Implant Survival in Immediately Loaded Full-Arch Rehabilitations Following an Anatomical Classification System—A Retrospective Study in 1200 Edentulous Jaws

Abstract

This retrospective study analyzed implant survival of immediate implant-supported fixed complete denture (IFCD) treatment options (TOs) based on the level of alveolar atrophy (CC). Records of 882 patients receiving a total of 6042 implants at one private referral clinic between 2004 and 2020 were considered. The mean follow-up period was 3.8 ± 2.7 years. Cumulative implant survival rates (CSRs) were analyzed as a function of CCs and TOs according to Mantel-Haenszel and Mantel-Cox. Hazard risk ratios for implant loss were compared using Cox regression. Confounding factors were identified using mixed Cox regression models. The 2- and 5-year CSRs were 98.2% and 97.9%, respectively. Maxillary 2- and 5-year CSRs were lower (97.7% and 97.3%) compared to mandibular CSRs (99.8% and 98.6%) (p = 0.030 and 0.0020, respectively). The CC did not influence CSRs of IFCDs in the mandible (p = 0.1483 and 0.3014, respectively) but only in the maxilla (p = 0.0147 and 0.0111), where CSRs decreased with increasing atrophy. TOs did not statistically differ in terms of survival rate for a given level of alveolar atrophy. The adaption of IFCD treatments to the level of atrophy and patient-specific risk factors can result in high CSRs, even at different levels of bone atrophy.

Full text

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J.Clin.Med.2021,10,5167.https://doi.org/10.3390/jcm10215167www.mdpi.com/journal/jcm
Article
ImplantSurvivalinImmediatelyLoadedFull‐Arch
RehabilitationsfollowinganAnatomicalClassification
System—ARetrospectiveStudyin1200EdentulousJaws
JoãoManuelMendezCaramês
1,2,3,
*,DuarteNunodaSilvaMarques
1,2,3
,GonçaloBartoloCaramês
1
,
HelenaCristinaOliveiraFrancisco
1,2
andFilipeAraújoVieira
1

1
InstitutodeImplantologia,AvenidaColumbanoBordaloPinheiro,1070‐064Lisbon,Portugal;
duarte.marques@campus.ul.pt(D.N.d.S.M.);caramesgoncalo@gmail.com(G.B.C.);
helenafrancisco@campus.ul.pt(H.C.O.F.);fmaraujo.vieira@gmail.com(F.A.V.)
2
FaculdadedeMedicinaDentária,UniversidadedeLisboa,1600‐277Lisbon,Portugal
3
LIBPhys‐FCTUID/FIS/04559/2013,FacultyofDentalMedicine,UniversityofLisbon,
1600‐277Lisbon,Portugal
*Correspondence:carames@campus.ul.pt;Tel.:+351‐91972‐7353;Fax:+351‐21721‐0989
Abstract:Thisretrospectivestudyanalyzedimplantsurvivalofimmediateimplant‐supportedfixed
completedenture(IFCD)treatmentoptions(TOs)basedonthelevelofalveolaratrophy(CC).
Recordsof882patientsreceivingatotalof6042implantsatoneprivatereferralclinicbetween2004
and2020wereconsidered.Themeanfollow‐upperiodwas3.8±2.7years.Cumulativeimplant
survivalrates(CSRs)wereanalyzedasafunctionofCCsandTOsaccordingtoMantel‐Haenszel
andMantel‐Cox.HazardriskratiosforimplantlosswerecomparedusingCoxregression.
ConfoundingfactorswereidentifiedusingmixedCoxregressionmodels.The2‐and5‐yearCSRs
were98.2%and97.9%,respectively.Maxillary2‐and5‐yearCSRswerelower(97.7%and97.3%)
comparedtomandibularCSRs(99.8%and98.6%)(p=0.030and0.0020,respectively).TheCCdid
notinfluenceCSRsofIFCDsinthemandible(p=0.1483and0.3014,respectively)butonlyinthe
maxilla(p=0.0147and0.0111),whereCSRsdecreasedwithincreasingatrophy.TOsdidnot
statisticallydifferintermsofsurvivalrateforagivenlevelofalveolaratrophy.Theadaptionof
IFCDtreatmentstothelevelofatrophyandpatient‐specificriskfactorscanresultinhighCSRs,
evenatdifferentlevelsofboneatrophy.
Keywords:edentulousmandible;edentulousmaxilla;implant‐supportedprosthesis;full‐arch;
atrophy;retrospectivestudy

1.Introduction
Implant‐supportedfixedcompletedentures(IFCDs)representawell‐established
treatmentmodalityforedentulism[1–3],especiallyimmediatelyloadedIFCDshave
gainedincreasingpopularityamongcliniciansandpatients[4–7].Specifically,maxillary
andmandibularIFCDshavebeenshowntoresultinpredictablesuccessratesevenin
configurationssupportedbyaslowasfourimplants,providedthatsufficientprimary
implantstabilitycanbeachieved[8–10].
Prolongededentulismisassociatedwithprogressingresorptionofalveolarprocesses
[11,12].Thismayrequireadjustmentoftheimplantrestorationscheme.Asaresult,many
differenttreatmentoptionsofimmediateIFCDshavebeensuggested[10,13].Further
additionalaugmentativeproceduresmaybeconsidered,whichmayimpactthelong‐term
clinicalprognosis[12,14].Theexistingliteratureevidencesthatmaxillaryandmandibular
edentulismmaybetreatedsuccessfullyusingalternativetreatmentapproachesinvolving
four,six,ormoreimplants[15].However,mostoftheavailablescientificliteratureon
Citation:Caramês,J.M.M.;Marques,
D.N.d.S.;Caramês,G.B.;Francisco,
H.C.O.;Vieira,F.A.ImplantSurvival
inImmediatelyLoadedFull‐Arch
Rehabilitationsfollowingan
AnatomicalClassificationSystem—
ARetrospectiveStudyin1200
EdentulousJaws.
J
.Clin.Med.2021,10,5167.
https://doi.org/10.3390/jcm10215167
AcademicEditor:IzumiAsahina
Received:6October2021
Accepted:30October2021
Published:4November2021
Publisher’sNote:MDPIstays
neutralwithregardtojurisdictional
claimsinpublishedmapsand
institutionalaffiliations.

Copyright:©2021bytheauthors.
LicenseeMDPI,Basel,Switzerland.
Thisarticleisanopenaccessarticle
distributedunderthetermsand
conditionsoftheCreativeCommons
Attribution(CCBY)license
(https://creativecommons.org/license
s/by/4.0/).

