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Effect of Glycolic Acid, Maleic Acid, and EDTA in the Removal of Smear Layer from Root Canal Dentin

ABSTRACT

Objective:

To assess the efficacy of 5% Glycolic Acid (GA), 17% ethylenediaminetetraacetic acid (EDTA) and 7% maleic acid (MA), in removing the smear layer (SL).

Material and Methods:

For the experiment, forty single-rooted human teeth were selected. To perform the chemo‑mechanical preparation, the root canals were instrumented to an apical size of #30, along with simultaneous irrigation of 2.5% NaOCl. The samples were allotted to the experimental groups based on the final irrigating solution (n=10): (1) The GA group: 05%, (2) the EDTA group: 17%, (3) the MA group: 7%, and (4) the control group: Distilled water. The teeth were evaluated for the presence or absence of SL using SEM.

Results:

Comparing the 5% GA, 7% MA and 17% EDTA groups, no statistically significant differences were found at the coronal and middle thirds (p>0.05). However, in the apical third, MA had greater efficacy than EDTA (p=0.002) and GA (p=0.041), with a significant difference in the SL removal, while there was no significant difference between the latter (p=0.148).

Conclusion:

Thus, it was concluded that 7% maleic acid as a final irrigating solution is more efficacious than 17% EDTA and 5% glycolic acid in eliminating the smear layer from the apical portion of the root canal.

Keywords:
Endodontics; Root Canal Therapy; Smear Layer; Edetic Acid

Introduction

Endodontic treatment through instrumentation seeks to achieve the objective of mechanically debriding the root canal and facilitating the delivery of disinfecting solutions and, thereby, their action. However, endodontic files, while instrumenting the canal, produce debris comprising of dentin remnants, organic tissue, and bacteria, called the smear layer (SL) [1[1] McComb D, Smith DC, Beagrie GS. The results of in vivo endodontic chemomechanical instrumentation--a scanning electron microscopic study. J Br Endod Soc 1976; 9(1):11-18. https://doi.org/10.1111/j.1365-2591.1976.tb01231.x
https://doi.org/10.1111/j.1365-2591.1976...
,2[2] Gwinnett AJ. Smear layer: morphological considerations. Oper Dent Suppl 1984; 3:2-12.]. This layer interferes with the infiltration of irrigants and medicaments into the tubular structure of dentin. Thereby restricting their effects on bacteria deep-seated within these tubules [3[3] Wang Z, Shen Y, Haapasalo M. Effect of smear layer against disinfection protocols on Enterococcus faecalis-infected dentin. J Endod 2013; 39(11):1395-1400. https://doi.org/10.1016/j.joen.2013.05.007
https://doi.org/10.1016/j.joen.2013.05.0...
]. It can also resist the bonding of root canal sealers to the dentin walls, increasing the potential of microleakage [4[4] Clark-Holke D, Drake D, Walton R, Rivera E, Guthmiller JM. Bacterial penetration through canals of endodontically treated teeth in the presence or absence of the smear layer. J Dent 2003; 31(4):275-81. https://doi.org/10.1016/s0300-5712(03)00032-0
https://doi.org/10.1016/s0300-5712(03)00...
,5[5] Kokkas AB, Boutsioukis ACh, Vassiliadis LP, Stavrianos CK. The influence of the smear layer on dentinal tubule penetration depth by three different root canal sealers: an in vitro study. J Endod 2004; 30(2):100-2. https://doi.org/10.1097/00004770-200402000-00009
https://doi.org/10.1097/00004770-2004020...
].

Ethylenediaminetetraacetic acid (EDTA) and sodium hypochlorite (NaOCl) in combination are often used in irrigation regimens to eradicate the SL [6[6] Mello I, Kammerer BA, Yoshimoto D, Macedo MC, Antoniazzi JH. Influence of final rinse technique on ability of ethylenediaminetetraacetic acid of removing smear layer. J Endod 2010; 36(3):512-4. https://doi.org/10.1016/j.joen.2009.11.004
https://doi.org/10.1016/j.joen.2009.11.0...
]. However, EDTA, while an effective chelator, has a downside as its cytotoxic, ineffective in the critical apical third in removing the SL, hinders the bond between resin sealer and root canal dentin and results in the reduction of freely available chlorine ions when used alongside NaOCl [7[7] Ballal NV, Kundabala M, Bhat S, Rao N, Rao BS. A comparative in vitro evaluation of cytotoxic effects of EDTA and maleic acid: root canal irrigants. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2009; 108(4):633-8. https://doi.org/10.1016/j.tripleo.2009.05.039
https://doi.org/10.1016/j.tripleo.2009.0...

