|Year : 2017 | Volume
| Issue : 2 | Page : 95-100
Comparison of efficiency of manual(H-Files) and two rotary niti retreatment systems(Mtwo R files and HyFlex NT files) in removing Gutta-percha from root canals obturated with two different sealers by using stereomicroscope - An in vitro study
Pravin Kumar, Himanshu Sood, Surekha Puri Bhat, Jitendra Lohar, Sandhya Kapoor Punia, Rahul Bhargava
Department of Conservative Dentistry and Endodontics, Darshan Dental College and Hospital, Udaipur, Rajasthan, India
|Date of Web Publication||6-Nov-2017|
Department of Conservative Dentistry and Endodontics, Darshan Dental College and Hospital, Udaipur, Rajasthan
Source of Support: None, Conflict of Interest: None
Objectives: The aim of this study was to compare manual and two nickel titanium (NiTi) rotary retreatment systems in removing gutta-percha obturated with two different sealers.
Materials and Methods: Sixty extracted, human, single-rooted mandibular premolars were selected. Endodontic treatment was performed using ProTaper Universal NiTi rotary instruments. Half of the samples were obturated with Tubliseal and remaining half were obtutared with AH Plus sealer with cold lateral compaction method. Subsequently, twenty teeth were retreated with manual retreatment system, and each twenty teeth was retreated with two different rotary retreatment systems. The roots were then grooved longitudinally, and both root halves were subjected to assessment under stereomicroscope, and images were taken with a digital camera. These images were evaluated for residual obturating material using AutoCAD software. Analysis of variance test and Bonferroni multiple comparison test were used for statistical analysis.
Results and Conclusion: Results of the present study showed that no system was able to completely remove all debris from the root canals. The minimum amount of debris was seen in the group obturated using Tubliseal sealer and retreated with Hyflex NT retreatment system followed by Mtwo retreatment system and finally the manual retreatment protocol. Regarding the time taken, Mtwo retreatment files took least time to remove the obturating material in all sealer groups.
Keywords: AH Plus, AutoCAD, Hedstrom file, Hyflex NT, Mtwo, Tubliseal
|How to cite this article:|
Kumar P, Sood H, Bhat SP, Lohar J, Punia SK, Bhargava R. Comparison of efficiency of manual(H-Files) and two rotary niti retreatment systems(Mtwo R files and HyFlex NT files) in removing Gutta-percha from root canals obturated with two different sealers by using stereomicroscope - An in vitro study. Endodontology 2017;29:95-100
|How to cite this URL:|
Kumar P, Sood H, Bhat SP, Lohar J, Punia SK, Bhargava R. Comparison of efficiency of manual(H-Files) and two rotary niti retreatment systems(Mtwo R files and HyFlex NT files) in removing Gutta-percha from root canals obturated with two different sealers by using stereomicroscope - An in vitro study. Endodontology [serial online] 2017 [cited 2021 May 7];29:95-100. Available from: https://www.endodontologyonweb.org/text.asp?2017/29/2/95/217704
| Introduction|| |
The main objective of nonsurgical retreatment is to remove all filling material from the root canal and to regain access to the apical foramen. The techniques used to remove gutta-percha from root canals include manual endodontic hand instruments (Imura et al. 1996, Schirrmeister et al. 2006a), ultrasonics (Ladley et al. 1991), lasers (Farge et al. 1998), and heat-carrying instruments (Wolcott et al. 1999) as well as nickel titanium (NiTi) rotary instruments (Imura et al. 2000).
Conventionally, the removal of gutta-percha using manual files with or without solvent can be a tedious, time-consuming process, especially when the root filling material is well condensed. Therefore, rotary NiTi instruments have been used for the removal of filling materials from root canal walls, and various studies have reported their efficacy, cleaning ability, and safety.
The aim of present study was to compare the efficacy of two rotary file systems, i.e. Hyflex NT (Coltene Whaledent, Switzertland) and Mtwo retreatment files (VDW, Munich, Germany) with that of manual H-files (Dentsply Maillefer, Balligues, Switzerland) in removing gutta-percha and sealer from the root canals obturated using two different sealers, evaluated using AutoCAD software (Autodesk, USA).
| Materials and Methods|| |
Sixty noncarious single-rooted mandibular premolars with fully formed apices were included in the study. Gingival remnants were removed and crowns were thoroughly cleaned. Subsequently, all teeth were stored in sterile saline solution.
