Hyflex CM Files Research Articles

Comparison of the Amount of Debris Extruded From the Apex During Retreatment Procedures Using Several File Systems and to Gauge the Effect of Same and Different Taper on the Debris Extrusion: An In Vitro Study.

To determine the amount of apical extrusion between various file systems during the retreatment procedure and to determine the effect of taper on the same. Seventy mandibular extracted premolars were taken, and preparation was performed using a Woodpecker file (Woodpecker Medical Instrument Co., Ltd., Guilin, China) (25/0.06). The gutta-percha (GP) was removed from each specimen with H file (#40/0.02) to simulate retreatment in seven groups (n = 10) using ProTaper Next (PTN;Dentsply, Maillefer, Ballaigues, Switzerland) (PTN) (30/0.07), Reciproc (25/0.08), Hyflex CM (30/0.06), Mtwo (30/0.05), Neoendo flex (30/0.04), Neoendo hybrid (30/0.04), and Flexicon file (30/0.06). The specimens were held with the help of a rubber stopper and put in the Eppendorf tube of volume 4 mL (pre-weighed before retreatment). The debris that was on the root surface of the specimen was washed with distilled water with 1 mL volume, kept in the oven, and then again weighed after 7 days. Apical extrusion was found in the following order: HYFLEX CM (LEAST) < FLEXICON < PROTAPER NEXT < RECIPROC < NEOENDO FLEX < NEOENDO HYBRID < MTWO (HIGHEST). W Hyflex CM and Flexicon files showed lesser extrusion of debris than others.

Assessing Percentage of Touched Surfaces and Changes in Cross-sectional Area in Oval Shaped Root Canals after XP-endo Shaper, IRaCe and HyFlex CM Instrumentation Using AutoCAD Software

AIM: This study aimed to calculate the percentage of touched surfaces and changes in the cross-sectional area of oval-shaped root canals after preparation using (XP-endo Shaper, IRace, and HyFlex CM) rotary systems using AutoCAD software. MATERIALS AND METHODS: Sixty extracted single-rooted mandibular premolars were collected and divided into three main groups according to the rotary system used (n = 20). Each tooth was impeded in a resin block, coded, sectioned, and photographed under a stereomicroscope, before and after instrumentation. Microphotographs were analyzed using AutoCAD software. Two-way ANOVA was used to evaluate the mean percentage of the touched surface and mean cross- sectional area between the groups and tooth segments, followed by Tukey’s post hoc test for pair-wise comparisons. RESULTS: The percentage of touched canal walls was significantly different between IRace group and each of XP-endo Shaper and HyFlex CM groups (p &lt; 0.001). A statistically significant difference was recorded for the mean change in the cross-sectional areas of the root canal between IRace group and both HyFlex CM and XP-endo Shaper groups, respectively (p &lt; 0.001). For all groups, there was a significant difference in the change in the cross- sectional area between all segments (coronal, middle, and apical). CONCLUSIONS: Within the limitations of this study, the XP-endo Shaper and HyFlex CM files had a higher cutting efficiency and maintained better root stability than the IRaCe system by preserving the dentin of the oval root canal. This was observed at all the canal levels in the coronal, middle, and apical segments.

Comparative evaluation of the effect of glide path creation with Nitiflex hand K- file, Proglider and Path file on canal transportation and concentricity in apically curved canals - An In- Vitro study.

Abstract&#x0D; Aim:&#x0D; To compare and evaluate the effect of glide path creation with Nitiflex hand K- file, Proglider and Path file on canal transportation and concentricity in apically curved canals.&#x0D; Objectives:&#x0D; To compare the degree of canal transportation and concentricity between:&#x0D; 1) Glide path preparation with Nitiflex hand-K file vs Proglider file followed by combination of Hyflex EDM and CM file instrumentation&#x0D; 2) Glide path preparation with Proglider file vs Path file followed by combination of Hyflex EDM and CM file instrumentation&#x0D; 3) Glide path preparation with Nitiflex hand- K file vs Path file followed by combination of Hyflex EDM and CM file instrumentation&#x0D; Materials and methods:&#x0D; Forty ISO 20, 0.02 taper, Endo Training Blocks (Dentsply Maillefer) were acquired and divided into following four groups (n = 10): group A, Control group without glide path preparation; group B, Glide path preparation with Nitiflex hand-K file; Group C: Glide path preparation with Proglider file; Group D: Glide path preparation with Path files. In all the groups, combination of Hyflex EDM and CM file instrumentation was done after glide path creation. Pre- and post-instrumentation digital images were processed with Image J Version 1.8.0 software to identify the center of the canal, and then superimposed using Adobe Photoshop 7.0 software. Unpaired/independent t test and One Way ANOVA were used for intergroup comparison of difference of mean scores.&#x0D; Results:&#x0D; In comparison to other groups, training blocks instrumented with Proglider files and a combination of Hyflex EDM and CM files had reduced deviation in canal axis.&#x0D; Conclusion:&#x0D; Following the combination of Hyflex EDM and CM file instrumentation with an earlier glide path created with Proglider file, canal concentricity and canal geometry are better preserved.&#x0D; Key words: Glide path, canal transportation, proglider, path files, Hyflex EDM

