2023 Clinical guidelines for posterior restorations based on Coverage, Adhesion, Resistance, Esthetics, and Subgingival management.pdf

Restauraciones indirectas

1. CLINICAL RESEARCH

Clinical guidelines for posterior

restorations based on Coverage,
Adhesion, Resistance, Esthetics,

and Subgingival management

The CARES concept: Part | - partial adhesive
restorations

‘Jorge André Cardoso D
Posto Univers, Portugal

MCimDent and Postgraduate Tutor in Prosthodontics Kings College London, London, UK
Private Practice Espino, Portugal

Paulo Julio Almeida, 0140, 290
Porto University, Portugal

Viting Professor, Porto University, Portugal
Private Practice, Gaia, Portugal

Rul Negro. DD
Porto University, Portugal
Prvate Practice, Porto, Portugal

‘Joo Vinha Oliveira, 9110
ISCS-N University, Portugal

MAS and Assistant, Microinvasive Aesthetic Dentistry, University of Geneva, Switzerland
rate Practice, Neuchatel. Switzerland

Pasquale Venuti OND
Naple Frederic I Unversity (cum laude), tay
Private Practice, MrabelaEclano Katy

‘Teresa Tavera DD.
Porto University, Portugal
rate Practice. Espinho, Portugal

‘Ana Sezinando DW) PhD
LUsbon University, Portugal
Prvate Practice. Porto, Portugal

Consgonsence 1 0 Jonge Ae Cardoso
(hl cine ua 2 344, 3 4500142 Espo, Porugk Ta «35195621312: Ema operen

244 | mers Det ee tte mes

2. Abstract

Important changes have occurred over the lat dec«
des in the clinical aplication of the strategies for
posterior restorations - rom amalgam to composites
In direct restorations and from tadiional resistance
form crowns to adhesive partial restorations such as
oniays. Despite much evidence avaabe or these ad
vances, there ae stil very few estabished guidelines
or common cinical questions: When does an indirect
restoration present a clinical advantage over a direct
‘one? When should one perform adhesive cusp cover-
‘age such as an onlay? When to implement resistance
form designs in adhesive restorations? Which condi
tions create imitations fo adhesion so hata resistance

CARDOSO ET AL

foe preparation with à tr matenal such as a vd
ional crown might be more appropriate? In order to
provide cinica guidelines, the present authors consi
er five parameters to support and claify decisions =
Coverage of cusps, Adhesion advantages and Imita-
‘ons, Resistance forms to be implemented, Esthetic
‘concerns, and Subginghal management - the CARES
‘concept. In Par of ths three-part review article. the
focus ison clinical decisions for partal adhesive res
torations regarding indications for direct versus ind
rect materias as well asthe need for cusp coverage
{andlor resistance form preparations based on remain
Ing tooth structure and esthetics

Int Esthet Dent 2025:18:244-268)

1245

3. CLINICAL RESEARCH

Introduction

Concepts involving minimal intervention
ethical balanced with the patients esthetic
requirements, seem tobe the deis focus
for an evidence-based practice of restora-
tive dentistry. Restoring posterior teeth pre-
sents specif demands, inherent diferen
from the demands of anterior teeth. Pos-
terior teeth ae a) anatomically and histo-
logicaly disinet and 2) withstand occlusal
forces that a significantly higher and have
diferent deectons compared with anterior
teeth. These two differences have an im-
portant impact on how to restore tooth
structure in damaged posterior teeth

The quantitative analysis ofthe remain
ing tooth structure regarding the decision
between an adhesive versus a resistance
form restoration is not well defned for
posterior teeth, Moreover, when a posterior
adhesive restoration is chosen, there are
‘extensive recommendations in the ltera-
ture regarding preparation designs or in-
lays onlays and overays. The reasons for
this varity are rather obvious — itis ifeult
to measure the progressive degree of issue
loss and the influence of diferent prepar-
‘ation designs in clinical studies. Cinica de-
‘isons, such as selective cusp coverage,
the influence of tooth vialty, the extent of
verical reduction, and the amount of cir
cumerental involvement of preparations,
stil lack clarification and consensus. Al
though iti difcut to provide staighfor-
‘ward and absolute protocols, tis important
to formulate cnica! guidelines, or at least
thought processes, that are not only based
‘on evidence but are alo pragmatic in the
sense hat they should be clinical helpful -
easy to understand and implement = 10 à
‘ast majority of prattioner In his context
the main objectives of the present article
+ Cover the specife and relevant bio-

‘mechanics of posterior teeth

246 | merca mln Omen ere titane Stet

+ Present sequential degrees of issue loss
that canbe related to clnical real,

+ Explin how each degree of issue iss is
related toa decison theshold regarding
preparation design, according to, val
able evidence,

+ Provide simple-to-use directions for re-
storative sateges, rom simple replace-
ment of lost tissue to preventive cusp
‘coverage, making use of adhesion or
resistance sole or in combination, and
trying tomaitainnatural esthetics, hen
‘ever possible, as well as dealing with
subgingival areas ~ the basis for the
CARES concept

Biomechanics of posterior vs
anterior teeth

Anterior and posterior teeth citer in terms.
of ther anatomy and histology. rs consen-
sual thatthe poster teeth protec the an-
terior ones by bearing more intense, vert
cal compressive load, and thatthe anterior
teeth protect the posterior ones rom tensile
forces by guiding a disclusion mechanism in
lateroprotusve movements Posterior teeth
are wider, mulirooted, have later cusps,
‘and have a distinct distribution of dentin and
enamel tssue at the dentinoenamel junc-
tion (DE). This complex histologic junction
‘of a highly sf ang bitte material = enamel
‘with an elastic tissue (dentin) proudes the
tooth wih the unique capaciy to withstand
loads in the posterior region. This stucture
is characterized as a less mineralized iter-
face that gradualy intereites the two
tissue types, withthe capacity to undergo
transitonal deformation Although this area
ispresentinalltetn, ts surface area is more
extensive in posterior teeth and has a spect-
ic design Its important to understand this
histologic interconnectivty ~ the convex
enamel and concave dentin surfaces (re-
sembling a sigmoid curve) - to establish
more effective restorative strategies (Fig 1)?

