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 Table of Contents  
Year : 2022  |  Volume : 34  |  Issue : 2  |  Page : 96-101

A comparative evaluation of retrievability of three different obturating systems using protaper universal rotary retreatment files: An in vitro cone-beam computed tomography analysis

1 Department of Conservative Dentistry and Endodontics, College of Dental Science and Hospital, Indore, Madhya Pradesh, India
2 Department of Oral and Maxillofacial Surgery, College of Dental Science and Hospital, Indore, Madhya Pradesh, India

Date of Submission17-Dec-2020
Date of Decision27-Apr-2021
Date of Acceptance23-Jul-2021
Date of Web Publication01-Jul-2022

Correspondence Address:
Dr. Shrija Paradkar
50, Chanakya Puri, Annapurna Road, Indore, Madhya Pradesh
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/endo.endo_152_20

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Aim: The aim of this in-vitro study was to comparatively evaluate the ease of retreatment in canals, obturated through GuttaFlow 2, GuttaCore, and conventional Lateral compaction technique using ProTaper Universal Retreatment (PTUR) Files.
Materials and Methods: Sixty single-rooted mandibular premolars were selected and the canals were instrumented with ProTaper Universal rotary files up to size #F3. Samples were randomly divided into three experimental groups of 20 teeth each and obturated using three different obturating systems (GROUP I-Lateral compaction technique, GROUP II-GuttaFlow 2, GROUP III-GuttaCore). All the groups underwent cone-beam computed tomography (CBCT) analysis following which retrieval of the previous root canal filling was done using the PTUR files. Post retreatment CBCT images were used to assess the amount of remaining obturating material at varying depths (3 mm, 6 mm, and 12 mm) for all three groups. Statistical analysis was performed using repeated measures analysis of variance and ANOVA.
Results: Irrespective of the obturating system used, filling material could not be removed completely from the root canal walls. Significantly more amount of obturating material was observed in the apical third than the middle third and coronal third of the root canal space (P < 0.05). When comparing the groups, the maximum percentage of remaining obturating material was seen in Group III (GuttaCore) followed by Group I (lateral compaction), with the least being observed in Group II (GuttaFlow2).
Conclusion: The GuttaCore technique utilizing carrier-based gutta-percha had the maximum amount of remaining obturating material after retreatment when compared to the GuttaFlow2 and Lateral Compaction techniques.

Keywords: GuttaCore, GuttaFlow 2, lateral compaction, obturation, retreatment

How to cite this article:
Paradkar S, Goyal K, Saha SG, Bhardwaj A, Saha MK, Nirwan AS. A comparative evaluation of retrievability of three different obturating systems using protaper universal rotary retreatment files: An in vitro cone-beam computed tomography analysis. Endodontology 2022;34:96-101

How to cite this URL:
Paradkar S, Goyal K, Saha SG, Bhardwaj A, Saha MK, Nirwan AS. A comparative evaluation of retrievability of three different obturating systems using protaper universal rotary retreatment files: An in vitro cone-beam computed tomography analysis. Endodontology [serial online] 2022 [cited 2022 Aug 8];34:96-101. Available from: https://www.endodontologyonweb.org/text.asp?2022/34/2/96/349571

  Introduction Top

Various techniques of obturation including vertical compaction, lateral compaction, thermoplasticized obturation, and carrier-based obturation have been developed to achieve a three-dimensional fluid-tight seal in root canal systems.[1],[2]

The success of root canal treatment depends on the proper sealing of the root canal system. Improper apical seal leads to microleakage further causing the recurrence of bacterial infection, which can be prevented by proper obturation technique. Over the years, pitfalls with one technique have often led to the development of newer methods of obturation like warm lateral compaction, warm vertical compaction, carrier-based techniques. Lateral Compaction of gutta-percha is, however, still considered as the gold standard technique.[1]

GuttaFlow2 (Coltene/Whaledent) is a mixture of gutta-percha powder, poly-dimethylsiloxane and silver particles. It has the capacity to expand slightly (0.2%) while setting, thus improving its sealing ability and flowability.[3],[4] This allows for its superior adaptation to the root canal walls as well as to the gutta-percha points. GuttaFlow2 is delivered in two different ways: A capsule that is to be triturated for 30s and an automix syringe.

