Successful individualized endodontic treatment of severely curved root canals in a mandibular second molar: A case report

BACKGROUND

The incidence rate of severely curved root canals in mandibular molars is low, and the root canal treatment of mandibular molars with this aberrant canal anatomy may be technically challenging.

CASE SUMMARY

A 26-year-old Chinese female patient presented with intermittent and occlusal pain in the left mandibular second molar. The patient had undergone filling restoration for caries before endodontic consultation. With the aid of cone beam computed tomography (CBCT), a large periapical radiolucency was observed, and curved root canals in a mandibular second molar were confirmed, depicting a severe and curved distolingual root. Nonsurgical treatments, including novel individualized preparation skills and techniques and the use of bioceramic materials as an apical barrier, were performed, and complete healing of the periapical lesion and a satisfactory effect were achieved.

CONCLUSION

A case of severely curved root canals in a mandibular second molar was successfully treated and are reported herein. The complex anatomy of the tooth and the postoperative effect were also evaluated via the three-dimensional reconstruction of CBCT images, which accurately identified the aberrant canal morphology. New devices and biomaterial applications combined with novel synthesis techniques can increase the success rate of intractable endodontic treatment.

Mandibular incisors with two canals are associated with the presence of the distolingual root in mandibular first molars: a cone-beam computed tomographic study

Background

This study aimed to evaluate the root canal configurations and the association between mandibular first molars and distolingual root (DLR) and mandibular incisors using cone-beam computed tomography (CBCT).

Methods

Mandibular first molars and incisors were evaluated using CBCT images of 150 patients. Mandibular first molars were classified according to the presence or absence of DLR. The curvature of the DLR was evaluated using Schneider’s method in buccolingual and mesiodistal orientations. The angle of the mesiolingual–distolingual–distobuccal canal orifices (ML–DL–DB) was evaluated at the pulpal floor level. The mandibular central and lateral incisors were classified as either single canal or two canals. The association between the root canal system of the mandibular first molar and mandibular incisors was evaluated. Data were analyzed using the Chi-square test, Student’s t-test, and odds ratios from binary logistic regression. The significance level was set at 5%.

Results

The frequency of mandibular first molars with DLR was 27.0% and that of mandibular incisors with two canals was 25.8%. The curvature of the DLR was 37.1° in the buccolingual orientation and 10.4° in the mesiodistal orientation. The angle of ML–DL–DB was 79.0°. The presence of two canal systems in mandibular incisors was associated with the presence of DLR in the mandibular first molar (left central incisors: p = 0.001, odds ratio = 4.25; left lateral incisors: p < 0.001, odds ratio = 3.8; right central incisors: p = 0.003, odds ratio = 3.86; right lateral incisors: p = 0.001, odds ratio = 3.44) but not with the curvature of the DLR or angle of the ML–DL–DB orifice (p > 0.05).

Conclusions

The mandibular first molar showed a high incidence of separate DLRs. It was confirmed that DLR in the mandibular first molar is highly associated with the presence of two-canal system in the mandibular incisors. This association can aid clinicians in successful endodontic treatments.

Three-dimensional analysis of coronal root canal morphology of 136 permanent mandibular first molars by micro-computed tomography

Background/purpose

Minimally invasive endodontic approach become a research hotspot and may prevent the fracture of endodontically-treated teeth. This research aims to measure the coronal root canal morphology of permanent mandibular first molars in 3D and propose a new minimally invasive endodontic approach based on this measurement.

Materials and methods

Data of 136 permanent mandibular first molars were involved and reconstructed in 3D models with canals. Then, the morphology characteristics of the coronal root canal were measured.

