8. Effect of Crosshead Speed on Magnetic Retentive Force
Y. Ogawa1, Y. Umekawa1,2, T. Ishigami1,2, Y. Takeuchi1,
N. Tsukimura1,2, K. Ohtani1,2 and S. Ohno1
1Department
of Partial Denture Prosthodontics, Nihon University
School of Dentistry, Japan
2
Division of
Clinical Research, Dental Research Center, Nihon University School of
Dentistry, Japan
Introduction
There
have been many reports regarding magnetic retentive force. However, in these
reports, the crosshead speeds for which the magnetic retentive force has been
measured are not the same. The purpose of this study is to evaluate the retentive
force of a magnetic attachment for different crosshead speeds.
Materials and
Methods
GIGAUSS
D600 (GC, Japan) magnets
were used as test samples (n=5) and square acrylic resin pillars (10×10×30 mm)
(Tokyo Giken, Japan) were prepared. The magnetic attachment was installed at the
center of the acrylic resin. The retentive force of the magnetic attachment was
measured using a customized testing jig and a universal testing machine (EZ-Test,
Shimadzu, Japan)(Fig. 1). The crosshead speed was set to 43 different levels in
the range between 0.5 mm/min and 500 mm/min. This
testing jig was constructed with a linear ball slide (THK company, Tokyo) to
prevent the sidewise movement of the specimen during traction. Statistical analysis was performed by using
the Dunnett test (p=0.05).
Fig. 1 Testing jig
Results
The retentive
force for crosshead speeds in the range between 0.5 mm/min and 500 mm/min is
shown in Fig. 2. It was found
that the retentive force of GIGAUSS D600 magnets was 5.12 N at crosshead speed
of 0.5 mm/min, 4.99 N at 5.0 mm/min, 4.96 N at 6.0 mm/min, and 4.41 N at 20
mm/min.
Figure 3 shows the retentive force for
crosshead speeds in the range between 0.5 mm/min and 20 mm/min.
Fig. 2
Retentive force of magnetic system for various crosshead speeds
Fig. 3
Retentive force of magnetic system for crosshead speeds
in the range between 0.5 mm/min and 20 mm/min
Discussion
There have been many reports regarding
magnetic retentive force. However, in these reports, the crosshead speeds for
which the magnetic retentive force has been measured are not the same. This
experiment was performed in order to establish the influence of the crosshead
speed on the magnetic retentive force.
Conclusions
1.
The strongest retentive
force was observed when the speed was lowest.
2.
The retentive force of
GIGAUSS D600 magnets decreased as the crosshead speed of magnetic attachment
increased.
3.
There was no statistically
significant difference in retentive force between crosshead speed=0.5 mm/min
and crosshead speed=5.0 mm/min, whereas statistically significant difference in
retentive force was observed between crosshead speed=0.5 mm/min and crosshead
speed=6.0 mm/min (p=0.05).
Acknowledgment
This study was supported in part by Grant
from Dental Research Center, Nihon University School of Dentistry.
References
1. Y. Umekawa, T. Ishigami, Influence of keeper tilt angle on retentive force, J J Mag Dent 17(2):98-100, 2008.
2. Funda Akaltan, Gulsen Can, Retentive characteristics of different dental magnetic systems, J Prosthet Dent 74(4):422-427, 1995