Static Cyclic Fatigue Resistance in Abrupt Curvature,Surface Topography,and Torsional Strength of R-Pilot and ProGlider Glide Path Instruments

IntroductionThis study aimed to compare ProGlider (Dentsply Sirona, Ballaigues, Switzerland) and R-Pilot (VDW, Munich, Germany) instruments in terms of their cyclic fatigue resistance using an artificial stainless steel canal showing an abrupt apical curvature, torsional resistance according to the ISO specification, and topographic changes on the instrument surface after glide path management in mesial canals of mandibular first molars with the abrupt curvature selected based on their micro–computed tomographic examination.MethodsEighty instruments were used: 40 ProGlider (size 0.16, .02v taper) and 40 R-Pilot (size 0.125, .04 taper) instruments. The cyclic fatigue resistance was tested in a static test model using an artificial canal with an abrupt apical curvature (angle of curvature of 90° and radius of curvature of 2 mm). The torsional resistance test was performed according to ISO 3630-1 specifications. To determine surface topography of the unused and used instruments, mesial root canals of mandibular molars with an abrupt apical curvature were selected to prepare a glide path with either the ProGlider or R-Pilot instrument. An optical profilometer and scanning electron microscopy were used to determine the surface properties. Normally distributed torsional and cyclic resistance data were analyzed using the Student t test, whereas quantitative data obtained by the optical profilometer were analyzed with the Kruskal-Wallis H test with a 5% significance threshold.ResultsThe R-Pilot showed significantly higher cyclic fatigue and torsional resistance than the ProGlider (P < .05). Angular deflection values were similar between instruments (P < .05). Measurements made from the blade area showed that the surface roughness values of the ProGlider were larger. Cutting blade measurements showed that unused instruments had significantly greater roughness values than used ones (P < .05). Although there was a 14% increase between the blade edge radii of the used and unused R-Pilot instruments, this difference was determined as 61% in ProGlider instruments.ConclusionsThe R-Pilot exhibited greater cyclic fatigue strength than the ProGlider when tested in an artificial canal with an inner diameter of 1.0 mm and an abrupt apical curvature. Torsional resistance of the R-Pilot was higher than the ProGlider, but the angular deflection values were similar. Glide path preparation in a mesial root canal with an abrupt apical curvature did not increase the surface roughness of both instruments but resulted in a greater blade edge radius.     

Evaluation of Design,Metallurgy, Microhardness,and Mechanical Properties of Glide Path Instruments: A Multimethod Approach

IntroductionThis study aims to compare the design, metallurgy, microhardness, and mechanical properties of 3 glide path nickel-titanium (NiTi) instruments.MethodsA total of 132 ProGlider (Dentsply Sirona, Ballaigues, Switzerland), Edge Glide Path (EdgeEndo, Johnson City, TN), and R-Pilot instruments (VDW, Munich, Germany) (44 per group) were selected. Design was assessed through stereomicroscopy (blades, helical angle, measuring lines, and deformation) and scanning electron microscopy (symmetry, cross section, tip, and surface finishing). NiTi ratios were measured by energy-dispersive X-ray spectroscopy and phase transformation temperatures by differential scanning calorimetry. Microhardness and mechanical performance (torsion, bending, and buckling resistance tests) were also evaluated. Statistical analyses were performed with the Mood median test with a significance set at 5%.ResultsThe Edge Glide Path had the lowest number of blades and the R-Pilot the greatest helical angle. All instruments had an almost equiatomic NiTi ratio, while showing different cross sections and tip geometries. The Edge Glide Path had a smoother surface finishing. The R-Pilot showed martensitic characteristics at room temperature, whereas mixed austenite plus R-phase was observed in the other instruments. The R-Pilot had higher results on the microhardness (436.8 hardness Vickers number), maximum torsion (0.9 Ncm), and buckling load (0.7 N) tests (P < .05), whereas the Edge Glide Path had a superior angle of rotation (683.5°) and the ProGlider was more flexible (144.1 gf) (P < .05).ConclusionsDifferences in the design of the instruments and the phase transformation temperatures accounted for their mechanical behavior. The R-Pilot showed the highest torque, buckling, and microhardness, whereas the ProGlider instrument was the most flexible.     

