Segmented arch technique /certified fixed orthodontic courses by Indian dental academy

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


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Introduction
Rationale of SAT
Preliminary Bracket Alignment
Deep overbite correction
Open bite correction
Space Closure
Root correction

2

Introduction:


Designed to deliver light continuous forces.



“continuous” arch wire.



Segmented arch consists of multiple wire cross
sections.



SA does not connect brackets & tubes on adjacent
teeth.


3

Rationale
Consolidation of teeth into units:


Segmentation allows the treatment to proceed by consolidation
of teeth into units.



Few teeth are considered for each segment.



Continuous arch-forces are distributed to the adjacent teeth.


4


5

Rationale
Varying Cross-section of Arch wire:


Active units



Reactive units



Wires used to displace the teeth should have low LDR.


6

Increasing the Inter bracket distance:


Forces used during intersegmental mechanics are applied at
large distances.



Continuous arch – Active & Reactive forces occur on the
adjacent teeth.


7



Increases the space available for
longer activations.


8

Prefabrication & Precalibration:
•

Continuous arch –Difficult to determine the forces.

•

Segmentation allows the use of precalibrated springs
to deliver the desired forces.


9

Clinical Efficiency:


No. of arches are made during treatment in continuous
arch therapy.



In segmental approach continual replacement of arch
wires are not required


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Preliminary Bracket Alignment
• Initial stage of treatment.
• Brackets of the teeth are ideally aligned.
• Goal : Consolidated segments


11

Attachments & Placement
Attachments:- Slot - 0.022 x 0.028
-Hooks, auxiliary tubes, Head gear tubes.
-Cuspid bracket- 0.175 X 0.025
vertical/horizontal tube.


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Molar attachments

Lingual hinge cap
(0.032 X 0.032)

13

•

Attachments with 1st, 2nd, 3rd order angulations are
available.

•

Help clinician to get good occlusion.

•

Second order angulations can be individualized during
banding.


14

Burstone OrthosTM Attachment
Prescription


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Placement of Attachments
Objectives:








No 2nd order steps
Minimal 1st order bends
All slots are parallel to the occlusal plane.
Variations in the tooth position & morphology.


17

Second order level:-

Criteria:
-Occluso-gingival level
-Angulation with respect to ‘z’ or faciolingual axis.


18



Level of attachments is established first for the
posteriors.

-Maxillary arch: centrals, laterals, canines,1st &2nd molars.
-Mandibular arch: centrals, laterals, canines,1st &2nd
molars.


19

Second order Angulation:
- OPG
Objectives:-Proper root dispersion, & occlusion.


20



Angulations of anterior teeth are
assessed



Using PA cephalograms &
assessed to the treatment occlusal
plane.



All slots should lie in the same line
& roots should have proper root
dispersion.

21

First order placement:
-Attachments are centered mesiodistally on the crown
-Parallel to the incisal edges/buccal cusp tip.


22



Objectives of PBA:-



Normalize the teeth Intrasegmentally.
-Rotations, B-L positions
-Occlusogingival discrepancies.
-Teeth torqued.




Improve the Intersegmental relationship.
Improve the Intermaxillary relationship.


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Basic lingual arches:


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Upper horse shoe shape


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Lingual Arch Wires:







Establishing & maintaining the upper and lower arch widths.
Correcting intra-arch rotations or inter-segmental rotations.
A-P asymmetries.
Difference in the occlusal planes.
Buccolingual & M-D axial inclinations of the post. teeth.
Reducing the undesirable side effects.


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Lingual Hinge Cap -0.032 X 0.032
-Ligation of the lingual arch


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

Buccal Stabilizing Segment:

-To connect the individual teeth into one unit
- For Alignment

-To act as stop anteriorly.
-Point of connection.
-0.018 TMA welded to the molar.


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Deep Overbite Correction
Differential diagnosis & Treatment plan.
3 basic ways -

Intrusion of Ant. teeth

Extrusion of post. teeth


29



Intermaxillary growth space



Skeletal vertical dimension



AB Relationship



Occlusal plane cant



Esthetics


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Intermaxillary Growth Space:


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

Skeletal Vertical Dimension


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


Occlusal Plane cant desired after the treatment
Esthetics


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Principles of Anterior Intrusion
-Controlling force magnitude & constancy
-Anterior single point contact
-Point of force application
-Selective Intrusion
-Control of reactive units
-Avoiding Extrusive mechanics




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Controlling force Magnitude:
-Magnitude of forces used for intrusion should as low
as possible.
-Side Effects: Root resorption



Extrusion of buccal segments


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FORCE VALUES FOR INTRUSION
TOOTH MOVEMENT

FORCE (gm)

