Skeletal and Soft Tissue Point A and B Changes Following Orthodontic Treatment of Nepalese Class I Bimaxillary Protrusive Patients

Transcription

1 Originl Article Skeletl nd Soft Tissue Point A nd B Chnges Following Orthodontic Tretment of Neplese Clss I Bimxillry Protrusive Ptients Jgn Nth Shrm ABSTRACT Objectives: To test the hypothesis tht there is no correltion in the interreltionships of skeletl nd soft tissue points A nd B with nterior teeth retrction. Mterils nd Methods: Thirty dult Clss I bimxillry protrusion ptients treted with predjusted pplinces fter first premolr extrction were included. Pretretment nd posttretment vribles were compred using pired t-test, nd the reltionship of soft nd hrd tissue vribles ws studied using Person correltion coefficient nd liner regression eqution. Results: Men point A nd soft tissue point A (sa) were retrcted 2.7 mm (P,.001) nd 1.7 mm (P,.001), nd men point B nd soft tissue point B (sb) were retrcted 2.1 mm (P,.001) nd 1.2 mm (P,.001), respectively. Men rtio of retrction of point A with sa nd point B with sb ws 1.5:1 nd 1.7:1, respectively. A significnt degree of correltion existed between retrction of point A nd soft tissue point A (r , P,.01) nd point B nd soft tissue point B (r , P,.01). Liner regression nlysis used to predict the chnges in sa nd sb showed significnt reltionship between point A nd sa (r , F , R , P,.001) nd point B nd sb (r , F , R , P,.001). Decreses in hrd nd soft tissue convexity were due to the retrction of the skeletl nd soft tissue points A nd B in ddition to the lips retrction. Conclusions: The hypothesis is rejected. Retrction of skeletl point A nd B led to retrction of sa nd sb under controlled root positions. Nerly proportionte chnges existed in the skeletl points nd overlying corresponding soft tissue points. (Angle Orthod 2010;80:91 96.) KEY WORDS: Point A; Point B; Soft tissue point A; Soft tissue point B; Bimxillry protrusion INTRODUCTION Dentolveolr flring of the nterior teeth with resultnt protrusion of lips nd convexity of the fce re unique fetures of bimxillry protrusion. Protrusive lips nd convex fcil profile usully result in poor fcil esthetics becuse of the forwrdly plced dentolveolr segments. Becuse of poor fcil esthetics nd the negtive perception of protrusive dentition nd lips in society, most ptients with bimxillry protrusion seek orthodontic tretment to reduce the protrusive lips. 1 Thus, the ptient, despite Associte Professor, Deprtment of Orthodontics, College of Dentl Surgery, B.P. Koirl Institute of Helth Sciences, Dhrn, Nepl. Corresponding uthor: Dr Jgn Nth Shrm, Associte Professor nd Hed, Deprtment of Orthodontics, College of Dentl Surgery, B.P. Koirl Institute of Helth Sciences, Dhrn, Nepl (e-mil: dr.jnshrm@yhoo.com) Accepted: My Submitted: Jnury G 2010 by The EH Angle Eduction nd Reserch Foundtion, Inc. hving Clss I norml occlusion nd meeting the criteri of Andrew s keys to norml occlusion, still wishes to undergo n orthodontic tretment tht involves extrction of first premolrs to improve the fcil esthetics. Tretment of these cses involves bckwrd movement of nterior teeth with certin mount of uprighting of the incisors to correct excessive proclintion so tht strighter profile is chieved. Since the objective of treting bimxillry protrusion cses is to chieve n estheticlly superior profile nd hrmonious lip reltionship, it is importnt to study the chnges in reltionship of soft tissues to skeletl nd dentl structures tht ctully define the tretment outcome with orthodontic tooth movement. 2 Soft tissue nlyses by Holdwy, 3 Ricketts, 4 nd Burstone 5 hve contributed gretly to the fundmentl literture on the soft tissue reltionship with dentoskeletl structures. Reidel 6 stressed tht the soft tissue profile is closely relted to the skeletl nd dentl structures. Subtelny 7 indicted tht not ll prts of soft tissue profile directly follow the underlying skeletl profile. Burstone 5 suggested tht direct reltionship DOI: /

