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Chelating gels may initially assist in root canal preparations to help establish a glide path. While irrigation surveys have investigated liquid chelators and gels to a minor extent, no endodontic survey has focused on EDTA gels and why clinicians use them. All 395 members of the Australian Society of Endodontology (ASE) were emailed an 11-question survey concerning chelation gel usage via Qualtrics. Paper copies were also distributed at ASE events. Descriptive statistics were performed for practitioner and chelating gel data. Cross-tabulations of the practitioner type with the case percentage usage of gels were analyzed with the chi square test (adjusted p value < 0.0083). The overall response rate was 181/395 (46%). For 174 eligible responses, those who never/rarely used a gel were as follows: endodontic residents 12/14 (86%), endodontists 53/71 (75%), general dentists 39/86 (45%), and other members 0% (0/3). Most gel users said that gels helped establish a glide path. Those who never/rarely used chelating gels commented that they held no benefits over liquid EDTA. Endodontists were less likely to use a chelation gel than general dentists (p < 0.0083). Older clinicians had higher gel usage than younger ASE members (p < 0.0083), indicating a possible trend to diminished gel usage over time amongst ASE members. In conclusion, most ASE members find no need for a chelating gel, raising questions about their clinical effectiveness. Studies would therefore be warranted to investigate gel efficacy and improved clinical outcomes. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the feasibility of preclinical training, specifically in root canal preparation, using a virtual educational system equipped with an operating microscope. Ten postgraduate general dentistry trainees and practitioners undergoing postgraduate training in endodontics participated. The telesimulation course included three steps: theory, demonstration of practical work by the teacher and lastly practical training by the participants. The digital environment including the dental microscope was presented, and the feedback was collected with a questionnaire. The majority of participants considered that the online video conference format allowed them to acquire theoretical content but also practical knowledge and skills, owing to the contribution of the operating microscope. The technical feasibility of endodontic telesimulation was demonstrated. The operating microscope has a potential role in distance education, enabling teaching to occur synchronously and collaboratively. This allows learners to interact with each other and demonstrators in real time. [ABSTRACT FROM AUTHOR]

The purpose of this study was to evaluate the effect of side flattening of cutting flutes on the cyclic resistance and torsional resistance of nickel-titanium files. Both novel flattened Platinum V.EU (PL) and standard nonflattened CC Premium V.EU (CC) rotaries were tested. For cyclic fatigue tests, all the files were rotated in an artificial root canal with a curvature of 45° and a radius of 6.06 mm at 300 rpm (n = 15 in each group). The number of cycles to failure (NCF) was calculated. For torsional tests, the files were rotated at 2 rpm clockwise until fracture occurred. The maximum torque value at fracture was measured and the toughness and distortion angle were computed. Subsequently, 5 fragments were randomly selected in each experiment, the cross-section and longitudinal direction of the fragments were photographed using a scanning electron microscope. An unpaired t-test was performed at a significance level of 95%. There was a statistically significant difference in NCF between CC and PL (P <.05). CC showed higher NCF than PL. There was no statistically significant difference between CC and PL with regards to the parameters related to torsional resistance (distortion angle, ultimate strength, and toughness) (P >.05). Within the limitations of this study, side flattening of the file did not improve cyclic resistance or torsional resistance of the files. As side flattening may reduce a file's cyclic resistance, such files should be used with caution in clinical practice. [ABSTRACT FROM AUTHOR]

The aims of this study were to determine the efficacy of the KontrolFlex™ Accufile™ compared to the READY•STEEL™ Flexofile® using an electronic apex locator and to evaluate the instrument's design via scanning electron microscopy. Actual canal lengths of 30 extracted teeth were determined under magnification. An alginate model was used to determine experimental canal lengths with the Root ZX II apex locator (EAL) and size #10 Accufiles and Flexofiles. Differences between actual lengths and experimental lengths were compared with Student's t test. The average experimental lengths were short of the actual length by −0.10 mm (±0.34) and −0.12 mm (±0.16) for the Accufile and Flexofile, respectively with no statistical difference (p > 0.05). SEM images revealed similar non‐cutting Batt tips and a square cross‐section for the Accufile and triangular for the Flexofile. Both files provided similarly high levels of reliability when used with the Root ZX II EAL. [ABSTRACT FROM AUTHOR]

This study evaluated the accuracy of the Wirele‐X (Forum Tec, Ashkelon, Israel), a novel Bluetooth‐enabled wireless electronic apex locator. Thirty‐one extracted teeth with mature apices were used. Under 10X magnification, the actual canal lengths were determined. The teeth were embedded in alginate and electronic canal lengths were obtained using the Root ZX II and Wirele‐X electronic apex locators. The actual canal lengths and electronic canal lengths were compared with Student's t‐test. The average distance from the file tip to the actual canal length was −0.11 mm (±0.16) for the Root ZX II, and − 0.07 mm (±0.21) for the Wirele‐X. There were no statistically significant differences between the two electronic apex locators in their ability to determine the actual canal length (p > 0.05). The wireless apex locator (Wirele‐X) and the wired apex locator (Root ZX II) were found to be equally accurate. [ABSTRACT FROM AUTHOR]

