正畸资料的生物机械原理

ThebiologicalbasisoftheorthodonticTherapyFengshanChenTongjiUniversity第1页Law1

Inorthodontics,toothmovesthroughboneandbringstheperiodontalligamentwithit.第2页ThebasisofthePeriodontalLigament(PDL)Normalwidth0.25mmor250micrometers.Cells,fibers,groundsubstance.第3页CellsofPDLFibroblastsOsteoblasts,osteoclastsCellrestsofMalassezMesenchymalstemcellsTheyallproliferateatdifferentstagesoftoothmovement.Youmustknowwhatfunctionseachhasintoothmovement.第4页FibersofthePDLCollagenandoxytalanSomeofthemarestretched,tornandruptured,whereasothersarecompressedandundergoasepticnecrosis第5页第6页GroundsubstanceofthePDLProteoglycansandotherproteinsTheircontentsandexpressionarealteredupontoothmovementWatersqueezedinandoutduringtoothmovement第7页AlveolarBoneThincorticalboneandporous(laminadura)FluidpumpedinandoutofthePDLTrabecularboneunderneathMustremodelbeforeteethcanbemoved第8页C:CellF:FiberAB:AlveolarboneG:GingivityCE:第9页Law2

Toothcannotmoveunlessboneappositionandresorptiontakeplace.

第10页SusanM.OttUnivofWashington第11页

Law3

Therewillbenotoothmovementunlessthereisaforce.第12页ThebasisofForceTheforcemusthavetherightcharacteristicssuchasthemagnitudeandduration----itmustmeetcertainthreshold.第13页ForceTypesLight,continuousforcesNeverdeclinestozero.InterruptedforcesDeclinestozeroIntermittentforcesDeclinestozero第14页ForceMagnitude(Level)Intherangeof10to200grams.Varieswiththetypeoftoothmovement.Light,continuousforcesarecurrentlyconsideredtobemosteffectiveininducingtoothmovement.Heavyforcescausedamagesandfailtomovetheteeth.第15页ForceDurationThreshold---6hrsperday.Notoothmovementifforcesareappliedlessthan6hrs/d.From6to24hrs/d,thelongertheforceisapplied,themoretheteethwillmove.第16页

Law4

Orthodontictoothmovementisnottheonlytypeoftoothmovement.第17页EruptionActivePassiveLateraldriftsPhysiologicalDuetolossofadjacentteethOrthodontictoothmovementTypesofToothMovement第18页TypesofToothMovementIntrusionExtrusionTippingBodilymovementRotation第19页第20页第21页第22页MechanismsofToothMovementPiezoelectrictheory.第23页第24页MechanismsofToothMovementPressure-tensiontheory.第25页第26页第27页第28页第29页TheOptimalForce“HighenoughtostimulatecellularactivitywithoutcompletelyoccludingbloodvesselsinthePDL”(Proffitetal.2023).Activelybeinginvestigatedinascientificfieldknownasmechanotransduction.第30页第31页

Law5

Orthodontictoothmovementcannotoccurunlesscellsareatwork.第32页Force---fluidflow---cell-levelstrainDeformationofcellmembraneleadingtocytoskeletalchangesSecondmessengerpathwaysGeneupregulationinfibroblasts,osteoblastsandosteoclasts第33页EffectofthelightforceonthePDLLight,continuousforcesOsteoclastsformedRemovinglaminaduraToothmovementbeginsThisprocessiscalled“FRONTALRESORPTION第34页“Frontalresorption”becauseitoccursbetweentherootandthelaminadura.第35页LightforceleadingtofrontalresorptionPhase1–MechanicalcompressionandtensionoftheperiodontiumPhase2---Mechanicallyinducedcellularandgeneticresponses;notoothmovementPhase3---AcceleratedtoothmovementduetofrontalboneresorptionPhase1Phase3Phase2Toothmovement(mm)Time(ArbitraryUnit)第36页EffectsofheavyforceonthePDLHeavy,continuousforcesBloodsupplytoPDLoccludedAsepticnecrosisPDLbecomes“hyalinized”–“HYALINIZATION”Thisprocessiscalled“UNDERMININGRESORPTION”.第37页“Underminingresorption”becauseitoccursontheundersideoflaminadura,notbetweenlaminaduraandtheroot.第38页

Law6

FrontalresorptionoccursinthePDL,whereasunderminingresorptionoccursunderneaththelaminadura.第39页HeavyforceleadingtounderminingresorptionPhase1–MechanicalcompressionandtensionoftheperiodontiumPhase2---Continuingmechanicalcompression;littlecellularandgeneticresponses;notoothmovementPhase3---Cellsrecruitedfromtheunderminingsideoflaminadura,notwithinthePDL,toinduceunderminingboneresorptionPhase1Phase3Phase2Toothmovement(mm)Time(ArbitraryUnit)第40页Phase1Phase3Phase2Toothmovement(mm)Time(ArbitraryUnit)Phase1Phase3Phase2Toothmovement(mm)Time(ArbitraryUnit)Frontalresorption

UnderminingingResorption第41页

Law7

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