Abstracts of The 7th International Conference on
MagneticApplications in Dentistry
March 3 - March 21, 2008Session 1
Chair: Kazuo Nakamura (Tokyo)
[POSTER][DISCUSSION]
1. Clinical application of removable bridge prosthese with magnotelescopic crownEri Makihara, Shin-ichi Masumi, Masahiro Arita and Mayumi YagiThere are many female patients who refuse to apply removable partial denture from their aesthetic problem, even though fixed bridge is poor convalescence from the prosthodontic standpoint.
In this case report, we fabricated a removable bridge for the patient who didn’t want to wear a removable partial denture because of an aesthetic problem.
A 54-years-old female patient had missing teeth of 11, 12, 13, and 14. 5 inner crowns with keeper of magnetic attachment were fixed to the abutment teeth of 15, 16, 17, 21, and 22．The inner and outer crowns were made with an Au-Ag- Pd alloy. Magnetic assemblies were fixed into the outer crowns and then one-piece removable bridge from 22 to 17 was set.
A magneotelescopic crown is useful for not only removable partial denture, but also removable bridge prosthese. Both patient and us were satisfied with the prosthese.
[POSTER][DISCUSSION]
2. Prognosis for the Overdentures with Magnetic Attachment： Cases with the Reinforcement Structure
Toshiaki Hasuike, Shuji OhkawaDivision of Removable Prosthodontics, Department of Restorative & Biomaterials Sciences, Meika University School of Dentistry
The overdentures with magnetic attachment are susceptible to fracture as compared with the conventional denture, because the abutment becomes the fulcrum. Especially the overdentures, designed no labial flange of denture base over the abutment, have stronger possibility of fracture. The aim of this study was to evaluate the clinical long-term success of the reinforcement structure in the denture base around the magnetic assembly.
Twelve patients received 19 magnetic attachments prepared by 1 operator. Twelve dentures and 19 abutments were followed up for between 5 years 10 months and 7 years 10 months (average period: 6 years 10 months) with inspection. A few clinical problems occurred, including quite small chipping and color change of the denture base on the abutment. However, no tooth was extracted, and no denture was fractured.
It could be asserted that this reinforcement structure in the denture base around the magnetic assembly, designed no labial flange of denture base over the abutment, have a favorable clinical prognosis.
[POSTER][DISCUSSION]
3. Replacement of a damaged crown by magnetic attachment to improve dental esthetics
T. Ando, H. Mizutani, J. Wadachi, T. Moriyama, M. Kubota, N. Takano, F. Narukawa, D. Okusa, Y. IgarashiSection of Removable Prosthodontics, Graduate School, Tokyo Medical and Dental University
The aim of prosthetic treatment is to restore damaged morphology and function. But cosmetic disturbance frequentry results from prosthetic devices, particularly partial denture.
The patient (51-years-old, female) complained of detachment of 44, 45 cantilever bridge. The 45 tooth was indeed damaged by caries and was extracted. After making the lower immediate partial denture (T-bar on 43, double Akers clasps on 33, 34 were designed), the patient complained bad-looking clasps. In order to avoid cosmetic disturbance, the 44 tooth was applied magnetic attachment as direct retainer, with creating ferrule effect to strengthen abutment. The bracing of the denture was not enough only with this one abutment, so the indirect retainer by double Akers clasps were designed on 34, 35 teeth. The patient was satisfied with denture retention and sensusness.
Seven years after the denture setting, the patient addressed the clinic with complaint of broken artificial tooth. The increased occlusal loads and insufficient thickness of acrylic resin due to space limitation were the main reason of failure. To increase resistance of 44 artificial tooth, an acrylic faced metal cast crown enable to contain the magnetic assembly were employed. As a result, the partial overdenture was advantage for sensusness and strength was achieved.
