ThebiologicalbasisoftheorthodonticTherapyFengshanChenTongjiUniversity正畸資料的生物機械原理第1頁Law1

Inorthodontics,toothmovesthroughboneandbringstheperiodontalligamentwithit.正畸資料的生物機械原理第2頁ThebasisofthePeriodontalLigament(PDL)Normalwidth0.25mmor250micrometers.Cells,fibers,groundsubstance.正畸資料的生物機械原理第3頁CellsofPDLFibroblastsOsteoblasts,osteoclastsCellrestsofMalassezMesenchymalstemcellsTheyallproliferateatdifferentstagesoftoothmovement.Youmustknowwhatfunctionseachhasintoothmovement.正畸資料的生物機械原理第4頁FibersofthePDLCollagenandoxytalanSomeofthemarestretched,tornandruptured,whereasothersarecompressedandundergoasepticnecrosis正畸資料的生物機械原理第5頁正畸資料的生物機械原理第6頁GroundsubstanceofthePDLProteoglycansandotherproteinsTheircontentsandexpressionarealteredupontoothmovementWatersqueezedinandoutduringtoothmovement正畸資料的生物機械原理第7頁AlveolarBoneThincorticalboneandporous(laminadura)FluidpumpedinandoutofthePDLTrabecularboneunderneathMustremodelbeforeteethcanbemoved正畸資料的生物機械原理第8頁C:CellF:FiberAB:AlveolarboneG:GingivityCE:正畸資料的生物機械原理第9頁Law2

Toothcannotmoveunlessboneappositionandresorptiontakeplace.

正畸資料的生物機械原理第10頁SusanM.OttUnivofWashington正畸資料的生物機械原理第11頁

Law3

Therewillbenotoothmovementunlessthereisaforce.正畸資料的生物機械原理第12頁ThebasisofForceTheforcemusthavetherightcharacteristicssuchasthemagnitudeandduration----itmustmeetcertainthreshold.正畸資料的生物機械原理第13頁ForceTypesLight,continuousforcesNeverdeclinestozero.InterruptedforcesDeclinestozeroIntermittentforcesDeclinestozero正畸資料的生物機械原理第14頁ForceMagnitude(Level)Intherangeof10to200grams.Varieswiththetypeoftoothmovement.Light,continuousforcesarecurrentlyconsideredtobemosteffectiveininducingtoothmovement.Heavyforcescausedamagesandfailtomovetheteeth.正畸資料的生物機械原理第15頁ForceDurationThreshold---6hrsperday.Notoothmovementifforcesareappliedlessthan6hrs/d.From6to24hrs/d,thelongertheforceisapplied,themoretheteethwillmove.正畸資料的生物機械原理第16頁

Law4

Orthodontictoothmovementisnottheonlytypeoftoothmovement.正畸資料的生物機械原理第17頁EruptionActivePassiveLateraldriftsPhysiologicalDuetolossofadjacentteethOrthodontictoothmovementTypesofToothMovement正畸資料的生物機械原理第18頁TypesofToothMovementIntrusionExtrusionTippingBodilymovementRotation正畸資料的生物機械原理第19頁正畸資料的生物機械原理第20頁正畸資料的生物機械原理第21頁正畸資料的生物機械原理第22頁MechanismsofToothMovementPiezoelectrictheory.正畸資料的生物機械原理第23頁正畸資料的生物機械原理第24頁MechanismsofToothMovementPressure-tensiontheory.正畸資料的生物機械原理第25頁正畸資料的生物機械原理第26頁正畸資料的生物機械原理第27頁正畸資料的生物機械原理第28頁正畸資料的生物機械原理第29頁TheOptimalForce“HighenoughtostimulatecellularactivitywithoutcompletelyoccludingbloodvesselsinthePDL”(Proffitetal.).Activelybeinginvestigatedinascientificfieldknownasmechanotransduction.正畸資料的生物機械原理第30頁正畸資料的生物機械原理第31頁

Law5

Orthodontictoothmovementcannotoccurunlesscellsareatwork.正畸資料的生物機械原理第32頁Force---fluidflow---cell-levelstrainDeformationofcellmembraneleadingtocytoskeletalchangesSecondmessengerpathwaysGeneupregulationinfibroblasts,osteoblastsandosteoclasts正畸資料的生物機械原理第33頁EffectofthelightforceonthePDLLight,continuousforcesOsteoclastsformedRemovinglaminaduraToothmovementbeginsThisprocessiscalled“FRONTALRESORPTION正畸資料的生物機械原理第34頁“Frontalresorption”becauseitoccursbetweentherootandthelaminadura.正畸資料的生物機械原理第35頁LightforceleadingtofrontalresorptionPhase1–MechanicalcompressionandtensionoftheperiodontiumPhase2---Mechanicallyinducedcellularandgeneticresponses;notoothmovementPhase3---AcceleratedtoothmovementduetofrontalboneresorptionPhase1Phase3Phase2Toothmovement(mm)Time(ArbitraryUnit)正畸資料的生物機械原理第36頁EffectsofheavyforceonthePDLHeavy,continuousforcesBloodsupplytoPDLoccludedAsepticnecrosisPDLbecomes“hyalinized”–“HYALINIZATION”Thisprocessiscalled“UNDERMININGRESORPTION”.正畸資料的生物機械原理第37頁“Underminingresorption”becauseitoccursontheundersideoflaminadura,notbetweenlaminaduraandtheroot.正畸資料的生物機械原理第38頁

