INDIAN DENTAL ACADEMY
Leader in continuing dental education
Magnetic fields in the environment can either
be natural or artificial. We are exposed to
either of these fields at homes, in automobiles,
by wearing wrist watches and walking under
high power lines. These magnetic fields were
tested and proven that they had no adverse
effects on humans. The tests and reports have
given entry to magnets in the field of Medicine
and Dentistry several decades ago.
The first use of magnets in Dentistry was by
Behran and Egan in 1953. Who used it as
implants for denture retention. The use of
magnets for orthodontic tooth movement was
first described by Blechman and Smiley who
bonded earth magnets made of Aluminum-
Nickel - Cobalt to the teeth of adolescent cats
to produce tooth movement. Other rare earth
magnets, Samarium. - Cobalt, introduced by
Becker in 1970 .
Neodymium - Iron - Boron (Nd2Fe14B) have
been of special interest as these alloys have
properties superior to previously used
magnetic alloys like Al – Ni-Co, Ferrite and
Platinum - Cobalt magnets, which had their
limitations, particularly in relation to their
size, high cost and risk of demineralization.
Rare earth magnets which have exceptionally
high maximum energy product values and high
resistance to demagnetization permit their use
in devices where small size and superior
performance are desired, as in the field of
PHYSICS OF MAGNETS
In biomagnetic experiments, three parameters
need to be considered:
1. Gradient: The gradient usually characterizes
the inhomogeneity of the field. The physical
difference between an inhomogeneous field
and a homogeneous field is that, an
inhomogeneous field exerts an accelerating
force upon particles which are more para-or
more dia-magnetic than their surroundings,
and this accelerating force apparently accounts
for all observed biomagnetic effects.www.indiandentalacademy.com
2. Field intensity: (H). To compute the field B
produced by a permanent magnet in the
surrounding environment, the relationship used
is: B = µH, where H = field intensity, or
magnetomotive force (oersteds), and B = field
flux density (gauss) and µ= 1, for air and most
other biologic material. Therefore, B = H for
any magnetic operation.
For the most efficient use of magnetic material
(i.e., the smallest size magnet for a given
output), a magnet should be designed to operate
at the point of maximum energywww.indiandentalacademy.com
3. Direction of field vector: The direction of
electron spin in the third shell of the atom
produces a magnetic moment, which accounts
for the magnetic field. A limited volume of
these tiny electromagnets form domains of
internal field energy, which can be reoriented
in direction to establish external field energy.
(Once magnetized, a permanent magnet
requires no further energy to maintain the
PROPERTIES OF MAGNETS
Where ever there is an electric current flowing
there is always a magnetic field. In principle, the
magnetic field can either be static or time
varying. A static field is formed in the case of
direct current, and time varying field is produced
by altering current sources. A time varying
magnetic field which has periodic variations in
intensity induces Eddy current within the body.
In dentistry, hard magnetic materials or Ferro,
magnetic materials with magnets of static
constant field are used. The static kind of
magnetic field is usually characterized by lines.
In the case of a bar magnet with north pole at one
end and south pole at the other, the flux lines
start from the north pole and following a smaller
or wider curved path, return to the magnet at the
south pole.. However, as some orthodontic
situations when intrusion of posterior teeth is not
only static, but depending on mandibular
movements the field will become more like a
time varying field.
All magnets obey this law which states
that the force between two magnetic
poles is proportional to their magnitudes
and inversely proportional to the square
of the distance between them.
Rare earth magnets tend to loss their magnetism
at room temperature. Pierre Currie observed that
magnets tend to lose their properties if subjected
to a specific temperature which causes their
domain to return to random distribution. This
point of temperature is called Currie Point. In
Orthodontics, this has been overcome by using
magnets which are combined with other
elements so that they can be incorporated in
appliances and also be heat sterilized.
HIGH FORCE TO VOLUME RATIO
Introduction of new magnetic alloys allowed
the use of permanent magnets in dentistry.
