UNIVERSIDADE ESTADUAL PAULISTA
“JÚLIO DE MESQUITA FILHO”
Instituto de Ciência e Tecnologia
Campus de São José dos Campos
ORIGINAL ARTICLE DOI: https://doi.org/10.4322/bds.2023.e3978
1
Braz Dent Sci 2023 Oct/Dec;26 (4): e3978
Effect of adhesive primer application on shear bond strength
of self-adhesive cement to tooth structure and two different
CAD/CAM milled blocks
Efeito da aplicação do primer adesivo na resistência ao cisalhamento do cimento autoadesivo à estrutura dentária e a dois
diferentes blocos fresados CAD/CAM
Moamin I. ISSA1 , Marwah Ismael ABDULAZEEZ2 , Abdalbseet A. FATALLA1
1 - University of Baghdad, College of Dentistry, Department of Prosthodontics. Baghdad, Iraq.
2 - University of Baghdad, College of Dentistry, Department of Restorative and Esthetic Dentistry. Baghdad, Iraq.
How to cite: Issa MI, Abdulazeez MI, Fatalla AA. Effect of adhesive primer application on shear bond strength of self-adhesive cement to
tooth structure and two different CAD/CAM milled blocks. Braz Dent Sci. 2023;26(4):e3978. https://doi.org/10.4322/bds.2023.e3978
ABSTRACT
Objective: This study was conducted to evaluate the inuence of the G-CEM ONE adhesive enhancing primer on
the shear bond strength of self-adhesive resin cement (G-CEM ONE) to both tooth structure and two different CAD/
CAM blocks (GC Initial LiSi and Cerasmart 270). Material and Methods: Forty specimens (cylindrical-shaped,
5 mm in diameter and height) were milled from both CAD/CAM blocks (20 specimens from each block type).
Forty sound upper premolars were sectioned to the level of peripheral dentin, then randomly divided into four
groups (n = 10): A1: GC Initial LiSi without adhesive enhancing primer; B1: Cerasmart 270 without adhesive
enhancing primer; A2: GC Initial LiSi with adhesive enhancing primer; B2: Cerasmart 270 group with adhesive
enhancing primer application. The CAD/CAM blocks were cemented on teeth using a self-adhesive resin cement
(G-cem one). The shear bond strength was assessed using a computerized universal testing machine. A digital
microscope was used to study the mode of failure. The shear bond strength values data were analyzed statistically
using paired
t
-test and independent
t
-test at the signicance level of (0.05). Results: A signicant difference was
shown in the shear bond strength values among groups (
P
=0.000). The highest shear bond strength value was
revealed in group A2, while group B1 exhibited the lowest shear bond strength value. Conclusion: Using the
adhesive enhancing primer on the tooth’s surface improved the resin cement’s bond strength to CAD/CAM blocks.
Additionally, GC Initial LiSi exhibited higher bond strength than Cerasmart 270, with or without the primer.
KEYWORDS
Adhesive; CAD/CAM; Dentin; Resin cement; Shear strength.
RESUMO
Objetivo: Este estudo foi conduzido para avaliar a inuência do primer adesivo G-CEM ONE na resistência
ao cisalhamento do cimento resinoso autoadesivo (G-CEM ONE) tanto na estrutura dentária quanto em dois
diferentes blocos CAD/CAM (GC Initial LiSi e Cerasmart 270). Material e Métodos: Quarenta corpos de prova
(formato cilíndrico, 5 mm de diâmetro e altura) foram fresados em blocos CAD/CAM (20 corpos de prova de
cada tipo de bloco). Quarenta pré-molares superiores sadios foram seccionados até o nível da dentina mais
externa e, em seguida, divididos aleatoriamente em quatro grupos (n = 10): A1: GC Initial LiSi sem primer
adesivo; B1: Cerasmart 270 sem primer adesivo; A2: GC Initial LiSi com primer adesivo; B2: Grupo Cerasmart
270 com aplicação de primer adesivo. Os blocos CAD/CAM foram cimentados nos dentes com cimento resinoso
autoadesivo (G-CEM ONE). A resistência ao cisalhamento foi avaliada utilizando uma máquina de ensaios
universal computadorizada. Um microscópio digital foi utilizado para estudar o modo de falha. Os dados dos
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Braz Dent Sci 2023 Oct/Dec;26 (4): e3978
Issa MI et al.
