Commensal E. coli limits Salmonella gut invasion during inflammation by producing toxin-bound siderophores in a tonB-dependent manner.

The gastrointestinal tract is densely colonized by a polymicrobial community known as the microbiota which serves as primary line of defence against pathogen invasion. The microbiota can limit gut-luminal pathogen growth at different stages of infection. This can be traced to specific commensal strains exhibiting direct or indirect protective functions. Although these mechanisms hold the potential to develop new approaches to combat enteric pathogens, they remain far from being completely described. In this study, we investigated how a mouse commensal Escherichia coli can outcompete Salmonella enterica serovar Typhimurium (S. Tm). Using a salmonellosis mouse model, we found that the commensal E. coli 8178 strain relies on a trojan horse trap strategy to limit S. Tm expansion in the inflamed gut. Combining mutants and reporter tools, we demonstrated that inflammation triggers the expression of the E. coli 8178 antimicrobial microcin H47 toxin which, when fused to salmochelin siderophores, can specifically alter S. Tm growth. This protective function was compromised upon disruption of the E. coli 8178 tonB-dependent catecholate siderophore uptake system, highlighting a previously unappreciated crosstalk between iron intake and microcin H47 activity. By identifying the genetic determinants mediating S. Tm competition, our work not only provides a better mechanistic understanding of the protective function displayed by members of the gut microbiota but also further expands the general contribution of microcins in bacterial antagonistic relationships. Ultimately, such insights can open new avenues for developing microbiota-based approaches to better control intestinal infections.

The effect of rotation speed of XP-endo Shaper on apically extruded debris during endodontic procedures: an In Vitro study / El efecto de la velocidad de rotación de XP-endo Shaper sobre los desechos extruídos apicalmente durante los procedimientos de endodoncia: un estudio in vitro

Abstract The aim of this study was to evaluate the effect of using a higher rotation speed with the XP-endo Shaper (XPS) on apically extruded debris and operation time during endodontic treatment and retreatment procedures. Sixty mesial roots of mandibular first molar teeth were randomly assigned to four groups (Initial treatment groups: XPS used at 1000 or 3000rpm rotation speeds and Retreatment groups: XPS used at 1000 or 3000rpm rotation speeds). During the initial treatment and retreatment procedures preweighed eppendorf tubes were used to collect apically extruded debris, and the operation time was recorded in seconds. The extruded debris was quantified by subtracting the preinstrumentation from the postinstrumentation weight of the Eppendorf tubes. Data were analysed using two-way ANOVA at a significance level of 0.05. In all groups, the use of the XPS at 1000 or 3000rpm rotation speeds had no statistically significant effect on the amount of apically extruded debris (p>0.05). The use of the XPS at a 3000rpm rotation speed significantly decreased the instrumentation time (p<0.05). In summary, the use of the XPS at high rotation speeds in initial treatment and retreatment procedures did not have a significant effect on the amount of apically extruded debris but significantly decreased the operation time.

Resumen El objetivo de este estudio fue evaluar el efecto del uso de una mayor velocidad de rotación con XP-endo Shaper (XPS) sobre los desechos extruidos apicalmente y el tiempo de operación durante el tratamiento endodóntico y los procedimientos de retratamiento. Sesenta raíces mesiales de los primeros molares mandibulares se asignaron aleatoriamente a cuatro grupos (grupos de tratamiento inicial: XPS usado a velocidades de rotación de 1000 o 3000rpm y grupos de retratamiento: XPS usado a velocidades de rotación de 1000 o 3000rpm). Durante el tratamiento inicial y los procedimientos de retratamiento se utilizaron tubos Eppendorf pesados previamente para recoger los desechos extruidos apicalmente, y el tiempo de operación se registró en segundos. Los residuos extruidos se cuantificaron restando la preinstrumentación del peso postinstrumentación de los tubos Eppendorf. Los datos se analizaron mediante ANOVA bidireccional a un nivel de significación de 0,05. En todos los grupos, el uso del XPS a velocidades de rotación de 1000 o 3000rpm no tuvo un efecto estadísticamente significativo sobre la cantidad de detritos extruidos apicalmente (p>0.05). El uso del XPS a una velocidad de rotación de 3000rpm disminuyó significativamente el tiempo de instrumentación (p<0.05). En resumen, el uso del XPS a altas velocidades de rotación en los procedimientos de tratamiento inicial y retratamiento no tuvo un efecto significativo en la cantidad de detritos extruidos apicalmente, pero disminuyó significativamente el tiempo de operación.

