Journal of Investigative and Clinical Dentistry (2014), 5, 1–7

ORIGINAL ARTICLE Endodontics

Adhesive bonding to pulp chamber dentin after different irrigation regimens Rajni Nagpal1, Naveen Manuja2 & Inder Kumar Pandit3 1 Department of Conservative Dentistry and Endodontics, Kothiwal Dental College and Research Centre, Moradabad, Uttar Pradesh, India 2 Department of Pediatric Dentistry, Kothiwal Dental College and Research Centre, Moradabad, Uttar Pradesh, India 3 Department of Pediatric Dentistry, DAV (c) Dental College, Yamunanagar, Haryana, India

Keywords adhesive, irrigation, microleakage, pulp chamber, resin–dentin interface. Correspondence Professor Naveen Manuja, Department of Pediatric Dentistry, Kothiwal Dental College and Research Centre, Moradabad, Uttar Pradesh 244001, India. Tel: +91-99-9704-8380 Email: [email protected] Received 21 January 2014; accepted 4 April 2014. doi: 10.1111/jicd.12107

Abstract Aim: The aim of the present study was to determine the effect of ethylenediaminetetraacetic acid (EDTA) and NaOCl irrigation on the microleakage and interfacial morphology of adhesives bonded to pulp chamber dentin. Methods: The pulp chamber roof of 72 extracted permanent molars was removed. Samples were equally divided into six groups. Pulp chamber dentin was bonded with either Adper Easy One (group 1), Adper Prompt L-Pop (group 2), or Adper Single Bond 2 (Group 3), after irrigation with either normal saline (groups 1a, 2a, 3a) or 17% EDTA and 5.25% NaOCl (groups 1b, 2b, 3b). Composite resin restorations were placed in the pulp chamber. Ten samples per group were subjected to microleakage test and scanning electron microscopic analysis was done in two samples from each group. Data were statistically analyzed using Mann–Whitney and Kruskal Wallis tests at a significance level of P < 0.05. Results: EDTA and NaOCl irrigation of the pulp chamber significantly reduced microleakage in Adper Easy One. However, it had no significant effect on the microleakage of Adper Prompt L-Pop and Adper Single Bond 2. Conclusions: EDTA and NaOCl irrigation of the pulp chamber was not deleterious to the bonding of any of the adhesives tested. While this irrigation regimen had no significant effect on the microleakage of Adper Prompt L-Pop and Adper Single Bond 2, it significantly reduced the microleakage scores in Adper Easy One.

Introduction One of the recent trends in endodontics has been the development of adhesive techniques for the restoration of access cavities, obturation of root canals with resinbased obturating materials, and luting of esthetic posts with resin cements. Materials utilizing dentin adhesive technology have been borrowed from restorative dentistry and applied to endodontics. Original multicomponent adhesive systems are gradually being replaced with simplified, consolidated adhesive systems that are more user-friendly. Despite major simplifications in dental adhesion, bonding to pulp chamber or radicular dentin remains unpredictable. ª 2014 Wiley Publishing Asia Pty Ltd

Endodontic treatment and subsequent final restoration represent the two elements of an endodontic-restorative continuum. The lack of adhesion and sealing between the 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 non-surgical root canal treatment.1 The 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.2 Currently, there are two major strategies for adhesion in resin-based materials. One strategy involves etch-and-rinse 1

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adhesives that remove the smear layer and superficial hydroxyapatite through etching with an acid etchant, whereas the second strategy involves self-etch adhesives that modify the smear layer. The latter approach simplifies the bonding procedure by reducing the number of clinical steps. In dentin, strong self-etch adhesives exhibit rather deep demineralization effects and lead to a bonding mechanism and ultra-morphology, similar to that produced by etch-and-rinse adhesives. The bonding mechanism of mild self-etch adhesives to dentin is also based on hybridization, with the difference that only submicron hybrid layers are formed, and resin tag formation is less pronounced. Most of the research involving adhesives has focused on coronal dentin, while radicular dentin represents a different bonding substrate with structural and compositional differences between radicular and coronal dentin. Furthermore, endodontic irrigants can adversely affect the bonding of adhesives to radicular dentin, either by inhibiting polymerization of resins at the interface or by changing the mechanical and physical properties of the dentin substrate itself.3–5 The effect of endodontic irrigants on contemporary adhesive systems is controversially discussed in literature, as it varies with the specific adhesive system, time, concentration, and sequence of irrigants used, and still requires further investigation.6–8 When used as an endodontic irrigant, ethylenediaminetetraacetic acid (EDTA) has an efficient chelating action, dissolving mineralized tissues and promoting smear-free surfaces.9 To obtain a maximum cleansing effect after instrumentation, it is necessary to use chelating agents (EDTA), followed by a tissue solvent (NaOCl).10–12 Thus, the aim of the present study was to analyze the effect of EDTA and NaOCl irrigation of the pulp chamber

