the ideal restoration of endodontically treated teeth structural and esthetic considerations a...

SCIENTIFIC SESSION

238THE EUROPEAN JOURNAL OF ESTHETIC DENTISTRY

70-6.&t/6.#&3t46..&3

The ideal restoration of endodonti-

cally treated teeth structural and

esthetic considerations: a review of

the literature and clinical guidelines

for the restorative clinician

Konrad Meyenberg, DMD Private Office for Reconstructive Dentistry

Zrich, Switzerland

Correspondence to: Konrad Meyenberg

Private Office for Reconstructive Dentistry, Rennweg 58 / Eingang Oetenbachgasse 26, 8001 Zrich, Switzerland;

E-mail: [email protected]; Web: www.zahnaerzte-rennweg.ch

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One of the most challenging dilemmas

faced by todays clinician is the manage-

ment of the structurally and esthetically

compromised endodontically treated

tooth. Certainly, in recent years there has

been a tendency to take the simplified

approach of extraction and implant

but this does not always prove to be as

simple as we would like to think. Has

the popularity of dental implantology

made the restorative dentist complacent

in regards to the possibilities that good

endodontic, periodontal and restorative

treatments can achieve? Without doubt

the dental implant option has its place,

and rightly so, but in many cases, I sus-

pect, the endodontic/restorative option

does not always receive its due merits.

Whenever we are faced with such a

compromised tooth, we have to con-

sider the following question: is the tooth

maintainable? If so, then this is surely

our primary goal. However, the question

is complicated by the context ie, is this

a young patient? Is this a bridge abut-

ment? Is there an esthetic challenge, ie,

a dark tooth? In the younger patient, it

may be desirable to maintain a poten-

tially hopeless tooth for as long as pos-

sible in order to buy time and delay the

day of implant placement and its subse-

quent eventual failure. Retreatment of a

tooth is, more often than not, simpler with

a broader range of options than retreat-

ment of a failed implant, particularly in

the esthetic zone. If this can be done


70-6.&t/6.#&3t46..&3

for the younger patient, then why cant

it be done for the older patient? On the

other hand, perhaps it is more predict-

able in a given case to remove the tooth

and restore it with a dental implant res-

toration. These and other issues are real

concerns we have as practitioners and it

is important to have objective as well as

the subjective criteria on which to base

our decision for the choice of restorative

protocol.

Are all endodontically treated teeth

really less predictable than a dental

implant-supported restoration? Are they

really more likely to fail? Do they really

have a poor prognosis? Do implants re-

ally have fewer complications? Is retreat-

ment as easy? Do anterior and posterior

teeth behave the same? When is the

prognosis of the tooth unfavorable and

at what point is extraction and an im-

plant the best option? These and many

other relevant questions are eloquently

addressed below by our essayist and

EAED Active Member, Dr Konrad Mey-

enberg. My hope is that this paper will

serve to help us to question our treat-

ment choices more critically in this area,

suggest useful answers to many of the

questions in this dilemma, provide us

with objective criteria on which to base

our judgements and finally offer solu-

tions so that we can make better choices

for the treatment of our patients.

Dr Tidu Mankoo, BDS

Moderator/Editors Introduction

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Abstract

In restorative dentistry, the non-vital tooth

and its restoration have been extensively

studied from both its structural and es-

thetic aspects.

The restoration of endodontically

treated teeth has much in common with

modern implantology: both must include

multifaceted biological, biomechanical

and esthetic considerations with a pro-

found understanding of materials and

techniques; both are technique sensitive

and both require a multidisciplinary ap-

proach. And for both, two fundamental

principles from team sports apply well:

firstly, the weakest link determines the

limits, and secondly, it is a very long way

to the top, but a very short way to failure.

Nevertheless, there is one major dif-

ference: if the tooth fails, there is the op-

tion of the implant, but if the implant fails,

there is only another implant or nothing.

The aim of this essay is to try to an-

swer some clinically relevant concep-

tual questions and to give some clinical

guidelines regarding the reconstructive

aspects, based on scientific evidence

and clinical expertise.

Rebuilding the ideal tooth from an endodontically treated tooth what does this mean?Essentially, the goal is to restore the ap-

pearance and biomechanical properties

comparable to those of a vital, complete-

ly intact tooth. In addition, the coronal

restoration should prevent bacterial re-

colonisation of the endodontically treat-

ed root canal system.1

Clinically, most of non-vital teeth must

be considered as structurally and es-

thetically compromised.2 The fracture

rate and as a consequence the risk for

tooth loss is considerably higher com-

pared to vital teeth.

Part 1: Structural considerations

What are the causes of fractures?

There are several causes for the in-

creased risk of cracks in endodontically

treated teeth to be considered. Cracks

predispose the tooth immediately or af-

ter some time to fracture. The following

four factors contribute to this predisposi-

UJPO'JHTo Structural loss of tooth substance due

to pre-endodontic restorative proce-

dures or the endodontically induces

access cavity preparation and root

canal enlargements.5,6

Increased brittleness by age induces

changes in the dentin and the loss of

free unbound water from the root ca-

nal lumen and the dentinal tubules in

pulpless teeth.7-11

Weakening effects by endodontic ir-

SJHBOUT /B0$M &%5" BOENFEJDB-tions (CaOH2 PO EFOUJO FGGFDUT PGbacterial interactions with the dentin

substrates, corrosive effects of restor-

ative materials, and negative mechan-

ical effects through crack inducing or

crack propagating endodontic and

restorative methods and instruments,

including endodontic files.12-16

The reduced level of proprioception

of non-vital teeth causes a reduced

level of control of forces by the normal

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protective neuromuscular inhibition

mechanism.17

Some of these factors may be influ-

enced or modified to improve the prog-

nosis, however the most important factor

for success is to avoid any unnecessary

loss of tooth substance in general and

to preserve as much as possible after

removal of all decayed material.

Recent research shows that dentin

has some very effective inherent proper-

ties to inhibit crack progression (fracture

UPVHIFOJOHNFDIBOJTNT

UP PQUJNBMMZdistribute local stresses and to partially

repair defects, as long as a tooth is vi-

tal.8,9 However, a non-vital tooth will lose

some of these properties over time. A

key consideration is that the amount of

collagen fibers in endodontically treated

Fig 2 Fracture of first upper premolar due to deep cavity with endodontic treatment.

Fig 1 Cracks in lower first molar due to deep cavity.

Fig 4 Fracture originating from the apex of a canine due to the use of inadequate endodontic techniques.

Fig 3 Fracture of palatal root of upper first molar due

to endodontic treatment.

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teeth decreases, which means that this

dentin is much less fatigue resistant.17

In addition, even vital dentin loses some

of its initial strength over its lifetime: it

shows a different fracture behavior as

the mineral content increases over time

and causes a less favorable fracture be-

havior because of the increased brittle-

ness.18,19

Restorative options: what is the ideal concept?

As a consequence, any attempts to

restore a non-vital tooth must include

not only the use of restorative materi-

als with properties similar to the dental

components, but also the use of clinical

concepts that allow to compensate the

inherent reduction of the mechanical re-

sistance of endodontically treated teeth.

A true so-called biomimetic con-

cept20 therefore does not only implicate

the use of particular materials similar in

their properties to dentin and enamel,

but also sometimes the use of particular

materials with different properties to re-

store the incomplete tooth as a whole in

all its mechanical, biological and esthet-

ical aspects,21 above all if the remaining

tooth structure is compromised.

Post or no post are posts destructive?

In the past, fractures of teeth often have

simply been attributed to inadequate re-

storative procedures, be it by the use of

inadequate core materials or the use of

posts and screws. The introduction of ad-

hesive techniques and their successful

integration in almost all current restora-

tive procedures has allowed the clinician

to dispense with posts in many indica-

tions, as they are no longer required for

the retention of a core build-up.

However, mindful clinicians can still

observe a relatively high rate of vertical

root fractures despite the absence of

posts and even with the use of adhe-

sive techniques above all in curved

and small roots; indeed some authors

report up to 20% of vertical fractures of

endodontically treated teeth. Man-

dibular molars and maxillary premolars

are most often affected.25,26 Provided

there is enough coronal dentin structure

NPSFUIBOUXPUIJSETBWBJMBCMFJUTFFNTthat there is no difference between teeth

restored with or without posts in this re-

spect.27 Interestingly in this article, 86%

of molars with vertical root fractures had

the fracture in a root without a post.

Therefore, as long as no active posts

or screws are used, which may produce

detrimental lateral forces on the den-

tin walls,28 and as long as inadequate

placement techniques with risk of per-

forations are not used, posts per se

may not be considered as destructive.

When is a post indicated?