Results

Overall, the distribution of root canal orifices was more centralized than other landmarks. The landmarks were located more mesiobuccally to the center of the occlusal plane of molars. Specifically, the measurements of the maximum curvature of coronal root canals in the axial direction were: in 3-canals 2-rooted teeth, the average angles of curvatures were 23°,25°,11° for mesiobuccal (MB), mesiolingual (ML) and distobuccal (DB) canals, respectively; in 4-canals 2-rooted teeth were 23°,25°,12°,16°for MB, ML, DB, and distolingual (DL) canals, respectively; in 4-canals 3-rooted teeth were 25°,27°,17°,39° for MB, ML, DB, and DL canals, respectively. The degrees of coronal root canal curvatures in the horizontal direction were: in 3-canals teeth, the average angles of curvatures were −1°,47°,-2° for MB, ML and DB canals, respectively; in 4-canals 2-rooted teeth were −4°,41°,-25°,48° for MB, ML, DB, and DL canals, respectively; in 4-canals 3-rooted teeth were −3°,33°,-43°,79° for MB, ML, DB, and DL canals, respectively.

Conclusion

The results of this study are similar to those previously obtained using CBCT and can help us design endodontic approaches.

Comparison of Cyclic Fatigue Resistance of Novel TruNatomy Files with Conventional Endodontic Files: An In Vitro SEM Study

AIM AND OBJECTIVE

To compare and analyze the cyclic fatigue resistance of novel TruNatomy files against the conventionally used rotary files and reciprocating files in a simulated canal system with curvatures in the middle, apical portions root, and S-shaped canal employing scanning electron microscopy.

MATERIALS AND METHODS

Endodontic files tested in the study include ProTaper, HyFlex EDM, Reciproc blue, and TruNatomy files operated in a simulated root canal system. A total of 96 files were employed in this study. They were categorized into four groups. Group 1 employed 24 TruNatomy files, group 2 employed 24 ProTaper gold files, group 3 employed 24 HyFlex EDM files, and group 4 employed 24 Reciproc blue files. All the groups employed eight files each under three subgroups namely A, B, and C representing middle, apical, and double curvatures, respectively. Artificial grooves were incorporated in the stainless steel blocks having three different curvatures. All the file systems were operated with a torque-controlled electric motor. The files were engaged in the artificial canal until the occurrence of fracture. The time required for the fracture was noted. Length of fractured tip was measured using the digital Vernier caliper. The number of cycles of failure (NCF) was calculated. The fractured parts were subjected to scanning electron microscope to analyze the mode of fracture.

RESULTS

TruNatomy files had the highest mean NCF values of 588.01 in middle curvature, 1,321 in apical curvature, and 642.5 in S-shaped curvature HyFlex EDM and Reciproc blue file system exhibited comparable cyclic fatigue resistance among them. ProTaper gold file system exhibited least mean NCF values of 158.13 in the middle, 196.5 in the apical curvature, and 116.88 in the S-shaped canal system. Middle portion fractured first than the apical curvature. The mean length of fractured segments was found to be insignificant among the experimental study groups tested.

CONCLUSION

All the file systems employed in the study had good cyclic fatigue resistance while TruNatomy files had the highest cyclic fatigue resistance while HyFlex EDM and Reciproc blue had comparable fatigue resistance. ProTaper gold file system had the least fatigue resistance at different radius of curvature in the simulated canal system in the apical and middle portions and S-shaped root canal.

CLINICAL SIGNIFICANCE

The selection of file systems in cleaning and shaping protocols is an enigma to the endodontics. This in vitro study explored the selection protocols for the execution of root canal preparation. Heat treatment of nickel-titanium (NiTi) endodontic files had improved the cyclic fatigue résistance significantly enhancing the clinical life of file systems.

Factors Affecting the Removal Time of Separated Instruments

INTRODUCTION

Separated endodontic instruments may adversely affect the outcome of endodontic treatment. The combination of ultrasonic techniques and dental operating microscopes appears to be effective in the removal of separated instruments compared with more randomized techniques. This study evaluated the roles of root canal curvature and separated instrument length on the time needed to loosen and retrieve the instrument fragments.

METHODS

The retrieval procedures of 128 separated instruments referred to a private endodontic practice for retreatment by general practitioners were evaluated in patients who were monitored for a minimum of 6 months. Preoperative cone-beam computed tomographic images were used to measure separated instrument lengths in relation to the degrees of canal curvatures. Ultrasonic instruments were used in the initial phase to remove the tooth structure and to loosen the fractured instrument. In the second phase, ultrasonic instruments, wire loops, or XP Shapers (FKG Dentaire SA, La Chaux-de-Fonds, Switzerland) were used for fragment removal. The time periods for all procedures were recorded. Statistical analysis was completed applying log-normal regression, structural equation modeling, and linear regression using Stata Version 14.2 software (StataCorp LLC, College Station, TX).

