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American Journal
ORTHODONTICS
of.
Volume 88 Number 4
Founded in 1915
Copyright
0 1985 by The C. V. Mosby Company
ORIGINAL
Dentofacial orthopedics in relation
somatic maturation
October, 1985
ARTICLES
to
An analysis of 70 consecutive cases treated with the
Herbst appliance
Hans Pancherz, D.D.S., Odont. Dr., and Urban HBgg, D.D.S., Odont. Dr.
Malmii,
Sweden
Mandibular treatment changes were related to somatic maturation in 70 consecutive cases of Class II malocclusion
(52 boys and 18 girls, aged 10 to 18 years) treated with the Herbst appliance for an average period of 7
months. Sagittal and vertical alterations in mandibular condylar growth and sagittal changes in molar and incisor
tooth position were analyzed by means of mouth-open profile roentgenograms. The somatic maturity level of
the patients was assessed by means of longitudinal growth records of standing height. The treatment period was
related to the peak height velocity by dividing the patients into three growth-period groups: prepeak, peak, and
postpeak. Herbst treatment ‘resulted in Class I dental arch relationships in all patients. Post-Herbst treatment
changes were not evaluated in this study. Sagittal condylar growth was increased and the mandibular molars and
incisors were moved anteriorly. When the mandibular skeletal and dental changes were related to the subjects’
somatic maturation, significant differences between the different growth periods existed in boys and tendencies
were noted in girls as follows: (1) sagittal condylar growth was most pronounced in the peak period, (2) anterior
molar movement was equally large in all growth periods, and (3) anterior incisor movement was most extensive in
the postpeak period. To take advantage of the increase in condylar growth response and to reduce the time
of posttreatment retention, it is suggested that Herbst therapy be instituted close to peak height velocity.
(AM J ORTHOD 88: 273-287, 1985.)
Key words: Orthodontics,
velocity growth curves, cephalometry,
T
he most suitable period for growth intervention in orthodontic treatment is the subject of debate.
Some authors’-“3 claim that the patient’s level of somatic
development strongly influences the outcome of various
orthodontic measures and that there are suitable and
From the Department of Orthodontics,
School of Dentistry,
University
of Lund.
skeletal changes, dental changes
reliable methods to assessthe maturation level in clinical work. Other authors”-” assert that somatic maturation has comparatively little intiuence on the success
of orthodontic treatment and that the methods devised
to estimate individual maturity in clinical work are too
uncertain. Neither of the two conflicting opinions, however, is predicated on analyses of sufficient numbers of
patients treated under standardized conditions.
273
274
Pancherz
and
Hiigg
Fig. 1. Intraoral photographs of a Class II, Division 1 malocclusion treated with the Herbst appliance
A, Before treatment. B, Start of treatment. C, After treatment.
Table 1. Mandibular morphology and mandibular-cranial base relationships in 93 Class II malocclusions
(B = Boys, G = Girls)
Herbst
Variable
(mm or degrees)
Mandibular
jaw base
length (pgn-co)
P-angle (MLipgn-co)
Go-angle
(MLIRL)
Sagittal mandibular
jaw
position (s-n-pg)
Vertical mandibular
jaw
position (MLINSL)
B
G
B
G
B
G
B
G
B
G
group
(n = 70)
Control
group
(n = 23)
n
Mean
SD
n
Mean
SD
52
18
52
18
52
18
52
18
52
18
111.5
111.3
24.9
24.0
124.X
126.9
76.8
16.9
31.4
31.9
6.69
4.04
2.90
2.92
23
23
110.0
5.13
24.7
-
3.42
6.05
6.51
23
125.2
--
6.87
3.51
4.50
5.80
6.76
23
77.3
2.38
23
-
29.6
-
5.62
Table II. Occurrence of various events in 70 Herbst subjects and 23 control subjects (B = Boys, G = Girls,
D = Sex difference)
Herbst
Prepeak
Vaiiable
(years)
Age at peak
height velocity
Age at start of
examination
period
Age at end of
examination
period
Length of examination
period
Age at peak
height velocity
*Significance
**Significance
***Significance
B
G
D
B
Peak
D
B
G
D
B
G
D
Mean
SD
II
Mean
SD
n
Mean
SD
29
2
14.3
(12.5)
0.76
17
9
0.76
0.65
6
7
12.0
(11.1)
(1.1)
12.6
(11.5)
(1.1)
0.6
0.81
17
9
0.48
0.54
6
7
0.84
17
9
0.50
0.49
6
7
0.15
17
9
0. IO
0. II
6
7
12.9
11.0
1.9**
14.4
12.5
I .9”
15.1
13.1
2.0*
0.7
0.6
0.1
0.86
1.20
29
2
13.4
12.2
I .2***
12.8
12.0
0.8**
13.4
12.7
0.7**
0.6
0.6
0.0
29
2
29
2
Total
at 5% level.
