LiuYing ChenJie XueQing LiuXin WangTao LiangShan-shan

【Keyword】Maxillarymalposedcanine；Sagittalfacialtype；Cephalo

【中圖分类号】R782.13【文献标识码】B【文章编号】1005-0019（2015）01-0049-02

Eruptiondisturbanceisafrequentlyobservedprobleminaseriesofprocessesthatresultsinconversionfromthedeciduoustothepermanentdentition.Themaxillarycaninesaresusceptible，theprevalenceofmaxillarybuccallymalposedcanine（MBMC）hasbeenreportedtobe27%inChinesedescent.Thepositionofcanineplaysanimportantrolefordentalarchmorphology.Eruptiondisturbanceorimpactedofmaxillarycaninesmayleadtomanykindsofproblemwhichincludethedestructionofintegrityofthedentition，archlengthshorter，poorocclusion，temporo-mandibularjointdisorders，andevenfacialappearanceandmentalhealth.Somestudieshavereportedtheinterrelationshipbetweenimpactedmaxillarycaninesandthemorphologyofthemaxilla.YoojunKimetal[1]showedtheshapeofthemaxillaryarchwasnarrowerandlongerinthepalatallyimpactedcaninegroupcomparedwiththebuccallyimpactedcaninegroup，andthepalatallyimpactedcaninegrouphadadeeperpalatalvaultthandidthebuccallyimpactedcaninegroup.TIANYu-louetal[2]foundthatimpactedmaxillaryanteriorteethmightresultinshortmaxillarybasalbone.AndtwocaninesimpactionhasthegreatestimpactonsagittalfacialtypeandtendstobeClassⅢfacialtype.However，therelationshipbetweenMBMCandsagittalfacialtypeisnotreported.Inthestudy，CephalometricanalysisforpatientswithlabialmaxillarycaninedislocationinordertoexaminetherelationshipbetweenMBMCandsagittalfacialtypeandevaluatethedentofacialmorphologicalcharacteristicsofpatientswithmaxillarymalposedcanines，providingatheoreticalbasisforclinicaltreatment.

MATERIALANDMETHODS

Atotalof50Chinesechildren（28girlsand32boys）withMBMC，wereselectedasfromthefilesoforthodonticpatientswhohadbeentreatedatourclinicsinTheAffiliatedHospitalofQingdaoUniversityinShandong，China.TheMBMCwasdeterminedbyclinical.AccordingtothenumbersoftheMBMC，subjectswereclassifiedtotwomaingroups（25casewithbilateralmalposed，25casewithunilateralmalposed）.

Theageofthepatientsrangedfrom11to16years.Thesubjectswereselectedonthebasisofthefollowingcriteria：maxillarycaninesbuccallymalposed，allpermanentteethhaderupted，nopreviousorthodonticorprosthodontictreatment，andnocraniofacialanomalies，noprematurelossofdeciduousteeth（exceptthethirdmolars）.

LateralpretreatmentcephalogramsweretracedforeachpatientwithWinceph8.0.Alltracingswereperformedby1investigatorandverifiedbytheother.Incasesofdisagreement，anew，mutuallyagreeduponlandmarkwasrecorded.Thenormalvaluesofthestudywerereferencedorthodontictextbook.

Anindependent2-samplettestwascarriedouttocomparethe2groups.StatisticalanalysiswasperformedbyusingSPSSforWindowssoftware（version17.0）

RESULTSCephalometricmeasurements（means±SD）inthe2groupswerecomparedwiththenormalandthecomparisonbetween2groupsofmeasuredvaluesintable1.Morestatisticallysignificantdifferenceswereobservedincomparisonwiththelattergroup.Theunilateralmaxillarybuccallymalposedcaninegroup（UMBMC），SNA，ANBislessthanthenormalvalue，thedifferencewassignificant（p<0.05），NA-PA，L1-NB（。）islessthanthenormalvalue，thedifferencewassignificant（p<0.05）.ThebilateralmaxillarybuccallymalposedcanineGroup（BMBMC），SNA，ANB，L1-MP，LI-NB（。）Islessthanthenormalvalue，thedifferencewassignificant（p<0.05）.U1-L1，U1-L1（mm）isgreaterthanthenormalvalue，therewasasignificantdifferenceinmeasurements（p<0.05）.

Figure1.DiagramofcephalometricmeasurementTable1.Comparisonofcephalometricin2groups（X±s，n=25）

Mean1forUMBMC；Mean2forBMBMC

P1forcomparisonbetweenpatientswithUMBMCandnormal.

P2forcomparisonbetweenpatientswithBMBMCandnormal.

