Deformed and fractured instruments in the removal of root canal filling material using different techniques, in vitro

Bushra Faiz Alhawsawi; Mohammed Alomari; Saud Orfali

doi:10.4103/jioh.jioh_114_17

ORIGINAL RESEARCH

Year : 2017 | Volume : 9 | Issue : 3 | Page : 122-125

Deformed and fractured instruments in the removal of root canal filling material using different techniques, in vitro

Bushra Faiz Alhawsawi¹, Mohammed Alomari², Saud Orfali³
¹ Endodontic Lecturer, Riyadh Colleges of Dentistry and Pharmacy, Riyadh, Saudi Arabia
² Professor, Chairman of Restorative Department, Riyadh Colleges of Dentistry and Pharmacy, Riyadh, Saudi Arabia
³ Endodontic Consultant, General Director of Dental Services, Ministry of Health, Dental Department, Riyadh, Saudi Arabia

Date of Web Publication

27-Jun-2017

Correspondence Address:
Bushra Faiz Alhawsawi
Endodontic Lecturer, Riyadh Colleges of Dentistry and Pharmacy, Riyadh
Saudi Arabia

Source of Support: None, Conflict of Interest: None

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DOI: 10.4103/jioh.jioh_114_17

Abstract

Aims and Objectives: The aims and objectives of the study were to evaluate deformed and fractured instruments in removing gutta-percha (GP) from the root canal using various techniques. Materials and Methods: Root canals of sixty extracted human permanent premolar teeth were prepared and filled with laterally condensed GP and AH26 sealer, and the specimens were incubated for 2 weeks. Then, roots were divided randomly into five groups (12 roots of each group). The root fillings were removed with Gates-Glidden, D-Race instruments, ProTaper Universal Retreatment instruments (alone or with Hedstrom files). Fractured or deformed instruments were noted. The data were analyzed with one-way analysis of variance and Tukey's post hoc test to demonstrate difference between groups. Results: Overall, 35 instruments were fractured or deformed in the study, of them 29 Hedstrom files were deformed. Conclusion: Within the limitations of this study, it can be concluded that all GP removal techniques did not clean the canals completely, but deformity and fracture instruments were more. Maximum Hedstrom files were deformed.

Keywords: Fractured instruments, gutta-percha removal, Hedstrom files

How to cite this article:
Alhawsawi BF, Alomari M, Orfali S. Deformed and fractured instruments in the removal of root canal filling material using different techniques, in vitro. J Int Oral Health 2017;9:122-5

How to cite this URL:
Alhawsawi BF, Alomari M, Orfali S. Deformed and fractured instruments in the removal of root canal filling material using different techniques, in vitro. J Int Oral Health [serial online] 2017 [cited 2023 Dec 5];9:122-5. Available from: https://www.jioh.org/text.asp?2017/9/3/122/209051

Introduction

Long-term success of endodontic therapy relies on thorough debridement of the root canal system followed by three-dimensional obturation. Inability to achieve these goals results in persistence of intracanal pathogens, eventually leading to treatment failure.^[1] The main goal of nonsurgical root canal retreatment is to enhance healing by reestablishing healthy periapical tissues to reobturate the canals after complete removal of the old filling material.^[2],[3]

Therefore, old root canal filling material should be removed from canal system to regain access to microorganisms and pulp tissue remnants that might be responsible for periapical inflammation and thus posttreatment disease. Safe and efficient removal of filling material from canal systems is essential for optimal root canal retreatment. Ideally, all filling material and sealer should be removed from the canal space.^[4]

The commonly used root canal filling material is gutta-percha (GP). There are different techniques and methods to remove the GP from root canal system. One of the most common removal techniques is using Hedstrom files alone or in combination with Gates-Glidden drills with or without solvents.^[5] The use of combination between hand and rotary files or solvent was found to be effective in removing the filling material from canals.^[6]

Furthermore, other techniques proposed to remove the GP and root canal materials included solvent, heated instruments, ultrasonic instruments, and lasers. Recently, various nickel titanium rotary instruments have been developed to facilitate removal of root canal materials.^[5]

Endodontic failures proposed can include apical percolation, root perforation, unfilled canals, coexisting periodontal lesion, incomplete obturation, under- and over-extension of filling materials, and coronal leakage.^[7]

Nevertheless, some cases retreated on technical indication revealed that the potential for pathologic processes to develop indication was low (6%). Thus, a relationship showed the analysis material often accompanied by over-instrumentation and overfilling.^[8] Usually, the bacteria found outside the apical foramen and did not respond to nonsurgical strategies and must be treated by means of periradicular surgery.^[9]

Therefore, the aim of this study was to evaluate deformed and fractured instruments to remove root canal filling material (GP) using various methods and techniques including rotary Re-endo systems ProTaper Universal retreatment and D-Race used.

