Projects of Japanese Dental Science Federation in 2018
Investigation of materials and research on new medical device and technology introduction

The Japanese Society of Magnetic Applications in Dentistry
Survey and Research for clinical evaluation of magnetic dental attachments and formulation(updating) of clinical practice guidelines
Clinical Practice Guidelines for Dental Magnetic Attachments 2018
Issue No. JDSF-DSP1-2018-2121-1

Prepared by:
Masayuki Hideshima (Medical Committee Chair; Tokyo Medical and Dental University), Chikahiro
Okubo (President, Tsurumi University), Shuji Okawa (Vice President; Meikai University), Shinichi
Masumi (Former President, Kyushu Dental College), Yukyo Takada (Chairperson of ISO Committee;
Tohoku University)

Related Committees:【Medical Committee】: Masayuki Hideshima1 (Chair), Yoshitada Umekawa2 , Shogo Ozawa3 , Toshihiro
Kawano4 , Mai Kono5 , Yasunori Suzuki6 , Joji Tanaka8, Kan Nagao9，Akira Nishiyama1, Kazumoto
Hoshiai3.
【ISO Working Committee】: Yukyo Takada9 (Chair), Tomohiko Ishigami2, Yoshitada Umekawa2, Ryo
Kanbara3, Yoshinori Nakamura3, Eri Makihara4, Shinichi Masumi4【Safety Standards Review Committee】: Jun Takebe3 (Chair), Chikahiro Okubo6 , Masatake Akutagawa 8 ,Tomohiko Ishigami2, Fujio Tuchida11, Yashunori Suzuki6, Disuke Kurihara6, Mikage Hasegawa2, Tohru
Kurabayashi1, Thoshio Tuchihashi, 12, Hiroshi Mizutani1, Toshio Hosoi6

1Tokyo Medical and Dental University, 2Nihon University School of Dentistry, 3Aichi Gakuin University

School of Dentistry, 4Kyushu Dental College, 5 Health Sciences University of Hokkaido, 6Tsurumi
University School of Dentistry, 7Meikai University School of Dentistry, 8Chiba Prefecture, 9Tokushima
University, 10Tohoku University School of Dentistry, 11Kanagawa Prefecture 12 Nihon Medical University,
Faculty of Medicine,Table of Contents

I. Introduction Preface
II. Formulation and updates of clinical practice guidelines for dental magnetic attachment
1. Background of the development of practice guidelines
2. Survey and selection of clinical questions for magnetic attachments in dental practice
3. Evidence collection methods
4. Process and Criteria for Determining Recommendation Levels
5.Consensus method
6. Determination of recommendations and evaluation profile
7. References
III. International Standardization of Magnetic Attachment
1. History of International Standardization
2. Structure of ISO 13017 and outline of the supplemental version
3. References
IV. Clinical Questionnaire and Evaluation/Recommendation Profile for Clinical Guidelines
1. Implant
CQ1．In case of implant-supported overlay dentures, is magnetic attachments (MAs) more effective
than applying other type of retainers?
CQ2．In implant-supported overlay dentures, are applying MAs to implant abutments more successful
than applying them to natural teeth?
CQ3．Applying MAs to implant-supported overlay denture cases, are maxillary cases more successful
than mandibular ones?
CQ4．Applying MAs to implant-supported overlay denture cases, are multiple abutments with MAs
more effective than a single abutment?
2. Defects
CQ5. In few remaining mandibular teeth, are applying MAs more effective than other type of retainers?
CQ6. In free-end saddle removable partial dentures, are applying MAs more effective than other type ofretainers?
3. Occlusion/Periodontics
CQ7. In partially edentulous without occlusal contact, are applying MAs more successful than othertype of retainers?
CQ8. In partially edentulous with undulating occlusal planes, are applying MAs more effective thanother type of retainers?
CQ9. When remaining abutments are with periodontal disease, are applying MAs more successful thanother type of retainers?
4. Arrange / Form
CQ 10. Applying MAｓ to multiple abutment teeth, are symmetrical arrangements more effective thanasymmetrical ones?
CQ 11. Applying MA ｓ to remaining abutment teeth, is flat type keeper more effective thandome-shaped keeper for stability of the denture?
5. Manage/etc
CQ 12. When setting MAs to removable partial dentures, is the applied pressure method more successful
than the minimum pressure ones?
Ⅴ．Conclusion

1

Survey and Research for clinical evaluation of magnetic dental attachments and formulation(updating) of clinical practice guidelines
Clinical Practice Guidelines for Dental Magnetic Attachments 2018
Issue No. JDSF-DSP1-2018-2121-1

The Japanese Society of Magnetic Applications in Dentistry
Masayuki Hideshima (Medical Committee Chair; Tokyo Medical and Dental University), Chikahiro Okubo(President, Tsurumi University), Shuji Okawa (Vice President; Meikai University), Shinichi Masumi(Former President, Kyushu Dental College), Yukyo Takada (Chairperson of ISO Committee; Tohoku
University)

I. Introduction
The Japanese Society of Magnetic Dentistry was founded in 1980 as a research group for new dentureattachments, and was promoted to an academic society in 1991.
Since the establishment of the society, each organization affiliated with the society has conducted
prognostic studies on the clinical application of magnetic attachments, and after the promotion to thesociety, a clinical evaluation committee was established to accumulate data on the long-term progress ofmagnetic dental attachments (hereinafter referred to as "magnetic attachments") based on a common
protocol.
On the other hand, the ISO task force committee was established in 2007 for the international
standardization of magnetic attachments, and has undergone examinations by the International
Organization for Standardization (ISO). As a result, Japanese magnetic attachments acquired
ISO13017 certification on July 15, 2010, achieving international standardization of magnetic
attachments1) .
In recent years, the need for evidence-based medicine and improvement in the quality of medical carehave prompted various academic societies to develop guidelines for medical practice, and in 2009, theMedical Committee of our society selected 12 representative CQs from 147 CQs and began formulating
guidelines for medical practice2-5). For CQs with low levels of evidence, a questionnaire survey was
conducted among relevant experts, and a Delphi survey was also conducted to converge opinions byfeeding back the results of the survey 6-9). The "Practice Guidelines for Magnetic Attachments 2013"
were completed by reflecting the evaluations of the internal consensus committee members and theexternal evaluation committee members6-9).
2

In this report, we revised the contents of each CQ in the "Guidelines for the Practice of Magnetic
Attachments 2013" and added a CQ on MRI. The ISO Committee for the International Standardizationof Magnetic Attachments has been working on the revision of ISO 13017 issued in 2012 and its
supplement (ISO 13017: Amd.1) and its unification1). We have prepared a report as " Clinical Practice

Guidelines for Dental Magnetic Attachments 2018".
We hope that this report will be of some help in the selection and treatment of magnetic attachments
and in their inclusion in insurance coverage.

3II. Development and Update of Practice Guidelines for Magnetic Attachments "Clinical Practice Guidelines
for Magnetic Attachments 2018"
1.

Background of the development of the clinical practice guideline
In recent years, the rapid changes in population composition and disease structure, as well as theneed for evidence-based medical care and improvement in the quality of medical care as accountability
to society for clarifying human rights and the right to choose medical care, have prompted various
academic societies to develop practice guidelines. The Japanese Society of Magnetic Dentistry has also
been developing practice guidelines over three phases (one phase: two years) since 2009, led by the
Medical Committee. In the second phase, 8 courses were asked to develop practice guidelines inaccordance with the GRADE system. In the meantime, symposia on practice guidelines were held
under the themes of "Establishment of Practice Guidelines for Magnetic Attachments," "Troubles with
Magnetic Attachments," and "Application of Magnetic Attachments to Implants vs. Natural Teeth" inorder to inform members of the significance of practice guidelines and the method of formulation8,9) .
Because of the lack of relevant literature, especially for the selected CQs, the symposium introduced
and discussed how to proceed with the work of evidence collection and the Delphi method6-9) when there
is a lack of evidence. In Phase II, 71 members of the consensus group were selected for the Delphi
survey, and questions were developed to evaluate the effectiveness of magnetic attachments on 11
outcomes on a scale of -5 to +5, with 38 participants responding to two questionnaires, which resulted
in a certain aggregate trend7-9 ).
Of the 14 CQs, 2 CQs on missing forms were combined into 1 CQ, and the other CQs on MRI were
excluded because they corresponded to TA (Technology Appraisals), and draft guidelines weredeveloped for 12 CQs.
After the above process, in Phase III, we asked the consensus group that conducted the Delphi
survey to evaluate the draft guideline, which was brushed up with feedback from the consensus group,and then asked external evaluators from other societies to conduct the final evaluation. The draft
guideline was then finalized by asking external evaluators from other societies to make final
evaluations.)
In recent years, the main method for formulating medical practice guidelines has been to evaluate theevidence and determine the level of recommendation using the system devised by the GRADE(Grading of Recommendations Assessment, Development and Evaluation) Group11,12) , and the system
is now being used by the Japan Medical Evaluation Service (JMEDS). The MINDS (Medical
Information Network Distribution Service)12) of the Japan Medical Evaluation Organization and theJapanese Dental Association also recommend the GRADE system. In this method, three factors aretaken into account: the physician's expertise, experience, and skills; patient factors; and the quality ofevidence. The recommendation is determined by comprehensively judging four major factors: quality ofevidence, balance of benefits and disadvantages, values and preferences, and cost and resource
utilization4,5) .
However, because of the special nature of prosthetic dentistry and the difficulty of applying the
GRADE system mutatis mutandis due to the lack of accumulated evidence in the new field of magnetic
dentistry, we have also incorporated evaluation methods that take advantage of the characteristics anduniqueness of our society. For example, in prosthodontics and magnetic attachments, modelexperiments and simulation experiments are more reproducible and provide sufficient evidence for4outcomes such as maintenance and durability, etc. Therefore, S (simulated/model experiments) was
added to A (high), B (low) and C (very low) as one of the evidence levels13).
This time, we conducted a literature search again for the 12 CQs selected five years ago, revised theoutlines, recommendations, and other contents, and added one CQ on MRI (IP: Interventional
Procedure). Furthermore, the ISO Task Force Committee is now working on the revision andamendment of ISO 13017 (ISO 13017: Amd.1), which was published in 2012, and the history of the ISO
13017 standardization has been added1). The investigation of the Delphi method by the consensus
group was not conducted this time due to time and expense constraints.
At present, there are many CQs for which there is insufficient evidence, and we believe that not only
the Magnetic Dentistry Society but also the dental community as a whole should urgently address thisissue as a research theme. It is necessary to continue many reorganization works such as addition of
CQs, revision of recommendations, and development of a system to accept users' opinions andsuggestions on the contents of recommendations.
2. Survey and selection of clinical questions for magnetic attachments in dental practice
For the selection of clinical questions (CQ: Clinical Question) for magnetic attachments (MA), a
questionnaire survey was sent by e-mail to experienced officers of the society, requesting a wide rangeof responses from dentists at their facilities and general clinicians in the community2 ). The survey was
also distributed to the participants of the 19th Annual Meeting, published on the Society's website andin the Society's journal3) and sent by mail to the academic members of the dental associations in eachprefecture.
The CQs consisted of Patient, Intervention, Comparison, and Outcome. The survey was conducted inaccordance with the PICO format, with examples provided and multiple responses requested.
As a result of the survey, 117 respondents were obtained, and a total of 147 CQs were collected1-4). The
number of CQs categorized into five groups according to content is as follows.
(1) Implant-related: 21 questions(2) Comparison with other systems in terms of defect style: 51
Comparison with other systems in terms of occlusion and periodontal disease: 17(4) Placement and form of abutment teeth: 27(5) Management and others: 31
From the above CQs, a total of 14 CQs were selected as representative CQs: 4 on implants, 3 on
missing styles, 3 on occlusion/periodontal disease, 2 on abutment placement/form, and 2 onmanagement/others.
With the cooperation of the Safety Management Committee, we added CQ13 on MRI to 5.
Management, and developed evaluation profiles and recommendation statements by referring to the"Manual of Safety Standards for MRI".

