Retreatment System Research Articles

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%).

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.

Cleaning Ability of Irrigants and Orange Oil Solvent Combination in the Removal of Root Canal Filling Materials.

Objective:This study investigated the influence of different irrigants and the use of orange oil solvent in the removal of filling materials during root canal retreatment.Methods:Forty maxillary premolars were shaped using the ProTaper System up to file F3 (size 30, 0.09 taper) and filled by Tagger’s hybrid technique using the AH Plus. Samples were randomly assigned to four groups (n=10) according to the irrigating protocol during endodontic retreatment with the ProTaper Universal Re-treatment System: G1, 2% chlorhexidine (CHX) gel; G2, 2% CHX gel with an orange oil solvent; G3, 5% sodium hypochlorite (NaOCl); and G4, 5% NaOCl with an orange oil solvent. Afterwards, the samples were longitu-dinally split into two halves, and the root wall images were prepared by scanning electron microscopy. Two pre-calibrated evaluators analyzed the images using a filling materials remnants score system. Data were statistically analyzed using the Kruskal–Wallis and Dunn’s tests (p<0.05).Results:All samples had residual filling materials in the root canal walls after instrumentation. According to the presence of the filling material remnants in the total area of samples, the groups were ranked in the follow-ing order: G2=G4>G1=G3. No statistical differences were found when the CHX and NaOCl were used (p>0.05). Groups in which a solvent was used showed a less effective cleaning ability (p<0.05). The use of NaOCl with solvent presented the highest amounts of filling materials remnants in the critical apical area (p<0.05).Conclusion:The use of orange oil with NaOCl or CHX does not improve the removal of residual root canal filling materials.

Evaluation of apically extruded debris during removal of gutta-percha and ResilonTM using different instrumentation techniques

Background/Aim. Apical extrusion of material is considered as one of the very important factor for endodontic treatment success. Microorganisms, necrotic tissue, filling material and irrigants, which can be extruded apically during endodontic retreatment, may jeopardize the success of the therapy. The aim of this in vitro study was to quantitatively evaluate the amount of apically extruded debris during endodontic retreatment of teeth obturated with two different materials, using one hand and three rotary instrumentation techniques. Methods. Ninety-six extracted single-rooted teeth were endodontically treated and enlarged to size 40 using BioRaCe system, and then randomly divided into 8 groups of 12 specimens each. Half of the specimens were obturated with gutta-percha and AH Plus? sealer and another half with RealSeal SE system, using lateral condensation technique. Retreatment was performed using: Hedstr?m files; ProFile rotary files; ProTaper Retreatment system and D-RaCe system. Apically extruded debris was collected in pre-weighed Eppendorf tubes and evaluated using an electronic microbalance. Data were analyzed statistically using t-test and analysis of variance. Results. In the AH Plus/gutta-percha group, all tested rotary instruments gave significantly less extruded debris compared with Hedstr?m files (p &lt; 0.05). In theRealSeal group, there was significant difference between DRaCe and Hedstr?m instruments (p &lt; 0.05). Conclusion. All retreatment techniques resulted in apical extrusion. DRaCe system produced significantly less extruded debris compared to hand files. No significant difference was found when comparing two instruments specially designed for retreatment: D-RaCe and ProTaper systems.

Evaluation of Effectiveness of Two Different Endodontic Retreatment Systems in Removal of Gutta-percha: Anin vitroStudy

To determine the effectiveness of two different endodontic retreatment systems for the removal of laterally compacted gutta-percha (GP). Sixty-three freshly extracted human maxillary central incisors were used for the study. The teeth were instrumented with K-flex files and obturated using lateral condensation technique with GP and AH Plus sealer. The teeth were divided into three retreatment groups, each group consisting of 21 teeth. Group I: D-RaCe desobturation files (D-RaCe); group II: ProTaper Universal retreatment files (PTUR); group III: Hedstrom files (H-file). After removal of GP, the teeth were split longitudinally and divided into three equal parts: Cervical, middle, and apical third. The middle and apical thirds of all root halves were examined using scanning electron microscope (SEM). The total surface area covered by the residual debris was evaluated using Motic Image plus 2.0 software. Statistical analysis was done by one-way analysis of variance (ANOVA) test with a p-value <0.05 used to determine significance and Tukey's multiple post hoc tests used for comparison between the groups, and 't' test was done for comparison between the thirds within the same group. The PTUR retreatment files showed overall better performance compared with D-RaCe files and H-files. The PTUR files performed better at middle third compared with others. The PTUR files and D-RaCe files performed equally at apical third better than H-files. ProTaper retreatment files are better compared with D-RaCe files and H-files for the retreatment of the previously endodontically treated teeth. Highest efficacy for the removal of GP was shown by ProTaper Universal System followed by D-RaCe and H-file.

