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 Table of Contents  
ORIGINAL ARTICLE
Year : 2016  |  Volume : 28  |  Issue : 2  |  Page : 171-175

A scanning electron microscope evaluation of smear layer removal from root canals prepared by manual or rotary instrumentation using three different irrigating systems: An in vitro study


1 Department of Conservative Dentistry and Endodontics, Bhojia Dental College and Hospital, Bhud, Baddi, Solan, Himachal Pradesh, India
2 Department of Pediatric and Preventive Dentistry, Gian Sagar Dental College and Hospital, Ram Nagar, Banur, Rajpura, Punjab, India

Date of Web Publication9-Dec-2016

Correspondence Address:
Simran Pal Singh Bindra
608 L, Model Town, Ludhiana, Punjab
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0970-7212.195434

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  Abstract 


Introduction: Smear layer removal after root canal instrumentation requires the use of irrigating solutions, either alone or in combination. The mechanical debridement efficacy of an irrigation delivery/agitation system is dependent on its ability to deliver the irrigant to the apical and noninstrumented regions of the canal space and to create a strong enough current to carry the debris away from the canal walls.
Materials and Methods: Ninety extracted single-rooted anterior teeth were included in the study and divided into two groups of 45 each. Biomechanical preparation was done with hand files in Group A and with rotary files in Group B. Three subgroups were further made from each group, wherein Max-I-Probe, Endosonic files, and EndoActivator irrigation systems were used in subgroups I, II, and III, respectively. After irrigation with 10% citric acid, specimens were split and the root surfaces were evaluated under scanning electron microscope at cervical, middle, and apical levels.
Results: The removal of smear layer was more complete in coronal and middle thirds than in the apical third. No significant difference was found on the removal of smear layer in manually or rotary instrumented groups. When mean scores for all the groups were obtained, Max-I-Probe hand file (Group IA) was found to be most effective in cleaning smear layer in cervical third of root canals, whereas Endosonic rotary showed the best result in both middle and apical third.
Conclusion: EndoActivator system did not enhance the removal of smear layer as compared with Endosonic system and the conventional Max-I-Probe irrigation with NaOCl and 10% citric acid. removal of smear layer was more complete in coronal and middle thirds than in the apical third.

Keywords: EndoActivator; Endosonic; Max-I-Probe; smear layer.


How to cite this article:
Bindra SP, Chhabra A, Damanpreet, Garg N, Jindal V, Sharma S. A scanning electron microscope evaluation of smear layer removal from root canals prepared by manual or rotary instrumentation using three different irrigating systems: An in vitro study. Endodontology 2016;28:171-5

How to cite this URL:
Bindra SP, Chhabra A, Damanpreet, Garg N, Jindal V, Sharma S. A scanning electron microscope evaluation of smear layer removal from root canals prepared by manual or rotary instrumentation using three different irrigating systems: An in vitro study. Endodontology [serial online] 2016 [cited 2019 Aug 25];28:171-5. Available from: http://www.endodontologyonweb.org/text.asp?2016/28/2/171/195434




  Introduction Top


Mechanical cleaning and shaping is the most time-consuming and difficult aspect of endodontic treatment.[1] Throughout the biomechanical preparation, copious irrigation is done to remove loose, necrotic, and contaminated materials and to disinfect the root canals and dentinal tubules.[2] In addition to superficial debris, a layer of sludge material is always formed over the surface of the instrumented root canals. This layer was termed smear layer by McComb and Smith in 1975.[3]

To eliminate the smear layer after biomechanical preparation, irrigating solutions are used. An ideal root canal irrigant should be able to clean the root canal, provide antimicrobial property, and remove smear layer and debris.[4] Most commonly used irrigants in endodontics are normal saline, sodium hypochlorite (NaOCl), hydrogen peroxide, ethylenediaminetetraacetic acid (EDTA), chlorhexidine, and citric acid.[5] NaOCl has the tissue-dissolving capacity and antimicrobial activity which make it an excellent irrigating solution,[6] but it has only a limited effect on the dissolution of smear layer. Smear layer is best removed by the use of acid solutions.[5] Commonly used irrigants for the removal of smear layer are EDTA 17% and 1–50% citric acid.[7],[8]