1. Implant
CQ1．In case of implant-supported overlay dentures, is magnetic attachments (MAs) more effective
than applying other type of retainers?
CQ2．In implant-supported overlay dentures, are applying MAs to implant abutments more successful
than applying them to natural teeth?
CQ3．Applying MAs to implant-supported overlay denture cases, are maxillary cases more successful
5than mandibular ones?

CQ4．Applying MAs to implant-supported overlay denture cases, are multiple abutments with MAs
more effective than a single abutment?
2. Defects
CQ5. In few remaining mandibular teeth, are applying MAs more effective than other type ofretainers?
CQ6. In free-end saddle removable partial dentures, are applying MAs more effective than other typeof retainers?
3. Occlusion/Periodontics
CQ7. In partially edentulous without occlusal contact, are applying MAs more successful than othertype of retainers?
CQ8. In partially edentulous with undulating occlusal planes, are applying MAs more effective thanother type of retainers?
CQ9. When remaining abutments are with periodontal disease, are applying MAs more successful
than other type of retainers?
4. Arrange / Form
CQ 10.Applying MAｓ to multiple abutment teeth, are symmetrical arrangements more effective thanasymmetrical ones?
CQ 11.Applying MA ｓ to remaining abutment teeth, is flat type keeper more effective thandome-shaped keeper for stability of the denture?
5. Manage/etc
CQ 12. When setting MAs to removable partial dentures, is the applied pressure method more
successful than the minimum pressure ones?
CQ 13. When undergoing MRI examination, do applying MAs cause more artifacts in the examinedgraphic images than other type of retainers?

＊Other devices refer to various attachments other than clasps and magnetic attachments

3. Methods of evidence collection
Literature searches were conducted using MEDLINE, Medical Journal Web (Ver. 4), Cochrane Oral
Health Group Trials Register, Cochrane Central Register of Controlled Trials (CENTRAL), EMBASE,
UMIN Clinical Trials Registry (UMIN-CTR), etc. The search principle was to search for references thatwere searchable in the databases by October 2012. Randomized controlled trials (RCTs), cohort studies,case-control studies, cross-sectional studies, observational studies, and case reports were searched, andtheir citations were hand-searched.

6

4. Process and criteria for determining the level of recommendation
The most important role of a guideline is to clearly state the level of recommendation. In this guideline,
the GRADE system was used as a reference, and the following process was used to determine the level ofrecommendation, taking into consideration the special characteristics of prosthodontics.

Process for determining the level of recommendation

Factors Considered in Making Recommendations
Level of evidence in terms of study design
Level of Evidence

Research Design

A（High）

Randomized controlled trials, Systematic review

B（Low）

observational study

C（Very Low）

Case Reports, Case Studies

S

Model experiments and demonstrations using engineering methods

Quality of Evidence
Quality of Evidence

Meaning

H（High）

Little to no change in estimated effects

M（Midle）

There may be a possibility of changing in estimated effect7

L（Low）

Possible change in estimated effect

VL（Very Low）

Estimated effects are very uncertain

In the case of evidence from engineering methods, the possibility of changing the estimatedeffect was evaluated based on whether the environment was fully realized in vivo and whether
the estimation was based on an understanding of the problems with engineering methods13).

5. Consensus method
Due to the clinical specificity of prosthetic dental practice, there is not always a high level ofevidence for many CQs. When the quality of evidence is not sufficiently high for a guideline foreach CQ, or when there are conflicting opinions, recommendations and opinions based on
expert consensus were appended.
The consensus was formed by choosing between the Delphi method for the consensus group(determined by the subcommittee for each CQ, taking into account the areas of expertise) and astandard questionnaire survey of members.
*About the Delphi method
Questionnaire surveys using the Delphi method were conducted in the following cases7-10) .
As a result of collecting evidence by the aforementioned methods･When no references could be found at all･When the number of references is small and the quality of evidence is very low (VL)･When the literature search results in conflicting opinions and it is difficult to make a
judgment.
The Delphi method was conducted in the following steps.
Phase 1: Questionnaires were solicited from guideline developers for each CQ for which noevidence could be obtained from the literature search. The questionnaires were compiled andthe first questionnaire was prepared.
Phase 2: Questionnaires were distributed to the consensus group, who were asked to predict
the numerical value of each item and to indicate their level of agreement by giving a score. The
second questionnaire was prepared by tabulating the scores and expressing them in a8

frequency distribution for each question, as well as improving the points raised by theconsensus members.
The third step: The results of the first questionnaire (results for the consensus group as awhole, with the questions distributed by frequency distribution) and the second questionnaire
were distributed to the consensus group, and the respondents were asked to indicate their levelof agreement with the content of each item again by giving a score. Here, respondents wereallowed to change their scores based on the results of the first survey. The scores weretabulated, and the degree of convergence of the responses and the degree of agreement
between the first and second responses were used as references to examine the overall degreeof agreement.
Following the above procedure, the effectiveness of magnetic attachments was evaluated foreach of the 9 CQs for which no relevant literature was found or the quality of evidence was low,using an 11-point scale from -5 to +5 for the following 11 outcomes: maintenance, mastication,
pronunciation, esthetics, comfort, responsiveness, durability, periodontal health, burden, harm,and cost. A Delphi questionnaire was used to evaluate the 11 outcomes on a scale of -5 to +5.
Thirty-six members and 35 non-members of the consensus group were selected for the survey,
and questionnaires were sent by e-mail or mail. A total of 38 respondents, 25 of whomanswered all questions including implants and 13 of whom answered only general prosthetics,
were obtained in two surveys8-10).

Selection of recommendations by the Delphi method
median≦−２−２＜median＜＋２＋２≦medianDegree of convergence：High

NN

U

PP

Degree of convergence：Middle

N

U

P

Degree of convergence：Low

U

U

U

Convergence: High Distribution range of 3 or less after excluding those with frequencies of 2 or less
Convergence: Medium The distribution range is 4-6 when the frequencies less than or equal to 2 are excluded.
Convergence: Low The distribution range is more than 7 when those with a frequency of 2 or less are excluded9Outcome Factors for Magnetic Attachment
Treatment OutcomesClassification among the primary factors in determining the level of recommendation

Retentive force

Effectiveness (denture maintenance and stability)

Masticatory function

Effectiveness (Treatment Outcome)Pronunciation

Effectiveness (Treatment Outcome)

Aesthetics (appearance)

Effectiveness (Treatment Outcome)Comfort (fit)Downsides

Repairability (Repair)Downsides (ease of repair)

Durability (prolongation of

Downsides (ability to maintain prosthetic dentition)

abutment teeth, etc.)
Periodontal healthDownsides (Does it induce gingival inflammation?)

Overload

Downsides (burden on abutment teeth, periodontal tissues, etc.)

Harm (tooth damage, pain)

Downsides (treatment time, discomfort and pain associated with treatment)

Expression of degree of recommendation
PP：Recommended (positive strong recommendation)
P: Recommendable (weak positive recommendation)
N: Not recommended (negative weak recommendation)
NN: Not recommended (negative strong recommendation)
U: Unable to determine

6. determination of recommendation and evaluation profile
Evaluation profile
OutcomeQuality of

Evaluation

Delphi method

Evidence(validity, etc.)

evaluation

1.Retentive force
2.Masticatory function
3.Pronunciation
4.Aesthetics (appearance)
10

5.Comfort (fit)
6.Repairability (Repair)
7.Durability (prolongation ofabutment teeth, etc.)
8.Periodontal condition
9.Overload
10. Harm (tooth damage, pain)
11.CostRecommendation

Judgment as a whole

As for the overall recommendation, as mentioned above, clinical decisions and outcomes of
prosthodontic practice are greatly influenced by the patient's own values and other factors, so thatin practice it is necessary to match this recommended profile with the profile of the patient's values.
However, in this guideline, an overall recommendation level was purposely presented after
consultation by the guideline development committee to provide suggestions to users. Therefore, it
must be understood that the above assumptions must be made when using this overall
recommendation.
In addition, when multiple recommendations are described in the overall recommendation (e.g.,
N to P), it indicates that the importance of each treatment outcome based on the evidence iscompeting and that it is difficult to select a single recommendation. In this case, it means that thedecision should be based on a thorough understanding of the patient's own values, medical
resources, and the skill of the practitioner.

7. Consensus reached on practice guideline 2013 for magnetic attachments(Application of magnetic attachments to implants vs. natural teeth)
The following consensus was obtained from the previously developed "Practice Guidelines for
Magnetic Attachments 2013"10) and the symposium "Application of Magnetic Attachments to Implants
vs. Natural Teeth "9).
The literature on the progress of MA application to implant abutments has been gradually increasing
in recent years, and clinical reports by experts indicate that MA tends to have less overburden on
implant abutments, better predictability, and better progress9,10).
11

On the other hand, there is little literature on the progress of MA application to natural teeth, andsince MA is sometimes applied to prolong the life of upset teeth, it is effective with weakrecommendations, but its predictability and progress are inferior to those of implant abutments9,10).
Therefore, a consensus was reached that MA on implant abutments is more predictable and has a bettercourse than natural abutments9,10) .
The consensus group, external evaluation committee members, and the Japanese Association of Dental
Medicine have commented that this guideline is premature because of the paucity of literature on thesubject. We plan to submit the information to the Japanese Dental Association, the Japan Federation of
Dental Medicine, and other organizations for their evaluation. We are deeply grateful for the cooperationof our members and consensus committee members, and we hope for their further support.

８. References
1) Yukyo Takada: Report of the ISO Task Force Committee Toward International Standardizationof Magnetic Attachments for Dental Use, - ISO/TC 106 Hong Kong Conference - (in Japanese).,
Journal of Magnetic Dentistry, 27(1): 22-27, 2018.
2) Hideshima M, Igarashi Y, Ichikawa T, et al: Preliminary Questionnaire Survey for formulating
Clinical Practice Guidelines for Magnetic Attachments Applications - Analysis and Selection of
the Clinical Questions (CQ) -. J J Mag Dent 19: 29-34, 2010.
3) Medical Committee of the Japanese Society of Magnetic Dentistry: Request for Preliminary
Questionnaire Survey for Formulating Clinical Practice Guidelines for Magnetic Attachments
Applications - Analysis and Selection of the Clinical Questions (CQ) - (in Japanese), Journal ofMagnetic Dentistry, Vol. 19, No. 1, 119-120, 2010.
4) Hideshima M, Igarashi J, Ichikawa T, et al: Questionnaire survey on practice guidelines formagnetic attachments - Survey and selection of clinical questions (CQ) (in Japanese). Journal ofMagnetic Dentistry, Vol. 20, No. 1, 114, 2011.
5) Hideshima M, Igarashi Y, Ichikawa T, et al: Questionnaire Survey for Formulating Clinical
Practice Guidelines for Magnetic Attachments Applications - Analysis and Selection of theClinical Questions (CQ) -. J J Mag Dent 20: 5-10, 2011.
6) Nagao K, Goto T, Ishida Y, Ichikawa T: What is the Delphi method? (in Japanese). Journal ofMagnetic Dentistry(in Japanese), Vol. 21, No. 1, 32-36, 2012.
7) M. Hideshima, T. Ichikawa, H. Koshino, K. Hoshiai, J. Tanaka, S. Ozawa, Y. Suzuki, Y.
Umekawa, T. Ishigami, K. Nagao, M. Sone, M. Kono, J. Wada, J. Wadachi Y. Suzuki, Y. Umekawa,
T. Ishigami, K. Nagao, M. Sone, M. Kono, J. Wada, J. Wadachi: Formulating clinical practiceguidelines for magnetic attachment applications: The process and results of a survey using theDelphi J J Mag Dent 22: 47-53, 2013.
8) Hideshima M: If you have a problem with magnetic attachments: Based on the clinical practiceguidelines. (in Japanese). Journal of Magnetic Dentistry, Vol. 22, No. 1, 19-23, 2013.
9) Hideshima, M.: Medical Committee [Practice Guideline Planning] Application of Magnetic
Attachment to Implant vs. Natural Teeth, Guideline Development History and Practice
Guideline for Application of Magnetic Attachment to Free End Dentures(in Japanese). Journal of12the Japanese Society of Magnetic Dentistry, Vol. 23, No. 1, 45-49, 2014.
10) " Clinical Practice Guidelines for Magnetic Attachments 2013" edited by the Japanese Society ofMagnetic Dentistry: Website of the Japanese Society of Magnetic Dentistry,
http://jsmad.jp/guideline.
11)Atkins D, et al. GRADE Working Group. Grading quality of evidence and strength ofrecommendations. BMJ；328：1490，2004.
12) Aihara M, Mihara K, GRADE Working Group, et al. GRADE System for Clinical Practice
Guidelines (in Japanese). Toppan Media Co.
13) The Japanese Society for Prosthetic Dentistry (ed.): Guidelines for Prosthetic Dental Practice;
Guidelines for Prosthetic Dental Practice of Missing Teeth 2008 (in Japanse). 1-117, Tokyo, 2009.
120.

