Reciproc Research Articles

Apically extruded debris of different file systems used with various kinematic movements during retreatment: An in vitro study.

This study aimed to examine the amount of apically extruded debris and time during retreatment with five current file systems, which exhibit various kinematic movements. One hundred upper central incisors were shaped with manual files and filled using the thermoplastic injection method. The root canal fillings in each group (n=20) were removed using the Genius (GN), ProTaper Next (PTN), Reciproc (RCP) Blue, Tango-Endo (TE) and Twisted File Adaptive (TFA) file systems. The apically extruded debris was collected in preweighed Eppendorf tubes. Time to reach working length and total time were also recorded. The PTN, RCP Blue and TFA instruments caused significantly less apically extruded debris and shorter total retreatment time than the GN and TE file systems (p < 0.05). The time to reach the working length was the shortest in the PTN group compared to the other groups (p < 0.05). All file systems extruded debris while removing the root canal filling.

AN INVESTIGATION OF THE METAL FATIGUE OF DIFFERENT NICKEL-TITANIUM ROTARY INSTRUMENTS AFTER PROLONGED USE

Objective:This study aimed to compare the cyclic fatigue (CF) resistance of nickel-titanium (Ni-Ti) endodontic instruments from ProTaper (PTU), ProTaper Next (PTN), Wave One (WO), and Reciproc (RPC). Materials and Methods:In our study, PTU, PTN, WO, and RPC rotary files were divided into the experimental and control groups containing an equal number of samples. The experimental group files were used in the shaping of 80 extracted human lower premolar and lower molar teeth. The experimental and control group kits were then placed in the test apparatus and observed until they fractured. Fracture times were recorded and statistically evaluated. Results:In the one-to-one comparisons of the experimental and control group files, while the differences between the fracture times of the experimental and control group files were found to be statistically insignificant in RPC, WO, PTU, and PTN X1 files (p&amp;gt;0.05), fracture time differences were statistically significant in all PTN X2 files (p&amp;lt;0.05). As a result of the pairwise comparison of the experimental and control groups, the difference between the experimental and control groups of the WO and RPC files used with reciprocal movement was found to be statistically insignificant (p&amp;gt;0.05). Conclusion:The files used with reciprocal movement were found to be safer in terms of metal fatigue when compared to the other files used with rotational movement after the preparation.

Influence of ultraconservative access cavities on instrumentation efficacy with XP-endo Shaper and Reciproc, filling ability and load capacity of mandibular molars subjected to thermomechanical cycling.

To evaluate the influence of ultraconservative access cavities (UltraAC) on canal shaping and filling ability and load capacity of mandibular molars after root canal preparation with XP-endo Shaper (XP) or Reciproc (RC), under simulated clinical conditions. Traditional access cavities (TradAC) were used for comparison. Forty extracted mandibular molars were scanned by micro-computed tomographic and, based on similar anatomical features, were divided into four groups (n=10), according to the type of access cavity and canal instrumentation protocol: TradAC/RC, TradAC/XP, UltraAC/RC and UltraAC/XP. All root canal procedures were performed with the teeth placed in a dental mannequin. Teeth were scanned after root canal instrumentation and filling. Unprepared canal area, dentine removed, accumulated hard tissue debris (AHTD), canal transportation, presence of voids and filling material remnants within the pulp chamber were analysed. After restorative procedures, the teeth were subjected to thermomechanical cycling and to a load capacity test. Statistical analyses were performed using two-way anova test, considering the randomized blocks design (P<0.05). The percentage of unprepared canal area was significantly lower in TradAC groups when compared to UltraAC groups (P<0.05), regardless of the instrument used. The UltraAC/XP group had significantly lower percentage of root dentine removed when compared to other groups (P<0.05). UltraAC/XP and TradAC/XP groups had significantly lower percentages of AHTD than UltraAC/RC and TradAC/RC groups (P<0.05). Regarding canal transportation, in the MB root canals, the TradAC/XP group had significantly lower values than other groups (P<0.05). In general, in ML and distal root canals, TradAC/XP and UltraAC/XP groups had significantly lower values of canal transportation when compared to other groups (P<0.05). Moreover, the UltraAC/RC had the greatest canal transportation values in MB and distal canals. The UltraAC groups had significantly greater percentages of voids and volume of remaining root filling material within the pulp chamber after cleaning procedures than TradAC groups (P<0.05). There was no difference in the load capacity amongst groups (P<0.05). The UltraAC/XP and UltraAC/RC groups had significantly greater areas of unprepared canal walls, significantly more voids and volume of root filling material remnants within the pulp chamber after canal filling. UltraAC/XP was associated with significantly less root dentine removal and significantly more AHTD whilst TradAC/XP had overall significantly less canal transportation. No differences were observed in the load capacity amongst groups.

