Rapid palatal expansion (RPE) is considered

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1 Benedict Wilmes, DDS, DMD, PhD 1 Mnuel Nienkemper, DDS 2 Dieter Drescher, DDS, DMD, PhD 3 1 Associte Professor, Deprtment of Orthodontics, University of Duesseldorf, Duesseldorf, Germny. 2 Postgrdute Student, Deprtment of Orthodontics, University of Duesseldorf, Duesseldorf, Germny. 3 Professor nd Hed, Deprtment of Orthodontics, University of Duesseldorf, Duesseldorf, Germny. APPLICATION AND EFFECTIVENESS OF A MINI-IMPLANT AND TOOTH-BORNE RAPID PALATAL EXPANSION DEVICE: THE HYBRID HYRAX Aim: Rpid pltl expnsion (RPE) is used for tretment of skeletl crossites. It my e comined with fce msk if the mxill is to e protrcted. Conventionl tooth-orne pplinces rely on n lmost complete dentition to trnsmit the reltively high forces to the ony structures of the mxill nd midfce. In most situtions, tooth-orne pplinces produce dverse effects such s uccl tipping of the lterl teeth, imposing the risk of recessions nd vestiulr one fenestrtions. To overcome these drwcks, n RPE pplince ws developed tht utilizes mini-implnts nteriorly in the plte for skeletl nchorge. Becuse this device is lso ttched to the first molrs, it cn e denominted s one- nd tooth-orne pplince (hyrid hyrx). The ojective of this clinicl pilot study ws to investigte its dentl nd skeletl effects. Methods: RPE ws performed in 13 ptients (seven femles, six mles; men ge 11.2 yers). In 10 ptients with skeletl Clss III occlusion, fce msk ws used simultneously for mxillry protrction. Three-dimensionl scns of the individul study models were digitlly superimposed for the ssessment of the dentl effects. Skeletl effects were evluted y lterl cephlogrms tken efore nd fter RPE nd protrction. Results: The time needed to chieve the intended expnsion rnged from 4 to 14 dys (men 8.7 ± 3.6 dys). The men expnsion in the first premolr/first primry molr region ws 6.3 ± 2.9 mm nd 5.0 ± 1.5 mm in the first molr region. The Wits pprisl chnged from 5.2 ± 1.3 mm to 2.5 ± 1.5 mm (men improvement 2.7 ± 1.3 mm). The right first molr migrted 0.4 ± 0.6 mm mesilly nd the left one 0.3 ± 0.2 mm. Conclusions: The hyrid hyrx is effective for RPE nd cn e employed especilly in ptients with reduced nterior dentl nchorge. Since most teeth re not in the pplince, regulr orthodontic tretment cn strt erly. The comintion of the hyrid hyrx with fce msk for mxillry protrction ppers to e effective in minimizing mesil migrtion of the dentition. World J Orthod 2010;11: Key words: rpid pltl expnsion, Clss II tretment, mini-implnt, mxillry protrction CORRESPONDENCE Dr Benedict Wilmes Deprtment of Orthodontics University of Duesseldorf Moorenstr Duesseldorf Germny Emil: wilmes@med.uni-duesseldorf.de Rpid pltl expnsion (RPE) is considered the optimum orthodontic procedure to widen the mxill skeletlly. Angell 1 first descried this method in 1860; it received comprehensive dispprovl t tht time due to the lck of rdiologic confirmtion. This verifiction ws produced in 1908 y Lndserg. Nevertheless, it ws not until the middle of the 20 th century tht RPE ws rodly estlished nd reintroduced in the United Sttes. 2 Tody, RPE is considered midpltl suture distrction osteo - genesis. For the tretment of ptients 323

