Applicability of Three Tooth Size Prediction Methods for White Brazilians

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1 Originl Article Applicility of Three Tooth Size Prediction Methods for White Brzilins Cmilo Aquino Melgço ;Mônic Tirre Arújo ; Antônio Crlos Oliveir Ruells ABSTRACT The ojectives of this study were to evlute the pplicility of the methods of Moyers; Tnk nd Johnston; nd Berné nd Flores-Mir to Brzilin individuls nd to propose new regression equtions using the lower four permnent incisors s predictors for the sum of the widths of the lower permnent cnine nd premolrs. Five hundred dentl study csts (250 mle nd 250 femle white ptients) were used. The methods of Moyers nd Tnk nd Johnston were tested on smple consisting of 240 femle nd 223 mle ptients. The method of Berné nd Flores- Mir nd the new regression equtions were sed on the complete smple. At the 50th nd 75th percentile levels, Moyers tles tended to underestimte the ctul sum of the lower permnent cnine nd premolrs for mle nd femle smples, with sttisticlly significnt differences. Although the sme sttisticl significnt differences were found when Tnk nd Johnston s nd Berné nd Flores-Mir s methods were used, these differences were not cliniclly relevnt. The new regression equtions proposed demonstrte similr correltion nd determintion coefficients to those found in other studies sed on the lower four permnent incisors s predictors. Vlidting studies (sed on similr smples) must e conducted to confirm the pplicility nd precision of the proposed new regression equtions. KEY WORDS: Tooth width prediction; Mixed dentition nlysis; Regression equtions INTRODUCTION Nnce 1 descried the men Leewy Spce s 3.4 mm in the mndile nd 1.8 mm in the mxill. Thus, rch length discrepncy cn e defined s the difference etween the mount of dentl rch spce tht is ville nd the mount of tooth size tht needs to e ccommodted. 2 7 Arch length is generlly diminished during the trnsition from mixed to permnent dentition, prticulrly in the mndiulr rch. 1,8 Becuse conserving or regining spce is criticl in the mndile, rch length discrepncy nlysis is commonly performed in this rch. 9,10 Methods to estimte the mesiodistl width of unerupted permnent cnines nd premolrs re n importnt nd fundmentl procedure for every ptient Student Grdute (MS), Orthodontics, Universidde Federl do Rio de Jneiro, Rio de Jneiro, Brzil. Professor, Orthodontics, Universidde Federl do Rio de Jneiro, Rio de Jneiro, Brzil. Corresponding uthor: Cmilo Aquino Melgço, Espírito Snto Street n o 1.111/1.401, Belo Horizonte, Brzil (e-mil: cmiloquino@ig.com.r) Accepted: June Sumitted: April y The EH Angle Eduction nd Reserch Foundtion, Inc. in the mixed dentition stge. 3,8,10 23 Three methods re commonly used. Rdiogrphic methods: sed on peripicl nd 45 cephlometric rdiogrphs. 5,24,25 Nonrdiogrphic methods: sed on correltion nd regression equtions, s prediction tles; 2,7,11 Comintions of oth methods Methods sed on 45 cephlometric rdiogrphs re considered the most precise. 3,5,24,26,29,30 However, they require time, specific equipment, nd re less prcticl. 11,16,17 Becuse of the dvnces in sttisticl softwre, simple nd multiple regression eqution models hve een dopted in mny studies, 2,3,7,11,18,23,30,31 ut the ccurcy of regression equtions or prediction tles could e questioned when pplied to different rcil group or popultions of different ethnic origin. 1,3 5,14,24,31 39 This study ims to evlute the pplicility of the methods of Moyers; Tnk nd Johnston; nd Berné nd Flores-Mir to estimte the mesiodistl widths of lower permnent cnines nd premolrs in white Brzilin individuls from Rio de Jneiro nd to propose new regression equtions using the widths of the lower four permnent incisors s predictors. 644

