Effect of Active Oxygen Fluid (Blue®m) as a Root Canal Irrigant Against Enterococcus Faecalis.

PURPOSE: To evaluate the antimicrobial effect of a new active oxygen fluid (Blue®m) as a root canal irrigant against Enterococcus faecalis compared to sodium hypochlorite (NaOCl). MATERIAL AND METHODS: Forty-five extracted single-canaled human teeth were selected, received root canal preparation, autoclaved, and contaminated with Enterococcus faecalis. The specimens were randomly allocated into three groups: Group (A) served as the negative control, receiving irrigation with saline (n = 15); Group (B) was irrigated with 5.25% NaOCl (n = 15); and Group (C) was irrigated with 10 mL of Blue®m (n = 15). Microbial sampling from the root canals was performed before and after irrigation. The difference between the pre-irrigation and post-irrigation colony-forming units (CFU/mL) was calculated. The data was analysed using a one-way ANOVA followed by post-hoc Tukey tests. The significance level was set at 5%. RESULTS: Blue®m statistically significantly reduced the bacterial load compared to saline (p = 0.009), but NaOCl was most effective, outperforming both (p 0.0001). CONCLUSION: Irrigation with Blue®m demonstrated antibacterial efficacy against Enterococcus faecalis, but it was not as effective as NaOCl.

Optical microscopy evaluation of root canal filling removal by beginner operators in posterior teeth.

This study analyzed the effectiveness of root canal filling removal in lower molars performed by beginner operators using optical microscopy. A total of 55 mandibular first and second molars with mesial roots exhibiting an average curvature of 10-20° were selected based on preoperative radiographs. Instrumentation was done with ProTaper Gold (Dentsply Sirona) up to F2 (25/.08), using 2ml of 2.5% NaOCl irrigation solution after each file. Root canal obturation was performed using gutta-percha points with cold lateral condensation and Sealapex (Kerr Dental). Coronal fillings were made with composite resin and stored in distilled water for two years. Removal of the root canal fillings was performed with AF Retreatment Rotary (AFRR) and AF Blue R3 (AFBR3) (Fanta Dental Materials) under reciprocating motion with 2.5% NaOCl irrigation. Cross-sections of the coronal, middle, and apical thirds were analyzed at 40x magnification using a STEINDORFF POL microscope with a digital camera. Image analysis was conducted using Image J software, version 1.54, to determine the efficiency of root canal filling removal by percentage. Statistical analysis via one-way ANOVA revealed significant differences between distal and mesial roots (P < 0.05). Specifically, for mesial roots, the removal efficiency was 70.65% in the coronal third, 54.66% in the middle third, and 21.32% in the apical third. Significant difficulties were noted due to fractured files, calcifications, and debris accumulation in the isthmuses. The study concluded that the protocol using Fanta files demonstrated significant differences in removal efficiency correlated with root curvature, compounded by the inexperience of beginner operators. The findings highlight the challenges faced by novice practitioners in achieving effective root canal filling removal.

CBCT assessment of mandibular molar furcation following root canal retreatment using engine-driven instruments.

This study employed e-Vol DXS cone beam computed tomography (CBCT) software to assess dentin remnants in the furcation area of mesial canals in mandibular molars during root canal retreatment (RCR). Four groups (Reciproc®, ProTaper Next®, Race Evo®, Protaper Gold®) were subjected to RCR, and CBCT images were captured before (T1) and after (T2) treatment. Measurements of remaining dentin thickness at 1 mm and 3 mm below the furcation were scrutinized. Results revealed no significant differences in mean thicknesses of mesiobuccal (MB) and mesiolingual (ML) canals at 1 mm and 3 mm from the furcation pre-treatment (T1). Post-treatment (T2) showed analogous findings, with no significant differences in mean thicknesses. However, disparities were found between MB and ML canals at both distances, both before and after retreatment. In essence, the evaluated instruments exhibited safety in RCR, implying that they are appropriate for use in critical areas of mandibular molars without inducing excessive wear. This study underscores the reliability of these instruments in navigating danger zones during RCR, and contributes valuable insights for dental practitioners who handle complex root canal scenarios in mandibular molars.

