Removal of gutta-percha/zinc-oxide-eugenol sealer or gutta-percha/epoxy resin sealer from severely curved canals: an in vitro study

Effectiveness of H-files and Pro-Taper universal systems in removing Gutta-percha during endodontic retreatment: A comparative study

Objective

This research was aimed at assessing the effectiveness of manual H-files versus a combination of a Pro-Taper universal rotary canal preparation system and retreatment system in removing gutta-percha (GP) during endodontic retreatment, by using a digital radiography technique.

Methods

This ex vivo study used a non-probability consecutive sampling technique. The study sample comprised 60 extracted anterior permanent teeth, each with one root with a straight root canal (RC). After preparation, RCs were obturated with GP and sealer. Subsequently, teeth were stored for 2 weeks in a humid environment at 37 °C. Thirty teeth each were randomly assigned to the control (group I), and experimental (group II) groups. GP removal was performed with H-files {group I) or a combination of a Pro-Taper universal rotary canal preparation system and retreatment system (group 2). Digital radiographs were acquired with Carestream digital radiovisiography software (Kodak; version-VER.6.10.8.3-A), and the presence of residual GP was analyzed. AutoCAD (2006) software was used to demarcate the RC and residual root filling. The residual GP in both groups was compared with independent sample t-tests.

Results

The remaining root filling did not significantly differ when GP was removed with conventional Hedstrom files versus a combination of Pro-Taper Universal preparation and retreatment file systems. The residual GP was confined to the apical third of the canals in both groups.

Conclusions

Pro-Taper Universal preparation and retreatment file systems have similar effectiveness to manual H-files in GP removal in straight canals.

Critical analysis of research methods and experimental models to study removal of root filling materials

Despite enjoying high favourable outcome rates, root canal treatment is not always successful. Root canal retreatment is a widely practised option for managing a non-healing root treated tooth. A basic distinction between retreatment and initial treatment is the requirement to remove the existing root filling material occupying the root canal space. Only then, can the technical deficiencies and possible causes of failure be addressed. Hence, the successful removal of the root filling material is critical to achieving the objectives of retreatment. Many different materials and techniques have been used for root canal filling, which have been documented in a plethora of studies; these are mainly laboratory studies investigating the removal of root filling materials. To help guide future research, which may then better inform clinical practice in relation to retreatment procedures, the focus of this narrative review is on the research methods and experimental models employed to study the removal of root filling materials. The current available literature demonstrates great variation in the research methodologies used to study the removal of root filling material, including direct visualization by splitting tooth samples or clearing, three-dimensional radiographic imaging including using microcomputed tomography or cone-beam computed tomography, and a combination of these techniques. Depending on the research method employed, variation also exists in quantification of root filling material removal; these include measurements of surface area, volume or weight, and criteria-based (semi-quantitative) assessment. Experimental models, using human teeth or resin models, differ with respect to standardization techniques and replication of the clinical scenario including initial sample preparation, canal filling, allocation and technical aspects of retreatment procedures. Future models should replicate, as closely as possible, the clinical scenario. Currently, microcomputed tomography provides a highly detailed, non-invasive and non-destructive method of objectively assessing and quantifying root filling removal.

Micro CT pilot evaluation of removability of two endodontic sealers

PURPOSE

This study compared the removability of AH Plus and EndoSequence BC sealers using in vitro micro-computed tomography.

METHODS

Ten single-canal, extracted human teeth were cleaned and shaped with ProTaper NEXT rotary files to size X5 (50/0.06) (Dentsply-Sirona). Canals were obturated with a single cone gutta-percha and either AH Plus (Dentsply-Sirona) (Group A) or EndoSequence BC (Brasseler) (Group B). ProTaper Universal Retreatment files (Dentsply-Sirona) were used to remove obturation materials after 90 days at 37^oC/100% humidity. Each tooth was scanned using micro-computed tomography (SkyScan 1272; Bruker) at an isotropic resolution of 6 μm from which the percent of material removed was calculated. Two-sample t-tests and one-way ANOVA were used for analysis.

