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Abstracts of the 19th International Conference on Magnetic Applications in Dentistry

February 28 to March 17, 2020

Session 1

Chair: Yukyo Takada (Tohoku University)


#1. Attractive force of magnets and magnetic fields — Strength and range of impact by the attractive force of magnets

○Hirofumi Yamaguchi1,2, Masatoshi Takahashi2, Genichi Togawa2, Yukyo Takada2

1 Division of Advanced Prosthetic Dentistry, Tohoku University Graduate School of Dentistry

2 Division of Dental Biomaterials, Tohoku University Graduate School of Dentistry


Most of the dental magnetic attachments used in Japan utilize a closed magnetic circuit. They show very good retentive force for their small size. However, some magnetic attachments used in other countries utilize an open magnetic circuit. In this study, we investigated the attractive force of magnets and the range of impact exhibited by the magnetic fields. Cylindrical neodymium and ferrite magnets were set up in various combinations. The keeper was made of SUS XM27 stainless steel. Attractive force was measured using a measuring device that matched ISO 13017. The pattern of magnetic fields formed was observed using iron powder. In combinations that involved one type of magnet, the attractive force and range of impact by the magnetic fields increased as the number of magnets increases possibly due to a decrease in demagnetizing fields. Combinations that involved different kinds of magnets; the magnet in contact with the keeper had the greatest influence on attractive force. The range of impact by magnetic fields did not change remarkably with the combination of magnets made of different materials. It is possible to control the range of magnetic fields without altering the attractive force by combining different kinds of magnets.


#2. Influence of magnetic attachment for implant on MRI scan

Maruo R,Imaizumi N,Muto R,Suzuki Y,Ohkubo C

Depart of Removable Prosthodontics,Tsurumi University School of Dental Medicine



In recent years, due to advances in medical technology, MRI have been frequently used. Along with this, it has been considered that metal artifacts during MRI imaging affect diagnosis. In This time, influence of the magnetic attachment for implants will be discussed.

【Materials and Methods】

Magnetic attachments for implants (Magfit MIP, Magfit IP), cast keeper, and healing abutment were used as samples. Each sample was placed in an acrylic container (150 mm x 150 mm x 150 mm), and filled with an aqueous solution of nickel nitrate using an acrylic jig. Four types of imaging methods were used: spin echo, F spin echo, STIR, and gradient ecoh. The images obtained by shooting were adjusted with ImageJ (NIH) and the area of ​​the artifact was compared.

【Results, Discussion】

The magnetic attachments for implants showed obviously artifacts in all imaging methods, but there were little artifacts in healing abutments. The gradient ecoh method produced the largest artifact among the different imaging methods. The size of the artifact of Magfit IP was larger than for Magfit MIP. The diameters of the artifact were about 15 to 20 mm for Magfit IP and approximately 15 mm for Magfit MIP.


#3. Effect of keeper after MRI irradiation on attractive force

Shin-ichi Masumi1, Eri Makihara1, Hiroshi Ikeda2, Hiroshi Shimizu2, Masafumi Oda3, Yasuhiro Morimoto3, Takafumi Watanabe1, Shogo Tsuda1, Mayumi Yagi1, Masahiro Arita1, Takumi Masumi1 and Akira Kikuchi4

1 Division of Occlusion & Maxillofacial Reconstruction, Department of Oral Function, Kyushu Dental University

2 Division of Biomaterials, Department of Oral Functions, Kyushu Dental University

3 Division of Oral and Maxillofacial Radiology, Department of Science of Physical Function, Kyushu Dental University

4 NEOMAX Engineering


The purpose of this study was to evaluate the attractive force of the dental magnetic attachment before and after MRI irradiation against the keeper.

Duplicate the lower non-magnetic table of the ISO tensile test jig with an immediate polymerization resin, and then attaching the magnetic assembly to the upper non-magnetic table of the jig and each keeper to the lower duplicated resin table. The attractive force before irradiation was measured with a universal tensile tester. Next, a resin-made table with a keeper was placed in a mold that assumed the upper and lower incisors, premolars, and molars, and the attractive force was measured after MRI irradiation for about 16 minutes.

There was no significant difference in the suction force before and after irradiation, and it was found that there was no problem with the attractive force even if MRI irradiation was performed for the patient with keeper.

Session 2

Chair: Chikahiro Ohkubo (Tsurumi University)


#4. Patient Reported Outcome of immediate loaded mandibular 2-implant overdentures retained by magnetic attachments: 3 years follow-up

Y. Uehara1, M. Kanazawa1, A. Miyayasu1, R. Shimada1, M. Negoro1, D. Sato2, S. Minakuchi1

1 Gerodontology and Oral Rehabilitation, Graduate school of Medical and Dental Science, Tokyo Medical and Dental University

2 Oral Implantology and Regenerative Dental Medicine, Graduate school of Medical and Dental Science, Tokyo Medical and Dental University



There is much evidence about immediate loading of mandibular implant overdenture. But the long-term prognosis of immediate loading is lacking. This study aimed to evaluate the patient-reported outcomes of immediate and conventional loaded mandibular 2-implant overdentures retained by magnetic attachments.


Nineteen patients with edentulous mandibles were enrolled in this study. Patients were randomly divided into the immediate loading group (IL group) and the conventional loading group (CL group). The keepers of the magnet attachments were connected to the implants on the day of implant surgery for IL group, while for CL group, keepers are connected in 3 months. OHRQoL was evaluated by the Japanese version of the Oral Health Impact Profile for edentulous subjects (OHIP-EDENT-J), and 100 mm VAS was used to measure satisfaction ratings.