at 1% level.
at 0.1% level.
Postpeak
n
(1.8)
G
group
Herbst
(0.5)
(0.1)
sample
B
G
Mean
13.8
11.8
SD
0.94
1.09
Swedish
reference
samplez4
B
G
Mean
14.1
12.0
1.16
1.22
1.20
1.17
0.18
0.09
SD
1.08
1.02
Volume 88
Number 4
Dentofacial
orthopedics
in relation
to somatic maturation
Fig. 2. The Herbst appliance. A, Working position of the appliance with the teeth in occlusion. B, Partial
maxillary and mandibular anchorage. C, Total maxillary and mandibular anchorage.
Herbst
Control group
group
PrepeaklPostpeak mean
difference
1.4***
PeakiPostpeak
mean
difference
Prepeak
Prepeak
Peak
HerbstlControl
mean
di’erence
n
Mean
SD
n
Mean
0.5
1.2*
21
13.8
0.76
2
(12.9)
0.5*
-o.s***
- 2.4***
- I .6***
-0.5
21
11.3
0.85
2
(12.5)
0.7**
- o.t3**
- 2.5***
- 1.7***
-0.4
21
11.8
0.84
2
(13.0)
0.8**
-0.1
-0.1
0.0
21
0.5
0.03
2
(0.5)
0.0
0.1
275
276
Pancherz
and Hiigg
OLP
VELOCITY
mm
Fig. 3. Measures of mandibular condylar, molar, and incisor
changes. Mandibular tracings of mouth-open profile roentgenograms superimposed on the anterior and inferior mandibular
bone contours. - - - - Before the examination period. -After
the examination period.
(Condyle superior)-The
most superior point of the
co,
condyle determined by a tangent parallel to OL
(Condyle posterior)-The
most posterior point of the
COP
condyle determined by a tangent parallel to OLP
i
(Incision)-The
incisal tip of the most prominent mandibular central incisor
m
(Molar)-The
mesiobuccal cusp tip of the mandibular
permanent first molar
IL
(lncisal line)-The axis of the most prominent mandibular central incisor through i
(Mandibular line)-The tangent to the lower border of
ML
the mandible
OL
(Occlusal tine)-A line through m and the buccal cusp
tip of the mandibular first premolar. The line from the
initial roentgenogram was used as a reference line for
measurements on roentgenograms both before and after examination.
(Occlusal line perpendiculare)-A
line perpendicular to
OLP
OL through the most anterior point of the bony chin
symphysis. The line from the initial roentgenogram was
used as a reference line for measurements on roentgenograms both before and after examination.
When commonly used orthodontic appliances are
employed, it is obviously difficult to design a study that
analyzes the effects of orthodontic measures in relation
to somatic maturation. Removable appliances (for example, functional appliances, headgear) are generally
worn part-time and require the patient’s cooperation.
Furthermore, the treatment time with these appliances
is prolonged over several years making it difficult to
differentiate between treatment effects and normal
growth changes, especially as suitable untreated control
subjects are generally not available for an extended
period of time.
On the other hand, with the Herbst appliance”.” it
is possible to create an experimental situation similar
to that in animal studies of growth interventive mea-
AGE
Fig.
