Comparative Evaluation of the Apical Sealability of AH Plus and RealSeal SE Using 5.25% Sodium Hypochlorite with 17% EDTA and 10% Citric Acid as Irrigants—An In Vitro Study

ABSTRACT

Background:

Apical microleakage is considered to be a common reason for the clinical failure of endodontic therapy. Three dimensional sealing of the root canal is one of the main goals of endodontic treatment and is essential for preventing reinfection of the canal and for preserving the health of the periapical tissues, Recently Epoxy resin sealers have been used because of their reduced solubility apical seal and micro-retention to root dentine.

Aim and Objective:

This in vitro study was done to evaluate and compare the apical sealability of AH Plus and RealSeal SE using 5.25% sodium hypochlorite with 17% EDTA and 10% citric acid as irrigants. Materials and methods: 44 single-rooted premolars were selected and the teeth are randomly divided into 4 groups (n=10) and 2 control groups (n=2). The extent of dye penetration, from the apical to the coronal part of the root canal, was assessed using a stereomicroscope at 10x magnification for all groups.One-way ANOVA and Kruskal-Wallis tests were performed to compare statistically significant differences among the groups, using SPSS software version 10.0.

Results:

Group IV (Citric acid + RealSeal SE) showed a statistically lower mean microleakage when compared to all other groups.

Conclusion:

From, the present study, it was concluded that, RealSeal SE sealer with 10% citric acid as irrigant (group IV) showed better apical sealability followed by RealSeal SE sealer with 17% EDTA as irrigant (group III), when compared to AH Plus groups which showed least sealability.

INTRODUCTION

The initial goals of root canal therapy include thorough cleaning of the root canal space, establishing a hermetic seal at the apex, and complete filling of the root canal systems. Due to the intricate nature of root canal anatomy, achieving complete disinfection, sealing all canal systems, and creating a fluid-resistant seal pose significant challenges.[1] In 1977, Lester and Boyde characterized the smear layer as organic matter confined within moved inorganic dentin.[2] This smear layer comprises both organic and inorganic components, which encompass remnants of odontoblastic processes, microorganisms, and necrotic substances.[3]

A variety of solutions have been proposed for use as irrigants in root canal therapy.[4] Among these options, sodium hypochlorite (NaOCl) remains the most widely recommended irrigating solution in endodontics, primarily due to its unique ability to dissolve necrotic tissue remnants. NaOCl possesses several properties that enhance its effectiveness in the chemomechanical cleaning of root canal systems. However, when NaOCl is used for root canal irrigation, it may dissolve the organic components but leave behind a smear layer of mineralized tissue.

Research has indicated that combining NaOCl with ethylenediaminetetraacetic acid (EDTA) is an effective approach for eliminating the smear layer. The combination of these irrigants has shown to be more effective in terms of antimicrobial properties than using NaOCl alone. EDTA reacts with the calcium ions present in dentin, forming soluble calcium chelates. A continuous rinse with 5 ml of 17% EDTA, as a final rinse for 3 minutes, efficiently removes the smear layer from the walls of the root canal.[5] Citric acid, another chelating agent, has also been found to be an effective irrigant when used in alternating cycles with NaOCl. Utilizing 10% citric acid for the final irrigation step has proven to yield positive results in the removal of the smear layer.

Microleakage within the root canal is defined as the passage of bacteria, fluids, and chemical substances between the tooth structure and the filling material used in the root canal.[6] A relatively recent approach to improving the sealing efficacy of root fillings draws inspiration from the field of obturation materials.[7] These obturation materials and sealers were developed using dentin adhesion technologies borrowed from restorative dentistry. Currently, a variety of root canal cements are employed in combination with gutta-percha to fill the root canal after biomechanical preparation. Resin-based filling materials have been steadily gaining popularity and are now widely accepted as suitable choices for root canal fillings.[8] Epoxy resin sealers, in particular, are favored for their reduced solubility,[9] apical seal,[10] and micro-retention to root dentin.[11] Excellent apical sealing results have been demonstrated with epoxy resin-based sealers.[12,13]