on the microleakage of subsequently-placed adhesive restorations using one-step self-etch adhesives and an etchand-rinse adhesive. Materials and methods For the present study, 72 caries-free extracted human molars were collected. Teeth were cleaned and stored in distilled water until use. Pulp chambers were deroofed using a diamond disc. Roots were sectioned 2 mm apical to the furcation. The pulp tissue was extirpated with the help of excavators and broaches. Canal orifices were widened with Gates Glidden drill no. 2-3 (Mani, Tochigi, Japan), and root ends were sealed with intermediate restorative material (IRM; Dentsply Caulk, Milford, DE, USA). Samples were randomly divided into six groups (n = 12) according to three different adhesive systems (Table 1) and two different irrigation regimens: groups 1a, 1b, 2a, 2b, 3a, and 3b. Group 1a: Adper Easy One with normal saline Pulp chambers were continuously irrigated with normal saline solution for 1 min, followed by rinsing with distilled water for 1 min. Subsequently Adper Easy One (3M ESPE, St Paul, MN, USA) was applied following the manufacturer’s instructions. Group 1b: Adper Easy One with 17% EDTA and 5.25% NaOCl Pulp chambers were irrigated with 17% EDTA for 1 min, followed by 5.25% NaOCl for 1 min. Distilled water for

Table 1. Composition and manufacturers’ directions for adhesives Adhesive systems

Composition and pH

Manufacturer’s instructions

Manufacturer

Adper Single Bond 2

Dimethacrylates, HEMA, polyalkenoid acid copolymer, 5-nm silane-treated colloidal silica, ethanol, water, photoinitiator

3M ESPE, St Paul, MN, USA

Conditioner 36

Phosphoric acid (36%), highly-dispersed silicon dioxide, detergent, pigment, water (pH = 0.6)

Adper Prompt L-Pop

Di-HEMA phosphate, bisphenol A diglycidal ether dimethacrylate, water (pH < 1)

Adper Easy One

HEMA, bis-GMA, methacrylated phosphoric esters, 1, 6 hexanediol methacrylate, vitrebond copolymer, finely dispersed bonded silica with 7-nm filler particles, ethanol, water, initiators based on camphorquinone and stabilizers (pH > 2)

Apply etchant on the enamel and dentin surfaces for 15 sec, rinse for 10 sec with three-way syringe Slight air dry to prevent extensive dehydration, apply 2– 3 consecutive coats of adhesive with gentle agitation, air dry for 5 sec, light cure for 10 sec Mix, apply with agitation for 15 sec, air dry, reapply, air dry, light cure for 10 sec Apply adhesive with gentle agitation for 20 sec, air dry for 5 sec, light cure for 20 sec

2

Dentsply DeTrey, Konstanz, Germany

3M ESPE, St Paul, MN, USA 3M ESPE, St Paul, MN, USA

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1 min was used as the final flush before bonding with Adper Easy One. Group 2a: Prompt L-Pop with normal saline Pulp chambers were continuously irrigated with normal saline solution for 1 min, followed by rinsing with distilled water for 1 min. Subsequently, Prompt L-Pop (3M ESPE) was applied following the manufacturer’s instructions. Group 2b: Prompt L-Pop with 17% EDTA and 5.25% NaOCl Pulp chambers were irrigated with 17% EDTA for 1 min, followed by 5.25% NaOCl for 1 min. Distilled water for 1 min was used as the final flush. Finally, Prompt L-Pop adhesive was applied following the manufacturer’s instructions.

