Cambios en Dimensión Transversal.expansión Maxilar

8/17/2019 Cambios en Dimensión Transversal.expansión Maxilar

1/8

D e n t a l a n d S k e l e t a l 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

L e sl i e A W i l l a n d Z a n e E M u h l

M a n y m e t h o d s a r e a v a il a b l e f o r a c h ie v i n g m a x i l la r y e x p a n s i o n . D e n t a l

e x p a n s i o n c a n b e a c c o m p l i s h e d u s i n g a v a r i e t y o f a p p l i a n c e s d e p e n d i n g o n

t h e a m o u n t o f e x p a n s i o n d e s i r e d a n d t h e a g e o f t h e p a t i e n t . S i g n if i c a n t

s k e l e ta l e x p a n s i o n m a y b e a c h i e v e d w i t h a f i x e d j a c k s c r e w e x p a n d e r , t h o u g h

t h e a m o u n t o f s k e l e ta l e x p a n s i o n a n d t h e s t a b i l i ty o f s u ch e x p a n s i o n i s

v a r i a b l e . N o s k e l e t a l e x p a n s i o n s h o u l d b e e x p e c t e d i n a p a t i e n t w h o h a s

r e a c h e d s k e l e t a l m a t u r i t y . S e m i n O r t h o d 2 0 0 0 ; 6 :5 0 - 5 7 .) C o p y r i g h t © 2 0 0 0 b y

W B S a u n d e r s C o m p a n y

A w i d e v a r ie t y o f m o d a l i t i e s f o r o r t h o d o n t i c

t r e a t m e n t i n t h e t ra n s v e r s e d i m e n s i o n h a v e

b e e n r e p o r t e d i n t h e l i t e r a t u r e . T h e s e a p p l i -

a n c e s i n c lu d e b a n d e d , b o n d e d , a n d r e m o v a b l e

a p p l i a n c e s , a s w e l l as a p p l i a n c e s n o t t y p ic a l ly

u s e d f o r e x p a n s i o n , s u c h a s h e a d g e a r a n d f u n c -

t i o n a l a p p l i a n c e s . P a t i e n t s f r o m 4 y e a r s o f a g e

i n t o t h e i r f i f th d e c a d e o f l i fe a r e r e p o r t e d a s

b e i n g e f fe c t iv e l y t r e a t e d . W h e n e v a l u a t in g t h e

e f f i c a c y o f a g i v e n a p p l i a n c e , i t i s u s e f u l t o

c o n s i d e r t h e f o l l o w i n g a s p e ct s : H o w m u c h d e n t a l

e x p a n s i o n i s a c h i e v e d w i t h th i s a p p l i a n c e ? I s

s k e le t a l e x p a n s i o n d e s i r e d , a n d h o w m u c h s k el -

e t a l e x p a n s i o n i s a c h i e v e d r e l a t i v e t o d e n t a l

e x p a n s i o n ? H o w s t a bl e a re b o t h t h e d e n t a l a n d

s k e l et a l e x p a n s i o n o b t a i n e d ? D o e s u n w a n t e d

d e n t a l t i p p i n g o c c u r c o n c o m i t a n t w i th e x p a n -

s i o n? A t w h a t a g e s i s t h e a p p l i a n c e e f f e c ti v e ?

T r e a t m e n t o d a l i t i e s

M a n y s t u d ie s h a v e b e e n c a r r i e d o u t t o e v a lu a t e

t h e p e r f o r m a n c e o f a p p l ia n c e s in e x p a n d i n g t h e

m a x i l l a r y d e n t a l a r c h a n d / o r t h e m a x i l la . I t is

o f t e n d i f fi c ul t t o c o m p a r e a p p l i a n c e s , b e c a u s e

c o m p a r a b l e m e a s u r e m e n t s o f t e n d o n o t e x i s t .

F~vm the Department of Growth and Development, Harvard

School of Dental M edicine, Boston, MA, and the Department of

Orthodontics, University of IUinois College of Dentistr); Chicago, IL.

Address correspondence to Dr. Zane E Muh l, UIC College of

Dentistry, Department of Orthodontics MC 841, 801 S. Paulina

St.~vet, Chicago, IL 606 12.

Copyright © 200 0 by W.B. Saunders Company

1073-8746/00/0601-0006510. 00/0

M o s t o ft e n m e a s u r e m e n t s w e r e t a k e n f r o m d e n -

t a l c as t s, b u t i n a f e w i n s t a n c e s , f r o n t a 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 w e r e a v a i l a b l e . F o r t h e p u r -

p o s e s o f t h i s r ev i ew , t h o s e s t u d i e s t h a t i n c l u d e a

l o n g - t e r m f o l l o w - u p a r e o f p a r t i c u l a r i n t e r e s t ,

b e c a u s e s t a b i l it y o f t h e e x p a n d e d a r c h i s a

p r i m a r y c o n c e r n .