Comparative Analysis of Continuous versus Reciprocating Instruments in Retreatment of Flat-oval Root Canals.

Flat-oval root canals of incisors can be problematic in retreatments. This study assessed the efficacy of continuous and reciprocating rotation instruments in retreatment of flat-oval root canals in lower incisors via micro-computed tomography (micro-CT). File systems studied were ProTaper universal retreatment rotary system associated with ProTaper Next (PTUR+PTN), D-RaCe associated with iRaCe (DR+iR), Reciproc (REC), and WaveOne (WO). Thirty-two mandibular incisors with flat root canal were divided into 4 groups (n=8). The groups were initially prepared with PTN, iRaCe, REC, and WO, then instrumented, filled, and subjected to micro-CT analyses. All the canals were then retreated with the PTUR+PTN, DR+iR, REC, and WO, and then subjected to new micro-CT analysis which allowed quantification of residual filling material volume and change in the diameter of the root canal apical third. Endodontic retreatment time was also quantified. Data were analyzed with One-Way ANOVA and post hoc t tests. None of the systems completely removed the filling material. The groups differed in terms of remnant filling material volume (PTUR+PTN=2.9±1.1 mm3; DR+iR=3.6±3.1 mm3; REC=4.9±1.9 mm3; WO=3.1±1.9 mm3) and retreatment time (PTUR+PTN=1:36±0:12 sec; DR+iR=0:57±0:13 sec; REC=2:10±0:44 sec; WO=2:03±0:31 sec), but had similar values in terms of change in apical root canal diameter (P>0.05). Based on this in vitro study, the type of endodontic instrument did not affect the diameter of the root canal apical third. However, PTUR with ProTaper Next had the lowest residual filling material volume and second lowest retreatment time, in flat-oval root canals in mandibular incisors.

Postoperative Pain After Using Reciprocating Motion with Reciproc Files Versus Adaptive Motion with Twisted File Adaptive in Instrumentation of Necrotic Mandibular Molars: A Randomized Clinical Trial.

Objective:The objective of the present study was to assess the effect of using Reciproc (RC), (VDW GmbH, Munich, Germany) files with reciprocating motion versus Twisted File Adaptive (TFA, Kerr, Orange, California, USA) system with adaptive motion on post-instrumentation and post-obturation pain of necrotic mandibular molars.Methods:Fifty-eight patients with mandibular molar assessed at 3 intervals; 6, 12 and, 24 hrs. Mann Whitney U and Friedman test was used for data analysis, and the significance level was set to (P≤0.05).Results:There was no statistically significant difference in the mean values of post-instrumentation pain at each time interval for the RC and TFA groups (P>0.05). Pain decreased in each group with a statistically significant difference from preoperative condition to all six post-instrumentation time intervals (P<0.001). In each group, post-instrumentation mean pain values at 6, 12, and 24 hrs were higher than post-obturation pain values at 6, 12, and 24 hrs with a statistically significant difference (P<0.001).Conclusion:TFA and RC had a similar impact on post-instrumentation and post-obturation pain. The post-instrumentation pain was higher than post-obturation pain in both groups.

Synchrotron radiation-based micro-computed tomographic analysis of apical transportation of different Nickel-Titanium rotary systems in curved root canals: An in vitro study.

In the last few decades, the availability of synchrotron sources has initiated revolutionary advances in X-ray imaging. The study aimed to evaluate the incidence of apical transportation after root canal preparation with ProTaper Gold (PTG), Hyflex electro discharge machining (HEDM), Reciproc (RPC), and WaveOne Gold (WOG) using synchrotron radiation-based micro-computed tomographic (SR-μCT) analysis. Forty mandibular molars were assigned to four experimental groups (n = 10) according to the file system used for the root canal preparation: Group 1: PTG (25/0.08), Group 2: HEDM (25/0.08), Group 3: RPC (25/0.08), and Group 4: WOG (25/0.07). The specimens were scanned on SR-μCT system before and after the root canal preparation. Apical transportation was assessed at 1, 2, 3, 4, and 5 mm section. Two-way analysis of variance and Wilcoxon Mann-Whitney test was used. No significant difference was found between the groups. Transportation in the mesial direction was of greater magnitude than distal transportation for all the files systems. SR-μCT can be used as a reliable diagnostic tool for further implications.

