Parental and Dentist Satisfaction with Primary Anterior Zirconia Crowns: A Case Series Analysis

Abstract

This retrospective cohort study evaluated overall parental satisfaction of zirconia crowns (ZC) placed on primary maxillary anterior teeth with that of two independent, blinded dentists. 131 ZC placed in 37 children, aged 24.8–62.2 months (mean = 42.8), who had at least one recall visit a minimum of 6 months after placement were rated (average = 13.3). Crown colour match, crown contour and crown durability were evaluated by parents and compared to photographic evaluations of two independent raters. Overall parental satisfaction was also evaluated. The overall retention rate was 99.7% and parental satisfaction was 100%. Colour match was rated excellent by 84% of parents and 36% of dental evaluators. Crown contour was rated excellent by 97% of parents and 55% of dental evaluators. The length of follow-up had no effect on colour match or crown contour. ZC comprises an aesthetic and durable option for restoring carious primary maxillary incisors and were well-accepted by parents. Parents were less critical than dental evaluators of crown appearance.

Full text

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Children2021,8,451.https://doi.org/10.3390/children8060451www.mdpi.com/journal/children
Article
ParentalandDentistSatisfactionwithPrimaryAnterior
ZirconiaCrowns:ACaseSeriesAnalysis
LawrenceYanover
1,
*,WilliamWaggoner
2
,AriKupietzky
3
,MotiMoskovitz
3
andNiliTickotsky
4
1
PrivatePractice,126LakeshoreRd,St.Catharines,ONL2N2T5,Canada
2
PrivatePractice,8981WestSaharaAve#110,LasVegas,NV89031,USA;wwaggoner1@gmail.com
3
DepartmentofPediatricDentistry,HebrewUniversityHadassahSchoolofDentalMedicine,
P.O.Box12272,Jerusalem9112102,Israel;drkup@netvision.net.il(A.K.);motim@md.huji.ac.il(M.M.)
4
DepartmentofImmunology,WeizmannInstituteofScience,Rehovot76100,Israel;nilitiko@gmail.com
*Correspondence:kidsdentist5937@yahoo.ca
Abstract:Thisretrospectivecohortstudyevaluatedoverallparentalsatisfactionofzirconiacrowns
(ZC)placedonprimarymaxillaryanteriorteethwiththatoftwoindependent,blindeddentists.131
ZCplacedin37children,aged24.8–62.2months(mean=42.8),whohadatleastonerecallvisita
minimumof6monthsafterplacementwererated(average=13.3).Crowncolourmatch,crown
contourandcrowndurabilitywereevaluatedbyparentsandcomparedtophotographicevalua‐
tionsoftwoindependentraters.Overallparentalsatisfactionwasalsoevaluated.Theoverallreten‐
tionratewas99.7%andparentalsatisfactionwas100%.Colourmatchwasratedexcellentby84%
ofparentsand36%ofdentalevaluators.Crowncontourwasratedexcellentby97%ofparentsand
55%ofdentalevaluators.Thelengthoffollow‐uphadnoeffectoncolourmatchorcrowncontour.
ZCcomprisesanaestheticanddurableoptionforrestoringcariousprimarymaxillaryincisorsand
werewell‐acceptedbyparents.Parentswerelesscriticalthandentalevaluatorsofcrownappear‐
ance.
Keywords:pediatricdentistry;restorativedentistry;zirconiapediatriccrowns

