ABSTRACT
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t reat m ent w it h four prem olar ext ract ions
Guilherme JANSON, Alexandre NAKAMURA, Sérgio Estelita BARROS, Roberto BOMBONATTI, Kelly CHIQUETO
Department of Pediatric Dentistry, Orthodontics and Community Health, Bauru School of Dentistry, University of São Paulo, Bauru, SP, Brazil.
Corresponding address: Dr. Guilherme Janson - Departamento de Odontopediatria, Ortodontia e Saúde Coletiva - Faculdade de Odontologia de Bauru - Universidade de São Paulo - Alameda Octávio Pinheiro Brisolla 9-75 - Bauru - SP - 17012-901 - Brazil - Phone/Fax: 55 14 32344480 - e-mail: jansong@ travelnet.com.br
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our prem olar ext ract ions is a successful prot ocol t o t reat Class I m alocclusion, but it is DOHVVHI¿FLHQWZD\ZKHQFRPSDUHGZLWKRWKHU&ODVV,,WUHDWPHQWSURWRFROV2EMHFWLYH 7KHREMHFWLYHRIWKLVVWXG\ZDVWRHYDOXDWHWKHLQÀXHQFHRIDQWHURSRVWHULRUGLVFUHSDQF\RQ WKHVXFFHVVRIIRXUSUHPRODUH[WUDFWLRQVSURWRFRO)RUWKDWWUHDWPHQWHI¿FLHQFLHVRI&ODVV, and com plet e Class I I m alocclusions, t reat ed wit h four prem olar ext ract ions were com pared. Met hods: A sam ple of 107 records from 75 Class I ( m ean age of 13.98 years - group 1) and 32 Class I I ( m ean age of 13.19 years – group 2) m alocclusion pat ient s t reat ed w it h four SUHPRODUH[WUDFWLRQVZDVVHOHFWHG7KHLQLWLDODQG¿QDORFFOXVDOVWDWXVRIHDFKSDWLHQWZDV evaluat ed on dent al cast s w it h t he PAR index. The t reat m ent t im e was calculat ed based RQWKHFOLQLFDOFKDUWVDQGWKHWUHDWPHQWHI¿FLHQF\ZDVREWDLQHGE\WKHUDWLREHWZHHQWKH percent age of PAR reduct ion and t reat m ent t im e. The PAR index and it s com ponent s, t he WUHDWPHQW WLPH DQG WKH WUHDWPHQW HI¿FLHQF\ RI WKH JURXSV ZHUH VWDWLVWLFDOO\ FRPSDUHG w it h t t est s and Mann- Whit ney U- t est . Result s: The Class I I m alocclusion pat ient s had a JUHDWHU¿QDO3$5LQGH[WKDQ&ODVV,PDORFFOXVLRQSDWLHQWVDQGVLPLODUGXUDWLRQ&ODVV, PRQWKVDQG&ODVV,,PRQWKVDQGWUHDWPHQWHI¿FLHQF\&RQFOXVLRQ7KH t reat m ent of t he com plet e Class I I m alocclusion w it h four prem olar ext ract ions present ed w orse occlusal result s t han Class I m alocclusion ow ing t o incom plet e m olar relat ionship correct ion.Ke yw or ds:7UHDWPHQWSURWRFROV(I¿FLHQF\7RRWKH[WUDFWLRQ
I N TROD UCTI ON
Class I I and Class I I I m alocclusions have in com m on a m olar r elat ionship discr epancy, w hich can or cannot r equir e cor r ect ion depending on t h e t r eat m en t p r ot ocol8 , 1 3 , 2 6. Wh en t r eat m en t
is plan n ed w it h or w it h ou t ex t r act ion of f ou r p r em o l a r s, a Cl a ss I m o l a r r el a t i o n sh i p s i s ex pect ed at t he end of t r eat m ent . How ever, if on ly t w o pr em olar s ar e ex t r act ed in a sin gle ar ch, t he init ial m olar r elat ionship discr epancy should be m aint ained, w hile t he ot her occlusal charact er ist ics ar e nor m alized4,8,14,16,26.
