Quality of Root Canal Fillings and Procedural Errors for In Vivo Studies Prepared in Different Clinical Settings and with Rotary Systems: A Systematic Review.

BACKGROUND This systematic review of the literature aimed to identify published studies and evaluate them on the quality of root canal fillings (RCF) and procedural errors with rotary systems for in vivo studies prepared for different clinical settings. MATERIAL AND METHODS A full literature exploration was conducted in Clarivate Analytics' Web of Science, Elsevier's Scopus, Embase, and PubMed for studies published between January 2020 and March 2024. A manual search was also performed by reviewing the references of selected papers. The following keywords were used: quality of root canal filling(s) OR quality of root canal obturation, root canal obturation OR endodontic treatment, clinical setting (academic, private, governmental), AND/OR procedural errors and rotary instrumentation. RESULTS Sixteen clinical studies were included in this review. The acceptance percentages for obturation length, density, and taper were 76.3%, 74.7%, and 82.5%, respectively, indicating significantly high, good ratios. The overall RCF recorded showed that 68.2% of root canal obturations were considered acceptable. Acceptable rates remained higher than unacceptable rates in academic, hospital, and private settings, and percentages ranged from 65.2% to 93.0%. Only 5 studies reported procedural errors, namely, ledge formation, separated instruments, apical perforation, transportation, lateral perforation, and root/foramen perforation. CONCLUSIONS Using rotary instruments for different root canal treatment steps as instrumentation and obturations is highly recommended. Among different clinical setting and practice, these instruments resulted in a good and acceptable RCF, overall quality performed by those instruments, and few procedural errors.

Microrobotics in endodontics: A perspective.

Microorganisms are the primary aetiological factor of apical periodontitis. The goal of endodontic treatment is to prevent and eliminate the infection by removing the microorganisms. However, microbial biofilms and the complex root canal anatomy impair the disinfection process. Effective and precise endodontic therapy could potentially be achieved using advanced multifunctional technologies that have the ability to access hard-to-reach surfaces and perform simultaneous biofilm killing, removal, and detection of microorganisms. Advances in microrobotics are providing novel therapeutic and diagnostic opportunities with high precision and efficacy to address current biofilm-related challenges in biomedicine. Concurrently, multifunctional magnetic microrobots have been developed to overcome the disinfection challenges of current approaches to disrupt, kill, and retrieve biofilms with the goal of enhancing the efficacy and precision of endodontic therapy. This article reviews the recent advances of microrobotics in healthcare and particularly advances to overcome disinfection challenges in endodontics, and provides perspectives for future research in the field.

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

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

Efficacy of a novel remotely-generated ultrasonic root canal irrigation system for removing biofilm-mimicking hydrogel from a simulated isthmus model.

AIM: To evaluate the efficacy of a novel ultrasonic irrigation device, remotely-generated irrigation with a non-invasive sound field enhancement (RINSE) system, in removing biofilm-mimicking hydrogel from a simulated isthmus model and compare it with sonically- and ultrasonically-activated irrigation systems. METHODOLOGY: A polycarbonate root canal model containing two standardized root canals (apical diameter of 0.20 mm, 4% taper, 18 mm long with a coronal reservoir) connected by three isthmuses (0.40 mm deep, 2 mm high, 4 mm long) was used as the test model. The isthmuses were filled with a hydroxyapatite powder-containing hydrogel. The canals were filled with irrigant, and the models were randomly assigned to the following activation groups (n = 15): EndoActivator (EA), ultrasonically activated irrigation (UAI), and RINSE system (RS). Syringe irrigation (SI) with a 30G needle served as the control. Standardized images of the isthmuses were taken before and after irrigation, and the amount of hydrogel removed was determined using image analysis software and compared across groups using anova (p < .05). RESULTS: Hydrogel removal was significantly higher with the RS (83.7%) than with UAI, EA, or SI (p ≤ .01). UAI (69.2%) removed significantly more hydrogel than SI and EA (p < .05), while there was no significant difference between SI (24.3%) and EA (25.7%) (p = .978). CONCLUSIONS: RINSE system resulted in the most hydrogel removal, performing better than UAI or EA. The effect of RS was also not reliant on the insert or tip entering the pulp chamber or root canal, making it particularly useful in conservative endodontics.

