HISAMATSU, ATSUTA, AND MATSUMURAINT CHIN J DENT

Effect of surface conditioning agents on the repair bond strength of an
indirect hybrid composite
Noriko Hisamatsu, DDS, PhD,a Mitsuru Atsuta, DDS, PhD,b and Hideo Matsumura,
DDS, PhDbaFixed Prosthodontics Division, Nagasaki University Hospital of Dentistry, andDepartment of Fixed Prosthodontics, Nagasaki University School of Dentistry,
Nagasaki, Japanb

Purpose: The objective of the current study was to evaluate the effect of silane primers and unfilled resin
bonding agents when used for bonding between layers of a light-activated indirect composite material(Cesead II).
Materials and Methods: Disk specimens were prepared with the dentin portion of the composite material
and abraded with a silicon-carbide rotary cutting instrument. The specimens were conditioned with varying
combinations of silane primer (Add-on Primer, Clearfil Porcelain Bond Activator, Clearfil Porcelain Bond
Activator + Clearfil Mega Bond-Primer, Porcelain Liner M, unprimed) and bonding agent (Clearfil Mega
Bond-Bond, Modeling Liquid, Stain Diluent, no-bonding agent). After placement of the enamel portion of
the same brand of composite material on each surface of the dentin material, the specimens werelight-exposed, and either wet- or dry-stored at 37˚C for 24 hours. Shear bond strengths were determined andthe results were analyzed by analysis of variances and post-hoc tests (p<0.05).
Results: Of the combinations tested, the Add-on Primer or Porcelain Liner M silane material combined with
the Modeling liquid or Stain Diluent bonding agent showed the greatest bond strength. The groups with nobonding agent generally resulted in poor repair bond strength.
Conclusion: The use of specific combinations of silane primer and bonding agent is recommended to achieve
reliable 24-hour bond strength between layers of the Cesead II composite.
(Int Chin J Dent 2002; 2: 5-14.)
Clinical Significance: The results of the current study demonstrate that the ground surface of a hybrid
composite material (Cesead II) can be repaired in dental laboratories by combined application of a silane
primer and a light-activated bonding agent, if the composite material has not aged in the oral environment.
Key words: bonding, composite, repair, silane.

INTRODUCTION
Composite-to-composite bonding is required in varying clinical situations such as seating indirectcomposite restorations with a resin-based luting agent,1-10 addition of a new composite material to an old

5

HISAMATSU, ATSUTA, AND MATSUMURAINT CHIN J DENT

one,11-13 and repair of fractured restorations.14-15 Bonding techniques for composite materials are also used indental laboratories. These procedures include bonding of artificial composite teeth to denture base resins,and layering of dentin and incisal portions of prosthodontic veneering composites.16-17 The composition ofcomposite materials varies considerably among manufacturers, curing modes and material indications, andbonding methods focus on organic matrices as well as inorganic fillers. Bonding between the two composite
material layers is generally achieved in the presence of an oxygen-inhibited surface unpolymerized layer. It
is difficult, however, to bond an additional material to an aged, ground or polished material surface. Bothmechanical and chemical retention systems are being employed for composite-to-composite bonding. Whilea number of bond strength results have been reported for bonding composite materials in the clinic, only
limited information is available on the bonding of laboratory cured prosthodontic composite materials,
especially as related to laboratory repairing processes. In the current study, the repair bond strengths between
dentin and incisal layers of an indirect composite were determined with the aim of evaluating bonding
performance of the light-activated hybrid material treated with silane primers and bonding agents.

MATERIALS AND METHODS
A light-activated indirect composite material designed for veneering restorations and fixed partial dentures(Cesead II, Kuraray Medical, Tokyo, Japan) was selected as a substrate (shade DA3) and repair material(shade E1). This material is categorized as a hybrid composite, and it contains splintered inorganic fillers,
inorganic micro fillers, and prepolymerized composite filler particles. Four silane primers and three bonding
agents were used in the current study. The information on these materials is summarized in Table 1. The four
primers contain a silane monomer but no initiator, whereas the three bonding agents contain a photo-initiator
but no silane coupler. All materials except for the Porcelain Liner M two-liquid primer (Sun Medical.
Moriyama, Japan) were supplied by Kuraray Medical (Tokyo, Japan).
The dentin portion of the Cesead II paste (DA3) was filled into a cylindrical plastic mold (10 mm indiameter by 2.5 mm height) and polymerized with a laboratory light-curing unit (Alpha-Light II, J. Morita
Corp., Osaka, Japan) for 180 s. Of a total of 336 specimens, 320 specimens were cured between two pieces ofglass plate, and the remaining 16 specimens (groups 1 and 2) were cured without shielding the top surfaces so
as to produce an oxygen-inhibited surface unpolymerized layer. After light exposure, the 320 specimens
were ground flat with 400 grit silicon-carbide abrasive paper, followed by abrasion with a silicon carbide
rotary cutting instrument (HP13, Shofu Inc., Kyoto, Japan).

