The Aetiology, Diagnosis and Management of Mandibular Asymmetry

Transcription

1 44 Orthodontic Updte My 2008 Mtthew SY Chi Frhd B Nini nd Dljit S Gill The Aetiology, Dignosis nd Mngement of Mndiulr Asymmetry Astrct: An understnding of the etiology of mndiulr symmetry nd thorough methodicl dignostic pproch is essentil for the pproprite mngement of ptients presenting with dentofcil symmetry. The im of this review rticle is to descrie the developmentl, pthologicl, trumtic nd functionl cuses of mndiulr symmetry, to provide guide to dignosis through clinicl exmintion nd specil investigtions nd, finlly, to outline the mngement of ptients presenting with mndiulr symmetry, focusing prticulrly on the tretment of developmentl symmetries. Clinicl Relevnce: This rticle presents review of the etiology, dignosis nd mngement of mndiulr symmetries with prticulr focus on developmentl symmetries. Ortho Updte 2008; 1: The word symmetry is derived from the Greek word symmetri which mens of like mesure. Symmetry is defined s correspondence in size, shpe nd reltive position of prts on opposite sides of dividing line or medin plne. Asymmetry is descried s lck or sence of symmetry. When pplying this to the humn fce, it illustrtes n imlnce or disproportionlity etween the right nd left sides. A degree of symmetry is norml nd cceptle in the verge fce. It my e cused y rnge of fctors tht ffect the underlying skeletl structure or soft tissue drpe. However, the importnce of erly dignosis nd the detection of progressive custive conditions is essentil for the mngement of fcil symmetry. This rticle will focus on symmetries of the mndile nd on some of the spects of mxillry symmetry. The cuses of mndiulr symmetry cn e divided into (Tle 1): Cuses Developmentl Pthologicl Trumtic Functionl Tle 1. Cuses of mndiulr symmetries. Developmentl; Pthologicl; Exmples Hemimndiulr elongtion Hemimndiulr hyperplsi Hemifcil microsomi Achondroplsi Hemifcil hypertrophy Torticollis Hemifcil trophy (Prry-Romerg syndrome) Tumours nd cysts Infection Condylr resorption Condylr frctures Mndiulr displcement Trumtic; Functionl. Mtthew SY Chi, BDS, MFDS RCS(Eng), MSc, MOrth, FTTA in Orthodontics, Estmn Dentl Hospitl nd Mydy Hospitl, London, Frhd B Nini, BDS, FDS RCS, MSc, MOrth RCS, FDSOrth RCS, Consultnt Orthodontist, St George s nd Kingston Hospitls nd Dljit S Gill, BDS(Hons), BSc(Hons), MSc, FDS RCS, MOrth, FDSOrth RCS, Consultnt Orthodontist/Hon Senior Lecturer, UCL Estmn Dentl Institute, London, Honorry Consultnt Orthodontist, Gret Ormond Street Hospitl, London, UK.

2 My 2008 Orthodontic Updte 45 c Figure 2. () Ptient presenting with left-sided hemimndiulr hyperplsi. () Note the right-sided chin point devition which is clerly visile from elow. (c) An OPG rdiogrph of the sme ptient demonstrting incresed verticl mndiulr growth on the left side, incresed lveolr height, leftsided lterl open ite, nd displcement of the inferior dentl cnl on the left. c Figure 1. () Ptient presenting with left-sided hemimndiulr elongtion. Note the chin point devition to the right, wy from the ffected side. () This condition is often ssocited with miniml compenstory cnting of the mxill. (c) The sme ptient with crossite on the unffected side. Developmentl The conditions, hemimndiulr elongtion nd hemimndiulr hyperplsi, were originlly descried together s condylr hyperplsi. However, the former terms re now used insted to descrie these two distinct conditions nd hve superseded the term condylr hyperplsi. Hemimndiulr elongtion Hemimndiulr elongtion ws first descried y Owegeser nd Mkek 1 nd is developmentl deformity of unknown etiology ffecting the mndile unilterlly. It commonly presents with progressively incresing trnsverse displcement of the chin point in young dulthood. The occlusion follows the displced skeletl pttern so tht the