2 Wilmes et l WORLD JOURNAL OF ORTHODONTICS h d c e f g insertion of mini-implnts in the lterl posterior lveolr process nd lck of ville one in the middle of the plte posteriorly, in the present pproch, the first molrs were chosen s the posterior nchorge unit. Anteriorly, there is sufficient one ville for mini-implnts in the middle of the plte. 12 Since this pplince is oth tooth- nd one-orne, it cn e designted hyrid hyrx. 11,13 The im of this study ws to ssess the clinicl pplicility nd 3D effects of RPE using the hyrid hyrx. The skeletl effects of the comintion hyrid hyrx nd fce msk for mxillry protrction were lso evluted. Fig 1 The vrious components of the Benefit system. () Mini-implnt; () lortory nlog; (c) impression cp; (d) wire utment; (e) rcket utment; (f) stndrd utment; (g) slot utment; (h) screwdriver for fixtion of the utments. with Clss III occlusion cused y retrognthic mxill, RPE is comined with fce msk for protrction. Since the orthopedic forces re trnsmitted to the skeletl structures vi nchor teeth, distriution of the forces to s mny teeth s possile, s well s completion of their root development, is considered essentil. In spite of these considertions, dverse effects such s uccl tipping, gingivl recessions, fenestrtions of the uccl cortex, nd root resorptions of the posterior teeth were repetedly reported. 3,4 To void such complictions, orthodontists hve dvocted pure one-orne RPE devices. 5,6 However, the insertion nd removl of such distrctors re invsive since they need flp preprtion. Further, they increse the risk of root lesions nd infections. 5,7 As consequence, distrctors of this type could not estlish themselves s stndrd devices for RPE. To minimize the surgicl procedure, Hrzer et l introduced the Dresden Distrctor, which is ttched solely to n implnt nd mini-implnt Miniimplnts ttrcted gret ttention in recent yers ecuse they re verstile, minimlly invsive, nd low cost. 11 Due to the risk of root lesions during the METHOD AND MATERIALS RPE with the hyrid hyrx ws performed in 13 ptients (seven femles, six mles; men ge 11.2 yers). Ten of these 13 ptients were simultneously treted with fce msk for protrction of the mxill. Clinicl ppliction nd construction of the hyrid hyrx pplince After locl nesthesi, soft tissue thickness ws mesured using dentl proe so region with thin mucos coverge could e identified. This is importnt to chieve sufficient primry stility nd void long lever rms In young ptients, predrilling is not needed due to the low one minerliztion. After insertion of two Benefit mini-implnts (2 9 mm; Figs 1 nd 2), nds were fitted to the mxillry first molrs t this first ppointment. After ppliction of trnsfer cps (Fig 1c), silicone impression (Provil) ws tken. In situtions in which the distnce etween the mini-implnts ws too smll, the trnsfer cps were trimmed to fit side y side. The ngle etween the two trnsfer cps ws secured y connecting them introrlly with Trnsond LR (3M). The impressions were completed y inserting lortory nlogues (Fig 1) into the trnsfer cps, s well s y inserting the molr nds. The resulting lortory model reflected the introrl sitution (Fig 3). 324

3 VOLUME 11, NUMBER 4, 2010 Wilmes et l Fig 2 Two mini-implnts (2 9 mm, Benefit system, PSM Mondel) fter insertion in the nterior plte next to the midpltl suture nd ner the second nd third pltl ruge. Fig 3 Cst with the two lortory nlogs (see Fig 1) nd the two molr nds. Fig 4 Hyrid hyrx pplince on the cst. Fig 5 The hyrid hyrx in situ. Susequently, two stndrd utments (Fig 1f) of the Benefit system were screwed onto the lortory nlogues nd regulr split plte screw (Hyrx, Denturum) ws connected y lser welding to the two utments nd the molr nds (Fig 4). Prllelism of the two miniimplnts is dvisle, ut not prerequisite: Even if they re not solutely prllel, the pplince cn e fitted