The efficacy of a novel SWEEPS laser-activated irrigation compared to ultrasonic activation in the removal of pulp tissue from an isthmus area in the apical third of the root canal.

This study aimed to evaluate the efficacy of Shock Wave Enhanced Emission Photoacoustic Streaming (SWEEPS) in the removal of remaining pulp tissue from the root canal isthmus area in lower molars and compare it with ultrasonically activated irrigation (UAI) and conventional needle irrigation (NI). Forty-one lower molars with isthmuses between mesial canals were included in the study. The teeth were randomly distributed into experimental groups (n = 12/each) based on the final irrigation protocol (SWEEPS, UAI, or NI) and a control group (C) (n = 5). The traditional access cavity of the mesial part of each tooth was made in all samples. The mesial root canals in the experimental groups were instrumented with a Wave One Gold Primary (25/.07) file using 3% sodium hypochlorite (NaOCl) while the distal canal served as a control for the presence of pulp tissue. No treatment was performed in the C group. Sections from the isthmus region were processed for histopathology to measure the remaining pulp tissue (RPT). The results were analyzed using analysis of variance and the Kruskal-Wallis test (α = 0.05). There were no significant differences in the relative surface area of root canals and isthmus among the groups (p > 0.05). Samples in the SWEEPS group had significantly less RPT than UAI, NI, and C (p = 0.003, 0.014, 0.003, respectively). There were no significant differences between the UAI and NI (p = 0.583). SWEEPS was the most efficient in debridement of the root canal isthmus area. UAI and NI showed similar but lower efficiency.

An Appraisal on Newer Endodontic File Systems: A Narrative Review.

AIM: This narrative review aims to explore and elicit the newer endodontic file systems used for root canal treatments. BACKGROUND: The primary goals of endodontic therapy continue to be the mechanical enlargement and shaping of the intricate endodontic root canal systems to aid in disinfection. Nowadays endodontists have access to a wide range of endodontic file systems for root canal preparations with various design characteristics and benefits. REVIEW RESULTS: ProTaper Ultimate (PTU) files' tip have a triangular convex cross-section, an offset mass of rotating design, a maximum flute diameter of 1.0 mm, and are constructed of gold wire, hence, commonly applied in conditions with restricted accessibility or an extremely curved canal. TruNatomyhas advantages over other cutting-edge file systems like maximum flute diameter of the corona, reduced distance between active cutting flutes, and shorter handles in comparison to SX instruments. In comparison to PTU files, ProTaper Gold (PTG) files are noticeably more elastic and fatigue-resistant. Compared to files in the F1-F3 range, size S1 and S2 files have a significantly longer fatigue life. MicroMega One RECI is more resistant to cyclic fatigue because of its heat treatment and reciprocating action and the C-wire heat treatment of the former gives it flexibility and controlled memory, enabling the prebending of the file. The RECIPROC blue demonstrated enhanced flexibility, increased fatigue resistance, and lower microhardness while maintaining the same surface qualities. CONCLUSION: As per the necessity and requirement on case to case basis, every endodontic file system has advantages and disadvantages as mentioned in this narrative review. According to the need, an endodontist can select the file system which is required specifically. Although several studies are comparing these various systems in the literature, this narrative review aims to give the clinician a summary of some recently launched endodontic rotary file systems available in the market and their clinical uses. CLINICAL SIGNIFICANCE: As per the priority and need of the case, whether removal and extrusion of debris, reduction of micro-organisms, keeping canal anatomy, and cutting efficiency, a specific required file system can be utilized.

Influence of glide path kinematics during endodontic treatment on the occurrence and intensity of intraoperative and postoperative pain: a systematic review of randomized clinical trials.