13

Ⅲ． International Standardization of Magnetic Attachments
1. History of International Standardization
In 2005, the Japanese Society of Magnetic Dentistry, led by the Japan Society of Magnetic
Dentistry, obtained a grant from the New Energy and Industrial Technology Development
Organization (NEDO) under the research theme of "Optimization of Magnetic Attachments for
Dental Use and Creation of International Standards" and launched an effort toward
international standardization of magnetic attachments by establishing the Magnetic
Attachment Standardization Committee. The efforts toward the international standardization ofmagnetic attachments began with the establishment of the Magnetic Attachment
Standardization Committee (Fig. 1).

Optimization and International Standardization of the Magnetic Dental Attachment
by New Energy and Industrial Technology Development Organization (NEDO)

Fig 1: Participating organizations at the time of the establishment of the Magnetic Attachment Standardization Committee

In 2007, at the ISO/TC106 Berlin meeting, a New Work Item Proposal (NP) was submitted to
Subcommittee 2 (SC2), which develops standards for prosthetic materials. At the following meeting of
ISO/TC106 in Gothenburg in 2008, WG22 (Working group 22) Magnetic attachments was newly
organized in SC2. Japan became the chairing country of WG22, and the Magnetic Attachments
Standardization Committee produced a convener (chairperson) and a Japanese expert. At this meeting,
the Japanese draft standard (Dentistry - Magnetic Attachments) was adopted as a working draft (WD)and approved as ISO/ WD 130171. In the same year, the NEDO support was terminated, and an ISO
task force committee was established in the Japan Society of Magnetic Dentistry to take over thedevelopment of the ISO standard (Figure 2).
In May 2009, the NEDO-supported follow-up project was selected as the next grant, and the14

Standardization Committee for Magnetic Dental Attachments was reorganized with the members of the
ISO task force committee. At the ISO/ TC106 Osaka meeting in September of the same year, the CD(committee draft) ballot for ISO/ WD 13017 was approved, and the committee was promoted to ISO/CD
13017 in the CD ballot held in March 2010. The DIS (draft International Standard) ballot for ISO/CD
13017 was approved at the ISO/ TC106 General Assembly, and the standard was promoted to ISO/DIS
13017 in the June 2011 DIS ballot without any negative votes. Furthermore, ISO/ FDIS 13017 wasapproved through FDIS (Final Draft International Standard) balloting in June 2012, and ISO 13017
was published as an international standard on July 15, 2012, thus achieving the international
standardization of magnetic attachments2) (Figure 3).
Follow-up project of
NEDO started
Creation of international
standards by NEDO
started2005

Creation of international
standards by NEDO
finished

ISO China meeting

2006

Establishment of theMagnetic Attachment
Standardization Committee

2007

2008

ISO Berlin meeting
NWIP

WD→CD
ISO Osaka meeting

2009
ISO Gothenburg meeting
Original Japanese draft → WD
Establishment of WG22
↓

2010

2011

ISO Rio de Janeiro
meeting

CD→DIS

Establishment of ISO Working
Committee
Fig 2. International standardization of magnetic attachments (2005-2011)

Fig 3: ISO/FDIS 13017 voting results

15However, it was developed in a short period of four years after the ISO task force was established, andin addition, there were points that were unsatisfactory as a provision for measuring retentive force thatcan fully evaluate the uniqueness of domestic magnetic attachments that show strong retentive force
even though they are small in size. Therefore, based on the progress of international standardization of
the maintenance force measurement method for magnetic attachments, which we have been working onin parallel since 2010, we started activities to apply for the supplemental version of ISO 13017 at thesame time as the publication of the international standard. The draft standard was submitted with ahigh degree of completeness due to the preparations that had been made since 2010, and therefore, it isusually considered as a work in progress.
Although deliberation would be made from the Draft WD, the wish for deliberation from the Draft
International Standard (DIS) was also passed at the same time. (Figure 4)

First year of METI
(Ministry of Economy,
Trade and Industry)
supportISO Fenix meeting
FDSI(DIS → FDIS)

2011

2012

ISO Paris meeting

FDIS
voting
6.20

Second year of
METI support

ISO Inch-longmeeting
NWIP

2013

Third year of
METI support

ISO Berlin
meeting

DIS voting

2014
NP voting
7.28

2015
ISO13017
Amd.1(E)

ISO13017
7.15
Figure 4: International standardization of magnetic attachments (2011-2015)

The draft Amendment was subsequently revised, and after the 2013 Inchon meeting, it was elevatedto ISO13017: DAM.1 (Draft International Standard as supplement) through DAM ballot (DIS ballot as
supplement) 4). During the DAM ballot, Germany objected that the amendments made at the Inchon
meeting were not fully reflected in the draft Amendment. However, it turned out that the draft
Amendment circulated for DAM balloting before the Inchon meeting was a systemic deficiency causedby the fact that it was circulated before the Inchon meeting, and the German approval was obtained. In
addition, Australia proposed a request for additional friction provisions, which was revised with16

sufficient evidence and approved for FDAM (draft final international standard for addendum) ballot at
the Berlin meeting in 2014. At the Berlin meeting, the results of interlaboratory tests conducted in three
countries (Japan, Germany, and China) were reported (Figure 5) and discussed on the improvement of
the specimen fixation method, the definition of maintenance force and its calculation method, and thedefinition of friction force during vertical specimen movement. After returning to Japan, we revised andadded to the current DAM.1 according to the points raised and submitted the draft FDAM.1 to the SC2
secretariat5).

(a)

Japan

(b) China(c) Germany

Fig 5. Interlaboratory testing (specimen table and fixation method for post-keeper)

FDAM registration was completed in 2015, and in September, FDAM ballot elevated it to FDAM.1(the final draft International Standard for the addendum). At that time, the integration of ISO 13017
and Amd.1 (the supplemental version) was pointed out by Germany, and a slight modification of theformat was pointed out by the UK, but the revised version of FDAM was submitted after the Bangkok
meeting in September 2015. The integration of ISO 13017 and Amd.1 (supplemental version) was
proposed and approved at the time of the periodic review in 2017, which is conducted every five years
after the publication of an international standard6). Thus, ISO 13017:2012/Amd.1 (the supplement to
ISO 13017) was published in November 20157 (Figure 6).

17

First year of METI
(Ministry of Economy,
Trade and Industry)
supportFDIS
votingISO Paris
meeting

2012

Third year of

METI support

METI support

ISO Inch-longmeeting

ISO Berlin
meeting

NP applyDAM
circulation

ISO Bangkok meeting

FDAM
voting

DAM voting

2013

ISO13017

Second year of

NP voting
Amd.1

2014

2015
DAM.1

2016
ISO13017: AMD1
establishedFig 6International standardization of magnetic attachments in dentistry (2012-2016)

The international standardization of magnetic attachments, which started in 2005, has beenaccomplished after 11 years with the publication of two international standards, ISO 13017 andISO 13017:2012/Amd.1 (supplemental version).

The two international standards will be

integrated for the periodic review in 2017(Figure 7).

ＩＳＯ １３０１７ （Original standard version）

ＩＳＯ １３０１７ （Amendment1）

18

Fig 7 ISO 13017and Amendment 1(Supplemental ed.)

2. Structure of ISO 13017 and outline of the supplemental edition
Figure 8 shows the structure of ISO 13017 and the supplement to the standard by Amd. 1(supplement). Underlines indicate the parts supplemented by Amd.1.
ISO 13017 consists of items 1 to 8, and is mainly supplemented by Amd. 1, which covers the
preparation of specimens (5.1 Maintenance force) in 5. and test methods (6.3 Maintenance force, 6.4
Corrosion resistance) in 6.
In 3. Terms and definitions, terms and definitions related to dental magnetic attachment types,
magnets and magnetic structures, keepers, magnetic circuits, etc. are given. For example, magnetic
attachments without a magnetic circuit are defined as "magnet" and those with a magnetic circuitas "magnet structure (magnet) assembly" to clarify that magnetic attachments in Japan aremagnet structures.

Contents of ISO 13017 and compensation by the Supplement edition
1. Scope
2. Normative references
3. Terms and definitions
4. Requirements
4.1 Material
Declaration of composition
4.2 Hazardous elements
Ni＜0.1％, Cd, Be＜0.02％
4.3 Risk analysis
Compliant with ISO14971
4.4 Magnetic flus leakage
Display obligation if it is 40ｍT or more

4.5 Retentive force
Not less than 85％ of the standard value

4.6 Corrosion resistance

5. Preparation

6. Test methods

5.1 Retentive force

6.1 Information, Instructions

Pre-treatment of specimen

5.2 Static immersion test
5.3 Anordic polarization
curve

and making

6.2 Magnetic flux leakage
6.3 Retentive force
Apparatus(device)
Fixing materials
Fixing procdure
Methods and evaluation

Definition of retentiveforce
6.4 Corrosion resistance
Minimum limit of determination

7. Information and instruction for use

Eluted ion amount according to ISO22674
Not less than breakdown potential of 316L

Fig 8

8. Marking and labellingContents of ISO 13017 and compensation by the Supplement edition.

The requirements in Section 4 consist of 4.1 Materials, 4.2 Hazardous Elements, 4.3 Risk Analysis,
4.4 Leakage Field, 4.5 Maintenance Force, and 4.6 Corrosion Resistance. 4.1 Materials uses the19ISO standard classification that defines magnets, and only major constituent elements areindicated to prevent leakage of trade secrets. 4.6 Corrosion resistance: Corrosion resistance ofstainless steel 316L or higher for orthopedic use for biological use was specified to maintain quality
and to prevent distribution of pirated copies.
In 5. Preparation of specimens, preparation of specimens at the time of testing is specified, and in
5.1 Sustaining force, the pretreatment method is added according to Amd. 1.
Amd. 1 specified in detail the method of measuring 6.3 maintenance force, the jig to be used (Figs.
9 and 10), the method of calculating the maintenance force (Fig. 11), and the measurement methodwith high accuracy and reproducibility (Fig. 12). 6.4. In corrosion resistance, in order to clarify thequantitative analysis of impurity element ions in static immersion tests, the lower limit ofquantification and detection limit of the chemical analysis method were introduced, and accuratequantification was specified.
7. and 8. specify descriptions and labeling contents to support the product.

