Curved Root Canals Research Articles

Optimization of difficult endodontic treatment with nickel-titanium files in martensitic and austenitic phase

INTRODUCTION. Nickel-titanium alloys and cutting-edge design of endodontic files continue to revolutionize. In addition to variations in the design of nickel-titanium files, manufacturers have implemented several proprietary manufacturing processing procedures to improve their mechanical properties.AIM. The aim of the study was to improve the quality of mechanical instrumentation of highly curved root canals based on the data of laboratory and experimental analysis of rotary endodontic instruments made of nickel-titanium alloys of various modifications.MATERIAL AND METHODS. As part of the research, the following endodontic rotary files systems were studied during instrumentation of curved root canals: group 1 – Mtwo (VDW); group 2 – Race Evo (FKG), group 3 – Ultrataper next (Eurofile). A metallographic analysis of the instruments was performed, a morphological structure of the root dentin after instrumental was examined by scanning electron microscopy, as well as the amount of extruded debris was studied.RESULTS. Groups 2 and 3 showed significant deterioration after three applications. Mtwo files showed a statistically higher amount of surface damage after five uses (p < 0.05). The smallest amount of extruded debris was found in the group 2, while the largest number of root dentin irregulations was found in the groups 1 and 3 (p < 0.001).CONCLUSIONS. A different degree of the surface damage of the instruments was revealed, depending on the number of treated root canals. The safest and most effective endodontic system for the mechanical preparation of curved root canals is the Race EVO.

Evaluation of Obturating Material Removal from Root Canal by Hedstrom and Rotary Retreatment File

An in vitro investigation was conducted to assess the efficacy of Hedstrom and Rotary Retreatment File using Cone Beam Computed Tomography (CBCT) in removing obturating material from moderately to severely curved root canals. Thirty-six removed human molar teeth were split into two groups based on the canal curvature using the Schafer and Schneider method. Each group consisted of 18 teeth. Teeth in Group A had roots that were moderately curved (angles between 10 and 20 degrees), whereas teeth in Group B had roots that were severely curved (angles more than 20 degrees). Following decoronation, each root was ready for obturation using the appropriate rotary files, following the manufacturer’s recommendations. Using the CBCT image, the total surface area of the root canals in the axial cross-section and the volume analysis of the obturated area were calculated. H files were used to retreat half of each group, while Rotary (ProTaper) retreatment files were used for the other half, in accordance with their retreatment protocol. It was noted how long it took to reach the working length and remove all obturating items. Cone beam computed tomography and Auto CAD software are used to analyze the surface area and volume of any residual obturating material in the canal after it has been completely removed. An analysis of the data using the ANOVA test was conducted between four groups. When p < 0.05 was reached, it was deemed statistically significant. Rotary retreatment files were discovered to be the most efficient method for removing obturating material and to take the least amount of time to achieve working length. Compared to the Rotary retreatment file, the H file left greater residue in the root canal. Compared to moderately curved root canal groups, severely curved root canal groups have noticeably more residues. In all four groups, the apical part had more residues than the middle and coronal portions. The obturating substance in the root canal could not be entirely removed using any of the retreatment procedures. Furthermore, there was no advantage in terms of root-filling removal’s effectiveness.

Computational fluid dynamics investigation on the irrigation of a real root canal with a side-vented needle

