|Year : 2020 | Volume
| Issue : 4 | Page : 181-186
A comparative evaluation of apical extrusion of debris during endodontic instrumentation with continuous rotation and reciprocating motion: An in vitro study
Shrija Paradkar1, Suparna G Saha1, Anuj Bhardwaj1, Mainak Kanti Saha2, Khushboo Goyal1, Ruchi Verma1
1 Department of Conservative Dentistry and Endodontics, College of Dental Science and Hospital, Indore, Madhya Pradesh, India
2 Department of Prosthodontics, College of Dental Science and Hospital, Indore, Madhya Pradesh, India
|Date of Submission||24-Dec-2019|
|Date of Decision||25-Jan-2020|
|Date of Acceptance||03-Nov-2020|
|Date of Web Publication||18-Jan-2021|
Dr. Shrija Paradkar
50, Chanakya Puri, Annapurna Road, Indore, Madhya Pradesh
Source of Support: None, Conflict of Interest: None
Aim: The aim is to compare the apical extrusion of debris during endodontic instrumentation with continuous rotation and reciprocating motion.
Materials and Methods: Sixty extracted single-rooted mandibular premolar human teeth were randomly assigned to four groups of 15 teeth each. The canals were then instrumented with the following instrument systems: ProTaper Next (PTN; Dentsply Maillefer, Ballaigues, Switzerland), 2Shape (TS; MicroMega, Besancon, France), Reciproc Blue (RB; VDW, Munich, Germany) and WaveOne Gold (WOG; Dentsply Sirona, Ballaigues, Switzerland). Apically extruded debris during instrumentation was collected into pre-weighed Eppendorf tubes. The Eppendorf tubes were then stored in an incubator at 70°C for 5 days. The weight of the dry extruded debris was established by subtracting the pre-instrumentation weight from postinstrumentation weight of the Eppendorf tubes. The data were analyzed using one-way analysis of variance and Tukey's Post hoc tests.
Results: Among the instruments tested in the present study, the least amount of extrusion of debris was seen with TS rotary file system (Group IA) followed by RB (Group IIA) and WOG (Group IIB) (P < 0.05), the results, however, were not found to be statistically significant between them. The maximum amount of debris extrusion was observed with PTN (Group IB) with a statistically significant difference when compared to TS, RB, and WOG file system (P > 0.05).
Conclusion: All instruments were associated with apical extrusion of debris with TS rotary file system associated minimum extrusion and PTN, resulting in maximum extrusion of debris.
Keywords: 2Shape, apical extrusion, ProTaper Next, Reciproc Blue, WaveOne Gold
|How to cite this article:|
Paradkar S, Saha SG, Bhardwaj A, Saha MK, Goyal K, Verma R. A comparative evaluation of apical extrusion of debris during endodontic instrumentation with continuous rotation and reciprocating motion: An in vitro study. Endodontology 2020;32:181-6
|How to cite this URL:|
Paradkar S, Saha SG, Bhardwaj A, Saha MK, Goyal K, Verma R. A comparative evaluation of apical extrusion of debris during endodontic instrumentation with continuous rotation and reciprocating motion: An in vitro study. Endodontology [serial online] 2020 [cited 2021 Mar 2];32:181-6. Available from: https://www.endodontologyonweb.org/text.asp?2020/32/4/181/307319
| Introduction|| |
Successful endodontics is based on the sound principles of debridement and disinfection to eliminate viable bacteria and toxins from the root canal space to sustain an environment conducive to peri-radicular healing. However, one inherent problem related to all root canal shaping and cleaning procedures is that the debris may be extruded through the apex into the peri-radicular tissues.
The extrusion of debris apically may have the potential to disrupt the balance between microbial assault and host defense leading to the development of acute inflammation and flare-ups, which is most often associated with postoperative pain, swelling/edema, and delay in healing process during or after completion of root canal therapy, all of which may necessitate emergency patient visits.
The various factors which influence the amount of debris extruded are radial lands, flute depth, tapers, cross-section, different operational kinematics, cutting efficacy, the technique involved, the number of instruments required, speed, and the motion of rotation of the file systems used.
It is a common opinion among authors that extrusion of some debris is inevitable during root canal instrumentation and that a methodology that completely avoids this phenomenon has not yet been developed. However, some systems may extrude less debris than others.
