Quantitative and perceived visual changes of the nasolabial fold following orthodontic retraction of lip protrusion

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1 Originl Article Quntittive nd perceived visul chnges of the nsolil fold following orthodontic retrction of lip protrusion Eui Seon Bek ; Soonshin Hwng ; Yoon Jeong Choi c ; Mi Ryung Roh d ; Tung Nguyen e ; Kyung-Ho Kim f, Chooryung J. Chung g,h ABSTRACT Ojectives: The ojectives of this study were to evlute the quntittive nd perceived visul chnges of the nsolil fold (NLF) fter mximum retrction in dults nd to determine its contriuting fctors. Mterils nd Methods: A totl of 39 dult women s cone-em computed tomogrphy imges were collected retrospectively nd divided into the retrction group (ge ) tht underwent mximum retrction following 4 premolr extrction nd the control group (ge ) with minor chnges of the incisors. Three-dimensionl morphologic chnges of hrd nd soft tissue including NLF were mesured y pre- nd posttretment cone-em computed tomogrphy. In ddition, perceived visul chnge of the NLF ws monitored using the modified Glol Aesthetic Improvement Scle. The influence of ge, initil severity of NLF, nd initil soft tissue thickness ws evluted. Results: Anterior retrction induced significnt chnges of the fcil soft tissue including the lips, periorl, nd the NLF when compred with the controls (,.01). erceived visul chnges of the NLF ws noted only in women younger thn ge 30 (,.05), with the odds rtio (95% confidence intervl) of 2.44 ( ), indicting greter possiility for improvement of NLF esthetics in young women of the retrction group when compred with the controls. Conclusions: Orthodontic retrction induced quntittive nd perceived visul chnges of the NLF. For dult women younger thn ge 30, the ppernce of the NLF improved fter mximum retrction despite the greter posterior chnge of the NLF. (Angle Orthod. 2018;88: ) KEY WORDS: Nsolil fold; Soft tissue; Orthodontic retrction; Lip protrusion; CBCT; Glol Aesthetic Improvement Scle INTRODUCTION The improvement of fcil esthetics s well s occlusion hs long een one of the most importnt Grdute Student, Deprtment of Orthodontics, Gngnm Severnce Hospitl, The Institute of Crniofcil Deformity, College of Dentistry, Yonsei University, Seoul, Kore. Assistnt rofessor, Deprtment of Orthodontics, Gngnm Severnce Hospitl, The Institute of Crniofcil Deformity, College of Dentistry, Yonsei University, Seoul, Kore. c Associte rofessor, Deprtment of Orthodontics, The Institute of Crniofcil Deformity, College of Dentistry, Yonsei University, Seoul, Kore. d Assistnt rofessor, Deprtment of Dermtology, Cutneous Biology Reserch Institute, Yonsei University, College of Medicine, Seoul, Kore. e Associte rofessor, Deprtment of Orthodontics, University of North Crolin School of Dentistry, Chpel Hill, NC, USA. f rofessor, Deprtment of Orthodontics, Gngnm Severnce Hospitl, The Institute of Crniofcil Deformity, College of Dentistry, Yonsei University, Seoul, Kore. tretment ojectives in dult orthodontics. Especilly for mlocclusions dignosed s imxillry or ilveolr protrusion, premolr extrction followed y mximum retrction of the nterior teeth is commonly ccepted s necessry tretment modlity regrdless of the reltively idel occlusion per se ecuse orthodontic retrction induces the drmtic improvement of the overll fcil esthetics. 1 g rofessor, Deprtment of Orthodontics, Gngnm Severnce Hospitl, Seoul, Kore. h Visiting Scholr, Deprtment of Orthodontics, University of North Crolin School of Dentistry, Chpel Hill, NC, USA. Corresponding Author: Chooryung J. Chung, DDS, hd, rofessor, Deprtment of Orthodontics, Gngnm Severnce Hospitl, 211 Eonjuro, Gngnm-gu, Seoul, , Kore (e-mil: crchung@yuhs.c) Accepted: Jnury Sumitted: Octoer ulished Online: Mrch 23, 2018 Ó 2018 y The EH Angle Eduction nd Reserch Foundtion, Inc. DOI: /

