Research article
ISSN 2234-7658 (print) / ISSN 2234-7666 (online)
http://dx.doi.org/10.5395/rde.2013.38.2.73
Effect of different air-drying time on the
microleakage of single-step self-etch adhesives
Horieh Moosavi1,
Maryam Forghani2*,
Esmatsadat Managhebi3
1
Dental Materials Research Center
and Department of Operative
Dentistry, School of Dentistry,
Mashhad University of Medical
Sciences, Mashhad, Iran
2
Dental Research Center and
Department of Endodontics, School
of Dentistry, Mashhad University of
Medical Sciences, Mashhad, Iran
3
Dental Materials Research Center,
School of Dentistry, Mashhad
University of Medical Sciences,
Mashhad, Iran
Received March 25, 2013;
Revised April 21, 2013;
Accepted April 27, 2013.
Objectives: This study evaluated the effect of three different air-drying times on
microleakage of three self-etch adhesive systems. Materials and Methods: Class I
cavities were prepared for 108 extracted sound human premolars. The teeth were
divided into three main groups based on three different adhesives: Opti Bond All in One
(OBAO), Clearfil S3 Bond (CSB), Bond Force (BF). Each main group divided into three
subgroups regarding the air-drying time: without application of air stream, following
the manufacturers instruction, for 10 sec more than manufacturers instruction. After
completion of restorations, specimens were thermocycled and then connected to a fluid
filtration system to evaluate microleakage. The data were statistically analyzed using
two-way ANOVA and Tukey-test ( = 0.05). Results: The microleakage of all adhesives
decreased when the air-drying time increased from 0 sec to manufacturers instruction (p
< 0.001). The microleakage of BF reached its lowest values after increasing the drying
time to 10 sec more than the manufacturers instruction (p < 0.001). Microleakage of
OBAO and CSB was significantly lower compared to BF in all three drying time (p <
0.001). Conclusions: Increasing in air-drying time of adhesive layer in one-step selfetch adhesives caused reduction of microleakage, but the amount of this reduction may
be dependent on the adhesive components of self-etch adhesives. (Restor Dent Endod
2013;38(2):73-78)
Key words: Air-drying; Microleakage; Self-etch adhesive
Moosavi H, Dental Materials
Research Center and Department
of Operative Dentistry, School of
Dentistry, Mashhad University of
Medical Sciences, Mashhad, Iran
2
Forghani M, Dental Research Center
and Department of Endodontics,
School of Dentistry, Mashhad
University of Medical Sciences,
Mashhad, Iran
3
Managhebi E, Dental Materials
Research Center, School of
Dentistry, Mashhad University of
Medical Sciences, Mashhad, Iran
*Correspondence to
Maryam Forghani, DDS, MSc.
Assistant Professor, Dental
Research Center and Department of
Endodontics, School of Dentistry,
Mashhad University of Medical
Sciences, Mashhad, Iran
TEL, +989155088028; FAX,
+985118829500; E-mail,
Forghaniradm@mums.ac.ir
Introduction
Recently introduced dental adhesives offer simplified clinical application and
eliminate technique sensitivity.1 The major benefit of the one-step self-etching
systems is that they are less technique sensitive than multi-step systems. While the
adhesive system becomes simpler, careful product management is still required in
order to attain optimum bonding procedures. However, according to recent studies,
the bond quality of these products were affected by several factors, such as enamel
surface treatment, smear layer thickness, grit size of the bur, moisture condition of
the adhesive surface, drying time after application of the adhesives, and number
of multiple coating.2-5 The etching effect of the self-etch adhesives attributed to
hydrogen ions derived from the acidic monomers.6 Water is an essential component in
the adhesives, which allows them to generate the hydrogen ions.7 The moisture control
of the adhesive surface can be considered in two parts: the surface moisture before the
application of the adhesive agent and the removal of the solvent after application.8
Since self-etching adhesives contain acidic functional monomers and water, which
This study was supported by a grant from the Research Council of the Mashhad University of Medical Sciences, Mashhad, Iran (This paper has been taken
from proposal # 900221 and thesis #2546).
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/
by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Copyrights 2013. The Korean Academy of Conservative Dentistry.
