a comparison of one-stage and two-stage non extraction alternatives in matched class ii samples

8/3/2019 A Comparison of One-stage and Two-stage Non Extraction Alternatives in Matched Class II Samples

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O R I G IN A L A R T I C L E SA com parison of one-stagenonext rac t ion a l t e rnat i vesClass II samples

and two-s tagein matchedFedon A . L iv ie ra tos , D D S , MS and Lys le E . Johns ton , J r . , D D S , P hD "Athens, Greece, and An n Arbor, Mich.I n t he t rea tmen t o f C lass I I ma locc lus ion , an ea r l y phase o f f unc t iona l app l i ance t rea tm en t i sc o m m o n l y u s e d t o s im p l i fy s u b s e q u e n t f i xe d a p p l i a n c e t h e r a p y a n d t o o p t im i z e t h e d e v e l o p m e n t o fthe fac ia l ske le ton . Unfor tunate ly , thes e expe cta t ions en jo y li tt le su ppo r t in the re fereed l ite rature .The p resen t s tudy the re fo re was unde r taken to exam ine the bene f i t s o f a two -s tageb iona to r /edgew ise reg imen i n compar i son to t he more conven t i ona l one -s tage edgew ise a l t e rna t i ve .To m in im ize p ro f i c iency b ias , we ex am ined the reco rds o f t he one - and two -s tage C lass IInonex t rac t i on pa t i en ts who rece i ved t rea tmen t be tween 1980 and 1990 by a s i ng le expe r i encedc l in ic ian . On the ba s is o f desc r ip t ive data f rom 96 sets o f i n i t i a l s tudy mode ls and l a te ra lcepha log rams , d i sc r im inan t ana l ys i s was used to i den t i f y two subsamp les o f 36 pa t i en ts who we rere la t ive ly s im i la r be fo re t r ea tme n t and thus e qua l l y suscep t i b le t o t he two t rea tmen ts . O f these 72"bo rd e r l i ne " pa ti en ts, 19 subse quen t l y unde rwen t a change i n t r ea tmen t p lan ( t o ex t rac t ion o rsu rge ry ) , leav ing 25 two -s tage and 28 s ing le -s tage n onex t rac t i on pa t i en ts on whom to base acom par iso n o f t rea tm ent e f fec ts . Ex cep t fo r a s l igh t post t reatm ent d i f fe rence in age (and, hence,s ize ), t he two g roups unde rw en t ske le tal chang es tha t l e ft t hem essen t i a l ly i nd i s t i ngu i shab le a t t heend o f t r ea tmen t . I n bo th g roups , t hese ske le ta l chang es w e re l a rge l y respons ib le f o r mo la r andover je t cor rec t ion s that we re near ly identica l in the two grou ps. Th e ra tes o f chang e, how ever ,d i ffe red s ign if icant ly . As a resu l t, the two-s tage t rea tme nts s tar ted ear l ie r and f in ished la ter .A l t hough the p rese n t da ta do no t add ress the re la t ive impac t o f the two s t ra teg ies on the 10% to15% a t each ta il o f the d i s t r i bu ti on , t he ea r l y phase o f f unc ti ona l app l i ance t rea tm en t con fe r red noobv ious , measu rab le bene f i t s on the cen t ra l 75%. The re fo re fo r mos t nonex t rac t i on C lass I I pa t i en ts ,t he cho i ce o f t r ea tmen ts may we l l cons t i tu te a p rac t i ce m anagem en t , r a the r t han a b io log i c ,dec i s i on . (AM J ORTHO D DENTOFACORTHOP 1995; 108:118-31 .)

T h r o u g h o u t t h e h is to r y o f t h e sp e ci al ty ,o r t h o d o n t i s t s h av e t u rn ed t i m e an d ag a i n t o g ro w t hm o d i f i ca t i o n a s a ro u t i n e t r ea t m en t fo r s k e l e t a lC l a s s I I m a l o cc l u s io n . A s n o t ed b y S . K l o eh n , zch i l d r en w ere o f t en t r ea t ed " . . . f o r six o r e i g h ty ea r s u n d e r t h e i m p res s i o n t h a t w e w ere s t i m u l a t-i n g g ro w t h o f t h e m an d i b l e an d f ac ia l b o n e s . " I tw as n o t u n t i l t h e ad v en t o f t h e cep h a l o m e t r i ct ech n i q u e t h a t t h e i n n o cen t , o p t i m i s t ic a s s u m p t i o n so f t h e b o n e -g ro w i n g e r a co u l d b e t e s ted . U n fo r t u -n a te l y, t h e ea r l y s t u d i e s fo s t e r ed a n u m b er o f p e r -s i s t en t and in f luen t ia l misconcept ions .B a s e d i n p a r t o n a t h e s i s s u b m i t t e d i n p a r t i a l f u l fi l l m e n t o f t h e d e g r e e o fm a s t e r o f s c i e n c e , D e p a r t m e n t o f O r t h o d o n t i c s a n d P e d i a t r i c D e n t i s t r y ,T h e U n i v e r s i t y o f M i c h i g a n . D r . L i v i e r a t o s w a s t h e r e c i p i e n t o f t h e 1 9 9 4M i l o H e l l m a n A w a r d o f t h e A m e r i c a n A s s o c i a t i o n o f O r t h o d o n t is t s .S u p p o r t e d b y N I D R g r a n t D E 0 8 7 1 6 a n d b y d o n a t i o n s fr o m t h e U n i v e r -s i ty o f M i c h i g a n O r t h o d o n t i c A l u m n i A s s o c i a t io n a n d f r o m o t h e r f r ie n d so f t h e d e p a r t m e n t .a R o b e r t W . B r o w n e P r o f e s so r o f D e n t i s t ry a n d C h a i r m a n , D e p a r t m e n t o fO r t h o d o n t i c s a n d P e d i a t r i c D e n t is t r y .C o p y r i g h t 1 9 9 5 b y t h e A m e r i c a n A s s o c i a t i o n o f O r t h o d o n t i s t s .0889-5406/95/$3.00 + 0 8/1/576031 1 8

Fo r ex am p l e , in t h e a s s e s s m en t o f t o o t h m o v e-m en t , t h e u s e o f c r an i a l b as e s u p e r i m p o s i t i o n 2 l edt o t h e en d u r i n g n o t i o n t h a t u p p e r m o l a r s can n o t b emo ved d i s ta l ly . Simi lar ly , b y tak ing l inear g rowth asa s ign of i somet ry3 (p ro p o r t i o n s r em a i n co n s t an tonly i f t h e r eg re s s i o n l in e p as s es t h ro u g h t h e o r i gi nof the p lo t4 ; fo r mos t fac ia l d im ens ions , i t do esn o tS), B ro d i e co n c l u d ed t h a t t h e p a t t e rn o f g ro w t hi s u n ch an g in g an d i m m u t ab l e . 6 In co n j u n c t i o n w i t ht h e p o p u l a r a s s u m p t i o n t h a t g ro w t h i s u n d e r t i g h tg en e t i c co n t ro l ( t h e s o -ca ll ed "g en e t i c p a rad ig m "7 ) ,B ro d i e ' s ce p h a l o m e t r i c s t u d i e s e f f ec t iv e l y u n d e rc u tthe b io log ic ra t ionale fo r ear ly , g rowth modi f ica t iont r ea t m en t . Pe rh ap s a s a r e s u l t , A m er i can o r t h o d o n -t i s t s tu rned to ser ia l ex t rac t ion and sophis t i ca ted ,f i xed ap p l i an ce t r ea t m e n t s d es i g n ed t o m as k , r a t h e rt h an co r r ec t , s k e l e t a l d i s h a rm o n i es i n ad o l e s cen t san d y o u n g ad u l t s .A l t h o u g h A m er i can o r t h o d o n t i s t s p r ac t i cedw i t h g rea t s u cces s w i th i n t h es e t ech n i ca ll y d em an d -ing, albei t art i f icial l imits , their European col-l eag u es ex p l o red a v a r i e t y o f g ro w t h m o d i f i ca t i o n


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American Journal o f Orthodontics and Dentofacial Orthopedics L iv i e ra to s a n d Jo h n s to n 1 1 9Volume 108 , No. 2

a l te r n a ti v e s d e s c e n d e d f r o m t h e m e t h o d o f A n -d r e s e n a n d H f i u p l 8 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 s . "O v e r t h e p a s t 2 0 y e a r s o r s o, h o w e v e r, m a n y A m e r i -c a n o r t h o d o n t i s t s , f a c e d b y a p e r s i s t e n t " b u s y n e s s "p r o b l e m a n d b e s e t b y m o u n t i n g p r e s s u r e s fr o mp a r e n t s a n d r e f e r r i n g d e n t i s t s t o " d o s o m e t h i n g "( p r e f e r a b l y e a rl y , o f t e n , a n d w i t h o u t p r e m o l a r e x -t r a c ti o n ) , h a v e t u r n e d o n c e a g a i n t o s k e l e ta l m o d -i f ic a t io n a s a r o u t i n e t r e a t m e n t f o r C l as s I I m a l o c -c l u si o n . A l t h o u g h m a n y c l in i c ia n s a p p a r e n t l y s e ee a r l y f u n c t i o n a l a p p l i a n c e t r e a t m e n t a s a p r a c t i c a ln e c e s s it y , t h e y a l s o a r g u e t h a t i t w i l l s e r v e t op r o d u c e o p t i m a l f a c i a l e s t h e t i c s a n d , i n a d d i t i o n ,s o m e h o w r e d u c e b o t h t h e n e e d f o r e x t ra c t io n a n dt h e l e n g t h a n d c o m p l e x i t y o f th e s u b s e q u e n t f i x eda p p l i a n c e t r e a t m e n t . U n f o r t u n a t e l y , t h e r e i s l i tt lei n t h e w a y o f o b j e c t i v e s u p p o r t f o r t h e s e s u p p o s e da d v a n t a g e s ( s e e J o h n s t o n 9 ) , a n d , t o c o m p o u n d t h ep r o b l e m , m a n y w o r k e r s s e e r a n d o m i z e d c l i n ic a lt ri a ls a s t h e o n l y va l i d s o u r c e o f c o m p a r a t i v e d a t a .

