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From ‘Direct Versus Indirect’
Toward an Integrated Restorative
Concept in the Posterior Dentition
NJM Opdam R Frankenberger P Magne
Clinical Relevance
The decision whether a required dental restoration should be direct or indirect is made
daily in clinical practice. Guidelines for this decision are presented.
SUMMARY
Traditionally, indirect restorations are expect-
ed to have better longevity than direct resto-
rations. The introduction of adhesive dentistry
and the minimally invasive approach of restor-
ative treatment has changed this. In this
article, the differences in longevity between
direct and indirect restorations in the posteri-
or dentition are explained. In addition, the
advantages and disadvantages of direct and
indirect restorations placed in a minimally
invasive way and using a proper adhesive
technique are described.
INTRODUCTION
Numerous dental restorations are placed each day
in human teeth, mainly to restore defects caused
by caries but also those caused by tooth wear
(mechanical and erosive) and fracture.
1
In addi-
tion, because dental restorations have limited
longevity, a significant part of restorative work
by dentists includes replacing defective existing
restorations.
2,3
Basically, restoration replacement results in a
restorative cycle of defective restorations being
replaced by larger restorations that will someday
fail again, which will lead to even larger restora-
tions, possible root canal therapy, more risk for
complications, and eventually tooth loss. This
restorative cycle of death of the tooth was de-
scribed by Elderton
4
in 1988 and Simonsen
5
in
1991. To reduce and maybe even interrupt this
restorative cycle, which could possibly lead to
prolonged tooth retention, different approaches
must be considered:
Postpone the first restoration as long as possible by
using advanced diagnostic methods and caries
detection techniques.
Use less aggressive excavation and caries removal
methods to maintain pulp vitality.
*NiekJ.M.Opdam,PhD,DDS,RadboudInstitutefor
Molecular Life Sciences, Department of Dentistry, Radboud
university medical center, Nijmegen, The Netherlands
Roland Frankenberger, DMD, PhD, Chair, Department of
Operative Dentistry and Endodontics, Philipps University of
Marburg and University Hospital Giessen and Marburg,
Campus Marburg, Marburg, Germany
Pascal Magne, D.M.D., M.Sc., Ph.D, The Don and Sybil
Harrington Professor of Esthetic Dentistry, Herman Ostrow
School of Dentistry of USC, Division of Restorative Sciences
*Corresponding author: PO Box 9101, Nijmegen, NL 6500
HB, Netherlands; e-mail: niek.opdam@radboudumc.nl
DOI: 10.2341/15-126-LIT
Ó
Operative Dentistry, 2016, 41-3, 000-000
Reduce the amount of tooth substance loss by using
minimally invasive preparation and restorative
techniques.
Improve the restoration seal, bonding, and overall
quality for longer restoration survival
Use a more conservative approach toward restora-
tion replacement and maintenance by postponing,
repairing, or refurbishing rather than always
replacing completely.
Historically, indirect restorations, especially
crowns, were considered long-lasting restorations,
and the aim was for the restoration to be permanent.
However, almost no restoration is really permanent,
except the last one in a patient’s lifetime. Tradition-
ally, in a tooth that will be restored with an indirect
restoration, all direct restorative materials are
removed or are covered by the indirect restoration
in an attempt to promote the restoration’s longevity.
This is mainly based on the assumption that an
indirect restoration will have a better marginal fit
and that indirect restorative materials are more
resistant to deterioration over time due to wear,
fracture, and discoloration. These traditional restor-
ative concepts may be obsolete for two reasons:
1. Even though differences are noted in vitro, the
clinical longevity of modern adhesive restorative
materials, whether placed directly or indirectly or
under ideal and less than ideal circumstances,
does not differ significantly (Table 1).
2. Under less than ideal circumstances, certain risk
factors may be present that are not related to the
quality of the restorations or the different prop-
erties of direct and indirect restorations. These
risk factors, such as high caries risk or bruxism,
may impair restoration and tooth longevity inde-
pendent from the type of material.
6,7
For too long, the longevity of the restoration itself
has been the focus of the attention. Today, it appears
that it is more important to preserve the underlying
tooth and the functioning of the dentition as a whole.
In a good restorative concept, it is important to keep
open future options for restorations as the present
available restoration will fail in the future and will
need replacement, repair, or adjustment. This is the
essence of the biomimetics approach,
8
in which the
aim is not to create the strongest restoration but
rather a restoration that is compatible with the
mechanical, biologic, and optical properties of un-
derlying tissues. This article will discuss recent
developments in restorative dentistry that aim to
preserve a well-functioning dentition during a
lifetime.