Irrigants and pulp chamber adhesion

methylene blue for 48 h and rinsed under running water. Samples were air dried at room temperature for 24 h and were sectioned to evaluate dye penetration under stereomicroscope (SMZ10; Nikon, Tokyo, Japan) at 109 magnification. The scoring criteria for microleakage are listed in Table 2. Scanning electron microscopy Restored samples were sectioned vertically through the centre of the restoration and polished. Acid-base treatment was done, and the samples were then dehydrated in ascending ethanol concentrations (50%, 75%, and 95% for 20 min each, and 100% for 1 h) before being transferred to a critical point dryer for 30 min. The specimens were gold sputter coated, and the resin–dentin interface was examined under scanning electron microscope. Statistical analysis

Group 3a: Adper Single Bond 2 with normal saline Pulp chambers were continuously irrigated with normal saline solution for 1 min, followed by rinsing with distilled water for 1 min. Subsequently pulp chambers were acid etched (conditioner 36) and bonded with Adper Single Bond 2 (3M ESPE).

Microleakage scores were statistically analyzed by Kruskal–Wallis non-parametric analysis and Mann–Whitney U-tests using SPSS Base 15.0 software (SPSS, Chicago, IL, USA) at significance level of P < 0.05.

Results Group 3b: Adper Single Bond 2 with 17% EDTA and 5.25% NaOCl Pulp chambers were irrigated with 17% EDTA for 1 min, followed by 5.25% NaOCl for 1 min. Distilled water for 1 min was used as the final flush. Acid etching was done, and Adper Single Bond 2 was applied following the manufacturer’s instructions. Procedure The pulp chambers of all samples were filled with composite resin Filtek Z350 (3M ESPE), which was light cured for 40 sec at 600 mW/cm2 using a QTH light-cure unit (Spectrum 800; Dentsply Caulk). Ten samples from each group were subjected to microleakage analysis, and two samples per group were observed under scanning electron microscope (Leo 435 VP; Leo Electron Microscopy, Cambridge, UK) for evaluation of the interfacial seal. Microleakage test Samples were dried superficially and coated with two layers of sticky wax, leaving a 1-mm window around the restoration margin. The samples were then immersed in 2% ª 2014 Wiley Publishing Asia Pty Ltd

Microleakage study Microleakage scores and statistical analysis results are presented in Table 3. None of the groups completely prevented dye leakage. Dye leakage was observed in all the adhesives when normal saline was used as an irrigant. EDTA and NaOCl irrigation had no significant effect on the microleakage of Prompt L-Pop (groups 2a and 2b, P = 0.744) and Single Bond adhesives (groups 3a and 3b, P = 0.323). EDTA and NaOCl irrigation significantly reduced microleakage in Adper Easy One (groups 1a and 1b, P = 0.023). Scanning electron microscopy Scanning electron microscopic observations of the resin– dentin interfaces obtained are summarized in Figures 1–3.

Table 2. Scoring criteria for microleakage Microleakage score

Degree of leakage

0 1 2 3

No leakage Leakage extending into pulp chamber Leakage involving pulp floor Leakage involving root canal

3

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Table 3. Microleakage scores observed in different study groups Dye leakage scores Study groups (n = 10)

0

1

2

3

Mean

Standard deviation

Group Group Group Group Group Group

0 3 0 0 0 0

5 6 2 2 4 2

1 1 3 4 2 2

4 0 5 4 4 6

1.9a 0.8b 2.3a 2.2a 2.0a 2.4a

0.994 0.632 0.823 0.788 0.942 0.843

1a 1b 2a 2b 3a 3b

Same superscript letters indicate no statistically significant difference.

Figure 2. (a) Cross-section of the interface obtained in vitro between Adper Prompt L-Pop and pulp chamber dentin after irrigation with normal saline. (b) Cross-section of the interface obtained in vitro between Adper Prompt L-Pop and pulp chamber dentin after ethylenediaminetetraacetic acid and NaOCl irrigation.

Discussion

Figure 1. (a) Cross-section of the interface obtained in vitro between Adper Easy One and pulp chamber dentin after irrigation with normal saline. (b) Cross-section of the interface obtained in vitro between Adper Easy One and pulp chamber dentin after ethylenediaminetetraacetic acid and NaOCl irrigation.

