Biomechanics of headgears in orthodontics /certified fixed orthodontic courses by Indian dental academy

INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com


INTRODUCTION:
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To achieve a harmonious dentofacial relationship as a result of
orthodontic treatment, extraoral devices using the neck or
cranium as anchorage have been employed.
These extraoral appliances have been used to influence the
maxillary and mandibular growth patterns by inhibiting and/or
redirecting their normal growth potentials in children before and
during maximal pubertal growth.
The efficient use of the headgear requires a sound knowledge of
basic biomechanics. Understanding how to control the direction
and magnitude of the forces produced by various headgear
designs is paramount in achieving desirable clinical results.


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Decreasing the patient's length of treatment and improving the
treatment results would be only two of the benefits derived from
applying well-planned force systems.

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The use of headgear therapy is very common in the treatment of
Class II and class III malocclusions as well as to distalise the
maxillary dentition. Extraoral maxillary traction appliances are
used to improve the dental relationship between the maxilla and
the mandible, as well as the skeletal relationship between the two
jaws.


COMPONENTS OF HEADGEAR:
The principal components are
 Force delivering unit: usually a facebow or a J hook that delivers
force to the intra oral location
 Force generating unit: this is the active unit- usually springs of
elastic bands
 Anchor unit: its location depends on the direction of the force
applied, and is usually from the neck or the head.
Force is transmitted to the dental arch by
 Facebow: the force is delivered to the first molar by the face bow
which is engaged in the buccal tube. It can be attached to
removable appliances also. The facebow has an inner and an outer
bow. The inner bow is available in either 0.045-0.051 inch,
dependent on the size of the headgear tubes on the first molars.
The outer bow is usually 0.072 inch.

The different methods of making the inner bow stop mesial to the
first molar buccal tube are
 u- loop: advantage is that the length of the arm can be altered
by adjusting the loop;
 Bayonet bend: horizontal inset bend that keeps the anterior
segment of the bow away from the brackets.
 Friction stops: stops can be fixed at the desirable location by
crimping it
 Stop screws: the position of these screws can be changed and
can be re-used.
Outer bow is attached to the anchor unit and can be of different types
depending on its length:
 short- outer bow shorter than the inner bow
 medium- outer bow almost the same length as that of the inner
bow
 long- outer bow is longer than the inner bow

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Facebows can be used to control all three dimensions: vertical,
sagittal and transverse both dental and skeletal.
Facebows can be used to apply force to specific teeth or to the
entire arch. It can serve as an orthopedic appliance to modify
mandibular and maxillary growth vectors.
Facebows are primarily used for their ability to produce sagittal
changes. This is the traditional use of the straight pull or the
cervical pull.
High pull is often used for the vertical, intrusive force which can
be applied to the maxillary molars or the entire maxillary arch.
Maxillary molar buccal tubes can be either occlusal or gingival.
Advantage of placing the tube gingivally is that the tube is closer
to the center of rotation of the molar, which reduces the molar
tipping effect and is advantageous in conditions where only molar
movement is desired.

If the facebow is used for orthopedic correction, it is
advantageous to place the tube occlusally because the patient finds
it easier to insert the inner bows into the tubes. If omega loops are
to be used, then these loops can block gingivally placed headgear
tubes.
Adjustments to the inner bow can be made in
 buccolingually
 superoinferiorly
 anteroposteriorly
Buccolingual: If the bow is inserted into one headgear tube, the
other bow should be expanded 5 mm buccal to the opposite tube.
As the patient fully engages the appliance, he must constrict the
inner bow slightly. This will create expansive force on the molars.
If maxillary expansion is desired and facebow is being used, a
greater amount of expansion must be built in the inner bow. If
constriction of the maxillary arch is desired, then the inner bow
must be constricted.
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Superoinferiorly: when the patient closes his mouth
and relaxes his lips, the anterior junction of the inner
and outer bows should not be pushing either lip in a
vertical direction and it should be in a passive position.
 Anteroinferiorly: the facebow should be placed so that
the inner and outer bow junction is just anterior to the
point where the lips seal. It may be necessary to enlarge
or constrict the loops in the inner bow to achieve this
position.
Unilateral face-bows – Hershey (AJO 1981)
 Face-bows which successfully and predictably provide
an asymmetrical delivery of distal force to their innerbow terminals are termed "unilateral face-bows”.
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There are four types of unilateral facebow designs available:
 Power-arm face-bow. In this design,
one outer bow is longer and/or wider
than the other, with the longer or
wider bow tip located on the side
anticipated to receive the greater distal
force. While effective in producing
unilateral distal forces, the power-arm
face-bow also generates lateral forces
which tend to move the favored molar
tooth into lingual cross-bite and the
other molar into buccal cross-bite.
Soldered-offset face-bow. Here the outer bow is attached to the
inner bow by a fixed soldered joint placed on the side favored to
receive the greater distal force.

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Swivel-offset face-bow. In this design the outer bow is attached
to the inner bow through a swivel joint located in an offset
position on the side favored to receive the greater distal force.
Spring-attachment face-bow. Here an open coil of spring is
wrapped around one of the inner-bow terminals of a
conventional bilateral face-bow. The coil is placed distal to the
stop on the side favored to receive the greater distal force.
Yoshida et al in AJO 1998 evaluated the effects and side effects
of asymmetric face-bows. They suggested that the power arm
face-bow is thought to be relatively recommendable because it
showed an acceptable asymmetric effect and is easily fabricated
from a commercially available face-bow. They concluded that all
asymmetric face-bows generate lateral forces as side effects as
long as the force delivery system with a combination of an
asymmetric face-bow and a neck strap or head cap is applied.

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J hook: each J hook consists of a 0.072 inch wire contoured so
as to fit over a small soldered stop on the archwire, usually
between the upper lateral incisors and the canines.

