Functional appliances

Question 1

Functional appliances are most effective at

Answer 1

Changing the anterioposterior occlusion between upper and lower arches
Usually in patients with mild to moderate class II skeletal discrepancy

Question 2

Functional appliances work by

Answer 2

Most work by changing the position of the mandible, posturing it forwards (and often open)
Stretch muscles
-apply forces to bones and teeth
Use growth
Often followed with fixed appliances as they are not as effective at correcting tooth irregularities and improving arch alignment

Question 3

Functionals apply forces to teeth and bones

Answer 3

Condyle out of glenoid fossa

Question 4

Who - patient selection in terms of malocclusion

Answer 4

Class II div 1 incisors with increased overjet most common
Class II molars
Can be used for Class II div 2 patients
-harder to treat due to increased overbite
-converted to class II div 1 (pre-functional removable appliance or sectional fixed appliance0 then treated with functional appliances

Question 5

Class II aetiology

Answer 5

3 possibilities

• maxillary protrusion
• mandibular retrusion (MOST COMMON)
• or both

Question 6

Assessment of skeletal pattern

Answer 6

Clinical assessment (usually enough)
-assess visually
-posture test
Cephalometric analysis

Question 7

Clinical assessment

Answer 7

Pt sitting upright
Look at profile
‘Posture test’
-bring mandible forward - does pt look better or worse?

Question 8

Ceph analysis

Answer 8

SNA = ideal?
SNB = ideal?
ANB = ideal around 2
MMPA
-useful to have baseline ceph to know where lower incisors were

Question 9

Successful treatment depends on

Answer 9

Pt 
-keen
-motivated
Dentist
-enthusiastic
-experienced

Question 10

Avoid functional appliances in which patients?

Answer 10

Non-motivated pts
Class I molar relationship
High MMPA (maxillary mandibular planes angle)

Question 11

Ideal time for functional appliance

Answer 11

Depends on stage of development
-dental - late mixed/ permanent dentition
-emotional - motivation (early treatment can improve pt’s self-esteem)
-physical - height (actively growing, in time with pubertal growth spurt)
If used in late mixed dentition, treatment is usually shorter so treatment burdon reduced compared to early mixed dentition then pause whilst adult dentition erupts, then fixed appliances

Question 12

Measurement of height

Answer 12

Measurement of standard height
Height curve 
-standing - skeletal growth
Velocity curve (more useful)
-rate of growth per year

Question 13

Rapid growth

Answer 13

Girls 10-12
Boys 11-13
Peak pubertal growth

Question 14

Choice of functional appliance

Answer 14

Twin block - most popular in UK
Activators
-medium-opening activator (MOA)
-Andresen
-Harvold
-Bionator
Frankel

Question 15

Twin block

Answer 15

Well tolerated by patients
Separate upper and lower appliance which fit together using posterior bite blocks with interlocking bite-planes, which postures mandible forwards
Removable functional appliances
Worn 24 hrs except sports and cleaning - means rapid correction is possible
Midline screw in upper (to expand and avoid crossbite)

Question 16

Advantages of twin block

Answer 16

Aesthetic
Pt can move mandible
Full-time wear
Robust
Can expand upper arch/ reactivate (by modifying appliance)
Integrate with fixed appliances
-at same time (sectional)
-following twin blocks

Question 17

Medium opening activator

Answer 17

One piece functional appliance with minimal acrylic to improve patient comfort
Cribs 64/46 region
Lower posterior teeth free to erupt (can help correct increased OB)
Useful in trying to reduce a deep overbite

Question 18

Fixed (Herbst)

Answer 18

Not used as much, not as robust and difficult to repair plus more expensive (but most popular in US)
Section attached to upper buccal segment and lower buccal segment joined by rigid arm that postures mandible forwards
Fixed so removes most compliance factors
As successful at removing OJs as twin-block
Slightly better tolerated than twin-block

Question 19

Fixed (Herbst) advantage

Answer 19

Piston arrangement forces them forwards and even stay in the whole time when eating

Question 20

Frankel appliance

Answer 20

Soft tissue borne
Postures mandible forwards
Buccal shields alter soft tissue balance (holds cheeks away from teeth and stretches the periosteum
Difficult to repair

Question 21

Mode of action of functional appliances

Answer 21

Questionable evidence of mandibular growth but it does seem to work in a lot of cases
Dental
-1. upper labial segment retroclines
-2. lower labial segment proclines
-3. controlled eruption of lowers into class I
Skeletal
-forward movement of mandible
–is condyle primary or secondary growth site??? not decided
-inhibits normal forward growth of maxilla
Soft tissue and muscles to lesser extent

Question 22

Functional appliances effects statistics

Answer 22

27% skeletal

73% dento-alveolar

Question 23

How long are they worn for

Answer 23

If worn full time, about 9 months to reduce overjet

Question 24

Definition of functional appliance

Answer 24

Functional appliances utilise, eliminate or guide the forces of muscle function, tooth eruption and growth to correct a malocclusion

Question 25

Failure rate of functional appliances

Answer 25

Around 20%, usually due to lack of patient compliance