• Users Online: 183
  • Home
  • Print this page
  • Email this page
Home About us Editorial board Ahead of print Current issue Search Archives Submit article Instructions Subscribe Contacts Login 

 Table of Contents  
Year : 2019  |  Volume : 31  |  Issue : 1  |  Page : 63-67

Effect of continuous soft chelating irrigation protocol on removal of smear layer

Department of Endodontics and Conservative Dentistry, Y. M. T Dental College, M. D. S Endodontics and Conservative Dentistry, Mumbai, Maharashtra, India

Date of Web Publication19-Jun-2019

Correspondence Address:
Prof. Vibha Hegde
401 Shobha Suman, M. M. Malviya Road, Mulund (West), Mumbai - 400 080, Maharashtra
Login to access the Email id

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/endo.endo_58_18

Rights and Permissions

Aim: The purpose of this study was to compare the efficacy of continuous soft chelating irrigation protocol with conventional irrigation protocol.
Methodology: sixty extracted single-rooted human teeth were randomly divided into 5 groups (n =12) and instrumented using Protaper Universal nickel-titanium rotary instruments. In conventional irrigation group each canal was subsequently irrigated with 5.25% NaOCl followed with 17%EDTA (Group A), SmearClear (Group B) or SmearOFF (Group C). After that, all the specimens were subjected to irrigation with 5.25% NaOCl. In continous soft chelating irrigation group The irrigation while instrumentation and after instrumention was done with Chloroquick Low (9% hebp + 3% NaOCl) (Group D) and Chloroquick High (18% hebp + 5.25% NaOCl) (Group E). teeth were then processed for scanning electron microscopy (SEM), and the removal of the smear layer was examined in the coronal, middle, and apical thirds.
Result: The efficacy of various agents for smear layer removal was assessed by comparison of groups using Kruskal Wallis ANOVA and Mann- Whitney U test. The results showed that there were no significant differences in Conventional irrigation protocol groups and continuous irrigation protocol group at coronal and middle thirds of root canals but at apical third Chloroquick High was able to remove more smear layer statistically when compared to all the groups (p_0.029).
Conclusion: this in-vitro study both the protocols conventional as well as continuous soft chelating irrigation protocols were able to remove smear layer at coronal and middle third of the root canals but at apical third only continues soft chelating irrigation protocol performed with Chloroquick High shows better removal of smear layer.

Keywords: Ethylenediaminetetraacetic acid, etridonic acid, smear layer, smearclear, smearoff

How to cite this article:
Hegde V, Thakkar P. Effect of continuous soft chelating irrigation protocol on removal of smear layer. Endodontology 2019;31:63-7

How to cite this URL:
Hegde V, Thakkar P. Effect of continuous soft chelating irrigation protocol on removal of smear layer. Endodontology [serial online] 2019 [cited 2022 Nov 30];31:63-7. Available from: https://www.endodontologyonweb.org/text.asp?2019/31/1/63/260531

  Introduction Top

Literature is suggestive that the dentin wall gets covered with smear layer after shaping of the root canals with instruments.[1],[2] Disregarding the controversy over its retention, it has been recognized that the smear layer itself may be infected and may protect the bacteria within the dentinal tubules.[3] Smear layer not only contains organic components but also has an inorganic component in the form of dentin chips and the debris which prevents[1] the penetration of intracanal disinfectants[4] and sealers into dentinal tubules, which in turn affects the final seal of the root canal filling.[5],[6],[7]

Irrigants are of paramount importance of complete debridement of the root canals with mechanical instrumentation.[3] Studies have shown there is no single potent solution appropriate for removing both organic and inorganic parts of the smear layer. To eliminate this smear layer, a mix of sodium hypochlorite (NaOCl) and a strong chelating agent such as ethylenediaminetetraacetic acid (EDTA) is recommended.[8] Crumpton et al. proposed that complete removal of smear layer can be achieved by 17% EDTA for 1 min followed by 5.25% NaOCl.[9],[10] On the other hand, the application of a strong chelating agent like EDTA for more than a min and 1 ml of volume has been reported to be associated with dentinal erosion.[11],[12]

Smearclear (Sybron Endo, Orange, CA, USA) is a product introduced for eliminating the smear layer. It contains 17% EDTA solution in conjunction with a cationic (cetrimide) and an anionic surfactant to improve its action. SmearOFF (Vista Dental Products) is proprietary EDTA and chlorhexidine mix. It is prepared with a combination of wetting agents and surface modifiers for the best outcomes. These solutions are used only as a final rinse.