These rare earth magnets, which belong to
Lanthinide series, are 20 times stronger than
, , Aluminium- Nickel - cobalt. Thus for the
same force magnitude a 20 time smaller
magnetic unit can be applied with rare earth
magnets because the oral cavity dictates the
size of the appliance, the increase in F/V ratio
(also known as Miniaturizing Effect) makes
the use of magnets in dentistry a beneficial
In physical forms, the new magnetic
alloys are characterized by a high coercive
force (high magnetic field strength) which
indicates their ability to encounter
demagnetization forces, a high reminence
of magnetic induction, which indicate the
extent of spontaneous magnetization and
high energy product thus their ability to
attract or repulse
MAXIMAL FORCE AT SHOR DISTANCES
Conventional appliances such as coils, springs,
elastics etc, react according to Hookes Law, where,
force (f) is proportional to a constant such as the
elastic modulus(µ), time and the distance (d).
Magnetic forces react according to Coulombs law
where the force is proportional to the inverse
square of the distance (F X- 1/d2). The rare
magnets give maximal force at short distance in
comparison to elastics, which attain maximum
force on more distance for example on mouth
THREE DIMENSIONAL CENTRIPETAL
ORIENTATION, OF ATTRACTIVE
When two magnets are displaced in all three planes they
attract to a complete overlap centripetal attraction in all
three spatial dimensions, as this is called, therefore gives the
operator complete tooth control on precise engagement. No
interruption of magnetic force lines by intermediate media.
Another unique feature of magnetic forces is that any media
interposed between two magnets cannot bar the passage of
magnetic force lines. Intra oral magnets are attracted to each
other even if soft and hard tissues are interposed in the gap
between the two magnets
NO FRICTION IN ALTERNATIVE
Attracting magnets are useful in controlling the
three spatial dimensions. This feature is called
Centripetal Orientation. when an attractive force
configuration is used, friction forces like arch wire
in the slot are excluded. But in the use of repulsive
forces, Muller Prongs guiding elements are used
for centripetal orientation. But these may induce
friction in the appliance and may call for increase
in force threshold to compensate for the loss of
NO ENERGY LOSS
Elastics are the best examples of force
systems that deteriorate over a short time.
The viscoelastic properties of elastics are
prone to relaxation. In contrast, rare earth
magnets can maintain energy if protected
against corrosion, thermal and other
TYPES OF MAGNETIC
In various dental applications the following
materials have been used:
Platinum - Cobalt (Pt - Co)
Aluminium - Nickel - Cobalt (Al - Ni - Co)
Chromium - Cobalt - Iron
Samarium - Cobalt (Sin - Co)
Neodymium –Iron-Boron (Nd Fe B)
The first three above mentioned magnets were
expensive and bulky and were used with their
limitation till rare earth magnets were developed in
Finally, Samarium Cobalt rare earth magnets were
found to be suitable for orthodontic use due to
various reasons.Neodymium- Iron - Boron was
introduced which are 70% more powerful than a
same size Sm - Co, magnets but are susceptible to
corrosion and very brittle.
ADVANTAGES OF MAGNETS
It eliminates patient co-operation as it is
totally operator controlled.
It produces less pain and discomfort
Continuous force is exerted
Treatment time is reduced.
Magnetic tooth movement is biologically
more acceptable with reduced periodontal
disturbance, root resorption and caries.
Appliance adjustments are minimal,
therefore it takes less chair time
Better force, working range control is
achieved by maintaining the distance
Better directional force control
Magnets suffer from tarnish and corrosion
These tarnish and corrosion products are
Concerns have been expressed on the
biological effects of static magnetic field.
Bulk of magnets is still a concern in space
It is bitter to taste and not very cost effective.
SAMARIUM - COBALT MAGNETS
(SmCo5 & Sm2Co17 )
It is a powdered metallurgically processed inter-
metallic alloy of Cobalt and rare earth metal.
Superior magnetic properties when compared to other
rare earth magnets except Neodymium - Iron Boron
Even with a flat shape there is hardly any
demagnetization making it ideal and small for
The force necessary in orthodontics can be obtained
from a small size of the magnet measurable in
Magnetic properties are invariable in course of time i.e.
have high resistance to demagnetization with time.