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

Aim: This study used micro-computed tomography (CT) to compare the efficacy of three techniques for removing the root canal filling in single oval-shaped root canals after using laterally compacted gutta-percha/bioceramic sealer (BCS). Materials and Methods: Root canals in 30 single-rooted teeth will be instrumented with the ProTaper NEXT (Dentsply Maillefer, Ballaigues, Switzerland) and obturated using lateral condensation technique with gutta-percha and BCS. The teeth were divided randomly into three groups (n = 10). Removal of the root fillings was performed using one of the following techniques: group 1: ProTaper Universal Retreatment System with continuous rotational motion (RM); Group 2: Reciproc files with reciprocating adaptive motion; and Group 3: retreatment was done using Gates Glidden (GG) drills and H files. The teeth were scanned with CT scans. The percentage of remaining filling material was recorded. The data were analyzed statistically using the one-way ANOVA test and Tukey's post hoc test. Two-way ANOVA was used to study the effect of the interaction of file type and root segment, at a 95% confidence level (P

Comparison of the amount of apically extruded debris produced by four retreatment techniques: an ex vivo study

Objetivo: o objetivo deste estudo foi comparar a quantidade de detritos apicalmente extruídos durante a remoção do material obturador do canal radicular usando instrumentos de retratamento rotativo de níquel-titânio e limas de Hedström. Material e Métodos: sessenta incisivos mandibulares com um único canal foram instrumentados e obturados por compactação lateral fria. Para retratamento, os espécimes foram divididos aleatoriamente em quatro grupos (n = 15): limas de Hedström com ou sem solvente; Sistema D-RaCe e sistema de retratamento Mtwo. Os detritos extrusados ??apicalmente durante a remoção do material de enchimento do canal foram recolhidos em tubos Eppendorf pré-pesados. Os tubos foram então armazenados em uma incubadora a 70 ° C por 5 dias. O peso dos detritos extrudidos a seco foi estabelecido subtraindo o pré-tratamento e o peso pós-tratamento dos tubos Eppendorf para cada grupo. Os pesos médios do material extrudido foram analisados ??por ANOVA de uma via. Resultados: os resultados mostraram que todas as técnicas de retratamento causaram a extrusão apical de detritos, mas não houve diferença estatisticamente significante entre os grupos (p&gt; 0,05). Conclusão: nas condições deste estudo, todas as técnicas de retratamento causaram extrusão de detritos apicais.

Analysis of the presence of filling material in oval root canals using computed microtomography after endodontic retreatment performed by different techniques

Aim: The aim of this study was to evaluate the presence of filling material in oval root canals after endodontic retreatment performed by different techniques, considering the area (mm2), location and root third using computed microtomography (µ-CT). Methods: Thirty human lower central incisor underwent biomechanical preparation, root filling and filling removal using two techniques (n=15): MN- manual retreatment technique (Gates Glidden burs and stainless steel manual files); and RT- rotary retreatment technique (ProTaper Universal and ProTaper Retreatment Systems). Cross-sectional images of the teeth were made using µ-CT to identify the presence of remaining filling in all root thirds of the canal walls. The remaining material detected in 150 µ-CT sections was identified and its area quantified (mm2) for each root third individually. Results: Data analysis showed no difference in the remaining area of filling material (p=0.8611) for the both techniques. Higher frequency of remaining material was verified in the lingual wall of the root canals. Regardless of the retreatment technique, the apical third showed lager areas of remaining filling material. More areas of remaining material were detected in the cervical third of the RT group, whereas for the MN group, most areas were observed in the middle and apical thirds. Conclusion: According to our results, no significant differences were verified between the efficiency of the rotary and manual techniques for removing filling material due to the interferences caused by the root canal anatomy.