Torsional Resistance of ProGlider,Hyflex EDM,and One G Glide Path Instruments

IntroductionThe present study aimed to compare the torsional resistance of ProGlider (Dentsply Sirona, Ballaigues, Switzerland), Hyflex EDM (Coltene-Whaledent, Altstätten, Switzerland), and One G (Micro-Mega, Besancon, France) glide path instruments.MethodsFifteen ProGlider (16.02∼08), 15 Hyflex EDM (10.05), and 15 One G (14.03) instruments were collected and tested for torsional strength using a custom-designed testing device. Data were analyzed using 1-way analysis of variance and Tukey post hoc tests with 5% significance level. The tested specimens were examined under a scanning electron microscope.ResultsThere was no significant difference between Hyflex EDM and ProGlider regarding their torsional resistance values (P > .05). One G showed the lowest torsional resistance (P < .05). Hyflex EDM exhibited the highest angle of rotation values among the instruments (P < .05).ConclusionsHyflex EDM and ProGlider instruments had significantly higher torsional fatigue resistance than One G instruments, whereas Hyflex EDM showed the highest angle of rotation values. The differences in the torsional resistances might be associated with their different design features and manufacturing processes.     

Cyclic Fatigue Resistance of Novel Glide Path Instruments with Different Alloy Properties and Kinematics

Introduction

The aim of the present study was to evaluate the cyclic fatigue resistance of the WaveOne Gold Glider (Dentsply Maillefer, Ballaigues, Switzerland), R-Pilot (VDW, Munich, Germany), and ProGlider (Dentsply Maillefer) glide path instruments.

Microcomputed Assessment of Transportation,Centering Ratio,Canal Area,and Volume Increase after Single-file Rotary and Reciprocating Glide Path Instrumentation in Curved Root Canals: A Laboratory Study

IntroductionThe aim of this study was to compare the transportation and centering abilities of the ProGlider (PG; Dentsply-Sirona, Ballaigues, Switzerland), WaveOne Gold Glider (WOGG; Dentsply-Sirona), and R-Pilot (RP; VDW, Munich, Germany) file systems and the changes in the structure model index (SMI), surface area, and root canal volume (after creating the glide path in the mandibular first molar teeth’s mesial canals with moderate curvature) using the micro–computed tomographic (micro-CT) method.MethodsIn the present study, 24 mandibular first molar teeth with 2 separate mesial canals and moderate (10°–20°) curvature were used. After scanning with micro-CT imaging before the procedure, the teeth were divided into 3 groups, PG, WOGG, and RP (n = 10/each group), followed by the glide path procedure. After the root canal preparation, changes in the root canals regarding the volume, surface area, SMI, transportation made by the files, and the change of their centering ability in the apical, middle, and coronal third were analyzed by micro-CT imaging. The data were statistically evaluated using 1-way analysis of variance and the Kruskal-Wallis test with a significance level set at 5% (P < .05).ResultsThe WOGG and RP file systems showed better centering abilities at all thirds compared with the PG file system (P < .05). No significant difference was found in the apical third between the groups in terms of canal transportation degree (P > .05). However, in the WOGG and RP groups, less transportation was observed in the middle and coronal thirds compared with the PG group (P < .05). When the SMI changed, after the root canal preparation was compared, no significant differences were found between the groups (P > .05). Nevertheless, the changes in volume and surface area of the root canal in the WOGG and RP groups were significantly lower than in the PG group (P < .05).ConclusionsThe WOGG and RP file systems caused similar levels of change in the root canal systems based on all parameters. Moreover, it was determined that the PG file system caused a significantly higher volume and surface area increase than the WOGG and RP file systems.     

Effect of Glide Path Creating on Cyclic Fatigue Resistance of Reciproc and Reciproc Blue Nickel-titanium Files: A Laboratory Study

Introduction

The purpose of this article was to compare the cyclic fatigue resistance of Reciproc and Reciproc Blue files (VDW GmbH, Munich, Germany) that were used to prepare root canals of mandibular molar teeth with or without a glide path.