mndiulr dentl centreline does not coincide with the midfcil line. However, the centreline my e coincident with the chin point. There will lso e crossite oserved on the unffected side nd possily scissor ite on the ffected side. Since there is such smll verticl component to the norml growth, there re typiclly no lterl open ites of the uccl segments or compenstory trnsverse cnting of the mxillry occlusl plne (Figure 1, ). Rdiogrphiclly, there is cler elongtion of the ffected side of the mndile, principlly locted in the condylr region nd the ody of the mndile. Hemimndiulr hyperplsi Hemimndiulr hyperplsi, lso descried y Owegeser nd Mkek, 1 is three-dimensionl developmentl enlrgement of one side of the mndile including the condyle, condylr neck, rmus

3 46 Orthodontic Updte My 2008 Figure 3. () Ptient presenting with hyrid form of hemimndiulr hyperplsi (left side) nd hemimndiulr elongtion (right side). () A pnormic rdiogrph illustrting oth the hyperplsi nd elongtion of the mndile. nd ody. It typiclly only ffects one side of the mndile nd the enlrgement is chrcterized y ruptly stopping t the midline of the mndiulr symphysis. It is distinct from hemimndiulr elongtion s there is oth horizontl nd significnt verticl component to the norml mndiulr growth pttern. There is n increse in the height of the ffected side, giving the fce rotted ppernce. The mouth slopes to the ffected side ut is not restricted in opening. The condition usully commences in puerty nd hence the mxillry dentition on the ffected side will overerupt to compenste for the excessive verticl mndiulr growth, which results in chrcteristic trnsverse cnt of the mxillry occlusl plne. The teeth will often remin in occlusion on the ffected side. However, if the verticl component of the excessive mndiulr growth is rpid, then dentl eruption my not keep pce with verticl rml growth nd lterl open ite will occur on the ffected side, prticulrly if the tongue ecomes interposed. The trnsverse component of the norml mndiulr growth my result in mndiulr dentl midline discrepncy. However, the dentl midlines my well remin coincident, leit with ltered ngultion of the mndiulr incisors (Figure 2). Rdiogrphiclly, pnormic tomogrm will show tht the scending rmus is elongted verticlly with enlrgement of the condyle. There is lso n elongtion nd thickening of the condylr neck. The ngle of the mndile is rounded, whilst the lower order is owed downwrds to lower level compred to Hemimndiulr elongtion Unilterl horizontl enlrgement of mndile Trnsverse displcement of chin point No trnsverse cnting of occlusl plne Norml lveolr one height ove ID cnl of ffected side the opposite side. There is n increse in the height of the mndiulr ody, which ppers to increse the distnce etween the molr roots nd the mndiulr cnl. The unffected side ppers to hve norml height. This growth defect is clerly demrcted y the symphysis (Figure 2). Hyrid forms of hemimndiulr hyperplsi nd Hemimndiulr hyperplsi Unilterl three dimensionl enlrgement of mndile Trnsverse chin displcement mye miniml. Chin my e rotted Trnsverse cnting of occlusl plne Incresed lveolr one height ove ID cnl of ffected side Tle 2. Differences etween hemimndiulr elongtion nd hemimndiulr hyperplsi. Brnchil rch 1st 2nd Derivtives Tle 3. Derivtives of the 1st nd 2nd rnchil rches. Meckel s crtilge (mlleus, nterior ligment of mlleus, sphenomndiulr ligment), mndile, incus. From the pouch: uditory tue, middle er cvity, tympnic memrne nd externl uditory metus. Mxillry nd mndiulr divisions of the Trigeminl nerve (V). Reichert s crtilge (stpes, styloid process, stylohyoid ligment, lesser cornu nd ody of the hyoid one). Fcil crnil nerve (VII). hemimndiulr elongtion exist where ptients exhiit fetures of oth conditions (Figure 3, ). The differences etween the two conditions re highlighted in Tle 2. Hemifcil microsomi Hemifcil microsomi is congenitl disorder tht results in deficiency in the hrd nd soft tissues on

