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http://dx.doi.org/10.5125/jkaoms.2012.38.5.284 pISSN 2234-7550·eISSN 2234-5930 ORIGINAL ARTICLE Anterior open bite with temporomandibular disorders treated with intermaxillary traction using skeletal anchorage system Hye-Sun Kim, Sang-Hoon Lee, Taegyun Youn, Hyung-Gon Kim, Jong-Ki Huh Department of Oral and Maxillofacial Surgery, Gangnam Severance Hospital, College of Dentistry, Yonsei University, Seoul, Korea Abstract (J Korean Assoc Oral Maxillofac Surg 2012;38:284-94) Objectives: The anterior open bite with temporomandibular disorders (TMD) is one of the most challenging cases both orthodontically and surgically. We introduce an intermaxillary traction treatment for patients with anterior open bite and TMD using a skeletal anchorage system (SAS). Materials and Methods: This study was comprised of 52 patients with anterior open bite and TMD. A total of four mini-screws were inserted, two screws each into the maxilla and mandible, to obtain a class II pattern of elastic application with 120-200 g force. Adjunctive muscle relaxation treatments, such as splint therapy, medication, and botulinum toxin injection were applied during or before intermaxillary traction. At least one treatment among adjunctive muscle relaxation treatment, mentioned above, was applied to 96.2% of patients. We evaluated the clinical characteristics of patients, TMD symptom changes, amount of open bite improved. The degree of open bite improvement was compared between the open bitereduced group (21 patients) and not-reduced group (5 patients). Results: TMD symptoms (muscle/joint pain, joint sound, mouth opening) remained or improved in most patients, and worsened in about 10% of patients for each items. Anterior open bite was improved by a mean of 1.75 mm (P <0.01) during treatment. The open bite-reduced group exhibited a significant open bite improvement compared to the not-reduced group (P <0.05), with 37% of open bite improvement occurring during the first 3 months of treatment. Conclusion: The intermaxillary traction technique using SAS is a valid modality for correction of anterior open bite and improvement of TMD symptoms. Key words: Open bite, Malocclusion, Temporomandibular disorders, Intermaxillary traction [paper submitted 2012. 7. 24 / revised 2012. 9. 20 / accepted 2012. 9. 21] I. Introduction Approachestoopenbitetreatmentmaybelargelyclassified intoorthodontictreatmentandsurgicaltreatment.Treatment throughtheintrusionofposteriorteethiswidelyacceptedin termsoforthodontictreatmentratherthantreatmentthrough the extrusion of anterior teeth. Nonetheless, it has been difficulttoattainthetargetedamountofmolarintrusionby meansoftheexistingorthodontictreatmentmethods1.Asa meansofsurgicaltreatment,orthognathicone-jawsurgery ortwo-jawsurgerywasperformed.Forone-jawsurgery,Le Jong-Ki Huh Department of Oral and Maxillofacial Surgery, Gangnam Severance Hospital, College of Dentistry, Yonsei University, 211, Eonju-ro, Gangnam-gu, Seoul 135-720, Korea TEL: +82-2-2019-4560 FAX: +82-2-3463-4052 E-mail: [email protected] This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/), which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. CC 284 fortIosteotomyaloneusingsuperiorrepositioningofthe maxillaorbilateralsagittalsplitosteotomyalonehasbeen performed2.Nonetheless,surgicallyestablishedpositions haveshowedconsiderableskeletalrecurrenceofincreasein facialheight,decreaseinverticaloverbite,ormolarintrusion duetovariousreasons3. Umemorietal.1startedtousetitaniumscrewsforopen bitetreatment,namingthemtheskeletalanchoragesystem (SAS).SincethenSAShasbeenappliedinavarietyofopen bitecases.Byprovidingabsoluteanchorage,SASenabled performing the intrusion of posterior teeth, which was difficulttodoorthodontically.Itshowedtreatmenteffectsthat weresignificantlycomparablewiththeeffectsoftreatmentof openbitecasesusingorthognathicsurgery4.Additionally,itis simpleandeconomicalmethodcomparedwithitstreatment effects,SASisemergingasanattractiveopenbitetreatment methodforbothorthodontistsandsurgeons5. Anterior open bite has been known as a significantly frequentformofmalocclusioninpatientswithtemporoman- Anterior open bite with temporomandibular disorders treated with intermaxillary traction using skeletal anchorage system dibulardisorders(TMD)6-8.Note,however,thattherehave beenfewreportsofintermaxillarytractionusingSASforthe treatmentofanterioropenbitewithTMD.Inpresentstudy, weintroducedhowtoapplyintermaxillarytractionusing SASandinvestigatedandanalyzedclinicalcharacteristics andtreatmenteffectsforpatientswithanterioropenbiteand TMDwhovisitedourclinicsbetween2005and2011. II. Materials and Methods 1. Patient selection Sixty-five patients whose chief complaint was TMD, visiteddepartmentoforalandmaxillofacialdepartmentof GangnamSeveranceHospitalbetweenAugust2005andJuly 2011wereincludedinthisstudy.Theyexhibitedanterior openbiteandreceivedintermaxillarytractiontreatmentusing SASandelastics.Weinvestigateditems-patientdistribution, clinicalcharacteristicsrelatedtoTMD -of52patients(8 males, 45 females) after patient exclusion according to criteriaasfollows.Andimprovementamountsandpatternsof anterioropenbitewereinvestigatedwith26patientswhose openbiterecordswerefullywritten. <ExclusionCriteria> 1)Patientswhoweretreatedbynotonlyintermaxillary traction,butalsoorthodontictreatmentforcorrectionof anterioropenbite. 