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Available online at www.sciencedirect.com
elsInternal adaptation, marginal accuracy and microleakage of
apressable versus a machinable ceramic laminate veneers
Moustafa Nabil Aboushelib a, Waleed AbdelMeguid Elmahy b,
Mohammed Hamed Ghazy c,*aDental Biomaterials Department, Faculty of
Dentistry, Alexandria University, EgyptbRestorative Department,
Faculty of Dentistry, Alexandria University, EgyptcConservative
Dentistry Department, Faculty of Dentistry, Mansoura University,
Egypt
1. Introduction
Ceramic laminate veneers are considered as conservative
solution for patients requiring improvement of the shape,
colour, or position of their anterior teeth.1,2 These thin
and
brittle restorations are bonded using adhesive resin cements
which establishes a chemical bond between the ceramic and
the tooth structure using standard hydrofluoric acid etching
and silane application. Once properly cemented, ceramic
veneers become an integral part of the tooth structure and
share part of applied loading stresses during masticatory
a r t i c l e i n f o
Article history:
Received 6 December 2011
Received in revised form
19 April 2012
Accepted 20 April 2012
Keywords:
Laminate veneers
Margin
Gap
Leakage
Film thickness
a b s t r a c t
Objectives: The aim of this study was to evaluate the internal
adaptation and marginal
properties of ceramic laminate veneers fabricated using
pressable and machinable CAD/
CAM techniques.
Materials and methods: 40 ceramic laminate veneers were
fabricated by either milling
ceramic blocks using a CAD/CAM system (group 1 n = 20) or
press-on veneering using lost
wax technique (group 2 n = 20). The veneers were acid etched
using hydrofluoric acid,
silanated, and cemented on their corresponding prepared teeth.
All specimens were stored
under water (37 8C) for 60 days, then received thermocycling
(15,000 cycles between 5 and
55 8C and dwell time of 90 s) followed by cyclic loading
(100,000 cycles between 50 and 100 N)
before immersion in basic fuchsine dye for 24 h. Half of the
specimens in each group were
sectioned in labio-lingual direction and the rest were
horizontally sectioned using precision
cutting machine (n = 10). Dye penetration, internal cement film
thickness, and vertical and
horizontal marginal gaps at the incisal and cervical regions
were measured (a = 0.05).
Results: Pressable ceramic veneers demonstrated significantly
lower (F = 8.916, P < 0.005)
vertical and horizontal marginal gaps at the cervical and
incisal margins and lower cement
film thickness (F = 50.921, P < 0.001) compared to machinable
ceramic veneers. The inferior
marginal properties of machinable ceramic veneers were
associated with significantly
higher microleakage values.
Conclusions: Pressable ceramic laminate veneers produced higher
marginal adaptation,
homogenous and thinner cement film thickness, and improved
resistance to microleakage
compared to machinable ceramic veneers.
Clinical significance: The manufacturing process influences
internal and marginal fit of
ceramic veneers. Therefore, dentist and laboratory technicians
should choose a
manufacturing process with careful consideration.
# 2012 Elsevier Ltd. All rights reserved.
* Corresponding author. Tel.: +20 2 0105025275.E-mail address:
[email protected] (M.H. Ghazy).
0300-5712/$ see front matter # 2012 Elsevier Ltd. All rights
reserved.http://dx.doi.org/10.1016/j.jdent.2012.04.019journal
homepage: www.intl. evierhealth.com/journals/jden
-
structural defects. Nowadays, computer assisted design and
computer assisted milling technology (CAD/CAM) requires
nothing more than few keyboard clicks in order to design and
fabricate accurate restorations. Nevertheless, the shade and
colour of machinable ceramic produced ceramic veneers are
limited by the colour of the selected block used to mill
these
restorations.2325
Up to the authors knowledges, there are no investigations
in the literature evaluating the influence of the
fabrication
technique on the internal adaptation marginal accuracy and
microleakage of ceramic laminate veneers, Therefore, it was
the objective of this laboratory study to investigate these
parameters using pressable and machinable ceramics. The
null hypothesis to be tested was that neither the pressable
nor
the machinable ceramic veneer fabrication technique would
have an effect on the internal adaptation, marginal accuracy
and microleakage of ceramic veneers.
