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 Table of Contents  
Year : 2016  |  Volume : 28  |  Issue : 2  |  Page : 132-136

Effectiveness of hand and rotary instruments in retreatment of teeth filled with resin-based filling material: An in vitro study

1 Department of Conservative Dentistry and Endodontics, Genesis Institute of Dental Sciences and Research, Ferozepur, Punjab, India
2 Department of Conservative Dentistry and Endodontics, Sri Sukhmani Dental College and Hospital, Dera Bassi, Punjab, India

Date of Web Publication9-Dec-2016

Correspondence Address:
Vanita Keshav
#B-61, Keshav House, New Cantonment Road, Faridkot - 151 203, Punjab
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0970-7212.195424

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Introduction: Determination of the canal wall cleanliness and to detect the residual filling material after removal of old obturating material.
Materials and Methods: Thirty single-rooted premolar teeth were instrumented with rotary universal Protaper to size F2 and filled with resilon. The removal of root canal fillings was done with manual Hedstrom files and rotary Protaper retreatment files (RPRs) with orange oil as a solvent. Two-dimensional images of the obturated and retreated roots were evaluated with AutoCAD for percentage of remaining filling material. This area was confirmed under the scanning electron microscope. The data were statistically analyzed by t-test to identify differences.
Results: Statistically significant differences were obtained for remaining filling material between hand and rotary both the groups. It was found that the canals instrumented with RPRs had lesser percentage of remaining filling material as compared to the hand files. Residual filling material and debris was found mostly in the apical portion of the root canal, however middle and cervical portions were relatively clean.
Conclusion: RPRs were efficient in removing resilon from root canals as compared to the hand files.

Keywords: Remaining filling material; resilon; rotary Protaper retreatment files.

How to cite this article:
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

How to cite this URL:
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 [serial online] 2016 [cited 2023 Feb 5];28:132-6. Available from: https://www.endodontologyonweb.org/text.asp?2016/28/2/132/195424

  Introduction Top

The general population today shows an increased awareness toward dental health. Endodontic treatment has provided the patients with an option of retaining teeth that were previously extracted some few decades ago.[1] Although the success rate of root canal therapy is high, in some cases, the pathology might persist even after the treatment is complete. This could be due to inadequately filled canals, missed canals, iatrogenic perforation, and reaction to overextended filling material. Under any circumstances of failure, orthograde retreatment is considered as the first treatment option. According to epidemiological studies for outcome of endodontic retreatment, 89% of teeth were retained in the oral cavity and were functional for at least 5 years.[2]

The success rate of endodontic retreatment depends on the amount of removal of existing filling material.[3] Various chemical solvents were used in the past for removing the filling material along with the hand instruments.[4] However, many rotary systems used either in addition or alone for retreatment proved better than the hand.[5],[6] Nickel titanium (NiTi) rotary Protaper retreatment system integrated with three retreatment files with different lengths and tapers are available in market for removing the root canal filling material.

Since years, Gutta-percha (GP) has been the gold standard for obturating the root canal. Moreover, this filling material can be easily extracted out of the canal if required during retreatment.[7],[8] Despite being an easy to fill and retrieve material, it shows poor sealing property.[9] Lately, to overcome the shortcomings of GP, another endodontic filling material named resilon with resin-based sealer under the name “RealSeal” was introduced. Previous studies have shown retreatment of GP with manual and mechanical systems, this study compared hand and rotary systems for retreatment of resin-based filling material.

There are a number of methods available that have been used in the past to detect the success or failure of endodontic retreatment but all these methods were unpredictable.[8],[10],[11] The present study used AutoCAD software (Mechanical Desktop Power Pack, Microsoft, Redmond, USA) to efficiently calculate the area of remaining filling material in the root canal and this residual area was confirmed under the SEM Either of the systems have been used in the past to evaluate the remaining area, whereas the present study combined both the software and SEM study for more detailed and accurate results.

The purpose of this study was to compare the percentage of remaining filling material in canals filled with resilon after retreatment with manual and mechanical systems.

  Materials and Methods Top

Thirty freshly extracted human single-rooted mandibular premolar teeth were collected. The teeth were set free of the blood and soft debris by washing under running tap water. To rule out the teeth with open apices, internal resorption and calcified canals, buccolingual, and mesiodistal radiographs of all the teeth were taken. Decuspidization of teeth was done to get proper reference points. Working length was calculated by subtracting 1 mm from the real length that was measured by inserting #10 K-file into the canal till the file exited from the apex.