GuttaCore is a carrier-based obturation system which consists of an internal core of cross-linked gutta-percha surrounded by a layer of α-phase gutta-percha. This carrier-based system claims to enhance the adaptation of gutta-percha to the canal wall as well as ensures the flow of material into the lateral canals.[5] Since the carrier is also made up of gutta-percha, it can be easily removed from the root canals making retreatment easy, when compared to Thermafil which instead consists of a plastic carrier.

Failure of endodontic treatment which warrants the need for retreatment may be attributed to inadequate debridement, undetected and untreated root canals, inadequate obturation, or coronal leakage.[6] The success rate of root canal therapy varies between 86% and 98%.[7] Over the years, nonsurgical endodontic retreatment has replaced apical surgery for treating endodontically failed cases. Ideally, during retreatment, the obturating material should be removed adequately so that irrigants and intracanal medicaments effectively gain access to the complexities of the canal.[8] The ideal filling material should be readily removable from the root canal when necessary.

Removal of obturating material can be achieved using several methods such as use of hand instruments, Ultrasonic vibrations, chemical methods, heated pluggers as well as Nickel-titanium rotary instruments.[9] Thermal, mechanical, chemical and a combination of the three methods are used to remove the gutta-percha and the sealer which can also cause apical extrusion while removing gutta-percha from the canal irrespective of the technique used. This may lead to irritation of periapical tissue, periapical inflammation, postinstrumentation flare-up, or even failure of apical healing.[10] Solvents were not used during retreatment as GP softened by the use of solvents can be forced into complex root canal anatomy which in turn accentuates the challenge of removal of obturating material.[11] In this study, rotary NiTi instruments have been used for the removal of root canal filling materials as various studies have reported their efficacy, cleaning ability, and safety. Studies have shown that rotary NiTi instruments required less time for gutta-percha removal than when compared to H-files and K-flex files. This might be because of the greater speed of mechanized instruments.[8] Consequently, potential new filling materials should be assessed for ease and efficiency of their removal from root canals.

Therefore, a study was conducted to evaluate using cone-beam computed tomography (CBCT), the effective removal of gutta-percha from canals obturated with three different obturating techniques using ProTaper Universal Retreatment (PTUR) Files.

  Materials and Methods Top

Specimen preparation

Sixty freshly extracted single-rooted mandibular premolars with completely formed apices were selected for the study. Ethical clearance (CDSH/IEC/2020/2021/010) was obtained from the Institutional Ethical Committee which was in accordance with the Declaration of Helsinki. Criteria for tooth selection included a single canal, no visible root caries, fractures, or cracks, no signs of internal or external resorption and a canal curvature of <15° (Schneider 1971) using AutoCAD software (Autodesk Inc., San Rafael, CA, USA. The teeth were disinfected in a solution of 0.1% thymol for 24 h as per CDC (Centre for Disease Control and Prevention) guidelines and stored in saline until the samples were used. The teeth were verified with digital radiography in a buccolingual and mesiodistal direction to ascertain the presence of a single straight canal. The teeth were then decoronated with a carborundum disk and the length of all teeth was standardized to 17 mm. Endodontic access was made and a glidepath was created using #10 k-file. Working length was ascertained by placing a size #10 K-file into the root canal until it was visible at the apical foramen followed by subtraction of 1 mm from that length.

Preparation of root canals

Chemo mechanical preparation was done using ProTaper Universal Rotary files (Dentsply Sirona Endodontics, Ballaigues, Switzerland) at a speed of 300 rpm and 1.5–4 N/cm torque as per manufacturer's instructions using a gentle in and out brushing motion with an electric and torque-controlled endodontic motor (X-Smart, Dentsply Maillefer, Switzerland). The canals were prepared up to size #F3. During instrumentation, the root canals were irrigated with 5 ml of 5% NaOCl and 3 ml of 17% EDTA followed by rinsing with 5 ml of normal saline using 30G side vented needle. Canals were then dried with sterile paper points.

Obturation of root canals

Teeth were randomly divided into three experimental groups with 20 samples each, based on the obturation technique used.

Group I-lateral compaction technique

Obturation was performed using a master gutta-percha cone of size #30/0.02 and accessory gutta-percha points with AH plus root canal sealer. The excess coronal gutta-percha was removed with a heated instrument.

Group II-GuttaFlow 2

The obturation was performed with GuttaFlow 2 as a root canal sealer along with size #30/0.06 gutta-percha master cone as a carrier. The excess coronal gutta-percha was removed with a heated instrument.