INTRUSION

PER SIDE

2 UPPER CENTRAL INCISORS

15 – 20

30 –40

4 UPPER INCISORS

30 – 40

60 – 80

6 UPPER ANTERIORS

60

120

2 LOWER CENTRAL INCISORS

12.5

25

4 LOWER INCISORS

25

50

6 LOWER ANTERIORS

50

100

2 UPPER CANINES

25

-

2 LOWER CANINES

25

-

MOLAR EXTRUSION

60 – 100

120 – 200


TOTAL IN MIDLINE

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



Force constancy is obtained by using low LDR
springs.
Intrusive Arch-0.018 x 0.025 with 3mm helix


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Anterior Single Point Contact:
-Intrusion arch is not placed in the anterior brackets.
-Torque
-Allows the clinician to know the force systems involved.
(Statically Determinant)
-Anterior alignment arch wires can be placed.




39





Point of Force Application:
Force applied to the Cres
will not produce any labial
/lingual rotation.
Intrusion arch is placed
anterior to the labial surface.


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

Selective Intrusion:


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Control of the Reactive Units:
-Minimization of force magnitudes.
Side Effects: Plane of occlusion in the buccal segments is altered.



•

Forces of intrusion should be kept low.

•

More no.of teeth should be incorporated.

•

Retraction is done initially.

•

Occipital HG


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• Equal & opposite extrusive effect


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

Avoiding Extrusive Mechanics:

-CL-II elastics
-CL-III elastics
-Cervical HG

Pts requiring true intrusion.


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Principles of Anterior Intrusion


Use of optimal magnitudes of force



Point contact in the anterior region



Selection of the point of force application with respect
to the Cres.



Selective intrusion



Control over the reactive units



Avoidance of undesirable eruptive mechanics.


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Continuous Intrusion Arch
•
•
•


Post.Anchorage unit
Ant.segment
Intrusion arch(0.017x0.025 TMA).
0.018 round TMA stops are welded – to serve as tie
backs.


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Three-Piece Intrusion Arch


Intrude the flared incisors, control their axial
inclinations & retract with good anchorage control.



Point contact of force application.



Pt’s with proclined incisors have to be treated
differently.


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




Post-Anchorage unit
Ant.segment with a posterior extension
Intrusion cantilevers
Chain elastic.


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



Distal extensions end 2-3mm distal to the Cres of he
anterior segment.
Design of the appliance -low friction.


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

Anterior Segment & Direction of Intrusive force


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CANINE INTRUSION:




A cantilever from the auxiliary tube of the molar tied to
the canine bracket.
The cantilever is bent to the lingual to give a lingual
force.


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CANINE INTRUSION:


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Extrusion of Posterior Segments


Higher forces promote posterior eruption.



Canting of the occlusal plane should be avoided.



Extrusion arch is similar to the intrusion arch.



Eruptive appliances should be used in growing children.



Extrusion occurs rapidly than intrusion.


56



2 types of extrusion can be achieved
with extrusion arch.
Type-I Combines extrusion with rotation
of the buccal segment. Applied in the
lower arch.
Type-II Used in the upper arch when
parallel eruption of buccal segments is
required


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Types of extrusive mechanics
•
•
•

Tip-back mechanism
Base arch mechanism
Parallel eruption of buccal segments


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Tip back mechanism:Indications:


Growing pt with a forward rotation.
Deep curve of spee in the lower arch.
Arch length inadequacy.


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Tip back mechanism consists:





0.036 inch lingual arch
0.018x0.025 anterior segment
Buccal stabilizing segment of 0.018x0.025.
0.018x0.025 tip back spring


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



CRot is placed around the root of the 2nd molar.
Eruption & rotation of buccal segments.
Increase in the arch length


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Base Arch Mechanism:
 Also called as Intrusive arch.
 Buccal and anterior arch wires are identical.

0.018x0.025 SS


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Ligature is tied to the helices to prevent
flaring of anterior teeth.
• Effects:
-Eruption & rotation of the buccal
segments.
-Roots of the buccal segments move
forward.
-No increase in the arch length.
•


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Parallel Eruption of the Buccal Segment:



Used in the upper jaw
Cervical HG with long outer bow .


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


Natural plane of occlusion must be monitored
0.018x0.025 wire is placed as an indicator wire.


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Closing Anterior Open Bite : Extrusion Arch


Open bites occur less frequently.



Treatment involves a wide variety of approaches.



Dental compensations – Vertical elastics.
Extrusion Arch: reverse action of the intrusion arch.



Effective way to close the open bite without Pt compliance



Choice of dental compensation is based on lip-tooth distance.


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Extrusion Arch


Action at the Molar:-


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Extrusion Arch


Timing: Undesirable actions at the
molars will be insignificant if the
EA is kept only for a minimum
time. (Isaacson)



Segment of SS wire has to be
placed in the posterior segment.


