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 Table of Contents  
Year : 2022  |  Volume : 34  |  Issue : 3  |  Page : 168-172

Effect of glide path files with different metallurgy on intracanal bacterial extrusion by HyFlex electrical discharge machining file: An in vitro study

1 Department of Conservative Dentistry and Endodontics, ITS Centre for Dental Studies and Research, Ghaziabad, Uttar Pradesh, India
2 Department of Oral and Maxillofacial Pathology and Microbiology, ITS Centre for Dental Studies and Research, Ghaziabad, Uttar Pradesh, India

Date of Submission08-Feb-2022
Date of Decision01-Apr-2022
Date of Acceptance13-Apr-2022
Date of Web Publication30-Sep-2022

Correspondence Address:
Dr. Priyanka Soni
Department of Conservative Dentistry and Endodontics, ITS Centre for Dental Studies and Research, Muradnagar, Ghaziabad, Uttar Pradesh
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/endo.endo_39_22

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Introduction: Glide path preparation permits predictable debridement and shaping of radicular space while reducing procedural errors like apical extrusion of debris and microorganisms which can postpone healing. The aim of this study was to comparatively evaluate the effect of glide path files with different metallurgy on apically extruded Enterococcus faecalis.
Materials and Methods: Forty human mandibular bicuspids were selected, decoronated, and autoclaved. The samples were placed in a test apparatus of sterilized glass vials and inoculated with E. faecalis. The specimens were randomly allocated into four major groups (n = 10) each depending on the glide path file used – Group I with Proglider, Group II with EdgeGlidePath Files, Group III with Neoniti GPS, and Group IV without rotary glide path instruments using HyFlex electrical discharge machining (EDM). After glide path preparation, final canal preparation was done with HyFlex EDM. The apically extruded E. faecalis was counted as colony-forming unit and was converted into log values. Statistical analysis was evaluated using Kruskal–Wallis H Test and Mann–Whitney U-test using SPSS software; version 22.0 (SPSS INC., Chicago, IL, USA).
Results: Group IV without glide path preparation technique showed maximum extrusion of E. faecalis in comparison to other groups (P < 0.05). Groups I and II showed a similar quantity of extruded bacteria. Group III showed significantly higher bacterial extrusion than Groups I and II.
Conclusions: Glide path preparation groups showed less amount of apically extruded E. faecalis. EDGEGlidePath files showed lesser apically extruded E. faecalis in comparison to Proglider and Neoniti GPS.

Keywords: Bacterial extrusion, EDGEGlidePath, Glide path, Neoniti GPS, Proglider

How to cite this article:
Soni P, Kumar P, Taneja S, Jain A. Effect of glide path files with different metallurgy on intracanal bacterial extrusion by HyFlex electrical discharge machining file: An in vitro study. Endodontology 2022;34:168-72

How to cite this URL:
Soni P, Kumar P, Taneja S, Jain A. Effect of glide path files with different metallurgy on intracanal bacterial extrusion by HyFlex electrical discharge machining file: An in vitro study. Endodontology [serial online] 2022 [cited 2023 Jan 31];34:168-72. Available from: https://www.endodontologyonweb.org/text.asp?2022/34/3/168/357702

  Introduction Top

The success of endodontic treatment is grounded on the sound principles of cleaning, disinfection, and three-dimensional obturation, creating a favorable environment for the healing of periradicular tissues.[1] Various studies have shown that during chemomechanical preparation, extrusion of dentinal shavings, necrotic content, irrigating solution, microorganisms, and their products into the periradicular region can occur.[2],[3],[4] The extruded materials can be correlated to inflamed periapical tissues and postoperative flare-ups, which may postpone healing.[5],[6] Enterococcus faecalis is predominantly associated with failed root canals, persistent periapical lesions, and flare-ups.[7] The severity of acute periradicular inflammation depends on the amount of bacteria (quantitative factor) as well as virulence (qualitative factor) of the microbial species which is apically extruded.[8] Qualitative factors cannot be controlled clinically, but quantitative factors may be reduced by selecting technique or procedure that lowers extrusion in the apical region.[1]

Several studies suggested that the different systems of root canal preparation and the major factors associated with bacterial and debris extrusion apically are instrument design.[1] NiTi rotary instruments, regardless of several benefits such as reduced operator fatigue and centered and well-tapered preparation of root canal, are associated with certain disadvantages like file separation mainly due to excessive torsional and flexural stresses and taper lock.[8]

These mishaps can be prevented by coronal preflaring and glide path preparation of the radicular space.[8] Earlier preparation of glide path was accomplished by the utilization of stainless steel hand files. However, establishing a glide path using hand instruments requires much effort and is time-consuming, particularly in dilacerated or extremely narrow root canal anatomies.[9] Therefore, with the advent of technology, the nickel–titanium rotary glide path files has been introduced in the field of endodontics to enhance safety and preciseness of the procedure.[7]

Earlier multiple file systems were established by different manufacturers for glide path preparation. More recently, newer glide path single-file systems have been launched to achieve convenient and efficient procedures.