Comparison of two different file systems on postoperative pain after root canal instrumentation: A randomized controlled trial

Abstract Introduction: In this study post instrumentation pain is evaluated between rotary hyflex CM files and conventional k-files at different time intervals. Methodology: fifty patients were equally assigned into two groups and instrumented using hyflex cm or conventional files. VAS for pain was noted before the start of a root canal and after the procedure at 12, 24, and 48 hours. Results: There was no significant difference at 12, 24, and 48 hours with P values being 0.127, 0.867, and 0.846 respectively. Conclusion: There is no significant difference in causing post-instrumentation pain between hyflex CM and conventional files at different time intervals. However, when accessing preop pain of the conventional file group, it had more pain mean score compared to hyflex group. According to this study, Conventional files may be able to slightly decrease the chances of post-instrumentation pain more than hyflex CM instrumentation.

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.

Comparison of cyclic fatigue resistance of three different rotary NiTi systems – An in-vitro study

Background: Nickel–titanium (NiTi) alloys created a revolution in the instrumentation of endodontics. However, they undergo unexpected fracture during the instrumentation of curved root canals due to cyclic fatigue. Hence, innumerable scientific and manufacturing researches are focused on fabricating NiTi rotary instruments with greater cutting efficiency and increased fatigue resistance. Aim: The aim of this study is to compare and evaluate the cyclic fatigue resistance of three different NiTi rotary file systems: Hyflex CM, Endostar E3, and Mani Silk. Materials and Methods: In this in-vitro study, 30 Hyflex CM (25/0.06), 30 Mani Silk (25/0.06), and 30 Endostar E3 (25/0.06) instruments were included. The static cyclic fatigue test was performed using a custom-made jig. The artificial canal was made of stainless-steel jig with an inner diameter of 1.5 mm, 45° angle of curvature, and radii of curvature of 5 mm. All the instruments were rotated according to the manufacturer's recommendations until failure occurred. The time taken to failure was recorded in seconds for each group using a digital chronometer. The data were analyzed statistically using the one-way analysis of variance, Post hoc test of Bonferroni was performed to identify pair-wise significance through SPSS 21.0 software (SPSS Inc, Chicago, IL, USA). The statistical significance was set at 5%. Results: Hyflex CM had the statistically highest fatigue resistance followed by Mani Silk and Endostar E3 (P &lt; 0.05). Conclusion: Within the limitations of the present in vitro study, it was found that cyclic fatigue resistance of Hyflex CM files was higher than the cyclic fatigue resistance of Mani Silk and Endostar E3 files.

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.

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.

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.

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.

An in-vitro comparative study of cyclic fatigue resistance of twisted files, Hyflex cm, Hyflex edm and Edgefile X3 after immersion in sodium hypochlorite and/or sterilization

An in-vitro comparative study of cyclic fatigue resistance of twisted files, Hyflex cm, Hyflex edm and Edgefile X3 after immersion in sodium hypochlorite and/or sterilization - IJCE- Print ISSN No: - 2581-9534 Online ISSN No:- 2581-8988 Article DOI No:- 10.18231/j.ijce.2021.007, IP Indian Journal of Conservative and En

Scanning electron microscopy analysis of conventional and controlled-memory nickel titanium files before and after multi-uses in root canals.

The current study aimed to examine changes in the physical properties of conventional and CM nickel-titanium instruments after repeated clinical use, disinfection-sterilization processes, using scanning electron microscopy (SEM). Sixty extracted mandibular molar mesial roots were used in this ex vivo study. The 60 teeth underwent final apical shaping (#25/.06) by the Revo-S SU (Revo-S Group: #25/.06; Micromega; n=10) and Hyflex CM (Hyflex CM group: #25/.06; Coltene-Whaledent; n=10) groups. One instrument of each group was used to shape six different teeth (Revo-S SU in 3 MB and 3 ML canals, and Hyflex CM in 3 MB and 3 ML canals), sequentially. The physical changes evident on the surfaces of the files after sequential use and sterilization processes were analyzed by SEM after the first, third, and sixth use. The first SEM examination was performed immediately after removal from the packages. Following first SEM examination, the files were sterilized before the first use as would be customary in practice. Qualitative evaluations were made by two evaluators, according to the following criteria: tip deformation, cutting edge deformation, debris, and microfracture. Revo-S showed a significant difference in cutting edge deformation, tip deformation, and microcrack formation, as compared to Hyflex CM. There was no significant difference between the groups in debris with the increasing number of uses. In this study, Hyflex CM (CM nickel-titanium) files showed better performance in terms of deformation and microcrack formation as the number of uses increased than did Revo-S (conventional nickel-titanium) files.

