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Removable OrthodonticRemovable OrthodonticAppliancesAppliances

Removable Appliances Removable Appliances (RA’s)(RA’s)

• Indications• Advantages & disadvantages• Brief history & development• Major uses of removables

• Growth modification• Limited tooth movement• Retention• Adjuncts to treatment• Mild to moderate malocclusions

Removable AppliancesRemovable Appliances

Can be taken out of the mouth for cleaning by the patient and adjustment by the orthodontist

Apply their forces by means of springs, screws, and bows of various types

Can tip teeth only

Removable AppliancesRemovable Appliances

IndicationsIndications

For simple movements of teeth in a mild to moderate malocclusions

For transmission of forces to blocks of teeth

As an adjunct to Fixed appliancesUseful means of applying Extra oral

traction to segments of teeth / whole arch

IndicationsIndications

Mild Arch ExpansionFlat anterior bite plane / Buccal capping

– To influence the development of buccal segment teeth and/or

– To free the occlusion with the lower archRetention after Orthodontic therapy

Development of Development of RemovablesRemovables

• USA- fixed appliances- Edward Angle

• Minimal usage of removable appliancesPrecise positioning of teeth

• Europe-removable appliances• Geographic separation • Social welfare systems-limited tx. for

masses• Scarcity of precious metals for fixed

appliancesAlterations in function produced by

removables give stable correction of malocclusion

Removables in EuropeRemovables in Europe

• Growth Guidance with Functional Appliances

• Change mandibular posture • Open & forward

• Pressure from stretch of muscle & soft tissues transmitted to teeth & bone

moving teeth and modifying growth

Today Dichotomy Today Dichotomy DisappearedDisappeared

Instantaneous exchange of ideas & info.

Politics, economics, travel, electronic age

Basic Tooth MovementsBasic Tooth Movements

Basic Tooth MovementsBasic Tooth Movements

Basic Tooth MovementsBasic Tooth Movements

Basic Tooth MovementsBasic Tooth Movements

Basic Tooth MovementsBasic Tooth Movements

Basic Tooth MovementsBasic Tooth Movements

ANCHORAGEANCHORAGE

“For every action there is an equal and opposite reaction” (Newton’s 3rd law)

The area from which the force is applied to move the teeth.

“Resistance to unwanted tooth movement”- Proffit,

1993

“Anchorage is the term used to describe the resistance to reactionary forces generated by the active components of the appliances”

HOW TO CONSERVE / INCREASE HOW TO CONSERVE / INCREASE ANCHORAGE ANCHORAGE ((Anchorage ReinforcementAnchorage Reinforcement))

1. Clasp more teeth

2. Move only one or two teeth at a time

3. Use lighter forces

4. Occlusal capping

5. Add headgear

ANCHORAGEANCHORAGE

ANCHORAGEANCHORAGE

ANCHORAGEANCHORAGE

Removable Appliances Removable Appliances AdvantagesAdvantages

• Appealing to patients especially adults

• Inexpensive• Easy to make and adjust• Initially less chair time• Allow for some types of growth

guidance• Removable for socially sensitive

occasions

Removable Appliances Removable Appliances AdvantagesAdvantages

• Palatal coverage increases anchorage• Overbite reduction in a growing child,

without a lower appliance• Acrylic can be thickened to form flat

anterior bite plane/buccal capping• Useful as a passive retainer/space

maintainer• Can be used to transmit forces to

blocks of teeth

Removable Appliances Removable Appliances DisadvantagesDisadvantages

• Totally cooperation dependant !!!• Limited to less complex movement• Affect speech• Limited range of movement• Good technician required• Inter-maxillary traction not practical• Lower RA’s are difficult to tolerate• In efficient for multiple individual

tooth movements

ComponentsComponents

A = ACTIVE COMPONENTS

R = RETENTIVE COMPONENTS

A = ANCHORAGE

B = BASEPLATE

Base Plate (Acrylic)Base Plate (Acrylic)

Maintenance Plate

•Stabilize•Space maintenance•Replace tooth•Bite Plane•Posterior overlay

Base PlateBase Plate

Has 3 functions– Provides foundation to support other

components– Contributes to anchorage– May be built up into bite planes

Anterior Bite plane– Principal use is for the reduction of

overbite in a growing patient.– Decreases the eruption of incisors while

allowing the molars to erupt.