(I¿FLHQF\RI&ODVV,,PDORFFOXVLRQFRUUHFWLRQ h a s b e e n co m p a r e d b e t w e e n t h e d i f f e r e n t t r eat m ent pr ot ocols for t his m alocclusion13,21,22,28.
The t w o pr em olar ext ract ions pr ot ocol pr esent ed bet t er occlu sal r esu lt s in a sh or t er t r eat m en t t im e w hen com par ed w it h non- ex t ract ion and four prem olar ext ract ions prot ocols, probably due
WRGLI¿FXOWLHVDVVRFLDWHGZLWKPRODUUHODWLRQVKLS cor r ect ion in t hese t r eat m ent appr oaches13,14,18.
Ho w e v e r, t h i s sp e cu l a t i o n ca n n o t b e e a si l y dem on st r at ed becau se t h e com par ison s w er e perform ed bet ween different t reat m ent prot ocols.
Thus, t his st udy was designed t o com pare cases wit h and wit hout requirem ent of m olar relat ionship correct ion, but using t he sam e t reat m ent prot ocol. For t h at , t r eat m en t ef f icien cy of Class I an d com plet e Class I I m alocclusions, t reat ed wit h four pr em olar ext ract ions w er e com par ed.
M ATERI AL AN D M ETH OD S
The sam ple size was calculat ed consider ing DYDOXHRIDQGIRUĮW\SH,HUURUDQG ǃW\SH,,HUURU7KHYDOXHRIWKHPHDVXUHPHQW YDULDQFHıVWDQGDUGGHYLDWLRQZDVEDVHGRQD previous st udy7. Since weight ed PAR score ranging
Group 1 Group 2
Class I (n=75) Class II (n=32)
n % n % p
Female 47 62.67 14 43.75 0.070§
Male 28 37.33 18 56.25
Initial Age 13.98±2.07 13.19±1.57 0.056€ § Chi-square test
€ t test
Table 1- Compatibility of Class I and complete Class II malocclusion groups regarding sex and age r elat ionship, it was t he m inim um differ ence t o
be det ect ed bet w een gr oups29. Thus, a m inim um
of 16 pat ient s in each gr oup was r equir ed. The VDPSOHZDVUHWURVSHFWLYHO\VHOHFWHGIURPWKH¿OHV of t he Or t hodont ic Depar t m ent at Baur u School of Dent ist r y. Accor ding t o t he obj ect ives of t his st udy, t he pr im ar y inclusion cr it er ia was pat ient r ecor ds pr esent ing Class I and com plet e bilat eral Class I I div ision 1 m alocclusions t r eat ed w it h IRXU¿UVWSUHPRODUH[WUDFWLRQVDQGVWDQGDUG¿[HG edgew ise appliances. Addit ionally, t he pat ient s VKRXOGSUHVHQWDOOSHUPDQHQWWHHWKXSWRWKH¿UVW m olar s and no dent al anom alies of num ber, size, and form . Pat ient s had not been subm it t ed t o RME or or t h odon t ic- su r gical appr oach . Con sider in g t hese cr it er ia, 75 Class I ( 47 fem ale, 28 m ale – gr oup 1) and 32 Class I I ( 14 fem ale, 18 m ale – gr oup 2) m alocclusion pat ient s w er e select ed fr om all t r eat ed and docum ent ed pat ient s. Gr oup 1 pr esent ed an init ial m ean age of 13.98± 2.08 years ( range, 10.54–23.13 years) and group 2 had an init ial m ean age of 13.19± 1.58 year s ( range, 10.48–18.58 years) . Considering t hat pat ient s had unequal dist ribut ion bet ween t he groups ( 1: 2) , t he sam ple size was r ecalculat ed t o com pensat e t his VSHFL¿FGLVSURSRUWLRQ$WRWDOVDPSOHVL]HZLWKD m inim um of 48 pat ient s was r equir ed ( N= 16 and 1 FRQ¿UPLQJ WKDW WKH QXPEHU RI VHOHFWHG pat ient s was adequat e.