BACKGROUND: Preliminary canal enlargement (glide path preparation) may play a significant role in the development of pain. The aim of this systematic review of randomized clinical trials was to assess the influence of glide path kinematics during endodontic treatment on the occurrence and intensity of intraoperative and postoperative pain. METHODS: A search was performed in June 2019 in six electronic databases (PubMed, Scopus, LILACS, SciELO, Embase and Web of Science) and two grey literature databases (OpenGrey and OpenThesis). The bibliographic references of the eligible articles were also hand-searched. The included clinical studies assessed the occurrence and intensity of intraoperative and/or postoperative pain after root canal preparation without glide path preparation (WGP) or with glide path preparation using manual (M-GP), continuous rotary (CR-GP), or reciprocating (R-GP) instruments. The primary outcome was the occurrence and intensity of intraoperative and postoperative pain, while analgesic consumption was the secondary outcome. The full texts of the eligible studies were analyzed by two reviewers who performed calibration exercises to verify the risk of bias and quality of the individual studies using the Joanna Briggs Institute Critical Appraisal tool. RESULTS: From 1283 identified articles, only six studies were included in the qualitative analysis of the results, with a total sample of 884 patients/teeth. Three studies presented a high risk of bias, while three studies presented a moderate risk. Two studies reported that CR-GP causes lower pain levels than M-GP and WGP, and three studies showed no differences between CR-GP and R-GP. Regarding analgesic consumption, two studies found no differences among glide path kinematics, and one study reported lower consumption for CR-GP than for M-GP. Because of the limited number of studies and methodological differences, no statistical analyses were performed for the glide path kinematics comparisons. CONCLUSIONS: Compelling evidence indicating a significantly different occurrence and intensity of pain among glide path kinematics is lacking. The systematic review protocol was registered in the PROSPERO database [CRD42020139989].

Comparison of postoperative pain after foraminal enlargement of necrotic teeth using continuous rotary system and reciprocating instrument: A randomized clinical trial.

OBJECTIVES: This single-blind, randomized clinical trial (RCT) aimed to compare the duration, intensity, and incidence of postoperative pain after foraminal enlargement (FE) with continuous rotary systems and reciprocating instruments. MATERIALS AND METHODS: Sixty qualified patients were randomly divided into the following two groups: the ProTaper Next group and the WaveOne group. Participants were selected from patients who had both asymptomatic necrosis and asymptomatic apical periodontitis with a single root canal. Endodontic treatment was performed in one visit, and the patients were asked to record their pain severity and analgesic consumption during a 7-day follow-up period using a visual analog scale (VAS). The data were analyzed using the Mann-Whitney U-test and Chi-square test (P < 0.05). RESULTS: A significant difference was observed between the two groups during the first two days of follow-up (P < 0.05). Pain experience was higher in FEs that had been created by reciprocating instruments than by continuous rotary systems. There were no significant differences in VAS pain scores over the other days (P > 0.05). None of the patients had severe postoperative pain during the follow-up period. No significant differences were observed in the prevalence of analgesic consumption between either group (P > 0.05). CONCLUSIONS: This RCT indicates that in the 2-day follow-up period after endodontic treatment, FEs created by reciprocated instruments associated more postoperative pain than continuous rotary systems.

WITHDRAWN: Hand and ultrasonic instrumentation for orthograde root canal treatment of permanent teeth.