Effectiveness of supplementary antimicrobial procedures in disinfecting lateral canals as evaluated by a novel ex vivo analytical approach.

This ex vivo study devised an analytical ex vivo method for infection/disinfection of simulated lateral canals located in the middle and apical segments of the root. The antibacterial effects of supplementary approaches were tested in this model. Extracted mandibular premolars had their main root canals enlarged and then two lateral canals (100 µm in diameter) were created in the root, one in the apical and the other in the middle portion. Micro-computed tomography was used for specimen selection and to confirm the quality of the simulated ramifications. The specimens were contaminated with a mixed bacterial culture from subgingival bacterial biofilm added to pure Enterococcus faecalis strain ATCC 29212 grown overnight, using special strategies to facilitate culture medium penetration within the lateral canals. The following procedures were tested for disinfection: NaOCl/passive ultrasonic irrigation (PUI), NaOCl/XP-endo Finisher, ozonated water/continuous ultrasonic irrigation (CUI), and NaOCl/conventional irrigation with 30-G needles (control). Bacteriological samples were taken from the main canal before (S1) and after (S2) each supplementary protocol, and also from each lateral canal after treatment (S3). DNA extracted from the samples was subjected to quantitative real-time polymerase chain reaction. All S1 main canal samples were positive for bacterial presence. Bacterial counts in the main root canal substantially decreased by 99.2% after PUI, 99.1% after ozone/CUI, 99% after XP-endo Finisher, and 96% in the control group (P < 0.01 for all groups). There were no significant differences between groups (P > 0.05). The same was observed when comparing the effects of the supplementary approaches in the apical and middle lateral canals (P > 0.05). Only a few lateral canals showed no detectable bacteria. The method proposed here proved effective for ex vivo infection/disinfection studies. All supplementary approaches induced a substantial bacterial reduction in the main canal, with no significant differences between them. However, in terms of lateral canal disinfection, none of the tested approaches showed significant effects when compared to the control group.

Effectiveness of EndoActivator, PATS Vario system, and XP-endo Finisher files on smear layer removal under scanning electron microscope: A comparative study.

CONTEXT: The smear layer may harbor many bacteria; hence, alternative methods are used to disrupt and remove biofilm. AIM: The aim of the study was to compare the effectiveness of EndoActivator, PATS Vario System, and XP-endo Finisher files on smear layer removal using a scanning electron microscope. SUBJECTS AND METHODS: Sixty single-rooted extracted premolars with Vertucci Type 1 configuration were decoronated and divided into four groups. The groups were instrumented with the rotary ProTaper file system. All specimens were flushed with 1 ml of 3% sodium hypochlorite. Group 1 was irrigated with a conventional needle and syringe. In Group 2, the irrigant was activated with an EndoActivator. In Group 3, the irrigant was activated with PATS Vario system, and in Group 4, XP-endo Finisher files were used after biomechanical preparation to remove debris and smear layer. All specimens were finally rinsed with 3 ml of 3% sodium hypochlorite. The teeth underwent longitudinal splitting and grooving in the coronal, middle, and apical thirds, and then, the samples were taken for scanning electron microscopy to evaluate the amount of smear layer removal in each third. RESULTS: The middle and coronal thirds Showed that almost similar efficacy to remove smear layer in both Group II and Group III. At the apical third, Group III showed comparatively better results than Group I, II, and IV, respectively. CONCLUSION: Equal amount of smear layer was seen with EndoActivator and PATS Vario system when used as sonic irrigation devices.

Evaluation of apically extruded debris during root canal filling material removal in teeth with external apical root resorption: a comparison of different obturation techniques.