73
Moosavi H et al.
might interfere with subsequent resin polymerization, airdrying time might be an influential factor in determining
dentin bond qualities.7 The monomers are dissolved in
organic solvents such as ethanol and acetone, which
improve monomer penetration between the collagen fibrils
of demineralized dentin and play an important role in the
removal of water during solvent evaporation.1,9 The high
quality of the hybridization process depends on successful
monomer infiltration into the dentinal matrix and the
removal of water and solvents from the surface prior to
polymerization.10 Acetone and ethanol are the most popular
solvents used for the adhesive agents. Usually acetone is
more volatile than ethanol and it is easier to remove after
application, but there is less chance for ideal handling
and this resulted in more technique sensitivity.11 Residual
solvents may compromise the polymerization of adhesives
and also directly affect the bond integrity, providing
defects within the polymerized adhesive and pathways
for nanoleakage.12-14 Marginal leakage of resin composites
has been a significant concern for clinical practitioners
that can be resulted in pulp pathology, hypersensitivity,
secondary decay, degradation of bond area, and marginal
staining.15 However, complete evaporation of solvents
is difficult to achieve. A clinical approach to accelerate
solvent evaporation recommended by the manufacturers
is the use of an air stream. Although air drying of applied
adhesive is recommended to evaporate solvents in the
adhesives, variations in air-drying time probably occur in
clinical application particularly in complex cavity with high
C-factor.7-9 This study evaluated the influence of the airstream duration on the microleakage of different self-etch
adhesive systems in Class I composite resin restorations
with a fluid filtration method. The null hypothesis was that
there was no difference in the leakage of self-etch adhesive
systems with various times of solvent evaporation.
Materials and Methods
One hundred and eight noncariouse human premolars,
extracted for orthodontic reasons were selected under a
protocol approved by the Ethics Committee of Mashhad
University of Medical Sciences (900221/2011). Teeth were
disinfected in 0.5% chloramine T solution and stored
in distilled water until starting the experiment. Class I
cavities (2 2 4 mm) were made using straight fissure
diamond burs (SS White Burs, Inc., Lakewood, NJ, USA)
in a high-speed handpiece under copious water spray. The
roots removed at 2 mm below the cement-enamel junction
(CEJ) with an aluminum oxide disc (Sof-Lex, 3M ESPE, St.
Paul, MN, USA) mounted on a low speed handpiece.
Prepared teeth were then divided randomly into three
main groups (n = 36) based on three different self-etch
adhesives which was used:
Group 1: Opti Bond All in One (OBAO, Kerr Corp, Orange,
CA, USA)
Group 2: C learfil S 3 Bond (CSB, Kuraray Medical Inc.,
Tokyo, Japan)
Group 3: Bond Force (BF, Tokuyama, Tokyo, Japan)
Adhesives were applied on the dentin surface according
to the manufacturers instruction (Table 1). Each of the
three main groups was subdivided into three subgroups A,
B and C (n = 12) for application of different duration of air
stream for adhesive evaporation:
Subgroup A: without application of air stream
Subgroup B: according to the manufacturers instruction
Subgroup C: 1 0 seconds more than manufacturers
instruction
Primed dentin surfaces were dried with oil-free
compressed air at 25 (normal temperature) with 0.2 MPa
air pressure for three different times from 5 cm above the
dentin surface using a three-way syringe attached to a
Table 1. Chemical formulation and manufacturer's directions of the adhesives applied
Materials
Composition
Opti Bond All in One
(OBAO)
GPDM, GDM, HEMA, Bis-GMA, water, ethanol,
acetone, silica filler, CQ, sodium hexafluorosilicate
Clearfil S3 Bond
(CSB)
10-MDP, HEMA, Bis-GMA, water, ethanol,
silanated colloidal silica, CQ
Bond Force
(BF)
Methacryloyloxyalkyl acid phosphate, HEMA,
Bis-GMA, TEGDMA, water, isopropyl alcohol,
Glass Filler, CQ
Application procedures
Apply two coats with agitation for 20 sec each
Dry with air pressure for 5 sec
Light cure for 10 sec
Apply for 20 sec
Dry with air pressure for 5 sec
Light cure for 10 sec
Apply for 20 sec
Dry with moderate, strong air pressure for 5 sec
after weak air pressure for 5 sec
Light cure for 10 sec
HEMA, 2-hydroxyethyl methacrylate; Bis-GMA, bisphenol-A-diglycidyl methacrylate; TEGDMA, triethyleneglycol dimethacrylate;
CQ, camphorquinone; 10-MDP, 10-methacryloyloxydecyl dihydrogen phosphate; GPDM, glycerol phosphate dimethacrylate; GDM,
glycerol dimethacrylate.
