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~,t- J,. a >> Hom e I TO C
Three Dimensional Diagnosis and
Management of Class II Malocclusion
in the Mixed D ent i t ion
James A. M cNam ara Jr Joh n E. Peterson Jr an d Richard G. Alexan der
Class II malocclusion is a commonly observed problem, occurring in about
one third of the United States population. The numerous treatment ap-
proaches that have been advocated to treat this malocclusion presumably
produce differing treatment effects within the skeletal, dentoalveolar, and
soft tissue components of the face. In the first section of this article, the
three-dimensional components of Class II malocclusion are described, with
transverse maxillary discrepancy, mandibular skeletal retrusion, and in-
creased lower an terior facial height observed as com mon findings in a mixed
dentition sample of Class II subjects. Second, the literature concerning two
seemingly diverse treatm ent methods extraoral traction and functional jaw
orthopedics) is reviewed in detail. Last, cephalometric data are presented
from a retrospective clinical study and is used to evaluate the treatment
effects prod uced by cervical tractio n and th e FFI-2 applianc e of Fr~inkel in
comparison with an untreated sample of mixed dentition Class II patients.
The results of this study indicated that although both skeletal and dentoal-
veolar components of Class II, Division 1 malocclusion were altered in the
Class I direction by either a fac ebow or a Fr~inkel appliance, these t wo
appliance systems accomplished the correction in dramatically differing
ways. Cervical traction affected the skeletal and dentoalveolar components
of the maxilla and mandible, w here as the FR-2 appliance had less of an effect
on maxillary and dentoalveolar comp onents a nd a greater effect on mandibu-
lar length. Thus, these two treatment modalities produce decidedly different
tre atm ent effects in patients with Class II malocclusions. Semin O rthod
1996;2:114-137.)
Co p y r i g h t © 1 9 96 b y W B Sa u n d e r s C om p a n y
a ss I I m a l o c c l u s i o n is a c o m m o n l y o b s e r v e d
c l i n i c a l p r o b l e m , o c c u r r i n g i n a b o u t o n e
th i rd of the Un i t ed S ta t e s popu la t ion . 1-4 Thi s
c l a ss i fi c a ti o n o f m a l o c c l u s i o n s e e m s t o b e m o r e
p r e v a l e n t in i n d iv i d ua l s o f N o r t h e r n E u r o p e a n
a n c e s t r y ( 3 0 t o 4 0 ) t h a n i n o t h e r r a c ia l a n d
From the Department o f Orthodontics and Pediatric Dentistry,
School ofDentistry; Department ofAnatomy and CellBiology, School
of Medicine; and Center or Human Growth and Development,
University of Michigan, A nn Arbor, MI; Departments of Orthodon-
tics and Pediatric Dentistry, Loma Linda University, Loma Linda,
CA; Department o f Orthodontics, BaylorDental College,Dallas, TX.
Address correspondence to James A . McNamar a, Jr, DDS , PhD,
Department of orthodontics and Pediatric Dentistry, School of
Dentistry, The University of Michigan, Ann Arb ~ MI48 109-I07 8.
Copyright © 1996 by W.B. Saunders Company
1073-8746/96/0202-000655.00/0
e thn ic g ro ups (eg , 14 to 18 in b l acks ) , w i th
a b o u t 8 t o 1 0 o f t h e o v e r a ll p o p u l a t i o n
h a v i n g o v e r j e t s g r e a t e r t h a n 6 m m . B e c a u s e C l a ss
I I m a l o c c l u s i o n i s r e c o g n i z e d e a s i l y b y h e a l t h
profes s iona l s , a s we ll a s by pa t i en t s and the i r
fami l i e s , e spec ia l ly in ins t ances of exces s ive over -
j e t , t h e c o r r e c t i o n o f C la ss I I p r o b l e m s m a y
c o n s t i t u t e n e a r l y h a l f o f t h e t r e a t m e n t p r o t o c o l s
i n a t y p ic a l N o r t h A m e r i c a n o r t h o d o n t i c p r a c -
tice.
O v e r t h e y e a r s , n u m e r o u s p r o t o c o l s h a v e
b e e n a d v o c a t e d f o r t h e t r e a t m e n t o f C la ss I I
m a l o c c l u s i o n . T h e s e t r e a t m e n t s i n c l u d e a v a r i e ty
o f fi x e d a p p l ia n c e s , e x t r a c t i o n p r o c e d u r e s , e x t r a-
o r a l t r a c t i o n a n d a r c h e x p a n s i o n a p p l i a n c e s , a n d
f u n c t i o n a l j a w o r t h o p e d i c a p p l i a n c e s . S o m e p r a c -
t i c ione rs s e l ec t on ly a few of these m oda l i t i e s in
4
Seminars in Orthodontics, Vol 2, No 2 June), 1996: pp 11 4-137
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: ¢J . a >> Hom e [ TOC
Class II M ixed Den tition Treatment 115
t h e t r e a t m e n t o f Cl as s I I m a l o c c l u s i o n , d e p e n d -
i n g o n t h e e x p e r i e n c e, p e r s o n a l p r e f e r e n c e , a n d
prev iou s success ra t e o f t he c l in i c ian . E ach t rea t -
m e n t a p p r o a c h , h o w e v e r , d if f e r s in i t s e f f ec t s o n
t h e s k e l e ta l a n d d e n t o a l v e o l a r s t r u c t u r e s o f t h e
c r a n i o f a c i a l r e g i o n , s o m e t i m e s a c c e l e r a t i n g o r
l i m i t in g t h e g r o w t h o r m o v e m e n t o f th e v a r i o u s
s t r u c t u r e s i n v o l v e d , p r o d u c i n g f a v o r a b l e , a n d
o c c a s i o n a ll y u n f a v o r a b l e , g r o w t h c h a n g e s .
In the f i r s t s ec t ion o f th i s a r ti c l e , t he th ree -
d i m e n s i o n a l c o m p o n e n t s o f C la ss I I m a l o c c lu -
s i o n i n t h e m i x e d d e n t i t i o n a r e d e s c r i b e d . S e c -
o n d , t h e l i t e r a tu r e c o n c e r n i n g t w o s e e m i n g l y
d i v e rs e t r e a t m e n t m e t h o d s e x t r a o r a l t r a c t i o n
a n d f u n c t i o n a l j a w o r t h o p e d i c s ) t h a t c u r r e n t l y
a r e a d v o c a t e d f o r t h e t r e a t m e n t o f Cl as s I I
ma locc lus ion i s rev iewed. In the l a s t s ec t ion of
t h e a r t i c l e c e p h a l o m e t r i c d a t a f r o m a r e t r o s p e c -
t iv e cl i ni c al s t u d y c o m p a r e s t h e t r e a t m e n t e f f e ct s
o f b o t h m o d a l i t i e s t o a n u n t r e a t e d C l as s I I
p o p u l a t i o n . A l t h o u g h b o t h o f t h e s e g e n e r i c t y pe s
o f t r e a t m e n t s h a v e b e e n u s e d f o r n e a r l y a c e n -
tury , and ind iv idua l ly have been s tud ied in de -
t a i l , s u rpr i s ing ly few s tud ies have d i rec t ly com-
p a r e d t h e t r e a t m e n t e f f e ct s p r o d u c e d b y t h e se
m e t h o d o l o g i e s .
Components of Class I I Malocclus ion
Th e s imp l i c i ty o f t he Angle c l a s s if i ca t ion of
ma lo cc lus ion 5 be l i e s the fac t t ha t Class I I ma loc -
c lus ion i s no t a s ing le d i agnos t i c en t i ty . Angle
based h i s c l a s s i f i ca t ion sys t em so le ly on the
p o s it i o n o f t he p e r m a n e n t u p p e r f ir s t m o l ar s .
U n d e r l y i n g t h is o c cl u s a l c o n d i t i o n c a n b e n u m e r -
o u s s k e l e t a l a n d d e n t o a l v e o l a r c o m b i n a t i o n s ,
some in tu i t ive ly obvious , some no t . Idea l ly , a
g i v e n t r e a t m e n t m o d a l i t y s h o u l d d i r e c t ly o r
s o m e t i m e s i n d i r e c tl y ) a f f e c t th e p a r t i c u l a r s k el -
e ta l a n d d e n t o a l v e o l a r c o m p o n e n t s o f th e s p e -
ci f ic Class II pat ien t .
A l t h o u g h t h e r e i s s u b s t a n ti a l l i t e r a tu r e c o n -
c e r n i n g t h e c o m p o n e n t s o f C la ss I I m a l o c c lu -
s ion , ~15 few s tud ies have focu sed on how f re -
q u e n t l y t h e v a r i o u s f a c t o r s t h a t c a n c o n t r i b u t e t o
a Clas s I I occ lusa l re l a t ionsh ip occur . Notab le
excep t ions inc lud e the inves t iga t ions o f Hen ry , 16
Moyers e t a ll7 an d Mc Nam ara . 18 H en ry a5 pro-
p o s e d f o u r c a t e g o r i e s i n t o w h i c h m o s t c a s e s o f
Class I I d iv i s ion 1 ma lo cc lus ion can be c l a ss i fi ed :
1 ) m a x i l l a r y d e n t o a l v e o l a r p r o t r u s i o n , 2 ) m a x -
i l la r y b a s a l p r o t r u s i o n , 3 ) m i c r o m a n d i b l e , a n d
4 ) m a n d i b u l a r d e n t o a l v e o l a r r e t r u s i o n . M o y e r s
e t a P 7 p r e s e n t e d a n a r b o r i z a t i o n t h a t a l l ow s t h e
i d e n t i f i c a ti o n o f v ar i o u s g r o u p s o f f a ct o r s t h a t
c a n d e t e r m i n e a c l u s t e ri n g o f C la ss I I m a l o c c l u -
s i o n s w i t h s i m i l a r s k e l e t a l a n d d e n t o a l v e o l a r
cha rac te r i s t i c s .
F o r t h e p u r p o s e o f t h is a rt i c le , t h e c o m p o -
n e n t s o f C la s s I I m a l o c c l u s i o n a s d e f i n e d b y
M c N a m a r a 18 a r e u s e d t o d e s c r i b e t h e a n t e r o p o s -
t e r i o r a n d v e r t ic a l e l e m e n t s o f C la s s I I m a l o c c l u -
s i o n , a s o b s e r v e d c e p h a l o m e t r i c a l l y . T h e d a t a
f r o m t h i s s t u d y h a v e b e e n r e a n a l y z e d a n d a r e
p r e s e n t e d l a t e r . I n t h i s s t u d y , t h e f r e q u e n c y o f
C la ss I I c o m p o n e n t s i n 2 7 7 p a t ie n t s o f N o r t h e r n
E u r o p e a n a n c e s t r y w as e x a m i n e d . T h e a g e r a n g e
8 ye a r s 0 m o n t h s t o 1 0 y e a r s 11 m o n t h s w i t h a n
a v e r a g e a g e o f 9 y e a r s 0 m o n t h s ) is r e p r e s e n t a -
t iv e o f a t y p ic a l m i x e d - d e n t i t i o n p o p u l a t i o n o f
Class I I pa t i en t s . T he c r i t e r i a fo r i nc lus ion of a
s u b j e c t i n t h e s t u d y w e r e t h e p r e s e n c e o f a t l e a st
a n e n d - t o - e n d m o l a r a n d c a n i n e r e l a t i o n s h i p s a s
d e t e r m i n e d f r o m t h e l a t e r a l h e a d f i l m . N o s k e l -
e t a l c r i t e r i a were used .
F o r e a s e o f a n a l y si s, m e a s u r e s o f c r a n i o f a c i a l
s t r u c t u r e a r e d i v i d e d i n t o t h e f o l l o w in g s ix c o m -
p o n e n t s : f o u r h o r i z o n t a l m a x i l l a r y s k el e ta l , m a x -
i l la r y d e n t o a l v e o l a r , m a n d i b u l a r d e n t o a l v e o l a r ,
a n d m a n d i b u l a r s k e l et a l) a n d t w o v e r ti c a l c o m p o -
n e n t s m a n d i b u l a r p l a n e a n g l e a n d l o w er a n te -
r io r fac i a l he igh t ) .
1 Anteroposterior Components
T h e r e l a ti o n s h i p o f th e u p p e r a n d l o w e r t e e t h
c a n b e a f f e c t e d b y v a r i o u s sa g i tt a l c o m p o n e n t s o f
C l as s I I m a l o c c l u s i o n , e i t h e r a l o n e o r i n c o m b i n a -
t ion . Mos t , bu t no t a ll , o f t he va r i a t ions in these
c o m p o n e n t s a r e i n t u it i ve l y o bv i o u s .
a Max i l l ary s ke l e t a l pos i t i on
B o t h h a r d a n d
sof t t i s sue fac tors mus t be a s ses sed in eva lua t ing
the po s i t ion o f the max i l l a re la t ive to c ran ia l base
a n d c r a n i a l s tr u c t u r e s . O f c ri t ic a l i m p o r t a n c e i s
the sof t ti s sue prof i l e , pa r t i cu la r ly the naso lab ia l
a n g l e a n d t h e c a n t s l o p e ) o f t h e u p p e r li p.
Idea lly , t he naso lab ia l ang l e shou ld be 102 ° -+ 8 °
i n b o t h b o y s a n d g ir ls o f N o r t h e r n E u r o p e a n
ance s t ry 19 F ig 1) , w i th m or e a cu te naso lab ia l
a n g l e s o b s e r v e d i n o t h e r r a c i al a n d e t h n i c g r o u p s
eg , b l acks,Z°Japanese21). In add i t ion , t he ca n t o f
t h e u p p e r l i p s h o u l d b e a n g l e d s l ig h t ly in a n
ante r io i nfe r io r d i rec t ion 8 ° _+ 8 ° i n whi t e ma les ;
14 ° _+ 8 ° in wh i te fem ales re la t ive to the nas ion
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: , ¢J ,. a >> Ho me I TOC
1 1 6 McNamara Peterson an d Alexander
Figure 1. The naso-labial angle is for med by the
intersect ion of tangents to the base of the nose and to
the upper l ip . The value for the naso-labia l angle is
s imilar for male and female pat ients . Reprinted with
pe rm iss ion f ro m McN am ara ) 9 )
p e r p e n d i c u l a r 19 F i g 2 ) . C a r e s h o u l d b e t a k e n t o
a v o i d o v e r r e t r a c t i o n o f t h e u p p e r l ip , e s p e c i a l ly
i n i n s t a n c e s o f m a x i l l a r y s k e l e ta l r e t r u s i o n , a
c o n d i t i o n t h a t o c c a s i o n a l l y o c c u r s i n C l a s s I I
m a l o c c l u s i o n .
A l t h o u g h t h e v e rt i ca l p o s i t i o n o f t h e m a x i l l a
r e l at i v e t o t h e u p p e r l i p) i s b e s t e v a l u a t e d a t t h e
t i m e o f t h e c l in i c a l e x a m i n a t i o n , t h e a n t e r o p o s t e -
r i o r p o s i t i o n o f t h e b o n y m a x i l l a i s a n a l y z e d m o s t
70
60
50
40
30
2 0
10
0
RETRUSION
65 3
PROTRUSION
16 1
6 8 N 9 ~
2 6
<-5mm -5 to-3mm -2 to 2mm 3 to 5ram >5m m
Figure 3. G raphic representa t io n o f the dis tr ibut ion
of the m easure f ro m P oin t A to the nas ion p e rpend icu-
lar . In this and subseque nt graphs , the n umbe rs a t the
top of each bar represen t the pe rcentage of subjects in
the sample with values in the range indicated.
e a si ly t h r o u g h c e p h a l o m e t r i c a n al y si s. T w o c e p h a -
l o m e t r i c m e a s u r e s o f a n t e r o p o s t e r i o r m a x i l l a r y
p o s i t i o n a r e n a s i o n p e r p e n d i c u l a r t o P o i n t A 22
F i g 3 ) a n d t h e S e l l a - N a s i o n P o i n t A S N A )
angl e 23,24 F ig 4 ) . W he n these m e asu res a re
a p p l i e d t o t h e m i x e d d e n t i t i o n s a m p l e , T b o t h
m e a s u r e s i n d i c a te t h a t t h e p o s i t i o n o f t h e m a x -
illa is normal i n t h e m a j o r i t y o f C l a ss I I i n d i v i d u -
a ls . I n t h o s e p a t i e n t s i n w h o m t h e p o s i t i o n o f t h e
m a x i l l a is a b n o r m a l , t h e m a x i l l a t e n d s t o b e
r e t r u s i v e m o r e f r e q u e n t l y t h a n p r o t r u s i v e . P a -
t i e n t s s h o w i n g a l o n g l o w e r a n t e r i o r f a c i a l h e i g h t
a n d a st e e p m a n d i b u l a r p l a n e a n g l e o f t e n h a v e
Figure 2. The cant of the upper l ip . This angle is form ed by the intersect ion of a tangent to the up per l ip and the
nas ion perpendicular . A) Male . B) Female . The up per l ip tends to be more protrus ive in female than in male
pat ients . Overre trac t ion o f the upp er l ip should be avoided. Reprinted with permiss ion fro m McNamara. 19)
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: ,l-'.l~; ~ >>
Class II Mixed D entition Treatment
Home I TOC
1 1 7
60%
50% [
RETRUSION
47.3
PROTRUSION
40%
30%
20%
10%
0%
10.2
<76° 76-79° 80-84o 85-87
3.3
>87°
Figure 4. Graphic representat ion of the dis t r ibut ion
of the SNA angle in the mixe d dentition sample.
b o t h a m a x i ll a a n d m a n d i b l e t h a t a re r e t r u d e d
re la t ive to c ran ia l base s t ruc tu res .
