REMOVABLE APPLIANCES

Dr. SHAIKH ANALHAQ A.

Definition

REMOVABLE APPLIANCE ARE ORTHODONTIC DEVICES WHICH CAN BE TAKEN OUT BY THE PATIENT FOR CLEANING AND WHICH ARE DESIGNED TO APPLY FORCES TO THE TEETH BY MEANS OF SPRINGS SCREWS AND OTHER MECHANICAL COMPONENTS.

1.Tipping movement 2.Can be removed -for cleaning of teeth & appliance -if in pain -on socially sensitive occasion 3.Less conspicuous 4.Can be undertaken by general practitioner with adequate training 5.Manufactured in lab -less chair side time -more patients can be treated 6.Inexpensive

1.Only simple malocclusion can be corrected 2.Multiple rotations cannot be corrected 3.Uncooperative patients may leave out the appliance- prolongs treatment 4.Multiple tooth movement - one at a time- prolongs Rx duration 5.Lower appliance not well tolerated 6.Cases other than I premolar extraction cannot be treated easily

Advantages Disadvantages

Growth modifications during mixed dentition.Limited tipping, rotation required.Arch expansion.Retention after fixed treatment.

Indications

Components of removable appliances

Retentive ComponentsBaseplate Active components

Retentive Components

Retention: Means whereby displacement of appliance is resisted.

Clasp: any hook or band attached to a natural tooth and used to anchor a partial denture or an orthodontic appliance.

CLASPS

The name clasp is derived from a French word “UYPTAN” which means “to embrace”. Clasps are the retentive components of the orthodontic appliances.

IDEAL REQUIREMENTS Unobtrusive. Not impinge. Close contact to the tooth. Usable in both deciduous and

permanent dentition. Adequate retention.

No active force on the anchor tooth. Rigid Easy to fabricate and also replace if

needed. Not interfere in the growth of jaws and

eruption of teeth.

USES

• To secure the appliance in position• To prevent rolling of appliances • To resist forces of displacement• To provide retention & anchorage• For engaging elastics

MODE OF ACTION

• Clasp engage onto the undercuts (constricted areas on the teeth.)

• Two types of undercuts.– Buccal / Lingual Cervical undercuts.– Mesial / Distal Proximal undercuts.

Circumferential Clasp

• Fabricated using wire 0.9mm• -Also known as ‘C’ clasp or Three Quarter ClaspSimple clasp used to engage buccocervical undercut Cannot be used in partially erupted teeth

Jackson’s Clasp

- V.H. Jackson 1906 - Fabricated using 0.9mm wire - Also known as Full clasp or ‘U’ clasp - Engages both buccocervical undercutsSimple design Offers adequate retention Inadequate retention in partially erupted teeth

Triangular Clasp

-Fabricated using 0.6mm wire -used between adjacent posterior teeth -Indicated for additional retention

Adam’s Clasp -Also known as Liverpool Clasp, Universal Clasp, Modified Arrowhead Clasp

Parts Bridge Arrowhead Retentive arms

• Adams clasp / modified arrowhead clasp / liverpool clasp / universal clasp.

• C. PHILIPS ADAMS in May 1950.• Most widely used clasp.• Distobuccal and mesiobuccal undercuts.• Does not separate teeth like a arrowhead

clasp.• 0.7mm posteriors

0.6mm anteriors.

Advantages

• Small neat and unobtrusive.• Any tooth.• Both deciduous and permanent

dentition.• Even on semi erupted tooth.• No specialized pliers required.• Can be modified as needed.• No. of variations are available.

Disadvantages

• Unwanted palatal tipping if gets activated.

• May lead to elongation of tooth if is fitting tightly.

• Can be repaired only if fractured through the arrowheads.

• Cannot be given on proclined anteriors.

