Smear layer

this presenation includes definition, history, various components of smear layer, importance of smear layer, whether to remove it while doing root canal and restoration or not?

1. DR MEENAL ATHARKAR
MDS
DEPT OF ENDODONTICS AND
CONSERVATIVE DENTISTRY

2. 
INTRODUCTION

DEFINITIONS

HISTORY

COMPONENTS OF SMEAR LAYER

BONDING AND SMEAR LAYER

FUNCTIONAL IMPLICATIONS

FUNCTIONAL IMPLICATIONS

SMEAR LAYER REMOVAL V\S SMEAR LAYER RETENTION.

METHODS OF REMOVAL

CONCLUSION

REFERENCES

3. 
Unknownandunrecognizedforyears,thesmearlayerhas
becomeaforcetobereckonedwithduringthelastdecade.
Thefullsignificanceofthesmearlayerhasbeenslowtobe
perceived.Itsincreasingimportancehasparalleledtheinterestperceived.Itsincreasingimportancehasparalleledtheinterest
inadhesivebondingtotoothstructure.Itseffectasasocalled
“Cavityliner”isjustbeginningtobeappreciated.

4. 
AssuggestedbyDavidPashley,thesmearlayersasacavity
linermayunquestionablehavebothbeneficialanddetrimental
effects.Thusthereisaneedtoalterthetraditionalprocedures
ofrestorativetreatmenttotakeadvantageofthebeneficial
effectsandtoavoidthedetrimentaleffectseffectsandtoavoidthedetrimentaleffects

5. 
Accordingtoskinner’s:
Tenaciousdepositofmicroscopicdebristhatcoverstheenamel
anddentinsurfacesthathavepreparedforarestoration.

AccordingtoOperativeDentistryJournal(1984).

AccordingtoOperativeDentistryJournal(1984).
Thetermsmearlayerappliesto“anydebrisproducediatrogenically
bythecutting,notonlyofdentin,butalsoofenamel,cementumand
eventhedentinoftherootcanal”.

6. 
TheAmericanAssociationofEndodontists.
Definedsmearlayerasa“surfacefilmofdebris
retainedondentinorothertoothsurfaceslikeenamel,
cementumafterinstrumentationwitheitherrotaryinstruments
orendodonticfiles”.orendodonticfiles”.

AccordingtoCohen.
Definedsmearlayeras“anamorphous,relatively
smoothlayerofmicrocrystallinedebriswhosefeatureless
surfacecannotbeseenwiththenakedeye”

7. 
AccordingtoDCNA(1990)
Whentoothstructureiscut,insteadofbeinguniformly
sheared,themineralizedmatrixshatters.Considerable
quantitiesofcuttingdebris,madeupofverysmallparticlesof
mineralizedcollagenmatrix,areproduced.Existingatthemineralizedcollagenmatrix,areproduced.Existingatthe
strategicinterfaceofrestorativematerialsandthedentin
matrixmostofthedebrisisscatteredovertheenameland
dentinsurfacetoformwhatisknownassmearlayer.

9. 
Theearlieststudiesontheeffectsofvariousinstrumentson
dentaltissueswerethosereportedbyLammie,Draycottin
1952andStreet(1953).
Theseattemptswerelimitedprincipallytolightmicroscope.Theseattemptswerelimitedprincipallytolightmicroscope.
[Lightmicroscope,hasconsistentlyfailedtoidentifythe
smearlayer,principallyduetothefactthatthelight
microscopedependsuponhistologicsections].

10. 
Charbeneau,PeytonandAnthony[1957] were
amongthefirsttoquantifyandrankthe
differencesbetweenbursandabrasivesbyusinga
profilometertorecordthesurfacetopographyof
cutandabradeddentaltissues.cutandabradeddentaltissues.

In1961ScottandO’Neil usedtransmission
electronmicroscopytostudythenatureofthecut
toothsurface

11. 
ItwasnotuntiltheadventofScanningelectronmicroscopethat
thegrindingdebriswasfirstreferredtoasthesmearlayerby
Boyde,SwitsurandStewartin1963andfurtherdefinedbyEick
andothersin1970,whichreferredtoitasthesmearlayer.

In1970Eickandco.workersdiscussedtheroleoffrictionand

In1970Eickandco.workersdiscussedtheroleoffrictionand
abrasioninthedrillingofteeth.Theyaccountedfortheformationof
smearlayerespeciallyindentinbyabrittleandductiletransition
andalternatingruptureandtransferofapatiteandcollagenmatrix
intothesurface

12. 
In1982,Goldmanandothersstudiedsmearlayersafterthe
useofendodonticinstrumentation.

Cameron(1983)&Maderetal.(1984):discussedthesmear
materialintwoparts-first,superficialsmearlayerand
second,thematerialpackedintothedentinaltubules.second,thematerialpackedintothedentinaltubules.

Packingofsmeardebriswaspresentinthetubulestoadepth
of40µm.

13. Theexactproportionatecompositionofthesmearlayerhasnot
beendeterminedbutScanningelectronmicroscope
examinationshavedisclosedthatitscompositionisboth
organicandinorganic.organicandinorganic.
INORGANIC:-Madeupoftoothstructureandsomenon-
specificinorganiccontaminants.

14. ORGANIC:componentsconsistof

Heatedcoagulatedproteinsi.e.gelatinformedbythe
deteriorationofcollagenheatedbycuttingtemperatures.

Necroticorviablepulptissue.

Odontoblasticprocesses.

Saliva.

Bloodcells.

Microorganisms.