A s h a s b e e n d i s c u s s e d e l s e w h e r e , 1-12 m a n yt y p e s o f o r t h o d o n t i c c l i n ic a l t ri a l s w o u l d b e f a t a l l yc o m p r o m i s e d b y a v a r i e t y o f e th i c a l a n d p r a c t i c a lp r o b l e m s ( t i m e , c o s t , s a m p l e a t t r i t i o n , i n f o r m e dc o n s e n t ) . R e t r o s p e c t i v e s t u d i e s, i n c o n t ra s t , a r eq u i c k , c o s t e f f e c t iv e , a n d e t h i c a l l y u n a m b i g u o u s . I nt h e a b s e n c e o f c a r e fu l p l a n n i n g , h o w e v e r , t h e i rr e s u l ts a l s o t e n d t o b e b i as r i d d e n a n d u n i n t e r p r e t -a b l e . F o r t u n a t e l y , i t i s p o s s i b l e t o c o n t r o l , o r a tl e a s t m i n i m i z e , m a n y o f t h e s e b i a s e s . A c c o r d i n g l y , i tw i ll b e t h e p u r p o s e o f th i s i n v e st i g a t io n t o c o n d u c ta r e la t i v e ly b i a s - fr e e r e t r o s p e c t i v e c o m p a r i s o n o fs i n g l e - s t a g e e d g e w i s e a n d t w o - s t a g e b i o n a t o r / e d g e -w i s e t r e a t m e n t s .P A T IE N T S A N D M E T H O D S

The pa t ien t s w hose r ecor ds ( la te r a l cepha logr amsand s tudy mode ls ) w er e ana lyzed in th i s inves t iga t ionw e r e t r e a t e d b y a n e x p e r i e n c e d o r t h o d o n t i s t w h o g a v e u sf ree access to his f i les . We sought growing white pat ients(7 to 14 years) , who had bi lateral Class I I , Divis ion I (atl eas t a ha l f s tep) malocc lus ions and w ho had beent r ea ted be tw e en 1980 and 1990. For a ll sub jec ts , thec l in ic ian ' s in i t ia l in ten t ion ( as judged by the t r ea tme ntp lan) w as nonext r ac t ion the r apy , e i the r in one s tage( edgew ise ) o r in tw o s tage ( f unc t iona l /edgew ise ) . N oother inc lus ion f i l t e r s ( e . g . , ou tcome or "cooper a t ion" )w er e used .T h e f u n c ti o n a l p h a s e o f t r e a t m e n t w a s c a r r i ed o u t b ym e a n s o f t h e b i o n a to r , a n a p p l i an c e t h a t M c N a m a r a a n dBr ud on 13 have ca l led " per h aps the mo s t w ide ly usedf unc t iona l appl iance in the w or ld today . " I n the ve r s ionused her e ( an appl iance s imi la r to the Ca l i f or n ia b io-na tor ' 3 ) , the ac r y l ic oppos ing the occ lusa l and l ingua l

s u r fa c e s o f t h e m a n d i b u l a r m o l a r s is t ri m m e d t o p e r m i tf r ee e r upt ion and m es ia l migr a t ion . Conversely , e r up t ionf ace t s and occ lusa l s tops cont r o l the e r upt ion of themaxi l la ry mola r s and pr ev ent the i r mes ia l migr a t ion . Themaxi l la ry inc i sor s a r e cons t r a ined by an inc i sa l she l f tha tpe r mi t s r e t r ac t ion by the lab ia l bow . The f ixed appl iancet r e a t m e n t s w e r e e f f e c t e d w it h a n o n t o r q u e d , n o n a n g u -lated, 0.022- inch edgewise appliance in general adher-e n c e t o t h e p r i n ci p l es c o m m o n l y r e f e r r e d t o a s " T w e e dmech anics" - anchor age pr epar a t io n , d i r ec t iona l ex t r a -oral t ract ion, and Class I I e las t ics .I n the end , a to ta l o f 96 pa t ien t s , 49 tw o- s tage and 47one- s tage , met the va r ious inc lus ion c r i t e r ia and thusf o r m e d t h e " p a r e n t " s a m p l e . B e c a u s e t h e s e p a t i e n t sw er e t r ea ted by a single or thodont i s t w ho do cum ented a llo u t c o m e s ( n o t j u s t t h e b e s t ) a n d b e c a u s e w e a c c o u n t e df or a l l 96 pa t ien t s ( no t jus t those f or w hom the or ig ina lt r ea tment p lan pr oved adequa te ) , our des ign se r ved tominimize p r o f i c i e n ~ d e t e c t i o n , an d t rans fer bias . Mor esignificantly, however , i f dif ferences in ou tcom e are to beseen as someth ing mor e than a r e f lec t ion of the in i t i a ld i f f e r ences tha t may have pr ompted the or ig ina l a s s ign-m e n t o f t r e a tm e n t s , i t i s n e c es s a ry t o c o m p a r e o u t c o m e sin gr oups of pa t ien t s w ho w er e mor phologica l ly s imi la rb e f o r e t r e a t m e n t . B e c a u s e t r e a t m e n t p l a n s c o m m o n l yar e based on a mul t ip le inputs , the iden t i f i ca t ion of a"bor de r l ine , " equa l ly suscept ib le s t r a tum o f pa t ien t s i s amul t iva r ia te s ta t i s ti ca l p r oblem .

S tepw ise d i sc r iminant ana lys i s ( Subpr ogr amD I SCRI MI N A N T, S ta t i s t i ca l Package f or the Soc ia l Sc i -ences , vers ion 3.1, SPSS, Inc. , Chicago, I l l .) was used tochar ac te r ize the ana tomic bas i s o f the in i t i a l t r ea tmentdec is ion . O f the 56 pr e t r ea tment desc r ip t ive va r iab lestha t f ue led the d i sc r iminant ana lys i s , 41 w er e ob ta inedf r om the in i t i a l l a te r a l cepha logr ams tha t w er e d ig i t i zedw i th a t r anspar en t d ig i t i z ing pad ( Scr ip te l RD T- 1212,Scr ip te l Cor p . , Columbus , O hio) and a commer c ia lcepha lomet r ic pr ogr am ( D entof ac ia l P lanner , ve r s ion5 .32 , D entof ac ia l Sof tw ar e , Tor onto , Canada) 13 f r omthe in i t i a l s tudy mode ls ( photocopies magni f ied about20% to r educe the impac t o f d ig i t i za t ion e r r or ) , and 2( age and sex) f r om the examina t ion f or ms . The cepha lo-me tr ic analys is has be en descr ib ed elsewhere~-12; i ts keyf ea tur es a r e summar ized in Table I . The mode l ana lys i sf ea tur ed s tandar d measur es of a r ch w id th ( a t the ca -nines , second premolars , and f ir s t molars) , arch length( in two segm ents , 6-1-614), available sp ace ( in four seg-ments , 6-3-1-3-6) , arch depth, and lower anter ior i r regu-lar i ty. 14 O f thes e 56 de scr ipt ive var iables , a l in ear com -bina t ion of th r ee , age and l inea r m easur es of over je t andthe sever i ty of the Clas s I I mola r r e la t ionsh ip , p r oducedan highly s ignif icant (p < 0.01) discr imination betweenthe 49 tw o- s tage and the 47 one- s tage pa t ien t s .

I n s tandar d iza t ion f or m, the d i sc r iminant f unc t ionw as of the f or m, D z = 0.88 (age) - 0.64 (OJ) + 0.38( mola r r e la t ionsh ip) , w her e D z i s t h e " c o n f o u n d e r s u m -mar iz ing '15 d i sc r iminant s cor e ca lcu la ted f or each of the96 subjects . As ma y be seen in Fig. 1, ,4, the tw o-s tage


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120 Liv ier ato s an d Jo hn st on American Journal of Orthodontics and Dentofacial OrthopedicsAugust 1995T a b l e I . D e s c r i p t i ve c e p h a l om e t r i c an a l ys i s