The main reason to use a post today

is no longer to increase the retention

and resistance of a core build-up, since

there are very effective adhesive tech-

niques available. As discussed, provid-

ed there is sufficient tooth structure avail-

able, there is no longer a need to place

a post. In premolars with limited

amount of tooth destruction and molars

where, in general, more dentin walls with

greater surface area can be engaged

to be bonded as compared to anterior

teeth, a direct bonded core build-up is

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not be compensated simply by adhe-

sive techniques using fiber posts and

composite cores. In a recent long-term

study over 7 to 11 years, the mechani-

cal failures reached 7 to 11% and were

always related to a lack of coronal tooth

structure.

If anterior teeth and premolars pre-

sent with large defects that require

crowning, however, adequate transfer

of forces from the crown into the core

build-up and from there into the root is

not possible without a post. Importantly,

the function of the post is not only the

increase of the retention of the core, but

also the optimization of the resistance

form. In addition, the mechanical prop-

erties of a composite core alone may

also not be sufficient in the case of a

narrow abutment diameter and cannot

reduce high stresses in the critical cervi-

cal area, which in such a case, is prone

to horizontal fractures. A clinical study

PWFS UPZFBSTXJUIDSPXOTCPOEFEdirectly to a reduced macroretention ge-

ometry without posts clearly showed

that the concept can work for molars

(8795% success, depending from the

BNPVOUPGSFTJEVBMDBWJUZXBMMT

CVUEJEnot work for premolars, if there were no

cavity walls at all and the crown was just

bonded directly into the residual pulp

DIBNCFSTVDDFTTSBUFTherefore, the purpose of a post and

core as a unit is primarily to transfer the

loads into the root and secondly, the

post is used as a reinforcing element of

the core build-up.

The downside of this concept is the

weakening effect on the root itself;

to compensate for this, the ferrule effect

must be incorporated into the restoration

design.

clinically the concept of choice; it can be

regarded clinically as well established,

reliable and perhaps preferable to con-

ventional post-core concepts. In addi-

tion, by avoiding posts, the risk of cracks

due to thin residual root walls or perfora-

tions can be eliminated.

For anterior teeth and heavily compro-

mised premolars, however, this state-

ment is limited to teeth that present with

small to moderate defects and that will

later not be crowned.

For posterior teeth, the best prognosis

is achieved if in addition to a bonded

core foundation a ferrule effectis cre-

ated by the final restoration. This means

that full cuspal coverage is used, be it

a partial or full crown. Adhesive tech-

niques alone without cuspal coverage

may still lead to catastrophic failures

over time (ie, untreatable long axis frac-

UVSFTBOEDBOOPUCFSFHBSEFEBTDMJOJ-cally safe.

It must be stated at this point that the

ferrule effect is the most effective way of

mechanical stabilization, ie, of optimiz-

ing the resistance form, of any endodon-

tically treated teeth.Given the weaker

structure, as previously discussed, the

effect of the better load distribution into

the cervical zone and the avoidance of

any wedging effect by the post or core

build-up into the coronal part of the root

cannot be overemphasized. Therefore,

in order to provide a ferrule in situa-

tions without sufficient tooth structure

above the zone of the biological width,

orthodontic extrusion or surgical crown

lengthening should be considered. A

ferrule length of 1.5 to 2 mm is recom-

mended.

It must also be stated that, obviously,

the lack of coronal tooth structure can-

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The ferrule effect may also compen-

sate unexpected breakdown of adhe-

sion after bonding and luting proce-

dures in unqualified dentin conditions.

A safe clinical concept always implies

the incorporation of a belt and braces

approach to offset routes of potential

failure.

A special indication for a post is the

immature root, presenting with a large

root canal.

Obviously neither gutta-percha nor

MTA nor composite have a significant

reinforcing effect. In this instance, the

only significant reinforcing effect is

achieved with a post. This is in line with

the clinical observation of increased risk

of fracture in immature teeth left without

post and core-build up after endodontic

treatment.

If a post is indicated: what post concept should be used: stiff or flexible?

If something can break, it will break, and

it will always break at the weakest point

this basic finding and classic rule for

construction is also true for this applica-

tion and may explain the significant con-

troversies regarding what would be the

best of all the available concepts. The

question may be not whether something

will break, but rather where it will break.

Almost all dental materials have been

used clinically for posts. Still clinically

relevant today are gold-alloys, chrome-

cobalt, titanium, zirconia and glass fib-

er posts. Carbon fiber posts have no

clinical significance due to poor clinical

performance and disastrous potential;

therefore they will not be discussed in

this article.

#BTJDBMMZUIFSFBSFUXPDPOGMJDUJOHJT-sues causing some disagreements on

the ideal material of a post.2 From a me-

chanical standpoint, it is evident that a

post stiffer than dentin can take up more

load but induces more stress in some api-

cal parts of the root, which can increase

the risk of a vertical root fracture. Con-

versely, a post that has an elastic modu-

lus closer to dentin will, in fact, induce

less stress concentration apically in the

root, but more in the cervical region.

In addition, the interface between

post and core and between core and

dentin is also subjected to stress, so one

can expect to see more root fractures

JSSFQBSBCMF GSBDUVSFTXJUITUJGGFSQPTUTmade from metallic or ceramic materi-

als, whereas more flexible posts would

show more post fractures, debonding of

core materials and loss of retention (pos-

TJCMZSFQBJSBCMFXJUITVCTFRVFOUQSPC-lems of leakage and caries. The latter

may lead to endodontic reinfection and

catastrophic coronal destruction of tooth

substance, thus leveling out the poten-

tial advantage of this latter concept over

the first one.

The dilemma for the clinician is the

meaningful interpretation of the litera-

ture, as countless studies have been

published in this field, most of them being

in vitro studies with questionable clinical potential relevance. Numerous theoreti-

cal studies using finite element analysis

have also been performed, which would

all need to be verified according to clas-

sic engineering principles in a real mod-

el, but only a minority of the in vitro stud-ies have been performed with dynamic

or fatigue loading under a simulated

oral environment. Another difficulty is

that study results are also influenced by

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the structural condition, various types of

natural teeth utilized and the respective

loading pattern.

One of the more clinically relevant in vitro studies compared cast posts and DPSFTUJUBOJVN5JQPTUTXJUIDPNQPT-ite cores, zirconia posts with composite

cores and zirconia posts with ceramic

cores, using, in all groups, adhesive

techniques and a ferrule of 1 to 2 mm

on central incisors where all teeth were

crowned. The most favorable results

JOUFSNTPGGSBDUVSFTUSFOHUI/BOETVSWJWBMSBUFDPVMECFBDIJFWFEwith the stiffest concept (zirconia posts

XJUIBDFSBNJDDPSF

BOEUIF MFBTU GB-vorable with the cast post and core sys-

UFN/In contrast to this study with ideal tooth

substrate, another study compared dif-

ferent degrees of tooth destruction, us-

ing fiber posts and composite cores or

composite cores alone on premolars.

It was shown that posts had a significant

positive effect on fracture strength if only

1 or 2 cavity walls were left, whereas no

EJGGFSFODFDPVMECFGPVOEJGPSDBWJUZwalls were left. However, if a completely

flat profile without any substance above

the preparation line is used, most likely

the post will debond as predominant

mode of failure.

Two facts are of special importance in

the judgment of studies comparing dif-

ferent concepts:

The results of these in vitro studies largely depend on the presence or

BCTFODFPGBGJOBMSFTUPSBUJPODSPXOPrincipally, differences in materials of

posts and cores level out from the mo-

ment where a crown is placed.

If metal-free post and core concepts

are to be successfully used, the es-

tablishment of proper bonding be-

tween all substrates is of paramount

importance.51 If bonding fails, much

less favorable stress patterns occur

both in the root, above all in the critical

cervical area, and in the post and core

itself.52 As a clinical consequence,

loss of retention of the core and post

is still unfortunately the major compli-

cation.

Most of the clinical studies are difficult

to interpret in their outcome, since the

amount of tooth loss and the condition

of the remaining dentin (pre-existing

cracks, aging, endodontic treatment

NPEBMJUJFTBSFOPULOPXOBOENBZIBWFinfluenced the choice of the concept.

The scientific dilemma is very nicely

expressed in a systematic review about

the simple final question, whether a

crown or a filling is more effective in the

clinical performance for an endodonti-

cally treated tooth. The authors con-

clude There is insufficient evidence

to support or refute the effectiveness

of conventional fillings over crowns for

the restoration of root filled teeth. Until

more evidence becomes available cli-

nicians should continue to base deci-

sions on how to restore root filled teeth

on their own clinical experience, whilst

taking into consideration the individual

circumstances and preferences of their

patients.

This statement shows not only the

complexity of the topic, but also that

clinical multifactorial reality does not al-

low clear definition of one simple gener-

ally valid concept.

