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 Table of Contents  
ORIGINAL ARTICLE
Year : 2018  |  Volume : 5  |  Issue : 4  |  Page : 132-138

Micro-computed tomographic comparative evaluation of efficacy of different rotary instrument systems for removal of gutta-percha/bioceramic sealer from oval root canals (in vitro study)


1 Department of Endodontic, Faculty of Oral and Dental Medicine, Cairo University, Cairo, Egypt
2 Department of Oral Diagnostic Science, Faculty of Dentistry, King Abdulaziz University, Jeddah, Saudi Arabia

Date of Web Publication25-Jan-2019

Correspondence Address:
Samia Mohamed Elsherief
Department of Endodontics, Faculty of Oral and Dental Medicine, Cairo University, Cairo; Faculty of Dentistry, Um-Alqura University, Mecca
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jdrr.jdrr_52_18

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  Abstract 


Aim: This study used micro-computed tomography (CT) to compare the efficacy of three techniques for removing the root canal filling in single oval-shaped root canals after using laterally compacted gutta-percha/bioceramic sealer (BCS). Materials and Methods: Root canals in 30 single-rooted teeth will be instrumented with the ProTaper NEXT (Dentsply Maillefer, Ballaigues, Switzerland) and obturated using lateral condensation technique with gutta-percha and BCS. The teeth were divided randomly into three groups (n = 10). Removal of the root fillings was performed using one of the following techniques: group 1: ProTaper Universal Retreatment System with continuous rotational motion (RM); Group 2: Reciproc files with reciprocating adaptive motion; and Group 3: retreatment was done using Gates Glidden (GG) drills and H files. The teeth were scanned with CT scans. The percentage of remaining filling material was recorded. The data were analyzed statistically using the one-way ANOVA test and Tukey's post hoc test. Two-way ANOVA was used to study the effect of the interaction of file type and root segment, at a 95% confidence level (P < 0.05). Results: The highest mean value was recorded in the apical that was extremely significantly higher than the coronal and middle segments in all groups. ProTaper and GG groups showed a statistically higher mean value compared to Reciproc (P = 0.023). However, there was no significant difference between ProTaper and GG files. Conclusions: Reciproc file removes more filling materials than ProTaper and GG with H files. Within the limitation of this study, none of the techniques completely removes the filling materials from the large oval root canal.

Keywords: Bioceramic sealer, Gates Glidden, H files, oval root canals, ProTaper NEXT, ProTaper retreatment system, Reciproc file, three-dimensional micro-computed tomography


How to cite this article:
Elsherief SM, Abdel-Wahed N, Abdel-Latif ZA. Micro-computed tomographic comparative evaluation of efficacy of different rotary instrument systems for removal of gutta-percha/bioceramic sealer from oval root canals (in vitro study). J Dent Res Rev 2018;5:132-8

How to cite this URL:
Elsherief SM, Abdel-Wahed N, Abdel-Latif ZA. Micro-computed tomographic comparative evaluation of efficacy of different rotary instrument systems for removal of gutta-percha/bioceramic sealer from oval root canals (in vitro study). J Dent Res Rev [serial online] 2018 [cited 2019 Aug 19];5:132-8. Available from: http://www.jdrr.org/text.asp?2018/5/4/132/250786




