HyFlex CM Research Articles

Effect of immersion in sodium hypochlorite on cyclic fatigue resistance of RaCe, HyFlex CM and XP-endo shaper files

This study assessed the effect of sodium hypochlorite on cyclic fatigue resistance of RaCe, HyFlex CM and XP-endo Shaper files. In this in vitro, experimental study, 90 RaCe, HyFlex CM and XP-endo Shaper files (n = 30 of each) were divided into two groups (n = 45). Group 1 included 15 files of each rotary system, which were immersed in 37°C sodium hypochlorite (5.25%) for 5 min. Group 2 files were immersed in 37°C saline for 5 min. The files underwent cyclic fatigue testing using simulated root canals in which, the rotary files could freely rotate until fracture. Time of fracture was recorded by a chronometer and the number of cycles until fracture was calculated. Data were analyzed using two-way ANOVA and Bonferroni test (α = 0.05). No significant difference existed in the mean number of cycles or rotation time of files between saline and sodium hypochlorite (P > 0.05). The mean rotation time of RaCe was significantly shorter than that of HyFlex and XP-endo Shaper in both solutions (P < 0.05). The mean number of cycles of RaCe was significantly lower than that of HyFlex and XP-endo Shaper files in both solutions (P < 0.05). The mean number of cycles of HyFlex was significantly lower than that of XP-endo Shaper (P < 0.05). Immersion of rotary files made of different alloys in 5.25% sodium hypochlorite for 5 min had no effect on their fracture resistance. However, type of file alloy affected its fatigue resistance such that XP-endo Shaper showed the highest and RaCe showed the lowest fatigue resistance.

Comparative evaluation of bending property and torsional resistance of three nickel–titanium files: A finite element analysis

Aims: We aimed to investigate the effect of instrument length on the torsional resistance and bending property of three nickel–titanium files, namely ProTaper Gold (PTG), ProTaper Next (PTN), and HyFlex CM (HCM) using finite element analysis.Materials and Methods: Three-dimensional models of each aforementioned system were created using the computer-assisted design (CAD) software SolidWorks® 2016 (Dassault Systèmes, SolidWorks Corp., Concord, MA, U. S.). Then, all models were imported to the ANSYS® Workbench 16 (Canonsburg, PA, U. S.) where the simulation was computed. The boundary conditions used to simulate the behavior of the endodontic instruments were in compliance with the ISO 3630 1 specification standards.Results: It was observed that in bending test, HCM model exhibited load of 510.35 MPa with displacement of 6.05 mm, followed by PTG model (465.48 MPa) and 11.21 mm displacement, then PTN file model (440.74 MPa) and 10.30 mm displacement, whereas in torsional test the rigidity curve for HCM file (1.9673 N mm/Radian) lies much below PTG (6.4615 N mm/Radian) which clearly shows that HCM is flexible as compared to PTG and PTN.Conclusion: Considering the high flexibility of the HCM file, it can be effectively used in severely curved root canals and PTG and PTN files in moderately curved root canals. It was also recommended that HCM files should not be kept in canals for a longer time because stresses might reach to ultimate level quickly which can cause fracture.

Dentinal defects after root canal preparation with rotary nickel-titanium files using different irrigants: An in vitro study.

Aim:This in vitro study aims to detect the dentinal defects associated with different irrigants during biomechanical preparation using rotary nickel-titanium (Ni-Ti) files (Hyflex CM).Materials and Methods:For the study, 120 extracted mandibular incisors were taken. Depending on the irrigant used, teeth were divided into six groups (n = 20). In Group 1, teeth were not biomechanically prepared considered as, control group. In Group 2, Group 3, Group 4, Group 5, and Group 6, biomechanical preparation was with Hyflex CM rotary Ni-Ti files using saline, 3% sodium hypochlorite (NaOCl), 17% ethylenediaminetetraacetic acid (EDTA), SmearClear, and 2% chlorhexidine (CHX), respectively, as irrigant. IsoMet Saw was used to section samples at 3, 6, and 9 mm from the apex perpendicular to the long axis of tooth. Segments were seen at 30x magnification under a digital stereomicroscope.Statistical Analysis:Statistical analysis was done using two-tailed t-test.Results:Maximum number of dentinal defects was seen with 17% EDTA, followed by 3% NaOCl, SmearClear, and 2% CHX.Conclusions:Irrigation with 17% EDTA causes more dentinal defects as compared to irrigation with 3% NaOCl, SmearClear, and 2% CHX.