Fig 9

Overview of the jig for measuring retention force (left) and the low-friction linear slider (right)

20

Fig 10. Retentive Force Measuring Jig

Fig 11. Retentive Force Curve

Fig12: Dynamic frictional force and change in the jig for measuring maintenance force

3. References
1) ISO 13017: 2012(E), Dentistry -Magnetic attachments.
2) Y. Takada: ISO Task Force Report: Toward International Standardization of Magnetic
Attachments for Dental Use (in Japanese), Journal of Magnetic Dentistry, 20(1): 81-85, 2011.
3) Y. Takada: Report of the ISO Task Force Committee: Toward the International Standardization
21

of Magnetic Dental Attachments, - ISO/TC 106 Paris Conference - (in Japanese), Journal ofMagnetic Dentistry, 22(1): 65-68, 2013.
4) Takada, Y.: Report of the ISO Task Force Committee: Toward International Standardization ofMagnetic Dental Attachments, - ISO/TC 106 Inchon Meeting -, (in Japanese). Journal of Magnetic
Dentistry, 23(1): 72-76, 2014.
5) Takada, Y.: Report of the ISO Task Force Committee: Toward International Standardization ofMagnetic Dental Attachments, - ISO/TC 106 Berlin Meeting , (in Japanese) . Journal of Magnetic
Dentistry, 24(1): 48-53, 2015.
6) Y. Takada: Report of the ISO Task Force Committee Toward International Standardization ofMagnetic Dental Attachments, - ISO/TC 106 Bangkok Conference (in Japanese)-, Journal ofMagnetic Dentistry 25(1): 39-44, 2016.
7) ISO 13017: 2012(E)/Amd.1, Dentistry -Magnetic attachments.

22

V. Clinical Questions and Evaluation/Recommendation Profiles
The following is a list of 12 CQs, their evaluation profiles, and recommended profiles. For details,
please refer to the website of the Japanese Dental Association and the Clinical Guideline
Library of the Japanese Association of Dental Surgeons.
＊MA: Magnetic Attachment＊Other devices described in each CQ refer to various attachments other than clasps and MAs.
CQ1: In case of implant-supported overlay dentures, are magnetic attachments (MAs) more
effective than other types of retainers?
【Recommended profile】
Although MAs are slightly inferior to bar and O-ring attachments in terms of retentive force andmasticatory function, they are effective in terms of comfort and maintenance of periodontal health.
Long-term follow-up reports indicate that MAs are as effective as other attachments as abutment
teeth for implant overdentures, and may be recommended in appropriate cases after fully
explaining the current available evidence to the patient.
Quality of
Evidence

Outcome

Evaluation(validity, etc.)

1.Retentive force

M

N

2.Masticatory function

M

N

3.Pronunciation

M

U

4.Aesthetics (appearance)

LU

5.Comfort (fit)M

P (for female)

6.Repairability (Repair)

L

U

M

U

L

P

7.Durability (prolongation ofabutment teeth, etc.)

8.Periodontal condition

Delphi method
evaluation

9.Overload
10. Harm (tooth damage,pain)
11.CostRecommendation

Judgment as a wholeP【Background and Purpose】
Implant overdenture has become an important treatment option for the edentulous jaw. The paper

23describes cases in which two implants are connected by a bar and given a sleeve attachment as animplant abutment, and cases in which a single implant is used, a ball attachment, or an MA is attached.
The MAs reported in the paper are mainly used in Europe, and there are few reports with a high level ofevidence regarding compact and magnetic Japanese-made MAs. Therefore, we analyzed various
outcomes and examined the usefulness of MAs for implants.

【Outline】
Three comparative studies were reported in which two implants were placed in the edentulous
mandible and overdentures were fabricated, and attachments including MAs were applied1-6). According
to the results, after 5 years of use, the bar-type attachment had the highest retentive force, and MA had
the lowest value among those compared6). In an evaluation using test foods, it was reported thatmasticatory function was significantly decreased after using MA compared to bar and ball
attachments5) . On the other hand, no significant differences were observed between attachment types
in the evaluation using jaw movement and electromyography2).
There were no significant differences in periodontal parameters (bone resorption, attachment loss,
plaque index, and periotest value) around the implants after 10 years. However, MA had the lowest bone
resorption and attachment loss values4). In a study comparing the use of both ball and MA, 11 of 18
patients ultimately chose the ball attachment and 5 chose the MA. the group that chose the MA wasmostly female, and they appreciated the comfort and ease of cleaning. These reports support the MA'sfeatures, such as the buffering mechanism against harmful lateral forces and the ease of operation. The
usefulness of MA overdentures was also demonstrated by model experiments7) and case studies8).

【References】
１） Ellis JS, Burawi G, Walls A, Thomason JM. Patient satisfaction with two designs of implant
supported removable overdentures; ball attachment and magnets.Clin Oral Implants Res. 2009
Nov;20(11):1293-8.
２） van der Bilt A, van Kampen FM, Cune MS. Masticatory function with mandibularimplant-supported overdentures fitted with different attachment types. Eur J Oral Sci. 2006
Jun;114(3):191-6.
３） Cune M, van Kampen F, van der Bilt A, Bosman F. Patient satisfaction and preference with magnet,
bar-clip, and ball-socket retained mandibular implant overdentures: a cross-over clinical trial. Int J
Prosthodont. 2005 Mar-Apr;18(2):99-105
４） Naert I, Alsaadi G, van Steenberghe D, Quirynen M. A 10-year randomized clinical trial on theinfluence of splinted and unsplinted oral implants retaining mandibular overdentures: Peri-implant
24

５）
６）

７）
８）

outcome．Int J Oral Maxillofac Implants. 2004 Sep-Oct;19(5):695-702.
van Kampen FM, van der Bilt A, Cune MS, Fontijn-Tekamp FA, Bosman F. Masticatory function
with implant-supported overdentures. J Dent Res. 2004 Sep;83(9):708-11.
Naert I, Gizani S, Vuylsteke M, Van Steenberghe D. A 5-year prospective randomized clinical trial
on the influence of splinted and unsplinted oral implants retaining a mandibular overdenture:
prosthetic aspects and patient satisfaction. J Oral Rehabil. 1999 Mar;26(3):195-202.
Takeshita S, Kanazawa M, Minakuchi S. Stress analysis of mandibular two-implant overdenturewith different attachment systems. Dent Mater J. 2011 Nov; 30(6): 928-934.
Tanaka J, Hoshino K. Prosthetic design guideline for effective userge of magnetic attachments:
Application to restorations suppotted by implants. J J Mag Dent. 2003; 12(１): 10-26.

【Authors】

Shogo Ozawa, Kazumoto Hoshiai, Yoshinobu Tanaka
Department of Removable Prosthodontics, School of Dentistry, Aichi Gakuin University

CQ2: In case of implant-supported overlay dentures, is the application of MAs to implant
abutments superior to applying them to natural teeth?
(Composite defect of mandibular bilateral free end and middle, and abutment teeth should bebicuspids or premolars adjacent to the defect.)【Recommended profile】(In a composite defect of mandibular bilateral free ends and middle, application of MA may be recommended
in terms of retentive force, masticatory function, etc. (weak level of recommendation).

Quality of
Evidence

Evaluation(validity, etc.)

1.Retentive force

M

U

P

2.Masticatory function

M

U

PP

OutcomeDelphi method
evaluation

3.PronunciationU

4.Aesthetics (appearance)U

5.Comfort (fit)MU

6.Repairability (Repair)
7.Durability (prolongation ofabutment teeth, etc.)

U
U

M

U

U

8.Periodontal condition

U

9.Overload

U25

10. Harm (tooth damage,
pain)

M

U

U
U

11.Cost

Judgment as a whole P

Recommendation

Details of the Delphi method evaluation
mediandegree ofconvergence

recommendation

1.Retentive force

2

M

P

2.Masticatory function

3

H

PP

3.Pronunciation

0

H

U

4.Aesthetics (appearance)

0

H

U

5.Comfort (fit)

0

H

U

6.Repairability (Repair)

1.5

H

U

0

H

U

8.Periodontal condition

0

H

U

9.Overload

0

H

U

10. Harm (tooth damage, pain)

0

H

U

11.Cost0

M

U

Outcome7.Durability(prolongation
abutment teeth, etc.)

RecommendationofP【Background and Purpose】
Partial dentures with a periodontal ligament-mucosa-implant support mechanism with a small
number of implants are effective in improving the esthetic problems of partial dentures due to clasps
and denture movement during function. The purpose of this guideline is to establish an index toevaluate the effectiveness of MA as an implant-supported partial denture abutment compared withnatural teeth.

【Outline】
In a prognostic study of MAs applied to natural teeth, problems with the Gingival Index, periodontal
pocket deterioration, and fracture of the abutment tooth occurred in less than 9% of the cases studied,26

and problems with the denture occurred in 4% of cases1). The results of a follow-up study of 36
edentulous patients with two mandibular overdentures with ball, bar, or magnet abutments at 4, 12, 60,
and 120 months showed that marginal bone resorption at the end of the 10-year follow-up period of MA
was comparable to that of healthy natural teeth, and that the survival of the implants was similar tothat of healthy natural teeth. The survival rate of implants was also reported to be 100%2) . However,these literature search results did not compare implants and natural teeth in mandibular bilateral freeedge and intermediate composite defects, so we conducted a questionnaire survey using the Delphi
method. The results of the Delphi questionnaire showed that the application of MA to implant
overdentures was effective in improving retentive force and masticatory function. The results of thequestionnaire survey on the period of time when MA was applied to natural teeth and implant
overdentures showed that it took 6.3 years for a partial denture with a free end defect, 10.4 years for an
implant overdenture, 4.4 years for a difficult partial denture (misaligned bite), and 5.5 years for an
implant overdenture. Implant overdentures showed a better outcome compared to natural teeth, with
the implant overdenture showing 7.8 years.
From the above results, it was concluded that the application of MA to implant overdenture can berecommended in terms of retentive force and masticatory function in the case of bilateral free end andintermediate composite defects in the mandible.
Clinically, it is important to increase the interproximal line and realize a rectangular support
distribution by placing implants in a position where the implant and abutment teeth are symmetrical as
much as possible, taking into consideration the placement of the remaining teeth. If there is sufficientbone volume, it is important to place the implant posterior to the free end defect to take full advantage ofthe support capacity of the implant and to position the Fulcrum line as posteriorly as possible to widen
the support area. If the anatomical constraints allow the placement of implants anterior to the free end
defect and the application of MA, it is possible to contribute to esthetic improvement as a maintenancesource.
Magnetic attachments are useful as an implant-supported partial denture for free end defects because
they are expected to provide maintenance by magnetic force and support by plane-to-plane contact
between the magnet and the keeper.
The disadvantage of implant-supported partial denture is denture fracture as well as root-supported
overdenture. If the thickness of the denture base is thin enough to cover the implant, the denture is27

likely to fracture at the implant as a fulcrum.

【References】
1) Hisako Yoshikawa, Hiroyuki Okuda, Shinji Uchida, Yasuo Azezaki, Masataka Minami, Akira Kawano,
Harukazu Kanehira, Teruta Maeda, Hiroshi Inoue. Usage and prognosis of dentures with magnetic
attachments Dentistry (in Japanese). Journal of Magnet Dentistry, 1988;61(2):105-111
2) Naert I, Alsaadi G, van Steenberghe D, Quirynen M. A 10-year randomized clinical trial on theinfluence of splinted and unsplinted oral implants retaining mandibular overdentures : peri-implant
outcome. Int J Oral Maxillofac Implants. 2004 19(5):695-702【Authors】
Yasunori Suzuki, Chikahiro Okubo
Department of Removable Prosthodontics, Tsurumi University School of Dental Medicine

CQ3: When applying magnetic MAs to implant-supported overlay dentures, are maxillary
applications superior to than mandibular ones?
【Recommended profile】
There seems to be no clear difference in the prognosis of maxillary and mandibular implant
overdentures to which MA is applied. The effect of MA application to maxillary implant
overdentures is expected to be an improvement in phonatory function and comfort. The reason forthis is that the application of MA in the maxilla allows the release of the palatal portion of thedenture, which may reduce the patient's pronunciation-related problems and discomfort.