RESULTS

All separated instruments were successfully retrieved. Using the protocol in this study, 89.8% of the instruments were removed using ultrasonic instruments alone with a mean time of 221 seconds. The instrument removal time was dependent on both the instrument length and the root canal curvature. Additionally, preparation times were proportionately longer with increasing separated instrument lengths when the loop device was required.

CONCLUSIONS

The preparation phase appears to have an important role in the retrieval of separated instruments. Preparation times for both non-loop and loop groups demonstrate that length and curvature are independent predictors of the log-transformed time. Generally, procedure times were extended with increasing file lengths and higher degrees of canal curvature.

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

Objectives

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

Materials and Methods

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

Results

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

Conclusions

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

Root canal curvature as a prognostic factor influencing the diagnostic accuracy of radiographic working length determination and postoperative canal axis modification: an in vitro comparative study

Background

Radiographic analysis of tooth morphology is mandatory for accurate calibration of the degree of canal curvature angle and radiographic working length to its real dimensions in case difficulty assessment protocols. This study aimed to determine the impact of the degree of root canal curvature angle on maintaining the real working length and the original canal axis of prepared root canals using a reciprocating rotary instrumentation technique.

Methods

Radiographic image analysis was performed on 60 extracted single-rooted human premolar teeth with a moderate canal curvature (10°–25°) and severe canal curvature (26°–70°). Working length and longitudinal canal axis were determined using cone-beam computed tomography (CBCT) and digital periapical radiography. The real canal length was determined by subtracting 0.5 mm from the actual canal length. Root canals were prepared using the WaveOne Gold reciprocating file (Dentsply Maillefer, Ballaigues, Switzerland).

Results

There was no significant relation of the degree of canal curvature angle to the accuracy of radiographic working length estimated on CBCT and digital periapical radiographic techniques (P > 0.05). Postinstrumentation changes in the original canal axis between moderate and severe canal curvature angles, assessed on CBCT and periapical digital radiographic images were statistically non-significant (P > 0.05).

Conclusions

A standardized digital periapical radiographic method performed similarly to the CBCT technique near to its true working length. No significant interaction exists between the diagnostic working length estimation, postoperative root canal axis modification, and the degree of canal curvature angle, using reciprocating rotary instrumentation technique.

Efficacy of different irrigation technique in simulated curved root canals

The aim of this study was to assess the influence of the canal curvature on the efficacy of sonically, ultrasonically, and laser-activated irrigation in removing a biofilm-mimicking hydrogel (BMH) from simulated canal irregularities. Transparent resin blocks containing a curved root canal (40° or 60°) were used as test models. A 4-mm groove at 1 mm from the apex was filled with BMH. Five different irrigation procedures were performed (n=20): needle irrigation (NI), EndoActivator (EA), Eddy, ultrasonically activated irrigation (UAI) (Irrisafe), and laser-activated irrigation (LAI) using a pulsed erbium laser (PIPS approach). All protocols were executed for 3×20s. Images of the groove were taken before and after irrigation, and the percentage BMH removal was calculated using image analysis software. In the 40° canal curvature model, the highest BMH removal was observed for UAI (99.9%), yielding a significantly better removal than that of EA (57.2%) and NI (53.8%), but not of LAI (96.8%) and Eddy (99.4%). In the 60° canal curvature model, UAI removed 99.5%, which resulted in significantly greater hydrogel removal than all other groups (P < 0.05). The difference between LAI (82.5%) and Eddy (78.1%) was not statistically significant, but both were more effective than EA (13.5%) and NI (7.3%). Canal curvature negatively affects the cleaning efficacy of different irrigation methods. The effect was most pronounced for the sonic techniques, while this was not the case for UAI. This could be ascribed to the prebent ultrasonic tip. Despite the position of the laser tip at the orifice level, fluid streaming during LAI resulted in substantial BMH removal beyond the curve.