The 16 specimens, each with an

oxygen-inhibited layer, were left unground and were used as experimental controls. A piece of double coatedtape with a circular hole 5 mm in diameter was positioned on the top surface of each of the 336 specimens.
The 320 ground and abraded specimens were divided into 40 groups (groups 3 to 42), which were thentreated with the materials shown in Table 2. Each of the 40 groups consisted of eight identically treatedspecimens. In each group, the silane-primed surfaces and bonding-agent-treated surfaces were gently
air-dried, while the surfaces to which the CMB Bond material was applied were light-exposed with the curing
unit for 10 s. After surface preparation, a brass ring (6 mm inside diameter by 2 mm height and 1 mm

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HISAMATSU, ATSUTA, AND MATSUMURAINT CHIN J DENT

thick-wall) was placed so as to surround the 5 mm diameter area defined by the tape. The ring was filled withthe enamel portion of the Cesead II material (E1) and light-cured for 180 s.
Thirty minutes after preparation, the specimens in the odd numbered groups were stored in a dry
environment maintained by an incubator at 37˚C for 24 hours, and the specimens in the even numberedgroups were immersed in 37˚C water for 24 hours. Shear bond strengths were then determined with amechanical testing machine (AGS-10kNG, Shimazu Corp., Kyoto, Japan) at a crosshead speed of 0.5
mm/minute. Shear bond strength was defined as the force at failure divided by bonded surface area. For eachcondition, the average bond strength and standard deviation of eight replications were calculated. The bondstrength results other than those in groups 1 and 2 were compared by analysis of variance (ANOVA), and a
Duncan new multiple range test with the value of statistical significance set at the 0.05 level. Comparison
between each group and the corresponding control group (group 1 or 2), and comparison between dry and wet
conditions with an identical surface preparation were performed using mean comparison contrasts. The
failure mode was categorized into five types as shown in Fig. 1.
Table 1. Materials assessed.
Materials/trade names

Abbreviation

Lot number

Functional monomer

Initiator

Indirect composite material
Cesead II, Dentin, DA300542A, 00577A, 00588A, 00602A

Light

Cesead II, Enamel, E100055A, 00078A, 00086C, 00087A

Light

00097A

None

Silane primer
Clearfil Porcelain Bond Activator

CPB Activator

Clearfil Porcelain Bond Activator

CPB Activator+ Clearfil Mega Bond, Primer

Silane+ CMB Primer

0035A

Silane + MDP

None

Estenia Add-on Primer

Add-on Primer

00012E

SilaneNone

Porcelain Liner M A liquid

Liner M

VE1

4-META

None

VE1

SilaneNone

B liquid
Unfilled resin bonding agent
Cesead Stain Diluent

Stain Diluent

00028D

Light

Clearfil Mega Bond, Bond

CMB Bond

00088ALight

Estenia Modeling Liquid

Modeling Liquid

00017C

Light

4-META: 4-methacryloyloxyethyl trimellitate anhydride; MDP: Methacryloyloxydecyl dihydrogen phosphate.

RESULTS
Three-way ANOVA run on the shear testing results showed that the interaction among silane primer,
bonding agent, and storage condition was not significant (p = 0.2699). The results were therefore analyzed
by two-way ANOVAs. Two-way ANOVAs revealed a significant interaction between silane primer and

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HISAMATSU, ATSUTA, AND MATSUMURAINT CHIN J DENT

bonding agent in both dry- and wet-stored groups (p<0.01). The results were then analyzed separately by
one-way ANOVAs and post-hoc Duncan new multiple range tests.

A

B

Fig. 1. Classification of failure modes.