Background: Once the chemo-mechanical preparation of root canals is finished, achieving a complete seal of the root canal system becomes crucial in determining the long-term success of endodontic treatment. The important goals of root canal obturation are to minimize leakage and achieve an adequate seal. Thus, a material that possesses satisfactory mechanical characteristics, is biocompatible, and has the ability to penetrate the dentine tubules adequately is needed. Aim: This study aimed to compare the penetrability and bond strength between two calcium silicate-based sealers and an epoxy resin-based sealer, as well as examine the relationship between penetrability and bond strength for the different sealers. Method and materials: Thirty-nine recently extracted single-rooted human premolar teeth were instrumented and divided evenly into three groups (n = 13), according to the sealer used for obturation: AH Plus Jet, EndoSequence, and AH Plus Bioceramic Sealer. Three teeth (30 slices) were randomly selected out of each for analysis using confocal laser scanning microscopy to assess penetrability. The remaining ten teeth (90 slices) in each group were subject to push-out tests using a universal testing machine. All teeth were sectioned into nine transverse slices of 0.9 mm thickness for their respective tests (apical, middle, coronal). Results: AH Plus Jet exhibited significantly lower penetrability and significantly higher bond strength compared to EndoSequence BC sealer (p = 0.002) and AH Plus Bioceramic Sealer (p = 0.006). There was no significant difference between EndoSequence BC sealer and AH Plus Bioceramic Sealer in terms of either penetrability or bond strength. No correlation was found between penetrability and bond strength. Conclusions: Within the limitation of this study and regardless of the location in the canal, the bioceramic based root canal sealers appeared to perform better than the epoxy resin-based sealer in terms of dentinal penetration rate. Further studies are required to compare other biomechanical properties of bioceramic sealers including setting characteristics and bacterial leakage. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate Ca(OH)2 extrusion in relation to delivery technique, apical size and depth of placement. Plastic blocks had j‐shaped canals shaped to apical sizes #35 and #45 (n = 32 each). Amounts of calcium hydroxide extrusion was determined relative to apical taper, depth of insertion and whether syringe or spiral filler at 500 rpm was used. Blocks were immersed in pH‐sensitive gel and observed for colour change. Extent of extrusion was expressed in mm2. Extrusion occurred in 48/64 of the samples. At 3 mm from the canal terminus, the device affected the frequency of extrusion, with syringe placement causing extrusion significantly (P < 0.01) more frequently, irrespective of apical size. Extrusion was significantly greater at 2 mm short of the canal terminus (median 27.44 mm2) compared to 3 mm (median 19.69 mm2). Under in‐vitro conditions, a spiral filler at 500 rpm, 3 mm short of the apex, minimised extrusion of Ca(OH)2 from root canals. [ABSTRACT FROM AUTHOR]

Finite element analysis has been a valuable research tool for rotary nickel‐titanium endodontic files over the last two decades. This review aims to summarise and critique the methodology as used in currently available endodontic literature for finite element analysis of rotary nickel‐titanium instruments. An electronic literature research in PubMed and Scopus databases was performed using the appropriate search terms, and the titles and abstracts were screened for relevance. The review revealed an inconsistent approach to the finite element method, particularly with regards to the boundary conditions in which the instruments are tested. Moreover, there is a lack of experimental data to validate in silico findings. A standardised protocol to finite element analysis of rotary endodontic instruments could be considered for future studies. [ABSTRACT FROM AUTHOR]

The aim of the study was to examine the effect of operator experience on the quality of instrumentation of molar canals using the TF Adaptive file system (SybronEndo, Orange, CA) on a 3D‐printed molar replica model. Three novice and two expert operators instrumented the root canals of three replicas each and resulting pre‐ and postinstrumentation 12 micron voxel size‐microCT volumes of each replica were digitally registered. Relative modified canal wall surface fraction and canal transportation (1–9 mm from the apex) were calculated and analysed by anova. Instrumentation by expert operators resulted in overall higher (P = 0.002) modified wall surface fraction in the distal but not the mesial and higher (P = 0.002) combined from all canal level transportation in the mesiobuccal canals but not the mesiolingual and distal canals. Instrumentation efficiency but also transportation using the TF Adaptive file system can be higher among expert, compared to novice, operators, depending on the canal type. [ABSTRACT FROM AUTHOR]

Rotary root canal instruments manufactured from nickel-titanium alloy have proved to be a valuable adjunct for root canal therapy. Over the past two decades, instrument design has been considerably modified; progress has been made in manufacturing, as well as alloy processing. Clinical procedures and ideal working parameters are still being refined as new instruments continue to be introduced to the market. This review is intended to summarize clinical and laboratory findings for several current instruments. Some guidelines and usage parameters are also detailed. [ABSTRACT FROM AUTHOR]