After EDTA and NaOCl irrigation, Adper Easy One demonstrated good interfacial seal along the entire interface without any gaps. Both Prompt L-Pop and Single Bond depicted a generalized gap with poor interfacial adaptation, regardless of the irrigation regimen used. 4

Coronal leakage is an important cause of endodontic treatment failure.13 However, achieving predictable dentinal adhesion in endodontically-treated teeth is more difficult when compared with bonding to coronal vital dentin. This is because the root canal system presents a unique environment with interplay of various factors, such as the use of irrigants, medicaments, and differences in dentin substrate, all of which can affect the success of adhesive procedures. In the present study, all adhesive systems showed leakage when normal saline was used as an irrigant. Bonding to deep dentin, as found on the pulp chamber walls, can be occasionally more difficult to achieve compared to superficial dentin, as deeper dentin surfaces contain large tubule diameters and a high tubule density, making them a more challenging bonding substrate.14 The cavity configuration factor, showing a ratio of five bonded walls to one unbonded wall, might also adversely affect resin– dentin bonding.15 ª 2014 Wiley Publishing Asia Pty Ltd

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Figure 3. (a) Cross-section of the interface obtained in vitro between Adper Single Bond 2 and pulp chamber dentin after irrigation with normal saline. (b) Cross-section of the interface obtained in vitro between Adper Single Bond 2 and pulp chamber dentin after ethylenediaminetetraacetic acid and NaOCl irrigation.

It was observed that EDTA and NaOCl irrigation had no effect on the microleakage of Prompt L-Pop and Single Bond adhesives when compared with normal saline irrigation. However, irrigation with EDTA and NaOCl significantly reduced the microleakage of the Adper Easy One adhesive. Contrary to our results, NaOCl has been previously shown to jeopardize the polymerization of adhesive resins.16,17 This compromised bonding has been attributed to the fact that NaOCl leads to biological oxidation of some components in the dentin matrix, forming protein-derived radicals that would compete with the propagating vinyl free radicals generated by the light activation of resin adhesives, resulting in premature chain termination and incomplete polymerization.18–20 However, in the current study, the sequential use of EDTA and NaOCl could account for the different results. Endogenous dentin matrix metalloproteinases (MMP) have been reported to contribute to extracellular collagen matrix degradation in hybrid layers after adhesive dentinbonding procedures. Thompson et al. suggested that ª 2014 Wiley Publishing Asia Pty Ltd

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endodontic irrigants, including chlorhexidine and EDTA, might help protect the hybrid layer from this process. They demonstrated that 17% EDTA significantly inhibits endogenous MMP activity of human dentin within 1– 2 min. This might minimize hybrid layer degradation after resin-bonding procedures in the root canal space.21 EDTA decalcifies peritubular dentin in the early stage of irrigation. The subsequent application of NaOCl might facilitate further exposure of the inorganic material through the removal of the organic matrix,22 and thus increase the demineralizing effect. Deproteinization by NaOCl transforms demineralized, collagen-rich dentin into a porous structure with multiple irregularities in peritubular and intertubular dentin, with good retention of adhesive resin into the modified dentin substrate.23 Nagpal et al.24 also observed no difference in dye leakage between groups with and without NaOCl pretreatment. Collagen removal by NaOCl treatment increases wettability of the dentin surface, because deproteinization results in a hydrophilic surface, and chemical interactions between the resin and deproteinized dentin are more likely to occur.25 Elimination of the exposed collagen using NaOCl allows for the achievement of a rougher, porous surface similar to enamel, which allows for good mechanical retention.25 Various studies have reported that collagen removal and the application of adhesive resin directly on exposed dentinal apatite significantly improve the bond strength.26–28 As 17% EDTA can cause dentin erosion when used for a longer duration, a 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.29,30 The aggressiveness of a self-etching system is related to its acidity, as it has to be able to penetrate the smear layer and demineralize the underlying dentin to form authentic hybrid layers. Aggressive systems, such as Prompt L-Pop (pH 1.0), might form hybrid layers as thick as those created by phosphoric acid. De Munck et al.31 reported on the formation of a 3–5 l-thick, hydroxyapatite-depleted hybrid layer for the strong self-etch adhesive Adper Prompt L-Pop. However, Adper Easy One is an ultramild, all-in-one, self-etch adhesive with a pH >2.5.32 Therefore, dentin conditioning with EDTA proved to be beneficial for Adper Easy One, but not so for Prompt L-Pop. There is sufficient literature to support the use of EDTA prior to bonding of mild and ultra-mild self-etch adhesives to dentin. EDTA acts as a mild chelating agent at a neutral pH that produces different effects on dentin, depending on its concentration and time of exposure.33,34 EDTA contains carboxylic acid groups, giving it the ability to remove hydroxyapatite selectively. Because most of the intrafibrillar minerals remain, the structural support by the minerals is preserved, and resin infiltration is 5