Morphological measurements of two separate mesiobuccal canals in maxillary first molars using micro-computed tomography

OBJECTIVES

To obtain radicular measurements of two separate mesiobuccal (MB) root canals in maxillary first molars using micro-computed tomography (μCT) with customized software.

MATERIALS AND METHODS

Human maxillary first molar MB roots (N = 36) with two separate canals (MB1, MB2) and apical foramina were scanned by μCT and analyzed with Kappa2 software to reconstruct three-dimensional (3D) surface models of roots and canals. These models were sectioned at 0.1 mm intervals perpendicular to the central axis of each canal. Canal widths, 3D curvatures, and surrounding dentine thicknesses were measured concurrently on each section. Dentine thicknesses were analyzed statistically for differences between each direction and the different levels of both canals.

RESULTS

Dentine walls around MB1 were thicker than MB2 (p < 0.05). Thinnest dentine was most often located at disto-inside direction in both canals. Canal widths were significantly smaller in MB2 than MB1 (p < 0.01). Apical constrictions were smaller (p < 0.05) and further (p < 0.05) from the apex in MB2 than MB1. Canal curvatures were greatest in the apical third of both canals (p < 0.001), and they were greater in MB2 than MB1 (p < 0.05).

CONCLUSIONS

MB2 canals had shorter lengths, smaller widths, and more severe curvatures and were surrounded by thinner dentine walls. In MB2, apical constrictions were between 1 and 2 mm from the apex, compared to about 1 mm for MB1.

CLINICAL RELEVANCE

These detailed measurements and in-depth 3D analyses of maxillary first molar MB roots with two separate canals and apical foramina provide morphologic references for root canal therapy.

A Comparison of Mtwo and RaCe Rotary Instruments in the Preparation of Curved Canals

AIM

The aim of this study was to compare the effectiveness of Mtwo and RaCe rotary instruments in cleaning and shaping root canals curvature.

MATERIALS AND METHODS

The present study was conducted on 160 simulated canals in resin blocks with an angle curvature of 15°-30°. These 160 simulated canals were divided into two groups, where each group consisted of 80 blocks. In the first group, the canals were prepared using Mtwo rotary system (VDW, Munich, Germany). In the second group, the canals were prepared using RaCe instruments (La Chaux-De-Fonds, Switzerland). The data were recorded using SPSS version 23 software (Microsoft, IL, USA).

RESULTS

The results obtained by using the Mtwo rotary instruments showed that these instruments were able to clean and shape in the right-to-left motion curved canals, at different levels, without any deviation and in perfect symmetry, with a p value = 0.000. The data showed that greater the depth of the root canal, greater the deviations of the RaCe rotary instruments. These deviations occurred in three levels, which are the following: S2 (p = 0.004), S3 (p = 0.007), and S4 (p = 0.009). The Mtwo files can go deeper and create a greater angle in S4 level (21°-28°) compared to RaCe instruments with an angle equal to 19°-24°.

CONCLUSION

The present study noted a clinical significant difference between Mtwo rotary instruments and RaCe rotary files used for the canal preparation and indicated that Mtwo instruments are a better choice for the curved canals.

CLINICAL SIGNIFICANCE

There are a large number of procedures and instruments used in the preparation of the root canal. Mtwo and RaCe rotary files were the instruments taken under comparison, in order to determine which of them would perform better.

The incidence of nickel-titanium endodontic hand file fractures: A 7-year retrospective study in a tertiary care hospital

Aim:

The present retrospective cross-sectional study aims to evaluate the incidence and factors associated with nickel-titanium hand file fractures in root canal-treated teeth in a tertiary care hospital of western India.

Methodology:

The diagnostic records of intraoral periapical (IOPA) radiographs were analyzed to check for file fractures in the root canal-treated teeth. As a part of standardized departmental protocol, Hand ProTaper Universal file system (Dentsply, India) was used for chemomechanical preparation for root canal treatment. The file fractures were analyzed with reference to age group, type of teeth, curvature of the canal, site of file fracture in the canal, length of file fracture, level of file fracture, distance of the file fracture from the apex, and obturation status of the file-fractured tooth. Chi-square test was applied to assess the significance difference between the tested groups.

