The canine retraction /certified fixed orthodontic courses by Indian dental academy

INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com


CUSPID RETRACTION – THE FIRST STEP

The canine – its special

Key role in canine protected occlusion
Anterior smile and facial aesthetics
Long Root, proximity to cortical plates
Class 1 canine relationship is a prime
orthodontic treatment objective
Cuspid retraction the first step

The canine – its special
Severely malpositioned canines –a
biomechanical challenge
Placing a super elastic wire in severely
displaced situations will only magnify side
effects ,extend time in therapy without
results


Does segmental cuspid retraction
followed by incisor retraction
conserve anchorage ?

NO

Segmental canine retraction
indicated to relieve severe
crowding, correct a class1 relation
ship,maintain the midline


Factors For Biomechanical Design
You need to control
1.Force magnitude and direction
2.Force constancy(Low Load Deflection)
3.Control over the center of rotation
4.Change in M/F ratio with deflection


Control over the Center of rotation
will define the type of tooth
movement
Axial inclination of the canines is an
important factor


Single force on a
1. mesially inclined
tooth
tips it further
mesially.
•M:F 12:1 for
root movement
2. Upright tooth
tips it mesially
•M:F 10:1 for
translation
3. Distally inclined
Tooth
uprights it
•M:F 7:1 for
tipping

Do you think a NiTi wire will generate
a M:F ratio of 12:1 to upright this tooth ??
Should you go segmental ??

The ‘T’ loop is the answer !!


‘T’ Loop
Introduced by Burstone in 1982
Most researched and documented spring in
orthodontics
Perhaps least used !!!
Differential space closure
Min Patient Cooperation-Fail Safe
Axial inclination control
Rotations
Optimum biologic response
Convenience

10 mm
2 mm
4 mm
BETA
(POSTERIOR) SEGMENT

5 mm
ALPHA
(ANTERIOR) SEGMENT

Standard ‘T’ loop (0.017x0.025” TMA)

Alpha
moment

Beta
moment
‘T’ loop pre-activated

Neutral position:
0 mm activation
0 gm force
Concept of differential moments:
activation 6 mm – M:F at anterior seg. 5:1
3 mm deactivation - M:F at anterior seg. 8:1
6 mm deactivation - M:F at anterior seg. 12:1
Interesting to note how the Crot of the canine
remains practically constant throughout the
retraction

Centered V Bend
Intrusive forces=extrusive forces
Opposing moments /2 couple system
Off-centered V bend
Moment greater in the
posterior segment
reinforces anchorage

0.017x0.025” TMA/centered T loop
Activation: 6 mm
F/A = 33 gm/mm
1126 gm-mm

1002 gm-mm

201 gm

168 gm
Deactivation: 1 mm
M/F=6.0

M/F=5.6

0.017x0.025” SS/vertical loop

Activation: 0.2 mm
F/A = 1000 gm/mm

200 gm

0 gm

Deactivation: 0.2 mm
Clinically impossible !!!

‘T’ loop has a low load deflection rate
of 33 gm per millimeter.
An error in activation of 1 mm results in an
error of only 33 gm.
Extremely forgiving !!
As compared to SS, which produces double the
Error.

Burstone did his home work !!
Have you !?!

6 mm activation
M/F=6:1
Tipping

2 mm Deactivation
M/F=10:1
Translation
4 mm Deactivation
M/F =12:1
Root Movement

FORCE SYSTEM GENERATED BY ‘T’ SPRING
FOR INTER-BRACKET DISTANCE OF 25 MM
DISPLACEMENT

FORCE
(GM)

0
1
2
3
4
5
6
7

ANTERIOR
M/F
(D)

POSTERIOR
M/F
(D)

0
42
85
124
170
216
262
310

0
40
21
15
12
10
9
7.6

0
42
22
16
12
10
9
7.5


SEGMENTAL CUSPID RETRACTION
Minor Cuspid Retraction
Favorable root inclination,mild crowding
Placing cuspid in class1 relationship


Minor Cuspid retraction
Cuspid Retraction > 2mm
Controlled tipping
M/F = 8:1
Controlled Tip
017x025 TMA ,45Degree
bend in beta leg to produce
a posterior M/F of 11/1
First order antirotation
bends on the legs

The‘

T


loop
’

0.017 x 0.025” TMA wire


5mm


10mm


4mm


10 mm
2 mm
4 mm

BETA
(POSTERIOR) SEGMENT

5 mm

ALPHA
(ANTERIOR) SEGMENT


Pre-activation bends
β

D = L- A
2

α

β

α
1

2

5

6

3

4


Anti-rotation bends

1

2


Why bypass mechanics?
Unfavorable movement of the incisors
-one of the major disadvantages of PEA
Need to maintain incisor position
Fluctuating forces
Multiple forces and moments at each
bracket-wire interface


Walking the canine:
Normal component of force and frictional resistance
Tooth tips until opposing corners contact the wire
Wire deflects
Moments are generated to upright the tooth


Canine uprighting – couples generated by
wire-bracket contact
Beware: do not see your patient before 4 wks
min. 4 weeks time for uprighting

Force required to retract canine =
100 gm + force to overcome
frictional resistance (100 gm)

OSTEOGENIC DISTRACTION OF
CANINES: EXCITING PROSPECTS


6 mm and 11 days – believe it or not !!


Thank you
For more details please visit


The canine retraction /certified fixed orthodontic courses by Indian dental academy

Recommandé

Recommandé

Contenu connexe

Tendances

Tendances (20)

Similaire à The canine retraction /certified fixed orthodontic courses by Indian dental academy

Similaire à The canine retraction /certified fixed orthodontic courses by Indian dental academy (20)

Plus de Indian dental academy

Plus de Indian dental academy (20)

The canine retraction /certified fixed orthodontic courses by Indian dental academy