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8/9/2019 Final Restoration

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IntroductionIntroduction

Endodontically treated teeth often requireEndodontically treated teeth often require

partial or complete coverage restorationspartial or complete coverage restorations

according to the amount of remaining toothaccording to the amount of remaining toothstructurestructure

Caries, access cavity, excessive removal ofCaries, access cavity, excessive removal of

radicularradicular dentine during endodontic treatmentdentine during endodontic treatment

increase the risk of fractureincrease the risk of fracture

Therefore, restoration of these teeth should beTherefore, restoration of these teeth should be

considered for function and aestheticconsidered for function and aesthetic


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The use of posts in endodontically treated teethThe use of posts in endodontically treated teeth

is still questionableis still questionable

But it is accepted that posts do not increase theBut it is accepted that posts do not increase thefracture resistance of endodontically treatedfracture resistance of endodontically treated

teeth and are used only to retain the core whenteeth and are used only to retain the core when

there is too less retention for the artificialthere is too less retention for the artificial

crowncrown


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The preparation of post hole in an intactThe preparation of post hole in an intact

endodontically treated tooth may weaken suchendodontically treated tooth may weaken such

a tootha tooth In the case of substantial horizontal loss of theIn the case of substantial horizontal loss of the

clinical crown, there is no restorativeclinical crown, there is no restorative

alternative other than fabricating a post andalternative other than fabricating a post and

corecore buildupbuildup


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Numerous post systems have been used,Numerous post systems have been used,

including custom cast posts and preincluding custom cast posts and pre--fabricatedfabricated

postsposts However the use of metal alloys posts andHowever the use of metal alloys posts and

cores under the allcores under the all--ceramic crowns exhibitsceramic crowns exhibits

aesthetic problem as, light transmission isaesthetic problem as, light transmission is

impeded by metallic posts limiting theimpeded by metallic posts limiting the

aesthetic appearance of allaesthetic appearance of all--ceramic crownsceramic crowns


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Tooth coloured preTooth coloured pre--fabricated post and corefabricated post and core

systems such as fibre reinforced compositesystems such as fibre reinforced composite

(FRC) and(FRC) and zirconiazirconia ceramic posts have beenceramic posts have beenused because the metalused because the metal--free, allfree, all--ceramicceramic

crowns have become more popular as a resultcrowns have become more popular as a result

of the increasing demand from patients andof the increasing demand from patients and

clinicians for the aesthetic replications of theclinicians for the aesthetic replications of thenatural dentitionnatural dentition


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Generally, preGenerally, pre--fabricated posts are round that may befabricated posts are round that may be

a problem for the oval canala problem for the oval canal

Conversely, preConversely, pre--fabricated posts are the best choicefabricated posts are the best choice

for small circular canalsfor small circular canals

Adaptation of the preAdaptation of the pre--fabricated post into the rootfabricated post into the root

canal is good because the drill that has the samecanal is good because the drill that has the same

diameter with the post is used for preparation of thediameter with the post is used for preparation of thepost spacepost space

Accurate fit of the posts into the root canals increaseAccurate fit of the posts into the root canals increase

the fracture resistance of endodontically treated teeththe fracture resistance of endodontically treated teeth


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The use of preThe use of pre--fabricated posts have becomefabricated posts have become

more popular because these systems requiremore popular because these systems require

fewer appointments and are less timefewer appointments and are less time--

consumingconsuming


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AIMAIM

The aim of this in vitro study was to compare theThe aim of this in vitro study was to compare the

fracture resistance and fracture mode offracture resistance and fracture mode of

endodontically treated maxillary centralendodontically treated maxillary central

incisors restored with the different postincisors restored with the different post

systems namelysystems namely

titanium,titanium,

zirconiazirconia ceramic andceramic and

prepre--fabricated FRCfabricated FRC

posts that have different modulus of elasticityposts that have different modulus of elasticity


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Materials and MethodsMaterials and Methods

