In Vitro Evaluation of Smear Layer and Debris Removal and Antimicrobial Activity of Different Irrigating Solutions.

OBJECTIVE: The aim of this in vitro study was to compare the smear layer and debris removal and antimicrobial activity of two dual-action irrigating solutions for continuous chelation (Triton; Brasseler, Savannah, USA and Dual Rinse HEDP; Medcem GmbH, Weinfelden, Switzerland) with a dual step irrigation protocol with sodium hypochlorite (NaOCl) followed by ethylenediaminetetraacetic acid (EDTA). METHODS: Thirty single-rooted single-canal teeth were divided into three groups (n=10) and irrigated with Triton, Dual Rinse HEDP mixed with 6% NaOCl and 6% NaOCl/17% EDTA. The teeth were observed under a scanning electron microscope (SEM) to assess the canal wall cleanliness. In addition, 80 dentine discs were contaminated with Candida albicans and 80 discs with Enterococcus faecalis and irrigated with Triton, Dual Rinse HEDP mixed with 6% NaOCl and 6% NaOCl/17% EDTA or not treated (n=20). Fifteen discs were used to evaluate colony-forming units, while 5 discs were analysed by SEM. Data were analysed using the Shapiro- Wilk, Kruskal-Wallis and One-Way ANOVA tests. RESULTS: Triton was statistically more effective than Dual Rinse HEDP and NaOCl/EDTA in removing debris (p<0.05), except with NaOCl/EDTA in the coronal third. Triton was more effective than Dual Rinse HEDP in removing the smear layer from the apical and middle thirds (p<0.05). All the irrigation protocols significantly re- duced the number of E. faecalis. The Triton group showed the lowest number of remaining C. albicans (p<0.05). CONCLUSION: Triton was the most effective irrigation solution in removing debris and as effective as NaOCl/ EDTA in removing the smear layer. Triton showed the highest efficacy against C. albicans. New irrigating solutions that provide continuous chelation may provide an alternative to current irrigation protocols.

Comparison of shaping ability of the Reciproc Blue and One Curve with or without glide path in simulated S-shaped root canals.

Objectives: This study aimed to assess the impact of a glide-path on the shaping ability of 2 single-file instruments and to compare the centering ability, maintenance of original canal curvatures and area of instrumentation in simulated S-shaped root canals. Materials and Methods: Forty simulated S-shaped root canals were used and were prepared with One Curve (group OC), One G and OC (group GOC), Reciproc Blue (group RB) and R-Pilot and RB (group PRB) and scanned before and after instrumentation. The images were analyzed using AutoCAD. After superimposing the samples, 4 levels (D1, D2, D3, and D4) and 2 angles (Δ1 and Δ2) were established to evaluate the centering ability and modification of the canal curvatures. Then, the area of instrumentation (ΔA) was measured. The data were analyzed using 2-way analysis of variance and Tukey's test for multiple comparisons (p < 0.05). Results: Regarding the centering ability in the apical part (D3, D4), the use of the glide-path yielded better results than the single-file groups. Among the groups at D4, OC showed the worst results (p < 0.05). The OC system removed less material (ΔA) than the RB system, and for Δ1, OC yielded a worse result than RB (p < 0.05). Conclusions: The glide-path improved the centering ability in the apical part of the simulated S-shaped canals. The RB system showed a better centering ability in the apical part and major respect of the canal curvatures compared with OC system.

Orthodontic Extrusion vs. Surgical Extrusion to Rehabilitate Severely Damaged Teeth: A Literature Review.

The need to rehabilitate severely compromised teeth is frequent in daily clinical practice. Tooth extraction and replacement with dental implant represents a common treatment choice. However, the survival rate for implants is inferior to teeth, even if severely damaged but properly treated. In order to reestablish a physiological supracrestal tissue attachment of damaged teeth and to arrange an efficient ferrule effect, three options can be considered: crown lengthening, orthodontic extrusion and surgical extrusion. Crown lengthening is considered an invasive technique that causes the removal of part of the bony support, while both orthodontic and surgical extrusion can avoid this inconvenience and can be used successfully in the treatment of severely damaged teeth. The aim of the present narrative review is to compare advantages, disadvantages, time of therapy required, contraindications and complications of both techniques.

Antimicrobial and Antibiofilm Properties of Graphene Oxide on Enterococcus faecalis.