Safety of large preparation with different instruments in the buccal canals of maxillary molars.

This study aimed to evaluate the influence of large apical preparations with Reciproc (REC), Hyflex CM (HCM) and Twisted File Adaptive (TFA) systems using micro-computed tomography (MCT). Ninety mesiobuccal (MB) and distobuccal (DB) root canals of maxillary molars (n=45) were scanned using MCT before and after the shaping procedures. The root canals (n=15) were prepared until REC 40.06, HCM 40.04 and TFA 35.04. The root canal transportation (RCT), centring ability (CA), change in volume of the root canal and at different levels (VC), remaining dentine thickness (RDT), removal of dentine wall (RDW) and working time (WT) were evaluated. Data were analysed using the Kruskal-Wallis and Dunn tests, and the one-way ANOVA and Tukey tests with a level of significance set at 5%. No significant difference among the instruments was found regarding the RCT, CA, RDT, RDW and WT (P>0.05), in larger apical preparations in curved MB and straight DB canals of maxillary molars.

Micro-CT analysis of dentinal microcracks on root canals filled with a bioceramic sealer and retreated with reciprocating instruments

This study aimed to analyze the potential occurrence of dentinal defects after the removal of a root canal filling with two different sealers using Reciproc (RC) or Reciproc Blue (RB). The mesial roots of 60 mandibular molars with a Vertucci type IV configuration were selected. The samples were initially instrumented with Reciproc (R25) and then divided into the following four experimental groups according to the endodontic sealer and retreatment instrument (n = 15): BC Sealer/Reciproc (BCRC); BC Sealer/Reciproc Blue (BCRB); AH Plus/Reciproc (AHRC); and AH Plus/Reciproc Blue (AHRB). Then, the samples were scanned under micro-CT after obturation and removal of the filling material. Two analyses were conducted. First, an evaluation was performed on all the axial images, and another analysis evaluated each millimeter of the 10 mm from the apex. Dentinal defects were observed in all the samples. All of the identified defects in the images after filling material removal were present in the corresponding images after obturation. The use of AH Plus and EndoSequence BC Sealer, and filling material removal using RC and RB instruments did not induce dentinal defects.

Synchrotron radiation-based micro-computed tomographic analysis of dentinal microcracks using rotary and reciprocating file systems: An in vitro study.

Background:Advances in both X-ray sources and X-ray optics have dramatically improved the feasibility of these techniques in various fields.Aims:We aimed to evaluate the frequency of dentinal microcracks observed after root canal preparation with ProTaper Gold (PTG), Hyflex electrodischarge machining (HEDM), Reciproc (RPC), and WaveOne Gold (WOG) using synchrotron radiation-based micro-computed tomographic (SR-μCT) analysis.Subjects and Methods:Forty mandibular molars were assigned to 4 experimental groups (n = 10) according to the file system used for the root canal preparation: Group 1: PTG (25/0.08), Group 2: HEDM (25/0.08), Group 3: RPC (25/0.08), and Group 4: WOG (25/0.07). The specimens were scanned on SR-μCT system before and after root canal preparation. The pre- and postoperative cross-sectional images (N = 183,200) of the mesial roots were screened to identify the presence of dentinal microcracks. The number of microcracks was determined as a percentage for each group.Statistical Analysis:There was no necessity of statistical analysis in the present study. The number of microcracks was determined as a percentage for each group.Results:Among the four file systems tested, HEDM (0.9%) has shown a fewer number of new dentinal microcracks.Conclusions:SR-μCT can be used as a reliable diagnostic tool for further implications.

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

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

Assessment of mechanical properties of WaveOne Gold Primary reciprocating instruments.

