Dental Problems

Functional Jaw Orthopaedics

In achieving dentofacial efforts, fixed orthodontic appliances generate mechanical forces that are transmitted to teeth. In functional orthodontic appliances, the neuromuscular activity is tapped to alter stresses on teeth and jaw bones. In this article, functional jaw orthopaedics is discussed briefly. Read on to know more.

Functional jaw orthopaedics


Frankel (1974): A functional appliance can be defined as a removable or fixed appliance which favorably changes the soft tissue environment.
Mills (1991): A functional appliance can be defined as a removable or fixed appliance which changes the position of the mandible so as to transmit forces generated by the stretching of the muscles, fascia and/or periosteum, through the acrylic and wirework to the dentition and the underlying skeletal structures.


Functional appliances can be removable or fixed and can also be classified as the following:

  • Tooth borne passive: example -bionator.
  • Tooth borne active: example -Clark twin block.
  • Tissue borne: example -Frankel functional regulator.

The appliances have also been classified, depending upon the components used. Such an appliance has been termed hybrid appliance. The three basic components included are as follows:

  • Eruption -bite planes:

    These may be anterior, flat or inclined and constructed out of either acrylic or wire. They act by encouraging a differential eruption of teeth and by removing intercuspal interferences.

  • Linguo-facial muscle balance -shields or screens:

    The equilibrium theory of tooth position states that over time tooth movement occurs in response to any alteration in the homeostatic relationship existing between the forces from the tongue on one side and the lips and cheeks on the other. The vestibular shields and lip pads of the functional regulator hold the lips and cheeks away from the teeth, thereby disrupting the equilibrium and permitting an unopposed buccal movement of the teeth.

  • Mandibular repositioning -construction or working bite:

    All functional appliances are constructed to a ‘construction’or ‘working’bite. Such registrations are based on the assumption that, by displacing the mandible form its rest position and stretching the muscles attached to it, reflex activity will restore the mandible to a posture determined by the unstretched muscles.


  • Use of functional appliances alone:

    Some patients can be treated by use of functional appliances only, so that an acceptable occlusion can be established. These cases generally have a mild skeletal discrepancy, proclined upper incisors and no dental crowding.

  • Use of functional appliances in combination with fixed appliance:

    This is used most commonly to improve the anteroposterior relationship before starting the fixed appliance treatment. In particular, they are extremely useful in Class II cases and go a long way in reducing the amount of a comprehensive fixed therapy required. It may also reduce the need for orthognathic surgery at a later date.


  • Interceptive treatment:

    Early interventions with functional appliances may be indicated when one wishes to utilize their growth-enhancing effect. In addition, they are extremely effective at reducing the relative prominence of the proclined upper incisors, which are particularly susceptible to dentoalveolar trauma.


Rationale for use:

The theoretical basis behind the functional appliance therapy is that a new pattern of function within the orofacial system (i.e., in the tongue, lips or muscles of mastication), directed by the appliance, leads to the development of a new morphologic pattern (i.e., an altered dental or skeletal relationship). Evidence for these theories come from both animal experiementation and human cephalometric studies.

Effects on the dento-skeletal complex:

The skeletal, dentoalveolar and soft-tissue effects of these appliances have been reviewed by Dare and Nixon (1999).

Skeletal effects:

It has been reported that growth takes place at the condyles during the growth of the mandible by means of a functional therapy. Some amount of growth restriction of the maxilla has also been reported recently.

Dentoalveolar effects:

The dentoalveolar effects of functional appliances include the following:

  • Inhibition of the downward and forward eruption of the maxillary teeth
  • Retroclination of the upper incisors
  • Proclination of the lower incisors
  • Lower labial segment intrusion and
  • Leveling of the curve of Spee and tipping of the occlusal plane.

Effects on soft tissues:

These include the following:

  • Removal of the lip trap and improved lip competence
  • Removal of adaptive tongue activity
  • Lowering of the rest position of the mandible and
  • Removal of soft-tissue pressures from the cheeks and lips

When to treat?

Several factors should be taken into consideration before deciding to go ahead with the appliance therapy.

  • The best time to start the functional therapy is in the late mixed dentition. Thus, several functional appliances -for example, the medium opening activator for an early reduction of a deep overbite as well as for an early reduction of a deep overbite as well as for sagittal correction can be used in this period. Rather than a generalization, girls and boys, along with early maturers should be assessed individually.
  • Advantage can be taken of the pubertal growth spurt so that this active growth phase can be harnessed to optimize the amount of growth restraining effect or growth enhancing effect.
  • In the maxilla, generally the growth needs to be retarded and thus is the growth spurt is not over even after appliance therapy, some amount of growth may lead to a recurrence of the problem. In the mandible on the other hand the growth needs to be enhanced by taking the help of the growth spurt. However, as the growth spurt measured by a longitudinal monitoring of stature, cannot be predicted with any great clinical accuracy, some authors have questioned the use of this appliance.
  • Yang (1997) has suggested the use of a Horse shoe appliance for the treatment of Class II malocclusion, originally suggested by Schwarz (1966). It consists of 2 separate plated for the upper arch and lower arch, and has the advantages of easy construction and prevents extrusion and individual movements of teeth as it covers the whole of upper and lower dentition.

Limitations and complications of functional appliances:

They cane be listed out as:

  • Discomfort, as both the upper and lower teeth are joined together.
  • It mainly depends on the patient’s compliance.
  • It can be used only if a favorable horizontal growth pattern is present in cases of Class II correction.
  • It has to be removed during mastication, particularly when strongest forces are applied.
  • It may interfere with speech.
  • Treatment is often increased -the two-stage treatment may prolong treatment by upto 18 months.
  • Laboratory and technical resources are required for construction and adjustment
  • High cost

The above article discusses briefly about the

functional jaw orthopaedics


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