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http://dx.doi.org/10.5395/rde.2013.38.2.73
Effect of different air-drying time on microleakage
Class I cavity
restoration
Plexiglass
18 gauge stainiess
steel tube
Oxygen tank
Oxygen
input
Oxygen
output
Fluid flow
Air bubble
PBS
Erien
Microsyringe
Figure 1. Schematic illustration of the fluid filtration apparatus used to measure the microleakage of the resin composite
restorations bonded with the assigned adhesives in this study.
dental unit. After polymerization of the adhesives using a
light curing unit (Optilux 500, Demerton-Kerr, Orange, CA,
USA), cavities were restored 1 mm incrementally with the
resin composite supplied by the same manufacturer with
the assigned adhesive, group 1, Herculite XRV (Kerr); group
2, Clearfill APX (Kuraray); group 3, Estelite Sigma quick
composite (Tokuyama). After storage in 37 distilled water
for 24 hours, the restorations were finished and polished
with aluminum oxide discs (Sof-Lex) and the specimens
were thermocycled (Nemo Inc, Mashhad, Iran) at 5 and
55 2 for 500 cycles. For leakage assessment, the
specimens were assigned in a fluid filtration system. For
connecting the specimens to a fluid filtration system, the
canal orifices from apically position were widened with
2 and 3 Gates-Glidden drills and pulp tissue was deleted
carefully. The pulp chambers were then rinsed with saline
solution. Measurement of fluid movement was made
through the 18-gauge needle in the Plexiglass connected
to the cut surface of crown segments (Figure 1). Evaluation
were performed by measurement of fluid flow through each
specimen under 23/4 psi of water pressure every 2 minutes
for four times (2, 4, 6, 8 minutes)after connecting the
samples to fluid filtration system.
These four fluid flow values were averaged to a single
http://dx.doi.org/10.5395/rde.2013.38.2.73
mean value for raising the accuracy of extracted data (L/
min/cmH2O). Data were analyzed statistically using twoway ANOVA and Tukey test ( = 0.05).
Results
The results of the leakage measurements are presented
in Tables 2 and 3. ANOVA test demonstrated a statistically
significant interaction between the type of adhesive
and air-drying time (p < 0.001). It showed that the
leakage of the restoration restored with all the adhesives
were significantly decreased when the air-drying time
increased from no drying to the time recommended by the
manufacturers instruction (p < 0.001). Microleakage of BF
reached its lowest values after increasing the drying time
to 10 seconds more than the manufacturers instruction
(p < 0.001), but in OBAO and CSB groups increasing in
drying time over the manufacturers time suggestion had
no significant effect on their microleakage (Table 3). Tukey
test showed a significant difference in leakage of OBAO
and BF, also between CSB and BF in all three drying time
(p < 0.001). However, there were no significant differences
in microleakage of OBAO and CSB in different drying time
(Table 3).
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Moosavi H et al.
Table 2. The ANOVA results of this experiment
Model
Adhesive system
Drying time
Adhesive system X Drying time
df
2
2
4
Mean square
4.647 10-9
4.928 10-8
4.187 10-10
F value
75.180
797.443
6.774
p value
0.001
0.001
0.001
Table 3. Comparison between microleakage (Unit: L/min/cmH2O, mean SD, n = 12) of adhesive systems in each drying-time
Drying-time
Materials
OBAO
CSB
BF
No air-drying
Manufacturers instruction
(7.01 1.02) 10-5 a A
(6.34 1.48) 10-5 a A
(9.40 1.18) 10-5 b A
(9.35 1.59) 10-6 a B
(8.96 3.80) 10-6 a B
(3.19 0.72) 10-5 b B
10 sec more than
manufacturers instruction
(5.48 1.44) 10-6 a B
(4.30 2.28) 10-6 a B
(1.34 0.41) 10-5 b C
Means within each group with the same superscript letter are not significantly by Tukey test (small letter, column; capital
letter, row). OBAO, Opti Bond All in One; CSB, Clearfil S3 Bond; BF, Bond Force.