MeasureMaxillary position

S N AA-Na ver t i ca lMaxillary sizeP N S - AMandibular position

SN BY-axisB-Na ver t i ca lPo-NaBPo-Na ver t i ca lS - A t

Mandibular sizeA r - G nC o - G n

Maxillary dentitionU 1 - S NU 1 - N AU I - N AP T V - U 6Mandibular dentition

L1-NBF M I AI M P AL1 -APoL I - N BMaxillomandibular relationship

A N Bl t o lW i t s ( F O P )oJ (FOP)O B ( F O P )M o l a r R e l

VerticalSN-PPS N - F O PF M AS - G oN - A N SA N S - M eN - M e

ProfileNasolab ia l ang leU p p e r Z a n g l eL l ip -E p lane

Description

Angle se l la -nas ion-AA poin t to nas ion ver t i ca l (perpend icu la r to FH th rough Na)Pos te r io r nasa l sp ine to A (mo re re l i ab le A-P tha n ANS)Angle se l la -nas ion-BA n g l e b e t w e en F H a n d S - G nB-poin t to Nas ion Ver t ica lPogon ion to nas ion-BPogon ion to nas t ion ver t i ca lSe l la to a r t i cu la r e - a c rude me asure o f condyla r pos i t ionAr t icu la re to gna th ionC o n d y l i o n t o G n a t h i o nAngle be twe en long ax is ] and se l la -nas ion l ineAng le be tween long ax is 1 - and nas ion -A l ineFac ia l su r face o f averaged 1_ to nas ion -A l inePte rygoid ver t i ca l to d i s ta l 6 , pa ra l le l to FO P (Ricke t t s )Ang le be tween long ax is 1 and nas ion-B l ineAngle be twee n Frankfor t l ine and long ax is 1Ang le be tween m andibu la r p lane (Do wns) and long ax is 1Inc i sa l edge of 1 to A-pogo nion l ineFac ia l su r face o f 1 to nas ion-B l ineA n g l e A - n a s i o n - BIn te r inc i sa l angula t ionA-po in t to B-po in t , pa ra l le l to func t ion occ lusa l p lane (FOP )Dis tance be tween inc i sa l edges o f 1 and 1 taken a long FOPDis tance be twee n inc i sa l edges o f 1 and I t ake n perp . to FO PDis tance be tween m es ia l con tac t p ts . 6 and 6 taken a long FOPA n g l e b e t w e e n s e l la - n a s io n a n d A N S - P N S l i n e sA n g l e b e t w e e n s e l la - n a s io n a n d F O PA n g l e b e tw e e n F H a n d m a n d i b u l a r p l a n e ( t a n g e n t )D i s t a n c e b e t w e e n s e l la a n d g o n i o n - p o s t e r i o r f a c e h e i g h tD i s t a n c e b e t w e e n n a s i o n a n d A N S - u p p e r a n t e r i o r f a ce h e ig h tD i s t a n c e b e t w e e n A N S a n d m e n t o n - l o w e r a n t e r i o r f a c e h e i g htD i s t a n c e b e t w e e n n a s i o n a n d m e n t o n - t o t a l a n t e r i o r fa c e h e ig h t

A n g l e b e t w e e n c o l u m e l l a a n d u p p e r l ipAng le be twee n FH and tang en t to soft -t is sue ch in and upp er l ipDis tance be tween lower l ip and E-p lan e (nose-ch in tangen t )

p a t i e n t s t e n d t o h a v e n e g a t i v e d i s c r i m i n a n t s c or e s. I n o u rs i g n c o n v e n t i o n , a C l a s s I I m o l a r r e l a t i o n s h i p ( m e a s u r e da l o n g 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 f r o m m e s i a l 6_ t om e s i a l 6 ) w o u l d b e g i v e n a n e g a t i v e s i g n ; th e u s u a l C l a ssI I o v e r j e t , a p o s i t i v e s i g n . A s a r e s u l t , t h e t w o - s t a g ep a t i e n t s t e n d e d t o b e y o u n g e r a n d m o r e s e v e re l y a f -f e c t e d .

O n t h e b a s i s o f e a ch p a t i e n t ' s d i s c r i m i n a n t s co r e, t h ee x t r e m e 2 5 % ( p a t i e n t s w i t h s c o re s g r e a t e r t h a n - + 1 .3 )w e r e t h e n d i s c a r d e d ( F i g . 2 ) , l e a v i n g a c e n t r a l 7 5 % ( 3 6

o n e - s t a g e , 3 6 t w o - s t a g e ) t h a t w e r e s i m i l a r a t t h e o u t s e ta n d t h u s r e l a t i v e l y f r e e o f susceptibil i ty b i a s . E x a m i n a t i o no f t h e ir p o s t t r e a t m e n t r e c o r ds , h o w e v e r , r e v e a le d t h a t 1 9o f t h e s e 7 2 p a t i e n t s ( 8 o n e - s t a g e , 1 1 t w o - s t a g e ) s u b s e -q u e n t l y u n d e r w e n t a c h a n g e i n t r e a t m e n t p l a n , e it h e r t op r e m o l a r e x t r a c t i o n o r s u rg e r y . I n t h e e n d t h e r e f o r e t h es t u d y w a s b a s e d o n a n a n a l y si s o f d a t a f r o m t h e 2 5t w o - s t a g e a n d 2 8 o n e - s t a g e p a t i e n t s ( F i g . 1 , B ) f o r w h o mt h e o r i g i n a l t r e a t m e n t p l a n p r o v e d a d e q u a t e .T h e e x t e n t t o w h i c h t h e d i s c r i m i n a n t f u n c t i o n l e d to


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American Journal of Orthodontics and Dentofacial Orthopedics L iv i e ra to s a n d Jo h n s to n 121Volume 108, No. 2

S t a n d a r d i z e d D i s c ri m i n a n t S c o r e sA . P a r e n t S a m p l e sF r e q u e n c y1 6 ~

1441 2 4to - I

! I I , l J l ! l~ , ! . . . . . . ! ! ! ~ . . . . . . . . . .-5.0 -4.0 -3.0 -2.0 -1.0 0~.0 1.0 2.0 '3.0 4.0 5.0S t a n d a r d i z e d D i s c r i m i n a n t S c o r e

m T w o - S t a g e ( N , 4 9 ) ~ O n e - S t a g e ( N - 4 7 ) "B , B o r d e r l i n e S u b - S a m p l e sF r e q u e n c y1 6

14- I ~,1 2 -1 0

8-6 ~ I ~

20 i i l l l l i ] ] ] i ii I I I I I i ] l r l I 1~] , Io l~J ]l ] 11 ] J] I ] i i J ]l i ll-5.0 -4.0 -3.0 -2.0 -1.0 0. 1.0 2.0 3 .0 4.0 5.0

S t a n d a r d i z e d D i s c r i m i n a n t S c o r eT w o - S t a g e ( N , 2 5 ) ~ O n e - s t a g e ( N - 2 8 )

Fig. 1. Discriminant sco res. A, Parent samples. B, Borderlinesubsamples , pa t ien ts fo r whom nonextrac t ion therapy p roveda d e q u a te .Arrows denote g roup cen tro ids .

t he i den t i f i ca t i on o f s t ruc tu ra l ly comparab le samples( i.e ., subjects re la t ively f ree o f suscept ibi l ity bias) m ay bejudged f rom the supe r impos i t i on o f g roup ave rages*dep ic ted in Fig. 3 , A and th e d escr ipt ive sta ti s tics for thein i t i a l va lues o f t he va r ious cepha lome t r i c and s tudymode l va r i ab l e s summar i zed in Tab le I I . Even a f t e r t hesample had been t r immed, the single-stage pat ients weresti l l , on average, a year older and thus slightly larger.How ever , t he re was ve ry l i tt l e d i f f e rence in fo rm: I f t hetwo-s t age pa t i en t s a re en l a rged 3% (a shape p re se rv ingl inea r t r ansfo rma t ion whose magni tude was in fe r redf r o m t h e p r e t r e a t m e n t m e a n s ) , t h e t w o g r o u p s b e c o m ealmost iden t ica l (Fig. 3 , B) .P o s t t r e a t m e n t a n a l y s i s

To character ize the skele ta l , denta l , and sof t - t i ssuechanges t ha t occur red dur ing the one - o r two-s t age o ft r ea tment , p rogre ss ( end o f func t iona l phase fo r t he

* P r e p a r e d w i t h t h e a i d o f " A v e r a g e , " a c u s t o m i z a t i o n o f D e n t o f a c ia lP l a n n e r , v 4 . 2 2 , D e n t o f a c i a l S o f t w a r e , T o r o n t o , C a n a d a .

A : t : IJ

Fig, 2, In i t ial t r a c in g s -g ro u p a ve ra g es fo r e x t re me p a t ie n ts .A, U nadjusted. B, Two-stag e patients en large d 5%. Note thatex t reme b iona tor /edgew ise pa t ien ts, in add i t ion to be ingsmal le r a t ou tse t (A) , tended to p resent wi th more se vereskeletal d iscrepan cy (B), due in large mea sure to re lativelysmall man dible. In th is and al l sub seq uen t f igures, red = two-stage treatments; b lue = one -stage treatments.

ea rly, two-s t age t r ea tmen t s ) and a f t e r t r ea tment ( end o fedgewise t r ea tmen t i n bo th g roups) l a t e ra l cepha logramsand s tudy mode l s were sub jec t ed to t he same desc r ip t iveanalysis used to genera te the discr iminant funct ion. Inaddi t ion, de ta i led regional superimposi t ion, descr ibedelsewhere , a-12;16 was us ed to qu an tify th e so urc e o f themola r and ove r j e t co r rec t ions : t oo th movement ( i nc i so rand mola r movement r e l a t i ve t o basa l bone ) and ske l -e t a l change -maxi l l a ry (Max) and mandibu la r g rowth(Man d) r e l a t i ve t o c ran ia l ba se and the ne t e f fec t o f th i s


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1 2 2 Liv i er a to s an d Jo hn s to n Amer ican Journa l o f Or thodon ti cs and Den tofacia l Or thoped icsAugus t 1995

Tab le I I . B o r d e r l i n e s u b s a m p l e : D e s c r i p t i v e a n d i n f e r e n t i a l s t a t i s t i c s f o r s e l e c t e d p r e t r e a t m e n tc e p h a l o m e t r ic a n d d e m o g r a p h i c v a r i a b l e s

2-s tage (n = 25)M e a s u r e 5' DE ~ = ~ ) M e a n S D

1-s tage (n = 28)M e a n S D

Maxil lary pos i t ionS N A 1 . 0 8 2 .4 3 . 8 8 2 . 4 2 . 8 0 . 0 4A - N A v e r t i c a l 1 . 1 - 0 . 6 3 . 9 - 0 . 7 2 . 9 0 . 0 3

