• The Journal of Advanced Prosthodontics
• /
• v.8 no.1
• /
• pp.9-15
• /
• 2016

PURPOSE. Although magnetic attachment is used frequently for overdenture, it is reported that attractive force can be decreased by abrasion and corrosion. The purpose of this study was to establish the clinical basis about considerations and long term prognosis of overdenture using magnetic attachments by investigating the change in attractive force of magnetic attachment applied to the patients. MATERIALS AND METHODS. Among the patients treated with overdenture using magnetic attachments in Dankook University Dental Hospital, attractive force records of 61 magnetic attachments of 20 subjects who re-visited from July 2013 to June 2014 were analyzed. Dental magnet tester (Aichi Micro Intelligent Co., Aichi, Japan) was used for measurement. The magnetic attachments used in this study were Magfit IP-B Flat, Magfit DX400, Magfit DX600 and Magfit DX800 (Aichi Steel Co., Aichi, Japan) filled with Neodymium (NdFeB), a rare-earth magnet. RESULTS. Reduction ratio of attractive force had no significant correlation with conditional variables to which attachments were applied, and was higher when the maintenance period was longer (P<.05, r=.361). Reduction ratio of attractive force was significantly higher in the subject group in which attachments were used over 9 years than within 9 years (P<.05). Furthermore, 16.39% of total magnetic attachments showed detachment of keeper or assembly. CONCLUSION. Attractive force of magnetic attachment is maintained regardless of conditional variables and reduction ratio increased as the maintenance period became longer. Further study on adhesive material, attachment method and design improvement to prevent detachment of magnetic attachment is needed.

• The Journal of Korean Academy of Prosthodontics
• /
• v.37 no.1
• /
• pp.1-22
• /
• 1999

In order to investigate various physical and biological properties of dental magnetic attachments studies on retentive characteristics, corrosion properties, cytotoxicity of different magnetic systems for dental applications were done. For the study of retentive characteristics changes of retentive force by increasing air gap, wear properties of various attachment systems and loss of magnetic force by heat treatment were measured. Forte study of corrosion property of magnet covering metal electrochemical corrosion was done in artificial saliva and 0.9% NaCl solution between $-1,000mV_{SCE}\;and\;+1,000mV_{SCE}$. Anodic polarization curves are obtained about 6 types of samples and 2 types of solution. Corroded surfaces were examined with metallurgical microscope, scanning electron microscope and surface profilometer. For the study of cytotoxicity of magnetic attachment and its field cell growth and agar overlay test were done. The results of this study were as follows. 1. In Magnetic attachments using closed circuit retentive force at zero air gap was greater than magnets using open circuit, but decrease of retentive force by increasing air gap was also greater than open systems. 2. After 40,000 cycles of wear test all mechanical attachment resulted in varing degree of retention loss but in magnetic attachments no loss of retentive force was observed. 3. The magnetic attachment using Neodymium magnet showed early loss of retentive force about $200^{\circ}C$ but attachment using Samarium magnet showed some resistance to heat treatment and complete retention loss was observed about $500^{\circ}C$. The keeper was not influenced by heat treatment in retention. 4. In electrochemical corrosion test Dyna magnetic attachment covering metal showed the highiest corrosion resistance and Shiner magnet covering metal showed the least corrosion resistance and examination of corroded surface with metallurgical microscope, scanning electron micro-scope and surface profilometer also showed same results with anodic polarization corves. 5. The result of cell culture tests on the magnet covered with metal showed least recognizable cytotoxicity.

• The Journal of Korean Academy of Prosthodontics
• /
• v.39 no.4
• /
• pp.336-350
• /
• 2001

The purpose of this study was to investigate corrosion tendency and to compare corrosion resistance of three dental magnetic attachments and its keeper alloy by coercive, electrochemical method. By using petentiodynamic polarization technique, magnetic elements and its keeper alloy of Magfit EX600 system(MF, MFK), Dyna ES regular system(DN, DNK) and Shiner SR magnet system(SR, SRK) were corroded electrochemically in 0.9% NaCl electrolytic solution. Open-circuit potential and anodic polarization curve was measured with Potentiostat(model 273 EG&E) and polarization curve was created by current density per square area following scanning of increased series of voltage in the rate of 1.0mV per second. Before and after electrochemical corrosion, the surface roughness test was done. Thereafter the change of mean surface roughness value(Ra) and mean peak value(Rt) of surface roughness was compared one another. In order to observe the corroded surface of each specimen, metallurgical light microscopic(${\times}37.5$) and scanning electron microscopic view(SEM ${\times}100$) was taken and compared one another. Conclusion is followings. 1. All of six covering metal of dental magnetic attachments and its keeper alloy were corroded in various degree after electrochemical corrosion. 2. The corrosion resistance of which used in this experiment is the following in high order; DNK, MFK, DN, MF, SRK and SR. 3. Especially Shiner magnet system and its keeper alloy were more severely corroded after electrochemical corrosion and the change of Ra Rt value were more increased than others. 4 Metallurgical and scanning electron microscopic view showed the pitting corrosion tendency of all experimental alloy but DNK and SR. 5. Covering metal of magnet was more corroded than its keeper alloy.

