Canine retraction final

CANINE RETRACTION
IN PRE-ADJUSTED
EDGEWISE APPLIANCE
www.indiandentalacademy.com

Canine retraction is an integral part of
many orthodontic treatment procedures and
considerable emphasis has been placed on those
mechanisms which are used to accomplish it.
Some of these mechanisms move the canine
distally in a bodily manner, others tip the canine,
necessitating a subsequent uprighting phase.
Most of them incorporate some mechanisms to
avoid the undesirable distolingual rotation as the
canines are moved distally.
INTRODUCTION

When considering canine retraction a
thorough knowledge on the following is
required
The basic principles involved in tooth
movement
The type of anchorage required for that
particular patient
The types of retraction mechanics
The force systems available for each type of
retraction mechanics.
Clinical considerations

BASIC PRINCIPLES OF TOOTH MOVEMENT
CENTER OF RESISTANCE
That point on a tooth, where when
a force is applied, the tooth translates
or moves bodily & all points on the
tooth move in the same direction
together.
CENTER OF ROTATION
That point around which the tooth
rotates when force is applied.

FORCE – is the load applied to an object that will tend
to move it to a different position in space.
A :When the line of force
passes through the center of
resistance bodily movement
of teeth occurs
B. When the line of force
does not pass through the
center of resistance, a
moment is produced and
rotation occurs.
MOMENT – is the force acting at a distance. Is defined
as the product of force times the perpendicular distance
from the center of resistance.

MOMENT TO FORCE RATIO –. the relationship
between the force and the counter balancing couple is
expressed as the moment to force ratio. It determines the
type of tooth movement.
The rotating tendency induced by a
single force at the bracket, will continue
to tip the tooth unless a counter moment
or counter – rotating tendency is
applied at the bracket to achieve the
desired type of tooth movement
This counter moment or secondary
moment is applied at the bracket by the wire or a ‘V’
bend – and should be equal in magnitude but
opposite in direction to the initial moment to achieve
bodily movement

Moment to force ratios of 1:7 produces controlled
tipping.
M /F ratio is 8:10 –bodily movement of teeth occurs.
Ratios greater than 10 produce torque.
COUPLE -Is two parallel forces of equal magnitude
acting in opposite directions . Rotations are also
achieved with moments of couple.

RETRACTION MECHANISM CAN BE
GENERALLY CLASSIFIED INTO 2 TYPES
FRICTION OR SLIDING MECHANICS
Sliding the brackets along the arch wire OR sliding
the arch wire through bracket and tubes
Friction occurs at the bracket – wire interface, affects
force levels, higher force is required to overcome friction
and to exert optimum force for tooth movement
FRICTIONLESS MECHANICS
Distal movement of the canine with the arch wire.
closing loop‘s which was activated in the office by opening
the closing loop and moving the arch wire through the
posterior bracket slots

Classification based on extraction space closure
requirements- to achieve treatment objectives
Type A – 75% to 100% of extraction space closure is
achieved by retraction of ANTERIORS
Type B – Almost equal amount of movement of
ANTERIORS and POSTERIORS towards
each other
Type C – 75% to 100% of extraction space closure by
mesial movement of POSTERIORS
ANCHORAGE CONSIDERATION

FRICTION MECHANICS
ADVANTAGES OF SLIDING MECHANICS:
Minimal wire-bending time
Sufficient space for activations
Patient comfort
Less time consumption for placement
The most significant difference between the
mechanics of standard edgewise and the
preadjusted edgewise appliance was seen during
space closure.Level bracket slot arrangement and
the absence of bends in the arch wire allowed the
use of friction mechanics.

DISADVANTAGES
No established guidelines on amounts of force to
be used during space closure
Tendency for initial overactivation of elastic and
spring forces, causing initial tipping and inadequate
rebound time for uprighting
Generally slower than loop mechanics due to
presence of friction.
Force degradation of elastics and springs.

MECHANICS INVOLVED
To move a tooth bodily the force applied has to pass
through the center of resistance of the tooth. However as
the force is applied at the bracket level of the crown, the
concerned tooth experiences both force and moment.
Moments of force produced by elastic chain placed at
bracket level and not at center of resistance.