4 My 2008 Orthodontic Updte 47 Figure 4. () Ptient presenting with right-sided hemifcil microsomi. Lck of mndiulr growth on the right side hs resulted in chin displcement to the ffected side. () A pnormic rdiogrph illustrting the lck of mndiulr growth on the right side. predominntly one side of the fce. The condition is thought to e cused y defect in the prolifertion nd migrtion of erly emryonic neurl crest cells, which results in defects of the 1st nd 2nd rnchil rch structures (Tle 3). However, the 1st rch structures re primrily involved, leding to the underdevelopment of the temporomndiulr joint, mndiulr rmus, mstictory muscles nd the er. Owing to the reduced size of the mstictory muscles, the fcil ones do not mture normlly. In severe cses, lrge portions of the mndile, such s the condyle or rmus, fil to develop. This my result in mndiulr symmetries of vrying severity (Figure 4, ). The occlusion my e ffected with crowding nd unilterl crossite on the ffected side. Tooth development cn lso e distured on the ffected side nd the prevlence of hypodonti is five times more common in these ptients thn the norml popultion. 2 Owing to the ssocition of the specific crnil nerves with the rnchil rches, vrying degrees of nerve plsy my e exhiited. Hemifcil hypertrophy Hemifcil hypertrophy is rre form of overgrowth tht my cuse symmetry in the crniofcil structures, including soft nd hrd tissues. It my lso ffect the occlusion. The hypothesis for the etiology of this condition is n symmetric distriution of neurl crest cells. Torticollis Intr-uterine pressure during pregnncy nd pressure during irth my hve effects on the musculoskeletl system of the foetl skull nd ody. This my led to musculr torticollis (shortening of the sternocleidomstoid muscle) or posturl scoliosis, which cn led to mndiulr symmetries. It should e noted tht there cn e significnt genetic contriution to this condition. Hemifcil trophy (Prry-Romerg syndrome) This is rre disorder tht is chrcterized y progressive trophy of underlying soft tissues nd ones on one side of the fce. Hemifcil trophy is disorder of uncertin etiology. It is more common on the left side nd in femles. The fcil chnges include the tissues round the nose nd nsolil fold nd lter progresses to the ngle of the mouth, eyes, ers nd neck. It follows the distriution of the trigeminl nerve. This my e ccompnied y hyperpigmenttion of the skin, seizures nd fcil pin. It my lso cuse muscle nd fcil one trophy. This cn led to the development of mndiulr symmetry (Figure 5). Pthologicl Tumours Tumours of the orofcil region my ffect the soft tissues, slivry glnds, nerves nd one. These re commonly symmetric in presenttion, eing distinguished from developmentl normlities y their clinicl ehviour nd effects. The locl effects result from compression, invsion, ulcertion or destruction of djcent structures, which my mnifest s chnges in nerve Figure 5. Ptient presenting with hemifcil trophy (Prry-Romerg syndrome) of the right side of the fce. Note the mndiulr growth on the left side resulting in n symmetry on the right side where the trophy hs occurred. senstion, lymph node enlrgement or pin. The melolstom is common odontogenic tumour tht my occur in childhood. It is loclly ggressive enign tumour tht develops from the remnnts of the odontogenic epithelium nd my present in the mndile symmetriclly. It is chrcterized y multiloculr or honeycom ppernce rdiogrphiclly in the ody nd rmus of the mndile. Tumours rrely develop in the condylr hed of the mndile. If they do occur there will e devition of the chin point to the unffected side. Rdiogrphiclly, there will e unilterl condylr enlrgement. Typicl exmples of tumours include osteochondrom, osteom or chondrosrcom.

