Vertical control in straight wire appliance & intrusion mechanics /certified fixed orthodontic courses by Indian dental academy

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


Vertical control in
SWA, Intrusion
Mechanics
and
Utility arches

Introduction
Overbite – mm measurement / % - overlap of
the mandibular incisors by the max. incisors.
50% overbite – deep overbite.
Overbite control – closely related to arch
leveling process.
Occurs after levelling & aligning of
individual teeth.


Vertical control – management of
 Deep Bite &
 Open Bite.

Deep bite – 2 types:
True.
Pseudo.
True – infra eruption of post. teeth.
Pseudo – supra eruption of ant. teeth.


Development of Deep bite:
Ant. teeth – erupt – until contact made with –
 Opposing ant. teeth.
 Soft tissue of the palate.
 Tongue inhibits – eruption.
Class II or III MO – facilitates - / reversed overjet
 over eruption of ant. teeth.
 Unrestricted eruption – lower 2nd molars – Cl II
deepening of curve of spee in post. part.


Correction – various tooth movts:
Eruption or extrusion of post. teeth.
Distal tipping of post.teeth.
Proclination of incisors.
Intrusion of incisors.
Combination


Eruption / extrusion of post. teeth.
Stable process – accompanies vert. facial dev.
Contributing factor – bite opening – deep bite patients.
vertical facial ht. – growing patients –
accommodates extrusion of post. teeth during ortho trt.
 Not stable – adults – low mand. plane angles.
Musculature – resists extrusion.
 High angle cases – weak musculature – stable results.
Permanent opening of mand. plane - undesired


Distal tipping of post. teeth.

Stable process – growing patients.
Low angle adult cases – not stable.
High angle cases – stable – to be avoided.
Proclination of incisors.

Proclination – retroclined incisors  in ant. region.
Lower arch – LI crowns – proclined.
Upper arch – crown proclination & root torque
control.


Intrusion of anterior teeth.
Not normally reqd in growing patients.
Face grows vertically – restricting the normal
eruption of ant. teeth – allow bite to open.
Adult cases – musculature resists post. changes.
:. bite opening in adults –
proclination

of incisors

Intrusion.

Advantages:
 Controlling VD – by preventing post. eruption –

mandible rotate closed / prevented opening.
 No encroachment – inter occlusal space – Stability.
 Prevention of post. eruption during growth – AB to

OP reln. Improved.
Eg. Sk Cl II not worsened by post. extrsn & rotn.

Principles of ant. intrusion.
 Use of optimal magnitude of forces & delivery

with low LDR springs.
 Use of point contacts in ant. region ( statically
determinant system)
 Position of force – selection of the point of
application of force with respect to CR.
 Selective intrusion based on ant. tooth geometry.
 Control – reactive units – post. Anchorage unit.
 Inhibition – erupn. of post. teeth.


Controlling force magnitude & constancy:

Lowest force – capable of intrsn. – used.
Heavy forces – 2 effects.
  in rate of root resorption.
 On the anchorage unit –

Maxilla – Extrusion & steepening of the occl. plane.
Mandible – flattening.
Moment – intrsn arch - anchorage unit. Due to dist from
incisors to molars.

 Force constancy – low load defln. rate spring.

Lose less force / mm deactivation.
More accurate upon activation than high LDR spring.
 Ant. single point contact.

Intrusion arch – not directly placed into brackets.
Tied to ant. segments – 2 points of contact.
.


Advantages.

If placed into br.  torque to ant. segment.
Labial root torque -  intr. force.
Lingual root torque -  intr. force on ant. segment.

Force system statically determinant.
Clinician precisely know the force system involved.

Telescoping of trt.
Br. – used for initial alignment segments + intrusion.

Point of force application.

Intrusive force  CR  intrusion ,
no labial or lingual rotn. of the tooth.
Patients with procumbent incisors – intrusive force
–
farther from CR –
 moment   lingual root movt.
Management:
Retract
Apply

ant. – upright axial incln.- intrude.

vertical force – lingual to CR.


 Selective intrusion.

Indescriminate levelling –
continous arch or sectional wire – undesirable side
effects.
Decision which teeth to intrude – Intelligent trt.
planning & accomplishing – creative use of mech.
In Cl II div. 2 – CI intruded > LI.


Indiscriminate levelling –
LI extrusion.
Moments – roots – converge
mesially.

Proper mech. – intrude CI to
proper reln. with LI, then include
LI & continue intrusion.

Control of reactive units.

Best method – control of anchorage unit - 
forces.
Effect – moment produced – intrusive force.
Large due to long moment arm.
2 side effects:
 Plane of occln. of buccal segment altered.
 Due to equal & opp. extrusive force – buccal
segments.