Anterior Bite PlaneAnterior Bite Plane

RetentionRetention

• Hawley• Circumferential• Spring• Invisible – Essix• Positioner

Hawley RetainerHawley Retainer

With or without ant. or post. biteplate

Circumferential RetainerCircumferential Retainer

Spring RetainerSpring Retainer

Invisible Essix RetainerInvisible Essix Retainer

Vacupressureformed

Biostar Machine

PositionerPositioner

Adjuncts to TreatmentAdjuncts to Treatment

Biteplate

Nightguard

Removable Appliances Removable Appliances Used in Mild to Moderate Used in Mild to Moderate MalocclusionMalocclusion

RetentionRetention

Achieved by clasps of various types

Adams’ cribs - molars and premolarsSouthend clasps - incisorsBall hooks - interdental embrasure

Clasps & RestsClasps & Rests• Adams

•C

Clasps & RestsClasps & Rests

•Ball

•Arrowhead

Clasps & RestsClasps & Rests

•Occlusal rest

Adams’ cribsmolar clasps in 0.7mm stainless steel round wirepremolar / deciduous clasps in 0.6mm wire

Southend 0.6 mm wire

Ball hooks 0.7 or 0.6 mm wire with soldered ball on end

RetentionRetention

Southend ClaspSouthend Clasp

Active ComponentsActive Components

• Expansion – screws• Repositioning teeth – springs• Space closing – labial bow &

springs

Transverse Expansion by ScrewsTransverse Expansion by Screws

Coffin springs in 1.25 SS are used

Expansion ScrewsExpansion Screws

Expansion ScrewsExpansion Screws

Expansion ScrewsExpansion Screws

Active ComponentsActive Components

SPRINGS - 0.5mm or 0.7mm wire to move single teeth or groups of teeth

Constructed in 18/8 austenitic stainless steel

The more wire incorporated, the greater the range of the spring and the lighter the force exerted

FORCE AND DEFLECTION OF STAINLESS STEEL SPRINGS

MECHANISM OF ACTIONMECHANISM OF ACTION

Most orthodontic springs are variants Most orthodontic springs are variants of simple cantilever. For a round wire, of simple cantilever. For a round wire, the force generated by a small the force generated by a small deflection within its elastic limit is given deflection within its elastic limit is given as:as: F = k .d .r4

l3

FORCE AND DEFLECTION OF STAINLESS STEEL SPRINGS

F = k .d .r4

l3

where

r = radius of the wired = deflection of the wirel = length of the springk = stiffness of the wire (Young’s Modulus)

FORCE AND DEFLECTION OF STAINLESS STEEL SPRINGS

Increasing the radius of the wire by 2 will result in the force applied increasing by 16 times;

Increasing the length of the spring by 2 will reduce the force applied by 8 times

SpringsSprings

Force In most cases the force used to produce

tipping movement in a single rooted tooth should be in the range of 25 – 50g.

Deflection The expected rate of tooth movement is

between 1mm to 2mm a month, which means monthly adjustments are sufficient if an activation of 3mm is used

Stability RatioStability Ratio

The stability ratio is the stiffness in the direction of unwanted tooth displacement divided by the stiffness in the intended direction of tooth movement.

Ideally for a spring it should be greater than 1 but never less than 1.

Coils Are incorporated to increase the length of the

spring thus reducing their stiffness.

Point of contactPoint of contact

When a tooth is contacted by a spring at a single point, it will move in the direction of resultant force, which is perpendicular to the tangent at the point of contact with the tooth.

If the resultant force does not pass through the long axis of the tooth, rotation will be induced.