1.Introduction
Thereisincreasingdemandfromparentsfordentiststoprovideimprovedaesthetic
solutionswhenrestoringtheirchildren’steethandthereareanincreasingnumberofop‐
tionstoprovidethistreatment[1,2].Whereminimalcariesisdetected,discingofaffected
interproximalcariesmaybecarriedoutalongwithimprovedoralhygiene,topicalfluo‐
rideapplicationandreducedsnackingonfermentablecarbohydrates.Aminimalinvasive
dentistryapproachmightincludetheuseofsilverdiaminefluoridetoarrestdecaybut
thisleavescariouslesionsblackenedandlacksaestheticappeal.Repairofsmallcarious
lesionscanbeapproachedwithcosmeticmaterialssuchasresin‐modifiedglassionomers
orbondedcompositeresins.Aestheticfullcrowncoverageforprimaryanteriorteethfor
teethseverelyaffectedbyearlychildhoodcariesorwithahighriskofrecurrentcaries,
wouldincludefullcoveragerestorationsbondedontothetoothsuchasresincomposite
stripcrowns(RCSC)andcrownsthatareretainedonthetoothbycementation.Thelatter
includepre‐veneeredstainlesssteelcrowns(VSSC)andthenewerzirconiacrowns[1,3,4].
TheRSCShasexcellentaesthetics,multipleresinshades,theabilitytofitincrowded
spacesandeaseofrepair[5,6].TheVSSCislesstechnique‐sensitivebuthasalabialveneer
withfewershades,afacingthatcandebondandnoabilitytoadjustcrowncontour[7,8].
Preformedanteriorzirconiacrowns(ZC)wereintroducedin2008toofferanother
aestheticoptionfortherestorationofprimaryanteriorteeth.Zirconiacrownsarecolour‐
stable,resistanttofractureordebonding[9,10],biocompatible[11,12]andautoclavableif
contaminated[13]butcomeinlimitedshadesandshapes.Sizesmustbecarefullyselected
Citation:Yanover,L.;Waggoner,
W.;Kupietzky,A.;Moskovitz,M.;
Tickotsky,N.ParentalandDentist
SatisfactionwithPrimaryAnterior
ZirconiaCrowns:ACaseSeries
Analysis.Children2021,8,451.
https://doi.org/10.3390/
children8060451
AcademicEditors:ZiadD.Baghdadi
andGianlucaM.Tartaglia
Received:23March2021
Accepted:25May2021
Published:26May2021
Publisher’sNote:MDPIstaysneu‐
tralwithregardtojurisdictional
claimsinpublishedmapsandinstitu‐
tionalaffiliations.

Copyright:©2021bytheauthors.Li‐
censeeMDPI,Basel,Switzerland.
Thisarticleisanopenaccessarticle
distributedunderthetermsandcon‐
ditionsoftheCreativeCommonsAt‐
tribution(CCBY)license(http://crea‐
tivecommons.org/licenses/by/4.0/).

