Magnets in orthodontics. /certified fixed orthodontic courses by Indian dental academy

MAGNETS IN ORTHODONTICS

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Magnets and Magnetism
Properties of Magnets
Applications of Magnets in Orthodontics
Biological effects of magnets and safety
concerns.
Conclusion.


MAGNETS
The first known magnets were the lodestones, which
were stones that were magnetized naturally.
The Greeks and the Chinese were amused by the
stones’ ability to attract metal over a short distance,
as if by magic.
Later they learnt to use lodestones in compasses to
determine direction.
Today magnets are used extensively.e.g. in VCR’s,
audio cassettes, ATM and credit cards, and the
electronics industry.
The largest magnet existing on Earth is the planet
Earth itself.

Why does magnetism occur?
Magnetism occurs due to a quantum physical
effect called exchange coupling, which results
in the alignment of the magnetic dipole
moments of the atoms.
This persistent alignment of magnetic dipole
moments in magnetic materials is responsible
for the phenomenon of magnetism.


Properties of magnets
All magnets have
magnetic fields around
them.
The field emerges from
one pole of the magnet
conventionally known
as the North Pole and
returns to the other or
South Pole.


A magnetic field induces changes in the medium
surrounding the magnet, such as air. This is called the
flux density of the magnet
The flux produced by the magnets causes them to
attract or repel other magnets, and attract other
materials containing iron.
The force produced by any two magnets is inversely
proportional to the square of the distance between
them.
f α 1/d2
Thus, the force between two magnets falls
dramatically with distance.

The development of high energy magnets in the
1970’s resulted in magnets capable of producing high
forces relative to their sizes.
This was due to the property of magneto-crystalline
anisotropy, which allows single crystals to be
preferentially aligned in one direction, thus increasing
the magnetism.
Recently, the development of rare earth magnets such
as Samarium-Cobalt and Neodymium-Iron-boron
have taken place.
These have a higher ability to be magnetized, and
also have high coercivity, which is the ability of the
magnet to resist demagnetization.

Disadvantages of high energy magnets :
Brittle
Low corrosion resistance
Irreversible magnetic loss on heating, even
to modest temperatures.
In case of magnets embedded in acrylic
appliances to move teeth, the loss of flux
due to the exothermic setting reaction of
acrylic (80-90º C) is to be taken into
account.

Applications of Magnets in Orthodontics.
Magnets were initially used in dentistry for fixation
of dentures. (Freedman,1953; Thompson, 1964;
Winkler,1967)
They were also implanted surgically into molar
regions of edentulous mandibles for retention of
complete dentures.(Behrman 1960,1964.)
The development of rare earth magnets with
improved properties resulted in growing interest in
their use as an alternative to traditional force systems
in orthodontics.
In 1978, Blechman and Smiley were the first to report
the use of magnetic force to move teeth (in a cat).
Since then, a number of applications have been
developed for magnets in orthodontics.

1. Relocation of Unerupted teeth.
The cause of impaction, in particular of the palatally
impacted maxillary canine, is related to aberration in
the eruption process, and not due to arch length
deficiency.
Thus a shorter root of the upper lateral incisor
frequently can cause palatal impaction of the upper
canine because of a lack of guidance.
This calls for the application of a therapeutic
procedure by which the normal eruption mechanism
can be simulated.

Conventional traction methods have been found to be
associated with gingiva inflammation, bone
recession, reduced attached gingiva, periodontal
pockets, exposed cementoenamel junction, and root
resorption of the impacted and adjacent teeth.
Magnetic traction can avoid these side effects.
The use of two attracting magnets in the treatment of
unerupted teeth was described by Sadler, Meghji and
Murray ( BJO 1989).
One magnet was bonded to the impacted tooth, while
a second stationary magnet was incorporated in a
removable acrylic appliance. The location of the
stationary magnet decided the direction of force.
Activation was done by repositioning the magnet on
the plate occlusally.

