Efficacy of reciprocating and rotary NiTi instruments for retreatment of curved root canals assessed by micro-CT

Effectiveness of different supplementary protocols for remaining filling material removal in endodontic reintervention: an integrative review

The aim of this study was to perform an integrative review to identify the most effective supplementary protocols used after filling material (FM) removal and root canal reinstrumentation, during endodontic reintervention. The literature search was performed on the electronic databases PubMed and Latin American and Caribbean Health Sciences Literature (LILACS), using a combination of specific scientific descriptors. Selection criteria accepted articles published in English, Spanish and Portuguese languages, up to August 2021, involving in vitro and ex vivo studies. After applying the eligibility criteria, 46 articles were included for qualitative analysis. The tool for qualitative analysis of quasi-experimental studies of the Joanna Briggs Institute was used to determine the risk of bias of the included articles. The selected articles provided important data regarding the following supplementary protocols: sonic and ultrasonic activation of the irrigating solution; the use of ultrasonic inserts, XP-endo system instruments, and photon-induced photoacoustic streaming for mechanical debridement; and new devices as GentleWave system, and the self-adjusting file. Overall, all supplementary protocols demonstrated efficacy in removing the remaining FM. The implementation of various supplementary protocols can effectively remove the remaining FM from the root canal walls, although complete removal is not always achieved. However, it was not possible to determine the most effective protocol. Conversely, their association can enhance remaining FM removal. Remaining FM attached to root canal walls hinders proper chemical-mechanical preparation during endodontic reintervention. Supplementary protocols optimize the remaining FM removal, enhancing cleaning and disinfection of root canal.

Comparative analysis of novel heat-treated retreatment file system on the removal of obturating material using nano-computed tomography

Introduction

The aim of nonsurgical retreatment is to remove the previous filling material followed by chemo-mechanical preparation of the canal to achieve proper disinfection of the root canal system. This is then followed by re-obturation. This study evaluates the time taken to retrieve the gutta-percha and the quantity of remaining filling material after retreatment with two different file systems. The quantity of remaining filling material was assessed using nano-computed tomography (CT) due to its increased accuracy.

Materials and Methods

Forty extracted single-rooted teeth were split into two groups at random and decoronated and obturated at a standard root length of 16 mm. Solite RS3 (SRS-3) Retreatment and ProTaper Universal Retreatment (PTUR) systems were used to retrieve the gutta-percha after a preoperative nano-CT scan. Postoperative nano-CT scan was taken and both the scans were superimposed to quantify the remaining filling material. The time taken to remove gutta-percha was measured using a stopwatch. The statistical analysis comparing the two groups was conducted using the independent t-test.

Results

The quantitative analysis of remaining filling material using nano-CT showed no statistical difference between both the file systems used (P > 0.05). However, SRS-3 took significantly less time in the removal of gutta-percha (P < 0.05).

Conclusion

Hence, we can conclude that there is no significant difference in the amount of remaining filling material between both the file systems. However, time taken to remove the gutta-percha was lesser in SRS-3 compared to PTUR file system.

Intracanal removal and apical extrusion of filling material after retreatment using rotary or reciprocating instruments: A new approach using human cadavers

AIM

This study compared intracanal removal of filling as well as the frequency and volume of extruded material after retreatment with either HyFlex or Reciproc instruments in mandibular teeth from cadavers.

METHODOLOGY

The root canals of 14 pairs of contralateral single-rooted teeth in mandibles of cadavers were instrumented with Reciproc R40 and filled using lateral compaction. The mandibles were scanned in a micro-computed tomographic (micro-CT) device before and after retreatment procedures. The contralateral teeth were assigned to two groups (n = 14) according to the retreatment protocol using either HyFlex or Reciproc instrument systems. In the HyFlex group, the HyFlex Remover instrument was worked 3 mm short of the working length (WL), followed by HyFlex CM 40.04 and 50.04 at the WL. In the Reciproc group, the R50 instrument was worked up at the coronal two thirds, followed by two more cycles until the WL was reached. Pre- and post-operative micro-CT images were analysed for extrusion and intracanal removal of filling material.

RESULTS

After retreatment, extrusion of filling material occurred in 11 (78%) and 14 (100%) teeth from HyFlex and Reciproc groups respectively (p > .05). A similar volume of extruded material was observed after retreatment with both systems (p > .05). A significant decrease in the intracanal filling volume was verified after retreatment with both tested systems (p < .05). However, residual filling material was found in all root canals, regardless of the system. The amount of filling material removed (HyFlex = 80.8%; Reciproc = 65.9%) and the operation time was similar between systems (p > .05).

CONCLUSIONS

A high frequency of filling material extrusion was observed after retreatment with the two systems in a cadaver model, with no significant difference between them. Both protocols obtained similar efficacy in filling material removal procedures, although none completely cleaned the canals.

Micro-CT evaluation of the removal of root fillings using rotary and reciprocating systems supplemented by XP-Endo Finisher, the Self-Adjusting File, or Er,Cr:YSGG laser

Objectives

This study aimed to compare the effectiveness of a single-file reciprocating system (WaveOne Gold, WOG) and a multi-file rotary system (ProTaper Universal Retreatment, PTUR) in removing canal filling from severely curved canals and to evaluate the possible adjunctive effects of XP-Endo Finisher (XPF), the Self-Adjusting File (SAF), and an erbium, chromium: yttrium, scandium, gallium garnet (Er,Cr:YSGG) laser using micro-computed tomography (μCT).

Materials and Methods

Sixty-six curved mandibular molars were divided into 2 groups based on the retreatment technique and then into 3 based on the supplementary method. The residual filling volumes and root canals were evaluated with μCT before and after retreatment, and after the supplementary steps. The data were statistically analyzed with the t-test, Mann-Whitney U test, analysis of covariance, and factorial analysis of variance (p < 0.05).

Results

PTUR and WOG showed no significant difference in removing filling materials (p > 0.05). The supplementary techniques were significantly more effective than reciprocating or rotary systems only (p < 0.01). The supplementary steps showed no significant differences in canal filling removal effectiveness (p > 0.05), but XPF showed less dentin reduction than the SAF and Er,Cr:YSGG laser (p < 0.01).

Conclusions

The supplementary methods significantly decreased the volume of residual filling materials. XPF caused minimal changes in root canal volume and might be preferred for retreatment in curved root canals. Supplementary approaches after retreatment procedures may improve root canal cleanliness.