Modifications

Adams clasp with single arrowhead:

Adams clasp with J hook

Adams clasp with additional arrowhead

Adams clasp with distal extension

Double clasp on maxillary central incisors

Schwarz Clasp

Designed by C. M. SchwarzOldest & for a considerable amount of time most

generally usedAdj: Arrowhead bent towards papilla to engage

undercuts Can be used in deciduous or permanent teeth Skill to fabricate Can be used only on posterior teeth

Duyzings Clasp

-Simple design-engages buccal undercut of molars-half clasp can also be constructedAdj: Bending towards the tooth or undercut area

Southend Clasp

-0.7 mm wire-spans two adjacent margins of anterior teethAdj: readapting into interdental areaEsthetically more pleasing

Ballend Clasp

• Wire having a knob or ball like structure on one end• utilizes interdental undercuts• Indicated when additional retention required

Delta Clasp

• Designed by William J. Clark• Similar to Adams clasp in

principle• Retentive loops were triangular in shape hence the

name• Engage interdental undercuts• USED IN TWIN BLOCK APPLIANCESAdj: -hold retentive loop and twist inwards -bending towards interdental undercut as it

emerges from acrylic

ADVANTAGES

• Design of the closed loop does not open up with repeated removal.

• Less subject to breakage.• Provides excellent retention on lower

premolars.• Suitable for use on most posterior teeth.

Crozat Clasp

• Crozat in 1920• Along with the u clasp a stright wire is soldered on

the base (Cresent).• Strong retention is possible

Active components

Labialbow Springs Elastics Screws

LABIAL BOWS

• Labial bow is an essential component of removable orthodontic appliances

• It can be either active or passive

• The principal function of the bow is to retrude the anterior teeth

• It can be used for retentive purposes

Parts of labial bow

• The incisor segment • Vertical loops • The occlusal or cross

over section • The retentive ends

Types• Short labial bow • Long labial bow• Roberts retractor• Reverse labial bow• Begg’s labial bow • Mills retractor • Fitted labial bow • High labial bow with apron springs• Split labial bow

Short labial bowIndications • Retraction of anteriors• Anterior spacing with proclination • Overjet reduction There should be good contact between canine

and premolar

• 0.7mm wire used

• Fabrication:- labial segment of wire is placed at the junction of the incisal and middle third.

Vertical segment starts from mesial third of canine, should be perpendicular to the incisor segment & should be away from gingiva

Occlusally, it passes between canine and premolar

Retentive ends adapted on the lingual or palatal side.

Activation - Compressing the U-loop by 1mm

Long labial bowIndications • Anterior space closure • Overjet reduction • Closure of the space distal to the canine • As a retaining device at the end of fixed

therapy • Guidance of canine during canine retraction

using palatal retractor

• 0.7 mm wire used in active purpose • 0.9 mm wire used in passive purpose • Fabrication - same as short labial bow but

occlusal wire passes between two premolars • Activated by compressing the U-loop

Roberts retractor

• It was first designed by G.H Robert• Indication

it is suitable only for retraction of four incisors following retraction of canines

• This is a flexible bow which is constructed from 0.5 or 0.6 mm wire inserted into a stainless steel tubing to give support to either end of the bow

• Fabrication Labial segment of wire is placed at the junction of the incisal and middle third Extends only two thirds of the mesiodistal width of the lateral incisorsA coil of 3mm internal diameter placed mesial to canineDistal part is supported in a stainless steel tubing

• It is activated by closing the coil or giving palatal bend at the emergence of the coil

Reverse labial bow

• Indication For retaining tooth positions For minor tooth movements

• 0.7 mm wire used • Fabrication:-loops are placed distal to the

canine and the free ends of the U-loops are adapted occlusally between the premolar and canine

• This is too stiff for effective incisor retraction • The stability ratio is poorActivation First the U-loop is opened this results in lowering of

the labial bow in the incisor region . A compensatory bend is given at the base of the

loop

Begg’s labial bow(Wrap Around / Around the Globe Bow)

• Popularized by P.R . Begg• It is used as retainer after fixed orthodontic

therapy • 0.9 mm wire is used

• Fabrication consists of labial wire that extends till the last erupted

molar U-loop is incorporated at the pre molar and molar area

to close the band spaces

• Advantage of this bow is that there is no cross- over wire between the canine and premolar there by eliminating the risk of space opening up

