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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. 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%. 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. 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. [ABSTRACT FROM AUTHOR]

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. 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%. 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. 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. [ABSTRACT FROM AUTHOR]

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. 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. 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. 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. [ABSTRACT FROM AUTHOR]

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. 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. 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). 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. [ABSTRACT FROM AUTHOR]

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. 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. 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. 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. [ABSTRACT FROM AUTHOR]

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

Abstract 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. Highlights • Environmental temperature may drastically affect the cyclic fatigue resistance of nickel-titanium files. • Reciproc Blue instruments were statistically more resistant to cyclic fatigue than Reciproc M-Wire at all the temperature conditions tested. • The fatigue resistance of both file types tested was proportionally higher as the environmental temperature decreased (0°C > 20°C > 35°C > 39°C), with differences ranging from 35%–421%. • The 2 different instruments analyzed displayed different transformation temperatures. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Introduction The purpose of this study was to compare the formation of microcracks after canal preparation performed with different single-file systems as One Shape (Micro-Mega, Besancon, Cedex, France), F6 SkyTaper (Komet Italia Srl, Milan, Italy), HyFlex EDM (Coltene/Whaledent AG, Altstatten, Switzerland), WaveOne (Dentsply Maillefer, Ballaigues, Switzerland), Reciproc (VDW, Munich, Germany), and WaveOne Gold (Dentsply Maillefer). Methods Eighty-four human extracted mandibular central incisors (40–60 y) were selected and divided into 6 experimental groups ( n = 12 teeth) and a control group (unprepared teeth): One Shape (group 1), F6 SkyTaper (group 2), HyFlex EDM (group 3), WaveOne (group 4), Reciproc (group 5), and WaveOne Gold (group 6). Roots were then sectioned at 3, 6, and 9 mm from the apex, and the surface was observed under a stereomicroscope. Data were analyzed using logistic regression ( P < .05). Results No cracks were observed in the control group. All the systems tested caused cracks, mainly in the apical section (3 mm). HyFlex EDM (33.3%) and WaveOne Gold (58.3%) showed fewer microcracks than other experimental groups ( P < .01); however, no significant difference was found between them in crack formation ( P > .05). There was no difference among the other experimental groups ( P > .05). Conclusions All the instruments tested created dentinal cracks. Within the limitations of this study, the flexibility of nickel-titanium instruments because of heat treatment seems to have a significant influence on dentinal crack formation. HyFlex EDM and WaveOne Gold caused less microcracks than the other instruments tested. [ABSTRACT FROM AUTHOR]

Introduction: The purpose of this study was to evaluate the torsional and cyclic fatigue resistance of the new Hyflex EDM OneFile (Coltene/Whaledent AG, Altstatten, Switzerland) manufactured by electrical discharge machining and compare the findings with the ones of Reciproc R25 (VDW, Munich, Germany) and WaveOne Primary (Dentsply Maillefer, Ballaigues, Switzerland). Methods: One hundred-twenty new Hyflex EDM One- File (#25/0.08), Reciproc R25, and WaveOne Primary files were used. Torque and angle of rotation at failure of new instruments (n = 20) were measured according to ISO 3630-1 for each brand. Cyclic fatigue resistance was tested measuring the number of cycles to failure in an artificial stainless steel canal with a 60° angle and a 3-mm radius of curvature. Data were analyzed using the analysis of variance test and the Student- Newman-Keuls test for multiple comparisons. The fracture surface of each fragment was examined with a scanning electron microscope. Results: The cyclic fatigue of Hyflex EDM was significantly higher than the one of Reciproc R25 and WaveOne Primary (P < .05 and P < .001, respectively). Hyflex EDM showed a lower maximum torque load (P < .05) but a significantly higher angular rotation (P < .0001) to fracture than Reciproc R25 and WaveOne Primary. No significant difference was found comparing the maximum torque load, angular rotation, and cyclic fatigue of Reciproc R25 and WaveOne Primary (P > .05). Conclusions: The new Hyflex EDM instruments (controlled memory wire) have higher cyclic fatigue resistance and angle of rotation to fracture but lower torque to failure than Reciproc R25 and WaveOne Primary files (M-wire for both files). [ABSTRACT FROM AUTHOR]

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

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]