5 48 Orthodontic Updte My 2008 Cysts nd other pthology Dentigerous cysts, kertocysts nd lympho-epithelil cysts hve symmetric presenttions in the mndiulr region. The condition firous dysplsi my lso ffect the symmetry of the mndile. Exmintion Extr-orl clinicl Dignostic ids Note the position of the midpoint of the chin in reltion to the fcil midline. If discrepncy exists, check if there is trnsverse cnt in the mxillry occlusl plne nd note the reltionship of lower dentl centreline to the midline of the chin. Infections Vrious infections cn present symmetriclly. Exmples of those tht my cuse mndiulr symmetry include dento-lveolr scesses nd cute protitis. These re chrcterized y their rpidity of onset, pin, pyrexi, mlise nd ssocited regionl lymph node involvement. Condylr resorption There re numer of conditions tht my cuse resorption of the mndiulr condyles. These include juvenile rheumtoid rthritis, poststeroid therpy nd orthognthic surgery. Rheumtoid rthritis s child cn ffect the temporomndiulr joint unilterlly or ilterlly, cusing chnges in mndiulr function nd structure. Destruction of the joint nd disc cn e seen s the condition ffects one nd crtilge. If unilterl condylr resorption occurs, then this my result in mndiulr symmetry. Often, multiple joints within the ody re ffected, which helps to mke the dignosis. Condylr resorption following orthognthic surgery cn e cuse of skeletl relpse nd the mechnisms re poorly understood. The predisposing fctors for condylr resorption following orthognthic surgery include pre-opertive temporomndiulr joint dysfunction, eing young nd femle, nd hving high mndiulr plne ngle with mndiulr retrusion. 3 Femles my e more commonly ffected thn mles owing to hormonl fctors. Trumtic Condylr frctures Trum to the condylr region during childhood my result in growth rrest nd impired function. However, the mjority of cses remin undignosed. 4 If growth rrest does occur, this my produce chin symmetry towrds the side of the ffected condyle. The loss of function is usully cused y n nkylosis in the temporomndiulr region. This is initited y the intr-rticulr leeding nd resulting hemtom formtion tht follows trumtic episodes in children. Functionl Intr-orl clinicl Imging Occlusion Pthology Tle 4. Exmintion nd dignostic ids. Mndiulr displcements A uccl crossite occurs when the uccl cusp of mndiulr molr occludes uccl to the uccl cusp of the corresponding mxillry tooth. Slight trnsverse nrrowing of the mxill or ssocited dentition my result in mndiulr to mxillry cuspto-cusp occlusl interferences, resulting in lterl displcement of the mndile s the ptient tries to chieve mximl intercusption on closure. Some uthors hve suggested tht mndiulr growth is restricted on the side of the crossite nd my result in shortening of the rml height on tht side nd contriute to the development of mndiulr symmetry. 5 However, there is not yet ny firm evidence to support this theory. Dignosis Extr-orl clinicl Exmintion cn revel symmetry in three plnes of spce: verticl, ntero-posterior nd trnsverse dimensions. Both skeletl nd soft tissue evlutions must e conducted ilterlly to mke comprisons. Devitions in the dorsum nd tip of the nose, philtrum of the upper lip nd chin point need to e estlished nd should e ssessed in reltion to the fcil midline (Tle 4). Asymmetries in the mndile cn e estlished from frontl views. However, inferior nd superior views must not e discounted s they cn revel the extent of the symmetry in reltion to the rest of the fce. If mndiulr symmetry exists, it is lso importnt to check for co-existing cnt in the mxillry occlusl Check for dentl centreline discrepncies nd occurrence of crossites. If crossite exists, check for mndiulr displcement. Rdiogrphs, photogrphs, CT scn. Study models or rticulted study models with fceow trnsfers. Biopsies, histopthology, silogrphy. Figure 6. Ptient illustrting mxillry cnt with the use of tongue sptul. plne (Figure 6). A trnsverse mxillry cnt is relted to symmetricl verticl growth of the mndiulr rmi. On the side of excessive growth, the mxillry teeth continue to erupt to mintin occlusl contct with the opposing mndiulr dentition, producing cnt. The significnce of mxillry cnt is tht this will require correction with surgery if the mndiulr symmetry is to e corrected. It should e noted tht even estheticlly plesing fces exhiit degree of skeletl symmetry with slight tendency to right-sided dominnce. 6 Mndiulr symmetry is demonstrted in growing children etween the ges of 7 yers nd 16 yers. This does not lwys ecome cliniclly significnt s it my