Heat-treated NiTi instruments and final irrigation protocols for biomechanical preparation of flattened canals.

This study evaluate shaping ability of heat-treated NiTi-alloy instruments associated with different final irrigation protocols in flattened root canals. Thirty human mandibular incisors with flattened root canals were divided into 5 groups (n = 10): (XP) Original Protocol XP-endo Shaper; (XP-WT) Original Protocol XP-endo Shaper with working time variation; (XP-K) XP-endo Shaper with kinematics variation; (XP-WTK) XP-endo Shaper with kinematics and working time variations; (Hyflex) Hyflex CM. For the variation in working time protocols the same sample of the XP-endo Shaper groups with and without kinematic variation were used. To evaluate final irrigation protocols, groups 1, 3 and 5 were submitted to 3 protocols: (NI) No irrigation (n = 2); (CI) conventional irrigation (n = 4), and (EndoVac) irrigation (n = 4). The samples were scanned by microcomputed tomography and prepared for scanning electron microscopy evaluation. Quantitative data were evaluated using the parametric ANOVA test, with statistical significance level set at 5%, and qualitative data obtained were compared to establish the agreement between examiners through the Kappa test. It was observed that in the analysis of XP-endo Shaper protocols, the additional working time did not cause difference in any of parameters evaluated (p > 0.05) in relation to time recommended by manufacturer. Compared to Hyflex, XP-K showed highest mean volume increase (p < 0.05) and lowest percentage of untouched walls (p < 0.05). In the qualitative evaluation, final irrigation protocol with EndoVac provided the best cleaning results when associated with XP-K and with Hyflex. Thus, supplementary techniques are effective tools to enhance cleaning and to promote higher touch of walls during root canal preparation.

Assessment of apical pressures at different automated irrigant flow rates: an ex vivo study based on computational fluid dynamic analysis

Objective: The current study aimed at assessing the induced apical pressure at various simulated irrigantflow rates. Materials and Methods: Forty eight freshly extracted single-rooted premolars were decoronatedand prepared to size 30 0.04 taper using HY-Flex CM rotary file system and were scanned using cone-beamcomputed tomography (CBCT). The scanned images were reconstructed to three-dimensional Computer-aideddesign models (CAD) and the 3D needle was also reconstructed. Finally, simulations were done by placing the30 gauge open-ended needle 3 mm short of the working length. Results: There was a statistically significantdifference (p&lt;0.05) among the different groups compared. 1 ml/min flow rate induced the least apical pressures(p&lt;0.05) as compared to the other types. Conclusion: 1 ml/min flow rates induced the least apical pressureswhen open-ended needles are used for irrigation. KEYWORDSApical pressure; Computational fluid dynamic analysis; Flow rate; Irrigation; Root canal.

Comparative evaluation of push-out bond strength of AH-Plus, MTA-Fillapex and Epiphany SE root canal sealers: An Ex-Vivo study.