Etridonic acid (HEBP) which is a soft chelating agent that appears to have a nominal effect on dentine walls and still acts on the smear layer. Lottanti et al. showed that HEBP could be used in combination with NaOCl without affecting its proteolytic or antimicrobial properties.[13],[14] In contrast to EDTA, HEBP is a weak decalcifying agent and hence cannot be used as a mere final rinse; therefore, it is suggested that HEBP has to be mixed with NaOCl to be used as a complete root canal irrigation solution. Chloroquick (innovationsendo, India) is a combination of NaOCl and HEBP. Chloroquick high contains 18% HEBP and 5.25% NaOCl, whereas chloroquick low contains 9% HEBP and 3% NaOCl both need to be premixed with surfactant tween 80 for a complete root canal irrigation solution.

Therefore, this study aims to compare the efficacy of continuous soft chelating irrigation protocol with the chloroquick solutions to conventional irrigation protocol on smear layer removal in coronal, middle, and apical thirds of the instrumented root canals.

  Materials and Methods Top

Sixty freshly extracted human premolar teeth with single and straight root canal were preferred and stored in distilled water. Average root length of 12 mm was retained by decoronating the teeth and then divided into five groups (n = 12) randomly. Working length was determined with #10 K-files and deduction of 1 mm was done from recorded root length as a safety factor.

  • Group A EDTA (control) – 1 ml of 17% EDTA for 1 min followed by 3 ml of 5.25% NaOCl
  • Group B smear clear (EDTA + surfactants) – 1 ml of smear clear (Sybron Endo, Orange, CA) for 1 min followed by 3 ml of 5.25% NaOCl
  • Group C smear off (EDTA + Chlorhexidine + surfactant) – 1 ml of smear off (Vista dental,) for 1 min followed by 3 ml of 5.25% NaOCl
  • Group D chloroquick low (HEBP + NaOCl) – 1 ml of chloroquick low solution (9%HEBP + 3%NaOCl) for 1 min and final rinse with 3 ml same solution
  • Group E chloroquick high (HEBP + NaOCl) – 1 ml of chloroquick high solution (18%HEBP + 5.25%NaOCl) for 1 min and a final rinse with 3 ml of the same solution.

Conventional irrigation protocol was pursued for the first three groups. After using each file and before proceeding to the next canals were irrigated with 2 ml of 5.25% NaOCl. After instrumentation, all teeth underwent final irrigation as mentioned in GROUP A, B, and C.

Continuous soft chelating irrigation protocol was followed for two groups Group D and Group E. After the use of each file, canal was irrigated with 2 ml of respective chloroquick solution. After instrumentation, all teeth underwent final irrigation as mentioned above.

In-between two solutions, 5 ml of distilled water was used for rinsing canal walls and solutions were introduced with the help of a 30G side vented needle (innovationsendo), which penetrated within 1–2 mm from the working length. At the end, 5 ml of distilled water were used to rinse root canal walls which were dried with paper points.

At the end of the entire procedure, two longitudinal grooves were prepared with the help of diamond disc without cutting into the canal. Grooves were prepared on the buccal and lingual surfaces of each root. A Chisel was used for splitting the teeth. Then, the specimens were mounted on the metallic stubs and investigated under a scanning electron microscope (FEI Quanta 200 FE-SEM MK2, Netherlands). Images were obtained at ×2000 at coronal (9 mm to apex), middle (6 mm to apex), and apical (3 mm to apex) third of each specimen.

Scoring criteria used was given by Torabinejad, Khademi et al. where scores were given as follow score 1 = no smear layer; all tubules were clean and open and smear layer was absent on the surface of the canals; score 2 = moderate smear layer; smear layer was not present on the surface of the canal, but debris were present in tubules; score 3 = heavy smear layer; the debris were observed in tubules and smear layer enclosed the dentin wall surfaces.