This study aimed to evaluate cyclic fatigue resistance and bending properties and torque/force generation of WaveOne Gold (WOG) Primary in comparison with WaveOne (WO) Primary and Reciproc (RE) R25. A cyclic fatigue test revealed that the WOG Primary took significantly longer time to fracture compared with the WO Primary (p<0.05). The WOG Primary had the smallest load values at a deflection of 0.5 and 2 mm (p<0.05), as measured with a cantilever bending test. Torque/force measurement demonstrated that maximum upward force and maximum counterclockwise torque values in the WOG Primary were significantly lower than those in the RE R25 (p<0.05). Under the present experimental condition, the WOG Primary showed a higher cyclic fatigue resistance compared with the WO Primary, a higher flexibility compared with the WO Primary and RE R25, and generated a significantly lower maximum torque compared with the RE R25.

Transportation assessment in artificial curved canals after instrumentation with Reciproc, Reciproc Blue, and XP-endo Shaper Systems.

In the present study, we compared the transportation of three different instrumentation systems in different levels of standardized artificial curved canals. Sixty epoxy resin blocks containing simulated canals were divided into three groups (n=20) according to the instrument used for canal preparation: Reciproc (REC), Reciproc Blue (REC Blue), and XP-endo Shaper (XPS). Pre- and post-instrumentation digital images of each specimen were superimposed by Photoshop software to evaluate the different amount of transportation. The Kruskal-Wallis and Wilcoxon were the non-parametric tests applied for the intergroup and intragroup analyses, respectively. The significance level was set at 5%. The XPS showed significantly less canal transportation than REC Blue at five levels (P<0.05) and significantly less canal transportation at seven evaluated levels when compared with the REC (P<0.05). REC Blue showed significant less canal transportation than REC at four of the eight evaluated levels (P<0.05). All evaluated instruments showed a significantly higher amount of resin removal toward the inner wall compared to the outer wall of the curvature (P<0.001). Although the XPS showed significantly less canal transportation than REC and REC Blue, all systems produced transportation from the original canal anatomy.

Comparative evaluation of shaping ability of rotary and reciprocating nickel-titanium single file instruments on simulated root canals

Introduction: Effective cleaning of the root canal system is the primary objective of rotary instrumentation. For three-dimensional obturation of the root canal system, ideal preparation should have a continuously tapering funnel shape from the orifice to the apex. The study aimed to evaluate the shaping ability of two rotary and two reciprocating nickel-titanium (NiTi) single-file instruments on simulated root canals using image analysis software. Materials and Methods: Forty resin blocks with simulated canals of 30° curvature were divided into four experimental groups containing ten samples in each group. The canals were prepared using Reciproc (VDW, Munich, Germany), WaveOne (Dentsply, Maillefer, Ballaigues, Switzerland), OneShape (Micro-Mega, Besancon, France), and F360 (Komet, Brasseler, Lemgo, Germany) size 25 NiTi systems using X Smart Plus (Dentsply). Pre- and post-preparation canals were photographed in a standardized manner and were superimposed. The inner and outer walls of canal curvature were evaluated to determine the most significant change using the image analysis software. Results: The amount of resin removed from the inner walls was less with rotary single-file NiTi systems when compared with reciprocating. Preparation time was less with rotary instruments. No instrument separation was noted. All instrument systems maintained the original canal curvature. Conclusion: Rotary single-file systems maintained the canal curvature better than reciprocating single-file systems.

Influence of different motions on the cyclic fatigue resistance of Reciproc and Reciproc Blue endodontic instruments.

Aim:The aim of this study was to evaluate the cyclic fatigue resistance of Reciproc (RCP) and RPC Blue (RCPB) instruments used in continuous rotation, “RECIPROC” mode, and “WAVEONE” mode.Materials and Methods:Sixty RCP and 60 RCPB R25 files were used. For each file type, three groups (n = 20) were defined depending on the used kinematics: continuous rotation, “RECIPROC” mode, and “WAVEONE” mode. A stainless-steel artificial canal with 60° angle and 5-mm radius of curvature was milled reproducing the size and taper of the used files. The test device was electrically heated to 35°C to simulate the clinical environment. All files were reciprocated or rotated until fracture. The time to failure and the length of the fractured fragments were measured. A fractographic examination was performed by scanning the electron microscopy to confirm the cause of fracture. Collected data underwent a two-way analysis of variance (α = 0.05).Results:RCPB files exhibited better cyclic fatigue resistance than RCP. The “RECIPROC” motion yielded greater cyclic fatigue resistance than the “WAVEONE” movement; the least resistance was observed in the continuous rotation groups. No significant differences were found among groups in terms of length of the fractured fragment. The fractographic analysis confirmed that all scanned samples separated due to cyclic fatigue.Conclusions:Within the limitation of the present study, the “RECIPROC” mode increased the cyclic fatigue resistance of the tested instruments compared to “WAVEONE” mode and continuous rotation. To prevent RCP and RCPB file separation, motion kinematics other than the native “RECIPROC” movement should be discouraged in the clinical setting.