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facilitated. Shafiei et al.35 reported that EDTA conditioning significantly decreases microleakage of self-etch adhesives. In another study, pretreatment with EDTA was found to improve the dentin bond strength of Clearfil SE Bond, and produced a stronger and more homogenous hybrid layer.36 Kasraei et al.37 also reported significantly higher microtensile bond strength of one-step, self-etch adhesives in EDTA–NaOCl-treated groups compared to control groups. With the use of scanning electron microscopy, an excellent characterization of the ultramorphological interface is possible due to enhanced resolution. However, polishing the restored disks, followed by demineralization and deproteinization, can induce artifacts. Dehydration techniques and high vacuum could also have provoked changes to the interfaces analyzed. Yet the challenging conditions during scanning electron microscopic examinations are beneficial to reveal the weakest link of the evaluated interfaces. After EDTA and NaOCl irrigation, Adper Easy One demonstrated good interfacial seal when

References 1 Galavan RR Jr, West LA, Leiwhr FR, Pashley DH. Coronal microleakage of five materials used to create an intracoronal seal in endodontically treated teeth. J Endod 2002; 28: 59–61. 2 Eakle WS. Fracture resistance of teeth restored with class II bonded composite resin. J Dent Res 1986; 65: 149–53. 3 Ari H, Erdemir A. Effect of endodontic irrigant solutions on mineral content of root canal dentin using ICP-AES technique. J Endod 2005; 31: 187–9. 4 Sim TP, Knowles JC, Ng YL, Shelton J, Gulabivala K. Effect of sodium hypochlorite on mechanical properties of dentine and tooth surface strain. Inter Endod J 2001; 34: 120–32. 5 Santos JN, Carrilho MR, De Goes MF et al. Effect of chemical irrigants on the bond strength of a selfetching adhesive to pulp chamber dentin. J Endod 2006; 32: 1088–90. 6 Erdemir A, Eldeniz AU, Belli S, Pashley DH. Effect of solvents on bonding to root canal dentin. J Endod 2004; 30: 589–92. 7 Wachlarowicz AJ, Joyce AP, Roberts S, Pashley DH. Effect of endodontic irrigants on shear bond strength of

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observed under scanning electron microscopy, whereas both Prompt L-Pop and Adper Single Bond 2 depicted generalized gaps with poor interfacial adaptation, regardless of the irrigation regimen used. Further clinical evaluation is required to validate the findings. Future studies should aim to investigate the effect of other endodontic irrigants on the adhesion of contemporary simplified adhesive systems to pulp chamber dentin, as the effect varies with the specific adhesive system used. Conclusion In the present study, the effect of EDTA and NaOCl irrigation on the microleakage of composite restorations varied with the specific adhesive system tested. There was no significant effect on the microleakage of Adper Prompt LPop and Adper Single Bond 2 adhesives, while a significantly reduced microleakage was observed in Adper Easy One after EDTA and NaOCl irrigation.

