All-ceramic or metal-ceramic tooth-supported fixed dental prostheses (FDPs)? A systematic review of the survival and complication rates. Part II: Multiple-unit FDPs

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Article

Reference

All-ceramic or metal-ceramic tooth-supported fixed dental prostheses (FDPs)? A systematic review of the survival and complication rates.

Part II: Multiple-unit FDPs

PJETURSSON, Bjarni Elvar, et al .

Abstract

To assess the 5-year survival of metal-ceramic and all-ceramic tooth-supported fixed dental prostheses (FDPs) and to describe the incidence of biological, technical and esthetic complications.

PJETURSSON, Bjarni Elvar, et al . All-ceramic or metal-ceramic tooth-supported fixed dental prostheses (FDPs)? A systematic review of the survival and complication rates. Part II:

Multiple-unit FDPs. Dental Materials , 2015, vol. 31, no. 6, p. 624-639

DOI : 10.1016/j.dental.2015.02.013 PMID : 25935732

Available at:

http://archive-ouverte.unige.ch/unige:79012

Disclaimer: layout of this document may differ from the published version.

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dental materials 31 (2015)624–639

Availableonlineatwww.sciencedirect.com

ScienceDirect

j ou rn a l h om ep a ge :w w w . i n t l . e l s e v i e r h e a l t h . c o m / j o u r n a l s / d e m a

Review

All-ceramic or metal-ceramic tooth-supported ﬁxed dental prostheses (FDPs)? A systematic review of the survival and complication rates.

Part II: Multiple-unit FDPs ^夽

Bjarni Elvar Pjetursson

^a,∗

, Irena Sailer

^b

, Nikolay Alexandrovich Makarov

^b

, Marcel Zwahlen

^c

, Daniel Stefan Thoma

^d

aDivisionofReconstructiveDentistry,FacultyofOdontology,UniversityofIceland,Reykjavík,Iceland

bDivisionofFixedProsthodonticsandBiomaterials,ClinicofDentalMedicine,UniversityofGeneva,Switzerland

cInstituteofSocialandPreventiveMedicine,UniversityofBerne,Berne,Switzerland

dClinicofFixedandRemovableProsthodonticsandDentalMaterialScience,UniversityofZurich,Zurich, Switzerland

a r t i c l e i n f o

Articlehistory:

Received7July2014 Receivedinrevisedform 24February2015

Accepted27February2015

Keywords:

All-ceramic Metal-ceramic Fixedpartialdentures Systematicreview Survival

Success Longitudinal Failures

Technicalcomplications Biologicalcomplications

a bs t r a c t

Objective.Toassessthe5-yearsurvivalofmetal-ceramicandall-ceramictooth-supported ﬁxeddentalprostheses(FDPs)andtodescribetheincidenceofbiological,technicaland estheticcomplications.

Methods.Medline(PubMed),EmbaseandCochraneCentralRegisterofControlledTrials(CEN- TRAL)searches(2006–2013)wereperformedforclinicalstudiesfocusingontooth-supported FDPswithameanfollow-upofatleast3years.Thiswascomplementedbyanadditional handsearchandtheinclusionof10studiesfromaprevioussystematicreview[1].Survival andcomplicationrateswereanalyzedusingrobustPoisson’sregressionmodelstoobtain summaryestimatesof5-yearproportions.

Results.Fortystudiesreportingon1796metal-ceramicand1110all-ceramicFDPsfulfilledthe inclusioncriteria.Meta-analysisoftheincludedstudiesindicatedanestimated5-yearsur- vivalrateofmetal-ceramicFDPsof94.4%(95%CI:91.2–96.5%).Theestimatedsurvivalrate ofreinforcedglassceramicFDPswas89.1%(95%CI:80.4–94.0%),thesurvivalrateofglass- infiltratedaluminaFDPswas86.2%(95%CI:69.3–94.2%)andthesurvivalrateofdensely sinteredzirconiaFDPswas90.4%(95%CI:84.8–94.0%)in5yearsoffunction.Eventhough thesurvivalrateofall-ceramicFDPswaslowerthanformetal-ceramicFDPs,thedifferences didnotreachstatisticalsignificanceexceptfortheglass-infiltratedaluminaFDPs(p=0.05).A significantlyhigherincidenceofcariesinabutmentteethwasobservedfordenselysintered zirconiaFDPscomparedtometal-ceramicFDPs.Significantlymoreframeworkfractures werereportedforreinforcedglassceramicFDPs(8.0%)andglass-infiltratedaluminaFDPs

夽ThispaperwasoriginallyintendedforpublicationwiththesetofpapersfromtheAcademyofDentalMaterialsAnnualMeeting,8–11 October2014,Bologna,Italy;publishedinDENTAL31/1(2015).

∗ Correspondingauthorat:DepartmentofReconstructiveDentistry,FacultyofOdontology,UniversityofIceland,Vatnsmyrarvegi16,101 Reykjavik,Iceland.Tel.:+3545254871.

E-mailaddress:bep@hi.is(B.E.Pjetursson).

http://dx.doi.org/10.1016/j.dental.2015.02.013

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(12.9%)comparedtometal-ceramicFDPs(0.6%)anddenselysinteredzirconiaFDPs(1.9%) in5yearsinfunction.However,theincidenceofceramicfracturesandlossofretention wassigniﬁcantly(p=0.018and0.028respectively)higherfordenselysinteredzirconiaFDPs comparedtoallothertypesofFDPs.

Conclusions.Survivalratesofalltypesofall-ceramicFDPswerelowerthanthosereportedfor metal-ceramicFDPs.Theincidenceofframeworkfractureswassignificantlyhigherforrein- forcedglassceramicFDPsandinfiltratedglassceramicFDPs,andtheincidenceforceramic fracturesandlossofretentionwassignificantlyhigherfordenselysinteredzirconiaFDPs comparedtometal-ceramicFDPs.

1. Introduction

Socio-economicfactors,betterprophylaxisandoralhygiene regimenswith patientsincludedinregular recall programs have led to an increased number of teeth and to a shift from fully to more partially edentulous patients over the past decades [2]. This resulted in more single and multiple tooth gaps that can be restored with ﬁxed tooth- or implant-supportedreconstructions. Inorder tosupportthe decision-making process for either one option, evidence- based clinical data are needed reporting on survival and

complicationratesforbothtypesofreconstructions.Whereas for implant-supported reconstructions, systematic reviews provide very recent evidence comparing metal- and all- ceramicreconstructions[3,4],asystematicpoolingofnewer clinicaldataontooth-supportedreconstructionsislimitedto all-ceramicreconstructions[5].

Traditionally,metal-basedreconstructions forﬁxedden- tal prostheses(FDPs) wereconsidered asthegold standard [6].Alloys,mainlygold-based,werefullyorpartiallyveneered with feldspathic ceramics. The evolution in material sci- ence led to the introduction of new framework materials

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(ceramics) and partially a change inclinical concepts (e.g.

monolithicratherthanveneeredframeworkmaterials)[7–10].