4. CARDOSO ET AL

Tissue loss and occlusal load usualy needs to reach the dentin to ensure
anterior teeth where enamel preparation

The concept that tooth resistance is in- can be minimized Posterior e
directly proportional to tissue loss, U

aso de

fact mand more resstant restoraive materais

hat restorations are never lifelong and may than those required for ante

need replacement, and the favorable cón- example layered feldspathic porcelain does
idence of adhesive procedures sup- not guarantee acceptable long-term results

port minimaly nase approaches. How- in cusp coverage restorations in posterior

ver, the relationship between tissue loss teeth, whereas & does in anterior teeth In

andresistance compromise does not follow the posterior region, more resistant, re

he same proportional correlation in poster- inforced glass-ceramics should be used as

ior and anterior teeth. For example, an en- adhesive materials

dodontc access cavity associated withthe

loss of one palatal Materials for posterior partial

may not pose a high facture risk and the adhesive restorations

need for à ful-coverage strategy is debat

teeth. For

able However, there seems to be sufficient Some review studies show signicanty
‘evidence for the need for a fu-coverage higher long-term survival for ceramics com
jestoration in an anterior tooth with paatal pared vá

marginal palatal ridges’ In viro studies pantal ceramic and composte restorations
show that simiar lesions in po (of about 90% at 5 years! The 10-year sur

signiteanty benett from paria vial ate for ceramic restorations seems to
plete cusp coverage wth a preparation that be around 85%. but this rate probably drops

5. CLINICAL RESEARCH

10 80% in composites. Nonetheless, most
reviews state that there ae sl not enough
‘wel-conducted studies to clearly prove the
lnical superior of ceramics ®

‘Composite resins can provide accept
able long-term clinical behavior ata lower
‘cost than ceramics and are easiy avalable
to most dental professional. Their use is
very appealing in posterior teeth since they
‘can be used drecty in a noninvasive or
‘minimally invasive approach and are easier
10 repair. making them appropriate for
‘younger patients and for testing occlusal
‘changes in more extensive renabiltations
They also provide less abrasion on the of
posing teeth compared with ceramics?
With the use of compost resins indirect,
restorations allow a better anatomylcontact,
Point, the materia shrinkage is ite tothe
‘cement gap. and better physical properties
are provided due to the improved conver
sion of poymenzation® Nevertheless, there
are no significant differences concerning
the sunwal of direct versus indirect com-
posite resin in the medium to long term’
The main concern with composite mater-
las with an organic max is the loss of
Physical and optical properties due to hy-
{ross in the oral environment. However
they are easy fabricated chairsie through
CADICAM technology. CAD/CAM alows
the use of composite resin blocks with im
proved physical properdes.? but ls sul
unénoum whether they provide significant
advantages regarding organic degradation
‘over waditonal resins in long-term oral
function,

à ceramic material is chosen, mono-
lite leuciesemiorced or thium distiate
glass mat ceramics seem 10 be the safest
‘option when adhesion is performed due to
thee high facture resistance within the
etchable ceramics group. They ae also ver
sae as they can be pressed or CADICAM
milled and easiy stained for adequate es
thetics for posterior teeth. Both materials

2448 | merca vt oy re time sine

have acceptable behavior in cnica tudes,
but llum dilicate wit tkely have better
long-term performance in more chaleng-
ing situations due to. higher inns
flexural svength*

‘Adhesive cementation can be cared
‘out with ight-cured resin cement orheated
composite with proper treatment of the
restoration interface dentin, enamel, dentin
sealing resin coat or composite buidup)
and proper surface condiioning of the
restoration. Heated composite may provide
some advantages compared with resin ce-
ment as a luting agent such as easier re-
‘moval and beter Biomechanical properties.
However, there is sil no evidence to prove
that they provide clinical advantages in the
long term compared with resin cement?

Coverage, Adhesion, and
Resistance

Based on the above clinica factors, is im
portant to uy to apply a rational thought
Process that provides helpful, logical and
Simplifed guidelines to implement when
making choices for restorations. In order to
do this an anal of sequential degrees of
tissue Los ls considered below as wel as
the cinical implications In order to clarity
the insights, the diferent aspects of the
CARES concept ~eoverage, adhesion reten
tion, esthetics, and subgingival manage-
ment = are presented in parle.

How much residual functional issue
is maintainable?

Tocorecty analyze tissue loss ‘maintainable
functional tissue must be defined. The frst
requirement is that & should be supported
undemeath by heathy noncarious tissue
Even though there is some evidence of
tissue remineraization when sealed from
the oral environment. tom a prosthodontic
Perspective Isis not agusabe. Ris lsonot

6. Ti! Siena act anc cr acom when econ en penne cp courage

entra cavity depth

CARDOSO ET AL

+ The most decisive factor seems tobe the combination of avy
depth versus waltniness
+ Couties deeper tan 4 mm (sn ET) wiligißcanty erat

Internat fom cusp coverage remaining wäls ave 3 mmr les

Buccalaná lingual wats dern

+ In roto eaves (10 3 mm te wäl pee 1 bees than
12 mm or coverage indication

+ These ae thought processes rather tan sit quienes and
ica context muy have an intuence

(Sue toimerproxmal secondary cares

lear whether restorative materials can etfec-
tively substtute dentin under unsupported
‘enamel Moreover, here ae technical hat
lenges in successtuly removing carious +
sue rom underneath occlusal enamel, Once
unsupported tissue i removed, the second
requisite sa minimal wal thickness that must
be maintaied, the measurement of which is
GK clear in the Werature, Most authors rec-
lommend a minimum wat thickness of be-
‘ween 1 and 2 mm in order for à posterior
tooth to be directly restored without cusp
coverage Therefor. ts recommendedthat
‘unsupported tissue be removed and thin
als be vertically reduced uni a minimum
wal thickness of 1 mm is achieved

Replacement of lost tissue or
‘preventive cusp reduction?