A successful root canal (RC) treatment depends upon creation of a fluid impervious seal that is commonly built by using a RC sealer along with gutta-percha. The bond strength of the RC sealer is a hallmark as it will minimize the risk of treatment failure by reducing the possibility of filling detachment from dentin. To evaluate and compare the push-out bond strength of AH-Plus and MTA-Fillapex with Gutta-Percha and Epiphany Self Etch/Resilon system using the Universal Testing Machine. About 60 mandibular premolars with single canals were prepared apically with Hyflex CM files upto size #30. Out of total, 20 teeth were obturated with AH-Plus/GP (group 1), 20 with MTA-Fillapex/GP (group 2), and other 20 with Epiphany Self Etch/Resilon system (group 3). Teeth were sectioned into three slices of 2 mm each and were subjected to Universal Testing Machine. The data obtained were tabulated and statistically evaluated using SPSS version 21.0 statistical analysis software (IBM, Chicago, Illinois, USA). The mean push-out bond strength was highest for AH-Plus (14.32 MPa) followed by MTA-Fillapex (12.18 MPa) and then Epiphany SE (8.44 MPa). The results were statistically significant. Significantly, higher push out bond strength was displayed by AH-Plus sealer than MTA-Fillapex and least being Epiphany SE sealer. The push out bond strength was significantly highest at apical third and lowest at coronal third.

Influence of heat treatment of nickel-titanium instruments on the accuracy of an electronic apex locator integrated with endodontic motor.

Manufacturers have produced a wide variety of nickel-titanium (NiTi) alloys, but the available literature is limited on the accuracy of some integrated electronic apex locators (EAL) used with different NiTi heat treatments in working length (WL) determination. This study aims to evaluate ex vivo , the influence of different heat treatments of NiTi instruments, and the diameter of the apical preparation on the accuracy of an EAL used during root canal preparation using an integrated EAL and motor unit. Nineteen extracted human mandibular incisors were included in the study. The WL control was determined by the visual method. Instruments of Mtwo, Reciproc, Reciproc Blue, WaveOne Gold, Twisted File Adaptive, and Hyflex CM systems, with diameters from 0.25 mm to 0.50 mm, were used to measure WL during root canal preparation. The electrical resistivity of instruments with a diameter of 0.25 mm from each system was evaluated using an Inductance, Capacitance, and Resistance (LCR) meter. Data were statistically analyzed using Fisher's exact test and Kruskal-Wallis test. The different heat treatments and different diameters did not influence the precision of the EAL (P > 0.05). The heat treatment and the diameter of the apical preparation did not influence the accuracy of WL determination by an EAL integrated with the endodontic motor.

Comparison of apical debris extrusion during root canal preparation in primary molars using different file systems: an invitro study.

This study aimed to compare the amount of debris extrusion of four endodontic systems made of Nickle-Titanium alloy. This invitro study was done on 80 extracted primary molars. They were selected by cone-beam computed tomography and randomly divided into four groups (n = 20) to be prepared to the apical size of 25 by one of the systems: Reciproc, Protaper Universal, Neolix, or Hyflex CM. Debris was collected into Eppendorf microtubes and placed in an incubator to evaporate the washing solution. Debris was weighed by a digital scale of 0.01 g precision. Data were statistically analysed using SPSS software. Tukey's comparison was used to determine the difference between the four file systems (α = 0.05). Debris extrusion after Reciproc preparation (0.00320) was significantly higher than the other (P < 0.05), with no significant difference having been observed among the other systems (P > 0.05). It can be concluded that all systems under investigation exhibited debris extrusion.

Retreatment of Experimental Carrier-Based Obturators with the Remover NiTi Instrument: Evaluation of Apical Extrusion and Effects of New Kinematics.

