Saudi Endodontic Journal

: 2021  |  Volume : 11  |  Issue : 1  |  Page : 19--23

Comparative evaluation of various chelating agents on the microhardness of root canal dentin: An in vitro study

Prateek Jalan, Tina Puthen Purayil, Nidambur Vasudev Ballal, Sneha Suresh Kumar 
 Department of Conservative Dentistry and Endodontics, Manipal College of Dental Sciences, Manipal, Manipal Academy of Higher Education, Manipal, Karnataka, India

Correspondence Address:
Dr. Tina Puthen Purayil
Department of Conservative Dentistry and Endodontics, Manipal College of Dental Sciences, Manipal Academy of Higher Education, Manipal, Karnataka


Introduction: This study aims to compare and evaluate the effects of Irritrol and 17% ethylenediaminetetraacetic acid (EDTA) on the root dentin microhardness. Materials and Methods: A diamond disc was used to decoronate 15 human noncarious maxillary central incisors at the cemento-enamel junction. Thirty root segments were set in an acrylic block with the dentinal surface exposed. All root segments were irrigated with sodium hypochlorite solution before treating with test solutions. Microhardness (Vickers hardness number [VHN]) values of each specimen were determined using Vickers indenter before and after treatment with test solutions (Irritrol and EDTA). The mean lengths of the two diagonals formed due to indentation were used to compute the microhardness value. VHNs were determined using these measurements. Mean differences between (Irritrol and EDTA) and within the (before and after) group were compared using Student's t-test. Intragroup comparison was done using F-test (one-way ANOVA) at different areas of radicular dentin. α =0.05 was the set level of significance. Results: Both the test solutions showed a reduction in microhardness in coronal and middle third of root canal dentin, but the reduction in apical third (P < 0.05) was significantly more with respect to EDTA when compared to Irritrol. Conclusion: Irrigation using 17% EDTA and Irritrol decreased the root dentin microhardness; however, in the apical third, there was a less decrease in microhardness by Irritrol when compared to EDTA.

How to cite this article:
Jalan P, Purayil TP, Ballal NV, Kumar SS. Comparative evaluation of various chelating agents on the microhardness of root canal dentin: An in vitro study.Saudi Endod J 2021;11:19-23

How to cite this URL:
Jalan P, Purayil TP, Ballal NV, Kumar SS. Comparative evaluation of various chelating agents on the microhardness of root canal dentin: An in vitro study. Saudi Endod J [serial online] 2021 [cited 2021 Jan 25 ];11:19-23
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The goal of the root canal treatment is to eradicate the preexisting inorganic and organic remnants of operative procedures and also to reduce microbial volume and microbial by-products. Root canal irrigants have a significant role to minimize the number of bacteria, necrotic tissue, and residual debris that is formed due to root canal instrumentation.[1] However, a single endodontic irrigant does not have all of the required properties, and a mixture of two or more irrigants is required to attain desirable effects.[2]

Sodium hypochlorite (NaOCl) has been used most frequently as an irrigant during root canal treatment, and it is available in different concentrations ranging from 0.5% to 5.25%. Due to its broad-spectrum antimicrobial actions, it is used as an adjunct in endodontic therapy. NaOCl has the capacity to dissolve the organic structures of the root canal. The volume and contact time of NaOCl along with the tissue area exposed to the solution contribute to its tissue-dissolving effect. Regardless of its action on the organic components of the root canal, there is no effect on the inorganic components.[3] The reduced dentin microhardness may be due to the dissolving effect of NaOCl on the dentin collagen component. It can also be explained by the phosphate level reduction when NaOCl comes in contact with dentin.[4]

During root canal instrumentation, a smear layer is formed which adheres to the walls of the canal and seals the orifices of dentinal tubules. The use of chelators such as ethylenediaminetetraacetic acid (EDTA), maleic acid, and citric acid has been attempted for the smear layer removal from an instrumented root canal.[5],[6] This may result in significant changes of root dentin both physically and mechanically and eventually may cause a decrease in dentin microhardness. A decrease in microhardness can influence the capacity of sealers to adhere to and seal the walls of the root canal.[5],[7] EDTA and NaOCl have gained wide acceptance as an effectual regimen for irrigation to remove inorganic and organic constituents of the smear layer.[8] Oliveira et al. reported that EDTA and NaOCl solutions decrease the root canal dentin microhardness in comparison to different concentrations of chlorhexidine (CHX).[9] Unaffected root dentin has a microhardness between 40 and 75 Vickers Hardness Number (VHN).[10],[11]

