Yoshikawa et al.

Asian Pac J Dent 2016; 16: 23-28

Bond strength of resin composites to cavity floor and cavity wall
dentinTakako Yoshikawa, DDS, PhD (1), Alireza Sadr, DDS, PhD (2), Makoto Arakawa, DDS,
PhD (3), and Junji Tagami, DDS, PhD (1)(1) Cariology and Operative Dentistry, Department of Oral Health Sciences, Graduate School of
Medical and Dental Sciences, Tokyo Medical and Dental University (TMDU), Tokyo, Japan, (2) IB3T
Laboratory, Department of Restorative Dentistry, School of Dentistry, University of Washington, Seattle,
WA, USA, and (3) Department of Dental Hygiene, Chiba Prefectural University of Health Sciences,
Chiba, Japan
Purpose: To evaluate the effect of dentin location and dentinal tubule orientation on resin composite bondstrength to dentin of the cavity floor and cavity wall using various adhesive systems.
Materials and Methods: Box-form cavities were prepared on human molars. Each specimen was restored with
one of three adhesives Clearfil SE Bond, Single Bond, or Clearfil tri-S Bond followed by filling or buildup using
Z100 resin composite. After light-curing at 600 mW/cm2 for 40 s, the specimen was cut perpendicular to thebonded surface parallel to the floor or wall to obtain beams. The microtensile bond strength to the cavity floor orwall specimens was determined. Data were analyzed using the Bonferroni test.
Results: Single Bond and Clearfil tri-S Bond showed significantly lower bond strength to the cavity floor
compared with that of the cavity wall (p < 0.05). However, there was no significant difference in bond strength
between the cavity floor and wall using Clearfil SE Bond (p > 0.05). Clearfil SE Bond showed significantly
higher bond strength to the cavity floor than that of Single Bond and Clearfil tri-S Bond (p > 0.05).
Conclusion: Single Bond and Clearfil tri-s Bond bond strength to the cavity floor dentin was lower than to thecavity wall dentin. However, there was no significant difference in bond strength between the cavity floor andcavity wall using Clearfil SE Bond.
(Asian Pac J Dent 2016; 16: 23-28.)
Key Words: bond strength, dentin location, dentinal tubule orientation, resin composite

Introduction
Resin composite polymerization leads to volumetric shrinkage, and light-cured composites develop higher
stresses in the cured material because the polymerization reaction occurs faster than in self-cured composites [1].
Therefore, the maximum interfacial stress generated at the cavity wall is two-fold greater in light-cured
composite restorations than in self-cured composite restorations [2]. This stress has been shown to lead to greatergap formation between the resin and cavity surfaces than self-cured resin composite restorative materials.
Many reports of the measurement of resin composite bond strength to superficial flat dentin surfaces haveshown that dentin bond strength decreases during bonding to deep dentin [4-8]. It has been reported that the resin
composite bond strength was two-fold greater in the more superficial dentinal layers when compared with deeper
portions [5]. Resin composite bond strength registered on dentin close to the pulp has also consistently been only
30%-40% of the strength found on peripheral dentin [5]. Remaining dentin thickness has an important influenceon the reduction in bond strength of dentin bonding systems. Moreover, varying bond strengths to dentin,
particularly deep dentin, have been reported with different adhesive systems [7,8].
In clinical application, most bonding substrates are the three-dimensional dentin walls of Class I-V cavities.
The microtensile bond strength (µTBS) of resin composite that is bonded to a box-like Class I dentin cavity floor
has been shown to be affected by cavity configuration (C-factor) and depth [7,9,10]. Furthermore, the resin
composite bond and adaptation to the cavity wall is influenced by the dentinal tubule location and orientation[11].
Hybrid layer formation is considered essential for creating a strong bond between resin and dentin [12].

23Yoshikawa et al.

Asian Pac J Dent 2016; 16: 23-28

However, the thickness of the hybrid layer is less important when the resin composite is bonded to a dentin
substrate that is perpendicular to flat dentin, and the bond strength between the resin and dentin is independent of
the thickness of the hybrid layer [8,13]. Thus, we thought that it would be interesting to evaluate the bonding
performance of adhesive systems with different curing modes to box-formed cavity walls and floors.
The purpose of this study was to evaluate the effects of dentin location, dentinal tubule orientation on resin
composite bond strength to box-formed cavity floors and walls using various adhesive systems.

