|Year : 2013 | Volume
| Issue : 3 | Page : 86-89
Effect of endodontic irrigants on microtensile bond strength of a self-etching adhesive system
Abdulkadir Sengun1, Hasan Orucoglu2, Hayriye Esra Ülker3
1 Department of Restorative Dentistry, Faculty of Dentistry, Kirikkale University, Kirikkale, Turkey
2 Department of Endodontics, Faculty of Dentistry, Abant Izzet Baysal University, Bolu, Turkey
3 Department of Restorative Dentistry, Selcuk University, Konya, Turkey
|Date of Web Publication||25-Sep-2013|
Hayriye Esra Ülker
Department of Restorative Dentistry, Selcuk University, Faculty of Dentistry 42075, Selcuklu, Konya
Source of Support: None, Conflict of Interest: None
Aim: The aim of this in vitro study was to evaluate the effect of two different irrigation solutions, alone or in combination, with different application times on the dentin bond strength of a self-etching adhesive. Materials and Methods: Twenty-eight extracted non-carious human third molars were randomly distributed into seven groups according to the irrigant. The crowns of the molars were sectioned vertically through bucco-lingual direction. Solutions of 5% sodium-hypochlorite (NaOCl), 3% hydrogen-peroxide (H 2 O 2 ), and a combination of NaOCl and H 2 O 2 were applied to the dentin surface for various lengths of time. The adhesive system (Clearfil SE Bond; Kuraray, Japan) was applied according to the manufacturers' directions and then the dentin surfaces were built up with a hybrid composite resin (Clearfil AP-X Kuraray, Japan). Specimens were sectioned into 15 sticks; each of them had a 0.65 mm 2 bonding area. Microtensile bond strength was determined (MPa), and the results were statistically analyzed using one-way ANOVA and Tukey's HSD test. Results: Irrigation with NaOCl alone showed similar micro-tensile bond strength values with the control group (P > 0.05). In comparison to control group, irrigation with H 2 O 2 alone for 5 min and 30 min and the irrigation with H 2 O 2 /NaOCl combination each for 15 min decreased the microtensile bond strength. Conclusion: The use of H 2 O 2 significantly reduced the bond strengths of the self-etching adhesive when applied alone or in combination with NaOCl for a long time.
Keywords: Microtensile bond strength, root canal irrigation, self-etching adhesive
|How to cite this article:|
Sengun A, Orucoglu H, Ülker HE. Effect of endodontic irrigants on microtensile bond strength of a self-etching adhesive system. J Res Dent 2013;1:86-9
|How to cite this URL:|
Sengun A, Orucoglu H, Ülker HE. Effect of endodontic irrigants on microtensile bond strength of a self-etching adhesive system. J Res Dent [serial online] 2013 [cited 2021 Apr 11];1:86-9. Available from: http://www.jresdent.org/text.asp?2013/1/3/86/118909
| Introduction|| |
Decrement in the architecture of endodontically treated teeth is a common disadvantage of endodontic procedures. The reduction in the tooth dimension impairs the physical strength of the tooth and results in reduced filling material attachment. , Even the disinfection of the entire root canal system is crucial for endodontic therapy, the irrigation solutions may bring additional weaknesses to the adhesion capabilities of the restorative composite resins to the tooth. The type, application method, and the application time of the irrigation solution may have significant effects on the tooth-composite attachment. Sodium-hypochlorite (NaOCl), hydrogen-peroxide (H 2 O 2 ), and their combination have been widely used as irrigants in endodontic therapy for many years.  NaOCl application results in the gross debridement, lubrication, destruction of microbes, dissolution of tissues, removal of the collagen layer, and dehydration of the dentin. 
Lack of adhesion and sealing between the final restoration and the tooth structure may reduce the prognosis of nonsurgical root canal treatment because penetration of microorganisms from a coronal direction potentially re-infects the root canal system. ,, Resin composites are now in common use in the restoration of endodontically treated teeth, because of the technological advancements in the dentin bonding systems. The restoration of endodontically treated teeth with adhesive systems offers many advantages over the use of traditional, non-adhesive materials. For instance, bonded resins permit transmission of functional stresses across the bonded interface to the tooth, with the potential to reinforce the weakened tooth structure. , When a composite resin is used to restore the access cavity of a molar or to serve as a core material, it is very important to achieve a high-quality bond to cavity-wall dentin, to enhance retention, and to maximize the coronal seal.  However, recent studies have reported the negative effects of endodontic irrigants on bond strengths of resinous materials to dentin. ,,
The aim of this in vitro study was to evaluate the effect of two different irrigation solutions, alone or in combination, with different application times on the dentin bond strength of a self-etching adhesive. The null hypothesis of this study was that NaOCl and H 2 O 2 irrigation solutions both alone or in combination do not affect the dentin bond strength the self-etching adhesive.