Ceramics as part of reconstructive materials fulﬁll the need for esthetics. However, low-strength materials such asfeldspathic-basedceramicsand(reinforced)glass-ceramic materialsappeartobemoresuitableforsinglecrownsthan for FDPs [7,11]. In order to overcome the limited material properties, high-strength ceramics were introduced in dentistry. Zirconiaas the moststableofthese materialsis availableforCAD/CAMtechnologyandoffersahigherﬂex- uralstrength(900–1400MPa)andahigherfracturetoughness (5–10MPam^1/2)[12,13].Zirconiaismainlyusedasaframework materialforsinglecrownsandFDPs[14–16].Zirconiausedas frameworkmaterialappearstowithstandtheclinicalforces duringchewingandregularfunctionandfractureratesarelow andcomparabletometal-basedFDPs[17].However,incontrast tometal-basedFDPs,ahigherrateoftechnicalcomplications (majorchippings)wasreported[18,19].Theadhesionbetween zirconiaandveneeringceramicsisreportedtobethecritical issueforthisobservation[20].

In a systematic review, analyzing the survival and complicationsratesofall-ceramicandmetal-ceramicreconstructions, an imbalanceinterms ofthe number ofstudies forall-ceramicandmetal-basedFDPswasobserved[1].Clin- ical studies on newer materials such as zirconia, lithium disilicate reinforced glass ceramics and glass-inﬁltrated alumina (In-Ceram Alumina) or glass-inﬁltrated alumina- zirconia (Inceram-Zirconia) were available,but onlyfew of themprovidedlongertermdata.Sincethattime,theevidence increasedandclinicaldataareavailableforanumberofall- ceramicmaterialsforFDPs.Theaimofthepresentsystematic reviewwastherefore,

(i) toupdatethe previoussystematicreview[1]on tooth- supported FDPs with an additional literature search includingretrospectiveandprospectivestudiesfrom2007 to2013;

(ii) toassessthe3-yearsurvivalrateoftooth-supportedﬁxed dentalprostheses(FDPs)andtodescribetherateofbio- logical,technicalandestheticcomplications;

First electronic search 580 Titles

Independently selected by 2 reviewers 71 titles

Agreed by both 71 titles Abstractsobtained

Discussion Agreed on 71 abstracts

Full text obtained

Total full text articles for single crowns 41

(Sailer et al. 2014)

Final number of studies included:

40 Further hand searching

0 studies

Total full text articles for the

“fixed dental prosthesis”

review:

37

Excluded full text articles: 7 [23-29]

Articles from Sailer et al. 2007: 10

Fig.1–Searchstrategy.

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(iii) tocomparethesurvivalandcomplicationratesofmetal- basedFDPsandall-ceramicFDPs.

2. Materials and methods

2.1. Searchstrategy

Thissystematicreviewwasdesignedasanupdatetoapre- viouslypreparedpublicationwiththesameobjectives[1].For thatpurpose,Medline(PubMed),EmbaseandCochraneCen- tral Register of Controlled Trials (CENTRAL) searches were performed forclinical studies,including articles published fromDecember1st,2006uptoDecember31,2013intheDen- talliterature.ThesearchwaslimitedtotheEnglishlanguage (Fig.1).

2.2. Focusedquestions

“What are the survival and complication rates of tooth- supportedFDPsafterameanobservationperiodofatleast 3years?”“Arethesurvivalandcomplicationsratesofmetal- ceramicandall-ceramictooth-supportedFDPssimilaraftera meanobservationperiodofatleast3years?”

2.3. PICO

ThePICO forthe presentsystematicreviewwas deﬁnedas follows:

P Population:subjectswithanteriorand/orposteriorﬁxed tooth-supportedFDPs

I Intervention:all-ceramicFDP C Comparison:metal-ceramicFDP

O Outcome:clinicalsurvivalandtechnical,biologicaland estheticcomplicationrates

2.4. Searchterms

Thefollowingfoursearchesandsearchtermswereapplied:

Populationandintervention

crowns[MeSH]OR crown[MeSH]ORdentalcrowns[MeSH]

ORcrowns,dental[MeSH]ORDenture,Partial,Fixed[Mesh])) OR(crown*[allfields]ORfixedpartialdenture*[allfields]OR FPD[allfields]ORFPDs[allfields]ORfixeddentalprosthe- sis[allfields]ORfixeddentalprostheses[allfields]ORFDP[all fields]ORFDPs[allfields]ORbridge*[allfields]

comparison

ceramic[MeSH] OR ceramics[MeSH] OR metal ceramic restorations[MeSH])) OR (ceramic*[All Fields] OR all- ceramic[all ﬁelds] OR Dental Porcelain[All Fields] OR metal-ceramic[AllFields]

outcome

Survival[Mesh]ORsurvivalrate[Mesh]ORsurvivalanaly- sis[Mesh]ORdentalrestorationfailure[Mesh]ORprosthesis failure[Mesh]ORtreatmentfailure[Mesh].

Thesearch combination in the builderwas “population ANDinterventionANDcomparisonANDoutcome”.

Anadditionalhandsearchwasperformedidentifyingrel- evant studiesbyscreeningthereferencelistofallincluded publications.

2.5. Inclusioncriteria

Clinical publications were considered if all of the following criteriawere suitable:(i)humantrialswithaminimum amount of10patients withFDPs,(ii)mean follow-up ofat least 3 years in function, (iii) randomized controlled trials (RCT),controlledclinicaltrials(CCT),prospectivecaseseries, cohortstudies,retrospectivestudies,(iv)patientsneededto beexaminedclinically,and(v)reporteddetailsofmaterials characteristics,methodsandresults.

2.6. Exclusioncriteria

Studiesnotmeetingallinclusioncriteriawereexcludedfrom thereview.Publicationsdealingwiththefollowingtopicswere alsoexcluded: invitroandpreclinical studies,studieswith afollow-upoflessthan3years,reportsbasedonquestion- naires,interviewsandcharts.

2.7. Selectionofstudies

Two authors (IS, NAM) independently screened the titles derived from the searches based on the inclusion criteria.

Disagreementswere resolved bydiscussion.Following this, abstractsofalltitlesagreedonbybothauthorswereobtained, andscreenedformeetingtheinclusioncriteria.Ifnoabstract wasavailableinthedatabase,theabstractoftheprintedarti- cle was used. Basedon the selection of abstracts, articles were thenobtainedinfulltext. Iftitleand abstractdidnot providesufﬁcientinformationregardingtheinclusioncrite- ria,thefullreportwasobtainedaswell.Again,disagreements wereresolvedbydiscussion.

Theﬁnal selectionbased oninclusion/exclusion criteria was madefor thefull textarticles. For this purposeMate- rials and Methods,Resultsand Discussionofthese studies werescreened.Thisstepwasagaincarriedoutby2readers (IS,NAM)anddouble-checked.Anyquestionsthatcameup duringthescreeningwerediscussedtoaimforconsensus.In addition,15publicationsfromtheprevioussystematicreview [1]wereincludedintheanalyses.

2.8. Dataextractionandmethodofanalysis

Allincludedarticleswereindependentlyscreenedanddata extractedusingdataextractiontablesbytworeviewers(DTH, BPJ).Anydisagreementswereresolvedbydiscussiontoaim forconsensus.Inaddition,dataoftheincludedpublications ofthepreviouslypublishedreview[1]wereextractedaswell.

Dataonthefollowingparameterswereextracted:author(s), yearofpublication,studydesign,plannednumberofpatients, actual number of patients at end of study, drop-out rate, mean age,agerange, operators,materialframework, brand nameofframeworkmaterial,veneeringmaterial,brandname of veneering material, type of manufacturing procedure, number of FDPs, number of abutment teeth, number of (non)vitalabutmentteeth,numberofpontics,locationofFDP

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Table1–Studyandpatientcharacteristicsofthereviewedstudiesforall-ceramicFPDs.