P3forcomparisonbetweenpatientswithUMBMCandBMBMC

NS，Notsignificant

NSIntheBMBMC，ANB，LI-MPislessthanUMBMC，thedifferencewassignificant（p<0.05）.U1-NA，isgreaterthannormalvalue，therewasasignificantdifferenceincephalometricmeasurements（p<0.05）.

DISCUSSION

Thecoordinationofthemaxillaandmandiblepositionrelationsisimportantfororthodontics，orthognathicsurgeryclinicaldiagnosisandtreatmentplanning.Currently，thesagittalskeletalpatternisdefinedbythethepositionalrelationshipbetweenthemaxillaryandmandibular.AccordingtonumericalsizeofANB，patientsweredividedintothefacialtypeofclassⅠ，classⅡandclassⅢ.Maxillaryandmandibularsagittalcoordinationimpactontheentirefacialappearanceandstomatognathicsystemfunctionsgreatly.Thefacialtyperelationshipinsubjectswithhypodontiaorcanineimpactionhasbeenstudiedpreviously.Ben-Bassatetal[4]showedthatpatientswithcongenitallymissingteethhaveacharacteristicskeletodentalpatternandanteriortoothabsencehasapredominantinfluenceontheskeletodentalconfiguration.Tavajohi-KermaniHetal[3]foundthatpatientswithcongenitalmissingteethcancausemaxillaryhypoplasia.WisthetalandSarnasandRunefoundthatthemaxillawasmoreretrognathicandshorter，andthesagittaljawrelationshipwassmallerthannormal.TIANYu-louetal[2]reportedthatimpactedmaxillaryanteriorteethmightresultinshortmaxillarybasalbone.Someotherstudieshaveconcludedthathypodontiahaslittleornoeffectoncraniofacialmorphology.[5、6]Littleisknown，however，abouttheassociationbetweenmaxillarymalposedcaninesandsagittalfacialtype.Theaimofthepresentstudywastoinvestigatetheassociationbetweenmaxillarybuccallymalposedcanineasandsagittalfacialtype.

ThestudyfoundthatSNA，NA-PAandL1-NBweresmallerthanthenormalvalueinthe2groups.ThissignifiesthattheMBMCcanresultinshortmaxillarybasalbone.TheMBMCcanindicateslackchewingfunction，meaningthatmightreducethegrowthofpromotingthegrowthanddevelopmentofalveolarjawaffectedtherebyfurther.

Convexity，L1-MP，ANBandWitsappraisalweresmallerwhileU1-NAandU1-NAweregreaterthanthenormalvalueintwogroups；L1-NBweresmallerwhileU1-L1wasgreaterthannormalvalueingroupofBMBMC.ThissignifiesthatMBMCshoweddislocationclassⅢskeletalpatterntrendisduetothelackofdevelopmentofthemaxilla.

AnotherangleU1-NA，U1-NAdistance，L1-NBangle，L1-NBdistance，changeL1-MPangleindicatorsshowtheupperandlowerfrontteethMBMCoccursinpatientswithupperandlowerfrontteethcompensatory，thusdisguisingfacetypeuncoordinatedduetoinsufficientdevelopmentofthemaxillacaused.

Thestudyshowthatmaxillarycaninesbuccallymisalignedmightresultinshortmaxillarybasalbone.TheBMBMChasthegreaterinfluencethantheUMBMConsagittalfacialtypeandtendstobeClassⅢfacialtype.

Conclusion

Thisstudysuggeststhatorthodontistsshouldfocusonfacialtypewhendiagnosisandtreatmentofpatientswithmaxillarybuccallymalposedcanine.Earlyattentionandearlytreatmenttoavoidmissingantreatmentopportunitybecauseofadelay.

Wemadethefollowingconclusionsfromthisstudy：

1.Madethelengthofmaxillarybasalbonereduced，showedatrendofclass3facialtype.

2.Twocomparedwithonegroup，theinfluenceonsagittalfacialtypeisgreater.

參考文献

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[2]TianYL1，PiaoML，ZhaoZJ，Therelationshipbetweenmaxillaryanteriorimpactedteethandsagittalfacialtype.ShanghaiKouQiangYiXue.2014，23（1）：99-102.

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[5]RoaldKL，WisthPJ，ThunoldK，BoeOE.Changesincraniofacialmorphologyofindividualswithhypodontiabetweentheagesof9and16.ActaOdontolScand.1982；40：65–74.

[6]YukselS，UcemT.Theeffectoftoothagenesisondentofacialstructures.EurJOrthod.1997；19：71–78.