C

D

E

A: composite-composite interface separation; B:

composite-composite interface separation with crack propagation inside the substrate material; C:
composite-composite interface separation with crack propagation inside both the substrate andadded materials; D: cohesive failure of both sides of the composite material; and E: cohesive failure
inside the substrate material.

International Chinese Journal of Dentistry
2002 Outstanding Article AwardInternational Chinese Journal of Dentistry announces the first Outstanding Article Award.
Award:A cash prize of US$ 500 and a certificate of commendation are awarded for the most outstanding article
published in the International Chinese Journal of Dentistry.
Criteria:
Original articles, clinical reports, and dental technology articles published in the Journal between issue 1
and issue 4 are considered for the award. The winning article will be selected by a committee on the basis ofscientific impact on the dental professional communities, and interest to the readers.
The 2002 Award is sponsored by the International Chinese Journal of Dentistry and the following award
sponsors.
Award Sponsors:
Kuraray Medical Inc., Tokyo, Japan, http://www.kuraray.co.jp/dental
Sun Medical Co., Ltd., Moriyama, Japan, http://www.sunmedical.co.jp
Toho Dental Products, Saitama, Japan
Tokuyama Dental Corp., Tokyo, Japan, http://www.tokuyama-dental.co.jp
3M Health Care Limited, Sagamihara, Japan, http://www.3m.com/espe/

8

HISAMATSU, ATSUTA, AND MATSUMURAINT CHIN J DENT60

Sh e ar b on d s tre n gt h (MPa )50

Silane+Bonding

Bonding

SilaneNoneControl

40

30

20

10

0
1 33 31 41 39 37 9

7 29 17 27 25 21 15 11 5 13 23 19 35 3
Group

Fig. 2. Shear testing results for the dry-stored groups.
Table 2 and Figs. 2 and 3 summarize the shear testing results, statistical groupings, and failure modes.
Except for the controls, average bond strength varied from 46.3 MPa (group 33, Add-on Primer and Stain
Diluent) to 18.6 MPa (group 3, no silane and no bonding agent) in the dry-stored groups, whereas the averagevalues ranged from 46.0 MPa (group 34, Add-on Primer and Stain Diluent) to 20.1 MPa (group 4, no silane
and no bonding agent). The combination of the Add-on Primer silane material and the StainDiluent bonding
agent was categorized into the greatest bond strength groups (categories f and m), and the untreated group
was categorized into the lowest bond strength groups (categories a and g) for both dry and wet conditions(p<0.05). Bond strengths of the control groups were 50.7 MPa for the dry-stored group, and 52.7 MPa for the
wet-stored group respectively. Of the surface-ground groups (groups 3 through 42), only group 33 showedbond strength statistically comparable to the control (group 1, p = 0.1074).
Among the 20 dry-stored groups with the exception of group 1, four combinations consisting of one of thetwo silane primers (Add-on Primer and Liner M) and one of the two bonding agents (Modeling Liquid andStain Diluent) showed the greatest bond strength (category f). Another four groups (groups 3, 11, 19, and 35),

9

HISAMATSU, ATSUTA, AND MATSUMURAINT CHIN J DENT

in which no bonding agent was used, were categorized into the lowest bond strength category (category a).
Bond strength ranking somewhat changed for the wet-stored groups, although the combination of the Add-on
primer and the Stain Diluent again showed the greatest bond strength (category m).

60

Sh e ar b on d s tre n gt h (MPa )50

Silane+Bonding

Bonding

SilaneNoneControl

40

30

20

10

0
2 34 38 32 10 42 8 22 40 30 28 24 20 18 16 26 6 12 14 36 4
Gr o upFig. 3. Shear testing results for the wet-stored groups.
Bond strengths were statistically evaluated in the dry-stored and wet-stored groups by using mean
comparison contrasts. The results are summarized in Table 3. Of a total of 21 combinations, bond strength
was significantly greater in the six wet-stored groups than in the corresponding dry-stored groups. No
significant difference in bond strength was found between dry- and wet-stored groups for the remaining 15
combinations.
Evaluation of debonded surfaces after shear testing indicate that high-bond strength groups tend to showcohesive failure inside the composite material rater than at the adhesive interface, and that low-bond strength
groups tend to exhibit adhesive failure (Table 2). All the specimens in groups 3, 4, 11, and 12, in which no10

