One Curve Research Articles

Investigation of four nickel titanium endodontic instruments, with cyclic fatigue resistance, scanning electron microscopy, and energy dispersive x-ray spectroscopy.

The aim of this study was to compare of four different nickel-titanium (Ni-Ti) endodontic files and evaluate in terms of cyclic fatigue resistance and metallurgical properties. Four different type Ni-Ti root canal files Protaper Next X2 (PTN) (Dentsply Maillefer, Ballaigues, Switzerland), One Curve (OC) #25.06 (Micro Mega, Besancon, France), EndoPlus Flex Plus Gold X2 (EPG) (Turkuaz Dental, Denizli, Turkey), and EndoPlus Flex Plus Blue #25.06 (EPB) (Turkuaz Dental, Denizli, Turkey) files were tested for cyclic fatigue resistance (n = 20). During experiments artificial zirconia block canal was used. The artificial canal designed with curvature 60° and 5-mm radius. The number of cyclic to fracture (NCF) was noted. Fractured length (FL) parts of Ni-Ti files were recorded to assessment of fracture volumetric point. All fractured surfaces of Ni-Ti files were assessed by scanning electron microscope (SEM) to confirm the type of fractures. Descriptive evaluation become accomplished for the fundamental composition of units with the aid of using energy-dispersive x-ray spectroscopy (EDX). NCF data were evaluated via Bonferroni test with post hoc multiple comparison method. OC showed the highest NCF values (p < .05). The standardization of the study was confirmed as the FL of files was statistically similar in length (p > .05). SEM analysis confirmed that all scanned samples were fractured due to cyclic fatigue. EDX analysis confirmed that EPB established the poorest Ni content file. RESEARCH HIGHLIGHTS: The cyclic fatigue-related failure of One Curve was significantly more resistant than Protaper Next and EndoPlus files. Scanning electron microscopy images showed that One Curve and Protaper Next have round tips Energy dispersive x-ray spectroscopy showed that all four endodontic instruments mainly have Nickel and Titanium elements.

Assessment of Debris Extrusion in Curved Canals: An In Vitro Analysis of Various Single-File Endodontic Instrumentation Systems.

Rotary single-file endodontic systems are commonly used for root canal treatment. However, very few studies have evaluated the apical extrusion of debris generated by these systems during canal preparation at normal body temperature in laboratory conditions. The aim of this study was to evaluate the amount of apically extruded debris caused by seven different single-file endodontic instrumentation systems at body temperature in mandibular molar teeth with curved root canals. One hundred forty mandibular first permanent molars were randomly divided into seven groups (n = 20) to be prepared by one of the following systems at 35°C: Reciproc Blue (REC Blue), WaveOne Gold (WOG), One Reci (OR), Neoniti, HyFlex EDM (HEDM), One Curve (OC), or XP Shaper (XPS). Debris was collected into preweighted Eppendorf tubes. The weight of the extruded debris was recorded by subtracting the weight of the tooth-free apparatus from the post-procedure weight. Data were analyzed by one-way ANOVA and Tukey's tests (p < 5%). REC Blue, WOG, and OR groups extruded significantly more debris from the apex than XPS, OC, and Neoniti groups (p < 0.05). No significant difference was observed among the XPS, OC, Neoniti, and HEDM groups (p > 0.05). All the instruments were associated with debris extrusion. However, REC Blue, WOG, and OR extrude significantly more debris than other instruments. The amount of debris with different files was REC Blue > OR > WOG > HEDM > OC > Neoniti > XPS. XPS, Neoniti, and OC caused significantly less extrusion of debris than REC Blue, WOG, and OR.

Impact of Angle of File Access and Location of Canal Curvature on the Dynamic Cyclic Fatigue of Nickel Titanium Rotary Instruments.