Transportation assessment in simulated curved canals after retreatment with rotary and reciprocating systems

Objetivo: este estudo avaliou a capacidade dos sistemas rotatórios (ProTaper-Retreatment e Mtwo-Retreatment) e alternativos (Reciproc e WaveOne) em manter a forma original do canal após o retratamento do canal radicular. Material e Métodos: quarenta blocos de resina curva com canais radiculares simulados foram preparados e preenchidos. Depois disso, cada bloco foi distribuído aleatoriamente em 4 grupos (n = 10) de acordo com o sistema de retratamento utilizado. Imagens estereomicroscópicas de cada bloco foram tomadas antes e após os procedimentos de retratamento. A avaliação do transporte do canal foi obtida para todo o comprimento do canal e para duas regiões de canais independentes: partes retas e curvas. ANOVA seguido pelo teste de Tukey foi utilizado (P &lt;0,05). Resultados: para todo o canal ProTaper-Retreatment o sistema apresentou os menores valores de transporte seguidos pelos sistemas Reciproc, MTwo-Retreatment e WaveOne (P &lt;0,01). Na parte reta, o sistema ProTaper-Retreatment produziu o menor transporte de canal seguido pelos sistemas Reciproc e MTwo-Retreatment (P &lt;0,05); na parte curva, os sistemas ProTaper-Recreativo e Reciproc produziram o menor transporte de canal, seguido pelo sistema MTwo-Retreatment (P &lt;0,05). O sistema WaveOne resultou nos maiores valores de transporte em ambas as partes do canal (P &lt;0,05). Conclusão: no geral, o sistema ProTaper-Retreatment produziu menos transporte de canal em ambas as partes dos canais simulados do que os outros sistemas testados após os procedimentos de retratamento.

The efficacy of photon-initiated photoacoustic streaming in the removal of calcium silicate-based filling remnants from the root canal after rotary retreatment.

The aim of the study was to evaluate the efficacy of photon-initiated photoacoustic streaming (PIPS) in the removal of filling remnants from root canals after rotary phase of retreatment and to examine the difference in the amount of residual material considering the type of sealer. Thirty-six extracted single-rooted human teeth were instrumented and randomly divided into three groups according to the filling material used: group 1: EndoSequence BC Sealer (Brassler, USA), group 2: MTA Fillapex (Angelus Solucoes Odontologicas, Londrina, Brasil), and group 3: AH Plus sealer (Dentsply DeTrey, Konstanz, Germany). Cold lateral condensation technique was used. After 2weeks, the root canals were retreated with a rotary phase retreatment system (ProTaper Universal Retreatment, Maillefer, Ballaigues, Switzerland), followed by Er:YAG laser-activated irrigation (photon-initiated photoacoustic streaming, PIPS). The specimens were scanned in a micro-computed tomographic (micro-CT) device after root canal filling, after the rotary retreatment, and after the PIPS. There was significant reduction in the amount of filling material after the rotary phase of retreatment in all groups (p<0.05), the highest in the MTA Fillapex group (p<0.001) and no difference between the EndoSequence BC and the AH Plus (p=0.608). There was significant reduction of the filling remnants after the PIPS in all groups (p<0.05). The MTA Fillapex was the most easily removed during rotary phase of the retreatment, and there were no differences in the amount of the remaining filling material between EndoSequence BC and the AH Plus groups after rotary phase of the retreatment. The PIPS improved the removal of filling remnants in all groups.

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.

The Efficacy of the WaveOne Reciprocating File System versus the ProTaper Retreatment System in Endodontic Retreatment of Two Different Obturating Techniques

IntroductionThis ex vivo study aimed to evaluate the efficacy of retreating GuttaCore (Dentsply Tulsa Dental Specialties, Tulsa, OK) and warm vertically condensed gutta-percha in moderately curved canals with 2 different systems: ProTaper Universal Retreatment (Dentsply Tulsa Dental) and WaveOne (Dentsply Tulsa Dental). MethodsEighty mesial roots of mandibular molars were used in this study. The mesiobuccal canals in each sample were prepared to length with the WaveOne Primary file (Dentsply Tulsa Dental). The canals were obturated with either a warm vertical approach or with GuttaCore and divided into 4 retreatment groups with the same mean root curvature: warm vertical retreated with ProTaper, warm vertical retreated with WaveOne, GuttaCore retreated with ProTaper, and GuttaCore retreated with WaveOne. The warm vertical groups were obturated using a continuous-wave technique of gutta-percha compaction, and the GuttaCore groups were obturated according to the manufacturer's instructions. After allowing sealer to set, each specimen was retreated with either the ProTaper Universal Retreatment files D1, D2, or D3 or with the WaveOne Primary file to the predetermined working length. The time taken to reach the working length was recorded. Instrument fatigue and failure were also evaluated. ResultsThe post hoc 2-sample t tests showed that the overall mean total time taken to reach the working length for the warm vertical groups was significantly greater than that observed for the GuttaCore groups (mean = 87.11 vs 60.16 seconds, respectively), and the overall mean total time taken to reach the working length for WaveOne was significantly greater than that observed for ProTaper (99.09 vs 48.18 seconds, respectively). Two-way analysis of variance showed a significant main effect for both the type of experiment groups (F1,76 = 15.32, P = .0002) and the type of retreatments (F1,76 = 54.67, P < .0001). Also, the WaveOne Primary file underwent more separations than the ProTaper files. ConclusionsThe WaveOne Primary file underwent more separations and was unable to remove gutta-percha as efficiently as the ProTaper Universal Retreatment files. Also, canals obturated with GuttaCore were retreated more efficiently and with fewer file separations than the canals obturated using continuous wave of warm gutta-percha.