T h u s , i n e v a l u a t i n g t h e a n t e r o p o s t e r i o r p o s i -
t i o n o f t h e m a x i l l a , it is i m p o r t a n t t o t a k e b o t h
s o f t a n d h a r d t i s s u e f a c t o r s i n t o c o n s i d e r a t i o n .
W h e n t h e r e a p p e a r s t o b e a c o n f l i c t b e t w e e n t h e
f i n d i n g s o f t h e c l i ni c al e x a m i n a t i o n a n d t h e
c e p h a l o m e t r i c a p p r a i s a l o f t h e h a r d t is su e , t h e
p r u d e n t p r a c t i t i o n e r u s u a l l y w i l l r e l y p r i m a r i l y
o n t h e f i n d i n g s o f th e c l i n ic a l e x a m i n a t i o n i n
c h o o s i n g a m o n g a n u m b e r o f d i f f e ri n g t re a t-
m e n t o p t i o n s .
b Maxi l lary dentoalveolar pos i tion To e l imi -
n a t e t h e i n f l u e n c e o f m a x il l a r y a n d m a n d i b u l a r
pos i t ion re l a t ive to the c ran ia l base whe n es t ima t -
i n g t h e p o s i t i o n o f t h e u p p e r i n c i s o r r e l a ti v e t o
t h e m a x i ll a , t h e d i s t a n c e f r o m t h e f a c i a l s u r f a c e
o f t h e u p p e r i n c i s o r t o a v e r t ic a l li n e d r a w n
p e r p e n d i c u l a r t o th e F r a n k f o r t h o r i z o n t a l p l a n e
e x t e n d e d t h r o u g h P o i n t A 22 is r e c o m m e n d e d . I n
a w e l l - b a l a n c e d f a c e , t h i s m e a s u r e m e n t s h o u l d
be 4 to 6 m m . 22,25,26 W he n this m ea su re is ap pl ied
t o t h e m i x e d d e n t i t i o n C l as s I I s a m p l e , i s a l m o s t
h a l f h a v e a n o r m a l l y p o s i t i o n e d u p p e r i n c is o r
( F ig 5 ) , a n d a b o u t 2 0 h a v e m a x i l l a r y d e n t o a l -
v e o l a r p r o t r u s i o n . O n th e o t h e r h a n d , 3 0 h a v e
a re t rus ive pos i t io n of the u pp er in c i sor ( i e, l e ss
t h a n 4 m m a h e a d o f t h e P o i n t A v e r t i ca l ) .
T h e i m p l i c a t i o n s o f t h e s e o b s e r v a t i o n s a r e
o b v i o u s. I n a n y C l as s I I t r e a t m e n t p r o t o c o l t h a t
i n v o lv e s e i t h e r t h e f o r w a r d r e p o s i t i o n i n g o f t h e
m a n d i b l e ( e g, f u n c t i o n a l a p p l i a n c e t h e r a p y , m a n -
d i b u l a r a d v a n c e m e n t s u r g e r y ) o r t h e r e t r a c t i o n
o f t h e m a x i l l a ( e g , e x t r a o r a l t r a c t i o n , L e F o r t I
o s t e o t o m y ) , a n e x i s t i n g r e t r u d e d i n c i s o r p o s i t i o n
s h o u l d b e c o r r e c t e d ( e g , f l a r ed , i n t r u d e d ) b e -
f o r e t h a t p h a s e o f t r e a t m e n t t o a v o id i nc i sa l
60%
50%
40%
30%
20%
10%
0%
RETRUSION
22.2
7.9
< 2 mm 2-3 mm
48.5
4-6mm
PROTRUSION
16.2
5.3
7-8 mm >6m m
Figure 5. The distribution of the distance from the
facial surface of the upper incisor to a vertical l ine
drawn perpendicular to the Frankfort horizontal
through Point A.
i n t e r f e r e n c e . O n e o f t h e m o r e s i g n i f ic a n t f a c t o rs
t h a t c a n i n h i b i t C l a ss I I c o r r e c t i o n , r e g a r d l e s s o f
t h e n a t u r e o f th e o r t h o d o n t i c o r o r t h o p e d i c
m o v e m e n t a n d r e g a rd l e ss o f w h e t h e r t e e t h a r e
r e m o v e d t o s o l v e a t o o t h - s i z e / a r c h - s i z e d i s c r e p -
ancy, is uninten tional incisal coupling P r e m a t u r e ,
u n i n t e n t i o n a l c o n t a c t b e t w e e n t h e u p p e r a n d
l o w e r i n c i so r s c a n i n h i b i t C l as s I I c o r r e c t i o n
s ig n i fi c an t ly , r e g a r d l e s s o f t h e t r e a t m e n t p r o t o -
co l used .
c Ma ndib ular dentoalveolar pos i tion The d i s -
t a n c e f r o m t h e t i p o f t h e l o w e r i n c i s o r t o th e
A-P ogo nion l ine 26,27 can be used to d e te rm ine
t h e a n t e r o p o s t e r i o r p o s i t i o n o f th e l o w e r i n ci s o r
i n r e l a t i o n t o b a s a l s t r u c t u r e s . I n t h e m i x e d -
d e n t i t i o n C l as s I I g r o u p , a p p r o x i m a t e l y t wo -
t h i r d s h a v e a n o r m a l l y p o s i t i o n e d l o w e r i n c i s o r
(F ig 6) , w i th on ly 15 in a pro t r us ive pos i t ion
a n d 2 0 i n a r e t r u s iv e p o s i t i o n . T h e g o a l o f
70%
60%
50%
40%
30%
20%
10%
0%
66.9
RETRUSION ~ PROTRUSION
15.2
10.5
4 1 ~ ~ ~ 3 6
<2rnm -2to-lrnm 0-3ram 4- 5mm >5ram
Figure 6. The distance from the facial surface of the
lower incisor to a line drawn between Point A and
pogonion .
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Ar ' . i, : e >> Ho m e I TO C
118
McNam ara Peterson and Alexander
vi r tua l ly a l l Clas s I I t he rap ies i s t o or i en t t he
l o w e r in c i s or s o v e r b a sa l b o n e i n h a r m o n y w i t h
t h e s u r r o u n d i n g s o f t t is su e . G i v e n th e l a c k o f
p o t e n t i a l o s s e o u s a d a p t a t i o n i n t h e m a n d i b l e ( i n
c o m p a r i s o n t o t h e m a x i l l a v i a r a p i d m a x i l l a r y
e x p a n s i o n ) , s i g n i fi c a n t u p r i g h t i n g o f t h e l o w e r
i n c i so r s m a y n e c e s s it a t e t h e r e m o v a l o f p e r m a -
n e n t t e e th a s p a r t o f t h e t r e a t m e n t p r o t o c o l .
d . Ma ndi b u l ar s ke l e t a l pos i t i on . T w o m e a s u r e s
a r e u s e d t o e v a l u a te t h e p o s i t i o n o f t h e m a n d i b l e
re l a t ive to the c ran ia l base and c ran ia l s t ruc tures :
P o g o n i o n t o t h e n a s i o n p e r p e n d i c u l a r 22 ( F ig 7 )
an d the Sel la-Nasio n-Basio n (SNB) ang le 23,24 (Fig
8 ) . T h e s e m e a s u r e s i n d i c a t e t h a t a d e f ic i e n c y in
t h e a n t e r o p o s t e r i o r p o s i t i o n o f t h e m a n d i b l e i s a
c o m m o n f i n d i n g i n C l as s I I m a l o c c l u s i o n , w i t h
a b o u t 6 0 % o f t h e p a t i e n ts s h o w i n g m a n d i b u l a r
s k e l e t a l r e t r u s i o n . S i m i l a r f i n d i n g s h a v e b e e n
no ted in an adul t Class I I s ample . 25 Given the
f r e q u e n c y o f m a n d i b u l a r r e t r u s i o n i n t h e m i x e d
d e n t i ti o n , p r o t o c o l s a i m e d a t e n c o u r a g i n g a
p o s i t i v e m a n d i b u l a r g r o w t h r e s p o n s e , e i t h e r p r i -
m a r i l y o r s e c o n d a r i l y ( t o b e d i s c u s se d l a t e r ),
o f t e n a r e n e e d e d .
2. Vert ical Comp on e n t s
Al though Clas s I I ma locc lus ion usua l ly i s pe r -
ce ived a s a s ag i t t a l p roblem, the ve r t i ca l d imen-
s i o n o f t h e p a t i e n t a l s o m u s t b e c o n s i d e r e d . A s
has be en sho wn by Schud y, 28,29 var ia t ion s in facia l
h e i g h t m a y c o n c e a l o r i n t e n s i fy t h e c l i n ic a l
a p p e a r a n c e o f th e m a l o c c l u s io n .
a . Decreased ver t i ca l d i mens i on . A s i s wel l
k n o w n i n p r o s t h o d o n t i c s a n d s u r g i c a l m a x i l l a r y
i m p a c t i o n , a d e c r e a s e i n v e r t i ca l d i m e n s i o n
60
50
40
R E T R U S I O N P R O T R U S I O N
30.2 29.2 30.3
30
10%
O%
9.2
< -12 mm -12 to-9mm -8 to-5mm -4 - 1ram >-1 mm
Figure 7. The pos i t ion of the chin at pogon ion
relative to the nasion perpendicular. Note that the
chin po int is retrusive in abo ut 60% o f the sample.
60
R E T R U S I O N
50
40.4
4 0
0
21.8
o i
0
0
<73 ° 73 75 ° 76 78 °
P R O T R U S I O N
10.2
79-81 ° >81 °
Figure 8. Graphic representat ion o f the dis tr ibut ion
of the SNB angle.
c a u s e s t h e m a n d i b l e t o r o t a t e u p w a r d a n d f o r -
w a r d ( Fi g 9 A ). T h i s s a m e p h e n o m e n o n o c c u r s i n
t h e C l a ss II o r t h o d o n t i c p a t i e n t , i n t h a t a s h o r t
l o w e r a n t e r i o r f a c i a l h e i g h t c a n c a m o u f l a g e a
mandib le tha t i s s t ruc tura l ly sma l l r e l a t ive to the
midface . Th ese p a t i en t s typ ical ly have a low
m a n d i b u l a r p l a n e a n g l e , a d e e p o v e r b i t e w i t h a
s t r o n g c h i n p o i n t , a n d e i t h e r r e t r u d e d o r f l a r e d
u p p e r i n c i s o r s . M a n d i b u l a r d e n t o a l v e o l a r r e t r u -
s ion a l so occurs .
b . I ncreased ver t i ca l d i mens i on .
A p a t i e n t w i t h
a n i n c r e a s e d l o w e r a n t e r i o r f a c i a l h e i g h t ( F ig
9 B ) o f t e n i s c h a r a c t e r i z e d b y a r e t r u d e d m a n -
d ib le (and occas iona l ly the m axi l l a a s we l l ) , a
p o o r l y d e f i n e d c h i n p o i n t w i t h a h y p e r a c t i v e
m e n t a l i s m u s c l e ( g o l f - b a l l c h i n ) , a n d a te n -
d e n c y t o w a r d o r a n a n t e r i o r o p e n b i t e . A b u m p
o n t h e n a s a l c o n t o u r ( d o r s a l h u m p ) o f t e n i s
o b s e r v e d c l i n i c a l l y i n p a t i e n t s w i t h b o t h m a x i l -
A
Figure 9. The relationship of the vertical dimen sion
of the face to the antero poster ior pos i t ion of the chin.
(A) A decrease in lower anterior facial height results
in a forward and upward rota t ion of the chin point .
(B) An increase in lower anter ior facial height results
in a downward and backward rota t ion of pogonion.
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: d-'J~£ ?:- >>
Class H Mixed Dentition Treatment
H o m e I T O C
119
l a r y a n d m a n d i b u l a r s k e l e t a l r e t r u s i o n a n d a
Clas s I I ma locc lus io n .
T o e v a lu a t e th e f r e q u e n c y o f o c c u r r e n c e o f
t h e s e c o n d i t i o n s i n t h e C l a ss I I m i x e d d e n t i t i o n
s a m p l e , 18 t w o m e a s u r e s o f v e r t ic a l d i m e n s i o n a r e
e x a m i n e d . W h e n t h e m a n d i b u l a r p l a n e a n g l e
r e l at i v e t o t h e F r a n k f o r t h o r i z o n t a l is m e a s u r e d
( F ig 1 0 ), a p p r o x i m a t e l y 4 0 o f t h e s a m p l e h a s a
n e u t r a l v e rt ic a l d i m e n s io n . A m a n d i b u l a r p l a n e
a n g l e g r e a t e r t h a n 3 1 . 5 ° i s o b s e r v e d i n 1 7 .5 o f
the s am ple , i nd ic a t ing exces s ive ve r t i ca l deve lop-
m e n t . O n l y 1 0 o f t h e s a m p l e h a s a s h o r t l o w e r
a n t e r i o r f a c i al h e i g h t , a n d t h is d e c r e a s e i n f a c ia l
he ig h t o f t en i s a s soc ia t ed wi th Class I I d iv i s ion 2
m a l o c c l u s i o n . A n e v a l u a t i o n o f l o w e r a n t e r i o r
f a c ia l h e i g h t ( F ig 1 1) , m e a s u r e d f r o m a n t e r i o r
n a s a l s p i n e t o m e n t o n , i n d i c a t e s t h a t m o r e t h a n
h a l f o f t h e i n d i v i d u al s h a v e a n o r m a l f a c e h e i g h t
m e a s u r e m e n t . A l m o s t 3 5 o f t h e s a m p l e h a v e
exces s ive lower an te r io r fac i a l he igh t .
Th e re su l t s o f t h i s eva lua t ion ind ic a te tha t ,
a l t h o u g h C l as s I I p a t i e n t s m o s t f r e q u e n t l y h a v e a
n e u t r a l v e r t i c a l d i m e n s i o n , a b o u t o n e t h i r d h a v e
e x c e ss i ve v e rt i c al d e v e l o p m e n t . D e c r e a s e d v e r ti -
c al d e v e l o p m e n t i s l es s c o m m o n , o c c u r r i n g o n l y
i n a b o u t 1 0 o f C l as s I I s u b j ec t s i n t h e m i x e d
d e n t i t i o n s a m p l e . A s m e n t i o n e d p r e vi o u sl y , i n -
c r e a s e s i n l o w e r a n t e r i o r f a c i a l h e i g h t o f t e n a r e
a s s o c i a t e d w i t h a c h i n p o i n t t h a t i s p o s i t i o n e d
d o w n w a r d a n d b a c k w a r d , w h e r e a s d e c r e a s e s i n
lower an te r io r fac i a l he igh t a re a s soc ia t ed wi th a
f o r w a r d a n d u p w a r d p o si t io n o f p o g o n i o n . T h e s e
c h a n g e s a r e o f c r it i ca l i m p o r t a n c e w h e n p l a n -
n i n g t h e t r e a t m e n t o f a C la ss I I p a t i e n t , i n t h a t
i n c r e a s i n g t h e v e r t ic a l d i m e n s i o n d u r i n g C l as s I I
60%
50%
40%
30%
20%
10%
0%
S H O R T L O N G
41.9
14 0 m6 0
<18° 18-20° 21-26°
30.9
27-31 o >31 °
Figure 10. The dis t r ibut ion of the angle form ed by
the intersect ion of the mand ibular plane an d the
Frankfort horizontal.
60%
5 0 %
4 0 %
30%
20%
10%
0%
S H O R T
53.1
L O N G
18.4
16.2
I W
4.3 l
<56mm 56-58mm 59-65mm 66-68mm
>68mm
Figure 11. The distribution of the distance between
anterior nasal spine and menton. Increased lower
anterio r facial heigh t is a com mo n finding.
t r e a t m e n t w i l l t e n d t o c a m o u f l a g e p o s i t i v e
c h a n g e s i n m a n d i b u l a r l e n g t h . Thus i f maximum
advanceme nt of the chin point is desired as a goal of
treatment increases in the vertical growth o f the pati ent
durin g treatment should be minimized.
3 Transverse Co mp one nts
a. Maxillomandibular discrepancies. A d i m e n -
s i o n o f t e n o v e r l o o k e d i n t h e e v a l u a t i o n o f th e
Class I I pa t i en t i s t he t ransv e rse re l a t io nsh ip of
t h e m a x i l l a t o t h e m a n d i b l e . M o s t C l as s I I p a -
t i e n t s a p p e a r t o h a v e a n o r m a l r e l a t i o n s h i p o f
t h e b u c c a l s e g m e n t s w h e n t h e p a t i e n t i s i n
cen t r i c occ lus ion . Tol l a ro e t a l , s0 however , have
s h o w n t h a t a n u n d e r l y i n g t r a n s v e r s e d i s c r e p a n c y
of 3 to 5 mm exi s t s i n den ta l a rches w i th Clas s I I
m a l o c c l u s i o n a n d s e e m i n g l y n o r m a l b u c c a l r e l a-
t i o n s h i p s . T h i s u n d e r l y i n g t r a n s v e r s e d i s c r e p -
a n c y c a n b e u n m a s k e d c l i n i c a l l y b y h a v i n g t h e
p a t i e n t p o s t u r e t h e m a n d i b l e i n a n a n t e r i o r
p o s i t i o n s o t h a t t h e c a n i n e s a r e p o s i t i o n e d i n a
Clas s I r e l a t ionsh ip . More s ign i f i can t t r ansve rse
d i s c r e p a n c i e s a r e e v i d e n c e d b y u n i l a t e r a l o r
b i l a t e ra l pos t e r io r c ros sb i t e s in cen t r i c occ lus ion .