4. Distance and velocity curves of standing height.
sures related to somatic maturation.‘“-” The Herbst appliance is a fixed functional appliance worn 24 hours
a day. It does not require the cooperation of the patient
and the treatment time is short (6 to 8 months).
The aim of this study was to relate mandibular skeletal and dental changes to the level of somatic maturation in growing subjects with Class II malocclusions
treated with the Herbst appliance.
SUBJECTS
The original sample of consecutive patients treated
with the Herbst appliance at the Orthodontic Department, Faculty of Odontology, Malmii, Sweden, comprised 73 cases of Class II malocclusion. Three subjec&
discontinued treatment after 2 to 3 weeks and were not
included in this study. The remaining 70 subjects (52
boys and 18 girls, aged 10 to 16 years) were treated
with the Herbst appliance (Fig. 1) for an average period
of 7.1 months (SD = 1.7 months).
Twenty-three untreated Class II subjects, all boys
aged 9 to 14 years, were used as a control group for
an average period of 6.2 months (SD = 0.4 months).
Selected cephalometric recordings describing mandibular morphology and mandibular-cranial base relationships are shown in Table I. The measuring points
and reference lines used have been defined in an earlier
report. I4
The design of the appliance used in patient treatment
is shown in Fig. 2. At the start of treatment, the mandible in each patient was advanced to an end-to-end
incisal relationship. Partial maxillary and mandibular
anchorage was employed in 20 subjects and total maxillary and mandibular anchorage in 50 subjects. No
Vohme 88
Number 4
Dentofacial orthopedics in relation to somatic maturation 277
significant difference with respect to mandibular treatment changes (variables, see Methods) existed between
these two anchorage systems.
METHODS
Analysis of profile roentgenograms
Sagittal and vertical changes in mandibular condylar
growth, and sagittal changes in mandibular molar and
incisor tooth position occurring during the examination
period were analyzed by means of mouth-open profile
roentgenograms. In the Herbst group, roentgenograms
were taken (1) at the start of treatment before the appliance was inserted and (2) after treatment on the day
the appliance was removed. In the control group, roentgenograms were taken before and after the examination
period.
The registrations from the roentgenograms were
made on matt acetate tracing film on which the reference
points were marked with a finely sharpened 5H pencil.
Where double projection gave rise to two points, the
midpoint was used. Linear measurements were made
to the nearest 0.5 mm and angular measurements to the
nearest 0.5”. No correction was made for linear magnification (approximately 7% in the median plane). The
measuring points and reference lines used are shown in
Fig. 3.
Measuring procedure
Mandibular tracings from before and after the examination period were superimposed with the anterior
and inferior mandibular bone contours used for orientation (Fig. 3). The original occlusal line (OL) and
occlusal line perpendiculare (OLP) were used as a reference grid for sagittal and vertical registrations (Fig.
3). The profile roentgenographic analysis comprised
four linear measurements (variables l-4) and one angular measurement (variable 5). Changes of the variables that occurred during the examination period were
registered as
after minus, before diflerences:
1. co,-OLP--Sagittal condylar growth
2. co,-OL--Vertical condylar growth
3. m-OLP--Sagittal molar position change
4. i-OLP-Sagittal incisor position change
5. IL/ML--Incisor
inclination change
Sagittal here refers to a relation with the functional
occlusal plane and not the head-carrying plane or the
Frankfort horizontal.
Analysis of growth curves
Longitudinal growth records of standing body
height over a 5- to lo-year period were available for
all subjects. The growth records were obtained from
the childrens’ school clinics and from the Orthodontic
\
Peak
-1 0 +l
years
Fig. 5. Division of the velocity curve of standing height into three
growth periods: peak (the period at peak height velocity 2 1
year), prepeak (the period before peak), and postpeak (the
period after peak).
Department in Malmo. At the Orthodontic Department,
body height measurements were made to the nearest 1
mm with registrations performed about every month.
At the school clinics, body height measurements were
made to the nearest 0.5 cm. Registrations were done
every year or every second year from 7 years of age
onward. Data from the school clinics were included in
the analysis only when they covered a period before
the subjects were registered at the Orthodontic Department .