The objective of this study is to evaluate the retreatment time and weight of apically extruded debris yielded by two different kinematics during the removal of different root canal filling materials. Forty straight single-rooted extracted teeth were instrumented with HyFlex CM files and obturated with two different techniques: 25.04 HyFlex experimental carrier-based obturators (Coltène/Whaledent, Altstätten, Switzerland) (group 1) or 25.04 single gutta-percha cones (Roeko Coltène/Whaledent, Altstätten, Switzerland) (group 2) and Guttaflow Bioseal as the sealer. Samples were divided into four subgroups (n = 10) according to the used kinematics for the removal of root canal filling materials: continuous rotation (A) or retreatment motion (B) with a Remover and HyFlex EDM Nickel-Titanium instruments activated with a CanalPro Jeni micromotor (Coltène/Whaledent, Altstätten, Switzerland). Time for retreatment was digitally recorded, and debris extruded from the apex was collected in Eppendorf tubes and weighted with an analytical balance. Data on retreatment time and apical extrusion were statistically analyzed with the Kruskal–Wallis test (p < 0.05). Working length was achieved in all the retreated samples. The removal of root filling material resulted significantly faster with the Jeni mode (p < 0.001), and the difference was significant for the removal of both filling materials (p < 0.05). No significant differences on debris extrusion between single cone and experimental obturators groups were noted (p > 0.05), and no significant differences between kinematics (continuous rotation vs. Jeni motion) were observed (p > 0.05). All the tested retreatment strategies lead to an extrusion of material from the apex, and the weight of apically extruded debris was similar. The use of the innovative CanalPro Jeni kinematics accelerates the time for the removal of root filling materials.

Evaluation of apical root defects during canal instrumentation with two different nickel-titanium (NiTi) systems by optical coherence tomography (OCT) scan

Background/purposeCanal instrumentation with rotary nickel-titanium (NiTi) instruments might weaken the dentinal wall. This study aims to investigate the apical root defects during canal instrumentation with two NiTi rotary systems by using optical coherence tomography (OCT) scans. Materials and methodsTwenty mandibular incisors were selected and divided into two groups instrumented using HyFlex CM (HCM) and ProTaper Universal (PTU) systems. OCT scans were taken immediately after canal instrumentation with file #25, #30 and #40. Each cross-sectional reconstructed image of 1, 2 and 3 mm from the apex was examined, root cracks were scored, and dentin thickness was measured at 12 sites. The risk sites with dentin thickness less than 0.30 mm were recorded. ResultsIn HCM group, no cracks were observed after instrumentation with file #30/.06, while in PTU group, root cracks were found in 6 teeth with a total score of 9 after using F3 (#30/.09) (P < 0.05). After file #40, 8 teeth with cracks had a score of 14 in PTU group, while one tooth was observed crack with a score of 1 in HCM group (P < 0.05). The number of risk sites in PTU group was 49 (13.16%), which was significantly more than the 28 (7.78%) in HCM group (P < 0.05) when canals were instrumented with file #30. ConclusionWithin the limitations of this study, when the canals of mandibular incisors were instrumented with size #30 and #40 files, OCT scans showed less root defects in HCM group.

Evaluation of the root filling quality with experimental carrier-based obturators: a CLSM and FEG-SEM analysis.

This study evaluated tubule penetration of GuttaFlow Bioseal with cold single cone or carrier-based technique, under confocal laser scanning microscopy (CLSM). Twenty straight single-rooted teeth were instrumented with Hyflex CM and divided in two groups (n = 10) according to the obturation method: single cold gutta-percha cones; experimental carrier-based obturators. GuttaFlow Bioseal, labelled with Rhodamine B dye, was used as sealer in both groups. Teeth transversally sectioned were observed under CLSM. Percentage of sealer penetration and integrity of sealer layer perimeter were measured. Surface and microstructural characteristics of obturators and gutta-percha cones were compared by FEG-SEM and EDX analysis. No significant differences were found between groups for each examined parameter. Significant differences (P < 0.05) were reported mainly within groups. Integrity was similar among and within groups. FEG-SEM/EDX analysis of obturators revealed the presence of Ba and Zn. Carrier-based obturation technique associated with GuttaFlow Bioseal does not seem to affect sealer penetration into dentinal tubules.

