Retreatment Files Research Articles

A comparative evaluation of removal of gutta percha using two retreatment file system: An in vitro study

A comparative evaluation of the efficiency of two retreatment file systems in removing Gutta-percha from the root canals. Forty mandibular premolar teeth with single roots were specifically collected and decoronated with diamond disc so that the root lengths were standardized.Working length (WL) determination was done and root canal preparation done using Hyflex CM rotary files which was followed with meticulous irrigation and obturation was performed with gutta-percha, by the lateral condensation technique. AH-Plus sealer was used. The specimens were then divided in a random manner into two groups, in which retreatment was performed using two retreatment systems, Mtwo and REndo. These were further subdivided into two subgroups groups, i.e. one group using root canal solvent and another without solvent. Retreatment will be considered accomplished when gutta-percha was fully removed from the canal and none could be observed on the retreatment instruments and the same was confirmed radiographically. Longitudinally sectioning was done to split the root in to two halves-Mesial & Distal and was observed for the remnants under scanning electron microscope with 40x and 100x magnification. Photographs of the specimens were taken using a digital camera and the area of the remaining obturating material was determined using the AutoCAD16 software.: The area of remaining guttapercha in mesial and distal half for all the samples were evaluated using the Autocad software(Version 2016) and the mean as well as standard deviation of each group were used for statistical analysis (SPSS 22.00 for windows; SPSS inc, Chicago, USA).Statistical analysis was done using factorial ANOVA and Tukey HSD Post Hoc test. Difference between two groups was determined using student t-test and the level of significance was set at p < 0.05. The results revealed that Mtwo R file system was found to be a more efficient rotary system for endodontic retreatment when compared to REndo(p<0.05) and use of solvent acts as an adjuct for retreatment in both file systems (p<0.05).

XP endo® file: An update review

Clinical research has still focus on three-dimensional (3D) cleaning, shaping, and obturation of the oval root canal by improving irrigation, creating new alloys for instruments, and creating new sealers. This article only deals the MaxWire® technology instruments XP Endo® Shaper, Finisher, and XP Endo® Retreatment file and analyzes how they are effective in 3D cleaning and shaping, in biofilm removal, triple antibiotic paste removal, and also for debris and smear layer removal.

Evaluation of the accuracy of different apex locators in determining the working length during root canal retreatment.

Background. This study aimed to assess the accuracy of three electronic apex locators (EALs) (Dentaport ZX [J Morita, Tokyo, Japan], Propex Pixi [Dentsply Maillefer, Ballaigues, Switzerland], and iPex II [NSK, Tokyo, Japan]) during root canal retreatment. Methods. The root canal lengths of 90 extracted single-rooted human teeth were determined under a dental operating microscope at ×10 magnification. The actual working length (AWL) was 0.5 mm less than the root length. Electronic measurements were performed with the three EALs. The root canals were instrumented and filled to the actual working length using the lateral compaction technique. After seven days, the teeth were retreated until the retreatment file was applied to the root canal at the working length determined by EALs, and then, the three EALs were used for determining the retreatment working length. Data were analyzed using chi-squared and Kruskal–Wallis tests. Results. In the retreatment, the accuracy of EALs was reported at %83.3 for Dentaport ZX, %83.4 forPropex Pixi, and %80 for iPex II within a tolerance of 0.5± mm of the AWL. Conclusion. Under the limitations of this study, Dentaport ZX, Propex Pixi, and iPex II can be a useful adjunct during retreatment. Clinicians should be aware that residual materials in the root canal during retreatment can affect the accuracy of EALs.

Comparative evaluation of retreatment techniques by using different file systems from oval-shaped canals.