Effect of adhesive primer application on shear bond strength of self-adhesive cement to tooth structure and two different CAD/CAM milled blocks
Issa MI et al. Effect of adhesive primer application on shear bond strength
of self-adhesive cement to tooth structure and two different
CAD/CAM milled blocks
INTRODUCTION
Recent advances in dental technologies have
increased the popularity of different computer-
aided design /computer-aided manufacturing
(CAD/CAM)-machinable materials, including
glass ceramics, resin-based Composites, and
polymer-inltrated ceramics [1]. Among these
materials, ceramics have the advantage of
natural-looking, wear resistance, durability, and
biocompatibility [2,3]. Yet, ceramic restorations
could be more susceptible to chipping due to
their brittle nature [4]. Lithium disilicate (LiSi)
glass-ceramic is one of the most widely used
ceramic systems in aesthetic dentistry due to its
high optical and mechanical properties. GC Initial
LiSi is a fully crystallized lithium disilicate CAD/
CAM ceramic with the advantage of decreasing
the chair side time as it does not require further
heat treatment after milling [5,6].
Although composite resin blocks have lower
exural strength than ceramics, they have the
advantages of low abrasiveness to the antagonist,
ease of modication and repair, reduced milling
time, and less wear of milling tools [7,8].
CAD/CAM composite resin matrix ceramics
were developed to combine the advantages of
composites and ceramics [9,10]. These blocks
can be classied into two types depending on
their microstructure: materials with a polymer-
infiltrated ceramic network (PICN) such as
VITA Enamic and materials with dispersed
fillers; nanohybrid-composite with inorganic
ceramic fillers such as Cerasmart and Lava
Ultimate [11]. PICN materials consist of a glass/
ceramic network, frequently pre-sintered, that
has been silanated by capillary action and then
inltrated with a resin matrix, while materials
with dispersed llers consist of a methacrylate-
based matrix similar to that of direct composite
materials reinforced by different types and sizes
of silanated fillers [12]. Cerasmart is a resin
nano-ceramic block containing composite resin
material (BisMEPP, UDMA, DMA) with 71% silica
and barium glass nanoparticles by weight [13].
Durable bonding between the cement and
restorative material is crucial for the longevity
of the indirect restoration. Adhesive luting of
the restoration has two bonding interfaces; thus,
the type of resin cement signicantly impacts the
restoration’s clinical outcome [14]. Introducing
self-adhesive resin cement could simplify the
multi-steps of adhesive bonding and minimize the
possibility of handling errors and post-operative
sensitivity [15]. This type of cement provides
micromechanical retention due to the presence
of acidic monomers that could demineralize and
penetrate the tooth surface. Additionally, the
reaction between the acidic monomers of the
cement and hydroxyapatite of the tooth substrate
results in chemical retention. Yet, some studies
have stated that self-adhesive resin cement
provides poor adhesion to dentine that could
reduce the bond strength [16,17].
A new self-adhesive resin cement called
G-CEM ONE (GC Corporation, Tokyo, Japan)
was recently introduced with an additional
agent, G-CEM ONE Adhesive enhancing primer)
GC Corporation, Tokyo, Japan) [18]. This
primer is comprised of acidic monomers such as
4-2-(methacryloyloxy)ethoxy] carbonyl phthalic
acid (4-MET) and 10-methacryloyloxydecyl
dihydrogen phosphate (10-MDP) that could
enhance the infiltration of the cement in the
dentinal tubules. Moreover, the “touch-curing
catalyst” in the primer is claimed to enhance the
chemical polymerization of the cement [19,20].
Limited information is available in the
literature concerning this adhesive primer; thus,
the present study was applied to investigate the
influence of G-CEM ONE adhesive enhancing
primer on the shear bond strength (SBS) of self-
adhesive resin cement; G-CEM ONE to both tooth
valores de resistência ao cisalhamento foram analisados estatisticamente por meio do teste t pareado e teste t
independente ao nível de signicância de (0,05). Resultados: Foi demonstrada diferença signicativa nos valores
de resistência ao cisalhamento entre os grupos (P =0,000). O maior valor de resistência ao cisalhamento foi
revelado no grupo A2, enquanto o grupo B1 exibiu o menor valor de resistência ao cisalhamento. Conclusão:
A utilização do primer adesivo na superfície dentária melhorou a resistência de união do cimento resinoso aos
blocos CAD/CAM. Além disso, o GC Initial LiSi apresentou maior resistência de união que o Cerasmart 270,
com ou sem primer.