High Currie Point, of 680ºC allowing heat sterilization
and manipulation with heat up to 200ºC without
Corrosion resistance is comparatively high since they are
parylene coated to prevent leaking, of toxic substances.
They can also be encased in stainless steel jackets.
They should be handled with care as they are brittle but
are stronger than Neodymium- Iron - Boron magnets.
Hence they are difficult to process but can be filed
slightly with dental tools
These are the latest rare earth magnets they are
materials of choice because of the following
High energy product value 260 Kj/ m³as
compared to 190Kj/m³ of the samarium cobalt
Better bio compatibility
High energy product implies stronger forces of
Very susceptible to corrosion
Risk of destroyed magnetic properties
To avoid liberation of cytotoxic product
into the oral cavity it is necessary to coat
these magnets with parylene and then
embed them into the acrylic blocks
BIOLOGICAL CONCEPT OF MAGNETIC
FORCE AND HISTOLOGIC CHANGES
Treatment with traditional orthodontic
appliances in human subjects has shown a
decrease from normal in the levels of citric
acid and calcium in the blood. It was
suggested by these findings that the
movement may cause a stress that induces
various bio-chemical changes.
. In studying the methods of reducing
stress induced by traditional orthodontic
appliances,it was found that there were
no subcutaneous changes as inflammation
or adverse reaction under the magnets.
There was an apparent inhibitory effect of
magnets on the epithelial recycling
evidenced by the reduced thickness of
epithelium under attracting or repelling
Resorption of bone accessed under magnets after
3-4 weeks, as evidenced by the increased
number of Howship lacunae, containing
osteoblasts. There was inhibitory effect on the
bone lining osteoblasts, which by feed back
system promoted osteoblasts differentiation.
Magnets made the erythrocytes thinner and
longer enabling them to pass through the
compressed capillaries in the periodontal
ligament during orthodontic loading. This
reduces the chances of necrosis of bones and
It was found that a biologically optimal intrusive force
was 450 gms a study by Serny and Sandler found no
bio-hazardous effect with rare magnets
Lars Bondemark and Jude Kurol studied changes in
human dental pulp and gingival tissue on exposure to
magnetic field. They found no difference in clinical
Encouraging result like increased proliferation and
systematic activity in fibroblasts on the use of static
magnetic field has been reported by Mac Donald
(1993). Also a doubling in the Alkaline Phosphate in
osteoblasts like cells were noted.
MAGNETIC FORCE SYSTEMS IN
Magnetic force systems are now popularly used
Relocating impacted teeth (Vardimon et. al.
Expansion of arch (Alexander 1987)
Distalization / Mesialization of teeth
Intrusion of posterior teeth in open bite cases
Class II correction with functional appliances
Skeletal correction with functional appliances
Closure of diastema
Up righting and derotation of teeth
Puma hemi facial microsomia.
Class II correction with magnetic twin block
Non extraction and extraction cases
Magnetic appliance for treatment of snoring
patients with and without sleep apnoea.
Extrusion of fractured teeth
MAGNETS FOR CANINE
According to a study conducted by John
Daskalogiannaskis and Kenneth Roy
Mclachlan (1996). They used an assembly of
magnets for retraction of canines as these
magnets provided higher rate of orthodontic
translation by delivering a constant force to
Cases in which the first premolars had been extracted
canine were retracted by having a
A Nance /Transpalatal arch for reinforcing anchorage
A vertical loop was made in 0.017x 0.025 inch TMA
wire with a helix between the premolar and the molar
for receiving a magnet.
Another wire 0.018x0.025 SS arch wire was
fabricated as vestibular wire which was inserted in
the auxiliary tube( this assembly is for 0.18slot
appliance)this vestibular wire receives two 2x3x5
mm in size Neodymium-Iron –Boron magnet and the
magnet on the helix with the loop comes in between
these two magnet such that the mesial magnet and the
middle magnet are in repelling mode where as the
distal magnet and the middle magnet are in attractive
Thus this appliance with
magnets provided a
constant force for the
retraction of the canines
and this method is two
times faster than the
conventional methods of
retraction as they use
interruptive force which
degrades after sometime
If there is a need to close premolar spaces
simultaneously, another three magnet
arrangements may be used. The upper
magnetic force system is arranged as
previously described. The magnets are
arranged so as to permit the upper magnets to
fall between the lower two magnets, with a 2
mm wire gap between all the attractive poles.