The efficiency of different irrigation activation techniques in the removal of calcium silicate-based endodontic sealer from artificially created groove

This study evaluated the removal of a calcium silicate-based sealer (EndoSeal MTA) with needle irrigation (NI), passive ultrasonic irrigation (PUI), XP-endo Finisher (XPF) and EDDY. A total of 56 human mandibular premolars were instrumented up to size 40.04 taper. The roots were separated longitudinally, and grooves were prepared with an ultrasonic tip at one-half of each root canal. The grooves were covered with EndoSeal MTA and re-attached roots were investigated based on the activation techniques applied. The results showed that significantly more material (p < 0.05) was removed in the EDDY group compared to the NI, PUI and XPF groups in the apical region. In the coronal region, no significant difference was observed between EDDY, XPF and PUI (p > 0.05), whereas all the latter were significantly more effective than NI (p < 0.05). These findings show that the removal of EndoSeal MTA can be more effective with EDDY compared to XPF, PUI and NI in the apical region.

Effect of solvent on root canal filling material removal by two different rotary file systems in C-shaped root canals

This study compared the percentage reduction of total obturation materials, gutta-percha and sealer, using two rotary file systems with/without solvent in retreating C-shaped root canals and to evaluate the effect of the solvent on instrument separation. C-shaped root canals were scanned using micro-CT to identify the root canal morphology and randomly assigned to four groups (n = 12). Retreatment was performed using ProTaper Universal Retreatment (PTUR) or XP-endo systems with/without solvent. The number of separated instruments were recorded. The samples were scanned pre- and post-retreatment. The percentage reduction of total obturation materials, gutta-percha and sealer, were calculated. The percentage reduction of gutta-percha in the PTUR without solvent group was significantly lower than the other groups (P = 0.018). The number of separated instruments in the solvent groups were significantly lower than the no solvent groups (P < 0.05). Solvent increased gutta-percha removal, when using PTUR and decreased the occurrence of separated instruments for both systems.

Full counterclockwise rotary motion kinematics enhances the removal of gutta-percha and bioceramic sealer from root canals: A computed tomographic study

Background and Aim

Complete removal of gutta-percha and sealer is an important step during retreatment. The aim of this study was to assess the efficacy and time taken by full counterclockwise rotary motion of a reciprocating file in the removal of gutta-percha and BioRoot™ RCS bioceramic sealer.

Materials and Methods

Thirty-six extracted human mandibular premolars were instrumented with Mtwo rotary files and obturated using lateral condensation technique with gutta-percha and BioRoot™ RCS bioceramic sealer. The teeth were divided into three retreatment groups (n = 12) based on the kinematics used: Group I, Mtwo retreatment (Mtwo-R) files; Group II, Reciproc files used in reciprocation mode (Reciproc-R); and Group III, Reciproc files used in full counterclockwise motion (Reciproc-CCW). The efficacy of gutta-percha and bioceramic sealer removal was assessed by volume of gutta-percha removed using cone-beam computed tomography and area of remaining gutta-percha and bioceramic sealer using ImageJ software after longitudinal sectioning. Statistical analysis was done by one-way analysis of variance test and Tukey's multiple post hoc tests.

Results

Reciproc-CCW motion was significantly efficient in the removal of gutta-percha and bioceramic sealer in comparison to Mtwo-R files and Reciproc-R. The time taken for gutta-percha and sealer removal was least for Reciproc-R (325.5 ± 101.68 seconds) and was statistically significant in comparison to the other groups.

Conclusion

Within the limitations of the study, Reciproc-CCW was an effective method of removal of gutta-percha and bioceramic sealer during retreatment.

Postoperative pain after endodontic reintervention: a randomized clinical trial

The present randomized clinical trial compared the prevalence and intensity of postoperative pain in cases of endodontic reintervention using manual or engine-driven reciprocating instruments. As secondary objectives, the analgesic intake and time required for the root canal filling removal and re-instrumentation were also evaluated. Forty-eight individuals with an endodontically treated single-rooted tooth diagnosed with asymptomatic apical periodontitis were included in the study. Patients were randomly assigned to two comparison groups (n=24/group): reintervention with stainless steel manual instruments or a nickel-titanium reciprocating system (Reciproc; VDW, Munich, Germany). The endodontic reintervention was performed in two sessions with a calcium hydroxide-based intracanal medication applied for 14 days before root canal obturation. Working time for the root canal filling removal and re-instrumentation was recorded with a digital stopwatch. After each visit, postoperative pain intensity was assessed at 12, 24, and 48 hours and seven days using the Numerical Rating Scale (NRS). The patients were also asked about analgesic intake. Data were analyzed using Pearson chi-square, T and Mann-Whitney U tests (α=0.05). No significant differences between groups were found regarding the prevalence and intensity of pain or the need for analgesic intake at any time point (P > 0.05). Working time was significantly shorter in the reciprocating group (18 versus 41 minutes). In conclusion, manual and reciprocating instruments achieved the same results in terms of prevalence and intensity of postoperative pain and analgesic intake. However, filling material removal and re-instrumentation of the root canals were more than twice as fast when using the reciprocating system.

Effectiveness and safety of rotary and reciprocating kinematics for retreatment of curved root canals: a systematic review of in vitro studies

Objectives

This systematic review (register-osf.io/wg7ba) compared the efficacy and safety of rotary and reciprocating kinematics in the removal of filling material from curved root canals.

Materials and Methods

Only in vitro studies evaluating both kinematics during retreatment were included. A systematic search (PubMed/MEDLINE, Scopus, and other databases, until January 2021), data extraction, and risk of bias analysis (Joanna Briggs Institute checklist) were performed. Efficacy in filling removal was the primary outcome.

Results

The search resulted in 2,795 studies, of which 15 were included. Efficacy was measured in terms of the remaining filling material and the time required for this. Nine studies evaluated filling material removal, of which 7 found no significant differences between rotary and reciprocating kinematics. Regarding the time for filling removal, 5 studies showed no difference between both kinematics, 2 studies showed faster results with rotary systems, and other 2 showed the opposite. No significant differences were found in apical transportation, centering ability, instrument failure, dentin removed and extruded debris. A low risk of bias was observed.

Conclusions

This review suggests that the choice of rotary or reciprocating kinematics does not influence the efficacy of filling removal from curved root canals. Further studies are needed to compare the kinematics safety in curved root canals.

In Vitro Analysis of the Fatigue Resistance of Four Single File Canal Preparation Instruments

Instrument separation during root canal therapy is inevitable in endodontics with several unfavorable clinical consequences. Therefore, examining the cyclic flexural fatigue resistance of commonly used rotary endodontic files is crucial. This study aimed to determine the cyclic flexural fatigue resistance of four nickel–titanium (NiTi) rotary files used as a single canal preparation technique: WaveOne, Reciproc, Protaper F2, and Unicone medium instruments. According to the manufacturer’s instructions, each file was rotated freely within a 1.3 mm deep and 1.3 mm wide V-shaped groove in a stainless-steel block with a 40° and 5 mm radius of curvature. Cyclic fatigue resistance was compared between the NiTi files by verifying the time needed to crack. The data were analyzed using one-way analysis of variance (ANOVA) followed by Scheffé post hoc with a significant level set at p < 0.05. Our results demonstrated that the WaveOne instrument had the highest cyclic flexural fatigue resistance among the tested groups (p ≤ 0.05), while Unicone had the lowest cyclic flexural fatigue resistance. This study concluded that WaveOne size 25/0.08 could illustrate a superior cyclic flexural fatigue resistance when instrumenting root canals with the lowest possibility to cause instrument separation.