Nevertheless, there is still a need

for clear clinical guidelines, based on

scientific evidence paired with clinical

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expertise. Only this combination finally

leads to clinical evidence.

As a conclusion from numerous clini-

cal studies, it must be stated that there is

OPTVQFSJPSDPODFQUJOBMMSFTQFDUT#PUIdirect and indirect concepts and gold,

Ti, fiber and zirconia posts work well if

the respective concepts are properly ex-

ecuted. The single most important point

is to preserve as much remaining tooth

structure as possible.

Two additional arguments may require

consideration for the reconstructive cli-

nician: a) fiber posts offer the highest potential for reintervention due to their

relative ease of removal, however their

successful use clinically is much more

technique sensitive,58 and b) post and cores with a high modulus of elasticity

NFUBM PS [JSDPOJB PGGFS B IJHIFS GSBD-ture resistance as a foundation of the

crown,50 which may be of significance

for the long-term success of all-ceramic

crowns.59,60

What about bonding a post into the root canal space? Does bond-ing help in cases with extended amount of tooth destruction? What is the ideal surface condi-tioning of fiber posts?Looking at the results of a recent clini-

cal 10-year fiber post study, a surpris-

JOHMZIJHIBOOVBMGBJMVSFSBUFPGJTreported and an overall failure rate of

XJUIGJCFSQPTUGSBDUVSFTBOE11% post debondings.61 The highest

probability of a failure was reported for

anterior teeth with no cavity walls.

This is confirmed by another clini-

cal study62 where premolars of varying

degrees of destruction were restored

with different concepts of build-ups. All

teeth were finally crowned with porcelain

GVTFEUPNFUBM1'.DSPXOT"OPWFSBMMfailure rate in this 6-year survival study of

XBTSFQPSUFE8IFOPOMZBDJSDVMBSferrule of 2 mm or less was left, the fail-

ure rate increased to nearly 90 to 100%

GPSUIFOPQPTUDPODFQUUPUPGPSprefabricated posts, and to around 70%

for the customized post concept.

The results clearly suggest that pre-

fabricated fiber posts are superior

to customized fiber posts (glassfiber

CBOESFTJOJNQSFHOBUFEPSDPNQPTJUFcores without any posts, if there are only

2 walls or less remaining. However, even

if in addition to the bonded core a pre-

fabricated fiber post is used, the con-

cept obviously fails to be convincingly

successful in cases with extended tooth

destruction.

*ODPOUSBTUUPUIJTPWFSBMMGBJMVSFrate over 6 years of non-metallic posts

and build-ups, a 10-year report of pre-

fabricated metal posts and cast metal

QPTUTBOEDPSFTSFTVMUFEJOBBOEPWFSBMMGBJMVSFSBUF

RetentionThe almost doubled overall failure rate

of fiber posts and the surprisingly high

debonding rate must raise the question

about the effectiveness and efficiency

of this concept in general practice. Per-

haps it is unsurprising given the inher-

ently more technique-sensitive concept

of the required adhesive techniques and

the lack of a simple clear user protocol.

A recent study compared the reten-

tion of different fiber posts with different

surface conditionings (performed ac-

cording to the manufacturers recom-

NFOEBUJPOTBOE MVUJOHBHFOUT JOEFO-

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tin Ti-posts luted with conventional zinc

phosphate-cement served as the con-

trol group. The control Ti-post showed,

together with some combinations of the

test group, the highest pull-out strength,

whereas some combinations of the test

group showed surprisingly low values.

This is in line with another study, where

adhesively luted fiber posts were not

superior to gold posts either adhesively

luted or conventionally cemented with

glass ionomer cement.65

Adhesion to radicular dentinAdhesively luting a post into root den-

tin is a controversial issue. Conflicting

results have been published about the

efficacy of bonding to radicular dentin.

Probably due to the structural differenc-

es in radicular dentin, bond strengths

improve from the apical to the coronal

section. Comparing the use of compli-

cated separated dentin bonding and lut-

ing procedures with simpler self-etching

cements, it seems clinically more relia-

ble to use self-etching and self priming

cements taking into account the poten-

tially somewhat lower bond strength to

dentin.66-71 Inadequate ability to cure

the luting agents precludes the use

of light-curing materials. Dual-cure or

chemically curing materials should be

used instead, since different fiber posts

indeed differ in their light transmitting

properties, however posts with optimal

mechanical properties do not allow

enough light penetrating all over the

whole length of the post to sufficiently

polymerize light-cured materials.72

Adhesion to post surfaceTo improve bond strength to the pre-

fabricated fiber posts, chemical (silane,

etching with hydrogen peroxide for

NJO PS NFUIZMFOF DIMPSJEF GPS Tor micromechanical treatments (sand-

CMBTUJOHPSBDPNCJOBUJPOPGCPUIIBWFbeen proposed. Surprisingly, sand-

blasting seems to not affect the mechan-

ical properties of the fiber posts.75 Sand-

blasting with silanization is, therefore, an

efficient, simple and predictable way of

surface conditioning a fiber post before

bonding.77,78 However, fiber posts are

susceptible to water degradation, and

damaging the surface will increase this

phenomenon. Thus, a predictable bond-

ing procedure that completely seals the

post surface and avoids any voids is of

paramount importance to preserve frac-

ture resistance.79 Some manufacturers

now use a coating on their posts to fur-

ther simplify and improve the bonding.80

Nevertheless, care should be taken to

consider both the manufacturers rec-

ommendations and their scientific basis.

Mechanical propertiesMajor differences in the mechanical

properties of different brands of posts

is another critical point. Since there

are now countless brands of posts on

the market with a sometimes-unknown

origin, a proper selection based on in-

dependent scientific investigations is

imperative to avoid basic mechanical

failures.81,82 Using a fatigue resistance

test, a difference of roughly 7,000 cy-

cles until fracture for the worst and up

to 2,000,000 cycles for the best post in

UIJTSFTQFDUFRVJWBMFOUUPOPCSFBLBHFcould be shown. The quality of the man-

ufacturing processes including type of

fiber and matrix, pre-tensioning of fibers,

bond between fibers and matrix, among

other factors, play an important role.

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Fig 5 Case 1: initial radiograph of non-vital cen-tral incisors with different degree of remaining tooth

substance, final radiograph of build-ups with short

GJCFSQPTUTQMBDFEPVUMJOFEGPSCFUUFSWJTJCJMJUZ

Fig 6 Case 1: initial clinical situation, large com-posite build-ups, discolorations.

Fig 7 Case 1: abutment teeth after removal of ex-isting composite cores.

Therefore, both a sensitive indication

and technique is mandatory for the suc-

cessful use of the concept of fiber posts

combined with composite cores (Figs 5

UP

Fig 8 Case 1: abutment teeth after internal bleach-ing.

Fig 9 Case 1: build-ups of abutment teeth com-pleted with fiber posts and composite core, buccal

view.

Fig 10 Case 1: build-ups of abutment teeth com-pleted with fiber posts and composite core, occlusal

view.

Fig 11 Case 1: final clinical result.

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Concluding remarks regarding the structural aspects

The following statements regarding the

structural aspects may be made:

Where a crown is fabricated and a

proper ferrule effect is created, neither

the material (Ti, gold alloys, zirconia,

HMBTTGJCFSOPSUIFTIBQFBOEMFOHUIof the post are a significant influence,

as long as clinically reasonable con-

cepts are used.

Conversely, insufficient coronal tooth

structure will always lead to an in-

creased failure rate independent of

the concept of restoration.

Increasing the coronal diameter of the

post helps to reduce the fracture risk

of all posts, however the residual den-

tin wall thickness needs to be consid-

ered.

Huge differences in the quality of fib-

er posts require a careful selection to

avoid post fractures.

Materials with potential of corrosion

TUBJOMFTT TUFFM CSBTT NBZ JOEVDFfractures of materials and dentin and

therefore should not be used.

Adhesive cementation of fiber posts

is mandatory.

Adhesive cementation of metallic

posts is not mandatory.

Core build-ups should always be

bonded, even if a metal post is not

bonded.

Regarding the clinical reality, the fol-

lowing additional statements must be

made:

$FSBNJD QPTUT [JSDPOJB DBOOPU CFremoved after luting, offer no potential

for reintervention and should therefore

be used in selected cases only.

For abutment teeth presenting large

defects and requiring crowning, or

longer span bridges, or in general

heavy loads, metallic posts are pref-

FSBCMFPWFSGJCFSQPTUT'JHTUP

Fig 12 Case 2: initial radiograph of second lower premolar with fiber post and PFM crown.