6 My 2008 Orthodontic Updte 49 represent fluctution in norml growth. 7,8 Intr-orl clinicl Dentl midlines The mxillry nd mndiulr dentl midlines should idelly e coincident with the midline of the fce. If there is discrepncy in the mndiulr dentl midline, it is importnt to recognize whether it is of skeletl or dentl origin. If the mndiulr dentl midline is coincident with the chin point, then the discrepncy is likely to e skeletl in origin nd therefore correction my require n orthognthic pproch. If the dentl midline is not coincident with the chin point, dentl cuse should e considered. Exmintion of the upper nd lower dentl midlines should e crefully undertken in two different mndiulr positions: In centric reltion (retruded contct position, RCP); In centric occlusion (intercuspl position, ICP). The position of the chin point nd mndiulr displcements should lso e noted during these movements. True mndiulr symmetries will demonstrte similr midline discrepncies in centric reltion nd centric occlusion. However, lterl functionl displcements of the mndile re usully the result of occlusl interferences following initil tooth contcts, nd the chnge in midlines will reflect this. Displcements cn occur in the sme or opposite direction to the mndiulr symmetry nd my work to msk or ccentute the symmetry. Occlusion Occlusion in the verticl plne Mxillry nd mndiulr cnts cn e oserved y sking ptients to ite on tongue sptul nd compring this horizontl reference with the inter-pupillry plne, in the sence of verticl oritl dystopi. Occlusion in the trnsverse plne There is often no mndiulr displcement ssocited with true skeletl crossites. However, if there is displcement, then the dentl midlines cn chnge in the sme or opposite direction to the mndiulr symmetry. Dentl crossites cn originte from occlusl interferences, which cuse the mndile to shift lterlly or nteriorly so tht the posterior teeth cn etter interdigitte. A chnge in dentl midlines etween centric reltion nd centric occlusion will ecome pprent if lterl mndiulr displcement exists. There my lso e shift in the chin point when this occurs. Seril nd reproducile clinicl records of the ptient, including imging nd study models, re required to determine if n symmetry is progressive, efore the tretment cn e considered. Imging Rdiogrphs The pnormic rdiogrph llows comprison of the shpe of the mndiulr rmi nd condyles ilterlly. It lso provides n overview of the dentl nd ony structures of the mndile, providing informtion regrding pthology, the numer of teeth nd ny other hrd tissue nomlies. However, owing to the focl trough used in pnormic tomogrphy, there cn e distortions in different res of the imge. Posterior-nterior cephlometric rdiogrphs llow the comprison of left nd right hrd tissue structures. Distortion nd unequl enlrgement re minimized. Midlines of the skeletl structures nd the dentition cn e exmined s they re oth seen on this projection. However, these rdiogrphs cn e misleding s result of vrition in the orienttion of the trnsmetl xis. It is recommended tht these views e tken y clinicins in specilist cre environment. Exmintion of this rdiogrph llows the locliztion of the symmetry y using midsgittl reference plne (where there tends to e the most symmetry). There re three methods used to exmine this imge, including the ntomic pproch, the isection pproch nd tringultion pproch. Other rdiogrphic views, including the trnscrnil nd trnsphryngel views of the temporomndiulr joints, cn lso e tken to investigte pthology, rthritic disese nd trum to this re. Photogrphs Extr-orl photogrphs must e tken in frontl view, with profile nd three-qurter profile views from oth left nd right sides in ptients with symmetry. Superior nd inferior views of the mndile Figure 7. () A three-dimensionl CT scn cn e used to ssess the underlying skeletl deformity. () An exmple of Technetium isotope scn used to ssess the growth ctivity of skeletl sites. In the exmple shown there is no incresed uptke in the condylr regions.