An endodontist who was unaware of groups and coding evaluated and scored all the images to exclude observer bias. The repeated evaluation was done to ensure intra-examiner consistency.

  Results Top

Descriptive statistics were expressed as numbers for each group. The efficacy of various agents for smear layer removal was assessed by comparison of groups using Kruskal–Wallis ANOVA and Mann–Whitney U-test. In the above tests, P ≤ 0.05 was taken to be statistically significant. All analyses were performed using SPSS software (ver. 20; SPSS Inc., Chicago, IL, USA).

The results for smear layer scores in each group at the coronal, middle, and apical are conferred in [Table 1], [Table 2], [Table 3]. The examination of the surface of the root canal walls at coronal third groups showed less or no smear layer [Figure 1], and there was no statistically significant difference (P = 0.643). Most samples at middle thirds showed no smear layer or minimal smear layer present [Figure 2], and there was no statistically significant difference at the middle layer of root canals (P = 0.615). Chloroquick high group showed better smear layer removal at the apical thirds [Figure 3]. Chloroquick high showed statistically significantly better results (P = 0.029) as compared to the other groups. Mann–Whitney U-test displayed that chloroquick high can remove better smear layer compared to chloroquick low (P = 0.028). Choloroquick low has related chelating ability as compared to other solutions with no statically significant difference at apical third.
Table 1: Efficacy of various agents in smear layer removal in the coronal third of the canal

Click here to view
Table 2: Efficacy of various agents in smear layer removal in the middle third of the canal

Click here to view
Table 3: Efficacy of various agents in smear layer removal in the apical third of the canal

Click here to view
Figure 1: Scanning electron microscope images of coronal third treated with all the irrigating agent groups

Click here to view
Figure 2: Scanning electron microscope images of middle third treated with all the irrigating agent groups

Click here to view
Figure 3: Scanning electron microscope images of apical third treated with all the irrigating agent groups

Click here to view

  Discussion Top

This examination provides an insightful understanding of the smear layer removal capability of conventional irrigation protocol and continuous soft chelating irrigation protocol. Satisfactory irrigation, disinfection, and obturation are the main principles of root canal treatment. Accumulation of smear layer is observed while shaping of canals which need tobe eliminated with the help of irrigating solutions. The objective of using an irrigant to reduce the smear layer from the canal wall cannot be obtained by the use of a sole irrigating solution. Therefore, the combined application of multiple irrigating solutions is mandatory for optimal removal of smear layer.[8] The novel chloroquick solution is a mix of HEBP (a soft chelating agent) and NaOCl which can disinfect root canals as well as reduce smear layer. The highlight of such combination of NaOCl and HEBP is that the NaOCl does not surrender its biological, antibacterial, and tissue dissolving properties,[13],[14] whereas the reduction and elimination of the inorganic element are done with the help of HEBP.[15],[16]

The outcome of this current research reveals eradication of smear layer was more decisive in middle and coronal third in comparison to the apical third. These results are in accordance with the study done by Abbott, et al. and numerous studies, which have proven to have an effective cleaning action in the middle and coronal third of the root canals regardless of the nature of irrigation solutions, volume, and time.[17],[18],[19] In coronal and middle third areas where a large canal diameter allows better flow of irrigants, efficient fluid dynamics and greater time of contact with dentine surface facilitates the irrigant to act on the smear layer comprehensively.[3],[18],[20]

Role of surfactant has been discussed and reviewed by numerous authors, in the current study smearclear, smearoff and chloroquick contains surfactant. Abou-Rass and Patonai confirmed that reduction of surface tension of endodontic solutions improved their flow into slender and narrow root canals.[21] Thus, an improved penetration into apical complexities of canals can be seen with the addition of surfactants to irrigation solution. In the present study, smearclear and smear off despite having additional surfactant do not show the significant removal of smear layer in the apical third when compared to the control group of 17% EDTA, which does not have any additional surfactant. This result is in accordance with the observations of Lui et al.[22] and also, other studies which have shown that calcium chelating ability of the solution is not improved by reducing the surface tension of the solution.

