MICROSCOPY RESEARCH AND TECHNIQUE 77:446–452 (2014)
Effect of Different Irrigation Protocols on the Radicular Dentin Interface and Bond Strength with a Metacrylate-Based Endodontic Sealer LISANDRO GONC¸ALVES,1 YARA TERESINHA CORREA SILVA-SOUSA,1* WALTER RAUCCI NETO,1 ~ SOUSA-NETO,2 AND EDSON ALFREDO1 CLEONICE SILVEIRA TEIXEIRA,1 MANOEL DAMIAO 1 2
School of Dentistry, University of Ribeir~ ao Preto, Ribeir~ ao Preto, S~ ao Paulo, Brazil Ribeir~ ao Preto School of Dentistry, University of S~ ao Paulo, Ribeir~ ao Preto, S~ ao Paulo, Brazil
KEY WORDS
endodontics; root canal filling materials; dental-bonding agents; scanning electron microscopy
ABSTRACT This study assessed the influence of different endodontic chemical substances on the adhesion of the Epiphany SE/Resilon system (with and without resinous solvent) to radicular dentin walls, using the push-out test and scanning electron microscopy (SEM). Forty-eight root canals of human canines were prepared biomechanically with ProTaper rotary files (crowndown technique) and the radicular dentin was treated with either 17% EDTA, 2% chlorhexidine gel (CHX) or 2.5% NaOCl (control). The root canals were filled with Resilon cones and Epiphany SE sealer with and without resinous solvent. Six groups of eight canals each had their roots sectioned transversally to obtain 1-mm thick slices. Data were subjected to statistical analysis by ANOVA and Tukey’s tests. The specimens treated with 17% EDTA (1.59 6 0.91) presented higher bond strength (P < 0.05) than those treated with 2.5% NaOCl (0.93 6 0.27) and 2% CHX (0.92 6 0.22). Significantly higher bond strength (P < 0.05) was observed when the Epiphany SE was prepared with (1.37 6 0.78) than without (0.92 6 0.33) solvent. Adhesive failures were predominant in all groups. SEM analysis showed greater homogeneity of the filling mass when the solvent was added to the sealer. Treatment of root canal walls with 17% EDTA, and addition of a resinous solvent to Epiphany SE produced the highest adhesion to radicular dentin. Microsc. Res. Tech. 77:446–452, 2014. V 2014 Wiley Periodicals, Inc. C
INTRODUCTION Adhesion, one of the most important physicochemical properties of an endodontic sealer, is defined as its capacity to adhere to the root canal walls and promote the union of the gutta-percha cones to each other and to the dentin (Sousa-Neto et al., 2005). Advances in endodontic adhesive technology have focused on minimizing apical and coronal marginal leakage by increasing the bond strength between the filling material and the root canal walls (Tay et al., 2005). It is believed that a perfect union between the root canal filling material and the root canal walls, forming a monoblock structure, can increase the resistance of the roots of endodontically treated teeth to fracture (Belli et al., 2011; Teixeira et al., 2004). The dual-cure methacrylate resin-based sealer EpiphanyTM Soft Resin Endodontic Obturation System (Pentron Clinical Technologies, Wallingford, CT) has been introduced to replace conventional sealers. The sealer matrix consists of mixture of urethane dimethacrylate (UDMA), polyethylene dimethacrylate (PEGDMA), bisphenol-A-glycidyl dimethacrylate (BisGMA), ethoxylated BisGMA, and barium sulphate, silica, calcium hydroxide, bismuth oxide, photoinitiators stabilizers and pigments (Shipper et al., 2004; Versiani et al., 2006). This system also contains a self-etch primer (EpiphanyTM Primer, Pentron Clinical TechnolC V
2014 WILEY PERIODICALS, INC.
ogies) and a radiopaque solid material composed of thermoplastic synthetic polyester polymers similar to gutta-percha (ResilonTM; Pentron Clinical Technologies) (Shipper et al., 2004; Teixeira et al., 2004). Epiphany sealer is claimed to adhere chemically to the Resilon cones and to radicular dentin walls by hybridization of intertubular dentin (collagen-dependent process) and also by the creation of intratubular tags (Shipper et al., 2004; Teixeira et al., 2004). A resinous solvent (Epiphany Thinning Resin; Pentron Clinical Technologies) consisting of a mixture of ethoxylated bisphenol-A-dimethacrylate (EBPADMA), photoinitiators, amines and stabilizers, is also supplied. According to the manufacturer’s instructions the use of 1–2 drops of the solvent can be used to adjust sealer viscosity, when necessary. In addition, this technique maneuver improves the wettability of the sealer, which is essential for adhesion to dentin surface since it favors the diffusion of the filling material through surface irregularities (Rached-Junior et al., 2009) *Correspondence to: Yara Teresinha Correa Silva-Sousa, Rua Celia de Oliveira Meirelles, 350, 14024-070, Ribeir~ ao Preto, S~ ao Paulo, Brazil. E-mail: [email protected] Received 18 September 2013; accepted in revised form 21 March 2014 REVIEW EDITOR: Prof. Alberto Diaspro DOI 10.1002/jemt.22365 Published online 9 April 2014 in Wiley Online Library (wileyonlinelibrary.com).
IRRIGATION PROTOCOLS ON SEALER INTERFACE AND BOND STRENGTH
enhancing the possibility of forming a higher density hybrid layer. Since the EpiphanyTM SE (Self Etch) development this root canal sealer has been widely studied (Nassar et al., 2011; Prado et al., 2013; Shokouhinejad et al., 2010; Versiani et al., 2006). The main difference of this material to the epoxy-amine resin-based sealers, is related to the self-etch primer incorporation to the sealer, eliminating the separate priming step. According to the manufacturer, the resin matrix main bases of the sealer original formulation (EBPADMA and BisGMA) were maintained and a resin monomer—2hydroxyethyl methacrylate (HEMA)—and a methacrylic acid resins were added (Costa et al., 2010). Studies on push-out bond strength comparing other resin cements showed no improvement in the adhesion of the filling material to intraradicular dentin using 1mm thick root slices (De-Deus et al., 2009; Shokouhinejad et al., 2010). Other factors may influence the adhesion of the filling material to the radicular dentin, among which the treatment of the root canal walls stands out (Crumpton et al., 2006; Morris et al., 2001; Prado et al., 2013). The presence of smear layer on dentin surface is considered a negative factor in root canal adhesion because it acts as a physical barrier between the filling material and dentin walls (El-Ma’aita et al., 2013; Kokkas et al., 2004) Chemical irrigants have major influence on the root canals debridement during shaping and cleaning procedures (Crumpton et al., 2006; Kokkas et al., 2004). Different irrigations protocols should expose the collagen network, without causing collapse of its normal structural integrity and during the filling phase, the intimate contact of resin-based materials with treated root canal dentine should ideally result in excellent mechanical and chemical bonding (Costa et al., 2010; De-Deus et al., 2009). Sodium hypochlorite (NaOCl) is widely used as endodontic irrigant and it has been systematically applied in concentrations ranging from 0.5 to 5.25%. The useful application of NaOCl is related to its excellent antimicrobial action, dissolving organic materials and necrotic remnants tissues capacity and the reduced toxicity at low concentrations (Bystr€om and Sundqvist, 1985). However, NaOCl has disadvantages, such as corrosion of endodontic instruments, inefficacy against some microorganisms when used at low concentrations and toxicity to the periapical tissues when used at high concentrations (Ferraz et al., 2007; Jeansonne and White, 1994). Considering the NaOCl higher concentrations a previous study found that root canals irrigated with 5% NaOCl did not alter the sealer–dentin interface (Morris et al., 2001). One of the NaOCl chemical reactions within the root canal that could negatively influence the resin-based sealers is related to its dissociation into sodium chloride and oxygen, which may inhibit the polymerization of adhesive materials (Nikaido et al., 1999). Ethylenediaminetetraacetic acid (EDTA) is one of the most effective chelating agents used in the endodontic therapy (Crumpton et al., 2005). It has the capacity of chelating calcium ions calcium, promoting dentin demineralization and smear layer removal, which open the tubule entrances and increase sealer Microscopy Research and Technique