onto the mini-implnt. The complete pplince ws inserted 7 to 10 dys fter plcing the mini-implnt. During the insertion, screwing of the two utments on the mini-implnt lternted with the finl djustment of the molr nds (Fig 5). During this time, the hyrid hyrx should e gently pressed ginst the miniimplnt to fcilitte fixtion. To llow dequte time to instll the hyrid hyrx, light-curing cr ylic resin (Bnd-Lok, Relince Orthodontic Products) should e used for molr nd cementtion. If simultneous protrction of the mxill ws intended, segmentl rchwires were inserted into the molr tues (Figs 5 nd 6). The sgittl split screw ws ctivted twice dy y 90 degree turn immeditely fter insertion of the hyrid hyrx (Fig 7). This resulted in dily ctivtion of 0.8 mm. RPE ws continued until 30% overcorrection ws chieved (Fig 8). After this, the hyrid hyrx remined in situ for 3-month retention phse, during which the mxillry incisors migrted mesilly spontneously (Figs 9 nd 10). In 10 of 13 ptients, fce msk ws prescried for pproximtely 6 months to simultneously protrct the mxill. The pplied elstics (5 oz, 1 4 inch; RMO Orthodontics) were nterocudlly ngulted (Fig 6). In one of 13 ptients, the mximum expnsion of the sgittl split screw ws ttined efore sufficient expnsion of the mxill ws chieved. Thus, the hyrid hyrx ws removed, second impression tken, nd new pplince fricted. To prevent relpse, the first hyrid hyrx ws reinserted until the second one could e used. 325

4 Wilmes et l WORLD JOURNAL OF ORTHODONTICS Fig 6 Ptient with fce msk for (simultneous) protrction of the mxill. Fig 6 Semischemtic illustrtion of hyrid hyrx with simultneous protrction of the mxill y fce msk. The pplied force is trnsferred to the mxill vi the molrs n nterior mini-implnts. Fig 7 (left) Activtion of the sgittl split screw. Fig 8 (right) Sitution t the completion of RPE. Fig 9 Sme ptient s in Fig 8 fter 3 months of retention with the hyrid hyrx still in situ. The mxillry incisors hve spontneously migrted mesilly. Fig 10 Sme ptient s in Figs 8 nd 9. Pnormic rdiogrph t the end of the retention phse with the hyrid hyrx in situ. Evlution of the dentl RPE effects Pre- nd post-rpe models (6 to 9 months fter RPE) were scnned with cone em computed tomogrphy. Trnsversl expnsion nd tooth tipping (first premolr/first primry molr nd first molr) were mesured using DigiModel softwre (Orthoproof). The overll trnsversl effect ws quntified y guging the distnce of four corresponding points efore nd fter expnsion (Fig 11). Tooth tipping ws evluted y clculting the difference of the uccl surfce ngle of the first premolr/first primry molr nd first molr efore nd fter RPE (Fig 12). To ssess the symmetry of the expnsion, s well s the molr mesil migrtion, the 3D scns were digitlly superimposed using the threepoint method of the DigiModel softwre (Figs 13 nd 14). 326

5 VOLUME 11, NUMBER 4, 2010 Wilmes et l Fig 11 Three-dimensionl scns employing cone em computed tomogrphy () efore nd () fter expnsion. Fig 12 Cut of the 3D scn efore expnsion. The ngle of the uccl surfce of the first premolr is mesured to verticl to the occlusl plne. Fig 13 Digitl superimposition of two 3D scns using the three-point method of the DigiModel softwre. Fig 14 (right) Assessment of the expnsion symmetry nd sgittl molr migrtions using the superimposed 3D scns. 327