The moment of force is created in 2 planes of space.
A. Crown rotation- One moment tends to rotate the
canine mesial out as force application is buccal to the
centre of rotation
B. Crown tipping- Second moment tends to cause distal
tipping of tooth as the point of force appliance is
occlusal to centre of resistance.
The wire bracket interaction tends to counteract this
moment by applying an opposite moment.www.indiandentalacademy.com

As distal tipping of the crown takes place, the tooth slides
along the arch wire till binding occur between the arch wire and
the bracket. This produces a couple at the bracket which results
in distal root movement and hence uprighting of the tooth.
The wire deflects to produce a
couple which uprights the tooth.www.indiandentalacademy.com

As the tooth uprights the moment decreases until
the wire no longer binds. Then the canine retracts
along the arch wire till distal crown tipping again
causes binding. This process is repeated until the
tooth is retracted or the force gets depleted.This initial
tipping of crown followed by root uprighting is called
walking of canine.
The magnitude of the root uprighting depends on
the size, shape and material of the wire and the width
of the bracket. The larger the load deflection rate of
the wire, the greater the force from its deflection and
hence greater the moment produced.
- The wider the bracket, the larger is the moment arm
and hence greater is the moment.

RETRACTION FORCE SYSTEMS AND
METHODS EMPLOYED IN SLIDING
MECHANICS
Elastomeric chains or power chains
Elastic module with ligature (Bennett's method)
Elastic thread.
Elastic bands hooked over prefabrication ligature hook.
Coil springs
J Hook Head Gear
Sliding jig and traction.
Mulligan’s V Bend sliding mechanics.
Employing tip edge brackets on canines.

ELASTOMERIC CHAINS OR POWER CHAINS
Introduced in 1960’s for canine retraction,
diastema closure, rotation correction and arch
construction.
Engaged by stretching 50-70% of its length to
give varied force levels as required
50-70% of force is lost in first 24 hours, at 3
weeks only 30% remains, pre-stretching has
been suggested, but only 5% gain in force value
Wide variation in force level, prudent to use a
force gauge to determine desired initial force
level www.indiandentalacademy.com

ADVANTAGES
Inexpensive, easily applied without archwire
removal.
Independent of patient co-operation.
easy to apply without removing arch wire
DISADVANTAGES
Absorbs water & saliva, staining.
Break down of internal bonds, permanent
deformation causing rapid loss of force.
Stress relocation leads to loss of force and hence
gradual loss of effectiveness.www.indiandentalacademy.com

Tooth movement, pH and temperature
changes, fluoride rinses, salivary enzymes
and masticatory forces have all been
associated with deformation, force
degradation and relaxation behaviour of
Elastomeric chains.
Lose 50 – 70% of their initial force
during the first day of load application
and at the end of 3 weeks retain only 30 –
40% of their original force.

TYPES
E chain are available in 3 configuration
Closed loop chain
Short filament chain
Long filament chain:-generally deliver a
lower initial force and exhibit a greater rate of
force decay at the same extension.

ELASTIC MODULE WITH LIGATURE
This method popularized by Bennett and McLaughlin.
A single elastic module of the type used to secure arch
wires to brackets is attached to the canine by ligature wire
extending from the molar.
These elastic tie backs are activated 2-3mm or to twice
then original size to generate approximately 100 – 150 gms
of force.

If the arches are properly leveled this light force
allows for effective retraction with minimal tipping of
teeth and maintenance of arch leveling.
Bennett recommended 0.019 x 0.025” rectangular
wire in 0.022” slot to be most effective, providing
maximum rigidity while allowing adequate freedom for
sliding
Retraction rate of 1mm/month.

Alternate delivery systems have been found to be
disadvantageous to elastic module in the following
aspects.
a. Power chains – gives variable force
- difficult to keep clean
- may falls off
b. Elastics - Require patient compliance.
c. SS coil springs - Deliver excess force and
- Unhygienic

ELASTIC THREAD
Elastic thread is inserted under the arch wire in a figure
of 8 configuration from the canine to premolar and firmly
knotted.
The premolar is firmly / tightly ligated to the molar by a
stainless steel ligature wire.
Elastic thread is obtainable in two different forms
1: Cotton covered:- Is easier to knot firmly but becomes
dirty in use.
2 : Plain uncovered elastic :-Remains clean in mouth but
with passage of time can loosen. The sizes available are
0.625mm (0.025”) and 0.75mm (0.030”).