Bacce t t i e t a131 eva lua ted two grou ps of un-
t r e a t e d s u b j e c ts ( a C l as s I I g r o u p a n d a n o r m a l
o c c l u s i o n g r o u p ) d u r i n g t h e t r a n s i ti o n f r o m t h e
d e c i d u o u s t o t he m i x e d d e n t i t i o n . T h e y n o t e d
t h a t t h e t r a n s v e r s e d i s c r e p a n c y t h a t e x i s t e d i n
t h e C l a ss I I g r o u p i n t h e d e c i d u o u s d e n t i t i o n
pers i s t ed in to the mix ed d en t i t i on . Bace t t i e t a131
a l so n o t e d t h a t a l l C la s s I I s u bj e c t s m a i n t a i n e d
f u l l Cl as s I I m o l a r a n d c a n i n e r e l a t io n s h i p s , a n d
m e a n o v e r je t i n c r e a se d w h e n c o m p a r e d w i t h
m e a n o v e r j e t i n t h e d e c i d u o u s d e n t i t i o n . T h e s e
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: ¢J . ~ >> Hom e I TOC
12
McNamara Peterson and Alexander
o b s e r v a t i o n s a r e s i m i l a r t o t h o s e o f A r y a e t a P 2
and Bi sha ra e t a l , 33 bo t h of which ind ica te tha t i n
t h e a b s e n c e o f t h e r a p e u t i c i n t e r v e n t i o n o r a
c h a n g e i n th e o r o f a c i a l e n v i r o n m e n t ( e g, th e
e l i m i n a t i o n o f a h a b i t o r a n a i r w a y o b s t r u c t i o n ) ,
C l a s s I I m a l o c c l u s i o n g e n e r a l l y i s n o t s e l f -
cor rec t ing . T hus the Clas s I I occ lusa l re l a t ion-
s h i p t e n d s t o b e s e l f - p e r p e t u a t i n g , a n d c o n t i n u e
to be a s soc ia t ed wi th a cons t r i c t ed t ransve rse
occ lusa l re l a t ionsh ip .
M c N a m a r a 26 a n d S p i l l an e 34 h a v e r e c o m -
m e n d e d t h a t i n m i l d t o m o d e r a t e C l as s I I p a -
t i e n ts w i t h r e a s o n a b l y w e l l - b a l a n c e d f a c e s , o r t h o -
p e d i c e x p a n s i o n o f t h e m a x i l la t h r o u g h r a p i d
m a x i l l ar y e x p a n s i o n d u r i n g t h e e a r ly m i x e d
d e n t i t i o n n o t o n l y w il l c r e a t e s o m e a d d i t i o n a l
a r c h s p a c e t o a l lo w f o r t h e e r u p t i o n o f t h e
p e r m a n e n t i n c i so r s, b u t a l so m a y e n c o u r a g e t h e
s p o n t a n e o u s c o r r e c t i o n o f t h e o c c l u s al r e l a t io n -
s h i p . M a i n t a i n i n g t h e m a x i l l a i n a w i d e n e d
p o s i t i o n r e l a t i v e t o t h e m a n d i b u l a r d e n t i t i o n
d u r i n g t h e p o s t e x p a n s i o n p e r i o d e n c o u r a g e s a
t r a n s i e n t f o r w a r d m a n d i b u l a r p o s t u r i n g , i n t h a t
t h e p a t i e n t o c c l u d e s m o r e c o m f o r t a b l y in a
s l igh tly an t e r io r pos i t ion . I n th i s i ns t ance , t h e
t e e t h t h e m s e lv e s a c t a s a n e n d o g e n o u s f u n c -
t i o na l a p p l ia n c e , p r o d u c i n g a f o r w a r d m a n d i b u -
l a r r e p o s i t i o n i n g a n d u l t i m a t e l y a s l i g h t b u t
c l i n i c a l l y s i g n i f i c a n t i n c r e a s e i n m a n d i b u l a r
l e n g t h . I f s p o n t a n e o u s C l as s I I c o r r e c t i o n d o e s
n o t o c c u r , d e f i n i t i v e c o r r e c t i v e t h e r a p i e s c a n b e
in i t i a t ed , usua l ly in the l a t e mixed or ea r ly
p e r m a n e n t d e n ti t io n .
b. Tooth-size/arch-size discrepancies.
Anothe r i s -
s u e t h a t m u s t b e a d d r e s s e d i n t h e t r e a t m e n t o f
C l as s I I m a l o c c l u s i o n i s t h e r e l a t i o n s h i p o f t o o t h
s i ze to a rch s ize . Ho we e t aP 5 in a com pa r i so n of
u n c r o w d e d a n d c r o w d e d a d u l t d e n t i t i o n s , f o u n d
a r e l at i o n s h ip b e t w e e n b o n y b a s e d i m e n s i o n s
( e g, a s i n d i c a t e d b y m e a s u r i n g m a x i l l a r y i n t e r m o -
l a r w i d t h ) a n d d e n t a l c r o w d i n g , w it h m u c h l es s
o f a n a s s o c i a t io n f o u n d b e t w e e n t o o t h s i ze a n d
d e n t a l c r o w d i n g . T h e y r e p o r t e d t h a t t h e d i f fe r -
e n c e i n t r a n s p a l a t a l w i d t h b e t w e e n t h e t w o g r o u p s
w as a b o u t 6 m m , w i th t h e u n c r o w d e d g r o u p h a v e
t h e l a r g e r v a l u e s ( 3 7 . 4 _+ 1 . 7 m m i n m e n ,
3 6 .2 + 1 .9 m m i n w o m e n ) .
A s e c o n d
s tudy22 ~6
i n d i c a t e d t h a t a b o u t 2 . 5 t o
3 .0 m m o f t ra n s p a l a t a l w i d t h i n c r e a s e o c c u r s i n
a n u n t r e a t e d p o p u l a t i o n f r o m 7 to 1 5 y e a r s o f
a g e . T h e l a t t e r st u d y al s o d e m o n s t r a t e d t h a t i f a
c h i l d h a d a v e r y n a r r o w d e n t a l a r c h ( e g , a
t r a n s p a l a t a l w id t h o f l es s t h a n 3 1 m m ) i n t h e
ea r ly mixed dent i t i on , i t i s un l ike ly tha t t he
p a t i e n t w i ll a t t a i n a d e q u a t e a r c h d i m e n s i o n s
t h r o u g h n o r m a l g r o w t h p r o c e ss e s a l o n e. I n m a n y
p a t i e n t s w i t h m i l d t o m o d e r a t e a r c h l e n g t h
d i s c r e p a n c i e s o b s e r v e d i n t h e m i x e d d e n t i t i o n , a
P h a s e I t r e a t m e n t o f ea r ly o r t h o p e d i c e x p a n s i o n
o f th e m a x i l la , w it h o r w i t h o u t p r i o r d e n t a l
d e c o m p e n s a t i o n o f t h e m a n d i b u l a r d e n t a l ar c h
usin g a r em ov ab le ex pa ns io n ap pl i an ce 22,34,37 is
r e c o m m e n d e d b e f o r e a t t e m p t i n g d e fi n it iv e C la ss
I I c o r r e c t i o n .
c. Summary.
T h e e v a l u a t i o n o f th e t r a n s v e r s e
d i m e n s i o n i n C l as s I I p a t i e n t s i n d i c a t e s t h a t t h e
g o a l s o f m o s t C l a s s I I t r e a t m e n t s s h o u l d i n c l u d e
t h e c o r r e c t i o n o f o b v i o u s o r c a m o u f l a g e d d i s c r ep -
a n c i e s b e t w e e n t h e m a x i l l a a n d m a n d i b l e . A l -
t h o u g h m o s t c l in i c ia n s r e c o g n i z e t h e n e e d t o
e l i m i n a t e u n i l a t e r a l o r b i l a t e r a l p o s t e r i o r c r o s s -
b i t es a s p a r t o f a t r e a t m e n t r e g i m e n , o f t e n t h e
typ ica l t r ansve rse d i s c repancy in the Clas s I I
p a t i e n t w i t h a se e m i n g l y n o r m a l b u c c a l o c c l u s a l
r e l a t i o n s h i p i s o v e r l o o k e d . A l t e r a t i o n o f t h e
t r a n s v e r s e d i m e n s i o n b y a v a r i e ty o f m e t h o d s ,
i n c l u d in g r a p i d m a x i l l a r y e x p a n s i o n , e x p a n d i n g
t h e i n n e r b o w o f a f a c e b ow , o r w i d e n i n g a s p a r t
o f f u n c t i o n a l a p p l i a n c e t h e r a p y , m u s t b e c o n s id -
e red in addi t ion to s ag i t t a l and ve r t i ca l cor rec -
t ion.
Overv i ew and onc l usi ons
T h e o b v i o u s o v e r a l l c o n c l u s i o n t h a t c a n b e
d r a w n f r o m t h i s t h r e e - d i m e n s i o n a l c o m p o n e n t
a n a ly s is i s t h a t t h e t e r m C l a s s I I m a l o c c l u s i o n
i s no t a s ing le d i agnos t i c en t i ty , bu t can re su l t
f r o m n u m e r o u s c o m b i n a t io n s o f c o m p o n e n t s .
Th e cep ha lom et r i c s tud ies of Wyl i e , 3s Dre l i ch , 39
Craig, 4° Blai r, 4a Sassouni , 42 and Moy ers , 17 am on g
o t h e r s , h a v e r e p o r t e d w i d e v a r i a t i o n i n t h e s i z e
a n d s h a p e o f t h e v a r io u s c r a n i o fa c i a l c o m p o -
n e n t s o f C l as s I I . A ll c e p h a l o m e t r i c s t u d ie s b y
necess i ty , however , dea l w i th o n ly the s ag i t ta l and
v e r t ic a l e l e m e n t s o f C l as s I I m a l o c c l u s i o n a n d
t h a t c o n c o m i t a n t t r a n s v e r s e d e f i c i e n c i e s i n t h e
m a x i l la , m a n d i b l e o r b o t h a l so m u s t b e t a k e n
i n t o c o n s i d e r a t i o n w h e n f o r m u l a t i n g a n a p p r o -
p r i a t e t r e a t m e n t p l a n f o r a s p e ci f i c p a t i e n t .
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~,t- .t,. a >> Ho me I TO C
Class H Mixed Dentition Treatment
121
Class I I Trea tmen t S tra teg ies
My objectall sublime
I shaU achieve n time--
To make he punishment it the crime.
T h i s q u o t e f r o m t h e s e c o n d a c t o f t h e G i l b e r t
and Sul l ivan mus ica l ,
The Mikado
wri t t en in
1 8 8 5 , i n e s s e n c e s h o u l d s u m m a r i z e t h e o v e r a l l
goa l o f t r ea t me nt fo r a spec if i c Clas s I I pa t i en t , i n
t h a t t h e t r e a t m e n t r e g i m e n s e l e c t e d s h o u l d a d -
d r e s s th e u n d e r l y i n g n e e d s o f t h e g i v e n p a t i e n t .
T h e m a n a g e m e n t o f Cl as s I I m a lo c c l u s io n h a s
v a r i e d o v e r t h e y e a rs , as a n u m b e r o f m o d a l i t i e s
h a v e b e e n d e v e l o p e d a n d a d v o c a t e d f o r m i x e d
d e n t i t i o n p a t i e n t s , i n c l u d i n g t h e e x p a n s i o n p r o -
c e d u r e s m e n t i o n e d p r e v i o u s l y . P e r h a p s t h e t w o
m a j o r t y pe s o f t r e at m e n t s m o s t f r e q u e n t l y u s e d
i n m i x e d d e n t i t i o n p a t i e n t s a r e e x t r a o r a l t r a c -
t i o n a n d f u n c t io n a l j a w o r t h o p e d i c s , b o t h o f
w h i c h a d d r e s s t h e s k e l e t a l a n d d e n t o l a v e o l a r
e l e m e n t s o f t h e C l a ss I I c o n f i g u r a t i o n . I n s o m e
p r a c t ic e s , o n e o f t h e s e a p p r o a c h e s i s u s e d a s t h e
m a j o r t r e a t m e n t a p p r o a c h t o C la ss I I c o r r e c t io n ,
t o th e e x c l u s i o n o f t h e o t h e r . T h e t r e a t m e n t
e f f e c ts p r o d u c e d b y tw o e x a m p l e s o f t h e se g e -
n e r i c c a t e g o r i e s o f t r e a t m e n t , c e r v i c a l tr a c t i o n ,
a n d t h e f u n c t i o n r e g u l a t o r ( FR - 2) o f F rf i nk e l ,
w i l l be examined in de ta i l .
x t r ao r a l T r a c ti o n
P e r h a p s t h e m o s t c o m m o n a d j u n c t u s e d in t h e
t r e a t m e n t f o r d i s t o c l u si o n i s e x t r a o r a l t r a c t i o n , a
fami ly of app l i a nces typ ica lly used to re s t r i c t t he
n o r m a l d o w n w a r d a n d f o r w a r d g r o w t h o f t h e
m a x il la . T h e f o r ce s p r o d u c e d a f f ec t th e n o r m a l
c r a n i o f a c ia l g r o w t h o f t h e p a t i e n t , a l l o w i n g f o r
t h e c o r r e c t i o n o f t h e C l as s I I o c cl u s a l c o n d i t i o n .
U s e o f e x t r a o r a l f o r c e s to m o d i f y t h e g r o w t h
o f t h e m a x i l l a h a s a l o n g h i s to r y , d a t i n g b a c k t o
the work of K ings ley in the 19 th cen tury . 43
I n t e r e s t i n e x t r a o r a l t r a c t i o n w a s d i m i n i s h e d i n
the f i r s t ha l f o f t he 20 th cen tury , b u t was rev ived
b y O p p e n h e i m 44 a n d l a t e r b y K l o e h n 4547 w h o
r e c o m m e n d e d t h e a p p l i c a ti o n o f li g h t f o r ce s f o r
t h e m a s s d i st a l m o v e m e n t o f t e et h . K l o e h n ' s
o r i g i n a l d e s i g n f e a t u r e d a f a c e b o w , t h e i n n e r
b o w o f w h i c h w a s a t t a c h e d t o t h e m a x i l l a r y f ir s t
m o l a r s , w i t h t h e o u t e r b o w c o n n e c t e d b y el a st ic s
t o a n o c c i p i t a l a n c h o r i n g d e v i c e . H e l a t e r m o d i -
f i e d t h a t d e s i g n t o i n c l u d e o n l y a ce r v i c a l n e c k
s tr a p. T h e m e t h o d o f a t t a c h m e n t a n d t h e a n g u l a-
t i o n o f t h e o u t e r b o w o f th e f a c e b o w c o u l d b e
a l t e r e d t o d e t e r m i n e t h e d i r e c t i o n o f p u l l. U s u -
a lly, t he ou te r bow was ad jus t ed to l ie above the
p l a n e o f o c c l u s i o n t o d i r e c t th e f o r c e t h r o u g h
t h e c e n t e r o f r es i s t an c e a n d p r e v e n t d i s ta l t ip -
p i n g o f t h e m o l a r s d u r i n g t r e a t m e n t .
I n r e v i e w i n g t h e l i t e r a t u r e o n e x t r a o r a l t r a c -
t i o n , i n v e s t i g a t o r s h a v e r e a c h e d c o n t r a d i c t o r y
c o n c l u s i o n s r e g a r d i n g t h e e f f e c t s o f s u c h t h e r a p y .
T h e s e d i f f e r e n c e s c a n b e e x p l a i n e d , i n p a r t , b y
t h e s p e c i fi c t r e a t m e n t p r o t o c o l s u s e d b y t h e
prac t i t i one r .
Th e type of ex t raora l t r ac t io n dev ice , a s we l l a s
t h e m a g n i t u d e o f t h e f o r c e a p p l i e d a n d t h e
d i r e c t i o n o f p u l l , h a v e b e e n s h o w n t o b e i m p o r -
t an t cons id e ra t ion s . 4~51 Th e ce rv ica l ( low-pul l o r
K l o e h n ) f a c e b ow , t h e t y p e o f f a c e b o w s e e n
mos t f requent ly in c l in i ca l p rac t i ce today , t yp i -
ca l ly i s used in pa t i en t s w i th de c rea sed ve r t i ca l
fac i a l d imens ions . In cont ra s t , a h igh-pul l f ace -
b o w g e n e r a l l y i s u s e d i n i n d i v i d u a l s i n w h o m
i n c r e a s e s i n v e r t i c a l d i m e n s i o n a r e t o b e m i n i -
m i z e d o r a v o i d e d . T h e f a c e b o w i s a t t a c h e d t o a n
o c c i p it a l a n c h o r i n g u n i t ( h e a d c a p ) t o p r o d u c e a
m o r e v e r ti c a ll y d i r e c t e d f o r c e . As a g r o w t h g u i d -
a n c e a p p l i a n c e , a h i g h p u l l f a c e b o w c a n d e c r e a s e
t h e v e r ti c a l d e v e l o p m e n t o f t h e m a x i l l a , t h e r e b y
a l lo w i ng f o r a u t o r o t a ti o n o f t he m a n d i b l e a n d
m a x i m i z i n g t h e h o r i z o n t a l e x p r e s si o n o f m a n -
d ibu la r g rowth . 52 A f acebo w a l so can be an-
c h o r e d s i m u l t a n e o u s l y t o a c e r v i c a l n e c k s t r a p
a n d a h e a d c a p , a c o m b i n a t i o n o f t e n t e r m e d a
c o m b i o r s t r a i g h t - p u l l f a c e b o w .