Ort hodont ic m echanics included 0.022x0.028-LQFK ¿[HG VWDQGDUG HGJHZLVH DSSOLDQFHV DQG H[WUDFWLRQ RI IRXU ¿UVW SUHPRODUV &DVHV ZLWK sev er e init ial ant er ior t oot h cr ow ding r equir ed in it ial can in e r et r act ion , f ollow ed b y lev elin g an d alig n m en t w it h t h e u su al w ir e seq u en ce FKDUDFWHUL]HG E\ DQ LQLWLDO LQFK WZLVWÀH[ or a 0.016- inch nit inol, follow ed by 0.016, 0.018, 0 . 0 2 0 , an d 0 . 0 1 9 x 0 . 0 2 5 - in ch st ain less st eel archwire ( Unit ek, Monrovia, California, USA) . Deep bit e was correct ed w it h accent uat ed and reversed cur ve of Spee. The ext ract ion spaces w er e closed w it h “ en m asse” r et ract ion of t he ant er ior t eet h, wit h elast ic chains on a rect angular archwire. Class I I pat ient s used ext raoral appliance for anchorage r einfor cem ent and ant er opost er ior r elat ionship cor r ect ion . Wh en n ecessar y, Class I I elast ics
w er e also used t o aid in Class I I ant er opost er ior cor r ect ion.
The pat ient s’ r ecor ds w er e used t o det er m ine t heir init ial age ( I - Age) , sex, dat e of t r eat m ent onset , dat e of t r eat m ent com plet ion, and t ot al WUHDWPHQWWLPH777KHLQLWLDODQG¿QDORFFOXVDO st at uses were evaluat ed using t he peer assessm ent rat ing ( PAR) index29, w hich was calculat ed on t he
pr et r eat m en t an d post t r eat m en t den t al st u dy m odels of each pat ient , according t o t he Am erican w eig h t in g s su g g est ed b y DeGu zm an , et al.6
,QLWLDO DQG ¿QDO RFFOXVDO FKDUDFWHULVWLFV w er e ranked by scor es for m olar and pr em olar AP r elat ionship, over j et , over bit e, m idline, and cr ow d in g t o q u an t if y t h e in it ial m alocclu sion sever it y ( I - PAR) , t he occlusal t r eat m ent r esult s ( F- PAR) , and t he per cent age of PAR r educt ion ( PcPAR) , w hich is a bet t er est im at e of occlusal im pr ovem ent11.
Since t he PAR index analyzes a set of occlusal ch a r a ct e r i st i cs a t t h e sa m e t i m e a n d d o e s n ot d i scr i m i n at e t h e d eg r ee of p ar t i ci p at i on of each in t h e t ot al scor e, t h e post t r eat m en t scor es obt ained for each PAR com ponent w er e com par ed individually t o det er m ine t he success rat e achieved. Ther efor e, t he PAR scor e at t he end of t r eat m ent was separat ed int o it s several com ponent s t o allow an individual evaluat ion. The WUHDWPHQWHI¿FLHQF\LQGH[7(,ZDVHYDOXDWHGE\ t he relat ionship bet ween PcPAR and TT in m ont hs, expr essed as TEI = PcPAR/ TT13. The TEI incr eased
w hen a gr eat er PcPAR and/ or a shor t er TT was obser ved.
