INTRODUCTION

Functional appliance have been known since the beginning of the 20th century. Dentists are aware of the role of perioral musculature in malocclusion. The forces created under control can be used to eliminate malocclusion. Myofunctional therapy is defined as the treatment that transmits, climates or guides natural forces of the orofacial musculature that are transmitted to the teeth and alveolar bone through the medium of loose fitting passive appliances to achieve changes in jaw position and tooth alignment.

Graber (1963) described three M's "Muscles, malformation and malocclusion" and effects of function and malfunction to mechanics oriented profession that was at that time treating patients according to cephalographs.

Pierre Robin (1902) presented first appliance at an orthodontic meeting in France. The appliance was one piece or 'monobloc' appliance constructed to hold the mandible in a forward position.

Woods MG (1996) concluded that myofunctional appliance can be used to reduce the severity of the malocclusion, before a routine fixed-appliance detailing phase.

MODE OF ACTION OF FUNCTIONAL APPLIANCE THERAPY

Haupl (1935) concluded that the only mode of force appliance that can build up tissue is "passive" since with continuous active forces bone remodelling cannot take place.

• A primary objective of functional appliance is to take advantage of natural forces and transmit them to selected areas to produce the desired changes.

• Recently Collett AR (2000) concluded that myofunctional therapy helps in mandibular growth stimulation.

• Success of functional appliance therapy depends on neuromuscular response. Therefore children with neuromuscular disease like cerebral palsy, poliomyelitis can not be treated successfully with functional therapy.

CLASSIFICATION OF MYOFUNCTIONAL APPLIANCES

I. Group I appliance These appliances transmit muscle force directly to the teeth. e.g. inclined plane, oral screen.

Group II appliance These appliances reposition the mandible downward and forward (except in class III malocclusion), activating the attached and associated invasculature. The resultant force that is created is transmitted to teeth as well as to other structures. Both maxilla and mandible are involved. e.g. Activator.

Group III appliance These appliances bring about mandibular changes through musculature only. Their major operating area is in the vestibule outside the dental arches. Supporting bone and teeth are influenced by changing the muscle balance through cheek shields and lip pads. e.g. Frankel FR.

II.Tooth borne active appliances: These are largely modifications of activator and bionator designs that include expansion screws or springs to move teeth. e.g. Expansion activator, Orthopaedic corrector. •Tooth borne passive appliances. These appliances have no intrinsic force generating capacity from springs or screws and depend only on soft tissue stretch and usual activity to produce treatment effects e.g. activator, bionater. •Tissue borne appliance. The appliance has minimal contact with teeth and is located in vestibule. e.g. Functional regulator.

III.Myotonic ApplianceThese appliance depend on muscle mass for their action.Myodynamic applianceThese appliances depend on muscle activity for their action.

IV.Removable Functional AppliancesThese appliances can be removed and inserted into mouth by patient.Fixed functional appliances. These appliances cannot be removed by the patient.

Advantage

• Permit normal function of the lips and tongue in relation to dental arches. • Early treatment can intercept a developing malocclusion at a time when maxillary incisors are more vulnerable to fracture and loss. It also avoids the psychological disturbances associated with malocclusion. • Normal oral hygiene can be maintained. • Less chair side time spent and less frequent adjustment appointments.

DISADVANTAGES

• It is only effective in patients who are in active growth phase and can not be used in adult patients in whom growth has ceased. • The tooth movements are limited to simple tipping of the teeth only. Do not permit controlled individual tooth movements such as rotations and torque. • Cannot be used in patients with increased lower face height; a vertical growth pattern and proclined lower incisors. • Patient's cooperation is essential for successful treatment i.e. it depends on patient for timely wear of appliance. • These appliances are often bulky and make it difficult for the patient to breath through mouth and may interfere with speech.

INDICATIONS

• Patients who are in active growth phase. • Mild to moderate sagittal skeletal discrepancy. • Reduced, normal or moderately increased anterior face height. • Anticipated down ward and forward mandibular growth direction. • No missing teeth. • No severely rotated or tipped teeth. • Lower incisors well aligned to the profile. • Minimal excess of space or crowding of the dental arches. • Normal airways (nose breath). • Patient should be positively interested in treatment.

CONTRAINDICATIONS

• Patients who are near prepubertal growth, post puberty and adults. • Unfavourable facial morphology i.e. increased lower anterior face height and with vertical growth pattern. • Severally malposed teeth and severe crowding and spacing. • Poor patient cooperation. • Patient is a mouth breather, suffers from adenoids, allergies or has speech problems.

DIAGNOSIS

A careful diagnosis of the individual patient is an important basis for the decision to treat a malocclusion with functional appliance. (a) Facial morphology: A particular concern is the anterior vertical face height. Patients with an increased lower face height generally have a posterior direction of condylar growth with very little vertical growth. This promotes a clockwise or backward rotation of the mandible during treatment resulting in an undesirable increase in anterior face height. (b) Dentoalveolar compensation: In a patient with a class II malocclusion, dentoalveolar structures will after have attempted to compensate for the skeletal discrepancy which is mostly seen as a proclination of lower incisors where as the maxillary incisors will be more upright with a decrease in maxillary alveolar protrusion. Recognising compensatory development is important both for the timing of treatment and with respect to treatment approach. (c) Growth pattern Patients with a normal or reduced anterior face height in most instances have a downward and forward growth pattern of the mandible. In contrast patients with an increase lower face height tend to grow more in a vertical direction. (d) Stage of maturation Functional appliances are most efficient in an active growth phase and should normally only be used in growing patients. The best time is either early around 7 to 8 years of age when the skeletal growth rates in most children demonstrate an early increase or later during puberty.

The various analysis used for diagnosis for functional appliance therapy:

• Down Analysis • Steiner Analysis • Dental Analysis • Functional Analysis

Timing of Treatment

• In boys treatment is usually initiated at the beginning of the growth spurt where as in girls who usually have a less of pronounced spurt, treatment should ideally be started 1 to 2 years before the pubertal growth maximum and not delayed until the onset of the spurt.