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ARTICLE IN PRESS
Influence of chemical irrigants on the tensile bond strength of
an adhesive system used to cement glass fiber posts
to root dentin
Rina Andréa Pelegrine, MSc,a Alexandre Sigrist De Martin, PhD,a
Rodrigo Sanches Cunha, PhD,b André Antonio Pelegrine, PhD,a and
Carlos Eduardo da Silveira Bueno, PhD,a Campinas, São Paulo, Brazil
SÃO LEOPOLDO MANDIC DENTAL RESEARCH CENTER AND CATHOLIC UNIVERSITY OF CAMPINAS
Objective. The aim of this study was to evaluate the influence of endodontic irrigants on the tensile bond strength of
an adhesive system used to cement glass fiber posts to dentin.
Study design. Fifty bovine roots were divided into 5 groups according to the solution used during instrumentation: G1,
0.9% NaCl (control); G2, 1.0% NaOCl; G3, 2.5% NaOCl; G4, 5.25% NaOCl; G5, 2% chlorhexidine gel ! 0.9%
NaCl. The root canals were obturated with gutta-percha and AH Plus sealer, and the glass fiber posts were cemented
with Clearfil SE Bond/RelyX ARC. The specimens were submitted to tensile strength testing and the results were
analyzed by analysis of variance.
Results. There were no statistically significant differences regarding the irrigant solution factor (P " .70).
Conclusion. It was concluded that the different irrigant solutions did not affect the tensile bond strength of the fixation
system used to cement the intraradicular glass fiber posts to dentin. (Oral Surg Oral Med Oral Pathol Oral Radiol
Endod 2010;xx:xxx)
Generally, root-filled teeth present with a greater loss of
tooth structure, resulting from caries, earlier restorations,
fractures, and endodontic acess preparation. The use of
posts in endodontically treated teeth with insufficient
coronal tooth structure is a universal accepted procedure.1
Initial post systems are retentive to root canals mechanically; therefore, there is much loss of tooth structure.2 With the evolution of adhesive systems, resin
cements, and restorative materials, endodontically
treated teeth began to be reconstructed conservatively, and
many intraradicular post systems have become available
for this purpose.3-7 Nevertheless, obtaining an effective
adhesion to root canals is a challenge, considering their
unfavorable geometry and the limitations inherent to the
physical-chemical properties of adhesive materials.8
Many of the limitations are related to polymerization
shrinkage, that often exceeds the bond strength of dentin
adhesives to dentin, resulting in gap formation along the
surfaces with the weakest bonds.9,10
Endodontic procedures performed before the luting
of posts also may interfere in adhesiveness to the root
canal.2,11-18 The use of irrigant solutions is an essential
complement to mechanical preparation, aiding in the
removal of pulp remnants and in the elimination of
residual bacteria from the complex root canal system.19
The routine use of sodium hypochlorite (NaOCl) in
endodontics is justified by its unquestionable importance because of both its wide-spectrum antimicrobial
activity20 and its properties as a tissue solvent,8,19,20
although it is known to be highly irritant to the periapical tissues, mainly at high concentrations.21 Chlorhexidine is a potent antiseptic with a broad-spectrum
antimicrobial action, substantivity, and low grade of toxicity;22,23 therefore, is unable to dissolve pulp tissue.23
Nonetheless, there is no consensus in the related
literature about the possible effects of the irrigant
agents commonly used during the biomechanical preparation of root canals regarding adhesive degradation.
Bearing in mind that the bonding properties of adhesive
materials to the dental substrate are critical for the
longevity of posts used as retainers for prosthetic
crowns, the objective of the present study was to evaluate the influence of 3 different concentrations of
NaOCl and of 2% chlorhexidine gel on the tensile bond
strength of an adhesive system used to cement glass
fiber posts to root dentin.
a
School of Dentistry, São Leopoldo Mandic Dental Research Center.
School of Dentistry, Catholic University of Campinas.
Received for publication Feb 16, 2009; returned for revision May 6,
2010; accepted for publication May 9, 2010.
1079-2104/$ - see front matter
© 2010 Mosby, Inc. All rights reserved.
doi:10.1016/j.tripleo.2010.05.005
b
MATERIALS AND METHODS
Tooth preparation
Fifty recently extracted bovine roots of similar size
and shape were selected by measuring the buccolingual
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Pelegrine et al.
and mesiodistal widths in millimeters, allowing a maximum deviation of 10% from the determined mean.7
The teeth were stored in 0.1% thymol solution (Pharmacia Medicamenta, Campinas, Brazil) for a maximum
period of 4 months. The soft tissue deposits were removed with a hand scaler (SS White Duflex, Rio de
Janeiro, Brazil), and the coronal portion of each tooth
was sectioned 15.0 mm coronally from the root apex,
using a diamond double-faced disk (KG Sorensen, Barueri, Brazil) in a slow-speed handpiece, cooled with
air/water spray. The roots were embedded in self-curing acrylic resin (JET, São Paulo, Brazil), the canals
were instrumented by the modified step-back technique24 with manual K-type files (Dentsply/Maillefer,
Ballaigues, Switzerland) with an apical matrix set at a
diameter corresponding to file #60, and flaring was
completed using Gates-Glidden burs no. 6 and 5
(Dentsply/Maillefer).