Abstract: Introduction: The aim of the present study was to use cone-beam computed tomography (CBCT) to analyze root canal anatomy and symmetry of maxillary and mandibular first and second molar teeth of a white population. Methods: A total of 201 patients who required CBCT examinations as part of their dental diagnosis and treatment were enrolled in the present study. Overall, 596 healthy, untreated, well-developed maxillary and mandibular molar teeth (161 maxillary first molars, 157 maxillary second molars, 117 mandibular first molars, and 161 mandibular second molars) were examined by CBCT to establish the symmetry in root and canal anatomy between right and left sides in the same patient by evaluating the number of roots and root canals and the root canal configuration. Results: Three separate roots with 3 separate canals was the normal anatomy of maxillary first and second molars. Most mandibular first and second molars had 2 separate roots, and the majority had 3 canals. In the present study, first molars, both maxillary and mandibular, exhibited greater asymmetry than the second molars. Maxillary first molars were found to be symmetrical in 71.1% of patients, whereas maxillary second molars were symmetrical in 79.6%. The remaining 28.9% and 20.4% of patients, respectively, showed asymmetry. Around 30% of the mandibular first molars and 20% of the mandibular second molars showed asymmetry. Conclusions: The results of the present study reported a percentage of symmetry that varied from 70%–81%. These variations in symmetry should be taken in high consideration when treating 2 opposite molars in the same patient, because their anatomy may be different in up to 30% of the cases. [Copyright &y& Elsevier]

Abstract: Introduction: The aim of this study was to evaluate the resistance to flexural fatigue of Reciproc R25 (VDW, Munich, Germany), WaveOne Primary (VDW, Munich, Germany), Mtwo (Sweden & Martina, Padova, Italy), and Twisted File (TF; SybronEndo, Orange, CA) instruments used in continuous rotation or in 2 different reciprocating motions. Methods: A total of 180 nickel-titanium files from 4 brands marketed, 2 for use in reciprocating motion (ie, Reciproc R25 and WaveOne Primary) and 2 for use in continuous rotation (ie, Mtwo and TF both taper .06/0.25 tip diameter), were tested. Forty-five instruments for each brand were divided into 3 groups (n = 15) on the basis of the motion tested: continuous rotation (group 1: 300 rpm) and reciprocal motion (group 2: “RECIPROC ALL” mode and group 3: “WAVEONE ALL” mode). The resistance to cyclic fatigue was determined by counting the number of cycles to failure in a 60° curve with a 5-mm radius. Data were analyzed through 2-way analyses of variance. Results: The cyclic fatigue resistance of the 2 reciprocating motion instruments (ie, “RECIPROC ALL” and “WAVEONE ALL”) was significantly higher than the continuous rotation in each brand (P < .001). No significant difference was observed in cyclic fatigue between the 2 different reciprocal motions tested in each brand (P > .05). When considering the appropriate clinical motion for each brand, no significant difference in cyclic fatigue was found between TF, Mtwo, and Reciproc R25 instruments, whereas the cyclic fatigue resistance of WaveOne files was less than the other 3 brands (P < .05). Conclusions: Reciprocal motion showed a significantly higher cyclic fatigue resistance in all brands compared with continuous rotation. No differences were found between the 2 reciprocating motions. [Copyright &y& Elsevier]

Abstract: Introduction: The purpose of this study was to evaluate the effect of autoclave sterilization on cyclic fatigue resistance of rotary endodontic instruments made of traditional and new nickel-titanium (NiTi) alloys. Methods: Four NiTi rotary endodontic instruments of the same size (tip diameter 0.40 mm and constant .04 taper) were selected: K3, Mtwo, Vortex, and K3 XF prototypes. Each group was then divided into 2 subgroups, unsterilized instruments and sterilized instruments. The sterilized instruments were subjected to 10 cycles of autoclave sterilization. Twelve files from each different subgroup were tested for cyclic fatigue resistance. Means and standard deviations of number of cycles to failure (NCF) and fragment length of the fractured tip were calculated for each group, and data were statistically analyzed (P < .05). Results: Comparing the results between unsterilized and sterilized instruments for each type of file, differences were statistically significant (P < .05) only between sterilized and unsterilized K3XF files (762 versus 651 NCF). The other instruments did not show significant differences (P > .05) in the mean NCF as a result of sterilization cycles (K3, 424 versus 439 NCF; Mtwo, 409 versus 419 NCF; Vortex, 454 versus 480 NCF). Comparing the results among the different groups, K3 XF (either sterilized or not) showed a mean NCF significantly higher than all other files (P < .05). Conclusions: Repeated cycles of autoclave sterilization do not seem to influence the mechanical properties of NiTi endodontic instruments except for the K3 XF prototypes of rotary instruments that demonstrated a significant increase of cyclic fatigue resistance. [Copyright &y& Elsevier]

