetic attachment and the circumferenceof the keeper are analyzed. In this study, we confirmed the range of magnetic field leakage and analyzed
the elements of the magnet assembly and the keeper at around 3 mm in the construction model. In the final
analysis, the accuracy of analysis in this model is high.
3．The relationship between attractive force and magnetic flux density
The attractive force of a magnet can be expressed as F = (1/2μ0)・S・B2{μ0: space permeability, S: attractive
surface area, B: magnetic flux density}.5 The attractive force of a magnetic attachment is affected more by
the magnetic flux density than the attractive surface area. Therefore, the attractive force can be increased
efficiently by increasing the magnetic flux density. The magnetic circuit changes by replacing part of akeeper of a magnetic attachment with a nonmagnetic material, resulting in an increase in the magnetic flux
density on the attractive surface. The attractive force was affected more by an increase in the magnetic flux

density than by a decrease in the attractive surface area, resulting in an increase in the attractive force.
However, the results of this analysis showed that the reduction rate of the attractive force was larger in the
optimal model than in the basic model. This is because the optimal model sets the nonmagnetic material in
the center of the magnet assembly and keeper, so as to increase the magnetic flux density as much as
possible. Therefore, in the optimal model, since the attractive surface of the keeper is inclined and detached,
the magnetic flux density distribution inside the magnetic assembly and the keeper are strongly influenced,
so that the reduction rate of the attractive force becomes larger than that of the basic model considered.

Conclusion
The results of this analysis using a three-dimensional finite element method for determining the effect of
the inclination angle of the attractive surface on the magnetic flux density distribution and the attractive
force in the magnet attachment, which produced an optimal structural design, produced the following
conclusions:
1. The influence on the magnetic flux density distribution by the inclination angle of the attractive surface
was larger in the optimal model than in the basic model. rface was larger in the optimal model than in
the basic model.
2. The reduction rate of the attractive force by the inclination angle of the attractive su
3. The results of this analysis suggested that the magnetic attachment with the optimal structural design isstrongly influenced by the inclination angle of the attractive surface.

References
1．H. Kumano, Y. Nakamura, R. Kanbara, et al.: A three-dimensional finite element evaluation of magnetic
attachment attractive force and the influence of the magnetic circuit, Dent Mater J, 33(5), 669–673,
2014.
2．H. Nagai, H. Kumano, R. Kanbara, et al.: Optimal structural design of magnetic attachments using athree-dimensional finite element method, J J Mag Dent, 26, 1–7, 2017.
3．T. Miyata, J. Niimi, A. Ando, et al.: Influence of heating of a magnetic attachment on the attractive force,
J J Mag Dent, 17, 44–50, 2008.
4．Y. Tegawa, Y. Kinouchi: Influences on attractive force in different clinical uses of a cup yoke magnetic
attachment, J J Mag Dent, 5, 31–38, 1996.
5. Y. Nakamura: Stress analysis of an overlay denture and a magnetic attachment using finite element
method, Nihon Hotetsu Shika Gakkai Zasshi, 42(2), 234–245, 1998.

Effect of changes in the protocol of fixing a magnetic attachment onto thestage of an ISO device that measures retentive forces
M. Takahashi, K. Numazaki, H. Sakatsume, M. Kanyi, K. Sato, K. Sasazaki, and Y. Takada
Division of Dental Biomaterials, Tohoku University Graduate School of Dentistry
Abstract
Retentive forces are an important and sensitive aspect of dental magnetic attachments. The existing ISO
13017/Amd. 1 on measurements of retentive forces outlines the method of fixing magnetic attachments on atable that has been reported to be complicated. The aim of this study was to establish whether the location,
method of temporary stabilization, and adjustment of the center of magnetic attachments on the table of an
ISO measuring device influence retentive forces.
Two types of magnetic attachments, GIGAUSS D600 and HYPER SLIM 3513, were mounted on ameasuring device connected to a digital force gauge.
The position at which a magnetic attachment is fixed on a table has no influence on retentive forces, since
there was no significant difference between values measured when set up and placed on the left, right, back,or front as compared with the center (reference) position.
The use or avoidance of double-sided adhesive tape to stabilize the magnetic assembly did not affect theretentive forces since there was no significant difference in measurements for the various styles of temporary
fixation.
Gross adjustments using the X-Y stage have a negative effect, as some of the retentive forces measured
were statistically significantly lower than the reference values for both attachments.

