Intrusion arches /certified fixed orthodontic courses by Indian dental academy

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

Bite opening can mainly be done by• Absolute intrusion
• Relative intrusion
• Extrusion of posterior teeth/distal tipping
• Proclination of incisors
• Combination




Tooth movements of bite opening• 1.Absolute intrusion of incisors-(after growth over)

– Required when hyperdivergent growth pattern


–In Adult patients-molar extrusion is not compensated by
vertical ramal growth.


2.Relative intrusion of incisors- Inc kept where they are,
mandible grows and posterior teeth erupt.
• Eruption of posterior teeth is a normal molar vertical
change in a growing individual-therefore stable


• Increase in vertical face height-accommodates if any

orthodontic extrusion occurs –leveling the Curve of
Spee , intermaxillary elastics


3-a Extrusion of posterior teeth-not compensated in adults• Low mandibular plane angle-not stable-musculature
resists extrusion
• High angle cases-weaker musculature-teeth may
remain stable-opening of the mandibular planeundesirable


3-b Distal tipping of posterior teeth-similar to the previous
situation – wedging effect


4.Proclination of incisors-in case of retroclined incisorscorrects deep bite.




Combination of the aboveAnterior-Bite plate effect• Proclination
• Incisor intrusion
• Posterior extrusion


The importance of 2nd molarsEarly banding esp. in low angle and deep bite cases.
Inclusion of 2nd molars-lever for extrusion of premolars
and assists molar intrusion.




Burstone’s Basic principles for intrusionLight , constant force – else resorption,here optimal
forces on PDL & continuous movt with no reactivation
Single point of force application – statically
determinate system vs wire in brackets.
Sequential intrusion-first most extruded tooth ,
centrals foll by laterals
Good anchorage control
Analysis of forces and moments in each biomechanical
situation

Mechanism of action


Cetlin’s Intrusion arch


Cetlin’ s Intrusion arch
Normally inclined incisorsRectangular sectional on incisors


Intrusion arch tied to sectional wire-b/w central
and lateral
Light(2 oz) force-counter labial tipping


Labially inclined-PFA moved distally
Rectangular-0.018x 0.025 inch/0.021 x 0.025
Wire extended distally-2 helices bent-Rt. angles to
intrusion arch


Helices=point of force application-slightly in front
of Cres.
Light elastic force


Lingually inclined-PFA moved front
Rigid rectangular -0.018 x 0.025/0.021 x 0.025sectional on centrals


Wire bent forward and upward-hooks bent
Inserted into intrusion arch
Light elastic force


30 mm


Mulligan’ s appliance
Mulligan’s 2 x 4 appliance –can be used in the Begg/Edgewise
set upUpper molars do not require tipping-helix bent into arch wire2-3mm mesial
Anchor bend ,continuation of the helix
No cuspid circles required

‘Rowing effect’-strong www.indiandentalacademy.com
moments at molars- retract incisors

Utility arches


Utility arches- one of the most versatile auxiliary
arch wiresOriginally developed to counteract the tipping occuring in
the buccal segments in ext cases by utilizing the so-called
immutable lower anteriors as anchor unit-to hold molar and
2nd PM upright during retraction.
Noted that buccal segments not only held upright , also
lower inc were intruded with the light,continuous pressure.
‘Step down base arch’ / ‘Ricketts lower utility arch’
to level the curve of Spee in lower arch by Ricketts

Basic components of utility arches-

Wire material- -blue elgiloy
- in .018 slot .016 x .022- slot (maxilla) & .016 x .016mandibular
- in .022 slot-.019 x .019
Continuous rectangular steel wire-bypass mechanics

Functions
Position lower molar to allow for cortical anchorage
Manipulation & alignment of lower inc segment from
the lower molars –
align/extrude/intrude/advance/retract without
disturbing/depending on canines/PM.
Stabilization of L arch-allos segmental treatment of
buccal segments-intrude lower segment without inv
canines,then include canines at later stage.separate
leveling and rotation correction of buccal segments
possible.

