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Year : 2023  |  Volume : 26  |  Issue : 3  |  Page : 288-291
Comparison of single and multiple file rotary endodontic instruments for debris and irrigant extrusion: An in vitro study

Department of Conservative Dentistry and Endodontics, Inderprastha Dental College and Hospital, Ghaziabad, Uttar Pradesh, India

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Date of Submission24-Jan-2023
Date of Decision04-Feb-2023
Date of Acceptance06-Mar-2023
Date of Web Publication16-May-2023


Aim: The aim of this study was to assess and compare the quantity of apically debris which was extruded apically by TruNatomy (TN), ProTaper Next (PTN), HyFlex electric discharge machining (EDM), and HyFlex controlled memory (CM), following root canal preparation.
Materials and Methods: Sixty extracted single-canal mandibular premolars were used. The root canal preparation was done with TN, HyFlex EDM, PTN, or HyFlex CM files. The preweight debris, which was extruded apically, was collected in the Eppendorf tube and later on incubated at 670°C for 3 days and weighed again to record the extruded debris.
Results: The result showed that there was a significant reduction in debris extrusion by TN system, followed by PTN system, HyFlex EDM, and maximum extrusion in HyFlex CM (P < 0.05). Between the PTN and TN groups as well as between the HyFlex EDM and HyFlex CM groups, statistically significant difference was not observed (P > 0.05).
Conclusion: Apical debris extrusion is the inherent nature of the all file systems. Nevertheless, the TN file system produced substantially minimum debris extrusion among other systems compared in the study.

Keywords: HyFlex controlled memory; HyFlex electric discharge machining; ProTaper next; TruNatomy

How to cite this article:
Mehra D, Sinha DJ, Singh S, Verma N, Rani P, Parvez B. Comparison of single and multiple file rotary endodontic instruments for debris and irrigant extrusion: An in vitro study. J Conserv Dent 2023;26:288-91

How to cite this URL:
Mehra D, Sinha DJ, Singh S, Verma N, Rani P, Parvez B. Comparison of single and multiple file rotary endodontic instruments for debris and irrigant extrusion: An in vitro study. J Conserv Dent [serial online] 2023 [cited 2023 Sep 27];26:288-91. Available from:

   Introduction Top

The goal of a successful root canal treatment is thorough debridement, disinfection, and obturation to maintain a healthy dentition by providing an environment promoting the periradicular healing.[1] The primary cause of periapical inflammatory lesion is microbial infection of root canal space, and a successful endodontic treatment can lead to prevention and elimination of apical periodontitis.[2] During shaping and cleaning procedures, the extrusion of infected material, pulpal tissue remnants, dentinal chips, irrigation solutions, and microorganisms in the periapical tissues is commonly encountered.[3] Due to this, physical or chemical irritants have the potential to disturb the periradicular tissues' integrity, which can result in flare-ups between appointments and pain following treatments; both of which are unpleasant outcomes for doctor and patient.[3] All root canal preparation techniques usually cause apical debris extrusion, but amount varies accordingly with the instrumentation techniques and file systems used. An important role was played by several factors, instrument design, chemical irrigants used, motion, etc., in apical extrusion.[4]

ProTaper Next

Dentsply Maillefer, Ballaigues, Switzerland, introduced the ProTaper universal files' next-generation file system in 2013 with the addition of variable tapers and an off-centered rectangular cross-section.[5]

HyFlex controlled memory (Coltene Whaledent)

In Hyflex CM introduced in 2011, a new rotary file system was introduced that machined from a controlled memory (CM) wire (CM) with symmetrical cross-section, double fluting, noncutting tip, variable pitch, and negative rake angle.[5]

HyFlex electric discharge machining

The revolutionary “Electrical Discharge Machining” technology is responsible for the HyFlex EDM's exceptional qualities. This cutting-edge manufacturing procedure employs spark erosion to harden the NiTi file's surface, increasing cutting effectiveness and fracture resistance.[6]

TruNatomy (Dentsply, Ballaigues, Maillefer, Switzerland)

Recent developments include the development of TruNatomy heat-treated NiTi instruments (TN; Dentsply Sirona). The TN instrument has a slip shaping feature and off centered parallelogram cross- section that permits larger debridement area . File is more flexible and fatigue resistant due to a unique heat treatment and design.[7]

Previously, in in vitro studies have been conducted on the apical debris extrusion from HyFlex CM and ProTaper Next (PTN) files, but a very little literature are available on the apical debris and irrigant extrusion from TruNatomy (TN) files. Therefore, the present study was designed to relatively assess the debris and irrigant extrusion apically from these files.

