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Int Chin J Dent 2006; 6: 71-78.

Effect of dentin coating on microleakage and bond strength ofadhesive resin cements
Hisanori Kurashige, DDS, PhD,a Shiro Suzuki, DDS, PhD,b Hiroyuki Minami, DDS,
PhD,a and Takuo Tanaka, DDS, PhDa
Department of Fixed Prosthodontics, Kagoshima University Graduate School of Medical and Dental
Sciences, Kagoshima, Japan, and Department of Prosthodontics and Biomaterials, University of
Alabama at Birmingham, School of Dentistry, Birmingham, AL, USA
Purpose: This study determined the effect of the application of dentin coating materials on microleakage andshear bond strengths of adhesive resin cements.
Materials and Methods: One hundred and five bovine dentin specimens for dye penetration testing and shear
bond testing were ground flat with #600 grit silicon-carbide paper. The specimens were divided into fifteengroups of seven specimens each, and they were subdivided into two dentin-coated (Touch&Bond andBrush&Bond) and non-coated (control) conditions of five groups each. One out of the five groups was subjected
to a microleakage test, which was performed by immersing the specimens in 5% methylene-blue for 24 hours.
The remaining four groups were used for shear bond test. Shear bond specimens were fabricated by bonding
Ni-Cr alloy disks with adhesive resin cements (Panavia F or C&B Metabond) both with and without
post-treatment of proprietary dentin conditioners to the coated surfaces. The mean values of microleakage andshear bond strength for each group were statistically analyzed by two-way analysis of variance (ANOVA) and
Bonferroni/Dunn test at a 95% confidence level.
Results: The dentin coated specimens showed significantly less dye penetration than the non-coated specimens.
For both adhesive resin bonded groups, shear bond strengths of Brush&Bond coated specimens without
post-treatment (7.8 MPa for C&B Metabond specimens, 1.5 MPa for Panavia F specimens) significantly
increased (16.0 MPa and 21.7 MPa, respectively) through the use of dentin conditioners onto the coated surface.
Conclusion: It was suggested that appropriate post-treatments to the coated surfaces were necessary whenadhesive resin cements were used for luting prostheses. (Int Chin J Dent 2006; 6: 71-78.)
Key Words: adhesive resin, dentin coating, dentin conditioner, microleakage, bond strength.

Introduction
Dentin exposure occurs when enamel is removed during tooth preparation. In cases of preparation for fullcoverage crowns, more than a million dentinal tubules are exposed,1 and this provokes postoperative sensitivity
in vital teeth if an appropriate procedure is not employed. Exposed dentin is usually covered with provisional
restorations retained by temporary cement.2

However, these are often subject to problems including

microleakage, dislodgement, and even fracture.

These contribute to the onset of post-preparation tooth

3,4

sensitivity and potential pulp damage.

Therefore, it is important to maintain dentin protection during theprovisional phase of treatment so that physical and/or chemical stimuli do not result in postoperative sensitivity.
Dentin protection is essential in preventing bacterial infection and maintaining pulp health. In endodonticallytreated teeth, coronal seal has been shown to be a major factor in the long-term success of endodontic treatment.5
Dentin has less resistance to acid attack when compared to enamel; thus, it is more susceptible to caries.
Secondary caries after final restoration of a tooth affects dentin surfaces more predominately than enamel
margins. Regardless of the pulpal condition of a prepared tooth, it is important to protect dentin from factorsthat result in a poor prognosis. These include physical and chemical stimuli, microleakage, bacterial infection
and the effect of bacterial by-products.
Studies have demonstrated that new dentin coating system and dentin bonding agents used to protect dentin
surfaces can exhibit microleakage that extends into dentinal tubules.6-8 The use of such agents for reducing
sensitivity after crown preparation has also been shown to be an effective clinical treatment.9-13 Some materials

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Int Chin J Dent 2006; 6: 71-78.

applied to coat the dentin surfaces may have adverse effects on the bond of luting agents. Teeth treated with ahydrophilic dentin primer system demonstrated a significant reduction in crown retention when polycarboxylatebased or zinc phosphate cements were used as the luting agents,14 while the bond strength of crowns cemented todentin pretreated with dentin bonding agents seemed to depend upon the combination of luting agent and dentin
bonding agent.15
The purpose of this study was to evaluate the effect of the application of dentin coating material on
microleakage and shear bond strength of luting agents to these surfaces.

