Fracture incidence of instruments from a single-file reciprocating system by students in an endodontic graduate programme: a cross-sectional retrospective study

Reciprocating Torsional Fatigue and Mechanical Tests of Thermal-Treated Nickel Titanium Instruments

INTRODUCTION

This study aimed to evaluate the mechanical properties of Reciproc, Reciproc Blue, One RECI, and R-Motion, specifically focusing on their flexibility and buckling resistance and to assess their torsional fatigue behavior under 2 different reciprocation angles (150°/30° or 70°/30°).

METHODS

A total of 160 instruments (40 per brand) were tested. Flexion and buckling tests were conducted using a Universal testing machine (DL 200 MF). For the flexion test, instruments were positioned at a 45° angle and flexed toward the ground plane. In the buckling test, the load was applied along the instrument's axis. A 20 N load cell and a test speed of 15 mm/s were used for both tests. Torsion test was performed using a torsiometer. The test speed was 100 rpm and the instruments were driven by an endodontic motor in 150°/30° and 70°/30° reciprocating angles. One-way analysis of variance post hoc Tukey tests and Student's t test were used for statistical comparisons (α = 5%).

RESULTS

The instruments exhibited significant differences in flexibility (P < .05), with One RECI demonstrating the highest flexibility and Reciproc the lowest. In terms of buckling resistance, Reciproc showed the highest values, while One RECI had the lowest (P < .05). Reciproc and Reciproc Blue displayed greater torque to fracture compared to One RECI and R-Motion (P < .05). Reducing the reciprocation angle did not affect the torque to fracture (P > .05). However, the reduced angle of 70°/30° significantly increased the time to fracture for all instruments when compared to angle of 150°/30° (P < .05).

CONCLUSIONS

The tested instruments demonstrated notable differences in their mechanical performance, highlighting variability in flexibility, buckling resistance, and torsional behavior. Reducing the reciprocation angle prolonged the time to fracture without affecting maximum torque, underscoring the influence of reciprocation kinematics on instrument performance.

Temperature-Dependent Effects on Cyclic Fatigue Resistance in Three Reciprocating Endodontic Systems: An In Vitro Study

This study aimed to analyze the effect of 1% sodium hypochlorite (NaOCl) solution at different temperatures on endodontic file resistance to cyclic fatigue. A total of 90 files, Reciproc NiTi M-Wire® (REC) (n = 30), WaveOne Gold® (WOG) (n = 30), and Reciproc Blue® (RB) (n = 30) were activated under constant irrigation with 1% NaOCl at 5, 37, and 60 °C in a stainless-steel artificial canal (curvature angle = 60°; radius = 5 mm). The time to the fracture and the maximum and minimum load were recorded for each instrument, and data were subjected to statistical analysis. A higher number of cycles to fracture at 5 °C was observed between WOG and RB compared to the REC system (p < 0.05). The RB files were more resistant to cyclic fatigue fracture at 60 °C than WOG and REC (p < 0.05). No statistically significant differences were found between the mean values of the three file types used at 37 °C. The high temperature of NaOCl significantly affects the lifespan of endodontic files, making them more prone to fractures due to cyclic fatigue. The files manufactured with heat treatment showed a longer life than M-wire reciproc files.

Impact of anatomical and clinical variables on the success of endodontic instrument fragment retrieval

PURPOSE

Separation of instrument fragments can impede the progress of endodontic treatment, and effective management of this complication is crucial for treatment success. This study examined the factors that impact the success of retrieval of separated instrument fragments by postgraduate endodontic residents.

METHODS

A retrospective analysis was conducted on a total of 224 teeth associated with instrument fragment separation that were managed by postgraduate residents specializing in endodontics between January 2020 and March 2024. Data were extracted from patient records, periapical radiographs, and clinical notes. Chi-squared test and t-test were employed to identify factors significantly influencing retrieval success. Associations between successful retrieval and variables were assessed using binary logistic regression models.

RESULTS

Fragment retrieval was successful in 32% of the examined cases. Retrieval was more likely to be successful for anterior teeth than for premolars and molars (P = 0.003). Fragment separation in the coronal third of the canal had a higher retrieval success rate (P < 0.001). Longer separated fragments were also associated with increased retrieval success (t = 3.035, P = 0.003).

CONCLUSION

The study revealed that factors critically influencing the successful retrieval of separated instrument fragments included the tooth type, the level of separation within the canal, and the fragment length. These findings highlight the importance of careful case selection in order to optimize management outcomes.

