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 Table of Contents  
ORIGINAL ARTICLE
Year : 2021  |  Volume : 33  |  Issue : 2  |  Page : 102-106

A comparison of different hand and rotary endodontic glide path files for buckling resistance: An in vitro study


1 Department of Conservative Dentistry and Endodontics, D Y Patil Dental School, Pune, Maharashtra, India
2 Department of Conservative Dentistry and Endodontics, Vasantdada Patil Dental College and Hospital, Sangli, Maharashtra, India

Date of Submission10-Sep-2020
Date of Decision17-Feb-2021
Date of Acceptance07-Apr-2021
Date of Web Publication11-Jun-2021

Correspondence Address:
Dr. Ruchika Gupta
C/O Pradeep Patil, Flat Number 505, Anand Tarang Society, Near Hotel Rasrang, Alandi Road, Charholi, Pune, Maharashtra
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/endo.endo_126_20

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  Abstract 


Introduction: The purpose of the present study was to compare the buckling resistance between the hand files and rotary files and compare the buckling resistance between pathfinding files made out of different alloys.
Materials and Method: The test instruments were divided into two major groups based on the mode of use, hand instruments and rotary instruments. These groups were further divided into six subgroups. Six subgroups of endodontic files containing three samples were tested for buckling resistance by applying load in axial direction using a universal testing machine. The maximum load required to generate a lateral elastic displacement of 1 mm was recorded for each instrument. Data were analyzed using two-way analysis of variance and Newman–Keuls multiple post hoc tests using software SPSS version 19. P value was considered < 0.05.
Results: The results indicated that the buckling resistance decreased in the following order: Hand C Plus file > Rotary One G file > Hand C pilot files > Rotary ProGlider file > Hand PathFinder Carbon Steel > Rotary HyFlex Electric Discharge Machining (EDM) file.
Conclusion: The stainless steel instruments (C + and C-Pilot) were more resistant to buckling than carbon steel (Pathfinder CS) and nickel-titanium instruments (ProGlider and HyFlex EDM). Buckling resistance may influence instrument's performance during the negotiation of constricted canals, and the C Plus in hand file group showed significantly better results than the other instruments tested. Metallurgy and modulus of elasticity of the instruments play a significant role in buckling resistance as One G file in rotary file group showed highest buckling resistance (conventional austenite nickel-titanium) than ProGlider (M-wire NiTi) and HyFlex (EDM + Controlled Memory).

Keywords: Buckling resistance, C pilot, C Plus, endodontic treatment, glide path, HyFlex Electric Discharge Machining, One G, pathfinder CS, pathfinding files, ProGlider


How to cite this article:
Gupta R, Mohite P, Patil S, Bansal N. A comparison of different hand and rotary endodontic glide path files for buckling resistance: An in vitro study. Endodontology 2021;33:102-6

How to cite this URL:
Gupta R, Mohite P, Patil S, Bansal N. A comparison of different hand and rotary endodontic glide path files for buckling resistance: An in vitro study. Endodontology [serial online] 2021 [cited 2021 Oct 18];33:102-6. Available from: https://www.endodontologyonweb.org/text.asp?2021/33/2/102/318129




  Introduction Top


In endodontic treatment, the establishment of the glide path, which is the initial step in chemomechanical preparation, is crucial as it provides smooth approach toward root apex.[1] This step permits the endodontist to acquire an unmediated understanding of the complexity of the root canal system and also allows to set up unrestricted access to the root apex and measure the apical size.[2]

The endodontic glide path is defined as a smooth tunnel from the orifice of a root canal to the physiological terminus of a root that allows for predictable cleaning and shaping to follow.[1] An effectual glide path decreases torsional stress, multiplies the life duration of endodontic shaping instruments, and decreases various endodontic mishaps.[3],[4],[5] Endodontic instruments used for the scouting of narrow root canals should have mechanical properties of torsion and buckling, allowing them to meet with the load forced on them during apical advancement. Endodontic glide path instruments with sufficient buckling resistance ease both the position of the canal orifices and approach to the apical third of the root canal.[6],[7]

Buckling can be defined as the elastic lateral deformation of an endodontic instrument when subjected to a compressive load in the direction of its axis.[8] Buckling resistance of endodontic instruments is crucial during scouting of constricted root canal to prevent resilient distortion that obstructs their advancement toward the root canal's apex.