Results:

A total of 19,810 IOPA X-rays were screened and 2728 root canal-treated teeth were found and of these 2728 cases, 109 file-fractured teeth were observed.

Conclusion:

The total incidence of file fractures was 3.9/100 root canal-treated cases, and mandibular molars with severely curved canals (>25°) had shown the maximum incidence of file fractures.

Comparative analysis of canal-centering ratio, apical transportation, and remaining dentin thickness between single-file systems, i.e., OneShape and WaveOne reciprocation: An in vitro study

Aim

This study aimed to compare the canal-centering ability, apical transportation, and remaining dentin thickness (RDT) of OneShape and WaveOne (WO) systems using cone-beam computed tomography.

Objective

The objective of this study was to evaluate the efficiency of two rotary systems in maintaining original root canal anatomy.

Materials and Methods

Forty extracted human single-rooted mandibular premolars were used in the present study. Preinstrumentation scans of all teeth were taken, canal curvatures were calculated, and the samples were randomly divided into two groups with twenty samples in each group: Group 1 - OneShape (OS) rotary system and Group 2 - WO reciprocation system. Postinstrumentation scans were performed using DICOM software and the two scans were compared to determine the canal-centering ability, canal transportation, and RDT at 1, 3, and 5 mm from the root apex.

Results

Using Student's unpaired t-test, results were as follows: for canal-centering ability and RDT, Group 1 showed nonstatistically significant difference at 1 and 5 mm, while statistically significant difference (P < 0.05) at 3 mm was obtained. For canal transportation, Group 1 showed statistically significant difference (P < 0.05) at 1 and 3 mm and nonsignificant difference was obtained at 5 mm, but for Group 2, nonstatistically significant difference (P > 0.05) was obtained at 1, 3, and 5 mm. When comparing the RDT between both the groups, the difference was not statistically significant (P > 0.05).

Conclusion

WO single reciprocation file has better canal-centering ability, maintains original canal curvature, causes lesser canal transportation, and preserves more dentine as compared to OS.

Clinical and Radiographic Evaluation of Procedural Errors during Preparation of Curved Root Canals with Hand and Rotary Instruments: A Randomized Clinical Study

Background:

The process of cleaning and shaping the canal is not an easy goal to obtain, as canal curvature played a significant role during the instrumentation of the curved canals.

Aim:

The present in vivo study was conducted to evaluate procedural errors during the preparation of curved root canals using hand Nitiflex and rotary K3XF instruments.

Materials and Methods:

Procedural errors such as ledge formation, instrument separation, and perforation (apical, furcal, strip) were determined in sixty patients, divided into two groups. In Group I, thirty teeth in thirty patients were prepared using hand Nitiflex system, and in Group II, thirty teeth in thirty patients were prepared using K3XF rotary system. The evaluation was done clinically as well as radiographically. The results recorded from both groups were compiled and put to statistical analysis.

Statistical Analysis:

Chi-square test was used to compare the procedural errors (instrument separation, ledge formation, and perforation).

Results:

In the present study, both hand Nitiflex and rotary K3XF showed ledge formation and instrument separation. Although ledge formation and instrument separation by rotary K3XF file system was less as compared to hand Nitiflex. No perforation was seen in both the instrument groups.

Conclusion:

Canal curvature played a significant role during the instrumentation of the curved canals. Procedural errors such as ledge formation and instrument separation by rotary K3XF file system were less as compared to hand Nitiflex.

Comparison Of Pre-Operative Curvature With Postoperative Curvature In Root Canals Treated With K-3 Rotary Systems

BACKGROUND

With root canal treatment, the organic debris and micro-organisms from pulp space is removed and an ideal canal preparation is achieved that is conducive of hermetic obturation. The purpose of this study was to correlate the pre-operative canal curvature with the postoperative curvature in human extracted teeth prepared with K-3 rotary systems.

