Microleakage of porcelain veneer restora (6)
See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/7277433
Microleakage of porcelain veneer restorations
bonded to enamel and dentin with a new selfadhesive resin-based dental cement
Article in Dental Materials · March 2007
DOI: 10.1016/j.dental.2006.01.013 · Source: PubMed
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4 authors, including:
Gabriela Ibarra
Oregon Health and Science University
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d e n t a l m a t e r i a l s x x x ( 2 0 0 6 ) xxx–xxx
available at www.sciencedirect.com
journal homepage: www.intl.elsevierhealth.com/journals/dema
Microleakage of porcelain veneer restorations bonded to
enamel and dentin with a new self-adhesive resin-based
dental cement
Gabriela Ibarra a,∗ , Glen H. Johnson a , Werner Geurtsen a , Marcos A. Vargas b
a
b
School of Dentistry, Department of Restorative Dentistry, University of Washington, Seattle, WA, USA
College of Dentistry, Department of Operative Dentistry, University of Iowa, Iowa City, USA
a r t i c l e
i n f o
a b s t r a c t
Article history:
Cementation technique of bonded ceramic restorations is a time-consuming and technique-
Received 29 September 2005
sensitive procedure critical to long-term success.
Received in revised form 19
Objective. Evaluate the performance of a self-adhesive, modified-resin dental cement (Rely-
December 2005
X UniCem, 3M-ESPE) for the cementation of ceramic veneer restorations without previous
Accepted 10 January 2006
conditioning of the tooth surface, and in combination with a one-bottle adhesive and a
self-etching adhesive.
Methods. Thirty-six premolars received a veneer preparation that extended into dentin.
Keywords:
Leucite-reinforced pressed glass ceramic (Empress 1) veneers were cemented follow-
Self-adhesive resin cement
ing manufacturers’ instructions, according to the following treatment groups (n = 9): (1)
Ceramic veneers
Variolink–Excite Ivoclar–Vivadent (V + E control), (2) Unicem + Single Bond 3M-ESPE (U + SB),
Microleakage
(3) Unicem + Adper Prompt L-Pop 3M-ESPE (U + AP), (4) Unicem 3M-ESPE (U). After 24 h stor-
Dentin adhesion
age at 37 ◦ C, teeth were thermocycled (2000 cycles) at 5 and 55 ◦ C, immersed in ammoniacal
Enamel adhesion
silver nitrate for 24 h, placed in a developer solution overnight and sectioned using a slowspeed saw. Three 1 mm longitudinal sections were obtained from each tooth and evaluated
for leakage with a microscope (1× to 4×). Imaging software was used to measure stain penetration along the dentin and enamel surfaces.
Results. ANOVA with SNK (˛ = 0.05) revealed that on dentin, U had significantly less leakage
than U + SB and U + AP, but no different than V + E; on enamel U had leakage values that were
significantly greater than the groups with adhesives.
Significance. The self-adhesive cement U gave low leakage on dentin that was comparable
to the cement that employed an adhesive for sealing dentin, whereas this cement benefits
from use of an adhesive when cementing to enamel.
© 2006 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.
1.
Introduction
The use of bonded ceramic restorations in dentistry has
increased appreciably due to the development of adhesive
materials that allow for more conservative restorative techniques as well as the ability of achieving excellent esthetic
appearance and adequate strength [1]. Among these bonded
ceramic restorations, ceramic veneers have gained popularity
∗
Corresponding author at: Department of Restorative Dentistry, University of Washington, 1959 N.E. Pacific Street, Box 357456, Seattle,
WA 98195-7456, USA. Tel.: +1 206 543 5948; fax: +1 206 543 7783.
E-mail address: gibarra@u.washington.edu (G. Ibarra).
0109-5641/$ – see front matter © 2006 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.
doi:10.1016/j.dental.2006.01.013
DENTAL-913;
No. of Pages 8
2
d e n t a l m a t e r i a l s x x x ( 2 0 0 6 ) xxx–xxx
as a conservative restoration, where a thin ceramic covering
is bonded, preferentially to enamel, after minimal preparation
on tooth structure [2,3].
The cementation technique, which is a time-consuming
and technique-sensitive procedure, is key to the long-term
success of these types of restorations. The strength and
the durability of the bond between the porcelain, the luting
cement and the enamel/dentin interface play an important
role in the outcome of ceramic veneers, particularly when
dentin is involved [3]. It is not uncommon that, particularly
in the gingival third of a veneer preparation, dentin will be
exposed due to the thin layer of enamel present at this site [4].
In this case, the cementation procedure becomes even more
critical because high failure rates in veneers have been associated to large exposed dentin surfaces and the cervical margin
has been regarded as a problematic area to achieve perfect
marginal adaptation [3].
A self-adhesive, resin-based dental cement (Rely-X
UniCem, 3M-ESPE), which advocates no pre-treatment of
tooth surfaces, thus simplifying the cementation procedure, has recently been introduced. This cement has an
organic matrix composed of multi-functional phosphoric acid
methacrylates, which react with inorganic fillers (72 wt.%)
that are basic in nature or with hydroxyapatite from tooth
structure. Water that is released from the setting reaction
is thought to play a role in its neutralization, raising the
pH value from 1 to 6. The setting of the cement is based
on a free radical polymerization reaction initiated by either
photoactivation or a redox system [5,6].
The cement has been recommended for luting all metalbased and ceramic crowns, as well as partial coverage ceramic
and indirect composite restorations, with the exception of
veneers [5,6].