The aim of this study was to evaluate the antibacterial properties of graphene oxide (GO) against Enterococcus faecalis in vitro conditions and when used to coat dentin surface to prevent E. faecalis adhesion. The ATCC strain of E. faecalis 29212 has been used to perform a viability test. The pellet was suspended in ultrapure water, NaCl, PBS buffer, CaCl2 and MgCl2, Luria-Bertani broth solutions. The viability was evaluated by the colony forming unit counting method. Atomic force microscopy images and the measure of surface zeta potential variation were analyzed. Dentin discs were covered with a film of GO (n = 15) or were not treated (n = 15). Bacterial suspension was added to each sample of dentine discs and microbial counts were calculated. Statistically significant differences between two groups were assessed by a two-tailed unpaired t-test. Bacteria cell morphology was investigated with scanning electron microscopy. The highest growth inhibition was obtained in ddH2O and CaCl2 solution while, in PBS and NaCl, GO had poor antibacterial efficacy with a growth enhancing effect in the latter. GO on dentin discs demonstrated high antibacterial activity. GO film has demonstrated acceptable adhesion properties to root dentin and a role in the inhibition of bacterial film proliferation and biofilm formation.

The Outcome of Primary Root Canal Treatment in Postirradiated Patients: A Case Series.

Osteoradionecrosis (ORN) of the jaw is considered the most severe long-term adverse effect that can occur in radiation therapy patients. Teeth extractions and dental diseases are the main risk factors for ORN in irradiated patients. The aim of this case series was to evaluate the outcome of primary root canal treatments performed on patients who underwent head and neck radiotherapy and to evaluate any ORN related to the endodontic treatment. In this case series, primary root canal therapies (absence of radiolucency) were performed on 10 teeth of 8 patients who underwent radiotherapy for head and neck cancers. Radiation doses to the periapical area were calculated using the radiotherapy planning computed tomographic scan. After a 277-day mean follow-up, all patients were asymptomatic, no teeth showed periapical radiolucency, and no ORN was observed. Even if a limitation of buccal opening occurred after radiotherapy and complicated the endodontic procedures, root canal therapy seemed to be safe and a valid alternative to tooth extraction.

Endodontic management of an autotransplanted mandibular third molar: A simplified approach.

BACKGROUND AND OVERVIEW: In this case report, the authors aim to review the standard protocols for endodontic treatment of autotransplanted molars and report on the 5-year follow-up of a clinical transplantation case. CASE DESCRIPTION: The authors transplanted a mandibular third molar into the position of the adjacent second molar. The authors performed extraoral apicoectomy and retrograde restoration after atraumatic extraction of the donor tooth and before transplantation. The authors did not perform conventional orthograde root canal treatment after transplantation. The patient was followed up 5 years after the autotransplantation. Results of follow-up radiography showed a regular root surface without evidence of periapical lesions or root resorption. CONCLUSIONS AND PRACTICAL IMPLICATIONS: If appropriate sterility of the working field is maintained during surgery and a tight apical seal is achieved during the extraoral treatment, orthograde endodontic treatment should be delayed or avoided.

Histologic Response of Human Pulp and Periapical Tissues to Tricalcium Silicate-based Materials: A Series of Successfully Treated Cases.

Pulpal/periapical responses of human teeth that are treated successfully with tricalcium silicate-based materials are extremely difficult to obtain because of the typical unavailability of these teeth for histologic examination. The present case series reports histologic and histobacteriologic findings of 3 human teeth that had undergone pulpotomy, orthograde retreatment, and apicoectomy/root-end filling using tricalcium silicate-based endodontic materials. The teeth were extracted after 34 days, 7 weeks, and 20 months, respectively, because of unusual circumstances. The extracted teeth were processed, paraffin embedded, sectioned, stained with hematoxylin-eosin or the modified Brown and Brenn technique, and examined with light microscopy. The recurrent observation for the 3 cases presented was the absence of inflammatory or foreign body reactions of the host tissues in contact with tricalcium silicate-based materials after different observation periods despite the identification of bacteria in dentinal tubules close to the site of operation. Wound healing was rapid with repair/regeneration of lost tissues with cementum and new bone trabeculae. Although the level of evidence for a case series is low because of the anecdotal nature of the reported episodes, the histologic results reported in the present case series illustrate the highly biocompatible and bioactive nature of the tricalcium silicate-based materials used in treating these cases.

Antibiofilm Activity of Three Different Irrigation Techniques: An in Vitro Study.