Differential scanning calorimetric investigations of three rotary nickel-titanium instrument systems before and after simulated clinical uses

BackgroundThe transformation temperatures were important values, influencing the mechanical properties and clinical performance of nickel-titanium instruments. The aim of this study was to determine the transformation temperatures of three rotary nickel-titanium (NiTi) instruments: Reciproc, HyFlex CM Pro, and Neoniti before and after simulated clinical uses.MethodsNinety new NiTi instruments of three single-file instruments: Reciproc, HyFlex CM Pro, and Neoniti were divided into three groups. Thirty instruments of each group were divided into 3 subgroups (10 instruments for each subgroup): new, one-time simulated clinical used and sterilised, and three times simulated clinical used and sterilized subgroups. The instruments were in the as-received condition for the new subgroups, one time used in the plastic endo-training blocks and sterilised for the one-time subgroups, and three times used in the plastic endo-training blocks and sterilised for the three times subgroups. Each instrument in subgroups was cut into four small segments of 4–5 mm. All segments of instruments were analysed using Differential Scanning Calorimetry (DSC). Data was collected and analysed using SPSS version 20.0 with ANOVA test or Kruskal–Wallis test at the significant level of 0.05.ResultsThere was not significant difference between before and after simulated clinical use with sterilised procedure in three NiTi instrument systems. The austenite-finish (Af) temperatures of three instrument systems were higher than that of the human body (37 °C), of these, the Af temperature of Neoniti was highest and that of HyFlex CM Pro was lowest.ConclusionsThe austenite-finish (Af) temperatures of three NiTi instruments were higher than that of human body temperature, therefore, material was in the phase transformation from martensite to austenite, gives the instruments more flexibility when used in the clinical situation.

Comparative assessment of apically extruded debris using Protaper Next, Hyflex CM and EdgeFile X7 nickel titanium instruments (An in vitro Study)

Aim: To compare the amount of extruded debris with three endodontic NiTi engine driven systems, Protaper Next, Hyflex CM and EdgeFile X7. Material and Methods: A total number of 42 freshly extracted human premolars were selected. Teeth were divided randomly into three equal groups (14 teeth each group) according to type of Ni-Ti rotary file system; (A) Protaper Next, (B) Hyflex CM and (C) EdgeFile X7. Standard Access cavity prepared and checked for patency using K file #10 and #15. Root canal instrumentation on the single canal lower premolars was done. Debris was collected after root canal instrumentation in pre-weighed Eppendorf tubes. The Eppendorf tubes were weighed 2 times on the analytical balance. First weight: Before instrumentation. Second weight: After evaporation of moisture and irrigant and incubation. Welch test was used for comparison between the three groups. Results: There was no statistically significant difference between the amounts of debris extrusion of the three groups Conclusion: All endodontic rotary instruments tested produced apical extrusion of debris.

A comparative investigation between ProTaper Next, Hyflex CM, 2Shape, and TF-Adaptive file systems concerning cyclic fatigue resistance.

Background. This study aimed to compare the cyclic fatigue resistance of ProTaper Next, Hyflex CM, 2Shape, and TF-Adaptive nickel-titanium endodontic file systems with various alloy properties and production methods and investigate the fractured cross-sectional surface of files due to cyclic fatigue by scanning electron microscopy (SEM). Methods. A total of 120 instruments were used (n=30). For standardization, #25/.06 apical diameter and taper angle were selected for each file system. The experiment of files was subjected to a static cyclic fatigue model. The time for files’ failure was recorded with a digital chronometer and multiplied by the rotation speed to calculate the number of cycles. Kolmogorov-Smirnov, one-way ANOVA, and post hoc Bonferroni analysis were used for statistical analysis. Statistical significance was set at P < 0.05. Results. The number of cycles for the failure of files was compared between the groups, and significant differences were found (P < 0.05). The number of cycles for instrument failure was recorded from the highest to the lowest as follows: Hyflex CM, TF-Adaptive, ProTaper Next, and 2Shape. Conclusion. The files were fractured at different average numbers of cycles in an artificial canal in all the groups. The Hyflex CM demonstrated better cyclic fatigue resistance than TF Adaptive, ProTaper Next, and 2Shape file systems. Factors such as production patterns, alloy properties, and the phase in which the files were produced might affect the lifespan of file systems.

