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Year : 2020  |  Volume : 23  |  Issue : 1  |  Page : 79-83

Apical extrusion of debris after canal shaping with three single-file systems

1 Department of Endodontics, Faculty of Dentistry, Ain Shams University, Cairo, Egypt; Department of Periodontics, Dental College of Georgia, Augusta University, Georgia, USA
2 Department of Endodontics, Faculty of Dentistry, Ain Shams University; Department of Endodontics, Faculty of Dentistry, British University in Egypt, Cairo, Egypt
3 Department of Endodontics, Faculty of Dentistry, Ain Shams University; Department of Endodontics, Faculty of Dentistry, Misr International University, Cairo, Egypt

Date of Submission17-Jun-2019
Date of Acceptance07-Sep-2019
Date of Web Publication10-Jan-2020

Correspondence Address:
Dr. M M Elashiry
Department of Periodontics, Dental College of Georgia, Augusta University, 1120 15th Street, CB 2717, Augusta, GA. 30912

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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/njcp.njcp_319_19

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Objectives: The aim of this study was to evaluate the quantity of apically extruded debris after canal shaping with three single-file systems. Materials and Methods: Sixty mesiobuccal canals of mandibular molars were divided into three experimental groups according to the used file systems—WaveOne Gold, RECIPROC Blue, and HyFlex EDM One file. Debris extruded during canal shaping were collected in preweighed vials. Each canal was irrigated with 5 mL of distilled water via a 30 G side-vented needle. The amount of the debris extruded from each canal was calculated by subtracting the preinstrumentation from postinstrumentation measurement. The preparation times were recorded. Data were analyzed using analysis of variance (ANOVA) and posthoc Tukey tests with α = 0.05. Results: WaveOne Gold extruded the least amount of debris. Results between WaveOne Gold and HyFlex EDM were significantly different. No significant differences in canal shaping time were detected among the three groups (P > 0.05). Conclusion: WaveOne Gold showed the best results regarding apical debris extrusion. Difference between WaveOne Gold and HyFlex EDM suggests that file design and motion kinematics affect the quantity of debris extrusion.

Keywords: Apical extrusion, debris, reciprocation, weighing

How to cite this article:
Elashiry M M, Saber S E, Elashry S H. Apical extrusion of debris after canal shaping with three single-file systems. Niger J Clin Pract 2020;23:79-83

How to cite this URL:
Elashiry M M, Saber S E, Elashry S H. Apical extrusion of debris after canal shaping with three single-file systems. Niger J Clin Pract [serial online] 2020 [cited 2021 Dec 5];23:79-83. Available from:

   Introduction Top

Proper canal cleaning and shaping are critical for successful root canal treatment.[1] Flare-ups in the form of pain or swelling may occur between or after treatment. Apical extrusion of dentin chips, bacteria, and/or irrigants have been considered one of the major causes for this complication.[2],[3]

Many studies[4],[5] compared the amount of debris extruded after canal shaping with different file systems and techniques. Those studies did not identify any file system that was capable of preparing root canals without debris extrusion.[6],[7] File design and motion kinematics have been suggested as factors that affect the extent of apical debris extrusion[8],[9]

In 2008, a rotary instrumentation technique was introduced that utilizes a single file for shaping canals instead of using a sequence of files.[10] These single-file systems were reported to have better shaping ability and reduction in the amount of apical debris extrusion.[11] To date, different single-file systems are commercially available. WaveOne Gold files (Dentsply Maillefer, Ballaigues, Switzerland) were introduced as a modification of the original WaveOne files. WaveOne Gold files are reciprocating files and utilize M-wire alloy technology.[12] RECIPROC Blue (VDW, Munich, Germany) is another single-file system that prepares the canal in a reciprocating motion. It is also a modified version of the original RECIPROC system. These files are produced with nickel-titanium M-wire alloy that goes through innovative heat treatment. This thermal process modifies the molecular structure to improve resistance to cyclic fatigue and increases flexibility.[13] Similar to the gold color of WaveOne Gold files, the blue color of these files is due to the specific heat treatment received during manufacturing.[14] HyFlex EDM OneFile (COLTENE/Whaledent AG, Switzerland) is a single-file system that is used in a rotation motion. These files are manufactured using a unique process called “electric discharging machine.” The technique uses spark erosion, which enhances the fracture resistance and improves cutting efficiency. HyFlex EDM files have a memory-controlled effect.[15]

The aim of this study was to evaluate the amount of debris extruded apically after canal shaping with the aforementioned single-file systems. The canal shaping time of each file system was also recorded. The null hypothesis tested was that there is no difference among the three single-file systems in the quantity of apical debris extrusion.