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bond strength (Prado et al., 2013; Sayin et al., 2007; Serper and Calt, 2002). Chlorhexidine gluconate (CHX) is used in a number of dental procedures and its potential application in endodontic therapy has also been investigated. This antimicrobial agent has a broad spectrum of activity against microorganisms commonly isolated from endodontic infections, with a prolonged and gradual release at therapeutic levels and low toxicity. CHX at 2% has been shown to have the same antimicrobial action as that of 5.25% sodium hypochlorite (Jeansonne and White, 1994). However, Zehnder (2006) emphasized that CHX cannot be advocated as the main standard irrigant in endodontic cases because it is unable to dissolve necrotic tissue remnants, and is less effective on gram-negative bacteria than on gram-positive bacteria. The use of CHX gel as an intracanal auxiliary chemical substance showed antimicrobial action against Enterococcus faecalis, and its viscosity produced good mechanical cleaning of the root canal system (Ferraz et al., 2007). Laboratorial studies have shown that irrigation of root canals with CHX did not alter (Santos et al., 2006) or reduced the sealer bond strength to root dentin (Prado et al., 2013). Considering the changes incorporated into the Epiphany structure and the possibility of adjusting its viscosity with a solvent, it would be interesting to determine whether the new formulation of Epiphany improves its adhesive properties to the root canal walls treated with different irrigants. Therefore, this study evaluated the influence of different endodontic chemical substances on the adhesion of the Epiphany SE/ Resilon system, with and without solvent, to radicular dentin using the push-out test and the filling material/ radicular dentin interface by scanning electron microscopy (SEM). MATERIALS AND METHODS The study was approved by Ethics Committee of University of Ribeir~ ao Preto, SP, Brazil (protocol 013/ 08). Maxillary human canines stored in 0.1% thymol solution steam at 9 C were washed in running water for 24 h to eliminate thymol residues, and were examined macroscopically and radiographed in a buccopalatal direction. Forty-eight teeth were selected on the basis of their roots, which should be completely formed, and present a single canal without calcifications or accentuated curvature. The crowns were removed at the cementoenamel junction with a watercooled diamond disk (KG Soresen, Barueri, SP, Brazil), and the roots were trimmed coronally to a uniform length of 17 mm. A #10 K-file (Dentsply-Maillefer, Ballaigues, Switzerland) was passively introduced into each root canal until its tip was seen at the apical foramen. The working length was established by subtracting 1 mm from this length. Teeth that presented laterally displaced foramina with real canal length less than 16 mm were replaced. The canals were instrumented with the ProTaper Universal rotary system (Dentsply-Maillefer, Ballaigues, Switzerland) according to the crown-down technique. The cervical third was prepared with the instrument SX and the middle and apical thirds were prepared the instruments S1, S2, F1, F2, F3, F4 and
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F5, which corresponds to a #50 K-file. The instruments were attached to the handpiece of an oscillatory system (TEP-E10R, NSK Nakanishi; Kanuma, Tochigi, Japan) activated by an electric engine (Endo Plus VK Driller, S~ ao Paulo, SP, Brazil). Throughout the biochemical preparation, the canals were irrigated with 2 mL of 2.5% NaOCl at each change of file. After biochemical preparation, the radicular dentin was submitted to the following pretreatment chemical protocols: 17% EDTA, 2% CHX gel or 2.5% (NaOCl) (control). The irrigants were delivered by NaviTip needles (Ultradent Products Inc., South Jordan, UT, USA) coupled to disposable plastic syringes (Ultradent Products Inc.; South Jordan, UT, USA). The canals were filled with 2 mL of the respective substances for 3 min, followed by flushing with 10 mL of distilled water and drying with absorbent paper points (Tanari-Tanariman Industrial, Manacapuru, AM, Brazil). The root canals were filled with Resilon cones and Epiphany SE sealer with and without resinous solvent (Epiphany Thinning Resin). Six groups (n 5 8) were originated for each combination of dentin treatment and filling material. The Epiphany SE pastes (10 mm of each one) were delivered on a glass plate, mixed during 15 s until a homogenous paste was obtained and taken to the root canal with a lentulo spiral (Maillefer, Ballaigues, Switzerland) attached to a low-speed handpiece (Dabi Atlante, Ribeir~ ao Preto, SP, Brazil) to avoid bubble formation. In the groups in which the resinous solvent was used, two drops of the product were delivered on the plate and mixed with the sealer. After insertion of the main Resilon cone, which was previously tested for apical fit, accessory cones were inserted according to the lateral compaction technique. The cones were cut with a heated instrument and vertically condensed with a plugger (Maillefer, Ballaigues, Switzerland). Sealer excess was removed with cotton pellets followed by photoactivation for 40 s at the cervical root third with a halogen light-curing unit (Ultralux Dabi Atlante, Ribeir~ ao Preto, SP, Brazil), keeping the light guide tip in contact with the cervical portion of the root. In all groups, the canal entrances were sealed with a quick-setting temporary restorative filling material (Cimpat; Septodont Brasil, Barueri, SP, Brazil) and the teeth were placed immediately at 37 C and 95% humidity for a period three times greater than the regular setting time of the sealer (135 min) before the bond strength test. For preparation of the slices, the roots were fixed on acrylic plates with wax (Kota Import, S~ ao Paulo, SP, Brazil) and were sectioned in a precision cutting machine (Minitom; Struers, Westlake, OH) at 375 rpm. Nine 1-mm thick slices were obtained from each root (3 per root third), producing 432 specimens (Fig. 1). The first slice of each third was selected for the push-out test. For this test, a stainless steel support was used to hold the specimens in an Instron 4444 universal testing machine (Instron Corporation, Canton, MA) in such a way that the side with the smaller diameter of the root canal faced upwards and was aligned to the shaft that would exert pressure load on the sealer (apical-coronally) until debonding occurred. A 6-mmlong shafts with tip diameter of 0.6 mm for the apical
Fig. 1. Schematic presentation of the root canal thirds with the 9 1mm thick slices, with their dimension and composition.
third and 1 mm for the coronal and middle thirds were used. This method assured the alignment of the specimen in an accurate and reproducible manner and also maintained the shaft centralized and avoided its contact with the dentin during testing, when the material is pushed and dislodged from the canal wall. The force needed to dislodge the filling material (F in kN) was transformed into tension (r in MPa) by dividing the force by the adhesive area of the filling material (SL in mm2), using the following equation: r 5 F/SL. After the push-out test, the slices were examined with a stereomicroscope (ZEISS, Stemi 2000-C, Germany) at 325 magnification to determine the failure modes that occurred due to displacement of the sealer from the specimen. Failure was considered adhesive if the sealer was totally separated from dentin (dentin surface without sealer), cohesive if the fracture occurred within the sealer (dentin surface totally covered by the sealer), and mixed when a mixture of adhesive and cohesive modes (dentin surface partially covered by the sealer) occurred. The second and third slices obtained from each canal third were prepared for SEM analysis of the filling material/radicular dentin interface and the homogeneity of the filling mass, respectively. The second slices were fixed on metallic stubs, sputter-coated with a gold–palladium alloy (Bal-Tec AG, Balzers, Liechtenstein) and examined with a scanning electron microscope (JSM 5410; JEOL, Tokyo, Japan) operating at 15 kV. SEM micrographs of representative areas were obtained at 350 magnification for localization of representative areas and then at 3350 magnification to evaluate the homogeneity of the filling material and the presence of failures at the interface with dentin. For analysis of the homogeneity of the filling mass, the third slices were decalcified in hydrochloride acid 4 N during 48 h and deproteinized in 2.5% NaOCl during 5 min, promoting the complete dissolution of dentin and exposure of the filling material. After being washed twice in distilled water during 4 min, the filling material was sputter-coated with gold-palladium and subjected to SEM analysis (Fig. 2). Mean values were statistically compared. The Kolmogorov–Smirnov test showed that the results were consistent with a normal distribution curve. Parametric statistical analysis was performed by ANOVA and post hoc Tukey test at 5% significance level (SPSS 17.0 software; SPSS, Chicago, IL). RESULTS The mean, maximum, minimum and standard deviation of the bond strength values (in MPa) for the Microscopy Research and Technique
IRRIGATION PROTOCOLS ON SEALER INTERFACE AND BOND STRENGTH
Fig. 2. SEM micrographs of the root filled specimens. A:, B: Specimens obturated with sealer Epiphany SE without solvent showing large empty spaces in the filling mass and interfacial gaps (arrows)
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350 and 3350, respectively. C:, D: Specimens obturated with sealer Epiphany SE with solvent showing a more homogeneous filling mass with few interfacial gaps (arrows), 350 and 3350, respectively.
