| Abstract|| |
Aim: To evaluate the effect of different root canal irrigants on the sealing ability of two self-etch adhesives, using dye penetration method, within the pulp chamber.
Materials and Methods: 72 extracted human molars were divided into six groups, according to the irrigant and self-etch adhesives used. After de-roofing the pulp chamber with a carborundum disc, the pulp was extirpated using excavator and broaches. In 36 samples, pulp chambers were bonded with Xeno V after irrigation with either 2% CHX (Group1: Xe-CHX) ; 17% EDTA + 5.25% NaOCl (Group2: Xe- EDTA + NaOCl) or normal saline (Group3: Xe-NS) and in other half samples, pulp chambers were bonded with Adper Easy One after irrigation with either 2% CHX (Group 4: Ad-CHX); 17%EDTA + 5.25% NaOCl (Group5: Ad-EDTA+NaOCl) or normal saline (Group 6: Ad-NS). All the samples were restored with Filtek Z350. Ten teeth from each group were assessed for dye penetration. Two samples in each group were viewed under scanning electron microscope to observe resin-dentin interfacial adaptation. Data was statistically analyzed using Mann-Whitney and Kruskal Wallis tests at a significance level of P < 0.05.
Results: Mean microleakage scores and standard deviation observed were: Group 1 (Xe-CHX): 2.8 ± 0.42, Group 2 (Xe-EDTA + NaOCl): 2.3 ± 0.82, Group 3 (Xe-NS): 2.9 ± 0.31, Group 4 (Ad-CHX): 1.2 ± 0.91, Group 5 (Ad-EDTA + NaOCl): 0.8 ± 0.63, Group 6 (Ad-NS): 1.9 ± 0.99.
Conclusions: Adper Easy One showed significantly less leakage than Xeno V when normal saline was used as an irrigant. EDTA treatment followed by NaOCl application significantly reduced microleakage and improved the interfacial adaptation with Adper Easy One. CHX did not significantly affect the sealing ability of both one-step self-etch adhesives tested.
Keywords: Dye penetration; pulp chamber dentin; root canal irrigants; sealing ability; self-etch adhesives
|How to cite this article:|
Agrawal R, Tyagi SP, Nagpal R, Mishra CC, Singh UP. Effect of different root canal irrigants on the sealing ability of two all-in-one self-etch adhesives: An in vitro study. J Conserv Dent 2012;15:377-82
|How to cite this URL:|
Agrawal R, Tyagi SP, Nagpal R, Mishra CC, Singh UP. Effect of different root canal irrigants on the sealing ability of two all-in-one self-etch adhesives: An in vitro study. J Conserv Dent [serial online] 2012 [cited 2019 Jun 26];15:377-82. Available from: http://www.jcd.org.in/text.asp?2012/15/4/377/101917
| Introduction|| |
Effective cleaning, shaping of the root canal, as well as creation of a fluid tight seal is an essential goal for successful endodontic treatment. Coronal lakage is considered as a negative contributor to the prognosis of endodontic treatment.  Many in vitro studies have demonstrated that root canal fillings exposed to saliva may become contaminated regardless of the materials and obturation techniques used. ,, Thus, despite apical leakage still being considered an important factor for endodontic failures, in the last few years, more attention has been focused on procedures performed to achieve an effective coronal sealing soon after the completion of root canal therapy. Lack of adhesion and sealing between final restoration and tooth structure can permit movement of microorganisms or their toxins along canal walls or through voids in root canal filling to periapical tissue reducing the prognosis of nonsurgical root canal treatment  This is particularly important in multirooted teeth where accessory canals may be present.  Although it is critical to maintain a coronal seal to prevent microleakage, but till date no sealer-cement or an obturation technique has proven to prevent 100% percolation through the canal. ,
Restoration of endodontically treated teeth with adhesive restoration permits transmission of functional stresses across the bonded interface to the tooth, with the potential to reinforce weakened tooth structure. , Main challenge for a dental adhesive is its ability to bond equally and effectively to two substrates of different nature i.e., enamel and dentin. Recently, the one-step self-etch system has been introduced which incorporates all the components of an adhesive system (etchant, primer, and bonding resin) into a single bottle, resulting in a reduced step, user-friendly adhesive. , However, these newer adhesives are being introduced at a very fast rate, without comprehensive testing to substantiate their performance.
