Dental archforms in dentoalveolar Class I, II and III

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1 Originl Article Dentl rchforms in dentolveolr Clss I, II nd III Mrtin Slj ; Stjepn Splj ; Durvko Pvlin c ; Dvor Illes d ; Mlden Slj e ABSTRACT Ojective: To test the hypothesis tht no differences exist in dentl rch dimensions etween dentolveolr Clsses I, II, nd III, nd etween mle nd femle sujects, s mesured on virtul three-dimensionl (3D) models. Mterils nd Methods: Smples included rndomly selected plster dentl csts of 137 white ptients (43 Clss I, 50 Clss II, nd 44 Clss III) from the Deprtment of Orthodontics, School of Dentl Medicine, University of Zgre, Croti. Dentl models were scnned nd digitized using ATOS II SO ( Smll Ojects ) scnning technology (GOM mh, Brunschweig, Germny). Eight liner nd two proportionl mesurements were clculted for oth upper nd lower dentl rches. Results: In men, significnt difference in the upper dentl rch ws present in the incisor region, nd in the lower dentl rch, differences were found in nd s (P,.05). Significnt differences were noted etween mle groups in the upper molr dimension (P 5.022) nd in the lower molr nd cnine dimensions (P,.05). Clss III mles hd the gretest lower molr nd cnine / s nd the smllest lower cnine /molr. Clss III women hd wider nd shorter mndiulr rches when compred with Clss I nd Clss II femles. Conclusion: The hypothesis ws rejected. The dimensions of the dentl rches re relted to gender nd to dentolveolr clss. Clss I nd II sujects hve similr dimensions of mxillry dentl rch, ut Clss II sujects hve trnsverse deficit in the mndile. In Clss III sujects, the mxillry dentl rch is insufficient in trnsverse nd sgittl dimensions, nd the mndiulr rch domintes in the trnsverse ut not in the sgittl dimension. (Angle Orthod. 2010;80: ) KEY WORDS: Archform; Three-dimensionl model INTRODUCTION Mny studies hve reported on dentl rchform, nd numer of reserchers hve tried to estlish the form unique to certin mlocclusions, ethnic groups, Assistnt Professor, Deprtment of Orthodontics, School of Dentl Medicine, University of Zgre, Zgre, Croti. Assistnt Professor, Deprtment of Peditric Dentistry nd Orthodontics, School of Medicine, University of Rijek, Rijek, Croti. c Associte Professor, Deprtment of Orthodontics, Dentl School, Sn Antonio Helth Science Center, University of Texs, Sn Antonio, United Sttes. d Assistnt Professor, Deprtment of Prosthodontics, School of Dentl Medicine, University of Zgre, Zgre, Croti. e Professor nd Deprtment Chir, Deprtment of Orthodontics, School of Dentl Medicine, University of Zgre, Zgre, Croti. Corresponding uthor: Dr Mrtin Slj, Deprtment of Orthodontics, School of Dentl Medicine, University of Zgre, Gundulicev 5, Zgre, Croti (e-mil: mslj@sfzg.hr). Accepted: Ferury Sumitted: Novemer G 2010 y The EH Angle Eduction nd Reserch Foundtion, Inc. nd genders. 1 3 Descriptions of dentl rchforms vry from geometric forms (ellipse, prolic curve) to mthemticl functions. 4 6 Cliniclly, it is importnt tht rchform does not chnge during orthodontic tretment ecuse occlusl stility depends on preservtion of the ptient s originl rchform. 7,8 Preformed rchwires hve een used frequently, lthough mny reports hve rought up the fct tht ppliction of the sme rchwire in ll cses cn negtively ffect posttretment occlusl stility Most studies mesured the trnsverse dimensions of the dentl rches nd investigted the differences etween Clss I norml occlusion nd different mlocclusions According to these studies, in oth mles nd femles, men mxillry nd mndiulr s showed smll vritions in Clss I norml occlusions, nd in Clss I, II/1, II/2, nd III mlocclusions. The min differences were seen in the premolr nd molr res. Mxillry tended to e similr in Clss III nd similr or lrger in Clss I mlocclusion, Clss II/1, nd Clss II/2. DOI: /