BACKGROUND: Endodontic treatment of root canals or root canal treatment is a frequently performed dental procedure and is carried out on teeth in which irreversible pulpitis has led to necrosis (death) of the dental pulp (nerve). Removal of the necrotic tissue remnants and cleaning and shaping of the root canal are important phases of root canal treatment. Treatment options include the use of hand and rotary instruments and methods using ultrasonic or sonic equipment. OBJECTIVES: The objectives of this review were to determine the relative clinical effectiveness of hand instrumentation versus ultrasonic instrumentation alone or in conjunction with hand instrumentation for orthograde root canal treatment of permanent teeth. SEARCH METHODS: We searched the Cochrane Oral Health Group Trials Register, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE and LILACS. We searched the reference lists of relevant articles in an attempt to locate additional published and unpublished trials. No language restriction was applied. The last electronic search was conducted in December 2007. SELECTION CRITERIA: Randomised controlled trials involving people over 18 years of age with single and multiple permanent teeth with a completely formed apex and with no evidence of internal resorption requiring root canal treatment were included. Patients undertaking re-treatment of a tooth were excluded. DATA COLLECTION AND ANALYSIS: Screening of eligible studies was conducted in duplicate and independently. Results were to be expressed as fixed-effect or random-effects models using mean differences for continuous outcomes and risk ratios for dichotomous outcomes with 95% confidence intervals. Heterogeneity was to be investigated including both clinical and methodological factors. MAIN RESULTS: No eligible randomised controlled trials were identified. AUTHORS' CONCLUSIONS: This review illustrates the current lack of published or ongoing randomised controlled trials and the unavailability of high level evidence, based on clinically relevant outcomes, for the effectiveness of ultrasonic instrumentation used alone or as an adjunct to hand instrumentation for orthograde root canal treatment.Future randomised controlled trials might focus more closely on evaluating the effectiveness of combinations of these interventions with an emphasis on not only clinically relevant but also patient-centred outcomes.

Impact of root canal preparation performed by ProTaper Next or Reciproc on the quality of life of patients: a randomized clinical trial.

AIM: To compare the impact of the two different root canal preparation systems on the quality of life of patients and correlate postoperative pain with the impact on quality of life. METHODOLOGY: A randomized clinical trial was conducted with 58 patients allocated into two groups based on the root canal preparation system employed: ProTaper Next (PN) or Reciproc (R). Data collection involved the administration of a questionnaire addressing demographic and clinical characteristics, the OHIP-14 (quality of life) and a visual analog scale (pain). The latter two were the outcomes of interest and were administered in the first 24 h after root canal treatment. The data were submitted to descriptive analysis, bivariate analysis, Poisson univariate and multiple regression, and Spearman's correlation test, with a 5% significance level. RESULTS: A greater frequency of impact after treatment was found for the items 'uncomfortable to eat food' and 'felt self-conscious'. No significant difference between groups was found regarding the severity of impact for total OHIP-14 score or any of the domain scores. CONCLUSIONS: The two root canal preparation systems exerted a similar impact on quality of life. Postoperative pain was correlated with impact on quality of life, affecting chewing function, self-consciousness and stress. Thus, it is important for dentists to provide care capable of preventing or treating the negative consequences of such therapy.

Evaluation of Intra Root Canal Er,Cr:YSGG Laser Irradiation on Prosthetic Post Adherence.

PURPOSE: In clinical prosthetics procedures, including endodontics and post fixation, the presence of a smear layer can reduce the post bond strength. An Er,Cr:YSGG laser, which emits at 2780 nm, can promote a smear-layer-free surface due to the ablation process. Considering these aspects, the purpose of this work was to evaluate the influence of Er,Cr:YSGG laser irradiation using either a radial or an axial fiber tip on the bond strength of three resin cements to the fiber-reinforced composite posts. MATERIALS AND METHODS: Ninety recently extracted single rooted human teeth had their root canal instrumented and were randomly distributed into nine experimental groups, in which three resin cements (total-etching Variolink II, self-etching Panavia F, and self-adhesive RelyX Unicem Aplicap) and three root canal treatments (no treatment, laser irradiation using the radial fiber tip, laser irradiation using the axial fiber tip) were used. Specimens were then sectioned into three sections (cervical, middle, and apical thirds) with two slices on each section. A push-out test was performed on each slice, and the values were recorded as MPa. The push-out data were analyzed by a Ryan-Joiner normality test followed by a two-way ANOVA test and Tukey pairwise comparison. The statistical analysis was performed on each third section separately, with a 5% significance level. RESULTS: Laser irradiation with axial fiber tip significantly increased the post bond strength of RelyX Unicem Aplicap on middle third of specimens (p < 0.001) when compared to other root canal treatments (unlased or irradiated with radial tip). Considering the Panavia resin cement, laser irradiation with either axial or radial tips promoted a significant increase on the post bond strength of middle third when compared to unlased specimens (p < 0.001); however, laser irradiation did not influence the post bond strength of Variolink resin cement. CONCLUSIONS: The use of the Er,Cr:YSGG laser for clinical prosthetics procedures enhances the post bond strength of Panavia and RelyX Unicem Aplicap resin cements, mainly at middle third of roots, and does not interfere with the bond strength of Variolink resin cement. For the RelyX Unicem Aplicap system, the use of axial tip is most advantageous and can be recommended for future clinical application.