Influence of Continuous or Reciprocating Motion on Cyclic Fatigue Resistance of 4 Different Nickel-Titanium Rotary Instruments

IntroductionThe aim of this study was to evaluate the resistance to flexural fatigue of Reciproc R25 (VDW, Munich, Germany), WaveOne Primary (VDW, Munich, Germany), Mtwo (Sweden & Martina, Padova, Italy), and Twisted File (TF; SybronEndo, Orange, CA) instruments used in continuous rotation or in 2 different reciprocating motions.MethodsA total of 180 nickel-titanium files from 4 brands marketed, 2 for use in reciprocating motion (ie, Reciproc R25 and WaveOne Primary) and 2 for use in continuous rotation (ie, Mtwo and TF both taper .06/0.25 tip diameter), were tested. Forty-five instruments for each brand were divided into 3 groups (n = 15) on the basis of the motion tested: continuous rotation (group 1: 300 rpm) and reciprocal motion (group 2: “RECIPROC ALL” mode and group 3: “WAVEONE ALL” mode). The resistance to cyclic fatigue was determined by counting the number of cycles to failure in a 60° curve with a 5-mm radius. Data were analyzed through 2-way analyses of variance.ResultsThe cyclic fatigue resistance of the 2 reciprocating motion instruments (ie, “RECIPROC ALL” and “WAVEONE ALL”) was significantly higher than the continuous rotation in each brand (P < .001). No significant difference was observed in cyclic fatigue between the 2 different reciprocal motions tested in each brand (P > .05). When considering the appropriate clinical motion for each brand, no significant difference in cyclic fatigue was found between TF, Mtwo, and Reciproc R25 instruments, whereas the cyclic fatigue resistance of WaveOne files was less than the other 3 brands (P < .05).ConclusionsReciprocal motion showed a significantly higher cyclic fatigue resistance in all brands compared with continuous rotation. No differences were found between the 2 reciprocating motions.     

Effect of the Glide Path Establishment on the Torque Generation to the Files during Instrumentation: An In Vitro Measurement

Introduction

The purpose of this study was to compare in vitro torque generation during instrumentation with or without glide path establishment.

Energy Consumption of ProTaper Next X1 after Glide Path with PathFiles and ProGlider

Introduction

Instrument failure caused by excessive torsional stress can be controlled by creating a manual or mechanical glide path. The ProGlider single-file system (Dentsply Maillefer, Ballaigues, Switzerland) was recently introduced to perform a mechanical glide path. This study was designed to compare the effect of a glide path performed with PathFiles (Dentsply Maillefer) and ProGlider on torque, time, and pecking motion required for ProTaper Next X1 (Dentsply Maillefer) to reach the full working length in simulated root canals.

Methods

Forty Endo Training Blocks (Dentsply Maillefer) were used. Twenty were prepared with a mechanical glide path using PathFiles 1 and 2 (the PathFile group), and 20 were prepared with a mechanical glide path using a ProGlider single file (the ProGlider group). All samples were shaped with ProTaper Next X1 driven by an endodontic motor connected to a digital wattmeter. The required torque for root canal instrumentation was analyzed by evaluating the electrical power consumption of the endodontic engine. Electric power consumption (mW/h), elapsed time (seconds), and number of pecking motions required to reach the full working length with ProTaper Next X1 were calculated. Differences among groups were analyzed with the parametric Student t test for independent data (P < .05).

Results

Elapsed time and electric power consumption were significantly different between groups (P = .0001 for both). ProGlider appears to perform more efficiently than PathFiles in decreasing electric power consumption of ProTaper Next X1 to reach the full working length.

Conclusions

This study confirmed the ability of ProGlider to reduce stress in ProTaper Next X1 during shaping through a glide path and preliminary middle and coronal preflaring.     

Effect of Fatigue on Torsional Failure of Nickel-Titanium Controlled Memory Instruments

Introduction

The purpose of this study was to understand how fatigue affects the torsional properties of both traditional nickel-titanium (NiTi) and NiTi controlled memory (CM) files.

Methods

Typhoon (TYP; Clinician's Choice Dental Products, New Milford, CT) 25/.04 and 40/.04 rotary files in both NiTi and CM were tested to obtain the mean number of cycles of failure (N_f) using a 3-point bending apparatus. New files were then precycled to 4 conditions (0%, 25%, 50%, and 75% of the N_f), and torsional resistance tests were performed. Each file was exposed to torsional stress until failure, and at that point the torque and distortion angles were measured. The fracture surface of each fragment was examined with a scanning electron microscope.