A total of 50 human maxillary central incisorsA total of 50 human maxillary central incisors

free of cracks, caries and fractures, which havefree of cracks, caries and fractures, which have

at least 21 mm total length were used in thisat least 21 mm total length were used in this

studystudy

All teeth were randomly divided into fiveAll teeth were randomly divided into five

groups of 10 teeth eachgroups of 10 teeth each


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A total of 50 human maxillary central incisors free of cracks,A total of 50 human maxillary central incisors free of cracks,

caries and fractures, which have at least 21 mm total lengthcaries and fractures, which have at least 21 mm total length

were used in this studywere used in this study

All teeth were randomly divided into five groups of 10 teethAll teeth were randomly divided into five groups of 10 teetheacheach


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BuccolingualBuccolingual andand mesiodistalmesiodistal dimensions weredimensions were

determined with a digitaldetermined with a digital calipercaliper

The root dimensions were assessed withThe root dimensions were assessed withonewayoneway analysis of variance (ANOVA) toanalysis of variance (ANOVA) to

demonstrate any significant difference betweendemonstrate any significant difference between

groups(P > 0.05)groups(P > 0.05)

The most similar sizes available among theThe most similar sizes available among the

post systems used in this study were chosenpost systems used in this study were chosen


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After completion of the endodontic treatment, theAfter completion of the endodontic treatment, the

teeth were cut 15 mm coronal to the most apical pointteeth were cut 15 mm coronal to the most apical point

and perpendicular to the long axis of the teethand perpendicular to the long axis of the teeth

In the control group, after completion of endodonticIn the control group, after completion of endodontic

treatmenttreatment syntacsyntac enamel/dentine bonding system wasenamel/dentine bonding system was

applied and was filled with a composite resinapplied and was filled with a composite resin

Fifty maxillary central incisors received 1 mm width,Fifty maxillary central incisors received 1 mm width,90 shoulder with rounded inner line angles90 shoulder with rounded inner line angles

The preparations had a wall convergence ofThe preparations had a wall convergence of

approximately 6approximately 6


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Root canal filling was removed with the gatesRoot canal filling was removed with the gates--

gliddenglidden, leaving 3 mm of root canal filling in the, leaving 3 mm of root canal filling in the

apical portion for groups 1apical portion for groups 14.4.

Each post was marked at a distance of 15 mm fromEach post was marked at a distance of 15 mm from

its apical endits apical end

All posts were sectioned horizontally with a waterAll posts were sectioned horizontally with a water--

cooled diamond fissure burcooled diamond fissure bur

Thus, retention surface of each post in the rootThus, retention surface of each post in the root

portion was 10 mmportion was 10 mm


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In test group 1, roots were preparedIn test group 1, roots were prepared

SyntacSyntac primer and adhesives were applied step byprimer and adhesives were applied step by

step into the inner walls of the root canalstep into the inner walls of the root canal

HeliobondHeliobond was applied simultaneously into the innerwas applied simultaneously into the inner

walls of the root canals and onto each postwalls of the root canals and onto each post

The posts wereThe posts were lutedluted with a dualwith a dual--curing compositecuring composite

lutingluting cement (cement (VariolinkVariolink 2)2) After insertion of the posts into the root canals,After insertion of the posts into the root canals,

compositecomposite lutingluting cement wascement was photopolymerizedphotopolymerized 40 s40 s

from mesial, distal, buccal and palatal surfacesfrom mesial, distal, buccal and palatal surfaces


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A dimensionally standardized core was builtA dimensionally standardized core was built--up withup with

a lighta light--polymerizing composite material by using thepolymerizing composite material by using the

transparent mouldtransparent mould

Total abutment height of 6 mm measured from theTotal abutment height of 6 mm measured from the

buccal CEJ comprised 4 mm of core material and abuccal CEJ comprised 4 mm of core material and a

dentine ferrule that measured 2 mmdentine ferrule that measured 2 mm buccallybuccally and 1and 1

mm proximally.mm proximally.