Abstract: Introduction: The purpose of this study was to assess the resistance to cyclic fatigue of three nickel-titanium (NiTi) files after the immersion in sodium hypochlorite (NaOCl) solution in conditions similar to those used in clinical practice. Methods: A total of 150 new Twisted Files (SybronEndo, Orange, CA), Revo S SU files (Micro Mega, Besancon, France), and Mtwo files (Sweden and Martina, Padova, Italy), size 25.06, were tested. Fifty files of the same brand were randomly assigned to five groups (n = 10) and submitted to the following immersion protocol in 5% NaOCl at 37°C for 16 mm: no immersion (control), 5 minutes statically, 1 minute statically, 5 minutes dynamically (300 rpm/min), and 1 minute dynamically. Resistance to cyclic fatigue was determined by counting the numbers of cycles to failure in a 60° curve with a 5-mm radius. Data were analyzed by two-way analyses of variance. Results: Resistance to cyclic fatigue of the same NiTi file was not significantly affected by immersion in NaOCl (P > .05). The Twisted File showed a higher resistance in all groups than Revo S SU (P < .001). The comparison between the same groups of Twisted Files and Mtwo files or between Mtwo and Revo S files did not show significant differences (P > .05) except for two cases: group 2 of the Twisted Files and Mtwo files and group 5 of the Mtwo and Revo S SU files (P < .05). Conclusions: Static or dynamic immersion in NaOCl for 1 minute or 5 minutes did not reduce the cyclic fatigue resistance of NiTi significantly. However, the type of instrument influences cyclic fatigue resistance. In our study, Twisted Files were more resistant followed by Mtwo and Revo S SU files. [Copyright &y& Elsevier]

Abstract: Introduction: Fractured rotary nickel-titanium (NiTi) instruments have been classified into those that fail as a result of cyclic flexural fatigue or torsional failure or a combination of both. Clinically, NiTi rotary instruments are subjected to both torsional load and cyclic fatigue, and ongoing research aims to clarify the relative contributions of both factors to instrument separation. Methods: To date, there is no specification or international standard to test cyclic fatigue resistance of endodontic rotary instruments. As a consequence, several devices and methods have been used to investigate in vitro cyclic fatigue fracture resistance of NiTi rotary endodontic instruments. In nearly all studies reported in the endodontic literature, the rotating instrument was either confined in a glass or metal tube, in a grooved block-and-rod assembly, or in a sloped metal block. Results: There has been no mention of the “fit” of the instrument in the tube or groove. As the instrument is likely to be fitting loosely, the description of the radius of curvature in those studies is likely to be overstated (ie, the file was actually bent less severely than reported, adding a variability in the amount of flexural stress). Conclusions: This review analyzed several devices that have been used in endodontic literature for cyclic fatigue testing and found that differences in the methodology affected the fatigue behavior of rotary instruments and, consequently, the outcome of these studies. An international standard for cyclic fatigue testing of NiTi rotary instruments is required to ensure uniformity of methodology and comparable results. [Copyright &y& Elsevier]

Abstract: Objectives: To evaluate whether custom modification resulting in an anatomically shaped post and whether the span/diameter ratio (L/D) would affect the mechanical properties of fiber-reinforced composite posts. Methods: Preformed glass-fiber posts (Group 1) and modified glass-fiber posts (Group 2) and glass-fiber rods (Groups 3 and 4) (n =20) were loaded to failure in a three-point bending test to determine the maximum load (N), flexural strength (MPa) and flexural modulus (GPa). The span distance tested for Group 3 was 10.0mm, while for Group 4 was 22.0mm. Data were subjected to different statistical analysis with significance levels of P <0.05. Results: The maximum load recorded for Groups 1 and 2 was 72.5±5.9N and 73.4±6.4N respectively, while for Groups 3 and 4 was 215.3±7N and 156.6±3.6N respectively. The flexural strength for Groups 1 and 2 was 914.6±53.1MPa and 1069.2±115.6MPa, while for Groups 3 and 4 was 685.4±22.2MPa and 899.6±46.1MPa. The flexural modulus recorded for Groups 1 and 2 was 32.6±3.2GPa and 33.4±2.2GPa respectively, while for Groups 3 and 4 was 13.7±0.3GPa and 34.4±0.3GPa respectively. Conclusions: The flexural properties of an anatomically custom modified fiber post were not affected by the modification procedure and the span-diameter ratio is an important parameter for the interpretation of flexural strength and flexural modulus values. [Copyright &y& Elsevier]