To evaluate the impact of different file access angles and root canal curvature's location on the fatigue failure of One Curve (OC) and E3 Azure (EZ) NiTi files using a dynamic model at simulated body temperature. Eighty new instruments with similar tip sizes and taper (#25/0.06) from two NiTi rotary systems, One Curve and E3 Azure, were tested at simulated body temperatures (37°C) using a custom-made dynamic cyclic fatigue device. Instruments were divided into four subgroups according to the location of root canal curvature (a coronal curve 5 mm from the root canal orifice and an apical curve 10 mm from the root canal orifice) and the angle of file access (0° or 30°). Instruments were operated in simulated stainless-steel canals having a 60° curve and a 3 mm radius. A custom-made device produced controlled vertical pecks during file rotation. Time to failure (sec) was registered, and the length of the fragment segments was measured (mm). Data were analysed statistically with One-Way ANOVA and Tukey post hoc tests. The significance level was set at 5%. All separated instruments were examined by scanning electron microscope. One-way ANOVA (p<0.05) found a significant difference among the tested instruments. Post Hoc analysis revealed lower cyclic fatigue resistance when the angle of file access was 30º, and the root canal curvature was located coronally for both files (p<0.0001). Three-way ANOVA showed that the angle of file access was the most influential contributor to cyclic fatigue, followed by the location of file curvature and, finally, the file type (p<0.0001). The fractographic examination revealed a predominantly ductile fracture mode for all tested instruments. The lengths of all fractured segments showed no significant difference (p>0.05), indicating an accurate trajectory during testing. OC files had superior cyclic fatigue resistance than EZ files; coronal curvatures negatively impacted cyclic fatigue resistance compared to apical curvatures, while the angle of file access presented the highest impact on dynamic cyclic fatigue.

Apical extrusion of debris when using OneCurve, ProTaper Next and TruNatomy in curved canals.

The extrusion of apical debris is related to various factors, and may be affected by variations in technique or instrumentation system. Although the extrusion cannot be completely prevented, it is crucial to minimize the amount of extruded material. The present study aimed to compare apical debris extrusion by the novel TruNatomy (TRN), OneCurve (OC) and ProTaper Next (PTN) instruments in curved root canals. A total of 60 multi-rooted human mandibular molar teeth with moderate and severe curvature were selected and randomly divided into 3 groups. The root canals were prepared with the OC, TRN and PTN files. For collecting the debris extruded through the apical foramen, Eppendorf tubes were used. After the vaporizing period, the tubes were re-weighed, and the amount of the extruded debris was calculated by subtracting the initial weight from the final weight. Statistical analysis was performed with the Shapiro-Wilk and Kruskal-Wallis tests. The statistical significance level was set at p < 0.05. The least amount of debris was extruded with TRN and the greatest with PTN, but the difference between the groups was not significant (p = 0.257). All instrumentation systems were associated with debris extrusion. The tested file systems presented similar results in terms of apical debris extrusion in curved canals. The novel TRN system demonstrated promising results, comparable to OC and PTN.

Efficacy of passive ultrasonic activation and photon-initiated photoacoustic streaming on apical extruded debris of different rotary systems in curved canals

Aim: The aim of this study was to investigate the impact of photon-initiated photoacoustic streaming (PIPS) and ultrasonic activator Ultra X (UX) on the extrusion of debris using the One Curve (OC) rotary system and the Reciproc Blue (RB) system in curved canals. Methodology: Ninety extracted mandibular first molar teeth were divided into six groups (n = 15), Group (1): OC with PIPS, (2) OC with UX, (3) OC with conventional needle irrigation (CNI), (4) RB with PIPS, (5) RB with UX, and (6) RB with CNI. The irrigation activation methods were used in the final irrigation with 2.5 cc of distilled water. The apically protruded debris was collected into pre-weighed Eppendorf tubes. By deducting the tube's initial weight from the final weight, the weight of dry protruded debris was calculated. Two-way ANOVA test was used to analyze the results statistically. Results: A significant difference was found among all groups (p &lt; 0.05). No statistically significant difference was found among the instrumentation systems, regardless of the irrigation technique employed (p &gt; 0.05). The statistically significant difference was found among the PIPS, UX, and CNI irrigation systems, regardless of the rotary systems (p &lt; 0.05). CNI caused significantly less debris extrusion than the UX ultrasonic irrigation activation systems. Conclusion: The UX irrigation activation system caused the highest amount of debris extrusion in curved canals. PIPS can be preferred to ultrasonic devices as irrigation activation systems. How to cite this article: Akman M, Bozkurt DA, Zogheib C. Efficacy of passive ultrasonic activation and photon-initiated photoacoustic streaming on apical extruded debris of different rotary systems in curved canals. Int Dent Res 2023;13(1):13-18. https://doi.org/10.5577/idr.2023.vol13.no1.3 Linguistic Revision: The English in this manuscript has been checked by at least two professional editors, both native speakers of English.

