I am sorry for the layout, and no pictures, but this article shows one orthodontist approach. Just search for the word 'tying".
It was done, I met one kid who had it wired on, but most us were just forced by parents to wear it, some of us all day, in public, everywhere. It would have made more sense to wear it to school and enjoy headgear free playtime but social pressure prevented that.
American Journal of ORTHODONTICS
Volume 59, Number 3, March, 1971
ORIGINAL ARTICLES
Controlling the magnitude,
direction, and duration of
extraoral force
Maclay M. Armstrong, D.D.S., M.S.D.*
Seattle, Wash.
T he purpose of this article is twofold: First, it will demonstrate the
clinical application of precise control of t,he magnitude, direction, and duration
of extraoral force and, second, cases will be presented to demonstrate how control
of these three mechanical variables dramatically increases the efficiency and
effectiveness of extraoral force in the treatment of malocclusion.
The subject will be introduced by showing a case (Case 1) in which 44
ounces of bilateral extraoral force was applied in a precise and predictable
direction 24 hours per day for 97 days (Fig. 1). The patient was 11 years 5
months of age at the beginning of treatment; dentally, she was in the late
mixed-dentition stage. She had an ANB angle of 6 degrees, a Frankfortmandibular
plane angle of 32 degrees, an end-to-end molar relationship, 11 mm.
of overjet, and a slight open-bite. There was adequate space in the lower arch.
The appliance consisted of edgewise bands on the upper and lower incisors
and first molars, The objective in the lower arch was to round out the flattened
arch form, to move the incisors slightly labially, and to maintain arch length
(Fig. 1, P). The objective in the upper arch was to simultaneously move the
upper first molars and four incisors distally and bodily, as a unit, by applying
‘(heavy” continuous, directional, extraoral force. A 0.021 by 0.025 inch edgewise
wire was used to control the incisors. Eleven days after banding, the extraoral
force was applied.
Fig. 1, A through H, demonstrates the predictable change. The original
models were taken 355 months before treatment began. Except for normal tooth
eruption, the malocclusion remained essentially the same. Progress records
taken after 97 days of controlled extraoral force show a normal molar relation
and elimination of the 11 mm. of overjet.
*Associate Professor, Loyola University School of Dentistry, Chicago, Ill.
217
218 Armstrong
Fig. 1. Case 1. A, Right side of original and progress models showing the result of 97
days of extraoral force. B, Left side of original and progress models showing result of
97 days of extraoral force. C, Intraoral view of right side after 97 days. D, intraoral view
of left side after 97 days. E, Original and progress models, maxillary occlusal view.
F, Original and progress models, lower arch. G, Periapical radiograms taken on the ninetyseventh
day of extraoral force. H, Front view of original and progress models showing
result of 97 days of extraoral force.
Bodily distal movement was effortlessly achieved in this young patient by
precisely controlling the three mechanical variables of extraoral force-magnitude,
direction, and duration. No extrusive force was applied to the upper
molars. The upper canines and premolars migrated distally at Lhe same rate as
the molars. Periapical roentgenograms (Fi g. 1, G) of the upper first molars and
Volwne 59
Number 3 Three mechanical variables of extraoral force 219
incisors were taken immediately after the rapid bodily tooth movement was
accomplished. There was no evidence of root resorption or bone loss. The upper
second molars appeared in good position for normal eruption. Total treatment
time at this point was 108 days. Extraoral force was then reduced to nighttime
wear for 6 weeks to maintain or “retain” the corrected arch relationship. This
was followed by an observation period pending eruption of the remaining teeth.
Mechanical variables of extraoral force
Orthodontists are currently giving more attention to the mechanical variables
of extraoral traction. Direction of force is usually expressed as horizontal
or vertical in relation to the occlusal plane. It seems apparent that there is an
optimum direction for the application of extraoral force in each case for efficient
and effective treatment. 1*6 j I69I 891 9s2 312 4 Debate continues, however, concerning
force magnitude, heavy versus light force, force duration, and continuous
versus interrupted force.
Graberll says that when more than 400 Gm., or 1 to 2 pounds, of cervical
force per side is transmitted to all the teeth in the maxilla, this magnitude of
interrupted force is too great for tooth movement, that it exceeds the toothmoving
threshold and should be employed when retarding growth of the
maxilla. Damon30 reported, in a University of Washington graduate thesis, that
heavy (3 pounds per side) interrupted force intrudes teeth and may even move
the maxilla. Haas13 advocates 3 to 5 pounds of cervical force and demonstrates
apparent movement of the maxilla (orthopedic change) as well as movement
of the teeth (dental change). Poulton231 24 and Rickettszg demonstrate marked
distal bodily movement of upper teeth by applying occipital extraoral traction,
usually for 12 to 14 hours per day. Ricketts suggests that the maxilla is not
“immutable” and may be affected by extraoral force.
Very little is found in the literature on the effects of continuous extraoral
traction, heavy or light. In general, duration of extraoral force is 12 to 14 hours
per day, which is usually determined by voluntary patient cooperation and, as
a result, quite often is much less.
Until recently, the precise magnitude of force used in extraoral appliances
has received little attention. Heretofore, the most common (and only comfortable)
appliances depended for force application on elastic straps and rubber
bands. Since elastic and plastic materials have the inherent property of “creep”
after they are applied by the patient, there is a continuous loss of force until
the time it is reactivated. Thus, magnitude of force is neither constant, calibrated,
nor precisely controllable.
In 1947, MuelleF designed a cervical appliance consisting of an aluminum
tube 3/116in ch in diameter and an extension coil spring. This same basic cervitally
borne design was commercially available for a number of years but ultimately
fell into disuse. Although it was not calibrated or particularly comfortable,
it was the first attempt to replace elastics.