2)Patientswhoweretreatedbyintermaxillarytractionfor treatmentofopenlockorhabitualluxation. 3) Patients with anterior open bite due to a long habit continued since their growth period, such as finger suckingsincechildhood. 4)Patientswhodidnotwearelasticscontinuouslydueto their non-cooperation during intermaxillary traction treatment. Allpatientshadatleast6monthsoftreatmentperiodby consideringtheperiodofmuscularadaptation.Datawere collectedbasedonthemedicalrecordsofthehospitalby retrospectivestudy.Thisstudywasperformedafterreview andapproval(IRB#3-2012-0115)bytheInstitutionalReview BoardofGangnamSeveranceHospital. 2. Treatment protocol of intermaxillary traction Atotaloffour1.6×8mmscrews(Orlus;OrtholutionCo., Seoul,Korea)wereusedfor therespective placementof twoscrewsinthemaxilla(upperjaw)andtwoscrewsin themandible(lowerjaw).Thescrewswereplacedusing onlyadriverunderlocalanesthesiawithoutcorticalbone drillingpriortotheirplacement.Ingeneral,screwswere placedbetweenthecanineandpremolarintheupperjaw and between the first and second premolars in the lower jaw.However,placementsiteswereeachmodifiedslightly according to the thickness of the interproximal bone or periodontalconditionineachpatient.Accordingly,rubber bandsweremadetotaketheformofclassIIelasticswhen applied;thusensuringthatanterior-superiortractionforce wasappliedtothemandible.Twoweeksaftertheplacement ofscrews,elasticswereappliedwithforceofabout120200gapproximately.Thescrewswereremovedincasethat anterioropenbitewasclosedandretainedatleast6months orincasethattherewerenofurtherchangesinanterioropen biteforatleast6months.Duringtheretentionperiod,rubber bandswereappliedonlyduringsleepeverydayorevery otherday. 3. Evaluation tools 1)Patientdistribution Regarding the conditions of the patients at the initial examination,weinvestigatedthetimingofopenbiteinitiated in each patient, the profile, changes of condylar shape, and changes in anterior open bite when forced on chin topanterio-superiorly.Inthefirstplace,toinvestigatethe timingofopenbiteinitiatedineachpatient,weclassifiedthe patientsintogroupsshowedanterioropenbiteattheinitial examination,groupsshowedanterioropenbiteduringorafter treatmentofocclusalstabilizationsplint,andgroupsshowed anterioropenbiteafterorthognathicsurgery.Inthegroup withhistoryoforthognathicsurgery,weinvestigatedonlythe patientsforwhichatleast1yearhadpassedafterthesurgery toensuredifferentiationfromanysurgicalrelapsethatmay occurimmediatelyaftersurgery.Theprofilesofpatients wereclassifiedintoretrognathic,normal,andprognathic byanalyzingtheirlateralcephalometricradiographs.We investigatedwhetherornottherewasanychangeintheshape ofthecondylarheadbasedontheirpanoramicradiographs and lateral tomograms by classifying detailed items into the following: (1) normal bone; (2) morphological bony change;adaptivenormalchangeincondylarheadsuchas flatteningofthecondylarhead,osteophyteformation,or subchondralsclerosiswhilemaintaininganobviouscortical bonelayer;(3)erosivebonychange;lossofcorticalbone layerinthecondylarheadandonthetemporalbonesurface9. 285 J Korean Assoc Oral Maxillofac Surg 2012;38:284-94 Evaluationofcondylarchangewasrecordedbasedonthe severesideamongcondyleonbothsides.Impressiontaking wasperformedtoconfirmocclusionineachpatient.The occlusionofstudymodelandtheocclusionofactualpatient werecompared.Inaddition,weinvestigatedandrecorded whethertherewasadecreaseintheamountofanterioropen biteintheactualpatientbyapplyingexternalforcetothe chintopintheanteriorandsuperiordirectionsusingathumb attheinitialclinicalexamination.(Fig.1) 2)Evaluationmethods-temporomandibulardisorders Beforeorduringintermaxillarytractiontreatment,several adjunctivetreatmentsformusclerelaxation -splinttherapy, medication,botulinumtoxininjection(Botox;AllerganInc., Irvine,CA,USA) -wereappliedandinvestigated.Muscle painontemporalis,masseter,digastricmuscle,jointpain, joint sound (clicking/popping/crepitus), and maximum mouthopeningwererecordedatbothinitialexaminationand afterintermaxillarytractiontreatment.Thechangesinthe maximummouthopeningbeforeandafterthetreatmentwere statisticallyanalyzedusingthepairedttest. 