[8] Neelakantan P, Subbarao C, Subbarao CV, De-Deus G, Zehnder M. The impact of root dentine conditioning on sealing ability and push-out bond strength of an epoxy resin root canal sealer. Int Endod J 2011; 44(6):491-8. https://doi.org/10.1111/j.1365-2591.2010.01848.x
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-9[9] Grawehr M, Sener B, Waltimo T, Zehnder M. Interactions of ethylenediamine tetraacetic acid with sodium hypochlorite in aqueous solutions. Int Endod J 2003; 36(6):411-7. https://doi.org/10.1046/j.1365-2591.2003.00670.x
https://doi.org/10.1046/j.1365-2591.2003...
].

Maleic Acid (MA), an organic acid in concentrations of seven percent, has been introduced as an alternative irrigating solution to remove the SL, and was found to be more effective in the apical third as opposed to EDTA [10[10] Ballal NV, Kandian S, Mala K, Bhat KS, Acharya S. Comparison of the efficacy of maleic acid and ethylenediaminetetraacetic acid in smear layer removal from instrumented human root canal: a scanning electron microscopic study. J Endod 2009; 35(11):1573-6. https://doi.org/10.1016/j.joen.2009.07.021
https://doi.org/10.1016/j.joen.2009.07.0...
,11[11] Ulusoy Öİ, Görgül G. Effects of different irrigation solutions on root dentine microhardness, smear layer removal and erosion. Aust Endod J 2013; 39(2):66-72. https://doi.org/10.1111/j.1747-4477.2010.00291.x
https://doi.org/10.1111/j.1747-4477.2010...
]. Relative to EDTA, it was found to be less cytotoxic and enhanced the bond of resin-based sealer to root dentin [8[8] Neelakantan P, Subbarao C, Subbarao CV, De-Deus G, Zehnder M. The impact of root dentine conditioning on sealing ability and push-out bond strength of an epoxy resin root canal sealer. Int Endod J 2011; 44(6):491-8. https://doi.org/10.1111/j.1365-2591.2010.01848.x
https://doi.org/10.1111/j.1365-2591.2010...
].

Among the group of alpha hydroxy acids like citric acid and MA, Glycolic Acid (GA) is commonly extracted from sugarcane. It has been suggested as an alternative to EDTA owing to its biodegradability [12[12] Bello YD, Porsch HF, Farina AP, Souza MA, Silva EJNL, Bedran-Russo AK, et al. Glycolic acid as the final irrigant in endodontics: Mechanical and cytotoxic effects. Mater Sci Eng C Mater Biol Appl 2019; 100:323-9. https://doi.org/10.1016/j.msec.2019.03.016
https://doi.org/10.1016/j.msec.2019.03.0...
,13[13] Barcellos DPDC, Farina AP, Barcellos R, Souza MA, Borba M, Bedran-Russo AK, et al. Effect of a new irrigant solution containing glycolic acid on smear layer removal and chemical/mechanical properties of dentin. Sci Rep 2020; 10(1):7313. https://doi.org/10.1038/s41598-020-64450-1
https://doi.org/10.1038/s41598-020-64450...
] and as an alternative etchant for enamel and dentin [14[14] Cecchin D, Farina AP, Vidal C, Bedran-Russo AK. A Novel Enamel and Dentin Etching Protocol Using α-hydroxy Glycolic Acid: Surface Property, Etching Pattern, and Bond Strength Studies. Oper Dent 2018; 43(1):101-10. https://doi.org/10.2341/16-136-L
https://doi.org/10.2341/16-136-L...
]. Compared to EDTA and Citric Acid, GA had greater antibacterial activity E. faecalis, comparable surface tension, less cytotoxic and comparable efficacy against the SL formed on the root canal [12[12] Bello YD, Porsch HF, Farina AP, Souza MA, Silva EJNL, Bedran-Russo AK, et al. Glycolic acid as the final irrigant in endodontics: Mechanical and cytotoxic effects. Mater Sci Eng C Mater Biol Appl 2019; 100:323-9. https://doi.org/10.1016/j.msec.2019.03.016
https://doi.org/10.1016/j.msec.2019.03.0...
,13[13] Barcellos DPDC, Farina AP, Barcellos R, Souza MA, Borba M, Bedran-Russo AK, et al. Effect of a new irrigant solution containing glycolic acid on smear layer removal and chemical/mechanical properties of dentin. Sci Rep 2020; 10(1):7313. https://doi.org/10.1038/s41598-020-64450-1
https://doi.org/10.1038/s41598-020-64450...
,15[15] Bello YD, Farina AP, Souza MA, Cecchin D. Glycolic acid: Characterization of a new final irrigant and effects on flexural strength and structural integrity of dentin. Mater Sci Eng C Mater Biol Appl 2020; 106:110283. https://doi.org/10.1016/j.msec.2019.110283
https://doi.org/10.1016/j.msec.2019.1102...
,16[16] Cecchin D, Bringhenti IL, Bernardi JB, Leal LO, Souza MA, Bedran-Russo A K, et al. Alpha-hydroxy glycolic acid for root dentin etching: Morphological analysis and push out bond strength. Int J Adhes Adhes 2019; 90:138-43. https://doi.org/10.1016/j.ijadhadh.2019.02.010
https://doi.org/10.1016/j.ijadhadh.2019....
].

