Removable appliances Flashcards by Y Clayton

What are removable appliances

Orthodontic devices that are designed to apply force to the teeth by means of a spring, screw or another mechanical component and can be taken out by the patient for cleaning

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What are the actions of removable appliances

Active

Passive

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What do passive removable appliances do

Maintain the position of the teeth

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What do active removable appliances do

Bring about tooth movement via incorporation of active forces within the appliance

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What type of movement can be achieved with removable appliances

Tipping movement

Movement of blocks of teeth

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What are the indications for removable appliances

Active treatment of simple malocclusions

- Passively as a space maintainer or retainer post op

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List the occlusal discrepancies that can be treated with removable appliances

Tipping teeth mesially/distally along arch
Tipping teeth labially/buccal
Reduction of overbite
Reduction of overjet
Expansion of the arch

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Instructions for patients for removable appliance prescription

Wear appliance all day and night
Remove for contact sports
Clean teeth and appliance after every meal and at night
Avoid sticky foods
Know how to insert and remove
Return to dentist if it breaks

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When to monitor progress of removable appliance

Every 4 weeks for reactivation if active appliance

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Advantages of removable appliances

Can be removed for brushing 
Easy to adjust 
Passive or active 
Bite planes can be incorporated 
Lower risk of iatrogenic damage than fixed appliances

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Disadvantages of removable appliances

Issue with compliance 
Only tilting movement possible - limited to certain indications 
Good technician required 
Initially affects speech 
LRA hard to tolerate due to tongue
Palatal inflammation

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Ideal properties of a removable appliance

Comfortable and well tolerated 
Durable under oral function 
Hygienic 
Adequate retention 
Force and anchorage components

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What should be included in the laboratory prescription for removable appliances

Active components and the diameters for each component
Retentive factors and their diameters
Layout of the baseplate
Modifications where required e.g. bite planes

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List the components of removable appliances

Active components
Retentive components
Anchorage components
Baseplate components

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What are the types of active components

Springs
Bows
Screws
Elastics

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What is the most commonly used active component

Springs

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How much force is required to tip a single rooted tooth

25-50 grams

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What is the diameter of palatal and buccal springs? What activation is required

Palatal - 0.5mm with 3mm activation

Buccal - 0.7mm with 1-2mm activation

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Describe the action of springs

Point of application is adjusted to give desired movement

The further the spring is from centre of resistance of the tooth, the greater the degree of tilting

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Ideal requirements of springs

Continuous force
Correct magnitude
Exert force over full range of tooth movement

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List the palatal springs

Finger spreader
Z spring
T spring
Coffin spring

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Indications for a finger spreader spring

Movement of teeth in line of the arch e.g. mesial/distal movement of incisors, premolars or canines

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Indications for a Z spring

Proclination of incisors over the bite

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Indications of T spring

Move premolars buccally over the bite

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Indications for a coffin spring

Transverse upper arch expansion

What is the wire diameter for coffin springs

Heavy wire - 1.25mm

What is the buccal spring?

Buccal canine retractor

Indications for buccal canine retractor

Retract buccally placed canines

Relate the flexibility of bows to the action

More flexible = can reduce larger overjets

List the common types of Bows

Labial bow | Roberts retractor

Describe labial bow construction

- 0.7mm wire (less flexible) - U loops 3-3 - Adjustment via 1mm activation

Indications for labial bow

- Minor OJ reduction - Align irregular alignment of incirors - Passive in retainers

Indications for Roberts retractor

- Reduction of large overjet due to flexibility

Construction of Roberts retractor

- 0.5mm with buccal arms sheathed in tubing | - 3mm activation required

What is the disadvantages of screw appliances

``` Less versatile Bulkier More expensive Requires patient cooperation with turning screw Movement limited by width of PDL ```

What does the direction of movement depend on with screw appliances

The position of the screw in the appliance

How much tooth movement is achieved by a turn of the key in a screw appliance

0.2mm movement per turn

Describe the type of forces applied by screw appliances

Large intermittent forces

What is movement limited by in screw appliances

Width of the pdl

What happens if pdl width is exceeded in screw appliances

Crushes pdl cells and hinders tooth movement

Indications for use of screw appliance

Procline upper incisors (labial movement of incisors) Distal movement of molars Expansion fo upper buccal segments (crossbites) Buccal movement of an individual tooth or segment

What are the types of retentive components in URA

Adams clasp for posterior retention Labial bow or southend clasp for anterior retention

What is an adams clasp? And describe its construction

Major retentive component It is 0.7mm SS wire Used on 6s mainly and has arrowheads engaging undercuts mesiobuccal and distobuccal

Where is a southend clasp placed?

0.7mm wire on upper 1-1 to utilise interproximal undercut

Where is a labial bow used?

0.7mm wire on upper 2-2

When is additional retention (anterior) required?

When there is active displacement forces e.g. springs

What are the additional retention components

- Anterior retention (adams clasp or southend) | - Adams clasp anterior to the 6 (e.g. on primary molar or premolar)

What is anchorage?

Source of resistance to the forces (and unwanted movement) generated in reaction to the active components of an appliance

What is Newotn's third law of motion?

Every force produces an equal and opposite reaction to the forces applied

What are the sources of anchorage in an URA?

- Palate - Teeth in contact with the URA - Use of EOT

What are the types of anchorage?

Simple - small tooth moved using a big tooth Compound - tooth is moved by two or more teeth Reciprocal - two teeth pitted against each other

How can the URA baseplate be modified?

- Anterior bite plane | - Buccal capping (posterior bite plane)

What are anterior bite planes?

- Flat layer of acrylic built up behind upper incisors to form a plane to which they can occlude

What are posterior bite planes?

- Coverage of occlusal surfaces of relevant buccal teeth allowing for disclusion of anterior teeth and eruption of lower incisors

When to use anterior bite planes?

- Used when overbite needs to be reduced by eruption of lower buccal segment

When are posterior bite planes used?

- Where occlusal interferences need to be eliminated to allow tooth movement BUT reduction of overbite is undesirable

In the treatment of which malocclusion would you use posterior capping?

Unilateral anterior crossbite

Describe the malocclusion that is still commonly treated with URA and describe the appliance design

Anterior crossbite in mixed dentition | - Z spring with posterior bite planes

Describe an appliance used to expand the upper arch (with bilateral crossbite)

- Screw appliance with posterior bite planes

Why may an appliance not fit when you try it in?

- Teeth have erupted/moved since impression was taken | - Delay in impression taking

What are the causes of frequent breakage of URAs?

- Poor compliance - Pt habitually clicks appliance in and out of place - Eating inappropriate food with appliance in place

What can result in anchorage loss?

- Patient factors - part time wear, breakage of appliance, failure to attend check ups - Operator factors - poorly designed, over activation of components

How long should active URA treatment last? How often are the recalls?

- 4-6 week recall | - Total treatment time 4-6 months

What happens if URA has not solved the malocclusion within 6 months?

Move on to another option - you should not exceed >6 months

How may anterior teeth can be moved with an URA?

1-2 ONLY

How may you determine lack of compliance with an URA?

- No wear or tear of appliance - Pt still lisping +/- excess saliva production - Frequent breakages - No marks around palatal mucosa - No movement of tooth/teeth

Removable appliances Flashcards

(66 cards)