METHODS

The root canal preparation was carried out on extracted human molars and premolars using K-3 endodontic rotary files. A pre and post-operative image of the teeth using digital radiograph were taken in order to compare pre and post-operative canal curvature. The images were saved in an images retrieval system (Gendex software, USA). Change in the canal curvature was measured using the software measuring tool (Vixwin software, USA). Student paired t-test and Pearson correlation test was applied at 0.05 level of significance.

RESULTS

There is a statistically significant difference between pre-operative and post-operative canal curvature (p-value <0.001) and a strong positive correlation (91% correlation) between pre-operative and post-operative canal curvature in teeth prepared with the K-3 rotary files.

CONCLUSIONS

A significant difference between pre and post instrumentation curvature was found. Degree of canal curvature was not correlated with time taken for canal preparation.

Effect of master apical file size and taper on irrigation and cleaning of the apical third of curved canals

OBJECTIVE

Canal preparation generates a substantial amount of debris and smear layer (SL). The size and taper of the Master Apical File (MAF) affects on penetration of irrigants and subsequently canal cleaning efficacy. The aim of this study was to evaluate the effect of MAF size and taper on penetration of irrigants to the apical third of curved mesiobuccal (MB) canals of mandibular first molars.

MATERIALS AND METHODS

Eighty-nine human mandibular first molars were divided into one control group (n=5) without rotary instrumentation and 6 experimental groups (n=14 each) that were prepared with the following RaCe rotary files as MAF: 25.04 (group1), 25.06 (group 2), 30.04 (group 3), 30.06 (group 4), 35.04 (group 5) and 35.06 (group 6). All the experimental groups were rinsed with 2 ml of 17 % EDTA followed by 2 ml of 5.25% NaOCl. Debridement of the MB canals was evaluated using scanning electron microscope (SEM). The data were statistically analyzed using Kruskal-Wallis and Mann-Whitney U tests (P<0.05).

RESULTS

Group 6 (MAF=35.06) showed 100% acceptable debridement. This rate was 92.9% for MAF=35.04. In group 4 (MAF=30.06) smear layer (SL) was removed in the three-forth of the samples and debris was removed in 92.9% of them. Acceptable debridement was not achieved in most samples of groups 1 and 2 (25.04 and 25.06, respectively) and the mentioned two groups had statistically significant difference in this respect with the other groups (P<0.05).

CONCLUSION

Based on this study, 30.06 may be considered as the minimum MAF size for acceptable debridement.

Evaluation of surface preparation and maintenance of canal curvature following instrumentation with hand 'K' file and three different Ni-Ti rotary systems: A radiographic and SEM study

Aim:

To determine the shaping ability and cleaning efficiency of hand K-flexofiles, ProTaper, LightSpeed and Mtwo instruments during the preparation of curved root canals in extracted human teeth.

Materials and Methods:

A total of 120 root canals of mandibular and maxillary molars with curvature more than 20° were divided into four groups of 30 each. In group A, canals were prepared using hand K-flexofiles following the crown down technique. In group B LightSpeed, in group C ProTaper, and in group D Mtwo rotary instruments were used to prepare the root canals. Using pre- and post-instrumentation radiographs, straightening of the canal curvature was determined with Corel Draw 9.0 software tools. The amount of debris and smear layer were quantified at three different areas (coronal, middle, and apical thirds) of root canal using SEM. The collected data were analyzed statistically using Student's paired ‘t’ test.

Results:

The mean change in curvature for hand K-files was 7.71°, for ProTaper files 6.03°, for Mtwo 5.43°, and for LightSpeed instruments were found to be 4.57°. The percentage change in the curvature for all the four groups was statistically highly significant (P< 0.01). LightSpeed instruments maintained the original canal curvature significantly (P< 0.01) better than the other instruments. For leftover debris, the minimum percentage was found to be associated with ProTaper (65.48%) followed by Mtwo (66.22%), LightSpeed (71.67%) and the maximum with hand K-files (74.16%). However, the difference in mean leftover debris between ProTaper and Mtwo was not significant.

Conclusion:

ProTaper and Mtwo resulted in good cleaning, and LightSpeed maintained the original canal curvature better than the ProTaper, Mtwo, or Hand K-files.