2. Materials and methods
j o u r n a l o f d e n t i s t r y 4 0 ( 2 0 1 2 ) 6 7 0 6 7 7
671cycle. The adhesive resin cement is subjected to dynamic
loading, thermal cycling, and is influenced by the
hydrolytic
effect of water and different chemicals present in the
mouth.3,4
External marginal adaptation of ceramic veneers, which is
defined as the vertical distance between the finish line of
the
prepared tooth and the margins of the fabricated veneers5
plays an important role for their success. Close proximity
between the margin of the restorations and the tooth
structure
protects the adhesive resin cement from excessive exposure
to
the oral cavity leading eventually to slow process of
gradual
disintegration of its chemical, physical, and mechanical
properties resulting in microleakage, recurrent decay, dis-
colouration of the tooth structure, and fracture of the
cemented veneers. On the other hand, internal marginal
adaptation is a direct measure of the cement film thickness
underneath the restoration and is significantly influenced
by
the accuracy of fabrication process used.6,7
While external marginal adaptation could be measured
using different imaging methods as stereo or scanning
electron microscopy, internal marginal adaptation requires
sectioning of these restorations in order to assess the
cement
film thickness underneath the cemented restorations.8,9
Holmes measured various points between the casting and
the tooth and clarified the terminology for misfit and
defined
the internal gap as the perpendicular measurement from the
axial wall to the internal surface of the restoration.10 Non
destructive techniques which rely on measuring the thickness
of low viscosity impression silicon material used in place
of
the resin cement were also used in previous
investigations.11
13 Ucar et al. concluded that weighing the light body
addition
silicon is a convenient method for 3 dimensional evaluation
the 3 dimensional internal fit of dental crowns.14 These
parameters play a significant role which directly influences
the clinical performance of ceramic veneers. From one hand,
these thin shells have supra-gingivally placed margins
directly
exposed to the oral cavity and on the other hand the
thickness
of resin cement is a parameter that significantly influences
the
shade and colour of these restorations.1518
Traditionally, ceramic veneers are fabricated using layer-
ing technique which incorporates refractory dies used to
support the condensed layers of the ceramic slurry.19 This
technique gives the ceramist full control over the layers
incorporated resulting in a naturally looking restoration.
On
the contrary, it requires investing time and effort in order
to
produce accurately fitting restorations. Duplicating the
work-
ing model with brittle refractory material is a sensitive
process
and removal of the refractory material after firing the
veneers
are sensitive procedures.20 A new generation of ceramic
materials were introduced to the dental field using pressing
technology.21,22 Pressable ceramics are fabricated by
burning
out wax patterns using the conventional lost wax technique
and melting and pressing ceramic ingots under controlled
pressure, temperature, and vacuum using computer pro-
grammed press ovens. These ovens are equipped with a
pneumatic press that activates an alumina plunger used to
compress molten ceramic ingots. Press-on ceramics allow
accurate reproduction of the anatomical features carved in
thewax pattern and controlled processing of the ceramic
material
resulting in an accurate restoration with minimal internalA
silicon index was made for a defect free maxillary right
central incisor in a student typodent (Frasaco, Tettnang,
Germany) with interchangeable hard resin teeth. Incisal lap
preparation for ceramic laminate veneers was made with
1.5 mm incisal edge reduction; 0.7 mm labial reduction
extended to proximal contact regions, and a chamfer finish
line placed 1.5 mm lingual to the incisal edge on the
palatal
wall. Depth orientation grooves were cut followed by tapered
diamond point and finishing stones.2628 The sectioned
silicon index (Virtual Putty fastset, Ivoclar Vivadent,
Schaan,
Liechtenstein) was used to ensure even tooth reduction, Fig.
1.
The tooth was polished with a nylon bristle brush and
polishing paste at 5000 rpm in a slow speed handpiece. A
heavy and light body impression (Virtual Putty fastset,
Ivoclar
Vivadent) was taken for the full arch including the prepara-
tion and then poured in extra hard stone to produce the
working cast and die.
Fig. 1 Digital image demonstrating cut section of the
silicon index used to verify preparation dimensions andused as a
reference using preparation and waxing
procedure.
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76722.1. Pressing fabrication technique
20 ceramic laminate veneers were fabricated using the
pressing technique (IPS e.max press A3; Ivoclar Vivadent). A
single layer of die spacer material (20 mm) was applied on
gypsum dies of the prepared tooth and allowed to dry. A wax
pattern was manually built on each gypsum die to restore the
anatomical features of the unprepared tooth using the
sectioned silicon index as a reference, Fig. 1. Five wax
patterns
were attached to the pressing ring using a 3 mm round wax
sprue and a freshly vacuum mixed investment material was
cast on a vibrating table. Following chemical setting of the
investment, 45 min, the ring was transferred to a preheated
burn out oven (800 8C) after removal of the plastic base.
