Skeletal and dental effects of molar distalization using a modified palatal anchorage plate in adolescents

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1 Originl Article Skeletl nd dentl effects of molr distliztion using modified pltl nchorge plte in dolescents Noor Lith S ed ; Chong Ook Prk b ; Mohmed Byome c ; Je Hyun Prk d ; YoonJi Kim e ; Yoon-Ah Kook f ABSTRACT Objective: To evlute nd compre skeletl effects nd the mount of molr distliztion in mxill using modified pltl nchorge plte (MPAP) vs hedger pplinces in dolescent ptients. Mterils nd Methods: Pre- nd posttretment lterl cephlogrms of 45 Clss II mlocclusion ptients were nlyzed; 24 were treted with MPAP pplinces (ge, 12.4 yers) nd 21 with hedger (ge, 12.1 yers). Fixed orthodontic tretment strted with the distliztion process in both groups. Thirty-two vribles were mesured nd compred between both groups using multivrite nlysis of covrites. Results: There ws no significnt min effect of the pplince type on the tretment results (P 5.063). Also, there ws no significnt min effect of the pplince type on both pre- nd posttretment comprisons (P nd.135, respectively). The MPAP nd hedger groups showed significnt distliztion of mxillry first molrs ( mm nd mm, respectively; P,.001). Sgittl skeletl mxillomndibulr differences were improved fter tretment (P,.001), with no significnt differences between the two groups. No significnt difference in tretment durtion ws found between the groups. Conclusions: The MPAP showed significnt skeletl effect on the mxill. Both MPAP nd hedger resulted in distliztion of mxillry first molrs. Therefore, it is recommended tht clinicins consider the ppliction of MPAP, especilly in noncomplint Clss II ptients. (Angle Orthod. 2015;85: ) KEY WORDS: Modified pltl nchorge plte; Mxillry molr distliztion; Hedger; Skeletl effect Grdute student, Deprtment of Dentistry, College of Medicine, The Ctholic University of Kore, Seoul, Kore. b Privte prctice, Clinicl Professor t Deprtment of Orthodontics, The Ctholic University of Kore; Seoul Ntionl University; nd Kore University, Seoul, Kore. c Reserch Assistnt Professor, Deprtment of Dentistry, College of Medicine, The Ctholic University of Kore, Seoul, Kore, nd Visiting Professor, Deprtment of Postgrdute Studies, Universidd Autonóm del Prguy, Asunción, Prguy. d Associte Professor nd Chir, Postgrdute Orthodontic Progrm, Arizon School of Dentistry & Orl Helth, AT Still University, Mes, Ariz, nd Adjunct Professor, the Grdute School of Dentistry, Kyung Hee University, Seoul, Kore. e Associte Professor, Deprtment of Orthodontics, Seoul St. Mry s Hospitl, College of Medicine, The Ctholic University of Kore, Seoul, Kore. f Professor, Deprtment of Orthodontics, Seoul St. Mry s Hospitl, College of Medicine, The Ctholic University of Kore, Seoul, Kore. Corresponding uthor: Dr Yoon-Ah Kook, Deprtment of Orthodontics, Seoul St. Mry s Hospitl, College of Medicine, The Ctholic University of Kore, 222 Bnpo-dero, Seocho-gu, Seoul , Republic of Kore (e-mil: kook190036@yhoo.com) INTRODUCTION It is chllenging to perform distliztion of mxillry molrs without tipping nd extrusion tht could cuse relpse. Trditionlly, hedger hs shown successful results in Clss II tretment. 1,2 While its effect is combintion of distl movement of molrs, inhibition of mxillry growth, nd rottion of the plte, 3,4 it is dependent on ptient coopertion nd my cuse psychologicl distress. 5,6 Also, it is difficult to chieve bodily tooth movement. To void the negtive spects of hedger, severl introrl pplinces such s distl jet, Herbst, nd pendulum springs hve been developed to distlize molrs 7 9 ; however, they hve some drwbcks. For Accepted: July Submitted: June Published Online: September 5, 2014 G 2015 by The EH Angle Eduction nd Reserch Foundtion, Inc. DOI: /

