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.