After
2 h, preheated ceramic ingots were placed inside the ring
and
transferred to the pressing oven (P500; Ivoclar Vivadent)
which
was automatically programmed to complete the pressing
cycle. Pressable ceramic laminate veneers were devested by
gentle airborne particle abrasion using 50 mm glass
particles
and cutting and finishing the location of the sprue.
2.2. Machining fabrication technique
Multichromatic blocks (Multishade A3; Ivoclar Vivadent) were
used to mill 20 veneers (CEREC 3D1 3.0, CEREC Mc XL, Sirona
dental system, Charrlotte, USA). A powder imaging spray was
thoroughly applied on the surface of the gypsum die of the
prepared tooth in order to form a reflection medium that is
necessary for the optical impression. 3D camera (Charge-
Coupled Device) was positioned over the powdered die and the
3D image was captured for each specimen in labial, palatal
and
incisal directions. The acquired optical image was
transferred
into the CAD software and the preparation finish line was
marked on the digital model. After selection of the required
anatomy, the contours were adjusted by labelling the
curvature lines.
2.3. Cementation procedure
Each ceramic laminate veneer was etched using 9.6% hydro-
fluoric acid gel for 30 s (Porcelain Etch Gel, Pulpdent
Corp.,
Watertown, MA, USA), washed, dried, and finally coated with
a
silane primer (Variolink S bond primer; Ivoclar Vivadent)
which was left to completely dry for 3 min. A freshly mixed
resin cement (Variolink A3) was applied on the fitting
surface
of each laminate veneer which was then seated on the
prepared tooth using fixed pressure of 250 g for one min.
Excess cement was wiped off and the resin cement was light
polymerized for 60 s first from the lingual surface then
from
the Labial surface.29
2.4. Artificial ageing programme
The cemented laminate veneers were stored under water for
60 days then received thermo-cycling (15,000 cycles between
5
and 55 8C with 90 s immersion time at each temperature)
using
water as transfer medium followed by cyclic loading (100,000
cycles between 50 and 100 N at 4 Hz). Up on completion
ofartificial ageing, the entire external surface of the
restorations
and the supporting tooth was coated with two layers of
nailvarnish without covering the margins before immersion in
penetration dye (15% basic fuchsine dye) for 24 h.
2.5. Sectioning technique
The root portion of each restoration was sectioned 2 mm
below
the cervical line and the coronal section was imbedded in
transparent chemically polymerized acrylic resin. For each
fabrication technique, half of the specimens were vertically
sectioned in a labio-lingual direction (n = 10) and the other
half
was sectioned in a horizontal direction using a diamond
coated
disc and a precision cutting machine (Mikracut 120, Metkon,
Germany). At least two intact mid sections (0.5 mm thick)
were
obtained from each specimen. Each section was polished on a
rotating metallographic polishing device (M3000, Buehler,
Ltd.,
Evanston, IL, USA) using ascending grit tungsten carbide
coated
paper. The polished sections were ultrasonically cleaned in
distilled water for 60 s to remove surface contaminants.
2.6. Internal adaptation, marginal accuracy andmicroleakage
The cut sections were examined under stereo microscope (SZ
11, Olympus, Japan) under different magnifications and using
scanning electron microscope (XL 30; Philips, Eindhoven, the
Netherlands). On vertical sections, marginal accuracy was
measured as the maximum distance between the finish line of
the underlying prepared tooth and the margin of the ceramic
laminate veneer on both the cervical and the incisal
margins.
Internal adaptation (also defined as cement film thickness)
was
measured as the maximum distance (perpendicular line to the
prepared surface) between the inner surface of the labial wall
of
veneer and the outer surface of the prepared tooth at five
fixed
locations. Measurements were also made on the horizontal
sections. Microleakage was defined as the distance the dye
was
able to penetrate at both the cervical and the incisal
margins.
One way analysis of variance was used to analyse the data
and based on the sample size (n = 10), chosen level of
significance (a = 0.05), and medium effect size difference
(F = 0.25) the chosen statistical test had adequate power to
detect significant differences which could be used to
interpret
clinical recommendations.
3. Results
Because of limitations related to sample size used in this
study
(n = 10), Levenes test of homogeneity of variables was used
(8.8)
which indicated homogenous distribution of data confirming
also acceptable standard error of Skewness of data (0.37).