A pivotal decision to make is when preven-
te reduction for adheswe coverage is ap-
propriate or when to perform adheswe
replacement limited to lost tissue since this
wil lead to completely diferent retora-
tive approaches. This decision will depend
mosty on structural factors and the cnica!
(Context such as funcional oad
Swuctural factors to be considered
(atte):
+ Central cavty depth including the endo-
omic access caviy. i present (pul.
chamber roo loss

‘evant cir errores ¡rms | 249

7. CLINICAL RESEARCH

+ Buccal and Ingual was

+ Irterproimal marginal âges and contact
poin.

+ Enamel cracks

+ Conical lesions

AS demonstrated in several in tro studies,
these factors act inerdependenty in their
contrbution to overall fracture risk, making
lincal decisions citicut First, iis import
antto dstingush classical in vito studies on
Cusp coverage before adhesive procedures
(amalgam, o's, and other cast metas tom
‘contemporary studies that should now be
“considered, where adhesive technology is
used wah resins and ceramics. The interax-
al dentin in the tooth center (dentin around
‘and above the pulp chamber) has been
“consistent established to be the most Im
portant factor in posterior tooth resstance
The amount of interaxial dentin can be ex-
pressedas a conjunction o the cavity depth
and peripheral dentin loss. Therefore, inter-
axial dentin loss depends on the cavity
“depth Gncludiag endodontic access cavity)
as well as the remaining wal thicknesses.
‘The mote the inerasal denin loss, the
more ley the remaining wal willbe prone
to residual stresses and facture Athough
several authors have proposed guidelines
for the minimal wall thickness threshold in
order to decide whether cusp coverage
should be performed, there is not enough
Scientific clay on this.

Invitro studies suggest that cavty depth
is significantly more important than buceo
lingual wall thickness For example, in vit
ro studies show that molars wth MOD cav-
ities with up to 3-mm depth do not seem
tohave signifcanti increased fracture risk
even with wals as thin as 05 mm Once
the occlusal preparation depth reaches
5 mm asin deep caves of vial teth orn
endodonticaly treated teeth (ETT) where
the pulp chamber becomes part of the oc-
clus cavity, the risk of fracture is high,

250 | mewn dette Onn ne tne tam

leven with 35:mm-thick walls!” On the
‘other hand. a simple endodontic access.
‘cavity, and consequently 3 preparation
deeper than 5 mm, without any other asso-
ciated structural oss, does not cause asig-
icant reduction in toot tfness. How-
ever, if the access cavity is associated with
the loss of marginal ridges and contact
points, the tooth is structurally compro-
mised* Therefore, there is an intede-
Pendent relationship that needs to be con-
Sidered between cavity depth, remaining
wall thickness, and marginal ridge/contact
point involvement

The presence of enamel cracks Incom-
plete fractures without noticeable separa-
tion) is another factor to consider regarding
the decision about cusp coverage” since
they can progress into the dentin. Trans
ilumination can be very helpful to Wentiy
these cracks. Cracks that might demand a
restoratwe approach will cause a defined.
light blockage in a transitumination analysis.
Craze Ines, on the other hand, are physio-
logic Andings on enamel and are not con-
sidered to be biomechanicaly susceptible
zones. they will provide a continuous ight
passage in a tansilumination analysis” If
the examination reveals that cracks are
present, most authors recommend that the
respective cusps be covered because the
riskof propagation and facture seems high
However, what à not clear is whether the
preparation should continue to completely
remove the asymptomatic cracks, in case
they extend further than the required space
for the restorative materia

Cervical lesions can affect stress dé.
tribution and resistance, but compose
resin restorations can effectively reestablish
biomechanical characterstes to. values
similar to urvesored teeth Therefore, the
presence of cervical lesions may not be a
decisive factor for cusp coverage if com-
Poste resin restorations are to be per-
formed. However in case addtional anal

8. preparation is considered in order to
{crease resistance. oF for esthetic reasons as
discussed below, then the cervical margin
‘wil have to extend to the cervical lesion
Nevertheless, the etiology of the lesion
needs to be addressed abrasion, abraction,
‘erosion, and periodontal recession for ade-
{quate prevention or treatment. This fre-
{quently imvoves improving local soft issue
‘conditions. idemifing and controling
‘brushing (abrasion), dietary habits (erosion.
and occlusal management.

“The functional Io i an important fac-
tor for making decisions about cusp cover-
age A tooth more posteriory postioned in
the mouth, the presence of bruxism, and
the absence of protective anterior guidance
during excursions wal potentaly promote
higher ads. Bruxism is known to be assoc
{ated with higher prevalence of mechanical
technical complications in prosthodontic
eatments The presence of erosion also
a modiing factor that can reduce enamel
thickness. If left untreated, not on) can it
deteriorate the remaining dental tissue but t
{can also damage restorative materials that
‘contain organic components such as com-
posite reins These factors wil make a de-
Ccsionin favor of coverage more Ike, even
in teeth with less sructura loss.

Notwithstanding how interdependent
these factors may act, mistakes in cincal
{decisions may compromise tooth survival.
wäh high biologic and financial costs for
example where an imeparabe fracture could
have been prevented if some or al ofthe
remaining cusps had been conecty cov-
fered, Therefore, i is important to present
cinical guidelines that constitute a balance
‘between minimaly imasive procedures and
protective strategies in cases with signi
Can fracture isk In order to do this, quart
‘Heaton of the remaining structure needs 10
be considered, based on avaiable in viro
and cinica evidence.

CARDOSO ET AL

When should a simple adhesive
replacement of lost issue be performed.
without cusp coverage?

