Functional appliances-Orthodontic Lecture note

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
  •   Fixed

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
  1. Patient should be on pubertal growth spurt
  2. Patient should be well motivated
  3. Moderate to severe skeletal discrepancy
  4. Posterior positioned mandible
  5. Well aligned arches
  6. Average or low FMPA angle
  7. 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


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