2 920 SLAJ, SPALJ, PAVLIN, ILLES, SLAJ Compred with Clss I norml occlusions, mndiulr ws similr or nrrower in Clss I mlocclusion, similr or lrger in oth Clss II sudivisions, nd similr or nrrower in Clss III sujects. 12,18 22 Clss I mlocclusions hve men mxillry nd mndiulr nd lveolr rch s smller thn those of Clss I norml occlusion. 19 Mxillry is deficient in Clss III, nd mndile is similr in Clss I norml occlusions nd Clss III, or is incresed in Clss III Clss II/2 cses pper to hve mxillry rch s smller thn those of norml Clss I occlusions, ut lrger thn the Clss II/1 group. Mndiulr in Clss II ws smller thn with norml occlusions. 18,20,22 Some studies, however, did not find mjor differences in dentl rch in sujects with nd without mlocclusion. 13,17 The trditionl odontometric tools were the sliding clipers, ut recently three-dimensionl (3D) scnners nd specilized softwre hve een developed to provide ccurte digitl models of dentl structures tht llow us to do sophisticted nd more precise mesurements. 24 Therefore, the im of this study ws to investigte rch dimensions defined on virtul 3D dentl rches in dentolveolr Clss I, II, nd III, nd the differences etween mle nd femle sujects. The hypothesis ws tht no differences exist etween dentolveolr clsses or in gender dimorphism. MATERIALS AND METHODS Smples included rndomly selected plster dentl csts of 137 white sujects (43 Clss I [19 mles nd 24 femles], 50 Clss II [22 mles nd 28 femles], nd 44 Clss III [25 mles nd 19 femles]) referred to the Deprtment of Orthodontics, School of Dentl Medicine, University of Zgre, for consulttion nd/or tretment. The csts corresponded to 71 femle nd 66 mle sujects etween 15 nd 18 yers old. Smple inclusion criteri were s follows: (1) Angle s ilterl dentolveolr Clss I, II, nd III, present on molrs; (2) permnent dentition without mesiodistl extended restons; nd (3) overjet of not more thn 4 mm. Clss I mlocclusions hd mild or moderte crowding (men, mm; rnge, mm). Both Clss II/1 nd II/2 were included, ut cses with overjet of more thn 4 mm were excluded. Dentl models were scnned nd digitized using ATOS II SO ( Smll Ojects ) scnning technology (GOM mh, Brunschweig, Germny), nd 3D virtul models were creted. The scnner hs point spcing in the mm rnge, mesuring re of mm 2, nd 1,400,000 mesured points. Fringe ptterns were projected onto the oject s surfce with white light projection nd recorded y Figure 1. Virtul 3D model. two cmers. The system self-dependently checked its clin nd the influence of the mient conditions. The 3D coordintes for ech cmer pixel were clculted, nd polygon mesh of the surfce of the oject surfce ws generted. With ATOS Viewer version softwre, 12 points on the most prominent lil tooth surfces were digitlly mrked on ech model (upper nd lower). These points were picked to represent the clinicl rcket points (midpoint of the fcil xis of the clinicl crown). Ech point ws utomticlly defined y softwre in 3D coordinte system with ssocited vlues (x, y, z) (Figure 1). All lndmrks of the points were mde y senior investigtor nd checked y nother investigtor to verify the ccurcy of lndmrk plcement. From these lndmrks, eight liner nd two proportionl mesurements were clculted for oth upper nd lower dentl rches: N Centrl interincisor : the distnce etween centrl incisor clinicl rcket points N Lterl interincisor : the distnce etween lterl incisor clinicl rcket points N Intercnine : the distnce etween cnine clinicl rcket points N First interpremolr : the distnce etween first premolr clinicl rcket points N Second interpremolr : the distnce etween second premolr clinicl rcket points N Intermolr : the distnce etween first molr clinicl rcket points N Cnine : the distnce from line connecting cnine clinicl rcket points to the origin etween centrl incisors N Molr : the distnce from line connecting first molr clinicl rcket points to the origin etween centrl incisors N Cnine W/D : the of the nd the cnine N Molr W/D : the of the nd the molr.