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fixedrehabilitationofafullyedentulouspatientdoesnotestablishanassociationbetween
implantsurvivalratesandthelevelofboneatrophy.
Theimportanceofdiagnostics,treatmentplanningandchoiceofanadequate
rehabilitationschememaybesupportedbydifferentclinicaldecisionsupportsystems
(CDSS).Clinicaldecisionsupportsystems(CDSS)canbepowerfultoolstoassistclinical
treatmentdecisionsbasedonpatient‐specificdiagnosticfindings[16].Despiteapotential
demand,theuseofsuchsystemsinthedentalfieldhasremainedlowtodate[17,18].
Polakovskaetal.providedanexampleofhowCDSSmayhelpprovidetreatment
suggestionsbasedonthealveolaranatomicdimensions[19].Differentsystemstoclassify
thelevelofprogressingatrophyassociatedwithedentulismhavebeendescribedinthe
literature[11,20].Jensenetal.andPapadimitriouetal.havedescribedthefirstattempts
tousesuchclassificationstoselectaspecifictherapeuticschemeforIFCDs[21,22].Amore
comprehensiveCDSSforIFCDswasrecentlyproposed[23].ThisCDSSaimsto
standardizeandproposerestorative/regenerativetreatmentschemesdependingonthe
levelofalveolaratrophyfromalistofwell‐establishedmaxillaryandmandibularIFCD
implantschemes.Thesystemconsidersadecisionprocessbasedontheanatomiclevel
andpatternofatrophyofthealveolarprocessandonpatient‐specificriskfactorstoselect
aspecifictreatmentoptionfromasetofpredefinedimplantrehabilitationandsurgical
workflowschemes.
ToevaluateapossibleassociationbetweentheCSRsofIFCDsandthelevelof
alveolaratrophy,weretrospectivelyanalyzedimplantsurvivalinasetof882patients
treatedwithimmediateIFCDsbyapplyingthementionedCDSS[23].Implantsurvival
wasanalyzedasafunctionofanatomicclassificationsandindividualtreatmentoptions
oftheCDSS.Thisstudyalsodiscussesthepotentialinfluenceofconfoundingfactors.
2.MaterialsandMethods
2.1.TreatmentandFollow‐UpRegimes
Thisretrospectivestudyanalyzedclinicalrecordsofatotalof882patientsthat
consecutivelyreceivedroutineimmediateIFCDsfollowingarecentlypublishedCDSS
[23].Treatmentswereprovidedinaprivatereferralclinic(ImplantologyInstitute,Lisbon,
Portugal)fromNovember2004untilMarch2020underacertifiedqualitymanagement
systemandstandardizedfollow‐upprotocol.Thepatientswereenrolledinatwo‐weekly
recallregimeduringthefirsttwelveweeksaftersurgery,followedbyregularrecallsfor
professionaloralhygieneevery4months.Postsurgicalrecallregimesincludedremoving
theprosthesisandevaluatingtheimplantsatthetwo‐weekandtwelve‐weektimepoints
andincaseofimplantorprostheticcomplications.Comprehensivemedicalre‐evaluation
oftherehabilitationandimplanthealthstatuswereperformedevery4monthswith
prosthesisremovalyearly.Inaddition,thepatientswereinstructedtoimmediatelyreport
anycomplicationsoradverseeventsrelatedtotheirrestoration.Follow‐upinformation
wasrecordedusingdedicatedsoftwareandemployedtoderivequalityindicatorsforthe
operationandmanagementofthecenter.
Alltheimplantswereplacedconventionallyaccordingtothemanufacturers’
instructionsbyasingleexperiencedsurgeon(J.M.M.C.).Ancillaryprocedureslikeguided
boneregenerationorsinusliftprocedureswereperformedaccordingtothepredefined
schemesoftheCDSS[23].Consistencyinpretreatmentdiagnostics,patientassessment,
andpatientclassificationwassupportedbyusingidenticalCBCTdeviceanddevice
settingsusinga0.20mmvoxelsize,80kV,15mA,andanexposuretimeof12s(Planmeca
Promax,Planmeca,Helsinki,Finland).Thepatientsaffectedbysystemicorlocal
conditionsthatcompromisedpostoperativehealingorosseointegrationwereexcluded
fromimplanttreatment.
Alltheimplantswereimmediatelyrestoredwithacrylicprovisionalsandfinally
restoredwithaporcelain‐veneeredzirconia,monolithiczirconia,metallo‐ceramicor
acrylic‐metalhybridprosthesis.Anexceptiontotheimmediateloadingprotocolwas

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foundinninepatientsinvolvingatotalof21implants.Thesamplesizeofthisanalysis
wasaconveniencesampledeterminedusingpatientrecordsdisplayingadequate
diagnosticinformationwithidenticalpresurgicalCBCTandfulfillingidenticaltreatment
andfollow‐upcriteria.
2.2.Definitions
Theintervalbetweenloadingandfailuredefinedthetimetoimplantfailure.The
implantswereconsideredfailediftheypresentedsignsandsymptomsthatledtoimplant
removaloriftheimplantwasputintosleep[24].Removedimplantscomprisedthe
implantsthatfailedduetothelackofosseointegrationorduetomechanicalfailure.Early
andlateimplantfailuresweredefinedasfailuresbeforeoraftersixmonthspost‐
placement,respectively[25].
Thefollowingnominalandcategoricalfactorswereconsideredintheanalysisof
implantfailure:
1. CDSS‐relatedfactors,i.e.,anatomiccategory(CCs),treatmentoptions(TOs)and
treatmentcategories(TCs).TheappliedCDSSdefinedfivedifferentmaxillaryand
mandibularCCswiththreeTOsperCC[23].
CCsweredefinedonahemi‐mandibulartreatmentunit,i.e.,atthequadrantlevel
andbasedontheverticalandhorizontaldimensionsatthreedifferentpredefined
positionsofthealveolarprocessfromCBCTscansatbaseline.TOs(A,B,orC)were
definedbythetreatingclinicianbasedontheplannedprostheticdesignandunder
considerationoffactorscomprisingriskfactorslikesystemicconditions,smoking,
bruxism,etc.,socioeconomicfactors,theabilityforself‐careandoralhygieneaswellas
thepatient’spreferences.IndividualTOsdefinedthecharacteristicsofimplant
restoration,i.e.,number,type,position,andangulationoftheplacedimplant,bone
grafting,aswellasthetypeofprostheticrestoration(fixed(A,B)vs.removable(C)).
Treatmentoptionsasappliedasafunctionoftheanatomicclassificationsare
schematicallyillustratedinFigure1.

Figure1.OverviewoftreatmentcategoriesoftheappliedCDSSwith2‐yearand5‐yearcumulative
survivalrates(2‐yrand5‐yr,respectively).Anatomiccategoriesdefiningthelevelofatrophy
(CCs)werebasedonthealveolardimensions.TheCDSSdefinesthreetreatmentoptions(TOs),
i.e.,therapeuticimplantconfigurations,permaxillaryandmandibularCC.Onlythefixedoptions,
TOAandTOB,areshownforsimplicityreasons.OrangeregionsinCCIVandCCVdepict
regionswithboneaugmentation.
TreatmentsdeviatedfromthepredefinedschemeoftheCDSSifconsidered
necessaryandincludedtransitionsfrompreexistingrestorationsunderconsiderationand

