This power point gives a detailed information about magnets in orthodontics, basic terminology of magnets their application in orthodontics, orthodontic appliance with magnets Introduction History,Terminologies ,Classification,Application in orthodontics(Magnetic Twin block,MAD I,MAD II, MAD III) Conclusion

1. MAGNETS IN
ORTHODONTICS
By
Dr Gejo johns

2. CONTENTS
 Introduction
 History
 Terminologies
 Classification
 Application in orthodontics
 Conclusion
 References

3. Introduction
• Orthodontics and dento-facial orthopaedics are therapeutic
approaches that modify the occlusion, facial form and
function through the application of prolonged, mechanical
forces. Traditional force delivery systems included the use
of wires, springs and elastics

4. HISTORY OF MAGNETS
• Magnet was originally discovered from a place called
Magnesia in Greece when a shepherd named Magnes
accidentally came across a stone(lodestones) which
attracted iron nails in his shoes
• This type of rock was subsequently named magnetite, after
either Magnesia or Magnes himself

5. • A magnet is a material or object that produces a Magnetic
field . This magnetic field is invisible but is responsible for
the most notable property of a magnet: a force that pulls
on other ferromagnetic materials, such as iron and attracts
or repels other magnets.

6. • An object that exhibits an external magnetic field
• Two poles (north and south)
North pole is the end that points to the north
magnetic pole of the earth when the magnet is freely
suspended
• Magnetic field that surrounds a magnet emerges from
one pole of the magnet, conventionally the north pole,
and returns to the other or south pole of the magnet

7. Magnets were First used in dentistry -to improve the retention of
dentures and maxillofacial prosthesis(Behrman and Egan in 1950
in newyork academy of prosthodontics)
Magnets for orthodontic tooth movement - first described by
Blechman and Smiley in 1978 : bonded earth magnets of
Samarium-cobalt ( SmCo ) to the teeth of adolescent cats to
produce tooth movement
Advantage
• good force control at short distances,
• no friction
• no material fatigue

10. Magnets were used initially as bulky and they are concerns
about possible toxicity.
However, the current available literature evaluating magnetic
fields shows no evidence of any direct or acute toxic effects.
Magnets usage is Improved safety with better coating and
introduction of rare earth magnets lead to dramatic
reduction in magnet size

11. TERMINOLOGIES
• Magnetism refers to the physical phenomena arising from
the force caused by magnets, objects that produce fields
that attract or repel other objects.
A physical phenomenon and a form of energy that can be
either static or time varying

12. Magnetic field
• Space around a magnet where its influence is felt
• In any magnetic field, the poles of a bar magnet experience
forces of attraction or repulsion
• The poles of magnets are those points near the end of the
magnet where its magnetism appears to be concentrated
• Magnetic field is a vector (magnitude and direction)
• Direction of the magnetic field at any point in space is the
direction indicated by the north pole of a small compass
needle placed at that point

13. Magnetic field lines
• Means of visualizing the direction of the
magnetic field.
• They are not real entities, as a magnetic
field is a continuous function that exists at
every point in space.
• Magnetic fields are detected by the force
they exert on other magnetic materials and
moving electric charges

14. Magnetic flux
• Magnetic flux is a measure of quantity of magnetism, that
is the strength and extent of the magnetic field
• The magnetic field is stronger in regions where the field
lines are relatively closer together and weaker where they
are relatively far apart
• It can be measured with a fluxometer

15. Coulomb’s Law
• in 1785, the French physicist Charles-Augustin de
Coulomb.
• The force between two magnetic poles is proportional to their
magnitudes and inversely proportional to the square of the
distance between them
• This means that the force between any two magnets falls
dramatically with distance
• like charges repel and opposite charges attract

16. Curie Point
• Pierre Curie observed that magnets tend to
lose their properties if subjected to a
specific temperature - Curie 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 heat
sterilized

18. Coercivity
• It is the measure of the resistance of the material to
demagnetization
• A high coercivity is needed to prevent the magnets from
demagnetization when they encounter fields produced by
other sources

