Functional Appliances Definition
- Appliances which change the position of mandible as to
transmit the forces generated by stretching the muscles, fascia and periosteum
to the dentition and underlying skeletal structures are called as functional
appliances.
- Functional appliances are mainly based on functional matrix
theory by Moss (1968).
- According to that theory mandibular growth can be altered by
functional alteration of the rest position of the mandible.
History
of development of functional appliances
• Robin 1902- monobloc
• Andresen 1908- Activator
• Herbst 1934- Herbst
• Balters 1960- Bionator
• Bimler 1964 – Bimler
• Frankel 1967- Frankel
• Clark 1977-Twin Block
Classification of Functional
appliances
Two types
Removable functional
appliences
Activator type
- Twin block
- Andreson
- Bionator
- Harvold
Frankel type
Eg: Frankel appliance
Fixed functional appliences
Eg: Herbst appliance
Twin block appliance
Two blocks
·
Upper block
·
Lower block
Upper block
- Two adam’s clasps
- Molar capping
- U loop labial bow
Lower block
- Two adam’s clasps
- Molar capping
- Ball clasps/Cleats
Andresen appliance
·
Mono block
·
Base plate covering the palate and lingual
aspect of lower ridge
·
Labial bow anterior to the upper incisors
·
Buccal faceting
Bionater appliance
·
Light appliance with minimal bulk
·
Lingual horse shoe of acrylic
·
Palatal spring which is shaped like a reversed
coffin spring
·
Labial bow is extended distally
Harvold
Frankel appliance
Flexible appliance more wire components less acrylicthree
main types
Herbst appliance
Mode of action of functional
appliances
Mainly it functions on anterior growth rotation of the
mandible. Anterior growth rotation is the rotation which grows the mandible in
antero superior direction.whn patient wears the functional appliance mandible
tent to draw forward, which in turn increases the pulling of muscles and
ligaments acting on mandible. As a result anterior growth rotation gets
activated. Finally by activating the u loop labial bow upper incisors will be
retroclined.
- Skeletal effects
- Dentoalveolar effects
- Soft tissue effects
Skeletal effects
Many studies have found an apparent increase in mandibular
growth of 1-2mm during active treatment.
Restraint of forward growth of the maxilla.
Dentoalvelar effects
·
Inhibition of downwards and forwards eruption of
maxillary teeth.
·
Retroclination of upper incisors
·
Proclination of lower incisors
Effects on soft tissues
Removal of lip trap and improved lip competence
Removal of adaptive tongue activity
Removal of soft tissue pressures from the cheeks and lips
Clinical use
Classic one stage treatment
Some patients can be treated to an extremely acceptable
result with functional appliences
Such cases usually have a mild skeletal discrepancy,
proclined upper incisors and no dental crowding.
Interceptive treatment
Effective at reducing the relative prominence of proclined
upper incisors, which are particularly susceptible to dentoalveolar trauma
Two stage treatment
Improving the anteroposterior relationship with anchorage reinforcement
at the beginning of fixed appliance treatment
Compromise treatment
Some patients who are unstable for fixed appliences (such as
physically handicapped patients) may gain some benefit, both occlusally and
facially, from functional appliances.
Timing of treatment
Pubertal growth spurt
·
Male Age 14 + 2 years
·
Female Age 12+ 2 years
Case selection for the
Functional appliance
- Patient should be on pubertal growth spurt
- Patient should be well motivated
- Moderate to severe skeletal discrepancy
- Posterior positioned mandible
- Well aligned arches
- Average or low FMPA angle
- Facial profile improves when mandible posture
forward(chin not promonent)
Appliance management
- Patient motivation
- Records
- Impression and occlusal registration
- Bite registration
- Fitting of appliance
- Instructions to the patient
- Assesment of the progress
- Reactivation of the appliance
- Retention
