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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. [ABSTRACT FROM AUTHOR]

Introduction The purpose of this study was to present a new periapical and endodontic status scale (PESS) that is based on the complex periapical index (COPI), which was designed for the identification and classification of periapical bone lesions in cases of apical periodontitis, and the endodontically treated tooth index, which was designed for endodontic treatment quality evaluation by means of cone-beam computed tomographic (CBCT) analysis. Methods Periapical and endodontic status parameters were selected from the already known indexes and scientific literature for radiologic evaluation. Radiographic images (CBCT imaging, digital orthopantomography [DOR], and digital periapical radiography) from 55 patients were analyzed. All parameters were evaluated on CBCT, DOR, and digital periapical radiographic images by 2 external observers. The statistical analysis was performed with software SPSS version 19.0 (SPSS Inc, Chicago, IL). Chi-square tests were used to compare frequencies of qualitative variables. The level of significance was set at P ≤ .05. Results Overall intraobserver and interobserver agreements were very good and good, respectively. CBCT analysis found more lesions and lesions of bigger dimension ( P < .001). CBCT imaging was also superior in locating lesions in the apical part on the side compared with DOR and in the diagnosis of cortical bone destruction compared with both methods ( P < .001). Through CBCT analysis, more root canals and more canals associated with lesions were found. The most informative and reproducible periapical and endodontic status parameters were selected, and a new PESS was proposed. Conclusions The classification proposed in the present study seems to be reproducible and objective and adds helpful information with respect to the existing indexes. Future studies need to be conducted to validate PESS. [ABSTRACT FROM AUTHOR]

Introduction To obtain essential information in clinical endodontics, cone-beam computed tomographic (CBCT) imaging can be used in all phases of treatment including diagnosis, treatment planning, during the treatment phase, and through post-treatment assessment and follow-up. The purpose of this article was to review the use of CBCT imaging in the diagnosis, treatment planning, and assessing the outcome of endodontic complications. Methods Literature was selected through a search of PubMed electronic databases for the following keywords: tooth root injuries, tooth root radiography, tooth root perforation, tomography, cone-beam computed tomography, endodontic complications, tooth root internal/external resorption, root fractures, and broken instruments. The research was restricted to articles published in English. One hundred twelve articles met the inclusion criteria and were included in this review. Results Currently, intraoral radiography is the imaging technique of choice for the management of endodontic disease, but CBCT imaging appears to have a superior validity and reliability in the management of endodontic diagnosis and complications. Conclusions Endodontic cases should be judged individually, and CBCT imaging should be considered in situations in which information from conventional imaging systems may not yield an adequate amount of information to allow the appropriate management of endodontic problems. CBCT imaging has the potential to become the first choice for endodontic treatment planning and outcome assessment, especially when new scanners with lower radiation doses will be available. [ABSTRACT FROM AUTHOR]

Introduction The aim of this study was to evaluate the cyclic fatigue resistance of ProTaper Universal (PTU; Dentsply Maillefer, Baillagues, Switzerland) and ProTaper Gold (PTG, Dentsply Maillefer) nickel-titanium rotary files at room and intracanal temperatures. Methods A total of 120 files were used to test the cyclic fatigue resistance of PTU (S1 and F2) and PTG (S1 and F2) in an artificial canal at room temperature (20°C) and at intracanal temperature (35°C). The number of cycles to failure and the fracture length of the fragment were recorded, and data were subjected to statistical analysis. Results PTG registered no differences in fatigue life between the 2 temperatures tested ( P > .05), whereas PTU showed a statistically significant reduction in fatigue life at intracanal temperature compared with room temperature ( P < .05). PTG instruments exhibited a statistically higher resistance to cyclic fatigue than PTU instruments both at room and intracanal temperatures ( P < .05). There were no statistically significant differences among the fracture length of separated instruments ( P > .05). Conclusions Intracanal temperature influenced the cyclic fatigue resistance of instruments produced with traditional nickel-titanium, whereas it did not influence the fatigue life of instruments produced with gold heat treatment. Gold heating treatment enhances the resistance to cyclic fatigue of ProTaper instruments. [ABSTRACT FROM AUTHOR]