To the extent of our knowledge, the smear layer removal efficacy of both GA and MA has been evaluated separately and has not been compared in the previous literature so far. Thus, this study aimed to assess the efficacy of 5% GA, 7% MA and 17% EDTA as a final irrigating solution on the SL removal following biomechanical preparation of the root canal system.

Material and Methods

Sample Size Estimation

With a 95% confidence level and 80% power based on previously published literature [13[13] Barcellos DPDC, Farina AP, Barcellos R, Souza MA, Borba M, Bedran-Russo AK, et al. Effect of a new irrigant solution containing glycolic acid on smear layer removal and chemical/mechanical properties of dentin. Sci Rep 2020; 10(1):7313. https://doi.org/10.1038/s41598-020-64450-1
https://doi.org/10.1038/s41598-020-64450...
], and standard deviation of 2 and a mean difference of 2.8, a minimum sample size of 10 per group was required.

Sample Preparation

Forty extracted human maxillary incisor teeth with completely developed roots and single, round canals, verified on a radiograph were selected for the study. Teeth showing resorption or filled canals were excluded. The institutional review board granted ethical clearance (IEC-704/2019) for the same. The teeth were kept in a storage solution of 0.2% sodium azide at 4°C until use (Millipore Sigma, St. Louis, MO, USA). The teeth were decoronated with a diamond disk (Horico Dental, Berlin, Germany) to reach a standard root length of 12mm.

The working length was determined using a #10 K file (Mani Inc- Tochigi Ken, Japan) inserted until seen at the apical foramen, observed under the 3.2x dental loupes. 1mm was decreased from this to achieve the desired working length. Sticky wax was used to seal the apices against extrusion. The canals were instrumented with a rotary file (Protaper Gold Dentsply, Maillefer, Ballaigues, Switzerland) up to size F3 using an endomotor (CanalPro 2; Coltène/Whaledent AG, Altstätten, Switzerland). Irrigation was performed intermittently between each instrument with 5ml of 2.5% NaOCl for 1 minute, using a 30 gauge side-vented needle (Vista Dental Inc. USA) placed 2mm short of the working length. Finally, to remove any remaining debris or formed residue, the canals were irrigated with 5ml of distilled water.

Irrigation Regimen

The samples were allocated into four experimental groups at random based on the final irrigating solution to be used (n=10):

  • Group 1: 5% GA (Tokyo Chemical Industry Pvt Ltd, India);

  • Group 2: 17% EDTA (Vista APEX, Racine, WI, USA);

  • Group 3: 7% MA (Sigma-Aldrich Corp., St. Louis, MO, USA);

  • Group 4: Distilled water (Control).