Introduction
One of the most important aspects of dental magnetic attachments is the retentive force. However,retentive force is sensitive to changes in the test methods and conditions. ISO 13017/Amd. 1 was publishedin 2012/20151,2 and includes a detailed test procedure method for measuring retentive force that wasdeveloped and adopted as an international standard. Repeatability and accuracy of the retentive force datameasurements are attainable using the measuring device and method prescribed in ISO 13017. The findingsof our previous study proved that the test procedure in the ISO 13017 standard serves as a useful guide formeasuring retentive force for first-time users.3,4 However, participants who contributed to this verification
test4 and members of domestic/international ISO meetings stated that “the method of fixing a dental
magnetic attachment on the table is complicated,” and “there is a possibility that the relative location on
the table where the sample magnetic attachment is fixed has an influence on retentive force.” To improvethe clarity of ISO 13017, a revision on the fixation method of a sample magnetic attachment wasconsidered useful.

Objective
The aim of this study was to determine whether the method of fixing a magnetic attachment on a tableinfluences the retentive force measured. This involves the manner in which temporary stabilization isachieved, the relative location on the table where specimens are placed, and the use of an X-Y adjustment
table for aligning grossly mismatched magnetic attachment centers. The retentive force of a dental
magnetic attachment fixed in various conditions and locations was measured, and the relationship between
the fixation method and retentive force was evaluated.

Materials and Methods
Dental magnetic attachments
Two dental magnetic attachments were used: GIGAUSS D600 (GC) and HYPER SLIM 3513 (Morita).

Retentive force measuring device
The measuring device used in this study matches the basic description in ISO 13017:2012/Amd. 1:2015.
This device allows the pulling of magnetic attachment when fixed on a table in a direction strictly
perpendicular to the mating surface without any inclination. This is achievable through the incorporationof a linear motion bearing a slide guide of low friction resistance (0.02 N). The device was connected to adigital force gauge (ZPS, Imada). The crosshead speed was controlled by the use of a hydraulic check unit
(Kinecheck 3022-19-1-1/4, Meiyu Airmatic).
Double-sided adhesive tape
Two types of double-sided adhesive tape were used: a thin type (thickness of 110 μm) and a thick type(thickness of 400 μm).
Test procedure for measuring retentive forces
Retentive forces of dental magnetic attachments were measured in accordance with the test procedure
stipulated in ISO 13017. The crosshead speed was set at 4.5 mm/min. Data (retentive force readings) was
obtained corresponding to the nine different conditions of fixation different from those stipulated by theISO. The standard reference conditions for fixation according to the ISO 13017 manual are as follows:
1. A magnetic assembly was temporarily secured on a lower table by use of a thin type of double-sided
adhesive tape on the mating face before transfer and steady fixation of the same assembly on the upper
table by use of a cyanoacrylate adhesive applied on the upper surface of the assembly.
2. After removal of the double-sided adhesive tape, a keeper was temporarily attached to the assembly in aposition in which the center of the assembly and that of the keeper matched and the two were congruent.
Thereafter, the keeper was fixed on the lower table by use of a cyanoacrylate adhesive applied on its
bottom surface.
Experimental fixation conditions
Several aspects involving the conditions of magnetic attachment fixation were varied in this study as
follows:
1. Magnetic attachments fixed in different positions of the table (Fig. 1)a) center (C)—as is specified in the ISO standardb) back (B)c) front (F)d) left (L)e) right (R)
2. Method of intermediate stabilization of the magnetic assembly on the lower tablea) use of a thin type of double-sided adhesive tape: 110 μm—as specified in the ISO standardb) use of a thick type of double-sided adhesive tape: 400 μmc) no temporary adhesion done using tape. The magnetic assembly was placed on the lower table withthe mating surface directly in contact with the table. Glue was applied to the free surface before
lowering the upper table so as to transfer and firmly attach the assembly.
3. Centering of the magnetic attachment specimen on the tables (Fig. 2)
The magnetic assembly was, at the time of fixation, deliberately set in positions that involved grossdisplacement of the center of the keeper on a horizontal plane along the X, Y, or combined XY axis awayfrom that of the assembly. This resulted in a surface overlap of both the assembly and the keeper that

covers about 1/3 of the diameter. Afterward, the X-Y stage was used to adjust the setup, making the centerof the assembly and the keeper congruent. The retentive forces were measured after each adjustment.
a) Initially shifted along the X-axis directionb) Initially shifted toward the Y-axis directionc) Initially shifted toward the X + Y axis direction

center

back

front

left

right

  
Fig. 1 Different locations on the table

X+Y-axial

Y-axialX-axialadjustment

Fig. 2 Center displacement/overlap
positions before adjustment

Statistical analysis
The data generated were statistically analyzed using ANOVA and Tukey’s HSD test (α = 0.05).

