Effect of an extra layer of hydrophobic

Journal of Investigative and Clinical Dentistry (2016), 0, 1–8

ORIGINAL ARTICLE
Dental Biomaterials

Effect of an extra layer of hydrophobic resin on the
microleakage of Cl V composite resin restorations with a
universal adhesive system
Mahmoud Bahari1,2, Narmin Mohammadi2, Parnian Alizadeh Oskoee2, Siavash Savadi Oskoee2 &
Farnaz Davoodi2
1 Dental and Periodontal Research Center, Faculty of Dentistry, Tabriz University of Medical Sciences, Tabriz, Iran
2 Department of Operative Dentistry, Faculty of Dentistry, Tabriz University of Medical Sciences, Tabriz, Iran

Keywords
etch-and-rinse, hydrophobic resin,
microleakage, self-etch, universal adhesive.
Correspondence
Dr F. Davoodi, Department of Operative
Dentistry, Faculty of Dentistry, Tabriz
University of Medical Sciences, Tabriz
5166614711, Iran.

Tel: +98-41-33355965-9
Email: farnaz_davoodi67@yahoo.com
Received 9 March 2016; accepted 7 June
2016.
doi: 10.1111/jicd.12234

Abstract
Aim: The aim of the present study was to evaluate the effect of the application
of a hydrophobic resin on the microleakage of Cl V composite resin restorations using a universal adhesive system applied in the self-etch (SE) and etchand-rinse (ER) modes.
Method: Cl V cavities were prepared on the buccal surfaces of 64 human premolar teeth and divided into four groups (n = 16): ER, ER with hydrophobic
resin (ERH), SE, and SE with hydrophobic resin (SEH). Microleakage at occlusal and gingival margins was evaluated using 0.5% methylene blue dye penetration technique under stereomicroscope at 40 9 magnification. Data were
analyzed using Kruskal–Wallis and Mann–Whitney U-tests (P < 0.05).
Results: At the enamel margins, the ER group had significantly less microleakage than the SE and SEH groups (P < 0.001), but had no significant difference
compared with the ERH group (P > 0.05). There was also no statistically-significant difference between the SE and SEH groups (P > 0.05). At the dentinal
margins, the SE group had significantly less microleakage compared with the
ER (P < 0.001) and ERH groups (P = 0.005). Furthermore, microleakage of
the SEH group was significantly less than the SE group (P < 0.001).
Conclusion: Applying an extra layer of hydrophobic resin significantly
decreased microleakage in the SE mode at the dentinal margin, but had no significant effect in the ER mode.

Introduction
Traditionally, adhesive systems are divided into two
groups: etch-and-rinse (ER) and self-etch SE.1 Considering the controversy over professional and clinical judgements in the selection of an appropriate adhesive strategy,
some manufacturers have introduced a new adhesive system that is much more flexible than the previous systems.
This new system has been dubbed the universal adhesive
(multipurpose or multimode) system, which could be
used in the SE or ER mode based on the clinical judgement of the dentist.1
ª 2016 John Wiley & Sons Australia, Ltd

It has been reported that one-step SE systems result in
water permeability of dentin and osmotic blistering of the
enamel, finally affecting the clinical durability of the
bond.2–5 By considering the same water content in the SE
and universal systems, bond degradation might also take
noz et al.6 showed that, complace in these systems.1 Mu~
pared to other systems, the universal systems exhibit more
negative results in at least one of these characteristics:
nanoleakage, degree of conversion (DC), and bond
strength. However, they pointed out that the universal
adhesives yield better results in the ER mode compared

to the SE mode. Previous studies have shown that the use
1

Effect of hydrophilic resin on microleakage

of phosphoric acid with the universal adhesive systems
results in better bond quality in the enamel margin.7–9
An increased amount of solvents and hydrophilic
monomers in the adhesive system has an adverse effect
on the adhesive layer, which could hinder the formation
of a high cross-linking polymer, decrease the DC, and
increase the permeability of the adhesive layer.10 To eliminate these drawbacks it is suggested to apply an additional layer of a hydrophobic resin coat over the
polymerized simplified adhesives. This resin layer
increases the thickness and uniformity of the adhesive
layer and decreases fluid flow across the adhesive layer.
Excellent results have been seen after the placement of
hydrophobic resin coat over one-step SE adhesives.10
Perdig~ao et al.1 demonstrated that the use of a
hydrophobic resin in association with universal systems in
the ER mode was effective for enamel bond strength. In