Session 2
Chair: Yosuke Kinouchi (Tokushima University)
[POSTER][DISCUSSION]
4. Corrosion resistance of magnetic assemblies composing the domestic cup yoke type dental magnetic attachments
Y. Takada, O. OkunoIn this study, the corrosion behavior of magnetic assemblies was electrochemically evaluated by their pitting potentials obtained from the anodic polarization curves. The anodic polarization curves of cup yoke-type magnetic assemblies (Magfit DX800 (Aichi Steel), GIGAUS D800(GC), Hiper Slim, and Hicorex Slim (Hitachi Metals)) were measured in a 0.9% NaCl solution at 37oC (n=3). Ferritic (444, XM27, and 447J1) and austenitic (316L) stainless steels used for the yokes and the shield ring, respectively, were also examined as controls. The element distributions of the laser welding areas between the yoke and the shield ring were analyzed using XMA with WDS (n=5). The anodic polarization curves showed that all magnetic assemblies broke down within the range of 0.75-1.3V in the vicinity of the shield ring made of 316L. However, the pitting potential of each magnetic assembly was significantly higher than that of 316L. XMA showed an increase in Cr content on the surface of the shield ring relative to the inside (p<0.05) because the weld bead deeply covered the surface of the shield ring. Laser welding resulted in increasing the pitting potential of the magnetic assemblies. This study was fully supported by the NEDO grant (05IS051) and the Grant-in-Aid for Scientific Research (B) of JSPS (18390511).[POSTER][DISCUSSION]
5. Corrosion Characteristics of Dental Magnetic Attachments
1Department of Biomaterials Science, Baylor College of Dentistry, Texas A&M Health Science Center2Division of Dental Biomaterials, Tohoku University, Graduate School of Dentistry
In this study, the corrosion behavior of four stainless steels and three precious alloys used for dental magnetic attachment systems is characterized. Static immersion tests (n=5) were performed in NaCl + lactic acid solution (pH2.3) at 37°C as specified in the ISO standard 10271. After 1 week, the concentrations of elements released were measured using an ICP-MS. The data were analyzed using ANOVA/Tukey's HSD (α=0.05). For electrochemical measurements, OCP and anodic polarization were performed in a NaCl solution (pH 7.4) at 37°C. The corrosion parameters were statistically analyzed using non-parametric methods (α=0.05). In all stainless steels, all alloying elements in each type of alloy were dissolved out of the specimens. In the precious alloy group, Cu, Ag, Pd, Pt, and Ir were detected from each specimen. The Type 4 gold alloy and Au-Ag-Pd alloy showed a higher total dissolved element in each specimen when compared with that from all the tested stainless steels. The breakdown potentials for XM 27 and 447JI were significantly higher than those of the other metals in 0.9%NaCl under the deaerated condition. The overall corrosion resistance of stainless steels is better than those of the dental casting alloys tested. This study was fully supported by the NEDO grant (05IS051).[POSTER][DISCUSSION]
6. The effect of tooth connection with a magnetic extracoronal attachment using the Three Dimensional Finite Element Method
The First Department of Prosthodontics , School of Dentistry,
Aichi –Gakuin University
Unilateral treatment of a distal extension partial denture is considered to be contraindicated since the functional pressure applied to the denture is directly transmitted to the most distal abutment tooth due to the difference in the amount of tissue displacement between the periodontal membrane and the mucosa. However, there are patient requests for unilateral prosthetic partial designs and clinicians may be obliged to consider these alternative designs for restorative prosthetic treatment using these designs. In these treatment conditions, a lack of attention to proper design and the condition of abutment teeth could lead to the root fracture or attachment breakage.
In the clinical treatment situations, the preservation of remaining periodontal tissue support is made by increasing the number of prosthetic abutment tooth supports. However, The decision in the number of interconnected abutment teeth is made based on the dentists’ clinical experience, and evaluations of treatment conditions. There may be no solid evidence to base a certain treatment decision regarding prosthetic design. In this present study, we investigated the effect of abutment teeth connection with a magnetic extracoronal attachment using the finite element method.Session 3
Chair: Kazumoto Hoshiai (Aichi-Gakuin University)
[POSTER][DISCUSSION]
7. Influence of Sterilization on Magnetic Attachment
D. Okano, E. Muraishi, F. Tsuchida, N. Takishin and T. HosoiDepartment of Removable Prosthodontics, Tsurumi University School of Dental Medicine
【Purpose】Sterilization is important in dental treatment. However the sterilization method suitable for magnetic attachments is not established. Sterilization can alter the surface properties of magnetic attachments or lower the attractive force because heating can weaken magnetic assemblies and keepers, and chemicals can corrode metals. The purposes of this study were to investigate the influence of sterilization on the magnetic attachments, and to optimize and standardize the sterilization method for magnetic attachments.
