Removable Appliances

Question 1

Name 3 types of orthodontic appliances

Answer 1

1. Removable appliances
   
   • Upper removable
   • Lower removable
   • Retainers
2. Fixed appliances
3. Functional appliances

Question 2

What is a removable appliance?

Answer 2

Removable appliances are orthodontic devices which can be taken out of the mouth by patient for cleaning

Question 3

What is the mode of action of removable appliances?

Answer 3

Tip teeth around a fulcrum (usually about half way up the root)

Question 4

Name 4 complex movements fixed appliances can cause

Answer 4

1. Bodily movement
2. Rotation
3. Intrusion / Extrusion
4. Root control

Question 5

What is bodily movement?

Answer 5

Tip of the tooth and root move in the same direction

Question 6

Name 5 advantages of removable appliances

Answer 6

1. Simple to use
2. Less chairside time than fixed appliances
3. Less demanding on oral hygeine than fixed appliances
4. Relatively simple to add pontic teeth
5. Well accepted by patients

Question 7

Why is there less chairside time when using removable appliances rather than fixed appliances?

Answer 7

Manufacturing is carried out outside of the clinical area

Question 8

Name 4 disadvantages of removable appliances

Answer 8

1. Limited range of tooth movement
2. Require more laboratory time which is costly
3. Lower removable appliances are uncomfortable
4. They are removable

Question 9

Name 4 reasons why removable appliances are in declining use

Answer 9

1. Fixed appliances now more efficient
2. Postgraduate orthodontic training courses are longer
3. More cases treated by specialists
4. Poorer treatment outcomes with removable appliances

Question 10

Name 3 components of removable appliances

Answer 10

1. Active components
2. Retentive components
3. Baseplate

Question 11

Name 4 potential active components of a removable appliance

Answer 11

1. Springs
2. Screws
3. Labial bows
4. Elastics (rarely used)

Question 12

Describe springs which are used in removable appliances

Answer 12

• 18:8 stainless steel (18% Cr, 8% Ni)
• Corrosion resistant
• Usually 0.5mm or 0.7mm thickness
• Optimum force is 25-60g
• 1mm per months for movement

Question 13

Describe the principles of changing the force of Cantilever Spring

Answer 13

• Increasing diameter by 1 unit increases force to the power of 4
• Increasing length by 1 unit decreases force to the power of 3

Question 14

Describe adjustment and activation of springs

Answer 14

• 0.7mm requires less activation than 0.5mm
• Usually aim to have 2-4mm activation
• Too small is rapid force decay as tooth moves
• Too large is difficulty to insert appliance

Question 15

Describe the principles of activation

Answer 15

Direction of force applied is perpendicular to the tangent at the point of contact

Question 16

What is the function of retentive components of the removable appliance?

Answer 16

Retain the appliance in the mouth

Question 17

Name 3 types of clasps used on removable appliances

Answer 17

1. Adams clasps
2. Southend and Half-Jackson (incisors)
3. Ball ended clasps

Question 18

Describe an Adams Clasp

Answer 18

• Engage undercuts on molars or premolars
• 0.7mm SS
• Arrow head should engage undercut but should not impinge on soft tissues

Question 19

What is a baseplate made of?

Answer 19

Cold cured acrylic resin

Question 20

Name 3 functions of baseplates

Answer 20

1. Hold various components together
2. Anterior biteplane
3. Posterior biteplane

Question 21

What is the function of anterior biteplane?

Answer 21

Reduce a deep overbite

Question 22

What is the function of posterior biteplanes?

Answer 22

Temporarily produce a vertical opening between the anterior teeth to allow proclination of lingually placed upper incisors

Question 23

Name 6 most widely used biteplanes

Answer 23

1. Anterior / Posterior biteplanes
2. URA - Midline expansion screw
3. Palatal springs to procline upper incisors
4. Palatal finger spring
5. Robert’s retractor
6. Buccal canine retractor

Question 24

Describe how an anterior biteplane can correct a deep overbite

Answer 24

• Posterior teeth separated by 2-3mm
• Disclusion of the posterior teeth
• Allows increased eruption of posterior teeth
• Ensure opposing teeth contact and overbite corrected

Question 25

Describe how midline expansion appliances work

Answer 25

- Used for correction of crossbite - Crib 6s and 4s (or Ds) - Midline screw adjusted by patient once or twice per week - 1 turn of screw expands by 1mm

Question 26

Why may a posterior biteplane be build into a midline expansion appliance?

Answer 26

Discludes the posterior teeth to allow free movement and expansion

Question 27

Describe palatal finger spring retractor

Answer 27

- Retracting canines and premolars - Crib 6s - 0.5mm springs - Activate by 1/2 width of canine or premolar

Question 28

Describe Robert's Retractor

Answer 28

- Retracting incisors in Class II Div 1 relationship - Crib 6s - 0.5mm labial bow supported by SS tube - Should be just behind incisal edges when passive

Question 29

Describe buccal canine retractor

Answer 29

- Retracting canines to relieve crowding or reduce overjet - Crib 6s - 0.7mm springs - Activate by 1/3 width of the canine

Question 30

Describe the clinical procedure of a removable appliance

Answer 30

- Impression using alginate - Appliance design on the lab form - Lab casts up a working model one which appliance constructed

Question 31

What is the clinical procedures when fitting a removable appliance?

Answer 31

- Check patient details - Check baseplate (height baseplate) - Insert and check retention - Activate active components

Question 32

Describe 5 instructions which should be given to patients following the fitting of a removable appliance

Answer 32

1. Full time wear including while eating 2. Removed only when cleaning or sport 3. Contact orthodontist if any problems 4. Brush teeth properly after each meal if possible 5. Diet advice and OHI

Question 33

Describe the follow up procedures for a removable appliance

Answer 33

- 4 to 6 week intervals - Check for ulceration or discomfort - Assess progress - Check retention

Question 34

Name 4 signs appliances are not being worn

Answer 34

1. No tooth movement 2. Patient unable to speak with appliance 3. Springs still active 4. Patient has difficulty inserting and removing appliance

Question 35

Name 4 things to do when it is obvious a patient is not wearing their appliance

Answer 35

1. Reinforce instructions to patient and parent 2. Adjust if necessary 3. Don't carry out extractions until patient definitely wearing full time 4. Reconsider whether patient is suitable for treatment