3 DENTAL ARCHFORM 921 All dt were nlyzed using STATISTICA 7.1 sttisticl softwre (SttSoft Inc, Tuls, Okl). Becuse dentl rch dimensions (s, s, nd s) were normlly distriuted, one- nd two-wy nlysis of vrince (ANOVA) with post hoc Bonferroni tests ws used to test the significnce of differences etween Angle s dentolveolr clsses nd genders. Mesurement error nd introserver greement were clculted on the sis of doule lndmrk plcements nd liner mesurements performed on 30 rndomly selected csts with 1-month intervl from the first nlysis. Introserver greement ws ssessed y mens of intrclss correltion coefficient (ICC), nd mesurement error ws clculted y the squre root of the residul men squre from the ANOVA tle. An lph level of.05 ws considered sttisticlly significnt. Introserver greement in locting points on 3D models nd mesurements ws excellent (ICC $ 0.94), nd mesurement error ws smll nd cceptle (#0.23 mm in locting the points nd #0.26 mm for liner mesurements). Biologicl vrition of every mesurement ws ssessed s stndrd devition nd ws lwys higher ($0.42 mm) thn mesurement error. RESULTS Becuse two-wy ANOVA showed significnt effect of gender, dentl rch dimensions (s, s, nd s) were nlyzed seprtely for mles nd femles. The results re shown in Tles 1 through 4. In men, sttisticlly significnt difference in upper dentl rch ws found only in the incisor region nd in the lower dentl rch, where we found differences in nd s (Tle 1, P,.05). Men in the Clss III group hd wider lower dentl rches thn those in the Clss I nd Clss II groups. Significnt differences were oserved etween the mle groups in upper molr dimension (P 5.022) nd in lower molr nd cnine dimensions (P,.05). The Clss I group hd the longest upper nd lower dentl rches, nd the Clss III group the shortest (Tle 1). Significnt differences were found in lower molr /, lower cnine /, nd lower cnine /molr (Tle 2). Clss III mles hd the iggest lower molr nd cnine / s nd the smllest lower cnine /molr s. Clss III women siclly hd somewht wider nd shorter mndiulr rches thn did Clss I nd II femles, ut the difference ws sttisticlly significnt only in the lower second premolr (P 5.012) nd lower molr / s (Tles 3 nd 4). Tle 1. Min Differences in Arch Widths nd Depths According to Dentolveolr Clsses in Mle Sujects Results of ANOVA nd Bonferroni Post Hoc Test Vrile Clss N x c s d F e df1/df2 f P Mxillry Mxillry Mndiulr Mndiulr Visul nlysis of pproximtion of mesurement points showed tht the mxillry dentl rch in Clss III is insufficient in trnsverse nd sgittl dimension compred with those in Clss I nd Clss II for oth genders (Figure 2). The mndiulr dentl rch in Clss III dominted in the trnsverse ut not in the sgittl dimension for oth genders (Figure 3). DISCUSSION I / II III I / II III I g / II gh 2.79 III h 3.50 I gh / II g 2.28 III h 1.54 I g / II gh 2.70 III h 2.21 I / II III I g / II gh 2.68 III h 2.22 I gh / II g 1.23 III h 1.47 Mens tht do not shre superscripts differ t P,.05 ccording to results of the Bonferroni post hoc test. Numer of cses; c men; d devition; e F sttistic; f degrees of freedom, g pired differences results of Bonferroni post hoc test, h pired differences results of Bonferroni post hoc test. Preformed rchwires tht meet the needs for tretment of specific group of mlocclusions cn enhnce orthodontic therpy nd gurntee posttretment stility nd the sence of relpse. Studies tht re focused on ssessing the chrcteristics of dentl rch dimensions, in prticulr dentolveolr clsses, im to meet this gol. Mesurements were tken in the permnent dentition t ges 15 to 18 yers, when future trnsverse growth chnges cn hrdly e expected. 