Initial endodontic treatment
The teeth were decoronated so as to achieve a standardized working length of 15 mm. Accesses opening were made in all specimens. Working length was established by subtracting 1 mm from the length of instruments that just became visible at the apex. Endodontic treatment was performed using ProTaper Universal NiTi rotary instruments. Canals were enlarged using Glyde for facilitation up to F3 at working length. During instrumentation, all canals were irrigated between each instrument change with 2.5 ml of 5.25% NaOCl. A final flush was performed with 5 ml of 17% ethylenediaminetetraacetic acid (EDTA) for 30 s followed by a rinse with 5 ml of saline.
The specimens were then divided into two Groups A and B of 30 teeth each. After drying the canals with paper points, obturation was carried out by cold lateral condensation. Group A was obturated with gutta-percha and Tubliseal as the sealer of choice, and in Group B, the specimen were obturated with gutta-percha and AH Plus sealer. The quality and extent of obturation were confirmed radiographically. The access cavities were sealed with Cavit-G and stored at 100% humidity for 2 weeks.
Later, each group was further subdivided into three subgroups on the basis of type of retreatment systems used. In all the subgroups, RC solve was used as root canal solvent for 3 min before removal of gutta-percha.
- Subgroup A1: (n = 10), the samples were retreated using Gates–Glidden (GG) drills and H-files. At first GG-drill size 2 was used in the coronal third of root canal. Then GG-drill size 1 was used up till the middle third. Then H-files sizes 40-15 were used in a circumferential push-pull motion until size 15 reached the working length. Apical preparation was performed with H-file size no. 30
- Subgroup A2: (n = 10), the samples were retreated using Mtwo retreatment file system. The root canal obturation was removed to the working length using Mtwo R25/0.05 and Mtwo R15/0.05 retreatment instruments in a brushing motion. Then Mtwo retreatment files were used up till the working length
- Subgroup A3: (n = 10), the samples were retreated using Hyflex NT rotary files. Hyflex files were used according to manufacturer's instructions for removal of obturating material from root canals. Hyflex NT files size 40-20 with 0.06% taper was used until the 20# file reached the working length. After that, apical preparation was performed with 30# Hylex NT file.
The same procedure was repeated with subgroups B1, B2, and B3.
Time taken by all retreatment systems to remove the root canal filling was noted with the help of stopwatch. During the chemomechanical preparation, canals were irrigated along with each change of instrument with 2.5 ml of 5.25% NaOCl. Once prepared all samples were irrigated with 5 ml of 17% EDTA solution. A final rinse with 5 ml of saline was done. Retreatment was considered complete when the last instrument easily reached the working length, and no further obturating material was observed on the instruments.
Method of data collection
The teeth were grooved in a buccolingual direction with a diamond disk and sectioned longitudinally using a chisel and mallet. Both root halves were subjected to assessment under stereomicroscope and images were taken with a digital camera. These images were evaluated for residual obturating material using AutoCAD software by calculating the volume of remaining obturating material. The remaining filling material and debris/canal ratios were considered as a unit of analysis and expressed as percentage of filling material left after reinstrumentation.
Statistical analysis was performed using one-way Analysis of variance test and Bonferroni multiple comparison test. SPSS (Statistical package for social services) software by IBM (USA) was used.
| Results and Interpretations|| |
Evaluation of canal wall cleanliness after retreatment
H-files-GG drill left the maximum amount of debris in the root canals obturated with either of the two sealers [Figure 1] and [Figure 2]. Mtwo retreatment files showed intermediate results among all three groups. [Figure 3] and [Figure 4]. However, Hyflex NT left the least amount of debris in the root canals in both groups [Figure 5] and [Figure 6]. When the mean areas (that signify the volume) of remaining debris were compared in each third of the canal the maximum amount of debris was found in the apical third as compared to the middle and coronal third of the canals [Table 1],[Table 2] and [Graph 1].