T rea tmen t
Effects Produced by
x t r a o r a l
T r a c t i o n
E x t r a o r a l t r a c t i o n h a s b e e n s h o w n t o p r o d u c e a
v a r i e t y o f s k e l e t a l a n d d e n t o a l v e o l a r e f f e c t s i n
Class I I pa t i en t s . A l t hou gh the re i s som e agree -
m e n t a m o n g i n v e s t i g a to r s a s t o t h e e f f e c t s p r o -
d u c e d , t h e c li n ic a l m a n a g e m e n t o f th e a p p l i -
a n c e , t h e d i r e c t i o n o f f o r c e a p p l i e d a n d t h e
a m o u n t o f f o r c e u s e d m a y e x p l a in s o m e o f t he
d i f f e r e n c e s a m o n g i n v e s t ig a t io n s .
1 Anteroposterior Dim ension
a. Maxilla ry skeletal position.
A p r i m a r y t r e a t -
m e n t e f f e c t o f e x t r a o r a l t r a c t i o n i s t h e r e s t r ic t i o n
of maxi l l a ry ske le t a l g rowth . T he re i s v i r tua l ly
u n i v e r s a l a g r e e m e n t t h a t, a s a r e s u l t o f tr e a t-
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~,r J,. a >> Hom e I TO C
22
McNamara Peterson and Alexander
m e n t , P o i n t A is r e p o s i t i o n e d p o s t e r i o r l y r e la t i v e
t o th e r e m a i n d e r o f th e fa ce , 47 53-60re su l t ing in a
red uc t io n in ma xi l la ry pr og na thi sm . 45,54,61~5 Weis-
l an de r 66 has sh own tha t t h i s t ec hni qu e a l so
i n f l u e n c e s t h e c r a n i a l b a s e b y p r o d u c i n g a c o u n -
t e r c lo c k w i s e t i lt i n g o f t h e s p h e n o - e t h m o i d p l a n e
d u r i n g 3 to 4 y e a r s o f t r e a t m e n t w i t h a h e a d g e a r .
b. Ma xilla ry dentoalveolarposition. Dista l move-
m e n t o f t h e m a x i l l a r y m o l a r s i s a t y p ic a l tr e a t -
m e n t e f fe c t p r o d u c e d b y c er v ic a l h e a d g e a r
th er ap y. 45,54,57,59,6°,62,66-72 In co n tr as t, H u b b a r d et
a173 r e p o r t e d a m e s i a l m o v e m e n t o f t h e f i r s t
m o l a r . E x t r u s i o n o f t h e m a x i l l a r y m o l a r s a l s o h a s
b e e n ob se rv ed , 54,56,63,74-78 wi th two 7~ to th re e 75
t i m es a s m u c h e x t r u s i o n r e p o r t e d a s w o u l d b e
e x p e c t e d d u r i n g n o r m a l g r o w t h . O n t h e o t h e r
h a n d , m o l a r e x t r u s i o n w a s n o t o b s e r v e d b y
Hu bb ar d e t a l . 7~
Melsen , 71 us ing th e imp lan t me th od ofBj6 rk , 79
s t u d i e d t h e e f f e c t o f c e r v i ca l - p u ll h e a d g e a r o n
t h e c r a n i o f a c i a l c o m p l e x , i n p a r t t o d e t e r m i n e
w h e t h e r t h e s p e ci f i c a n g u l a t i o n o f t h e o u t e r b o w
re la t ive to the occ lusa l p l ane was c l in ica l ly s ign if i -
c a nt . I n o n e g r o u p o f c h i l d re n , t h e o u t e r b o w
was t i l t ed 20 degrees above the occ lusa l p l ane ;
a n d i n t h e s e c o n d g r o u p , t h e o u t e r b o w w a s
a n g l e d 2 0 d e g r e e s b e l o w t h e o c c l u s a l p l a n e . I n
t h e f i rs t g r o u p w i t h t h e o u t e r b o w a n g l e d u p -
w a r d , o n l y s l ig h t t o o t h m o v e m e n t wa s o b s e r v e d ,
b u t t h e e n t i re m a x i l la r y c o m p l e x m o v e d p o s t e r i-
o r l y a n d i n f e r i o r ly r e l at i v e t o t h e a n t e r i o r c r a n i a l
base . M el sen 71 s t a t ed tha t t h i s me th od of face -
b o w a d j u s t m e n t i s a p p r o p r i a t e f o r t h o s e p a t i e n t s
w i t h t r u e m a x i l l a r y s k e l et a l p r o t r u s i o n . I n t h e
s e c o n d g r o u p , m o r e t o o t h m o v e m e n t wa s o b -
s e r v e d , p a r t i c u l a r l y a d i st a l t ip p i n g o f t h e u p p e r
f i rs t m o l a r . T h e e x t r a o r a l t r a c t i o n h a d n o a p p r e -
c i ab l e i n f l u e n c e o n t h e m a x i l l a r y c o m p l e x .
M e l s e n 7~ s t a t e d t h a t o r i e n t i n g t h e o u t e r b o w o f
t h e f a c e b o w b e l o w t h e o c c l u s a l p l a n e m a y b e
a p p r o p r i a t e i n p a t i e n t s w it h m e s i al l y m i g r a t i n g
o r t i p p e d u p p e r f i r st m o l a r s o r b o t h .
c. Man dibu lar dentoalveolar position. T h e r e i s
v i r tua l ly no l i t e ra tu re th a t addres ses the e f fec t o f
t h e c e r v i ca l - p u ll f a c e b o w o n t h e m a n d i b u l a r
d e n t i t i o n o t h e r t h a n t h e t r e a t m e n t e f f e c ts t h a t
a r e p r o d u c e d i n a ss o c i a t io n w it h f ix e d a p p l i a n c e
t r e a t m e n t .
d. M andi bula r skeletalposition. T h e a n t e r o p o s -
t e r i o r r e l a t i o n s h i p o f t h e c h i n h a s b e e n c o r r e -
l a te d t o t h e a m o u n t o f v e r ti c al o p e n i n g p r o -
d u c e d d u r i n g t r e a t m e n t . A d o w n w a r d a n d
b a c k w a r d r o t a t i o n o f t h e m a n d i b l e a n d a s im i l a r
m o v e m e n t o f P o in t B a n d p o g o n i o n h a s b e e n
r e p o r t e d , a s h a s a n o p e n i n g o f t h e m a n d i b u l a r
pl an e angle . 51,74-76 Kl oe hn 45 a nd Ri ng en be rg 57
r e p o r t e d n o c h a n g e i n t h e S N B a n g le , b u t o t h e r
inve s t igato rs not ed e i t he r po s te r io r 64'74-76 or
a n t e r i o r 56'6° m o v e m e n t o f P o i n t B .
2. Vert ical D imen s i on
T h e r e i s n o u n i v e r s a l a g r e e m e n t a s t o t h e e f f e c t
o f c e r v i c a l h e a d g e a r t r e a t m e n t o n t h e v e r t ic a l
d i m e n s i o n , a s i n v e s t i g a t o r s h a v e d i f f e r e d i n d e -
s c r i b i n g t h e e f f e c t o f th i s t y p e o f t h e r a p y o n t h e
va r ious a spec t s o f ve r t i ca l f ac i a l meas ures .
a. Mandibular plan e angle and l ower anterior
facial height. An
o p e n i n g o f t h e m a n d i b u l a r
p l a n e a n g l e a s t h e m a n d i b l e i s h i n g e d o p e n h a s
b ee n re p or te d by m an y inv estig ato rs. 58,66,74-76,78
A n o p e n i n g o f t h e b i t e a n d a n i n c r e a s e i n lo w e r
a n t e r i o r f a c i a l h e i g h t a l s o h a s b e e n a f r e q u e n t
fi n d in g . 28,29,54,65,74,8°-82 K le in 54 a n d R ic ke tt s 27 re -
p o r t e d t h a t e x t r a o r a l f o r c e t e n d s t o o p e n t h e Y
a x i s a n g l e a n d l e n g t h e n t h e f a c e m o r e t h a n
w o u l d o c c u r w i th n o r m a l g r o w t h . A h i g h - p u l l
h e a d g e a r h a s b e e n r e c o m m e n d e d t o r e d u c e t he
e x t r u s i o n o f th e u p p e r f i rs t m o l a r . I n c o n t r a s t,
R i n g e n b e r g , 57 B a u m r i n d s l a n d H u b b a r d 73 r e -
p o r t e d a cl o s u re o f th e m a n d i b u l a r p l a n e a n g l e
w i t h t r e a t m e n t , w h e r e a s o t h e r s r e p o r t e d n o
c h a n g e
.45,56,60,63,82-85
b. Occlusal pla ne angle.
Inves t iga tors have d i f -
f e r e d a s t o t h e e f f e c t o f e x t r a o r a l t r a c t i o n o n t h e
o r i e n t a t i o n o f t h e o c c l u sa l p l a n e r e la t iv e t o t h e
c r a n i a l b a s e . T h e a n a t o m i c o c c l u s a l p l a n e n o r -
mal ly c loses wi th age. 86 Klein, 54 King 6~ an d Hu b-
b a r d 73 r e p o r t e d t h a t t h e a n g l e o f t h e o c c l u sa l
p l a n e r e m a i n s r e la t i ve l y u n c h a n g e d d u r i n g t r e a t-
men t , wher eas Sandusky , 56 Merr i f i e ld , 76 and Can-
g i al o si 6° r e p o r t e d a n i n c r e a s e i n t h e a n g l e o f t h e
occ lusa l p l ane re l a t ive to the c ran ia l base . Hub-
b a r d 73 n o t e d a s l i gh t d o w n w a r d t i p p i n g o f t h e
a n t e r i o r p a r t o f t h e p a l a t a l p l a n e . T h e f u n c t i o n a l
occ lusa l p l ane c losed s l igh t ly w i th t rea tm en t a s
well.
c. alata l plane angle.
T h e p a l a t a l p l a n e h a s
b e e n s h o w n t o t i p a n t e r i o r l y w i t h a n u n e v e n
d e s c e n t , r e s u l t i n g i n t h e a n t e r i o r n a s a l s p i n e
t i p p i n g m o r e i n f e r i o r l y t h a n t h e p o s t e r i o r n a s a l
sp in e. 54'56 58'60'69'73'76'78 O n th e o th e r h an d ,
K l o e h n 45 a n d B o e c l e r 85 n o t e d n o c h a n g e i n t h e
a n g u l a t i o n o f t h e p a l a t a l p l a n e .
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: ¢J . a >> Hom e I TOC
lass H Mixed Dentition Treatment
123
3 T r a n sv e r se D i m e n s i o n
Mos t c l in i ca l s tud ies o f ex t ra ora l t r a c t ion ha ve
u s e d c e p h a l o m e t r i c s a s t h e p r i m a r y a n a l yt i c al
t o o l . T h u s , c o n s i d e r a t i o n i n t h e l i t e r a t u r e o f
c h a n g e s i n t h e t r a n s v e r s e d i m e n s i o n w i t h e x t r a -
o r a l t r a c t i o n h a s b e e n m i n i m a l . T h e o n l y in v e st i-
g a t i o n t o c o n s i d e r t r a n s v e r s e c h a n g e s i s t h a t o f
G h a f a r i , s7 w h o c o n d u c t e d a c o m p a r a t i v e s t u d y o f
t h e s t r a i g h t - p u l l h e a d g e a r a n d F R - 2 a p p l i a n c e o f
F r fi n ke l . T h e i n n e r b o w o f th e f a c e b o w w as
a d j u st e d a t e v e r y a p p o i n t m e n t t o a v oi d a n y
c o n s tr i c ti o n o r m a j o r e x p a n s i o n o f t h e i n t e r m o -
l a r d i s t a n c e , r e s u l t i n g i n a t o t a l e x p a n s i o n o f
the inn e r bow of 1 .5 to 2 .0 ram. s7 Gha fa r i 87 no ted
i n c r e a s e s n o t o n l y i n i n t e r m o l a r d i s t a n ce , b u t i n
in t e rcan ine d i s t ance a s we l l. These inves t iga tors
h y p o t h e s i z e d t h a t t h e c h a n g e i n i n t e r c a n i n e
d i s t an c e , a r e g i o n n o t d i r e c tl y a f f e c t e d b y th e
f a c eb o w , m a y h a v e b e e n a r e s u l t o f a s h i e l d i n g
e f f e c t b y t h e i n n e r b o w o n t h e l i p a n d c h e e k
m u s c u l a t u r e , a n i n d i c a t i o n o f t h e i n f l u e n c e o f
t h e b u c c a l a n d l a b i a l m u s c u l a t u r e o n t o o t h
pos i t ion .
FunctionalJaw Orthopedics
D u r i n g t h e l a s t 2 0 y e a r s , t h e r e h a s b e e n a n
i n c r e a s e i n t h e p o p u l a r i t y o f f u n c t i o n a l j a w
o r t h o p e d i c u s e d t o c o r r e c t C l a ss I I m a l o c c l u s i o n .
A ll o f t h e s o - ca l le d f u n c t i o n a l a p p l i a n c e s h a v e
o n e a s p e ct in c o m m o n : t h e y i n d u c e a f o r w a r d
m a n d i b u l a r p o s t u r i n g a s p a r t o f t h e t r e a t m e n t
e f fec t . P resumably , t h i s a l t e ra t ion in the pos tura l
ac t iv i ty o f t he mu sc les o f t he c ran iofa c ia l co m-
p l e x u l t i m a t e l y le a d s t o c h a n g e s i n b o t h s k e l et a l
a n d d e n t o a l v e o l a r r e l a t i o n s h i p s t o t h e p o i n t t h a t
t h e u n d e r l y i n g m a l o c c l u s i o n i s r e s o l v e d . T h e s e
a p p l i a n c e s i n c l u d e t h e a c t i v a to r88-9° an d its der iva -
t ives : the bio nato r , m,92 the Bim ler ap pl i an ce 9~ the
o p e n a c t i v a to r o f K l a m m t , 94 t h e k i n a t o r 94 a n d t h e
t w in b l o c k a p p l i a n c e . 95 T h e s e a p p l i a n c e s a r e
c o n s i d e r e d p r i m a r i l y t o o t h - b o r n e i n t h a t t h e y
c o n t a c t t h e t e e t h a s p a r t o f a n c h o r i n g t h e a p p l i -
a n c e i n t h e m o u t h , a n d t y p ic a ll y t h e l i n g u a l
reg io n of the or a l cav i ty i s used a s the b ase of
o p e r a t i o n .
A n o t h e r t y p e o f a p p l i a n c e , t h e H e r b s t a p p l i -
ance , 96 i s a t t ac hed d i rec t ly to the t ee th by a
v a r ie t y o f a n c h o r i n g u n i ts . T h e H e r b s t b i t e-
j u m p i n g m e c h a n i s m h a s b e e n r e i n t r o d u c e d u s -
ing the or ig ina l ba nd ed des ign by Pancher z , 97 99
al t ho ug h cas t , 1°° s ta inless s teel crow n, am an d
ac ry l i c sp l inO °z ve rs ions of He rbs t app l i ances
a l s o a r e a v a i l a b l e . T r e a t m e n t t i m e t e n d s t o b e
r e d u c e d u s i n g t h e H e r b s t a p p l i a n c e w h e n c o m -
p a r e d w i th t h e p r e v io u s ly m e n t i o n e d f u n c t io n a l
appl i ances , i n tha t s ign i f i can t den toa lveo la r , a s
we l l as ske le t a l adap ta t io ns ,
occ ur . 98 1°3
W h e n c o n s i d e r i n g a c o m p a r i s o n b e t w e e n e x -
t r a o r a l t r a c t i o n a n d f u n c t i o n a l j a w o r t h o p e d i c s ,
t h e r e i s a t e n d e n c y t o g r o u p a ll f u n c t i o n a l
a p p l i a n c e s i n t o t h e s a m e t h e o r e t i c a l f r a m e w o r k .
There i s a d i s t inc t d i f fe rence be tween the ac t iva -
t o r / b i o n a t o r f a m il y o f f u n c t io n a l a p p l ia n c e s,
dev ices tha t cons i s t p r im ar i ly o f ac ry l ic and wi re
tha t con tac t t he sof t t i s sue a s we l l a s the t ee th ,
a n d t h e v a r i e t y o f c u r r e n t l y a v a i l ab l e H e r b s t
a p p l i a n c e s t h a t i n c o r p o r a t e a r i g i d b i t e - j u m p i n g
m e c h a n i s m a t t a c h e d d i r e c t ly t o t h e t e e t h , w i t h
m i n i m a l b o n y a n d s o f t t i ss u e c o n t a c t . A s i m i l ar
d i s t i n c t i o n a m o n g f u n c t i o n a l a p p l i a n c e s c o n -
c e r n s t h e f u n c t i o n r e g u l a t o r ( F R) o f F r /i n k el , a n
a p p l i a n c e t h a t h a s a d i f f e r e n t b as i s o f o p e r a t i o n
a n d a d i f f e r e n t t h e o r e t i c a l b a si s t h a n m o s t o t h e r
f u n c t i o n a l a p p l i a n c e s .