HISAMATSU, ATSUTA, AND MATSUMURAINT CHIN J DENT

bonding agent was used, resulted in type A adhesive failure.
Table 2. Shear testing results, statistical categories, and failure modes.
Group
1
2

Silane primer

Bonding agent(Control, dry-stored)(Control, wet-stored)

Mean
(MPa)

SD
(MPa)

50.7
52.7

2.5
2.6

Statisticalcategory

Failure modeA B C D E
0 0 0 8 0
0 0 0 8 0

Dry-stored groups
3
None
5
None
7
None
9
None
11
CPB Activator
13
CPB Activator
15
CPB Activator
17
CPB Activator
19
CPB Activator + CMB Primer
21
CPB Activator + CMB Primer
23
CPB Activator + CMB Primer
25
CPB Activator + CMB Primer
27
Add-on Primer
29
Add-on Primer
31
Add-on Primer
33
Add-on Primer
35
Liner M37
Liner M
39
Liner M
41
Liner M

None
CMB Bond
Modeling Liquid
Stain Diluent
None
CMB Bond
Modeling Liquid
Stain Diluent
None
CMB Bond
Modeling Liquid
Stain Diluent
None
CMB Bond
Modeling Liquid
Stain Diluent
None
CMB Bond
Modeling Liquid
Stain Diluent

18.6
24.2
36.6
37.4
24.8
23.2
26.9
32.8
21.1
31.8
22.3
32.2
32.7
36.6
42.2
46.3
20.8
38.1
40.7
41.0

2.9
6.6
2.9
4.0
4.2
10.6
4.1
5.0
5.3
6.6
4.8
9.2
3.1
7.0
3.2
9.8
1.9
6.0
3.7
4.7

a
a, b
d, e
d, e
a, b
a, b
b, c
c, d
a, b
c, d
a, b
c, d
c, d
d, e
e, f
f
a, b
d, e
e, f
e, f

8
1
0
0
8
5
5
6
5
1
4
1
0
0
0
1
4
0
0
0

0
7
1
0
0
0
2
2
1
2
1
3
0
1
0
3
3
2
0
0

0
0
7
4
0
3
1
0
2
5
3
4
7
7
6
4
1
6
5
4

0
0
0
2
0
0
0
0
0
0
0
0
1
0
2
0
0
0
3
3

0
0
0
2
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1

Wet-stored groups
4
None
6
None
8
None
10
None
12
CPB Activator
14
CPB Activator
16
CPB Activator
18
CPB Activator
20
CPB Activator + CMB Primer
22
CPB Activator + CMB Primer
24
CPB Activator + CMB Primer
26
CPB Activator + CMB Primer
28
Add-on Primer
30
Add-on Primer
32
Add-on Primer
34
Add-on Primer
36
Liner M38
Liner M
40
Liner M
42
Liner M

None
CMB Bond
Modeling Liquid
Stain Diluent
None
CMB Bond
Modeling Liquid
Stain Diluent
None
CMB Bond
Modeling Liquid
Stain Diluent
None
CMB Bond
Modeling Liquid
Stain Diluent
None
CMB Bond
Modeling Liquid
Stain Diluent

20.1
29.3
42.1
43.0
27.3
26.9
30.7
30.8
30.9
42.0
32.9
29.8
36.6
38.6
43.2
46.0
24.2
44.4
41.2
42.6

3.2
3.8
3.9
2.9
4.6
4.7
3.4
5.0
9.1
3.4
7.4
8.4
1.9
7.7
3.6
7.9
4.3
6.8
1.4
2.6

g
h, i
k, l, m
l, m
h, i
h, i
i
i
i
k, l, m
i, j
h, i
j, k
k, l
l, m
m
g, h
l, m
k, l, m
l, m

8
1
0
0
8
4
4
6
4
0
2
1
0
0
0
0
3
0
0
0

0
7
0
0
0
1
3
2
1
1
1
5
0
2
0
1
4
2
0
0

0
0
8
5
0
3
1
0
3
7
5
2
8
6
7
7
1
6
5
2

0
0
0
1
0
0
0
0
0
0
0
0
0
0
1
0
0
0
3
4

0
0
0
2
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
2

Table 3. Means comparison contrast results between dry- and wet-stored groups.