Introduction The aim of this study was to assess differences in cyclic fatigue (CF) life of contemporary heat-treated nickel-titanium rotary instruments at room and body temperatures and to document corresponding phase transformations. Methods Forty Hyflex EDM (H-EDM) files (Coltene, Cuyahoga Falls, OH [#25/.08, manufactured by electrical discharge machining]) and 40 TRUShape (TS) files (Dentsply Tulsa Dental Specialties, Tulsa, OK [#25/.06v, manufactured by grinding and shape setting]) were divided into 2 groups ( n = 20) for CF resistance tests in a water bath either at room (22°C ± 0.5°C) or body temperature (37°C ± 0.5°C). Instruments were rotated in a simulated canal (angle = 60°, radius = 3 mm, and center of the curvature 5 mm from the tip) until fracture occurred. The motor was controlled by an electric circuit that was interrupted after instrument fracture. The mean half-life and beta and eta Weibull parameters were determined and compared. Two instruments of each brand were subjected to differential scanning calorimetry (DSC). Results While TS instruments lasted significantly longer at room temperature (mean life = 234.7 seconds; 95% confidence interval [CI], 209–263.6) than at body temperature (mean life = 83.2 seconds; 95% CI, 76–91.1), temperature did not affect H-EDM behavior (room temperature mean life = 725.4 seconds; 95% CI, 658.8–798.8 and body temperature mean life = 717.9 seconds; 95% CI, 636.8–809.3). H-EDM instruments significantly outlasted TS instruments at both temperatures. At body temperature, TS was predominantly austenitic, whereas H-EDM was martensitic or in R-phase. TS was in a mixed austenitic/martensitic phase at 22°C, whereas H-EDM was in the same state as at 37°C. Conclusions H-EDM had a longer fatigue life than TS, which showed a marked decrease in fatigue life at body temperature; neither the life span nor the state of the microstructure in the DSC differed for H-EDM between room or body temperature. [ABSTRACT FROM AUTHOR]

Abstract: The purpose of this study was to assess the geometry of non‐round root canals after preparation with TRUShape (a novel instrument with s‐shaped longitudinal design) in comparison to conventional rotary instrumentation using micro‐computed tomography. Twenty distal root canals of mandibular molars were randomly distributed in two groups to be shaped with either TRUShape or Vortex rotaries. Percentages of unprepared surface and volume of dentin removal for the entire canal and for the apical 4 mm were calculated. Canal transportation and the structure model index (SMI) were assessed. Data were compared with Student t‐tests. Shaping with both techniques resulted in similar prepared surface and volume of dentin removed, as well as the extent of canal transportation. The SMI shape factor was significantly lower for TRUShape preparations (P = 0.04) suggesting less rounding during rotary preparation. Although both instruments were suitable for the preparation of oval canals, TRUShape appeared to better conform to the original ribbon‐shaped anatomy. [ABSTRACT FROM AUTHOR]

Objectives: The aim of the present study was to evaluate cytotoxic effects and cytokine production of calcium silicate-based sealers (EndoSeal, EndoSequence BC Sealer, and MTA Fillapex) using an in vitro root canal filling model and three-dimensional (3D) cell culture. AH Plus as a reference was compared to contemporary calcium silicate cements regarding cell viability and cytokine production. Material and methods: Root canals of 30 human maxillary incisors were prepared using a single-file reciprocating technique. The samples were randomly distributed and canals filled with either AH Plus, EndoSeal, EndoSequence BC Sealer, and MTA Fillapex ( n = 6). In the negative control group, the root canal remained unfilled. Sealers were placed into the canals along with a gutta-percha cone placed to working length. Balb/c 3T3 fibroblasts, cultured in a type I collagen 3D scaffold, were exposed to filling material and the respective root apex for 24 h. Cytocompatibility of the materials was evaluated using the methyl-thiazoldiphenyl-tetrazolium (MTT) assay. The production of IL-1β, IL-6, and IL-8 was analyzed using enzyme-linked immunosorbent assay (ELISA). One-way analysis of variance was performed, and when the F-ratios were significant, data were compared by Duncan's multiple-range test. The alpha-type error was set at 0.05. Results: EndoSeal, Endosequence BC Sealer and AH Plus showed cell viability that was similar to the negative control group ( P > 0.05), while MTA Fillapex sealer was cytotoxic ( P < 0.05). Varying production of IL-1β, IL-6, and IL-8 was detected in all samples. Conclusions: In an in vitro root canal filling model with 3D cell culture, AH Plus, EndoSeal, and EndoSequence BC Sealer were cytocompatible. Clinical relevance: These results may suggest that AH Plus, EndoSeal and EndoSequence BC Sealer may achieve better biological response when compared to MTA Fillapex. [ABSTRACT FROM AUTHOR]