BackgroundRoot canal therapy is one of the main treatments for root canal diseases, and effective irrigation is the key to successful treatment. Side-vented needle is one of the commonly used needle types in clinic. In the real root canal, due to the influence of the curvature of the root canal, the irrigation flow field in different needle directions shows obvious differences. At the same time, changes in root canal curvature and working depth will lead to changes in irrigation efficiency and the flow field. Both the mainstream of the irrigation flow and the shear stress near the wall changes significant. Consequently, either the replacement in the root canal or the removal efficiency of the smear layers is apparently modified.Materials and methodsIn this paper, the permanent root canal of the maxillary first molar prepared until 15/04 were scanned by micro-CT, and then imported into the software for 3D reconstruction. The key parameters of flushing efficiency of 30G side needle at different working depths of 4.75 mm, 5 mm, 5.25 mm and 5.5 mm were compared. Meanwhile, the simulated models with different curvatures of 0°, 5°, 10°, 20° and 30° based on the real root canal were reconstructed to investigate the curvature effect on the irrigation efficiency.ResultsThe results show that moderate working depth (such as 4.75 mm and 5.25 mm in present paper) helps to improve the replacement capacity of irrigation flow. At the same time, the apical pressure decreased as the working depth increased. The curvature of the root canal seriously affects the removal depth of the smear layers of the root canal. A root canal with a large curvature (especially 20° and 30°) can significantly improve the difficulty of irrigation.Conclusions(1) Moderate working depth helps to improve the displacement capacity, the ERD of the irrigation flow is generally improved at the working depths of 4.75 mm and 5.25 mm, and the apical pressure will decrease with the increase of working depth. (2) The large curvature of the root canal can significantly improve the difficulty of irrigation. The curvature of the root canal can severely influence the removal depth of the smear layer on the wall. It can be found both the span and the depth of the ESS for little curvatures (5° and 10°) root canals are higher than those for large curvatures (20° and 30°).

Debris and Smear Layer Removal in Curved Root Canals: A Comparative Study of Ultrasonic and Sonic Irrigant Activation Techniques.

The aim of this study was to compare the cleaning efficacy of three irrigant activation devices with a control of non-activated syringe and needle irrigation in curved root canals. Sixty human curved roots were endodontically prepared and divided into four groups (n = 15) with similar root curvature distributions. Final irrigation using 4% NaOCl was performed with a syringe and needle (30-G) alone, or with Eddy sonic powered irrigation system (polymeric tip #0.25/0.06), Endosonic ultrasonic activation (polymeric tip #0.25/0.03), or Irrisafe ultrasonic activation (stainless-steel tip, #0.25/0.00). SEM was used to evaluate cleaning efficacy, employing five-score systems for debris and smear layer. While no significant difference in debris removal was observed between Endosonic or Irrisafe activation and non-activated irrigation, Eddy sonic powered irrigation system significantly improved debris removal in the apical third of curved root canals. Smear layer removal was effective in coronal and mid-root sections for all groups but less so in the apical third. Thus, Eddy sonic powered irrigation system demonstrated higher efficacy in removing debris from the apical third of curved root canals compared with non-activated syringe and needle irrigation. However, all three irrigant activation systems exhibited no difference from the non-activated control in smear layer removal.

Cyclic Fatigue of Different Reciprocating Endodontic Instruments Using Matching Artificial Root Canals at Body Temperature In Vitro.

Reciprocating motion expands the lifetime of endodontic instruments during the preparation of severely curved root canals. This study aimed to investigate the time to fracture (TTF) and number of cycles to failure (NCF) of different reciprocating instruments (n = 20 in each group) at body temperature using a dynamic testing model (amplitude = 3 mm). Reciproc Blue (RPB), size 25/.08, WaveOne Gold (WOG) 25/.07, Procodile (Proc) 25/.06, R-Motion (RM_06) 25/.06 and R-Motion (RM_04) 30/.04 instruments were tested in their specific reciprocating motion in artificial matching root canals (size of the instrument ± 0.02 mm; angle of curvature 60°, radius 5.0 mm, and centre of curvature 5.0 mm from apical endpoint). The number of fractured instruments, TTF, NCF, the and lengths of the fractured instruments were recorded and statistically analysed using the Chi-Square or Kruskal-Wallis test. Both TTF (median 720, 643, 562, 406, 254 s) and the NCF (3600, 3215, 2810, 2032, 1482 cycles) decreased in the following order RM_06 > RPB > RM_04 > Proc > WOG with partially significant differences. During testing, only six RM_06 instruments fractured, whereas 16/20 (RPB), 18/20 (Proc), and 20/20 (RM_04, WOG) fractures were recorded (p < 0.05). Within the limitations of the present study, blue-coloured RPB and RM instruments exhibited a significantly superior cyclic fatigue resistance compared to SE-NiTi and Gold-wire instruments. Heat treatment, cross-sectional design and core mass significantly influenced the longevity of reciprocating instruments in cyclic dynamic testing.

