: 2021  |  Volume : 33  |  Issue : 3  |  Page : 128--132

Apical debris extrusion of single-file systems in curved canals

Ecehan Hazar1, Olcay Özdemir2, Mustafa Murat Koçak1, Baran Can Sağlam1, Sibel Koçak1,  
1 Department of Endodontics, Faculty of Dentistry, Zonguldak Bülent Ecevit University, Zonguldak, Turkey
2 Department of Pediatric Dentistry, Faculty of Dentistry, Zonguldak Bülent Ecevit University, Zonguldak, Turkey

Correspondence Address:
Dr. Ecehan Hazar
Department of Endodontics, Faculty of Dentistry, Zonguldak Bülent Ecevit University, Kozlu, Zonguldak


Objectives: The aim of this study was to compare the apical debris extrusion after using three different single-file systems. Materials and Methods: Mesial roots with curved canals of extracted mandibular molar teeth were randomly divided into three experimental groups according to preparation techniques: the XP-endo Shaper, WaveOne Gold, and One Curve. Previously weighed Eppendorf tubes were used to collect the debris which was placed in a 35°C hot water bath. The weight of the empty tube was subtracted from the final weight after instrumentation and recorded as the amount of extruded debris. The data were analyzed using the Kruskal–Wallis test at a 5% level of significance and compared all groups. Results: XP-endo Shaper presented less debris extrusion than WaveOne Gold and One Curve (P < 0.05). There was no significant difference between the WaveOne Gold and the One Curve files (P > 0.05). Conclusions: All the tested file systems caused debris extrusion. XP-endo Shaper caused less debris extrusion than WaveOne Gold and One Curve files.

How to cite this article:
Hazar E, Özdemir O, Koçak MM, Sağlam BC, Koçak S. Apical debris extrusion of single-file systems in curved canals.Endodontology 2021;33:128-132

How to cite this URL:
Hazar E, Özdemir O, Koçak MM, Sağlam BC, Koçak S. Apical debris extrusion of single-file systems in curved canals. Endodontology [serial online] 2021 [cited 2021 Dec 4 ];33:128-132
Available from: https://www.endodontologyonweb.org/text.asp?2021/33/3/128/327266

Full Text


The debris, including; microorganisms, irrigation solutions, pulp, and dentinal tissues may extrude beyond the apical foramen during instrumentation, which may result in a delay of the apical healing process, disrupt the balance between host defense and microbial aggression, and persistency of inflammation/infection and even failure of treatment.[1] Besides, convey of microorganisms and debris in the periapical area is the main cause of postoperative pain and flare-ups.[2] Therefore, the limitation of apical extrusion during the endodontic treatment can influence both comfort of the patient and the clinical outcome.

Recently, several novel nickel-titanium (NiTi) files have been produced with special alloying processes, different kinematics, and designs. All instrumentation techniques and instruments cause some degree of root canal content extrusion into periapical tissues.[1],[3],[4],[5] However, the amount of debris extrusion may vary due to different factors, including the blade design, cross-section, and the radial land of the instrument, or selected preparation techniques such as reciprocation, continuous rotation, or adaptive motion.[1],[3],[4],[5],[6],[7],[8]

WaveOne Gold (WOG, Dentsply Maillefer, Baillagues, Switzerland) is a reciprocating single-file system that is produced with a special gold alloy technology. Gold technology provides improved resistance to cyclic fatigue and higher flexibility.[9] WOG has a parallelogram-like cross-section with two cutting edges and an off-center design. The file engages 150° counterclockwise and 30° clockwise, turning 360° after three cycles of reciprocation. The apical size of the WOG primary file is #25 and has a variable taper along with the file (25/0.07). The XP-endo Shaper is a single-file rotary instrument produced from a MaxWire NiTi alloy with a constant taper of 1% and 0.30 mm apical diameter. Based on this special alloy, the instrument expands and contracts at the body temperature, and the taper increases to 4%.[10] The helical shaft design and six cutting edges at the tip of the file may be claimed to be the characteristic of the instrument. One Curve (OC, Micro-Mega, Besancon, France) is a single-file NiTi system produced by a C-Wire NiTi alloy using a proprietary heat treatment. Owing to the controlled memory NiTi alloy, the OC instruments allow the instrument pre-bending for consistency of root canal anatomy and conservation of the curvature as claimed by the manufacturer.[11] The apical size of the file is #25 and has a 0.06 taper with a variable cross-section design along the blade. The file has a variable cross-section consist of three-blades and two-blades to centered ability and increases cutting efficiency and also has an electropolished surface.[12],[13]

A comprehensive literature search revealed that apical debris extrusion of the OC system at the severely curved root canals has not been evaluated, and limited information is available about the comparison of these instruments. This study investigated the apical debris extrusion in curved root canals using WaveOne Gold, One Curve, and XP-endo Shaper systems. The null hypothesis tested was, there was no difference between WaveOne Gold, One Curve, and XP-endo Shaper files with regard to the debris extrusion in curved canals.