2 466 BAEK, HWANG, CHOI, ROH, NGUYEN, KIM, CHUNG Following orthodontic retrction, evident soft tissue chnges re induced in the midsgittl periorl regions, ut considerle mounts of chnges re lso extended to the prsgittl regions of the middle nd lower one-third of the fce such s the nsolil folds (NLFs). 2,3 NLFs originte from sgging of the skin, prominence of the uccl ft pd, nd muscle function nd chnges in the underlying one structure in conjunction with the ntomicl nd histologicl fetures. Together with the chnges in the lips, morphologicl or volumetric chnges in the NLFs re considered s the erliest nd distinctive signs of fcil ging ut, for the young popultion, thick cheek ft pd my reltively cuse the NLFs to exhiit concve ppernce s well. 4 Given tht orthodontic retrction induces overll dimensionl chnges of the periorl soft tissue, the morphologicl nd esthetic chnges of the NLFs re lso suspected. However, oth ojective nd sujective informtion regrding these chnges in the NLFs re limited in the literture. Thus, the ojectives of this study were to quntify the morphologic nd perceived chnges of the NLFs fter mximum retrction in dults nd to determine the contriuting fctors tht my influence the chnges of the NLFs. MATERIALS AND METHODS rticipnts This study ws pproved y the institutionl review ord of Gngnm Severnce Hospitl, Yonsei University. The ptients consisted of 39 women (18 yers) treted in the Deprtment of Orthodontics, Gngnm Severnce Hospitl, Yonsei University. The prticipnts who hd pre- nd posttretment cone-em computed tomogrphy (CBCT) imges were collected retrospectively nd divided into retrction group (n ¼ 22, ge rnge 18 45) nd the control group (n ¼ 17, ge rnge 18 36). The inclusion criteri for the retrction group were the following: skeletl clss I to clss II, dignosed s imxillry dentolveolr protrusion, treted following extrction of four premolrs, finished with more thn 4 mm of nterior-posterior chnge of the upper nd lower incisor tip when superimposed on the nterior crnil se. 5 Inclusion criteri for the control group were the following: skeletl clss I to clss II, within the norml rnge of lips reltive to Ricketts E-line, treted nonextrction, finished with less thn 1.5 mm of nterior-posterior chnge of the upper nd lower incisor tip. tients with fcil symmetry (.2 mm of Me devition) nd deformity were excluded (Tle 1). Dt Acquisition CBCT scns were tken using x Zenith 3D (Vtech, Seoul, Kore) y n experienced rdiologicl technologist. The ptients were instructed to stnd stright in mximum intercuspl position with light contct of the lips nd fce relxed. A scn cptured 632 slices, with exposure prmeters of 105 kv nd 5.4 mas, cquired for 24 seconds, with voxel size of 0.3 mm nd field of view of cm encompssing the fce, jws, nd entire crnil se. The otined DICOM dt were reconstructed into three-dimensionl (3D) imges using OnDemnd 3D softwre (Cyermed Co., Seoul, Kore). The pre- nd post-tretment CBCT dt were superimposed y utomtic voxel-y-voxel registrtion on stle structures of the nterior crnil se using the OnDemnd 3D fusion module. 5 Coordinte System nd Lndmrks On the superimposed 3D CBCT imges, the horizontl reference plne ws estlished prllel to the Frnkfort plne, pssing through nsion (N). The midsgittl verticl reference plne ws set ccording to the plne perpendiculr to the Frnkfort plne nd pssing through the N nd sion. 6 The coronl verticl reference plne ws set perpendiculr to the horizontl nd midsgittl verticl plnes, pssing through N. A Crtesin coordinte system ws used with N s the origin of coordinte system (0, 0, nd 0) throughout the x-y, x-z, nd y-z plnes to represent the xil, coronl, nd sgittl plnes, respectively. ositive coordinte vlues were indicted y vlues to the left, posterior, nd superior to the origin. Lndmrks were defined s shown in Tle 2. 7,8 Lndmrk positioning nd mesurements were performed on 3D volume rendering soft tissue surfce imges. Susequent djustment on multiplnr reconstructed two-dimensionl cross-sectionl imges ws performed. To mesure quntittive chnges of NLF res, four lndmrks oth on the deepest point of the left nd the right sides were defined long NLFs t the pretretment sunsle level (NLF1) nd 15-mm verticlly downwrd from the pretretment sunsle level (NFL2). Considering the verticl positionl chnge of sunsle etween pre- nd posttretment, NLF1 nd NLF2 on the posttretment imge were clirted on the x-z plne to the sme verticl level of pretretment in the superimposed imge (Figure 1). Clinicl Assessments of the NLFs The initil condition of the NLF ws ctegorized y the modified Wrinkle Severity Rting Scle (WSRS),