RESULTS

The percent removal of materials in the coronal third was 92.9% ± 7.3% (Group A) and 93.2% ± 6.1% (Group B). Removal in the middle third was 94.9% ± 8.5% (Group A) and 96.5% ± 6.1% (Group B). Apical third removal was 76.2% ± 27.9% (Group A) and 70.1% ± 30.8% (Group B). No statistically significant differences were determined between the two sealers or among the sectional thirds within each group (P > 0.05).

CONCLUSION

AH Plus and EndoSequence BC sealers exhibit the same removability at all canal levels of 70% to 96%, with better removal coronally.

Retreatment of Root Canals Filled with BioRoot RCS: An In Vitro Experimental Study

INTRODUCTION

The purpose of this study was to compare the speed of removal of root canal filling material and re-establishment of apical patency in root canals filled with a tricalcium silicate-based sealer (BioRoot RCS [BRCS]; Septodont, Saint-Maur-des-Fossés, France) versus a zinc oxide-eugenol sealer (Pulp Canal Sealer [PCS]; Sybron Endo Kerr, Orange, CA) and to analyze the effect of the operator's experience.

METHODS

One hundred twenty root canals of 40 Dentalike dental simulators (Dentsply Sirona, York, PA) were shaped with a WaveOne (Dentsply Sirona) reciprocating file using short 3-mm strokes. Root canals were obturated using a single gutta-percha cone and either BRCS or PCS. Samples treated either with BRCS or PCS were equally dispatched between experienced practitioners and junior practitioners. The time required to remove root filling material and establish apical patency was recorded for each root canal. Samples were compared according to the sealer used and the practitioner's experience (Mann-Whitney test).

RESULTS

One hundred fifteen root canals were successfully retreated. No differences in the time required to remove the filling material were observed between the 2 materials for mesiobuccal or distobuccal canals (P > .05). In contrast, the procedure was longer for palatal canals filled with BRCS compared with PCS (79.10 vs 182.45 seconds, P < .01). Experienced practitioners took significantly less time than junior practitioners (P < .05).

CONCLUSIONS

BRCS can be successfully removed from root canals as quickly as a zinc oxide-eugenol sealer in both mesiobuccal and distobuccal canals but not in palatal ones. The duration of the procedure was affected by the operator's experience independent of the filling material used or the canal type.

Bioactive Glass-Based Endodontic Sealer as a Promising Root Canal Filling Material without Semisolid Core Materials

Endodontic treatment for a tooth with damaged dental pulp aims to both prevent and cure apical periodontitis. If the tooth is re-infected as a result of a poorly obturated root canal, periapical periodontitis may set-in due to invading bacteria. To both avoid any re-infection and improve the success rate of endodontic retreatment, a treated root canal should be three-dimensionally obturated with a biocompatible filling material. Recently, bioactive glass, one of the bioceramics, is focused on the research area of biocompatible biomaterials for endodontics. Root canal sealers derived from bioactive glass-based have been developed and applied in clinical endodontic treatments. However, at present, there is little evidence about the patient outcomes, sealing mechanism, sealing ability, and removability of the sealers. Herein, we have developed a bioactive glass-based root canal sealer and provided evidence concerning its physicochemical properties, biocompatibility, sealing ability, and removability. We also review the classification of bioceramics and characteristics of bioactive glass. Additionally, we describe the application of bioactive glass to facilitate the development of a new root canal sealer. Furthermore, this review shows the potential application of bioactive glass-based cement as a root canal filling material in the absence of semisolid core material.

A micro-computed tomographic study of remaining filling materials of two bioceramic sealers and epoxy resin sealer after retreatment

Objective

This study evaluated the presence of residual root canal filling material after retreatment using micro-computed tomography (micro-CT).