2 658 SA AED, PARK, BAYOME, PARK, KIM, KOOK Figure 1. The MPAP plced on the plte of ptient with lte mixed dentition. instnce, the distl jet hs been known to led to mesil rottion of the molrs during distliztion, nd the pendulum pplince hs resulted in distl tipping of molrs, nchorge loss, nd tendency for reciprocl effects In generl, the side effects of these pplinces re nchorge loss t the rective prt cusing flring of the incisors, distl tipping, nd rottion of the distlized molrs. To reduce these shortcomings, severl studies hve considered the ppliction of temporry nchorge devices (TADs). 13,14 TADs hve been pplied to the buccl plte of bone to chieve molr distliztion However, the buccl pproch poses n incresed risk of contct with the roots of djcent teeth, nd the rnge of ction might be limited by the interrdiculr spce in dolescents. Tble 1. Demogrphic Dt MPAP Group (n 5 24) Hedger Group (n 5 21) P Vlue Gender Mle Femle Severity 1/4 cusp /2 cusp 6 8 3/4 cusp 8 8 Full cusp 2 1 Second molr eruption sttus Erupted Coronl 7 13 Middle 1 2 Skeletl ge CVS CVS CVS CVS CVS CVS MPAP indictes modified pltl nchorge plte; Coronl, the crown of the second molr is within the verticl level of the coronl third of the first molr root; Middle, the crown of the second molr is within the verticl level of the middle third of the first molr root. Chisqure test. Figure 2. Lndmrks nd reference lines: 1, sell; 2, nsion; 3, orbitle; 4, porion; 5, condylion; 6, nterior nsl spine (ANS); 7, posterior nsl spine (PNS); 8, point; 9, mxillry centrl incisor root pex; 10, mxillry centrl incisor incisl edge; 11, mndibulr centrl incisor incisl edge; 12, mndibulr centrl incisor root pex; 13, mxillry first molr root pex; 14, mxillry first molr crown; 15, B point; 16, pogonion; 17, gnthion; 18, menton; 19, gonion; 20, pterygoid point; 21, true verticl line; 22, Frnkfort horizontl plne; 23, verticl reference line; 24, columell; 25, subnsle; 26,upper lip; 27, lower lip; 28, soft tissue B point; 29, soft tissue pogonion. Tric et l. 18 hve introduced the plte for skeletl nchorge. The plcement of TADs in the plte elimintes the need for reimplnting mini-screws s in the buccl pproch. Therefore, pltl bone thickness nd density s well s pltl soft tissue thickness hve recently been evluted in dolescents Currently, the modified pltl nchorge plte (MPAP) offers simple nd effective nonextrction pproch for distliztion of the mxillry dentition in dults. 22 However, the effect of pltl pltes on the growth of the mxill hs not been evluted. Moreover, no comprison hs been mde of the tretment effects with MPAP pplinces vs hedger. Therefore, the purpose of this study ws to evlute the mount of molr distliztion nd skeletl effects in mxill resulting from molr distliztion using MPAPs nd to compre these effects with those of hedger pplinces in dolescent ptients. MATERIALS AND METHODS The smple of this retrospective study consisted of lterl cephlogrms of 45 Clss II division 1

3 TREATMENT EFFECTS OF MPAP IN ADOLESCENTS 659 Figure 3. Liner mesurements: 1, verticl distnce of mxillry centrl incisor root pex to horizontl reference line (HRL); 2, horizontl distnce of mxillry centrl incisor root pex to verticl reference line (VRL); 3, verticl distnce of mxillry centrl incisor crown to HRL; 4, horizontl distnce of mxillry centrl incisor crown to VRL; 5, verticl distnce of mxillry first molr root pex to HRL; 6, horizontl distnce of mxillry first molr root pex to VRL; 7, verticl distnce of mxillry first molr crown to HRL; 8, horizontl distnce of mxillry first molr crown to VRL. mlocclusion ptients; 24 were treted with MPAP pplinces (ge, yers; 18 girls) t the Deprtment of Orthodontics, Seoul St. Mry s Hospitl, The Ctholic University of Kore, nd 21 with cervicl pull hedger (ge, yers; 10 girls) t privte prctice office. The inclusion criteri were ge rnge from 10 to 16 yers, Clss II division 1 mlocclusion with norml divergent growth pttern, moderte mxillry crowding (,5 mm) nd protrusion, nonextrction tretment, molr distliztion vi either MPAPs or hedger exclusively, nd bsence of crniofcil syndromes. Approvl to conduct this study ws grnted by the Institutionl Review Bord (KC11RASI0790). The MPAP pplince hs been described previously. 