Removable appliances in orthodontics

Question 1

42% of removable appliance cases in GP

Answer 1

Showed “no improvement” (as measured by the PAR index)

Question 2

Advantage

Answer 2

Removable

Question 3

Distadvantage

Answer 3

• It’s removable! – not in the mouth – not
working, can be lost/ damaged…
• Can only tip teeth
• Affects speech
• Poorly tolerated in lower arch
• Intermaxillary traction not possible
• Inefficient for multiple tooth movements

Question 4

One-point contact at tooth crown

Answer 4

Can only tip teeth

Question 5

Fully controlled movement

Answer 5

Need attachment to tooth

-full 3D control

Question 6

Designing a removable appliance

Answer 6

Keep
It
Simple
Stupid

Question 7

Components (ARAB)/ Design

Answer 7

• Active components - how to move teeth
• Retention – stop it falling out
• Anchorage – stop the wrong teeth moving
• Baseplate and Biteplanes

Question 8

Active components: moving teeth with removable appliances

Answer 8

Springs
-palatal springs
-(buccal springs)
Screws
Elastics
*decreasing order of preference*

Question 9

Properties of springs

Answer 9

Force of spring depends on

• thickness of wire
• length of wire
• amount of deflection

Question 10

Length of wire

Answer 10

Force is proportional to (1/length^3)

Coil near acrylic increases length

Question 11

Thickness of wire

Answer 11

Force is propertional to diameter ^4

Use 0.5-0.6mm diameter wire for active components

Question 12

Z-spring

Answer 12

Incisor spring

Question 13

T-spring

Answer 13

Longer so exerts less force and given space for expansion

Question 14

Palatal finger spring

Answer 14

0.5-0.6mm sire
Coil near acrylic (increases length)
Coil on side away from direction of movement
Can use any teeth
-not good on buccally placed teeth

Question 15

Screws

Answer 15

Closed or open

Question 16

Adjustment of screws

Answer 16

Quarter turn = 0.2mm
1 turn per week = just <1mm per month
2 turn per week = just <2mm per month

Question 17

Indications for screws

Answer 17

Moving blocks of teeth

Can move tooth and use for retention

Question 18

Screws

Answer 18

Moving upper labial segment

Question 19

Orthodontic elastics

Answer 19

Poor control

Rarely used

Question 20

Posterior retention - Adams cribs

Answer 20

MB and DB undercuts

Only need undercut of 0.25mm

Question 21

Anterior retention

Answer 21

Due to inclination there will be a downward vector
C-clasp
Southend clasp

Question 22

Anchorage

Answer 22

The control of unwanted tooth movement
Newton’s 3rd law of motion
-to every action is an equal and opposite reaction
25g-30g on canines ideal force

Question 23

How not to lose anchorage

Answer 23

• Light forces
• Only move one tooth per side
• Large anchor unit
• more teeth included in appliance design
• Headgear?

Question 24

Problems with headgear

Answer 24

Co-operation
Safety
-pts were actually wearing 6.5 hours instead of 12 hours

Question 25

Headgear safety

Answer 25

Catapulting accident | Night-time dismantling

Question 26

Problems of eye injury

Answer 26

``` Hihg risk of infection Excellent culture medium Difficult to control with antibiotics Sympathetic ophthalmitis -safety mechanisms essential ```

Question 27

Baseplate

Answer 27

* Connects components * Carries passive wirework * Additional anchorage * Carries biteplanes

Question 28

Biteplanes

Answer 28

Anterior biteplane • Flat • Inclined Posterior biteplane

Question 29

Flat anterior bite plane

Answer 29

Reduces overbite

Question 30

Inclined bite plane

Answer 30

Post functional appliances | Anterior: to retain functional appliance treatment, proclines lower incisors (unfortunately)

Question 31

Posterior biteplane

Answer 31

Free occlusion

Question 32

Cases to treat with removable appliances

Answer 32

``` • Disimpaction of first molars • Class III - Anterior crossbite • Posterior crossbite (with associated mandibular displacement) in mixed dentition or expansion prior to functional appliances • Space maintenance • (Overbite correction) ```

Question 33

Adjusting Adams Cribs

Answer 33

Gently roll arrowhead in or out with pliers

Question 34

Z-spring adjustment

Answer 34

Pull forwards and upwards, away from baseplate

Question 35

Fitting of a URA

Answer 35

* Check lab ticket * Explain how the appliance works * Try-in * Adjust retentive components if required * Activate * Adjust bulky biteplanes if appropriate * Demonstrate then check pt can fit and remove * Instructions when to wear, how to clean etc * Document everything you have done

Question 36

Visit by visit assessment

Answer 36

* Talk to patient (and parent) * Assess for signs of wear * Assess progress, measure changes * Assess OH * Assess retention * Check if active component is active * Reassess anchorage * Document findings and plan

Question 37

Which spring is the preferred method of reducing overjet?

Answer 37

Robert's retractor