This paper investigates the influence of cavity configuration and post-endodontic restoration on the fracture resistance, failure mode and stress distribution of premolars by using a method of fracture failure test and finite elements analysis (FEA) coupled to Weibull analysis (WA). One hundred premolars were divided into one control group (Gcontr) (n = 10) and three experimental groups, according to the post-endodontic restoration (n = 30), G1, restored using composite, G2, restored using single fiber post and G3, restored using multifilament fiberglass posts (m-FGP) without post-space preparation. Each experimental group was divided into three subgroups according to the type of coronal cavity configuration (n = 10): G1O, G2O, and G3O with occlusal (O) cavity configuration; G1MO, G2MO, and G3MO with mesio-occlusal (MO); and G1MOD, G2MOD, and G3MOD with mesio-occluso-distal (MOD). After thermomechanical aging, all the specimens were tested under compression load, and failure mode was determined. FEA and WA supplemented destructive tests. Data were statistically analyzed. Irrespective of residual tooth substance, G1 and G2 exhibited lower fracture resistance than Gcontr (p < 0.05), whereas G3 showed no difference compared to Gcontr (p > 0.05). Regarding the type of restoration, no difference was highlighted between G1O and G2O, G1MO and G2MO, or G1MOD and G2MOD (p > 0.05), whereas G3O, G3MO, and G3MOD exhibit higher fracture resistance (p < 0.05) than G1O and G2O, G1MO and G2MO, and G1MOD and G2MOD, respectively. Regarding cavity configuration: in G1 and G2, G1O and G2O exhibited higher fracture resistance than G1MOD and G2MOD, respectively (p < 0.05). In G3, there was no difference among G3O, G3MO and G3MOD (p > 0.05). No difference was found among the different groups and subgroups regarding the failure mode. After aging, premolars restored with multifilament fiberglass posts demonstrated fracture resistance values comparable to those of an intact tooth, irrespective of the different type of cavity configuration. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the bond strength of resin dentin interfaces created with adhesives applied on root dentin using the water wet or ethanol wet bonding teclmique. The morphology of resin dentin interfaces was evaluated using confocal microscopy. Methods: Four experimental resin adhesives (R#A to R#D) and one commercial three- step/etch and rinse adhesive were applied to the root canal dentin of endodontically treated single canal incisors using the water (control) or ethanol wet bonding technique. The ethanol wet bonding substrate was achieved by keeping the root canal immersed in absolute ethanol (100%) for 3 minutes. The root dentin bonded specimens were sectioned into beams, stored in distilled water (24 hours) and fmally tested for microtensile bond strengths (μTBS). Additional dentin surfaces were conditioned and bonded as previously described. They were prepared for the microscopy study and finally observed using confocal microscopy. Results: The ethanol wet bonding technique gave higher bond strength values for all the adhesives tested: in Group 1 (water wet bonding technique) no significant difference was found between the resins tested; the only exception being the most hydrophilic Resin #4 showing the highest bond strength values (P< 0.05). In Group 2 (ethanol wet bonding technique) no statistical differences were present between Resin #A and Resin #D. Resin #C showed the highest bond strength values. Confocal microscopy showed better resin diffusion and hybrid layer formation when the ethanol wet bonding was used. [ABSTRACT FROM AUTHOR]

• Using micro-CT to evaluate the efficacy of a novel laser activated irrigation in the removal of intracanal filling remnants. • The SWEEPS® was more effective than PUI, when used in combination with NaOCl, in the removal of filling remnants during root canal retreatment. • Additional activated irrigation of root canal with a solvent after the retreatment improved the removal of filling remnants from curved root canal. This study aimed to evaluate the effect of Er:YAG laser-initiated shockwave-enhanced emission of photoacoustic streaming (SWEEPS®) and passive ultrasonic irrigation (PUI) combining thymol-based solvent or sodium hypochlorite (NaOCl) in the removal of filling remnants from curved canals. Forty-eight curved root canals were instrumented and filled with an epoxy-resin-based sealer and gutta-percha. The canals were retreated with a Wave One Gold primary file (tip size 25; variable taper) and sodium hypochlorite (NaOCl). After the retreatment, the samples were randomly divided into four groups according to the additional irrigation protocol: PUI/NaOCl, PUI/solvent, SWEEPS®/NaOCl or SWEEPS®/solvent. The volume of filling material in root canal was measured after root canal filling, after mechanical retreatment, after final irrigation protocol and after additional irrigation protocol, using micro-CT. The results were analyzed using Kruskal-Wallis test with the post-hoc Mann-Whitney U test and Wilcoxon test (α=0.05). In the PUI group, irrigation with the solvent or NaOCl resulted in similar filling reduction (p = 0.224). In the SWEEPS® group, irrigation with NaOCl resulted in a significantly greater filling reduction compared to the solvent (p = 0.021). The SWEEPS®/NaOCl group was more effective than the PUI/NaOCl group (p = 0.008). No significant differences were found between PUI/solvent and SWEEPS® groups (p >0.05) and PUI/NaOCl and SWEEPS®/solvent group (p >0.05). Although all tested protocols improved the removal of filling remnants from curved root canal, the SWEEPS® was more successful than PUI when NaOCl was used. Both tested techniques showed similar efficacy when in combination with the solvent. [Display omitted] [ABSTRACT FROM AUTHOR]