Proglider (Dentsply Maillefer, Ballaigues, Switzerland) is manufactured using M-Wire technology. It is a one-file system with square cross-section and 0.16-mm tip diameter.[10],[11]

EdgeGlidePath (Edge Endo, Albuquerque, NM) is based on FireWire technology, which is a novel heat-treated nickel–titanium wire.[12]

While Neoniti GPS (Neolix, châtres-la-Forêt, France) is a single NiTi rotary file. It is manufactured by using electrical discharge machining (EDM) technology. According to the manufacturer, Neoniti GPS has high cutting efficiency, frontal and tangential edges, and built-in abrasive properties.

HyFlex EDM (Coltene/Whaledent, Altst€atten, Switzerland) is a continuous rotary one-file system. HyFlex EDM files are produced with the controlled memory alloy using technology based on EDM.[13]

Till date, none of the studies have compared the effect of these NiTi rotary glide path files on the intracanal bacterial extrusion followed by instrumentation with HyFlex EDM file, which is related to the final outcome of the root canal therapy. Therefore, this study comparatively evaluated the effect of three different glide path files of different metallurgy (Proglider, EdgeGlidePath, and Neoniti GPS) followed by instrumentation with HyFlex EDM file on the intracanal bacterial extrusion.

The null hypothesis tested was (a) no difference in intracanal bacterial extrusion with or without glide path preparation followed by instrumentation with HyFlex EDM and (b) no difference in intracanal bacterial extrusion after preparation of glide path with different glide path instruments (Proglider, EdgeGlidePath, and Neoniti GPS).

  Materials and Methods Top

Specimen selection

The ethical clearance for this study was obtained from the institutional ethical board with registration number-ITSCDSR/IIEC/2018-21/CONS/04. Informed consent was obtained from the patient for using their extracted teeth for the study. A tooth bank was made, and out of this bank, forty extracted human single-rooted mandibular bicuspids with straight canal curvature (0°-10°), mature apices, and free from cracks, and caries and fracture were selected. Teeth with internal resorption, calcified canal, and root canal without apical patency were rejected. The sample size was confirmed with software OpenEpi, Version 3. Digital radiographs of each tooth were taken in buccolingual and mesiodistal directions to ensure a single canal. The selected sample was stored in 0.1% thymol solution until use.

Specimen preparation

A standardized endodontic access cavity was prepared using No. 2 round diamond point in airotor handpiece under constant water cooling, and access cavity was refined using Endo Z bur (Dentsply, Maillefer, Ballaigues, Switzerland). The coronal part of the tooth was sectioned horizontally using a diamond disc under copious irrigation so as to obtain a final length of 15 mm. An ISO size 10 K-file was placed into the canal until it was just visible at the apical foramen. A working length of 14 mm was attained by reducing 1 mm from the final length.

Test apparatus preparation

The test apparatus was prepared as described by Reddy and Hicks.[6] A 30 ml glass vial filled with 10 ml saline and fitted with a rubber stopper was taken, the rubber stopper was perforated using a heated instrument. The outer surface of each of the roots was applied with two layers of nail varnish to restrict the leakage of bacteria. To make a hole in nail varnish, a sterilized ISO size 15 K-File was inserted 1 mm beyond the apex for achieving standardized foramen size and patency and to remove any obstruction caused due to externally applied nail varnish. Samples were then inserted under pressure into perforated rubber stoppers and fitted at cementoenamel junction using epoxy adhesive. The apical portion of the specimen was suspended inside the vial. The vial was performed as a collecting container for apically expelled bacteria. A 23-gauge needle is perforated through the rubber stopper to vent the vial so that the air pressure inside the vial will be equalized with outer pressure. The entire test apparatus was then autoclaved (temperature – 12100b0C, pressure – 15 psi, and time – 15 min). Thermophillus bacterial spore strips along with samples were placed in the autoclave while autoclaving to ensure complete sterilization of the test apparatus. Destruction of thermophilus bacterial spores after autoclaving confirmed the complete sterilization of samples.