Post-endodontic pain in curved canals prepared with different rotary instrumentation techniques: A randomized controlled trial.

Curved root canals are associated with the highest number of procedural errors during endodontic instrumentation. Recently, numerous rotary instruments have been developed, with both manual and automated mechanisms, to facilitate endodontic treatment and manage the complications related to it. The aim of the study was to assess post-endodontic pain after using the HyFlex® EDM OneFile (HEDM), WaveOne® Gold (WOG) and XP-endo® Shaper (XPS) systems in the preparation of curved canals in patients with asymptomatic irreversible pulpitis. A total of 45 molars with curved canals and asymptomatic irreversible pulpitis were randomly divided into 3 equal groups based on the instrumentation used: HEDM (group A); WOG (group B); and XPS (group C). All teeth were prepared according to the manufacturers' instructions. Postendodontic pain was assessed using the visual analog scale (VAS) at 6, 12, 18, 24, 48, and 72 h after root canal instrumentation. The data was analyzed using the one-way analysis of variance (ANOVA) and the paired-samples t test with the Bonferroni correction, with a p-value of 0.05 set for statistical significance. The highest levels of post-endodontic pain were recorded at 6 h after treatment. Then, the values gradually decreased until the pain nearly vanished after 72 h. No statistically significant differences were observed in the VAS scores between groups A and B. At the same time, group C showed the lowest VAS scores at all follow-up time points. The use of the XPS system resulted in the lowest pain scores at all follow-ups. The HEDM and WOG groups showed no differences in the pain scores throughout the whole follow-up period.

Evaluation of Canal Transportation Using Single File Rotary Systems, One Shape, Waveone GOLD and Reciproc in Simulated Curved Canals (in Vitro Study)

Objectives maintaining root canal anatomy through minimal canal transportation by using Rotary single file systems: One Shape, Wave One Gold and Reciproc systems used in simulated artificial curved root canals. Materials and Methods 30 simulated curved root canals in clear resin blocks were used in this s tudy and divided into three groups containing 10 samples each: group (1) represented canals instrumented with Rotary One Shape files, group (2) canals instrumented with reciprocating Wave One Gold files while Group (3) canals were prepared with Reciproc files. All canals were imaged pre- and post- instrumentation at three levels, 2,3 and 5 mm apically and compared using Adobe Photoshop software program. Amount of transportation were assessed. The three groups were compared with ANOVA and LSD statistic tests Results the mean transportation at 3mm level of the canal had no significant difference among all groups, all shown transportation. At 2mm, and 5mm levels there were significant difference between groups, G2 shown the least transportation among all groups. Conclusions Within the limits of this study, the canal preparation with Wave One Gold files showed lesser transportation than One Shape and Reciproc files.

A Comparative Evaluation of Centering Ratio of VDW.ROTATE NiTi File in Simulated Curved Root Canals: An In Vitro Study

A Comparative Evaluation of Centering Ratio of VDW.ROTATE NiTi File in Simulated Curved Root Canals: An In Vitro Study

Root canal curvature influences uncontrolled removal of dentin and cleaning efficacy after ultrasonic activation.