The specimens were randomly distributed into five
groups according to the chemical irrigant used: G1,
0.9% sodium chloride (NaCl, Becker; São Paulo, Brazil); G2, 1.0% NaOCl (Siafarma, Campinas, Brazil);
G3, 2.5% NaOCl (Siafarma); G4, 5.25% NaOCl (Siafarma); and G5, combination of 2% chlorhexidine gel
(Essencial Pharma, Itapetininga, Brazil) and 0.9% NaCl
(Becker). The root canals were irrigated with 20 mL of
each irrigant solution during cleansing and shaping,
with the exception of G5, which was irrigated with 5
mL 2% chlorhexidine and 20 mL 0.9% NaCl.
Once the instrumentation was concluded, all of the
groups were irrigated with 5 mL 17% ethylenediaminetetraacetic acid (EDTA, Siafarma) for 3 minutes
combined with ultrasonic vibration (CT4 tips; GBC
Innovations, San Diego, CA, USA). Final irrigation
was performed with the respective irrigant solution for
each group. The canals were dried with #60 absorbent
paper points (Dentsply/Maillefer, Petrópolis, Brazil)
and obturated with M gutta-percha cones (Dentsply/
Maillefer, Petrópolis) and endodontic sealer AH Plus
(Dentsply/Maillefer, Ballaigues) using the down-packing phase of the continuous-wave condensation technique.25
Immediately after endodontic obturation, a Largo bur
no. 5 (Dentsply/Maillefer, Ballaigues) was introduced
to remove excess obturating material up to a depth of 9
mm. As recommended by the manufacturer, glass fiber
posts (Reforpost RX no. 3; Angelus, Londrina, Brazil)
were selected. The canals were irrigated with 1.0 mL
17% EDTA for 1 minute to remove debris and remnants of obturating cement and were then washed with
0.9% NaCl and dried with absorbent paper points.
Before cementation, the posts were immersed in 70%
alcohol for 1 minute to remove residues and oils, acid
etched with 37% phosphoric acid (FGM Dentscare,
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Joinville, Santa Catarina, Brazil) for 15 seconds and
submitted to the silanization process using Clearfil Porcelain Bond Activator (Kuraray, Kurashiki, Japan) and
Clearfil SE Primer (Kuraray). After 1 minute, the posts
were dried with a light jet of air and cemented.
The self-etch 2-step adhesive system Clearfil SE
bond (Kuraray) was applied on the intraradicular preparations. Initially, Clearfil SE primer was introduced to
the prosthetic space with the aid of a microbrush and
spread for 20 seconds. The excess material was removed by a paper point and Clearfil SE bond applied.
A paper point was introduced once again and the adhesive was light cured for 60 seconds using a halogen
light-curing unit operated at 800 mW/cm2 (XL 3000;
3M Espe, St. Paul, MN, USA). For evaluation of the
light intensity, we used the Cure Rite digital radiometer
(Dentsply/Caulk, Milford, DE, USA).
RelyX ARC resin cement (3M Espe) was manipulated according to the manufacturer’s instructions and
introduced into the canal with a Lentulo spiral drill #60
(Dentsply/Maillefer, Ballaigues) in a low-speed handpiece. The posts were positioned and light-cured for 40
seconds. Cement excess was removed with a microbrush before light-curing. The samples were stored in a
humid environment at 37°C for 7 days18 before traction
of the posts commenced. All sample preparation was
done by the same operator.
Tensile strength test
For the tensile strength test, an acrylic resin cylinder
fitted on top with a metallic loop was made over the
coronal portion of the post (Fig. 1). After the resin was
polymerized, the test specimen was placed in a Universal Testing Machine (DL 2000; EMIC, São José dos
Pinhais, PR, Brazil), and an axial tensile load was
applied at 0.5 mm/min until failure.
Statistical analysis
A 1-factor analysis of variance model was adopted
(1-way analysis of variance). Associations that presented P values !5% (.05) were considered to be
statistically significant ( type Ierror probability).
RESULTS
The means and standard deviations of the tensile
strength values for each group are shown in Table I. No
statistically significant difference was observed among
the irrigant solutions tested (P " .70).
