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Table of Contents   
ORIGINAL RESEARCH  
Year : 2020  |  Volume : 31  |  Issue : 4  |  Page : 579-584
Comparison of the efficacy of different Ni-Ti instruments in the removal of gutta-percha and sealer in root canal retreatment


1 Department of Endodontics, Center for Operative Dentistry and Periodontology, University of Dental Medicine and Oral Health, Danube Private University (DPU), Krems, Austria
2 Department of Endodontics, Center for Operative Dentistry and Periodontology, University of Dental Medicine and Oral Health, Danube Private University (DPU), Krems, Austria; Department of Operative Dentistry and Periodontology, Center for Dental Medicine, Oral and Maxillofacial Surgery, Medical Center, University of Freiburg, Freiburg i.Br., Germany

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Date of Submission30-Dec-2018
Date of Decision26-Jun-2019
Date of Acceptance15-Aug-2019
Date of Web Publication16-Oct-2020
 

   Abstract 


Aims: To evaluate and compare the efficacy of four rotary instrumentation systems in root canal retreatment and to determine retreatment time. Materials and Methods: To achieve the purpose of this study, canals of 60 distal roots in mandibular molar teeth were selected and randomly divided into four groups A, B, C and D (n = 15). Using step-back technique, the canals were prepared and filled with gutta-percha and AH Plus employing cold lateral compaction technique. The root filling material was removed with the following retreatment systems: Group A: Mtwo R, group B: D-RaCe, group C: ProTaper R and group D: R-Endo. In order to record retreatment time, a stopwatch was used. The samples were split longitudinally, examined under a stereomicroscope, photographed and assessed with AutoCAD software. Finally, the percentages of remaining filling material were calculated and the extracted data were analyzed using one-way ANOVA and Tukey HSD test. Results: All examined groups showed traces of remaining filling material within the canals. No statistically significant difference was found among the four groups in the coronal, middle, and apical thirds. The same result was obtained with regard to retreatment time (P > 0.05). However, within each one of the groups, significant difference was observed in the three regions (P < 0.05). Conclusions: Based on the findings of this study, none of the examined systems could completely remove root filling material from the root canals. However, they were all found to be effective in this regard. The most amount of remaining filling material was found in the apical third.

Keywords: D-RaCe, Mtwo R, ProTaper R, R-Endo

How to cite this article:
Nasiri K, Wrbas KT. Comparison of the efficacy of different Ni-Ti instruments in the removal of gutta-percha and sealer in root canal retreatment. Indian J Dent Res 2020;31:579-84

How to cite this URL:
Nasiri K, Wrbas KT. Comparison of the efficacy of different Ni-Ti instruments in the removal of gutta-percha and sealer in root canal retreatment. Indian J Dent Res [serial online] 2020 [cited 2020 Oct 31];31:579-84. Available from: https://www.ijdr.in/text.asp?2020/31/4/579/298426



   Introduction Top


The use of new methods and materials in root canal therapy has shown to be highly successful specifically in terms of tooth function and retention.[1],[2] However, primary root canal therapy might not always result in healing and the recurrence of root canal infection hinders the desired outcome. For example, failure to sufficiently disinfect the root canal system and micro leakage could have a negative outcome. Bacteria such as  Enterococcus faecalis Scientific Name Search emain after initial root canal therapy in areas that were out of reach for instrumentation and irrigation.[3],[4],[5]

Retreatment methods are more difficult to implement than those being used in initial treatment as they require innovative instrumentation and magnification systems as well as special training.[6] The complete removal of filling material from the root canal is a necessity for a satisfactory outcome.[7] When a proper diagnosis is made and all the technical phases of retreatment are cautiously completed, nonsurgical retreatment could be highly successful. The prognosis for root canal retreatment mainly depends on cleaning and disinfection.[4] The aim of this study was to evaluate and compare the efficacy of Mtwo retreatment, D-RaCe, ProTaper retreatment, and R-Endo in the removal of gutta-percha/sealer from root canals in the coronal, middle, and apical thirds. This study also intended to determine the time for retreatment.