This study evaluated the correlation between root canal curvature and the effects of ultrasonic irrigation in the following parameters: volume of uncontrolled dentin removal (UDRVol), maximum depth of dentin defects, removal of accumulated hard tissue debris (AHTD), and canal transportation in prepared curved root canals. Twenty-four human permanent mandibular molars were divided into two groups according to root canal curvature: moderate curvature (MC: mean 25°); and severe curvature (SC: mean 48°). The specimens were scanned using an X-ray microcomputed scanner (Skyscan 1172) before and after cleaning and shaping and after the final irrigation protocol with ultrasonic irrigation. There was a moderate correlation between the degree of root canal curvature and the volume of remaining AHTD (p<0.05) and between the degree of root canal curvature and maximum depth of defects due to uncontrolled removal of dentin (p<0.05). The teeth in the SC group had a greater maximum depth of defects on the dentin wall in the apical third than the teeth in the MC group (p <0.05). Both groups had a significant reduction of AHTD in all canal thirds, but the amount of remaining AHTD in the middle and apical thirds and the whole canal was significantly greater in the SC than in the MC group (p <0.05). Canal transportation was not influenced by the canal curvature in all thirds (p >0.05). This study concluded that root canal curvature affects significantly the uncontrolled removal of dentin and remaining AHTD volume after the final irrigation protocol with ultrasonic irrigation.

Impact of Angle of File Access and Location of Canal Curvature on the Dynamic Cyclic Fatigue of Nickel Titanium Rotary Instruments.

To evaluate the impact of different file access angles and root canal curvature's location on the fatigue failure of One Curve (OC) and E3 Azure (EZ) NiTi files using a dynamic model at simulated body temperature. Eighty new instruments with similar tip sizes and taper (#25/0.06) from two NiTi rotary systems, One Curve and E3 Azure, were tested at simulated body temperatures (37°C) using a custom-made dynamic cyclic fatigue device. Instruments were divided into four subgroups according to the location of root canal curvature (a coronal curve 5 mm from the root canal orifice and an apical curve 10 mm from the root canal orifice) and the angle of file access (0° or 30°). Instruments were operated in simulated stainless-steel canals having a 60° curve and a 3 mm radius. A custom-made device produced controlled vertical pecks during file rotation. Time to failure (sec) was registered, and the length of the fragment segments was measured (mm). Data were analysed statistically with One-Way ANOVA and Tukey post hoc tests. The significance level was set at 5%. All separated instruments were examined by scanning electron microscope. One-way ANOVA (p<0.05) found a significant difference among the tested instruments. Post Hoc analysis revealed lower cyclic fatigue resistance when the angle of file access was 30º, and the root canal curvature was located coronally for both files (p<0.0001). Three-way ANOVA showed that the angle of file access was the most influential contributor to cyclic fatigue, followed by the location of file curvature and, finally, the file type (p<0.0001). The fractographic examination revealed a predominantly ductile fracture mode for all tested instruments. The lengths of all fractured segments showed no significant difference (p>0.05), indicating an accurate trajectory during testing. OC files had superior cyclic fatigue resistance than EZ files; coronal curvatures negatively impacted cyclic fatigue resistance compared to apical curvatures, while the angle of file access presented the highest impact on dynamic cyclic fatigue.

Assessment of Debris Extrusion in Curved Canals: An In Vitro Analysis of Various Single-File Endodontic Instrumentation Systems.

Rotary single-file endodontic systems are commonly used for root canal treatment. However, very few studies have evaluated the apical extrusion of debris generated by these systems during canal preparation at normal body temperature in laboratory conditions. The aim of this study was to evaluate the amount of apically extruded debris caused by seven different single-file endodontic instrumentation systems at body temperature in mandibular molar teeth with curved root canals. One hundred forty mandibular first permanent molars were randomly divided into seven groups (n = 20) to be prepared by one of the following systems at 35°C: Reciproc Blue (REC Blue), WaveOne Gold (WOG), One Reci (OR), Neoniti, HyFlex EDM (HEDM), One Curve (OC), or XP Shaper (XPS). Debris was collected into preweighted Eppendorf tubes. The weight of the extruded debris was recorded by subtracting the weight of the tooth-free apparatus from the post-procedure weight. Data were analyzed by one-way ANOVA and Tukey's tests (p < 5%). REC Blue, WOG, and OR groups extruded significantly more debris from the apex than XPS, OC, and Neoniti groups (p < 0.05). No significant difference was observed among the XPS, OC, Neoniti, and HEDM groups (p > 0.05). All the instruments were associated with debris extrusion. However, REC Blue, WOG, and OR extrude significantly more debris than other instruments. The amount of debris with different files was REC Blue > OR > WOG > HEDM > OC > Neoniti > XPS. XPS, Neoniti, and OC caused significantly less extrusion of debris than REC Blue, WOG, and OR.