Er r or st u dy
,QLWLDODQG¿QDO3$5VFRUHVZHUHUHFDOFXODWHG by t he sam e exam iner ( AYN) in t he pr et r eat m ent and post t r eat m ent st udy m odels of 20 random ly VHOHFWHG SDWLHQWV DIWHU GD\V IURP WKH ¿UVW m easur em ent . The casual er r or s w er e est im at ed by Dahlber g’s for m ula ( Se2 G2/ 2n) , w her e S2 is
Class I (n=75) Class II (n=32)
Mean SD Mean SD P
I-PAR 23.64 5.45 26.18 7.53 0.052 F-PAR 2.40 3.08 5.12 5.69 0.001* PcPAR 89.46 14.39 79.18 24.58 0.008*
Table 2 - Comparison of Class I and complete Class II malocclusion groups regarding PAR score
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I-PAR=initial malocclusion severity F-PAR=occlusal treatment results PcPAR=percentage of PAR reduction
Class I (n=75) Class II (n=32)
% Mean Rank % Mean Rank Z (U) p
AP 23.33 50.05 43.95 63.32 -2.755 0.005* Overjet 30.42 52.54 33.40 57.42 -1.174 0.240 Overbite 28.33 52.51 20.12 57.46 -1.006 0.314 Midline 3.33 54.42 0 53.00 0.928 0.353 Crowding 14.17 56.21 2.34 48.81 1.578 0.114 U Mann-Whitney U test
6WDWLVWLFDOO\VLJQL¿FDQWDW3
F-PAR=occlusal treatment results
Table 3- Comparison of Class I and complete Class II malocclusion groups regarding F-PAR individual components, and proportion of each PAR component in F-PAR
St a t ist ica l a n a ly se s
Com p at ib ilit y of t h e g r ou p s r eg ar d in g t h e proport ion of sexes was evaluat ed wit h chi- square t est s, w h ile t h e I - Age sim ilar it y bet w een t h e gr oups was evaluat ed w it h t t est .
The PAR index variables ( I - PAR; F- PAR; PcPAR) w er e com par ed bet w een t he gr oups using t t est s.
Th e o c c l u s a l r e s u l t s o b t a i n e d f o r e a c h com ponent of t he PAR index w er e indiv idually com par ed bet w een t he gr oups w it h t he Mann-Whit ney U- t est . A nonparam et r ic t est was used because t he values of each PAR com ponent did not show nor m al dist r ibut ion. The per cent age of cont ribut ion from each PAR com ponent t o t he t ot al value of t he F- PAR was also calculat ed.
7KHWUHDWPHQWWLPHDQGWUHDWPHQWHI¿FLHQF\ i n d ex w er e co m p ar ed w i t h t t est s, an d t h e in f lu en ce of t h e v ar iab les Molar Relat ion sh ip ( MR) ; Sex ( S) ; I - Age; I - PAR, F- PAR and PcPAR on t r eat m ent t im e was evaluat ed by m ult iple linear r egr ession analysis.
RESULTS
7KH3$5HYDOXDWLRQGLGQRWSUHVHQWDVLJQL¿FDQW syst em at ic er r or, and t he casual er r or was w it hin accep t ab le lev el ( PAR= 1 . 5 ) . Th e g r ou p s w er e
sim ilar r egar ding t he pr opor t ion of sexes, init ial age and t r eat m ent t im e ( Table 1) .
The init ial sever it y ( I - PAR) of Class I and Class I I m alocclusions w er e sim ilar in t he gr oups. The bet t er occlu sal r esu lt s an d su ccess r at e w er e DFKLHYHG LQ JURXS WKDW KDG D VLJQL¿FDQWO\ sm aller F- PAR and a gr eat er PcPAR ( Table 2) .
Molar and pr em olar AP r elat ionship was t he RQO\ ¿QDO 3$5 LQGH[ FRPSRQHQW WKDW VKRZHG VWDWLVWLFDOO\ VLJQL¿FDQW GLIIHUHQFH EHWZHHQ WKH gr oups, and it s gr eat er scor e value r epr esent s a w or se AP r elat ionship obt ained in gr oup 2. Molar and prem olar AP relat ionship cont ribut ed only wit h 23% of t he t ot al F- PAR value obt ained in Gr oup 1, w hile 43.95% of t he t ot al F- PAR value obt ained in Gr oup 2 was due t o it ( Table 3) .