3)Evaluationmethods-anterioropenbite For measurement of amount of anterior open bite, the shortestdistancebetweenincisaledgeofupperincisorand lowerincisorwasutilizedandrecorded10.Themeasurement ofamountofanterioropenbitewasrecordedascumulative statisticsatbeforetreatment,3,6,9,12monthssincestart oftreatment,andafterthetreatmentfinished.Weclassified thepatientsintothegroupshowinganopenbitereduced (reducedgroup)andthegroupshowingnoopenbitereduced (notreducedgroup)accordingtowhetherornottherewasa decreaseintheamountofanterioropenbitewhenanterior- superiorforce wasappliedonchintop.Bydoingso,we presentedboththecumulativestatisticsduringthetreatment period and the sectional statistics divided into each 0-3, 3-6,6-9and9-12months.Statisticaldataprocessingwas performed using a statistical analysis software program (Statviewversion9.2;SASInstituteInc.,NC,USA).The statistically significant differences among measurement values were tested using independent two sample t test togetherwiththeWilcoxonranksumtest,whichwasalso performedasanonparametrictestconsideringthenumberof samples.Inaddition,repeatedmeasuresforANOVAwere carriedouttoverifythestatisticalsignificanceoftheamounts ofopenbiteimprovementaccordingtotheperiodicchanges. III. Results 1. Patient distribution Theaverageageofthepatientsasourstudysubjectswas 26.1years(13to51years)atthetimeofstartingintermaxillary tractiontreatment.Forthepatientdistributionbyage,12were intheirteens(23.1%),28wereintheirtwenties(53.8%),7were intheirthirties(13.5%),3wereintheirforties(5.8%),and2 wereintheirfifties(3.8%). Inclassifyingthepatientsaccordingtotherecognitiontime ofopenbiteinitiation,thenumberofpatientsobservedto haveanterioropenbiteattheinitialexamination,regardless ofpatient’srecognitionaboutexacttiming,was17(32.7%), with23(44.2%)patientsshowinganopenbiteduringor aftertreatmentusingocclusalstabilizationsplint,4(7.7%) patientsexhibitinganopenbiteafterorthognathicsurgery, and8(15.4%)patientsfallingunderthe“others”category. Amongthepatientswhoshowedanopenbiteaftertreatment Fig. 1. Open bite reduced group when forced on chin top. A. Not forced on chin top. B. Forced on chin top. Hye-Sun Kim et al: Anterior open bite with temporomandibular disorders treated with intermaxillary traction using skeletal anchorage system. J Korean Assoc Oral Maxillofac Surg 2012 286 Anterior open bite with temporomandibular disorders treated with intermaxillary traction using skeletal anchorage system intotwogroups -24people(80%)intheopenbitereduced group(reducedgroup)and6people(20%)intheopenbite notreducedgroup(notreducedgroup). usinganocclusalstabilizationsplint,14experiencedanopen biteimmediatelyaftertreatmentusingthesplinttherapy.The 9otherpeoplehadahistoryofhavingundergonetreatment usingthesplinttherapy,butthetimetheyshowedanopen bitedidnotcorrespondtothetimetheyworeanocclusal stabilizationsplint.Amongthoseinthe“others”category, 2peopleshowedanopenbiteafterorthodontictreatment, 3experiencedanopenbiteaftertemporomandibularjoint (TMJ)opensurgery,1startedtohaveanopenbiteduringthe treatmentofTMD,and2peopleshowednorecordsabout timingofopenbitestarted. According to the result of investigating the profiles of patientsexcept7peoplewholackedrecordsoftheirprofiles, the number of patients with retrognathic profile was 27 (51.9%),withpatientshavinganormalprofilenumbering18 (34.6%);therewasnocaseofanypatientwithprognathic profile.Inexaminingtheircondylarchanges,thenumberof patientsshowingonlymorphologicalbonychangewas14 (26.9%),with24people(26.2%)representedbypatients showingobviouscondylarresorptionthrougherosivebony change and 14 people (26.9%) showing normal bone. Regarding age of patients, all patients in their forties or oldershowedmorphologicalorerosivebonychangeinthe condylarhead.Accordingtotheresultofinvestigatingthe changesinamountofanterioropenbitewhenforcedanteriorsuperiorly on chin top at initial examination, except 22 patientwholackedrecords,thepatientgroupsweredivided FortreatmentofTMDaswellastoaidmuscularadaptation duringtractiontreatment,adjunctivetreatmentformuscle relaxationwasapplied.Weusedanteriorpositioningsplints forsplinttherapyandadministeredmusclerelaxantsandnonsteroidalanti-inflammatorydrugsformedicationtherapy. Injectionofbotulinumtoxinwasperformedifnecessaryby applying25-30unitsperside(massetermuscleormasseter andtemporalismuscles).Amongthepatientswhounderwent intermaxillarytractiontreatment,50(96.2%)receivedatleast oneormorekindsofadjunctivemusclerelaxationtreatment mentionedabove,twopatients(3.8%)didnotreceiveany adjunctivetreatment.(Fig.2) TMJsymptomswereevaluatedbeforeandafterintermaxillarytractiontreatmentusingthefollowingitems:muscle pain,jointpain,jointsound,andmaximummouthopening. Most TMJ symptoms were improved or maintained, and thecaseofworseningTMJsymptomsaccountedforabout 10%orlessofthepatientsforeachitem.