Children2021,8,4512of10
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tofitthegivenarchspaceandexistingtoothsizeandshapebecausetheycannotbeeasily
altered.Theyonlycomeinoneortwoshadessothismustbecarefullyevaluatedforideal
estheticresults.Thetoothmustbereducedtoacceptthecrownsizeselectedaszirconia
cannotbeadjustedtoprovideanacceptablefit.Withpropertechnique,haemorrhageand
moisturecontaminationcanbecontrolledpriortoluting,ascementationwillbeaffected
byacontaminatedfieldsimilartowhatisexpectedforthebondingofresinmaterials.The
crownsmustbeheldinalignmentwhilethecementcures,otherwiseestheticsareim‐
pactedthuspatientcomplianceisrequired,althoughthisissimplerandfasterthanthat
requiredforRSCS[1,4].
AcceptanceofZCcontinuestogrowintherestorationofdecayedprimaryanterior
teeth,whichisduetoanumberoffactors.Thecostofprovidingtreatmentissimilarto
alternatefullcoverageoptionsdependentuponlocalfactors.Durabilityisbetterthanpop‐
ularRSCS,includingfractureresistance,marginalintegrityandcolourstability[14,15].
WithincreasingclinicianacceptanceofZC,itisimportanttoevaluatetheparentalsatis‐
factionofrestorativeoptions.Inpreviousstudies,theuseofZCforrestorationofprimary
anteriorteethhasmetparentapprovalandwasmorewidelyacceptedthanVSSCand
RSCS[9,15,16].Themainaimofthisretrospectivestudywastoevaluateparentalsatisfac‐
tionwiththeclinicalappearanceofZCplacedontheirchildrenplacedbyasinglepro‐
vider.Oursecondaryaimwastocompareparentalsatisfactionwiththeratingsofinde‐
pendentdentalexaminers.Wealsohopedtoevaluateifthethreecrownbrandsusedin‐
fluencedparentalsatisfaction.
2.MaterialsandMethods
Theconvenientsamplecomprisedof131zirconiacrownsplacedin37childrenwho
hadcariousprimaryincisorswithextensivecaries(evaluatedbyclinicalandradiographic
examination)onasinglesurfaceormoderatecariouslesionsontwoormoresurfaces.The
studygroupcomprised27boysand10girls,aged24.8–62.2months(median=40.6
months).Asinglepractitioner(LY)experiencedwithplacingZCcompletedalloftheres‐
torationsandconductedallclinicalevaluationsbetween2015and2018.
Inclusioncriteria:Includedinthestudywereallchildrenwhohadzirconiacrowns
placedbythesamepractitionerbetweenJanuary2015andMarch2018andhadatleast
onerecallvisitatleast6monthsafterplacement.
ThestudyprotocolwasapprovedbytheInstitutionalHumanSubjectsEthicsCom‐
mittee,HebrewUniversity,HadassahSchoolofDentalMedicine.Allproceduresper‐
formedwereinaccordancewiththeethicalstandardsoftheinstitutionalandnational
researchcommittee(Referencenumber0554‐18‐HMO).Informedconsentwasobtained
fromallparents/legalguardiansofparticipatingsubjectstoallowtheirinformationtobe
usedinthestudy.
2.1.TreatmentProcedure
Patientbehaviourmanagementutilizedoralsedationwithhydroxyzineandnitrous
oxideinhalationtotreat16patients(78crowns)andgeneralanaesthesiawasselectedfor
21patients(53crowns).Localanaesthesiawasadministeredforallpatients(lidocaine2%
with1:100,000epinephrine,DentsplySirona,Canada)followedbyrubberdamplacement
andcrownpreparation.Teethwerepreparedfollowingmanufacturerrecommendations,
usingastandardprotocolincorporatingaretentivedesignthatincludedparallelism,re‐
tentiveareasleftbycariesremovalandtheuseofhorizontalstriationsonsmoothsurfaces
toenhanceretention.Ifcarieshadreachedthepulp,aformocresolpulpotomywasper‐
formed[17],followedbyzincoxideeugenolfillingoverthepulpstumps.
Morethanonekindofzirconiacrownwasutilized.Crownbrandselectionwasdic‐
tatedbythefacilitylocationwherethecrownswereplacedandincludedEZCrowns
(SprigOralHealthTechnologies;LoomisCA,USA),NuSmile(NuSmile;HoustonTX,
USA)andChengcrowns(ChengCrowns;ExtonPA,USA).Whenmultiplecrownswere
placed,thesamebrandwasusedforallrestorations.WithNuSmilecrowns,pinktry‐in

