Contemporary Clinical Dentistry
  Home | About us | Editorial board | Search
Ahead of print | Current Issue | Archives | Advertise
Instructions | Online submission| Contact us | Subscribe |


Login  | Users Online: 1784  Print this pageEmail this pageSmall font sizeDefault font sizeIncrease font size 

 Table of Contents  
Year : 2014  |  Volume : 5  |  Issue : 1  |  Page : 37-41  

A Scanning electron microscopic evaluation of intracanal smear layer removal by two different final irrigation activation systems

1 Department of Conservative Dentistry and Endodontics, Private Practice, New Delhi, Maulana Azad Institute of Dental Sciences, India
2 Department of Conservative Dentistry and Endodontics, KLE VK Institute of Dental Sciences, Belgaum, Karnataka, India

Date of Web Publication13-Mar-2014

Correspondence Address:
Ankur Dua
Departments of Conservative Dentistry and Endodontics, Maulana Azad Institute of Dental Sciences, Bahadur Shah Zafar Marg, New Delhi - 110 002
Login to access the Email id

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0976-237X.128661

Rights and Permissions

Aim: The aim of this study was to compare smear layer removal at apical 1 mm level after final irrigation activation with an EndoVac system and Max-I probe. Materials and Methods: Fifty freshly extracted maxillary central incisors were randomly divided into two groups after completing cleaning and shaping with ProTaper rotary files. In one group, final irrigation was performed with an EndoVac system while in the other group final irrigation was performed with a 30 gauge Max-I probe. 3% sodium hypochlorite and 17% ethylenediaminetetracetic acid were used as final irrigants in all teeth. After instrumentation and irrigation, the teeth were sectioned longitudinally into buccal and palatal halves and viewed under a scanning electron microscope for evaluation of the smear layer. Statistical analysis was performed using the Kruskal Wallis and Mann-Whitney U tests. Results: The EndoVac group showed significantly better smear layer removal compared with the Max-I probe at the apical 1 mm level. Conclusion: An apical negative pressure system (EndoVac) results in better debridement at apical 1 mm when compared with side-vented closed ended needle irrigation (Max-I probe).

Keywords: EndoVac, max-I probe, root canal irrigation, scanning electron microscope, smear layer

How to cite this article:
Dua D, Dua A, Uppin VM. A Scanning electron microscopic evaluation of intracanal smear layer removal by two different final irrigation activation systems. Contemp Clin Dent 2014;5:37-41

How to cite this URL:
Dua D, Dua A, Uppin VM. A Scanning electron microscopic evaluation of intracanal smear layer removal by two different final irrigation activation systems. Contemp Clin Dent [serial online] 2014 [cited 2020 Aug 8];5:37-41. Available from:

   Introduction Top

Successful endodontic treatment depends on the effective removal of smear layer from root canals through chemo-mechanical instrumentation. Various root canal irrigants have been introduced, and most of them have satisfactory properties. Past studies have shown that a combination of 5.25% sodium hypochlorite and 17% ethylenediaminetetraacetic acid is quite effective in flushing out debris and smear layer from the root canals. [1],[2] However, none of the irrigants with the conventional irrigation system are effective in cleaning the apical 1 mm of the root canal, which has maximum anatomical areas that are the most difficult and critical to debride. [3],[4],[5],[6]

Many problems are associated with the conventional irrigation systems used. The irrigant is delivered with a syringe and needle and is expressed under positive pressure into the canals. It has been shown that the irrigant does not go more than 1 mm beyond the needle tip and therefore the apical few millimeters are never irrigated. [7],[8] To make the irrigant reach the apical 1-2 mm, the needle should go close to the working length, [9] which in turn increases the risk of apical extrusion of irrigant. The commonly used irrigant, sodium hypochlorite, is very toxic to the surrounding tissues and causes acute symptoms if forced beyond the apex. [10]

The mechanical cleaning and shaping has also improved with rotary Ni-Ti files. However, it was found that debris is always present in the apical 1 mm. [11],[12] This is because the irrigant never reaches the apical most few millimeters.

Various newer irrigation systems have been introduced to increase the mechanical flushing action of irrigants for better removal of smear layer, which was not possible with conventional syringe irrigation with needles and cannulas. Recently, a 30 G irrigation needle covered with a brush (NaviTip FX) was introduced. There have been machine-assisted agitation systems (CanalBrush), the Quantec-E irrigation system, that allow for continuous irrigation agitation during rotary instrumentation. However, the literature shows no significant difference with these systems when compared with syringe needle irrigation.