addition, the use of a hydrophobic resin with a universal
adhesive showed better dentinal bond strength in the SE
mode.
Considering the ever-increasing clinical use of new universal systems, in the present study, we investigated the
effect of an extra layer of a hydrophobic resin coat on the
microleakage of Cl V composite resin restorations using
the universal adhesive systems in the SE and ER modes.
Materials and methods
In the present in vitro study, 64 sound human premolar
teeth extracted for orthodontic reasons were used.9 The
teeth were stored in 0.5% chloramine T solution until
used for the purpose of the study. All the teeth were
scaled and cleaned with a pumice and rubber cup.
Cavities measuring 3 mm mesiodistally, 3 mm occlusogingivally, and 2 mm in depth, with the occlusal and
gingival walls placed 1.5 mm above and below the
cemento–enamel junction, were prepared with a straight
fissure 008 (Diatech Dental AG, Heerbrugg, Switzerland)
diamond bur using a high-speed handpiece under an air–
water spray.9 The burs were replaced with new ones after
each five preparation rounds.8 All the margins were butt

joined without any bevels.9 Then the samples were randomly divided into four groups.

M. Bahari et al.

and the solvent was evaporated using a mild current of
air. Thereafter, the adhesive was light cured for 10 s using
Demetron A2 (Kerr/Sybron, Orange, CA, USA) at a light
intensity of 1000 mw/cm2.6 In the next stage, Z250 (3M
ESPE, St Paul, MN, USA) composite resin was placed in
the cavity and light cured with the same light-curing unit
for 20 s.6
Group 2
Group 2 used the universal adhesive system in the ER
mode with a hydrophobic resin (ERH group). The procedural steps were similar to those in group 1, except that,
before placing the composite resin, a very thin layer of a
hydrophobic resin (Heliobond, Ivoclar Vivadent, Schaan,
Liechtenstein) was placed in the cavity using a microbrush, and air current was applied to achieve a very thin
layer. Light curing was then carried out for 10 s using the
same light-curing unit.1
Group 3

Group 3 used the universal adhesive system in the SE
mode without a hydrophobic resin layer (SE group). One
layer of the universal adhesive system was applied to the
cavity surface for 20 s, and then the solvent was evaporated using a mild current of air. Light curing was then
carried out for 10 s using the same light-curing unit.6 In
the next stage, the cavities were restored in a manner similar to that in groups 1 and 2.6
Group 4
Group 4 used the universal adhesive system in the SE
mode with a layer of hydrophobic resin (she group). All
the procedural steps were similar to those in group 3,
except that before placing the composite resin, a very thin
layer of a hydrophobic resin (Heliobond, Ivoclar Vivadent, Liechtenstein) was applied using a microbrush, and
a current of air was used to achieve a very thin layer.
Light curing was then carried out using the same lightcuring unit.1

Group 1

The characteristics of the applied materials are
represented in Table 1

Group 1 used the universal adhesive system in the ER
mode without a hydrophobic resin (ER group). After
etching the tooth surface with 37% phosphoric acid
(Kerr, Orange, CA, USA) for 15 s and irrigation for 10 s,
a mild current of air was applied to the tooth surface for
2 s. Then a layer of the universal adhesive system (Bisco,
Schaumburg, IL, USA) was applied to the cavity walls,

In the next stage, the samples were incubated in distilled
water at 37°C for 24 h.11 The samples underwent a thermocycling procedure consisting of 500 rounds in the temperature range of between 5  2 and 55  2°C, with a
dwell time of 30 s, and a transfer time of 10 s in a water
bath in order to simulate the oral conditions.12 The teeth
were then dried and covered with two layers of nail

2

ª 2016 John Wiley & Sons Australia, Ltd

M. Bahari et al.

Effect of hydrophilic resin on microleakage

Table 1. Compositions and manufacturers of study materials
Materials

Composition

Manufacturer

Hydrophobic resin
Gel etchant
Composite resin Z250
Bisco universal adhesive

Bis-GMA, TEGDMA
37.5% phosphoric acid, silica thickener
UDMA, Bis-EMA, Bis-GMA, Zirconia glass, colloidal silica
10MDP,HEMA,Bis-GMA, ethanol, initiator, water