Good marginal adaptation of all-ceramic crowns cemented
with Rely-X UniCem to dentin has already been documented
[5]. Preliminary studies have shown good results when bonding pressed ceramic inlay restorations to dentin and enamel
margins [7].
If the self-adhesive cement could be used predictably for
the cementation of ceramic veneer restorations, it would serve
as a user-friendly universal cement. However, more studies
are needed before final recommendations for the clinical use
of this cement can be made.
The clinical success of cemented restorations has been
evaluated by measuring marginal fit and microleakage for
many years, in spite of the fact that there is no restoration
or luting material able to achieve a complete marginal seal
[8,9]. In the case of all-ceramic restorations, microleakage has
been correlated with the loss of the integrity of the bond
to tooth structure, and this has been associated with other
problems such as secondary caries, post-operative sensitivity,
pulpal inflammation, staining and plaque accumulation [9–11]
due to the clinically undetectable passage of bacteria, fluids,
molecules or ions between tooth structure and the cemented
restoration [12].
The aim of this study was to test the hypothesis that
the application of a new self-adhesive resin cement, used
as a luting agent, would result in good marginal integrity of
ceramic veneers to dentin as well as enamel, without prior
conditioning of the tooth surface or in combination with
other adhesive systems that previously condition enamel and
dentin.
Altogether, the hypothesis tested was that the microleakage of the new self-adhesive luting cement is similar to a
conventional resin cement when bonding a porcelain veneer
to enamel and dentin.
2.
Materials and methods
Thirty-six human premolars, previously stored in a
NaN3 + NaCl solution for no more than 6 months, were
prepared for porcelain veneer restorations. The preparations
were made with a #834 016 bur (Brasseler, Savannah, GA
31419, USA) to establish a 0.3 mm depth cut, and finished
with a fine rounded tip diamond #6844 016 (Brasseler, Savannah, GA 31419, USA). The preparation’s margins ended as
butt joint at the incisal edge and a chamfer that extended
approximately 1 mm beyond the CEJ. An impression of
each of the preparations was made with a vinyl polysiloxane
impression material (Aquasil LV and Aquasil, Caulk, Dentsply;
Lot 020608) using copper rings for material retention. The
teeth were then stored in artificial saliva solution and the
impressions were sent to a commercial laboratory (Nakanishi Dental Laboratory Inc., Seattle, WA). Leucite-reinforced
pressed ceramic (Empress I) porcelain veneer restorations
were fabricated in an A-1 shade based on the Vita shade
guide, etched with hydrofluoric acid and silanated in the
laboratory.
The teeth were then divided into four treatment groups
according to the cementation procedure (Table 1). Group
1: restorations cemented using a conventional resin-based
cement and its proprietary adhesive system as a control (Variolink II [Base Yellow 210/A3, Lot E 43489; Catalyst Lot E 34696] and Excite [Lot E41824], Ivoclar/Vivadent).
Group 2: restorations cemented using self-adhesive, modifiedresin dental cement (Rely-X UniCem Maxicaps, 3M-ESPE;
Lot 143650) in combination with enamel and dentin conditioning with phosphoric acid and a one-bottle adhesive system (Single Bond, 3M-ESPE). Group 3: restorations
cemented using a self-adhesive resin-based dental cement
(Rely-X UniCem Maxicaps, 3M-ESPE; Lot 143650) in combination with a self-etching adhesive system (Adper Prompt
L-Pop, 3M-ESPE; Lot 147563) to condition enamel and dentin.
Group 4: restorations cemented with a self-adhesive resinbased dental cement (Rely-X UniCem Maxicaps, 3M-ESPE;
Lot 143650) without previous conditioning of enamel and
dentin.
Before cementation, all veneers were tried-in, cleaned with
phosphoric acid and re-silanated (Rely-X Ceramic Primer; Lot
2721) in accordance with clinical practice.
Light-curing of the adhesives and the cement was carried
out with a Demetron 401 light unit (Demetron/Kerr, Danbury, CT) as indicated in Table 1. Light output was measured every six samples to ensure proper resin polymerization
(750 mW/cm2 ).
The specimens were stored in artificial saliva at 37 ◦ C for
72 h and were thermocycled in 5 and 55 ◦ C water temperatures
for 2000 cycles with 20 s dwell time at each temperature and a
transfer time of 10 s, for a total of 60 s per cycle.
3
d e n t a l m a t e r i a l s x x x ( 2 0 0 6 ) xxx–xxx
Table 1 – Application technique for seating ceramic veneer restorations with different adhesive systems and luting
cements
Treatment
Materials
Excite/Variolink
Veneer preparation
Substrate preparation
Seating instructions
2.1.