Physiological roles of the lower arch – when incisal contact lost,Mn
reached forward to search out proprioceptive input –
activator/reaching effect –beneficial muscular response for treating
Cl II MO.
Overtreatment – avoids tying overbite control to overjet control.
Role in Mixed dentition-allows inc alignment & molar control by
stepping around deci buccal occlusion.
Arch length control-Uprighting lower molar – 2mm space on each side
-Advancement of lower incisors – 2mm space gain for every 1mm
of proclination
-Expansion in buccal segment teeth – canines – 1mm exp=1mm
arch length gain
PM/ deci molars-1mm exp=1/2 mm gain
molars – 1mm exp=1/3mm gain.

Basic mechanism of action


•Passive utility arch


Through the incorporation of loops –performs more
functions than intrusion.
1.

Expansion

2. Contraction
3. Protrusion
4. Retrusion
5.

Intrusion


Intrusion utilityStepped gingivally at the molars
5mm space between anterior border of auxiliary
tube and post. vertical segment.


Activation-2 ways
Bench (1988) –tip back bend in molar – wire sinced
after pulling 2-3 mm posteriors from the distal end of
the molar tube.
Posterior tipping of molars seen


Gable bend directed occlusally- another method of
activation
-unwanted posterior tipping avoided


Intrusion utility arch –
With-Retrusion utility
Protrusion utility


Three piece intrusion (base) arch
Bhavna Shroff,
Won M. Yoon
Steven J. Lindauer
Charles J. Burstone
Angle Orthodontist 1997 No. 6, 455 - 461: Simultaneous
intrusion and retraction using a three-piece base arch

Continuous arch wire
In a case with flared incisors-continuous arch wireworsens the axial inclinations of anterior teeth.


Advantages over continuous intrusion arch:Prevent further proclination of already proclined incisors
Simultaneous correction of deep bite correction and space
closure in patients with flared incisors.
Allows for redirecting the force parallel to L A of incisor
-Intrusive force and its direction-effectively controlled.
Allows variation of force from one side to another – if required
Simultaneous control in vertical & anteroposterior planes
Low load deflection rate- constant force
Predictable, reproducible,& Statically determinate force system

Solution- Segmented mechanics
1st solution-distal extensions


2nd solution – Three-piece intrusion base arch


Design
The intrusion archRigid wire - .018 x .025 or .021 x .25 SS wire extending
distally to the lateral incisor–placed passively-anterior
brackets. Stepped around canine
Distal extensions-end 2-3 mm distal to Cres
Anterior segment-stepped around the canine bracket to
avoid interference during intrusion


Bilateral tipback spring -.017 x.025 TMA

Amount of intrusive force -4 Mx incisors=60g in midline


Segmented mechanics
Right and left buccal segments-aligned-.017 x .025 SS
TPA- custom made-0.036” SS
0.032 x0.032 SS-preformed
Controls molar position
In extraction cases - Canines retracted separately –included in
the buccal segments on each side – allow space for intrusion.
E-chain from anterior segment to molar hook.

Decision to intrude Mx &/or Mn incisors depends on:
1. Amount of Mx inc show at rest
2. Length of upper lip
3. Interlabial gap at rest
4. Severity of curve of Spee
5. Presence of palatal impingement

Segmented mechanics
Assessment of location of C res:
Lateral cephalogram-to determine A-P & vertical
position of C res
4 incisors –usually estimated-half way b/w crest of
alveolar bone and root apex of lateral incisor-sagittal
plane


Biomechanics
To intrude along LA of inc:
Point of force application(PFA) moved anteriorly +small distal
force=redirect the intrusive force along the long axis of inc – pure
intrusion.


For simultaneous intrusion & retraction:
Intrusive force applied lingual to C res along with small
distal force.
Resultant force – parallel to L A of incisors but lingual.

Retraction – result of moment around anterior segment

Action of elastic force between anterior and posterior segments


Biomechanics


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Intrusion arches /certified fixed orthodontic courses by Indian dental academy

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