Irrigation was conducted with 5ml of the test solution for 1 minute with the irrigation needle placed 2mm short of the working length and a final rinse of 5ml distilled water for 1 minute. Paper points were used to obtain a dry canal (Dentsply Maillefer, Switzerland). On both the facial and lingual aspects, two longitudinal grooves were prepared with a diamond disc (Horico Dental, Germany), ensuring the preparation would not penetrate the canal. Using a chisel, the roots were split into halves. For each sample, the half with the more evident portion of the apical third was evaluated. Three external markings were made on this half with a fine-tip pen on the external root surface, perpendicular to the long axis, to divide it into cervical, middle, and apical thirds measuring 4mm in length from the root tip. The markings served as references to make 3 grooves in the canal wall, delimiting the root into thirds (cervical, middle, and apical).

Scanning Electron Microscopic Analysis

Increasing concentrations of ethyl alcohol (25%, 50%, 75%, and 100%) were used to dehydrate the specimens for 15 minutes. The specimens were finally mounted and sputtered using a gold ion sputter and evaluated through the Scanning Electron Microscope (SEM) (Carl Zeiss VO MA18 with Oxford EDS(X-act). Images obtained at a magnification of 1000x. The presence or absence of the SL was assessed at coronal, middle and apical thirds of the canal using the criteria given by Torabinejad et al. [17[17] Torabinejad M, Khademi AA, Babagoli J, Cho Y, Johnson WB, Bozhilov K, et al. A new solution for the removal of the smear layer. J Endod 2003; 29(3):170-5. https://doi.org/10.1097/00004770-200303000-00002
https://doi.org/10.1097/00004770-2003030...
]:

  1. No SL: No SL on the surface of the root canals; all tubules were clean and open.

  2. Moderate SL: No SL on the surface of the root canal, but tubules contained debris.

  3. Heavy SL: The SL covered the root canal surface and the tubules.

These were evaluated by two independent examiners unaware of the experimental groups to which the samples belonged.

Data Analysis

Chi-Square and Fisher Exact tests were used for the analysis of the data. A 5% level of statistical significance was adopted. The software SPSS was used for data analysis (IBM Corp., Armonk, NY, USA).

Results

For the interpretation of scores, the inter-examiner agreement was evaluated by the coefficient of Kappa test. In the coronal third, the Kappa scores were 0.81, 0.49 and 0.36 for MA, GA and EDTA, respectively; in the middle third, it was 0.10, 0.62 and 0.16 and in the apical third, the scores were 0.07, 0.40 and 0.58. However, in certain areas, the agreement between examiners was inadequate, wherein a third independent observer scored the images.

The percentages of SL distribution after the use of the different irrigating agents amongst the different thirds of the canal are represented in Figure 1. In coronal and middle thirds, there were no statistically significant differences between GA, MA and EDTA (p>0.05). Though, there was a significant difference among the test solutions in the apical third, in which MA was significantly more effective in removing the SL when compared to EDTA (p=0.002) and GA (p=0.041). Between GA and EDTA, there was no statistically significant difference (p=0.148). In the control (distilled water) group, all the specimens had heavy SL in all three sections of the canal.

Figure 1
Comparison of the percentage of smear layer removal among the test irrigants at coronal, middle, and apical thirds of the root canal system.

Figure 2 represents the images obtained by SEM of the canal walls treated with the various experimental solutions.

Figure 2
Photomicrographs of root canal walls instrumented with the test irrigants in the coronal, middle and apical thirds.

Discussion

The effectiveness of 17% EDTA, 7% MA and 5% GA as the final irrigating solution in eliminating the SL from the canal walls at the coronal, middle and apical thirds was assessed in this study. The outcomes showed that 7% MA was more effective in the removal of SL when contrasted with 17% EDTA and 5% GA in the apical third of the root canal. All the tested irrigating solutions were effective, with no significant differences between them, in the middle and coronal third. The finding is as per published literature that have revealed EDTA to be less successful in the apical third compared with the coronal and middle thirds for the removal of SL [10[10] Ballal NV, Kandian S, Mala K, Bhat KS, Acharya S. Comparison of the efficacy of maleic acid and ethylenediaminetetraacetic acid in smear layer removal from instrumented human root canal: a scanning electron microscopic study. J Endod 2009; 35(11):1573-6. https://doi.org/10.1016/j.joen.2009.07.021
https://doi.org/10.1016/j.joen.2009.07.0...
,17[17] Torabinejad M, Khademi AA, Babagoli J, Cho Y, Johnson WB, Bozhilov K, et al. A new solution for the removal of the smear layer. J Endod 2003; 29(3):170-5. https://doi.org/10.1097/00004770-200303000-00002
https://doi.org/10.1097/00004770-2003030...