The Max-I probe is a needle with a closed end and a side port that is said to deliver the irrigant in the apical third without the risk of perfusion beyond the apex. [9]

The EndoVac system is another new irrigation system that uses negative pressure to draw the irrigant down the canal to the apex. This system claims to deliver the irrigant in the apical 1-2 mm without any risk of perfusion of irrigant beyond the apex. [13]

The present in vitro study is an attempt to compare the efficacy in intracanal smear layer removal at 1 mm from working length after final irrigation with an EndoVac irrigation system and side-vented closed ended needle (Max-I probe).

   Materials and Methods Top

Fifty freshly extracted intact, non-carious, human permanent maxillary incisor teeth were selected for the study. Teeth with straight and single patent root canal and without any anatomical variations, no visible root caries, no signs of external or internal resorption and with completely formed apices were used in the study. Pre-operative radiographs were taken, which were screened, and any teeth that did not meet the required criteria were excluded from the study. The external surfaces of the teeth were debrided using ultrasonic scalers and stored in sterile saline solution at room temperature. Each tooth was numbered on the buccal and palatal surfaces of the root. A flat occlusal surface was made as a reference for determining working length, and pulp chamber of each tooth was accessed. A #15 K-file (Kendo, VDW, Germany) was then introduced into the root canal until its tip was just visible at the apical foramen. The working length for the preparation was determined by deducting 1 mm from the length recorded when the file was just visible at the apex of the root. Root apices were covered with sticky wax. Cleaning and shaping of all teeth was performed by using Gates Glidden drills and ProTaper (Dentsply Maillefer, Ballaigues, Switzerland) rotary files. The coronal portion of the canal was flared using Gates- Glidden drills 1 to 3. ProTaper rotary files were used for preparation of middle and apical third. All teeth were enlarged to the master apical file size of 50/.06 to minimize the confounding factor of differences in the remaining tissue after mechanical preparation. To ensure patency, recapitulation to working length was performed after each rotary instrument with a #10 K file. During instrumentation, 1 mL of 3% NaOCl (Vishal Dentocare, Ahmedabad, India) was used at each change of file. Samples were randomly divided into three groups depending on the type of irrigation system used for final irrigation.

Group A (Positive control): No final irrigation was performed after instrumentation was completed (n = 10).

Group B: Final irrigation was performed using an MAX-I probe (Dentsply Rinn, York, PA, USA) and a syringe. After instrumentation was completed, 30 s of irrigation was performed with 17% EDTA (Canalarge, Ammdent, Chandigarh, India) keeping the needle just short of binding point but no closer than 2 mm from the working length. Then, three cycles of irrigation was performed using 3% NaOCl, 17% EDTA and 3% NaOCl. The irrigation needle was placed at working length and irrigation with NaOCl for 30 s was accomplished. The irrigant was then left undisturbed in the canal for 60 s. This was followed by irrigation with EDTA for 30 s and then left undisturbed for 60 s. The last irrigant was NaOCl, using the same method for the same amount of time. A small (1-2 mm), constant apico-coronal movement of the needle was maintained during expression of irrigant (n = 20).

Group C: Final irrigation was performed using an EndoVac (Discus Dental Smart Endodontics, Higuera Street, Culver City, CA, USA) irrigation system. After instrumentation was completed, 30 s of irrigation was performed with 1 mL of 17% EDTA using a macrocannula. This was performed by using the EndoVac delivery/evacuation tip at the canal orifice while the macrocannula was constantly moved up and down in the canal from the point where it started to bind to the point just below the canal orifice. Then, three cycles of microirrigation were performed using 3 mL each of 3% NaOCl, 17% EDTA and 3% NaOCl. During a cycle of microirrigation, the pulp chamber was maintained full of irrigant while the microcannula was placed at the working length for 6 s and then moved in the apico-coronal direction until 30 s had elapsed. The irrigant was then left undisturbed for 60 s. This completed one microirrigation cycle. Similarly, the other two cycles of microirrigation were performed (n = 20).