Jackscrew ppliances

T w o g e n e r a l t y pe s o f j a c k s c r e w a p p l i a n c e s a r e

m o s t o f t e n u s e d t o e x p a n d t h e m a x i ll a . In

p a t i e n t s i n w h o m g r o w t h h a s n o t c e a s e d , s k e l e t a l

e x p a n s i o n is a c h i e v e d a l o n g w i t h d e n t a l e x p a n -

s i on . T o o t h - b o r n e , o r H y r a x , a p p l i a n c e s a r e f i x e d

t o th e t e e t h o n l y , e i t h e r b y o r t h o d o n t i c b a n d s , o r ,

i n t h e s t u d i es r e p o r t e d , b y b o n d a b l e a c r y li c p a d s

t h a t c o v e r t h e o c c l u s a l s u r f a c e s o f t h e b u c c a l

s e g m e n t s a n d e x t e n d o v e r t h e b u c c a l a n d l i n g u a l

s u r f a c e s o f t h e t e e t h . T i s s u e - b o r n e a p p l i a n c e s ,

p a r t i c u l a r l y th e H a a s - t y p e a p p l i a n c e , i n c l u d e a n

a c r y l i c b u t t o n , m o l d e d t o th e p a l a t e , i n w h i c h

t h e j a c k s c r e w is e m b e d d e d a n d t o w h i c h t h e

b a n d s a r e a t t a c h e d . P r o p o n e n t s o f th e t i ss ue -

b o r n e a p p l i a n c e c l a im t h a t g r e a t e r s k e le t a l e x p a n -

s i o n is a c h i e v e d w i t h t h e H a a s - t y p e a p p l i a n c e

t h a n t h e t o o t h - b o r n e e x p a n d e r , b e c a u s e f o r c e i s

t r a n s m i t t e d m o r e d i r e c t l y t o t h e p a l a t a l s h e l v e s .

T h e f i x e d j a c k s c r e w a p p l i a n c e c a n p r o d u c e a

s i g n if i c an t m o l a r e x p a n s i o n , w i t h r e p o r t e d

a m o u n t s r a n g i n g f r o m a m e a n o f 4 .6 9 m m 1 t o 7 .9

m m . 9 S k e le t a l e x p a n s i o n r a n g e d f r o m 4 6 3 t o

5 8 4 o f d e n t a l e x p a n s i o n , t h o u g h m a n y st u d ie s

d i d n o t m e a s u r e t h i s , a n d t h e s e a u t h o r s e v a l u -

a t e d t h is o n d e n t a l c a s ts . A s s e s s i n g s k e l e t a l e x p a n -

5 0 Semina rs in Orlhodonlics, Vol 6 , No 1 March), 2 000: pp 50-5 7


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MaxiUary Expans ion 51

s i o n f r o m d e n t a l c a st s is p r o b l e m a t i c , b e c a u s e

e v e n if t h e a p p r o p r i a t e l a n d m a r k s a r e r e g i s t e r e d

o n t h e c a s t s, t h e o v e r l y i n g s o f t t i s su e o b s c u r e s t h e

u n d e r l y i n g b o n y s t r u c t u r e s , a n d i s n e c e s s a r il y

i n c l u d e d i n t h e m e a s u r e m e n t . N o n e o f t h e

s t u d ie s e m p l o y i n g a f i x e d j a c k s c r e w a p p l i a n c e

m e a s u r e d s k e l e ta l e x p a n s i o n d i r e c t l y f r o m f r o n -

t al r a d i o g r a p h s , e v e n t h o u g h t h is a p p l i a n c e t h e o -

r e t ic a l ly s h o u l d b e t h e m o s t e f f e c ti v e fo r p r o d u c -

i n g s k e l e t al a s w e l l a s d e n t a l c h a n g e . A s u m m a r y

o f d e n t a l a n d s k e l e ta l e x p a n s i o n a n d r e l a p s e

r e p o r t e d f o r t h e t w o t y pe s o f f ix e d j a c k s c r e w

a p p l i a n c e s i s s h o w n i n T a b l e 1 .

A s i g n i f i c a n t si d e e f f e c t o f m a x i l l a r y o r t h o p e -

d i c e x p a n s i o n h a s b e e n d o w n w a r d d i s p l a c e m e n t

o f t h e m a x i l la . T h i s i s c a u s e d b y t i p p i n g o f t h e

p o s t e r i o r t e e t h a s t h e t w o h a l v e s o f t h e m a x i l l a

s e p a r a t e . T h is b i t e o p e n i n g c a n b e f a v o r a b l e

w h e n t h e p a t i e n t h a s a C l a ss I I s k e l e t a l p a t t e r n ,

b u t i s m o r e f r e q u e n t l y u n d e s i r a b l e b e c a u s e C l a s s