15. 
Smearlayerisproductofdentalinstrumentation,whichcovers
thenormalstructuralcomponentsofdentinby1-2msand
penetratesseveralmicrometers1-5msintothetubulestoform
smearplugs.Ithastwophasessmearplugs.Ithastwophases
◦Solidphase;madeupofcuttingdebris.Primarilydenatured
collagensmineral.
◦Liquidphase;Madeuptotortuousfluidfilledchannels
aroundthecuttingdebris.

16. 
Smearlayer,mayalsobeadeterrenttothebondingprocess,
sinceitmayserveasabarriertothepenetrationofresintothe
underlyingdentinsubstrate.

Bacteriaentrappedinthesmearlayercansurviveandmultiply
beneaththerestoration.Manyauthorsontheotherhand
believeittobeaprotectivebarrieragainstbacterialandtoxin
penetration.

17. Reasonshavebeencitedforretainingsmearlayeronthe
bondingsubstrate:

Retentionofsmearlayerlowerdentinpermeability

Preventsdecreaseinbondstrengthseenwithsomebonding
systemsasdeeperdentinisprepared.systemsasdeeperdentinisprepared.

Greatlylowerstheeffectofpulpalpressureonbondstrength.

18. Morerecentgenerationofdentinadhesivesinvolvesmodificationofthe
smearlayerasitisbelievedtogreatlyimprovethebondstrengthtodentin.
Theremovalofsmearlayeranddemineralizationofdentinmatrixmay
facilitatebondingthroughanumberofmechanismslike.

Theexposedcollagenprovidesreactivegroupsthatcanchemicallyinteract
withprimers.

Aminogroupsmayactasacatalysttopolymerizationreactions.

Exposedcollagenpromotesmicromechanicalbondingtoresinby
providingaframework.

19. 
Thefirstandsecondgenerationsofadhesivesachievedlow
bondstrengthpartlybecauseoffailureswithinthesmearlayer
orbetweenthesmearlayerandunderlyingdentin.

Thethirdgenerationofadhesiveprocedureforconditioning
dentininvolved
1.Modificationofsmearlayertoimprovesitsproperties
2.Removalofsmearlayerwithoutdisturbingtheplugsthat
occludedthedentinaltubules

20. 
Thefourthgenerationreliedontotalremovalofsmearlayer
andsmearplugs.Resintagswereproducedinthedentinal
tubules;thesetagscontributedtotheretentionofresinsi.e.
totaletchtechnique.

Thefifthgenerationbasedonconceptofhybridization.

Thefifthgenerationbasedonconceptofhybridization.
Hybridlayer:-Anintermediatelayerofresin,collagenand
dentinproducedbyacidetchingofdentinandresininfiltration
intotheconditioneddentin.

Inthisgenerationsmearlayerdissolvedratherthanremoval.

21. Thesixthgeneration,inthisgenerationsmearlayeris
modifiedtoimprovebondstrengthtodentin.
Smearlayerisretainedandservesasanaturalbarriertothe
pulp.Preventbacterialinvasionandlimittheoutwardflowof
fluidthatimpairbondingefficiency.fluidthatimpairbondingefficiency.
Penetrationofmonomerintothesmearlayerandsubsequent
polymerizationreinforcestheattachmentofsmearlayerto
dentinandformsamicromechanicalandperhapsachemical
bondtotheunderlyingdentinalsurface.

22. THESMEARPHENOMENON:

IndentalcontentEirichin1976statedthatsmearingoccurs
when“hydroxyapatitewithinthetissueiseitherpluckedoutor
brokenorsweptalongandresetsinthesmearedoutmatrix”.

Studieshaveshownthattemperaturewillriseupto600
o
Cin

Studieshaveshownthattemperaturewillriseupto600
o
Cin
dentinwhenitiscutwithoutacoolant.Thisvalueis
significantlylowerthanthemeltingpointofapatite(1500-
1800
o
C).

23. Thishasledmosttoconcludethatsmearingisaphysico-
chemicalphenomenonratherthanathermaltransformationof
apatiteinvolvingmechanicalshearingandthermaldehydration
oftheprotein.
PlasticflowofhydroxyapetiteisbelievedtooccuratlowerPlasticflowofhydroxyapetiteisbelievedtooccuratlower
temperaturethanitsmeltingpointandmayalsobea
contributingfactortosmearing.

25. 
Thesmearlayerconsistsoftwoseparatelayers,asuperficial
layerandalayerlooselyattachedtotheunderlyingdentin.
Dentindebrisenterstheorificesofthedentinaltubulesand
actsasplugstooccludetheendsofthetubules.actsasplugstooccludetheendsofthetubules.

Thesmearlayerisnotalwaysfirmlyattachedandneitherisit
continuousoverthesubstrate.

Smearlayersfoundondeepdentincontainmoreorganic
materialthanthosefoundonthesuperficialdentin.

26. 
Clinicallyproducedsmearlayershaveanaveragedepthof
from1-5mm(Goldmanet.al.1981,Maderet.al.1984).The
depthenteringthedentinaltubulemayvaryfromaveryfew
mmto40mm.mmto40mm.

27. 
Cengizet.al.(1990)proposedthatthepenetrationofsmear
layerintodentinaltubulescouldbecausedbycapillaryaction
asaresultofadhesiveforcesbetweenthedentinaltubulesand
thesmearmaterial.
Onecanconcludethatasmearlayerispresentonall

Onecanconcludethatasmearlayerispresentonall
restorativelyorendodonticallypreparedteethunlessthedentin
surfacewastreatedwithanacidorchelatingagent.

28. Severalfactorsmaycausethedepthofthesmearlayertovary
fromtoothtotooth:
a.Dryorwetcuttingofthedentin.
b.Thetypeofinstrumentusedand
c.Theamountandchemicalmakeoftheirrigationsolution.