Introduction The purpose of this study was to evaluate the cyclic fatigue resistance of 3 different nickel-titanium reciprocating instruments. Methods A total of 45 nickel-titanium instruments were tested and divided into 3 experimental groups ( n = 15): group 1, WaveOne Primary instruments; group 2, Reciproc R25 instruments; and group 3, Twisted File (TF) Adaptive M-L1 instruments. The instruments were then subjected to cyclic fatigue test on a static model consisting of a metal block with a simulated canal with 60° angle of curvature and a 5-mm radius of curvature. WaveOne Primary, Reciproc R25, and TF Adaptive instruments were activated by using their proprietary movements, WaveOne ALL, Reciproc ALL, and TF Adaptive, respectively. All instruments were activated until fracture occurred, and the time to fracture was recorded visually for each file with a 1/100-second chronometer. Mean number of cycles to failure and standard deviations were calculated for each group, and data were statistically analyzed ( P < .05). Instruments were also observed through scanning electron microscopy to evaluate type of fracture. Results Cyclic fatigue resistance of Reciproc R25 and TF Adaptive M-L1 was significantly higher than that of WaveOne Primary ( P = .009 and P = .002, respectively). The results showed no statistically significant difference between TF Adaptive M-L1 and Reciproc R25 ( P = .686). Analysis of the fractured portion under scanning electron microscopy indicated that all instruments showed morphologic characteristics of ductile fracture that were due to accumulation of metal fatigue. Conclusions No statistically significant differences were found between the instruments tested except for WaveOne Primary, which showed the lowest resistance to cyclic fatigue. [ABSTRACT FROM AUTHOR]

Introduction The aim of the present study was to evaluate the difference in cyclic fatigue resistance between Vortex Blue (Dentsply Tulsa Dental, Tulsa, OK) and Profile Vortex nickel-titanium (Dentsply Tulsa Dental) rotary instruments. Methods Two groups of nickel-titanium endodontic instruments, ProFile Vortex and Vortex Blue, consisting of identical instruments in tip size and taper (15/.04, 20/.06, 25/.04, 25/.06, 30/.06, 35/.06, and 40/.04) were tested. Ten instruments from each system and size were tested for cyclic fatigue resistance, resulting in a total of 140 new instruments. All instruments were rotated in a simulated root canal with a 60° angle of curvature and a 5-mm radius of curvature of a specific cyclic fatigue testing device until fracture occurred. The number of cycles to failure and the length of the fractured tip were recorded for each instrument in each group. The mean values and standard deviation were calculated, and data were subjected to 1-way analysis of variance and a Bonferroni t test. Significance was set at the 95% confidence level. Results When comparing the same size of the 2 different instruments, a statistically significant difference (P < .05) was noted between all sizes of Vortex Blue and Profile Vortex instruments except for tip size 15 and .04 taper (P = 1.000). No statistically significant difference (P > .05) was noted among all groups tested in terms of fragment length. Conclusions Vortex Blue showed a significant increase in cyclic fatigue resistance when compared with the same sizes of ProFile Vortex. [ABSTRACT FROM AUTHOR]

Abstract Introduction Maxillary first molar second mesiobuccal (MB2) root canal prevalence may change among different populations. The aim of this study was to analyze the worldwide prevalence of the MB2 root canal and understand its possible relation with sex, age, side, and root configuration using in vivo cone-beam computed tomographic (CBCT) assessment. Methods Observers from 21 regions were calibrated to achieve a similar CBCT assessment methodology and instructed to collect data from 250 maxillary first molars in previously existing examinations. Intra- and interrater reliability tests were performed. The sample size included 5250 molars and was defined by way of a preliminary trial. Data collected included MB2 presence, sex, age, side, number of roots per tooth, and mesiobuccal root configuration. The z test for proportions in independent groups was used to analyze the differences among subgroups. P <.05 was considered significant. Results The worldwide CBCT-assessed MB2 prevalence was 73.8%, ranging from 48.0% in Venezuela to 97.6% in Belgium. The prevalence in males and females was 76.3% and 71.8%, respectively (P <.05). Significantly higher MB2 proportions were found in younger patients and 3-rooted molar configurations. The group intraclass correlation coefficient and the percentage of agreement for the MB2 presence were 0.95 and 0.91, respectively. The intrarater Cohen kappa value was above 0.61 for all observers. Conclusions MB2 prevalence in the analyzed regions varied widely. The differences may be associated with specificities within each region but also patient demographics. Males, younger patients, and 3-rooted configurations were associated with higher MB2 proportions. [ABSTRACT FROM AUTHOR]