T h e f u n c t i o n r e g u l a t o r ( F R) g r o u p o f a p p l i-
ances , i nc lud i ng th e FR-2 app l i an ce (F ig 12) tha t
i s u s e d r o u t i n e l y i n t h e c o r r e c t i o n o f C la s s I I
p r o b l e m s , w a s d e v e l o p e d b y R o l f F r f in k e l o f t h e
f o r m e r G e r m a n D e m o c r a t i c R e p u b l i c . 1 °4 -m I n
c o n t r a s t t o t h e H e r b s t a p p l i a n c e a n d t o e x t r a o r a l
t r a c t io n , t h e p r i m a r y f o c u s o f t r e a t m e n t w i t h th e
F R is t h e m u s c u l a t u r e o f t h e c r a n i o f a c i a l c o m -
plex . F r~ inke l s t a t e s tha t h i s app l i ance s sh ould be
v iewed f i r s t a s an or thopedic exe rc i s e dev ice , i n
t h a t i t a i ds i n t h e m a t u r a t i o n , t r a i n in g , a n d
r e p r o g r a m m i n g o f th e o r o fa c ia l n e u r o m u s c u l a r
s y st e m . T h i s a p p l i a n c e s y s t e m w a s d e v e l o p e d
a c c o r d i n g t o t h e b a s ic p r i n c i p l e s o f R o u x n 2
c o n c e r n i n g f u n c t i o n a l o r t h o p e d i c s , p r i n c ip l e s
t h a t h a v e b e e n a p p l i e d c l i n i c a l l y i n t h e f i e l d o f
g e n e r a l o r t h o p e d i c s f o r m a n y y ea r s.
A c c o r d i n g t o F r f i n k e l , t h i s o r t h o p e d i c e x e r -
c is e d e v i c e h as b e e n d e s i g n e d t o o v e r c o m e f u n c -
t i o n a l d i s o r d e r s a n d r e e s t a b l i s h p h y s i o l o g i c a l
condi t ions w i th in the orofac ia l complex . F r~ inke l
and F r f inkeP °9 s t res s tha t t he FR fami ly of app l i -
a n c e s a r e n o t o r t h o d o n t i c a p p l i a n c e s i n t h e
t r a d i t i o n a l s e n se , i n t h a t t h e y a r e n o t m e a n t for
u s e i n p r e c i s e t o o t h p o s i t i o n i n g . I n f a c t , t h e y
s t a t e t h a t t h e F R a p p l i a n c e i s i n f e r i o r t o o t h e r
t y p e s o f b o t h f i x e d a n d r e m o v a b l e a p p l i a n c e s i n
t h a t r e g a r d . R a t h e r , t r e a t m e n t w i t h t h i s a p p l i -
a n c e i s d i r e c t e d t o w a r d t h e c o r r e c t i o n o f f u n c -
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~ , r J , . a >> Ho m e ] T O C
24
McNamara Peterson and Alexander
J
.il
Figure 12. The FR-2 appliance of Fr/inkel. A) Fron t
view. B) Sagittal view. Th e vestib ular shields of the
appliance have a direct effect on the craniofacial
musculature. Reprinted with permiss ion from McNa-
marafl6)
t i o n a l d i s o r d e r s a s s o c i a t e d w i th s k e l e t o d e n t a l
m a l f o r m a t i o n s .
A s m e n t i o n e d p r ev io u sl y , o n e o f th e p r i m a r y
e f f e c t s a s s o c i a t e d w i t h m o s t f u n c t i o n a l a p p l i -
a n c e s i s a c h a n g e i n t h e p o s t u r a l p o s i t i o n o f t h e
m a n d i b l e . I n t h e t r e a t m e n t o f m a n d i b u l a r s k el -
e t a l r e t r u s i o n , f o r e x a m p l e , t h e m a j o r a i m o f
f u n c t i o n a l o r t h o p e d i c s i s t o o v e r c o m e t h e p o o r
p o s t u r a l p e r f o r m a n c e o f th o s e m u s c l e s t h a t d e t e r -
m i n e t h e p o s t u r a l p o s i t i o n o f t h e m a n d i b l e a s
we l l a s mandibula r movement . F r f inke1111 s t a t e s
t h a t c h a n g e s i n m a n d i b u l a r p o s t u r a l p o s i t i o n
a n d u l t i m a t e l y i n t h e s iz e a n d s h a p e o f th e
m a n d i b l e a r e n o t a c h i e v e d b y a m e c h a n i c a l
a d v a n c e m e n t o f t h e m a n d i b l e , b u t r a t h e r b y
mod i f i ca t ion s in the p os tur a l ac t iv ity o f t he
a s s o c i a te d m u s c u l a t u r e .
A l l F r f i n k e l a p p l i a n c e s a r e c h a r a c t e r i z e d n o t
b y l a r g e a m o u n t s o f ac r y li c in t h e l i n g u a l a n d
pa la t a l a reas a s a re the ac tiva tor - and b io na tor -
t y p e a p p l i a n c e s ) , b u t r a t h e r b y v e s t i b u l a r s h i e ld s
tha t l i e i n the bucca l ves t ibu le ou t s ide the den ta l
a r c h e s . T h e s e a p p l i a n c e s a r e c o n s t r u c t e d t o
p r e v e n t f a u l ty m u s c u l a r f u n c t i o n s a n d t o s ti m u -
l a t e n o r m a l p o s t u r a l a c ti v it y o f a ll m u s c l e s t h a t
d i r e c t l y o r i n d i r e c t l y h e l p t o e s t a b l i s h a c o m p e -
t en t o ra l s ea l. A cco rd i ng to F r f inke l , l °s t he
a c h i e v e m e n t o f a c o m p e t e n t l i p se a l is a n e s s e n -
t ia l a i m o f t h is t y p e o f f u n c t i o n a l j a w o r t h o p e -
dics.
Treatment Effects Produ ced by the
Function egulator
T h e F R- 2 h a s b e e n s t u d i ed b y a n u m b e r o f
inves t iga tors dur ing the l a s t 25 yea rs . The f ind-
ings of the c l in i cal s tud ies , however , o f t en a re
c o n t r a d i c t o r y a n d s h o u l d b e i n t e r p r e t e d i n li g h t
o f m a n y f a c t o rs , n o t t h e l e a st o f w h i c h i s t h e
c l in i c al m a n a g e m e n t o f t h e a p p l i a n c e . T h e t r e a t -
m e n t e f f ec t s p r o d u c e d d u r i n g f u n c t i o n r e g ul a -
t o r t h e r a p y a r e v e r y t e c h n i q u e s e n si ti v e.
1. A n t e r o p o s t e r i o r D i m e n s i o n
a. Maxillary skeletal position. T h e l i t e r a t u r e
va r i e s as to the e f fec t o f t he FR-2 on the a n te ro -
p o s t e r i o r p o s i t i o n o f t h e m a x i l l a. M o s t st u d i e s
e i t h e r s h ow m i n o r o r n o i n f l u e n c e o n t h e a n t e ro -
po st er io r po sit io n of t he ma xilla . 1°3,113-116 In con -
t ra s t, C r e e k m o r e aa7 n o t e d r e d u c e d f o r w a r d
g r o w t h o f t h e m a x i l l a i n p a t i e n t s t r e a t e d w i t h t h e
F R . T h i s d i v e r g e n c e i n f i n d i n g s m a y b e a r e s u lt o f
d i f fe re nces in t echn ique , a s i s d i s cus sed in the
n e x t s e c t io n .
b. Maxillary dentoalveolar position. A c c o r d i n g
to Har vold , a ls t he cor rec t ion of Clas s I I occ lusa l
r e l a t io n s h i p s c a n r e s u l t f r o m i n h i b i t i n g t h e d o w n -
w a r d a n d f o r w a r d e r u p t i o n o f t h e m a x i l la r y
b u c c a l s e g m e n t s i n g r o w i n g i n d i v i d u a l s . A s t h e
c r o s s o v e r w i r es o f t h e F R - 2 a p p l i a n c e c o n t a c t t h e
m a x i l l a r y p o s t e r i o r t e e t h F ig 13 ) , i n h i b i t i o n o f
p o s t e r i o r t o o t h e r u p t i o n t h e o r e t i c a l l y c o u l d o c -
c u r d u r i n g F R t r e a t m e n t . M c N a m a r a e t a l H6 h a v e
s h o w n t h a t a l t h o u g h t h e h o r iz o n t a l m o v e m e n t
of the upper f i r s t mola rs i s s l i gh t ly re s t r i c t ed
c o m p a r e d w i t h u n t r e a t e d C l a s s I I c o n t r o l s ; t h e
v e r t i c a l m o v e m e n t o f t h e m a x i l l a r y f i r s t m o l a r s
r e m a i n s u n a f f e c t e d b y F R t r e a t m e n t i n c o m p a r i -
son to cont ro l va lues .
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~ CI . a >> Hom e [ TOC
Class II M ixed Den tition Treatment
25
;2 2 .22 .2 / ._ .
,, i
Figure
13. The FR-2 appliance of Frfinkel. (A) Maxil-
lary view. (B) Mandibular view. (Reprinted with permis-
sion from McNamara. 26)
The FR appliance has been shown to have a
variable effect on the position of the upper
incisor. Sch ulhof, 119 Cr eekm ore, 117 Ro be rt son 114
and Hamilton 12° noted pro nou nce d retroclina-
tion of the upper incisors during Frfinkel treat-
ment, whereas McNamar a H6 report only slight
posterior tipping of the up per incisor. In some
patients, posterior tipping of the upper incisor
may be beneficial, in others not. Frfinkel s treat-
ment m eth od requires notchi ng of the maxillary
post erior deci duou s teeth. Robe rts on 114 and
Cree kmor e 117 state, and Sch ulho f119 implies, that
that their samples had no such notching. Frfinkel
states that the lack of notching may lead to an
unfavorable tipping of the up per incisors in a
posterior direction and ultimately a restraint of
maxillary growth.
c M a n d i b u l a r d e n to a l v e o la r p o s i ti o n The Har-
vold theory of dentoalveolar Class II correction
throug h differential erupti on of teeth als predicts
increased erupt ion of the lower molar as a result
of FR tre atme nt. Cre ekm ore , 117 Righellis Hs an d
McNamara n6 no ted additional vertical move-
ment of the lower molars in the FR group.
Schulhof119 rep ort ed that Fr/inkel tr eat ment pro-
duces additional mesial movement of the lower
molar over that which is expected during norma l
growth, whereas most oth er studies do not.
Lower incisor proclination is a com mo n find-
ing in many of the clinical studies that have
considered the treatment effects produced by
the FR. a17,119-121 Someti mes lower inci sor proclina-
tion occurs normally, as when lower incisors
trapped behind the lower lip are freed as existing
skeletal and muscular imbalances are corrected.
In other instances, anterior lower incisor move-
ment is not desired, but may result from im-
proper technique, particularly concerning the
management of the lower labial pads. Pad posi-
tioning that is too far superior to the dept h of the
vestibule or too far anterior to the mandibular
alveolus (or both) can lead to lower incisor
proclination because the pads can have a lip
bumper effect on the orbicularis oris muscle,
rather than the desired restrictive effect on
mentalis
act ivi ty. 1°7 111 If
proper appliance man-
agement is maintained, labial tipping of the
lower incisors is mini mize d. 116
d Mandi bu l ar ske l e t a l pos i t i on The initial stud-
ies of FR treatment showed conflicting results
concerning the effect on mandibular growth.
For example, Schulhof, a19 Cr ee km or e 117 an d Rob-
ertson a14 were unabl e to d etect any increase in
mand ibu lar length, whereas Fr/inkeP 22 and
Righellis 11s not ed increases in mand ibu lar length
during treatment.
Falck 123 stud ied the lon g-t erm effect of FR
treatment on the skeletal and dentoalveolar
structures of the craniofacial complex. The mate-
rial of this study consisted of standardized serial
lateral cep halo grams of 103 childre n with a Class
II malocclusion associated with mandib ular retru-
sion, 58 of who m were treated with eit her the
FR-1 or FR-2 appliance. Forty-five untreated pa-
tients served as controls. A comparison of pre-
treatm ent mor phol ogy indicated that the two
groups were almost identical at the begi nning of
the study period. The subjects were followed
fr om 7 to 15 years o f age. Falck 123 no te d a
forward movement of pogoni on of 14 mm in the
treated group and 7.3 mm in the untreated
group, indicating a significant difference in man-
dibular growth increments between the two
groups.
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: FJ . a >> Home I TOC
126
McNam ara Peterson an d Alexander
Fr/inke1111 reana lyze d a po r t io n of the pa t i en t s
i n F a lc k ' s s tu d y. H e r e p o r t e d a n i n c r e a s e i n
m a n d i b u l a r l e n g t h o f 1 8. 9 m m i n th e F R g r o u p
a s c o m p a r e d w i th 1 3. 8 m m i n t h e u n t r e a t e d
group , a d i f fe rence tha t was s t a t i s t i ca l ly s ign i f i -
can t . No s t a t i s t i ca l ly s ign i f i can t d i f fe rence were
n o t e d i n m a x i l l a r y l e n g t h o r i n l o w e r a n t e r i o r
f a c ia l h e i g h t b e t w e e n t h e t w o g r o u p s . P o s t e r i o r
f a ci a l h e i g h t ( r a m u s l e n g t h ) , h o w e v er , wa s g r e a t e r
i n t h e F R g r o u p , a n d t h e f a c i al ax i s a n g l e c l o s e d
i n t h e F R g r o u p , i n d i c a t i n g a m o r e h o r i z o n t a l
v e c t o r o f f a c ia l g r o w t h .
M c N a m a r a e t a P 16 s t u d i e d 1 0 0 p a t i e n t s t r e a t e d
w i t h t h e F r / i nk e l a p p l i a n c e . T h e y d i v i d e d t h e
s a m p l e i n t o a y o u n g e r g r o u p ( 8 . 5 y e a r s a t t h e
b e g i n n i n g o f t r e a t m e n t ) a n d a n o l d e r g r o u p
( 1 1. 5 y e a r s a t t h e b e g i n n i n g o f t r e a t m e n t ) . T h e s e
p a t i e n t s w e r e c o m p a r e d w i t h 4 1 u n t r e a t e d C l a s s
I I c o n t ro l s , a g a i n d i v i d e d b y a g e. G r e a t e r i n -
c r e a s e s i n m a n d i b u l a r g r o w t h i n c r e m e n t s w e r e
n o t e d i n t h e o l d e r t r e a t e d g r o u p t h a n i n t h e
y o u n g e r t r e a t e d g r o u p , a n d b o t h t r e a t m e n t
g r o u p s h a d l a r g e r m a n d i b u l a r g r o w t h in c r e -
m e n t s t h a n t h e i r r e s p e ct i ve m a t c h e d c o n t r o l
g r o u p s . B o t h t r e a t e d g r o u p s s h o w e d a n i n c r e a s e
i n l o w e r a n t e r i o r f a c i a l h e i g h t , b u t n o c h a n g e i n
t h e m a n d i b u l a r p l a n e a n g l e o r i n m a x i l l a r y
p o s i t i o n , in c o m p a r i s o n t o c o n t r o l s .
A l a t e r s t u d y b y M c N a m a r a e t a l 1°3 c o m p a r e d
p a t i e n t s t r e a t e d w i t h t h e F r f i n k e l a p p l i a n c e a n d
w i t h t h e a c r y l i c s p l i n t H e r b s t a p p l i a n c e i n c o m -
p a r i s o n t o u n t r e a t e d C l as s I I c o n t r o l s . G r e a t e r
d e n t o a l v e o l a r a d a p t a t i o n w a s p r o d u c e d b y th e
H e r b s t a p p l i a n c e t h a n b y t h e F r / in k e l a p p l i a n c e .
2 Vertical Dim ensi on
M o s t o f t h e c h a n g e s i n v e r t ic a l d i m e n s i o n h a v e
b e e n i n c o r p o r a t e d i n t o t h e d i s c u ss i o n o f s a g it t al
c o r r e c t i o n d e s c r i b e d p r e v io u s ly . T h u s , o n l y a
s u m m a r y o f th e v e r ti c al c h a n g e s p r o d u c e d b y F R
t r e a t m e n t w il l b e p r o v i d e d h e r e . T h e 2 - y ea r
c l in i c al s t u d y b y M c N a m a r a e t al u i n d i c a t e d t h a t
m a n d i b u l a r l e n g th in c r e a s e d b y 8 2 o v e r c o n -
t r o l v a l u e s i n t h e i r o l d e r a g e g r o u p a n d 6 0 i n
t h e y o u n g e r a g e g r o u p . H o w e v e r , s u c h i n c r e a s e s
i n m a n d i b u l a r l e n g t h a r e n o t n e c e s s a r il y e x -
p r e s s e d b y a n a d v a n c e m e n t o f t h e c h i n p o i n t t o a
c o m p a r a b l e d e g r e e . C h a n g e i n t h e h o r i z o n t a l
p o s i t i o n o f t h e c h i n v a r i e s i nv e r s e ly w it h t h e
a m o u n t o f in c r e a s e d l o w e r a n t e r i o r f a ci al h e i g h t
p r o d u c e d d u r i n g t r e at m e n t. M a x i m u m a n t e r i o r
r e p o s i t i o n i n g o f t h e c h i n i s o b t a i n e d b y a n
i n c r e a s e d i n m a n d i b u l a r l e n g t h w i t h o u t a c o n -
c o m i t a n t i n c r e a s e i n l o w e r a n t e r i o r f a c i a l h e i g h t .