Study Yearof

publication

Frameworkmaterial Study

design

No.ofpatients instudy

Age range

Mean age

Setting Drop-out

(inpercent)

Sola-Ruizetal. 2013 Lithiumdisilicatereinforcedglassceramic Prosp. 19 n.r. 49 University 0%

Rinkeetal. 2013 Zirconia Prosp. 75 26–76 49.4 University 19%

Raigrodskietal. 2012 Zirconia Prosp. 16 36–60 48 University 6%

Peleazetal. 2012 Zirconia RCT 37 23–65 n.r. University 0%

Sagitkayaetal. 2012 Zirconia Prosp. 28 n.r. 38 University 0%

Kernetal. 2012 Lithiumdisilicatereinforcedglassceramic Prosp. 28 n.r. 47.5 University 7%

Lopsetal. 2012 Zirconia Prosp. 28 n.r. 46.2 University 14%

Saxetal. 2011 Zirconia Prosp. 45 n.r. 48.3 University 53%

Sorrentinoetal. 2011 Zirconia Prosp. 37 21–68 45.3 University 0%

Makarounaetal. 2011 Lithiumdisilicatereinforcedglassceramic RCT 19 n.r. 47 University 26%

Schmittetal. 2011 Zirconia Prosp. 15 29–73 50.1 University 0%

ChristensenandPloeger 2010 Zirconiaandglass-inﬁltratedalumina RCT 259 16–89 50 Privatepracticemulti-center 4%

Beueretal. 2010 Zirconia Prosp. 38 27–71 50.9 University 0%

Roedigeretal. 2010 Zirconia Prosp. 75 26–76 49.4 University 11%

Wolfartetal. 2009 Lithiumdisilicatereinforcedglassceramic Prosp. 29 25–68 47.9 Multi-Center 7%

Eschbachetal. 2009 Glass-inﬁltratedalumina-zirconia Prosp. 58 n.r. 46.8 University 3%

Saileretal. 2009 Zirconia RCT 59 n.r. 54.4 University 5%

Wolfartetal. 2009 Zirconia Prosp. 48 23–75 55 University 4%

Beueretal. 2009 Zirconia Prosp. 19 27–71 50.9 University 0%

Edelhoffetal. 2008 Zirconia Prosp. 18 n.r. n.r. University 6%

MolinandKarlsson 2008 Zirconia Prosp. 18 40–84 59 Specialistsandprivatepractice 0%

Tinschertetal. 2008 Zirconia Prosp. 46 20–58 n.r. University 13%

Esquiveletal. 2008 Lithiumdisilicatereinforcedglassceramic Prosp. 21 30–62 n.r. University 0%

Wolfartetal. 2005 Lithiumdisilicatereinforcedglassceramic Prosp. 29 25–68 47.8 University 17%

MarquartandStrub 2005 Lithiumdisilicatereinforcedglassceramic Prosp. 43 22–65 39.9 University 0%

Suàrezetal. 2004 Glass-inﬁltratedalumina-zirconia Prosp. 16 23–50 n.r. University 0%

Olssonetal. 2003 Glass-inﬁltratedalumina Retrosp. 37 28–84 54 Privatepractice 16%

VultvonSteyernetal. 2001 Glass-inﬁltratedalumina Prosp. 18 25–70 n.r. Universityandprivatepractice 0%

Sorensenetal. 1998 Glass-inﬁltratedalumina Prosp. 47 19–66 n.r. University 2%

n.r.,“notreported”;RCT,randomizedcontrolledclinicaltrial.

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(anterior,posterior,maxilla,mandible),reportedmeanfollow- up,follow-uprange,publishedFDPsurvivalrate,numberof FDPslost (anterior,posterior),reportedbiologicalcomplica- tions (caries, periodontal, rootfracture), reported technical complications (framework fracture, minor chipping, major chipping,lossofretention),estheticcomplications(marginal discoloration),reportednumberofpatientsfreeofcomplica- tions.Basedontheincludedstudies,theFDPsurvivalratewas calculated.Inaddition,thenumberofeventsforalltechnical, biologicalandestheticcomplicationswasextractedandthe correspondingtotalexposuretimeofthereconstructionwas calculated.

2.9. Statisticalanalysis

Failureandcomplicationrateswerecalculatedbydividingthe numberofevents(failuresorcomplications)inthenumerator bythetotalFDPexposuretimeinthedenominator.

Thenumeratorcouldusuallybeextracteddirectlyfromthe publication.Thetotalexposuretimewascalculatedbytaking thesumof:

(1) ExposuretimeofFDPsthatcouldbefollowedforthewhole observationtime.

(2) ExposuretimeuptoafailureoftheFDPsthatwerelost duetofailureduringtheobservationtime.

(3) Exposure time up to the end of observation time for FDPsthatdidnotcomplete the observationperioddue to reasons such as death, change of address, refusal to participate, non-response, chronic illnesses, missed appointmentsandworkcommitments.

Foreachstudy,eventratesfortheFDPswerecalculatedby dividingthetotalnumberofeventsbythetotalFDPexposure timeinyears.Forfurtheranalysis,thetotalnumberofevents wasconsideredtobePoissondistributedforagivensumof FDPexposureyearsandPoissonregressionwithalogarithmic link-functionandtotalexposuretimeperstudyasanoffset variablewereused[21].

Robuststandarderrorswerecalculatedtoobtain95%con- fidence intervals of the summary estimates of the event rates. To assess heterogeneity of the study specific event rates,theSpearmangoodness-of-fitstatisticsandassociated p-value were calculated. If the goodness-of-fit p-valuewas below0.05.Five-yearsurvivalproportionswerecalculatedvia therelationshipbetweeneventrateandsurvivalfunctionS, S(T)=exp(−T×eventrate),byassumingconstanteventrates [22].The95%confidenceintervalsforthesurvivalproportions werecalculatedbyusingthe95%confidencelimitsoftheevent rates.MultivariablePoissonregressionwasusedtoformally compare construction subtypes and to assess other study characteristics.AllanalyseswereperformedusingStata^®,ver- sion13.1.

3. Results

3.1. Studycharacteristics

A total of 40 studies fulﬁlled the inclusion criteria of the

presentsystematicreview.Sevenstudieswere excludedfor Table2–Studyandpatientcharacteristicsofthereviewedstudiesformetal-ceramicFPDs. StudyYearofFrameworkStudydesignNo.ofpatientsAgerangeMeanageSettingDrop-out publicationmaterialinstudy(inpercent) Svanborgetal.2013Co-CrRetrosp.14939–9066.8Privatepractice16% Peleazetal.2012Co-CrRCT3723–65n.r.University0% Wollebetal.2012GoldmetalRetrosp.5234–8461Universitystudents14% Heschletal.2013GoldmetalRetrosp.9621–6450.3University71% Makarounaetal.2011GoldmetalRCT18n.r.47University56% Bräggeretal.2011GoldmetalRetrosp.8436–8462Universityn.r. Christensenetal.2010GoldmetalRCT25916–8950Privatepracticemulti-center4 Boeckleretal.2010TitaniumProsp.2327–6955.3University17% Saileretal.2009GoldmetalRCT59n.r.54.4University18% DeBackeretal.2008GoldmetalRetrosp.270n.r.n.r.UniversityStudents19% Eliassonetal.2007Co-CrRetrosp.45n.r.n.r.University7% Hochmanetal.2003GoldmetalRetrosp.30n.r.n.r.UniversityStudentsn.r. Walton2002GoldmetalRetrosp.35713–74n.r.Singlespecialistn.r. Napankangasetal.2002GoldmetalRetrosp.13239–8256.8UniversityStudents17% Reichen-GradenandLang1989GoldmetalRetrosp.5826–72n.r.UniversityStudentsn.r. n.r.,“notreported”;Co-Cr,cobalt-chromium;RCT,randomizedcontrolledclinicaltrial.