Table 1: Review Articles on the Longevity of Dental Restorations
Restoration Type AFR Authors Year Journal Research Type
Direct restorations
Amalgam 3% Manhart and Hickel 2004 Operative Dentistry Review
Amalgam 1% Heintze and Rousson 2012 Journal of Adhesive Dentistry Meta-analysis
Posterior composite 1% Heintze and Rousson 2012 Journal of Adhesive Dentistry Meta-analysis
Posterior composite 2% Opdam and others 2014 Journal of Adhesive Dentistry Meta-analysis
Glass-ionomer cement 7% Manhart and Hickel 2004 Operative Dentistry Review
Indirect restorations: inlays
Inlay-composite 3% Manhart and Hickel 2004 Operative Dentistry Review
Inlay-gold 1% Manhart and Hickel 2004 Operative Dentistry Review
Inlay-ceramic 2% Manhart and Hickel 2004 Operative Dentistry Review
Ceramic CAD/CAM 2% Manhart and Hickel 2004 Operative Dentistry Review
Ceramic CAD/CAM 2% Wittneben and others 2009 International Journal of Prosthodontics Systematic review
Ceramic-CEREC 1% Fasbinder 2006 Journal of the Canadian Dental Association Review
Indirect restorations: crowns
IPS Empress crowns 1% Heintze and Rousson 2010 International Journal of Prosthodontics Systematic review
All-ceramic crown 2% Pjetursson 2007 Clinical Oral Implants Research Systematic review
Metal-ceramic crown 1% Pjetursson 2007 Clinical Oral Implants Research Systematic review
All-ceramic FPD 2% Sailer and others 2008 Clinical Oral Implants Research Systematic review
Metal-ceramic FPD 1% Sailer and others 2008 Clinical Oral Implants Research Systematic review
Zirconia crowns: tooth supported 1% Larsson and Wennerberg 2014 International Journal of Prosthodontics Systematic review
Zirconia crowns: implant supported 1% Larsson and Wennerberg 2014 International Journal of Prosthodontics Systematic review
Abbreviations: AFR, annual failure rate; CAD/CAM, computer-aided design/computer-aided manufacturing; FPD, fixed partial denture.
2Operative Dentistry
LONGEVITY OF RESTORATIONS
Clinical data on the longevity of dental restorations
are widely available but have to be interpreted with
caution. Prospective clinical trials are considered the
best option to measure the longevity of dental
restorations. Several systematic reviews based on
prospective clinical trials have been published and
Table 1 shows the results for several types of
restorations. It is remarkable that direct composite
restorations, indirect ceramic and composite resto-
rations, and crowns of several designs do not differ
that much in annual failure rates, which vary
between 1% and 2%, according to recent review
articles.
1,9–16
These studies conclude that indirect
restorations, especially crowns, do not have better
longevity.
A few drawbacks to these studies need to be
mentioned. First, restorations in prospective clin-
ical studies are mostly placed by calibrated
operators in a university setting, which leads to
optimal restorations that possibly last longer than
those placed under real-life routine conditions in a
general practice setting.
17
Second, patient selec-
tion for prospective studies likely includes moti-
vated patients without such problems as high
caries risk or bruxism, factors that are known to
have a negative effect on the longevity of dental
restorations.
6,7,18,19
Therefore, it can be expected that a lower survival
of restorations will be found in a general dental
practice environment. Data are available from cross-
sectional studies,
2,20–22
but this study design has
been shown to grossly underestimate restoration
longevity and results in findings of higher longevity
for older materials. Thus, past conclusions that
longevity of restorations in dental practices was as
low as 3 years (median) for composites and 5 years
for amalgam
21
are not justified as these calculations
are based on these deceptive data for failed restora-
tions.
23
Data from longitudinal studies on longevity of
dental restorations in a general practice environ-
ment are limited, and most are related to specific
dentists
6,7,24
or public health dental care.
25–27
From
these practice-based studies, annual failure rates of
1%-3% for composites have been found dependent on
several factors, and these data are comparable to the
outcomes of university studies. From an insurance
database in the United Kingdom, 10-year survival
rates of crowns have been reported to be 48% for
porcelain fused to metal and 68% for full metal
crowns.
28
Therefore, it can be concluded that longevity data
are no longer a justification for making a choice
between direct and indirect restorations and be-
tween resin composite, metal, or ceramic materials.
SIZE OF THE DEFECT
Traditionally, small defects in teeth are treated with
a direct restoration. For larger defects, including
cusp replacement and deep cervical outline, different
restorative options are available, either direct or
indirect:
1. For large posterior and anterior defects, a direct
composite restoration can be a feasible solution.
Several studies have shown that a direct compos-
ite is suitable for restoration of large defects,
including cusp replacement, and for treating
cracked teeth,
6,29–33
The skills of the operator,
who should be able to deliver an adequate
restoration with appropriate morphology as well
as proximal and intermaxillary contacts, seem to
be the predominant limiting factor.