The microbial infection of the endodontic space occurs in a necrotic tooth as a result of dental caries, trauma, periodontal disease, or previous root canal therapy. The disruption of the biofilms and the reduction of the bacterial load inside root canals are crucial for the success of root canal therapy. The aim of this study was to compare, in vitro, the antibiofilm efficacy of a novel passive sonic irrigation (PSI) device with passive ultrasonic irrigation (PUI) and conventional needle irrigation (CNI). Forty-four single-rooted human teeth were inoculated with a culture of E. faecalis for 28 days. The specimens were randomly divided into three groups: PUI, CNI, and PSI (n = 12). The activation protocols were performed using both 17% EDTA and 5.25% NaOCl. Residual bacterial biofilm was taken by means of a canal brush and colony-forming unit (CFU) were counted. The data were analyzed using one-way ANOVA and Games-Howell's post hoc tests. A major reduction in CFU was observed in the PSI and PUI groups, in comparison with the CNI group. No difference was found (p > 0.05) in terms of CFU reduction between PSI and PUI. PSI could be as effective as PUI in the removal of bacterial biofilms from straight root canals.

Influence of activation mode and preheating on intracanal irrigant temperature.

This ex vivo study assessed the effectiveness of two activation modes to increase the intracanal temperature of 5.25% NaOCl solution and the time for a preheated-irrigant to return to its initial temperature. Ten single-rooted extracted human teeth were used. Thermocouples were adapted to the root surface and the temperature was registered following two activation modes: ultrasound (US) and thermal. Furthermore, a preheated-solution (45°C/60°C) was flushed into root canal to test the time needed to return to its initial temperature. Data were analysed using two-way ANOVA and Tukey's post-hoc tests (P = 0.05). Statistical analysis showed differences between the activation modes. US and thermal activation increased from 37 to 40.4°C and to 62.8°C respectively in 60 s. Time for preheated-irrigant to return to its initial temperature was longer for 60°C. Preheating irrigant at 60°C and using thermal activation to keep it warm may represent a further step of the irrigation protocol.

Influence of environmental temperature, heat-treatment and design on the cyclic fatigue resistance of three generations of a single-file nickel-titanium rotary instrument.

The aim of the present study was to evaluate the effect of environmental temperature, heat-treatment*** and design on the cyclic fatigue resistance of OneShape (OS), OneShape new generation (OSNG) and One Curve (OC) NiTi rotary single-file instruments. Cyclic fatigue testing of NiTi instruments was performed in an artificial canal with a 5-mm radius of curvature and a 60° angle of curvature located 5 mm from the tip of the instrument. During the experiment 3 different temperatures were used in a thermostatic bath with electronic and infrared controls: 0°, 20° and 35 °C. Sixty OneShape, 60 OneShape new generation and 60 One Curve instruments were rotated in the artificial canal until fracture occurred and the number of cycles to fracture (NCF) and the length of the fractured fragment (FL) was recorded. Data were analyzed by one-way ANOVA test at the 5% significance level. Fatigue resistance was significantly higher as the environmental temperature decreased, with differences ranging from 61 to 791%. OC instruments were significantly more resistant to cyclic fatigue than OS and OSNG instruments at all the temperatures tested (P < 0.05). There was no significant difference with respect to the length of the fractured file fragments for all the instruments tested at all the temperatures tested (P > 0.05). Within the limitation of the present study, fatigue resistance of the files was significantly increased when the environmental temperature decreased. OC instruments were significantly more resistant to cyclic fatigue than OS and OSNG instruments at all the temperatures tested.

Environmental Temperature Drastically Affects Flexural Fatigue Resistance of Nickel-titanium Rotary Files.

INTRODUCTION: The aim of the present study was to analyze how a low environmental temperature can affect the fatigue life of instruments made by different types of heat-treated nickel-titanium alloys. METHODS: The flexural cyclic fatigue of 40 new specimens for each of the following systems was tested for cyclic fatigue resistance: ProTaper Universal F2 (Dentsply Maillefer, Ballaigues, Switzerland), ProTaper Gold F2 (Dentsply Tulsa Dental Specialties, Tulsa, OK), Twisted Files SM2 (SybronEndo, Orange, CA), Mtwo #25.06 (VDW, Munich, Germany), and Vortex Blue #30.04 and #40.06 (Dentsply Tulsa Dental Specialties). Instruments were tested at 2 different environmental temperatures: 20°C (±2°C) for room temperature (RT) group and -20°C (±2°C) for the cooled environment (CE) group (n = 20). The number of cycles to failure (NCF) and the length of the fractured fragment (FL) were recorded. The means and standard deviations of NCF and FL were then calculated; NCF data were statistically analyzed using a paired t test between groups RT and CE for each instrument tested (P < .05), whereas FL data were analyzed using analysis of variance (P < .05). RESULTS: The mean NCF values measured were significantly higher for the CE groups than the RT groups in all the systems tested (P < .05). The increase in cyclic fatigue resistance varied from 274%-854%. No differences in FL were registered among the different groups (P < .05). CONCLUSIONS: A low environmental temperature determines a drastic increase in the flexural fatigue resistance of NiTi endodontic instruments manufactured with traditional alloy and different heat treatments.