Maxillary sizeP N S - A 0 . 8 5 1 . 4 2 . 5 5 1 . 8 2 . 6 - 0 . 6 4

M a n d i b u l a r p o s i t io nSN B 0 . 8 7 6 . 0 3 . 2 7 7 . 1 2 . 3 - 1 . 3 1Y - A x i s 1 . 4 5 6 . 1 2 . 2 5 5 . 7 2 . 3 0 . 6 1B - N a v e r t i c a l 1 . 4 - 1 1 . 2 5 . 3 - 9 . 7 3 . 9 - 1 . 1 7Po - N a B 0 . 5 1 . 5 1 . 5 1 . 7 1 . 7 - 0 . 5 0P o - N a v e r t i c a l 1 . 7 - 1 1 . 5 6 . 5 - 9 . 5 4 . 7 - 1 . 2 8S - A R 0 . 8 3 4 . 7 3 . 0 3 4 . 8 3 . 0 - 0 . 2 1

M a n d i b u l a r s i zeA r - G n 0 . 6 1 0 3 . 2 4 . 9 1 0 5 . 9 4 . 9 - 2 . 0 2 *C o - G n 0 . 9 1 1 0 . 5 4 . 7 1 1 3 . 8 4 . 9 - 2 . 4 8 *

Maxil lary dent i t ionU 1 - S N 1 . 7 1 0 4 . 4 8 . 1 1 0 6 . 0 6 . 6 0 . 8 0U 1 - N A 1 . 8 2 1 . 9 8 . 0 2 3 . 6 6 . 9 - 0 . 8 1U 1 - N A 0 . 9 3 . 2 2 . 7 3 . 8 2 . 6 0 . 8 7P T V - U 6 1 . 3 1 2 . 7 3 . 0 14 . 7 3 . 6 - 2 . 1 6 "

Mandibu lar den t i t i onL 1 - N B 1 . 4 2 6 . 0 6 . 4 2 4 . 5 6 . 5 0 . 8 6F M I A 1 . 7 6 0 . 6 6 . 3 6 2 . 6 7 . 0 - 1 . 1 0I M P A 1 . 8 9 7 . 0 6 . 1 9 6 . 1 7 . 0 0 . 5 2L 1 - A P o 0 . 6 - 0 . 6 1 .8 - 0 . 9 2 . 3 - 0 . 3 4L 1 - N B 0 . 6 4 . 3 1 . 9 3 . 8 2 . 2 0 . 8 4Max i l lomandibu lar r e la t ions hipA N B 0 . 6 6 . 4 1 . 8 5 . 4 1 . 9 2 . 0 3 *1 t o 1 1 . 9 1 2 5 . 6 9 . 6 1 2 6 . 6 9 . 3 - 0 . 3 6W i t s ( F O P ) 1 . 0 3 . 9 2 . 2 2 . 5 2 . 1 2 . 2 8 *O J ( F O P ) 0 . 8 8 . 1 2 . 0 7 . 8 2 . 0 0 . 5 7O B ( F O P ) 0 . 7 4 . 4 2 . 5 4 . 1 2 . 3 0 . 5 5M o l a r R e l 0 . 4 - 1 . 8 1 . 3 - 1 . 4 1 . 1 - 1 . 1 8

VerticalS N - P P 1 . 2 7 . 9 2 . 6 7 . 6 2 . 7 0 . 3 8S N - F O P 1 . 3 1 8 . 3 3 . 5 1 7 . 7 3 . 3 0 . 6 8F M A 1 . 1 2 2 . 4 3 . 6 2 1 . 3 4 . 4 0 . 9 8S- G o 2 . 4 6 9 . 0 5 . 3 7 1 . 8 5 . 4 - 1 . 9 2N - A N S 1 . 2 5 1 . 4 2 . 5 5 2 . 4 3 . 5 - 1 . 0 8A N S - M e 2 . 2 6 3 . 8 5 . 3 6 4 . 3 6 . 1 - 0 . 2 7N - M e 2 . 4 1 1 2 . 7 5 . 8 1 1 4 . 4 5 . 7 - 1 . 11

ProfileN a s o l a b i a l a n g l e 2 . 2 1 1 9 . 9 8 . 4 11 7 . 6 7 . 6 1 . 0 4U p p e r Z a n g l e 1 . 3 7 0 . 0 4 . 2 7 1 . 9 4 . 7 - 1 . 6 0L l i p - E p l a n e 0 . 5 0 . 3 2 . 1 - 0 . 3 2 . 7 0 . 9 2

A g e - 1 0 . 4 1 . 05 1 1 . 4 1 . 3 - 3 . 1 1 " ** p < 0 . 0 5 ; * * p < 0 . 0 1 .

g r o w t h , a p i c a l b a s e c h a n g e ( A B C H ) . E a c h m e a s u r e m e n tw a s e x e c u t e d p a r a l le l t o th e m e a n f u n c t i o n a l o c c l u s a lp l a n e ( F O P ; p r e t r e a t m e n t / p o s t t r e a t m e n t a v e r a g e ) a n dw a s g i v e n a s ig n a p p r o p r i a t e t o i ts i m p a c t , p o s i t i v e , if i th e l p e d t o c o r r e c t t h e m o l a r r e l a t i o n s h i p o r r e d u c e t h e

o v e r j e t ( a s w o u l d b e t h e c a s e , s ay , w i t h m e s i a l m o v e m e n to f t h e l o w e r m o l a r s a n d i n c i s o r s ) , a n d n e g a t i v e , i f i t m a d et h e m w o r s e ( e . g ., 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 o r m e s i a lm o v e m e n t o f t h e u p p e r d e n t i t io n ) . G i v e n th i s c o n v e n -t io n , t h e a l g e b r a ic s u m o f th e a n t e r o p o s t e r i o r s k e l e ta l


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American Journa l o f Orthodon tics and Den tofac ia l Orthoped ics L iv ie ra to s a n d Jo h ns to n 1 2 3Volume 108,No. 2

j j I ~A +

\

JF ig . 3 . In i t i a l t rac ings-border l ine group averages. A, Unad-justed. B, Two -stage pat ients enlarg ed 3% to comp ensa te forresidual mea n age-d i f ferenc of 1 year.

a n d d e n t a l e f f e c t s m u s t e q u a l t h e c h a n g e i n m o l a rr e l a t i onsh i p and ove r j e t ( F i g . 4) . Accor d i ng l y , t h i s ac -c o u n t i n g s u p p o r t s a b e t w e e n - t r e a t m e n t o r b e t w e e n -p h a s e c o m p a r i s o n , n o t o n l y o f t h e m a g n i t u d e o f th e s et wo cor r ec t i ons , bu t a l so o f t he i r sour ce ( i .e ., ske l e t a l o rden t a l ) . Beca use o f t he t echn i ca l d i f f i cu lt y o f th i s pa r t o ft he cepha l omet r i c ana l ys i s , a l l t r ac i ng , supe r i mpos i t i on ,a n d m e a s u r e m e n t w e r e d o n e b y h a n d ; n o d i g i t iz a t io n w a su s e d .Error study

W i t h t h e a i d o f a t a b le o f r a n d o m n u m b e r s , n i n e s e tso f r e c o r d s ( fiv e o n e - s t a g e a n d f o u r t w o - s t a g e ) w e r es e l e c t e d a n d r e a n a l y z e d . T h i s p r o c e s s P r O d u c e d 2 2

CB

M a n ds k e l e t a l c h a n g e = A B C H = M a x M a n dFig. 4 . Scheme of reg ional sup er imp osi t ion-p i tchfork d ia-gram. Algeb raic sum of skeletal cha nge s (measured relative toCB, anterior cranial ba se registered at SEpoint) and m olar andincisor movement relat ive to basal bone equals molar (6/6)and overjet (1 /1) corrections. Note also that total uppe r andlower molar crown-movements (displacement of mesial con-tact points of 6 an d 6) are deco mp ose d into b odi ly (root-apex)and t ipp ing components, where t ipp ing = to ta l - bod il y.dou bl e de t e r m i na t i ons f o r t he desc r i p t i ve ana lyses and1 3 f o r t h e v a r io u s m e a s u r e m e n t s o f c h a n g e i n f e r r e d f r o mr e g i o n a l s u p e r i m p o s i t io n s . D a h l b e r g ' s f o r m u l a , S D E =~ DDZ /2N, wh er e D i s t he d i f f e r ence be t w een dou b l ed e t e r m i n a t i o n s , w a s t h e n u s e d t o c a l c u l a t e t h e e r r o rs t a n d a r d d e v i a ti o n s f o r e a c h v a r i a b l e J 7

S t a t i s t i c a l a n a l y s i sDescr i p t i ve s t a t i s t i c s ( means and s t anda r d dev i a -

t i o n s ) w e r e c a l c u l a t e d f o r a l l m e a s u r e m e n t s . B e t w e e n -means d i f f e r ences f o r i n i t i a l and f i na l f ac i a l f o r m, t r ea t -m e n t c h a n g e , a n d d i f f e r e n c e s b e t w e e n c h a n g e s d u r i n gt h e f i rs t a n d s e c o n d p h a s e s o f t h e t w o - s t a g e t re a t m e n t sw e r e a n a l y z e d b y m e a n s o f c o m p l e t e l y r a n d o m i z e dt t e s t s . M ul t i p l e con t r a s t s can l ead t o i n f l a t ed T ype Ie r r o r r a t e s a n d t h u s m u s t b e i n t e r p r e t e d w i t h c a u t i o n . A swi l l be s een , however , r e l a t i ve l y f ew con t r a s t s p r oveds i gn i f i can t , and t hose t ha t d i d wer e no t w i de l y s ca t t e r ed ,bu t i ns t ead f e ll in t o a sma l l num ber o f eas il y i n t e r p r e t -ab l e ca t egor i e s .R E S U L T S

A l t h o u g h t h e d i s c r im i n a n t f u n c t i o n e m p l o y e do n l y t h r e e v a r i a b l e s , i t i d e n t if i e d t w o g r o u p s o fC l a ss I I p a t i e n ts w h o s e f a c e s w e r e m o r p h o l o g i c a l l ys i m i la r b e f o r e t r e a t m e n t ( T a b l e s I I a n d I I I ; F i g .3 , B ) . D e s p i t e h a v i n g b e e n s u b j e c t e d t o d i f fe r e n tr e g i m e n s , t h e t w o g r o u p s w e r e e s s e n t ia l l y i d e n ti c a l


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1 2 4 Liv i er a to s an d Jo hn s t on Amer ican Journa l o f Or thodont ics and Den to fac ial Or thoped icsAugus t 1995

A0 + I

B- - + u

Fig . 5 . Pos t trea tment t rac ing s-b ord er l in e g roup averages. A,Unad jus ted . B, One-s tage pa t ien ts en la rged 1% to com pen-sate for residual age dif ferences of 6 months.