Also
Data was analysed with ShapiroWilk test to confirm the
assumption of normal distribution of the data (0.165),
therefore,
parametric statistics were used to evaluate the data.
Statistical analysis revealed that machinable ceramic
veneers, Fig. 2, were associated with significantly higher
marginal gap values compared to pressable ceramic veneers,
Fig. 3. Significantly higher horizontal (F = 8.916, P <
0.005) and
vertical (F = 43.393, P < 0.001) gaps were observed with
machin-able ceramic veneers compared to the pressable veneers.
Moreover, machinable ceramic veneers were associated with
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673significantly higher (F = 50.921, P < 0.001) cement film
thickness
which was irregular compared to pressable veneers. Cement
film thickness values were almost identical when measured in
either vertical or horizontal sections made for the same
specimen.
Higher marginal gaps resulted in significantly higher
microleakage at incisal (F = 37.708, P < 0.001) and
cervical
(F = 18.245, P < 0.001) margins observed for machinable
ce-
ramic veneers, Fig. 2. Few specimens belonging to both
groups
demonstrated micro-cracks after completion of cyclic loading
programme. Previous data are summarized in Table 1.
4. Discussion
The results of the present investigation justify rejection of
the
null hypothesis as there was significant influence of the
Fig. 2 (A) Horizontal cut section of machinable veneer
demons
associated microleakage. (B) Vertical cut section of
machinable
microleakage. Distance between two red lines represent
vertica
demonstrating uneven cement film thickness, marginal gap, an
surface of the veneer. Red line represent internal cement film
tfabrication technique on the internal adaptation, marginal
accuracy, and microleakage of the tested ceramic veneers.
For
many decades, fabrication of refractory die material was
used
for the production of porcelain laminate veneers where the
porcelain slurry was directly built on the heat resistant
material. After firing, the refractory material was removed
using airborne particle abrasion incorporating glass beads
which may also compromise marginal accuracy of the
veneers.30 This technique required extensive laboratory work
in order to duplicate the working die with a refractory one
and
during building the porcelain slurry. The marginal quality
of
laminate veneers fabricated using refractory technique
depends on the accuracy and skill of the dental ceramist.
In the pressable ceramic technique, wax patterns are
directly built on the prepared working model giving the
dentist
more control during shaping, carving, and sealing the
margins. During pressing, the molten porcelain ingot is
trating uneven cement film thickness, marginal gap, and
veneer demonstrating cervical marginal fit and associated
l misfit. (C) Vertical cut section of machinable veneer
d associated microleakage. Notice angle lines on the fitting
hickness at incisal edge.
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7674pressed under controlled pressure, temperature, and vacuum
insuring accurate reproduction of fine details especially at
the
margins. On the other hand, software limitations in
designing
restorations, and hardware limitations of the camera, scan-
ning equipment, and milling machines could produce errors in
the CAD/CAM technique especially during manual tracing and
fine milling of the finish line which justifies the findings of
this
study.31 An additional problem with computer-milled ceramic
restorations is that the cutting tool may be larger in
diameter
than some parts of the tooth preparation, such as the inner
surface of the incisal edge causing misfits, Fig. 2C, resulting
in
a inferior marginal properties.32
Marginal fit, accuracy or adaptation is synonymous for a
key criterion used in the evaluation of fixed restorations
and
could be defined as a parameter that measures the proximity
between the margin of the restoration and the finish line on
the prepared tooth in two directions.33,34 In this study,
all
Fig. 3 (A) Horizontal section of pressable veneer ceramic
demo
the finish line. Distance between blue and red lines represent
v
pressable veneer demonstrating marginal fit at the cervical
reg
demonstrating marginal fit at the incisal region. Observe
roundspecimens were fabricated on working dies directly repro-
duced from a single master tooth which eliminated any
possible differences between the specimens. In cut sections,
it
was possible to precisely measure marginal accuracy in both
horizontal and vertical dimensions. In vertical sections,
higher
marginal adaptation at the incisal and cervical regions were
observed for press-on veneers. Similar finding were observed
at the mesial and distal margins in horizontal sections.