Materials and Methods
Specimen preparation
The materials, components, manufacturers, batch numbers, and bonding procedures used in this study are listed
in Table 1. Eighteen intact, erupted, non-carious third molars that were frozen immediately after extraction wereused in this study. These molars were collected in accordance with protocol No. 725, as approved by theappropriate institutional review board.
Table 1 Study materials
Material/Manufacturer

Componentsa

Batch No.

Bonding
instructionb

Clearfil SE Bond (SE)(Kuraray Noritake Dental Co., Ltd.,Tokyo, Japan)

Primer: HEMA, dimethacrylates,
photoinitiator, water

00539Aa (20 s), b, c,d, e (10 s)

Bond: MDP, HEMA, Bis-GMA,
dimethacrylates, photoinitiator, microfiller

00760A

Uni-etch: 35% phosphoric acid

4JA

Bond: Bis- GMA, HEMA, dimethacrylates,
methacrylates, pendent polyalkenoic acidcopolymer, photoinitiator, ethanol, water

3KF

Bond: MDP, HEMA, Bis-GMA,
photoinitiator, water, ethanol

00083A

Single Bond (SB)
(3M ESPE, St. Paul, MN, USA)

Clearfil tri-S Bond (TS)(Kuraray Noritake Dental Co., Ltd.)f (15 s), g, h, i,e (10 s)c (5 s) d, e

Z100
(3M ESPE)

Bis-GMA, TEGDMA, dimethacrylate
4NJ
e (40 s)polymer, zirconia / silica filler,
photo initiator, Filler load: 84.5 wt %aAbbreviations: HEMA, 2-hydroxyethylmethacrylate; MDP, 10-methacryloyloxydecyl dihydrogen phosphate; Bis-GMA,
bisphenyl-glycidyl-methacrylateb
Procedures: (a) apply primer; (b) dry with gently air-blowing; (c) apply adhesive; (d) gently air blow (e) light-cure; (f)acid-etch; (g) rinse with water; (h) blot-dry; (i) apply 2 coats of adhesive

The occlusal enamel (Fig. 1A) was ground away using a model trimmer under running water to expose a flat
dentin surface, which was then wet-ground with #600 SiC paper. Box-form cavities (3 mm wide × 5 mm long ×
2 mm deep) were prepared on the flat dentin surfaces using a diamond point (#211, ISO #110 014; Shofu Inc.,
Kyoto, Japan) with copious water spray and were finished with a carbide steel bur (#600, ISO #071 012;
Dentech Co., Tokyo, Japan) (Fig. 1B). Each specimen was restored with one of three adhesives: Clearfil SE
Bond (Kuraray Noritake Dental, Co., Ltd., Tokyo, Japan), Single Bond (3M ESPE, St. Paul, MN, USA), andClearfil tri-S Bond (Kuraray Noritake Dental, Co., Ltd.). A Z100 resin composite (Shade A3; 3M ESPE) was
then used to fill in the cavities (Fig. 1B). The resin composite was light-cured at 600 mW/cm2 for 40 s using anexperimental quartz-tungsten halogen light-curing unit (GC Corp., Tokyo, Japan) that was connected to a slide

24Yoshikawa et al.

Asian Pac J Dent 2016; 16: 23-28

regulator and had a control system for lamp voltage and an adjustable light intensity, with a light tip (diameter, 7mm). The light intensity on the surface of the specimens was measured using a curing radiometer (Model 100;
Demetron Research Co., Danbury, CT, USA).