Introduction:Endodontic failure resolves after complete removal of obturating material followed by disinfection, cleaning, shaping and three-dimensional obturation.Materials and Methods:Seventy single-rooted mandibular premolars, with single oval-shaped root canal were included. They were decoronated at a length of 16 mm from the apex. Shaping and cleaning were performed, and obturation was done using the warm lateral compaction technique. The teeth were divided into seven groups according to retreatment procedures (Hand files; ProTaper Universal retreatment files; MTwo® Retreatment system; R-Endo® Retreatment system; ProTaper Universal retreatment files with solvent and ultrasonics; MTwo® R with solvent, and ultrasonics and R-Endo® with solvent and ultrasonics). The data were obtained and subjected to the statistical analysis.Results:All instrumentation techniques left obturating material with least in Group 6 and maximum Group 5. The mean time taken for complete retreatment procedure was minimum in Group 2 and maximum with Group 1.Conclusion:MTwo® R with solvent and ultrasonics, R-Endo®, and R-Endo® with solvent and ultrasonics were effective in gutta-percha removal from coronal third, middle third, and apical third, respectively. Significance: Nonsurgical endodontic retreatment using rotary files helps in gaining access to infected teeth. During retreatment procedure, this helps disinfectant to reach in critical areas of the root canal system, thereby decreasing the microbial load, leading to achieve healthy periradicular tissues.

Efficacy of Passive Ultrasonic Activation Assisted Hand vs. Rotary Retreatment Files in the Removal of Root Canal Filling Material: An In Vitro Study

Efficacy of Passive Ultrasonic Activation Assisted Hand vs. Rotary Retreatment Files in the Removal of Root Canal Filling Material: An In Vitro Study

Evaluation of gutta-percha removal from the dentinal tubules using different instrumentation techniques with or without solvent: An In vitro study

Aim: The cleanliness of dentinal tubules was compared after using different techniques for the removal of root filling material during root canal retreatment with and without solvent. Materials and Methods: Root canals of 90 extracted teeth were prepared and filled in vitro using lateral compaction with gutta-percha and sealer. In the control group (n = 10), the canals were left unfilled. In four experimental groups (n = 20 each), the root fillings were removed after 2 weeks using Hedstrom file, one of two rotary nickel–titanium instruments (ProTaper and Mtwo retreatment files), or a neodymium-doped yttrium aluminum garnet laser with H-file. Each experimental group was further subdivided into two subgroups (n = 10) according to whether the solvent N,N-dimethylformamide was used or not. After final irrigation, the samples were split longitudinally and photographed. The dentinal tubules' cleanliness was evaluated at the microscopic level by a scanning electron microscope in the coronal, middle, and apical thirds of each root half. Results: The number of open tubules was more prevalent in the control group, followed by the nonsolvent subgroups, than in the solvent subgroup (P

Evaluation of apical extrusion during conventional retreatment with three endodontic systems

Background/Aim: The aim of this study was to compare the apical extrusion during endodontic retreatment using three different endodontic systems. Material and Methods: 120 extracted human teeth were ex vivo endodontically treated and retreatment was performed using three different endodontic systems. Samples were divided into 3 groups, A-retreatment with Hedstroem hand files, B-retreatment with Pro Taper Retreatment files and C-retreatment with Pro Taper Gold files. Apically extruded material was collected in pre-measured Eppendorfs on a laboratory scale (10-5g). The amount of the extruded material was measured after the retreatment. The data were analysed using the the statistical software: STATISTICA 7.1 and SPSS for Windows 20. Results: The statistical analysis of the data revealed significant differences between the three endodontic retreatment systems (P< 0.05). Apical extrusion in the A endodontic system is significantly greater than the rotary (B and C) endodontic systems. Conclusions: In ex vivo conditions the results of this study showed significant statistical difference between three investigated endodontic retreatment systems concerning the amount of apically exuded material. The largest amount of material suppressed periapically was proven for Hedstroem hand instruments.

Evaluation of apically extruded debris during the removal of canal filling material using three different Ni-Ti systems and hand files in teeth with simulated apical root resorption.