By means of a computer program, individual distance and velocity curves of standing height were constructed (Fig. 4). The velocity curves were smoothed
by spline function.23 By visual inspection the peak
height velocity was identified on the velocity curves
and three growth periods established (Fig. 5): prepeak,
peak, and postpeak. The examination period in each
subject was assigned to one of the three growth periods.
If the examination period coincided with more than one
growth period, the subject was assigned to the growth
period that covered most of the examination period.
The distribution of the Herbst and control subjects in
relation to the peak height velocity is shown in Fig. 6.
The occurrence of events is given in Table II.
Statistical methods
The arithmetic mean (Mean) and standard deviation
(SD) were calculated for each variable. To assess the
statistical significance of the changes that occurred dur-
278
Puncherz
and
H&g
CONTRO
BOYS
‘L
HERBST
BOYS
21-22::Z
IS-171F.P
162
- 53
4
-b
I
I
-3
-2
years
I
-I
HERBST
GIRLS
I
PHV
+2
Pre-Peak
+3
+4
years
Post -Peak
Fig. 6. Distribution of 70 Herb.9 subjects (cases1 to 70) and 23 control subjects in relation to the peak
height velocity (PHV). Division of the subjects into three growth-period groups: prepeak, peak, and
postpeak. The length of the examination period (-)
is shown.
Table Ill. Size of method error (ME) in the
cephalometric analysis of landmark changes
Variable
Sagittal condylar
growth (co,-OLP)
Vertical condylar
growth (co,-OL)
Sagittal molar position (m-OLP)
Sagittal incisor position (i-OLP)
Incisor inclination
(IL/ML)
ME
0.40 mm
0.52 mm
0.47 mm
0.31 mm
I .60”
ing the examination period, t tests for paired samples
were performed; to compare the Herbst and control
subjects and the different growth periods, t tests for
independent samples were performed. The levels of
significance used were P < 0.001 (***), P < 0.01
(**), and P < 0.05 (*). P 3 0.05 was considered not
significant (NS).
The size of the combined method error (ME) in
locating, superimposing, and measuring the changes of
the different cephalometric landmarks that occurred
during the examination period was calculated with the
formula
ME
=
Z;dZ
J x
where d represents the difference between two registrations of a pair and n is the number of duplicate
registrations. Cephalograms before and after treatment
from ten randomly chosen Herbst subjects were traced
and superimposed with measurements recorded on two
occasions. The results of the ME calculations are given
in Table III.
RESULTS
Herbst treatment resulted in Class I dental arch relationships in ail 70 patients investigated (Figs. 9-l 1).
The changes in the cephalometric variables measured
are given in Table IV.
Volume 88
Number 4
Dentofacial
orthopedics
in relation to somatic maturation
279
Pre - Peak
Peak
Post - Peak
4
mm
b
65432
I
0
I
2
3
4
5
6
7
8
mm
Flg. 7. Mandibular condylar and incisor changes contributing to overjet correction in 52 boys (-)
and 18 girls (- - - -) treated with the Herbst appliance. The subjects were arranged in relation to the
peak height velocity in the order given in Fig. 6.
In the evaluation of the effects of the Herbst appliance, comparison with the control group could be made
only for boys in the prepeak period. Herbst treatment
resulted in the following changes: sagittal condylar
growth was increased (1.5 mm, P < 0.001); vertical
condylar growth seemed unaffected; the mandibular
molars were moved anteriorly (1.5 mm, P < 0.001);
the incisors were moved anteriorly (2.4 mm, P <
0.001) and proclined 8.4” (P < 0.001).
In the evaluation of changes occurring during Herbst
treatment in relation to somatic maturation, a comparison between all three growth periods could be made
in boys. Because of an insufficient sample size in girls,
a comparison in this sex could only be made between
the peak and postpeak periods. The comparison demonstrated that sag&al condylar growth in boys was significantly greater in the peak period than in the prepeak
(1 .O mm, P < 0.05) and postpeak (1.5 mm, P < 0.05)
periods. Vertical condylar growth was significantly
larger in the peak and postpeak periods when compared
to the prepeak period (1.1 mm, 0.001 < P < 0.05).
