Functional & Orthopedic Appliances

• Removable appliances are known as functional appliances.
• They use the musculature's function to restore equilibrium and move the dentition.
• Functional appliances enhance oral physiology and dental position, transmitting muscular forces to the teeth.
• They stimulate muscle reaction impacting occlusion indirectly.
• Functional appliances have the potential to affect maxillary growth, condyles, and facial sutures; they are known as orthopedic appliances for this reason.

Orthopedic Action

• Functional appliances reposition the mandible forward relative to its usual position, displacing the mandibular condyle downward and forward.
• This creates tension in the periosteum, which induces bone growth.
• The amount of growth is largely genetically determined and not easily changed with orthodontics, which means that extra condyle growth is minimal.

Mandibular Unlocking

• The mandible is trapped by the maxilla because the upper teeth cover the lower ones.

• Functional appliance therapy requires:

  • an increased overjet, ensures the anteroposterior contact between the upper and lower incisors will not stop the mandible growing forward
  • a slightly overexpanded upper arch to prevents the "shoe effect," further allowing the mandible to grow forward.

• Mandibular advancement causes elevators and retractor muscles to contract, pulling the mandible back to its original position.

• This backward and upward force is passed to the functional appliance, which relays it to the upper maxilla, inhibiting its growth through retractive forces from muscular origin.

Dental Action

• Functional appliances include acrylic on occlusal surfaces of posterior and/or anterior areas to manage dental eruption through the location, amount, and cuts of the acrylic.
• Vertical plane appliances affect both incisors and molars, depending on occlusal contact.

Vertical Plane Action

• Posterior interocclusal acrylic is not present, allowing the posterior teeth to erupt vertically through extrusion.
• Posterior interocclusal acrylic thickness exceeds the interocclusal resting distance.
  • Mandibular elevator muscles cause a strong occlusal surface contact against the interocclusal acrylic.
  • This results in posterior teeth experiencing intrusion.
• Anterior interincisal acrylic is not present; the anterior teeth are free to erupt vertically through extrusion.
• Anterior interincisal acrylic is present; the anterior teeth are kept from vertically erupting or extruding.

Transversal Plane Action

• Some functional appliances have acrylic or wire wings that avoid the pressure of the cheeks on the teeth, altering the pressure balancing and supporting expansion by action.
• Others feature palatal and/or lingual components that come into contact with the posterior teeth, increasing passive expansion by delivering mandibular lateral movements.
  • This causes opposing pressures on the support zones. Functional appliances can incorporate springs or screws in the middle zone for active dental arch expansion, where the appliance applies force for expansion.
• Active dentoalveolar expansion can be done on one or both arches with springs or screws.

Sagittal Plane Action

• Contraction of the mandibular muscles tends to pull the mandible back and up.
• The functional appliance transmits this to the lower incisors, causing:
  • Vestibuloversion of the lower incisors occurs if the acrylic comes into contact with the lingual sides of these incisors.
  • Linguoversion of the upper incisors occurs as long as an element (acrylic or wire) touches the vestibular faces of these incisors.

General Indications

• They ensure the most significant potential growth of the bone bases.
• Treatment is effective before the canines and premolars develop, during the onset of pubertal growth.
• Effective at controlling vertical deep bites, and allows the free dental eruption of the back areas.
• They need less chair time and longer appointment intervals than fixed appliances.
• Emergencies are less of an issue since the equipment can be removed, which makes it helpful for individuals who live far away from the office.
• Allow for successful prevention of periodontal disease and tooth decay during therapy.

Generic Appliance Indications

• Patients in active growth with high bone and dental eruption potential.
• Indicated for skeletal Class II mandibular causes.
• Indicated for Class II skeletal mixed causes, when functional appliances with extraoral anchorage are used in combination.
• Brachyfacial patterns indicate the best prognosis for correction of skeletal Class II through functional appliances.
• Required in skeletal Class II, 1 division because the overjet is necessary to advance the mandible.
  • Better if there is incisal retrusion because they produce upper incisor retrusion and lower incisor vestibuloversion.
• Interceptive treatments correct malocclusion before the dentition shifts.
• Retainers after fixed multibracket appliances.

Non-Orthopedic Appliances: Lingual Grids

• Wire components are used to treat open bite by blocking the tongue between upper and lower incisors.
• They can be used with removable appliances, or attachments fixed (quad-helix, lingual arch, transpalatal bar).
• They can be upper or lower appliance

Removable Active Plates

• Active plates or Schwartz plates, are removable appliances that can move teeth and produce dental movements.

• They use inconsistent forces.

• Consist of:

  • acrylic base
  • anchorage elements
  • active elements
  • additional auxiliary elements.

• The acrylic spreads anteriorly to the cingulum of the incisors and posteriorly to the last erupted molar.

• The thickness of acrylic should be ~ 2mm.

• The acrylic functions to:

  • fasten the plate's active components.
  • provide retention and anchorage.
  • turn-on the tooth with force if applicable.

Components for Anchorage

• The hooks or retainers are what hold the plate in place in the mouth and keep it from moving around.

• They are made of 0.7mm wire.

• Adams, ball retainer, circumferential, Schwarz's arrowhead point, loop, and Duyzings.

• Adams Hook is most commonly used.

  • It's commonly made of 0.7 wire.
  • It is most commonly placed at the first molars.

Vestibular Arch

• Stabilizing and anchoring elements run along the vestibular sides of the four incisors.
• It includes a U-shaped loop that stretches down to the canine's gingival third.

Active Elements

• Springs are constructed from various gauges of wire and when activated, exert pressure on the tooth and cause it to become displaced.
• Screws known as expansion screws have the most universal expansion of the arcade.
  • They bend the teeth rather than move them in a single block.
  • They’re great for small expansions.
  • In general, the screw is turned on once a week.
  • Screws enable activation by a quarter turn, which corresponds to a weekly displacement of 0.25 mm.

Indications for Plates

• Lateral crossbites of maxillary dentoalveolar origin.

• Vestibulo-lingual inclination movements of isolated teeth.

• They are generally limited to prepubertal patients, since cooperation is sparse with pubertal or adolescent patients.

• Useful in adults, though effects are similar to adolescents.

Advantages of Plates

• Uses intermittent forces.
• Copies the normal growth of the bone with the palatal sutures.
• Hygiene is greater.
• Great Aesthetics
• Lower Costs
• Simple to arrange
• Faster checkpoints
• Simpler to use

Disadvantages of Plates

• A limited amount of mobility.
• It can cause phonetic problems.
• Complex for arch leveling
• Movement is restricted.
• Full patient participation.
• Long term treatment span
• Absence of any orthopedic effects.
• Skeletal-dental abnormalities have poor outcomes.
• They regularly change.