As usual the base arch wires are used to guide
tooth movement and reinforce anchorage.
Also intramaxillary magnetic forces can be
applied in order to close spaces
This magnetically active functional
appliance was developed by Darendilier
It can be used for the correction of
mandibular deviations (MAD I).
Class II malocclusions (MAD II).
Class III corrections (MADIII).
For skeletal open bite cases (MAD IV).
He had used Samarium Cobalt magnets in attractive
and repelling mode to achieve orthodontic and
In MADII, attracting magnets are used on a two piece
upper and lower activator. This allows freedom for
In class II malocclusions with open bite it is
combined with posterior repelling magnets on the
maxillary plate for expansion of' the arch which is
called magnetic expansion device (MED).
MAD IV is used for skeletal open bite cases with
posterior repelling magnets and also anterior
He had also used Neodymium - Iron - Boron magnets
in MAD IV
The MAD IV-a is used in cases where the anterior
segment of the maxilla is vertically correct or
overdeveloped (gummy smile)., the posterior and
anterior magnets are placed in full contact (Fig A).
The MAD IV-b is used when an additional extrusive
effect is needed in the maxillary anterior region. The
anterior magnets are positioned with a vertical
opening of 2-3mm, while the posterior magnets are
placed in full contact. (Fig B).
The MAD IV-c is used when only anterior extrusion
is needed. The posterior magnets are omitted, and the
anterior magnets are placed with an opening of 1-
2mm, (Fig C).
A. Combined MED and MAD III appliance. B. Bonded
upper plate, with two mid palatal samarium cobalt magnets
forming MED. C. Removable lower plate with magnets.
It was introduced by Dellinger in (1986) as a
non-surgical alternative treatment for skeletal
open bite. It consists of upper and lower bite
blocks with Samarium Cobalt magnets in
Stainless Steel cases embedded in them. The “
energised bite blocks" extended only in the
posterior segment with a lingual heavy wire
connecting bite blocks of each arch. Lateral
flanges were incorporated in the lower split to
resist shearing forces and development of bite
results in autorotation of the mandible, closure
of anterior open bite and reduction of lower
anterior facial height were reported.
ACTIVE VERTICAL CORRECTOR
A fixed magnetic appliance was introduced by
Varun Kalra and Charles Burstone (1989).
The appliance consists of an upper and lower
acrylic splints with Samarium Cobalt magnets in
stain less steel casting embedded in them in the
The acrylic blocks are bonded and extended along,
the posterior segment only with a wire continuing
from these splints to the incisor surfaces which are
also bonded lingually to these teeth.
Thus the repelling force is transmitted to the
Hypothesis for this appliance
(1) If all erupted teeth in the upper and lower arches
could be intruded with an appliance, the mandible
would auto-rotate upward and forward into the
interocclusal space created.
(2) If this appliance could displace the condyle
downward and forward, away from the posterior part
of the glenoid fossa, stimulation of condylar growth
might occur. Both these effects, an increase in length
of the mandible and an upward and forward
autorotation of the mandible, would be beneficial in
treating Class II malocclusions associated with
increased lower facial height and a retrusive
The working bite was taken
with the mandible in centric
relation and opened 7 to 8 mm
in the permanent first molar
The appliance consisted of
upper and lower acrylic splints
that were bonded on the
occlusal halves of the
permanent first molars,
deciduous molars or
premolars, and canines.
Samarium cobalt magnets
measuring 20 x 8 x 2 mm were
encased in a stainless steel case
0.007-inch thick and
embedded into the upper and
lower acrylic splints in a
In addition a 0.028-inch wire
was embedded in the acrylic.
This wire rested on the lingual
surfaces of the four permanent
incisors and was individually
bonded to them; thereby
intrusive forces were
transmitted to the entire arch
Clark used Samarium Cobalt and neodymium-Iron-
Boron in his well acclaimed and accepted twin block.
