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Orthodontics > Removable Appliances in Orthodontics > Flashcards

Removable Appliances in Orthodontics Flashcards

1
Q

What are the advanages of removable appliance?

A

It can be removed for brushing/aesthetics
Palatal coverage increases anchorage
Easy to adjust
Less risk of iatrogenic damage than with fixed
Acrylic can be thickened to form flat anterior bite-plane or buccal capping
Useful as passive retainer or space maintainer
Can be used to transmit forces to blocks of teeth

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2
Q

What are the disadvantages of removable appliance?

A

They can only tip teeth
Because removable, they wont be working when not in the mouth
Affects speech
Poorly tolerated in lower arch
Intermaxillary traction not possible (noramlly used to close spaces)
Inappropriate for multiple individual tooth movement

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3
Q

What is the risk with fixed that isn’t a problem for removable?

A

Demineralisation

Removable can be taken out, do OH isn’t a problem

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4
Q

Why is fixed better?

A

Have fully controlled movement - need attachement to the tooth to do this
Have full 3D control

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5
Q

What are the components to a removable appliance?

A 
ARAB
Active component - what moves the teeth
Retention - stop it falling out 
Anchorage - stop the wrong teeth moving 
Baseplate and biteplanes
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6
Q

What are the different active components (what moves the teeth in the removable appliance)?

A

Springs - palatal or buccal springs
Screws
Elastics
- in decreasing order of preference

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7
Q

What does the force of the spring depend on?

A

Thickness of wire
Length of wire
Amount of deflection

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8
Q

What is the thickness of the wire used for spings, why?

A

0.5-0.6mm- exerting a light force on the teeth
Thicker wire = greater force
0.5mm wire can be coated in acrylic

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9
Q

When will a spring with a coil work more efficiently?

A

If it is activated in the direction that the wire has been wound, so that as the coil unwinds the tooth moves
The shorter the coil = the greater the force

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10
Q

What happens if the spring is overactivated?

A

This increases the force on the tooth. moves the centre of resistance more apically

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11
Q

What is a Z spring used for?

A

Anterior cross-bite - used on incisors
Used to procline the upper incisor
Loop to make the wire longer - exerting less force and gives space to expand

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12
Q

What are T springs used for?

A

Used for buccal movement of canines and premolars

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13
Q

What is a palatal finger sping and what is it used for?

A

0.5-0.6mm wire
Coil in acrylic and coil on side away from the direction of movement
it is used for mesio-distal tooth movement when teeth located correctly in bucco-lingual direction

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14
Q

What are screws used for?

A

More expensive than springs
Helpful when moving a number of teeth together e.g. if expanding the upper arch
if have a posterior cross-bite - dont put Z spings on each tooth

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15
Q

How does the most commonly used screw work?

A

Consists of 2 halves on a threaded cylinder turned by a means of a key which separates the 2 halves by a pre-determined distance - usually 0.2 for each 1/4 turn

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16
Q

What is activation of screw limited by?

A

The width of periodontal ligament

To exceed this would crush the ligament cells and cessation of tooth movement

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17
Q

If do 1 1/4 turn per week how much tooth movement will you get?

A

<1mm

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18
Q

If dor 2 1/4 turns per week of screw how much tooth movement will you get?

A

<2mm

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19
Q

Why are orthodontic elastics not used on removable applicances?

A

Poor control

20
Q

What’s used for posterior retention?

A

Adams cribs

21
Q

Where are Adam’s cribs placed?

A

On 1st molars and premolars
Engage the MB and DB undercuts of 1st molars
Only need undercut of 0.25mm

22
Q

Why is anterior resistance needed?

A

If have an anterior cross-bite on UR1 need z-spring to procline it
Force is put on the UR1 labially to push it forwards
There will be a downwards vector of force too, procline and downwards forve displacing the appliance

23
Q

What is done to resist the downwards force from the z-spring?

A

Z-spring on the upper right 1

and C-clasp on the upper left 2 to resist the downwards force from the z-spring

24
Q

What else can be used for anterior rentention if doing something to posterior teeth?