Mechanical debridement efficacy of an irrigation system depends on its ability to deliver the irrigating solution to the apical and noninstrumented areas of the root canal space and flush out debris away from the canal walls.[9] During the conventional needle irrigation, replenishment and fluid exchange do not extend much beyond the tip of the irrigating needle.[10] Vapor lock which causes trapped air in the apical third of root canals may obstruct the exchange of irrigants and hamper the debridement effectiveness of irrigants.[11] Therefore, various irrigant delivery systems have been developed to augment the flow and delivery of irrigating solutions within the root canal system.[12]

The purpose of this study was to evaluate the removal of smear layers produced by the newer anterior twisted instruments under scanning electron microscope (SEM) in comparison to hand instruments using 10% citric acid as irrigant using three different irrigation systems.


  Materials and Methods Top


The present study was carried out in the outpatient Department of Conservative and Endodontics Dentistry, Bhojia Dental College and Hospital, Baddi, in association with the Department of CRF, IIT, Ropar, for SEM. Ninety extracted single-rooted anterior teeth were included in the study to evaluate and compare the efficacy of various irrigations systems on the removal of smear layer. Samples were stored in 5.25% NaOCl (Dentpro, Amrit Chemicals Ltd., Mohali, Punjab, India) for 30 min for the removal of organic debris, then in chloramine T until further steps.

Sample preparation

Superficial grooves were put mesiodistally with the help of a metallic disc and mandrel along the longitudinal axis, approximately 0.5 mm in depth. Specimens were decoronated to obtain a standardized root length of 13 mm.

Root canal instrumentation

Glide path was made using ISO no. 10 K file, and the working length was determined visually by placing a small no. 10 K file inside the root canal until it was just visible at the apical foramen. About 1 mm length was subtracted from the total length to give a working length of 1 mm short of the apex. Teeth were divided into two groups of 45 samples each. Ten percent of citric acid was used for irrigation in all samples and was always freshly prepared by dissolving 100 g of citric acid in 10 ml of distilled water.

Group A

Here, the specimens were prepared using Gates Glidden (Dentsply Maillefer; Ballaigues, Switzerland) and hand K-files (Dentsply Maillefer; Ballaigues, Switzerland) in a corono-apical direction. Gates Glidden (No. 3 and 2) were used in decreasing the size to prepare coronal and middle third of the canal. Apical part was prepared by using hand files starting with larger file size of 55 and subsequently using smaller number files deeper into the canal in sequential order till size no. 40 at the working length. Root canals were irrigated between each instrument using a 3 mL of 3% NaOCl solution via a 27-gauge needle placed as deep as possible into the canal without resistance. After the biomechanical preparation, the samples were further divided into three subgroups of 15 samples each.

Subgroup IA

Root canals were flushed with 5 ml of irrigating solution using plastic syringe with a closed-end 30-gauge needle, i.e, Max-I-Probe inserted within 1–2 mm of working length of the root canal without binding. Irrigation was done for 60 s.

Subgroup IIA

Before using MM1500 air sonic handpiece, the water to handpiece was turned off from the dental unit. Irrigant was placed into the canal with a syringe and 25-gauge needle before introducing a sonic irrigation file. #15 ShaperSonic was used passively in the canal to cavitate the irrigating solution. Irrigating file was placed 1–2 mm short of the working length. The rheostat pedal was fully depressed and maintained a 3–5 mm vertical motion for 1 min.

Subgroup IIIA

Final irrigation was done with 5 ml of irrigant which was placed into the canal with a syringe and 25-gauge needle and was activated with EndoActivator System (Dentsply, Tulsa, OK) at 10,000 cycles per minute (cpm), with a size 25/0.04 polymer tip. Working tips used were placed as deep in the root canals as possible without encountering resistance, but not deeper than the predetermined WL minus 1 mm. It was then smoothly moved in 2–3 mm vertical up and down vertical strokes to facilitate unobstructed backflow of the irrigation solution.

Finally, in all the samples from all the subgroups, the canals were flushed with 5 mL of normal saline and dried with sterile paper points.

Group B

The instrumentation was done in crown down canal preparation using a gentle in-and-out motion with rotary twisted files in accordance with the manufacturer's instruction. The root canals were irrigated following the same protocol as in Group A. After the biomechanical preparation, the samples were further divided into three subgroups as follows:

Subgroup IB

Irrigation with Max-I-Probe (n = 15). Irrigation was done same as in subgroup IA.