Evaluating the cutting efficiency of NiTi instruments with reciprocating motions

Aim: This study tested a setup for in vitro experimental analysis of axial forces and torque during the preparation of artificial canals using nickel-titanium reciprocating endodontic files. Methods: The cutting efficiency of Reciproc (RC) and WaveOne (WO) reciprocating size 25/.08 instruments (n = 10) was evaluated, taking into account their dimensional and geometrical features. Measurements of the diameter at each millimeter from the tip, pitch length, helical angle, and cross-sectional design and area were assessed. Cutting efficiency tests were carried out on a specific bench device by measuring the torque and axial force required during artificial canal shaping. Statistical analysis was performed using one-way ANOVA (α = 0.05). Results: The WO samples showed larger A3 mean values than did the RC instruments (P &lt;.0001), despite having equal diameters at 3mm from the tip (D3) (P = .521). The mean values of pitch length were higher for RC than for WO instruments (P &lt;.0001), with consequently smaller helical angles (P &lt;.0001). For the cutting efficiency tests, the required torque was lower for the RC group when compared to the WO group, but it was significant only in the first stage of insertion in the artificial canals (P = .008). Regarding the apical force, the RC instruments reached higher values when compared to the WO instruments (P = .04) in the second stage of cutting action. Conclusion: Reciproc instruments demonstrated statistically higher cutting efficiency when compared to WaveOne instruments.Uniterms: cutting efficiency; M-Wire; reciprocating motion; Reciproc; WaveOne

Residual smear layer after root canal instrumentation by using Niti, M-Wire and CM-Wire instruments: A scanning electron microscopy analysis.

Objective:The purpose of this study was to compare the amount of residual smear layer after root canal instrumentation by using Ni-Ti, M-Wire, and CM-Wire instruments.Materials and Methods:Seventy-two mandibular incisors were randomly divided into six groups according to the system used: WaveOne (WO), Reciproc (RP), Unicone (UC), ProTaper Next (PN), Mtwo (MT), and HyFlex (HF). Afterward, the specimens were cleaved in the mesiodistal and buccolingual direction for analysis by scanning electron microscopy.Results:Considering both directions and root canal thirds, there was no difference between HF, MT, and PN. RP, UC, and WO presented a significant difference between the directions, and the cervical third showed a significantly smaller quantity of residual smear layer compared with the apical third. When the systems were compared among them, there was a significant difference only between RP and WO.Conclusions:Residual smear layer observed after instrumentation with the different systems was similar, except for quantities between the reciprocating systems.

Evaluation of four instruments with different working motion using artificial plastic model with C-shaped single canal

The purpose of this study was to evaluate four instruments with different working motion for preparation of a C-shaped single canal wall using the same artificial plastic models reproduced from a human tooth. One tooth with root canal morphology C1 (the shape is an uninterrupted “C” with no separation or division) was selected among three-dimensional micro-computed tomography (micro-CT) imaging data of extracted human teeth. Imaging data were then converted into STL form data, and twenty-four C-shaped root canal model blocks were manufactured using this STL form data. These blocks were randomly divided into four groups of six blocks each and instrumented as follows: stainless steel K-files (SSK), Self-Adjusting File (SAF), ProTaper NEXT (PTN) and RECIPROC (REC). Micro-CT images taken before and after canal preparation were superimposed, and instrumented canal area, percentage of instrumented canal area, part of instrumented canal area, volume of instrumented canal and time taken for instrumentation were evaluated for each group. The greatest instrumented canal area, percentage of instrumented canal area and volume of instrumented canal were as follows (in decreasing order): SSK > SAF > PTN > REC (P < 0.05). The longest time taken for instrumentation was as follows (in decreasing order): SAF > SSK > PTN > REC (P < 0.05). The conscious shaping of SSK and the lattice structure of SAF were instrumented all root canal walls equally. PTN and REC required less time taken for instrumentation, but showed unequal instrumentation.

