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 Table of Contents  
Year : 2022  |  Volume : 34  |  Issue : 3  |  Page : 184-188

Comparative evaluation of effectiveness of manual and various rotary retreatment techniques for removal of root canal filling material: An in-vitro study

Department of Conservative Dentistry and Endodontics, MGV's K. B. H. Dental College and Hospital, Nashik, Maharashtra, India

Date of Submission18-Mar-2022
Date of Decision18-Apr-2022
Date of Acceptance02-May-2022
Date of Web Publication30-Sep-2022

Correspondence Address:
Dr. Apoorva Rajendra Jagtap
Bldg No. 7/402, Vihang Shantivan Soc, Near Vrindavan Society, Thane West - 400 601, Maharashtra
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/endo.endo_78_22

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Aim: This study intended to compare the effectiveness of manual files H-files and ProTaper universal retreatment (PTUR), R-Endo retreatment, and gutta-percha removal (GPR) Mani retreatment rotary files for removing root canal filling material.
Materials and Methods: Eighty mandibular premolars with single canal were selected. The canals were enlarged with ProTaper rotary files up to F2 and obturated using the lateral condensation technique. Then, the samples were randomly divided into four groups and retreated using hand files and rotary retreatment files. The area of remaining root canal filling material was evaluated by splitting the tooth using a stereomicroscope with ×10 and auto computer-aided design software and the percentage of remaining filling material on canal walls was calculated with equation: area % of remaining filling material = area of remaining material ×100/area of canal. One-way ANOVA was carried out to compare the groups and post hoc Tukey's test for pairwise association with each of four groups.
Results: Group A (H-files) showed 61.87% of remaining filling material, Group B (PTUR) showed 24.94%, Group C (R-Endo) showed 37.12%, and Group D (GPR Mani) showed 45.95% of remaining root canal filling material.
Conclusions: All the groups showed residual root canal filling material. Least was seen in group retreated using PTUR files and maximum was seen in group retreated with H-files.

Keywords: Auto computer-aided design, retreatment, stereomicrscope

How to cite this article:
Jagtap AR, Aher G, Gulve M, Kolhe SJ. Comparative evaluation of effectiveness of manual and various rotary retreatment techniques for removal of root canal filling material: An in-vitro study. Endodontology 2022;34:184-8

How to cite this URL:
Jagtap AR, Aher G, Gulve M, Kolhe SJ. Comparative evaluation of effectiveness of manual and various rotary retreatment techniques for removal of root canal filling material: An in-vitro study. Endodontology [serial online] 2022 [cited 2022 Nov 30];34:184-8. Available from: https://www.endodontologyonweb.org/text.asp?2022/34/3/184/357703

  Introduction Top

Success of endodontic treatment depends on complete cleaning and three dimensional obturation of the root canal system.[1] Inability to achieve these goals results in persistent intracanal pathogens and treatment failure. The success rate seen in nonsurgical retreatment is 74%–98% and considered treatment choice in failed endodontic cases.[2] Persistent microbial infection along with intricate root canal system is the major component leading to failure in endodontic treatments.[3]

The amount of material removed during retreatment determines the success and failure rate of retreatment.[4] Conventional retreatment, peri-radicular surgeries, or extraction are various measures for managing failed endodontic treatment.[5] The preliminary goal of retreatment is the removal of previous root canal filling material and biomechanical preparation.[6] This intends to allow an effective debridement and the action of irrigating solutions on the microorganisms which causes the posttreatment disease.[7]

Currently, removal of root canal filling material is performed by means of solvents, hand files, rotary instruments, and ultrasonics.[8] The use of hand instruments for the filling removal is very common, but it is time-consuming and also presents limited results.[9] Various studies have concluded that NiTi files showed higher torsional and bending properties than K-types files.[10]

Very few studies are carried out till date to evaluate and compare manual and various rotary NiTi retreatment systems using a stereomicroscope and auto computer-aided design (CAD) software.