Group III-GuttaCore

The obturation was performed using a combination of AH plus root canal sealer and a GuttaCore™ Obturator #30/0.06 which was inserted into the canal after being thermoplasticized in a ThermaPrep oven. The carrier was twisted off, and the excess of gutta-percha was removed with a heated instrument.

Teeth were radiographed in buccolingual and mesiodistal directions to confirm the adequacy of the root canal fillings. The teeth were positioned in a custom-made specimen holder in which they were aligned perpendicularly to the beam. Assessment of quality of obturation was done by calculating the filled area in each tooth at the apical, middle, and coronal third of the root canal at intervals of 3, 6, and 12 mm, respectively, using a CS9300 CBCT scanner (Carestream Healthcare India [P] Ltd, India) in high-resolution dental mode (i.e., 90-micron resolution, 0.09–0.5 mm isotropic voxels, at a voltage of 60–90 kV and 2–15 mA) with “On Demand 3D software” (Cybermed Inc, Seoul, Korea). A single operator used the software tool to outline the area of obturating material in each third (cervical, middle, and apical). The teeth were then kept at 37°C with 100% humidity for 7 days to allow the sealer to set.

Retrieval of the obturating material from the root canals

After 7 days, all the groups were subjected to retreatment procedure using PTUR Files at a speed of 500–700 rpm and 3 N/cm torque according to manufacturer's recommended sequence with D1 file in coronal 1/3rd, D2 file in middle 1/3rd followed by D3 file till the apical 3rd of the canal in a brushing motion. During the removal of filling material, root canals were irrigated intermittently with 5.25% NaOCl. Final rinse was carried out with normal saline. The retreatment procedure was assessed as complete when there was no root filling material/sealer covering the instruments and the irrigating solution coming out of the canal appeared clear of debris.

A second CBCT scan was done and the area of residual obturating material in each third (cervical, middle, and apical) was measured by using “On-Demand 3D software.” The area of remaining filling material as well as canal wall was calculated in mm2 using CBCT analysis.

The area of root canal wall covered by remaining filling material (both in mesiodistal and buccolingual canal area) was calculated in terms of percentage by dividing the area of remaining filling material with the total surface area of the canal wall.

Statistical analysis

The data were statistically analyzed using SPSS version 16.0 software (IBM Corp. Chicago, IN, USA) with repeated measures analysis of variance, ANOVA. A P = 0.05 was considered to be statistically significant.

  Results Top

Regardless of the obturating material used in the study, some obturating material was left within the root canals after re-instrumentation with ProTaper Retreatment Files. However, when the percentage of residual obturating material was compared at each third (coronal, middle, and apical) among the three groups, there was no statistically significant difference (P = 0.154).

[Table 1] shows that the maximum percentage of residual obturating material was observed in Group III (GuttaCore) followed by Group I (Lateral Compaction), with the least amount of obturating material in Group II (GuttaFlow2).
Table 1: Mean values (mm2) of residual obturating material

Click here to view

[Table 2] shows that after retreatment, more residual obturating material was observed in the apical third (3 mm) followed by the middle third (6 mm) and least at the coronal thirds (12 mm), independent of the material used.
Table 2: Mean and standard deviation of various treatments

Click here to view

  Discussion Top

Root canal treatment, if improperly performed, leads to post-operative complications which may result in failure of endodontic therapy thus warranting retreatment.[12] With significant advancements in the field of endodontics, nonsurgical endodontic retreatment has become the treatment of choice for failed cases as it is usually less invasive when compared to surgical procedures.[8] Complete removal of preexisting filling material from root canals is a prerequisite for successful retreatment.[9]

Previous studies have used various methodologies, such as longitudinal splitting of roots,[13] clearing techniques rendering them transparent[14] and computed tomography,[15] to determine remaining filling material. Vertical sectioning of the roots may not be an accurate technique due to some inadvertent loss of obturating material. The clearing techniques with digitized images are time-consuming and different chemicals used may disturb the remaining filling material within the root canals during the evaluation process. Radiographic evaluation does not reveal all the residual material as it provides a two-dimensional image of a 3-D object.[16],[17]

In this study, therefore, CBCT has been used to allow 3D reconstruction and visualization of the morphological features of teeth as it is considered a non-invasive method. It is simple, efficient, and sensitive enough to identify small areas of residual filling materials on the root canal walls.[18] It also offers reproducible data and allows the assessment of endodontic retreatment by comparing the amount of filling material inside the root canals before and after retreatment procedures. This method was also followed in previous retreatment studies performed by Marfisi et al.[15] and Neelakantan et al.,[19] who demonstrated the efficiency of this method in evaluating the amount of remaining filling material. The only limitation of CBCT is its inability to distinguish between sealer and gutta-percha.