The introduction of Resilon has presented a challenge to traditional gutta-percha obturation materials.[1] Resilon is a thermoplastic synthetic polymer-based root canal filling material made of polycaprolactone (PCL), a biodegradable aliphatic polyester, and other primary polymers. Additionally, it contains barium sulfate, bismuth oxychloride, and bioactive glass filler particles. PCL and di-methacrylates typically make up 25–40% and 3–10% of the Resilon polymeric matrix, respectively. The presence of dimethacrylate monomers in the polymer is what gives it the ability to bond with resins made of methacrylates. By combining self-etching adhesives and methacrylate-based resin sealers with Resilon, the concept of monoblock bonding for root canal obturation was developed.[14]

RealSeal SE is a next-generation self-etching adhesive sealer composed of an amalgam of ethoxylated bisphenol A dimethacrylate (EBPADMA), 2-hydroxyethylmethacrylate (HEMA), bisphenolA-glycidyl methacrylate (BIS-GMA), acidic methacrylate resins, silane-treated barium borosilicate glasses, silica, hydroxylapatite, Ca-Al-F-silicate, bismuth oxychloride, amines, peroxide, photo-initiator, stabilizers, and pigment. It offers the chance to lessen the sensitivity of the technique and the duration of the application process for bonding to the root canal. The purpose of RealSeal SE is to adhere to the dentin in the root, forming a monoblock structure with the goal of creating a fluid-tight seal. The multifaceted self-etching bonding mechanism involves the infiltration of resin monomers into the cleaned dentine surface followed by polymerization to create a micromechanical interlocking between the resin and dentin collagen.[15]

In endodontics, achieving three-dimensional sealing of the root canal is a primary objective. This is necessary to keep the periapical tissues healthy and prevent the canal from becoming infected again, which will ultimately guarantee the success of root canal therapy.[16] The root canal system and the tissues around it should be effectively blocked by a good orthograde filling material.[14] Consequently, various types of endodontic sealers have been recommended to achieve this goal, making the assessment of apical sealing ability a critical aspect of endodontic research.[16]

Hence, the present study was conducted to evaluate and compare the in vitro apical sealability of AH Plus and RealSeal SE root canal sealers using 5.25% NaOCl with 17% EDTA and 10% citric acid as irrigants.

AIM

The aim of this in vitro study was to evaluate and compare the apical sealability of AH Plus and RealSeal SE using 5.25% NaOCl with 17% EDTA and 10% citric acid as irrigants.

OBJECTIVES

The specific objectives of this study were as follows:

1. To evaluate the apical sealability of AH Plus using sodium hypochlorite and EDTA solution.

2. To evaluate the apical sealability of AH Plus using sodium hypochlorite and citric acid solution.

3. To evaluate the apical sealability of RealSeal SE using sodium hypochlorite and EDTA solution.

4. To evaluate the apical sealability of RealSeal SE using sodium hypochlorite and citric acid solution.

5. To compare the apical sealability of AH Plus using sodium hypochlorite with EDTA and citric acid solution.

6. To compare the apical sealability of RealSeal SE using sodium hypochlorite with EDTA and citric acid solution.

7. To compare the apical sealability of AH Plus with RealSeal SE, wherein EDTA and citric acid were used as irrigants.

MATERIALS AND METHODS

This in vitro study was done in the Department of Pedodontics and Preventive Dentistry, Rajah Muthiah Dental College and Hospital. The teeth, extracted for periodontal/orthodontic reasons, were collected, and in total, 44 single-rooted premolars were selected and the teeth were randomly divided into four groups (n = 10) and two control groups (n = 2).

Group 1: Irrigation with 17% EDTA and obturated with AH Plus and Gutta-percha

Group 2: Irrigation with 10% citric acid and obturated with AH Plus and Gutta-percha

Group 3: Irrigation with 17% EDTA and obturated with RealSeal SE and Resilon

Group 4: Irrigation with 10% citric acid and obturated with RealSeal SE and Resilon

Group 5: Positive control group

Group 6: Negative control group.