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

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. 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. 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). 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.

Efficacy of Ethylenediamine Tetraacetic Acid and Calcium Hydroxide in the Removal of Root Canal Filling During Retreatment

Objective: To compare the effect of Ethylenediamine tetraacetic acid (EDTA) and calcium hydroxide [Ca(OH) 2 ] in the removal of root canal filling material during retreatment procedure. Methodology: Eighty extracted, single-rooted human teeth were used. Root canals were shaped with a crown-down technique using Ni-Ti rotary instruments (ProTaper, Dentsply Maillefer, Switzerland) and filled with a cold lateral condensation method. AH Plus was used as a sealer. After filling, the teeth were divided into 4 groups and root fillings were removed by ProTaper Universal rotary retreatment system. In each group different irrigation and disinfection protocols were followed; Group I. Sodium hypochlorite (5.25%) + EDTA (17%-1 min.) Group II. Sodium hypochlorite (5.25%) Group III. Sodium hypochlorite (5.25%) + Ca (OH)2 Group IV. Sodium hypochlorite (5.25%) + Ca(OH) 2 + EDTA (17%-1 min.). Irrigation with 17% EDTA was performed only before D 3 -Retreatment instrumentation in all groups. AutoCAD system was used to detect the amount of residual root canal filling material. The results were statistically analyzed by SPSS (Statistical Package for Social Sciences) for Windows 15.0, one way ANOVA and Tukey’s HSD tests. The significance was evaluated at the level of p 0.05). Conclusions: Irrigating the canals with EDTA enhanced the removal of root canal filling during retreatment. However, disinfecting the canals with Ca(OH) 2 had no effect in the removal of filling material. Keywords: Retreatment, Sodium Hypochlorite, Ethylenediamine tetraacetic acid, calcium hydroxide.

Effect of retreatment instruments on microcrack formation: a microcomputed tomography study.

The purpose of this study was to compare the occurrence of microcracks in teeth prepared with different retreatment systems using microcomputed tomography (micro-CT). Forty-two freshly extracted mandibular premolar teeth were used. The root canals were instrumented with stainless steel K-files to an apical size of 35/.02 using the balanced-force technique and were obturated using the passive compaction technique. The specimens were divided into 3 experimental groups according to retreatment system used (n = 14): ProTaper Universal retreatment (PTUR), Mtwo retreatment (MTR), or D-RaCe retreatment (D-RC) systems. Each specimen was scanned using a high-resolution micro-CT system before instrumentation, after obturation, and after the removal of the filling material. The images were evaluated, and the presence of microcracks was recorded. The PTUR system demonstrated the highest percentage, while MTR and D-RC retreatment systems resulted in similar numbers of microcracks. Clinicians should be aware that all retreatment systems may cause microcracks.

Comparison of efficiency of manual(H-Files) and two rotary niti retreatment systems(Mtwo R files and HyFlex NT files) in removing Gutta-percha from root canals obturated with two different sealers by using stereomicroscope - An in vitro study

Objectives: The aim of this study was to compare manual and two nickel titanium (NiTi) rotary retreatment systems in removing gutta-percha obturated with two different sealers. Materials and Methods: Sixty extracted, human, single-rooted mandibular premolars were selected. Endodontic treatment was performed using ProTaper Universal NiTi rotary instruments. Half of the samples were obturated with Tubliseal and remaining half were obtutared with AH Plus sealer with cold lateral compaction method. Subsequently, twenty teeth were retreated with manual retreatment system, and each twenty teeth was retreated with two different rotary retreatment systems. The roots were then grooved longitudinally, and both root halves were subjected to assessment under stereomicroscope, and images were taken with a digital camera. These images were evaluated for residual obturating material using AutoCAD software. Analysis of variance test and Bonferroni multiple comparison test were used for statistical analysis. Results and Conclusion: Results of the present study showed that no system was able to completely remove all debris from the root canals. The minimum amount of debris was seen in the group obturated using Tubliseal sealer and retreated with Hyflex NT retreatment system followed by Mtwo retreatment system and finally the manual retreatment protocol. Regarding the time taken, Mtwo retreatment files took least time to remove the obturating material in all sealer groups.

