Separated Instrument in Endodontics: Frequency, Treatment and Prognosis

Can perception of fractured endodontic files benefit 1st degree dental students and dental educators: A questionnaire-based survey

PURPOSE

This study aimed (i) to assess the perception of dental undergraduate (1st degree dental students) learners about endodontic file separation (EFS) and knowledge of its avoidance, as well as (ii) to aid dental educators in conceptualizing and designing student-directed courses for better understanding. The rationale of this study was to provide both learners and educators with a tool to help self-assess/impart knowledge and devise simple yet innovative modern ways of teaching in the field of endodontics. The study utilized a self-reporting dataset from one institution to disclose this limitation.

MATERIALS

A validated self-administered questionnaire from a previous study was converted into an online Google form link consisting of 15 multiple-choice questions. This was distributed to 100 Year 4 and Year 5 1st degree dental students. Pearson chi-square test was used for statistical analysis (p < 0.05).

RESULTS

The response rate was 81%. The majority of the learners expressed that performing endodontic treatment in permanent (100%) posterior teeth of old-aged people causes EFS (95.1%). Ninety-nine percent answered that EFS was a gender-independent factor, 72.8% perceived that patient anxiety leads to EFS, and 88.9% said that the apical third was more prone to instrument fracture and had the poorest prognosis (95.1%). Hundred percent, 93.8%, 100%, 92.6%, 100%, and 97.5% of respondents, respectively, perceived that the role of operator, coronal flare, ethylenediaminetetraacetic acid (EDTA) gel, cleaning endodontic instrument, reusing instrument, and choice of instrument affects the occurrence of EFS. A total of 71.6% said hand files fractured, while 86.4% perceived that stainless steel alloy files separated easily, and 69.1% of learners perceived that EFS occurred often during the cleaning and shaping stage.

CONCLUSIONS

The perception of 1st degree dental students regarding EFS and knowledge of its avoidance was good. Results from this study confirmed that the 1st degree dental students' clinical training courses and study modules adopted and designed by their dental educators were well-suited and appropriate.

Broken Instrument Removal Methods with a Minireview of the Literature

Instrument fracture in the root canal system is an unpleasant incident that may occur during root canal treatment. Comprehensive cleaning of the root canal system is often impossible in the presence of a broken instrument. Therefore, it is often imperative to remove the broken fragment from the root canal system. To date, various methods have been proposed for the removal of broken instruments from the root canal system. However, no consensus has been reached on a safe technique with a high success rate for broken instrument removal. This case series reports six cases of successful removal of broken instruments using different methods including the ultrasonic, tube-and-glue, tube-and-wire, tube-and-internal shaft, and the forceps techniques and also provides a brief review of the relevant literature.

Assessment of Incidence, Management and Contributory Factors of Root Canal Instrument Separation in an Endodontics Post- Graduate Program: A Retrospective Clinical Study

BACKGROUND

The successful outcome of nonsurgical root canal treatment (NS-RCT) is largely dependent on the technical quality of the procedure.

OBJECTIVE

To investigate the incidence of separated instruments in endodontic postgraduate clinics between January 2018 and December 2021, and to determine the potential contributory factors that increase the risk of instrument separation.

MATERIALS AND METHODS

A retrospective observational study was conducted in the Department of Endodontics, Faculty of Dentistry, King Abdulaziz University, Jeddah, Saudi Arabia. Data was collected to determine the incidence of separated instruments and their associated variables. Seven variables were analyzed separately: nonsurgical initial or retreatment case, tooth type, tooth arch, tooth location, canal type, root curvature, level of fracture, and file type.

RESULTS

A total of 3150 cases were treated, of which 108 cases had separated instruments. The overall incidence of instrument separation was 3.4% while 53.7% of separated instruments occurred in the mandibular molars, followed by 42.6% in the maxillary molars. The highest frequency of instrument separation was recorded in the mesiobuccal canal (35.2%). The level of separation was found to be statistically significant in relation to the management (P < .001).