Etch with H3 PO4 × 60 s
Rinse × 30 s
Air dry
Silanate internal
aspect × 60 s
Allow solvent to
evaporate
Apply adhesive to
internal aspect
Air-thin
DO NOT light cure
H3 PO4 : etch
enamel × 15–30 s and
dentin × 10–15 s
Rinse: 5 s at least
Single bond/Unicem
Prompt L-pop/Unicem
Etch with H3 PO4 × 60 s
Rinse × 30 s
Air dry
Silanate internal
aspect × 60 s
Allow solvent to
evaporate
Apply one coat of
adhesive to internal
aspect
Air-dry for 2–5 s
DO NOT light cure
H3 PO4 : etch enamel and
dentin × 10 s
Etch with H3 PO4 × 60 s
Rinse × 30 s
Air dry
Silanate internal
aspect × 60 s
Allow solvent to
evaporate
Lightly scrub one layer
of adhesive to internal
aspect: 15 s
Air-thin
DO NOT light cure
Slightly dry surface
Rinse: 30 s
Adhesive: lightly scrub
one layer on enamel
and dentin: 15 s
Air-thin
Remove excess
water—do not over-dry
dentin
Adhesive: apply several
layers
Blot excess water—leave
moist surface
Air-dry: 1–3 s. Avoid
pooling
Cure: 20 s
Apply base cement to
veneer and tooth
Maintain pressure for
several seconds and
tack: 10–20 s
Remove excess cement
with brush
Light-cure × 40 s
Air dry: 2–5 s
Adhesive: apply a
second coat without
rubbing
Air dry
DO NOT light cure
Apply mixed cement to
veneer
Tack-cure excess
cement × 2–4 s and
remove
Light-cure × 40 s
DO NOT light cure
Apply mixed cement to
veneer
Tack-cure excess
cement × 2–4 s and
remove
Light-cure × 40 s
Adhesive: apply 2 coats
Unicem
Etch with H3 PO4 × 60 s
Rinse × 30 s
Air dry
Silanate internal
aspect × 60 s
Allow solvent to
evaporate
Leave dentin and
enamel surface
moist/glossy
Apply mixed cement to
veneer
Tack-cure excess
cement × 2–4 s and
remove
Light-cure × 40 s
Microleakage evaluation
The apices of the roots were sealed with an acrylic resin
(Duralay Inlay Pattern Resin, Reliance) and the teeth were then
coated with two layers of quick dry nail varnish that extended
up to 1 mm from the margins of the ceramic veneer restorations. Care was taken not to over dry the enamel surrounding
the margins while the nail varnish dried.
The teeth were placed in 50 wt.% ammoniacal silver
nitrate for 24 h, rinsed extensively with water, and placed in
freshly mixed developer solution (Kodak Developer D-76, CAT
1464817, 0251 C5 02749) under a strong light for 12 h. After
rinsing them with water and sand blasting the porcelain surface carefully, a 1 mm layer of composite was bonded to the
veneer (All Bond 2, Bisco, Lot 0200002521; Filtek Z 250 B 1 shade,
3M-ESPE, Lot 9BB) to provide sufficient bulk for handling, and
light-cured for 40 s. The roots were removed and the crowns
were sectioned in a cervical–incisal direction with a diamond
blade to obtain three slices (∼1 mm) from each tooth (Fig. 1).
Sections were analyzed for leakage at the cervical and
incisal margins by means of a light microscope (Nikon Eclipse
E400, Japan) at 1×, 2× and 4×, using an image analysis com-
Fig. 1 – Section of the crown showing the interface of
enamel (E) and dentin (D) with the porcelain veneer (PV)
and the overlying composite (C). Penetration of the
ammoniacal silver nitrate can be observed on the dentin
side (arrow).
4
d e n t a l m a t e r i a l s x x x ( 2 0 0 6 ) xxx–xxx
puter program (Meta Vue, Universal Imaging Corp., Downingtown, PA). Microleakage values were obtained by measuring
stain penetration for the total surface length, separately for
dentin and enamel, and were expressed as a percentage of
the total length of the veneer preparation.
2.2.
Statistical analysis
Since there were four different cement-bonding combinations
(i.e., treatments) and samples were independent, a singlefactor analysis of variance model was employed to test for
significant main effects, separately for dentin and for enamel.
If main effects were significant (˛ = 0.05) and test for equal variance was not significant, the Student–Newman–Kuel’s post
hoc test for multiple comparison of means was conducted
to determine which means differed. When the assumption
of equal variances was not met, the Games–Howell post hoc
test was used to identify which means differed. All hypothesis
testing was conducted at the 95% level of confidence.
2.3.
SEM evaluation
After cementation, one tooth from each group was prepared
for SEM evaluation. The teeth were stored in water for 4 weeks
and were fixed for 72 h in 2.5% glutaraldehyde in 0.1 M Nacacodylate buffer. Cross-sections of an approximate thickness
of 1 mm (Fig. 1) were obtained from the teeth using a watercooled slow-speed diamond saw (Buehler Isomet 1000TM ,
Buehler Ltd., Lake Bluff, IL, USA) and each section was sequentially polished with 600 and 800 grit of silicon carbide paper, 6
and 1 m diamond slurries and 0.04 m aluminum oxide. The
specimens were dehydrated in an ascending series of ethanol
and critical-point dried with HMDS, mounted on aluminum
stubs and gold-sputter coated to prepare them for analysis
under a field-emission scanning electron microscope (FE-SEM,
Hitachi S-4000).
3.
Results
3.1.
Microleakage analysis
A total of 144 specimen sections were available for evaluation
of microleakage at the interface. Three sections were obtained
from each of the 48 teeth and information was gathered from
both sides of each section. Microleakage was observed in most
of the specimens, especially on the dentin side, which is consistent with existing evidence [13–18].
Mean microleakage values for the dentin side were 44.1%
in the Variolink and Excite group (E + V), 55.5% in the Single
Bond and Unicem group (SB + U), 54.7% in the Prompt and
Unicem group (AP + U) and 28.1% in the Unicem group (U)
(Fig. 2). ANOVA test was significant and the test for equal variances was not significant. The Student–Newman–Kuel’s (SNK)
test to compare means (˛ = 0.05) revealed that on dentin: U
had significantly less leakage than SB + U and AP + U but was
not different than E + V and that E + V, SB + U, AP + U were not
shown to differ.