3 CHANGES OF NASOLABIAL FOLD FOLLOWING RETRACTION 467 Tle 1. Initil Chrcteristics of the rticipnts Chrcteristics Control Group, n ¼ 17; Men 6 SD Retrction Group, n ¼ 22; Men 6 SD Vlue Age, yers NS ANB, NS U1 to A-og, mm ,.001 L1 to A-og, mm ,.001 U1 to SN, IMA, NS Upper lip to E-line, mm ,.001 Lower lip to E-line, mm ,.001 Tretment durtion, months ANB indictes A-point-Nsion-B-point ngle; U1, upper incisl tip; A-og, A-point to pogonion line; L1, lower incisl tip; SN, sell-nsion line; IMA, lower incisor mndiulr plne ngle; E-line, Ricketts E-line; SD, stndrd devition; NS, nonsignificnt. NS indictes..05. specific vlidted scle for quntifying fcil folds 9 using initil CBCT soft tissue imges y one investigtor. The scoring of fold severity ws sed on visul ssessment of the length nd pprent depth of the NLF without reference to seline. Modified WSRS uses the following three-point scle: 1 ¼ sent, no visile NLF; 2 ¼ mild, shllow ut visile NLF with slight indenttion with minor fcil feture; 3 ¼ Tle 2. Definitions of Lndmrks Lndmrk Arevition Definition Skeletl A-point A The point of mximum concvity in the midline of the lveolr process of the mxill B-point B The point of mximum concvity in the midline of the lveolr process of the mndile ogonion og The most nterior midpoint of the chin on the outline of the mndiulr symphysis Menton Me The most inferior midpoint of the chin on the outline of the mndiulr symphysis Dentl Upper incisor incisl tip Isi The midpoint of the tip of the crown of ech upper centrl incisor Upper incisl root pex Is The tip of the root pex of ech upper centrl incisor Lower incisor incisl tip Iii The midpoint of the tip of the crown of ech lower centrl incisor Lower incisl root pex Ii The tip of the root pex of ech lower centrl incisor Midfcil soft tissue Cheek point Ck The point t intersection of verticl projection from pretretment exocnthion nd horizontl projection from pretretment lrcurvture Soft tissue nsion N The midpoint on the soft tissue contour of the se of the nsl root t the level of the frontonsl suture eriorl soft tissue Sunsle Sn The midpoint on the nsolil soft tissue contour etween the columell crest nd the upper lip Soft tissue A-point A The most nterior concve point etween sunsle nd the nterior point of the upper lip Soft tissue B-point B The most posterior midpoint on the liomentl soft tissue contour tht defines the order etween the lower lip nd the chin Soft tissue pogonion og The most nterior midpoint of the chin Soft tissue menton Me The most inferior midpoint on the soft tissue contour of the chin, locted t verticl projection from menton on the soft tissue Lip Christ philitri Cph The point t ech crossing of the vermilion line nd the elevted mrgin of the philtrum Lile superius Ls The most nterior midpoint of the vermilion line of the upper lip Upper lip point UL The most nterior midpoint of upper lip Stomion superius STMs The midpoint of the lower order of the upper lip Stomion Inferius STMi The midpoint of the upper order of the lower lip Lower lip point LL The most nterior midpoint of lower lip Lile inferius Li The most nterior midpoint of the vermilion line of the lower lip Cheilion Ch The point locted t ech lil comissure t the most lterl intersection of upper nd lower lip Nsolil folds Nsolil fold 1 NLF1 The deepest point on nsolil fold t the horizontl level of initil sunsle Nsolil fold 2 NLF2 The deepest point on nsolil fold t horizontl level of 15mm elow initil sunsle Left nd right lndmrks used.