PALAVRAS-CHAVE
Adesivo; CAD/CAM; Dentina; Cimento resinoso; Força de cisalhamento.
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Braz Dent Sci 2023 Oct/Dec;26 (4): e3978
Issa MI et al.
Effect of adhesive primer application on shear bond strength of self-adhesive cement to tooth structure and two different CAD/CAM milled blocks
Issa MI et al. Effect of adhesive primer application on shear bond strength
of self-adhesive cement to tooth structure and two different
CAD/CAM milled blocks
structure and two different CAD/CAM blocks;
GC Initial LiSi [lithium disilicate] and Cerasmart
270, and evaluating the mode of failure. The rst
null hypothesis is the application of the adhesive
enhancing primer doesn’t affect the shear bond
strength between the tooth structure and CAD/
CAM blocks. The second null hypothesis, there
is no difference in the shear bond strength of
different CAD/CAM blocks to tooth structure
using self-adhesive resin cement.
MATERIALS AND METHODS
Preparation of CAD/CAM specimens
Forty cylindrical-shaped specimens (5 mm
in diameter and height) were milled from both
CAD/CAM blocks using an In-Lab MC X5 milling
device (Sirona, Germany). 20 specimens from
GC Initial LiSi (GC Corporation, Tokyo, Japan)
and 20 specimens from Cerasmart 270 (GC
Corporation, Tokyo, Japan). The bonding surface of
each cylinder was then treated with silicon carbide
abrasive paper #grit 80 under water cooling using
a grinding and polishing machine (MOpao 160E,
China) to provide standardized roughness [21].
The specimens were then ultrasonically cleaned
in an ultrasonic unit with distilled water for
5 minutes to remove contaminants.
Preparation of teeth specimens
This work has been approved by the research
ethics committee (ref. number 808, project number
808223 at 18.5.2023). Forty sound human upper
1st premolars extracted for orthodontic purposes
were collected. The selected samples were intact
and free from caries, cracks, and restorations.
The teeth were washed with distilled water and
stored in normal saline 0.9% at room temperature.
Each tooth specimen was then embedded in acrylic,
which was used as a holding block. A line 3 mm
occlusal (above) the cemento-enamel junction was
drawn on each tooth to determine the area to be
embedded in acrylic. A custom-made silicon mold
with dimensions (1.5× 1.5× 2 cm) was used to
aid in the construction of standardized acrylic
holding blocks, this mold acted as a container
to hold the acrylic during the setting time. Each
tooth was then attached to the dental surveyor and
embedded along its long axis in cold cure acrylic
(Veracril, Colombia) till the drawn line and the
acrylic allowed to set. The occlusal surface of each
tooth was reduced down to the level of the central
groove to expose the peripheral dentine surface.
Tooth reduction was done using a diamond disc in
a straight handpiece mounted to a dental surveyor
with water cooling. The cut surface of each tooth
was then finished with silicon carbide abrasive
papers grit #220, then grit # 500 with water cooling
using the same grinding and polishing machine that
was used for nishing the CAD/CAM specimens
to provide a standardized surface roughness of all
specimens [21]. The prepared tooth and CAD/CAM
specimens are shown in Figure 1.
Sample grouping
The prepared samples were assigned into
two groups (20 teeth for each group) according
to the type of the cemented CAD/CAM block.
Each group was subdivided into two subgroups
(10 teeth for each subgroup) according to the
application or not of the adhesive primer:
Group A1: GC Initial LiSi group without
adhesive enhancing primer application.
Group B1: Cerasmart 270 group without
adhesive enhancing primer application.
Group A2: GC Initial LiSi group with
adhesive enhancing primer application.
Group B2: Cerasmart 270 group with
adhesive enhancing primer application.
The list of the main materials used in this
study is shown in Table I.
Cementation procedure
Bonded surface treatment of CAD/CAM blocks
The bonded surface of each block
was conditioned and treated following the
Figure 1 - The prepared tooth and CAD/CAM specimen.