The microleakage values for the enamel side were 2.5% in
the E + V group, 3.1% in SB + U group, 2.2% in the AP + U group
Fig. 2 – Mean percent microleakage values between
porcelain veneers and dentin. The numbers identify mean
subsets not shown to differ at ˛ = 0.05. The vertical bars
show the value of a single standard deviation.
and 10.8% in the U group (Fig. 3). ANOVA test for main effects
was again significant, as was the test for equal variances
due to a higher standard deviation associated with enamel
microleakage for U. For this reason, the Games–Howell test
(˛ = 0.05) was employed to compare means. This test revealed
that on enamel, U had leakage values that were significantly
greater than any of the groups where an adhesive system
was used in combination with the luting cement. In the latter
groups, leakage was minimal and no statistically significant
difference was found amongst them (Fig. 3).
3.2.
Scanning electron microscopy analysis
The interface of the samples cemented with E + V, SB + U
and AP + U showed good adaptation of the cement to the
enamel surface. No gap formation between the cement and
the enamel was evident in the E + V group, which is consistent
with the microleakage values obtained for these specimens
(Fig. 4). It appeared that the use of an adhesive resulted in
consistently good adaptation of the cement to the enamel,
regardless of the type of conditioning, as was demonstrated
by similar leakage values when using phosphoric acid and the
self-etching adhesive system (Figs. 5 and 6).
The samples treated only with unicem (U) showed a gap
between the cement and the enamel, which is in accordance with the high leakage values observed in this group
(Figs. 7 and 8).
Fig. 3 – Mean percent microleakage values between
porcelain veneers and enamel. The numbers identify mean
subsets not shown to differ at ˛ = 0.05. The vertical bars
show the value of a single standard deviation.
d e n t a l m a t e r i a l s x x x ( 2 0 0 6 ) xxx–xxx
Fig. 4 – Scanning electron microscopy image showing good
adaptation at the enamel–cement interface (arrows) in a
sample cemented with E + V. An almost imperceptible
transition seemed to take place at the
enamel–cement–porcelain interface, where minimal
leakage values were observed.
5
Fig. 6 – Scanning electron microscopy image showing good
adaptation at the enamel–cement interface (arrows) in a
sample cemented with AP + U. Minimal leakage values
were also observed in these set of specimens.
Fig. 7 – Scanning electron microscopy image showing gap
formation at the enamel–cement interface (arrows). An
imperceptible transition seemed to take place at the
cement–porcelain interface, where no leakage was
observed.
Fig. 5 – Scanning electron microscopy image showing good
adaptation at the enamel–cement interface (arrows) in a
sample cemented with SB + U. An almost imperceptible
transition seemed to take place at the
enamel–cement–porcelain interface, where minimal
leakage values were also observed.
4.
Discussion
The use of dyes is one of the oldest techniques to measure
microleakage and the use of a 50 wt.% silver nitrate solution
has been considered an acceptable technique for this purpose
6
d e n t a l m a t e r i a l s x x x ( 2 0 0 6 ) xxx–xxx
Fig. 8 – Scanning electron microscopy image showing gap
formation at the enamel–unicem interface (arrows). An
imperceptible transition seemed to take place at the
cement–porcelain interface, where no leakage was
observed.
[19]. A disadvantage of this tracer is that the silver nitrate
particle is an extremely small particle that measures approximately 0.059 nm in radius and the solution has an acidic pH
of ∼4.2 [9,20]. Therefore, penetration of the silver particle at
the interface is frequently observed and it has been suggested
that it may be greater because of dissolution of remnant calcium phosphate salts at the adhesive interface, resulting in
increased porosity due to a light etching effect by the mildly
acidic solution. To avoid this potential drawback, the use of
a buffered solution of ammoniacal silver nitrate with a pH of
∼9.5, has been reported [20] and was used in the current study.
4.1.
Dentin interface
Without any conditioning, the self-etching cement Rely-X
Unicem (3M-ESPE) (U) showed improved sealing of dentin at
the cervical margin when compared to a conventional resin
cement for which the smear layer was removed by the use
of phosphoric acid, although this was not statistically significant in this study. These findings are in accordance with Behr
et al. [5] who found similar marginal adaptation based on dye
penetration and SEM replica analysis, to that obtained with
conventional cements on dentin margins.
The use of two different adhesive systems, a one-step totaletch (Single Bond, 3M-ESPE) and a one-step self-etch (Rely-X
Adper Prompt, 3M-ESPE), to condition the enamel and dentin
prior to cementation, did not improve the sealing ability of
(U) in dentin, when compared to the control. De Munck et
al. [21] reported similar TBS values when bonding to dentin
using Rely-X Unicem without previously etching the dentin
with H3 PO4 or a conventional cement as a control. However,
when the dentin was etched prior to cementation with RelyX Unicem, the TBS values significantly decreased. Similarly,
in the present study, when the dentin was pre-treated with
either H3 PO4 or an acidic monomer from the self-etching system, increased leakage was observed. Pre-etching may remove
all of the buffer capacity of dentin, interfering with its ability
to raise the pH of the acidic resin as it sets, thereby lowering
its conversion (David Pashley, personal communication).
According to Behr et al. [5], in images obtained with transmission electron microscopy, a lack of a hybrid layer is evident
at the dentin interface when the self-adhesive cement is used.