【Materials and Methods】Three kinds of magnetic attachments; PHYSIO MAGNET (NISSIN Co.), GIGAUSS(GC Co.) and MAGFIT(AICHI STEEL Co.) were examined. Autoclave and EOG sterilization were chosen as sterilization method and the surface roughness and the attractive force of each attachment were measured.
【Result and Conclusion】In all magnetic attachments, increase of the surface roughness and decrease of the attractive force are observed. Therefore it was thought that the range of the change was too small to be a problem in clinically. To compare EOG sterilization with autoclave, there were fewer changes of the property of the magnetic attachment by EOG sterilization than autoclave. EOG sterilization was evaluated as the sterilization method suitable for the magnetic attachment.
[POSTER][DISCUSSION]
8. Influenceof the Angle of Attracvtive Surface of Root Cap Affect Abutment for Overdenture
Yuusuke Katakura1,Tetsuo Ohyama1,2,Eiichi Nagai1,2,Tomohiko Ishigami1,2,Hitoshi Toyoma1,2 Shigeru Ohno1,Yoshimasa Takeuchi1 and Mikage Hasegawa11)Department of Partial Denture Prosthodontics，Nihon University School of Dentistry2)Division of Clinical Research，Dental Research Center，Nihon University School of Dentistry
The magnetic attachment shows maximum retentive force in the vertical direction on the attractive surface of the keeper and the magnetic assembly. In addition, it can strengthen support of the prosthesis by setting the keeper in parallel with occlusal plane, but the anterior tooth that was inclined might received harmful rotative power by occlusal force. Therefore we examined the influence that the angle of inclination of the root cap top surface on the abutment tooth and denture support tissue using finite element method.
These four models were used for analysis of mandibular complete dentures with the root cap for the right lower cuspid tooth. We set the tooth was inclined 15 degrees. The top surface set the state that was parallel to occlusal plane with 0 degrees, and the root cap set four kinds of models that 15, 30 and 45 degrees and the surface inclined in the labial side. The mandibular bone base was completely constraint all degree of freedom, and analyses were executed total loads of 9.8N.
According to our results, it is consequently suggested that the load of the abutment tooth was reduced with the model that set 15 degree inclined tooth.
Session 4
Chair: Yukyo Takada (Tohoku University)
[POSTER][DISCUSSION]
9. Measurement Device for Movement of the Larynx using Magneto-Impedance SensorK.Tanida1, Y.Ikeda1, Y.Sato1, M.Akutagawa2, Y.Kinouchi2, T.Ichikawa3, S.Hongama3
1Graduate School of Advanced Technology and Science The Univ. of Tokushima2 Institute of Technology and Science The Univ. of Tokushima3 Institute of Health Biosciences The Univ. of Tokushima
The objective of this study is to develop a screening device for the swallowing difficulty using Magneto-Impedance (MI) sensor.
Videofluorography (VF) is effective to the diagnosis of swallowing difficulty.
The Repetitive Saliva Swallowing Test (RSST) is also one of the effective screening methods.
In this study, we developed the screening device to automate the RSST using a MI sensor.
The screening device is consisted of a MI sensor and a magnet.
A magnet was attached on the larynx, and a MI sensor was attached on breastbone.
The movement of magnet, which movement of larynx according to swallowing, was detected with MI sensor as a change in the magnetic field.
However, the subject of senior adult moves its body, when swallowing.
In this time, we developed the screening device, which consisted of two MI sensor, to cancel body movement by senior adult when swallowing.
We could confirm the screening device can detect the movement of larynx.
However, when the subject was the senior adult and patient of the swallowing difficulty, we were hard to obtain enough result.
For the future, we will try to do a further measurement targeted for the senior adult.
[POSTER][DISCUSSION]
10. Evaluation of Leakage Flux out of a Sandwich type Magnetic Attachment
M. Nishida1, Y. Tegawa2, and Y. Kinouchi11 Institute of Technology and Science, The University of Tokushima,2 School of Medicine, The University of Tokushima
The dental magnetic attachments are a device used in the mouth to retain a denture. The tissues in the mouth are exposed to the magnetic fields leaking out of the magnetic attachments for a long time. Therefore, we evaluated the strength of the leakage magnetic fields of a sandwich type magnetic attachment.The shape of magnetic assembly is designed to be a disk with 4.0mm in diameter and 1.5mm in thickness, and a keeper is a disk with 4mm in diameter and 1.0mm in thickness. Magnetization J of the magnet is assumed to be 1.3 T. Keeper is soft magnetic stainless steel with 1.6 T in saturation flux density Bs. Non-magnetic stainless steel is also used to protect the magnet from corrosion in the mouth. Leakage magnetic flux has been analyzed by the use of FEM.The safety of the leakage magnetic fields was evaluated by using the WHO’s guideline. The limits of exposure to static magnetic fields for the general public in continuous is 40mT.
