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Anewmethodologyfortheevaluationoftheaccuracyofdigitalimplantimpressionforedentulousjaw
AdolfoDiFiore1,RobertoMeneghello2,LorenzoGraiff1,GianpaoloSavio3,MatteoTurchetto3 ,EdoardoStellini1
1) DepartmentofNeuroscience,ClinicofDentistry,UniversityofPadua.2) DepartmentofManagementandEngineering ,UniversityofPadua.3) DepartmentofCivil,ArchitecturalandEnvironmentalEngineering,UniversityofPadua.
Introduction Digital vsTraditionalimpressionforfull-arch
Material Method Conclusion
Enderet al2011 Mastermodel/ referencescanning Thescandataweresuperimposedusingspecialdiagnosissoftwarewhichusesbest-fitalgorithms tomatchtwosurfaces.
The accuracyofthedigital impression issimilar tothatoftheconventional impression
Enderet al2013/2015/2016 Mastermodel/referencescanner5times
The Referencemodelwasscannedwith referencescanner5times inthesamex-y-zdirection.
Thedigital impression isless accurateandshowsadifferentpatternofdeviationthantheconventional
impression.
Güth etal2013 Industrial computed tomography/calibratedreferenceobjects
The datasetsweresuperimposedbyabestfitalgorithm withthereferencedatasetgainedfromindustrial computedtomography(CT), anddivergenceswereanalysed
thedigitalimpressionshowedstatisticallysignificantlyhigheraccuracy comparedtothe
conventionalprocedure.
Gimènez etal2014/2015/2015/2015 3-Dcoordinatedmeasuringmachine(CMM)/ mastermodel
Measurementsinvolved fivedistances(27-25,27-22,27-12,27-15,27-17).Thedataobtained weresubtractedfromthoseofthe
CMMvalues.
Thescanneddistanceaffectedthepredictabilityoftheaccuracyofthescanner,and theerror increasedwiththe increasedlengthofthescannedsection.
Papaspyridakos etal2016 Mastercastsandconventionalimpressioncasts/ extra-oralhigh-
resolutionscanner.
TheSTLdatasetsfromthefivegroupsofdigitalandconventionalimpressionsweresuperimposedwiththeSTLdataset fromthe
mastercasttoassessthe3Ddeviations.
Theaccuracy ofdigital impressions wasnotdifferentthantheimplant-level,
splintedimpressions forfull-arch
Güth etal2016 Mastermodelinwhichametalbarwasinsertedtoconnectthe37and47/coordinatemeasuringmachine.
Themodelwasdirectlydigitizedusinganintraoralscanner andindirectlydigitizedafterimpression.Data wereanalysedusingsoftwaretodeterminetheaberration ofthebarlength, thelinearshiftandtheangledeviationcausedby themethod.
Thisinvitrostudyshowsthatintraoral scanningsystemsseemtoshowthesameorevenhigheraccuracy thantheconventionalimpressionwith
subsequentindirectdigitalization.
15.GüthJF,Edelhoff D,Schweiger J,Keul C.Anewmethodfortheevaluationoftheaccuracyoffull-archdigitalimpressionsinvitro.ClinOralInvestig.2016Sep;20(7):1487-94.
Thepassivefitisaprimaryfactorforlongtermclinicalsuccessandsurvivalofanimplant-supportedfixeddentalprosthesis(FDP).However,theinsufficientaccuracyduringtheimpression-makingtechniqueand/ormanualstepsduringprosthesisfabricationmayleadtomisfitoftheprosthesisandsubsequenttotechnical,mechanical,andbiologicalcomplicationsuchasocclusaldiscrepanciesscreworabutmentloosening,fractureoftheprostheticcomponents,implantfractures,andlossofosseointegration .Theprecisetransferofthethree-dimensional(3D)intraoralimplantrelationshiptothemastercastisacriticalsteptoachieveapassivefit.Today,conventionalimpressionwithdifferenttechniquesandmaterialsrepresentacommonlyusedprocedureingeneraldentalpractice,butwiththedevelopmentoftheintraoraldigitalimpressionmanytraditionalprostheticprocedureshavebeeneliminated.However,inliterature,regardingthedigitalintraoralimpressionforfull-archthereareacontradictoryresult. Someauthorsconcludedthattheintraoraldigitalimpressionforfull-archshowedsimilaraccuracytooftheconventionalimpression.Instead,anotherresearchshowedthatthedigitalimpressionwerelessaccuraterespectthetraditionalimpression.Nevertheless,thecontradictoryresultscanbeexplainedbythedifferentmethodsofanalysisoftheaccuracyforintraoraldigitalimpression.