Vardimon et al (AJO-DO
1991,introduced a magnetic
attraction system, with a
magnetic bracket bonded to
an impacted tooth and an
intraoral magnet linked to a
Hawley type retainer.
Vertical and horizontal
magnetic brackets were
designed, with the magnetic
axis magnetized parallel and
perpendicular to the base of
the bracket, respectively.
The vertical type is used for
impacted incisors and canines,
and the horizontal magnetic
bracket is applied for
impacted premolars and
molars.

A

B

C

D


A three-dimensional analysis of the magnetic forces found the
small magnetic bracket combined with a large pole surface
area of the intra-oral magnet to exhibit the most efficient
convergent guidance.
In deep impaction, the Nd2Fe14B magnetic bracket was coldsterilized before surgery, and the surgical flap was then
sutured over the bonded magnetic bracket.
Attraction was initiated 1 to 2 weeks after healing. Thus tooth
emergence into the oral cavity replicated normal eruption
conditioning.
The system operated at an attractive force level of 0.2 to 0.5
N. Adjustment was accomplished by temporarily interposing a
magnetic spacer between the two magnetic units.
No side effects were observed in a restricted number of
treated cases, and treatment time was reduced.

Advantages
Better rapport with the patient.
No manipulation of wires, springs or elastics.
Since a palatal force is possible, health of the labial cortical
plate and zone of attached gingiva are optimized in buccally
erupting canines.
Can be used in molar and premolar impactions with ease
Less adjustments required, less pain to the patient.
3 D control over the erupting tooth. The stationary magnet on
the plate can be placed eccentrically with respect to the intraoral bracket, to produce normal eruption and less need for
uprighting the tooth later.
As the magnet is completely sealed off from the oral cavity,
there is no chance of inflammation or infection. Also, normal
alveolar bone levels and epithelial attachment are maintained.

Pradeep CS et al (Indian
Orthodontic Conference
1999) presented 2 cases in
which removable acrylic
appliances incorporating
magnets were used to erupt
impacted canines.
In the first case, the patient
had bilaterally impacted
upper canines.
Occlusal view showed them
to be horizontally impacted.
The left side canine was
chosen as the experimental
tooth.

Disimpaction was carried
out using Samarium cobalt
type magnets (4x4x2 mm),
one of which was bonded
to the impacted tooth after
surgical exposure, and the
flap replaced.

The second magnet was
incorporated into an acrylic
removable appliance.

After 4 weeks of
wearing the
appliance, occlusal
radiographs showed
uprightment of the
horizontally impacted
canine.


After 6 weeks the there was a noticeable
bulge in the palatal mucosa and the
canine could be easily palpated under the
mucosa.
After 2 months of treatment, ulceration of
the mucosa over the canine was visible.
In the second case, an impacted upper left
canine was similarly treated.

Pradeep et al also reported the use of
parylene coated Samarium cobalt
magnets bonded to lingual surface of
central incisors for closing mid line
diastemas in 5 cases.


2. Space closure with magnets.
Mueller(EJO 1984) used rectangular magnets applying
117.5 grams of attracting force for median diasrema
closure.
In 1987, Kawata et al soldered Sm-Co magnets plated
with chromium and nickel to Edgewise brackets for
administration of mesio-distal magnetic forces.

Progressed maxillary and mandibular magnetic brackets designed to arrange an
ideal arch by themselves

In cases involving
extraction, canines were
retracted conventionally
until magnetic brackets
on the 2nd premolars
exerted enough force on
the canines.
The authors reported
reduced treatment time,
resulting in neither pain
nor discomfort, nor
periodontal problems.


Daskalogiannakis and Mc
Lachlan(AJO DO 1996) used rare
earth magnets to provide
continuous activation to canine
retracting loops, and reported that
the continuous force levels
achieved by the use of magnets
resulted in twice as much
movement as compared to the
controls where force levels
decayed with time.