  Materials and Methods Top

A comparative study was conducted using human extracted mandibular premolars and no human intervention. The sample size was determined using the following formula:

n = ([Zα/2 + Zβ] 2 × 2 × σ2)/(d)2,

Where, Zα/2 = the critical value of the normal distribution at α/2 (for a confidence level of 95%) = 1.96, Zβ = the critical value of the Normal distribution at β (for a power of 80%) = 0.84, σ2 = the variance = 465.729 (obtained from previous study), and d = assuming 45% of the difference between two sample means to detect significance = (45/100) × (165.5–123.0) = 19.125 (obtained from previous study). By inserting these values in above formula, n = ([1.96 + 0.84] 2 × 2 × 465.729/(19.125) 2 n = ([7.84] × 931.458)/(365.766) n = (7302.631)/(365.766) n = 19.97.

(Minimum sample size required in each group) n ≈ 20 (in each group).

So, total sample size required for this study having four groups (n) =20 × 4 = 80.

Sample preparation

Eighty human mandibular premolar teeth with single canal were selected and cleaned of calculus and debris with ultrasonics. Preoperative radiographs of all teeth in mesiodistal and buccolingual directions were taken. Teeth were decoronated using a disc leaving 13 mm of root. 10 No. K-file was introduced until seen at the apical foramen and working length was determined after subtracting 1 mm from this measurement. Instrumentation was performed by a single operator. ProTaper (Dentsply Maillefer, Ballaigues, Switzerland) rotary files up to F2 was used to clean the canals using 17% ethylenediaminetetraacetic acid (EDTA). After each instrumentation, the canals were irrigated with 2 ml of 3% sodium hypochlorite. The final sequence of irrigation was done with 5 mL of 17% EDTA and 5 mL of saline. The root canals were obturated with cold lateral compaction of gutta-percha and AH Plus Sealer (Dentsply DeTrey, Konstanz, Germany). Accessory gutta-percha cones were laterally compacted using 2% finger spreaders until they could not be introduced more than 5 mm into the canal. A heated plugger was used to remove the excess of the gutta-percha and compacted using a cold plugger. Radiographs were taken of all teeth in mesiodistal and buccolingual direction to check the adequacy of the canal filling. The root orifices were sealed with temporary filling TMP-RS temporary filling (Prime Dental Products Pvt., Ltd., Maharashtra, India) and stored at 37°C in 100% humidity for 2 weeks to allow complete setting of the sealer.

Retreatment of samples

The samples prepared were randomly divided into four Groups with 20 roots in each group. Retreatment procedure was carried out without the use of solvent.

Group A: Root canal filling material was removed from the coronal and middle thirds with sizes 3 and 2 Gates-Glidden drills, followed by H-files (Mani Inc., Japan) of sizes 35, 30, and 25 for the apical third with a circumferential quarter-turn push–pull motion until the full working length was reached.

Group B: Root canal filling material was removed using ProTaper retreatment rotary files with a rotary X-Smart Endo Motor and Handpiece (Dentsply Maillefer, Ballaigues, Switzerland) at a constant speed of 500 rpm and a torque of 2 Ncm in brushing motion according to the manufacturer's instructions. D1 with tip 30, taper 0.09, and length 16 mm; D2 with tip 25, taper 0.08, and length 18 mm; and D3 with tip 20, taper 0.07, and length 22 mm were used sequentially to remove gutta-percha from coronal, middle, and apical thirds, respectively. These files were used with light apical pulses of pressure until the working length was reached and no further filling material could be removed.

Group C: Root canal filling material was removed using R-Endo rotary files which consist of Rm, Re, R1, R2, and R3. They were used with a rotary X-Smart Endo Motor and Handpiece (Dentsply Maillefer, Ballaigues, Switzerland) at a constant speed of 300 rpm and low torque of 2 Ncm. A size 25, 0.04 taper Rm hand file (K file) was used with ¼ turn pressure directed toward the apex to create a pathway, thus allowing the centering and the alignment of the next instrument. A size 25, 0.12 taper Re NiTi rotary file was used 1–3 mm apical to orifice with circumferential filing. A size 25, 0.08 taper R1 NiTi rotary file was used to penetrate the coronal third through repeated apically directed pushing motions. R2 and R3 with size 25 and taper 0.06 and 0.04 respectively was used in middle and apical third.