Class I (n=75) Class II (n=32)
Mean SD Mean SD p
TT 28.95 10.39 28.10 7.02 0.673€
TEI 3.44 1.25 2.98 1.25 0.085€
Multiple regression analysis
ȕFRHI¿FLHQWV SD p R2
AP -1.41 2.19 0.522 0.044¥
Sex -0.56 1.90 0.768 Initial Age -0.14 0.49 0.774 I-PAR 0.17 0.21 0.410 F-PAR 0.70 0.91 0.441 PcPAR 0.17 0.20 0.392 € t test
¥ Multiple regression analysis I-PAR=initial malocclusion severity F-PAR=occlusal treatment results PcPAR=percentage of PAR reduction
Table 4- Comparison of Class I and complete Class II malocclusion groups regarding treatment time (TT - in months) and
WUHDWPHQWHI¿FLHQF\LQGH[7(,DQGPXOWLSOHUHJUHVVLRQDQDO\VLVZLWKWUHDWPHQWWLPHDVWKHGHSHQGHQWYDULDEOH
D I SCUSSI ON
Molar r elat ionship cor r ect ion is an essent ial ob j ect iv e of Class I I m alocclu sion t r eat m en t w it h f ou r pr em olar ex t r act ion s, w h ich can be LQÀXHQFHGE\VRPHIDFWRUV3DWLHQWVH[DQGDJHLV associat ed w it h t he craniofacial gr ow t h pot ent ial, and pat ient com pliance degr ee can also change according t o t hese variables9,20,30. Considering t hat
SDWLHQW JURZWK DQG FRPSOLDQFH LQÀXHQFH &ODVV I I m alocclusion cor r ect ion, com pat ibilit y of t he gr oups r egar ding sexes pr opor t ion and init ial age allow ed an unbiased m olar relat ionship correct ion HYDOXDWLRQ7DEOH$OWKRXJKQRWVLJQL¿FDQWO\WKH slight ly sm aller init ial m ean age and t he gr eat er PDOHSDWLHQWSURSRUWLRQRIJURXSEHQH¿WHG&ODVV I I m alocclusion t r eat m ent since, at t his m ean age range, Class I I t reat m ent at a younger age is m ore favorable because t her e w ill be gr eat er gr ow t h changes t hat can be redirect ed wit h t reat m ent10,23.
0DOHVDUHEHQH¿WHGLQ&ODVV,,WUHDWPHQWDWWKLV m ean age because t heir gr ow t h spur t occur s lat er t han in fem ales, and occur s a lit t le lat er t han t he init ial m ean age r epor t ed. Ther efor e, t r eat m ent was conduct ed in a lar ge num ber of m ales dur ing t heir peak gr ow t h spur t10,23. How ever, t his was
not enough t o ensur e a sim ilar occlusal r esult t o gr oup 1.
Th e si m i l a r i n i t i a l m a l o ccl u si o n se v e r i t y obser ved in t he gr oups could be consider ed an unexpect ed r esult because Class I I m alocclusion has an ant er opost er ior discr epancy t hat is not pr esent in Class I ( Table 2) . How ever, t he over j et
was t he only differ ent m alocclusion t rait bet w een t h e g r ou p s. Th er ef or e, it w as n ot en ou g h t o p r od u ce a sig n if ican t in t er g r ou p d iscr ep an cy r egar ding t he t ot al PAR value.
The w or st occlusal r esult and PcPAR cor r ect ion of Class I I m alocclu sion t r eat m en t d oes n ot se e m t o b e a sso ci a t e d w i t h t h e e x t r a ct i o n pr ot ocol because bot h w er e t r eat ed w it h four-pr em olar ext ract ions ( Table 2) . I ncisor cr ow ding or labial t ipping is easily solved dur ing ant er ior r et r act ion an d t h ey w ou ld u n lik ely af f ect t h e PcPAR cor r ect ion. How ever, Class I I t r eat m ent w it h or w it hout four pr em olar ext ract ions always r eq u ir e m olar r elat ion sh ip cor r ect ion , an d a GH¿FLHQW DQWHURSRVWHULRU FRUUHFWLRQ FDQ DIIHFW t he PcPAR cor r ect ion4, 12- 14, 17, 19. Thus, if init ially
t her e is a Class I r elat ionship, as in gr oup 1, four pr em olar ext ract ions w ill not affect t he t r eat m ent r esult s, but if t her e is a com plet e init ial Class I I m olar r elat ionship, as in gr oup 2, it s incom plet e correct ion can com prom ise t he t reat m ent result s.
