removable appliances

Question 1

What are the advantages?

Answer 1

Can stop tx where necessary

Question 2

What are the disadvantages?

Answer 2

Depends on compliance from pt
Only one point contact at crown so can only tip (compared to 3 for fixed)
Can be lost/damaged
Affects speech
Poorly tolerated in lower arch
Can’t have intermaxillary traction or multiple tooth movements

Question 3

What are the components of an upper removable?

Answer 3

ARAB

Active components
Retention
Anchorage
Baseplate and biteplanes

Question 4

What are the active components?

Answer 4

Springs (palatal and buccal)
Screws
Elastics

Most to least preferable^

Question 5

What are properties of springs?

Answer 5

Force depends on-
-thickness of wire (for active use 0.5-0.6mm, force=diameter^4)
-length of wire (force= 1/length^3, coil adds length)
-amount of deflection

Question 6

What types of spring are there?

Answer 6

Z spring/incisors spring (looks like a deformed safety pin)
T spring (looks like a dog bone/bow tie)
Palatal finger spring (look like hairdryer)- coil near acrylic and away from direction of movement, can use on any teeth but not so good on buccally placed teet

Question 7

What is a screw?

Answer 7

Looks like a spider
Embedded in acrylic
Can be open/closed
Pushes brace apart for expansion across arch
There’s an arrow to show how to turn screw
Quarter turn=0.2mm
1 turn a week= <1mm/month
2 turns a week= <2mm/month

Question 8

What are indications for screws?

Answer 8

Moves blocks of teeth
Can move individual teeth
Use for retention

Question 9

What are contraindications of elastics?

Answer 9

Poor control
Can cause gingival damage

Rarely used

Question 10

What are Adam’s cribs?

Answer 10

For posterior retention
Arrowheads tuck into MB and DB undercuts
Only need 0.25mm undercut

Question 11

Why do we need anterior retention?

Answer 11

Spring will act on tooth
Causing a force
The forces acts in a horizontal and vertical direction
Appliance will displace due to lack of retention

Question 12

What are some clasps for anterior retention?

Answer 12

C clasp (looks like little hook)
Southend clasp (looks like outline of teeth at gingival margin)

Question 13

Why is anchorage important?

Answer 13

Newton’s third law of motion

To every action is an equal and opposite reaction

Question 14

What is the ideal force?

Answer 14

25g
Excess=100g

Question 15

What is anchorage in removables?

Answer 15

Palatal vault (acrylic)

Question 16

How do you keep the anchorage?

Answer 16

Light forces
Only move one tooth per side
Large anchor unit
Headgear

Question 17

What is a base plate?

Answer 17

Connects components
Carries passive wirework
Additional anchorage
Carries biteplanes

Question 18

What is a biteplane?

Answer 18

Anterior- flat/inclined

FLAT
reduces OB by freeing up posteriors so they can erupt leaving a space at the incisors for movement

INCLINED
For class II, control whole of bottom jaw, proclines lower incisors

Posterior- opens up anterior teeth and frees occlusion

Question 19

When would you treat w removable appliances?

Answer 19

Disimpaction of first molars
Class III- anterior CB
Posterior CB (w mandibular displacement) in mixed dentition/expansion prior functional
Space maintenance (eg. Ds and Es extracted)
OB correction

Question 20

How might you adjust the removable?

Answer 20

Tighten Adam’s cribs- gently roll arrowhead in/out w pliers

Pull Z-spring forwards and upwards away from baseplate

Question 21

How do you fit the removable?

Answer 21

1. Check lab ticket
2. Explain how it works
3. Try-in
4. Adjust components if loose
5. Activate
6. Adjust bulky biteplanes
7. Demonstrate and check pt can fit/remove
8. Instructions when to wear, how to clean, adjust screws?
9. Document everything

Question 22

How do you assess visit by visit?

Answer 22

Talk to pt
Assess signs of wear
Assess progress, measure changes
Assess OH
Assess retention
Check active component is active
Reassess anchorage
Document findings and plan

Question 23

How do you correct an anterior cross bite of UR1?

Answer 23

Z spring UR1 0.5mm SS (active c.)
C clasp UL1 0.6mm SS (retention)
Acrylic posterior capping (biteplane)
Adam’s cribs on 6s 0.7mm SS (retention and anchorage)
Acrylic baseplate (anchorage)

Question 24

How do you correct a posterior crossbite?

Answer 24

Midline screw
Adam’s cribs on 6s 0.7mm SS (retention and anchorage)
Acrylic baseplate (anchorage)

Question 25

What are disadvantages of headgear?

Answer 25

Cooperation
-12hrs per day (actual 6.5hrs reported)

Safety
-catapult into eye (dismantle at night)- high risk of infection, excellent culture medium, difficult to control w antibiotics, sympathetic ophthalmitis
- there is a safety mechanism now- locks into place