23,24 The MPAPs were instlled by single opertor using three 8-mm-length nd 2.0-mm-dimeter miniscrews (Jeil Corportion, Seoul, Kore) in the prmedinn re to void interference with the growth of the suture. A pltl br with two hooks extending long the gingivl mrgins of the teeth ws bonded to the mxillry first molrs. Distliztion ws initited by Figure 4. Angulr mesurements: 1, SNA; 2, SNB; 3, fcil ngle (FH/N-Pg); 4, pltl plne ngle (FH/ANS-PNS); 5, occlusl plne ngle (FH/OP); 6, mndibulr plne ngle (FH/Go-Me); 7, mxillry centrl incisor inclintion; 8, mxillry first molr inclintion; 9, incisor mndibulr plne ngle (IMPA); 10, nsolbil ngle; 11, mentolbil fold ngle. engging elstics or NiTi closed-coil springs between the MPAP rm notches nd the hooks on the pltl br, pplying pproximtely 300 g of force per side (Figure 1). All hedger cses (cervicl pull) were treted by one opertor. The outer bows of the hedger were djusted upwrd to pss close to the center of resistnce of the mxillry first molrs. Ech ptient ws given wering-time recording crd for motivtion, nd most of the ptients reported stisfctory records. Tble 1 shows the demogrphic dt of the two groups including the severity of Clss II molr reltionship (very mild, 1/4 cusp; mild, 1/2 cusp; moderte, 3/4 cusp; nd severe, full cusp), the eruption sttus of the mxillry second molr, nd the skeletl ge ccording to the method of Bccetti et l. 25 Cephlometric Mesurements The pre- (T1) nd posttretment (T2) lterl cephlogrms were digitized using V-Ceph 5.5 (Cybermed, Seoul, South Kore). The horizontl reference line ws the FH plne, nd the verticl reference line ws perpendiculr line pssing through the pterygoid. Thirty-two liner nd ngulr mesurements were mde by one exminer (Figures 2 4). Differences between T1 nd T2 were clculted.

4 660 SA AED, PARK, BAYOME, PARK, KIM, KOOK Tble 2. Comprison Between Cephlometric Vribles of MPAP nd Hedger Groups t Pretretment MPAP Group Hedger Group 95% CI Vrible Men SE Men SE Lower Bound Upper Bound P Vlue Skeletl SNA, u SNB, u ANB, u Wits, mm Hvold, mm Fcil ngle, u Pltl plne ngle, u Mndibulr plne ngle, u A-point to N perpendiculr, mm A-point to TVL, mm B-point to TVL, mm Mxillry length, mm Mndibulr length, mm Dentl First molr crown VRL, mm First molr root VRL, mm ,.001 First molr cusp FH, mm First molr root FH, mm First molr FH ngle, u Centrl incisor crown VRL, mm Centrl incisor root VRL, mm Centrl incisor crown FH, mm Centrl incisor root FH, mm Centrl incisor FH ngle, u Occlusl plne ngle, u IMPA, u Overjet, mm Overbite, mm Soft tissue Nsolbil ngle, u Mentolbil fold, u Upper lip to TVL, mm Lower lip to TVL, mm Soft tissue pgonion to TVL, mm MANCOVA, djusted mens ccording to second molr eruption sttus. MPAP indictes modified pltl nchorge plte; TVL, true verticl line; VRL, verticl reference line; CI, confidence intervl for difference. Significnce level: P,.016 ccording to Bonferroni correction. Ten rndomly selected cses from ech group were redigitized nd nlyzed 2 weeks lter by the sme exminer. Intrexminer relibility ws evluted by intrclss correltion coefficient nd ws..9. Sttisticl Anlysis Sttisticl evlution ws performed using SPSS 16.0 (SPSS Inc, Chicgo, Ill). Pired t-test ws used to evlute the skeletl, dentl, nd soft tissue chnges from T1 to T2 within ech group. A multivrite nlysis of covrites (MANCOVA) ws performed to evlute the differences pre- nd posttretment nd the tretment effects between the groups. An independent-smple t-test showed no significnt difference in ge (P 5.433), nd chi-squre test showed no significnt differences in frequency distribution of gender (P 5.073), severity (P 5.636), or skeletl ge (P 5.128) between the groups. However, significnt difference ws found in the second molr eruption sttus (P 5.025; Tble 1). Therefore, this vrible ws used s covrite in the MANCOVA. Sttisticl significnce ws set t.05, nd by pplying Bonferroni correction, it becme RESULTS There ws no significnt min effect of the type of the pplince on the comprison of pre- nd posttretment vribles (P nd.135, respectively; Tbles 2 nd 3). Also, there ws no significnt effect of the second molr eruption sttus on both comprisons (P nd.532, respectively). Similrly, there ws no significnt min effect of the type of the pplince or second molr eruption sttus on the tretment effects (P nd.396, respectively; Tble 4).