2. Inlay/onlay restorations are also considered to be
an option for larger defects. They have the
advantage of precision and better control on the
final morphology and occlusion. However, the
need for a tapered preparation design may result
in increased tooth tissue loss. This can be
prevented by using immediate dentin sealing
34,35
and direct composite buildups to remove under-
cuts. Inlay/onlay restorations fit in a modern
restorative concept; however, technique sensitiv-
ity and demands for the operator are not reduced
compared with direct restorations.
3. For a long time, crowns were considered the best
restorations for severely compromised teeth. Dis-
advantages of crowns are that they require
sufficient ferrule and that the outline should be
extended considerably toward the cervical region
which may result in loss of more tooth substance.
The costs for crowns are considerable; therefore,
some restorative dentists recommend alternative
concepts.
36
Furthermore, traditional crown prep-
arations cut many sound areas that have never
been attacked by caries. This primarily means
that the probability of endodontic complications is
significantly increased compared with more de-
fect-oriented preparations.
4. Indirect restoration with elevated margins.
When an indirect restoration is placed, typically
all existing restorations are replaced or covered with
the indirect restoration, which results in a consider-
able amount of tooth substance loss when trying to
Opdam, Frankenberger & Magne: Direct Versus Indirect 3
achieve a divergent preparation design without
undercuts, especially when a full crown is placed. A
restorative technique has been introduced to deal
with the problem that indirect adhesive inlays are
difficult to cement without rubber dam or matrix in
situ to protect the area from contamination when a
deep subgingival proximal outline is present.
37–39
With this restorative concept, called deep margin
elevation, the outline of the indirect restoration is
elevated to the supragingival level.
There are other clinical approaches to this dilem-
ma. Deep gingival margins can be exposed by
surgical apical displacement of the supporting bone
and gingiva. This may, however, compromise the
attachment level and generate possible anatomical
complications such as the proximity of root concav-
ities and furcations. Once exposed to the oral
environment, those areas can be problematic to
maintain and may generate other complications. In
the more conservative deep margin elevation tech-
nique, a base of composite resin is used to elevate the
subgingival proximal margins underneath direct or
indirect bonded restorations (Figures 1 through 3).
The procedure, also called coronal margin relocation,
is performed under rubber dam isolation with the
placement of a matrix. In addition to the supragin-
gival elevation of the margin, immediate dentin
sealing and an adhesive composite resin base are
used to reinforce undermined cusps, fill undercuts,
and provide the necessary geometry for the inlay/
onlay restoration.
ADHESION WITH LARGER RESTORATIONS
Traditionally, metal-based crowns are luted with
glass-ionomers, zinc-carboxylate, or zinc-phosphate
cement, materials that are somewhat forgiving in a
relatively moist environment. The newer all-ceramic
concepts require adhesive cementation based on
composite bonding technology, as the preparations
are less retentive, and optimal bonding of the
restoration to the tooth is demanded.
A possible problem arising with cementing full
ceramic crowns with a subgingival margin is how to
maintain a dry working field for the adhesive
procedure. In operative dentistry, moisture control
is often obtained with a rubber dam, but this is not
the only option. Use of cotton rolls and suction as
well as special devices, such as an isolation mouth-
piece (Isolite Systems, Santa Barbara, CA, USA) and
a proper matrix and wedge as applied with direct
restorations, offer good moisture control even with
subgingival restorations. For subgingival indirect
restorations, placement of a wedge and matrix is
difficult as it would compromise the fit of the
restoration. Therefore, unless margins are clearly
relocated supragingivally, placement of a rubber
dam can be done but probably will not prevent
contamination from the sulcus and hence an indi-
rect, subgingivally placed adhesive restoration
seems to be a lucky shot when it comes to the
quality of the marginal fit.
The previously described deep margin elevation
technique could provide a solution for this problem
as the first subgingival part of a large restoration
could be placed using a specially designed matrix
(Figures 1-3), enabling the best possible moisture
control. Thereafter, a rubber dam could be placed
easily and a (supragingival) direct or indirect
restoration could be placed adhesively without too
many problems.
THE ULTIMATE CHALLENGE: PATIENTS WITH
SEVERE EROSION AND TOOTH WEAR
The ultimate challenge for restorative treatment is a
patient who suffers from severe tooth wear, espe-
cially one who is still relatively young. The main
etiologic factors of severe tooth wear, including loss
of vertical dimension, are erosion and bruxism. In
particular, heavy bruxism can cause deterioration of
teeth and dental restorations. For these patients the
strongest restorations are required, but at the same
time it has to be recognized that these restorations
will have to be replaced in the future. Therefore, a
treatment that mostly includes an increased vertical
dimension would be minimally invasive and at the
same time offer fracture-resistant restorations. Even
wear/erosion accompanied by difficult anterior oc-
clusal relationships (deep Class II or edge to edge)
can be resolved in a minimally invasive way through
occlusal therapy using the centric relation and the
Dahl principle.
