Myofunctional Appliances Question And Answers

Myofunctional Appliances

• Basic classification of functional appliances
  • Removable functional appliances: They can be removed and inserted into the mouth by patient at his/her own will, e.g. Frankel, activator etc.
  • Fixed functional appliances: They are fitted on the teeth by orthodontist and cannot be removed by the patient at his/her own will, e.g. herbst and jasper jumper.
  • Semi fixed functional appliances: They have certain fixed components, e.g. Denholtz, bass appliances etc.
• Classification by Profitt
  • Tooth borne passive appliances: They have no intrinsic force generating components such as springs or screws. They depend on soft tissue stretch and muscular activity to produce desired treatment results, e.g. Activator, bionator and herbst.
  • Tooth borne active appliances: They include modification of activator and bionator which consists of expansion screws or other active components such as springs to provide intrinsic force for transverse or anterioposterior changes.
  • Tissue borne appliances: They are located in the vestibule and have little or no contact with dentition, e.g. Functional regulator of Frankel.
• Classification by Tom Graber
  • Group 1: Teeth supported appliances, e.g. Catalans, inclined plane etc.
  • Group 2: Teeth or tissue supported appliances, e.g. activator, bionator etc.
  • Group 3: Vestibular positioned appliances with isolated support from tooth/tissue, e.g. oral screen, Frankel appliance, lip bumper.
• Classification based on transmission of force
  • Group 1 appliances: They transmit muscle force directly to the teeth for the purpose of correction of malocclusion, e.g. oral screen, Inclined planes
  • Group 2 appliances: They reposition the mandible and resultant force is transmittd to the teeth and other structures, e.g. activator and bionator
  • Group 3 appliances: They reposition the mandible but their area of operation is vestibule outside the dental arch, e.g. Frankel appliance and vestibular screen.
• Classification into myotonic and myodynamic appliances
  • Myotonic appliances: They depend on muscle mass for their action.
  • Myodynamic appliances: They depend on muscle activity for their function.

• It is a myofunctional appliance.
• It is group 2 appliance, i.e. tooth born appliance (Passive).
• It is used in patients having retruded mandible.
• Used in actively growing patient.

• Class 2, div 1 malocclusion.
• Class 2, div 2 malocclusion after aligning incisors.
• Class 3 malocclusion.
• Class 1 malocclusion with open bite.
• Class 1 malocclusion with deep bite.
• For post-treatment retention
• As a preliminary treatment before major fixed appliance therapy to improve skeletal jaw relations.
• Children with lack of vertical development in lower facial height.
• In crossbite correction.
• As a habit breaking appliance.
• In obstructive sleep apnea.

• In correction of class I problems of crowded teeth.
• In children with excess lower facial height and extreme vertical mandibular growth.
• In children whose lower incisors are severely proclined.
• In children with nasal stenosis on chronic untreated allergy of nose.
• In nongrowing individuals.
• In noncompetent patient.
• In retroclined maxillary incisors.
• In intra-arch irregularities.

• Activators influence new pattrn of mandibular closure by musculoskeletal adaptation.
• Appliance loosely fis into the mouth.
• Patient has to move the mandible forwards to engage the appliance.
• This results, in stretching of elevator muscle of mastication which starts contracting thereby producing “myotactic reflex”.
• This myotactic reflex generates kinetic energy which causes:
  • Prevention of further forward growth of the maxillary dentoalveolar process.
  • Movement of the maxillary dentoalveolar process distally.
  • A reciprocal forward force on the mandible.

• According to this theory, when force generated during swallowing and speech, it transmit and stretches blood vessels then interstitial fluid depletion occur then stretching of elastic fibers and then the force is transmitted to the bone and causes bone bending.
• This method is used in vertical activators where potential energy is used in opening of mandible, i.e. >10 mm.

• It is removable, so oral hygiene maintenance is good.
• The intervals between appointment is long.
• The appointments are usually short due to need of minimum adjustment.
• Economical.
• Treatment is possible in deciduous and mixed dentition.
• Tissue injury does not occur.
• It removes abnormal habits.
• It is weared in night only.