2 92 SHARMA my not lwys exist becuse of vrition in the thickness of the soft tissue covering the skeletl fce. 8 Bimxillry protrusion is commonly seen mlocclusion in estern Nepl. However, in Clss I bimxillry protrusion cses treted with first premolr extrction, pucity of literture exists regrding the reltionship of skeletl point A nd B with soft tissue point A (sa) nd B (sb) following orthodontic tretment in the indexed literture. Thus, this study ws undertken to relte the skeletl point A nd B chnges with the soft tissue points A nd B of Neplese Clss I bimxillry protrusion ptients treted with extrction nd fixed mechnotherpy so tht clinicin s ttention is drwn more towrds the picl bses nd the tooth pices thn the dily clinicl scenrio. The im of this study ws to test the hypothesis tht there is no correltion in the interreltionships of skeletl nd soft tissue points A nd B with nterior tooth retrction. MATERIALS AND METHODS Pretretment nd posttretment lterl cephlogrms of 30 dults hving Clss I bimxillry protrusion (15 girls, 15 boys) of men ge 18.4 yers, treted t the Deprtment of Orthodontics, College of Dentl Surgery, B.P. Koirl Institute of Helth Sciences were selected for this study. A written consent ws obtined before tretment fter ptients greed to the tretment plnning. This study ws pproved nd certified for its completion by the reserch committee of the B.P. Koirl Institute of Helth Sciences, Dhrn, Nepl. Smple selection criteri included: (1) Minimum ge 16 yers (2) Clss I first molr, cnine, nd premolr reltionship (3) Well ligned rches with no or miniml crowding (4) Protrusive upper nd lower lips (5) Pre nd post rdiogrphs with good hrd nd soft tissue outlines nd teeth in full occlusion, lips resting in nturl position. (6) All pretretment nd posttretment cephlogrms were tken from the sme mchine in the stndrd position by the sme opertor. All ptients were treted with inch Roth, predjusted pplinces fter extrction of first premolrs. All ptients were treted with mximum nchorge mechnics using pltl nd lingul rches or second molrs bnding or hedgers, depending upon the ptient complince. Mild pltl root torque in the upper rch nd lingul root torque in the lower rch were incorported in the incisor retrction wire to prevent lbil movement of the roots nd compenste for ny wire ply with the brckets. Since ll ptients hd pssed their 16th birthdy, it ws presumed tht the influence of growth on point A nd B chnges would be cliniclly insignificnt nd hve miniml effects on the tretment results. Posttretment rdiogrphs were tken fter removl of fixed pplinces. A constructed Frnkfort horizontl (FH) plne, drwn t n inferior ngle of 7 degrees to SN plne through point S, ws referred to s modified plne nd denoted by FH. Frnkfort horizontl perpendiculr ws constructed perpendiculr to the FH plne through point S nd denoted by FHp. The liner mesurements were done from FHp plne to skeletl nd soft tissue points A nd B (Figure 1, Tble 1). A mximum of four cephlogrms per dy were nlyzed. Liner prmeters were mesured with digitl vernier cliper nd ngulr prmeters with protrctor, which recorded up to 0.01 mm nd 0.5 degrees, respectively. The dt were entered in Microsoft Excel nd mster file ws creted in the spredsheet. Descriptive sttistics for men, medin, mode, stndrd devition, rnge, nd frequencies were clculted using the SPSS progrm version 11.5 (SPSS Inc, Chicgo, Ill). The cephlometric vlues of pretretment nd posttretment cephlogrms were evluted using pired t-test becuse the distribution of the dt ws pproximtely norml. Independent t-test ws used to see ny sexul differences in the outcome vribles. P,.05 ws considered significnt in the study. A liner regression eqution model to predict the chnges in the soft tissue points A nd B ws clculted using the formul: Y 5 + bx (where Y 5 dependent vrible, sa or sb, nd X 5 independent vrible, point A or B). For the purpose of testing the intr-investigtor error, 20 cephlogrms were retrced fter 8 weeks by the sme opertor. The trcings were nlyzed using pired t-test nd then Lin s concordnce method 9 for ny significnt difference between the two trcings. RESULTS No sttisticlly significnt differences were found between the observtions mde t two different times for the purpose of error testing using the pired t-test nd Lin s concordnce coefficient (Tble 2). Men ge ws 18.4 yers (rnge yers) t the strt of tretment. No sttisticlly significnt sexul differences were noted between the mle nd femle smples when compred for ech vrible using independent t- test. Upon incisor retrction, the men point A retrcted by 2.7 mm (P,.001) nd men sa retrcted by 1.7 mm (P, 0.001). Similrly, the point B retrcted by