Comparison of warm vertical compaction and cold lateral condensation of α, ß gutta-percha and resilon on apically extruded debris during retreatment.

BACKGROUND: This study was performed to evaluate the amount of apically extruded debris removed from a root canal filled with cold lateral condensation (CLC), and warm vertical compaction (WVC) techniques, using b or a phase gutta-percha with AH-Plus (Dentsply DeTrey, Konstanz, Germany) or Resilon (Resilon Research LLC, Madison, WI) with RealSeal SE (SybronEndo, Amersfoort, The Netherlands). MATERIALS AND METHODS: About 100 human incisor teeth were prepared with a #25.06 NiTi rotary system and divided into five groups according to the filling material used: Group 1: CLC (gutta-percha, AH-Plus); Group 2: WVC (b phase gutta-percha, AH-Plus); Group 3: WVC (a phase gutta-percha, AH-Plus); Group 4: CLC (Resilon, RealSeal SE); and Group 5: WVC (Resilon, RealSeal SE). Extruded debris during the retreatment procedure was collected in preweighed Eppendorf tubes. The times required for retreatment were recorded. RESULTS: The amount of debris extrusion was significantly greater with WVC than CLC in the gutta-percha and Resilon groups (P < 0.001). Using a phase gutta-percha resulted in significantly more debris extrusion than b phase gutta-percha (P < 0.001). In the WVC groups, Resilon caused significantly more debris extrusion than gutta-percha (P < 0.05). Retreatment was faster for CLC than WVC (P < 0.05). CONCLUSIONS: In the retreatment procedure, the amount of apically extruded debris and retreatment duration were dependent on the type of obturation material and technique used.

Pain after root canal treatment with different instruments: A systematic review and meta-analysis.

The aims of this systematic review were to compare the incidence and intensity of postoperative pain after single-visit root canal treatment using manual, rotary, and reciprocating instruments. An extensive literature search in PubMed, EMBASE, Cochrane Library, and Web of Science was performed to identify investigations that evaluated the effects of different instruments on postendodontic pain. Meta-analyses and additional analyses, including subgroup and sensitivity analyses, were conducted. We included seventeen trials in this study. Pooled results showed that patients treated with rotary instruments experienced a significantly lower incidence of postoperative pain (RR, 0.32, p = .0005) and reduced pain intensity than did patients treated with manual instruments. In addition, patients treated with multiple rotary-file systems experienced a significantly lower incidence of postoperative pain than did those treated with reciprocating systems (RR, 0.73; p < .0001). The use of rotary instruments contributed to a lower incidence and intensity of postoperative pain than did the use of hand files in patients who received single-visit root canal treatment. In addition, the use of multiple rotary-file systems contributed to a lower incidence of postoperative pain than did the use of reciprocating systems.

Influence of continuous rotation or reciprocation of Optimum Torque Reverse motion on cyclic fatigue resistance of nickel-titanium rotary instruments.

