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下颌骨的生长发育口腔正畸学教研室刘月华TheGrowthandDevelopmentofMandibleDepartmentofOrthodonticsLiuYuehua,DDS,PhD,M.Orth.RCS(Edin)下颌骨的发生（Sperber，GH，1989）图示下颌骨副软骨的发生部位Atbirth:Bodyisstilldefined.Alveolarprocessscarcelypresent.Ramiareproportionallyshort.Condylesarepoorlydefined.SymphysealgrowthstilloccursincreasingwidthMandiblesymphysiscloses1-2years.Threemajorparts:body,rami,alveolarprocess下颌骨的三向生长生长方式：◆髁突软骨成骨◆骨膜下的骨表面增生Themandibleisacompositebonewithendochondralgrowthatthecondyleandintramembranousboneformation.◆长度的增长◆宽度的增长◆高度的增长下颌骨的三向生长下颌骨各部分的生长方向（Enlow，DH，1990）下颌骨长度增长◆下颌升支前缘吸收陈骨、后缘及外侧增生新骨；◆下颌骨外侧增生新骨、内侧吸收陈骨；◆下颌骨的增长，以磨牙区为最多，由第二乳磨牙至下颌角的距离，在新生儿约为10mm，６岁时约20mm，成人约45-50mm。◆Posteriorborderoframus-intramembranousboneformationbyperiostealtissues.Simultaneousresorptionofboneontheanteriorborderoframus.◆Surfacedepositionandrepositiononcompletesurfaceofmandibular-remodelling.◆Mandibularlingualtuberosity(intramembranous)-appositionalgrowthforhorizontalelongationofthemandibularbodyonthelingualsurface(betweenmostposteriormolarandmandibularforamen)Themandibleappearsto“grow”inadownwardandforwardmannerwhenvisualizedonsuperimposedserialcephalometrictracingregisteredoncranialbase.A:Simultaneousdisplacementoccursintheoppositedirection,displacingthechinanteriorlyandinferiorly.B:Actualgrowthtakesplaceinawidevarietyofregionaldirectionwiththepredominentgrowthtrendposteriorlyandsuperiorly.下颌骨宽度的增长◆下颌骨外侧面增生新骨，内侧面吸收陈骨；◆髁突随颞凹向两侧生长，使升支宽度增加；◆下颌骨前部在乳牙萌出后，宽度较少增加，下颌尖牙间宽度在１１岁以后几无增加。下颌骨高度的增长◆下颌升支高度的生长主要靠下颌髁突新骨的生长；◆喙突的同时生长；◆下颌体的生长，主要是靠下颌牙齿萌出时牙槽突的增高及下颌骨下缘少量增生新骨。◆Themandibularcondyle-Endochondralgrowthbyinterstitualandappositionalproliferationofcartilage◆Surfacedepositionandresorptiononcompletesurfaceofmandibular-remodellinginferiorborderofmandiblecoronoidprocessbecomefullydifferentiated◆Alveolarprocess(intramembranous)-Growswhenteethbegintoerupt-resorbswhenteetharelostThecombinationofcondylarandramusgrowthbringsabout:◆Abackwardtranspositionoftheramus,therebypermittingelongationofthebodyofthemandible.◆Adisplacementofthebody(anddentition)inananteriordirection.◆Averticallengtheningoftheramus,providingdisplacementofthemandibleinferiorlyandverticaldimensionforalveolargrowth.◆Amoveablearticulationduringvariousgrowthchanges.下颌支的骨改建机制(remodelling)下颌升支肌肉附着处的横断面（Enlow，D.H.1990）Verticalsectionthroughtheramusandthecoronoidprocessshowingthecharateristicpatternofresorption下颌支向侧方扩大，“Ｖ”字形原理Theremodellingmechanisminvolvedinthissuperiorandlateralrelocationisbasicallytheexpanding“V”principle.Asthecoronoidterminibecomehigher,theygrowapartattheirapicies.