Tanta Dental Journal

ORIGINAL ARTICLE
Year
: 2017  |  Volume : 14  |  Issue : 2  |  Page : 76--82

Evaluation of root canals filled with bioceramic sealer after retreatment with two different techniques


Dalia A Sherif, Ali M Farag, Abeer M Darrag, Neveen A Shaheen 
 Department of Endodontic, Faculty of Dentistry, Tanta University, Tanta, Egypt

Correspondence Address:
Dalia A Sherif
Department of Endodontic, Faculty of Dentistry, Tanta University, Tanta
Egypt

Abstract

Purpose: To evaluate the remaining filling material (gutta-percha/EndoSequence bioceramic sealer) on root canal walls after retreatment using ProTaper universal retreatment (PTUR) system with and without chloroform solvent. Materials and methods: Thirty extracted human premolars with type I root canal system were used. After crown removal and working length determination, all root canals were prepared using nickel–titanium rotary ProTaper system and obturated using gutta-percha as a core filling material with EndoSequence bioceramic sealer. All roots were randomly divided into two equal main groups (n = 15) according to retreatment technique. Group I: filling materials was removed using PTUR system and chloroform as a solvent; while group II: filling materials was removed using PTUR system without solvent. Both groups were cleaved longitudinally and examined under scanning electron microscope to evaluate root canal filling remnants. Results: PTUR system with the aid of chloroform recorded highest values of score percentage of remaining filling material at all tested root canal levels. The values of score percentage of remaining filling materials were significantly lower at coronal level compared to other tested levels. Conclusion: Using chloroform during removal of root canal filling material using rotary instruments was associated with larger amount of residual root canal filling material compared to using rotary instruments only.



How to cite this article:
Sherif DA, Farag AM, Darrag AM, Shaheen NA. Evaluation of root canals filled with bioceramic sealer after retreatment with two different techniques.Tanta Dent J 2017;14:76-82


How to cite this URL:
Sherif DA, Farag AM, Darrag AM, Shaheen NA. Evaluation of root canals filled with bioceramic sealer after retreatment with two different techniques. Tanta Dent J [serial online] 2017 [cited 2017 Oct 22 ];14:76-82
Available from: http://www.tmj.eg.net/text.asp?2017/14/2/76/207302


Full Text



 Introduction



Nonsurgical root canal retreatment is indicated in cases of post-treatment disease because intraradicular infection is the major cause of failure in primary endodontic treatment and the effective removal of the filling material is an essential part of retreatment procedures [1]. Remaining root canal filling materials makes a challenge for endodontists because it can impair removal of microorganisms from the root canal and the action of chemical disinfectants [2].

The use of root canal sealer in conjunction with gutta-percha core material remains the most widely accepted obturation technique in endodontics. However, gutta-percha lacks the property of bonding to radicular dentin, therefore the sealer should be capable of producing a bond between core material and dentin wall [3]. Recently, different filling materials and sealers have been developed on the basis of dentin adhesion technology in an attempt to seal the root canal more effectively and maintaining the integrity of sealer–dentin interface [4].

EndoSequence bioceramic-based sealer is a newly introduced sealer which is based on calcium phosphates silicate compounds. It is supplied as a premixed injectable hydrophilic sealer utilizing bioceramic technology. This highly biocompatible sealer does not shrink upon setting and ultimately creates a strong chemical bonding with dentin [5].

Once root canal retreatment is indicated, core filling material and sealers should be removed. Several techniques have been proposed to remove filling materials from root canal system, including the use of endodontic hand files, rotary systems, ultrasonic, laser, heat and the use of adjunctive solvents [6].

Furthermore, new rotary nickel–titanium systems that were specially designed for retreatment procedures have been introduced to the field of endodontics. ProTaper universal retreatment (PTUR) system is one of these systems that include conventional shaping and finishing files in addition to retreatment instruments [1].

Chloroform and other solvents supplemented by nickel–titanium rotary instruments were used to facilitate removal of root canal filling material rapidly. Chloroform was used as a solvent due to its known capacity for dissolving gutta-percha and limited toxicity when used clinically in a controlled manner [7].

However, it is important to select effective and efficient techniques during the retreatment phase of root canals, using of rotary instrumentation in retreatment of root canal system has been shown to be more effective in cleanliness of root canal. Furthermore, the applications of solvents along with endodontic files have been reported controversy. Therefore, two retreatment protocols using rotary endodontic files with or without solvent were used in this study to compare the cleanliness of root canal filled with bioceramic-based sealers.