Patient satisfaction tended to be high in both groups from the early stage of implant placement.

The improvement of OHIP only showed in IL group up to the first 3 months after implant surgery, and in both groups after 6 months.

Three years after implant placement, patient-reported outcomes were suggested to be maintained at high levels in both groups.


#5. Comparison of masticatory performances between immediately loaded and conventionally loaded mandibular two-implant overdentures with magnetic attachments

Watanabe M1, Kanazawa M1, Miyayasu A1, Shimada R1,Negoro M1,Uehara Y1, Sato D2 , Sato Y1, Minakuchi S1

Gerodontology and Oral Rehabilitation, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University

Oral Implantology and Regenerative Dental Medicine, Graduate school of Medical and Dental Sciences, Tokyo Medical and Dental University



The aim of this study is to compare the masticatory performances between immediately loaded and conventionally loaded mandibular two-implant overdentures with magnetic attachments.

Material and Method

Nineteen participants with edentulous mandibles were randomly assigned to an immediately loaded group or a conventionally loaded group. In the immediately loaded group, a magnetic attachment was applied on the same day as implant surgery, and in the conventionally loaded group, a magnetic attachment was applied 3 months after implant surgery. Both masticatory performances, measured by a color-changeable chewing gum and a gummy jelly, and maximum occlusal force were assessed at baseline and at 1, 3, 6, 12, 24, 36 and 48 months after implant insertion.


At the 6‐month evaluation time‐point, the immediately loaded group exhibited a significantly higher gummy jelly score than the conventionally loaded group. There were no significant differences in masticatory performance measured by the color‐changeable chewing gum between the two groups at any evaluation time‐point.


The masticatory performance, measured by a gummy jelly, is improved by 2-IOD of immediate loaded at an earlier time-point than of conventional loaded.

Session 3

Chair: Tetsuo Ohyama (Nihon University)


#6. A case report of a removable partial denture using a magnetic attachment considering the load-bearing capacity of abutment teeth


Division of Removable Prosthodontics, Department of Restorative and Biomaterials Sciences, Meikai University School of Dentistry


In this presentation, we report on a case in which two different types of magnetic attachments, depending on the load-bearing capacity of the abutment teeth, were applied to one removable partial denture.

The patient, a 59-year-old male, complained of masticatory dysfunction. He had a partially edentulous maxilla (Kennedy Class II). After the initial preparation, the distal root of the mandibular right second molar was fitted with a coping magnetic attachment in consideration of its load-bearing capacity as an abutment tooth, and we decided to fabricate an extracoronal magnetic attachment using an EC Keeper Tray (GC, Japan) for the mandibular right first and second premolars.

The definitive denture had the first molar as a homemade metal tooth and the second molar as a hard resin tooth (SR-Orthosit-PE, Ivoclar-Vivadent AG, Liechtenstein). In addition, GIGAUSS (GC) was used for a magnetic attachment (the coping type was the D400, and the D600 was applied to the extracoronal type).


#7. Mandibular IOD using riegel telescope with magnetic attachment


1)Dept. of Removable Prosthodontics, Tsurumi University School of Dental Medicine

2)Center of Maxillofacial Implantology, Tsurumi University Dental Hospital



Retention and stability of mandibular complete denture for fully edentulous patients can be improved by implant placement. In this case, three implants were placed in the mandibular jaw, and riegel telescope denture with magnetic attachments was delivered to obtain well function.


Three implants (Branemark MK II RP 10 mm, Nobel Biocare) were placed between the metal foramen mentale in the edentulous mandibular jaw. Riegel telescope system was selected as a retainer of mandibular implant overdenture (IOD), the milling bar and outer crown were fabricated with optimal fitting. Three implants were connected by a milling bar with two holes which two rods can be inserted. The keeper and magnetic attachment (Hyper slim 5213, Neomax) were attached to the rods and outer crown of the denture, respectively. The riegel telescope, metal backing, and T-shape structured framework were cast with Au-Pt alloy and then accurately constructed.

Results, Discussion

Approximately 18 years were passed after delivery, there were little bone resorption around implants and patient’s satisfaction could be kept by well denture stability. Magnetic attachment is useful device for not only direct retainer on the root and implant but also fixing of the rods in the riegel telescope.


#8. Mechanical analysis of implant support in removable partial denture design applied a magnetic attachment

R. Kanbara,H. Kumano,R. Aoyama, W. Fujinami, Y. Nakamura,K. Shoji,H. Nagai, J. Takebe

Department of Removable Prosthodontics, School of Dentistry, Aichi Gakuin University


The purpose of this study was to investigate the effect of implant support on the tissue around the abutment tooth and the behavior of the removable partial denture using three-dimensional finite element method in the design of the removable partial denture applied a magnetic attachment.

The analysis model was constructed using a mandibular plaster model and a skull model. The missing teeth were right lower second premolar, first and second molar, left lower second premolar, and first molar. The basic model used a retainer with RPI clasp on both first premolar and the magnetic attachment on left second molar. The analysis items were two types of the basic model and the implant support model in which implants were embedded in right free end missing of the basic model. The analysis conditions were set for these models, and three-dimensional finite element analysis was performed.

The results of this analysis, the mechanical effect of the implant support in the design of removable partial denture decreased the displacement of the denture, and showed the relaxation of the stress of the tissue around the abutment tooth on the implant side.