Results
Objective: Theaim ofthepresentstudywastointroduceanewmethodtoevaluatetheaccuracyofdigitalimpressionforfull-archimplant-supportedfixeddentalprosthesis.MaterialandMethods: Avirtualmodelofamandibularedentulouswithsixscan-abutmentpositionedverticallyatdifferentheightwasdesignedbyaCADsoftwareandsubsequentlymanufacturedinzirconiabyaCNCmachinetool(mastermodel).Themastermodelwasmeasuredwith acoordinatemeasuringmachine(CMM).Thecoordinatesoftheprobedpointsweretransferredintoa3DCADsoftware(Rhinoceros5.0 Beta)andanalysedwithataskspecificevaluationprotocoltoestimatethepositionandorientationofeachscan-abutment.Themeasuringsystemiscapableofamaximumpermissibleerror(E,inmicron)thatis10timeslowerthanboththeperformanceofscannerscommonlyusedinframeworkdigitalmanufacturingandtheexpectedpositionerrorsofthescan-abutmentsurfaces:E1(z)=2.5+5L/1,000μm,E2(xy)=1.8+5L/1,000μm,E3(xyz)=2.8+5L/1,000μm (withL,inmillimeters,equaltothemeasureddistance,accordingtoInternationalOrganizationforStandardizationnorm10360).Themastermodelwasdirectlydigitizedusingfivedifferentintraoralscanner(n=15forgroup)(ScanA,ScanB,ScanC,ScanD,ScanE).TheSTLfile ofthedigitalimpressionwassenttoGeomagic StudioSoftwaretocleanthemeshfromportionsnotrelatedtotheresearchandaftertheSTLfilewassenttothe3DCADgeometricmodellingsoftware(Rhinoceros5.0Beta).Thesoftwareapplicationcalled“Scan-abut”wasrealizedasaplug-inforRhinoceros5.0.Scan-abutselectsautomaticallythemajorsurfacesofthescan-abutment(cylindricalandplanarea)usingcurvatureanalysis.Toevaluatethepositionalaccuracyofeachimpression,theestimatedreferencepointsofthemastermodelwere aligned,usingaleast-squarebestfittingalgorithm,tothecorrespondingscan-abutmentpositionsonthemesh;thealgorithm“optimizes”thepositionandorientationoftheimpressionwhileconsideringthe3Ddistancesbetweeneachscan-abutmentonthemeshandtherelativescan-abutmentonmastermodel.Three-dimensionaldistancesbetweenreferencepointsofdigitalimpressionandreferencepointsofmastermodelalongthex-,y-,andz- axeswerecalculatedateachpositionforallimpression.TheWilcoxonmatched-pairssigned-ranktest(one-tailed)wasusedtocomparegroups.Thelevelofstat.significancewassetasα=0.05andwithastatisticalpowerof80%.Essential Results:Statisticalsignificantdifferenceswerefoundbetweengroups.Themean3Ddeviationvaluerespectthemastermodel(trueness)was31.5µm(SD8.9µm)forScanA,31.7µm(SD5.1µm)forScanB,71.3µm(SD55.0µm)forScanC,365.5µm(SD143.5µm) forScanDand107.5µm(SD28.1µm)mmforScanE.TherewasnostatisticallysignificantdifferencebetweenScanAandScanB(p-value=0.47),butasignificantdifferencewasassessedbetweenallthegroups.Conclusions:Basedontheresultsofthisinvitrostudy,theScanAandtheScanBdemonstratedthehighestaccuracy.Threeintraoralscannerdevicedidnotachievethenecessarylevelofaccuracytobeusedforfull-archimplant-supportedfixeddentalprosthesis.
