|Year : 2021 | Volume
| Issue : 1 | Page : 20-24
An assessment of the efficacy of a rotary and a reciprocating retreatment file system for removal of gutta-percha from root canals: An in vitro cone-beam computed tomography study
Kapil Dasaram Wahane, Shraddha Shekhar Kulkarni, Sadashiv Daokar, Kalpana Patil, Karishma Patel, Trupti Thorat
Department of Conservative Dentistry and Endodontics, CSMSS Dental College and Hospital, Aurangabad, Maharashtra, India
|Date of Submission||06-Feb-2020|
|Date of Decision||13-Mar-2020|
|Date of Acceptance||20-Jul-2020|
|Date of Web Publication||23-Mar-2021|
Dr. Shraddha Shekhar Kulkarni
Department of Conservative Dentistry and Endodontics, CSMSS Dental College and Hospital, Aurangabad, Maharashtra
Source of Support: None, Conflict of Interest: None
Aim: The aim of this study was to compare the NeoEndo and WaveOne retreatment systems concerning the effective removal of epoxy resin-based sealer and gutta-percha during the retreatment of straight root canals.
Materials and Method: Sixty extracted, human mandibular first premolars with single straight roots were selected based on cone-beam computed tomography (CBCT) evaluations. The root canals were instrumented with the ProTaper system up to the F3 file and filled with gutta-percha and epoxy resin-based sealer using the cold lateral condensation technique. After 1 month, the samples were randomly divided into two groups (n = 30) according to the retreatment system used: NeoEndo and WaveOne. A CBCT device scanned specimen after the root filling and retreatment procedures, and the decrease in the volume of filling material after each retreatment protocol was measured. The results were analyzed using the paired t-test and additional box-and-whisker plots.
Results: The WaveOne removed significantly more material than the NeoEndo (P = 0.005) system.
Conclusion: The WaveOne system was more effective than the NeoEndo retreatment system during the removal of filling material.
Keywords: Cone-beam computed tomography, epoxy resin based sealer, NeoEndo, retreatment, WaveOne
|How to cite this article:|
Wahane KD, Kulkarni SS, Daokar S, Patil K, Patel K, Thorat T. An assessment of the efficacy of a rotary and a reciprocating retreatment file system for removal of gutta-percha from root canals: An in vitro cone-beam computed tomography study. Endodontology 2021;33:20-4
|How to cite this URL:|
Wahane KD, Kulkarni SS, Daokar S, Patil K, Patel K, Thorat T. An assessment of the efficacy of a rotary and a reciprocating retreatment file system for removal of gutta-percha from root canals: An in vitro cone-beam computed tomography study. Endodontology [serial online] 2021 [cited 2022 Aug 12];33:20-4. Available from: https://www.endodontologyonweb.org/text.asp?2021/33/1/20/311746
| Introduction|| |
The leading cause of posttreatment disease after root canal treatment is persistent secondary intraradicular infection. Teeth with apical periodontitis that either persisted or developed after initial root canal treatment are most often indicated for retreatment procedure.
Another most common indication for retreatment is failed root canal treatment due to incomplete cleaning and disinfection of root canals, inadequate filling of root canals (unfilled, overfilled, or incomplete filling), and unsatisfactory or untimely coronal tooth restoration.
The clinical rate of success of retreatment has been estimated to vary between 50% and 90%. The ultimate goal of nonsurgical root canal retreatment is to re-establish healthy periapical tissues.
There are different techniques currently in use for removal of filling materials. These are use of endodontic hand files, automated devices, solvents, ultrasonics, and lasers. Earlier endodontic retreatments were challenging as well as time-consuming.
It has been considered that the use of rotary instruments could reduce the fatigue and time of endodontic retreatments in comparison with hand files. Rotary nickel–titanium (NiTi) instruments are efficient than hand files. Advantages of rotary files are maintenance of canal shape and shorter working time, whereas disadvantages are the higher incidence of file fracture and more remaining filling material after retreatment.
There are many retreatment files available for dentists to work with. One of the most sought-after retreatment file is the ProTaper Universal rotary retreatment file system. It includes three instruments with different lengths and tapers. These instruments are used in following sequence for removal of filling material: D1 with taper 30/09 and length 16mm for coronal one third removal,D2 with taper 25/08 and length 18mm for middle one third removal and D3 with taper 20/07 and length 22mm for apical one third removal.
Another new rotary system recently introduced is NeoEndo retreatment file system. According to the manufacturer's guidelines, these files are used with a gentle touch, never forced, and used at recommended speed and torque setting. This system includes three files: N1 for coronal one-third preparation, N2 for middle one-third, and N3 for apical one-third. N1 and N2 are 16 mm and 18 mm length, respectively, and N3 is manufactured at 22 mm and 25 mm.
A new concept has been introduced for shaping the root canal from start to end with one single file. Roane et al. introduced the balanced force technique using instrument in rotational reciprocation motion for the preparation of curved root canals. They were the first to introduce the use of hand files with unequal clockwise and counterclockwise movements in reciprocation. This led to development of one single file system of shaping root canal system.