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Extrusion Arch


Action at the Incisor:-

Extrusion -Single tooth
-Groups of teeth.

• Magnitude of extrusive forces used are100gms for 4 incisors
• 0.016X0.022 SS wire is used

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Space Closure
Biomechanical Basis of extraction space closure


2 methods to close extraction sites
-Segmental springs
-Loops in the continuous wire


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

Anchorage classification:-


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Single cuspid retraction Vs En-mass retraction



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Adequately designed appliances based on the desired
biomechanics.
En-mass space closure reduces the treatment time.
Separate canine retraction is done in anterior crowding
cases.


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Space closure –A Biomechanical Perspective


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


Force systems for Grp B space Closure.
M/F-10/1 is needed for Translation.


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Grp-A anchorage: Mesial force on the posterior teeth
should be minimized.
-Forces & moments acting on the posterior teeth can be
minimized by using extraoral force.


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

Differential tooth movement:


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Grp-A anchorage: Space closure with differential
moments.




Increasing the posterior M/F ratio encourages root movement &
decreasing the M/F ratio causes tipping type of tooth
movement.
Magnitude of the vertical force – difference between anterior &
posterior moments.


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Determinants of space closure:





Amount of crowding
Anchorage
Axial inclination of canines & incisors.
Midline discrepancies & Lft/Rht symmetry
Vertical dimension


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Space closure

Considerations for anchorage control &
Differential tooth movement
 Size of the Anchorage units No. of teeth .
 Differential force systems-Variable moments & Forces
-Forces act in 3 planes of space.


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Segmental En-mass Extraction space closure
•
•
•
•

T-loop space closure springs are used
Principle of SA-Ant & Post units are considered as one
large tooth.
Rt & Lft buccal segments are connected by TPA.
Design uses 0.0175x0.025 TMA wire.


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General Concepts for Segmented T-loop use


Passive form of a spring



Activation of the spring requires
application of forces & moments.



Neutral position –Only moments
are applied.


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General Concepts for Segmented T-loop use


Differential Anchorage: Unequal α & β moments.



Higher moment is applied to the anchor teeth.



Differential moments –Off-centered V-bend.



Centering the T-loop -produces equal & opposite moments.


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Symmetric Space Closure – Grp B Anchorage


Simplest form of space closure.



Equal translation of Ant & Post segments.



T-loop centered



Distance =Interbracket Distance - Activation
2


86



Space closure is monitored periodically.
-amount of remaining space
-axial inclinations


87

Space Closure – Grp A Anchorage
•

T-loop is positioned closer to the post. Attachment.


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Space Closure – Grp C Anchorage


Post. Protraction is the difficult space
closure.



Extrusive effect on the anterior teeth.



CL-III elastics – to augment the
protraction


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Separate Canine & Incisor Retraction




Anterior crowding
Midline disrepancies
Moment is produced on the canine during separate canine
retraction.


90



3 ways to counteract this moment:


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Cuspid-Cuspid Bypass wire: Prevent Rotation
 Alter arch width
 Eliminate side effects from vertical forces.

0.017 X 0.025SS


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Incisor Retraction


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Canine & Incisor Root Movement


Control of axial inclinations of teeth is important.



Good axial inclination & root parallelism-stable result.



Root correction involves-Individual/Groups of teeth.



Enmass root movement



Separate canine root following separate canine retraction.



Separate incisor root correction


98

Diagnosis & Evaluation of root correction


Clinically-Inclination of canine & incisor brackets.



Lateral films-Axial inclinations


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Enmass Root Movement


Second phase of space closure after tipping movement.



Moments are delivered by Root springs.



Moments generated cause the crowns to flare and roots
to retract.



Ligature tie –to prevent the space from opening.


100

Selection of wire in the anterior segment:
•
•


Rigid wire placed in the 6 anterior teeth.
Undersized wire – rotation of the incisors.
3 major root springs for enmass root movement


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102



Root springs:


103



Cuspid root movement:


104



Incisor root movement:

0.021 x 0.025 TMA root spring


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References:Biomechanics In Orthodontics – Marcotte.
Biomechanics In Clinical Orthodontics-Ravindra Nanda.
 Rationale of the Segmented arch –Burstone AJO (1962).
Deep overbite correction by intrusion – Burstone
AJO(1977).




Biomechanics of Deep Overbite Correction-Burstone
(Semin Orthod 2001).


106



Segmented approach to simultaneous intrusion and space
closure: Biomechanics of the three-piece base arch
appliance-Bhavna Shroff AJODO-1995.



Closing Anterior Open bite :The Extrusion Arch –
Isaacson & Lindau Semin Orthod 2001.



The Segmented arch approach to space closure – Burstone
1982 AJO


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