   Materials and Methods Top


Sixty distal roots of extracted first mandibular molars with single, straight root form, and fully formed apices were selected. The distal roots with internal and external resorption, fracture, calcification, and multi canals were excluded. Radiographs were taken. Soft tissue and calculus were removed mechanically from the root surface with periodontal curette and disinfected by immersion in NaOCl 2.25% for two hours. Afterwards, they were rinsed with distilled water and kept in NaCl 0.9% until they were used. The samples were randomly divided into four groups (n = 15) and the distal roots surfaces were dyed with three different colors of nail polish. Group A (Mtwo R): Red, group B (D-RaCe): Blue, group C (ProTaper R): Colorless, and group D (R-Endo): Black.

Root canal preparation and filling

Having prepared access cavity, a size 10 C-Pilot® (VDW, Munich, Germany) was inserted into the canal until it was seen at the apical foramen. Working length was then determined to be 1 mm shorter than the inserted file. The samples were prepared using step-back technique. The canals were enlarged up to a size 25 K file as master apical file and flared to a size 55 K file. The coronal flaring was performed with size 55 K file. The patency was performed with size 10 C-Pilot®. After each instrument, the canals were irrigated with 2 ml of 2.25% NaOCl. The final irrigation was performed with 5 ml of 17% EDTA for 30 s followed by 2 ml of 2.25% NaOCl and then 2 ml of distilled water.

Afterwards, the canals were dried with paper points. The roots were filled with size 25 gutta-percha, AH Plus (Dentsply DeTrey, Konstanz, Germany) sealer, and accessory gutta-percha using lateral compaction technique. Regardless of root length, gutta-percha/sealer was homogeneously extended to 12 mm from the apex to the coronal third allowing the use of heated hand plugger. On the other hand, the volumes of filling material were the same for all the samples. The access cavities were sealed with cotton pellets and temporary filling such as Coltosol F (Coltene/Whaledent, Langenau, Germany). Finally, the teeth were radiographed in the buccolingual direction to determine the quality of the filling procedure and the presence of bubbles. The samples were then stored in 100% humidity for 14 days to allow setting of the filling material.

Root canal retreatment

Group A

Mtwo retreatment instruments (VDW, Munich, Germany) were used to remove the filling material in a crown-down technique as follows: R25 (size 25, 0.05 taper) and R15 (size 15, 0.05 taper). Final apical preparation was performed with Mtwo instrument (size 30, 0.05 taper). After being used in two root canals, the Mtwo retreatment instruments were discarded. They were used with a VDW silver endo-motor (VDW, Munich, Germany).

Group B

D-RaCe (FKG Dentaire SA, La Chaux-de-Fond, Switzerland) retreatment instruments were used to remove the filling material in this group. The D-RaCe set consists of two NiTi instruments: DR1 (size 30, 0.10 taper) and DR2 (size 25, 0.04 taper). DR1 was used for removal of filling material in the coronal third and DR2 was used in the middle and apical thirds. Moreover, final apical preparation was performed with iRace instrument (size 30, 0.04 taper). DR1 was discarded after being used in three root canals. DR2, on the other hand was used once.

Group C

In this group, ProTaper retreatment instruments (Dentsply Maillefer, Ballaigues, Switzerland) were used to remove the filling material as follows: D1 (size 30, 0.09 taper) for the coronal third, D2 (size 25, 0.08 taper) for the middle third, and D3 (size 20, 0.07 taper) for the apical third until the working length was reached. Final apical preparation was performed with F3 instrument (size 30, 0.09 taper). D1 was discarded after being used in three root canals. However, D2 and D3 were discarded after being used in two root canals.