C o n v e r se l y , a s i g n i fi c a n t i n c r e a s e i n m a n d i b u l a r
l e n g t h c a n b e c a m o u f l a g e d b y a c o r r e s p o n d i n g
inc rease in lower fac i a l he igh t . Such inc reases
h a v e b e e n s h o w n t o b e a r e s u l t o f F R t re a t -
m en t. 116
3 Transverse Dime nsion
T h e r e i s v i r tu a l ly u n iv e r s a l a g r e e m e n t t h a t t h e
v e s t i b u l a r s h i el d s o f t h e F R l e a d t o a s p o n t a n e o u s
ex pa ns io n of the den tal arche s , s7,124-13° Mo sch
(c i t ed by F r f inkeP 31) s tud ied 400 pa t i en t s t r ea t e d
o n l y w i t h t h e F r /i n k e l a p p l i a n c e a n d o b s e r v e d
t h a t a s a r e s u lt o f w i t h h o l d i n g c h e e k p r e s s u r e
t h r o u g h t h e u s e o f th e v e s t i b u l a r s h i e ld s a n d t h e
l o w e r la b i a l p a d s , a s p o n t a n e o u s w i d e n i n g o f t h e
d e n t a l a r c h e s o c c u r r e d r o u t i n e l y . M o s c h n o t e d a
m e a n i n c r e a s e i n t r a n s p a l a ta l w i d th o f o v e r 4 m m
i n b o t h t h e p r e m o l a r a n d m o l a r r e g io n s d u r i n g a
2 - y ea r t r e a t m e n t t i m e . N o d a t a r e g a r d i n g m a n -
d i b u l a r a r c h e x p a n s i o n w e r e p u b l i s h e d .
McD ouga l l e t a1124 me asu red s e r i a l den ta l
cas t s f rom 60 pa t i en t s t r ea t ed wi th the F r / inke l
a p p l i a n c e a n d c o m p a r e d t h e m t o s e ri al d en t a l
c a st s f r o m 4 7 u n t r e a t e d i n d i v id u a l s . T h e r e s u lt s
o f th i s s t u d y i n d i c a t e d t h a t e x p a n s i o n o f t h e
m a x i l l ar y a n d m a n d i b u l a r d e n t a l a r c h e s o c -
c u r r e d r o u t i n e l y w i th F r / in k e l a p p l i a n c e t h e r a py .
T h e e x p a n s i o n w a s n o t l i m i t e d t o a p a r t i c u l a r
r e g i o n o f t h e d e n t a l a r c h , a l t h o u g h i n a b s o lu t e
t e r m s t h e g r e a t e st a m o u n t o f e x p a n s i o n o c-
c u r r e d i n t h e p r e m o l a r a n d m o l a r r e g i o n s ,
w h e r e a s a l e s s e r a m o u n t o c c u r r e d i n t h e c a n i n e
r e g i on . T h e a v e r a ge a m o u n t o f m a x il l a r y a r c h
e x p a n s i o n w a s 4 t o 5 m m , w i t h 3 t o 4 m m
o b s e r v e d i n t h e m a n d i b u l a r a r c h .
C o m p a r i s o n o f T r e a t m e n t S t r at e g ie s
I n l i g h t o f t h e p r e v i o u s l i t e r a t u r e r e v ie w t h a t
i n d i c a t e s t h a t c e r v i c al f a c e b o w t h e r a p y a n d f u n c -
t io n r e g u l a t o r t r e a t m e n t a p p a r e n t l y p r o d u c e
d i f f e r i n g t r e a t m e n t e f f ec t s, a s t u d y w as u n d e r -
t a k e n t o c o m p a r e t h e s e t w o m o d a l i t i e s d i r e c t l y .
T h i s c o m p a r a t i v e a p p r o a c h h a s b e e n u s e d b e -
f o r e t o c o n t r a s t e x t r a o r a l t r a c t i o n t o v a r i o u s
t y p es o f f u n c t i o n a l a p p l i a n c e s . F o r e x a m p l e ,
Meach, 1~2 Jakobsson, T B a u m r i n d e t a l sz a n d
De rr i ng e r 133,1~4 have co mp ar ed ex t ra ora l t r ac -
t ion to the ac t iva tor . Only a few s tud ies have
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: , I - ' . 1 , - ~ -- > >
Class H M ixed Den t i t ion Trea tmen t
H o m e I T O
27
c o m p a r e d t h e f u n c t i o n r e g u l a t o r a n d e x t r a o r a l
t r a c t i o n directly. 113,117,135-137
Selection o f Subjects
S e r ia l c e p h a l o m e t r i c r a d i o g r a p h s o f t h r e e g r o u p s
of Clas s I I , d iv i s ion 1 pa t i en t s were eva lua ted .
R e c o r d s f r o m p a t i e n t s t r e a t e d w i t h t h e f u n c t i o n
r e g u l a t o r ( FR - 2) o f F r fi n k el w e r e c o m p a r e d w i t h
r e c o r d s o f p a t i e n t s t r e a t e d w i t h a c e r v ic a l - pu l l
f a c e b o w c o m b i n e d w i th i n c i so r b r a c k e t i n g a n d
a r c h w ir e s , a n d a l so w it h l o n g i t u d i n a l c e p h a l o -
g r a m s o f u n t r e a t e d c h i l d r e n w i t h C la s s I I m a l o c -
c l u si o n . R e c o r d s o f t h e F r / in k e l p a t i e n t s a n d
c o n t r o l s u b j ec t s w e r e p a r t o f sa m p l e s p r e v i o u s l y
desc r ibed and eva lua ted by Mc Na ma ra e t a l. 1x6
a. Exclusionary rules. A f t e r e a c h g r o u p o f r e -
c o r d s w a s a s s e m b l e d , s p e c i f ic e x c l u s i o n a r y r u l e s
were appl i ed . 116 A p a t i en t o r sub jec t was e l imi -
n a t e d f r o m t h e s t ud y if o n e o r m o r e o f th e
f o l l o w in g c o n d i t i o n s w a s f o u n d t o a p p l y ( s e ve r a l
o f t h e r u l e s w e r e n o t r e l e v a n t t o t h e c o n t r o l
s a m p l e ) .
1 . Absence of Clas s I I ma loc c lus ion . A n end- to-
e n d C l as s I I m o l a r a n d c a n i n e r e l a t i o n s h i p
(or worse ) was neces sa ry for inc lus ion in the
study.
2 . R e t r o c l i n a t i o n o f t h e u p p e r i n c is o r s p r i o r t o
t rea tment , a s in Clas s I I , d iv i s ion 2 ma locc lu-
s ion.
3 . I n a d e q u a t e t i m i n g o f r a d i o g r ap h s . T o b e
i n c l u d e d i n t h e s t u d y , t h e p r e t r e a t m e n t r a d i o -
g r a p h h a d t o b e t a k e n 2 . 5 m o n t h s o r l e s s
b e f o r e t r e a t m e n t , a n d t h e p o s t t r e a t m e n t r a d io -
g r a p h h a d t o b e t a k e n w i t h i n 1 m o n t h f o l l o w -
i n g t r e a t m e n t .
4 . P o o r r a d i o g r a p h i c q u a l i t y . S o m e a n a t o m i c a l
l a n d m a r k s w e r e n o t i d e n t i fi a b l e .
5. E r r o r s i n m a n d i b u l a r p o s i t i o n - - o b v i o u s p o s-
t u r i n g o f th e m a n d i b l e f o r w a r d a s i n d i c a t e d
b y t h e r e l a ti v e p o s i t i o n o f t h e p o s t e r i o r b o r -
d e r o f t h e r a m u s a n d t h e a n t e r i o r b o r d e r o f
the a t las in ser ia l f i lms .
Pa t i en t s a l so were e l im ina te d f r om in i t i a l cons id-
e r a t i o n i f t h e c l i n i c i an j u d g e d t h a t t h e p a t i e n t s
c o o p e r a t i o n w as p o or . T h i s j u d g m e n t w a s b a s e d
n o t o n t h e s u c c es s o f t r e a t m e n t b u t , r a t h e r , o n
r e p o r t s f r o m p a r e n t s a n d p a t i e n t s a n d f r o m
c l in i ca l s ig n s o f a p p l i a n c e w e a r ( e g , h y p e r e m i a i n
spec i f i c a reas o f t he ora l sof t t i s sue in FR pa -
t ients ) .
b Sample groups
1. Friinkel FR ) Group. R e c o r d s o f 1 51 p a t i e n t s
w h o f i n i s h e d F R - 2 t r e a t m e n t w i t h i n a 2 - y e a r
p e r i o d w e r e s u b m i t t e d b y e i g h t p r a c ti t i o -
ne rs .116 These pa t i en t s were t rea t ed accord ing
to the p ro to co l o f Fr f inke l, m a l so a s desc r ibed
b y M c N a m a r a . 26 N o o t h e r t y p e o f o r t h o d o n t i c
i n t e r v e n t i o n w a s p r o v i d e d d u r i n g t h e s t u d y
i n t e r v a l. T h e a p p l i c a t i o n o f t h e e x c l u s i o n a r y
ru le s red uce d the F r~ inke l s am ple to 100
pa t i en t s (Table 1 ) .
Facebow Group. The in i t i a l 75 pa t i en t s i n th i s
g r o u p u n d e r w e n t a f ir st p h a s e o f o r t h o d o n t i c
t r e a t m e n t w i t h a c e r v i c a l t r a c t i o n h e a d g e a r
a t t a c h e d t o t h e m a x i l l a r y f ir s t m o l a r s . T h e y
a ls o h a d b o n d s o r b a n d s p l a c e d o n t h e u p p e r
c e n t r a l a n d l a t e r a l i n c i s o r s t h a t w e r e c o n -
n e c t e d b y a n a r c h w i r e t o t h e f ir st p e r m a n e n t
mo la rs ( the so-ca l l ed 2 × 4 hoo k-u p) . Pa t i en t s
typ ical ly were to ld to wea r the fa cebo w 12 to
1 4 h o u r s p e r d ay . A f t e r t h e e x c l u s i o n a r y r u l e s
w e r e a p p l i e d , t h e f a c e b o w s a m p l e w a s r e -
duced to 61 pa t i en t s (Table 1 ) .
3. Contro l Group. C h a n g e s o v e r t h e c o u r s e o f
t r e a t m e n t w i t h t h e F R a n d c e r v i c a l f a c e b o w
w e r e c o m p a r e d w i t h c h a n g e s r e c o r d e d f o r a
s a m p l e o f u n t r e a t e d C l as s I I c h i l d r e n f r o m
t h e University of Michigan Elem entary and Second-
ary School Growth Stu dy. s6 138 The sub jec t s i n
t h e c o n t r o l s a m p l e w e r e s u b j e c t e d t o t h e
e x c l u s i o n a r y r u l e s a p p l i e d t o t h e t r e a t m e n t
s a m p l e s , e x c e p t f o r p a r a m e t e r s t h a t w e r e
r e l e v a n t o n l y t o t r e a t e d p a t i e n ts . T h i s p l a n
r e s u l t e d i n t h e s e l e c t i o n o f r e c o r d s f o r 4 1
s u b j ec t s o f u n t r e a t e d C l as s I I m a l o c c l u s i o n .
A f t e r t h e e x c l u s i o n a r y r u l e s w e r e a p p l i e d t o
d e f i n e t h e s a m p l e g r o u p s , o n e a d d i t i o n a l s e l e c -
t i o n c r i t e r i o n w a s a d d e d , t h a t b e i n g c h r o n o l o g i -
c a l a g e . T h e g r o u p s w e r e d e f i n e d f u r t h e r b y
.
Table 1. Patient Selection
After Age at
Group Initial Exclusions Final Start Duration
Fr f i nke l 151 100 26 9 .1 y r 24 mo nt h s
H e a d g e a r 7 5 6 1 3 4 9 . 0 y r 2 1 m o n t h s
C o n t r ol 4 1 4 1 2 0 9 . 2 y r 2 6 m o n t h s
N O T E . I n it ia l , n u m b e r o f r e c o r d s s u b m i t t e d f o r i n c l u s io n ;
a f t e r e xc l us i ons , nu mb e r o f sub j e c t s r e m a i n i n g a f t e r e xc l us i on-
a ry ru l e s a pp l i e d s e e t e x t fo r de sc r i p t i on) ; f i na l , f i na l s a mpl e
s iz e ; a ge a t s t a r t , a ve ra ge a ge o f t he s a mp l e s a t t he t i m e of t he
i n it i al l a te r a l h e a d f i lm ; d u r a t i o n , d u r a t i o n o f t h e t r e a t m e n t /
obse rva t i on i n t e rva l .
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: , t- J,. ~ >> Ho me [ TO C
28
McNamara Peterson and Alexander
e x c l u d i n g p a t i e n t s a n d s u b j e c t s w h o w e r e y o u n -
ge r tha t 7 .5 yea rs o r o ld e r th an 11 yea rs o f age a t
t h e b e g i n n i n g o f t h e t r e a t m e n t / o b s e r v a t i o n p e -
r i o d . T h e a p p l i c a t i o n o f t hi s la s t c r i t e r i o n t o t h e
F r fi n k el s a m p l e r e d u c e d t h e s i ze o f t h e s a m p l e t o
26 (17 g i r l s and 9 boys ) . S imi l a r ly , t he facebow
g r o u p w a s c o m p o s e d o f 34 p a t i e n t s ( 1 9 g i rl s a n d
1 5 b o y s) a n d t h e c o n t r o l g r o u p w a s c o m p o s e d o f
20 sub jec t s (12 g i r l s and 8 boys ) . A t the end of
t h e s e l e c t i o n p r o c e s s , t h e g r o u p s w e r e w e l l
m a t c h e d a c c o r d i n g t o c h r o n o l o g i c a l a g e , w i t h a n
a v e r a g e a g e o f a b o u t 9 y ea r s a t t h e b e g i n n i n g o f
t r e a t m e n t f o r a l l g r o u p s ( T a b l e 1 ) . T h e t r e a t -
m e n t / o b s e r v a t i o n i n t er v a l w as a p p r o x i m a t e l y 2
y e a r s f o r e a c h g r o u p ( T a b l e 1 ).
e t hod
o f A na ly s i s
E a c h c e p h a l o m e t r i c h e a d f i l m w a s t r a c e d b y tw o
i n v e s ti g a t o r s ( J E P a n d J A M ) t o v e r if y a n a t o m i c
o u t l i n e s a n d l a n d m a r k p l a c e m e n t . L a n d m a r k
l o c a t i o n s t h e n w e r e d i g i t i z e d u s i n g a c u s t o m i z e d
d i g i t i z i n g p r o g r a m . F o r l o n g i t u d i n a l a n a l y s i s ,
s e r i a l l a t e r a l c e p h a l o g r a m s w e r e s u p e r i m p o s e d
o n t h e b a s i o n - n a s i o n l i n e w i t h r e g i s t r a t i o n o n
t h e p t e r y g o m a x i l l a r y fis sur e. 26 139 S u p e r i m p o s i -
t i o n w a s c h e c k e d a g a i n s t t h e p o s t e r i o r c r a n i a l
out l ine as wel l .
T h e c e p h a l o m e t r i c a n a ly s is u s e d w a s a m o d i -
f i e d a n d e x p a n d e d v e r s i o n o f t h e a n a ly s is u s e d
rou t in ely by th e sen ior auth or . 22,26,116 Fr om the
d i g i t i z e d l a t e r a l c e p h a l o g r a m s , 2 8 m e a s u r e m e n t s
w e r e d e r i v e d f o r e a c h p a t i e n t a t e a c h t i m e
in te rva l (Tables 2 and 3) .
T h e F R a n d f a c e b o w g r o u p s h a d v a r y i n g
m a g n i f i c at i o n s t h a t r a n g e d f r o m 7 t o 8 ,
w h e r e a s t h e c o n t r o l g r o u p s u b j e c t s h a d a 1 2 . 9 2
m a g n i f i c a t i o n . A l l l i n e a r c e p h a l o m e t r i c m e a -
s u re s w e r e c o n v e r t e d to a n 8 e n l a r g e m e n t to
s t a n d a r d i z e t h e d a t a .
Sta t i s t ica l e t hods
A n a n a ly s is o f v a r i a n c e i n i ti a ll y w as p e r f o r m e d
a m o n g a l l t h r e e g r o u p s . I f a l ev e l o f s ig n i f i c a n c e
l es s t h a n 0 . 05 w as o b s e r v e d , S c h e f f e ' s m e t h o d o f
m u l t i p l e c o m p a r i s o n s w a s u s e d t o d e t e r m i n e
d i f f e re n c e s a m o n g g r o u p s.
