|Year : 2018 | Volume
| Issue : 2 | Page : 87-92
A comparative evaluation of retrievability of Guttapercha, Resilon and CPoints for retreatment, using two different rotary retrieval systems - An ex vivo study
Aswathy Prasad, Rajesh Sasidharan Nair, Jeyabalaji Mano Christaine Angelo, Vijay Mathai, RV Vineet, Sarah R Christopher
Department of Conservative Dentistry and Endodontics, Sree Mookambika Institute of Dental Sciences, Kanyakumari, Tamil Nadu, India
|Date of Web Publication||5-Apr-2018|
Dr. Aswathy Prasad
Department of Conservative Dentistry and Endodontics, Sree Mookambika Institute of Dental Sciences, Kulasekharam, Kanyakumari - 629 161, Tamil Nadu
Source of Support: None, Conflict of Interest: None
Introduction: Nonsurgical retreatment of failure cases requires regaining access to the entire root canal system through complete removal of the core filling material and sealer.
Aims: The aim of this study was to compare the retrievability of gutta-percha (GP), Resilon, and CPoints, using Protaper and Mtwo rotary retreatment systems.
Materials and Methods: Sixty freshly extracted mandibular premolars were decoronated and biomechanically prepared and obturated using GP, Resilon, and CPoints along with their corresponding sealers, in twenty teeth each. The teeth were divided into 6 groups of 10 teeth each. The filling was removed after 2 weeks with Protaper and Mtwo rotary retreatment files and the teeth were analyzed using cone beam computed tomography, to assess the remaining percentage volume of obturation material from each group.
The data were statistically analyzed by ANOVA (post hoc test) followed Dunnett's t-test to evaluate statistical significant between the groups and paired t-test to find statistical significant before and after treatment.
Results: The analysis of the results showed that the mean volume percentage of the residual material is low for Resilon group with Protaper retreatment file (16.35 ± 2.69%) and high in the groups obturated by CPoint and removed by Mtwo retreatment file system (29.67 ± 2.34%).
Conclusions: Canals obturated with CPoints and endosequence bioceramic sealer are the least retreatable among the study groups.
Keywords: Cpoints, gutta-percha, Mtwo retreatment files, Protaper retreatment files, Resilon, root canal retreatment
|How to cite this article:|
Prasad A, Nair RS, Angelo JM, Mathai V, Vineet R V, Christopher SR. A comparative evaluation of retrievability of Guttapercha, Resilon and CPoints for retreatment, using two different rotary retrieval systems - An ex vivo study. Saudi Endod J 2018;8:87-92
|How to cite this URL:|
Prasad A, Nair RS, Angelo JM, Mathai V, Vineet R V, Christopher SR. A comparative evaluation of retrievability of Guttapercha, Resilon and CPoints for retreatment, using two different rotary retrieval systems - An ex vivo study. Saudi Endod J [serial online] 2018 [cited 2018 Jun 20];8:87-92. Available from: http://www.saudiendodj.com/text.asp?2018/8/2/87/229349
| Introduction|| |
The success of an endodontic therapy depends on the achievement of the endodontic triad of debridement, disinfection, and three-dimensional obturation. The clinical success rate of endodontic treatment ranges between 50% and 90%., The preferred treatment of failing endodontic cases is nonsurgical retreatment. This treatment usually results in successful outcomes.
Most widely accepted root canal filling material is gutta-percha (GP) in conjunction with a variety of sealers. Lack of adhesive property, inability to strengthen the tooth after obturation, lack of rigidity, shrinkage on cooling, and its hydrophobic nature led to the development of newer obturation materials.,,
Resilon™, a synthetic resin-based polycaprolactone polymer, was developed as a GP substitute which when used with RealSeal SE™ (self-etch dual-cure, hydrophilic resin sealer) form an adhesive bond at the interface of the synthetic polymer-based core material, canal wall, and sealer with monoblock effect.,
CPoint system is new water expandable obturating material that has a two component design, with a central core of Trogamid T and Trogamid CX and good handling characteristics. It has a hydrophilic polymer coating, which is a cross-linked copolymer of acrylonitrile and venyl pyrollidone, polymerized and cross linked using allyl methacrylate. This special coating helps it to radially expand and push the sealer into the lateral portals of root canal to seal the canal and makes it virtually impermeable to bacterial microleakage.,
Various methods have been used to remove GP from root canal which includes the use of K-type or H-type files along with solvents such as chloroform, xylene, eucalyptol, halothane or orange solvents, gates-glidden drills, and heated pluggers for coronal third material removal followed by hand instrumentation or ultrasonic technique. Flexible rotary instruments in low-speed hand pieces can also be used for the removal of obturation material from the root canals. In this study, the obturation material in the root canal is removed with the help of rotary retreatment Ni-Ti file systems which is less time-consuming and more efficient than hand instrumentation., The conventional use of hand instruments for the removal of obturation material required more time and was tedious, whereas rotary systems were faster in removing the material from root canal system. Rotary retreatment file system plasticizes obturation materials by the heat produced by friction on rotation and the specific flute design tends to pull the GP into the file flute making the removal of obturation material more efficient.,,,,, However, in some studies, GP showed increased retrievability by hand instrumentation when compared to other obturation materials.