A. . .. . . O ' I i

Fig . 6 . Pre trea tment t rac ing s-g rou p averages fo r one- andtwo-s tage patients los t to extraction or surgery. A, U nadjusted.B, Two-stage patients en large d 3% as in Fig. 3 to com pens atefor residual age-differential.

at the end of treatment (Tables IV and V; Fig.5, A). Indeed, although the two-stage patientsstarted a year earlier, they were on average 6.5months older (and thus a bit larger) at the end oftreatment. As may be seen in Fig. 5, B, after a 1%enlargement of the one-stage average (a transfor-mation whose size was inferred from the descrip-tive data of Table IV), the group tracings superim-pose almost exactly.Treatment effects inferred from regional super-imposition are summarized in Table VI. Becausethe two-stage treatments took, on average, a yearand a half longer, Table VII shows the varioustreatment effects expressed as yearly rates. With

respect to the molar and overjet corrections, thesingle phase edgewise treatment proved signifi-cantly more "efficient." Finally, as may be seen inTables VIII and IX, the functional phase of thetwo-stage treatments was responsible for the ma-jority of the molar correction; the remainder of thetreatment effects were approximately evenly di-vided between stages.DISCUSSIONExperimental designOn the basis of the discriminant function (andthe testimony of clinician who trea ted the patients),


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A m e r i c a n J o u rn a l o f O r t ho d o nt ic s a n d D e n to f ac i al O r th o p ed i cs L i v i e r a t o s a n d J o h n s t o n 125Volume 108, No. 2

T a b l e I I h B o r d e r l i n e s u b s a m p l e s : D e s c r i p t i v e a n d i n f e r e n t i a l s t a t i s t i c s f o r s e l e c t e d p r e t r e a t m e n ts t u d y - m o d e l m e a s u r e s

M e a s u r e S D E ~ = ~ )2 - s t a g e ( n = 2 5 )

M e a n S D1 - s t a g e ( n = 2 8 )

M e a n S DA r c h l e n g t h

M a x i l l a 0 . 5 7 3 . 0 4 . 9 7 4 . 2 4 . 8 - 0 . 8 9M a n d i b l e 0 . 3 6 1 . 5 5 . 3 6 3 . 5 4 . 3 - 1 . 41

A r c h d e p t hM a x i l l a 0 . 3 2 9 . 9 2 . 2 2 9 . 6 2 . 9 0 . 4 0M a n d i b l e 0 . 2 2 4 . 5 1 . 7 2 4 . 8 2 . 2 0 . 6 2

A v a i l a b l e s p a c eM a x i l l a 1 . 1 7 6 . 4 4 . 5 7 7 . 7 5 . 0 - 0 . 9 8M a n d i b l e 0 . 5 6 7 . 0 3 . 6 6 8 . 2 5 . 0 - 0 . 9 7

[ n t e r c a n i n e w i d t h ( 3 - 3 )M a x i l l a 0 . 5 2 9 . 4 1 . 9 3 0 . 5 3 . 1 - 1 . 5 0M a n d i b l e 0 . 2 2 4 . 7 1 .9 2 4 . 9 2 . 3 0 . 3 4

I n t e r p r e m o l a r w i d t h ( 5 - 5 )M a x i l l a 0 . 4 3 9 . 6 2 . 4 4 1 . 5 3 . 4 - 2 . 3 0 *M a n d i b l e 0 . 3 3 6 . 3 2 . 1 3 7 . 1 2 . 7 - 1 . 1 3

I n t e r m o l a r w i d t h ( 6 - 6 )M a x i l l a 0 . 4 4 5 . 0 2 . 1 4 6 . 7 3 . 6 - 2 . 1 2 "M a n d i b l e 0 . 4 4 1 . 6 2 . 0 4 2 . 6 3 . 3 - 1 . 2 2

I r r e g u l a r i t y i n d e xM a n d i b l e 0 . 6 5 . 7 4 . 3 4 . 8 1 . 8 1 . 0 0

"1o < 0.0 5.

i t m a y b e i n f e r re d t h a t t h e r e w a s a t e n d e n c y f o ry o u n g e r p a t i e n t s w i t h m o r e s e v e r e m a l o c c l u s i o n s tob e t r e a t e d i n t w o s t a g e s . I n p r a c t i c e , h o w e v e r , i t i sl i k el y t h a t t h e t r e a t m e n t d e c i s io n s w e r e n o t q u i t es o c l e a r c u t . P e r h a p s a s a re s u l t, t h e r e w a s e n o u g hn o i s e i n t h e s y s t e m t o p r o d u c e c o n s i d e r a b l e o v e r l a pb e t w e e n g r o u p s ( F i g . 1 ). G i v e n t h i s o v e r l a p , i t w a sp o s s i b l e t o d e l i n e a t e s a m p l e s t h a t w e r e s i m i l a r i nt e r m s o f p r e t r e a t m e n t f a c i a l f o r m ( F i g . 3 ) a n d t h u sr e l a t i v e l y f r e e o f c o n t a m i n a t i o n b y s u s c e p t i b i l i t yb ia s .

F u r t h e r m o r e , a l l t h e p a t i e n t s w h o m e t t h es t u d y ' s i n c l u s i o n c r i t e r i a w e r e a c c o u n t e d f o r . A ne x a m i n a t i o n o f t h o s e l o s t to e x t r a c t i o n o r s u r g e r yr e v e a l s n o o b v i o u s m o r p h o l o g i c d i f f e r e n c e s t h a tw o u l d s e r v e to b i a s t h e o u t c o m e ( F i g . 6 ). I t m u s t b ee m p h a s i z e d , h o w e v e r, t h a t n o n e x t r a c t i o n t r e a t m e n tp r o v e d i n a d e q u a t e i n f u l ly a q u a r t e r o f t h e b o r d e r -l i n e s u b s a m p l e s . T h e p r e s e n t r e s u l t s c o m e , t h e r e -f o r e , f r o m t h e m o s t s u c c e s s f u l t h r e e q u a r t e r s o f as l ig h t ly t r i m m e d s a m p l e a n d t h u s p r o b a b l y r e p r e -s e n t s o m e t h i n g o f a n o v e r s t a t e m e n t o f t h e " m a n -a g e m e n t " p o t e n t i a l o f b o t h f o r m s o f n o n e x t ra c t i o nt r e a t m e n t .

F i n a ll y , a l l o u r p a t i e n t s w e r e t r e a t e d b y a s i n g lee x p e r i e n c e d c l i n ic i a n , p r e s u m a b l y w i t h a c o m m o nd e g r e e o f s k il l a n d d i l ig e n c e , b o t h i n e x e c u t i n g t h et r e a t m e n t a n d i n d o c u m e n t i n g it s o u t c o m e . W e

m u s t e m p h a s i z e , h o w e v e r , t h a t w e c a n n o t s p e c i f yt h e e x t e n t t o w h i c h t h i s c o m m o n l e v e l o f c l i n i c a lp r o f i c ie n c y a n d t h e s p e c if i c c l in i c a l m e t h o d s a n dg o a l s u s e d h e r e a r e c o m p a r a b l e t o t h o s e o f a n" a v e r a g e " p r a c t i t i o n e r f a c e d w i t h th e m a n a g e m e n to f a n " a v e r a g e " C l a s s II p a t i e n t . I n o t h e r w o r d s , w ed o n o t k n o w t h e e x t e n t t o w h i c h th e p r e s e n t r e s u l t sc a n b e g e n e r a l i z e d . A l l w e c a n s a y is t h a t o u rd e s i g n g e n e r a t e s b e t w e e n - t r e a t m e n t c o m p a r i s o n st h a t a r e r e l a t i v e ly b i a s f r e e a n d t h u s o f p o t e n t i a lc l i n i c a l i n t e r e s t t o t h e s p e c i a l t y .Treatment comparisons

A t t h e c o m p l e t io n o f t re a t m e n t , t h e t w o g r o u p sw e r e e s s e n t i a l ly i d e n ti c a l . U l t im a t e l y , t h e r e w a s n os i g n i f i c a n t c e p h a l o m e t r i c a n d s t u d y - m o d e l d i f f e r -e n c e s , a n d t h e t w o g r o u p s u n d e r w e n t a l m o s t i d e n -t i c a l m o l a r a n d o v e r j e t c o r r e c t i o n s . T o o t h m o v e -m e n t s e r v e d t o c o r re c t i r r eg u l a ri t y , b u t c o m m o n l yc o n t r i b u t e d l i t tl e , if a n y th i n g , to t h e i m p r o v e m e n to f a n t e r o p o s t e r i o r d e n t a l r e l a t i o n s h ip s . F o r b o t ht r e a t m e n t s , t h e s o u r c e o f t h e s e c h a n g e s w a s d i f fe r -e n t i a l j a w g r o w t h ( A B C H ) , t h e m a g n i t u d e o f w h i c hw a s s i g n if i c a nt l y g r e a t e r i n t h e t w o - s t a g e p a t i e n t s .T h i s f i n d i n g , h o w e v e r , i s m i s l e a d i n g , g i v e n t h a t t h et w o - st a g e t re a t m e n t s , o n a v e ra g e , to o k m o r e t h a n ay e a r a n d a h a l f l o n g e r to c o m p l e t e . C l e a rl y , o n e w a yt o s e e a l o t o f g r o w t h i s to t r e a t a l o n g t i m e . G i v e n