Materials and Methods

Freshly extracted permanent human premolar teeth were collected from private dental clinics in Riyadh district. Teeth were stored in screw-top bottles containing 2% thymol solution at room temperature.

A total of sixty extracted mandibular and maxillary premolar teeth were selected for this study, and preoperative digital radiograph in mesiodistal views was made for every tooth to assess its root canal morphology.

Teeth selection was made on the basis of the following inclusion criteria:

Single root
With curvature <20°
No gross coronal caries
No root caries, resorption, or fracture
Root with single patent canal
Absence of root canal fillings.

Preoperative digital radiography using X-ray machine was made for all collected teeth and the radiographs were captured in mesiodistal views [Figure 1].

Figure 1: Preoperative digital radiographs in mesiodistal views

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After selection of the teeth, soft debris on the root surface was removed. Access opening was achieved by sectioning at the cementoenamel junction using handpiece with carborundum discs. The working length of each root was established 1 mm short of this length and it was standardized (15 mm) for all root samples.

Root encasement was prepared for each sample root to facilitate handling of roots during root canal preparation and obturation and during GP removal. Clear plastic spectrophotometer cuvettes (1 cm square) were used to retain the acryl around the roots (the apical 3 mm of root apex should be protruded above the cuvette). The cuvettes were cut into 10 mm length, trimmed, and polished before use. Red wax sheet (2 mm thickness) was used to hold the coronal 2 mm of each root by making a hole in it (the root surface was allowed to protrude to the same level of the wax surface). Another wax sheet was used beneath the first sheet to hold firmly the file handle protruded from the coronal part of the root.

The open-ended cuvettes were then placed over each root, in a way, making sure that the long axis of each canal was parallel to the axis of the cuvettes. A melted red wax was poured around the cuvettes to hold it in place and to prevent acrylic resin leakage. Then, a clear acrylic resin was introduced around the root in layers until the cuvettes were totally filled with resin, taking care to exclude air bubbles and also assuring the apical 3 mm of the root was not covered with acrylic resin. After this, all samples were retained back into the screw-top bottles containing thymol ready to be used in the study.

A holder made from silicone impression material (Elite H-D Zhermack, Rovigo, Italy) was used to facilitate the handling of root/acrylic blocks during root canal preparation [Figure 2].

Figure 2: (a) Cuvettes surround roots before purring acrylic reason, (b) root/acrylic blocks, (c) silicon model holder

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Root canal preparation

Canals of all groups were prepared using step-back technique with circumferential filing motion (Harty, 1982). The apical stop was prepared first with a series of K-files (sizes 15–35) used in circumferential filing motion around the periphery of the canal wall at the full working length (15 mm).

Cleaning and shaping of root canal was considered completed when the canal walls felt smooth and the master apical file (size 40) could reach the working length without any difficulty; further, the canal space was checked by a finger spreader (Dentsply, Maillefer, Ballaigues, Switzerland) inserted loosely to within 1–3 mm of the working length. Then, all canals were dried using paper point's size 40 (Dentsply, Maillefer, Ballaigues, Switzerland) and obturated with GP and AH26 sealer (Dentsply, DeTrey, Konstanz, Germany) using lateral condensation technique.

A size 40 GP cone (Dentsply, Maillefer, Ballaigues, Switzerland) as master apical cone was used to fill the canal. The canal walls were coated first with sealer using the master apical cone, and then the cone was placed full canal at the working length. A finger spreader (size 25) was used to condense laterally the GP and creating spaces for the fine accessory GP points (Dentsply, Maillefer, Ballaigues, Switzerland) until the spreader can no longer be introduced into the canal more than 4 mm. The excess GP at the canal opening was removed using heated plugger (Dentsply, Maillefer, Ballaigues, Switzerland) and its remnant was vertically condensed.