Fracture Strength of Endodontically Treated Teeth with Different Access Cavity Designs.

INTRODUCTION: The purpose of this study was to compare in vitro the fracture strength of root-filled and restored teeth with traditional endodontic cavity (TEC), conservative endodontic cavity (CEC), or ultraconservative "ninja" endodontic cavity (NEC) access. METHODS: Extracted human intact maxillary and mandibular premolars and molars were selected and assigned to control (intact teeth), TEC, CEC, or NEC groups (n = 10/group/type). Teeth in the TEC group were prepared following the principles of traditional endodontic cavities. Minimal CECs and NECs were plotted on cone-beam computed tomographic images. Then, teeth were endodontically treated and restored. The 160 specimens were then loaded to fracture in a mechanical material testing machine (LR30 K; Lloyd Instruments Ltd, Fareham, UK). The maximum load at fracture and fracture pattern (restorable or unrestorable) were recorded. Fracture loads were compared statistically, and the data were examined with analysis of variance and the Student-Newman-Keuls test for multiple comparisons. RESULTS: The mean load at fracture for TEC was significantly lower than the one for the CEC, NEC, and control groups for all types of teeth (P < .05), whereas no difference was observed among CEC, NEC, and intact teeth (P > .05). Unrestorable fractures were significantly more frequent in the TEC, CEC, and NEC groups than in the control group in each tooth type (P < .05). CONCLUSIONS: Teeth with TEC access showed lower fracture strength than the ones prepared with CEC or NEC. Ultraconservative "ninja" endodontic cavity access did not increase the fracture strength of teeth compared with the ones prepared with CEC. Intact teeth showed more restorable fractures than all the prepared ones.

Blue Thermomechanical Treatment Optimizes Fatigue Resistance and Flexibility of the Reciproc Files.

INTRODUCTION: The aim of the present study was to evaluate the influence of Blue thermal treatment on the bending resistance and cyclic fatigue of conventional M-Wire Reciproc files (VDW, Munich, Germany). The roughness pattern and the microhardness of the files were also assessed. METHODS: Flexibility of standard Reciproc R25 files and the corresponding Blue prototypes was determined by 45° bending tests according to the ISO 3630-1 specification. Instruments were also subjected to cyclic fatigue resistance, measuring the time to fracture in an artificial stainless steel canal with a 60° angle and a 5-mm radius of curvature. The fracture surface of all fragments was examined with a scanning electron microscope. The roughness of the working parts was quantified by using a profilometer, and the microhardness test was performed using the Vickers hardness tester. Results were statistically analyzed using the Student t test with a level of significance set at P < .05. RESULTS: Reciproc Blue instruments presented a significantly longer cyclic fatigue life and significantly lower bending resistance than the original Reciproc instrument (P < .05). Regarding the roughness pattern, there was no significant difference between Reciproc Blue and the original Reciproc instruments (P > .05), whereas Reciproc Blue revealed significantly lower microhardness than the original Reciproc instrument (P < .05). CONCLUSIONS: Reciproc Blue nickel-titanium showed improved all-around performance when compared with conventional M-Wire superelastic nickel-titanium, demonstrating improved flexibility and fatigue resistance, and reduced microhardness while maintaining similar characteristics of the surface.

Fracture resistance of endodontically treated teeth restored with a bulkfill flowable material and a resin composite.

