Functional appliances Flashcards
Functional appliances are most effective at
Changing the anterioposterior occlusion between upper and lower arches Usually in patients with mild to moderate class II skeletal discrepancy
Functional appliances work by
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
Functionals apply forces to teeth and bones
Condyle out of glenoid fossa
Who - patient selection in terms of malocclusion
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
Class II aetiology
3 possibilities
- maxillary protrusion
- mandibular retrusion (MOST COMMON)
- or both
Assessment of skeletal pattern
Clinical assessment (usually enough)
-assess visually
-posture test
Cephalometric analysis
Clinical assessment
Pt sitting upright
Look at profile
‘Posture test’
-bring mandible forward - does pt look better or worse?
Ceph analysis
SNA = ideal? SNB = ideal? ANB = ideal around 2 MMPA -useful to have baseline ceph to know where lower incisors were
Successful treatment depends on
Pt -keen -motivated Dentist -enthusiastic -experienced
Avoid functional appliances in which patients?
Non-motivated pts
Class I molar relationship
High MMPA (maxillary mandibular planes angle)
Ideal time for functional appliance
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
Measurement of height
Measurement of standard height Height curve -standing - skeletal growth Velocity curve (more useful) -rate of growth per year
Rapid growth
Girls 10-12
Boys 11-13
Peak pubertal growth
Choice of functional appliance
Twin block - most popular in UK Activators -medium-opening activator (MOA) -Andresen -Harvold -Bionator Frankel
Twin block
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)
Advantages of twin block
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
Medium opening activator
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
Fixed (Herbst)
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
Fixed (Herbst) advantage
Piston arrangement forces them forwards and even stay in the whole time when eating
Frankel appliance
Soft tissue borne
Postures mandible forwards
Buccal shields alter soft tissue balance (holds cheeks away from teeth and stretches the periosteum
Difficult to repair
Mode of action of functional appliances
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
Functional appliances effects statistics
27% skeletal
73% dento-alveolar
How long are they worn for
If worn full time, about 9 months to reduce overjet
Definition of functional appliance
Functional appliances utilise, eliminate or guide the forces of muscle function, tooth eruption and growth to correct a malocclusion
Failure rate of functional appliances
Around 20%, usually due to lack of patient compliance
