正畸資料的生物機(jī)械原理

ThebiologicalbasisoftheorthodonticTherapyFengshanChenTongjiUniversity第1頁Law1

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

Toothcannotmoveunlessboneappositionandresorptiontakeplace.

第10頁SusanM.OttUnivofWashington第11頁

Law3

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

Law4

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

Law5

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

Law6

FrontalresorptionoccursinthePDL,whereasunderminingresorptionoccursunderneaththelaminadura.第39頁HeavyforceleadingtounderminingresorptionPhase1–MechanicalcompressionandtensionoftheperiodontiumPhase2---Continuingmechanicalcompression;littlecellularandgeneticresponses;notoothmovementPhase3---Cellsrecruitedfromtheunderminingsideoflaminadura,notwithinthePDL,toinduceunderminingboneresorptionPhase1Phase3Phase2Toothmovement(mm)Time(ArbitraryUnit)第40頁P(yáng)hase1Phase3Phase2Toothmovement(mm)Time(ArbitraryUnit)Phase1Phase3Phase2Toothmovement(mm)Time(ArbitraryUnit)Frontalresorption

UnderminingingResorption第41頁

Law7

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