Abstract: The aim of this study was to compare the effectiveness of the Mtwo R (Sweden & Martina, Padova, Italy), ProTaper retreatment files (Dentsply-Maillefer, Ballaigues, Switzerland), and a Hedström manual technique in the removal of three different filling materials (gutta-percha, Resilon [Resilon Research LLC, Madison, CT], and EndoRez [Ultradent Products Inc, South Jordan, UT]) during retreatment. Ninety single-rooted straight premolars were instrumented and randomly divided into 9 groups of 10 teeth each (n = 10) with regards to filling material and instrument used. For all roots, the following data were recorded: procedural errors, time of retreatment, apically extruded material, canal wall cleanliness through optical stereomicroscopy (OSM), and scanning electron microscopy (SEM). A linear regression analysis and three logistic regression analyses were performed to assess the level of significance set at p = 0.05. The results indicated that the overall regression models were statistically significant. The Mtwo R, ProTaper retreatment files, and Resilon filling material had a positive impact in reducing the time for retreatment. Both ProTaper retreatment files and Mtwo R showed a greater extrusion of debris. For both OSM and SEM logistic regression models, the root canal apical third had the greatest impact on the score values. EndoRez filling material resulted in cleaner root canal walls using OSM analysis, whereas Resilon filling material and both engine-driven NiTi rotary techniques resulted in less clean root canal walls according to SEM analysis. In conclusion, all instruments left remnants of filling material and debris on the root canal walls irrespective of the root filling material used. Both the engine-driven NiTi rotary systems proved to be safe and fast devices for the removal of endodontic filling material. [Copyright &y& Elsevier]

Abstract: Tooth discoloration varies in etiology, appearance, localization, severity, and adhesion to tooth structure. It can be defined as being extrinsic or intrinsic on the basis of localization and etiology. In this review of the literature, various causes of tooth discoloration, different bleaching materials, and their applications to endodontically treated teeth have been described. In the walking bleach technique the root filling should be completed first, and a cervical seal must be established. The bleaching agent should be changed every 3–7 days. The thermocatalytic technique involves placement of a bleaching agent in the pulp chamber followed by heat application. At the end of each visit the bleaching agent is left in the tooth so that it can function as a walking bleach until the next visit. External bleaching of endodontically treated teeth with an in-office technique requires a high concentration gel. It might be a supplement to the walking bleach technique, if the results are not satisfactory after 3–4 visits. These treatments require a bonded temporary filling or a bonded resin composite to seal the access cavity. There is a deficiency of evidence-based science in the literature that addresses the prognosis of bleached nonvital teeth. Therefore, it is important to always be aware of the possible complications and risks that are associated with the different bleaching techniques. [Copyright &y& Elsevier]

Statement of problem.: When cuspal coverage is required, there is no evidence that indirect composite resin restorations are superior to direct restorations in terms of biomechanical behavior. Purpose.: The purpose of this in vitro study was to compare the fracture resistance of cusp-replacing direct and indirect composite resin restorations in endodontically treated molars. Material and methods.: Forty-five human mandibular molars were selected and divided into 3 groups (n=15): DIR specimens, restored with direct composite resin (Estelite Sigma) restorations; IND specimens, restored with indirect composite resin (Estelite Sigma) restorations, and control specimens, which remained intact. Endodontic treatment was performed using NiTi ProTaper rotary instruments, and teeth were filled using lateral condensation of gutta-percha and sealer. Extensive Class II MO cavities were prepared, and the 2 mesial cusps were reduced, allowing a 2-mm layer of composite resin. All teeth were prepared to the same dimensions, considering reasonable human variation. Specimens were loaded to failure and the fracture loads were recorded (N). The mode of fracture was determined using a stereomicroscope and classified as favorable or unfavorable failure. The data were subjected to a Kruskal-Wallis test, multiple-comparison Mann-Whitney test, and a chi-square test (α=.05). Results.: Significant differences (P<.001) were observed between the control group and both DIR and IND groups. However, no significant difference was found between the DIR and IND groups. The chi-square test did not show a significant difference in the frequencies of favorable/unfavorable failure modes among the 3 groups (P=.981). Conclusions.: No significant difference was observed in the fracture resistance of endodontically treated molars restored to original contours with an extensive cusp-replacing direct or indirect composite resin restoration. (J Prosthet Dent 2008;99:225-232) [Copyright &y& Elsevier]