Group D: Root canal filling material was removed using gutta-percha removal (GPR) Mani retreatment files. They consist of first instrument 1S with size 70 and 0.04 taper, used only in the canal entrance. File 2S with size 50 and 0.04 taper was used in the coronal third of the canals, followed by 3N with size 40 and 0.04 taper in the middle third, and 4N with size 30 and 0.04 taper in the apical third. These instruments were operated at 1000 rpm and 2 Ncm torque, according to the manufacturer's recommendations, with push–pull motion with slight apical pressure.

During retreatment, canals were irrigated using 2 ml of 3% sodium hypochlorite after each instrument change and debris were removed from files. Retreatment was considered complete after working length was reached, and no more gutta-percha could be seen.

Gutta-percha removal evaluation

Roots were grooved longitudinally, in buccolingual direction, into two halves with diamond disc. Samples were examined under a stereomicroscope at ×10. After being photographed with a digital camera, the images were transferred to image analysis software (AutoCAD) to measure the area of residual filling material on root canal walls. The area of the residual filling material and of canals was recorded, and the percentage of remaining filling material on canal walls was calculated with the following equation: area % of remaining filling material = area of remaining filling material ×100/area of canal wall.

  Results Top

The statistical analysis was performed using a commercially available software Statistical Package for Social Sciences (SPSS) Software version 21(IBM Statistics). One-way ANOVA test was carried out for comparing the groups and determining whether significant differences existed among the tested groups. Further, post hoc Tukey's test was used to understand multiple individual pairwise association among each of four groups in this study, which is depicted in [Table 1] and [Table 2], respectively.
Table 1: Comparison of statistics of remaining filling material in all four groups using one-way ANOVA test

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Table 2: Intergroup comparison between experimental group using Tukey's post hoc test

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Group A (H-files) compared with Group D (GPR Mani retreatment files) showed significant difference (P = 0.001*) and that compared with Group B ProTaper universal retreatment (PTUR) and C (R-Endo retreatment files) showed highly significant difference (P < 0.001**) in the percentage of remaining root canal filling material. Group B (PTUR) showed the least percentage of remaining filling material among all the group. Statistically significant difference was seen when compared with Group C (R-Eendo retreatment files) (P = 0.022*). And highly statistical difference was seen when compared with group D ( GPR Mani retreatment files (P < 0.001**). Group C (R-Endo retreatment files) had a lesser percentage of remaining root canal filling material when compared to Group D (GPR Mani retreatment files), but it was not statistically significant (P = 0.157).

  Discussion Top

Various epidemiological studies have shown that majority of endodontic clinical failure cases which needed nonsurgical treatment, apical surgery, or extraction were recognized in first 3 years after the endodontic treatment.[11] Nonsurgical retreatment is favored since surgical treatment has known to cause more pain and discomfort.[12] “RETREATODONTICS” was the term quoted by late Dr Herbert Schilder in 1986 and suggested that “Retreatment of Endodontic Failures” is the future of endodontics.[13]

A significant number of studies have shown the use of various techniques for the removal of root canal filling material using H-files, rotary files with or without the use of heat solvent, and/or ultrasonic application.[14],[15] Horvath et al. suggested that the use of solvent leads to more accumulation of gutta-percha and sealer residual in the dentinal tubules.[16] Therefore, in this study, the solvent is not used.

Single rooted premolars were selected to reduce the variation and complication during canal preparation.[2],[17] Teeth were decoronated to obtain standardized working length.[18],[19] The working length was determined by subtracting 1 mm from this measurement according to Weine.[20] The most commonly used obturation material is gutta-percha in combination with a sealer. AH Plus Sealer has shown high mechanical properties, radiopacity, long shelf life, and low polymerization shrinkage and solubility and is therefore used in this study.[21]

There are numerous methods to evaluate the remaining root canal filling material after retreatment using radiographs, making the teeth transparent, or using scoring system, cone-beam computed tomography (CT), or micro-CT.[4],[18] Most common method is radiograph. According to Takahashi et al.,[7] vertical splitting and viewing under stereomicroscope is considered as an appropriate method, since it is easy to use and offers advantages over other techniques.[19] While analyzing the filling material left after retreatment, no attempt was made to differentiate between sealer and gutta-percha for practical purposes.[17],[18],[22]

The present study suggests that the remaining root canal filling material found was least in group retreated with (Group B) PTUR files at 24.94%, followed by (Group C) R-Endo files at 37.12%, (Group D) GPR Mani files at 45.95%, and maximum amount of material was seen in group retreated with (Group A) H-file at 61.87%.