These
results are directly related to the fabrication technique of
choice like previously reported by Tinschert in 200435 and
Reich et al.32 Nevertheless, marginal adaptation and cement
film thickness values reported in this study were higher
than those observed for conventional porcelain veneers
(50195 mm).36Potincy and Klim,37 presented an overview of
the CEREC Acquisition Center with Bluecam system (Sirona
Dental Systems, Charlotte, NC) and available materials. The
results showed that on the basis of the growth of CAD/CAM,
nstrating even cement film thickness and marginal gap at
ertical and horizontal marginal gap. (B) Vertical section of
ion. (C) Vertical cut section of pressable veneer
ation of the veneer in this region.
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ole
e at
j o u r n a l o f d e n t i s t r y 4 0 ( 2 0 1 2 ) 6 7 0 6 7 7
675the manufacturer has made substantial improvements to all
aspects of the CEREC AC system-including hardware, software
and materials-during the past 25 years. They concluded that
the dentists can create laboratory-grade restorations in
their
offices with little disturbance to work-flow patterns. This
is
possible, because of innovations to the system that make
CAD/
CAM feasible for most dental practices.
In a step towards improving production accuracy of
machinable ceramics, blue light was incorporated in the
scanning device of the CEREC system which has improved
scanning potentials especially in highly curved areas
claiming
an accuracy to capture 19 mm details without the need to
powder the teeth. The newly released version of the
designing
software (3D 4.0) has improved features related to automatic
detection of the margins of the restorations which is also a
step towards preparing an accurate digital model. Compared
to earlier versions, these new improvements are expected to
improve final fit of the milled restorations as manufacturer
claim a scanning and cutting accuracy of (19 mm). However,
limited access at incisal edge or internal channels of
implant
abutment may restrict full access of the milling tool in
these
regions.38 Additionally, the type and curvature of finish
line
are parameters that directly influences vertical misfit at
finish
line region.39
An interesting observation for both pressable and machin-
able ceramic veneers was that the value of vertical misfit
was
much higher than horizontal misfit, almost double the value,
indicating that it was more difficult to seat the veneers in
Table 1 Internal adaptation, marginal accuracy, and micr
Variable Fabrication technique
Cement film thicknessa Pressable
Machinable
Horizontal misfit Pressable
Machinable
Vertical misfit Pressable
Machinable
Incisal microleakage Pressable
Machinable
Cervical microleakage Pressable
Machinable
SD: standard deviation; F: frequency; P: significant at P >
0.5.a Cement film thickness was presented as the average value
measurvertical direction. This observation could be related to
the
labially applied pressure which neglected adequate vertical
seating or due to premature contact at the incisal edge of
the
restoration which was commonly observed for machinable
ceramic laminate veneers, Fig. 2C. Milling of the fine
details
present on the inner surface of the incisal edge presents a
challenge for CAD/CAM technique due to the limited access of
the milling tool in this narrow region.
Cement film thickness is measure of the internal fit or
adaptation of the restoration. Not only lower cement film
thickness was observed for pressable ceramic veneers in this
study but an even thickness as well, Fig. 3, which indicated
better seating compared to irregular and thicker cement film
thickness observed for machinable ceramic veneers. These
findings were in agreement with May et al.40who stated that
the
cement space should be uniform to facilitate seating without
compromising retention or resistance forms. Application oftwo
coats of die spacer material could facilitate easier seating of
the veneers, maintain even cement film thickness, and reduce
polymerization stresses.41 In a previous study, it was
observed
that polymerization stresses resulted in strengthening the
bonded veneers due to generation of compressive forces on
the
external surface, however, thermo-cycling could eliminate
such strengthening effect.42
According to CAD/CAM milling technology, restorations
with adequate marginal adaptation may not necessarily
demonstrate adequate internal adaptation.43 Reich et al.32
also reported that systems which depend on optical impres-
sion experience problems with rounded edges due to the
scanning resolution and positive error, which simulates
peaks
at the edges. A thick cement film beneath the bonded veneer
could interfere with the mechanical integrity of the
restora-
tion, increase polymerization pre-stresses, or influence
final
shade and translucency of the restoration. Several
incidences
of bulk cracks could be related to lack of rigid support
under
the bonded veneers or extension of surface flaws under the
influence of thermo-cycling and dynamic fatigue.44 Under
clinical conditions, it is recommended to maintain prepara-
tion finish line in enamel in order to reduce chances of
fracture
under functional loads.45
The artificial ageing programme used in this study
accelerated mechanical fatigue plus thermal and chemical
degradation of the restoration and resin cement.46,47
Increased
dye penetration was associated with inferior marginal
accuracy and thicker cement film thickness of the machinable
akage of tested veneers.