Removal of filling material using rotating or reciprocating systems with or without solvent: microCT analysis

This study evaluated by the efficacy of rotary and reciprocating systems to remove filling material by micro-CT. Sixty human canines were instrumented up to F3 by ProTaper Universal system and filled with AH Plus/ gutta-percha. Specimens were submitted to 1,200 thermal cycles, scanned by microCT SkyScan 1176 and randomly distributed in groups according to the filling material removal protocol (n = 10): ProTaper Universal, ProTaper Universal/xylol, ProTaper Next, ProTaper Next/xylol, Reciproc and Reciproc/xylol. After filling removal, specimens were analyzed by microCT to separately verify the presence of gutta-percha and sealer remnants. The data (mm3) were analyzed by two way ANOVA and Tukey´s test (5%). For the remaining gutta-percha, the use of xylol provided the highest values for Reciproc (7.60 ± 0.73), which was statistically different from the other groups (p < 0.05) that presented lower values and were statistically similar to each other (p > 0.05). For the remaining sealer, xylol provided the highest values (21.25 ± 6.94) different (p < 0.05) from the use of instruments alone (11.47 ± 9.45). ProTaper Next presented the lowest values (8.16 ± 1.37) for the remaining sealer, different (p < 0.05) from that of Reciproc (24.67 ± 6.32). The qualitative analysis revealed that all groups presented some remaining root filling material, with the highest volumes presented by Reciproc and Reciproc/xylol. In conclusion the rotary systems provided greater removal of filling material regardless of the use of xylol. The use of xylol negatively interfered with the action of the reciprocating system in the removal of the gutta-percha and sealer.

Efficacy of Reciprocating Instruments in the Removal of Bioceramic and Epoxy Resin-Based Sealers: Micro-CT Analysis

The objective of this study was to evaluate the efficacy of reciprocating instruments in the removal of bioceramic and epoxy resin-based sealers using micro-CT analysis. Root canals of 40 extracted human teeth were instrumented with a size R25 Reciproc instrument. Specimens were randomly divided into two groups (n = 20) according to the root canal filling material. In the first group, root canals were obturated with AH Plus sealer and Reciproc R25 gutta-percha. In the second group, a combination of bioceramic gutta-percha (TotalFill BC) and bioceramic sealer (TotalFill BC) was used. After one week, the retreatment of all specimens was performed using Reciproc instruments. To analyze the differences in the filling remnants, specimens were scanned in a micro-CT device after obturation and after the retreatment procedure. Statistical analysis was performed using the Mann-Whitney U test (p < 0.05). A combination of bioceramic sealer and bioceramic gutta-percha was more effectively removed from canals using a reciprocating instrument, with a filling remnants volume of 4.01 ± 3.13 mm³, in comparison to the combination of epoxy resin-based sealer and gutta-percha (6.96 ± 2.70 mm³) (p < 0.05). A reciprocating instrument was more effective in removing bioceramic sealers than epoxy resin-based sealers, although none of the root canal filling materials were completely removed from the root 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.

Efficacy of Removing Thermafil and GuttaCore from Straight Root Canal Systems Using a Novel Non-Surgical Root Canal Re-Treatment System: A Micro-Computed Tomography Analysis

The present study aims to evaluate the effectiveness of an XP-endo non-surgical root canal re-treatment system in removing both GuttaCore and Thermafil gutta-percha carrier-based root canal filling materials from straight root canal systems using micro-computed tomography (micro-CT) analysis. The study was performed on 20 single-rooted upper teeth, which were randomly allocated into the following study groups: Group A, Thermafil and AH Plus sealer (n = 10); Group B, GuttaCore and AH Plus sealer (n = 10). Before and after the non-surgical root canal re-treatment procedure, the samples were submitted for a micro-CT analysis. The volume of the root canal filling material (mm³), the volume of the remaining root canal filling material (mm³) and the time (minutes) needed to remove the root canal filling material were also recorded. Student's t-test was used to analyze the results. No statistically significant differences were found between the volume of the remaining root canal filling material in the GuttaCore and Thermafil root canal filling systems at the coronal third (p = 0.782), middle third (p = 0.838) or apical third (p = 0.882) of the straight root canal systems; however, the GuttaCore required a statistically significant (p = 0.037) shorter amount of time (4.72 ± 0.76 min) to be removed than the Thermafil carrier-based root canal filling material (5.92 ± 1.42 min). The XP-endo Finisher non-surgical endodontic re-treatment system removes both GuttaCore and Thermafil gutta-percha carrier-based root canal filling materials from straight root canal systems, although removal of the GuttaCore gutta-percha carrier-based root canal filling material required less time.

Impact of root canal curvature and instrument type on the amount of extruded debris during retreatment

Objectives

The aim of the current study was to assess whether the amount of extruded debris differs for straight and severely curved root canals during retreatment using H-files, R-Endo, Reciproc and ProTaper Universal Retreatment (PTU-R) files. Additionally, the area of residual filling material was evaluated.

Materials and Methods

Severely curved (n = 104) and straight (n = 104) root canals of maxillary molar teeth were prepared with WaveOne Primary file and obturated with gutta-percha and AH Plus sealer. Root canal filling materials were removed with one of the preparation techniques: group 1: H-file; group 2: R-Endo; group 3: Reciproc; group 4: PTU-R (n = 26). The amount of extruded material and the area of the residual filling material was measured. The data were analyzed with 2-way analysis of variance (ANOVA) and 1-way ANOVA at the 0.05 significance level.

Results

Except for Reciproc group (p > 0.05), PTU-R, R-Endo, and H-file systems extruded significantly more debris in severely curved canals (p < 0.05). Each file system caused more residual filling material in severely curved canals than in straight ones (p < 0.05).

Conclusions

All instruments used in this study caused apical debris extrusion. Root canal curvature had an effect on extruded debris, except for Reciproc system. Clinicians should be aware that the difficult morphology of the severely curved root canals is a factor increasing the amount of extruded debris during the retreatment procedure.

Canal transportation using Mani GPR or HyFlex NT during the retreatment of curved root canals: A micro-computed tomographic study

This study assessed the apical transportation using Mani GPR or HyFlex NT during the retreatment of curved root canals. Thirty-eight roots were analysed using micro-CT for the comparison of apical transportation produced by two retreatment systems. Longitudinal transportation, horizontal transportation, variation in the canal angle of curvature and variation in the canal/root width ratio were analysed. Longitudinal transportation was frequently observed, regardless of the system used. The canals retreated with Mani GPR showed a significantly higher horizontal transportation at 1 mm from the root apex (P < 0.01) and greater variation of the canal curvature angle (P < 0.01). The canal/root width ratio was similar between groups (P > 0.05). In conclusion, longitudinal transportation occurred more frequently in the mesial canal walls. Mani GPR showed greater horizontal transportation at 1 mm short of the apex, and higher variation of the canal curvature angle compared with HyFlex NT.