Results
1. Retentive force measured in accordance with the test procedure stipulated in ISO 13017(reference values)
The retentive force values of both GIGAUSS and HYPER SLIM measured in accordance with the test
procedure in ISO 13017 were more than 85% in absolute value as compared with the figures quoted in the
manufacturer’s literature accompanying the package.
2. The influence on retentive force associated with the placement of the assembly at
different relative locations on the table
The retentive force values measured with the assembly in different positions on the table are represented
in Fig. 3. There were no significant differences in either GIGAUSS or HYPER SLIM data as comparedwith the reference value (p>0.05).

6.0
Retentive force (N)Retentive force (N)

6.0

4.0

2.0

0.0

C

B

F

L

4.0

2.0

0.0

R

C

B

F

L

R

(a) GIGAUSS(b) HYPER SLIM
Fig. 3 Retentive forces for magnetic attachments fixed at different relative positions on the table
3. The influence of intermediate fixation conditions on the retentive force
Retentive forces according to the varying temporary conditions of fixation are shown in Fig. 4. All of
the data for both GIGAUSS and HYPER SLIM did not differ significantly from the reference value(p>0.05).

6.0

Retentive force (N)Retentive force (N)

6.0

4.0

2.0

0.0

thin

thick

-

4.0

2.0

0.0

thin

thick

-

(a) GIGAUSS(b) HYPER SLIM
Fig. 4 Retentive forces according to various conditions of temporary fixation
4. The influence that gross adjustments of the center of the magnetic assembly and keeper
has on the retentive force
The retentive forces measured when there was initial deliberate mismatch of the center of the magnetic
assembly away from that of keeper along various directions on the horizontal axis and the consequentadjustment done are shown in Fig. 5. In GIGAUSS, the values measured after displacement along the Xaxis and Y-axis directions were significantly lower than the reference values (p<0.01). In HYPER SLIM,
the values measured after displacement along the Y-axis direction were significantly lower than thereference value (p<0.05).

Retentive force (N)

**

6.0

**

Retentive force (N)

6.0

4.0

2.0

0.0

*
4.0

2.0

0.0

-

X

Y

X-Y

-

X

Y

X-Y

(a) GIGAUSS(b) HYPER SLIM
Fig. 5 Retentive force of magnetic attachments after adjusting for gross displacement along various axes on
the horizontal plane (* and ** indicate p<0.05 and 0.01, respectively)