The leakage magnetic field of the sandwich type of magnetic attachment is larger than that of the cup type, because the magnet of the sandwich type is not completely covered with the yoke as the cup type. In addition, the leakage flux becomes large when the gap length between a magnetic assembly and a keeper becomes long. However, that does not exceed the WHO's guideline 40mT at the position corresponding to the tissue in the mouth.Session 5
Chair: Shin Ishikawa (Ehime)
[POSTER][DISCUSSION]
11. Influence of heating of a magnetic attachment on the attractive force
Miyata T. , Niimi J. , Ando A. , Syouji K. , Kumano H. , Masuda T. , Hasegawa N. , Nakamura Y. and Tanaka Y.The First Department of Prosthodontics , School of Dentistry, Aichi – Gakuin University
A magnetic attachment has achieved excellent clinical results, and has been recognized as a clinically significantly tool with numerous advantages compared with a conventional mechanical retainer. A Nd magnet, recently available on the market, has been widely adopted in commercial magnetic attachments. The magnet has the temperature related characteristic of magnetic force loss at low relative temperatures. This is considered to be a disadvantages of the Nd magnet. The clinical use conditions including the sterilization procedures and the laboratory processing should be thus considered for evaluation.
We compared the attractive force of each magnetic assembly before and after heating to investigate the influence of heating.
[POSTER][DISCUSSION]
12. Influence of the arrangement of the magnetic attachments in the remaining dentition upon the denture mobility
M.Hideshima, M,Toko, M.Fukumoto, T.Andoh, A. Nishiyama, M. Sato, H. Mizutani,Section of Removable Prosthodontics, Graduate School, Tokyo Medical and Dental University
Objectives: There is not sufficient indication how we arrange dental magnetic attachments in the remaining dentition in order to acquire effective retentive force with the overdenture. Therefore we investigated the movements and retentive forces of the experimental denture in various arrangement of the magnetic attachments with the simulated model.
Materials and methods: Eight magnetic root keepers were symmetrically arranged in the regions of both second incisors, canines, first and second molars on the flat acrylic base supposing maxillary dentition. Corresponding acrylic plate was fabricated as the experimental denture plate and 8 magnetic attachments were fixed in the opposing area of each corresponding root keeper. Four metal hooks were attached in the regions of between both second incisors and canines, and first and second molars and lifting chain was attached to each hook.
Using the universal testing machine, lifting chains were pulled up until the experimental plate dislodge and maximum retentive force of was measured when the arrangement of the attachments and location of the lifting chains was changed.
Results and Conclusions: Maximum retentive force showed more than 22N with 8 magnets, 8N with 4 ones, 7N with 3 ones and 4N with 2 ones when pulled with 4 chains attached to the corresponding hooks. When 2 magnets were applied, symmetrical arrangement showed more retentive force than that of the asymmetrical adjacent arrangement. When 3 magnets were applied, adjacent 2 abutments and contra-lateral arrangement represented more retentive force than that of the 3 isolated abutments.
Session 6
Chair: Masatake Akutagawa (Tokushima University)
[POSTER][DISCUSSION]13. The comparison between Domestic and Foreign Magnetic Attachments
The First Department of Prosthodontics, School of Dentistry, Aichi –Gakuin University
Magnetic attachment of different manufacture, may offer differences in physical property and quality including greater stability and retention, ease of manipulation, superior esthetic applications, and reduction of stress to abutment teeth in the various clinical settings shown through research and development. There are several magnetic attachments available on the foreign market. However, since many of these products are available only through commercial means, development process and proprietary details of design and specifications are not readily available in academic journals, and thus even accurate development time remains unknown. In this preliminary study on seven foreign-made magnetic attachments that were obtained and compared to the GC GIGAUSS. We measured attractive force of magnetic attachments, and investigated the change in surface morphology of keepers after applying cyclic loads to measure the mechanical strength of keeper.[POSTER][DISCUSSION]
14. Influence of the magnetic attachment on blood flow to the surrounding oral mucosa
Fukuzawa R., Hasegawa N., Syouji K., Ando A., Nakamura Y. and Tanaka Y.The use of a magnet and magnetism has been drawing attention in the modern society, and they have been widely applied in the medical field in recent years. It is a major research task for us to confirm the safety of a magnet in the human body. Several studies including cytotoxicity test and corrosion test have been conducted. Several reports have been suggested that the magnetism increases blood flow, but not solid data exist regarding a magnetic attachment. The present paper reports interesting findings that we obtained from the detailed and clear observation of the influence of magnetic field on human blood flow.The following three experiments were conducted to confirm the influence of magnetic field on human blood flow of the surrounding oral mucosa.