4 468 BAEK, HWANG, CHOI, ROH, NGUYEN, KIM, CHUNG Figure 1. Three-dimensionl cephlometric lndmrks nd mesurements. (A) Three-dimensionl fcil soft tissue lndmrks. Bsic upper lip thickness is defined s the liner distnce from 3 mm elow A-point to sunsle. (B) Comprison of lndmrks on the superimposed cone-em computed tomogrphy imges. Drk grey, pretretment; white, posttretment. moderte, modertely deep NLF with cler fcil feture visile t norml. Clinicl visul chnge of the NLF ws evluted using the modified Glol Aesthetic Improvement Scle (GAIS), reproducile grding system sed on the visul sujective ssessment of the length nd pprent depth of the fold 10 y six experienced specilists: two dermtologists, one plstic surgeon, nd three orthodontists with. 7 yers of clinicl experience. For the evlution templte, pir of prend posttretment reconstructed soft tissue surfce CBCT imges were presented on one slide, representing either frontl or three-qurter views from the left side (Figure 2). The modified GAIS uses the following three-point scle: 1 ¼ improved, ovious improvement in ppernce from the initil condition; 0 ¼ no chnge, the ppernce is essentilly the sme s the initil condition; 1 ¼ worsened, the ppernce is worse thn the initil condition. The templtes long with dditionl 20 duplicted sets were presented to evlute introserver consistency. Assessments were conducted independently nd the investigtors were not informed of the tretment regimen. GAIS scores drwn y six specilists were verged per prticipnt for the sttisticl evlution. intervl ). The smple size ws clculted with power of 80%. 11 The differences etween pre- nd posttretment were nlyzed y pired t-test, nd the comprisons etween the groups were performed using independent 2-smple t-tests with flse discovery rte method. To determine ge effect, independent t-tests with the flse discovery rte method nd chi-squre tests were used. To identify correltions mong quntittive chnges of NLFs, erson s correltion ws nlyzed. Generlized estimting equtions were used to compre distriution of the GAIS score, nd odds rtio ws clculted. All of the mesurements were sttisticlly clculted using SAS version 9.3(SAS Institute, Cry, N.C.). Sttisticl Anlysis The positioning of lndmrks ws repeted for 10 rndomly selected CBCTs y the sme opertor t 2- week intervls. Averged intrclss correltion coefficients were nd the Dhlerg s method errors were, 1 mm (rnge of ). The intrclss correltion coefficient for introserver reliility of the WSRS ws Weighted kpp coefficients of GAIS rnged from 0.36 to 0.71 (men 0.65, 95% confidence Figure 2. re- nd posttretment imge templtes used for the modified Glol Aesthetic Improvement Scle.

5 CHANGES OF NASOLABIAL FOLD FOLLOWING RETRACTION 469 RESULTS Three-Dimensionl Chnges in the NLFs Following Anterior Retrction The retrction group showed sttisticlly significnt chnges in the sgittl plne xis for the dentl (,.01), periorl nd lip soft tissue lndmrks (,.05). NLF1 nd NLF2 indicted significnt posterior movement in the retrction group y nd mm, respectively, which ws significntly different when compred with the control group (,.001). Verticl chnges (xil xis) were more prominent in the retrction group for lndmrks representing medil soft tissue in the periorl (soft tissue A point) nd lip res (christ philtri (Cph), lilis superius (Ls), upper lip point (UL), nd lilis inferius (Li)) thn prsgittl soft tissue such s cheilion (Ch), which showed no significnt verticl chnges in oth groups (,.05). The upper lip vermilion order (Ls nd Cph) nd UL moved downwrd, while the Li moved upwrd only in the retrction group nd not in the control group (,.01; Tle 3). Clinicl Fctors Associted With the Quntittive Chnges of the NLFs Intrinsic fctors, such s ge, 12 initil soft tissue thickness, 13 initil severity of NLFs (WRSR), 14 or chnges of the surrounding ft pd 4 my directly or indirectly influence the overll chnges of the NLFs. Accordingly, the influences of these cndidte fctors long with the quntittive chnges of NLFs were