  Introduction Top


The primary aim of root canal treatment is complete microorganism eradication, through proper root canal debridement and disinfection and fluid-tight seal of the canals effectively. Orthograde root canal retreatment is indicated when there is root canal treatment failure. There are multiple reasons for endodontic failure that requires complete removal of previous root canal filling materials. Among these reasons are coronal and/or apical leakage, improper biomechanical preparation of the root canal system, and inadequate root canal filling.[1],[2] For successful retreatment, the removal of filling material from root canal systems is mandatory to remove remaining necrotic tissue and/or microorganisms that may be the main cause of the persistent disease.[3] Adequate removal of root canal filling enables three-dimensional (3D) chemomechanical, disinfection of the root canal system, proper re-filling of the root canal system.[4],[5] The bioceramic sealer (BCS, Brasseler USA, Savannah, GA, USA) exhibited a lower cytotoxic effect compared with AH Plus.[6] Bioceramic (BC) materials formed of calcium silicate phosphate that become hard on setting, so the capability to retreat canals obturated using BCS is a current issue to be discussed.[7] For retreatment, many techniques with or without solvents have been used, including stainless steel hand files, heat, laser, and ultrasonic and automated techniques using different rotary instruments.[1],[8],[9],[10],[11] Many researches have confirmed the ProTaper Universal Retreatment kit (Dentsply Maillefer, Ballaigues, Switzerland) efficacy in root canal filling removal. The ProTaper Universal Retreatment System (Dentsply Maillefer, Ballaigues, Switzerland) consists of three rotary files to be used in each third of the root canal: D1 – 30/.09, 16 mm; D2 – 25/.08, 18 mm; and D3 – 20/.07, 22 mm. These files have convex triangular cross-sections.[12],[13],[14] The introduction of the concept of root canal preparation using a single NiTi file system with reciprocating motion (Reciproc; VDW, Munich, Germany) was confirmed to have more effective mechanical properties compared to a full rotary NiTi system.[15] Some studies investigated the rotary system with reciprocating motion in root canal retreatment with acceptable results.[16],[17],[18],[19] Oval-shaped canals represent a great challenge during root canal cleaning, shaping procedure. In retreatment procedures, complete removal of filling materials from oval root canal is difficult.[20] Many studies have reported that hand and rotary instrumentation of oval-shaped canals leaves untouched buccal and lingual recesses that might contain microorganisms and necrotic debris.[21],[22],[23],[24],[25] Micro-computed tomography (micro-CT) is a noninvasive 3D imaging technique used widely in density; in the endodontic, micro-CT has been used in retreatment studies as micro-CT analysis is a reproducible, nondestructive method that permits a detailed 3D morphologic imaging of the object, quantitatively and qualitatively.[26],[27],[28]

The purpose of the study was micro-CT analysis to compare the effectiveness of ProTaper Universal Retreatment files, Reciproc, and Gates Glidden (GG) with H files, for retreatment of oval root canal of extracted human teeth that were obturated using gutta-percha/BCS.


  Materials and Methods Top


The research was approved by the Research Ethics Committee at Faculty of Dentistry, King Abdulaziz University (No. 006-16).

Sample selection

Thirty extracted human single oval-rooted teeth were selected, with closed apex with neither caries, crack, nor fracture. Soft tissues and calculus were mechanically removed from the roots. Teeth were then immersed for 24 h in a 3% sodium hypochlorite (NaOCl) solution to eliminate remnants of soft tissues.

Sample preparation

All endodontic procedures were performed by a single operator. The access cavities were prepared. Size 15 K-type files (Dentsply Maillefer, Ballaigues, Switzerland) were inserted through canals 1 mm beyond the apical foramen to establish apical patency. The working length (WL) was established 1 mm shorter than the tooth length. The canals were instrumented with a size 20 hand file to the WL. The canals were prepared with three ProTaper Next Rotary Instruments (Dentsply Tulsa Dental Specialties, Tulsa, OK, USA) following the manufacturer's instructions (X1, X2, and X3). Instruments were cleaned after each use, being used for five canals before discarding. Five percent NaOCl was used as irrigating solution between each file. The irrigating solution was delivered with a 30-gauge Max-i-Probe needle (Dentsply-Rinn, Elgin, IL, USA) placed loosely 1 mm short of the WL. Five mL of 17% ethylenediaminetetraacetic acid (Sigma Lab Chem. Inc., Pittsburgh, PA, USA) for 1 min. Finally, the canals were irrigated with 5 mL of 5% NaOCl for 3 min, and then, the canals were dried with paper points.

Root canal filling

Matching gutta-percha cone fitted with tug-back. This master cone was covered with BCS (Dentsply De-Trey, Konstanz, Germany) which were mixed according to the manufacturer's instructions; then, gutta-percha was slowly inserted into the root canal till it reached WL. Cold lateral compaction with a size 25 finger spreader and size 20 accessory gutta-percha cones was performed until the spreader could not be introduced more than 2 mm into the root canal. The coronal gutta-percha was removed with a hot plugger; specimens were digitally radiographed to confirm the quality and length of the root canal filling. Access cavities were temporarily sealed with Cavit (ESPE, Seefeld, Germany), and the samples were stored for 7 days at 37°C and 100% humidity.

Before the retreatment procedure, the samples were numbered and randomly distributed into three groups.