 Materials and Methods

This in vitro study was performed under the regulations of the ethics committee (protocol number: 2020-17-05/02). Forty-five extracted human mandibular molar teeth were selected. Teeth having mature apices with apical patency, without previous endodontic treatment or resorption/calcification, were included. All tissue remnants on the root surfaces were mechanically removed. Mesial and distal roots were separated from each other, and only mesial roots were used in the study. The coronal part of the specimens was flattened with a diamond disc for standardization. The mesial roots were inspected using a dental operating microscope (Leica Microsystems, Wetzlar, Germany) under ×16 magnification and examined by digital radiographs (MyRay, Imola, Italy), and those with two independent apical foramina (Vertucci class IV) were selected. The angle of curvature was measured using a software program (AutoCAD; Autodesk Inc., CA, USA) using Schneider's method.[14] The teeth with curvature angles between 25° and 45° were included. After coronal access preparation, a #10 K-file was inserted into the canal until its tip was visible at the apical foramen. The working length was determined by subtracting 1 mm from this length. In addition, the size of apical foramen was determined by a #15 K-file. The tooth in which the file extruded beyond the foramen without any resistance was discarded. During this procedure, the roots were examined under ×16 magnification using a dental operating microscope.

All instruments were used with a setup at 35°C hot water bath because of the special alloy XP-endo Shaper to ensure the standardization. All instruments were used only once for each specimen. In all groups, the file was taken out from the canal after three pecking movements, and the debris accumulation on the file was cleaned. Two milliliter of distilled water was used to irrigate the canals after each instrument, a #10 K-file was used for recapitulation. Then, the root canal was again irrigated with 2 ml distilled water. This procedure was repeated five times and a total of 20 ml distilled water was used for irrigation of each specimen to standardize the irrigation process. A single operator completed all procedures.

The specimens were randomly assigned to three experimental groups (n = 15) as follows:

Group 1: WOG Primary file (25/0.07) was used with an endodontic motor (X-Smart Plus, Dentsply Maillefer, Ballaigues, Switzerland) at the “WaveOne Gold” reciprocal modeGroup 2: One Curve file was used with the same endodontic motor; file (25/0.06) was used with continuous rotation at 300 rpm and 2.5 Ncm torque valuesGroup 3; XP-endo Shaper file was used with the same endodontic motor; file #30, with continuous rotation at 800 rpm and 1 Ncm torque values.

Myers and Montgomery method was used to collect the debris during preparation.[15] The cover of the tube was removed, and the initial weight was determined with a 10 −5 g precision scale (Radwag, Radom, Poland). The tubes were weighed three times and averaged. This was recorded as the initial weights.

The specimens were fixed in covers at the cementoenamel junction and a 27-G needle was inserted to balance the air pressure. After the instrumentation, the tooth, cover, and needle were removed. The root surface was irrigated with 1 ml distilled water to collect the debris. After the storage period in an incubator (5 days, 70°C) for evaporation, the tubes, including the debris, were reweighed three times and averaged to obtain the final weight. The initial weight was subtracted from the final weight and recorded as the amount of extruded debris. The distribution of data was determined using the Shapiro–Wilk test to verify the assumption of normality. The data were analyzed using the Kruskal–Wallis test at a 5% level of significance using SPSS 21.0 software (IBM Corp, Armonk, NY, USA).


The mean values and standard deviations of the groups are presented in [Table 1]. Measurable amounts of debris extrusion were obtained in all groups. XPS group showed less debris extrusion than WOG and OC groups (P < 0.05). The difference between WOG and OC files was not significant (P > 0.05).{Table 1}


The infected debris extrusion may influence the occurrence and incidence of pain after root canal treatment. However, it is impossible to determine the amount and quantity of apical extrusion of debris or bacteria in clinical practice. Therefore, numerous laboratory studies are commonly used to compare NiTi systems and understand how different kinematics and design affect debris extrusion. It is well known that laboratory studies may not mimic the back pressure provided by vital periapical tissues. Therefore, in vitro results cannot directly correlate to clinical conditions. The current results may guide clinicians in the selection of instruments for the treatment of curved root canals.