Discussion
The results of this study showed that microleakage of the
single-step self-etch adhesives varied when the duration
of air-drying was altered. Dye, bacteria, and radioisotope
penetration methods, and light microscopic or scanning
electron microscopic (SEM) methods have been used for
measurement of leakage around the restorative materials
that they provide qualitative information only.15 Fluid
filtration method, introduced and developed by Pashleys
group, has been extensively used for 30 years for research
purpose to understand the physiology of dentin, as well
as the effects of various restorative treatments on dentin
permeability. It permits quantitative, nondestructive
measurement of microleakage in a longitudinal manner. The
fluid filtration method permits quantitative measurement
of leakage. Fluid filtration systems enhance reliability,
reproducibility and comparability.16 Inherent solvents of
the adhesives behave like a transporter media and lower
resin viscosity in adhesive solutions, allowing the resin
monomers to penetrate into the demineralized porous
dentin surfaces.17 However, residual solvent can inhibit
polymerization and weakens the mechanical properties of
the adhesive resin, so they should be removed from the
adhesive to a sufficient degree.14,18 The tested adhesives
contain different types of solvents, OBAO, acetone and
ethanol; BF, isopropyl alcohol; CSB, ethanol. Water is a poor
solvent for hydrophobic monomers, so alcohol or acetone is
added to the solution.19 Alcohol has higher vapor pressure
compared to water and provides better evaporation by
air-drying.14 Water-alcohol mixtures form hydrogen bonds
between their molecules that facilitate evaporation of the
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solvent compared to pure water.20 Acetone has higher vapor
pressure and lower boiling temperature when compared
to alcohol, which translates into faster evaporation of
it.9 However, it was reported that even for an acetonebased adhesive, spontaneous evaporation exhibits only
after 5 minutes of its application, which is clinically
unacceptable.19 Furthermore, the adhesives used in the
present study contain HEMA, which is a co-monomer that
acts as a wetting agent and diffusion promoter for resin.21
One drawback of HEMA is that it strongly retains water
in hydrogels which is difficult to evaporate. One of the
methods used to improve the solvent evaporation rate is
air-drying prior to light irradiation.22,23 This study evaluated
the effect of different air-drying time on microleakage of
single-step self-etch adhesives. The data in the present
study suggested that increasing in air-drying time from
no drying to the time recommended by the manufacturers
instructions time led to significant decrease in microleakage
for three adhesives. Whereas increasing air-drying time
more than manufacturers instruction resulted in significant
decrease in microleakage only for BF adhesive. So these
differences may be due to various compositions and the
main application protocol of manufacturer. Air-drying
provides better solvent evaporation and leaves only the
priming resin at the dentin surface, resulting in higher
degree of conversion.24,25 Jacobsen et al. reported that
the bond strength of all-in-one adhesives was affected by
the air-drying time and reached its highest values after
an air-drying time of 10 seconds or longer.22 Argolo et al.
evaluated the influence of the dwell time between the
application of ethanol-based adhesive and light activation
on the dentin bond strength and degree of conversion.26
http://dx.doi.org/10.5395/rde.2013.38.2.73
Effect of different air-drying time on microleakage
They found that longer dwell time (60 seconds) resulted in
better bond strength and greater percentage of conversion
and this may be due to better solvent volatilization.
Furuse et al. evaluated the influence of the degree of
solvent evaporation on the bonding capacity of onestep, self-etching adhesives, and also reported more
adhesive failures were observed with shorter air-blowing
durations than manufacturers instructions.27 For OBAO
and CSB increasing in drying-time over the manufacturers
instruction did not decrease the microleakage. Ogura et al.
evaluated the effect of warm air-drying on dentin bond
strength, and found prolonged warm air-drying detrimental
to some adhesives.28 This finding indicated that some
residual solvent is required for improving the degree of
cure. However, the microleakage of BF reached its lowest
values after increasing the drying time to 10 seconds
more than the manufacturers instruction. The vapor
pressure (at 25) of isopropyl alcohol is 44 mm Hg, for
ethanol is 54.1 mm Hg and for acetone is 200 mm Hg.29
These indicate that evaporation of isopropyl alcohol by
air-drying is more difficult than acetone and ethanol. In
the present study CSB and OBAO exhibited better sealing
ability compared to BF. Functional monomer of CSB is
10-MDP (10-methacryloxydecyl dyhidrogen phosphate).
Yoshida et al. investigated interaction of 10-MDP with
dentin and reported that this monomer interact chemically
with hydroxyapatite and its bond appeared very stable,
as confirmed by the low solubility of its calcium salt in
water.6 Higher bond strength of the 10-MDP to dentin may
improve sealing properties of the CSB adhesive. 30 Good
sealing ability of OBAO may be related to its application
method, because the manufacturer recommends
application of two coats of adhesive before air-drying.
Previous studies demonstrated that by applying more
coats of adhesives, the bond strength can be improved
and microleakage was decreased.31-33 It is purposed in
future research to work about other properties of self-etch
adhesives with regarding the role of different solvents and
dentinal substrates. Also, doing a long term clinical trial
about this subject will be necessary for supporting the in
vitro studies.
Conclusions
Under the conditions of the current investigation, it
can be concluded that the optimal drying time of some
adhesives may deviate from the manufacturers directions
for use. This is especially important in clinical situations
that cavity complexity might interfere with the access of
air stream to each part of the bonded surface, so clinicians
should be aware of the probably solvent present in
adhesives and carefully evaporate it particularly in cavities
with complex geometry to achieve best clinical results.
http://dx.doi.org/10.5395/rde.2013.38.2.73
Acknowledgement
Authors would like to thank for vice chanceller of research
of Mashhad University of Medical Sciences for approve the
grant for doing the research. The results presented in this
study have been taken from a student thesis no: 2546,
propsal code 900221.
Conflict of Interest: No potential conflict of interest
relevant to this article was reported.
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