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restorationofpreexistingimplants.Suchpreexistingimplantswerenotconsideredinthis
analysis.
2. Patient‐relatedfactorsincludedgender,ageatthetimeofimplantplacement,the
presenceandnumberofsystemiccomorbiditiesincludingcardiacarrhythmia,
arthritis,diabetestypeIorII,cardiovasculardisease,hepatitisB,HIV,arterial
hypertension,hyperthyroidism,osteoporosisandrheumatoidarthritisaswellasthe
self‐reportedsmokinghabitsandassociateddailycigaretteconsumption.
3. Implantationsite‐relatedfactors,includingjawtype(maxilla,mandible)andjaw
location,ascategorizedintoanterior(incisorsandcanine)orposteriorpositions
(premolarandmolarpositions).
4. Procedure‐relatedfactors:implantsystembybrand,type,diameterandlengthand
thepresenceofregenerativebonegraftprocedures.
2.3.DataCollectionandStatisticalAnalysis
Atotalof882patientsand6047implantswereincludedintheanalysis,respectively.
DataanalysiswascarriedoutinSPPSforstatisticalanalysis(SPPSsoftware,version24,
SPPSInc.,Chicago,IL,USA)byanindependentstatistician.Descriptivecharacteristics
werereportedasthemeansandstandarddeviations(SD),mediansandinterquartile
ranges(IQR)andabsoluteranges.Thedifferencesbetweendescriptivevaluesatthejaw,
CCandTOlevelswereevaluatedforstatisticalsignificance(p<0.05)usingFisher’sexact
test.
CSRsweredeterminedbyKaplan–Meieranalysis.Correspondingp‐valuesforthe
comparisonofsurvivalcurveswerecalculatedusingtheMantel–Coxtest.Two‐andfive‐
yearCSRvalueswerestatisticallycomparedusingtheMantel–Haenszeltest.Hazardrisk
ratiosfortheimplantlossoutcomeasafunctionofanatomicclassificationandtreatment
optionwerecalculatedusingCoxregressionusingtheeffectofthepatientasarandom
effect.TheFirthcorrectionwasusedwhenlevelshadzeroevents.Confoundingfactors
werederivedfromindividualCoxregressionmodelsusingonefactorasafixedeffectand
theeffectofthepatientasarandomeffect.MixedCoxregressionmodelswereusedto
identifytheoverallriskfactorsforimplantlossaftereliminatingcovariatefactorsusing
backwardselectionoffactorsthatdisplayedap<0.20intheone‐to‐oneassociations.
3.Results
3.1.DescriptivePatientandStudyPopulation‐RelatedCharacteristics
Theaveragepatientandstudypopulationandtreatment‐relatedcharacteristicsare
summarizedinTables1–3,respectively.Inparticular,thepatientswereonaverage66.2±
11.6(24–98)yearsoldatinterventionandreceivedonaverage6.9±2.8(2–14)implants
whichwerefollowedupforanaverageperiodof3.8±2.7(0–14.8)years.Twohundred
eight(23.6%)patientswereactivesmokersconsumingonaverage16.0±7.9cigarettesper
day,affecting1560(26%)placedimplants.Threehundredseventy‐three(42.3%)
individualsdisplayedonaverage1.2±0.5comorbiditiesaffecting2545(42%)placed
implants.Onepatientwaslostfromthecohortduetotherapy‐unrelateddeath.Two
thousandeighthundredone(46%)implantswereplacedinthemaxilla,3257(54%)—in
themandible.Twohundredsixty‐one(29.6%)patientsreceivedmaxillaryimplants(24.6%
(1488)oftheimplants),303(34.4%)—mandibularimplants(22.2%(1342)oftheimplants),
318(36.1%)patients—bimaxillaryreconstructions(53.3%oftheimplants(3228)).Overthe
totalfollow‐upperiod,111(1.8%)implantsin86(9.8%)patientsfailedafteranaverage
loadingtimeof0.9±1.2(0.1–7.3)years;60(54%)and51(46%)implantsfailedearlyand
late,respectively.Twenty‐one(2.4%)patientslostmorethanone(2–4)implantaffecting
46implants(41%ofthefailedimplants).In9(43%)ofthesepatients,18(39%)and19(43%)
implantsfailedonlyearlyoronlylate,respectively,whileonlythree(14%)patients
experiencedacombinationofearlyandlatefailures(nineimplants,20%).

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Table1.Averagecharacteristicsofthestudypopulation.Abbreviations:SD,standarddeviation;
IQR,interquartilerange.Note:avaluesrelatetothecohortwithadiagnosedsystemichealth
condition(n=373),bvaluesrelatetothesmokingcohort(n=208),cvaluesrelatetothecohortof
patientsthatlostoneormoreimplants(n=111),dvaluecorrespondstotheimplantlevel(n=6047),
evalueincludesanyreplacementimplantsforthelostimplants.
Patient/Implant
CharacteristicsMean±SDMedian(IQR)Range
Age(years)66.2±11.666.0(59.0–73.8)24–98
Numberof
comorbiditiesa1.2±0.51(0–1)2–5
Cigarettesperdayb16.0±7.915.0(10.0–20.0)2–40
Placedimplantsper
patiente6.9±2.86.0(4.0–9.0)2–14
Lostimplantsper
patientc1.3±0.61.0(1.0–1.0)1–4
Follow‐upperiodin
yearsd3.8±2.73.2(1.4–5.8)0–14.8
Timetoimplantloss
inyearsc0.9±1.20.4(0.3–1.1)0.1–7.3
Table2.Descriptivepatientandcohort‐relatedcharacteristics.Abbreviations:SD,standard
deviation;IQR,interquartilerange;N/A,notapplicable,i.e.,calculationnotsuitableatthepatient
orimplantlevel.
FactorCharacteristicsNumberofPatients
(n=882)
NumberofImplants
(n=6047)
GenderFemale560(63%)3742(62%)
Male322(37%)2305(38%)
Age<65402(46%)2889(48%)
≥65480(54%)3158(52%)
SystemicconditionPresent373(42%)2545(42%)
Absent509(58%)3502(58%)
Comorbidities
0509(58%)3502(58%)
1298(34%)2056(34%)
264(7%)405(7%)
310(1%)72(1%)
>31(0%)12(0%)
SmokingActive208(24%)1560(26%)
Non‐smoker674(76%)4487(74%)
Proceduretype
Maxilla261(30%)1488(24.6%)
Mandible303(34%)1334(22%)
Bimaxillary318(36%)3225(53%)
Numberoflost
implants
0796(90%)N/A
165(7%)N/A
218(2%)N/A
32(0%)N/A
41(0%)N/A
Timingoftheimplant
failure
Early50(56%)60(54%)
Late39(44%)51(46%)
Timingofthe
clusteredimplant
Early9(43%)N/A
Late9(43%)N/A
Earlyandlate3(14%)N/A

