PTN X2 Research Articles

Static and Dynamic Cyclic Fatigue Resistance of Nickel-Titanium Rotary Instruments in a Double-Curved Stainless Steel Artificial Canal

The present study aims to measure the number of cycles leading to fracture (NCF) of instruments in static and dynamic cyclic fatigue situations under body temperature in stainless steel double-curved canals. The framework was constructed to establish the movement of instruments occurring at a stable body temperature. A step motor, a holding system for an endodontic handpiece, created the movement in and out of the artificial canal of the file mounted on the handpiece. A total of 30 instruments of ProTaper Universal and ProTaper Next (Dentsply Sirona, Maillefer, Ballaigues, Switzerland) were divided into three groups of 10 per group. For group 1 (10 PTU F2), files were rotated in static cycles. For groups 2 (10 PTU F2) and 3 (10 PTN X2), files were rotated in dynamic cycles. Files were rotated using proprietary programs, and the times the files were rotated before fracture were recorded. Data were analyzed using survival probabilities and regression with life data. The ProTaper Next in the dynamic cycles had the largest NCF, and the ProTaper Universal in the static condition had the least. New modes of rotation, material, and design have affected the cyclic fatigue resistance of the instrument.

Torsional, Static, and Dynamic Cyclic Fatigue Resistance of Reciprocating and Continuous Rotating Nickel-Titanium Instruments

IntroductionThe aim of this study was to evaluate torsional, dynamic, and static cyclic fatigue resistance of the reciprocating One RECI (OR; Micromega, Besançon, France), WaveOne Gold (WOG; Dentsply Maillefer, Ballaigues, Switzerland), rotary One Curve (OC, MicroMega), and ProTaper Next X2 (PTN X2; Dentsply Sirona, Charlotte, NC) instruments. MethodsA total of 120 OR (n = 30), WOG (n = 30), OC (n = 30), and PTN X2 (n = 30) nickel-titanium instruments were used. Torque and rotation angle until failure under static torsion loading were measured according to ISO 3630-1. Static and dynamic fatigue resistance was measured as the time to fracture in an artificial stainless steel canal with a 60° angle and 5-mm radius of curvature at intracanal temperature. The results were analyzed with 1-way analysis of variance and the post hoc Tukey test. The alpha-type error was set at 5%. Fracture instruments from torsion and fatigue tests were examined with a scanning electron microscope. ResultsOR showed higher static fatigue resistance and rotation angle at fracture than WOG, OC, and PTN X2 (P < .05). WOG exhibited higher torsional resistance than the others (P < .05). The cyclic fatigue tests in dynamic mode had higher TTF than static for the PTN X2 and WOG groups (P < .05). In the dynamic tests, OR and WOG showed higher TTF than OC and PTN X2 (P < .05). ConclusionsUnder these experimental conditions, One RECI exhibited suitable mechanical properties with the highest cyclic fatigue resistance and angle of rotation among the tested instruments.

Micro–computed Tomographic Evaluation of Dentinal Microcracks after Preparation of Curved Root Canals with ProTaper Gold, WaveOne Gold, and ProTaper Next Instruments

IntroductionThe aim of this study was to evaluate the influence of rotary (ProTaper Next [PTN; Dentsply Maillefer, Ballaigues, Switzerland] and ProTaper Gold [PTG, Dentsply Maillefer]) and reciprocating (WaveOne Gold [WOG, Dentsply Maillefer]) systems in dentinal microcrack generation after the preparation of curved root canals using micro–computed tomographic analysis. MethodsTwenty-four human mandibular molars with curved roots were scanned in a micro–computed tomographic device using an isotropic resolution of 6.78 μm and randomly assigned into 1 of 3 experimental groups (n = 8) according to the root canal instrumentation system used (PTN, PTG, or WOG). Then, the root canals were prepared up to PTN X2, PTG F2, and WOG Primary instruments in the PTN, PTG, and WOG groups, respectively. After canal preparation, each specimen was scanned again. Pre- and postoperative cross-sectional images of the roots (N = 35,304) were analyzed to identify the presence of dentinal microcracks. ResultsOverall, 26% of the images presented dentinal defects (n = 9188). Dentinal microcracks were observed in 24.6%, 26%, and 27.4% of the postinstrumentation images from the PTN, PTG, and WOG groups, respectively. However, all of these dentinal microcracks were already present in the corresponding preoperative images. No new microcracks were generated after the preparation of curved root canals of mandibular molars using the aforementioned systems. ConclusionsRoot canal instrumentation with PTN, PTG, and WOG systems did not induce the formation of new dentinal microcracks.