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Headgears are available in a wide variety of configurations, each
programmed to deliver force in a predetermined direction. The
direction of force determines the general direction in which a
tooth, a group of teeth or skeletal unit responds.


CLASSIFICATION
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1. Headgears can be classified according to the area of attachment into
 cervical area of the neck (cervical strap)
 occipital area of the head (occipital strap)
 the chin (chin cup)
 frontal or reverse pull
 combination of cervical and occipital (straight pull or combee)
 very high pull (parietal)
2. according to the purpose of usage:
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A. growth modulators
1. Protractors
2. Retractors
3. To control vertical excess
A. reverse pull
A. high pull
A. chin cup
B. straight pull
C. cervical pull
D. combination
B. for space regaining
C. molar distalisation
D. intrusion of maxilla www.indiandentalacademy.com

SELECTION OF HEADGEAR:
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1. Headgear anchorage location: location of the anchorage unit
determines the type of force that will be applied to the unit. The relation
of the force to the Cres of the unit to which it is applied determines the
effects that will be produced by the orthopedic force.
 High pull headgear: this applies a superior (intrusive) and distal
force to the maxilla and the maxillary dentition.
 Cervical pull: this produces an inferior (extrusive) and distalising
force on the maxilla.
 Combination headgear: no moment is produced and a distalising
force is applied to the maxilla.
Since the Cres of the molar is located in the mid root region, force
vectors above this point will result in a distal root movement. Forces
below this point will result in a distal crown movement. Similar
considerations apply to the maxilla.


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2. Age: according to proffit, the ideal age to begin modifying
growth is around 8 years (because in some cases, juvenile
acceleration of jaw growth occurs at the age of 7-8 yrs just before
pubertal growth spurt). It is important to begin growth
modification early in girls, since girls undergo pubertal changes
by an average of 2 yrs before boys. The treatment of skeletal
malocclusions is usually done at the age of 8-9 yrs in girls and 1011 yrs in boys depending on the developmental status.

Selection based on MPA (according to Alexander)
 A low angle or normal growing (SN-MP< 37 0) case is suitable for
cervical headgear.
 If SN-MP is between 37-410, a combination headgear is used.
 If SN-MP>410, then a high pull HG is used.

Based on occlusal plane requirements:
Action desired
extrusion and steepening
extrusion and flattening
intrusion and steepening
intrusion and flattening
distal force and flattening
distal force and steepening
distal force and no moment

headgear type
cervical HG; outer bow even or low
cervical HG; outer bow very high
high pull HG: outer bow postr to
Cres
high pull HG; outer bow antr to
Cres
combination; outer bow above Cres
combination; outer bow below Cres
combination; outer bow at Cres


IDEAL PATIENTS FOR TREATMENT WITH HEADGEARS:
1. Patients with maxillary excess:
 Ideal patients for treatment with extraoral force against the maxilla show
 skeletal class II malocclusion with a component of excessive
horizontal or vertical growth of the maxilla
 some protrusion of maxillary teeth
 Reasonably good mandibular dental and skeletal morphology as this
will be minimally affected by extraoral forces.
 Potential for continued mandibular growth
2. Patients with horizontal maxillary deficiency:
 These patients are ideal candidates for treatment with extraoral forces
using the reverse pull headgear. This causes reciprocal downward and
backward rotation of the mandible. Ideal patients should have
 normally positioned or slightly retrusive but not protrusive maxillary
teeth
 normal or short but not long anterior facial height
 ideal age of 8 yrs

3. Patients with vertical maxillary excess:
 In these patients, restriction of vertical maxillary growth is needed
along with an augmentation of mandibular growth that is left.
Control of vertical eruption of teeth in both the arches is
important.
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high pull headgear for upper molars is given
Interocclusal bite blocks can also aid in prevention of eruption of
posterior teeth. E.g. high pull HG with functional appliances.

Ideal patients are
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long face patients
skeletal open bite


USES OF HEADGEARS:
 Anchorage reinforcement is the most common use of
headgear and is used when intraoral sources are insufficient.
 distalisation of upper molars when used in the treatment of
class II
 space maintenance after extraction
 canine retraction using J hooks – for anchorage conservation
 overjet reduction – Ashers facebow is used to retract upper
and lower anteriors simultaneously
 intrusion of molars and incisors using high pull headgear
 Growth redirection: when used as an orthopedic appliance,
headgears can redirect or inhibit maxillary growth and allow
normal growth to express clinically by removing
dentoalveolar compensations.


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Expansion or contraction of the arch: distal driving of molars
can result in cross bite as the arch expands posteriorly. This
can be avoided by having the facebow expanded in the molar
region by about 3-5 mm. This method can be used for the
correction of crossbite with headgears.
Uprighting of molars
space closure
torquing roots
Correction of rotations of molars.
Restriction of mesial drift of teeth associated with age.
Reduction of the eruption of teeth into the intermaxillary
growth space.


HEADGEAR BIOMECHANICS:
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The prescription in orthodontics is force application. The
mechanical influence of the appliance produces a reaction in the
biologic system under stress. Local response can be anticipated
in the affected tissues. If force is applied during growing period,
a modification of growth dynamics is evident. Force systems a
headgear can deliver depends on the magnitude, direction, point
of application and its line of action. To determine the effect of
the headgear force, the line of action of the force with respect to
the body to which it is applied – tooth, arch or the maxilla has to
be examined. Hence, knowledge of the approximate location of
the body’s center of resistance is essential to choose the force
system desired in treatment mechanics.


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Force magnitude: Recommended force values per side for
 full permanent dentition – 400-600 gms
 early mixed dentition – 150-250 gms
 late mixed dentition – 300-400 gms
 Retention in permanent dentition – 150-400 gms.

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Duration: according to Graber, forces of 12-16 hour duration
applied as intermittent forces appear to be the most effective for
orthopedic changes. Because the headgear is tooth borne,
intermittent force minimizes tooth movement while still
providing for skeletal change. An intermittent heavy force is less
damaging to the periodontium and the teeth.