1) Master Model… Avirtualmodelofamandibularedentulouswithsixscan-abutmentpositionedverticallyatdifferentheightwasdesignedbymeanofacomputeraideddesign(CAD)software(DassaultSystemes SolidWorksCorporation,Waltham,MA,USA).
ThevirtualmodelwasmanufacturedinzirconiabyaCNCmachinetool(DyamachItalias.r.l.,Mussolente VI,Italy)toserveasaclinicallyrelevantsimulationmodel.
2) Calibration…
Softtissuewassimulatedusingsilicone(Vestogum,3MESPE,StPaul,MN,USA)
Themastercastwas measured withacoordinatemeasuring machine(SmartScope FlashCNC300)
3) Mesh Processing…
5) Analysis…
Areferencesystemonthemastercastwasdefined
Lowerplaneofthemastermodelwasmeasuredwith12pointsanditwasdefinedastheXYplane.
Theexternalcircumferencewasscannedwith8pointsandthecenter wasdefinedasoriginofthereferencesystem.
Acquisitionofscan-abutmentpositiononthereferencesystem
Measurementof9points ontheupper planeofthescan-abutment
Acquisitionof4circular sections(260points)perpendicular totheaxis ofthescan-abutment
Constructionofafitting cylinder offitting throughmesh points
Constructionofafittingplane throughmesh points
4) Construction ofGeometric elementson mesh…
Intersection oftheaxis ofthecylinderwiththeupper plane todefine areferencepoint foreach scan-abutment.
All thedigital impression was sent toGeomagic StudioSoftwaretoclean themesh fromportions not relatedtotheresearch andafter themesh was sent tothe3DCADgeometric modellingsoftware(Rhinoceros 5.0)
Thesoftwareapplication called “Scan-abut”wasrealized as aplug-inforRhinoceros.Thesoftware"scan-abut"selects automatically thesurfaces ofthescan-abutment (cylindrical areaandplan area)
Theleast-square bestfitting algorithm “optimizes”thepositionandorientationoftheimpression while considering the3Ddistances between each scan-abutmentandtherelativescan-abutment onthemastermodel.
P=previus version ofscanningsystem /**=mean ofprecision*=showed local deviations at one endofthedental arch ofupto100μm /Bold type :CMMmeasurements
13.Patzelt SB,Emmanouilidi A,Stampf S,Strub JR,Att W.Accuracy offull-archscans using intraoral scanners.Clin Oral Investig.2014Jul;18(6):1687-94
ScanA ScanB ScanC ScanD ScanE
TecnologyActivewavefrontsampling (3Dvideo
technology)
Confocal opticalimaging technologyand ultrafast optical
sectioning
Active Triangulationandconfocalmicroscopy
Confocalmicroscopy
combined withamoirédetection
Activetriangulationandsingleimage
capture
Max [µm] 47,30 40,93 243,18 676,76 146,70Min [µm] 18,13 22,65 30,20 117,26 39,86Mean [µm] 31,54 31,78 71,29 365,56 107,20Dev.St [µm] 8,95 5,15 55,00 143,51 28,11
Cost $16995+ plusmonthly $20000-40000 $30000-35000 $20000 $20000
Cloud point 800000 100000 400000 250000 250000Dimension File 38467KB 4800KB 15800KB 9560KB 10330KBOpacification yes no no no no
Output File p,pay-x-STL .dmc (.CS3,.SDT,.CDT,.ID) Stlfree .Csz andStlfreeInofficemilling no no yes no yes
Colour no yes yes no yes
12.Vandeweghe S,Vervack V,Dierens M,DeBruyn H.Accuracy ofdigital impressions ofmultipledental implants:anin vitrostudy.Clin Oral Implants Res.2016May6.
1.EnderA,Mehl A.Fullarchscans:conventionalversusdigitalimpressions--anin-vitrostudy.Int JComput Dent.2011;14(1):11-21.