29. 
Filingacanalwithoutirrigationorcuttingwithoutwaterspray
willproduceathickerlayerofdentindebrisandtheuseof
coarsediamondbursproducesasmearlayerthantheuseof
carbideburs.carbideburs.

Thedifferencesintopographicaldetailaftercuttingdentinand
enamelwithsteelandtungstenbursandabradingitwith
diamondareclearlyevident.

30. Fig
Scanning electron micrograph showing the galling pattern
on a dentin surface cut with a water –cooled, tungsten
carbide bur. X 150

31. 
Steelandtungstencarbidebursproduceanundulatingpattern,
thetroughofwhichrunsperpendicularwiththedirectionof
movementofthehandpiece.Finegroovescanbeseen
runningperpendiculartotheundulationsandparallelwiththe
directionofrotationofthebur.Suchaphenomenonisdirectionofrotationofthebur.Suchaphenomenonis
referredtoas“Galling”andthefrictionalhumprepresentsa
“reboundeffect”ofthebursagainstthetissue

32. 
Thegallingphenomenonappearsmoremaskedwithtungsten
carbidebursrunathighspeed.

Anexaminationofbothsteelandtungstencarbidebursshows
arapiddeteriorationofthecuttingedgesthroughwhatappears
tobeabrittle.tobeabrittle.

Brittlesignificantlydiminishesthecuttingefficiencyofthe
bur,probablyincreasesfrictionalheatandcausessmearing.

33. 
Steelandtungstencarbidebursathighermagnificationcanbe
seentohaveobliteratedthenormalstructuraldetailofthe
tissue.

Debris,irregularinshapeandnon-uniforminsizeandDebris,irregularinshapeandnon-uniforminsizeand
distribution,remainsonthesurfaceevenafterthoroughlavage
withwater.

Themechanismbywhichbursremovedentaltissueis
significantlydifferentfromtheabradingactionofadiamond.

34. 
Ontheotherhand,abrasiveparticles,passingacrossthe
tissue,ploughtroughsinwhichsubstrateisejectedaheadof
theabradingparticleandelevatedintoridgesparallelwiththe
directionoftravelofparticle.
Severalfactorsgovernthesizeofthegrooves,including

Severalfactorsgovernthesizeofthegrooves,including
particlesize,pressureandhardnessoftheabrasiverelatedto
thesubstrate.

35. Fig
SEM showing grooves traversing a dentin surface abraded with
diamond X 300.

37. 
Asignificantdifferenceexistsbetweendiamondbursused
withandwithoutcoolantorwaterspray.

Intheabsenceofcoolantsmeareddebrisdoesnotforma
continuouslayerbutexistsratheraslocalizedislandswith
discontinuitiesexposingtheunderlyingdentin.discontinuitiesexposingtheunderlyingdentin.

Coolantofthewaterspraydoesnotpreventsmearingbut
appeartosignificantlyreducetheamountanddistributionof
it.

38. 1]DENTALMATERIALS:

Dentalmaterialscientistshavebeenconcernedaboutthe
smearlayerinsofarasitmaskstheunderlyingdentinmatrix
andmayinterfacewiththebondingofadhesivedentalandmayinterfacewiththebondingofadhesivedental
cementssuchaspolycarboxylateandglassionomerwhich
mayreactchemicallywiththedentinmatrix.

39. 
Presumablyallowingcementstoreactchemicallywiththe
smearlayerratherthanwiththematrixofsoundtubulardentin
producesaweakerbondduetothefactthatthesmearlayer
canbetornawayfromtheunderlyingmatrix.canbetornawayfromtheunderlyingmatrix.

40. RESTORATIVEDENTISTRY:

Viewedinthistheoreticalperspectivesifonecouldproducea
trulyadhesivefillingmaterialthathadnoshrinkageupon
polymerizationandaco-efficientofthermalexpansionclose
tothatoftoothstructure,thenonewouldwanttoremovethetothatoftoothstructure,thenonewouldwanttoremovethe
smearlayerandomittheuseofanycavitylinerorvarnishthat
didnotreactchemicallywithbothdentinandtheresin.

42. 
Therearethreepossibleroutesformicroleakage.
◦Withinorviathesmearlayer.
◦Betweenthesmearlayerandthecavityvarnishorcement
◦Betweenthecavityvarnish/cementandtherestorative
material.material.
Atnumerouspointswithinsuchacomplexthree
dimensionalstructure,the3routesintersectpermitting
microbialproductsaccesstodentinaltubulesandunderlying
pulp.

43. 
Thequestionofmicroleakageofrestorativematerialsis
beyondthescope.Itisworthmentioninghowever,thatthere
areatleast2or3routesbywhichsubstancescanleakintothe
pulp.

First,eveniftherewerenogapbetweendentinandrestorative
materialbacterialproductscouldtheoreticallydiffusearoundmaterialbacterialproductscouldtheoreticallydiffusearound
thematerialviasmallchannelsandintersticeswithinthe
smearlayer.

Unfortunatelyonecannotperfectlyadaptamalgamorany
otherrestorativemattothewallsofapreparedcavity.Thus
therearevoidsandspacesbetweenamalgamanddentinthat
allowconsiderablemicroleakage.Mostcliniciansuseacavity
varnishorlinertosealdentin.

44. 
Etchingthedentinofroots,whetherdonetherapeuticallyorbythe
actionofmicro-organismofplaquecanremovethethinlayerof
coveringcementumorsmearlayerorboth.conditioningwithacids
willremovethesmearlayerplugsexposingpatentdentinaltubuleswillremovethesmearlayerplugsexposingpatentdentinaltubules
totheoralcavity.Thiscanleadtosensitivityofthedentin.