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Force direction or vector: this depends on the location of the
extraoral attachment and the location of the outer bow.

Center of resistance of maxilla:
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Miki 1979 and Hirato
1984 reported that the
location of the center of
resistance in the midface of
the human skull is between
the first and second upper
premolars anteroposteriorly,
and between the lower
margin of orbitale and the
distal apex of the first molar
vertically in the sagittal
plane.


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Lee in AJO 1997 determined the Cres of the maxilla
using holographic inferometry. They found that the
Cres of the maxilla was located at the distal contacts of
the maxillary first molars, one half the distance from
the functional occlusal plane to the inferior border of
the orbit. Hence the application of 500 gms per side of
force applied 15 mm above the occlusal plane and
directed 200 downward from the occlusal plane
produced pure translatory movement of maxilla.
Protraction of maxilla below the CRes produces
counterclockwise rotation of the maxilla. They
suggested that by varying the force system, the amount
and direction of maxillary rotation might be controlled.

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The center of resistance of the
dentomaxillary complex when
viewed in the sagittal plane is
located on a line perpendicular to
functional occlusal plane at the
distal contact of first maxillary
molars. When viewed in the
frontal plane, there are two
centers of resistance since the
dentomaxillary
complex
is
essentially comprised of two
bones that articulate with each
other at the mid palatal suture. If
forces are applied in the presence
of a 0.036 stainless steel TPA or a
sutural expander, then the two
units act as a single unit.

Clinical location of the Cres: (angle
1999 Stanley Braun)
 The location of the Cres clinically is
important. This can be done by
holding an amalgam plugger or
similar instrument in the maxillary
vestibule when the teeth are in
occlusion and the soft tissues and
lips are relaxed. The amalgam
plugger is positioned at the Cres of
maxilla. The instrument is then
palpated externally and a mark is
made on the skin surface
corresponding to it. The procedure
is done for the other side also. The
outer bow may then be adjusted so
that the force vector passes through
this point.

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Tanne et al concluded that the Cres of the maxilla was located at
the posterosuperior ridge of the pterygomaxillary fissure. He
suggested that the nasomaxillary complex was suspended by a
sutural system similar to the desmodontal system of a tooth,
possessing a Cres.

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Since the handle for applying force to the maxilla is the teeth, a
given force vector must be analyzed relative to both the Cres of the
dental units (which lies between the bicuspid roots) as well as to the
Cres of the skeletal unit. If no rotational effect is desired, then the
force vector must pass through the Cres of both the skeletal and
dental units. The force passing through both centers of resistance
will lead to pure translatory reactive movement with the centers of
rotation at infinity.

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When planning the direction in which
the dental and skeletal units should
move to approach a given treatment
goal, the effect of growth on the
development of these structures must
also be considered. The force vector and
the growth vector together determine
the resultant vector of spatial
displacement. The tendency towards
extrusion or intrusion in the molar or
incisor regions will be determined by the
direction of force vector and notably by
the rotational tendencies derived from
the relation of the force vector to the
center of resistance.
The least rotational and vertical change is obtained in an arrangement
wherein the applied force vector passes through the Cres of the upper
arch and the maxilla and this is the desired condition for vertical
control.

TYPES OF HEADGEARS:
CERVICAL HEADGEAR:
 This was first introduced by SILAS
KLOEHN in 1947. It is the most
commonly used facebow in clinical
practice. Typically it is used in growing
patients
with
decreased
vertical
dimension. The purpose of the facebow
is to restrict the forward growth of the
maxilla. The vector of force is below the
occlusal plane producing both extrusive
and distalising effects.
Component parts:
 molar tubes with headgear tubes
 inner and outer bow soldered together in
the center
 A neck strap that is placed around the
back of the neck to provide traction to
the dentition.

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Effects of cervical headgear:
 to erupt the entire upper jaw
 tends to move the upper jaw distally
 Steepen the occlusal plane.
 Expansion of the upper arch.

Effect of different positions of the outer bow:
when the outer bow is bent upwards:
The forces that are produced are
A distalising force to the upper teeth, which is good for correction
of class II relation.
When the outer bow is bent upwards, bringing it down to the
occlusal plane tends to produce a negative moment that flattens the
occlusal plane. Hence the steepening effect of the cervical headgear
is nullified.
Eruption of the entire upper arch tends to increase the mandibular
plane angle and tends to worsen the class II skeletal relationship.
this type is good for patients with forward growth rotation

when the outer bow is bent
downwards:
Forces that are produced are

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Positive moment on the occlusal plane
is seen that tends to steepen the occlusal
plane since the pull is below the Cres.
Extrusive force and a distalising force.

When the outer bow and inner
bow are in the same level, no
moment is produced and there is a
net distalising and extrusive force.
When the outer bow is shorter than the inner bow, the headgear strap
hook is placed too far anteriorly. This results in a greater tendency to
steepen the occlusal plane when the straps are engaged. The pull of the
bow is further forward from the Cres and this tends to steepen the
occlusal plane. When the outer bow is long, there is a tendency to
flatten the occlusal plane.

Kloehn headgear can be used to
 distalise the entire maxillary segment
 anchorage reinforcement
 retraction of upper incisors
 correction of class II molar relationship
 Correction of crossbites.
 Cervical headgear is used early in the treatment of class II
malocclusions to inhibit forward displacement of maxilla or
maxillary teeth, while rest of the dentofacial structures continue
their normal growth.
Advantages
 Direction of pull is advantageous in treatment of short face class
II maxillary protrusive cases with low MPA and deep bites.
Disadvantages:
 It normally causes extrusion of the upper molars. This
movement is seldom desirable except in patients with reduced
lower anterior facial height. It is contraindicated in patients with
steep mandibular planes and in open bite cases.

