Measuring Methods of the Attractive Force of Magnetic Attachment

Terao Y., Nakamura Y., Ishida T., Ando A., Nakamura H., Kumano H., Shoji K., Tanaka Y.

The First Department of Prosthodontics, School of Dentistry, Aichi-Gakuin University

INTRODUCTION

Several studies have reported upon the attractive force measurements of magnetic attachments since their original development. However, measurements of these attractive forces are difficult due to multiple concerns. These concerns include spacial effects such as positioning and location, and determinations of effective distance of attractive forces. Due to the nature and types of magnetic attachment physical properties, various problems have been shown to occur without three dimensional accommodation of the spacial effects. A reliable methodology has yet to be established.

OBJECTIVE

The following are representative problems that may occur during attractive force measurements:

Vertical direction control location
Horizontal direction control location
Precision positioning of magnetic assemblies and keepers

Because of these problems, it has been difficult to obtain reproducible and reliable values. In the present study, we devised the novel positioning device or JIG for a tension test to minimize the spacial positioning problems, and obtained attractive force measurement values of a proprietary magnetic attachment. This paper reports the reproducible value obtained.

MATERIALS

Custom made positioning device/JIG

Fig 1 - A . Custom made JIG

JIG consists of an upper and lower part. Bilateral sticks attached to the upper JIG are engaged into the lower JIG and move vertically guided by the JIG. These sticks were made perpendicular to the upper and lower JIG. We also made and exclusive die that fits into this JIG. ( Fig 1 - A )

Fig 1 - B. Structures of JIG

Holes of lower JIG have bearing structure, and small balls are arranged in a spiral lengthwise arrangement in the holes. When the stick of upper JIG went through these arrangements of guiding small balls, a rule of a vertical direction of a tension test was enabled without frictional resistance, and, at a tension test, power of absorption only for a magnet came to be reflected by values. ( Fig 1 - B )

GIGAUSS C ( 300 400 600 ) D ( 400 600 800 1000 ) ( GC )(Fig 2)
EZ Test ( SHIMADZU )(Fig 2)

Fig 2. GIGAUSS and EZ Test

EXPERIMENTAL METHODS

1. The keeper was attached to the center of the exclusive die. Subsequently, the keeper and magnetic assembly were adsorbed using a magnifying glass to assure the maximum adsorption area.

2. We installed this die to the lower part of JIG and a paired die to the upper part of JIG. (Fig 3)

3. We applied adhesive to the base of a magnetic assembly, slowly lowered the upper part of JIG, and adhered a magnetic assembly to the upper die

4. Measurement was carried out. The measurement condition is shown in Fig 4.

Fig 3.

Fig 4.

RESULTS

The Fig.5 shows the results of GIGAUSS D.

Fig 5. results of GIGAUSS D

Gray bar graph shows free pulling direction.

Blue bar graph shows the control with custom made JIG.

Green and yellow bar show each standard deviation.

Significantly high value and very small standard deviation were obtained in case of using exclusive JIG compared with the free pull direction as shown in the figure.

The Fig 6. shows the results of GIGAUSS C.

Fig 6. results of GIGAUSS C

As with GIGAUSS D, significantly high value and very small standard deviation were obtained in case of using exclusive JIG compared with the free pull direction.

DISCUSSION

By regulating sideslips peculiar to the magnet using the exclusive JIG, and measuring attractive force only in the vertical direction, a significant difference was observed compared with the free pull direction.

Considering small standard deviation, an error between products can be measured by increasing the number of samples.

CONCLUSION

The exclusive JIG enabled to regulate the alignment of separation and pulling direction. The positioning device described in this study was shown to improve the quality of measurement data obtained for an aligned magnetic assembly and keeper. These measurement values are of greater consistency and with less variation as shown by the data gathered and evaluated.

REFERENCES

1. Tanaka, Y.: Dental Magnetic Attachment - new prothodontic treatment used the magnet -, Ishiyaku Publishers, Inc. (Tokyo), 1992.

2. Tanaka, Y.: Dental Magnetic Attachment, Q&A, Ishiyaku Publishers, Inc. (Tokyo), 1995.

3. Nakamura, Y.: Stress analysis of overlay denture and a magnetic attachment using finite element method. J Jpn Prosthodont Soc, 42: 234-245, 1998.

Discussion Board