Fig 13 $BTFSBEJPHSBQIZFBSTBGUFSUIFSBQZshowing post fracture, composite core debonding

and crown dislodgement.Fig 14 Case 2: clinical view showing fractured fiber post and extensive caries destruction under-

neath debonded composite core.

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70-6.&t/6.#&3t46..&3

References, Part 1 .BOOPDDJ'#IVWB#

Stern S. Restoring teeth following root canal re-treat-ment. Endodontic Topics 2011;19:125152.

2. Kishen A. Mechanisms and risk factors for fracture pre-dilection in endodontically treated teeth. Endodontic 5PQJDTo

(IFS.&+S%VOMBQ3.Anderson MH, Kuhl LV. Clinical survey of fractured teeth. J Am Dent Assoc o

$IBO$1-JO$15TFOH4$Jeng JH. Vertical root frac-ture in endodontically versus nonendodontically treated UFFUIBTVSWFZPGcases in Chinese patients. Oral Surg Oral Med Oral Pathol Oral Radiol Endod o

5. Reeh ES, Messer HH, Douglas WH. Reduction in tooth stiffness as a result of endodontic and restora-tive procedures. J Endod 1989;15:512516.

6. Asundi A, Kishen A. Digital photoelastic investigations on the tooth-bone interface. +#JPNFE0QUo

7. Jantarat J, Palamara JE, Lindner C, Messer HH. Time dependent properties of human root dentin. Dent .BUFSo

8. Kishen A, Asundi A. Experi-mental investigation on the role of water in the mechani-cal behavior of structural EFOUJO+#JPNFE.BUFS3FT"o

9. Kruzic JJ, Nalla RK, Kin-ney JH, Ritchie RO. Crack blunting, crack bridging and resistance-curve fracture mechanics in dentin: effect PGIZESBUJPO#JPNBUFSJBMTo

(BMF.4%BSWFMM#8%FOUJOpermeability and tracer tests. J Dent 1999;27:111.

11. Jameson MW, Hood JA, 5JENBSTI#(5IFFGGFDUTPG

dehydration and rehydra-tion on some mechanical properties of human dentin. +#JPNFDIo1065.

12. Grigoratos D, Knowles J, Ng YL, Gulabivala K. Effect of exposing dentin to sodium hypochlorite and calcium hydroxide on its flexural strength and elastic modulus. Int Endod J o

(PMETNJUI.(VMBCJWBMBK, Knowles JC. The effect of sodium hypochlorite irri-gant concentration on tooth surface strain. J Endod 2002;28:575579.

4BMFI""&UUNBO8.Effect of endodontic irriga-tion solutions on microhard-ness of root canal dentin. J %FOUo

4PV[B#JFS$"4IFNFTIH, Tanomaru-Filho H, Wesselink PR, Wu M. The ability of different nickel-titanium rotary instruments to induce dentinal damage during canal preparation. J &OEPEo

16. Ferrari M, Mason PN, Goracci C, Pashley DH, Tay FR. Collagen degradation in endodontically treated teeth after clinical function. +%FOU3FTo

17. Randow K, Glanz PO. On cantilever loading of vital and non-vital teeth. An experimental clinical study. Acta Odontol Scand o

#BKBK%4VOEBSBN//B[-ari A, Arola D. Age, dehy-dration and fatigue crack HSPXUIJOEFOUJO#JPNBUFSJ-als 2006;27:25072517.

19. Viguet-Carrin S,Garnero P,Delmas PD. The role of collagen in bone strength. Osteoporos Int o

20. Magne P, Douglas WH. Rationalization of esthetic restorative dentistry based on biomimetics. J Esthet Dent 1999;11:515.

21. Ni CW, Chang CH, Chen TY, Chuang SF. A multipara-metric evaluation of post-restored teeth with simulat-FECPOFMPTT.FDI#FIBW#JPNFE.BUFSo

22. Tsesis I, Rosen E, Tamse A, Taschieri S, Kfir A. Diagno-sis of vertical root fractures in endodontically treated teeth based on clinical and radiographic indices: a systematic review. J Endod o

'VTT;-VTUJH+5BNTF"Prevalence of vertical root fractures in extracted endo-dontically treated teeth. Int &OEPE+o

$PQQFOT$3.%F.PPSRJG. Prevalence of vertical root fractures in extracted endodontically treated teeth. *OU&OEPE+

25. Tamse A, Fuss Z, Lustig J, Kaplavi J. An evaluation of endodontically treated vertically fractured teeth. J Endod 1999;25:506508.

26. Vire DE. Failure of endodon-tically treated teeth: clas-sification and evaluation. J &OEPEo

27. Salvi GE, Siegrist Guldener #&"NTUBE5+PTT"-BOHNP. Clinical evaluation of root filled teeth restored with or without post-and-core systems in a specialist practice setting. Int Endod J o

28. Kishen A, Kumar GV, Chen NN. Stressstrain response in human dentin: rethinking fracture predilection in post-core restored teeth. Dent 5SBVNBUPMo

29. Zarow M, Devoto W, Sara-cinelli M. Reconstruction of endodontically treated posterior teeth with or without post? Guidelines for the dental practitioner. Eur J &TUIFU%FOUo

4PV[B&.EP/BTDJNFOUPLM, Maia Filho EM, Alves CM. The impact of post preparation on the residual dentin thickness of maxil-

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'FSSBSJ.$BHJEJBDP.$Goracci C, Vichi A, Mason PN, Radovic I, Tay F. Long-term retrospective study of the clinical performance of fiber posts. Am J Dent 2007;20:287291.

1JFSSJTOBSE-#PIJO'3FOBVMU1#BSRVJOT.$PS-ono-radicular reconstruction of pulpless teeth: a mechani-cal study using finite ele-ment analysis. J Prosthet %FOUo

#JOEM"3JDIUFS#.SNBOOWH. Survival of ceramic computer-aided design/manufacturing crowns bonded to preparations with reduced macroretention geometry. Int J Prosthodont o

4BUIPSO$1BMBNBSB+&Palamara D, Messer HH. Effect of root canal size and external root surface mor-phology on fracture suscep-tibility and pattern: a finite element analysis. J Endod o

#PMIVJT)1#%F(FF"+Feilzer AJ, Davidson CL. Fracture strength of different core build-up designs. Am J %FOUo

)FZEFDLF(#VU[')VT-sein A, Strub JR. Fracture strength after dynamic load-ing of endodontically treated teeth restored with different post-and-core systems. J 1SPTUIFU%FOUo

4DINPMEU4+,JSLQBUSJDL5$Rutledge RE, Yaccino JM. Reinforcement of simulated immature roots restored with composite resin, mineral trioxide aggregate, gutta-percha, or a fiber post after thermocycling. J Endod o

.BOHPME+5,FSO.*OGMV-ence of glass-fiber posts on the fracture resistance and failure pattern of endodonti-cally treated premolars with varying substance loss: An in vitro study. J Prosthet %FOUo

lary molars. J Prosthet Dent o

,SFKJ*%VD0%JFUTDIJ%EFCampos. Marginal adapta-tion, retention and fracture resistance of adhesive com-posite restorations on devital teeth with and without posts. 0QFS%FOUo

'PLLJOHB8"-F#FMM".Kreulen CM, Lassila LV, Vallittu PK, Creugers NH. Ex vivo resistance of direct composite complete crowns with and without posts on maxillary premolars. Int &OEPE+o

(V[Z(&/JDIPMT+**Ovitro comparison of intact endodontically treated teeth with and without endo-post reinforcement. J Prosthet %FOUo

4PV[B&.EP/BTDJNFOUPLM, Maia Filho EM, Alves CM. The impact of post preparation on the residual dentin thickness of maxil-lary molars. J Prosthet Dent o

)FZEFDLF(#VU['4USVCJR. Fracture strength and survival rate of endodon-tically treated maxillary incisors with approximal cavities after restoration with different post and core systems: an in vitro study. J %FOUo

'FSSBSJ.$BHJEJBDP.$Grandini S, De Sanctis M, Goracci C. Post placement affects survival of endodon-tically treated premolars. J %FOU3FTo

4UBOLJFXJD[/38JMTPOPR. The ferrule effect: a literature review. Int Endod J o

+VMPTLJ+3BEPWJD*Goracci C, Vulicevic ZR, Ferrari M. Ferrule effect: a literature review. J Endod o

4PSFOTFO+".BSUJOPGG+5Intracoronal reinforcement and coronal coverage: a study of endodontically treated teeth. J Prosthet %FOUo

/H$$%VNCSJHVF)#"M#BZBU.*(SJHHT+"Wakefield CW. Influence of remaining coronal tooth structure location on the fracture resistance of restored endodontically treated anterior teeth. J Pros-thet Dent 2006;95:290296.