TABLE 1. Mean and standard deviation of the bond strength values (MPa) for the displacement of the filling material from the specimens of each group, during the push-out test Treatment of radicular surface Sealers Epiphany SE
Epiphany SE 1 solvent
Data
2.5% NaOCl 1 17% EDTA
2% CHX gel
2.5% NaOCl
Mean
Mean Maximum Minimum SD Mean Maximum Minimum SD
0.99 3.23 0.18 0.82 2.18 4.23 0.45 1.26
0.85 2.05 0.14 0.50 0.98 1.98 0.44 0.44
0.93 2.03 0.27 0.48 0.94 2.40 0.24 0.66
0.92 6 0.33
displacement of the filling material from the specimens during the push-out test are presented in Table 1. The 17% EDTA dentin surface treatment produced significantly higher adhesion values (1.59 6 0.91 MPa) (P < 0.05) when compared to the other treatments (2% CHX gel: 0.92 6 0.22 MPa; 2.5% NaOCl: 0.93 6 0.27 MPa), which were statistically similar to each other (P > 0.05). The addition of solvent to the sealer produced significantly higher (P < 0.05) adhesion values (1.37 6 0.78 versus 0.92 6 0.33 MPa). The analysis of the interaction between radicular dentin treatment and the use of Epiphany sealer with Microscopy Research and Technique
1.37 6 0.78
and without resinous solvent showed that the root canal treated with 17% EDTA and filled with Epiphany SE with solvent promoted the highest adhesion values (2.19 6 0.85 MPa) (P < 0.05), while the other five groups presented statistically similar (P > 0.05) adhesion values. There were no statistically significant differences (P > 0.05) among the root canal thirds (coronal: 0.99 6 0.72; middle: 1.17 6 0.87 and apical: 1.27 6 1.01 MPa). The analysis of the failure mode after the push-out test showed a predominance of adhesive failures in all
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TABLE 2. Failure mode distribution observed after the displacement of the filling material from the specimens of each group, during the pushout test Failure mode (%) Adhesive Sealer Epiphani SE Epiphany SE 1 solvent Epiphany SE Epiphany SE 1 solvent Epiphani SE Epiphany SE 1 solvent Total
Radicular dentine treatment
Resilon/SE sealer
Dentin/sealer
Mixed
Cohesive
2.5% NaOCl 1 17% EDTA 2.5% NaOCl 1 17% EDTA 2% CHX 2% CHX 2.5% NaOCl 2.5% NaOCl
30 28 6 18 25 16 21
55 36 92 80 67 81 68
15 36 2 2 8 3 11
0 0 0 0 0 0 0
groups, especially at the sealer/dentin interface. In the specimens treated with 17% EDTA and obturated with Epiphany SE/Resilon with solvent, there were a significant number of mixed failures, compared to the other groups. Cohesive failures were not observed in any specimen. Failure mode distribution is presented in Table 2. A panel of SEM micrographs of the cone/sealer/canal interfaces in specimens obturated with Resilon cones and Epiphany SE sealer with and without resinous solvent after radicular dentin treatment with different substances is presented in Figure 2. Irrespectively of the endodontic irrigant, the specimens obturated with sealer Epiphany SE without solvent presented large empty spaces between the Resilon cones and between the cones and dentin surface (Figs. 2A and 2B). On the other hand, the specimens obturated with sealer Epiphany SE mixed with solvent presented a more homogenous filling of the canal, with fewer gaps at the cone/sealer/dentin interfaces, regardless of dentin treatment (Figs. 2C and 2D). DISCUSSION The chemomechanical procedures for the shaping and cleaning of root canal walls make possible intimate contact between the filling material, intertubular and peritubular dentine (Prado et al., 2013; Vilanova et al., 2012). Furthermore, an endodontic sealer should have good adhesion because, under static conditions, it contributes to minimize or eliminate spaces that could serve as pathways for infiltration of fluids between the sealer and the radicular dentin walls. Under dynamic conditions, good adhesion is important to improve the stability of the root filling mass inside the canal space during post space preparation (Tagger et al., 2002). Therefore, this study evaluated the influence of different irrigants used in endodontic therapy for the treatment of canal walls on the push-out bond strength of Epiphany SE/Resilon system (adjusting or not sealer viscosity with solvent) to radicular dentin using the push-out test. The filling capacity of the Epiphany SE/ Resilon system and the filling material/root dentin interface were examined by SEM. In the present study, the 17% EDTA as final chemical treatment produced the highest push-out bond strength of the Epiphany SE/Resilon system to the radicular dentin, while the other treatments produced similar push-out bond strengths to each other. Corroborating with these results, Garcıa-Godoy et al. (2005) and Vilanova et al. (2012) has already reported that
the use of EDTA instead of NaOCl as the active final rinse ensured higher push-out strengths of methacrylate resin-based sealers to root canal dentine. The capacity of the EDTA solutions to chelate calcium ions and remove smear layer from the dentin walls may explain these results. The influence of smear layer to the interaction between root canal walls and filling materials has already been discussed (El-Ma’aita et al., 2013; Sousa-Neto et al., 2005). The smear layer is a negative factor in root canal adhesion because it is weakly adhered to dentin surface and forms an interface between the filling material and the root canal walls, hence reducing the adhesion of sealers by affecting sealer penetration to form intratubular tags (Alfredo et al., 2008; Sousa-Neto et al., 2005) and favoring the occurrence of marginal leakage (RachedJunior et al., 2009). Therefore, the capacity of NaOCl of dissolving the organic components of the smear layer (H€ ulsmann et al., 2003) associated with the chelating action of 17% EDTA on the inorganic components promoting dentin demineralization, removing completely the smear layer (Shokouhinejad et al., 2010). A smear-free surface permits a more intimate contact of the filling material with dentin and a deeper penetration of the sealer into the dentinal tubules (Kokkas et al., 2004; Serper and Calt, 2002). The use of 2% CHX gel and 2.5% NaOCl resulted in lower push-out bond strength in the present study. This is consistent with the findings of previous studies, which found that the pretreatment with these substances did not improve sealer adhesion to dentin (Ferraz et al., 2007; Santos et al., 2006). Considering the cleansing perspective, the NaOCl acts exclusively on the organic portion of the smear layer and alone does not promote an effective treatment of dentin surface (Nassar et al., 2011). According to Zhang et al. (2010), and Vilanova et al. (2012) the NaOCl has reduced smear layer removing capacity compared with EDTA allowing lower sealer penetration inside the dentinal tubules. Considering the higher bond strength results of the present and previous studies (Vilanova et al., 2012; Zhang et al., 2010) obtained with EDTA pretreatment it could be inferred that NaOCl should not be the last irrigant used in the canal before obturation. Furthermore the CHX gel viscosity might have contributed to the filling of interfibrillar spaces by residues of this substance (Lambrianidis et al., 2006). This phenomenon hinders the diffusion of the methacrylate sealer, which contains high-molecular weight monomers, through the exposed collagen fiber mesh, thus Microscopy Research and Technique
IRRIGATION PROTOCOLS ON SEALER INTERFACE AND BOND STRENGTH