Comparison of the Self-Adjusting File and Hedström File Used as Supplementary Instruments for the Remaining Filling Material Removal During Retreatment of C-Shaped Canals: A Micro-CT Study

Objective:

The aim of this study was to evaluate the use of Self-adjusting file (SAF) system and Hedström (H) file for removing remaining filling material (RFM) from C-shaped canals.

Methods:

20 C-shaped mandibular second molars with C1 configurations were instrumented, filled with tagger´s hybrid technique. Samples were divided into 2 groups (n=10). Reciproc R25 and a Mtwo 35/04 file were used for retreatment in both groups. Then, a 2.0 SAF file (group I) and a #35 H file (group II) were used as supplementary steps for RFM removal. Micro-CT scanning was performed after every procedure. Total volumes were calculated and converted into percentages. Also, the minimum wall thickness at 3, 5, 7 mm from apex was calculated. The Prism 7.0 software was used as the analytical tool with a significance of 5%.

Results:

Initial obturation removal was approximately 64% in group I and 67% in Group II. The apical third had the highest values of RFM. The use of a H file significantly reduced the RFM compared to SAF in the total canal length respectively (30% vs 18%) and at 1-3 mm and 3-6 mm when compared to the use of SAF. A statistically significant decrease of RFM and minimum wall thickness were observed in both groups (P<0.05).

Conclusion:

None of the retreatment techniques completely removed RFM. The apical region was the more unaffected area. Also, the SAF file was less effective than the H file in removing the RFM. Although C-shaped canals possesses thinner dentinal wall thickness, no excessive dentine removal was observed after each instrument use.

Effect of Sonic Agitation of a Binary Mixture of Solvents on Filling Remnants Removal as an Alternative to Apical Enlargement-A Micro-CT Study

BACKGROUND

This work aimed to evaluate the efficacy of sonic agitation of a binary mixture of solvents (methyl ethyl ketone/tetrachloroethylene) on filling remnants removal and compare the effects of solvent agitation with the enlargement to the next instrument size.

METHODS

Twenty-four mandibular incisors were prepared with ProTaper Next (X1, X2) and obturated with the single-cone technique and AH Plus sealer. The teeth were retreated with ProTaper Universal Retreatment and ProTaper Next and divided into two groups (n = 12) according to the final instrument (X3 or X4). All canals were submitted to a supplementary procedure consisting of a mixture of solvents-methyl ethyl ketone/tetrachloroethylene, agitated with EndoActivator. The volume of filling remnants was assessed through micro-computed tomography in the apical 5 mm. Statistical analysis was performed with a significance level of 5%.

RESULTS

The supplementary procedure of agitation of the solvent mixture was beneficial in both groups (p < 0.05). There were no statistically significant differences between canals re-prepared until X4 and canals re-prepared until X3 plus solvent (p > 0.05).

CONCLUSIONS

An additional step with a two-solvent solution potentiated by EndoActivator showed to be very effective for the removal of gutta-percha and resinous sealer remnants from apical root canals of mandibular incisors, avoiding further enlargement.

The Efficacy of Rotary, Reciprocating, and Combined Non-Surgical Endodontic Retreatment Techniques in Removing a Carrier-Based Root Canal Filling Material from Straight Root Canal Systems: A Micro-Computed Tomography Analysis

The aim of this study is to analyze and compare the efficacy of three non-surgical endodontic retreatment techniques in removing a carrier-based root canal filling material from straight root canal systems. The study was performed on 99 single-rooted extracted teeth using the ProTaper Gold endodontic rotary system up to the F2 file (Dentsply Maillefer, Baillagues, Switzerland), which were sealed with GuttaCore (Dentsply Maillefer, Ballaigues, Switzerland) and AH plus epoxy resin sealer (Dentsply DeTrey, Konstanz, Germany) and randomly assigned to the following non-surgical retreatment techniques: ProTaper Retreatment endodontic rotary instruments (D1–D3 files, Dentsply Maillefer, Ballaigues, Switzerland; n = 33, PTR), Reciproc Blue endodontic reciprocating instrument (R50, VDW, Munich, Germany; n = 33, RCB50), and a combined root canal retreatment technique between Gates-Glidden drills (sizes #3 and #2, Dentsply Maillefer, Ballaigues, Switzerland) and Hedstrom files (file size 35, 30, and 25, Dentsply Maillefer, Ballaigues, Switzerland; n = 33; H-GG). All of the teeth were submitted twice to a micro-computed tomography (micro-CT) scan, before and after non-surgical endodontic retreatment procedures. The volume of root canal filling material (mm³), volume of remaining root canal filling material (mm³), non-surgical endodontic retreatment working time (min), proportion of remaining root canal filling material (%), and efficacy of root canal filling material removal between the non-surgical endodontic retreatment techniques were analyzed using ANOVA one-way statistical analysis. Statistically significant differences were observed between the proportions of remaining root canal filling material of PTR and H-GG (p = 0.018), between the non-surgical endodontic retreatment working times (min; p < 0.001), and between the efficacies of root canal filling material removal by the non-surgical endodontic retreatment techniques (p = 0.009). However, the non-surgical endodontic retreatment systems allow for similar carrier-based root canal filling material removal.

Effect of ultrasonic cleaning on the bond strength of fiber posts in oval canals filled with a premixed bioceramic root canal sealer

Objective

This study aimed to evaluate the effect of ultrasonic cleaning of the intracanal post space on the bond strength of fiber posts in oval canals filled with a premixed bioceramic (Bio-C Sealer [BIOC]) root canal sealer.

Materials and Methods

Fifty premolars were endodontically prepared and divided into 5 groups (n = 10), based on the type of root canal filling material used and the post space cleaning protocol. A1: gutta-percha + AH Plus (AHP) and post space preparation with ultrasonic cleaning, A2: gutta-percha + BIOC and post space preparation with ultrasonic cleaning, B1: gutta-percha + AHP and post space preparation, B2: gutta-percha + BIOC and post space preparation, C: control group. Fiber posts were cemented with a self-adhesive luting material, and 1 mm thick slices were sectioned from the middle and cervical third to evaluate the remaining filling material microscopically. The samples were subjected to a push-out test to analyze the bond strength of the fiber post, and the results were analyzed with the Shapiro-Wilk, Bonferroni, Kruskal-Wallis, and Mann-Whitney tests (p < 0.05). Failure modes were evaluated using optical microscopy.

Results

The results showed that the fiber posts cemented in canals sealed with BIOC had lower bond strength than those sealed with AHP. The ultrasonic cleaning of the post space improved the bond strength of fiber posts in canals sealed with AHP, but not with BIOC.