OutcomeDelphi method evaluation（25 persons）
degree ofrecommendation
medianconvergence

1.Retentive force

0

H

U

2.Masticatory function

0

H

U

3.Pronunciation

0

H

U

28

4.Aesthetics (appearance)

0

H

U

5.Comfort (fit)

0

H

U

6.Repairability (Repair)

0

H

U

0

H

U

8.Periodontal condition

0

H

U

9.Overload

0

H

U

10. Harm (tooth damage, pain)

0

H

U

11.Cost0

HU

7. Durability (prolongation ofabutment teeth, etc.)

Recommendation

Judgment as a whole U【Background and Purpose】
Compared to the mandible, the maxilla tends to have thinner cortical bone, more trabecular bone, andcoarser bone quality. In general, the survival rate of maxillary implants is reported to be lower than thatof mandibular implants. However, there have been no reports comparing the prognosis of
implant-supported MA in the maxilla and mandible. Therefore, we conducted a questionnaire survey
using the Delphi method in order to reach a consensus on the comparison between the maxilla and the
mandible when an implant-supported overdenture is fabricated and MA is applied, based on theopinions of experts.

【Outline】
The overdenture with implants in the edentulous maxilla is expected to improve the maintenancestability of the denture, and it may be possible to fabricate an edentulous palatal denture that does notcover the palatal portion of the maxilla. The advantage of a palatal-free denture is that it is expected to
improve comfort and pronunciation. On the other hand, there is no literature report on the comparison
with implant overdentures in the mandible, so we conducted a questionnaire survey using the Delphi
method. The results showed that there was no difference in the postoperative course of the maxilla andmandible for the 11 outcomes. The convergence of each outcome was high, suggesting that there were nodifferences between the maxillary and mandibular implant overdentures in terms of maintenance,29

masticatory function, phonatory function, esthetics, comfort, responsiveness, durability, health ofsurrounding tissues, burden, harm, and cost.
When asked if they would choose MA as the abutment for a maxillary two implant overdenture, thetwo groups were divided into two groups: those who strongly recommended MA and those who did not.
The two groups were strongly recommended and not recommended to use MA as the abutment for
maxillary overdentures. No clear difference in postoperative course or functional outcome of each
implant system has been reported. Clinically, MA should be applied to cases in which the characteristics
of each attachment can be utilized, depending on factors such as the condition of the jaw crest and thecondition of the appliance. The number of implants in the maxilla tends to be larger than that in themandible when MA is applied to the maxilla. In general, four implants are recommended for theedentulous maxilla. A standardized study on the application of MA for maxillary implant overdenture isneeded in the future.

【Authors】

Shogo Ozawa, Kazumoto Hoshiai, Yoshinobu Tanaka,
Department of Removable Prosthodontics, School of Dentistry, Aichi Gakuin University

CQ4: When applying magnetic MAs to implant-supported overlay dentures, are multiple
abutments with MAs more effective than single abutments?
【Recommended profile】
The application of MAs to multiple implant-over-denture abutments seems to be effective in termsof retentive force.

Outcome
1.Retentive force

Quality of

Evaluation

Delphi method

Evidence(validity, etc.)

evaluation

H

P

P

2.Masticatory functionP

3.PronunciationU

4.Aesthetics (appearance)

U30

5.Comfort (fit)U

6.Repairability (Repair)U

7.Durability(prolongation
abutment teeth, etc.)

ofPP

8.Periodontal condition

U

9.OverloadU

10. Harm (tooth damage, pain)

H

U

U
NN

11.Cost

Judgment as a whole P

Recommendation

Delphi method evaluation

Outcomemediandegree of convergence

recommendation

1.Retentive force

5

H

PP

2.Masticatory function

3

M

P

3.Pronunciation

0

H

U

0

H

U

0

H

U

0

H

U

(prolongation of abutment
teeth, etc.)

3

H

PP

8.Periodontal condition

0

H

U

9.Overload

0

H

U

10. Harm (tooth
damage, pain)

0

H

U

11.Cost-4H

NN

4.Aesthetics(appearance)
5.Comfort (fit)
6.Repairability(Repair)
7.Durability

Recommendation

P【Background and Purpose】
The mandibular implant overdenture is designed to have a minimum number of two implants, allowing

31

for rotational settling of the denture and requiring only maintenance. However, if function and safety
can be ensured, fewer implants are preferable, and the application of a single implant overdenture with
MA has been considered. The purpose of this guideline is to create an index to determine whether or not
the application of MA to multiple implant overdentures is more effective than to single implant
overdentures.
【Outline】
There are no in vivo studies comparing or analyzing the CQ of whether or not the application of MA tomultiple implant overdentures is more effective than to single implant overdentures. All of them were in
vitro studies. In a model experiment using an overdenture with two or one MA applied to a mandibular
anterior abutment, the MA applied to two abutments showed approximately twice the retentive force
compared to a single abutment1). The MA (flat or domed) applied to two or one implant abutment andthe MA (flat or domed) applied to an overdenture showed approximately twice the retentive force when aload was applied to the overdenture. In a study on the lateral force to the implants when a load wasapplied to the overdenture with two or one MA (flat or domed), a larger lateral force was observed with
one implant than with two implants when a unilateral load was applied in the median plane. However,different results were observed depending on the loading point and the type of MA2) .
A questionnaire survey using the Delphi method showed that the MAs were effective in terms ofretentive force, masticatory function, and durability, and that the application of MAs to multiple
abutments was more expensive than to single abutments in terms of treatment cost. The results suggestthat MAs are effective for the maintenance of multiple implant overdentures.
A clinical study comparing patient satisfaction, treatment cost, and treatment time of single and dual
implant overdentures with ball attachments in edentulous mandible patients showed no significant
difference in patient satisfaction between single and dual implant overdentures. No significant
differences were found in patient satisfaction with either one- or two-tooth implants. In addition, it wasreported that treatment costs and treatment time up to one year after surgery were particularly low for
single abutment implants, and maintenance time was the same3). However, clinical evaluation is not
yet complete3). However, clinical evaluation is not sufficient at present, and future clinical studies with ahigh level of scientific support and evidence regarding treatment efficacy and postoperative course areneeded. Clinically, a one-supporting implant overdenture is placed in the midline of the mandible, andthe implant is required to play a maintenance role. It is also important to fabricate a denture with32

minimal movement.

【References】
1) Xiaorong Wang, Chikahiro Ohkubo, Toshio Hosoi, Hidemasa Shimpo, Daisuke Kurihara, Toshiyuki
Murata. Retentive foces of 3 types of attachments for root-retained overdentures. Prosthodont Res
Pract.2007 6:104-82) Maeda Y, Horisaki M, Yagi K. Biomechanical rationale for a single implant-retained mandibular
overdenture: an in vitro study. Clin Oral Implants Res. 2008 Mar19(3):271-5
3) Walton JN, Glick N, Macentee MI. A randomized clinical trial comparing patient satisfaction andprosthetic outcomes with mandibular overdentures retained by one or two implants. Int J
Prosthodont. 2009 Jul-Aug;22(4):331-9【Authors】
Yasunori Suzuki, Chikahiro Okubo
Department of Removable Prosthodontics, Tsurumi University School of Dental Medicine【CQ５】In cases in which individuals have few mandibular teeth, is the application of MAs more
effective than the use of other types of retainers?

【Recommended profile】
MAs application to overdentures with a few remaining teeth may be recommended in terms of denture
maintenance, esthetics, comfort, and overload (weak level of recommendation).

OutcomeQuality of

Evaluation

Delphi method

Evidence(validity, etc.)

evaluation

1.Retentive force

M

P

2.Masticatory function

M

P

4.Aesthetics (appearance)

VL

U

5.Comfort (fit)MP

3.Pronunciation

6.Repairability (Repair)33

7.Durability (prolongation of

VL

U

8.Periodontal condition

VL

U

9.Overload

LU

abutment teeth, etc.)

10. Harm (tooth damage,pain)
11.CostRecommendation

Judgment as a whole P[Background and Purpose]
Currently, clasps are the standard choice of abutment for partial dentures, but the choice of abutment
varies widely, and there are no clear standards for the choice of abutment. The purpose of this guideline
is to establish an index for the effectiveness of MA as an abutment device for overdentures with a few
remaining teeth, compared to other clasp dentures.

[Outline]
There have been no studies that scientifically compared and analyzed the progress of the applicationof MAs to overdentures with a few remaining teeth with other devices. In a photoelastic experiment inwhich six types of maintenance devices (telescopic crown, Gerber system, Dolder bar system, Dalbo
system, MA, and RPI clasp) were used on mandibular bilateral canine teeth, and loads were applied tothe occlusal surfaces of overdentures, the load on the abutment teeth was MA was reported to have thelowest loading on the occlusal surface of the overdenture1).

In an experiment in which studattachments, Locator Root, OP anchors, and MAs were subjected to loading and unloading, the retentive
force of all attachments decreased except for the OP anchor, but the MAs showed only a slight decrease
in retentive force, and the retentive force was the most stable before and after loading2). The MA
showed only a slight decrease in retentive force, and the retentive force was the most stable before andafter loading2). In a model experiment using overdentures, OP anchors, MA, and metal copings were
tested in air and water, and the results showed that the retentive force of OP anchors significantly
decreased in water, while that of MA did not change. MAs have been reported to exhibit the same
retentive force even in the oral cavity3).

34

In a report on the effect of MA on abutment teeth, in a case with one mandibular canine tooth
remaining, stress on the cortical bone under the denture base during occlusion was alleviated bydesigning the upper surface of the keeper root plate to be perpendicular to the tooth axis4), and byincreasing the height of the keeper root plate, the amount of displacement of the labially inclined
abutment tooth was increased. Therefore, it has been reported that the height of the keeper root plateshould be set as low as possible when prosthetic treatment with MA is performed on a tilted residual
tooth5).
In case reports, it has been reported that the use of an MA as an abutment device is esthetically muchbetter than the use of a clasp, and that the use of an MA on an abutment tooth that was not suitable forthe use of a clasp as a denture hook improved the crown-root ratio and was useful in protecting theabutment tooth.6,7) In addition, it was also suggested that the use of an MA on an abutment tooth thatwas not suitable for the use of a clasp as a denture hook improved the crown-root ratio, which was usefulin protecting the abutment tooth 6,7,8,9) .
The above results indicate that MAs are excellent in terms of maintenance and durability because
they are resistant to lateral and rotational forces that are harmful to the abutment teeth and because
the maintenance force is semi-permanent. Clinical reports indicate that MA is also effective in terms ofburden and esthetics.
Based on the above points, it is recommended to make a comprehensive decision by considering theintraoral and abutment tooth conditions, the patient's needs, and the prognosis.