Introduction The purpose of this study was to assess the ex vivo torsional performance of a novel rotary system in small root canals after 2 different glide path preparations. Methods Each independent canal of 8 mesial roots of mandibular molars was randomly assigned to achieve a reproducible glide path with a new set of either PathFile #1 (Dentsply Maillefer, Ballaigues, Switzerland) and #2 or ProGlider (Dentsply Maillefer) after negotiation with a 10 K-file. After glide path preparation, root canals in both groups were shaped with the same sequence of ProTaper Gold (Dentsply Tulsa Dental Specialties, Tulsa, OK) following the directions for use recommended by the manufacturer. A total of 16 new sets of each instrument of the ProTaper Gold (PTG) system were used. The tests were run in a standardized fashion in a torque-testing platform. Peak torque (Ncm) and force (N) were registered during the shaping procedure and compared with Student t tests after normal distribution of data was confirmed. Results No significant differences were found for any of the instruments in peak torque or force after the 2 different glide path preparations ( P > .05). Data presented in this study also serve as a basis for the recommended torque for the use of PTG instruments. Conclusions Under the conditions of this study, differences in the torsional performance of PTG rotary instruments after 2 different glide path preparations could not be shown. The different geometry of glide path rotary systems seemed to have no effect on peak torque and force induced by PTG rotary instruments when shaping small root canals in extracted teeth. [ABSTRACT FROM AUTHOR]

Objectives: In endodontic practice, clinicians should be aware of possible root canal anatomic variations. The aim of this study was to assess using CBCT acquisitions regarding whether one root canal anatomy of a tooth is associated with a specific anatomy of another tooth. Methods: A total of 106 CBCT acquisitions were obtained using a CBCT scanner with 200μm voxel size. Numbers of roots and canals of the entire dentition were described. Bivariate analyses and logistic regressions were conducted to explore root canal anatomy on one tooth according to age, gender, jaw, side and the others teeth. Multiple correspondence analysis (MCA) was performed to correlate the different numbers of canals profiles. Results: A total of 2424 teeth were analyzed. Independently from the other variables, the presence of an additional root canal on a mandibular incisor increases the risk of having an additional root canal on a mandibular premolar (OR [95%] 3.7 [1.0;13.2]). The mandibular molar variability increases in women compared to men (OR [95%] 0.4 [0.1; 0.9]). MCA showed correspondence between 2-canals maxillary incisor and canines and 5-canals maxillary molars, and some correlation between additional canal on maxillary and mandibular premolars. Conclusions: Although CBCT examinations are conducted in the first intention of making a diagnosis or prognostic evaluation, medium FOV acquisitions could be used as an initial database thus furnishing preliminary evaluations and information. In endodontic practice, clinicians should be aware of possible root canal anatomic variations. The visualization of all canals is considered essential in endodontic therapy. The use of multi-correspondence analysis for statistics in endodontic research is a new approach as a prognostic tool. [ABSTRACT FROM AUTHOR]

A new rotary instrument has been developed to simplify the glide path preparation in root canals before shaping procedures. The purpose of this study was to compare the peak torque and force induced by nickel-titanium PathFile multiple-instrument system and the recently developed M-Wire ProGlider single instrument during glide path preparation of mesial root canals in extracted mandibular molars. Each independent canal of eight mesial roots of mandibular molars was randomly assigned to achieve a reproducible glide path with a new set of either PathFile #1 and #2 or ProGlider after negotiation with a 10 K-file. Tests were run in a standardized fashion using a torque-testing platform. Peak torque (N cm) and force (N) were registered and analysis of variance and Tukey post-hoc tests were applied. Preliminary data for stationary torque at failure were also obtained and compared with peak torque for each instrument. PathFile #1 and #2 instruments showed statistically lower peak torque ( p = 0.001) and peak force ( p = 0.008) than ProGlider. Torque at failure according to ADA No. 28/ISO 36030-1 was not significantly different from peak torque during glide path preparation for ProGlider instruments while it was significantly higher for PathFile #1 and #2 ( p < 0.001). Under the conditions of this study, PathFile instruments developed significant lower peak torque and force during glide path preparation compared to ProGlider, which is possibly subjected to a greater contact with the canal walls due to the increase in its flute diameter at middle and coronal levels. [ABSTRACT FROM AUTHOR]

Introduction New designs and alloys have been developed to increase cyclic fatigue (CF) resistance of rotary files. The aim of this study was to compare CF resistance of ProTaper Universal (PTU; Dentsply Tulsa Dental, Tulsa, OK) and ProTaper Next (PTN, Dentsply Tulsa Dental) instruments at different points of curvature. Methods A total of 420 files (240 PTU, S1, F1, F2, and F3 and 180 PTN, X1, X2, and X3) were divided in 14 groups of 30 instruments each. Instruments in groups S1-5, F1-5, X1-5, F2-5, X2-5, F3-5, and X3-5 were tested at 5 mm from the tip. Groups S1-12, X1-12, and F1-12 were tested at 12 mm from the tip because S1, X1, and F1 instruments have the same diameter at that level. Groups F2-8, X2-8, F3-8, and X3-8 were tested at 8 mm (F2/X2 and F3/X3, respectively, had the same diameter at 8 mm). All files were rotated at 300 rpm until fracture. CF resistance was tested in stainless steel curved canals (60°, r = 3 mm). Time to fracture was recorded. The mean half-life and beta and eta were calculated for each group and were compared with Weibull analysis. Results PTN instruments will last significantly longer than PTU files with a probability higher than 98% at all tested levels except for S1, which was the significantly the most resistant instrument to CF at 5 mm from the tip. Conclusions PTU S1 was significantly the most resistant instrument at 5 mm from the tip. PTN files were significantly more resistant to CF than PTU instruments at all the other tested levels. [ABSTRACT FROM AUTHOR]