Results

TYP CM files had an N_f 7 times higher than that of TYP files (P < .05). No difference in torque between the CM files and the conventional NiTi files of either file size was detected (P > .05). The torque of the size 40/.04 files was significantly higher than the torque of the size 25/.04 files (P < .05). In the 40/.04 files group, TYP files in the 75% precycling group had a significantly lower torque than files in the group with no precycling (P < .05), whereas slight precycling (25%) significantly reduced the distortion angle on TYP CM files (P < .05). The CM files of both sizes had a significantly higher distortion angle than the corresponding NiTi files (P < .05). The fractured files in the precycling groups showed the typical pattern of torsional failure.

Conclusions

Within the same amount of precycling (25%, 50%, and 75%), the cyclic fatigue life of TYP CM instruments was significantly higher than that of the TYP instruments. However, the torque value of TYP CM was similar to TYP files. The larger instruments were not only less resistant to cyclic fatigue but were affected most by prestressing of both TYP and TYP CM files.     

Buckling Resistance of Various Nickel-Titanium Glide Path Preparation Instruments in Dynamic or Static Mode

IntroductionThe aim of this study was to compare the buckling resistance of nickel-titanium (NiTi) instruments for glide path preparation depending on the test mode (static vs dynamic).MethodsThe conventional PathFile (PF; Dentsply Sirona, Ballaigues, Switzerland) and heat-treated ProGlider (PG, Dentsply Sirona) and WaveOne Gold Glider (WG, Dentsply Sirona) were evaluated. The instrument tips were placed in a small dimple prepared in an aluminum cube in a customized device. The file was then pushed in the axial direction at a 1.0-mm/s crosshead speed with rotation (dynamic mode) or without rotation (static mode). The dynamic mode of WG used its dedicated reciprocating rotation, whereas the others were rotated continuously at 300 rpm. The axial load and lateral buckling displacement were simultaneously measured. Data were analyzed statistically using 2-way analysis of variance (P = .05).ResultsThe buckling resistance in the dynamic mode was higher than in the static mode for PG and WG (P < .05), whereas PF was not influenced by test modes (P > .05). In the dynamic mode, the PG required the highest buckling load followed by PF and WG (P < .05). In the static mode, the WG showed the lowest load (P < .05). The dynamic mode showed significantly more upper level lateral buckling displacement than in the static mode (P < .05).ConclusionsWhen the glide path preparation instruments moved in the dynamic mode as in clinical situations, the buckling resistance of the heat-treated NiTi glide path instruments was higher than in the static condition. The heat-treated instruments may have better buckling resistance than the conventional NiTi instrument in clinical situations.     

Effectiveness of a Manual Glide Path on the Preparation of Curved Root Canals by Using Mtwo Rotary Instruments

IntroductionNickel-titanium rotary instruments reduce procedural errors and the time required to finish root canal preparation. The goal of this study was to evaluate the effectiveness of a manual glide path on the preparation of curved root canals with Mtwo rotary system.MethodsForty buccal root canals with angles of curvature between 25 to 76 degrees were randomly divided into 4 groups (n = 10); 2 groups were instrumented with Mtwo instruments to the full length, and in the other 2 groups a glide path with #08-15 K files was performed before instrumentation with Mtwo system. Digital double radiographic technique was used to determine apical transportation and the change in angle of curvature. Also working time was calculated.ResultsNo statistically significant differences in the angle of canal curvature, apical transportation, and the working time were found between groups with glide path and no glide path. No significant differences were found when comparing the results of 3 variables between degrees of curvature.ConclusionThe use of a manual glide path before Mtwo rotary system did not influence the apical transportation in curved root canals.     

Root Canal Preparation and Enlargement Using Thermally Treated Nickel-Titanium Rotary Systems in Curved Canals

