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ORIGINAL ARTICLE
Year : 2020  |  Volume : 10  |  Issue : 3  |  Page : 265-270

Synergistic effect of manual dynamic agitation and ethylenediaminetetraacetic acid containing 0.25% cetrimide on smear layer removal: An in vitro study


Department of Restorative Dentistry and Periodontology, Endodontic Division, Faculty of Dentistry, Chiang Mai University, Chiang Mai, Thailand

Date of Submission02-Nov-2019
Date of Decision23-Nov-2019
Date of Acceptance10-Jan-2020
Date of Web Publication27-Aug-2020

Correspondence Address:
Dr. Tanida Srisuwan
Department of Restorative Dentistry and Periodontology, Endodontic Division, Faculty of Dentistry, Chiang Mai University, Chiang Mai
Thailand
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/sej.sej_161_19

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  Abstract 


Introduction: This study aims to study the efficiency of manual dynamic agitation (MDA) combined with ethylenediaminetetraacetic acid (EDTA) containing 0.25% cetrimide in smear layer removal of mechanically prepared root canals after final irrigation.
Materials and Methods: The root canals of 120 premolars were prepared using Mtwo® rotary instruments. The roots were randomly divided into six groups (n = 20): negative control (G1), irrigated with normal saline, and positive control (G2), irrigated with 17% EDTA followed by 2.5% sodium hypochlorite (NaOCl). The reaming four groups were irrigated with 17% EDTA followed by 2.5% NaOCl with MDA and agitated with gutta-percha (G3), irrigated with 17% EDTA followed by 2.5% NaOCl (both with MDA) (G4), irrigated with 17% EDTA containing 0.25% cetrimide followed by 2.5% NaOCl (both with MDA) (G5), and irrigated with SmearClear™ EDTA followed by 2.5% NaOCl (both with MDA) (G6). Subsequently, the specimens were evaluated under scanning electron microscopy. The amount of smear layer in each specimen, 1 mm, 3 mm, and 5 mm of the apical third of the root canal, was scored using Gutmann's scoring system. Data were statistically analyzed using the Kruskal–Wallis and Mann–Whitney U tests.
Results: The least smear layer score was observed in Group 5 (P < 0.05). Utilizing MDA with EDTA and NaOCl (Groups 4-6) led to significantly reduced smear layer score compared to negative and positive control. Even MDA for NaOCl alone (Group 3) had significantly cleaner walls compared to negative and positive control (P < 0.05).
Conclusions: Supplementation with MDA in the final root canal irrigation step promoted a significantly cleaner surface of the mechanically prepared root canal wall at the apical level. Further, the use of EDTA containing 0.25% cetrimide significantly improved smear layer removal.

Keywords: Cetrimide, ethylenediaminetetraacetic acid, irrigation technique, manual dynamic agitation, smear layer


How to cite this article:
Krongbaramee T, Poochitpakorn S, Dewi A, Louwakul P, Srisuwan T. Synergistic effect of manual dynamic agitation and ethylenediaminetetraacetic acid containing 0.25% cetrimide on smear layer removal: An in vitro study. Saudi Endod J 2020;10:265-70

How to cite this URL:
Krongbaramee T, Poochitpakorn S, Dewi A, Louwakul P, Srisuwan T. Synergistic effect of manual dynamic agitation and ethylenediaminetetraacetic acid containing 0.25% cetrimide on smear layer removal: An in vitro study. Saudi Endod J [serial online] 2020 [cited 2020 Sep 26];10:265-70. Available from: http://www.saudiendodj.com/text.asp?2020/10/3/265/293575




  Introduction Top


Smear layers consist of inorganic dentin and organic components and are unintentionally created during root canal preparation, diminishing the effectiveness of irrigants, medicaments, and also the sealing ability of obturating materials.[1],[2],[3],[4] Difficulties in smear layer removal at the apical part of the root canal have been observed due to entrapped air bubbles. This bubble entrapment is called the vapor lock effect.[5],[6] To date, various methods have been proposed to disperse the irrigant. These methods aim to improve the ability of the irrigants to remove the smear layer, for example, using agitation techniques (either manual or machine assisted), and the addition of surfactants into the irrigating solution.[7],[8],[9],[10]

The manual dynamic agitation (MDA) technique, using a well-fitting gutta-percha cone, moving in short strokes, is a simple method, which effectively breaks the vapor lock at the apical part of the root canal.[7],[11] This technique has a capability in smear layer removal similar to or greater than various types of machine-assisted irrigation techniques. Examples of these techniques are RinsEndo, passive ultrasonic irrigation (PUI), and sonic irrigation, when used with sodium hypochlorite (NaOCl).[12] However, whether using MDA with other irrigants having chelating properties, for example, ethylenediaminetetraacetic acid (EDTA), would improve smear layer removal has never been evaluated. Moreover, the improvement of irrigating solution properties, in terms of penetration and flow capability, is another interesting topic.