Results of the present study display that, the continuous soft chelating irrigation shows the significantly better removal of smear layer than conventional irrigation protocol at the apical third level when 18% HEBP was used in combination with 5.25% NaOCl (chloroquick high). Whereas 9% HEBP in combination with 3% NaOCl (chloroquick low) did not show any significant difference when compared to conventional irrigation protocol groups. These results can be attributed not only to the chelating agent being in the canal for a longer time but also to the chelating procedure occurring while instrumentation, unlike conventional irrigation protocol where removal of smear layer is done only once instrumentation is completed.[21] Paqué et al. revealed that the accumulation of hard tissue debris in root canals when irrigated with an amalgamation of NaOCl and etradonic acid was significantly less than when irrigation was performed with 2.5% NaOCl alone.[14] Another advantage of this combination is that it has better tissue dissolution capacity by keeping the hypochlorite-hypochlorous acid equilibrium toward hypochlorite.[13],[23] This combination is effective on the inorganic as well as organic part of smear layer at the same time.

A study performed by De-Deus et al. on the impact of strong (MTAD) or soft HEBP chelating solution on the bond strength of resilon epiphany root canal sealers. It was demonstrated that a soft chelating irrigation protocol optimizes bonding quality of the sealers because of the better opening of dentin tubules which were covered with the smear layer.[24]

The result of this study is in contrast to the recently published research by Kuruvilla et al. where 7%malic acid was significantly efficient in eliminating the smear layer as compared to 17% EDTA and 18% etidronic acid.[25] This observation may be attributed to the fact that 18% etidronic acid which is a soft chelating agent was merely used as a final rinse irrigation protocol and not combined with sodium hypochlorite.

There is limited literature available on the use of the continuous soft chelating agent for smear layer removal. Future research should be aimed toward the effect of both these protocols on the dentinal walls of the root canal. In the present study, continuous soft chelating irrigation protocol has shown promising results to eliminate the smear layer.

  Conclusion Top

Within the constraint of this present in-vitro study, both conventional, as well as continuous soft chelating irrigation protocols, were able to remove the smear layer at coronal and middle third of the root canals. At apical third, continuous soft chelating irrigation protocol accomplished with chloroquick high (18%HEBP) showed the better removal of smear layer.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