40
Indirect restorations that need
sacrifice of a substantial amount of tooth substance
are therefore not the first choice, although in these
patients crowns are often still recommended. Clini-
cal studies of restorations in patients with severe
tooth wear are limited and include only a few studies
with direct composites,
31,33,41
and those resulted in
different levels of success. Several case reports have
been published on minimally invasive indirect
techniques using computer-aided design/computer-
aided manufacturing (CAD/CAM) tabletop restora-
tions or semidirect treatments using a mold intra-
orally and or using ceramic restricted to labial
veneers.
42–44
Posterior composites seem to be the most success-
ful materials offering the most fracture-resistant
4Operative Dentistry
Figure 1. Clinical case indicated for the
deep margin elevation technique.
Figure 2. Super-curved matrix modified for
elevation.
Figure 3. Post-elevation bitewing radio-
graph.
Opdam, Frankenberger & Magne: Direct Versus Indirect 5
restorations in cases of bruxism. In vitro studies
confirm these results when fracture resistance of
composites and ceramics bonded to dentin are tested.
If this is the case, and clinical results should be
obtained especially for indirect ceramic restorations
in treating patients with tooth wear, then the
question is why indirect restorations should be made
if the purpose is to strengthen the tooth. Full metal
restorations possibly have the best properties in this
respect but are surely in decline. A recently
published randomized clinical trial comparing indi-
rect and direct restorations for premolar teeth with a
cusp fracture showed no difference in performance.
32
CONCLUSIONS AND RECOMMENDATIONS
Traditionally, reasons to choose indirect restorations
ranged from indirect restorations are stronger to
indirect restorations last longer, the defect is too
large for a direct restoration, and subgingival
margins in cementum require an indirect restora-
tion. As can be concluded from this article, these
reasons are no longer supported in contemporary
dentistry. However, there are still some situations in
which there are good reasons to choose an indirect
over a direct technique, including the following:
In large rehabilitations in which the dentition has
to be restored extensively, indirect techniques
allow for preoperative design with wax-up or
digital wax-up and better management of occlusion
and vertical dimension.
In cases where optimal form and esthetics are
required, indirect techniques have advantages,
especially when ceramic materials are used.
In cases in which a direct restoration is too difficult
for the operator to make, sometimes an indirect
restoration can be more successful.
Alternatively, direct restorations are more pre-
ferred
When minimally invasive techniques are required,
especially in high-risk and young patients.
When low-cost treatments are the only option.
When the dentist is skilled in direct techniques; for
such operators, direct techniques are indicated in
more situations.
In conclusion the following recommendations may
be made:
1. Crowns have limited indications, namely, to
replace an existing crown, for implant restora-
tions, and occasionally to serve as bridges for
abutment teeth. In most other cases less invasive
options should be preferred.
2. Indirect or direct techniques should be minimally
invasive and adhesive. Modern restorative tech-
niques should include immediate dentin sealing,
adhesive bases when required, and deep margin
elevation in cases where indirect restorations
have to be made.
3. The operator’s skill in direct techniques is an
important factor. Training in large direct com-
posites should be part of the dental training
program.
4. Indirect techniques should aim for predictable full
mouth rehabilitations, as reconstructions can be
supported by a preoperative diagnostic buildup/
wax-up made by the dental technician or the
dentist. CAD/CAM techniques might become
increasingly important for these techniques.
5. For a subgingival outline the deep margin
elevation technique may be the best option for
indirect restorations. This technique can also be
useful when placing deep and large direct
restorations.
6. Ceramics offer the best esthetic properties, but
because of their mechanical properties, they
should be limited to the esthetic zone, especially
for patients with bruxism.
Regulatory Statement
This work was conducted in accordance with all the provisions
of the local human subjects oversight committee guidelines
and policies of the College of Dental Sciences, Radboud
University Medical Centre, in the Netherlands.
Conflict of Interest
The authors have no proprietary, financial, or other personal
interest of any nature or kind in any product, service, and/or
company that is presented in this article.
(Accepted 1 May 2015)
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42. Gru¨ tte r L, & Vailati F (2013) Full-mouth adhesive
rehabilitation in case of severe dental erosion, a mini-
mally invasive approach following the 3-step technique
European Journal of Esthetic Dentistry 8(3) 358-375.
43. Vailati F, Gruetter L, & Belser UC (2013) Adhesively
restored anterior maxillary dentitions affected by severe
erosion: Up to 6-year results of a prospective clinical
study European Journal of Esthetic Dentistry 8(4)
506-530.
44. Gu¨ th JF, Almeida E Silva JS, Ramberger M, Beuer F, &
Edelhoff D (2012) Treatment concept with CAD/CAM-
fabricated high-density polymer temporary restorations
Journal of Esthetic and Restorative Dentistry 24(5)
310-318.
8Operative Dentistry