 Plane of occln.

maxilla – steepens.
mandible – flattens.

To minimize –


Intrsn forces.



Teeth in the anchorage unit.

Retract

as much as possible initially -  length of
moment arm

Occipital

head gear – force directed ant. to C.R –

post. anchorage unit.


 Equal & Opp. extrusive force.

Force – acting at aux. tube of molar –
Buccal to CR of molar/ buccal segment.
Moment  tip buccal segments lingually
roots moving buccally.

Prevented by
Lingual arch – maintains axial inclins. & arch width.
Fabricated width of intrn. arch less critical.

Avoiding extrusive mechanics.

Patients – genuine intrusion Cl II or Cl III elastics,
Cervical headgear – high outer bows to max. arch –
to be avoided.

Canine root – mesioangular incln.
Placement of continuous archwires – extrude incisors –
canine root moves distally.

Solution:
Bypass the canine with continuous arch &
Perform separate canine movement.


Methods to correct deep bite.
 Bite plates.
 Utility arches.
 Reverse curve Niti / SS.
 Burstone intrusive arch.
 Kalra SIR, appliance.


Utility Arches.
Designed – Robert M. Ricketts – early 1950’s.
Originally designed for enhancing anchorage during
canine retraction.

History:
Continuous archwires ( flat or reverse curve of spee)
- Levelling & aligning –
Ant. flared out
PM overerupted.
Molars uprighted or tipped back.

Class III elastics & head gear used to prevent.

Canine retraction with sectional wires –
Molars & PM’s tipped mesially.
Canines tipped distally & extruded.

1950's Robert Ricketts - counteract the tipping in
the buccal segments - utilizing - immutable lower
incisors as an anchor unit,
Round arch segments - laced from the lower molars
and PM’s to the lower incisors.


Buccal segments maintained in an upright
position,
lower incisors intruded with this light, continuous
pressure.
Development - Step-down base arch, or Ricketts'
Lower Utility Arch.
Double tube with no torque – designed.
Sp. Blue Elgiloy wires – 0.016” x 0.016”
Force generated – 100 gms –four incisors.

Design And Function:
 Extremely functional design.

Molar section – 2-3 mm beyond the molar tube
Stepped down 3- 5mm – bypass the PM & Canine.
Stepped up 2-3 mm distal to the LI br.
Follows the contour of the ant. segment.

Ant. segment – labial root torque – 10 - 15°.
Molar segment – buccal root torque.
- tip back of 30 - 45°.
Toe in – molar segment – extraction cases.
Expansion – 2 cm – on each side.


Effect on Molars.
 Tends to upright the molars.
 Crowns tip distally, rots move mesially
 Tip back bend – straight distalizing force –

distolingual rotn.
Effect on Incisors.
 Continous arch – flaring of the anteriors.
 Crowns – mesially, roots – lingualy, hit against

cortical bone. Labial root torque – prevents this.
 Most effective force - intrusion - // to long axis.

Function & roles of the Utility arch.
 Used to position the lower molars – snable them

to use cortical anchorage.
 Loss of proprioception – incisal occlsn. –
mandible relocates – Cl II corrections.
 Torque placed – incisors & molars – helps to
define ideal archform.
 Possible to treat ant. & post. segemnts
simultaneously to overcorrection.


 It helps to maintain arch length, increase/

decrease it
Uprighting

the molars.
Advancement of the lower incisors
Expansion of the buccal segments.
Saving “E” spce.


Fabrication
 0.016x 0.016 Blue Elgiloy wire used.
 Wire not heat trtd. When arch is formed.
 Step 1. vertical step down – 10 mm from the end

– 3 – 5mm height. Horizontal section – 3mm
distal to the LI br.- step up bend
 Step 2. bent horizontally. Slight inward angle –
10 - 15°. Ant. arch form swept into the wire.
 Step 3. opp side completed. Buccal segment
gently contoured & buccal bridges flared

 1 cm expansion on each side.
 Distal leg twisted buccally. Places

labial root torque & prevents gingival
impingement of the distal vertical legs.
 Incisors intruded - 45° tip back – molar
section.
Final arch form –
Well contoured ant. segment with labial root
torque.
Flared buccal segments.
Post. legs // to each other, 45° buccal root
torque.
Tip back – uprights molars & gains space.

Classification:
Passive utility arch:
Stabilisation or space maintainence.
Mixedentition – hold space – transitional period.
Permanent den.- maintain anchorage.
Intrusive utility arch.