The removal of the coronal tooth structure was carried out at the cementoenamel junction using a diamond disc while maintaining water coolant. To establish the canal lengths, a size 15 K file (Mani Inc., Japan) was inserted into each root canal until the file’s tip became visible at the apical foramen. The working length was determined to be 1 mm short of the apex. The canal systems were instrumented to the working length using a size 40 K file, following a step-back technique. Prior to the insertion of each file, 1 mL of 5.25% NaOCl was used as a chemical auxiliary substance for all groups. After file usage, 5 mL of saline was employed to remove the chemical auxiliary substance. Subsequently, the root canals were irrigated with 3 mL of either 17% EDTA or 10% citric acid for a duration of 3 minutes to eliminate the smear layer. The solutions were replaced every 1 minute at a rate of 1 mL per minute and rinsed with 2 mL of saline solution before being dried with paper points.[17] Roots were filled using the lateral condensation technique, either with gutta-percha and AH Plus sealer or Resilon and RealSeal SE. The sealer was introduced into the root canal using a lentulospiral #25, and then the primary cone, #40/.02, was inserted up to the working length. The lateral compaction technique was employed with a finger spreader, and accessory cones were laterally placed and compacted. This process was repeated until no more accessory cones could be fitted into the root canal.[18] Any excess cone was trimmed at the orifice level using a heated ball burnisher.[19] In the case of RealSeal SE, light curing was applied for 40 seconds using a standard light-curing unit in accordance with the manufacturer’s instructions.[20]

The root surfaces were coated with nail varnish, leaving only the apex uncoated. In the positive control group, the roots, which were not filled with core material and sealer, were coated with two layers of nail varnish, leaving the apical foramen exposed. The negative control group, on the other hand, had the root canals filled with core material and sealer before being entirely covered with two layers of nail varnish. After the obturation process, all samples were placed in a saline solution at 37°C for 48 hours. Subsequently, they were immersed in a 2% methylene blue dye and centrifuged at 3,000 rpm for 5 minutes. The specimens were then rinsed under running tap water for 5 minutes. The roots were carefully grooved longitudinally with a diamond disc and split with a chisel, ensuring that the root canal filling remained intact. The roots were then split into halves. The extent of dye penetration, from the apical to the coronal part of the root canal, was assessed using a stereomicroscope at 10x magnification. The mean values of leakage for each group were calculated and recorded with the assistance of GSA Image Analyser software (Bansemer and Scheel GbR, Rostock, Germany). For statistical analysis, one-way ANOVA and Kruskal–Wallis tests were performed to compare statistically significant differences among the groups, using SPSS software version 10.0. The significance level was set at α = 0.05.[21] The results from the analysis were then presented in tabular form.

RESULTS

When the apical microleakage among the groups was compared using the one-way ANOVA test, it was observed that Group IV, in which irrigation was performed with 10% citric acid and obturated with RealSeal SE and Resilon, exhibited a statistically lower mean microleakage and standard deviation. This was reflected in a significant P-value (P < 0.05). Table 1 indicated a statistically significant difference among the groups, prompting further comparisons between each group using the Kruskal–Wallis test. Upon comparing the apical microleakage of Group I (EDTA + AH Plus) and Group II (Citric acid + AH Plus) using the Kruskal–Wallis test, no statistically significant difference was found, as indicated by the non-significant P-value [Table 2]. When comparing the apical microleakage of Group I (EDTA + AH Plus) and Group III (EDTA + RealSeal SE), Group III showed a statistically lower mean microleakage and standard deviation compared to Group I [Table 3].

Table 1.

One-way ANOVA comparison of apical sealability of all groups

Group	n	Mean	Std. Deviation	F	P
Group I (EDTA + AH Plus)	10	1.928	0.963	9.821	0.01 (Significant)
Group II (Citric acid + AH Plus)	10	1.318	0.899
Group III (EDTA + RealSeal SE)	10	0.710	0.507
Group IV (Citric acid + RealSeal SE)	10	0.317	0.182
Total	40	1.068	0.922

Table 2.

Kruskal–Wallis test comparison of apical sealability of Group I (EDTA + AH Plus) and Group II (Citric acid + AH Plus)

Group	n	Mean	Std. Deviation	P
Group I (EDTA + AH Plus)	10	1.928	0.963	0.12 (Not Significant)
Group II (Citric acid + AH Plus)	10	1.318	0.899

Table 3.

Kruskal–Wallis test comparison of apical sealability of Group I (EDTA + AH Plus) and Group III (EDTA + RealSeal SE)

Groups	n	Mean	Std. Deviation	P
Group I (EDTA+AH Plus)	10	1.928	0.963	0.001 (Significant)
Group III (EDTA+RealSeal SE)	10	0.710	0.507

The apical microleakage of Group I (EDTA + AH Plus) and Group IV (Citric acid + RealSeal SE) was compared, and Group IV displayed a statistically lower mean microleakage and standard deviation [Table 4]. When comparing the apical microleakage of Group II (Citric acid + AH Plus) and Group III (EDTA + RealSeal SE), no statistically significant difference was observed between the mean microleakage of these two groups [Table 5]. Upon comparing the apical microleakage of Group II (Citric acid + AH Plus) and Group IV (Citric acid + RealSeal SE), it was revealed that Group IV exhibited a statistically lower mean microleakage [Table 6]. Finally, when comparing the apical microleakage of Group III (EDTA + RealSeal SE) and Group IV (Citric acid + RealSeal SE), it was evident that Group IV displayed a statistically lower mean microleakage and standard deviation when compared to Group III [Table 7].