Shaping Ability of ProTaper Next, Hyflex CM, and V-Taper 2H Nickel-Titanium Files in Mandibular Molars: A Micro-computed Tomographic Study.

Although micro-computed tomography (MCT) evaluation of the shaping ability of ProTaper Next (PTN) and Hyflex CM (HCM) files has been reported, to our knowledge, no study has assessed the performance of V-Taper 2H (VT) files. The aim of this study was to evaluate and compare the shaping ability of PTN, HCM, and VT systems in the mesial canals of mandibular molars using MCT. Thirty extracted first and second mandibular molars were scanned using MCT and randomly assigned to HCM, PTN, and VT groups. Images obtained before and after preparation were evaluated for the increase in the root canal volume, untouched surface area, and amount of accumulated hard tissue debris. One-way analysis of variance (ANOVA) and Kruskal-Wallis test were used to compare the variables in the groups (α=5%). There were no statistically significant between-group differences in the postoperative measurements (P>0.05). The canal volume increased in all three groups: PTN (73.84%), VT (73.48%), and HCM (49.29%). The largest and smallest untouched areas were observed in the PTN (41.37%) and VT (30.85%) groups, respectively (P>0.05). The debris formed during canal preparation was 1.84%, 2.16%, and 2.42% in the VT, PTN, and HCM groups, respectively (P>0.05). Based on our in vitro study, the PTN, HCM, and VT systems showed similar shaping abilities. None of the tested canals were completely free from debris, while the untouched surface area was considerably large. The VT system had the most favorable results with the smallest untouched surface area and least debris were. We would recommend further trials to endorse these findings.

Cyclic fatigue resistance of reduced-taper nickel-titanium (NiTi) instruments in doubled-curved (S-shaped) canals at body temperature.

Background. This study was conducted to compare the cyclic fatigue resistance of VDW.ROTATE, TruNatomy Prime, HyFlex CM, and 2Shape nickel-titanium (NiTi) rotary instruments in double-curved canals in a simulated clinical environment. Methods. Eighty NiTi files were used for the fatigue testing in stainless steel canals compatible with instrument sizes until fracture occurred (n=20): VDW.ROTATE (04./25#), TruNatomy Prime (04./26#), HyFlex CM (04./25#) and 2Shape TS04./25#( 1). For each instrument, the number of cycles to fracture (NCF) was calculated, and the fractured fragment length (FL) was measured. To verify that the files were fractured due to cyclic fatigue, the fractured surfaces of the files were evaluated under a scanning electron microscope. Data were statistically analyzed using the Kruskal–Wallis and Student’s t-tests at the %95 confidence level. Results. The failure of the files due to cyclic fatigue was first seen in the apical curvature before the coronal curvature (P<0.05). The highest fatigue resistance was observed in VDW.ROTATE and HyFlex CM files in both curvatures (P<0.05). There were no significant differences in the fatigue resistance between the HyFlex CM and VDW.ROTATE files or between the 2Shape and the TruNatomy files (P>0.05). There was no difference in the fractured lengths of the files between the apical and coronal curvatures (P>0.05). Conclusion. In artificial S-shaped root canals, VDW.ROTATE and HyFlex CM files exhibited higher fatigue resistance compared to 2Shape and TruNatomy files.

Influence of different rotary systems on the amount of apically extruded debris in mandibular molars (An In vitro study)

Objective: The aim of the study was to compare and evaluate Hyflex CM files and M-Pro files versus Protaper Next files regarding the amount of apically extruded debris in the mesial root canals of mandibular molars.Methodology: Sixty three human permanent mandibular molars were utilized in the study. Empty Eppendorf tubes were weighed using an analytical balance three times and an average weight was calculated (W1). Then, a hole was created in the stopper of the Eppendorf tubes and mesial roots were inserted. The roots were randomly assigned into 3 groups according to the instrumentation technique used: Group I: Protaper Next (n=21), Group II: Hyflex (n=21) and Group III: M-Pro (n=21). Distilled water was used as an irrigant in all groups. After instrumentation, the vials were placed in an incubator for 3 days and the apically extruded debris collected in the Eppendorf tubes were weighed again (W2) after instrumentation. Welch test was used for comparison between the three groups.Results: There was no statistically significant difference between the amount of debris extrusion of the three groups (P=0.204). Conclusion: Within the limitation of this study it was concluded that all systems were associated with extrusion of debris.