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crownswereusedtoconfirmfitandwhiteuncontaminatedcrownswereusedforcemen‐
tation.Withothermanufacturers,theactualcrownwasusedforatrialfitandoncese‐
lected,cleanedwithIvoclean(IvoclarVivadent;Mississauga,ON,Canada)priortoce‐
mentationtoremovesalivaryandhemorrhagiccontaminantsandmaintainbondstrength
tozirconia[18].Aftertoothpreparationandsizeselection,gingivalbleedingwascon‐
trolledbydelayingcementationuntilanothertreatmentwascompletedaswellasapply‐
ingpressure.Theteethwerethenrinsedanddried,followedbycrowncementationac‐
cordingtomanufacturerguidelines.FujiPluscement(GCAmerica;Alsip,IL,USA)was
placedin124crownswhileLinkAce(GCAmerica;Alsip,IL,USA)wasplacedin5teeth
andBioCem(NuSmile;Houston,TX,USA)wasplacedin2crowns.Teethwerephoto‐
graphedpreoperativelyandcrownswerephotographedimmediatelypostoperativelyus‐
inganOlympusTG4cameraonmacrosettingandnoflash(OlympusAmerica;Bethle‐
ham,PA,USA).Whenthechildwasdueforarecallexamination,postoperativeradio‐
graphswereobtainedandaclinicalexaminationthatincludedphotographingthere‐
storedmaxillaryanteriorteethwascompleted.
Toassessparentalsatisfaction,asurveyoftheparentsofparticipatingsubjectswas
conductedatthesamerecallexaminationthephotographswereobtained.Parentswere
givenaquestionnairetocompleteatchair‐sidewiththepatientpresent,andaskedtoscore
parameterssuchascrowncolor,size,durabilityandtheiroverallsatisfactionwiththe
crowns(Table1),usingaratingsimilartotheclinicalphotographicassessmentdoneby
thedentists[19].Parentshadtheabilitytolookclearlyattheirchild’srestoreddentition
atthistime.Theywerealsoaskediftheywouldchoosethisprocedureagainfortheirchild
orrecommendittoafriend.Thedentistwhoprovidedtreatment(LY)wasalsopresent
chairsidetoclarifyanyissuesraisedduringthecompletionofthequestionnaire.
Thephotographratingsystemusedbythetwoindependentdentalevaluatorshas
previouslybeenpublishedintwoevaluationstudiesofRCSC[20,21]andonestudyofZC
[19].Eachdentistreceivedthedigitalclinicalphotographsandratedtheclinicalresult
independently.Theresultsofeachdentistevaluationwerereviewedandwheretherewas
anydisagreement,theconsensuswasreachedthroughdiscussion.
Thephotographicassessmentcategories(Table1)inthisstudywereasfollows:col‐
ourmatchwasrated1for“nonoticeabledifferencefromadjacentteeth”,2fora“slight
shademismatch”and3foran“obviousshademismatch”.Crowncontourwasrated1
appearing“verycosmetic,nicelycontouredandnatural‐looking”,2for“acceptableap‐
pearancebutcouldhavebeencontouredbetter,perhapslonger,shorter,wider,thinner”,
3for“notaesthetic,detractingfromtheappearanceofthemouth”,4for“notpresent”.
Crowndurabilitywasrated1ifthe“crownappearsnormal;nocracks,chipsorfractures”,
2for“smallbutnoticeableareasoflossofmaterial”,3for“largelossofcrownmaterial”
and4for“completelossofcrown”.Theparentalassessmentwasmodifiedslightlyfor
simplicity.Colour‐matchratingwasidenticalfortheparentsurvey.Crowncontourwas
simplifiedtorating1for“nicelycontouredandnatural‐looking”,2was“acceptablebut
couldhavebettershape”and3as“unacceptable”.Examplesofclinicalcasesareseenin
Figures1and2.Crowndurabilitywassimplifiedtorating1for“crownappearsintact
withnochips,cracksorfracture”,2for“small,noticeablechips,cracksorfracture”,3for
“largechips,cracksorfracture”and4if“crownismissing”.Whenacrownandtooth
weremissing,theresponsewas1for“toothlostnaturally”,2for“trauma”andthreewas
“extractionduetoinfection”.Overallsatisfactionwasevaluatedasfollowswithayesor
noresponsetothequestions;“Overall,wereyousatisfiedwiththeresultsofthecrowns?”.
“Wouldyouchoosethisprocedureifonceagainoffered?”.“Wouldyourecommendthis
proceduretoafriendwithachildhavingasimilarproblem?”.Theresultsoftheparent
questionnaireandthatoftheindependentdentalevaluators(AKandWW)werethen
compared.
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Children2021,8,4514of10
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Table1.Assessmentcriteriaforparentsanddentalevaluators.
AssessmentCriteriaParentDentalEvaluators
ColourMatch
1ThereisnodifferencefromotherteethNonoticeabledifferencefromadjacent
teeth
2ThereisaslightmismatchfromadjacentteethSlightshademismatch
3ThereisanobviousmismatchfromadjacentteethObviousshademismatch
CrownContour
1Crownnicelycontouredandnatural‐lookingCrownappearsverycosmetic,nicely
contouredandnatural‐looking
2Crownacceptablebutcouldhavebettershape
Crownappearsacceptablebutcould
havebeencontouredbetter,perhaps
longer,shorter,wider,thinner
3CrownunacceptableCrownnotaesthetic,detractsfromthe
appearanceofthemouth
CrownDurability
1Crownappearsintactwithnochips,cracksorfractureCrownappearsnormal;nocracks,
chipsorfracture
2Crownhassmall,noticeablechips,cracksorfractureSmallbutnoticeableareasoflosso
f

material
3Crownhaslargechips,cracks,fractureLargelossofcrownmaterial
4
Crownismissing
1lostnaturally
2trauma
3extractionduetoinfection