Effects of a pre-enlargement on fracture incidence of reused reciprocating instruments: A clinical study

This study assessed the impact of pre-enlarging the root canal using a size 25 K-file on the fracture incidence of three reciprocating instruments after multiple uses. After a glide path performed with a size 15 K-file, the instruments (Reciproc R25, Reciproc Blue R25, and WaveOne Gold Primary) were initially used in 936 root canals. Then, for the second and third uses (933 and 927, respectively), a pre-enlargement using a size 25 K-file at the working length was done. Periapical radiographs assessed fragment location and length, and chi-square tests compared observed and expected frequencies (α = 5%). The fracture incidence during reuse ranged from 0% to 0.64%. Reciproc did not fracture during reuse (P = 0.99), but experienced two fractures in the third use (P = 0.000). Reciproc Blue and WaveOne Gold each had one fracture during the second (P = 0.000) and third (P = 0.000) uses. Following a pre-enlargement using a size 25 K-file for the second and third uses in 1,860 canals, only 6 instruments fractured (0.32%), suggesting that this approach may prolong the lifespan of these instruments and serve as an alternative for their reuse with a reduced risk of fracture.

Fracture Incidence of New Reciprocating Nickel-Titanium (NiTi) Files: A Cross-Sectional Retrospective Study

Aim This study aimed to evaluate the frequency of fractures in a new single-file reciprocating system used by endodontists. Methods Reciprocal systems were used to evaluate endodontist-treated patients' periapical radiographs and dental records. For the study, the kind of tooth, the quantity of root canals completed, the quantity of broken instruments, and the fragment's size were all recorded. A fracture risk calculation was made for every kind of tooth, root canal, and root third. The new reciprocating systems' fracture incidence was compared at a 5% significant level using the chi-squared test varied between 2 and 6 mm. Results There were a total of 5,066 root canals (2,128 teeth) from 1,818 patients. In single-file reciprocating systems, the incidence of fractured files relative to the number of instrumented canals was 22 (0.43%). The mesiobuccal root canal of mandibular molars and maxillary molars had the greatest breakage rates, which were 7 (36%) and 6 (27%), respectively. Conclusion The incidence of instrument fractures was lowered when linked to the usage of the Premium Blue reciprocating system in endodontic therapy.

Effect of different instrumentation techniques on students' performance and outcomes of nonsurgical root canal treatment

OBJECTIVES

This study compared, retrospectively, the incidence of clinical errors and effects on treatment outcomes, when students were exposed to two different instrumentation techniques: a hybrid rotary technique (HYB), consisting of both hand instrumentation with hand stainless steel and Ni-Ti files plus the use of a rotary system (Vortex Blue, Dentsply Sirona), versus a full reciprocation instrumentation technique (WaveOne Gold [WOG], Dentsply Sirona).

METHODS

A total of 368 endodontic cases (n = 184) in anterior and premolar teeth, completed by dental students at the University of Michigan School of Dentistry from 2013 to 2022, were used for the study. The groups were evaluated by two calibrated clinicians, observing the incidence of clinical errors: file separations, over-instrumentation, ledges and transportations. Treatment outcomes were also observed. Data were analyzed statistically by Fisher's exact test and Mann-Whitney U test (p < 0.05).

RESULTS

No significant difference in file separations, ledges, and transportation was observed between the two groups. However, the WOG Group experienced significantly more over-instrumentation than HYB group, although this did not significantly affect tooth survival or periapical index (PAI). Cases with PAI scores of 5 were found to have significantly less tooth survival compared to the other PAI scores.

CONCLUSIONS

It can be concluded that both techniques in our study are well suited to advancing the endodontic dental education of students and novice operators, anticipating relatively successful outcomes of tooth survival, as long as the cases selected are less severe in progression preoperatively.

Multimethod analysis of large- and low-tapered single file reciprocating instruments: Design, metallurgy, mechanical performance, and irrigation flow

AIM

To compare eight large- and low-tapered heat-treated reciprocating instruments regarding their design, metallurgy, mechanical properties, and irrigation flow through an in silico model.

METHODOLOGY

A total of 472 new 25-mm E-Flex Rex (25/.04 and 25/.06), Excalibur (25/.05), Procodile (25/.06), Reciproc Blue R25 (25/.08v), WaveOne Gold Primary (25/.07v), and Univy Sense (25/.04 and 25/.06) instruments were evaluated regarding their design (stereomicroscopy, scanning electron microscopy, and 3D surface scanning), metallurgy (energy-dispersive X-ray spectroscopy and differential scanning calorimetry), and mechanical performance (cyclic fatigue, torsional resistance, cutting ability, bending and buckling resistance). Computational fluid dynamics assessment was also conducted to determine the irrigation flow pattern, apical pressure, and wall shear stress in simulated canal preparations. Kruskal-Wallis and one-way anova post hoc Tukey tests were used for statistical comparisons (α = 5%).

