removable appliances Flashcards
What are the advantages?
Can stop tx where necessary
What are the disadvantages?
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
What are the components of an upper removable?
ARAB
Active components
Retention
Anchorage
Baseplate and biteplanes
What are the active components?
Springs (palatal and buccal)
Screws
Elastics
Most to least preferable^
What are properties of springs?
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
What types of spring are there?
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
What is a screw?
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
What are indications for screws?
Moves blocks of teeth
Can move individual teeth
Use for retention
What are contraindications of elastics?
Poor control
Can cause gingival damage
Rarely used
What are Adam’s cribs?
For posterior retention
Arrowheads tuck into MB and DB undercuts
Only need 0.25mm undercut
Why do we need anterior retention?
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
What are some clasps for anterior retention?
C clasp (looks like little hook)
Southend clasp (looks like outline of teeth at gingival margin)
Why is anchorage important?
Newton’s third law of motion
To every action is an equal and opposite reaction
What is the ideal force?
25g
Excess=100g
What is anchorage in removables?
Palatal vault (acrylic)
How do you keep the anchorage?
Light forces
Only move one tooth per side
Large anchor unit
Headgear
What is a base plate?
Connects components
Carries passive wirework
Additional anchorage
Carries biteplanes
What is a biteplane?
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
When would you treat w removable appliances?
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
How might you adjust the removable?
Tighten Adam’s cribs- gently roll arrowhead in/out w pliers
Pull Z-spring forwards and upwards away from baseplate
How do you fit the removable?
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
How do you assess visit by visit?
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
How do you correct an anterior cross bite of UR1?
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)
How do you correct a posterior crossbite?
Midline screw
Adam’s cribs on 6s 0.7mm SS (retention and anchorage)
Acrylic baseplate (anchorage)
What are disadvantages of headgear?
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