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variousreasons,ranging frommultiplepublications onthe samepatientcohorttoinsufficientlyreporteddataonFDPs [23–29]. 28 studies, published between 1998 and 2013, on all-ceramic FDPs and 15 studies, published between 1989 and 2013, on metal ceramic FDPs, were included in this review (Tables 1 and 2). The median year of publications forall-ceramicFDPs was2009 and formetal-ceramic FDPs 2010. For all-ceramic FDPs,the majority or 28 studies had a prospective design and only one had a retrospective design. In contrast, for metal-ceramic FDPs the majority of the included studies or 10 were retrospective and the remaining5studies were prospective.Fouroftheincluded studies (Peleaz et al., 2012, Makarouna, 2011, Christensen, 2010 and Sailer et al., 2009) were randomized controlled clinicaltrailscomparingdifferenttypesofall-ceramicFDPs with metal-ceramic FDPs. The included studies on all- ceramic FDPs reported on reconstructions made out of reinforcedglassceramics,glass-infiltratedalumina(InCeram Alumina),glass-infiltrated alumina-zirconia(InCeramZirco- nia), and densely sintered zirconia (Table 1). The studies ofmetal-ceramic FDPsreported on reconstructions having frameworkoutofgoldmetal,cobaltchromium ortitanium (Table2).

The majority of the included studies, or 35 out of 40 wereconductedinuniversitysettings.Theremainingstud- ies were executed in specialist clinics or private practices (Tables1and2).

The29studiesusingall-ceramicmaterialsincluded1225 patients, where as the 15 studies on metal-ceramic FDPs included 1669 patients. The age of the patients ranged between16and90yearsatthetimeoftreatment.Thepropor- tionofpatientswhocouldnotbefollowed-upforthecomplete studyperiodwasavailablefor90%ofthestudiesandranged from0%to71%.Themeandrop-outrateofpatientswas8%

forstudiesreportingonall-ceramicFDPsand19%forstudies onmetal-ceramicFDPs(Tables1and2).

3.2. FDPsurvival

Formetal-ceramicFDPs,15studiesprovideddataon1796FDPs afteramean follow-uptimeof7.0years.Outofthese,145 FDPswerereportedtobelost.Theannualfailureratewasesti- matedat1.15%(95%CI:0.72–1.84%)(Fig.2),translatingintoa 5-yearsurvivalrateformetal-ceramicFDPsof94.4%(95%CI:

91.2–96.5%)(Table3).

The results for all-ceramic FDPs was divided split into reconstructions based on reinforced glass ceramic, glass- infiltratedalumina(InCeramAluminaandInCeramZirconia) and densely sintered zirconia.For reinforced glassceramic FDPs,7studiesprovideddataon208FDPs.Afterameanfollow- up timeof6.0years,29FDPswere reportedtobelost.The annualfailureratewasestimatedat2.31%(95%CI:1.23–4.35%) (Fig.3)translatinginto a5-yearsurvivalrateforreinforced glassceramicFDPsof89.1%(95%CI:80.4–94.0%)(Table3).For glass-infiltratedaluminaFDPs,6studiesprovideddataon229 FDPs.Afterameanfollow-uptimeof4.1years,28FDPswere reportedtobelost.Theannualfailureratewasestimatedat 2.97%(95%CI:1.20–7.35%)(Fig.4)translatingintoa5-yearsur- vivalrateforglass-infiltratedaluminaFDPsof86.2%(95%CI:

69.3–94.2%) (Table3).Fordensely sinteredzirconiaFDPs,16 studiesprovideddataon673FDPsfromwhich62FDPswere reportedtobelostafterameanfollow-uptimeof4.5years.The annualfailureratewasestimatedat2.02%(95%CI:1.24–3.31%) (Fig.5)translatingintoa5-yearsurvivalratefordenselysin- teredzirconiaFDPsof90.4%(95%CI:84.8–94.0%)(Table3).

Atthe5-yearfollow-up,theannualfailureratesofdifferent typesofFDPsrangedfrom1.15%to2.97%andthe5-yearsur- vivalrangedfrom86.2%to94.4%.Investigatingformallythe relativefailureratesofdifferenttypesofFDPs,usingmetal- ceramicFDPsasreference,all-ceramicFDPsshowedhigher annual failurerates. Moreover,forglass-inﬁltratedalumina FDPsthisdifferencereachedstatisticalsigniﬁcance(p=0.052) (Table4).

Fig.2–Annualfailurerateofmetal-ceramicFDPs.

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Table3–Annualfailureratesandsurvivalofmetal-ceramicandall-ceramicFDPs.

Study Yearof

publication

Totalno.

ofFDPs

Mean follow-uptime

No.of failure

TotalFDPs exposuretime

Estimatedannualfailure rate^*(per100FDPyears)

Estimatedsurvivalafter 5years^a(inpercent) Metalceramic

Svanborgetal. 2013 201 4.6 7 915 0.77 96.2%

Peleazetal. 2012 20 4.2 0 83 0 100%

Wollebetal. 2012 76 5.3 1 400 0.25 98.8%

Heschletal. 2013 28 6.3 1 177 0.56 97.2%

Makarouna 2011 19 2.5 1 48 2.08 90.1%

Bräggeretal. 2011 82 12.1 2 992 0.20 99.0%

ChristensenandPloeger 2010 87 3.0 5 261 1.92 90.9%

Boeckleretal. 2010 31 2.7 1 84 1.19 94.2%

Saileretal. 2009 38 2.7 0 104 0 100%

DeBackeretal. 2008 322 11.4 72 3675 1.96 90.7%

Eliassonetal. 2007 51 4.3 3 217 1.38 93.3%

Hochmanetal. 2003 49 6.3 6 324 1.85 91.2%

Walton 2002 515 7.4 37 3363 1.10 94.6%

Napankangasetal. 2002 204 7.6 7 1478 0.47 97.7%

Reichen-GradandLang 1989 73 6.4 2 465 0.43 97.9%

Total 1796 7.0 145 12,586

Summaryestimate(95%CI)^a 1.15(0.72–1.84) 94.4%(91.2–96.5%)

Reinforcedglassceramic

Sola-Ruizetal. 2013 21 10.0 6 210 2.86 86.7%

Kernetal. 2012 36 10.1 4 363 1.10 94.6%

Makarouna 2011 18 4.7 6 84 7.14 70.0%

Wolfartetal. 2009 36 6.9 2 247 0.81 96.0%

Esquiveletal. 2008 30 3.3 5 100 5.00 77.9%

Wolfartetal. 2005 36 4.0 0 120 0 100%

Marquartetal. 2005 31 4.2 6 129 4.65 79.3%

Total 208 6.0 29 1253

Glassinﬁltratedalumina

Eschbachetal. 2009 65 4.5 2 295 0.68 96.7%

Suarezetal. 2004 18 3.0 1 53 1.89 91.0%

Olssonetal. 2003 42 6.3 5 266 1.88 91.0%

vanSteyernetal. 2001 20 5.0 2 95 2.11 90.0%

Soerensenetal. 1998 61 3.0 7 165 4.24 80.9%

Total 229 4.1 28 943

Denselysinteredzirconia

Rinkeetal. 2013 99 6.3 19 627 3.03 85.9%

Raigrodskietal. 2012 20 4.7 0 94 0 100%

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dentalmaterials31(2015)624–639 Table3–(Continued)