Evaluation of Cyclic Fatigue and Bending Resistance of Coronal Preflaring NiTi File Manufactured with Different Heat Treatments

Coronal preflaring NiTi files should possess proper hardness, resistance to fracture and flexibility. This study compared the bending resistance and cyclic fatigue resistance of three orifice preflaring NiTi files. HyFlex EDM Orifice opener (#25/12), HyFlex CM (#25/08) and One Flare (#25/09) were tested (n = 46/instrument). Bending resistance was assessed with the stress when perpendicular displacement was applied to a 3 mm point from the file tip, and was performed at either room temperature (RT, n = 10) or body temperature (BT, n = 10). Cyclic fatigue resistance was tested with an artificial ceramic root canal at RT (n = 10) and BT (n = 10), and the number of cycles to failure (NCF) was obtained. The bending resistance and the NCF results were analyzed by two-way ANOVA and Tukey’s test. Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) analyses were performed (n = 3, respectively). HyFlex EDM exhibited the highest bending resistance, followed by One Flare and HyFlex CM (p &lt; 0.05), irrespective of the tested temperature. At RT, HyFlex CM demonstrated the highest NCF (p = 0.001), while HyFlex EDM had the highest NCF at BT (p &lt; 0.001). The tested NiTi files were composed of austenite and martensite according to the DSC and XRD results. HyFlex EDM had the highest bending resistance and NCF measured at BT.

Vertical root fracture resistance and dentinal crack formation of root canal-treated teeth instrumented with different nickel-titanium rotary systems: an in-vitro study.

To compare the vertical root fracture (VRF) resistance of root canal-treated teeth instrumented with four different nickel-titanium (NiTi) rotary file systems and examine the dentinal crack pattern and direction using a new classification. Eighty mature mandibular premolars were selected and decoronated, leaving 13mm of the root. The root samples were mounted in acrylic resin and divided randomly into five groups of different NiTi file systems: Group 1-control, Group 2-T-Pro, Group 3-HyFlex CM, Group 4-TG6 and lastly Group 5-ZenFlex. Samples in Group 2 and Group 3 were instrumented up to size 25/0.04, whereas Group 4 and Group 5 were instrumented up to size 25/0.06. Obturation was performed with AH Plus sealer and gutta-percha using single cone technique. Subsequently, all samples were subjected to occlusal compressive force until they were fractured. The force (N) needed to cause root fracture was recorded. The crack patterns and directions were also inspected under magnification and classified using a new and simple classification. The highest (VRF) resistance was noted in the control group (453.15 ± 92.23N), followed by T-Pro (387.43 ± 76.81N), HyFlex CM (381.88 ± 52.73N), ZenFlex (369.15 ± 89.41N) and finally TG6 (346.05 ± 72.08N), but there was no significant difference between T-Pro and HyFlex (P = 0.438). A significantly higher prevalence (P = 0.001) of Type 1 crack pattern was observed, especially in samples instrumented with TG6. Majority of the cracks ran buccolingually except in some samples instrumented with ZenFlex (P = 0.898). Smaller file taper increased the VRF resistance of root canal-treated teeth. Majority of the dentinal crack exhibited Type 1 pattern and ran buccolingually.

Comparative evaluation of sealing ability of three bioactive obturation materials

Aim: The aim of this study was to evaluate and compare the sealing ability of three obturating materials used with single-cone technique: C Point/Endosequence BC sealer, gutta-percha/Endoseal MTA and gutta-percha/GuttaFlow bioseal using bacterial leakage model with Enterococcus faecalis. Materials and Methods: Seventy-six extracted human single-rooted mandibular premolars with straight canals prepared using Hyflex CM up to 45/04 and assigned to 3 experimental groups according to the root canal filling material as Group A - C Point/Endosequence BC sealer; Group B - guttapercha/Endoseal MTA; Group C - guttapercha/GuttaFlow bioseal. Split-chamber bacterial leakage model was prepared and microleakage analysis was made every 24 h for up to 9 weeks. The presence of E. faecalis was confirmed by light microscopy and Gram staining. Results: A survival analysis was performed using Kaplan–Meier plots and a log-rank test and it was found that Group A showed the best apical seal followed by Group C and then Group B at the end of the observational period. The difference in bacterial leakage among Group A and C versus Group B was statistically significant (P &lt; 0.05), but there was no significant difference between Group A and Group C. Conclusion: C Point/Endosequence BC sealer and GP/Guttaflow bioseal sealer has shown better apical seal with single-cone technique as compared to GP/Endoseal MTA.