3. Molar intrusion and correction of anterior
open bite
Dellinger(AJO 1986) reported on the Active Vertical
Corrector, an “energized bite block”appliance, which
uses Samarium cobalt magnets oriented in repulsion
to produce a posterior intrusive force of 600-700 g per
magnetic unit.
This appliance was worn in combination with headcap
and chin strap for at least 12 hours per day.
It was postulated that this appliance was more
efficient than usual bite block therapy due to the
intermittent electromagnetic field produced by
mandibular movements, which would enhance tooth
movements.

Example of the Active Vertical
Corrector (AVC). Occlusal and
tooth contact views of
mandibular appliance (A) and
maxillary appliance (B).

Seated Active Vertical
Corrector (AVC).


The AVC intrudes
posterior teeth by
reciprocal action as
noted by the arrows.

Intrusion of posterior
teeth results in closure
of the open bite and
autorotation of the
mandible

Initial anterior photograph of male patient
aged 8 years 11 months, taken before
patient began wearing AVC

Posttreatment anterior photograph of
male patient aged 9 years 6 months,
taken after patient wore appliance for
4½ months.


Woods and Nanda (Angle Orthod 1988) studied the intrusion
of posterior teeth in growing baboons, with magnetic and
acrylic bite blocks.
They postulated that since similar responses were produced
with both magnetic and non-magnetic bite blocks, it would
appear that the depression of buccal teeth seen in this study
could be attributed as much to the muscular response to the
artificially-increased vertical dimension as to the presence of
the repelling magnets.
In another study done on non-growing baboons, Woods and
Nanda (AJODO 1991) found significant intrusion of posterior
teeth with magnets as compared to acrylic bite blocks.
However, the effects of the magnets were reduced as
compared to growing animals.In the absence of other evidence
the authors hypothesised that electromagnetic fields might be
involved in increasing the response within bone to potential
intrusive forces delivered by the repelling magnets.

Kiliardis et al ( EJO 1990) randomly divided a 20 patients
aged 9-16 years, with anterior open bite into two treatment
groups: one with the Active Vertical Corrector and the other
with acrylic posterior bite blocks of same thickness as
magnetic appliance.
In the first group, a quick response in dental and skeletal
vertical relationship was seen. In all growing individuals,
especially those in early mixed dentition stage, the open bite
closed in less than 4 months. The cause of open bite closure
was due to intrusion of posterior teeth.
In the older adolescents, there were smaller changes, and
relapse was observed in two cases.
A major side effect of treatment with magnetic appliance was
the tendency for development of unilateral cross bite (in up to
half the patients), followed by a tendency for developing full
scissor bite on the opposite side.

This was due to the lateral forces that are normally developed
when repelling magnets move toward each other.
In the Bite Block group, main improvement occurred in the
first weeks after insertion, followed by a plateau period.
Though the improvement was neither as rapid or extensive as
with the first group, no transverse problems were noticed.
The major difference in their modes of action is that magnets
continuously transfer forces to the posterior teeth depending
on the distance between the repelling magnets.
Bite block on the other hand, transfers intermittent forces to
the teeth, only when it is in contact with them.
Transverse problems with magnetic appliance could be
diminished by using less powerful magnets, or decreasing
treatment time, or by providing a guiding flange to counteract
lateral forces.


Kuster and ingervall (EJO 1992) compared the effects of
stainless steel spring loaded and cemented magnetic bite
blocks for correction of anterior open bite in children.
There was significantly greater improvement in the group
treated with magnetic bite blocks (average improvement of
3mm in overbite) as compared to spring loaded group.
This was due to intrusion of posterior teeth resulting in
anterior mandibular rotation, as well as eruption of incisors.
Interestingly, the authors did not report any development of
cross bite in their magnetic cases.
The authors however cautioned that there was a tendency for
relapse following correction, and advised active retention for a
long period. They suggest a regime of cemented bite blocks
followed by a longer period of removable bite blocks.