ProTaper Next (PTN) file system (Dentsply Maillefer, Ballaigues, Switzerland) is composed of a set of instruments that are designed with variable tapers and have an off-centered rectangular cross-sectional design which generates snake-like swaggering movement along its active portion resulting in a decreased screw-in effect and harmful taper-lock. It is used with continuous rotation and has five shaping instruments: X1 (17/0.04), X2 (25/0.06), X3 (30/0.07), X4 (40/0.06), and X5 (50/0.06).
2Shape (TS) (MicroMega, Besancon, France) file system is made of T-wire heat-treated alloy with an asymmetric triple helix cross-section with two main cutting edges for improved cutting efficiency and one secondary cutting edge for improved removal of debris. It includes only two files for shaping and one optional file for apical finishing in continuous rotation with asymmetrical cross section. The TS system is composed of TS1 (25/.04), TS2 (25/.06), F35 (35/.06), and F40 (40/.04) files.
Reciproc Blue (RB) (VDW, Munich, Germany) is a thermally treated nickel-titanium single file system in reciprocation, which is the improved version of the original Reciproc. It has S-shaped cross-sectional design having two cutting edges, an increased resistance to cyclic fatigue and greater flexibility. The innovative heat treatment transforms the molecular structure of the alloy, thus giving the instrument a blue color and a flexible structure. The available sizes are Reciproc® blue 25 (25/0.08), Reciproc® blue 40 (40/0.06) and Reciproc® blue 50 (50/0.05).
WaveOne Gold (WOG) system (Dentsply Sirona, Ballaigues, Switzerland) has a parallelogram-shaped off-centered cross-section with 85° cutting edges in contact with the canal, having a variable and reducing taper. It is designed with a reverse cutting helix, operates in a 150° counter-clockwise direction and disengages 30° in a clockwise direction; thus, the net movement is 120° cutting cycle. This single-file reciprocating system has four tip sizes: Small (20/0.07), Primary (25/0.07), Medium (35/0.06), and Large (45/0.05).
| Materials and Methods|| |
Preparation of samples
Sixty freshly extracted single straight rooted human mandibular premolars with completely formed apices extracted for orthodontic/periodontal reasons were collected. The teeth were disinfected in a solution of 0.1% thymol for 24 h and stored in saline until the samples were used. All teeth were analyzed using digital radiography in the buccolingual and mesiodistal directions to evaluate the root canal morphology.
Endodontic access cavities were prepared using diamond burs with a high-speed handpiece under water cooling, canal patency was established with a size #10 K-file (Dentsply Maillefer). The apical diameter corresponding to the size of 15 K-file was used. To ensure standardization and to obtain a reference point, the buccal cusp edge of each tooth was flattened using a water-cooled, high-speed diamond disc and the length of all teeth were standardized at 17 mm. A size 10 K-file was introduced into the canal until the tip of the file was observed at the apical foramen. The working length (WL) was determined by subtracting 1 mm from this measurement and was reconfirmed using a digital radiograph (RadioVisioGraphy).
Instrumentation and debris collection
The experimental model described by Myers and Montgomery (1991) was used. A hole was created on the cap of an Eppendorf tube, and a tooth was inserted up to its cementoenamel junction. Then, each cap with the tooth attached to its Eppendorf tube were fitted into vials covered with aluminum foil to prevent the operator from viewing debris extrusion during the instrumentation process. Flowable light cure resin was placed at the junction of the tooth and the cap of an Eppendorf tube and then light cured, which acted as a barrier to prevent the ingress of any excess irrigating solution. A 27G needle was inserted alongside the tooth in the cap as a drainage cannula to equalize air pressure inside and outside the Eppendorf tube.
The Eppendorf tubes were then numbered and weighed to 10∼4 precision using a microbalance. Five consecutive measurements were taken for each tube, the heaviest and the lightest weights were discarded, and the arithmetic mean of the remaining three weights was regarded as the initial weight of the Eppendorf tube.
The samples were broadly randomized into two experimental groups based on the instrumentation technique used-
- Group I - Continuous rotation
- Group II – Reciprocation.
The samples were then further subdivided into two subgroups based on files used (n = 15).
Group IA - 2Shape
The canals were instrumented using TS NiTi instrument system. The instrumentation sequence was TS1 (25/0.04) followed by TS2 (25/0.06) at a rotational speed of 400 rpm and 2 N/cm torque based on the manufacturer's instructions. The files were used in a progressive movement in three waves (three up-and-down movements) with circumferential filing movement to reach the WL.
Group IB - ProTaper Next
The canals were instrumented using PTN files in a brushing outstroke motion at 300 rpm and 2 N/cm torque according to the manufacturer's instructions. The instrumentation sequence was X1 (17/0.04), followed by X2 (25/0.06) till the WL.