RESULTS

Instruments presented variations in blade numbers, helical angles, and tip designs, with all featuring non-active tips, symmetrical blades, and equiatomic nickel-titanium ratios. Cross-sectional designs exhibited an S-shaped geometry, except for WaveOne Gold. Univy 25/.04 and Reciproc Blue displayed the smallest and largest core diameters at D3. Univy 25/.04 and E-Flex Rec 25/.04 demonstrated the longest time to fracture (p < .05). Reciproc Blue and Univy 25/.04 exhibited the highest and lowest torque to fracture, respectively (p < .05). Univy 25/.04 and Reciproc Blue had the highest rotation angles, whilst E-Flex Rec 25/.06 showed the lowest angle (p < .05). The better cutting ability was observed with E-Flex Rec 25/.06, Procodile, Excalibur, and Reciproc Blue (p > .05). Reciproc R25 and E-Flex Rec showed the highest buckling resistance values (p < .05), with WaveOne Gold being the least flexible instrument. The impact of instruments' size and taper on wall shear stress and apical pressure did not follow a distinct pattern, although Univy 25/.04 and E-Flex Rec 25/.06 yielded the highest and lowest values for both parameters, respectively.

CONCLUSIONS

Low-tapered reciprocating instruments exhibit increased flexibility, higher time to fracture, and greater angles of rotation, coupled with reduced maximum bending loads and buckling strength compared to large-tapered instruments. Nevertheless, low-tapered systems also exhibit lower maximum torque to fracture and inferior cutting ability, contributing to a narrower apical canal enlargement that may compromise the penetration of irrigants in that region.

Detection of the separated endodontic instrument on periapical radiographs using a deep learning-based convolutional neural network algorithm

The study evaluated the diagnostic performance of an artificial intelligence system to detect separated endodontic instruments on periapical radiograph radiographs. Three hundred seven periapical radiographs were collected and divided into 222 for training and 85 for testing to be fed to the Mask R-CNN model. Periapical radiographs were assigned to the training and test set and labelled on the DentiAssist labeling platform. Labelled polygonal objects had their bounding boxes automatically generated by the DentiAssist system. Fractured instruments were classified and segmented. As a result of the proposed method, the mean average precision (mAP) metric was 98.809%, the precision value was 95.238, while the recall reached 98.765 and the f1 score 96.969%. The threshold value of 80% was chosen for the bounding boxes working with the Intersection over Union (IoU) technique. The Mask R-CNN distinguished separated endodontic instruments on periapical radiographs.

Cyclic Fatigue of Different Reciprocating Endodontic Instruments Using Matching Artificial Root Canals at Body Temperature In Vitro

Reciprocating motion expands the lifetime of endodontic instruments during the preparation of severely curved root canals. This study aimed to investigate the time to fracture (TTF) and number of cycles to failure (NCF) of different reciprocating instruments (n = 20 in each group) at body temperature using a dynamic testing model (amplitude = 3 mm). Reciproc Blue (RPB), size 25/.08, WaveOne Gold (WOG) 25/.07, Procodile (Proc) 25/.06, R-Motion (RM_06) 25/.06 and R-Motion (RM_04) 30/.04 instruments were tested in their specific reciprocating motion in artificial matching root canals (size of the instrument ± 0.02 mm; angle of curvature 60°, radius 5.0 mm, and centre of curvature 5.0 mm from apical endpoint). The number of fractured instruments, TTF, NCF, the and lengths of the fractured instruments were recorded and statistically analysed using the Chi-Square or Kruskal-Wallis test. Both TTF (median 720, 643, 562, 406, 254 s) and the NCF (3600, 3215, 2810, 2032, 1482 cycles) decreased in the following order RM_06 > RPB > RM_04 > Proc > WOG with partially significant differences. During testing, only six RM_06 instruments fractured, whereas 16/20 (RPB), 18/20 (Proc), and 20/20 (RM_04, WOG) fractures were recorded (p < 0.05). Within the limitations of the present study, blue-coloured RPB and RM instruments exhibited a significantly superior cyclic fatigue resistance compared to SE-NiTi and Gold-wire instruments. Heat treatment, cross-sectional design and core mass significantly influenced the longevity of reciprocating instruments in cyclic dynamic testing.