Reducing the surface tension of aqueous endodontic solutions, such as EDTA, improves their dentin wetting ability[13] and increases their flow into narrow root canals.[14] Therefore, adding a surfactant to chelating agents would increase their efficacy. A quaternary ammonium compound, cetrimide, is used to reduce surface tension with powerful antiseptic properties.[15] McComb and Smith found REDTA which includes cetrimide as a surfactant to be the most effective in smear layer removal.[1],[16] Our previous study observed that adding cetrimide at a concentration of 0.25% improves smear layer removal.[17] Therefore, it is interesting to evaluate the effectiveness of irrigants in smear layer removal when MDA is applied in various steps, including when EDTA with surfactant is used. To date, no study has evaluated the synergistic effect of EDTA using MDA techniques in smear layer removal. Therefore, the aim of this study was to evaluate the efficiency of MDA combined with EDTA containing 0.25% cetrimide in smear layer removal of mechanically prepared root canals after final irrigation.

The null hypothesis (H0) was there would be no difference in smear layer removal whether MDA or the supplementation of cetrimide in root canal irrigation was utilized. The purpose of this study is to determine and develop irrigation protocol to apply for clinical practice.


  Materials and Methods Top


Specimen preparation

This study was approved by the Human Experimental Committee of Faculty of Dentistry, Chiang Mai University, Thailand (#47/50). One hundred and twenty single-rooted mandibular premolars with straight root canals were included in the study. All the selected teeth had been recently extracted from patients between the ages of 18 and 25 years for orthodontic purpose and stored in 0.5% chloramine. The teeth were radiographed to verify any abnormalities. Teeth with caries or any sign of cracks were excluded from the study. The crown of the tooth was removed to achieve a tooth length of 16 mm. To standardize the specimens, teeth that had initial root canal sizes greater than that of a No. 25 K-file at the apical third were excluded from the study. Subsequently, the teeth were separately embedded in a silicone putty to imitate a closed root canal system.[12] All specimens were mechanically prepared using an Mtwo® rotary instrument (VDW, Munich, Germany) up to size 40/0.04 at a working length of 15 mm. During root canal preparation, 20 mL of 2.5% NaOCl (Sigma-Aldrich, St. Louis, MO, USA) was used to irrigate the canal with a 27-G, side-vented needle placed 1 mm short of the working length. All specimens were kept in a 37°C humidified atmosphere of 95% air and 5% CO2 until used.

Experimental groups

Prepared specimens were randomly divided into six groups (n = 20) depending on the irrigating protocol. In general, side-vented needles, positioned 1 mm short of the working length, were used to irrigate the root canals. The total volume of irrigating solution (14 mL), rate of irrigation (2 mL/min for NaOCl and 1 mL/min for EDTA), and time spent for the rinsing procedure were carefully adjusted to be comparable in every group. The experimental groups [Figure 1] were designed as follows.
Figure 1: Schematic diagram representing the experimental procedures

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Negative control (Group 1)

Five milliliters of normal saline solution (NSS) were used to constantly irrigate the root canal. Then, 1 mL of NSS was left in the canal for 1 min and then refreshed with 3 mL and finally rinsed with 5 mL.

Positive control (Group 2)

Five milliliters of 2.5% NaOCl were used to constantly irrigate the canal. Then, 1 mL of 17% EDTA (Sigma-Aldrich, Madrid, Spain) at pH 7.3 was added into the canal and left for 1 min. Subsequently, the canal was refreshed with 3 mL of 2.5% NaOCl and finally rinsed with 5 mL.

Group 3

Five milliliters of 2.5% NaOCl were used to constantly irrigate the canal. Then, 1 mL of 17% EDTA at pH 7.3 was added into the canal and left for 1 min. Subsequently, the canal was refreshed with 3 mL of 2.5% NaOCl supplemented with MDA for three cycles (1 min/cycle/1 mL). In brief, a 0.4/40 tapered, well-fitting, gutta-percha cone was used by pulling it up and down in short gentle stroke at 100 times/minute cycle. Finally, the canal was rinsed with 5 mL of 2.5% NaOCl.

Group 4

A similar protocol was used as in Group 3, supplemented with EDTA application with one cycle of MDA.

Group 5

A similar protocol was used as in Group 4. EDTA containing 0.25% cetrimide (Ajax Finechem, NSW, Australia) at pH 7.3 was used with one cycle of MDA.