A range of procedural errors can occur when performing endodontic treatment on posterior teeth. These errors may decrease the success rate in endodontic practice. This study assessed the prevalence of procedural errors and the quality of endodontic treatments in maxillary molars and premolars using cone-beam computed tomography (CBCT). CBCT scans from two private radiology centers were assessed retrospectively to ensure the same calculated sample size of 327 teeth for each of the four maxillary posterior tooth types (a total of 1,308 endodontically treated teeth). Image sets were evaluated for procedural errors categorized as follows: obturation length (overfilling or underfilling by >2 mm short of the root apex), missed canals, perforations, strip perforations (with extrusion of material into the furcation area), separated instruments in the root canal space, and root fracture. Data were analyzed with SPSS version 20 (SPSS Inc., Chicago, IL, USA), and frequency data was assessed using the Monte Carlo test at the 0.05 level of significance. The procedural errors most commonly reported in the present study were from most frequent to least frequent: underfilled canals (50.0%), missed canals (27.5%), overfilled canals (12.5%), apical perforations (5.0%), separated instruments (3.1%), and root fractures (1.9%). No strip perforations (with extrusion of material into the furcation area) were seen in the study (0%). Underfilled and missed root canals were the most frequent procedural errors identified in the present study. These findings underline the importance of more consideration of critical working length management during all stages of root canal treatment, greater awareness of root canal anatomy, and the use of imaging and diagnostic devices that enhance the ability to identify and treat root canals both safely and effectively. [ABSTRACT FROM AUTHOR]

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.

This scoping review aimed to synthesize and explore the current boundaries and limitations of laboratory research on the effectiveness of continuous chelation irrigation protocol in endodontics. This scoping review was reported according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) Extension for Scoping Reviews. Literature search was conducted on Pubmed and Scopus to identify all laboratory studies evaluating smear layer and hard-tissue debris removal or, antimicrobial efficacy, or dentine erosion induced by continuous chelation. Two independent reviewers performed the all review steps and the relevant items were recorded. Seventy-seven potentially relevant studies were identified. Finally, 23 laboratory studies met the eligibility criteria for qualitative synthesis. Seven studies focused on the smear layer/debris removal outcome, 10 on antimicrobial activity, and 10 on dentine erosion. In general, the continuous chelation protocol was equally or more effective in the cleanliness of root canals and antimicrobial activity compared with traditional sequential protocol. In addition, etidronate solutions seemed to be milder chelating agents compared to those with EDTA, thus resulting in reduced or no dentine erosion and roughness modification. Yet, the methodological differences among the included studies limit the results' generalizability. The continuous chelation seems to be equally or more effective in all investigated outcomes when compared with the traditional sequential protocol. The methodological variability among the studies and shortcomings in the methods employed limit the generalizability and clinical relevance of the results. Standardized laboratory conditions combined with reliable three-dimensional investigation approaches are necessary to obtain clinically informative findings., (© 2023. The Author(s).)