The Ability of Different Nickel-Titanium Rotary Instruments to Induce Dentinal Micro-cracks during Root Canal Preparation

Abstract Objective The aim of this study was to investigate the incidence of cracks in root dentin after root canal preparation with SmartTrack files, ProTaper Next files, and HyFlex CM files. Materials and Methods Sixty extracted single-rooted human mandibular premolars with one canal were used for the study. Fifteen teeth were left unprepared and served as control; another 15 were instrumented with SmartTrack files up to 30/0.06, and the remaining 30 were shaped with ProTaper Next till X3 and HyFlex CM files up to 30/0.04. After root canal preparation, all the roots were sectioned perpendicular to the long axis at 2, 4, and 6 mm from the apex, and the sections were then observed under a stereomicroscope. The absence or presence of cracks was recorded. Results No cracks were observed in the control group. There was presence of cracks at all the levels in all the experimental groups. There was a significant difference in crack formation when the groups were compared whereas this difference was not significant when the levels were compared (p &gt; 0.05). In the SmartTrack group, there was crack in 73% samples whereas in HyFlex CM and ProTaper Next, the number of samples with cracks was 27% and 53%, respectively. In the apical region, the number of samples that shows cracks was 29% whereas the number of cracks in the middle and coronal regions was 20%. Conclusion Within the limitations of this study, root canal preparation with rotary nickel-titanium (Ni-Ti) instruments can cause crack formation in root canal dentin. The ProTaper Next and HyFlex instruments have a tendency to cause fewer dentinal cracks compared with the SmartTrack instruments.

Comparative evaluation of the shaping ability of rotary systems of varying metallurgy in curved canals and its analysis using cone-beam computed tomography: An in vitro study

Background: This study compared the shaping ability of four nickel-titanium rotary file systems of varying metallurgy along curved canals. Aim: The aim of the present study is to compare the shaping ability of rotary systems of varying metallurgy in curved canals and its analysis using cone-beam computed tomography (CBCT). Materials and Methods: Forty mesiobuccal canals of mandibular first molars with an angle of curvature ranging from 20° to 40° were divided according to the instrument used in canal preparation into four groups of 10 samples each: Hyflex CM (Group I), Vortex Blue (Group II), Flexicon (Group III), and K3XF (Group IV). All samples were instrumented according to the manufacturer's guidelines and prepared to size 30, 0.06-taper master apical file. Canals were scanned and evaluated using an NNT CBCT unit before and after preparation at different levels from the apex. The data were subjected to statistical analysis. Statistical Analysis: The intergroup comparison in terms of canal transportation and the time taken for canal preparation was done by the one-way analysis of variance (ANOVA) test with Bonferroni post hoc test. The intragroup comparison in terms of canal transportation was done by the repeated measures ANOVA test with the post hoc Bonferroni test. For the canal-centering ability, the Kruskal–Wallis test with Mann–Whitney U-test was used for the intergroup comparison and the intragroup comparison was done by Friedman's test with Wilcoxon signed-rank test. Results: Hyflex CM and Vortex Blue files showed significantly least canal transportation and highest canal-centering ability values as compared to Flexicon and K3XF file systems. Conclusion: The metallurgy and file design of Hyflex CM and Vortex Blue file systems resulted in superior shaping ability, with the instruments remaining more centered in the canal than Flexicon and K3XF.

The influence of the manufacturing process of rotary files on the shaping of L-shaped canals.