16,25 The dvntge of this method is the use of points representing the clinicl rcket slot on lil tooth surfces insted of on incisl edges nd on tips of the uccl cusps. Points defined in this mnner represent the ctul clinicl orthodontic rchform nd simultion

4 922 SLAJ, SPALJ, PAVLIN, ILLES, SLAJ Tle 2. Differences in Arch Width/Depth Rtios According to Dentolveolr Clsses in Mle Sujects Results of ANOVA nd Bonferroni Post Hoc Test Vrile Clss N x c s d F e df1/df2 f P molr / I / II III cnine / I / II III molr / I g /63,.001 II gh 0.21 III h 0.23 cnine / I g / II g 1.25 III h 2.97 cnine /molr I / II III cnine /molr I g / II g 0.04 III h 0.05 Mens columns tht do not shre superscripts differ t P,.05 ccording to results of the Bonferroni post hoc test. Numer of cses; c men; d devition; e F sttistic; f degrees of freedom, g pired differences results of Bonferroni post hoc test, h pired differences results of Bonferroni post hoc test. of the effects of rchwire form used in orthodontic therpy. Most conventionl odontometric studies nd iometric nlyses of rchform were done with mesurements tken directly y sliding clipers on plster csts. 12,18,19 Such studies often re not repetle, nd some mteril defects, like little holes or dmge, cn cuse mistkes. Methods sed on photogrphing nd photocopying plster cst hve mjor shortcomings ecuse of the omission of the third dimension. In this study, we used 3D digitl models nd softwre to utomticlly very precisely clculte distnces etween defined points. In this wy, our model dtse is lwys ville nd models re kept. This study provides evidence tht the dimensions of the mxillry nd mndiulr dentl rches could e relted to Angle s Clss nd gender. Differences in rchform nd dimension re more pronounced in Clss III mles nd correspond to dentolveolr compenstion mechnisms. When nlyzing pproximtion of mesurement points, one cn see tht the upper dentl rch in Clss III is insufficient in the trnsverse nd sgittl dimensions compred with Clss I nd Clss II for oth genders (Figure 2). The upper dentl rch in Clss I nd Clss II is longer nd nrrower in oth the mle nd femle groups. The Clss II group ws etween Clss I nd Clss III, presenting shpe tht ppers more like Clss I in the frontl segment, ut wider in the posterior segment of the upper dentl rch. In Figure 3, which represents the pproximtion of mesurement points of the mndiulr dentl rch, Clss III domintes in the trnsverse ut surprisingly not in the sgittl dimension. A longer nd, in front, nrrower dentl rch represented the Clss I groups for oth genders. As cn e expected, ccording to pproximtions, the shortest nd the nrrowest mndiulr dentl rch Tle 3. Min Differences in Arch Widths nd Depths According to Dentolveolr Clsses in Femle Sujects Results of ANOVA Vrile Clss N x s c F d df1/df2 e P Mxillry Mxillry Mndiulr Mndiulr I / II III I / II III I / II III I / II III I / II III I / II III I / II III I / II III Numer of cses; men; c devition; d F sttistic; e degrees of freedom.