Control of magnitude
A family of comfortable, directional extraoral appliances has been designed
and developed over a period of 5 years. Protected calibrated coil springs are
used as the resilient means to provide :I controlled magnit.ude r~l’ forces M’ith
these appliances, precise, nondissipating force is now possible because stainless
st,eel coil springs do not lose force frorn creep (less than I per cent). The force
gauges are actually incorporated as an integral part of the appliances, provitling
visible force calibrations at a glance. These directional ealibra.tecl coilspring
appliances were developed and tested on clinica. patients.
Directional appliances in use
The most widely used extraoral appliance is the neckstrap or cervical strap
attached to a double face-bow (Fig. 2, -4). Many orthodontists use it routinely
in almost all cases.8 Fig. 2, E shows a tracing of a patient wearing a neckstrap
and a double face-bow. The neckstrap is represented by the schematic coil
spring; it is attached to the long, high outer bow at point OB (Fig. 2, E). It is
apparent that the direction of pull in relation to the upper arch or occlusal
plane is downward as well as backward. This direction of force would result in
the movement illustrated at HB in Fig. 2, E; it will cause extrusion as well as
distal bodily movement unless muscle forces prevent or minimize these extrusive
forces. Even when the outer bow is lowered to a position that is level with
the inner bow (IB in Fig, 2, E) , the direction of pull is still the same. The only
difference is that the outer bow does not a.pply a moment of force to the upper
molar root. Instead of distal bodily movement and ext.rusion, t,he upper molars
tip distally and extrude as illustrated at LB in Fig. 2, i?.
Distal bodily movement of the upper first molars is one of the most difficult
tooth movements to achieve; extrusion is t,he quickest and easiest. In fact, a
tooth ground out of occlusion erupts or extrudes without any external force
application. Extrusion of the upper first molars and/or downward growth or
movement of the maxilla is seldom desirable except in the treatment of a few of
the skeletal closed bites or in some of the Class III malocclusions. In most treatment,
therefore, about half of t,he cervical strap force is wasted in pulling downward
on the upper molars.
Another cervically borne appliance is the cervical gear with J hooks (Fig.
2, C). Fig. 2, D shows a head film of a patient wearing this type of appliance.
(For illustration purposes, the concavity of the neck has been outlined.) The
cervical appliance is attached by J hooks at point ~4. to the upper arch wire
which is, in turn, tied t,o the upper anterior t,eeth. The J hooks can also be
attached in the same general area to horizontal loops bent in a heavy 0.015 inch
round wire which inserts into the upper first molar tubes. The letters CR in
Fig. 2, D denote the center of resistance of the upper incisors or upper molars. It
is generally accepted that the center of resistance resides in the middle third
of the root.5l I2 This is the point where force must be applied to achieve bodily
tooth movement without tipping.
Furthermore, if the objective of treatment is to move the upper molars
and/or incisors distally and bodily without extrusion, the force must be applied
at CR (Fig. 2, P) in a. direction parallel with the occlusal plane, OP.
Fig. 2, D clearly shows that the line of pull of the cervical gear, CG, is far
below and is not parallel with the occlusal plane. This appliance could have
Fig. 2. A, Neckstrap to double face-bow. B, “Straight-pull” cervical gear. C, Cervical
with J hooks. D, Head film taken with cervical gear on patient. E, Tracing of neckstr
a dc ruble face-bow showing direction of pull. F, Tracing of Class II malocclusion H
deel 5 overbite, showing direction of pull of cervical gear with J hooks.
gear
ap to
rith a
222 Armstrong
Fig. 3. A, Headcap to double face-bow. B, “High-pull” headgear. C, Tracing showing
direr :tion of pull of headcap with a double face bow.
the
an orthopedic effect by stimulating nasofrontal suture growth and by rotating
the anterior part of the maxilla downward. I4 In some patients with unesthetic
smile lines (gummy smiles) this is usually contraindicated. The downward and
distal pull of the cervical gear results in distal crown tipping, extrusion, and
clockwise tipping of the upper arch. This appliance and its direction of pull
would be useful in that rare malocclusion characterized by an anterior openbite
resulting from infra-erupted and somewhat flared upper incisors, in which
the open-bite needed to be closed by extrusion of the upper anterior teeth and
distal tipping of the crowns of the upper posterior teeth.
Volume 59
Number 3 Three mechanical variables of extraoral force 223
Bodily movement versus distal crown tipping
When the cervical gear is attached to the heavy 0.045 inch round arch wire
at point A (Fig. 2, D) , the wire acts as a long lever, applying a strong distal
crown-tipping moment to the upper first molars while the downward pull tends
to extrude them. Many molars that have been tipped back relapse to their
original position in a very short time unless occlusal forces upright the teeth
by distal root movement. Therefore, retention of these teeth in a distally tipped
position could merely forestall the relapse until the time the retaining appliance
is removed. When the 0.045 inch arch wire is modified to rest against the
crowns of the upper anterior teeth, the distal and downward pull of the cervical
gear often results in distal crown tipping and the characteristic “rabbiting”
of the upper incisors.
In Fig. 2, P a tracing of a Class II malocclusion with a deep overbite shows
the distal and extrusive direction of pull (CG) to be far below the center of
resistance (CR) of either the upper incisors or the upper molars. Placing a
bite plate would not alter the direction of pull but would merely open the bite,
causing the mandible to rotate down and back. This increases the severity of
the Class II relation. In this orthopedic treatment, if the distal component of
force (D in Fig. 2, P) of the cervically borne appliances successfully restrains
the maxilla from naturally growing forward, the downward component of force
(E) could not help but enhance the natural downward (and, in these cases,
deleterious) vertical growth of the maxilla.
Fig. 2, B shows another version of the cervical gear, the “straight pull,” in
which straps have been placed in an attempt to achieve a straight pull parallel
with the occlusal plane. Because of the location of the ears, extending these
straps does not significantly alter the direction of the pull to the upper teeth
or arch. It is still downward and back and, more important, occlusal to the
center of resistance of the upper teeth.