)FZEFDLF(1FUFST.$The restoration of endodon-tically treated, single-rooted teeth with cast or direct posts and cores: a system-atic review. J Prosthet Dent o

50. Dietschi D, Duc O, Krejci *4BEBO"#JPNFDIBOJ-cal considerations for the restoration of endodontically treated teeth: a systematic review of the literature, Part II (Evaluation of fatigue behavior, interfaces, and in WJWPTUVEJFT2VJOUFTTFODF*OUo

51. Krejci I, Duc O, Dietschi D, de Campos E. Marginal adaptation, retention and fracture resistance of adhe-sive composite restorations on devital teeth with and without posts. Oper Dent. o

4BOUPT"'.FJSB+#5BOBLB$#9BWJFS5"#BMMFTUFSRY, Lima RG, Pfeifer CS, Versluis A. Can fiber posts increase root stresses and reduce fracture? J Dent Res 2010;89:587591.

3BTJNJDL#+8BO+.VTJ-LBOU#-%FVUTDI"4"review of failure modes in teeth restored with adhe-sively luted endodontic dowels. J Prosthodont o

'FEPSPXJD[;$BSUFS#de Souza RF, de Andrade Lima Chaves C, Nasser M, 4FRVFJSB#ZSPO14JOHMFcrowns versus conventional fillings for the restoration of root filled teeth. Cochrane Database Syst Rev 2012:16:CD009109.

55. Fokkinga WA, Kreulen CM, #SPOLIPSTU&.$SFVHFSTNH. Up to 17-year controlled

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clinical study on post-and-cores and covering crowns. +%FOUo

4JHOPSF"#FOFEJDFOUJ4,BJUTBT7#BSPOF."OHJ-ero F, Ravera G. Long-term survival of endodontically treated, maxillary anterior teeth restored with either tapered or parallel-sided glass-fiber posts and full-ceramic crown coverage. +%FOUo

57. Jung RE, Kalkstein O, Sailer I, Roos M, Hmmerle CH. A comparison of composite post buildups and cast gold post-and-core buildups for the restoration of nonvital teeth after 5 to 10 years. Int J 1SPTUIPEPOUo

'FSSBSJ.#SFTDIJ-(SBO-dini S. Fiber posts and endodontically treated teeth: a compendium of scientific and clinical perspectives, ed 1. Wendywood, South Africe: Modern Dentist Media. Wendywood, 2006.

59. Malament KA, Socransky SS. Survival of Dicor glass-ceramic dental restorations over 20 years: Part IV. The effects of combinations of variables. Int J Prosthodont o

60. Malament KA, Socransky SS, Thompson V, Rekow D. Survival of glass-ceramic materials and involved clinical risk: variables affecting long-term survival. Pract Proced Aesthet Dent 4VQQMo

61. Naumann M, Koelpin M, #FVFS'.FZFS-VFDLFM)10-year survival evaluation for glass-fiber-supported postendodontic restoration: a prospective observa-tional clinical study. J Endod o

62. Ferrari M, Vichi A, Fadda GM, Cagidiaco MC, Tay '3#SFTDIJ-1PMJNFOJ"Goracci C. A randomized controlled trial of endodonti-cally treated and restored premolars. J Dent Res 2012;91:72S78S.

(NF[1PMP.-MJE#Rivero A, Del Ro J, Celemn A. A 10-year retrospective study of the survival rate of teeth restored with metal prefabricated posts versus cast metal posts and cores. +%FOUo

8SCBT,5,BNQF.5Schirrmeister JF, Altenburg-er MJ, Hellwig E. Retention of fiber posts dependent on different resin cements. Schweiz Monatsschr Zahn-NFEo

65. Kremeier K, Fasen L, Klaib-FS#)PGNBOO/*OGMVFODFof endodontic post type (glass fiber, quartz fiber or HPMEBOEMVUJOHNBUFSJBMPOpush-out bond strength to dentin in vitro. Dent Mater o

66. Ferrari M, Mannocci F, Vichi "$BHJEJBDP.$.KS*"#POEJOHUPSPPUDBOBMstructural characteristics of the substrate. Am J Dent o

$BMJYUP-3#BOEDB.$Clavijo V, Andrade MF, Vaz LG, Campos EA. Effect of resin cement system and root region on the push-out bond strength of a translu-cent fiber post. Oper Dent o

68. Huber L, Cattani-Lorente M, 4IBX-,SFKDJ*#PVJMMBHVFUS. Push-out bond strengths of endodontic posts bonded with different resin-based luting cements. Am J Dent 2007;20:167172.

69. Monticelli F, Ferrari M, Toledano M. Cement system and surface treatment selection for fiber post lut-ing. Med Oral Patol Oral Cir #VDBM&o

#BSBCBOUJ/.BEJOJ-Krokidis A, Acquaviva PA, Cerutti F, Cerutti A. Polymerization degree and cementation methods of two different self-adhesive lut-ing cements used for glass fiber post cementation. Minerva Stomatol 2012;61: o

71. Sterzenbach G, Karajouli G, /BVNBOO.1FSP[*#JUUFSK. Fiber post placement with core build-up materials or resin cements An evalu-ation of different adhesive approaches. Acta Odontol 4DBOEo

72. Radovic I, Corciolani G, Magni E, Krstanovic G, Pavlovic V, Vulicevic ZR, Ferrari M. Light transmission through fiber post: the effect on adhesion, elastic modu-lus and hardness of dual-cure resin cements. Dent .BUFSo

.POUJDFMMJ'0TPSJP34BEFLFT, Radovic I, Toledano M, Ferrari M. Surface treatments for improving bond strength to prefabri-cated fiber posts: a lit-erature review. Oper Dent o

:FOJTFZ.,VMVOL4Effects of chemical sur-face treatments of quartz and glass fiber posts on the retention of a compos-ite resin. J Prosthet Dent o

75. Radovic I, Monticelli F, Goracci C, Cury AH, Coniglio I, Vulicevic ZR, Garcia-Godoy F, Ferrari M. The effect of sandblasting on adhesion of a dual-cured resin composite to methacrylic fiber posts: microtensile bond strength and SEM evaluation. J Dent o

76. Soares CJ, Santana FR, Pereira JC, Araujo TS, Menezes MS. Influence of airborne-particle abrasion on mechanical proper-ties and bond strength of carbon/epoxy and glass/bis-GMA fiber-reinforced resin posts. J Prosthet Dent o

77. Valandro LF, Yoshiga S, de Melo RM, Galhano GA, Mallmann A, Marinho CP, #PUUJOP.".JDSPUFOTJMFbond strength between a quartz fiber post and a resin cement: effect of post sur-

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face conditioning. J Adhes Dent 2006;8:105111.

78. Zicari F, De Munck J, Scotti R, Naert I, Van Meerbeek #'BDUPSTBGGFDUJOHUIFcement-post interface. Dent Mater 2012;28:287297.

79. Vano M, Carvalho C, Sedda M, Gabriele M, Garca-Godoy F, Ferrari M. The influ-ence of storage condition and duration on the resist-ance to fracture of different fiber post systems. Am J %FOUo

80. Schmage P, Nergiz I, Marko-poulou S, Pfeiffer P. Resist-ance against pull-out force of prefabricated coated FRC posts. J Adhes Dent o

81. Cheleux N, Sharrock PJ. Mechanical properties of glass fiber-reinforced endo-EPOUJDQPTUT"DUB#JPNBUFSo

82. Grandini S, Goracci C, Monticelli F, Tay FR, Ferrari M. Fatigue resistance and structural characteristics

of fiber posts: three-point bending test and SEM evaluation. Dent Mater 2005;21:7582.

(SBOEJOJ4$IJFGGJ/Cagidiaco MC, Goracci C, Ferrari M. Fatigue resistance and structural integrity of different types of fiber posts. Dent Mater J 2008;27:687

Part 2: Esthetic considerations

Introduction

In addition to the numerous issues dis-

cussed in part 1 of this paper, non-vital

teeth are frequently esthetically com-

promised. This frequently presents sig-

nificant and special challenges when it

comes to meeting the demand for nat-

ural-looking, esthetically pleasing teeth

sought by our patients today.

The aim of the second part of this pa-

per is to try to answer several clinically

relevant conceptual questions and to

provide some clinical guidelines regard-

ing the management of the esthetic as-

pects, based on scientific evidence and

clinical expertise.

Why are most endodontically treated teeth dark?

The discoloration of endodontically

treated teeth is a common observation.

In the posterior region, this phenom-

enon is seldom esthetically disturbing

or is largely addressed with full crowns,

since endodontically treated posterior

teeth present mostly with large recon-

structions that require optimal stabiliza-

tion by full or partial crowns.

In the anterior zone, however, esthet-

JDTDBOCFTUSPOHMZEJTUVSCFECZOFHB-tive effects:

Discolouration of the clinical crown.