Various factors, such as persistant infection, iatrogenic errors, root fractures, and association of periradicular and periodontal lesions, contribute to the failure of an endodontic therapy, which might require nonsurgical, surgical retreatment, or at the worst, extraction of the involved tooth.,,,
For retreatment, it is essential to remove all the filling materials that hinder contact of irrigating solutions and intracanal dressings with the root canal walls. To allow retreatment when indicated, the obturating material should be removed from the root canal.,
The aim of the present study was to compare the retrievability of GP, Resilon, and CPoints, using Protaper and Mtwo rotary retreatment systems. The volume percentage of residual obturating material in the root canal walls will be analyzed using cone beam computed tomography (CBCT).
The study hypothesis was that CPoint would be the most difficult to be removed, since this material can expand hygroscopically, which facilitates it to conform to the canal irregularities and push the companion hydrophilic bioceramic sealer, Endosequence BC, into concavities, lateral portals of exit and the tubules of the dentin walls, thus helping in the formation of a good seal within the root canal, making it least retreatable.
| Materials and Methods|| |
Sixty single-rooted mandibular premolars freshly extracted for orthodontic purpose were collected based on the inclusion criteria (stored in saline and used within 3 months of extraction) and exclusion criteria (fractured teeth, more than one root canal, resorption, open apices, caries, obturated teeth, curved rooted teeth) and disinfected in 0.5% chloramine-T for 1 h and stored in saline (Baxter, India Pvt. Limited, Tamil Nadu, India.) till use. Diagnostic X-ray was taken to confirm the existence of a single straight canal, fully formed apex and no signs of internal resorption, calcification or previous endodontic therapy, caries or restorations. Soft tissue and calculus were removed mechanically from the root surface. Ethical clearance was obtained from institutional review board (IHEC/2015/A/13).
The teeth were decoronated using a diamond disc (SS White, New Jersey, USA) to attain a 15 mm root length. Working length was determined with size #15 K-file (Mani Dental. Inc., Japan), by inserting the file into the canal until the tip of the file is just visible at the apical foramen and reducing 1 mm from this length from coronal reference point to the tip. Biomechanical preparation was done in crown-down technique using Protaper Ni-Ti rotary system (Dentsply, Maillefer, Switzerland, USA). Patency of the canal was maintained throughout the procedure by passing #10 K-file (Mani Dental Inc., Japan) approximately 1 mm through the apex. All canals were enlarged up to F2 at working length with adequate irrigation using 5.25% sodium hypochlorite (Azure Laboratories Pvt. Ltd., Maharashtra, India) and 17% EDTA (Azure Laboratories Pvt. Ltd., Maharashtra, India) for smear layer removal following the irrigation protocol.
Teeth were randomly selected and divided into six groups of 10 teeth each. In Group I and II, the canals were filled with Protaper GP of F2 size (Dentsply Maillefer, Switzerland) and AH Plus sealer (Dentsply DeTrey, USA) using lateral condensation technique.
The canals in Group III and IV were obturated with Resilon cones (Sybron Endo, Orange, CA, USA) coated with Real Seal SE sealer (Sybron Endo, Orange, CA, USA) and lateral condensation was followed.
In Group V and VI, canals were filled using the CPoint (EndoTechnologies, LLC, Shrewsbury, MA, USA) along with Endosequence BC sealer (Brasseler, Savannah, Georgia, USA) without drying the canal. The teeth were radiographed to confirm the adequacy of the root filling. After placing a temporary restoration of Cavit (3M ESPE, Germany), each tooth stored in a humidor at 37°C for 2 weeks to allow the sealer to set completely.