Subgroup IIB

Irrigation using Endosonic files (n = 15). Irrigation was done same as in subgroup IIA.

Subgroup IIIB

Irrigation using EndoActivator (n = 15). Irrigation was done same as in subgroup IIIA.

Laboratory procedure

After splitting along the longitudinal axis, samples were dehydrated in ascending concentrations of ethyl alcohol (30–100%) and subsequently desiccated. Each specimen was mounted on an aluminum stub and then coated with gold-palladium particles to render a conductive surface. The specimen was divided into cervical, middle, and apical thirds. Then, the surfaces were evaluated under SEM at ×2000 magnification. Representative microphotographs from cervical, middle, and apical thirds were taken for all the specimens. The microphotographs were assessed blindly by a single examiner and reassessed by the same examiner after 15 days interval to avoid the visual memory. The scores were given to the images according to the scoring criterion given by Torabinejad et al.[13]

The final result of the smear layer analysis of each root canal specimen was obtained by calculating the percentage of each score on the images. The results were tabulated and subjected to statistical analysis.


  Results Top


Removal of smear layer from the surfaces of root canals revealed the presence of more abundant and larger dentinal tubules in the cervical third of root canals compared with those seen in the middle and apical thirds of the root canal system [Figure 1] and [Table 1]. Smaller and fewer dentinal tubules were observed in the apical third of the canals than those in the rest of the root canals. However, no significant differences were found between manual and rotary instrumentation in smear layer removal in all parts of root canal [Table 2].
Figure 1: Comparison of efficacy on smear layer removal in permanent root canals by various root canal irrigation devices

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Table 1: Mean±standard deviation of smear scores on the root canal walls in different groups at different levels

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Table 2: Intercomparison of smear layer removal capacity of Group A with Group B

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  Discussion Top


In the present study, ninety extracted permanent anterior teeth were selected because these teeth show less canal aberrations. These crowns were decoronated at cementoenamel junction using a water-cooled diamond disc. This was done to eliminate any variables in access preparation and to have a stable reference for all measurements. Crown down technique was done for instrumentation in both the groups to prevent the extrusion of debris in periapical area. In Group A, instrumentation was done with hand files, and in Group B, it was done using Twisted Files (SybronEndo, Orange, CA, USA). Twisted Files have a triangular cross-section with constant tapers and are manufactured by twisting a triangular piece of nickel–titanium wire and adding three new design features; R-phase heat treatment, twisting of the metal wire, and a special surface conditioning.[14] Because of this manufacturing process, these files are believed to be superior to the traditional file systems when their flexibility, cyclic fatigue resistance, cutting efficiency, and ability to maintain the original canal shape with minimal transportation were compared.[15]

To avoid the anatomic variables, the Master Apical File, rotary and hand instrument taper were standardized. The apical portion of each canal was enlarged to a size 40 files. This preparation helped the placement of the irrigation and agitation devices, 1–2 mm short of WL because penetration depth of the irrigation needle affects the mechanical efficacy of irrigation and the removal of debris.[16]

Ferrer Luque et al.[17],[18] had established that different concentrations of citric acid at 10, 25, and 50% were effective in removing smear layer with ultrasonic and hand techniques. In our study, in both the groups, the smear layer was removed using saline, 3% NaOCl, and 10% citric acid. Traditionally, the conventional irrigation with syringes was considered an efficient method of irrigation before the advent of passive ultrasonic activation.[19] Group IA and IB in this study were irrigated using Max-I-Probe system. While using Max-I-Probe, the aim was “needle deep” irrigation, when the total volume of irrigant is delivered within 1 mm of the working length.[20] Pavlovic and Zivkovic [21] found that a laterally perforated needle for irrigation allows better cleaning of root canal walls as compared to the conventional needles.

In the other two groups, sonic irrigation devices were studied. Sonic irrigation was performed using MM1500 Sonic Air in an air-driven handpiece. The air pressure transmits sonic waves along RispiSonic and ShaperSonic instruments with an adjustable frequency range of 0–1500 Hz. Coronal two-third was prepared using RispiSonic, and simultaneous debriding of the apical and coronal thirds was carried out using ShaperSonic instruments.