Finally, all samples were randomly divided into five groups (12 roots each) and each group was numbered and kept in a plastic jar and in the incubator at 37°C in 100% humidity for 2 weeks prior the GP removal.

Gutta-percha/sealer removal

After a period of 2 weeks, the temporary filling of each group was removed; each root sample (acrylic/root block) was hold by the silicon holder over the cuvettes, and GP was removed (retreated) according to the following technique.

Group one (Gates-Glidden and Hedstrom Files)
Group two (ProTaper Universal Retreatment Rotary Files Alone)
Group three (ProTaper Universal Retreatment Rotary Files with Hedstrom Files)
Group four (D-Race Retreatment Rotary Files Alone)
Group five (D-Race Retreatment Rotary Files with Hedstrom Files).

Method of evaluation

Data collected sheet was designed to record sample number, group number, fractured instrument, and deformed instrument.

Furthermore, apical cleanliness was assessed on radiographs by two examiners.

Descriptive statistics including means and standard deviation were calculated for each group, and the result from all tested groups was submitted to one-way analysis of variance and Tukey's post hoc test to demonstrate different between groups' means.

Results

In the whole study, it was found that four instruments were fractured and 31 instruments were deformed as seen in [Table 1]. Most deformed instruments were Gates-Glidden and Hedstrom files, eight Hedstrom files size 20 and size 25, were deformed. Only one Hedstrom file size 40 was fractured.

Table 1: Fractured and deformed instruments

Click here to view

When GP removed with proTaper alone, it was found that two D3 files were deformed and one ProTaper size (D3) was fractured. When using six ProTaper with Hedstrom files (three each of size 35 and size 40), Hedstrom files were deformed but no ProTaper files were fractured or deformed.

When the using D-Race with Hedstrom file, only one Hedstrom file size 40 and one D-Race file size (DR1) were fractured.

Interestingly, D-Race alone technique had no fractured or deformed happened.

Discussion

Therefore, in this study, a step-back preparation technique was used for all samples. In addition, the same type of GP and sealer (AH26) was used in a cold lateral condensation technique. A cold lateral condensation is one of the most widely used techniques for root canal obturation and it is commonly used in many retreatment studies.^{[10],[11],[12]}

Samples were incubated for 2 weeks to allow complete set of the sealer to exclude the effect of sitting time on study result. However, most of the retreatment studies had an incubation period ranged from 3 days to 8 months using different types of sealers.^{[11],[13],[14],[15]} Regarding AH26 sealer, Saad et al.^[6] used AH26 with an incubation period of 1 week, Hülsmann and Stotz ^[10] for 2 months, and de Carvalho Maciel and Zaccaro Scelza ^[16] for 3 months. In this study, an incubation period of 2 weeks was used due to the time limit of the research project.

Different techniques have been used for the evaluation of endodontic filling material remnants including traditional radiographs; digital radiograph or traditional radiograph was digitized and analyzed using software or using common way of evaluation of endodontic filling remnants making teeth transparent.^[14],[15] More recently, computed tomography (CT) scan and micro-CT were used to assess endodontic filling material removal.^[17],[18]

In this study, digital radiographs were used for all root canal samples in mesiodistal views, and the assessments were then done using image analysis “Onex program,” by calculating the mean length of filling material remnants in coronal, middle, and apical each portion and also by ranking of apical cleanliness.^[19]

Instrument fracture and deformation are the important factors of GP removal success during the retreatment procedure.^[10],[11] In this study, we found a few instruments fractured which is opposite to the findings of Rödig et al.,^[20] who reported more incidents of D-Race files fracture. In general, we found that H-files are liable to fracture or deform more than rotary files.

Conclusion

Under the limitation of this study, it concluded that the combination of D-Race with Hedstrom files was cleaned the apical canal completely, and, in general, it was the best efficient cleaning technique. Comparing Hedstrom file, ProTaper file, D-Race file, and Hedstrom file is more likely to fracture and deform care need to be taken when using Hedstrom files in the removal of GP, it is liable to fracture and deformity.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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