Cone beam computed tomography analysis before retreatment
CBCT images for all teeth [Figure 1] were obtained with CS9300 equipment (Carestream Healthcare India [P] Ltd) in the high-resolution dental mode at 74 kV, 2.5 mA. A single scout image, i.e., lateral view was taken in accordance with the teeth position, and a 360° scan was acquired afterward. The total scan time was 20 s. The time required for the reconstruction of volumetric images after the sample's complete exposure was approximately 1 min. The volume of the filling material in the canals was analyzed using the CS 3D Imaging software (Carestream Health Inc. Internal version 22.214.171.124 [10/10/2014]).
|Figure 1: Cone beam computed tomographic image of obturated teeth; (a) Tooth obturated with gutta-percha and AH Plus sealer, (b) Tooth obturated with Resilon and RealSeal SE sealer, (c) Tooth obturated with CPoint and endosequence bioceramic sealer|
Click here to view
For all teeth from Group I, III, and V, retreatment was initiated using Protaper retreatment files (Dentsply Maillefer, Switzerland, USA) used in a brushing action according to the instructions of the manufacturer: D1 (30/.09) for removing materials from the coronal third, D2 (25/.08) for removing materials from the middle third, and D3 (20/.07) for removing material from the apical third. Root canal filling in Groups II, IV, and VI was removed using Mtwo retreatment files (VDW, Munich, Germany) in a simultaneous technique to the working length till size R2 (size 25, 0.05 taper) in a brushing action with lateral pressing movements until no evidence of filling material on the flutes of files or paper point was achieved. To achieve standardization during retreatment, one set of instrument was used per tooth.
CBCT analysis after retreatment
The CBCT images [Figure 2] of teeth after the removal of obturation material were recorded and the volume of the residual filling material was analyzed. The volume percentage of remaining filling material on canal walls was calculated with the following equation:
|Figure 2: Cone beam computed tomography image of teeth postremoval with retreatment files; (a) Group I, (b) Group III, (c) Group V removed using Protaper retreatment files, (d) Group II, (e) Group IV, (f) Group VI removed using Mtwo retreatment files|
Click here to view
Volume % of remaining filling material = volume of remaining filling material/total volume of material in canal before removing ×100.
The data obtained from the CBCT analysis were statistically analyzed by Statistical Package for Social Sciences version 16.0 (SPSS Inc., Chicago, IL, USA). The ANOVA (post hoc test) followed by Dunnett's t-test was applied to find statistical significant between the groups. Paired t-test applied to find statistical significant before and after treatment. P < 0.05 considered statistically significant at 95% confidence interval.
| Results|| |
As shown in [Table 1], the mean volume percentage of material in the root canal has significantly reduced after removal in all groups, with the P = 0.001 (P< 0.05 considered statistically significant in all groups).
|Table 1: Mean volume before retreatment, after removal, and percentage of total of different groups|
Click here to view
The highest retrievability was for Group III with the least mean volume percentage of 16.35 ± 2.69% and the least was for Group VI with the highest mean volume percentage of 29.67 ± 2.34%.
It can also be inferred that the canals obturated with CPoints and Endosequence Bioceramic sealer were the most difficult to be cleaned with both Protaper and Mtwo rotary retreatment systems whereas the canals obturated with Resilon and RealSeal SE were comparatively cleaner than all the other obturation materials.
There is no statistically significant difference in the mean volume percentage between Group I and II, Group III and IV, and Group V and VI. From these results, it can be inferred that all the groups showed a significant difference in the remaining obturation material after removal with the two rotary systems, with lesser amount of material left with Protaper retreatment file removal than Mtwo retreatment file system even though there is no statistical significant difference in removal efficacy between the files.
| Discussion|| |
The three different materials in this study show three different sealing efficiencies which affects the retrievability of the material from root canal. Hence, the retrievability of each obturating material from the canal walls was evaluated, by measuring the percentage volume of residual root canal obturating material of the total volume of root canal, after the obturating material is removed by two retrieval systems.
The volume of obturation material in the canal, pre- and post-removal using the Protaper retreatment file systems in Group I, III, and IV and with Mtwo retreatment system in Groups II, IV, and VI, were assessed using CBCT as in the studies by Patel et al. 2009, and Marfisi et al.