Materials and Methods
The materials used in this study are presented in Table 1.

Touch&Bond and Brush&Bond (Parkell,

Farmingdale, NY, USA) were used as dentin coating materials. 	
 Both materials contain a 4-META moleculealong with other co-monomers and are self-etching dentin bonding systems. Two adhesive resin cements, C&B
Metabond (Parkell) and Panavia F (Kuraray	
 Medical, Tokyo, Japan) were used as the luting agents. Dentin
Activator (Parkell) with C&B Metabond and ED Primer (Kuraray	
 Medical) with Panavia F were individuallyused as a post-treatment to coat dentin before luting.
Table 1.

Materials used.

Material/Trade nameComponent

Manufacturer

Lot number

Dentin coating material
Brush&Bond
Touch&Bond

4-META, MMA, Polyacrylates
4-META, MMA, UDMA

Parkell
Parkell

L-200 200208, S-060
L-990006, S-990706

CementC&B Metabond
Panavia F

4-META, MMA, TBBO
MDP, Bis-GMA, Filler

Parkell
Kuraray Medical

P, ER1; Liq, EL1; Cat, EK22
61175

Dentin conditioner
Dentin Activator
ED Primer

Citric acid, Ferric chloride
HEMA, 5-NMSA, MDP

Parkell
Kuraray Medical

1091
A, 00148A; B, 00033A

Temporary cement
Freegenol Temporary Pack

Zinc oxide, Rosin

GC Corp.

270351

Metal adhesive primer
Alloy Primer

MDP, VBATDTKuraray Medical

0105AAOne hundred nineteen extracted bovine anterior teeth were used. Their roots and pulps were removed, and theorifices of pulp chambers were sealed with C&B Metabond after conditioning the dentin using Dentin Activator
to prevent dye penetration and contaminant from that surface. The teeth were stored in 37°C distilled water for
24 hours. The labial surfaces of all tooth crowns were ground flat with a #400 silicon-carbide paper under water
irrigation to expose dentin, and polished with a #600 grit paper.
The flow chart of specimen fabrications is presented in Fig. 1. One hundred five bovine teeth sealed with
C&B Metabond were randomly selected for dye penetration testing and shear bond testing. The teeth weredivided into three groups, including two dentin-coated (Touch&Bond and Brush&Bond) groups and a
non-coated group of 35 specimens each to serve as a control. Group 1 was used for Touch&Bond. The material
was applied to the ground dentin surfaces for 20 s, air-dispersed, and photo-polymerized for 5 s. The second
layer of Touch&Bond was applied, gently air-dried and polymerized for 10 s.

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Group 2 was used forKurashige et al.

Int Chin J Dent 2006; 6: 71-78.

Brush&Bond. The Brush&Bond was applied to the surface for 20 s, gently air-dried and photo-polymerized for10 s. After the photo-polymerization, the superficial oxygen-inhibited layer was removed with an alcohol swab.
Group 3 (control) received no dentin coating.

Fig. 1.

Design for fabricated specimens.

Fig. 2.

Schematic illustration of shear bond test.