关节部的生长与改建◆髁突向后上方生长，形成头大颈小的形态；◆髁突的位置根据Ｖ字形原理，向Ｖ字开阔的侧方生长。髁状突的生长（Goose，DH，1982）髁状突软骨的作用SeveremandibulardeficiencyfromTMJinfection.颏部的生长◆灵长类中只有人类具有颏的特征；◆颏部是骨改建的结果；◆颏部对侧面外形具有重要意义。四、牙列与合的发育（一）合的建立◆婴儿在无牙齿萌出时，无合关系；◆婴儿第６个月乳牙萌出时开始建合；◆成人第三磨牙萌出时才完成建合。◆向前的动力◆向后的动力◆内外的动力平衡◆垂直向的动力平衡（二）建合的动力平衡（肌肉）◆萌牙前期的颌间关系◆乳牙合◆替牙合◆恒牙合（三）合的发育阶段乳牙合期◆第７-８个月时下颌乳中切牙萌出，在２-３岁时上颌第二乳磨牙萌出，到３岁半时，乳牙牙根形成。◆一般萌出顺序为：IIIIVIIIVSequenceoferuptionofprimaryteeth:Central&lateralincisors6-9months,firstmolars,canines12-18months,secondmolars20-24months.Mandibularteethusuallyprecedemaxillaryteethby1-4months.乳牙列间隙变化◆生长间隙：３-６岁，前牙部分；◆灵长间隙(primatespace):上颌乳尖牙近中或远中。Inthemaxillaryarch,theprimatespaceismesialtothecanines.Inthemandibulararch,theprimatespaceisdistaltothecanine.Spacingintheprimaryincisorregionisnormallydistributedamongalltheincisors,notjustinthe“primatespace”locationswherepermanentspacesexistinmostmammalianspecies.终末平面的类型◆垂直型(flushterminalplane)◆近中型(mesialstep)◆远中型(distalstep)2-4岁无间隙、无磨耗、E远中呈直线4-6岁有间隙、有磨耗、E近中移动正常乳牙合的特征正常乳牙合的特征◆前牙合关系：覆盖很浅，覆合较深；◆前牙部分具有生长间隙及灵长间隙；◆终末平面以垂直型及近中型较多，对恒牙合的建立意义较大；◆上颌乳尖牙的近中舌侧面与下颌乳尖牙的远中唇侧面相接触。（二）替牙合期６-１２岁，“丑小鸭”阶段Periodwhenbothprimaryandpermanentteetharepresentinthemouth.恒牙萌出时间及顺序上：6-1-2-4-5-3-7-8下：6-1-2-3-4-5-7-8Mostcommoneruptionsequence:5-8.5yrs.earlymixeddentition9-13yrs.latemixeddentition18-25yrs或为：上：6-1-2-4-3-5-7-8下：6-1-2-4-3-5-7-8Anothersequenceoferuptionfairlycommoninthemandibulararchis:Thesequenceoferuptionofthepermanentteethismoreimportantthantheexacttimeoferuption.EruptionofthefirstpermanentmolarsGivesthekeytotheocclusionThreewaysaClassImolarrelationshipcandevelop:(i)Mesialstepterminalplane:permanentmolarseruptdirectlyintoaClassIrelationship.(ii)Straight(Flush)terminalplane:eruptinglowerfirstpermanentmolarsmaygivemesialforcemovinglowersecondprimarymolarsforwardtoallowaClassImolarrelation.(iii)Latemesialshiftofastraightterminalplane.-mostcommonwaythataClassImolarrelationresults.-permanentmolarseruptend-to-end.-becauseofdimensionaldifferencesbetweentheprimaryandpermanent3,4and5(LeewayspaceofNance),afterexfoliationoftheprimaryteeththelowerfirstpermanentmolarsmovemesiallyintoaClassIocclusions.替牙间隙（Leewayspace)=（C+D+E）—（3+4+5）上颌单侧约0.9mm下颌单侧约1.7mm替牙间隙（Leewayspace)Ontheaverage,thecombinedwidthofthemandibulardeciduouscanineandfirstandseconddeciduousmolarsis1.7mmgreaterthanthepermanentsuccessors.Thedeciduousversuspermanenttoothdimensionforthecomparablemaxillaryarchsegmentisonly0.9mm.Mesialdriftisconsequentlygreaterinthemandibulararch,oftencompensatingforaflushtermin