A comparative evaluation of smear layer removal using two rotary instrument systems with ethylenediaminetetraacetic acid in different states: A SEM study :[PAUTHORS], Indian Journal of Dental Research (IJDR)

ORIGINAL RESEARCH
Year : 2011 | Volume : 22 | Issue : 1 | Page : 10--15

A comparative evaluation of smear layer removal using two rotary instrument systems with ethylenediaminetetraacetic acid in different states: A SEM study

KK Wadhwani, AP Tikku, Anil Chandra, Vijay Kumar Shakya
Department of Conservative Dentistry & Endodontics, Faculty of Dental Sciences, Chhatrapati Shahuji Maharaj Medical University (earlier KGMC), Lucknow, India

Correspondence Address:
K K Wadhwani
Department of Conservative Dentistry & Endodontics, Faculty of Dental Sciences, Chhatrapati Shahuji Maharaj Medical University (earlier KGMC), Lucknow
India

Abstract

Aim: The aim of the study was to evaluate the ability of 17% ethylenediaminetetraacetic acid (EDTA) solution and 19% EDTA gel to remove debris, and smear layer produced during root canal preparation with two NiTi files systems, Mtwo and Protaper. Materials and Methods: Twenty freshly extracted human anterior teeth with single root canal were collected. The crowns were sectioned at the cemento-enamel junction, and working length was measured. These samples were randomly divided into four groups of five samples each. In each group, 2ml of 3 % sodium hypochlorite solution was used with first instrument. The groupings were as follows. Group 1: 2 ml of 17% EDTA solution and 2 ml of 3% NaOCl were used alternatively each time a new file was employed. This group was prepared with Mtwo rotary files. Group 2: The samples in this group was prepared with Mtwo rotary files. EDTA gel (19%) was used and the samples were irrigated with 2 ml of 3% NaOCl. NaOCl and EDTA gel were used alternatively. Group 3: Five samples were prepared with Protaper file. Irrigation regime was the same as in Group 1. Group 4: Five samples were prepared with Protaper files and irrigation regime was the same as in Group 2. SEM study was done and the collected data were submitted for statistical analysis. Results: There was no statistically significant difference with the varied instruments used (Mtwo and Protaper files), and 17% EDTA solution and 19% EDTA gel. Conclusion: Both the NITI instruments produced a similar dentin surface on root canal wall when used with EDTA gel and EDTA solution

How to cite this article:
Wadhwani K K, Tikku A P, Chandra A, Shakya VK. A comparative evaluation of smear layer removal using two rotary instrument systems with ethylenediaminetetraacetic acid in different states: A SEM study.Indian J Dent Res 2011;22:10-15

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Wadhwani K K, Tikku A P, Chandra A, Shakya VK. A comparative evaluation of smear layer removal using two rotary instrument systems with ethylenediaminetetraacetic acid in different states: A SEM study. Indian J Dent Res [serial online] 2011 [cited 2023 Jun 6 ];22:10-15
Available from: https://www.ijdr.in/text.asp?2011/22/1/10/79967

Full Text

The effectiveness of endodontic space cleaning depends on both instrumentation and irrigation. Irrigation plays a main role in successful debridement and disinfection. The most widely used irrigant for root canal treatment is sodium hypochlorite (NaOCl) at concentrations of 0.5-5.25%.

The tissue-dissolving capacity and microbicidal activity of NaOCl make it an excellent irrigating solution but it has only limited effect on the dissolution of smear layer. Acid solutions have been recommended for removing the smear layer, including sodium salt of ethylenediaminetetraacetic acid (EDTA), most active at a concentration of 15-17% and pH of 7-8; citric acid solutions used at concentrations of 10, 25, and 50%; and orthophosphoric acid at concentrations of 10, 32, and 37%. [1]

The main purpose of root canal instrumentation is to shape and clean the root canal, which includes the removal of infected dentin and organic tissue by instrumentation and irrigation system.

All the endodontic instruments create debris and smear layer as a consequence of their action on canal walls.

This layer can form two zones: the first zone of 1-2 mm thickness is made up of organic matter and dentin particles and the second zone, extending into dentinal tubules to a depth of 40 mm (smear plug), is formed largely of dentin chips. [2]

It is known that smear layer may harbor bacteria, preventing the canal from being disinfected. Some researchers have the opinion that smear layer can prevent irrigants and medicaments from gaining access to the infected dentinal tubules and may act as an obstacle to the complete sealing of the root canal. In addition, an infected smear layer containing bacteria and necrotic tissue may act as a substrate for bacteria, letting them penetrate deeper into the dentinal tubules.

According to American Association of Endodontists (2000), smear layer is defined as a surface film of debris retained on dentin or other surface, after instrumentation with either rotary instruments or endodontic files. It consists of dentin particles' remnants of vital or necrotic pulp tissue, bacterial components and retained irrigants. [3]

In addition, it has been demonstrated that the removal of this layer promotes dentin permeability, [4] enhancing diffusion and the action of intracanal medicament, [5] allowing and producing greater penetration of filling material into lateral canals and dentinal tubules. [6],[7]

Generally, it is considered and desired to remove the smear layer because of its potential deleterious effects.