Predictive Machine learning Models for necessity Supplemental Anesthesia in Endodontic treatment

Purpose: In cases of irreversible pulpitis, controlling intraoperative endodontic discomfort is extremely difficult, and patient satisfaction plays a big part in this. In order to forecast a diagnostic's and a treatment's outcome, machine learning (ML) has recently been implemented in the fields of medicine and dentistry. The goal of this work was to create machine learning (ML) models that could predict the need for further anesthesia. Methods: According to inclusion and exclusion criteria, this study included 128 individuals with endodontic discomfort. All patients underwent a clinical evaluation and endodontic diagnostic procedures. All interpretation results were entered into a prepared data sheet. All info were statistically evaluated using Github software version ydata-profilling vv4.1.2, configuration config.json, was employed to review the explanatory data for machine learning models for all examination and investigation aspects. By using Pearson correlation, chi 2, Random Forest, and LightGBM, the final feature importance was determined. 20% of the test set and 80% of the train set are observation sets used to build models. Logistic regression F1 and k-nearest neighbors (KNN) F1 were used to assess the performance of the ML model on the train and test sets. Results: For Machine learning models, 11 of the 20 features—such as pulp stone or calcification of the pulp space, pain duration, age, percussion, palpation, response persistent after EPT, dental history, curved root canal, pain persistent after a cold test, and pain severity during a cold test—were important. In logistic regression, F1 for the train set was 0.793, while for the test sets, it was 0.878. Regression using a logistic model had an accuracy of 0.81. KNN F1 for train was 0.781, while for test it was 0.829. The Machine learning model's k-nearest neighbors (KNN) F1 accuracy was 72.86. Conclusion: The trained machine learning models can predict if further anesthetic will be required during endodontic treatment based on the specific feature.

A new method to measure the mechanical properties of rotary endodontic Ni-Ti files: Measurement of 6-axis force/torque and automatic root canal preparation.

The purpose of this study was to develop a new instrument to measure the mechanical properties of rotary endodontic Ni-Ti files (ProTaper Gold F2, ProTaper Ultimate F2, and HyFlex EDM Onefile), and to evaluate the overall utility of the device. The instrument was capable of analyzing the 6-axis force/torque generated by the files during cyclic dynamic movement in a metal curved artificial root canal, and doing automatic cyclic dynamic filing in a resin root canal with a preset vertical force limit by adopting a negative feedback mechanism. By analyzing the 6-axis force/torque, we were able to estimate the position and contact points of the files in the curved root canal. ProTaper Gold showed the highest force/torque in all directions. HyFlex EDM had the highest hysteresis ratio, centering ratio value and NCF (number of cycles to fatigue fracture), while the lowest vertical force.

Effect of preset torque setting on torque/force generation, shaping ability and surface changes of nickel titanium rotary instrument in different root canal curvature locations: An ex vivo study.

The aim of this study was to evaluate how preset torque settings influence the torque, vertical force, and root canal-centering ability of ProGlider and ProTaper NEXT nickel-titanium rotary instruments in canals with different curvature locations. Based on micro-computed tomography, mesial roots of human mandibular molars (25°-40° curvature) were allocated to the apical curvature (apical 1-5 mm) or the middle curvature (apical 5-9 mm) groups, and mandibular incisors (curvature <5°) to the straight canal group. Each group was subjected to automated instrumentation and torque/force measurement with the preset torque of 1, 2.5, or 5 N•cm. Canal-centering ratios were determined with micro-computed tomography. Instrument fracture occurred only in the 2.5 and 5 N•cm groups in curved canals. The preset torque setting and curvature location did not influence canal shaping ability.