Studies on cervical headgear:
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Cook et al in AJO 1994 studied growing children with Class
II, Division 1 malocclusions who were treated with two different
techniques: one group with orthopedic cervical headgear/lower
utility arch (CHG/LUA) and another with cervical headgear alone.
The outer bow was bent 200 upward and the inner bow was
expanded. A force of 450 gms was used on either side. The authors
found that CHG produced Class II correction through maxillary
orthopedic and orthodontic changes, did not cause the upper molar
to extrude beyond the amount seen with normal eruption, and did
not produce an opening rotation of the mandible even in those
patients who had dolichocephalic facial patterns.

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Mirja Kirjavainen in AJO 1997 evaluated the effects of the
cervical headgear therapy with an expanded inner bow to treat Class
II malocclusion and dental arches.

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The cervical headgear was used with a 10 mm expanded inner
bow and a 15° upward bend of the long outer bow, 12 to 14
hours a day with a force of 500 gm per side. Class I relationships
were achieved in all subjects in 15 months. At the same time, the
maxillary and mandibular dental arches were widened.
Melsen et al in AJO 2003 studied the intramaxillary molar
displacement 7 years after treatment with Kloehn headgear and
cervical traction. Two groups of 10 patients were studied. In one
group, the outer bow was tilted upward by 200 and in another
group, it was tilted down by 200. In the group that had the outer
bow tilted downwards, molar correction was faster. In both the
groups, the maxilla was moved backward and downward. A
strong tendency of the molars to return to the key ridge was
demonstrated, and there was no evidence that the Class I
relationship obtained by extraoral traction was more stable than
that obtained by functional or intramaxillary appliances.

OCCIPITAL HEADGEAR:
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The occipital headgear consists of a facebow
which fits over the occiput of the head. The
force generated by a high pull (occipital) has
both distalising and intrusive forces since
the force is exerted above the occlusal plane.
Such forces are used in conditions where
vertical control of the molars is important.
As growth guiding appliance, a high pull
headgear can decrease the vertical
development of the maxilla, thereby
allowing for autorotation of the mandible
and maximizing the horizontal expression of
mandibular growth.
Occipital pull with short outer bow (force anterior to Cres)
This results in a force system at the unit’s Cres with a moment that
tends to flatten the occlusal plane and creates distalising and intrusive
components.

b.
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occipital pull with force
passing through Cres
In this configuration, there is no
moment that is created and hence
there is no change in the cant of
the occlusal plane. Intrusive and
distal components of force are
produced.

c. occipital pull with long outer
bow( force posterior to Cres)
 The force system at the unit’s
Cres has a moment that tends to
steepen the occlusal plane.
Intrusive and distalising forces are
produced. This system might be
required in class II open bite
patients.

Advantages:
 These headgears can be used in patients with steep mandibular
planes and in cases wherein mandibular growth is more vertical
than horizontal. They can also be used in certain open bite cases
caused due to excessive eruption of buccal teeth.
Studies on high pull headgear:
 Firouz et al in AJO 1992 examined the skeletal and dental
effects of the high-pull extraoral appliance, when the resultant
force was directed through the level of trifurcation of the
maxillary molars. Patients wore the headgear for a 6-month
period, an average of 12 hours a day. The authors found that by
directing the force of the headgear approximately through the
center of resistance of the maxillary molars, it was possible to
translate the molars in the direction of the applied force. Hence
both intrusion and distal movement of the molars can be
achieved at the same time..


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Burke and Jacobson in AJO 1992 evaluated vertical
changes in growing patients with high MPA Class II,
Division 1 malocclusions who were treated with
cervical and occipital headgears applied from different
angles relative to the occlusal plane. They found greater
vertical changes in pts with cervical HG. The changes
in occlusal plane between the two types of headgears
were most significant. Posterior maxillary dentoalveolar
changes between the two groups were significant.


COMBINATION HEADGEAR.
Combination headgears have both occipital
and cervical traction springs. This is perhaps
the most versatile type because the pull can
be readily controlled by selecting the force
level of the springs and by controlling the
length of the outer bow. For distal translation
of the upper posteriors, a distal traction is
needed that passes through the Cres, neither
above nor below. The combination type
headgear will allow a distal force straight
through Cres by having equal occipital and
cervical components on the outer bow, which
is angled upwards to allow the force to pass
through the Cres.

J PULL HEADGEAR:
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This headgear consists of two separate
curved hooks which are attached directly
onto the maxillary archwire in the anterior
region. This type of headgear is most
commonly used for the retraction of the
canines and incisors rather than for
orthopedic purposes. J-hook HG is
limited in use only with a maxillary fixed
appliance and a continuous arch wire. It is
preferable if all the teeth are included in
the archwire. The intraoral point of
attachment is directly to the maxillary
archwire, distal to the lateral incisors. This
HG is mainly used to retract and intrude
the maxillary incisor teeth and to prevent
or correct ‘gummy smiles’.


ASYMMETRIC HEADGEARS:
Haack&Weinstein AJO 1958:
 Fundamental
principle involved in the
distribution of the forces to the right and left
molars is the geometry of the direction of the
right and left forces emanating from the
cervical elastic band. If these forces are
symmetrical with reference to the midsagittal
line of the head, then the distribution of the
reactionary forces at the right and left molars
will be equal, irrespective of the design of the
rigid portions of the appliance (or the point of
attachment of face-bow to arch wire).
If the direction of forces from the cervical elastic band is asymmetrical with
respect to the midsagittal line of the head, then the anterior-posterior
components of the reactionary forces on the right and left molars will be
unequal, the molar nearest the resultant of the two elastic band forces
receiving the greater force. Small lateral forces on the molars are always
developed by this eccentric design.