The EndoActivator system is a sonically driven canal irrigation system. In general, 10,000 cpm has been shown to optimize debridement and promote disruption of the smear layer and biofilm. Therefore, after placing the 5 ml of 10% citric acid in the canal with syringe, the EndoActivator 25/0.04 polymer tip was activated at 10,000 cpm for 1 min.

At an ultrastructural level, as visualized in SEM, debris were evident as irregular, disorganized sludge-like material covering and masking the openings of dentinal tubules and any depressions in the canal wall. Micrographs for assessing the efficacy of debris and smear layer removal were taken at ×2000 magnifications in the coronal, middle, and apical parts of the canal walls according to a scale developed by Torabinejad et al.[13]

Although one group was prepared using hand files and other group was prepared using rotary twisted files, no significant difference was found on the removal of smear layer in manually or rotary instrumented groups. Similar results were found by Ahlquist et al.[22] who compared the rotary instrumentation technique with Twisted Files and hand instrumentation with K-files using 0.5% NaOCl.

The results of smear scores obtained in our study were in accordance with the studies which showed that the smear layer was not removed completely in the apical third of the root canal by using 1 mL of BioPure MTAD (Dentsply Tulsa Dental) or 1 mL of 17% EDTA, followed by 3 mL of 5.25 NaOCl.[23],[24] However, very few studies reported that there was no statistically significant difference between the apical, middle, and coronal third of the canal walls.[24]

When mean scores for all the groups were obtained, Max-I-Probe hand file (Group IA) was found to be most effective in cleaning smear layer in cervical third of root canals, whereas Endosonic rotary showed the best result in both middle and apical third. These findings were similar to de Gregorio et al's.[6] study who showed that by using ultrasonic and sonic activation in simulated lateral canals, better irrigation in the apical third was attained as compared to the traditional needle irrigation alone. Our results are also similar to Uroz-Torres et al.[25] who found better smear layer removal by Max-I-Probe when compared to EndoActivator. Numerous studies have reported passive sonic irrigation to be significantly more effective than hand filling alone, though ultrasonic irrigation superseded sonic in all of the studies.[26]

These results are similar to those reported by Rödig et al.[16] EndoActivator performed better in coronal and middle third than at apical third of canal. This showed that agitation of the irrigant did not increase the efficacy of debris removal, which was significantly more effective at the coronal than at the apical level.


  Conclusion Top


Within the limitations of our study, the EndoActivator system did not enhance the removal of smear layer as compared with Endosonic system and the conventional Max-I-Probe irrigation with NaOCl and 10% citric acid. The removal of smear layer was more complete in coronal and middle thirds than in the apical third. Further research entailing different solutions, volumes, and activation times of the irrigant would be necessary to fully evaluate the effectiveness of the Endosonic and EndoActivator System in smear layer removal after root canal instrumentation. The results demand the need for better irrigant protocols to completely remove debris from the apical third of the canal.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

1.
Raisingani D, Meshram GK. A scanning electron microscopic evaluation of manual and automated instrumentation using 4% sodium hypochlorite and EDTA. Int J Clin Pediatr Dent 2010;3:173-82.  Back to cited text no. 1
    
2.
Hariharan VS, Nandlal B, Srilatha KT. Efficacy of various root canal irrigants on removal of smear layer in the primary root canals after hand instrumentation: A scanning electron microscopy study. J Indian Soc Pedod Prev Dent 2010;28:271-7.  Back to cited text no. 2
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3.
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. 3
    
4.
Balaji TS. Effect of various root canal irrigants on removal of smear layer and debris. A scanning electron microscopy study. Pak Oral Dent J 2010;30:205-10.  Back to cited text no. 4
    
5.
Zehnder M, Kosicki D, Luder H, Sener B, Waltimo T. Tissue-dissolving capacity and antibacterial effect of buffered and unbuffered hypochlorite solutions. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2002;94:756-62.  Back to cited text no. 5
    
6.
de Gregorio C, Estevez R, Cisneros R, Heilborn C, Cohenca N. Effect of EDTA, sonic, and ultrasonic activation on the penetration of sodium hypochlorite into simulated lateral canals: An in vitro study. J Endod 2009;35:891-5.  Back to cited text no. 6
    
7.
Czonstkowsky M, Wilson EG, Holstein FA. The smear layer in endodontics. Dent Clin North Am 1990;34:13-25.  Back to cited text no. 7
    