7 50 Orthodontic Updte My 2008 Functionl symmetry Orthodontic tretment Restortion of functionl occlusion Non-orthodontic tretment Occlusl djustment Occlusl splints Skeletl symmetry Orthodontic tretment Growth modifiction Orthodontic cmouflge Surgicl tretment Pthology Tle 5. Mngement of mndiulr symmetries. Orthognthic surgery Distrction Osteogenesis Genioplsty Soft tissue surgery Tret ny dentl infection or refer to hospitl if other pthology contcts or interferences cn e detected. This investigtion should supplement detiled clinicl exmintion of the occlusion in sttic nd dynmic function. Pthologicl specil investigtions If pthology is suspected of cusing the symmetry, the ptient should e referred for specilist cre. Incisionl nd excisionl iopsies will llow histologicl dignosis. This will revel the nture of the hrd or soft tissue pthology, for exmple, firo-osseous lesions or tumour-like lesions. Silogrphy is the rdiogrphic exmintion of the mjor slivry glnds y introducing rdio-opque contrst medium into the ductl system. It will llow the detection of the size, nture nd origin of swelling or mss in the re. my lso form useful record. A front view of the ptient in occlusion iting on tongue sptul will give record of trnsverse occlusl cnting. The intr-orl views will provide importnt informtion out the occlusion. These should e tken in centric reltion nd centric occlusion in cses exhiiting mndiulr displcement. Lser scnning Opticl surfce scnning hs een used to monitor three-dimensionl fcil growth. 9 This is non-invsive technique nd the ssocited softwre llows the digitiztion nd comprison of imges over time. Over 60,000 points re recorded in 10 seconds producing n ccurcy of 0.5 mm. 10 Hence, it is possile to exmine fcil symmetry quntittively. Lser scnning hs lso een used in plstic surgery to study fcil symmetry. 11 Computed tomogrphy (CT) CT scnners use X-rys to produce sectionl imges ut the rdiogrphic film is sustituted with sensitive gs or crystl detectors. These convert the X-ry ems pssed from the ptient into digitl dt. It provides excellent imging of the hrd nd soft tissues with more mnipultion of the tomogrphic sections. However, they re oth expensive nd tend to require high rdition dosge. They cn e used for the investigtion of pthology, including tumours nd temporomndiulr joint imging. Sectionl imges nd 3D reconstructions (Figure 7) cn lso e used to study developmentl deformities nd to locte the position of ny ony deformity. Rdioisotope imging Rdioisotope imging (Figure 7) uses rdioctive compounds tht hve n ffinity for trget tissues. Once they re concentrted in trget tissue, the rdition emissions re detected nd imged using gmm cmer. This llows n investigtion of function nd structure of the trget tissue. Technetium is the most commonly used isotope nd is used to imge ones nd slivry glnds. It cn e used to investigte tumour pthology, especilly in the slivry glnds nd, more importntly, detect the function nd growth in the condylr hed. This form of imging is rrely used nowdys ecuse of the excess rdition exposure nd the high numer of flse positive results. Stereophotogrmmetry Stereophotogrmmetry is method of cquiring three dimensionl imges using multiple photogrphs of the sme oject tken t different ngles. In orthodontics, this cn e used to quntify fcil morphology nd detect chnges in growth nd development of the fce. It cn e used to monitor fcil symmetry s it is oth non-invsive nd reproducile. Articulted study models The functionl occlusion of ptient cn e ssessed more ccurtely with the use of study models tht hve een rticulted with fceow trnsfer. It is importnt to tke jw registrtion in centric reltion so tht ny premture Mngement of mndiulr symmetries The mngement of mndiulr symmetries is summrized in Tle 5. Functionl symmetry Restortion of functionl occlusion Orthodontic tretment cn e used to eliminte crossites tht led to functionl displcements of the mndile. Options involve removle or fixed pplinces. Upper removle pplinces cn eliminte posterior crossite with the use of midline expnsion screw. Fixed pplince pproches include the use of the qudhelix, rpid mxillry expnsion nd uxiliry expnsion rches used in conjunction with routine onded pplinces. 12 Occlusl djustment nd occlusl splints Very minor occlusl djustments cn e mde to remove premture contcts tht cuse mild devitions of the mndile. Skeletl symmetry Figure 8. A hyrid functionl pplince llowing differentil eruption of the mxillry teeth on the left side to compenste for n occlusl cnt.