The canals were dried with absorbent paper points and the entrance to each of the canals was protected with a cotton pellet to prevent penetration of the dentinal debris into the canals during decoronation. A #15 K-file with rubber stopper set at working length was placed on the external surface of the tooth and working length was marked with a scalpel. Teeth were then marked at 1 mm from the working length with a scalpel. Using diamond discs with water, the crown was removed at the cement-enamel junction and deep grooves were made on the buccal and palatal surfaces of the roots without perforating the canal. The roots were then split longitudinally using a chisel. One half of each root was selected for examination under a scanning electron microscope.

After assembly on coded stubs, the specimens were gold sputtered and examined under a scanning electron microscope. The dentinal wall of the apical 1 mm was observed for the presence/absence of smear layer. Photomicrographs were taken of the canal walls at 1 mm from the working length of each specimen at 1000X magnification. These photomicrographs were evaluated individually by an examiner who was blind to the irrigation regimens and scores were attributed according to the following scoring criteria developed by Mayer et al. in 2003. [7]

Smear layer

Score 1 - All dentinal tubules are open and no smear layer is present

Score 2 - Some dentinal tubules are open and others covered by thin smear layer

Score 3 - A few dentinal tubules are open and others covered by thin homogenous smear layer

Score 4 - All dentinal tubules are covered by a homogenous smear layer without any open tubules visible

Score 5 - Thick homogenous layer completely covering the canal walls.

Attributed scores were tabulated and submitted to statistical analysis. The Mann-Whitney U test and non-parametric tests such as Kruskal Wallis test were used for comparisons between the various groups.

   Results Top

[Table 1] shows the mean and standard deviation for three groups at the 1 mm level. At the 1 mm level, the EndoVac system showed significantly cleaner root canals when compared with the Max-I probe irrigation (P = 0.0001) [Table 2]. [Figure 1], [Figure 2], [Figure 3] show representative scanning electron micrograph photographs for groups A, B and C, respectively, at the 1 mm level.
Figure 1: Group A (positive control) at 1 mm from working length

Click here to view
Figure 2: Group B (Max-I probe) at 1 mm from working length

Click here to view
Figure 3: Group C (EndoVac system) at 1 mm from working length

Click here to view
Table 1: Mean, SD and median values in the three groups (A, B and C) for smear layer

Click here to view
Table 2: Pair-wise comparison of the three groups (A, B and C) with respect to smear layer scores at 1 mm by the Mann-Whitney U test

Click here to view

   Discussion Top

The ultimate goal of root canal preparation is canal debridement to promote apical healing. [14] After biomechanical preparation, a layer of debris composed of organic and inorganic material is formed on the root canal walls, obliterating the dentinal tubule entrances and root canal ramifications. [15] The smear layer may prevent or delay considerably the penetration of antimicrobial agents into the dentinal tubules [16] as well as interfere with the adhesion of root canal sealers to the canal walls thus compromising the quality of obturation. [17],[18] Various methods have been employed to eliminate debris and smear layer from the root canal; however, none of the methods employed completely eliminate bacteria from the apical 1 mm of the root canal. [19],[20]

Sodium hypochlorite is the most widely used chemical solution in the biomechanical preparation of the root canal system. [21] However, despite its excellent antimicrobial activity and capacity of dissolving organic materials, this solution alone does not effectively remove the smear layer. [21],[22] The association of EDTA and NaOCl solutions has proven to be effective in removing the smear layer. [3] EDTA acts upon the inorganic components of the smear layer while NaOCl dissolves the collagen, leaving the entrances to the dentinal tubules more open and exposed. Studies have shown that the use of a high-volume final flush with 17% EDTA followed by NaOCl effectively removes the smear layer. [23] However, none of the irrigants with the conventional irrigation system are effective in cleaning the apical one-third of the root canal. [2]

Various irrigation systems have been developed that claim to work effectively in the apical third of the root canal. [24]

In the current study, root canal instrumentation was performed with rotary nickel-titanium instruments that create a significant smear layer and hence are more challenging for irrigation systems. Apical preparations were extended to size 50/0.06 file to allow adequate penetration of solutions to the apical third of each root canal. A closed system of root canal was created to simulate in vivo situations, in which there is possible gas entrapment inside the root canal. The results of our study showed that the EndoVac system produced significantly cleaner canals at 1 mm from working length compared with the Max-I probe. This can be attributed to the design of the EndoVac microcannula and the placement of the 12 suction holes along the side of the last 0.07 mm of the microcannula. As the apical size increases, there are decreased chances of these holes contacting the root canal wall and becoming blocked. The larger area surrounding the microcannula also allows for increased volume of irrigant to the microcannula tip and a resulting increase in volume. [25]