Fig. 3, A illustrates the double face-bow used with a headcap that fits on
the top and back of the head above the ear. In relation to the upper teeth, its
direction of pull is distal and intrusive as compared to the cervically borne
appliances whose direction is distally and extrusive.
Fig. 3, C shows the effect on the upper molars of changing the position of
the outer bows. If the outer bow is at point A, the line of pull is apical to the
center of resistance and causes distal tipping of the root as well as intrusion,
as shown in the drawing A of the individual molars in Fig. 3, C. When the
outer bow is at point B, the direction of pull is through the center of resistance,
and the upper molars will move bodily in a distal and intrusive direction (B).
Finally, with the outer bow at C, the line of force is occlusal to the center of
resistance; this results in intrusion and distal crown tipping (C). The direction
of pull provided by the headcap is especially advantageous in treating a Class
II case with a high mandibular plane angle, where it is important not to
extrude the upper posterior teeth and is, in fact, advantageous to intrude them.
Fig. 3, B demonstrates another popular version of the headcap-borne appliance
attached by J hooks to the upper anterior teeth. It also results in a distal
intrusive movement or a distal counterclockwise rotation of the upper arch.
Fig. 4. A, Early model of horizontal-pull calibrated coil-spring headgear. B, Calibrated coilspring
force units. C, Combination headcap-neckstrap with double face-bow.
Precise horizontal force
By far the greatest percentage of orthodontic cases fall into one or all of the
following three categories: (I) the Class II malocclusion characterized by teeth
and/or upper jaw that are too far forward in relation to the lower jaw, (2)
the Class I case with crowding in one or both arches, more commonly in the
upper arch, and (3) the Class I double protrusion. In the treatment of the
majority of these problems, the optimum direction of extraoral force should be
in a distal horizontal direction, parallel or almost parallel with the occlusal
plane. It should be on a vertical level either through or somewhere between the
center of resistance of the upper first molar roots and arch wire tubes.
Some of the objectives in applyin, w this force are ( 1) to move the upper
molars or the maxillary arch distally, either bodily or with some tipping without
extrusion, (2) to prevent forwarcl movement of the upper posterior teeth
in extraction cases without concurrent extrusion, and (3) to restrain forward
growth of the maxilla without increasing its vertical growth. A fourth objective,
and one which is the basis for this article, is the application of known,
heavy, continuous, horizontal extraoral force through the center of resistance
of the upper teeth in the late mixed dentition, with the expectation of moving
the upper teeth, the maxillary alveolar process, and/or the maxilla itself
distally.
Because of the location of the ear, a comfortable, simple-to-place appliance
that provides this type of distal force has been difficult to design. This accounts
for one of the major reasons why occipital and variable headgears have not
been widely used by the specialty. Moreover, no workable appliance of this
type has been designed to provide bilateral tooth-borne force in the 2- to 41/zpound
range (4 t.o 9 pounds to the maxilla). Fig. 4, ,4 shows a11 early attempt
with calibrated coil springs.
With the calibrated coil-spring appliances, it is now possible to circumvent
the ear (Fig. 4, B) by using a combination of the headcap-neckstrap with a
double face-bow and to apply distal force in this most important horizontal
Votwne 59
Number 3 Three mechanical variables of extraoral force 225
direction at almost any vertical level, angle, or desired force magnitude. Extraoral
force applied in this direction (toward the ear, parallel with the OCC~US~~
plane, and through the center of resistance) moves the upper teeth of the
maxillary arch bodily in a distal direction, without extrusion or distal tipping.
In Fig. 4, C, the patient is wearing a combination headcap-neckstrap with
a 1:l force ratio, or 16 ounces on each side of the headcap and 16 ounces on each
side of the neckstrap. This provides a net horizontal force of approximately 29
ounces to each side (10 to 12 per cent of the cumulative force is lost because of
the divergent angle between the pull of the two appliances). Therefore, the
sum total of horizontal force to the maxilla is double this amount-around 58
ounces, or slightly over 31/a pounds. It was this appliance that produced the
dramatic treatment result illustrated in the first case presented at the beginning
of the article. The use of this appliance can also be very effective in preventing
forward movement of the upper posterior teeth in extraction cases.
Bilateral horizontal force has been used routinely in the al/,- to 3-pound
range (a total to the maxilla of 5 to 7 pounds). On occasion, even greater forces
have been employed. This “massive” magnitude of force is more than has been
considered advisable in the past, or even possible with the conventional appliances
in use. Now, by employing the combination headcap-neckstrap with the
double face-bow, not only can the question of heavy force versus light force to
the upper teeth and/or maxilla be evaluated, but the effect of heavy versus
light horizontal force may also be included in the evaluation.
The combination extraoral appliance can be adjusted in two planes of space
in relation to the occlusal plane. They may be vertical or angular. Fig. 5, A
through D, illustrates how this type of extraoral traction provides a rather
wide range of precisely adjustable direction in the vertical plane.
Fig. 5, A., B, and C, shows that when the short outer bows of the double
face-bow are bent either up or down, the vertical level of force can be raised or
lowered. The tracing in Fig. 5, D illustrates the level and direction of horizontal
pull achieved by adjusting the outer bows to points A, B, and C when there
is equal force on the headcap and neckstrap (1:l ratio). With the outer bows
at point A, the line of force will be horizontal, parallel with the occlusal plane
and through the center of the upper molar crown, resulting in distal crown
tipping without extrusion, as shown in A in the drawings of the individual
teeth in Fig. 5, D. Fig. 5, A shows the outer bow adjusted on a patient to position
A or level with the inner bow.
Frequent adjustments must be made when the outer bow is in this low position.