Table 4.

Kruskal–Wallis test comparison of apical sealability of Group I (EDTA + AH Plus) and Group IV (Citric acid + RealSeal SE)

Groups	n	Mean	Std. Deviation	P
Group I (EDTA + AH Plus)	10	1.928	0.963	0.001 (Significant)
Group IV (Citric acid + RealSeal SE)	10	0.317	0.182

Table 5.

Kruskal–Wallis test comparison of apical sealability of Group II (Citric acid + AH Plus) and Group III (EDTA + RealSeal SE)

Groups	n	Mean	Std. Deviation	P
Group II (Citric acid + AH Plus)	10	1.318	0.899	0.07 (Not Significant)
Group III (EDTA + RealSeal SE)	10	0.710	0.507

Table 6.

Kruskal–Wallis test comparison of apical sealability of Group II (Citric acid + AH Plus) and Group IV (Citric acid + RealSeal SE)

Groups	n	Mean	Std. Deviation	P
Group II (Citric acid + AH Plus)	10	1.318	0.899	0.006 (Significant)
Group IV (Citric acid + RealSeal SE)	10	0.317	0.182

Table 7.

Kruskal–Wallis test comparison of apical sealability of Group III (EDTA + RealSeal SE) and Group IV (Citric acid + RealSeal SE)

Group	n	Mean	Std. Deviation	P
Group III (EDTA + RealSeal SE)	10	0.710	0.507	0.01 (Significant)
Group IV (Citric acid + RealSeal SE)	10	0.317	0.182

DISCUSSION

Achieving three-dimensional sealing of the root canal is a fundamental objective in endodontic treatment. This sealing is essential to prevent canal reinfection and maintain the health of periapical tissues, thereby ensuring the success of root canal therapy. Ideally, the root canal sealer should establish a strong bond between the core material and the root dentine to effectively prevent leakage.[22]

Dentin surface treatment with various irrigation regimens can influence the chemical and structural composition of human dentin, affecting the quality and adhesion of root canal filling materials to the dentin.[15] The debate over whether to retain or remove the smear layer remains controversial. The smear layer can potentially trap bacteria within dentinal tubules, but its removal creates open pathways for microorganism ingress. The presence of the smear layer can alter the sealing properties of endodontic sealers.[6]

NaOCl solutions are widely recommended in endodontics due to their capacity to dissolve necrotic tissue remnants and strong antimicrobial properties. However, NaOCl at 5.25% and 37°C may not completely remove the smear layer from the apical third of the canals.[23] It is noteworthy that NaOCl leaves an oxygen-rich layer on the root dentin surface, inhibiting free radical polymerization, potentially reducing bond strength, and increasing microleakage.[24]

As a result, in the present study, 5.25% NaOCl solution was used. Since no single irrigation solution has been found capable of both demineralizing the smear layer and dissolving organic tissue, chelating agents like EDTA or citric acid are recommended to remove and prevent the formation of the smear layer associated with root canal instrumentation.[25] Citric acid, at concentrations ranging from 1% to 50%, has been used for smear layer removal, with recent research suggesting that even weaker solutions of citric acid (6–19%) are effective.[26] Citric acid offers similar effects in terms of smear layer removal compared to EDTA but is less cytotoxic.[27] Therefore, in this study, a 10% citric acid solution was employed.

