How do functional appliances work?
Functional appliances utilise, eliminate of guide the muscles of mastication, tooth eruption and growth to correct malocclusion
When are functional appliances most effective?
When a patient is growing, if possible to coincide with the patients growth spurt
What are functional appliances most effective at changing?
The are most effective at changing the AP occlusion between upper and lower arches
Dento-alvelor vs skeletal changes
73% Dento-alveolar
27% Skeletal
Mode of Action of functional appliances
1) Muscles of mastication - posturing mandible forwards, stretches muscles and soft tissues, pressures are transmitted to dental arches
2) Dentition - Intermaxillary class 2 force transmitted onto teeth results in tipping, retro-clination of upper incisors and pro-clination of lower incisors, distal tipping upper teeth, mesial tipping lower teeth
3) Remodelling at condyle - very slight 1mm forward mandibular growth as condylar cartlidge is secondary
Aims of function appliances
- Overjet reduction
- To correct buccal segment relationship
- To change soft tissue environment
- To build posterior anchorage for extractions with fixed appliances
Indications for functional appliances
- Increased overjet
- Mandibular retrognathia
- Growing patient - utilise growth phase
- Motivated patient
- Class 1 buccal segments
- Increased overbite
- lower/average vertical proportions
- Retroclined lower incisors/proclined upper incisors
Contra-indications for functional appliances
- Non-growing patient (generally over 12/13)
- Increased vertical proportions/high angle (may make worse)
- Backwards mandibular growth rotations
- AOB cases
- Proclined lower incisors (may make worse) - unless planning exts
- Poor compliance eg sensory issues
- Care with prognathic chin
Key elements of functional appliance design
- Sufficient retention, Adams or ball-ended clasps
- Edge to edge incisor relationship
- 70degrees inclined bite blocks
- 7-8mm blocks in premolar region (at least 5mm)
- or - midline expansion screw
- Labial bow or southend clasps on upper incisor region
Removable functional appliances
- Clark twin block
- Frankel
- Andresen activator
- MOA Medium opening activator
- Bionator
- Harvold
Fixed functional appliances
- Herbst
What does toothborne mean?
Stability and force from being attached to the teeth
What does tissueborne mean?
Primarily supported by soft tissues - eg Frankel - positioned in the vesibule between the cheeks/lips/gums
What to check when reviewing a functional?
- Patients motivation
- Patients speech
- Fit of the appliance
- Treatment progress
- Overjet
- Canine/molar relationships
- Centrelines
- Reverse overjet
- Are there lateral open bites present
- Remind patient of instructions, tighten clasps and book review appointment