These magnets were embedded in the inclined
surfaces of the twin blocks. In attractive mode they
ensured the twin blocks are always in contact even at
night when usually the masticatory slackness causes
the twin blocks to go out of contact. When the
magnets are used in the repelling mode it reduces the
need for reactivation,by including an additional
forward posture of the mandible. These were used in
different ways for treating Class II and Class III
malocclusions and also for correction of facial
They were introduced by Kawata et al., in 1987.
They consisted of Samarium - Cobalt magnet with an
edge wise brackets on one surface to receive arch
wires and a mesh on the inferior surface to facilitate
direct bonding to teeth. The magnets were coated
with Nickel and Chromium to prevent corrosion.
They were designed to deliver 250 gms of force and
to form an ideal arch in both maxilla and mandible on
completion of treatment
Though shorter treatment time and good bio-
compatibility were seen, dimensions of the brackets
to obtain necessary force levels and complexity of
laboratory preparation were seen as main
brackets (frontal view).
. Rear view of maxillary
Rear view of
of magnetic brackets
in crowded dental
teeth by use of
A new appliance introduced by Chafe
(1995) for stimulating an autogenous
costochondral graft in hemi facial
microsomia consists of Samarium Cobalt
magnets embedded in upper and lower
acrylic bite blocks in the repelling mode.
The long axis of the magnets were
perpendicular to the blocks interface
encouraging results were reported.
This appliance was reported by Mars Bernhold
and Bondemark in 1998. During sleep when
the masticatory muscles are physiologically
relaxed, there is an obvious risk that the
mandibular complex moves backward and
closes the air flow in the upper air way space.
Two intra oral occlusal splints, maxillary and
mandibular each with four parylene coated
Neodymuim - Iron - Boron magnets are used.
Full tooth coverage is required for the splints
to prevent unwanted tooth movements.
It was also reported that this appliance increased the
hypo pharyngeal airway space ,tongue base was
lowered and the contact between the tongue and the
soft palate reduced significantly .
Maxillary permanent canines are the most commonly
impacted tooth in 0.9 - 2.2% of the patients.
Orthodontic movement of the impacted canine after
surgical exposure is most commonly carried out.
DISADVANTAGES OF SURGICAL
2. Gingival Inflammation
3. Bony recession
4. Apical migration of epithelial attachment
5. Exposure of cemento enamel junction
6 .Communication of the impacted tooth with the
oral cavity can cause periodontal tissue
8 .Root resorption
Samarium Cobalt magnets
Neodymium - Iron - Boron
Sandler in 1992 described a user and
patient friendly method of treating
unerupted teeth. Neodymium - iron -
Boron magnet is attached to the
unerupted tooth and a second larger
magnet is incorporated in a removable
Preparation of' magnet involves tying a
thin stainless Steel ligature around it and
then coating this unit with unfilled resin.
The ligature acts as a handle for the
magnet at operation and also ensures that
the magnet is bonded to the tooth in
Magnet prepared for bonding
Composite resin provided an impermeable
barrier, preventing any ionic diffusion that
would lead – to corrosion as well as facilitating
the attachment of the magnet to the unerupted
teeth at operation.
The second larger magnet 5 x 5 x 2mm is
incorporated into a removable appliance. It is
completely surrounded by the acrylic of the
appliance, which again will prevent ionic
The only adjustment that is sometimes
required is the repositioning of the larger
magnet 2 - 3mm occlusally, once the two
magnets are in apposition.
Fig. 4. Appliance in place.
Fig. 5. Upper left canine just erupting through the mucosa.
Fig. 6. Larger magnet repositioned to allow further
Fig. 7. Sufficient eruption to allow attachment to be placed.
Sufficient eruption for bracket attachment
ADVANTAGES OF THIS
1.No unpleasant or uncomfortable manipulation
of wires, springs or elastics.
2.A low continuous force that increase over
3.Since a palatably directed force is possible, the
health of the labial plate and zone of attached
gingiva are optimized.
Vardimon et al
Vardimon et al., in 1991 introduced a new
magnetic attracting system, with a magnetic
bracket bonded to an impacted tooth and an
intra oral magnet linked to a handy type
retainer. Horizontal and vertical magnetic
brackets were designed with the magnetic axis
magnetized perpendicular and parallel to the
base and bracket respectively.