8 My 2008 Orthodontic Updte 51 Distrction osteogenesis is descried s the induction of cllus of one y osteotomy or corticotomy followed y distrction of proximl nd distl ends to increse one length. It hs een used to tret mndiulr symmetries where the mndiulr rmus nd ody re to e lengthened. 14 This is indicted in severe cses of mndiulr symmetry, for exmple due to hemifcil microsomi or condylr frctures t n erly ge. Figure 9. () Ptient presenting with right-sided mndiulr symmetry. () The sme ptient with corrected symmetry following orthodontics nd imxillry orthognthic surgery. Surgicl procedures s djuncts or lone The lower order osteotomy (genioplsty) of the mndile cn reposition the chin point trnsversely or verticlly in order to ddress the symmetry. It is one of the most stle movements compred to mnging mndiulr symmetries y other orthognthic movements. 15 When the rmus or ody hs degree of symmetric shping tht is contriuting to the overll symmetry of the mndile, then implnts or recontouring of the one surfces cn e undertken. Growth modifiction In cses where mndiulr symmetry or deficiency is identified t young ge, growth modifiction my e ttempted. Hyrid functionl pplinces re specificlly tilored to ddress certin growth processes nd development y comining severl components. 13 The components my ct y the following mechnisms: eruption (iteplnes), linguofcil muscle lnce (shields or screens) nd mndiulr repositioning (construction ites or jw registrtions). It hs een suggested tht these pplinces cuse selective dento-lveolr eruption nd, to lesser extent, encourge degree of norml mndiulr growth to occur to compenste for symmetricl deficiencies in growing ptients (Figure 8). However, evidence for this is lcking. Orthodontic cmouflge If the mndiulr skeletl symmetry is cceptle, nd ny norml growth hs cesed, ut dentl midline shift still exists, then this my e cmouflged orthodonticlly. A numer of techniques cn e used in conjunction with fixed pplinces to correct dentl midline discrepncies including: Asymmetric extrction ptterns; The use of symmetric lcecks; Push-pull mechnics; Asymmetric elstics. Surgicl tretment Orthognthic surgery Mndiulr symmetries tht cnnot e cmouflged y orthodontics lone will require surgicl repositioning of the mndile. This is indicted once norml mndiulr growth hs cesed. Mndiulr symmetries cn often led to secondry mxillry deformity. When the mndiulr symmetry hs verticl component of growth, the mxill will compenste in growth nd cuse trnsverse occlusl cnt. A Le Fort I osteotomy to reposition the mxill my e required if n occlusl cnt is present. Surgicl correction for the mndile usully involves ilterl sgittl split osteotomy procedure, which crries the risk of dmge to the inferior lveolr nerve. Pre-surgicl orthodontics will involve the relief of crowding nd lignment of the rches followed y decompenstion to unmsk the true extent of skeletl discrepncy nd llow mximl chnge with the surgery. There should e no ttempt to correct the dentl midlines t this stge s the correction will occur mostly with the surgicl movements. The mndiulr dentl midline should e mde coincident with the midline of the chin, llowing correction with symmetric mndiulr repositioning t surgery. Post-surgicl orthodontics is usully short in durtion nd minly consists of detiling the occlusion (Figure 9, ). Distrction osteogenesis Soft tissue surgery Excessive musculr contrction (especilly the sternocleidomtoid muscle) in torticollis cn cuse twisting of the hed nd result in mndiulr symmetry. The restriction of growth on the ffected side cn e relieved if the contrcted muscles re surgiclly detched t n erly ge. 16 Pthology If the nture of the mndiulr symmetry is due to pthologicl cuse, then referrl to the pproprite specilty is required for further mngement unless dentl cuse cn e identified. Conclusion Mndiulr symmetries cn hve mny cuses. However, with detiled clinicl exmintion nd further investigtions, the correct dignosis cn e mde. This is essentil s the pproprite mngement for the ptient must ddress oth the ptient s concerns s well s the cuse. These cn rnge from simple mesures to complex multidisciplinry pproches. Some of these cn e crried out y the generl dentl prctitioner, whilst others will require specilist. However, they should im t n esthetic nd functionl result. Acknowledgements We re grteful to Mr Steve Jones (Consultnt Orthodontist) for providing us with Figure 8 nd to Mr Tim Lloyd (Consultnt Mxillofcil Surgeon) for