Comparison of the efficacy of sonic irrigation and conventional syringe irrigation in the removal of curcumin and triple antibiotic paste from root canals.

Background. The present study aimed to compare the efficacy of sonic irrigation and conventional syringe irrigation (CSI) in terms of curcumin (CUR) and triple antibiotic paste (TAP) removal from a standardized groove artificially created in root canals. Methods. The root canals of 72 anterior maxillary teeth were prepared using the Reciproc system to size R50. The teeth were split longitudinally, and a standardized groove was created in the apical region of one root half. The standardized grooves were filled with CUR or TAP with the exclusion of six teeth that served as the negative control group, and then the root halves were reassembled. The teeth were divided into two subgroups according to the irrigation protocols used: sonic activation with EndoActivator (EA) or CSI (n=15). After the removal of the medicament, the residual medicament was assessed under a stereomicroscope. Kruskal-Wallis and Mann-Whitney U tests were used for statistical analyses (P = 0.05). Results. The EA sonic activation method was significantly more efficient in removing CUR medicament from the root canals. Considering the medicament types, more CUR than TAP was removed from the root canals using both CSI and the EA (sonic activation) system (P < 0.05). Conclusion. As compared with CSI, the EA was not significantly more efficient in removing TAP, but it was significantly more effective than CSI in removing CUR.

Effects of the endodontic access cavity on apical debris extrusion during root canal preparation using different single-file systems.

OBJECTIVES: This study was conducted to evaluate the effects of traditional and contracted endodontic cavity (TEC and CEC) preparation with the use of Reciproc Blue (RPC B) and One Curve (OC) single-file systems on the amount of apical debris extrusion in mandibular first molar root canals. MATERIALS AND METHODS: Eighty extracted mandibular first molar teeth were randomly assigned to 4 groups (n = 20) according to the endodontic access cavity shape and the single file system used for root canal preparation (reciprocating motion with the RCP B and rotary motion with the OC): TEC-RPC B, TEC-OC, CEC-RPC B, and CEC-OC. The apically extruded debris during preparation was collected in Eppendorf tubes. The amount of extruded debris was quantified by subtracting the weight of the empty tubes from the weight of the Eppendorf tubes containing the debris. Data were analyzed using 1-way analysis of variance with the Tukey post hoc test. The level of significance was set at p < 0.05. RESULTS: The CEC-RPC B group showed more apical debris extrusion than the TEC-OC and CEC-OC groups (p < 0.05). There were no statistically significant differences in the amount of apical debris extrusion among the TEC-OC, CEC-OC, and TEC-RPC B groups. CONCLUSIONS: RPC B caused more apical debris extrusion in the CEC groups than did the OC single-file system. Therefore, it is suggested that the RPC B file should be used carefully in teeth with a CEC.

The Effects of Different Endodontic Access Cavity Design and Using XP-endo Finisher on the Reduction of Enterococcus faecalis in the Root Canal System.

