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2. Introduction
โข Magnetic fields can be either Natural or
artificial.
โข These fields were tested and proven to have
no adverse effects on humans.
โข These test results have made possible the
use of magnets in the field of dentistry.
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3. โข The first use of magnets in Dentistry was by
Behran and Egan in the year 1953.
โข They used it as implants for denture
retention.
โข First use of magnets for tooth movement
was described by Blechman and Smiley by
experimenting on cats.
โข Becker in 1970 introduced rare earth
magnets having properties superior to
previously used magnetic alloys.
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4. Properties of magnets
โข Magnetic field can be either Static or Time
varying.
โข Static field produced by Direct current
โข Time varying field by alternating current
โข Static field characterized by flux lines
which start at the north pole and following a
smaller or wider curved path,return to the
magnet at the south pole.
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5. Propertiesโฆโฆ..
โข COULOMBS LAW:
States that the force
between two magnetic poles is proportional
to their magnitudes and inversely
proportional to the square of the distance
between them.
โข CURIE POINT:
Pierre Currie observed magnets to loose
their properties if subjected to a specific
temperature which is called Curie point.www.indiandentalacademy.com
6. Propertiesโฆโฆ...
โข High force to volume ratio:
โข Introduction of rare
earth magnets has led to the use of smaller
magnets delevering a higher force than the
bulkier ones.
โข An increase in the force to volume
ratio{miniaturizing effect}makes the use of
magnets in Dentistry a beneficial modality.
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7. Propertiesโฆโฆ..
โข Maximal force at short distances:
โข Rare earth magnets give maximal
force at short distances in comparison to
elastics,which attain maximum force at
longer distances.
โข Three Dimensional Centripetal orientation
of attractive magnetic forces gives the
operator a complete tooth control on precise
engagement. www.indiandentalacademy.com
8. Propertiesโฆโฆโฆ.
โข No interruption of magnetic force lines by
intermediate media.
โข When using attractive forces frictional
forces are excluded.
โข Rare earth magnets can maintain energy if
protected against corrosion, thermal and
other biologic pertuberances unlike other
force delivery systems that deteriorate over
a short time.
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9. โข A study by J.A Von Fraunhofer in 1992
found that magnets with a seperation of less
than 2mm obeyed coulombs law
โข 0 -2mm seperation effective forces were
reduced
โข Seperation beyond this created values
which are lesser than those required for
physiological tooth movement
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13. โข Types of Magnetic materials:
โข In various dental
applications the following materials have
been used.
โข 1. Platinum-cobalt
โข 2. Aluminium-Nickel-Cobalt
โข 3. Ferrite
โข 4. Chromium-Cobalt-Iron
โข 5. Samarium-Cobalt
โข 6. Neodymium-iron-Boron.
โข
โข
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14. โข SAMARIUM -COBALT MAGNETS
โข A powdered metallurgically
processed inter-metallic alloy of Cobalt and
rare earth metals when compared with other
rare earth magnets.
โข Required force obtained from a small size
of the magnet making it ideal for
orthodontic use.
โข Have high resistance to demagnetization
with time.
โข High Curie point-680 centigrade
โข They are Parylene coated to prevent leaking
of toxic substances.
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15. โข Biologic concept of Magnetic force and
Histologic changes.
โข It was found that magnetic forces
inflicted a minimum of stress that induces
various bio-chemical changes in a patient
during orthodontic tooth movement.
โข No subcutaneous changes as
inflammation or adverse reaction under the
magnets.
โข Resorption of bone occurred under
magnets after 3-4 weeks.
โข Reduced chances of necrosis of
bone as magnets make erythrocytes thinner.
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16. โข Lars Bondemark and Jure Kurol studied
changes in human pulp and gingival tissue
on exposure to magnetic field and found no
changes.
โข Mac Donald 1993 reported an increased
proliferation and systemic activity in
fibroblasts on the use of static magnetic
fields.
โข Astudy by Cerny and Sandler found no
bioharzardous effect with rare earth
magnets.