Influence of sealer and supplementary approach on filling material removal during endodontic retreatment.

Both root canal sealer-based and supplementary protocols may influence removal of filling material during endodontic retreatment. Mesial root canals of extracted mandibular molars were prepared using HyFlex EDM 25/.08, and filled with a calcium silicate sealer (Bio-C Sealer), or an epoxy resin (AH Plus), using the single cone technique (n = 12). Retreatment was performed using ProDesign Logic (PDL) RT and PDL 35/.05. The specimens were randomly divided into two experimental groups (n = 12), and the sealers were distributed similarly. A supplementary protocol was performed with PDL 50/.01 or XP-endo Finisher. Root canal transportation and volume, in addition to the remaining filling material percentage were evaluated using high-resolution (5 µm voxel size) micro-CT. Statistical analysis was performed using t-tests (α = 0.05). Root canals filled with AH Plus presented high residual filling material (p < 0.05). Both protocols decreased residual volume of filling material in the apical third (p < 0.05). PDL 50/.01 increased the apical root canal volume (p < 0.05). No difference was observed between the systems regarding canal transportation (p > 0.05). In conclusion, AH Plus is more difficult to remove from the apical third than Bio-C Sealer. PDL 50/.01 and XP-endo Finisher enabled greater removal of filling materials in the apical third, in the retreatment of curved root canals, without promoting apical transport.

Evaluation of the stress generated during biomechanical preparation with nickel–titanium rotary endodontic file using finite element analysis

Introduction: Adequate biomechanical preparation of root canals is the essence of successful endodontic therapy. Roots with curved canal framework led to endodontic complexity. The hassles in the preparation of such complex canals have prompted the inauguration of nickel–titanium (Ni-Ti) instruments with properties of shape memory and superelasticity. They benefit root canal preparation with causing less aberration, yet intracanal separation due to fatigue remains a concern. The study was intended to evaluate and compare the stresses developed during biomechanical preparation with Ni-Ti rotary file in straight, moderate, and severely curved root canals using finite element analysis (FEA). Materials and Methods: Six real sizes, three-dimensional root models were designed in SolidWorks software with varying angles of curvature (2°–45°), and using the same software, ProTaper Gold F2 rotary file was developed. All the designed root models with the rotary file inserted into each model were subjected to FEA. ANSYS Software (version 17.2 Company, Commonwealth of Pennsylvania, USA) 2015 was used to simulating root canal shaping, and the stresses generated in all the root canal models were observed. Results: Highest mean stress was observed with 45° models which was 235.95 MPa, followed by a 30° simulated model showed 220.36 MPa and least stress of 125.22 MPa was observed with 2° models (P &gt; 0.05). Conclusions: Increased canal curvature has definitely resulted in generation of more amount of stress.

Radiographic assessment of the effect of conservative access cavity preparation and different root canal tapers preparation on apical transportation of curved root canals (in vitro study)

Radiographic assessment of the effect of conservative access cavity preparation and different root canal tapers preparation on apical transportation of curved root canals (in vitro study)

Numerical investigation of injection characteristics on normal saline irrigation quality in curved root canals using computational fluid dynamics

ObjectivesThe primary aim of this research was to find the effects of Normal saline injection rate and position on irrigation quality in curved root canals. MethodsComputational Fluid Dynamics (CFD) was used to simulate irrigation in root canals. Root canal geometries were obtained by considering the complete shaping of a rotary file in four root groups with 0, 10, 30, and 60° of curvatures. Fluid surface tension, bouncy, gravity, and air entrance were considered in the numerical simulation using Ansys-CFX software. For each root canal, the flow regime and wall shear stresses were calculated at three different syringe plunger speeds, and three different injection locations of a beveled open-ended needle and their effects on the irrigation quality were investigated in this paper. ResultsWall shear stress is considered the main parameter determining irrigation quality. It was calculated for all 36 test cases. Injection rate and normal saline accumulating near the apex and their effects on washed area ratio were shown for the test cases. Results showed significant effects of injection characteristics, incredibly faster injection, and deeper needle position on the irrigation quality of curved root canals. ConclusionsA higher injection rate and deeper needle position are required to achieve the best irrigation quality and a more washed area ratio in root canals with greater curvature.

