Pg canin retracton

A SIMPLIFIED APPROACH
TOWARDS
PG CANINE RETRACTION SPRING
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INTRODUCTION
The newer orthodontic materials such as TMA with
wide spectrum of mechanical properties, have added to
the versatility of orthodontic treatment.
BURSTONE stated “The TMA should permit the
design of future appliances which deliver the
SUPERIOR FORCE SYSTEMS WITH SIMPLIFIED
CONFIGURATION”.
Here the TMA has been successfully replaced stainless
steel to simplify PG canine retraction spring.

AIM OF THE STUDY
To compare efficacy of original PG canine
retraction, and modified spring :
1. To compare rate and amount of canine
retraction.
2. To compare canine tipping and rotation.
3. To compare anchorage loss.

CANINE RETRACTIONCANINE RETRACTION

The canines are key stones of occlusion. Correct
positioning of the canine after retraction in I-pre molar
extraction cases is imperative for function, stability,
and esthetics.
This requires the creation of a bio mechanical
system to deliver a predetermined force and a
relatively constant moment-to-force ratios in order to
avoid distal tipping and rotation.

Friction mechanics :
Sliding the canine through arch wire gives undesirable
side effects.
• Binding,
• Friction,
• Extrusion and rotation,
• Distal tipping,
• Bending of arch wire, there by…
Temporary or permanent stops in the tooth movement.

 Frictionless mechanics :
• Accomplishes space closure by means of
retraction springs.
• Making it possible to apply predetermined and
precise forces which can meet the biomechanical
requirements for planned tooth movements.
• Friction and binding of the tooth are
eliminated.
• Tipping and rotations can be controlled.

PG CANINE RETRACTION
SPRING – POUL GJESSING – IN 1985
The spring is pre calibrated to deliver
predictable moment to force ratios in all three
planes of space, to produce a controlled, bodily
displacement within the desired range of
activation.

NEED FOR MODIFICATION
 ORIGINAL SPRING IS
• Complex and bulky,
• Less comfortable to the patient,
• Problem in maintaining oral hygiene,
• Complex fabrication,
• Difficult in activation.

THE MODIFIED SPRINGTHE MODIFIED SPRING

SELECTING TMA OVER STAINLESS
STEEL
1. TMA deflected twice than S.S. as far without
permanent deformation,
2. Working range is 1.6 times that of S.S.,
3. Modulus of elasticity less than that of S.S.,

4. Extra oral anchorage demands are less than
those for s.s.,
5. Spring back is superior to that of S.S.,
6. Corrosion resistance comparable to S.S.
7. The forces that are produced by TMA are 0.4
times than that of s.s.

FUNDAMENTAL
BIOMECHANICS
FUNDAMENTAL
BIOMECHANICS

THE CR OF CANINE :
Shown to be located in the center of the root one third
of the distance from the alveolar crest to the apex.

FOR TRANSLATION OF CANINE
:
The displacement of canine depends on the relationship
between the line of force and the center of resistance
(CR)
Application of force through CR.

Force application Distal tipping
M = F X D
D = 11 mm

Force application
Rotation
M = F X D
D = 4 mm

Force application
Anti tip couple
Moment to force ratio = 11

Force application
Anti rotational couple
Moment to force ratio = 7

PG CANINE RETRACTION
SPRING
Anti rotation bend
35º
Anti tip bend
Beta bend
15º
12º
30º
Occlusal loop
Apical loop
2 mm
10 mm
5.5 mm

Distal horizontal activation of 100 gm

MODIFIED PG CANINE RETRACTION
SPRING
Anti tip bend
Beta bend
Anti rotation bend

 The Alpha, Beta and anti rotation bends are increased,
since slightly more than double as compare to original
spring. TMA gives 0.4 of force as compare to S.S
 With Distal sweep

EVALUATION OF MODIFIED PG
SPRING :
To match the horizontal activation of 100 gm.

 The apical loop of test springs are opened by 0.5 mm,
1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm each spring is
activated to measure the force.
DIAL CALIPERS has been used for above.
 DONTRIX GAUGE was used for force measurement.

2.5 mm
 The 2.5 mm loop after activation showed horizontal
force matched of 100 gm force approximately with
Dontrix gauge.
Above design has been selected for modified spring.

Horizontal activation can be done by activating the
spring until the legs of loop come close together.

CRITERIA FOR CASE
SELECTION
• MODERATE TO MAXIMUM ANCHORAGE CASES.
• CLASS-I OR CLASS-II MOLAR RELATION.
• I-BICUSPID EXTRACTION CASES.
WHICH REQUIRES INDIVIDUAL CANINE
RETRACTION.
Age selection :
13 to 25 yrs both in boys and girls.

TREATMENT MECHANICS
:
 Leveling of buccal segments
 The retraction started at the same time on both sides,
Pre Adjusted Edgewise system, 018 slot, ROTH
prescription.
 Springs are fabricated from
 016 X O22 stain less steel wire (for original spring),
 016 x 022 inch TMA wire (for modified spring).

TEMPLATE USED FOR SPRING
FABRICATION
Modified spring original spring

ACTIVATIONS :
 EVERY 4 WEEKS ( 1 visit )
RIGHT SIDE :
 Modified PG spring (TMA)
 Activated 2.5 mm
LEFT SIDE :
 Original PG spring (S.S.)
 Activated by two loops are separated by 1mm

ADVANTAGES OF MODIFIED PG
SPRING
 Increased rate and amount of canine
retraction,
 Decreased canine tipping and rotations,
 Decreased anchor loss.
 Less deformation and distortion,
 Properties are not lost during bending
and activations,

 Reduced bulk,
 More comfortable for patient,
 Ease of fabrication,
 Less chair side time for fabrication,
 Easily adjustable.

CASE
REPORTS

CASE-I
Beginning of
canine retraction
Rt side 5.75 mm
Lt side 6 mm

AFTER
12 WEEKS…..
( 3rd
visit )
Rt side 5.75 mm space
closed.
Lt side 4 mm space
closed.

AFTER
20 WEEKS…..
( 5th
visit )
Lt side 6 mm
space closed.

CASE-II
Beginning of
canine retraction
Rt side 5.25 mm
Lt side 5 mm

Comparison with IOPA
Before canine retraction

AFTER
8 WEEKS…..
( 2nd
visit )
Rt side 3.75 mm
space closed
Lt side 2.5 mm
space closed

AFTER
20 WEEKS…..
( 5th
visit )
Rt side space closed
3rd visit
Lt side space closed
5th
visit

Comparison with IOPA
After canine retraction

CASE-III
Beginning of
canine retraction
UPPER
Rt side 7 mm
Lt side 5.5 mm

LOWER ARCH
RT SIDE 6.75 MM
LT SIDE 6.5 MM

AFTER
4 WEEKS…..
( 1st
visit )
UPPER ARCH
Rt 2 mm Lt 1.25 mm
space closed

Lower arch rt side 1.85
mm, lt side 1.25 mm space
closed.

AFTER
12 WEEKS…..
( 3rd
visit )

Rt side 6 mm space4 closed,
Lt side 5 mm space closed.
Rt side 7 mm space closed
Lt side 2.5 mm space closed

Case-IV
Beginning of
canine retraction
Rt side 7 mm,
Lt side 7 mm.

Rt side 7 mm,
lt side 5 mm space closed.

CONCLUSION
In this age of stupendous technological
development and research, many appliance
systems flooded orthodontic fraternity.
As mentioned in this paper modification for
canine retraction spring is no exception.
The truth of future orthodontics is to use this
simple modified canine retraction spring to our
at most advantage not compromising on
treatment goals.

Pg canin retracton

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