(Fig.3)Theaverage maximummouthopeningincreasedfrom45.0mmbefore treatment to 46.5 mm after treatment finished with no statisticalsignificanceonpairedttest. Fig. 2. Adjunctive treatment for muscle relaxation. (BTI: botulinum toxin A injection) Fig. 3. Symptom changes of temporomandibular disorders between before and after treatment of intermaxillary traction using skeletal anchorage system. (MMO: maximum mouth opening, Y: symptoms exist, N: symptoms not exist) Hye-Sun Kim et al: Anterior open bite with temporomandibular disorders treated with intermaxillary traction using skeletal anchorage system. J Korean Assoc Oral Maxillofac Surg 2012 Hye-Sun Kim et al: Anterior open bite with temporomandibular disorders treated with intermaxillary traction using skeletal anchorage system. J Korean Assoc Oral Maxillofac Surg 2012 2. Results - temporomandibular disorders 287 J Korean Assoc Oral Maxillofac Surg 2012;38:284-94 3. Improvement amount and treatment duration of anterior open bite Theaveragetreatmentdurationbyintermaxillarytraction was19months.Evaluationoftheamountsofanterioropen biteimprovementwasperformedon26patientswhohave fullywrittenmedicalrecordsonbothtwoitems -changes on anterior open bite when forced on chin top at initial examination,fullyrecordedofamountofoverbiteoneach regularfollow-upvisit.Atinitialexamination,thepatients showedanaverageamountofopenbiteof-2.42(±2.38) mm.Theamountofopenbiteshowedstatisticallysignificant decrease(P <0.01)astreatmentprogressed,therebyatthe timeoftreatmentfinished,theamountofoverbitegainedwas 1.75(±1.33)mmonaverage.(Table1,Figs.4,5) Investigatingwhetherornotanterioropenbitegetsreduced whenanteriorsuperiorforcedonchintopamong26patients, 21patientswereinreducedgroupand5patientswerenot reducedgroup.Amongthe21patientofreducedgroup,19 showedanimprovementintheiropenbitesand2hadtheir openbitesunchanged;therewasnocaseofapatient’sopen biteworsening.Amongthe5patientsinthenon-reduced group,4showedanimprovementintheiropenbites;there wasnocasesofpatient’sopenbiteremainingunchanged, with one patient’s open bite worsening. To compare the amountofanterioropenbitebetweenreducedgroupand not-reduced group periodically, reduced group showed a statisticallysignificantamountofopenbiteimprovement (P <0.01),butthesamecannotbesaidforthenon-reduced group. Statistically, both independent two sample t test asaparametrictestandWilcoxonranksumtestasanonparametric test were performed and both presented the sameresultofstatisticalsignificance.Fortheconvenience ofdescribingdescriptivestatistics,wepresentedtheresult ofparametrictestinthispaper.Inbothperiodiccumulative statisticsandsectionalstatistics,thereducedgroupshowed asignificantlylargeamountofopenbitedecrease(P <0.05) comparedwiththenot-reducedgroupupto3monthsfrom traction treatment started. As the treatment progressed periodicallyuptotreatmentfinished,thereducedgroupalso showedasignificantlylargeopenbitedecrease(P <0.05) compared with the not-reduced group in the cumulative statistics.(Tables2,3) Table 1. Amount of overbite gained (=open bite closed) by treatment period (mean±SD, n=26) Treatment period (months) 3 6 9 12 Final results P -value* Amount of overbite gained (mm) 0.64±0.64 1.04±0.92 1.28±0.92 1.48±1.09 1.75±1.33 0.0017 (SD: standard deviation) *Statistical analysis by repeated measures for ANOVA. Hye-Sun Kim et al: Anterior open bite with temporomandibular disorders treated with intermaxillary traction using skeletal anchorage system. J Korean Assoc Oral Maxillofac Surg 2012 Fig. 4. Intraoral photographs during intermaxillary traction treatment using skeletal anchorage system. A. Start of traction. B. 3 months later. C. 9 months later. D. 1 year 3 months later. Hye-Sun Kim et al: Anterior open bite with temporomandibular disorders treated with intermaxillary traction using skeletal anchorage system. J Korean Assoc Oral Maxillofac Surg 2012 288 Anterior open bite with temporomandibular disorders treated with intermaxillary traction using skeletal anchorage system Fig. 5. A. Lateral cephalometric radio graphs. Left: pretreatment, middle: anterior open bite closed, right: the most posterior teeth extruded for occlusion seating. B. Superimposition of cephalometric tracings before (black line) and after (gray line) intermaxillary tract ion treatment using skeletal anchorage system. Left: superimposed on sella-nasion plane at sella, middle: superimposed on palatal plane at ante rior nasal spine, right: superimposed on mandibular plane at menton. Hye-Sun Kim et al: Anterior open bite with temporomandibular disorders treated with intermaxillary traction using skeletal anchorage system. J Korean Assoc Oral Maxillofac Surg 2012 Table 2. Comparison of overbite gained (=open bite closed) between the “open bite reduced group” and “not reduced group” when forced on chin top-statistical data by cumulative treatment period (mean±SD, n=26) Treatment period 3 months 6 months 9 months 12 months Final result P -value** Open bite, when forced on chin top Y (n=21) N (n=5) 0.76±0.64 1.14±0.90 1.37±0.96 1.69±0.89 2.05±1.14 0.0003 0.10±0.22 0.60±0.96 0.90±0.65 0.58±1.50 0.50±1.46 0.8357 P -value* 0.0351 0.2411 0.3165 0.0379 0.0159 (SD: standard deviation, Y: open bite reduced group, N: open bite not reduced group) *Statistical analysis by independent two sample t