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Braz Dent Sci 2023 Oct/Dec;26 (4): e3978
Issa MI et al.
Effect of adhesive primer application on shear bond strength of self-adhesive cement to tooth structure and two different CAD/CAM milled blocks
Issa MI et al. Effect of adhesive primer application on shear bond strength
of self-adhesive cement to tooth structure and two different
CAD/CAM milled blocks
manufacturer’s recommendations. For all groups,
the bonded surface was conditioned with
hydrouoric acid 5% for 20 seconds in groups
(A1&A2) and 60 seconds in groups (B1&B2),
then washed and dried. After that, a silane
coupling agent (G- multiprimer) was applied for
60 seconds and then air dried.
Surface treatment of the teeth
The bonded surfaces of the teeth in Groups
(A1 and B1) were left without any treatment,
while for Group (A2 and B2) the G-cem one
adhesive enhancing primer was applied to
the bonded interface of each tooth and left
undisturbed for 10 seconds after the end of
the application and then dried thoroughly for
5 seconds under maximum air pressure.
Cementation with the resin cement
The self-adhesive resin cement (G-cem
one) was applied on the bonded surface of each
CAD/CAM specimen which was then seated on
the tooth under a constant load of 5 Kg with
the aid of a dental surveyor, the excess cement
was removed, and each surface was light cured
for 20 seconds with Curing Pen light cure
device (Eighteeth, Changzhou, China) (Light
intensity:1000 Mw/cm2). The specimen was then
removed from the cementation device and stored
in distilled water for 24 hours [22].
Assessment of shear bond strength
A computer-controlled universal testing
machine (Laryee Tchnology co.,Ltd., Model:
DWD-50,China) was used to assess the shear
bond strength. The shear force was applied on the
adhesive interface of each specimen using a knife-
edge chisel rod at a crosshead speed of 1 mm/min
and 50 KN load cell, as shown in Figure 2. Then,
the maximum failure load was recorded in Newton
(N) when the fracture occurred. The shear bond
strength values in MPa were calculated by dividing
the failure load (N) by the bonding area (mm2).
( )
( )
()
2
/
Shear bond strength SBS value
failureload value N area mm
=
(1)
Statistical analysis
Statistical Package for Social Science (SPSS)
was used to analyze the collected data, and the
normality of the distribution of variables was
assessed using the Shapiro–Wilk test. Paired
t
-test
was used to study the effect of the adhesive primer
Table I - Chemical composition and manufacturer of materials used
Material Manufacturer Chemical composition (wt%)
GC Initial ™ LiSi Block GC Corporation, Tokyo, Japan SiO2: 81%, P2O5: 8.1%, K2O: 5.9%, Al2O3: 3.8%, TiO2: 0.5%, CeO2: 0.6%
LOT 2112081
CERASMART™ 270 Block GC Corporation, Tokyo, Japan Bis-MEPP, UDMA, DMA, Silica (20 nm), barium glass (300 nm) 71 wt%
LOT 2202071
G-CEM One self-adhesive
cement
GC Corporation, Tokyo, Japan Paste A: fluoroaluminosilicate glass, UDMA, dimethacrylate, initiator,
stabilizer, pigment, silicon dioxide, MDP, Paste B: SiO2, trimethoxysilane,
MgO, UDMA, 2-hydroxy-1,3 dimethacryloxypropane, MDP, 6-tert-butyl-2,4-
xylenol, 2,6-di-tert-butyl-p-cresol, EDTA disodium salt dehydrate, vanadyl
acetylacetonate, TPO, ascorbic acid, camphorquinone,
LOT 2206061
G-CEM One adhesive
enhancing primer
GC Corporation, Tokyo, Japan Ethanol, MDP, 10-methacryloyloxydecyl dihydrogenthiophosphate,
4-META, 2-hydroxy-1,3-dimethoxypropane, vanadyl acetylacetonate,
2,6-di-tert-butyl-p-cresol
LOT 2206061
G-Multi Prime
GC Corporation,
Tokyo, Japan MDP, MDTP, γ-MPTS, methacrylate, monomer, ethanol
LOT1611181
Figure 2 - Test specimen in the computer-controlled testing
machine.