Preparation of the Enterococcus faecalis suspension

One milliliter of pure culture of E. faecalis ATCC 29212 cultivated in brain heart infusion broth for 24 h was added to freshly prepared brain heart infusion broth in a test tube to prepare a suspension of pure culture of E. faecalis. Then McFarland standard number 0.5 was used to ensure that bacterial concentration was reached to 1.5 × 108 CFU/ml. 9.95 mL of 1% sulfuric acid was added to 0.05 ml of 1% barium chloride to form 0.5 McFarland standard of barium sulfate. A turbidimeter was used to match the turbidity of inoculated broth to confirm that the broth contained 1.5 × 108 CFU/ml of E. faecalis.

Inoculation with Enterococcus faecalis

Ten microliter of E. faecalis suspension was taken with a sterile micropipette and was filled in the canals. No. 10 K-file was instrumented in a gentle inward and outward motion, which facilitates insertion of E. faecalis down to the entire root canal length cautiously 1 mm short of the apical foramen. The infected samples were then incubated for 24 h at 37°C for the multiplication of E. faecalis. Class I vertical laminar air-flow cabinet was used for preparation and sampling procedure to ensure complete aseptic condition to avoid contamination.

Grouping of the samples

Samples were randomly allocated into four groups (n = 10) depending on NiTi rotary instruments employed for the preparation of glide path. All the glide path files and HyFlex EDM files were used with Endodontic motor (X-Smart, Dentsply Sirona) operated with a 16:1 contra angle.

GROUP I (PROGLIDER): The glide path was prepared at 300 rpm and 2.5 Ncm torque

GROUP II (EDGEGLIDEPATH): In Group II, glide path was prepared using EdgeGlidePath, a rotary glide-path file with a progressive taper from 2% to 7% and tip diameter 0.17 at 300 rpm and 2.5 Ncm torque

GROUP III (NEONITI GPS): In Group III, Neoniti GPS, a single NiTi rotary file with taper 0.3 and tip diameter 0.15 was operated at the speed of 300 rpm and 1.5 Ncm torque

In Groups I, II, and III, after glide path preparation, the final instrumentation was done using HyFlex EDM (25/0.08) at 500 rpm and 2.5 Ncm circumferential motion in the middle third and then in a pecking motion till the working length

GROUP IV (HYFLEX EDM): No glide path instrumentation was done in this group. The instrumentation was done with HyFlex EDM (25/.08) at 500 rpm and 2.5 Ncm torque in a circumferential motion in the middle third and then in a pecking motion till the working length.

During instrumentation of the root canal for all the groups, 1 mL of distilled water was utilized as an irrigant after every change of instrument. The irrigants were delivered using a 30 gauge side-vented endodontic irrigation needle (Ident, India). The needle was inserted passively into the root canal and placed 3 mm away from the apical constriction without binding.

Postinstrumentation quantification of apically extruded Enterococcus faecalis

After biomechanical preparation,0.1ml of solution was collected from all the experimental vials to count the bacterial colonies. Serial dilutions of 0.1 ml saline were made to get to a dilution factor of 102. Then, 1 μL drop was inoculated on the culture plates containing brain heart infusion agar plates and streaking was done with a cotton swab. The incubation of plates was done at 37°C for 24 h. The classical bacterial counting technique was employed after 24 h to measure the bacteria, and they were counted as number of CFU and were converted to log values.

Statistical analysis

Statistical testing was done utilizing the Statistical package SPSS 22.0 (SPSS Inc., Chicago, IL, USA). Intergroup difference was evaluated using Kruskal–Wallis H-test. Between-group differences were compared using Mann–Whitney U-test. Significance was set at 95%.

  Results Top

All the instrumentation tested caused a quantifiable amount of bacterial extrusion. The Group IV without glidepath preparation technique extruded the highest amount of intracanal bacteria in comparison to the groups in which glide path was prepared (Groups I, II, III) (P < 0.05). Group II showed a nonsignificantly lesser amount of bacterial extrusion than Group I. Group III showed a significantly higher amount of bacterial extrusion compared to Group I and II [Table 1]. The order of apical extrusion of E. faecalis was highest in Group IV and least in Group II.
Table 1: Comparison of mean of log values of apically extruded Enterococcus faecalis for all the groups

Click here to view

  Discussion Top

Negotiation and glide path preparation as the initial steps of chemomechanical preparation can be regarded as important steps for the establishment of access to the apical part of canal which, in turn, reduce the apical extrusion of debris and microorganisms.[11] Therefore, in this study, the influence of various single glide path preparation file on apical extrusion of E. faecalis was evaluated.