|Figure 1: Remaining debris left in Group A after retreatment with H-file|
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|Figure 2: Remaining debris left in Group B after retreatment with H-file|
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|Figure 5: Remaining debris left in Group A after retreatment with Hyflex NT|
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|Figure 6: Remaining debris left in Group B after retreatment with Hyflex NT|
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|Table 1: Intergroup comparison of the debris present in each third of the canal using one-way analysis of variance|
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|Table 2: Inter subgroup comparison of P values in each third of tested specimens using post hoc Tukey's test|
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In Group A (Tubliseal sealer), the statistical analysis further showed significant difference (P< 0.05) between the efficiency of Mtwo retreatment files when compared with the H-files for retreatment in the coronal third area. There was observed statistically significant difference in the efficiency of Hyflex NT retreatment files in comparison to the H-files in the apical third area (P< 0.05) and statistically highly significant difference in the coronal third area (P< 0.001).
In Group B (AH Plus sealer), the statistical analysis showed significant difference (P< 0.05) when Mtwo retreatment files were compared with H-files in the coronal third area. In the middle third area, the statistical difference was significant (P< 0.05), whereas in the apical third, it was highly significant (P< 0.001) when Hyflex NT retreatment files were compared with Mtwo retreatment files.
On further assessment, it can be inferred that the Mtwo retreatment system when tested against Tubliseal sealer showed statistically significant (P< 0.05) better cleaning efficiency than when compared against the AH Plus sealer [Figure 3] and [Figure 4].
Evaluation of time taken by different retreatment systems [Table 3] and [Graph 2]. Mtwo retreatment system took least time to remove the obturating material. The H-files/GG-drills took the maximum time for removal of obturating material in both groups. The statistical analysis further showed a highly significant difference in the time taken between manual and rotary retreatment systems (P< 0.001). Significant difference in time taken for retreatment was seen among two rotary retreatment systems(P < 0.05).
|Table 3: Inter subgroup comparison of mean time taken (min) to remove the obturating material from the root canals using one-way analysis of variance and Bonferroni multiple comparison test|
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| Discussion|| |
The clinical success rate of endodontic retreatment has been estimated between 50% and 90%., The variability of the outcome of endodontic retreatment is related to various factors: The patient's age and types of teeth treated, the presence of alterations in the natural course of root canals, the possibility of removing the coronal restorations to access the pulp chamber, the techniques used to remove the existing filling material, and thus, in the present study, GG drills and H-files were used in comparison with Hyflex NT files and Mtwo retreatment files to facilitate the removal of gutta-percha from the root canals obturated with two different sealers (AH Plus and Tubliseal).
Mtwo rotary retreatment files were selected as they have S-shaped cross-section and have increased pitch in apicocornal direction. The depth of the space designed for dentine removal is increased behind the blades, which provides the large space for dentine removal and leads to more efficient gutta-percha and sealer removal. The Mtwo file has an H-file-like motion (up and down). Its capacity for good material removal is due to its structure. The H-file has a positive Rake angle, making dentine removal efficient; it comes with a #25-file with 0.05 tapering in the coronal and a #15-file with 0.05 tapering in the middle and apical section.
The other system used in the present study was Hyflex NT, as for this new system the manufacturer claims its use in specified conditions such as calcified canals, in retreatment and removal of gutta-percha. It comes in 0.04 and 0.06 taper with sizes 15-40#, in 0.04 taper and 20-40 with size 0.06 taper with orifice enlarger of 0.08 with 25# size. Some instruments (20/0.02, 20/0.06, 30/0.04, and 40/0.04) have triangular cross section with three blades and three flutes; others (0.04/20 and 0.04/25) have quadrangular cross section with four blades and four flutes. Hyflex NT is indicated in specific clinical conditions such as calcified canals, straight canals, retreatment, and removing gutta-percha. There is no study published in literature comparing the retreatment efficacy of Hyflex NT system.
