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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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Ar J~ e >> Hom e I TOC

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and Class II, division 2 (Angle) malocclusion. Angle

Orthod 1954;24:106-119.

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