AIM: To evaluate the resistance to cyclic fatigue of ProTaper Next (PTN; Dentsply Sirona, Ballaigues, Switzerland), Revo-S (Micro-Mega, Besançon, France), Mtwo (Sweden & Martina, Padova, Italy), Twisted Files (TF, SybronEndo, Orange, CA, USA) and EndoWave (J Morita Corporation, Osaka, Japan) used in continuous rotation or in reciprocation of Optimum Torque Reverse motion (OTR). METHODOLOGY: A total of 120 nickel-titanium files were tested. Twenty-four instruments for each brand were divided into two groups (n = 12) on the basis of the motion tested: continuous rotation (Group 1) or reciprocation of OTR motion (Group 2). Resistance to cyclic fatigue was determined by recording time to fracture (TtF) in a stainless steel artificial canal with a 60° angle of curvature and 5 mm radius of curvature. The TtF data were analysed by using two-way analysis of variance (anova) and Bonferroni's post hoc tests at 0.05. RESULTS: Mtwo and TF had significantly higher TtF when compared with all other instruments, both in continuous rotation and in reciprocation of OTR motion (P < 0.0001 and P < 0.05, respectively). No difference was observed between Mtwo and TF (P > 0.05), in both motions. PTN was associated with higher cyclic fatigue resistance than Revo-S and EndoWave, both in continuous rotation and in reciprocation of OTR motions (P < 0.0001). No difference was observed between Revo-S and EndoWave, in both motions (P > 0.05). Reciprocating OTR motion improved TtF of all instruments (P < 0.0001). CONCLUSIONS: Reciprocation of OTR motion improved significantly cyclic fatigue resistance of all instruments tested compared with continuous rotation. Mtwo and TF had significantly higher cyclic fatigue than the other instruments, in both continuous rotation and reciprocation of OTR motion.

Technical quality of root canal treatment performed by undergraduate students using hand instrumentation: a meta-analysis.

The technical quality of root canal treatment (RCT) may impact on the outcome. The quality of education received during undergraduate school may be linked to the quality of treatment provided in general dental practice. In this context, the aim of this systematic review was to answer the following focused questions: (i) What is the frequency of acceptable technical quality of root fillings, assessed radiographically, performed by undergraduate students? (ii) What are the most common errors assessed radiographically and reported in these treatments? For this purpose, articles that evaluated the quality of root fillings performed by undergraduate students were selected. Data were collected based on predetermined criteria. The key features from the included studies were extracted. GRADE-tool assessed the quality of the evidence. MAStARI evaluated the methodological quality, and a meta-analysis on all studies was conducted. At the end of the screening, 24 articles were identified. Overall frequency of acceptable technical quality of root fillings was 48%. From this total, 52% related to anterior teeth, 49% to premolars and 26% to molars. The main procedural errors reported were ledge formation, furcation perforation, apical transportation and apical perforation. The heterogeneity amongst the studies was high (84-99%). Five studies had a high risk of bias, eight had a moderate risk, and 11 had low risk. The overall quality of evidence identified was very low. The conclusion was that technical quality of root fillings performed by undergraduate students is low, which may reveal that endodontic education has limited achievement at undergraduate level. A plan to improve the quality of root fillings, and by extrapolation the overall quality of root canal treatment, should be discussed by the staff responsible for endodontic education and training.

Fracture of nickel titanium rotary instrument during root canal treatment and re-treatment: a 5-year retrospective study.

AIM: To evaluate retrospectively the incidence of K3 nickel titanium rotary instrument fracture in referred cases during root canal treatment and re-treatment. METHODOLOGY: Clinical and radiographic reports of 12 867 endodontic cases treated at the King Abdulaziz medical city between January 2010 and November 2015 were reviewed to obtain information on intracanal fractured instruments with respect to the treatment performed, tooth type and the size and at what level the instrument fractured (coronal, middle or apical). The degree of canal curvature was classified into mild (<10° ), moderate (10-25° ) or severe (>25° ). Logistic regression was used to test the incidence of instrument fracture in relation to the root canal treatment performed and tooth type. Chi-square tests were used to analyse the fracture incidence in the treated teeth in respect to fracture level and fractured file diameter. The level of significance was set at 0.05. RESULTS: Root canal treatment was performed on 8946 cases, whilst re-treatment was performed on 3921 cases. The fracture incidence was higher during re-treatment cases (2.96%) than in primary root canal treatment (0.74%) (P < 0.001) with a 1.41% incidence overall. There was a trend for more fractures in maxillary (1.68%) and mandibular (1.35%) molar teeth. Moreover, 56.6% of the fractured instruments occurred in severely curved canals, and the apical third of the root canal was the most common site for instrument fracture (85.7%), followed by middle (13.2%), and coronal (1.1%) thirds, mostly with file sizes 20 and 25 (59.9% and 25.27%, respectively). CONCLUSION: The fracture incidence of K3 instruments was significantly greater during root canal re-treatment than root canal treatment, mainly with small instruments and in the apical third of the canals.