   Materials and Methods Top

This study was approved by the research ethics committee of the Ain Shams University (Cairo, Egypt) under the approval no. FDASU-RECID 021607. Sixty mesiobuccal canals of extracted human permanent mandibular molars were used in this study. The teeth were immersed in 5.25% NaOCl for 10 min to remove soft tissue and organic debris. Only teeth with mature apices and without noticeable root defects or abnormal morphology were selected. The teeth were randomly allocated to three groups (n = 20)—Group 1: WaveOne Gold Primary files (25.07), Group 2: RECIPROC Blue R25 (25.08), and Group 3: HyFlex EDM OneFile (25.08).

An access cavity was prepared in each tooth using a high-speed handpiece and a round bur using water cooling. Canal patency and glide path determination were achieved using a size 10 K-file. The length of the mesiobuccal canal was determined by introducing a size 15 K-file into the canal till the tip of the file was visible from the apex. The working length (WL) was determined by subtraction of 1 mm from the canal length. For all groups, the apical foreman of each tooth was only enlarged to size 15 prior to shaping with the respective single-file system.

For the WaveOne Gold group, the size 25 primary file with a 7% taper was used according to the manufacturer instructions (150° counter-clockwise and 30° clockwise). After adjusting the WL, the file was introduced into the canal with in-and-out picking motion until the full WL was attained. For the RECIPROC Blue group, theR25 with a size of 25 and 8% taper was used according to the manufacturer's instructions. The RECIPROC Blue files also utilize reciprocating motion and were used in a similar manner to WaveOne gold using picking in-and-out motion until the files reached the full WL; however, different settings in the endodontic motor were selected. For the HyFlex EDM group, the size 25 primary file with 8% taper was used according to the manufacturer instructions using a speed of 400 rpm and maximum torque of 2.5 Ncm. A picking in-and-out motion was used for canal shaping. All the files were used with an endodontic motor using rotation or reciprocation motion (X-SMART PLUS).

Irrigation was performed using 5 mL of distilled water delivered via a 30 G side-vented needle for each canal. One milliliter of distilled water was used to wash the exterior of the mesial root. The time that was taken by each file to reach the full WL was recorded.

Weight measurements

Debris that extruded through the apical foramen was collected using a 10 mL glass vial with a stopper.[16] Each vial was preweighed three times using a microbalance with a precision of 10-4g (Mettler-Toledo, Greifenesee, Switzerland) to obtain its mean weight. Each tooth was then inserted under pressure into the rubber stopper up to the cementoenamel junction. A 25 G needle was inserted into the rubber stopper to balance the air pressure within and outside the glass vial as shown in [Figure 1]. The vial with the inserted tooth and needle was secured in a tube so that the glass vial was not touched during the shaping procedure. The tube was masked so that the operator had no direct vision of the roots of the teeth. After canal shaping, each glass vial was heated at 180°C for 5 h to completely evaporate the irrigating solution. Three consecutive weight measurements were subsequently performed for each vial. The weight of the extruded debris was determined by subtracting the mean prepreparation measurement from the mean postpreparation measurement.
Figure 1: Showing the apparatus that was used in this study. A 10 ml glass vial with a stopper was used to collect the debris after canal preparation, where a 25-gauge needle was inserted into the rubber stopper to balance the air pressure within and outside the glass vial

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Statistical analysis

The data were statistically analyzed using one-factor analysis of variance (ANOVA). Posthoc pairwise comparisons were conducted using the Tukey test (GraphPad Prism version 7.00 for Windows, GraphPad Software, La Jolla California, USA). Statistical significance was preset at α = 0.05.