Conclusions

BIOC decreased the bond strength of fiber posts in oval canals, regardless of ultrasonic cleaning.

Cyclic Fatigue Resistance of Multiused Reciproc Blue Instruments during Retreatment Procedure

INTRODUCTION

Root canal retreatment procedure may reduce the mechanical resistance of nickel-titanium instruments and increase the frequency of instrument fracture. The aim of the present study was to evaluate the effect of multiuse of Reciproc Blue R25 instruments on cyclic fatigue resistance during retreatment procedure in mandibular molar teeth.

METHODS

Forty-eight Reciproc Blue R25 files were included in the study. In control group, 12 new Reciproc Blue R25 instruments were subjected to cyclic fatigue test by using a stainless steel artificial canal with a 90° angle and 3-mm radius of curvatures. In experimental groups, Reciproc Blue R25 files (n = 12) were used to remove the root canal filling (RCF) material of 1, 2, and 3 molar teeth, respectively. Then cyclic fatigue tests of these 36 instruments were performed. The number of cycles to fracture (NCF) and the length of the fractured fragment were calculated for each instrument. Working time for retreatment procedures was determined in seconds with a digital chronometer. The data were analyzed by using one-way analysis of variance followed by post hoc Tukey test and mixed-effect analysis (P = .05).

RESULTS

No significant difference was found between NCF values of new and first time used files (P > .05), but NCF values of new and first time used files were significantly higher than those of second and third time used files (P < .05). The second and third time used files revealed no difference (P > .05). As the number of uses increased, the average time for retreatment procedure statistically extended (P < .05).

CONCLUSIONS

Reciproc Blue R25 instrument can be used to remove RCF material of 2 molar teeth. However, because of its decreased NCF values, multiple use over 2 molars may not be suggested.

Surface deformation of several nickel-titanium rotary instruments after removal of the root canal filling materials: a scanning electron microscope evaluation

The aim of the present study was to investigate and compare the surface deformations of different NiTi rotary files after retreatment under scanning electron microscope (SEM). A total of 240 upper central incisor teeth were obturated with vertical compaction technique and divided into 6 groups. Root canals were retreated by ProTaper Next (PTN), Twisted File Adaptive (TFA), Reciproc (RPC), ProTaper Universal Retreatment (PTR), R-Endo and Mtwo-R NiTi rotary systems. The files investigated under SEM at different magnifications and photomicrographs were captured. The photomicrographs were classified and scored. Kruskal-Wallis and Dunn tests were performed for statistical analyze at 5% significance level. PTR and RPC groups were free of defects like file separation, curving and unwinding but PTN and TFA groups showed 50% file separation. According to the photomicrographs that were captured at high magnification; there were no statistically difference between groups at the coronal thirds of the files (P > 0.05), at the middle third PTN and TFA groups showed statistically more deformation than the other groups (P < 0.05). At the apical third Reciproc was statistically showed less deformation than the other all groups (P < 0.05). Within the limitation of this in vitro study, all NiTi files showed surface deformation in SEM observation after retreatment procedures. There was less deformation in PTR and RPC groups according to other.

Efficacy of Two Different Nickel-Titanium Rotary Systems in Retreatment Procedure With or Without Laser-Activated Irrigation: An In Vitro Study

Objective: The aim of this study was to compare the efficacy of HyFlex EDM (Coltene/Whaledent, Altstätten, Switzerland) and ProTaper Universal Retreatment Nickel-Titanium (NiTi) Systems [The ProTaper Universal Retreatment (PTR), Dentsply Maillefer, Ballaigues, Switzerland] in the removal of the root canal filling materials with or without laser activated irrigation. Materials and methods: The root canals of 60 human mandibular premolars were instrumented with K files up to size 35 at a working length; the step-back procedure was performed in 1 mm increments up to size 50. Next, the teeth were obturated using the lateral compaction technique with gutta-percha and resin-based sealer, and they were randomly divided into two groups (n = 30) according to the retreatment systems: PTR and HyFlex EDM NiTi rotary files. Then, each group was divided into two subgroups (n = 15), laser [photon-induced photo-acoustic streaming (PIPS); Fotona, Ljubljana, Slovenia] activated irrigation and conventional needle irrigation group. Following these procedures, the specimens were evaluated using micro-computed tomography. Results: There was no significant difference between the instrumentation systems regarding the cleaning efficacy (χ² = 0.754; p = 0.86). Additionally, PIPS method did not have a significant effect on the removal of the filling material compared to conventional needle irrigation. Conclusions: Both instrumentation systems were effective in removing the filling material, but neither was able to remove the filling material completely. PIPS method did not show a significant additional effect regarding the removal of filling material.

The effect of blue thermal treatment on endodontic instruments and apical debris extrusion during retreatment procedures

AIM

To determine the effect of blue thermal treatment on Reciproc (VDW, Munich, Germany) endodontic instruments and the amount of apically extruded debris during retreatment procedures.

METHODOLOGY

Thirty extracted mandibular molar teeth having mesial roots with a degree of curvature less than 20° and having an initial apical size equivalent to a size 10 K-file were selected. The mesial roots of the teeth were removed from the cementoenamel junction to obtain a 15-mm root length. The mesiobuccal canals were prepared to size F2 using the ProTaper Universal system (Dentsply Sirona, Ballaigues, Switzerland), filled with gutta-percha and 2Seal (VDW) using the lateral compaction technique and then randomly divided into two groups (n = 15). The root fillings were removed with one of the following instruments using a crown-down preparation technique: M-Wire Reciproc or Reciproc Blue (both VDW). Apically extruded debris was collected in pre-weighed Eppendorf tubes. The Eppendorf tubes were then stored in an incubator at 70 °C for five days to evaporate the distilled water. The data were analysed using the Mann-Whitney U test (P = 0.05).

RESULTS

Reciproc Blue (1.42 ± 0.4491 mg) extruded significantly less debris apically than M-Wire Reciproc (2.56 ± 1.0232 mg) (P < 0.05).

CONCLUSIONS

Blue thermal treatment of Reciproc instruments was associated with less debris extrusion during retreatment procedures.

Evaluation of two shaping systems and two sonic irrigation devices in removing root canal filling material from distal roots of mandibular molars assessed by micro CT

AIM

To compare two preparation systems and two sonic irrigation devices during the removal of root filling material from oval distal canals of extracted mandibular molars.