Lately, endodontic instruments that are manual or motor-driven are available precisely for pathfinding. Not many studies have researched, few of the mechanical properties of these endodontic instruments.[2],[6],[7],[9],[10] Numerous factors have been presented to influence their performance, but buckling resistance is a necessary property that has not been the content of much research. The present study was conducted to evaluate and compare the buckling resistance of various old and new pathfinding endodontic instruments.

To the best of our knowledge, ours is the first study to evaluate and compare the buckling resistance of newly introduced endodontic instruments such as ProGlider, One G, and HyFlex Electric Discharge Machining (EDM) file.


  Materials and Method Top


The pathfinding files evaluated in the present study were divided into two major groups based on the mode of use, i.e., hand instruments and rotary instruments.

Group I – Hand Pathfinding instruments (C pilot files [VDW, Munich, Germany], C Plus files [Maillefer/Dentsply, Ballaigues, Switzerland], and Pathfinder Carbon Steel [Sybron Endo]).

Group II – Rotary Pathfinding instruments (ProGlider [Maillefer/Dentsply, Ballaigues, Switzerland], One G file [Micro–Mega], HyFlex EDM Glide path file [Coltene]).

These groups were then divided into six subgroups based on the type of files. Each subgroup had three samples. All the tested glide path files in the study were of 25 mm in length.

Methodology

Six subgroups each containing three samples of endodontic glide path files were evaluated for buckling resistance by administering load in axial direction through a universal testing machine. The most significant load until buckling was registered. 20 N load cell was used in the study for evaluation of buckling resistance. The handle of the respective glide path file was secured to the head of the universal testing machine, and the instrument tip was set down in contact with the bottom of a small cavity created in an aluminum plate. The cavity was prepared with a round bur and was 1 mm in diameter and 0.5-mm deep. The administration of load was done in the axial direction from the handle to the tip, with a speed of 1 mm/min until a lateral elastic (compressive) displacement of 1 mm took place. In the buckling test course, it was feasible to procure a diagram of load (N) deformation (mm) for each endodontic instrument. The greatest load required to induce instrument's elastic displacement up to 1 mm was considered as the buckling resistance of that respective glide path instrument [Table 1] and [Table 2]. Collected data were statistically analyzed by a commercially available software program SPSS version 19 (SPSS Inc. Chicago, IL, USA). Comparison of two main groups (Hand and Rotary) and three subgroups with respect to buckling resistance was done using two-way analysis of variance [Graph 1]. A pairwise comparison of two main groups (Hand and Rotary) and three subgroups with respect to buckling resistance was made by Newman–Keuls multiple post hoc procedures.
Table 1: Buckling resistance of pathfinding hand endodontic instruments Group I (in newton)

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Table 2: Buckling resistance of pathfinding rotary endodontic instruments Group II (in newton)

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  Results Top


Mean values of buckling resistance for tested six subgroups are illustrated in [Table 1] and [Table 2]. Statistical analysis manifested a significant difference in the highest load required to buckle the six instruments tested (*P < 0.05). The highest values were perceived for C Plus files in the hand file group and for One G file in rotary file group. The lowest values were observed for Pathfinder CS instruments in hand file group and for HyFlex EDM file in rotary file group [Table 1] and [Table 2].


  Discussion Top


Endodontics goal as expressed so distinctly by Schilder, root canal system must be cleaned and shaped; cleaned of their organic remnants and shaped to receive a three-dimensional hermetic filling of the entire root canal space. Chemomechanical preparation of the root canal system starts with the most crucial and fundamental root canal negotiation steps. Scouting of a narrow curved canal presents a challenge for the clinician. Reaching the apical part of the root canal is a challenging and strenuous job, which cannot always be successfully attained.[2] Endodontic mishaps such as ledges and perforations can occur which can endanger the treatment positive outcome.[11] Since sizes 06, 08, and 10 of K-type glide path files perform a less resistance to buckling, they are not feasible for creating glide path in small calcified and curved root canals.[12]