Another factor that supports the better cleaning efficacy of EndoVac in the apical 1 mm when compared with the Max-I probe is the vapor lock effect. The presence of apical vapor lock created by the organic decomposition of NaOCl into a bubble of carbon dioxide and ammonium adversely affects debridement efficacy when using a positive pressure system. [26] In the closed system, irrigant extrusion beyond 1-1.5 mm of a side-venting needle could generate a liquid film along the air bubble-canal wall interface. [27] The fluid stagnation in this "dead water zone" (apical area where the solutions are not exchanged by irrigation) fails to provide adequate irrigant replacement, resulting in gross debris retention in this region. Also, irrigation with an acidic or calcium chelating agent creates a demineralized collagen matrix on the surface of the radicular dentin on removal of the smear layer. [28],[29] In the absence of strong turbulent fluid flow, debris particles could be trapped by this porous interlacing fibrillar network as they were displaced by the irrigant toward the orifice. [26] The design of the microcannula however eliminates this vapor-lock effect thus allowing apical exchange of irrigants. Moreover, macrocannula removes as much debris as possible before a microcannula is used thus allowing better action of the latter and preventing the chances of blockage of the microcannula.

The results of our study are in accordance with the studies of Nielsen et al. [13] and Mohan Abarajithan et al., [30] with the EndoVac irrigation system showing better debridement than conventional needle irrigation at the apical level of root canal. Our study showed that the EndoVac irrigation system is an effective root canal irrigation system for the removal of intracanal smear layer in the apical area. Nevertheless, these in vitro results cannot be extrapolated to in vivo situations. Hence, further research is required and more in vivo studies need to be performed to evaluate this method of irrigation.

   Conclusion Top

Within the limitations of the present study, it could be concluded that the apical negative pressure system (EndoVac) used in the study is significantly more effective than the side-vented closed ended needle (Max-I probe) in removal of smear layer at the apical 1 mm level.

   Acknowledgment Top

The authors deny any conflicts of interest. The authors would like to thank Dr. Beena Rani Goel for providing the EndoVac system for this study. They would also like to thank Mr. Gurulingam, Indian Institute of Science, Bangalore, for technical assistance and Mr. Shivalingappa Javali for assistance in statistical analysis.