 Materials and Methods



Specimens selection and preparation

Thirty recently extracted, fully developed single rooted human mandibular premolars with approximately straight root canals, similar morphology and dimensions were collected. Approval for this research was obtained from Faculty of Dentistry, Tanta University, Research Ethics Committee. The purpose of the present study was explained to the patients and informed consents were obtained to use their teeth on the research according to the guidelines on human research published by Research Ethics Committee at Faculty of Dentistry, Tanta University.

Selected teeth were cleaned of any soft tissues or calculus deposits on their root surfaces then thoroughly washed under running water and stored in sterile normal saline solution until use. The coronal portions of all teeth were removed with water-cooled, slow speed double-faced diamond disc (Dica, Dendia, USA) leaving the remaining root segment of nearly 16 ± 1 mm long to standardize the length of all specimens [8]. Hand stainless steel K-file (Dentsply Maillefer, Ballaigues, Switzerland) (#15/0.02) was inserted to establish the working length [9].

All root canals were prepared using nickel–titanium rotary ProTaper system (Dentsply Maillefer) consisting of three shaping (SX, S1, S2) and three finishing files (F1, F2, F3) with a continuous movement up to an apical size corresponding to F3 (#30/0.09) in a crown-down manner using 20:1 reduction rotary handpiece powered by torque limited electric motor (Endo-Mate TC; NSK, Tokyo, Japan) at a constant speed of 250 rpm according to the manufacturer's instructions.

Throughout instrumentation procedure, root canals were irrigated between the use of each succeeding file with freshly prepared 5 ml of 2.5% sodium hypochlorite solution (Clorox Co., 10th of Ramadan, Egypt) using a plastic disposable syringe with a 30 G closed-end needle (NaviTip; Ultradent, USA). Each specimen was finally irrigated with 1 ml of 17% EDTA (Pulpdent Corp., Watertown, Massachusetts, USA) for 1 min to remove the smear layer followed by a final rinse of 5 ml of sterile saline solution and dried with sterile paper points (DiaDent Group International, Burnaby, B.C. Canada) to be ready for obturation [10].

All root canals were obturated using gutta-percha (Meta Biomed, Horsham, Pennsylvania, USA) core filling material with EndoSequence bioceramic sealer (Brasseler USA, Savannah, Georgia, USA) using cold lateral compaction technique according to manufacturer's instructions. All samples were kept moist in gauze moistened with sterile normal saline solution at 37°C for 1 week to allow complete sealer setting [11]. All roots were randomly divided into two main groups according to retreatment techniques.

Group I: ProTaper universal retreatment system with solvent (n = 15)

Removal of the primary root canal filling material was performed using PTUR instruments with the aid of chloroform (ADWIC, El-Nasr Pharmaceutical Chemicals Co., Egypt) solvent. Retreatment files were operated with a low speed in a sequential crown-down manner using a brushing motion with lateral pressure [12]. D1 file (#30/0.09) was used for initial penetration and removal of filling in the coronal third of the root canal, then 0.2 ml chloroform solvent was placed in the reservoir space prepared by D1 and left for 2 min to soften the gutta-percha, then it was removed by D2 and D3. D2 file (#25/0.08) was used up to the middle third and finally D3 file (#20/0.07) was used up to full working length. The solvent was refreshed between D2 and D3 [9],[10],[13].

Complete removal of the filling material was obtained when full working length was achieved, no remnant filling material was observed on the file and then confirmed radiographically [14]. Finally, apical preparation was performed with ProTaper instruments F3 (#30/0.09) followed by F4 (#40/0.06) up to full working length [15], using the same irrigating regimen used during root canal instrumentation.

Group II: ProTaper universal retreatment system without solvent (n = 15)

Removal of the primary root canal filling material was performed as in group I using retreatment rotary files but without using chloroform solvent.

Evaluation of root canal filling remnants using scanning electron microscopy

Before longitudinal root sectioning, a small cotton pellet was placed inside the coronal opening of each sample to prevent the entrance of dentinal shavings or debris into the root canal. Two longitudinal grooves parallel to the long axis of the root were made in the buccal and lingual aspects of each sample of group I and group II without penetrating the canal space using a diamond disc. All superficial debris that resulted from the grinding process was removed by rinsing the root surface under running water and using a soft brush [16], then roots were cleaved into two longitudinal halves using a plastic instrument to expose root interior [13],[17]. Roots showing evidence that the grooves had penetrated into the root canal or exhibiting an irregular cleavage were discarded and replaced by new samples [18]. The half containing the most visible part of interior canal was conserved and coded for evaluation of remaining root canal filling material.