The results showed that there was a difference in extrusion of E. faecalis apically with or without glide path preparation, followed by instrumentation with HyFlex EDM. Furthermore, there was a difference in apical extrusion of intracanal bacteria after the preparation of glide path with different glide path instruments (Proglider, EdgeGlidePath, and Neoniti GPS). Thus, both the null hypothesis were rejected.

EdgeGlidePath (Group II) showed the least amount of intracanal bacterial extrusion compared to other glide path groups (Group I and Group III). This might be due to differences in cross-sectional design, taper, and metallurgy of all the instruments. EdgeGlidepath has a triangular cross-section (three-point contact) which might leave sufficient space for dentinal chip clearance toward the coronal orifice, whereas Proglider has a square cross-section, Neoniti GPS has a rectangular cross-section that provides less debris clearance space. Furthermore, EdgeGlidePath has a progressive taper of 2%–7% along its length that facilitates the removal of coronal dentin restriction and has a similar effect as that of the crown down preparation. This facilitates the significant amount of debris removal from the coronal third by providing a sufficient volume of irrigant to flush out debris from the canal. EdgeGlidePath has better flexibility as it is composed of FireWire, which is an innovative heat-treated nickel–titanium wire. The phase transformation behavior of the nickel–titanium instruments and enhanced instrument's flexibility are influenced by heat treatment. A flexible file plays an essential part in the effective maintenance of the original anatomy of the radicular space, resulting in less risk of transportation, ledges, or apical zips, avoiding over cutting of dentin resulting in less extrusion of debris intracanal bacteria.[14] Versluis et al.[15] reported that the files with triangular cross-section have more flexibility than square cross-sections for the file with the same taper and diameter. Lee et al. (2019)[12] reported better flexibility and cyclic fatigue resistance of EdgeGlidePath file when compared to Proglider. Tanalp et al.[16] and Kustarci et al.[17] concluded that the minimum extrusion of debris was associated with crown down techniques, whereas full linear filing motion resulted in maximum debris extrusion.

Proglider (Group I) showed significantly less apical extrusion than Neoniti GPS (Group III). This might be because of the difference in cross-sectional design and taper of instruments. Proglider has a square cross-section with progressive taper (2%–8%), whereas Neoniti GPS has a rectangular cross-section with constant taper (3%). Proglider, because of its variable taper, prepares the coronal and middle part of canal in crown down manner. The initial preparation of this section helps to decrease the quantity of microorganisms that may be pushed peri-apically. Goerig et al.[18] concluded that initial coronal flaring may enhance the control over the instrument during apical preparation of the canal, whereas Neoniti GPS, because of its constant taper, could not prepare the coronal part of the canal in a crown down manner.

Group IV (no glide path preparation) showed the maximum amount of extruded intracanal bacteria. This might be due to the fact that cross-sectional design, longer pitch, and 8% taper of HyFlex EDM file. The HyFlex EDM file has three different horizontal sections along the working area: quadratic, trapezoidal, and triangular in the apical, middle, and coronal parts, respectively.[12],[14] There are always four points of contact for the file with the canal walls that enhance the cutting efficacy, which, in turn, produces more debris. Furthermore, there is not much space for debris or intracanal bacterial clearance toward the coronal orifice; instead, the intracanal bacteria is pushed apically. Üreyen Kaya et al. (2019)[19] reported that HyFlex EDM increased taper and size of apical preparation might enhance the apical intracanal bacterial extrusion.

One of the limitations of this study was that there was no element representing the resistance of the periapical tissue to extrusion of E. faecalis. Therefore, the present results may have to be considered as comparatively values between the two system, rather than as absolute amount of E. faecalis.

The results of the study suggested that the preparation of glide path is an adjunct to the main instrumentation protocol results in reduced apical extrusion of E. faecalis.