2 APPLICABILITY OF PREDICTION METHODS MATERIALS AND METHODS Five hundred dentl study csts (250 from white Brzilin femle ptients nd 250 from white Brzilin mle ptients: verge ges of 13.8 nd 14.4 yers, respectively) were selected from the orthodontic rchives of the Fculdde de Odontologi d Universidde Federl do Rio de Jneiro, Brzil. Impressions nd study csts were otined from lginte impression mteril using high-qulity orthodontic model stone (Dentl Stone Type III; Vigodent S/A Indústri e Comércio, Rio de Jneiro, RJ, Brzil). The smple size ws determined y sttistic clcultion, on the sis of previous pilot study of 100 cses. All permnent teeth (excluding third molrs) should e present nd fully erupted. No previous orthodontic tretment, mesiodistl cvities, frctures, tooth congenitl defects, tooth wer, or restortions should e present. These criteri were dopted y mny uthors. 3,7,14,18,23,28,37 41 An electronic digitl cliper (0 150 mm ME 00183, Lee Tools, Rio de Jneiro, Brzil, Kje Intermres Comercil Importção & Exportção LTDA, Chin) with n ccurcy of 0.02 mm nd repetility of 0.01 mm (mnufcturer specifictions) ws used to mesure the teeth. To etter djust for interdentl spces, the mesuring tips were nrrowed. 14,18 The cliper ws held t the tooth s gretest mesiodistl dimeter (contct points), prllel to the occlusl surfce nd perpendiculr to the tooth s long xis. 15,18,23,26,32,37,40 Only 15 csts were mesured per dy. To determine mesurement reliility, one investigtor mesured 10 plster csts rndomly selected (first to first permnent molrs, 240 tooth mesures) three times, with intervls of 10 dys. Three prediction methods used in this study Moyers 2 method: proility chrts t 50th nd 75th percentile levels were used to estimte the widths of lower permnent cnines nd premolrs. The sum of the lower four permnent incisors ws smller thn 19.5 mm or lrger thn 25.5 mm (limits of Moyers 5 tles) in 10 femle ptients nd 27 mle ptients. Thus, the smple consisted of 240 femle nd 223 mle ptients. Tnk nd Johnston 11 method: mesiodistl widths of inferior permnent cnine nd premolrs were estimted y summing 10.5 mm to the hlf of the sum of the lower four permnent incisor. This smple lso consisted of 240 femle nd 223 mle ptients. Berné nd Flores-Mir 7 method: mesiodistl widths of lower permnent cnine nd premolrs were estimted y the following regression eqution. Y X X X2, where X0 is the sum of the of the upper nd lower 645 permnent centrl incisors plus the widths of the upper permnent first molrs, X1 is 0 for the mndile nd 1 for the mxill, nd X2 is 0 for femle nd 1 for mle. The smple consisted of 250 mle nd 250 femle ptients. New regression equtions were determined using the lower four permnent incisors s predictors for the sum of the widths of lower permnent cnine nd premolrs. Correltion nd the determintion coefficients were lso otined. The smple consisted of 250 mle ptients nd 250 femle ptients. The results of this study re sed only on the mndiulr rch nd represent the verge of the right nd left sides. Intrclss correltion coefficient (ICC) ws used to determine mesurement consistency. To compre mle nd femle results, nonpired Student s t-test ws used. To compre the results of different methods in the sme smple, pired Student s t-test ws used (P.05). 5,15,17,24,34,38,40,42 44 RESULTS A high vlue of ICC ws found, indicting gret mesurement reliility. There ws no sttisticl significnt difference etween the left nd right sides of the upper nd lower rches in oth sex groups. There ws significnt sttisticl difference etween the widths of mle nd femle teeth. Mle teeth generlly were lrger. In the mle smple, Moyers 2 chrts t the 50th nd 75th percentile levels tended to underestimte the ctul sum of the lower permnent cnine nd premolrs y 1.20 nd 0.41 mm, respectively. The stndrd devition of these differences ws 0.89 mm for oth percentile levels. Tnk nd Johnston s 11 method tended to underestimte the ctul sum of the lower permnent cnine nd premolrs y 0.24 mm with stndrd devition of 0.87 mm. Berné nd Flores-Mir s 7 method tended to overestimte the ctul vlues y 0.17 mm with stndrd devition of 0.84 mm (Tle 1). In the femle smple, Moyers 2 chrts t the 50th nd 75th percentile levels tended to underestimte the ctul sum of lower permnent cnine nd premolrs y 1.29 nd 0.48 mm, respectively. The stndrd devition of these differences ws 0.78 mm for oth percentile levels. Tnk nd Johnston s 11 nd Berné nd Flores-Mir s 7 methods tend to overestimte the ctul sum y 0.20 nd 0.08 mm with stndrd devition of 0.78 nd 0.87 mm, respectively (Tle 2). New regression equtions were proposed for mle nd femle ptients to estimte the sum of mesiodistl widths of permnent cnine nd premolrs sed on the sum of the lower four permnent incisors. Mle ptients: Y X.