| Materials and Methods|| |
Twenty-eight extracted non-carious human molars with fully developed apices were stored in normal saline and used within six months after extraction. The crowns of the teeth were sectioned vertically through the bucco-lingual direction with a low-speed diamond saw with water cooling (Isomet; Buehler, Lake Bluff, IL, USA). The sections were ground with #400-grit SiC paper under running water until the pulp chambers disappears. By this way flat dentin surfaces covered with homogenous smear layers were created. The specimens were randomly assigned to 7 groups (n = 4). Solutions of 5% NaOCl, 3% H 2 O 2 , and a combination of 5% NaOCl and 3% H 2 O 2 were applied to the dentin surface for various times [Table 1].
After applying the irrigation solutions, the specimens were rinsed with distilled water for 5 minutes and then the dentin surfaces were dried with air. A two-step self-etching adhesive system (Clearfil SE Bond; Kuraray Medical, Tokyo, Japan) was applied to the surfaces following the manufacturers' directions and light-cured (Bluephase® , Ivoclar Vivadent AG, Liechtenstein, Austria) for 10 seconds. A hybrid composite resin (Clearfil AP-X; Kuraray Medical Inc, Okayama, Japan) was used to complete the bonding the procedure; dentin surfaces were covered with 4-mm composite resin. The restored specimens were stored in the tap water at 37° C for 24 h. Each specimen was sectioned with a slow-speed saw (Isomet; Buehler Ltd., Lake Bluff, IL) under the water cooling into multiple beams using the ''non-trimming'' version of the microtensile test. Each beam had an approximately 0.65-mm 2 of bonding area. Fifteen beams were obtained for each study groups. When the external beams from the periphery were excluded, four beams were obtained from the central part of each tooth-composite specimen. Sixteen were obtained for each test condition. Fifteen of these 16 beams were randomly selected for microtensile bond strength tests (n = 15). Beams from the peripheral dentin were not included in the study.
Beams were fixed to the universal testing machine (Microtensile Tester; Bisco, Schaumburg, IL) using cyanoacrylate glue (Zapit; DVA, Corona, CA, USA) and stressed at a cross-head speed of 1 mm/min until failure. The cross-sectional area at the site of failure was measured to the nearest 0.01 mm with a digital calliper (Model CD-6BS; Mitutoyo, Tokyo, Japan), and the microtensile bond strength was calculated from this measurement and expressed in MPa.
Failure modes were evaluated at ×20 magnification with a stereoscopic microscope and classified as follows: a, adhesive failure between the dentin and the resin; c, cohesive failure in the resin; d, cohesive failure in the dentin; m, mixed failure (including adhesive failure between the dentin and the resin and cohesive failure of the resin or the dentin). Mean microtensile bond strength of each group was analyzed using one-way ANOVA. Post hoc comparisons were performed using Tukey's HSD test. Statistical significance was set in advance at P = 0.05.
| Results|| |
Statistical analysis with one-way ANOVA revealed that microtensile bond strength results were significantly affected by irrigation solutions (P < 0.05). The mean microtensile bond strength results, standard deviations, and significant differences between the groups are presented in [Table 2]. Different small superscript letters indicate the significant differences. Irrigation with NaOCl alone for 5 minutes and 30 minutes showed similar micro-tensile bond strength values with the control group (P > 0.05). The mean bond strength of the irrigation with H 2 O 2 and NaOCl combination each for 2, 5 minutes was also not significantly different from the control group (P > 0.05). However, in comparison to the control group, the irrigation with H 2 O 2 alone for 5 minutes and 30 minutes and the irrigation with H 2 O 2 and NaOCl combination each for 15 minutes decreased the microtensile bond strength. In particular, the lowest bond strength among all the groups was H 2 O 2 for 5 minutes.
|Table 2: Mean (±Standard deviation - SD) of microtensile bond strength data (MPa) |
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For all study groups, the most frequent pattern of failure was adhesive failure [Table 3]. In the 5 minutes 5% NaOCl and in the control group, the two step self-etching adhesive tended to show more cohesive failure in the dentin. Any cohesive failure was observed in 5 minutes 3% H 2 O 2 group.