Apically extruded debris associated with different instrumentation systems and irrigation needles

Aim Of this study is to compare apically extruded debris associated with canal shaping using 2Shape, ProTaper Universal and Reciproc systems using two different irrigation needle tips, open-ended and side-vented. Patients and methods Sixty freshly extracted human mandibular premolars were randomly divided into six groups (n = 10) as follows; group 1 and 2, 2Shape system was used in root canal preparation, in groups 3 and 4, ProTaper Universal preparation system was used, but In groups 5 and 6, Reciproc preparation was performed. In groups 1, 3 and 5 irrigation was done with open-ended needle while in groups 2, 4 and 6 side-vented needle was used. One Eppendorf tube for each tooth was weighed with an electronic weighing machine before instrumentation procedures. During instrumentation, irrigation was performed after every instrument with 1 ml distilled water. On completion of the preparation, teeth were removed from the Eppendorf tubes. All of the tubes were incubated at 37°C for 15 days, to evaporate the irrigant. After the incubation period, the tubes were weighed again. The difference between initial and final tubes weights was calculated, and statistical evaluation was performed using two-way analysis of variance at 5% level of significance. Results A statistically significant difference was observed between all groups (P≤0.05). The highest mean extruded debris value was recorded with group 3 while the lowest value was recorded with group 6. Open-ended needles were associated with significantly more extruded debris than side-vented needles regardless of the instrumentation system used (P≤0.05). Conclusion All the tested rotary instruments resulted in extrusion of debris beyond the apical foramen to an extent but Reciproc system is associated with less amount of apically extruded debris in comparison with 2Shape, ProTaper Universal systems. Side-vented needles extruded significantly less debris than open-ended needles.

Effects of Reciproc, ProTaper Next and WaveOne Gold on Root Canal Walls: A Stereomicroscope Analysis.

Introduction:The aim of this study was to analyse the potential occurrence of dentinal defects after root canal preparation using three engine-driven instruments. Methods and Materials:Eighty permanent mandibular incisors were selected. Twenty teeth did not undergo preparation, and the remaining teeth were divided into three groups (n=20): Reciproc (REC), ProTaper Next (PTN) and WaveOne Gold (WOG). The samples were dyed with methylene blue, sectioned perpendicularly to the long axis in 3-, 6- and 9-mm slices and were finally observed under a stereomicroscope (under 25×). The absence/presence of dentinal defects was documented by two blind observers. The data were analysed using Pearson’s chi-squared test with a confidence level of 95% (P=0.05). The time to prepare the samples was recorded, and the groups were compared using F-test (ANOVA). Results:The control group did not present any defects, and the differences between the control and experimental groups were statistically significant (P<0.05). WOG, PTN and REC caused microcracks on 60%, 33.33% and 18.33% of the samples, respectively. No significant differences between the groups in the 3-mm sections (P=0.126) were observed. There were significant differences in the 6-mm (P=0.042) and 9-mm sections (P<0.001). When WOG and PTN were used to perform root canal preparation, a significant difference was found in the average time (P=0.047). Conclusion:All the used instruments caused dentinal defects in the root dentin. All the instruments were used to perform the preparation with a similar average time.

A micro-computed tomographic evaluation of dentinal microcrack alterations during root canal preparation using single-file Ni-Ti systems.

The aim of the present study was to evaluate the length of dentinal microcracks observed prior to and following root canal preparation with different single-file nickel-titanium (Ni-Ti) systems using micro-computed tomography (micro-CT) analysis. A total of 80 mesial roots of mandibular first molars presenting with type II Vertucci canal configurations were scanned at an isotropic resolution of 7.4 µm. The samples were randomly assigned into four groups (n=20 per group) according to the system used for root canal preparation, including the WaveOne (WO), OneShape (OS), Reciproc (RE) and control groups. A second micro-CT scan was conducted after the root canals were prepared with size 25 instruments. Pre- and postoperative cross-section images of the roots (n=237,760) were then screened to identify the lengths of the microcracks. The results indicated that the microcrack lengths were notably increased following root canal preparation (P<0.05). The alterations in microcrack length in the OS group were more significant compared with those in the WO, RE and control groups (P<0.05). In conclusion, the formation and development of dentinal microcracks may be associated with the movement caused by preparation rather than the taper of the files. Among the single-file Ni-Ti systems, WO and RE were not observed to cause notable microcracks, while the OS system resulted in evident microcracks.