Materials and Methods

Extracted human teeth (single- and double-rooted, n = 21/each; C-shaped, n = 15) were prepared with ProFile and randomly assigned to three subgroups for obturation with gutta-percha and three different sealers (EndoSeal MTA, EndoSequence BC sealer, and AH Plus). After 10 days, the filling material was removed and the root canals were instrumented one size up from the previous master apical file size. The teeth were scanned using micro-CT before and after retreatment. The percentage of remaining filling material after retreatment was calculated at the coronal, middle, and apical thirds. Data were analyzed using the Kruskal-Wallis test and Mann-Whitney U test with Bonferroni post hoc correction.

Results

The tested sealers showed no significant differences in the percentage of remaining filling material in single- and double-rooted teeth, although EndoSeal MTA showed the highest value in C-shaped roots (p < 0.05). The percentage of remaining filling material of AH Plus and EndoSeal MTA was significantly higher in C-shaped roots than in single- or double-roots (p < 0.05), while that of BC sealer was similar across all root types. EndoSeal MTA showed the highest values at the apical thirds of single- and double-roots (p < 0.05); otherwise, no significant differences were observed among the coronal, middle, and apical thirds.

Conclusions

Within the limitations of this study, a large amount of EndoSeal MTA remained after retreatment, especially in C-shaped root canals.

Retreatability of Root Canals Obturated Using Gutta-Percha with Bioceramic, MTA and Resin-Based Sealers

INTRODUCTION

The aim of this study was to evaluate the retreatability of root canals obturated with gutta-percha (GP) and three different endodontic sealers [iRoot SP (bioceramic sealer), MTA Fillapex (MTA-based sealer) and AH-26 (epoxy resin-based sealer)] using the ProTaper Universal Retreatment (PTR) system.

METHODS AND MATERIALS

Forty extracted single-rooted human teeth were prepared with universal ProTaper files up to F4 (40/0.06). Specimens were randomly divided into four groups according to obturation technique/material: single-cone GP/AH-26, lateral compaction of GP/AH-26, single-cone GP/iRoot SP, and single-cone GP/MTA Fillapex. Root fillings were removed with PTR. The time taken to reach the working-length (TWL) was recorded. Roots were longitudinally sectioned and each half was evaluated using a stereomicroscope. Three observers scored each third of all specimen. Obtained data were analyzed using the Kruskal-Wallis, Mann-Whitney U, Welch and Games-Howell tests. The level of significance was set at 0.05.

RESULTS

In single-cone GP/MTA Fillapex group the TWL was significantly shorter. The remnant of filling material in the apical and middle thirds of groups was similar and higher than the coronal thirds.

CONCLUSION

None of the tested sealers were completely removed from the root canal system.

Efficacy of reciprocating instruments for removing filling material in curved canals obturated with a single-cone technique: a micro-computed tomographic analysis

INTRODUCTION

The aim of this study was to evaluate the efficacy of nickel-titanium reciprocating instrument techniques and passive ultrasonic irrigation (PUI) for retreatment in curved canals and obturated with correspondent single cones.

METHODS

Twenty molars were selected with mesial-buccal canals with curvatures between 20° and 40°, and they were instrumented with a Reciproc R25 instrument (VDW, Munich, Germany) in a reciprocating motion and obturated with single cones and AH Plus sealer (Dentsply Maillefer, Ballaigues, Switzerland). The teeth were divided into 2 groups (n = 10) according to the instrument used for the removal of filling material: group 1: Reciproc R25 instrument and group 2: WaveOne Primary instrument (Dentsply Maillefer). The analysis of the remnant filling material was made through micro-computed tomographic imaging after the use of reciprocating instruments and again after the use of PUI with xylene. The effective time of retreatment was registered.

RESULTS

The filling material of the root canal was efficiently removed (P < .05) for both groups. The percentage of removal of filling materials was 93% for the Reciproc group and 92% for the WaveOne group. There were no statistical significant differences (P > .05) between the groups in relation to the removal of filling material ability and the time needed for the procedure. The effective time for the removal of filling material was 78.7 seconds and 89.5 seconds for the Reciproc and WaveOne groups, respectively.

CONCLUSIONS

It was concluded that both instruments efficiently but not completely removed the filling material from inside the root canals. The use of xylene with PUI increased the removal of filling material a little, but it was not statically significant.