To compare the weight of apically extruded debris produced during the removal of root canal filling material using various files in extracted teeth with simulated apical root resorption. The root canals of one hundred and twenty extracted mandibular premolar teeth were prepared with Revo-S files and filled using a cold lateral compaction technique with gutta-percha and a resin-based sealer (AdSeal; Meta-Biomed, Cheongwon, Korea). Sixty teeth were randomly assigned to four control groups (hand file, ProTaper Universal retreatment file, D-RaCe retreatment file, and Reciproc file) for the removal of root canal filling material. The apical portion of the remaining 60 teeth was modified to simulate apical root resoption, and the teeth were then randomly divided into 4 experimental groups (using thesame techniques as in thecontrol groups) for the removal of root canal filling material. Apically extruded debris was collected into pre-weighed Eppendorf tubes and then dried. The mean weight of the apically extruded debris was assessed with an analytical balance to an accuracy of 10-4 g. Data were analysed using two-way analysis of variance and a Tukey's post hoc test. In the simulated apical root resorption groups, all file systems were associated with significantly more debris extrusion compared to the groups without simulatedresorption (P<0.05). The amount of apically extruded debris was greatest in the hand file groups compared with the other groups (P<0.05). In the groups with simulated apical root resorption, theReciproc systemwas associated with the least weightofapically extruded debris (P<0.05), whereas there was no significant difference between the ProTaper Universal retreatment and D-RaCe files (P>0.05). In the groups without simulated apical root resorption, there was no significant difference between Reciproc, ProTaper Universal retreatment and D-RaCe retreatment files (P>0.05). The time required to remove the root canal filling material was as follows: hand file>ProTaper Universal retreatment=D-RaCe retreatment>Reciproc (P<0.05). The weight of apically extruded debris was significantlygreater in teeth with simulated apical root resorption than in those teeth without simulated apical root resorption. Hand files were associated with significantlymore apically extruded debris in all groups during removal of root canal filling material.

Comparison of the Efficacy of Different Techniques for the Removal of Root Canal Filling Material in Artificial Teeth: A Micro-Computed Tomography Study.

This study aimed to assess the efficacy of canal filling material removal using three different techniques after filling with a Gutta–Percha (GP) cone and calcium silicate-based sealer, by measuring the percentage of volume debris of GP and sealer remaining intracanal with micro computed tomography (micro-CT). The filling material was removed from 30 plastic teeth by a nickel–titanium (Ni–Ti) rotary retreatment system. Final irrigation was performed with 2 mL of saline and 10 specimens were randomly allocated to a conventional group. In the passive ultrasonic irrigation (PUI) group, ultrasonic irrigation was added to the conventional group (n = 10). In the Gentlefile Brush (GF Brush) group, irrigation with GF Brush was added to the conventional group (n = 10). Remaining filling material was measured using micro-CT imaging analysis. The total mean volume of residual filling material after retreatment in the conventional group, PUI group and GF Brush group were 4.84896 mm3, 0.80702 mm3, and 0.05248 mm3, respectively. The percentage of filling material remaining intracanal was 6.76% in the conventional group, 1.12% in the PUI group and 0.07% in the GF Brush group. This study shows that the cleaning effect of the GF Brush system is superior to those of Ni–Ti retreatment files and the PUI system in the apical area.

Dentinal Tubule Penetration and Retreatability of a Calcium Silicate–based Sealer Tested in Bulk or with Different Main Core Material

IntroductionThe aim of this study was 2-fold: to evaluate the penetration of a tricalcium silicate–based endodontic sealer (EndoSequence BC Sealer; Brasseler USA, Savannah, GA) into dentinal tubules without a core material (sealer) or with .02 or .04 tapered bioceramic gutta-percha points and to compare the time required to remove the root fillings . MethodsRoots of extracted human mandibular incisors (N = 60) were prepared with 0.04 taper nickel-titanium rotary files to #35 and randomly assigned into 3 groups (n = 10/group) according to the obturation method used:1. obturating with sealer only,2. sealer + .02 point, and3. sealer + .04 point. The sealer was labeled with rhodamine B for analyzing dentinal tubule penetration under a confocal laser scanning microscope. The remaining specimens (n = 30) were used to measure the time for removal of the root canal fillings with retreatment files. The data were analyzed using 1-way analysis of variance and post hoc Games-Howell tests for dentinal tubule penetration and the Kruskal-Wallis test for retreatment time. ResultsSignificantly greater sealer penetration and sealer-penetrated area was achieved when the sealer was used with a .04 gutta point (P < .05), whereas there was no difference between the sealer and .02 gutta point groups (P > .05). All test groups showed a similar depth of sealer penetration (P > .05). Groups with the gutta-percha points required a similar time to remove root filling (P > .05), whereas the working length could not be achieved in the sealer group. ConclusionsThe use of a matched-taper bioceramic gutta-percha point enhanced the dentinal tubule penetration of the tested tricalcium silicate–based sealer. The use of a core material in conjunction with sealer facilitates removal of the root filling to the working length.