This agrees with De Munck et al. [21] who reported no evidence
of dentin demineralization even considering the initial low pH
of the cement (pH
Microleakage of porcelain veneer restorations
bonded to enamel and dentin with a new selfadhesive resin-based dental cement
Article in Dental Materials · March 2007
DOI: 10.1016/j.dental.2006.01.013 · Source: PubMed
CITATIONS
READS
70
265
4 authors, including:
Gabriela Ibarra
Oregon Health and Science University
11 PUBLICATIONS 201 CITATIONS
SEE PROFILE
All content following this page was uploaded by Gabriela Ibarra on 16 December 2016.
The user has requested enhancement of the downloaded file. All in-text references underlined in blue are added to the original document
and are linked to publications on ResearchGate, letting you access and read them immediately.
d e n t a l m a t e r i a l s x x x ( 2 0 0 6 ) xxx–xxx
available at www.sciencedirect.com
journal homepage: www.intl.elsevierhealth.com/journals/dema
Microleakage of porcelain veneer restorations bonded to
enamel and dentin with a new self-adhesive resin-based
dental cement
Gabriela Ibarra a,∗ , Glen H. Johnson a , Werner Geurtsen a , Marcos A. Vargas b
a
b
School of Dentistry, Department of Restorative Dentistry, University of Washington, Seattle, WA, USA
College of Dentistry, Department of Operative Dentistry, University of Iowa, Iowa City, USA
a r t i c l e
i n f o
a b s t r a c t
Article history:
Cementation technique of bonded ceramic restorations is a time-consuming and technique-
Received 29 September 2005
sensitive procedure critical to long-term success.
Received in revised form 19
Objective. Evaluate the performance of a self-adhesive, modified-resin dental cement (Rely-
December 2005
X UniCem, 3M-ESPE) for the cementation of ceramic veneer restorations without previous
Accepted 10 January 2006
conditioning of the tooth surface, and in combination with a one-bottle adhesive and a
self-etching adhesive.
Methods. Thirty-six premolars received a veneer preparation that extended into dentin.
Keywords:
Leucite-reinforced pressed glass ceramic (Empress 1) veneers were cemented follow-
Self-adhesive resin cement
ing manufacturers’ instructions, according to the following treatment groups (n = 9): (1)
Ceramic veneers
Variolink–Excite Ivoclar–Vivadent (V + E control), (2) Unicem + Single Bond 3M-ESPE (U + SB),
Microleakage
(3) Unicem + Adper Prompt L-Pop 3M-ESPE (U + AP), (4) Unicem 3M-ESPE (U). After 24 h stor-
Dentin adhesion
age at 37 ◦ C, teeth were thermocycled (2000 cycles) at 5 and 55 ◦ C, immersed in ammoniacal
Enamel adhesion
silver nitrate for 24 h, placed in a developer solution overnight and sectioned using a slowspeed saw. Three 1 mm longitudinal sections were obtained from each tooth and evaluated
for leakage with a microscope (1× to 4×). Imaging software was used to measure stain penetration along the dentin and enamel surfaces.
Results. ANOVA with SNK (˛ = 0.05) revealed that on dentin, U had significantly less leakage
than U + SB and U + AP, but no different than V + E; on enamel U had leakage values that were
significantly greater than the groups with adhesives.
Significance. The self-adhesive cement U gave low leakage on dentin that was comparable
to the cement that employed an adhesive for sealing dentin, whereas this cement benefits
from use of an adhesive when cementing to enamel.
© 2006 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.
1.
Introduction
The use of bonded ceramic restorations in dentistry has
increased appreciably due to the development of adhesive
materials that allow for more conservative restorative techniques as well as the ability of achieving excellent esthetic
appearance and adequate strength [1]. Among these bonded
ceramic restorations, ceramic veneers have gained popularity
∗
Corresponding author at: Department of Restorative Dentistry, University of Washington, 1959 N.E. Pacific Street, Box 357456, Seattle,
WA 98195-7456, USA. Tel.: +1 206 543 5948; fax: +1 206 543 7783.
E-mail address: gibarra@u.washington.edu (G. Ibarra).
0109-5641/$ – see front matter © 2006 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.
doi:10.1016/j.dental.2006.01.013
DENTAL-913;
No. of Pages 8
2
d e n t a l m a t e r i a l s x x x ( 2 0 0 6 ) xxx–xxx
as a conservative restoration, where a thin ceramic covering
is bonded, preferentially to enamel, after minimal preparation
on tooth structure [2,3].
The cementation technique, which is a time-consuming
and technique-sensitive procedure, is key to the long-term
success of these types of restorations. The strength and
the durability of the bond between the porcelain, the luting
cement and the enamel/dentin interface play an important
role in the outcome of ceramic veneers, particularly when
dentin is involved [3]. It is not uncommon that, particularly
in the gingival third of a veneer preparation, dentin will be
exposed due to the thin layer of enamel present at this site [4].
In this case, the cementation procedure becomes even more
critical because high failure rates in veneers have been associated to large exposed dentin surfaces and the cervical margin
has been regarded as a problematic area to achieve perfect
marginal adaptation [3].
A self-adhesive, resin-based dental cement (Rely-X
UniCem, 3M-ESPE), which advocates no pre-treatment of
tooth surfaces, thus simplifying the cementation procedure, has recently been introduced. This cement has an
organic matrix composed of multi-functional phosphoric acid
methacrylates, which react with inorganic fillers (72 wt.%)
that are basic in nature or with hydroxyapatite from tooth
structure. Water that is released from the setting reaction
is thought to play a role in its neutralization, raising the
pH value from 1 to 6. The setting of the cement is based
on a free radical polymerization reaction initiated by either
photoactivation or a redox system [5,6].