As the upper molars tip distally, the anterior portion of the inner bow
descends. To maintain a comfortable position between the upper and lower lips,
this inner bow must be adjusted superiorly. This position can be used to prevent
the upper molars from moving forward in extraction cases. If the outer bow is
bent up to point B (Fig. 5, D and B) , the line of pull will be through the center
of resistance of the root, achieving distal bodily movement (Fig. 5, B) . Position
B was the level used in the first case presented. Finally, if the outer bow is
adjusted up to point C (Fig. 5, D) the line of pull will be through the apex
of the upper molar root, resulting in distal root tipping. Fig. 5, C shows the
Fig. 5. A, Outer bow level with inner bow, position A, for distal crown tipping. B, Outer
bow at position B for distal bodily movement. C, Outer bow at position C for distal root
tipping. D, Tracing showing three different levels of the outer bows and their direction of
pull in the vertical plane with a 1 :l force ratio between the headcap and neckstrap.
same patient with the outer bow bent up high to position C. This position may
be used to lock the distal cusps of the upper first molars into occlusion with the
distal aspect of the lower first molars (C in the drawings of the individual teeth
in Fig. 5, 0).
The angle of horizontal force in relation to the ocelusal plane can be adjusted
as described in the following discussion. A head film taken with the
combination appliance in place is illustrated in Fig. 6, A. HC depicts the coil
springs of the headcap, and NX represents the springs of the neckstrap. OB
is the short outer bow. When a short outer bow is used, the angle between its
attachment with the headcap and neckstrap in the great majority of cases is
Fig. 6. A, Head film taken with combination headgear in place, showing the %-degree
angle between the pull of the headcap and neckstrap. B, Head film with properly centered
force-vector protractor.
55 degrees, plus or minus 5 degrees (Fig. 6, A). Bearing this in mind, it is
possible to compute each force vector for the various ratios between the headcap
and neckstrap. From this, a force-vector protractor can be made (Fig. 6, B).
For example, HC-2 to NX-1 shows the ratio of 1 ounce on the headcap for 1
ounce on the neckstrap. The vector immediately above, HC-2 to NS-1, is the
resultant of 2 ounces on the headcap for every ounce on the neckstrap, and so on.
Fig. 6, B shows a head film with the force-vector protractor properly centered
between the springs of the headcap and neckstrap and their point of
attachment with the short outer bows. This superimposition clearly demonstrates
the line of pull for the various force ratios and shows their relationship
to the teeth and jaws of the patient. Virtually any angle of horizontal force can
be achieved and utilized in differential treatment by adjusting the force on the
headcap in relation to the neckstrap. Looking at this same head film (Fig. 6,
B), it is easy to visualize the effect of raising or lowering the outer bows for
changing the level of horizontal force in the vertical plane.
Treatment effects of controlled extraoral force
The following cases were also treated with the combination headcapneckstrap-
face-bow appliance. Case 2 (Fig. ‘7) the patient was a girl, 11 years
9 months of age, in the late mixed dentition. She had a high Frankfort-mandibular
angle (32 degrees) and a Class II open-bite malocclusion with an ANB
angle of 9 degrees (Fig. 7, A, B, and E). Edgewise bands were placed on the
upper and lower first molars and incisors. Lower arch length was maintained
with a stopped arch wire. In the upper arch, a 0.025 inch torqued edgewise
arch wire was placed to control the incisors. Forty-four ounces of continuous
(face-bow tied in) distal horizontal force was applied through the center of
resistance to each first molar. The banding appointment was 6 months after
initial records were taken, and the combination appliance was placed 1 month
later. The progress records (Fig. 7) were taken after 108 days of extraoral
force, or 143 days after the bands were placed.
Even taking into consideration the unusual forward growth spurt of the
Fig. 7. Case 2. A, Right side of original and progress models after 108 days of extraoral
force. B, Left side of original and progress models after 108 days. C, Original and
progress models, maxillary occlusal view. D, Original and progress models, mandibular
occlusal view. E, Head film taken with combination headgear in place on first day of
wear. F, Head film taken after 108 days of headgear wear. G, Periapical films taken on
the one hundred eighth day. H, Composite tracing made from E and F.
mandible (Fig. 7, H), the amount of change was quite dramatic for 108 days.
Note the spacing created by the distal bodily movement of the upper first
molars. The head film shown in Fig. 7, E was taken when the combination
appliance was first tied in. A 1 :I force ratio was used. Note the high position of
the short outer bow; it provides a line of pull through the center of resistance of
Volume 59
Number 3 Three mechanical variables of extraoral force 229
Fig. 8. Case 3. A, Right side of original and progress models after 42 days of combination
headgear. B, Left side of original and progress models after 42 days. C, Intraoral maxillary
occlusal view after 42 days. D, Original and progress models, maxillary occlusal view.
the upper molars to achieve distal bodily movement. Observe the Class II
molar relationship and the amount of overjet. The next head film (Fig. 7, P)
was taken after 108 days of continuous extraoral traction. Note the reduction
of overjet. Of interest is the vertical inclination of the upper first molars. If
necessary, the upper second molars that have rolled out to the buccal may be
extracted at a later date to permit their replacement by the upper third
molars. The head films shown in Fig. 7, E and P were used to make the composite
tracing (Fig. 7, H) , which shows the amount of tooth movement achieved
by the application of controlled extraoral force in the direction indicated by
the arrow. Once again, the premolars and canines were not banded but migrated
distally as the upper molars moved back bodily. Quite remarkably, the lower
jaw grew forward more than 2 mm. in the short time that elapsed between the
two head films. The patient was asked to return to the office for the sole purpose
of having the bite double checked. The head films proved to be correct, for she
was still unable to bite farther back.
No measurable root resorption or bone loss appeared on the intraoral roentgenograms
(Fig. 7, G) that were taken on the one hundred and eighth day of
extraoral force.