Influence of clinical use on physical-structural surface properties and electrochemical potential of NiTi endodontic instruments.

AIM: To investigate the surface morphology and electrochemical potential of superelastic (SE), M-Wire (MW) and shape memory technology (SMT) NiTi instruments before and after single clinical use in vivo. METHODOLOGY: A total of 60 ProTaper Universal F2 (PTU-SE), ProTaper Next X2 (PTN-MW), Typhoon (TYP), Hyflex (HF) and Vortex Blue (VB), the last three SMT, and size 25, .06 taper (n = 6 of each type) files were examined. Scanning electron microscopy (SEM), X-ray energy-dispersive spectroscopy (EDS) and electrochemical potential analysis were employed before and after clinical use. Statistical analysis was performed with one-way analysis of variance and Bonferroni's post hoc test. Significance was determined at the 95% confidence level for both tests. RESULTS: SEM observations of new instruments indicated the presence of marks left by the machining process during manufacturing and EDS revealed the existence of an oxide coating on shape memory instruments. After clinical use, the five types were associated with propagation of transverse cracks 3 mm from the tip. The surface oxide layer of TYP, HF and VB instruments had microcracks in multiple directions, whilst TYP and HF had fragmentation in chip form of the oxide layer. EDS analysis demonstrated a significant reduction of the oxide layer in shape memory instruments, except for VB. Electrochemical potentials were higher for shape memory instruments than for M-Wire and superelastic NiTi instruments, respectively (P < 0.05). CONCLUSIONS: It appears that shape memory technology NiTi instruments have a dysfunctional oxide layer after clinical use. Additionally, they featured higher electrochemical potential relative to NiTi instruments manufactured from M-Wire, and conventional superelastic NiTi alloy.

Effect of interrupted motion on the cyclic fatigue resistance of reciprocating nickel-titanium instruments.

AIM: To compare the cyclic fatigue resistances of WaveOne Gold (Denstply Sirona, Ballaigues, Switzerland), WaveOne (Dentsply Sirona) and Reciproc (VDW, Munich, Germany) in interrupted reciprocation. METHODOLOGY: Three groups of 18 instruments each of WaveOne Gold Primary, WaveOne Primary and Reciproc R25 were subjected to cyclic fatigue tests in reciprocation and interrupted reciprocation. The instruments in group 1 were tested in reciprocation, whereas in groups 2 and 3, reciprocation was interrupted for 1 s in every 5 s and 10 s, respectively. Cyclic fatigue resistance was tested using dynamic test devices in stainless steel, curved canals (60°, r = 5 mm) until fracture, and the time to fracture values were recorded. The lengths of the fractured tips were also recorded, and fractured surfaces were examined with a scanning electron microscope (SEM). Data were evaluated by one-way analysis of variance and Tukey's tests. RESULTS: The cyclic fatigue resistance of WaveOne Gold Primary was not affected by the interruptions (P > 0.05) and exhibited significantly greater cyclic fatigue resistance than WaveOne Primary and Reciproc R25 in all groups (P < 0.05). Interruptions reduced the cyclic fatigue resistance of WaveOne Primary and Reciproc R25 significantly (P < 0.05). CONCLUSION: Interrupted reciprocation reduced the cyclic fatigue resistance of Reciproc R25 and WaveOne Primary. The cyclic fatigue resistance of WaveOne Gold Primary was greater than that of WaveOne Primary and was not dependent on the occurrence of interruptions.