METHODOLOGY

The distal canals in 40 extracted mandibular molars were shaped using the ProTaper Next system (Dentslpy Sirona, Ballaigues, Switzerland), filled with Gutta Percha X2 (Dentsply Sirona), along with AH Plus sealer (Dentsply De Trey, Konstanz, Germany) and randomly divided into two groups (n = 20) according to volume of initial filling, preparation diameter and working length. One group was retreated using the Reciproc system (VDW, Munich, Germany), and the other using the 2Shape system (Micro-Mega, Besançon, France). A micro-CT scan was taken after the initial root filling and after retreatment to evaluate the volume of filling material remnants. The teeth were divided into four groups to test the supplementary effect of two sonic irrigation devices on removing filling material: Eddy (VDW) and MM1500 (Micro-Mega). In the first and second groups, 2Shape was followed subsequently by MM1500 and Eddy; in the third and fourth groups, Reciproc was followed by MM1500 and Eddy. A third micro-CT was taken to compare the remaining root filling material in all groups. Wilcoxon's signed rank tests, Mann-Whitney and Kruskal-Wallis tests were used for statistical analysis.

RESULTS

No significant difference was found for the volume of filling material removed between the Reciproc and 2Shape in the entire canal (P = 0.355). The volume dropped significantly from its initial value after removing the bulk of the root filling by 95.8% (from 4.71 to 0.22 mm³ ) with the 2Shape (P < 0.001) and by 94.0% (from 5.05 to 0.33 mm³ ) with the Reciproc (P < 0.001). Sonic activation significantly decreased the residual volume of filling material remnants by 3.21% (P = 0.013) in the first group, 1.38% (P = 0.012) in the second group, 1.83% (P = 0.008) in the third group and 1.83% (P = 0.012) in the fourth group. At the end, the percentage of residual material was not significantly different among the groups in the entire canal (P = 0.163).

CONCLUSION

In the distal oval canals of extracted mandibular molar teeth, there was no significant difference between the 2Shape and Reciproc systems in removing gutta-percha/sealer. Sonic activation with MM1500 and Eddy significantly improved filling material removal.

Influence of solvent and a supplementary step with a finishing instrument on filling material removal from canals connected by an isthmus

AIM

To evaluate the effectiveness of a solvent (eucalyptol) in improving filling material removal from canals connected by isthmuses, and the additional cleaning effect of a finishing instrument.

METHODOLOGY

The mesial canals from 32 mandibular molars (Vertucci's type II morphology) were instrumented and filled with the single-cone technique using Reciproc R25 gutta-percha points (VDW, Munich, Germany) combined with Sealer 26 (Dentsply, Petrópolis, RJ, Brazil). Each root was then subjected to retreatment using the Mtwo instrument system (VDW), with or without a solvent (n = 16 per group). The volume of filling material in the canals was assessed by micro-computed tomographic (micro-CT) scans taken before and after retreatment. Canals with remnants of filling material received a supplementary procedure with the XP-endo Finisher R instrument (FKG Dentaire, La Chaux-de-Fonds, Switzerland), with or without eucalyptol, and another micro-CT scan was taken. All retreatment procedures were performed inside a cabinet under a controlled temperature (37 °C). Filling material removal was evaluated in the 5-mm apical canal system for the canal+isthmus space or the isthmus alone. Statistical analyses were performed to compare the removal of filling material with and without eucalyptol, and after a supplementary approach with XP-endo Finisher R. The level of significance was set at 5% for all statistical tests (P < 0.05).

RESULTS

The amount of filling material removed from the canal+isthmus with Mtwo instruments was 83.2% when no solvent was used and 83.8% using the solvent (P > 0.05). When the isthmus area was evaluated separately, most specimens were associated with a reduction in the filling material, with no significant difference between the groups with or without using a solvent (P > 0.05). The supplementary step with XP-endo Finisher R significantly improved removal of filling material from both canal and isthmus area (P < 0.05), regardless of the use of a solvent (P > 0.05).

CONCLUSION

The use of eucalyptol did not improve filling material removal from Vertucci's type II molar mesial canals and isthmuses. XP-endo Finisher R significantly enhanced removal of filling material from the canals and isthmuses.

Effect of obturation technique with immediate and delayed post space preparation on apical voids and bond strength of apical gutta-percha

Objective

The purpose of this study was to evaluate the effect of immediate and delayed post space preparation on the sealing ability of two root canal obturation techniques by using micro-computed tomography imaging and a push-out test.

Methods

The root canals of 40 human maxillary premolar teeth were instrumented and divided into four groups: (A) single cone (SC) followed by immediate post space preparation, (B) continuous wave of condensation (CWC) followed by immediate post space preparation, (C) SC followed by delayed post space preparation, and (D) CWC followed by delayed post space preparation. Micro-CT scans were performed for volumetric analysis of voids and filling materials in the apical 4-mm portion. A push-out test was performed, and failure modes (adhesive, cohesive, or mixed) were assessed. Data were analyzed using the Kruskal-Wallis test and one-way analysis of variance.

Results

No significant differences were observed among the four groups in terms of the percentage volume of voids of the apical 4 mm or the bond strength of apical gutta-percha.

Conclusions

The percentage volume of voids and bond strength of apical gutta-percha were similar and were not significantly influenced by the timing of post space preparation or the obturation technique.

Efficacy of a thermally treated single file compared with rotary systems in endodontic retreatment of curved canals: a micro-CT study

OBJECTIVES

This study aimed to compare WaveOne Gold with ProTaper and RaCe systems regarding remaining filling material, apical transportation (AT), and working time (WT) after (i) filling removal and (ii) shaping of curved canals.

METHODS

Thirty mesiobuccal canals of maxillary molars were prepared and filled. After 30 days, they were randomly assigned into three groups (n = 10), according to the instruments used for filling removal and shaping, respectively: WOG-WaveOne Gold Primary and Medium; PTG-ProTaper Retreatment and ProTaper Next; RCG-D-RaCe and RaCe. Micro-CT analysis assessed the residual filling material and AT. WT was recorded. Data were statistically analyzed (α = .05).

RESULTS

There was no significant difference between groups in the amount of filling material at any evaluated moment (P > .05). All groups presented low AT values. The WT was similar in all groups in filling removal (P > .05), and in shaping step WOG was faster than PTG and RCG (P < .05).

CONCLUSIONS

Neither system could completely remove the filling material. The instruments evaluated were safe and the reciprocating system was faster than the rotary systems in shaping the canals.

CLINICAL RELEVANCE

This study provided consistent information on filling material removal capacity of WaveOne Gold. Considering that all tested systems were safe, WaveOne Gold may be an alternative with cost-effectiveness and shorter learning curve for endodontic retreatment.

Comparison of the effectiveness of various rotary and reciprocating systems with different surface treatments to remove gutta-percha and an epoxy resin-based sealer from straight root canals

AIM

To compare the Reciproc Blue, Reciproc and ProTaper Universal Retreatment systems with regard to the effective removal of epoxy resin-based sealer and gutta-percha during the retreatment of oval, straight root canals.