• 대한치과보철학회:학술대회논문집
• /
• 2001.04a
• /
• pp.59-59
• /
• 2001

• 대한치과보철학회:학술대회논문집
• /
• 1999.04a
• /
• pp.79.1-79.1
• /
• 1999

• 대한치과보철학회:학술대회논문집
• /
• 1999.04a
• /
• pp.79.2-80
• /
• 1999

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.5 no.1
• /
• pp.27-32
• /
• 1996

This paper deals with the distributions of magnetic flux of an electro-magnetic chuck which is one of the most commonly used chucking attachments in a surface grinding machine. The measured results showed good correspondence with the theoretical results which were previously presented by the same author. The normal and tangential components of the magnetic flux density were measured using the gauss meter. The measured results indicated that the magnetic flux density was periodically changing over the transverse position to the magnetic pole. The normal component of magnetic flux decreases very rapidly for the increased z position.

• The Journal of Korean Academy of Prosthodontics
• /
• v.45 no.1
• /
• pp.34-47
• /
• 2007

Statement of problem: Conventional mandibular complete denture lacks in support and stability for edentulous patients to use. Purpose: To enhance support and stability of mandibular complete denture, 2 implants were inserted on the inter-mental foramina space of edentulous patients. With 2 magnetic attachments on the inner side of the overdenture, we gave immediate loads and evaluated the stability of the implants, the responses of the supporting tissues, and the satisfaction of the patients. Material & methods: 6 edentulous patients (5 male, 1 female) each recieved 2 SLA implants in the inter-mental foramina region and implants were immediately loaded with overdenture with magnet attachments. To evaluate the implants stability and the peri-implant tissues, clinical exams, RFA tests and radiographic exams were preformed at the 1 week, 2wks, 6wks, 12wks, and 24wks. post- surgery. Results: The mean surgery time was $45.7{\pm}7.7mins$., while the denture delivery time was $45.5{\pm}12.6mins$. Only 2 of 14 implants were failed. Survived implants that remained were clincally and radiographically stable. Mean ISQ values were relatively stable, showing $69.71{\pm}5.55$, $69.00{\pm}9.48$, $67.92{\pm}7.86$, $67.92{\pm}9.58$, $70.08{\pm}7.61$, $71.92{\pm}6.43$ at the 1 wk, 2 wks, 6 wks, 12 wks, 24 wks. follow up check. Crestal bone changes were $-1.18mm{\pm}0.68mm$, $-1.35{\pm}0.69mm$, $-1.47{\pm}0.68mm$ at the 6wks, 12wks, 24wks. follow up check. Bleeding on probing(BOP index) was not significant. Conclusion: Mandibular ovedentures with 2 magnetic attachments over two interforaminal implants on edentulous patients for immediate function is a recommendable novel treatment for edentulous patients which shows stability on the implants and supporting tissue.

• The Journal of Korean Academy of Prosthodontics
• /
• v.40 no.1
• /
• pp.88-97
• /
• 2002

The purpose of this study was to evaluate a cases which was treated with magnetic attachments on the patients in edentulous mandible and maxilla. Author made magnetic overdenture for two patients and then clinical examination were used for evaluation of the function and change in retention during 30months. Patients showed difficulty in oral hygiene care at the beginning but they go used to it soon. It was effective in promotion of denture retention and stability and also gave patient emotionally uplifting psychologic state. This study suggest that magnetic attachment was effective for the treatment of patients presenting a few remaining teeth or teeth under severe caries or mobility.

• The Journal of Korean Academy of Prosthodontics
• /
• v.46 no.6
• /
• pp.586-590
• /
• 2008

Construction of an obturator for rehabilitation of a patient who underwent a maxillectomy is vital. Routinely a constructed obturator includes denture portion. A patient who may present anatomical limitations due to surgical or radiotherapy complications often challenges the clinician. Purpose: This clinical report describes a patient with severe trismus after surgical resection and radiotherapy treatment of a tumor in the upper left maxilla. Conclusion: This report describes the concepts of using a rotational path insertion for an obturator and a separately constructed maxillary denture. The stability and retention of the obturator were obtained from anatomical features. Where as these were achieved through magnetic attachments and the remaining edentulous ridge to ensure esthetic and function of the prosthesis.