6- Principles of Removable Appliances

Question 1

Question 2

2 main types of appliances and when to use them

Answer 2

Question 3

Another way of - Types of appliances

Answer 3

Question 4

Removable appliances - Advantages + Distadvantages

Answer 4

Question 5

Tooth movement with removable appliances- limitations

What movements are possible with removable appliances

Answer 5

Question 6

Removable appliance design - 7 things a removable appliance should be:

Answer 6

Question 7

4 components of removable appliances

Answer 7

1. Active component
2. Retention
3. Anchorage
4. Base plate

Question 8

Active component - removable appliances

Definition
3 examples of active components:

Answer 8

Question 9

Retention - removable appliances
Definition
Examples?

Answer 9

Adam’s clasp - main retention of posterior teeth
Southend clasp - retention for anterior teeth

Question 10

Adam’s clasp

1 What is it + where is it used?
2 How is it constructed?
3 Explain 2 features
4 how can it be adjusted
5 Name 2 other teeth it can be used on for addition retention ?

Answer 10

1- major retention component
Adams clasp used on molars

2- Constructed in 0.7mm hard stainless steel wire

3 - Arrowheads engage in undercuts on mesiobuccal and distobuccal aspects of molar, but does not contact adjacent teeth
Clasp should fit model closely where embrasures are crossed to avoid damage by opposing teeth

4- using Adam’s pliers

5-
- premolars for addition retention
- deciduous molars

Question 11

Southend clasp

1 Used for?
2 Construction / made of

Answer 11

1 - Anterior retention - MAIN anterior retention
used for additional retention anteriorly

2- Construction - 0.7mm wire

Placed around gingival margins of upper central incisors

Question 12

Fitted labial row

1 What is it
2 Construction
3 When is it effective

Answer 12

1- used for additional anterior retention
(Used less commonly than Southend clasp)

2- construction - 0.7mm wire

3- only effective if incisors are proclined

Goes from 2-2

Question 13

Planning retention

When are Adam’s clasps needed?

When are additional clasps needed?

Answer 13

Question 14

Anchorage

1 What is it and what needs to be considered?
2 Resistance to tooth movement is related to?(3)
3 3 types of anchorage

Answer 14

1-
Site from which the forces are applied
Newtons 3rd law - for every action there’s an equal and opposite reaction
How we resist unwanted tooth movement

2-
- surface area of roots (MAIN factor)
- type of tooth movement, teeth can be tipped more readily than moved bodily
- Intercuspation of teeth may contribute

Eg tooth with large SA eg molars provide good anchorage whereas lower incisor with small root SA will provide little anchorage

4. Simple anchorage - using a large tooth as anchorage to move a small tooth
5. Compound anchorage - using a group of teeth as anchorage - (used in removable appliances -baseplate connects teeth together)
6. Reciprocal anchorage

Fixed appliances may use any of the 3 anchorage
Removable appliances mostly always use compound anchorage except for in bilateral expansion where reciprocal anchorage is used

Reciprocal anchorage - eg if midline diastema (equal and opposite directions)

Question 15

Baseplate

1 material
Purpose: (5)

Answer 15

Question 16

What is the simplest active component?

Answer 16

Spring

Question 17

Springs

1 Explain what springs used for?
2 Construction/ Made from:
3 Ideal requirements of a spring are: (3)

Answer 17

1. Commonest force component
2. Construction - hard stainless steel wire

3 - Ideal requirements of a spring are:
• Continuous force
• Correct magnitude
• Exerted over full range of tooth movement

Question 18

Spring Design

How do we know what force to apply/ Formula for spring design:

2 features we want for springs:

What is wire width for buccal or palatal springs?

Answer 18

To keep force low - need long length and thin wire

Can increase length by having a coil
Radius of wire as thin as possible:
- Palatal springs wire width = 0.5mm
- Buccal springs wire width 0.7mm

Question 19

Spring design

1 What force do we use for a single rooted tooth? Why this force?
2 Deflection of spring for buccal and palatal and why (how much is it bent)
3 What is the rate of tooth movement? How often do springs need to be adjusted?