After the glide path was obtained, each root canal was prepared using universal rotary Protaper system (Dentsply Maillefer, Switzerland). Conventional crown down technique was followed for instrumenting the canals and were prepared till apical size F2. Apical gauging was done with #25 K-file. In between instrumentation, the canals were irrigated with 2 ml of 3% NaOCl and 17% ethylenediaminetetraacetic acid (EDTA). The final rinse was performed with 17% EDTA solution. The canals were set free off the moisture by drying with the absorbent points. Resilon points were laterally condensed along with the RealSeal sealer (Sybron Endo Products, USA) to obturate the canals. Temporary material was used to seal the root canal openings. Storage of the specimens was done under 100% humid environments and at 37°C for 2 weeks.

Method of evaluation

Two-dimensional images of the obturated roots were obtained in buccolingual and mesiodistal direction. AutoCAD 2009 was used to evaluate these images and calculate the area (as outlined using the software) in square millimeters of the root filling mass [Figure 1].
Figure 1: Area of root filling material using AutoCAD software

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Group division

Division of the specimens was then done into two groups of 15 teeth each. The groups were named Group A and Group B.

Retreatment technique

The temporary filling material was removed from each canal and orange oil (RC Solve) was left over the canal opening for 3 min (as per manufacturer's instructions). After the filling material softened, a path for further instrumentation was then created using #20 and #15 K-type files.

Now, for Group A, Hedstrom file (H file) (Dentsply Maillefer, Switzerland) was used for removing the root filling material.

For Group B, rotary Protaper retreatment files (RPRs) (Dentsply Maillefer, Switzerland) were used for removing the root filling material.

Reinstrumentation of the canals was then done in both the groups to increase the size of the original master apical file to two sizes larger (H file used in Group A and rotary Protaper in Group B). When the master apical file achieved the working length and there was no filling material covering the instrument, the preparation at that point was considered to be complete.

Method of evaluation after retreatment

Once the retreatment procedure was complete, two-dimensional images of the retreated roots were obtained. AutoCAD software was used again to calculate the area (as outlined using the software) in square millimeters of the remaining filling material left in the canals [Figure 2]. Finally, the percentage of area of remaining filling material was calculated as the ratio obtained between the filled and the residual areas in the canals.
Figure 2: Area of residual filling material using AutoCAD software

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The canal wall cleanliness was then confirmed under the scanning electron microscope (SEM) JEOL 6100 [Figure 3] and [Figure 4].
Figure 3: Apical third of root canal (×200) after retreatment with Protaper retreatment files

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Figure 4: Apical third of root canal (×200) after retreatment with Hedstrom files

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Statistical analysis

Statistical analysis of the data was performed for evaluating the areas of remaining filling material. Means and standard deviations of areas of total root canal filling material and remaining filling material were obtained. Thereafter, data were analyzed by means of Student's t-test.

  Results Top

Mean of the remaining filling material for both the groups along with t-value is shown in [Table 1]. The data [Graph 1] shows the comparative values of percentage of residual filling material of two groups, and it was found that resilon retreated with RPRs showed less amount of residual area when compared to retreatment done with conventional hand file. Moreover, under SEM evaluation, dentinal tubules were found to be more open and cleaner in the apical third when resilon was removed with RPRs than with the hand files. Out of the three thirds of the canal, coronal portion was found to be cleanest, followed by middle third and maximum filling material was present in the apical third of the canal.
Table 1: Mean of the remaining filling material for both the groups along with t-value

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  Discussion Top

Every bit of the existing filling material along with the debris should be removed from the root canal for a successful endodontic retreatment which if not impossible is a challenge.[12],[13] For removing the obturating material from the canal, stainless steel hand files, heat,[14] ultrasonics,[15] laser,[16] and rotary instruments [8],[17] with or without solvents have been used in the past. Previous studies have proved the better efficiency and safety of the NiTi rotary instruments in removing the filling material along with the sealer during retreatment.[5],[6] Resilon, composed of bioactive glass, barium sulfate, and bismuth oxychloride, is a polymer-based root canal filling material. Infection and penetration by microorganisms become difficult as this material forms bond with the dentin wall and core.[18] Because of its property of bonding with the dentin wall, it is referred as Resilon Monoblock system.

This study used RPR files and H file for the removal of resin-based filling material from the root canals during retreatment. The rotary instruments in the present study were used with an electric motor at a constant speed and low torque. The rotary retreatment files D1, D2, and D3 were used at a speed of 500 rpm for D1 and 400 rpm for D2 and D3 with 3Ncm torque. Out of both the techniques, none was able to clear the filling material from canals completely as reported in previous studies.[19],[20],[21] The better efficacy of rotary files in comparison to the manual files could be explained on the characteristics of the cross-sectional design of the instruments. Significant amounts of filling material were removed by RPR files in spirals around the instrument. It is the design of the flutes and its rotary motion which helps in pulling the material out of the canal.[22] Moreover, Protaper retreatment files both soften the resin-based filling material by rotation and cut it. Based on the results, this action was particularly evident in the coronal and the middle third.