As stated above, posterior teeth with suff-
‘lent interail dentin central occlusal cav-
y upto4 mm de, val teeth, without an en-
odonsic access caviy, buccal or ingual
‘wal thickness of at least 1 mm, absence of
{racks or other signs of heavy mechanical
and chemical stresses ~ do not seem to
need preventive cusp coverage” (Figs 2
and 3 A direct adhesive restoration limited
to lost Ussue seems the most reasonable
treatment to perform. Any addtional tooth
preparation should be limited 10 beveling
‘enamel margins for adhesive optimization
Even though 1 mm is being considered as
{the minimum thickness (for up 10 4-mm=
deep central cates to avoid cusp cover-
age. judgment of the clinical context such
25 high occlusal loads, enamel cracks or
{erosive action may igitmize a decision to
cover the cusps in these cases, even with
2-mm-hick walls With shalow centalcav-
‘ies upto 4-mm deep, anda remaining wall
thickness of 10 2 mm, the use fan indirect
restoration without cusp coverage (an inlay)
‘may not provide significant advantages over
a drect composite restoration as restes a
more invasive preparation ata higher cost
wihout à clear cnica! advantage Since
‘the restorative volume is reduced in these
shallow cates the polymerization depthis.
efecine, shrinkage and stress on the re-
maning als is potentialy lowe, and an et.
fective contact point is ciicalypreictable
(#9 31% Athough these numerica tecom-
‘mendations can be helpful they should be
seen mote as an evidence based thought
process; a fleble clinical guideline rather
than a sit decison ree.

When should preventive reduction for
adhesive cusp coverage be performed?

en the cavity depih is 5 mm or more = as
Is the case of ETT or deep cavities in vial

Denon cir emociones rss | 251

9. CLINICAL RESEARCH

OS
socees cones

210 — DECISION ON AXIAL EXTENSION OF THE CUSP COVERAGE

252 | nem

10. CARDOSO ET AL

195 lit aon win cates on emo an star amos arc te. reia
are esca nas pas Ra es aser u tc gland te et
Fat cto

teeth -andis associated with marginal ridge
loss, then cusp coverage needs to be con-
sidered, even for teeth with remaining wals
‘of mm thickness. In these deeper cavities,
‘the volume of nteraal dentin loss is signi
cant higher, and more sess is present in
the preserved wals (Fig 21

itis worth mentioning the suggestion of
some authors to use Aber or short fber-
reinforced direct compostes in ärge cavities
35 a possble atematve to more complex
indirect restoraive weatment. The idea be
hind this that the improved biomechanic-
al and physical properties of these direct
materials may reduce the need for cusp
(Coverage in large cavities, including ETT, a5
is shown in some in vito studies However,
other in viro studies show that fberrein-
forced compostes cannot replace the need
for cusp coverage.”

Selective or complete cusp coverage?
Ie Is generally accepted that indirect pos
terior restorations can be classed as nays
(no cusp is covered), onlays (at least one
‘cusp covered), and overays al cusps are
covered), The choice for maintaining some
‘cusps (onlay restoration) or covering at
‘cusps (overay restoration) depends, agan.
‘on structural and functional factors (Fig 2)
“There can be structural factors indicating a
need for coverage in the mesial cusps
(deeper cavity, inner walls or ridge los in
the mesial area) but not in the distal area
Tissue preservation would be the obvious
advantage of maintaining some cusps, but
‘here are some disadvantages depending on
the situation. In patents with a high cares
sk, the interproximal area that has been
preserved may develop lesion in the fu
ture, A revision treatment might be simple it

ed

11. CLINICAL RESEARCH

the previous restoration is à resin since a
predictable adhesive repair protocol can be
Performed Ifthe previous restoration is a
‘ceramic, some diftcuties regarding repars
‘can be expected, Even though bonding of
ceramics with thn luting esin agent shows
‘excellent long term behavior, in the present
authors experience. repairing ceramic trace
tres with higher volumes of composte
resin does not seem to produce the same
predictable clinical resul, probably due
to diferent elasic modal. An adgtionat
Perspective is that tooth-restoration inter-
faces on the occlusal surface in teeth that
are gh susceptibie to deflectve forces
may also present a weak point for margin
degradation * Therefore. before deciding to
preserve some cusps, the clinician should
“consider the age, carious and functional isk
‘ofthe patient and management of secondary
‘caries or fractures

How much veria! reduction is needed for
‘cusp coverage?

Studies suggest between 1 10 2 mm as
the minimum verical eduction for cusp
‘coverage. depending on material choice
CADICAM composte resin and lithium die
slicatereinforced glas-ceramics seem to
need ess reduction (round 1 mn” while
CADICAM feldspathic and eucite enforced
gass-ceramies need more occlusal volume
(closer to 2 mm: Fig 4) When the enamel
is preserved on the occlusal surface, such
asin cases with a raised vertical denension
‘where occlusal reduction isnot needed, the
‘materia thickness can be reduced due to
the higher sifinss ofthe substrate

úOcclusal preparation design for cusp
coverage

Cases of complete cusp coverage. where
no addtional axial preparation i performed,
have been refered to in the terre as
overay table tops or ‘occlusal veneers In
these cases, where most of the remaining

254 | newton dette Det ee tne amer

‘wall height is more coronal to the tooth
equator. there seems to be no biomechan-
ical reasons for addetonal axial preparation
as explained later in this article This design
Is also possible when there are no esthetic
demands to cover à buccal wal in a dé
‘colored tooth, for example The occlusal
reduction should be concave folowing the
natural concaviy of the posterior occlusal
surfaces (ig 4). This anatomical preparation
has been shown to be significantly benef-
al a5 ensures adequate thickness in the
central suicus® Although no further anal
preparation s needed, there are sil afew
possiblities regarding the peripheral fish
ing Une on this type of preparation. simple
90-degree but joint would be the simplest
margin to perform. However, preparing the
enamel parallel to its prisms is not ideal
Bonding srengthto a surface thats parallel
Lo enamel prisms can behalf of what can be
achieved in surfaces that ae perpendicu-
lar Therefore the propostion by some au-
thors to use alight chamfer ora bevel at the
margin may have bene in terms of mar-
inal imtegtty and the maximal enamel sur
face for adhesion (Fig 4) Yet Ris most di
cut with these conservative margins to
optcaly hide a anstion ofthe restorative
interface. In esthetic stuatons, such as in
the case of maxilay premolars, a diferent
‘approach might be needed, as discussed
later inthis atc

When should marginal rages and the
Contact point be included?