BACKGROUND: Root canal retreatment is necessary when initial treatment fails. Nickel-titanium systems help remove filling materials; however, some methods can cause canal content extrusion, resulting in inflammation and delayed healing. This study aimed to examine the impact of different preparation techniques and endodontic file systems on apical debris volume to limit material dispersion to periradicular tissues. METHODS: Ninety extracted maxillary incisors were evaluated. Simulated apical root resorption was created by removing the apical 2 mm of the root. The teeth were divided into two groups: one filled with a single cone and the other with cold lateral compaction (CLC). Each group was further divided into three subgroups (n = 15 each): Subgroup 1 used Reciproc R25 for removal and R50 for final preparation; Subgroup 2 used ProTaper Universal Retreatment (PTUR) files D1, D2, and D3 for removal and ProTaper Next X5 for finalization; and Subgroup 3 used VDW.Rotate Retreatment (VDW.RotateR) for removal and VDW.Rotate 50.04 for completion. Debris from retreatment was collected in pre-weighed tubes to determine the amount. The apical extrusion data underwent a two-way analysis of variance. RESULTS: The Reciproc group had a mean extruded debris weight of 0.54 ± 0.24 mg, higher than the PTUR (0.28 ± 0.15 mg) and VDW.RotateR (0.39 ± 0.29 mg) groups (p < 0.05). The single-cone technique (SCT) resulted in a mean debris weight of 0.34 ± 0.23 mg, lower than the CLC technique, which had a mean of 0.46 ± 0.27 mg (p < 0.05). SCT had a shorter retreatment duration (111.12 ± 33.46 s) compared to CLC (176.26 ± 52.26 s) (p < 0.05). CONCLUSION: The Reciproc file system and the CLC obturation technique resulted in greater apical debris extrusion than the other methods. SCT was quicker than CLC. The Reciproc groups are more susceptible to apex extrusion during retreatment.

Cyclic fatigue resistance of two pediatric rotary files manufactured with different heat treatments: an in-vitro study.

Nickel-titanium (NiTi) instruments offer many advantages during endodontic instrumentation; however, the fracture risk within the canal remains a concern. Manufacturers continuously develop and introduce instruments to the market with supposedly enhanced cyclic fatigue resistance and increased flexibility, achieved through different proprietary manufacturing processes, the details of which have not been made public. In recent years, two rotary systems specially designed for deciduous teeth have been commercially available, but information about their performance is lacking. This investigation aimed to identify which manufacturing process provides better cyclic fatigue resistance: the AF-H Wire technology used in the AF baby rotary files (AF-f) or the CM-Wire technology used in the i3 Gold deciduous teeth rotary files (i3G-f). Forty rotary International Organization for Standardization (ISO) 25/04 files were tested in artificial canals with a standard geometry of 60° angle and 2.5 mm radius until fracture. The number of cycles to fracture was calculated, and the length of the fragments was measured. A scanning electron microscope (SEM) was used to examine the fracture surfaces and fragments. Energy dispersive spectroscopy (EDS) was used to determine the percentage weight of NiTi in each file. The statistical analysis (Mann-Whitney test) showed that the cyclic fatigue resistance of the AF-f was significantly higher (p < 0.0001) than that of the i3G-f. Additionally, there was a significant difference (p = 0.0419) in the length of the fractured fragments. All instruments showed one or more types of manufacturing defects and presented similar NiTi percentages by weight. The manufacturing process is critical to cyclic fatigue resistance, and there seems to be responsible for the difference in cyclic fatigue resistance between these similar instruments.

Apically extruded debris evaluation with the use of ProTaper Ultimate and TruNatomy files systems with and without glider preparation in primary tooth.

Information regarding the influence of resorption and glide paths on debris extrusion in primary teeth is lacking. Therefore, we evaluated debris extrusion with and without resorption and with and without the use of a path file in primary molar teeth prepared with ProTaper Ultimate (PTU) Prime and TruNatomy (TRN) Prime rotary file systems. Forty resorbed and forty non-resorbed primary molar teeth were collected. Both groups were divided into four subgroups (n = 10). The Eppendorf tubes were weighed pre-debris. The distal canals of the teeth were prepared with PTU Prime and TRN Prime file systems, with and without the use of path files. The debris-filled tubes were weighed, and the weight of only the extruded debris was calculated by subtraction. The data were analyzed using a three-way analysis of variance (ANOVA) test. The presence of tooth resorption significantly increased debris extrusion, and the use of a path file significantly decreased debris extrusion (p < 0.001). The binary and ternary interactions of the three evaluated parameters among the groups showed no significant differences in terms of the amount of debris extruded (p > 0.05). While debris extrusion was observed in all groups, the use of a glide path file in primary teeth before the preparation process resulted in less debris extrusion.