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failure(≥two
implants)
Table3.Descriptivetreatmentandprocedure‐relatedcharacteristics.Abbreviations:SD,standard
deviation;IQR,interquartilerange;N/A,notapplicable,i.e.,calculationnotsuitableatthepatient
orimplantlevel.
FactorCharacteristicsNumberofPatients
(n=882)
NumberofImplants
(n=6047)
Jawtypeandlocation
AnteriormaxillaN/A(–)1223(20%)
PosteriormaxillaN/A(–)2034(34%)
AnteriormandibleN/A(–)1256(21%)
PosteriormandibleN/A(–)1534(25%)
Lengthoftheimplant
≤8mm116(13%)274(5%)
8–14mm854(97%)4465(74%)
15–21mm22(2%)1275(21%)
>21mm17(2%)33(1%)
RegenerativesurgeryYes320(36%)2489(41%)
No562(64%)3558(59%)
Implantsystem
Straumann391(35%)2365(39%)
ZimmerBiomet643(58%)3438(57%)
Otherbrand81(7%)244(4%)
3.1.1.DistributionofFollow‐UpTimes
Follow‐uptimesformaxillaryandmandibularTCsrangedfrom2.6±2.1(IVB)to4.1
±2.6(IIB)yearsandfrom1.4±0.0(IIC)to8.5±0.4(VB)years,respectively.
3.1.2.RiskFactor‐RelatedCharacteristics
Averagepatientagesatimplantationrangedfrom59.2±10.5(IIIA)to69±9.6(VB)
yearsformaxillaryandfrom64.6±10.1(IIIA)to74.7±8.2(VA)yearsformandibular
treatments,respectively.DifferencesbetweenindividualmaxillaryandmandibularCCs
reachedstatisticalsignificance(p<0.0001).
MandibularCCVdisplayedthehighestpatientage(73.3±8.3years).Exceptfor
maxillaryCCIIIandVandmandibularCCV,patientagewasnotstatistically
significantlydifferentattheTOlevel.Interestingly,forthemandibulartreatment
subcohort,anincreaseinpatientagetendedtocorrelatewithincreasingCCclassification
andlevelofatrophy,respectively.
IndividualsinthemaxillaryandmandibularTCsdisplayedfrom0.2±0.4(IB)to0.6
±0.8(IA)(p=0.4282)andfrom0.0±0.0(VB)to0.7±0.8(IIIB)(p=0.0983)comorbidities
perpatient,respectively.DifferencesdidnotattainstatisticalsignificanceattheCClevel
butwerestatisticallysignificantattheTOlevelformaxillaryACIII(p=0.0094)and
mandibularACII(p=0.0140),III(p=0.0026)andV(p=0.0320),respectively.
ThepercentageofsmokingindividualsperTCrangedfrom8%(IB)to48%(IIIA)in
themaxillarygroupandbetween0%(IVBandVB)and41%(IIA)inthemandibular
group.DifferencesattheCClevelreachedstatisticalsignificance(p=0.0139andp=0.0002,
respectively).DifferencesbetweenindividualTOsreachedstatisticalsignificancefor
maxillaryACIII(p=0.0154)aswellasformandibularACII(p=0.0061)andIII(p=0.0003).
3.2.CDSS‐RelatedCharacteristics
ThedistributionofstudycharacteristicsandimplantfailuresasafunctionofCDSS‐
relatedcategoriesandp‐valuesasderivedusingFisher’sexacttestarelistedinTable4.

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Table4.DescriptivestatisticsofstudyvariablesstratifiedbyCCsandTOsoftheCDSS.Numberoftreatments(n=2596treatmentunits)andnumberofimplants(n=6047)arereported
asthetotalnumberandpercentagesrelativetoindividualCCs.Follow‐uptimesarereportedattheimplantlevelastheaveragevaluesandSD.Gender(ratiooffemaleandmale
patients),patientage(averagevaluesandSDs),thenumberofsystemicconditions(averagevaluesandSDs)andsmokinghabits(totalnumberofsmokersandrelativepercentagesof
smokersintheTC)arereportedatthetreatmentlevel.Bracketed%valuesreportedattheTOlevelrefertothe%relativetotheindividualCCs.Bracketed%valuesreportedattheCC
levelsrefertothe%relativetothetotalvalueonthemaxillaryormandibularlevel;p‐valuesrelatedtodifferencesattheTOandCClevelwereobtainedusingFisher’sexacttest;p‐
valuesindicatingstatisticalsignificancearemarkedinbold.Abbreviations:SD,standarddeviation.
Maxilla Mandible
IIIIIIIVVIIIIIIIVV
Numberoftreatments
A101(89%)62(16%)52(15%)75(46%)120(85%)37(55%)82(20%)179(37%)232(95%)20(83%)
B12(11%)320(84%)306(85%)87(54%)21(15%)30(45%)332(80%)308(63%)12(5%)4(17%)
C0(0%)0(0%)0(0%)0(0%)0(0%)0(0%)2(0%)2(0%)0(0%)0(0%)
<0.0001<0.0001<0.00010.3458<0.00010.3924<0.0001<0.0001<0.00010.0011
∑ 113(10%)382(33%)358(31%)162(14%)141(12%)<0.000167(5%)416(34%)489(39%)244(20%)24(2%)<0.0001
Numberofimplants
A309(93%)193(17%)161(20%)236(46%)381(86%)103(62%)235(26%)531(46%)474(93%)40(83%)
B23(7%)965(83%)651(80%)275(54%)63(14%)62(38%)673(74%)624(54%)34(7%)8(17%)
C0(0%)0(0%)0(0%)0(0%)0(0%)0(0%)2(0%)4(0%)0(0%)0(0%)
p<0.0001<0.0001<0.00010.0845<0.00010.00141<0.00010.0044<0.0001<0.0001
∑ 332(10%)1158(36%)812(25%)511(16%)444(14%)<0.0001165(6%)910(33%)1159(42%)508(18%)48(2%)<0.0001
Averagenumberofimplantspertreatment/quadrant(calculated/theoretical)
A3.1/33.1/33.1/33.1/33.2/32.8/32.9/33/32/22
/
2
B1.9/23/32.1/23.2/33/32.1/22/22/22.8/32/2
CN/AN/AN/AN/AN/AN/A1/1or22/1or2N/AN/A
Ø2.93.02.33.23.12.52.22.42.12.0
Follow‐uptimeinyears(implantlevel)
A3.8±33±2.72.6±1.82.9±2.14.1±2.63.5±2.74.4±3.33±2.54.3±2.93±1.5
B3.9±2.24.1±2.63.5±2.32.6±2.13.2±1.64.6±2.94.5±2.94±2.73.9±1.98.5±0.4
CN/AN/AN/AN/AN/AN/A1.4±06.5±0.7N/AN/A
p0.7060<0.00010.00020.00700.11830.00860.3091<0.00010.8617<0.0001
ABC3.8±33.9±2.63.3±2.32.7±2.14±2.5<0.00013.9±2.94.5±33.6±2.74.3±2.83.9±2.5<0.0001