Case 3 (Fig. S), in which the patient was a 13-year-old boy, demonstrates
rapid distal tipping of the upper first molars. This movement was gained in
42 days by the application of 44 ounces of continuous (face-bow tied in) nondissipating
force to each upper first molar, below the center of resistance,
through the crown. In this case, the short outer bow was level with the inner
bow. (The head film shown in Fig. 6, A is of this patient; it was taken before
Fig. 9. Case 4. A, Right side of original and progress models after 1 10 days of combination
headgear force. B, Left side of original and progress models after 110 days. C, Front view
of original and progress models after 110 days. D, intraoral photograph of left side after
110 days. E, Composite tracing made from head films taken the day extraoral force began
and 110 days later. F, Periapical radiograms taken on the one hundred tenth day of
extraoral force.
tooth movement and shows the “low” position of the outer bow.1 No force was
wasted in extruding the upper molars-the only teeth that were banded. Fig.
8, A and B, shows how far the upper first molars tipped back, as well as the
distal migration of the unbanded upper premolars.
Fig. 8, C presents an intraoral progress ocelusal \iew showing the space
acquired. This case would suggest that the combination headcap-neckstrapdouble
face-bow combination is more efficient than t,he cervical appliance alone,
even for tipping the teeth.
In Case 4 (Fig. 9) an ll$Ls-year-old girl in the late mixed dentition had a deep
overbite, 6 mm. of overjet, slight maxillary protrusion, slight maxillary crowding,
and just adequate arch length in the lower jaw. She had an ANB angle of
6 degrees, with a Frankfort-mandibular plane angle of 29 degrees. The lower
first molars and incisors were banded, with a stopped arch wire placed to mainVolume59
Number 3 Three mechanical variables of extraoral force 231
tain arch length. The corresponding teeth in the upper arch were banded. The
objective of treatment was not only to move the upper first molars and incisors
distally and bodily as a unit but also to intrude the upper incisors as they
moved distally. One month after banding, an upper edgewise arch wire was
placed with active (30 degrees) torque. It was bent gingivally in front of the
first molar tubes to provide the necessary intrusive force on the upper incisors.
At the same appointment, 44 ounces of continuous (face-bow tied in) horizontal
force was applied to the middle third of the upper first molar roots.
Fig. 9, A, B, and C, shows the reduction in the overjet and overbite after
110 days and the increase in size of the canine eminence in relation to the upper
incisors. It demonstrates how much the upper incisors were moved distally
and intrusively. The bands were placed 3 months after the original records
were taken.
The tipped first molar (Fig. 9, D), which was the result of the reciprocal
intrusive force applied to the upper incisors by the edgewise arch wire, was
later corrected by adjusting the outer face-bow superiorly, thus raising the
horizontal level of extraoral force above the middle third of the molar root.
This adjust.ment quickly restored the molar to its upright position. One month
before the progress records were taken, a spur was placed on the inner bow to
assist with incisor intrusion. The inner bow was adjusted to apply a total of
approximately 20 ounces of intrusive force to the spur and the four incisors.
The composite tracing, made from a head film taken at the time the combination
headgear was placed and a progress head film taken 110 days later (Fig.
9, E), illustrates simultaneous distal bodily movement of the upper first molars
and upper incisors and intrusion of the upper incisors. Periapical films (Fig.
9, P) were taken immediately following removal of the heavy extraoral force;
again, no sign of root resorption is evident.
In Case 5 (Fig. lo), the patient was a girl 10 years 8 months of age, in the
late mixed dentition. Her only problem was one of severe crowding of the upper
arch, particularly in the upper right canine area (Fig. 10, A and B). It is of
interest to note that the patient had a Frankfort-mandibular plane angle of
36 degrees. Treatment was started 15 months after the original models were
taken, but there was no change in the arch length problem at the time treatment
began.
Once again, 44 ounces of continuous (face-bow tied in) force was applied to
each first molar. Progress models (Fig. 10, A, B, and E) again illustrate the
significa,nt tooth movement that resulted from controlling the magnitude, direction,
and duration of extraoral force. In Fig. 10, C and D, intraoral photographs
show the extra space created by the distal bodily movement of the upper first
molars. In this case, the upper incisors were banded merely to achieve artistic
improvement (Fig. 10, E). This was accomplished with the use of a round wire
which was not tied back. The lower teeth were not banded (Fig. 10, P). The
composite tracing (Fig. 10, H), was made from head films taken at the time
extraoral traction was placed and 101 days later. Once again, we see the distal
migration of the unhanded upper premolars. The arrow indicates the level
and direction of extraoral force, which prevented molar extrusion and any open232
Armstrong .Qmer. 6. Orthodoat.
Marcb1971
Fig. 10. Case 5. A, Right side of original and progress models after 101 days of combination
force. 6, Left side of original and progress models after 101 days. C, intraoral view
of right side after 101 days. D, intraoral view of left side after 101 days of force.
E, Original and progress models, maxillary occlusal view. F, Original and progress models,
mandibular view. G, Periapical films taken on the one hundred first day. H, Composite
tracing made from head films taken the day extraoral force began and 101 days later.
ing of the bite in this high-angle case. There was no evidence of bone loss or root
resorption in the intraoral roentgenograms taken on the one hundred and first
day of treatment (Fig. 10, G), after rapid and marked distal bodily movement
of the upper first molars.
Case 6 (Fig. 11) was that of a lo-year-old boy with a very high FrankfortVolume
59
Number 3
Three mechanical variables of extraoral force 233
Fig. 11. Case 6. A, Progress head film taken on the first day of combination force.
8, Progress head film taken after 2 months of interrupted and 4 months of continuous
force. C, Periapical radiograms taken the same day as head film in B. D, Composite tracing
made from A and B.
mandibular plane angle of 44 degrees and a constricted upper arch with crowding.
A palatal expansion appliance was used to widen the arch. During this
time, the upper teeth appeared to move forward-the first molars 2 mm. and the
incisors 1.5 mm. Fig. 11, A shows a head film taken after the palate was expanded.