5Crownhasbeenrepairedorreplaced
OverallParent
Satisfaction
YesorNoOverall,wereyousatisfiedwiththeresultsofthecrowns
YesorNoWouldyouchoosethisprocedureifonceagainoffered
YesorNoWouldyourecommendthisproceduretoafriendwitha
childhavingasimilarproblem


Children2021,8,4515of10
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Figure1.Restorationoffouranteriorteethwithpulptherapyononetooth.Parentratedteeth52,51,61,62as“slight
mismatchfromadjacentteeth”.Crowncontourwas“nicelycontouredandnaturallooking”.Dentistsratedteeth52,51as
“slightshademismatch”and61,62as“nonoticeabledifferencefromadjacentteeth”.Tooth51hadapulpotomy.Dentists
rated52crowncontouras“acceptablebutcouldhavebeencontouredbetter,perhapslonger,shorter,wider,thinner.Teeth
51,61,62“appearverycosmetic,nicelycontouredandnaturallooking.

Figure2.Restorationoftwoanteriorteeth.Parentsratedtooth51and61colourmatchas“nonoticeabledifferencefrom
otherteeth”.Crowncontourwas“nicelycontouredandnaturallooking”.Dentistsratedcolourmatchas“slightshade
match”andcrowncontouras“notaesthetic,detractsfromtheappearanceofmouth”.