Group IIA - Reciproc Blue
The canals were instrumented using RB instrument (size 25, 0.08 taper) with the Reciproc program of an endodontic motor. The file was used with a slow, in-and-out pecking motion according to the manufacturer's instructions until the file reached the WL.
Group IIB - WaveOne Gold
In this group, canals were instrumented using WOG Primary file (25/0.07) with the WOG program of an endodontic motor. The WOG file was used with a gentle inward stroking motion with short 2–3 mm amplitude as per the manufacturer's instructions until the file reached the WL.
The canal of each tooth in all groups was irrigated with a total of 10 mL distilled water during instrumentation.
Evaluation of apically extruded debris
On completion of the canal preparation, the Eppendorf tubes were removed from the vials. The debris adherent to the external surface of the root apex was collected by washing the root with 1 ml distilled water into the Eppendorf tube. The tubes were then stored in an incubator at 70°C for 5 days to evaporate the distilled water before weighing the dry debris. The Eppendorf tubes, including the extruded debris, were weighed again following a process similar to that used for the initial weighing of the tube. The amount of the extruded debris in grams was calculated by subtracting the initial weight of the Eppendorf tube from the weight of the tube containing the dry debris. The data thus obtained were tabulated for statistical analysis.
Data obtained were statistically analyzed using SPSS version 21 (SPSS Inc., Chicago, IL, USA). The amount of extruded debris was analyzed statistically, and the level of significance was set at P < 0.05.
| Results|| |
[Table 1] shows the comparison of the mean values of debris extrusion between the four different file systems using one-way analysis of variance and it was found that the difference between these groups was found to be statistically significant (P < 0.05). The least amount of extrusion of debris was observed with TS file system, while the maximum amount of debris extrusion was observed with PTN file system.
|Table 1: Comparison of mean values of debris extrusion between the four different file systems|
Click here to view
The amount of debris extrusion in increasing order is as under:
IA < IIA < IIB < IB
[Table 2] shows individual pairwise comparison of mean values of debris extrusion with different file systems with each other using the Post Hoc Tukey test. Statistically significant difference was observed between TS and PTN, PTN and RB and PTN and WOG (P < 0.05).
There was, however, no statistically significant difference between TS and RB, TS and WOG and RB and WOG (P > 0.05) with comparable and similar mean values. The highest mean value was observed with PTN file system and it was significantly higher than all other file systems.
| Discussion|| |
Mid treatment flare-up, postoperative pain, and swelling associated with root canal treatment may be attributed to the extrusion of debris present within and created during the instrumentation of the root canal system into the peri-radicular tissues. Impaired host immune response against extruded microorganisms, necrotic pulp tissue and dentin particles, over-instrumentation, or foreign-body reactions to obturation materials may further contribute to this severely painful condition posing a challenge to the clinician.
Several methodologies have been developed to evaluate the amount of apically extruded debris., The most accepted method involves the model proposed by Myers and Montgomery, which comprises an effective procedure of isolation and collection of apically extruded debris. Some investigators have suggested simulating the resistance of periapical tissues using an agar gel/floral foam. However, the foam may absorb some of the irrigant and debris when used as a barrier, thus giving erroneous results. Therefore, in the present study, the foramina of the specimens were suspended in the air with zero back pressure, and no attempt was made to simulate periapical resistance.
In this study, the WL of the canal was fixed at 1 mm short of the apical foramen, which is in accordance with a study conducted by Myers and Montgomery. The teeth with an apical diameter corresponding to number 15 k-file were used to limit the width of apical constriction. It has been reported that there is an increase in the amount of the apically extruded material proportional to an increase in the diameter of the apical patency.
As suggested by Tanalp and Güngör, the usage of sodium hypochlorite for irrigation was avoided in the current study to avoid any possible weight increase due to crystallization of sodium hypochlorite, which cannot be separated from the cutting debris, leading to biased weights. Irrigation was strictly restricted to a total of 10ml of bi-distilled water, which leaves no residue once evaporated.
The various engine-driven NiTi file systems available in the market today have different cross-sectional designs and offer varying operational kinematics, all of which are associated with some amount of debris extrusion. Hence, the present study was conducted to analyze and compare the amount of extrusion of debris associated with two continuous rotation (TS, PTN) and two reciprocation motion (RB, WOG) file systems.