Modified twin bracket to receive a
nonmagnetized prism-shaped magnet.
In a deep impaction case, the surgical
mucoperiosteal flap was sutured over the
bonded magnetic bracket. Attraction was
initiated 1- 2 weeks after healing. Thus the
tooth emergence into the oral cavity replicated
normal eruption condition. The attracting force
level was in the range of 0.2 - 0.5N.
Adjustment was accomplished by temporarily
interposing a magnetic space between the two
magnetic units. No side effects were
Non eruption of maxillary canines.
A, Before surgery view. B, Raising a
mucoperiosteal flap. C, Bonding the magnetic
brackets and suturing back the flap partially over
the brackets. www.indiandentalacademy.com
A, Vacuum-molded maxillary appliance with
intraoral magnets attached by self-curing acrylic,
no clasp attachments are required because of the
attractive force system.
B, At progressed stage, acrylic has to be removed
from the removable appliance to eliminate
interferences with the erupted canines.
D,Canines emerged into
the mouth with no
Less invasive procedure.
Effective attractive forces at short
Controlled spacial guidance
TECH NIQUE PROPOSED BY
Ali Darendelider in 1994 showed a different approach
to the use of fixed and removable magnets in
treatment of impacted canine. He used it on a 12-year
old girl with palatally impacted upper right canine;
the root of the impacted tooth was completely
developed. Space gaining was achieved using
conventional appliances. A partial cast of the erupted
upper left canine was made for controlling a magnet
to fit the palatal surface of the impacted canine.
The pre-shaped 3mm. x 4mm. x 5mm
Samarium Cobalt magnet was then
coated with a thermoplastic material and
a mesh was bonded to the tooth side.
The deciduous canine was extracted prior
A. Magnet contoured to
cast of erupted left
canine. B. Mesh bonded
to tooth side of magnet.
A. Surgical exposure of impacted
canine. B. Magnet bonded to exposed
crown. C. Passive removable plate in
place after closure of flap over impacted
tooth and magnet.
Magnet mounted to acrylic
plate, 6.5mm from bonded
Impacted canine visible under
palatal mucosa; removable plate
Ballista spring" sectional arch wire with
attached magnet tied to continuous arch
Eruption of impacted canine crown
Button bonded to
impacted canine for
After fixed appliance
Hyeon –shik Hwang and Ki-Heon Lee (2001)
reported a case study in which the over erupted
molars were intruded with corticotomy and magnets
A molar can over erupt due to a lost antagonist and
this antagonist cannot be replaced because of the over
eruption of the molar.
The use of conventional fixed appliance can cause
undesirable extrusion of adjacent teeth and also it
takes longer time.
Molars can be intruded quickly using corticotomy
and magnets without side effects and also in adult
patients in whom the growth is already over.
Corticotomy is performed under LA muco
gingival flaps are raised on both buccal and
lingual side and the cortical bone is exposed
beyond the apical region. After the
corticotomy the flaps are returned to their
Appliance is fabricated on working models
with orthodontic bands on the over erupted
molar; wires are soldered onto the buccal and
lingual side of the band to make room for the
magnet. A removable appliance is fabricated
with Adams and cantilever springs for
.The cantilever spring are placed facing the
A disk shaped Neodymium-Iron-Boron magnet
is used on the band and the spring in the
This assembly of the magnets brings about
faster intrusion and eliminates the need for any
kind of grinding of the opposing teeth for the
replacement of the missing teeth.
These functional appliances were developed by
For class II and class III malocclusion. They are
called FOMA II and FOMA III respectively.
FOMA II consists of an upper magnet located
anterior to a lower magnet in a non-displaced fair
relationship. Both magnets are, incorporated in upper
and lower plates.
The FOMA Ill consists of an upper and lower plates
with magnets incorporated into each plate. The upper
magnet is retracted periodically to stimulate maxillary
development/advancement and mandibular
retardation. All magnets are kept in an attractive
The upper plate of a FOMA III
, Upper plate of a FOMA
III in an experimental
The FMS incorporates some principles of the
Schwartz appliance and was introduced by
Vardimon and his associates. It consists of
upper and lower removable plate that each
contain an magnetic unit; both units are
arranged in an attractive pole orientation.