Comparison of the incidence of postoperative pain in single sitting root canal treatment after using two reciprocating systems and two continuous rotary systems: An in vivo study.

The aim of the present study was to compare the incidence of postoperative pain in single sitting root canal treatment after using two reciprocating and two continuous rotating file systems. One hundred and four permanent mandibular canine and first premolar teeth were selected for the study and were divided into two groups 1 and 2 comprising 52 teeth each. Group 1 was treated using reciprocating file systems and was subdivided into two subgroups A and B using WaveOne Gold (WOG) and Reciproc Blue (RB), respectively. Group 2 was treated using continuous rotating file systems and was divided into two subgroups A and B using One Curve (OC) and Vortex Blue (VB), respectively. Treatments were performed in a single sitting. After the visit, the patients were given a prescription for ibuprofen 400 mg to be taken every 6 h if they experience pain. Participants were asked to rate the intensity of the postoperative pain on a visual analog scale according to four classes (no pain, mild pain, moderate pain, and severe pain) after 24 h, 48 h, 72 h, and 7 days. Patients were also asked to record the number of prescribed analgesic medication tablets taken at these time points. There was a statistically significant difference (P = 0.00) among the reciprocating file systems and continuous file systems regarding the incidence of postoperative pain after 24, 48, and 72 h which signifies that pain incidence and duration is less with respect to reciprocation instrumentation as compared to continuous instrumentation. The use of Reciproc instrumentation system (WOG and RB) showed significantly less intensity and duration of posttreatment pain compared to the single-file rotary system (OC and VB) in patients with symptomatic irreversible pulpitis with apical periodontitis.

Analysis of apical extrusion of debris using one curve, Confi Taper, Trushape® 3D conforming and reciproc blue files

Aim: To evaluate and compare apical extrusion of debris using One Curve, Confi Taper, TRUShape®3D Conforming and Reciproc Blue file systems. Methods: 60 extracted single rooted mandibular premolar human teeth were randomly divided into 4 groups (n=15). Premolars were instrumented using one of the following instruments ONE CURVE, CONFI TAPER, TRUShape® 3D CONFORMING AND RECIPROC BLUE FILES. Pre-weighted Eppendorf tubes were used to collect the apically extruded debris during instrumentation. Then the amount of debris collected was calculated by subtracting the weight of the Eppendorf tube before and after preparation. Then the data was analysed using Kruskal wallis test. At 0.5 significant level. Results: Some amount of debris extrusion was found with all the instruments from the apex. Highest amount of apical extrusion of debris was found in Reciproc Blue followed by Trueshape 3D Conforming, Confi Taper and least apical extrusion seen in One Curve. Conclusions: Under the limitations of this in-vitro study, the amount of apically extruded debris measured for the used instruments was REC Blue&gt; Trueshape® 3D Conforming&gt;ConfiTaper&gt; One Curve.

Shaping ability of rotary and reciprocating single-file systems in combination with and without different glide path techniques in simulated curved canals

Background/purposeGlide path management (GPM) is a consequential clinical step that serves to influence predictably successful root canal therapy. However, the effect of GPM on the shaping ability of single-file system remains controversial. This study compared the performance of rotary single-file One Curve (OC) and reciprocating single-file Reciproc Blue (RCB) in combination with/without different glide path techniques: no glide path preparation (NG), PathFile (PF), ProGlider (PG) and WaveOne Gold Glider (WOGG), respectively. Materials and methods80 simulated curved canals (n = 10 canals/per group) were instrumented to an apical size of 0.25 mm using OC and RCB in combination with/without different glide path techniques, respectively. The amount of resin removal, canal transportation, and the degree of canal straightening were measured in Photoshop CS6 software. Statistical analysis of the data was performed by using Kruskal–Wallis test, followed by Dunn's post hoc test with Bonferroni correction (α = 0.05). ResultsPost–glide path analysis found that WOGG and PG produced less canal transportation and curvature straightening than PF (P < 0.05). Post-shaping analysis showed that OC groups removed significantly less resin than RCB groups (P < 0.05). The PG and WOGG subgroups in both OC groups and RCB groups produced less transportation and curvature straightening than NG and PF subgroups (P < 0.05). OC + PG subgroup and OC + WOGG subgroup yielded the least canal transportation and curvature straightening (P < 0.05). ConclusionPG and WOGG can improve the shaping ability of OC and RCB instrument. OC, especially when combined with PG and WOGG, has a less aggressive dentin cutting and more centered preparation than the RCB instrument.