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In test group 2, roots were prepared in the same wayIn test group 2, roots were prepared in the same way

ZirconiaZirconia ceramic posts were fitted into the rootceramic posts were fitted into the root

canals, and a core pattern was built up with acanals, and a core pattern was built up with a

modelling waxmodelling wax

Standardised sized wax patterns were prepared toStandardised sized wax patterns were prepared to

desired shape with a hand instrument and they weredesired shape with a hand instrument and they were

thenthen spruedsprued and investedand invested

The cores were heatThe cores were heat--pressed frompressed from zirconiazirconia--enrichedenriched

glassglass--ceramic directly over preceramic directly over pre--fabricatedfabricated zirconiazirconia

ceramic posts at 900ceramic posts at 900ooCC


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Investment was removed, all surfaces were carefullyInvestment was removed, all surfaces were carefully

air abradedair abraded

The bottom surfaces of the cores were etched withThe bottom surfaces of the cores were etched with

5% hydrofluoric acid (IPS Empress)5% hydrofluoric acid (IPS Empress) for 30 s, and allfor 30 s, and allpost surfaces and the bottom surfaces of the corespost surfaces and the bottom surfaces of the cores

werewere silanizedsilanized for 60 s and driedfor 60 s and dried

The postsThe posts--andand--cores were cemented with Variolinkcores were cemented with Variolink--22

into the prepared teeth in accordance with theinto the prepared teeth in accordance with the

procedure in test group 1procedure in test group 1


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In test group 3, roots were prepared with 1.4 mm inIn test group 3, roots were prepared with 1.4 mm in

diameter drill of the same diameter as the posts thatdiameter drill of the same diameter as the posts that

was available in the FRCwas available in the FRC PostecPostec kitkit

After the tryAfter the try--in processes of the posts in the rootin processes of the posts in the rootcanals, each post was cut to a length 3 mm coronal tocanals, each post was cut to a length 3 mm coronal to

the preparationthe preparation

The cementation procedures were performed asThe cementation procedures were performed as

described abovedescribed above

Composite cores were built up like in test group 1Composite cores were built up like in test group 1


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In test group 4, titanium posts were used to createIn test group 4, titanium posts were used to create

anchorage for composite coreanchorage for composite core

A tapered No. 2 drill from theA tapered No. 2 drill from the KometKomet ER post kit wasER post kit was

used to enlarge the root canals in preparation forused to enlarge the root canals in preparation forendodontic post placementendodontic post placement

After the tryAfter the try--in processes of the posts in root canals,in processes of the posts in root canals,

each post was cemented with a zinc phosphateeach post was cemented with a zinc phosphate

cementcement

Dimensionally standardized composite cores wereDimensionally standardized composite cores were

then built up as described abovethen built up as described above


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Root surfaces were marked 3 mm below the crown margin toRoot surfaces were marked 3 mm below the crown margin to

simulate the biologic width (20) and covered with 0.3 mm insimulate the biologic width (20) and covered with 0.3 mm in

thickness waxthickness wax

Specimens were then embedded inSpecimens were then embedded in autopolymerizingautopolymerizing acrylicacrylic

resin surrounded by plastic mouldresin surrounded by plastic mould After the first signs of the polymerization, teeth were removedAfter the first signs of the polymerization, teeth were removed

from the resin blocks, and the waxes on the root surfaces werefrom the resin blocks, and the waxes on the root surfaces were

removed by using a handremoved by using a hand instrument.instrument.

SiliconSilicon--base impression materialbase impression material was injected into resin base,was injected into resin base,and the teeth were reinserted into resin base which simulatesand the teeth were reinserted into resin base which simulates

periodontal ligamentperiodontal ligament

All samples were stored inAll samples were stored in deionizeddeionized water for 24 h at 37 Cwater for 24 h at 37 C

before testing procedurebefore testing procedure


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(A) apical root filling(A) apical root filling

(B) pre(B) pre--fabricated postfabricated post

(C) root dentine(C) root dentine

(D) coronal dentine above the(D) coronal dentine above theshouldershoulder

(E) all(E) all--ceramic copingsceramic copings

(F) core(F) core

(G) resin block(G) resin block

(H) silicone simulated(H) silicone simulated

periodontal ligamentperiodontal ligament


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Specimens were mounted in a universal loadSpecimens were mounted in a universal load--testingtesting

machine and were loaded until fracture at a crossmachine and were loaded until fracture at a cross--

head speed of 0.5 mm/minhead speed of 0.5 mm/min

The fracture loads were determined asThe fracture loads were determined as NewtonsNewtons