4..EnderA,Mehl A.In-vitroevaluationoftheaccuracyofconventionalanddigitalmethodsofobtainingfull-archdentalimpressions.QuintessenceInt.2015Jan;46(1):9-17.3.EnderA,Mehl A.In-vitroevaluationoftheaccuracyofconventionalanddigitalmethodsofobtainingfull-archdentalimpressions.QuintessenceInt.2015Jan;46(1):9-17.
5.EnderA,Attin T,Mehl A.Invivoprecisionofconventionalanddigitalmethodsofobtainingcomplete-archdentalimpressions.JProsthet Dent.2016Mar;115(3):313-20.
2.EnderA,Mehl A.Accuracyofcomplete-archdentalimpressions:anewmethodofmeasuringtruenessandprecision.JProsthet Dent.2013Feb;109(2):121-8.
7. Giménez B,Özcan M,Martínez-Rus F,PradíesG.Accuracyofadigitalimpressionsystembasedonparallelconfocallasertechnologyforimplantswithconsiderationofoperatorexperienceandimplantangulationanddepth.Int JOralMaxillofac Implants.2014Jul-Aug;29(4):853-628.Giménez B,PradíesG,Martínez-Rus F,Özcan M.Accuracyoftwodigitalimplantimpressionsystemsbasedonconfocalmicroscopywithvariationsincustomizedsoftwareandclinicalparameters.Int JOralMaxillofac Implants.2015Jan-Feb;30(1):56-64.
9.Giménez B,PradíesG,Martínez-Rus F,Özcan M.Accuracyoftwodigitalimplantimpressionsystemsbasedonconfocalmicroscopywithvariationsincustomizedsoftwareandclinicalparameters.Int JOralMaxillofac Implants.2015Jan-Feb;30(1):56-64.10.Giménez B,Özcan M,Martínez-Rus F,PradíesG.Accuracyofadigitalimpressionsystembasedonactivewavefront samplingtechnologyforimplantsconsideringoperatorexperience,implantangulation,anddepth.Clin ImplantDentRelat Res.2015Jan;17Suppl 1:e54-64).11.GiménezB,Özcan M,Martínez-Rus F,PradíesG.AccuracyofaDigitaliImpression SystemBasedonActiveTriangulationTechnologyWithBlueLightforImplants:EffectofClinicallyRelevantParameters.ImplantDent.2015Oct;24(5):498-504.
14.PapaspyridakosP,HirayamaH,ChenCJ,Ho CH,Chronopoulos V,WeberHP.Full-archimplantfixedprostheses:a comparativestudyontheeffectofconnectiontypeandimpressiontechniqueonaccuracyoffit.Clin OralImplantsRes.2016Sep;27(9):1099-105.6.GüthJF,Keul C,Stimmelmayr M,Beuer F,Edelhoff D.Accuracyofdigitalmodelsobtainedbydirectandindirectdatacapturing.Clin OralInvestig.2013May;17(4):1201-8.
Di Fioreetal[µm]
Ender etal2011[µm]
Patzeltetal2013[µm]
Enderetal2013[µm]
Gimènez etal2014/15
[µm]
Ender etal2015[µm]
Papaspyridakosetal2016[µm]
Vandeweghe
etal2016[µm]
Ender etal
2016**[µm]
Guthetal2016[µm]
ScanA 31±9 40±14p 38± 14p / 45±38p 45±23p / 35±12 60±29 89±48
ScanB 32±5 / / / / / 19(SD?) 28±7 43±20 /ScanC 71±55 49±14p 333±65
p59±16p
88± 106p 37±14*p / 61±23 49±12 /
ScanD 365±144 / 74± 27 / 151±1080 / / / / /
ScanE 107±28 / / / / / / / / /
Conclusion Basedontheresultsofthis invitrostudy,theScanAandtheScanBdemonstratedthehighestaccuracy. TheintraoralscannerdeviceC,D,Edidnotachievethenecessarylevelofaccuracytobeusedforfull-archimplant-supported fixeddentalprosthesis.