On the same day, the patient was instructed to wear the combination
appliance 24 hours a day. Note especially the level of the outer bows. A force
of 32 ounces was applied to each side of the arch, for a net total of 31/2 pounds
of horizontal force per side. Because of poor cooperation from the patient, the
facebow was tied in after 2 months. Within a week, the upper expansion appliance
came loose and was removed, and bands were placed on the upper first
molars only. The time lapse between the head films shown in Fig. 11, A and 11, B
was 6 months, including 2 months of interrupted (poor cooperation) and 4
months of continuous (tied-in) extraoral force. Notice the distal movement of the
upper first molars and, remarkably, the distal movement of the unbanded upper
incisors (Fig. 11, B). Fig. 11, D shows the composite tracing. There was no
change in the mandibular plane and no measurable movement of the maxilla. The
poor quality of the head film shown in Fig. 11, A may account for this, although
there was also no measurable difference in the position of the maxilla when compared
to the original head film.
In Fig. 11, C, intraoral roentgenograms taken after 4 months of continuous
234 Armstrong
Fig. 12. Case 7. A, Right side of original and progress models after 101 days of combination
force. B, Left side of original and progress models after 101 days of force. C, Intraoral
view of right side, taken the day the combination appliance was placed. D, Intraoral view
of right side 101 days later, E, Intraoral view of left side, taken the day the combination
appliance was placed. F, Intraoral view of left side after 101 days. G, Intraoral front
view, taken the day the combination appliance was placed. H, Intraoral front view, taken
101 days later. I, Composite tracing made from head films taken the day the combination
appliance was placed and 101 days later. J, Periapical films taken on the one hundred
first day of force.
Voltbme 59
Number 3 Three mechanical variables of extraoral force 235
Fig. 12 cont’d. For legend, see opposite page.
“massive” extraoral force show no root resorption or bone loss. The space between
the first and second molars would suggest that either the maxilla moved in a
posterior direction or the upper second molars underwent distal translation.
The patient in Case 7 (Fig. 12) was an U-year-old girl in the late mixeddentition
stage. She had an ANB angle of 5 degrees, a Frankfort-mandibular
plane angle of 20 degrees, an end-to-end molar relationship, marked crowding
in the upper arch, and a moderately deep overbite. There was a l&month period
between the original models and the beginning of treatment (Fig. 12, A and
.B). The films shown in Fig. 12, C, E, and G were taken on the day extraoral
force was applied.
The treatment objective was to band the upper and lower molars and incisors,
move the upper molars bodily in a distal direction, intrude the upper incisors,
and maintain adequate space in the lower arch. One week after banding, 39s
pounds of extraoral force (face-bow tied in) was applied to each upper first
molar. A series of arch wires, beginning with a Twist-Flex were used. One
month later, 0.020 inch round wires were placed and, 2 months later, an edgewise
arch wire was placed in the upper arch but not tied back. Seventeen days
iater, progress records were taken. Intraoral photographs taken after 101 days
of controlled extraoral force (Fig. 12, D, 8’, and H) show a dramatic change
in tooth position.
The composite tracing (Fig. 12, I), made from head films taken the day
extraoral traction was placed and 101 days later, is more revealing. Snperimposition
on SN clearly demonstrates that the maxilla moved distally approximately
3 mm. and downward 1 mm. Although not anticipated in this
low-angle case, the movement of the maxilla was not detrimental. Superimposition
on the maxilla shows 4 t,o 5 mm. of distal bodily molar movement, for a
total distal molar movement of about 7 mm. in relation to the lower teeth.
Perhaps the 71/2 pounds of horizontal force caused the maxilla to slide
downward 1 mm. on its sutures, the line of least resistance, as it moved distally
3 mm. In retrospect, even though the patient had a low mandibular plane
angle, 31/e pounds to each upper first molar may have been more force than
indicated in this treatment. Less force would undoubtedly have moved only
the molars. In this case, perhaps more intrusive horizontal force (more force
on the headcap in relation to the neckstrap) would have pre\-ented t.hc nmxilla
from descending. Clinical effects of t.his direction 01’ forw WI-(’ c~lm.t~rttl~ hitlg
csplored.
Periapical rocntgenograms t,a,kcn on 1.11~o ut h11u~l~1 RI ICI first (hy i II’I~.
12, J) show no signs of root resorption, bone loss, or upper second molar involvement.
In spite of the heavy forcq the patient said that tht: “headgear
was never uncomfortable. :’
All the patients presented in this article were es&cd and motiva.tcd 1,)
their rapid and visible progress. Surprisingly, aft,er the normal s-day period
of adjusting to the appliances, the patients did not experience discomfort
from the heavy force generated by the combination headcap-neckstrap-double
face-bow. This is not to imply that continuous wear is imperative for results
when the magnitude and direction of extraoral force are being controllctl.
Obviously, the reverse is true. Greater treatment response is achieved per
hour of applied force when magnitude and direction are controlled and when
known nondissipating force is applied at the optimum vertical level in the
optimum direction, For example, most of the cases shown previously were
“retained” in their new position by nighttime traction, usually for 2 to 4
months, depending on bhe ca.sc. Kvrn t.his short duration (!l hours per night)
of heavy directional force resulted in additional distal bodily tooth movement.
Fourteen hours of voluntary headgear wear moves the upper first molars
bodily considerably faster and f&her than when the neckstrap is used alone.
The combination appliance has been usrd in many “old” cases &at were started
and did not make significant progress with the nctkstrap, WPII though thn
patients wore it conscientiously.
Since the objective of this article is t,o present the results of precisely controlling
all three mechanical variables of extraoral force, only those cases in
which the duration of force was continuous, achieved by tying in the facebow,
have been shown.
Combination appliance components
Fig. 13, A shows a top view of the double face-bow with short outer bows.
A short, heavy outer bow is preferred, since it does not deflect or deform as
much as a long outer bow when heavy force is applied. The short bow can be
bent almost straight out laterally to provide the clearance necessary to prevent
the headcap and neckstrap from encroaching on the cheeks. A second
advantage of the short bow is that the pull of the headcap and that of the
neckstrap are more parallel in relation to each other and to the ocelusal
plane.