A common question is when to include the
marginal ridge andlor the contact point in
the restoration A lost marginal ridge will ob
Viousy be included i a decison is made to
‘cover its adjacent cusps. The doubt usually
arises when a decision is made to cover the
cusps adjacent toa marginal ridge that iin“
act with is contact point. In most cases.
is recommended to include iin the restor-
ation. especialy when the remaining

12. CARDOSO ET AL

CONSERVATIVE ESTHETIC RESTORATION CONTACT

Kr’,

P
2
2
E
<
=
©
E
5
u
x
w
A
a
E
x
a
<

marginal

je 5 less than mm thick lab> When should retentive designs be
ence of DEI, presents cracks or the inter- added to ‘occlusal veneer’ or table
face willbe in an opposing occlusal contact top’ overlays?

‘also depends on its verica

When to perform an ‘occlusal veneer or
iterproxmal area. In younger patients. table top’ ont? When to further prepare?
here can be enough space to ensure a Howto provide more volume tothe restor
minimum of 15 mm for restorative thick: 3

ness, which can include the marginal idge structural damage? Not ony are these com
in the restoration but st not reach the con- mon decision points, they also fame the

act point, However in worn teeth, the con- issue in simple logical and cnicaly rele
ontext. The easy answer f that these

tact point s usually more occlusa, and in vant

Coder to ensure a minimal restorative thick- decisions ae elated to the remaining

ness, the contact point needs tobe includ- structure, namely the enamel. The ificuty,
€ inthe preparation Deciding to preserve however is how to relate the structural loss
a marginal rdge and/or contact paint can 10. specii preparation design

pose the same risks as when some cusps I is accepted that restorations cannot

re preserved - secondary caes, restora: 1ey 5
ive fracture or marginal ge fracture due espe
thin volumes. sion to dentin s not predctabe inthe ong

‘on micromechanical adhesion,

ly enamel is absent since adhe

13. CLINICAL RESEARCH

term. The more the remaining walls are
‘compromised venicaly. the less enamel is
present and a higher vectorial result hor-
zontal loads induced inthe adhesive nter-
face. An extreme example would be a com
pletely fat preparation atthe gingiva level
that would be tkely to fat due to two Iac-
tors: a) The high vertical restoration volume
‘would subject the bonding interface to a
more intense tensile load: and b) The re-
‘duced enamel thickness in the gingiva area
‘would result in less predictable bonding
Therefore. itis logical to establish a minimal
height of he remaining mals, below which
the restoration must rly not only on adhe-
sion (the table top) but aso on grasping
splinting or somehow introducing ada
tional mechanisms of resistance. However
there are no studies that objectively address
this decison, only expert recommendations.
Inthe erature to date, the decision to go
from a table top’ to a veneeray/'voniay'
(overt with addtional buccal coverage) is
justifed by ether the esthetic needto cover
the visible buccal surface or by a subjective
recommendation regarding more "extensie"
damage

In order to overcome the lack of clarity
regarding tis decision the present authors
propose the use ofa grading division forthe
minimal peripheral height that will date
clica decisions. is important o note that,
this evaluation is performed ater canes re-
moval and the clearance of unsupported
enamel as well as after the verical 1e-
duction of thin wall until à minimum of
-mm thickness is reached, as stated earl.
‘Areasonable and pracica evaluation tresh-
la for wall height can be around the equa-
tor Although it has some variably i isto
‘cated roughly around half theciinical crown,
2 to 3 mm coronal to the cementoenamel
Junction in posterior teeth inthe buccal and
lingual areas. Tis criterion can be import-
‘ant for the predictability of adhesive reten-
tion to enamel and, consequently impact

256 | mewn ett Onn ne tne tate

on the cinical decision Apicaly to this area,

the enamel thickness stats to signicanty

reduce below 1 mm fig 2). With refer
lence in mind, but knowing that this should

be seen more as a thought process than a

strict guideline, the present authors can

suggest three grades that wil have a clica.
impact on the restorative decision, based

‘on the amount of remaining wal height per

tooth periphery:

+ Mig tissue loss: Remaining wats with
‘enamel above haf the height of the in
leat crown (> 3 mm in more than two
thirds ofthe too peripheny

+ Moderate tissue loss: Remaining wats
‘ith enamel above haf the height ofthe
inical crown > 3mm) between one third
‘and Wo thirds ofthe tooth’s periphery.

+ Severe sue loss: Remaining wals with
‘enamel above haf the height of the in
icalcrown(> 3mm) less than one third
‘of the tooth’ periphery.

In cases wth mid tissue Loss, the restora-
tive technique can be a simple cusp cover-
age according to the cena stated above,
‘without any addtional design - a table
top’ or ‘occlusal veneer’ There is stil a
large peripheral enamel extension above.
the equator line, ticker than 1 mm. Adhe-
sion will provide the restoration with the
‘micromechanical stability to prevent &
from dislodging along the insertion path
(retention) or another oblique path
(resistance: Fg 5)

‘Cases wth moderate tesueloss have ess
Sumounding verical structure and enamel
thickness for adhesion, and the present
authors believe that these situations de-
‘mand an addtional adhesive area and/or
‘complementary resistance measures These
measures can include (Fig 2
1. Adal preparation. shoulder/chamter/

long bete ofthe wal, allowing the res

toration to partaly or completely brace

the tooth structure also referred 10.263

14. CARDOSO ET AL

ns mn dep viva als ol crim ane ate The aa INCA rios ef ee uo
‘Sorecamy spread nde er dm stn onthe topa lr et xg nang Adega remar nen
(mer ron o ads al Be pere were peer Mare sme abe op net ein Was sted va we nes or
tors prepa x ron Conact ports wen cui ne prepare sac ein em ace ve
um site ae op as rte strain ater bond al cp) and jeu pospone Bono da.