sco r e w a s si m i l a r b et w een t h e g r o u p s, b u t at t h e en d of or t h od on t i c t r eat m en t t h e AP UHODWLRQVKLSZDVGH¿FLHQWLQJURXSGXHWRWKH GLI¿FXOW\WRWUHDWDFRPSOHWH&ODVV,,WRD&ODVV, r elat ionship13,14,QIDFWWKH¿QDO$3UHODWLRQVKLS
scor e r epr esent ed alm ost half of t he F- PAR in gr oup 2, w hile gr oup 1 show ed an F- PAR value wit h a m ore equilibrat ed score dist ribut ion am ong t h e PAR com pon en t s, w it h ou t a pr edom in an t fact or det erm ining t reat m ent lim it at ions ( Table 3) .
Alt hough t he PcPAR r educt ion was sm aller in t he Class I I t han in t he Class I gr oup due t o t he GLI¿FXOW\WRFRUUHFWPRODUUHODWLRQVKLSWUHDWPHQW t im e was sim ilar in t he gr oups, pr obably because RUWKRGRQWLF WUHDWPHQW ZDV ¿QLVKHG EHIRUH WRWDO Class I I correct ion ( Table 4) . This sim ilar t reat m ent WLPHFRQWULEXWHGWRDVLPLODUWUHDWPHQWHI¿FLHQF\ index ( TEI ) in t he gr oups in spit e of t he sm aller PcPAR r educt ion of t he Class I I gr oup. Per haps, if gr oup 2 pat ient s w er e t r eat ed up t o a bet t er m olar r elat ionship, it s t r eat m ent t im e w ould be longer t han t he Class I gr oup. How ever, w hen t he occlusal r esult s ar e essent ially dependent on pat ient com pliance, a longer t r eat m ent t im e does not always m ean an act ual t r eat m ent pr ogr ess t owar ds planned obj ect ives if t he pat ient is not en g ag ed or con cer n ed in ob t ain in g t h e b est r esult s t hat or t hodont ic t r eat m ent can pr ovide. Consequent ly, and cont rar y t o com m on sense, lon g er t r eat m en t s ar e f r eq u en t ly associat ed w it h less sat isf act or y r esu lt s, an d ad d it ion al act ive t r eat m ent could not im pr ove t he r esult s of noncom pliant pat ient s27. I n t hese cases, t w o
opt ions should be consider ed by t he pr ofessional in t h e p at ien t ’s b est in t er est : 1 - or t h od on t ic t r eat m ent of noncom pliant pat ient s should not be cont inued in t he hope of at t aining a bet t er r esult27; 2- w henever possible, a com pliance fr ee
appliance could be at t em pt ed24, alt hough m inim al
pat ient cooperat ion and caut ion w it h hy giene, appoint m ent s and appliance br eakage w ill always be necessar y t o adequat ely conduct or t hodont ic t r eat m ent27.
The regression analysis showed t hat none of t he independent var iables explained t r eat m ent t im e sat isfact orily ( Table 4) . This absence of correlat ion b e t w e e n t r e a t m e n t t i m e a n d su cce ss r a t e corroborat es t he t hought t hat t reat m ent prot ocols w it h h ig h r eq u ir em en t of p at ien t com p lian ce h a v e l o w su cce ss p r e d i ct a b i l i t y r e g a r d l e ss o f t h e t r eat m en t t i m e sp en t5 , 1 3 , 1 4 , 2 4 , 2 7. Th u s,
m olar r elat ionship cor r ect ion did not cont r ibut e VLJQL¿FDQWO\WRH[SODLQWUHDWPHQWGXUDWLRQEHFDXVH so m e p a t i e n t s h a d , si m u l t a n e o u sl y, l o n g e r t r eat m ent t im e and gr eat er F- PAR scor e due t o unsat isfact or y cor r ect ion of m olar r elat ionship. AP cor r ect ion was not im pr oved w hen t r eat m ent t im e w as ex t en ded in t h e ef f or t of obt ain in g
a b et t er t r eat m en t r esu lt . Br ief ly, if p at ien t com pliance is not obt ained, t r eat m ent t im e w ill KDYH QR LQÀXHQFH RQ $3 FRUUHFWLRQ ZKHQ &ODVV I I m echanics is fully pat ient - dependent . Ot her var iables had y et sm aller pr edict iv e values t o det er m ine t r eat m ent t im e because, t heor et ically, obt aining an ideal occlusion is usually t aken as a st r ong clinical param et er t o det er m ine appliance r em oval. Bu t , if an ideal occlu sion can n ot be o b t a i n e d , t r e a t m e n t e n d i n g w i l l b e co m e a subj ect ive decision and t r eat m ent t im e can var y accor ding t o unconvent ional param et er s.