The combination headcap-neckstrap-face-bow appliance offers the following
advantages over a high-pull-cervical gear combination with J hooks attached
to the anterior teeth : (1) It is less bulky, (2) it is more comfortable to
wear, (3) it is easier to adjust the force magnitude, (4) it is vertically adjustable
in relation to the center of resistance, (5) it attaches to the upper first
molars rather than the smaller root-resorption-prone upper incisors, (6) it
provides for the use of a midline spur to achieve a rather precise and conVolume
59
Number 3 Three mechw&ul uariubks of extraoral fame 237
Fig. 13. A, Double face-bow used with combinution appliance and tie-in staple. B, Inner
bow with stops. C, Intraoral view with inner bow tied in.
trolled intrusive force on the incisors, (7) short outer bows resist deformation,
whereas J hooks are much longer and bend markedly in response to force, and
(
the inner bow can be tied in (continuous force), whereas J hooks cannot.
Fig. 13, B shows the inner bow with stops and tie-in staple. These are prepared
to accommodate all arch lengths. There are three stops, but only the stop
with the black dot is welded. The other two friction stops are placed to keep
the weakened weld area away from the point of greatest stress, where the
inner bow is inserted into the molar tube (virtually eliminating breakage of
the inner bow). The tie-in staple is welded on both sides of the inferior surface
of the inner bow and is used in those cases in which continuous extraoral force
is desired.
Fig. 13, C shows the inner bow tied in and the compensatory downward
‘bend of the inner bow. The higher the outer bows are bent in relation to the
inner bows, the greater the upper deflection at the anterior portion of the
inner bow when force is applied by the headcap and the neckstrap. Without
the compensatory downward bend, the inner bow would push up uncomfortably
on the upper lip. For this reason, the straight 0.050 inch inner bow is preferred
over the 0.045 inch or over any size of inner bow with omega loops. The facebows
are made of a highly resilient wire, and both the inner and outer bows
are reinforced with sleeves that increase strength and rigidity. A midline
spur can be placed on the inner bow to intrude the banded upper incisors.
In this application, the outer and inner bows can be adjusted in relation to
each other to provide virtually any range of precise intrusive force to the midlint
spur and the lIpper anterior teeth, Additional intrusive force :ttfjust.rnc~nt
can he made bvY increasing or decrea.sing t,he fo~c on the headcap in rrlat~ioli
to the neckstrap.
In the usual -force application wit,h tile combination appliance, thctrc is IIO
extrusive component; t,herefore, for any given amount. of force, there is nrl1cl\
less chartw of loose molar bands t,han with the downward pull of Ore neckstrap.
If heavy force is applied (:?I,$ pounds per side), however, care should be take11
to make well-fitting molar bands and to make certain that the headgear t\lbc
is securely attached to the band.
Fig. 1.4, A shows how easy it is for the assistant to fit and adjust, the headcap
to the indicated force. The adjustable, severable nylon tab of the headcap
makes fitting and adjustment to the correct force magnitude simple. Because
of the length of the tab, one size fits all patients. When necessary, the headcap
can be trimmed around the ear to avoid irritation. The cap portion may
also be padded for additional comfort. Since the extra length with padding
is more comfortable for the patient with the short, outer bow7 a. 10.5-inch
neckstrap is preferred t,o the usual 7 inch one (Fig. 14, K) . The fitting procedure
is easier when the patient is either standing or seated in an upright position. Attachment
of the headcap to the face-bow i Fig. 14, C) and then the neckstrap (Fig.
14, D) is accomplished with equal ease for the patient, as well as the assist,ant,.
Fig. 14, E shows the short outer bows bent out to clear the cheeks so that
t,here is no discomfort, even with the use of heavy force. Fig. 14, P illustrates
the distribution of the extraoral force over a wide area of the head and neck,
permitting the application (Jf up to 3% ounces of force on each side of each
appliance and providing a bilateral net horizontal force of approximately 31/!
pounds. The combined total force applied to the maxilla would not exceed
7 pounds. Clinical experience indicates that extremely heavy extraoral force
is not uncomfortable to the pat,ient as long as there is no downward or extrusive
component, such as that characteristic of cervical appliances used alone. It
is the extrusion of teeth that C~LISCS traumatic occlusion, mobility, and soreness.
This unnecessary extrusive componrnt virtually prevents the application
of heavy cervical force.
Fig. 15, A and 11, shows a heavy force headcap that, provides twice the force
(up to 4 pounds per side) as the previously shown headcap. The size and tit
of the headcap are critical when one is using more than 2 pounds per side. The
cap should be large enough that the junction of the two headcap straps and the
spring anchor stra.p (Fig.. 15, 11) is below the curvature of the side of the head,
as close to the ear as possible without, impinging. (‘are in fitting will avoid
pressure spots and discomfort. In order to tolerate this magnitude of force (up
to 4 pounds per side), the cap portion (Fig. 15, R) should be made of a semiflexible,
well-padded material 1 or more inches wide. Fig. 15, G and 1) shows a
unilateral force combination appliance.
Patient acceptance
Most patients have been surprisingly receptive to wearing the eombination
appliance cont,inuously 24 hours a day. Its comfort is a major reason.
Three mechanical variables of extraoral force 239
Fig. 14. A, Assistant adjusting headcap to force. 6, Assistant adjusting neckstrap to force.
C, Patient putting on headcap. D, Patient putting on neckstrap. E, Top view of face-bow.
F, Back view of combination appliance.
When the appliance is used properly, the treatment response is visibly apparent
to everyone. Favorable treatment results are routi>nely attained with
reliability and speed, and the duration of the extraoral force is assured by
tying in the face-bow when indicated.