INTRODUCTION: The aim of this study was to evaluate the effect of using the XP-endo Finisher (XPF; FKG Dentaire, La Chaux de Fonds, Switzerland) in teeth that have a traditional access cavity (TEC) and a contracted access cavity (CEC) design on the amount of decrease in the number of Enterococcus faecalis bacteria within the root canal system. METHODS: Eighty mandibular first molar teeth were selected and randomly divided into 2 groups: TEC and CEC (n = 40/group). After access cavity preparation in the 2 groups, 80 mesiobuccal root canals were contaminated with Enterococcus faecalis for 4 weeks. After the first sampling (S1), in order to perform root canal instrumentation, the TEC and CEC groups were further divided into 4 subgroups (10 teeth/group): Reciproc (VDW GmbH, Munich, Germany) and ProTaper Next (Dentsply Maillefer, Ballaigues, Switzerland) with or without XPF. Bacterial sampling from the root canals was performed with sterile paper points before (S1) and after (S2) instrumentation to determine the bacterial load. The bacterial reduction was counted as colony-forming units/mL and analyzed statistically by 3-factor repeated measures analysis of variance. Multiple comparisons of the main factor effect were performed using the Bonferroni correction (α < .05), all at 5% significance. RESULTS: The number of E. faecalis bacteria in all the samples with different cavity designs were significantly reduced after instrumentation. The lowest value of bacterial decrease percentage was observed in the CEC-Reciproc-XPF (82.8%) group. CONCLUSIONS: The bacterial reduction counts of E. faecalis were a similar level in the TEC and CEC cavities, and the use of XPF did not show significant differences between groups.

Fracture strength of endodontically treated teeth restored with different fiber post and core systems.

The aim of this study was to investigate the effects of different post and core systems, CAD/CAM crown placement on fracture strength of endodontically treated mandibular premolar teeth. One hundred forty single-rooted premolar teeth were randomly divided into a control group and six experimental groups as follows: control group (Group 1); FiberSite post luting with Clearfil DC Core Plus (Group 2); RelyX Fiber post luting and core build up with Clearfil DC Core Plus (Group 3); RelyX Fiber post luting with Clearfil DC Core Plus and core build up with Filtek Bulk Fill Posterior (Group 4); specimens that received CAD/CAM crowns after the same procedures performed in Groups 2, 3, and 4, respectively (Groups 5, 6, and 7). Fracture strength tests were performed, and the failure modes were recorded. Data were statistically analyzed using one-way ANOVA and post hoc Tukey tests. The highest fracture resistance was observed in the control group and among the experimental groups in Group 4. Groups 3 and 5 showed similar fracture resistance followed by Group 2. The lowest fracture resistances were seen in the samples of Groups 6 and 7. While the fracture strength of Group 2 increased after the crown placement (Group 5), the fracture strength of Group 3 and Group 4 decreased (P < 0.05). While the specimens in Groups 1, 2, 3, and 4 predominantly showed favorable failure, unfavorable failure was more frequent in Groups 5, 6, and 7.

Cyclic fatigue resistance of HyFlex EDM, Reciproc Blue, WaveOne Gold, and Twisted File Adaptive rotary files under different temperatures and ambient conditions.

Background. This study examined the effects of changes in temperature and environmental conditions on the cyclic fatigue resistance of Reciproc Blue, HyFlex EDM, WaveOne Gold, and Twisted File Adaptive. Methods. Forty-five Reciproc Blue (25/.08), 45 HyFlex EDM (25/.08), 45 WaveOne Gold (25/.07), and 45 Twisted File Adaptive (25/.08) files were tested for cyclic fatigue at room temperature (20°C) in air and water and at body temperature (35°C) in water. All the instruments were rotated in artificial canals made of stainless steel with an inner diameter of 1.5 mm, 60° angle of curvature and a radius of curvature of 5 mm until fracture occurred; the time to fracture was recorded in seconds, using a digital chronometer. Mann-Whitney U test was used for the statistical analysis of data, with SPSS 21.0. Results. Cyclic fatigue resistance was significantly higher in all the groups in water at an ambient temperature of 20°C compared with air and water at temperatures of 20°C and 35°C, respectively (P<0.05). The intragroup analysis revealed that HyFlex EDM had the highest cyclic fatigue resistance, followed by Reciproc Blue, WaveOne Gold, and Twisted File Adaptive in both air and water at 20°C (P<0.05). HyFlex EDM exhibited the highest cyclic fatigue resistance in water at 35°C, whereas there was no significant difference between the other groups (P>0.05). Conclusion. Within the limitations of the present study, an increase in the ambient temperature significantly decreased the cyclic fatigue resistance of the tested NiTi files.