Endodontic Orthograde Retreatments: Challenges and Solutions

Endodontic orthograde retreatments are considered one of the possible treatment options in case of post-treatment diseases considering the promising results present in the literature. Despite this, a plethora of articles have been published on this topic, and drawing conclusions could be challenging. For this reason, this review aims to summarize the crucial points on each aspect of non-surgical endodontic retreatments, discussing and comparing the current protocols, techniques, materials, and indications. Taking into consideration data from the literature, in terms of diagnosis, CBCT should be considered the first choice, since it can thoroughly affect the diagnosis and treatment plan. Regarding the procedural phases, some conclusions can be drawn: when present, coronal restoration materials such as crowns, partial prostheses, post, and core should be removed; the use of magnification devices, ultrasonic instruments, and an in-depth interpretation of radiographic images with both 2D and 3D images are strongly recommended during the orifice location; additional protocols such as irrigants activation, ultrasonic cleaning, and rotary or reciprocating instrumentation of treated canals are strongly recommended for filling materials removal and to achieve a high-quality chemo-mechanical disinfection; perforations should be treated as soon as possible, and the material of choice to treat them is the MTA or other calcium-silicate-based repair materials; the presence of ledges does not intrinsically reduce the success rate of RCRts if properly managed; in case of instrument fragments, their removal should be considered as the first treatment option, however many variables should be considered to select the proper technique or consider the option of bypassing.

Effectiveness of root canal instrumentation for the treatment of apical periodontitis: A systematic review and meta-analysis

BACKGROUND

The development of endodontic instruments has rapidly advanced, but their impact on endodontic outcome parameters remains unclear.

OBJECTIVES

This systematic review aimed to answer the following PICOT questions: In patients with apical periodontitis (P) what is the effectiveness of root canal instrumentation ([Q1] performed with contemporary techniques [I] in comparison with 'traditional' techniques [C]] and ([Q2] performed with contemporary engine-driven NiTi instruments [I] compared with other types of contemporary engine-driven NiTi instruments [with different design and/or technology] [C]) in terms of clinical and patient-related outcomes (O)?

METHODS

After PROSPERO protocol registration, a literature search was conducted using Clarivate Analytics' Web of Science, Scopus, PubMed and Cochrane Central Register of Controlled Trials. Grey literature and major journal contents were examined. Two independent reviewers performed the study selection, data extraction and appraisal of included studies. A quantitative meta-analysis was considered, and statistical heterogeneity and overall quality of evidence were assessed.

RESULTS

Nine studies were identified showing substantial methodological differences. Five studies addressed PICOT 1 and three PICOT 2, whereas one study aimed both. A random-effects meta-analysis model was considered for the outcome 'radiographic evidence of normal periodontal ligament space or reduction of apical lesion size' (PICOT 1) based on three studies with 332 evaluable participants and showed that contemporary instrumentation was associated with a more favourable outcome (p = .005) compared with root canal preparation with stainless steel instruments (odds ratio = 2.07 [95%-confidence interval = 1.25-3.44]) with no evidence of statistical heterogeneity (I2  = 0%) but low quality of evidence.

DISCUSSION

Albeit a few studies fulfilled eligible criteria, no study had a low risk of bias. Compelling evidence indicating significantly different outcome rates using different endodontic instruments when treating teeth with apical periodontitis is lacking.

CONCLUSIONS

In terms of healing, the results of the meta-analysis determined the higher effectiveness of root canal instrumentation performed with contemporary techniques in comparison with conventional stainless steel instruments in patients with apical periodontitis followed for a minimum of 1 year with low quality of evidence. No differences could be demonstrated between preparations with traditional stainless steel and contemporary NiTi instruments for other clinical and patient-related outcomes.

REGISTRATION

PROSPERO (CRD42021274642).

Design, metallurgy, mechanical properties, and shaping ability of 3 heat-treated reciprocating systems: a multimethod investigation

OBJECTIVE

This study aimed to compare 3 reciprocating systems regarding design, metallurgy, mechanical properties, and shaping ability.

MATERIALS AND METHODS

New Reciproc Blue R25, WaveOne Gold Primary, and REX 25 instruments (n=41 per group) were analyzed regarding design, metallurgy, and mechanical performance, while shaping ability (untouched canal walls, volume of removed dentin, and hard tissue debris) was tested in 36 anatomically matched root canals of mandibular molars. Results were compared using one-way ANOVA post hoc Tukey and Kruskal-Wallis tests with a significant level set at 5%.