McComb D, Smith DC. A preliminary scanning electron microscopic study of root canals after endodontic procedures. J Endod 1975;1:238-42.  Back to cited text no. 1
Mader CL, Baumgartner JC, Peters DD. Scanning electron microscopic investigation of the smeared layer on root canal walls. J Endod 1984;10:477-83.  Back to cited text no. 2
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. 3
Orstavik D, Haapasalo M. Disinfection by endodontic irrigants and dressings of experimentally infected dentinal tubules. Endod Dent Traumatol 1990;6:142-9.  Back to cited text no. 4
White RR, Goldman M, Lin PS. The influence of the smeared layer upon dentinal tubule penetration by plastic filling materials. J Endod 1984;10:558-62.  Back to cited text no. 5
Economides N, Liolios E, Kolokuris I, Beltes P. Long-term evaluation of the influence of smear layer removal on the sealing ability of different sealers. J Endod 1999;25:123-5.  Back to cited text no. 6
Shahravan A, Haghdoost AA, Adl A, Rahimi H, Shadifar F. Effect of smear layer on sealing ability of canal obturation: A systematic review and meta-analysis. J Endod 2007;33:96-105.  Back to cited text no. 7
Yamada RS, Armas A, Goldman M, Lin PS. A scanning electron microscopic comparison of a high volume final flush with several irrigating solutions: Part 3. J Endod 1983;9:137-42.  Back to cited text no. 8
Calt S, Serper A. Time-dependent effects of EDTA on dentin structures. J Endod 2002;28:17-9.  Back to cited text no. 9
Crumpton BJ, Goodell GG, McClanahan SB. Effects on smear layer and debris removal with varying volumes of 17% REDTA after rotary instrumentation. J Endod 2005;31:536-8.  Back to cited text no. 10
Torabinejad M, Cho Y, Khademi AA, Bakland LK, Shabahang S. The effect of various concentrations of sodium hypochlorite on the ability of MTAD to remove the smear layer. J Endod 2003;29:233-9.  Back to cited text no. 11
Tay FR, Gutmann JL, Pashley DH. Microporous, demineralized collagen matrices in intact radicular dentin created by commonly used calcium-depleting endodontic irrigants. J Endod 2007;33:1086-90.  Back to cited text no. 12
Lottanti S, Gautschi H, Sener B, Zehnder M. Effects of ethylenediaminetetraacetic, etidronic and peracetic acid irrigation on human root dentine and the smear layer. Int Endod J 2009;42:335-43.  Back to cited text no. 13
Paqué F, Rechenberg DK, Zehnder M. Reduction of hard-tissue debris accumulation during rotary root canal instrumentation by etidronic acid in a sodium hypochlorite irrigant. J Endod 2012;38:692-5.  Back to cited text no. 14
Arias-Moliz MT, Ordinola-Zapata R, Baca P, Ruiz-Linares M, Ferrer-Luque CM. Antimicrobial activity of a sodium hypochlorite/etidronic acid irrigant solution. J Endod 2014;40:1999-2002.  Back to cited text no. 15
Tartari T, Guimarães BM, Amoras LS, Duarte MA, Silva e Souza PA, Bramante CM, et al. Etidronate causes minimal changes in the ability of sodium hypochlorite to dissolve organic matter. Int Endod J 2015;48:399-404.  Back to cited text no. 16
Girard S, Paqué F, Badertscher M, Sener B, Zehnder M. Assessment of a gel-type chelating preparation containing 1-hydroxyethylidene-1, 1-bisphosphonate. Int Endod J 2005;38:810-6.  Back to cited text no. 17
Zehnder M, Schmidlin P, Sener B, Waltimo T. Chelation in root canal therapy reconsidered. J Endod 2005;31:817-20.  Back to cited text no. 18
Abbott PV, Heijkoop PS, Cardaci SC, Hume WR, Heithersay GS. An SEM study of the effects of different irrigation sequences and ultrasonics. Int Endod J 1991;24:308-16.  Back to cited text no. 19
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;38:285-90.  Back to cited text no. 20
Abou-Rass M, Patonai FJ Jr. The effects of decreasing surface tension on the flow of irrigating solutions in narrow root canals. Oral Surg Oral Med Oral Pathol 1982;53:524-6.  Back to cited text no. 21
Lui JN, Kuah HG, Chen NN. Effect of EDTA with and without surfactants or ultrasonics on removal of smear layer. J Endod 2007;33:472-5.  Back to cited text no. 22
Christensen CE, McNeal SF, Eleazer P. Effect of lowering the pH of sodium hypochlorite on dissolving tissue in vitro. J Endod 2008;34:449-52.  Back to cited text no. 23
De-Deus G, Namen F, Galan J Jr., Zehnder M. Soft chelating irrigation protocol optimizes bonding quality of resilon/Epiphany root fillings. J Endod 2008;34:703-5.  Back to cited text no. 24
Kuruvilla A, Jaganath BM, Krishnegowda SC, Ramachandra PK, Johns DA, Abraham A, et al. Acomparative evaluation of smear layer removal by using EDTA, etidronic acid, and maleic acid as root canal irrigants: An in vitro scanning electron microscopic study. J Conserv Dent 2015;18:247-51.  Back to cited text no. 25
[PUBMED]  [Full text]  


  [Figure 1], [Figure 2], [Figure 3]

  [Table 1], [Table 2], [Table 3]

This article has been cited by
1 Multiparameter image analysis to evaluate dentinal tubules patency after using different irrigation protocols
MohamedAhmed Elsayed
Scientific Dental Journal. 2022; 6(1): 36
[Pubmed] | [DOI]


Similar in PUBMED
   Search Pubmed for
   Search in Google Scholar for
 Related articles
Access Statistics
Email Alert *
Add to My List *
* Registration required (free)

  In this article
Materials and Me...
Article Figures
Article Tables

 Article Access Statistics
    PDF Downloaded683    
    Comments [Add]    
    Cited by others 1    

Recommend this journal