evluted. Given tht morphologic profile chnge occurs in spurts from the second to the third decdes especilly in women, 15 the prticipnts were suctegorized ccording to ge sugroups of younger thn ge 30 (, 30 yers) nd equl or older thn ge 30 (30 yers). The initil sic upper lip thickness ws significntly greter in the retrction group when compred with the control group (,.05), ut the distriution pttern of initil WSRS score ws comprle etween sugroups. Following the posterior movement of the nterior teeth nd the lips, significnt posterior movement of the cheek (Ck), NLF1, nd NLF2 ws noted in the sugroup of ptients younger thn ge 30 when compred with the corresponding control group (,.05). However, no significnt chnges were noted in the Ck, NLF1, nd NLF 2 for sugroup of ptients ged equl to or older thn the ge of 30 when compred with the corresponding controls (Tle 4). For the sugroup of ptients younger thn ge 30, the nterior-posterior quntittive chnges long Y xis (Dy) of NLFs (NLF1 Dy nd NLF2 Dy) showed moderte to high positive correltion with hrd (upper incisor incisl tip (Isi Dy) nd lower incisor incisl tip (Iii Dy)) nd soft tissue (UL Dy, lower lip point (LL Dy), Ch Dy nd Ck Dy) chnges following retrction (,.001, r ¼ ). However, for the sugroup of ptients equl to or older thn ge 30, NLF1 Dy or NLF2 Dy showed limited correltion only with lip soft tissue (UL Dy, LLDy nd ChDy; r ¼ ,,.05, dt not shown). Clinicl Visul Chnges of NLFs After Orthodontic Tretment GAIS The mjority of GAIS scores were within no-chnge criteri (GAIS 0), followed y improved (GAIS 1) nd worsened (GAIS 1) criteri, ut higher verged GAIS score ws noted in the retrction group of ptients younger thn ge 30 when compred with the corresponding control group (,.05). Accordingly, significnt difference in ech score ctegory distriution ws found only etween the retrction group of women younger thn ge 30 nd the corresponding control group (,.01). For the sugroups of ptients younger thn ge 30, the odds rtio (95% CI) ws 2.44 ( ), indicting tht the possiility for improvement of GAIS score in the retrction group ws 2.44 times greter thn the control group. For women equl to or older thn ge 30, no sttisticlly significnt difference ws noted for GAIS etween the retrction nd control groups (Tle 5, Figure 3). DISCUSSION Mximum retrction induces quntittive nd perceived visul chnges of the NLFs. Quntittively, NLFs moved posteriorly long with the periorl soft tissue following nterior retrction, nd the mount of chnge positively correlted with the mount of chnge of surrounding tissue, especilly in young women younger thn ge 30. The posterior movement of the deepest re of the NLFs my imply deepening of the folds tht my cuse unfvorle effects in fcil ppernce. Contrry to preconceived concerns, posterior chnges in the NLFs did not worsen ut, rther, improved the ppernce of NLFs in young women. Antomiclly, the medil side of NLFs is tightly ssocited with the muscle fiers nd fixed to the mxill y ligments, wheres the lterl side of the NFLs contins reltively lrge mount of sucutneous ft tht is very moile nd redily undergoes oesity- nd ge-relted chnges of dipose tissue or decrese of derml elsticity. 12,14 Cliniclly, chnges in the NLFs re clssified into skin sgging type, mnifested s deep furrow tht disppers in supine position; one retrusion type, mnifested s concve depression due to the retrusion of one round the

6 470 BAEK, HWANG, CHOI, ROH, NGUYEN, KIM, CHUNG Tle 3. Three-Dimensionl Hrd nd Soft Tissue Chnges, mm Lndmrk Control Group, n ¼ 17 Dx Dy Dz Men 6 SD Vlue * Men 6 SD Vlue * Men 6 SD Skeletl A NS NS NS B NS NS NS og NS NS NS Me NS NS NS Dentl Isi NS NS NS Is NS NS NS Iii NS NS NS Ii NS NS NS Midfcil soft tissue Ck NS NS NS N NS NS NS eriorl soft tissue Sn NS NS NS A NS NS NS B NS NS NS og NS NS NS Me NS NS NS Lip Cph NS NS NS Ls NS NS NS UL NS NS NS STMs NS NS NS STMi NS NS NS LL NS NS NS Li NS NS NS Ch NS NS NS Nsolil folds NLF NS NS NS NLF NS NS NS Vlue * Dx, chnges long X xis; Dy, chnges long Y