RESULTS

All instruments showed symmetrical cross sections with asymmetrical blades, no radial lands, no major defects, and an almost equiatomic nickel and titanium ratio. The highest R-phase start temperatures were observed with WaveOne Gold (46.1°C) and REX (44.8°C), while Reciproc Blue had the lowest R-phase start (34.5°C) and finish (20°C) temperatures. WaveOne Gold had the lowest time to fracture (169 s) and the highest maximum load (301.6 gf) (P <0.05). The maximum torque of Reciproc Blue (2.2 N.cm) and WaveOne Gold (2.1 N.cm) were similar (P >0.05), but lower than REX (2.6 N.cm) (P <0.05). No statistical differences were observed among instruments in the angle of rotation (P >0.05) and in the shaping ability in both mesial and distal canals (P >0.05).

CONCLUSION

Although the overall design, temperature transition phases and mechanical behavior parameters were different among tested instruments, they were similar in terms of shaping ability.

CLINICAL RELEVANCE

All tested heat-treated NiTi reciprocating systems showed similar shaping ability, without clinically significant errors.

Negotiating the second mesiobuccal canal: A comparison of nickel titanium files through the experience of undergraduate dental students

OBJECTIVES

The aim of this study was to compare the ability of undergraduate students to reach working length (WL) in second mesiobuccal root canals (MB2) of maxillary first molars (n = 210) by using Reciproc Blue without glide path preparation, and One Curve with glide path preparation.

METHODS

The students (n = 105) attended theoretical and practical courses. The first group (n = 53) shaped MB2 root canals using the One Curve system and then Reciproc Blue; the second group (n = 52) shaped MB2 root canals following the reverse sequence. Participants completed a questionnaire. The chi-square and Mann-Whitney U test were used for statistical analysis using significance of p < 0.05.

RESULTS

The full WL was reached and shaping procedures were completed without complications in Reciproc Blue and One Curve groups at rates of 86.67% and 82.85%, respectively (p > 0.05). Treatment time was shorter in Reciproc Blue (p < 0.05). More (62.9%) students felt the One Curve system safer, while 61% felt the Reciproc Blue system faster.

CONCLUSIONS

Within the limitations of this study, instrument kinematics and glide path preparation did not interfere with undergraduate students' ability to achieve the WL in MB2 root canals.

Quality of root canal treatment performed by undergraduate students using nickel-titanium reciprocating versus hand instruments

PURPOSE

To compare the technical quality of root canal treatment (RCT) depending on the incidence of procedural errors performed by undergraduate students using nickel-titanium reciprocating and conventional hand instrumentation techniques, and to assess the impact of case difficulty and localization of the teeth (maxillary or mandibular molars).

METHODS

Dental records and periapical radiographs of molars that were treated with either hand or reciprocating WaveOne (WO) instruments were evaluated retrospectively. The technical quality of RCTs, the incidence of ledge formation, perforation, instrument fracture, overinstrumentation, underfilling, overfilling, inadequate root canal filling, and the effects of case difficulty and tooth localization were compared using the chi-square test with a significance of 5% (α = 0.05).

RESULTS

While overinstrumentation was more frequent in the WO group (247 teeth), the incidence of inadequate root canal fillings was higher in the hand instrumentation group (245 teeth) (p < 0.01). No significant difference was observed in the incidence of other procedural errors (p > 0.05). The number of teeth with acceptable technical quality in preparation and obturation was 172 (69.6%) in the WO group, whereas it was 142 (58%) in the hand instrumentation group, presenting a significant difference between the instrumentation techniques (p < 0.01). Higher technical quality rates were observed with WO instrumentation in the high difficulty category and in maxillary teeth (p < 0.01).

CONCLUSION

Higher technical quality in preparation and obturation can be achieved with WO reciprocating instruments and file-matched greater tapered gutta-percha cones. No significant difference was observed between the groups in the incidence of procedural errors except for overinstrumentation and insufficient root canal filling. WO instrumentation and obturation with file-matched greater tapered gutta-percha cones provided better technical quality in the high difficulty category and in maxillary teeth.