Study Yearof

publication

Totalno.

ofFDPs

Mean follow-uptime

No.of failure

Estimatedannualfailure rate^*(per100FDPyears)

Estimatedsurvivalafter 5years^a(inpercent)

Peleaz 2012 20 4.2 1 83 1.20 94.2%

Lopsetal. 2012 28 6.5 2 182 1.10 94.7%

Saxetal. 2011 57 7.6 15 433 3.46 84.1%

Sorrentinoetal. 2011 48 5.0 0 240 0 100%

Schmittetal. 2011 15 4.0 0 60 0 100%

Beueretal. 2010 18 2.9 1 53 1.89 91.0%

Roedigeretal. 2010 99 4.2 7 413 1.69 91.9%

Saileretal. 2009 38 3.2 0 121 0 100%

Wolfartetal. 2009 24 4.0 1 97 1.03 95.0%

Beueretal. 2009 21 2.5 2 53 3.77 82.8%

Edelhoffetal. 2008 22 3.1 0 69 0 100%

MolinandKarlsson 2008 19 5.0 0 95 0 100%

Tinschertetal. 2008 65 3.1 0 202 0 100%

Total 673 4.5 62 3062

Overallresults 2906 6.1 264 17,844

a BasedonrobustPoissonregression.

Table4–Summaryofannualfailurerates,relativefailureratesandsurvivalestimatesforFDPswithmetal-ceramicFDPsasreference.

TypeofFDPs Totalnumber

ofFDPs

MeanFDPs follow-uptime

Estimatedannual failurerate^*

5-Yearsurvivalsummary estimate^*(95%CI)

Relativefailure rate^**

p-Value^**

Metal-ceramic 1796 12,586 7.0 1.15(0.72–1.84) 94.4%(91.2–96.5%) 1.00(Ref.)

Reinforcedglassceramic 208 1253 6.0 2.31(1.23–4.35) 89.1%(80.4–94.0%) 2.01(0.95–4.25) 0.068

Glass-inﬁltratedalumina 229 943 4.1 2.97(1.20–7.35) 86.2%(69.3–94.2%) 2.58(0.99–6.69) 0.052

Denselysinteredzirconia 673 3062 4.5 2.02(1.24–3.31) 90.4%(84.8–94.0%) 1.76(0.90–3.41) 0.096

∗BasedonrobustPoissonregression.

∗∗BasedonmultivariablerobustPoissonregressionincludingalltypesofFDPs.

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Fig.3–AnnualfailurerateofreinforcedglassceramicFDPs.

3.3. Biologicalcomplications

3.3.1. Secondarycaries

Eighteenstudiesreportedontheincidenceofsecondarycaries onthe abutmentlevel. From 3351FDPabutmentsincluded inthose studies,52abutments developedsecondary caries.

Theoverallannualcomplicationratewas0.29%,translating intoa5-yearcomplicationrateof1.4%(Table5).Fordifferent typesofFDPstheannualrateofsecondarycariesrangedfrom 0.11%to0.65%.Thelowestannual complicationrate0.11%

wasreportedforreinforcedglassceramicFDPsandthehigh- estcomplicationrate0.65%wasreportedfordenselysintered

Fig.4–Annualfailurerateofglass-inﬁltratedaluminaFDPs.

zirconiaFDPs.Investigatingtherelativecomplicationratesof different typesofFDPs,using metal-ceramicFDPsasrefer- ence,denselysinteredzirconiaFDPsexperiencedsigniﬁcantly higherrateofsecondarycaries(p=0.001)(Table6).

Information about loss ofthe entirereconstruction due tosecondarycarieswasgivenin38studies.From2145FDPs includedinthesestudies55werelostduetosecondarycaries.

Theoverallannualfailureratewas0.43%,translatingintoa 5-yearfailurerateof2.1%(Table5).FordifferenttypesofFDPs theannualrateoffailuresduetocariesrangedfrom 0.09%

to0.54%.Thelowestannualfailurerate0.09%wasreported forreinforcedglassceramicFDPsandthehighestfailurerates

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Table5–OverviewofbiologicalandtechnicalcomplicationsofdifferenttypesofFDPs.

Complication Numberof

abutmentsor FDPs

Estimated annual complication rates(95%CI)

Cumulative 5-year complication rates(95%CI)

Numberof abutmentsor

FDPs

Overallresults–allFDPs MetalceramicFDPs ReinforcedglassceramicFDPs

Cariesonabutments 3351 0.29^*(0.14–2.94) 1.4%^*(0.7–2.9%) 2497 0.24^*(0.10–0.57) 1.2%^*(0.5–2.8%) 199 0.11^*(0.01–0.94) 0.5%^*(0.06–4.6%)

FDPslostduetocaries 2145 0.43^*(0.21–0.88) 2.1%^*(1.1–4.3%) 1053 0.54^*(0.24–1.22) 2.7%^*(1.2–5.9%) 190 0.09^*(0.01–0.76) 0.4%^*(0.05–3.7%)

FDPslostdueto periodontaldisease

2096 0.23^*(0.10–0.54) 1.2%^*(0.5–2.7%) 1004 0.06^*(0.03–0.11) 0.3%^*(0.1–0.6%) 190 0.60^*(0.10–3.52) 2.9%^*(0.5–16.1%)

FDPslostdueto abutmenttooth fracture

2107 0.17^*(0.12–0.25) 0.9%^*(0.6–1.3%) 1053 0.19^*(0.11–0.30) 0.9%^*(0.6–1.5%) 190 0.09^*(0.02–0.44) 0.4%^*(0.1–2.2%)

Lossofabutmenttooth vitality

243 0.44^*(0.11–1.80) 2.2%^*(0.5–8.6%) n.a. n.a. n.a. n.a. n.a. n.a.

Marginaldiscolorations 253 3.91^*(1.46–10.46) 17.7%^*(7.0–40.7%) 20 4.82^*(1.33–11.88) 21.4%^*(6.4–44.8%) 118 0.72.^*(0.23–2.19) 3.5%^*(1.2–10.4%)

Frameworkfracture 2640 0.45^*(0.25–0.82) 2.2%^*(1.2–4.0%) 1530 0.12^*(0.04–0.40) 0.6%^*(0.2–2.0%) 208 1.68^*(0.84–3.33) 8.0%^*(4.1–15.3%)

Ceramicfractures 2129 1.56^*(0.85–2.86) 7.5%^*(4.2–13.3%) 1305 1.03^*(0.42–2.56) 5.0%^*(2.1–12.0%) 187 1.34^*(0.99–1.82) 6.5%^*(4.8–8.7%)

Ceramicchipping 1659 2.71.^*(1.52–4.83) 12.7%^*(7.3–21.4%) 781 1.79^*(0.81–3.96) 8.6%^*(4.0–18.0%) 213 1.07^*(0.48–2.36) 5.2%^*(2.4–11.1%)

Lossofretention 1702 0.64^*(0.35–1.16) 3.1%^*(1.7–5.6%) 955 0.42^*(0.16–1.09) 2.1%^*(0.8–5.3%) 142 0.58^*(0.35–0.97) 2.9%^*(1.7–4.7%)