The amount of anterior molar movement was similar
in all three growth periods. The mandibular incisors
were moved anteriorly significantly more in the post-
280
Pancherz and H&g
Table IV. Mandibular skeletal and dental changes in 70 Herbst subjects and 23 control subjects (B = Boys,
G = Girls, D = Sex difference)
Herhst
Prepeak
Variable
(mm or degrees)
I. Sagittal condylar
growth (co,-OLP)
2. Vertical
growth
condylar
(co,-OL)
3. Sagittal molar
sition (m-OLP)
pc-
4. Sagittal
position
incisor
(I-OLP)
5. Incisor
(IL/ML)
inclination
n
B
G
D
B
G
D
B
G
D
B
G
D
B
G
D
29
2
29
2
29
2
29
2
29
2
‘t, +, Changes in sagittal tooth position
*Significance
at 5% level.
**Significance
at 1% level.
***Significance
at 0. I% level.
Peak
Postpeak
Mean
SD
n
Mean
SD
n
Mean
SD
2.3
(1.5)
(0.8)
1.2
(1.5)
(-0.3)
cl.7’
(~2.3)’
(-0.6)
~2.4’
(t2.3)’
(0.1)
8.3
0.85
17
9
1.53
0.84
6
7
17
9
0.94
0.53
6
7
0.79
17
9
1.18
0.64
6
7
0.98
17
9
0.92
0.97
6
7
4.42
I7
9
4.02
3.38
6
7
1.8
2. I
-0.3
2.3
1.4
0.9
+I .8’
~1.6’
0.2
+3.5’
c2.1’
I .4*
11.5
9.4
2.1
I .23
0.82
0.91
3.3
2.6
0.7
2.3
I.2
l.I”*
+I .x1
-1.9’
-0.1
c2.l’
+?.?I
-0. I
X.0
8.2
-0.2
(6.8)
(1.5)
(Fig.
group
1.21
I.25
I .07
0.49
1.26
1.05
6.51
3.36
2)
peak period than in the prepeak period (1.1 mm,
P < 0.05) and peak period (1.4 mm, P < 0.01). The
proclination of the mandibular incisors tended to be
more pronounced in the postpeak period than in the
prepeak (3.2”, NS) and peak (3.5”, NS) periods. In
girls no significant differences in condylar growth and
tooth position changes existed when the peak and postpeak periods were compared.
When the changes that occurred during Herbst treatment were evaluated in relation to sex, a comparison
between the boys and girls could be made only for the
peak and postpeak periods. In the peak period, sagittal
and vertical condylar growth were more pronounced in
the boys than in the girls. However, the sex difference
was statistically significant for vertical condylar growth
only (1.1 mm, P < 0.01). The amount of anterior
movement of the mandibular molars and incisors was
about the same in both sexes. In the postpeak period.
there were no significant sex differences in sagittal and
vertical condylar growth or in the amount of anterior
molar movement. The mandibular incisors, however,
were moved anteriorly to a greater extent in boys
than in girls (1.4 mm, P < 0.05). In both sexes the
lower incisors tended to be advanced more than the
molars. This was especially apparent in the postpeak
period.
Overjet correction
In the Herbst subjects, the mandibular contribution
to overjet correction consisted of the sum of sagittal
changes in condylar growth and in incisor tooth position
(Fig. 7). In the total patient material, the average sum
of these changes amounted to 5.0 mm. On average, the
values tended to be largest in the peak boys.
The interrelationship between the condylar and incisor changes that contributed to overjet correction varied considerably among the subjects, irrespective of sex
and somatic maturation (Fig. 7). The following tendencies were, however, noted: in the boys condylar
changes dominated in the peak period and incisor
changes in the postpeak period. In the girls condylar
and incisor changes were, on average, equally large in
the different growth periods.
Class II molar correction
In the Herbst subjects, the mandibular contribution
to Class II molar correction consisted of the sum of
sagittal changes in condylar growth and in molar tooth
position (Fig. 8). In the total patient material, the average sum of these changes amounted to 4.3 mm. On
average, the values tended to be largest in the peak
boys.