From the results, we can infer that Group VI had the highest mean volume percentage of remaining filling material than all the other groups, showing the least retrievability of CPoint with Protaper retreatment system.
CPoint showed the highest volume percentage of residual filling material among all the experimental materials. This can be due to the hydrophilic property of CPoint, to expand laterally in the canal system utilizing the moisture from the canal as well as the sealer. This expansion pushes the associated bioceramic sealer, to be pushed into the lateral canals and dentinal tubules increasing the physical adhesion of the material.,,, Moreover, the endosequence bioceramic sealer forms chemical bond with the root canals by the production of hydroxyapatite and water, and the nanoparticle size of the bioceramic particles allows its deeper penetration into the canal irregularities and dentinal tubules, facilitating the improved bonding of CPoints to the root canals., The water produced as by-product is utilized by the CPoint to expand laterally in the canals. The polymer technology of CPoint is manipulated in a such a manner by the manufacturers that the obturation point shows controlled expansion by only radial expansion rather than axial direction which helps in swelling up of the material only laterally.,,,,,,, The anisotropic expansion of the material stops, once resistance is felt, thus preventing the fracture of root, that would possibly be generated during lateral expansion.,
Group I and II showed lesser mean volume percentage of remaining filling material when compared to Group V and VI whereas was higher than Group III and IV.
This showed higher retreatment efficacy of GP when compared to CPoint groups and lesser retreatment efficacy when compared to Resilon groups.
GP had left more residual filling material in the canal than Resilon groups. This could be due to the nonadhesive property of GP and the adhesive property of AH Plus sealer which could bond with the dentinal wall but not with the obturation cone. Hence, the removal of GP with rotary instrumentation left more of the sealer adhered to the canal walls, leaving more residual material in the canals compared to the Resilon group. GP was comparatively easily retrievable as the rotary movement of files created friction in GP, heating it up and softening the material, thus facilitating its easy removal.,,,,,
The easy retrievability of Resilon could be attributed to its monoblock formation property, in which the sealer can bond to both the obturation cone as well as the dentinal wall, creating a single continuous obturation, allowing the complete removal of material, as a whole, without leaving traces of sealer as seen with GP removal. It can also be attributed to the incomplete polymerization of the resin sealer, that may be due to the effect of possibly present residual sodium hypochlorite, which is a strong oxidizing agent creating an oxygen rich layer on the canal walls, which inhibits the free-radical polymerization before retrieval would have been attempted. This substantiates the easy retrievability of Resilon., The inability of sealer to completely coat the canal walls due to incomplete removal of smear layer interfering with the bonding can also be attributed to the easy retrievability of the Resilon obturation. The high configuration factor of the root canals during polymerization of resinous endodontic sealers may cause gaps along the dentin filling interface and the concurrent polymerization shrinkage with the reduction of volume of monomer, producing stress in the material, causing debonding from the root canal walls, reducing adaptation and further microleakage. These may be considered the factors for ease of retrievability of Resilon and resin-based sealer in this study.,,
This result is in accordance to studies done by Ezzie et al., de Oliveira et al., Schirrmeister et al., Cunha et al., Kumar and Aliveni et al., Beshr et al. and contradicts the result of the study by Hassanloo et al., Tasdemir et al.,, and Zarei et al. In a study by Iriboz and Sazak Öveçoǧlu in 2014, both Resilon and GP showed similar retrievability during retreatment.
| Conclusions|| |
Hence, within the limitations of this ex vivo study, it may be concluded that the canals obturated with CPoints and endosequence bioceramic sealer are the least retreatable among the study groups.
We would like to acknowledge Dr. Sharath Babu, Dr. Sharadh Shahai, Dr. Ankita, and Mr. Deepak Bhadur for technical support.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
| References|| |
Wilcox LR, Krell KV, Madison S, Rittman B. Endodontic retreatment: Evaluation of gutta-percha and sealer removal and canal reinstrumentation. J Endod 1987;13:453-7.
Pirani C, Pelliccioni GA, Marchionni S, Montebugnoli L, Piana G, Prati C, et al.
Effectiveness of three different retreatment techniques in canals filled with compacted gutta-percha or thermafil: A scanning electron microscope study. J Endod 2009;35:1433-40.