Ifdentinissensitive,thenaccordingtothehydrodynamictheoryof
dentinsensitivity,thedentinaltubulemustbepatentandmustallow
movementoffluidacrossdentin.

45. 
Iffluidcanmove,itseemsreasonabletoassumethatbacterial
productsfromplaquecoveringthosesurfacesofsensitive
dentinmayalsopermeatedentinintothepulp.

Thepresenceofsmearlayerwillpreventbacterialpenetration
ofthetubulesbutwillpermitbacterialproductstodiffuseofthetubulesbutwillpermitbacterialproductstodiffuse
slowlyintothepulp.

Thismayproduceamild,lowgradeinflammatoryresponse
thatthatlowersthepainthresholdintheaffectedteeth,making
themmoresensitivethantheywouldbeintheabsenceof
plaque

46. 
Severalstudiesindicatethatmostoftheresistancetotheflow
offluidacrossdentinisduetothepresenceofsmearlayer.
Etchingdentingreatlyincreasestheeasewhichfluidcanmove
acrossdentin.Thisisaccompaniedclinicallybyincreasedacrossdentin.Thisisaccompaniedclinicallybyincreased
sensitivityofdentintoosmotic,thermalandtactilestimuli.

47. 
Thepresenceofsmearlayerhasalargeinfluenceon
permeabilityofdentin.Substancesdiffuseacrossdentinata
ratethatisdirectlyproportionaltotheirconcentrationgradient
andthesurfaceareaavailablefordiffusion.andthesurfaceareaavailablefordiffusion.

Theremovalofsmearlayerincreasesthedentinpermeability
by5to6timesinvitrobydiffusionbutincreasesitby25to
36timesbyfiltration.

48. DIFFUSION:
Occursfromareasofhigherconcentrationtolower
concentration.Theconcentrationofsubstancesisdissipated
overadistance.
FILTRATION:

Transportofmaterialthroughdentinisduetopresenceofa

Transportofmaterialthroughdentinisduetopresenceofa
pressuregradient.Thereisnochangeintheconcentrationof
substancesdissolvedinthefluidasthefluidandallthatis
dissolvedinitmadetoflowfromonepointtoanother.The
drivingforceispressure.

Thusmovementoffluidacrossdentinbyfiltrationismuch
moresensitivetothedegreeofocclusionoftubules,i.e.the
presenceorabsenceofasmearlayer,thanisthemovementof
substancesbydiffusion.

49. 
Thephysiologicalconsequencesofthesmearlayerand
whetheritshouldbepresentorabsentunderrestorationsare
rathercomplicatedquestions.Toagreatextenttheyseemto
berelatedtothepresenceofbacteriaunderrestorations.berelatedtothepresenceofbacteriaunderrestorations.

Aninvitrostudyshowedthatwatercleanedcavitieswiththe
smearlayerremainingunderneaththecompositerestoration
showedthepresenceofnumerousbacteria,whereasinthe
antisepticallycleanedcavities,bacteriawereabsent.

50. 
Thefactthatbacteriamultiplyoncavitywallsevenifthereisno
appreciablecommunicationtotheoralcavityseemstoindicatethat
certainmicroorganismsgetsufficientnourishmentfromthesmear
layeranddentinalfluid.

Theseconsiderationsfavorstheopinionthatmostofthesmear

Theseconsiderationsfavorstheopinionthatmostofthesmear
layershouldberemovedandanysmearlayerremainingforinstance
atthetubuleshouldbeantisepticallytreatedbeforetheapplication
ofliningoralutingcement.Ithasalsobeensuggestedthatbacteria
arenotpresentinfreshlypreparedsmearlayers.

51. 
Thereisnoevidencethatcommonpermanentrestorativematerials
aresufficientlyantibacterialtokillbacteriaentrappedwithinthe
smearlayer,especiallywhenafluidfilledcontractiongap,5-20mm
wideseparatestherestorationfromthesmearlayer.BasesofZnO
andCa(OH)
2
mayhavegoodantisepticeffectsbutunfortunately
underpermanentrestorations,thesebasescannotbeplacedonall
cavitywalls.PureCa(OH)
2
isanexcellentantibacterialtemporary
dressingandshouldbeappliedundertemporaryfillings.Itisalso
possiblebutnotprovedthatCa(OH)
2
mayreinforcetheremaining
smearplugsintheouteraperturesofdentinaltubules.

52. Inastudy11yearsagotheyfoundthatetchingthecavityprior
totheplacementofthecompositeresinresultedinamassive
invasionofbacteriaindentinaltubules.Thiswasseeninall
teethafter3-4weeks.Thecorrespondingcavitiescleanedbyteethafter3-4weeks.Thecorrespondingcavitiescleanedby
waterandwithsmearlayerlefthadabacteriallayeronthe
cavitywallsbutpracticallynoinvasionintothedentinal
tubules.Obviouslysmearplugsintheaperturesofthetubules
hadpreventedbacterialinvasion.

53. 
Inflammationwaspresentunderallinfectedcavities,being
somewhatmorepronouncedontheetchedcavities,butthe
differencewasnotgreat.Thusanotherconclusionfromthis
studywasthatsmearplugsdidnotpreventbacterialtoxins
fromdiffusingintothepulp.Fromopenedtubules,bacteriafromdiffusingintothepulp.Fromopenedtubules,bacteria
mayeasilyreachthepulpandmultiplythereforeremovalof
smearplugsshouldbeavoided.