9 52 Orthodontic Updte My 2008 providing us with Figures 6 nd 9. References 1. Owegeser HL, Mkek MS. Hemimndiulr hyperplsi hemimndiulr elongtion. J Mx Fc Surg 1986; 14: Monhn R, Seder K, Ptel P, Alder M, Grud S, O Gr M. Hemifcil microsomi. J Am Dent Assoc 2001; 132: Hwng SJ, Hers PE, Seifert B, Siler HF. Non-surgicl risk fctors for condylr resorption fter orthognthic surgery. J Crnio-Mxillo-Fcil Surg 2004; 32: Proffit WR, Vig WL, Turvey TA. Erly frcture of the mndiulr condyles: frequently n unsuspected cuse of growth disturnces. Am J Orthod 1980; 78: Schmid W, Mongini F, Felisio A. A computer sed ssessment of structurl nd displcement symmetries of the mndile. Am J Cochrne Synopses Interspce/interdentl rushes for orl hygiene in orthodontic ptients with fixed pplinces Goh HH. Interspce/interdentl rushes for orl hygiene in orthodontic ptients with fixed pplinces. Cochrne Dtse of Systemtic Reviews 2007, Issue 3. Art. No.: CD DOI: / CD pu2. Ptients with fixed orthodontic rces need to mke extr efforts to keep their teeth clen. It hs een recommended y dentists nd hygienists tht specil interdentl or interspce rushes re required to mintin clen teeth. These specil rushes nd the rces men tht toothrushes need replcing more frequently nd therefore men n increse in cost. There is no evidence to show tht this recommendtion is supported y clinicl investigtions. Orthodontic tretment for prominent upper front teeth in children Hrrison JE, O Brien KD, Worthington HV. Orthodontic tretment for prominent upper front teeth in children. Cochrne Dtse of Systemtic Reviews 2007, Issue 3. Art. No.: CD DOI: Orthod Dentofcil Orthop 1991; 100: Peck S, Peck L, Ktj M. Skeletl symmetry in estheticlly plesing fces. Angle Orthod 1991; 61: Melnik AK. A cephlometric study of mndiulr symmetry in longitudinlly followed smple of growing children. Am J Orthod Dentofcil Orthop 1991; 101: Liukkonen M, Sillnmki L, Peltomki T. Mndiulr symmetry in helthy children. Act Odontol Scnd 2005; 63: Nute SJ, Moss JP. Three-dimensionl fcil growth studied y opticl surfce scnning. Br J Orthod 2000; 27: Moss JP, Coomes AM, Linney AD, Cmpos J. Methods of three dimensionl nlysis of ptients with symmetry of the fce. Proc Finn Dent Soc 1991; 87: O Grdy KF, Antonyshyn OM. Fcil symmetry: three-dimensionl nlysis using lser surfce scnning. Plst / CD pu2. Prominent upper front teeth re n importnt nd potentilly hrmful type of orthodontic prolem. This condition develops when the child s permnent teeth erupt nd children re often referred to n orthodontist for tretment with dentl rces to reduce the prominence of the teeth. If child is referred t young ge, the orthodontist is fced with the dilemm of whether to tret the ptient erly or to wit until the child is older nd provide tretment in erly dolescence. The evidence suggests tht providing orthodontic tretment, for children with prominent upper front teeth, in two stges does not hve ny dvntges over providing tretment in one stge, when the children re in erly dolescence. Reinforcement of nchorge during orthodontic rce tretment with implnts or other surgicl methods Skeggs RM, Benson PE, Dyer F. Reinforcement of nchorge during orthodontic rce tretment with implnts or other surgicl methods. Reconstr Surg 1999; 104: Gill D, Nini F, McNlly M, Jones A. The mngement of trnsverse mxillry deficiency. Dent Updte 2004; 31: Vig PS, Vig KWL. Hyrid pplinces: component pproch to dentofcil orthopedics. Am J Orthod Dentofcil Orthop 1986; 90: Tehrnchi A, Behni H. Tretment of mndiulr symmetry y distrction osteogenesis nd orthodontics: report of four cses. Angle Orthod 2000; 70: Proffit WR, Turvey TA, Philips C. Orthognthic surgery: hierrchy of stility. Int J Adult Orthod Othognth Surg 1996; 11: Ferguson JW. Surgicl correction of the fcil deformities secondry to untreted congenitl musculr torticollis. J Crnio-Mxillo-Fcil Surg 1993; 21: Cochrne Dtse of Systemtic Reviews 2007, Issue 3. Art. No.: CD DOI: / CD pu2. Anchorge is the resistnce to unwnted tooth movement during orthodontic tretment. Control of nchorge is importnt in tretment plnning nd often dicttes tretment ojectives. It hs een suggested tht more effective nchorge reinforcement my e offered y surgiclly plced temporry nchorge devices. There is little evidence to support the use of surgicl nchorge systems over conventionl mens of orthodontic nchorge reinforcement. However there is evidence from one recent tril tht showed mid-pltl implnts re n cceptle lterntive to conventionl techniques for reinforcing nchorge. The review uthors were le to find only limited evidence on the use of surgicl mens of preventing nchorge loss compred with conventionl techniques nd the dt showed equivlence, ut not superiority of either type.