Comparative evaluation of clinical efficacy and volumetric changes in pulpectomized primary molars using hand K-file, ProTaper rotary file, and Kedo-SG blue file: an in-vitro cone beam computed tomography analysis.

The accomplishment of a successful pulpectomy depends on multiple factors that involve targeted removal of the causative irritants and soft and hard tissue debris by mechanical and chemical means. Compare and evaluate the efficacy of canal preparation and volumetric filling using conventional files and two rotary file systems using cone beam computed tomography (CBCT). Thirty freshly extracted human primary second molars were randomly divided into three groups of 10 teeth each. After access opening and working length determination, pre-operative volume analysis was done using CBCT. The canals were then instrumented by either hand K-files, ProTaper rotary files or Kedo-SG Blue rotary files. Post-operative volume analysis was performed using CBCT. All the canals were obturated using Metapex and scanned again using CBCT. Mean values of the pre- and post-operative canal volumes were analyzed using one-way Analysis of Variance (ANOVA). Inter- and intra-group volumetric changes were analyzed statistically using a post hoc test. The mean difference in volume after canal preparation and obturation was the highest in the Kedo-SG Blue group, followed by the ProTaper group and the least in the hand K group (p = 0.001). Inter-group comparison showed statistically significant differences between the hand K group and ProTaper group (p = 0.001), the ProTaper group and Kedo-SG Blue group (p = 0.001), and the hand-K group and Kedo-SG Blue group (p = 0.02). The volume of preparation and obturation was the highest using Kedo-SG Blue, followed by the ProTaper file systems.

Impact of final rinse with saline or alcohol solution on root canal sealability.

Endodontic irrigation protocols are not only used to clean and disinfect the root canal system, but also to condition the canal wall dentine for subsequent root filling. In this study we tested whether a final irrigation step with saline solution or 80% ethanol improved root canal sealabilty by two popular sealers, an epoxy resin (AH Plus) and a hydraulic calcium silicate cement-based product (BioRoot RCS). Root canals in extracted single-rooted human teeth were instrumented and filled with a matched gutta-percha cone and sealer. During instrumentation and prior to root filling, sealer-specific irrigation protocols were applied. These involved a combined sodium hypochlorite/1-hydroxyethylidene-1,1-diphosphonic acid application, which was followed by irrigation with ethylenediaminetetraacetic acid (EDTA) for AH Plus. Protocols were followed by a 5-ml ultimate rinse with saline solution or 80% ethanol. No such final rinse was the control (N = 9). Canals were then dried with matched paper points. One week after root filling and storage of the teeth at 37°C in a humid environment, Rhodamine B was used to trace leakage. Two-way ANOVA revealed that the type of sealer had a significant (P < 0.05) impact on apical dye penetration while the final rinse did not (P > 0.05). AH Plus provided the slightly better seal (P < 0.05). Leakage occurred between the sealer and the dentin with AH Plus, and between the sealer-to-dentin as well as the sealer-to-gutta-percha interface with BioRoot RCS. In summary and under current conditions, there was no benefit from applying saline or ethanol as an ultimate rinsing solution prior to drying the canal with matched paper points.

Impact of different activation procedures on sodium hypochlorite penetration into dentinal tubules after endodontic retreatment via confocal laser scanning microscopy.

