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ORIGINAL ARTICLE
Year : 2022  |  Volume : 12  |  Issue : 2  |  Page : 175-179

Effect of SmearOFF and ethylenediaminetetraacetic acid on the surface roughness and microhardness of human root canal dentin – An ex vivo study


Department of Conservative Dentistry and Endodontics, Manipal College of Dental Sciences, Manipal, Manipal Academy of Higher Education, Manipal, Karnataka, India

Date of Submission28-Jul-2021
Date of Decision16-Sep-2021
Date of Acceptance02-Oct-2021
Date of Web Publication20-Apr-2022

Correspondence Address:
Dr. Nidambur Vasudev Ballal
Department of Conservative Dentistry and Endodontics, Manipal, Manipal College of Dental Sciences, Manipal Academy of Higher Education, Manipal - 576 104, Karnataka
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/sej.sej_162_21

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  Abstract 

Introduction: The removal of smear layer using chelating agents often involves decalcification of the dentin that affects its physical properties. Hence, the objective of this study was to assess the outcome of SmearOFF and 17% ethylenediaminetetraacetic (EDTA) solutions on the surface roughness and microhardness of human root canal dentin.
Materials and Methods: Twenty-three extracted human mandibular single-rooted premolars were split into 46 sections and placed into an autopolymerizing acrylic resin and were grated flat using silicon carbide abrasive papers. Forty-five samples were arbitrarily categorized into three groups as per experimental solutions used: control group (n = 15), 5 ml of 0.9% saline for 1 min + 5 ml of distilled water for 1 min, EDTA group (n = 15), 5 ml of 17% EDTA for 1 min + 5 ml of distilled water for 1 min, and the SmearOFF group (n = 15), 5 ml of SmearOFF for 1 min + 5 ml of distilled water for 1 min. The samples were then assessed for surface roughness using an atomic force microscope. The same samples were then assessed for microhardness using Vickers microhardness tester. The data were statistically analyzed using one-way analysis of variance, and the mean values were juxtaposed using Tukey's honest significant difference test.
Results: The lowest surface roughness value was seen in the control group, followed by 17% EDTA and SmearOFF in an increasing order. The highest decrease in microhardness was seen in the SmearOFF group samples, followed by 17% EDTA group samples and least in the control group (P < 0.001).
Conclusion: SmearOFF produced more surface roughness and caused a greater reduction in microhardness of root canal dentin in contrast to 17% EDTA.

Keywords: Ethylenediaminetetraacetic microhardness, root canal dentin, SmearOFF, surface roughness


How to cite this article:
Narkedamalli RK, Kini S, Chhaparwal S, Ballal NV. Effect of SmearOFF and ethylenediaminetetraacetic acid on the surface roughness and microhardness of human root canal dentin – An ex vivo study. Saudi Endod J 2022;12:175-9

How to cite this URL:
Narkedamalli RK, Kini S, Chhaparwal S, Ballal NV. Effect of SmearOFF and ethylenediaminetetraacetic acid on the surface roughness and microhardness of human root canal dentin – An ex vivo study. Saudi Endod J [serial online] 2022 [cited 2022 Nov 30];12:175-9. Available from: https://www.saudiendodj.com/text.asp?2022/12/2/175/343548


  Introduction Top


The favorable outcome of an endodontic treatment relies on various factors such as access design, cleaning and shaping, irrigation techniques, and obtaining a three-dimensional seal. Instrumentation of the root canals is responsible for the formation of smear layer that obliterates the dentinal tubules.[1] Of all the methods available for the eradication of debris and tissue remnants from the root canals, irrigation is the best. Flushing of the root canals with appropriate irrigants helps in gross debridement, lubrication, and eradication of microorganisms along with tissue dissolution. Elimination of smear layer preceding obturation is the most important method and is often neglected by most of the clinicians which can greatly affect the prognosis of the endodontic therapy. Irrespective of the consequences of the presence of smear layer on the prognosis of endodontic treatment, it is still crucial to intercept the development of smear layer or eliminate the existing one.[2]