Efficacy of two rotary retreatment systems in removing Gutta-percha and sealer during endodontic retreatment with or without solvent: A comparative in vitro study.

Objectives:The aim of this in vitro study was to compare the efficacy of two retreatment rotary systems in the removal of Gutta-percha (GP) and sealer from the root canal walls with or without solvent.Materials and Methods:Forty-eight extracted human mandibular first premolars were prepared and obturated with GP and AH Plus sealer. Samples were then randomly divided into four groups. Group I was retreated with MtwoR rotary system without solvent, Group II was retreated with MtwoR rotary system with Endosolv R as the solvent, Group III with D-RaCe rotary system without solvent, and Group IV with D-RaCe rotary system and Endosolv R solvent. The cleanliness of canal walls was determined by stereomicroscope (×20) and AutoCAD software. Kruskal–Wallis test and Mann–Whitney U-test were used to compare the data.Results:Results showed that none of the retreatment systems used in this study was able to completely remove the root canal filling material. D-RaCe with or without solvent showed significantly (P > 0.05) less filling material at all levels compared to MtwoR with/without solvent.Conclusion:Within the limitation of the current study, D-RaCe rotary retreatment system is more effective in removing filling material from root canal walls when compared to MtwoR rotary retreatment system.

Comparative Evaluation of Stress developed on Rotary Retreatment Instruments during Retrieval of Gutta-percha

The aim of the study is to compare the maximum stress distribution on the rotary retreatment instruments within the root canal at cervical, middle, and the apical one-third during retreatment of gutta-percha. A human mandibular premolar was scanned, and three-dimensional geometry of the root was reconstructed using finite element analysis (FEA) software package (ANSYS). The basic model was kept unchanged; tooth models were created using the same dimensions and divided into two groups as follows: Group I: ProTaper Universal retreatment system and group II: Mtwo rotary retreatment system. The stress distribution on the surface and within the retreatment files was analyzed numerically in the FEA package (ANSYS). The FEA analysis revealed that the retreatment instruments received the greatest stress in the cervical third, followed by the apical third and the middle third. The stress generated on the ProTaper Universal retreatment system was less when compared with the Mtwo retreatment files. The study concludes that the retreatment instruments undergo higher stress in the cervical third region, and further in vivo and in vitro studies are necessary to evaluate the relationship between instrument designs, stress distribution, residual stresses after use, and the torsional fracture of the retreatment instrument. The stress developed on the rotary retreatment instruments during retrieval of gutta-percha makes the instrument to get separated. There is no instrument system, i.e., suitable for all clinical situations and it is important to understand how the structural characteristics could influence the magnitude of stresses on the instrument to prevent its fracture in use.

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

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

EVALUAREA MATERIALULUI DE OBTURAŢIE DE CANAL RESTANT DUPĂ DEZOBTURARE, FOLOSIND PROTAPER ROTATIV CU SAU FĂRĂ SOLVENŢI

The purposes of retreatment are to eliminate the cause for failure of initial endodontic treatment and to preserve the tooth as well. The aim of this study is a comparative evaluation of efficacy of Protaper rotaty retreatment instruments for gutta-percha removal with or without solvents specific both to the sealer and gutta-percha. Materials and methods: Forty single-rooted extracted teeth were randomly divided into 4 groups according to different methods of retreatment. The teeth were prepared with Protaper Universal system (Dentsply-Maillefer, Ballaigues, Switzerland) and filled using lateral condensation of gutta-percha and AH Plus (Dentsply DeTrey, Konstanz, Germany). All root canal fillings were removed using Protaper Universal Retreatment system (Dentsply-Maillefer, Ballaigues, Switzerland). During the retreatment procedure, in group 1 Resosolv (Pierre Rolland, Merignac, France) was used; in group 2 eucalyptol was used, in group 3 Endosolv E (Septodont, Paris, France) was used and in group 4 no solvent was used. The times required for retreatments and radiographycal evaluation after retreatment were recorded. Results: All root canals showed filling material remnants and group 1 with specific solvent for AH Plus recorded the shortest time. Conclusions: Although it is not possible to eliminate the entire filling material on the canal walls, the duration of retreatment was reduced by the use of a solvent specific to the sealer compared with a gutta-percha solvent or no solvent.