Torsional Resistance of Heat-Treated Nickel-Titanium Instruments under Different Temperature Conditions.

This study compared the torsional resistance of heat-treated nickel-titanium (NiTi) instruments under different temperature conditions. Four thermomechanically treated single-use NiTi rotary instruments were selected for this study: OneShape (OS), OneCurve (OC), WaveOne Gold (WOG) and HyFlex EDM (HFE). Each instrument was further subdivided by temperature into 2 subgroups. Maximum torque and the distortion angle until fracture occurred were evaluated. Differential scanning calorimetry analysis was performed to measure the phase transformation temperature. Statistical analysis was performed using a two-way ANOVA and t-test (p < 0.05). Fractured fragments were observed using scanning electron microscopy (SEM). The two-way ANOVA showed no significant differences for different temperature conditions. At both room (RT) and body temperature (BT), OS was predominantly austenite while HFE was martensite. OC and WOG were predominantly martensite at RT and mixed phase at BT. At BT, more than half of WOG was martensite, while half of OC was austenite. SEM examination showed no topographical differences between instruments in different temperature groups. In relation to a limitation of this study, there was no difference in torsional resistance of NiTi rotary instruments between the BT and RT conditions. This implies that clinicians do not need to consider a decrease of torsional resistance of heat-treated NiTi instruments at BT.

Influence of kinematics and incidence angles on the cutting efficiency of two single-file nickel-titanium rotary instruments.

To compare the cutting efficiency of F6 Sky Taper (F6ST) and One Curve (OC) with different kinematics and cutting inclinations. Cutting efficiency of 80 new F6ST and OC was tested at 90° and 70° inclination in relation to the sample, in continuous rotation and reciprocation, against standardised gypsum samples for 120 seconds using a customised device. Data expressed as weight loss and length of the sample cut were analysed using two‐way analysis of variance and Tukey t‐test (P<.05). F6ST showed significantly higher cutting efficiency in reciprocation, while OC in continuous rotation. Regardless of inclination, F6ST showed statistically higher values than OC in reciprocation, while OC exhibited higher cutting ability in continuous rotation. The 70° inclination significantly improved the cutting efficiency of both files. Reciprocation improved the cutting efficiency of F6ST while continuous rotation enhanced cutting ability of OC. An inclined insertion improved the cutting ability, independently from the movement.

Evaluation of the Cyclic Fatigue of Two Single Files at Body and Room Temperature with Different Radii of Curvature.

Background: To compare the influence of different temperatures and curvature radii on the cyclic fatigue resistance of F6 SkyTaper (F6ST) and One Curve (OC) single file nickel-titanium rotary instruments. Methods: A total of 120 instruments of F6ST and OC #25.06 were evaluated in 5 mm and 3 mm curvature radii at two temperatures (20 °C ± 1 °C and 37 °C ± 1 °C) in 16 mm stainless steel artificial canals associated with a curvature of 60°. The cyclic fatigue of tested files was assessed by employing a customized testing apparatus and expressed as times to fracture (TtF). A statistical analysis was performed with the significance level set at 95%. Results: All instruments decreased their TtF at 37 °C except for OC in the 3 mm radius, in which no significant difference was detected between 20 °C and 37 °C. A 3 mm curvature radius negatively affected TtF of all tested instruments, except for F6ST at 20 °C. F6ST had higher TtF than OC in the 3 mm radius at 20 °C, with no significant difference between them in the other tested conditions. Conclusions: Under the limits of the present in vitro study, body temperature impaired cyclic fatigue resistance of all files, except for OC in the 3 mm curvature radius. All instruments exhibited lower times to fracture in the 3 mm radius, excluding F6ST at 20 °C.

Effect of number of uses on the cyclic fatigue resistance of single-file rotary instruments

Aim: The purpose of this study was to evaluate and compare the cyclic fatigue resistance of two different single file nickel-titanium instruments -Reciproc blue (RB) and One Curve (OC)- used for single or in a certain number of times.&#x0D; Material and Methods: One Curve (n=40) and Reciproc Blue (n=40) files were used in this study. The instruments were divided into two subgroups (n=20); those to be used for the first time(N) and those that were previously used (U) in the clinic for the root canal treatment of a vital mandibular molar with three root canals. Cyclic fatigue testing of these instruments was performed in an artificial stainless-steel canal with 60° curvature, 5 mm radius 1.5 mm width, and 3.0 mm depth. All the tested files were rotated/reciprocated under the continuous irrigation with distilled water at 37°C until fracture occurred. The time to failure (TTF) in seconds and the number of cycles to failure (NCF) were recorded. Data were statistically analyzed and the significance level was set at P &lt; 0.05.&#x0D; Results: A significant difference was observed among the four groups and between RB-N/RB-U, OC-N/OC-U, RB-N/OC-N, and RB-U/OC-U, regarding TTF and NCF values (P &lt; 0.05). Predicted time for % 99 survival were RB-N &gt;RB-U &gt; OC-N &gt; OC-U. The TTF value of RB is greater than OC in both the new instrument groups and the used instrument groups.&#x0D; Conclusions: RB showed higher cyclic fatigue resistance than OC files in both new and used instrument groups. Reuse of RB and OC instruments significantly reduced the cyclic fatigue resistance of the instrument.

Shaping ability of three thermally treated nickel-titanium systems in S-shaped canals.

This study aimed to compare the shaping ability of ProTaper Next (PTN), HyFlex EDM (HEDM) and One Curve (OC) systems manufactured via different thermal treatment methods in simulated S-shaped canals. Sixty S-shaped canals in clear resin blocks were enlarged to a final apical size of 25 using PTN, HEDM and OC instruments (n = 20 canals/group). Composite images were obtained by superimposing pre- and post-preparation images. The amount of removed resin was measured perpendicularly to the canal surface in 22 points. Prepared canal width and canal transportation at different levels were determined. Canal aberrations were also recorded. Data were statistically analysed using analysis of variance, the Kruskal-Wallis and the chi-square tests at a 0.05 significance level. OC produced the most conservative enlargement and better maintained particularly the apical curvature of the S-shaped canals than HEDM and PTN. OC and HEDM better maintained the canal terminus and coronal curvature than PTN.

Comparative evaluation of dentin volume removal and centralization of the root canal after shaping with the ProTaper Universal, ProTaper Gold, and One-Curve instruments using micro-CT.

Background. The main goal of our study was to assess the volume of dentin removed and transportation in root canals using ProTaper Universal (PTU), ProTaper Gold (PTG) and One-Curve (OC). Ni-Ti rotary instruments in extracted human teeth using by micro-CT. Methods: Thirty human upper 1st premolar teeth with two separate root canals and sturdy, mature root tips were used in the present study. Specimens were decoronated and root length was standardized for micro CT scanning before root canal preparation done. The teeth were randomly separated into three categories (n = 10) according to the rotary NiTi system used for canal instrumentation, i.e., PTU (Dentsply, Maillefer), PTG (Dentsply, Maillefer), and OC (Micro-Mega SA). After root canal preparation, samples were scanned again on micro-CT by the same scanning parameters. Surface area, canal volume, structure model index (SMI), percentage of uninstrumented area and transportation parameters were obtained for each sample before and after micro-CT analyse. Results: No significant differences between the PTG and PTU in terms of the total volume of removed dentin, surface area and percentage of uninstrumented areas were found. However, regarding to parameters above, OC showed a lower efficacy than PTG and PTU in coronal section. Regarding canal transportation, PTG and OC showed lower mean transportation values at all levels. Conclusion: This paper demonstrated the root canal shaping abilities of the PTU, PTG, and OC NiTi file systems. The PTG and OC systems were associated less canal transportation and a better ability to preserve dentinal walls than PTU. There was no significance different between all rotary file systems for SMI values however, PTU and PTG showed greater canal volume and surface area change than OC file systems in coronal section.

Impact of Peracetic Acid on the Dynamic Cyclic Fatigue of Heat-Treated Nickel-Titanium Rotary Endodontic Instrument.