6 Wilmes et l WORLD JOURNAL OF ORTHODONTICS Fig 15 () Pre- nd () posttretment overjet nd (c) prend (d) posttretment profile of one of the 10 ptients who wore fce msk. c d Evlution of the skeletl protrction effects Pre- nd posttretment lterl cephlogrms of the 10 ptients wering fce msks were scnned, nd the Wits vlues were clculted nd compred. RESULTS All 26 mini-implnts were primrily stle with n dequte mximum insertion torque (5 to 15 Ncm), nd they were still stle t the time of the hyrid hyrx insertion nd t its removl. The time needed to chieve the plnned expnsion rnged from 4 to 14 dys (men 8.7 ± 3.6 dys). The men expnsion in the first premolr/first primry molr region ws 6.3 ± 2.9 mm nd 5.0 ± 1.5 mm in the first molr region. The men difference etween right nd left expnsion in the region of the first molr ws 0.8 ± 0.5 mm. The men uccl tipping of the first premolr/first primry molr mounted to 3.2 ± 0.8 degrees on the right nd 4.0 ± 0.7 degrees on the left side. The men tipping of the first molr ws 5.3 ± 0.9 degrees on the right nd 6.5 ± 1.7 degrees on the left side. During protrction, the right first molr migrted 0.4 ± 0.6 mm mesilly nd the left one 0.3 ± 0.2 mm. The Wits vlue chnged from 5.2 ± 1.3 mm to 2.5 ± 1.5 mm (men improvement 2.7 ± 1.3 mm). See Fig 15 for pre- nd posttretment photogrphs of one of the ptients who wore fce msk. 328

7 VOLUME 11, NUMBER 4, 2010 Wilmes et l c d Fig 16 Sme ptient s in Figs 8 to 10. Introrl sitution fter removl of the hyrid hyrx; mini-implnts re still stle. Fig 16 Components of the Beneplte system for the connection of mini-implnts. () Beneplte with rcket; () Beneplte with wire; (c) Beneplte stndrd; nd (d) fixtion screw. Fig 16c Skeletl retention y the insertion of miniplte. c DISCUSSION The hyrid hyrx with two mini-implnts with exchngele utments is effective for RPE. An nterior mini-implnt insertion pproximtely 2 mm from the pltl suture seems to e preferle. Sufficient one is ville only in this re. 12 The 3D scn evlution of the dentl csts to mesure the mount of expnsion nd mesil migrtion of the molrs ws very suitle. In some instnces, however, the tipping ws difficult to ssess due to the curvture of uccl sur fces. In this sitution, frontl cephlogrms might offer n dvntge, ut the rdition exposure does not justify their ppliction. The chieved men expnsion in this study ws less thn in other studies. 20 This cn e explined y the fct tht in this study, RPE ws utilized not only for mxillry expnsion, ut lso for protrction y fce msk. In ptients in whom this ws the primry gol, the expnsion ws deliertely limited to ctivte the midfcil sutures. The ppliction of the hyrid hyrx is surgiclly minimlly invsive compred with pure one-orne RPE devices, such s distrctors. 5,6 To employ the first molrs s posterior nd mini-implnts s nterior nchorge units provides severl dvntges. Appliction is possile in ptients with: Inferior nterior dentl nchorge due to missing primry molrs or primry molrs with resored roots Immture premolr roots A need for erly Clss III tretment with fce msk nd in whom RPE supports the mxillry dvncement y wekening the midfce sutures, thus enhncing the skeletl effects of the extrorl trction Reduced dentl dverse effects, ie, uccl tipping nd mesil migrtion It seems dvisle to retin the skeletl expnsion for some time y fixing miniplte (Beneplte, PSM Mondel) 21 on the mini-implnts with two tiny screws (Fig 16). An dditionl pproch my e the use of the mini-implnt supported hyrix hyrx with miniplte (Mentoplte) plced in the nterior portion of the mndile, thus voiding n unesthetic fce msk