. The upper magnetic unit comprises a stainless
steel magnetic housing with a single prong
attached to it. The magnetic housing
incorporates two cylindrical rare earth magnets
(SmCo5). If expansion of the maxillary, arch is
required, an expansion screw is linked to the
magnetic housing and prong.
The lower magnetic unit consists of a magnetic
housing that encompasses two cylindrical rare earth
magnets (SmCo) corresponding to those in the upper
magnetic housing .The lower magnetic housing has a
posterior inclined wall that forms an oblique plane.
Guidance of the mandible into the CPCP is provided
by the sliding of the mandibular oblique plane along
the maxillary, prong on mouth closure. In accordance
with therapeutic requirements, an expansion screw
can be linked to the lower unit. The anchoring units
of the plates include Adams, Triangular (Arrowhead)
and Elastic Clasps
Almost all class II malocclusions
can be treated clinically by one of
the following four types of FMS:
Type1 An upper
with an expansion
with a lower
with no expansion
Type II an upper
unit with an
combined with a
unit with an
Type III An upper
magnetic unit with
combined with a lower
magnetic unit with no
Type IV An upper
magnetic unit with expansion
and protraction screws with a
lower magnetic unit with
MODE OF ACTION OF FMS
Two definitions are important in understanding the mode of
action of the FMS.
SPATIAL MAGNETIC FORCE SYSTEM
This refers to the dissociations of the attractive magnetic, force
into its three vector components:
The vertical force(fx)acting along the craniofacial
axis(x)causing jaw closure
The lateral shearing force (fy) acting along the transverse axis
(y), producing medial mandibular shift from any lateral
The sagittal shearing force (fz) acting along the posteroanterior
axis, generating mandibular advancement in protrusive
This describes the attraction of a mobile mandibular
magnet by a stationary, maxillary magnet toward a
full overlap of their magnetic interfaces at the
CPCP[constructive protrusive closure position] from
any point within a spatial domain of mandibular
movements confirmed by attractive force system.
A maximal vertical attractive force (fx) of almost 3
Newton acts between the upper and lower magnetic
units at occlusion which enables normal physiologic
oral activity during active periods and constraints of
the mandible in the CPCP during rest periodswww.indiandentalacademy.com
The FMS is designed for all three force components
of the attractive magnetic force system and the
mechanical component (prong, oblique plane) act
synergistically to guide and constrain the jaw in the
CPCP. Regardless of the anteroposterior
displacement or other movement of the mandible
which it undertakes, it always moves to the CPCP in
the shortest three dimensional way. This centripetal
spatial orientation feature extends the duration the
mandible is located in the most functionally
efficacious corrective position and thus increases the
A class II bimaxillary protrusion case treated with
magnets was reported by Darendelier and Jobor
They used full bonded upper and lower magnets of
SmCo, bonded to individual teeth at the appropriate
level forming the autonomous fixed appliance. The
individual Magnets delivering, a force of 20 - 30 gins
to close all the diastemas present. The magnets were
coated with composite resin to prevent corrosion. It
was also coated to prevent toxic damage. After the
diastemas were, closed the patient was treated with
magnetic activator device (MAD II) for full
correction of skeletal and dental class II relationship.
to cast for indirect
MAGNETS IN ARCHES
This was reported by Muller (1984), who
bonded rectangular magnets (SmCo)
delivering 11.7 gms of force of attraction on
each maxillary central incisor to close a
midline diastema. She also mentioned the
possibility of bonding the magnets palatally for
better aesthetics. Absence of friction and no
reactivation were needed, which were
Magnetic expansion studies conducted by
Vardimon et a, on female macala facicularis
monkeys. He then compared with conventional
jackscrew expansion and concluded that
repelling magnetic (SMC05) expansion from
tooth bonded or palatally pinned appliance
delivered ideal forces compared to the
jackscrew appliance which caused atrogenic
Darendileder et al., (1993) used mid palatal
repelling magnets (SMC05) expansion device
(MED). He showed both dental and skeletal
expansion in his case report.