Abstract: Introduction: Many clinicians use household bleach to irrigate root canals. Sodium hypochlorite solutions are also available from dental suppliers. We compared physicochemical features of these products and investigated their impact on pulp tissue dissolution. Methods: Six different brands of household bleach were bought from drugstores. These were compared with Chlor-XTRA and technical NaOCl solutions of controlled concentration and alkalinity regarding their chlorine content (wt% NaOCl), pH, alkaline capacity, osmolarity, surface tension (Wilhelmy plate method), and price. Bovine pulp tissue (n = 10 specimens per group) dissolution at 37°C by test and control solutions adjusted to 1.0% NaOCl was assessed. Reduction in tissue weight was compared between groups by one-way analysis of variance, followed by Bonferroni correction (P < .05). Results: The pH of undiluted solutions ranged between 11.1 and 12.7. Batches of the same product differed in NaOCl content. No product contained more than an equivalent of 0.1 mol/L NaOH. One household bleach brand (Safeway Bleach Summit Fresh) was slightly alkalized; the other solutions under investigation were not. Osmolarity was similar between products. The surface tension of Chlor-XTRA and Safeway Bleach Summit Fresh was about half that of the other solutions. Tissue dissolution was statistically similar (P > .05) among all solutions. Price was about 100-fold higher per liter of Chlor-XTRA compared with household bleach. Conclusions: Other than its price, the Chlor-XTRA solution had no unique features. In contrast to an earlier report, reduced surface tension did not result in greater soft tissue dissolution by NaOCl. [Copyright &y& Elsevier]

Abstract: Introduction: The aim of this study was to evaluate the radiographic features of permanent three-rooted mandibular first molars with radix entomolaris (RE), investigate the correlation between anatomical classification and radiographic type of RE, and to determine the most effective horizontal beam angulation for the diagnosis of RE. Methods: Twenty-five extracted mandibular first permanent molars with RE were selected for taking radiographs in 7 horizontal angulations. By using set criteria, 3 evaluators assessed morphologic and radiographic features of the RE and optimum beam angulation for RE diagnosis. Intraexaminer variability was analyzed with Cohen kappa test. Results: Three types of curvature of RE presented with 3 distinct types of typical radiographic appearance on orthoradial radiographs. We classified the radiographic features of RE into 3 types, as follows: type i, type ii, and type iii. Seven teeth showed type i radiographic features. Zero-degree, 5-degree, 15-degree, and 25-degree radiographs were significantly better than the mesially angulated –15-degree and –25-degree images for detecting the type i RE images (P < .05). Fifteen-degree, 25-degree, and –25-degree horizontal beam angulations showed significantly more accurate diagnoses of RE in 8 type ii images (P < .05). Only 25-degree–angled radiographs were found to have a high diagnostic yield of type iii RE images (P < .05). A significant correlation was found between morphologic and radiographic types of RE (P < .05, contingency coefficient = 0.473). Intraexaminer variability was low, with kappa = 0.68 (P < .05). Conclusions: RE presents 3 types of typical radiographic features on orthoradial radiographs. Additional 25-degree mesial horizontal-angled radiographs are essential for preoperative identification and evaluation of RE, especially types ii and iii. [Copyright &y& Elsevier]

Abstract: Introduction: This study set out to compare the efficacy of laser-activated and ultrasonically activated root canal disinfection with conventional irrigation, specifically its ability to remove bacterial film formed on root canal walls. Methods: Seventy human premolars were shaped to an apical size #20, taper .07, sterilized, and contaminated in situ with oral bacteria for 1 week and incubated for 2 more weeks. Irrigation was done with 6% NaOCl (group 1), NaOCl ultrasonically activated with blunt inserts (group 2), or a pulsed erbium:YAG laser at nonablative settings (group 3) for a total of 60 seconds each. Positive and negative controls were also included. Aerobic bacterial sampling was performed, and the incidence of positive samples after 24 and 48 hours as well as bacterial counts (colony-forming units) were determined. Fixed and demineralized sections 1 mm and 4 mm off the apex were Brown-Brenn stained and assessed for remaining intracanal bacteria/biofilm and dentinal tubule penetration. Results: All 3 canal disinfection protocols significantly reduced bacterial counts (P < .001). None of the 3 techniques predictably generated negative samples, but laser-activated disinfection was superior to the other 2 techniques in this aspect (P < .05). Histologic sections showed variable remaining bacterial presence in dentinal tubules at the 4-mm level and significantly less bacterial biofilm/necrotic tissue remaining at the 1-mm level after laser-activated irrigation (P < .05). Conclusions: Under the conditions of this combined in situ/in vitro study, activated disinfection did not completely remove bacteria from the apical root canal third and infected dentinal tubules. However, the fact that laser activation generated more negative bacterial samples and left less apical bacteria/biofilm than ultrasonic activation warrants further investigation. [Copyright &y& Elsevier]