REVERSE PULL HEADGEAR
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Maxillary
protraction
is
recommended for skeletal Class III
patients with maxillary deficiency.
Delaire and others used face mask
for maxillary protraction. Petit later
modified Delaire’s concept by
increasing the amount of force
generated and thus reducing the
overall treatment time. In 1987,
McNamara introduced the use of
bonded acrylic expansion appliance
with acrylic occlusal coverage for
maxillary
protraction.
Turley
improved patient co-operation by
fabricating customized facemasks.

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The principle of maxillary
protraction is to apply tensile
force on the circumaxillary
sutures and thereby stimulate
bone apposition in the suture
areas; in doing so, the maxillary
teeth become the point of force
application, and the face
(forehead, chin, zygoma) or
occipital area becomes the
anchorage source. Literature
reveals that early treatment with
a maxillary protraction appliance
is effective in correcting the
Class III malocclusion due to
maxillary retrusion.


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Class III skeletal patterns often
exhibit a high incidence of deficient
transverse maxillary growth and
maxillary expansion is often the first
treatment procedure. McNamara
and Turley have recommended the
use of bonded rapid palatal
expansion appliance for several
days before beginning protraction in
order
to
facilitate
maxillary
movement. After active protraction
of the maxilla, retention is vitally
important in maintaining the
treatment effects of the facemask.
Petit suggested the Fränkel III
regulator be used for 6 months
postprotraction.

Treatment effects of face mask:
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The maxilla moves downward and forward with a
slight upward movement in the anterior and downward
movement in the posterior palatal plane as the result of
protraction force; at the same time posterior teeth
extrude somewhat. As a consequence, downward and
backward rotation of the mandible improves the
maxillomandibular skeletal relationship in the sagittal
dimension but results in an increase in lower anterior
facial height. This rotation is a major contributing
factor in establishing an anterior overjet improvement.
According to sung et al in AJO 1998, face mask
produced an increase in the effective length of the
maxilla and a decrease in the length of the mandible.
Protraction groups show an inhibition of mandibular
growth.

Design and construction
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An adjustable anterior wire
with hooks is connected to the
midline
framework
to
accommodate a downward and
forward pull on the maxilla with
elastics. To minimize opening of
bite as the maxilla is repositioned,
the elastics are attached near the
maxillary
canines
with
a
downward and forward pull of 300
to the occlusal plane. Maxillary
protraction generally requires
300-600 gms of force per side.
Patients are instructed to wear the
appliance for 12 hrs a day.

Design and construction of the anchorage system
Banded palatal expansion appliance

In the mixed dentition, banded palatal expansion appliance is
constructed by using bands fitted on the maxillary primary second
molars and permanent first molars. Molar bands are joined by
soldering a heavy wire (0.043 inch) to the palatal plate and a hyrax
type screw is placed in the midline. The appliance is activated twice
daily (0.25 mm per turn) for one week. In patients with constricted
maxilla, activation is carried out for two weeks or more depending on
the discrepancy.
Bonded palatal expansion appliance

This appliance incorporates a hyrax type screw into a wire
framework made from 0.040 inch that extends around the buccal and
lingual surfaces of the dentition. The primary molars and permanent
first molars are covered with acrylic. A separate wire is bent to cross
the occlusion between the primary first and second molars and ends
with a hook for protraction with elastics.

Appliance design:

The facial mask consists of a forehead pad and a chin pad
that are connected with a heavy steel support rod. A crossbow is
connected to support this rod to which are attached rubber
bands to produce a forward and downward elastic traction on
the maxilla. The position of the pads and the crossbow can be
adjusted simply by loosening and tightening set screws within
each part of the appliance.


The orthopedic facial mask system introduced by
McNamara in 1987 has a bonded RPE in addition to the facial
mask and elastics. Protraction with expansion can also be done
using a banded palatal expander, a quad helix, slow expansion etc


SEQUENCE OF ELASTICS.
SIZE
At the time of delivery
3/8 ”
After 2 weeks
1/2 ”
Increased to a maximum of 5/16”




FORCE
8 oz
14 oz

DURATION
2 weeks

Young patients (4-9 years of age) should wear the mask on a full time
basis except during meals. Duration is 4-6 months. They can be retained
with only night time wear or with a maintenance plate, chin cup or FR
III. In older patients, it is worn at all times except during school.


Force application:


According to Delaire, Nanda et al in AJO 1978 and other
biomechanical studies and clinical reports on maxillary protraction,
upward and forward rotation of the maxilla occurs when
protraction force on molars is applied parallel to the occlusal plane.
This type of maxillary rotation can be minimized when the force is
applied in the canine area, 20° to 30° below the occlusal plane.
Nanda found that with the same line of force, different midfacial
bones were displaced in different directions depending on the
moments of force generated in the sutures. Kokich and Shapiro in
AJO 1979 found that anterior positioning of the maxillary complex
was associated with a small amount of counterclockwise rotation
during treatment. Protraction of maxilla below the Cres produces
counterclockwise rotation of maxilla. Hata et al in AJO 1987 found
that the counterclockwise rotation can be counteracted by applying
a heavy downward vector of force.

FACE MASK WITHOUT EXPANSION






Baik (AJO 1995) studied on protraction with labiolingual
stabilization of maxilla. He compared this with a group of patients
with protraction and expansion using banded RME. His study was in a
group of maxillary deficient children, 8-13 yrs of age. He found
significantly greater forward movement of the maxilla (+2 mm) in
protraction with RME compared to protraction with out RME
(+0.9mm). In the same study, greater forward movement of the
maxilla (+2.8mm) was found when protraction was initiated during
maxillary expansion compared with protraction after expansion.
This study shows that better results are obtained with protraction
during expansion. Also, protraction without expansion is inferior.
According to several authors, palatal expansion is used to disarticulate
the maxilla and initiate cellular response in the circummaxillary sutures,
allowing a more positive reaction to the protraction forces.