Comparative analysis of torque and apical force to assess the cutting behaviour of ProTaper Next and ProTaper Universal endodontic instruments.

This study assessed the cutting properties of two Nickel Titanium file systems with different designs and manufacturing materials. ProTaper Next X1 and X2 (PTN; Dentsply Sirona) and ProTaper Universal S2 and F1 (PTU; Dentsply Sirona) instruments were employed. The cutting parameters, that is torque and apical forces, were determined using a specially designed bench-testing machine. Dimensional and geometric parameters were considered to evaluate the results. The average maximum torque values showed statistically significant differences (P<0.05) among all instruments. Apical force for PTN X2 and PTU F1 instruments initially decreased and then experienced a rapid increase in the last 2mm of the canal. For PTN X1 and PTU S2, apical force increased during the entire test. When compared to PTU files, PTN required higher torque and apical forces during the shaping procedure. The results lead us to conclude that PTN instruments demonstrated a lower cutting efficiency than PTU.

Root Canal Shaping Effect of Instruments with Offset Mass of Rotation in the Mandibular First Molar: A Micro–computed Tomographic Study

IntroductionThe aim of this study was to evaluate the root canal shaping effect of 2 nickel-titanium rotary instruments with offset mass of rotation compared with an instrument with a conventional centered mass of rotation. MethodsThirty-six extracted human mandibular first molars with 2 independent mesial canals and 1 oval distal canal were selected and divided equally into 3 groups for instrumentation with ProTaper Next (PTN; Dentsply Maillefer, Ballaigues, Switzerland), Revo-S (RS; Micro-Mega, Besançon, France), and ProTaper Universal (PTU, Dentsply Maillefer) systems (n = 12). For apical preparation, PTN X2 (#25/0.06), RS SU (#25/0.06), and PTU F2 (#25/0.08) were used in the mesial canals and PTN X3 (#30/0.07), RS AS30 (#30/0.06), and PTU F3 (#30/0.09) were used in the distal canals. Specimens were scanned before and after instrumentation using a SkyScan 1272 scanner (Bruker micro-CT, Kontich, Belgium) at 10-μm isotropic resolution. Changes in the canal area, volume, structure model index (SMI), and untouched canal area were evaluated. Canal transportation and centering ratio were measured at 1, 3, 5, and 7 mm from the apical foramen. Data were statistically analyzed using 1-way analysis of variance with the Tukey post hoc test. ResultsThe PTN and RS systems showed significantly less transportation and better centering ability compared with the PTU system at 1 mm from the apical foramen (P < .05). All instrumentation increased the canal area, volume, and SMI values without significant differences among the 3 groups (P > .05). ConclusionsRegardless of the differences in the cross-sectional design, alloy type, and taper variation, instruments with offset mass of rotation showed better root canal shaping ability compared with an instrument with a centered mass of rotation.

In Vitro Comparison of Cyclic Fatigue Resistance of ProTaper Next, HyFlex CM, OneShape, and ProTaper Universal Instruments in a Canal with a Double Curvature

IntroductionThe aim of this study was to compare the resistance to cyclic fatigue of ProTaper Next X2 (PTN X2; size 25, 0.06 taper), Hyflex CM (HCM; size 25, 0.06 taper), OneShape (OS; size 25, 0.06 taper), and ProTaper Universal F2 (PTU F2; size 25, 0.08 taper) nickel-titanium files in an artificial root canal with a double (S-shaped) curvature. MethodsA total of 160 new PTN X2, OS, HCM, and PTU F2 files were tested in an artificial stainless steel canal with a double curvature. Forty files from each system were rotated until fracture to calculate the number of cycles to failure. The length of each fractured fragment was recorded. Data were analyzed by using one-way analysis of variance and Tukey post hoc tests. ResultsThe resistance to cyclic fatigue of the PTN X2 and HCM instruments was significantly greater than the OS and PTU F2 instruments in the apical curvature (P < .05). There was no statistical difference in the cyclic fatigue resistance of the PTN X2 and HCM instruments in the apical curvature (P > .05). In addition, there was no statistical difference between the OS and PTU F2 instruments in the apical curvature (P > .05). PTN X2, OS, HCM, and PTU F2 instruments showed similar cyclic fatigue resistance values in the coronal curvature (P > .05). ConclusionsThis study showed that PTN X2 and HCM instruments exhibit greater resistance to cyclic fatigue than OS and PTU F2 instruments in the apical curvature of an artificial canal with a double curvature.