5 TREATMENT EFFECTS OF MPAP IN ADOLESCENTS 661 Tble 3. Comprison Between Cephlometric Vribles of MPAP nd Hedger Groups t Posttretment MPAP Group Hedger Group 95% CI Vrible Men SE Men SE Lower Bound Upper Bound P Vlue Skeletl SNA, u SNB, u ANB, u Wits, mm Hvold, mm Fcil ngle, u Pltl plne ngle, u Mndibulr plne ngle, u A-point to N perpendiculr, mm A-point to TVL, mm B-point to TVL, mm Mxillry length, mm Mndibulr length, mm Dentl First molr crown VRL, mm First molr root VRL, mm ,.001 First molr cusp FH, mm First molr root FH, mm First molr FH ngle, u Centrl incisor crown VRL, mm Centrl incisor root VRL, mm Centrl incisor crown FH, mm Centrl incisor root FH, mm Centrl incisor FH ngle, u ,.001 Occlusl plne ngle, u IMPA, u Overjet, mm Overbite, mm Soft tissue Nsolbil ngle, u Mentolbil fold, u Upper lip to TVL, mm Lower lip to TVL, mm Soft tissue pogonion to TVL, mm MANCOVA, djusted mens ccording to second molr eruption sttus. MPAP indictes modified pltl nchorge plte; TVL, true verticl line; VRL, verticl reference line; CI, confidence intervl for difference. Significnce level: P,.016 ccording to Bonferroni correction. Severl skeletl vribles showed significnt chnges between pre- nd posttretment vlues within ech group. ANB decresed 1.53u u in the MPAP group nd 2.30u u in the hedger group. The Wits lso decresed mm nd mm, respectively (P,.001; Tble 4). Nonetheless, there ws no significnt difference between the groups regrding ll of the skeletl vribles bsed on univrite nlysis (Tble 4). Sgittlly, the mounts of distl movement of the mxillry first molr crown were mm in the MPAP group nd mm in the hedger group. Menwhile, the first molr root ws distlized mm nd mm, respectively. Verticlly, the MPAP group showed slight extrusion of the mxillry first molr ( mm), while the hedger group demonstrted significnt extrusion ( mm; P,.001). In ddition, both groups showed no significnt distl tipping of the mxillry first molr (P nd.993, respectively). However, univrte nlysis showed no significnt difference between the groups regrding dentl vribles (Tble 4). For the centrl incisor, the MPAP group showed significnt retrction, extrusion, nd lingul inclintion (P,.001), while the hedger group showed significnt extrusion (P,.001). Nevertheless, univrite nlysis showed no significnt difference between the groups regrding these vribles (Tble 4). Regrding soft tissue, in the MPAP group, the upper lip ws significntly retrcted ( mm; P,.001), nd the nsolbil ngle ws incresed 22.67u u, lthough not significntly. Likewise, in the hedger group, the chnge ws not significnt ( mm nd 0.18u u, respectively). Soft

6 662 SA AED, PARK, BAYOME, PARK, KIM, KOOK Tble 4. Comprison of Tretment Effects Between MPAP nd Hedger Groups MPAP Group (T1 T2) Hedger Group (T1 T2) 95% CI Vrible Men SE P Vlue b Men SE P Vlue b Lower Bound Upper Bound P Vlue c Skeletl SNA, u , SNB, u ANB, u , , Wits, mm , , Hvold, mm , Fcil ngle, u Pltl plne ngle, u Mndibulr plne ngle, u A-point to N perpendiculr, mm , A-point to TVL, mm , , B-point to TVL, mm , Mxillry length, mm Mndibulr length, mm , , Dentl First molr crown VRL, mm , First molr root VRL, mm , First molr cusp FH, mm , First molr root FH, mm , First molr FH ngle, u Centrl incisor crown VRL, mm , Centrl incisor root VRL, mm Centrl incisor crown FH, mm , , Centrl incisor root FH, mm , Centrl incisor FH ngle, u , Occlusl plne ngle, u IMPA, u Overjet, mm , , Overbite, mm , , Soft tissue Nsolbil ngle, u Mentolbil fold, u Upper lip to TVL, mm , Lower lip to TVL, mm Soft tissue pogonion to TVL, mm MPAP indictes modified pltl nchorge plte; TVL, true verticl line; VRL, verticl reference line; CI, confidence intervl for difference. Significnce level: P,.016 ccording to Bonferroni correction. b Pired t-test. c MANCOVA, djusted mens ccording to second molr eruption sttus. tissue vribles demonstrted no significnt difference between the groups (Tble 4). Tretment durtion showed no significnt difference between the MPAP ( months) nd hedger groups ( months). The survivl rte of the miniscrews ws 97.2%, with just three cses showing signs of soft tissue inflmmtion round the MPAP. DISCUSSION Distliztion of the mxillry molrs is often performed to gin spce or to correct Clss II dentl reltionships using TADs. MPAPs hve been developed to offer simple nd effective nonextrction pproch for distliztion. 23,24 Noncomplince pplinces for molr distliztion produced bout 71% molr distliztion nd 29% reciprocl nchorge loss. 7 However, TAD-nchored molr distlizing pplinces showed mm of distliztion of the mxillry first molrs without flring of nterior teeth. 26 Sr et l. 27 demonstrted 2.81 mm of first molr distliztion using skeletl nchorge. In greement, the mount of distliztion of the MPAP group in our study ws 3.1 mm, with 3.3 mm of incisor retrction. In ddition to the retrction of nteriors in the MPAP group, there ws extrusion nd lingul inclintion, while the hedger group showed only significnt extrusion. This might be due to differences between the two tretment strtegies. In the MPAP group, the

