Rapid-prototyping-in-dentistry-technology-and-appl

DOI10.1007/s00170-005-2523-2ORIGINALARTICLEIntJAdvManufTechnol(2006)29:317–335QingbinLiu·MingC.Leu·StephenM.SchmittRapidprototypingindentistry:technologyandapplicationReceived:14July2004/Accepted:14December2004/Publishedonline:17August2005©Springer-VerlagLondonLimited2005AbstractMedicalimaginghasbeenusedtoprovideinforma-tionfordiagnosticandtherapeuticpurposes.Theuseofphysicalmodelsprovidesaddedvaluesintheseapplications.Rapidproto-typing(RP)techniqueshavelongbeenemployedtobuildcom-plex3Dmodelsinmedicine.However,publicationsregardingthedentalapplicationofRPtechnologiesarestillrare.ThispaperreviewsanddiscussesthebasicsandapplicationsofRPtech-niquesindentistry:(1)constructionofacomputeraideddesign(CAD)model,includingdataacquisition,dataprocessing,andthecorrespondingmachinesandCADpackages,(2)typicalRPsystemsandhowtochoosethem,and(3)currentandpotentialuseofRPtechniquesindentistry.PracticalapplicationexamplesofRPtechniquesindentistryareprovided.KeywordsComputeraideddesign·Dentistry·Medicalimaging·Rapidprototyping1IntroductionMedicalimagingtechnologiesinvolvefromX-rayradiologytomoreadvancedandrefinedmedicalimagingmodalitiessuchascomputerizedtomography(CT),magneticresonanceimag-ing(MRI),andlaserdigitizing[1–4].Thesenewtechnologiesareabletoprovidedetailedthree-dimensionalpicturesoftheanatomyoftheareaofinterestandthereforevaluabledatafordiagnosticandtherapeuticusage[5,6].Techniqueshavebeendeveloped,togetherwithsoftwareandhardware,torepresentthedatain3Dona2Dscreen.Giventhevisualizationprovidedbysophisticatedsoftwarepackages,thefabricationofphysicalQ.Liu(
)·M.C.LeuDepartmentofMechanicalandAerospaceEngineering,UniversityofMissouri,Rolla,MO65409,U.S.A.E-mail:[e-mail]s,PortHuron,MI48061-8042,U.S.A.modelsmayseemsuperfluous.However,thedisplayofa3Dvol-umeona2Dscreendoesnotprovidesurgeonswithacompleteunderstandingofthepatient’sanatomy.Surgeonsmustlearntointerpretthevisualinformationinordertoreconstructmentallythe3Dgeometry.Recently,head-mounteddisplays,stereoscopicglasses,andhologramshavebeenemployedtocomplementthe2Dscreentoprovidemorerealisticrepresentationsof3Dvol-umemodels.Unfortunately,thereisstillnophysicalfeeloftheareaofinterest,liketheinfectionareaorfracturesize,untilanoperationisperformed[7].Inshort,thereareseveralvisual-izationissuesthatarebeingaddressedbutnotyetresolvedbyvirtualmodels.Theconstructionofphysicalmodelsisoftenne-cessary.Physicalmodelsareattractivetosurgeonsbecausetheyoffertheopportunitytoholdthemodelinhandandviewinanaturalfashion,thusprovidingsurgeonsadirect,intuitiveun-derstandingofcomplexanatomicdetailswhichotherwisecannotbeobtainedfromimagingonscreen.Theuseofphysicalmodelsalsocreatesimprovedprerequisitesforplanningandsimulationofcomplexsurgery.Withaphysicalmodelathand,asurgeonisabletoexerciseonthemodelwiththeusualsurgicaltools,en-ablinghim/hertorehearsedifferentsurgicalplansrealistically.Basedonthis,surgerycanbesimulatedinawaythatisnotpossibleevenwiththelatestvisualizationtechnologies.Suchanintensiveplanningofsurgicalproceduresallowstheselectionofthebesttechnicalapproach.Additionally,thecommunicationbetweenthesurgeonandthepatientbeforeacomplicatedsur-gicalprocedurecanbeclearlyimprovedbytheuseofphysicalmodels[8].AphysicalmodelcanbemanufacturedbasedonX-rayCTorMRIdata.Severalmethodscanbeemployedtofabricateaphysicalprototype.Thesemethodscanbedividedintotwocategories:subtractiveandadditive.Theyallstartwitha3Dcomputeraideddesign(CAD)modeloftheanatomicalarea,whichusuallycanbederivedfromX-rayCTorMRIdata.Thesubtractivetechniqueusedistheconventionalnumericallycon-trolled(NC)machining,generallymilling[8].Inthiscasetheshapeofthemodelismilledfromablockofpolyurethaneorotherfoam.Theadvantagesincludelowmaterialcostsandthepossibilitythatthesemodelscanbeworkedonwithsurgical318instruments.Thismethodhastwolimitations.Onelimitationresultsfrommillingmachines,whichhaverestrictedmotionca-pability.Complexgeometriesaredifficulttoprogramandcanresultintool/workpiececollisions,andtheyareoftenthecasesinmedicalapplication[9].Theotherlimitationliesinthema-terialsusedtofabricatethephysicalmodel.Thematerialsem-ployedshouldbehard,tough,andsterilizable.Kleinetal.[10]employedpolyurethanefoamtofabricatethemilledmodelinpediatriccraniofacialsurgery.Qualityofthemilledmodelswaslimitedbecausethepolyurethanefoamisbrittleandsoftandthematerialisnotsterilizable.Therefore,additivemethodsareadvantageoustofabricatethephysicalmodelsofanatomicalde-tails.ThemainadvantageofRPisthatmedicalmodelscanbecreatedthathaveundercuts,voids,andcomplexinternalgeome-triessuchasneurovascularcanalsorsinuses.Theycanalsobetranslucentandtheinternalgeometriescanbeeasilyseen.Themainproblemwithmillingisthatverysmallgeometriesaredif-ficulttomake,andfixturingisaproblemandaccesstoundercutsandcomplexshapesisdifficult.Rapidprototypingreferstothefabricationof3Dphysicalmodelsdirectlyfromacomputer-aideddesignmodel[11–13].Themodelisbuiltlayerbylayeraccordingto3Ddata.Incom-parisontosubtractivetechnology,theadditivetechnologiescanproducearbitrarilycomplexstruc