Gorni FG, Gagliani MM. The outcome of endodontic retreatment: A 2-yr follow-up. J Endod 2004;30:1-4.
Chhaparwal S, Ballal NV, Menezes ND, Kammath SU. Effect of chelating agents on sealing ability of Biodentine and mineral trioxide aggregate. Saudi Endod J 2017;7:16-22. [Full text]
Kumar AG, Aliveni A. Evaluation of gutta-percha and Resilon retreatment – An in-vitro
study. Indian J Dent Adv 2009;1:12-5.
Al-azzawi AK. The efficiency of ProTaper rotary retreatment files in the removal of two different root filling materials. Mal Dent J 2011;8:237-42.
Marfisi K, Mercade M, Plotino G, Duran-Sindreu F, Bueno R, Roig M, et al.
Efficacy of three different rotary files to remove gutta-percha and Resilon from root canals. Int Endod J 2010;43:1022-8.
Oliet S, Sorin SM. Effect of aging on the mechanical properties of hand-rolled gutta-percha endodontic cones. Oral Surg Oral Med Oral Pathol 1977;43:954-62.
Shipper G, Ørstavik D, Teixeira FB, Trope M. An evaluation of microbial leakage in roots filled with a thermoplastic synthetic polymer-based root canal filling material (Resilon). J Endod 2004;30:342-7.
Pathivada L, Munagala KK, Dang AB. Smartseal: New age obturation. Ann Dent Spec 2013;1:13-5.
Imura N, Kato AS, Hata GI, Uemura M, Toda T, Weine F, et al.
Acomparison of the relative efficacies of four hand and rotary instrumentation techniques during endodontic retreatment. Int Endod J 2000;33:361-6.
Hülsmann M, Bluhm V. Efficacy, cleaning ability and safety of different rotary NiTi instruments in root canal retreatment. Int Endod J 2004;37:468-76.
Gu LS, Ling JQ, Wei X, Huang XY. Efficacy of ProTaper universal rotary retreatment system for gutta-percha removal from root canals. Int Endod J 2008;41:288-95.
Giuliani V, Cocchetti R, Pagavino G. Efficacy of ProTaper universal retreatment files in removing filling materials during root canal retreatment. J Endod 2008;34:1381-4.
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.
Jayasenthil A, Sathish ES, Prakash P. Evaluation of manual and two-rotary NiTi retreatment systems in removing gutta-percha obturated with two root canal sealers. ISRN Dent 2012;2012:208241.
Wasnik P, Banga KS. Endodontic retreatment effectiveness of NiTi rotary instruments versus stainless steel hand files: An in vitro
study. Endodontol 2013;1:89-94.
Jaiswal K, Meenal G, Akolkar K, Roshan S, Kolhe S, Aher G. Efficacy of three retreatment systems Mtwo, Protaper R, and R-Endo in removing Gutta-percha from root canals as compared to manual instrumentation: An in vitro
study. J Int Oral Health 2015;7:80-3.
Hammad M, Qualtrough A, Silikas N. Three-dimensional evaluation of effectiveness of hand and rotary instrumentation for retreatment of canals filled with different materials. J Endod 2008;34:1370-3.
Imura N, Pinheiro ET, Gomes BP, Zaia AA, Ferraz CC, Souza-Filho FJ, et al.
The outcome of endodontic treatment: A retrospective study of 2000 cases performed by a specialist. J Endod 2007;33:1278-82.
Ruddle CJ. Nonsurgical retreatment. J Endod 2004;30:827-45.
Farzaneh M, Abitbol S, Friedman S. Treatment outcome in endodontics: The Toronto study. Phases I and II: Orthograde retreatment. J Endod 2004;30:627-33.
Dammaschke T, Steven D, Kaup M, Ott KH. Long-term survival of root-canal-treated teeth: A retrospective study over 10 years. J Endod 2003;29:638-43.
Patel S. New dimensions in endodontic imaging: Part 2. Cone beam computed tomography. Int Endod J 2009;42:463-75.
Patel S, Dawood A, Whaites E, Pitt Ford T. New dimensions in endodontic imaging: Part 1. Conventional and alternative radiographic systems. Int Endod J 2009;42:447-62.
Bodrumlu E, Uzun O, Topuz O, Semiz M. Efficacy of 3 techniques in removing root canal filling material. J Can Dent Assoc 2008;74:721.
