UnitTenCASEREPORT——RetreatmentUsingaModified-TipInstrumentRetreatmentsarecommonindicationsintheeverydaylifeofanendodonticpractice.Theremovalofoldfillings,pastes,andobstructionsmaybeattemptedwiththeuseofclassicalsolventssuchaschloroformandxylene(1,2).However,theremovalofhardpastesrepresentsatechnicalproblem,becausetheyarenotsoluble,theycannotbebypassed,andtheyblocktherootcanalsystem.Ultrasonicinstrumentationhasbeensuggestedintheliterature(3-6)aseffectiveforretreatments.Itallowstheremovalofhardpaste(3)withouttheneedforsurgicalintervention.However,theprocessistime-consumingandrequiresanextraexpensewiththeultrasonicunit(3).Atechniqueforremovinghardpastesfromtherootcanalispresented.Theuseofamodified-tipfilehasproventobeeffective,easy,andfast.Thistechniqueallowedtheretreatmentoffourdifficultcaseswithoutsurgicalintervention,asshownherein.Anorthodonticwirecutterisusedtocutoffthetip(4mm)ofK-typefiles(#30and#35).BecauseK-typefilespresentquadrangularsections,trimmingthetipoffwiththewirecutterproducesasharpedgeattheworkingendofthefile.ThisprocedureturnstheK-typefileintoapotentinstrumenttobeusedwithapicalpressureandreamingmotion.Themodifiedinstrumentisusefultoremovehardpastesmechanically,aswellastogainlengthinextremelycalcifiedrootcanals.CLINICALCASESCaselA60-yr-oldfemalewasreferredforendodonticretreatmentinthesecondrightlowerpremolarforprostheticreasons.Theinitialwiremeasurementrevealedashortlengthduetoanextremelycalcifiedcanal.Amodified#35K-typefilewasabletogainlength,closetowhatwasdesired.Thestep-backtechniquewasusedtopreparetherootcanalthatwasthenfilledwithlaterallycondensedgutta-perchaandazincoxide-eugenolsealer.Case2A28-yr-oldfemaleComplainedofpaintopercusioninthefirstrightupperpremolar,indicatingtheneedforretreatment,becausetherootcanalwasonlypartiallyfilled.Theinitialwiremeasurementwasshortbecauseofseverecalcificationoftheapicalarea.Themodified#35K-typefilewasusedwithapicalpressuretogainapicallength.Thefinalfillingwithlateralcondensationofgutta-perchaandazincoxide-eugenolsealercouldthenbeperformed.Case3A35-yr-oldmalepresentedtotheEndodonticClinicoftheUniversityofIllinoiswithanindicationforretreatmentintheleftuppercanine.Afterremovalofthecrown,allattemptstonegotiatethecanalwithxylolfailed.Themodifiedinstrumentwasintroducedinthecanalwithreamingmotionandapicalpressure.Thehardpastewasremovedandtheproperwiremeasurementwasachieved.Case4A50-yr-oldfemalepresentedextensivedecaybelowthefixedbridgeofthesecondlowerleftmolar.Apicalosteitisatboththemesialanddistalrootsindicatedtheneedforretreatment.Thebridgewasremoved.However,thehardpastecouldnotbedissolvednorremovedwithfiles.Therootcanalswerenegotiatedwithamodified#35K-typefile.Thesecanalswerefilledwithlateralcondensationofgatta-perchaandazincoxide-eugenolsealer.Apicalhealingisinprogressnow,4monthsaltertheprocedure.DISCUSSIONThemodifiedK-typefilehasproventobeausefulinstrumenttoremovehardpastesmechanically,aswellastogainapicallengthinseverelycalcifiedrootcanals.Drawbacksinthistechniquearetheneedforfrequentradiographstocontrolbothdirectionandprogressofthefiles,andthefactthatK-typefileswillnotbendtogoaroundcurves.Referencesl.NguyenNT.Obturationoftherootcanalsystem.In:CohenS,BurnsRC,eds.Pathwaysofthepulp,3rded.St.Louis,CVMosby,1984:294-72.SieraskiSM,ZilichRM.Silverpointretreatment:reviewandcasereport.JEndodon1983;9:35-93.KrellKV,NeoJ.Theuseofultrasonicendodonticinstrumentationintheretreatmentofpaste-filledendodonticteeth.OralSurg1985;60:100-24.]ongH,EIDeebM.Removalofhardpastefillingsfromtherootcanalbyultrasonicinstrumentation.JEndodon1987;13:295-85.StamosDG,HaaschGC,Chenailb,GersteinH.Endosonics:clinicalimpressions.JEndodon1985;11:181-7.6.StamosDG,StamosD,PerkinsS.Retretodonticsandultrasonics.JEndodon1988;14:39-42VOCABULARYl.obturation充填2.solvent溶劑3.bypass側道通路4.ultrasonic超聲的5.reamer根管擴大針6.cutter切斷鉗7.workinglength工作長度8.premolar前磨牙9.incisor切牙10.prosthetic修復學11.gutta-percha牙膠12.percussion叩診13.overfilling超充填14.radiographX線片15.odontology牙醫學16.oldfillings舊填充材料17.chloroform氯仿(哥羅仿)18.rootcanalsystem根管系統19.file根管銼20.trimming修整21.apicalpressure根尖向壓力22.endodonticretreatment根管治療、牙髓治療23.canine尖牙24.molar磨牙25.step-backtechnique逐步后退技術26.sealer封閉劑27.mobility松動度28.stop止動片2