ADVANTAGES
Neat method.
More comfortable.
Bodily movement of the canine tooth is achieved.
Easier to replace inorder to reactivate at each visit
without removing the arch wire.
DISADVANTAGES
Thread is wasted in tying the Knot.
The knot will untie unless it is pulled very tight.
Knot causes irritations to the cheek if it is not carefully
tucked out of the way.
Difficult to regulate the forces.
This technique not recommended for use when the
canine can be engaged only by a thin arch wire.www.indiandentalacademy.com

INTRA OR INTERMAXILLARY ELASTTICS TO
KOBAYASHI LIGATURE
The Kobayashi ligatures are SS ligatures incorporating a
welded hook for intra or intermaxillary elastics.

They are loosely tied to the canine bracket and can be
left as a hook pointing mesially or can be tied so that
the hook faces distally and is then bent forward.
It is a useful method of applying light forces to tip
the canine distally along a thin flexible arch wire.
It is not a good method of applying traction to an
already upright canine which requires further
retraction by bodily movement.

ADVANTAGES
Simple to put on.
Readily measurable constant light force to tip the canine
along the arch wire, in the range of 40 – 100gms.
Can be applied by the patient hooking the elastic bands
over the ligatures.
DISADVANTAGES
Not an effective method of applying traction to slide the
canine bodily along the arch wire because the strong elastics
required for bodily movement cause rotation and excessive
bending of the canine.
Relies on patients compliance in wearing elastics and
wearing them correctly.

CLOSED COIL SPRING
Coil springs were introduced in orthodontic as early as
1931.
The various materials that have been used for making
springs are :- Stainless steel, Niti , Co – Cr - Ni Alloy

ADVANTAGES OF NITI COIL SPRINGS
Shape memory and super elasticity.
Low modules of elasticity, moderately high strength, high
resilience and low corrosion.
Deliver constant amount of form till they reach the
terminal end of deactivation stage.
Produce constant force over a wide range of activation
and generally close space with single activation.
Can be easily placed and removed without arch wire
removal.
Do not need to be reactivated at each appointment.
A cooperation not required.
DISADVANTAGES OF NITI SPRINGS
Relatively unhygienic compared to elastic force systems.

DIFFERENT WAYS OF USING COIL SPRINGS
Coil springs threaded on to the arch wire and compressed
between the canine brackets.
Coil spring compressed between a soldered stop on the
arch wire and canine bracket.
Compressed between an incisor bracket and the canine.
Compressed by a tie back ligature.
Expanded tied back coil spring.
Coil spring compressed between canine brackets
Coil spring measured 3/4th
of distance canine pulled twice
its length and compressed.
The arch wire should closely fit the bracket slot, and
cinches distal to molar.www.indiandentalacademy.com

Advantages
Force applied is easily measured.
The long length of coil will transmit a relatively constant
force over a long distance.
Requires little reactivation.
Disadvantages
Increase in intercanine width as the coil spring on the
anterior curvature of the arch wire exerts a lateral as well as
distal component of force.
Length of coil spring can be irritating to the patients lip.

Coil spring between soldered stop and canine
bracket
Small piece of wire soldered on either side to act as stop.
Generally placed at distal margin of lateral incisor.
Two length of closed coil springs, a little more than half
of the distance of stop and canine are selected and then
compressed.
The arch wire should closely fill the slot.
Advantages
Less irritating to the patient than long continuous coil.
Neat
Forces applied are easily measured.
Disadvantages
Annealing of the wire during soldering.
Increase in intercanine width may occur.
Spring required reactivation more frequently.
To reactivate a compressed coil spring 2mm length of

Coil spring between incisor bracket and canine tooth
Coil spring is compressed between central incisor and
canine bracket.
Excellent method of closing upper incisor spaces / central
diastema, using the force exerted by the reciprocal action of
the coil spring.
Coil springs compressed by a tie back ligature
Two 3 – 4mm length of closed coil spring opened to twice
their length then recompressed are threaded to the arch wire
to lie mesial to the canines.
Using soft SS ligature is placed mesial to springs twisted
and tied to premolars.
Arch wire should be rigid and should fill the slot.www.indiandentalacademy.com

Advantages
Coil spring short and less irritating.
Easily activated by retying or tightening the tie back
ligature.
Disadvantages
Long ligature likely to be damaged.
Tied back expanded coil spring
This technique uses a coil spring is opened on
activating pulling the canine distally rather than pushing it
as the compressed spring does.
Can be used to tilt back a mesially inclined canine
along a thin flexible arch wire or can be used to bodily
retract the causes sliding it along a right arch wire.www.indiandentalacademy.com

Advantages
Coil spring can be removed any time without removing the
arch wire.
Forces can be measured.
Spring activated by simply tightening the ligature.
Intercanine width is not increased as coils lies behind the
canine.
Disadvantages
Susceptible to damage.
Ligature can fracture.
Spring tends to act as food trap.