3 646 MELGAÇO, ARAÚJO, RUELLAS TABLE 1. Predicted Vlues Bsed on the Methods of Moyers; Tnk nd Johnston; nd Berné nd Flores-Mir. Mle Smple Mle Ptients Predicted Vlues of Permnent Cnine nd Premolrs Actul Vlues of Permnent Cnine nd Premolrs Difference Predicted Minus Actul Vlues Significnce (P Vlue)* Moyers 50% (1988) P.01 Moyers 75% (1988) P.01 Tnk nd Johnston (1974) P.01 Berné nd Flores-Mir (2005) c P.01 indictes stndrd devition. Smple size 223 cses. c Smple size 250 cses. * Sttisticl significnce P.01. TABLE 2. Predicted Vlues Bsed on the Methods of Moyers; Tnk nd Johnston; nd Berné nd Flores-Mir. Femle Smple Femle Ptients Predicted Vlues of Permnent Cnine nd Premolrs Actul Vlues of Permnent Cnine nd Premolrs Difference Predicted Minus Actul Vlues Significnce (P Vlue)* Moyers 50% (1988) P.01 Moyers 75% (1988) P.01 Tnk nd Johnston (1974) P.01 Berné nd Flores-Mir (2005) c P.01 indictes stndrd devition. Smple size 240 cses. c Smple size 250 cses. * Sttisticl significnce P.01. TABLE 3. Predicted nd Actul Vlues of the Sum of Lower Permnent Cnine nd Premolrs Predicted Vlues Bsed on Regression Eqution Actul Vlues of Permnent Cnine nd Premolrs Difference Significnce (P Vlue)* Femle P.622 Mle P.444 indictes stndrd devition. Smple size 250 cses. * Sttisticl significnce P.01. Femle ptients: Y X. The difference etween predicted nd ctul widths of permnent cnine nd premolrs ws, on verge, 0.03 mm for the mle nd 0.04 mm for the femle ptients. This difference ws not sttisticlly significnt. The stndrd devition of the difference ws 0.87 nd 0.77 mm, respectively (Tle 3). The vlues of constnts nd found in this study re compred with other studies in Tle 4. Correltion nd determintion coefficients were determined nd compred with others otined in different studies (Tle 5). DISCUSSION Tooth nd fcil chrcteristics differ mong popultions of different rcil or ethnic origin. 3,5 7,10,14,23,24,30,32 41,45 Some of the most used methods to predict widths of unerupted permnent teeth were developed for United Sttes children. 2,11,26 Studies to confirm the pplicility nd effectiveness of these methods in different popultions re pproprite. A digitl cliper ws used to determine more ccurte nd precise mesures, s stted y mny u-

4 APPLICABILITY OF PREDICTION METHODS 647 TABLE 4. Comprison Among Vrious Vlues of nd Constnts Regression Coefficients Present study 9.20 (femle)/8.90 (mle) 0.55 (femle)/0.58 (mle) Bllrd nd Wylie (1947) Tnk nd Johnston (1947) Moyers (1988) 8.25 (femle)/10.79 (mle) 0.52 (femle)/0.45 (mle) Vn Der Merwe et l. (1991) Al-Khdr (1993) Jroonthm nd Godfrey (2000) Lee-Chn et l. (1998) Digne et l. (2003) Regression equtions derived from Moyers tles (1988) t the 50th percentile. TABLE 5. Comprison Among Correltion (r) nd Determintion (r 2 ) Coefficients Found in This nd Other Studies Mle Femle Mle Femle r r 2 r r 2 r r 2 Present study Tnk nd Johnston (1974) Berné nd Floris-Mir (2005) Indictes coefficient not determined. thors. 15,42,43 The vlue of ICC (0.995) found in this study is in ccordnce with the vlues found y other investigtors. 7,13,22,26 28,35,44,46 This indictes gret mesurement reliility. Thus, ll tooth mesures of the 500 dentl csts were performed only once. No differences etween the right nd left sides of the lower rch were found. All prediction methods used in this study were sed on the verge of oth sides. Sttisticl significnt differences were found etween mle nd femle tooth widths. Thus, dt nlysis ws performed seprtely for ech sex. This is in ccordnce with studies of mny uthors. 2,3,5 7,13,16 18,27,32,34,39,40 However, others do not consider sex differences. 3,4,11,24 26,28,31 In oth the mle nd femle smples, Moyers 2 tles t the 50th nd 75th percentile levels tended to underestimte the ctul sum of lower permnent cnine nd premolrs. The differences were sttisticlly significnt (Tles 1 nd 2). These results hve een confirmed efore 3,6,14,16,23,24,39 ut do not gree with other studies, which found tht these percentile levels (especilly the 75th) tended to overestimte. 