Irritrol, two-in-one endodontic irrigating solution, has been introduced which consists of CHX, EDTA, and a proprietary blend of surfactants. According to the manufacturer, Irritrol is a one-step disinfecting endodontic irrigant, used as a final rinse following irrigation with NaOCl.[12] In the study done by Agrawal et al., Irritrol was more effective in improving the postobturation apical seal compared to 7% maleic acid when used as a final irrigant.[13] Until now, no studies have compared the consequence of Irritrol and 17% EDTA on the microhardness of root dentin. Hence, this study aimed to compare and assess the effects of Irritrol and 17% EDTA on the root dentin microhardness.

 Materials and Methods

After acquiring ethical clearance (Institutional Ethical Committee [IEC]-715/2017) from the IEC, 15 noncarious human maxillary central incisors, after surface debridement with a scaler, were kept in 0.2% thymol solution (Spectrum chemical mfg., NJ, USA) at 4°C until the start of the experiment. Following tooth decoronation at the cemento-enamel junction with the use of a diamond disc (Horico, Berlin, Germany), pulp tissue removal was done with a barbed broach (Diadent, chungcheongbuk-do, Korea). A diamond disc was used to vertically section the roots from the cervical to the apical extent splitting the roots into buccal and lingual components. Following sectioning of the teeth, the sections were cleaned with distilled water to remove any traces of debris. The thirty sectioned segments were set in an acrylic block while exposing the dentin surface. This surface was flattened and smoothened using silicon carbide abrasive papers (SNAM abrasives, Bangalore, India) of decreasing roughness (180, 320, 600, 800, and 1000 grit) on a circular grinding machine with distilled water to eliminate surface scratches. The sectioned segments were finally polished on a rotary disc with alumina (fine particle size) suspension. The one half of each of the sections served as the control, whereas the other half served as the test group. Before the test solutions were applied to each root section, the root dentin microhardness of all the thirty specimens were evaluated using Vickers indenter (Matsuzawa, MMT-X, Japan) with a load of 200 g and a dwell time of 20 s. At a gap of 100 μm from the pulp–dentin junction, three indentations were made in one half of the coronal, middle, and apical parts of the root sections. An optical microscope with image analysis software and a digital camera was used to visualize the diamond-shaped indentations, enabling the precise digital measurement of the diagonals of the diamond-shaped indentations. The microhardness value was computed using the mean length of the diagonals. These estimations were converted into the corresponding VHNs. Later, the root segments were irrigated with a 5 ml solution of 5.25% NaOCl (Enzed chloro products, Hyderabad, India) for 1 min. The specimens were then divided randomly into two groups of n = 15.

Group 1: Irritrol (EDS, NJ, USA)Group 2: 17% EDTA (Merck, Darmstadt, Germany).

Using an open-ended 27 G needle, 5 ml of the test solution was directly delivered on the root dentin, ensuring the other half of the root was uniformly covered, for 1 min. Finally, 5 ml of distilled water (KMC Pharmacy, Manipal, Karnataka, India) was used to rinse all the samples to remove all residues of the test irrigants. Again, three indentations were made at the other half of the coronal, middle, and apical segments of the sections at 100 μm from the pulp-dentin interface, and the root canal dentin microhardness was measured by the same procedure as mentioned above.

Statistical analysis

Analysis of the data was done using the SPSS IBM, version 22.0, Chicago, IL, USA. Student's t-test was utilized for comparison of the mean differences between the group of samples irrigated with irritrol and EDTA and within (before and after) group. Intra-group comparison within each group was done using the F-test (one-way ANOVA) at different areas of radicular dentin. α =0.05 was set as the level of significance.


In this study, each specimen acted as its own control. Pre- and post-microhardness were in the acceptable range for both the irrigants (Irritrol and EDTA). As compared to baseline measurements, both irritrol and EDTA lead to a decrease in the root canal dentin microhardness.