Root canal retreatment

Removal of the root fillings was performed using one of the following techniques:

  • Group 1: ProTaper retreatment files D1, D2, and D3 were used with RM. A ProTaper Universal F3 file was used at WL for final apical preparation. The samples were irrigated with 2 mL of 2.5% NaOCl between each file
  • Group 2: Reciproc R25 file used with reciprocating motion clockwise/counterclockwise) for filling removal. Final canal preparation was done with an R40 file. The instruments were used in the Groups 1 and 2 using an “in-and-out” brushing motion
  • Group 3: Retreatment was initiated using GG drills (Dentsply Maillefer) to remove gutta-percha from the coronal third; H files were used sequentially in crown-down technique to remove gutta-percha from middle and apical thirds. Final canal preparation was done using size 40 H file at WL.


Imaging

Radiographic examination was performed using micro-CT (SKY SCAN–1172/MICRO-CT, USA).

Statistical analysis

Statistical analysis was then performed using a commercially available software program (SPSS 19; SPSS, Chicago, IL, USA). As data were parametric, significance of the difference between different root segments within the same file type and difference between files within each segment was compared using one-way ANOVA test and Tukey's post hoc test, respectively. Two-way ANOVA was used to study the effect of the interaction of file type and root segment variables. The level of significance was set at P < 0.05.


  Results Top


Comparison of different root segments within the same file type

Using ProTaper file, the highest mean value was recorded in the apical segment. ANOVA test revealed that the mean value of the apical segment was extremely significantly higher than the coronal and middle segments (P = 0.00). Tukey's post hoc test revealed no significant difference between coronal and middle segments [Table 1] and [Figure 1].
Table 1: Descriptive statistics and comparison of different root segments within the same file type (one-way ANOVA)

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Figure 1: Column chart showing mean value in different segments within the ProTaper file

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Using Reciproc file, the highest mean value was recorded in the apical segment. ANOVA test revealed that the mean value of the apical segment was extremely significantly higher than the coronal and middle segments (P = 0.00). Tukey's post hoc test revealed no significant difference between coronal and middle segments [Table 1] and [Figure 2].
Figure 2: Column chart showing mean value in different segments within the Reciproc file

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Using GG file, the highest mean value was recorded in the apical segment. ANOVA test revealed that the mean value of the apical segment was extremely significantly higher than the coronal and middle segments (P = 0.00). Tukey's post hoc test revealed no significant difference between coronal and middle segments [Table 1] and [Figure 3].
Figure 3: Column chart showing mean value in different segments within the Gates Glidden file

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Comparison between different file types in each root segment

In the coronal segment, the highest mean value was recorded with Reciproc file, while the lowest mean value was recorded with GG file. ANOVA test revealed no statistically significant difference between different files (P = 0.447) [Table 2] and [Figure 4].
Table 2: Descriptive statistics and comparison of different file types in each root segment (one-way ANOVA)

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Figure 4: Column chart showing mean in different root segments using different files

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In the middle segment, the highest mean value was recorded with ProTaper file, while the lowest mean value was recorded with GG file. ANOVA test revealed no statistically significant difference between different files (P = 0.797) [Table 2] and [Figure 4].

In the apical segment, the highest mean value was recorded with GG file, while the lowest mean value was recorded with Reciproc file. ANOVA test revealed that GG and ProTaper files recorded a statistically significant higher mean value in comparison to Reciproc file (P = 0.019). Tukey's post hoc test revealed no significant difference between GG and ProTaper files [Table 2] and [Figure 4].

Interaction of root segments and file type variables (two-way ANOVA)

ProTaper and GG files showed a statistically higher mean value compared to Reciproc (P = 0.023). However, there was no significant difference between ProTaper and GG files. Apical segment showed a statistically higher mean value compared to coronal and middle segments (P = 0.000). However, there was no significant difference between coronal and middle segments. Two-way ANOVA test revealed that the interaction of root segments and file type variables caused a statistically significant difference (P = 0.002) [Table 3] and [Table 4].
Table 3: Descriptive statistics and comparison of different root segments and file types (two-way ANOVA)

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Table 4: Results of two-way ANOVA test for interaction of file type and root segment variables

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  Discussion Top


Keeping the normal attachment apparatus around the naturally retained tooth is very important. Therefore, adequate endodontic treatment is the cornerstone to preserve natural teeth.