Before scanning electron microscopy (SEM) (JSM-5300 Scanning Microscope; JEOL, Peabody, Massachusetts, USA) analysis, the samples were mounted on metallic stubs, dehydrated at 37°C, put in sequential ascending concentrations of alcohol (30, 50, 70, 90%) and finally in 100% for 5 min then dried and gold-sputtered to render the surface electrically conductive [19],[20].

A general survey of the root canal walls from the apex to the coronal part was performed under SEM, the coronal, middle and apical thirds of all root halves were examined and SEM digital images of each third were taken at a magnification of ×1000. The amount of residual filling material at the three predetermined portions of each root canal was evaluated by the following scoring system according to Somma et al.[21] and no attempt was made to distinguish between filling material or sealer remnants.

Score 0: None to slight presence (0–25%) of dentinal surface covered with residual debrisScore 1: Mild/moderate presence (25–50%) of dentinal surface covered with residual debrisScore 2: Moderate/severe presence (50–75%) of dentinal surface covered with residual debrisScore 3: Severe or complete presence (75–100%) of dentinal surface covered with residual debris.

Statistical analysis

Statistical analysis was performed using SPSS (version 16; SPSS Inc., Chicago, Illinois, USA). Kruskal–Wallis analysis was used to reveal statistically significant differences among tested groups and among tested root canal levels. Whenever statistically significant difference was recorded among the levels, Mann–Whitney pair-wise comparison test was then performed to compare between each two tested levels. All tests analysis was performed at a significance level of P value less than or equal to 0.05.

 Results



Both retreatment techniques used in this study left some remaining filling materials inside the root canal. The overall descriptive analysis of the different retreatment techniques, the score percentages of group I and group II were recorded at the three root canal levels coronal, middle and apical as shown in [Table 1].{Table 1}

Comparison between group I and group II was performed at all tested root canal levels. Statistical analysis demonstrated no statistically significant differences between both methods of filling removal at coronal, middle and apical root canal levels recording P values of 0.289, 0.0598 and 0.2709, respectively.

When considering group I, a statistically significant difference was found among tested scanning levels (P = 0.0043). Mann–Whitney test revealed statistically significant differences between coronal versus apical and coronal versus middle root canal levels. While there was no statistically significant difference between middle versus apical levels (P = 0.156).

Regarding group II using PTUR without solvent, a statistical significance difference was recorded among the tested levels (P = 0.0039). Mann–Whitney test recorded statistical significance differences between middle versus apical levels and coronal versus apical levels, while no significance difference was found between coronal and middle levels.

 Discussion



The main goals of endodontic treatment are to clean and disinfect the root canal system and to seal the system in three dimensions to prevent recontamination. Primary endodontic treatment has been reported to be successful in achieving these goals; however failure may occur after treatment [22].

In several cases of endodontic failure, a choice to perform a nonsurgical retreatment is needed to retain the normal function and create an environment conducive to periradicular healing in the retreated tooth [6]. Effective removal of the filling material is an essential part of retreatment procedure in order to uncover remaining necrotic tissue or bacteria that may be responsible for the persistent disease and to achieve better cleaning and disinfection of the interior root canal system. [1],[23].

Removal of the filling material during root canal retreatment is a challenge for clinicians, therefore this study was performed to evaluate the effectiveness of two retreatment protocols using PTUR system with or without solvent on the cleanliness of root canal filled with bioceramic-based sealers.

Several attempts have been made to ensure standardization of the experimental groups in this study. Extracted human mandibular premolars with approximately similar dimension and single root canal system were used. Furthermore, the lengths of samples were standardized to16 ± 1 mm and root canal preparation was performed up to master apical file corresponding to F3 (#30/0.09) in all groups.

Many studies have reported the efficacy, cleaning ability, and safety during endodontic filling removal using rotary nickel–titanium retreatment instruments [24], so PTUR system used in this study. One of various techniques for facilitating removal of primary endodontic obturation is chemical dissolution of gutta-percha using solvents [23]. Chloroform was used in this study as a solvent due to its known capability for dissolving gutta-percha and limited toxicity when used clinically. Moreover, chloroform has the ability to significantly reduce intracanal levels of Enterococcus faecalis, which is the main causative organism in endodontic secondary infection [25].

Various methods have been applied to evaluate the residual filling materials on dentin surfaces following different removal techniques, but each of these methods has their inherent drawbacks. However, only SEM permits an extremely comprehensive observation of root canal filling remnants or debris [17], with a more detailed view using different degrees of magnifications [6]. So it was used in this study.

The findings of the present study revealed that none of the used retreatment techniques was capable of removing the filling material completely without any residues, which was confirmed in previous studies on the efficacy of various retreatment techniques to remove various root canal filling materials [21],[26],[27],[28].