19. Classification of Magnets
• DIAMAGNETIC
• PARAMAGNETIC
• FERROMAGNETIC
– SOFT (IRON)
– HARD (PERMANENT MAGNETS)
• AlNiCo (Aluminium Nickel Cobalt)
• CoPt (Cobalt Platinum)
• Ferrite (Ceramic)
• Rare Earth
– SmCo (Samarium Cobalt)
– NdFeB( Neodymium Iron Boron)
– SmFeN (Samarium Iron)

20. Diamagnetic Substances
• They have a weak ,negative susceptibility to magnetic fields
• They are weakly repelled and exhibits no permanent magnetism
• When the applied field is removed the magnetism disappears
• Are usually considered to be non-magnetic
• Eg : water, wood, most organic compounds and many metals such as
bismuth, silver, gold, lead, stainless steel and copper

21. Paramagnetic Substances
• They have small ,positive susceptibility to magnetic fields
• Paramagnetism is a form of magnetism which occurs only in the
presence of an externally applied magnetic field
• When an external magnetic field is applied, the dipoles will tend to
align with the applied field, resulting in a net magnetic moment in the
direction of the applied field
• Iron and rare-earth salts are paramagnetic substances, as well as
elements such as sodium, potassium and oxygen

22. Ferromagnetic Substances
• They have a large, positive susceptibility to an external
magnetic field
• They are strongly attracted to magnets and are able to retain
their magnetic properties after the external fields has been
removed
• Common ferromagnetic materials are iron, nickel, cobalt,
chromium dioxide and AlNiCo (aluminium-nickel-cobalt alloy)

23. • Ferromagnetic materials can be termed as either hard or
soft depending on how well they retain their magnetic
properties after removal of an applied magnetic field
• Soft magnet can be easily magnetised or demagnetised. Eg:
iron
• Hard magnet is able to retain magnetic properties after
being magnetised and can be made into permanent
magnets

24. Types of magnets
Permanent Magnets
• Permanent magnets create their own persistent magnetic field
• All permanent magnets are made from ferromagnetic materials
• The magnetic properties of materials depend mainly on the chemical
composition and on the heat treatment they receive after fabrication
• The behaviour of magnetic material is highly sensitive to small
amounts of impurities and temperature

25. AlNiCo Magnets
• First type of permanent magnets to be used for biomedical purposes
• Alloys based on cobalt, aluminium, nickel and iron
• Developed from the 1930s to the 1960s and offered considerable
improvements in magnetic hardness compared to the steel magnets that
were previously available
• Alnicos are two phase alloys, consisting of a strong ferromagnetic phase and
a paramagnetic phase
• They are produced either by casting or by pressing and sintering powder
compacts

26. Cobalt-Platinum Magnets
• They were discovered in the 1930s by Jellinghaus and were made
available in the 1950s
• They consist of equal percentages of cobalt and platinum which forms
a continuous solid solution to produce an isotropic magnet
• They had improved properties and corrosion resistance compared with
the Alnicos available at that time
• Despite their superior properties they did not gain widespread use in
medical or dental applications because of their high cost.

27. Ferrite Magnets
• Ferrite or ceramic magnets are the most widely used permanent magnetic
material and play an important role in bulk magnet applications
• Hard ferrite magnets are not commonly used in biomedical applications
• They are more resistant to demagnetisation than the Alnico materials which
make them suitable for use in complex shaped magnets
• They produce a low magnetic field but are very cheap to produce which
makes them ideal for their current application

28. Rare Earth Magnets
• Although magnets had dental applications in the 1950s the
high cost of magnetic materials was a significant deterrent to
their use, until the development of rare earth magnets in the
1970s
• The development and availability of rare earth magnetic alloys
have led to the increase use of magnets in orthodontics
• Rare earth magnets are capable of producing high forces
relative to their size due to the property of magnetocrystaline
This property allows single crystals to be preferentially aligned
in one direction which increases the magnetism

29. • Another advantageous characteristic of the rare earth
magnets is their very high coercivity, compared to AlNico
and barium ferrite magnets. High coercivity means these
magnets have a superior ability to resist demagnetisation.
This is the result of their intrinsic properties and the
manufacturing process
• Eg: samarium cobalt, neodymium iron boron and samarium
iron nitride