【References】
1) Carlos Labaig, Rafael Marco, Antonio Fons, Eduardo J.Selva：Biodynamics of attachments used inoverdentures: experimental analysis with photoelasticity．Quintessence Int. 1997 8(3):183-90.
2) Vygandas Rutkunas，Hiroshi Mizutani, Hidekazu Takahashi：Evaluation of stable retentive
properties of overdenture attachments．Stomatologija. 2005 7(4):115-20.
3) X.Wang，C.Ohkubo，T.Hosoi，H.Shimpo，D.Kurihara，T.Murata：Retentive Forces of 3 Types ofAttachments for Root-retained Overdentures. Prosthodontic Res. Pract. 2007 6:104-108.
4) Yusuke Katakura, Tetsuo Oyama, Tomohiko Ishigami, Eiichi Nagai, Daisuke Yamanaka, Takuo
Azukibata, Satomi Tadokoro, Yasuhiro Shiraishi: Effect of different inclination angles of the uppersurface of abutment root plate on the surrounding cortical bone in overdenture (in Japanese).
35

Journal of Magnetic Dentistry 2009 18;19-24.
5) Fujimoto T, Ishigami T, Otani K, Oyama T, Sawano M, Takamura M, Mashima A, Katakura Y,
Kurata A, Sakurai H: Effect of keeper root plate height on abutment teeth of overdentures (inJapanese). Journal of Magnetic Dentistry 2006 15;29-34.
6) Kawaguchi H.: Postoperative course of magnetic dentur (in Japanese)e. Journal of Magnetic
Dentistry 2010 19;11-16.
7) Fujinami W, Hoshiai K, Tanaka T, Yamada H, Imaizumi Y, Shigemori T, Ohashi H: A case oflong-term follow-up with magnetic attachments (in Japanese). Journal of Magnetic Dentistry 2005
14;48-52.
8) Furuya A, Kawawa T: A case of maintenance, stability and esthetics of denture by magnetic
attachment (in Japanese). Dentistry Esthetics 2001 13;137-140.
9) R.Tanaka，F.Tsuchida，M.Abe，T.Hosoi，Y.Maeda，K.Sugiyama，Y.Mizuno：Magnetic Attachment
on the Proximal Surface of an Abutment Tooth．JJ Mag Dent. 2004 13;33-37．

【Authors】
Toshihiro Kono, Shogo Tsuda, Shinichi Masumi
Division of Occlusion & Maxillofacial Reconstruction, Kyushu Dental College【CQ６】

In cases involving removable partial dentures with a free-end saddle, is the application of MAs
more effective than the use of other types of retainers?
(In case of Bilateral free end defects with bicuspids or canines as abutment teeth)【Recommended profile】
Application of MA s to free end dentures may be recommended in terms of denture maintenance, esthetics,
comfort, responsiveness, and durability (Weak level of recommendation).

Outcome
1.Retentive force

H

Quality of

Evaluation

Delphi method

Evidence(validity, etc.)

evaluation

P

P

36

2.Masticatory function

H

U

3.Pronunciation

U
U

4.Aesthetics (appearance)

L

P

P

5.Comfort (fit)H

P or UP

6.Repairability (Repair)

L

P

P

M

P

U

8.Periodontal conditionL

U or NU

9.Overload

S，L

P or UU

10. Harm (tooth damage, pain)M

P or UU

11.CostM

NU

7.Durability(prolongationofabutment teeth, etc.)

Recommendation

Judgment as a whole P【Background and Purpose】
Background and Purpose
In partial denture cases, the progress of the abutment tooth determines the success or failure of thedenture, so it is important to diagnose the degree of pretreatment and the type of abutment device to be
applied. Currently, the standard choice is a clasp denture, but the choice depends on the status of theabutment teeth, and no clear criteria have been established for the choice of pretreatment and abutment
appliance. The purpose of this guideline is to establish an index to determine whether or not MA is more
effective than other clasp dentures when applied to the abutment of a loose end denture.
【Outlines】
There have been no studies that scientifically compared and analyzed the progress of the applicationof MA to the abutment of a free end denture with that of other denture systems. However, a 10-year
follow-up study of more than 100 metal-base dentures (84% loose end dentures) with MA applied
showed that the survival rate of the abutment teeth was 95% at 5 years and 88% at 10 years, which wascomparable to that of conus dentures reported by others and better than that of clasp dentures1-4). In
addition, an RCT comparing three types of bilateral canine-supported overdentures (MA, root face plate,and edentulous) and analyzing the stability of the denture, masticatory efficiency, and patientsatisfaction showed no significant differences among the three, suggesting that the stability of thedenture itself is more influential than the device5).
37In a Delphi survey conducted by our society among experts, the results converged on the view that
denture maintenance, esthetics, comfort, and responsiveness (e.g., repair) were effective. However, there
are many negative opinions about the course of periodontal tissues, and literature shows an increasing
trend in pocket depth1-5).
The application of MA to free end dentures improves the crown-root ratio and reduces the anchorage
point, thereby reducing tooth movement, extending the life (durability) of the abutment teeth, andstabilizing the denture. In addition, with the improvement of industrial technology, the closed circuit of
MA has low attenuation of magnetic force, stable long-term retentive force, excellent esthetics because of
its small size and fit within the prosthesis, and good fit and comfort when worn. Furthermore, it can beeasily repaired in the event of breakage, and is judged to be highly adaptable.
On the other hand, MA is applied in the form of an overdenture, so the cleanability of the abutment
teeth is poor, and periodic cleaning instructions are required.
Clinically, it is most frequently applied to bicuspids and canines adjacent to defects1). Therefore, clasp
dentures are often applied to sound teeth unless there is concern about bone implantation or significant
discordance in crown morphology, and MA is considered to be difficult to apply.
If the abutment tooth requires root canal treatment or crown restoration, the choice is between crownrestoration and clasp denture or MA with a root faceplate, and the choice is equal in each case. In thecase of gingival recession, imbalance of crown-root ratio, unstable occlusion, strong occlusal force, andfixed connection of the opposing dentition, it is desirable to apply MA because denture movement andoverload of the abutment teeth are expected. However, in cases of tooth movement and poor periodontal
tissues, MA is not applicable because the condition is aggravated by the application of MA.
In addition, a crown with an extra-dental crown attached to the crown is also recommended for crownrestorations.
Based on the above points, it is recommended that a comprehensive judgment be made by taking into
consideration the status of the abutment teeth and oral cavity (abutment teeth, periodontal tissues,
occlusal condition, etc.), the patient's needs, psychological aspects, physical and social background, andother factors.
【References】
1) Kazumoto Hoshiai, Takanobu Tanaka, Nobuhiro Hasegawa, Masako Kawakita, Wakako Fujinami,
Koichiro Wakayama, Tatsuya Hikosaka, Hideaki Hirai, Toshikiyo Miyata, Koichi Kumano andMizuki Sakane. Postoperative survey of magnetic attachments in metal dentures t (in Japanese).
Journal of Magnetic Dentistry. 2004; 13(1): 1-8.
2) Ito R, Hoshiai K, Tanaka Y, Ishigami T, Ishibashi T, Bando E, Sasaki H. Longitudial Study ofMagnetic Attachments -Investigation ob Probing Depth on Abutment teeth-. J J Mag Dent. 2010;
19(2): 35-39.
3) Shigemori T, Hoshiai K, Watanabe K, Ito R, Kawaguchi T, Yokoyama T, Miwata M, Kimura N,
Tanaka Y. Longitudial Study of Magnetic Attachments -Characteristic of Long-term Success Cases-.
JJ Mag Dent. 2010; 19(2): 40-43.
4) Hoshiai K, Tanaka Y, Hasegawa N, Kawakita M, Fujinami W, Wakayama K, Imaizumi Y,
38

Matumoto T, Sakane M. Longitudial Study of Metal Plate Denture with Magnetic Attachments．JJ
Mag Dent. 2004; 13(2): 26-29.
Jonkman RE, van Waas MA, van ‘t Hof MA, Kalk W. An analysis of satisfaction with complete
immediate (over) Denture. J Dent. 1997 Mar;25(2):107-111.
Mizutani A, Nakamura K, Ai M. A Follow-up Study of Dentures with Magnetic Attachments Usinga Surgeon's Questionnaire (in Japanese). Journal of the Japan Prosthodontic Society. 1997;
41:902-909.
Nakamura Y, Nakamura H, Maruyama C, Ochiai KT, Tanaka Y, Caputo AA. Comparison of Lord
Transmission by Removable Partial Dentures with Magnetic Attachments, JJ Mag Dent. 2006;
15(2): 22-27.
Ando, A., Nakamura, Y., Kambara, R., Ohno, Y., Tanaka, T. Stress Analysis of Extracoronal
Magnetic Attachment Periapical Tissue by Three-Dimensional Finite Element Method. Journal ofMagnetic Dentistry. 2009 Sep; 18(1): 32-41.
Ohno Y, Kanbara R, Nakamura Y, Shoji K, Kumano H, Yoshihara K, Ando A, Iwai T, Takada Y,
Tanaka Y. Mechanical Analysis of Unilateral Extension Partial Denture Design. JJ Mag Dent.
2010; 19(2): 56-61

5)
6)

7)

8)

9)

【Authors】
Masayuki Hideshima1, Junchiro Wada2
1

Clinic for Sleep Disorders (Apnea and Snoring) , University Hospital, Tokyo Medical and Dental University
Department of Prosthodontics, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental

2

University

CQ7：In case of partially edentulous patients without occlusal contact, are MAs superior to othertype of retainers?
(In case of a horizontal crossbite with only one molar remaining on each side of the upper and lower jaws,
or a bicuspid or premolar adjacent to the defect as abutment.)【Recommended profile】
The application of MAs to cases of misaligned occlusion may be recommended in terms of themaintenance of the prosthetic device, masticatory function, esthetics, comfort, responsiveness,durability, and periodontal health in terms of prognostic outcomes (Weak level recommendation).

Outcome
1.Retentive force

Delphi method evaluation（38 persons）
degree ofrecommendation
medianconvergence
3

M

P

39

2.Masticatory function

3

M

P

3.Pronunciation

0

M

Ｕ

4.Aesthetics (appearance)

4

M

P

5.Comfort (fit)

3

M

P

6.Repairability (Repair)

3

M

P

7.Durability (prolongation of abutment teeth, etc.)

3

M

P

8.Periodontal condition

2

M

P

9.Overload

0

M

Ｕ

10. Harm (tooth damage, pain)

0

M

Ｕ

11.Cost0

M

Ｕ

Recommendation

Judgment as a whole P【Background and Purpose】
In cases of misaligned occlusion, it is often necessary to improve the occlusal plane and crown-root ratio
due to the protrusion and movement of the remaining teeth. In addition, the denture cannot avoid
sinking due to the deficiency of the bite, and the jaw position supported by the denture becomes unstable.
The "magnetic attachment" is essentially a root-supporting appliance in the form of a root-supporting
surface attachment that has a non-grasping retentive force based on the attractive force of a magnet,
and can improve the crown-root ratio and reduce lateral forces. Furthermore, it can be applied totelescopic crowns as typified by the "Magno-telescopic crown", to extra-canonical attachments, and canbe used in combination with other abutment devices, making it possible to design a "rigid support".
A literature search on "magnetic attachments" and "crossbite" revealed a few case reports in theliterature and at academic conferences, but no useful case reports on long-term outcomes were found.
Therefore, we conducted a questionnaire survey using the Delphi method. The results obtained from theDelphi method concluded that the application of magnetic attachments to patients with misaligned bites
is recommended in terms of the maintenance of prosthetic appliances, masticatory function, esthetics,
comfort, responsiveness, durability, and periodontal tissue health in terms of postoperative course.
In addition to this conclusion, considering the diversified forms of abutment devices using magnetic
attachments and the fact that magnetic attachments can be used as abutment devices for implants as40

well as natural teeth, it is recommended that magnetic attachments be used in cases of misaligned
occlusion after a comprehensive examination and diagnosis of the oral and maxillofacial functions andperiodontal tissue conditions. The application of magnetic attachments to cases of misaligned occlusion
should be determined based on a comprehensive examination and diagnosis of the jaw and oral
functions and the periodontal tissues.