[POSTER][DISCUSSION]
15. Effects of Dental Alloys and a Magnetic Keeper on MRI. Part 1 Analysis from Dicom Data
H. Mizutani, D. Destine, M. Hideshima, M. Sato, J. Wadachi, A. Nishiyama, K. Nakamura, S. Ishikawa, D. Okusa, H. Sasaki, S. Matsuzaki, Y. Igarashi
Section of Removable Prosthodontics, Graduate School, Tokyo Medical and Dental University
Three clinically used dental alloys ( Pd: Au-Ag-Pd alloy, Au: Au-Pt-Ag alloy, Co: Co-Cr-Mo alloy ) and a magnetic attachment keeper (Fe: Fe-Cr-others) were used in this study. Also the self-curing resin (Re ) were used as a control. All their .shapes were the same as the keeper (4mm diameter, 0.6mm thickness ) . Five of each type of samples were prepared and every sample was fixed into a 50mm cubic resin-made agar phantom. The phantom with one sample was placed on the table of 1.5T MRI apparatus and was imaged in T1 and T2 weighted methods. Signal intensity ( SI ) around the samples in the region of interest ( ROI approximately 2780pixels ) was calculated with a free software ImageJ and coefficient of variation was compared for evaluation of the homogeneity of the SI. Welch modified t test was used for statistical analysis ( p≤0.05 ). Results: Different magnitudes of artifacts were observed for individual alloys. The mean SI values for Co, Pd were significantly different from that of Re control but the differences were not significant in CV. The largest significant differences in mean SI and CV compared with those of Re control were Fe, then Co, Pd, Au.
Session 7
Chair: Masahiro Arita (Kyushu Dental College)[POSTER][DISCUSSION]
16. Management for a spillway on the Denture fixing the magnetic assembly
Satomi Tadokoro1，Tetsuo Ohyama1,2，Tomohiko Ishigami1,2，Kenji Ohtani1,2，Yoshitada Umekawa1,2，Shinya Nakabayashi1，and Yutaka Mitsuhashi1
1Department of Partial Denture Prosthodontics NUSD
2Division of Clinical Reserch Center NUSD
In generally, Denture was made a spillway for fix the magnetic assembly, using a self-curing resin. In clinical practice, we often notice cracks and discolorations surrounding the spillway of the denture. In this study, It was compare with the influence of a surface treatment method after push out a self-cureing resin from a spillway. These methods were applying a light-cured glazing and coating material (NANOCOAT LabⓇ(GC)) on the push out a self-curing resin , and not appling it the coloration and surface texture using thermal cycling. We made two groups of specimens using the polymerizing method surrounding the spillway. These were Non-Pressed cure Group (NPG) and Pressed cure Group (PG). Ten specimens were made with NANOCOAT processing to NPG and ten to PG respectively. It was made four types of specimens (NPG-NANOCOAT, NPG-NonNANOCOAT, PG-NANOCOAT, PG-NonNANOCOAT), each made up ten of samples.The result of this study shows1. When the magnetic assembly was fixed, it was a validity method to use a light-cured glazing and coating material for the self-curing resin surface surrounding the spillway.The magnetic assembly was fixed with a self-curing resin under pressure, where it was possible to fix the assembly without making a significant gap.[POSTER][DISCUSSION]
17. Successful case of a denture with magnetic attachment replaced by cone crown telescope
Hasegawa N., Fukuzawa R., Syouji K., Itou F.*, Okada M.*, Nakamura Y. and Tanaka Y.The First Department of Prosthodontics, School of Dentistry , Aichi-Gakuin University*Department of Dental Laboratory, Aichi-Gakuin University Dental Hospital
Overcoping telescopic denture design is based upon the use of telescoping overcoping on domed crowns with coping full coverage crowns. This prosthetic removable design results in a very strong supporting structure, and has improved long-term postoperative prognosis compared to a clasp denture based upon an increased number of supporting abutments. Clinically this design is complex and complicated with a high requirement for good laboratory fit and processing. There may be difficulties in adjustment of the retentive force as well. Removable prosthetic devices with magnetic attachments embedded in and out of the crown have been widely applied in recent years. We report treatment of complications and successful repair and use of magnetic attachments in a denture treatment that specifically used the telescopic crown technique. This case report documents difficulties and the clinical problems that may be overcome.
