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The effects of magnetic and electromagnetic fields on
biological functions were reviewed at different levels from molecules
to individual animals. First, we discussed possible and basic
mechanisms by which magnetic or electromagnetic exposure would
influence the biological processes. Secondly, we showed examples of
the influences. These involved enzyme reactions, diamagnetic
orientations of macromolecules and cells, membrane functions
including ion transport and hormone secretion, cell proliferation,
nucleic acid and protein syntheses in vitro, genetic phenomena such
as mutation and chromosomal aberrations embryonic development and
pregnancy, pineal functions, and finally tumor growth in vivo.
Keywords : electromagnetic field, membrane transport,
cell proliferation, biological effects
The MAGFIT is the first magnetic attachment to be manufactured
in Japan. Since its introduction into the market in 1992, it has
become popular all over the country in a rather short time. During
this period, we have received various demands and comments from
several clinicians. Although the MAGFIT's design makes it the
smallest attachment available, the most frequent comments concerned
its size. Users desired a smaller attachment. Based on these demands,
we have improved the MAGFIT SYSTEM and developed the new MAGFIT-EX
SYSTEM.
In this report we explain the structure, working principles and performance of this new magnetic attachment.
The MAGFIT-EX retains the sandwich-type construction, but it has been designed to be smaller for easier for clinical application without sacrificing its retentive force.
Keywords : magnetic attachment, sandwich-type magnetic
attachment, neodymium magnet, MAGFIT-EX attachment
It is sometimes encountered in clinical use of a magnetic
attachment that the attachment is required to cut partially due to
restricted space in the mouth and is subjected to undesirable
displacement of a keeper or a magnetic assembly due to deformation of
dentures and the alveolar ridge. The objective here is to evaluate
the reduction effects on magnetic force caused by such cutting and
displacement for a cup yoke type of magnetic attachment (Hicorex
Super 4015®, a magnetic
assembly : 4mmø×1.5mmt, a keeper: 4mmø×0.8mmt). Force reduction is analyzed by a three
dimensional magnetic moment method to examine allowable quantities of
cutting and displacement, e.g., the quantities to give 10% reduction
of magnetic force. As a result, the edge of a keeper may be allowed
to cut by 0.4 to 0.5mm to give 10% reduction, and its thickness can
be reduced as thin as 0.5mm. The side of the assembly can be cut by
0.3mm for the reduction. Partial cutting of the top corner of the
assembly gives almost no effect. Magnetic force is very sensitive for
an inclination of the keeper to the assembly, i.e., only 0.3 degree
inclination gives the 10% reduction. Lateral displacement of 0.3mm
between the keeper and the magnetic assembly gives 10% reduction as
well as cutting of the assembly.
Keywords : magnetic attachment, cup yoke type, magnetic
force, attractive force
A dental magnetic attachment "MAGFIT", developed in 1992 has
acquired broad popularity in Japan in a relatively shot period since
its introduction.
The MAGFIT is constructed of two parts, a magnetic assembly and a keeper. Generally, the former is installed into the denture base and the latter is attached to an abutment tooth. From our clinical experiences, we recommended the keeper be attached to the root cap through the so called cast-weld method. However, in various clinical situations, another technique could also be a choice. This method is the soldering method which is a more common laboratory technique in dentistry. If a keeper can be soldered to the root cap, clinical application of the magnetic attachment can be expanded. However we do not have enough information on this matter.
The present report aims at providing general information regarding the possibility of introducing the of soldering technique on the magnetic attachment procedure. The investigation was carried out on several kinds of dental alloys and soldering fluxes.
A summary of the result is as follows:
1) Soldering of magnetic stainless steel to general dental alloys is possible
2) The most adequate flux for this purpose is OXYNON®(Degussa).
Keywords : magnetic stainless steel, flux, soldering
Magnetic keepers used as dental magnetic system are liable to
suffer corrosion, because of applying stainless steel for the
magnetism. Therefore, visual inspections, microscopic observations
and elemental analyses on magnetic keepers (AUM20, SUS447J1, SUS430)
were performed.
The results were follows:
1. Approximately half of each kind of keepers was inspected some tarnish.
2. Change of surface form or color and/or corrosion were observed by the microscope.
3. Ca, K, P, Si, Al,. Ti and S expect for elements as received were detected by elemental analyses.
Keywords : magnetic keeper, clinical observation,
tarnish, corrosion, elemental analysis
Keepers of magnetic attachments are exposed to various
conditions in the process of laboratory procedures.
This investigation reports Knoop hardness, the surface roughness, the grain size and the macroscopic observations after heat and acid treatments as for four kinds of keepers : AUM20, SUS447J1, SUS430 and SUS430N.
The results were as follows :
1. Knoop hardness decreased in case of SUS447J1.
2. Any keepers was not shown statistically significantly different results concerning the surface roughness.
3. The grains of SUS447J1 grew in particular.
4. In the visual observations, oxide films could not be removed from keepers by acid treatments in case of AUM20 and SUS430 new type.
Keywords : magnetic keeper, Knoop hardness, surface
roughness, grain size
For the purpose of applying dental casting of Fe-Pt-Nb magnet
to removable crowns and bridges, Fe-39.5at%Pt-0.75at%Nb alloys, which
is the component typically employed, were used. To determine the
optimum casting conditions for the alloys, surface roughness after
casting, magnetic properties and attractive force were examined for
the specimens cast into several kinds of titanium investment for
crowns and bridges. From those results, appropriate investment and a
mold temperature were obtained. Those results were as follows :
(1) It is clear that those alloys are able to dental cast.
(2) As for surface roughness, the influence of the materials of investment were recognized, and a specimen cast into Titavest CB showed favorable surface. hardly any influences due to mold temperature except for the room temperature were observed. And almost of all the results obtained were favorable. However, various kinds of casting defects were also observed on the surface of the specimens.
(3) As for magnetic properties, there were no apparent influences caused of the materials of investment. So, they showed similar value. Regarding to the influence of the mold temperature, the magnetic properties showed higher values in a region from 200 to 600°C.
(4) As for attractive force, the maximum value over 700gf was obtained, and it is suggested to be able to apply for the dental use such as removable crowns and bridges.
Keywords : Fe-Pt-Nb magnets, dental casting, crown and
bridge, magnetic properties, attractive force
Corrosion is the most crucial clinical aspect of a magnetic
attachment. This report provides the experimental results of a
corrosion test performed on two types of magnetic attachments ; the
MAGFIT-EX® and the HICOREX
SUPER®.
The keepers of the attachments were treated in seven different ways to simulate clinical procedures and then immersed in a 0.9% saline solution. After immersion, the samples were examined for weight increase and given an elution test.
The findings were as follows :
1) Both keepers without heat treatment showed no difference in corrosion levels.
2) After heat treatments simulated clinical procedures such as cast-welding or soldering, the weight of the HICOREX SUPER® increased significantly. The weight of the MAGFIT-EX® remained the same.
3) Elution tests reveals that Fe and Cr ions were mainly present. The HICOREX SUPER® eluted greater amount of these ions than the MAGFIT-EX® keeper.
Keywords : magnetic attachment, corrosion, corrosion
resistance, elution test, MAGFIT-EX attachment