   References Top

1.Crumpton BJ, Goodell GG, McClanaban 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. 1
2.Baumgartner JC, Mader CL. A scanning electron microscopic evaluation of four root canal irrigation regimens. J Endod 1987;13:147-57.  Back to cited text no. 2
3.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. 3
4.Khedmat S, Shokouhinejad N. Comparison of the efficacy of the three chelating agents in smear layer removal. J Endod 2008;34:599-602.  Back to cited text no. 4
5.Senia ES, Marshall FJ, Rosen S. The solvent action of sodium hypochlorite on pulp tissue of extracted teeth. Oral Surg Oral Med Oral Pathol 1971;31:96-103.  Back to cited text no. 5
6.Baker NA, Eleazer PD, Averbach RE, Seltzer S. Scanning electron microscopic study of the efficacy of various irrigating solutions. J Endod 1975;1:127-35.  Back to cited text no. 6
7.Mayer BE, Peters OA, Barbakow F. Effects of rotary instruments and ultrasonic irrigation on debris and smear layer scores: A scanning electron microscopic study. Int Endod J 2002;35:582-9.  Back to cited text no. 7
8.Ram Z. Effectiveness of root canal irrigation. Oral Surg Oral Med Oral Pathol 1977;44:306-12.  Back to cited text no. 8
9.Kahn FH, Rosenberg PA, Gliksberg J. An in vitro evaluation of the irrigating characteristics of ultrasonics and subsonic handpieces and irrigating needles and probes. J Endod 1995;21:277-80.  Back to cited text no. 9
10.Witton R, Henthorn K, Ethunandan M, Harmer S, Brennan PA. Neurological complications following extrusion of sodium hypochlorite solution during root canal treatment. Int Endod J 2005;38:843-7.  Back to cited text no. 10
11.JeonI S, Spångberg LS, Yoon TC, Kazemi RB, Kum KY. Smear layer production by 3 rotary reamers with different cutting blade designs in straight root canals.Oral Surg Oral Med Oral Path Oral Radiol Endod 2003;96:601-7.  Back to cited text no. 11
12.Peters OA, Barbakow F. Effects of irrigation on debris and smear layer on canal walls prepared by two rotary techniques: A scanning electron microscopic study. J Endod 2000;26:6-10.  Back to cited text no. 12
13.Nielsen BA, Craig Baumgartner J. Comparison of EndoVac system to needle irrigation of root canals. J Endod 2007;33:611-5.  Back to cited text no. 13
14.Bystrom A, Happonen RP, Sjogren U, Sundqvist G. Healing of periapical lesions of pulpless teeth after endodontic treatment with controlled asepsis. Endod Dent Traumatol 1987;3:58-63.  Back to cited text no. 14
15.Orstavik D, Haapasalo M. Disinfection by endodontic irrigants and dressings of experimentally infected dentinal tubules. Endod Dent Traumatol1990;6:142-9.  Back to cited text no. 15
16.Lynne RE, Liewehr FR, West LA, Patton WR, Buxton TB, McPherson JC. Invitro antimicrobial activity of various medication preparations on E. faecalis in root canal dentin. J Endod 2003;29:187-90.  Back to cited text no. 16
17.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. 17
18.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. 18
19.Moodnik RM, Dorn SO, Feldman MJ, Levey M, Borden BG. Efficacy of biomechanical instrumentation: A scanning electron microscopic study. J Endod 1976;2:261-6.  Back to cited text no. 19
20.Moorer WR, Wesselink PR. Factors promoting the tissue dissolving capability of sodium hypochlorite. Int Endod J 1982;15:187-96.  Back to cited text no. 20
21.da Silva LA, Sanguino AC, Rocha CT, Leonardo MR, Silva RA. Scanning electron microscopic preliminary study of the efficacy of Smear Clear and EDTA for smear layer removal after root canal instrumentation in permanent teeth. J Endod 2008;34:1541-4.  Back to cited text no. 21
22.Pérez-Heredia M, Ferrer-Luque CM, González-Rodríguez MP.The effectiveness of different acid irrigating solutions in root canal cleaning after hand and rotary instrumentation. J Endod 2006;32:993-7.  Back to cited text no. 22
23.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. 23
24.Gu LS, Kim JR, Ling J, Choi KK, Pashley DH, Tay FR. Review of Contemporary irrigant agitation techniques and devices. J Endod 2009;35:791-804.  Back to cited text no. 24
25.Brunson M, Heilborn C, Johnson DJ, Cohenca N. Effect of apical preparation size and preparation taper on irrigant volume delivered by using negative pressure irrigation system. J Endod 2010;36:721-4.  Back to cited text no. 25
26.Tay FR, Gu LS, Schoeffel GJ, Wimmer C, Susin L, Zhang K, et al. Effect of vapor lock on root canal debridement using a side-vented needle for positive-pressure irrigant delivery. J Endod 2010;36:745-50.  Back to cited text no. 26
27.Liao Q, Zhao TS. Modeling of Taylor bubble rising in a vertical mini noncircular channel filled with a stagnant liquid. Int J Multiphase Flow 2003;29:411-34.  Back to cited text no. 27
28.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. 28
29.Uroz-Torres D, González-Rodríguez MP, Ferrer-Luque CM. Effectiveness of the EndoActivator System in removing the smear layer after root canal instrumentation. J Endod 2010;36:308-11.  Back to cited text no. 29
30.Abarajithan M, Dham S, Velmurugan N, Valerian-Albuquerque D, Ballal S, Senthilkumar H. Comaprison of EndoVac irrigation system with conventional irrigation for removal of intracanal smear layer: An invitro study. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2011;112:407-11.30.  Back to cited text no. 30


  [Figure 1], [Figure 2], [Figure 3]

  [Table 1], [Table 2]

This article has been cited by
1 Efficacy of irrigant activation techniques in removing intracanal smear layer and debris from mature permanent teeth: a systematic review and meta-analysis
S. S. Virdee,D. W. Seymour,D. Farnell,G. Bhamra,S. Bhakta
International Endodontic Journal. 2017;
[Pubmed] | [DOI]


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

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

 Article Access Statistics
    PDF Downloaded241    
    Comments [Add]    
    Cited by others 1    

Recommend this journal