30. Samarium-cobalt Magnets
• Introduced by Becker
• Developed in the 1960s and 1970s
• Various inter-metallic compounds of samarium-cobalt are
possible including SmCo3, Sm2Co7, SmCo5 and Sm2Co17
• Characterized by high saturation magnetisation and Curie
temperature

31. • Have relatively high Curie temperatures, in the range of
500-750 degrees Celsius (°C) for SmCo5 and 780-850 °C for
Sm2Co17
• Costly than other rare earth magnets but are chosen in
preference than those with a lower Curie temperature,
such as Neodymium, when they are needed for high
temperature applications

32. Neodymium-iron-boron Magnets
• Developed in 1984
• They have extremely high magnetic saturation, good resistance
to demagnetisation and the highest value of energy production
• Their excellent magnetic properties allow the production of
very small magnets
• They are less costly to produce than Sm-Co alloys and hence
are now the main rare earth permanent magnet in use today

33. • The main limitation of the neodymium magnet is that it had a
low Curie temperature, as low as 300°C
• This is a distinct disadvantage for dental applications as
magnets are embedded in acrylic appliances
• On curing methyl methacrylate reaches a temperature of
between 80 and 90 degrees. This could cause a significant
amount of flux loss due to the exothermic setting reaction of
the acrylic

34. Samarium-iron-nitride Magnets
• These magnets may be a superior choice to NdFeB magnets
in the future because it has high resistance to
demagnetisation, high magnetism and better resistance to
temperature and corrosion
• Is still under development, but could become available for
medical and dental applications in the future

35. Advantages and Disadvantages
Advantages
• Constant force (No force decay
over time)
• Predictable force level
• Frictionless mechanism
• Tooth movement is more
biologically acceptable
• Minimum appliance adjustment
• Less chair side time
• Minimum patient co-operation
• No need for elastics, springs etc
Disadvantages
•Tarnish and Corrosion products are
cytotoxic
•Bulk
•Appropriate size design is difficult as
it is hard and brittle
•Thermal sensitivity
•Cost

36. Applications in orthodontics

38. Magnetized edge wise brackets
• KAWATA et al – 1987 AJODO
• The magnetic material that we first employed clinically was a
cast alloy consisting of 25% to 30% chromium,15% to 25%
cobalt, and 45% to 60% iron. The size of the magnet originally
used was 6 X 8 X 2 mm.
• New material: Cr plated samarium cobalt, 250gms (sufficient to
move canines and other teeth) making our appliance smaller in
size while enhancingthe force level.

40. • The samarium-cobalt magnets were prepared by attaching an
edgewise bracket to the surface of the magnet and plating it
with chromium to prevent corrosion of the magnet and with
nickel to solder the bracket to the surface.
• The layer of nickel allowed the edgewise bracket to be soldered
to the surface below 5000 C . Finally, a mesh base was soldered
onto the rear of the magnetic bracket, allowing the bracket and
magnet combination to be bonded to the surface of the teeth
by means of a direct bonding system.
• The magnetic brackets were designed to form an ideal arch in
both the maxilla and mandible on the completion of treatment

41. • The edgewise bracket chosen was a traditional one with an
0.018-inch slot width.
• With this arrangement, each bonded bracket can be used
for mesiodistal magnetic force.
• If the distance between the malpositioned teeth is over 3
mm and the magnetic force is thus not sufficient to retract
these teeth, a power chain can be added to assist the
magnetic force in the initial stage.

42. • When these teeth come closer together, that is, within 3
mm, the power chain is removed and the additional
retraction can be done through the available magnetic
force.
• This procedure has reduced treatment time as compared
with traditional methods.