5 DENTAL ARCHFORM 923 Tle 4. Differences in Arch Width/Depth Rtios According to Dentolveolr Clsses in Femle Sujects Results of ANOVA nd Bonferroni Post Hoc Test Vrile Clss N x c s d F e df1/df2 f P molr / cnine / molr / cnine / cnine / molr cnine / molr I / II III I / II III I gh / II g 0.15 III h 0.23 I / II III I / II III I / II III Mens tht do not shre superscripts differ t P,.05 ccording to results of the Bonferroni post hoc test. Numer of cses; c men; d devition; e F sttistic; f degrees of freedom, g pired differences results of Bonferroni post hoc test, h pired differences results of Bonferroni post hoc test. corresponded to Clss II sujects, oth mles nd femles. Wider mndiulr rches nd nrrower mxillry rches were found in Clss III sujects compred with Clss I sujects in some other studies. 21 Clinicins speculte tht the reson my e nsl ostruction, low tongue position in the mndiulr spce, or hits such s thum sucking. Other opinions hve een expressed s well. Brun et l. 5 found tht the upper dentl rches in the Clss III group re 5.1 mm wider thn those in the Clss I group. Other uthors descried this finding s surprising. In this study, we found tht oth mle nd femle mndiulr dentl rches re wider in the Clss III group thn in Clss II nd Clss I groups. Specific mesiodistl dimensions 21 of mndiulr teeth my provide possile explntion. Sperry et l. 26 reported tht Clss III ptients often hve wider lower teeth thn Clss I nd II sujects. Other uthors hd similr finding A shorter nd lrger mndiulr rch in sujects with Figure 2. Approximtion of mesurement points in the upper (U) dentl rch in Clss I, II, nd III in mles (M) nd femles (F). Clss III could e consequence of dentl compenstion in tht ptients with tht mlocclusion tend to hve the mndiulr incisors inclined to the lingul, nd the lterl teeth inclined to the uccl. This hs een ttriuted to restriction of mxillry growth nd development. 18 According to Nojim et l., 30 dentl rch dimensions could e ethniclly relted, ut the rchforms re not relted to specific ethnic group or to Angle s dentl Clss. This finding concerning Angle s Clsses is contrry to results seen in our dt. Nevertheless, ccording to our findings, it seems resonle to use different shpes nd sizes of preformed rchwires, ccording to the ptient s originl rchform. Becuse the differences re most ovious in Clss III cses, it would e wise to use squred rchwires, which re wider in posterior segment, in the tretment of Clss III mlocclusions. Specil ttention must e tken to not expnd the posterior segment of the mndiulr dentl rch in Clss III ptients for stility resons, ut in Clss II sujects it would e dvisle to use preformed rchwires in the mndile to expnd the posterior segment. Figure 3. Approximtion of mesurement points in the lower (L) dentl rch in Clss I, II, nd III in mles (M) nd femles (F).

6 924 SLAJ, SPALJ, PAVLIN, ILLES, SLAJ Additionl multivrite nlyses re needed to discern how mny rchforms could e relted to prticulr dentolveolr clss, wht the most common forms re, nd wht percentge of vriility could e presented in the most common forms. CONCLUSIONS N Dimensions of the dentl rches re relted to gender nd to dentolveolr clss. N All dimensions re more pronounced in mles thn in femles. N It would e wise to use preformed rchwires for resons of stility. REFERENCES 1. Pepe SH. Polynomil nd ctenry curve fits to humn dentl rches. J Dent Res. 1975;54: Ferrrio VF, Sforz C, Mini A Jr, Trtgli G. Humn dentl rch shpe evluted y Eucliden-distnce mtrix nlysis. Am J Phys Anthropol. 