Magnets

MAGNETSMAGNETS
ININ
ORTHODONTICSORTHODONTICS
www.indiandentalacademy.comwww.indiandentalacademy.com

 IntroductionIntroduction
 Types of magnetic materialsTypes of magnetic materials
 Properties of magnetsProperties of magnets
 Application of magnets in orthodontics.Application of magnets in orthodontics.

 In 1953, magnets were first used for dentureIn 1953, magnets were first used for denture
retention byretention by BEHRAN & EGAN.BEHRAN & EGAN.
 Use of magnets in orthodontic-Use of magnets in orthodontic- BLECHMAN &BLECHMAN &
SMILEY.SMILEY.

PROPERTIESPROPERTIES OF MAGNETSOF MAGNETS
 Flux DensityFlux Density

 In dentistry, ferromagnetic materials withIn dentistry, ferromagnetic materials with
static field are used.static field are used.
 Magnetocrystalline Anisotropy.Magnetocrystalline Anisotropy.
 Coercivity.Coercivity.

 Coulombs lawCoulombs law:-:-This law states that force betweenThis law states that force between
two magnetic poles is directly proportional totwo magnetic poles is directly proportional to
magnitude & inversely proportional to square ofmagnitude & inversely proportional to square of
the distance between them.the distance between them.
 Curie pointCurie point:-:-Pierre Curie(1859-1906)Pierre Curie(1859-1906)

 High force to volume ratio.High force to volume ratio.
 Maximal force at shorter distances.Maximal force at shorter distances.

 No interruption of magneticNo interruption of magnetic
force lines by intermediateforce lines by intermediate
media.media.
 No friction in attractive forceNo friction in attractive force
configuration.configuration.
 No energy loss.No energy loss.

TYPES OF MAGNETIC MATERIALSTYPES OF MAGNETIC MATERIALS
 Platinum-cobalt(Platinum-cobalt(Pt-coPt-co))
 Aluminium-Nickel-Cobalt(Aluminium-Nickel-Cobalt(Al-Ni-CoAl-Ni-Co))
 FerriteFerrite
 Chromium-cobalt-IronChromium-cobalt-Iron
 Samarium Cobalt(Samarium Cobalt(SmCoSmCo))
 Neodymium-Iron-Boron(NdNeodymium-Iron-Boron(Nd22FeFe1414BB))

 SAMARIUM-COBALT (SmCoSAMARIUM-COBALT (SmCo55&Sm&Sm22CoCo1717))
MAGNETSMAGNETS:-:-
-high resistance to demagnetization.-high resistance to demagnetization.
-corrosion resistance-corrosion resistance..

 AdvantagesAdvantages:-:-
-Continuous force is exerted.-Continuous force is exerted.
- Eliminates the patient co-operation.- Eliminates the patient co-operation.
-No friction.-No friction.
 DisadvantagesDisadvantages:-:-
-Tarnish &corrosion products are cytotoxic.-Tarnish &corrosion products are cytotoxic.
-Cost factor-Cost factor

 Biological effect of magnetic forces:-Biological effect of magnetic forces:-
AAronsonronson:-thinning of epithelium under:-thinning of epithelium under
attracting & repelling magnets.attracting & repelling magnets.
McDonaldMcDonald -- proliferative activity of fibroblastsproliferative activity of fibroblasts
in presence of static magnetic fieldin presence of static magnetic field
Lars Bondemark & KurolLars Bondemark & Kurol studied changes instudied changes in
human dental pulp and gingival tissue.human dental pulp and gingival tissue.

APPLICATIONS OF MAGNETICAPPLICATIONS OF MAGNETIC
APPLIANCESAPPLIANCES
1.1. Tooth intrusionTooth intrusion
2.2. ExpansionExpansion
3.3. Tooth ImpactionTooth Impaction
4.4. Space closureSpace closure
5.5. Molar distalizationMolar distalization
6.6. Magnetic Edgewise bracketsMagnetic Edgewise brackets
7.7. Functional AppliancesFunctional Appliances..
8.8. Retainers.Retainers.

 Tooth IntrusionTooth Intrusion:-:-
Active Vertical Corrector-Active Vertical Corrector-DellingerDellinger(1986)(1986)
-Samarium cobalt magnets in the repelling mode-Samarium cobalt magnets in the repelling mode
are used.are used.

 Fixed Magnetic ApplianceFixed Magnetic Appliance:-:-
-introduced by-introduced by VARUN KALRA & CHARLES BURSTONEVARUN KALRA & CHARLES BURSTONE..
Appliance consists of an upper &lower acrylic splints withAppliance consists of an upper &lower acrylic splints with
samarium cobalt magnets in stainless steel castingsamarium cobalt magnets in stainless steel casting
embedded in a repelling mode.embedded in a repelling mode.