The modes of fracture were also recorded andThe modes of fracture were also recorded and

classified as repairable if located in the cervical thirdclassified as repairable if located in the cervical third

of the roots and catastrophic if located below using aof the roots and catastrophic if located below using a

stereostereo--microscopemicroscope


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The force was applied with an angle of 135The force was applied with an angle of 135oo2 mm2 mm

below the incisal edge on the palatal surface of thebelow the incisal edge on the palatal surface of the

crowns using a steel ball with 6crowns using a steel ball with 6--mm diametermm diameter


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ResultsResults

Mean fracture loads for all groups are presented inMean fracture loads for all groups are presented in

the table belowthe table below


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ResultsResults

The highest fracture resistance was recorded inThe highest fracture resistance was recorded in

descending orderdescending order

group 4 (titanium post/composite core) at 581.34 Ngroup 4 (titanium post/composite core) at 581.34 N

group 1 (group 1 (zirconiazirconia post/composite core) at 497.5Npost/composite core) at 497.5N

group 3 (FRC post/composite core) at 494.61Ngroup 3 (FRC post/composite core) at 494.61N

group 2 (group 2 (zirconiazirconia post/ceramic core) at 474.61Npost/ceramic core) at 474.61N

and group 5 (control) at 420.42 Nand group 5 (control) at 420.42 N


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ResultsResults

Titanium post and composite core (group 4) showed aTitanium post and composite core (group 4) showed a

significantly higher fracture resistance in comparisonsignificantly higher fracture resistance in comparison

with the control groupwith the control group

OneOne--way ANOVA andway ANOVA and TukeysTukeys test detected notest detected nosignificant difference in fracture resistance betweensignificant difference in fracture resistance between

group the 1, 2, 3 and 5 (P < 0.05)group the 1, 2, 3 and 5 (P < 0.05)


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ResultsResults

The modes of fracture for all groups are presentedThe modes of fracture for all groups are presented

belowbelow


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ResultsResults

Glass FRC posts and composite cores (group 3)Glass FRC posts and composite cores (group 3)

displayed more catastrophic fracturesdisplayed more catastrophic fractures

5 catastrophic fractures were located at mid5 catastrophic fractures were located at mid--root orroot or

in the apical thirdin the apical third

5 repairable fractures occurred in the coronal third5 repairable fractures occurred in the coronal third

In group 1 (In group 1 (zirconiazirconia post/composite core),post/composite core),

2 catastrophic fractures were located at mid2 catastrophic fractures were located at mid--root orroot orin the apical thirdin the apical third

8 repairable fractures occurred in the coronal third8 repairable fractures occurred in the coronal third


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ResultsResults

In group 2 (In group 2 (zirconiazirconia post/ceramic core),post/ceramic core),

1 catastrophic fracture was located in the apical1 catastrophic fracture was located in the apical

third of the root;third of the root;

9 repairable fractures occurred in the coronal third9 repairable fractures occurred in the coronal third In group 4 (titanium post/composite core) similar toIn group 4 (titanium post/composite core) similar to

group 2,group 2,

one catastrophic and nine repairable fracturesone catastrophic and nine repairable fractures

In groupIn group 5 (control),5 (control),

two catastrophic and eight repairable fracturestwo catastrophic and eight repairable fractures

were occurred.were occurred.


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DiscussionDiscussion

This study compared the fracture resistance of theThis study compared the fracture resistance of the

endodontically treated maxillary central incisorsendodontically treated maxillary central incisors

restored with different post systemsrestored with different post systems

In this study, extracted human teeth were used as testIn this study, extracted human teeth were used as testspecimensspecimens

The main disadvantage of the use of human teeth isThe main disadvantage of the use of human teeth is

the relatively large variation in size and mechanicalthe relatively large variation in size and mechanical

properties, often resulting in large standard deviationsproperties, often resulting in large standard deviations

Also, dentinal changes can be caused by differentAlso, dentinal changes can be caused by different

water content, pulpal condition before toothwater content, pulpal condition before tooth

extraction, patient age, and composition of dentineextraction, patient age, and composition of dentine