I I p a t t e r n s p r e d o m i n a t e . I t h a s b e e n h y p o t h -

e s iz e d t h a t b o n d e d j a c k s c re w a p p l i a n c e s p r e v e n t

t h i s b i t e o p e n i n g f o r t w o r e a s o n s . F i r s t , it i s a

m o r e r i g i d a p p l i a n c e a n d i s t h o u g h t t o p r e v e n t

d e n t a l t i p p i n g . I n a d d i t i o n , i t s t h i c k n e s s i n t r u d e s

o n t h e f re e w a y s p a c e , t u r n i n g t h e e x p a n d e r i n t o

a f u n c t i o n a l a p p l i a n c e . A s t h e p a t i e n t b i t e s o n

t h e o c c l u s a l a c r y li c , m u s c l e f o r c e s w i ll p r e v e n t

t h e m a x i l l a f r o m b e i n g i n f e r i o r l y d i s p l a c e d .

S a r v e r a n d J o h n s o n 17 e v a l u a t e d t h e s k e l e ta l

c h a n g e s t h a t o c c u r r e d i n 20 a d o l e s c e n t s d u r i n g

r a p i d p a l a t a l e x p a n s i o n w i t h a b o n d e d H y r a x

a p p l i a n c e . T h e y c o m p a r e d t h e s e c h an g e s w i th

t h o s e r e p o r t e d b y W e r t z, 8 w h o u s e d s i m i l a r

m e a s u r e m e n t s t o e v a l u a t e s k e l e ta l c h a n g e s w i t h

a b a n d e d j a c k s c r e w a p p l i a n c e . S a r v e r a n d

J o h n s o n 17 f o u n d t h a t v e r t ic a l d i s p l a c e m e n t o f

t h e m a x i l l a , a s m e a s u r e d b y t h e d i s t a n c e b e t w e e n

t h e S N p l a n e a n d P N S , w a s s i g n i f ic a n t l y l e ss in

t h o s e p a t i e n t s w h o h a d t h e b o n d e d a p p l i a n c e .

O t h e r i n d i c a t i o n s o f v er t i c al c h a n g e , s u c h a s t h e

m a n d i b u l a r p l a n e a n g l e a n d t h e d i s t a n ce f ro m

S N t o A N S , w e r e n o t s i g n i f i c a n t l y d i f f e r e n t .

H o w e v e r , t h e y c o n c l u d e d t h a t th e d o w n w a r d a n d

a n t e r i o r d i s p l a c e m e n t o f t h e m a x i l l a m a y b e

m i n i m i z e d o r n e g a t e d w i th t h e u s e o f t h e b o n d e d

a p p l i a n c e . 17

A s a n z a e t a l 7 a l s o c o m p a r e d t h e e f f e c t o f a

b o n d e d H y r a x a p p l i a n c e w i th t h a t o f a b a n d e d

H y r a x , s t u d y i n g 1 4 a d o l e s c e n t s . T h e y f o u n d t h a t

t h e b o n d e d g r o u p d i s p l a y e d l es s i n c r e a s e i n t h e

t o t a l f a c ia l h e i g h t a s m e a s u r e d b e t w e e n A N S a n d

m e n t o n , a s w e l l as l e ss i n f e r i o r m a x i l l a r y d i s p l a c e -

m e n t a t p o s t e r i o r n a s a l s p i n e . I t a p p e a r s t h a t t h e

b o n d e d a p p l i a n c e d o e s t e n d t o m i n i m i z e i nf e -

r i o r m o v e m e n t o f t h e m a x i l l a , b u t r e s u l ts a r e n o t

u n i v e r s a l l y s i g n i f i c a n t .

T h e r e d o n o t s e e m t o b e a n y c o n s i s t e n t tr e n d s

i n e i t h e r s t ab i l it y o r i n t h e p r o p o r t i o n o f sk e l e ta l

e x p a n s i o n a m o n g t h e s t u d ie s r e p o r t e d . T h i s i s

p r o b a b l y t h e r e s u l t o f a l a r g e n u m b e r o f v a r i a b le s

b e t w e e n t h e s t u d i e s, s u c h a s r e t e n t i o n p r e -

a b l e 1 . E x p a n s i o n a n d S t a bi li t y o f F i x e d J a c k s c r e w A p p l i a n c e s

Author Sample Size

Expansion ram) Relapse mm)

Den tal Skeletal Denta l Skeletal

Tooth -borne app l iances

Sandikqio~lu and Hazar5 10 6.2 2.7 0.8 0.1

Akkaya et al6 12 9.05 NO 0.22 NO

Asanza et al7 7 6 .01 (banded) NO NO NO

7 5 .94 (bonded)

Berge r et al 24 4.7 3.6 0.3 0.69

L inder -Aaronsen and L indgren ~ ? 7.9 NO 4.34 NO

Unspec i f ied type o f f ixed app l iances

Wertz 8 56 6.5 2.58 1.88 0.56

Battagel and Ryan9 ? 4.0 NO 1.0 NO

Tissue-borne appliances

Chang et al ° 25 4.8 NO 0.2 NO

Ladner and Muhl 3 30 6 .0 3 .0 NO NO

S/irnas et a111 1 7.2 2.1 6.0 0.8

Spillane and McNam ara lz ? 6 .0 NO 1.2 NO

Moussa et a113 55 6.9 NO 1.2 NO

H a n d e l m a n

T

5 6.3 NO 0.64 NO

da Silva Filh o et a115 32 5.5 2.8 NO NO

Kreb s 16 23 6.0 2.3 0 0.5

Abbreviation: NO, not observe d.