Orthopedic effects require greater forces than do
orthodontic movements. Successful maxillary protraction can be
achieved by using 300-500 gm of force per side in the primary
and mixed dentition. Most studies recommend wearing the
headgear for duration of 12 hrs/day. According to Hata et al,
effective forward displacement of the maxilla can be obtained
clinically by applying a force 5 mm above the palatal plane. In
deep bite cases, a forward pull from the level of the maxillary
arch with a concomitant anterior rotation of the maxilla aids in
treatment. Several clinical studies report that a 300-450 forward
and downward protraction force applied to the canine region
produces an acceptable clinical response.


Sutures involved in maxillary protraction:


Several circum-maxillary sutures
play an important role in development
of the naso-maxillary complex. A
change in these sutures during
treatment in the growing period
occurs. The sutures are
a. Frontomaxillary,
b. Nasomaxillary,
c. Zygomaticomaxillary,
d. Zygomaticotemporal,
e. Pterygopalatine,
f. Intermaxillary,
g. Ethmomaxillary,
h. Lacrimomaxillary and
i. Zygomaticofrontal.




Most of the orthopedic effects are seen within 3-6 months
after maxillary expansion. Prolonged use of protraction forces
results in dentoalveolar changes including mesial movement of
maxillary molars and proclination of maxillary incisors. Studies
have shown that the effects on the maxilla remained stable. In
patients who were followed up after protraction, the anterior
position of the maxilla was maintained post treatment.



Gallagher et al in AJO 1998 found that in the post
treatment follow up for face mask therapy patients, the maxilla
showed a relative relapse by not displacing forward as much as
normal. The anterior rotation caused by treatment was negated.
The mandible followed a normal downward and forward growth
pattern.

Treatment timing:


According to Kim et al in AJO 1999 and several other
authors, treatment should be started as early as possible to
produce a more significant response from protraction therapy.
Treatment changes in the younger group are larger than those in
the older group. Protraction face mask therapy is still effective
but to a lesser degree in growing patients older than 10 years of
age. The optimal timing for intervention is at the time of
eruption of the upper central incisors. A positive overjet and
overbite at the end of treatment appears to maintain the anterior
occlusion at the end of treatment. Better skeletal and dental
response is obtained in the primary and early mixed dentitions.


Indications for facemask therapy








The facemask is a most effective tool for treating skeletal Class
III malocclusion with a retrusive maxilla and a hypodivergent
growth pattern.
Patients presenting initially with some degree of anterior
mandibular shift and a moderate overbite have an improved
treatment prognosis.
Correcting the anterior crossbite usually results in a downward
and backward rotation of the mandible that diminishes its
prognathism. The presence of an overbite helps to maintain the
immediate dental correction after treatment.
For patients presenting with a hyperdivergent growth pattern
and a minimal overbite, a bonded palatal expansion appliance to
control vertical eruption of the molars is recommended. During
retention, a mandibular retractor or a Class III activator with a
posterior bite block can be used for vertical control.

CHIN CUP THERAPY


The objective of early treatment with a chin cup is to
provide growth inhibition or redirection and posterior
positioning of mandible.

Force magnitude and direction.

There are two types of chin cup- the occipital pull
chin cup that is used for patients with mandibular
protrusion and the vertical pull chin cup that is used in
patients presenting with a steep mandibular plane and
excessive anterior facial height. Most studies recommend
an orthopedic force of 300-500 gm per side (AJO 1987).
 Patients are instructed to wear the appliance 14
hours/day. The orthopedic force is usually directed either
through the condyle or below the condyle.

HEADGEARS WITH OTHER APPLIANCES
HEADGEARS WITH REMOVABLE APPLIANCES:
Margolis acrylic cervico occipital anchorage:

Margolis in 1976 incorporated extraoral force with removable
appliances for pts with class II malocclusions, using them both in
active and retentive phases of treatment. The Margolis appliance is
called an ACCO. Modified maxillary removable Hawley type
appliance permits the use of extraoral forces against the maxillary
dentition. Multiple ball end clasps and occlusal coverage can
increase the resistance to dislodgement by extraoral traction.
Margolis used this appliance to hold the torque correction achieved
with fixed appliances. This appliance was later modified by the
addition of 1 mm buccal tubes to the labial wire and soldering them
vertically at the canine-lateral incisor embrasure to receive the Jhook extraoral force arms. An inclined plane was added to eliminate
functional retrusion and free the mandible for all possible forward
growth.



A new ACCO is made after
extraoral forces and inclined
plane have created a class I
buccal segment. The ACCO
should be worn both day and
night with a minimum of 12 hrs
nocturnal
headgear
wear.
ACCO can be continued to be
used as a retainer after active
treatment and extraoral force
can be applied as indicated with
the ACCO to treat any residual
sagittal abnormality or tendency
to return to original class II
relationship.

Jacobson’s splint


Jacobson used a splint similar to the
ACCO with extra oral traction for
correction of mild class II
malocclusions. The reduction in
overjet and the sagittal discrepancy
reduce the deforming action of the
abnormal perioral muscle function.
The force magnitude for this type of
removable appliance must not be
too great to prevent dislodgement of
the appliance.




The direction of pull of the extra oral force should coincide roughly
with that of the Y-axis or a line extending from the symphysis to a
point 1.5 cm in front of the external auditory meatus. This prevents
the unfavorable basal maxillary tipping and extrusion of teeth. The
Jacobson craniomaxillary splint is used with occlusal coverage to aid
in retention and to prevent maxillary eruption while allowing
unimpeded upward and forward eruption of the mandibular buccal
segment that assists in sagittal correction.


Verdon combination appliance:
 An appliance similar to Jacobson’s splint was used. The
basic appliance of choice is a modified active plate. The
major objective is to effect a change through a
distalising influence on the maxillary arch leaving the
mandibular arch alone. An occipital headcap is used to
prevent tipping down the anterior palatal plane. A
cervical strap can be used but the force values are
significantly smaller, producing more dentoalveolar and
less basal effects.