Economides N, Gogos C, Kodonas K, Beltes C, Kolokouris I. An ex vivo
comparison of the push-out bond strength of a new endodontic filling system (Smartseal) and various gutta-percha filling techniques. Odontology 2012;100:187-91.
Dadresanfar B, Iranmanesh M, Mohebbi P, Mehrvarzfar P, Vatanpour M. Efficacy of two rotary NiTi instruments in removal of Resilon/Epiphany obturants. Iran Endod J 2012;7:183-8.
Hegde V, Arora S. Fracture resistance of roots obturated with novel hydrophilic obturation systems. J Conserv Dent 2015;18:261-4.
] [Full text]
Arora S, Hegde V. Comparative evaluation of a novel smart-seal obturating system and its homogeneity of using cone beam computed tomography:In vitro
simulated lateral canal study. J Conserv Dent 2014;17:364-8.
] [Full text]
Hegde V, Arora S. Sealing ability of a novel hydrophilic vs. Conventional hydrophobic obturation systems: A bacterial leakage study. J Conserv Dent 2015;18:62-5.
] [Full text]
Baig AR, Ali SN, Saoji H. Smart seal: Unique obturation system in dentistry. Int J Appl Dent Sci 2016;2:1-2.
Hassan N, Diab A, Ahmed G. Bond degradation resistance and interface characterization of a water-expandable endodontic obturation point. M J Dent 2016;1:10-1.
Shawkat ES, Shortall AC, Addison O, Palin WM. Oxygen inhibition and incremental layer bond strengths of resin composites. Dent Mater 2009;25:1338-46.
Shwailiya SA, Al-Hashimi MK. The effect of Resilon system on the fracture resistance of endodontically treated roots using two instrumentation techniques. An in vitro
study. J Bagh Coll Dent 2011;23:42-5.
Lin ZM, Jhugroo A, Ling JQ. An evaluation of the sealing ability of a polycaprolactone-based root canal filling material (Resilon) after retreatment. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2007;104:846-51.
Chacko G, Nadig RA, Vinitha M, Nair GC, Usha G, Vedavathi B, et al
. Biodegradation of Resilon root canal filling material – An in vitro
study. Endodontol J 2014;26:291-5.
Ezzie E, Fleury A, Solomon E, Spears R, He J. Efficacy of retreatment techniques for a resin-based root canal obturation material. J Endod 2006;32:341-4.
de Oliveira DP, Barbizam JV, Trope M, Teixeira FB. Comparison between gutta-percha and Resilon removal using two different techniques in endodontic retreatment. J Endod 2006;32:362-4.
Schirrmeister JF, Meyer KM, Hermanns P, Altenburger MJ, Wrbas KT. Effectiveness of hand and rotary instrumentation for removing a new synthetic polymer-based root canal obturation material (Epiphany) during retreatment. Int Endod J 2006;39:150-6.
Cunha RS, De Martin AS, Barros PP, da Silva FM, Jacinto RC, Bueno CE, et al. In vitro
evaluation of the cleansing working time and analysis of the amount of gutta-percha or Resilon remnants in the root canal walls after instrumentation for endodontic retreatment. J Endod 2007;33:1426-8.
Beshr K, Mohammad SG, Rokaya ME, Mustafa A, Elkhltat E, Baroudi K. Retreatment efficacy of three rotary Ni-Ti systems using computed tomography. J Oral Health Dent Manag 2015;14:115-9.
Hassanloo A, Watson P, Finer Y, Friedman S. Retreatment efficacy of the epiphany soft resin obturation system. Int Endod J 2007;40:633-43.
Taşdemir T, Er K, Yildirim T, Celik D. Efficacy of three rotary NiTi instruments in removing gutta-percha from root canals. Int Endod J 2008;41:191-6.
Taşdemir T, Yildirim T, Celik D. Comparative study of removal of current endodontic fillings. J Endod 2008;34:326-9.
Zarei M, Shahrami F, Vatanpour M. Comparison between gutta-percha and resilon retreatment. J Oral Sci 2009;51:181-5.
Iriboz E, Sazak Öveçoǧlu H. Comparison of ProTaper and Mtwo retreatment systems in the removal of resin-based root canal obturation materials during retreatment. Aust Endod J 2014;40:6-11.
[Figure 1], [Figure 2]