In the present study, ProTaper retreatment files removed more root canal filling material as compared to H-files. This finding was in accordance with studies conducted by Malhotra et al.[23] and Khalilak et al.[9] The efficiency of PTUR files can be attributed to negative cutting angles which produce cutting action instead of planning of gutta-percha against the canal wall. It produces frictional heat which plasticizes the gutta-percha, thus helping in easy retrieval of filling material from the canal.[2]

Groups retreated with R-Endo retreatment files showed a higher percentage of root canal filling material in the canals as compared to groups treated with PTUR files. The statistical difference between Group C and Group B was found to be significant. Lesser root canal filling material after retreated with PTUR can be attributed to convex triangular cross-section which renders a large internal area in contrast to R-Endo which has no radial land and round blank.[5],[14]

In the present study, GPR Mani retreatment files showed a higher percentage of root filling material as compared to PTUR files. The statistical difference between the GPR Mani files and PTUR was found to be highly significant.[2],[6],[23] The cutting edge of GPR Mani is made of R-phase NiTi which is different from general superelastic NiTi files, also causes screw effect. Studies conducted by Alberto Rubino et al.[6] and Joseph et al.[2] also showed similar results.

R-Endo retreatment files showed a lower percentage of root canal filling material in the canals as compared to GPR Mani retreatment file. However, the statistical differences were not significant. Greater rigidity and lesser flute space of GPR Mani files leave more root canal filling material in the canal itself.[24] This particular finding in the study was in accordance with studies conducted by Sharma et al.[25]

R-Endo retreatment files showed lower percentage of filling material in the canal as compared to H-file-retreated group, and the difference was statistically significant. According to Akpinar et al.,[26] design of flutes of H-files facilitate the removal of gutta-percha in large pieces leaving behind filling material in small size. This can attribute to the lesser efficiency of H-files in removal of filling material as compared to R-Endo retreatment files.

In the present study, GPR Mani retreatment files have shown better efficiency as compared to H-files. Group A compared with Group D showed a statistically significant difference which could be attributed to the positive rake angle of lateral cutting edges.[8] This particular file system also has an advantage that it is hard to fracture around the tip part as there is no concentration of stresses due to noncutting tip, and if they do fracture, N3 and N4 fracture at the neck, which makes retrieval of the file from the canal easy. This finding is in accordance with Joseph et al.[2]

To obtain better apical cleaning, re-instrumentation at the working length with instruments greater than those used in the initial treatment is necessary.[27] Some studies have shown that apical enlargement by two sizes beyond the initial preparation size can significantly reduce the root canal filling material in straight root canals. Furthermore, during root canal retreatment, excessive removal of dentin should be avoided, in order to reduce the risk of perforations, cracks, and vertical fractures.[6],[28]

Limitation of the study

  1. This study was conducted on straight root canal of premolars, whereas retreatment can occur in varied root canal anatomies. Therefore, the conclusion of this study cannot be directly implied to teeth with aberrant canals
  2. Since this was an in vitro study, the period between obturation and retreatment of samples was only 15 days; however in clinical conditions, cases of retreatment are encountered at variable periods of time.

  Conclusions Top

Within the limitation of this study, it can be concluded that all the groups treated with different retreatment techniques left behind material in the root canals. Rotary retreatment files proved to be more efficient than manual retreatment files. Least amount of root filling material was removed by ProTaper among the other retreatment rotary files used in this study which was attributed to its unique design. Manual H-Files showed the greatest root canal filling material which was due to time-consuming procedure and lack of flexibility.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