BACKGROUND: Infected dentinal tubules are a possible source of bacteria that are responsible for the failure of root canal treatment. Therefore, disinfection of dentinal tubules by increasing the penetration of the irrigation solution is important for success in retreatment cases. This study utilized confocal laser scanning microscopy (CLSM) to assess and compare the impact of XPR, ultrasonic irrigation (UI) and sonic activation (SA) on NaOCl penetration into dentinal tubules following endodontic retreatment. METHODS: A total of forty mandibular premolars were enrolled in this investigation. Following root canal preparation up to ProTaper X3 file (30/0.07), root canals were obturated with gutta-percha and bioceramic root canal sealer with single cone technique. The root canal filling materials were removed using ProTaper nickel-titanium rotary retreatment files until the working length was reached. The retreatment procedure was finalized using the ProTaper Next X4 (40/0.06). The teeth were divided into four groups based on the irrigation activation technique: control (conventional needle irrigation), SA, UI and XPR. During the final irrigation procedure, Rhodamine B dye was introduced to 5% NaOCl for visualization via CLSM. Subsequent to image acquisition, the maximum penetration, penetration percentage, and penetration area were calculated. Data were statistically analyzed using the Kruskal-Wallis, Friedman, and Bonferroni Dunn multiple comparison tests through R software (p < 0.05). RESULTS: In the middle third, UI yielded a significantly higher penetration percentage than the control group (p < 0.05). The UI and XPR groups showed increased penetration percentages in the coronal and middle thirds compared with the apical third (P < 0.05). Maximum penetration was notably reduced in the apical third than in comparison with the coronal and middle thirds in all groups (p < 0.05). In the control, SA and XP groups, the penetration area was ranked in descending order as coronal, middle and apical (p < 0.05). Conversely, in the ultrasonic group, the penetration area was significantly lower in the apical third than in the middle and coronal thirds (p < 0.05). CONCLUSIONS: UI enhanced the penetration percentage in the middle third of the root compared with that in the control group. XPR and SA showed no significant effect on NaOCl penetration following retreatment.

Effect of glide path preparation on the apical debris extrusion for three single-file systems.

BACKGROUND: The dentinal debris produced during root canal preparation can be extruded through the apical foramen, which may cause undesired consequences, such as the postoperative inflammation of periapical tissues. OBJECTIVES: The aim of the present in vitro study was to evaluate the effect of glide path preparation on apical debris extrusion for the Reciproc®, WaveOne Gold® and One Curve file systems. MATERIAL AND METHODS: A total of 72 mandibular incisors were divided into 6 groups according to the nickel-titanium (NiTi) system used and glide path preparation: group Rp - Reciproc; group Rp-O - Reciproc after glide path preparation; group WG - WaveOne Gold; group WG-O - WaveOne Gold after glide path preparation; group OC - One Curve; and group OC-O - One Curve after glide path preparation. The preand post-instrumentation weight of Eppendorf tubes was measured. The pre-weight was subtracted from the post-weight to calculate the amount of apically extruded debris. The data was analyzed using the one-way analysis of variance (ANOVA) with the statistical program PASW Statistics for Windows, v.18.0. RESULTS: No statistically significant differences were found between the single-NiTi file systems with different kinematics in terms of apical debris extrusion, with or without glide path preparation (p > 0.05). CONCLUSIONS: The amount of apically extruded debris was not affected by the kinematics of different single-NiTi file systems. Moreover, creating a glide path had no effect on the apically extruded debris in straight root canals.

The effect of final irrigation with different solutions on smear layer removal and dentin erosion: A scanning electron microscope study.

AIM: This study aimed to compare the effectiveness of initial irrigation with sodium hypochlorite (NaOCl) and final irrigation with QMix, 40% citric acid, and 17% ethylenediaminetetraacetic acid (EDTA) on smear layer removal and dentin erosion. METHODOLOGY: Forty extracted human mandibular premolar teeth were randomly divided into four groups (n = 10) according to the type of final irrigants used: 17% EDTA, QMix, citric acid, and control (normal saline). Canals were mechanically prepared using ProTaper Next instruments to an apical size of X3. Subsequently, the roots were sectioned in a buccolingual direction. Scanning electron microscopy (SEM) was used to assess the presence of the smear layer and the amount of dentin erosion in the coronal, middle, and apical thirds of the root canals. RESULTS: In regards to smear layer removal, there was a significant difference between the control group and the other tested groups. Moreover, it was significantly higher in the coronal and middle thirds than in the apical third. However, there were no significant differences between the groups of EDTA, QMix, and citric acid. Concerning dentin erosion, citric acid produced significantly more dentin erosion than the other tested groups. CONCLUSION: Final irrigation with solutions had a higher ability to remove the smear layer in the coronal and middle thirds compared to the apical third. Of all the solutions tested, 40% citric acid had the most pronounced impact on dentin erosion, followed by 17% EDTA and QMix.