Discolouration of the cervical region.

Discolouration of the gingiva and mu-

cosa.

There are various causes of these en-

dodontically induced intrinsic discolora-

tions:

Intrapulpal haemorrhage.

Pulpal necrosis.

Incomplete removal of pulp tissue

during the endodontic treatment.

Endodontic irrigants, medications

and root canal filling material (root

BOEDFSWJDBM[POF Restorative materials (cervical zone

BOEDSPXO Coronal leakage.

Dentin sclerosis.

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Unfortunately almost all root canal seal-

ers including Zinc Oxide-Eugenol and

")UPBMFTTFSFYUFOUMFBEUPEJTDPM-PSBUJPOBCPWFBMMJOUIFDFSWJDBM[POFAlso the use of MTA, be it grey or white,

will ultimately lead to a greyish appear-

ance or darkening of the root.5,6

Furthermore, the calcification pro-

cess in the dentin through obliteration

of the dentinal tubules and changes in

the free water content before and after

endodontic treatment and through ag-

ing processes, contributes to an altered

optical appearance in addition to the in-

creased brittleness.7-10

How can we improve the color of UIFUPPUITVCTUBODF #MFBDIJOHor replacing discoloured coronal dentin?

Although some of the above mentioned

negative factors can be clinically modi-

fied, it is evident that a non-vital tooth

inevitably loses some esthetic qualities

in terms of the color. As a matter of prin-

ciple, replacing discolored dentin to cor-

rect the color is not the preferable op-

tion from a structural viewpoint. In part 1,

the mechanical aspects to support this

axiom have already been extensively

discussed.

Therefore, bleaching the existing

substance is always the better option,

if we agree on the principle that hav-

ing a discolored tooth is preferable to

having no tooth. Most discolorations

are bleachable except those caused by

metal ions (amalgam, or silver and other

IFBWZNFUBMDPOUBJOJOHNBUFSJBMT2 So the only indication to remove discolored

dentin may be if small spots that do not

contribute to the structural resistance of

the tooth are heavily discolored and do

not respond to the bleaching procedure.

Do bleaching procedures lead to external resorption?

Cervical root resorption is a serious

complication that is difficult to treat11,12

and ultimately can lead to tooth loss.

There are various reasons for this phe-

nomenon. Orthodontic treatment and

tooth trauma are the most common pre-

disposing factor. Internal bleaching may

increase the combinatory risk, however

it seems to be limited to cases where

extensive concentrations of H2O2 com-

bined with heat (the thermo-catalytic

NFUIPE XBT VTFE The presence of defects at the cemento-enamel junc-

tion seem to play a major role, allowing

the bleaching agent to penetrate into the

periodontal space.15

The recommendations today are

therefore not to heat the bleaching agent

in the access cavity, to seal the residual

root filling well before application of the

bleaching agent and to generally use

less aggressive bleaching chemicals

instead of high concentrations of H2O2.

The best clinical compromise of ef-

fect, side-effects, risks and long-term

experience is in the use of the so called

walking bleach technique16 where,

classically, sodium perborate is mixed

with water.

In the authors long-term experience,

this is clinically as efficient as other more

aggressive chemicals, provided a cor-

rect cervical and coronal seal of the

bleaching cavity have been realized.

The cervical seal is preferably achieved

with a modified glass ionomer cement,

classically applied at the level of the con-

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nective tissue attachment, whereas the

coronal seal is achieved with adhesively

luted composite to ensure an optimal

penetration of the bleaching agent into

the dentin. Hence, leaving the access

cavity open and using at-home tech-

niques with open trays is not advisable.17

Success largely depends from the ap-

plication duration of the bleaching agent

oEBZToUJNFTBOECZGBSPVUQFS-forms alternative quick in-office tech-

niques in the long run.18 In a recent study

it could also be shown that this concept

compares very favorably to more ag-

gressive mixtures of chemicals in terms

of H2O2 leakage at different root locations

with and without external defects.19,20

Since cervical defects are difficult to

detect with conventional radiographs

and require cone beam computed to-

NPHSBQIZ$#$5UFDIOJRVFT21 the use of this less-aggressive concept makes

additional sense in avoiding added un-

known risks while producing good es-

thetic results.

Do bleaching procedures weaken the tooth or may dark roots also be bleached?

Recent research clearly shows that

bleaching chemicals weaken tooth sub-

stance.

Since the endodontic treatment itself

already weakens the dentin consider-

ably through chemical and mechanical

effectsCZUPJOTUSFOHUI25 additional care must be taken if a bleach-

ing procedure is being considered.

First of all, internal removal of dis-

colored dentin should be avoided. It

does not lead to better results with the

described bleaching technique and will

further compromise the strength of the

residual tooth structure. This is an im-

portant consideration particularly if ad-

ditional reconstructive measures are to

be executed26 and if the potential for re-

intervention is taken into account.

Second, as mentioned, bleaching

agents themselves lead to a weakening

of the tooth structure through the chemi-

cal modification of the dentin.27,28 A re-

cent publication supported the use of

sodium perborate mixed with water in

this respect, since this combination led

to a significantly smaller additional open-

ing of the dentinal tubules compared to

all other bleaching agents. Interestingly

DBSCBNJEF QFSPYJEF DBVTFE UIFworst effect.29

Another important consideration is

the influence of bleaching on dentin

bonding. As emphasized in part 1, the

quality of the internal reconstruction af-

ter endodontic therapy is of key impor-

tance in reconstituting the resistance to

fracture. Using an adhesive approach is

advisable but technique sensitive and,

in general, all bleaching agents lead to

reduced bond strengths and increased

microleakage. Consequently, the use

of antioxidants has been advocated to

counteract this effect (eg, sodium ascor-

CBUFBOEPSEFMBZJOHUIFCPOEJOHQSP-cedure for at least 10 days after washing

out the bleaching agent The antioxi-

dant is especially necessary and should

be mandatory if bonding with simplified

single bond dentin adhesives, or if de-

layed bonding is not warranted or pos-

sible.

However, good dentin adhesion can be

achieved if: a) sodium perborate mixed with water is used to bleach, b) the tooth is left with saline solution for 7 days after

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70-6.&t/6.#&3t46..&3

removal of the bleaching agent, and c) a scientifically and clinically well estab-

lished self-etching 2-step dentin bonding

TZTUFNFH$MFBSGJM4&CPOEJTVUJMJ[FE For enamel, the same principle of waiting

after washing off the bleaching agent is a

simple and successful strategy. Recent

proposals for new resin formulations that

are supposed to allow immediate bond-

ing after bleaching have not proved as

effective.

Since adhesion within the root remains

a challenge even in ideal experimental

Fig 15 $BTFEJTDPMPSFEOPOWJUBMSJHIUDFOUSBMincisor with PFM crown, initial clinical situation.

Fig 16 $BTF JOJ-tial radiographic situ-

ation. A carbon com-

posite post had been

placed.

Fig 17 $BTFBCVUNFOUUPPUIBGUFSDSPXOBOEpost removal.

Fig 18 $BTFIPMMPXDPNQPTJUFCVJMEVQGPSJOUFS-nal bleaching of coronal part of the abutment tooth.

conditions owing to unfavorable ovoid

root canal configurations and dentin mi-

crostructure in the deeper parts of the

root canal the root should not be

further compromised by using bleach-

ing techniques inside the root canal.

As long as the intracoronal bleaching

is performed within the access cavity

reaching to the level where the connec-

tive tissue attachment ends coronally,

the results constitute a sufficient com-

promise esthetically,26 even in the criti-

DBMDFSWJDBM[POF'JHTo

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70-6.&t/6.#&3t46..&3

Fig 19 $BTFDPNQMFUFECVJMEVQPGBCVUNFOUtooth with bonded fiber post and core, after internal

bleaching with sodium perborate and water.

Fig 20 $BTF HMBTT DFSBNJD DSPXO MBZFSJOHtechnique.

Fig 21 $BTFGJOBMDMJOJDBMSFTVMU Fig 22 $BTF GJOBM SBEJPHSBQIshowing good adaptation of the short

fiber post and bonded core to the den-

UJOBMXBMMTMJHIUDVSFENBUFSJBMTVTFE

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70-6.&t/6.#&3t46..&3

What about the predictability and stability of bleaching procedures?