1993;90: Cssidy KM, Hrris EF, Tolley EA, Keim RG. Genetic influence on dentl rch form in orthodontic ptients. Angle Orthod. 1998;68: Ferrrio VF, Sforz C, Mini A Jr, Trtgli G. Mthemticl definition of the shpe of dentl rches in humn permnent helthy dentitions. Eur J Orthod. 1994;16: Brun S, Hnt WP, Fender DE, Legn HL. The form of the humn dentl rch. Angle Orthod. 1998;68: Noroozi H. Re: the form of humn rch. Angle Orthod. 2000; 70: Felton MJ, Sinclir PM, Jones DL, Alexnder RG. A computerized nlysis of the shpe nd stility of mndiulr rch form. Am J Orthod. 1987;92: De L Cruz AR, Smpson P, Little RM, Artun J, Shpiro PA. Long term chnges in rch form fter orthodontic tretment nd retention. Am J Orthod. 1995;107: Strng RHW. Fctors of influence in producing stle result in tretment of mlocclusions. Am J Orthod. 1946;32: Strng RHW. The fllcy of denture expnsion s tretment procedure. Angle Orthod. 1949;19: Grdner SD. Posttretment nd postretention chnges following orthodontic therpy. Angle Orthod. 1976;46: Syin MO, Turkkhrmn H. Comprison of dentl rch nd lveolr s of ptients with Clss II division 1 mlocclusion nd sujects with Clss I idel occlusion. Angle Orthod. 2004;74: Stley RN, Stuntz WR, Peterson LC. A comprison of rch s in dults with norml occlusion nd dults with Clss II division 1 mlocclusion. Am J Orthod. 1985;88: Enlow DH, Hns MG. Essentils of Fcil Growth. Phildelphi, P: WB Sunders; Buschng PH, Stroud J, Alexnder RG. Differences in dentl rch morphology mong dult femles with untreted Clss I nd Clss II mlocclusion. Eur J Orthod. 1994;16: Moorrees CFA, Gron AM, Leret LML, Yen PKJ, Frohlich FJ. Growth studies of the dentition: review. Am J Orthod. 1969;55: Wlkow TM, Peck S. Dentl rch in Clss II division 2 deep-ite mlocclusion. Am J Orthod Dentofcil Orthop. 2002;122: Uysl T, Memili B, Usumez S, Sri Z. Dentl nd lveolr rch s in norml occlusion, Clss II division 1 nd Clss II division 2. Angle Orthod. 2005;75: Kuntz TR, Stley RN, Bigelow HF, Kremenk CR, Kohout FJ, Jkosen JR. Arch s in dults with Clss I crowded nd Clss III mlocclusions compred with norml occlusions. Angle Orthod. 2008;78: Al-Khtee SN, Au Alhij ESJ. Tooth size discrepncies nd rch prmeters mong different mlocclusions in Jordnin smple. Angle Orthod. 2006;76: Uysl T, Usumez S, Memili B, Sri Z. Dentl nd lveolr rch s in norml occlusion nd Clss III mlocclusion. Angle Orthod. 2005;75: Huth J, Stley RN, Jcos R, Bigelow H, Jkosen J. Arch s in Clss II-2 dults compred to dults with Clss II-1 nd norml occlusion. Angle Orthod. 2007;77: Ling JYK, Wong RWK. Dentl rch s of southern Chinese. Angle Orthod. 2009;79: Lee SP, Delong R, Hodges JS, Hyshi K, Lee JB. Predicting first molr using virtul models of dentl rches. Clin Ant. 2008;21: Bishr SE, Jkosen RJ, Treder J, Nowk A. Arch chnges from 6 weeks to 45 yers of ge. Am J Orthod Dentofcil Orthop. 1997;111: Sperry TP, Worms FW, Iscson RJ, Speidel TM. Toothsize discrepncy in mndiulr prognthism. Am J Orthod. 1977;72: Lvelle CLB. Mxillry nd mndiulr tooth size in different rcil groups nd in different occlusion ctegories. Am J Orthod. 1972;6: Nie Q, Lin J. Comprison of intermxillry tooth size discrepncies mong different mlocclusion groups. Am J Orthod Dentofcil Orthop. 1999;116: Hnt WP, Brun S, Chinhr A, Legn HL. The reltionship of rch length to ltens in dentl rch. Am J Orthod Dentofcil Orthop. 2000;118: Nojim K, McLughlin RP, Isshiki Y, Sinclir PM. A comprtive study of White nd Jpnese mndiulr clinicl rch forms. Angle Orthod. 2001;71: