Headgear..

Geared-upGeared-up
OrthodonticsOrthodontics
Use of HG in day to dayUse of HG in day to daywww.indiandentalacademy.com

• History
• Classification
• Components
• Biomechanics
– Direction
– Magnitude
– Duration
• Clinical points
– Bending of Inner bow
– Bending of Outer bow
• Practical management
• Uses
– For the orthodontics
purpose (with fixed
appliance)
• Anchorage
reinforcement
• Distal movement
• Molar rotation
– For orthopaedic purpose
(with removable/fixed
appliances)
• Splint Headgear
• Activator headgear
• Patient motivation
• Warning and safety
www.indiandentalacademy.com

HistoryHistory
Changing views of treatment with
extra-oral anchorage

ClassificationClassification
of Head-gearsof Head-gears
Headgear appliances are often
described by their relationship
to the occlusal plane :
•Above the Occlusal plane = high pull
•In line with Occlusal plane = combi-pull
•Below the Occlusal plane = low pullwww.indiandentalacademy.com

High Pull Head-gear
No change

Combi-Pull Head-gear
No change

Low Pull Head-gear
No change

ComponentsComponents
1. Molar tube
2. Facebow
3. Force
module
4. Head strap

Components of Head-gear assembly
No change

Molar Tube:
No change

Facebows – types:
No change

Inner-outer bow type
• Commonly used with fixed or
functional/removable appliance.
• Inner bow is available in either:
– 0.045 inch
– 0.051 inch
• Outer bow diameter is :
– 0.072 inch

J-hook type
• An alternative method
of applying extra-oral
forces to a fixed
appliance.
• The hooks are termed
‘J’ hook on account of
their shape and are
attached directly to the
arch wire usually in the
incisor region.

131211
• Each J-hook consist of a 0.072 inch wire
contoured so as to fit over a small
soldered stop on the arch wire.
1 3 1 2 1 1

Force Modules
No change

Head strap
No change

BiomechanicsBiomechanics
1. Direction
2. Magnitude
3. Duration

Force (The only prescription in orthodontics)
• Since force is the treatment agent, it is
imperative to master the fundamental of
biomechanics.
• The design of the force system
predetermines the general direction in
which
– the tooth,
– group of teeth, or
– skeletal unit
responds. www.indiandentalacademy.com

• The quantity of force can be controlled
rather well.
• However, exact prediction of the tissue
response and the growth behaviour in an
individual case is highly speculative.
• It is therefore mandatory to monitor the
mechanics according to the reactions
observed at each treatment visit.

Center of Resistance
• Applying a force through
the center of resistance
will lead to a pure
translatory movement
along the force vector.
• Unless the force direction
is parallel with the
occlusal plane, tooth will
also move vertically
(intrusion & extrusion).

• Applying a force away
from the center of
resistance will lead to a
combination of tranlatory
and rotational movement.
• The amount of rotational
effect will depend on the
distance of the force
vector at right angle from
the center of resistance.

• The relative amounts of
angular change and
translation are determined
by the length of the
shortest distance between
the line of force and the
center of resistance.

• Since the kind of reaction to an applied force
system is so strongly dependent on the sit of
the center of resistance, it is of paramount
importance to estimate where its location will
be.

It is Postulate that …
• The nasomaxillary complex, suspended
as it is by a sutural system comparable
to the desmodermal system of a tooth,
therefore possess a center of resistance.

Some of naso-maxillary complex sutures
• Zygomatico-maxillary
• Fronto-maxillary
• Naso-maxillary
• Zygomatico-maxillary
• Zygomatico-temporal
• Palato-maxillary

• A force vector would
have to pass through
the center of resistance
of the dentition and
through the center of
resistance of the
maxilla if no rotational
effects are to be
induced.

• According to observed
clinical reactions the
location of the center
of resistance of the
maxillary complex
must be somewhere in
the area of the
postero-superiorpostero-superior
aspect of theaspect of the
zygomatico-maxillaryzygomatico-maxillary
suture.suture.

A word of caution:-
• The location of the center of resistance of a
biologic entity cannot be exactly determined in
advance and furthermore is subjected to
alteration by tissue and other factors.

Cervical Anchorage
with low-pull Headgear
Anti-clockwise
Rotation
Clockwise
Rotation
Translation

Occipital Anchorage
with combi-pull Headgear
Anti-clockwise
Rotation
Clockwise
Rotation
Translation

Parietal Anchorage
with high-pull Headgear
Anti-clockwise
Rotation
Clockwise
Rotation
Translation

Direction of force application is further
affected by:
1. Length of outer-bow of the facebow.
2. Angulation of the outer-bow relative to
the inner-bow, in the horizontal plane.

• Rather than considering in detail all
possible combinations of variables, it is
best to understand only a few.
• The essential issue is the relationship
between the direction of the extra-oral
force and the center of resistance of the
unit to be moved.

Varying Outer Bow Length
No change

Magnitude of ForceMagnitude of Force

Magnitude of Force
No change

Clinical pointsClinical points

The effect of a typical kloehn cervical
headgear

Headgear with edgewise strap up and
initial levelling wire

Control on inter-molar width with
Transpalatal Arch (TPA)

Use of headgear for retraction of molar and premolars

For the expansion of upper arch

Patient MotivationPatient Motivation

Controlling Factors
• The effectiveness of HG therapy is
influenced by factors controlled by the
orthodontist, such as :
– Direction & Magnitude of HG force
• And by factors that are largely under the
control of the patient, such as:
– Duration of HG wear or patient compliance.

• High degree of co-operation on the part of the
patient is a must.
• Best to fit the headgear at the commencement
of the treatment, because it is difficult to
increase the patient’s motivation part way
through treatment.
• Motivation can often be maintained with the
use of charts which the patient completes to
record the time the appliance is worn each
day.
This is an optional slide as Prof can talk a lot on this topic.

Warning and SafetyWarning and Safety

Inform both, the patient and his/her parents :-
1. Hold the bow in the mouth while the traction
force is engaged or disengaged.
2. Immediately hold and restrain the bow if it
becomes loose.
3. No vigorous activity when wearing the
headgear.
4. Never wear the headgear without the safety
device being in place.
5. Report any damage or breakage of the
appliance as soon as possible.
6. Stop wearing the headgear, and contact the
orthodontist if the bow comes out at night.www.indiandentalacademy.com

Headgear..

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Headgear..