Law6

FrontalresorptionoccursinthePDL,whereasunderminingresorptionoccursunderneaththelaminadura.正畸資料的生物機械原理第39頁HeavyforceleadingtounderminingresorptionPhase1–MechanicalcompressionandtensionoftheperiodontiumPhase2---Continuingmechanicalcompression;littlecellularandgeneticresponses;notoothmovementPhase3---Cellsrecruitedfromtheunderminingsideoflaminadura,notwithinthePDL,toinduceunderminingboneresorptionPhase1Phase3Phase2Toothmovement(mm)Time(ArbitraryUnit)正畸資料的生物機械原理第40頁Phase1Phase3Phase2Toothmovement(mm)Time(ArbitraryUnit)Phase1Phase3Phase2Toothmovement(mm)Time(ArbitraryUnit)Frontalresorption

UnderminingingResorption正畸資料的生物機械原理第41頁

Law7

Frontalresorptionfacilitatesorthodontictoothmovement,whereasunderminingresorptionimpedesorthodontictoothmovement.正畸資料的生物機械原理第42頁AnchorageNewton’slaw:foreveryaction,thereisreaction.Definedas“resistancetounwantedtoothmovement.”The“anchoragevalue”ofanytoothisroughlyequivalenttoitsrootsurfacearea.Thus,molarsandcaninesgenerallyhavehigheranchoragevaluesthanincisorsandbicuspids.正畸資料的生物機械原理第43頁AnchoragetypesReciprocalanchorage.Reinforcedanchorage.Stationaryanchorage.Corticalanchorage.正畸資料的生物機械原理第44頁ReciprocalanchorageBothunitsmoveroughlyequaldistance.Exemplifiedbyclosingadiastemabetweentwocentralincisors.正畸資料的生物機械原理第45頁ReinforcedanchorageUnitAhassubstantiallymoreanchoragevaluethanUnitB.Thus,UnitAmoveslittlebutUnitBmovesalot.Exemplifiedbyretractinganteriorteethtocloseanextractionspacebyusingposteriorteethasareinforcedanchorageunit.UnitBUnitA正畸資料的生物機械原理第46頁BiomechanicsofToothMovementCenterofResistance---Apointonthetootharoundwhichthetoothshallmove.Formostteeth,CORis2/5waybetweentheapexandthecrestofthealveolarbone.CenterofRotation---Thepointaroundwhichrotationoccurswhenanobjectisbeingmoved.正畸資料的生物機械原理第47頁正畸資料的生物機械原理第48頁ForceandCoupleForceIsappliedbyorthodonticappliances.Inducestipping,translation,intrusion,extrusionand/orrotation.CoupleTwoforcesofoppositedirectionsandwithnon-overlappingpointsofapplication.Translationofteethoccursinresponsetoappropriateforcecouples.正畸資料的生物機械原理第49頁正畸資料的生物機械原理第50頁PotentialComplicationsofOrthodonticToothmovementThepulpRootresorptionAlveolarboneheight正畸資料的生物機械原理第51頁OrthodonticeffectsonthepulpRareiflight,continuousforcesareapplied.Occasionallossoftoothvitality.HistoryofprevioustraumaExcessiveorthodonticforcesMovingrootsagainstcorticalboneEndodonticallytreatedteethcanbemovedlikenaturalteeth,withpropermanagement.正畸資料的生物機械原理第52頁RootresorptionMoreaccurately,resorptionofrootcementumanddentin.NormalageingprocessinmanyindividualsLikelyoccurringinmanycasesbutnottothedegreeofclinicalsignificance.Rootresorptioninducedbylightorthodonticforcesisreversible(byregenerationandrepairofcementumand/ordentin).Canleadtotoothmobilityinseverecases.正畸資料的生物機械原理第53頁正畸資料的生物機械原理第54頁GeneralizedRootResorptionAffectsmost,ifnotall,teeth;maxillaryincisorsmoresusceptiblethanotherteeth.Couldbemoderateorseverebutcommonlyintherangeofupto2.5mm.Etiologylargelyunknownbutpredisposingfactorsincludeconicalrootswithpointedapices,distortedtoothform,orahistoryoftrauma.正畸資料的生物機械原理第55頁LocalizedRootResorptionCan’talwaysbedistinguishedfromgeneralizedrootresorption.Maxillaryincisorsmoresusceptiblethanotherteeth.Onlyinrarecasescanthec