This case report summarizes the effects of headgear-activator therapy on 10 patients with Class II malocclusions. Key findings include: 1) Five of the 10 cases showed distal movement of the lower first molars, which has not been previously reported. 2) Growth stimulation of the mandible was observed in some patients, with mandibular growth above average compared to a control group. 3) Abnormal oral functions, like tongue thrusting and lip biting, were eliminated in all patients. 4) The headgear-activator appliance was considered an effective tool for controlling vertical growth problems and Class II malocclusions in growing mixed-dentition patients.

1. CASE REPORT
Skeletal, dental, and functional effects of
headgear-activator therapy on Class II malocclusion
in Japanese: A clinical case report
Toshio Deguchi, DDS, PhD, MSD*
Nagano-ken,Japan
Ten orthodontic patients in whom a headgear-activator appliance was used in the first phase of
treatment for Class II malocclusion were clinically evaluated. All patients had abnormal perioral
muscle function at the initial examination. Myofunctional methods were used before and during
active treatment. Pretreatment and posttreatment cephalometrictracings were evaluated to examine
the effect of the appliance on dental, skeletal, and soft tissue structures. Five of the 10 cases
illustrated distal movement of the lower first molar, a phenomenon not mentioned previously in the
literature. Growth stimulation of the mandible was also observed in this patient sample, with some
subjects demonstrating above-average mandibular growth when compared with a control group of
normal subjects. Abnormal oral function was eliminated, and all patients had clinically acceptable
results at the end of the treatment period. The headgear-activator appliance can be considered an
effective tool for the control of vertical growth problems in growing mixed-dentition patients. (AMJ
ORTHOODENTOFACORTHOP1991;100:274-85.)
In Japan activator use in orthodontics is not
new. The Andresen activator was introduced by Tak-
ahashi in 1941t for the treatment of Class II malocclu-
sion. However, over the last 25 years many Japanese
orthodontists have abandoned the activator for the early
treatment of Class II malocclusion. Recently, American
orthodontists have renewed their interest in using the
modified activator in the treatment of Class II maloc-
clusion.
Most of the articles in the literature support the
hypothesis that anterior displacement of the mandible
can enhance the growth of the condyles in monkeys26
by means of an occlusal guide plane and in human
beings7"° by means of functional jaw orthopedics
and unloading of the condyles. Other articles report
contradictory data in monkeys1~,Iz and in human
beings. 13-15
McNamara and Carlson~ studied 64 rhesus mon-
keys when evaluating neuromuscular and skeletal ad-
aptations to orthodontic procedures with anterior dis-
placement of the mandible. They reported positive al-
terations in the amount and direction of growth at the
condyle in the infant and juvenile animals.
*Chairman and professor, Department of Orthodontics. Matsumoto Dental
College, Nagano-ken, Japan; D[plomate of the American Board of Ortho-
dontics.
8/4/17798
Pfeiffer and Grobety17.18 and Teuscher~9 also re-
ported good results when both horizontal and vertical
jaw growth was controlled with activator and extraoral
force. This combined treatment modality has also
been reported in the treatment of Class II open bite
cases with low or normal Frankfort-mandibular
angles. 50-22
Since 1978, I have been interested in the use of the
headgear-activator appliance for the first phase of Class
II treatment with abnormal perioral function because
this appliance seems to offer mechanical and biologic
advantages in the correction of Class II malocclusion.
This article deals with 10 cases of Class II nialoc-
clusion in Japanese children, eight with deep overbites
and two with open bites. In treatment of Class II mal-
occlusion with deep overbite the objectives were as
follows (Figs. 1, A and B): (1) vertical control of max-
illary buccal segments, (2) inhibition of forward growth
of the maxilla, (3) acceleration of growth of the man-
dible, (4) retraction and limited intrusion of maxillary
incisors, and (5) correction of abnormal perioral func-
tion (Fig. 2).
For the open bite cases (Fig. 1, C), the appliance
was mainly designed for (1) intrusion of maxillary buc-
cal segments, (2) stimulation of forward growth of the
mandible, (3) natural eruption of both maxillary and
mandibular incisors, and (4) correction of abnormal
perioral function (Fig. 2).
274