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5 9 W i ll a n d M u h l

scribed and worn, expansion protocol, timing of

records relative to expansion, and length of

follow-up. Thus, it is impossible based on this

review to accurately compare tissue-borne and

tooth-borne appliances with regard to stability or

efficacy in pro duc ing skeletal expansion. In gen-

eral, skeletal expansion seems to be approxi-

mately 30% to 50% of the amount of dental

expansion, although the figure reported by

Berger et aP is significantly higher.

No study has reported on the a mou nt of arch

length or peri meter gained in palatal expansion.

However, Nimka rn et al is com par ed several meth-

ods of evaluating the amount of arch width

needed to alleviate crowding in the maxillary

arch (Pont's index, Schwarz' analysis, and McNa-

mara's molar width). They found that Schwarz'

analysis came closest to predicting the actual

amou nt of required arch expansion. Pont' s in-

dex and McNamara's width overestimated the

amou nt of needed arch expansion 2.5 mm to 4.7

mm and 2.7 mm to 3.7 Inln, respectively. Accord-

ing to N imka rn et al) s McNa mara gives a single

value for the ideal mola r width in males (37.4

mm) and females (36.2 mm), whereas the two

indices involve a calculation that requires mea-

surement of the sum of the incisor widths.

Nimk arn et aP s also pointe d o ut t hat it makes a

difference where the expansion takes place (mo-

lars v premolars ) as to how muc h expans ion will

suffice, but they caution that in their study, a

large am oun t of variation in arch crowding was

not explained by arch width.

R e m o v a b l e x p a n d e r s

Several investigators used removabl e jackscrew

appliances to ex pand the maxilla, goys en 19 placed

in 17 children, aged 6 years 4 mont hs to 10 years

9 months (with a mean of 8 years 6 months), an

appliance with acrylic covering the posterior

maxillary occlusal surfaces to disarticulate the

occlusion. The screw was activated twice per

week for a total weekly expansion of 0.5 ram.

Basal expansion with this appliance was found to

be less than that resulting from the quad-helix.

Sandlk£1o~lu an d Hazar 5 incl uded a tre atme nt

group of 10 children with removable appliances

in their study repo rted above. The mola r expan-

sion with this appliance was 4.0 ram, and the

skeletal expansion was 1.5 mm. No relapse was

measure d. Brin et al 2° fou nd dental expans ion of

3.3 mm and skeletal expa nsion of 6.0 mm, which

is very unusual. No amounts of relapse were

reported.

N o n s c r e w x p a n d e r s

Another type of appliance widely used for maxil-

lary expansion is the palatal arch (Table 2).

Made of .036- or .038-inch wire, it is attached to

the palatal aspect of the first molar bands, and is

activated by expansion before cementation. Lat-

eral forces delivered by the wires against the

teeth serve to expand the dental arch. The

quad-helix incorporates four helices in the pala-

tal arch, and is used primarily for younger

children for dental expansion.

It is note worth y tha t Boysen et a119 fou nd

more basal expansion with the quad-helix than

with a removable jackscrew applia nce. However,

it is not known how much dental expansion was

attemp ted, because e ach type of applianc e was

activated merely until the crossbite, and ac compa-

nying lateral shifts were cor rected . It should also

be n ote d that Adkins et al z2 rep ort ed that buccal

teeth tipped an average o f 7.3 ° as the mea n

expan sion of 6.5 mm was achieved.

Most of the patients who received tre atment

with the quad-helix appliance were in the decidu-

ous or mixed dentition, and no ne were older, on

average, than approximately 12 years. Although

several studies did report skeletal change, either

sutural openi ng or increase d maxillary width on

post eroan terio r (PA) radiographs, there was little

in th e way of postt reat ment follow-up, so it is not

possible to determine how much of the skeletal

expansion produced by this appliance is main-

tained in the long term.

The transpalatal arch is also used for dental

expa nsio n. Inger vall et a124 used this appli ance to

Table 2. Expansion and Stability of Palatal Arches

A u ~ o r

Sample Expansion mm) Relapse mm)

Size D ental Skeletal De ntal Skeletal

Bell and Le

Compte2l

Adkins et a122

Boysen et a119

Sandikcioglu

and Hazar5

Haberson and

Myers23:

W arch

10 5.7 yes 30%-40% ?

? 6.5 yes ? ?

yes

17 5.6 (ratio) ? ?