Background: Intentional replantation (IR) to treat disease of endodontic origin remains controversial. While IR has been advocated by some clinicians as another valid treatment option, others consider it as a treatment procedure of last resort., Objective: To systematically review and critically evaluate the effectiveness of IR compared with nonsurgical root canal treatment/retreatment or apical surgery in terms of clinical and patient-related outcomes in managing permanent teeth with apical periodontitis (AP)., Methods: A literature search of five databases (PubMed, Embase, Scopus, Web of Science and Cochrane Central register of Controlled Trials), and the grey literature (Networked Digital Library of Theses and Dissertations, Open Access Theses and Dissertations, DART-Europe E-theses Portal, British Library E-Theses Online Service), from inception to November 2021, was conducted. Randomised clinical trials, comparative clinical trials (CCTs), nonrandomised, retrospective, and prospective comparative cohort and case-control two arm studies which evaluated clinical and/or patient-related outcomes of permanent teeth with AP treated with IR compared with nonsurgical root canal treatment/retreatment or apical surgery were identified. The quality of the studies was appraised using the Cochrane risk of bias tool for randomized trials (RoB 2.0), the Robins-I for nonrandomized controlled clinical trials and the Newcastle-Ottawa scale for observational studies. Two independent reviewers were involved in the literature selection, performed the data extraction and the appraisal of the studies identified; disagreements were resolved in conjunction with a third reviewer., Results: No comparative study was identified from the literature search. Four longitudinal studies (one prospective and three retrospective) were identified during the screening of titles and abstracts but were excluded after reading the full text, because only IR was evaluated (single arm studies)., Discussion: The available evidence on IR is mainly based on observational studies, which reported high overall mid- to long-term survival, and low complication rates. The results suggest that IR may represent an alternative treatment procedure to solve problems of endodontic origin. However, in the absence of high-quality evidence from CCTs, clinical decision-making should be on a case-by-case basis and in accordance with the clinician's experience and the patient's preference., Conclusion: Clinical studies showed that IR may be a treatment modality to manage problems of endodontic origin. However, clinical trials comparing the effectiveness of IR with nonsurgical root canal treatment/retreatment or apical surgery are still required given the paucity of evidence., (© 2022 International Endodontic Journal. Published by John Wiley & Sons Ltd.)

The aim of this study was to evaluate the debridement efficacy of sonic irrigation (EDDY; VDW, Munich, Germany and EndoActivator; Dentsply-Sirona, Ballaigues, Switzerland) and ultrasonically activated irrigation (Irrısafe; Satelec Acteon, Merignac, France) in a simulated canal isthmus connecting curved canals. Transparent resin blocks were produced containing two curved canals connected with an isthmus. The isthmus was then filled with dentin debris. Three irrigant activation cycles were performed and the amount of remaining debris was compared analysing pictures taken after each activation cycle. Data were statistically analysed using one-way ANOVA and post hoc Tukey tests at a significance level of p < 0.05. EDDY showed greater efficiency in removing dentin debris from the simulated isthmus than the other techniques tested. An increase in the activation time enhanced the efficiency of both EDDY and ultrasonically activated irrigation in debris removal., (© 2023 Australian Society of Endodontology Inc.)

Objective: To evaluate the success rate of retrieving separated instrument, the root canal volume changes using cone-beam computed tomography and the retrieval time using Ruddle's technique, Terauchi file retrieval kit (TFRK) and Endo Rescue kit., Methods: Sixty human mandibular first molars were selected, and a 4-mm portion of #25/.04 rotary files were separated in the middle third of moderately curved mesio-buccal canals. Teeth were randomly assigned into three groups (n=20): R group, in which separated files were retrieved according to Ruddle's technique; T group, in which separated files were retrieved using TFRK and E group, in which separated files were retrieved using Endo Rescue kit. Values were analyzed using IBM SPSS. Results presented as mean+-standard deviation and 95% confidence interval for the root canal volume and time and frequency (%) for success rate. Comparisons of differences in time, canal volume and success rate between groups were assessed., Results: Retrieval was successful in R and T groups (70% and 80% respectively) without any significant difference between them (p=0.715), while E group hadn't any successful samples (0.0%) with significant difference compared to R and T groups (p<0.001, p<0.001). E group showed the highest increase in canal volume followed by R group, while T group exhibited the lowest increase in canal volume. There was no significant difference in the mean retrieval time between R and T groups (p=0.815)., Conclusion: TFRK provides a more conservative way for retrieval of separated instrument from the middle third of moderately curved canals. (EEJ-2023-01-01).

Objective: The present study aimed to evaluate the influence of different access cavity designs on the biomechanical behaviour of a three-rooted maxillary first premolar using finite element analysis (FEA)., Methods: Three experimental FEA models were generated: the intact tooth (IT) model, the traditional access cavity (TAC) model, and the conservative access cavity (CAC) model. In both TAC and CAC models, root canals preparation was simulated as follows: the mesiobuccal and distobuccal canals with a final tip size of 30 and taper of 0.04 and the palatal canal with a final tip size of 35 and taper of 0.04. Cyclic loading of 50 N was simulated on the occlusal surface of the three models. The number of cycles until failure (NCF), the location of failure, stress distribution patterns, maximum von Mises (VM), and maximum principal stress (MPS) were all evaluated and compared., Results: Both types of access cavity preparation caused a reduction in the lifelog of the tooth; when compared to the IT model the TAC model had a lifelog of 94.82% while the CAC model had a lifelog of 95.80%. The maximum VM stresses value was registered on the occlusal surface of the TAC model (7 MPa), while the minimum was on the occlusal surface of the IT (6.2 MPa). MPS analysis showed that the highest stress value was recorded on the occlusal surface of the CAC model (7.71 MPa), while the least was recorded on the occlusal surface of the TAC model (3.77 MPa). Radicular stresses were always of minimal value regardless the model., Conclusion: The relation between the access cavity margins and the functional load points is a deciding factor that influences the biomechanical behaviour and fatigue life of endodontically treated teeth. (EEJ-2023-01-03).