‘tong wap overlay ora ful contour ‘ad- stil present” The amount of remaining
hesve crown, respectively. tooth structure to wich a restoration can
2. The use of the pulp chamber in cases bond or engage around (Terre effec)
of endodonticaly treated teeth - an seemsto bemore important than the use of

endocrown, à post” Therefore. posts may eventualy be
3. Bothof the above - an endocrown with more indicate for buid-up reconstructions
peripheral ail preparation ‘rice to ful-contour resistance form crowns,

where more extensive tissue losses com-
The use of posts does not seem to provide promise tooth flexural strength. However
benefts in partial adhesive posterior restor- no fundamentalist doctrines for or against
lations when cusp coverage is performed the use of posts have been clearly support-
‘since enough remaining suture is usualy edby scientific evidence In borderine cases

sl 257

15. CLINICAL RESEARCH

even in adhesive restorations, the cinician
may decide that the buildup needs adtion-
al retenton/resstance, and a post may be
used according to certain considerations
(discussed in Parts I and I of ths arte
series)

In cases of severe tissue loss. endo-
crowns can be considered, However, when
achesionisnot predictable. resistance-form
preparations for fullcontour crowns (ds-
used in Par It of ths article series) may
havea better prognosis

Which resistance messures can be added
to partial aahesive restorations? Peripheral

xl preparation or using the pulp cham-
ber (endocrown)?

Shoulders and chamfers asa form of peri
pheral axial preparation have been asso-
‘lated with higher long-term sural of
foniays™ A marginal design in slica-based
‘ceramic materials demands particular atten-
tion since these materials are more proneto
marginal chipping than composite resns
However as discussed iil, hum dis
‘cate seems to be the most reasonable cer
“amic materal to consider for posterior ad
hesive restorations since thinner preparation
designs have been providing good clinical
results. The shouider may provide a safer
marginal design biomechanicaly than a
bevel and 1 mm can be considered the
minimum thickness for the material in the
anal area Since thickness of enamel drops
below 1 mm apically to the equator level
a common doubt exists: a) Should the
axial preparation be limited to enamel and
‘compromise ceramic thickness, especially
below the equator leve? orb) Should the
‘ceramic thickness be maintained, respec»
tie of the oss of some ofthe enamel area?
The thickness of monolithic ceramics can
bbe reduced in the occlusal area if enamel

258 | mms Onn ne tne inner

present. However, when an aval prepar-
ation is added to the occlusal reduction —
a so-called vonlay or Veneertay or à ful
adhesive “crown ~ the matenalis subject to
trent tensile forces. For monolthiccer-
amics in the posterior area, the iterature
seems to favor heeping the ceramic thick-
ness adequate and aloning some prepar-
ion into the dentin in the axial areas.
“while tying to maintain some enamel at
least in the margins when the preparation
needs to extend below the equator for
structural or esthetic reasons. Therefore,
Cervical lesions should be covered by the
ceramic restoration, ensuring that a prev-
ous direct composte is performed to re-
duce lesion depth. preventing undercuts
‘and unnecessary tooth preparation. How-
ever, in premolar teeth, especially in resto
ations mainly for esthetic reasons, it seems
reasonable forthe preparation to remain in
the enamel, using the same strategy as for
‘veneers in anterior teeth

Another important consideration is that
the buccal or Ingual axa preparation mar-
gin should extend into the imerproximal
zones to gradually connect tothe ishing
line in hat area whenever marginal ridges
have been reduced, so thatthe contact point
isincluded within the restoration Fg 6)

Endocrown - use ofthe pulp cham
Whitin the case of an onlay or overay the
pulp chamber is previously restored with a
rec restoration, the endocrown uses the
pulp chamber for additonal adheswe area
and resistance ofthe indirect restoration i
se Figs 27, and 8). Recent reviews reveat
highiong term successratesofendocrowns,
‘comparable with post and crown resto
ations for molars and premolars“ Although
Promising, this modality needs to be con-
sidered careful due tothe limited number
ot available cinica studies. It is not clear
‘whether adding a peripheral aval emule”

17. CLINICAL RESEARCH

FERRULE’ BUTT JOINT EXTENSION INTO
rocas DESIGN OR | MARGINS PULP CHAMBER

AR <P

13

ENDOCROWNS

ms can easy reach
xe. Even though an effective

curing depth of up to 8 mm has been

Previous buildup and dentin sealing

le signitcant advantage essary preparation of tooth

ing studies exist inthe iter

Denen

Less an endocrown has been chosen forthe
dations rom filed with a

à recent review include an extension of butdup (fi 6

jp chamber witha ‘Freshly cut dentin should be simulan

18. Cf composite resin (Rowable or packabie
This wil prevent denin contamination and
ypersensituty during temporizaion and
dissipate the polymerization tension ofthe
‘adhesive interface while bonding, thus in-
{teasing immediate dentin bond strength
compared with adhering the restoration dí
ty onto the dentin without previous seal-
ing Besides a few in vivo studes, daa ae
lacking regarding long-term cínica advan
ages of dentin sean, except ha seems
to increase long-term restoration survival
hen the dentin occupies more than 50%
‘of the surface for anterior veneers”

When should the transition be made
from an adhesive restoration toa
resistance-form crown in the clinical
decision?

Using the same pragmatic logic of remain-
ing verical height per tooth periphery. in
(Cases o severe issue loss - remaining wals
above hall the tooth’ height (> 3 mm). in
less than one tht ofthe os periphery =
‘the amount of enamel avaiable for adhe-
sion is significant imied. As previous
stated, there are promising clinical data
{concerning the long-term performance of
adhesive endocrowns in cases with a Imit-
‘ed amount of peripheral enamel. Given the
{900d clinica results even incases wthouta
‘ferrule’ design. endocrowns can be consid-
‘ered in teeth with severe issue Los; for ex-
‘ample. when alte wal ae lessthan 3 men
ie stil supragingial exhibiting atin but
fully present enamel layer throughout the
periphery. though there have been prom
sing studies for the cinial performance of
‘endocrowns, a wadional high-stength res-
{erative material with a resstance form prep-
{aration (crown) stil has important ong term
‘scientific support that justes its use in se-
verely damaged teeth. When adhesion snot
reliable limited or absent enamel, it isthe
‘crown engagement. grasping or embrasure