4,10,17,29,30,37,40,45,47 However, some uthors found no differences when Moyers 5 method (75th percentile) ws used. 5,24,39 When Tnk nd Johnston s 11 method ws pplied in the mle nd femle smples, there ws sttisticlly significnt difference (P.01), ut no clinicl relevnt difference (less thn 1 mm) ws found etween the predicted nd ctul sum of lower permnent cnine nd premolrs (Tles 1 nd 2). These results re in ccordnce with some studies. 5,39 However, other uthors found n overestimtion when this method ws used. 24,37 The vriility in results found when the methods of Moyers nd Tnk nd Johnston were pplied in Brzilin individuls my e explined y the differences in smple sizes nd origins. These two methods were developed for North Americn individuls nd were tested in mny others of different origins. There re differences in coloniztion nd ethnic chrcteristics of the popultion when individuls of United Sttes nd Brzil re compred. In Brzil, there re severl different chrcteristics within the popultion of the sme ethnic origin. Most of the studies conducted in Brzil were sed on smll or middle size smples (this study hs the lrgest smple). Berné nd Flores-Mir s 7 method hd not een tested in different popultions esides the originl one. In the femle smple, no sttisticl difference ws found etween the predicted nd ctul sum of the lower permnent cnine nd premolrs. In the mle group, lthough sttisticlly significnt difference ws present, it ws not clinicl relevnt (less thn one mm) (Tles 1 nd 2). Similr popultion origins nd coloniztion (Ltin Americ) re oserved in this study nd in the studies of Berné nd Flores-Mir. In this study, new regression equtions were developed using the widths of the lower four permnent incisors s predictors for the sum of the widths of lower permnent cnine nd premolrs. The correltion coefficients found (Tle 5) were higher thn those found in Tnk nd Johnston 11 nd re similr to those proposed y Berné nd Flores-Mir. 7 On n verge, no

5 648 MELGAÇO, ARAÚJO, RUELLAS sttisticl significnt difference ws found etween the predicted nd ctul vlues. The stndrd devition of the differences is in ccordnce with those in the literture. 7,11,13,17,24,25,31,37,38 The simple liner regression is defined y the formul: Y X. The prmeter of interest is the slope in the liner regression ( constnt). This study found coefficients of 0.55 for femle nd 0.58 for mle ptients (Tle 4). These vlues re similr to those found in mny studies, 2 4,11,17,37,38 indicting tht resonle correltion exists etween the lower four permnent incisors nd the ctul widths of lower permnent cnine nd premolrs in white Brzilin individuls. CONCLUSIONS No clinicl relevnt difference ws oserved etween predicted nd ctul widths of the lower permnent cnine when the methods proposed y Tnk nd Johnston (1974) nd Berné nd Floris- Mir (2005) were pplied. The predicted widths determined y Moyers tles t 50th nd 75th percentiles underestimte the ctul widths of the lower permnent cnine nd premolrs for mle nd femle ptients. The regression equtions proposed in this study re good prediction method to determine widths of the lower permnent cnine nd premolrs. Vlidting studies (sed on similr smples) must e conducted to confirm the pplicility nd precision of the new regression equtions proposed. REFERENCES 1. Nnce HN. The limittions of orthodontic tretment I mixed dentition dignosis nd tretment. Am J Orthod Orl Surg. 1947;33(4): Moyers RE. Hndook of Orthodontics. 4th ed. Chicgo, Ill: Yer Book; 1988: Vn Der Merwe SW, Rossouw P, Vn Wyk Kotze TJ, Trutero H. An dpttion of the Moyers mixed dentition spce nlysis for Western Cpe Cucsin popultion. J Dent Assoc S Afr. 1991;46: Al-Khdr BH. Prediction of the size of unerupted cnines nd premolrs in Sudi Ar popultion. Am J Orthod Dentofcil Orthop. 1993;104: Pul S, Almeid MAO, Lee PCF. 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