Group D

R-Endo (Micro-Mega, Besancon, France) consists of five instruments: Rm (size 25, 0.04 taper), Re (size 25, 0.12 taper), R1 (size 25, 0.08 taper), R2 (size 25, 0.06 taper), and R3 (size 25, 0.04 taper). To remove the filling material in this group, three NiTi instruments, namely, R1, R2, and R3 were used as follows: R1 for the coronal third, R2 for the middle third, and R3 for the apical third until the working length was reached. Final apical preparation was performed with Hero Shaper instrument (size 30, 0.04 taper). R1 was discarded after being used in three root canals. R2 and R3 were discarded after two uses.

It needs to be mentioned that the instruments for groups B, C, and D were used with an x-smart plus endo-motor (Dentsply Maillefer, Ballaigues, Switzerland). Speed and torque for all the groups were set according to the manufacturers' instructions. Final apical preparation files were used for four root canals and then they were discarded. Retreatment time for all groups, except for the final apical preparation, was recorded using a digital stopwatch. After each instrument, the stopwatch was paused and the time was recorded. In addition, in the current study retreatment procedures were performed using 4.5 × magnifying loupes (Zeiss, Jena, Germany). Removal was considered complete for all root canals when no filling material could be detected inside the canals using a stereomicroscope at 20 × magnification (Bresser, Rhede, Germany).

In all groups, samples were irrigated with 2 ml of 2.25% NaOCl between each instrument. Final irrigation was performed with 5 ml of 17% EDTA for 30 s, followed by 2 ml of 2.25% NaOCl. Afterwards, the distal roots were decoronated with a diamond disc to 12 mm of the reference surface. Following that, the distal roots were split longitudinally with a diamond disc and both root halves were photographed with a camera which was attached to a stereomicroscope at 20 × magnification (Bresser, Rhede, Germany). Using AutoCAD software, the root canals were divided into three parts of 4 mm. Afterwards the root canals and the areas with residual filling material were demarcated. The areas of residual filling material and root canals were measured in mm2. The percentage of the remaining filling material was calculated using the following equation:



The analysis of the residual root filling material of the four groups after retreatment in the coronal, middle, and apical thirds on the canal walls is presented in [Figure 1].
Figure 1: The analysis of the residual gutta-percha/sealer on the root canal walls after retreatment in coronal, middle, and apical thirds in groups a (Mtwo R), b (D-RaCe), c (ProTaper R), and d (R-Endo)

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Statistical analysis

Statistical analysis was performed with SPSS software (IBM SPSS Statistics 19.0, IBM, Armonk, NY, USA). One-way analysis of variance (ANOVA) was used to assess the residual filling material. Moreover, a Tukey HSD test was used to perform multiple comparisons (α = 0.05).


   Results Top


Descriptive statistics for the remaining gutta-percha/sealer for all the four groups are presented in [Table 1]. Furthermore, box-plot graph in [Figure 2] display the percentage of the residual gutta-percha/sealer after retreatment in the coronal, middle and apical thirds in detail. The results revealed that there was no significant difference with regard to root canal filling remnants among the four experimental groups in the coronal, middle, and apical thirds (P > 0.05).
Table 1: Percentage of the residual gutta.percha/sealer (mean}standard deviation) after retreatment on the root canal walls and ANOVA results (P-value) in all groups

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Figure 2: Percentage of the residual gutta-percha/sealer on the root canal walls after retreatment in the three different areas with boxplot

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In group A, the least amount of residual gutta-percha/sealer was found in the coronal third. The results also showed that apical third had the highest residual of gutta-percha/sealer. The difference between the coronal and apical thirds was significant (P < 0.05). However, there was no statistically significant difference between the apical and middle thirds with respect to residual of gutta-percha/sealer.

Based on the results of D-RaCe in group B, the least residual filling material was observed in the coronal third. Furthermore, compared to the coronal third, the middle and apical thirds showed the highest residual filling material. However, no statistically significant difference was found between the coronal and middle thirds in this regard.