At the consultation, the parents and the patient are advised that the headgear
is part of the fixed appliance and that it is permanently attached as
l.ong as it is needed to do the job. The phrase “tied in” is avoided because it
connotes either punishment or other than the usual procedure. Both parents
240 Arnwhrony .tncr’r.. .I. O?thvdortt.
Man-h 1071
Fig. 15. A, Heavy-force headcap, side view. 8, Heavy-force headcap, top view. C, Unilateral
application of the combination headcap-neckstrap-face-bow. D, Side view of the
unilateral combination appliance.
and patients are advised of the many overriding advantages of continuous
headgear wear, such as the much shorter treatment time, less headgear wear
in the long run, and the better and more consistent treatment results achieved
with less complicated mechanotherapy. Finally, and certainly very important
to the parents, is the elimination of their responsibility to see that the child
wears the extraoral appliance the required number of hours each and every
day which, after 2 months, inevitably leads to nagging by the parents and
rebellion by the child. Fortunately, most of the patients receiving interceptive
or late mixed-dentition treatment are of junior high school age or less. These
younger patients offer much less initial resistance to continuous wearing of the
combination appliance. Moreover, once the first visible progress is made (usually
within 4 to 5 weeks), even the patient who exhibited strong initial resistance
usually becomes an interested and motivated participant in treatment, for he can
see for himself that his cooperation is producing results.
Treatment timing
Clinical response in the early permanent dentition to continuous extraoral
force has not proved rapid enough to justify full-time wear of the appliance.
Here the role of extraoral force in treatment is limited to the creation of 2
Volume 59
Number 3 Three mechanical variables of extraoral force 241
or 3 mm. of space per side or the prevention of the forward movement of upper
posterior teeth during extraction-space closure. The duration of wear is reduced
to 14 hours per day. Class II correction by extraoral force alone, at this older
dental age, requires more cooperation than can be expected or asked of most
patients.
It appears that tissue responsei s most rapid in the mixed-dentition stage,8rl3
when substantial, visible tooth movement can be accomplished in a relatively
short period of time (4 to 6 months on the average). Fortunately, this is the
stage at which patients are usually at their most cooperative.
All factors considered, interceptive treatment with the combination headgear
appears to be especially effective and efficient in the late mixed dentition.
By definition, the late mixed-dentition stage is that stage before all deciduous
teeth are lost, especially before the upper permanent canines have erupted.
Ideally, the upper canines will break through the soft tissue within 6 months
after correction of the interarch and/or intraarch problem by use of continuous
extraoral force.
The unerupted premolars and canines migrate distally after the upper
first molars have done SO.~2~3 12 4I n the Class II case, if the upper canines have
erupted before headcap force has been applied, correction of the Class II
malocclusion is much more difficult.8 This is even more true if the upper second
molars have completely erupted.‘g
Clinical evidence to date suggests that, when the upper first molars are
rapidly moved bodily in a distal direction, the unerupted tooth buds of the
upper second molars are, in turn, translated distally, showing little evidence
of rolling out buccally or tipping distally. On the other hand, when the upper
second molars have erupted or are in the process of breaking through the soft
tissue, they often roll buccally and tip distally.
In some of the latter cases, it will be necessary to extract the upper second
molars. The upper third molars then erupt into the second molar spaces.
Certainly, this is not the ideal solution. However, in view of the alternative
treatment of upper first-premolar extraction with a much more complicated
mechanotherapy, and in view of the more pleasing esthetic appearance of the
denture with all of the premolars present, this appears to be the treatment of
choice.
Treatment response
In the vast majority of patients of the same dental age, there is a fairly
uniform dentoalveolar response to the application of more than a given number
of pounds of extraoral force (heavy), in a certain direction, 24 hours per day.
By using this controlled force and relating it to the patient’s dental age, the
orthodontist can, with a fair degree of certainty, anticipate the amount of
tooth movem.ent that will occur between appointments. Differences in treatment
response are related more to differences in the dental developmental age than
to differences in the biologic response between patients. Contrast the treatment
response of any person in the mixed dentition to that in the adult dentition,91 l3
or even the rate of tooth movement in the late mixed dentition to the slower
rate of movement in the early permanent dentitiun. Perhaps the? treatmenr
variation between the latter two may be related more to the erupted position
of the upper canines and second molars.“. Z’
Lack of precise control of the mechanical variables in treatment may be
responsible for the general feeling among many orthodontists that there is a
great biologic variation between patients of the same dental age which results
in the wide difference in treatment response. Although there are exceptions,
clinical experience to date with the use of controlled force indicates that the
biologic variation is not this great.
Root resorption
Close examination of postforce and posttreatment periapical roentgenograms
and head films obtained during more than 5 years of clinical experience would
suggest that continuous heavy force and rapid bodily tooth movement (achieved
with the use of calibrated coil springs) do not cause significant root resorption.
Clinical experience would further suggest, that the cause of root resorption is
related more to any or all of the following: long-duration treatment,? tipping
movements of teeth, and slow, long-term intermittent tooth movement.
In answer to the question of how heavy continuous forces can be applied
without causing cemental and root resorption, “one can only cite that less is
known about cemental responses to environmental stimuli than for any other
component of the periodontal complex. This topic requires much experimental
study before we can attempt to explain or even predict clinical responses4”20
Conclusion
The objective in treatment of Class II malocclusion in the late mixed dentition
is to establish normal occlusion and normal muscle balance by distal
bodily movement of the upper first molars and incisors, along with associated
remodeling of the maxillary alveolar process in the direction of tooth movement.
The establishment of normal muscle balance is consistent with the theory
of the functional matrix in growth,21 and the restoration of normal occlusion
enhances the ability of the upper and lower jaws LO grow downward and forward
together.
Sincere appreciation is extended to Donald C. Hilgerq chairman of the Department of
Orthodontics, Loyola University School of Dentistry, Chicago, for his suggestions in the
preparation of this article, and to Mr. Clifford L. Freehe, director of dental photography at
the University of Washington, for his assistance in preparing the photographic reproductions.
REFERENCES
1. Barton, John J.: Personal communication, Minneapolis, Minn., 1968.
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voltLms 59
Number 3 Three mechanical variables of extraoral force 243
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lSO6 N. 175th St.