Answer 19

1- For single rooted tooth = 25g → 50g
• Smaller forces → insufficient for adequate rate of tooth movement
• Larger forces → delay tooth movement and cause discomfort

2-
• palatal springs activate 3mms
• buccal springs activate 1mm
• if less → insufficient force
• if more → difficult to insert spring correctly

3- Rate of tooth movement = 1 to 2mms per month - need to adjust springs once a month

Question 20

Types of springs (5)

Answer 20

Z spring and T springs are the main 2 used in removable

Question 21

Palatal Finger Spring

1- Uses
2- Construction
3- Explain 2 design features
4- How do we activate it?

Answer 21

1- To move teeth in line of arch

2- Construction - 0·5mm wire

3- Design
- coil to increase wire length and positioned to unwind as tooth moves
- protect spring from damage by guard

4- Adjustment - activate 3mms at junction of coil and free arm
- check correct direction of movement

Tips tooth mesially or distally - if want tooth to move distal then place at mesial aspect of tooth and vice versa

Question 22

Retracting canines

Is tipping (from removable appliance) or bodily tooth movement (from fixed) needed?

Answer 22

Bodily retraction by fixed appliances needed to prevent gross tilting

General rule -> if extracting to relieve crowding, a fixed appliance needed to bodily retract canines (or premolars)

Question 23

Z spring

1 Uses
2 Construction
3 Position

Answer 23

1 - Proclination of incisors

2- Construction - 0·5mm wire

3 - Position - perpendicular to palatal surface of tooth

4- Adjustment - at each limb
(Does this mean limbs are bent?)

It is in Z shape
To activate need to open each coil - moves tooth by tilting or tipping action

Question 24

Explain what you can see

Answer 24

Top left - Anterior cross bite. Upper incisor biting inside lower incisor
Want to correct in early mixed dentition

Solution = as not many dentition, good to use removable appliance
Z springs on upper incisors - can see in top right image these have been activated- will procline incisors forward
Need good rentetion - so Adam’s clasps on 6s and Ds or if 4 was present

Prop open bite with postierior capping so have clearance to push incisor over the bite

Question 25

2 common uses of Z spring

Answer 25

1. Correcting **Anterior cross bite** - can procline the upper incisors - central or laterals 2. Can be used for in standing upper canine / upper central or lateral incisors

Question 26

Explain what you can see

Answer 26

Instanding upper canine Z springs Adam’s clasps on 6,4,4,6 Posterior capping to prop open the occlusion - otherwise occlusal interference

Question 27

T spring 1- Uses 2- Construction 3- Adjustment 4- Disadvantages

Answer 27

1- move premolars buccally (correcting an instanding **premolar** - with premolar cant fit Z spring ) 2- 0·5mm wire 3- pull spring away from baseplate 4- vertical displacing effect therefore need good retention (Ideally Adam’s clasps on 6s or 4s or Southend clasp - need 2 lots of retention) (Normally would also use posterior capping)

Question 28

Coffin spring 1- Uses 2- Construction 3- Adjustment 4- Advantages

Answer 28

Rarely used 1- transverse upper arch expansion 2- heavy wire 1.25mm 3- pull laterally 4- differential expansion

Question 29

Buccal canine retractor 1- Uses 2- Construction 3- Adjustement 4- Disadvantages

Answer 29

Rarely used 1- Retraction of buccally placed canine by tilting/tipping (but usually need bodily retraction using fixed appliance) 2- 0·7mm wire 3- Activate 1mm 4- • may be uncomfortable • difficult to adjust • less flexible than finger spring \

Question 30

Bows 1- Bows can either be: 2- What are flexible or less flexible bows used for? 3- Name 2 types of bows we use:

Answer 30

1- Bows are either: 1. Passive - used on retainers 2. Active - used to retract incisors 2- Flexible bows = used to reduce moderate overjet Less flexible bows = used to reduce a small overjet or irregularities 3- 1. Robert’s retractor 2. Labial bow (with U loops)

Question 31

Retracting incisors / Trying to reduce an overjet Which of below would you use tipping and which bodily movement ?