Introduction: This study aimed to compare the micro-shear bond strength (µSBS) performances of two resin-based calcium silicate-based cement (CSC) (TheraCal PT and TheraCal LC), Biodentine, and two modified-MTA CSC materials (NeoMTA 2 and BioMTA+) to bulk-fill restorative material., Materials and Methods: Fifty 3D printed cylindrical resin blocks with a central hole were used (2 mm in depth and 4 mm in diameter). CSCs were placed in the holes (per each group n = 10) and incubated for 24 h. Cylindrical polyethylene molds (2 mm in height and diameter) were used to place the bulk-fill restorative materials on the CSCs and polymerize for 20 s. Then, all specimens were incubated for 24 h at 37 °C at a humidity of 100%. Specimen's µSBSs were determined with a universal testing machine. Data were analyzed with one-way ANOVA (Welch) and Tamhane test., Results: Statistically higher µSBS was found for TheraCal PT (29.91 ± 6.13 MPa) ( p < 0.05) respect to all the other materials tested. TheraCal LC (20.23 ± 6.32 MPa) ( p > 0.05) reported higher µSBS than NeoMTA 2 (11.49 ± 5.78 MPa) and BioMTA+ (6.45 ± 1.89 MPa) ( p < 0.05). There was no statistical difference among TheraCal LC, NeoMTA 2 and Biodentine (15.23 ± 7.37 MPa) and between NeoMTA 2 and BioMTA+ ( p > 0.05)., Conclusion: Choosing TheraCal PT as the pulp capping material may increase the adhesion and µSBS to the bulk-fill composite superstructure and sealing ability., Competing Interests: Gianluca Plotino is an employee of a private dental practice. The authors have no competing interests., (© 2023 Falakaloğlu et al.)