Various irrigants render the root canal system free of organic debris, microorganisms, pulp remnants, smear layer, and endotoxin. Complete removal of the smear layer requires use of chelating agents followed by tissue solvents, because no single solution is capable of providing both effects alone. Accordingly, alternating the use of ethylenediaminetetraacetic acid (EDTA) and sodium hypochlorite (NaOCl) solutions has been advocated as an effective irrigation regimen to remove organic and inorganic remnants. ,, Chlorhexidine digluconate has been recommended as a root canal irrigant due to its broad spectrum antimicrobial action, substantivity, and low grade of toxicity.  However, these irrigants used during biomechanical preparation can potentially affect bonding of subsequently placed adhesive restorations either by directly affecting the bonding procedure or by affecting the structural and mechanical properties of bonding substrate i.e., pulp chamber dentin. ,
Adhesive materials are frequently compared on parameters like bond strength and microleakage. Typically, dentin shear bond strengths reported for adhesive resins are 20 to 30 MPa, which can vary depending on the testing methods used. Microleakage is more important for endodontic applications than bond strength, as a material with relatively low bond strength to dentin may be a good obturating material preventing microleakage effectively.  Till date none of the current adhesive materials has been proved to provide a hermetic seal.
Although multitude of studies report microleakage patterns after adhesive procedures in class V cavities in coronal dentin, there is scarcity of data evaluating the bonding of self-etch adhesives to pulp chamber in endodontically treated teeth, which is the deepest possible coronal dentin. Therefore, the purpose of this study is to evaluate and compare microleakage of two one-step self-etch adhesives placed within the pulp chamber following different irrigation regimens.
| Materials and Methods|| |
Seventy-two human molars freshly extracted due to periodontal reasons were collected and cleaned and stored in normal saline water and used within 6 months of extraction. Teeth with any caries, cracks, abrasions, attrition, and restorations were excluded from the study. Roof of the pulp chamber was exposed using a carborundum disc (Bego, Germany) horizontally 1.5 mm coronal to the cementoenemel junction and roots were sectioned 2 mm apical to the bifurcation with water coolant. Pulp tissue was removed carefully with the help of excavator and broaches (Spirocolorinox, Dentsply Maillefer, Switzerland). Canal orifices were widened with Gates Glidden (Gates drills, Mani, Inc., Tochigi, Japan) drill no. 2-3. Root ends were sealed with amalgam (DPI Alloy, Dental Products of India, Mumbai, India).
Teeth were randomly divided into two groups of 36 teeth each according to the one-step self-etch adhesive used: Xeno V (Dentsply De Trey, Konstanz, Germany) and Adper Easy One (3M ESPE, St Paul, USA). Each group was further sub-divided into three groups of 12 teeth each, according to the irrigation solution used: 2% CHX (Dentachlor, Ammdent, Mohali, India); 17% EDTA (SmearClear, Kerr, SybronEndo, Glendora, USA) and 5.25% NaOCl or saline.
Group 1: Xe-CHX (XenoV with 2% CHX) Pulp chambers were continuously irrigated with 1 ml of 2% chlorhexidine for 60 s.
Group 2: Xe-EDTA + NaOCl ( XenoV with 17% EDTA followed by 5.25% NaOCl) Pulp chambers were continuously irrigated with 1 ml of SmearClear for 60 seconds followed with 3 ml of 5.25% NaOCl for 60 s.
Group 3: Xe-NS (XenoV with saline as control) Pulp chambers were continuously irrigated with normal saline solution for 60 s.
Group 4: Ad-CHX (Adper Easy One with 2% CHX) Pulp chambers were continuously irrigated with 1 ml of 2% chlorhexidine for 60 s.
Group 5: Ad-EDTA+NaOCl ( Adper Easy One with 17% EDTA followed by 5.25 % NaOCl ) Pulp chambers were continuously irrigated with 1 ml of SmearClear for 60 s followed with 3 ml of 5.25% NaOCl for 60 s.
Group 6: Ad-NS (Adper Easy One with saline as control) Pulp chambers were continuously irrigated with normal saline solution for 60 s.
Distilled water was used in all the above samples for 60 s as final flush and were blot dried.
Pulp chambers in groups 1, 2, and 3 were bonded with Xeno V and groups 4, 5, and 6 were bonded with Adper Easy One adhesive according to manufacturer's directions [Table 1]. All the samples were restored with composite resin Filtek 350 (3M, ESPE, St. Paul, USA) in one to two increments and condensed with condenser and were light cured at 500 mw/ cm 2 by Spectrum 800 (Dentsply, Caulk, Milford, USA) for 20 s. Ten teeth from each group were used for dye penetration and two speciemens were subjected to scanning electron microscopic analysis.
|Table 1: Adhesive systems, their composition and manufacturer's directions|
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Speciemens were coated with two layers of nail polish leaving 1 mm window around restoration margin and were immersed in 2% methylene blue for 2 days. They were washed under running water and air dried at room temperature for 24 h. All teeth were than sectioned for evaluation under stereomicroscope and were scored [Table 2].