54. 
Anotherimportantconsequenceofetchingandremovalof
smearplugsandperitubulardentinatthesurfaceisthatthe
areaofwettubulesmayincreasefromabout10-25%ofthe
total.Subsequentlyitisdifficulttogetthedentindrybecause
fluidcontinuestobesuppliedfrombelowthroughthetubules.fluidcontinuestobesuppliedfrombelowthroughthetubules.
Thismoisturewouldnotseemtofavoradhesiveormechanical
bondingtodentin.

55. 
Inseveralexperimentswefoundthat37%phosphoricacidor50%
citricacidappliedfor15secondsor1minutedoesnotresultinany
appreciablepulpalreaction,inflammationornecrosis.

Acidetchants,detergents,athinmixofphosphatecements,GICand

Acidetchants,detergents,athinmixofphosphatecements,GICand
resindonotproduceanyappreciabledamageandinflammationto
thepulpnotevenwhenappliedtoexposedpulp.

However,forreasonsthecutdentinshouldnotbetreatedwithacid
orEDTAinsuchawaythatthetubulesbecomeopenandwidened.

56. I.ROLEOFSMEARLAYERINAPICALLEAKAGE:

Thesmearlayer’spresenceplaysasignificantpartinanapicalleakage,its
absencemakesthedentinmoreconducivetoabetterandcloseradaptation
oftheGutta-perchatothecanalwallwiththesmearlayerintact,apical
leakagewillbesignificantlyincreasedwithoutthesmearlayer,theleakageleakagewillbesignificantlyincreasedwithoutthesmearlayer,theleakage
willstilloccurbutatadecreasedrate.

PlasticizedGutta-perchacanenterthedentinaltubuleswhenthesmear
layerisabsent.ThiscanestablishamechanicalblockbetweentheGutta-
perchaandthecanalwall.

57. II.EFFECTOFSMEARLAYERONSEALERS:

Becauseofthebacterialcontentofthesmearlayeranyapical
extrusionofthesmearlayerduringinstrumentationorobturation
candefectoneofthegoalsofendodontictherapy.

Endodonticsealeractasagluetoensureagoodadaptationof
Gutta-perchatothecanalwalls.Ifthesmearlayerisnotremoved,
theGutta-perchamayoccasionallybegluedtothedentininthe
smearlayeraswellastoexposedpartsofthecanalwall.Notbeing
firmlyattachedtothedentin,thesmearlayermaylaminateoffthe
canalwallandcreateafalseseal,voidsinthefill,andmicroleakage.

58. 
Thetypeofsealerusedhasdifferentimplicationsoncethe
smearlayerisremoved.Apowderliquidcombination,the
mostofwhichisGrossman’ssealercontainssmallparticlesin
thepowderthatcouldentertheorificesofthedentinaltubules
andhelpcreateareactioninterfacebetweensealerandcanalandhelpcreateareactioninterfacebetweensealerandcanal
wall.

Ca(OH)
2
basedsealershavetheadvantageofpromotingthe
appositionofcementsatthecanalapexandsealingitoff
againstmicroleakage.

59. III.POSTCEMENTATION:

Recentresearchhasembracedthemodalitiesofcomposite
resins,GIC,andDBAtryingtosorttheseout,hopingtofinda
techniquetoimprovethetensilestrengthofcementedposts

Removalofsmearlayerincreasesthecementationbondand
thetensilestrengthofthecementingmedium.GICarethetensilestrengthofthecementingmedium.GICare
effectiveinpostcementationaftersmearlayerremoval
becausetheGIChasabetterunionwithtoothstructure.SEM
studieshaveshownthatwiththeunfilledresins,serratedposts
arerecommendedoversmoothposts,andparallelpostsshow
moreretentiveabilitythantaperedposts

60. 
WhenanunfilledBISGMAresinwasusedafterNaoclrinse,
thestrengthoftheresinbondwasbetterthanthatof
polycarboxylatecement.

WhenthesmearlayerwasremovedbyflushingwithEDTA
andNaoclrinse,theBISGMAresinflowedintotheexposedandNaoclrinse,theBISGMAresinflowedintotheexposed
dentinaltubulesandintotheserrationsonthepostimproving
retention.

Withtheremovalofsmearlayerandanunfilledresinbonding
agentshorterpostscanbeused.

61. 
Smearlayerremovalorretentionisacontroversythatfluctuates
withthevariousmodalitiesofrestorativedentistryand
endodontics.

Oneopinionistoleavethesmearlayerintactonthetooth

Oneopinionistoleavethesmearlayerintactonthetooth
surfacebecauseitisthoughttoactasaphysicalbarrierin
preventingtheingressofbacteriaandtheirproductsintothe
underlyingdentin.

Pashley(1991)havereportedadecreaseof86%inthe
permeabilityofdentin,whenthesmearlayerispresent.

62. 
Clinicianssupplementingthisviewshouldkeepinmindthat
thesmearlayerisacidiclabileatapHof6.0-6.8andless.Itis
inadvertantly-destroyedwhenthePHdrops.Example:-
Aroundplaqueaccumulatedareas,orbyproteolyticenzymes
excretedbycertainmicro-organismsorbyacidetching.Smear
layeronanexposedrootsurfacedissolvesmorereadily
comparedtoonepresentontheocclusalsurface.

63. 
Theotherschoolofthoughtistoremovethesmearlayer
becauseofthebeliefthatthesmearlayeritselfmaycontain
manybacteria.Ithasbeendemonstratedthatthesmearlayer
maybecapableofpreventingdiffusionofbacteriaassuch,but
notthebacterialproducts.notthebacterialproducts.

Studiesbysomeauthorsalsoshownadecreaseinmicro
leakagewhenthesmearlayerisabsentprobablybecauseof
smearlayerpermitsagoodadaptationoftherestorative
materialtothecavitywalls.