In addition, Group 1, 2, and 3 were subdivided into five groups of seven specimens each. One out of the fivegroups was subjected to a microleakage test and the remaining four were used for shear bond test.
To evaluate dye penetration evaluation the specimens for the microleakage test were immersed in a 5%
solution of methylene blue at room temperature for 24 hours after the dentin surfaces were treated. They werethen removed from the dye solution, received superficial dye removal, and allowed to dry at room temperaturefor one hour. The specimens were sectioned labio-lingually with a diamond disk and observed by a lightmicroscope under 40x magnification. The dye penetration was measured at the five deepest points for eachspecimen. In short, the extent of dye penetration was determined at 35 points for each condition. The values foreach specimen were averaged, and the data were statistically analyzed with analysis of variance (ANOVA),
followed by Bonferroni/Dunn test at a 95% confidence level to compare individual groups.
To evaluate shear bond strengths the remaining 12 groups were used, including four groups each of two
dentin-coated and non-coated conditions. For shear bond specimen fabrication the area to apply dentin coating
materials was limited to a diameter of 10 mm with the use of masking tape. After coating, a temporary cement,
Freegenol Temporary Pack (GC Corp., Tokyo, Japan), was then applied to the coated surfaces using a 10 mmdiameter plastic plate. The specimens were then stored in 37°C water for 1 hour to set the temporary cement.
After this water storage period, the temporary cement was mechanically removed and the surface was cleaned
with an alcohol swab. The masking tape was placed onto the coated surface so that the adhesive area waslimited to 5 mm in diameter.
Coated dentin specimens were randomly divided into two groups to be luted with C&B Metabond and Panavia
F. In addition, C&B Metabond and Panavia F specimens were divided into two groups. The dentin conditioner,(Dentin Activator or ED Primer) was applied to the coated dentin as post-treatment for one group. The othergroup received no post-treatment. After the post-treatment, metal rods were luted with two resin cements tomeasure shear bond strengths. The metal rods (10 mm diameter and 3 mm height) were cast in a Ni-Cr alloy73Kurashige et al.

Int Chin J Dent 2006; 6: 71-78.

(Rexillium II, Jeneric/Pentron, Wallingford, CT, USA). The disk surfaces were polished with a #600-grit paper,then air-abraded with 50 µm alumina. In the case of Panavia F, Alloy Primer (Kuraray	
 Medical) was also
applied to the metal surfaces after they had been air-abraded.
After each surface treatment, cast disks were cemented directly to coated dentin surfaces according to
manufacturers’ directions. Non-coated specimens served as a control group for each cement. After cement
excess was carefully removed with a brush, the specimens were stored at room temperature for 1 hour. They
were then placed in 37°C water and stored for an additional 24 hours before shear bond testing. The bondstrengths were determined with a universal testing machine at 1.27 mm/minute crosshead speed (Fig. 2). Seven
specimens were tested for each condition of shear bond testing.

The mean values of each group were

statistically analyzed with two-way ANOVA, with the conditions of dentin coating materials and post-treatments
for respective cements as independent factors. Differences among the groups were analyzed by a Bonferroni/
Dunn test at a 95% confidence level.
After determining shear bond strengths, both tooth and metal surfaces were observed by scanning electron
microscope (SEM) to analyze the failure patterns. Fourteen teeth were used for observation of cross-sectionalsurfaces by SEM. The 12 types of specimens for shear bond testing and two specimens which were only treatedwith each coating material to dentin were prepared for observation by SEM. Completed specimens wereembedded with an auto-polymerized acrylic resin and cross-sectioned with a rotary diamond disk. They werethen treated with 6 N hydrochloric acid (HCl) for 30 s and rinsed with distilled water to remove the inorganic
phase. This is followed by 10% sodium hypochlorite (NaOCl) for 5 minutes to remove the organic componentsof the dentin using a technique described in the literature.16 This permits better observation of the dentin coating
materials that penetrated into dentinal tubules. Specimens were dried and gold/platinum sputtered for SEM
observation.

Results
The results of dye penetration are presented in Table 2. The dye reached to the pulp chambers in all thecontrol specimens. When dentin-coating materials were applied, the depths of dye penetration significantly
decreased as compared to the control (p<0.05). The value of Brush&Bond specimens averaged 0.08 µm, whilethat of Touch&Bond specimens was 0.16 µm. There was no significant difference between Brush&Bond andTouch&Bond (p>0.05). SEM observations revealed that dentin surfaces were completely covered with a layerof each dentin coating material.
Table 2.

Results of dye penetration for coating materials.

Dentin coating material

Dye penetrationSD

Non-coated (Control)
Touch&Bond
Brush&Bond

1.38
0.16
0.08

0.34
0.09
0.03

(mm)

Statistical categoryabb

Statistical category: Identical letters indicate that they are not statistically different (p>0.05).