Mechanical characteristics of counterfeit Reciproc instruments: a call for attention.

AIM: To report the main differences seen by direct visual inspection between original and counterfeit Reciproc instruments, together with an evaluation of instrument bending resistance, cyclic fatigue, surface finish, Vickers microhardness and chemical composition. METHODOLOGY: The visual aspects of original Reciproc R25 (VDW, Munich, Germany) and counterfeit Reciproc R25 instruments (claimed to be original, supposedly with dimensions similar to those of Reciproc R25 files, bought at www.mercadolivre.com.br) were evaluated under direct observation, stereomicroscopy and scanning electron microscope. The flexibility of original and counterfeit Reciproc R25 was determined via 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 5-mm radius of curvature. The fracture surfaces of all fragments were examined under a scanning electron microscope. Roughness of the instruments was quantified using a profilometer, and the microhardness test was carried out using a Vickers hardness tester. Energy-dispersive X-ray microanalysis (EDX) was also carried out. Results were analysed statistically using the Student's t-test at a significance level of P < 0.05. RESULTS: Although the packaging of the original and counterfeit instruments was similar, a number of differences were observed such as ISO colour coding, measurement marks, stopper and morphologic characteristics. Original Reciproc instruments had significantly longer cyclic fatigue life and significantly lower bending resistance than counterfeit Reciproc instruments (P < 0.05), as well as significantly lower microhardness and roughness (P < 0.05). EDX results revealed differences in the chemical composition of the instruments (P < 0.05), indicating that the instruments were manufactured with different raw material. CONCLUSION: Original Reciproc files outperformed counterfeit instruments in all tests. It is thus important that identification strategies for these counterfeit instruments be developed, thereby preventing their inadvertent use.

Torsional fatigue resistance of pathfinding instruments manufactured from several nickel-titanium alloys.

AIM: To evaluate the torsional properties of pathfinding nickel-titanium (NiTi) rotary instruments manufactured from several NiTi alloys, ProGlider (M-wire), Hyflex GPF (conventional NiTi Wire and controlled memory wire), Logic (conventional NiTi wire and controlled memory wire) and Mtwo (conventional NiTi wire). METHODOLOGY: A total of 56 NiTi instruments from Glidepath rotary systems (n = 8) were used: Logic (size 25, .01 taper), Logic CM (size 25, .01 taper), ProGlider (size 16, .02 taper), Hyflex GPF (size 15, .01 taper), Hyflex GPF CM (size 15, .02 taper; size 20, .02 taper) and Mtwo (size 10, .04 taper). The torsion tests were performed based on ISO 3630-1 (1992). Three millimetres of each instrument tip was clamped to a small load cell by a lever arm linked to the torsion axis. Data were analysed using a one-way analysis of variance (anova) and Tukey test with a significance level at a = 5%. RESULTS: The Logic size 25, .01 taper had significantly higher torsional strength values (P < 0.05). The ProGlider was significantly different when compared with Hyflex GPF size 15, .01 taper and size 15, .02 taper (P < 0.05). The Logic CM size 25, .01 taper had significantly higher torsional strength than Hyflex GPF size 15, .01 taper and size 15, .02 taper (P < 0.05). No difference was found amongst Mtwo size 10, .04 taper and Hyflex GPF groups (size 15, .01 taper; size 15, .02 taper; size 20, .02 taper). In relation to the angle of rotation, Logic CM size 25, .01 taper and Hyflex GPF size 15, .01 taper had the highest angle values (P < 0.05). The ProGlider had the lowest angle values in comparison with all the groups (P < 0.05) followed by Mtwo size 10, .04 taper. The Logic size 25, .01 taper had significantly higher angle of rotation values than ProGlider and Mtwo size 10, .04 taper (P < 0.05). CONCLUSION: The Logic size 25, .01 taper instrument made of conventional NiTi alloy had the highest torsional strength of all instruments tested. In addition, the ProGlider instrument manufactured from M-Wire alloy had the lowest angle of rotation to fracture in comparison with the other instruments.