DISCUSSION
An unfavorable interaction of NaOCl with adhesive
systems, considering the potential of this solution to
affect mechanical dentin properties via degragation of
organic dentin components, has been reported in sev-
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Pelegrine et al. e3
Table I. Mean and standard deviation for the tensile
strength (TS) in kgf observed for the different irrigant
solutions tested
Irrigation solution
Group
Group
Group
Group
Group
1,
2,
3,
4,
5,
NaCl (control)
1% NaOCl
2.5% NaOCl
5.25% NaOCl
2% chlorhexidine
n
Mean
SD
10
10
10
10
10
24.661a
28.537a
27.537a
25.572a
28.831a
9.776
11.704
9.681
8.801
9.389
a
Groups with the same letter did not show any statistical significant
difference.
Fig. 1. A, Bovine root; B, acrylic resin; C, glass fiber post; D,
qcrylic resin cylinder; E, metallic loop.
eral studies,2,11,12,14 whereas others have shown an
improvement in adhesion after treatment with
NaOCl.13,17,18 In the present study, we tested the
NaOCl concentrations commonly used for irrigation of
root canals, ranging from 1% to 5.25%.19
The results of this study show that NaOCl did not
reduce adhesiveness compared with the groups irrigated with chlorhexidine and saline. This adhesiveness
similarity was due, at least in part, to its ability to
dissolve organic material. Organic tissue remaining favors the formation of a smear layer rich in organic
components, making it difficult for acid substances to
act, which is essential to adhesive processes.13
Sodium chloride is not used as an irrigating solution
in endodontic treatment. It was used in this study to
establish a control, enabling assessment of the effects
of NaOCl and chlorhexidine during endodontic procedures.
In addition to the different concentrations of
NaOCl, 2% chlorhexidine gel was also evaluated,
because it is an irrigant with an antibacterial activity
similar to that of NaOCl.22 However, owing to the
viscosity of the chlorhexidine gel, its application was
followed by an additional irrigation with 0.9% NaCl
to facilitate removal of the gel during aspiration.
Some earlier studies2,14,26 observed no reduction in
adhesiveness to dentin when chlorhexidine was used.
However, Wachlarowicz et al.18 observed a significant reduction in adhesiveness in teeth irrigated with
chlorhexidine compared with NaOCl. In the present
study, the tensile values required to remove the posts
when the specimens were submitted to treatment
with 2% chlorhexidine gel could probably be attributed to the viscosity of the gel, which might have
favored the mechanical cleansing of the root canal
walls and its anatomic complexities, thus promoting
the effective removal of dentin debris and tissue
remnants.22
The use of EDTA combined with ultrasonic vibration
is an effective method in removing the smear layer,27
allowing the final irrigant solution to penetrate into
dentinal tubules or other confined areas protected by the
smear layer.28 This makes it possible to evaluate the
effect of the irrigants tested on post retention via dentin
adhesive interaction with dentin walls.
All groups presented appropriate retention, because
the posts should present tensile strength values of "200
N, a limit considered by Bonfante et al.29 as the minimum requirement to ensure clinical success. The post
configuration (parallel with the apical conicity and with
undercuts along its entire length) probably contributed
to the values achieved (means ranging from 24.66 to
28.83 kgf, which are equivalent to 241.80 and 282.70
N, respectively).
Despite the particulars of each irrigant solution
tested, another hypothesis for the absence of significant
statistical differences among the tensile strength means
is that the slight etch of the adhesive system used
(Clearfil SE Bond) may have provided smaller dentin
permeability and, as a consequence, the fluid flow inside the dentinal tubules was probably reduced, thus
minimizing the effects of occasional chemical residues
in the dentinal tubules.15
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Pelegrine et al.
CONCLUSION
According to the results of this study, it was possible
to conclude that the different irrigant solutions tested
did not influence the tensile bond strength of the adhesive system used in this study to cement glass fiber
posts to root dentin.
REFERENCES
1. Perdigão J, Gomes G, Augusto V. The effect of dowel space on
the bond strengths of fiber posts. J Prosthet Dent 2007;16:
154-64.
2. Erdemir A, Ari H, Güngüneş H, Belli S. Effect of medications
for root canal treatment on bonding to root canal dentin. J Endod
2004;30:113-6.
3. Akkayan B, Gülmez T. Resistance to fracture of endodontically
treated teeth restored with different post systems. J Prosthet Dent
2002;87:431-7.
4. Sahafi A, Peutzfeldt A, Asmussen E, Gotfredsen K. Bond
strength of resin cement to dentin and to surface-treated posts of
titanium alloy, glass fiber, and zirconia. J Adhes Dent 2003;5:
153-62.
5. Galhano GA, Valandro LF, de Melo RM, Scotti R, Bottino MA.
Evaluation of the flexural strength of carbon fiber–, quartz fiber–,
and glass fiber– based posts. J Endod 2005;31:209-11.