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
Gender(female/malepatients)(treatmentlevel)
A49/5234/2833/1947/2891/299/2832/5086/93198/3416/4
B8/4183/137199/10758/2912/915/15186/146247/616/64/0
C0/00/00/00/00/00/02/02/00/00/0
p0.36070.78000.87560.62360.10730.04100.0050<0.00010.00590.9999
∑ 57/56217/165232/126105/57103/380.000624/43220/196335/154204/4020/4<0.0001
Averagepatientageattreatment(treatmentlevel)
A65.2±11.466.2±11.359.2±10.561.4±10.163.3±11.765±13.466.5±13.864.6±10.170.7±12.474.7±8.2
B68.9±17.266.3±1164.9±11.760.3±10.769±9.671.8±11.666.3±1166.7±10.666.9±11.366.5±1.5
CN/AN/AN/AN/AN/AN/A68±069±0N/AN/A
p0.93310.42860.00270.55520.01430.0769650.92870.14390.60280.0125
ABC65.6±12.266.3±11.164.1±11.860.8±10.464.1±11.6<0.000168±13.266.3±11.665.9±10.570.5±12.473.3±8.3<0.0001
Averagenumberofsystemiccomorbidities(treatmentlevel)
A0.6±0.80.4±0.60.3±0.50.5±0.90.5±0.70.4±0.60.3±0.60.5±0.60.6±0.80.6±0.5
B0.2±0.40.5±0.60.5±0.70.4±0.60.6±0.70.4±0.70.5±0.60.7±0.80.5±0.50±0
CN/AN/AN/AN/AN/AN/A1±03±0N/AN/A
p0.05470.19370.00940.58340.67790.52160.01400.00260.86630.0320
ABC0.6±0.80.5±0.60.5±0.70.4±0.80.5±0.70.42820.4±0.70.5±0.60.6±0.80.6±0.70.5±0.50.0983
Treatmentsinsmokingindividuals(treatmentlevel)
A18(18%)17(27%)25(48%)17(23%)38(32%)9(24%)34(41%)58(32%)31(13%)2(10%)
B1(8%)84(26%)91(30%)24(28%)5(24%)12(40%)82(25%)54(18%)0(0%)0(0%)
CN/AN/AN/AN/AN/AN/A0/2(0%)0/2(0%)N/AN/A
p0.68710.87540.01540.58710.61010.19440.00610.00030.37231.0000
∑ 19(17%)101(26%)116(32%)41(25%)43(30%)0.013921(31%)116(28%)112(23%)31(13%)2(8%)0.0002
Numberoffailedimplants
A3(100%)1(6%)4(14%)4(33%)12(92%) 0(0%)1(11%)6(46%)13(100%)0(N/A)
B0(0%)16(94%)25(86%)8(67%)1(8%)2(100%)8(89%)6(46%)0(0%)0(N/A)
C0(0%)0(0%)0(0%)0(0%)0(0%)0(0%)0(0%)1(8%)0(0%)0(N/A)
p0.08330.00030.00010.24820.00230.15730.01960.78150.0003–
∑ 3(4%)17(23%)29(39%)12(16%)13(18%)<0.00012(5%)9(24%)13(35%)13(35%)0(0%)<0.0001
%ageoffailedimplants
A1.0%0.5%2.5%1.7%3.1%0.0%0.4%1.1%2.7%0.0%

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B0.0%1.7%3.8%2.9%1.6%3.2%1.2%1.0%0.0%0.0%
CN/AN/AN/AN/AN/AN/A0.0025.0%N/AN/A
p0.99990.33430.48640.39910.70370.13980.46490.04400.9999–
ABC0.9%1.5%3.6%2.3%2.9%0.00981.2%1.0%1.1%2.6%0.0%0.1627

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3.2.1.CharacteristicsoftheCDSS‐RelatedTreatmentProvision
Treatmentprovision‐relatedaspectsoftheCDSS,schematicallyillustratedinFigure
1,wereinvestigatedbyanalyzingthedistributionofstudycharacteristicsasafunctionof
CCsandCC/TOcombinationsasreportedinFigure2andTable4,respectively.

Figure2.(A)NumberofdifferentCCspermaxillaryandmandibulararch.(B,C)Totalnumberof
treatments(B)andimplants(C)pertreatmentcategory.(D)Relative%ageofanteriorimplantsto
totalimplantsperCC.(E)RelativedistributionofimplantsperCCasafunctionofimplantlength
(shortimplants(≤8mm),regularimplants(8–14mm),longimplants(15–21mm)andzygomatic
implants(>21mm)).(F)FrequencyofbonegraftingperCC.(G,H)Totalnumberoffailedimplants
(H)andtotalnumberoffailedimplantsinpatientsthatlost≥twoimplants(G)asafunctionofTC,
respectively.

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AsevidencedbytheplotinFigure2A,521(90%)and534(86%)ofthetreated
maxillaryandmandibulararcheswereclassifiedassymmetricdisplayingonetypeofAC
inbothquadrants.
TreatmentandimplantnumberswerehighestinCCswithintermediatebone
quantity(CCIIandIII)accountingtogetherfor740(64%)and905(74%)maxillaryand
mandibulartreatmentsand1970(60%)and2069(74%)oftheplacedimplants,respectively
(Figure2B,C).
MaxillaryCCswithhighandintermediatebonequantity(ACI,II,III)were
preferablytreatedwithTOsA(89%),B(84%)andB(85%)(p<0.0001each),respectively.
ThecaseswithlimitedmaxillarybonequantityCCIVwerecomparablytreatedwithTO
A(46%)andB(54%)(p=0.3458),respectively.Treatmentsofthepatientswithstrongly
atrophiedmaxillae(CCV)weremainlyprovidedasTOA(85%)(p<0.0001).Exceptfor
theprominentlyusedTOBinCCIIwithtwoimplantsperquadrant,maxillary
restorationswereusuallyprovidedwith3.0–3.2implantsperquadrant.Asfurther
evidencedbyFigure2F,bonegraftinginCCIVandVwasmarkedlyincreased(>80%)
comparedtoCCI–III(<45%).Further,aconstantincreaseinshort(<8mm)andzygomatic
implants(>21mm)inthedirectionofhigherclassedCCalongwithreduceduseoflong
implants(15–21mm)inCCIVandVwasapparent(Figure2E).
Mandibulartreatmentswerecharacterizedbyatrendforconfigurationswithfewer
andshorterimplantsperquadrantinthedirectionofincreasingalveolaratrophy.
Specifically,CCsII,III,IVandVdisplayedaclearshifttoonespecificTO(p<0.0001each),
i.e.,IIB(80%),IIIB(63%),IVA(95%)andVA(83%).PreferredmandibularTOsrequired
2.0implantsperquadrantonaveragecomparedtothecorrespondingalternativeTOsin
thecorrespondingCCswith2.8–3.0implants.TOsaspartofCCIwerecomparably
distributedbetweenTOA(2.8implantsperquadrant)andB(2.1implants)(p=0.3924).
Furthermandibulartreatmentsdisplayedahigherincidenceofanteriorimplants(45%of
theimplants)comparedtomaxillarytreatments(38%oftheimplants)(Figure2D).
Comparedtomaxillaryprocedures,mandibularproceduresalsoinvolvedarelativelylow
percentageofbonegrafting(<34%).
Straumannbonelevel(StraumannGroup,Basel,Switzerland)andZimmerBiomet
externalhex(ZimmerBiomet,Warsaw,IN,USA)representedthemostfrequentimplant
types,withcorrespondingbrandsaccountingforupto96%oftheplacedimplants(Table
2).Comparedtofixedprostheses(TOsAandB),removableoptions(TOsC)wereonly
deliveredinthetotaloffourmandibulartreatmentsinACsIIandIII,respectively.
3.2.2.ImplantLossperCategoryoftheCDSS
Thedistributionoffailedimplantsinthepatientsdisplayingsingleandmultiple
(clustered)implantlossesisillustratedinFigure2G,HandreportedinTable4,
respectively.Acenter‐weighteddistributionofabsoluteimplantlossasafunctionofCCs
thattailedtowardshigherCCswasidentifiedinthemaxilla.Incontrast,mandibular
absoluteimplantlossesincreasedfromCCItoCCIV.Differencesinabsolutenumbersof
lostimplantsbetweenCCsinbotharcheswerestatisticallysignificant(p<0.0001).
Relativeimplantloss,i.e.,thepercentageoflostimplantscomparedtothetotal
numberofplacedimplantsinthemaxilla(2.3%)wasstatisticallyhighercomparedtothe
mandible(1.3%)(p=0.0106).Thisparameteralsodisplayedanapparenttrendforhigher
relativefailureratesinthehigher‐rankedCCs(CCIV)inbothjaws.Differencesbetween
CCswereonlystatisticallysignificantinthemaxilla(p=0.0098)butnotinthemandible
(p=0.1627)(Table4).
ExceptformandibularCCIII(p=0.0044),nosignificantdifferencesbetween
individualTOscouldbeidentified.