Abstract: Introduction: This study investigated the torsional properties of new and used Revo-S Shaping Universal (SU) endodontic instruments. Methods: Torsional profiles were established following the American National Standards Institute/American Dental Association Specification No. 28. Unused SU instruments (group 1, control; n = 30) and instruments used in simulated root canals twice (group 2, n = 30) or six times (group 3, n = 30) were tested. Analysis of variance with the Bonferroni/Dunn post hoc test (α = 0.05) was used to analyze the torque and angle of rotation at fracture. Results: The maximum torque at fracture did not differ significantly among instruments in group 1 and groups 2 and 3. The angle of rotation at fracture decreased significantly (P < .01) from group 1 to groups 2 and 3. Conclusions: The repeated use of the SU rotary instruments significantly reduced the angle of rotation at fracture but did not reduce the torque at fracture. [Copyright &y& Elsevier]

Abstract: Introduction: The aim of this study was to assess the shaping potential of a novel nickel-titanium instrument, the self-adjusting file (SAF), in long oval root canals in distal roots in mandibular molars. Methods: Twenty mandibular molars with long oval distal root canals were selected and scanned preoperatively and postoperatively by using micro–computed tomography at an original resolution of 20 μm. Canals were shaped with the SAF, three-dimensionally reconstructed, and evaluated for volume, surface area, canal transportation, and prepared surface. Data were statistically contrasted by using paired t tests and regression analysis. Results: Preoperatively, canal volume was 7.73 ± 2.13 mm3, and canal area was 42.83 ± 8.14 mm2. Volumes and surface areas increased significantly (P < .001) by 4.84 ± 1.73 mm3 and 3.34 ± 1.73 mm2, respectively, and no gross preparation errors were detected. Unprepared canal surface varied between individual canals, and mean unprepared surface was 23.5% ± 8.9%. Prepared areas were significantly larger compared with rotary canal preparation done in a previous study. Canal transportation scores were higher in the coronal root canal third (106 ± 50 μm) compared with the apical third (81 ± 49 μm). Conclusions: In vitro, preparation of long oval-shaped root canals in mandibular molars with the SAF was effective and safe. Moreover, shapes generated with the SAF were more complete compared with rotary canal preparation. [Copyright &y& Elsevier]

Abstract: Introduction: The aim of this part of an ongoing study was to describe the dentin removal ability of a novel nickel-titanium instrument, the self-adjusting file (SAF), by using micro–computed tomography. Methods: Twenty maxillary incisors were scanned preoperatively at 20-μm resolution and postoperatively after up to 6 minutes of preparation with an SAF with 1.5-mm or 2-mm diameter. SAFs were operated with continuous irrigation in a handpiece that provided an oscillating, in-and-out movement. Changes in canal volume compared with preoperative values as well as unprepared canal surface area were determined. Data were normally distributed and compared by analysis of variance and regression analyses. Results: Preoperatively canal volumes were statistically similar in both groups (9.86 ± 3.97 mm3 and 9.80 ± 2.67 mm3). Volumes increased during preparation to 13.58 ± 3.85 mm3 (after 6 minutes with SAF 1.5 mm) and 16.43 ± 3.64 mm3 (after 5 minutes with SAF 2.0 mm), and overall canal shapes were adequate. Unprepared canal surface area decreased from 63.0% ± 15.1% (2 minutes with SAF 1.5 mm) to 8.6% ± 4.1% (5 minutes with SAF 2.0 mm). Conclusions: Preparation of straight root canals in maxillary anterior teeth left little canal surface uninstrumented after shaping with the SAF. The timeframe of clinical application will depend on the amount of desired dentin removal and done with an SAF selected on the basis of apical gauging. [Copyright &y& Elsevier]

Abstract: Introduction: This study evaluated the prepared surface areas of oval-shaped canals in distal roots of mandibular molars using four different instrumentation techniques. Methods: Teeth were prescanned and reconstructed using micro–computed tomography (MCT) scans at low resolution (68 μm). Forty-eight molars with ribbon-shaped/oval distal root canals were selected and randomly assigned to four groups. Distal canals (n = 12 each) were prepared by circumferential filing using Hedström files to apical size #40 (group H/CF); with ProTaper nickel-titanium rotaries to finishing file 4 (F4) considering the distal canal as 1 canal (group PT/1); ProTaper to F4 considering buccal and oral aspects of the distal canal as 2 individual canals (group PT/2); ProTaper to F4 in a circumferential filing motion (PT/CF). Before and after shaping, teeth were evaluated using MCT at 34-μm resolution. The percentage of prepared surface was assessed for the full canal length and the apical 4 mm. Statistical analysis was performed using analysis of variance and Bonferroni/Dunn multiple comparisons. Results: Preoperatively, canal anatomy was statistically similar among the groups (p = 0.56). Mean (± standard deviation) untreated areas ranged from 59.6% (±14.9, group PT/2) to 79.9% (±10.3, PT/1) for the total canal length and 65.2% to 74.7% for the apical canal portion, respectively. Canals in group PT/1 had greater untreated surface areas (p < 0.01) than groups PT/2 and PT/CF. Among all groups, amounts of treated surface areas were statistically similar in the apical 4 mm. Conclusions: Preparations of oval-shaped root canals in mandibular molars left a variable portion of surface area unprepared regardless of the instrumentation technique used. However, considering oval canals as two separate entities during preparation appeared to be beneficial in increasing overall prepared surface. [Copyright &y& Elsevier]

