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Ortho > Removable appliances > Flashcards

Removable appliances Flashcards

1
Q

What are removable appliances

A

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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2
Q

What are the actions of removable appliances

A

Active

Passive

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3
Q

What do passive removable appliances do

A

Maintain the position of the teeth

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4
Q

What do active removable appliances do

A

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

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5
Q

What type of movement can be achieved with removable appliances

A

Tipping movement

Movement of blocks of teeth

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6
Q

What are the indications for removable appliances

A
  • Active treatment of simple malocclusions

- Passively as a space maintainer or retainer post op

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7
Q

List the occlusal discrepancies that can be treated with removable appliances

A
  • Tipping teeth mesially/distally along arch
  • Tipping teeth labially/buccal
  • Reduction of overbite
  • Reduction of overjet
  • Expansion of the arch
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8
Q

Instructions for patients for removable appliance prescription

A
  • 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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9
Q

When to monitor progress of removable appliance

A

Every 4 weeks for reactivation if active appliance

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10
Q

Advantages of removable appliances

A 
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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11
Q

Disadvantages of removable appliances

A 
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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12
Q

Ideal properties of a removable appliance

A 
Comfortable and well tolerated 
Durable under oral function 
Hygienic 
Adequate retention 
Force and anchorage components
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13
Q

What should be included in the laboratory prescription for removable appliances

A

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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14
Q

List the components of removable appliances

A

Active components
Retentive components
Anchorage components
Baseplate components

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15
Q

What are the types of active components

A

Springs
Bows
Screws
Elastics

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16
Q

What is the most commonly used active component

A

Springs

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17
Q

How much force is required to tip a single rooted tooth

A

25-50 grams

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18
Q

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

A

Palatal - 0.5mm with 3mm activation

Buccal - 0.7mm with 1-2mm activation

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19
Q

Describe the action of springs

A

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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20
Q

Ideal requirements of springs

A

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

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21
Q

List the palatal springs

A

Finger spreader
Z spring
T spring
Coffin spring

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22
Q

Indications for a finger spreader spring

A

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

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23
Q

Indications for a Z spring

A

Proclination of incisors over the bite

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24
Q

Indications of T spring

A

Move premolars buccally over the bite

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25
Q

Indications for a coffin spring

A

Transverse upper arch expansion

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26
Q

What is the wire diameter for coffin springs

A

Heavy wire - 1.25mm

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27
Q

What is the buccal spring?

A

Buccal canine retractor

28
Q

Indications for buccal canine retractor

A

Retract buccally placed canines

29
Q

Relate the flexibility of bows to the action

A

More flexible = can reduce larger overjets

30
Q

List the common types of Bows

A

Labial bow

Roberts retractor

31
Q

Describe labial bow construction

A
  • 0.7mm wire (less flexible)
  • U loops 3-3
  • Adjustment via 1mm activation
32
Q

Indications for labial bow

A
  • Minor OJ reduction
  • Align irregular alignment of incirors
  • Passive in retainers
33
Q

Indications for Roberts retractor

A
  • Reduction of large overjet due to flexibility
34
Q

Construction of Roberts retractor

A
  • 0.5mm with buccal arms sheathed in tubing

- 3mm activation required

35
Q

What is the disadvantages of screw appliances

A 
Less versatile 
Bulkier 
More expensive 
Requires patient cooperation with turning screw 
Movement limited by width of PDL
36
Q

What does the direction of movement depend on with screw appliances

A

The position of the screw in the appliance

37
Q

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

A

0.2mm movement per turn

38
Q

Describe the type of forces applied by screw appliances

A

Large intermittent forces

39
Q

What is movement limited by in screw appliances

A

Width of the pdl

40
Q

What happens if pdl width is exceeded in screw appliances

A

Crushes pdl cells and hinders tooth movement

41
Q

Indications for use of screw appliance

A

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

42
Q

What are the types of retentive components in URA

A

Adams clasp for posterior retention

Labial bow or southend clasp for anterior retention

43
Q

What is an adams clasp? And describe its construction

A

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

44
Q

Where is a southend clasp placed?

A

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

45
Q

Where is a labial bow used?

A

0.7mm wire on upper 2-2

46
Q

When is additional retention (anterior) required?

A

When there is active displacement forces e.g. springs

47
Q

What are the additional retention components

A
  • Anterior retention (adams clasp or southend)

- Adams clasp anterior to the 6 (e.g. on primary molar or premolar)

48
Q

What is anchorage?

A

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

49
Q

What is Newotn’s third law of motion?

A

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

50
Q

What are the sources of anchorage in an URA?

A
  • Palate
  • Teeth in contact with the URA
  • Use of EOT
51
Q

What are the types of anchorage?

A

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

52
Q

How can the URA baseplate be modified?

A
  • Anterior bite plane

- Buccal capping (posterior bite plane)

53
Q

What are anterior bite planes?

A
  • Flat layer of acrylic built up behind upper incisors to form a plane to which they can occlude
54
Q

What are posterior bite planes?

A
  • Coverage of occlusal surfaces of relevant buccal teeth allowing for disclusion of anterior teeth and eruption of lower incisors
55
Q

When to use anterior bite planes?

A
  • Used when overbite needs to be reduced by eruption of lower buccal segment
56
Q

When are posterior bite planes used?

A
  • Where occlusal interferences need to be eliminated to allow tooth movement BUT reduction of overbite is undesirable
57
Q

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

A

Unilateral anterior crossbite

58
Q

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

A

Anterior crossbite in mixed dentition

- Z spring with posterior bite planes

59
Q

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

A
  • Screw appliance with posterior bite planes
60
Q

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

A
  • Teeth have erupted/moved since impression was taken

- Delay in impression taking

61
Q

What are the causes of frequent breakage of URAs?

A
  • Poor compliance
  • Pt habitually clicks appliance in and out of place
  • Eating inappropriate food with appliance in place
62
Q

What can result in anchorage loss?

A
  • Patient factors - part time wear, breakage of appliance, failure to attend check ups
  • Operator factors - poorly designed, over activation of components
63
Q

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

A
  • 4-6 week recall

- Total treatment time 4-6 months

64
Q

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

A

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

65
Q

How may anterior teeth can be moved with an URA?

A

1-2 ONLY

66
Q

How may you determine lack of compliance with an URA?

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

Ortho (20 decks)

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