A correlation between the amount of extruded debris and canal curvature was presented.[16] The correlation was related to less debris movement from the curvature in the coronal direction, and a possible need for more pecking movements to reach the full working length with the files. Therefore, to evaluate the instruments under difficult conditions, the curved mesiobuccal canals of mandibular molars were selected. Similarly, a positive correlation was reported between the amount of extruded debris and the diameter of the apical foramen.[17] Therefore, in the present study, in case of the extrusion of #15 K-file beyond the apical foramen, the tooth was excluded. A commonly used method to collect the debris that was described by Myers and Montgomery was used.[15]

Sodium hypochlorite was not used to irrigate the root canals to eliminate the formation of crystals or lead to the deposition of salts after evaporation.[18] Therefore, to prevent an increase in the debris weight, only distilled water was used as an irrigation solution, as shown in previous studies.[8],[15],[17],[18]

According to the present results, all single-file systems caused debris extrusion similar to the previous results. Different studies reported that all instrumentation systems, including using in different kinematics, hand instrumentation, and single or multiple file systems, various irrigation techniques cause different amounts of apical debris extrusion.[6],[7],[19],[20],[21],[22],[23] Within the tested instruments, the XPS caused significantly less debris extrusion compared with WOG and OC instruments. Thus, the null hypothesis was rejected. This finding supported previous results which reported that reciprocating movement may create more debris extrusion than continuous rotation.[1],[5],[20],[21],[24] On the contrary, WOG and OC files demonstrated comparable results. This conflicting result may be related to the physical properties of XPS which differs from both WOG and OC. The reduction of the contact area between the file and canal wall may result in less binding of the file and lead to more space around the file to accommodate the debris.[25],[26] Both the files have more mass areas compared to the XPS file, and the design of XPS which may provide a possible oscillation-like movement in the root canal, leading to a movement of debris in the coronal direction.

Several studies reported a correlation between the taper of the instrument and the amount of extruded debris. The greater taper was associated with higher levels of extrusion.[22],[27],[28] The results of the present study supported this finding, XPS file which has the lowest taper size, extruded less debris than both WOG and OC files.

In the present study, the next generations of WaveOne (Dentsply Maillefer, Ballaigues, Switzerland) and One Shape (Micro-Mega, Besancon, France) single-file systems, which are claimed to have increased flexibility due to special heat treatments, were investigated. The taper and cross-section of the OC instrument are similar to the One Shape file. However, the cross-section of the WOG file is a parallelogram, and its taper (0.07) which is less than the WaveOne file. Gummadi et al. investigated the debris extrusion of WaveOne (25/0.08 reciprocal) and One Shape (25/0.06 rotational) systems in straight canals and reported less extrusion in the One Shape group.[21] Saricam and Kayaoglu reported that OC and its previous generation One Shape files caused similar debris extrusion in straight root canals.[29] The One Shape file has a triangular cross-section in the apical and an “S” shaped cross-section in the coronal part. WaveOne file has a modified convex triangular cross-section in the apical and convex triangle cross-section in the coronal. They considered that the reciprocating movement could act as a piston and extrude debris toward the periapical direction due to the file's triangular cross-section and high taper. On the contrary, our study revealed similar debris extrusion between OC and WOG files. This result may be related to the differences in methodology (such as canal curvatures), or variations in both cross-section and taper of the WOG file compared to the first generation. There are also a few studies that reported similar results in the debris extrusion between rotational and reciprocational instruments.[6],[22],[23] Tüfenkçi et al. evaluated the effect of the OC and Reciproc Blue (reciprocal movement, VDW, Munich, Germany) single-file systems on the amount of debris extrusion in the traditional and contracted endodontic cavity.[30] Similarly, they reported that there is no significant difference between file systems in traditionally prepared endodontic cavities.

There are a limited number of studies in the literature investigating debris extrusion of the XPS single-file system. Uslu et al. reported that debris extrusion of the XPS file was less than reciprocating Reciproc Blue single-file system.[8] Our results supported this finding and the XPS file extrudes less debris than the WOG single-file system which works in reciprocation.

Alves et al. found the volume of debris extruded by the XPS and Reciproc R25 (25/0.08) files similar under micro-computed tomography (micro-CT) analysis.[6] However, as a possible limitation of the micro-CT method, they reported that extruded debris may not reach a sufficient radiological density to be visualized.[6] In addition, the volume of debris was considered instead of weighing the amount of debris. Therefore, these conflicting results may be related to the differences in methodology.


Recently, no report is available comparing OC, WOG, and XPS files with each other; thus, there is no possibility for a direct comparison with past studies. Under the in vitro conditions of this study, all the tested single-file systems caused extruded debris from the apical foramen. XPS files caused significantly less extrusion than WOG and OC files. The taper of the instrument may be a fact on the amount of extruded debris.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.


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