Intragroup comparison of the radicular microhardness between all the root canal segments when treated with irritrol or EDTA is depicted in [Table 1] and [Table 2]. Pre- and post-treatment microhardness values of EDTA group demonstrated a significant microhardness reduction at each third of the radicular dentin (P < 0.001). However, irritrol group had a significantly decreased level of microhardness only in the coronal and middle parts of the radicular dentin (P < 0.001 and P < 0.05), with no statistically significant reduction in the apical part (P = 0.06).

However, on intergroup comparison, both irritrol and EDTA showed statistically significant differences in the reduction in microhardness only (pre- and post-treatment) at the apical portion of radicular dentin (P < 0.05) [Table 3]. At the coronal and middle thirds of radicular dentin, the decrease in microhardness proved to be statistically insignificant (P = 0.9).{Table 1}{Table 2}{Table 3}


The root canal dentin hardness in this study differed at the coronal, middle, and apical thirds but was well within the range documented in existing literature. In this study, all the specimens were treated with experimental solutions for 1 min as suggested by Calt and Serper et al., that duration of 1 min with 17% EDTA was sufficient.[14]

The present study revealed that the use of both the experimental irrigants (17% EDTA and Irritrol) showed a decrease in dentin microhardness. However,? after using irritrol, the reduction in microhardness in the apical third was less in comparison to 17% EDTA. This finding is in accordance with the studies done by previous researchers in which EDTA showed a significantly higher reduction in microhardness when compared to other irrigants, especially in the apical third.[15],[16],[17],[18],[19] This could be due to variations in the structure at the apical region of the human teeth such as, accessory canals, varying quantity of irregular secondary dentin, cementum-like tissue, dentin sclerosis, and reduced amounts of noncollagenous proteins (NCP's) which have been suggested as possible reasons for the significant changes at the apical region.[20] The removal of smear layer by irritrol according to the manufacturer's assertion is less aggressive compared to the conventional irrigants, thus resulting in less demineralization of root dentin.[12]

Seventeen percent EDTA demonstrated a marked decrease in dentin microhardness in all the thirds when compared to irritrol and this result is in accordance with the results obtained in several studies, which showed that EDTA can lead to a significant decrease in the root canal dentin microhardness in comparison to other irrigants.[21],[22],[23],[24]

Standardization of the prepared samples was done by analyzing the Vickers hardness values of every tested group before treatment. Furthermore, posttreatment indentations were made at symmetrical constant points at the same locations. Tooth sectioning was done longitudinally, as Curz-Filho et al. observed that it will accurately depict clinical situations.[25]

Microhardness testing is a simple and nondestructive technique to determine the root canal hardness. The diagonal of the Vickers indenter is a third of the dimension of the Knoop indenter's longest diagonal, and there is double the penetration into the sample for the Vickers indenter as compared to the Knoop indenter for a particular load. Therefore, the Vickers test is not as susceptible to surface conditions but more susceptible to the errors of measurement when uniform loads are applied. However, Vickers hardness test was preferred in this study as it is more practical for the evaluation of surface microhardness changes in deeper hard tissues. Due to its highly accurate readings, and the use of a single indentation type for all surfaces, this method is widely accepted.[26]

According to Pashley et al., dentin showed a declining microhardness from superficial to deep areas. Dentin microhardness showed an inverse relation with tubular density. In addition, the irrigation solution contact period also plays a determining role in the microhardness of dentin.[27]

A significant decrease in dentin microhardness can result in weakening of the tooth. In a clinical scenario, weakening of the tooth structure is detrimental. Hence, an irrigant such as irritrol can be used, which is efficient enough to cleanse the canal, and also not detrimental to the microstructural integrity of the tooth.

A limitation of this study is that the fluid dynamics used does not mimic the clinical situation, as the teeth were split, and thus a vapor lock effect was not achieved. In addition, instead of using microhardness, nanoindentation method could have been employed. It allows the measurement of the elastic modulus and hardness of the small features and can characterize early damage to the hard tissues caused by external factors.

As this study did not mimic the entire clinical scenario, a future study where the clinical environment is mimicked could help to validate our findings.


On the basis of the results obtained from the study, it can be concluded that both 17% EDTA and irritrol caused decreased microhardness of root dentin with irritrol showing significantly less reduction in root dentin microhardness in the apical third.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.


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