Abstract: Introduction: The purpose of this study was to assess canal preparation outcomes in vitro by novice clinicians after standardized teaching sessions. Methods: All students received a training session. In experiment 1, twenty canals of mandibular molars were prepared with GT and ProTaper rotaries by 10 students. Standardized radiographs were exposed before and after canal preparation, and canal curvature was measured; canals were assessed for patency and preparation time. In experiment 2, mandibular molars (20 canals) were submitted to microcomputed tomography before and after canal preparation with ProTaper and GT rotaries by 2 dental students. Canals were metrically assessed for changes (volume, surface, cross-sectional shape, transportation) during canal preparation by using software. Results: In experiment 1, canal curvature decreased by 7.6° and 7.8° for GT and ProTaper preparations; there were no broken instruments, and 2 canals lost patency. The time for GT preparation was longer than for ProTaper (29.7 ± 6.8 vs 19.4 ± 8.1 minutes, P <.05). In experiment 2, canal volumes and surface areas increased (P < .001), and prepared canals were rounder in cross-section and more tapered. Mean canal transportation ranged between 0.14 ± 0.05 mm and 0.23 ± 0.09 mm for apical and coronal canal thirds. There were no significant differences between the instruments or the operators regarding center of mass shifts; qualitative and quantitative data for canal transportation were similar to earlier studies with experienced operators. Conclusions: Both rotary instruments performed adequately with inexperienced operators who received a brief structured training session. [Copyright &y& Elsevier]

Abstract: Introduction: Usage of U.S. endodontists regarding rotary root canal instruments is not well-documented. Therefore, the aim of this study was to retrieve data from a representative sample of endodontists regarding contemporary usage of rotary instruments. Methods: A questionnaire addressing (1) nickel-titanium (NiTi) rotary instrument usage and (2) expectations for future instrument design was constructed. An online survey was e-mailed to 954 endodontists in California (n = 358), Iowa (n = 25), Massachusetts (n = 120), Minnesota (n = 49), New York (n = 217), Texas (n = 144), and Wisconsin (n = 41). Data were collected from respondents by using a web-based interface during a 4-month period. Valid responses were received from 359 endodontists, representing a 38% response rate. Chi-square tests and correlation coefficients were used to analyze the data; the level of significance was set at .05. Results: Usages varied by region, graduation date, and type of practice. Recent graduates were more likely to use NiTi rotary instruments for every treatment (P = .007), multiple NiTi systems (P = .002), torque control motors (P = .03), and Gates Glidden instruments (P = .001) than were older endodontists. More than 50% of respondents used NiTi rotary instruments in several patients before discarding, and 57% reported cleaning the instruments with a combination of ultrasonics and sterilization. Crown-down was the most frequently used preparation strategy. There were few differences regarding geographic regions. More than 70% of respondents expected similar but improved files during the next 10 years. Conclusions: Differences exist among U.S. endodontists regarding current NiTi instrument use, and expectations for future development might be correlated with level of exposure and training. [Copyright &y& Elsevier]

Abstract: The purpose of this study was to customize an application framework by using the MeVisLab image processing and visualization platform for three-dimensional reconstruction and assessment of tooth and root canal morphology. One maxillary first molar was scanned before and after preparation with ProTaper by using micro–computed tomography. With a customized application framework based on MeVisLab, internal and external anatomy was reconstructed. Furthermore, the dimensions of root canal and radicular dentin were quantified, and effects of canal preparation were assessed. Finally, a virtual preparation with risk analysis was performed to simulate the removal of a broken instrument. This application framework provided an economical platform and met current requirements of endodontic research. The broad-based use of high-quality free software and the resulting exchange of experience might help to improve the quality of endodontic research with micro–computed tomography. [Copyright &y& Elsevier]