Discussion
1. Retentive force measured in accordance with the test procedure stipulated in ISO 13017(reference values)
ISO 13017 prescribes that the measured figure should be of a value that is more than 85% of that quoted
in the manufacturer’s literature accompanying the package. The measured retentive force values of both
dental attachments in this study under ISO-stipulated conditions fulfilled the requirement. Therefore,
figures acquired under ISO-compliant conditions (center of the assembly placed at the center of the table,
temporary stabilization achieved using thin double-sided tape, and centers of magnetic attachment
congruent) were considered to be the reference values in this study.
2. Influence on retentive forces associated with the placement of the assembly at different
relative locations on the table
It was demonstrated that the relative location in which a magnetic attachment is fixed on the table has
no influence on the retentive force, since there was no significant difference between values representing
any of the locations (B, F, L, R) and the reference value (C). The slide guide (linear motion bearing) whose
inclusion in retentive force measuring devices is specified in ISO 13017 is highly efficient and contributed
to this stable result.
3. Influence of intermediate fixation conditions on retentive forces
The choice to use or avoid transient stabilization of a magnetic attachment using double-sided adhesive
tape did not affect the retentive force because there was no significant difference in measured values
corresponding to the various temporary fixation conditions. Ordinarily, double-sided adhesive tape is used
to secure the position of the magnetic assembly at the center of the table and avoid movement before
further stabilization with cyanoacrylate glue. However, as the findings proved that there was no differencein the retentive force despite the placement of the magnetic attachment at various locations on the table,
we consider the temporary fixation step irrelevant.
Although not shown in the results above, some of the values of retentive forces attained when either
thick tape or no tape was used were lower (statistically insignificant) than the reference values. This isbecause the process of dislodging the attachments from the tables, which is done several times as in thisexperiment, may leave the surface of the assembly and the keeper that are fixed to the tables by the use ofglue slightly damaged. Damages on the bottom surface of the assembly may have a negative effect on the
precise alignment of the mating surfaces that interferes with the accuracy. However, ISO 13017 does notdeal with scenarios of multiple use of a magnetic attachment. This observation does not have a direct
impact on the usage of dental magnetic attachments but serves as a caution when conducting repetitivemeasurements as for experimental or research purposes.
4. The effect of gross displacement and consequent adjustment involving the center of the magnetic
attachment on the retentive force
When a deliberate shift to mismatch the center of the magnetic assembly from that of keeper andconsequent readjustment was done, some of the retentive forces measured were statistically significantly
lower than the reference values for both GIGAUSS and HYPERSLIM. Ideally, when the X-Y stage is
moved along the horizontal plane, to correct minor displacements after the fixation of the magnetic
assembly set with centers matching as much as visibly possible, there should be no effect on the retentive
forces. However, in situations of gross displacement resulting in overlap, lateral movements on the table
could result in tipping or movement of the magnetic attachment elements at an inclined angle, which may
negatively interfere with the adhesion, leading to weak results. Therefore, although the center of theelements of the magnetic attachment (assembly and keeper) can be adjusted to correspond by using the XY stage after fixation to the tables, it is highly advisable to align the setup correctly as much as possible atthe fixation stage.
5. New proposal for the fixation method
The test procedure in the current standard specifies that a magnetic assembly or magnet is first fixed on
the upper table, and then a keeper or a magnet is fixed on the lower table. We propose that the reverse
procedure could be more useful. It involves fixing a keeper or magnet to the lower table first and then amagnetic assembly or magnet to the upper table. The proposed method would eliminate the need for using
double-sided adhesive tape and would make easier the process that involves matching the center of amagnetic assembly to that of keeper before fixation.

Conclusion
Retentive forces can be measured almost accurately using the ISO 13017 test procedure, as long as themagnetic attachment is not fixed in a position where the center of the magnetic assembly is grossly
displaced from that of the keeper.

Acknowledgments
The authors gratefully acknowledge contributions from the following individuals of Tohoku University
School of Dentistry: Mr. Yuki SUGAI, Mr. Akitsuna TAKAHASHI, Mr. Isao TOYA, and Mr. Motoaki
NAGAHAMA.

References
1. ISO 13017:2012. Dentistry—Magnetic attachments.
2. ISO 13017:2012/Amd. 1:2015 Dentistry—Magnetic attachments.
3. R. Kanbara, K. Shoji, Y. Nakamura, M. Takahashi, Y. Takada, S. Tanaka, Y. Ohno, and Y. Tanaka:
Evaluation of testing procedure accuracy described for the measurement of magnetic attachment attractive
force in ISO 13017, J J Mag Dent, 23(2), 7–12, 2014.
4. M. Takahashi, H. Sakatsume, M. Kanyi, K. Sato, K. Sasazaki, and Y. Takada: The usefulness of theprocedure for measuring retentive force of dental magnetic attachments as stipulated in the ISO 13017
standard, J J Mag Dent, 25(2), 19–23, 2016.

Working toward the international standardization of dental magnetic
attachments—Commission report of the ISO Corresponding Committee in 2017—
Y. Takada
Chairman of the ISO Corresponding Committee
Division of Dental Biomaterials, Tohoku University Graduate School of Dentistry
Abstract
The international standardization of dental magnetic attachments has continued for more than ten
years since applying for NP (New work item proposal) at ISO/ TC 106 (Berlin meeting) in 2007.
Finally, an international standard, which can perfectly bring out the best of magnetic attachments
made in Japan, has been completed in 2015 because of additional establishment of ISO 13017: 2012/
Amd.1 at the same year. The completion of the standard gave a halt of holding the SC 2/ WG 22
meeting at the ISO/ TC 106 (Tromsø meeting) in 2016. Meanwhile, the ISO Corresponding
Committee has formulated a revised version of the standard which is composed of the integration of
ISO 13017 and ISO 13017: 2012/ Amd.1. The revised version was sent to SC 2 secretariat at early
April, and the revised version was subjected to NP voting at end of June in 2017. As a result, it was
passed as a new business, and some members of the ISO Corresponding Committee attended ISO/TC 106 (Hong-Kong meeting) held at August in 2017. The brief summary of the revised version, andthe state of the SC 2/ WG 22 meeting at ISO/ TC 106 (Hong-Kong meeting) were informed in thisreview.