GuttaFlow Bioseal as Monocone Obturation Technique in Curved Root Canals: A Scanning Electron Microscopy Study

The obturation quality of GuttaFlow Bioseal in curved root canals is not commonly investigated although there has been a current approach toward utilizing this material in extracted molars in recent years. This study assessed the obturated surface area, extrusion of root filling material beyond the apical foramen and duration of obturation procedure in curved root canals using monocone obturation technique. Access cavity was prepared in 20 human mandibular molars. Root canals with curvature of more than 10 as determined according to Schneider’s method were included. Samples were prepared using Hyflex CM rotary files and divided into two groups (n=10): Group 1 [gutta-percha cone and GuttaFlow Bioseal] and Group 2 [gutta-percha cone and RoekoSeal Automix root canal sealer]. The duration of obturation procedure was recorded and obturation radiographs were taken. Samples were bisected and the mesial roots were sectioned horizontally to obtain 3 root segments; apical, middle and coronal. All resected roots were mounted on brass stubs, sputter-coated with thin platinum coating and observed under scanning electron microscope (SEM) at 70x magnification. The SEM images were transferred to the SketchAndCalc Area Calculator software. No statistically significant differences in the obturated surface area and extrusion of root filling material were observed between Group 1 and 2, irrespective of the status of root canal curvature. Duration for obturation in severe root canal curvatures between Group 1 and 2 were statistically significant. Obturated surface area and extrusion of root filling material were not affected by the root canal curvature, however duration for obturation using GuttaFlow Bioseal in severe root canal curvatures was slightly longer.

Geometric Analysis of Curved Canals Prepared by HyFlex EDM Versus HyFlex CM Rotary Nickel Titanium Files: An In-Vitro Study

Geometric Analysis of Curved Canals Prepared by HyFlex EDM Versus HyFlex CM Rotary Nickel Titanium Files: An In-Vitro Study

Effects of repeated sterilization cycles on the surface alterations of ProTaper Next, TF Adaptive, HyFlex CM, and 2Shape instruments.

Background. This study aimed to evaluate the effects of repeated sterilization cycles on the surface alterations of various nickel-titanium instruments, including ProTaper Next (PTN), TF Adaptive (TFA), HyFlex CM (HCM), and 2Shape (2S). Methods. Twenty-four new NiTi files of four different alloys were selected. The instruments in each group were divided into two equal groups, as follows: control and sterilization. The first group was chosen as the control without applying any sterilization procedure, while in group 2, five cycles of sterilization procedures were applied. The surface topographies were evaluated using scanning electron microscope (SEM) and atomic force microscope (AFM). The root mean square (RMS) and maximum height (MH) values and three-dimensional images were recorded. The data were analyzed with the Shapiro-Wilk test, one-way ANOVA, and post hoc Tukey tests. The statistical significance level was set at P ≤ 0.05. Results. Before the experiment, HCM demonstrated the highest RMS value, and 2S showed the lowest. After the procedures, the RMS and MH values deteriorated on the surface of PTX, TFA, and 2S (P < 0.001). The HCM was not affected by sterilization processes (P > 0.05). Conclusion. The initial irregularity on the surface did not affect the rate of alteration. The HCM files demonstrated superior surface properties after several cycles of sterilization. The PTN, TFA, and 2S presented similar surface responses after five cycles of autoclave sterilization.