Abstract: Objectives: To evaluate the flexural modulus and flexural strength of different types of endodontic post in comparison with human root dentin. Methods: Three different types of fiber-reinforced composite (FRC) posts and three metal posts each comprising 10 specimens (n =10) and 20 dentin bars were loaded to failure in a three-point bending test to determine the flexural modulus (GPa) and the flexural strength (MPa). Three randomly selected fiber posts of each group were evaluated using a scanning electron microscope (SEM) to illustrate the differences in mode of fracture. Data were subjected to a one-way ANOVA to determine significant differences between groups and the Bonferroni t-test multiple comparison was applied to investigate which mean values differed from one another with significance levels of P <0.05. Results: The flexural modulus recorded for the dentin bars was 17.5±3.8GPa. The values for posts ranged from 24.4±3.8GPa for silica fiber posts to 108.6±10.7GPa for stainless steel posts. The flexural strength for dentin was 212.9±41.9MPa, while the posts ranged from 879.1±66.2MPa for silica fiber posts to 1545.3±135.9MPa for cast gold posts. The ANOVA test analysis revealed significant differences between groups (P <0.05) for flexural modulus and flexural strength mean values. Significance: FRC posts have an elastic modulus that more closely approaches that of dentin while that for metal posts was much higher. The flexural strength of fiber and metal posts was respectively four and seven times higher than root dentin. [Copyright &y& Elsevier]

Abstract: The aims of this study were to compare Resilon (Resilon Research LLC, Madison, CT) in conjunction with either a bonding (Epiphany; Pentron Clinical Technologies, Wallingford, CT) or a nonbonding endodontic sealer (Pulp Canal Sealer; Kerr Corporation, Orange, CA) to EndoRez (Ultradent Products Inc, South Jordan, UT) and gutta-percha with regards to the physical properties and flexural stress in standardized dentin cylinders and the flexural stress of Resilon and gutta-percha. The external surface of 50 maxillary central incisors was reduced by means of mechanical milling to obtain dentin cylinders with an external diameter of 3 mm and minimum length of 12 mm. Root canals were prepared to obtain a standardized cylindrical preparation of 1.3 mm in diameter at the center of the root. The cylinders were randomly divided into five groups (n = 10): group 1: obturation with gutta-percha and Pulp Canal Sealer; group 2: obturation with Resilon, Epiphany primer, and Epiphany; group 3: obturation with Resilon and Pulp Canal Sealer; group 4: obturation with EndoRez methacrylate-based endodontic sealer; and group 5: dentin cylinders were not obturated. Ten gutta-percha (group 6) and Resilon (group 7) pellets for the Obtura gun were also tested. A three-point bending test was used to measure the maximum load values of specimens from groups 1 to 5 and the flexural strength and flexural modulus values for specimens from groups 6 and 7. Statistical analysis was performed to determine significance differences (p < 0.05). An analysis of variance test showed no significant difference among groups 1 to 5 (p = 0.697; F = 0.60). An independent sample t test showed statistically significant differences between groups 6 and 7 in flexural strength (p = 0.000) and flexural modulus (p = 0.000). Within the limits of this study, it may be concluded that the currently available endodontic-filling materials and their recommended adhesive procedures are not able to influence the mechanical properties of root canal dentin and that the flexural properties of Resilon and gutta-percha are too low to reinforce roots. [Copyright &y& Elsevier]