Fig. 1 Preparation of a cavity bonding substrate

Tensile bond strength measurement
The specimens were stored in water maintained at 37°C in the dark for 24 h. Then, the restored floor/wall
specimens were sectioned perpendicular to the bonded surfaces using a diamond saw (Isomet, Buehler Co., Lake
Bluff, IL, USA) under copious water lubrication (Figs. 1C). Each slab was cut into beams with a bonded area ofapproximately 0.9 mm2 using a diamond saw under copious water lubrication. The trimmed specimens were
mounted on a µTBS jig (KDA, Tokyo, Japan) with cyanoacrylate adhesive (Model Repair II Blue;
Dentsply-Sankin Co., Ohtawara, Japan) and stressed to failure under tension at 1 mm/min in a universal testingmachine (EZ test; Shimadzu, Kyoto, Japan). Each specimen was then inspected using a scanning electron
microscope (SEM) to determine the mode of fracture. The bond strength to floor and wall dentin were
statistically analyzed using the Fisher’s PLSD test at a significance level of 5%.
SEM observation of fractured surfaces
After the tensile bond test, each fractured dentin specimen was fixed in 10% neutral buffered formalin [14]. The
dentin and composite-paired specimens were then trimmed and placed on SEM stubs, coated with gold-sputter,and observed using an SEM (JSM-5310LV; JEOL, Akishima, Japan) to microscopically assess the patterns offailure. The fractured surfaces were classified into one of four groups: interfacial failure; mixed failure; cohesive
failure within the resin (adhesive layer or composite); and cohesive failure within the dentin.

Results
The tensile bond strength results are summarized in Table 2. Single Bond and Clearfil tri-S Bond showedsignificantly lower bond strength to the cavity floor than to the cavity wall (p < 0.05). However, there was no
significant difference in bond strength with Clearfil SE Bond between the cavity floor and wall (p > 0.05).
Overall, bond strength was significantly lower for Clearfil tri-S Bond than Clearfil SE Bond (p < 0.05).
Clearfil SE Bond showed significantly higher bond strength to the cavity floor compared with that of Single
Bond and Clearfil tri-S Bond (p > 0.05). Single Bond showed significantly higher bond strength to the cavity

25

Yoshikawa et al.

Asian Pac J Dent 2016; 16: 23-28

floor compared with that of Clearfil tri-S Bond (p > 0.05). Clearfil SE Bond and Single Bond showedsignificantly higher bond strength to the cavity wall compared with that of Clearfil tri-S Bond (p > 0.05).
However, there was no significant difference in bond strength between Clearfil SE Bond and Single Bond to thecavity wall (p > 0.05).
Table 2 Mean tensile bond strength of the bonding system to the cavity floor and cavity wall dentin

Type of substrate / Material

Tensile bond strength (MPa)Single Bond
Clearfil tri-S Bond

Clearfil SE Bond50.1 (6.1) A

Cavity wall

46.1 (6.6) a, B

30.0 (2.7) a, A, B

Cavity floor
50.1 (2.9) A
29.7 (2.8) a, A
20.6 (1.8) a, A
Same lower-case superscript letters indicate significant differences in the strength of the bonding substrates (p < 0.05).
Same upper-case superscript letters indicate significant differences in the strength of the bonding systems (p < 0.05).
Table 3 Failure mode
Interfacial failure
SE
SB
TS

Mixed failure

Cohesive failure in resin Cohesive failure in dentin

Cavity wall

1

4

1

0

Cavity floor

1

5

0

0

Cavity wall

6

0

0

0

Cavity floor

6

0

0

0

Cavity wall

3

1

2

0

Cavity floor

4

1

0

1

2
3
4
Fig. 2 Dentin side of fractured specimen to cavity floor by Clearfil SE Bond. Failure mode indicated mixed failure.
Fig. 3 Dentin side of fractured specimen to cavity wall by Clearfil SE Bond. Failure mode indicated mixed failure.
Fig. 4 Dentin side of fractured specimen to cavity floor by Single Bond. Failure mode indicated interfacial failure at
the top of the hybrid layer.

5
6
7
Fig. 5 Dentin side of fractured specimen to cavity wall by Single Bond. Failure mode indicated interfacial failure at
the top of the hybrid layer.
Fig. 6 Dentin side of fractured specimen to cavity floor by Clearfil tri-S Bond. Failure mode indicated interfacial
failure.
Fig. 7 Dentin side of fractured specimen to cavity wall by Clearfil tri-S Bond. Failure mode indicated interfacial
failure.

26

Yoshikawa et al.