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126 Liv iera tos an d Jo hn sto n American Journal of Orthodontics and Dentofacial OrthopedicsAugust 1995T a b l e I V . B o r d e r l i n e s u b s a m p l e s : D e s c r i p t i v e a n d i n f e r e n t i a l s t a t i s t i c s f o r s e l e c t e d p o s t t r e a t m e n tc e p h a l o m e t r i c a n d d e m o g r a p h i c v a r i a b le s

Measure2-stage (n = 25)

M e a n S DMaxillary position

SNA 81.1A-Na Vertical - 2.3

Maxillary sizePNS-A 53.1

Mandibular positionSNB 77.3Y-axis 56.3B-NA vertical - 10.1Po-NaB 2.3Po-Na vertical - 9.3S-At 36.9

Mandibular sizeAr-Gn 114.3Co-Gn 121.4

Maxillary dentitionU1-SN 102.3U1-NA 21.2U1-NA 2.3PTV-U6 15.7

Mandibular dentitionL1-NB 28.5FMIA 59.8IMPA 98.2L1-APo 1.5L1-NB 5.0Maxillomandibular relationshipANB 3.81 to 1 126.6Wits (FOP) 1.9oJ (Fop) 3.0OB (FOP ) 2.1Molar relation 1.8

VerticalSN-PP 8.9SN-FOP 16.2FMA 22.0S-Go 77.1N-ANS 55.9ANS-Me 69.7N-Me 123.9

ProfileNasolabial angle 117.8Upper Z angle 76.9L l ip-E plane - 2 . 7

Age 14.5

1-stage (n = 28)M e a n S D

4.4 80.6 2.7 0.494.8 -2 .6 3.0 0.36

3.0 52.5 2.4 0.80

3.7 77.4 2.3 -0 .1 22.1 55.7 3.6 0.786.5 -9 .7 4.2 -0. 261.5 2.5 2.0 -0 .3 57.6 -8 .7 5.3 -0. 343.7 35.9 3.1 1.11

7.0 112.3 5.2 1.177.3 119.7 5.2 1.02

5.6 104.5 4.9 -1 .5 26.6 23.9 5.0 -1 .7 02.6 3.0 1.8 -1 .1 53.8 15.1 3.7 0.64

5.2 27.2 5.7 0.866.0 60.9 6.9 -0 .6 05.7 97.6 6.9 0.351.7 1.8 1.6 -0 .6 32.0 4.8 2.1 0.261.8 3.2 1.9 1.197.8 125.8 5.6 0.431.9 1.0 1.8 1.770.8 2.9 0.9 0.621.1 1.7 1.1 1.171.3 2.3 1.3 -1 .5 5

3.2 8.5 2.5 0.494.0 16.3 3.3 - 0.024.0 21.5 5.8 0.326.7 76.0 6.1 0.623.3 55.2 3.7 0.826.7 67.8 6.8 1.067.6 121.3 7.4 1.22

9.4 115.8 8.1 0.814.4 77.6 5.7 - 0.492.5 - 2.7 2.3 - 0.081.5 14.0 1.1 1.50

t h e m a r k e d d i f f e r e n c e i n t r e a t m e n t t i m e , it w o u l ds e e m a p p r o p r i a t e t o e x a m i n e t h e e f fi c i e n c y o f t h et w o s t r a t e g i e s b y a n a l y z i n g t r e a t m e n t c h a n g e e x -p r e s s e d o n a p e r - y e a r b a s i s .

A s m a y b e s e e n i n T a b l e V I I , th e y e a r ly r a te s o fc h a n g e f o r s k e l e t a l i m p r o v e m e n t ( A B C H ) , m o l a rc o r r e c t i o n , a n d o v e r j e t r e d u c t i o n f a v o r s i n g l e - p h a s ee d g e w i s e . I n d e e d , e v e n w h e n t h e f u n c t i o n a l p h a s e


10/14

A m e r i c a n J o u rn a l o f O r t ho d o nt ic s a n d D e n to f ac ia l O r th o p ed i cs L i v i e r a t o s a n d J o h n s t o n 1 2 7Volume 108, No. 2

Tab l e V. Borderline sample: Descriptive and inferential statistics for selected posttreatmentstudy-model measures

M e a s u r e2 - s t a g e ( n = 2 5 )

M e a n S D1 - s t a g e ( n = 2 8 )

M e a n S DA r c h l e n g t h

Maxi lla 70.6 3.7 72.1 3.8 - 1.41Man dib le 60.1 3.4 60.8 3.3 - 0.76

A r c h d e p t hMaxi lla 27.4 1.8 27.8 1.7 - 0.77Man dib le 22.8 1.9 23.1 1.5 - 0.67

A v a i l a b l e s p a c eMaxi lla 75.4 3.9 76.8 4.1 - 1.23Man dib le 64.5 3.5 65.8 3.4 - 1.24

I n t e r c a n i n e w i d t h ( 3 - 3 )Maxil la 32.2 1.8 32.8 2.2 - 1.12Man dib le 24.9 1.3 25.1 1.8 - 0.26

I n t e r p r e m o l a r w i d t h ( 5 - 5 )Maxil la 42.7 2.0 44.0 3.0 - 1.65Man dib le 36.3 2.0 36.9 2.4 - 0.89

I n t e r m o l a r w i d t h ( 6 -6 )Maxilla 47.2 2.2 48.4 35 - 1.50Man dib le 41.9 2.1 42.7 2.8 - 1.06

I r r e g u l a r i t y i n d e xMan dib le 2.4 2.0 2.4 1.7 - 0.02

of the two-stage trea tme nt is compared with single-phase edgewise, the difference in mandibular ad-vancement relative to cranial base (2.9 and 2.4 mmper year, respectively) is not statistically significant.Both rates, however, are somewhat higher than the1.7 to 1.8 mm per year reported for untreatedcontrols, 18 a finding that agrees with earl ier claims9that both fixed and functional appliances may pro-duce a slightly elevated rate of mandibular ad-vancement. Our use of the word advancementrather than growth acknowledges the obvious factthat the present method of regional superimposi-tion cannot distinguish between mandibular growthand bodily functional shifts.

Examinat ion of the raw dat a for Co-Gn, a directmeasure of mandibular length, implies that duringthe functional-appliance phase there was a slightlygreater rate of mandibular growth (3.2 mm peryear; p < .05) than t hat seen during the one-stageedgewise treatments (2.3 mm per year). As hasbeen noted, however, this 0.9mm per year of extragrowth did not have a comparable differentialimpact on symphyseal advancement measured par-allel to the mean functional occlusal plane (0.5 mm,nonsignificant). McNamara and associates19 havereported similar findings: Increases in the rate ofmandibular growth of 1.2 and 1.8 mm per year in

two Frfinkel appliance samples resulted in a lesserrate of advancement of pogonion (relative to na-sion vertical, 0.7 and 1.3 mm per year, respectively).Of greater significance, however, is the question ofwhether the present two-stage treatment, as awhole, produces mandibular growth effects that gobeyond those seen during a single-phase edgewisetreatment.

Ultimately, there were no significant between-means differences in mandibular length (Co-Gn),both in terms of annua l rate (two-stage, 2.6 mm peryear; single-stage, 2.3 mm per year) and final size(Table IV). Further, the two groups did not differin terms of the overall rate of symphyseal advance-ment during treatment (Mand, Table VII). How-ever, Mand showed a significant between-stage dif-ference: 2.9 mm per year during the functionalphase and 1.6 mm per year during the fixed phase(Table IX). Thus, it can be hypothesized that thebionator phase produced a measurable anteriorfunctional shift and that condylar growth in thesecond phase (proceeding at a relatively constantrate) served gradually to re-establish condyle-fossarelationships without contributing to a comparableadvancement of the chin. In support of this inter-pretation, it should be noted that the rate ofincrease in mandibular length (Co-Gn) was 3.2 mm


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1 2 8 L iv ie ra to s a n d Jo hn st on American Journa l o f Orthodon tics and Den tofac ia l Orthoped icsAugust 1995

Tab le V l . Overall treatment change for the skeletal and dental components of the molar andoverjet corrections

M e a s u r e S D E ( n = 1 3 )2-s tage (n = 25) 1 -s tage (n = 28)

M e a n S D M e a n S D tS k e l e t o n

Maxill a (max) 0.7 -2 .4 1.7 - 1.4 1.1 -2. 53**Ma ndi ble (ma nd) 1.0 8.2 4.1 5.9 1.8 2.73**Apic al base chan ge (ABC H) 0.7 5.8 2.8 4.5 1.5 2.19"

D e n t i t i o nU6 relation to max

Bodi ly 0.6 - 1.2 1.7 - 0. 6 2.3 - 1.01Tip pin g 0.9 - 1.2 1.5 - 0.0 2.0 - 2.45*To ta l 0.3 - 2.4 1.9 - 0.7 1.8 - 3.45* *

L6 relation to mandBod ily 1.1 2.7 2.1 2.2 1.9 0.90Tip pin g 1.1 - 2.0 2.7 - 1.9 2.1 - 0.07To ta l 0.6 0.7 1.6 0.3 1.4 1.08U1 rel atio n to max 0.5 0.5 2.8 1.2 1.9 -1 .0 9

L1 rela tion to man d 0.6 - 1.3 2.2 -0 .9 1.8 -0 .8 1T o t a l c o r re c t i o n

Mo la r (616) 0.5 4.1 1.9 4.1 1.6 0.01Overje t (l ll ) 0.6 5.0 2.2 4.8 2.1 0.26

T r e a t m e n t t i m e - 49.5 16.7 30.9 9.5 5.06***/7 < 0.05; ** p < 0.01.