The effects of QMix and EndoActivator on postoperative pain in mandibular molars with nonvital pulps: a randomized clinical trial.

AIM: The purpose of this study was to compare the effects of different irrigation solutions when used EndoActivator on postoperative pain. METHODOLOGY: A total of 104 subjects with nonvital pulps were selected and randomly assigned to four experimental groups; (G) 1 (n = 26) 2.5% NaOCl + conventional endodontic syringe, (G) 2 (n = 26) 2.5% NaOCl + EndoActivator, (G) 3 (n = 26) 2.5% NaOCl + QMix + conventional endodontic syringe, (G) 4 (n = 26) 2.5% NaOCl + QMix + EndoActivator. All the patients were prescribed ibuprofen 400 mg to be taken every 8 h in case of pain. The patients were asked to rate the severity of the postoperative pain on a visual analog scale (VAS) for 8th, 24th, 48th, and 72nd hours after the visit. The data were analyzed using Kruskal-Wallis, Mann-Whitney U, and Chi-Square tests. RESULTS: G4 resulted in lesser postoperative pain levels on 8th, 24th, 48th, and 72nd hours than the G2, G3, and G1 did. There was no significant difference between G4 and G2 and between G3 and G1 in terms of the postoperative pain levels at any time interval (P > 0.05). CONCLUSION: It was determined that the postoperative values of the groups, in which EA was used, were statistically significantly lower than in the other groups. The combined use of QMix and EA provided the most significant decrease in the postoperative pain values. CLINICAL RELEVANCE: Successful management of postoperative pain is an important issue for the clinician. The combined use of Qmix and EA can be recommended to the clinicians.

Comparison of postoperative pain intensity after using reciprocating and continuous rotary glide path systems: a randomized clinical trial.

OBJECTIVES: The aim of this study was to compare postoperative pain intensity after root canal treatment with One G (OG) vs. R-Pilot (RP) files used for glide path preparation. MATERIALS AND METHODS: Ninety-three single-canaled mandibular premolar teeth with asymptomatic non-vital pulp were randomly assigned into 3 groups (n = 31): OG, RP, or without glide path (WGP). After creating the glide path, the root canals were prepared using sequential Mtwo rotary files to size 30/0.05. One endodontic specialist carried out single-visit endodontic treatment. The patients were asked to rate the severity of postoperative pain on a visual analogue scale at 24, 48, and 72 hours after the visit. They were also asked to record their intake of prescribed analgesics taken. The data were analyzed using the χ2, Friedman, Kruskal-Wallis, and Mann-Whitney U tests. RESULTS: In all 3 groups, postoperative pain decreased significantly at each time interval (p < 0.05). At 24 hours, the OG group had less postoperative pain than the WGP group (p < 0.05). However, no significant difference was found between the RP group and the others. No statistically significant difference was found among the WGP, OG, and RP groups in postoperative pain intensity at 48 or 72 hours or in analgesic tablet intake at the 3 assessed time intervals. CONCLUSIONS: The OG group had less postoperative pain than the WGP group in the first 24 hours. The OG and RP systems were similar regarding postoperative pain intensity and analgesic intake.

Effect of Sodium Hypochlorite and EDTA on Surface Roughness of HyFlex CM and HyFlex EDM Files.