Clinicians' perspectives, inducements, preferences, and clinical experiences regarding the use of electronic apex locator and apex locator integrated engine-driven instrumentation: a cross-sectional study.

BACKGROUND: This study aimed to investigate the perspectives, preferences, and clinical experiences regarding using electronic apex locator and apex locator integrated instrumentation of dentists and endodontists. METHODS: A web-based questionnaire consisting of 3 parts and 23 closed-ended questions to achieve the objective of the study was carried out in ethical conditions between August and October 2023. The first part of survey included demographic information, while the second part was about evaluating electronic apex locator usage. In the last part, only participants' use of apex locator-integrated instrumentation was evaluated. Data were analyzed at a significance level of p < 0.05. RESULTS: A total of 297 clinicians, including 59 endodontists and 34 endodontic residents/Ph.D. students participated in the questionnaire. Endodontists and endodontic residents/Ph.D. students perform statistically significantly more root canal treatments per week on average (p = 0.001). For the working length determination method (multiple option question), 78.5% of participants use an electronic apex locator and 39.7% apex locator-integrated engines. However, the preference rate for electronic apex determination technique was generally 95.6%, with the full rate confirmation of endodontists and endodontic residents/Ph.D. students (100%). A total of 21 endodontists out of 59 prefer apex locator integrated engine-driven instrumentation. Although many of these specialized clinicians use this technique, they stated that they measure electronic working length passively for confirmation of the working length before (90.5%) and after the preparation (66.7%). CONCLUSIONS: Dentists, as well as endodontists, are skeptical about apex locator-integrated engine-driven instrumentation. Using this technique as a supporter rather than a primary way for preparation within safe limits may give safer results in terms of treatment outcomes.

Evaluation of the efficacy of different irrigation activation techniques in removing of calcium hydroxide on teeth with the simulated internal root resorption cavity: a confocal laser scanning microscope analysis.

The aim of this study is to evaluate the effect of different irrigation activation methods on root canal sealer penetration in teeth with simulated internal root resorption (IRR) and calcium hydroxide (CH) applied using a confocal laser scanning microscope (CLSM). 60 incisors with a single root and a single canal were included in the study. IRR cavities were created in the middle third of the root canal, and CH was placed. The samples were randomly divided into 4 groups (n = 15) according to the irrigation activation method to be tested: standard needle irrigation (SNI), sonic activation (EDDY), photon-induced photoacoustic flow (PIPS), and shock wave enhanced emission photoacoustic flow (SWEEPS). After irrigation activation applications, the root canals were obturated. Sections of 1.0 ± 0.1 mm were taken from the apical, middle, and coronal regions of each sample. The penetration area (µm2) and maximum penetration depth (µm) of the root canal sealer were examined by CLSM and analyzed using ImageJ software. Statistical analysis was performed with a one-way ANOVA and post-hoc Tukey test at the P < 0.05 significance level. Among all irrigation activation methods tested, both the penetration area and maximum penetration depth of the root canal sealer were greater in the coronal region than in the apical region (p < 0.05). In the IRR region, there was no difference in terms of maximum penetration depth between PIPS and SWEEPS (p > 0.05), it was highest in SWEEPS (p < 0.05). PIPS and SWEEPS were better than other irrigation activation methods in the penetration of root canal sealer in the resorption areas of teeth with IRR.

Comparative evaluation of the accuracy of electronic apex locators and cone-beam computed tomography in detection of root canal perforation and working length during endodontic retreatment.