Clin ica l im plica t ion s
So m e o ccl u sa l o b j e ct i v e s o f o r t h o d o n t i c t r eat m ent ar e inher ent t o t he pr ot ocol choice. Th u s, if f ou r pr em olar ex t r act ion s pr ot ocol is chosen, a Class I m olar r elat ionship should be est ablished at t he end of t r eat m ent r egar dless of t h e in it ial an t er opost er ior r elat ion sh ip4 , 2 5 , 2 6.
%HFDXVHRIWKHGHPRQVWUDWHGGLI¿FXOW\WRFRUUHFW t he AP r elat ionship, a four pr em olar ext ract ions pr ot ocol should be used w it h caut ion w hen t he init ial m olar relat ionship is severely displaced from Class I and pat ient gr ow t h pot ent ial is r educed or absent . I n t hese cases, pr em olar ext ract ions in a single ar ch can be t he best choice concer ning occlu sion . Th is ex t r act ion p r ot ocol d oes n ot r equ ir e m olar r elat ion sh ip ch an ges t o cor r ect canine r elat ionship and over j et , incr easing t he pr edict abilit y of t he occlusal r esult s due t o t he sm aller need of pat ient com pliance wit h anchorage r einfor cem ent and int er m axillar y elast ics3,4,14,15.
I n Class I I m alocclu sion s, ev en w h en t h e or t hodont ist is convinced t hat pat ient com pliance w ill be good and t hat t he gr ow t h pot ent ial could h elp t o ach iev e a Class I m olar r elat ion sh ip, t h e fou r pr em olar ex t r act ion s pr ot ocol sh ou ld be used w it h caut ion, since it pr oduces gr eat er incisor r et ract ion t han t w o m ax illar y pr em olar ext ract ions1,4,14DQGWKHSDWLHQWSUR¿OHPD\QRW
EHEHQH¿WHGZLWKWKHVHVRIWWLVVXHFKDQJHV7KXV RUWKRGRQWLVWV VKRXOG GH¿QLWHO\ LQFOXGH WKH WZR pr em olar ext ract ions pr ot ocol in t heir t r eat m ent opt ions. How ever, it is necessar y t o have in m ind WKDW WKLV SURWRFRO UHTXLUHV VSHFL¿F RUWKRGRQWLF m echanic guidance on how t o cor r ect ly posit ion WKHWHHWKZKHQD¿QDO&ODVV,,PRODUUHODWLRQVKLS is in t en ded, allow in g t h e est ablish m en t of an ex cellen t st at ic an d f u n ct ion al occlu sion w it h sm aller incisor r et ract ion, soft t issue changes, p a t i en t co m p l i a n ce n eed s a n d u n su ccessf u l r esult s2- 4,14- 16,26,31.
CON CLUSI ON S
and gr eat er success rat e t han com plet e Class I I m alocclusions sim ilar ly t r eat ed;
M o l a r r e l a t i o n s h i p c o r r e c t i o n w a s t h e unsuccessful t r eat m ent obj ect ive t hat pr im ar ily FRQWULEXWHGIRUDPRUHGH¿FLHQWRFFOXVDOUHVXOWLQ com plet e Class I I m alocclusions;
Tr eat m ent t im e sim ilarit y was t he det erm inant IDFWRUIRUWKHVLPLODUWUHDWPHQWHI¿FLHQF\LQGH[HV of bot h m alocclusions.
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