|Table 3: Distribution of failure types per group based on the light microscope observations |
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| Discussion|| |
In the present study, the effects of NaOCl, H 2 O 2 , and the combination of NaOCl/H 2 O 2 on the dentin bond strength of a two-step self-etching adhesive to the cavity wall was determined. The NaOCl irrigation achieved equivalent dentin bond strength values with those obtained in the control group. In other words, no unfavorable effect was observed with the use of NaOCl irrigation for the tested two-step self-etching adhesive. The use of NaOCl irrigation in combination with H 2 O 2 has also no detrimental effect on the dentin bond strength except used for a long time such as 30 minutes. This clinically acceptable performance of NaOCl irrigation was explained by the removal of the collagen smear layer.  Vargas et al.,  Prati et al.,  and Saboia et al.  have reported that NaOCl treatments increased the bond strength of some adhesive systems, and they concluded that removal of the collagen layer may be beneficial for some resins to create proper dentinal bonding. In their SEM observations, when the collagen fiber was removed, they found that resin penetration into the dentin was deeper, and they claimed that unprotected collagen layer may interfere with the resin penetration into the dentin. Because of this, they reported that the collagen layer did not significantly contribute to the bond strength of the resin to the dentin, and they advised removal of this layer for longer bond duration.
Nikaido et al.,  and Perdigao et al.,  showed that NaOCl treatment damaged the organic components of the dentin; therefore, monomer penetration into the demineralized dentin was not sufficient to create proper bond strength. They claimed that the collagen fibrils were important in the adhesion mechanism and chemical irrigants caused significantly low bond strengths to the dentin. On the other hand, Yiu et al., showed that elution of the residual sodium hypochlorite could result in incomplete polymerization of the resin monomers at the junction between the adhesive and the demineralization front.  In the present study, a relatively short application of NaOCl for 5 minutes or 30 minutes and a combination of H 2 O 2 with NaOCl each for 2.5 minutes, which simulated the endodontic irrigation in the ordinal clinic, showed no adverse effect on bonding because less NaOCl may remain at the bonding interface.
The results of this study indicated that H 2 O 2 application generally decreased the bond strength of the self-etching adhesive resin. Among the all groups, the lowest bond strength was obtained with 5 minutes H 2 O 2 group. Several factors may be associated with adverse effects of hydrogen peroxide on bond strength. Hydrogen peroxide is capable of generating hydroxyl radical, an oxygen-derived free radical that is known to accumulate in the dentin and inhibit polymerization of the resin. , An initial decrease in the enamel bond strength after bleaching with peroxide compounds has also been reported. ,, After the use of chemical irrigants in the root canal, residual chemical irrigants and their products are likely to diffuse into the dentin along the dentin tubules. Residual chemical irrigants and their products in the fluid may contaminate the dentin surface, which may affect the penetration of the resin in to the dentin structure or the polymerization of the monomer in the demineralized dentin.  Failure-type evaluation confirmed this finding; H 2 O 2 application increased the incidence of adhesive failure type. Furthermore, any cohesive failure was observed in 5 minutes 3% H 2 O 2 group. Lower microtensile bond strength values are often accompanied by increased frequency of adhesive failure.
In this study, the two-step self-etching adhesive, Clearfil SE Bond, showed excellent performance on pulp chamber dentinal walls with or without NaOCl application. Vongphan et al., demonstrated that sodium hypochlorite significantly reduced the bond strengths of the adhesive when a total-etching was applied.  It can be speculated that in the total-etch system, acid-etching procedures on the pulp chamber dentinal region are major factors that affect the bond strength. Self-etching bonding systems have weak acids in their primer composition. Therefore, weak acidic compositions of primer can result in less change in the dentinal wall structure than the strong acids of total-etch systems.  However, Ercan et al., (2009) showed that pretreatment with NaOCl, H 2 O 2 or chlorhexidine solutions had a negative effect on the shear bond strength of self-etching bonding systems  and in a current study, influence of endodontic irrigants on resin sealer bond strength to radicular dentin was evaluated and sodium hypochlorite adversely affected bond strength of the AH Plus group. 
| Conclusion|| |
Within the limits of the current study, the use of H 2 O 2 significantly reduced the bond strengths of the self-etching adhesive when applied alone or in combination with NaOCl for a long time.
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[Table 1], [Table 2], [Table 3]