Noar et al
(AJO-DO
1996) carried
out lab based
experiments to
examine the
effect of
orientation of
magnets on the
force levels
achieved.


The results showed there that there was a reduction in
repulsive force in the tilted alignment as compared to
perfect alignment of magnets.
In addition, the skewed and edge to edge alignment cases
actually showed attractive forces at close distances.
This study highlights that the orientation of the magnets
is of the utmost importance. In the mouth, when the
mandible moves, the magnets will frequently be
misaligned and will rarely be producing their maximum
reported repulsive force.
It was concluded that the claims that bite-block
appliances containing magnets enhance the intrusion of
buccal segments in cases with Anterior open bite,
because of the force produced between the repelling
magnets could not be supported by the results of this lab
based study.

Hwang and Lee (AJODO 2001) reported the use of magnetic
force in conjunction with a corticotomy procedure, to intrude
over erupted molars following loss of their antagonist.
Corticotomy is a surgical technique in which a fissure is made
through the cortical bone that surrounds a tooth so that the
tooth is embedded within a bone block that is connected to the
adjacent blocks through only the medullary bone.
In this way, the tooth acts like a handle by which the bands of
the less dense medullary bone are moved as a block. The bone
blocks are moved with the teeth, rather than moving the teeth
within the bone.
In these situations, a heavier force of more than 90 g was
applied on the molar because it was necessary to move the
bone block with the tooth. Although there was no discomfort
or root resorption, further research is needed to determine an
optimal force value for use after corticotomy.

Pretreatment

Corticotomy

Magnetic appliance

Post intrusion


4. Molar distalization:
Gianelly et al ( JCO 1988, AJO
DO 1989) reported the intra-arch
placement of repelling magnets
against the maxillary molars in
conjunction with a modified
Nance appliance cemented on the
first premolars, to distalize the
Class II molars.
The modified Nance appliance
was anchored to the first
premolars to encourage the distal
drift of the second premolars.
Bilateral distal extensions (0.045inch wire) with loops at the end
were soldered to the labial aspect
of the premolar bands so that the
loops approximated the molar
tubes.

An 0.014-inch ligature wire was placed through the loop and
extended anteriorly to encircle a tieback hook mesial to the
magnets. When tightened, the repelling magnets are held in
contact.
When second molars were not present, the fastest molar
movement was observed and Class I molar relationships were
attained within 2 to 5 months.
When second molars were present, treatment time increased as
there were 2 teeth to move distally. When magnets were used
in the treatment of adults, the results were less predictable and
the time factor increased.
The appliances were well tolerated by patients and were used
successfully to move molars distally with relatively minor
anchorage loss.
Consistently, 80% of the space created represented distal
movement of the molars. Thus for every 5 mm of space
opened, the molars were moved posteriorly 4 mm while the
premolar-incisor segment moved forward 1 mm
Significantly, patient co-operation was dispensed with.

Itoh et al (JCO 1991) described
an appliance called the Molar
Distalization System, which also
made use of repelling magnets.
The mesial magnet of each pair is
mounted so that it can move
freely along a sectional wire.
A sliding yoke, with ligation
hooks mesial to the mesial
magnet, brings the repelling
magnets together to activate the
magnetic force.
A primary molar or premolar in
good condition is selected as the
anchor tooth in and a Nance
holding arch is placed to reinforce
anchorage.
The distal end of the MDS
terminates in a three-pronged
fork, with the middle prong sized
for insertion into the headgear
tube.

Ligating around the two outer prongs secures the MDS to the
molar tube.
The constant magnetic force of about 8oz results in rapid distal
movement of the first molars.
This movement separates the magnets, which must be
reactivated by being placed back in contact every two weeks.
Bondemark and Kurol (EJO 1992) carried out distalization of
1st and 2nd molars simultaneously, in a group of 10 patients,
using a similar appliance, but including the second premolars
as anchorage.
They reported that all maxillary molars were distalized into
Class I relationship during a mean time of 16.6 weeks.
Whereas the mean molar crown movement was 4.2 mm,
anchorage loss in anterior region was about 1.8 mm. Mean
distal tipping of the 1st and 2nd molars was 8 and 5.6 degrees
respectively.