10 5.3 1.9 1.1 0.4

11 yes yes ? ?


4/8

Maxillary Expansion 53

correct unilateral crossbites in 35 children from

6 years, 8 months to 15 years, 11 months. With 20

children, buccal root torque was added to the

molar not in crossbite, and both molars were

expan ded equally. Crossbite correc tion oc curred

in both groups a mea n of 91 days after insertion

of the appliance. The gro up that had one molar

with buccal root torque demonstrated more

sutural opening, although both values were less

than 1 mm, and the torque d molar did not move

significantly.

Thus, it seems clear that although palatal

arches can open the maxillary suture, sutural

expansion is minimal, and palatal arches are best

used for dental expansion in children with pri-

mary or mixed dentition.

Slow Expansion

An alternative to traditional rapid palatal expan-

sion, slow expansion uses lower, ortho ped ic forces

and takes months instead of weeks to accomplish

the same amoun t of expansion. Its propo nents

consider that with lower forces, there is less

sutural trauma and less dental tipping. A Minne

expander (Ormco Corporation, Glendora, CA)

is usually used for slow expansion, although a

traditional jackscrew applia nce c an also be used

and t urned less frequently. The M inne ex pand er

consists of a spring-lo aded jackscrew a ttach ed to

four orth odont ic bands. The jackscrew is turned

to compress the spring, which slowly expands

while delivering continuous force. Lower force

levels are possible bec ause the jackscrew c an be

activated in small increments.

Hicks 25 eval uated the stability of slow expa n-

sion in 5 subjects, aged 10 to 15 years. Dental

expansion ranged from 3.8 to 8.7 mm, with

skeletal expans ion compr ising 24 to 30 of

the dental expansion in the 10- to 11-years olds,

but only 16 in the 15-year-old. Mossaz-Joelson

and Mossaz z6 comp ared bon ded and band ed

Minne expanders and foun d no difference in the

amou nt of dental and skeletal expansion or

relapse. Skeletal expansion comprised about half

of the dental expansi on. Finally, Akkaya et al 6

compa red arch changes in a group with a bon ded

Hyrax appliance with those fro m a grou p using a

bonded Minne expander. Molar expansion was

not significantly different between the 2 groups,

with the slow-expansion group exhibiting 9.81

mm of expansion and 0.2 mm of relapse. No

skeletal changes were measured.

Functional ppliances

Several studies have reported that significant

dental expansion can be achieved with various

functional appliances, and in several instances,

significant skeletal expansion was achieved as

well (Table 3). Althou gh relapse dat a were incom-

plete at best, it appeared that dental relapse

could be significant, ran ging from 19 to 100 .

In fact, Ow en 3~ no te d that while t ransverse in-

creases gained with the Frankel appliance could

alleviate arch-length deficiencies, it could not

corr ect a crossbite.

BeGole et aP 2 report ed on the a mou nt of

molar expansion normally occurring during fixed

edgewise therapy. They found that in nonextrac-

tion cases, the maxillary molar width increased

by 2.96 mm, and in extraction therapy, the

molars narrowed by 0.22 mm. After treatment,

the nonextraction patients demonstrated 0.52

mm of relapse, while extraction patie nts showed

an additio nal exp ansi on of 0.67 mm. Kirjavainen

et aP a reporte d on expansion achieved with a

Kloehn-type cervical headgear. Dental expan-

sion ranging from 2.8 mm to 5.1 mm was

reported, but no skeletal expansion or anaounts

of relapse were reported.

Timing of Expansion

To discuss the optimal timing for maxillary

expansion, it is useful to review the transverse

growth of the maxilla and the face. Bj6rk and

Skieller 34 rep ort ed in 1974 on their study of nine

boys. Frontal cephalometric radiographs were

Table 3. Expansion and Stability of Functional

Appliances

Sample Expansion mm) Relapse mm)

Author Size Dental Skeletal Dental Skeletal

Ffratli and l]lgen27:

FR3 appliance ? 2.0 1.2 NO NO

Gibbs and Hunt2S:

Andresen

appliance ? 2.3 NO 0.9 NO

Bionator

appliance ? 1.9 NO 0.6 NO

Frankel appliance ? 3.6 NO 0.7 NO

Hime and OwenS9:

FR2 appliance ? 0.45 NO 0.45 NO

McDougal et a13°:

FR1 and FR2

appliance ? 3.9 4.4 NO NO

Owen31:

FR 1 and FR2

appliance ? 3.3 3.7 NO NO


5/8

5 Will and Muhl

t a k e n a n n u a l l y f r o m a g e 4 u p t o a g e 2 0 i n s o m e

o f t h e b o y s . M e t a l l i c i m p l a n t s w e r e p l a c e d i n t h e

i n f r a z y g o m a t i c c r e s ts , o n t h e p a l a t e o n e i t h e r

s id e o f t h e m i d p a l a t a l s u t u r e , a n d i n t h e a n t e r i o r

m a x i l l a . T h e s e s e r v e d a s r e g i s t r a t i o n p o i n t s f o r

s u p e r i m p o s i t i o n o f t h e f i lm s . B j o r k a n d S k i e l l e r s4

f o u n d t h a t t h e t r a n s v e r se g r o w t h o f t h e m a x i l l a

f o l l o w e d d i s t a n c e a n d v e l o c i t y c u r v e s s i m i l a r t o

t h o s e f o r b o d y h e i g h t , w i t h s im i l a r t im e s o f

g r o w t h s p u r t a n d g r o w t h c o m p l e t i o n . I n a d d i -

t i on , t h e y f o u n d t h a t w h i le p o s t e r i o r g r o w t h w a s

t h r e e t i m e s t h a t o f th e a n t e r i o r m a x i l la , t h e

d e n t a l a r c h w i d t h s h o w e d o n l y o n e q u a r t e r t h e

i n c r e a s e o f t h a t o f t h e b a s a l m a x i l l a . I n 1 9 9 0 ,

K o r n a n d B a u m r i n d 35 u s e d a s i m i l a r t e c h n i q u e

t o s t u d y t h e g r o w t h o f 31 c h i l d r e n f r o m 8 . 5 to

1 5. 5 y e a r s o f a g e . T h e y f o u n d a n a v e r a g e a n n u a l

r a t e o f t r a n s v e r s e g r o w t h o f 0. 4 3 - + 0 . 18 m m p e r

y e a r , a n d c o n f i r m e d t h a t p o s t e r i o r g r o w t h w a s

g r e a t e r t h a n a n t e r i o r g r o w t h .

I n t h e l a s t d e c a d e , s e v e r a l i n v e s t i g a t o r s h a v e

p u b l i s h e d n o r m s o f t ra n s v e rs e c r a n i o fa c i a l p a r a m -

e t e r s . E x a m i n e d t o g e t h e r , t h e y p r o v i d e s i gn i fi -

c a n t i n f o r m a t i o n a b o u t t r a n s v e r s e f a ci a l g r o w t h.

I n 1 9 92 , A t h a n a s i o u e t a136 p u b l i s h e d t h e n o r m s

h e o b t a i n e d i n a c r o s s - s e c t io n a l s t u d y o f 5 8 8

A u s t r i a n s c h o o l c h i l d r e n , a g e d 6 t o 1 5 y e a r s .

E i g h t l i n e a r d i s t a n c e s ( 6 s k e l e ta l , 2 d e n t a l ) , 1 0

r a t io s a m o n g t h e s e w i dt h s, a n d t w o a n g u l a r

m e a s u r e m e n t s f o r m e d h i s a n a l y s i s . B e c a u s e o f

c o n c l u s i o n s r e a c h e d i n a n e a r l i e r w o r k, A t h a n a -

s i o u e t a 136 d i d n o t s e p a r a t e h i s s a m p l e b y g e n d e r .

A l l l i n e a r m e a s u r e m e n t s s h o w e d p r o g r e s s i v e i n -

c r e a s e s , w i t h s e v e r a l w i d t h s ( i n n e r o r b i t a l , n a s a l

c a vi ty , m a x i l l a r y s k e l e t a l b a s e , m a n d i b u l a r i n t e r -

g o n i a l ) i n c r e a s i n g r e l a t i v e t o t h e i n t e r o r b i t a l

w i d t h , i n d i c a t i n g s o m e d i f f e r e n t i a t i o n i n t r a n s -

v e r s e g r o w t h a m o n g s t r uc t u r e s . F u r t h e r m o r e ,

t h e y n o t e d t h a t t h e m a x i l l a r y i n t e r m o l a r w i d t h

d i d n o t i n c r e a s e b e t w e e n 9 a n d 1 2 y e a r s o f a g e ,

a n d t h e m a n d i b u l a r i n t e r m o l a r w i d t h s h ow e d n o

s i g n if i c a nt c h a n g e o v e r th e e n t i r e c o u r s e o f

s t ud y . I t s h o u l d , h o w e v e r , b e n o t e d t h a t t h e

m a x i l l a r y b as a l w i d th s h o w e d a l a c k o f c h a n g e

b e t w e e n 1 1 a n d 1 3 y e a r s o f a g e , s i m i l a r to t h e

m a x i l l a r y m o l a r , a n d n o n e o f t h e g r o w t h c h a n g e s

p r e s e n t e d w e r e t e s t e d f o r s i gn i fi c a nc e . A t h a n a -

s i o u e t a136 r e s t a t e d t h e c o n c l u s i o n f i rs t m a d e b y

K r o g m a n t h a t t r a n s v e r s e j a w g r o w t h is a f fe c t e d

m i n i m a l l y b y a d o l e s c e n t g r o w t h c h a n g e s , a n d

t h e s m a l l , s t e a d y in c r e a s e s A t h a n a s i o u r e p o r t e d