64. 
Bondingorobturation,tothesmearlayermustbeconsidereda
weakunionbecausethesmearlayercanbetornawayfromthe
underlyingmatrix.Inendodontics,oncethelayerisremoved,a
betteradaptationofobturatingmaterialsandsealersbecomebetteradaptationofobturatingmaterialsandsealersbecome
possible.

Dentinpermeationbydiffusionis5to6timesandbyconvection
25to36times.Thisattributeallowsanimprovedpenetrationof
disinfectants,medicamentsandobturatingmaterials.

65. 
Thesmearlayer’spresenceplaysasignificantpartinan
increaseordecreaseinapicalleakage.

Itsabsencemakesthedentinmoreconductiontoabetterand
closeradaptationoftheGutta-perchatothecanalwall80%of
obturatedteethwillleakafter96hoursregardlessoftheobturatedteethwillleakafter96hoursregardlessofthe
presenceorremovalofsmearlayerwiththesmearlayerintact,
apicalleakagewillbesignificantlyincreasedwithoutsmear
layer,theleakagewillstilloccurbutatadecreasedrate.

66. Thequantityofsmearlayerremovedbyamaterialisrelatedto
itspHandthetimeofexposure(Morgan&Baumgartner
1997).

67. SODIUMHYPOCHLORITE

Naocl,anormalorganicsolvent,theacceptedirrigantin
endodontics,ispowerlesstoremovethesmearlayerbyitself;endodontics,ispowerlesstoremovethesmearlayerbyitself;
itmustbeusedwithanotheragenttobeeffective,

Naocl–Can’tdestroybacteriawithinthetubulesclosedby
asmearlayercovering.

68. 
DestructionofbacteriabyNaocltakesplaceintwophases.
1)Penetrationintobacterialcell.
2)Chemicalcombinationwithprotoplasmofthebacterialcell
thatdestroysit.Naocl+H
2
O
2
flushesarealsoineffective.

Extendedexposureofthesmearlayertohydrogenperoxide
willcauseadenseamorphousprecipitatetoformonthesmear
layer.

69. CHELATINGAGENTS

Theuseofchelatingagentsoftensthesmearlayer,allowingits
successfulremoval.

Althoughtheyarenotbactericidal,butconsidered
antibacterialtotheextentthattheeliminatethebacteriaantibacterialtotheextentthattheeliminatethebacteria
contaminatedsmearlayer.

TheEDTA{Ethylenediaminetetraaceticacid}17%for10
minuteswhichreactswithcalciumindentinandformssoluble
calciumchelate.

70. 
Nygard-ostby(1963)-
found that
EDTA decalcified dentin to a depth of 20 –30mm in
5 min.

Fraser (1974)-stated that chelating agents are
negligible in the apical third of the root canal.

Goldman [1982]–Recommended alternate use of
Naocl& EDTA

71. 
Naocl EDTA to remove Smear layer
Removes RemovesRemoves Removes
Organic material mineralized dentin there by
including collagenousexposing Collagen
matrix of dentin

Hence better adaptation of obturation material to dentin.

72. DifferentpreparationsofEDTAhavebeenused
asarootcanalirrigant.

RCprep(PremierDentalProducts,PlymouthMeeting,PA,

RCprep(PremierDentalProducts,PlymouthMeeting,PA,
USA)i.e.amixtureof15%EDTAand10%ureaperoxide
leaveasmearlayerratherthanremoveitaftercanal
instrumentation.

ThismayhavedisadvantagesinthehermeticsealingofRoot
Canals.

73. 
Thisproductalsoincludesawaxthatleftaresidueontheroot
canalwallsdespitefurtherinstrumentationandirrigationand
whichmaycompromisetheabilitytoobtainahermeticseal
(Biesterfeld&Taintor1980(Biesterfeld&Taintor1980

Accordingtofewstudiespaste-typechelatingagents,though
havealubricatingeffect,donotremovethesmearlayer
effectivelywhencomparedtoliquidEDTA.

75. REDTA,RothInternational,USA
•Aquaternaryammoniumbromide(cetrimide)hasbeenadded
to17%EDTAsolutionstoreducesurfacetensionandincrease
penetrabilityofthesolution(vonderFehr&Nygaard-Ostby
1963).
•McComb&Smith(1975)reportedthatwhenthiscombination
(REDTA)wasusedduringinstrumentation,therewasnosmear
layerremainingexceptintheapicalpartofthecanal.

76. 
AfterusingREDTAinvivo,itwasshownthattherootcanal
surfaceswereuniformlyoccupiedbypatentdentinaltubules
withverylittlesuperficialdebris(McCombetal.1976)

77. EDTAC(EDTA+Cetavlon):
Optimalworkingtime15minintherootcanalandnofurther
chelatingactioncouldbeexpectedafterthis(Goldberg&Spielberg
1982).
•Circumpulpalsurfacehadasmoothstructureandthatthedentinal
tubuleshadaregularcircularappearance(Oldberg&Abramovich)

78. Bis-dequalinium-acetate(BDA)
•Dequaliniumcompoundandanoxinederivativehasbeenshown
toremovethesmearlayerthroughoutthecanal,evenintheapical
third(Kaufmanetal.1978,Kaufman1981).third(Kaufmanetal.1978,Kaufman1981).
•BDAiswelltoleratedbyperiodontaltissuesandhasalowsurface
tensionallowinggoodpenetration.
•ItisconsideredlesstoxicthanNaOClandcanbeusedasaroot
canaldressing.