T h e e r r o r o f t h e m e t h o d h a s b e e n p r e v io u s ly
ca lcu la t e d by M cN am ara 1°3 in a s imi l a r s tudy . As
t h e m e t h o d s a n d e q u i p m e n t f o r t h e p r e s e n t
s t u d y ar e p a r t o f a r o u t i n e l y u s e d s t a n d a r d i z e d
p r o t o c o l , t h e e r r o r o f t h e m e t h o d i s i m p l i e d t o
be wi th in acce p tab le l imi t s fo r t h is study .
Resu l t s
a. Comparison of Starting Form. As i n o u r p r e -
v i o u s s t u d i e s , w e e x a m i n e d t h e e q u i v a l e n c e o f
s t a rt i n g f o r m b y c o m p a r i n g p r e t r e a t m e n t s ke l-
e t a l a n d d e n t o a l v e o l a r c e p h a l o m e t r i c v a l u e s
(Table 2) .
Skeletal measures. O f t h e 1 8 sk e l e ta l m e a s u r e s ,
the re were no s t a t i s t i ca l ly s ign i f i can t d i f fe rences
i n s t a r t i n g f o r m w i t h r e s p e c t t o t h e F r f i n k e l a n d
c o n t r o l g r o u p s . T h e r e w e r e d i f f e r e n c e s , h o w -
e v er , b e t w e e n t h e s e t w o g r o u p s a n d t h e f a c e b o w
g r o u p . F o r e x a m p l e , m a x i l l a r y s k e l e t a l p o s i t i o n
w a s s l ig h tl y m o r e r e t r u s i v e i n t h e c o n t r o l g r o u p
than in the facebow gro up (Table 2 ) . S imi la r ly,
t h e m a n d i b l e w a s m o r e r e t r u s i v e i n t h e c o n t r o l
g r o u p t h a n i n th e f a c e b o w g r o u p . I n a d d i t i o n ,
lower an te r io r fac i a l he igh t was l e s s in the face -
b o w g r o u p t h a n i n th e c o n t r o l s .
Dentoalveolar measures. O f t h e 1 0 m e a s u r e s
u s e d t o e v a l u a te d e n t o a l v e o l a r p o s i t i o n , o n l y t h e
l o w e r i n c i s o r t o p o g o n i o n r e l a t i o n s h i p d i f f e r e d
w h e n t h e F R g r o u p w a s c o m p a r e d w i t h c o n tr o l s
( T a b l e 2 ) . T h e u p p e r i n c i s o r i n t h e f a c e b o w
g r o u p w a s l o c a t e d m o r e a n t e r i o r l y r e la t iv e t o t h e
p t e r y g o m a x i l l a r y f i ss u r e t h a n i n e i t h e r t h e F R o r
c o n t r o l g r o u p s .
b. Analysis of treatment effects. The ana lys i s o f
t h e e f f e c t s o f t r e a t m e n t u s e d t h e s a m e 2 8 v ar i -
a b l e s t h a t w e r e u s e d t o c o m p a r e s t a r t i n g f o r m s .
B e c a u s e t h e i n t e r v a l b e t w e e n t h e f i r st a n d s ec -
o n d h e a d f i l m s v a r i e d sl i gh t ly a m o n g g r o u p s , t h e
d a t a p r e s e n t e d i n T a b l e 3 h a v e b e e n s t a n d a r d -
i z e d t o r e f l e c t a 2 4 - m o n t h t r e a t m e n t / o b s e r v a -
t i o n i n t e r v a l f o r a l l g r o u p s .
Maxillary skeletal relationships. T h e f u n c t i o n
r e g u l a t o r h a d l it tl e i m p a c t o n t h e g r o w t h o f t h e
maxi l l a . In con t ra s t , s ign i f i can t i nh ib i t ion of the
f o r w a r d m o v e m e n t o f t h e m a x i l la wa s n o t e d i n
t h e f a c e b o w g ro u p . F o r e x a m p l e , P o i n t A m o v e d
f o r w a r d 0 . 4 m m i n t h e c o n t r o l g r o u p r e l a t i v e t o
t h e n a s i o n p e r p e n d i c u l a r ( T a b l e 3 ) . I n c o n t r a s t ,
P o i n t A w a s d i s p l a c e d p o s t e r i o r l y ( - 2 . 8 m m ) i n
t h e f a c e b o w g r o u p . I n a d d i t i o n , t h e S N A a n g l e
i n c r e a s e d b y 0 .8 ° i n t h e c o n t r o l g r o u p b u t d e -
c r e a s e d ( - 2 . 2 ° ) i n t h e f a c e b o w g r o u p . T h e
inc rease in midfac ia l l eng th a l so was l e s s in the
f a c e b o w g r o u p .
Maxillary dentoalveolar relationships. C h a n g e s i n
t h e h o r i z o n t a l p o s it i o n s o f t h e u p p e r u p p e r
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?,l- .lC ~ >>
Class H Mixed Dentit ion Treat ment
Hom e I TOC
1 2 9
T a b l e 2 . C o m p a r i s o n o f S ta r t in g F o r m s
Headgear n = 34) Friinkel n = 26) Control n = 20) Significance
x SD x SD
x SD H-F H-C F-C
Maxillary Skeletal
Condyl ion-ANS (mm ) 91.6 3.9 89.0
Midfacial lengt h (Co-Pt.
A) (ram ) 88.7 3.9 87.0
SNA angle 81.5 3.4 80.4
N a s io n p e r p e n d i c u l a r /
po in t A (mm) -0 .1 2 .2 -1 . 0
Maxi l lary Dental
Uppe r i nc i sor hor i zont a l
(mm) 57.2 3.6 54.6
U p p e r i n c i s o r / p o i n t A
(mm) 5.7 1.6 4.9
Upper m olar hor i zont a l
(mm) 24.3 2.5 22.7
Upper incisor vert ical
(mm ) 47.0 3.6 47.1
Uppe r m olar ver t ica l
(mm) 40.0 2.5 40.4
Mandibul ar Denta l
Lower i nc i sor hor i zont a l
(mm) 7.3 2.6 8.6
Lower incisor-APo 0.8 1.6 0.3
Lower molar hor i zont a l
(mm) 32.2 2.3 32.4
Lower inc isor vert ical
(ram ) 39.0 3.0 39.3
Lower mo lar vert ical
(mm ) 29.3 2.6 29.1
Mandibular Skeletal
Mandibul ar l ength
(Co-Gn) (mm ) 106.9 4.2 105.3
P o g o n i o n / N p e r p ( m m ) - 7 . 9 4 .1 - 9 . 9
Facial plane angle 85.5 2.3 84.4
SNB ang le 76.0 3.3 74.9
ANB angle 5.5 1.3 5.5
Art icular e-gnath ion 98.4 4.1 97.4
Vertical
Ante rior facial ht
(ANS-Me) (m m) 61.0 4.9 61.4
Posterior facial ht
(Co-Go) (mm ) 51.1 3.8 49.7
Corpus length (Go-Po)
(mm ) 70.3 3.8 69.0
SN plane 8.4 2.5 8.6
Palatal pla ne 2.2 3.0 1.2
Occlusal pla ne 10.4 2.9 11.2
Man dibula r plane angle 23.2 3.7 25.5
Facia l ax is angl e -0 . 4 4 .0 -2 . 4
3.5 89.3 4.3 * * NS
3.4 87.1 4.1 NS NS NS
2.0 79.5 2.5 NS * NS
2.2 -2 .0 2.9 NS t NS
3.4 54.1 4.0 t t NS
2.0 4.2 1.9 NS t NS
2.6 23.2 2.7 * NS NS
4.3 49.2 4.3 NS NS NS
3.0 41.4 2.4 NS NS NS
3.4 7.9 3.5 NS NS NS
2.0 2.0 1.8 NS *
3.0 32.4 2.4 NS NS NS
2.8 40.5 2.9 NS NS NS
2.0 30.3 2.3 NS NS NS
4.6 106.6 4.1 NS NS NS
4.9 -12 .4 4.7 NS t NS
2.6 83.2 2.5 NS t NS
2.3 74.1 2.1 NS * NS
1 6 5 4 1 8
NS NS NS
4.4 98.9 4.2 NS NS NS
3.9 63.7 4.2 NS * NS
4.3 49.9 3.7 NS NS NS
3.7 69.0 3.8 NS NS NS
2.4 8.1 1.9 NS NS NS
2.6 0.7 2.5 NS * NS
3.8 12.0 3.3 NS NS NS
5.6 27.1 4.2 NS t NS
3.7 -3 .4 2.8 * t NS
Abbreviat ion: NS, not significant .
*= P< .05.
t = P< .01.
++= P < .001.
m o l a r a n d i n c i s o r w e r e m e a s u r e d b y d r o p p i n g a
p e r p e n d i c u l a r l i n e f r o m t h e m o s t p o s t e r i o r p o i n t
o n t h e p t e r y g o m a x i l l a r y f i s s u re to th e F r a n k f o r t
h o r i z o n t a l ( F ig 1 4) . D i r e c t l i n e a r m e a s u r e m e n t s
w e r e m a d e t o t h e m e s i a l c o n t a c t p o i n t o f t h e
u p p e r f i rs t m o l a r a n d t o t h e t i p o f t h e u p p e r
i n c i s o r . 116 T h e u p p e r i n c i s o r m o v e d a n t e r i o r l y
2 . 0 m m i n t h e c o n t r o l g r o u p , b u t p o s t e r i o r l y i n
t h e f a c e b o w g r o u p ( - 4 . 2 m m ) . T h e p o s i t i o n o f
t h e u p p e r i n c i s o r i n t h e F R g r o u p r e m a i n e d
r e l a t i v e l y u n c h a n g e d . S l i g h t l y s m a l l e r d i f f e r -
e n c e s i n h o r i z o n t a l r e s p o n s e w e r e n o t e d i n t h e
f i rs t m o l a r r e g i o n . N o d i f f e r e n c e s w e r e n o t e d
a m o n g g r o u p s i n t h e v e r t i c a l m o v e m e n t o f t h e
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AF Jce >> Home I TOC
1 3 0
McNamara, Peterson, and Alexander
Table 3 Compa rison of Treatment Effects
Headgear n = 34) Frdnkel n = 26) Control n = 20) Significance
x SD x SD
x SD H-F H-C F-C
Maxi l la ry Ske le ta l
C ondy l i on-A NS (m m ) 1 .2 1 .4 2 .4
Mi dfa c i a l l e ng t h (C o-P t.
A) (m m ) 0 .4 1 .6 2 .2
SNA ang le - 2.2 1.2 - 0.4
N a s i o n p e r p / p o i n t A
( r a m ) - 2 . 8 1 .2 - 0 . 4
Ma xi l l a ry De n t a l
U p p e r i n c i s o r h o r i z o n t al
( m m ) - 4 . 2 4 .2 - 0 . 2
U p p e r i n c i s o r / p o i n t A
( m m ) - 2 . 8 2 . 4 - 1 .2
U p p e r m o l a r h o r i z o n t a l
(m m) - 1.8 2.4 1.8
Uppe r i nc i so r ve r t i c a l
(m m ) 3 .0 2 .0 3 .0
U p p e r m o l a r v e r t ic a l
(m m ) 3 .0 1 .4 2 .6
M a n d i b u l a r D e n t a l
L o w e r i n c i s o r h o r i z o n t a l
(m m) - 1.8 1.6 1.2
L owe r i nc i so r -APo 0 .4 1 .2 2 .8
L o w e r m o l a r h o r i z o n t a l
( m m ) - 0 . 6 1 . 4 0 . 2
L owe r i nc i so r ve r t i c al
(m m ) 0 .2 1 .6 1 .0
L owe r m ol a r ve r t i c a l
(m m ) 1 .0 1 .2 2 .6
M a n d i b u l a r S k e le t al
M a n d i b u l a r l e n g t h
(C o-Gn) (m m ) 4 .8 2 .0 6 .4
P o g o n i o n / N p e r p en -
d i c u l a r ( r a m ) - 0 . 6 2 . 4 1 .4
Fa c i a l p l a ne a ng l e -0 . 1 1 .2 1 .0
SNB ang le 0.4 1.2 1.2
AN B ang le - 2.6 1.0 - 1.6
Ar t i c u l a re -gna t h i on 4 .6 1 .6 6 .0
Vert ica l
Ant e r i o r f a c i a l h t
(ANS-Me) (ram) 2.0 1.0 3.2
Pos t e r i o r f a c ia l h t
(Co-Go) (ram ) 2.8 1.6 4.2
C o r p u s l e n g t h ( G o -P o )
(m m ) 2 .4 1 .4 3 .4
S N p l a n e - 0 . 6 0 . 6 0 . 0
Pala ta l pla ne - 2.0 2.0 - 0.8
O c c l u s a l p l a n e - 0 . 0 3 . 2 0 . 8
M a n d i b u l a r p l a n e a n g l e 1 .0 2 . 0 - 0 . 2
Fa c i a l a x i s a ng l e -0 .6 2 .0 0 .4
1.8 1.4 1.2 i NS NS
1.8 2.0 0.8
~ ~
NS
1.4 0.8 1.2 ~ ~ ¢
1.4 0.4 1.0 ~ ~ *
2.6 2.0 0.8 ~ *
1.8 0.4 1.0
~ f
1.6 2.0 1.0 ~ NS
1.6 2.6 1.4 NS NS NS
1.4 2.8 1.0 NS NS NS
1 . 6 - 0 . 4 0 . 6
1.6 0.2 0.8 NS
1.0 0.6 1.0 * NS
1.4 1.6 1.0 * NS
1.0 0.8 1.0 NS
2.2 3.6 1.2 *
1.8 1.0 1.2 f NS
1.0 0.8 0.6 ~ * NS
1.0 0.8 0.8 i NS NS
1 .2 -0 . 1 0 .8 ~
1.1 3.4 1 .2 ~ *
1.6 1.0 1.0 ~ *
2.4 1.8 2 .0 * NS
1.6 3.0 1.4 * NS NS
0.6 -0 .2 1 .0 t NS NS
1 .6 -0 .6 1 .0 f f NS
3 . 6 - 0 . 2 2 . 6 N S N S N S
1.8 -0 .6 1 .0 f f NS
1.2 0.4 0.6 * * NS
Abbre v i a t i on : NS , no t s i gn i f i c a n t.
* = P < .05.
t = P< .01.
++= P < .001.
i n c i s o r o r t h e f i r st m o l a r r e l at i v e t o t h e F r a n k f o r t
h o r i z o n t a l T a b l e 3 ) .
Ma ndi bul ar skeletal relationships As m e a s u r e d
f r o m c o n d y l i o n t o g n a t h i o n , i n c r e a s e s i n m e a n
m a n d i b u l a r l e n g t h w e r e g r e a te r i n t he F R g r o u p
6 .4 m m ) t h a n i n t h e u n t r e a t e d c o n t r o l s 3 . 6
m m) . A s ta t i st i cal ly s ign i f i can t i nc rease in ma n-
d i b u l a r l e n g t h a l so w a s n o t e d i n t h e f a c e b o w
g r o u p r e la t i v e t o c o n t r o l 4 .8 m m ) . T h e c h i n
p o i n t a t p o g o n i o n r e la t iv e t o t h e n a s i o n p e r p e n -
d i c u la r m o v e d b a ck w a r d s li gh tl y - 0 . 6 m m ) i n
t h e f a c e b o w g r o u p , w h e r e a s a f o r w a r d m o v e -
m e n t o f p o g o n i o n o c c u r r e d i n t h e F rf in k el 1 .4
m m ) a n d c o n t r o l 1 .0 m m ) g r o u p s T a b le 3 ).
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At J,. a >> Home I TOC
Class H Mi xed Dentition Treatment
131
A ~ ~ ~ . ~
Figure 14. Determinat ion o f changes in the horizon-
tal position of the u pp er first mo lar and up pe r incisor.
(A) Distance from the mesial surface of the upper
molar to a l ine drawn from the pterygomaxi l lary
fissure perpendicular to the Frankfort horizontal
(pterygoid vertical). (B) Distance from the tip of the
upper incisor to the pterygoid vertical. (Reprinted
with permission from McNam ara. lm)
Mandibular dentoalveolar relationships
T h e a v e r-
a g e h o r iz o n t a l m o v e m e n t o f th e l o w e r m o l a r a n d
l o w e r i n c i s o r w a s m e a s u r e d b y e s t a b l i s h i n g t h e
f u n c t i o n a l o c c l u s al p l a n e ( F O P ) a n d t h e n d r a w -
i n g a l i n e f r o m t h e F O P t h r o u g h p o g o n i o n ,
e s ta b l is h i n g th e p o g o n i o n p e r p e n d i c u l a r ( Fi g
1 5 ) . M e a s u r e m e n t s w e r e m a d e f r o m t h e m e s i a l
c o n t a c t p o i n t o f t h e l o w e r m o l a r a n d t h e t i p o f
t h e l o w e r i n c i s o r t o t h e p o g o n i o n p e r p e n d i c u -
l ar . u 6 F o r w a r d m o v e m e n t s o f t h e l o w e r m o l a r
a n d l o w e r i n c i s o r w e r e r e p o r t e d a s a p o s i t i v e
v a l ue s . F o r w a r d i n c i s o r m o v e m e n t w a s n o t e d i n
t h e F r f i n k e l g r o u p ( 1 . 2 m m ) , w h e r e a s s l i g h t
d i st a l m o v e m e n t o f th e t i p o f th e l o w e r i n c i s o r
w as n o t e d i n t he c o n t r ol s ( - 0 . 4 m m ) a n d i n t h e
f a c e b o w g r o u p ( - 1 . 8 m m ) . L e s s d i f f e r en c e s
w e r e n o t e d i n th e m o l a r r e g i o n ( T a b l e 3 ) .