s e e m t o b e a r t h is o u t . H o w e v e r , th e s u p e r i m p o s i -

t i o n o f 7 0 t o 9 0 i n d i v i d u a l g r o w t h c u r v e s f o r e a c h

y e a r o f a g e w il l t e n d t o f l a t t e n o u t a n y i n d i v i d u a l

g r o w t h p e a k s . I n a d d it i o n , l u m p i n g f e m a l e s a n d

m a l e s t o g e t h e r w o u l d f u r t h e r o b l i te r a t e a n y o v er -

a l l g r o w t h p e a k s . H o w e v e r , t h e i n c l u s i o n o f ra t i o s

i s a w e l c o m e i n n o v a t i o n g i v e n t h e s e n s i t iv i ty o f

c e p h a l o m e t r i c n o r m s t o i n di v i du a l v a ri a t io n a n d

t e c h n i q u e - r e l a t e d p r o b l e m s s u c h a s m a g n if i c a -

t i o n a n d h e a d p o s i ti o n .

S n o d e l l e t a 13 7 s e p a r a t e d t h e i r s a m p l e b y

g e n d e r i n t h e i r l o n g i t u d i n a l s t u d y p u b l i s h e d i n

1 9 93 . T w e n t y -f i v e m a l e s a n d 2 5 f e m a l e s f r o m t h e

U n i v e r si t y o f C o l o r a d o g r o w t h s a m p l e w e r e i n-

c l u d e d i n t h e s t ud y , w i t h a n n u a l f i lm s s t a r t i n g a t

a g e 4 a n d e n d i n g a t a ge 2 0 fo r f e m a l e s a n d 9 5 f o r

m a l e s . A l l s u b j e c t s h a d C l a s s I s k e l e ta l a n d d e n t a l

p a t t e r n s . S n o d e l l e t a l ~7 u s e d f i v e s k e l e t a l a n d

f o u r d e n ta l t r a n s ve r s e m e a s u r e m e n t s , a n d a d d e d

f iv e v e r ti c a l m e a s u r e m e n t s w i t h w h i c h t o c o m -

p a r e t h e m a g n i t u d e o f g r o w t h. A s o p p o s e d t o

A t h a n a s i o u e t a l , 36 g o n i o n r a t h e r t h a n a n t e g o -

n i al n o t c h w a s u s e d f o r t h e l a n d m a r k f o r m a n -

d i b u l a r w i d t h , a n d c r a n i a l a n d b i z y g o m a t i c w i d t h s

w e r e i n c l u d e d i n s t e a d o f a n y o rb i t a l m e a s u r e -

m e n t s . S n o d e l l e t a l ~7 a l s o f o u n d a p r o g r e s s i v e

i n c r e a s e i n a ll p a r a m e t e r s , a l t h o u g h t h e i n -

c r e a s e s c a n n o t b e d i r e c tl y c o m p a r e d t o A t h a n a -

s i o u e t a l ' s 36 r e s u l t s a s a r e s u l t o f t h e l a t t e r ' s l a c k

o f g e n d e r s e p a r a t i o n . S n o d e l l e t a 13 7 d i d f i n d

s i g n i f i c a n t g e n d e r d i f f e r e n c e s a t 6 y e a r s o f a g e

t h a t i n c r e a s e d a t 1 2 a n d 1 8 y e a r s. A t 6 y e a rs o f

a g e , o n l y c r a n i a l w i d t h , f a c i a l w i d t h , a n d m a x i l -

l a r y w i d t h w e r e s i g n i f i c a n t l y d i f f e r e n t b e t w e e n

m a l e s a n d f e m a l e s . A t 1 8 y e a r s o f a g e , o n l y

m a n d i b u l a r f i r s t - m o l a r w i d t h w a s n o t s i g n if i -

c a n t l y d i f f e r e n t . S n o d e l l ' s 37 s t u d y a l s o d e t e r -

m i n e d t h e p e r c e n t a g e o f a d u l t s iz e t h a t t h e

6 - ye a r- o ld m e a s u r e m e n t r e p r e s e n t e d , a n d e s t a b -

l i s h e d t h e a g e a t w h i c h g r o w t h w a s c o m p l e t e a n d

a d u l t s iz e w a s r e a c h e d . A t 6 y e a r s o f a g e , f e m a l e s

h a d r e a c h e d a h i g h e r p e r c e n t a g e o f a d u l t si ze

t h a n m a l e s f o r a l l p a r a m e t e r s , w i t h v a l u e s r a n g -