The aim of the present study was to compare the effect of exposure to sodium hypochlorite (NaOCl) and ethylenediaminetetraacetic acid (EDTA) on the surface topography and roughness of HyFlex controlled memory (CM) and HyFlex electrical discharge machining (EDM) using atomic force microscopy (AFM). Twenty HyFlex EDM (25/.08) and 20 HyFlex CM (25/.06) files were divided into five groups (n = 4). One group served as a negative control group. The files in the other groups were exposed to 5.25% NaOCl and 17% EDTA solutions at 37°C for 5 and 10 min, respectively, and examined using AFM after each exposure. The data were analyzed using one-way ANOVA test. The lowest values were observed in the control group of HyFlex EDM files (p < .05). The highest values were observed in the HyFlex EDM and HyFlex CM files immersed in EDTA for 10 min (p < .05). In conclusion, the tested irrigants had a significant negative effect on the surface porosity of NiTi files. The immersion of NiTi files in irrigants during cleaning and sterilization procedures results in corrosion and surface deformation of the files, and this can lead to unexpected file fracture during clinical use. Thus, the investigation of effect of ethylenediaminetetraacetic acid (EDTA) and sodium hypochlorite (NaOCl) on surface topography of HyFlex files is important.

Push-out bond strength of intra-orifice barrier materials: Bulk-fill composite versus calcium silicate cement.

Background. The aim of this study was to compare the push-out bond strengths of calcium silicate-based ProRoot MTA and Biodentine cements and SureFil SDR and EverX Posterior bulk-fill composite resins. Methods. Twenty-four single-rooted maxillary central incisors were sectioned below the cementoenamel junction, and the root canals were instrumented using rotary files. Thereafter, a parallel post drill was used to obtain a standardized root canal dimension. The roots were randomly assigned to one of the following groups with respect to the intra-orifice barrier used: ProRoot MTA; Biodentine; SureFil SDR; EverX Posterior. Five 1-mm-thick sections were obtained from the coronal aspect of each root. Push-out bond strength testing was performed and data were analyzed with Kruskal-Wallis and post hoc Dunn tests (P<0.05). Results. SureFil SDR and EverX Posterior bulk-fill composite resins' bond strengths were significantly higher than ProRoot MTA and Biodentine calcium silicate cements. However, no statistically significant differences were observed between bulk-fill composite resins values and calcium silicate cement values. Conclusion. Within the limitations of present study, calcium silicate-based ProRoot MTA cement's push-out bond strength was lower than those of Biodentine, SureFil SDR and EverX Posterior materials.

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

INTRODUCTION: The purpose of this article was to compare the cyclic fatigue resistance of Reciproc and Reciproc Blue files (VDW GmbH, Munich, Germany) that were used to prepare root canals of mandibular molar teeth with or without a glide path. METHODS: Sixty Reciproc R25 and 60 Reciproc Blue R25 files were used. The Reciproc and Reciproc Blue groups were divided into 3 subgroups (ie, as received condition, used without a glide path, and used with a glide path). All the instruments were rotated in a stainless steel artificial canal with an inner diameter of 1.5 mm, a 60° angle of curvature, and a radius of curvature of 5 mm until fracture occurred. The number of cycle to fracture was calculated, and the length of the fractured segments was measured. The Kruskal-Wallis test was performed to statistically analyze the data using SPSS 21.0 software (IBM Corp, Armonk, NY) at a 5% significance level. RESULTS: The cyclic fatigue resistance of as received condition Reciproc Blue files was found to be higher than as received condition Reciproc files (P < .05). Reciproc Blue files used for root canal preparation showed higher cyclic fatigue resistance than Reciproc files used for root canal preparation (P < .05). There was no statistically significant difference between Reciproc and Reciproc Blue files used with a glide path and without a glide path (P > .05). There was no statistically significant difference in the mean length of the fractured fragments of the instruments (P > .05). CONCLUSIONS: Within the limitations of this in vitro study, it was concluded that creating a glide path using ProGlider files had no effect on the cyclic fatigue resistance of RPC and RPC Blue files.

Apically Extruded Debris during Root Canal Instrumentation with Reciproc Blue, HyFlex EDM, and XP-endo Shaper Nickel-titanium Files.