43. Patient was a girl, 11 years 10 months of
age in 1979
Class I malocclusion with a crowded
dental arch

44. • Orthodontic stimuli provided by the magnetic appliance
has reduced the systematic stress reactions seen with
conventional orthodontic mechanotherapy
• Canine retraction was rapid and consistent as compared
with traditional orthodontic appliances
• Treatment time was shorter, discomfort was eliminated,
and the orthodontic patients were free from periodontal
disturbances, root resorption and caries

46. Diastema closure
• Martinette Muller 1984 – EJO
• Group comprised four boys and three girls aged from 8 years 11
months to 12 years 1 ½ months.
• The width of the diastema varied from 0.7 mm to 1.9 mm
• Magnets were fixed to the labial surface of the central incisors

47. Use of magnets proved to be a successful method for closure of a diastema

49. Advantages:
• Minimal tooth tipping
• Less chair time
• Activation of the appliance is not Necessary
• Oral hygiene is easy
• Magnets are cheap and can be used again after sterilization
Disadvantages:
• Placement of the magnets needs great care
• during sawing magnets can break because they are brittle (hence
cannot be made thinner than 1mm)
• Breakage and loss of magnets

52. Magnets were more efficient in complete closure of mid line
diastema in less duration of time
Better 3-dimensional control of the movement of the teeth
can be achievable with magnets
Magnets are most bio-compatible and recyclable with least
adverse effects
Magnets were more efficient in up righting, root paralleling
provided accurate positioning of magnets on the teeth

54. Active Vertical Corrector
1986: Dellinger introduced “Active Vertical
Corrector” or energized bite block for open
bite correction.
A nonsurgical alternative for skeletal open
bite treatment.
AVC is a simple removable or fixed
orthodontic appliance that intrudes the
posterior teeth in both the maxilla and
mandible by reciprocal forces

55. • The AVC force system generated by repelling
magnets is considered superior to a static bite
block appliance energized only by the
intermittent force from the muscles of
mastication.
• The constant force system of the AVC results in
greater rapidity of tooth movement.
• It has been shown that increased cellular
activity occurs when tissues are subjected to an
intermittent electromagnetic field.

57. Unerupted teeth
• JONATHAN P.SANDLER – 1991 AJODO
• User- and patient-friendly method of treating unerupted teeth
• A neodymium iron boron magnet is attached to the unerupted
tooth, and a second, larger magnet is incorporated in a
removable appliance.
• The resulting forces provide a friction-free system, requiring little
or no adjustment, which rapidly encourages the unerupted tooth
into a position in which it may be bonded and thereby aligned by
more conventional methods.

58. CASE 1: 14-year-old girl bad an unerupted upper left
canine. A previous attempt to bond an attachment to
this tooth and apply traction to bring it into the mouth
was unsuccessful. It was decided to use the magnets
method, and within 4 months the tooth was sufficiently
erupted to allow placement of a more conventional
attachment for further alignment

59. CASE 2: A 12-year-old boy had a supernumerary tooth preventing the eruption of his upper left
central incisor. This extra tooth was removed, and a magnet was attached to tile incisal tip of
the incisor. The second magnet was embedded in an upper removable appliance behind an
acrylic replacement tooth. Four months later, the incisor had erupted sufficiently to allow a
bracket to be placed. Alignment was continued with a fixed appliance

60. B.O.I COLE ET AL – 2003 INTERNATIONAL JOURNAL OF
PEDIATRIC DENTISTRY

61. • Radiographs (panoramic or peri-apical views)
were taken to ascertain the cause of eruption
failure and severity of tooth impaction (Fig.
1).
• A removable appliance was fitted prior to
surgical tooth exposure (magnet placement)
to ensure that patients had the necessary
compliance to undergo their postoperative
orthodontic treatment (Fig. 2).

62. • Paralene coated NdFeB magnets (Magnet
Developments Ltd, Swindon, UK) were
encased in orthodontic composite
(Transbond, 3M, Unitek, Monrovia, CA, USA).
• Teeth were surgically exposed and encased
magnets (3 mm × 3 mm × 2 mm) were
cemented in place using orthodontic
adhesive (Transbond, 3M, Unitek) (Fig. 3).

63. • Patients were reviewed 1–2 weeks after surgery and their
removable appliances modified to accept an encased
magnet (5mm×5mm×3mm). The magnet was carefully
orientated to ensure the flat attractive surface was as
near parallel as possible to the first magnet bonded to the
tooth.
• Post-operative radiographs (panoramic or peri-apical
views) were taken to confirm correct magnet orientation
and as a baseline reference for monitoring tooth
movement.