The data were statistically analyzed by Kruskal-Wallis and Mann-Whitney U-tests using SPSS Base 15.0 software at significance level of P < 0.05.
Scanning electron microscopy
A total of 12 molars (2 samples per group) were used for SEM analysis. After being restored with composite, the sectioned surface of molars were ground on wet 210 grit SiC paper. Acid base treatment was done and then samples were dehydrated in ascending ethanol concentration (50%, 75%, and 95% for 20 min each and 100% for 1 h), then transferred to a critical point dryer for 30 min. The specimens were then gold sputter coated and the surfaces were examined under a SEM at 1000-5000X magnification.
| Results|| |
Dye leakage study
Dye penetration scores and statistical analysis results are depicted in [Table 3].
|Table 3: Microleakage scores, mean and standard deviation observed in different groups|
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None of the groups completely prevented dye leakage. Extensive dye leakage was observed in all the samples bonded with Xeno V irrespective of the irrigation regimens used. Highest mean microleakage score was observed with Xeno V after saline irrigation (Group3: 2.90 ± 0.3162) followed by Xeno V with CHX irrigation (Group1:2.80 ± 0.4216) and Xeno V with EDTA + NaOCl irrigation (Group2:2.30 ± 0.8233), respectively. There was no statistically significant difference between group 1 and group 2 (P=0.218); group 1 and group 3 (P = 0.739), and group 2 and group 3 (P = 0.123).
Least mean microleakage score was observed with Adper Easy One after EDTA+NaOCl irrigation (Group5:0.80 ± 0.6325) which was significantly less than with Adper Easy One and saline irrigation group 6 (1.90 ± 0.9944) (P = 0.023). CHX-treated Adper Easy One group (Group 4: 1.20+0.9189) depicted no significant difference in dye penetration with either group 5 (P = 0.393) or group 6 (P = 0.165).
For every irrigation regimen Adper Easy One performed better than Xeno V. Significantly less dye penetration was observed in: group 4 as compared to group 1 (P < 0.001); group 5 as compared to group 2 (P < 0.001) and group 6 compared to group 3 (P = 0.035).
Scanning electron microscopic observation of resin dentin interfaces of all groups demonstrated the presence of gaps along the entire interface showing poor adaptation [Figure 1]a-c, e, f except EDTA and NaOCl-treated group with Adper Easy One (group 5) which revealed excellent interfacial adaptation of resin to the pulpal dentin with a complete absence of gap [Figure 1]d. CHX-pretreated groups with Xeno V and Adper Easy One both revealed the presence of gaps; however, less gap was observed with Adper Easy One. Xeno V showed poor interfacial adaptation regardless of the irrigant used.
|Figure 1: (a) SEM micrograph of the dentin composite interface after 2% chlorhexidine treatment and bonded with Xeno V showing the presence of generalized interfacial gap. (b) SEM micrograph after 17% EDTA and 5% NaOCl treatment and bonded with Xeno V showing a slightly reduced interfacial gap. (c) SEM micrograph after 2% CHXtreated dentin and bonded with Adper Easy One showing a minimal interfacial gap with resin tags formation. (d) SEM micrograph after 17% EDTA and 5% NaOCl treatment and bonded with Adper Easy One showing perfect interfacial adaptation without a gap. (e) SEM micrograph of the dentin composite interface in the control group and bonded with Xeno V showing an interfacial gap with debris plugged into dentinal tubules. (f) SEM micrograph of the dentin composite interface in the control group and bonded with Adper Easy One showing less interfacial gap|
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| Discussion|| |
Adper Easy One revealed significantly (P < 0.05) better performance in comparison to Xeno V. This result may be attributed to different factors like pH, type of solvent, HEMA presence, vapour pressure, and wetting angle.
Adper Easy One has pH >2 which makes them "mild" self-etch adhesives in comparison to Xeno V which has pH <2 making it "intermediary strong" self-etch adhesive. In a mild self-etch adhesive system, residual hydroxyapatite around collagen fibers allow for additional chemical interaction with functional monomers of adhesives which may help prevent/retard marginal leakage and also better protect the collagen against hydrolysis and thus early degradation of the bond.  HEMA (2-hydroxyl ethyl methacrylate) is a hydrophilic monomer which decreases the contact angle. This increases wettability allowing simultaneous liquid spreading and penetration in dentin sub-surface and tubuli.  Adper Easy One contains water (28%) and ethanol (18%) in comparison to Xeno V which is water based (57%) and with t-butanol co-solvent.  As ethanol replaces water, it leads to interpeptide hydrogen bonding within collagen fibres that stiffens the matrix and minimizes its shrinkage thereby enlarging interfibrillar spaces and allowing more resin infiltration.  Thus, ethanol-based HEMA-rich self-etch adhesive (Adper Easy One) may have better bond strength than HEMA-free self-etch adhesive (Xeno V). Van Landuyt et al. reported that the presence of HEMA improved the bond strength of one-step self-etch adhesives.  Vineeta Nikhil et al. in their study evaluated the effect of HEMA and type of solvent on the tensile bond strength of three self-etch adhesives: Adper Easy One, G-bond, and Xeno V. They revealed that ethanol-based HEMA-rich self-etch adhesive was better than acetone and butanol containing HEMA-free self-etch adhesive. 