INTRODUCTION: The purpose of this study was to investigate the amount of apically extruded debris by Reciproc Blue (REC Blue; VDW, Munich, Germany), HyFlex EDM (HEDM; Coltene/Whaledent, Altstätten, Switzerland), and XP-endo Shaper (XPS; FKG Dentaire SA, La Chaux-de-Fonds, Switzerland) files during root canal preparation at body temperature. METHODS: Sixty extracted single-rooted mandibular premolar human teeth were randomly assigned to 3 groups (n = 20). The canals were instrumented using 1 of the following instruments: REC Blue, HEDM, or XPS. Apically extruded debris during instrumentation was collected into preweighed Eppendorf tubes. All the procedures were performed at 35°C. The amount of extruded debris was calculated by subtracting the weight value of the tooth-free apparatus from the postpreparation weight value. The data were analyzed using the Kruskal-Wallis test at a 5% significance level. RESULTS: All the instruments tested caused extrusion of some debris from the apical foramen. XPS extruded significantly less debris from the apex than REC Blue (P < .05). The difference among the HEDM group and the other groups was not significant (P > .05). CONCLUSIONS: Within the limitations of this in vitro study, the amount of apically extruded debris registered for the different files tested was REC Blue > HEDM > XPS, with a statistical difference only between XPS and REC Blue.

The effect of root canal preparation on the surface roughness of WaveOne and WaveOne Gold files: atomic force microscopy study.

OBJECTIVES: To examine the surface topography of intact WaveOne (WO; Dentsply Sirona Endodontics) and WaveOne Gold (WOG; Dentsply Sirona Endodontics) nickel-titanium rotary files and to evaluate the presence of alterations to the surface topography after root canal preparations of severely curved root canals in molar teeth. MATERIALS AND METHODS: Forty-eight severely curved canals of extracted molar teeth were divided into 2 groups (n = 24/each group). In group 1, the canals were prepared using WO and in group 2, the canals were prepared using WOG files. After the preparation of 3 root canals, instruments were subjected to atomic force microscopy analysis. Average roughness and root mean square values were chosen to investigate the surface features of endodontic files. The data was analyzed using one-way analysis of variance and post hoc Tamhane's tests at 5% significant level. RESULTS: The surface roughness values of WO and WOG files significantly changed after use in root canals (p < 0.05). The used WOG files exhibited higher surface roughness change when compared with the used WO files (p < 0.05). CONCLUSIONS: Using WO and WOG Primary files in 3 root canals affected the surface topography of the files. After being used in root canals, the WOG files showed a higher level of surface porosity value than the WO files.

Cyclic fatigue resistances of Hyflex EDM, WaveOne gold, Reciproc blue and 2shape NiTi rotary files in different artificial canals.

The aim of the present study was to compare the cyclic fatigue resistances of HyFlex EDM (HEDM), WaveOne Gold (WOG), Reciproc Blue (RB), and 2Shape (TS) NiTi systems having different metallurgic properties. HEDM, WOG, RB, and TS instruments were rotated in artificial canals which were made of stainless steel with an inner diameter of 1.5 mm, 45°, and 90° angles of curvatures and a radius of curvature of 5 mm until fracture occurred, and the time to fracture (TTF) was recorded in seconds. Also, number of cycles to fracture was calculated (NCF). Data were statistically analyzed using Kruskal-Wallis and t test. The statistical significance level was set at P < 0.05. When comparing the TTF of all the instruments tested in the artificial canal with 45° curvature, RB had statistically the highest cyclic fatigue resistance followed by HEDM and TS (P < 0.05), while the WOG showed the lowest cyclic fatigue resistance (P < 0.05). In artificial canal with 90° curvature, RB showed a significantly higher cyclic fatigue resistance than the other tested files (P < 0.05), while there was no significant difference among the TS, WOG and HEDM groups (P > 0.05). When the NCF values were taken into consideration, HEDM reported a significantly higher cyclic fatigue resistance than TS in both canal curvatures analyzed (P < 0.05). Within the limitations of the present study, RB NiTi files showed statistically higher cyclic fatigue resistance in artificial canals with 45° and 90° than the other NiTi files tested.

