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Aim: This study was twofold: (i) it aimed to investigate the morphometric changes of three temperature‐sensitive nickel–titanium (NiTi) instruments at different temperatures, and (ii) to conduct an in vivo real‐time analysis of intracanal temperature changes. Methods: Changes in the shape and length of XP‐Endo Shaper, XP‐Endo Finisher, and XP‐Endo Finisher‐R were evaluated in real time whilst heated in a temperature‐controlled water bath from 22 to 45°C. Instruments were fixed to a laminated water‐resistant 1 mm graph paper attached to a stone block. Instruments were imaged whilst subjected to increasing temperature using a digital camera attached to an operating microscope. From recorded videos, still frames were extracted at 10‐s intervals and changes in the length and shape of each instrument were measured and changes were plotted against time. Moreover, the intracanal temperature of distal roots of lower molars was measured in vivo for patients attending the clinic for non‐surgical root canal treatments. The temperature was measured using a K‐type thermocouple probe inserted into the mid‐root level after irrigating the canal with a solution set at room temperature (22°C) or heated to 45°C. The intraoral and intracanal temperatures were recorded using a video camera for 180 s at 5‐s intervals to plot the change in the intraoral and intracanal temperature, after both irrigation solution temperatures, with time. Results: The shape transformation of XP‐Endo Shaper began at 31.5 ± 2.0°C and reached its optimal transformation at 35.1 ± 1.0°C. For the Finisher and Finisher‐R, shape transformations began at 29.2 ± 1.9 and 26.9 ± 2.2°C reaching the optimal transformation at 33.9 ± 1.4 and 32.7 ± 1.7°C, respectively. The average decreases in lengths of XP‐Endo Shaper, Finisher, and Finisher‐R after full transformation were 0.43 ± 0.23, 1.07 ± 0.22, and 1.15 ± 0.22 mm, respectively. The intracanal temperature reached 32.9 ± 0.8 and 33.2 ± 1.0°C after 3 min of application of irrigation solutions set at 22 or 45°C, respectively. Conclusion: The tested instruments exhibited diverse changes in their shapes and lengths at varying temperatures. Despite the temperature of the irrigation solution, the intracanal temperature consistently remained lower than the intracanal temperature once equilibrium was reached. This highlights the importance of considering the temperature of irrigation solution during in vitro testing of endodontic instruments. [ABSTRACT FROM AUTHOR]

This article discusses the use of nickel-titanium (NiTi) rotary instruments in endodontics, specifically focusing on the challenges associated with instrument fractures. Early studies reported high fracture rates, leading to hesitation among clinicians to adopt these instruments. However, manufacturers have made design adjustments to mitigate the risk of fracture. The article proposes a multimethod approach for evaluating NiTi instruments, incorporating mechanical tests, metallurgical characterization, shaping ability, and irrigation efficiency. The authors argue that this comprehensive approach provides a more thorough understanding of the instruments' performance. They hope that their proposed model encourages other researchers to adopt a similar approach in their studies. [Extracted from the article]

Aim: This study compared the shaping ability of four new reciprocating and rotary nickel‐titanium instruments, with triangular or S‐shaped cross‐section, in the mesial canals of mandibular molars using micro‐computed tomographic (micro‐CT) evaluation. Methodology: Twenty‐four extracted mandibular molars with Vertucci's class IV configuration in the mesial root were selected for this study. The teeth were matched in fours according to anatomic similarities as revealed by micro‐CT and then distributed into four groups of 12 mesial canals each according to the instrumentation technique: Reciproc Blue, R‐motion, VDW.Rotate and RaCe EVO. The final apical size of instrumentation was 30/0.04 for three systems and 25/08 for the Reciproc Blue instrument. Micro‐CT scans were taken before and after preparation to evaluate the canal volume, area and unprepared surface areas, as well as the centring ability, and the canal: root width ratio. Results: Preparation with all systems significantly increased the volume and area of the canals (p <.05). There were no significant differences between groups regarding the amount of unprepared areas in both the apical and full canal lengths (p >.05). Variation in the centre of gravity showed no significant difference between groups either (p >.05). The canal: root width ratio at levels 0 and 4 mm apically to the coronal canal opening was significantly increased by all systems (p <.01), with no significant differences between groups (p >.05). The canal width never exceeded 40% of the root width. Conclusions: Reciprocating or rotary instruments, with a triangular or an S‐shaped cross‐section, performed equally in shaping Vertucci's class IV mesial canals of mandibular molars. [ABSTRACT FROM AUTHOR]

This narrative review will focus on the evolution, present and future of engine‐driven root canal preparation. Root canal preparation changed drastically when Walia in 1988 introduced the use of nickel‐titanium (NiTi) alloys in Endodontics. In 2013, five generations of NiTi endodontic instruments had been established based on their metallurgical, mechanical properties and design features. Since then, manufacturers have been introducing further major changes in instrument design and characteristics that have not been translated in new recognized generations of instruments. In general, those changes have demonstrated enhanced instrument properties, but it is not clear yet if all those improvements are directly translated to an improvement in clinical success. This narrative review attempts to address the present status of engine‐driven instruments in terms of both evidence from laboratory‐based studies and clinical data, to identify potential further generations of instruments, and last to anticipate future directions for research and development. [ABSTRACT FROM AUTHOR]

The aim of this review is to provide a critical overview of the physical properties (surface hardness, cutting efficiency, bending properties, flexibility and cyclic fatigue resistance) of NiTi instruments. Frequently used experimental models regarding these aspects will be presented and discussed with regard to their strengths and weaknesses. For all these aspects, a plethora of experimental models have been described. Based on a critical appraisal and especially taking the appropriate translation of experimental findings to clinical endodontics into account, suggestions for future research based on clearly defined and valid experimental methodologies will be provided. Up to now, very few attempts have been made to assess which particular physical properties of NiTi instruments exert an impact on the clinical outcome of root canal treatment. Departure from merely focusing on physical properties and fracture characteristics towards more biological aspects in terms of treatment outcome is essential. [ABSTRACT FROM AUTHOR]

Aim: To evaluate the shaping ability of several heat‐treated nickel–titanium systems used to prepare root canals with moderate and severe curvature, in extracted mandibular molars, by micro‐computed tomography, considering their variation in kinematics and design. Methodology: Curved‐mesial roots of mandibular molars were randomly selected and assigned into 4 balanced experimental groups (n = 10), established by determining homogeneous 3D parameters of volume and surface area: R‐Motion (RM) size 30, 0.04 taper (RM; FKG Dentaire), Reciproc Blue (RCB) size 25, 0.08 taper (RCB; VDW GmbH), HyFlex CM (HFX) size 30, 0.04 taper (HFX; Coltène Whaledent) and XP‐endo Shaper size (XPS) 30, 0.01 taper (XPS; FKG Dentaire). The volume of irrigation was established at 10 ml of 2.5% NaOCl. Throughout the entire root canal preparation procedures, the samples were fixed in a vice submerged in a container with water monitored at 37°C. Dimensional cross‐sectional measures of area, perimeter, roundness, major/minor diameters and 3‐dimensional (volume, surface area, structure model index – SMI) parameters as well as the smallest dentine thickness along the cervical and middle root thirds were evaluated by micro‐CT. Data were analysed using analysis of variance and post hoc Tukey tests (α = 5%). Results: Reciproc Blue and XPS had significantly greater mean increases in cross‐sectional area measurements, only in the middle third, when compared with RM and HFX (p <.05). RM, RCB and XPS had a similar increase in measurements of length and width of perimeter (p >.05), and HFX had significantly lower mean increases in perimeter values only when compared with XPS (p <.05). RCB and XPS had significantly greater mean increases in volume when compared with RM and HFX (p <.05). RM had a significantly lower difference in SMI after preparation, compared with RCB, HFX and XPS (p <.05). The smallest dentine thickness was observed after the use of RCB (p <.05), in the danger and safety zones. Conclusions: XP‐endo Shaper and RM had a shaping ability similar to that of instruments with larger tapers, achieved with less dentine removal in danger and safe zones in curved‐mesial canals of extracted molar teeth treated on a laboratory benchtop. [ABSTRACT FROM AUTHOR]

Aim: This randomized clinical trial aimed to assess the effect of two rotary (ProTaper Retreatment + ProTaper Gold and Hyflex EDM) and two reciprocating (Reciproc Blue and WaveOne Gold) NiTi systems on postoperative pain after root canal retreatment on single‐rooted incisor teeth. Methodology: One hundred and eighty patients scheduled for root canal retreatment were randomly assigned to one of the four groups according to the NiTi system (ProTaper Retreatment + ProTaper Gold, Hyflex EDM, Reciproc Blue or WaveOne Gold) used for the removal of root canal fillings and further canal preparation. The working length was determined to be 1 mm shorter than the '0.0' mark of the apex locator. Root canals were filled with gutta‐percha and an epoxy resin‐based root canal sealer using a lateral compaction technique. The teeth were restored using a resin composite material. A single operator performed the retreatments in a single visit. The incidence and intensity of postoperative pain were rated on a numeric rating scale by patients 24, 48 and 72 h after retreatment. The number of analgesic tablets (400 mg Ibuprofen) taken by patients was also recorded. Data were analysed using the Mann–Whitney U, Wilcoxon and chi‐square tests. Results: For the intensity of postoperative pain, the difference between the four groups was not significantly different (p >.05). No significant difference was found between the groups in terms of analgesic medication intake (p >.05). Conclusions: The rotary and reciprocating NiTi systems tested in this study were associated with similar intensity of postoperative pain and intake of analgesics following root canal retreatment on single‐rooted incisor teeth completed in one visit. [ABSTRACT FROM AUTHOR]

Aim: To evaluate the viability of the electrochemical dissolution of fragments of fractured NiTi instruments in root canals of extracted human maxillary molars, using two electrodes and the solution restricted to a small reservoir coupled to the pulp chamber. The primary hypothesis was that this method enables the reduction of fragment volume and re‐establishment of the root canal path with a size 08 K‐file, both in simulated canals and in extracted human maxillary molars. Methodology: Fragments of F1 ProTaper instruments were polarized in simulated root canals and in distobuccal root canals of extracted maxillary molars using a new method, with the solution restricted to a small acrylic microcell coupled to each resin block or pulp chamber. Two electrodes were used, where one was kept in contact with the intracanal fragment and another was positioned in the solution present in the acrylic microcell. After the tests, a size 08 K‐file was used passively to verify the possibility of bypassing the fragment, which was also confirmed by radiographic analysis. Micro‐CT analysis of the teeth was used before and after fragment dissolution to evaluate the volume, length and porosity of the fragments. The D'Agostino–Pearson normality test was used to verify the distribution of the data. A paired t‐test (P < 0.05) was used to compare the volume, length and porosity of the fragments before and after the dissolution tests. Results: After dissolution, all fragments could be bypassed with a size 08 K‐file in both simulated canals and in extracted teeth. The dissolution process did not result in significant reduction of neither the fragment length nor the fragment porosity. However, it resulted in a significant reduction of fragment volume (paired t‐test, P < 0.05). Conclusion: The electrochemical dissolution of fragments of NiTi files in root canals of extracted human maxillary molars using two electrodes, and the solution restricted to a small reservoir coupled to the pulp chamber resulted in a significant reduction of fragment volume. The re‐establishment of the root canal path with the passive insertion of size 08 K‐files was possible in all samples after the tests, both in simulated canals and in extracted teeth. [ABSTRACT FROM AUTHOR]

Aim: To compare the dissolution time of two solutions, a fluoride solution and a sodium hypochlorite solution, both saturated with sodium chloride, during the electrochemical dissolution of instruments consisting of conventional nickel‐titanium alloy and Gold thermomechanically treated nickel‐titanium alloy. Methodology: Two solutions, an NaF solution consisting of 12 g L−1 NaF with 180 g L−1 NaCl and an NaOCl solution consisting of 2.5% NaOCl with 180 g L−1 NaCl, were evaluated in a polarization test of a sample of 48 ProTaper Universal F1 (PTU F1) and WaveOne Gold Small (WOGS) instruments. The electric potentials were 0.5 V and 5 V for the NaF and NaOCl solutions, respectively. The electrochemical cell consisted of three electrodes for the polarization test of the PTU F1 and WOGS instruments, which had 6 mm of the tip immersed in the test solutions. The electric current was recorded for 540 s. If complete dissolution of the immersed tip occurred in less than the expected time, the experiment was considered complete. The time variations (in seconds) of the instruments in the solutions were measured. Data were subjected to statistical analysis using the Mann–Whitney, Kruskal–Wallis and Dunn tests. The corrosion patterns of the instruments were evaluated by scanning electron microscopy (SEM). Results: The NaF and NaOCl solutions were associated with significantly different (P = 0.000) dissolution times of the instrument, with mean values of 12.96 s and 83.63 s, respectively. There was no significant difference (P = 0.649) in dissolution time between the PTU F1 and WOGS instruments. Conclusions: NaF and NaOCl solutions were able to electrochemically dissolve PTU F1 and WOGS instruments. However, the NaF solution achieved dissolution in significantly less time. [ABSTRACT FROM AUTHOR]

The endodontic literature contains a plethora of studies on static and dynamic cyclic fatigue resistance tests performed on a large array of rotary or reciprocating nickel–titanium endodontic instruments. It was the aim of this review to summarize the currently available evidence to point out the different outcomes from static versus dynamic tests and to assess whether cyclic fatigue tests provide useful data and information for clinical practice. An electronic literature research in the database PubMed was performed using appropriate search terms, and the titles and abstract were screened for relevance. Language was restricted to English. The review reveals marked differences between the results obtained in static and dynamic tests, and also, the results for the same instruments assessed either under static or dynamic experimental conditions are widely inconsistent. Between the lowest and the highest value for one and the same pathfinding instrument was a factor of about 123 when cyclic fatigue was assessed either under static or dynamic experimental conditions. Moreover, standard deviations of up to 30% have been reported. Environmental temperature has a 500% impact on the lifetime of instruments. In conclusion, fatigue resistance tests conducted under room temperature should be regarded as having little meaning and the scientific and clinical benefits of fatigue resistance tests are very limited. These data should be provided by the manufacturer of the instruments. [ABSTRACT FROM AUTHOR]

Aim: To evaluate the torsional properties of the NiTi glide path reciprocating instruments R‐Pilot (VDW, Munich, Germany) and WaveOne Gold Glider (Dentsply Sirona, Ballaigues, Switzerland). Methodology: Ten R‐Pilot (size 12.5,.04 taper) and 10 WaveOne Gold Glider (size 15,.02v taper) instruments were used. The torque and angle of rotation at failure of new instruments (n = 10) were measured according to ISO 3630‐1. Three millimetres of each instrument tip was clamped to a small load cell by a lever arm linked to the torsion axis. The fracture surface of all fragments was examined with a scanning electron microscope. Data were analysed using the Student t‐test at a significance level of P < 0.05. Results: The maximum torsional strength of the R‐Pilot instruments was greater than the WaveOne Gold Glider (P < 0.05). In contrast, WaveOne Gold Glider instruments had significantly higher angular rotation to fracture than R‐Pilot instruments (P < 0.05). The scanning electron microscopy of the fracture surfaces revealed similar and typical features of torsional failure (ductile type) for both brands. The torsional failure displayed two zones: the first with microvoids in the centre of the instruments (core) and the second one represented by plastic deformation around the microvoids; this configuration occurred because of the shear stresses originated during the twisting. Conclusions: R‐Pilot instruments had a lower angle of rotation to fracture but a higher torque to failure than WaveOne Gold Glider instruments. [ABSTRACT FROM AUTHOR]

Aim: To evaluate the influence of three engine‐driven NiTi file systems manufactured from different NiTi alloys for the preparation of second mesiobuccal (MB2) canals in extracted maxillary first molars using a micro‐computed tomographic (micro‐CT) scanner. Methodology: Thirty maxillary molars with two canals in the mesiobuccal root were selected and randomly divided into three groups (n = 10): Reciproc [REC; size 25,.08 taper; VDW, Munich, Germany], ProDesign R [PDR; size 25,.06 taper; Easy, Belo Horizonte, Brazil] and Mtwo [MO; size 25,.06 taper; VDW, Munich, Germany]. Before and after root canal preparation of the MB2 canal, the teeth were scanned using a micro‐CT to evaluate canal transportation, centring ability, dentine thickness and volume change. The working time to achieve working length was also evaluated. All parameters were compared statistically using the Kruskal–Wallis and Dunn test for multiple comparisons, with a significance level of 5%. Results: There was no significant difference amongst the groups regarding canal transportation and centring ability (P > 0.05). However, the PDR size 25,.06 taper group had significantly lower canal volume and volume of dentine removal compared with a MO size 25,.06 taper and REC size 25,.08 taper (P < 0.05). A root perforation was detected in MO size 25,.06 taper and REC size 25,.08 taper groups, respectively. Regarding the working time, the PDR size 25,.06 taper required a significantly longer time to achieve working length than MO size 25,.06 taper and REC size 25,.08 taper (P < 0.05). Conclusions: All NiTi systems had similar canal transportation, centring ability and increase in apical volume after preparation of MB2 canals. However, the PDR size 25,.06 taper had less volume of dentine removal, absence of root canal perforation and required a longer time to accomplish the root canal preparation. [ABSTRACT FROM AUTHOR]

Aim: To determine the distortional angle and torsional load at the pseudoelastic limit of Reciproc Blue instruments and to verify the safety of using pre‐set dedicated motors designed for use with the original Reciproc instruments. Methodology: Two torsional conditions of Reciproc R25 and Reciproc Blue R25 were tested using a custom device. The first condition fixed the file tips at 3 mm and repetitively rotated them, with gradually increasing angles, from 10° to 270°, and the resulting torque was recorded (n = 15). The second test involved a single continuous rotation until fracture (n = 15). The pseudoelastic limits of the instruments were determined from their torque‐rotation curves. For statistical analysis, two‐way analysis of variance and t‐tests were used, at a 95% significance level. Tested specimens were examined using field‐emission scanning electron microscopy (FE‐SEM). Results: The angle at the pseudoelastic limit was significantly greater for Reciproc Blue than Reciproc, regardless of test mode (P < 0.05). When torsional loading was repeated, using gradually increasing rotational angles, the torsional resistance was significantly lower than for a single rotation (P < 0.05). However, under all test conditions, the pseudoelastic limit was below the pre‐set 170° of the dedicated reciprocating motor. FE‐SEM evaluation of the lateral aspects of the instruments revealed numerous longitudinal microcracks running along their long axis. For Reciproc Blue groups, the file shaft machining grooves were distorted after repetitive and continuous torsional tests. Conclusions: The 170° pre‐set angle of the dedicated endodontic motors for the Reciproc system was safe for Reciproc Blue in single or time‐restricted use. [ABSTRACT FROM AUTHOR]

Aim: To evaluate the bacterial reduction achieved by WaveOne Gold (Dentsply Sirona Endodontics, Ballaigues, Switzerland), Hyflex EDM (Coltene‐Whaledent, Altstätten, Switzerland), and XP‐endo Shaper (FKG Dentaire SA, La Chaux‐de‐Fonds, Switzerland) in canals infected with Enterococcus faecalis. The null hypothesis (H0) was that there would be no difference amongst the NiTi systems in reducing the root canal bacterial load. Methodology: Seventy‐four mandibular premolar teeth with straight and round root canals were selected. Sixty‐two root canals were contaminated with E. faecalis for 4 weeks and subjected to mechanical preparation with one of three single‐file NiTi rotary systems (WaveOne Gold, Hyflex EDM, and XP Endo Shaper). Twelve non‐contaminated root canals were used as negative controls. Bacterial samples were collected with sterile paper points (Dentsply Sirona Endodontics) before and after rotary instrumentation to quantify the bacterial load. Five roots from each instrumentation group were evaluated topographically from the coronal, middle and apical thirds by SEM. The bacterial reduction was calculated and analysed statistically by the Kruskal–Wallis and Dunn post hoc tests, all at 5% significance. Results: The samples taken before instrumentation showed approximately 9.64 log CFU bacterial load. Instrumentation with the Hyflex EDM and XP‐endo Shaper resulted in significantly greater bacterial reduction than those with WaveOne Gold (P = 0.00). All specimens had bacterial growth. SEM images supported the CFU/mL data. Thick and dense debris was observed in WaveOne Gold samples. Instrumentation resulted in the disruption of the biofilm‐like structure, and both areas of clean and open dentinal tubules and areas with thick debris were observed in Hyflex EDM and XP‐endo Shaper samples. Conclusions: Instrumentation in straight and round canals of premolar teeth with the Hyflex EDM and XP‐endo Shaper resulted in significantly greater bacterial reduction than WaveOne Gold. No instrumentation system rendered root canals completely free from bacteria. [ABSTRACT FROM AUTHOR]

Aim: To evaluate and compare the canal shaping ability of BioRace, ProTaper NEXT and Genius engine‐driven nickel‐titanium (NiTi) file systems in extracted mandibular first molars using micro‐computed tomography (MCT). Methodology: Sixty mesial root canals of mandibular first molars were randomly divided into three equal groups, according to the instrument system used for root canal preparation (n = 20): BioRace (BR), ProTaper NEXT (PTN) or Genius (GN). Root canals were prepared to the full WL using a crown‐down technique up to size 35,.04 taper instruments for BR and GN groups and size 30,.07 taper instruments for the PTN group. MCT was used to scan the specimens before and after canal instrumentation. Changes in dentine volume, the percentage of uninstrumented canal surface and degree of canal transportation were evaluated in the coronal, middle and apical thirds of canals. Data were analysed statistically using one‐way analysis of variance and Tuckey's post hoc tests with the significance level set at 5%. Results: There were no significant differences between the three groups in the terms of dentine removed after preparation and determination of the root canal volume, or percentage of uninstrumented canal surface (P > 0.05). No significant differences were found between the systems for canal transportation in any canal third (P > 0.05). Conclusions: The shaping ability of the BR, PTN and GN NiTi file systems was equally effective. All instrumentation systems prepared curved root canal systems with no evidence of undesirable changes in 3D parameters or significant shaping errors. [ABSTRACT FROM AUTHOR]

Aim: To evaluate the effects of the [NaF 12 g L−1 + NaCl 1 g L−1] solution used in the electrochemical dissolution process of fractured endodontic files, as well as its NiTi‐containing product, on dentine hardness, topography and human fibroblast viability. Methodology: Sixty single‐rooted human teeth were evaluated for dentine microhardness using the Vickers hardness test and the area and number of dentinal tubules by scanning electron microscopy. The samples were divided according to the dentine surface treatment: distilled water; 17% EDTA; [NaF 12 g L−1 + NaCl 1 g L−1]; and 17% EDTA + [NaF 12 g L−1 + NaCl 1 g L−1]. Thirty‐six single‐rooted human teeth were divided according to the irrigation protocol: Dulbecco's Modified Eagle's Medium + 10% foetal bovine serum; 5.25% NaOCl; [NaF 12 g L−1 + NaCl 1 g L−1]; and [NaF 12 g L−1 + NaCl 1 g L−1 + NiTi]. The extracts in contact with the apical foramen were used in the MTT assay to evaluate human fibroblast viability, with dilutions of 100%, 50%, 25% and 12.5%. Statistical tests used were paired t‐tests, one‐way anova, Tukey's test, Kruskal–Wallis test and Dunn's post‐test. Results: The [NaF 12 g L−1 + NaCl 1 g L−1] solution did not modify dentine microhardness or the average dentinal tubule area. However, EDTA induced changes in dentine structure and microhardness (P < 0.05). The [NaF 12 g L−1 + NaCl 1 g L−1] solution, and its NiTi‐containing product had lower cytotoxicity than NaOCl at dilutions of 25% and 50% (P < 0.01). Conclusions: The [NaF 12 g L−1 + NaCl 1 g L−1] solution did not alter dentine microhardness or damage the dentine structure. It also demonstrated lower cytotoxicity than NaOCl. [ABSTRACT FROM AUTHOR]

The role and effect of glide path preparation in root canal treatment remain controversial. This systematic review aims to compare apical transportation and canal centring of different glide path preparation techniques, with or without subsequent engine‐driven root canal preparation. A database search in PubMed, PubMed Central, Embase, Scopus, EBSCO Dentistry & Oral Sciences Source and Virtual Health Library was conducted, using appropriate key words to identify the effect of glide path preparation (or its absence) on apical transportation and canal centring. An assessment for the risk of bias in included studies was carried out. Amongst 2146 studies, 18 satisfied the inclusion criteria. Nine studies assessed glide path preparation per se, comparing apical transportation and canal centring of rotary systems and/or manual files; eleven further investigations examined the efficacy of the glide path prior to final canal preparation with different engine‐driven systems. Risk of bias and other study design features with potential influence on study outcomes and clinical implications were assessed. Based on the available evidence, and within the limitation of the studies included, preparation of a glide path using rotary sequences performs similarly (in most of the component studies) or significantly better than manual preparation when assessing apical transportation or canal centring. When compared to the absence of a glide path, canal shaping following glide path preparation was of similar, or significantly better quality, in regard to apical transportation or canal centring. [ABSTRACT FROM AUTHOR]

Aim: To evaluate the presence and propagation of defects and their effects on surfaces of nickel–titanium (NiTi) instruments using noncontact, three‐dimensional optical profilometry, and to assess the accuracy of this method of investigation. Methodology: The flute surface areas of instruments from two commercial instrumentation systems, namely Reciproc R25 (n = 5) and WaveOne Primary (n = 5), were assessed and compared before and after performing two instrumentation cycles in simulated root canals in clear resin blocks. All the analyses were conducted on areas measuring 211 × 211 μm, located 3 mm from the tips of the instruments. A quantitative analysis was conducted before and after the first and second instrumentation cycles, using the Sa (average roughness over the measurement field), Sq (root mean square roughness) and Sz (average height over the measurement field) amplitude parameters. All the data were submitted to statistical analysis at a 5% level of significance. Results: There was a significant increase (P = 0.007) in wear in both groups, especially between baseline and the second instrumentation cycle, with significantly higher wear values being observed on WaveOne instruments (Sz median values = 33.68 and 2.89 μm, respectively, for WO and RP groups). A significant increase in surface roughness (P = 0.016 and P = 0.008, respectively, for Sa and Sq) was observed in both groups from the first to the second instrumentation cycle, mostly in WaveOne specimens. Qualitative analysis revealed a greater number of defects on the flute topography of all the instruments after use. Conclusions: More defects were identified in WaveOne Primary instruments compared to Reciproc R25, irrespective of the evaluation stage. The investigation method provided an accurate, repeatable and reproducible assessment of NiTi instruments at different time‐points. [ABSTRACT FROM AUTHOR]

Abstract: In the past 10 years, several proprietary processing procedures for nickel titanium (NiTi) alloy were developed to improve the mechanical properties of NiTi endodontic instruments. Beside specific thermal and mechanical treatments, manufacturers introduced several machining procedures (e.g. twisting, electrical discharge machining), as well as techniques for final surface finishing. NiTi alloys used for endodontic instruments can be subdivided into instruments that mainly contain the austenite phase (austenitic: conventional NiTi, M‐Wire, R‐Phase) and those mainly containing the martensite phase (martensitic: CM Wire, Gold and Blue heat‐treated NiTi). Thermomechanically treated NiTi alloys have been reported to be more flexible with improved cyclic fatigue resistance and greater angle of deflection at failure when compared to conventional NiTi. These enhanced properties may be attributed to a modified phase composition containing varying amounts of R‐phase and martensite. Endodontic instruments made of austenitic alloys possess superelastic properties because of stress‐induced martensite transformation and consequently tend to spring‐back to their original form after deformation. In contrast, the martensitic instruments can easily be deformed due to the reorientation of the martensite variants and show a shape memory effect when heated. The use of martensitic alloy results in more flexible instruments, with an increased cyclic fatigue resistance compared with austenitic alloy. [ABSTRACT FROM AUTHOR]

Abstract: Aim: To examine the efficacy of a novel supplementary irrigant agitating brush (Finisher GF Brush, MedicNRG, Kibbutz Afikim, Israel) on the debridement of root canals prepared with a novel stainless steel rotary instrumentation system (Gentlefile; MedicNRG), or nickel titanium rotary instruments in oval root canals. Methodology: Mandibular premolars (n = 72) were selected and divided randomly into three experimental groups (n = 24) after microCT scanning: group 1, canal preparation to rotary NiTi size 20, .04 taper (R20); group 2, rotary NiTi to size 25, .04 taper (R25) and group 3, Gentlefile size 23, .04 taper (GF). Specimens were subdivided into two subgroups: subgroup A, syringe‐and‐needle irrigation (SNI); subgroup B, Finisher GF Brush (GB). Ten untreated canals served as controls. Specimens were processed for histological evaluation, and the remaining pulp tissue (RPT) was measured. Data were analysed using Mann–Whitney and Kruskal–Wallis tests (P = 0.05). Results: All experimental groups had significantly less RPT than the control (P < 0.05). Group 3B (GF‐GB) had significantly less RPT than groups 1B (R20‐GB) and 2B (R25‐GF; P < 0.05). When irrigated with SNI, there was no significant difference in the RPT between the three groups (P > 0.05). When instrumented with R20, there was no significant difference between SNI and GF (P < 0.05) whilst GB had significantly less RPT than SNI for R25 (P < 0.05). Conclusions: Supplementary irrigant agitation with the Finisher GF Brush improved the debridement of canals prepared with Gentlefile and size 25, .04 taper rotary NiTi. Root canal debridement did not significantly differ between the instruments when syringe irrigation was used. [ABSTRACT FROM AUTHOR]

Abstract: Aim: To evaluate the torsional properties of pathfinding nickel‐titanium (NiTi) rotary instruments manufactured from several NiTi alloys, ProGlider (M‐wire), Hyflex GPF (conventional NiTi Wire and controlled memory wire), Logic (conventional NiTi wire and controlled memory wire) and Mtwo (conventional NiTi wire). Methodology: A total of 56 NiTi instruments from Glidepath rotary systems (n = 8) were used: Logic (size 25, .01 taper), Logic CM (size 25, .01 taper), ProGlider (size 16, .02 taper), Hyflex GPF (size 15, .01 taper), Hyflex GPF CM (size 15, .02 taper; size 20, .02 taper) and Mtwo (size 10, .04 taper). The torsion tests were performed based on ISO 3630‐1 (1992). Three millimetres of each instrument tip was clamped to a small load cell by a lever arm linked to the torsion axis. Data were analysed using a one‐way analysis of variance ( anova) and Tukey test with a significance level at a = 5%. Results: The Logic size 25, .01 taper had significantly higher torsional strength values (P < 0.05). The ProGlider was significantly different when compared with Hyflex GPF size 15, .01 taper and size 15, .02 taper (P < 0.05). The Logic CM size 25, .01 taper had significantly higher torsional strength than Hyflex GPF size 15, .01 taper and size 15, .02 taper (P < 0.05). No difference was found amongst Mtwo size 10, .04 taper and Hyflex GPF groups (size 15, .01 taper; size 15, .02 taper; size 20, .02 taper). In relation to the angle of rotation, Logic CM size 25, .01 taper and Hyflex GPF size 15, .01 taper had the highest angle values (P < 0.05). The ProGlider had the lowest angle values in comparison with all the groups (P < 0.05) followed by Mtwo size 10, .04 taper. The Logic size 25, .01 taper had significantly higher angle of rotation values than ProGlider and Mtwo size 10, .04 taper (P < 0.05). Conclusion: The Logic size 25, .01 taper instrument made of conventional NiTi alloy had the highest torsional strength of all instruments tested. In addition, the ProGlider instrument manufactured from M‐Wire alloy had the lowest angle of rotation to fracture in comparison with the other instruments. [ABSTRACT FROM AUTHOR]

Abstract: Aim: To examine the cyclic fatigue resistances of R‐Pilot, HyFlex EDM and PathFile NiTi glide path files in S‐shaped artificial canals. Methodology: Twenty R‐Pilot (12.5/.04), 20 HyFlex EDM (10/.05) and 20 PathFile (19/.02) single‐file glide path files were included. Sixty files (n: 20/each) were subjected to static cyclic fatigue testing using double‐curved canals until fracture occurred (TF). The number of cycles to fracture (NCF) was calculated by multiplying the rpm value by the TF. The length of the fractured fragment (FL) was determined by a digital microcaliper. Six samples of fractured files (n: 2/each) were examined by SEM to determine the fracture mode. The NCF and the FL data were analysed using one‐way anova, post hoc Tamhane and Kruskal–Wallis tests using SPPS 21 software. The significance level was set at 5%. Results: In the double‐curved canal, all the files fractured first in the apical curvature and then in the coronal curvature. The NCF values revealed that the R‐Pilot had the greatest cyclic fatigue resistance, followed by the HyFlex EDM and PathFile in both the apical and coronal curvatures (P < 0.05). Conclusions: R‐Pilot NiTi glide path files, used in a reciprocating motion, had the greatest cyclic fatigue resistance amongst the tested NiTi glide path files in an artificial S‐shaped canal. [ABSTRACT FROM AUTHOR]

Abstract: Aim: To compare the torsional resistance of XP‐endo Shaper (XPS; size 30, .01 taper, FKG Dentaire, La Chaux‐de‐Fonds, Switzerland) instruments at body temperature with TRUShape (TRS; size 30, .06 taper, Dentsply Tulsa Dental Specialties, Tulsa, OK, USA), ProFile Vortex (PV; size 30, .04 taper, Dentsply Tulsa Dental Specialties) and FlexMaster (FM; size 30, .04 taper, VDW GmbH, Munich, Germany) nickel‐titanium rotary instruments. Methodology: A metal block with a square‐shaped mould (5 mm × 5 mm × 5 mm) was positioned inside a glass container. Five millimetres of the tip of each instrument was held inside the metal block by filling the mould with a resin composite. The instruments were tested for torsional resistance in saline solution at 37 °C. Data were analysed using one‐way analysis of variance ( anova) and Tukey post hoc tests. The significance level was set at P < 0.05. Results: FM had the greatest torsional resistance amongst the instruments tested (P < 0.001). There was no significant difference between FM and PV instruments (P = 0.211). The ranking for torsional resistance values was: FM > PV > TRS > XPS. Conclusions: FlexMaster and ProFile Vortex instruments were more resistant to torsional stress compared with TRUShape and XP‐endo Shaper instruments. The manufacturing process used to produce XP‐endo Shaper instruments did not enhance their resistance to torsional stress as compared with the other instruments. [ABSTRACT FROM AUTHOR]

Abstract: Aim: To isolate the effect of metallurgy in lateral and axial cutting efficacy against plastic and bovine dentine substrates by comparing two rotary systems with identical design but manufactured with either conventional nickel‐titanium or heat‐treated gold alloy. Methodology: A total of 258 ProTaper Universal (PTU) and ProTaper Gold (PTG) Shaping instruments were used. Bending behaviour was assessed to determine the appropriate displacement associated with a 2 N force in lateral cutting. Ten instruments of each type were used in lateral action for 60 s against bovine dentine or plastic substrates four consecutive times producing four notches in each specimen. Ten further instruments of each type were used in on axial action in four standardized simulated root canals fabricated from 4‐mm thick plastic or dentine discs. Both tests were performed at 300 rpm in a computer‐controlled testing platform. Notch area and torsional load were compared with Student's t‐tests. Repeated measures ANOVA was used to compare cutting efficiency across the four different time‐points. Pearson correlation coefficients between substrates were also determined. Results: For lateral action, all three PTG instruments cut significantly more effectively (P < 0.05) than PTU on the plastic substrate. S1 and S2 PTG cut significantly more after 120 and 180 s (P < 0.05) on bovine dentine substrate. For axial action, S1 and S2 PTG were significantly more efficient in cutting at 180 s on plastic and 120 s on bovine dentine (P < 0.05). Conclusion: Instruments made from heat‐treated nickel‐titanium gold alloy had equal or greater cutting efficiency when compared to those made from conventional nickel‐titanium. [ABSTRACT FROM AUTHOR]

Abstract: Aim: To compare the cyclic fatigue resistance (CFR) of PathFile, ProGlider and ScoutRaCe nickel‐titanium (NiTi) rotary instruments used in an S‐shaped artificial canal. Methodology: A total of 90 instruments were tested in an S‐shaped artificial canal (n = 30 for each group: PathFile (size 16, 2% constant taper), ProGlider (size 16, variable taper between 2% and 8% along the shaft) and ScoutRaCe (size 15, 2% constant taper). All files were rotated until fracture. The number of cycles to failure was counted to determine CFR. The length of each fractured fragment was measured in millimetres. The CFR was analysed statistically with the Kruskal–Wallis test. The fragment length was analysed using one‐way analysis of variance and Tukey's post hoc tests. Results: The ProGlider instruments were associated with significantly greater CFR than the PathFile and ScoutRaCe files in the apical curvature (P < 0.05). There was no significant difference between the CFR of the PathFile and ScoutRaCe files in the apical curvature (P > 0.05). ProGlider, PathFile and ScoutRaCe instruments exhibited similar CFR in the coronal curvature (P > 0.05). Conclusions: The ProGlider files had greater cyclic fatigue resistance than the PathFile and ScoutRaCe files in the apical curvature of an artificial S‐shaped canal. [ABSTRACT FROM AUTHOR]

Abstract: Aim: To compare the cyclic fatigue resistances of WaveOne Gold (Denstply Sirona, Ballaigues, Switzerland), WaveOne (Dentsply Sirona) and Reciproc (VDW, Munich, Germany) in interrupted reciprocation. Methodology: Three groups of 18 instruments each of WaveOne Gold Primary, WaveOne Primary and Reciproc R25 were subjected to cyclic fatigue tests in reciprocation and interrupted reciprocation. The instruments in group 1 were tested in reciprocation, whereas in groups 2 and 3, reciprocation was interrupted for 1 s in every 5 s and 10 s, respectively. Cyclic fatigue resistance was tested using dynamic test devices in stainless steel, curved canals (60°, r = 5 mm) until fracture, and the time to fracture values were recorded. The lengths of the fractured tips were also recorded, and fractured surfaces were examined with a scanning electron microscope (SEM). Data were evaluated by one‐way analysis of variance and Tukey's tests. Results: The cyclic fatigue resistance of WaveOne Gold Primary was not affected by the interruptions (P > 0.05) and exhibited significantly greater cyclic fatigue resistance than WaveOne Primary and Reciproc R25 in all groups (P < 0.05). Interruptions reduced the cyclic fatigue resistance of WaveOne Primary and Reciproc R25 significantly (P < 0.05). Conclusion: Interrupted reciprocation reduced the cyclic fatigue resistance of Reciproc R25 and WaveOne Primary. The cyclic fatigue resistance of WaveOne Gold Primary was greater than that of WaveOne Primary and was not dependent on the occurrence of interruptions. [ABSTRACT FROM AUTHOR]

Abstract: Aim: To evaluate the effect of three nickel‐titanium (Ni‐Ti) rotary systems with varying tapers on stress distribution and to analyse potential fracture patterns as well as the volume of fracture‐susceptible regions in two‐rooted maxillary premolars. Methodology: The root canals of three single‐rooted premolars were prepared with either HeroShaper (Micro‐Mega, Besançon, France) to (size 30, .04 taper), Revo‐S (Micro‐Mega) to AS30 (size 30, .06 taper) or ProTaper Universal (Dentsply Maillefer, Ballaigues, Switzerland) to F3 (size 30, .09 taper) Ni‐Ti files. The three root canals were scanned using micro‐computed tomography (μCT) (Skyscan 1174, Skyscan, Kontich, Belgium) and modelled according to the μCT data. An intact tooth model with a root length of 16 mm was also constructed based on μCT images of an extracted maxillary premolar with two roots. New models were constructed by replacing both of the original canals of the intact two‐rooted premolar model with the modelled canals prepared with the HeroShaper, Revo‐S or ProTaper Universal system. Occlusal forces of 200 N were applied in oblique and vertical directions. Finite element analysis was performed using Abaqus FEA software (Abaqus 6.14, ABAQUS Inc., Providence, RI, USA). Results: Upon the application of oblique occlusal forces, the palatal external cervical root surface and the bifurcation (palatal side of the buccal root) in tooth models experienced the highest maximum principal (Pmax) stresses. The application of vertical forces resulted in minor Pmax stress values. Models prepared using the ProTaper system exhibited the highest Pmax stress values. The intact models exhibited the lowest Pmax stress values followed by the models prepared with the HeroShaper system. Conclusion: The differences in Pmax stress values amongst the different groups of models were mathematically minimal under normal occlusal forces. Rotary systems with varying tapers might predispose the root fracture on the palatal side of the buccal root and cervical palatal root surface in two‐rooted premolars. [ABSTRACT FROM AUTHOR]

Abstract: Aim: To evaluate the resistance to cyclic fatigue of ProTaper Next (PTN; Dentsply Sirona, Ballaigues, Switzerland), Revo‐S (Micro‐Mega, Besançon, France), Mtwo (Sweden & Martina, Padova, Italy), Twisted Files (TF, SybronEndo, Orange, CA, USA) and EndoWave (J Morita Corporation, Osaka, Japan) used in continuous rotation or in reciprocation of Optimum Torque Reverse motion (OTR). Methodology: A total of 120 nickel‐titanium files were tested. Twenty‐four instruments for each brand were divided into two groups (n = 12) on the basis of the motion tested: continuous rotation (Group 1) or reciprocation of OTR motion (Group 2). Resistance to cyclic fatigue was determined by recording time to fracture (TtF) in a stainless steel artificial canal with a 60° angle of curvature and 5 mm radius of curvature. The TtF data were analysed by using two‐way analysis of variance ( anova) and Bonferroni's post hoc tests at 0.05. Results: Mtwo and TF had significantly higher TtF when compared with all other instruments, both in continuous rotation and in reciprocation of OTR motion (P < 0.0001 and P < 0.05, respectively). No difference was observed between Mtwo and TF (P > 0.05), in both motions. PTN was associated with higher cyclic fatigue resistance than Revo‐S and EndoWave, both in continuous rotation and in reciprocation of OTR motions (P < 0.0001). No difference was observed between Revo‐S and EndoWave, in both motions (P > 0.05). Reciprocating OTR motion improved TtF of all instruments (P < 0.0001). Conclusions: Reciprocation of OTR motion improved significantly cyclic fatigue resistance of all instruments tested compared with continuous rotation. Mtwo and TF had significantly higher cyclic fatigue than the other instruments, in both continuous rotation and reciprocation of OTR motion. [ABSTRACT FROM AUTHOR]

Abstract: Aim: To investigate the surface morphology and electrochemical potential of superelastic (SE), M‐Wire (MW) and shape memory technology (SMT) NiTi instruments before and after single clinical use in vivo. Methodology: A total of 60 ProTaper Universal F2 (PTU‐SE), ProTaper Next X2 (PTN‐MW), Typhoon (TYP), Hyflex (HF) and Vortex Blue (VB), the last three SMT, and size 25, .06 taper (n = 6 of each type) files were examined. Scanning electron microscopy (SEM), X‐ray energy‐dispersive spectroscopy (EDS) and electrochemical potential analysis were employed before and after clinical use. Statistical analysis was performed with one‐way analysis of variance and Bonferroni's post hoc test. Significance was determined at the 95% confidence level for both tests. Results: SEM observations of new instruments indicated the presence of marks left by the machining process during manufacturing and EDS revealed the existence of an oxide coating on shape memory instruments. After clinical use, the five types were associated with propagation of transverse cracks 3 mm from the tip. The surface oxide layer of TYP, HF and VB instruments had microcracks in multiple directions, whilst TYP and HF had fragmentation in chip form of the oxide layer. EDS analysis demonstrated a significant reduction of the oxide layer in shape memory instruments, except for VB. Electrochemical potentials were higher for shape memory instruments than for M‐Wire and superelastic NiTi instruments, respectively (P < 0.05). Conclusions: It appears that shape memory technology NiTi instruments have a dysfunctional oxide layer after clinical use. Additionally, they featured higher electrochemical potential relative to NiTi instruments manufactured from M‐Wire, and conventional superelastic NiTi alloy. [ABSTRACT FROM AUTHOR]

Abstract: Aim: To compare the pre‐sterilization cleaning of rotary Ni‐Ti files of different sizes previously used a. ex vivo and b. clinically by a washer–disinfector, a regular ultrasonic bath, and the same ultrasonic bath in combination with a recently developed cavitation intensifying method. Methodology: Two sets of two hundred rotary Ni‐Ti files, one previously used ex vivo and another one used clinically, were collected from the undergraduate and postgraduate clinics of the Academic Centre for Dentistry Amsterdam (ACTA). The instruments were immersed in an enzymatic solution and subsequently cleaned either by a washer–disinfector, a regular ultrasonic bath combined with a glass beaker, the same bath combined with a beaker lined with two cavitation intensifying sheets or with two standard plastic sheets. The positive control consisted of used files that did not undergo any cleaning and the negative control included new unused files. The instruments were then stained to reveal remaining protein material and scored under a stereoscopic microscope. The results were analysed by nonparametric statistical tests (α = 0.05). Results: No significant difference was found between the combination of the ultrasonic bath and the regular glass beaker and the same ultrasonic bath with the beaker lined with the cavitation intensifying sheets. The washer–disinfector left significantly more debris compared to the latter group when clinically used files were evaluated (P ≤ 0.001). The effect of instrument size on cleaning was not consistent. Conclusion: None of the tested methods was able to remove all residual protein material from the files; however, it could be noted that this study did not follow the reprocessing protocol provided by the manufacturer. [ABSTRACT FROM AUTHOR]

Aim To evaluate retrospectively the incidence of K3 nickel titanium rotary instrument fracture in referred cases during root canal treatment and re-treatment. Methodology Clinical and radiographic reports of 12 867 endodontic cases treated at the King Abdulaziz medical city between January 2010 and November 2015 were reviewed to obtain information on intracanal fractured instruments with respect to the treatment performed, tooth type and the size and at what level the instrument fractured (coronal, middle or apical). The degree of canal curvature was classified into mild (<10°), moderate (10-25°) or severe (>25°). Logistic regression was used to test the incidence of instrument fracture in relation to the root canal treatment performed and tooth type. Chi-square tests were used to analyse the fracture incidence in the treated teeth in respect to fracture level and fractured file diameter. The level of significance was set at 0.05. Results Root canal treatment was performed on 8946 cases, whilst re-treatment was performed on 3921 cases. The fracture incidence was higher during re-treatment cases (2.96%) than in primary root canal treatment (0.74%) ( P < 0.001) with a 1.41% incidence overall. There was a trend for more fractures in maxillary (1.68%) and mandibular (1.35%) molar teeth. Moreover, 56.6% of the fractured instruments occurred in severely curved canals, and the apical third of the root canal was the most common site for instrument fracture (85.7%), followed by middle (13.2%), and coronal (1.1%) thirds, mostly with file sizes 20 and 25 (59.9% and 25.27%, respectively). Conclusion The fracture incidence of K3 instruments was significantly greater during root canal re-treatment than root canal treatment, mainly with small instruments and in the apical third of the canals. [ABSTRACT FROM AUTHOR]

Aim To compare the cyclic fatigue properties of a novel file made using controlled memory Ni-Ti technology with those of files made from M-wire. Methodology Twelve files with similar cross-sectional geometry and tip size from each of the following groups were tested: Proflexendo made from CMT ( PE; size 30 0.04; Nexden, Houston, Tx, USA), ProFile Vortex made from M-wire ( PV; size 30 0.04; Dentsply Tulsa Dental, Tulsa, OK, USA) and ProTaper Universal made from regular alloy ( PU; F3; Dentsply Tulsa Dental). A custom-made cyclic fatigue device was made to evaluate the total number of cycles to failure for each system. A scanning electron microscope ( SEM) was used to examine the fractured surfaces of the fragments. The arithmetic means and standard deviations were calculated for the total number of cycles to failure. One-way analysis of variance was used to compare the mean cyclic failure amongst the three groups. Post hoc Tukey's test was performed to compare the difference of the means between the groups at a significance level of P < 0.05. Results Proflexendo had a significantly greater resistance to cyclic fatigue compared to other systems ( P < 0.001). Proflexendo files were able to withstand 500% more cycles to fracture when compared to ProFile Vortex files. Conclusions Manufacturing technique had a significant impact on the resistance to cyclic fatigue. Proflexendo files made from controlled memory Ni-Ti technology had the highest number of cycles to failure compared to ProFile Vortex made from M-wire files with similar taper and tip size. [ABSTRACT FROM AUTHOR]

Aim To compare apical transportation and canal straightening when using three continuous tapered rotary NiTi systems [F6 SkyTaper (Komet/Brasseler, Lemgo, Germany), Mtwo (VDW, Munich, Germany) and OneShape (Micro Méga, Besançon, France)] in severely curved root canals. Methodology A total of 60 root canals in extracted human teeth with angles of curvatures ranging between 25° and 35° and radii ranging between 4 and 9 mm were divided into three groups ( n = 20). Based on radiographs taken prior to instrumentation, the groups were balanced with respect to the angle and the radius of canal curvature ( P = 1.0 and P = 0.994, respectively). All canals were prepared to an apical size 30 according to the manufacturer's instructions. Pre- and post-instrumentation radiographs were superimposed and apical transportation and canal straightening were analysed using a computer imaging program. Preparation time and instrument failure were also recorded. Data were analysed statistically using anova and Student-Newman-Keuls test. Results During preparation, no file fractured. All instruments maintained the original canal curvature well with no significant differences between the instruments ( P = 0.542). Concerning apical transportation, no significant differences were obtained ( P = 0.414). Regarding preparation time, no significant differences were obtained between F6 SkyTaper and OneShape ( P > 0.05), but both were significantly faster than Mtwo ( P < 0.05). Conclusion Under the conditions of this study, all instruments respected the original canal curvature well and apical transportation was negligible. Instruments were safe to use. Preparation with F6 SkyTaper and OneShape was faster than with Mtwo. [ABSTRACT FROM AUTHOR]

Aim To describe a new method for the assessment of nanoscale alterations in the surface topography of nickel-titanium endodontic instruments using a high-resolution optical method and to verify the accuracy of the technique. Methodology Noncontact three-dimensional optical profilometry was used to evaluate defects on a size 25, .08 taper reciprocating instrument (WaveOne®), which was subjected to a cyclic fatigue test in a simulated root canal in a clear resin block. For the investigation, an original procedure was established for the analysis of similar areas located 3 mm from the tip of the instrument before and after canal preparation to enable the repeatability and reproducibility of the measurements with precision. All observations and analysis were taken in areas measuring 210 × 210 μm provided by the software of the equipment. Results The three-dimensional high-resolution image analysis showed clear alterations in the surface topography of the examined cutting blade and flute of the instrument, before and after use, with the presence of surface irregularities such as deformations, debris, grooves, cracks, steps and microcavities. Conclusions Optical profilometry provided accurate qualitative nanoscale evaluation of similar surfaces before and after the fatigue test. The stability and repeatability of the technique enables a more comprehensive understanding of the effects of wear on the surface of endodontic instruments. [ABSTRACT FROM AUTHOR]

Aim To assess and compare the mechanical properties of TRUShape ( TRS) with several nickel-titanium rotary instruments. Methodology Cyclic fatigue, torsional resistance, flexibility and surface microhardness of TRS (size 25, 0.06v taper), ProTaper Next X2 ( PTN X2, size 25, 0.06 taper), ProTaper Gold ( PTG F2; size 25, 0.08 taper) and ProTaper Universal ( PTU F2; size 25, 0.08 taper) instruments were evaluated. The topographical structures of the fracture surfaces of instruments were assessed using a scanning electron microscope. The cyclic fatigue resistance, torsional resistance and microhardness data were analysed using one-way analysis of variance ( anova) and Tukey's post hoc tests. The fragment length and bending resistance data were analysed statistically with the Kruskal-Wallis H-test and Mann-Whitney U-tests. The statistical significance level was set at P < 0.05. Results PTN and PTG instruments revealed significantly higher resistance to cyclic fatigue than TRS and PTU instruments ( P < 0.001). PTN instruments revealed significantly higher torsional resistance compared with the other instruments ( P < 0.001). PTG instrument had significantly higher flexibility than the other tested brands ( P < 0.05). However, for microhardness, the PTU had significantly higher surface microhardness values compared with other tested brands ( P < 0.05). Conclusions TRS instruments had lower resistance to cyclic fatigue and lower flexibility compared with PTG and PTN instruments. TRS, PTG and PTU instruments had lower resistance to torsional stress than PTN instruments. TRS and PTG instruments had comparable surface microhardness. [ABSTRACT FROM AUTHOR]

Aim To investigate the effect of irrigation on the surface roughness and fatigue resistance of HyFlex and M3 controlled memory (CM) wire nickel-titanium instruments. Methodology Two new files of each brand were analysed by atomic force microscopy (AFM). Then, the instruments were dynamically immersed in either 5.25% sodium hypochlorite (NaOCl) or 17% ethylene diamine tetraacetic acid (EDTA) solution for 10 min, followed by AFM analysis. The roughness average (Ra) and root mean square (RMS) values were analysed statistically using an independent sample t-test. Then, 36 files of each brand were randomly assigned to three groups (n = 12). Group 1 (the control group) was composed of new instruments. Groups 2 and 3 were dynamically immersed in 5.25% NaOCl and 17% EDTA solutions for 10 min, respectively. The number of rotations to failure for various groups was analysed using the one-way analysis of variance software. Results For M3 files, the Ra and RMS values significantly increased (P < 0.05) after the immersion. For the HyFlex file, the Ra and RMS values significantly increased (P < 0.05) only in EDTA, but not (P > 0.05) NaOCl. The resistance to cyclic fatigue of both HyFlex and M3 files did not significantly decrease (P > 0.05) by immersing in 5.25% NaOCl and 17% EDTA solutions. Conclusions Except the HyFlex files immersed in NaOCl, the surface roughness of other files exposed to irrigants increased. However, a change in the surface tomography of CM wire instruments caused by contact with irrigants for 10 min did not trigger a decrease in cyclic fatigue resistance. [ABSTRACT FROM AUTHOR]

Aim To assess the effect of sodium chloride concentration in fluoridated solutions during the electrochemical dissolution of fractured rotary endodontic instruments. Methodology Two solutions were assessed (solution 1: NaF 12 g L−1 + NaCl 1 g L−1, pH = 5.0; and solution 2: NaF 12 g L−1 + NaCl 180 g L−1, pH = 5.0) using two tests: the ProTaper Universal F1 ( PTU F1) instrument polarization test and the polarization test for intracanal PTU F1 fragments fractured in mandibular incisors. In the first test, two sets of five instruments were separately and partially immersed in each solution, and the electrical current was evaluated over 30 min. In the second test, 45 PTU F1 instruments were fractured within the root canals of mandibular incisors and subjected to potentiodynamic polarization for 30 min. The electrical current and the variations in the length of PTU F1 fragments were measured. The data were analysed statistically ( anova and Wilcoxon and Mann-Whitney tests, respectively). Results Solution 2 was associated with more corrosive effects in both tests. In the first test, the PTU F1 instruments immersed in solution 2 had a higher electrical current ( P < 0.001) and had a total dissolution time of approximately 540 s. In the second test, a larger difference between the baseline and final lengths of the fragments was noted in solution 2 ( P = 0.011). Conclusion Saturation of fluoridated solution with sodium chloride led to an increase in electrical current and microscopic reductions in the length of fractured instrument fragments subjected to electrochemical dissolution. [ABSTRACT FROM AUTHOR]

Aim To compare the centring ability and transportation of ProTaper Next (PTN), ProTaper Universal (PTU), Race 123 and RevoS using micro-computed tomography (μCT). Methodology Sixty mesial root canals of thirty mandibular molars were divided virtually into coronal, middle and apical thirds, and two reproducible reference points were marked on the external surface of the roots creating 360 measurement points. Samples were randomly allocated to four NiTi instrumentation techniques. Group 1: PTU up to F2 ( n = 16), group 2: PTN up to X2 ( n = 18), group 3: Race 123 up to T2 ( n = 12) and group 4: RevoS up to SU ( n = 14). To reproduce a clinical situation, samples were prepared on a phantom head using a surgical operating microscope. Samples were scanned pre- and postoperatively using μCT to compare and calculate the transportation and centring ratio. The data were analysed using parametric statistics. Results In the coronal and middle third of the root canals, there were significant differences in centring between PTN and PTU (coronal P < 0.001), PTN and RevoS (coronal P < 0.001), Race and PTU (coronal P < 0.01), Race and RevoS (coronal P < 0.01), PTN and RevoS (middle P < 0.01) and Race and RevoS ( P < 0.05). Furthermore, there were significant differences in centring between PTN root canal preparations and other instruments in the apical third (PTN and PTU P < 0.01, PTN and Race P < 0.001, PTN and RevoS P < 0.001). In terms of transportation, in the coronal third, there was a significant difference between PTN and PTU ( P < 0.05). However, there were no significant differences between the other instruments. In the middle third, significant differences were observed between PTN and PTU ( P < 0.05), PTN and RevoS ( P < 0.05), Race and PTU ( P < 0.05) and Race and RevoS ( P < 0.05). However, there were no significant differences between other systems. There was no significant difference in terms of transportation between the four systems in the apical third. Conclusions ProTaper Next prepared more centred root canal shapes when compared with Race, PTU and RevoS. In the coronal and middle third of the root canals, the differences in centring between PTN and PTU/RevoS were significant. PTN root canal preparations were more centred than those achieved with all other instruments in the apical third. [ABSTRACT FROM AUTHOR]

Aim To evaluate the ability of ProGlider instruments, PathFiles and K-files to maintain canal anatomy during glide path preparation using X-ray computed micro-tomography (micro- CT). Methodology Forty-five extracted maxillary first permanent molars were selected. Mesio-buccal canals were randomly assigned ( n = 15) to manual K-file, PathFile or ProGlider groups for glide path preparation. Irrigation was achieved with 5% Na OCl and 10% EDTA. After glide path preparation, each canal was shaped with ProTaper Next X1 and X2 to working length. Specimens were scanned (isotropic voxel size 9.1 μm) for matching volumes and surface areas and post-treatment analyses. Canal volume, surface area, centroid shift, canal geometry variation through ratio of diameter ratios and ratio of cross-sectional areas were assessed in the apical and coronal levels and at the point of maximum canal curvature. One-way factorial anovas were used to evaluate the significance of instrument in the various canal regions. Results Post-glide path analysis revealed that instrument factor was significant at the apical level for both the ratio of diameter ratios and the ratio of cross-sectional areas ( P < 0.001), with an improved maintenance of root canal geometry by ProGlider and PathFile. At the coronal level and point of maximum canal curvature, ProGlider demonstrated a tendency to pre-flare the root canal compared with K-file and PathFile. PathFile and ProGlider demonstrated a significantly lower centroid shift compared with K-file at the apical level ( P = 0.023). Post-shaping analysis demonstrated a more centred preparation of ProGlider, compared with PathFile and K-files, with no significant differences for other parameters. Conclusions Use of ProGlider instruments led to less canal transportation than PathFiles and K-files. [ABSTRACT FROM AUTHOR]

Aim To investigate the influence of interrupted rotation on cyclic fatigue of two nickel-titanium rotary instruments. Methodology Cyclic fatigue of 300 new ProTaper Next size X1; X2 and Mtwo size 10, .04 taper; size 15, .05 taper; size 20, .06 taper and size 25, .06 taper instruments was tested in continuous or interrupted rotation. Fifty files of the same brand and size were randomly assigned to five groups ( n = 10). Group 1 instruments were tested in continuous rotation; groups 2 and 3 in paused rotation for 1 s every 10 or 20 s, respectively; groups 4 and 5 in interrupted rotation for 5 s every 10 or 20 s, respectively. Cyclic fatigue was expressed in time to fracture (TtF) in an artificial canal with 60° angle and 5 mm radius of curvature. The fracture surface was examined with a scanning electron microscope ( SEM). Data were evaluated by two-way analysis of variance. Results Cyclic fatigue of groups 2 and 4 of ProTaper Next X2 and Mtwo size 25, .06 taper was significantly lower than that of group 1 of the same instruments ( P < 0.01). ProTaper Next X2 had significantly reduced cyclic fatigue in groups 3 and 5 ( P < 0.05). No differences were found by interrupting the rotation for 1 or 5 s in all instruments ( P > 0.05). Fatigue of other instruments was not affected by interrupted rotation ( P > 0.05). Conclusions Interrupted rotation reduced cyclic fatigue resistance of ProTaper Next X2 and Mtwo size 25, .06 taper, especially when a higher number of interruptions was performed. [ABSTRACT FROM AUTHOR]

The aim of this review was to provide a detailed analysis of the literature concerning the correlation between different movement kinematics and the cyclic fatigue resistance of NiTi rotary endodontic instruments. From June 2014 to August 2015, four independent reviewers comprehensively and systematically searched the Medline (PubMed), EMBASE, Web of Science, Scopus and Google Scholar databases for works published since January 2005, using the following search terms: endodontics; nickel-titanium rotary files; continuous rotation; reciprocating motion; cyclic fatigue. In addition to the electronic searches, manual searches were performed to include articles listed in the reference sections of high-impact published articles that were not indexed in the databases. Laboratory studies in English language were considered for this review. The electronic and manual searches resulted in identification of 75 articles. Based on the inclusion criteria, 32 articles were selected for analysis of full-text copies. Specific analysis was then made of 20 articles that described the effects of reciprocating and continuous movements on cyclic fatigue of the instruments. A wide range of testing conditions and methodologies have been used to compare the cyclic fatigue resistance of rotary endodontic instruments. Most studies report that reciprocating motion improves the fatigue resistance of endodontic instruments, compared to continuous rotation, independent of other variables such as the speed of rotation, the angle or radius of curvature of simulated canals, geometry and taper, or the surface characteristics of the NiTi instruments. [ABSTRACT FROM AUTHOR]

Aim To assess the amount of debris extruded apically during root canal preparation using various nickel-titanium instrumentation systems. Methodology Sixty extracted single-rooted mandibular premolar human teeth were randomly assigned to four groups ( n = 15 teeth for each group). The canals were then instrumented with the following instrument systems: Vortex Blue ( VB; Dentsply Tulsa Dental, Tulsa, OK, USA), K3 XF (SybronEndo, Orange, CA, USA), Reciproc ( VDW, Munich, Germany) and ProTaper Next ( PTN; Dentsply Maillefer, Ballaigues, Switzerland). Apically extruded debris during instrumentation was collected into pre-weighed Eppendorf tubes. The Eppendorf tubes were then stored in an incubator at 70 °C for 5 days. The weight of the dry extruded debris was established by subtracting the pre-instrumentation and post-instrumentation weight of the Eppendorf tubes for each group. The data were analysed using one-way analysis of variance ( anova) and Tukey's post hoc tests. Results Vortex Blue and PTN files were associated with significantly less apically extruded debris than the K3 XF and Reciproc files ( P < 0.05), but there was no significant difference between the VB and PTN files or between the K3 XF and Reciproc files ( P > 0.05). Conclusions All instruments were associated with apical extrusion of debris. VB and PTN files were associated with less debris extrusion compared to the other systems. [ABSTRACT FROM AUTHOR]

Aim The aim was to evaluate the incidence and type of defects that occurred with K3 rotary nickel-titanium instruments during routine clinical use. Methodology A total of 2397 K3 (G- PACKS, SybronEndo, West Collins, Orange, CA, USA) instruments were collected from a graduate endodontic clinic over 21 months. All the instruments were limited to a maximum use of 30 canal preparations. The collected instruments were measured by a digital caliper to determine whether any fractures had occurred and then were visually inspected for deformation and fracture under a stereomicroscope. The surfaces of fractured instruments were further evaluated under a scanning electron microscope. Data were analysed using chi-square test and Kruskal-Wallis test. Results The incidence of instrument defect was 5.63%, consisting of 3.59% fractures and 2.05% deformations. The defect rates of 0.04 and 0.06 files were statistically higher than the other taper groups ( P < 0.003) except for 0.08 files ( P > 0.05). For the fractured instruments, 63.95% failed from flexural fatigue, whilst 36.05% failed from torsion. Conclusion Flexural fracture was the major mode of fracture for instruments with larger taper. A routine check for instrument integrity particularly for 0.04 and 0.06 files at high magnification is recommended after each clinical use. [ABSTRACT FROM AUTHOR]

Aim To evaluate and compare the resistance to cyclic fatigue and torsional stress, flexibility and surface microhardness of ProTaper Gold ( PTG; Dentsply, Tulsa Dental Specialties, Tulsa, OK, USA) system with ProTaper Universal ( PTU; Dentsply Maillefer, Ballaigues, Switzerland). Methodology PTG and PTU instruments were rotated in simulated canals and the number of cycles to failure was recorded to assess their cyclic fatigue resistance. Torsional strength was measured using a torsiometer after fixing firmly the apical 3 mm of the instrument. A scanning electron microscope was used to characterize the topographic features of the fracture surfaces of the broken instruments. The instruments were tested for bending resistance using cantilever-bending test. Vickers microhardness was measured on the cross section of instruments with 300 g load and 15 s dwell time. Data were analysed statistically using independent t-tests. Statistical significance was set at P < 0.05. Results PTG instruments had a significantly higher resistance to cyclic fatigue and flexibility than PTU ( P < 0.001). The fractured cross-sectional surfaces revealed typical features of cyclic fractures, including crack origins, fatigue zones and overload fast fracture zones. On the other hand, PTU instruments were associated with higher resistance to torsional stress and microhardness than PTG instruments ( P < 0.001). After torsional tests, the fractured cross-sectional surfaces revealed skewed dimples near the centre of the fracture surfaces and circular abrasion streaks. Conclusions The PTG instrument had improved resistance to cyclic fatigue and flexibility compared with PTU. PTU instruments had improved resistance to torsional stress and microhardness compared with PTG. [ABSTRACT FROM AUTHOR]

Aim To evaluate the amount of apically extruded debris produced by ProTaper Universal ( PTU), ProTaper Next ( PTN), WaveOne ( WO) and Reciproc (R) systems after large apical preparations. Methodology Sixty mandibular premolars with a single canal were selected and randomly assigned into 4 groups ( n = 15) according to the system used for root canal preparation: PTU, PTN, WO and R groups. Canal preparations were performed up to size 40 in each group. Distilled water was used as an irrigant, and the apically extruded debris from each tooth was collected in pre-weighted glass vials and dried. The average weight of debris was assessed using a microbalance, and the data were analysed statistically using one-way analysis of variance and the post hoc Tukey multiple comparison test (α = 0.05). Results The PTU system was associated with significantly more debris than the other systems ( P < 0.05). No significant differences were found between PTN, WO and R systems ( P > 0.05). Conclusions All systems were associated with apical debris extrusion when canals were prepared to a large apical size. The PTU system was associated with more debris extrusion. [ABSTRACT FROM AUTHOR]

Aim To compare the cyclic fatigue resistance of D-RaCe and ProTaper rotary nickel-titanium (NiTi) retreatment files when used in curved artificial canals. Methodology A total of 120 new D-RaCe DR2 and ProTaper D3 retreatment files were tested in stainless steel artificial canals having 45° and 60° angles of curvature. Thirty instruments of each of the file systems were tested in both angles of curvature ( n = 30). The retreatment instruments were rotated until fracture to calculate the number of cycles to failure. The length of each fractured fragment was recorded. Data were analysed by independent sample t-test. Fractured surfaces of the instruments were analysed by scanning electron microscopy. Results In the canal with 45° angle of curvature, no significant difference was observed between the retreatment systems ( P > 0.05); on the other hand, in the canal with 60° angle of curvature, D-RaCe DR2 instruments had greater cyclic fatigue resistance than ProTaper D3 ( P < 0.05). No difference was observed between the retreatment instruments regarding the lengths of fractured fragments ( P > 0.05). The fracture surfaces of the instruments had morphologic characteristics of ductile fracture. Conclusions D-RaCe DR2 instrument exhibited greater cyclic fatigue resistance than ProTaper D3 only in root canals with 60° angle of curvature. [ABSTRACT FROM AUTHOR]

Aim To evaluate the surface and microstructural alterations of new and used HyFlex EDM prototypes and to test their fatigue resistance. Methodology Fifteen HyFlex EDM prototypes were used for in vitro instrumentation of severely curved root canals. Surface and microstructural characteristics of new and used files were compared by ESEM analysis equipped with energy dispersive X-ray spectrophotometry ( EDS) and optical metallographic imaging. Usage-induced degradation was assessed. Thirty additional HyFlex EDM prototypes and 20 standard manufactured HyFlex CM files were subjected to cyclic fatigue tests. Time to fracture was recorded, and results were validated using the Kruskal-Wallis test (α-level 0.05). Fatigued files were analysed by ESEM for fractographic evaluation. Results Surface and microstructural characterization of EDM prototypes revealed the typical spark-machined surface of a NiTi EDM alloy. No fractures were registered during root canal instrumentation. No evident surface alterations and minor degradation were observed between new and used instruments. The metallographic analysis of new and used files disclosed a homogeneous structure, mostly composed of lenticular martensite grains, and some residual austenite. The cyclic fatigue test showed an increase of fatigue resistance up to 700% on the EDM compared to CM files. Conclusions Spark-machined peculiar surface is the main feature of HyFlex EDM. Low degradation was observed after multiple canal instrumentations. Prototypes exhibited surprising high values of cyclic fatigue resistance and a safe in vitro use in severely curved canals. [ABSTRACT FROM AUTHOR]

Aim To compare the cyclic fatigue resistance of new generation OneShape and WaveOne instruments when used with different kinematics. Methodology An artificial canal, made of stainless steel with an inner diameter of 1.5 mm, a 60° angle of curvature and a curvature radius of 3 mm, was used for cyclic fatigue test of new generation OneShape and WaveOne instruments. Groups were as follows ( n = 20): 150°-30°, 210°-30°, 360°-30° and continuous rotation. The time to fracture was recorded in seconds, and the data were analysed statistically using a two-way anova and LSD tests ( P = 0.05). Results Cyclic fatigue resistance was significantly affected by the movement kinematics ( P < 0.001). The cyclic fatigue resistance of the new generation OneShape instruments increased significantly when operated in various reciprocation motions (150° CW-30° CCW, 210° CW-30° CCW and 360° CW-30° CCW) compared with the continuous rotation mode. New generation OneShape instruments had significantly more resistance to fracture under cyclic loading than WaveOne instruments ( P < 0.001). Conclusions When using new generation OneShape and WaveOne instruments, all the reciprocating motions (150° CW-30° CCW, 210° CW-30° CCW and 360° CW-30° CCW) resulted in extended fatigue life when compared with continuous rotation. [ABSTRACT FROM AUTHOR]

Over the years, NiTi alloys have become indispensable materials in endodontic treatment. With technological advancements in metallurgy, manufacturers have attempted to produce instruments with enhanced features. In parallel with these developments, endodontic motors have undergone improvements in terms of torque control and kinematics that are adjustable in different directions. This review presents an overview of the advancements in instrumentation kinematics and the effect of instrumentation kinematics on root canal shaping procedures and instrument performance. The literature search for this narrative review was conducted in Google Scholar, Scopus, PubMed and Web of Science using the keywords 'kinematics and endodontics' and 'reciprocation and endodontics'. In addition, historical literature was searched using the keyword 'nickel-titanium and endodontics'. Overall, 143 articles were included up to 2015. [ABSTRACT FROM AUTHOR]

Aim To assess and compare the resistance to cyclic fatigue, torsional stress, bending and buckling of ProGlider ( PG; Dentsply Maillefer, Ballaigues, Switzerland) instruments with PathFile ( PF; Dentsply Maillefer) pathfinding nickel-titanium rotary instruments. Methodology Size 16, .02 taper PG and PF instruments were rotated in simulated canals until failure, and the number of cycles to failure ( NCF) was recorded to evaluate their cyclic fatigue resistance. Torsional strength was measured using a torsiometer after fixing rigidly the apical 5 mm of the instrument. A scanning electron microscope was used to characterize the topographic features of the fracture surfaces of the instruments. The instruments were evaluated for bending resistance using a cantilever-bending test. The buckling resistance was measured by recording the maximum load required to form a lateral elastic displacement along the file axis using a universal testing machine. Data were statistically analysed using independent t-tests. Statistical significance was set at P < 0.05. Results ProGlider instrument had a significantly higher flexibility, higher resistance to cyclic fatigue and torsional stress than PF instruments ( P < 0.05). The fractured cross-sectional surfaces revealed typical features of cyclic fatigue and torsional fractures. There was no significant difference in the maximum load needed to buckle the two instruments tested ( P = 0.082). Conclusions ProGlider NiTi pathfinding instrument manufactured from M-Wire alloy had enhanced mechanical properties, including higher flexibility, higher resistance to cyclic fatigue and torsional stress compared with PathFile instrument made of conventional NiTi alloy. [ABSTRACT FROM AUTHOR]