There are various irrigants available for the smear layer removal such as ethylenediaminetetraacetic acid (EDTA), citric acid, maleic acid, and MTAD (mixture of tetracycline isomer (doxycycline), citric acid, and a detergent).[3],[4],[5],[6] Sodium hypochlorite (NaOCl) is a principal irrigant used for routine endodontic practice. It possesses antibacterial as well as tissue-dissolving properties but does not have any effect on the smear layer.[7] Few shortcomings of sodium hypochlorite include cytotoxic effects on the periapical tissues[8] and lack of substantivity. To overcome these disadvantages, irrigants such as chlorhexidine have been suggested as an adjunct which possesses a substantial antibacterial effect[9] and lesser cytotoxic effects. Chlorhexidine, however, has no effect on the smear layer too similar to that of NaOCl. Elimination of smear layer is often accomplished by using an auxiliary irrigant (chelator) such as EDTA.[10]

EDTA is a polyamino carboxylic acid which is the most widely used chelating agent in day-to-day clinical practice. The depth of decalcification of dentin when exposed to EDTA has been reported to be 20–30 μm as per previous literature.[11] EDTA liquid is commonly utilized in concentrations of 17% which can eliminate the smear layer effectively when exposed to the dentin for approximately 1 min.[12]

SmearOFF is an irrigant developed and introduced by Vista Dental Products which is a 2 in 1 solution containing a mixture of both EDTA and chlorhexidine along with a surfactant. It has been reported that there was no formation of precipitate after the interaction of the SmearOFF and NaOCl.[13] SmearOFF has been proven to be more efficacious in terms of smear layer elimination in contrast to 17% EDTA.[14]

Chelation can be defined as physicochemical procedure that involves the uptake of multivalent positive ions by specified chemicals. This can lead to significant changes in the radicular dentin and in the Ca: P ratio[15] by reacting with the calcium ions present in hydroxyapatite. Subsequently, there is a change in the dentinal microstructure which may eventually modify the initial distribution of organic and inorganic components. These changes can cause a decrease in microhardness, increase in the penetrability, and solubility of root canal dentin, thus increasing chances of coronal leakage and bacterial entry.[15]

Surface roughness is an important factor to be considered in terms of adhesion of the adhesive to the surface.[16] The change in the mineral or inorganic portion of the dentin and the elimination of smear layer may cause changes in dentin surface by increasing the roughness. This change may be beneficial in terms of adhesion and bonding of materials.

So far, there have been no studies assessing the outcome of SmearOFF on the surface roughness and microhardness of root canal dentin. Hence, the aim of this research was to analyze the effect of SmearOFF and 17% EDTA on the surface roughness and microhardness of human root canal dentin.


  Materials and Methods Top


Specimen preparation

Institutional Ethical Committee (IEC 668/2020) clearance was procured from Kasturba Medical College and Kasturba Hospital Institutional Ethics Committee (Reg No. ECR/46/Inst/KA/2013/RR-16) for utilizing extracted human teeth. Twenty-three single-rooted human premolars with single canal and mature root were anonymously collected from different clinics and cleaned thoroughly with ultrasonics to remove debris and calculus. Teeth with fracture, caries, or resorption were excluded. The teeth were preserved in 0.2% sodium azide (Millipore Sigma, St. Louis, MO, USA) at 4°C for 30 days. All the teeth were decoronated with the help of a diamond disc (Horico Dental, Berlin, Germany) under water coolant. The pulp tissue was extirpated using a barbed broach (Mani Inc-Tochigi Ken, Utsunomiya-shi, Japan). All the roots were subsequently split lengthwise using a low-speed diamond abrasive disc. The split root portions were then placed in an autopolymerizing acrylic resin with the radicular dentin exposed for facilitating manipulation. The dentin surfaces were then ground smooth with the help of a circular grinding machine using a series of silicon abrasive papers (500, 800, 1000, and 1200 grit) (3M India Ltd., Bengaluru, Karnataka, India) under distilled water followed by final polishing using 0.1-μm alumina suspension (Sol R; Eminess Tec Inc., Monroe, NC, USA) on a rotary felt disc.