The cement has been recommended for luting all metalbased and ceramic crowns, as well as partial coverage ceramic
and indirect composite restorations, with the exception of
veneers [5,6].
Good marginal adaptation of all-ceramic crowns cemented
with Rely-X UniCem to dentin has already been documented
[5]. Preliminary studies have shown good results when bonding pressed ceramic inlay restorations to dentin and enamel
margins [7].
If the self-adhesive cement could be used predictably for
the cementation of ceramic veneer restorations, it would serve
as a user-friendly universal cement. However, more studies
are needed before final recommendations for the clinical use
of this cement can be made.
The clinical success of cemented restorations has been
evaluated by measuring marginal fit and microleakage for
many years, in spite of the fact that there is no restoration
or luting material able to achieve a complete marginal seal
[8,9]. In the case of all-ceramic restorations, microleakage has
been correlated with the loss of the integrity of the bond
to tooth structure, and this has been associated with other
problems such as secondary caries, post-operative sensitivity,
pulpal inflammation, staining and plaque accumulation [9–11]
due to the clinically undetectable passage of bacteria, fluids,
molecules or ions between tooth structure and the cemented
restoration [12].
The aim of this study was to test the hypothesis that
the application of a new self-adhesive resin cement, used
as a luting agent, would result in good marginal integrity of
ceramic veneers to dentin as well as enamel, without prior
conditioning of the tooth surface or in combination with
other adhesive systems that previously condition enamel and
dentin.
Altogether, the hypothesis tested was that the microleakage of the new self-adhesive luting cement is similar to a
conventional resin cement when bonding a porcelain veneer
to enamel and dentin.
2.
Materials and methods
Thirty-six human premolars, previously stored in a
NaN3 + NaCl solution for no more than 6 months, were
prepared for porcelain veneer restorations. The preparations
were made with a #834 016 bur (Brasseler, Savannah, GA
31419, USA) to establish a 0.3 mm depth cut, and finished
with a fine rounded tip diamond #6844 016 (Brasseler, Savannah, GA 31419, USA). The preparation’s margins ended as
butt joint at the incisal edge and a chamfer that extended
approximately 1 mm beyond the CEJ. An impression of
each of the preparations was made with a vinyl polysiloxane
impression material (Aquasil LV and Aquasil, Caulk, Dentsply;
Lot 020608) using copper rings for material retention. The
teeth were then stored in artificial saliva solution and the
impressions were sent to a commercial laboratory (Nakanishi Dental Laboratory Inc., Seattle, WA). Leucite-reinforced
pressed ceramic (Empress I) porcelain veneer restorations
were fabricated in an A-1 shade based on the Vita shade
guide, etched with hydrofluoric acid and silanated in the
laboratory.
The teeth were then divided into four treatment groups
according to the cementation procedure (Table 1). Group
1: restorations cemented using a conventional resin-based
cement and its proprietary adhesive system as a control (Variolink II [Base Yellow 210/A3, Lot E 43489; Catalyst Lot E 34696] and Excite [Lot E41824], Ivoclar/Vivadent).
Group 2: restorations cemented using self-adhesive, modifiedresin dental cement (Rely-X UniCem Maxicaps, 3M-ESPE;
Lot 143650) in combination with enamel and dentin conditioning with phosphoric acid and a one-bottle adhesive system (Single Bond, 3M-ESPE). Group 3: restorations
cemented using a self-adhesive resin-based dental cement
(Rely-X UniCem Maxicaps, 3M-ESPE; Lot 143650) in combination with a self-etching adhesive system (Adper Prompt
L-Pop, 3M-ESPE; Lot 147563) to condition enamel and dentin.
Group 4: restorations cemented with a self-adhesive resinbased dental cement (Rely-X UniCem Maxicaps, 3M-ESPE;
Lot 143650) without previous conditioning of enamel and
dentin.
Before cementation, all veneers were tried-in, cleaned with
phosphoric acid and re-silanated (Rely-X Ceramic Primer; Lot
2721) in accordance with clinical practice.
Light-curing of the adhesives and the cement was carried
out with a Demetron 401 light unit (Demetron/Kerr, Danbury, CT) as indicated in Table 1. Light output was measured every six samples to ensure proper resin polymerization
(750 mW/cm2 ).
The specimens were stored in artificial saliva at 37 ◦ C for
72 h and were thermocycled in 5 and 55 ◦ C water temperatures
for 2000 cycles with 20 s dwell time at each temperature and a
transfer time of 10 s, for a total of 60 s per cycle.
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d e n t a l m a t e r i a l s x x x ( 2 0 0 6 ) xxx–xxx
Table 1 – Application technique for seating ceramic veneer restorations with different adhesive systems and luting
cements
Treatment
Materials
Excite/Variolink
Veneer preparation
Substrate preparation
Seating instructions
2.1.