explaining the lower push-out bond strength with CHX gel. The solvent addition to Epiphany SE presented significantly higher push-out bond strength than Epiphany SE without solvent. This material modification adjust the viscosity of the sealer and produces alterations on its structure by reducing the size of monomers, which increases the contact of the material with dentin and its penetration into the dentin tubules to create intratubular tags (Rached-Junior et al., 2009). This fact could also contribute to create a more homogeneous and dense hybrid layer, thus resulting in higher adhesion values. The higher adhesion values obtained with Epiphany SE with solvent may be correlated with the results of the qualitative SEM analysis, which showed a more compact obturation, and more homogeneous filling mass with few interfacial gaps, resulting in better filling of the root canal space and cone/sealer/dentin interface. When concerning the interaction between radicular dentin pretreatment and sealer solvent addition, in the present study the specimens irrigated with 17% EDTA and obturated with Epiphany SE added to solvent presented the highest adhesion values of all groups. The effects of EDTA on dentin surface together with the alterations occurred in sealer viscosity by the addition of the resinous solvent may explain the increased bond strength resulting from the combination of these factors, compared to the other groups. In the present study, no significant differences were found in the adhesion values among the apical, middle, and coronal root canal thirds. These results were not expected once there is a significant difference in collagen fibers density among root thirds; therefore the greater amount of collagen fibers of apical root third should promote a more effective adhesion (Nakabayashi and Saimi, 1996). A possible explanation for the results of the present study is the fact that the biomechanical instrumentation along the canals originates greater amount of residual smear layer in the apical third that is usually not effectively removed (Serafino et al., 2004). In addition, the photoactivation of the sealer at a distance of 10 mm from the coronal region resulted in less effective curing of the material at regions far from the light source, reducing the degree of polymerization of the sealer and its bond strength to dentin. Thus, probably these negative factors provided a less effective adhesion of the sealer to the apical root third that equalized with the other thirds bond strengths. The failure pattern was mainly adhesive in all groups, corresponding to 89% of the failure modes (68% occurred between dentin and sealer and 21% between Resilon cones and sealer). Mixed failures corresponded to 11% of the total, and no cohesive failure was observed. These results demonstrate that the monoblock structure (Belli et al., 2011; Versiani et al., 2006) was more fragile at the sealer/dentin interface. The occurrence of 25% of mixed failures in the specimens treated with 17% EDTA and obturated with Epiphany SE with solvent is consistent with the higher adhesion values verified in this group. Although the current resin-based sealers presented good adhesion results when compared with other types of sealers, this study open perspectives for further Microscopy Research and Technique
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research on the treatment of radicular dentin surface and improvements on filling materials and techniques. CONCLUSION The treatment of the root canal walls with 17% EDTA produced the highest adhesion of the filling material to radicular dentin. The addition of a resinous solvent to Epiphany SE resulted in greater homogeneity of the filling mass with higher adhesion values regardless the chemical irrigants used in the biomechanical preparation. REFERENCES Alfredo E, Silva SRC, Oz orio JEV, Sousa-Neto MD, Brugnera-J unior A, Silva-Sousa YTC. 2008. Bond strength of AH Plus and Epiphany sealers on root dentine irradiated with 980 nm diode laser. Int Endod J 41:733–40. Belli S, Eraslan O, Eskitascioglu G, Karbhari V. 2011. Monoblocks in root canals: A finite elemental stress analysis study. Int Endod J 44:817–26. Bystr€ om A, Sundqvist G. 1985. The antibacterial action of sodium hypochlorite and EDTA in 60 cases of endodontic therapy. Int Endod J 18:35–40. Costa JA, Rached-J unior FA, Souza-Gabriel AE, Silva-Sousa YTC, Sousa–Neto MD. 2010. Push-out strength of methacrylate resinbased sealers to root canal walls. Int Endod J 43:698–706. Crumpton B, Goodell G, McClanahan S. 2005. Effects on smear layer and debris removal with varying volumes of 17% REDTA after Rotary Instrumentation. J Endod 31:536–38. De-Deus G, Di Giorgi K, Fidel S, Fidel RAS, Paciornik S. 2009. Pushout bond strength of Resilon/Epiphany and Resilon/Epiphany selfetch to root dentin. J Endod 35:1048–50. El-Ma’aita AM, Qualtrough AJ, Watts DC. 2013. The effect of smear layer on the push-out bond strength of root canal calcium silicate cements. Dent Mater 29:797–803. Ferraz CCR, Gomes BPFA, Zaia AA, Teixeira FB, Souza-Filho FJ. 2007. Comparative study of the antimicrobial efficacy of chlorhexidine gel, chlorhexidine solution and sodium hypochlorite as endodontic irrigants. Braz Dent J 18:294–8. Garcıa-Godoy F, Loushine RJ, Itthagarun A, Weller RN, Murray PE, Feilzer AJ, Pashley DH, Tay FR. 2005. Application of biologicallyoriented dentine bonding principles to the use of endodontic irrigants. Am J Dent 18:281–90. H€ ulsmann M, Heckendorff M, Lennon A. 2003. Chelating agents in root canal treatment: Mode of action and indications for their use. Int Endod J 36:810–30. Jeansonne MJ, White RR. 1994. A comparison of 2.0% chlorhexidine gluconate and 5.25% sodium hypochlorite as antimicrobial endodontic irrigants. J Endod 20:276–9. Kokkas AB, Boutsioukis AC, Vassiliadis LP, Stavrianos C. 2004. The influence of the smear layer on dentinal tubule penetration depth by three different root canal sealers: An in vitro study. J Endod 30: 100–3. Lambrianidis T, Kosti E, Boutsioukis C, Mazinis M. 2006. Removal efficacy of various calcium hydroxide/chlorhexidine medicaments from the root canal. Int Endod J 39:55–61. Morris MD, Lee KW, Agee KA, Bouillaguet S, Pashley DH. 2001. Effects of sodium hypochlorite and rc-prep on bond strengths of resin cement to endodontic surfaces. J Endod 27:745–9. Nakabayashi N, Saimi Y. 1996. Bonding to intact dentine. J Dent Res 75:1706–15. Nassar M, Awawdeh L, Jamleh A, Sadr A, Tagami J. 2011. Adhesion of Epiphany self-etch sealer to dentin treated with intracanal irrigating solutions. J Endod 37:228–30. Nikaido T, Takano Y, Sasafuchi Y, Burrow MF, Tagami J. 1999. Bond strengths to endodontically-treated teeth. Am J Dent 12:177–80. Prado M, Sim~ ao RA, Gomes BP. 2013. Effect of different irrigation protocols on resin sealer bond strength to dentin. J Endod 39:689–92. Rached-Junior FJA, Souza-Gabriel AE, Alfredo E, Miranda CES, Silva-Sousa YTC, Sousa-Neto MD. 2009. Bond strength of Epiphany sealer prepared with resinous solvent. J Endod 35:251–5. Santos JN, Carrilho MRO, De Goes MF, Zaia AA, Gomes BPFA, Souza-Filho FJ, Ferraz CCR. 2006. Effect of chemical irrigants on the bond strength of a self-etching adhesive to pulp chamber dentin. J Endod 32:1088–90. Sayin TC, Serper A, Cehreli ZC, Kalayci S. 2007. Calcium loss from root canal dentin following EDTA, EGTA, EDTAC, and
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tetracycline-HCl treatment with or without subsequent NaOCl Irrigation. Int Endod J 33:581–4. Serafino C, Gallina G, Cumbo E, Ferrari M. 2004. Surface debris of canal walls after post space preparation in endodontically treated teeth: a scanning electron microscopic study. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 97:381–7. Serper A, Calt S. 2002. The demineralizing effects of edta at different concentrations and pH. J Endod 28:501–2. Shipper G, Ørstavik D, Teixeira FB, Trope M. 2004. An evaluation of microbial leakage in roots filled with a thermoplastic synthetic polymer-based root canal filling material (Resilon). J Endod 30:342–7. Shokouhinejad N, Sabeti MA, Hasheminasab M, Shafiei F, Shamsshiri AR. 2010. Push-out bond strength of Resilon/Epiphany self-etch to intraradicular dentin after retreatment: A preliminary study. J Endod 36:493–6. Shokouhinejad N, Sharifian MR, Jafari M, Sabeti MA. 2010. Pushout strength of Resilon/Epiphany self-etch and gutta-percha/AH26 after different irrigation protocols. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 110:88–92. Sousa-Neto MD, Coelho FI, Marchesan MA, Alfredo E, Silva-Sousa YTC. 2005. Ex vivo study of the adhesion of an epoxy-based sealer to human dentine submitted to irradiation with Er: YAG and Nd: YAG. Int Endod J 38:866–70.