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Plastic teeth can be standardized in size and materialPlastic teeth can be standardized in size and material

but do not properly simulate the modulus of elasticitybut do not properly simulate the modulus of elasticity

and bonding properties of human teethand bonding properties of human teeth


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In the present study, conical andIn the present study, conical and cylindrocylindro--conical posts wereconical posts were

usedused

It is known that parallel sided posts are more retentive thanIt is known that parallel sided posts are more retentive than

any other design. However, the use of them increases stressany other design. However, the use of them increases stressconcentration in dentine at the apical part of the posts as theyconcentration in dentine at the apical part of the posts as they

leave a thin dentinal wall at that region, and increases the riskleave a thin dentinal wall at that region, and increases the risk

of perforation and fractureof perforation and fracture

Tapered posts exhibit lower concentrations of stress in theTapered posts exhibit lower concentrations of stress in the

apical portion; therefore, they decrease the risk of catastrophicapical portion; therefore, they decrease the risk of catastrophicfracturefracture

However they have a high potential for wedging duringHowever they have a high potential for wedging during

loadingloading


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In the present study, the teeth were loadedIn the present study, the teeth were loaded palatallypalatally atat

135degr to the long axis135degr to the long axis

This angle reflects the positions, contacts and loadingThis angle reflects the positions, contacts and loading

characteristics of maxillary central incisors in Class Icharacteristics of maxillary central incisors in Class Iocclusionocclusion

However, submitting specimens to fatigue moreHowever, submitting specimens to fatigue more

accurately simulates intraoral conditions thanaccurately simulates intraoral conditions than

increasing a single load until fractureincreasing a single load until fracture


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In the present study, titanium posts with compositeIn the present study, titanium posts with composite

cores significantly increased the fracture resistancecores significantly increased the fracture resistance

Direct core restorations with titanium, glassDirect core restorations with titanium, glass--fibre andfibre and

zirconiazirconia posts are appropriate in respect to fractureposts are appropriate in respect to fractureresistanceresistance

With regard to strength, indirect core technique offersWith regard to strength, indirect core technique offers

no advantage over direct core techniqueno advantage over direct core technique

In addition, indirect technique is timeIn addition, indirect technique is time--consumingconsuming

because impression is taken to fabricate the core inbecause impression is taken to fabricate the core in

the clinical practice and the core is fabricated in thethe clinical practice and the core is fabricated in the

dental laboratorydental laboratory


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The greatest number of catastrophic fractures wereThe greatest number of catastrophic fractures were

recorded in Group 3recorded in Group 3

This result may be attributable to the fact that glassThis result may be attributable to the fact that glass--

fibre posts had the lowest modulus of elasticityfibre posts had the lowest modulus of elasticityamong the post types testedamong the post types tested

Lower modulus of elasticity results in high bendingLower modulus of elasticity results in high bending

of the post/core unit under load; consequently, highof the post/core unit under load; consequently, high

stress is exerted on the toothstress is exerted on the tooth


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In this study, all of theIn this study, all of the zirconiazirconia ceramic posts wereceramic posts were

fractured while none of glass FRC and titanium postsfractured while none of glass FRC and titanium posts

were fracturedwere fractured

Therefore, it should be taken into consideration thatTherefore, it should be taken into consideration thatremoving process ofremoving process of zirconiazirconia ceramic post from rootceramic post from root

canal is almost impossible when it fracturescanal is almost impossible when it fractures

This is main disadvantage ofThis is main disadvantage of zirconiazirconia ceramic postceramic post


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ConclusionConclusion

Within the limitations of this in vitro study, theWithin the limitations of this in vitro study, the

following conclusions were drawn:following conclusions were drawn:

Titanium posts with composite cores increasedTitanium posts with composite cores increasedthe fracture resistance of endodonticallythe fracture resistance of endodontically

treated teethtreated teeth

GlassGlass--fibre posts demonstrated the mostfibre posts demonstrated the most

catastrophic fracturescatastrophic fractures

ZirconiaZirconia posts with ceramic cores can beposts with ceramic cores can be

recommended as an aesthetic solutionrecommended as an aesthetic solution


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THANKYOUTHANKYOU

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