Complication Numberof

abutmentsor FDPs

FDPs

Glass-inﬁltratedaluminaFDPs DenselysinteredzirconiaFDPs

Cariesonabutments 168 0.41^*(0.22–0.74) 2.0%^*(1.1–3.6%) 487 0.65^*(0.27–1.56) 3.2%^*(1.3–7.5%)

FDPslostduetocaries 229 0.11^*(0.02–0.56) 0.5%^*(0.1–2.8%) 673 0.39^*(0.20–0.77) 1.9%^*(1.0–3.8%)

FDPslostdueto periodontaldisease

229 1.59^*(0.62–4.08) 7.6%^*(3.1–18.4%) 673 0.10^*(0.03–0.30) 0.5%^*(0.2–1.5%)

FDPslostdueto abutmenttooth fracture

229 0.11^*(0.01–1.02) 0.5%^*(0.05–5.0%) 635 0.21^*(0.11–0.38) 1.0%^*(0.6–1.9%)

Lossofabutmenttooth vitality

n.a. n.a. n.a. 243 0.44^*(0.11–1.80) 2.2%^*(0.5–8.6%)

Marginaldiscolorations 18 3.77^*(0.46–12.98) 17.2%^*(2.3–47.7%) 97 6.72^*(3.30–13.68) 28.5%^*(15.2–49.5%)

Frameworkfracture 229 2.76^*(1.01–7.52) 12.9%^*(4.9–31.3%) 673 0.39^*(0.24–0.65) 1.9%^*(1.2–3.2%)

Ceramicfractures 65 1.36^*(0.37–3.44) 6.6%^*(1.8–15.8%) 572 3.14^*(2.37–4.17) 14.5%^*(11.2–18.8%)

Ceramicchipping 90 7.55^*(1.09–52.24) 31.4%^*(5.3–92.7%) 575 4.33^*(1.93–9.72) 19.5%^*(9.2–38.5%)

Lossofretention 107 0.53^*(0.31–0.93) 2.6%^*(1.5–4.5%) 498 1.28^*(0.83–1.97) 6.2%^*(4.1–9.4%)

n.a.,“notavailable”.

∗BasedonrobustPoissonregression.

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Table6–RelativecomplicationratesfordifferenttypesofFDPs. TypeofcomplicationsMetalceramicFDPsReinforcedglassceramicFDPsGlass-inﬁltratedaluminaFDPsDenselysinteredzirconiaFDPs Relativecompl.rate*p-Value*Relativecompl.rate*p-Value*Relativecompl.rate*p-Value* Cariesonabutments1.00(Ref.)0.45(0.06–3.29)0.4321.73(0.53–5.63)0.3662.75(1.50–5.07)0.001 FDPslostduetocaries1.00(Ref.)0.16(0.02–1.37)0.0950.19(0.03–1.10)0.0640.72(0.26–2.01)0.535 FDPslostdueto periodontaldisease1.00(Ref.)10.8(1.82–64.31)0.00928.80(9.45–87.74)<0.00011.77(0.49–6.44)0.384 FDPslostduetoabutment toothfracture1.00(Ref.)0.46(0.09–2.26)0.3410.57(0.07–4.92)0.6121.11(0.52–2.38)0.784 Marginaldiscolorations1.00(Ref.)0.14(0.05–0.42)<0.00010.78(0.78–0.78)<0.00011.39(0.75–2.58)0.289 Frameworkfracture1.00(Ref.)13.81(3.65–52.28)<0.000122.72(5.13–100.69)<0.00013.23(0.91–11.42)0.069 Ceramicfractures (Chippingandfractures)1.00(Ref.)1.30(0.52–3.28)0.5781.31(0.54–3.18)0.5443.05(1.21–7.69)0.018 Ceramicchipping1.00(Ref.)0.60(0.21–1.72)0.3384.21(0.71–24.92)0.1132.42(0.81–7.25)0.115 Lossofretention1.00(Ref.)1.40(0.50–3.88)0.5231.28(0.48–3.47)0.6213.07(1.12–8.37)0.028 ∗BasedonmultivariablerobustPoissonregressionincludingalltypesofFDPswithmetalceramicFDPsasreference.

0.39%and0.54%fordenselysinteredzirconiaFDPsandmetal- ceramicFDPs,respectively.Thedifferencebetweendifferent typesofFDPsdidnotreachstatisticalsigniﬁcance(p=0.064, 0.095&0.535)(Table6).

3.3.2. Lossofvitality

Lossofabutmentvitalitywasreportedinthreestudies.Allof themreportingondenselysinteredzirconiaFDPs.Fouroutof 243abutmentteeth,reportedtobevitalatthetimeofcemen- tation,presentedlossofpulpvitalityduringtheobservation period.Theannualcomplicationratewas0.44%,translating intoa5-yearcomplicationrateof2.2%(Table5).

3.3.3. Abutmenttoothfracture

TheincidenceofFDPslostduetofractureofabutmentteeth wasreportedin36studiesevaluating2107FDPs,outofwhich 22werelost.Theoverallannualfailureratewas0.17%,trans- latingintoa5-yearfailurerateof0.9%(Table5).Fordifferent typesofFDPstheannualfailureratesduetoabutmenttooth fracturesrangedfrom0.09%to0.21%.Thedifferencebetween differenttypesofFDPsdidnotreach statisticalsigniﬁcance (p=0.341,0.612&0.784)(Table6).

3.3.4. Periodontaldisease

TheincidenceofFDPslostduetorecurrentperiodontaldis- ease, was reportedin37 studies evaluating 2096FDPs,out of which29 were lost. Theoverall annual failure rate was 0.23%,translatingintoa5-yearfailurerateof1.2%(Table5).

For differenttypesofFDPs,the annualfailure ratesdueto recurrentperiodontaldiseases rangedfrom0.06% to1.59%.

Thehighestannualfailureratewasreportedforreinforced glassceramicFDPs0.60%andglass-infiltratedaluminaFDPs 1.59%,translatingintoa5yearsfailureratesof2.9%and7.6%, respectively(Table5).Investigatingtherelativecomplication ratesofdifferenttypesofFDPs,usingmetal-ceramicFDPsas reference, significantly moreglass-infiltrated aluminaFDPs andreinforcedglassceramicFDPswerelostduetorecurrent periodontaldiseases(p<0.0001&0.009).

3.4. Technicalcomplications

3.4.1. Materialcomplications:frameworkfracture, ceramicchippingorceramicfracture

Theincidenceofframeworkfracturewasreportedin43out ofthe44studiesincludedinthepresentsystematicreview.

From 2640FDPsthatwere evaluated,72 were knowntobe lost duetoframework fractures.Theoverallannual failure ratewas0.45%,translatingintoa5-yearfailurerateof2.2%

(Table5).FordifferenttypesofFDPs,theannualfailureratesof frameworkfracturesrangedfrom0.12%to2.76%.Thehighest annualfailureratewasreportedforreinforcedglassceramic FDPs(1.68%)andglass-infiltratedaluminaFDPs(2.76%),trans- latingintoa5-yearfailureratesof8.0%and12.9%,respectively (Table 5). Investigating the relative complication rates of different typesofFDPs,using metal-ceramicFDPsasrefer- ence,significantly moreglass-infiltrated aluminaFDPs and reinforcedglassceramicFDPswerelostduetoframeworkfrac- tures (p<0.0001). Comparedtothe other ceramics, densely sinteredzirconiaexhibitedthehigheststabilityasframework materialwithanestimated5-yearfailurerateof1.9%(Table5).