64. • Patients were seen for a further review
at 1 month and then at 3-monthly
intervals until the magnets were
removed or, between these reviews if
problems occurred.
• Final arch alignment was undertaken
with fixed appliances if necessary (Fig.
5).

65. • This approach to unerupted teeth has a number of advantages over
more conventional methods of treatment.
1. First, it is both operator and user friendly.
2. No unpleasant or uncomfortable manipulations of wires, springs, or
elastics are required. Also
3. , no demands are placed on the manual dexterity of the clinician or
the patient.
• Magnets produce a low continuous force that actually increases over
time. This force may be more physiologic, as it encourages eruption at
least as quickly as with other methods involving traction.
• In addition to cases involving incisors and canines, it is now being used
successfully with premolars and molars, where more traditional
methods would have been difficult to manage

66. Impaction

67. Animal study
• 3-3.5yrs Macaca fascicularis monkey – Human
age 14 to 18yrs
• Impacted 1st PM and retained deciduous 2nd
molar
• Removal of deciduous tooth – space gained for
impacted tooth using coil spring
• Mucoperiosteal flap raised – horizontal brackets
bonded – healing 1week
• Hawley plate with magnets – 3 weeks - tooth
emerged

68. • 13yr old male
• Palatally impacted UpperCanine
with retained deciduous canine
• Deciduous canine removed and
impacted tooth exposed –
vertical magnetic bracket bonded
• Hawley plate with magnet (Nd-
Fe-B 2.5mm3) were given after 4
days

70. • A magnet, coated with acrylic and attached with a wire
extension arm, can be attached to a removable appliance.
The position of the magnet can be altered by adjusting the
extension arm. By bonding a metal bracket to the impacted
tooth after surgical exposure, the impacted tooth will be
under magnetic force with a direction controllable by
adjustment of the extension arm

72. Molar distalization
Anthony A. Gianelly et al – 1989 AJODO

73. • Intra-arch repelling magnets were placed against the maxillary molars
in conjunction with a modified Nance appliance cemented on the first
premolars. The acrylic palatal coverage of the Nance appliance extends
anteriorly to the incisor segment by means of an 0.045-inch wire
soldered to the lingual aspect of the premolars.
• The acrylic component is placed against both the palatal vault and the
incisors. Bilateral distal extensions (0.045-inch wire) with loops at the
end are soldered to the labial aspect of the premolar bands so that the
loops approximate the molar tubes. The reason that we anchor the
modified Nance appliance to the first premolars is that we want to
encourage the distal drift of the second premolars that normally
occurs as first molars are moved posteriorly.

76. • The modified Nance appliance serves two functions, one of
which is activation of the magnets. For this purpose, an
0.014-inch ligature wire is placed through the loop and
extended anteriorly to encircle a tieback hook mesial to the
magnets. When tightened, the magnets are held in contact.
The second function of the appliance is to contain the
reaction force arising from the action of the magnets.

77. • Repelling magnets, used in conjunction with a modified
Nance appliance, 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.
Patient cooperation was minimal. This represents an
advantage when one is comparing magnets with other
appliances used to move molars distally.

78. Maxillary Expansion
• Vardimon et al (1989) –
Stability of Palatal expansion
by magnet is more than
mechanical expansion in
monkeys

80. Functional Magnetic System
It is also known as Functional Orthopedic Magnetic
Appliances (FOMA),Magnetic Activator Devices (MAD).
It is used to correct to Class II (FOMA II) and Class III
malocclusion (FOMA III). It consists of an upper magnet,
located anterior to a lower magnet in a non-displayed jaw
relationship. Both magnets are incorporated in the upper
and lower plates

81. Functional Orthopedic Magnetic Appliance (FOMA II)
• Vardimon et al -1989
• Conventional functional appliances are passive
appliances that transfer forces produced by muscle
stretch from one jaw to another and guide lower
jaw in an advanced posture.
• FOMA II is an active appliance that directs magnetic
forces to the jaws and thereby constrains the jaw in
an advanced posture. FOMA II has upper and lower
attracting Neodymiumiron-boron magnets maintain
the mandible in an advanced sagittal position