Forty-five tooth samples were then arbitrarily categorized into three groups (n = 15) and exposed to different irrigants as per the following protocol:

  1. Control group – The samples were exposed to 5 ml of 0.9% saline (Otsuka Pharmaceuticals India Pvt. Ltd., Ahmedabad, Gujarat, India) for 1 min followed by 5 ml of distilled water for 1 min (Baxter Healthcare Corporation, Illinois, USA)
  2. EDTA group – The samples were exposed to 5 ml of 17% EDTA (NeoEDTA, Orikam Healthcare India Pvt. Ltd., Gurugram, Haryana, India) for 1 min and subsequently to 5 ml of distilled water for 1 min
  3. SmearOFF group – The specimens were exposed to 5 ml of SmearOFF (Vista Dental Products, Racine County, Wisconsin, USA) for 1 min and subsequently to 5 ml of distilled water for 1 min.


All the samples were irrigated in the respective irrigants/experimental solutions (5 ml) as discussed previously and then rinsed thoroughly to remove the remaining irrigants from the dentin surface. The samples were then dried using blotting paper and subjected to testing for surface roughness followed by microhardness.

Surface roughness measurement

The coronal portion of the root canal dentin was then assessed for surface roughness (Ra, μm) using an atomic force microscope (Veeco, Santa Barbara, CA, USA). The AFM probe was maneuvered in contact mode using silicon nitrate pyramidal strips for imaging the root canal dentin. The images [Figure 1] obtained after AFM analysis were analyzed using image processing software for the assessment of the surface roughness. The tip of the AFM probe was moved in contact with the dentin surface at three different locations measuring (10 μm × 10 μm). The average values of the three readings were used as a representative value of surface roughness for each image.
Figure 1: Mean values of surface roughness among the experimental groups

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Microhardness measurement

The same specimens were then subjected to microhardness testing using Vickers Hardness Tester (Matsuzawa Seiki Co Ltd, Tokyo, Japan). The indentations were made using a Vickers diamond indenter at three different locations in the coronal part of the root canal dentin under a 200-g load with a dwelling time of 20 s. The indentations were scrutinized using an optical microscope with a digital camera and image analysis software (HARDNESS PRO, SMS Labs, Sturbridge, Massachusetts, USA), permitting the precise digital computation of the diagonals. The mean length of the representative diagonals of each indentation was used to determine the microhardness value. The illustrative hardness value of every specimen was derived as the mean of the values obtained from the three indentations.

Statistical analysis

The values obtained from both the surface roughness and microhardness testing were statistically probed using one-way analysis of variance and the mean values were compared using Tukey's honest significant difference test. The level of significance was set at (P < 0.05).


  Results Top


The mean value of the surface roughness of the radicular dentin (Ra, μm) of the different experimental groups is demonstrated in [Figure 2]. The lowest surface roughness value was observed in the control group (0.9% saline), followed by 17% EDTA. The samples treated with SmearOFF had the highest surface roughness (P < 0.001). 3D atomic absorption spectroscopy pictures of samples exposed to experimental solutions are presented in [Figure 1].
Figure 2: Three-dimensional atomic force microscopic images of root canal dentin surfaces after treatment with the experimental irrigants

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The mean microhardness values of the samples are given in [Figure 3]. The dentin samples exposed to 0.9% saline (control group) had the lowest reduction in microhardness, followed by 17% EDTA. The highest reduction in microhardness was seen in the samples treated with SmearOFF (P < 0.001).
Figure 3: Mean values of microhardness among the experimental groups

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  Discussion Top


According to the recent concepts of the endodontic treatment, the root canal ought to be surface treated using chelators to eradicate the smear layer formed in the course of biomechanical preparation.[17.18] The application of chelating agents may cause numerous alterations in the physicomechanical characteristics of the root canal dentin.[19] In the current study, the root canal dentin was exposed to chelating agents to assess the changes induced in the surface roughness and microhardness. The irrigants used in the current study are commonly used chelating agents by clinicians. SmearOFF was chosen as the experimental solution for this study because of no formation of precipitate on interaction with sodium hypochlorite.[13] It demonstrated greater surface roughness and higher reduction in microhardness when compared to that of 17% EDTA.