EXTRA ORAL TRACTION
The arms of the extra oral traction are bent
into a small open circle (J hook) and hooked
directly on to the arch wire to contact mesial
of the canine bracket.
The direction of the pull should be as near
as possible along the occlusal plane, this
usually requires a straight pull headgear for
both maxillary and mandibular canine.
However, when this technique is used to
retract all four canines together a high pull
head gear is used for the maxillary canine
and a straight pull for the mandibular canine.

Advantages
Extremely conservative of anchorage.
Additional molar support by headgear
may be done.
Simultaneous overjet reduction might
occur during canine retraction due to the
distal force and binding of the archwire.
Can be applied to both upper and lower
arches simultaneously (use of Hickham’s
headgear system)

Disadvantages
As force application is intermittent this is slower than othe
method of canine retraction.
Highly dependent on patients cooperation.
Canine tipping and anterior extrusion may occur with
straight pull headgear.
Soreness of the corner of mouth from side piece arm can
occur.
The molar and buccal segment correction is usually a later
event in treatment compared to other system.
Mesio buccal rotation of canine.
Flaring of canine into buccal cortex.
One canine may retract faster than the other (this may be
due to patient hooking the traction arm on to the same side
first). www.indiandentalacademy.com

SLIDING JIG AND TRACTION
In this a jig is made in 0.022” round wire or 0.017
x 0.022” rectangular wire and slide on to the arch
wire is addition to a short piece of open coil spring of
about 4mm in length.
The coil spring lies in contact with mesial end of
canine bracket and circle of jig lies on the mesial
end of coil spring.
The traction can be applied to the jig by either
intra or inter maxillary elastics or by extra oral
traction

Advantages
Force exerted by the elastics is directed along the
arch wire and thus bodily movement of canine is
possible.
In cases of extraoral traction method, the jig
brings forward the point of application of J hooks
thus reducing the soreness at corner of mouth.
Disadvantages
Difficult to fabricate
Food entrapment
Can dislodge the brackets
Irritation to cheek.

Mulligan’s V Bend sliding mechanics
Introduced by Mulligan in 1970’s.
The basic principle was to apply differential moments to
the teeth via bends in the continuous arch wire while force
for retraction was applied by auxiliaries like E chain, coil
spring etc.
In 0.018” slot 0.016 SS wire , 0.022” slot 0.016 ,
0.018, 0.020 SS wires used for retraction.
The arch wire is not tied in the incisor bracket during
cuspid retraction, as this reduces
a. Distal root moment placed in cause
b. Causes incisors flaring
c. Causes severe mesial root movement of canine.

The wire is tied in 4 – 6 weeks for alignment then 45° V
Bend are added and 200gms of force is applied between
canine and molar.
The purpose of V Bend is to allow differential mesio
distal moments on canine and molars.
- If the bend is off centered it creates a short and long
segment.
The short segment is more rigid and hence applied
greater moment, so if maximal canine retraction is required
the bend is placed close to molars and bicuspids not banded.
- This causes strong distal crown moment on molar
which counteracts the auxiliary force tending to move
molar crown forward – Reinforcing anchorage.www.indiandentalacademy.com

Mandibular canine retraction
with V-bend sliding mechanics

USE OF TIP EDGE BRACKETS ON CANINES
Tip edge brackets used in cases of an upright or
distally tipped canine as the arch wire insertion can
causes bite deepening due to incisor extrusion.
This eliminates binding between wire and slot during
initial stages when major movements are accomplished.
As retraction is complete uprighting springs may be
used to correct canine angulation without causing
anterior extrusion. Full size rectangular wire can then
be placed for achieve desired tip / torque specifications.

FRICTIONLESS MECHANICS :-
( DISTAL MOVEMENT OF THE CANINE WITH
THE ARCH WIRE ) .
-Involves use of closing loops fabricated in either full
or sectional arch wires to induce tooth movement
-Designed to provide low load – deflection rate (force
per unit deactivation) and controlled M/F ratios
-Precise application of force systems giving three
dimensional control over tooth movement.