• Require very good patient cooperation.
• Post-treatment fied appliance therapy may be required.
• Treatment time/duration is longer.
• It may produce moderate mandibular rotation (anteriorly downwards), thus not used in case of longer lower facial height.
• Not of much help in cases of crowding.
• Response is very less or it cannot be seen in older people.
• Appliance is bulky and uncomfortable.

• Impression taking.
• Bite registration.
• Articulation of the model.
• Preparation of the wire elements.
• Fabrication of the acrylic portion.
• Trimming of the activator.

• The inter-maxillary record made to facilitate the fabrication of an activator is called as Construction bite.
• Construction bite helps in recording a three-dimensional relationship of mandible to maxilla.
• In horizontal bite (H activator) the mandible is advanced by 6 to 7 mm and vertical opening should be by 2 to 3 mm.
• In vertical bite (V activator) the mandible is advanced by 2 to 3 mm and vertical opening is by 7 to 8 mm.
• Only vertical opening is done in deep bite cases.
• In class 3 malocclusion bite is taken aftr retruding the mandible to a more posterior position.
• H activator is indicated in patient with Class 2 division 1 malocclusion having horizontal growth pattern.
• V activator is indicated in patient with Class 2 division 1 malocclusion having vertical growth pattern.

• The wax bite registration is placed on the occlusal surface between the upper and lower models.
• The models are then articulated in a reverse direction so that the anterior teeth face the hinges.
• This kind of articulation ensures sufficient access to the palatal surface of the upper and lingual surface of lower models during the fabrication of the appliances.

• The usual design requires an upper labial bow. The labial bow is made with 0.9 mm wire and consists of a horizontal section with 2 vertical loops.
• The ends of the vertical loops enter the acrylic body between the canine and deciduous 1st molar or 1st premolar. The labial bow can be active or passive.

• The appliance consists of 3 parts—maxillary part, mandibular part and interocclusal part.
• The appliance can be fabricated by using either heat cure resin or cold cure resin. In cases of heat cure resin, the models are fist waxed and then they are flasked.

• Trimming the bite part of the activator should be done by the clinician.
• Planned trimming of the activator in tooth contact area is carried out to bring about dentoalveolar changes so as to guide the teeth into good relation in all the 3 planes of the space.
• Selective trimming of acrylic is done in direction of the tooth movement.
• The acrylic surface that transmit the desired force by contact with the teeth are called guiding planes. The areas of the acrylic that contact the teeth become polished.

• Intrusion of the incisors is achieved by loading the incisal edges of these teeth with acrylic.
• In case labial bows are used, they should be placed below the area of greatest convexity, i.e. incisally, to aid intrusion.
• In case intrusion of posteriors is needed then only the cusp tips are loaded with acrylic.
• The fossae and fisures are free of acrylic.

• In case of extrusion of the incisors, the lingual surface is loaded above the area of greatest convexity in the maxilla and below area of greatest convexity in the mandible.
• The extrusive movements can be enhanced by placing a labial bow above the area of greatest convexity, i.e. in the gingival 1/3rd of the labial surface.
• In case of molars, extrusion is done by loading the lingual surface above the area of greatest convexity in maxilla and below the area of greatest convexity in the mandible.

• In case the incisors should be protruded, the lingual surface of the teeth is loaded with acrylic and a passive labial bow is given that is kept away the teeth to prevent perioral soft tissues contacting the teeth.
• The acrylic loading of the lingual surface can be of two typesentire lingual surface is loaded (or) only the incisal portion of the lingual surface is loaded.

• The teeth in buccal segment can be moved mesially and distally to help in treating Class-2 and Class-3 malocclusion.
• In Class-2 malocclusion, the maxillary molars are allowed to move distally while the mandibular molars are allowed to move mesially by loading the maxillary mesiolingual surface and mandibular distolingual surface.

• It is possible to trim the activator to simulate expansion of the buccal segment.
• This is done by allowing the contact of the acrylic on the lingual surfaces of the teeth to be moved transversely. Better expansion is possible by placing a Jaw screw in the activator.

• For first two weeks appliance should be weared for 2 to 3 hours in day time.
• For next three weeks appliance should be weared for 4 to 6 hours in day time.
• After three weeks appliance should be weared for 3 to 4 months initially.
• As hyperactivity of the muscle subsides appliance should be weared in night.