Etch with H3 PO4 × 60 s
Rinse × 30 s
Air dry
Silanate internal
aspect × 60 s
Allow solvent to
evaporate
Apply adhesive to
internal aspect
Air-thin
DO NOT light cure
H3 PO4 : etch
enamel × 15–30 s and
dentin × 10–15 s
Rinse: 5 s at least
Single bond/Unicem
Prompt L-pop/Unicem
Etch with H3 PO4 × 60 s
Rinse × 30 s
Air dry
Silanate internal
aspect × 60 s
Allow solvent to
evaporate
Apply one coat of
adhesive to internal
aspect
Air-dry for 2–5 s
DO NOT light cure
H3 PO4 : etch enamel and
dentin × 10 s
Etch with H3 PO4 × 60 s
Rinse × 30 s
Air dry
Silanate internal
aspect × 60 s
Allow solvent to
evaporate
Lightly scrub one layer
of adhesive to internal
aspect: 15 s
Air-thin
DO NOT light cure
Slightly dry surface
Rinse: 30 s
Adhesive: lightly scrub
one layer on enamel
and dentin: 15 s
Air-thin
Remove excess
water—do not over-dry
dentin
Adhesive: apply several
layers
Blot excess water—leave
moist surface
Air-dry: 1–3 s. Avoid
pooling
Cure: 20 s
Apply base cement to
veneer and tooth
Maintain pressure for
several seconds and
tack: 10–20 s
Remove excess cement
with brush
Light-cure × 40 s
Air dry: 2–5 s
Adhesive: apply a
second coat without
rubbing
Air dry
DO NOT light cure
Apply mixed cement to
veneer
Tack-cure excess
cement × 2–4 s and
remove
Light-cure × 40 s
DO NOT light cure
Apply mixed cement to
veneer
Tack-cure excess
cement × 2–4 s and
remove
Light-cure × 40 s
Adhesive: apply 2 coats
Unicem
Etch with H3 PO4 × 60 s
Rinse × 30 s
Air dry
Silanate internal
aspect × 60 s
Allow solvent to
evaporate
Leave dentin and
enamel surface
moist/glossy
Apply mixed cement to
veneer
Tack-cure excess
cement × 2–4 s and
remove
Light-cure × 40 s
Microleakage evaluation
The apices of the roots were sealed with an acrylic resin
(Duralay Inlay Pattern Resin, Reliance) and the teeth were then
coated with two layers of quick dry nail varnish that extended
up to 1 mm from the margins of the ceramic veneer restorations. Care was taken not to over dry the enamel surrounding
the margins while the nail varnish dried.
The teeth were placed in 50 wt.% ammoniacal silver
nitrate for 24 h, rinsed extensively with water, and placed in
freshly mixed developer solution (Kodak Developer D-76, CAT
1464817, 0251 C5 02749) under a strong light for 12 h. After
rinsing them with water and sand blasting the porcelain surface carefully, a 1 mm layer of composite was bonded to the
veneer (All Bond 2, Bisco, Lot 0200002521; Filtek Z 250 B 1 shade,
3M-ESPE, Lot 9BB) to provide sufficient bulk for handling, and
light-cured for 40 s. The roots were removed and the crowns
were sectioned in a cervical–incisal direction with a diamond
blade to obtain three slices (∼1 mm) from each tooth (Fig. 1).
Sections were analyzed for leakage at the cervical and
incisal margins by means of a light microscope (Nikon Eclipse
E400, Japan) at 1×, 2× and 4×, using an image analysis com-
Fig. 1 – Section of the crown showing the interface of
enamel (E) and dentin (D) with the porcelain veneer (PV)
and the overlying composite (C). Penetration of the
ammoniacal silver nitrate can be observed on the dentin
side (arrow).
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d e n t a l m a t e r i a l s x x x ( 2 0 0 6 ) xxx–xxx
puter program (Meta Vue, Universal Imaging Corp., Downingtown, PA). Microleakage values were obtained by measuring
stain penetration for the total surface length, separately for
dentin and enamel, and were expressed as a percentage of
the total length of the veneer preparation.
2.2.
Statistical analysis
Since there were four different cement-bonding combinations
(i.e., treatments) and samples were independent, a singlefactor analysis of variance model was employed to test for
significant main effects, separately for dentin and for enamel.
If main effects were significant (˛ = 0.05) and test for equal variance was not significant, the Student–Newman–Kuel’s post
hoc test for multiple comparison of means was conducted
to determine which means differed. When the assumption
of equal variances was not met, the Games–Howell post hoc
test was used to identify which means differed. All hypothesis
testing was conducted at the 95% level of confidence.
2.3.
SEM evaluation
After cementation, one tooth from each group was prepared
for SEM evaluation. The teeth were stored in water for 4 weeks
and were fixed for 72 h in 2.5% glutaraldehyde in 0.1 M Nacacodylate buffer. Cross-sections of an approximate thickness
of 1 mm (Fig. 1) were obtained from the teeth using a watercooled slow-speed diamond saw (Buehler Isomet 1000TM ,
Buehler Ltd., Lake Bluff, IL, USA) and each section was sequentially polished with 600 and 800 grit of silicon carbide paper, 6
and 1 m diamond slurries and 0.04 m aluminum oxide. The
specimens were dehydrated in an ascending series of ethanol
and critical-point dried with HMDS, mounted on aluminum
stubs and gold-sputter coated to prepare them for analysis
under a field-emission scanning electron microscope (FE-SEM,
Hitachi S-4000).
3.
Results
3.1.
Microleakage analysis
A total of 144 specimen sections were available for evaluation
of microleakage at the interface. Three sections were obtained
from each of the 48 teeth and information was gathered from
both sides of each section. Microleakage was observed in most
of the specimens, especially on the dentin side, which is consistent with existing evidence [13–18].
Mean microleakage values for the dentin side were 44.1%
in the Variolink and Excite group (E + V), 55.5% in the Single
Bond and Unicem group (SB + U), 54.7% in the Prompt and
Unicem group (AP + U) and 28.1% in the Unicem group (U)
(Fig. 2). ANOVA test was significant and the test for equal variances was not significant. The Student–Newman–Kuel’s (SNK)
test to compare means (˛ = 0.05) revealed that on dentin: U
had significantly less leakage than SB + U and AP + U but was
not different than E + V and that E + V, SB + U, AP + U were not
shown to differ.