Comparative assessment of manual, rotary and reciprocating instruments for removal of root fillings, using stereomicroscope: An in vitro study

Background: To investigate the efficiency of Hedstrom (H; Dentsply Maillefer) file, Protaper Universal Retreatment system (PTUR; Dentsply Maillefer), Mani NRT-GPR files (Mani, Japan) and WaveOne (WO; Dentsply Maillefer) Reciprocating files in removing Gutta Percha (GP) and sealer from root canals.&#x0D; Methods: Sixty canals with less than 10° curvature from extracted human maxillary incisors were used. Root canal reinstrumentation was performed with H, PTUR, Mani NRT-GPR and WO files. Amount of residual root filling material (Gutta-percha and or sealer) were measured by using stereomicroscope. Data of GP or sealer remnants were statistically analyzed using one-way analysis of variance and Tukey test.&#x0D; Results: There were no significant differences among 4 groups in terms of residual root filling material in the apical third (p &gt; 0.05). H-file group showed highest amount of root residual root filling as compared to groups.&#x0D; Conclusions: Reciprocating file system proved to be more efficient in removing the root canal fillings material than other retreatment file systems. H file group showed highest amount of root canal filling material.&#x0D; Bangladesh Med Res Counc Bull 2019; 45: 54-61

The Efficacy of Reciprocating Instruments versus Continuous Rotary Nickel-Titanium Instruments in Root Canal Retreatment with Different Filling Materials

The aim of this study was directed to rate the quality of differentEngine-driven retreatment files: ProTaper Retreatment files, Wave One system and OneShape system in removal of different filling materials. Material and methods: Nighty-six freshly extracted mandibular first molars were prepared with universal ProTaper rotary files till size F3 then categorized into two main groups (I and II) on the basis of type of material used in obturation. Group I: obturated with Gutta-percha, Group II: obturated with EndoREZ. Each One of them was categorized into three subgroups : sub group A, B and C on the basis of the system use (16 each), Subgroup A: using ProTaper Universal retreatment system, Subgroup B: using Wave One file, Subgroup C: using One Shape. Each subgroup was divided into two divisions according to the use of solvent or not (8 each). The residual obturating material was evaluated by the use of the stereomicroscope. Results: there was a significance unlikeness among tested groups, subgroups and subdivisions in the percentage of the residual obturating material Conclusion: Protaper retreatment instruments and Wave One file remove more filling material in comparison with OneShape file, regardless the amount of residual gutta percha filling material ,it was greater than with EndoREZ, Retreatment without the use of solvent was significantly faster and more effective than with solvent.

Evaluation of Efficacy of Different Instrumentation for Removal of Gutta-percha and Sealers in Endodontic Retreatment: An In Vitro Study

The aim of the present study was to evaluate the efficacy of different instrumentation for removal of gutta-percha and sealers in endodontic retreatment. A total of single-rooted mandibular premolars were collected. Access opening was performed in all specimens. The working length was determined by reducing 1 mm from the length of instruments that were seen reaching the apex. All the canals were dried with paper points. Lateral condensation technique was used to obturate the canals with gutta-percha and zinc oxide eugenol was used as a sealer. The specimens were randomly segregated into three experimental groups. Group I: ultrasonic retreatment tip, group II: R-Endo retreatment files, group III: Mtwo retreatment files. Roots were grooved into two halves with a diamond disc in a longitudinal, buccolingual direction. A stereomicroscope with ×40 magnification was used to image the quantity of gutta-percha and sealer on canal walls. With ultrasonic retreatment tip, least amount (1.96 ± 0.32) of gutta-percha and sealer remained, followed by Mtwo retreatment files (2.84 ± 0.24) and R-Endo retreatment files (3.18 ± 0.63). A statistically significant inter-group difference among different instrumentation groups was demonstrated by ANCOVA analysis. In the present study, ultrasonic retreatment tip file systems was found to be more effective in the removal of root canal filling material, followed subsequently by Mtwo retreatment file system and R-Endo retreatment file system. Thorough removal of filling material from the root canals is essential during root canal retreatment for probable cleaning and shaping of canal morphology. Thus, clinicians should be aware of the suitable and better instrumentation system that provides a clean and sterile root canal system without any debris. How to cite this article: Agrawal P, Ramanna PK, Arora S, et al. Evaluation of Efficacy of Different Instrumentation for Removal of Gutta-percha and Sealers in Endodontic Retreatment: An In Vitro Study. J Contemp Dent Pract 2019;20(11):1269-1273.