Graber appliance:
 It was used for the treatment of class II division I
malocclusions. The direction of force is high and
the appliance stands away from the molar and
premolar areas to allow expansion of the arch. This
acts similar to the buccal shields of Frankel
appliance. This appliance works as an active retainer
for class II correction maintaining individual tooth
positions.


HEADGEAR WITH FIXED APPLIANCES:
Edgewise appliance:




Various types of headgears are used with the edgewise
appliance depending on the type of malocclusion and the stage of
treatment for effecting dental and skeletal changes.
Kloehn type of headgear is the type most commonly used
mainly to reinforce anchorage. In growing patients, it produces
skeletal changes if high forces are used. The end of the outer bow is
bent up at an angle of 150 to prevent tipping of molars. This
produces opening of the bite due to extrusion of molars. Hence it
should only be used in patients with normal or deep overbites. In
patients with normal or low mandibular plane angles, kloehn face
bow can be used to obtain skeletal corrections.









Straight pull headgear is used on the upper arch if
extrusion of the teeth is not desired. This type is used
on the upper arch during retraction of the canines and
incisors.
High pull headgear with facebow is used to intrude
molars in selected cases of open bites.
Intrusion of buccal teeth produces a rotation of
mandible thereby closing the openbite and reducing the
LAFH.
High pull headgear using J-hook can be used in the
anterior segment for deep bite correction and for
correction of gummy smiles.

Straight wire appliance:
 When anchorage is critical, the anterior teeth are
retracted by the use of a modified Asher’s face bow
which can be hooked either to a neck strap to retract
the lower or upper anteriors or an anterior high pull
headcap to retract and intrude the upper incisors.
 Ashers high pull facebow with headcap is used to
retract the incisors using 12-15 oz of force.


Begg appliance:

Extraoral forces are usually not required with begg
since begg mechanics minimizes the need for anchorage
conservation. However, headgears can be used in
isolated cases for distalisation of teeth or when
orthopedic control of maxilla is favored over extraction
or orthognathic surgery. Such indications would include
severe skeletal class II problems with high ANB
differences combined with excessive maxillary
protrusion. Headgear would also be indicated in nonextraction cases requiring distal positioning of the
posterior teeth or maxilla to produce an acceptable
anteroposterior dental and skeletal relationship.

Level anchorage system:

High pull face bow headgear is used to the
maxillary molar or a high pull J hook headgear attached
to the maxillary area, with 1 pound pressure on each
side, worn 12 hours per day by a growing patient will
reduce the ANB approximately by 10. Anchorage space
in the lower arch needed to correct the ANB angle is
reduced by approximately 1 mm for each 6 months of
headgear wear.


HEADGEARS WITH FUNCTIONAL APPLIANCES
Headgears with activator

Levin et al in AJO 1985
reported the use of a cervical
headgear with the activator. A
cervical HG with a long outer
bow applying a force of 400 gms
was used. It was concluded that
activator
cervical
headgear
therapy results in a simulation of
normal mandibular occlusal
development and a redirection
of
maxillary
dentoalveolar
development. Mesofacial and
brachyfacial types appeared to
respond most favorably to
treatment.





Pfeiffer in AJO 1982 described the combination activator
— cervical headgear therapy. They preferred to use cervical
headgear, where necessary, for two reasons: (1) to extrude
maxillary molars, and (2) to apply orthopedic traction to the
maxilla and an activator to induce orthopedic mandibular
changes, restrain maxillary growth, and cause selective eruption
of teeth.
Cura et al in AJO 1996 compared the effects of activator
and activator with HG therepy. A high pull head gear was used
with a force of 400 gms per side for 17 hrs a day. They found
greater improvement in the sagittal base relationship in cases
treated with combination therapy than in patients who were
treated with activator alone.



Stockli and Teusher in their combination therapy said that
vertical and sagittal control oh maxillary growth was essential in the
management of class II patients. Their activator HG combination
achieved control in all the three planes of space. A high pull HG
was used for depression of molars and vertical control of the
maxilla.

Headgears with herbst appliance.


Was first reported by weislander in AJO 1984. It is indicated
only in cases of severe class II MO in early mixed dentition. In
order to transfer as much force as possible to the base of the
maxilla, splints may be used with an attempt to distribute the force
over the total dentoalveolar area for better anchorage purposes.
Orthopedic forces in human beings, usually in the magnitude of
500 to 1,000 gm of pressure on each side were suggested. When
the total maxillary dental arch is used as anchorage, forces up to
1,500 gm on each side can be applied without discomfort to the
patient. In most cases treated in the mixed dentition, appliances
were constructed for nighttime wear only, and 12 to 18 hours of
wear gave maximum treatment effect. The orthopedic effect of
treatment may increase if proper anchorage is used and if the
appliance is worn 24 hours.





Weislander in AJO 1993 evaluated the effect of treatment and
retention on a group of consecutive cases several years out of
retention and to compare the initial changes during Herbst treatment
with the long-term situation 8 years after treatment. An average
increase of 2mm was found in the mandibular body length. Prolonged
retention with activator was needed to minimize relapse. Findings
indicated that maxillary sutural remodeling might be more receptive
long-term to orthopedic treatment than the mandibular condylar
growth process.
Schiavoni in AJO 1992 evaluated the possibility of controlling
vertical dimension by using Herbst appliance and high pull headgear
in hyperdivergent facial patterns. The high-pull headgear had an
orthopedic restriction of the maxillary vertical development rather
than an effect on the sagittal plane. Elimination of anterior inferences
by orthodontic repositioning of the front teeth and preventing
extrusion of the posterior teeth allowed an anterior rotation of the
mandible, with improvement of the sagittal correction and beneficial
reduction in lower face height.