Answer 31

Need to consider if possible using tipping movement with removable appliance OR bodily tooth movement needed with fixed appliance- decide by: - inclination of incisors - size of overjet How proclined are incisors If incisors are fairly proclined and overjet is relatively modest may be able to tip teeth back BUT if incisors are only slightly proclined and large overjet then would end with very retroclined incisors so not suitable TOP- very proclined incisors and moderate overjet so may be able to use tipping to reduce overjet BOTTOM - very large overjet and incisors not very proclined - if we tipped these incisors back to reduce overjet they would be pointing backwards so need fixed appliance - bodily movement

Question 32

Can you reduce this overjet using a removable appliance:

Answer 32

Yes Modest overjet Very proclined and spaced incisors - only need to tilt teeth back and gather up space to reduce the overjet Overall very few cases where we can reduce overjet using removable appliances

Question 33

Robert’s retractor 1 what is it? 2 Construction 3 Adjustment

Answer 33

1- Flexible bow 2- 0·5mm wire with buccal arms sheathed in tubing to provide strength 3- - 3mms activation - the bow should lie half way up the incisor crowns - base plate is cut away palatally in advance of tooth movement

Question 34

Robert’s retractor Advantages (4) Disadvantages (2)typ

Answer 34

Type of bow we would use to reduce an overjet

Question 35

Labial bow (with U loops) 1- what is it 2- construction 3- adjustment

Answer 35

1- less flexible bow 2- 0.7mm wire 3- 1mm activation by closing U loops

Question 36

Labial bow (with U loops) Advantages - 2 Disadvantages - 2

Answer 36

Hawley retainer - has Adam’s clasps on 6s in 0.7mm wire, and labial bow with u loops from 3-3 Most common use - passively in hawley retainer

Question 37

Screw type appliance design 1 Uses 2 Force - provided by? 3 adjustment 4 disadvantages - 3

Answer 37

1 for movement of individual or groups of teeth 2 - Active force is provided by screw • Large intermittent force (not continuous) • but activation only small (0.2mm) 3 - 1 to 2 turns per week gives rate of tooth movement 1 to 2 mm per month 4- • expensive, bulky, need patient co- operation (LARGE FORCE UNLIKE springs and bows)

Question 38

Question 39

Screw type appliance design - Clinical indications What is Midline screw plate used for?

Answer 39

- expansion of upper buccal segments - (where narrow upper arch, will expand)

Question 40

Screw type appliance design - Clinical indications What is sectional screw plate used for?

Answer 40

Eg want to expand one side only out eg unilateral cross bite

Question 41

Screw type appliance design - Clinical indications When is screw placed in mesial distal direction?

Answer 41

If we want to move a molar tooth distally - place screw in mesial distal direction

Question 42

Screw type appliance design - Clinical indications Can it fix anterior crossbite

Answer 42

If we want to move all four incisors forward eg to correct anterior cross bite

Question 43

Screw type appliance design - Clinical indications

Answer 43

- expansion of upper buccal segments - buccal movement of individual segment - buccal movement of individual tooth - Distal movement of molar tooth - labial movement of upper incisors (if wanted to move all 4)

Question 44

How often are patients expected to wear removable appliances ? Warn patients of

Answer 44

1- - All the time - Should taken out for cleaning - morning and night and after each meal , and contact sports - Can keep in whilst eating 2- saliva pooling because something new in mouth - willl stop soon Upper appliance may affect speech - will resume normal speech after If problems occurs should return

Question 45

Contraindications of removable appliances

Answer 45

- epilepsy - recurrent fits As both can obstruct airway Would opt for fixed appliances

Question 46

Removable appliances Only able to Should be limited to Most commonly used for Also common,y used for

Answer 46