In our study, results indicate that the use of EDTA and NaOCl as irrigants reduced microleakage scores in both the self-etch adhesives but the effect was significant for Adper Easy One. EDTA decalcifies peritubular dentin in early stage of irrigation. Subsequent application of NaOCl may facilitate further exposure of the inorganic material through removal of the organic matrix,  and thus increase the demineralizing effect. Deproteinization by NaOCl transforms demineralized, collagen-rich dentin into a porous structure with multiple irregularities in peri- and intertubular dentin, with good retention of adhesive resin into the modified dentin substrate.  Wakabayashi  observed improvement of marginal sealing after deproteinization, while Pioch et al.  reported complete elimination of nanoleakage. The diameter of tubule orifice increases after NaOCl treatment of demineralized dentin due to loss of demineralized peri-tubular dentin. This substrate is rich in hydroxyapatite crystals and may result in a more stable interface over time as it is essentially made of minerals.  The remaining surface is also very wettable with the bonding system and is similar to enamel because only insignificant amounts of protein are left.  Various studies have reported that collagen removal and application of adhesive resin directly on exposed dentinal apatite significantly improve the bond strength. ,, As 17% EDTA can cause dentin erosion when used for longer duration, short exposure time of 1 min with EDTA, in the present study, was just sufficient to demineralize minimal depth of exposed dentin with less impact on mechanical dental properties. ,
Although comparatively less microleakage and better adaptation at the resin-dentine interface was observed with Adper Easy One after CHX pretreatment, the effect was not significant for both the self-etch adhesives. Our results are similar to study of Santos et al. who preferred to consider that chlorhexidine did not affect the interaction of the self-etching adhesive system to pulp chamber dentin because it is a nonoxidizing agent. Contrary to our study, Turkun et al.  and Meiers and Kresin  reported a positive effect of CHX on bonding of self-etch adhesives. Erdemir et al.  also reported that endodontic irrigation with a CHX solution significantly increased bond strength to root dentin which can be due to adsorption of CHX by dentin favoring the resin infiltration into dentinal tubules. However, dissimilar to our study they evaluated the effect of 0.2% of CHX on bonding of C and B Metabond to root canal dentin.
Microleakage was observed with both Adper Easy One and Xeno V control groups in this study which could be attributed to different characteristics of pulp chamber dentin. Bonding to pulp chamber dentin is difficult to achieve. The structure of the pulp chamber wall is complicated which includes collagen-rich predentin, sclerotic dentin, regular and irregular secondary dentin high density of tubules (65000 mm 2 ) with large tubule diameters, small amount of intertubular dentin, and many accessory canals. , In addition, because there have been no cavity preparation, a smear layer typically has not been formed. Consequently, bonding of the adhesive material to pulp chamber walls is different from bonding to other dentinal surfaces covered with smear layers. In addition, box shape pulp chamber may also influence the sealing ability of the materials because of polymerization shrinkage caused by the high C- factor (the ratio of bonded to unbonded surface area). The smaller the C-factor, the less the competition between the strength of the bond and the forces of polymerization contraction.
Further studies should aim to delineate guidelines for the time, concentration and sequence of endodontic irrigants with self-etch adhesives. This study evaluated the bonding potential to pulp chamber dentin; however, more research is required to investigate bonding of resin cements to root canal dentin. Furthermore, durability of these simplified adhesives in clinical conditions should be tested.
| Conclusions|| |
Within the limitations of this in vitro study, it can be concluded that
- Both Xeno V and Adper Easy One depicted microleakage when bonded to pulp chamber dentin. However, Adper Easy One leaked significantly less when compared to Xeno V;
- EDTA and NaOCl pre-treatment of pulp chamber dentin reduced microleakage scores in both the adhesives but the effect was significant only for Adper Easy One;
- CHX did not significantly affect the sealing ability of both one-step self-etch adhesives;
- Irrigation with EDTA and NaOCl or CHX did not negatively affect sealing ability of both the one-step self-etch adhesives tested.
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Reader, Department of Conservative Dentistry and Endodontics, Kothiwal Dental College and Research Center, Moradabad-244001, Uttar Pradesh
Source of Support: None, Conflict of Interest: None
[Table 1], [Table 2], [Table 3]