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Issa MI et al.
Effect of adhesive primer application on shear bond strength of self-adhesive cement to tooth structure and two different CAD/CAM milled blocks
Issa MI et al. Effect of adhesive primer application on shear bond strength
of self-adhesive cement to tooth structure and two different
CAD/CAM milled blocks
on the shear bond strength. An Independent
t
-test
was used to assess the differences in the shear
bond strength values between the different CAD/
CAM blocks.
Failure mode analysis
To study the mode of Failure, A Dino-Lite
digital microscope at a magnication of 50x was
used to examine the fractured specimens after
debonding.
The Failure modes were classified as
follows [23]:
1. Cohesive failure in dentin (CD).
2. Adhesive failure between the dentin and
resin cement (ADR).
3. Cohesive failure in the adhesive resin
cement (CR).
4. Adhesive failure between the resin cement
and the CAD/CAM block material (ARB).
5. Cohesive failure in the CAD/CAM block
material (CB).
RESULTS
The descriptive statistics of the data, including
the mean and standard deviation of the shear
bond strength values in MPa for all groups, are
shown in Figure 3. The samples in group A2 (GC
Initial LiSi with adhesive enhancing primer)
recorded the highest mean value of the shear
bond strength (19.082± 2.018 MPa), whereas
the lowest mean value (7.490± 1.277 MPa) was
recorded by group B1 (Cerasmart 270 without
adhesive enhancing primer).
Independent t-test was used to compare the
shear bond strength values between the groups
with and without the application of the primer
at a level of significance of 0.05 and showed
a statistically signicant difference among the
groups (
P
= 0.000; Table II). Independent
t
-test
test revealed a statistically signicant difference
in the shear bond strength values between the
different CAD/CAM blocks (Table III). The failure
modes distribution in percentages in each group
is shown in (Table IV and Figure 4).
DISCUSSION
The bonding performance of self-adhesive
resin cement remains an issue that is critical
for the longevity of the restoration. Previous
studies showed that the surface treatment of the
dentin could enhance the bond strength of the
self-adhesive resin cement [19,24-28]. Based on
the results of the present study, the treatment of
the tooth surface with the adhesive enhancing
primer could significantly improve the shear
bond strength of the self-adhesive resin cement.
Therefore, the rst null hypothesis was rejected.
The most reliable adhesive strategy for
the cementation of indirect restoration is still
debatable. The self-adhesive resin cement is based
on the presence of functional monomers that
Table II - Independent t-test comparing the shear bond strength
values between the groups with and without primer applications
Group Mean ± SD
t P
value
A1 15.847± 2.096 - 6.705 0.000
A2 19.082± 2.018
B1 7.490± 1.277 - 3.516 0.002
B2 10.853± 0.939
SD: Standard deviation.
Table III - Independent t-test comparing the shear bond strength
values between different CAD/CAM blocks groups
Group Mean ± SD
t P
value
A1 15.847± 2.096 10.726 0.000
B1 7.490± 1.277
A2 19.082± 2.018 11.688 0.000
B2 10.853± 0.939
SD: Standard deviation.
Figure 3 - Bar chart shows the mean values of shear bond strength ±
standard deviation.
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Braz Dent Sci 2023 Oct/Dec;26 (4): e3978
Issa MI et al.
Effect of adhesive primer application on shear bond strength of self-adhesive cement to tooth structure and two different CAD/CAM milled blocks
Issa MI et al. Effect of adhesive primer application on shear bond strength
of self-adhesive cement to tooth structure and two different
CAD/CAM milled blocks
could improve the chemical and micromechanical
retention, minimize the multi-steps of
cementation, and reduce the post-operative
sensitivity [29,30]. Yet, these monomers have
a lower PH than phosphoric acid, resulting in
a limited capacity for demineralization and
incomplete removal of the smear layer. Moreover,
a study observed that no resin tag or true hybrid
layer was formed when the self-adhesive cement
was used [27].
The factors mentioned above could be
responsible for the lower shear bond strength
values presented in the current study for both
GC Initial LiSi and Cerasmart 270 groups when
the self-adhesive resin cement was used without
the adhesive enhancing primer.