   Materials and Methods Top

Tooth selection

Source of data

Sixty mandibular extracted premolar teeth were collected, and confirmation of any fracture, resorption, absence of decay, calcification, open apices, and cracks were done visually and radiographically. Ultrasonic scaler was used to clean root surfaces and collected in saline solution. A high-speed diamond saw was used to decoronate the teeth at the cementoenamel junction at 16 mm root length. Working length was determined using a 10 number-K hand file keeping it 1 mm shorter to apex.

Experimental groups

Samples were mounted into the Eppendorf tubes and placed into glass vials before being wrapped in foil paper [Figure 1]a. These samples were randomly grouped into four experimental groups (n = 15 each group).
Figure 1: (a) Glass vial and sample mounted on the Eppendorf tube. (b) Eppendorf tubes after experiment

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Group 1 - TN files were used in the following order: orifice Modifier (20/0.08), Glider (17/0.02), and Prime File (26/0.04) at a constant 500 rpm and 1.5 N/cm torque. Following the preparation process, 2 mL distilled water was used for irrigation.

Group 2 - HyFlex EDM file's sequence was as follows: Orifice Modifier (25/0.12), Glider (10/0.05), and Shaping File 25/with 400 rpm speed and 2.5 N/cm torque.

Group 3 - HyFlex CM – The Shaping Files 20/04 and 25/04, as well as the 25/8 Orifice Opener, were used to prepare the canal. The files were used at a speed of 500 rpm and a torque of 2.5 N/cm.

Group 4 - PTN files were developed to use the following sequence: X1 (17/0.04) followed by X2 (25/0.06) at 300 rpm speed and 2.8 N/cm torque.

In total, 2 ml distilled water was utilized in each sample of all groups as an irrigant. Following biomechanical cleaning, debris was collected using all four file systems. The teeth and the Eppendorf tube were detached from glass vial and were weighed once more with the debris and irrigant (W2). To make sure moisture was removed, calcium chloride was added to an Eppendorf tube before being placed inside the incubator for 3 days at 6700 C. After moisture and irrigant evaporated, extruded debris was collected in preweighed Eppendorf tubes and weighed again (W3). The final amount of debris was measured by subtracting weight (mean) of the Eppendorf tubes (preweighed) by tube's weight (mean) containing remaining debris (W3-W1) [Figure 1]b.

   Results Top

The IBM SPSS Version 21.0. Armonk, NY:IBM Corp. was used for statistical analysis on the collected data, which resulted in tables and graphs that summarize and explain the findings in [Table 1] and [Figure 2], respectively. The mean values of extrusion weight were measured in milligrams (mg), standard deviation, and the range of extrusion (maximum and minimum values). When compared to other file systems used in the study, TN rotary files' mean value for apical debris extrusion was much lower across all groups.
Figure 2: Bar graph showing apical debris extrusion (mg). HyFlex EDM: Electric discharge machining, HyFlex PTN: ProTaper Next, HyFlex CM: Controlled memory

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Table 1: Distribution of mean and standard deviation of apical debris extrusion (mg) among the groups