In the present study, PTUR files were used which have three progressive tapers to enable removal, not only of GP but also the superficial layer of dentine. Specific convex triangular flute design and rotary motion of the PTUR instruments tend to pull GP into the flutes of the file and direct it towards the orifice along with the plasticizing effect of frictional heat allowing effective removal of GP.[20] Furthermore, the D1 file of PTUR system serves to flare the canal walls and has an active cutting tip for effective initial penetration into the obturation material in the coronal third, which results in better removal of the gutta-percha material.[21] While the cross-sectional design of PTUR files favors the removal of large amounts of GP in spirals around the instruments, the same cross-sectional design and the high centering ability of these files prevent it from contacting all the walls of the root canals, thereby deterring complete removal of filling material from the root canals.

Regardless of the obturating technique used in the study, all groups (Lateral Compaction, GuttaFlow 2, GuttaCore) had some amount of remaining obturating material with the apical third having a mean percentage of remaining filling material greater than the middle and the coronal third which may be attributed to increased anatomical variability and difficulty in the instrumentation of the apical third. Discrepancies of tip diameter of master apical file F3 (0.30 mm) of ProTaper Universal System and D3 file (0.20 mm) of PTUR System may be responsible for incomplete cleaning action at the apical third necessitating further root canal filing with larger files.[22] Furthermore, ProTaper retreatment files allowed better cleanliness in the coronal third which is in accordance with the finding by Bramante et al.[23]

No solvent was used in this study because it is seen that the combined use of solvents along with the hand or rotary files complicates debridement as these solvents may soften the root filling material which may flow into and coat the inaccessible canal irregularities or penetrate into the peri-radicular tissues making its further removal difficult.[24]

GuttaFlow 2 showed superior results in comparison to the lateral compaction technique followed by GuttaCore regardless of the depth of the evaluation of the root canal. GuttaFlow 2 is a silicone-based material that adapts closely to the dentinal walls but does not exhibit chemical bonding. It may be stated that more homogenous filling in the GuttaFlow 2 group may have enabled the filling to be removed as a whole leaving minimal residual material in the canals after retreatment.[25]

The results obtained with the Lateral Compaction group though inferior to GuttaFlow 2, were found to be superior to the GuttaCore. When canals were obturated with the cold lateral compaction technique, a significantly higher area percentage of voids and more interfacial gaps were observed. These voids may represent spaces left behind by the spreader during lateral compaction of accessory gutta-percha cones. Furthermore, it has been shown that canals obturated with lateral compaction technique have less gutta-percha content within the filled canal when compared to core-carrier techniques which may be attributed to its better removal than GuttaCore.[26],[27]

In this study, the maximum percentage of residual obturating material was seen with GuttaCore which is melted in a thermaprep oven before delivering it into the root canals, leaves a thin layer that tenaciously adheres to the canal walls and is also forced into the isthmuses, lateral canals and irregularities, complicating the root canal cleaning procedure during retreatment.[28]

Moreover, both Lateral compaction and GuttaCore were used in combination with a resin-based sealer, i.e., AH plus which has been reported to expand slightly on the setting, and has excellent penetrating ability into the dentinal tubule. In addition, its creep capacity and long setting time are responsible for its increased mechanical interlocking to root dentine, thereby, improving adhesion to the tooth structure making it difficult to remove.[29]

No study has yet been conducted comparing the properties of GuttaFlow 2 and GuttaCore, thus emphasizing the importance of the present study. GuttaCore being a relatively newer material has been shown to be a material of choice for complete 3D obturation of the root canal system however, retreatment procedure has posed difficulties in removing the obturating material from the root canal space. Hence, effective retreatment remains to be a constant challenge in the field of endodontics.

  Conclusion Top

Within the limitations of this study, it may be concluded that none of the obturating materials can be retrieved completely from the root canals using PTUR Files. Among the materials tested, the maximum amount of residual obturating material was observed with GuttaCore followed by lateral compaction with least in GuttaFlow 2. Significantly, the maximum amount of residual obturating material was observed in the apical third (3 mm) followed by the middle third (6 mm) and least at the coronal third (12 mm).

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Conflicts of interest

There are no conflicts of interest.

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  [Table 1], [Table 2]


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