Tagger M, Tagger E, Tjan AHL, Bakland LK. 2002. Measurement of adhesion of endodontic sealers to dentin. J Endod 28:351–4. Tay FR, Loushine RJ, Weller N, Kimbrough WF, Pashley DH, Mak Y, Lay CS, Raina R, Williams C. 2005. Ultrastructural evaluation of the apical seal in roots filled with a polycaprolactone-based root canal filling material. J Endod 31:514–9. Teixeira FB, Teixeira ECN, Thompson JY, Trope M. 2004. Fracture resistance of roots endodontically treated with a new filling material. J Am Dent Assoc 135:646–52. Versiani MA, Carvalho-J unior JR, Padilha MIAF, Lacey S, Pascon EA, Sousa–Neto MD. 2006. A comparative study of physicochemical properties of AH Plus and Epiphany root canal sealants. Int Endod J 39:464–71. Vilanova WV, Carvalho-Junior JR, Alfredo E, Sousa-Neto MD, SilvaSousa YT. 2012. Effect of intracanal irrigants on the bond strength of epoxy resin-based and methacrylate resin-based sealers to root canal walls. Int Endod J 45:42–8. Zehnder M. 2006. Root canal irrigants. J Endod 32:389–98. Zhang K, Kim YK, Cadenaro M Bryan TE, Sidow SJ, Loushine RJ, Ling JQ, Pashley DH, Tay FR. 2010. Effects of different exposure times and concentrations of sodium hypochlorite/ethylenediaminetetraacetic acid on the structural integrity of mineralized dentin. J Endod 36:105–9.
Microscopy Research and Technique
Effect of Different Irrigation Protocols on the Radicular Dentin Interface and Bond Strength with a Metacrylate-Based Endodontic Sealer LISANDRO GONC¸ALVES,1 YARA TERESINHA CORREA SILVA-SOUSA,1* WALTER RAUCCI NETO,1 ~ SOUSA-NETO,2 AND EDSON ALFREDO1 CLEONICE SILVEIRA TEIXEIRA,1 MANOEL DAMIAO 1 2
School of Dentistry, University of Ribeir~ ao Preto, Ribeir~ ao Preto, S~ ao Paulo, Brazil Ribeir~ ao Preto School of Dentistry, University of S~ ao Paulo, Ribeir~ ao Preto, S~ ao Paulo, Brazil
KEY WORDS
endodontics; root canal filling materials; dental-bonding agents; scanning electron microscopy
ABSTRACT This study assessed the influence of different endodontic chemical substances on the adhesion of the Epiphany SE/Resilon system (with and without resinous solvent) to radicular dentin walls, using the push-out test and scanning electron microscopy (SEM). Forty-eight root canals of human canines were prepared biomechanically with ProTaper rotary files (crowndown technique) and the radicular dentin was treated with either 17% EDTA, 2% chlorhexidine gel (CHX) or 2.5% NaOCl (control). The root canals were filled with Resilon cones and Epiphany SE sealer with and without resinous solvent. Six groups of eight canals each had their roots sectioned transversally to obtain 1-mm thick slices. Data were subjected to statistical analysis by ANOVA and Tukey’s tests. The specimens treated with 17% EDTA (1.59 6 0.91) presented higher bond strength (P < 0.05) than those treated with 2.5% NaOCl (0.93 6 0.27) and 2% CHX (0.92 6 0.22). Significantly higher bond strength (P < 0.05) was observed when the Epiphany SE was prepared with (1.37 6 0.78) than without (0.92 6 0.33) solvent. Adhesive failures were predominant in all groups. SEM analysis showed greater homogeneity of the filling mass when the solvent was added to the sealer. Treatment of root canal walls with 17% EDTA, and addition of a resinous solvent to Epiphany SE produced the highest adhesion to radicular dentin. Microsc. Res. Tech. 77:446–452, 2014. V 2014 Wiley Periodicals, Inc. C
INTRODUCTION Adhesion, one of the most important physicochemical properties of an endodontic sealer, is defined as its capacity to adhere to the root canal walls and promote the union of the gutta-percha cones to each other and to the dentin (Sousa-Neto et al., 2005). Advances in endodontic adhesive technology have focused on minimizing apical and coronal marginal leakage by increasing the bond strength between the filling material and the root canal walls (Tay et al., 2005). It is believed that a perfect union between the root canal filling material and the root canal walls, forming a monoblock structure, can increase the resistance of the roots of endodontically treated teeth to fracture (Belli et al., 2011; Teixeira et al., 2004). The dual-cure methacrylate resin-based sealer EpiphanyTM Soft Resin Endodontic Obturation System (Pentron Clinical Technologies, Wallingford, CT) has been introduced to replace conventional sealers. The sealer matrix consists of mixture of urethane dimethacrylate (UDMA), polyethylene dimethacrylate (PEGDMA), bisphenol-A-glycidyl dimethacrylate (BisGMA), ethoxylated BisGMA, and barium sulphate, silica, calcium hydroxide, bismuth oxide, photoinitiators stabilizers and pigments (Shipper et al., 2004; Versiani et al., 2006). This system also contains a self-etch primer (EpiphanyTM Primer, Pentron Clinical TechnolC V
2014 WILEY PERIODICALS, INC.
ogies) and a radiopaque solid material composed of thermoplastic synthetic polyester polymers similar to gutta-percha (ResilonTM; Pentron Clinical Technologies) (Shipper et al., 2004; Teixeira et al., 2004). Epiphany sealer is claimed to adhere chemically to the Resilon cones and to radicular dentin walls by hybridization of intertubular dentin (collagen-dependent process) and also by the creation of intratubular tags (Shipper et al., 2004; Teixeira et al., 2004). A resinous solvent (Epiphany Thinning Resin; Pentron Clinical Technologies) consisting of a mixture of ethoxylated bisphenol-A-dimethacrylate (EBPADMA), photoinitiators, amines and stabilizers, is also supplied. According to the manufacturer’s instructions the use of 1–2 drops of the solvent can be used to adjust sealer viscosity, when necessary. In addition, this technique maneuver improves the wettability of the sealer, which is essential for adhesion to dentin surface since it favors the diffusion of the filling material through surface irregularities (Rached-Junior et al., 2009) *Correspondence to: Yara Teresinha Correa Silva-Sousa, Rua Celia de Oliveira Meirelles, 350, 14024-070, Ribeir~ ao Preto, S~ ao Paulo, Brazil. E-mail: [email protected] Received 18 September 2013; accepted in revised form 21 March 2014 REVIEW EDITOR: Prof. Alberto Diaspro DOI 10.1002/jemt.22365 Published online 9 April 2014 in Wiley Online Library (wileyonlinelibrary.com).