Rabie and Hagg in Sem
Orthod 2003 investigated the effect
of adding HG to the herbst appliance
and in the retention period. A high
pull HG whose outer bow was
adjusted to be 300 above the occlusal
plane was used. The HG delivered a
force of 400-500 gms. Results showed
that the maxillary restraint and
improvement in jaw base was greater
in patients who had HG during the
treatment period. Rotation of the
palatal plane was seen in the herbst
group but not the HG- herbst group.
The authors concluded that adding
HG to the herbst resulted in
increased orthopedic effect on the
maxilla and a large increase in the jaw
base relationship.


Headgears with Bionator


Dahan et al in AJO 1989 described
the use of a bioactivator with high pull
headgear for treatment of class II
division I malocclusion cases. High-pull
headgear was adjusted to the buccal tube
units of the multianchorage system. The
headgear was worn every night (8 to 10
hours) during the first year of treatment.
They concluded that the combination of a bimaxillary appliance with
extraoral forces leads to rapid changes in the correction of Class II,
Division 1 skeletal conditions.


Headgears and Twin block


Parkin and sandler in AJO
2001 compared the effects of two
modifications of twin block. The
effect of twin block appliance
modified by the incorporation of a
high pull headgear and torquing
springs positioned on the maxillary
incisors was studied.
The headgear force was directed at the Cres of the maxilla in an
attempt to control the vertical position of the maxilla. Flying
headgear tubes situated next to the maxillary second premolars were
used to apply a force of 400 gm per side, worn for 120 hours per
week.



They found that in pts with headgear, the maxillary
plane appeared to have rotated in an anticlockwise
direction. Vertical eruption of the maxillary molars was
restricted by headgear. A restraint in the anteroposterior
position of the maxilla was demonstrated. The authors
concluded that the addition of high pull headgear in
patients with twin block allowed effective vertical and
sagittal control of the maxilla with no increase in
LFH/TFH.


Headgears with frankel appliance:


Owen et al in JCO 1985 modified
the FR by adding posterior bite blocks
and a headgear for the control of the
posterior maxilla. A high pull headgear
was used for posterior maxillary
control. The modified function
regulator appeared to offer advantages
in
combining
functional
jaw
orthopedics with directional force
headgear in the early comprehensive
treatment of long face patients.



They suggested that the vertical dimension or
anterior facial height (ANS-Me) could be held constant
or even decreased through the holding or intrusion of
the upper molars. Although no condylar growth was
demonstrated in this study, there was a potential for
increased mandibular growth.

HEADGEARS FOR MOLAR DISTALISATION:
According to Nanda et al
 By directing the forces through the Cres of the maxillary
molars, intrusion and distalisation of molars can be
achieved.
 An average of 500 gms was suggested to translate the
molars distally and at the same time initiate maxillary
changes that are normally associated with high force
levels.
 If the headgear is used for a short period of 6 months
with good patient co-operation, significant dental
improvement in the class II molar relation can be
achieved.

Disadvantages of headgear treatment:
Samuels et al AJO 1996 in a review of orthodontic facebow injuries and safety equipment found that the
cause of the injuries could be roughly grouped into
four categories.
1.
Accidental disengagement when the child was playing
while wearing the headgear
2.
Incorrect handling by the child during the fitting or
removal of the headgear
3.
Deliberate disengagement of the headgear caused by
another child
4.
Unintentional disengagement or detachment of the
headgear during sleep.

Assessment of patient compliance
Cureton AJO 1993. The methods currently used to determine
headgear wear are subjective. Some methods used are
 molar mobility,
 cleanliness of headgear tubes,
 cleanliness of headgear strap,
 ease of placement by patient,
 questioning patient,
 space creation between teeth,
 molar positioning comparing pretreatment models and/or
cephalograms,
 the position of the junction of the inner and outer bow of the
headgear compared with the previous appointment, and
 Anchorage maintenance.

Instructions to be given to the patient include:







Patients should be advised not to wear their headgear while
playing.
Before removing the face-bow, the patient must always remove the
headgear first.
Where a locking face-bow has been fitted, patients should check to
make sure it is seated correctly.
If any problems occur with the headgear, then patients should
cease wearing it and return to see the clinician as soon as possible.
If the appliance is detaching during sleep, the patient must cease
wearing it and return to see the clinician.
The patient and parent should also be advised that if any eye injury
is suspected to have been caused by any part of the orthodontic
appliance, however minor, then an immediate ophthalmologic
examination is necessary because penetrating injuries may be
relatively asymptomatic and immediate antibiotic therapy is
required if any resultant infection is to be controlled

Headgear timers


If the orthodontist had full knowledge of the actual
amount of wear between appointments, this would be a
significant boon to therapy. In addition, this could
markedly increase patient compliance. Northcutt was
one of the first to introduce a timing headgear. The
timing headgear unit consists of a miniature electronic
timer and is used with a digital readout meter. It was
initially used with a cervical pull appliance, but was later
available in a high-pull mode.










Selçuk type headgear-timer (STHT)
was introduced by Enis Guray 1997
The Selçuk type headgear timer was
reported to be 100% accurate, unaffected
by intensity of force variables, reliable,
easy to construct, safe, and inexpensive.
Clinical tests showed a significant
increase in headgear wear.
An objective appraisal of extraoral force
affects is enhanced by having a validating
measurement of actual appliance wear.
With the ability to control direction of
force and to measure intensity, it is now
possible to have an equally accurate
measure of the third element of the triad
—duration of wear.

CONCLUSION


The choice of appliance should be based on the
proper diagnosis of different aspects of the
malocclusion and not because a particular appliance is
thought to have a greater influence on modifying
growth. Clinicians should be thoroughly familiar with
the appliances they are using, including their potential
benefits and limitations. They should also be aware of
the effects of these appliances on the dentofacial
structures when formulating a treatment plan for each
individual patient. Regardless of the appliance used,
there is a large and similar amount of variation in
individual patient response to treatment.

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