The interrelationsip between the condylar and molar
Volume 88
Dentofacial
orthopedics
in relation
to somatic
maturation
281
Number 4
Herbst
Conrrol
group
group
Prepeak
Prepeak
PrepeaklPostpeak
mean difference
0.5
- 1.1***
-1.1*
PeaklPosTpeak
mean difSerence
Mean
SD
n
21
0.8
0.58
2
(2.0)
I .5***
0.0
-0.2
21
0.9
0.80
2
(1.3)
0.3
1.5*
0.5
0.1
0.0
-0.3
21
co.2’
0.33
2
(ta.5)
I .5***
0.3
1.1*
1.4**
-0.1
21
0.0
0.45
2
(-0.5)’
2.4***
-3.5
-1.2
21
-0.1
1.64
2
(-1.8)
8.4***
-3.2
changes that contributed to Class II molar correction
varied considerably among the subjects, irrespective of
sex and somatic maturation (Fig. 8). There was a tendency, however, for the condylar changes to dominate
in both sexes. This was especially apparent in the peak
boys.
CASE PRESENTATION
Three boys .whose Class II, Division 1 malocclusions were treated with the Herbst appliance at different
levek of somatic maturation are presented.
11
The patient (Fig. 9) was 11 years of age and had been
treated with the Herbst appliance for 6 months. Treatment
was performed during the prepeak period. The Herbst appliance was constructed-with partial maxillary and mandibular
anchorage (Fig. Z!). The mandibular contribution to overjet
reduction was 5.5 mm; sagittal condylar growth was 3.0 mm
and ‘the incisors were moved anteriorly 2.5 mm (proclined
4.5”). The mandibular contribution to ClassII molar correction (o&correction) was 4.0 mm; sagittal condylar growth
was 3.0 mm and ihe molars were moved anteriorly 1.Omm.
No retention was used after Herbst treatment.
C&E
Mean
HerbstiControl
mean difference
n
0.1
0.3
CASE
Peak
42
The patient (Fig. 10) was 13 years of age and had been
treated with the Herbst appliance for 7 months. Treatment
was performed du.ring the peak period. The Herbst appliance
was constructed with total maxillary and mandibular anchorage ( Fig. 2). The mandibular contribution to overjet reduction
was 6.5 mm; sagittal condylar growth was 5.0 mm and the
incisorswere moved anteriorly 1.5 mm (proclined 7.0”). The
mandibular contribution to Class II molar correction (overcorrection) was 7.0 mm; sagittal condylar growth was 5.0
mm and the molars were moved anteriorly 2.0 mm. An activator for interocclusaladjustments was used for 1 year after
Herbst treatment.
CASE
52
The patient (Fig. 11) was 16 years of age and had been
treated with the Herbst appliance for 8 months. Treatment
was performed during the postpeak period. The Herbst appliance was constructed with total maxillary and mandibular
anchorage (Fig. 2). The mandibular contribution to overjet
reduction was 6.5 mm; sagittal condylar growth was 1.Omm
and the incisors were moved anteriorly 5.5 mm (proclined
23.5”). The mandibular contribution to Class II molar correction (overcorrection)was 4.0 mm; sagittal condylar growth
was 1.O mm and the molars were moved anteriorly 3 .Omm.
An activator for interocclusal adjustments was used after
Herbst treatment.
DISCUSSION
The results of this investigation represented by the
Herbst appliance indicate that the level of somatic development influences the outcome of dentofacial orthopedic treatment. Although’the control subjects were
followed for a shorter period than the treated subjects,
the differences could not affect the results because
changes in the controls over the observation period ‘were
already very small.
282
Pancherz and H&g
Pre - Peak
Post-Peak
4
mm
65432101
2
3
4
5
6
7
8
b
mm
Fig. 8. Mandibular condylar and molar changes contributing to Class II molar correction in 52 boys
(-)
and 18 girls ( - - - - ) treated with the Herbst appliance. The subjects were arranged in relation
to the peak height velocity in the order given in Fig. 6.