CARDOSO ET AL

Inthe tooth structure (creating teri de-
Sign) that is mani responsible or the res-
tortion resistance These types of resist
ance form preparations, traditionally
referred to a5 crowns’ are fly discussed in
Par io thes article eres

Esthetics

Posterior teeth are less vibe and ar there:
{fore les of an esthetic concern, However,
this snot true for al patents as some have
higher esthetic expectations and may not
accept or understand an esthetic compro-
mis in favor of sue conservation. For this
reason, in order to manage these expecta-
tions ii important that clear explanations
and good communication is developed
before the stato treatment

Esthetics in posterior teeth can involve
a Blending of the optical properties of par-
tial restorations between the restored and
preserved areas within a tooth in more
vistay exposed buccal/occlusa areas: and
') Blending ofthe pica properiesbetween
the restored and adjacent tet,

Regarding optical integration in paria!
restorations, what needs tobe considered is
‘that in vial teeth, a successful immediate
‘optical blending of the restorative material
wäh the remaining sructure wil probably
be maintained in the long term However
‘uncovered areas in nonvital teeth are very
likely to become progressnely dscolored
ah time While some patients may accept
this color contrast and understand the con-
servatve advantage, others may be dssats-
‘hed, even in areas that seem lest exposed
during smile. Moreover, the preparation
depthiesteraive thickness needs to be ad-
dressed in case of décoration. Heavier
scoloraions may need a preparation that
goes into the dentin and might demand a
Subginghal margin. This can eventually
change the conseratve/adnesive restora-
tve decision that was exclusively based on

Denon cir oem | 261

19. CLINICAL RESEARCH

C— monolithic eucite-reinforced glass-ceramic D — Nonvital tooth intact

sistance form approach as enamel is re
‘moved, Therefore, options should be ds
cussed with a patent to find a balance
between à consenative approach and es
thetic satisfaction (Figs 4 and 6.

In tems of optical intégration with adja
cent teeth, especially relevant in maxilary
premolars, iti important to realize thatthe
se of monolithic ceramics is fr from being
as predictable regarding the match with nat
ura teeth as layered ceramics. However
‘monolithic mullayere blocks canbe he
ful to mimic diferent vanstucencis within
the restoration. Monolthic restorations that
are stained oF minima layered in nonfunc
tional teas need to be mastered inorder to
create optical ilusions of depth, trans
cency, and value/bighuness, especial the
adjacent teeth are natural and the patient is
young, In heavily discolored tee, the need
to hide the subsvate may require a prepar
ation depth of more than 1 mm, removing

remaining enamel and reducing bonding
performance.” For this reason. these sita
ations may aso demand adationalresstance
form measures or even the decision for a
fultcontour resistance form preparation
and forthe adhesive option to be discarded
Internal bieaching can also be performed,
anatyng riss and potential benefits, always
considering that color stabity in the long
termis not predictable ©

Fluorescence is a crical but often neg
lected part ofthe optical result that wit po
vide better metameric behavior (ess var
abity in diferent light conditions) and wil
result in ess shadowed cervical ares, espe
ciatyin dark substates ean increase value
Drigheness without affecting translucency,
especialy important to nonvial teeth that
lose fuorescence properties. Lithium di
sticate and zrconia, for example, have à
very low fluorescence and bightnessvalve
compared with natural vial teeth (ig 9)
For these reasons, implementation of

20. fuorescence is particulary important in
{dark teeth through the use of proper ceram-
le ingots and fluorescent laze or by layer-
ing fluorescent feldspathic porcelain.

Subgingival areas

As shown in Figure 2, once decisions have
been made regarding. frsty. the need for
coverage, and secondly, the choice of an
adhesive partial restoration. the subgingival
areas can be adéressed For mils to moder-
{ate tssue oss o be restored with partial ad-
este restorations, possible approaches to
manage these areas ae soft or hard issue
remoul (gnghectomy or osteotomy) or
margin etesation or a combination ofboth.
Extrusion can addtonally be considered
Strategies and indications for subgingival
‘management wil be thoroughly discussed
in Par Il of thes arce eres

Conclusions for partial adhesive
restorations within the CARES
concept

Posterior teeth die from anterior teeth by
having à distnct anatomy and a more com-
plex histologic distribution of the DEJ, en-
ing them to sustain higher loads. Clear
guidelines are important to enable clinicians
10 teat these cases wth minimal invasive
‘approaches and preparation strategies. such
as cusp coverage, that prevent ireparable
fractures, especialy in more compromised
‘endodonticaly reated teeth. A few consid-
erations are of paramount importance to
better understand and clanty the CARES
concept and to provide simpiied and
easy t0implement clinical suggestions
Coverage and Adhesion
+ Imerail dentin (central cavity depth and
remaining wall thickness) seems to be
the most relable parameter found in

CARDOSO ET AL

the tterature to decide 10 simpy replace
lost tissue Imainy adhesive or perform
Preventive cusp coverage reduction
{adhesive cusp coverage gras)

+ Cusp coverage extension options need
Lo consider the thickness ofthe restora-
{ie material and the possible moe
ment of marginal ridges and interprox-
imal contacts as well as the advantages
and limitations for each patient (carious
and functionalist
Sealing of dentin wih a preliminary de
rect tesi coat or compost buildup wil
improve bonding etfectweness, alow a
smoother surface, and alow less invasive
preparation designs.