【Authors】
Division of Removable Proshodontics Department of Restorative and Biomaterials Sciences, Meikai
University School of Dentistry
Shuji Okawa , Mineyo Sone

CQ8：In cases of partially edentulous with undulating occlusal planes, is the application of MAs

more effective than the use of other types of retainers?
(In case of a composite defect of the maxillary free end and middle, with an erupted premolar or anterior
tooth as abutment.)【Recommended profile】
In cases with a disturbed occlusal plane, occlusal reconstruction with the application of MAs is more effective thanwith annular or bar clasps.

OutcomeDelphi method evaluation（38 persons）
degree ofrecommendation
medianconvergence

1.Retentive force

1

M

U

2.Masticatory function

1

M

U

3.Pronunciation

1

M

U

4.Aesthetics (appearance)

3

M

P

5.Comfort (fit)

2

M

P

6.Repairability (Repair)

2

M

P

7.Durability (prolongation of abutment teeth, etc.)

1

M

U

41

8.Periodontal condition

1

M

U

9.Overload

0

M

U

10. Harm (tooth damage, pain)

0

M

U

11.Cost-1

M

U

Recommendation

Judgment as a whole P【Background and Objective】
When performing occlusal reconstruction for cases with a disturbed occlusal plane, there are several
choices of abutment devices, such as annular clasps, bar clasps, intracoronal attachments, extracoronalattachments, root attachments, bar attachments, telescopic crowns (cylinder and conus type), and so on.
However, there are no clear criteria for their selection. Therefore, the purpose of this study was todevelop an index for "whether occlusal reconstruction using MA is more effective than other systems incases with a disturbed occlusal plane". A questionnaire survey using the Delphi method was conducted
to reach a consensus based on the opinions of experts.
【Outline】
The CQ question of whether occlusal reconstruction using MA is more effective than other devices incases with a disturbed occlusal plane was again answered by a literature search, but as in the previous
study, no in vivo comparison or analysis could be found. All of the articles on occlusal reconstruction
were case reports on the application of implant overdenture, and their contents did not seem to beconsistent with this CQ. In light of the above, we reexamined the results of the Delphi method based on
the results of the previous study.
The case with a disturbed occlusal plane was defined as "a case of a maxillary free end-medialcomposite defect with an erupted premolar or premolar as the abutment tooth.
In two surveys using the Delphi method, it was judged that occlusal reconstruction using MA could berecommended from the viewpoints of esthetics, comfort, and responsiveness. The results of the
prognostic analysis for each abutment device showed that MAs had a better prognosis compared toannular and bar clasps. Therefore, it was judged that MAs could be recommended in comparison withclasps. When compared to other abutment devices, the condition of the abutment teeth and the crest of
the missing tooth greatly affected the postoperative course, and the results were undecided (cannot
judge). However, since there were few cases in which the prognosis was worse with MAs than with
non-clasp abutment devices, we judged that the choice of MAs was unlikely to worsen the postoperative
course of the patients.
However, when considered as a whole, at present, there is a lack of evidence to determine whether or
not occlusal reconstruction with the application of MA is more effective than other devices in cases with42

a disturbed occlusal plane, and many comparative studies and reports are desirable for future revisionsof the guidelines.

【Authors】
Hideki Aita1, Mai Kono2
1 Division of Gerodontics, Department of Biological Functions, Health Sciences University of Hokkaido

School of Dentistry
2Department of Dental Hygiene, Faculty of Health Science, Chiba Prefectural University of Health

Sciences

CQ9：When periodontal disease is affecting remaining abutments, is the application of MAs

superior to the use of other types of retainers?
（In case of the periodontal condition of the abutment tooth adjacent to the defect is P1 or P2
in a case of bilateral free end defects in the mandible.）【Recommended profile】
The application of MAs on abutment teeth with early periodontal disease is not well documented,
but it is highly regarded. The Delphi technique received generally good evaluations, except for cost,
and the overall recommendation was judged to be P.

OutcomeQuality of

Evaluation

Delphi method

Evidence(validity, etc.)

evaluation

1.Retentive force

PP

2.Masticatory functionP

3.Pronunciation

P

4.Aesthetics(appearance)

PP

5.Comfort (fit)P

6.Repairability (Repair)P

7.Durability(prolongation of abutment
teeth, etc.)

M

PP

PP

8.Periodontal condition

M

P

P

43

U

9.Overload
10. Harm (tooth
damage, pain)
11.Cost

M

P

U

M

PP

N

Judgment as a whole

Recommendation

P

Delphi method evaluation
degree ofrecommendation
convergence

Outcomemedian1.Retentive force

２

M

P

３

M

P

２

M

P

３

M

P

３

H

PP

２

L

U

２

M

P

２

M

P

-１

M

U

-１

M

U

-１

L

U

2.Masticatory
function
3.Pronunciation
4.Aesthetics(appearance)
5.Comfort (fit)
6.Repairability(Repair)
7.Durability(prolongationofabutment
teeth,
etc.)

8.Periodontal
condition
9.Overload
10. Harm (tooth
damage, pain)
11.CostRecommendation

Judgment as a whole P

44

【Background and Purpose】
When selecting an abutment tooth for a partial denture, it is necessary to confirm whether theremaining tooth is affected by periodontal disease. The purpose of this study is to develop an index toevaluate the usefulness of MA compared to other abutment systems when used with early-stage
periodontium.

【Outline】
The problem was to define the extent of periodontal disease and the nature of the condition. In fact, inthe first Delphi survey, the evaluators had different views on this issue, suggesting the need to unify
their views. Therefore, in the second survey, "Periodontal disease of the abutment tooth adjacent to thedefect in cases of bilateral mandibular free end defects was defined as P1 or P2" was added to the survey.
As a result, it was possible to investigate the effectiveness of MA for the abutment teeth with early
periodontal disease. The quality of the evidence was moderate.
Only a few case reports were found in the literature for the application to abutment teeth withperiodontal disease. The MAs were applied to cases in which long-term survival was difficult, and theMAs were used effectively as abutments for partial dentures with good postoperative outcomes,suggesting that the MA-applied abutments were sufficiently durable. The literature shows that the
cumulative survival of the abutment teeth is not significant. The literature shows that the cumulative
survival of the abutment teeth is comparable to that of the conus abutment teeth, which does notsuggest that MA harms the periodontal tissues. Although there is no literature available on the outcomeof periodontal tissue damage, the results of long-term postoperative case reports suggest that theapplication of MAs does not appear to cause damage to the abutment teeth.
If we believe that any abutment should not be applied to abutment teeth with periodontal disease, itwould be incompatible with the title of the CQ, and the effectiveness of MAs would not be evaluated.
However, there are a few reports of good clinical results obtained using MA in cases with advanced
periodontal disease and difficulty, so we judged that there is room to evaluate the effectiveness of MA.
Based on the results of the above literature and the evaluation of the Delphi method, we judged therecommendation to be P (weak recommendation).

【References】
45

・ N.Hasegawa, K.Hoshiai, Y.Tanaka et.al: Two case reports on Magnetic Attachments for patientwith severe periodontitis. JJ Mag Dent 13, 30-32, 2004.

【Authors】

Shogo Ozawa, Kazumoto Hoshiai, Yoshinobu Tanaka
Department of Removable Prosthodontics, School of Dentistry, Aichi Gakuin University

CQ10：When applying MAs to multiple abutment teeth, are symmetrical arrangem

ents more effective than asymmetrical ones?

【Recommended profile】
Symmetrical placement of abutment teeth for overdentures is recommended over asymmetricalplacement.

OutcomeQuality of

Evaluation

Delphi method

Evidence(validity, etc.)

evaluation

1.Retentive force

PP

2.Masticatory function

PP

3.PronunciationU

4.Aesthetics (appearance)U

5.Comfort (fit)U

6.Repairability (Repair)U

7.Durability (prolongation ofabutment teeth, etc.)

L

U

U

8.Periodontal condition

U

9.OverloadU

10. Harm (tooth damage,
pain)

U

46

11.Cost

U
Judgment as a whole P

Recommendation

Delphi method evaluation
degreeofrecommendation median
medianconvergence
1.Retentive force

３

M

P

2.Masticatory
function

３M

P

3.Pronunciation

０

M

U

4.Aesthetics(appearance)

０

M

U

5.Comfort (fit)

０

M

U

6.Repairability(Repair)

０

M

U

０

M

U

8.Periodontal
condition

０M

U

9.Overload

０

H

U

10. Harm (tooth
damage, pain)

０

H

U

11.Cost０

HU

7.Durability(prolongationofabutment teeth, etc.)

Recommendation

Judgment as a whole P【Background and Objectives】
The placement of abutment teeth in full-arch overdentures is strongly influenced by the patient's own
oral situation. However, it is unclear whether symmetrical or asymmetrical placement of abutment
teeth has any effect on prognosis. The purpose of this study is to develop treatment guidelines underthese circumstances.
【Outline】
There have been no in vivo studies comparing or analyzing the CQ of whether symmetrical abutment
placement is more effective than asymmetrical placement in full-arch overdentures. However, some47

clinical reports on various overdentures mention the placement of the abutment teeth. Although some ofthese studies can be read as showing symmetry, the level of evidence is low because of the difficulty of
randomization due to the nature of the studies, and because the studies do not focus on symmetry andtherefore cannot discuss causal relationships such as the incidence of caries in the abutment teeth.
Many of the studies were not able to discuss the causal relationship, such as the study of caries
incidence in the abutment teeth, because symmetry was not the main focus of the studies. However,since it is impossible to select the placement of remaining teeth in future studies by RCTs, it is expected
to be necessary to conduct studies in a way that does not rely on the level of evidence in the papers.
In the model experiment, there are few papers focusing on symmetry, but Miyashita's paper, which
was extracted by hand-search, discussed the symmetry of the stud-type attachment placed on themandibular canine and the displacement of the denture base under load, and the difference indisplacement under lateral loading of the denture between different designs is considered to be due tothe form of the stud-type attachment. The differences in the displacement of dentures under lateralloading are attributed to the shape of the stud type attachments.
The Delphi questionnaire survey showed very few values less than 0, so it can be said that there were
only a few opinions denying the validity of symmetrical placement. However, since many items had ascore of 0, the opinions that acknowledged the superiority of symmetry were concentrated in items suchas maintenance and mastication.
In this study, there were no literatures that reported the direct influence of MA on this CQ.
Based on the above points, there were few negative opinions about symmetry as a clinical realization,and many items were considered to be superior, and therefore, clinically, symmetrical placement is
considered to be preferable. However, there are no clinical reports with a high level of evidence anddirectness, nor are there any reports of model experiments focusing on symmetry. Based on the above
considerations, we do not strongly recommend the use of tooth autografting, for example, to ensure
symmetry.
【References】
1. Miyashita, Y., Shimamura, I., Kishi, M.: An experimental study on the influence of the placement
condition of abutment on the displacement of denture in an anchored overlay denture (in Japanese).
Dental Journal 98,1189-1219,1998.

【Authors】
Tetsuo Oyama, Yoshitada Umekawa, Tomohiko Ishigami
Department of Partial Denture Prosthodontics, Nihon University School of Dentistry48

Q11：When applying MAs to remaining abutment teeth, are flat type keepers more effective thandome-shaped keepers for stability of the denture?

【Recommended profile】
The flat type is recommended over the dome type depending on the number of abutments and loading points.

OutcomeQuality of

Evaluation

Delphi method

Evidence(validity, etc.)

evaluation

H

P

1.Retentive force
2.Masticatory function
3.Pronunciation
4.Aesthetics (appearance)
5.Comfort (fit)
6.Repairability (Repair)
7.Durability (prolongation ofabutment teeth, etc.)
8.Periodontal condition
9.Overload
10. Harm (tooth damage, pain)
11.CostRecommendation

Judgment as a whole P【Background and Purpose】
The root face plate (top face) of magnetic attachments can be flat, domed, or inverted-domed. However,there are no clear standards for their selection. The purpose of this guideline is to establish an index todetermine whether a flat or a dome-shaped magnetic attachment is more effective in overdentures.