2. Volume I00
Number 3 Case report
B
Fig. 1. Diagrams of variations in force delivery with combined headgear-activatorappliance indicating
direction of headgear pull (black arrows) and rotation or direction of maxillary and mandibulargrowth
provided by the appliance (dotted arrows). A, A case with deep bite and a normal FMA; B, a case
with deep bite and a large Frankfort-mandibular plane angle (FMA); C, a case with open bite and a
large Frankfort-mandibular plane angle. (See Figs. 4, 5, and 6 for examples.)
275
MATERIALS AND METHODS
The appliance (modified Andresen activator) is illustrated
in Fig. 3, A and B. Bite registration included a 4 to 6 mm
mandibular minimum posterior bite opening similar to that
reported by Teuscherj9 for deep bite cases. Ball clasps were
used for retention and for exertion of distal force on the
maxillary first molars. The headgear was of either the Inter-
landi or the high-pulltype, placingthe force through the center
of resistance of the maxilla (Fig. 1, A). The incisal edges
and the superior labial surfaces of both the maxillary and the
mandibular incisors were capped with activator acrylic to
facilitate intrusion in excessive overbite cases.
In the open bite cases, the headgear tubes were placed at
the mesiobuccal aspect of the upper molars to accomplish
isntrusion with high-pull forces. The acrylic lip on the max-
illary and mandibularincisaledges was removed to allow free
eruption.
The patients were instructed to wear the appliance at night
only. Treatment was begun with 400 to 500 gm of headgear
force per side.
The diagnostic records included headplates, study casts,
I
Fig. 2. Spatial relationships of appliance, tongue, and finger.
The activator appliance inhibits tongue thrust, lip biting, and
finger sucking.
and photographs obtained before (A), during (AB), and after
(B) active treatment. Millimetric measurementsof Ar-Pg dur-
ing A-AB and AB-B intervals were made to evaluate man-
dibular growth.

3. Am. J, Orthod. Dentofac. Orthop.
276 Deguchi September L991
Fig. 3. Intraorat views show inner and outer bows, labial wire, ball clasps, and activator portions. A
and B, The design of an appliance for deep bite cases. The lower posterior teeth may erupt. The
incisor teeth are capped with acrylic. C, An appliance designed for open bite cases. Posterior teeth
have an occlusal cover with a bite block and a more wide-open interocclusal space; the acrylic is cut
away from the incisors to permit their eruption.
Table III. Abnormal habits of 10 patients at
initial examination
Habits
Case no. sacking thrust breathing biting
1 (E. M.)* 0 +
2 (H. H,) +
3 (S. A,) + +
4 (A. I,) +
5 (N. O.) +
6 (K. K.) 0 + +
7 (K. Y.) +
8 (R. Y.) 0 + + +
9 (N. K.) + + +
10 (A. H.) + +
*Patient initials.
0 = History of the habit; + = presence of the habit.
Ar-Pg measurements in the study sample were compared
with the annual incremental measurements of Ar-Pg in a nor-
mal samplez~(Tables I and ID obtained from lateral headplates
of 16 boys and 16 girls (10 to 15 years old) with ideal oc-
clusion in the Growth Study sample at the Department of
Orthodontics, Matsumoto Dental Co[lege,
Table I. The annual increment of mandibular
growth in the control sample with normal
occlusion and good profile
Mandibular length
Ar-Pg (mm)
Age
(yr) Boys Girls
10-11
Mean 2.19 2.27
SD 1,39 1.84
11-12
Mean 4.13 4,35
SD 1,07 0.93
12-13
Mean 3.03 2.18
SD 1.37 1.43
13-14
Mean 3,82 2.31
SD 1.07 1.23
14-15
Mean 3.86 2.14
SD 1,08 1.25
CASE PRESENTATION
The study sample treated with the headgear activator ap-
pliance (Table II), was from the Orthodontic Department of
Matsumota Dental College. Most of the 10 cases were treated