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   Discussion Top

Root canal therapy's major goal is to widen the root canal system to remove any remaining pulpal tissue, bacterial species, chips, and necrotic tissue. The root canal systems must be chemically and mechanically prepared, which is a crucial prerequisite for the current root canal treatment.[8] Pathogens eradication from pulp and periapical region aids in the recovery of the periradicular tissues. A flare-up is an episode of postoperative discomfort that appears soon after a root canal procedure and necessitates urgent care with an unscheduled appointment. The incidence rate of these complications ranged from 1.4% to 16%.[9] Based on the precise amount of extruded debris at tip, the effectiveness of four different rotating systems was evaluated in this study. According to published research, debris extruded apically is influenced by the instrumentation techniques, design, and taper variation of the instrument.[10] This study investigated different NiTi systems with various instrumentation kinematic, design, and taper features. TN files, HyFlex EDM, PTN, and HyFlex CM rotary files were the four systems in consideration. TN is a recently introduced heat-treated NiTi system with special features of slender shape that provides more space for debridement, and these features make the TN files more flexible and resistant to fatigue. The characteristics of TN files are, an off-center parallelogram cross-sectional, device geometry, receding taper, and thinner pattern, which improve dentin structure and integrity of the preserved tooth.[11] The PTN is a NiTi file system with features of a rectangular cross-section, offset rotational mass, and variable taper. The PTN can move through a wider range of motion than comparable-sized files whose mass is symmetrical about the axis of rotation. This off-center design gives the file a snake-shaped “bragging” effect, improves the file's centering ability, and increases the file's range of motion[12] It can also reduce the chance of clogging the root canal system.[1] This design provides more cross-sectional space compared to a central mass file with an axis of rotation for improved cutting, loading, and successful coronal drainage of debris from the canal.[13] There is limited or no evidence in the literature for extruding debris using the TN file system. The amount of extruded debris during root canal preparation was not correlated to the number of rotary files used in the current study. The study investigated that TN files extruded the lowest debris amount compared to the PTN, HyFlex EDM, and HyFlex CM systems. This result was consistent with the past studies that indicated the quantity of extruded debris increased with pitch elongation.[14] In contrast to the other two cutting-edge systems under the study, the HyFlex CM has asymmetrical cross-section and three cutting edges that provide a small space for coronal debris extrusion. Because the tooth and dentin are less entangled, there is more space for coronal debris to be extruded.[15] In addition, the PTN's rocking motion may remove debris coronally as opposed to apically and less interference between the tooth and the dentinal tissue, creating more space for debris extrusion coronally.[16] The TN (4%) and PTN (6%), both showed the same taperness finding. However, compared to HyFlex CM 4%, TRN 4% extruded noticeably less debris in the apical direction.[17] In addition, the findings of published literature suggest that increased taper not always result into a greater debris extrusion to the tip, as was the case in the present study. A recently published systematic review found that rotary instrument's cross-section design had a greater effect on the quantity of debris extrusion apically than the instrumentation speed.[18],[19],[20] Zero back pressure was used in the design of this study; thus, it is likely that gravity dragged the lavage fluid out of the canal. This potential problem is present in in vitro designs without apical resistance, as previously discussed by Myers and Montgomery. The chemical and mechanical instrumentation of both vital and necrotic teeth contribute to and influence apical extrusion. The preexisting pulp stump in vital teeth serves as a barrier to stop debris from escaping, whereas necrotic teeth do not exhibit this resilience. The pulpal tissue located in the lateral and tip canals of vital teeth prevents irrigation fluid escaping from root canal; however, in a case of necrosis, the solution disperses once reaches to the apical portion.[21] However, these laboratory-based research might offer constrained conditions for creating accurate comparability between the investigated groups on particular variables. Future in vivo research will be required to examine the effects of apical debris extrusion on the success of endodontic therapy and posttreatment patient satisfaction.

   Conclusion Top

In this investigation, less debris was extruded using the TN system, which includes the PTN, HyFlex EDM, and HyFlex CM file systems. A TN system for use during root canal treatments preserves dentin tissue and has small access cavities. The result obtained from this study are congruent with those of earlier studies because apical extrusion of debris occurs spontaneously during root canal preparation. As a result, all the employed instrumentation file systems created apically extruded debris.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

   References Top

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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. 2
Siqueira JF Jr. Microbial causes of endodontic flare-ups. Int Endod J 2003;36:453-63.  Back to cited text no. 3
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Surakanti JR, Venkata RC, Vemisetty HK, Dandolu RK, Jaya NK, Thota S. Comparative evaluation of apically extruded debris during root canal preparation using ProTaper™, Hyflex™ and Waveone™ rotary systems. J Conserv Dent 2014;17:129-32.  Back to cited text no. 5
[PUBMED]  [Full text]  
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Correspondence Address:
Dr. Dakshita Joy Sinha
Department of Conservative Dentistry and Endodontics, Inderprastha Dental College and Hospital, Sahibabad, Ghaziabad - 201 010, Uttar Pradesh
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jcd.jcd_62_23

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