Asian Pac J Dent 2016; 16: 23-28

The failure mode results are summarized in Table 3. Most of the Clearfil SE Bond specimens showed mixed
failure of the cavity floor (Fig. 2) and walls (Fig. 3). All of the Single Bond specimens showed interfacial failure
at the top of the hybrid layer of the cavity floor (Fig. 4) and walls (Fig. 5). Most of the Clearfil tri-S Bond
specimens showed interfacial failure of the cavity floor (Fig. 6). Most of the Clearfil tri-S Bond specimens
showed interfacial failure (Fig. 7) and cohesive failure in resin of the cavity walls.

Discussion
In descending order, bond strength of the materials to the cavity floor was as follows: Clearfil SE Bond > Single
Bond > Clearfil tri-S Bond. The Single Bond adhesive system uses a phosphoric acid etching agent. In the caseof an etching agent, the bonding material may not fully infiltrate the collagen fibril network of the demineralized
dentin. Failure of the resin to adequately penetrate the collagen network in deeply etched dentin will produce a
porous zone at the hybrid layer base, resulting in a weak porous hybrid layer zone that is susceptible todegradation of the resin-dentin bond. Conversely, the self-etching primer system appears to allow the bonding
resin to completely penetrate the demineralized dentin. Thus, the self-etching primer system provides a highquality resin-impregnated layer that contributes to a strong bond between the bonding system and tooth wall.
The hybrid layer of Single Bond is about 2-6 times thicker than that of Clearfil SE Bond [15]. The quality of a
hybrid layer, rather than quantity, is considered more important for obtaining a good resin-dentin bond [16,17].
These findings are in agreement with an earlier study showing that the bond strength between resin and dentin
was independent of hybrid layer thickness [8,13].
There was no significant difference in bonding to the cavity wall between Clearfil SE Bond and Single Bond.
However, Clearfil tri-S Bond showed significantly weaker bond strength to the cavity wall than that of Clearfil
SE Bond and Single Bond. Failure mode of Clearfil SE Bond showed an almost mixed failure of bonding to thecavity wall. Most of Clearfil tri-S Bond specimens showed interfacial failure and cohesive failure in the bonding
layer. One-step self-etching systems are more hydrophilic and water absorbent than two-step self-etchingsystems [18]. Evaporating water from the one-step adhesives is difficult, and even if evaporation is successful,water rapidly diffuses back from the bonded dentin into the adhesive resin [19], resulting in water sorption
plasticized polymers and increases solubility, and decreases modulus of elasticity [18] and mechanical propertiesof the polymer [20]. Therefore, the one-step self-etching system Clearfil tri-S Bond showed cohesive failure in
the bonding layer and lower bond strength.
Single Bond and Clearfil tri-S Bond showed significantly lower bond strength of the cavity floor than that of
the cavity wall. Bond strength was significantly higher with parallel tubules than with perpendicular tubules. Theintertubular dentin has smaller dimensions in the floor than in the walls because the dentinal tubules are oriented
almost parallel to wall dentin. The hybrid layer is reportedly thinner in areas with parallel tubules [11],confirming that resin-dentin bond strength is not affected by hybrid layer thickness, which supports the findingsof previous studies [8,13].
There was no significant difference in bond strength between the cavity floor and wall for Clearfil SE Bond.
This was believed to be because of the effect of a difference in adhesive layer thickness. Clearfil SE Bond
contains microfillers in the bonding resin, and the thickness of the adhesive resin layer has been shown to range
from 40 to 200 µm [21]. Conversely, Single Bond produces a thin film of unfilled adhesive at 30-40 µm [22].
Thus, the thick adhesive resin layer of Clearfil SE Bond was likely to absorb some of the shrinkage stress that27

Yoshikawa et al.

Asian Pac J Dent 2016; 16: 23-28

occurred during light curing of the resin composites [23].
Acknowledgments
This work was supported by Grant-in-Aid for Scientific Research No. 22592115 and No. 16K11543 from the Japan Society
for the Promotion and Global Center of Excellence Program.

References
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.

