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http://dx.doi.org/10.5125/jkaoms.2012.38.5.284
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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.
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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
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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.
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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
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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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