The results of ProTaper R for group C revealed that the least amount of residual gutta-percha/sealer remained in the coronal and middle thirds. With regard to the three regions, more filling residue was observed in the apical region compared to the other regions and the difference was statistically significant (P < 0.05).

R-Endo showed the least residual gutta-percha/sealer in the coronal and the highest residual gutta-percha/sealer in the middle and apical thirds compared to the coronal third. The coronal third showed significant difference to the apical third (P < 0.05).

[Figure 3] illustrates the retreatment time in seconds. [Table 2] provides mean operating time required to remove gutta-percha/sealer for each group. As illustrated in [Table 2], R-Endo system required less time to remove root filling material than the other systems. However, the statistical analysis of the retreatment time for all the retreatment systems was not statistically significant (P > 0.05).
Figure 3: Operating time to remove gutta-percha/sealer among the four different retreatment systems in seconds with boxplot

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Table 2: Comparison of retreatment time among the four groups and ANOVA results (P-value)

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   Discussion Top


Initial root canal therapy does not always succeed and periradicular inflammatory lesions might remain or develop after the treatment. Cause of such failures is mainly microorganisms that have either withstood the conventional treatment procedures or reinfected the root canal system at later phases through coronal leakage.[8] In their study, Friedman and Mor[9] reported that when there was no prior apical periodontitis, the commonness of healed cases after both initial root canal therapy and orthograde retreatment ranged from 92% to 98% up to 10 years after therapy. They concluded that when prior apical periodontitis exists, the rate of healing decreases to the range of 74% and 86%, regardless of whether primary treatment or nonsurgical retreatment was performed.[9]

The present study focused on evaluating and comparing the efficacy of four retreatment systems. It also aimed to determine the time for the removal of root canal filling material. To achieve the purpose of this study, 60 distal roots of extracted human permanent mandibular were used. The straight and single root form was determined by visual examination. Regardless of root length, the roots were filled to 12 mm from the apex to the coronal third and after retreatment decoronated to 12 mm of the reference surface, which means that the samples were concisely standardized, such as the study by Hulsmann and Bluhm.[10]

Each tooth is unique since morphology is variable and there is no standardized apical canal size. Therefore, the choice of file size for root canal preparation such as master apical file depends on the morphology of the root canal, as well as the clinical situation and the decision of the clinician.[11] Hand instrumentation technique such as step back reduces errors, transportation, ledging, and apical perforation.[12] On this account, in the present study root canals were prepared using step back technique. The canals were enlarged up to a size 25 K file as master apical file and flared to a size 55. In line with previous studies, the coronal flaring was performed with the final file.[13],[14] The taper of K-files was increased from D0 (diameter) to D1 by 0.02 mm in width and length. Master gutta-percha cones size 25 have a tug back in all roots which is ideal for the preparation of samples as used in the study by Das et al.[15] It is worth mentioning that the present study followed Alves et al. study[16] in sampling.

Lateral compaction system is considered as the most well-known obturation technique in practice. It also has been taught in most institutions.[17] In the current study, lateral compaction was used for obturation of root canals, as employed by Alves et al.[16] and Zuolo et al.[18]

Considering the removal of gutta-percha and sealer, the most successful technique is the crown-down.[3] Therefore, the crown-down technique was used in the present study. Moreover, several methods and instruments have been used for the removal of gutta-percha/sealer such as hand instruments, ultrasonic, and rotary instruments with or without solvents.[16],[19] Based on the literature, in most of the research studies concerning retreatment procedures two or three Ni-Ti systems were compared.[20],[21] One of the distinguishing features of the present study is the use of four different Ni-Ti systems.