METHODOLOGY

Forty-five extracted, human mandibular first premolars with single straight oval canals were selected on the basis of cone beam computed tomography evaluations. The root canals were instrumented with the ProTaper Next system up to the X2 file, and filled with gutta-percha and epoxy resin-based sealer using the cold lateral condensation technique. After 1 month, the samples were randomly divided into three groups (n = 15) according to the retreatment system used: Reciproc Blue R40, Reciproc R40 and ProTaper Universal. The specimens were scanned at the resolution of 1.2 μm by a microcomputed tomography device after the root filling and retreatment procedures, and the decrease in the volume of filling material after each retreatment protocol was measured. The results were analysed using the Kruskal-Wallis test and additional box-and-whisker plots.

RESULTS

Although the volume of the filling material decreased significantly in all three groups (P < 0.05), none of the systems removed the material completely. The Reciproc system removed significantly more material than the ProTaper Universal (P < 0.001) and Reciproc Blue (P = 0.005) systems, with the latter two exhibiting equal volumes of remaining material (P = 0.068).

CONCLUSION

The Reciproc system was more effective than the Reciproc Blue and ProTaper Universal Retreatment systems during the removal of filling material from oval, straight canals, although none of the systems completely removed the filling material.

Efficacy of novel thermomechanically treated reciprocating systems for gutta-percha removal from root canals obturated with warm vertical compaction

Background. The present study aimed to test the efficacy of novel reciprocating systems in terms of gutta-percha removal of roots obturated with warm vertical compaction technique. Methods. Ninety straight rooted maxillary incisors were enlarged with hand files up to a # 50/02 apical size and obturated using warm vertical compaction technique. The specimens were divided into four groups according to system used for filling removal, as Reciproc Blue, Reciproc, WaveOne Gold and hand-instrumentation. The residual filling materials and time required for root canal removal were calculated. Statistical analyses were performed using one-way analysis of variance and Tukey tests with 5% significance threshold. Results. There were no significant differences among Reciproc, Reciproc Blue and WaveOne Gold (P > 0.05). Hand-instrumentation group left significantly greater root canal filling material (P < 0.05). The time required for root canal filling removal was significantly shorter in the Reciproc group followed by WaveOne Gold, Reciproc Blue and hand-instrumentation groups (P< 0.05). Conclusion. Efficacy of Reciproc Blue, WaveOne Gold and Reciproc instruments for root canal filling removal were similar and superior to hand-instrumentation.

Efficacy of the ProTaper retreatment system in removing Thermafil, GuttaCore or vertically compacted gutta-percha from curved root canals assessed by micro-CT

AIM

To evaluate ex vivo the efficacy of ProTaper Universal Retreatment files (Dentsply Sirona, Ballaigues, Switzerland) in removing Thermafil, GuttaCore (both Dentsply Sirona) or vertically compacted gutta-percha from curved root canals using micro-CT.

METHODOLOGY

Sixty curved molar roots with the same mean canal curvatures and radii in two directions were prepared using ProFile instruments (Dentsply Sirona) to size 30 with .04 taper and obturated with either Thermafil, GuttaCore or vertically compacted gutta-percha and AH Plus (n = 20). Specimens were retreated using the ProTaper Universal Retreatment files D1, D2 and D3 to working length, and root canal preparation was completed with ProTaper Next (Dentsply Sirona) to size ×4. Percentages of residual filling material and dentine removal were assessed using micro-CT imaging. Working time and procedural errors were recorded. Statistical analysis was performed using Kruskal-Wallis and Wilcoxon tests.

RESULTS

No significant differences between carrier-based and warm vertical compaction regarding residual filling material (14.2-19.3%) and dentine removal (2.7-3.2 mm³ ) were detected (P > 0.05). Time to reach working length was significantly faster for canals filled with GuttaCore than that observed for Thermafil and warm vertical compaction (P < 0.05). Five lateral perforations with the D3 file occurred during retreatment, one in the Thermafil and four in the vertical compaction group.

CONCLUSIONS

Remaining filling material and dentine removal were similar for all canal filling techniques. Regaining working length was significantly faster for GuttaCore compared with Thermafil and vertically compacted gutta-percha. Procedural errors occurred during retreatment of severely curved root canals with the ProTaper Universal Retreatment files in 5 of 60 canals (8%).

Micro-CT Evaluation of Gutta-Percha Removal by Two Retreatment Systems

INTRODUCTION

The aim of the present ex vivo research was to compare the remaining filling material and the volumes of dentine removed after retreatment of curved canals with two rotary systems naming ProTaper Universal Retreatment and Mani NRT-GPR using micro-computed tomography (micro-CT).

METHODS AND MATERIAL

Forty mandibular molars containing two completely separated canals, with curvature angle of 25-35° and a curvature radius <10 mm were prepared to the Mtwo instrument 35/0.04 and filled with warm gutta-percha and AH-Plus sealer. The teeth were randomly divided into 2 groups (n=20), according to the retreatment system evaluated: ProTaper Universal Retreatment (PR group) or Mani NRT-GPR (MR group). Retreatment was considered complete when the working length was reached and when smooth dentinal walls were observed, with no evidence of filling material adhered to instruments or in the irrigating solution. Preoperative and postoperative micro-CT images were obtained with an isotropic voxel size of 11.88 µm to observe the volume of residual filling material in the canals and dentine removed after retreatment. Statistical analysis was performed by Student's t-test (P<0.05).

RESULTS

The mean percentage of remaining filling material was 12.96% for PR group and 24.26% for MR group (P=0.0056). The percentage of dentin removal was greater in the PR group (5.02%) than MR group (1.36%) (P=0.0028). Both systems failed to completely remove the filling material from the canals.

CONCLUSION

ProTaper Universal Retreatment system was more effective than Mani NRT-GPR system regarding removal of root filling material and also removed significantly more dentine after retreatment of curved mesial root canals of mandibular molars.

Efficacy of ProTaper NEXT Compared with Reciproc in Removing Obturation Material from Severely Curved Root Canals: A Micro-Computed Tomography Study

INTRODUCTION

The aim of this study was to compare the remaining root canal obturation, volume of dentin removed, and apical transportation after retreatment of severely curved root canals by using Reciproc (REC) or ProTaper NEXT (PTN) systems.

METHODS

Twenty-eight mesial canals of mandibular molars were instrumented and then obturated with gutta-percha and sealer and allocated into 2 balanced groups (n = 14), the REC group (R25 file) and the PTN group (X3 and X2 files). Micro-computed tomography analysis was performed to assess the percentage of residual obturation material, the amount of dentin removed, and apical transportation. The effective time for the removal of obturation and procedural errors were recorded.