Somma F, Cammarota G, Plotino G, Grande NM, Pameijer CH. The effectiveness of manual and mechanical instrumentation for the retreatment of three different root canal filling materials. J Endod 2008;34:466-9.  Back to cited text no. 1
Joseph M, Ahalwat J, Malhotra A, Rao M, Sharma A, Talwar S. In vitro evaluation of efficacy of different rotary instrument systems for gutta percha removal during root canal treatment. J Clin Exp Dent 2016;8:355-60.  Back to cited text no. 2
Jadhav A, Sharma A, Shah N, Daule R. An in-vitro study to evaluate the efficacy of hand and rotary instruments; with and without RC solvent in root canal retreatment. IP Indian J Conserv Endod 2017;2:45-9.  Back to cited text no. 3
Keshav V, Passi S, Monga P, Mahajan P. Effectiveness of hand and rotary instruments in retreatment of teeth filled with resin-based filling material: An in vitro study. Endodontology 2016;28:132-6.  Back to cited text no. 4
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Alberto Rubino G, de Miranda Candeiro GT, Gonzales Freire L, Faga Iglecias E, de Mello Lemos É, Luiz Caldeira C, et al. Micro-CT evaluation of gutta-percha removal by two retreatment systems. Iran Endod J 2018;13:221-7.  Back to cited text no. 6
Takahashi CM, Cunha RS, de Martin AS, Fontana CE, Silveira CF, da Silveira Bueno CE. In vitro evaluation of the effectiveness of ProTaper universal rotary retreatment system for gutta-percha removal with or without a solvent. J Endod 2009;35:1580-3.  Back to cited text no. 7
Akhavan H, Azdadi YK, Azimi S, Dadresanfar B, Ahmadi A. Comparing the efficacy of Mtwo and D-RaCe retreatment systems in removing residual Gutta-percha and sealer in the root canal. Iran Endod J 2012;7:122-6.  Back to cited text no. 8
Khalilak Z, Vatanpour M, Dadresanfar B, Moshkelgosha P, Nourbakhsh H. In vitro comparison of gutta-percha removal with H-File and ProTaper with or without chloroform. Iran Endod J 2013;8:6-9.  Back to cited text no. 9
Betti LV, Bramante CM. Quantec SC rotary instruments versus hand files for gutta-percha removal in root canal retreatment. Int Endod J 2001;34:514-9.  Back to cited text no. 10
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Kvist T, Reit C. Postoperative discomfort associated with surgical and nonsurgical endodontic retreatment. Endod Dent Traumatol 2000;16:71-4.  Back to cited text no. 12
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Horvath SD, Altenburger MJ, Naumann M, Wolkewitz M, Schirrmeister JF. Cleanliness of dentinal tubules following gutta-percha removal with and without solvents: A scanning electron microscopic study. Int Endod J 2009;42:1032-8.  Back to cited text no. 16
Kfir A, Tsesis I, Yakirevich E, Matalon S, Abramovitz I. The efficacy of five techniques for removing root filling material: Microscopic versus radiographic evaluation. Int Endod J 2012;45:35-41.  Back to cited text no. 17
Garg A, Nagpal A, Shetty S, Kumar S, Singh KK, Garg A. Comparison of time required by D-Race, R-Endo and M-two instruments for retreatment: An in vitro study. J Clin Diagn Res 2015;9:47-9.  Back to cited text no. 18
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Weine FS. Endodontic Therapy. 5th ed.: St Louis Mosby; 1996. p. 398.  Back to cited text no. 20
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Malhotra K, Taneja S, Kumar P. Comparison of efficacy of hand and rotary instrumentation for removing a resin-based obturating material (EndoRez) in curved root canals during retreatment: An in vitro study. J Endod 2017;29:60-4.  Back to cited text no. 23
Lalit P, Godara N, Ravivarma K. Evaluation of efficiency of three NiTi instruments in removing gutta-percha from the root canal during retreatment – An in vitro study. Endodontology 2012;24:80-8.  Back to cited text no. 24
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Sharma R, Garg AK, Hans MK, Paul R. Effectiveness of various rotary file systems for removing gutta percha during retreatment using stereomicroscope – An in vitro study. Univ J Dent Sci 2018;4:61-8.  Back to cited text no. 25
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Rödig T, Reicherts P, Konietschke F, Dullin C, Hahn W, Hülsmann M. Efficacy of reciprocating and rotary NiTi instruments for retreatment of curved root canals assessed by micro-CT. Int Endod J 2014;47:942-8.  Back to cited text no. 28


  [Table 1], [Table 2]


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