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Fig.5–AnnualfailurerateofdenselysinteredzirconiaFDPs.

Theincidence,however,offracturesoftheceramicveneering thatneededrepairorreplacementwashighestfordenselysin- teredzirconiaFDPswithanannualcomplicationrateof3.14%, translatingintoa5-yearcomplicationrateof14.5%.Thisdif- ferencereachedstatisticalsigniﬁcance(p=0.018)(Table6).For othertypesofFDPstheannualrateofceramicfracturesranged from1.03% to1.36%,translatinginto a5-yearcomplication rateof5.0–6.5%(Table6).Theincidenceofceramicchipping thatcouldbesolvedwithpolishingwasreportedin32stud- iesincluding1659FDPs.Theoverallannualcomplicationrate was2.71%,translatingintoa5-yearcomplicationrateof12.7%

(Table5).FordifferenttypesofFDPs,theannualcomplication ratesrangedfrom1.07%to7.55%.Ceramicchippingwasthe mostfrequenttechnicalcomplicationreported,butthediffer- enceinceramicchippingbetweendifferenttypesofFDPsdid notreachstatisticalsigniﬁcance(p=0.338,0.113&0.115).

3.4.2. Lossofretention

Lossofretentionorfractureofthelutingcementwasanalyzed in25studiesreportingon1702FDPs.Theoverallannualcom- plicationratewas0.64%,translatingintoa5-yearfailurerate of3.1%(Table5).DenselysinteredzirconiaFDPsexperienced statisticallysigniﬁcantly(p=0.028)(Table 6) moreretention lossthan the other types ofFDPswith anannual compli- cationrateof1.28%anda5-yearcomplicationrateof6.2%.

ForothertypesofFDPstheannualcomplicationratesranged from0.42%to0.58%,translatingintoa5-yearfailureratesof 2.1–2.9%(Table5).

3.4.3. Marginaldiscoloration

Marginal discolorationor the occurrence of marginalgaps wasevaluatedin9studiesreportingon253FDPs.Theoverall annualcomplicationratewas3.91%,translatingintoa5-year complicationrateof17.7%(Table5).Thelowestincidenceof marginaldiscolorationwasseenforreinforcedglassceramic

withannualcomplicationrateof0.72%ora5-yearcomplication rateof 3.5%.For the other threetypes ofFDPs, the annualratesofmarginaldiscolorationrangedbetween3.77%

and6.72%withthehighestincidencereportedfordenselysin- teredzirconiaFDPs,representinga5-yearcomplicationrateof 28.5%(Table5).

4. Discussion

Systematicreviewshavebeenusedextensivelyinmedicinefor thelasttwodecadestosummarizethecumulativeinforma- tionontheoptimaltreatmentforclinicallyrelevantquestions and to support the clinicians in the decision-making process fordifferenttreatment options. Thisresearchmethod has slowly found its way into dental research. Systematic reviewshave mainlybeen usedtoanalyze and summarize resultsfromrandomizedcontrolledclinicaltrials(RCTs)[30].

IntheabsenceofRCTswithadequatestatisticalpowertocom- parehead-to-headmetal-ceramicandall-ceramicﬁxeddental prosthesis(FDPs)prospectiveandretrospectivecohortstudies andcaseserieswithstringentinclusioncriteriawereincluded inthissystematicreviewinordertosummarizetheavailable informationaboutsurvivalandcomplicationratesofmetal- ceramicandall-ceramicFDPsafteraobservationperiodofat least3years.Evenwithfollow-upperiodsofatleast3years, somecliniciansmayarguethatsuchaperiodisstilltooshort toobtainreliable informationonsurvivalandcomplication ratesofﬁxedreconstructions.Duetothefactthattheuseof all-ceramicFDPsisrelativelyrecent,ameanfollow-upperiod of3yearsormorewasanecessarycompromise.

Howeveritwasinterestingtoseethatthemedianyearof publicationwas2010formetal-ceramicFDPscomparedwith 2009forall-ceramicFDPs.Inasystematicreviewonthesame topicpublishedintheyear2007bythesameauthors,onlyﬁve studiesonmetal-ceramicFDPsfulﬁlledtheinclusioncriteria’s

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andonlyoneofthemwaspublishedbeforetheyear2000[1].

Thismustbeconsideredpeculiarasmetal-ceramicFDPshave beenconsideredthegoldenstandardinreconstructiveden- tistryoverdecades.Apositiveshifthastobenoticed,as15 studiesreportingonmetal-ceramiccouldbeincludedinthe presentsystematicreview.

Survival was defined as FDP remainingin situ with or withoutmodificationsandsuccesswasdefinedastheFDPs remainingin situ free ofall complications over the entire observationperiod.From theForrestplotsofstudy specific failurerates,itisevidentthatthesevarywidelyamongthe variousstudies.Thismaybeattributabletothepatientcohort observed,thedesignandextentoftheFDPs,themaintenance careprovidedandtheexperienceandclinicalset-up ofthe clinicians.

Afteranobservationperiodof3years,thelowestfailure ratewereobservedformetal-ceramicFDPs(5.6%)compared with a failure rates of 9.6% for densely sintered zirconia ceramicFDPs,10.9% forreinforcedglass ceramicFDPsand 13.8%forglass-inﬁltratedaluminaFDPs.Duetothedifferent compositionofdifferentceramicmaterialsitwasdecidednot topull, differenttypesofall-ceramic FDPs,into onegroup in the meta-analysis as was done in the previous review onthesametopic.Fouroftheincludedstudiesrandomized the patients according to material utilized.Three ofthem reported more failure of all-ceramic FDPs compared with metal-ceramicFDPs[19,31,32].Thelastonereportednofail- uresineithergroup[17].

Themostfrequentreasonforfailure ofreinforcedglass ceramic FDPs and glass-inﬁltrated alumina FDPs over the 3 years observation period was fracture of the reconstruction framework, reported for 8.0% and 17.2% of the reconstructionsrespectively. Thistechnicalfailure wasfre- quently related to using reinforced glass ceramic FDPs and glass-inﬁltrated alumina FDPs in the posterior area and where the diameter of the connectors was reduced below 4mm×4mm [33]. It has also been argued that all- ceramicFDPssuffer moreoftenfromparafunctionalhabits and malocclusion leading toframework fractures [34]. The frameworkfracture failureratewasrarer formetal-ceramic FDPs (0.6%) and densely sintered zirconia ceramic FDPs (1.9%). One aspect to consider for all-ceramic FDPs might bethelengthofthereconstruction.Studiesdemonstrateda higherrate offramework fractures withanincreasing FDP length[35,36].

Themostfrequenttechnicalcomplication waschipping oftheveneeringceramicwithanoverall complicationrate of12.7% after3-year observation period. The incidence of thiscomplicationrangedfrom 6.6%to31.4%dependingon the materialtype and was most frequently seen byglass- inﬁltratedaluminaFDPsanddenselysinteredzirconiaFDPs.

Ceramic chippingsformetal-ceramic FDPsappeartooccur morefrequently duringthe firstyear infunction. Therate ofchippingsmaythenslightlydecrease[23].Thehighinci- dence of chipping by densely sintered zirconia FDPs, may beduetothefactthatthefirstgenerationofzirconiaFDPs was made before speciallow-fusing ceramics with a ther- malexpansioncoefficientcompatiblewithzirconiahadbeen developed.Anotherreasonforthismightbethedifficultyof getting correctuniform thickness ofthe virtually designed

frameworks, which may notprovide propersupportto the veneeringceramic.