xis; Dz, chnges long Z xis; A, A-point; B, B-point; og, pogonion; Me, menton; Isi, upper incisor incisl tip; Is, upper incisor root pex; Iii, lower incisor incisl tip; Ii, lower incisor root pex; Ck, cheek; N, soft tissue nsion; Sn, sunsle; A, soft tissue A-point; B, soft tissue B-point; og, soft tissue pogonion; Me, soft tissue menton; Cph, christ philtri; Ls, lilis superius; UL, upper lip point; STMs, stomion superius; STMi, stomion inferius; LL, lower lip point; Li, lilis inferius; Ch, cheilion; NLF, nsolil fold; SD, stndrd devition. NS indictes..05. * vlue, pired t-test. vlue, independent 2-smple t-test with flse discovery rte method etween the control group nd the retrction group. pyriform perture; musculr type, mnifested s deep furrow in oth upright nd supine position due to the high tension resulting from muscle contrction; nd cheek ft pd type, mnifested s rod concve depression due to the reltively thick soft tissue mss on the lterl side of the NLFs. 4 Given tht skin elsticity nd soft tissue thickness decreses with redistriution of sucutneous dipose tissue with ging, 12,16 it ws initilly hypothesized tht greter perceived chnges my e noted in the older ge group. The overll chnges of the upper lips reltive to incisor movement ws 46% (14% 92%), similr to previous report, 2 with women older thn ge 30 exhiiting greter lip chnges thn the younger sugroup (53% vs 38%), s expected. However, the current prticipnts were composed of reltively young dults, where skin sgging type is reportedly rre to strt with, 4 nd chnges of ony structure similr to the one retrusion type were not noted. Thus, unlike the conventionl physiologic chnges of the NLFs due to mjor volumetric chnges nd sgging of the lterl side of the fold, the mjority of our ptients with notle NLF initilly my e clssified s the cheek ft type. Along with the ctive reorienttion of oth the soft nd hrd tissue on the medil side of the NLFs (ie, the periorl region) induced y orthodontic retrction tht overwhelmed the quntittive posterior chnges of the NLFs per se, the comintion of posterior chnge of the cheek region tht ws especilly noted in the young women younger thn ge 30 my hve lso contriuted to the overll esthetic improvement of the NLF. Soft tissue, especilly the cheek ft pd, is lso influenced y chnges in ody weight. Due to the retrospective nture of this study, only the sole effect of

7 CHANGES OF NASOLABIAL FOLD FOLLOWING RETRACTION 471 Tle 3. Extended Retrction Group, n ¼ 22 Comprison Dx Dy Dz Vlue Vlue Vlue Men 6 SD Vlue * Men 6 SD Vlue * Men 6 SD Vlue * Dx Dy Dz NS NS NS NS NS NS NS NS NS NS NS NS NS NS NS NS NS NS NS NS NS NS NS NS , NS.039,.001 NS NS , NS NS,.001 NS NS , NS NS,.001 NS NS , NS NS,.001 NS NS NS NS NS NS NS NS NS NS NS NS NS NS NS NS NS , ,.001 NS,.001, NS , NS.018 NS NS NS NS NS NS NS NS NS NS NS NS NS NS , ,.001 NS,.001, NS , ,.001 NS,.002, NS , ,.001 NS,.003, NS , NS NS,.004 NS NS , NS NS,.005 NS NS , NS NS,.006 NS NS , NS, NS , NS NS,.008 NS NS , NS NS,.009 NS NS , NS NS,.010 NS Tle 4. Initil Condition of the Nsolil Fold (WSRS) nd Soft Tissue Chnges According to Age Soft Tissue rmeters Control Group, n ¼ 13; Men 6 SD,30 Yers, n ¼ Yers, n ¼ 11 Retrction Group, n ¼ 15; Men 6 SD Vlue Control Group, n ¼ 4; Men 6 SD Retrction Group, n ¼ 7; Men 6 SD Vlue Initil upper lip thickness ,.001* * WSRS score c % (7) 46.7% (7) NS 25.0% (1) 0.0% (0) NS % (6) 40.0% (6) 75% (3) 71.4% (5) 3 0.0% (0) 13.3% (2) 0.0% (0) 28.6% (2) Totl 100% (13) 100% (15) 100% (4) 100% (7) Isi Dy ,.001* ,.001* Iii Dy ,.001* * UL Dy ,.001* ,.001* LL Dy ,.001* ,.001* Ch Dy ,.001* ,.001* Ck Dy * NS* NLF1 Dy ,.001* NS* NLF2 Dy ,.001* NS* WSRS, Wrinkle Severity Rting Scle; Isi, upper incisor incisl tip; Dy, chnges long Y xis; Iii, lower incisor incisl tip; UL, upper lip point; LL, lower lip point; Ch, cheilion; NLF, nsolil fold; SD, stndrd devition. NS indictes..05. c Dt presented s % (n). * vlue, independent 2-smple t-test with flse discovery rte method. vlue, chi-squre test (Fisher exct test).