The microleakage values for the enamel side were 2.5% in
the E + V group, 3.1% in SB + U group, 2.2% in the AP + U group
Fig. 2 – Mean percent microleakage values between
porcelain veneers and dentin. The numbers identify mean
subsets not shown to differ at ˛ = 0.05. The vertical bars
show the value of a single standard deviation.
and 10.8% in the U group (Fig. 3). ANOVA test for main effects
was again significant, as was the test for equal variances
due to a higher standard deviation associated with enamel
microleakage for U. For this reason, the Games–Howell test
(˛ = 0.05) was employed to compare means. This test revealed
that on enamel, U had leakage values that were significantly
greater than any of the groups where an adhesive system
was used in combination with the luting cement. In the latter
groups, leakage was minimal and no statistically significant
difference was found amongst them (Fig. 3).
3.2.
Scanning electron microscopy analysis
The interface of the samples cemented with E + V, SB + U
and AP + U showed good adaptation of the cement to the
enamel surface. No gap formation between the cement and
the enamel was evident in the E + V group, which is consistent
with the microleakage values obtained for these specimens
(Fig. 4). It appeared that the use of an adhesive resulted in
consistently good adaptation of the cement to the enamel,
regardless of the type of conditioning, as was demonstrated
by similar leakage values when using phosphoric acid and the
self-etching adhesive system (Figs. 5 and 6).
The samples treated only with unicem (U) showed a gap
between the cement and the enamel, which is in accordance with the high leakage values observed in this group
(Figs. 7 and 8).
Fig. 3 – Mean percent microleakage values between
porcelain veneers and enamel. The numbers identify mean
subsets not shown to differ at ˛ = 0.05. The vertical bars
show the value of a single standard deviation.
d e n t a l m a t e r i a l s x x x ( 2 0 0 6 ) xxx–xxx
Fig. 4 – Scanning electron microscopy image showing good
adaptation at the enamel–cement interface (arrows) in a
sample cemented with E + V. An almost imperceptible
transition seemed to take place at the
enamel–cement–porcelain interface, where minimal
leakage values were observed.
5
Fig. 6 – Scanning electron microscopy image showing good
adaptation at the enamel–cement interface (arrows) in a
sample cemented with AP + U. Minimal leakage values
were also observed in these set of specimens.
Fig. 7 – Scanning electron microscopy image showing gap
formation at the enamel–cement interface (arrows). An
imperceptible transition seemed to take place at the
cement–porcelain interface, where no leakage was
observed.
Fig. 5 – Scanning electron microscopy image showing good
adaptation at the enamel–cement interface (arrows) in a
sample cemented with SB + U. An almost imperceptible
transition seemed to take place at the
enamel–cement–porcelain interface, where minimal
leakage values were also observed.
4.
Discussion
The use of dyes is one of the oldest techniques to measure
microleakage and the use of a 50 wt.% silver nitrate solution
has been considered an acceptable technique for this purpose
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d e n t a l m a t e r i a l s x x x ( 2 0 0 6 ) xxx–xxx
Fig. 8 – Scanning electron microscopy image showing gap
formation at the enamel–unicem interface (arrows). An
imperceptible transition seemed to take place at the
cement–porcelain interface, where no leakage was
observed.
[19]. A disadvantage of this tracer is that the silver nitrate
particle is an extremely small particle that measures approximately 0.059 nm in radius and the solution has an acidic pH
of ∼4.2 [9,20]. Therefore, penetration of the silver particle at
the interface is frequently observed and it has been suggested
that it may be greater because of dissolution of remnant calcium phosphate salts at the adhesive interface, resulting in
increased porosity due to a light etching effect by the mildly
acidic solution. To avoid this potential drawback, the use of
a buffered solution of ammoniacal silver nitrate with a pH of
∼9.5, has been reported [20] and was used in the current study.
4.1.
Dentin interface
Without any conditioning, the self-etching cement Rely-X
Unicem (3M-ESPE) (U) showed improved sealing of dentin at
the cervical margin when compared to a conventional resin
cement for which the smear layer was removed by the use
of phosphoric acid, although this was not statistically significant in this study. These findings are in accordance with Behr
et al. [5] who found similar marginal adaptation based on dye
penetration and SEM replica analysis, to that obtained with
conventional cements on dentin margins.
The use of two different adhesive systems, a one-step totaletch (Single Bond, 3M-ESPE) and a one-step self-etch (Rely-X
Adper Prompt, 3M-ESPE), to condition the enamel and dentin
prior to cementation, did not improve the sealing ability of
(U) in dentin, when compared to the control. De Munck et
al. [21] reported similar TBS values when bonding to dentin
using Rely-X Unicem without previously etching the dentin
with H3 PO4 or a conventional cement as a control. However,
when the dentin was etched prior to cementation with RelyX Unicem, the TBS values significantly decreased. Similarly,
in the present study, when the dentin was pre-treated with
either H3 PO4 or an acidic monomer from the self-etching system, increased leakage was observed. Pre-etching may remove
all of the buffer capacity of dentin, interfering with its ability
to raise the pH of the acidic resin as it sets, thereby lowering
its conversion (David Pashley, personal communication).
According to Behr et al. [5], in images obtained with transmission electron microscopy, a lack of a hybrid layer is evident
at the dentin interface when the self-adhesive cement is used.
This agrees with De Munck et al. [21] who reported no evidence
of dentin demineralization even considering the initial low pH
of the cement (pH