Heliobond, Ivoclar Vivadent, Schaan, Liechtenstein

Kerr, Orange, CA, USA
3M ESPE, St Paul, MN, USA
Bisco, Schaumburg, IL, USA

varnish up to 1 mm away from the restoration margins.
The root apices were sealed with wax.11 All the samples
were immersed in 0.5% methylene blue solution for 8 h
at room temperature and then stored in distilled water
for 12 h.13 The samples were then sectioned in a buccolingual direction at the center of the restorations using a
diamond disk (Diamant Gmbh, D&Z, Berlin, Germany).
One disc was used for every four teeth. The samples were
evaluated under a stereomicroscope (Nikon, Tokyo,
Japan) at 940, and the depth of dye penetration at the
occlusal and gingival margins was investigated based on
the following classification: (a) score 0: no dye penetration; (b) score 1: dye penetration along the gingival/occlusal wall with no involvement of the axial wall; (c)
score 2: dye penetration along the gingival/occlusal wall
with involvement of the axial wall; and (d) score 3: dye
penetration beyond the axial wall toward the pulp (Figure 1).9

It should be pointed out that during the laboratory

steps, the teeth were placed within a wet piece of gauze in
the operator’s hand to prevent dehydration.
Statistical analysis was performed using Kruskal–Wallis
H-test. Pairwise comparisons were performed by the
Mann–Whitney U-test for occlusal and gingival margins.
Data were analyzed at a significance level of 0.05 for all
results.
Evaluation by scanning electron microscope
Samples for scanning electron microscope (SEM) were
prepared based on the protocol reported by Korkmaz
et al.14 Two teeth from each group were randomly
selected for SEM evaluation of adhesive interfaces. The
samples were sequentially polished with a series of silicone carbide abrasive papers, of 600, 800, 1200, 1500, and
2000 grit size, under running tap water as a lubricant to

(a)

(b)

(c)

(d)

Figure 1. Stereomicroscope images of dye
penetration at occlusal (O) and gingival (G)
margins of etch-and-rinse (a), etch-and-rinse
with hydrophobic resin (b), self-etch (c), and
self-etch with hydrophobic resin (d) groups at
940 magnification.

ª 2016 John Wiley & Sons Australia, Ltd

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Effect of hydrophilic resin on microleakage

M. Bahari et al.

smooth the surfaces. The samples were then brought into
relief by being etched with 10% phosphoric acid for 10 s,
followed by deproteinization in 5% sodium hypochlorite
for 5 min. After being rinsed with distilled water, each
sample was mounted on stubs and sputter coated with
gold. The samples were carefully observed under an SEM
(Tescan Vega II, Brno, Czech Republic) at the restorative
material–tooth interfaces, and photographs were taken.

Results

Enamel margin
The ER group had significantly less microleakage than the
SE and SEH groups (P < 0.001), but had no significant
difference compared with the ERH group (P > 0.05). The
ERH group showed better results compared with the SEH
and SE groups (P < 0.001). However, there was no statistically-significant difference between the SE and SEH
groups (P > 0.05).
Dentinal margin

Microleakage
Mean values  standard deviations and test scores for
microleakage measurements in the study groups are presented in Table 2.
Kruskal–Wallis test showed statistically-significant differences between test groups (P < 0.001). Thus, pairwise
comparisons were done using the Mann–Whitney U-test
(Figure 2). Accordingly, the results are discussed separately for enamel and dentinal margins.

The SE group had significantly less microleakage compared
with the ER (P < 0.001) and ERH groups (P = 0.005). Furthermore, microleakage of the SEH group was significantly
less than the SE, ER, and ERH groups (P < 0.001).
SEM observations
The ER samples at the enamel margin showed resin tags,
microporosities, and a uniform adhesive layer that could

Table 2. Mean  SD and scores of microleakage measurements
Enamel margin

Dentin margin

Score

SE

SEH

ER

ERH

SE

SEH

ER

ERH

0
1
2
3
Mean  SD

0
2
5
9
2.43  0.18

2
1
5
8
2.18  0.26

10
5
1
0
0.43  0.15

13
3
0
0
0.18  0.10

0
3
5
8
1.31  0.11

12
4
0
0
0.25  0.11

0
0
9
7
2.43  0.12

1
3
4
8
2.18  0.24

ER, etch-and-rinse; ERH, etch-and-rinse with hydrophobic resin; SD, standard deviation; SE, self-etch; SEH, self-etch with hydrophobic resin.

ERHO

(ER + resin/occlusal)

*