AIM: To determine and compare the fracture resistance of endodontically treated teeth restored with a bulk fill flowable material (SDR) and a traditional resin composite. METHODS: Thirty maxillary and 30 mandibular first molars were selected based on similar dimensions. After cleaning, shaping and filling of the root canals and adhesive procedures, specimens were assigned to 3 subgroups for each tooth type (n=10): Group A: control group, including intact teeth; Group B: access cavities were restored with a traditional resin composite (EsthetX; Dentsply-Italy, Rome, Italy); Group C: access cavities were restored with a bulk fill flowable composite (SDR; Dentsply-Italy), except 1.5 mm layer of the occlusal surface that was restored with the same resin composite as Group B. The specimens were subjected to compressive force in a material static-testing machine until fracture occurred, the maximum fracture load of the specimens was measured (N) and the type of fracture was recorded as favorable or unfavorable. Data were statistically analyzed with one-way analysis of variance (ANOVA) and Bonferroni tests (P<0.05). RESULTS: No statistically significant differences were found among groups (P<0.05). Fracture resistance of endodontically treated teeth restored with a traditional resin composite and with a bulk fill flowable composite (SDR) was similar in both maxillary and mandibular molars and showed no significant decrease in fracture resistance compared to intact specimens. CONCLUSIONS: No significant difference was observed in the mechanical fracture resistance of endodontically treated molars restored with traditional resin composite restorations compared to bulk fill flowable composite restorations.

Current Assessment of Reciprocation in Endodontic Preparation: A Comprehensive Review-Part I: Historic Perspectives and Current Applications.

INTRODUCTION: During the evolution of mechanical instrumentation in endodontics, an important role has been played by reciprocating stainless steel files using horizontal rotational, vertical translational, or combined movements. These kinds of systems are still in use mainly as an accessory to help in the first phases of the treatment. METHODS: The literature concerning these systems has been analyzed using selected criteria. RESULTS: The latest evolution of horizontal rotational reciprocating movement brought to the development of a different kind of movement in which the angles are asymmetrical and that appears to be ideal in conjunction with modern nickel-titanium (NiTi) files with a greater taper. Initially, this movement was limited to particular handpieces available on the market that was used with existing NiTi files to complete root canal instrumentation. Later on, specific files and proprietary motors were introduced into the market. The differences between reciprocating motion used for NiTi and stainless steel files are described and critically analyzed. CONCLUSIONS: A classification of the different mechanical reciprocating motions used is presented, thus enabling an easier understanding of these systems and anticipated future developments.

Current Assessment of Reciprocation in Endodontic Preparation: A Comprehensive Review--Part II: Properties and Effectiveness.

INTRODUCTION: Many reciprocating file systems (RFs) have recently been introduced. This article reviews the properties, effectiveness, and clinical outcomes of the RFs. METHODS: A PubMed electronic search was conducted by using appropriate key words to identify investigations on RFs. After retrieving the full-text relevant articles, the cross citations were also identified. RESULTS: This review summarizes the mechanical properties, shaping ability, preservation of the root canal anatomy, shaping time, cleaning effectiveness, microcrack formation, bacterial reduction, extrusion of debris, and removal of root canal filling materials of RFs. CONCLUSIONS: The favorable results of RFs indicate their potential application as viable alternatives to rotary file systems, yet no filing system is able to entirely prepare the dentin of canals, totally eliminate sessile and planktonic microorganisms, or remove the filling material completely from the root canal system.

Cyclic fatigue of instruments for endodontic glide path.

Endodontic glide path is the creation of a smooth patency from canal orifice to apex, which can be performed manually or with small tapered NiTi rotary instruments. The use of stainless steel (SS) hand K-files inserted in a reciprocating handpiece can be a possible alternative to create a mechanical glide path. The aim of this study was to compare the cyclic fatigue resistance between SS K-files used in a reciprocating motion and NiTi rotary instruments in artificial curved canals. Ten SS size 15 K-files used with the M4 handpiece (SybronEndo, Glendora, CA, USA) and ten PathFiles (Maillefer-Dentsply, Ballaigues, CH, Switzerland) NiTi rotary instruments size 16, 0.02 taper were tested for resistance to cyclic fatigue. The time to fracture inside an artificial curved canal was recorded for each instrument. Data were analyzed by one-way ANOVA and Tukey HSD test. Mean time (and SD) to failure was 464 s (±40.4) for the Group PF (NiTi rotary PathFile), and 1049 s (±24.8) for the Group M4 (SS K-files reciprocating) with a statistically significant difference between the two groups (p = 0.033). The SS 15 K-files used with the M4 handpiece showed a significant greater resistance to cyclic fatigue when compared to the NiTi rotary PathFiles. Therefore, the use of small size SS files in a reciprocating motion might be a rational choice for the creation of a mechanical endodontic glide path in curved root canals.

Cyclic fatigue resistance of newly manufactured rotary nickel titanium instruments used in different rotational directions.