3 SKELETAL AND SOFT TISSUE POINT A AND B 93 Figure 1. Cephlometric lndmrks, mesurements, nd reference plnes. (1) AFHp. (2) BFHp. (3) ssfhp. (4) sifhp. (5) SNA. (6) SNB. (7) ANB. (8) IIA. (9) IMPA. (10) U1SN. (11) SN-Go-Gn. (12) TUIFHp. (13) AUIFHp. (14) TLIFHp. (15) ALIFHp. (16) lsfhp. (17) lifhp. 2.1 mm (P,.001) nd sb retrcted by 1.2 mm (P,.001). The Person correltion coefficient (r) for A nd sa ws (P,.001) nd tht of point B nd sb ws (P,.001), showing sttisticlly significnt reltionship between these points. Liner regression nlysis used to predict the chnges in sa nd sb showed significnt reltionship between point A nd sa (r , F , P,.001). The coefficient of determintion R 2 ws Similrly for point B nd sb, the reltionship ws significnt (r , F , P,.001). The coefficient of determintion R 2 ws Angle SNA retrcted by 2.3 degrees nd ngle SNB retrcted by 1.9 degrees. The ANB ngle nd the Tble 1. Cephlometric Mesurements Used Vrible Description AFHp Horizontl distnce in mm from point A to constructed FH plne verticl. BFHp Horizontl distnce in mm from point B to constructed FH plne verticl. ssfhp Horizontl distnce in mm from soft tissue point A to constructed FH plne verticl. sifhp Horizontl distnce in mm from soft tissue point B to constructed FH plne verticl. SNA Angle between SN plne nd point A. SNB Angle between SN plne nd point B. ANB Angle between point A nd B t nsion. IIA Angle between the long xis of upper nd lower incisors. IMPA Angle between the mndibulr plne nd long xis of lower incisors. U1SN Angle between long xis of upper incisor nd SN plne. SN-Go-Gn Angle between mndibulr plne nd SN plne. TUIFHp Horizontl distnce in mm from the tip of the upper incisor crown to constructed FH plne verticl. AUIFHP Horizontl distnce in mm from the pex of the upper incisor to constructed FH plne verticl. TLIFHp Horizontl distnce in mm from the tip of the lower incisor crown to constructed FH plne verticl. ALIFHp Horizontl distnce in mm from the pex of the lower incisor root to constructed FH plne verticl. lsfhp Horizontl distnce in mm from the upper lip point to constructed FH plne verticl. lifhp Horizontl distnce in mm from the lower lip point to constructed FH plne verticl.

4 94 SHARMA Tble 2. Summry Tble for the Error of Study Anlyses (n 5 20) Vrible Lin s Concordnce Correltion Pc Pired t-test P vlue AFHp BFHp ssfhp sifhp SNA SNB ANB IIA IMPA U1SN SN-Go-Gn TUIFHp AUIFHp TLIFHp ALIFHp lsfhp lifhp mndibulr plne ngle (SN-Go-Gn) did not show ny significnt chnges. The men interincisl ngle incresed from degrees to degrees. The IMPA decresed from degrees to 94.1 degrees. The men posttretment U1 to SN ngle ws degrees. The tip of the upper incisor retrcted by 6.5 mm nd the tip of the lower incisor retrcted by 6.1 mm. Apices of upper nd lower incisors showed 1.2 mm nd 1.1 mm retrction following tretment. The upper nd lower lips retrcted t ls nd li by 3.7 mm nd 3.6 mm, respectively. The chnges in the bove prmeters were sttisticlly significnt (Tbles 3 through 5). The detrimentl effects of orthodontic tretment in the periodontium were miniml fter tretment except for mild blunting of the root pices in three cses under study. Tble 3. Pretretment Cephlometric Redings (n 5 30) Vrible Men SD Minimum Mximum AFHp BFHp ssfhp sifhp SNA SNB ANB IIA IMPA U1SN SN-Go-Gn TUIFHp AUIFHp TLIFHp ALIFHp lsfhp lifhp Angulr mesurements re in degrees nd liner mesurements re in millimeters. Tble 4. Posttretment Cephlometric Redings (n 5 30) Vrible Men SD Minimum Mximum AFHp BFHp ssfhp sifhp SNA SNB ANB IIA IMPA U1SN SN-Go-Gn TUIFHp AUIFHp TLIFHp ALIFHp lsfhp lifhp Angulr mesurements re in degrees nd liner mesurements re in millimeters. DISCUSSION In the present study, there ws significnt reltionship between retrction of skeletl point A (A) nd soft tissue point A (sa) following incisor retrction. The skeletl point A retrcted 2.7 mm (P,.001) nd soft tissue point A retrcted 1.7 mm (P,.001), estblishing rtio of 1.5:1 (r , P,.001). Skeletl point B retrcted 2.1 mm (P,.001) nd soft tissue point B retrcted 1.2 mm (P,.001), estblishing rtio of 1.7:1 (r , P,.001). Liner regression nlysis used to predict the chnges in sa nd sb showed significnt reltionship between point A nd sa (r , F , R 2 5 Tble 5. Men Cephlometric Chnges After Tretment (n 5 30) Vrible Men Chnges (Post-Pre) SD P vlue Sig AFHp *** BFHp *** ssfhp *** sifhp *** SNA *** SNB *** ANB NS IIA *** IMPA *** U1SN *** SN-Go-Gn NS TUIFHp *** AUIFHp * TLIFHp *** ALIFHp * lsfhp *** lifhp *** Angulr mesurements re in degrees nd liner mesurements re in millimeters. * P,.05; ** P,.01; *** P,.001. Sig indictes significnce; NS, not significnt.