A

Southend clasp

Utilised the undercut beneath the contact point between 2 incisors - fabricated in 0.7mm hard SS wire

25
Q

How is retention increased using a southend clasp?

A

bending the arrowheads towards teeth - arrowhead moved towards the tooth and also vertically towards the gingival crevice

26
Q

What does palatal spring activation lead to happen?

A

Palatal finger springs to distalise the canines - this force with procline the incisors
The ideal force to move them distally is 25g, this exerts 4-5g on incisors
If use thick wires of short wires, this will exert bigger force on the incisors

27
Q

How do you control anchorage?

A

using low forces to resist unwanted tooth movement

28
Q

What additional anchorage can be used with removable appliances?

A

Palatal vault - use this to push against when moving teeth

29
Q

How do you not lose anchorage?

A

Use light forces
Only move one tooth per side
Large anchor unit - more teeth included
Headgear - used more with fixed appliances

30
Q

What are the problems with headgear?

A

Co-operation

Safety

31
Q

What are the safety problems with headgear?

A

Catapulting accident

Night-time dismantling

32
Q

What are the problems with eye injury from headgear?

A 
High risk of infection 
Excellent culture medium
difficult to control with antibiotics 
Sympathetic opthalmitis - oral bacteria cultured in the eye = blindness, travel along optic nerve = both eyes
Safety mechanism is essential
33
Q

What is a baseplate? What does it do?

A

Connects components
Carries passive wire work
Additional anchorage
Carries biteplanes

34
Q

What is an anterior biteplane?

A

Can be flat or inclined

Increases the thickness of acrylic behind the upper incisors forming bite-plane for the lower incisors to occlude onto

35
Q

When is bite plae prescribed?

A

When either the overbite needs to be reduced or eruption of the lower buccal segement teeth or elimination of possible occlusal interferences is necessary to allow tooth movement to occur
Inclined biteplanes may lead to proclination or retroclination of the lower incisors, depending on thei angulation

36
Q

How does a flat anterior bite plane reduce overbite?

A

When appliance in place, now biting on acrylic, allows the posterior to overerupt reducing the overbite anteriorly

37
Q

What is the problem with anterior biteplane?

A

Lower incisors are pushed forwards - proclines lower incisors

38
Q

When is a posterior biteplane used?

A

To stop the incisors in crossbite and overlapping

It frees the occlusion anteriorly

39
Q

In which cases would you use removable appliances to treat?

A 
Disimpaction of 1st molars 
Class III anterior crossbite 
Posterior cross-bite in mixed dentition or expansion prior to functional appliance
Space maintenance
Overbite correction
40
Q

Where do you have adam’s cribs?

How do you tighten them?

A

6’s

Gently roll arrowhead in or out with pilers

41
Q

How is the Z-spring adjusted?

A

Z-spring for anterior cross-bite
Activate by puling forwards and upwards away from baseplate
want to engage tooth as close to gingival margin as possible

42
Q

What takes place when fitting a URA?

A

Check lab ticket
Explain how it works
Try-in
Adjust retnetive components e.g. adams cribs
Need to activate
Adjust bulky biteplanes
Demonstrate then check patient can fit and remove
Instructions - when to wear, how to clean
Document

43
Q

What is the visit by visit assessement of patient that wears URA?

A 
Talk to patient and parent 
Assess for signs of wear 
Assess progress, measure changes 
Assess OH
Assess retention 
Check if active component is active 
Reasses anchorage 
Document findings and plan
44
Q

How would you go about correcting crossbite UR1?

A

A - active component Z-spring UR1 10.5mm SS
R - retention: C-clasp UR1
A - anchorage: Acrylic baseplate
B - biteplane: Acrylic posterior capping
Adams cribs on 6’s 0.7mm diameter SS for retention and anchorage
If have crossbite check if displacement between RCP and ICP, makes treatment more straight forward
self-retaining, wont need a retainer

45
Q

How would you go about correcting aposterior crossbite?

A

Midline screw
Adams cribs on the 6’s 0.7mm diameter SS - retention and anchorage
Acrylic baseplate - anchorage

Orthodontics (16 decks)

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