test between the Y group and N group, **statistical analysis by repeated measures for ANOVA to evaluate periodic progress in each group. The amount of overbite gained (unit, mm). Hye-Sun Kim et al: Anterior open bite with temporomandibular disorders treated with intermaxillary traction using skeletal anchorage system. J Korean Assoc Oral Maxillofac Surg 2012 IV. Discussion Classificationofthetimingofopenbiterecognitionis Table 3. Comparison of overbite gained (=open bite closed) between the “open bite reduced group” and “not reduced group” when forced on chin top-statistical data by sectional treatment period (mean±SD, n=26) Treatment period (sectional) Y (n=21) N (n=5) P -value* 0-3 months 3-6 months 6-9 months 9-12 months 0.76±0.64 0.38±0.50 0.22±0.53 0.32±0.60 0.10±0.22 0.50±0.87 0.03±0.45 -0.32±1.07 0.0351 0.6814 0.7683 0.0761 Open bite, when forced on chin top (SD: standard deviation, Y: open bite reduced group, N: open bite not reduced group) *Statistical analysis by independent two sample t test. The amount of overbite gained (unit, mm). Hye-Sun Kim et al: Anterior open bite with temporomandibular disorders treated with intermaxillary traction using skeletal anchorage system. J Korean Assoc Oral Maxillofac Surg 2012 correlatedwiththeetiologicalfactorsofopenbite.Note, however,thatthisinvestigationwasperformedwithinthe categoryofpatientswithTMD;thereforeclassificationof thetimingofopenbiterecognitionshouldnottoberegarded straight ahead as the classification of causative factors. 289 J Korean Assoc Oral Maxillofac Surg 2012;38:284-94 Thisinvestigationwasintendedforbetterunderstandingof processofanopenbiteoccurrence.Firstly,thepatientgroup thatanterioropenbitewasobservedatinitialexamination regardlessofpatient’srecognitionformedrelativelylarge portionof32.7%(17patients).Thispatientgroupcanbe explainedintwoaspectsasmuscularfactorsandcondylar resorption. First, there were patients showing only joint spacenarrowingtogetherwithananterioropenbitewithout anymorphologicalchangeintheircondylarheadsintheir panoramic radiographs and lateral tomograms. We think theexcessivetensionofthemasticatorymuscleservesasan excessivelyheavyloadontheTMJportion,resultinginthe narrowingofthejointspaceand-insteadofmolarintrusion- theclockwiserotationofthemandiblewiththemostposterior molarplayingtheroleoftheleverfulcrum,consideredto induceananterioropenbite.Second,therewerepatients showinganobviousmorphologicalchangeintheircondylar heads in their radiographs. Most patients in this group showedtheaspectofanterioropenbiteduetoidiopathicor progressivecondylarresorption.Arnettetal.11,12presented two main causative factors of idiopathic or progressive condylar resorption-the continuous excessive physical stressontheTMJportionandthedecreasedadaptability ofpatients.Oneofthecontributingelementsfordecreased hostadaptabilityistheageofthepatient.Agegroupswhose environmentaladaptabilitydecreasearegroupoftwenties tothirtiespresentingprogressivecondylarresorptiondueto unknownreasonsandgroupsoffiftiestosixtiespresenting degenerativecondylarchanges11.Accordingly,thispatient distributionbyagewascorrespondedwiththedistribution inourstudy.Thoughbothidiopathiccondylarresorption and degenerative arthritis show mechanism differences, these have similar process of morphological change of condyle -ifseverephysicalstressisappliedexceedinghost adaptabilitytoTMJportion,morphologicalchangeoccursin thecondylarheadandintheglenoidfossa,therebyresulting inadecreaseintheposteriormandibularverticalheight.This showsdecreasedmandibulargrowthinagrowingchildand givesrisestoananterioropenbitetogetherwithprogressive mandibularretrusioninanadult11,13.Similarly,thepatient group with retrognathic profile accounted for the largest proportionat51.9%andtherewasnopatientgroupwith prognathicprofileinthisstudy. Intheclassificationofthetimingofopenbiterecognition, 23patients(44.2%)showedanopenbiteduringoraftersplint therapy.Thesplinttherapywaschosenasaconservative therapytodecreasetheloadonTMJandreducethehyper290 activityoftensemuscles.Butananterioropenbitemayoccur asasideeffectespeciallyinapatientwearingthesplintall daylongorapatientwearingapartialcoverageappliance. Ifasplintbecomeswornasaresultoflong-timeuseorif itisnotcheckedproperly,ananterioropenbitemayoccur duetotheselectivelyexcessiveeruptionofmolarteeth14.In addition,severalresearchwerereportedthatuseofsplint alteredthemasticatorymuscleactivity,soocclusalforcewere newlysetupandverticalheightgotchanged;thusresulting thepositionalchangeofmandibleitself,notthemovement ofteeth,whichleadstotheoccurrenceofananterioropen bite15,16.Basedontheresultsofthisstudy,9patients(17.3%) hadahistoryofhavingundergonesplinttherapy,butthe time of open bite recognition did not match the time of wearingasplint.Wethinktheyarepatientscombinedwith twocausativefactors -anterioropenbiteaftersplinttherapy orsplinttherapyduringprogressionofidiopathiccondylar