Mills retractor

• It is also called extended labial bow• Indication Large overjet For alignment of irregular incisors

• 0.7 mm wire is used • This labial bow has an extensive looping of the wire so

as to increase the flexibility and range of action • Poor patient acceptance• Complex design

Fitted labial bow

• Used to secure the incisors firmly after they been rotated

• It acts as retainer • It is not used in active tooth movement• 0.7 mm wire is used

High labial bow with apron spring

• Used in retraction of one or more teeth • Large overjet • It is very similar to a Roberts retractor • Highly flexible • Light force

• Fabrication A heavy base arch of 0.9mm to 1mm wire extends into the buccal sulcus apron spring made of 0.4mm wire is attached to the high labial bow

• Activation It is activated by bending the upright arms of the apron

springs towards the teeth 3mm activation at a time Disadvantages are difficulty in construction and soft

tissue injury

Split labial bow

• Used for anterior retraction

• Closer of midline diastema

SPRINGS

Most commonly used active elements

Requirements: springs should deliver optimum force should possess high degree of elasticity should have long range of action

Force systems delivered depend onIntrinsic properties- cannot be altered by operator -modulus of elasticity-yield strengthExtrinsic properties- operator can exercise control-length of wire -thickness of wire

Small changes in diameter and length have a profound impact on the force delivered

Effect of wire diameter on force delivered-amount of activation0.5mm- 3mm activation0.7mm- 1mm activation- little margin of error

Effect of wire lengthCoil- increase length of springLower force with same amount of activation

Classification of Springs

I. Based on direction of tooth movement1. Springs for mesio-distal tooth movement2. Spring for labio-lingual tooth movement3. Springs for expansion of archesII. Based on nature of support1. Self supported springs 2. Guided springs3. Auxiliary springsIII. Based on presence of loop or helix

Single Cantilever Spring active armParts coil retentive arm• 0.5-0.6mm wire• coil with internal diameter of 3mm• used to move teeth labio-lingually or mesio-diatally

Double Cantilever Spring / Z spring

• Constructed using 0.5 or 0.6 mm wire• Spring perpendicular to palatal surface of tooth• Indicated where incisors are to be proclinedActivation: Opening both coils If not perpendicular to palatial surface of teeth, it

tends to intrude teeth.

‘T’ Spring• Constructed using 0.5 mm wire• Buccal movement of premolars and molarsActivation: Pulling spring away from the baseplate

Coffin Spring

• Described by Walter.H.Coffin in 1881• Made in 2 segments, large enough to make contact

with all teeth to be moved• Made of 1.25 mm wire• Spring stands 1 mm away from the soft tissues

Indications: Transverse arch expansion – Unilateral crossbite with

lateral mandibular displacement

Advantage over screw – Differential expansion can be obtained.

Unless expertly made and adjusted, tends to be rater unstable.

Canine Retractors• Type of spring• used to move canine in distal direction

CLASSIFICATIONI. Based on location -buccal -palatalII. Based on presence of helix or loopIII. Based on mode of action -push type -pull type

Buccal Self Sopported Canine Retractor

• 0.7 mm wire• buccally placed canine is to be moved palatally and

distally• coil just distal to long axis of tooth

Activation: by 1mm Distal -closing the loop Palatal -anterior limb is bent towards the tooth after it emerges from the coil

Uncomfortable to patient Stability increased- flexibility compromised

Supported Buccal Canine Retractor

• identical in design to self supported retractor• 0.5mm wire supported in tubingActivation: by 2mm

Reverse Loop Canine Retractor

• can be used in shallow sulcusActivation: 1mmi. cut off 1mm from the free end & readapt itii. opening the coil

‘U’ Loop Buccal Canine Retractor

• can be used in sallow sulcusActivation: free end is cut by 1mm & readapted Requires frequent adjustment

Palatal Canine Retractor

-canine placed palatally requiring distal buccal movement

-coil of 3mm placed between the initial & final position of canine

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