However there is not much literature available for evaluating the role of solvents on canal cleanliness after retreatment using SEM. The results of the present study revealed that root canal filling materials removed using PTUR system without solvent recorded the lowest scores of residual material in all tested root levels [Figure 1]. This may be attributed to the ability of rotary systems to produce heat via a specific torque force with frictional movement, which facilitates dissolution and removal of heated gutta-percha [17]. Additionally, PTUR system is able to remove large amounts of gutta-percha through spirals running around the instruments, which produce both cutting and softening actions. Moreover, the presence of negative cutting angle and absence of radial land exert a cutting not a planning action on gutta-percha, this cutting action may facilitate removal of gutta-percha [29]. Furthermore, root canal refining using F3 file (#30/0.09) followed by F4 file (#40/0.06) was performed after using D3 retreatment file which has size 20 and taper 0.07 to ensure complete removal of the remaining filling material. This apical enlargement by two sizes beyond the initial preparation size significantly reduced the amount of residual filling material [30].{Figure 1}

Meyappan et al.[6] supported the results of this study, they reported a better performance of PTUR system and explained that this may be due to its flute design, progressive taper and length of its blades which pulls gutta-percha out and directs it to the orifice. This confirmed with Khalilak et al.[13] as they found that PTUR without solvent showed less visibly filling remnants.

In contrast to this finding, high percentage of reaming filling material after retreatment by PTUR was observed by Yuruker et al.[1] this controversy might be attributed to the fact that they did not enlarge the apical preparation of the root canal up to a size F4 file, which has a tip size of 40 as in this study, and they finished with D3 file which has a tip size of 20, which cannot engage the canal walls.

The current study revealed that using PTUR system with solvent recorded the highest remaining filling materials for all tested root sections [Figure 2]. This might be related to finding more remnants in dentinal tubules and irregularities of the root canal wall with increasing dissolution of the root filling material by using solvent. This might be explained by the fact that chloroform softens obturation materials, breaking it into small fragments and makes it more flowable [31], this softened obturation materials may easily be compacted into dentinal irregularities and tubules from where they can no longer be removed this make the removal of filling material even more difficult and time consuming [23].{Figure 2}

This finding is in agreement with the results obtained by several authors [3],[13],[19],[23],[32],[33] as they concluded that solvents leave a fine layer or film of softened gutta-percha leaving more residual filling materials on root canal walls and inside dentinal tubules.

Controversially, the results obtained by Hassanloo et al.[34] demonstrated that the use of solvent reduces the time of retreatment and the amount of residue. This controversy could be due to difference in methodology as they used resin blocks instead of natural teeth and using of different filling material as they used resin based obturation system (Resilon/Epiphany). Moreover, Rached-Júnior et al.[35] found that the lowest percentage of remaining filling material was observed when solvent was used. This difference may be attributed to using different retreatment techniques and a different type of solvent (PTUR, PTUR/xylol, ultrasound and ultrasound/xylol) in their study.

Additionally, in contrast to the present finding, Ramzi et al.[36] revealed that the use of chloroform combined with mechanical instrumentation was more efficient than mechanical instrumentation alone. This controversy could be attributed to the use of different filling material as they used resin based obturation system (Resilon/Epiphany) and different removal system (Mtwo R/Mtwo).

When the root canal sections were compared, the present results revealed that a greater amount of filling material remained in the apical third [Figure 3] than in the middle and coronal thirds, irrespective of the retreatment technique used. This may be attributed to the variable progressive taper of PTUR system resulting in cutting the superficial layer of coronal dentine [13], and greater anatomical variations in the apical third [17], which is a critical zone, demanding a considerable enlargement for the cleaning and shaping procedure [25], and difficulty of instrumentation in this area [37]. This finding was in agreement with several studies [6],[17],[21],[36],[37].{Figure 3}

In contrast, Hassanloo et al.[34] proved that significant reduction in the amount of residue in the apical 3 mm of the canal space. This disagreement could be attributed to the use of resin blocks instead of natural human teeth and different retreatment technique (K3) with final apical enlargement performed using much bigger K-type hand file up to size 55.

 Conclusion



Within the limitations of the present in-vitro study, the results suggested that:

None of the used retreatment techniques were capable of completely removes the filling material within root canalsUsing PTUR with the aid of chloroform during removal of root canal filling material was associated with larger amount of residual root canal filling material compared to using PTUR alone.

Greater amount of filling material remained in the apical than in the middle and cervical thirds, irrespective of the retreatment technique used.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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