Effect of Dynamic Immersion in Sodium Hypochlorite and EDTA Solutions on Cyclic Fatigue Resistance of WaveOne and WaveOne Gold Reciprocating Nickel-titanium Files.

INTRODUCTION: The purpose of this study was to evaluate the effect of sodium hypochlorite (NaOCl) and EDTA solutions on the cyclic fatigue resistance of WaveOne (WO) and WaveOne Gold (WOG) nickel-titanium reciprocating files. METHODS: A hundred WO (25/.08), and 100 WOG (25/.07) were randomly divided into 5 groups: group 1, no immersion; group 2, immersion in 5.25% NaOCl at 37°C ± 1°C for 5 minutes; group 3, immersion in 5.25% NaOCl at 37°C ± 1°C for 10 minutes; group 4, immersion in 17% EDTA at 37°C ± 1°C for 5 minutes; and group 5, immersion in 17 % EDTA at 37°C ± 1°C for 10 minutes. Then, the instruments were reciprocated in an artificial canal until fracture occurred, and the time to fracture was recorded. The data were statistically analyzed using 1-way analysis of variance and the Student t test via SPSS 21.0 software (IBM Corp, Armonk, NY) with the significance level set at P < .05. RESULTS: The cyclic fatigue resistance of the WOG was statistically higher than the WO in all the conditions tested (P < .05). There was no statistically significant difference among the different conditions tested in terms of cyclic fatigue resistance for both WO and WOG files (P > .05). Among the groups, there was no significant difference in the fracture lengths (P > .05). CONCLUSIONS: Within the limitations of the present study, it was determined that NaOCl and EDTA solutions did not have any effect on the cyclic fatigue resistance of WO and WOG files.

Comparison of Alterations in the Surface Topographies of HyFlex CM and HyFlex EDM Nickel-titanium Files after Root Canal Preparation: A Three-dimensional Optical Profilometry Study.

AIMS: The aims of the present study were to examine the surface topographies of intact HyFlex CM and HyFlex EDM nickel-titanium files and to compare alterations in the surface topographies of these files after root canal preparation of severely curved canals of molar teeth. METHODS: Eight HyFlex CM (25/.08) and 8 HyFlex EDM (25/.08) files were included in the present study. In total, 64 severely curved canals of molar teeth, with curvature angles ranging between 50° and 70°, were prepared with HyFlex CM and EDM (n = 32 in each group). Quantitative and qualitative analyses of the files' surface deformation were performed by using three-dimensional optical profilometry before and after root canal preparation. The data were analyzed with the Student t test at the 5% significant level by using SPSS 21.0 software. RESULTS: In the HyFlex EDM group, the qualitative evaluation revealed the presence of cracks and microcavities after use of the file for root canal preparation, whereas only minor surface deformation was observed in the HyFlex CM group. The average roughness, root mean square roughness, and peak to valley height values of the HyFlex EDM group were significantly higher than those of the HyFlex CM group before and after root canal preparation (P < .05). The surface roughness values were statistically significantly increased in the HyFlex CM group after root canal preparation (P < .05). In contrast, the increase in the HyFlex EDM group was not statistically significant (P > .5). CONCLUSIONS: Within the limitations of the present study, the HyFlex CM files showed significantly higher surface alterations compared with the HyFlex EDM files after the preparation of severely curved root canals.

Cyclic fatigue resistance of 2Shape, Twisted File and EndoSequence Xpress nickel-titanium rotary files at intracanal temperature.