4. Vohtme IO0
Numl.,er 3 Case report 277
Fig. 4A. Case 1. Pretreatment study models.
Fig. 4B. Before- and after-treatment profile views.
Table II. Growth of mandibular length (Ar-Pg) in 10 cases
Case no (sex, initial age)
Ar-Pg (ram)
A-AB (ram) Duration (too.) I AB-A'B' (ram) Duration (too.) AB-B (ram) Duration (ino.)
i
1 (F~ 9 yr 0 mo) 8.0 11 ND ND 3.0 18
2 (M, 11 yr 11 too) 1.5 6 ND ND 1.0 8
3 (F, 10 yr 10 too) 2,5 7 ND ND 4.5 18
4 (M, 9 yr 9 too) 8.5 24 ND ND 5.5 26
5 (F, 9 yr 10 too) 0.5 4 ND ND 5.0 25
6 (M, 8 yr i0 too) 5.5 24 ND ND 7.0 26
7 (F, 9 yr 9 mo) 3.0 5 ND ND 5.0 30
8 (F, 8 yr 2 mo) 6.5 15 ND ND 3.0 19
9 (F, 9 yr 0 mo) 9.5 23 ND ND 5.0 36
10 (F, 8 yr 0 too) 3.5 24 5.5 23 ND ND
ND = Not determined; A-AB -~ growth between the initial and the progress; AB-A'B' = growth between the progress and the observation
after the appliance was removed (A'B'); AB-B = growth between the progress and tile postaetive treatment.

5. 278 Deguchi A~,. J. Orthod. Demqfac. Orthop.
September 1991
O
i ;
"-~ i /
J
Fig. 4C. Cephalometric tracings at beginning and end of first phase of treatment, superimposed tracings
and changes in maxilla and mandible.
by me, The presence of oral habits is listed in "Fable I because
one of the criteria for case selection was the presence of
abnormal oral function. Three cases are presented to illustrate
the changes achieved.
Case 1 (Fig. 4) involved a relatively mild Class II, Di-
vision 1 problem with 4 to 6 mm advancement in the con-
struction bite but minirnal vertical opening, Posterior teeth
were free to erupt (see Fig. 3, A).
In Case 2 (Fig. 5, A, B. and C) treatment objectives in
the first phase of therapy for a severe Class [I, Division 1
malocclusion were (1) vertical control of maxillary growth,
(2) stimulation of the anterior growth of the mandible, (3)
correction of the Class II molar relationship, (4) correction
of incisor protrusion, and (5) elimination of the patient's lip-
biting habit. Because of the arch length deficiency, extraction
of the maxillary first premolars and the mandibular second
premolars was planned. Most of the treatment objectives were
achieved 5 months after placement of the appliance (Fig.
5, C, D, and E). Edgewise treatment started 1 year after
placement of the headgear-activator appliance, and total treat-
ment time was 2 years I l months. The results were accept-
able, with a more balanced profile. However, the Frankfort-
mandibular angle increased by 3".
Case 3 (Fig. 6) involved an anterior open bite and a Class
II tendency. Objectives in the first phase of treatment were
(1) restriction of the vertical growth of the maxilla and all
possible depression of posterior teeth, (2) stimulation of the
growth of the mandible, (3) natural eruption of incisors, and