Objective: The objective of this study was to evaluate the influence of the moment when reduced pressure is applied on dye penetration patterns. Study design: Nine hundred and sixty glass capillary tubes of different inner diameter (0.3 mm and 0.8 mm), divided into 48 groups, were submerged into dye in 3 different positions (horizontally, opening upwards, and opening downwards) under different vacuum conditions (passive, 5 kPa, 35 kPa, 70 kPa reduced pressure). When reduced pressure was applied half of the groups were submerged into dye before and half of the groups after the application of reduced pressure. Linear dye penetration was measured. Univariate analysis was performed with Mann-Whitney U test and Kruskal-Wallis test to select variables to be included in the regression model. A multiple logistic regression analysis with backward elimination was performed to assess the influence of different covariates on linear dye penetration. Results: The multivariate linear regression showed that the moment of vacuuming had the greatest positive effect on linear dye penetration value (β = 10.6, P < .0001). Also the level of pressure reduction had a positive effect on the outcome variable (β = 0.2, P < .0001) while the vertical positioning of the tubes has negatively affected the outcome variable both for the open end upside (β = −1.01, P = .024) and the open end downside (β = −1.05, P = .019). Diameter of the tubes (P = .442) and immersion time (P = .727) had no effect on the outcome of linear dye penetration. Conclusions: Even minimum air pressure reduction applied before immersion of the specimens allowed the dye to extensively penetrate the voids. [Copyright &y& Elsevier]

Abstract: During the past few decades endodontic treatment has benefited from the development of new techniques and equipment, which have improved outcome and predictability. Important attributes such as the operating microscope and ultrasonics (US) have found indispensable applications in a number of dental procedures in periodontology, to a much lesser extent in restorative dentistry, while being very prominently used in endodontics. US in endodontics has enhanced the quality of treatment and represents an important adjunct in the treatment of difficult cases. Since its introduction, US has become increasingly more useful in applications such as gaining access to canal openings, cleaning and shaping, obturation of root canals, removal of intracanal materials and obstructions, and endodontic surgery. This comprehensive review of the literature aims at presenting the numerous uses of US in clinical endodontics and emphasizes the broad applications in a modern-day endodontic practice. [Copyright &y& Elsevier]

Objective: To determine whether the shaping of oval-shaped root canals using 2 different preparation techniques resulted in significant morphologic differences. Study design: Forty lower premolars with oval-shaped root canals were divided into group A, instrumented with the Anatomic Endodontic Technology (AET) system, and group B, treated with ProTaper instruments. A modified Bramante technique was used to analyze changes in root canal diameters (ΔD), changes in surface area (ΔA), and the change in buccolingual and mesiodistal ratio (ΔR). The data were subjected to a Student t test at a significance level of P < 0.05. Results: Statistically significant differences were found between the 2 groups at coronal and middle levels. There was no statistically significant difference at the apical level. Conclusions: The 2 techniques produced a significant difference in the ultimate shape of the coronal and middle portions of oval-shaped root canals, with the AET system removing more tooth structure at these levels. However, no differences were observed at the apical third. [Copyright &y& Elsevier]

Abstract: Recent studies detected erosion of the dentinal walls following the use of EDTA as a final flush. Several authors have studied degradation of EDTA and it appears to be caused by an oxidation reaction. The objective of this paper was to verify through nuclear magnetic resonance (NMR) analysis if the oxidizing property of sodium hypochlorite inactivates EDTA. Solutions of sodium hypochlorite and EDTA were analyzed. EDTA tracing and the appearance of new signals indicative of by-products of the reaction, were studied at different time intervals with a NMR analysis. The tracings of NMR analysis confirmed that the reaction between sodium hypochlorite and EDTA lead to a very slow but progressive degradation of this compound. Mindful of the limitations of an in vitro study, the results of this study nevertheless demonstrated that a final flush with sodium hypochlorite cannot limit the chelating effects of EDTA in a clinically realistic time period. [Copyright &y& Elsevier]

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]

Introduction The aim of the present study was to evaluate the cutting efficiency of 2 new reciprocating instruments, Reciproc and WaveOne. Methods Twenty-four new Reciproc R25 and 24 new WaveOne Primary files were activated by using a torque-controlled motor (Silver Reciproc) and divided into 4 groups (n = 12): group 1, Reciproc activated by Reciproc ALL program; group 2, Reciproc activated by WaveOne ALL program; group 3, WaveOne activated by Reciproc ALL program; and group 4, WaveOne activated by WaveOne ALL program. The device used for the cutting test consisted of a main frame to which a mobile plastic support for the handpiece is connected and a stainless steel block containing a Plexiglas block (inPlexiglass, Rome, Italy) against which the cutting efficiency of the instruments was tested. The length of the block cut in 1 minute was measured in a computerized program with a precision of 0.1 mm. Means and standard deviations of each group were calculated, and data were statistically analyzed with 1-way analysis of variance and Bonferroni test (P < .05). Results Reciproc R25 displayed greater cutting efficiency than WaveOne Primary for both the movements used (P < .05); in particular, Reciproc instruments used with their proper reciprocating motion presented a statistically significant higher cutting efficiency than WaveOne instruments used with their proper reciprocating motion (P < .05). There was no statistically significant difference between the 2 movements for both instruments (P > .05). Conclusions Reciproc instruments demonstrated statistically higher cutting efficiency than WaveOne instruments. [ABSTRACT FROM AUTHOR]