[18] Baumgartner JC, Mader CL. A scanning electron microscopic evaluation of four root canal irrigation regimens. J Endod 1987; 13(4):147-157. https://doi.org/10.1016/s0099-2399(87)80132-2
https://doi.org/10.1016/s0099-2399(87)80...
-19[19] Mancini M, Armellin E, Casaglia A, Cerroni L, Cianconi L. A comparative study of smear layer removal and erosion in apical intraradicular dentine with three irrigating solutions: a scanning electron microscopy evaluation. J Endod 2009; 35(6):900-3. https://doi.org/10.1016/j.joen.2009.03.052
https://doi.org/10.1016/j.joen.2009.03.0...
]. Since EDTA is a chelator, its capacity to decalcify the root canal dentin is free from the high concentration of hydrogen ions and is found to be effective at a pH that is neutral. The fall in the pH results from a trade by hydrogen ions for calcium from dentin. This decrease in pH over a period of time causes the ensuing reduction in the efficacy of EDTA [20[20] Hülsmann M, Heckendorff M, Lennon A. Chelating agents in root canal treatment: mode of action and indications for their use. Int Endod J 2003; 36(12):810-30. https://doi.org/10.1111/j.1365-2591.2003.00754.x
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]. It has been shown that the dentinal tubules progressively sclerose in the apical third [21[21] Vasiliadis L, Darling AI, Levers BG. The amount and distribution of sclerotic human root dentin. Arch Oral Biol 1983; 28(7):645-9. https://doi.org/10.1016/0003-9969(83)90013-4
https://doi.org/10.1016/0003-9969(83)900...
,22[22] Paqué F, Luder HU, Sener B, Zehnder M. Tubular sclerosis rather than the smear layer impedes dye penetration into the dentine of endodontically instrumented root canals. Int Endod J 2006; 39(1):18-25. https://doi.org/10.1111/j.1365-2591.2005.01042.x
https://doi.org/10.1111/j.1365-2591.2005...
]. Thus, the activity of EDTA may not be as effective in the apical third.

Better results of MA in the removal of SL from apical portion of the canal as opposed to EDTA is in concurrence with previously published literature [7[7] Ballal NV, Kundabala M, Bhat S, Rao N, Rao BS. A comparative in vitro evaluation of cytotoxic effects of EDTA and maleic acid: root canal irrigants. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2009; 108(4):633-8. https://doi.org/10.1016/j.tripleo.2009.05.039
https://doi.org/10.1016/j.tripleo.2009.0...
,11[11] Ulusoy Öİ, Görgül G. Effects of different irrigation solutions on root dentine microhardness, smear layer removal and erosion. Aust Endod J 2013; 39(2):66-72. https://doi.org/10.1111/j.1747-4477.2010.00291.x
https://doi.org/10.1111/j.1747-4477.2010...
]. This might be ascribed to the possibly greater depth of demineralization of MA in the apical third, caused due to its lower pH of 1.3, which results in a greater decalcifying effect in a shorter time [23[23] Ballal NV, Mala K, Bhat KS. Evaluation of decalcifying effect of maleic acid and EDTA on root canal dentin using energy dispersive spectrometer. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2011; 112(2):e78-e84. https://doi.org/10.1016/j.tripleo.2011.01.034
https://doi.org/10.1016/j.tripleo.2011.0...
]. Trevelin et al. [24[24] Trevelin LT, Villanueva J, Zamperini CA, Mathew MT, Matos AB, Bedran-Russo AK. Investigation of five α-hydroxy acids for enamel and dentin etching: Demineralization depth, resin adhesion and dentin enzymatic activity. Dent Mater 2019; 35(6):900-8. https://doi.org/10.1016/j.dental.2019.03.005
https://doi.org/10.1016/j.dental.2019.03...
] discovered that when MA was utilized at a similar concentration for etching dentin, the penetration was more than GA, notwithstanding the low molecular weight of GA. Since sclerosis occurs in the dentinal tubules in the apical section of the canal [21[21] Vasiliadis L, Darling AI, Levers BG. The amount and distribution of sclerotic human root dentin. Arch Oral Biol 1983; 28(7):645-9. https://doi.org/10.1016/0003-9969(83)90013-4
https://doi.org/10.1016/0003-9969(83)900...
,22[22] Paqué F, Luder HU, Sener B, Zehnder M. Tubular sclerosis rather than the smear layer impedes dye penetration into the dentine of endodontically instrumented root canals. Int Endod J 2006; 39(1):18-25. https://doi.org/10.1111/j.1365-2591.2005.01042.x
https://doi.org/10.1111/j.1365-2591.2005...
], the demineralization impact of MA might be more pronounced, yielding the outcomes found in the current study. Further investigations to confirm this mechanism are warranted.