Background. The aim of this study was to compare the cyclic fatigue resistance of 2Shape, Twisted File (TF) and EndoSequence Xpress (ESX) nickel-titanium rotary files at intracanal temperature (35°C). Methods. Twenty 2Shape TS1 (25/.04), 20 TF (25/.04) and 20 ESX (25/.04) files were tested for cyclic fatigue at intracanal temperature (35°C). All the instruments were rotated in artificial canals which were made of stainless steel with an inner diameter of 1.5 mm, 60° angle of curvature and a radius curvature of 5 mm until fracture occurred; the time to fracture was recorded in seconds using a digital chronometer and the number of cycles to fracture (NCF) for each file was calculated. Kruskal-Wallis test with Bonferroni correction was performed to statistically analyze data using SPSS 21.0. Statistical significance was set at P<0.05. Results. NCF values revealed that the 2Shape had significantly the highest cyclic fatigue resistance, followed by TF and ESX at intracanal temperature (P<0.05). The difference was significant between the TF and ESX groups (P<0.05). There was no significant difference among the 2Shape, TF and ESX files with respect to the lengths of the fractured file fragments (P>0.05). Conclusion. Within the limitations of present study, it was concluded that the cyclic fatigue resistance of 2Shape files at the intracanal temperature is higher than that of TF and ESX files.

In vitro comparison of the cyclic fatigue resistance of HyFlex EDM, One G, and ProGlider nickel titanium glide path instruments in single and double curvature canals.

OBJECTIVES: It was aimed to compare the cyclic fatigue resistances of ProGlider (PG), One G (OG), and HyFlex EDM (HEDM) nickel titanium glide path files in single- and double-curved artificial canals. MATERIALS AND METHODS: 40 PG (16/0.02), 40 OG (14/0.03), and 40 HEDM (10/0.05) single-file glide path files were used in the present study. Sixty files were subjected to cyclic fatigue test by using double-curved canals and 60 files by using single-curved canal (n = 20). The number of cycles to fracture (NCF) was calculated and the length of the fractured fragment (FL) was determined by a digital micro-caliper. Twelve pieces of fractured files were examined with scanning electron microscope to determine fracture types of the files (n = 2). The NCF and the FL data were analyzed using one-way analysis of variance and post hoc Tukey test using SPSS 21 software (p < 0.05). RESULTS: In all of the groups, NCF values were significantly lower in double-curved canals when compared to single-curved canals (p < 0.05). For both of single- and double-curved canals, NCF values of HEDM group in apical and coronal curvatures were found to be significantly higher than NCF values of PG and OG groups (p < 0.05). In both of single- and double-curved canals, NCF value of PG group was found significantly higher than OG group (p < 0.05). CONCLUSIONS: Within the limitations of this study, HEDM glide path files were found to have the highest cyclic fatigue resistance in both of single- and double-curved canals.

The effects of autoclave sterilization on the cyclic fatigue resistance of ProTaper Universal, ProTaper Next, and ProTaper Gold nickel-titanium instruments.

OBJECTIVES: It was aimed to compare the cyclic fatigue resistances of ProTaper Universal (PTU), ProTaper Next (PTN), and ProTaper Gold (PTG) and the effects of sterilization by autoclave on the cyclic fatigue life of nickel-titanium (NiTi) instruments. MATERIALS AND METHODS: Eighty PTU, 80 PTN, and 80 PTG were included to the present study. Files were tested in a simulated canal. Each brand of the NiTi files were divided into 4 subgroups: group 1, as received condition; group 2, pre-sterilized instruments exposed to 10 times sterilization by autoclave; group 3, instruments tested were sterilized after being exposed to 25%, 50%, and 75% of the mean cycles to failure, then cycled fatigue test was performed; group 4, instruments exposed to the same experiment with group 3 without sterilization. The number of cycles to failure (NCF) was calculated. The data was statistically analyzed by using one-way analysis of variance and post hoc Tukey tests. RESULTS: PTG showed significantly higher NCF than PTU and PTN in group 1 (p < 0.05). Sterilization significantly increased the NCF of PTN and PTG (p < 0.05) in group 2. PTN in group 3 had significantly higher cyclic fatigue resistance than PTN group 4 (p < 0.05). Also, significantly higher NCF was observed for PTG in group 2 than in groups 3 and 4 (p < 0.05). CONCLUSIONS: PTG instrument made of new gold alloy was more resistant to fatigue failure than PTN and PTU. Autoclaving increased the cyclic fatigue resistances of PTN and PTG.