Abstract: Surface modifications of nickel-titanium instruments such as electropolishing may reduce fracture incidence but could potentially alter the instruments'' mechanical properties. We studied the impact of two surface types, machined and electropolished, of ProTaper shaping files on torque and force during simulated root canal preparation. Pilot holes of 0.5-mm diameter were drilled perpendicularly through 3-mm thick human dentin discs and served as standardized simulated root canals (SSRCs). A total of 300 SSRCs were prepared with ProTaper Sx, S1, and S2 instruments using an automated testing platform. Maximum torque (in Ncm) and maximum force values (in N) were measured. In three experimental groups (Sx, S1, and S2) preparation of SSRCs was performed using electropolished versus machined instruments in the same dentin disc. For all three tested instruments, peak torque was higher for electropolished files; apically exerted forces were similar, except for Sx, in which machined instruments developed higher forces. We conclude that surface treatment by electropolishing alters the cutting ability of nickel-titanium rotary instruments. [Copyright &y& Elsevier]

Abstract: In the current study, the impact of lubricant parameters on simulated root canal instrumentation was investigated. Using size 30 ProFile .06 instruments in milled artificial root canals in human dentin, the effects of sodium hypochlorite (1% NaOCl) and a chelator (18% etidronic acid) in aqueous irrigants on maximum torque, full torsional load, and maximum force values were gauged using a torque testing platform. Furthermore, the impact of the time a chelating lubricant was exposed to dentin as well as its galenic form (aqueous vs. gel-type) on the above outcome variables was evaluated. Aqueous lubricants significantly (p < 0.05, ANOVA, Newman–Keuls) reduced all outcome variables compared to dry conditions. The incorporation of a chelator further reduced these values (p < 0.05), whereas hypochlorite behaved similar to water. The chelator effect was immediate and did not increase with time. An aqueous lubricant was more beneficial than a gel-type counterpart. [Copyright &y& Elsevier]

Preparation of root canal systems includes both enlargement and shaping of the complex endodontic space together with its disinfection. A variety of instruments and techniques have been developed and described for this critical stage of root canal treatment. Although many reports on root canal preparation can be found in the literature, definitive scientific evidence on the quality and clinical appropriateness of different instruments and techniques remains elusive. To a large extent this is because of methodological problems, making comparisons among different investigations difficult if not impossible. The first section of this paper discusses the main problems with the methodology of research relating to root canal preparation while the remaining section critically reviews current endodontic instruments and shaping techniques. [ABSTRACT FROM AUTHOR]

Nickel-titanium rotary instruments are important adjuncts in endodontic therapy. This review attempts to identify factors that influence shaping outcomes with these files, such as preoperative root-canal anatomy and instrument tip design. Other, less significant factors include operator experience, rotational speed, and specific instrument sequence. Implications of various working length definitions and desired apical widths are correlated with clinical results. Despite the existence of one ever-present risk factor, dental anatomy, shaping outcomes with nickel-titanium rotary instruments are mostly predictable. Current evidence indicates that wider apical preparations are feasible. Nickel-titanium rotary instruments require a preclinical training period to minimize separation risks and should be used to case-related working lengths and apical widths. However, and despite superior in vitro results, randomized, clinical trials are required to evaluate outcomes when using nickel-titanium instruments. [Copyright &y& Elsevier]

The author reflects on the procedural mishaps and complications during root canal treatment and other endodontic therapy. He says that the technical nature of error causes biological problems that leads to the failure of the treatment. He discusses ledging, perforation on access, rotary instrument fracture, safe and effective irrigation, and vertical root fracture as factors to be considered in root canal treatment. He also mentions dentin, endodentic procedures, and longitudinal root fractures.

The aim of the current project was to study the antimicrobial efficacy of a newly developed irrigant, k21/E against E. faecalis biofilm. Root canals were instrumented and randomly divided into the following groups: irrigation with saline, 6% NaOCl (sodium hypochlorite), 6% NaOCl + 2% CHX (Chlorhexidine), 2% CHX, 0.5% k21/E (k21 - quaternary ammonium silane) and 1% k21/E. E. faecalis were grown (3-days) (1 × 107 CFU mL−1), treated, and further cultured for 11-days. Specimens were subjected to SEM, confocal and Raman analysis and macrophage vesicles characterized along with effect of lipopolysaccharide treatment. 3T3 mouse-fibroblasts were cultured for alizarin-red with Sortase-A active sites and Schrödinger docking was performed. TEM analysis of root dentin substrate with matrix metalloproteinases profilometry was also included. A cytotoxic test analysis for cell viability was measured by absorbance of human dental pulp cells after exposure to different irrigant solutions for 24 h. The test percentages have been highlighted in Table 1. Among experimental groups, irrigation with 0.5% k21/E showed phase separation revealing significant bacterial reduction and lower phenylalanine 1003 cm−1 and Amide III 1245 cm−1 intensities. Damage was observed on bacterial cell membrane after use of k21/E. No difference in exosomes distribution between control and 0.5%k21/E was observed with less TNFα (*p < 0.05) and preferential binding of SrtA. TEM images demonstrated integrated collagen fibers in control and 0.5%k21/E specimens and inner bacterial membrane damage after k21/E treatment. The k21 groups appeared to be biocompatible to the dental pulpal cells grown for 24 h. Current investigations highlight potential advantages of 0.5% k21/E as irrigation solution for root canal disinfection. [ABSTRACT FROM AUTHOR]