   Results Top

Weight measurements

Mean values of the apically extruded debris and their standard deviations (SDs) are shown in [Table 1]. The results showed that Group 1 extruded significantly less debris than Group 3. There was no significant difference between the amount of debris extrusion in Groups 1 and 2. Likewise, there was no significant difference between the amount of debris extrusion in Groups 2 and 3.
Table 1: Mean and standard deviation of the weight measurements of the extruded debris in grams after preparation with the three groups

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Preparation time

Mean values of the preparation time and their SDs are shown in [Table 2]. There was no significant difference in the time required for canal preparation among the three groups.
Table 2: Mean and SD of the time in seconds taken by each group to prepare the canals

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   Discussion Top

During the root canal treatment, the pain and/or swelling that may occur between appointments or after root canal treatment is considered a serious complication.[2],[17] Microorganisms may pass from the infected root canals to the periradicular tissues through the infected debris, causing an imbalance between microorganisms and the human immune system, resulting in increased inflammation. This complication upsurges the need for the design of new root canal files designs and development of instrumentation techniques that minimize debris extrusion.[3],[18]

The experimental model used in the present study to collect debris during canal preparation has been described previously, with minor modifications.[16],[19],[20] Resin block models were used in previous studies because the shape, size, taper, and curvature of the canals are standardized.[21],[22] In this study, natural teeth were chosen to better simulatein vivo situations because resin blocks lack natural tooth properties, such as dentin hardness, canal irregularities, and natural apical constriction.[23]

Only single-file systems were used in the present study because the different files from full sequence-file systems showed variable extents of extruded debris.[24] The WaveOne Gold, RECIPROC Blue, and HyFlex EDM One systems were selected for the study based on their improved characteristics and performance following the proprietary thermomechanical treatment they have received.[12],[14],[15]

The results of the present work indicated that all the single-file systems investigated caused apical debris extrusion, albeit to different extents.[4],[6],[25] Group 1 extruded the least amount of debris among the three systems. This finding may be attributed to the difference in motion kinematics and file design among the different systems; these parameters have been shown to influence the amount of debris extruded.[5] The present results are consistent with previous studies,[26],[27] in that the Group 1 extruded the least amount of debris compared with other systems investigated in the respective study. Group 1 file type utilizes reciprocating movement and has the cross-section of a parallelogram with two 85° cutting edges in contact with the canal wall. This off-center design alternates with a cross-section, where only one cutting edge contacts the canal wall. As the contact area between the file and the canal wall is reduced, there is less binding of the file with the canal wall. This results in more space around the file to accommodate the debris, which, in turn, minimizes inadvertent apical debris extrusion.[12],[26]

Group 3 file type utilizes a continuous rotation motion and has a variable cross-section design along its entire cutting length. The coronal third of the file has an almost triangular cross-section design, the middle third has a trapezoidal cross-section design while apical third has a quadratic cross-section design.[15] There are always four points of contact for the file with the canal walls that enhance the cutting efficacy. However, there is not much space for debris clearance. That may explain the increased debris extrusion in Group 3. In addition, Group 1 files have a regressing 7% taper while the Group 3 files have a constant 8% taper. This may also contribute to the difference in apical debris extrusion.[28]

Group 2 extruded less debris than Group 3 and more debris than Group 1. However, the results were not statistically significant. These findings are not consistent with the conclusion of a previous study.[29] In that study, the authors reported that the Group 2 files extruded more debris than the Group 3 files. The premolars used in that study probably have less canal curvature and canal irregularities than the molars used in the present work.[30]

Regarding the time required by each file type to reach the full WL, there was no significant difference among the three investigated file systems. There is no research in the literature comparing the preparation time among these three file systems. Hence, direct comparison with other studies is not possible. It appears that the differences in cross-section, taper, and cutting efficiency of each file type have no effect on the time required for these files to reach full WL.[26]

As the differences exist among the three single-file systems in the quantity of apical debris extrusion, the null hypothesis has to be rejected. In the presentin vitro study, there is no artificial barrier against apical extrusion that approximates the natural barrier provided by the periradicular tissues. This is the limitation of the study. However, this condition was consistent among the three groups.[29]

   Conclusion Top

Within the limitations of the present study, all files tested showed apical debris extrusion to some extent. The single-file systems investigated cannot eliminate this undesirable aspect of tooth canal shaping. However, the WaveOne Gold files had the best performance concerning apical extrusion and preparation time. The file design and motion kinematics influenced the amount of extruded debris in this study.


This project was funded by the Cultural Affairs and Mission Sector, Egyptian Ministry of Higher Education, Egypt.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

   References Top

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  [Table 1], [Table 2]


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