Feilzer AJ, de Gee AJ, Davidson CL. Setting stress in composite for two different curing modes. Dent Mater 1993; 9: 2-5.
Kinomoto Y, Torii M, Takeshige F, Ebisu S. Comparison of polymerization contraction stresses between self-and light-curingcomposites. J Dent 1999; 27: 383-9.
Causton BE. Improved bonding of composite restorative to dentin. Br Dent J 1984; 156: 93-5.
Mitchem JC, Gronas DG. Effect of time after extraction and depth of dentin on resin dentin adhesives. J Am Dent Assoc
1986; 113: 285-7.
Suzuki T, Finger WJ. Dentin adhesives: site of dentin vs. bonding of composite resins. Dent Mater 1988; 4: 379-83.
Tagami J, Tao L, Pashley DH. Correlation among dentin depth, permeability and bond strength of adhesive resin. Dent
Mater 1990; 6: 45-50.
Yoshikawa T, Sano H, Burrow MF, Tagami J, Pashley DH. Effects of dentin depth and cavity configuration on bond strength.
J Dent Res 1999; 78: 898-905.
Yoshikawa T, Wattanawongpitak N, Cho E, Tagami J. Effect of remaining dentin thickness on bond strength of various
adhesive systems to dentin. Dent Mater J 2012; 31: 1033-8.
Belli S, Dönmez N, Eskitaşcioğlu G. The effect of C-factor and flowable resin or fiber use at the interface on microtensile
bond strength to dentin. J Adhes Dent 2006; 8: 247-53.
Endo AV, Munk JD, Landuyt KV, Meerbeek BV. Effect of bulk-filling on the bonding efficacy in occlusal Class I cavities. J
Adhes Dent 2016; 18: 119-24.
Schüpbach P, Krejci I, Lutz F. Dentin bonding: effect of tubule orientation on hybrid-layer formation. Eur J Oral Sci 1997;
105: 344-52.
Nakabayashi N, Kojima K, Masuhara E. The promotion of adhesion by the infiltration of monomers into tooth substrates. J
Biomed Mater Res 1982; 16: 265-73.
Yoshiyama M, Carvalho RM, Sano H, Horner JA, Brewer PD, Pashley DH. Regional bond strengths of resins to human root
dentine. J Dent 1996; 24: 435-42.
Nakajima M, Sano H, Burrow MF, Tagami J, Yoshiyama M, Ebisu S, et al. Tensile bond strength and SEM evaluation ofcaries-affected dentin using dentin adhesives. J Dent Res 1995; 74: 1679-88.
Senawongse P, Harnirattisai C, Shimada Y, Tagami J. Effective bond strength of current adhesive systems on deciduousand permanent dentin. Oper Dent 2004; 29: 196-202.
Sano H, Shono T, Takatsu T, Hosoda H. Microporous dentin zone beneath resin-impregnated layer. Oper Dent 1994; 19:
59-64.
Burrow MF, Takakura H, Nakajima M, Inai N, Tagami J, Takatsu T. The influence of age and depth of dentin on bonding.
Dent Mater 1994; 10: 241-6.
Ito S, Hashimoto M, Wadgaonkar B, Svizero N, Carvalho RM, Yiu C, et al. Effects of resin hydrophilicity on water sorption
and changes in modulus of elasticity. Biomaterials 2005; 26: 6449-59.
Tay FR, Pashley DH. Have dentin adhesives become too hydrophilic? J Can Dent Assoc 2003; 69: 726-31.
Bastioli C, Romano G, Migliaresi C. Water sorption and mechanical properties of dental composites. Biomaterials 1990; 11:219-23.
Kubo S, Yokota H, Hayashi Y. Effect of low-viscosity resin-based composite on the microleakage of cervical restorations.
Am J Dent 2003; 16: 244-8.
Walshaw PR, Tam LE, McComb D. Bond failure at dentin-composite interfaces with ‘single-bottle’ adhesives. J Dent 2003;
31: 117-25.
Choi KK, Condon JR, Ferracane JL. The effects of adhesive thickness on polymerization contraction stress of composite. J
Dent Res 2000; 79: 812-7.

Correspondence to:Dr. Takako Yoshikawa
Cariology and Operative Dentistry, Department of Oral Health Sciences,
Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University (TMDU)
1-5-45, Yushima, Bunkyo-ku, Tokyo 113-8549, Japan
Fax: +81-3-5803-0195 E-mail: yoshikawa.ope@tmd.ac.jp
Accepted October 31, 2016.
Copyright ©2016 by the Asian Pacific Journal of Dentistry.
Online ISSN 2185-3487, Print ISSN 2185-3479

28