The disadvantages of the method as reported by the
authors were:
Time consuming and expensive construction.
Chances of relapse due to tipping component of
molar movement.
Loss of anchorage anteriorly in the form of increased
inclination and overjet.
The effectiveness of magnets for distalization of
molars has been compared with that of Ni Ti coil
springs in a number of studies, by Bondemark et al
(Angle Orthod 1994), Erverdi et al (BJO 1997, split
mouth study), and by Bondemark (EJO 2000). All of
these studies show Ni Ti Coil springs to be more
efficient in molar distalization as compared to
magnets.

5. Maxillary expansion
Repulsive magnetic forces for maxillary expansion were first
described by Vardimon et al in monkeys, AJO DO 1987.
Repulsive magnetic force was applied using direct as well as
indirect placement of magnets.
These were also compared with expansion through
conventional jackscrew, by means of the implant method.
The feasibility of magnetic force to produce orthopedic
changes was unequivocally demonstrated.
Advantages in the use of magnetic forces are a predetermined
force range with upper and lower limits (for example, 435 to
80 g) and thus the elimination of potential iatrogenic sequelae
in the form of uncontrolled force levels

Indirect placement of magnets in acrylic housing

Expansion achieved with the directly placed magnets

Direct placement of magnets with telescopic element


A clinical study on maxillary expansion with a
Magnetic Expansion Device (MED) has been
reported by Darendeliler, Strahm and Joho, (EJO
1994).
Using a bonded and a banded variety of the MED in 2
and 4 patients respectively, exerting 200-250 grams
of force, they found more pronounced skeletal
expansion with the banded appliance.
Stability was adequate after a post-retention period of
12.5 years.
The authors indicated that the use of light continuous
forces (250-500 grams) could generate dental and
skeletal movements, the degree depending on the
patient’s status.

6.Functional appliances for correction
of Class II malocclusion
The rationale for introducing magnets to the arsenal of functional
appliances is based on the unique characteristics of magnetic
forces,which are:
High force to volume ratio.
Maximal force at short distances.
3D centripetal orientation of attractive magnetic forces.
No interruption of forces by intermittent media.
No energy loss.
In addition, functional magnetic appliances may act more
effectively in propelling dormant genetic tendencies than
conventional functional appliances. E.g. a locked mandibular
growth pattern caused by Class II div 2 Malocclusion.

One of the major reasons for failure of conventional functional
appliances is incompetent sagittal displacement.
Normally interjaw tooth contact totals between 8 minutes and
20 minutes during a 24-hour period, but only 1 to 2 minutes
during nighttime.
Furthermore, Witt and Komposch found a physiologic
limitation in providing adequate vertical support to an
activator during sleeping time.
These facts indicate a possible limited effective duration—
that is, the patient might wear the appliance but in a
completely unproductive position.
Logically, increasing the construction bite beyond the habitual
posture position might provide vertical support.However,
increased bite clearance decreases the protrusion performance.


Vardimon et al (AJO-DO 1989)
introduced a new functional
appliance to correct Class ll
dentoskeletal malocclusions,called
the functional orthopedic magnetic
appliance (FOMA) II.
This uses upper and lower attracting
magnetic means (Nd2Fe14B) to
constrain the lower jaw in an
advanced sagittal posture.
In a study done with this appliance in
monkeys, it was found that the
functional performance of the
FOMA and the FOMA+FA was
superior to that of FA alone.
Also, there was greater increase in
mandibular length and less
proclination of incisors

Kalra et al (1989) described
the use of repelling magnets
in patients with Class II
div1 malocclusion in
association with increased
lower face height.
After 4 months treatment
with intrusive force of 90
gms per tooth in 10 patients,
the authors reported
significant increase in
length of mandible and
decrease in mandibular
plane angle.