The nickel-titanium alloy used in the production of nickel-titanium files contains approx. 56% nickel and 44% titanium by weight. To improve the properties of nickel-titanium files, the manufacturers introduce some innovations in the production process. Their purpose is primarily to decrease the stiffness of the instruments while increasing the resistance to cyclic fatigue, which reduces the risk of file separation. One of the most popular processes is the heat treatment of the nickel-titanium alloy. The aim of the research was to determine the influence of the manufacturing process of rotary files on the shaping of L-shaped canals. Fifty L-shaped resin canals were instrumented (10/group) with ProTaper Universal ®, ProTaper Next®, Hyflex CM®, Hyflex EDM®, or WaveOne Gold® files, with the same apical size of 25. Each L-shaped resin canal was photographed both before and after instrumentation. Differences between the change of the working length and apical transportation were analyzed statistically. The smallest mean loss of the working length was observed after instrumentation with Hyflex CM files. Statistically significant differences in the working length were found between ProTaper Universal and Hyflex CM (p = 0.0032), ProTaper Universal and Hyflex EDM (p = 0.021), and ProTaper Universal and WaveOne Gold (p = 0.0112) files. The lowest apical transportation was noted in the case of WaveOne Gold files. In terms of apical transportation, statistically significant differences were observed between ProTaper Universal and WaveOne Gold files (p = 0.0254). Shaping Lshaped canals with the ProTaper Universal file system resulted in the greatest changes in the working length (x = 0.35 mm) and apical transportation (x = 0.034 mm). The study, with its limitations, shows that in the files whose nickel-titanium alloy was subjected to a thermal treatment process, a smaller loss of the working length and lower values of apical transportation were observed.

Cyclic Fatigue Resistance of Heat-treated Nickel-titanium Instruments after Immersion in Sodium Hypochlorite and/or Sterilization

IntroductionThe purpose of this study was to assess the effects of sodium hypochlorite (NaOCl) immersion and sterilization on the cyclic fatigue resistance of heat-treated nickel-titanium (NiTi) rotary instruments. MethodsTwo hundred ten new 25/.06 Twisted Files (TFs; SybronEndo, Orange, CA) and Hyflex CM (Coltene Whaledent, Cuyahoga Falls, OH) files were divided into 7 groups (n = 15) for each brand. Group 1 (control group) included new instruments that were not immersed in NaOCl or subjected to autoclave sterilization. Groups 2 and 3 were composed of instruments dynamically immersed for 3 minutes in 5% NaOCl solution 1 and 3 times, respectively. Groups 4 and 5 consisted of instruments only autoclaved 1 and 3 times, respectively. Groups 6 and 7 recruited instruments that received a cycle of both immersion in NaOCl and sterilization 1 and 3 times, respectively. Instruments were subsequently subjected to a fatigue test. The surface morphology of fractured instruments was studied by field-emission scanning electron microscopy and x-ray energy-dispersive spectrometric (EDS) analyses. The means and standard deviations of the number of cycles to failure (NCF) were calculated and statistically analyzed using 2-way analysis of variance (P < .05). ResultsComparison among groups indicated no significant difference of NCF (P > .05) except for the groups of TFs sterilized 3 times without and with immersion in NaOCl (P < .05). HyFlex CM files exhibited higher cyclic fatigue resistance than TFs when files were sterilized 3 times, independently from immersion in NaOCl (P < .05). EDS analysis showed the presence of an oxide-rich layer on the Hyflex CM files’ external surface. No morphologic or chemical differences were found between files of the same brand subjected to different treatments. ConclusionsRepeated cycles of sterilization did not influence the cyclic fatigue of NiTi files except for TFs, which showed a significant decrease of flexural resistance after 3 cycles of sterilization. Immersion in NaOCl did not reduce significantly the cyclic fatigue resistance of all heat-treated NiTi files tested.

Comparison of Alterations in the Surface Topographies of HyFlex CM and HyFlex EDM Nickel-titanium Files after Root Canal Preparation: A Three-dimensional Optical Profilometry Study

AimsThe aims of the present study were to examine the surface topographies of intact HyFlex CM and HyFlex EDM nickel-titanium files and to compare alterations in the surface topographies of these files after root canal preparation of severely curved canals of molar teeth. MethodsEight HyFlex CM (25/.08) and 8 HyFlex EDM (25/.08) files were included in the present study. In total, 64 severely curved canals of molar teeth, with curvature angles ranging between 50° and 70°, were prepared with HyFlex CM and EDM (n = 32 in each group). Quantitative and qualitative analyses of the files' surface deformation were performed by using three-dimensional optical profilometry before and after root canal preparation. The data were analyzed with the Student t test at the 5% significant level by using SPSS 21.0 software. ResultsIn the HyFlex EDM group, the qualitative evaluation revealed the presence of cracks and microcavities after use of the file for root canal preparation, whereas only minor surface deformation was observed in the HyFlex CM group. The average roughness, root mean square roughness, and peak to valley height values of the HyFlex EDM group were significantly higher than those of the HyFlex CM group before and after root canal preparation (P < .05). The surface roughness values were statistically significantly increased in the HyFlex CM group after root canal preparation (P < .05). In contrast, the increase in the HyFlex EDM group was not statistically significant (P > .5). ConclusionsWithin the limitations of the present study, the HyFlex CM files showed significantly higher surface alterations compared with the HyFlex EDM files after the preparation of severely curved root canals.