Mean (mm) SD (mm) F P
106.7380 29.5838 50.921 0.001
340.3569 143.3908
105.5820 63.2381 8.916 0.005
230.9664 176.8251
242.4017 36.9710 43.393 0.001
545.8161 195.8031
308.4561 95.3308 37.708 0.001
831.7576 368.9927
233.5116 66.5306 18.245 0.001
509.9443 281.6729
five fixed locations.ceramic veneers. While several studies
questioned the
correlation between marginal adaptation and microleak-
age,48,49 the high horizontal and vertical misfits exposed
more
area of the resin cement to hydrolytic effect of water under
the
influence of thermo-cycling and this is might be the
plausible
cause of cement degradation and increased microleakage. For
an aesthetic restoration as laminate veneers, microleakage
is
considered as a direct failure requiring remake of the
restoration.33 Location of the margin,50,51 polymerization
method and type of adhesive resin,52 and type of finish line
and preparation design53 are factors that must be considered
in order to reduce microleakage under porcelain veneers.
In the present investigation, the maxillary central incisor
was selected to represent the most commonly indicated tooth
requiring a laminate veneer.21 Two fabricating techniques;
pressable and machinable ceramic, were compared as
regards to their internal adaptation, marginal accuracy,
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j o u r n a l o f d e n t i s t r y 4 0 ( 2 0 1 2 ) 6 7 0 6 7
7676and microleakage properties. All veneers were first seated
on their corresponding prepared die using finger pressure to
achieve proper seating followed by a constant load to insure
accurate measurements of cement film thickness, A point of
concern was whether similar microleakage pattern could be
achieved if natural teeth were used in place of the resin
dies.
Nevertheless, it is the restoration resin cement interface
that was of interest for this study as exploring the resin
cementtooth interface was beyond the scope of this
investigation.
5. Conclusion
Under the conditions of this investigation the following
conclusion could be drown: pressable ceramic laminate
veneers produced higher marginal adaptation, homogenous
and thinner cement film thickness, and improved resistance
to microleakage compared to machinable ceramic veneers.
Clinical implications
Pressing technique produced porcelain veneers with precise
marginal and internal adaptation which resulted in reduced
microleakage compared to CAD/CAM produced porcelain
veneers.
r e f e r e n c e s
1. Calamia JR, Calamia CHS. Ceramic laminate veneers:reasons for
25 years of success. Dental Clinics of North
America2007;51:399417.
2. Chen JH, Shi CX, Wang M, Zhao SJ, Wang H. Clinicalevaluation
of 546 tetracycline-stained teeth treatedwith porcelain laminate
veneers. Journal of Dentistry2005;33:38.
3. Cotert HS, Dundar M, Ozturk B. The effect of
variouspreparation designs on the survival of ceramic
laminateveneers. Journal of Adhesive Dentistry 2009;11:40511.
4. Nikzad S, Azari A, Dehga S. Ceramic (Feldspathic &
IPSEmpress II) vs. laboratory composite (Gradia) veneers;
acomparison between their shear bond strength to enamel;an in vitro
study. Journal of Oral Rehabilitation 2010;37:56974.
5. Celik C, Gemalmaz D. Comparison of marginal integrity
ofceramic and composite veneer restorations luted with twodifferent
resin agents: an in vitro study. International Journalof
Prosthodontics 2002;15:5964.
6. Peumans M, Van Meerbeek B, Lambrechts P, Vanherle G.Porcelain
veneers: a review of the literature. Journal ofDentistry
2000;28:16377.
7. Toh G, Setcos J, Weinstein A. Indirect dental
laminateveneersan overview original research article. Journal
ofDentistry 1987;15:11724.
8. Beuer F, Aggstaller H, Edelhoff D, Gernet W, Sorensen
J.Marginal and internal fits of fixed dental prostheses
zirconiaretainers. Dental Materials 2009;25:94102.
9. Bindl A, Mormann WH. Fit of all-ceramic posterior
fixedpartial denture frameworks in vitro. International Journal
ofPeriodontics and Restorative Dentistry 2007;27:56775.
10. Holmes JR, Bayne SC, Holland GA, Sulik WD.
Considerations
in measurement of marginal fit. Journal of Prosthetic
Dentistry1989;62:4058.11. Kararaya S, Sengun A, Ozer F. Evaluation
of internaladaptation in ceramic and composite resin inlay
bysilicon replica technique. Journal of Oral
Rehabilitation2005;32:448543.