6. Volt#he I00 Case report 279
Nvmber 3
Fig, 4D. Lateral views of casts at end of first phase of treatment.
Fig, 4E Intraoral views at end of second phase of treatment,
Fig. 5A, Cases at beginning of treatment.
(4) elimination of oral habits, Most of the treatment objectives
were achieved 6 months after use of the appliance. Treatment
was completed with an edgewise appliance. The tongue-thrust
habit abated to some extent but tended to persists.
DISCUSSION
The Interlandi and high-pull types of headgear-
activator appliance were effective in correcting the
Class II malocclusion at an early stage or in the late
mixed-dentition stage. All cases showed stable occlu-
sion, satisfactory skeletal growt h, and significant profile
improvement after removal of the appliance.
Pfeiffer and Grobety ~s stated that the activator Can
contribute to the correction of muscle dysfunction, ab-
normal respiration pattern, and pernicious habits. The

7. 280 Deguchi Am. J. Orthod. Dentofac. Orthop.
September 1991
Fig. 5B. Profile photographs.
0
Fig. 50, The tracings.

8. Volume 100 Case report 281
Number 3
Fig. 5D. Study casts at end of first phase of treatment.
Fig. 55. Intraoral photographs at end of second phase.
Fig. 6A. Study casts at beginning of treatment.
activator, as stated by Graber and Neumann, 26 is in-
dicated in cases in which primary dysfunction and a
favorable growth pattern exist.
In this study, the headgear-activator appliance was
used for Class lI malocclusions with different oral dys-
functions. The results showed that the appliance could
improve abnormal pressure habits and oral breathing if
administered with myofunctional therapy during appli-
ance wear.
Levin~-7reported the effects of the cervical headgear-
activator appliance on Class II correction. He stated
that both the brachyfacial and the mesiofacial types
showed the most favorable response to treatment with
the appliance.

9. 282 Degttchi Am..1. Orthod.Demcfac. Orthop.
September 1991
Fig. 6B. Profile photographs.
/ /
©
,/
/
Fig. 6G. The tracings,

10. Volume 100 Case report 283
Number 3
Fig. 6D. Study casts at end of first phase of treatment.
Fig. 6E. Intraoral photographs at end of second phase.
Pfeiffer and Grobety~7reported that in skeletal open
bite cases, the sagittal discrepancy could be improved
by restraining the vertical growth of the maxillary struc-
tures to bring the mandible up and forward (autorota-
tion). They also advised that for a dental deep bite with
a skeletal open bite it is useful to maintain or decrease
the vertical dimension in the molar region by intruding
the molars and then intruding the incisors for deep bite
correction.
In this sample, Cases 2 and 3 involved dolichofacial
patients, each with a steep mandibular plane angle. The
patient in Case 3 also had a skeletal open bite. In Case
2 vertical control of the maxillary structures was
achieved with the headgear component. Subsequent
placement of the full edgewise appliance corrected
the excessive overhite during the second phase of
treatment.
Although Teuscher~9stated that in high-angle cases
activator therapy has been regarded as contraindicated,
the combined activator-headgear appliance (occipital or
high-pull) could restrain the vertical growth of the max-
illary structures during the use of the appliance in the
first phase of treatment. This is usually beneficial.
Case 2 illustrates some changes not mentioned in
the literature, including distal movement of the lower
first molars. The following are some possible reasons
for the distal movement or the distal tipping of the lower
J
Fig. 7. Force diagram indicating direction of extraoral force
(large sofid arrow); distal force for upper and k~werdentition
(small solid arrows), a result of head-gearcompt,nent; and me-
sial force for lower dentition (dotted arrow), a result ofcombined
forward posturing, together with masticatory mu,~cleforce at-
tempting to place the anteriorly displaced mandible in original
position.
first molars: (1) The distal force of the headgear com-
ponent might be transferred to the lower first molars
because the occlusolingual acrylic resin of the appliance
was not trimmed (Fig. 6); (2) the distal movement of