Group 6

A similar protocol was used as in Group 4. SmearClear™ (commercial EDTA, Kerr, Salerno, Italy) was used with one cycle of MDA.

Smear layer evaluation

A 1-mm deep groove was cut along the entire length of each of the mesial and distal surfaces of each specimen using a diamond disk without exposing the root canal. Subsequently, all teeth were split longitudinally using a chisel. The smear layer evaluation was observed and qualitatively described under a scanning electron microscope (SEM) (JSM 6610 LV; JEOL, Akishima, Japan) at 1 mm, 3 mm, and 5 mm of the apical third of the root canal. The amount of the remaining smear layer was evaluated by two double-blinded researchers, previously calibrated using the Gutmann's scoring system.[18]

Gutmann's scores

  • Score 1: Dentinal tubules completely open or debris in <25% of the tubules
  • Score 2: Smear layer occupying about 25%–50%of the dentinal tubules
  • Score 3: More than half of the dentinal tubules were covered with the smear layer, but <75%
  • Score 4: More than 75% of the dentinal tubules were covered with the smear layer.


Intra- and interobserver reliability were tested using the kappa coefficient (κ =0.892, κ =0.821), and a discussion was held to resolve disagreement between the two. The Kruskal–Wallis and the Mann–Whitney U test were applied to evaluate the differences among treatments (P < 0.05).


  Results Top


The smallest amount of smear layer remaining on the root canal surface was observed in the group in which EDTA containing 0.25% cetrimide was used with MDA (Group 5) (P < 0.05), whereas the largest amount of smear layer was observed in the negative control, and gradually decreased in positive control and Groups 3, 4, and 6, respectively [Figure 2]. The results clearly showed that when MDA was applied with both irrigants (groups 4, 5, and 6), the amount of smear layer was significantly reduced compared to the group using MDA with NaOCl alone (Group 3) (P < 0.05). Interestingly, there were no samples in Group 5 having a smear layer score of 2 (more than 75% of dentinal tubules covered with smear layer). In general, the amount of smear layer was significantly less in all groups in which MDA was used.
Figure 2: This figure representing the Gutmann's score of smear layer in each experimental group. The most cleanliness root canal wall was observed in Group 5 (P < 0.05). Focusing on step using MDA, the groups using MDA with both irrigants (Groups 4, 5, and 6) had significantly cleaner root canal wall than the group using MDA with NaOCl alone, documented by dot green line (P < 0.05). Using supplementation of MDA during irrigation, even with NaOCl alone, the cleanliness was significantly improved (P < 0.05) as documented by dot red line. (Different capital letters revealed significant differences among groups). MDA: Manual dynamic agitation, NaOCl: Sodium hypochlorite

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SEM pictures representing the images recorded from the root canal walls 1 mm, 3 mm, and 5 mm of the apical third of the root canal [Figure 3] showed that the groups in which MDA supplementation was used (Groups 3, 4, 5, and 6) [Figure 3]g, [Figure 3]h, [Figure 3]i, [Figure 3]j, [Figure 3]k, [Figure 3], [Figure 3]l, [Figure 3]m, [Figure 3]n, [Figure 3]o, [Figure 3]p, [Figure 3]q, [Figure 3]r had cleaner root canal walls, exhibiting more patent dentinal tubules than did the groups without MDA (negative and positive control) [Figure 3]a, [Figure 3]b, [Figure 3]c, [Figure 3]d, [Figure 3]e, [Figure 3]f. It was clearly seen that in the negative control, using only NSS, the smear layer completely covered all dentinal tubules with some smear plugs [Figure 3]a, [Figure 3]b, [Figure 3]c. In positive control, using NaOCl/EDTA, but without MDA, a thin smear layer and debris still remained on the root canal walls [Figure 3]d, [Figure 3]e, [Figure 3]f. In Groups 4 and 6, fairly clean root canal walls were observed with some smear layer covering the dentinal tubules [Figure 3]j, [Figure 3]k, [Figure 3], [Figure 3]l and [Figure 3]p, [Figure 3]q, [Figure 3]r. The cleanest root canal walls, showing the largest number of patent dentinal tubules, were observed in the group in which EDTA containing 0.25% cetrimide was used with MDA supplementation (Group 5) [Figure 3]m, [Figure 3]n, [Figure 3]o.
Figure 3: Pictures from the scanning electron microscope (×2500) showing root canal walls at 1, 3, and 5 mm of the apical third of the root canal of all experimental groups. Smear layer completely covered the root canal walls in the control group at every levels (a-c). Smear layer was found partially covered the root canal wall with some dentinal plug (arrow) in the group using sodium hypochlorite/ethylenediaminetetraacetic acid without manual dynamic agitation supplementation (d-f). Root canal walls showing clean surfaces with small amount of smear layer being observed in the groups using manual dynamic agitation supplementation (g-r)