Among the instruments tested in the present study, the least amount of extrusion of debris was seen with TS rotary file system (Group IA) followed by RB (Group IIA) and WOG (Group IIB); the results however, were not found to be statistically significant between them. The maximum amount of debris extrusion was observed with PTN (Group IB) with a statistically significant difference when compared to TS, RB, and WOG file system.
The minimum amount of debris produced by TS may be attributed to the file design with a new asymmetrical cross-section having a triple helix with two main cutting edges for improved cutting efficiency and one secondary cutting edge for effective elimination of debris. This asymmetrical cross-section, therefore, provides a nonuniform and reduced contact between the instrument and the canal wall. In addition, 0.06 taper present in TS file is responsible for a more conservative preparation of the dentinal walls when compared to the greater taper of the RB (25/0.08) and WOG (25/0.07) files, both of which may allow greater debris extrusion. These findings are in accordance with the study conducted by Ghoneim WM, Shaheen NA who evaluated the extrusion of debris between TS and ProTaper Universal (PTU) and found that the TS system extruded less debris than the PTU rotary file system.
The RB (Group IIA) file system also showed relatively less extrusion of debris when compared to PTN. However, no significant difference was observed with TS and WOG file system. RB instruments are manufactured identical to their predecessor, i.e., Reciproc, barring the use of thermo-mechanical treatment of the alloy. Thermo-mechanical treatment enhances an instrument's mechanical properties, such as flexibility and cyclic fatigue resistance. The lesser debris extrusion may be due to file design with specific S-shaped cross-section and a larger space to accommodate dentine debris, absence of radial lands, thermally improved raw material, and noncutting tip for a gentle treatment near the apex.
WOG (Group IIB) reciprocating file system showed significantly less debris when compared to PTN, but, the amount of debris extrusion was more when compared to TS and RB with no statistically significant difference between them. These findings may be attributed to the properties of these instruments, which have 85° parallelogram cross-sectional design with an alternating offset and with every other millimeter of the file having one or two points of contact. It also has a constant helical angle and an additional space around the WOG instrument, which may provide space for debris accumulation and its coronal removal. In this study, although the RB files had a greater taper (0.08) than the WOG files (0.07), the amount of extruded debris was comparable. The gradual advance of instruments from the cervical to the apical third of the root using in-and-out movements and the small taper size difference between the two file systems tested may explain this result.
In the present study, the maximum amount of apical extrusion of debris was observed with PTN (Group IB) with a statistically significant difference with all the other groups. The findings of the present study could be attributed to the preparation technique associated with PTN, which does not involve a pure crown down technique. The canal preparation up to the WL is achieved by moving the initial instruments linearly, thus allowing debris to be extruded from the first instrument itself. PTN has an off-centered rectangular design, which means only two points of the rectangular cross-section touch the canal wall at a time, with a snake-like swaggering movement aiding in augering more debris out of the canal. However, a greater taper of instruments at the apical 3 mm may be responsible for removing more dentin from the apical third leading to significant debris being pushed out. The bilateral symmetrical rectangular off-centered cross-section and a variable taper design of PTN is similar to the WOG system; however, it may be speculated that the movement kinematics of the WOG instrument is the principal reason behind the lesser extrusion of debris as compared to PTN.
Bürklein and Schäfer and Bürklein et al. assessed the amount of apically extruded debris created when using rotary and reciprocating NiTi instrumentation systems. These studies showed that full-sequence rotary instrumentation was associated with less debris extrusion compared with the use of reciprocating single-file systems.
In the present study, however, the results obtained with continuous rotation and reciprocation were found to be comparable, the difference in the results for the present study may be attributed to the differences in various study designs, and it can be hypothesized to be a consequence of the different cross-sectional designs of the various rotation and reciprocating file systems.
As no previous study has been conducted comparing the apical extrusion of debris with the above file systems, it is important to emphasize that the results obtained in the present in vitro study may differ if applied clinically, in which periapical tissue acts as a physical barrier, thus, minimizing the apical extrusion of debris. This fact limits the extrapolation of the results and further studies may be required to corroborate the results of the present study with clinical findings.
| Conclusion|| |
Within the limitations of this study, it may be concluded that all the file systems caused some amount of apical extrusion of debris during canal preparation irrespective of the operational kinematics, the cross-sectional design of the instruments. Full-sequence rotary instrumentation was associated with less debris extrusion as compared to reciprocating single-file systems, although the difference between them was not statistically significant. The least amount of extrusion of debris was seen with the TS rotary file system, followed by RB and WOG, whereas the maximum amount of debris extrusion was observed with PTN.
The authors would like to thank IPS Academy for their support with the use of Analytical Balance.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2]