IntroductionThe purpose of this study was to evaluate root canal preparation and apical enlargement of curved canals using rotary heat-treated and heat/surface-treated systems by micro–computed tomographic imaging.MethodsCurved mesial root canals (n = 48) of mandibular molars (20°–40°) were prepared using ProDesign Logic (PDL; Easy Equipamentos Odontológicos, Belo Horizonte, MG, Brazil) 25/.01 and 25/.06 or HyFlex EDM (HFEDM) 10/.05, HyFlex CM 20/.04, and HFEDM 25/.08. Apical enlargement was performed using PDL 40/.05 or HFEDM 40/.04. Scanning (9 μm) was performed before and after preparation and after apical enlargement using micro–computed tomographic imaging. Volume, percentage of volume increase, debris, untouched root canal surface, and centering ability were analyzed. Statistical analysis was performed using Mann-Whitney, Wilcoxon, and unpaired t tests (α = .05).ResultsHFEDM promoted a higher volume increase of the root canals than PDL after preparation and after apical enlargement (P < .05). The apical enlargement promoted a significant decrease in debris and untouched surface in both groups (P < .05). The percentage of debris and untouched surface were similar between HFEDM and PDL after preparation and after apical enlargement (P > .05). Both systems promoted centered canals (P > .05).ConclusionsHFEDM instruments promoted greater volume of the root canal than PDL. However, the cleaning ability of the instruments was similar. The apical increase up to size 40 with both instruments provided less debris and untouched surfaces and allowed centralization of the curved root canals.     

Comparison of the effect of different glide path files on amount of apically extruded debris in curved root canals

It is essential to create a glide path before root canal preparation with nickel–titanium rotary files to avoid file breakage and preserve the original canal structure. The aim of this study was to compare the amount of apically extruded debris after using different glide path files. A total of 96 first mandibular molars with curved mesial roots were randomly divided into six groups (n = 16) which are K-files, Proglider, R-Pilot, TruNatomy Glider, WaveOne Gold Glider and group without a glide path. Apically extruded debris was measured after glide path and canal preparation. The highest amount of debris was found in the control group without a glide path and using a glide path file caused less debris and significant differences were observed between R-Pilot, TruNatomy Glider, ProGlider, WaveOne Gold Glider and K-file groups. It may be recommended to create a glide path before root canal shaping to reduce the amount of extrusion debris from the apical. Especially in curved and narrow root canals, it is recommended to use an R-Pilot file before root canal shaping in order to reduce the amount of apically extruded debris.     

Mechanical Properties of Various Glide Path Preparation Nickel-titanium Rotary Instruments

Introduction

The aim of this study was to compare the cyclic fatigue, torsional resistance, and bending stiffness of single-file glide path preparation nickel-titanium instruments.

Cutting efficiency of five different types of rotary nickel-titanium instruments

The purpose of this study was to compare the cutting efficiency of the following rotary nickel-titanium instruments: Alpha-File (Komet, Lemgo, Germany), FlexMaster (VDW, Munich, Germany), Mtwo (VDW, Munich, Germany), ProFile (Dentsply Maillefer, Ballaigues, Switzerland), and RaCe (FKG, La-Chaux-de-Fonds, Switzerland). New .06/25 and .04/35 instruments were used; sample size was 12 for each group. Cutting efficiency of all 120 instruments was determined in a rotary working motion by means of a computer-driven testing device. Special plastic samples with a cylindrical canal were used, and the maximum penetration depth of the instruments into the lumen was the criterion for cutting efficiency. Statistical analysis was performed by using analysis of variance and post hoc Student-Newman-Keuls test. Out of all .06/25 instruments, Mtwo and RaCe displayed significantly greater penetration depths than all other instruments, whereas for the other size FlexMaster, Mtwo, and RaCe were significantly superior to all other instruments (p < 0.05). For both sizes, the significantly lowest values were obtained by ProFile (p < 0.05). Under the condition of this study, Mtwo and RaCe displayed the greatest cutting efficiency.     

Evaluation of Root Canal Transportation,Centering Ratio,and Remaining Dentin Thickness Associated with ProTaper Next Instruments with and without Glide Path

IntroductionThe purpose of this study was to evaluate and compare the volume of removed dentin, transportation, and centering ability of ProTaper Next (PTN) system with and without glide path preparation by using cone-beam computed tomography (CBCT) imaging.MethodsSixty mesiobuccal canals of mandibular first molars with curvatures of 25°−35° were divided into 3 experimental groups (n = 20) according to the instrumentation technique as follows: group PG/PTN (glide path was created with ProGlider [PG]) and canals were shaped with PTN system), group PF/PTN (glide path was created with PathFile [PF]) and canals were shaped with PTN system), and group PTN (glide path was not performed and canals were shaped with PTN system only). Canals were scanned before and after instrumentation by using CBCT scanner to evaluate root canal transportation and centering ratio at 3, 5, and 7 mm from the apex and volumetric changes. Data were statistically analyzed, and the significance level was set at P < .05.ResultsThere was no significant difference among the tested groups regarding the volume of removed dentin and centering ratio (P > .05). At 3-mm and 5-mm levels, the PG/PTN group showed a significantly lower mean transportation value among the groups (P < .05). However, at 7-mm level, there was no significant difference in canal transportation among the groups (P > .05).ConclusionsPG/PTN instrumentation method revealed better performance with fewer canal aberrations when compared with instrumentation performed with PF/PTN or PTN only.     