Introduction: This study assessed the prevalence of radix entomolaris and 2 canals at the distal aspect of mandibular first molars among different geographic regions by means of cone-beam computed tomographic imaging., Methods: Precalibrated observers from 23 worldwide geographic locations followed a standardized screening protocol to assess 5750 cone-beam computed tomographic images of mandibular first molars (250 per region), gathering demographic data and recording the presence of radix entomolaris and a second canal at the distal aspect of teeth. Intra- and interrater reliability tests were conducted and comparisons among groups were performed using proportions and odds ratio forest plots. The significance level was set at 5%., Results: The results of intra- and interrater tests were above 0.79. The prevalence of radix entomolaris varied from 0.9% in Venezuela (95% confidence interval [CI], 0%-1.9%) to 22.4% in China (95% CI, 17.2%-27.6%). Regarding the proportion of a second distal canal, it ranged from 16.4% in Venezuela (95% CI, 11.8%-21.0%) to 60.0% in Egypt (95% CI, 53.9%-66.1%). The East Asia subgroup was associated with a significantly higher prevalence of an extra distolingual root, whereas the American subgroup, the American native ethnic group, and elderly patients were linked to significantly lower percentages of a second canal at the distal aspect of teeth. No significant differences were noted between male or female patients., Conclusions: The overall worldwide prevalence rates of radix entomolaris and a second canal at the distal aspect of the mandibular first molar were 5.6% and 36.9%, respectively. The East Asia geographic region and Asian ethnic group had a higher prevalence of a second distal root., (Copyright © 2021 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: The presence of multiple root canals is an important morphologic aspect of mandibular premolars. This study aimed to perform a worldwide analysis on the prevalence of a lingual canal in mandibular premolars and to evaluate its influence on patients' demographics in 23 countries using cone-beam computed tomographic images., Methods: Observers from 23 countries were instructed to evaluate cone-beam computed tomographic images of 300 first and 300 second premolars (13,800 teeth) regarding the presence of a lingual canal, canal configuration, and data related to patients' ethnicity, age, and sex following a standardized screening methodology. Intra- and interrater evaluations were performed using the Cohen kappa test and intraclass correlation coefficient. Proportion and odds ratio forest plots were calculated in order to compare groups. Statistical significance was set at 5%., Results: Both kappa and intraclass correlation coefficient values were above 0.60, and the percentage of agreement was 94.9% (first premolar) and 97.8% (second premolar). A significant statistical difference was observed between the worldwide proportion of a lingual canal in mandibular first (23.8%; range, 12.0%-32.7%) and second (5.3%; range, 1.0%-15.3%) premolars (P < .05). Asians and patients over 60 years old were associated with the lowest proportions of a lingual canal (P < .05), whereas Africans and younger groups were associated with the highest proportions (P < .05). The prevalence of a lingual canal in males (27.9%) was higher than females (20.0%) for the first premolar only (P < .05). Males were associated with 1.533 and 1.597 higher odds of presenting a lingual root canal in the first and second premolars, respectively., Conclusions: The worldwide proportion of a lingual root canal was 23.6% and 5.3% for the first and second premolars, respectively. Ethnicity, geographic region, age, and sex had an influence on the outcomes., (Copyright © 2021 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: A comparison between root canal transportation studies is nearly impossible because of nonstandardized transportation evaluation methods. The aim of the present review was to search, compare, and critically discuss transportation evaluation methods., Methods: A search of PubMed, Web of Science, Scopus, ScienceDirect, and reference lists of articles was conducted up to March 2020 using appropriate key words to identify transportation evaluation methods. The methods in the included articles were extracted, compared, and categorized., Results: Seventy-four articles using original methods were selected. All studies share 3 main steps: image acquisition, image measurements, and calculation of parameters. Images were acquired by photography, radiography, and computed tomographic imaging. Two types of measurements were used: the amount of removed material and the canal center point distance. The parameters were calculated and reported as distance or ratio. Relationships between the different transportation parameters were found and confirmed with mathematical simulation., Conclusions: Although methods were proposed as being novel, similarities between them were found, enabling the classification of the methods and identifying correlations. The canal center point distance is the most suitable for the description of canal transportation because it is comprehensible and it relates to the mathematical concept of translation. Removed material-based measurements are double the value of the canal center point distance. Ratio parameters are not suitable for reporting transportation., (Copyright © 2021 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: The aim of this study was to determine and compare the difference in the volume of dentin and enamel removed (DER) to prepare 3 different access cavities and to propose a standardization of the access cavities according to their volume of DER., Methods: One hundred twenty maxillary and mandibular molars and premolars were assigned to 3 subgroups for each tooth type (n = 10): the traditional endodontic cavity (TEC) group; the conservative endodontic cavity (CEC) group with partial unroofing and convergent walls; and the ultraconservative endodontic cavity (UEC) group, preserving most part of the pulp chamber roof and the occlusal surface. The sliced image data of cone-beam computed tomographic images before and after access cavity preparation were exported as Digital Imaging and Communications in Medicine files and imported into the MeVisLab framework system (MeVis Research, Bremen, Germany). After segmentation, the volumes of coronal dentin and enamel were measured, and the difference in the percentage of volume of DER for endodontic access cavity preparation was calculated. The data were subjected to statistical analyses (analysis of variance) with a level of significance set at P < .05., Results: The percentage of volume of DER was less than 6% for the UEC group, up to 15% for the CEC group, and more than 15% for the TEC group, with a statistically significant difference among all groups in all of the tooth types analyzed (P < .05)., Conclusions: The present study showed significantly different percentages of volume of DER among the groups analyzed (ie, UEC < CEC < TEC). A standardization of access cavity preparation was proposed according to the percentage of volume of DER., (Copyright © 2020 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: Negotiation, glide path, and preflaring are essential steps in root canal shaping procedures. This report aimed to discuss the terminology, basic concepts, and clinical considerations of negotiation, glide path, and preflaring procedures and the influence of these steps on root canal shaping., Methods: This systematic review was undertaken following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The protocol has been registered with the International Prospective Register of Systematic Reviews (number CRD42019127021). A comprehensive literature search was performed by 2 independent reviewers using a selected search strategy in 2 electronic databases (PubMed and Scopus) until January 28, 2019. A further search was performed manually in endodontic journals. Studies investigating or comparing at least 1 shaping property resulting from root canal instrumentation with a glide path or preflaring in human extracted teeth or clinical studies were included., Results: The literature shows that the definition of glide path and preflaring procedures remains controversial, which requires an elaboration in the American Association of Endodontists' Glossary of Endodontic Terms. After the removal of irrelevant and duplicated articles, 98 articles were included. The impact of glide path preparation and preflaring on working length determination, apical file size determination, canal transportation, separation of endodontic files, shaping time, dentinal microcrack formation, and extrusion of debris was discussed. Because of heterogeneity among the included studies, quantitative synthesis was not performed for most of the parameters., Conclusions: An evidence-based guideline is needed to define and correlate the basic concepts and current applications of each step of contemporary advancements in root canal instruments. Glide path preparation reduces the risk of debris extrusion, has no influence on the incidence of dentinal crack formation, and improves the preservation of the original canal anatomy. The creation of a glide path may have no impact on Reciproc files (VDW, Munich, Germany) in reaching the full working length. Preflaring increases the accuracy of working length determination. Further randomized clinical trials are required to evaluate the effect of a glide path and preflaring on root canal treatment outcomes., (Copyright © 2020 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