Currently, the chelating agents like EDTA are extensively being used to remove the smear layer formed during the chemo-mechanical preparation of the root canals. However, there are few studies comparing the action of these chelating agents in their liquid and gel forms.

The most popular of the chelating agents is EDTA, introduced by Nygaard-Ostby. [8] EDTA as an additive supports cleanliness of peripulpal dentin by demineralizing the superficial, irregular smear layer and smear plugs. Different types of EDTA preparation have gained popularity because almost all the manufacturers of nickel-titanium (NiTi) instruments recommend the use of lubricants during rotary root canal preparation. [9]

Investigations have shown that different morphology designs of rotary NiTi instruments result in variation of their debris removal and smear layer production. [10],[11]

Aims and objectives

The aim of the study was to evaluate the ability of 17% EDTA solution and 19% EDTA gel to remove debris, and smear layer produced during root canal preparation with two NiTi file systems, Mtwo and Protaper.

Materials and Methods

Materials used in this study

19% EDTA gel (MD-Chel Cream, Meta Biomed Co., Ltd., Mandaluyong, Korea) supplied in 5.4 ml (72gm)17% EDTA solution (CANALLARGE, Ammdent, Mohali, India)3% Sodium hypochlorite solution (Vishal Diagnostics, Lucknow, India)Protaper rotary files (Dentsply, Tulsa, OK, USA)Mtwo files (VDW, Munich, Germany)

Twenty freshly extracted human anterior teeth with single root canal were collected from Department of Oral and Maxillofacial Surgery, Faculty of Dental Sciences, C.S.M. Medical University, Lucknow.

The crowns were sectioned at the cemento-enamel junction and roots were immersed in physiological saline solution for 72 hours for hydration.

The working length was measured by deducting 1 mm from the length recorded when tips of #15 K-files (Dentsply Meallefer Tulsa, OK, USA) were visible at the apical foramina.

These samples were randomly divided into four groups of five samples each.

Group 1: In this group, 2 ml of 3% sodium hypochlorite solution was used with first instrumentation. Then, 2 ml of 17% EDTA solution and 2 ml of 3% NaOCl were used alternatively each time a new file was employed. This group was prepared with Mtwo rotary files according to manufacturer's recommendation.

Group 2: The samples in this group were also prepared with Mtwo rotary files. In this group, 19% EDTA gel was introduced in the canal with first instrument. After that, 2 ml of 3% NaOCl and 2 ml of 19% EDTA gel (measured in a 2 ml syringe) were used alternatively until the end of instrumentation.

Group 3: This group was prepared with Protaper file as per manufacturer's recommendations, In this group, 2 ml of 3% sodium hypochlorite solution was used with first instrumentation, then 2 ml of 17% EDTA solution and 2 ml of 3% NaOCl were used alternatively each time a new file was employed.

Group 4: This group was prepared with Protaper files. Irrigation regime in this group was 19% EDTA gel introduced in the canal with first instrument, and after that, 2 ml of 3% NaOCl and 2 ml of 19% EDTA gel were used alternatively until the end of instrumentation.

Finally, the root canals were irrigated with 5 ml of distilled water and dried with paper points and stored in dry sterilized containers and submitted for scanning electron microscope (SEM) study.

Sample preparation for SEM examination

Longitudinal grooves were made using a slow-speed carborundum disk on the root surface. Then, the root was split with a stainless chisel into two corresponding halves. The most suitable hemisectionof each tooth was selected for SEM examination.

The specimens were analyzed at 2000× magnification at middle third of the root.

Results

The cleaning of root canal walls was evaluated by an examiner who was unaware of the irrigation regimen and preparation mode employed for each group. Scoring criteria were according to the rating system developed by Rome et al.[12]

0: No smear layer; dentinal tubule open and free from debris

1: Moderate smear layer, outlines of dentinal tubules visible or partially filled with debris

2: Abundant smear layer preventing the visualization of dentinal tubules opening

The attributed scores were tabulated and submitted for statistical analysis.

Inference

With varied instruments used (Mtwo and protaper files), 17% EDTA solution seems to have an edge over 19% EDTA gel as the results obtained with 19% EDTA gel were less consistent and showed higher variability, But the difference was not statistically significant.