Having considered the findings of previous studies, an apical enlargement greater than the initial preparation size was performed in order to reduce filling material remnants in the root canals particularly in the apical third.[22],[23],[24] Therefore, the present study followed almost the same procedures as some other studies yet with bigger instruments as well as different taper. The final apical preparation was carried out as follows: In group A: Mtwo size 30, 0.05 taper, in group B: iRace size 30, 0.04 taper, in group C: F3 size 30, 0.09 taper, and in group D: Hero Shaper size 30, 0.04 taper. The taper of files size 30 in the groups A, B, C and D was increased from D0 (diameter) to D1 by 0.05, 0.04, 0.09, and 0.04 mm in width and length respectively. In the current study, samples were examined in the working length of 12 mm. It appears that diameters of file size 30, 0.09 were bigger than those of the other systems. The results of ANOVA test showed that there were no significant differences between file size 30, 0.09 and the other final files (P = 0.066) from D0 (1 mm) to D8 (8 mm). However, a statistically significant difference was observed between file size 30, 0.09 and the other systems from D9 (9 mm) to D12 (12 mm) (P = 0.000). Having said that, filling material in the coronal third was expected to get removed significantly better with F3 than the other systems. Nevertheless, no significant difference was observed in the coronal third with regard to residual filling material. This may be due to the fact that the final apical instruments were used four times and the cutting edges of size 30, 0.09 got blunt.[25]

This study contained the retreatment procedures performed using 4.5 × magnifying loupes. However, the final removal was considered complete when no filling material could be detected inside the canals using a stereomicroscope at 20 × magnification. In the study by Fatima et al.[26] all endodontic procedures were carried out at 10.9 × magnification. In our study, having performed retreatment procedures, both root halves were photographed with a camera equipped to a stereomicroscope at 20 × magnification. The strength of our study in comparison to other studies is taking advantage of higher magnification before and after retreatment procedures.[15],[26]

The difference in time for retreatment among the four groups was not statistically significant. The findings of the retreatment time cannot be compared directly with a previous study.[18] Similar studies have shown that retreatment systems required less time to remove gutta-percha/sealer from root canals.[21],[24],[27]

In the current study, speed and torque for all of the groups were set according to the manufacturers' instructions. None of the instruments were fractured during the retreatment procedure as in the study by Bhagavaldas et al.[14]

In our study, all specimens were split longitudinally with a diamond disc. In other studies, however, since micro-CT was used for evaluating the remaining filling material, the samples did not have to be split.[21],[28] In our study, like studies conducted by Bhagavaldas et al.[14] and Akhavan et al.[29] the samples were photographed under a stereomicroscope. The remaining filling material was assessed using AutoCAD software. In fact, AutoCAD software was employed to evaluate the preparation of the dentin walls in root canals.[30]

The findings of the present study, in line with others studies including those conducted by Zuolo et al.[18] Ersev et al.[20] Roeding et al.[21] Joseph et al.[23] and Fruchi et al.[28] confirmed that the removal of filling material was not complete in any of the root canals. In other words, all methods and instruments left filling material inside the root canals. Based on the results of this study, no significant difference was found among the four groups in the coronal, middle, and apical thirds. Regarding each group, however, results of a Tukey HSD test showed that there was statistically significant difference among some areas of the three regions. The findings of this study showed that all the retreatment systems can remove filling material from the root canals, indicating that all the files are recommended for the secondary therapy.


   Conclusions Top


The results revealed that the amount of the remaining filling material in the apical third is higher than that of the middle and coronal thirds. The apical third is probably the most important area to clean and disinfect in the course of successful retreatment. The development of techniques and instruments which predictably facilitate the removal of filling material in this area would be desirable. No difference was observed in the efficacy of the four different systems. Therefore, it can be concluded that all the systems are considered suitable and efficient for retreatment.

Financial support and sponsorship

Danube Private University (DPU).

Conflicts of interest

There are no conflicts of interest.



 
   References Top

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Correspondence Address:
Dr. Kaveh Nasiri
Department of Endodontics, Center for Operative Dentistry and Periodontology, University of Dental Medicine and Oral Health, Danube Private University (DPU), Krems
Austria
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ijdr.IJDR_946_18

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