Evaluation of Apical Transportation and Curve Straightening of Curved Root Canals after Preparation with Different Nickel - Titanium Rotary Systems (Comparative in Vitro Study)

The goals of endodontic preparation were to shape and clean the space of the root canal and remove microorganisms, affected dentin and pulp, the apical foramen and the canal curve should be protected from being transported during endodontic canal preparation. The aim of this study was to evaluate the curve straightening of curved root canals and apical transportation after preparation with four rotary systems. Forty mesial roots of the lower 1st molars teeth only the mesiobuccal canals were used, these roots were immersed into cold clear acrylic , the teeth roots divided into four groups according to rotary system used for preparation of the canals (ten roots for each group):. group I: ProTaper Next rotary system, group II: IRaCe Plus rotary system, group III: HeroShaper rotary system, group IV: ProTaper rotary system, instrumentation were done to size 30 master apical file and with copious irrigation, total amount of 10 ml of 2.5% of sodium hypochlorite (NaOCl) then rinsed the canals with distilled water 5 ml. radiograph was taken for all roots before and after instrumentation in one direction buccolingual using digital radiograph system. The degree of curve straightening of the root canal and the apical transportation were measured using Image J software and Adobe photoshop CS6 software. Statistical analysis was done and the result showed that group IV had the highest mean values in curve straightening and apical transportation, there were significant difference between group IV and all of the other groups and there were non- significant difference between group I , group II and group . All the four used rotary systems produced adequate geometry during canal preparations. However, some apical transportation in ProTaper group was seen, which might need a caution when used protaper in instrumentation of curved canal.

Efficiency and complications in root canal retreatment using nickel titanium rotary file with continuous rotation, reciprocating, or adaptive motion in curved root canals: a laboratory investigation

BackgroundIt is currently unknown whether rotary file motion affects the best outcome of root canal retreatment. This experimental study compared the efficacy, efficiency, and complications of single-use NiTi rotary files using continuous rotation, reciprocating, and adaptive motions in root canal filling removal in curved root canals. Reciproc blue R25 was used with reciprocating motion (RB), VDW.ROTATE retreatment files with continuous rotation (VR), and ProTaper NEXT X2 with continuous rotation (PTNc) or adaptive motion (PTNa).MethodsForty mesial root canals of extracted mandibular first and second molars with an angle of curvature between 20°–40° and a radius of curvature between 5 and 10 mm were collected. The specimens were instrumented and obturated with gutta-percha and AH Plus sealer using the continuous wave of condensation technique. The specimens were randomly divided into 4 retreatment groups (n = 10), RB, VR, PTNc, and PTNa. The percentage of root canal filling removal in each group was analyzed using Micro-Computed Tomography (µCT). The motor running time, total time, root canal complication, and instrument complication were recorded and statistically analyzed (p-value < 0.05).ResultsThe pre-operative root canal curvature and root canal filling volume were comparable among groups. The percentage of root canal filling removal from the whole canal in the PTNc, RB, PTNa, and VR group was 98%, 96%, 95%, and 93%, respectively. A significant difference was observed between the PTNc and VR groups for the whole canal and the apical-third part. The motor running time and total time were significantly different between the groups. Instrument fracture was observed at 40% in the VR and 20% in the PTNa group, but none in the RB and PTNc groups.ConclusionsThe ProTaper NEXT X2 with continuous rotation and RB files can be used with high efficacy and efficiency in curved root canal retreatment. Continuous rotation is more efficacious and efficient than adaptive motion when using the NiTi rotary file. Single file retreatment can be used in small canals with high efficacy, cost-effectiveness, and less time consumption.