Resistance:

+ In addon to adhesive occlusal cusp
coverage. some resistance mechanisms
may needtobe incorporated such a ur-
ther anil eduction o the use ofthe pulp
(Chamber oF both This ait eduction wäl
influence the grasping of walls and mai
‘mize the enamel surface for bonding
The exact crteria for addtional resist
ance measures are not clear, bu itis
reasonable to use the relative amount of
the height of the remaining wall inthe
tooth periphery as a parameter for this
decision

Esthetics:

+ Esthetes even in posterior teeth, may in
fluence the preparation design and depth
to be more cenácal in order to include
the buccal surface and its wansiion to
the interproximal areas.

suegra management
Once the decision is made to provide à
partal adhesive restoration, tssue re-
‘moval, the elevation of subgingival areas
or extrusion ae possible strategies to far
“tate impressions and bonding proces
res in accessible margins, as wil be de
Ccussedin Par I ofthisaricie series,

means atomes | 263

21. CLINICAL RESEARCH

References

1 ole Sete D Bou et The
Tan er 20022 482-89,

2 Bars. Mage? Bo Emiten.
bommate tn re ug a
ame approach res.
5 ato Te ar ater rot cart
sent Es Det 201210.
ca xa an Cr

Li GuCh fuctae ensure toot
i re src mt eet
eg Id 20124552452,

5 Sher Maar NA Thoma 05,
Busen Patron gE cron
era rosneses FOP Astemate
teen fhe sal ar compton
tes Pat Seg rou SCA, Ont ater
usos

6 fan AY SL LX FÜR Hamm.
oem cx poromarce
coma en rem a en.
every à mate rar
ma as Ope Den 20146 28-24
7 Rae Blu D Parano et
estmenOucome ont compeste
icons Aros 2030
ro 525 cast man or
9187 monte it. Feeders Rene
Den 208 866665

in 1 jeu pen 1996-20) à
mas says ef poset sus ent
ater 201631050005

9. cu Ene preset ers
Feb andi on mont
(een Open Den 20159:43-481

10 andes inet sn compostes.
2 Corer Der 201015184194,
patcance of rect vein
starve revew Corer Det
20182129

12 Mang A pent NM. Ose 3,
‘ent Sao Fem aan 1
CHOCA he tea a a
Cotes Den es 201695 87-095,

15 Saati Pre À Var Owen
Mango Cra sect compost
rome inne aor
procure tene lou cine
tl JNE Dent 20157 8.00,

LA Gea 2r tom
Sent agp occu eae
ronde y tores resortes Oper Dent
2200-5

15 Rocca GT Rata Kaps! Dec.
Enden ud concep and recedes
a Ronde ray ony Pat
Gains cv rezan 0
reno reson Ht Es Derk
soe

16 Le MR Cho BH Son. UCM,
eel ace creo ene and
remain compcate estan

22 For À Bar GT,
ressare ot oresvey rested mae
teenth teen MOD cay eres
1. Rae Mer Dour Ut
tion tot nes red of
Tonos 198916812816

19 Kaas a agro nd
tren loreto enc eme
an caco, Camera Contar
20, Bare. Mat 8, Mar Ciao
teo spare. Put recreos
far management! encuen
rito Brent 201020803 51.
Chan ince eat Set nd
‘sng tes BNC Or Hen 22202098
22 soonmon/, Oma Caron GE
peda road es 20155 127-156
3 Vana na Fao Borges A
aga ScanmuccT ect mues
eS o nano and
‘uence dentes Oper Det
nose

264 | mascar Si}

24 Pure Oat Comprar
tings india Alien esa Cin
esa 20087 7.79

25 Femere 2. Larson NC ng
"rey of entered he
bet stg or pang csi era
‘roca eons ng cane
‘rae Eat Resor Oot 202135
5

26 Fate Sy Da na Faq
beter endosomes estes
eres win tee
urls esis Den Mate 202.37
Seo

‘Stor Hess compas o
ne recreations aborto
sn compara sesment nO,
ng 201620 959-96.

25 arco Wena Recspece
ras onthe par pacer,
anos

23 Ware M franceses Z Mene,
Tomaso Mamo Um tao
pose ray cnc ao.
trachea tases Cin Cr et

52 Can 30 Aou om
yume ige a race esse
marrons Ince cosmo
‘rae an preparation deg Der Mtr
po]

rester ups tons tre
Mergen Owen Pepsin Terme
32 Senay Y Men T Uber ets
rt up commanereteatorson
su esr lendodotcay
teed mata peris. Posie Der
maus.

55 Fee Poser nant reve
rescates (FAR ron es 0
Sarees ia rico Ene
‘ent 200712482502

54 Pari à Dun borng rates
pe

22. 35 Gone FE Gama nest coe
sn permanent naar m made em
‘aes Am Phys Arpa 2008126
us

SE deCanaoMA Lacan PC ces
Det Guy A Magne Cet picos
concerning he enden vendes
(et wh he re agro
ar On es 248 Sao 1101-18

57 Nowra M Ste
rana Rts G Fer comes
fo Pot con at an
rare stem reve
Jos 01844 212-20

Sa duo à SombroakR Lengety
cea els sojsematc eve
Et Rec Oo 2018 2085.25

50 Tao A Morte an Nose
Srenes nie mana dra
‘rues a sra e arpa
epg tr 3 Det 200735897 902
0 Dept & Meow Romane M
Sig man ot tere dese ot
cames ad ons mesas ses
nina at cer. ca
‘ent 2007 9889-100

Gone, Sue Wot
ing Sb. intunce of reason
(eign ndceame cese on sor
rence and ore modes a pero
Beta conageresertors Jest
‘ent 2015 40 264-275

42 Maca, tr K Su Fer
(Secien Trasero toot nd th
eens 202285 1059-1084
3 Are aA Kam Mote.
Wes Cras Focas retro ma
fy revs weis arent a>
‘coun dee smote te ate.
‘eee à Pame es 20225 40150.
4 Span A LUS Pee Cena Y
Fonue fect meiosis JOR Cin
anses 20645139

15 DANNA de Coro nera a.
er CM eta ect nc.
du ol sh este wend

{a nena mie rent ai.
Endod zus eures

a esk Leet tac dress
On Cemen Bomann

CARDOSO ET AL

ant eo lec 3 Dent 2012
2002 ED gts 2027509,

7 Ging Ce WS Scere
‘tal Paemsece cc mit
ser tn edit eine sa a
yes space cal Den ar
0

0. Fer Portones Om Fen
Coco, CaoncnF Rec
eu eco sem onda
ay vts et 3 Eres Det
ae e

2 Samara Papas.
Sahara toutes meat etn
si, ts eeu Ci Court
ve Den 2021125 256

50 Vp CAM Pera MRCS FS.
mas. meer any a
eo Dan 20183039707

Io esingguposes Pess cote

core näherer neck