Bio Mechanics :
In Frictionless mechanics tooth movement is achieved
not by sliding the brackets through the wire but by the
activation of loops with specific bends ( pre-activation bends
- Alpha and Beta ) to achieve desired type of tooth
movement
Force is applied by pulling the arms of the loops away
and cinching them back at the molar tubes
Anterior bend or
ALPHA bend - alpha
moment
Posterior bend -
BETA bend -beta
momentBetaBeta AlphaAlpha

- A simple loop when activated is unable to generateA simple loop when activated is unable to generate
adequate counter moment required to achieve theadequate counter moment required to achieve the
desired tooth movementdesired tooth movement
- So , pre-activation bends are given - increases M/FSo , pre-activation bends are given - increases M/F
ratioratio
- They are placed within the loop or where the loop meetsThey are placed within the loop or where the loop meets
the wirethe wire

. When the springs are used two moments control
anchorage and vertical forces
The α moment produces distal of an of anterior
teeth while the β moment causes mesial root
movement of the posterior teeth by varying the
magnitude of these moments differential movement of
posterior and anterior segment can be achieved.
If the moments are equal - no vertical forces
are exerted
However if α and β moments are unequal
vertical forces are also generated.

A: Beta moment greater than
alpha moment producing net
intrusive force on the anterior
teeth and extrusive force on
posterior teeth.
B: Alpha moment greater than
beta moment producing net
intrusive force on posterior
teeth and extrusive force on
anterior teeth.
C:Equal alpha and beta
moments,producing no vertical
component of force.

The distance that the anterior and posterior segment
are to be moved depends on factor such as
- Amount of crowding
- Anchorage
- Axial inclination of canines an incisors.
- Midline discrepancy any and right / left
symmetry.
- Vertical dimension
The amount of anterior retraction or posterior
protraction needed should be determined before a loop
is designed.

a. For anterior retraction
- Loop placed closer to canine than molar
↓
- Gable bend added near the molar
↓
- Gable bend larger in posterior dimension
produce a large β moment and thus increases
posterior anchorage.
b. For posterior protraction –
- Loop located closer to the posterior segment.
↓
- Anterior Gable bend placed.
↓
Gable Bend has large α moment than β thus making
anterior segment as anchorage.

c. For both anterior retraction and posterior
protraction loop placed midway between anterior and
posterior segment.
↓
Gable bend at equal dimension used
↓
Equal α and β moment generated
↓
Reciprocal space closure occur
Regardless of the initial magnitudes of both α and β
moment, changes will occur during retraction.

As anterior teeth are retracted the magnitude of α
moment decreases faster than β.
↓
Enhancing posterior anchorage. Also as β moment
becomes relatively greater.
↓
Greater intrusive force on anterior teeth and greater
extrusive force on posterior teeth.
Concurrent with the decrease in both α and β
moment there is increase in M/F ratio thus producing a
pure translation.

Constancy of Force and Moments
Optimal biologic responses not only, depends on the
initial force magnitude but also on the rate of decay of
force taking place between activation.
According to Burstone the M/F ratio can be increased by
Increasing vertical dimension gingival to the bracket.
Increasing the horizontal dimension in the apical part of
the loop.
Decreasing the inter bracket distance.
Positioning the loop close to the tooth to be retracted.
Angulating the mesial and distal legs of the spring
Adding more wire gingival to the bracket.www.indiandentalacademy.com

The design of the spring influences not only the M/F
ratio but also load deflection rate the addition of
helices lowers the load deflection rate. It can be
changed by changing the wire composition. TMA
(Titanium Molybdenum Alloy) decreases load
deflection rate when compared to stainless steel.
Types of cuspid retraction springs
Ricketts maxillary and mandibular cuspid
retraction spring.
PG (Poul Gjessing) canine retraction spring
Burstone T loop retraction spring.
Vertical loops, L-loop, helical loops - nickel
titanium canine retraction spring.

CRITERIA FOR AN IDEAL CANINE RETRACTION
SPRING
Should promote translation sagittaly and horizontally
through an anti tip M/F ratio of 11:1 and an anti rotation
M/F ratio of 4:1.
Result in low load deflection ratio during generation of
retraction force in the range of 50 – 200 gms.
Result in no adverse interaction between anti tip and
anti rotation moments during activation.
Should be possible to use it in both 0.018 and 0.022 inch
slot.
Have limited dimension and allow for faciolingual
adjustments.