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3.3.CumulativeImplantSurvivalRateandAnalysisofRiskFactorsAssociatedwithImplant
Loss
Figures3and4andTable5comparetheKaplan–Meierplotsandthecorresponding
2‐ and5‐yearcumulativeimplantsurvivalrates(CSR)asafunctionofCCsandTO,
respectively.Thetotalcohort’soverall2‐ and5‐yearCSRswere98.2%and97.9%,
respectively.MaxillaryCSRswereconsistentlylower(97.7%and97.3%)comparedto
mandibularCSRs(99.8%and98.6%)after2and5years,respectively(p=0.030and0.0020).

Figure3.Kaplan–Meierplot,cumulativesurvivalratesfor(A)maxillaryimplantsand(B)mandibularimplantsasa
functionofanatomicalclassificationsaccordingtoCaramesetal.(CCs).

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Figure4.Kaplan–Meierplot,cumulativesurvivalratesofmaxillary(A–E)andmandibular(F–J)
implantsplacedinindividualanatomicalclassifications(CCI–V,individualgraphs)asafunction
ofTOs(A–C).

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Table5.Cumulativeimplantsurvivalrates(CSRs)asderivedfromtheKaplan–Meiersurvivalanalysis.ValuesrefertoindividualTOsandCCs(cumulatedoverindividualTOs);p‐
valuesrepresentlog‐rankvalues;p‐valuesindicatingstatisticalsignificancearemarkedinbold.
MaxillaMandible
IIIIIIIVVpIIIIIIIVVp
Cumulativesurvivalrates,2years
A99.0%99.5%97.1%98.1%97.2%100.0%99.6%98.8%97.5%100.0%
B100.0%98.4%96.03%96.5%98.4% 96.7%98.7%99.5%100.0%100.0%
CN/AN/AN/AN/AN/A N/A100.0%100.0%N/AN/A
p0.63580.30400.47330.33950.5930 0.06910.60320.40870.36130.9999
∑ 99.1%98.6%96.3%97.3%97.4%0.014798.8%99.0%99.2%97.7%100.0%0.1483
Total  97.67%  98.81% 0.0030
Cumulativesurvivalrates,5years
A99.0%99.5%97.1%98.1%96.5%100.0%99.6%98.8%97.5%100.0%
B100.0%98.1%95.5%96.5%98.4% 96.7%98.7%98.6%100.0%100.0%
CN/AN/AN/AN/AN/A N/A100.0%100.0%N/AN/A
p0.63580.27470.41420.33950.4817 0.06910.60320.83560.36130.9999
∑ 99.1%98.3%95.8%97.3%96.7%0.011198.8%99.0%98.6%97.7%100.0%0.3014
Total  97.34%  98.60% 0.0020

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Themaxillaryimplantsdisplayedstatisticallysignificantdifferencesat2and5‐year
CSRsbetweenindividualCCs(p=0.0147and0.0111,respectively),whiledifferences
betweenthecorrespondingmandibularCCsfailedtoreachstatisticalsignificance(p=
0.1483and0.3014,respectively).Overall,CSRsinthemaxillatendedtodecreaseinthe
directionofCCswithdecreasingbonequantity(CCItoV).Theyrangedfrom96.3%(CC
III)to99.1%(CCI)after2yearsandbetween95.8%(CCIII)and99.1%(CCI)after5years,
respectively.Individualvaluesinthemandiblerangedfrom97.7%(CCIV)to100%(CC
V)andwereidenticalforbothendpoints.
AttheTOlevel,noneoftheTOswithintheindividualCCsdisplayedstatistically
significantdifferences.BorderlinedifferenceswereonlyidentifiedbetweenTOA(100%)
andB(96.7%)inmandibularCCI(p=0.0691forbothendpoints).
AsreportedinTable6,hazardriskratiosforimplantloss(HRR)ofthemandibular
implantswere0.59(CI,0.393–0.884)timeslowercomparedtothemaxillaryimplants(p=
0.0106).AttheCClevel,HRRswerefurtherstatisticallysignificantlydifferentbetween
themaxillaryCCs(p=0.0441)butnotbetweenthemandibularCCs(p=0.2765)(Table6).
MaxillaryHHRstendedtoincreaseinthedirectionofCCswithdecreasingbonequantity
andwerehighestforACIII(HRR=1).CCI(HRR=0.27,p=0.0397)andCCII(HRR=
0.438,p=0.0118)displayedstatisticallysignificantlylowerHRRs.
Atthemandibularlevel,nocleartrendfortheHRRasafunctionofCCcouldbe
identified.CCIIdisplayedthelowest(HRR=0.834),CCIV—thehighestHRR(HRR=
2.104),withCCIVbeingtheonlyCCdisplayingborderlinesignificantdifferences(p=
0.0719).
Table6.Calculatedriskratiosfortheimplantlossoutcomeperanatomicclassification(maxillaryCCsI–Vandmandibular
CCsI–V)andindividualTOsperCC.ThevalueswerecalculatedfromtheCoxregressionanalysisusingtheeffectofthe
patientasarandomeffect.TheFirthcorrectionwasusedwhenlevelshadzeroevents.p‐valuesindicatingstatistical
significancearemarkedinbold.
Anatomic
Classification
(CC)
Treatment
Option
(TO)
SurvivedImplants
/LostImplants(%
Lost)
HazardRatio(95%
CI)p‐Valuep‐Valueforthe
OverallEffect
Maxilla‐3183
/
74(2.3%)10.01060.0098
Mandible‐2753
/
37(1.3%)0.590(0.393–0.884) 
Maxilla(CClevel)
I239/3(0.90)0.27(0.077–0.940)0.0397
0.0441
II1141/17(1.47)0.438(0.230–0.832)0.0118
III783/29(3.57)1
IV499/12(2.35)0.75(0.361–1.557)0.4405
V431/13(2.93)0.782(0.383–1.592)0.4982
Mandible(CClevel)
I163/2(1.21)1.109(0.238–5.153)0.8948
0.2765
II901/9(0.99)0.834(0.347–1.998)0.6832
III1146
/
13(1.12)1
IV495/13(2.56)2.104(0.935–4.730)0.0719
V48/0(0.00)0.839(0.007–6.306)0.9059
Maxilla(TOlevel)
IA306/3(0.97)1
0.7096
B23
/
0(0.0)1.916(0.014–19.74)0.7096
IIA192/1(0.52)1
0.3444
B949/16(1.66)2.634(0.334–20.74)0.3577
IIIA157/4(2.48)1
0.4383
B626/25(3.84)1.502(0.500–4.505)0.4684
IVA232/4(1.69)10.3832