Comparator Choice in Studies Testing Endodontic Instrument Fatigue Resistance: A Network Analysis

AimsEndodontic instruments are frequently compared against each other for their cyclic fatigue resistance (CFR). It is unclear what drives the comparator choice in CFR studies, and how comparators and comparisons have evolved over time. We aimed at evaluating CFR study networks, hypothesizing that indications and instrument properties (alloy, manufacturer) drive comparisons.MethodsA systematic review was performed via Medline and Embase (1986–2017). In vitro studies analyzing the CFR of ≥2 engine-driven instruments in an artificial curved root canal system were included. We classified instruments according to name, alloy, and manufacturer. Study networks were analyzed using social network analysis techniques.ResultsEighty-five studies on 56 different instruments (9 alloys, 17 manufacturers) were included. For instruments, a low-density (0.19), highly clustered (0.71) network with 3 separate subnetworks (for glide path, shaping, and retreatment instruments) emerged. Certain instruments (ProTaper Universal [Dentsply Maillefer, Ballaigues, Switzerland], Mtwo [VDW Dental, Munich, Germany]) served as hub nodes and possible gold standards. Conventional Nickel-Titanium was the most frequently used alloy. Few manufacturers dominated the network. The diversity of tested instruments, alloys, and manufacturers increased in recent years.ConclusionsComparisons of CFR were usually made along indications. Some instruments and alloys (conventional Nickel-Titanium) dominated the networks. Overall risk of bias by comparator choice seems moderate; however, the evidence on certain, less often tested instruments may not be robust. Factors underlying the network geometry (eg, sponsorship) should be explored.     

Cyclic Fatigue Resistance of Nickel-titanium Rotary Instruments according to the Angle of File Access and Radius of Root Canal

IntroductionThe aim of this study was to compare the influences from different access angles and curvature radii on cyclic fatigue resistance of nickel-titanium rotary files.MethodsTwo file systems (2Shape [TS; MicroMega, Besançon, France] and HyFlex CM [HCM; Coltène/Whaledent, Allstätten, Switzerland]) were used. A total of 192 instruments of TS #25/.04 (TS1), TS #25/.06 (TS2), HCM #25/.04, and HCM #25/.06 were evaluated at 3 insertion angles (0°, 10°, and 20°) and 2 radii (5 mm and 3 mm) in 16-mm stainless steel artificial canals with a 60° curvature. Cyclic fatigue resistance was determined by the number of cycles to failure (NCF) using a customized testing device. Data were analyzed statistically with the significance level established at 95%.ResultsIn the 3-mm radius canal, the instruments showed lower cyclic fatigue resistance than in the 5-mm radius canal (P < .05). HCM #25/.06 and all .04 taper instruments had a significant NCF reduction at 20° and 10° in the 3-mm radius canal (P < .05), whereas TS2 showed no significant differences. In the 5-mm radius of curvature, although .06 taper instruments had no significant NCF reduction for each angle tested, .04 taper files exhibited significant NCF reduction when tested at 20° (P < .05). Comparing the same size instruments, HCM had higher NCF than TS (P < .05). Instruments with a .04 taper exhibited higher NCF than the .06 ones with the same heat treatment (P < .05).ConclusionsAn inclined insertion into the canals decreased cyclic fatigue resistance of thermal-treated instruments with a .04 taper at all radii of curvature tested. The synergistic effect of a small radius of curvature and access angulation of heat-treated instruments decreases their fatigue resistance.     

Torsional Fatigue Resistance of Blue-treated Reciprocating Instruments

Introduction

The aim of the present study was to evaluate the influence of blue thermal treatment on the torsional resistance behavior of M-Wire Reciproc files (VDW, Munich, Germany).