epiphany sealer to dentin. J Endod 2007; 33: 152–5. Ari H, Yasar E, Belli S. Effect of NaOCl on bond strengths of resin cements to root canal dentin. J Endod 2003; 29: 248–51. Ciucchi B, Khettabi M, Holz J. The effectiveness of different endodontic irrigation procedures on the removal of the smear layer: a scanning electron microscopic study. Int Endo J 1989; 22: 21–8. Yamada RS, Armas A, Goldman M, Lin PS. A scanning electron microscopic comparison of a high volume final flush with several irrigating solutions: part 3. J Endod 1983; 9: 137–42. Baumgartner JC, Mader CL. A scanning electron microscopic evaluation of four root canal irrigation regimens. J Endod 1987; 13: 147–57. Zehnder M. Root canal irrigants. J Endod 2006; 32: 389–98. Saunders WP, Saunders EM. Coronal leakage as a cause of failure in rootcanal therapy: a review. Endod Dent Traumatol 1994; 10: 105–8. Pereira PNR, Okuda M, Sano H, Yoshikawa T, Burrow MF, Tagami J. Effect of intrinsic wetness and regional difference on dentin bond strength. Dent Mater 1999; 15: 46–53.

15 Feilzer AJ, de Gee AJ, Davidson CL. Setting stress in composite resin in relation to configuration of the restoration. J Dent Res 1987; 66: 1636– 9. € 16 Ozturk B, Ozer F. Effect of NaOCl on bond strengths of bonding agents to pulp chamber lateral walls. J Endod 2004; 30: 362–5. 17 Ishizuka T, Kataoka H, Yoshioka T et al. Effect of NaOCl treatment on bonding to root canal dentin using a new evaluation method. Dent Mater J 2001; 20: 24–33. 18 Morris MD, Lee K, Agee KA, Bouillaguet S, Pashley DH. Effects of sodium hypochlorite and RC-Prep on bond strengths of resin cement to endodontic surfaces. J Endod 2001; 27: 753–7. 19 Hawkins CL, Davies MJ. Hypochlorite-induced oxidation of proteins in plasma: formation of chloramines and nitrogen-centered radicals and their role in protein fragmentation. Biochem J 1999; 340: 539–48. 20 Lai SC, Mak YF, Cheung GS et al. Reversal of compromised bonding to oxidized etched dentin. J Dent Res 2001; 80: 1919–24. 21 Thompson JM, Agee K, Sidow SJ, McNally K, Lindsey K, Borke J.

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27 De Castro AK, Hara AT, Pimenta LA. Influence of collagen removal on shear bond strength of one bottle adhesive system in dentin. J Adhes Dent 2000; 2: 271–7. 28 Prati C, Chersoni S, Pashley DH. Effect of removal of surface collagen fibrils on resin dentin bonding. Dent Mater 1999; 15: 323–31. 29 Manuja N, Nagpal R, Pandit IK. Dental adhesion: mechanism, techniques and durability. J Clin Pediatr Dent 2012; 36: 223–34. 30 Zhang K, Kim YK, Cadenaro M et al. Effects of different exposure times and concentrations of sodium hypochlorite/ethylenediaminetetracetic acid on the structural integrity of mineralized dentin. J Endod 2010; 36: 105–9. 31 De Munck J, Vargas M, Iracki J et al. One-day bonding effectiveness of new self-etch adhesives to bur-cut enamel and dentin. Oper Dent 2005; 30: 39– 49. 32 Tay FR, Pashley DH. Aggressiveness of contemporary selfetching systems. I: depth of penetration beyond dentin

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smear layers. Dent Mater 2001; 17: 296–308. Cederlund A, Jonsson B, Blomlo FJ. Shear strength after ethylenediaminetetraacetic acid conditioning of dentin. Acta Odontol Scand 2001; 59: 418–22. Calt S, Serper A. Time-dependent effects of EDTA on dentin structures. J Endod 2002; 28: 17–9. Shafiei F, Memarpour M. Effect of EDTA conditioning on microleakage of four adhesive systems in composite restorations. J Dent 2008; 5: 150–5. Jacques P, Hebling J. Effect of dentin conditioners on the microtensile bond strength of a conventional and a selfetching primer adhesive system. Dent Mater 2005; 21: 103–9. Kasraei S, Azarsina M, Khamverdi Z. Effect of ethylenediamine tetra acetic acid and sodium hypochlorite solution conditioning on microtensile bond strength of one-step self-etch adhesives. J Cons Dent 2013; 16: 243–6.

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Adhesive bonding to pulp chamber dentin after different irrigation regimens.

The aim of the present study was to determine the effect of ethylenediaminetetraacetic acid (EDTA) and NaOCl irrigation on the microleakage and interf...
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