Removable orthodontic appliances: new perspectives on capabilities and efficiency
Removable Appliances 2
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Transcript of Removable Appliances 2
الرحمن الله الرحمن بسم الله بسم الرحيمالرحيم
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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