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.

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.

Introduction: The aim of the present study was to investigate the impact of ambient temperature on the life span of nickel-titanium (NiTi) files., Methods: Cyclic fatigue testing of NiTi instruments was performed in a stainless steel artificial canal. During the experiment, 4 different temperatures (0°C, 20°C, 35°C, and 39°C) were used in a thermostatic bath controlled using electronic and infrared controls. Eighty R25 Reciproc Blue (VDW, Munich, Germany) and 80 R25 Reciproc (VDW) instruments were reciprocated in the artificial canal until fracture occurred, and the time to fracture and the length of the fractured fragment were recorded. The phase transformation temperature for 3 instruments of each type was analyzed by differential scanning calorimetry. One-way analysis of variance and Bonferroni tests were used to statistically analyze the data at a 5% significance level (P < .05)., Results: Reciproc Blue instruments were significantly more resistant to cyclic fatigue than Reciproc at all the temperatures tested (P < .05). Fatigue resistance was proportionally higher as the environmental temperature decreased (0°C > 20°C > 35°C > 39°C). No significant difference was registered for the length of the fractured fragment of both instruments tested at all temperatures tested (P > .05)., Conclusions: Blue alloy significantly increases the cyclic fatigue resistance of Reciproc files compared with M-Wire alloy. Temperature significantly affects the life span of NiTi files. When the ambient temperature increases between 0°C and 35°C, the fatigue resistance of the files statistically decreases., (Copyright © 2018 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

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., (Copyright © 2018 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

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., (Copyright © 2017 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: The purpose of this study was to assess the effects of sodium hypochlorite (NaOCl) immersion and sterilization on the cyclic fatigue resistance of heat-treated nickel-titanium (NiTi) rotary instruments., Methods: Two hundred ten new 25/.06 Twisted Files (TFs; SybronEndo, Orange, CA) and Hyflex CM (Coltene Whaledent, Cuyahoga Falls, OH) files were divided into 7 groups (n = 15) for each brand. Group 1 (control group) included new instruments that were not immersed in NaOCl or subjected to autoclave sterilization. Groups 2 and 3 were composed of instruments dynamically immersed for 3 minutes in 5% NaOCl solution 1 and 3 times, respectively. Groups 4 and 5 consisted of instruments only autoclaved 1 and 3 times, respectively. Groups 6 and 7 recruited instruments that received a cycle of both immersion in NaOCl and sterilization 1 and 3 times, respectively. Instruments were subsequently subjected to a fatigue test. The surface morphology of fractured instruments was studied by field-emission scanning electron microscopy and x-ray energy-dispersive spectrometric (EDS) analyses. The means and standard deviations of the number of cycles to failure (NCF) were calculated and statistically analyzed using 2-way analysis of variance (P < .05)., Results: Comparison among groups indicated no significant difference of NCF (P > .05) except for the groups of TFs sterilized 3 times without and with immersion in NaOCl (P < .05). HyFlex CM files exhibited higher cyclic fatigue resistance than TFs when files were sterilized 3 times, independently from immersion in NaOCl (P < .05). EDS analysis showed the presence of an oxide-rich layer on the Hyflex CM files' external surface. No morphologic or chemical differences were found between files of the same brand subjected to different treatments., Conclusions: Repeated cycles of sterilization did not influence the cyclic fatigue of NiTi files except for TFs, which showed a significant decrease of flexural resistance after 3 cycles of sterilization. Immersion in NaOCl did not reduce significantly the cyclic fatigue resistance of all heat-treated NiTi files tested., (Copyright © 2018 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

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., (Copyright © 2017 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

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., (Copyright © 2017 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

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., (Copyright © 2016 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)