Importance Of Headgear

Headgear is an extra-oral appliance which makes use of cervical or cranial anchorage to apply forces to the jaws or teeth, with the purpose of growth modification or teeth movement.

PRINCIPLES IN THE USE OF HEAD GEARS

The following factor should be considered when planning the use of head gears.

1. Centre of reisitance of the dentition:

The centre of resistance for a molar is usually at the mid root region. Forces applied at the centre of resistance causes bodily movement.if forces are applied below the centre of resistance then it will cause a distal crown tipping but when applied above the centre of resistance, causes distal root tipping.

2. Centre of resistance of maxilla:

It exists at the posterosuperior aspect of zygomaticomaxillary suture.

• When acting on skeletal tissue they alter the activity of the sutures,preventing the maxilla to go further anteriorly.

• On dental component they tend to distalize the dentition.

• Depending on the type given along with distalization they tend to intrude/extrude the teeth and tip them.

COMPONENTS OF HEADGEAR:

The head gear - face bow assembly has three main components.

1. Face bow

2. The force element

3. The head cap or cervical strap

Face bow:

The face bow is a metallic component that helps in transmitting the extra-oral forces on to the posterior teeth. The face bow consists of outer bow, inner bow and the junction.

The outer bow : It is made of 1.5 mm stiff round wire and is contoured to fit around the face. The outer bow can be short, medium or long.

Short - Outer bow is lesser in length than inner bow.

Medium - Outer bow length is equal to inner bow. Long - Outer bow is longer than inner bow.

The distal end of the outer bow is curved to form a hook that gives attachment to the force

A Bayanet bend

3. Trever Johnson friction stops

4. Ladayni stop screws

The junction : It is the rigid joint of inner and outer bow. It can be simple soldered, wire. wrapped soldered or a welded joint. It is placed at the midline of the bows. When asymmetric forces are needed, the joint can be shifted from the midline.

Types of facebow:

Along with a cervical strap, two types of facebows can be use.

1. Inner-outer bow type. The inner bow is available in either 0.045 or 0.051inch, depending on the size of the headgear tube on the first molar brackets you like to use; the outer bow is usually 0.072 inch. Usually, we prefer the 0.051inch inner bow diameter since it appears not to deform as readily as the 0.045inch size. These facebows are also available prefitted in about five assorted sizes and are very convenient to use.

2. J-hook type. Each J-hook consists of a 0.072inch wire contoured so as to fit over a small soldered stop on the arch wire, usually between the upper lateral incisor & canine.

According to origin of force ,headgear divided into as follows:

Cervical – pull