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HISAMATSU, ATSUTA, AND MATSUMURAINT CHIN J DENT

Silane primer

Bonding agent

Dry WetS/NS

P-value

Control

Control12NS0.4564

None

None

3

4

NS

0.5816None

CMB Bond

5

6NS

0.0616None

Modeling Liquid

7

8

S

0.0436

None

Stain Diluent

9

10

S

0.0398CPB Activator

None

11

12

NS

0.3576CPB Activator

CMB Bond

13

14

NS

0.1736CPB Activator

Modeling Liquid

15

16

NS

0.1720CPB Activator

Stain Diluent

17

18

NS

0.4656CPB Activator + CMB Primer

None

19

20

S

0.0004CPB Activator + CMB Primer

CMB Bond

21

22

S

0.0002CPB Activator + CMB Primer

Modeling Liquid

23

24

S

0.0001CPB Activator + CMB Primer

Stain Diluent

25

26

NS

0.3808Add-on Primer

None

27

28

NS

0.1499Add-on Primer

CMB Bond

29

30

NS

0.4506

Add-on Primer

Modeling Liquid

31

32

NS

0.7238Add-on Primer

Stain Diluent

33

34

NS

0.9184

Liner M

None

35

36

NS

0.2088Liner M

CMB Bond

37

38

S

0.0204

Liner M

Modeling Liquid

39

40

NS

0.8462

Liner M

Stain Diluent

41

42

NS

0.5576

S: Significant (p<0.05); NS: Not significant (p>0.05).

DISCUSSION
The CPB Activator material and the CMB Primer material was combined with the aim of activating thesilane monomer contained in the former liquid with the acidic MDP monomer in the latter liquid. This
concept has been established for porcelain bonding.18 The current results, however, did not show any
apparent silane-acid combination effect except for the one case in which it was used together with the CMB
Bond material. Since the combination of the CMB Primer and the CMB Bond materials was originallyintroduced as a self-etching bonding system for tooth substrates, the bonding performance to composite
materials in the CMB system should be evaluated further with the use of three-liquid systems consisting of
the CMB Primer, CMB Bond, and one of the single-liquid silane agents.
The effect of the Liner M material on bond strength varied considerably with and without the use of

12

HISAMATSU, ATSUTA, AND MATSUMURAINT CHIN J DENT

bonding agents. Both monomer liquids of the Liner M material contain volatile methyl methacrylate (MMA)
monomer as the solvent. As a result, the composite surface primed with the Liner M material is coated with athin layer of silane and 4-META monomers. Bonding of an additional composite to the primed surface is
expected to be difficult in the absence of a flowable bonding agent, and indeed the results of groups 35 and 36
support this speculation. As shown in the statistical categories, bond strengths generated with the no-bonding
agent groups were not particularly good, and the results suggest that the use of an unfilled resin bonding agent
helps the Cesead II composite to achieve adequate 24-hour bond strength.
In the comparison of dry- and wet-stored groups, the bond strength of dry-stored groups was either
comparable to or less than that of the corresponding wet-stored groups. Specimens were stored at an identicaltemperature in both dry- and wet-conditions. Thus the only difference between the two conditions was thepresence/absence of water. The difference in coefficient of thermal conductivity between air and water, or
the difference in concentration of oxygen around previously laboratory-cured specimens, may affect the
post-curing properties of bonded specimens. Further evaluation including aging testing is necessary to
determine the exact influence of water on composite-to-composite interfacial bonding.
Of the various combinations evaluated in the current study, the combined use of a silane primer and an
unfilled resin bonding agent generally exhibited high bond strengths. The results suggest that both anappropriate functional monomer and reproduction of an oxygen-inhibited layer is indispensable to properinterfacial bonding between layers of the laboratory-processed hybrid composite.

ACKNOWLEDGMENT
This research is supported in part by a grant from MEXT-Japan, GAEYS (A), 12771188.

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Reprint request to:
Dr. Noriko Hisamatsu
Fixed Prosthodontics Division, Nagasaki University Hospital of Dentistry
1-7-1, Sakamoto, Nagasaki 852-8588, Japan
FAX: +81-95-849-7689
E-mail: norinori@net.nagasaki-u.ac.jp
Received on December 20, 2001. Revised on December 30, 2001. Accepted on January 2, 2002.
Copyright ©2002 by the Editorial Council of the International Chinese Journal of Dentistry.

14