Incidence of fracture of ProDesign Logic system instruments: A cross-sectional retrospective study

The aim of the present study was to analyze the incidence of fracture of ProDesign Logic system instruments in endodontic treatments performed by a specialist, in addition to identifying the dental group, arch, and the root canal thirds in which the fractures occurred more frequently. Digital radiographs and medical records were initially analyzed and resulted in the selection of 561 teeth (1302 canals) treated between 2018 and 2020, using the ProDesign Logic system instruments. These data were reassessed to determine the occurrence of fractures and identify the dental group and root canal thirds in which they occurred. Then, the data were statistically analyzed using the Fisher's Exact Test (p < 0.05). The general fracture rates were 8.5 and 3.69%, considering the number of teeth and canals treated, respectively. Mandibular first molars were the teeth most associated with the occurrence of fractures (19.1%). When the arches were compared, there was no statistical difference regarding the number of fractures in the different root canal thirds (p = 0.307). However, they were more frequent in the apical third in both arches (p = 0.000). The incidence of fracture of ProDesign Logic system instruments was relatively high and occurred more frequently in the apical third of molars.

A single-file endodontic treatment: A promising endodontic concept

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Fracture incidence of Reciproc instruments during root canal retreatment performed by postgraduate students: a cross-sectional retrospective clinical study

Objectives

To evaluate the fracture incidence of Reciproc R25 instruments (VDW) used during non-surgical root canal retreatments performed by students in a postgraduate endodontic program.

Materials and Methods

From the analysis of clinical record cards and periapical radiographs of root canal retreatments performed by postgraduate students using the Reciproc R25, a total of 1,016 teeth (2,544 root canals) were selected. The instruments were discarded after a single use. The general incidence of instrument fractures and its frequency was analyzed considering the group of teeth and the root thirds where the fractures occurred. Statistical analysis was performed using the χ² test (p < 0.01).

Results

Seven instruments were separated during the procedures. The percentage of fracture in relation to the number of instrumented canals was 0.27% and 0.68% in relation to the number of instrumented teeth. Four fractures occurred in maxillary molars, 1 in a mandibular molar, 1 in a mandibular premolar and 1 in a maxillary incisor. A greater number of fractures was observed in molars when compared with the number of fractures observed in the other dental groups (p < 0.01). Considering all of the instrument fractures, 71.43% were located in the apical third and 28.57% in the middle third (p < 0.01). One instrument fragment was removed, one bypassed, while in 5 cases, the instrument fragment remained inside the root canal.

Conclusions

The use of Reciproc R25 instruments in root canal retreatments carried out by postgraduate students was associated with a low incidence of fractures.

Techniques to address fractured instruments in the middle or apical third of the root canal in human permanent teeth: a systematic review of the in vitro studies

OBJECTIVE

The objective of this study is to investigate techniques for approaching fractured instruments in the root canal and to present possible outcomes in relation to dentin thickness, fracture resistance, technique success, and clinical time.

MATERIALS AND METHODS

The bibliographic research was carried out in PubMed, Cochrane, Lilacs, Web of Science, Scopus, grey literature, and manual search. Following the inclusion and exclusion criteria, the titles and abstracts of 506 articles were read. Of these, 60 articles were selected and read in full. Fourteen articles were included in this systematic review.

RESULTS

The most studied technique was the ultrasonic technique and obtained good general results. The more apically the instrument is located, the more difficult it is to remove, the more dentin is removed, and the lower the fracture resistance of the tooth. When removal is not possible, the bypass technique can be performed (bypassing), and on weakened teeth or with little dental remnants, the GentleWave System technique can be used.

CONCLUSION

This systematic review shows the evidence from laboratory studies that the curvature and the root third in which the fracture of instruments occurred is relevant to fracture resistance and success. The ultrasonic technique got the best results. Well-conducted clinical studies should be performed for clinical practice.

CLINICAL RELEVANCE

The approach of fractured instruments in the root canal is efficient with the use of ultrasound, bypass technique, and Gentle Wave System.

Evaluation of type of kinematics on glide path procedures and torsional fatigue resistance after preparation of moderately curved canals

Sixty moderately curved canals of mandibular molars classified as Vertucci's type IV canal configuration were selected by micro-CT 1174. The teeth were divided into two groups according to the kinematics used, whether reciprocating or rotary motion (n=30, totaling 60 mesial root canals). The instruments used to perform the glide path procedures had identical features (0.15 mm of tip size, 0.04 mm/mm taper, thermal treatment, and square cross-section), but differed in the direction of the cutting blade. The duration of the procedure and the absolute and percentage frequency of the instruments to reach the full working length were recorded. The torsional test (3630-1; 1992) was performed on both used and unused instruments, to evaluate a possible reduction in the torsional resistance when using the glide path procedure. Statistical analysis was performed using the unpaired t-test and the chi-square test, and the level of significance was set at 5%. The type of kinematics used affected the duration of glide path procedures, and the reciprocating motion seemed to induce less torsional stress during glide path procedures.