8 472 BAEK, HWANG, CHOI, ROH, NGUYEN, KIM, CHUNG Tle 5. GAIS Scores nd Distriution According to Age GAIS Control Group, n ¼ 13; Men 6 SD,30 Yers, n ¼ Yers, n ¼ 11 Retrction Group, n ¼ 15; Men 6 SD Vlue Control Group, n ¼ 4; Men 6 SD Retrction Group, n ¼ 7; Men 6 SD Vlue Averged GAIS score * NS* GAIS score c % (35) 42.8% (77) % (12) 33.3% (28) NS % (107) 52.2% (94) 62.5% (30) 33.3% (28) % (14) 5% (9) 12.5% (6) 33.3% (28) Totl 100% (156) 100% (180) 100% (48) 100% (84) OR (95% CI) 2.44 ( ) NS GAIS, Glol Aesthetic Improvement Scle; SD, stndrd devition; OR, odds rtio; CI, confidence intervl. NS indictes..05. c Dt presented s % (n). * vlue, independent 2-smple t-test with flse discovery rte method. vlue, generlized estimting equtions. tooth movement on NLF ws determined. Further investigtions including chnges in ody mss would e eneficil. Lndmrks long the midline reportedly exhiited the most prominent posterior chnges, nd the chnges grdully decresed to the outer re fter nterior retrction. 2 Accordingly, similr ut more prominent differences in midsgittl vs prsgittl soft tissue were noted in the verticl dimension. The fcil ging process involves verticl chnges of soft tissue: increse of prolium, decrese of vermilion height midsgittlly or descending mouth corners, or sgging cheeks prsgittlly. 17 Among these chnges, the erliest signs of ging pper in the prsgittl re surrounding the eye nd the NLFs rther thn the midsgittl re. 18 Although the verticl chnges of the NLFs could not e detected sed on lndmrk evlution, it is noteworthy tht mjor verticl soft tissue chnges following retrction were limited in the midsgittl re unlike the physiologic nture of fcil ging. Due to the complicted structurl fetures of NFL long with the limited nture of quntittive methods to mesure the chnges in soft tissue, only few studies hve reported ojective quntifiction of NLFs. 19 The use of CBCT imges enled efficient 3D hrd nd soft tissue quntifiction, nd the 3D superimposition techniques using the crnil se llowed dditionl djustment for precise soft tissue lndmrk positioning. 5 CBCT imges were lso pplied s templtes for sujective GAIS scoring. According to the pilot study, GAIS results were highly influenced y lighting conditions of the clinicl photos, presented fcil ngles, fcil mke-up, nd the exminer s field of expertise. The ppliction of reconstructed CBCT fcil imges without color nd texture ws effective in voiding the influence of these externl fetures nd lso enled the stndrdized presenttion of frontl nd three-qurter fcil views. CONCLUSIONS Orthodontic retrction induced quntittive nd perceived chnges of the NLFs. For dult women younger thn ge 30, the ppernce of the NLFs significntly improved fter Figure 3. Representtive pre- nd posttretment imges indicting the chnges of the nsolil folds using the modified Glol Aesthetic Improvement Scle. (A) Age 19, posterior chnges in the upper incisors long Y xis (Isi Dy) ws 8.1mm, mjority scored Glol Aesthetic Improvement Scle 1, improved. (B) Age 23, Isi Dy ws 8.3mm, mjority scored Glol Aesthetic Improvement Scle 0, no chnge. (C) Age 41, Isi Dy ws 6.8mm, mjority scored GAIS -1, worsened.

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