Although there were wide interindividual variations
in the skeletal and dental response to Herbst treatment,
sagittal condylar growth changes dominated on average
in the peak treatment period and tooth movements in
the postpeak treatment period (Table IV, Figs. 7 and
8). These findings are in agreement with those from
studies in monkeys fitted with mandibular protrusive
appliances. In younger animals the extent of condylar
growth was increased and the growth direction sagittally
oriented. *O,** In mature animals, on the other hand,
the adaptive potential of the condyle was reduced
while compensatory tooth movements were more pronounced~*0.22.*b.21
Maturity assessment in the present subjects was
done by means of individual velocity curves of standing
height, a method found suitable in clinical orthodontics.4 The peak period comprised a 2-year interval
around the peak height velocity (Fig. 5). This interval
Volume 88
Number
Dentofacial
orthopedics
in relation
to somatic
maturation
283
4
Fig. 9. CASE 11. A, Plaster casts from before treatment (leffj, after treatment (middle), and 5 years
posttreatment (right). B, Superimposed cephalometric tracings from before treatment ( - - - - ) and after
treatment (-).
Facial tracings superimposed on the nasion-sella line at sella. Mandibular tracings
superimposed on the anterior and inferior mandibular bone contours. The OL/OLP reference grid is
shown. C, Velocity curve of standing height. The treatment period ( .
) is shown.
was considered adequate for analysis of growth interventive measures because there seems to be a definite
alteration in growth rate before and after that period.5
It has been demonstrated in several human growth
studies that the timing of the pubertal growth of
the mandible is closely related to that of standing
height. 5x2*-34Furthermore, the peak of the pubertal
growth spurt of standing height and that of the mandible
is considerably less in girls than in boys.3’.32,35The
differences in the amount of condylar growth between
the sexes and the various maturity groups in the Herhst
subjects may therefore be explained by a corresponding
difference in the amount of basic condylar growth.5 In
the peak and postpeak girls. the difference in sagittal
condylar growth was relatively small (NS). This may
be explained by the fact that they differed significantly
(P < 0.05) in their maturity pattern, represented by the
age at peak height velocity (Table II). It is well known
&at the peak is larger and the intensity of the growth
spurt is more pronounced in early maturers for both the
mandible36 and standing height.37*38It seems likely that,
at least in boys in the earlier growth periods, the increase in sagittal condylar growth accomplished with
the Herbst appliance resulted from an equal addition to
basic condylar growth, irrespective of maturation.
The method of using velocity curves of standing
height for the evaluation of maturity-related growth
changes in the mandible seemed to be more accurate
in boys than in girls. This may be caused by the existence of a relatively larger gap between the occurrence
of the pubertal growth spurt of standing height and that
of the mandible in girls .5.33Furthermore, girls may show
a larger gain in mandibular growth than boys in the
postpubertal growth period, as is the case for standing
height.23
The dental changes with Herbst treatment were ba-
284
Pancho-z
and
Am. .I. Orthod.
Omhrr
19x5
Htigg
Fig. 10. CASE 42. A, Plaster casts from before treatment (lerr), after treatment (middle),
and 2 years
posttreatment (right). 6, Superimposed cephafometric tracings from before treatment (- - - -) and after
treatment (). Facial tracings superimposed on the nasion-sella line at sella. Mandibular tracings
superimposed on the anterior and inferior mandibular bone contours. The OL/OLP reference grid is
shown. C, Velocity curve of standing height. The treatment period (
) is shown.
sically a result of anchorage loss. The telescope mechanism produces an anteriorly directed force on the lower
teeth which thereby results in their mesial movement
and proclination (Figs. 9-l 1). In several cases the incisors were advanced more than the molars. This could
be explained by the fact that the telescope mechanism,
via the lingual arch wire, also exerts a downward force
on the lower front teeth which will thus be moved
further forward due to proclination and a leveling of
the Curve of Spee. Since it is thought that neuromuscular adaptation will occur less easily in older than in
younger subjects and because general muscle strength
increases with maturation,39 the forces upon the dentition exerted by the appliance will be enhanced in the
older subjects. This could explain the differences in
tooth movement found in the various maturity groups.