Influence of different viewing conditions on the detection of fractured endodontic instruments using periapical radiographs at 3 projection angles

OBJECTIVES

The objective of this study was to assess the influence of ambient lighting levels and horizontal viewing angle (HVA) on the radiographic detection of fractured endodontic instruments in root canals in extracted human mandibular molars.

STUDY DESIGN

Thirty-two root canals were selected. Endodontic instrument fracture was induced in 24 canals, and all canals were endodontially treated. Periapical radiographs were obtained at orthoradial, mesioradial, and distoradial projection angles. Five oral radiologists examined the radiographs for detection of fractured endodontic instruments under 3 ambient lighting levels (high, 450 lux; medium, 28 lux; and low, 2.5 lux) and 3 HVAs (90°, 67.5°, and 45°). Area under the receiver operating characteristic curve (AUROC), accuracy, sensitivity, and specificity were calculated and compared by 2-way analysis of variance using Tukey post hoc tests (α = .05).

RESULTS

AUROC data indicated that ambient lighting (P = .739) and HVA (P = .238) did not significantly influence the detection of fractured endodontic instruments. Overall mean diagnostic values were 0.745, 0.57, 0.46, and 0.90 for AUROC, accuracy, sensitivity, and specificity, respectively.

CONCLUSIONS

The viewing conditions assessed in this study did not influence the radiographic detection of fractured endodontic instruments in root canals.

Optimum glide path motion is safer than continuous rotation of files in glide path preparation

This study evaluated the resistance to flexural fatigue and torsional strength of files for glide path preparation in continuous rotation or Optimum Glide Path motion (OGP). ScoutRace 15.02 and ProGlider 16.02 files were used in a dynamic testing device during preparation of simulating curved root canals (40-degree curvature and 5 mm radius). For the torsional test, a machine was used to test torsion measured maximum torsional strength (N.cm). Two-way anova and Tukey's multiple comparisons test were used for statistical analysis. Files in OGP motion had a statistically better resistance to flexural fatigue (P < 0.05). ProGlider files took longer time to failure than ScoutRace files only when OGP was used (P < 0.05). The torsional test revealed that OGP produced significantly less torsional stress than rotary motions for both types of glide path files (P < 0.05) In conclusion, OGP motion increased substantially the mechanical safety of endodontic glide path files.

Reciproc Endodontic File Surface Defects After Single Use: An SEM Analysis

Objective:

The aim of this investigation was to detect defects that may occur to Reciproc endodontic files after a single use.

Materials and Methods:

A sample of convenience of Reciproc files (VDW GmbH, Munich, Germany) that were used to prepare root canals of anterior or posterior teeth were collected. The files were divided equally into two groups: Group 1 (R25) files were used to prepare mesial root canals of 50 human permanent mandibular molars, and Group 2 (R40) included 50 files that were used to prepare permanent maxillary incisor teeth. Files were analyzed after single use by using a scanning electron microscope at X120 to detect changes in surface morphology. The data were statistically analyzed by using the χ² test, and statistical significance was set at P < 0.05.

Results:

A total of 96 Reciproc NiTi files were collected; of those, 67 (70%) were unaffected and 29 (30%) showed overall surface deformations. The types of deformation were blade disruption (22%), surface pitting (12%), and unwinding and tip deformation (1%). No microcracks were detected, and none of the studied files showed fracture. R40 was three times more likely to be deformed and showed blade disruption compared with R25 (P < 0.05).

Conclusions:

Reciproc rotary NiTi files show high resistance to deformation after a single use. Blade disruption was the most frequent defect occurring in both the small and large files.

Clinical fracture incidence of rotary and reciprocating NiTi files: A systematic review and meta-regression

This systematic review was registered in PROSPERO (CRD42017075917) and aimed to investigate whether the available clinical evidence supports the hypothesis that reciprocating motion results in a lower incidence of nickel-titanium files fracture compared to continuous rotation. Clinical studies that reported the incidence of fracture of engine-driven nickel-titanium files were included. The main exposure was the kinematics, and the primary outcome was the incidence of files fracture. The overall incidence of files fracture was 2.27%, with a trend for higher incidence with rotary motion (2.43%) than with reciprocating (1.0%), though without significant differences. Multiple meta-regression models revealed that the use of nickel-titanium files in more than four teeth and less proficient operators were associated with a higher incidence of file fracture. There was no difference in the clinical incidence of fracture of nickel-titanium instruments between reciprocating and rotary motions; however, other factors were identified.