RESULTS

Obturation was effectively removed from the root canal in the REC and PTN groups (P ≤ .001), and the percentages of remaining obturation material were similar between both groups (84.8% PTN vs 86.5% REC) (P > .05). The amount of dentin removed (3.17 ± 2.64 mm(3) PTN versus 3.50 ± 2.82 mm(3) REC), apical transportation (at 1 mm: 0.096 ± 0.189 mm PTN versus 0.093 ± 0.186 mm REC; at 3 mm: 0.059 ± 0.069 mm PTN versus 0.082 ± 0.080 mm REC; at 5 mm: 0.097 ± 0.093 mm PTN versus 0.133 ± 0.138 mm REC), and the working time (269.69 ± 19.25 seconds PTN versus 268.62 ± 16.37 seconds REC) were also similar in both groups (P > .05). One file fractured in the REC group.

CONCLUSIONS

Both systems were equally effective in the removal of obturation from severely curved canals and can be used for retreatment. Neither system could completely remove the obturation material; therefore, additional techniques are needed to improve cleaning of the root canal.

Cleanliness of Canal Walls following Gutta-Percha Removal with Hand Files, RaCe and RaCe plus XP-Endo Finisher Instruments: A Photographic in Vitro Analysis

INTRODUCTION

Gutta-percha must be removed from the root canal space during retreatment to ensure a more favorable outcome. The aim of this study was to compare the efficacy of hand instruments, RaCe and RaCe plus XP-endo finisher instruments in removal of gutta-percha from root canal walls during retreatment.

METHODS AND MATERIALS

Thirty single-rooted premolars were prepared, obturated, and divided into three groups according to retreatment method; in group 1, retreatment was carried out by hand instruments, while in groups 2 and 3 retreatment was done using RaCe rotary files alone or accompanied by XP-endo finisher instruments, respectively. After retreatment, teeth were sectioned longitudinally and photographic images were taken. The amount of remaining gutta-percha in coronal, middle and apical thirds was quantified using Image J software. The two-way ANOVA and post hoc Tukey's tests were used to analyze data. The level of significance was set at 0.05.

RESULTS

RaCe cleaned the apical third significantly better than hand instrumentation. In the coronal third, RaCe+XP-endo finisher was more effective than RaCe. RaCe+XP-endo finisher was more effective than hand instrumentation in the entire root canal. The amount of remaining gutta-percha was the least in the apical part and increased toward the coronal part with the use of XP-endo finisher (P<0.05).

CONCLUSION

Rotary instrumentation was more effective in removing gutta-percha from the canal walls. Furthermore, use of XP-endo finisher file resulted in cleaner canal walls and was more effective in removing gutta-percha from the coronal toward the apical part of the canal.

Influence of Passive Ultrasonic Irrigation on the Removal of Root Canal Filling Material in Straight Root Canals

Objective

This study evaluates the efficacy of passive ultrasonic irrigation (PUI) in removing root canal filling material from endodontically treated teeth after using one of two reciprocating systems, Reciproc (VDW, Munich, Germany) or WaveOne (Dentsply Maillefer, Ballaigues, Switzerland), or one nickel-titanium (NiTi) rotary system, ProTaper Universal Retreatment (Dentsply Maillefer).

Methods

One hundred and twenty straight root canals of extracted human maxillary incisors were instrumented and then obturated. The specimens were divided into six groups (n=20) as follows: Group R, Reciproc R25 instrument without PUI; Group W, WaveOne Primary instrument without PUI; Group PT, ProTaper Universal Retreatment system without PUI; Group R-PUI, Reciproc R25 with PUI; Group W-PUI, WaveOne Primary with PUI and Group PT-PUI, ProTaper Universal Retreatment system with PUI. After removing the filling material, the teeth were cleaved longitudinally and photographed. The total canal space and remaining material were quantified with the aid of an imaging software tool. The Kruskal-Wallis test was used to identify significant differences between the groups.

Results

No statistically significant differences (P>0.05) in residual filling material were observed between the groups.

Conclusion

The use of PUI did not improve the removal of filling material from the root canals, regardless of the previously used instrumentation system.

Efficacy of protaper next and protaper universal retreatment systems in removing gutta-percha in curved root canals during root canal retreatment

Purpose:

The aim of this study was to compare the cleanliness of root canal walls after retreatment using ProTaper Next (PTN), ProTaper Universal Retreatment (PTR) nickel-titanium (NiTi) systems and Hedström hand files in curved mesial canals of mandibular molar teeth and the time required for gutta-percha and sealer removal.

Materials and Methods:

Ninety mandibular molar teeth with curved mesial roots were instrumented up to #35.04 with Mtwo NiTi rotary instruments and obturated using the continuous wave of condensation technique. Removal of gutta-percha and sealer was performed using one of the following: PTN and PTR NiTi systems and Hedström hand files. Samples were placed on the VistaScan phosphor plates in the mesio-distal direction and the radiographs were taken. The digital radiographs were analyzed using AutoCAD software. Also, the total time required for gutta-percha removal was calculated by a chronometer.

Results:

The total retreatment time was significantly shorter in the PTN and PTR groups compared with the manual group (p<0.05). There was a significant difference between the groups according to the total residual gutta-percha and sealer (p<0.05). The PTN and PTR groups left significantly less gutta-percha and sealer remnant than the manual group (p<0.001).

Conclusion:

Within the limitations of this study, the PTN and PTR groups showed less residual gutta-percha and sealer than the manual group. The NiTi rotary systems were significantly faster than the manual group in the time required for gutta-percha and sealer removal.

Filling Material Removal with Reciprocating and Rotary Systems Associated with Passive Ultrasonic Irrigation

Objective:

The purpose of this ex vivo study was to evaluate the filling material removal ability, and the time required to perform this procedure, of reciprocating and conventional rotary systems when associated with passive ultrasonic irrigation.

Methods:

The palatal roots of 40 maxillary molars were submitted to root canal preparation and filling. The desobturation of root canals was initially performed with Largo burs in the coronal portion (4 mm) to drill the gutta-percha and to facilitate the action of the instruments used then. Next, the palatal roots were randomly distributed (n=10) according to the systems and irrigation protocols used for filling material removal: ProTaper universal retreatment (PTR), PTR+passive ultrasonic irrigation (PUI) (PTR+PUI), Reciproc system (RS), and RS+PUI. Passive ultrasonic activation was performed in the root canals completely filled with 2.5% sodium hypochlorite solution using a smooth and straight ultrasonic tip, coupled to a low-power (20%) ultrasonic device for 1 min (3 cycles of 20 s). After retreatment, the roots were longitudinally sectioned to the remaining filling material quantification using an operating microscope. Environmental scanning electron microscopy (ESEM) micrographs at 97, 105, and 250 X magnifications were also taken to evaluate the quantity of filling material present at the apical portion of the palatal roots.

Results:

The RS group presented greater quantity of filling material attached to the root canal walls than the other groups (P>0.05). PTR+PUI and RS+PUI groups were statistically similar (P>0.05). Reinstrumentation of root canals using RS was faster than PTR, irrespective of the irrigation protocol used (P>0.05).

Conclusion:

The association between PUI and the different systems for reinstrumentation yielded greSater filling material removal. The reciprocating system was faster.