[POSTER][DISCUSSION]
18. Changes of Retentive Force of Radicular Attachments Before and After Wear Simulation –Focusing on Overseas Magnetic Attachments
H. Mizutani, A. Bazar, M. Hideshima, M. Sato, A. Nishiyama, T. Ando, K. Nakamura, N. Takano, S. Ishikawa, F. Narukawa, D. Okusa, Y. Igarashi
Section of Removable Prosthodontics, Graduate School, Tokyo Medical and Dental University
Objectives: To evaluate and compare maximum retentive force of overdenture attachments before and after various levels of wear simulation.
Materials and methods: Five specimens from 2 types of commercially available overdenture stud attachments; Essentric Rothermann (ER), ERA Overdenture Black (EOB) and 5 types of commercially available magnetic attachments Hyper Slim 4013 (HS), and overseas magnetic attachments MAGNA-CAP (M.CAP), Titanmagnetics (Ti.M), DYNA magnet (DYNA) and MICROPLANT (MP) were tested. All the attachments, except EOB were prefabricated and did not require casting, Plastic patterns of EOB attachments were cast from IV gold alloy. Tooth (implant) parts of all the attachments were centered on the heads of non-ferromagnetic screws and glued by cyanoacrylate resin. Denture parts of the attachments were fixed on the heads of the screws by self curing resin.
Wear simulation was performed for each specimen by a micromaterial testing machine (MMT-250NB-10 with a sensor interface PCD-320 and maximum retentive force were recorded by software package PCD-30A . Five thousand insertion-removable cycles were performed with 50 mm/min cross head speed in normal saline at 37ºC. Before, and after each 500 cycles, 3 records of maximum retentive force were recorded and averaged for each specimen .
Statistical analysis: one-way ANOVA and Scheffe post hoc tests (P< 0.05).Results: Maximum retentive force of stud attachments ER and EOB decreased suddenly and continued keeping the same level. Any cnanges were noticed among magnetic attachments. The decrease, which occurred on stud attachment was statistically significant.
Conclusions: Retentive properties of studs are more susceptible to wear than that of magnetic attachments. HS provide the highest retention among investigated magnetic attachments.
Session 8 NEDO Grant Symposium 2007 Foreign Magnetic Attachment
[POSTER][DISCUSSION]
19. Foreign Dental Magnetic Attachments
T. Hosoi1, C. Ohkbuo1, Y. Takada2, O. Okuno2, Y. Nakamura3, Y. Tanaka3, T. Ishigami4, Y. Umekawa4, A. Kikuchi5, Y. Kinouchi6, H. Mizutani7
1 Department of Removable Prosthodontics, Tsurumi University School of Dental Medicine2Division of Dental Biomaterials, Tohoku University Graduate School of Dentistry3The First Department of Prosthodontics, School of Dentistry , Aichi-Gakuin University4Department of Partial Denture Prosthodontics, Nihon University School of Dentistry5Hitachi Metals Co., Ltd.6Department of Electrical and Electronic Engineering Faculty of Engineering, The Univ. of Tokushima7Graduate School, Tokyo Medical and Dental University, Section of Removable ProsthodonticsOur research team which receives the support of the NEDO Grant aiming at "Development and Standardization of the Dental Magnetic Attachment" has tried to standardize internationally dental magnetic attachments used in the world. In this study, the following items were examined in order to obtain the basic data concerning relatively unfamiliar foreign-made dental magnetic attachments.
1. Characteristics
2. Internal structures and materials
3. Attractive force measurements and cyclic load testing
4. Influence of keeper tilt angle on retentive force
5. The leakage magnetic fields
This study was fully supported by NEDO grant (05IS051).