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B267/4(2.91)1.667(0.442–6.276)0.4501
VA369/12(3.15)1
0.4811
B62
/
1(1.59)0.498(0.056–4.384)0.5302
Mandible(TOlevel)
I
A103/0(0.00)1
0.2657
B60/2(3.23)8.261(0.672–
1139.716)0.2657
II
A234/1(0.43)1
0.6342
B665/8(1.19)2.752(0.344–22.00)0.3399
C2/0(0.00)42.459(0.29–
804.2432)0.9265
III
A525/6(1.13)1
0.095B618/6(0.96)0.773(0.235–2.542)0.6722
C3
/
1(0.25)14.769(0.683–319.2)0.086
IVA461/13(2.74)1
0.6813
B34/0(0.00)0.54(0.004‐4.088)0.6813
VA40
/
0(0.00)1
–
B8/0(0.00)1–
3.4.FactorsInfluencingImplantLoss
Thefactorsinfluencingtheriskofimplantlosswereanalyzedusingindividualand
mixedCoxregressionmodelsbeforeandaftereliminatingcovariatefactors.Asevidenced
fromthelistinginTable7,thefactorsCC(p<0.0001),age(p=0.0040),cigarettesperday
(p=0.0202),aswellasthenumberofimplants(p<0.0001)andimplantlength(p=0.0004)
wereidentifiedasthemainfactorsinfluencingtheriskofimplantloss.
Specifically,theanatomicclassificationsIIIandIV(HRR=1and0.806,respectively)
displayedsignificantlyhigherrisksforimplantlosscomparedtoCCsI(HRR=0.187,p=
0.0013),II(HRR=0.367,p=0.367)andV(HRR=0.384,p=0.0063).Furthermore,the
analysisrevealedanincreaseintheHRRbyafactorof1.026peryearofageincrease(p=
0.0047),1.027pereachadditionalcigaretteconsumed(p=0.0229),2.105peradditionally
placedimplantperjaw(p<0.0001)and1.072permmincreaseinimplantlength(p=
0.0004).
Table7.Theriskofimplantlossasafunctionofpotentialriskfactorsaftereliminatingcovariate
factorsusingamixedCoxregressionmodel.Thefactorswerereducedbybackwardeliminationif
displayingp<0.20intheone‐to‐oneassociations.p‐valuesindicatingstatisticalsignificanceare
markedinbold.
RiskFactorValueHazardRatio(95%CI)p‐Valuep‐Value
Overall
CCs
I0.187(0.067–0.521)0.0013
<0.0001
II0.367(0.220–0.610)0.0001
III1
IV0.806(0.474–1.366)0.423
V0.384(0.193–0.763)0.0063
Age1yearincrease1.026(1.007–1.044)0.00470.004
Cigarettes
perdayOnecigaretteincrease1.027(1.003–1.051)0.02290.0202
Implants
perjawOneimplantincrease2.105(1.820–2.433)<0.0001<0.0001

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Implant
lengthOnemmincrease1.072(1.031–1.113)0.00040.0004
4.Discussion
Thisretrospectivestudyanalyzedimplantsurvivalofimmediatelyloadedfull‐arch
reconstructionsaspartofarecentlypublishedclinicaldecisionsupportsystem(CDSS).
Thisclassificationsystemshouldbeinterpretedasanaidingtoolforimplant‐supported
full‐archreconstructionandnotaclinicaldecisiontree.Aspartoftheanalysis,implant
survivalwasanalyzedasafunctionofthedegreeofosseousatrophy,providedtreatment
schemes,andpotentialconfoundingriskfactors.Inthecontextoftheclassification,it
shouldbeconsideredthatcorrespondingrestorativeschemeswereprimarily
prostheticallydrivenandwerealwaysbasedondetailedpresurgicaldigitalprosthetic
planning.ItshouldfurtherbeconsideredthatalthoughtheappliedCDSSdefinedTOsfor
bothfixed(TOsAandB)andremovable(TOC)restorations,removableoptionswere
onlyprovidedinaneglectableportionoftheanalyzedsample(siximplantsintotal).
Consequently,theresultspresentedinthisanalysisprimarilyapplytofixedimplant‐
supportedcompletedentures.
Toourknowledge,fewpublicationshavesofarconsideredlargersamplesizesfor
theretrospectiveanalysisofimplantsurvivaloffull‐archrestorations[26,27].Thisstudy
wascarriedoutataprivatecenterfocusingonoralrehabilitationwithanationwide
referralbasis.Thelonginclusionperiodsofthisstudyallowedstudyingimplantsurvival
overawiderangeofvaryingparameters,includingimplantcomponents,surgicaland
prostheticprotocols,andtemporalchangesinpatientcharacteristics.However,thisaspect
alsoincreasedthenumberofpotentialinfluencingfactors,renderingtheanalyzeddata
samplemoreinhomogenousanditsanalysismoredifficult.Despitetheseadvantagesand
potentiallimitations,thestudysetupsupportstheextrinsicvalidityofthesampleasbeing
representativeofthemajorityofedentulouspatients.
Thedecisionforindividualtreatmentschemeswasbasedonapatient‐centeredand
risk‐basedapproach.Theoralhealthimpactprofileassessesoralhealth‐relatedqualityof
lifebyahierarchyoffunctionalandpsychologicalparameters.Patients’satisfactionand
expectationstowardsanimmediatefixedimplantprosthesisdeliveredonthesameday
ofthesurgerywasthemainconcernintherehabilitationofthissampleofpatients.Ina
studyonpatient‐centeredoutcomesofimmediatefull‐archscrew‐retainedrehabilitations,
Dierensetal.reportedasignificantincreaseinpatientsatisfactionandself‐reported
outcomessuchascomfort,functionandaestheticscomparedtothebaselinepriortothe
treatment[7].Structureddiagnosisandriskassessmentrepresentcrucialelementsfora
patient‐centeredconceptandcomprehensivepatient‐centeredtreatmentplan.Thisplan
requiresastructureddiagnosticprocess,andallthepatientstreatedinthissamplewere
treatedaccordingtothisperspective.Basedonthisconcept,itisunderstandablethat
individualalveolaranatomyprofilesmayrequiremorethanonetreatmentoption.
Thisanalysisrevealedanoverall5‐yearCSRof97.9%.Maxillaryvalues(97.3%)were
significantlylowerthanthecorrespondingmandibularvalues(98.6%).Consideringthat
thevaluesinthisanalysiswereobtainedoverarangeofdifferentlevelsofatrophy,patient
conditionsandtreatmentoptions,theywereingoodagreementwiththecorresponding
valuesof97–97.9%and98–98.9%,respectively,thatwerereportedaspartofrecent
systematicreviewsforcomparablefollow‐upperiods[1,15,28,29].
Further,theidentifiedhigherCSRsofimmediateIFCDsinthemandiblecompared
tothemaxillaarealsoinlinewithotherreportsandhavebeenattributedtothereduced
bonequalityandbonequantityintheedentulousmaxilla[28,30–32].
Toourknowledge,thisisthefirststudythatsystematicallyinvestigatedimplant
survivalofimmediateIFCDsasafunctionofthelevelofalveolaratrophyinabroader
patientpopulation.Fromthisanalysis,itbecameapparentthatdifferencesbetweenthe
relativeimplantloss,CSRsandriskratiosbetweenthemaxillaandthemandiblewere