resorptionwhichmayleadtoanterioropenbite. Inclassificationofthetimingofopenbiterecognition, 4patients(7.7%)showedanopenbiteafterorthognathic surgery. The positional change of bone segments, which occurs during orthognathic surgery, gives rise to a compressive force being applied to the condylar head in the glenoidfossa;ifitcontinues,itmaygiverisetoTMJpainand condylarresorption,therebycausingadelayedrelapseinthe mandible12,17,18.Intheirevaluationofthelong-termstability afterorthognathicsurgery,Hoppenreijsetal.19reportedthe frequent occurrence of progressive condylar resorption, especiallyinthecaseofmandibularadvancementsurgery throughsagittalsplitramusosteotomy.Condylarresorption afterorthognathicsurgeryisaggravatedbythemuscular action of the masseter muscle and the medial pterygoid muscle;thuscausingthemandibletoberetrudedposteriorly, whichgivesrisetoananterioropenbite12. Theexistingtreatmentofanterioropenbitethathasbeen suggestedsofararelargelydividedintoorthodontictreatmentandsurgicaltreatment.Inthe1980sto1990s,openbite treatmentthroughtheextrusionofanteriorteethwasmainly usedasakindoforthodontictreatment.Note,however,that theextrusionofanteriorteethleadstoshowpoorprofiles resultingfromtheclockwiserotationofthemandible.Also in the evaluation of long-term stability for 10 years by extrusionofanteriorteeth,over35%ofthepatientswere saidtoshowarelapseofmorethan3mm20.Molarintrusion providesmoreefficientandmorestabletreatmentresults, andattemptshavebeenmadetousebiteplates,springs,high pullheadgears,fixedappliances,verticalelastics,andmulti- Anterior open bite with temporomandibular disorders treated with intermaxillary traction using skeletal anchorage system loopedgewisearchwire(MEAW)forthis.Nonetheless,it hasbeendifficulttoattaintherequiredamountofmolar intrusion21-23.Surgicaltreatmentcansolvetheproblemof anterioropenbitemainlythroughsuperiorrepositioningof themaxillaandcounterclockwiserotationofthemandible, however the evaluation of long term stability revealed thatmaxillawasmainlyaccompaniedbyverticalrelapse. Approximately 10% of the patients who had underwent surgery showed a significant 2-4 mm relapse of anterior openbite24.Intheevaluationoftheone-yearpost-operative stabilitybyOliveiraandBloomquist25,theaveragerateof skeletalrelapsewasfoundtobe33.42%.Inaddition,there areseveralfactorscausingrelapse-condylarresorptionby acompressiveforceduetothemovementofbonesegments causesdelayedrelapseasmentionedabove,anincreaseinthe posteriorfacialheightoccurringduringthecounterclockwise rotationofthemandiblemayresultintheelongationofthe pterygomasseteric sling, and the mandibular symphysis movingawayfromthehyoidbonecauseelongationofthe suprahyoidmuscle2.Ontheotherhand,orthodontictreatment usingSAScanattainrelativelyeasilytherequiredamountof molarintrusion,whichhasbeendifficultusingtheexisting orthodontictreatmentmeansandhaveshowncomparable treatmenteffectwiththeeffectofsurgicaltreatmentinthe post-treatmentcephalometricanalysis4.Asinthecaseofa relativelylowrelapserateof10.36%inorthodontictreatment using SAS as reported by Lee and Park 21, orthodontic treatmentusingSAShasmeritsintermsofstabilityafter treatmentsinceitprovidestimefortheslowadaptationof musclescomparedwithsurgicaltreatment. Sincemalocclusionisrelatedtothemalpositionofthe mandibularcondyleintheglenoidfossa,itisanimportant causativefactorofTMD26,27.AsonecanseeintheepidemiologicalstudyconductedbyEgermarketal.28andHenrikson etal.29,anterioropenbiteiscloselyrelatedtoTMDamong otherkindsofmalocclusion.Therefore,specialconsideration forthosepatientswithTMDandanterioropenbitepatients has become acutely required. Regarding this in the case of surgical treatment, Aghabeigi et al. 30 reported that orthognathic surgery was not effective for anterior open bitepatientswithTMDbutwasfoundtoleadtocondylar resorption. Though, orthodontic treatment using SAS makes molar intrusioneffectivelyandhasseveralmerits - normalization of condylar position in glenoid fossa by counterclockwiserotationofmandible,havingenoughtime formuscleadaptationtonewlyposition31,32,therewasalsoa casewhereinadecreaseintheposteriorfacialheightrather increased loading on condyle; thus triggering condylar resorption. Besidessurgicaltreatmentandorthodontictreatmentof patientswithanterioropenbiteandTMD,attemptshave beenmadetoreducethecompressiveforceonTMJportion topreventtheprogressofcondylarresorption,whichmay leadtoananterioropenbite.Forthis,intermaxillarytraction bybuttonattachmentatbuccalcrownofpremolarshadbeen tried,buthassideeffectsofextrusionofbuttonattachedpremolars.IntermaxillarytractionbyPivotsplinthadalso beentried,butitwashardtoreducetheloadinginjointspace andhaslimitationtoresolveanterioropenbite14,33.Inthis study,weappliedthetreatmentofintermaxillarytraction usingSAS,andevaluatedsymptomchangesrelatedtoTMJ andimprovementamountofanterioropenbite.Beforestartingtreatment,wetookanimpressionandmadethestudy modelofupperandlowerdentitionofeachpatient,thenwe