Introduction
The international standardization of dental magnetic attachments started by submitting NP (NewBusiness Item Proposal) at the ISO/TC 106 (Berlin meeting) in 2007 and proceeded officially fromthe ISO/TC 106 (Gothenburg meeting) in 2008.1 Four years later, the international standard ISO
13017 for dental magnetic attachments was established in July 2012.2
Since ISO 13017 standard included some insufficient parts, such as retentive force because of its
short-term formulation, the necessity of an amendment for ISO 13017 was suggested by Japanese
members at the ISO/TC 106 (Paris meeting) held in September 2012.
The suggestion was passed by NP voting in the following year, and a draft of the amendment for
ISO 13017 was formulated.3 After three years of discussion, international standardization of theretentive force measurement method was established as ISO 13017: 2012/Amd. 1 (Amendment of
ISO 13017) in November 2015.4
It took over nine years to the finally complete ISO standards that can unfailingly demonstrate themerits of Japanese dental magnetic attachments that are compact, lightweight, and have strong
retentive force. Although the completion of the standards halted the SC 2/WG 22 meeting at the
ISO/TC 106 (Tromsø meeting) held in 2016, the WG 22 meeting in Hong Kong took place for theperiodic revision of ISO 13017 in 2017.
This article outlines the state of the Hong Kong meeting in 2017 and the concept of ISO 13017
integrated with its amendment.

Activities
The completion of the standard halted the SC 2/WG 22 meeting at the ISO/TC 106 (Tromsø
meeting) held in 2016. Meanwhile, the ISO Corresponding Committee has formulated a revised
version of the standard, which is composed of the integration of ISO 13017 and ISO 13017:
2012/Amd. 1. The revised version was sent to SC 2 secretariat in early April, and the revised version
was subjected to NP voting at the end of June 2017.
As a result, it was passed as a new business (Approval number: 14), the number of P member
countries who agreed with the deliberation from the DIS stage (Draft of International Standard: stage
40.00) was 5. However, the SC 2 secretariat recommended deliberation from WD (stage 20.00)
because nine P member countries agreed with deliberations from WD (stage 20.00 to 20.20) (Table
1).

Table 1Result of the NP voting at the end of June 2017

As the comments of each country were submitted at the time of NP voting, the answers wereprepared, and the modified WD was submitted to the SC2 secretariat in early August. The secretariat
officially announced that it would formulate standards from a WD (stage 20.00) over a three-year
period (Fig. 1). Since the standard has to be published (stage 60.60) in three years, we decided to aim
for the passing of DIS entry (stage 40.00) at this Hong Kong meeting.
Fig. 1 Results instructed by the SC2 Secretariat

日本磁気歯科学会雑誌

Ⅳ.

SC２／WG22会議

27巻

1号

2018年

なった．（図５）WG22のコンビーナ（座長）を今回の年次会議ISO／TC106は，香港大学の講担当している鱒見教授の必死の対応によって，義室及び会議室を使用し，香港大学の学生の支

翌日午前中にSC2／WG22会議を開催することが援を得て行われた．大学内は高低差があるもの

きまり，DIS登録からの審議をSC2／WG22会議の非常に美しい英国風の古い建屋がその歴史ので提案するチャンスを何とか得ることができ
Working goal in 2017
深さを醸し出していた．（図４）
た．（図６）午前10時からの会議は，天候と同
The chosen aim is to pass DIS entry (stage 40.00) at this Hong Kong meeting.

SC２／WG22会議は，８月23日に予定されて様に荒れ模様であったが，風は日本側に吹いたいたが，前日から香港・マカオを襲撃していたようで，一部の修正を除き，ほぼ日本案のまま
ISO/TC 106 Hong Kong meeting
未曾有の台風（レベル８）の影響で香港の公共で賛同を得ることができた．また，DISからの審Six members of the ISO Corresponding Committee,
Dr. S. Masumi (convener),Dr. T. Ishigami
機関がすべて止まってしまい，お店やレストラ
議もWG22で可決されたが，SC２総会で物言い(expert), Dr. Y. Takada (expert assistant), Dr. M. Takahashi (observer), Dr. E. Makihara (observer),が付き，一時DISからの審議が危ぶまれる場面もDr. H. Sasaki (observer), and Dr. Kent T. Ochiai (convener assistant), an American member,
め，当日予定されていた会議はすべて中止とな
attended the ISO/TC 106 Hong Kong meeting heldあったが，米国の支援を得て１票差という僅差
at Hong Kong University on August 20–26
2017
(Fig.
2).
り，ご多分に漏れずSC２／WG22会議も中止とで可決された．（図７）