IRRIGATION PROTOCOLS ON SEALER INTERFACE AND BOND STRENGTH
enhancing the possibility of forming a higher density hybrid layer. Since the EpiphanyTM SE (Self Etch) development this root canal sealer has been widely studied (Nassar et al., 2011; Prado et al., 2013; Shokouhinejad et al., 2010; Versiani et al., 2006). The main difference of this material to the epoxy-amine resin-based sealers, is related to the self-etch primer incorporation to the sealer, eliminating the separate priming step. According to the manufacturer, the resin matrix main bases of the sealer original formulation (EBPADMA and BisGMA) were maintained and a resin monomer—2hydroxyethyl methacrylate (HEMA)—and a methacrylic acid resins were added (Costa et al., 2010). Studies on push-out bond strength comparing other resin cements showed no improvement in the adhesion of the filling material to intraradicular dentin using 1mm thick root slices (De-Deus et al., 2009; Shokouhinejad et al., 2010). Other factors may influence the adhesion of the filling material to the radicular dentin, among which the treatment of the root canal walls stands out (Crumpton et al., 2006; Morris et al., 2001; Prado et al., 2013). The presence of smear layer on dentin surface is considered a negative factor in root canal adhesion because it acts as a physical barrier between the filling material and dentin walls (El-Ma’aita et al., 2013; Kokkas et al., 2004) Chemical irrigants have major influence on the root canals debridement during shaping and cleaning procedures (Crumpton et al., 2006; Kokkas et al., 2004). Different irrigations protocols should expose the collagen network, without causing collapse of its normal structural integrity and during the filling phase, the intimate contact of resin-based materials with treated root canal dentine should ideally result in excellent mechanical and chemical bonding (Costa et al., 2010; De-Deus et al., 2009). Sodium hypochlorite (NaOCl) is widely used as endodontic irrigant and it has been systematically applied in concentrations ranging from 0.5 to 5.25%. The useful application of NaOCl is related to its excellent antimicrobial action, dissolving organic materials and necrotic remnants tissues capacity and the reduced toxicity at low concentrations (Bystr€om and Sundqvist, 1985). However, NaOCl has disadvantages, such as corrosion of endodontic instruments, inefficacy against some microorganisms when used at low concentrations and toxicity to the periapical tissues when used at high concentrations (Ferraz et al., 2007; Jeansonne and White, 1994). Considering the NaOCl higher concentrations a previous study found that root canals irrigated with 5% NaOCl did not alter the sealer–dentin interface (Morris et al., 2001). One of the NaOCl chemical reactions within the root canal that could negatively influence the resin-based sealers is related to its dissociation into sodium chloride and oxygen, which may inhibit the polymerization of adhesive materials (Nikaido et al., 1999). Ethylenediaminetetraacetic acid (EDTA) is one of the most effective chelating agents used in the endodontic therapy (Crumpton et al., 2005). It has the capacity of chelating calcium ions calcium, promoting dentin demineralization and smear layer removal, which open the tubule entrances and increase sealer Microscopy Research and Technique
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bond strength (Prado et al., 2013; Sayin et al., 2007; Serper and Calt, 2002). Chlorhexidine gluconate (CHX) is used in a number of dental procedures and its potential application in endodontic therapy has also been investigated. This antimicrobial agent has a broad spectrum of activity against microorganisms commonly isolated from endodontic infections, with a prolonged and gradual release at therapeutic levels and low toxicity. CHX at 2% has been shown to have the same antimicrobial action as that of 5.25% sodium hypochlorite (Jeansonne and White, 1994). However, Zehnder (2006) emphasized that CHX cannot be advocated as the main standard irrigant in endodontic cases because it is unable to dissolve necrotic tissue remnants, and is less effective on gram-negative bacteria than on gram-positive bacteria. The use of CHX gel as an intracanal auxiliary chemical substance showed antimicrobial action against Enterococcus faecalis, and its viscosity produced good mechanical cleaning of the root canal system (Ferraz et al., 2007). Laboratorial studies have shown that irrigation of root canals with CHX did not alter (Santos et al., 2006) or reduced the sealer bond strength to root dentin (Prado et al., 2013). Considering the changes incorporated into the Epiphany structure and the possibility of adjusting its viscosity with a solvent, it would be interesting to determine whether the new formulation of Epiphany improves its adhesive properties to the root canal walls treated with different irrigants. Therefore, this study evaluated the influence of different endodontic chemical substances on the adhesion of the Epiphany SE/ Resilon system, with and without solvent, to radicular dentin using the push-out test and the filling material/ radicular dentin interface by scanning electron microscopy (SEM). MATERIALS AND METHODS The study was approved by Ethics Committee of University of Ribeir~ ao Preto, SP, Brazil (protocol 013/ 08). Maxillary human canines stored in 0.1% thymol solution steam at 9 C were washed in running water for 24 h to eliminate thymol residues, and were examined macroscopically and radiographed in a buccopalatal direction. Forty-eight teeth were selected on the basis of their roots, which should be completely formed, and present a single canal without calcifications or accentuated curvature. The crowns were removed at the cementoenamel junction with a watercooled diamond disk (KG Soresen, Barueri, SP, Brazil), and the roots were trimmed coronally to a uniform length of 17 mm. A #10 K-file (Dentsply-Maillefer, Ballaigues, Switzerland) was passively introduced into each root canal until its tip was seen at the apical foramen. The working length was established by subtracting 1 mm from this length. Teeth that presented laterally displaced foramina with real canal length less than 16 mm were replaced. The canals were instrumented with the ProTaper Universal rotary system (Dentsply-Maillefer, Ballaigues, Switzerland) according to the crown-down technique. The cervical third was prepared with the instrument SX and the middle and apical thirds were prepared the instruments S1, S2, F1, F2, F3, F4 and
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F5, which corresponds to a #50 K-file. The instruments were attached to the handpiece of an oscillatory system (TEP-E10R, NSK Nakanishi; Kanuma, Tochigi, Japan) activated by an electric engine (Endo Plus VK Driller, S~ ao Paulo, SP, Brazil). Throughout the biochemical preparation, the canals were irrigated with 2 mL of 2.5% NaOCl at each change of file. After biochemical preparation, the radicular dentin was submitted to the following pretreatment chemical protocols: 17% EDTA, 2% CHX gel or 2.5% (NaOCl) (control). The irrigants were delivered by NaviTip needles (Ultradent Products Inc., South Jordan, UT, USA) coupled to disposable plastic syringes (Ultradent Products Inc.; South Jordan, UT, USA). The canals were filled with 2 mL of the respective substances for 3 min, followed by flushing with 10 mL of distilled water and drying with absorbent paper points (Tanari-Tanariman Industrial, Manacapuru, AM, Brazil). The root canals were filled with Resilon cones and Epiphany SE sealer with and without resinous solvent (Epiphany Thinning Resin). Six groups (n 5 8) were originated for each combination of dentin treatment and filling material. The Epiphany SE pastes (10 mm of each one) were delivered on a glass plate, mixed during 15 s until a homogenous paste was obtained and taken to the root canal with a lentulo spiral (Maillefer, Ballaigues, Switzerland) attached to a low-speed handpiece (Dabi Atlante, Ribeir~ ao Preto, SP, Brazil) to avoid bubble formation. In the groups in which the resinous solvent was used, two drops of the product were delivered on the plate and mixed with the sealer. After insertion of the main Resilon cone, which was previously tested for apical fit, accessory cones were inserted according to the lateral compaction technique. The cones were cut with a heated instrument and vertically condensed with a plugger (Maillefer, Ballaigues, Switzerland). Sealer excess was removed with cotton pellets followed by photoactivation for 40 s at the cervical root third with a halogen light-curing unit (Ultralux Dabi Atlante, Ribeir~ ao Preto, SP, Brazil), keeping the light guide tip in contact with the cervical portion of the root. In all groups, the canal entrances were sealed with a quick-setting temporary restorative filling material (Cimpat; Septodont Brasil, Barueri, SP, Brazil) and the teeth were placed immediately at 37 C and 95% humidity for a period three times greater than the regular setting time of the sealer (135 min) before the bond strength test. For preparation of the slices, the roots were fixed on acrylic plates with wax (Kota Import, S~ ao Paulo, SP, Brazil) and were sectioned in a precision cutting machine (Minitom; Struers, Westlake, OH) at 375 rpm. Nine 1-mm thick slices were obtained from each root (3 per root third), producing 432 specimens (Fig. 1). The first slice of each third was selected for the push-out test. For this test, a stainless steel support was used to hold the specimens in an Instron 4444 universal testing machine (Instron Corporation, Canton, MA) in such a way that the side with the smaller diameter of the root canal faced upwards and was aligned to the shaft that would exert pressure load on the sealer (apical-coronally) until debonding occurred. A 6-mmlong shafts with tip diameter of 0.6 mm for the apical
Fig. 1. Schematic presentation of the root canal thirds with the 9 1mm thick slices, with their dimension and composition.