Etiology and Prevention of an Endodontic Iatrogenic Event: Instrument Fracture

Although benefiting from an unprecedented technological evolution, contemporary endodontics is still characterized by the recurrence of retreatments, due to the need to solve quite frequent incidents, accidents, or even failures of primary endodontic treatment. This survey aims to assess both the etiology and the prevention methods of one of the most troublesome endodontic iatrogenies: instrument separation during root canal shaping. The multifactorial nature of this occurrence entails identifying and taking into account all the causal and contributing factors. Their significant number and the possible involvement of any of them, starting with the complexity and variability of the root canals and ending with the technical specifications concerning the nickel-titanium rotary instrumentation system being used, highlight the necessity to develop valid guidelines to avert the occurring of such an upsetting situation.

Fracture incidence of WaveOne Gold files: a prospective clinical study

AIM

This prospective clinical study evaluated the incidence of instrument fracture observed after single-file root canal treatment of molars using WaveOne Gold instruments.

METHODOLOGY

Three standardized, experienced and calibrated specialists treated 750 maxillary and mandibular molars with curvatures less than 45° (2691 root canals) over a 12-month period. All the treatments were performed in a single session. A total of 1104 WaveOne Gold instruments were used, including 38 small, 750 primary, 228 medium and 88 large instruments. Intracanal procedures were performed according to the manufacturer's recommendations, and each instrument was used in a single clinical case. The instruments were examined after their removal from the canal, under an operating microscope at 8× magnification.

RESULTS

No fractures were observed in any of the 1104 instruments used.

CONCLUSIONS

No fractures of WaveOne Gold reciprocating instruments occurred during root canal preparations performed in maxillary and mandibular molars with curvatures less than 45° when used strictly according to the manufacturer's recommendations and applied in a single clinical case.

Undergraduate Students' Acceptance of a Reciprocating One-File System for Endodontic Treatment

OBJECTIVES

Reciprocating endodontic one-file systems are a comparatively new method for root canal shaping. Even though the mechanical properties are comparable to modern rotating mechanical systems, data about subjective assessment and application quality are scarce. This study evaluates the reciprocating one-file system in undergraduate education.

MATERIALS AND METHODS

A total of 42 undergraduate students without experience regarding reciprocating file systems filled in a questionnaire in four different points in time (t ₁-t ₄) anonymously. The questionnaire was based on a numerical rating scale ranging from 0 to 10.

STATISTICAL ANALYSIS

A least significant difference post-hoc analysis comparing the group average values was performed. The adjusted level of significance was p < 0.004 after Bonferroni correction.

RESULTS

All rating scores increased after the first theoretical instruction. After the first practical training in artificial root canals in resin blocks and extracted teeth (t ₂), the estimation of "time efficiency" (p = 0.002), "handling" (p < 0.001), and "overall impression" (p < 0.001) improved significantly. The "overall impression" remained constant and showed no significant changes after the first practical training.

CONCLUSIONS

Reciprocating systems seem to show a good acceptance among first time users. Initial concerns about "work safety" decrease during every step of the educational process. Reciprocating one-file systems are a safe and well-accepted method in undergraduate teaching.

The incidence of nickel-titanium endodontic hand file fractures: A 7-year retrospective study in a tertiary care hospital

Aim:

The present retrospective cross-sectional study aims to evaluate the incidence and factors associated with nickel-titanium hand file fractures in root canal-treated teeth in a tertiary care hospital of western India.

Methodology:

The diagnostic records of intraoral periapical (IOPA) radiographs were analyzed to check for file fractures in the root canal-treated teeth. As a part of standardized departmental protocol, Hand ProTaper Universal file system (Dentsply, India) was used for chemomechanical preparation for root canal treatment. The file fractures were analyzed with reference to age group, type of teeth, curvature of the canal, site of file fracture in the canal, length of file fracture, level of file fracture, distance of the file fracture from the apex, and obturation status of the file-fractured tooth. Chi-square test was applied to assess the significance difference between the tested groups.

Results:

A total of 19,810 IOPA X-rays were screened and 2728 root canal-treated teeth were found and of these 2728 cases, 109 file-fractured teeth were observed.

Conclusion:

The total incidence of file fractures was 3.9/100 root canal-treated cases, and mandibular molars with severely curved canals (>25°) had shown the maximum incidence of file fractures.