Both these rotary NiTi systems were compared with GG drills and H-files. The use of GG drill is a well-known technique to remove gutta-percha from the coronal and middle third of the root canal. H-files were used in a circumferential quarter turn push-pull filing motion, to remove gutta-percha and sealer until working length is achieved.
Organic solvents have been used to aid removal of gutta-percha and sealer. In this study, RC solve was used to aid in removal of gutta-percha and sealer.
To evaluate the remaining obturating material, the images taken on stereomicroscope were transferred to AutoCAD software. The results obtained were quantitative (expressed in percentages and mm 2) and not scores (as in qualitative evaluations); data were available for the whole root canal and/or specific areas.
In the current study, all retreatment techniques left gutta-percha/sealer remnants within the root canal. This finding is concurrent with previous results reported by numerous investigators using different retreatment instruments, techniques, and solvents.
In the present study, rotary retreatment systems left less amount of debris in the root canal after retreatment than the manual retreatment system, i.e. GG drills and H-files when used with two different sealers.
The better cleaning with rotary systems may be because of the frictional heat generated by rotary instruments which may lead to softening of the gutta-percha, and thereby, the working length is more easily reached. The rotary instruments are designed for removal of materials in apicocoronal direction during their use.
The results of the present study are in accordance with studies conducted by Schirrmeister et al. and Rödig et al. who also concluded that the rotary retreatment systems were more effective than manual retreatment system.,
The results of the present study concluded that Hyflex NT showed better removal of gutta-percha and sealer as compared to Mtwo retreatment system and manual retreatment group. The possible reason for better results with Hyflex NT may be because to its positive rake angle, cutting tip, more taper, i.e. 6%, and also due to a larger apical size preparation as compared to Mtwo retreatment file.
Mtwo retreatment files show better removal of obturating material as compared to manual group because of its cutting tip as well as frictional heat generation during gutta-percha removal. In manual retreatment group with H-files and GG-drill, no softening of gutta-percha takes place thus making it ineffective and tiresome.
Yadav et al. evaluated the efficacy of NiTi mechanical rotary instrumentation and H-file for gutta-percha/sealer removal. Under the experimental conditions, Mtwo and ProTaper retreatment files left less gutta-percha and sealer than H-files; however, complete removal of filling materials was not achieved by the three systems investigated. The findings of this study are concurrent with the results of the above-stated study as well.
When the mean area of remaining debris was compared in each third of the root canal, the maximum amount of debris was seen in apical third as compared to cervical and middle third of the root canal. In general, there is increased anatomical variability and difficulty of instrumentation in the area. The existence of curvatures in many planes of deep grooves and depressions on dentine walls in the apical third may well explain the presence of these less instrumented areas making it impossible to direct NiTi instruments against entire root canal walls.
On comparing the time taken by all retreatment systems, it was noted that rotary instruments (Hyflex NT and Mtwo) took less time to remove the obturating material as compared to manual retreatment system (GG-drill and H-files). This finding is consistent with the earlier results achieved by numerous investigators using different retreatment systems.
Mtwo retreatment was the fastest among all retreatment system tested. The probable reason behind this is active cutting tip and two cutting edges which helps in easy initial penetration and progression into gutta-percha. Hyflex NT took more time as compared to Mtwo retreatment system because of more number of instruments used for the procedure.
In general, AH Plus sealer showed more amount of debris left after retreatment as compared to Tubliseal sealer. AH Plus is an epoxy-amine resin-based root canal sealer. It is characterized by superior mechanical properties, high radiopacity, low solubility, minimum shrinkage, and high degree of stability.
Fisher et al. theorized that one explanation for the superior adhesiveness to root dentin shown by AH Plus can be based on the creation of a covalent bond by an open epoxide ring to amino groups in collagen network.
| Conclusion|| |
Within the limitations of the present study, we may conclude that:
- None of the techniques were effective in removing all the obturating material from the canals
- Under the experimental conditions, Hyflex NT showed least remaining debris in the root canals when compared with the other retreatment systems
- Retreatment with Mtwo retreatment system took the least time for completion when compared with other retreatment systems tested
- AH Plus sealer showed greater adherence to canal walls; hence, it was more difficult to remove.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]
[Table 1], [Table 2], [Table 3]