82. Functional Orthopedic Magnetic Appliance (FOMA III)
It consists of upper and lower acrylic plates
with a permanent magnet incorporated
into each plate. The upper magnet is linked
to a retraction screw. The upper magnet is
retracted periodically (e.g., monthly) to
stimulate maxillary advancement and
mandibular retardation. The attractive
mode neodymium magnets used in this
study produced a horizontal force of 98
gms and a vertical force of 371 gms
• Appliance is capable of achieving full
intermaxilllary Class III correction.

83. Magnetic Activator Device
Darendeliler and Joho (1993 )
MAD I (LATERAL DISPLACEMENT)
MAD II (CLASS II MALOCCLUSION)
MAD III (CLASS III MALOCCLUSION)
MAD IV (SKELETAL OPEN BITE)

84. Magnetic Activator Device II (MAD II)
• Upper and lower removable appliance, carrying magnets in
both buccal segments. Each appliance has a lingual acrylic
portion with two "C" type retention clasps on the first
molars, a labial bow, two samarium cobalt magnets
(Sm2Co17) and an occlusal bite plane to avoid cusp
interferences

85. Total magnetic force is 600 to 700 gm
In Class II cases with normal vertical proportions, the
magnets are placed distal to the upper canine and distal to
the lower first premolar

86. • 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

87. 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 retro-incisal area will help to
achieve symmetry and alignment of upper and
lower midlines

88. • In more severe Class II, Division 1 situations, a reactivation
of the appliance is necessary: Once the patient's
adaptation to the "magnets in contact" position has taken
place, reactivation of the appliance is achieved by moving
the lower magnets further posteriorly with the help of
additional lingual screws attached to the lower magnet

89. Magnetic Activator Device III (MAD III)
Darendeliler et al (JCO 1993)
A MAD III appliance was
constructed from a bonded upper
plate and a removable lower
plate, each carrying two buccal
magnets .

90. The lower buccal magnets were placed more
anteriorly and buccally than the upper buccal
magnets
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.
The total sagittal force between the upper and
lower plates was about 300g initially, increasing
to 600g as the crossbite and Class III condition
were corrected

91. Magnetic Activator Device IV (MAD IV)
• It uses anterior attracting
magnets as well as posterior
repelling magnets. The anterior
magnets guide the mandible
into a centered-midline position,
add an anterior closing effect,
and enhance the anterior
rotation of the mandible

92. • The MAD IV consists of removable upper and lower plates,
each of which contains three cylindrical neodymium
(Nd2Fe17B) magnets coated with stainless steel.

93. • The MAD IV-a is used in cases where the anterior segment
of the maxilla is overdeveloped (gummy smile). Because
posterior intrusion and mandibular autorotation are
needed, the posterior and anterior magnets are placed in
full contact

94. • 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

95. • 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,
depending on the severity of the anterior open bite

96. Magnetic Twin Block
• The role of magnetic twin block is specifically to accelerate
correction of arch relationship. the purpose of the magnets
is to encourage increased occlusal contact on the bite block
to maximize the favourable functional forces applied to
correct malocclusion.
• Mainly Samarium-cobalt and Neodymium-boron rare earth
magnets were used.

98. • Attractive magnets were in cooperated in occlusal inclined
planes that is effective in maintaining forward mandibular
posture when the patient is asleep.
• Patients who have magnets added to twin block during
treatment report increased occlusal contact by day and
observed also that the block are in contact on walking.

99. Retention
• Springate and Sandler – 1991 BJO,
used magnets for retention
• Allows more physiological tooth
movements during function
• Better oral hygiene

100. Conclusion
• Permanent magnets produce magnetic forces capable of
causing orthodontic tooth movement or orthopaedic
effects. Today, magnets are used in orthodontics for several
therapeutic reasons, namely to move teeth, to expand
arch, in combination with fictional appliances and to retain
treatment results. The superiority of therapeutic results
with various magnetic appliances, compared to those of
conventional orthodontic appliances is still in dispute and
requires further research

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