Another functional
appliance introduced by
Darendeliler and Joho,
(AJO-DO 1993) known as
the MAD II, consists of an
upper and lower removable
appliance, carrying
magnets in both buccal
segments.
In Class II cases with
normal vertical
proportions, the magnets
are placed distal to the
upper canine and distal to
the lower first premolar.


In deep bite situations, the
inclination of the magnets
and subsequent magnetic
force orientation is chosen
in such a way to produce
dental extrusion in the
premolar-molar area. The
magnets are placed to
produce an attracting force
between them and located
more posteriorly


In Class II open bite situations,
two pairs of lateral magnets in a
repelling configuration can be
used posteriorly, with the
objective that they will produce
molar and premolar intrusion,
with some distal movement in the
upper arch, while pushing the
mandible downward and forward.
An additional pair of attracting
midline magnets located at the
retroincisal area will help to
achieve symmetry and alignment
of upper and lower midlines

Joho and Darendeliler (EJO 1993) compared Class II
deep bite patients treated with the MAD II appliance
with untreated controls.
They found the appliance to augment the lower facial
height, and it was accompanied by almost immediate
functional adaptation.
The Functional Magnetic System, described by
Vardimon et al, incorporates some of the principles of
the Schwarz appliance. It consists of upper and lower
removable plates that each contain a magnetic unit,
both of which are in attractive configuration.

The upper magnetic unit
comprises a stainless
steel magnetic housing
incorporating two
SmCo5 magnets, with a
single prong attached to
it.
Expansion screw may
be incorporated if
required.
The lower magnetic unit
also has a magnetic
housing with two
cylindric rare earth
magnets corresponding
to those in the upper.

The lower magnetic
housing has a posterior
inclined wall that forms
an oblique plane.
Guidance of mandible
into constructive
protrusive contact
position (CPCP) occurs
by sliding of mandibular
oblique plane along the
maxillary prong on
mouth closure.
This is further enhanced
by a groove in the
oblique plane.

Anchoring units of the
plates include Adams,
triangular and elastic
clasps.
Depending on the
severity of Class II
malocclusion, any of 4
modifications of the
FMS can be used,
depending on
incorporation of
expansion and
protraction screws.

William J Clark has also reported a
modification of the Twin Block appliance that
incorporates magnets for Class II correction.
However, he states that the question of
whether to use attracting or repelling magnets
is yet to be resolved.


7.Functional Appliances for Class III
malocclusions:
Vardimon et al (AJO-DO 1990)
developed an intraoral
intermaxillary appliance for the
treatment of Class lll malocclusions
that exhibit midface sagittal
deficiency with or without
mandibular excess.
The functional orthopedic magnetic
appliance (FOMA) III consists of
upper and lower acrylic plates with
a permanent magnet incorporated
into each plate.
The upper magnet is linked to a
retraction screw and is retracted
periodically (e.g., monthly) to
stimulate maxillary advancement

The upper plate of a FOMA III consists of a 0.031-inch stainless steel
arch wire forming the metal substructure (a). The arch wire bypasses the
premolar-canine segment to permit eruption and crosses the occlusal
plane at the M1-M2 embrasure. The upper magnetic housing (b) is linked
to a retraction screw (c). The magnetic unit (b + c) is positioned along the
midpalatal line

The attractive mode
neodymium magnets used in
this study produced a
horizontal force of 98 gm
and a vertical force of 371
gm.
The ratio of horizontal to
vertical force vectors is
dictated by inclination of
magnetic interface in the
sagittal plane. The more
perpendicular the magnetic
interface is to the occlusal
plane (sin 90° = 1), the
greater is the horizontal
force vector (Fh = attractive
force ´ sin a).