For shear bond strength measurement, the results of two-way ANOVA indicated that significant differenceswere found between coating materials (p<0.0001) and treatment to coated dentin (p<0.0001). In addition,
significant interaction between coating materials and treatment to coated dentin (p<0.0001) were obtained. The

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results of shear bond testing and the destruction sites during the shear bond tests are presented in Table 3.
Electron micrographs of failure site are presented in Fig. 3.
Table 3.

Shear bond strengths, standard deviations in MPa, statistical categories, and failure modes.
C&B MetabondWithout DA
With DA

Non-coatedTouch&Bond
Brush&Bond

Panavia F
Without ED

With ED

Mean SDSCFM

Mean SDSCFM

Mean SDSC FM

Mean SD

SC FM

2.0
9.7
7.8

c
d
c, d

CD
CC
CC

32.4 5.6
11.4 2.8
16.0 1.4

f
d, e
e

CD
CC
CC

2.3
1.3
1.5

g CD
g CC
g CC

10.0 2.4
14.3 2.6
21.7 5.1

h CD
h CO
I CO

1.4
4.4
3.0

0.4
0.6
0.9

DA, Dentin Activator; ED, ED Primer, SD, Standard deviation.
SC, Statistical category; Identical lower case letters indicate that they are not statistically different (p>0.05). The C&B Metabondgroup and the Panavia group were not statistically compared in this table due to different surface preparation procedures.
FM, Failure mode; CC: failure occurred at the interface between cement and coating; CO: cohesive failure occurred at bothcement and coating; CD, failure occurred at the interface between cement and dentin.

When the specimens were luted with C&B Metabond, the shear bond strengths (SBS) of coated specimens(11.4 MPa for Touch&Bond and 16.0 MPa for Brush&Bond) were significantly lower than Non-coatedspecimens (32.4 MPa) treated with Dentin Activator. These results are shown in Table 3 and existed despite thedentin coating material and/or post-treatment with Dentin Activator (p<0.0003). The Brush&Bond coated grouptreated with Dentin Activator demonstrated significantly higher SBS compared with the group without Dentin
Activator (p<0.0001).

Scanning electron micrograph of the destruction was presented Fig. 3-a when thespecimen was luted with C&B Metabond after applying Dentin Activator. This photograph illustrates the
exposed dentin surface. When Touch&Bond or Brush&Bond was applied to dentin surfaces, the failure mainly
occurred at the cement/coating interface (Fig. 3b). Dentin surfaces were covered and protected with a layer of
each dentin coating material.

3a3bFig. 3a.
Debonded dentin surface of C&B
Metabond-bonded specimen
pretreated with Dentin Activator.
Debonding occurred dentin/C&B
Metabond interface.
Fig. 3b.
Debonded dentin surface of C&B
Metabond-bonded specimen coatedwith Brush&Bond followed by
pretreated with Dentin Activator.
Debonding occurred at C&B
Metabond/Brush&Bond interface.
Fig. 3c.
Debonded dentin surface of Panavia
F-bonded specimen pretreated withED Primer. Debonding occurred at
dentin/Panavia F interface.
Fig. 3d.
Debonded Ni-Cr alloy surface ofPanavia F-bonded specimen coatedwith Brush&Bond followed by
pretreatment with ED Primer, showing
cohesive/adhesive failure.

3c

3dWhen ED primer was not applied to coated surfaces before cementing, SBS of Panavia F ranged from 1.3 to
1.5 MPa, and specimen failure occurred entirely at the cement/coating interface. However, when Brush&Bond

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coated surfaces were treated with ED Primer, the SBS of Panavia F significantly increased compared to thecontrol with ED Primer (p<0.0001) as shown in Table 3. The failure of control occurred at cement/dentin
interface (Fig. 3c). The failures of the Brush&Bond coated specimens with ED Primer mainly occurred at thecement/coating interface and partially at the coating/dentin interface. For Brush&Bond/ED Primer/Panavia F,
the failure at the coating/dentin interface showed a greater area (Fig. 3d) compared to the groups ofTouch&Bond/ED Primer/Panavia F.