Although the glide path files evaluated in the current study had different sizes, tapers, and metallic alloy, they all are advocated for creating a glide path during chemomechanical preparation. That is the purpose of evaluating them here. Earlier Allen et al. in their study of comparative analysis of endodontic pathfinding instruments emphasized the need for instruments to resist buckling, but they used an assay to test the deflection of the instruments in which the load was applied perpendicularly to the instrument's axis.[6] Lopes et al. compared the buckling resistance of C Plus file with other pathfinding instruments. They applied load along the long axis of an instrument.[2]

In our study, the methodology adopted was the same as that of Lopes et al. The reason behind this is that during exploration of canal, forces are always exerted along the long axis of an instrument.[2],[10] C Plus file showed the highest buckling resistance that could be because of its greater taper (0.04 mm/mm) along the last 4 mm from the tip. Thus, C Plus file has a greater area to resist buckling. Furthermore, the HyFlex EDM glide path files had the lowest buckling resistance. Because Hyflex EDM file is highly flexible which is made up of NiTi alloy with unique manufacturing process.

C pilot file has a modified square cross-section, a larger area to resist buckling; it has a higher modulus of elasticity with respect to the NiTi alloy. Owing to these features, these glide path files showed buckling resistance, which was higher compared to other file group but lower as compared to C Plus file.

These findings are similar to the study of Lopes et al. in which they compared C-Pilot, C + file, and path file. Investigators observed highest buckling resistance for C + file and lesser for C-Pilot file and path file.[2]

Pathfinder CS showed buckling resistance which was least among the hand file group. However, pathfinding CS is stiffer than stainless steel alloy; it showed lower buckling resistance than C-pilot file, maybe because it has modified cross-section.

ProGlider files are manufactured from M-wire alloy. ProGlider files' buckling resistance was low compared to One G file, the reason behind low buckling resistance may be the design and taper of the file.

ProGlider file has a progressive taper in a range of 2%–8% along the entire shaft with a tip diameter of 0.16 mm,[10],[11] whereas One G file has a constant 3% taper along the entire shaft with a tip diameter of 0.14 mm. This structure of the file provides good buckling resistance because of its stable, larger core diameter. Metallurgy of ProGlider file, M-wire technology provides extreme flexibility.[13]

One G file showed the highest buckling resistance in the rotary file group. Possibly because, the design of One G file, it has three cutting edges on three different radiuses along the length of the instrument, producing excellent cutting action. Its cutting edges have an angular offset which avoids any screwing effects on the root canal wall. In addition, its nonworking safe tip is asymmetric, which assists the instrument for apical advancement, which is also facilitated by the greater degree of flexibility deriving from the small diameter.[14]

In the current study, the One G glide path file demonstrated to be the most expeditious system in a rotary file group in creating a glide path. Another justification of that could be that One G file is manufactured from conventional austenite NiTi compared to other two files ProGlider M-wire NiTi and HyFlex EDM controlled memory wire.

These findings are similar to an in vitro study by Patil et al. in which they compared ProGlider file (Maillefer/Dentsply, Ballaigues) and One G file (Micro–Mega) for buckling resistance and they also observed higher buckling resistance of One G file as compared to ProGlider file.[9]

HyFlex EDM file showed the least buckling resistance in the current study among all glide path files in both hand and rotary groups, the probable reason behind this could be because this file has unequaled flexibility and fracture resistance. HyFlex EDM files are manufactured using a unique manufacturing process called Electric Discharge Machining (EDM) which produces a highly flexible file and has excellent fracture resistance with better cutting efficiency. Apart from this file has a controlled memory along with 700% more resistance to cyclic fatigue concerning traditional NiTi, which in succession decreases the risk of various procedural errors.[15]


  Conclusion Top


Seeing the results of the current study, it can be concluded that

  • The C + and C-Pilot files (Stainless steel instruments) were more repellent to buckling as compared to the Pathfinder CS (Carbon steel) and ProGlider and HyFlex EDM (Nickel-Titanium instruments). Buckling resistance may affect the functioning of endodontic instruments during the exploration and scouting of narrow and curved root canals, the C + file in hand file group manifested notably superior results
  • Metallurgy and modulus of elasticity of the instruments play a significant role in buckling resistance as One G file in rotary file group showed highest buckling resistance (conventional austenite NiTi) than ProGlider (M-wire NiTi) and HyFlex (EDM + CM)
  • Instruments with higher modulus of elasticity showed better buckling resistance (C + and C-pilot) compared to those with lower modulus of elasticity (ProGlider and HyFlex EDM).