The application of adhesive enhancing
primer with the self-adhesive resin cement
showed a significant increase in the shear
bond strength values. This could be explained
by the functional monomers in the primer as
methacryloyloxydecyl dihydrogen phosphate
and 4-2-(methacryloyloxy)ethoxy]carbonyl
phthalic acid (4-MET). 10-MDP could link with
hydroxyapatite to form MDP–Ca salt that could
protect the exposed collagen [31]. Likewise, MDP
has a hydrophobic part that plays a signicant
role in the preservation of collagen, which seems
imperative for dentin bonding [32]. On the other
hand, 4-MET monomer has hydrophilicity and
could enhance the wetting and owability of the
primer [33]. Therefore, both monomers could
increase the resin inltration into the dentine,
allowing the self-adhesive resin cement to create
a thicker hybrid layer and a stronger bond with
the tooth.
Another contributing factor to the high
bond strength obtained with the primer is the
“touch-curing catalyst” that provides the self-
polymerization of the G-CEM cement when it
comes in contact with the primer; therefore, the
water absorption of the cement was decreased,
and this might overcome the negative impact of
the moisture which is critical for bonding to the
dentin [34]. Additionally, it has been shown that
applying the adhesive enhancing primer could
increase the free radical reactions, resulting in
Table IV - Mode of failure distribution in each group in (%)
Group CD ADR CR ARB CB
A1 0 80% 20% 0 0
A2 60% 0 40% 0 0
B1 0 80% 20% 0 0
B2 20% 40% 40% 0 0
CD: Cohesive failure in dentin; ADR: Adhesive failure between dentin and resin cement; CR: Cohesive failure in resin cement; ARB: Adhesive
failure between resin cement and CAD/CAM block material; CB: Cohesive failure in CAD/CAM block material.
Figure 4 - Modes of failure after shear bond strength test: (A) Cohesive failure in dentin; (B) Cohesive failure in resin cement; (C) Adhesive
failure between dentin and resin cement.
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Issa MI et al.
Effect of adhesive primer application on shear bond strength of self-adhesive cement to tooth structure and two different CAD/CAM milled blocks
Issa MI et al. Effect of adhesive primer application on shear bond strength
of self-adhesive cement to tooth structure and two different
CAD/CAM milled blocks
a higher degree of conversion and enhanced
mechanical properties of the self-adhesive resin
cement [35].
The results presented in this study are
consistent with previous studies [18-20] that
all showed an improvement in the shear bond
strength of self-adhesive resin cement after
treating the tooth surface with G-CEM ONE
Adhesive enhancing primer. The authors recorded
the highest bond strength with this primer
compared to the other materials tested in their
studies (polyacrylic acid, self-etch bond, NaOCl).
Likewise, Atalay et al. [22] pointed out that
the application of the adhesive enhancing primer
before G-CEM resin cement could increase the
SBS to both enamel and dentin. The authors
supported their ndings with SEM examination
that showed a more regular pattern of the bonded
interface with the use of the primer.
The current study revealed a statistically
signicant increase in the shear bond strength of
the self-adhesive resin cement to the GC Initial
LiSi with and without the primer as compared
to the Cerasmart 270; therefore, the second
null hypothesis was rejected. The different
chemical compositions and microstructure of the
tested CAD/CAM blocks and the type of surface
treatment performed on these materials could be
mainly responsible for this nding.
Different Chemical and mechanical methods
of surface treatment have been indicated to clean
the bonded surface, increase the surface energy
and wettability, and consequently improve the
adhesive bond between the restoration and resin
cement [36-38]. For lithium di-silicate ceramics,
HF etching seems to be the gold standard
method for surface treatment. The glassy phase
of ceramics dissolved with etching, leaving the
crystalline phase more visible. This was supported
by previous studies, which demonstrated an
improvement in the bond strength of different
CAD/CAM ceramics when conditioned with HF
acid before bonding [39-42].
Both sandblasting and HF etch are indicated
for nano-ceramics. In the current study, the
bonded surface of GC Initial LiSi and Cerasmart
270 was treated with 5% HF acid following the
manufacturers’ instructions. Thus, the highest
shear bond strength values obtained with GC
Initial LiSi could be attributed to their highly
glassy content as compared with Cerasmart 270,
the glassy phase dissolved HF acid, resulting in
the formation of micro retention that increased
the surface energy and improved the bond
between the cement and the restoration [43].