investigatedwhethermaximumintercuspitationcouldbe inducedonstudymodelornot,andcomparedtheocclusion betweenstudymodelandactualocclusionofpatients.One oftheaspectsdifferentiatingtreatmentbyintermaxillary tractionfromtheexistingorthodontictreatmentmethodsis thefactthatithasobtainedtreatmenteffectsonlybyelastic tractionaftermini-screwplacementinsteadofusingbracket orwireorthodontically.Theotherdifferentiatingpointisthe placementareaofmini-screwswhichisplacedonmolararea formolarintrusionorthodontically,butplacedonpremolar areaforintermaxillarytractionusedinthisstudy.Ifthereare somecasesthatobviousprematurecontactofpremolarson studymodelexist,weappliedintermaxillarytractionusing SASfirstforrelieveTMJsymptomandimproveanterior openbite,thenreferredtoorthodontisttoeliminatepremature contact ; these cases were excluded for this study. As a resultoftreatment,molarintrusionledtoimprovepatient’s profileofretrudedchinthroughclosureofanterioropenbite. Therefore,Bpoint(mostposteriorpointonthebonycurve between infradentale and pogonion) moved forward and thevalueofANB(angleformedbyApoint,nasion,andB point)becameimproved.(Fig.5)Therewasadecreaseinthe mandibularplaneangleandadecreaseintheanteriorfacial heightduetothecounterclockwiserotationofthemandible, therebyeasingthetensionofmusclesaroundthelips.An increaseinthejointspacemayalsobeexpectedduetothe counterclockwiserotationofthemandible,butitwasdifficult tomeasurejointspacechangeinlateralcephalometrics.From theresultoftracingthelateralcephalometrics,bothmolar intrusionandmildextrusionofanteriorteethwereoccurred 291 J Korean Assoc Oral Maxillofac Surg 2012;38:284-94 togetherbyexistingorthodonticapproach,butthetreatment effectwasappearedmainlybymolarintrusionratherthan anteriorteethextrusionbyintermaxillarytractionusingSAS inthisstudy.Inthecaseofpatientswithalargeamount ofanterioropenbite,themostposteriormolarsmayplay aroleasleverfulcrumbycondylarresorptiononanteriorsuperiorsurface,therebythemostposteriormolarscometo becompressedbybiteforcecontinuously.Ifintermaxillary tractiontreatmentappliedinthesepatients,additionallonger retentionperiodisrequiredafterclosureofanterioropen bitetoexpectocclusalseatingofthemostposteriormolars. (Fig.5)Asaresultoftreatmentbyintermaxillarytraction, the final amount of anterior open bite improvement was foundtobe1.75±1.33mmonaverage,andittook6months oftreatmentperiodtoachieveopenbiteimprovementof about1mm.Adjunctivetreatmentformusclerelaxationwas appliedtopatientsbeforeorduringintermaxillarytraction treatment.Theadjunctivetreatmentwasperformednotonly torelievemusclepainandrelaxthetensemuscles,butalsoto haveexpectationformaintainingthetreatmenteffectsafter treatmentfinishedbygivingmusclesenoughtimetoadapt tochangedskeletalposition.Inotherwords,repositioningof thecondylarhead,easingthetensionofsurroundingmuscles, andphysiologicaladaptationthroughintermaxillarytraction areimportantelementsforsolvingthesymptomsofTMD. Forthispurpose,weusedmedicationtreatment,physical treatment,injectionofbotulinumtoxin,andsplinttherapy34. Musclerelaxantsandnon-steroidalanti-inflammatorydrugs (NSAIDs) were mainly used for medication treatment. Musclerelaxantsareknowntocontroltheconvulsionand painwithdrawalreflexofthemasticatorymuscle35.Asfor physicaltreatment,hotwetpacktreatmentandmandibular exercisetreatmentwereused.Hotwetpackseasemuscles andhelpperformexercisetreatmentundertheconditionof relievedpain.Exercisetreatmentwasperformedtobuildup thestrengthofmuscles,preventthecontractionofjoints, and maintain the range of functional jaw movement 36. Injectionofbotulinumtoxinwascarriedoutwhenreducing thecontractionandstrengthofthemasticatorymusclewas additionallyrequired.Splinttherapyreducestheloadonthe TMJandreducesthehyperactivityofmuscles.Inthisstudy, anterior positioning splints were used for treatment with splinttherapy.Thissplintmakecondyletoplaceoncenteror slightlyanteriorinferiorportionofglenoidfossa,whichwas originallypositionedatposteriorsuperiorportionofglenoid fossa by excessive action of jaw-closing muscles before treatment;sothatitcanreducetheloadoncondyle,reduce 292 inflammationsurroundingjoint,increaserangeofmandibular movement,andrelievesymptomsofTMD37.Whenintermaxillary traction and splint therapy were performed in combination,intheinitialstage,wehadthepatientswear elasticsforintermaxillarytractionduringdaytimeandboth elasticsandanteriorpositioningsplintswhensleeping.When occlusionhadbecomestablealongwithincreasingoverbite, andtheirTMJsymptomshadimproved,wehadthemwear elasticswithoutanysplintonlywhensleeping. TheTMJsymptomsofthepatientsmostlyimprovedafter bothintermaxillarytractionforcondylarrepositioningand adjunctivetreatmentformusclerelaxation.Intheevaluation ofthetreatmentresults,however,patientsshowingnochange intheirTMJsymptomsbeforeandaftertreatmentaccounted foralargeproportion,thiscanbeinterpretedintwoways. First,sincetheywereanterioropenbitepatientsaccompanied