Sizes of wire used in max. arch
0.018 slot – 0.016 x0.022
0.022 slot – 0.018 or 0.019 square wires.

Retraction Utility arch

To achieve retraction & intrusion.
Loops into archwire – ant. vertical step
Greater range of retrcn.
Mainly used in the maxilla.
Protraction Utility arch.

Proclining & intruding upper and lower incisors –
Class II div 2.
Post. step flush with molar tube. Loop distal to the
ant. vertical step & occlusal to the horizontal
segment.

Tip back Springs ( Intrusion Springs ).

Originally proposed – Burstone
Upper & lower arches –levelled & aligned – rigid
SS wire – 0.017 x 0.025.
Used when true intrusion requd.
 Growing patients with forward growth rotation.
 Deep curve of spee in the lower arch.
 Deep overbite – extrusion of the incisors.
 Steep natural plane of occln.

Anchor molars reinforced.
TPA – upper, Lingual arch – Lower.
Intrusion spring –
With helix –SS – 0.017 x 0.025
Without helix – TMA – 0.017 x 0.025.

Fabrication:
Wire bent gingivally mesial to the molar tube .
Helix formed.


Mesial end bent into a hook.
Engaged distal to the LI.
When passive – mesial end – height of mucobuccal fold.
Three Piece Intrusion Arch.

Consists of the following parts.
 Post. anchorage unit.
 Ant. segment with post. extension.
 Intrusion Cantilevers.

Fabrication:
 Anterior segment – bent gingivally – distal to the
laterals.
 Then bent horizontally – step of 3 mm.
 Distal part – distal end of canine br. – formed
into a hook.
 Ant. segment – 0.021 x 0.025 SS wire – prevent
side effects – bending the wire during force
aplcn.

 Intrusion Cantilever – 0.017 x 0.025 TMA.
 Bent gingivally mesial to the molar tube & helix

formed.
 Mesial end of cantilever – bent into a hook.
Activation:
 Bend mesial to the helix at the molar tube.
 Passively – ant. end lies – vestibule.
 End brought down and engaged – horizontal
portion of the ant. segment.

Further distal placement of the force – lateral to
the LI.
Resultant forces – CR of ant. teeth.
E chain – attached to hook – simultaneous
intrusion & retraction.


Canine Intrusion.
Difficult to intrude six ant. teeth.
High foce levels requd.- large moments –
undesirable changes in the axial incln. of
post.teeth.
Achieved in 2 ways:
Cantilever

form aux. tube of molar tied to the canine br –
point contact.
0.017 x 0.025 TMA wire used.
Problem – labial flaring.
During cuspid retraction – applying more β moment
( post.) than α ( ant. ) moment.

K – SIR archwire.

Appliance for simultaneous intrusion & retrcn. Of
six teeth – should control:
 Magnitude of forces & moments.
 Moment to force ratio.
 Constancy of forces & moments.
 Friction.
Kalra Simultaneous intrusion & retraction
archwire – modifn. of segmented loop mech. of
Burstone & Nanda.

Continuous 0.019 x 0.025TMA wire with closed
7mm x 2 mm U loops at the extn. site.
For bodily movement & prevent tipping - 90° V
bend – at the level of each U loop.
V bend when centred – counter the moments –
activation forces of the clodong loops.
60° V bend – post to the center of inter br. dist. –
increased clockwise moment – molarAugments molar anchorage & intrsn. of ant. teeth.


Activation:
Trial activation – outside the mouth – releases
stress built on bending the wire.
Neutral position – U loop – 3.5 mm wide.
Activated – 3mm. Mesial & distal legs – barely
apart.
Control of Reactive forces:
Keep forces to a min.
Add teeth to the anchorage unit.
High pull head gear.

Intrusive force – 125 g.

Advantages:
Simplicity of design.
Easy to fabricate
Comfortable to the patient.
Low forces, Low LDR.
Activation – 8 week period.
Shortens trt. time.
Unsightly space distal to laterals avoided.

Open Bite:
Non extn. Trt. Preferred.
Some cases – extn. – to allow for eruption &
retroclination of incisors.
 Upper & lower arches – crowding & protrusion –
upper & lower PM extn.
 1st PM extn. – molars > 3-4mm class II.
 Br.placement – 0.5mm more gingival than normal.
 Early second molar banding – avoided.
 Class II or III elastics – to PM’s than Molars. Short
elastics minimize extrusion.


Thank you
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Vertical control in straight wire appliance & intrusion mechanics /certified fixed orthodontic courses by Indian dental academy

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Vertical control in straight wire appliance & intrusion mechanics /certified fixed orthodontic courses by Indian dental academy