ADVANTAGES OF FRICTIONLESS MECHANICS
Predetermined force systems can be exerted - within
the control of the orthodontist
No role of friction - optimum force levels accurately
achieved, less tax on anchorage
Desired type of tooth movement can be achieved by
control over M/F ratios by altering design , bends or
positions of the springs

DISADVANTAGES OF FRICTION LESS
MECHANICS
Extra wire bending & chair side time
Good understanding of biomechanics necessary
Undesirable movement of teeth easily possible if
not monitored properly
Appliance distortion intraorally affects
application of predetermined force systems
Uncomfortable to some patients.

RICKETTS RETRACTION SPRING
Maxillary cuspid retraction spring
Is a double vertical helical extended crossed T closing
loops spring which contains 70mm of wire.
It produce 50 gm per mm of activation
Because of additional wire used in its design and all
loops are being contracted during its activation.
3 – 4 mm of activation are sufficient for upper cuspid
retraction.

Mandibular cuspid spring
Is a compound spring with a double vertical
helical closing loop.
Contains 60mm of wire .
Made of 16 x 16 blue elgiloy.
Produces 75gm of force / mm of activation.
2-3mm of activation is required to produce the
desired force.

PG RETRACTION SPRING
Described by Poul Gjessing.
The spring consists of a double ovoid helix with a smaller
occlusally placed helix.
Available commercially in the preformed version,
constructed in 0.016 x 0.022” SS.
The predominant active element is the ovoid double helix
loop extending 10mm apically.
It is included in order to reduce the load deflection of the
spring and is placed gingivally so that activation will
cause a tipping of short arm (attached to the canine) in a
direction that will increase the couple acting on the
tooth.

The gentle rounded form avoids the effects of sharp
bends on load deflection.
- The use of large amount of wire in the vertical
dimension leads to maximum reduction of load
deflection.
- Minimizing horizontal wire increases rigidity in the
vertical plane.
Smaller occlusal loop serves to
- Lower the level of activation on insertion.
- Is formed so that activation further closes the loop.

The distal driving force is generated by pulling the distal,
horizontal leg through the molar tube.
A desirable force level of approximately 160 gms is
obtained when two section of double helix are separated by
1mm.
The PG universal retraction spring is designed for
controlled retraction of either canine or upper incisor.
The spring is precalibrated to deliver predictable M/F
ratio in 3 planes of space.
Bracket engagement Activated spring

C
PG Universal Retraction Spring can be adjusted for canine
retraction (A), uprighting of canine (B) or incisor Retraction (C)
B
A

BURSTONE T LOOP RETRACTION SPRING
Made of 0.017 x 0.025 TMA in an 0.022 slot
0.016 x 0.022 TMA in an 0.018 slot
Designed for Enmasse or separate incisor and canine
retraction in segmented arch technique.
The basic element of the spring is prefabricated highly
standardized universal springs which could be used on both
right and left sides.
These prefabricated versions have to be preactivated as
per a prescribed template.

Engaged into auxiliary tube of first molar and the
vertical tube on the Burstone’s canine bracket
The magnitude of force delivered is identified by
reading the horizontal separation of the vertical legs of
the T loop.

Initially M/F ratio is 6 – 8:1 which produce controlled
tipping. As space close and spring deactivates the force
level decrease and M/F ratio in both alpha and beta arm to
increase, so that the M/F ratio is 10:1 and translations
occurs. Further deactivation increase M/F ratio to 12:1
and root movement occurs.
Therefore, it is important that this spring is not
reactivated too soon. If reactivated too frequently the teeth
would undergo only tipping.
The T loop is available in 2 heights
a. Regular / long height
b. Short height
Activation is 3 – 4 mm.www.indiandentalacademy.com

Used for canine retraction / incisor retraction /
segmental en masse retraction
Differential anchorage obtained by application of
unequal alpha and beta moments.
In group A anchorage cases, higher moment
is applied to anchor teeth, T loop positioned closer
to posterior segment
In group B anchorage cases equal and
opposite moments and forces applied for symmetric
space closure, T loop positioned at the center
In group C anchorage cases, T loop is
positioned near the anterior segment – care is taken
to prevent possible extrusion of anteriorswww.indiandentalacademy.com

NEW METHODS OF CANINE RETRACTION
Retraction Using rare earth magnets
Distraction of the periodontal ligament
- Liou et al (1998) proposed a new concept – ‘dental
distraction’
- 6.5mm of canine retraction in 3 weeks
- Less than 0.5 mm anchor loss
- Tooth borne, custom made intra oral distraction
device
Dentoalveolar distraction osteogenesis for rapid
orthodontic canine retraction.