V e r ti c al m o v e m e n t s o f t h e m a n d i b u l a r i n c i s o r
a n d m o l a r w e re d e t e r m i n e d b y c o n s t r u c t i n g a
ve r t i ca l l i ne th ro ug h the inc i s a l t i p and the
mes ia l cusp of the mola r , r e spec t ive ly , pe r pen dicu -
l a r t o t h e f u n c t i o n a l o c c l u s a l p l a n e t o t h e p o i n t
o f i n t e r s e c t i o n w i th t h e m a n d i b u l a r p l a n e . I n -
c r e a s ed e r u p t i o n o f th e m o l a r w a s o b s e r v e d i n
t h e F R g r o u p i n c o m p a r i s o n w i t h c o n t r o l s a n d
t h e f a c e b o w g r o u p ( T a b l e 3 ) . L es s v e r ti c a l m o v e -
U
unctional Occlusal
~ ~ Pp:rOp°nind:cular
Figure 15. Horizontal mov emen t of the lower incisor
and lower molar. After establishing the functional
occlusal plane (FOP), the pogon ion perp endicular i s
cons tructed from the chin point perpen dicular to the
FOP. (A) Distance from the mesial contact po int o f the
lower molar to the pogonion perpendicular . (B)
Distance from the tip of the lower incisor to the
pogo nion perpendicular . (Reprinted with permiss ion
fro m McNamara.116)
m e n t o f t h e i n c i so r w as o b s e r v e d i n t h e F R a n d
f a c e b o w g r o u p s t h a n i n t h e u n t r e a t e d C l as s I I
s a m p l e .
Vertical relationships
L o w e r a n t e r i o r f a c i a l
h e i g h t , a s m e a s u r e d f r o m a n t e r i o r n a s a l s p i n e t o
m e n t o n , i n c r e a s e d i n b o t h t r e a t m e n t g r o u p s ,
w i t h t h e g r e a t e s t i n c r e a s e o b s e r v e d i n t h e F R
g r o u p . S i m i l a r in c r e a s e s i n p o s t e r i o r f a ci a l h e i g h t
w e r e n o t e d a s w e ll . T h e m a n d i b u l a r p l a n e a n g l e
d e c r e a s e d s l i g h tl y i n t h e F R a n d c o n t r o l g r o u p s
a n d i n c r e a s e d s l ig h t ly in t h e f a c e b o w g r o u p .
C o m p a r a b l e c h a n g e s i n t h e f a c ia l a x is a n g l e a ls o
w e r e o b s e r v e d .
D i s c u s s i o n
T h e r e s ul t s o f t h i s r e t r o s p e c t i v e s t u d y i n d i c a t e
t h a t t h e F R -2 a p p l i a n c e o f F rf in k e l, a n d t h e
c e r v i c a l - p u l l f a c e b o w c o m b i n e d w i t h a n t e r i o r
b r a c k e t s a n d a r c h w i r e , p r o d u c e s i g n i f i c a n t t r e a t -
m e n t e f f e c ts o n t h e c r a n i o f a c i a l s t r u c t u r e s o f
C l as s I I m i x e d d e n t i t i o n p a t i e n ts . T h e s e t r e at -
m e n t a p p r o a c h e s , h o w e v e r , a f f e c t t h e s k e l e ta l
a n d d e n t o a l v e o l a r s t r u c t u r e s i n d i f f e r i n g w ay s.
a Pretreatment comparisons This s tudy eva lu-
a t e d t h r e e g r o u p s o f in d i v i d u al s w i th C l a s s I I
m a l o c c l u s i o n . F r o m t h e i n i t ia l s a m p l e o f 2 67 s e ts
of reco rds (Table 1) , spec i f i c exc lu s iona ry ru l e s
w e r e a p p l i e d t o r e f i n e t h e s a m p l e . I n a d d i t i o n ,
s p e c if i c ag e p a r a m e t e r s a t t h e s t a r t o f t r e a t m e n t
w e r e d e f i n e d t o m a t c h t h e s a m p l e a c c o r d i n g t o
c h r o n o l o g i c a l a g e . A n e v a l u a t i o n o f s t a r t i n g
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~,r J,. a >> Ho me [ TO C
32
McNama ra Peterson and Alexander
f o r m ( T a b l e 2 ) s h o w e d t h a t t h e F r f i n k e l a n d
c o n t r o l g r o u p s w e r e w e l l - m a t c h e d a c c o r d i n g t o
the 28 va r i ab le s used in th i s s tudy . Desp i t e these
e f f o r t s t o m a t c h t h e g r o u p s s o m e s i g n i f i c a n t
d i f f e r e n c e s e x i s te d b e t w e e n t h e f a c e b o w g r o u p
a n d t h e o t h e r s a m p l e g r o u p s . S p ec i fi ca ll y , b o t h
t h e m a x i l l a a n d t h e m a n d i b l e w e r e s l ig h tl y m o r e
r e t r u d e d i n t h e c o n t r o l s a m p l e , a n d l o w e r a n t e -
r i o r f a c i a l h e i g h t w a s l e s s i n t h e f a c e b o w g r o u p
t h a n i n th e c o n t r o l . I n a d d i t i o n , b o t h t h e u p p e r
i n c is o r s a n d m o l a r s w e r e m o r e a n t e r i o r i n t h e
f a c e b o w g r o u p b e f o r e t r e a t m e n t t h a n i n t h e
c o n t r o l .
T h e s e d i f f e r e n c e s i n p r e t r e a t m e n t f o r m b e -
t w e e n t h e f a c eb o w g r o u p a n d t h e o t h e r t w o
gro ups i s a re f l ec t io n of suscep t ib i l i t y b i a s, ''14°
in tha t pa t i en t s were s e l ec t ed b y the c l in i c i an a s
b e i n g s u s c e p t i b l e t o a g i v e n t r e a t m e n t , i e , f a c e -
b o w t h e r a p y o r F R t r e a t m e n t . H i s t o r i c a l l y , t h e
t y p e o f h e a d g e a r u s e d i n t h i s s tu d y ( c e r v i c al
f a c eb o w ) h a s b e e n r e c o m m e n d e d f o r u s e i n
p a t i e n t s w i t h s h o r t l o w e r a n t e r i o r f a c i a l h e i g h t s
a n d p r o t r u s i v e m a x i l l a r y d e n t i t i o n s ( s ee p re v i -
ous d i s cus s ion of th i s is sue in th i s a r t i c l e ) . In
c o n t r a st , F r / in k e l t h e r a p y h a s b e e n r e c o m -
m e n d e d f o r tr e a t m e n t o f pa t i en t s w i th m a n d i b u -
l a r s k e l et a l r e t r u s i o n a n d a s s o c ia t e d n e u r o m u s c u -
l a r p r o b l e m s . T h e p r e t r e a t m e n t d e s cr i pt i ve
s t at i st i cs o f t he th ree s amp les s eem to re f l ec t
s o m e s u s c e p ti b i li t y b i as , w h i c h c o n f o u n d s t h e
a n a ly s is o f p o s t t r e a t m e n t c h a n g e s , e s p e c ia l l y w i t h
r e g a r d t o th e f a c e b o w g r o u p i n c o m p a r i s o n w i t h
t h e o t h e r g r o u p s .
b. Posttreatment comparisons. The ana lys i s o f
t h e t r e a t m e n t e f f e c t s p r o d u c e d b y t h e t w o t h e r a -
p ie s revea l s tha t t hese two moda l i t i e s have ve ry
d i f f e r e n t e f f e c t s o n t h e s k e l e t a l a n d d e n t o a l v e o -
l a r s t r u c t u r e s o f t h e c r a n i o f a c i a l c o m p l e x . F o r
e x a m p l e , t h e r e w a s a 3 m m d i f f e r e n c e b e t w e e n
t h e c h a n g e i n p o s i t i o n o f P o i n t A b e t w e e n t h e
f a c e b o w g r o u p a n d c o n t r o l d u r i n g t h e t r e a t m e n t
p e r i o d . S i m i l a r c h a n g e s w e r e o b s e r v e d i n t h e
S N A a n g l e a n d t h e i n c r e m e n t s o f m i d f a c i a l
l e n g t h i n c re a s e, a s m e a s u r e d f o r m c o n @ l i o n t o
P o i n t A . I n c o n t r a s t T h e F r ~ i n k e l a p p l i a n c e h a s
m i n i m a l e f f ec t o n m i d f ac i a l d e v e l o p m e n t .
O n e o f t h e m o s t s tr i k i n g d i f f e r e n c e s b e t w e e n
t h e t w o t r e a t m e n t s w a s w i t h r e g a r d t o t h e a n t e r o -
p o s t e r i o r p o s i t i o n o f t h e m a x i l l a r y i n c is o r s a n d
m o l a rs . T h e F R a p p l ia n c e t i p p e d t h e u p p e r
i n c i s o r p o s t e r i o r l y a n d d i d n o t a f f e c t t h e p o s i t i o n
o f t h e u p p e r m o l a r i n c o m p a r i s o n t o c o n t ro l . I n
c o n t r a s t , t h e f a c e b o w , c o m b i n e d w i t h p a r t i a l
a n t e r i o r a p p l i a n c e s , p r o d u c e d a si g n i fi c a n t p o s t e -
r i o r r e l o c a t i o n o f t h e u p p e r i n ci s or , a 6 m m
d i f f e r e n c e i n c o m p a r i s o n t o c o n t r o l v a l ue s . Si m i-
l ar ly , t h e u p p e r m o l a r w a s r e l o c a t e d a l m o s t 4 m m
p o s t e r i o r ly i n c o m p a r i s o n t o t h e u n t r e a t e d g r o u p .
T h u s , t h e f a c e b o w a n d f i x ed a p p l i a n c e c o m b i n a -
t i o n h a d a p r o f o u n d e f f e c t o n t h e p o s i t i o n o f t h e
m a x i l l a r y d e n t i t i o n i n c o m p a r i s o n t o c o n t r o l s.
O n e e x p l a n a t i o n f o r t h e d i f f e r e n c e i n u p p e r
i n c i s o r m o v e m e n t i s t h a t o f t e n i n C l a ss I I d i v is i on
1 p a t i e n ts , t h e u p p e r i n c i s o r s a r e s p a c e d a n d
f l a r e d b e f o r e t r e a t m e n t . O n e o f t h e o b j e c ti v e s o f
so-ca l l ed 2 × 4 t re a tm en t i s t o c lose the spaces
a n d t o r e d u c e t h e f l a r i n g o f t h e u p p e r i n c i s or s
t h r o u g h t h e a p p l i c a t i o n o f l i n g u a l c r o w n t o r q u e .
S u c h m o v e m e n t is a p p r o p r i a t e i n t h e se t y p e s o f
pa t i en t s .
T h e t w o a p p l i a n c e s h a d o p p o s i t e e f f e c t s o n
t h e m o v e m e n t o f th e l o w e r d e n t i ti o n , b u t t o a
m u c h l e s s e x t e n t t h a n i n t h e m a x i l l a . M o d e s t
l o w e r i n c i s o r p r o c l i n a t i o n w a s o b s e r v e d f o l l o w -
i n g F R t r e a t m e n t , w h e r e a s m o d e s t i n c i s o r r e t r o -
c l i n a t i o n w as n o t e d i n t h e f a c e b o w g r o u p . I n
a d d i t i o n , i n c r e a s e d m o l a r e r u p t i o n w a s n o t e d i n
t h e F R g r o u p c o m p a r e d w it h t h e o t h e r g r o u p s .
As has be en show n in this s am ple , a°3,aa6 as wel l
a s in o the r such s amples ,a a1,113.123 in cr ea se d in cr e-
m e n t s o f m a n d i b u l a r l e n g t h w e r e n o t e d f ol lo w -
i n g F R t r e a t m e n t . T h e s e f i n d i n g s a r e i n c o n t r a s t
t o t h o s e o f S c h u l h o f , u ° C r e e k m o r e n7 a n d R o b e r t -
son 114 w h o n o t e d n o i n c r e a s e d m a n d i b u l a r
growth , bu t whose s tud ies d i f fe red s ign i f i can t ly
f r o m t h e p r e s e n t s t u d y w i t h r e g a r d t o t h e t e c h n i -
c al m a n a g e m e n t o f t h e a p p l i a n ce .
A s ta t i st i cal ly s ign i f i can t i nc rease in m and ibu -
l a r l e n g t h w a s m e a s u r e d i n t h e f a c e b o w s a m p l e
i n c o m p a r i s o n w i t h t h e u n t r e a t e d C l as s I I s a m p l e .
T h i s i n c r e a s e i n m a n d i b u l a r l e n g t h l e n d s s u p -
p o r t t o t h e c o n c e p t o f a m a n d i b u l a r r e s p o n s e
d u r i n g t h e r a p y w i t h e x t r a o r a l tr a c t i o n . A l t h o u g h
t hi s c o n c e p t h a s b e e n p a r t o f t h e c o n v e n t i o n a l
w i s d o m o f m a n y o r t h o d o n t i c p r a c t it i o n e r s a n d
h a s b e e n m e n t i o n e d i n a r t i c l e s d e a l i n g w i t h t h e
Tw eed phi l oso phy , a41,142 l i t t le dat a h as be en pre-
s e n t e d p r e v i o u s l y t o s u p p o r t o r r e f u t e t h i s c o n -
c e p t . T h e d a t a f r o m t h e p r e s e n t s t u d y i n d i c a t e
i n c r e a s e d m a n d i b u l a r g r o w t h i n t h e f a c e b o w
s a m p l e i n c o m p a r i s o n w i t h c o n t r o l v a l u e s . P r e -
s u m a b l y t h e d i s r u p t i o n o f t h e o c c l u s i o n d u r i n g
f a c e b o w u s e m a y h a v e t h e e f f e c t o f a l t e r in g t h e
a n t e r o p o s t e r i o r p o s i t i o n o f t h e m a n d i b l e d u r i n g
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~,t- .i,. a >> Ho me I TO C
la ss H M ixed Den t i t ion Trea tmen t
133
treatment, perhaps in a manner similar to that
pro duc ed by rapid maxillary expansion, 26 particu-
larly in that the inner bow of the facebow
typically is widened during treatment. Alteration
of intercuspation du ring the cor rectio n of the
molar relationship with the facebow may lead to
a slight transient posturing forward of the man-
dible, which may result in a modest increase in
mandibular length.
Summary and onclusions
This article has examined the diagnosis and
treatment of Class II malocclusion from several
perspectives. Initially, the frequency of occur-
rence of various co mpone nts of Class II prob-
lems was examined by reanalyzing the cephalo-
metric data from a large number (N = 277) of
individuals in the mixed dentition. Mandibular
skeletal retrusion and increased vertical dimen-
sion were the most freque nt problems observed,
alth ough there was wide variation in the distribu-
tion of the com ponen ts within the sample popu-
lation. Transverse maxillary constr iction also was
shown to be a frequent compo nent , also indicat-
ing that Class II malocclusion cannot be treated
as a single diagnostic entity.
The se cond part of the article examined the
literature c oncer ning two of the most commo nly
used generic treatments for Class II malocclu-
sion, extraoral traction and functional jaw ortho-
pedics. Variations among the particular appli-
ances (eg, high-pull v cervical-pull facebow,
Herbs t ap pliance v FR-2 appliance of Fr/inkel)
and treatme nt effects were evaluated in an effort
to review what is known a bout these two types of
orthodontic and orthopedic interventions.
The third part of the article presented the
results o f a retrospective clinical study that c om-
pared directly the tr eatment effects pro duce d by
the cervical-pull facebow (in combination with
partial fixed appliances) and the function regula-
tor (FR-2) appli ance of Fr/inkel to an unt rea ted
sample of subjects with Class II malocclusion.
Patients treated with the FR appliance showed
increased increments of mandibul ar length and
lower anterior facial height in comparison with
untreated controls. The chin point moved slightly
forward in the FR group in comparison with
controls. Little effect was noted in maxillary
skeletal and dentoalveolar structures.
Facebow/fixed appliance t reatment pr oduced
different effects. The most profound changes
were evident in maxillary structures (eg, restric-
tion of the forward movement of the maxilla,
distal movement of the maxillary molars and
incisors) in comparison with controls. A modest
increase in mandibul ar length also was note d in
the facebow group, although the chin point
moved slightly backward in the facebow group
relative to controls.
The results of this retrospective study indicate
that the effects produce d by these two treatment
protocols indeed are different. Therefore, the
conscientious clinician should undert ake a thor-
ough evaluation of the Class II patient in all
three dimensions and subsequently tailor the
orthodontic and orthopedic protocols to address
the nee ds of the given patient.
As with all short-term (eg, 2-year) clinical
studies, and especially those that are retrospec-
tive in nature, no global conclusions can be
reached regarding the ultimate effects of the two
treatments considered in this study on the growth
of the craniofacial complex. For example, al-
thou gh this study indicated that maxillary growth
is inhibited significantly with cervical facebow
treatment, the pres ent study was in the mixed
denti tion of children. In essence, the study was
of a movin g target, in that the craniofacial
complex of these children still was growing.
Other studies have shown that mandibular growth
is increased above normal after treatment in the
mixed denti tion. Thus, long- term studies of treat-
ment effects produced by various orthodontic
and ort hopedi c appliances are indicated.
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