11. 284 Deguchi Am. J. Orthod.Dentofac. Orthop.
September 1991
the upper molars may guide the distal movement of the
lower molars through occlusal interdigitation; (3) some
doliehofacial patients may have weak masticatory mus-
cle activity that allows the mandible to drop back to
the original posterior position; or (4) lower incisors with
acrylic capping may be lingually guided by the me-
chanical force of the headgear, causing a distal tipping
of the lower buccal segments.
In the force diagram (Fig. 7), the solid line rep-
resents the distal headgear mechanical force of the ap-
pliance and the dotted line represents the force induced
by the masticatory muscle, which is commonly under-
stood to move the mandible and its dentition in a for-
ward direction for correction of the Class II molar re-
lationship. This distal force on the lower dentition may
be an advantage in Class II nonextraction treatment.
However, it is hypothesized that this force may coun-
teract the normal mandibular growth and restrain the
effects of the anterior mandibular displacement of the
bite registration.
Harvold is stated that selective control of molar ex-
trusion between the jaws during growth is a powerful
tool for the correction of Class II malocclusion. Class
II malocclusion in the Japanese population demon-
strates a retruded mandible that is rotated downward
and backward with a steep mandibular plane angle, 2s
while a comparable Class II malocclusion in the white
population shows a flatter mandibular plane angle. 29In
addition, vertical control of maxillary structures is more
important in the Japanese so that the mandible will not
be brought downward and backward, since the headgear
(occipital or high-pull type) component works against
the vertical growth of the maxilla.
Buschang et al.a° compared the mandibular growth
of 6- to 15-year-old French-Canadian children with nor-
mal occlusion and that of children with untreated Class
II malocclusion. They found that growth deficiencies
in children with Class II malocclusion were approxi-
mately 0.4 cm per year for boys and 0.2 cm per year
for girls, accumulating throughout the age range to pro-
duce significant differences by adulthood. Case 2
showed growth increments comparable to those of the
control sample (Tables II and III). The sample size was
small and, statistically, it cannot be said that the man-
dibular growth obtained was caused solely by the ap-
pliance. It is wel! established, however, that the acti-
vator does not inhibit the natural growth of the man-
dible,
I suggest that animal experiments be conducted to
examine the relationship between the distal force of the
lower dentition and the design of the activator and also
to evaluate whether the distal force of the lower den-
tition could act as a counterforce to the stimulation of
normal mandibular growth.
I express my sincere thanks to Dr. T.M. Graber and Dr.
M. Faysal Talass for their editorial assistance and manuscript
evaluation.
REFERENCES
1. Takahashi S. Geschichtliche Beobachtung fiber Orthodon-
tische Behandlungsmethodenmitbesonderer Berucksichtungder
Functions-Kieferorthopadieyon Andresen und Haupl. J Jpn Or-
thod Soc 1941;9:8-26(in Japanese).
2. Baume LJ, Derichsweiler H. Is the condylar growth center re-
sponsive to orthodontic therapy? An experimental study in Ma-
caca mulatta. Oral SurgOral reed Oral Pathol 1961;14:347-62.
3. Breitner C. Bone changes resulting from experimental
orthodontic treatment. AM J ORTHODORALStmC 1940;26:
521-47.
4. Elgoyhen JC, Moyers RE, McNamara JA Jr, Riolo ML. Cra-
niofacial adaptation toprotrusivefunction in youngrhesus mon-
keys. AMJ ORTHOD1972;62:469-80.
5. McNamara JA. Neuromuscular and skeletal adaptations to al-
tered functionin the orofacialregion. AMJ ORTHOD1973;64:578-
606.
6. Stockli PW, Willert HG. Tissue reactions in the temporoman-
dibularjointresulting from anteriordisplacementof the mandible
in the monkey. AM J ORTHOD1971;60:142-55.
7. BaumeLJ, Hauple K, StellmachR. Growth and transformation
of the temporomandibularjoint in an orthopedically treated case
of Pierre Robin's syndrome. AMJ ORTHOD1959;45:901-16.
8. Brown CJ. Cephalometric study of mandibular length change
during F,J.O. Treatment. [Master Thesis]. Michigan, 1959,
Univ. of Michigan.
9. Marschner CF, Harris JE. Mandibulargrowth and Class II treat-
ment. Angle Orthod 1966;36:89-93.
10. Meach C. A cephalometric comparisonof bone profile changes
in Class II Division 1 patients treated with extraoral force and
functional jaw orthopedics. AMJ ORTHOD1966;52:353-70.
11. Hiniker JJ, Ramfjord SP. Anterior displacementof the mandible
in adult rhesus monkey. J Prosthet Dent 1966;16:503-12.
12. Meikle MC. The effect of Class lI intermaxillary force on the
dentofacial complex in adult Macaca mulatta monkey. AM J
ORTHOD1970;58:323-40.
13. Bj6rk A. The principles of the Andresen method of orthodontic
treatment; a discussion based on cephalometric x-ray analysisof
treated eases. AM J ORTHOD1951;37:437-58.
14. Jacobsson SO. Cephalometricevaluation of treatment effect on
Class II, Division 1 malocclusion. AMJ ORrHOD1967;53:446-
57.
15. Harvold EP, VargevickK. Morphogeneticresponse to activator
treatment. AMJ ORTHOD1971;60:478-90.
16. McNamara JA, Carlson DS. Quantitative analysis of temporo-
mandibular joint adaptations to protrusive function. AM J OR-
THOD1979;76:593-611.
17. Pfeiffer JP, Grobrty D, The Class II malocclusion: differential
diagnosis andclinical applicationof activators, extraoral traction
and fixed appliances. AM J ORTHOD1975;68:499-544.
18. Pfeiffer JP, Grobety D. A philosophy of combined orthopedic-
orthodontic treatment. AMJ ORTHOD1982;81:185-201.
19. Teuseher U. A growth-relatedconcept for skeletal Class II treat-
ment. AMJ ORTHOD1978;74:258-75.
20. Fotis V, Melsen B, Droschl H. Vertical control as an important

