Removable Appliances Flashcards
Can GDP make/ prescribe URAs?
Yes - 42% cases done GDP
How do URAs work?
Can only tip teeth
One-point contact at tooth crown
Disadvantage removable appliance?
Removable - lost/damaged Only tip-teeth Affect speech Poorly tolerated in lower arch Insufficient multiple tooth movements
Main concept for designing URA?
ARAB Active component - move teeth Retention - stop it falling out Anchorage - stop wrong teeth moving Baseplate and bite planes
What are active components?
Move teeth e.g springs/ screws or elastics
Elastics least preferable
What is the force of a spring dependent on?
Force dependent on: thickness of wire, length of wire, amount of deflection
What diameter of spring should be used for spring?
0.5-0.6mm for active components
What springs should be used for incisors?
Z-springs
How should palatal finger springs be placed?
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
How are screws used?
Adjustment of screw = quarter turn - 0.2mm
1 turn per week = <1mm month
2 turn per week = <2mm month
Indications for placing screws?
Moving blocks of teeth
Can move teeth and used for retention
Used for posterior cross bite
Give example of posterior retention?
Adams crib
Go into MB and DB undercut
Only need undercut of 0.25mm
Give example of anterior retention?
C-clasp
Southend clasp
When anterior retention used?
Force (vertical and horizontal) can cause displacement of appliance
Push tooth over bite
Why is anchorage used?
To control unwanted tooth movement
What law is anchorage based on?
Newtons third law - to every action is an equal and opposite reaction
How to not lose anchorage?
Use light forces
Only move one tooth per side
Could use headgear
What are the problems with headgear?
Co-operation - needs to be worn 12 hours a day
Safety - safety mechanism essential (eye-injury)
What are baseplates?
Connect components
Caries passive wirework
Provide additional anchorage
Carry bite planes
What are different types of bite plane?
Flat anterior bite plane reduce overbite
Inclined anterior bite plane help proline lower incisors
Posterior bite planes - help free occlusion
What types of cases can be tx with URAs?
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
How to fit URA?
Adjust retentive component if required
Adjust bulky bite plane if appropriate
Activate
Check pt can fit and remove
How to assess progress?
Assess signs of wear Measure changes - progress Assess retention Check active component still active Reassess anchorgage