79. EGTA:
Calt&Serper(2000)comparedtheeffectsofethyleneglycol-bis(ß-
aminoethylether)-N,N,N¢,N¢-tetraaceticacid(EGTA)with
EDTA.
ThesmearlayerwascompletelyremovedbyEDTA,butitcausedThesmearlayerwascompletelyremovedbyEDTA,butitcaused
erosionoftheperitubularandintertubulardentine,whilstEGTAwas
notaseffectiveintheapicalthirdofrootcanals.
EGTAisreportedtobindcalciummorespecifically(Schmid
&Reilley1957).

81. Solvidont(DeTrey,A.G.,Zurich,Switzerland:1980
•CommercialformofBDA
•ItsuseasanalternativetoNaOClwassupportedexperimentally
(Kaufman1983a,b,Chandler&Lilley1987,Lilleyetal.1988,
MohdSulong1989).
.

82. Salvizol(RavensGmbh,Konstanz,Germany)
•Isacommercialbrandof0.5%BDApossessesthe
combinedactionsofchelationandorganicdebridement.
•Kaufmanetal.(1978)reportedthatSalvizolhadbettercleaning
propertiesthanEDTAC.

83. •
.WhencomparingSalvizolwith5.25%NaOCl,bothwere
foundcomparableintheirabilitytoremoveorganicdebris,but
onlySalvizolopeneddentinaltubules(Kaufman&Greenberg
1986).1986).
•
Bergetal.(1986)foundthatSalvizolwaslesseffectiveat
openingdentinaltubulesthanREDTA

84. Glyoxide:

Glyoxideisanirrigatingsolutioni.e.comprisedof10%urea
peroxide{Carbamideperoxide]inavehicleofanhydrous
glycerol.glycerol.

In1961Stewartproposedglyoxidetobeaneffectiveadjunct
toinstrumentationforcleaningoftheRootcanal.

Ithas–solventactionthan3%H
2
O
2
itenhancesrootcanal
lubricatingwithoutsofteningdentin.

85. Tetracyclines:
Tetracylines(includingtetracyclinehydrochloride,minocyclineand
doxycycline)areantibioticseffectiveagainstawiderangeof
microorganisms.
Tetracyclineshaveuniquepropertiesinadditiontotheir
antimicrobialaspect.

86. 
TheyhavelowpHinconcentratedsolution,andbecauseof
thiscanactasacalciumchelatorandcauseenamelandroot
surfacedemineralization(Bjorvatn1982).

Thesurfacedemineralizationofdentineiscomparablewith
thatofcitricacid(Wikesjo¨etal.1986).

87. Barkhordaretal.(1997)reportedthatdoxycyclinehydrochloride
(100mgmL-1)waseffectiveinremovingthesmearlayerfromthe
surfaceofinstrumentedcanalsandroot-endcavitypreparations.
TheyspeculatedthatareservoirofactiveantibacterialagentsTheyspeculatedthatareservoirofactiveantibacterialagents
mightremain,becausedoxycyclinereadilyattachestodentineand
canbesubsequentlyreleased(Bakeretal.1983,Wikesjo¨etal.
1986)..

88. MTAD:
Inanefforttoproduceanirrigantcapableofbothremovingthe
smearlayeranddisinfectingtherootcanalsystem.smearlayeranddisinfectingtherootcanalsystem.
Torabinejadetal.(2003)developedanewirrigatingsolution
containingamixtureofatetracyclineisomer,anacid,anda
detergent(MTAD).
TheirworkconcludedMTADtobeaneffectivesolutionforthe
removalofthesmearlayer

89. Itdoesnotsignificantlychangethestructureofthedentinal
tubuleswhenthecanalsareirrigatedwithsodiumhypochlorite
andfollowedwithafinalrinseofMTAD.
Thisirrigantdemineralizesdentinefasterthan17%EDTA(De-Thisirrigantdemineralizesdentinefasterthan17%EDTA(De-
Deusetal.2007)andbacterialpenetrationintofilledcanalsis
similarwithbothsolutions(Ghoddusietal.2007).

90. Organicacids
Citricacid:
Theeffectivenessofcitricacidasarootcanalirriganthasbeen
demonstrated(Loel1975,Tidmarsh1978)andconfirmedtobe
moreeffectivethanNaOClaloneinremovingthesmearlayermoreeffectivethanNaOClaloneinremovingthesmearlayer
(Baumgartneretal.1984).
Citricacidremovedsmearlayerbetterthanpolyacrylicacid,lactic
acidandphosphoricacidbutnotEDTA(Meryonetal.1987).

91. Waymanetal.(1979)showedthatcanalwallstreatedwith
10%,25%and50%citricacidsolutionweregenerallyfreeof
thesmearedappearance,buttheyhadthebestresultsin
removingsmearlayerwithsequentialuseof10%citricacid
solutionand2.5%NaOClsolution,thenagainfollowedbyasolutionand2.5%NaOClsolution,thenagainfollowedbya
10%solutionofcitricacid.

92. However,Yamadaetal.(1983)observedthatthe25%citric
acid–NaOClgroupwasnotaseffectiveasa17%EDTA–
NaOClcombination.Toitsdetriment,citricacidleft
precipitatedcrystalsintherootcanalwhichmightbe
disadvantageoustotherootcanalfilling

93. Lacticacid:
With50%lacticacid,thecanalwallsweregenerallyclean,but
withopeningsofdentinaltubulesthatdidnotappeartobe
completelypatent(Waymanetal.1979).completelypatent(Waymanetal.1979).

94. Tannicacid
•Bitter1989)introduced25%tannicacidsolutionasarootcanal
irrigantandcleanser.
•Canalwallsirrigatedwiththissolutionappearedsignificantly
cleanerandsmootherthanwallstreatedwithacombinationof
hydrogenperoxideandNaOCl,andthesmearlayerwasremoved..hydrogenperoxideandNaOCl,andthesmearlayerwasremoved..
•Sabbak&Hassanin(1998)refutedthesefindingsandexplainedthat
tannicacidincreasedthecross-linkingofexposedcollagenwiththe
smearlayerandwithinthematrixoftheunderlyingdentine,
thereforeincreasingorganiccohesiontothetubules.