Tab l e VII. Trea tment efficiency (change per year) for the skeletal and dental components of the molar andoverjet corrections2 - s t a g e ( n = 2 8 )

M e a s u r e M e a n S DS k e l e t o n

Maxill a (max) - 0.5 0.3Mandibl e (mand) 2.0 0.7Apical base change (ABCH) 1.5 0.6

D e n t i t i o nU6 relation to max

Bodi ly - 0.3 0.4Tipp ing - 0.3 0.5Tota l - 0.6 0.4

L6 relation to mandBodily 0.7 0.6Tipp ing - 0.4 0.8Tota l 0.3 0.5

U1 relation to max 0.2 0.7L1 relation to mand -0. 3 0.6

T o t a l c o r re c t i o nMol ar (6[6) 1.2 0.8Overj et (1~) 1.4 1.0

I - s t a g e ( n = 2 5 )te a n S D

-0. 5 0.5 -0.1 92.4 0.8 -1 .9 31.9 0.8 -2. 29*

-0. 2 0.9 -0. 160.0 0.8 -1 .8 8

-0. 2 0.7 -2.30*

0.9 0.8 -1 .0 8-0 .9 0.9 1.870.0 0.5 1.560.5 0.9 -1 .2 3

-0 .4 0.8 0.70

1.8 0.9 - 2.54*2.0 0.9 - 2.23*

*p < 0.05.

per year in the functional phase and 2.6 mm peryear in the fixed phase; the difference was nonsig-nificant. Thus our data support Korkhaus' earlierexplanation of the mode of action of the activator

in correcting ClaSs II molar relationships.2 It alsomatches Wieslander's characterization of the rela-tionship between mandibular changes occurringduring21 and after Herbst-appliance therapy (see


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American Journal of Or thodont ics and Dentofacial Or thopedics Li vi er at os a nd Jo hn s t on 129Volume 108, No. 2

T a b l e V II I . T w o - s t a g e t r e a t m e n t : T r e a t m e n t c h a n g e b y s t a g e s f o r t h e s k e l e t a l a n d d e n t a l c o m p o n e n t s o ft h e m o l a r a n d o v e r j e t c o r r e c t i o n s ( n = 2 1 )

M e a s u r eFirs t s tage

M e a n I S DSecon d s tage

M e a n S DSke le ton

Ma xil la (m ax) - 1 .2 1.0 - 1 .2 1.2 0.12M a n d i b l e ( m a n d ) 4 . 7 2 . 3 3 . 7 2 . 9 1 .2 3A p i c a l b a s e c h a n g e ( A B C H ) 3 .5 1 .8 2 .5 2 .1 1 .6 9

Dent i t i onU 6 r e l a t i o n t o m a x

Bod ily - 0 .5 1.4 - 0 .9 1.5 0.86Tip pin g - 0 .4 1.5 - 1 .0 1.5 1.34T ota l - 0 . 9 1 . 6 - 1 .9 1 .5 2 . 10"

L 6 r e l a t io n t o m a n dBo dily 1.2 1.2 1.5 1.6 - 0.73T ipp ing - 1 .1 1 . 3 - 1 . 0 1 .9 - 0 . 2 0To tal 0 .1 1.1 0.6 1.0 - 1 .28

U 1 r e l a t i o n t o m a x - 0 . 0 1 .6 0 . 2 2 . 4 - 0 . 3 4L 1 r e l a t i o n t o m a n d - 0 . 5 1 .2 - 0 . 7 1 .6 0 . 47

Total correctionM ola r (6~6) 2.8 2.1 1.2 1.5 - 2 .84* *Ov er je t (1[1) 3.0 1.8 1.9 2.3 1.61

T r e a t m e n t ti m e ( m o ) 23.6 12.4 29.0 12.3 - 1.44*p < 0.05; **p < 0.01.

T a b l e I X . T w o - s t a g e t r e a t m e n t : R a t e o f t r e a t m e n t c h a n g e ( p e r y e a r ) b y s t a g e s f o r t h e s k e l e t a l a n d d e n t a lc o m p o n e n t s o f t h e m o l a r a n d o v e r j e t c o r r e c t i o n s ( n = 2 1 )

Firs t s tage Secon d s tageS D M e a n S De a s u r e M e a n

Ske le tonM a xi l l a ( max ) - 0 . 6 0 . 6M a n d i b l e ( m a n d ) 2 . 9 1 .8A p i c a l b a s e c h a n g e ( A B C H ) 2 .3 1 .6

Dent i t i onU 6 r e l a t io n t o m a x

B od i ly - 0 . 0 0 . 9T ip p ing - 0 . 3 1 . 3T o ta l - 0 . 4 1 . 1

L 6 r e l a t i o n to m a n dB odi ly 0 . 8 1 . 3T ipp ing - 0 . 7 1 . 1T o ta l 0 . 1 0 . 7

U1 r e l a t ive to max 0 . 1 1 . 1L 1 r e l at i v e t o m a n d - 0 . 1 0 .8

Tota l correct ionM ola r (6~6) 2.1 2.3O ver jet (1~1) 2.1 2.3

- 0 . 5 0 . 4 - 0 . 9 51.6 1.2 2.81"*1.1 0.9 2.87**

- 0 . 4 0 . 6 1 .5 4- 0 . 4 0 . 6 0 .3 3- 0 . 8 0 . 6 1 .7 1

0.7 0.8 0.16- 0 . 4 0 . 7 - 0 . 7 4

0 . 3 0 . 5 - 0 . 910.0 0.8 0.26

- 0 . 3 0 . 8 0 . 890.6 0.6 2.83**0.8 0.8 2.61"

*p < 0.05; **p < 0.01.

h i s F i g . 3 , B ) . 2 e M o r e t o t h e p o i n t , o u r f in d i n g sm i r r o r t h e n e g a t i v e o u t c o m e s o f s e v e r a l r e c e n ts t u d i e s o f t h e l o n g - t e r m e f f e c t o f t h e H e r b s t a p p l i -a n c e o n m a n d i b u l a r g r o w t h . 2e'23 T h e f a c t t h a t s o m ef u n c t i o n a l - a p p l i a n c e a d v o c a t e s n o w e m p h a s i z e t h e

m i d f a c e r a t h e r t h a n t h e m a n d i b l e 2z'z4 i m p l i e s an e e d t o r e - e v a l u a t e t h e r o l e o f g r o w t h m o d i f i c a t i o n ,e s p e c i a l l y m a n d i b u l a r g r o w t h m o d i f i c a t i o n , i n c o n -t e m p o r a r y d e n t a l p r a c t i c e .O u r p a r t i c u l a r f a i l u r e t o d e t e c t a n y m a j o r t r e a t -


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130 Liv i er a tos an d Jo hn s to n Amer ican Journa l o f Or thodon t ics and Den tofacia l Or thoped icsAugus t 1995m e n t d i f fe r e n c e s, i t m u s t b e n o t e d , c o m e s f r o m a na n a l y s i s o f t h e p a t i e n t s w h o s e d i s c r i m i n a n t s c o r e sm a d e u p t h e c e n t r a l 7 5 % o f t h e p a r e n t s a m p l e , n o tf r o m t h o s e o n e i t h e r e n d o f t h e d i s t r ib u t i o n . A t o n ee x t r e m e , t h i s e x c l u s i o n i s p r o b a b l y o f l i t t l e s i g n i fi -c a n c e , g iv e n th a t t w o - s t a g e t r e a t m e n t s a r e l e ssc o m m o n l y u s e d i n o l d e r p a t ie n t s w i t h m i l d e r C l a s sI I m a l o c c l u s i o n s . A t t h e o t h e r e x t r e m e , h o w e v e r ,o n e f i n d s t h e y o u n g , s e v e r e 1 0 % t o 1 5 % f o r w h o mg r o w t h m o d i f i c a t i o n w o u l d b e m o s t d e s i r a b l e a n dw h o , p e r h a p s a s a r e s u l t , a r e m o s t l i k e l y t o b et r e a t e d i n t w o s t a g e s. T h u s , d e s p i t e t h e p r e s e n td a t a , m a n y p r o b a b l y s t il l w o u l d u s e a f u n c t i o n a l -a p p l i a n c e p h a s e i n s e v e re l y a f fe c t e d p a t i e n t s . A l -t h o u g h a n e f f e ct t h a t c a n b e d e t e c t e d o n l y i n th es e v e r e ly a f f ec t e d p a t i e n t w o u l d r e p r e s e n t a b io l o g i -c a l l y i n e x p l i c a b l e d i s c o n ti n u i t y , g r o w t h m o d i f i c a t i o ni n p a t i e n t s w i t h s e v e r e C l a s s I I m a l o c c l u s i o n s p e r -h a p s w a r r a n t s f u r t h e r i n v e s t i g a t i o n . T h e p r e s e n tr e s u l t s, h o w e v e r , a r e n o t e n c o u r a g i n g .