Prediction of Cyclic Fatigue Life of Nickel-Titanium Rotary Files by Virtual Modeling and Finite Elements Analysis

IntroductionThe finite element method (FEM) has been proposed as a method to analyze stress distribution in nickel-titanium (NiTi) rotary instruments but has not been assessed as a method of predicting the number of cycles to failure (NCF). The objective of this study was to predict NCF and failure location of NiTi rotary instruments by FEM virtual simulation of an experimental nonstatic fatigue test. MethodsProTaper Next (PTN) X1, X2, and X3 files (Dentsply Maillefer, Baillagues, Switzerland) (n = 20 each) were tested to failure using a customized fatigue testing device. The device and file geometries were replicated with computer-aided design software. Computer-aided design geometries (geometric model) were imported and discretized (numeric model). The typical material model of an M-Wire alloy was applied. The numeric model of the device and file geometries were exported for finite element analysis (FEA). Multiaxial random fatigue methodology was used to analyze stress history and predict instrument life. Experimental data from PTN X2 and X3 were used for virtual model tuning through a reverse engineering approach to optimize material mechanical properties. Tuned material parameters were used to predict the average NCF and failure locations of PTN X1 by FEA; t tests were used to compare FEA and experimental findings (P < .05). ResultsExperimental NCF and failure locations did not differ from those predicted with FEA (P = .098). ConclusionsFile NCF and failure location may be predicted by FEA. Virtual design, testing, and analysis of file geometries could save considerable time and resources during instrument development.

Evaluation of the Resistance to Cyclic Fatigue among ProTaper Next, ProTaper Universal, and Vortex Blue Rotary Instruments

IntroductionThe purpose of this study was to compare the fracture resistance to cyclic fatigue of ProTaper Next (PTN; Dentsply Tulsa Dental Specialties, Tulsa, OK), ProTaper Universal (PTU, Dentsply Tulsa Dental Specialties), and Vortex Blue (VB, Dentsply Tulsa Dental Specialties) rotary instruments. MethodsTwenty instruments each of PTN X1–X5, PTU S1–F5, and VB 20/04–50/04 were rotated until fracture in a simulated canal of 90° and a 5-mm radius using a custom-made testing platform. The number of cycles to fracture (NCF) was calculated. Weibull analysis was used to predict the maximum number of cycles when 99% of the instrument samples survive. ResultsVB 20/04–30/04 had significantly higher NCF than PTU S1–F5 and PTN X1–X5. VB 35/04–45/04 had significantly higher NCF than PTU S2–F5 and PTN X2–X5. PTN X1 had higher NCF than PTU S1–F5. PTN X2 had higher NCF than PTU F2–F5. The Weibull distribution predicted the highest number of cycles at which 99% of instruments survive to be 766 cycles for VB 25/04 and the lowest to be 50 cycles for PTU F2. ConclusionsUnder the limitations of this study, VB 20/04–45/04 were more resistant to cyclic fatigue than PTN X2–X5 and PTU S2–F5. PTN X1 and X2 were more resistant to cyclic fatigue than PTU F2–F5. The Weibull distribution appears to be a feasible and potentially clinically relevant model to predict resistance to cyclic fatigue.

Cyclic fatigue resistance of ProTaper Next nickel‐titanium rotary files

To compare the cyclic fatigue resistance of ProTaper Next files (PTN; Dentsply Maillefer, Ballaigues, Switzerland) with Twisted Files (TF; SybronEndo, Orange, CA, USA), HyFlex CM (HF; ColténeEndo/Whaledent, Inc, Cuyahoga Falls, OH, USA) and ProTaper Universal (PT; Dentsply Maillefer). Size 25, .06 taper for PTN X2, TF, HF and PT F1 size 20, .07 taper were rotated in simulated canals until failure, and the number of cycles to failure (NCF) was recorded to evaluate their cyclic fatigue resistance. A scanning electron microscope was used to characterize the topographic features of the fracture surfaces of broken files. The data of the NCF and fragment length values were analysed statistically using one-way analysis of variance and Tukey post hoc tests. Statistical significance level was set at P<0.05. Twisted Files had a significantly higher resistance to cyclic fatigue than the other instruments (P<0.05). No significant difference was found in NCF between PTN and HF (P>0.05); however, there was a significant difference (P<0.05) of both these systems with PT, which exhibited the lowest mean NCF. The ranking in the NCF values was: TF>PTN>HF>PT. The fracture cross-sections of all brands revealed similar fractographic features, including crack origins, fatigue zone and an overload fast fracture zone. The new ProTaper Next had greater resistance to cyclic fatigue compared with ProTaper and HyFlex CM but not the Twisted Files.