The capability of GA as an irrigating solution was assessed utilizing various concentrations ranging from 5 to 17%, in which 5% was found as effective as higher concentrations in eliminating the SL and caused less decrease in the dentin microhardness [12[12] Bello YD, Porsch HF, Farina AP, Souza MA, Silva EJNL, Bedran-Russo AK, et al. Glycolic acid as the final irrigant in endodontics: Mechanical and cytotoxic effects. Mater Sci Eng C Mater Biol Appl 2019; 100:323-9. https://doi.org/10.1016/j.msec.2019.03.016
https://doi.org/10.1016/j.msec.2019.03.0...
]. Additionally, a recent study revealed that 5% GA had lesser cytotoxicity when compared with 17% EDTA [25[25] Oh S, Perinpanayagam H, Lee Y, Kum JW, Yoo YJ, Lim SM, et al. Effect of acidic solutions on the microhardness of dentin and set OrthoMTA and their cytotoxicity on murine macrophage. Restor Dent Endod 2016; 41(1):12-21. https://doi.org/10.5395/rde.2016.41.1.12
https://doi.org/10.5395/rde.2016.41.1.12...
]. Consequently, the concentration of 5% GA was chosen in this study. The volume of EDTA recommended to eliminate the SL goes from 3 to 20 ml for each canal [26[26] Khademi A, Yazdizadeh M, Feizianfard M. Determination of the minimum instrumentation size for penetration of irrigants to the apical third of root canal systems. J Endod 2006; 32(5):417-20. https://doi.org/10.1016/j.joen.2005.11.008
https://doi.org/10.1016/j.joen.2005.11.0...
,27[27] Teixeira CS, Felippe MC, Felippe WT. The effect of application time of EDTA and NaOCl on intracanal smear layer removal: an SEM analysis. Int Endod J 2005; 38(5):285-90. https://doi.org/10.1111/j.1365-2591.2005.00930.x
https://doi.org/10.1111/j.1365-2591.2005...
]. In any case, the transport of a huge volume of the solution through a fine needle requires additional time and results in fatigue to the clinician. In this study, 5 ml of final irrigating solution was utilized. Mello et al. [28[28] Mello I, Robazza CR, Antoniazzi JH, Coil J. Influence of different volumes of EDTA for final rinse on smear layer removal. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2008; 106(5):e40-3. https://doi.org/10.1016/j.tripleo.2008.06.019
https://doi.org/10.1016/j.tripleo.2008.0...
] showed that 5 ml was as effectual as 10 or 15 ml of EDTA in eliminating the SL as a final rinse.