third and 1 mm for the coronal and middle thirds were used. This method assured the alignment of the specimen in an accurate and reproducible manner and also maintained the shaft centralized and avoided its contact with the dentin during testing, when the material is pushed and dislodged from the canal wall. The force needed to dislodge the filling material (F in kN) was transformed into tension (r in MPa) by dividing the force by the adhesive area of the filling material (SL in mm2), using the following equation: r 5 F/SL. After the push-out test, the slices were examined with a stereomicroscope (ZEISS, Stemi 2000-C, Germany) at 325 magnification to determine the failure modes that occurred due to displacement of the sealer from the specimen. Failure was considered adhesive if the sealer was totally separated from dentin (dentin surface without sealer), cohesive if the fracture occurred within the sealer (dentin surface totally covered by the sealer), and mixed when a mixture of adhesive and cohesive modes (dentin surface partially covered by the sealer) occurred. The second and third slices obtained from each canal third were prepared for SEM analysis of the filling material/radicular dentin interface and the homogeneity of the filling mass, respectively. The second slices were fixed on metallic stubs, sputter-coated with a gold–palladium alloy (Bal-Tec AG, Balzers, Liechtenstein) and examined with a scanning electron microscope (JSM 5410; JEOL, Tokyo, Japan) operating at 15 kV. SEM micrographs of representative areas were obtained at 350 magnification for localization of representative areas and then at 3350 magnification to evaluate the homogeneity of the filling material and the presence of failures at the interface with dentin. For analysis of the homogeneity of the filling mass, the third slices were decalcified in hydrochloride acid 4 N during 48 h and deproteinized in 2.5% NaOCl during 5 min, promoting the complete dissolution of dentin and exposure of the filling material. After being washed twice in distilled water during 4 min, the filling material was sputter-coated with gold-palladium and subjected to SEM analysis (Fig. 2). Mean values were statistically compared. The Kolmogorov–Smirnov test showed that the results were consistent with a normal distribution curve. Parametric statistical analysis was performed by ANOVA and post hoc Tukey test at 5% significance level (SPSS 17.0 software; SPSS, Chicago, IL). RESULTS The mean, maximum, minimum and standard deviation of the bond strength values (in MPa) for the Microscopy Research and Technique
IRRIGATION PROTOCOLS ON SEALER INTERFACE AND BOND STRENGTH
Fig. 2. SEM micrographs of the root filled specimens. A:, B: Specimens obturated with sealer Epiphany SE without solvent showing large empty spaces in the filling mass and interfacial gaps (arrows)
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350 and 3350, respectively. C:, D: Specimens obturated with sealer Epiphany SE with solvent showing a more homogeneous filling mass with few interfacial gaps (arrows), 350 and 3350, respectively.
TABLE 1. Mean and standard deviation of the bond strength values (MPa) for the displacement of the filling material from the specimens of each group, during the push-out test Treatment of radicular surface Sealers Epiphany SE
Epiphany SE 1 solvent
Data
2.5% NaOCl 1 17% EDTA
2% CHX gel
2.5% NaOCl
Mean
Mean Maximum Minimum SD Mean Maximum Minimum SD
0.99 3.23 0.18 0.82 2.18 4.23 0.45 1.26
0.85 2.05 0.14 0.50 0.98 1.98 0.44 0.44
0.93 2.03 0.27 0.48 0.94 2.40 0.24 0.66
0.92 6 0.33
displacement of the filling material from the specimens during the push-out test are presented in Table 1. The 17% EDTA dentin surface treatment produced significantly higher adhesion values (1.59 6 0.91 MPa) (P < 0.05) when compared to the other treatments (2% CHX gel: 0.92 6 0.22 MPa; 2.5% NaOCl: 0.93 6 0.27 MPa), which were statistically similar to each other (P > 0.05). The addition of solvent to the sealer produced significantly higher (P < 0.05) adhesion values (1.37 6 0.78 versus 0.92 6 0.33 MPa). The analysis of the interaction between radicular dentin treatment and the use of Epiphany sealer with Microscopy Research and Technique
1.37 6 0.78
and without resinous solvent showed that the root canal treated with 17% EDTA and filled with Epiphany SE with solvent promoted the highest adhesion values (2.19 6 0.85 MPa) (P < 0.05), while the other five groups presented statistically similar (P > 0.05) adhesion values. There were no statistically significant differences (P > 0.05) among the root canal thirds (coronal: 0.99 6 0.72; middle: 1.17 6 0.87 and apical: 1.27 6 1.01 MPa). The analysis of the failure mode after the push-out test showed a predominance of adhesive failures in all
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TABLE 2. Failure mode distribution observed after the displacement of the filling material from the specimens of each group, during the pushout test Failure mode (%) Adhesive Sealer Epiphani SE Epiphany SE 1 solvent Epiphany SE Epiphany SE 1 solvent Epiphani SE Epiphany SE 1 solvent Total
Radicular dentine treatment
Resilon/SE sealer
Dentin/sealer
Mixed
Cohesive
2.5% NaOCl 1 17% EDTA 2.5% NaOCl 1 17% EDTA 2% CHX 2% CHX 2.5% NaOCl 2.5% NaOCl
30 28 6 18 25 16 21
55 36 92 80 67 81 68
15 36 2 2 8 3 11
0 0 0 0 0 0 0
groups, especially at the sealer/dentin interface. In the specimens treated with 17% EDTA and obturated with Epiphany SE/Resilon with solvent, there were a significant number of mixed failures, compared to the other groups. Cohesive failures were not observed in any specimen. Failure mode distribution is presented in Table 2. A panel of SEM micrographs of the cone/sealer/canal interfaces in specimens obturated with Resilon cones and Epiphany SE sealer with and without resinous solvent after radicular dentin treatment with different substances is presented in Figure 2. Irrespectively of the endodontic irrigant, the specimens obturated with sealer Epiphany SE without solvent presented large empty spaces between the Resilon cones and between the cones and dentin surface (Figs. 2A and 2B). On the other hand, the specimens obturated with sealer Epiphany SE mixed with solvent presented a more homogenous filling of the canal, with fewer gaps at the cone/sealer/dentin interfaces, regardless of dentin treatment (Figs. 2C and 2D). DISCUSSION The chemomechanical procedures for the shaping and cleaning of root canal walls make possible intimate contact between the filling material, intertubular and peritubular dentine (Prado et al., 2013; Vilanova et al., 2012). Furthermore, an endodontic sealer should have good adhesion because, under static conditions, it contributes to minimize or eliminate spaces that could serve as pathways for infiltration of fluids between the sealer and the radicular dentin walls. Under dynamic conditions, good adhesion is important to improve the stability of the root filling mass inside the canal space during post space preparation (Tagger et al., 2002). Therefore, this study evaluated the influence of different irrigants used in endodontic therapy for the treatment of canal walls on the push-out bond strength of Epiphany SE/Resilon system (adjusting or not sealer viscosity with solvent) to radicular dentin using the push-out test. The filling capacity of the Epiphany SE/ Resilon system and the filling material/root dentin interface were examined by SEM. In the present study, the 17% EDTA as final chemical treatment produced the highest push-out bond strength of the Epiphany SE/Resilon system to the radicular dentin, while the other treatments produced similar push-out bond strengths to each other. Corroborating with these results, Garcıa-Godoy et al. (2005) and Vilanova et al. (2012) has already reported that