Palatal SpringsPalatal Springs::

Used where the tooth to be moved is in the line of the arch

The coil is positioned so that it ‘unwinds’ as the tooth moves

Made in 0.5mm SS for 1-5 0.6mm SS for 6 Stability is improved by incorporating guard

wire or boxing in by baseplate

For Buccal Teeth:For Buccal Teeth:

T-Springs in 0.6mm SS are used

Buccal Springs:Buccal Springs:

Used where a tooth is to be moved palatally as well as distally.

Classically made in two designs Self-supported one in 0.7mm wire. Its stability ratio

is less than 1. Supported one in 0.5mm SS with proximal part

covered by SS sleeve. Stability ratio is more than 1 and is also less stiff than the other. Can be activated by 2-3mm.

Bows For Incisors RetractionBows For Incisors Retraction

Labial Bows:

Made in 0.7mm SS is frequently used to reduce mild overjets and slight incisor irregularities.

Recurved labial bow or labial bow with reverse loop are used to increase the effective length of the wire thus reducing the stiffness

Robert’s RetractorRobert’s Retractor

Made from 0.5mm SS supported by tubing, is not as stiff as labial bow.

Recurved Labial BowRecurved Labial Bow

Adjustable Labial BowAdjustable Labial Bow

Clinical scenariosClinical scenarios

1. Upper incisor cross bite2. Class III incisors & deep bite3. Increased OJ - extract 1st premolars4. Palatal displacement of upper

premolar5. Upper canine displaced buccally6. Class 2 div 1 & compromised 6’s7. Lower 2nd premolar impeded

Simple Removable ApplianceSimple Removable Appliance

Where canines are bucally placed, use buccalcanine retractors, made in either 0.7mm wireor 0.5mm wire supported by 0.5mm internaldiameter tubing where it emerges from the acrylic

Canines can be pushed palatally into the line of the arch as they move distally

The labial segment can be retracted also with a 0.5mm labial bow with tubing support.

ACTIVATION OF LABIAL BOW: Press the vertical leg towards the tubing

Position of helix is very important - it must beplaced half-way between the starting position of the tooth and the desired finishing position

Helix too far anteriorly - tooth will move palatally

Helix too far distally - tooth will move buccally

WHY IS IT NECESSARY TO REDUCE THE OVERBITEBEFORE REDUCING THE OVERJET?

As incisors tip, the lower incisors prevent furtheroverjet reduction due to increasing overbite

By incorporating an anterior bite plane, the overjetcan be successfully reduced without increasing the overbite as the incisors tip palatally

Trimming to allow the incisors to retrocline: trim on palatal aspect, with bur parallel to palatal surface.Don’t trim from the occlusal surface - reduces widthof bite plane excessively.

PROBLEM 4: /5 deflected palatally, /6 has drifted mesially

RETENTION: Adams cribs 6 / 46 , southend clasp 1/1

ACTIVE COMPONENT: Screw section to /6 , Z-spring to /5

PROBLEM 5: Buccally placed canine /3

Retention: Adams cribs 6/6 and 4/4

ANCHORAGE REINFORCEMENT: Headgear tubes on 6/6

ACTIVE COMPONENT: Screw section to distalise /456

ANCHORAGE REINFORCEMENT:headgear to tubes on 6/6

Problem 6: Class II div 1, and both upper first permanent molars are carious

Adams cribs on 73/37, finger springs 5/5 and 4/4, fitted labial bow 21/12

Extract 6/6

Retract 5/5 (with or without headgear support)

Retract 4/4

Adams cribs 74/47, finger springs 3/3, Southend clasp 1/1

Upper 3/3 retracted

URA with labial bow to retract 21/12

Problem 7: an unerupted 5/ where extraction ofthe 4/ would give too much space

SpringsSprings

Anterior Alignment

Anterior Cross-bite Primary Anterior Cross-bite Primary DentitionDentition

Anterior Cross-bite Mixed Anterior Cross-bite Mixed DentitionDentition

SpringsSprings

Posterior space regaining

correct incorrect

Spring winding

SpringsSprings

Space Closure

THANK YOUTHANK YOU