There has been some debate about the

predictability and long-term effective-

ness of internal bleaching, with de-

scribed esthetic success rates of around

90% after 2 years, 75% after 5 years and

60% after 16 years. The potential causes

for the recurrence of discoloration have

been suggested as: a) the same sub-stances as those having caused the ini-

tial discoloration, or b) penetration of pig-ments from the oral cavity, or c) bacterial reinfection of the root canal system with

subsequent infiltration into the cervical

and coronal dentin.1

From long-term studies and clinical

observations, the following can be con-

cluded:

Internal bleaching is a technique-

sensitive approach. Potential rea-

sons for failures are numerous, with

coronal or apical leakage being the

most frequent, and short-cut treat-

ment protocols are more likely to have

QSPCMFNT#PUI UIF DPSPOBM BOE UIFapical-cervical seal, along with the

optical quality of the access restora-

tion, account for success or failure.

The prognosis of the bleaching pro-

cedure is more prone to recurrence

of discoloration if the tooth became

rapidly discolored after the endodon-

tic treatment.

Subjective and objective satisfaction

of the dentist or the patient may differ

substantially.

The potential for intervention and the

concept of a progressive (conserva-

UJWFBQQSPBDIEVSJOH UIF MJGFUJNFPGa discolored tooth are essential. Ag-

gressive reconstructive concepts

based just on esthetic considerations

and early crowning can lead to prema-

ture tooth loss. Therefore, bleaching

instead of removing tooth substance

is the preferable treatment, both for

non-reconstructive and reconstruc-

tive cases.26

May crowns or veneers compensate darkened coronal tooth structure?

First of all it is important to understand

the concept of illumination of the oral tis-

sues. The tooth with its clinical crown

and root, the gingiva, the bone and the

periodontium form an optical unit. Light

is transmitted by diffuse reflection into

the tissues. It is therefore critical not to

disturb this delicate system with discol-

Fig 23 Limited light conducting properties of fib-er posts with good mechanical properties preclude

the use of long posts, if light-cured materials are to

be used.

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70-6.&t/6.#&3t46..&3

orations or by the introduction of inad-

equate opaque or dark restorative ma-

terials. Of particular importance in this

respect is a soft color transition from the

cervical third of the clinical crown into

the adjacent gingival tissues.

Since the mid 1960s, dental techni-

cians and prosthodontists tried to imple-

ment this concept in order to improve

the esthetics of full crown margins. In the

1980s, PFM crowns without metal collars

were introduced, using shoulder and ve-

neering porcelains with better light con-

ducting properties to illuminate the adja-

cent tissues. Despite these efforts,

the results were never completely sat-

isfying when the underlying tooth struc-

ture was dark, or if there were vital and

rather translucent teeth to be matched.

Hence the search and development of

true light conducting materials as frame-

works with lower opacity than metal or

the pre-existing all-ceramic cores.

Today, in the case of vital teeth with

adequate tooth substance, more con-

servative bonded porcelain restorations,

such as veneers and anterior partial all-

ceramic crowns, are increasingly the

treatment of choice as compared to full

crowns, due to esthetic, technical and

biological advantages. It is impor-

tant to understand that the success of

these restorations is largely based on

the esthetic and mechanical advantag-

es of the natural uncompromised tooth

substrate as the foundation of the resto-

ration rather than an artificial substrate.

As a consequence of this success, the

concept has been extended to endo-

dontically treated teeth, with the idea be-

hind to convert darkened tooth structure

into vital looking tissues. Naturally

this is not only relevant to bonded lami-

nates and all-ceramic partial crowns,

as a wide variety of all-ceramic crown

systems exist today with excellent opti-

cal properties and long-term survival, in

particular, the new generation of glass-

ceramic materials. In addition, these

materials allow the provision of bonded

full coverage veneer type crowns with

SFEVDFEQSFQBSBUJPOTJNJMBSUPEF-HSFFWFOFFSQSFQBSBUJPO'JHTo

Consequently, the management of

discolored tooth substrate becomes

increasingly important. It should be re-

membered that all attempts to mask out

discolored tooth substance will invari-

ably end up with increased opacity and

therefore unnatural reflection of the light

instead of a diffuse reflection inside the

materials. This is of particular importance

when veneering a tooth with a discolored

cervical zone, as the fine veneer margins

cannot create the appropriate color tran-

sition from the tooth crown into the gin-

giva. If a full crown is provided in such a

case, a pleasing result can be achieved

by using opaque all-ceramic framework

materials, provided that adjacent struc-

tures are also more opaque and the gin-

gival tissue is thick, but this is rather the

exception than the rule.57,58 The same is

true if opaque cements are used to cover

dark underlying substance.

Above all, trying to mask out dis-

colored teeth should not result in over-

preparation:59 the mission statement of

Hippocrates primum nihil nocere (first EPOPIBSNTIPVMEBMTPCFUIFHVJEJOHQSJODJQMFIFSF'JHTBOE

Thus the clinical concept for man-

agement of discolored tooth substance

should always consider internal bleach-

ing as first option, even if the result will

not be absolutely perfect.

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70-6.&t/6.#&3t46..&3

If the tooth needs an additional indi-

rect restoration, a veneer or full cover-

age veneer-crown is an attractive and

less invasive solution. In the authors

own experience over the last 15 years

from when the concept first was used,

long-term results for esthetics and sur-

vival rates in both types of restorations

are comparable to all-ceramic crowns.

However, in the literature there are only

studies with vital teeth available at the

moment, which show a survival rate of

PWFS ZFBST GPS WFOFFST BOE100% for extended veneers over 5

years.60,61 The observation of small su-

perficial cracks not influencing survival

is similar to what can be observed within

the enamel of natural teeth.

One drawback certainly is if the dis-

colored tooth has already been restored

with a post. If removal of the post without

risk of damage to the root is viable, then

the internal bleaching can be performed

before a new post and core is fabricat-

ed. If this is considered too risky, metallic

posts and cores can at least be masked

with a tooth-colored opaquer and com-

posite to avoid to improve the substrate

color for an all-ceramic framework.

This leads to the next question: Can

tooth-colored posts enhance the color

of dark roots?

Tooth-colored posts have long been

advocated in esthetic dentistry. Since

early trials around 1965 by John McLean

with Alumina posts, the concept has

been further developed to mechanically

more reliable posts, with the introduc-

tion of the first Zirconia posts in 1995

and the first fiber posts in 1990.

The proposed reasons for tooth-color-

ed posts for esthetics in root treated

teeth are:

To illuminate the root and cervical re-

gion and thus brighten up darkened

tooth substance.

Fig 24 $BTFEJTDPMPSFEBCVUNFOU UFFUIXJUIcast post and cores, leading to a disturbance in the

illumination of the adjacent tissues.

Fig 25 $BTFGJOBMQJDUVSFXJUI1'.DSPXOT%VFto the symmetry of the case, the suboptimal color

transition from the abutment margins into the gin-

gival tissues fortunately does not disturb too much

in this case.

Fig 26 Case 5: left central incisor with polished cast post and core, right lateral incisor with tooth-

colored post and core.

MEYENBERG


70-6.&t/6.#&3t46..&3

To prevent any darkening effect of a post

on non-discolored tooth substance.

To create a tooth-colored basis for the

core and the crown.

While the first reason has already been

disputed early on by experienced cli-

nicians not being able to see any dif-

ference in the color between a metallic

post and a tooth-colored post put into

the same dark root under natural light

conditions, the second two points are

good arguments for tooth-colored posts.

In fact a recent study showed that there

is no difference in the cervical color of

abutment teeth between white and me-

tallic posts, however tooth-colored posts

and cores were beneficial for the overall

color of the all-ceramic crowns.65 This

is in line with observations of clinicians

aware of these subtle differences.66

Some care must be taken when trying

to translate in vitro studies about color influences into clinical practice. Some

subtle components of the color, such as

the quality of the internal diffuse reflec-

tion depending on the intensity of light

and the softness of the transition into the

marginal gingiva cannot be measured

Fig 27 Case 5: final picture showing the good reflection properties of the polished metal part of the

left central abutment tooth.

Fig 28 Case 6: abutment teeth with various de-grees of discolorations.

by photospectroscopic studies67 and

may lead to incorrect clinical recom-

mendations in specific cases.

However, given the clinical and sci-

entific evidence, there is actually little

reason to take out existing well adapted

and luted cast post and cores if the re-

maining dentin itself is not discolored

and does not require bleaching. It is

clinically sufficient to mask the buccal

part of the metal with a tooth-colored

opaquer. If space and residual thick-

ness of a gold alloy post and core do

not allow to do this, another smart ap-

proach is to polish the buccal part of

the exposed metal to a high gloss, thus

creating total reflection of the light at the

core surface.68 This concept has been

widely used by the author for years with

no adverse effects regarding the reten-

UJPOPGUIFMVUFEDSPXOT'JHToIn conclusion, it can be stated that

the color of the remaining tooth sub-

strate is of much greater importance

than the color of the post and cannot

be influenced positively by the post in

the cervical and apical region, however

having a tooth-colored post is beneficial

for the core.