Evaluation of remaining dentin thickness following use of three different rotary nickel-titanium retreatment files: A cone-beam computed tomography study.

Aim:The aim of the study is to measure the amount of remaining dentin thickness (RDT) following retreatment using three different rotary nickel–titanium (NiTi) systems.Methodology:Mesiobuccal roots of 45 extracted maxillary first molars were prepared up to F2 ProTaper File and obturated. After cone-beam computed tomography (CBCT) imaging, to evaluate the obturation, the samples were randomly assigned to three retreatment groups (n = 15). Group I was retreated with ProTaper Universal retreatment kit, Group II and III with MTWO and D-Race retreatment files, respectively. Postoperatively, all samples were subjected to CBCT imaging and evaluated with AutoCAD software (AutoDesk, Inc.) Mill Valley, California, U.S. to calculate the RDT. Data were statistically analyzed using one-way ANOVA and Tukey's post hoc tests, and the level of significance was set at P = 0.05.Results:The amount of RDT was significantly more in D-Race and MTWO groups when compared to ProTaper group.Conclusion:D-Race and MTWO instruments were associated with significantly more RDT than ProTaper.

Effect of Aging on Dentinal Crack Formation after Treatment and Retreatment Procedures: a Micro-CT Study.

In order to evaluate the volume of dentinal cracks taking into account the age of the dentin and the type of file system used for endodontic procedures, forty freshly extracted single-rooted lower incisive teeth presenting similar root volume, were divided into two groups according to the age of the patient: Group Young (18 - 30 years old) and Group Old (60 years old or more). Each specimen was scanned by microcomputed tomography (micro-CT) in three stages: (i) before any treatment, (ii) after endodontic treatment with Reciproc files (REC), and (iii) after subsequent endodontic retreatment. Each group was subdivided into two subgroups, according to the retreatment technique used: retreatment with REC or with ProTaper Universal Retreatment (PUR) files. For each subgroup, the images were analyzed for differences in the volume of dentinal cracks in the middle and apical thirds of the teeth , according to the dentin age. In both stages (before and after instrumentation), the micro-CT images of the old root dentin presented with higher volume of cracks than those of the young root dentin, statistical significance notwithstanding (p>0.01). The use of REC files appeared to have no statistically significant differences in the generation of cracks in any type of root dentin when compared with PUR files (p>0.01). When retreated with PUR, the old root dentin presented with a significantly higher volume of cracks (p<0.01) when compared with the old root dentin initially.

Comparison between Three Different Root Canal Rotary Instruments in retreatment: An in vitro study

Aim: The aim of this study was to compare Protaper Universal retreatment files, M-Pro, andTwisted files in retreatment.Methodology: Experimental groups were divided into three group; Group I: Protaper UniversalRetreatment (PTU; Dentsply Maillefer, Ballaigues, Switzerland), Group II: M-Pro (InnovativeMaterial and Devices, ShangHai, China), and Group III: Twisted File (TF; SybronEndo, Orange,CA). Each group was evaluated for time to reach the working length, amount of debris extrudedduring retreatment. Data were then collected, tabulated and statistically analyzed.Results: Statistical analysis showed that TF recorded the least time to reach the working length,while M-Pro showed the highest amount of debris extruded.Conclusion: Under the condition of the current study, TF was faster than M-Pro and PTU toperform gutta-percha removal in the retreatment of teeth. The use of M-Pro in retreatment increasedthe amount of apically extruded debris.