Discussion

There is not much literature available about the effectiveness of EDTA gel on root canal wall. The association of EDTA and NaOCl solution has proved effective in removing the smear layer formed during endodontic instrumentation. [13]

EDTA acts upon the inorganic components of the smear layer, and decalcify the peri and intertubular dentin and leaves the collagen exposed. Subsequently, the use of NaOCl dissolves the collagen, leaving the entrances of the dentinal tubules more open and exposed. [13] The duration for which these solutions remain in contact with the canal walls can be varied. [13]

In the present study, the cleaning efficacy of EDTA gel (19%) and solution (17%) was evaluated, with two commercially available NiTi file systems, Mtwo and Protaper [Table 1], [Table 2], [Table 3] and [Table 4]. Sufficient dissolution of the smear layer takes place at the middle third of root canals when using 17% EDTA solution and 19% EDTA gel preparation with either of the file systems [Figure 1], [Figure 2], [Figure 3] and [Figure 4].{Figure 1}{Figure 2}{Figure 3}{Figure 4}{Table 1}{Table 2}{Table 3}{Table 4}

In a recent study; irrigation with liquid 17% EDTA in comparison to 24% EDTA gel in human canine teeth showed no significant difference in smear layer removal. [14]

EDTA lubricants are well documented and commonly used in endodontics to remove the smear layer attached to dentinal matrix and to minimize the risk of instrument fractures. Analysis of demineralizing effects of paste-type 15% EDTA showed a reduction of weight loss and micro-hardness, but it remains unclear whether this has any clinical significance. [8]

Contact of EDTA with the periapical tissue cannot be excluded during endodontic instrumentation, but neither the liquid nor the gel application forms will reach a toxic level in the human body compared to concentrations used in the therapy of heavy metal intoxication. But this risk of periapical tissue damage or cytotoxicity can be reduced by using a material with thixotropic characters rather than a liquid substance. [9]

A study conducted a Osario et al. (2005) concluded that 0.1 M EDTA improved the resin-dentin bond strength of a total-etch adhesive when challenged with 10% NaOCl, in comparison to pretreatment with phosphoric acid using a total-etch adhesive or a self-etching adhesive. [15]

In the present study, biomechanical preparation of samples was done with two different NiTi files, Mtwo and Protaper. Mtwo has a cross-sectional design that resembles that of the S files. [16] The sequence used corresponded to the manufacturer's instructions. Five instruments were used: Mtwo 10/0.04, Mtwo 15/0.05, Mtwo 20/0.06, Mtwo 25/0.06, and Mtwo 30/0.05. Initial negotiation of root canal space was performed with a #15 manual K-file (FKG) used in a watch-winding motion to assure the presence of a glide path as far as the foramen. Mtwo system requires the introduction of each instrument directly to working length (WL), maintaining permanent rotation (300 r.p.m.), with slight in-and-out movement and whilst gradually forcing apically [Figure 1] and [Figure 2].

The protaper cross-sectional design resembles that of a reamer with three machined cutting edges and convex core. The ability of rotary instruments to remove dentine and pulpal debris during shaping is obviously connected to the flute and cross-sectional design. [17] The sequence used in this study was in a crown-down fashion [Figure 3] and [Figure 4].

All the instruments were inserted into root canal in a continuous in-and-out movement; they were never forced apically. Both the instruments present positive rake angles, progressive pitch in apical coronal direction and a non-cutting tip. [18],[19]

Despite differences being observed, this study demonstrates that both the NiTi instruments produced a similar dentine surface on root canal walls for all parameters considered [Figure 1], [Figure 2], [Figure 3] and [Figure 4].

The use of lubricant gel is recommended with all rotary endodontic instruments, as it acts as a chelator as well as a lubricant. As most of the gels available have EDTA as one of the main constituents, it is recommended that instead of 17% liquid EDTA, 19% gel should be preferred as the lubricant and smear layer remover.

Although the action of gel and solution forms of EDTA is the same, the advantage of lubricant in gel form is that it does not extrude from the root canal. Hence, gel should be preferred over liquid EDTA because of its thixotropic nature.

Conclusion

No statistically significant difference between EDTA solution and gel regimens was observed [Table 1].

In the present study, both instruments (Protaper and Mtwo) were evaluated with EDTA solution and gel regimens. Despite differences being observed, this study demonstrated that both the NiTi instruments produced a similar dentin surface on root canal wall for all parameters considered [Table 2].

In 17% EDTA solution group, the mean score of smear layer removal was found to be 0.50 ± 0.53, whereas in 19% EDTA gel group, the score was 0.70 ± 0.67. Though the mean value for 19% EDTA gel was slightly higher as compared to that in 17% EDTA solution, the difference between the two groups was not significant statistically (P = 0.470)

The box plot shows the distribution of minimum, maximum and median values in the two groups [Graph 1], [Graph 2], [Graph 3] and [Graph 4]. It is seen that in the solution group, the minimum value was 0 and the maximum value was 1. The median value was 0.50, whereas in gel group the minimum value was 0 and the maximum value was 2, while the median was No difference in mean score of two instruments was seen. Both the instruments showed the mean score to be 0.60.

[SUPPORTING:1]

[SUPPORTING:2]

[SUPPORTING:3]

[SUPPORTING:4]

Although the mean score obtained by 19% EDTA gel (0.80 ± 0.84) was just double of that obtained in 17% EDTA solution, the difference between two groups was not significant statistically (P = 0.470)

No difference in mean value was seen between the two agents when Protaper file was used for instrumentation

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