12. Volume 100 Case report 285
Number 3
ingredient in the treatment of severe sagittal discrepancies. AM
J ORTHOD1984;86:224-32.
21. Ganmond G. Hyperpropulsor activator. J Clin Orthod 1986;
20:405-11.
22. Returner KR, Mamandras AH, Hunter WS, Way DC. Cepha-
lometrie changes associated with treatment using the activtor,
the Fr~nkel appliance, and the fixed appliance. AM J ORTHOD
1985;88:363-72.
23. Deguchi T. Determination of developmental age in Japanese
adolescent. J Jap Orthod Soc 1984;43:346-55.
24. Ricketts RM. Esthetics, environment, and the low of lip relation.
AM J ORTrlOI~1968;54:272-89.
25. Engle G, Spolter BM. Cephalometric and visual norms for a
Japanese population. AM J ORTHOD1975;68:499-544.
26. Graber TM, Neumann B. Removable orthodontic appliances.
2nd ed. Philadelphia: WB Saunders, 1984;146-70.
27. Levin RI. Activator headgear therapy. AMJ ORTHOD1985;87:91-
109.
28. Miura F, Sakamoto T, Irie M. Roentogenographic cephalometric
analysis of maxillary protrusion case treated by activator. J ]-ap
Orthod Soc 1961;20:114-20.
29. Moyers RE, Rioro ML, Guire KE, WalnrightRL, Bookstein FL.
Differential diagnosis for Class II malocclusion. AM J ORTHOD
1980;78:477-94.
30. Buschang PH, Tanguay R, Demirjian A, LaPalme, Turkewlez
J. Mathematical models of longitudinal mandibular growth for
children with normal and untreated Class II, Division 1 mal-
occlusion. Eur J Ofthod 1988;10:227-34.
Reprint requests to:
Dr. Toshio Deguchi
Department of Orthodontics
1780 Gabbara Hirocka
Shiojire, Nagano, 399-07
Japan