EFFICACY OF MAXWIRE® ALLOY FILE IN REMOVING THE REMAINS OF ROOT CANAL FILLING MATERIAL IN VITRO

Today it is more and more preferred to preserve teeth with promising prognosis rather than to extract them. The efficiency and the precision of retreatment files to remove filling material are important factors of successful treatment. The aim of this study was to evaluate the efficiency of MaxWire® alloy file in removing root canal filling material after retreatment with endodontic retreatment instruments. Distal roots of twenty human mandibular molars with single and straight canals were selected for this study. All canals were instrumented up to #40/.04 with Bio-race system and apical preparation was finished with Kfile #50/.02. Obturation was performed using lateral condensation technique with ADSEAL sealer. Radiographs were performed in buccolingual and mesiodistal directions with periapical X-ray after obuturation. Teeth were randomly divided into two groups with ten teeth in each. Group 1: removal of root canal filling material was performed using D-race system. Group 2: removal of root canal filling material was performed using D-race system following XP endo Finisher R instrument. Radiographs were performed after retreatment. Residual material was calculated in percentage left in canals. Statistical significance between the two groups were analyzed with t-test. Remnants of root canal filling material was observed in both groups: 38.90% in Group 1 and 13.71% in Group 2, respectively. There was a significant difference between the groups in term of the total root canal filling material (p&amp;amp;lt;0.05). MaxWire® alloy file significantly increased the amount of removed root canal filling material after retreatment with endodontic retreatment instruments.

Efficacy of different techniques used for root canal retreatment

AimThis study compared the efficacy of gutta percha and sealer removal during retreatment using Protaper universal retreatment rotary files, D-Race rotary files and hand files with Gates Glidden. MethodsThirty six extracted single rooted teeth were selected for the current study. The canals were prepared using a modified crown-down technique then filled using the lateral compaction technique. Specimens were randomly divided into 3 equal groups each consisted of twelve specimens. Group one used manual files, group 2 used D-Race system while group 3 used Protaper retreatment system. Samples were split longitudinally and examined under the stereomicroscope. ResultsNo significant differences among the Protaper and the D-RaCe groups in the mean values of root canal filling remnants, whereas the hand files and Gates Glidden group differed significantly. ConclusionD-Race and Protaper retreatment files removed gutta percha and sealer more efficiently than hand files and Gates Glidden.

The efficiency of ProTaper rotary retreatment files in the removal of two different root filling materials

The ProTaper rotary retreatment files is one of the new files especially designedfor retreatment. The aim of this study is to test if root canals filled with Resilon pointsand RealSeal sealer (SybronEndo, USA) can be retreated using ProTaper rotaryretreatment files in the same manner as canals filled with gutta-percha and zinc oxideeugenol based sealer.Twenty extracted maxillary first molars with palatal roots having single straightcanal and fully formed apex were instrumented and randomly divided into two groupsof ten roots each according to the root filling material used (gutta-percha and zincoxide eugenol based sealer for group A and Resilon points and RealSeal sealer forgroup B). For all roots, removal of root filling material was done by using ProTaperrotary retreatment files (Dentsply-Maillefer, Ballaigues, Switzerland). The amount ofroot filling material remained and the time required for the removal process for allroots were recorded and statistically analyzed using SPSS version 15.The results showed that during retreatment procedures; removal of Resilon withRealSeal sealer from root canals can be achieved with ProTaper rotary retreatmentfiles but the amount of Resilon root filling material remained was more than GP andshowed a highly significant difference, it was also obvious that removal of Resilonroot filling material from root canals requires more time than roots filled with guttapercha.In conclusion, removal of resin based root filling material can be achieved withProTaper rotary retreatment files but it leaves more filling remnants and takes moretime than canals filled with gutta-percha.

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

To evaluate exvivo 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. 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. No significant differences between carrier-based and warm vertical compaction regarding residual filling material (14.2-19.3%) and dentine removal (2.7-3.2mm3 ) 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. 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%).