4a

4b

4c

4d

4e

4f

Fig. 4. Cross-sectional surfaces: 4a, Brush&Bond; 4b, C&B Metabond with Dentin Activator; 4c, Panavia F with ED Primer; 4d,Panavia F without ED Primer on Brush&Bond coated dentin surface; 4e, Panavia F with ED Primer on Brush&Bond coated dentin
surface; 4f, C&B Metabond with Dentin Activator on Brush&Bond coated dentin surface.

Cross-sectional micrographs are presented in Fig. 4.

The SEM for Brush&Bond (Fig. 4a) and Dentin

Activator/C&B Metabond (Fig. 4b) showed longer and greater numbers of resin tags compared to ED
Primer/Panavia F (Fig. 4c). When specimens were cemented to the coated surfaces with Panavia F without ED
Primer, crack formation was observed between cement/coating interface (Fig. 4d). However, cracks could not
be seen when ED Primer was used (Fig. 4e). When specimens were luted to the coated surfaces with C&B
Metabond, cracks could not be found regardless of the treatment of Dentin Activator (Fig. 4f).

Discussion
Sound tooth enamel has an inherent capacity to resist unfavorable stimuli. When dentin is exposed during
dental treatment, the danger of pulpal involvement increases as the tooth becomes more susceptible to bacterial
infection and other problems. Therefore, dentin protection plays an important role in maintaining the health ofrestored teeth. The results of the microleakage test demonstrated that the dentin coating materials used in thisstudy were successful in protecting exposed dentin from dye penetration. This suggests that these materials
could be effective in protecting exposed dentin from unfavorable stimuli in the clinical situation and acquiring
good prognoses. The results of the shear bond tests demonstrated that the failure pattern of bonded luting agentswas material or post-treatment dependent. The variation of shear bond strengths according to procedures was
illustrated in Table 3.

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The SBS of tested resin cements appeared to be affected by pretreatment of the coated surface and the cementused. The coated specimens demonstrated significantly lower SBS compared to non-coated specimens when
C&B Metabond was used. The specimens failed in shear predominantly at the cement/coating interface. Thismight be due to the weak bond of the cement to the coated surface. Higher bond strength might be expected if asuperficial unpolymerized layer existed on the coated surface; however, in this study, the oxygen-inhibited layer
was completely removed to better simulate clinical conditions. The surface was not only swabbed with alcohol
but also further contaminated by the use of temporary cement. Therefore, the improvement of a coated surface
appears to be the key to achieve better bonding. Shear bond strengths were improved by applying Dentin
Activator to the coated surfaces compared to untreated specimens, especially those coated with Brush&Bond. It
is speculated that there are two possibilities for this improvement. The first is the cleansing effect of citric acid,and the other is promotion of polymerization by ferric chloride in the Dentin Activator for C&B Metabond.17
However, it is suspected that bond strengths between C&B Metabond and coating surface are low, as the failure
occurred in cement/dentin coating materials in the micrograph (Fig. 3b). C&B Metabond could hardly beobserved on the coated surface.
When the specimens were bonded using Panavia F, SBS was dramatically improved by applying ED Primer
onto the Brush&Bond coated surfaces as compared to that of no post-treatment. It is speculated that interfacial
polymerization of Panavia F was enhanced by the catalyst in ED Primer. The failure can be seen at coating
material/dentin interface. From this result, it is suspected that ED Primer has a capacity to generate a chemicalbonding between coating material and Panavia F. In fact, Panavia F exhibited very poor bond strength to coatedsurfaces when they were not treated with ED Primer. This poor performance might be attributed to interfacial
separation between cement and dentin coating materials (Fig. 4d) due to polymerization shrinkage of Panavia F.
Therefore, the post-treatment using ED Primer is essential when Panavia F is used.
When considering dentin coating as a protection for exposed dentin during provisionalization, the site ofdebonding becomes a critical issue. It is better to have the debonding at the coating/cement interface rather thanat the coating/dentin interface. In that way, even if the bond fails, dentin remains protected by the adhesive
coating. Shear bond strength of the resin cements significantly improved by using dentin conditioner. Thebalance of bond strength to dentin substrate is important, as the interfaces could possibly be deteriorated overtime in clinical situations due to masticatory stresses.18 In the present study, no attempts of stress-fatigue weremade to the interfaces. Further investigations are suggested.