Abstract: Introduction: The goal of the present study was to test the fatigue resistance of nickel-titanium rotary files in a double curvature (S-shaped) artificial root canal and to compare those results with single curvature artificial root canals. Methods: Two nickel-titanium endodontic instruments consisting of identical instrument sizes (constant .06 taper and 0.25 tip diameter) were tested, ProFile instruments and Vortex instruments. Both instruments were tested for fatigue inside an artificial canal with a double curvature and inside a curved artificial canal with a single curvature. Ten instruments for each group were tested to fracture in continuous rotary motion at 300 rpm. Number of cycles to failure (NCF) was calculated to the nearest whole number, and the length of the fractured fragment was measured in millimeters. Data were statistically analyzed with a level of significance set at 95% confidence level. Results: The NCF value was always statistically lower in the double curved artificial canal when compared with the single curve (P < .05) in both the apical and coronal curvatures. Statistically significant differences (P < .05) were noted between instruments of the same size of different brand only in the single curve; ProFile registered a mean of 633.5 ± 75.1 NCF, whereas Vortex registered a mean of 548 ± 48.9 NCF. Conclusions: Regardless of the differences between the instruments used in the present study, the results suggest that the more complex is the root canal, the more adverse are the effects on the cyclic fatigue resistance of the instruments. [Copyright &y& Elsevier]

Abstract: Introduction: The aim of the present study was to evaluate the bending properties of Hyflex instruments, which exhibit a lower percent in weight of nickel (52 Ni %wt) and compare them with other commercially available nickel-titanium (NiTi) rotary instruments. Methods: Ten instruments with tip size 25, 0.06 taper of each of the following NiTi rotary instrumentation techniques were selected for the study: Hyflex, EndoSequence, ProFile, Hero, and Flexmasters. All instruments from each group were tested for stiffness by comparing their bending moment when they attained a 45-degree bend. Experimental procedures strictly followed testing methodology described in ISO 3630-1. All data were recorded and subjected to statistical evaluation by using analysis of variance test. Statistical significance was set at P < .05). Results: Statistical analysis of the data revealed that Hyflex files were found to be the most flexible instruments, with a significant difference (P < .05) in comparison with the other instruments. Among the other files, a significant difference has been reported for EndoSequence instruments compared with ProFile, Hero, and FlexMaster (P < .05), whereas no significant differences have been reported among those 3 files (P > .05). Conclusions: Results of the present study have illustrated an increased flexibility of the new NiTi alloy over conventional NiTi alloy, and they highlight the potential of the new manufacturing process. [Copyright &y& Elsevier]

Abstract: The aim of the present study was to investigate whether cyclic fatigue resistance is increased for nickel-titanium instruments manufactured by using new processes. This was evaluated by comparing instruments produced by using the twisted method (TF; SybronEndo, Orange, CA) and those using the M-wire alloy (GTX; Dentsply Tulsa-Dental Specialties, Tulsa, OK) with instruments produced by a traditional NiTi grinding process (K3, SybronEndo). Tests were performed with a specific cyclic fatigue device that evaluated cycles to failure of rotary instruments inside curved artificial canals. Results indicated that size 06-25 TF instruments showed a significant increase (p < 0.05) in the mean number of cycles to failure when compared with size 06-25 K3 files. Size 06-20 K3 instruments showed no significant increase (p > 0.05) in the mean number of cycles to failure when compared with size 06-20 GT series X instruments. The new manufacturing process produced nickel-titanium rotary files (TF) significantly more resistant to fatigue than instruments produced with the traditional NiTi grinding process. Instruments produced with M-wire (GTX) were not found to be more resistant to fatigue than instruments produced with the traditional NiTi grinding process. [Copyright &y& Elsevier]