Ultimately considering buckling resistance, a demanded mechanical property of an endodontic instrument can be concluded that the carbon steel instruments (Pathfinder CS) and nickel-titanium instruments (ProGlider and HyFlex EDM) seem to be less appropriate for negotiation of narrow curved and calcified root canals. However, further research on clinical and mechanical tests is required to evaluate how effectively the morphological characteristics, the cross-section, and the alloys chemical composition influence the buckling resistance of endodontic instruments.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Peters OA, Peters CI. Cleaning and shaping of the root canal system. In: Hargreaves KM, Cohen S, editors. Cohen's Pathways of the Pulp. 10th ed. St. Louis, MO: Mosby/Elsevier; 2010. p. 283-348.  Back to cited text no. 1
    
2.
Lopes HP, Elias CN, Mangelli M, Lopes WS, Amaral G, Souza LC, et al. Buckling resistance of pathfinding endodontic instruments. J Endod 2012;38:402-4.  Back to cited text no. 2
    
3.
Patiño PV, Biedma BM, Liébana CR, Cantatore G, Bahillo JG. The influence of a manual glide path on the separation rate of NiTi rotary instruments. J Endod 2005;31:114-6.  Back to cited text no. 3
    
4.
Hulsmann M, Peters OA, Dummer PM. Mechanical preparation of root canals: Shaping goals, techniques and means. Endod Top 2005;10:30-76.  Back to cited text no. 4
    
5.
Cassim I, van der Vyver PJ. The importance of glide path preparation in endodontics: A consideration of instruments and literature. SADJ 2013;68:322, 324-7.  Back to cited text no. 5
    
6.
Allen MJ, Glickman GN, Griggs JA. Comparative analysis of endodontic pathfinders. J Endod 2007;33:723-6.  Back to cited text no. 6
    
7.
Lopes HP, Elias CN, Amaral G, Vieira VT, Moreira EJ, Mangelli M, et al. Torsional properties of pathfinding instruments. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2011;112:667-70.  Back to cited text no. 7
    
8.
Beer FP, Johnston ER. Mechanics of Materials. 3rd ed. New York: McGraw-Hill; 1992.  Back to cited text no. 8
    
9.
Patil PH, Gulve MN, Kolhe SJ. Comparative evaluation of buckling resistance of Proglider and One-G file: An in vitro study. Endodontology 2018;30:21-4.  Back to cited text no. 9
  [Full text]  
10.
Kwak SW, Ha JH, Lee W, Kim SK, Kim HC. Buckling resistance, bending stiffness, and torsional resistance of various instruments for canal exploration and glide path preparation. Restor Dent Endod 2014;39:270-5.  Back to cited text no. 10
    
11.
Gutmann JL, Lovdahl PE. Problem Solving in Endodontics. Prevention, Identification, and Management. 5th ed. Maryland Heights, MO: Elsevier/Mosby; 2011.  Back to cited text no. 11
    
12.
Siqueira JF Jr., Lopes HP. Chemomechanical Preparation in Treatment of Endodontic Infections. London: Quintessence Publishing; 2011. p. 236-84.  Back to cited text no. 12
    
13.
Pereira ES, Peixoto IF, Viana AC, Oliveira II, Gonzalez BM, Buono VT, et al. Physical and mechanical properties of a thermomechanically treated NiTi wire used in the manufacture of rotary endodontic instruments. Int Endod J 2012;45:469-74.  Back to cited text no. 13
    
14.
Uslu G, Ozyurek T, Inan U. Comparison of cyclic fatigue resistance of ProGlider and One G Glide path files. J Endod 2016;42:1555-8.  Back to cited text no. 14
    
15.
Web Page. Available from: www.coltene.comHyflexEDMBrochure. [Last accessed on 2020 Sep 11].  Back to cited text no. 15
    



 
 
    Tables

  [Table 1], [Table 2]



 

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