5 SKELETAL AND SOFT TISSUE POINT A AND B 95 Figure 2. Men chnges in point A, soft tissue A, point B, nd soft tissue point B fter tretment. 0.29, P,.001). Similrly for point B nd sb, the reltionship ws significnt (r , F , R , P,.001). The sttisticlly significnt correltion between these points indicted tht with the bckwrd movement of the skeletl points A nd B, the soft tissue overlying these osseous points followed them, thus contributing to chnges in the lip positions t the bses (Figures 2 through 4). The upper lip response ws slightly higher when compred with the lower lip. This finding ws slightly different from the findings of LMstr, 10 where skeletl point A moved bck by 2.34 mm, soft tissue point A moved bck by 1.75 mm, skeletl point B moved bck by 1.89 mm, nd soft tissue point B moved bck by 1.73 mm. Thus, the rtio for the chnges of skeletl point A to soft tissue point A in his study in Clss II division 1 mlocclusion ws 1.4:1 (r , P,.001) nd tht of point B nd soft tissue point B ws 1.09:1 (r , P,.001). The difference could be relted to the difference in the mount of tooth movement in the mxill nd mndible in Clss II division 1 cses unlike Clss I bimxillry protrusion cses in the present study where they ll were high nchorge cses for both rches. Roos 11 in Clss II mlocclusion found the rtio of point A nd point B retrction to corresponding soft tissue point A nd B retrction to be 1:1.4 (r ) nd 1.2:1 (r ), respectively. Bimxillry protrusion cses generlly hve perfectly good occlusion. Ptients re undergoing orthodontic tretment solely for the correction of protrusive profile nd to improve the fcil esthetics. The clinicl relevnce of this study is tht the clinicins must position the incisors in the most esthetic position by initil up-righting nd some bodily movement. Thus, they must be cutious to prevent the Figure 3. Point A nd soft tissue point A chnges (n 5 30).

6 96 SHARMA Figure 4. Point B nd soft tissue point B chnges (n 5 30). reciprocl movement of the roots of nterior teeth lbilly during tretment. Therefore, it is very importnt to mintin the root positions nd retrct the incisors in this mlocclusion group. With the lbil movement of the roots, the skeletl convexity increses due to the forwrd movement of the skeletl points, which could become fctor for undesirble tretment results. 12 A further study with lrger smple size including the sexul vrition nd the differentition of thick nd thin lips is recommended. CONCLUSIONS N Retrction of skeletl points A nd B leds to retrction of sa nd sb under controlled root positions. N Lip retrction nd retrction of the skeletl nd soft tissue points A nd B improved the soft tissue profile nd decresed the soft tissue convexity. N Nerly proportionte chnges in the skeletl nd soft tissue points A nd B existed with slightly better response in the upper lip thn the lower lip. ACKNOWLEDGMENTS Dr Kirn Kumr HK, Assistnt Professor of Orthodontics nd Dr D.D. Brl, Assistnt Professor, Deprtment of Biosttistics. REFERENCES 1. Bills DA, Hndelmn CS, BeGole EA. Bimxillry protrusion: trits nd orthodontic correction. Angle Orthod. 2005;75: Diels RM, Klr V, Deloch N, Powers M, Nelson S. Chnges in soft tissue profile of Africn-Americns following extrction tretment. Angle Orthod. 1995;65: Holdwy RA. A soft tissue cephlometric nlysis nd its use in orthodontic tretment plnning. Prt I. Am J Orthod. 1983;84: Ricketts RM. Foundtion for Cephlometric Communiction. Am J Orthod. 1960;46: Burstone CJ. Lip posture nd its significnce in tretment plnning. Am J Orthod. 1967;53: Reidel RA. An nlysis of dentofcil reltionships. Am J Orthod. 1957;43: Subtelny JD. A longitudinl study of soft tissue fcil structures nd their profile chrcteristics, defined in reltion to underlying skeletl structure. Am J Orthod. 1959;45: Bloom LA. Periorl profile chnges in orthodontic tretment. Am J Orthod. 1961;47: Lin LI. A concordnce correltion coefficient to evlute reproducibility. Biometrics. 1989;45: LMstr SJ. Reltionships between chnges in skeletl nd integumentl points A nd B following orthodontic tretment. Am J Orthod. 1981;79: Roos N. Soft tissue profile chnges in Clss II tretment. Am J Orthod. 1977;72: Goldin B. Lbil root torque: effect on the mxill nd incisor root pex. Am J Orthod Dentofcil Orthop. 1989;95: