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Introduction: Mechanized endodontic treatment is an advent that has been constantly evolving. Objective: to characterize the instruments through scanning electron microscopy and perform mechanical tests of 45º bending, buckling and microhardness of ProTaper instruments. Materials and Methods: 10 nickel titanium instruments from each System were used: ProTaper Universal (PTUN), ProTaper Gold (PTGO), Protaper Ultimate (PTUL) and Protaper Next (PTNE). The SEM analysis was carried out using a SEM FEG quanta FEI 250. For the 45º bending and buckling tests, an EMIC LD 200MF universal testing machine was used. Vickers microhardness was performed using a Micromet 2003 Bueler microhardness meter. The results were subjected to the Shapiro-Wilks normality test for subsequent ANOVA testing, the significance level adopted was 5%. Results: The instruments studied presented the following order in relation to flexibility: PTUL>PTGO>PTUN>PTNE. The buckling resistance of the instruments presented the following order: PTUN>PTGO>PTNE=PTUL. The Vickers microhardness presented the following order PTUN= PTNE>PTGO=PTUL. Conclusion: PTUL instruments were the most flexible and PTUN were the most resistant to buckling. The microhardness of controlled memory instruments (gold wire) presents a softer alloy. The instruments had a good surface finish. [ABSTRACT FROM AUTHOR]

(1) Background: The failure of nickel–titanium (NiTi) rotary files is a complication related to endodontic instruments. The aim of this study was to compare the resistance to cyclic fatigue between rotary and reciprocating file systems. (2) Methods: Specific PICO: Population (P): artificial root canals; Interventions (I): instrumentation with NiTi rotary and reciprocating files; Comparison (C): rotary versus reciprocating files; Outcome (O): cyclic fatigue resistance. Studies were identified through bibliographic research using electronic databases (Medline, Embase, Scopus, SciELO, and WOS). The studies were combined using a random effects model by the inverse variance method. The effect size was the mean of the time to fracture (TTF) and number of cycles to fracture (NCF). Heterogeneity was assessed using the p value of the Q test for heterogeneity and the I2. (3) Results: TTF for rotary files was determined in 474.5 s and 839.1 for reciprocating without statistically significant differences. NCF for rotary systems was determined in 1444.2 and for reciprocating file systems in 4155.9 with statistically significant differences (p = 0.035), making reciprocating files more resistant. (4) Conclusions: Reciprocating files have better resistance to cyclic fatigue than rotary files. When tested in double curvature canals, reciprocating files also showed higher resistance. [ABSTRACT FROM AUTHOR]

Objective: To investigate the opinions and attitudes of dental practitioners towards intracanal separation of endodontic instruments and to create awareness regarding the management of separated instruments Study Design: Cross-sectional survey Place and Duration of Study: Department of Operative Dentistry Armed Forces Institute of Dentistry, Rawalpindi Pakistan, from Mar to Apr 2021. Methodology: An online questionnaire was circulated among 374 dentists of private and public hospitals in Rawalpindi and Islamabad. The questionnaire consisted of close-ended questions related to demographic details, dentists' awareness of instrument separation, the frequency of separated instruments, the causes of separation, the management of separated instruments, and the retrieval strategies if used. Results: Out of 374 study participants, 307(82.1%) of the participants thought that operator-related factors such as improper or overuse of the instrument were considered the most common factors for instrument separation during root canal procedures. 205(54.8%) thought unwinding, defective flutes and shiny areas were the most common factors affecting instrument separation. 241(64.4%) of the instruments are separated during cleaning and shaping. 135(36.1%) K files and 119(31.8%) H files were separated in this survey. Conclusion: Most dentists of Rawalpindi and Islamabad face the problem of endodontic instrument separation during rootcanal preparation.

Objective: To compare the consistency of working length control in hand instrumentation and engine-driven rotary files Wave One by comparing their pre and post-instrumentation working lengths. Study Design: Quasi-experimental study. Place and Duration of Study: Armed Forces Institute of Dentistry, Rawalpindi Pakistan, from Jun to Dec 2019. Methodology: A total of 90 mandibular first molars were selected. Two groups were drawn with 45 mesio buccal canals each. The First-Group was prepared with manual K-files, whereas the second group had rotary instrumentation using the WaveOne system. Pre and post-preparation working lengths were noted. Results: The mean pre-operative (18.5±1.03mm) and post-operative (18.15±1.09mm) working lengths of manually prepared and WaveOne prepared canals (18.8±3.43mm and 18.7±3.25mm respectively) presented statistically significant loss of postoperative working lengths. The comparison of the two groups gives a statistically significant result in manual preparation, showing a greater loss of working length as compared to canals prepared with WaveOne rotary files. Conclusion: Manual instrumentation causes a greater loss of working length by straightening the canal more than enginedriven WaveOne rotary files postoperatively.

Introduction Endodontic instruments during root canal treatment come into contact with dentinal debris, irrigation solutions and medication agents, which reminants should be eliminated before sterilization. The aim of the study was to verify the effectiveness of different cleaning methods for removing calcium hydroxide paste residues from the surfaces of the working parts of hand instruments, as well as to propose an effective protocol for cleaning endodontic instruments before sterilization. Material and methods Forty-two new hand endodontic instruments were used to remove calcium hydroxide paste from the filled canals of extracted teeth. After contamination with medication, they were divided into the four groups and subjected to individual decontamination methods - mechanical, chemical and ultrasonic, as well as a combined protocol. The instruments were then observed under a light microscope. The effectiveness of the methods was evaluated based on the amount of residual matter on the surface of the working parts of the instruments. Results The combined protocol showed a statistically significant difference in the achieved level of cleanliness compared to mechanical (ch2 = 12.00 p < 0.05) and chemical methods (ch2 = 12.00 p < 0.05), but there was no statistically significant difference compared to ultrasonic cleaning in disinfectant solution (ch2 = 2.4 p > 0.05). By applying combined protocol, instruments with completely clean surfaces were found, as well as the lowest values of contamination at the level of the entire group of instruments (8.33%). Conclusion The protocol that consisted of mechanical cleaning with a sponge soaked in chlorhexidine gluconate, chemical soaking in sodium hypochlorite, and ultrasonic cleaning in a disinfectant showed the best efficiency in removing calcium hydroxide residues.

One of the most important ways of prevention nosocomial infections in outpatient dental practice is disinfection and sterilization of endodontic fi les. The present study evaluated the effect of various methods of disinfection and sterilization on the cutting efficiency of fi les. It was revealed that cutting efficiency of endodontic fi les decreases after all types of sterilization, mostly after sterilization with dry hot air, and at least — after the chemical sterilization. Because the force applied on profile increases after each cycle of sterilization, in this case the probability of fi le breakage increases, too.

A fundamental aspect of the Endodontic field is the knowledge of root canal anatomy. Using a variety of techniques, the internal and external anatomy of teeth have been extensively investigated throughout the past century. Recent improvements in three‐dimensional computed tomography have enabled more detailed evaluations of root canal morphology in both clinical and laboratory settings. Essentially, researches have unveiled that the root canal constitutes a complex system, comprising not only the main root canal but also lateral components, including isthmuses, fins, accessory canals and apical ramifications. Undoubtedly, this intricate morphology poses a significant challenge when it comes to the process of shaping, cleaning and disinfecting the root canal system. This article aims to explore the anatomical aspects of the root canal system that impact the chemomechanical procedures. [ABSTRACT FROM AUTHOR]

Introduction: Exploration is an important step of root canal preparation, because it allows the clinician to negotiate the canal to its terminus and determine its complexity. Different instruments have been developed specifically for this purpose. This study compared the buckling resistance of hand stainless steel and pathfinding nickel-titanium rotary instruments in artificial canals with different depths. Materials and methods: A total of 30 PathFile, ScoutRace and C-Pilot instruments were evaluated. The buckling resistance was tested using acrylic resin blocks with a flat surface or with 3 mm and 6 mm deep artificial canals. The load required to generate a lateral displacement of 1 mm was recorded. Data were statistically analysed using one-way analysis of variance (ANOVA) and Student- Newman-Keuls test for multiple comparisons at a significance level of P < 0.05. Results: On the flat surface, C-Pilot showed the greatest buckling resistance. In 3 mm deep canals, PathFile showed resistance similar to that of C-Pilot files on the flat surface. In 6 mm deep canals, both nickel-titanium instruments showed greater buckling resistance than C-Pilot on the flat surface (P < 0.001). Conclusions: The buckling resistance of nickel-titanium pathfinding instruments increases with the depth of the canal. [ABSTRACT FROM AUTHOR]

One area of technological advancement has been the shift from stainless steel hand tools to nickel-titanium (Ni-Ti) rotary tools. This paper aims to perform an in vitro comparative study to evaluate the efficacy of five endodontic manual and rotary instruments such as Kerr files, Orodeka Plex V, ProTaper Flydent NiTi super files, and ProTaper Flydent NiTi super files in combination with an ultrasonic endodontic E3D Diamantata EMS scaler used for root canal shaping. The following aspects were highlighted: effective removal of smear layer (SL) from the dentinal tubules in the coronal 1/3, middle 1/3, and apical 1/3 of the root canal, appearance of cracks in the dentinal walls by SEM analysis, and highlighting of dentin mineral content and remnant debris by EDX analysis. In the study, 48 monoradicular, uninjured teeth were taken and divided into four groups, each with 12 teeth to be canal modeled, then longitudinally sectioned; the active surface was metallized for SEM-EDX analysis. From the SEM micrograph analysis, the morphology of the crystallites, the distribution of SL components, and the highlighting of instrumentation path traces/amplitudes were observed. By analyzing the SEM photomicrographs at 750 and 800× magnification, it was possible to highlight the cracks in the root dentinal walls. Thus, in comparison with Lots I and II which did not present cracks, in Lot III multiple cracks of the root dentinal walls were identified, especially in the coronal 1/3, and in Lot IV cracks were present with preponderance in the coronal and apical 1/3 of the root canals. The EDX images with atom mapping show very well the rather homogeneous elemental distribution for Ca, N, and P, respectively inhomogeneous for Na, Ca, Si, C, N, O, and P elements, as a result of the presence of remnant products from the processing of the root dentinal walls. Root canal instrumentation performed with both manual Kerr needle instrumentation by a convection technique and the rotary, Orodeka system, by crown-down technique, resulted in minimal SL formation in all three root canal areas, unlike the ProTaper FlyDent system. Most cracks were recorded in the case of the ProTaper Flydent rotary instruments and the one in which it was paired with a diamond ultrasonic scaler. The occurrence of dentinal cracks causes a decrease in dentinal microhardness, favoring the occurrence of root fractures., (© 2025 The Author(s). Microscopy Research and Technique published by Wiley Periodicals LLC.)

The fracture of endodontic instruments inside the canal represents a problem that is not always easy to solve. The reutilization of endodontic instruments after sterilization procedures raises the question of how these processes affect their physical and mechanical properties. Alterations can involve the surface of the instruments, as well as their cutting effectiveness, shape and resistance to torsional and cyclic fatigue. The methodology adopted for this systematic review followed the PRISMA guidelines for systematic reviews. The following search terms were used in PubMed and Scopus: “endodontic sterilization”, “endodontic autoclave”, “cyclic fatigue”, “torsional”, “cutting efficiency”, “sterilization”, “surface characteristics” and “corrosion”. After the screening phase, the application of exclusion criteria and the removal of duplicates, 51 studies were identified and divided into four outcomes: cyclic fatigue; deformation and torsional fatigue; corrosion or surface alterations; and cutting efficiency. Our study of the scientific literature highlights disagreements between studies on these effects. After autoclaving, instruments exhibit a reduction in the cutting efficiency, but NiTi alloy instruments have an improved resistance to cyclic and torsional fatigue.

The pre-flaring of the cervical and middle third is a technique used to model the canal, removing dentin interferences, and thus facilitating instrumentation. The objective of this work is to evaluate whether it can reduce the incidence of fractures of mechanized endodontic instruments. A literature review was carried out in PubMed, Scielo (Scientific Electronic Library Online) and Google Scholar during the period of 2008 to 2022. Prior canal widening aims to reduce the torsional stress of the file when inserted into the root canal, minimizing the risk of file fracture. It is concluded that the pre-enlargement of the cervical and middle third considerably reduces the number of fractures of mechanized endodontic instruments and, therefore, is a viable option during endodontic treatment. [ABSTRACT FROM AUTHOR]

The article presents the study which examines the mechanical behaviour of four brands of engine-driven nickel-titanium endodontic instruments, HyFlex CM, Twisted File, ProFile Vortex, and RaCe. It explores the materials and methods used in the study, which involves testing of instruments for bending resistance, cyclic fatigue, torsional resistance, Vickers hardness and toughness.

Objective: The purpose of this study was to evaluate the ability of a solution containing fluoride to dissolve rotary instrument fragments in a simulated root canal within a maximum of 60 min. Material and methods: Eighteen M-Wire alloy rotary instruments were divided into three experimental groups according to length. An electrochemical cell was prepared in the canals with three electrodes, and file fragments were immersed in fluoride solution. A constant anodic potential of 800 mV was applied. Statistical analysis was performed using the non-parametric Wilcoxon test for paired data. Group means were compared by ANOVA for normally distributed variables, and with the Kruskal-Wallis and Jonckheere-Terpstraen tendency tests for variables that were not normally distributed. The level of statistical significance was set at P < 0.005. Results: A significant loss of weight was observed, which increased with initial fragment weight (P < 0.001). Complete (n = 3) or almost complete dissolution of 5.0 mm and 10.0 mm file fragments was achieved. The average weight reduction was 36% for 17.0 mm file fragments. The anodic potential was correlated positively with the degree of weight loss (r = 0.85, P < 0.001). Conclusion: The electrochemical method enabled significant dissolution of NiTi instrument fragments within a maximum of 60 min. [ABSTRACT FROM AUTHOR]

The design features of the WaveOne Gold Primary system and some of its previous analogswill be discussed since they allow channel processing using only one file in 80-85% of clinical cases. In the second part of the article, we will discuss when it is still necessary to use more than one WaveOne Gold instrument with examples of specific complex clinical cases with curved canals. In the end, we will pay attention to the peculiarities of processing very large canals, which are also difficult for the doctor.

This study aims to develop and analyse a finite element model of the endodontic nickel-titanium (NiTi) instrument during the root canal treatment (RCT). The 3D model of the tooth and the endodontic instrument has been created using computer-aided design software. The nonlinear explicit dynamic analysis in the CAE package (ANSYS) has been used to analyse the mechanical behaviour of endodontic instruments such as total deformation, equivalent elastic strain, and equivalent stress during canal preparation. The mechanical behaviour of three commercially available endodontic NiTi alloy instruments such as WaveOne Gold (WOG), 2Shape 1 (TS1) and 2Shape 2 (TS2) endodontic files was evaluated using FEA. Consequently, the effect of deformation, equivalent stress and equivalent elastic strain on endodontic files during cleaning and shaping are investigated and compared. The results show that the total deformation and equivalent elastic strain are maximum in the TS1 endodontic file in comparison to TS2 and WOG files. Graphical abstract [ABSTRACT FROM AUTHOR]

Treatment of destructive forms of chronic periodontitis requires a therapeutic dentist to solve a number of tasks: strict adherence to the protocol, taking into account the initial situation, an individual approach to therapy, the use in the practice the clinically proven new dental technologies. Objective assessment of the general state of the human body and the destructive process of bone tissue of the maxillofacial area allows the doctor to choose the right approach to the treatment of destructive forms of periodontal disease and to evaluate the importance of each stage. This article describes the principles of modern highclass endodontic treatment. The necessary working instruments and technologies are described. The work is illustrated with clinical cases.

The presented article covers a range of issues arising in daily clinical practice of an endodontist. It is not a study in the classic sense of this word. Author, a therapist with extensive experience on the base of her own clinical cases shares the thoughts regarding methods and technologies of endodontic treatment, arises the discussion regarding the concepts of success and failure in endodontics. The article is based on problem-oriented principle, it encourages readers to reflect together with the author, has written on an interesting and even artistic language. Extremely useful material contributes to the development of clinical thinking of the practitioners and it is especially valuable for the beginners in dentistry.

Copyright of Knowledge: International Journal is the property of Institute for Knowledge Management and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Instrument fracture ranks among the most crucial complications during the endodontic treatment of a tooth. In order to better understand the practical limits of the instrument, the relation between the cyclic fatigue resistance and physical properties such as hardness, modulus of elasticity, creep and surface roughness were explored. Cyclic fatigue testing in an artificial root canal at intracanal temperature, nanoindentation and 3D microscopy were used for evaluation of four commonly used thermomechanically treated NiTi endodontic instruments (Unicone Plus 6/025, Unicone 6/025, Reciproc Blue R25 and WaveOne Gold Primary). Cyclic fatigue results were analyzed using the Kruskal–Wallis, Mann–Whitney and Bonferroni corrections. The wear resistance of Unicone 6/025 instruments was significantly lower compared to all other instruments (p < 0.05). WaveOne Gold Primary was significantly less resistant than Unicone Plus 6/025 and Reciproc Blue R25, while the difference between Reciproc Blue R25 and Unicone Plus 6/025 was insignificant (p > 0.05). These results are in correlation with measurements of local mechanical properties (hardness, elastic modulus and their ratios H/E and H3/E2). Even though surface roughness, area of cross-section and shape of instruments are important factors affecting instruments behavior, thermal processing appears to be the most important. [ABSTRACT FROM AUTHOR]

Background and Objectives: The aim of the present study is to compare the efficacy of three root canal preparation systems in the shaping of 3D-printed root canal replicas of single rooted teeth. Materials and Methods: Sixty 3D-printed root canal replicas were produced and divided into three groups, each consisting of twenty samples. Each group was shaped with a different instrument: Reciproc Blue R25/08 (VDW GmbH, Munich, Gemany), WaveOne Gold Primary 25/07 (Dentsply Sirona, Ballaigues, Switzerland), and ProTaper Gold F2 25/08 (Denstply Sirona). To ensure the reproducibility of pre- and post-operative CBCT images of the root canals, the endodontic printed replicas were placed in a mould of silicon impression material. A cone-beam computed tomography (CBCT) software was used to compare pre- and post-instrumentation images collected at three levels of the root canal length: 3, 6, and 9 mm from the apical foramen. The amount of transportation, centring ability, and curvature angle after shaping were evaluated for each system. The results were statistically analysed and compared using one-way analysis of variance (ANOVA). Results: Regarding the transportation of the root canal after shaping, significant differences between groups at 3 mm (p = 0.010721) and 6 mm (p = 0.000046) were recorded in the mesio-distal direction, while in the bucco-lingual significant differences were only observed at 6 mm (p = 0.000554). Reciproc Blue removed more dentin from the mesial and buccal wall of the root canal. When evaluating the centring ability of the three systems, significant differences were observed between the groups at the level of 9 mm (p = 0.037258) in the mesio-distal direction, and at the level of 6 mm (p = 0.038197) in the bucco-lingual direction. Significant differences of the canal curvature angle after shaping were also observed between groups (p = 0.000001). Reciproc Blue straightened the curvature the most, while ProTaper Gold the least. Conclusions: All systems produced minor root canal transportation. No instrument was able to achieve a perfect centring preparation of the root canal. All systems produced a small degree of root canal straightening. [ABSTRACT FROM AUTHOR]

In order to justify the selection of the optimal methods of sterilization of endodontic instruments studied the activity of new cutting and underwent repeated sterilization of endodontic instruments based on laboratory studies. In assessing the impact of different methods presterilizing cleaning and sterilization on the properties of endodontic instruments found that the ultrasonic treatment and a heat treatment to a greater extent change the properties of instruments. It was shown, in step presterilizing endodontic cleaning instruments manual washing practically no negative influence on the cutting of its activity, while an ultrasonic treatment greatly reduces it.

OBJECTIVE: To determine the frequency of manual and rotary instrument separation during endodontic treatment amongst experienced dental practitioners and house surgeons. METHODOLOGY: The present study was conducted in various dental teaching hospitals registered with Pakistan Medical and Dental Council (PMDC) from July 2018 to January 2019. The sample size calculation was obtained by taking 50% prevalence rate using Open EPI software (version 3.01) at 95% confidence interval and α=5% and was calculated to be 250. A self-administered questionnaire containing 22 closed ended questions was designed to evaluate different reasons of separation of manual and rotary endodontic instruments amongst experienced dental practitioners and house surgeons. RESULTS: A total of 250 participants were included in this study, out of them 192 were house officers and 58 were dental practitioners.122 (63.5%) of the house surgeons and 30(51.7%) of dental practitioners experienced instruments breakage during root canal treatment. When the types of files were assessed, the results showed that the separation of K- files was most frequent than H-files and Ni-Ti rotary files.106(55.2%) of the house surgeons and 23(39.7%) of the dental practitioners reported separation of K-files during root canal treatment. CONCLUSION: The present study concluded that majority of the house surgeons experienced K-file separation than H-file and Ni-Ti rotary files than Dental practitioners during root canal treatment.

In modern endodontics, nickel-titanium (NiTi) rotary instruments are used on a large scale for root canal shaping. Nevertheless, the separation of an instrument is a serious concern during shaping. The aim of this study is to determine and compare the torsional fracture characteristics of three types of NiTi endodontic instruments, each with different cross-section designs and movements performed during root canal shaping: Endostar E3 (Endostar, Poldent Co. Ltd., Warsaw, Poland); Reciproc R25 (VDW, Munich, Germany); and Protaper Next X2 (Dentsply Maillefer, Ballaigues, Switzerland). Fifteen instruments are used in this study, divided in three groups (n = 5): Group Endostar, Group Reciproc and Group Protaper. For testing, each instrument is used to shape five simulated root canals, following which its torsional stress to failure is measured. The fracture lengths of all three groups are roughly between 2 and 3 mm from the tip. Higher values of the moment of torsion in fracture, and smaller values of the maximum twisting angle are observed for Group Endostar, as well as closer to circular cross-sections. However, the values of the shear tension are similar for all three groups, because the disadvantage given by the fracture section shape for Groups Reciproc and Protaper is compensated either by size or by intrinsic properties of the instrument material. For the shear tension the Endostar values are insignificantly increased (Kruskal–Wallis test, p = 0.207), and in the case of the maximum twist angle the Protaper values are insignificantly increased (Kruskal–Wallis test, p = 0.287). Because of the instruments shape and conicity, the analysis had to be carried out separately with regard to the length of the fractured tip. Rules-of-thumb are extracted from the study for current practice: if a blockage of the first 2 to 3 mm part of the tip can be anticipated (by the excessive curving of the instrument), the handpiece must be adjusted to torque values that do not exceed 1.5 to 2.5 N · cm for Endostar and 1 to 2 N · cm for Reciproc and Protaper instruments. [ABSTRACT FROM AUTHOR]

Infection of the tooth's root canal requires what is called root canal treatment (RTC). The most important part of endodontic treatment is to shape the root canal and remove its infected portion using endodontic files of various protocols, kinematics and designs that suit the particular geometry. Cleaning and Shaping the canal efficiently remove the root canal bacterial biofilms or tissue remnants while keeping its natural geometry. The result is determined by shaping the ability of the relevant endodontic file. In the available literature, no norm has been established for the measurement of various endodontic files' ability to do effective shaping. We present in this study a method to analyse and measure the shaping ability of endodontic files of three different kinematics. [ABSTRACT FROM AUTHOR]

Copyright of Acta Facultatis Medicae Naissensis is the property of Nis University, Faculty of Medicine and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Introduction: This study compared the angular deflection at failure, maximum torque, and toughness of two nickel-titanium (NiTi) instruments under torsional stress: Reciproc (VDW, Munich, Germany) and WaveOne (Dentsply Maillefer, Ballaigues, Switzerland). Two NiTi instruments: Mtwo (VDW) and ProTaper (Dentsply Maillefer) served as controls. Methods: The instruments were subjected to torsional assays to evaluate the maximum torque and angular deflection at failure. A stress-strain (N × mm) curve was plotted using specific software and toughness was calculated as the integral of the area under the curve. Data obtained were statistically evaluated by ANOVA and Student-Newman-Keuls (SNK) test for multiple comparisons, with the significance level set at 5%. Results: Significant difference was observed in the angular deflection at failure for pairwise comparisons between ProTaper and the other instruments (P < 0.05). No significant differences were observed in the comparisons between the other instruments (P > 0.05). The maximum torque was ranked as follows: ProTaper > Reciproc > WaveOne > Mtwo; significant differences were observed between all instruments (P < 0.05). Differences in toughness were also detected between all instruments tested (P < 0.05), except for Reciproc versus WaveOne. Conclusion: The findings from this study revealed that Reciproc and WaveOne displayed similar mechanical behaviour in terms of angular deflection and toughness, typical of ductile metallic materials under torsion. This suggests that both instruments absorb comparable amounts of energy until fracture. Regarding torque, Reciproc exhibited the best results in comparison with WaveOne. [ABSTRACT FROM AUTHOR]

Objective: The aim of this study was to evaluate the efficacy of supplementary techniques (ultrasonic tip/XP-endo Finisher R) in removing remaining filling materials (gutta-percha/AHPlus/BCSealer) from oval-shaped root canals during non-surgical endodontic retreatment. Material and methods: Twenty-eight distal roots of human mandibular molars with single and oval-shaped canals were initially shaped with a R40 instrument and filled with gutta-percha points and AH Plus (n = 14) or BC Sealer (n = 14) followed by an initial micro-CT scanning. Initial filling material removal was performed in all 28 samples with an R50 instrument, and all samples submitted to a second micro-CT. Supplementary techniques with ultrasonic tips or XP-endo Finisher R instruments were performed in each sealer group, and all samples submitted to a third micro-CT. The volume of remaining filling material was calculated for the entire canal as well as for the coronal, middle, and apical thirds. Statistical analyses were performed using T, ANOVA 3-way, and Tukey tests. Results: Lower values of remnant filling material were found for BC Sealer (16.06 ± 14.34) compared to AH Plus (28.30 ± 10.54) (P < 0.001), and considering the supplementary technique, lower values of remnant filling material were found for the ultrasonic tip (18.95 ± 11.05) compared to XP-endo Finisher R (25.41 ± 15.81) (P = 0.025). Ultrasonic instruments significantly reduced the percentage of remaining filling material for both AH Plus (P = 0.04) and BC Sealer (P = 0.02) while XP-endo Finisher R was effective for AHPlus only (P = 0.04). The remaining filling material was observed in all samples regardless the filling material or the supplementary technique employed. Conclusions: Supplementary techniques increased filling material removal; however, none of them was able to render root canals completely free from root fillings. Ultrasonic tips should be considered a good option for endodontic retreatment, especially for bioceramic cases. Clinical relevance: Supplementary instrumentation techniques are effective tools to reduce the amount of filling materials during root canal retreatment. [ABSTRACT FROM AUTHOR]

The purpose of the mechanical root canal preparation is to clean it and give it the right shape. The preparation should be carried out in a way that maintains the original curvature and initial orientation of the apical end. Insufficient root canal preparation may prevent effective chemical decontamination and obturation to the full working length. The study aims to evaluate the shaping ability and effectiveness of the NiTi rotary and reciprocating endodontic instruments, compared to standard hand files using magnetic resonance imaging based on spin echo. Material and methods: A comparative study of severely curved root canals' shaping abilities using three NiTi systems and K-type hand files was performed, with 40 training "endo-blocks" presenting with "L-shaped" canal. The root canal topography and geometry "before" and "after" mechanical preparation obtained by the magnetic resonance imaging based on the spin echo was used. The main measurement was made using the RARE sequence, with slice thickness reduced to 100 micrometers. In order to improve the signal-to-noise ratio, NA = 25 was used. To minimize the measurement time, the field of view was limited to a cuboid 17 × 16 × 3 mm, with a resolution of 33 × 31 × 100 micrometers. Each 3D image consisted of 512 × 512 × 30 voxels. The imaging plane has been selected in such a way as to fully illustrate the course of curvature of the model root canal. For TR = 5 s and effective TE = 36 ms, TA was 1.5 h. Measurements were performed twice, before and after the preparation of endo-blocs with a selected type of endodontic tools. Results: The use of rotary NiTi instruments caused a substantial alteration in the curvature topography and angle of the canals and change in the curvature length. The substantial discrepancy was observed during the preparation of simulated root canals with the reciprocating instruments and the use of WaveOne files led to the largest volume variation. No dependence between the amount of material removed and the measured intracanal side was observed when NiTi instruments were used. Preparation with hand K-type files revealed a relationship between the measuring side and the amount of material removed, with the lower values obtained for the canals' internal curvatures. Conclusions: All the studied endodontic instruments allow a safe preparation of curved root canals in simulating in vivo conditions. The abbreviation of original root canals topography does not seem to be significantly altered following mechanical preparation of simulated, severely curved root canals. The spin echo-based magnetic resonance imaging technique can be utilized for visualization of the internal topography of the root's canals in vitro before and after their mechanical preparation in in vitro conditions. In the future, magnetic resonance microscopy may become a diagnostic tool supporting the work of a clinician. [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]

Nowadays a wide range of endodontic instruments, as well as methods for their processing, is presented in dentistry. Sterilization of endodontic instruments takes a special position in dentistry due to the characteristic features of the instruments used in the daily practice of the dentist. As an example, various endodontic files were processed by different methods: dry heat sterilization, glass bead sterilization, autoclaving and sterilization with the SteriFast device, based on UV radiation, that rays can kill only those microorganisms that are under their direct influence on the surface of the tool. In researches, it was proved that after practical use, physical and chemical sterilization, the functional characteristics of endodontic files were changed: cyclic fatigue, cutting efficiency, flexibility of instruments and its topographic features. However, today there are files that do not change their properties during autoclaving. It can be supposed that the extent of changes depend on the method of production of certain endodontic instruments. [ABSTRACT FROM AUTHOR]

Protaper Universal (PTU), Protaper Gold (PTG) (Maillefer, Ballaigues, CH), EdgeTaper (ET), and EdgeTaper Platinum (ETP) (Albuquerque, NM, USA) were tested for both torsional and flexural resistance. The aim of the present study was to evaluate the influence of proprietary heat treatment on the metallurgical properties of the aforementioned instruments. Four groups of 30 different instruments (size 20.07) were tested, then divided into two subgroups of 15 instruments—one for the cyclic fatigue test in a curved canal (90°—2 mm radius) at 300 rpm and 2.5 Ncm. The time to fracture (TtF) and fragment length (FL) were recorded. The other subgroup was subjected to the torsional test (300 rpm, 5.5 Ncm). The torque to fracture and TtF were recorded. All the instruments underwent a SEM analysis. The heat-treated instruments showed a significantly higher fatigue resistance than the non-heat-treated instruments (p < 0.05). No significant differences were found in the torsional resistance between the ET and PTU, and the ETP and PTG. However, when comparing all the groups, the heat-treated instruments showed less torsional resistance. The improvement from heat treatment was mainly found in the cyclic fatigue resistance. [ABSTRACT FROM AUTHOR]

This study focuses on the development of endodontic instruments manufactured from Cu-Al-Mn shape memory alloys (SMAs) which are more economical and easier to process as compared to conventional NiTi SMAs. Finite element analysis of three different numerical instruments was performed using material parameters of Cu-Al-Mn and conventional superelastic NiTi. Flexural and torsional stiffness of these instruments with the resulting von Mises stresses were evaluated under bending and twisting based on the ISO 3630-1 specification. All the studied Cu-Al-Mn endodontic files exhibited superior flexibility and lower reaction stresses as compared to NiTi endodontic files during bending, resulting from their low elastic modulus and starting stress value for the martensitic transformation. However, low torsional stiffness and high von Mises stress values related with the high angular displacement were obtained for Cu-Al-Mn endodontic instruments under torsional loading. Geometric differences of different models have been an important factor in adjusting the stiffness of endodontic instruments. Consequently, it was determined that Cu-Al-Mn SMA could be used as an alternative material in the manufacture of endodontic files that have large cross-sectional area and moment of inertia. [ABSTRACT FROM AUTHOR]

Instrument fracture ranks among the most crucial complications during the endodontic treatment of a tooth. In order to better understand the practical limits of the instrument, the relation between the cyclic fatigue resistance and physical properties such as hardness, modulus of elasticity, creep and surface roughness were explored. Cyclic fatigue testing in an artificial root canal at intracanal temperature, nanoindentation and 3D microscopy were used for evaluation of four commonly used thermomechanically treated NiTi endodontic instruments (Unicone Plus 6/025, Unicone 6/025, Reciproc Blue R25 and WaveOne Gold Primary). Cyclic fatigue results were analyzed using the Kruskal–Wallis, Mann–Whitney and Bonferroni corrections. The wear resistance of Unicone 6/025 instruments was significantly lower compared to all other instruments (p < 0.05). WaveOne Gold Primary was significantly less resistant than Unicone Plus 6/025 and Reciproc Blue R25, while the difference between Reciproc Blue R25 and Unicone Plus 6/025 was insignificant (p > 0.05). These results are in correlation with measurements of local mechanical properties (hardness, elastic modulus and their ratios H/E and H3/E2). Even though surface roughness, area of cross-section and shape of instruments are important factors affecting instruments behavior, thermal processing appears to be the most important.

Abstract Background In endodontic therapy, continuous rotary instrumentation reduced debris compared to reciprocal instrumentation, which might affect the incidence of post-endodontic pain (PP). The aim of our study was to assess whether PP incidence and levels were influenced by the choice of rotary or reciprocal instruments. Methods In this meta-analysis the Pubmed and EM databases were searched for prospective clinical randomized trials published before April 20, 2016, using combinations of the keywords: root canal preparation/instrumentation/treatment/therapy; post-operative/endodontic pain; reciprocal and rotary instruments. Results Three studies were included, involving a total of 1,317 patients, 659 treated with reciprocating instruments and 658 treated with rotary instruments. PP was reported in 139 patients in the reciprocating group and 172 in the rotary group. The PP incidence odds ratio was 1.27 with 95% confidence interval (CI) (0.25, 6.52) favoring rotary instruments. The mild, moderate and severe PP levels odds ratios were 0.31 (0.11, 0.84), 2.24 (0.66, 7.59) and 11.71 (0.63, 218.15), respectively. No evidence of publication bias was found. Conclusions Rotary instrument choice in endodontic therapy is associated with a lower incidence of PP than reciprocating instruments, while reciprocating instruments are associated with less mild PP incidence.

In modern endodontics, nickel-titanium (NiTi) rotary instruments are used on a large scale for root canal shaping. Nevertheless, the separation of an instrument is a serious concern during shaping. The aim of this study is to determine and compare the torsional fracture characteristics of three types of NiTi endodontic instruments, each with different cross-section designs and movements performed during root canal shaping: Endostar E3 (Endostar, Poldent Co. Ltd., Warsaw, Poland); Reciproc R25 (VDW, Munich, Germany); and Protaper Next X2 (Dentsply Maillefer, Ballaigues, Switzerland). Fifteen instruments are used in this study, divided in three groups (n = 5): Group Endostar, Group Reciproc and Group Protaper. For testing, each instrument is used to shape five simulated root canals, following which its torsional stress to failure is measured. The fracture lengths of all three groups are roughly between 2 and 3 mm from the tip. Higher values of the moment of torsion in fracture, and smaller values of the maximum twisting angle are observed for Group Endostar, as well as closer to circular cross-sections. However, the values of the shear tension are similar for all three groups, because the disadvantage given by the fracture section shape for Groups Reciproc and Protaper is compensated either by size or by intrinsic properties of the instrument material. For the shear tension the Endostar values are insignificantly increased (Kruskal–Wallis test, p = 0.207), and in the case of the maximum twist angle the Protaper values are insignificantly increased (Kruskal–Wallis test, p = 0.287). Because of the instruments shape and conicity, the analysis had to be carried out separately with regard to the length of the fractured tip. Rules-of-thumb are extracted from the study for current practice: if a blockage of the first 2 to 3 mm part of the tip can be anticipated (by the excessive curving of the instrument), the handpiece must be adjusted to torque values that do not exceed 1.5 to 2.5 N · cm for Endostar and 1 to 2 N · cm for Reciproc and Protaper instruments.

Background and Objectives: The aim of the present study is to compare the efficacy of three root canal preparation systems in the shaping of 3D-printed root canal replicas of single rooted teeth. Materials and Methods: Sixty 3D-printed root canal replicas were produced and divided into three groups, each consisting of twenty samples. Each group was shaped with a different instrument: Reciproc Blue R25/08 (VDW GmbH, Munich, Gemany), WaveOne Gold Primary 25/07 (Dentsply Sirona, Ballaigues, Switzerland), and ProTaper Gold F2 25/08 (Denstply Sirona). To ensure the reproducibility of pre- and post-operative CBCT images of the root canals, the endodontic printed replicas were placed in a mould of silicon impression material. A cone-beam computed tomography (CBCT) software was used to compare pre- and post-instrumentation images collected at three levels of the root canal length: 3, 6, and 9 mm from the apical foramen. The amount of transportation, centring ability, and curvature angle after shaping were evaluated for each system. The results were statistically analysed and compared using one-way analysis of variance (ANOVA). Results: Regarding the transportation of the root canal after shaping, significant differences between groups at 3 mm (p = 0.010721) and 6 mm (p = 0.000046) were recorded in the mesio-distal direction, while in the bucco-lingual significant differences were only observed at 6 mm (p = 0.000554). Reciproc Blue removed more dentin from the mesial and buccal wall of the root canal. When evaluating the centring ability of the three systems, significant differences were observed between the groups at the level of 9 mm (p = 0.037258) in the mesio-distal direction, and at the level of 6 mm (p = 0.038197) in the bucco-lingual direction. Significant differences of the canal curvature angle after shaping were also observed between groups (p = 0.000001). Reciproc Blue straightened the curvature the most, while ProTaper Gold the least. Conclusions: All systems produced minor root canal transportation. No instrument was able to achieve a perfect centring preparation of the root canal. All systems produced a small degree of root canal straightening.

OBJECTIVE: To determine the frequency of manual and rotary instrument separation during endodontic treatment amongst experienced dental practitioners and house surgeons. METHODOLOGY: The present study was conducted in various dental teaching hospitals registered with Pakistan Medical and Dental Council (PMDC) from July 2018 to January 2019. The sample size calculation was obtained by taking 50% prevalence rate using Open EPI software (version 3.01) at 95% confidence interval and a=5% and was calculated to be 250. A self-administered questionnaire containing 22 closed ended questions was designed to evaluate different reasons of separation of manual and rotary endodontic instruments amongst experienced dental practitioners and house surgeons. RESULTS: A total of 250 participants were included in this study, out of them 192 were house officers and 58 were dental practitioners.122 (63.5%) of the house surgeons and 30(51.7%) of dental practitioners experienced instruments breakage during root canal treatment. When the types of files were assessed, the results showed that the separation of K- files was most frequent than H-files and Ni-Ti rotary files.106(55.2%) of the house surgeons and 23(39.7%) of the dental practitioners reported separation of K-files during root canal treatment. CONCLUSION: The present study concluded that majority of the house surgeons experienced K-file separation than H-file and Ni-Ti rotary files than Dental practitioners during root canal treatment. [ABSTRACT FROM AUTHOR]

During root canal shaping, pain could result from the high level of force or vibration generated. This could be related to file kinematics or geometry. In the present study, a comparison is made between forces and vibrations generated by endodontic files having three different kinematics. Square pillar resin blocks were used as simulated root canals to study forces and vibrations generated by the file having reciprocating motion (WaveOne Gold), transline motion (Self-Adjusting File), and rotary motion (2Shape). The forces and vibrations were measured using the dynamometer and accelerometer, respectively. Recorded time domain signals were processed in MATLAB to calculate the root mean square value. A one-way analysis of variance and Tukey's test for post hoc comparison at 95% confidence interval were applied over the root mean square data of different files. From a statistical analysis of the file systems, the null hypotheses could not be accepted (P < 0.05) as 95% of the confidence interval. Differences between the means were statistically significant. The root mean square values of force and vibration for WaveOne Gold significantly exceeded those of Self-Adjusting File, 2Shape1, and 2Shape2 while the root mean square values of vibration for 2Shape1 and 2Shape2 were significantly less than the Self-Adjusting File; however, the root mean square value of force for the 2Shape2 was significantly more than for the Self-Adjusting File. Under the present experimental conditions, significant differences in the root mean square values of force and vibration of the three endodontic files of different kinematics have been observed. The WaveOne Gold file system generated higher apical force and vibration than the transline and rotary file system. [ABSTRACT FROM AUTHOR]

Aims.This study aims to estimate the microbial presence on the surface of different brand new NiTi endodontic instruments for clinical use. Materials and Methods. Eleven different types of NiTi rotary endodontic instruments, obtained from their fresh opened original packages, were assigned to three different groups, according to packaging type and sterilization and tested for bacterial contamination. Isolated bacteria were identified by using standard microbiological methods and then counted. Differences observed in groups were analyzed statistically by using the one-way analysis of variance (ANOVA) for dependent samples and the Tukey HSD post hoc test. Results. Statistical differences were found between instruments delivered in plastic boxes which bacterial count resulted higher than those obtained from instruments delivered in blisters (p<0.01). Conclusions. Some brand new endodontic instruments showed degrees of bacterial contamination that both quantitatively and qualitatively deserve to be considered in clinical procedures. [ABSTRACT FROM AUTHOR]

Objective: To compare the consistency of working length control in hand instrumentation and engine-driven rotary files Wave One by comparing their pre and post-instrumentation working lengths. Study Design: Quasi-experimental study. Place and Duration of Study: Armed Forces Institute of Dentistry, Rawalpindi Pakistan, from Jun to Dec 2019. Methodology: A total of 90 mandibular first molars were selected. Two groups were drawn with 45 mesio buccal canals each. The First-Group was prepared with manual K-files, whereas the second group had rotary instrumentation using the WaveOne system. Pre and post-preparation working lengths were noted. Results: The mean pre-operative (18.5±1.03mm) and post-operative (18.15±1.09mm) working lengths of manually prepared and WaveOne prepared canals (18.8±3.43mm and 18.7±3.25mm respectively) presented statistically significant loss of post-operative working lengths. The comparison of the two groups gives a statistically significant result in manual preparation, showing a greater loss of working length as compared to canals prepared with WaveOne rotary files. Conclusion: Manual instrumentation causes a greater loss of working length by straightening the canal more than engine-driven WaveOne rotary files postoperatively. [ABSTRACT FROM AUTHOR]

Objective: To investigate the opinions and attitudes of dental practitioners towards intracanal separation of endodontic instruments and to create awareness regarding the management of separated instruments Study Design: Cross-sectional survey Place and Duration of Study: Department of Operative Dentistry Armed Forces Institute of Dentistry, Rawalpindi Pakistan, from Mar to Apr 2021. Methodology: An online questionnaire was circulated among 374 dentists of private and public hospitals in Rawalpindi and Islamabad. The questionnaire consisted of close-ended questions related to demographic details, dentists' awareness of instrument separation, the frequency of separated instruments, the causes of separation, the management of separated instruments, and the retrieval strategies if used. Results: Out of 374 study participants, 307(82.1%) of the participants thought that operator-related factors such as improper or overuse of the instrument were considered the most common factors for instrument separation during root canal procedures. 205(54.8%) thought unwinding, defective flutes and shiny areas were the most common factors affecting instrument separation. 241(64.4%) of the instruments are separated during cleaning and shaping. 135(36.1%) K files and 119(31.8%) H files were separated in this survey. Conclusion: Most dentists of Rawalpindi and Islamabad face the problem of endodontic instrument separation during root canal preparation. [ABSTRACT FROM AUTHOR]

The purpose of the mechanical root canal preparation is to clean it and give it the right shape. The preparation should be carried out in a way that maintains the original curvature and initial orientation of the apical end. Insufficient root canal preparation may prevent effective chemical decontamination and obturation to the full working length. The study aims to evaluate the shaping ability and effectiveness of the NiTi rotary and reciprocating endodontic instruments, compared to standard hand files using magnetic resonance imaging based on spin echo. Material and methods: A comparative study of severely curved root canals’ shaping abilities using three NiTi systems and K-type hand files was performed, with 40 training “endo-blocks” presenting with “L-shaped” canal. The root canal topography and geometry “before” and “after” mechanical preparation obtained by the magnetic resonance imaging based on the spin echo was used. The main measurement was made using the RARE sequence, with slice thickness reduced to 100 micrometers. In order to improve the signal-to-noise ratio, NA = 25 was used. To minimize the measurement time, the field of view was limited to a cuboid 17 × 16 × 3 mm, with a resolution of 33 × 31 × 100 micrometers. Each 3D image consisted of 512 × 512 × 30 voxels. The imaging plane has been selected in such a way as to fully illustrate the course of curvature of the model root canal. For TR = 5 s and effective TE = 36 ms, TA was 1.5 h. Measurements were performed twice, before and after the preparation of endo-blocs with a selected type of endodontic tools. Results: The use of rotary NiTi instruments caused a substantial alteration in the curvature topography and angle of the canals and change in the curvature length. The substantial discrepancy was observed during the preparation of simulated root canals with the reciprocating instruments and the use of WaveOne files led to the largest volume variation. No dependence between the amount of material removed and the measured intracanal side was observed when NiTi instruments were used. Preparation with hand K-type files revealed a relationship between the measuring side and the amount of material removed, with the lower values obtained for the canals’ internal curvatures. Conclusions: All the studied endodontic instruments allow a safe preparation of curved root canals in simulating in vivo conditions. The abbreviation of original root canals topography does not seem to be significantly altered following mechanical preparation of simulated, severely curved root canals. The spin echo-based magnetic resonance imaging technique can be utilized for visualization of the internal topography of the root’s canals in vitro before and after their mechanical preparation in in vitro conditions. In the future, magnetic resonance microscopy may become a diagnostic tool supporting the work of a clinician.

Protaper Universal (PTU), Protaper Gold (PTG) (Maillefer, Ballaigues, CH), EdgeTaper (ET), and EdgeTaper Platinum (ETP) (Albuquerque, NM, USA) were tested for both torsional and flexural resistance. The aim of the present study was to evaluate the influence of proprietary heat treatment on the metallurgical properties of the aforementioned instruments. Four groups of 30 different instruments (size 20.07) were tested, then divided into two subgroups of 15 instruments—one for the cyclic fatigue test in a curved canal (90°—2 mm radius) at 300 rpm and 2.5 Ncm. The time to fracture (TtF) and fragment length (FL) were recorded. The other subgroup was subjected to the torsional test (300 rpm, 5.5 Ncm). The torque to fracture and TtF were recorded. All the instruments underwent a SEM analysis. The heat-treated instruments showed a significantly higher fatigue resistance than the non-heat-treated instruments (p < 0.05). No significant differences were found in the torsional resistance between the ET and PTU, and the ETP and PTG. However, when comparing all the groups, the heat-treated instruments showed less torsional resistance. The improvement from heat treatment was mainly found in the cyclic fatigue resistance.

The application of irrigating solutions is essential in chemomechanical treatment of tooth root canal. However, chemical and electrochemical aggressiveness of the solutions, which directly act on instruments, may damage their surface. The aim of this study was to investigate the sensitivity of the nickel-titanium (Ni-Ti) and stainless steel endodontic files to corrosive action of the sodium hypochlorite (NaOCl), chlorhexidine gluconate (CHX) and ethylenediamine tetraacetic acid (EDTA). Testing of sensitivity to corrosion of the instruments was performed by dynamic potentiometric method. Measurements were made in 5.25% NaOCl, 0.2% CHX and 17% EDTA. Ni-Ti instruments immersed in 5.25% NaOCl showed the most intensive corrosive changes and the lowest value of pitting potential of 1.1V. Stainless steel instruments immersed in 5.25% NaOCl showed higher value of pitting potential of 1.5V. Stainless steel instruments immersed in 0.2% CHX showed lower corrosive surface changes and higher value of pitting potential of 1.6V, whereas Ni-Ti instruments immersed in 0.2% CHX showed the pitting potential of 1.9V. The corrosion was not observed in both types of instruments after immersion in 17% EDTA. The use of 5.25% NaOCl and 0.2% CHX may cause severe surface corrosion of Ni-Ti and stainless steel endodontic files. [Projekat Ministarstva nauke Republike Srbije, br. 175102]

OBJECTIVE: To investigate the effect of nickel titanium rotary endodontic file immersion in hydrogen peroxide on cyclic fatigue resistance. METHODOLOGY: Twenty Six Protaper Universal (Dentsply Maillerfier) F1 files were randomly divided into two experimental groups. In Group I, Protaper universal variable taper F1 files were immersed in normal saline where as in Group II, the files were soaked in hydrogen peroxide (6% w/v) for 2 hours at 37°C. Cyclic fatigue of each file was checked by recording the number of rotations required to break a file in a 90°curve with a 5 mm radius. For statistical analysis of data, Two-way ANOVA was applied. A p value of <0.05 was considered significant. RESULT: Out of Twenty Six, Six files fractured spontaneously after immersion in hydrogen peroxide. Twenty files were subjected to fracture resistance testing. Statistically significant difference in cyclic fatigue resistace between the two groups was found (p=0.002). The files soaked in Group II required less revolutions to fracture than the ones immersed Group I. CONCLUSION: The immersion of NiTi endodontic files in hydrogen peroxide significantly reduces cyclic fatigue resistance. Therefore, immersion of the NiTi endodontic files in hydrogen peroxide solution for removal of clogged debris should be discouraged. [ABSTRACT FROM AUTHOR]

Introduction Separation (fracture) of endodontic instruments in the root canal during chemomechanical instrumentation is a complication that can compromise the final outcome of endodontic treatment. One of the most common factors that cause fatigue of endodontic instruments and consequent fracture is surface corrosion. The aim of this study was to investigate the ultrastructure of surface corrosion of endodontic instruments made of stainless steel and nickel-titanium after immersion in the most commonly used root canal irrigants. Material and Methods The study included 48 nickel-titanium and stainless steel endodontic hand files. All instruments were immersed in 5.25% sodium hypochlorite, 0.2% CHX and 17% EDTA. Surface corrosion was analyzed using a scanning electron microscope (SEM). Results Nickel-titanium instruments showed significantly higher susceptibility to corrosion after immersion in 5.25% sodium hypochlorite compared to stainless steel instruments (p