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17. โข A study by Lars Bondemark &Alf
Wennberg in 1994 showed
โข Uncoated Samarium Cobalt magnets
showed severe toxicity
โข Parylene coated Samarium magnets showed
mild toxicity
โข Coated &uncoated Neodymium magnets
showed negligible toxicity
โข Short term exposure to magnet fields did
not cause any cytotoxic effect on cells
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23. โข Magnetic Force systems in Orthodontics
โข 1.Relocating impacted teeth
โข 2.Expansion of arch
โข 3.Distal/mesialization of molars
โข 4.Intrusion of posterior teeth in open
โข bite cases
โข 5.Class 11 correction with functional
โข appliances
โข 6.Skeletal correction with functional
โข appliances
โข 7.Closure of diastemawww.indiandentalacademy.com
24. โข 9. Uprighting and Derotation of teeth
โข 10. Magnetic Brackets
โข 11. Class 11 correction with Magnetic
โข Twin block
โข 12.Magnetic appliance for treatment of
โข snoring patients with and without sleep
โข apnoea
โข 13. Extrusion of fractured teeth
โข 14.Extraction and Non-extraction cases
โข 15.Treatment of hemifacial microsomia
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26. โข Magnetic Appliance for an extraction case
โข Attractive magnetic forces are used to
bring about orthodontic tooth movement
โข Magnetic Appliance for a non-extraction
case
โข Derived from magnets in attraction or
repulsive mode
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27. Magnetic Activator Devise
โข Magnetic functional appliance developed
by Darendilier in 1993 for correction of
mandibular deviations
โข Active vertical correcter introduced by
Darendilier in in 1986 as a non surgical
alternative treatment for Skeletal open bite
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28. Fixed Magnetic Appliance
โข Introduced by Varun Kalra &Charles
Burstone in 1989
โข Appliance has the magnets in repelling
mode embedded in the upper and lower
acrylic splints
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29. Magnetic Twin Blocks
โข Clark used magnets in his Twin Block
โข Magnets were embeded in the inclined
surface of the twin block in attractive mode
โข When used in the repelling mode it reduces
the need for reactivation
โข Used in different ways for treating Class 11
and Class111 malocclusion
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30. Magnetic Brackets
โข Introduced by Kawata et al in 1987
โข Samarium Cobalt magnets with an
edgewise bracket on one surface to receive
the archwire and a mesh on the inferior
surface for direct bonding
โข Designed to deliver 250gms force
โข Complex lab procedures&dimensions of the
brackets to obtain necessary force levels
were seen as maximum disadvantageswww.indiandentalacademy.com
31. Propellent Unilateral Magnetic
Appliance
โข Introduced by Chafe 1995 for stimulating
an autogenous costochondral graft in
hemifacial microsomia
โข Consists of Samarium - Cobalt magnets
embedded in upper & lower acrylic bite
blocks in the repelling mode
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32. Magnetic Appliance For
treatment of Snoring Patients
โข Introduced in 1998 by Mars Bernhold &
Bondemark
โข Two intraoral occlusal splints each with
four parylene coated Neodynium magnets
are used
โข Full tooth coverage is required to prevent
unwanted tooth movements
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33. Deimpaction with Magnets
โข Used by Vardimone et al in 1991
โข He used a magnetic bracket bonded to an
impacted tooth & intraoral magnet linked to
a Hawley type retainer to guide the
erupting tooth
โข Darendeliler in 1994 used a small bonded
magnet on an impacted Canine
โข Sandler 1991used a similar method
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34. Functional Orthopedic Magnetic
Appliance
โข Developed by Vardimon in 1989 for
Class 11 & class 111 malocclusion
โข FOMA 11 consists of upper magnet located
anterior to lower magnet in a non displaced
jaw relationship
โข FOMA 111 consists of upper and lower
plates with magnets
โข all magnets kept in an attractive mode
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35. Autonomous Fixed Appliance
โข Darendelier &Jobor in 1992 used this to
treat a Class 11 Bimaxillary protrusion
โข Samarium Cobalt were bonded to individual
teeth at an appropriate level forming the
Autonomous Fixed Appliance
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36. Magnets for closing Diastemas
โข Muller in 1984 bonded rectangular
magnets delivering 117.5 gms of force of
attraction on each maxillary central incissor
to close a midline diastema
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37. Expansion with magnets
โข A study on Facicularis monkeys proved that
repelling magnets delivered ideal forces for
expansion compared to a jack screw
appliance
โข Darendililer et al in 1993 used mid palatal
repelling magnets and showed both dental
and skeletal expansion in his report
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38. Magnets For Molar Distalization
โข Molar Distalization was reported by
Gianelly et al in 1998,Bondemark et al
1990,Takami et al 1991 and Steger et al
1975
โข they used repelling magnets between upper
premolar and molar
โข Bondemark et al 1994 compared push coils
versus magnets for molar distalization
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44. Extrusion of fractured teth
โข Bondemark &Kurol in 1997 used magnets
to extrude the fractured root
โข Magnets used were in the attractive mode
with a minimum gap of 2mm
โข after the desired extrusion the tooth can be
restored
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47. โข Advantages of magnetic appliances
โข Eliminates patient co-operation
โข Produces less pain and discomfort
โข Continous force exerted
โข Treatment time reduced
โข Reduced periodontal disturbance
โข No friction
โข Less chair side time
โข Better force
โข Better directional control
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49. Recycling of Magnets
โข Bondemark &Kurol conducted extensive
studies on recycling of rare earth magnets
โข concluded that the biocompatability &force
stability is not effected
โข Darendililer felt that magnets should not be
recycled for ethical reasons
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50. โข Summary & Conclusion
Magnets can be used to give
predictable forces in either attraction or
repelling mode & can be made small
enough to suit most dental applications.
The evidence currently available
from biological safety testing would suggest
that the risk of harmful biological effects
are negligible.The high cost can be
overcome by reusing it after sterilization &
recycling.
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