BACKGROUND: To evaluate the accuracy of the electronic apex locators (EALs), and Cone-Beam Computed Tomography (CBCT) scanning, both in working length (WL) determination and in the detection of root canal perforations in retreatment cases. METHODS: Sixty human mandibular premolars were selected. After crown removal partially and canal access, root canals were instrumented and irrigated. The obturation process utilized gutta-percha and sealer with warm vertical compaction. Two groups were distinguished: one without perforation (Group 1) and the other with an apical third perforation (Group 2). Retreatment included filling removal, apical preparation, and irrigation. Actual working lengths (AWL) were determined using a stereomicroscope. CBCT images were used to measure CBCT working length (CWL), with adjustments for optimal views. Propex II and Dentaport ZX were used to measure electronic working length (EWL). Differences between EWL and AWL, as well as CWL, were analyzed to gauge accuracy. Data underwent Two-way ANOVA analysis. Measurements within ± 0.5 and ± 1 mm tolerance ranges were deemed successful for each device, followed by applying the Pearson Chi-square test. RESULTS: The study reveals no significant inter-group variations in device performance (p > .05). Dentaport ZX missed detecting perforation in two Group 2 (apical perforation) cases. For ± 1 mm tolerance, Propex II displayed the highest success in Group 2 (apical perforation). CONCLUSION: This study demonstrates the comparable performance of Propex II, Dentaport ZX, and CBCT in endodontic retreatment, providing insights into diagnostic reliability.

Effect of repetitive up-and-down movements on torque/force generation, surface defects and shaping ability of nickel-titanium rotary instruments: an ex vivo study.

BACKGROUND: The screw-in effect is a tendency of a nickel-titanium (NiTi) rotary endodontic file to be pulled into the canal, which can result in a sudden increase in stress leading to instrument fracture, and over-instrumentation beyond the apex. To reduce screw-in force, repeated up-and-down movements are recommended to distribute flexural stress during instrumentation, especially in curved and constricted canals. However, there is no consensus on the optimal number of repetitions. Therefore, this study aimed to examine how repeated up-and-down movements at the working length affect torque/force generation, surface defects, and canal shaping ability of JIZAI and TruNatomy instruments. METHODS: An original automated root canal instrumentation device was used to prepare canals and to record torque/force changes. The mesial roots of human mandibular molars with approximately 30˚ of canal curvature were selected through geometric matching using micro-computed tomography. The samples were divided into three groups according to the number of up-and-down movements at the working length (1, 3, and 6 times; n = 24 each) and subdivided according to the instruments: JIZAI (#13/0.04 taper, #25/0.04 taper, and #35/0.04 taper) or TruNatomy (#17/0.02 taper, #26/0.04 taper, and #36/0.03 tape) (n = 12 each). The design, surface defects, phase transformation temperatures, nickel-titanium ratios, torque, force, shaping ability, and surface deformation were evaluated. Data were analyzed with the Kruskal-Wallis and Dunn's tests (α = 0.05). RESULTS: The instruments had different designs and phase transformation temperatures. The 3 and 6 up-and-down movements resulted in a smaller upward force compared to 1 movement (p < 0.05). TruNatomy generated significantly less maximum torque, force, and surface wear than JIZAI (p < 0.05). However, TruNatomy exhibited a larger canal deviation (p < 0.05). No statistical differences in shaping ability were detected between different up-and-down movements. CONCLUSIONS: Under laboratory conditions with JIZAI and TruNatomy, a single up-and-down movement at the working length increased the screw-in force of subsequent instruments in severely curved canals in the single-length instrumentation technique. A single up-and-down movement generated more surface defects on the file when using JIZAI. TruNatomy resulted in less stress generation during instrumentation, while JIZAI better maintained the curvature of root canals.

Comparison of cyclic fatigue resistance of four pediatric rotary file systems at body temperature: an in vitro study.