Children2021,8,4516of10
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2.2.StatisticalAnalysis
Forthedentistevaluatorsandparentalassessmentgroups,analysiswasperformed
comparingthetwogroups,followedbycomparisonwithineachgroupbystratifyinginto
twointervals:22patientsfollowedforashorttermintervaloflessthantwelvemonths(6
–10.4months,mean8.1months)and15patientsfollowedforalongtermintervalofat
least12months(12.5–33.8months,mean21.0months).Chi‐squarestatisticalanalysiswas
usedtocomparethedentistevaluatorsandparentassessmentsofcolourmatchandcrown
contour.Thiswasalsodonewithineachgrouptodeterminetheeffectoftimefromtreat‐
mentontheassessmentvaluesofcrowncolourmatchandcontour.
3.Results
Onehundredandthird‐onecrownswithafollow‐uprangingfrom6to33.8months
(meanof13.5months)wereevaluated(Table2).Twenty‐eightchildrenhadallfourinci‐
sorsrestored,onechildhadthreeteethrestoredasonewasextractedandeightchildren
hadonlytwocentralincisorsrestored.Fifteenteethofeightchildrenhadpulptherapy
performed.TheresultsincludetheevaluationofaestheticsanddurabilityofZCat6–33.8
monthsfollow‐upvisitsfromphotographicassessmentaswellasfromtheparentques‐
tionnaire,completedbyall37parents.Colourmatch(Table3)wasratedby84%ofparents
as“nodifferencefromthenaturalteeth”and26%as“aslightmismatch”whilethedental
evaluatorsdeemed36%as“nonoticeabledifferencefromnaturalteeth”,60%as“aslight
mismatch”and4%as“anobviousmismatch”.Theparentsmorefrequentlyrankedthe
crownsas“nodifferencefromthenaturalteeth”andthisdifferencewasstatisticallysig‐
nificant(Chi‐squarep<0.05).Crowncontour(Table4)wasrated97%“nicelycontoured
andnatural‐looking”byparentsand3%as“acceptable”whilethedentalevaluatorsrated
55%“verycosmetic,nicelycontouredandnatural‐looking”,36%as“acceptablebutcould
havebeencontouredbetter”and9%as“notaesthetic”.Theparentsmorefrequently
rankedthecrownsas“nicelycontouredandnatural‐looking”andthisdifferencewassta‐
tisticallysignificant(Chi‐square,p<0.05).Secondaryresultsfromtheparentalassessment
anddentistevaluatedphotographs(Table5)showedassessmentvaluesofthecrowncol‐
ourmatchwerenotassociatedwithlengthoffollow‐uptime(Chi‐square,p<0.05).In
otherwords,thecolourmatchappearedstableregardlessofthelengthoftimebefore
evaluation.Regardingcrowndurability,neitherparentsnordentalevaluatorsobserved
anycracks,chips,fracturesorlossofmaterial.Onlyonecrowndebondedduringthestudy
andthiswasattwomonthsafterplacement,duetoacement‐to‐toothfailure.Anidentical
crownwasrecementedwithnofurtherissues.Thistoothwasincludedintheresults.
Withinthegroupof8patientswith15of28teethhavingpulpotomy,parentsrated
non‐pulpotomizedtoothcolourat35.7%having“nodifferencefromnaturalteeth”and
10.7%having“aslightmismatch”whilepulpotomizedtoothcolourwasrated35.7%hav‐
ing“nodifferencefromnaturalteeth”and17.9%having“aslightmismatch”(Table6).
Dentalevaluatorsratednonpulpotomizedtoothcolourat17.9%having“nodifference
fromnaturalteeth”and28.6%having“aslightmismatch”.Pulpotomizedtoothcolour
wasratedas7.1%“nodifferencefromnaturalteeth”and46.4%ashaving“aslightor
obviousmismatch”(Table6).The“obviousmismatch”wasonlyinonesubjectwhohad
twocentralincisorstreated.Eventhoughtherewasatrendofpulpotomizedteethhaving
slightlymorecolourmismatch,therewasnostatisticallysignificantdifferenceincolour
matchbetweenpulpotomizedandnon‐pulpotomizedteethnotedbyeitherparentsor
dentalevaluators(Chi‐square,p<0.05).
Allbutoneparentcompletedtheoverallsatisfactionpartofthequestionnaire.All
respondentsweresatisfiedwiththeresultofthecrowns.Theywouldchoosethisproce‐
dureifonceagainofferedandwouldrecommendthisproceduretoafriendwithachild
havingasimilarproblem.
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Children2021,8,4517of10
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Table2.Demographicdataofstudysubjects.
Patients37(male=27,female=10)
Teeth131
ChengCrowns22(7cases)
NuSmileCrowns91(25cases)
SprigCrowns18(5cases)
Pulpotomy15
Ageattreatment41.5months
Recalldurationmeantime13.3months
Shorttermrecallgroupduration6–10.4months(mean8.1,n=22)
Longtermrecallgroupduration12.5–33.8months(mean21.0,n=15)
Crownretentionrate99.7%(1crownrebondedat2months)
Sedation16patients,53crowns
Generalanaesthesia21patients,78crowns
Table3.Colourmatchrankbyparentsanddentalevaluators.
ColourMatchRank1Rank2or3*
Parent84%(n=95)26%(n=36)
DentalEvaluators36%(n=47)64%(n=84)
*Only5teethwereranked3andonlybydentalevaluators.Nosignificantdifferenceincolour
matchbetweenparentanddentist(Chi‐squarep<0.05).
Table4.Crowncontourrankbyparentsanddentalevaluators.
CrownContourRank1Rank2or3*
Parent97%(n=142)3%(n=4)
DentalEvaluators55%(n=73)45%(n=58)
*Only12teethwereranked3andonlybydentalevaluators;Nosignificantdifferenceincrown
contourrankingbetweenparentanddentist(Chi‐square,p<0.05).
Table5.Colourmatchrankingbyparentordentalevaluatorforshort‐termandlong‐termfollow‐up.
ColourMatchParentvs.DentistShortTermRecallGroupRe‐
call
LongTermRecallGroup
Recall
n=131crownsMeanrecall8.1month Meanrecall21.0months
Parent
Rank16134
Rank22016
DentalEvaluators 
Rank12918
Rank2or35232
Nosignificantdifferenceinrankduetomeanlengthoffollow‐upineithergroup(Chi‐square,p<0.05).
Table6.Colourmatchrankingbyparentordentalevaluatorforpulpotomizedteeth.
ColourMatchPulpotomizedTeethPulpotomy(n=15)NoPulpotomy(n=13)
Parent
Rank135.7%(n=10)35.7%(n=10)
Rank217.9%(n=5)10.7%(n=3)
DentalEvaluator
Rank17.1%(n=2)17.9%(n=5)
Rank2or346.4%(n=13)28.6%(n=8)
*Onlytwoteethwereranked3inonlyonesubjectbydentalevaluators;Nostatisticallysignificant
differenceincolourmatchrankingduetopulptherapyineithergroup(Chi‐square,p<0.05).