95. 
McComb&Smith(1975)comparedtheefficacyof20%
polyacrylicacidwithREDTAandfoundthatitwasnobetter
thanREDTAinremovingorpreventingthebuildupofsmear
layer,thoughttobeasaresultofitshigherviscosity.layer,thoughttobeasaresultofitshigherviscosity.

McCombetal.(1976)alsoused5%and10%polyacrylicacid
asanirrigantandobservedthatitcouldremovesmearlayerin
accessibleregions.

96. Polyacrylicacid
(DurelonliquidandFujiIIliquid):
40%
hasbeenreportedtobeveryeffective,andbecauseof
itspotencyusersshouldnotexceeda30sapplication
(Berryetal.1987).

97. SodiumhypochloriteandEDTA

Whenirrigatingarootcanalthepurposeistwofold:toremovethe
organiccomponent,thedebrisoriginatingfrompulptissueand
microorganisms,andthemostlyinorganiccomponent,thesmear
layer.Asthereisnosinglesolutionwhichhastheabilitytodissolve
organictissuesandtodemineralizethesmearlayer,thesequential
useoforganicandinorganicsolventshasbeenrecommendeduseoforganicandinorganicsolventshasbeenrecommended
(Koskinenetal.1980,Yamadaetal.1983,Baumgartneretal.
1984).

98. 
Goldmanetal.(1982)examinedtheeffectofvarious
combinationsofEDTAandNaOCl,andthemosteffective
finalrinsewas10mLof17%EDTAfollowedby10mLof
5.25%NaOCl.
The finding was confirmed by Yamada et al. (1983).The finding was confirmed by Yamada et al. (1983).

But used in combination with EDTA, NaOClis inactivated
with the EDTA remaining functional for several minutes.

99. ULTRASONICS

Preparationofrootcanalwithultrasonicdeviceisproviding
goodcanalcleaningbecausemechanicalandchemicaleffects
inremovingsmearlayerarejoinedbythistechnique.inremovingsmearlayerarejoinedbythistechnique.

Ultrasonicvibrationsandmaximaleffectofirrigatingagent,
whichisdirectedtowardinstrument’stip,areproviding
significantremovalofthesmearlayer

100. 
Cameron92hasreportedcompleteremovalofthesmearlayer
afterapplicationof4%NaOClovertwominutes.

WalkerandDelRio24,93,intwoseparatestudies,have
confirmedtheefficacyofultrasoundinremovalofthesmearconfirmedtheefficacyofultrasoundinremovalofthesmear
layer,butalsohaveshowninsignificantdifferencesregarding
effectsofwaterandNaOClsolutionswhenareusedin
ultrasonictreatment

101. 
Guerisoliandco-workers94havesuccessfullyremovedsmear
layerbycombining15%EDTACanddistilledwateror1%
NaOClwithultrasonictechnique.
BaumgartnerandCuenin95haveshownintheirstudiesthat

BaumgartnerandCuenin95haveshownintheirstudiesthat
NaOClinultrasonictechniquewasnotcompletelyefficientin
removingsmearlayerfromrootcanalwalls.

102. LASERS

Duringthelastdecade,lasertechniquehaswonimportant
placeinendodontictherapy.Amongother,itcanbeusedfor
smearlayerremovalandeliminationoftissuefragmentsinthesmearlayerremovalandeliminationoftissuefragmentsinthe
apicalpartofrootcanal,

Themainprobleminremovalofthesmearlayerbylaserisa
complicatedapproachtonarrowspacewithconsiderablylarge
tipswhenlaserbeamisdirected.

103. 
Severalinvestigatorshavereportedthattheeffectivenessof
lasersdependsonmanyfactors,includingthepowerlevel,the
durationofexposure,theabsorptionoflightinthetissue,the
geometryoftherootcanal,andthetip-to-targetdistance.geometryoftherootcanal,andthetip-to-targetdistance.

104. 
Dederichetal116andTewfiketal119usedvariantsofthe
neodymium-yttrium-aluminum-garnetlaserandreporteda
rangeoffindingsfromnochangeordisruptionofthesmear
layertoactualmeltingandrecrystallizationofthedentin.layertoactualmeltingandrecrystallizationofthedentin.

Thispatternofdentindisruptionwasobservedinotherstudies
withvariouslasers,includingthecarbondioxidelaser,the
argonfluorideexcimerlaser,andtheargonlaser.

105. 
Takedaetal,usingtheerbium-yttrium-aluminum-garnet
(Er:YAG)laserdemonstratedoptimalremovalofthesmear
layerwithoutthemelting,charring,andrecrystallization
associatedwithotherlasertypes.associatedwithotherlasertypes.

106. 
Contemporarymethodsofrootcanalinstrumentationproduce
alayeroforganicandinorganicmaterialcalledthesmearlayer
thatmayalsocontainbacteriaandtheirby-products.
Thislayercoverstheinstrumentedwallsandmaypreventthe

Thislayercoverstheinstrumentedwallsandmaypreventthe
penetrationofintracanalmedicamentsintothedentinaltubules
andinterferewiththecloseadaptationofrootfillingmaterials
tocanalwalls

107. REFERENCES:
1)Pathwaysofthepulp–Cohen.8
th
Edition.
2)Philipsscienceofdentalmaterials-11thEdition
3)Sturdevant’sArtandscienceofoperative
dentistry-4
th
Edition.
4)Internet-wikepedia