ンもほとんど閉まった状態となった．そのた

香港大学とその地図上の位置
Fig. 2 Hong図４
Kong University
and its position indicated on the map
The SC2/WG22 meeting scheduled on August 23 was canceled on account of an unprecedented
typhoon (Level 8) that was striking Hong Kong and Macau the previous day (Fig. 3).

図５

ホテルの窓から見た台風の様子

Fig. 3Typhoon view from the hotel window

As an emergency plan for a rescheduled WG meeting was announced at midnight on August 24,
our members got the opportunity to propose deliberations from DIS entry at the SC 2/WG 22
meeting on next morning (Fig. 4).

図６

８月24日午前3：12時点で予定されたWG会議の緊急プラン

25

Fig. 4 Emergency plan for rescheduled WG meetings at 3:12 a.m. on Aug. 24
Although the meeting from 10 a.m. was as chaotic as the weather, a gentle wind seemed to blow to
the Japanese side. We were able to obtain nearly the meeting approval of our proposal with a few
minor modifications. The deliberation from the DIS stage was also passed by the WG 22 and SC 2
plenaries (Fig. 5).

Fig. 5 SC2/WG 22 meeting and the SC2 plenary
Currently, the revised draft was accepted by SC2 Secretariat on October 24, 2017, and it isscheduled to be subject to DIS voting early next year.
Pleasures in Hong Kong, such as a dinner party of ISO/TC 106 and excellent night life, are shownin Fig. 6.

Fig. 6

Pleasures in Hong Kong

Overview of ISO 13017 integrated with ISO 13017: 2012/Amd. 1
An overview of ISO 13017 integrated with ISO 13017: 2012/Amd. 1 is shown in Table 2. ISO
13017 consists of clauses 1 to 8, and it is reinforced by the addition and revision of clause 5 (5.1
Retentive force) and clause 6 (6.3 Retentive force, 6.4 Corrosion resistance), in accordance with theamendment (Amd. 1) (See underlines in Table 2.).
The pretreatment of specimens was specified in clause 5. Concretely, the “cleaning protocol” forspecimens to measure the retentive force was added to sub-clause 5.1.
Clause 6 specified the test methods for evaluating whether the magnetic attachment shall satisfy therequirements stated in clause 4, mainly, specifying methods for measuring magnetic flux leakage,retentive force, and corrosion resistance.
The amendment (Amd. 1) enhanced the method for measuring retentive force in detail, making it
possible to perform accurate and reproducible measurements. In particular, the measurement
assisting device was specified to move vertically to the mating face, regulating the dynamic friction
force within 0.01 N (1 g).
Furthermore, the retentive force curve obtained by the attractive force measurement is specified inorder to clarify how to obtain the retentive force, and the difference between the measurement value
and the baseline was defined as the true maintenance force.
Corrosion resistance in clause 6.1 introduced the determination limit and the detection limit used in
the chemical analysis method in order to clarify the quantitative analysis of impurity element ions inthe static immersion test.
Table 2

Overview of ISO 13017 integrated with ISO 13017: 2012/ Amd. 1

Finally
The international standardization of dental magnetic attachments, which started in 2005, took 12
years to establish international standards, including preparations. As we succeeded in establishing acouple of international standards, ISO 13017 and ISO 13017: 2012/Amd. 1 (Amendment edition),
within the scheduled term, we were able to realize an exemplary formulation. We would like to ask
for your continued support and cooperation in the future.
To readers,Thank you very much.

From all members of the ISO Corresponding Committee in JSMAD

References
1. Y. Takada: Commission report of the ISO Corresponding Committee, J J Mag Dent, 20(1),81–85, 2011.
2. ISO 13017: 2012(E), Dentistry—Magnetic Attachments.
3. Y. Takada: Commission report of the ISO Corresponding Committee, J J Mag Dent, 22(1),65–68, 2013.
4. ISO 13017: 2012(E)/Amd. 1, Dentistry—Magnetic Attachments.

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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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