【Outline】
There are no human studies that have compared and analyzed the CQ of whether a flat or adome-shaped magnetic attachment is more effective in overdentures. The results of these studies were49all in vitro, and all of them were model experiments of a full denture overdenture with two implants
placed in the mandibular anterior region or one implant in the median region. The domed type showedsmaller values than the flat type when unilateral loading was applied to the first molar1), but the
opposite was true when loading was applied to the median mandibular anterior tooth, i.e., the flat typeshowed smaller values than the domed type2). In terms of the load on the crest, it was reported that
there was no significant difference between the two when unilateral loading was applied3). On theother hand, when bilateral loading was applied, the stress distribution on the crest of the domed denture
was greater than that of the flat denture in the photoelastic stress analysis4). The three-dimensional
displacement of the denture during loading was reported to be smaller for the domed denture than for
the flat denture2). In other words, when the loading point is set at the first molar, the domed type isconsidered to be more effective in terms of reducing the lateral force on the implant and the amount ofdenture displacement.
Next, regarding the lateral force on the implant in an overdenture using a single implant as theabutment, it was reported that the domed type showed smaller values than the flat type when unilateralloading was applied to the median and cusp, and vice versa when loading was applied to the firstmolar2).
The displacement of the domed denture was smaller than that of the flat denture, but there was no
statistically significant difference between the domed and flat dentures. In other words, when theloading point is set at the first molar, the flat type is considered to be more effective in terms of reducing
the lateral force on the implant body.
There are no epidemiological studies in the references for this CQ, and all of them are modelexperiments. In the field of prosthodontics, model experiments with high reproducibility andengineering techniques are considered to be reliable methods and can be used as evidence. However, it
should be noted that the experimental conditions in the literature differ. In other words, when modelexperiments are incorporated in the development of guidelines, the experimental conditions must be
properly understood and interpreted.

【References】
1)

Tomoya Gonda, Zongjie Yang, Toshi Takahashi, Masahiro Wada, Yoshinobu Maeda: Functional
characteristics of maintenance devices for implant overdentures: A comparison of magnetic
50

attachments, anchors and stud-type attachments, Journal of the Japanese Society of Oral
Implantology, 22(1): 15-20, 2009.
2)

Maeda Y, Horisaka M, Yagi K: Biomechanical rationale for a single implant-retained mandibular
overdenture: an in vitro study, Clin Oral Implants Res, 19(3): 271-75, 2008.

3)

GotoTakaharu, Nagao Kan, IchikawaTetsuo: Effects of Magnetic Attachment Form on Load Transfer to Abutmentsof Implant Overdenture, Journal of the Japanese Society of Magnetic Dentistry，17(1): 24-29, 2008.

4)

Hojo Satoru, OchiaiKent T, SadowskySteven S, ToyodaMinoru, CaputoAngelo: A Load Transfer by Magnetic andResilient Attachments for Mandibular Implant Overdentures, The Bulletin of Kanagawa Dental College, 32(1):15-19, 2004.

【Authors】
Takaharu Goto, Yuichi Ishida, Kan Nagao, Tetsuo Ichikawa

Department of Removable Prosthodontics, Tokushima University Graduate School of Biomedical
Sciences

CQ12：When applying MAs to removable partial dentures, is the applied pressure method superior
to minimum pressure ones?
(In cases with a small number of remaining maxillary teeth, the abutment should be one or
two premolars or bicuspids.)【Recommended profile】
Since the attachment of MAs (or magnetic structures) to dentures without pressure has aslightly negative effect on the life of the abutment and denture and on periodontal disease
and dental caries of the abutment teeth, it may be recommended that MAs be attachedunder pressurized conditions.

Outcome
1.Retentive force

Delphi method evaluation（38 persons）
degree ofrecommendation
medianconvergence
-2

L

Ｕ

51

2.Masticatory function

0

L

Ｕ

3.Pronunciation

0

H

Ｕ

4.Aesthetics (appearance)

0

M

Ｕ

5.Comfort (fit)

0

H

Ｕ

6.Repairability (Repair)

0

M

Ｕ

7.Durability (prolongation of abutment teeth, etc.)

-2

M

Ｎ

8.Periodontal condition

-2

M

Ｎ

9.Overload

0

H

Ｕ

10. Harm (tooth damage, pain)

0

H

Ｕ

11.Cost0

M

Ｕ

Recommendation

Judgment as a whole Ｎ【Background and Purpose]
Teeth and mucous membranes differ greatly in the amount of pressure displacement. It is easy to
imagine that the force applied to the abutment teeth during function can vary greatly depending onwhether the patient is allowed to occlude the denture when attaching the magnet to the denture orwhether the magnet is attached without occlusion. However, there are no reports on the effects ofmagnet attachment methods on dentures (maintenance, function, esthetics) and abutment teeth (loadbearing, periodontal tissue). Therefore, a questionnaire survey using the Delphi method was conductedwith the aim of forming a consensus on the attachment method of magnets based on the opinions ofexperts.

【Outline]
When magnets were attached to dentures without pressure, "Disagreement (negative weakagreement)" was obtained for the questions, "It is effective for durability (extension of abutment anddenture life, periodontal disease and dental caries)" and "It is effective for periodontal tissue health".
The results suggest that the use of no-pressure adhesion has a slightly negative effect on the durability
and health of periodontal tissues.
The experts' answers were highly convergent to "neither" for "phonetic function," "comfort," "burden on52

the patient and surgeon," and "harm. In other words, the results suggest that no matter how themagnets are attached, there is no effect on the pronunciation function, wearing comfort and discomfort,
physical and time burden on the patient and surgeon, or pain.
Because of the lack of evidence in this study, a questionnaire survey using the Delphi method was
conducted, but no strong recommendation (agreement) was obtained. The opinions converged on theopinion that it would be better to adhere the magnets to the denture under pressure, but it is not knownat all how much force to apply. Furthermore, when magnets are attached to dentures, the amount ofpressure impression that was made before the denture was fabricated must also be taken into
consideration. It is hoped that high quality evidence will be reported by the time the guidelines arerevised in a few years.

【Authors】
Kan Nagao, Takaharu Goto, Yuichi Ishida, Tetsuo Ichikawa
Department of Removable Prosthodontics, Tokushima University Graduate School of
Biomedical Sciences

CQ (IP) 13: When performing MRI studies in MA-eligible cases, is the spin-echo method lessartifactful?

(IP：Interventional Procedure)【Recommendation profile】
The spin echo (SE) method has less artifacts than the gradient echo (GRE) method when MRI is
performed in MA-eligible cases (weak level of recommendation).

OutcomeQuality of
Evidence

Evaluation(validity, etc.)

Delphi method
evaluation

1.Retentive force
2.Masticatory function
3.Pronunciation
4.Aesthetics (appearance)
53

5.Comfort (fit)
6.Repairability (Repair)
7.Durability (prolongation ofabutment teeth, etc.)

8.Periodontal condition
9.Overload
10. Harm (tooth damage,
pain)

M

P

11.CostRecommendation

Judgment as a whole P【Background and Purpose]
Magnetic attachments may cause large metal artifacts in MRI examinations. The purpose of thisguideline is to create an index to determine whether differences in imaging methods affect the reading
method when magnetic attachments are used in MRI examinations.

【Outline]
The magnetic attachment keepers have significantly different magnetic susceptibility from that of aliving body, causing artifacts such as distortion and loss of signal in MR images. There are many factorsthat affect the size of artifacts, and it is impossible to quantify the size of artifacts. To minimize the effectof artifacts, a sequence with a wide frequency range per pixel should be selected for the SE method, andin addition, an imaging method with a short echo time (TE) should be selected for the GRE method. If
the BW setting is not available due to the type of equipment, it can be changed in conjunction withchanging the TE. However, these settings reduce the SNR of the image and have a limited effect on the
reduction of artifacts. Therefore, if the area to be diagnosed by MRI or the selected imaging method isstrongly affected by the magnetic susceptibility, reading becomes difficult, and the keeper needs to be
removed in the dental office.

【References】
1) Florentina T. IIMURO. Magnetic Resonance Imaging Artifacts and the Magnetic Attachment System.
Dental Materials Journal 13(1):76-88,1994.

54

2) T. Tuchihashi, T. Maki, K. Suzuki, and I. Fujita. On metal artifact in SE method -Relationshipbetween various parameters and metal artifact-. Journal of the Japanese Society of RadiologicalTechnology 53:798-805,1997.
3) Fumihiro Masaki, Munetaka Naito, Tomohiko Ishigami, Noriyuki Miyao, Masayuki Hayashi,
Takanobu Tanaka, Eiichiro Arichi. Influence of Keeper Morphology of Magnetic Attachments on MR
Images. Dental Radiology 37:156-163,1997.
4) Tuchihashi, T, Fujita Isao, Maki T, Kitagawa M, Suzuki K. Influence of magnetic dental attachmentson MR images.

【Authors】
Yasunori Suzuki, Ryota Maruo, Chikahiro Okubo
Department of Removable Prosthodontics, Tsurumi University School of Dental Medicine

55

VI. Conclusion
We reported on the history of the development and revision of the medical practice guideline and theoutline of international standardization that the JSME has been working on.
Magnetic attachments were approved as a medical device by the Ministry of Health, Labour andWelfare in 1990. Since then, improvements have been made in industry-academia collaboration to
improve the retention force, miniaturization, durability, and biocompatibility, and the Japanesestandard was approved for international standardization as ISO 13017 in 2012. ISO 13017:2012/Amd.1(a supplement to ISO 13017), which includes standards for the measurement of maintenance force, waspublished in 2015, and the ISO task force committee is currently working to integrate the twointernational standards.
The protocol has been modified since 2015, and new multi-center investigations are being conducted
while continuing the existing investigations. The protocol has been modified since 2015, and a new
multicenter study is underway while the existing study continues.
The Medical Committee began formulating the guidelines in 2009, and conducted a wide-ranging
questionnaire survey of members. In addition, oral presentations and symposiums were planned at theannual meeting, and the practice guideline was disseminated to the members, achieving a certain levelof success. However, many CQs were difficult to collect evidence for when formulating the practiceguideline, and we realized that it was too early to formulate the practice guideline and that there weremany issues to be addressed, requiring supplementary surveys of clinical specialists using the Delphi
method, etc. In 2014, the 2013 edition of the practice guideline for magnetic attachments was publishedin the Practice Guideline Library of the Japanese Dental Association. In 2014, the 2013 edition of thepractice guidelines for magnetic attachments was published in the practice guideline library of theJapanese Association of Dental Surgeons.
This time, we conducted a literature search again for the 12 CQs selected five years ago, revised theoutline, recommendations, and other content, and added one CQ on MRI to the "Practice Guidelines for
Magnetic Attachments 2018," but further revisions and additions are necessary as the society continues
to conduct related research.
Dental magnetic attachments are clinically excellent in operability, durability, and corrosion resistance,and have good long-term outcomes. The Society has taken a cautious approach to the introduction of
insurance coverage, since there have been two sides to the issue, but the time has come to consider
advanced medical treatment, selected medical treatments, insurance coverage, etc. We hope that this56

report will be of some help in this regard.
We would like to express our deepest gratitude to the members of the Society and all those involved indental care, including the various committees, for their cooperation to date, and we sincerely hope for
their further support and guidance.
March, 1991
Acknowledgments
The authors would like to express their deepest gratitude to all those involved in the development andrevision of this report and the practice guideline. This report was supported by the "Research and Study
for Clinical Evaluation of Magnetic Dental Attachments and Establishment (Update) of Clinical Practice
Guidelines" (JDSF-DSP1-2018-212-1), a project of the Japanese Federation of Dental Societies.

57