i n g f r o m 8 0 f o r a d u l t n a s a l w i d t h t o 1 0 3 f o r

a d u l t l o w e r s e c o n d - m o l a r w i d th . M a l e v a lu e s

r a n g e d f r o m 7 5 t o 1 0 9 f o r t h e s a m e m e a s u r e -

m e n t s b e i n g r e p r e s e n t e d a t t h e e x t r e m e s . I n

c o n t r a s t , o n l y 7 1 t o 8 4 o f t h e a d u l t v a l u e w a s

r e a c h e d f o r v e r t ic a l p a r a m e t e r s b y a g e 6 . O n c e

a g a in , f e m a l e s h a d r e a c h e d a h i g h e r p e r c e n t a g e

o f a d u l t v a lu e s t h a n m a l e s . F e m a l e s w e r e s i m i -

l a r ly q u i c k e r t o c o m p l e t e g r o w t h , w i t h al l g r o w t h

c e a s i n g b y a g e 1 7, w h i l e m a l e s s h o w e d c o n t i n u e d


6/8

MaxiUary xpansion 55

growth beyon d 18 years for all parameters except

maxillary width. Snodell et a137 rep ort ed declin-

ing rates of maxillary growth from 6 to 14 years

of age with acceleration at age 14 to 15 years,

although the annual rates were not reported.

This decrease in growth velocity is in ag ree men t

with Athan asio u et alY Snodell et aP 7 also

reported that increases in maxillary first-molar

width were highly correlated with maxillary

growth, which also confirmed Athanasiou et

al's a6 report .

Cortella et aP s evaluated 36 subjects from the

Bolton-Brush Growth Study in 1997, but limited

their analysis to the basal maxilla and mandible.

They used landmarks from Ricketts analysis that

were the same as in Ath ana sio u et a l's ~a study.

Longitudinal films were traced and measured,

although some subjects did not have a film for

each year between ages 5 and 18 years. These

examiners also adjusted for magnification. All

values from Cortello et al's ~s study were smaller

than those repo rte d by Athan asiou et al, ~6 even

without correction for magnification. The ratio

between maxillary and mandibular width was

similar and showed a gradual decrease. However,

the values from Cortella et al as were generally

greater. Intraexaminer error was 1.03 mm.

This lack of agr eem ent between two sets of

published norms highlights the technical difficul-

ties in establishing firm norms, and reinforces

the advisability of using ratios rathe r than abso-

lute linear measurements.

Studies regarding the growth and maturation

of the intermaxillary suture are ano ther source

of informatio n relating to the optimal time to

expand the maxilla. These studies by necessity

nmst be histological examinations on normal

sutures, and samples are thus difficult to obtain.

In two stud ies p ub li shed in the 1970s, Melsen ~9,4°

used autopsy material to histologically examine

the matura tion o f the midpalatal suture. The

sample fo r the first study incl uded 33 boys and 27

girls, aged 0 to 18 years of age, who had died

without prior illness. Microradiog raphy en-

able d t he local izatio n o f growth activity. Melsen ~9

divided sutural maturation into three stages

based on its morphology. In the infantile stage,

the suture was broad and s mooth, but by approxi-

mately 10 years of age had deve loped into a more

typical squamous suture with overlapping sec-

tions. Mels en 39 called this stage the 'j uv en il e

stage. Finally, the ado les cent phase was seen at

ages 13 to 14 years, where the suture was more

wavy with increasing interdigitation. These inter-

digitations could not be separated without frac-

turing them. Melsen's categories were extended

in a 1982 study, 4° whic h eval uated the suture s

from 30 individuals, aged newborn to 27 years.

The suture in the oldest individuals was classified

as adult , tho ugh no specific ages were given to

distinguish this category. Adult sutures demon-

strated numero us bony bridge formations across

the suture, and nume rous synostoses were noted.

In ano the r study, Persson and Thil and er 4~

quantified suture closure by evaluating the de-

gree of obliterat ion in the suture. The sample for

this study was a grou p o f 14 males and 10 females

who had died suddenly. The earliest closure seen

in any portion of the suture was in a 15-year-old

female, bu t no closure was seen in 4 of the 7

individuals less than 20 years of age. One 27-year-

old female had no sutural obliteration. Althoug h

a marked degree of closure is rarely found until

the third decade, sutural obliteration progresses

rapidly during that time. The authors c onclud ed

that midpalatal suture closure is highly variable.

From these studies, it is suggested that pa-

tients who have passed their pubertal growth

spurt may have difficulty in undergoing tradi-

tional orthopedic maxillary expansion. The in-

creased interdigitation o f the suture may require

excessive force to separate. However, the litera-

ture is not conclusive on this topic, and factors

other than age and sutural fusion are important

in the ability to orthopedically expand the max-

illa.

onc lu s ion

Many treatment modalities are available for

achieving expansion. Significant skeletal expan-

sion may be achieved with a fixed jackscrew

expander, thoug h the a moun t of skeletal expan-

sion achieved and the stability of such ex pansi on

is variable. Dental expansion can be achieved

using a variety of appliances depending on the

amo unt of expansion desired an d the age of the

patient. No skeletal expansion should be ex-

pected in a patient who has reached skeletal

maturity.

References

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