The aim of this study was to investigate whether cyclic fatigue resistance is increased for nickel titanium instruments manufactured with improved heating processes in clockwise or counterclockwise continuous rotation. The instruments compared were produced either using the R-phase heat treatment (K3XF; SybronEndo, Orange, CA, USA) or the M-wire alloy (ProFile Vortex; DENTSPLY Tulsa Dental Specialties, Tulsa, OK, USA). Tests were performed with a specific cyclic fatigue device that evaluated cycles to failure of rotary instruments in curved artificial canals. Results indicated no significant difference in resistance to cyclic fatigue when rotary nickel titanium instruments are used in clockwise or counterclockwise continuous rotation. In both directions of rotation, size 04-25 K3XF showed a significant increase (P < 0.05) in the mean number of cycles to failure when compared with size 04-25 ProFile Vortex.

The influence of three different instrumentation techniques on the incidence of postoperative pain after endodontic treatment.

AIMS: Apical extrusion of infected debris to the periradicular tissues is one of the principal causes of postoperative pain and discomfort. Recent researches have shown that reciprocating instrumentation techniques seem to significantly increase the amount of debris extruded beyond the apex and, consequently, the risk of postoperative pain. The goal of the present study was to evaluate and compare postoperative pain using three different nickel-titanium instrumentation techniques: a rotary crown-down technique using TF instruments (SybronEndo, Orange, Ca), a reciprocating single-file technique using WaveOne instruments (Maillefer DEntsply, Baillagues, CH), and a novel instrumentation technique (TF Adaptive, SybronEndo, Orange, Ca), using a unique, proprietary movement, combining reciprocation and continuous rotation. METHODS: Ninety patients requiring endodontic treatment on permanent premolar and molar teeth with non vital pulps preoperatively were included in the study. The patients were assigned into three groups of 30 patients each, trying to make the groups very similar, concerning the number of root canals, presence of initial pain and periapical lesions. The teeth in group 1 (n = 30) were instrumented with a crown-down technique using TF instruments, whilst those in group 2 (n = 30) were instrumented with a single-file technique using Waveone 08 25. The third group (n = 30) used the 3-file Tf Adaprtive sequence. All techniques were performed following manufacturers' instructions and all canals were shaped, cleaned and obturated in a single-visit by the same operator. The assessment of postoperative pain was carried out at 3 days by using a visual analogue scale. VAS pain scores were compared using one-way ANOVA post hoc Tukey test. A value of p < 0.05 was required for statistical significance. RESULTS: Results for VAS pain scores showed a statistically significant difference was found between the WaveOne (p=0,021) technique and the other two techniques. No statistical significant differences were found between TF and TF Adaptive (p= 0,087). When evaluating patient experiencing sever pain the incidence of symptoms was significantly higher with the WaveOne technique. CONCLUSIONS: Since the incidence of preoperative pain, the type of tooth and the pulp and periodontal pathology were quite similar between the three tested groups, and all the other variables (operator, irrigation, obturation) were identical, we may conclude that the difference in postoperative pain can be mainly related to the different instrumentation techniques.

Cyclic fatigue resistance of four nickel-titanium rotary instruments: a comparative study.

AIMS: The aim of this study is to investigate cyclic fatigue resistance of four nickel - titanium rotary (NTR) instruments produced by a new method or traditional grinding processes. METHODS: FOUR NTR INSTRUMENTS FROM DIFFERENT BRANDS WERE SELECTED: group 1. Twisted File produced by a new thermal treatment of nickel - titanium alloy; group 2. Revo S SU; group 3. Mtwo and group 4. BioRaCe BR3 produced by traditional grinding processes. A total of 80 instruments (20 for each group) were tested for cyclic fatigue resistance inside a curved artificial canal with a 60 degree angle of curvature and 5 mm radius of curvature. Time to fracture (TtF) from the start of the test until the moment of file breakage and the length of the fractured tip was recorded for each instrument. Means and standard deviations (SD) of TtF and fragment length were calculated. Data were subjected to one-way analysis of variance (ANOVA). RESULTS: Group 1 (Twisted File) showed the highest value of TtF means. Cyclic fatigue resistance of Twisted File and Mtwo was significantly higher than group 2 (Revo S SU) and 4 (BioRace BR3), while no significant differences were found between group 1 (Twisted File) and 3 (Mtwo) or group 2 (Revo S SU) and 4 (BioRaCe BR3). CONCLUSIONS: The cyclic fatigue resistance of Twisted File was significantly frigher than instruments produced with traditional grinding process except of Mtwo files.