Children2021,8,4518of10
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4.Discussion
Parentsweremorelikelytoratebothcolourmatchtoadjacentteethandcrowncon‐
toursignificantlybetterthanthedentalevaluators,whoevaluatedfromdigitalphoto‐
graphs.Positiveparentaljudgementoftheirchild’srestoredteethmaytakeintoaccount
theoriginalappearanceoftheseteethwhichareoftendisfiguredandblackenedandthus
theparentsfeelsatisfiedwiththeimprovementtheywitness.Thedentistexaminerjudges
theresultaccordingtoadetailedlistofexpectedoutcomesandisnotemotionallyin‐
volvedinacceptanceofanyoutcome.Thephotographicevaluationalsoallowedalonger
andmoredetailedevaluationoftheclinicalresult.Thismayhaveledtothedentalevalu‐
atorsbeingmorecriticalofcolourmatchthantheparents.Parentsmayhavebeenfavour‐
ablyinfluencedbythelowfailurerateofthecrowns,withonlyonecrownlost,witha
simpleresolutionbycementinganewcrown[16].Thecrownfailurewasduetocement‐
to‐toothfailurewhichcanbereducedbycontrollingtoothsurfacecontamination,careful
caseselectionandconservativetoothreduction[4,19].
Theeffectofashort(6to10.4month)orlong(12to31.6month)timeperiodbetween
treatmentandexaminationbyeitherparentsordentistforcolourmatchdidnotdetect
anysignificantdeteriorationincolourmatchwithtime.Thenumberofcrownsratedfor
colourmatchaseither“nodifferencefromnaturalteeth”or“slightorobviousmismatch”
wasnotsignificantlydifferentbetweenpatientsassessedfairlysoonafterplacementor
muchlongerafterplacement.Becausethelengthoftimethecrownswereinthemouth
didnotaffecttheperceptionofcolourmatchbyparentsordentalevaluators,thiswould
seemtoindicatethereisverygoodcolourstabilityofZC,whichhasbeenobservedelse‐
where[15].Itshouldbenotedthatthemean‐timebeforeexaminationbetweenthegroups
wasnotdeemedsignificantlydifferentasthenumberofsubjectsineachgroupwasquite
small.
Whentheeffectofpulpotomyontoothcolourmatchwasevaluated,therewasno
statisticaldifferencenotedbetweenpulpotomizedandnon‐pulpotomizedtreatedteeth
byeithertheparentsordentalevaluators.Onlyoneobviousshademismatchwasnoted
bythedentalevaluatorsforacasewhereonlytwocentralincisorsweretreatedwitha
pulpotomy.PulpotomyhasbeenshowntoaffectcrowncolourmatchinastudyofRCSC
[21].TwootherstudiesevaluatinganteriorZCdidnotincludeteeththathadreceived
pulpotomysotheydidnotreportontheissue[15,16].Itwouldbeprudenttoleavepulpal
medicamentsbelowthegingivalmarginandplacetoothcolouredglassionomerorsimilar
materialinthesupragingivaltoothrestorationtobestmatchtheexistingtoothtomini‐
mizeanypossibleeffectofpulpotomyonthefinalcrowncolourmatch.Anecdotally,ZC
havebeenplacedoverteethtreatedwithsilverdiaminefluoride(SDF),whichresultsin
blackareasofarresteddecaywithoutapparentshadeproblems,buttheeffectofSDFon
ZCshademightbeworthfurtherinvestigation.
Thisstudywaslimitedbyasmallsamplesizeof37patientsand131teethaswellas
anaveragefollow‐upperiodof13.5months.Thedifficultyofretrospectivestudiesina
populationoflower‐incomefamilieswithyoungchildrenincludesdifficultyingetting
timelyandconsistentfollow‐upforrecallexaminations,nointerestinfurtherdentalcare
orareturntothefamilydentistforroutinepreventivevisits.Furthermore,clinicalobser‐
vationofprimaryanteriorteethprovidesafairlyshortwindowbetweentreatmentand
exfoliation,limitingstudytime[1,21].Althoughwehadplannedtocompareresultsfrom
differentZCcrownbrands,thesamplesizewastoosmall.Wemightinferfromtheposi‐
tiveparentalevaluationofallZCbrandsinthestudyandtheirhighsuccessratethatthere
mightbenosignificantdifferenceamongbrandsbutalargerstudygroupinafuturestudy
wouldberequiredtoconfirmthat.Otherlimitationsofthestudywerethatthedentist
evaluatorsmadetheirratingbaseduponclinicalphotographs,whileparentslookeddi‐
rectlyattheirchildren.Whilemanyphotographicimagescanbeexcellent,differencesin
lightingandcontrastcanprovideanimagethatmaybemoreorlessaestheticthanthe
clinicalevaluation.Althoughvariablesinlightinganddigitalprocessingcanimpactthe