Peracetic acid (PAA) is widely used as a sterilizing/disinfecting agent, and, in endodontics, it has been introduced as a promising irrigant in root canal treatment. It has been used at different concentrations to achieve various functions. However, endodontic instruments in contact with PAA of a certain concentration may affect their fatigue resistance. Therefore, the aim of this study was to investigate the impact of PAA on the cyclic fatigue resistance of three commercial heat-treated nickel-titanium (NiTi) rotary files. Three types of heat-treated NiTi rotary files were selected: One Curve (OC), ProTaper Gold (PTG), and Wave One Gold (WOG). Each type was divided into three subgroups (n = 6 for each file type): (1) untreated instruments; (2) files immersed in 0.002% PAA; and (3) files immersed in 0.35% PAA. The performance of each file type was tested in a simulated canal. The number of cycles to fracture (NCF) was determined to assess cyclic fatigue resistance of the files. Independent sample t-test was applied to compare each treated file within a subgroup with its respective control group, and one-way ANOVA was used for comparison among the main groups. All types of tested files revealed a significant decline in the cyclic fatigue resistance after exposure to 0.002% PAA except the PTG (P=0.209). After exposure of the files to a higher concentration (0.35% PAA), a dramatic reduction was demonstrated by all the groups. Before and after exposure of the files to PAA, PTG displayed the highest cyclic fatigue resistance, followed by the WOG, while the OC showed the lowest resistance. Exposure of heated-treated NiTi files to PAA in a relatively high or low concentration adversely affects the cyclic fatigue resistance. The PTG files demonstrated the best performance among the tested types and can be disinfected with 0.002% PAA for clinical purpose.

Characterization of the differential efficacy of austenitic vs martensitic NiTi rotary files in non-surgical root canal retreatment: a micro-CT analysis.

Aim: Our study aims to characterize the differential efficacy of martensitic and austenitic files in root canal retreatment regarding defiling ability, debris management and morphometric features. Materials and methods: A total of 10 human premolar teeth with two separate fully formed roots were selected, prepared with BioRace system (BR) up to a size BR2 (0.04/25). Root canals were filled and then divided according to the file type into two groups (n = 10). Two geometrically identical files have been used with the only difference between them is heat treatment; One Curve (OC) martensitic and One Shape (OS) austenitic. Preoperative and postoperative Micro-CT scans were done for all the samples, and the percent volume of residual filling materials was calculated. Canals reshaping and remaining debris in the canals were assessed by calculating the volume of the canals before and after retreatment using Micro-CT software. Results: The percentages of removed filling materials were similar between both groups (97.2% OC vs 97.8% OS). OS was significantly faster than OC (P < 0.05). Retreatment procedure did not significantly change volume, structure model index, surface area, and canal curvature. OS group transported the canals more than OC at the apical third (P < 0.05). There were no significant differences between both groups concerning un-instrumented surface area and accumulated hard tissue debris (AHTD) (P > 0.05). Conclusion: Under the circumstances of this study, neither file systems could completely remove the filling materials. However, OC resulted in less transportation than OS in the apical one third (P < 0.05). Also, OC resulted less AHTD than OS but with no statistical difference.

Shaping ability of ProTaper Gold, One Curve, and Self-Adjusting File systems in severely curved canals: A cone-beam computed tomography study.

Aim:The aim of the study was to evaluate and compare canal transportation (CT), centering ability (CA), and volumetric changes in severely curved canals prepared using ProTaper Gold (PTG), One Curve (OC), and Self-Adjusting File (SAF) systems via cone-beam computed tomography (CBCT).Materials and Methods:Sixty mesiobuccal canals of maxillary molars were selected. Pre- and postinstrumentation CBCT scans were taken in the same position. CT and CA were calculated at 1 mm, 4 mm, and 7 mm from the apex; change in volume for whole canal was measured and analyzed statistically.Results:SAF showed the least mean CT at all the levels with no statistically significant differences at 1 mm and 4 mm when compared to other groups while statistically significant differences were observed at 7 mm with PTG and OC. Regarding CA, SAF better maintained canal centricity than PTG and OC at all the levels assessed, though the differences were not statistically significant except at 7 mm where statistically significant difference was observed between SAF and OC. SAF removed less volume of dentin followed by PTG and the highest removal was shown by OC.Conclusion:SAF showed promising behavior with the least CT, most centered preparation, and minimal dentin removal.