7 TREATMENT EFFECTS OF MPAP IN ADOLESCENTS 663 upper lip ws more protruded nd the nsolbil ngle ws smller thn tht of the hedger group, lthough this ws not sttisticlly significnt. Moreover, both groups showed.5-mm overjet. In the MPAP group, the overjet ws corrected through retrcting nd retroclining the upper incisors. On the other hnd, the upper lip position ws slightly better in the hedger group, which might hve been due to subjective difference in fcil profile preference between the two different clinicins. Therefore, the correction of the overjet ws ccomplished by proclintion of the mndibulr incisors while mintining the mxillry incisors in their sgittl position. Yu et l. 28 concluded tht MPAP showed bodily molr movement without incisor flring, while bucclly plced mini-implnts demonstrted distl tipping nd extrusion of molrs nd flring nd intrusion of incisors. Our study showed 3.06 mm of distliztion of the first molrs for the MPAP group with 1.5u distl tipping. This bodily movement might hve been becuse of the specil design of the MPAP pplince (Figure 1). In the hedger group, the distl movement ws 1.8 mm nd the tipping ws 0.82u mesilly. Previous studies showed 6.4 nd 3.9 mm of first molr distliztion using TAD-nchored pplinces, with distl tipping of 10.9u nd 8.8u, respectively. 13,14 Menwhile, Burhn 29 showed 5.5 mm of molr distliztion, 4.9u of distl tipping, nd 2.7 mm loss of nchorge with Frog pplince; however, when combined with hedger, the vlues were 5.9 mm, 1.25u, nd 0.9 mm, respectively, which incresed bodily distliztion with less nchorge loss. The MPAP nd hedger groups produced similr skeletl effects such s reduction of ANB nd Wits pprisl. In greement, Kirjvinen et l. 30 reported similr results of decresed ANB by 1.3u, using the cervicl hedger. Verticlly, the MPAP group showed slight extrusion of mxillry first molrs, while the hedger group demonstrted significnt extrusion. This might be becuse the cervicl hedger hs limited control over the downwrd growth of the mxill. Menwhile, the MPAPs usully result in intrusion of molrs. 22,28 However, in this study, the intrusion ws msked by the downwrd growth of the mxill, resulting in extrusion, yet less thn in the hedger group. The effect tht the eruption sttus of second molrs hs on distliztion is still controversil. Severl uthors hve reported miniml or no significnt effect on the first molr movement, 11,31 33 while others hve demonstrted tht the second molr eruption sttus might negtively ffect first molr movement Moreover, distl tipping of first molrs ws less in ptients with erupted second molrs. 37 In ddition, the first molr movement rte ws lmost two times greter before the eruption of second molrs. 34 In our study, the second molr eruption hd no significnt min effect on the comprisons between the groups; however, its effect on molr distliztion ws not evluted. A previous study showed tht the tooth bud might ct s fulcrum, resulting in n incresed degree of tipping of the molrs. 37 This study compred fixed nd removble pplinces to show tht MPAP could be considered for tretment of Clss II ptients. Therefore, it is recommended tht clinicins consider the ppliction of MPAP especilly in noncomplint Clss II ptients. CONCLUSIONS N The modified pltl nchorge plte showed significnt skeletl chnges on the mxill. However, this ws not significntly different from the hedger group. N Both MPAP nd hedger resulted in significnt distliztion of mxillry first molrs with no significnt difference between them. In ddition, both groups showed miniml distl tipping. REFERENCES 1. Kloehn SJ. Orthodontics force or persusion. Angle Orthod. 1953;23: Mnn KR, Mrshll SD, Qin F, Southrd KA, Southrd TE. Effect of mxillry nteroposterior position on profile esthetics in hedger-treted ptients. Am J Orthod Dentofcil Orthop. 2011;139: Osvldik-Trpl M, Droschl H. 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