Marginal discoloration was, with the exception of reinforced glass ceramic FDPs (3.5%), a frequent technical complicationreportedforall-ceramicFDPsandmetal-ceramic FDPs, ranging from 17.2% to 28.5%. The drawback of this analysis was that it is based on very few observationsfor metal-ceramicandglass-inﬁltratedaluminaFDPsrepresent- inginaverywideconﬁdenceinterval.Inthetwostudiesusing apressed glass-ceramicnodiscolorationwasfound[37,38].

Thiscanpartlybeexplainedbythemanufacturingprocedures oftheframeworks.Thehighprecisionofthemanufacturing techniqueofpressableglass-ceramicshasbeendocumented in several investigations [39–41]. Amongthe studies reporting on marginaldiscolorationofdensely sintered zirconia ceramicFDPs,therewasaclearoutlierusingaprototypeCAM- system reporting the highest rate of gaps or discoloration [36].Apossibleexplanationcouldbethemisfitofthesepro- totype frameworks.InaRCTcomparingmetal-ceramic and denselysinteredzirconiaFDPs[17],thefitoftheframeworks was analyzed prior to the insertion of the reconstruction [42]. It was demonstrated that milled zirconia frameworks exhibitedlargerinternalgapsthanthoseconstructedusing conventionalmetal-ceramictechniques.Thislargermisfitof CAD/CAM reconstruction can explaina ratherhigh rateof marginaldiscoloration.

Withtheexceptionofcariesonabutmentlevelbydensely sintered zirconiaceramicFDPs(3.2%)and FDPslost dueto periodontaldisease byglass-inﬁltratedaluminaFDPs(7.6%) wastheincidenceofbiologicalcomplicationssuchascaries onabutmentlevel,FDPslostduetocaries,FDPslostdueto periodontaldisease,FDPslostduetoabutmenttoothfracture andlossofabutmenttoothvitalityrelativerare,rangingfrom 0.3%to2.9%(Table5).

When densely sintered zirconia was first introduced as frameworkmaterial,its excellentphysicalpropertiesledto the assumptionthatit maysuccessfullybeusedtoreplace the conventionalmetal-ceramicFDP.Thezirconiahasbeen proven to be a strong framework material with low incidence offrameworkfracture. Speciallyif notusedforlong edentulous spans (3 teeth or more) and criteria’s for con- nectordimensionarerespected. Onethe otherhand,there are stillissues withfitand frameworkdesign. Thepresent systematicreviewhasdemonstratedthatproblemssuchas discolorations,secondarycariesandlossofretentions,that canbedirectlyrelatedtosemioptimalfitaremorefrequentby denselysinteredzirconiaFDPscomparedwithmetal-ceramic FDPs and other types of all-ceramic FDPs. Moreover, high incidenceofceramicfracturesandchippingisanotherissue thathastakenintoaccountutilizingdenselysinteredzirconia FDPs.

Inthisreviewstringentstudyinclusioncriteriawereused.

Onlystudieswithaclinicalfollow-upexaminationofatleast 3 years were included to avoid the potential inaccuracies ineventdescription instudies thatbasedtheiranalysison patientself-reports.Clearly,alimitationofthepresentreview istheassumptionofaconstantannualeventratethroughout follow-uptimeafterreconstruction.Interpretingtheresults it must bekeptinmind thatthe mean observationperiod wason average7.0years formetal-ceramicFDPs,andonly

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4.7yearsforall-ceramicFDPs.Iftheannualfailurerateswere higherintheyears5–10thanintheyears0–5,thenaverage annualfailurerateswouldbeautomaticallyhigherforthose reconstructiontypesforwhichstudieswithlongerfollow-up wereavailable.Toreducetheimpactofsuchabias,theresults ofthe presentanalysiswere restrictedtoestimatingthe5- yearsurvival.Anotherlimitationofthisreviewisthatitwas mainlybasedonstudiesthatwereconductedinaninstitu- tionalenvironment,suchasuniversityorspecializedimplant clinics.Therefore,thelong-termoutcomesobserved,cannot begeneralizedtodentalservicesprovidedinprivatepractice.

5. Conclusion

Metal-ceramicFDPshadlowerfailureratesthenall-ceramic FDPs after a mean observation period of at least 3 years.

Frameworkfractureswerefrequentlyreportedforreinforced glassceramicandglass-infiltratedaluminaFDPs.Denselysin- tered zirconia was significantly more stable as framework material, but misfit lead to complications such as discolorations,secondary cariesand loss ofretention. Moreover, ceramicfractures and chipping ofceramics were frequent.

Inthe future, furtherreﬁnementsinthe productionofall- ceramicreconstructionsareindicated.

Conﬂict of interest

Theauthorsdoreporttohavenoconﬂictofinterest.

Acknowledgments

TheauthorsaregratefultoKristinHeimisdóttir,ÁstaÓskars- dóttirandGiselaMüller,StudyMonitor,ClinicofFixedand RemovableProsthodonticsandDentalMaterialScience,Uni- versity of Zurich, for their help in the preparation of the manuscript.

Excluded studies and reasons for exclusion.

[23]BehrM,WinklhoferC,SchreierM,ZemanF,KobeckC, BrauerI, etal.Riskofchippingorfacingsfailureofmetal ceramicﬁxedpartialprostheses–aretrospectivedatarecord analysis.ClinOralInvest2012;16:401–5. Reasonfor exclu- sion:chartreview.

[24]DeBackerH,VanMaeleG,DeMoorN,VandenBergheL.

Theinﬂuenceofgenderandageonﬁxedprostheticrestora- tion longevity: an up to 18- to 20-year follow-up in an undergraduateclinic.IntJProsthodont.2007;20:579–86.Rea- son for exclusion: multiplepublications on same patient cohort.

[25]DeBackerH,VanMaeleG,DeMoorN,VandenBerghe L.Long-termresultsofshort-span versuslong-span ﬁxed dentalprostheses:anupto20-yearretrospectivestudy.Int JProsthodont2008;21:75–85.Reasonforexclusion:multiple publicationsonsamepatientcohort.

[26]PelaezJ,CogolludoPG,SerranoB,LozanoJF,SuarezMJ.

A prospective evaluation of zirconia posterior ﬁxed dental prostheses: three-yearclinical results. JProsthet Dent

2012;107:373–9.Reasonfor exclusion: multiplepublication onsamepatientcohort.

[27]ReitemeierB,HanselK,KastnerC,WeberA,WalterMH.A prospective10-yearstudyofmetalceramicsinglecrownsand ﬁxeddentalprosthesisretainersinprivatepracticesettings.J ProsthetDent2013;109:149–55.Reasonforexclusion:nodata forFDPs,onlyabutments.

[28]SailerI,FeherA,FilserF,GaucklerLJ,LuthyH,Hammerle CH.Five-yearclinicalresultsofzirconiaframeworksforpos- teriorﬁxedpartialdentures.IntJProsthodont2007;20:383–8.

Reasonforexclusion:multiplepublicationsonsamepatient cohort.

[29]WaltonTR.Changesintheoutcomeofmetal-ceramic tooth-supported single crowns and FDPs following the introduction of osseointegrated implant dentistry into a prosthodonticpractice.IntJProsthodont2009;22:260–7.Rea- son for exclusion: multiple publicationson samepatient cohort.

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