References
1. Richardson D, Tao L, Pashley DH. Dentin permeability: effects of crown preparation. Int J Prosthodont 1991; 4: 219-25.
2. Brannstorom M. Reducing the risk of sensitivity and pulpal complications after the placement of crowns and fixed partial
dentures. Quintessence Int 1996; 27: 673-8.
3. Bergenholtz G. Inflammatory response of the dental pulp to bacterial. J Endodont 1981; 7: 100-4.
4. Pashley DH. Smear layer: physiological considerations. Oper Dent 1984; Suppl 3 Smear Layer on Pulp: 13-29.
5. Howdle MD, Fox K, Youngson CC. An in vitro study of coronal microleakage around bonded amalgam coronal-radicularcores in endodontically treated molar teeth. Quintessence Int 2002; 33: 22-9.
6. Patel S, Saunders WP, Burke FJ. Microleakage of dentin-bonded crowns placed with difficult luting materials. Am J Dent
1997; 10: 179-83.
7. Shiflett K, White SN. Microleakage of cements for stainless steel crowns. Pediatr Dent 1997; 19 :262-6.
8. Shortall AC, Fayyad MA, Williams JD. Marginal sealing of injection-molded ceramic crowns cemented with three adhesive
systems. J Prosthet Dent 1989; 61: 24-7.
9. Felton DA, Bergenholtz G, Kanoy BE. Evaluation of the desensitizing effect of Gluma Dentin Bond on teeth prepared forcomplete-coverage restorations. Int J Prosthodont 1991; 4: 292-8.
10. Quarnstrom F, Collier N, McDade E, McLean K, Munk A, Nicholls J. A randomized clinical trial of agents to reduce sensitivity
after crown cementation. Gen Dent 1998; 46: 68-74.
11. Suzuki S. Clinical evaluation of a new resin composite crown system to eliminate postoperative sensitivity. Int J Periodontics
Restorative Dent 2000; 20: 498-509.

77

Kurashige et al.

Int Chin J Dent 2006; 6: 71-78.

12. Trowbridge HO, Silver DR. A review of current approaches to in-office management of tooth sensitivity. Dent Clin North Am
1990; 34: 561-81.
13. Watanabe T, Sano M, Itoh K, Wakumoto S. The effects of primers on the sensitivity of dentin. Dent Mater J 1991; 7: 148-50.
14. Mansner IK, Goldstein GR, Georgescu M. Effect of two dentinal desensitizing agents on retention of complete cast coping
using four cements. J Prosthet Dent 1996; 75: 129-34.
15. Yim NH, Rueggeberg FA, Caughman WF, Gardner FM, Pashley DH. Effect of dentin desensitizers and cementing agents on
retention of full crowns using standardized crown preparations. J Prosthet Dent 2000; 83: 459-65.
16. Nikaido T, Burrow MF, Tagami J, Takatsu T. Effect of pulpal pressure on adhesion of resin composite to dentin: Bovine serum
versus saline. Quintessence Int 1995; 26: 221-6.
17. Imai Y, Kadoma Y, Kojima K, Akimoto T, Ikakura K, Ohta T. Importance of polymerization initiator systems and interfacial
initiation of polymerization in adhesive bonding of resin to dentin. J Dent Res 1991; 70: 1088-91.
18. Pashley EL, Comer RW, Simpson MD, Horner JA, Pashley DH, Caughman WF. Dentin permeability: Sealing the dentin incrown preparations. Oper Dent 1992; 17: 13-20.

Correspondence to:Dr. Hisanori Kurashige
Department of Prosthodontics, Kagoshima University Dental School
8-35-1 Sakuragaoka, Kagoshima 890-8544, Japan
Fax: +81-99-275-6218 E-mail: kura@dentb.hal.kagoshima-u.ac.jp
Received February 13, 2006. Accepted May 1, 2006.
Copyright ©2006 by the International Chinese Journal of Dentistry.

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