Springate (1991) used micro magnets
made of Neodymium - Iron – Boron
as a fixed retainer palatally in a
patient with persistent midline
spacing. No hindrance in maintaining
oral hygiene was an added advantage
to this successful treatment.
One of the effective methods to resolve a Class
II malocclusion is the distal movement of
upper molars to establish a class I relationship.
The premolars and canines are subsequently
moved back to class I positions and finally the
incisors are retracted.
Repelling magnets can provide continuous
force need to establish a class I molar
relationship in the early mixed dentition.
Gianelly et al., 1998 used intra arch repelling
magnets to distalize the maxillary molars. The
repelling surfaces of the magnets were brought
into contact by passing 014” SS wire through
the loop on the auxiliary wire, then tying back
a washer anterior to the magnets. Force
extended by the magnets began at 200-225gm
then as the space opened, with 1mm of space
between magnets, the applied force was only
After 7 weeks, the molars were in class I
Magnet therapy for distalization
Right and left lateral views with
repelling magnets in position.
Upper and lower
occlusal views 7
weeks after magnet
Lingual arch wire in
mandible will be
extended distally to
lower right molar
Takami itoli et al in 1991 reported a clinical study
designed to measure the molar distalization achieved
with repelling magnets in molar distalization system.
There was some amount of labial movement of the
anterior teeth approx 30-50% of the distal movement
of the molars
Initial discomfort to the buccal mucosa till the patient
got accustomed to the appliance
There was difficulty in brushing and there was food
lodgement between the teeth and magnets
The molar distalization seen was almost entirely a
bodily movement, with slight distal tipping and
THE EFFECT OF PULSATING
ELECTROMAGNETIC FIELDS ON
A study conducted by John A.Gerling and Peter M
Sinclair on guinea pig for the growth of the
mandibular condyles under the effect of 100 hertz for
8 hrs in day indicated that there was increase in
vascularity , secretion of cartilaginous inter cellular
matrix and woven bone formation but no significant
increase in the length of the mandible
But they suggested that these electromagnetic fields
with functional appliance can be used for mandibular
EXTRUSION OF FRACTURED
A sub gingival crown root fracture presents the
clinician with a difficult restorative problem
including reaching the fracture line and is
complicated by the need to maintain the periodontal
tissues in good health. The treatment available till
now was extraction and replacement with a bridge.
A new method has been reported by Bondemark and
Kurol (1997) by using magnetic force to extrude the
The magnetic system consisted of either one or two
cylindrical parylene or stainless steel coated,
Neodymium. - Iron - Boron magnets placed in the
coronal part of the remaining tooth with a thin layer
of composite axially over the root.
Another larger parylene coated Neodymium - Iron -
Boron magnet was embedded in the acrylic of a
They were arranged in attractive mode with a
minimum gap of 2mm.
After the desired extrusion, the tooth can be restored
Bondemark and Kurol conducted extensive studies on
Rare earth magnets used in orthodontics. They
concluded that recycling does not affect the
biocompatibility and force stability of the magnets
even though the recycling process involved
They also recommended that new partially encased
Samarium Cobalt magnets be stored in water for 24
hours before use to reduce the release of cytotoxic
Cernyl (1979, 1980) showed high cytotoxicity for
Neodymium - Iron - Boron magnets. However
Darendililer, felt that magnets should not be recycled
for ethical reasons and also because they demagnetize
during the recycling process.
Magnets can be used to give predictable forces
in either attraction or repelling mode. They can
be made small enough to suit most dental
The orthodontic stimuli provided by the
magnetic appliance has reduced the systemic
stress reaction seen with conventional
orthodontic mechanotherapy .
Treatment time is shorter ,no periodontal
problem and foremost no discomfort
Conceivable risks of harmful biological effects
are negligible with magnets.
Their high cost can be overcome by reusing it
after sterilization and recycling
The static magnetic fields control mobility by
accelerating the osteogenic rate and control
pain by blocking sensory neuron action
potential. These properties of static magnetic
field promise a pain free and mobility free
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