12. Reich S, Ahlen S, Gozdowski S, Lahbauer U. Measurement
ofcement thickness under lithium disilicate crowns using
animpression material technique. Clinical Oral
Investigation2011;15:51226.
13. Kohorst P, Junghanns J, Dittmer M, Borchers L, Stiesch
M.Different CAD/CAM processing routes for zirconiarestorations:
influence on fitting accuracy. Clinical OralInvestigation
2011;15:52736.
14. Ucar Y, Akva T, Akyil M, Brantley A. Internal fit evaluation
ofcrowns prepared using s anew dental crown fabricationtechnique:
laser sintered Co-CR crowns. Journal of ProstheticDentistry
2009;102:2539.
15. Omar H, Atta O, El-Mowafy O, Khan SA. Effect of
CAD-CAMporcelain veneers thickness on their cemented colour.Journal
of Dentistry 2010;38:95104.
16. Xing W, Jiang T, Ma X, Liang S, Wang Z, Sa Y, et
al.Evaluation of the esthetic effect of resin cements and
try-inpastes on ceromer veneers. Journal of Dentistry2010;38(Suppl.
2):e87e94.
17. ALGhazali N, Laukner J, Burnside G, Jarad F, Smith P,
PrestonA. An investigation into the effect of try-in pastes,
uncuredand cured resin cements on the overall color of
ceramicveneer restorations: an in vitro study. Journal of
Dentistry2010;38(Suppl. 2):e78e86.
18. Sedanur T, Bora B. Colour stability of laminate veneers:
anin vitro study. Journal of Dentistry 2011;39(Suppl.
3):e57e64.
19. Horn HR. Porcelain laminate veneer bonded to etchedenamel.
Review. Dental Clinic of North America 1983;27:67184.
20. Taskonak B, Anusavice K, Mecholsky J. Role of
investmentinteraction layer on strength and toughness of
ceramiclaminates. Dental Materials 2004;20:7018.
21. Calamia JR. Etched porcelain facial veneers: a newtreatment
modality based on scientific and clinicalevidence. New York Journal
of Dentistry 1983;53:2559.
22. Shuman IE. Aesthetic treatment with a pressed ceramicveneer
material: case reports. Dentistry Today 2004;23:804.
23. Mormann WH. The evolution of CEREC system. Journal
ofAmerican Dental Association 2006;137:7S13S.
24. Rekow D. Computer-aided design and manufacturing
indentistry: a review of the state of the art. Journal of
ProstheticDentistry 1987;58:5126.
25. Vafiadis D, Goldstein G. Single visit fabrication of a
porcelainlaminate veneer with CAD/CAM technology: a clinicalreport.
Journal of Prosthetic Dentistry 2011;106:714.
26. Shetty A, Kaiwar A, Shubhashini N, Ashwini P, Naveen
DN,Adarsha MS, et al. Survival rates of porcelain
laminaterestoration based on different incisal preparation
designs:an analysis. Journal of Conservative Dentistry
2011;14:105.
27. Walls A, Steek J, Wassell R. Crowns and
extra-coronalrestorations; porcelain laminate veneers. Journal of
ProstheticDentistry 2002;193:7382.
28. Brunton PA, Aminian A, Wilson NH. Tooth
preparationtechniques for porcelain laminate veneers. British
DentalJournal 2000;189:2602.
29. Christensen G. Why use resin cements. Journal of
AmericanDental Association 2010;141:2046.
30. Lim C, Ironside J. Grit blasting and the marginal accuracy
oftwo ceramic veneer systems a pilot study. Journal
ProstheticDentistry 1997;77:35964.
31. Martin N, Jedynakiewicz NM. Interface dimensions ofCEREC-2
MOD inlays. Dental Materials 2000;16:6874.
32. Reich S, Wichmann M, Nkenke E, Proeschel P. Clinical fit
ofall-ceramic three unit fixed partial dentures, generated with
three different CAD/CAM systems. European Journal of OralScience
2005;113:17483.
-
33. Baig MR, Tan KB, Nicholls JI. Evaluation of the marginal fit
ofa zirconia ceramic computer-aided machined (CAM) crownsystem.
Journal of Prosthetic Dentistry 2010;104:21627.
34. Bindl A, Mormann WH. Marginal and internal fit of
all-ceramic CAD/CAM crown copings on chamfer preparations.Journal
of Oral Rehabilitation 2005;32:4417.