6. Al-Omiri MK, Al-Wahadni AM. An ex vivo study of the effects
of retained coronal dentine on the strength of teeth restored with
composite core and different post and core systems. Int Endod J
2006;39:890-9.
7. Santos Filho PC, Castro CG, Silva GR, Campos RE, Soares CJ.
Effects of post system and length on the strain and fracture
resistance of root filled bovine teeth. Int Endod J 2008;41:
493-501.
8. Schwartz RS. Adhesive dentistry and endodontics. Part 2: bonding in the root canal system—the promise and the problems: a
review. J Endod 2006;32:1125-34.
9. Feilzer AJ, De Gee AJ, Davidson CL. Curing contraction of
composites and glass-ionomer cements. J Prosthet Dent
1988;59:297-300.
10. Tay FR, Loushine RJ, Lambrechts P, Weller RN, Pashley DH.
Geometric factors affecting dentin bonding in root canals: a
theoretical modeling approach. J Endod 2005;31:584-9.
11. Ari H, Yaşar E, Belli S. Effects of NaOCl on bond strengths of
resin cements to root canal dentin. J Endod 2003;29:248-51.
12. Ozturk B, Ozer F. Effect of NaOCl on bond strengths of bonding
agents to pulp chamber lateral walls. J Endod 2004;30:362-5.
13. Muniz L, Mathias P. The influence of sodium hypochlorite and
root canal sealers on post retention in different dentin regions.
Oper Dent 2005;30:533-9.
14. Santos JN, Carrilho MR, Goes MF, Zaia AA, Gomes BP, SouzaFilho FJ, et al. Effect of chemical irrigants on the bond strength
of a self-etching adhesive to pulp chamber dentin. J Endod
2006;32:1088-90.
15. Nikaido T, Takano Y, Sasafuchi Y, Burrow MF, Tagami J. Bond
strengths to endodontically-treated teeth. Am J Dent 1999;12:
177-80.
16. Goldman M, DeVitre R, Pier M. Effect of the dentin smeared
layer on tensile strength of cemented posts. J Prosthet Dent
1984;52:485-8.
17. Varela SG, Rábade LB, Lombardero PR, Sixto JM, Bahillo JD,
Park SA. In vitro study of endodontic post cementation protocols
that use resin cements. J Prosthet Dent 2003;89:146-53.
18. Wachlarowicz AJ, Joyce AP, Roberts S, Pashley DH. Effect of
endodontic irrigants on the shear bond strength of Epiphany
sealer to dentin. J Endod 2007;33:152-5.
19. Young GR, Parashos P, Messer HH. The principles of techniques
for cleaning root canals. Aust Dent J 2007;52:S52-63.
20. Estrela C, Estrela CR, Barbin EL, Spanó JC, Marchesan MA,
Pécora JD. Mechanism of action of sodium hypochlorite. Braz
Dent J 2002;13:113-7.
21. Zehnder M. Root canal irrigants. J Endod 2006;32:389-98.
22. Ferraz CC, Gomes BP, Zaia AA, Teixeira FB, Souza-Filho FJ. In
vitro assessment of the antimicrobial action and the mechanical
ability of chlorhexidine gel as an endodontic irrigant. J Endod
2001;27:452-5.
23. Okino LA, Siqueira EL, Santos M, Bombana AC, Figueiredo JA.
Dissolution of pulp tissue by aqueous solution of chlorhexidine
digluconate and chlorhexidine digluconate gel. Int Endod J
2004;37:38-41.
24. Mullaney TP. Instrumentation of finely curved canals. Dent Clin
North Am 1979;23:575-92.
25. Buchanan LS. The continuous wave of condensation technique:
a convergence of conceptual and procedural advances in obturation. Dent Today 1994;13:80-5.
26. Perdigão J, Denehy GE, Swift Junior EJ. Effects of chlorhexidine
on dentin surfaces and shear bond strengths. Am J Dent
1994;7:81-4.
27. Lui JN, Kuah HG, Chen NN. Effect of EDTA with and without
surfactants or ultrasonics on removal of smear layer. J Endod
2007;33:472-5.
28. Baumgartner JC, Cuenin PR. Efficacy of several concentrations
of sodium hypochlorite for root canal irrigation. J Endod
1992;18:605-12.
29. Bonfante G, Kaizer OB, Pegoraro LF, Valle AL. Tensile bond
strength of glass fiber posts luted with different cements. Braz
Oral Res 2007;21:159-64.
Reprint requests:
Rina Andréa Pelegrine, MSc
School of Dentistry
São Leopoldo Mandic Dental Research Center
Rua Sete de Setembro, 565, Vila Industrial
Campinas, SP
Brazil
CEP 13035-350
[email protected]