8 Wilmes et l WORLD JOURNAL OF ORTHODONTICS ACKNOWLEDGMENT Dr Benedict Wilmes is codeveloper of the Benefit mini-implnt system. CONCLUSION The hyrid hyrx is effective for rpid pltl expnsion. It cn e employed even in ptients with reduced dentl nchorge. The nterior teeth re not included in the pplince, nd regulr orthodontic tretment cn therefore e strted erly. The comintion of the hyrid hyrx with fce msk for mxillry protrction is helpful to minimize dverse effects, such s mesil migrtion of the nterior teeth. REFERENCES 1. Angell E. Tretment of irregulrities of permnent or dult teeth. Dent Cosmos 1860;1: , Timms DJ, Emerson C. Angell ( ). Founding fther of rpid mxillry expnsion. Dent Hist 199;32: Gri DG, Henriques JF, Jnson G, de Freits MR, Fernndes AY. Periodontl effects of rpid mxillry expnsion with tooth-tissue-orne nd tooth-orne expnders: A computed tomogrphy evlution. Am J Orthod Dentofcil Orthop 2006;129: Schuster G, Borel-Scherf I, Schopf PM. Frequency of nd complictions in the use of RPE pplinces Results of survey in the Federl Stte of Hesse, Germny. J Orofc Orthop 2005;66: Mommerts MY. Trnspltl distrction s method of mxillry expnsion. Br J Orl Mxillofc Surg 1999;37: Koudstl MJ, vn der Wl KG, Wolvius EB, Schulten AJ. The Rotterdm Pltl Distrctor: Introduction of the new one-orne device nd report of the pilot study. Int J Orl Mxillofc Surg 2006;35: Fuck L, Wilmes B, Drescher D. Rpid pltl expnsion with trnspltl distrctor [in Germn]. Kieferorthopädie 2008;22: Hnsen L, Tusche E, Hietschold V, Hotn T, Lgrvere M, Hrzer W. Skeletlly-nchored rpid mxillry expnsion using the Dresden Distrctor. J Orofc Orthop 2007;68: Hrzer W, Schneider M, Gedrnge T. Rpid mxillry expnsion with pltl nchorge of the hyrx expnsion screw Pilot study with cse presenttion. J Orofc Orthop 2004;65: Hrzer W, Schneider M, Gedrnge T, Tusche E. Direct one plcement of the hyrx fixtion screw for surgiclly ssisted rpid pltl expnsion (SARPE). J Orl Mxillofc Surg 2006;64: Wilmes B. Fields of ppliction of mini-implnts. In: Ludwig B, Bumgertel S, Bowmn J (eds). Mini-Implnts in Orthodontics: Innovtive Anchorge Concepts. Berlin: Quintessenz, Kng S, Lee SJ, Ahn SJ, Heo MS, Kim TW. Bone thickness of the plte for orthodontic miniimplnt nchorge in dults. Am J Orthod Dentofcil Orthop 2007;131 (suppl):s Wilmes B, Drescher D. A miniscrew system with interchngele utments. J Clin Orthod 2008;42: Wilmes B, Rdemcher C, Olthoff G, Drescher D. Prmeters ffecting primry stility of orthodontic mini-implnts. J Orofc Orthop 2006;67: Wilmes B, Ottenstreuer S, Su YY, Drescher D. Impct of implnt design on primry stility of orthodontic mini-implnts. J Orofc Orthop 2008;69: Wilmes B, Su YY, Sdigh L, Drescher D. Predrilling force nd insertion torques during orthodontic mini-implnt insertion in reltion to root contct. J Orofc Orthop 2008;69: Wilmes B, Su YY, Drescher D. Insertion ngle impct on primry stility of orthodontic miniimplnts. Angle Orthod 2008;78: Buchter A, Wiechmnn D, Koerdt S, Wiesmnn HP, Piffko J, Meyer U. Lod-relted implnt rection of mini-implnts used for orthodontic nchorge. Clin Orl Implnts Res 2005;16: Wilmes B, Drescher D. Impct of insertion depth nd predrilling dimeter on primry stility of orthodontic mini-implnts. Angle Orthod 2009;79: Koudstl MJ, Wolvius EB, Schulten AJ, Hop WC, vn der Wl KG. Stility, tipping nd relpse of one-orne versus tooth-orne surgiclly ssisted rpid mxillry expnsion: A prospective rndomized ptient tril. Int J Orl Mxillofc Surg 2009;38: Wilmes B, Nienkemper M, Drescher D. A miniplte system for improved stility of skeletl nchorge. J Clin Orthod 2009;43: Ludwig B, Glsl B, Bowmn J, Drescher D, Wilmes B. Miniscrew-supported Clss III tretment with the hyrid dvncer. J Clin Orthod (in press). 330