withTMD,iftreatmentoftheirTMDwasperformedprior totreatmentbyintermaxillarytraction,itcouldbewrittenin medicalrecord,immediatelybeforetractiontreatment,that TMJsymptomshadbeenrelieved;thentherecouldbeno changeinTMJsymptomsbeforeandafterintermaxillary tractiontreatment.Inothercaseswhichtherewasnochange in the TMJ symptoms, if TMD were related with sociopsychologicalfactorsorcompoundedwithpainonotherpart ofbody,theirTMDmayhavepersistedorfailedtorespond toanyacceptedtreatment. Weinvestigatedthedifferencesintheamountofopenbite improvementaccordingtowhetherornotanterioropenbite wasreducedbyanteriorsuperiorforceonchintop.Ifanterior openbitewasnotreducedbyforceonchintop,thecauses maybeconsideredintwoways.Firstly,inthelateralviewof occlusalpattern,awedge-shapedopenbitefromtheincisor tothemostposteriormolarcouldbeobserved,justsameas openbitepatternof‘reducedgroup’whenforcedonchintop. Inthiscase,theamountofanterioropenbiteisnotreduced byexternalforcebecauseofmuscularfactors-excessive strongstrengthofmasticatorymuscleorstiffenedmuscle. Second,intheviewofocclusalpatternonstudymodel,these arethecasesthatmaximumintercuspitationhadnotbeen inducedonstudymodel.Patientswhohavinghadabadhabit suchasfingersuckingortonguethrustingintheirchildhood orpatientsexhibitingstableocclusionstateofanterioropen bitebyextrudedpremolarteethwerebelongedtothesegroup ofocclusalpatternandexcludedfromthescopeofthisstudy. Inthecumulativestatisticsbytreatmentperiod,‘reduced group’ showed significantly greater amount of open bite improvementthan‘not-reducedgroup’atperiodicpointsof3 Anterior open bite with temporomandibular disorders treated with intermaxillary traction using skeletal anchorage system months,12months,finaltreatment.Inthesectionalstatistics bytreatmentperiod,whichreflectsimprovementspeedof anterioropenbite,‘reducedgroup’exhibitedsignificantly greateramountofopenbiteimprovementthan‘notreduced group’forupto3monthsfromtreatmentinitiation.Inother words,‘reducedgroup’finallyshowedgreateramountof openbiteimprovementthan‘notreducedgroup’,andabout 37%ofthisimprovementamountoccurredforthefirstthree monthsofintermaxillarytractiontreatment.Thenumerical figures from results above could be utilized to predict prognosisoftreatmentmoreeasilyforclinicians. Therewereseverallimitationstoperformthisstudy.First, sincethiswasaretrospectivestudy,wehadtoexcludesome patients,suchaspatientswhodidnothaveenoughrecords toperformthisstudyorpatientswhodidnotapplyelastics regularlyduetopoorcooperation,thereforethenumberof studyindividualswaslowercomparedwiththenumberof individualswhounderwenttheactualtreatment.Second, weevaluatedtheopenbitesofthepatientsinrelationtothe symptomsofTMD.SinceTMDwereoftenrelatedtothe psychologicalfactorofpatients,anditwasalsodifficult forevaluatorstobeobjective,therewerealsolimitationsto performstudy.Third,thisstudydidnotuseacontrolpatient group, suchaspatientgroupwhounderwent orthodontic treatmentorsurgicaltreatment;hencethedifficultyincomparingthetreatmentresultsobjectively.Inexistingliterature, authorsexpresseddifficultyinestablishingacontrolgroup inthetreatmentofopenbites.Theauthorswhoestablished acontrolgroupuseditonlytoexamineandascertainthe characteristicsofthepatientspriortotreatment,butthere were few cases wherein a control group was established in the true sense21. To address this problem, we believe prospectivestudiesneedtobecarriedoutonagreatnumber ofpatientsbasedinsomeobjectivecriteriaandindicationsto enableprovidingusefulinformationforclinicians.Forfuture researchonadvancedtreatmentbyintermaxillarytraction, studiesshouldbeperformedwithregardtothechangesof thecondylarpositionandjointspaceduringtreatment.Also, there is a need to conduct studies on long-term stability of intermaxillary traction treatment and how muscular adaptationactuallyhaseffectontreatmentresult. V. Conclusion Inthisstudy,weperformedtreatmentofanterioropenbite patientsfromtheperspectivesofTMDandthesepatients weretreatedbyintermaxillarytractionbySASandadjunc- tivemusclerelaxationtreatmentforcontrolofTMD;thus achievingaverageopenbitedecreaseof1.75mm(P <0.01) and improvement of TMD in about 90% of our study patients.Inaddition,whenanteriorandsuperiorforcewas applied on chin top, patients who showed reduction of anterioropenbiteexhibitedasignificantlygreateramountof openbiteimprovementcomparedwiththepatientswhodid not.Therefore,ifthefollowingconditionsaresatisfiedamong anterioropenbitepatientswithTMD-1)openbitepattern showsawedge-likeshapefromthemostposteriormolarto theincisorarea,2)occlusionisfavorablewhenmaximum intercuspitationisinducedinthestudymodelobtainedby impressiontaking,and3)thereisareductionintheamount ofanterioropenbitewhenanteriorandsuperiorforcewas appliedonchintop -webelievetreatmentbyintermaxillary tractionusingSASisaneffectivetreatmentmethodforthe improvementofbothanterioropenbiteandTMJsymptoms. 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