I n a d d i t i o n t o t a k i n g 1 8 m o n t h s l o n g e r , t h et w o - s t a g e t r e a t m e n t s a v e r a g e d 1 0 m o r e a p p o i n t -m e n t s , a l t h o u g h t h e o v e r a l l a p p o i n t m e n t r a t e ( 13p e r y e a r ) w a s l o w e r t h a n f o r th e s i n g l e - p h a s e e d g e -w i s e ( 1 7 p e r y e a r ) . T h i s d i f f e r e n c e w a s d u e t o am o r e l e i s u re l y p a c e d u r i n g t h e f u n c t i o n a l p h a s e o ft r e a t m e n t . T h e r e f o r e , f o r a f e w y e a r s , a p r a c t i c ec a n a c c o m m o d a t e m o r e t w o - s t a g e p a t i e n t s t ar t s .H o w e v e r , b e c a u s e f i n i s hi n g t h e m w i ll u l t i m a t e l yt a k e m o r e t i m e a n d r e q u i r e m o r e a p p o i n t m e n t s ,t h i s i n i t ia l a d v a n t a g e w o u l d s o o n b e l o s t . M o r e o v e r ,b e c a u s e t h e t w o - s t a g e t r e a t m e n t t i m e s w e r e s i g ni fi -c a n t l y m o r e v a r i a b l e ( S D = 1 6 .7 m o n t h s v s 9 .5m o n t h s ; F -- 3 . 1, p < 0 . 0 1 ) , e a r l y t r e a t m e n t m a yr e p r e s e n t s o m e t h i n g o f a c h a l l e n g e to t h e o r d e r l ym a n a g e m e n t o f a b u s y p r a c t ic e .

F o r t h e a v e r a g e o r t h o d o n t i s t , a b i t o f d i s o r d e ra n d s o m e e x t r a t im e m a y n o t b e a p r o b l e m . I n t h ee v e n t o f a g e n e r a l i z e d i n c r e a s e i n " b u s y n e s s , " h o w -e v e r, i t r e m a i n s t o b e s e e n w h e t h e r t w o - s t a g e t r e a t -m e n t s w o u l d c o n t i n u e t o c o m p e t e s u c c e ss f u ll y f o ro r t h o d o n t i c f a v o r a g a i n s t w h a t m a y w e l l b e e q u a l l yg o o d , b u t m o r e e f f i c i e n t a n d p r e d i c t a b l e , a l t e r n a -t iv e s . A l t h o u g h t h e q u e s t i o n s e e m s t o b e s e lf -a n s w e r i n g , t h i n g s a r e r a r e l y s o s i m p l e . W e s u s p e c tt h a t t h e d e c i s i o n t o u s e f u n c t i o n a l a p p l i a n c e s isf u n d a m e n t a l l y a p r a c t i c e - m a n a g e m e n t p r o b l e mw h o s e s o l u t i o n w i ll p r o b a b l y c o m e n e i t h e r f r o m t h ew o r l d o f b i o l o g y n o r t h e d a t a o f th i s i n v e s t ig a t i o n .F u r t h e r d i s c u s s i o n t h e r e f o r e w o u l d s e e m b e s i d et h e p o i n t .

W e t h a n k D r . E l i V . B e r g e r f o r g r a n t i n g u s f r e ea c c e s s t o h i s e x c e l l e n t r e c o r d s . H i s d i l i g e n c e i n d o c u -

m e n t i n g t h e r e s u l t s o f h i s l a b o r s a n d h i s w i l l i n g n e s s t o" p u t t he p i a st e r o n t h e t a b l e " - a l l o f i t - m a d e t hi si n v e s t ig a t i o n p o s s i b le . W e a l s o t h a n k D r . C a r r o l l - A n nT r o t m a n f o r h e r a s s is t a n c e d u r in g t h e p r e p a r a t i o n o f t h ism a n u s c r i p t .RE F E R E NC E S

1. K loehn SJ. Guiding alveolar growth and erup tion of teeth tor educe t r ea tm en t t im e and p roduce a m o re ba l anced den -ture and face. Angle Orthod 1947;17:10-33.2 . Brodie AG , Downs WB, Golds te in A , Myer E. Cephalo-metr ic appraisa l of or thodont ic result s . Ang le Orthod 1938;8:261-351.3 . Brodie AG. On the growth of the human head f rom thethi rd month to the e ighth year of l ife . Am J An at 1941;68:209-62.4 . G ould SJ . A l lom etry and s ize in ontogeny and phylogeny.Biol Rev 1966;41:587-640.5 . Fo rd JM. A cephalom etr ic inves t igat ion of human cranio-facia l growth as character ized by a Go mpe r tz growth equa-tion. [Master 's thesis. ] Cleveland: Case Western ReserveUniversity, De par tm ent of Orthodontics, 1974.6 . Brodie AG. Facia l pat terns : a theme on var ia t ion. AngleOrthod 1946;16:75-87.7. Carlson D S. Cra niofac ial biology as normal science. In:John ston L E Jr, ed. New vistas in orthodontics. Phila del-phia : Lea & Febig er 1985:12-37.8. An dres en V, Hfiupl K. Funktionskieferorthopfidie. Leipzig:H Meusser, 1936.9 . Johnston LE Jr . A comparat ive analys is of C lass I I t rea t -ments. In : M cNam ara JA Jr , Carlson DS, Vig PS, R ibbensKA, eds . Science and c l in ical judgment in or thodont ics .Monograph 18, Craniofacia l Grow th Ser ies . Ann A rbor :Center for Hum an G rowth and Deve lopment , The Univer-sity of M ichigan, 1986:103-48.10. Johnston LE Jr , Paquet te DE, Beat t ie JR , Cass idy DW Jr ,McCray JF, Kill iany DM. The reduction of susceptibili tybias in re t rospect ive compar isons of a l ternat ive t rea tmentstrategies. In: D rylan d Vig K, Vig PS, eds. Clinical researchas the basis o f clinical practice. Mon ograp h 25, CraniofacialGrowth Ser ies . Ann Arbor : Center for Human Growth andDevelopment, The University of Michigan, 1991:155-77.11. Paquet te DE, Beat t ie JR , Johnston LE Jr . A long- termcompar ison of nonextraction and prem olar-ext ract ion edge-wise therapy in "border l ine" C lass I I pat ients . AM JORTHOD DEN TOFAC ORTHO P 1992;102:1-14.12. Lupp anapo rnlarp S, Johnston L E Jr . The ef fects of premo-lar -ext ract ion: a long - term compar ison of outcomes in"clear-cut" ext ract ion and nonextract ion C lass I I pat ients .Angle Orthod 1993;63:257-72.13. M cN am ara JA J r , B rudon W L. O r thodon t i c and o r t hoped i ct r ea tm en t i n t he m ixed den t i t i on . A nn A rbor : N eedhamPress, 1993:112-3.14. Li t t le RM. The i r regular i ty index: a quant i ta t ive score ofma ndib ular ante rior alignment. AM J ORTHOD 1975;68:554-63 .15. Miet t inen OI . St ra t i f ica tion by a mul t ivar ia te confounderscore. Am J Epidemiol 1976;104:609-20.16. Keeling SD, Cabassa SR, King GJ. Systematic and randomerrors associa ted wi th John ston ' s ce phalom etr ic analysis . BrJ Orthod 1993;20:101-7.

17. Houston WJB. The analys is of er rors in or thodont ic mea-surements. AM J ORTHOD 1983;83:382-90.


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American Journal of Orthodontics and Dentofacial Orthopedics Livieratos an d Johnston 131Volume 108, No. 21 8. D o n a g h e y J B I I . A c e p h a l o m e t r i c e v a l u a t io n o f t o o t h m o v e -

m e n t a n d g r o w t h o f t h e j a w s i n u n t r e a t e d i n d i v i d u a l s , a g e s11- 15 . [ M as te r ' s t hes i s . ] S t L ou i s : Sa in t L ou i s Univer s i ty ,D e p a r t m e n t o f O r t h o d o n t ic s , 1 98 5.

1 9 . M c N a m a r a J A J r , B o o k s t e i n F L , S h a u g n e s s y T G . S k e l e t a la n d d e n t a l c h a n g e s f o l l o w i n g f u n c t i o n a l r e g u l a t o r t h e r a p yon C las s I I pa t i en t s . AM J OR T HOD 1985 ;88 :91- 110 .

2 0. K o r k h a u s G , P r e s e n t o r t h o d o n t i c t h o u g h t in G e r m a n y . A MJ ORTHOD 1960;46:270-85.

2 1 . W i e s l a n d e r L . I n t e n s i v e t r e a t m e n t o f s e v e r e C l a s s I I m a l -o c c l u s i o n s w i t h a h e a d g e a r - H e r b s t a p p l i a n c e i n t h e e a r l ymixed den t i t i on . AM J OR T HOD 1984 ;86 :1 - 13 .

2 2. W i e s l a n d e r L . L o n g - t e r m e f f e c t o f t r e a t m e n t w i t h t h e h e a d -g e a r - H e r b s t a p p l i a n c e i n t h e e a r l y m i x e d d e n t i t i o n . S t a b i l i tyo r r e l ap s e? AM J OR T HOD DE NT OFAC OR T HOP 1993 ;104 :319-29.

2 3 . P a n c h e r z H , F a c k e l U . T h e s k e l e t o f a c i a l g r o w t h p a t t e r np r e - a n d p o s t - d e n t o f a c i a l o r t h o p e d i c s : a l o n g - t e r m s t u d y o fC l a s s I I m a l o c c l u s i o n s t r e a t e d w i t h t h e H e r b s t a p p l i a n c e .E ur J Or thod 1990 ;12 :209- 18 .

2 4 . P a n c h e r z H , A n e h u s - P a n c h e r z M . T h e h e a d g e a r e f f e c t o ft h e H e r b s t a p p l i a n c e : a c e p h a l o m e t r i c l o n g - t e r m s t u d y . A MJ ORT HOD DEN TOFAC ORTHOP 1993;103:510-20.

Reprint requests to:D r . L y s l e E . J o h n s t o n , J r .D e p a r t m e n t o f O r t h o d o n t i c s a n d P e d i a t ri c D e n t i s tr yS c h o o l o f D e n t i s t r yT h e U n i v e r si t y o f M i c h i g a nA n n A r b o r , M I 4 8 1 09 -1 0 78

a comparison of one-stage and two-stage non extraction alternatives in matched class ii samples

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