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mostpronouncedundermoderatelyandseverelyatrophiedconditions.Thisfinding
raisesthequestionofwhetherthelowermaxillaryoverallCSRvalueswereassociated
withtreatmentprovisionandriskfactordistribution,especiallyinthehigher‐rankedCCs
(CCsIII–V),whichcallsforamorethoroughanalysis.
Specifically,the2‐and5‐yearmandibularandmaxillaryCSRsrevealedaconsistent
decreasewithanincreasinglevelofatrophy,whichreachedsignificantlevelsonlyinthe
maxilla.Thisobservationisinlinewiththegeneralnotionthatimplantplacementinthe
maxillaisregardedasmorechallengingcomparedtothemandible[33].Thisaspectmay,
atthesametime,alsosuggestapotentiallimitationoftheappliedclassification.Although
bonequantitywasthemaincriterionfordefiningthedifferentlevelsoftheclassification
system,bonequality(density)wasnotevaluated.Consideringthelowerbonedensityin
themaxilla,thisfactormayhelpexplaintheidentifieddifferences[30].
Interestingly,inthemandible(exceptforCCV),CSRvaluesinseverelyatrophic
conditionsweredistinctlylowerwhencomparedtonon‐ormoderatelyatrophiedstates.
ImplantlossesandclusteredlossesinthecorrespondingCCIVwerefurthermainlyand
exclusivelyassociatedwithTOA.Chrcanovicetal.recentlyattributedsuchclusteringto
thepresenceofspecificlocalandsystemicriskfactors[31].Ouranalysissuggeststhat
clusteringisconsistentlyassociatedwithlowerCSRsandhigherrisksforimplantlossof
specificTCs.However,forthespecificmandibularCCIV,nopotentialbiasassociated
withthedisparatedistributionofriskfactorsbetweenthesubcohortsTOAandBcould
beidentified,suggestingapotentialcausalrelationshipwiththecorresponding
therapeuticschemes.Specifically,TOAwasbasedonfourinterforaminalimplants,while
TOBinvolvedtwoadditionaldistalshortimplants,resultinginapotentiallymore
favorableanteroposteriorloaddistribution.
Interestingly,mandibular5‐yearCSRstendedtobehigherorequivalentfor
alternativetreatmentoptionsofoneCCwithsiximplantswhencomparedtofour
implantsirrespectiveofthelevelofmandibularatrophy.Despitethisconsistentpattern,
differencesbetweenmandibularTOsfailedtoreachstatisticalsignificance,whichisin
linewitharecentlyreportedsystematicanalysisontheeffectofimplantnumbersonlong‐
termimplantsurvival[15].Whiletheplacementoffourinterforaminalimplantsis
generallywell‐established,theplacementofsiximplantscomprisingshortmolarimplants
hasrecentlybeenproposed[8,15,34,35].Suchrestorationshavebeenreportedtoprevent
posteriorcantileversandpotentiallyreducemarginalboneloss[35–37].Ontheother
hand,sufficientevidencesuggeststhatprostheticcantileversmayresultinsuccessful
treatmentoptionsforfullyedentulouspatientswithhighlong‐termsurvivalrates[38].
Furtherinthiscontext,itneedstobeconsideredthatpossibleadditionalriskfactorslike
parafunctionalhabits(bruxism)orthenatureoftheantagonistwerenotevaluatedaspart
ofthisanalysis,whichmightbeconsideredalimitationoftheperformedanalysis.
Inthemaxillaimplantsurvival,relativeimplantlossandassociatedrisklevelswere
significantlyassociatedwiththelevelofalveolaratrophy.Specifically,CSRsdistinctly
decreasedwhencomparingnon‐atrophic(99%)tomoderatelyandseverelyatrophic
conditions(96–97%).Regardingapotentiallimitingbiasbyassociatedriskfactors,a
distinctincreaseinthepercentageofactivesmokersinthedirectionofthehigher‐ranked
CCswasnoted,whichappearedtocorrelatewithlowerimplantsurvival.Thisaspectwas
alsoreflectedbyidentifyingthelevelofcigaretteconsumptionasariskfactorforimplant
lossfromthemixedCoxregressionmodel.Thisobservationisinlinewithseveral
systematicreviewsthatreportedasignificantlyhigherriskofimplantfailureinsmoking
patientsthaninnon‐smokers,withimplantfailureriskrangingbetween1.87and2.38
[39,40].
Severemaxillaryboneatrophyhasbeenassociatedwithalossofavailablebone
volumeandincreasedlevelofsinuspneumatization,whichimpedeimplantplacement
[13].Inouranalysis,thiswasreflectedbyamarkedlyincreasedrateofbonegrafting,use
ofconfigurationswith≥siximplantsandanelevatedfrequencyofshortandzygomatic
implantsinthehighlyatrophicCCsIVandV.TreatmentsinthemoderatelyatrophiedCC

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IIIwerebycontrastmainlyprovidedaspartofanall‐on‐fourtyperestoration(TOB).This
specificTCalsoinvolvedarelativelymoderaterateofboneaugmentation,anaverageof
4.6implantsperjawandapronouncedlyhigherpercentageofanteriorimplants.
Interestingly,thisspecificTCalsodisplayedthelowestCSRvaluesofalltheappliedTCs,
whichwasslightlylowerthanthe97.7%reportedintheliteratureforthisconfiguration
[41].Forthiscomparison,however,itmustbeconsideredthatthisimplantconfiguration
hasexclusivelybeenappliedinmoderatelyatrophiedconditions(CCIII)aspartofthe
appliedtreatmentschemes.
Fromabiomechanicalperspective,maxillaryfull‐archconfigurationswithdistal
implantsmaydistributeappliedmechanicalloadstothemolaralveolarcrestregionmore
evenlywhencomparedtoall‐on‐fourtypeconfigurations.However,theirrealizationis
oftenimpededbydecreasedtrabecularbonedensityintheposterioratrophiedmaxilla
[13,42].Inthiscontext,itisinterestingtonotethattherelativeimplantlossintheposterior
maxillawashigher(2.6%)comparedtoanteriorpositions(1.7%)butappearedtobe
disproportionallyhigh(5.2%)inCCIIIBwhencomparedtoCCIIIA(2.3%).This
observationmaysuggestthattheelevatedbiomechanicalloadonposteriorimplantsin
thefour‐implantconfigurationCCIIIBmightnotbeadequatelycompensatedbythe
anatomicosseousconditionsoftheCC.ThespecificuseofTOBinCCIIImightneedto
bebalancedagainstthecorrespondingalternativeTOAtofurtherimprovethisCC’sCSR.
ImplantlossintheseverelyatrophicmaxillaryCCsIVandValsodisplayedmarked
clusteringofimplantlossassociatedwithlowerCSRsofTOBandA,respectively.TCIV
BwasbasedontwodistalpterygoidimplantsanddisplayedCSRvaluescomparableto
theliterature‐reportedvalue[10,43].Interestingly,incontrasttopreviousreportsforthis
configuration,adisparitybetweenanteriorandposteriorrelativeimplantlossof1.1%vs.
3.7%wasnoted[43].TreatmentintheseverelyatrophicmaxillaryCCVwasmainly
providedasTOAwithsixstraightimplantsaftersinusaugmentationcomparedtoTOB
withzygomaticimplants.BothTOscanbeconsideredcomplexandrequiredhorizontal
boneaugmentation;stillrelativelyhigh5‐yearCSRsof96.5%and98.4%,respectively,
wereobserved.
Finally,theriskfactoranalysisusingmixedCoxregressionmodelsconfirmeda
significantandpronouncedeffectofanatomicclassificationonimplantloss.Interestingly,
thehighesthazardratioswerereportedforCCIII,whileotherCCswit