SCIENTIFIC SESSION


70-6.&t/6.#&3t46..&3

Can soft tissue thickening compensate darkened cervical root structure?

A soft color transition from the crown

into the soft tissue is essential for an

esthetically pleasing result. In the pre-

ceding pages, the focus was placed

on the root and crown of the tooth and

how negative effects can be managed.

However, if discolorations are still pre-

sent in the critical cervical supra- and

subgingival zone, it makes sense to

consider influencing the soft tissue

characteristics.

The margin of the soft tissue cover-

ing the cervical part of the root plays

an important role as a curtain to hide

unpleasing structures. In addition, the

buccal bone plate has also some mask-

ing effect over a discolored root. A thick

bone plate can virtually completely mask

out the root discoloration. In periodontol-

ogy, there is little information available

about the masking effect of the soft tis-

sue. In oral implantology, however, some

studies have been performed looking at

the influence of various abutment ma-

terials on the color of the existing soft

tissues, and how variations in the soft

tissue thickness can modify the overall

color resulting from abutment and cov-

ering soft tissue. Since these abutments

all have a subgingival component and a

titanium implant base, this would appear

to offer a situation well in line with a dis-

colored root. Comparing zirconia, pol-

ished gold alloys and machined titanium

in a pig model, a visible difference was

always present if the tissue thickness

XBT CFMPX NN #FUXFFO UP NNin thickness, only zirconia (regardless of

BOZWFOFFSJOHEJEOPUJOEVDFBDIBOHF*GUIFUIJDLOFTTXBTNNPSNPSFUIFmaterial itself had no influence.69 In a

human study, comparing metal abut-

ments and PFM crowns with all-ceramic

abutments and crowns, the latter be-

haved better, but there was still a visible

difference for both groups compared

to the adjacent teeth.70 Another study

presented similar results,71 although no

correlation between the thickness of the

mucosa and the respective amount of

discoloration could be found.

In essence, the fiber content and the

degree of keratinization may play a more

important role for the masking ability

than the soft tissue thickness alone. In

this respect, the use of a connective tis-

sue graft taken from the palate with its

higher content of collagen fibers is the

most promising approach using an en-

velope technique to improve the esthetic

integration of the augmented tissue.

Some modifications in the technique, in-

cluding a microsurgical approach, have

been introduced to further decrease

Fig 29 Case 6: layered glass ceramic crowns with internal opaquer and varying opacities of

frameworks.

MEYENBERG


70-6.&t/6.#&3t46..&3

healing complications and unesthetic

tissue scars.

An additional benefit of this approach

is the easier tissue handling during the

reconstructive phase and the preven-

tion of post-reconstructive recessions

over time, which may expose further dis-

colored root parts. Indeed, since many

of the discolored teeth exhibit some cer-

vical tissue loss over time anyway, this

procedure can also be considered as a

preventive treatment of a cervical reces-

sion,76 dealing not primarily with health,

but with stable, esthetic tissue levels. It

may also serve to counteract the loss in

cervical tissue height that occurs by tis-

sue modeling during the aging process,

which is more noticed around discolor-

ed roots and is independent of the pres-

ence or absence of dental restorations.

As a conclusion, soft tissue thicken-

ing may not completely solve the prob-

lem of the discolored cervical hard and

soft tissue zone, but it can improve the

overall result by at least stabilizing soft

tissue contours and preventing further

exposure of discolored root surfaces.

Final consideration: at what point should we give up and extract?

It is fair to state that a tooth should be

saved as long as there is a predictable

way to functionally and biologically do

so with a reasonable prognosis. This

2-part article has shown various possi-

bilities to overcome classic biomechani-

cal and esthetic problems with respect

to minimizing reconstructive risks. The

basis for reconstructive survival in the

context of this article, however, is the

quality of the endodontic treatment as

the starting point.

It can also be stated that today too

many teeth are extracted in favor of im-

plants, with insufficient regard for the

extensive reconstructive options avail-

able to maintain them. Furthermore, the

Fig 30 Case 6: final picture of the four anterior teeth, showing an acceptable color transition be-

UXFFOUIFQPOUJDSJHIUMBUFSBMJODJTPSBOEUIFPUIFSabutment teeth.

Fig 31 Case 6: final picture of the right side, showing an acceptable color transition between the

QPOUJDMBUFSBMJODJTPSUIFWJUBMDBOJOFBOEUIFOPOvital discolored central incisor.

SCIENTIFIC SESSION


70-6.&t/6.#&3t46..&3

short- and long-term biologic, esthetic

and technical complications of implants

are not fully appreciated.77 Unfortu-

nately, poor endodontic treatment is still

a major factor in premature tooth loss.

However, if performed correctly, results

are at least as good as replacement with

implants for single units.77 It is striking

that despite this fact, today a tendency

towards a more extraction-oriented re-

constructive concept can be observed

in practice. There are two main reasons

for this.

The first reason is that in clinical de-

cision-making, the predictability of the

whole procedure is of primary impor-

tance in respect of complications and

cost. Obviously there is some pessimism

among clinicians regarding the progno-

sis of endodontic treatments in general

and this is not completely unfounded.

The combined failure rate of endodonti-

cally treated teeth in general practice is

higher than described in earlier reports:

PWFSZFBSTBDVNVMBUJWFGBJMVSFSBUFPGup to 20% is documented.78 In general,

the outcome of endodontic treatments

may have been overestimated in previ-

ously published reviews because of the

general lack of correct apical diagnosis.

*GIJHISFTPMVUJPO$#$5JTOPUVTFEPGUFOthe endodontic status cannot correctly

be analyzed. The authors of a current

review state: In conclusion, the serious

limitations of longitudinal clinical studies

restrict the correct interpretation of root

canal treatment outcomes. Systematic

reviews reporting the success rates of

root canal treatment without referring

to these limitations may mislead read-

ers.79 Therefore, the trend towards sim-

plified endodontic protocols may also

be based on incorrect interpretations of

previous studies and may produce less

successful results than expected or than

achieved with the classic concepts of

experienced endodontic specialists. A

MPOHUFSNTUVEZPWFSZFBSTDPOEVDU-ed in a private practice by a specialist,

documented an overall success rate of

91.5%.80 Initial endodontic treatments

IBEBIJHIFSTVDDFTTSBUFDPN-pared to the non-surgical retreatment

HSPVQ 5IJT TIPXT WFSZ DMFBSMZhow important the quality of the first en-

dodontic treatment is for the long-term

success. In addition, the coronal resto-

ration has a significant influence in the

success of the endodontic treatment.

Thus, to strive in every respect for an

optimal restoration is as essential as an

optimal endodontic treatment alone.81

The second reason is that measures

to potentially save a compromised tooth

can later preclude the placement of

an implant or make it very demanding.

Therefore, if an endodontic retreatment

due to recurrent apical pathology is

considered, above all, careful diagnos-

tic steps including soft and hard tissue

probing and radiographs are required.

Conventional radiographs do not allow

proper analysis and interpretation of the

root and remaining bone housing around

the root. The possible causes for the

endodontic failure (eg, crack, fracture,

perforation, insufficient root filling or ac-

DFTTPSZSPPUDBOBMTDBOOPUCFQSPQFSMZestablished without a high-resolution

$#$5BOEDPOTFRVFOUMZUIFQSPHOPTJTand appropriate treatment approach

can only be determined based on an

accurate diagnosis.

Periapical microsurgery should be

performed exclusively if non-surgical

endodontic retreatment is not viable,

MEYENBERG


70-6.&t/6.#&3t46..&3

and if the remaining bone housing is suf-

ficient. The surgical approach seems to

be more successful in the short term, but

MFTTTPJOUIFMPOHUFSNPWFSUP6 years for the non-surgical approach,

WFSTVTPWFSNPSFUIBOZFBSTGPSthe surgical approach.82 In addition, the

added bone loss caused by the surgical

access osteotomy and incomplete heal-

ing can make the placement of an im-

plant after a potential failure and eventful

extraction very difficult.

Ultimately, when we examine the treat-

ment outcome of implant versus non-vi-

tal tooth-supported restorations, there is

no clear winner in terms of sustainabil-

JUZFTUIFUJDTCJPMPHZBOEGVODUJPO#PUIsolutions require a perfect synergy of all

the fields of specialties involved and the

treatment steps to achieve the optimal

result for the individual patient.

AcknowledgementsThe author would like to thank Dr Tidu Mankoo for

the systematic and thorough editing of the whole es-

TBZ%S'SBOL1BRVGPSIJTTVQQPSUJOUIFEJTDVTTJPOof the endodontic aspects, and Walter Gebhard and

Nic Pietrobon for their contribution in creating the

dental ceramics.

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the ideal restoration of endodontically treated teeth structural and esthetic considerations a...

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