In this study, 2.5% NaOCl was utilized for the chemo‑mechanical arrangement between each instrument, which could eliminate the organic substance of SL. This is in accordance with a study that expressed that weakened NaOCl is just as effective as a greater concentration of NaOCl for the removal of the organic part of SL [17[17] Torabinejad M, Khademi AA, Babagoli J, Cho Y, Johnson WB, Bozhilov K, et al. A new solution for the removal of the smear layer. J Endod 2003; 29(3):170-5. https://doi.org/10.1097/00004770-200303000-00002
https://doi.org/10.1097/00004770-2003030...
]. In the current experiment, the apex was prepared up to ISO size no. 30. Khademi et al. [26[26] Khademi A, Yazdizadeh M, Feizianfard M. Determination of the minimum instrumentation size for penetration of irrigants to the apical third of root canal systems. J Endod 2006; 32(5):417-20. https://doi.org/10.1016/j.joen.2005.11.008
https://doi.org/10.1016/j.joen.2005.11.0...
] found that the minimum size of canal instrumentation for the infiltration of irrigating solutions into the apical part of the canal is #30. They suggest it for viably eliminating the SL and debris while avoiding the dangers of iatrogenic errors, particularly in narrow and curved canals. Presently, there are no standard recommendations for the ideal duration of the use of EDTA. A 1-minute time interval; was decided on in the current experiment, similar to previously published investigations [27[27] Teixeira CS, Felippe MC, Felippe WT. The effect of application time of EDTA and NaOCl on intracanal smear layer removal: an SEM analysis. Int Endod J 2005; 38(5):285-90. https://doi.org/10.1111/j.1365-2591.2005.00930.x
https://doi.org/10.1111/j.1365-2591.2005...
,29[29] Calt S, Serper A. Smear layer removal by EGTA. J Endod 2000; 26(8):459-61. https://doi.org/10.1097/00004770-200008000-00007
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,30[30] Kuah HG, Lui JN, Tseng PS, Chen NN. The effect of EDTA with and without ultrasonics on removal of the smear layer. J Endod 2009; 35(3):393-6. https://doi.org/10.1016/j.joen.2006.12.007
https://doi.org/10.1016/j.joen.2006.12.0...
]. Furthermore, on exposing the dentinal tubules for more than 1 minute, EDTA causes erosion, accordingly diminishing the microhardness of dentin and causing fragility of the root [31[31] Saleh AA, Ettman WM. Effect of endodontic irrigation solutions on microhardness of root canal dentine. J Dent 1999; 27(1):43-6. https://doi.org/10.1016/s0300-5712(98)00018-9
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,32[32] Niu W, Yoshioka T, Kobayashi C, Suda H. A scanning electron microscopic study of dentinal erosion by final irrigation with EDTA and NaOCl solutions. Int Endod J 2002; 35(11):934-9. https://doi.org/10.1046/j.1365-2591.2002.00594.x
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]. Distilled water which is utilized as a control, was observed to be ineffective in eliminating the SL, with results like past studies [33[33] Prado M, Gusman H, Gomes BP, Simão RA. Scanning electron microscopic investigation of the effectiveness of phosphoric acid in smear layer removal when compared with EDTA and citric acid. J Endod 2011; 37(2):255-8. https://doi.org/10.1016/j.joen.2010.11.011
https://doi.org/10.1016/j.joen.2010.11.0...
].

Other than traditional SEM, different modalities that might be utilized to assess the presence of SL are digital image analysis, micro‑computed tomography, atomic force microscopy, environmental SEM, and co‑site optical microscopy [34[34] De-Deus G, Souza EM, Marins JR, Reis C, Paciornik S, Zehnder M. Smear layer dissolution by peracetic acid of low concentration. Int Endod J 2011; 44(6):485-90. https://doi.org/10.1111/j.1365-2591.2010.01847.x
https://doi.org/10.1111/j.1365-2591.2010...
]. However, in this study, SEM was selected as it is a conveniently accessible instrument. Results observed in this study might be bound to just teeth with single roots having a practically straight root canal configuration. Posterior teeth with curved canals and complex root canal anatomy can be more challenging for effective cleaning. Subsequently, further studies should be performed using these experimental irrigating solutions to judge their efficacy in the removal of SL in teeth where the canal anatomy is more complex.

Conclusion

Within the constraints of this research, it can be concluded that 7% MA as a final irrigating solution is more effective than 17% EDTA and 5% GA in eliminating the SL in the apical portion of the human root canal.

Data Availability

The data used to support the findings of this study can be made available upon request to the corresponding author.

  • Financial Support
    None.

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Edited by

Academic Editor: Catarina Ribeiro Barros de Alencar

Publication Dates

  • Publication in this collection
    04 Sept 2023
  • Date of issue
    2023

History

  • Received
    03 Apr 2022
  • Reviewed
    04 Aug 2022
  • Accepted
    25 Aug 2022
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