Influence of Artificial Canal Lubricants on the Lifespan of One Curve File under Static and Dynamic Test Modes

Aim: This study was designed to determine the lifespan of One Curve (OC) heat-treated nickel-titanium (NiTi) rotary files operating under static and dynamic fatigue conditions using intracanal lubricants such as oil or sodium hypochlorite (NaOCl). Materials and Methods: The OC files were tested using an artificial zirconia canal. They were tested in air without any intracanal lubricant under static (Group 1) and dynamic (Group 4) modes, and after filling the canal with either oil (Group 2 and Group 5 under static and dynamic modes respectively) or 1% NaOCl (Group 3 and Group 6 under static and dynamic modes respectively). One Curve files were rotated freely in the canal at a speed of 350 rpm (continuous clockwise) under static mode until file failure occurred through fracture. In case of dynamic testing, the instruments were rotated at the same conditions in the canal, but with an additional back and forth movement until fracturing. The number of cycles to fracture (NCF) were recorded and statistically analysed using One Way ANOVA and Bonferroni tests. Results: Testing of the file in air demonstrated the lowest fatigue resistance, where the static test mode (NCF: 560 ± 8.25) was the worse than the dynamic mode (NCF: 636.81±14.49). On the other hand, the instruments tested under both static and dynamic modes in oil as an intracanal lubricant showed improved lifespans in terms of NCF (1193.89±7.96 and 1351.39 ± 7.06) compared to the same modes in NaOCl lubrication (878.89 ± 8.59 and 1093.82±39.08). Regardless of intracanal lubricant, the dynamic groups produced better results than the static ones. In terms of fractured length, significant differences were identified between the groups except between Group 2 and Group 6. Conclusions: Type of intracanal lubricant demonstrated a more influential effect on the file lifespan than the mode of cyclic fatigue (CF) test. The dynamic CF test utilising oil intracanal lubricant resulted the best improvement in the file lifespan.

Influence of surrounding temperature and angle of file access on cyclic fatigue resistance of two single file nickel-titanium instruments.

The purpose of this study was to evaluate the influence of surrounding temperature and angle of file access on cyclic fatigue resistance of F6 SkyTaper (F6ST) and One Curve (OC). 120 new files #25.06 were tested at two insertion angles (0° and 20°) at room (20°C±1°C) and body (35°C±1°C) temperatures in a 16-mm stainless steel artificial canal (60° curvature and 5-mm radius), using a customised device. Cyclic fatigue resistance was expressed as time to fracture (TtF) in seconds. Data were analysed statistically (P<0.05). All instruments exhibited lower TtF at 35°C (P<0.05). An access of 20° did not significantly influence the TtF of tested instruments, independently from the temperature. OC exhibited higher TtF of F6ST at 20°C with a 20° inclination (P<0.05). Under the present conditions, F6ST and OC showed a significant reduction of cyclic fatigue resistance at body temperature. A file inclined insertion did not affect the cyclic fatigue resistance of tested instruments at both temperatures.

Effects of a Novel NiTi Thermomechanical Treatment on the Geometric Features of the Prepared Root Canal System.

Objectives: This study aimed to compare the ex vivo performance of two rotary nickel–titanium (NiTi) systems with similar designs but manufactured from martensitic and austenitic alloys, the One Curve (OC) and One Shape (OS) rotary endodontic files, respectively. Methods: Forty separate mesial canals of 20 extracted mandibular molars were scanned using micro-computed tomography (CT), which were divided into 2 groups and instrumented with OC and OS, respectively. Post-instrumentation micro-CT scans were evaluated using validated computer algorithms to compare changes in canal thickness, surface area, structure model index (SMI) scores, volume of removed dentin, percentage of untreated canal surface, percentage of curvature straightening, and the amount of canal transportation. Results: Both files led to significant changes in the basic root canal geometry, with no preparation errors and no statistically significant differences. However, OC treatment resulted in significantly less curvature straightening (17.30%; 10.77%) (independent samples t test, p < 0.05) and less apical transportation (55.11 µm; 33.15 µm) (Mann–Whitney U, test p < 0.05) compared to OS treatment. Transportation values in the middle and coronal thirds were statistically similar (independent sample t-test, p > 0.05). OC treatment produced significantly less straightening and less apical transportation than OS.