The most common reason of root canal treatment failure is the presence microorganisms within the root canal. The aim of root canal retreatment is to eliminate the microorganism load. Therefore, complete removal of root filling materials assists better biomechanical preparation and allows adequate refilling of the cleaned root canal system.[1],[2],[29],[30],[31]

Unfortunately, most studies have shown that a significant residue of root filling materials remains inside the root canal after retreatment procedure whatever was the technique used.[32],[33]

This study was conducted on human extracted teeth with straight oval root canals, to evaluate the efficacy of specially designed NiTi rotary systems and manual hand files to remove gutta-percha/BCS root canal filling materials during retreatment.

The complex morphology of the canal may render it difficult to be clean adequately, especially in oval canals where the anatomical variations are greater. The file has to contact the root canal wall to remove as much as possible of remaining filling materials residue.[17],[34],[35],[36],[37]

One operator conducted all the endodontic procedures, to achieve procedures that are more standard and to minimize the human variation.

The cytotoxicity of solvents as chloroform or eucalyptol that used to dissolve gutta-percha in different retreatment technique was reported;[38] in addition, these solvents cause residual layer of gutta-percha on the root canal walls that penetrate into the dentinal tubules and interfere with sealer penetration and adhesion.[39] Hence, in this study, the protocol of using solvents was not followed.

Wilcox et al.[3] reported that the use of H files without solvent resulted in more effective cleanliness compared with hand instrumentation with solvent.

The single file reciprocating NiTi system, Reciproc (VDW), has been reported to be used for the removal of root fillings.[16],[17]

In this study, there was no instrument fracture; this might be attributed to the use of a low-torque motor with constant speed and the straight root morphology; this was in agreement with Martins et al.[28] Other comparable studies that used NiTi instruments reported a varying occurrence of instrument separation.[17],[39]

Many techniques used to evaluate the root canal filling residue as vertical sectioning. Capar et al. used mandibular molars with straight roots and reported that four specimens were damaged in the sectioning technique.[40]

Radiograph technique is 2D, so radiographs do not detect all remaining filling material.[2]

Micro-CT imaging was used to evaluate the remnants of gutta-percha left in the root canals after retreatment as it has been designed to precise undistorted 3D image system [Figure 5]. This noninvasive technique allows detailed visualization of the features without destruction of the teeth.[25],[41],[42]
Figure 5: Serial cross-sectional cuts of a sample after removal of gutta-percha using (A) ProTaper, (B) Gates Glidden and H file, and (C) Reciproc (a. coronal, b. middle, and c. apical)

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In this study, brushing motion of the instrument was used for gutta-percha removal, to facilitate greater amount of filling material removal, even in more flattened areas.

Rödig et al.[17] reported that the percentage of residual material evaluated by micro-CT was 5.1%–8.3%, which was nearly similar to the results of our present study.

ProTaper and GG files showed more remnant of filling compared to Reciproc (P = 0.023). However, there was no significant difference between ProTaper and GG files. This was in accordance with Zuolo et al., who reported that files used in reciprocating motion were more effective than files used in continuous motion.[16] On the other hand, Rios et al.[19] and Martins et al.[28] stated that reciprocating file systems are as effective as ProTaper retreatment system. Our results were in disagreement with Rödig et al.,[17] who stated that there was no significant difference between H files, ProTaper Universal Retreatment, and Reciproc. Apical segment showed more remnant of filling compared to coronal and middle segments (P = 0.000). However, there was no significant difference between coronal and middle segments; this might be attributed to the matching gutta-percha cones and the hardness of BC upon setting that might compromise retreatment of the apical canal space. These results were in accordance with Hess et al.[7]

Our results were contradicting to the results reported by Schirrmeister et al., who concluded that no significant differences between the root canal thirds when investigated using scanning electron microscope.[2]

These differences in results between different researches could be attributed to different study designs regarding root canal curvature and preparation technique.

The results of this study demonstrated results similar to previous studies that showed none of the retreatment techniques allowed complete removal of root canal filling material.[8],[11],[15],[16]


  Conclusions Top


Micro-CT is an accurate nondestructive 3D analysis technique for visualizing the remnants of endodontic filling materials within the root canal system. Remnants of filling materials were observed in all samples regardless of the group examined; new techniques and solvent materials should be developed to be able to completely remove BCS.

Acknowledgment

We would like to thank Prof. Dalia El Robi, Professor of Oral Pathology, Faculty of Oral and Dental Medicine, Cairo University, for her valuable assistance in the statistical analysis performed in this study.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4]



 

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