Six female Macaca -fascicularis monkeys were treated with
FOMA IIIs.
After 4 months of treatment, the following results were found:
The growth pattern of the cranial base (saddle angle) was not
altered.
Midfacial protraction did occur along a recumbent hyperbolic
curve with a horizontal maxillary displacement and an
anterosuperior premaxillary rotation.
Cumulative protraction of the maxillary complex was initiated
at the pterygomaxillary fissure with an additional contribution
provided by other circummaxillary sutures
(zygomaticomaxillary s., transverse s., premaxillary s.)
Inhibition of mandibular length was minimal, but a tendency
toward a vertical condylar growth pattern was observed.

The interaction between sutural and condylar growth sites appeared
biphasic, characterized by an immediate and rapid excitation of the
circummaxillary sutures followed by a delayed and slow suppression of the
condylar cartilage.
A later radiographic and histologic study by Vardimon et al (AJODO
1994), again on monkeys, revealed the following data:
Maxilla:
The target area of the protractive force was found to be localized in the
pterygomaxillary fissure.
Three dimensionally, the separation of the sutures at the PMF was found to
diminish in inferosuperior and lateromedial directions.
Radiographically, the horizontal and vertical displacements of the lower
PMF point were three and five times greater than the corresponding
displacements of the upper PMF point, respectively.
Mandible:
Radiographically, mandibular length was unaffected after 4 months of
treatment, and the distance condylion-pogonion was equally increased in
the treated (0.75 ± 0.78 mm) and the control animals (0.77 ± 0.32 mm).

Histologically, the condylar cartilage demonstrated increased
osteoclastic activity at the zone of endochondral ossification
and a decreased apposition rate at the adjacent bony
trabeculae.
Conceivably, the two target areas (PMF sutures versus
condylar cartilage) demonstrate two diverse time-related
responses that are either unrelated or interrelated to each other.
An unrelated tissue response suggests that tissue stimulation
(sutural) is always superior to tissue suppression (condylar).
Another possible unrelated tissue reaction implies diverse
response velocity (high sutural, low condylar).
An interrelated mechanism suggests that an applied force will
dissipate initially at the less resistant target area (sutures), and
will subsequently affect the more resistant target area
(condyle) once the sutural resistance exceeds a certain
threshold.
The fact that no pathologic change was found in the condylar
cartilage encourages a long-term use of the FOMA III
appliance, initiating treatment at an early skeletal age.

Darendeliler et al (JCO 1993)
reported a case of a 7.5 years old
female with Class III dental
malocclusion and bilateral cross bite
who was treated with a combined
MAD III and MED appliance.
Upper and lower buccally placed
magnets were used for correction of
A-P discrepancy.
The upper and lower magnets had a
tendency to move toward a fully
centered contact, thus creating a
forward force against the maxilla
and a backward force against the
mandible.
When combined with an MED, the
MAD III offers an alternative in the
early correction of Class III
malocclusions.

8. Treatment of obstructive sleep apnea,
snoring.
The OSAS is characterized by a number of symptoms:
Intermittent upper airway obstruction during sleep
Socially handicapping snoring,
Daytime sleepiness
In long-standing cases of the syndrome, headache,
hypertension, cardiac, and pulmonary
complications often ensue.
The automobile accident rate in OSAS patients is
reported to be two to three times higher.
Work performance, family and social interaction, and
other aspects of quality of life also appear to be
compromised
10% of men and 5% of women in the 30- to 40-year age
group are habitual www.indiandentalacademy.com
snorers,

The precise cause and pathogenesis of upper
airway occlusion during sleep remains uncertain.
Factors reported are:
Retrognathism of the maxilla and mandible,
Increased lower facial height,
Reduced anteroposterior size of the bony
pharynx
Elongated soft palate,
Enlarged tongue,
Decreased posterior airway space,
Inferior position of the hyoid bone.
The treatment is directed toward improving the
air flow by various surgical and nonsurgical
methods.