The nding of this study is in line with other
studies, which demonstrated higher SBS values
with the lithium di-silicate than with Cerasmart
after conditioning with HF [43,44].
It has been shown that air abrasion seems
to be the best surface treatment method for
indirect composite restorations. Studies revealed
that sandblasting resulted in higher surface
roughness than HF acid, leading to an increase
in the bonded surface area and, in turn enhance
the shear bond strength [45-47]. However, the
opposite was reported by other studies [43,48].
These contradicting results might be explained
by the different types of resin cement and CAD/
CAM blocks tested by the authors.
Regarding the mode of failure, the results
of the study presented a higher percentage of
adhesive failure between dentin and resin cement
in groups without adhesive enhancing primer
application (A1, B1). This could be attributed to
the self-adhesive cement that cannot completely
remove the smear layer, which can cause a
weak hybrid layer between the cement and the
dentin [49]. On the other hand, for groups with
the adhesive enhancing primer application (A2,
B2), most of the specimen failure was due to
cohesive failure in dentin or cohesive failure in
resin cement, and this complies with the results of
the SBS test that both support the positive effect
of the primer on the bond between the dentin
and the cement. This nding showed agreement
with a study revealed that cohesive failure was
the most encountered failure when the adhesive
enhancing primer was used [20].
Different methods have been advocated
to evaluate the effectiveness of the interfacial
adhesive bond of the restorations and adhesive
materials to the tooth; among these methods,
the shear bond strength test was used due to its
simplicity and low- technique sensitivity [50].
Moreover, the Macro shear test is performed
without the need for sectioning procedures
to obtain specimens, which may induce early
micro-cracking [51]. On the other hand, the
Micro shear tests have the advantage of smaller
bonding areas that could overcome concerns
regarding the heterogenous stress pattern
of Macro shear tests [50]. Yet, there is no
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Braz Dent Sci 2023 Oct/Dec;26 (4): e3978
Issa MI et al.
Effect of adhesive primer application on shear bond strength of self-adhesive cement to tooth structure and two different CAD/CAM milled blocks
Issa MI et al. Effect of adhesive primer application on shear bond strength
of self-adhesive cement to tooth structure and two different
CAD/CAM milled blocks
standardized recommended protocol for bond
strength assessment [52].
One of the limitations of this study was that
it was conducted in
vitro
; thus, it was difcult
to imitate the oral cavity environment. Another
limitation is that the adhesive enhancing primer
was tested with one type of self-adhesive cement.
Moreover, the SBS was measured after a short
time with no ageing, which could be more
clinically relevant.
CONCLUSIONS
Within the limitation of this study, the
following conclusions could be drawn:
1. The surface treatment of the tooth with the
adhesive enhancing primer improved the
shear bond strength of the self-adhesive
resin cement to the tooth and both types of
CAD/CAM blocks;
2. The shear bond strength of the self-adhesive
resin cement to the GC Initial LiSi with and
without the primer was higher than that of
the Cerasmart 270.
Acknowledgements
The authors would like to thank GC
Corporation, Tokyo, Japan and their dealer Vital
Allience Co Ltd. for their assistance and support.
Author’s Contributions
MII: Conceptualization, Methodology,
Resources, Data Curation, Writing – Review &
Editing. MIA: Investigation, Writing – Review &
Editing, Visualization. AAF: Conceptualization,
Methodology, Writing – Review & Editing.
Conict of Interest
The authors have no proprietary, nancial,
or other personal interest of any nature or kind
in any product, service, and/or company that is
presented in this article.
Funding
This research did not receive any specic
grant from funding agencies in the public,
commercial, or not-for-prot sectors.
Regulatory Statement
This study was conducted in accordance with
all the provisions of the local human subjects
oversight committee guidelines and policies of
the research ethics committee of the college of
dentistry, university of Baghdad. The approval
code for this study is (ref. number 808, project
number 808223 at 18.5.2023).
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Moamin I. Issa
(Corresponding address)
University of Baghdad, College of Dentistry, Department of Prosthodontics, Baghdad,
Iraq.
Email: moamin_alniama@codental.uobaghdad.edu.iq
Date submitted: 2023 Aug 02
Accept submission: 2023 Sept 13