35. Tinschert J, Natt G, Hassenpflug S, Spiekermann H. Status
ofcurrent CAD/CAM technology in dental medicine.International
Journal of Computerized Dentistry 2004;7:2545.
36. Harasani MH, Isidor F, Kaaber S. Marginal fit of
porcelainand indirect composite laminate veneers under in
vitroconditions. Scandinavian Journal of Dental
Research1991;99:2628.
37. Potincy D, Klim J. CAD/CAM in-office technology
inovationsafter 25 years for predictable, esthetic outcomes.
Journal ofAmerican Dental Association 2010;141:5S9S.
38. White SN, Suh PS, Yu Z, Johnson R. Effect of fit
adjustmenton CEREC CAD-CAM veneers. American Journal of
Dentistry1997;10:4651.
39. Cho L, Choi J, Yi YJ, Park CJ. Effect of finish line
variants onmarginal accuracy and fracture strength of
ceramicoptimized polymer/fiber-reinforced composite crowns.Journal
of Prosthetic Dentistry 2004;91:55460.
40. May KB, Russell MM, Razzoog ME, Lang BR. Precision of
fit:the Procera AllCeram crown. Journal of Prosthetic
Dentistry1998;80:394404.
41. Cho SH, Chang WG, Lim BS, Lee YK. Effect of die
spacerthickness on shear bond strength of porcelain laminate
44. Guess P, Stappert C. Midterm results of a 5-year
prospectiveclinical investigation of extended ceramic veneers.
DentalMaterials 2008;24:80413.
45. Chun YH, Raffelt C, Pfeiffer H, Bizhang M, Saul G, BlunckU,
et al. Restoring strength of incisors with veneers andfull ceramic
crowns. Journal of Adhesive Dentistry2010;12:4554.
46. Regina L, Archegas P, Freire A, Vieira S, Caldas B, Souza
E.Colour stability and opacity of resin cements and
flowablecomposites for ceramic veneer luting after
acceleratedageing. Journal of Dentistry 2011;39:80410.
47. Bonfante F, Coelho P, Guess P, Thompson V, Silva N.
Fatigueand damage accumulation of veneer porcelain pressed onY-TZP.
Journal of Dentistry 2010;38:31824.
48. Christgau M, Friedl KH, Schmalz G, Resch U.
Marginaladaptation of heat-pressed glassceramic veneers to dentinin
vitro. Operative Dentistry 1999;24:13746.
49. Christgau M, Friedl KH, Schmalz G, Edelmann K.
Marginaladaptation of heat-pressed glassceramic veneers to class
3composite restorations in vitro. Operative
Dentistry1999;24:23344.
50. Sim C, Neo J, Chua EK, Tan BY. The effect of dentin
bondingagents on the microleakage of porcelain veneers.
DentalMaterials 1994;10:27881.
51. Zaimoglu A, Karaagaclioglu L, Uctasli. Influence of
porcelainmaterial and composite luting resin on microleakage
ofporcelain laminate veneers. Journal of Oral
Rehabilitation1992;19:31927.
52. Maleknejad F, Moosavi H, Shahriari R, Sarabi N,
j o u r n a l o f d e n t i s t r y 4 0 ( 2 0 1 2 ) 6 7 0 6 7 7
677veneers. Journal of Prosthetic Dentistry 2006;95:2018.42. Magne
P, Versluis A, Douglas W. Effect of luting composite
shrinkage and thermal loads on the stress distribution
inporcelain laminate veneers. Journal of Prosthetic
Dentistry1999;81:33544.
43. Komine F, Iwai T, Kobayashi K, Matsumura H. Marginal
andinternal adaptation of zirconium dioxide ceramic copingsand
crowns with different finish line designs. DentalMaterials Journal
2007;26:65964.Shayankhah T. The effect of different adhesive types
andcuring methods on microleakage and the marginaladaptation of
composite veneers. Journal of ContemporaryDental Practice
2009;10:1826.
53. Hekimoglu C, Anil N, Yalcin E. A microleakage study
ofceramic laminate veneers by autoradiography: effect ofincisal
edge preparation. Journal of Oral Rehabilitation2004;31:2659.
Internal adaptation, marginal accuracy and microleakage of a
pressable versus a machinable ceramic laminate
veneersIntroductionMaterials and methodsPressing fabrication
techniqueMachining fabrication techniqueCementation
procedureArtificial ageing programmeSectioning techniqueInternal
adaptation, marginal accuracy and microleakage
ResultsDiscussionConclusionClinical implicationsReferences