the use of EDTA instead of NaOCl as the active final rinse ensured higher push-out strengths of methacrylate resin-based sealers to root canal dentine. The capacity of the EDTA solutions to chelate calcium ions and remove smear layer from the dentin walls may explain these results. The influence of smear layer to the interaction between root canal walls and filling materials has already been discussed (El-Ma’aita et al., 2013; Sousa-Neto et al., 2005). The smear layer is a negative factor in root canal adhesion because it is weakly adhered to dentin surface and forms an interface between the filling material and the root canal walls, hence reducing the adhesion of sealers by affecting sealer penetration to form intratubular tags (Alfredo et al., 2008; Sousa-Neto et al., 2005) and favoring the occurrence of marginal leakage (RachedJunior et al., 2009). Therefore, the capacity of NaOCl of dissolving the organic components of the smear layer (H€ ulsmann et al., 2003) associated with the chelating action of 17% EDTA on the inorganic components promoting dentin demineralization, removing completely the smear layer (Shokouhinejad et al., 2010). A smear-free surface permits a more intimate contact of the filling material with dentin and a deeper penetration of the sealer into the dentinal tubules (Kokkas et al., 2004; Serper and Calt, 2002). The use of 2% CHX gel and 2.5% NaOCl resulted in lower push-out bond strength in the present study. This is consistent with the findings of previous studies, which found that the pretreatment with these substances did not improve sealer adhesion to dentin (Ferraz et al., 2007; Santos et al., 2006). Considering the cleansing perspective, the NaOCl acts exclusively on the organic portion of the smear layer and alone does not promote an effective treatment of dentin surface (Nassar et al., 2011). According to Zhang et al. (2010), and Vilanova et al. (2012) the NaOCl has reduced smear layer removing capacity compared with EDTA allowing lower sealer penetration inside the dentinal tubules. Considering the higher bond strength results of the present and previous studies (Vilanova et al., 2012; Zhang et al., 2010) obtained with EDTA pretreatment it could be inferred that NaOCl should not be the last irrigant used in the canal before obturation. Furthermore the CHX gel viscosity might have contributed to the filling of interfibrillar spaces by residues of this substance (Lambrianidis et al., 2006). This phenomenon hinders the diffusion of the methacrylate sealer, which contains high-molecular weight monomers, through the exposed collagen fiber mesh, thus Microscopy Research and Technique
IRRIGATION PROTOCOLS ON SEALER INTERFACE AND BOND STRENGTH
explaining the lower push-out bond strength with CHX gel. The solvent addition to Epiphany SE presented significantly higher push-out bond strength than Epiphany SE without solvent. This material modification adjust the viscosity of the sealer and produces alterations on its structure by reducing the size of monomers, which increases the contact of the material with dentin and its penetration into the dentin tubules to create intratubular tags (Rached-Junior et al., 2009). This fact could also contribute to create a more homogeneous and dense hybrid layer, thus resulting in higher adhesion values. The higher adhesion values obtained with Epiphany SE with solvent may be correlated with the results of the qualitative SEM analysis, which showed a more compact obturation, and more homogeneous filling mass with few interfacial gaps, resulting in better filling of the root canal space and cone/sealer/dentin interface. When concerning the interaction between radicular dentin pretreatment and sealer solvent addition, in the present study the specimens irrigated with 17% EDTA and obturated with Epiphany SE added to solvent presented the highest adhesion values of all groups. The effects of EDTA on dentin surface together with the alterations occurred in sealer viscosity by the addition of the resinous solvent may explain the increased bond strength resulting from the combination of these factors, compared to the other groups. In the present study, no significant differences were found in the adhesion values among the apical, middle, and coronal root canal thirds. These results were not expected once there is a significant difference in collagen fibers density among root thirds; therefore the greater amount of collagen fibers of apical root third should promote a more effective adhesion (Nakabayashi and Saimi, 1996). A possible explanation for the results of the present study is the fact that the biomechanical instrumentation along the canals originates greater amount of residual smear layer in the apical third that is usually not effectively removed (Serafino et al., 2004). In addition, the photoactivation of the sealer at a distance of 10 mm from the coronal region resulted in less effective curing of the material at regions far from the light source, reducing the degree of polymerization of the sealer and its bond strength to dentin. Thus, probably these negative factors provided a less effective adhesion of the sealer to the apical root third that equalized with the other thirds bond strengths. The failure pattern was mainly adhesive in all groups, corresponding to 89% of the failure modes (68% occurred between dentin and sealer and 21% between Resilon cones and sealer). Mixed failures corresponded to 11% of the total, and no cohesive failure was observed. These results demonstrate that the monoblock structure (Belli et al., 2011; Versiani et al., 2006) was more fragile at the sealer/dentin interface. The occurrence of 25% of mixed failures in the specimens treated with 17% EDTA and obturated with Epiphany SE with solvent is consistent with the higher adhesion values verified in this group. Although the current resin-based sealers presented good adhesion results when compared with other types of sealers, this study open perspectives for further Microscopy Research and Technique
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research on the treatment of radicular dentin surface and improvements on filling materials and techniques. CONCLUSION The treatment of the root canal walls with 17% EDTA produced the highest adhesion of the filling material to radicular dentin. The addition of a resinous solvent to Epiphany SE resulted in greater homogeneity of the filling mass with higher adhesion values regardless the chemical irrigants used in the biomechanical preparation. REFERENCES Alfredo E, Silva SRC, Oz orio JEV, Sousa-Neto MD, Brugnera-J unior A, Silva-Sousa YTC. 2008. Bond strength of AH Plus and Epiphany sealers on root dentine irradiated with 980 nm diode laser. Int Endod J 41:733–40. Belli S, Eraslan O, Eskitascioglu G, Karbhari V. 2011. Monoblocks in root canals: A finite elemental stress analysis study. Int Endod J 44:817–26. Bystr€ om A, Sundqvist G. 1985. The antibacterial action of sodium hypochlorite and EDTA in 60 cases of endodontic therapy. Int Endod J 18:35–40. Costa JA, Rached-J unior FA, Souza-Gabriel AE, Silva-Sousa YTC, Sousa–Neto MD. 2010. Push-out strength of methacrylate resinbased sealers to root canal walls. Int Endod J 43:698–706. Crumpton B, Goodell G, McClanahan S. 2005. Effects on smear layer and debris removal with varying volumes of 17% REDTA after Rotary Instrumentation. J Endod 31:536–38. De-Deus G, Di Giorgi K, Fidel S, Fidel RAS, Paciornik S. 2009. Pushout bond strength of Resilon/Epiphany and Resilon/Epiphany selfetch to root dentin. J Endod 35:1048–50. El-Ma’aita AM, Qualtrough AJ, Watts DC. 2013. The effect of smear layer on the push-out bond strength of root canal calcium silicate cements. Dent Mater 29:797–803. Ferraz CCR, Gomes BPFA, Zaia AA, Teixeira FB, Souza-Filho FJ. 2007. Comparative study of the antimicrobial efficacy of chlorhexidine gel, chlorhexidine solution and sodium hypochlorite as endodontic irrigants. Braz Dent J 18:294–8. Garcıa-Godoy F, Loushine RJ, Itthagarun A, Weller RN, Murray PE, Feilzer AJ, Pashley DH, Tay FR. 2005. Application of biologicallyoriented dentine bonding principles to the use of endodontic irrigants. Am J Dent 18:281–90. H€ ulsmann M, Heckendorff M, Lennon A. 2003. Chelating agents in root canal treatment: Mode of action and indications for their use. Int Endod J 36:810–30. Jeansonne MJ, White RR. 1994. A comparison of 2.0% chlorhexidine gluconate and 5.25% sodium hypochlorite as antimicrobial endodontic irrigants. J Endod 20:276–9. Kokkas AB, Boutsioukis AC, Vassiliadis LP, Stavrianos C. 2004. The influence of the smear layer on dentinal tubule penetration depth by three different root canal sealers: An in vitro study. J Endod 30: 100–3. Lambrianidis T, Kosti E, Boutsioukis C, Mazinis M. 2006. Removal efficacy of various calcium hydroxide/chlorhexidine medicaments from the root canal. Int Endod J 39:55–61. Morris MD, Lee KW, Agee KA, Bouillaguet S, Pashley DH. 2001. Effects of sodium hypochlorite and rc-prep on bond strengths of resin cement to endodontic surfaces. J Endod 27:745–9. Nakabayashi N, Saimi Y. 1996. Bonding to intact dentine. J Dent Res 75:1706–15. Nassar M, Awawdeh L, Jamleh A, Sadr A, Tagami J. 2011. Adhesion of Epiphany self-etch sealer to dentin treated with intracanal irrigating solutions. J Endod 37:228–30. Nikaido T, Takano Y, Sasafuchi Y, Burrow MF, Tagami J. 1999. Bond strengths to endodontically-treated teeth. Am J Dent 12:177–80. Prado M, Sim~ ao RA, Gomes BP. 2013. Effect of different irrigation protocols on resin sealer bond strength to dentin. J Endod 39:689–92. Rached-Junior FJA, Souza-Gabriel AE, Alfredo E, Miranda CES, Silva-Sousa YTC, Sousa-Neto MD. 2009. Bond strength of Epiphany sealer prepared with resinous solvent. J Endod 35:251–5. Santos JN, Carrilho MRO, De Goes MF, Zaia AA, Gomes BPFA, Souza-Filho FJ, Ferraz CCR. 2006. Effect of chemical irrigants on the bond strength of a self-etching adhesive to pulp chamber dentin. J Endod 32:1088–90. Sayin TC, Serper A, Cehreli ZC, Kalayci S. 2007. Calcium loss from root canal dentin following EDTA, EGTA, EDTAC, and
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Microscopy Research and Technique