Non-surgical methods have included treatment with
dental appliances, usually removable functional
appliances.
The mandible is supposed to advance forward, and it is
assumed that widening of the upper airway space is
created and breathing during sleep enhanced.
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 airway space.
In such situations, a magnetic appliance may be more
effective than the conventional passive functional
appliance, because the magnet forces prevent the
closing by providing direct and continuous mandibular
advancement.

Bernhold and Bondemark
(AJO-DO 2001) used a
magnetic appliance to
treat 25 male patients
with handicapping
snoring or obstructive
sleep apnea
It consistedof a maxillary
and a mandibular
occlusal acrylic splint. In
each splint, four
cylindrical neodymiumiron-boron magnets were
embedded and oriented
to produce intermaxillary
forces that pulled the
mandible forward.

All patients easily accepted the magnetic appliance.
The main symptoms, snoring and daytime sleepiness,
decreased significantly.
The blood oxygen saturation during sleep was also
improved.
No aberrant effects on TMJ status.
The appliance made the mandible rotate downward
and backward, mean 7.8°, and this rotation mostly
camouflaged the forward movement of the mandible.

There was no significant influence on the hyoid bone position, but
the hypopharyngeal airway space increased, the tongue base was
lowered, and the contact between the tongue and soft palate was
reduced significantly.

Gavish et al (AJO-DO 2001) used the FMS (functional
magnetic system) to treat 28 patients with OSA
After 8 weeks of FMS treatment, it was found that the
respiratory disturbance index decreased significantly;
minimal oxygen saturation increased significantly,
reaching a normal value; day time tiredness improved;
snoring declined; the oral cavity anterior region
increased significantly, and the pharyngeal airway
passages did not change.
The functional magnetic system operated by increasing
the anterior region of the oral cavity, mainly vertically,
with no change in the posterior oral cavity region and
pharyngeal airway passages. .
They concluded that the functional magnetic system is a

9. Extrusion of crown-root fractured teeth
A subgingival 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.
Bondemark et al AJODO
1997 described the use of
magnets to extrude such
teeth with excellent
periodontal results.

Other Uses:
Springate and Sandler (BJO 1991) reported the use of
Nd-Fe-Bo micro-magnets as a fixed retainer which
does not hinder oral hygiene. Two such micro
magnets bonded to central incisors mesio-lingual
surface were used to retain closure of mid-line
diastema.
RAC Chate (EJO 1995) has reported the development
of the PUMA or Propellant unilateral magnetic
appliance, which uses magnets incorporated in
unilateral bite blocks for correction of hemifacial
microsomia.

Biological effects of magnets and
safety concerns:
Though magnets have been widely used in
orthodontics , there have been concerns regarding
their safety and possible harmful effects.
These are particularly attributed to corrosion products
of magnets and their cytotoxic effects, as well as the
possible harmful effects of the magnetic fields
themselves.
Bondemark et al (AJODO1994) showed that there is
a release of water-soluble cytotoxic components from
Sa-Co magnets. Hence, it is very important to use
non-cytotoxic or coated magnets .

A study by Bondemark et al (EJO 1995) to
investigate the biological effects of magnets on
human tissues, showed that weak static fields below
0.09T in commercially available orthodontic magnets
did not cause any histologically detectable changes in
human dental pulp or gingiva.
This study is in agreement with a number of previous
studies in animals and supports the claim that weak
static magnetic fields are harmless to oral tissues.
It is important to note that the WHO report of 1987
states that static magnetic fields upto 2T show no
significant health effects.

Conclusion
The development of powerful, rare earth magnets has
resulted in their application in many areas of
orthodontics.
However, at present the most promising clinical uses
for these magnets are mainly confined to tooth
movement for impacted teeth, and Class II and Class
III malocclusions, as well as for treatment of open
bite cases.
In particular the long term effects of correction of
open bite with magnetic appliances has to be
evaluated. Also smaller, thinner magnets are to be
developed for better results.

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