1.1. Deepening of extraction socket
Occlusal view
Buccal view
DISTRACTION OF THE PERIODONTAL LIGAMENT
SURGICAL PROCEDURE

2.2. Thinning interseptal
bone
3. Undermining
interseptal bone
(buccal, lingual,
& bottom grooving)

Canine distraction device is
placed close to center of
resistance to achieve bodily
movement

Liou and Huang (1998) stated that the process of
osteogenesis in the periodontal ligament during orthodontic
tooth movement is similar to the osteogenesis in the
midpalatal suture during rapid palatal expansion.
They proposed a new concept of ‘distracting the
periodontal ligament’ to elicit rapid canine retraction in 3
weeks. They coined the term ‘dental distraction’ for this
procedure.
At the time of first premolar extraction, the interseptal
bone distal to the canine was undermined with a bone bur,
grooving vertically inside the extraction socket along the
buccal and lingual sides and extending obliquely towards
the socket base.
Then a tooth borne, custom made intraoral distraction
device was placed to retract the canines into the extraction
space. The anchor units were the second premolar and first
molar.

Both the upper and lower canines were distracted 6.5
mm into the extraction space within 3 weeks.
New alveolar bone was generated land remodelled
rapidly in the mesial periodontal ligament of the canines
during and after distraction. It becomes
indistinguishable from the native alveolar bone 3
months after distraction.
During the distraction, 73% of the first molars did
not move mesially and 27% of them moved mesially less
than 0.5mm within 3 weeks.

The radiographic examination revealed that apical and
lateral surface root resorption of the canines was minimal.
They concluded that the periodontal ligament could be
distracted to elicit rapid canine retraction without
complications. This innovative approach can significantly
reduce orthodontic treatment time and merits further
investigation.

USE OF RARE EARTH MAGNETS
When two magnets are in
repulsion (A) or attraction
(B), resulting force is
hyperbolic curve. Its
magnitude is roughly
inversely proportional to
square of airgap between
two magnets (Coulomb's
law).
However, when three magnets are combined so that two
poles are in attraction and two in repulsion (C), there is
certain range of activation for which force magnitude
remains practically unchanged .

Constant force delivery system . A: rare earth block
magnets; B: vestibular wire; L: "corner-braces" to
increase stiffness; S: helix that allows middle magnet
to slide on vestibular wire .
This system did not require reactivation, as loop was
kept open by the magnetic force for entire
experimental period.
Prolonged constant force provides more effective tooth
movement than an impulsive force of short duration.
DISAVANTAGE- Expensive

REFERENCES
1- JCO 1991 Jun (364-369): Clinical Considerations
Use of Retraction Mechanics - JULIE ANN
STAGGERS, DDS, MS, NICHOLAS GERMANE,
DMD, MS
2:- JCO 1994 Sep (539-546): Force System Analysis of
V-Bend Sliding Mechanics - RAYMOND E.
SIATKOWSKI, DMD
3:- JCO 1992 Mar (165-178): The Tip-Edge Concept:
Eliminating Unnecessary Anchorage Strain -
CHRISTOPHER K. KESLING, DDS, MS
4:- JCO 1994 May (293-295): Comparison of NiTi
Coil Springs vs. Elastics in Canine Retraction -
ANDREW L. SONIS, DMD
5:- JCO 1987 Dec (857-870): Bioprogressive Simplified
Part 4 - Extraction Therapy - JAMES J. HILGERS,
DDS, MS

REFERENCES contd…
6:- AJO –1996 VOL MAY (489-495) Canine retraction
with rare earth magnets: An investigation into the
validity of the constant force hypothesis-John
Daskalogiannakis, DDS, MSc, and Kenneth Roy
McLachlan, PhD-Toronto, Ontario, and Winnipeg,
Manitoba, Canada.
7:- Textbook on biomechanics in clinical orthodontics-
by-Dr.ravindra nanda
8:- JCO 1990 Nov (678-683): Vertical Force
Considerations in Differential Space Closure - BIRTE
MELSEN, DO, VASSILI FOTIS, DDS, MSD,
CHARLES J. BURSTONE, D

THANK YOU

Canine retraction final

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