BACKGROUND: The aim of this study was to compare the cyclic fatigue resistance (CFR) of the newly developed pediatric nickel-titanium (NiTi) rotary file systems for root canal preparation of primary teeth. METHODS: Eighty pediatric NiTi rotary file systems files were used in this study, including 20 EasyInSmile X-Baby (25/0.04), 20 Scope miniScope (25/0.04), 20 EndoArt Pedo Gold (25/0.04), and 20 EndoArt Pedo Blue (25/0.04) files. Static CFR tests; performed on a custom-made stainless steel block with an inner diameter of 1.5 mm, an angle of curvature of 60° and a curved artificial canal with a radius of curvature of 5 mm. The test system was filled with distilled water and the temperature was kept constant at 35 ± 1 °C. The files were rotated in the simulated canal until fracture occurred. The number of cycles to failure (NCF) data was recorded, and all the fracture surfaces of the files were evaluated using scanning electron microscopy (SEM). One-way ANOVA and Tukey tests were used for statistical analysis of the data, and the significance level was set at p < 0.05. RESULTS: EndoArt Pedo Blue showed the highest NCF values (2668.10 ± 755.26), while the miniScope showed the lowest NCF values (453.65 ± 72.51), with a statistically significant difference between all the tested file systems (p < 0.05). There was no statistical difference in terms of fractured fragment lengths among all tested files (p > 0.05). CONCLUSION: The EndoArt Pedo Blue file system showed the best CFR performance among the four file systems specifically designed for primary teeth.

Efficacy of various techniques in calcium silicate-based intracanal medicament removal: a micro-CT analysis.

The purpose of this study was to evaluate the efficacy of different techniques in removing calcium silicate intracanal medicament (Bio-C Temp). Forty human single-canaled premolars were randomly distributed into five groups (n = 8). All root canals were instrumented, then filled with Bio-C Temp. Following 1-week incubation, the intra-canal medicament was removed using one of five techniques according to tooth group: conventional syringe irrigation, Endo Activator, passive ultrasonic irrigation (PUI), ProTaper Universal F3 and XP-endo Finisher (XPF). Micro-CT scanning was performed before and after removal of Bio-C Temp. All techniques significantly reduced the volume of Bio-C Temp (p < 0.001) without reaching complete elimination. The percentage of Bio-C Temp removed was significantly higher in the XPF group (98.2%) compared to conventional syringe irrigation (70.6%), the Endo Activator (75.7%), and the ProTaper Universal (76.6%). There was no significant difference between the XPF and PUI (95.1%) groups. None of the removal techniques were able to completely remove Bio-C Temp from the root canal. However, XPF was the most effective method, but was not statistically significant when compared to PUI. Clinical Relevance: This study demonstrated that both XPF and PUI outperform conventional irrigation in removing Bio-C Temp intracanal medicament.

Effect of phytic acid on chemical, structural, and mechanical characteristics of nickel-titanium endodontic files.

This study investigated phytic acid (IP6) effect on chemical, structural, and mechanical characteristics of nickel-titanium (NiTi) files. The tested files were equally divided into groups according to the immersion protocol: sodium hypochlorite (NaOCl), ethylenediaminetetraacetic acid (EDTA), IP6, EDTA followed by NaOCl, and IP6 followed by NaOCl. These groups were then compared in terms of Ni, Ti, and chromium (Cr) ions release from the files. Microstructural changes using field emission scanning electron microscope (Fe-SEM) and energy dispersive X-ray spectroscopy (EDX) and surface roughness were analyzed. The mechanical characterization was conducted using cyclic fatigue resistance test. Fractured segments were scanned under SEM. Statistical analysis was performed using one-way ANOVA, Tukey test, Kruskal-Wallis test and Mann-Whitney U test. Results showed that NaOCl caused significant release of Cr, followed by IP6 and EDTA (P < 0.05). When files were pre-immersed in EDTA, NaOCl tended to induce less release of Ti and Cr. EDX evaluation revealed that the main surface elements were Ni, Ti, carbon, and oxygen. EDTA group contained the highest amount of carbon, while the control group showed the lowest. Surface roughness evaluation revealed no significant differences between groups despite the minor increases after immersion in certain groups. Black areas were observed in the NaOCl group which indicated corrosion. However, the cyclic fatigue test showed no significant differences between the groups.