An innovative approach to enhancing root-filling sealing ability comes from the field of obturation materials. These materials and sealers were developed using dentin adhesion technologies borrowed from restorative dentistry. The introduction of the Resilon obturation system has challenged traditional gutta-percha obturation material. The RealSeal SE sealer, a self-etching moderately filled flowable composite with acidic monomers, aims to reduce technique sensitivity, especially in the apical third where primer application may be challenging.[1] Resilon consists of a filled PCL polymer that contains a blend of dimethacrylates and is designed to bond well to methacrylate-based resin sealers.[28] AH Plus is considered a gold standard sealer, known for its excellent sealing properties.[29]

In this study, the apical sealability of AH Plus and RealSeal SE was compared, and the results indicated that RealSeal SE demonstrated statistically significantly lower microleakage compared to AH Plus.[30] This result aligns with previous studies suggesting that Resilon/RealSeal SE has superior sealing ability compared to Gutta-percha/AH Plus.[31,32] This may be attributed to the fast setting and subsequent polymerization shrinkage of AH Plus, the lack of bonding between AH Plus and Gutta-percha, and the hydrophobic nature of AH Plus that may hinder its adaptation in incompletely dried canals.[33,34]

The presence of a monoblock effect with RealSeal SE may eliminate gaps associated with the core material and sealer, resist shrinkage, and strengthen the root.[35] Hydrophilicity and a higher flow rate may also contribute to the improved sealability.[31] RealSeal’s sluggish auto-curing dynamics may be seen as a benefit in reducing shrinkage stress accumulation, which promotes the life of the Resilon-sealer links.[29]

It has been claimed that this system creates a monoblock effect with the canal wall. Such a monoblock eliminates the gaps associated with the core material and sealer, resists shrinkage, and strengthens the root.[35] Also, hydrophilicity and higher flow rate may also attribute to better sealability.[31] The slow auto-curing dynamics incorporated in RealSeal may be considered an advantage in minimizing shrinkage stress buildup that favors the survival of the Resilon-sealer bonds,[29] wherein the apical microleakage following obturation was examined using four different root canal sealers: Acroseal, Endofill, RealSeal SE, and AH Plus. It was found that Acroseal had the highest mean microleakage and that there was no statistically significant difference between it and RealSeal SE, but there were significant differences when compared to Endofill and AH Plus which as in contrast to our results.[36]

In this study, the apical sealability of AH Plus using EDTA and citric acid solutions was compared, revealing that the citric acid group showed lower apical microleakage than the EDTA group, although the difference was not statistically significant (P-value = 0.12). This lack of significance might be due to the similar efficacy of both irrigants in smear layer removal.[37] Researchers determined the effect of EDTA and citric acid on smear layer removal in different regions of root canals and showed that the use of both 17% EDTA and 7% citric acid offers desired results, and they can remove smear layer from narrow and curved canals, especially from apical region.[38] In a previous study, they evaluated the efficacy of smear layer removal using chitosan and compared it with different chelating agents, 15% EDTA, 0.2% chitosan, 10% citric acid, 1% acetic acid and concluded that 15% EDTA, 0.2% chitosan and 10% citric acid effectively removed smear layer from the middle and apical thirds of root canal.[39]

One of the most crucial aspects of RealSeal SE is its degree of conversion, which affects bonding and biocompatibility.[14] The effects of NaOCl can be countered by reducing agents such as sodium ascorbate, citric acid, and ascorbic acid.[40] Similarly, the apical sealability of RealSeal SE using EDTA and citric acid solutions was compared, and the results showed that the citric acid group had significantly lower microleakage than the EDTA group. This difference may be attributed to the higher microleakage observed with EDTA when used with RealSeal SE. In vitro studies like this provide valuable insights and allow for comparisons, although it’s important to note that their results cannot be directly extrapolated to clinical settings. Further long-term in vitro studies with additional parameters that can simulate oral conditions are needed to provide more comprehensive support for the use of RealSeal SE.

SUMMARY AND CONCLUSION

Based on the results of this study, the following conclusions can be drawn:

1. RealSeal SE sealer in combination with 10% citric acid as an irrigant (group IV) demonstrated the best apical sealability among all the groups.

2. RealSeal SE sealer with 17% EDTA as an irrigant (group III) exhibited a higher level of apical sealability compared to AH Plus groups.

3. In terms of apical sealability, there was no significant difference observed when 17% EDTA and 10% citric acid were used as irrigants with AH Plus sealer.

In summary, RealSeal SE sealer, especially when used with 10% citric acid as an irrigant, showed superior apical sealability compared to AH Plus. These findings highlight the potential benefits of RealSeal SE in achieving effective apical sealing in endodontic treatments. Additionally, the study suggests that the choice between EDTA and citric acid as irrigants with AH Plus did not significantly affect apical sealability.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.