Removable Appliances

Question 1

Can GDP make/ prescribe URAs?

Answer 1

Yes - 42% cases done GDP

Question 2

How do URAs work?

Answer 2

Can only tip teeth

One-point contact at tooth crown

Question 3

Disadvantage removable appliance?

Answer 3

Removable - lost/damaged
Only tip-teeth
Affect speech
Poorly tolerated in lower arch 
Insufficient multiple tooth movements

Question 4

Main concept for designing URA?

Answer 4

ARAB
Active component - move teeth
Retention - stop it falling out
Anchorage - stop wrong teeth moving
Baseplate and bite planes

Question 5

What are active components?

Answer 5

Move teeth e.g springs/ screws or elastics

Elastics least preferable

Question 6

What is the force of a spring dependent on?

Answer 6

Force dependent on: thickness of wire, length of wire, amount of deflection

Question 7

What diameter of spring should be used for spring?

Answer 7

0.5-0.6mm for active components

Question 8

What springs should be used for incisors?

Answer 8

Z-springs

Question 9

How should palatal finger springs be placed?

Answer 9

Coil near acrylic to increase length
Coil on side away from direction of movement
Not good to use on ducally placed teeth
Can move teeth mesial/distal

Question 10

How are screws used?

Answer 10

Adjustment of screw = quarter turn - 0.2mm
1 turn per week = <1mm month
2 turn per week = <2mm month

Question 11

Indications for placing screws?

Answer 11

Moving blocks of teeth
Can move teeth and used for retention
Used for posterior cross bite

Question 12

Give example of posterior retention?

Answer 12

Adams crib
Go into MB and DB undercut
Only need undercut of 0.25mm

Question 13

Give example of anterior retention?

Answer 13

C-clasp

Southend clasp

Question 14

When anterior retention used?

Answer 14

Force (vertical and horizontal) can cause displacement of appliance
Push tooth over bite

Question 15

Why is anchorage used?

Answer 15

To control unwanted tooth movement

Question 16

What law is anchorage based on?

Answer 16

Newtons third law - to every action is an equal and opposite reaction

Question 17

How to not lose anchorage?

Answer 17

Use light forces
Only move one tooth per side
Could use headgear

Question 18

What are the problems with headgear?

Answer 18

Co-operation - needs to be worn 12 hours a day

Safety - safety mechanism essential (eye-injury)

Question 19

What are baseplates?

Answer 19

Connect components
Caries passive wirework
Provide additional anchorage
Carry bite planes

Question 20

What are different types of bite plane?

Answer 20

Flat anterior bite plane reduce overbite
Inclined anterior bite plane help proline lower incisors
Posterior bite planes - help free occlusion

Question 21

What types of cases can be tx with URAs?

Answer 21

Disimpaction first molars
Class III anterior cross bite
Posterior cross bite in mixed dentition or prior or expansion prior to functional appliance
Space maintenance
Overbite correction

Question 22

How to fit URA?

Answer 22

Adjust retentive component if required
Adjust bulky bite plane if appropriate
Activate
Check pt can fit and remove

Question 23

How to assess progress?

Answer 23

Assess signs of wear
Measure changes - progress
Assess retention
Check active component still active 
Reassess anchorgage