A single file reciprocating technique utilizing unequal clockwise and counterclockwise angles is four times safer and almost three times faster than using multiple rotary files to achieve the same final shape.
The reciprocating files are manufactured using M wire NiTi alloys that offer higher resistance to cyclic fatigue compared to traditional NiTi alloys. The new WaveOne reciprocating file system from Dentsply Maillefer is comprised a small (21.06), a primary, and a large file (40.08). The same technique is also indicated for retreatment purposes, in which the instruments are used with a brushing motion against the lateral walls of the canal to remove any residual filling material.
Cone-beam computed tomography (CBCT) can provide three-dimensional information regarding retreatment procedure outcomes. High-resolution computed tomography is an innovative, nondestructive, and reproducible device. It produces very thin sections and a true three-dimensional (3D) reconstruction of the object with cubic voxels and isotropic resolution. Therefore, we aimed to assess the efficacy of three different retreatment techniques for removal of gutta-percha from root canal using CBCT.
This is an in vitro study that was proposed to assess the remaining volume of gutta-percha after carrying out retreatment with rotary and reciprocating file systems.
The study hypothesis proposed was as follows:
Null hypothesis (H˚): There will be no difference in the efficacy of a rotary and a reciprocating retreatment file systems on removal of gutta-percha from root canals.
Thus, if u1 and u2 are mean values of remaining gutta-percha after retreatment with a rotary and reciprocating system, respectively, then,
H˚: u1 = u2
Alternate hypothesis (H1): There will be a difference in the efficacy of two rotary and a reciprocating retreatment file systems on removal of gutta-percha from root canals.
H1: u1 not similar u2
| Materials and Methods|| |
Preparation of specimens
Sixty extracted human permanent single-rooted teeth, free of caries, defects, or restorations were collected and stored in normal saline. The crowns were cut using a diamond disk accompanied with a water coolant to standardize a working length of 15 mm.
The exclusion criteria were as follows:
- Teeth with preexisting fractures or cracks
- Teeth with root caries
- Previously endodontically treated teeth
- Teeth with intracanal calcification
- Teeth with external resorption
- Teeth with internal resorption
- Carious teeth
- Teeth with an open apex
- Teeth with previous restorations.
Access opening was done using Endo-access bur (manufactured by Dentsply of length 21 mm and cutting surface of 10 mm). A size 10K file was inserted inside the canal to confirm canal patency. All the root canals were instrumented using Universal ProTaper file system (Dentsply Sirona). Crown-down preparation was initiated with S1 (purple). The apical extent of S1 was passively followed the portion of the canal secured with hand files. When a smooth glide path to the terminus was verified, sequentially S1 was introduced again and then S2 to the full working length. Apical finishing was done using finishing files F1 and F2 till the full working length. In every sample, it was necessary the use of F3 for finishing. Thus, all canals were enlarged up to F3 file.
Between instrumentation, each canal was irrigated with 1 mL of 5.25% sodium hypochlorite (NaOCl) (manufactured by PRIME Dental products Pvt. Ltd.) using 27G needle, then normal saline, and then 17% EDTA (manufactured by PRIME Dental products Pvt. Ltd.) for smear layer removal. Final irrigation was done with normal saline.
After final irrigation, the canals were dried with absorbent paper points (META BIOMED). Prepared root canals were obturated with ProTaper F3 Mastercone coated with epoxy resin based sealer (AH+ sealer, manufactured by Dentsply Sirona), by lateral condensation method. Hand spreader and additional size nonstandardized taper gutta-percha points were used. The canals were filled 1 mm short of root apex. Following canal filling, the access cavities were restored with temporary restoration material and the quality of root canal filling was confirmed on CBCT images. Then, all samples were stored at 37 degree and 100% relative humidity for 1 month.
The prepared samples were randomly divided into two experimental groups: Group 1 and Group 2 according to the retreatment system used.
The retreatment procedure was performed using WaveOne: Group 1 and NeoEndo: Group 2 retreatment file system for removal of gutta-percha from canal. After instrumentation root canals were flushed with one milliliter of 5.25% NaOCl using 27G needle.
After mechanical retreatment, the same sequence of irrigation was repeated as stated between instrumentation and final irrigation was done using normal saline. Then, it was dried with sterile absorbent points.
For evaluation of remnant of gutta-percha after using rotary and reciprocating retreatment files, all samples were scanned by computed tomography device (Orthophos XG 3D CBCT Machine of Sirona, 8 × 8 scan) for volumetric analysis. ITK-SNAP (Latest version 3.6) software was used for volume analysis. The CBCT images were obtained and converted into Digital Imaging and Communications in Medicines image format. These files were transferred into software and volumes in three milliliters were measured by semi-automatic segmentation procedure. In this way, volumetric analysis was done before and after removal of gutta-percha. Obtained data were recorded and subjected to statistical analysis for results.
| Results|| |
There were no significant differences in the initial filling volume of the filling material among the samples (P > 0.05)[Table 1].
|Table 1: Mean volume of gutta-percha before and after retreatment using different file systems|
Click here to view
The amount of filling material in the root canals decreased after two retreatment protocols (P < 0.05). However, none of the protocols succeeded in complete removal of the material from any root canal.