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  Discussion Top


The null hypothesis (H0) was there would be no difference in smear layer removal whether MDA or the supplementation of cetrimide in root canal irrigation was utilized. Therefore, in this study, mechanically prepared root canals of straight, single-rooted teeth were assigned to receive six different irrigating protocols, mainly either with NaOCl alone during MDA or with both NaOCl and EDTA during MDA. The results showed that when MDA was used with both irrigants, the amount of smear layer was significantly reduced. Therefore, the null hypothesis was rejected in this study.

The effectiveness of root canal irrigation relates to various factors, for example, volume and flow of solution, needle size, and depth of needle insertion.[19],[20] The direct contact of the solution with the root canal wall is the main requirement, because it permits efficient chemical actions. Therefore, various supplementation techniques, for example, MDA, PUI, sonic, and apical negative pressure, have been proposed to promote irrigants to flow into difficult-to-reach areas of the root canal, because conventional needles have been proven ineffective.[19],[20]

Various studies have revealed that MDA enhances the penetration of irrigants into the apical portion of the root canal, because it disrupts the entrapped gas.[20] In this study, the groups in which MDA was used showed greater smear layer removal than the groups without MDA supplementation, implying that MDA can promote irrigant flow into the root canal. Interestingly, when MDA was used with both NaOCl and EDTA, the smear layer was significantly less than when MDA was used with NaOCl alone. These findings indicate that improvement of flow, the so-called “hydrodynamic effect,”[19] of both irrigants certainly created a cleaner root canal surface. As generally known, NaOCl dissolves organic components, such as dental pulp tissue,[21] whereas EDTA is effective in the removal of inorganic components.[22] Therefore, adequate penetration of both irrigants into the root canal is crucial for effective smear layer removal.

Several studies have reported the comparable effectiveness in smear layer removal among MDA and other irrigation techniques, including PUI, sonic, and others.[12] However, the effectiveness of smear layer removal in the isthmus area is still uncertain and needs to be evaluated.[23] Currently, MDA is a technique of interest because it is a simple method, not requiring any special equipment. A previous study recommended the use of a tapered cone with MDA, because it showed significantly better in dentin debris removal than Safety-Irrigator™ and apical negative pressure systems, such as Endovac™.[24] In our study, a matched tapered gutta-percha cone was used for MDA, with which satisfactory results were observed.

Currently, not only supplemental irrigation techniques are being studied to improve the root canal cleanliness, but also novel irrigating solutions are also being developed as well. A variety of chemical agents have been added to the irrigants to reduce their surface tension, creating better flow and penetration of the solutions.[13],[14] A quaternary ammonium compound, cetrimide, has been adopted because it is a surface tension-reducing agent with powerful antiseptic properties.[15] An earlier study reported satisfactory action of EDTA containing cetrimide in smear layer removal.[1] However, some studies demonstrated that SmearClear™ (commercial EDTA containing cetrimide) did not result in better smear layer removal.[8],[25] Hence, our previous study did explore the suitable concentration of cetrimide to be added into EDTA and found that the addition of high concentrations of cetrimide did not improve the solution properties.[17] A 0.25% concentration of cetrimide was the most appropriate, showing the best solution penetration without deteriorating the microhardness of the root.[26] Therefore, the addition of appropriate surfactants along with MDA supplementation should be included in root canal irrigation protocol in clinical practice.

Despite the promising results, there are some limitations in this study. The root canals that were used in this study were large and straight. Whether similar results could be observed in narrow or curved canals is unknown and could be recommended for further investigation using different methods.


  Conclusions Top


Supplementation of MDA in the final root canal irrigation step significantly promotes a cleaner surface of the mechanically prepared root canal wall at the apical level than without the use of MDA. Furthermore, the use of EDTA containing 0.25% cetrimide significantly improves smear layer removal.

Acknowledgment

This research was supported in part by a research grant from the Faculty of Dentistry, Chiang Mai University. The authors thank VDW Thailand for the provision of equipment, Dr. Penpitcha Wanachantararak and Dr. Thanapat Sastraruji for their guidance and statistical analysis, and Dr. M. Kevin O Carroll, Professor Emeritus of the University of Mississippi School of Dentistry, USA, and Faculty Consultant at Chiang Mai University Faculty of Dentistry, Thailand, for his assistance in the preparation of the manuscript.

Financial support and sponsorship

Young researcher award R000016008.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

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