Chemical solvents act as an adjunct when used along with the mechanical methods during retreatment. Orange oil was selected as a solvent in this study because its biocompatibility, less cytotoxicity as compared to the other solvents such as chloroform, eucalyptol, and halothane.[23]

Furthermore, the tip of the D1 file is active which helps in penetrating the filling material as compared to the original Protaper shaping files that cannot penetrate the filling material easily and might lead to the fracturing of the file tip. However, the tips of D2 and D3 are nonactive which helps in preventing ledges and perforations during retreatment. Furthermore, as the mechanical and rotational movements of the file produce heat due to friction, this heat helps in plasticizing the filling material. Softened and plasticized filling material is less resistant and hence easier to remove.

Moreover, resilon formed monoblock due to which the core and the sealer could be better removed because they were bonded together. It was different from the conventional filling material (GP) in which both the sealer and the core are removed separately as shown by other studies. Many different methods such as longitudinal and transverse cleavage, cleavage of teeth, and photographic recordings [14] have been used in the past for evaluating the residual filling material in the root canals after retreatment. However, there were problems associated with the cleavage methods. During sectioning of teeth, certain amount of filling material can be disturbed leading to false readings and also these methods were unpredictable.

This study evaluated the remaining filling material with the help of the radiographs being analyzed by means of AutoCAD software.

After the radiographic analysis, the specimens in which the filling material was apparently absent were examined under the SEM for more detailed evaluation. A number of previous studies have used SEM to evaluate the canal wall cleanliness.[24],[25] SEM helps in detecting even that residual filling material on the walls of the canal which were not detected by the radiographs. Due to similar radioopacity of dentin and the thin layer of filling material, this material was not detected by radiographs.[26] More of the filling material was left in the apical third of the canal as compared to the middle third and coronal third. This could be due to increased variations in the anatomy in this region and also apical third is most difficult to instrument area. More remaining filling material and more debris in this area leaves this area prone to infection and hence failure of retreatment.

  Conclusion Top

Following could be concluded considering the parameters of this study:

  • Complete removal of the filling material was not possible. Inspite of using mechanical instrumentation, some amount of filling material and debris was left in the root canal
  • RPRs significantly showed the best results with regard to the area of filling material left inside the canals after retreatment
  • Apical third of the root canal showed the maximum amount of remaining filling material whereas coronal portion was relatively clean
  • The present study proved that even the resin-based filling materials could be removed from the root canal just similar to the conventional filling material using manual or mechanical systems.

As the retreatodontic era has arrived in a full swing, the endodontist's skills are being put to tests. The introduction of rotary retreatment files is a welcome step. However, further improvization in instruments, techniques, and evidence-based knowledge is the need of the hour.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

Schirrmeister JF, Wrbas KT, Schneider FH, Altenburger MJ, Hellwig E. Effectiveness of a hand file and three nickel-titanium rotary instruments for removing gutta-percha in curved root canals during retreatment. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2006;101:542-7.  Back to cited text no. 1
Salehrabi R, Rotstein I. Epidemiologic evaluation of the outcomes of orthograde endodontic retreatment. J Endod 2010;36:790-2.  Back to cited text no. 2
Yadav P, Bharath MJ, Sahadev CK, Makonahalli Ramachandra PK, Rao Y, Ali A, et al. Anin vitro CT comparison of gutta-percha removal with two rotary systems and Hedstrom files. Iran Endod J 2013;8:59-64.  Back to cited text no. 3
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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.  Back to cited text no. 13
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Wilcox LR, Swift ML. Endodontic retreatment in small and large curved canals. J Endod 1991;17:313-5.  Back to cited text no. 15
Friedman S, Moshonov J, Trope M. Residue of gutta-percha and a glass ionomer cement sealer following root canal retreatment. Int Endod J 1993;26:169-72.  Back to cited text no. 16
Viducic D, Jukic S, Karlovic Z, Bozic Z, Miletic I, Anic I. Removal of gutta-percha from root canals using an Nd:YAG laser. Int Endod J 2003;36:670-3.  Back to cited text no. 17
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.  Back to cited text no. 18
Schirrmeister JF, Hermanns P, Meyer KM, Goetz F, Hellwig E. Detectability of residual epiphany and gutta-percha after root canal retreatment using a dental operating microscope and radiographs – An ex vivo study. Int Endod J 2006;39:558-65.  Back to cited text no. 19
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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.  Back to cited text no. 21
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Scelza MF, Coil JM, Maciel AC, Oliveira LR, Scelza P. Comparative SEM evaluation of three solvents used in endodontic retreatment: An ex vivo study. J Appl Oral Sci 2008;16:24-9.  Back to cited text no. 23
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  [Figure 1], [Figure 2], [Figure 3], [Figure 4]

  [Table 1]

This article has been cited by
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Endodontology. 2022; 34(3): 184
[Pubmed] | [DOI]


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