The decrease in the amount of filling material after each retreatment protocol was analyzed using the paired t-test and additional box-and-whisker plots. P <0.05 was considered statistically significant. All statistical analyses were performed using IBM SPSS-20 (IBM Company, Palo Alto, California, US).
| Discussion|| |
Retreatment is considered a valid alternative for extraction in case of failure in endodontic treatment. The complete removal of root filling material is difficult, and it is one of the main goals of nonsurgical endodontic retreatment procedure. Attaining this goal can be achieved by accessing the apical foramen, the action of endodontic instruments, and irrigating solutions used during instrumentation. This procedure effectively eliminates the necrotic tissue and microorganisms from remaining inside the canal.
We chose to work with mandibular premolars because they are flattened mesiodistally and have a greater buccolingual dimension, making it harder for endodontic instruments to touch all of dentinal walls. The anatomy of the root canal system and the quality of the initial root filling are important factors that need to be considered during retreatment procedures. For this reason, this study used oval root canals to evaluate the retained filling material, especially because this type of canal anatomy is challenging to access with endodontic instruments.
The use of solvent as an aid in removing the filling mass is somewhat controversial. A solvent can facilitate penetration of the instrument into the filled canal, but its use may result in the formation thin and hard to remove layer of filling material adhered to the dentinal walls. We have not used any solvent in this study because owing to the risk of extrusion into the periapical region.
In the present study, the ability of the WaveOne and NeoEndo retreatment system to remove root filling material from the oval and straight root canals of mandibular premolars was analyzed. The WaveOne system was the most effective in the removal of gutta-percha and epoxy resin-based sealer, although none of the systems completely removed the filling material. Thus, the null hypothesis of the present study was rejected.
The removal of filling materials during retreatment procedures enables instruments and irrigants to reach all areas of the root canal system, which results in more effective intracanal cleaning and disinfection. According to a review, no existing retreatment protocol can completely remove root filling materials. The mean percentage of residual material ranges from 45.4% to 0.02%. Even in the present study, complete removal of epoxy resin-based sealer and gutta-percha using the reciprocating and rotary systems with the final irrigation protocol was not achieved.
Wilcox et al. and Friedman et al. have shown that epoxy-based resin sealers adhere to the dentin and are more difficult to remove. Therefore, in order to test the retreatment protocols in challenging conditions, AH plus sealer, an epoxy-based resin sealer, was used in present study.
During the removal of filling material, solvents were not used because previous studies found that the use of solvents led to more remnants of gutta-percha and sealer on the root canal walls and inside the dentinal tubules.
In the present study, the mean filling material decrease rate was 45.57% when the WaveOne was used for retreatment; this is significantly higher than rate achieved with NeoEndo. This result can be attributed to some design changes in reciprocating file system. The WaveOne file used is made of a special NiTi alloy called M-Wire, created by means of an innovative thermal treatment process. The benefits of this M-Wire alloy are increased flexibility and improved resistance to cyclic fatigue of the instruments. This reciprocating system produces a wider motion in the counterclockwise direction but shorter in the clockwise course, resulting in a more centered file in the canal. Associated with the marked taper of these files, this condition creates a greater contact area between the instrument and gutta-percha, allowing filling removal as effective as that obtained with continuous rotation.
There is insufficient information in the literature to compare the use NeoEndo retreatment files. One study concluded that NeoEndo was efficient than M-Two as well as ProTaper Universal. The efficiency can be attributed to parallelogram cross section, limiting the engagement zone and positive rake angle. It exhibits high fracture resistance and less chances treated which improves cutting efficiency, flexibility, and more resistance to cyclic fatigue. They are used in circumferential filing motion.
The remaining filling material after rotary was higher than reciprocating, and this might be attributed to the fact that all canals were enlarged up to a size F3 ProTaper file, which has tip size of 30 and 9% taper, whereas the N3 NeoEndo retreatment file has tip size of 20 and 7% taper, which meant the N3 file tip did not engage with canal walls.
The results of the present study differ from a previous study, which observed differences between rotary and reciprocating instruments. First, the authors used a two-dimensional (2D) method to evaluate the residual filling material (i.e., dental operating microscope). Thus, the data were evaluated in two millimeters and further transformed in percentage of the total canal area. In turn, the present study used volumetric analysis to measure the amount of residual filling material, which may have contributed for the different results. It was recently reported that the case of 2D radiographs failed to represent the real cleanliness of the canal and thus reduce effectiveness of retreatment procedures. Therefore, CBCT analysis is used.
Limitations of this study are instruments with different tapers are compared and micro-CT analysis is much more precise than CBCT analysis.
| Conclusion|| |
After careful evaluation and statistical analysis, the following conclusions were made:
- Samples in every experimental group demonstrated (average percentage: 64.34) remnants of filling material
- WaveOne was significantly more effective than NeoEndo retreatment system
- Within the limitations of the present study, none of the systems used could completely remove the root canal filling material [Table 2].
|Table 2: Percentage reduction in volume of gutta-percha after retreatment using WaveOne and NeoEndo retreatment system|
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Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2]