 EXPANSIONEXPANSION:-Vardimon et al(1987) demonstrated:-Vardimon et al(1987) demonstrated
palatal expansion using two types of magnetic devices inpalatal expansion using two types of magnetic devices in
Macaca fascicularis monkeys.Macaca fascicularis monkeys.
--Tooth borne applianceTooth borne appliance

 Tissue borne appliance (attached directly toTissue borne appliance (attached directly to
palate by endosseous pins).palate by endosseous pins).

 Tooth ImpactionTooth Impaction:-:- Vardimon,Graber,DrescherVardimon,Graber,Drescher
--Neodymium Iron Boron magnets can be used toNeodymium Iron Boron magnets can be used to
assist eruption of an impacted canine.assist eruption of an impacted canine.
 ManciniMancini(1996)-force levels are sufficient enough to(1996)-force levels are sufficient enough to
induce the cellular &biochemical changes are required toinduce the cellular &biochemical changes are required to
produce orthodontic tooth movement.produce orthodontic tooth movement.

space closurespace closure
-simple tooth movement without archwires :--simple tooth movement without archwires :-Muller(1984Muller(1984))
-Complex Intra &Interarch Mechanics:--Complex Intra &Interarch Mechanics:-Blechman(1985)Blechman(1985)
CL-II mechanics with a magnetic force
system in a CL-I extraction case

3 magnet configuration to enhance3 magnet configuration to enhance
CL-II mechanicsCL-II mechanics
3 magnet configuration3 magnet configuration
used to simultaneouslyused to simultaneously
move all 4 canines distallymove all 4 canines distally

CL-II mechanics using magnetic forceCL-II mechanics using magnetic force
system in CL-II extraction case.system in CL-II extraction case.
Repulsive CL-II mechanics in CL-IIRepulsive CL-II mechanics in CL-II
Nonextraction cases.Nonextraction cases.

 Molar DistalizationMolar Distalization..
--GianellyGianelly et al(1989):-repelling magnets in conjuntion with aet al(1989):-repelling magnets in conjuntion with a
modified Nance appliance was used.modified Nance appliance was used.
--Bondemark & Kurol:-Bondemark & Kurol:-repelling samarium cobalt magnetsrepelling samarium cobalt magnets
were used for distalization.were used for distalization.

 Magnetic Edgewise BracketsMagnetic Edgewise Brackets:-:-KawataKawata(1987)(1987)
-Samarium cobalt magnet with an edgewise bracket-Samarium cobalt magnet with an edgewise bracket
(o(o.018slot.018slot) .) .

 Functional Orthopaedic Magnetic AppliancesFunctional Orthopaedic Magnetic Appliances:-:-
Vardimon(1989)Vardimon(1989)
--for correction of CL-II&CL-III malocclusion.for correction of CL-II&CL-III malocclusion.

 Magnetic Twin BlockMagnetic Twin Block:-:-
Clark(1996)Clark(1996)
--Samarium cobalt magnetsSamarium cobalt magnets
were embedded in thewere embedded in the
inclined surface of theinclined surface of the
twin block in attractivetwin block in attractive
mode.mode.

 Magnetic Activator Device(MAD):-Magnetic Activator Device(MAD):-
--DarendilierDarendilier (1993) developed this magnetically active(1993) developed this magnetically active
functional appliance.functional appliance.
MAD I-mandibular deviationsMAD I-mandibular deviations
MAD II-CLII malocclusionMAD II-CLII malocclusion
MADIII-CLIII malocclusionMADIII-CLIII malocclusion
MADIV-skeletal open bite correction.MADIV-skeletal open bite correction.
MAD-II

MAD-II FOR CORRECTION OF CL-II,DIVISION 1MAD-II FOR CORRECTION OF CL-II,DIVISION 1
MALOCCLUSION.MALOCCLUSION.
Deep Bite
open Bite

 MAD IIIMAD III

 MAD - IVMAD - IV

MAD IV(a)
MAD IV( b)
MAD IV( c)

 Treatment of CL-IITreatment of CL-II
bimax with magnets-bimax with magnets-
Darendelier&Joho(199Darendelier&Joho(199
2)2)
-Autonomous fixed-Autonomous fixed
magnetic appliance.magnetic appliance.

 Propellant Unilateral Magnetic AppliancePropellant Unilateral Magnetic Appliance (PUMA)(PUMA)
- Chate(1995)Chate(1995)
Magnets are use to stimulate costo-chondral boneMagnets are use to stimulate costo-chondral bone
graft in Hemi facial microsomia.graft in Hemi facial microsomia.

 RetainersRetainers:-:-Springate &Springate &
Sandler(1991)Sandler(1991)
-micro magnets made-micro magnets made
of neodymium iron boronof neodymium iron boron
magnets as a fixedmagnets as a fixed
retainer in a patient withretainer in a patient with
persistent diastema.persistent diastema.

 BibiliographyBibiliography:-:-
--Dentofacial Orthopedics with functional appliances-T.M Graber,Dentofacial Orthopedics with functional appliances-T.M Graber,
Rakosi,Petrovic.Rakosi,Petrovic.
--

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