8.
Loel DA. Use of acid cleanser in endodontic therapy. J Am Dent Assoc 1975;90:148-51.  Back to cited text no. 8
    
9.
Moser JB, Heuer MA. Forces and efficacy in endodontic irrigation systems. Oral Surg Oral Med Oral Pathol 1982;53:425-8.  Back to cited text no. 9
    
10.
Chow TW. Mechanical effectiveness of root canal irrigation. J Endod 1983;9:475-9.  Back to cited text no. 10
    
11.
Tay FR, Gu LS, Schoeffel GJ, Wimmer C, Susin L, Zhang K, et al. Effect of vapor lock on root canal debridement by using a side-vented needle for positive-pressure irrigant delivery. J Endod 2010;36:745-50.  Back to cited text no. 11
    
12.
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. 12
    
13.
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;29:170-5.  Back to cited text no. 13
    
14.
Gambarini G, Grande NM, Plotino G, Somma F, Garala M, De Luca M, et al. Fatigue resistance of engine-driven rotary nickel-titanium instruments produced by new manufacturing methods. J Endod 2008;34:1003-5.  Back to cited text no. 14
    
15.
Larsen CM, Watanabe I, Glickman GN, He J. Cyclic fatigue analysis of a new generation of nickel titanium rotary instruments. J Endod 2009;35:401-3.  Back to cited text no. 15
    
16.
Rödig T, Döllmann S, Konietschke F, Drebenstedt S, Hülsmann M. Effectiveness of different irrigant agitation techniques on debris and smear layer removal in curved root canals: A scanning electron microscopy study. J Endod 2010;36:1983-7.  Back to cited text no. 16
    
17.
Ferrer Luque CM, González López S, Navajas Rodríguez de Mondelo JM. Mechanical instrumentation of the root canals. A study using SEM and computerized image analysis. Bull Group Int Rech Sci Stomatol Odontol 1996;39:111-7.  Back to cited text no. 17
    
18.
Ferrer Luque CM, González López S, Navajas Rodríguez de Mondelo JM. The area of dentinal diffusion at the time of the manual preparation of root canals. Bull Group Int Rech Sci Stomatol Odontol 1996;39:103-9.  Back to cited text no. 18
    
19.
van der Sluis LW, Gambarini G, Wu MK, Wesselink PR. The influence of volume, type of irrigant and flushing method on removing artificially placed dentine debris from the apical root canal during passive ultrasonic irrigation. Int Endod J 2006;39:472-6.  Back to cited text no. 19
    
20.
Sedgley CM, Nagel AC, Hall D, Applegate B. Influence of irrigant needle depth in removing bioluminescent bacteria inoculated into instrumented root canals using real-time imaging in vitro. Int Endod J 2005;38:97-104.  Back to cited text no. 20
    
21.
Pavlovic V, Zivkovic S. The effect of different irrigation techniques on the quality of cleaning of root canal walls. Serbian Dent J 2008;55:221-8.  Back to cited text no. 21
    
22.
Klyn SL, Kirkpatrick TC, Rutledge RE.In vitro comparisons of debris removal of the EndoActivator system, the F file, ultrasonic irrigation, and NaOCl irrigation alone after hand-rotary instrumentation in human mandibular molars. J Endod 2010;36:1367-71.  Back to cited text no. 22
    
23.
Stamos DE, Sadeghi EM, Haasch GC, Gerstein H. An in vitro comparison study to quantitate the debridement ability of hand, sonic, and ultrasonic instrumentation. J Endod 1987;13:434-40.  Back to cited text no. 23
    
24.
Caron G, Nham K, Bronnec F, Machtou P. Effectiveness of different final irrigant activation protocols on smear layer removal in curved canals. J Endod 2010;36:1361-6.  Back to cited text no. 24
    
25.
Uroz-Torres D, Gonzalez-Rodrıguez MP, Ferrer-Luque CM. Effectiveness of the EndoActivator system in removing the smear layer after root canal instrumentation. J Endod 2010;6:1-4.  Back to cited text no. 25
    
26.
Saini E, Kumari M, Taneja S. Comparative evaluation of the efficacy of three different irrigation devices in removal of debris from root canal at two different levels: An in vitro study. J Conserv Dent 2013;16:509-13.  Back to cited text no. 26
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