Children2021,8,4519of10
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shadeofthecrownsforevaluation,theimpactshouldbesimilaronthecrownsandadja‐
centunrestoredteethbutmightimpacttheexaminerevaluationsfromsubjecttosubject.
Thereshouldbenoimpactofthephotographicevaluationoncrowncontour.Asaflash
wasnotusedambientlightingconditionsmayhaveledtoinconsistentcolourinthecap‐
turedimages.Aphotographicsystemthatcontrolledallvariablesforaconsistentresult
willbesuggestedinthefuture.Additionally,thedentistevaluatorsexaminedphotosthat
wereclose‐upsoftherestoredteeth,whileparentswerelikelytoevaluatetheteethfrom
adistanceof12–18inches.Atthefollow‐upevaluationwhenthequestionnaireswere
giventotheparents,theoperatordentistwhohadplacedthecrownswasalsopresentto
answerquestionsregardingtheparentalevaluation.Itispossiblethathispresencemay
havecausedparentstobelessjudgmental,perhapsnotwantingtocriticizethedentist’s
workinfrontofhim.
Thisstudywasabletoevaluateteethatanaveragetimeof13.3months,slightly
longerthantwootherstudiesandwithasimilarnumberofteethevaluated,withparent
satisfactioninallstudiesconsistentlyhigh[15,16].Thenumberofteethandsubjectswas
muchgreaterbutthedurationofplacementlessthaninanotherstudy,butagainparent
satisfactionwasquitehighinbothstudies[9].Bothprospectiveandretrospectivestudies
hadsimilarresultsandallusedparentalquestionnairescompletedwiththepatientpre‐
sentandtheassistanceofadentistintheclinictoansweranyquestions,whichmayhave
affectedparentresponsesinallstudies.Thisstudyutilizedonlyonedentalprovider,
whichmayhaveaffectedresultscomparedtomultipleprovidersinotherstudies,alt‐
houghtheywerecalibrated.
5.Conclusions
Basedupontheresultsofthisstudythefollowingconclusionscanbemade.Overall
parentalsatisfactionwithzirconiacrownsfortherestorationofmaxillaryanteriorprimary
incisorswasexcellentandnostatisticaldifferencewasnotedamongcrownbrands.Par‐
entswouldchoosezirconiacrownsagainandalsorecommendthemtoafriend.Parents
werelesscriticalofcolourmatchandcrowncontourthandentistevaluatorsandindicated
ahighlevelofsatisfaction.
AuthorContributions:L.Y.,W.W.,A.K.andM.M.conceivedtheideas;L.Y.,W.W.andA.K.col‐
lectedthedata;L.Y.andN.T.analyzedthedata;andL.Y.andW.W.ledthewriting.Allauthors
havereadandagreedtothepublishedversionofthemanuscript.
Funding:Thisresearchreceivednoexternalfunding.
InstitutionalReviewBoardStatement:Thestudywasconductedaccordingtotheguidelinesofthe
DeclarationofHelsinki,andapprovedbytheInstitutionalandNationalResearchCommitteeof
HadassahMedicalOrganization(0554‐18‐HMO).Informedconsentwasobtainedfromallpar‐
ents/legalguardiansofparticipatingsubjectstoallowtheirinformationtobeusedinthisstudy.
InformedConsentStatement:Informedconsentwasobtainedfromallsubjectsinvolved
inthestudy.
DataAvailabilityStatement:Thedatasupportingthereportedresultsresideswiththecorrespond‐
ingauthor.
ConflictsofInterest:Theauthorsdeclarenoconflictofinterest.AuthorW.W.isChiefDentalOfficer
forNuSmileCrownsbutthisdidnotinappropriatelyinfluencethestudydesignortherepresenta‐
tionandinterpretationofreportedresearchresults.
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