The possibility cannot be excluded, however, that there
are differences in the amount of force exerted by the
musculature that depend upon the facial morphologic
pattern of the individual patient.40,4’ In the analysis of
mandibular morphology (p-angle and Go-angle) and
mandibular-cranial base relationships (the angles s-npg and ML/NSL) in the present study, no significant
differences were found in the three growth-period
groups.
The question of when Herbst treatment should be
instituted to be most effective in relation to the patient’s
level of somatic maturation cannot be answered easily.
A possible advantage of early (prepeak) treatment is
that, by normalizing the skeletal and soft-tissue morphology at a young age, it would provide a basis for
normal continuing development of these structures.42
On the other hand, early treatment in the mixed dentition seems to necessitate retaining the result until all
permanent teeth have erupted into a stable occlusion.
In subjects with unstable occlusal conditions, there is
Volume88
Dentofacial
orthopedics
in relation
to somatic
maturation
285
Number 4
Fig. 11. CASE 52. A, Plaster casts from before treatment pefij, after treatment (middle),
and 1 year
posttreatment (rig/tt). B, Superimposed cephalometric tracings from before treatment (- - - -) and after
treatment (). Facial tracings superimposed on the nasion-sella line at sella. Mandibular tracings
superimposed on the anterior and inferior mandibular bone contours. The OL/OLP reference grid is
shown. C, Velocity curve of standing height. The treatment period ( . . ) is shown.
a risk of occlusal relapse43because approximately 50%
of the total maxillary and mandibular changes that contribute to Class II correction are caused by tooth movementsw Furthermore, early treatment may be fruitless
in the long run as severe, skeletal Class II discrepancies
seem to strive constantly to reassert themselves, regardless of how early they are treated.
In comparison with the prepeak period, the peak
period seems suitable for Herbst treatment. The orthodontist can take advantage of the increase in condylar
growth and the time of retention could be shortened,
provided all permanent teeth have erupted and a stable
cuspal interdigitation is established. Furthermore, the
problems of relapse caused by unfavorable posttreatment growth will be reduced when treatment is performed at this later stage.
When remo’vable functional appliances (such as the
activator, Frankel, or bionator) are employed, waiting
for peak growth can easily result in insufficient time
for growth-related intervention. Since treatment with
these appliances often takes 2 to 4 years (that is, requires
periods exceeding the duration of the peak growth period), the final stages of treatment may occur in a nongrowing phase. Treatment with the Herbst appliance,
on the other hand, is of short duration and can usually
be completed within 6 to 8 months. This means that
the Herbst treatment method can be used successfully
even in postpubertal patients, provided condylar growth
is not completed.
Finally, a word of caution-the Herbst appliance
should not be used in nongrowing patients since skeletal
alterations will be minimal** and the treatment effects
are confined to the dentoalveolar area. Furthermore,
there will be an increasing risk of development of a
dual bite4’ with dysfunction symptoms of the temporomandibular joints as a possible consequence.46
286
Pancherz and H&g
This study
tology,
Malmii,
has been supported
by the Faculty
and the Swedish
Dental
Society.
of temporomandibular
young adult rhesus
of Odon-
82: 288-298,
joint adaptations
monkeys
(Macaca
to protrusive
function in
mulatta).
AM J ORTFIOII
1982.
Largo RH. Gasser T, Prader A, Stuetzle W; Huber PJ: Analysis
of the adolescent
spurt using smoothing
spiine functions.
Ann
Hum Biol 5: 421-434,
1978.
24. Tardnger J, HBgg U: The timing and duration
of adolescent
growth. Acta Odont Stand 38: 57-67, 1980.
25. McNamara
JA Jr, Carlson DS: Quantitative
analysis of temporomandibular
joint adaptations
to protrusive
function.
AM J
23.
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Volume 88
Number
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orthopedics
in relation
to somatic maturation
4
appliance
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A cephalometric
investigation.
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adult
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and
dual
Reprint requests to:
Dr. Hans Pancherz
Department
of Orthodontics
University
of Giessen
Schlangenzahl
14
D-6300 Giessen, F.R. Germany
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