  Conclusions Top

Within the limitation of the study, the following conclusions were drawn:

All instrumentation techniques used in this study showed extrusion from the apex of bacteria present in the canals

Preparation of glide path before instrumentation resulted less apical extrusion of intracanal bacteria when compared to instrumentation without glide path preparation

EdgeGlidePath extruded the least amount of intracanal bacteria compared to Proglider and Neoniti GPS.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

Mittal R, Singla MG, Garg A, Dhawan A. A comparison of apical bacterial extrusion in manual, ProTaper rotary, and one shape rotary instrumentation techniques. J Endod 2015;41:2040-4.  Back to cited text no. 1
Ferraz CC, Gomes NV, Gomes BP, Zaia AA, Teixeira FB, Souza-Filho FJ. Apical extrusion of debris and irrigants using two hand and three engine-driven instrumentation techniques. Int Endod J 2001;34:354-8.  Back to cited text no. 2
Tinaz AC, Alacam T, Uzun O, Maden M, Kayaoglu G. The effect of disruption of apical constriction on periapical extrusion. J Endod 2005;31:533-5.  Back to cited text no. 3
Dagna A, El Abed R, Hussain S, Abu-Tahun IH, Visai L, Bertoglio F, et al. Comparison of apical extrusion of intracanal bacteria by various glide-path establishing systems: An in vitro study. Restor Dent Endod 2017;42:316-23.  Back to cited text no. 4
Seltzer S, Naidorf IJ. Flare-ups in endodontics: I. Etiological factors. J Endod 1985;11:472-8.  Back to cited text no. 5
Reddy SA, Hicks ML. Apical extrusion of debris using two hand and two rotary instrumentation techniques. J Endod 1998;24:180-3.  Back to cited text no. 6
Gunes B, Yesildal Yeter K. Effects of different glide path files on apical debris extrusion in curved root canals. J Endod 2018;44:1191-4.  Back to cited text no. 7
Siqueira JF Jr., Rôças IN, Favieri A, Machado AG, Gahyva SM, Oliveira JC, et al. Incidence of postoperative pain after intracanal procedures based on an antimicrobial strategy. J Endod 2002;28:457-60.  Back to cited text no. 8
Paleker F, van der Vyver PJ. Glide path enlargement of mandibular molar canals by using K-files, the ProGlider file, and G-files: A comparative study of the preparation times. J Endod 2017;43:609-12.  Back to cited text no. 9
Ruddle CJ, Machtou P, West JD. Endodontic canal preparation: Innovations in glide path management and shaping canals. Dent Today 2014;33:118-23.  Back to cited text no. 10
Abdallah MA, Zaazou AM, Mokhless NA. A comparative study of the amount of apically extruded debris after using different types of glide path files. Alex Dent J 2017;42:80-4.  Back to cited text no. 11
Lee JY, Kwak SW, Ha JH, Abu-Tahun IH, Kim HC. Mechanical properties of various glide path preparation nickel-titanium rotary instruments. J Endod 2019;45:199-204.  Back to cited text no. 12
Uslu G, Özyürek T, Yılmaz K, Gündoğar M, Plotino G. Apically extruded debris during root canal instrumentation with Reciproc Blue, HyFlex EDM, and XP-endo shaper nickel-titanium files. J Endod 2018;44:856-9.  Back to cited text no. 13
Zanette F, Grazziotin-Soares R, Flores ME, Camargo Fontanella VR, Gavini G, Barletta FB. Apical root canal transportation and remaining dentin thickness associated with ProTaper Universal with and without PathFile. J Endod 2014;40:688-93.  Back to cited text no. 14
Versluis A, Kim HC, Lee W, Kim BM, Lee CJ. Flexural stiffness and stresses in nickel-titanium rotary files for various pitch and cross-sectional geometries. J Endod 2012;38:1399-403.  Back to cited text no. 15
Tanalp J, Kaptan F, Sert S, Kayahan B, Bayirl G. Quantitative evaluation of the amount of apically extruded debris using 3 different rotary instrumentation systems. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2006;101:250-7.  Back to cited text no. 16
Kustarci A, Akdemir N, Siso SH, Altunbas D. Apical extrusion of intracanal debris using two engine driven and step-back instrumentation techniques: An in-vitro study. Eur J Dent 2008;2:233-9.  Back to cited text no. 17
Goerig AC, Michelich RJ, Schultz HH. Instrumentation of root canals in molar using the step-down technique. J Endod 1982;8:550-4.  Back to cited text no. 18
Üreyen Kaya B, Erik CE, Sesli Çetin E, Köle M, Maden M. Mechanical reduction in intracanal Enterococcus faecalis when using three different single-file systems: An ex vivo comparative study. Int Endod J 2019;52:77-85.  Back to cited text no. 19


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