A favorable relation has been reported by Panighi and G'sell with respect to mineral content and microhardness of the tooth.[20] Hence, the calculation of microhardness value could furnish substantial indication regarding the loss or gain of mineral content in the dental hard tissue. The outcome of the current study illustrated that exposure to SmearOFF significantly led to a greater reduction in microhardness in contrast to 17% EDTA. This outcome can be accredited to the superior smear layer elimination capability of SmearOFF in comparison to that of EDTA.[14] The elimination of smear layer can lead to changes in the dentinal structure by altering the calcium and phosphorus levels which, in turn, might lead to the increased reduction of microhardness when compared to that EDTA. However, there are no studies till date to evaluate the changes in the mineral composition of dentin following exposure to SmearOFF and further research is warranted.

The time of exposure of dentin to each irrigating solution was kept as 1 min in accordance with similar studies conducted earlier.[3] These chelating agents can soften the dentinal walls, thus permitting faster biomechanical preparation of the root canals and help in negotiation of calcified or obliterated root canals.[21]

The analysis of surface roughness of the current study revealed that exposure of the dentin to SmearOFF led to the highest increase in the surface roughness when compared to that EDTA. This fact can be related to the better smear layer removal capacity of SmearOFF in contrast to that EDTA.[14] The opening of dentinal tubules and their patency after smear layer removal can lead to an increase in surface roughness. These results are analogous to the earlier research which illustrated a greater smear layer removal in samples treated with SmearOFF when compared to that of EDTA and also the decrease in the microhardness and increase in surface roughness of root canal dentin when exposed to chelating agents such as 17% EDTA.[14],[22] Increased surface roughness can be advantageous in terms of micromechanical bonding of restorative materials and/or root canal sealers which come with a prerequisite of surface irregularities of the adherent for better penetration of the adhesive.[22]

The preceding studies have demonstrated the appropriateness and feasibility of Vickers microhardness test for the evaluation of surface alterations of the dental hard tissue.[20],[21] Even though Knoop's hardness test was employed for assessing the surface alterations of dental hard tissues in other research,[23],[24] Vickers microhardness test was chosen for the present study due to its appropriateness. Use of nanoindentation has been proposed for better understanding and evaluation of the mechanical behavior of dental hard tissue.[25] Nanoindentation considers both the plastic and elastic deformation along with the time-dependent effects[26] unlike the traditional microhardness tests that require visualization and computation of indents and take only plastic deformation into account. Studies have reported that nanoindentation has been used to assess the alterations in the dental hard tissue contents in the course of demineralization–remineralization procedures.[27] The present study has been performed ex vivo, and hence, it was not possible to mimic the root canal environment and nanoindentation technique would have provided more accurate results. Hence, further studies using the nanoindentation technique should be performed to study the surface changes caused by SmearOFF on root canal dentin.


  Conclusion Top


Owing to the shortcomings of the current study, it can be concluded that SmearOFF produced more surface roughness and caused greater reduction in microhardness of root canal dentin in contrast to 17% EDTA. 0.9% saline (control) did not alter the surface roughness or microhardness of the root canal dentin.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

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Torabinejad M, Handysides R, Khademi AA, Bakland LK. Clinical implications of the smear layer in endodontics: A review. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2002;94:658-66.  Back to cited text no. 17
    
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Rao S, Ballal NV, Narkedamalli RK. Efficacy of SmearOFF, maleic acid, and ethylenediaminetetraacetic acid combined with sodium hypochlorite in removal of smear layer from curved root canals: In vitro study. Saudi Endod J 2021;11:221-7.  Back to cited text no. 18
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Doğan H, Çalt S. Effects of chelating agents and sodium hypochlorite on mineral content of root dentin. J Endod 2001;27:578-80.  Back to cited text no. 19
    
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Meredith N, Sherriff M, Setchell DJ, Swanson SA. Measurement of the microhardness and young's modulus of human enamel and dentine using an indentation technique. Arch Oral Biol 1996;41:539-45.  Back to cited text no. 23
    
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Hosoya Y, Marshall SJ, Watanabe LG, Marshall GW. Microhardness of carious deciduous dentin. Oper Dent 2000;25:81-9.  Back to cited text no. 24
    
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Khurana S, Gehlot PM, Hegde U. Surface nanohardness of normal and fluorosed enamel adjacent to restorative materials: An in vitro study and polarized light microscopy analysis. J Contemp Dent Pract 2020;21:1034-41.  Back to cited text no. 25
    
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