CONCLUSION

Nickel-titanium instruments tend to separate more inside the root canal system than stainless steel instruments. However, under the limitation of this study, the incidence of instrument separation is still quite low, even with postgraduate endodontic residents with limited experience.

Comparative evaluation of stress distribution against the root canal wall at three different levels using novel NiTi rotary files - A finite element analysis

Background

Recent innovations in the physical and mechanical features of endodontic file systems have diminished the prospect of stress generation and fracture risk in novel endodontic files.

Aim

The purpose of this research was to comparatively evaluate the stress distribution of recently introduced endodontic rotary files with distinct features and metallurgy at three different levels of the root canal wall by finite element analysis.

Materials and Methods

Forty endodontic files were used in this experiment after being inspected through a scanning electron microscope for any surface deformities. Based on their metallurgy and design, the scanned files were divided into four groups, each with 10 samples: Group A-2Shape files, Group B-F360, Group C-One Curve, and Group D-TruNatomy. To assess the mechanical behavior of these files, the stress produced by computer-aided models of these instruments on the dentinal wall of a simulated root canal was numerically analyzed using ANSYS® 15 Workbench finite element software.

Results

A one-way ANOVA was used to assess all the raw data with post hoc Tukey analysis, the Shapiro-Wilk test, and Levene's test. F360 files exerted the maximum stress on the dentinal wall, while TruNatomy files exerted the least stress at all the distinct levels of dentinal walls.

Conclusions

There was no statistically significant variation in the stress generated between the four groups. Therefore, it can be concluded that improvements in rotary file design and metallurgy have the potential to reduce the stress during canal shaping and the risk of instrument breakage during clinical use.

Removing Fractured Endodontic Files with a Tube Technique-The Strength of the Glued Joint: Tube-Endodontic File Setup

One recommended technique for removing broken root canal instruments is to glue the fragment into a cannula adapted to it (i.e., the tube technique). The aim of the study was to determine the influence of the adhesive kind and length of the joint on the breaking force. During the investigation, 120 files (60 H-files and 60 K-files) and 120 injection needles were used. Fragments of broken files were glued into the cannula using one of three materials: cyanoacrylate adhesive, composite prosthetic cement, or glass ionomer cement. The lengths of the glued joints were 2 and 4 mm. After the polymerization of adhesives, a tensile test was carried out to find a breaking force. The results were statistically analyzed (p < 0.05). For 4 mm lengths of glued joints, the breaking force was higher than for 2 mm for both file types (K and H). In the case of K-type files, the breaking force was higher for cyanoacrylate and composite adhesives than glass ionomer cement. For H-type files, no significant difference in joint strength was found between binders at 4 mm, while at 2 mm, a much better connection was obtained for cyanoacrylate glue than prosthetic cements.

Opto-magnetic imaging spectroscopy in analyzing rotary NiTi endodontic instruments

Intra-canal fracture of rotary NiTi instruments occurs due to torsional stress, cyclic fatigue, or a combination of these two factors. Broken instruments are a serious obstacle to shaping, cleaning, and filling of the root canal and can adversely affect the outcome of endodontic therapy. The aim of this study was to examine the magnetic properties and ultrastructural changes of new, used, and fractured NiTi instruments using opto-magnetic imaging spectroscopy (OMIS). The study included three sets of different types of rotary instruments: MTwo (VDW, Munich, Germany), Pro Taper Universal (Dentsply Maillefer, Ballaigues, Switzerland), and BioRace (FKG DENTAIRE Swiss Dental Products, Le Crêt-du-Locle Switzerland). Root canal shaping was performed on root canals with different curvatures, and after intra-canal fracture, instruments of the same type (new, used, and fractured) were analyzed using OMIS at the Faculty of Mechanical Engineering, University of Belgrade. The obtained results showed a coincidence of peak localization for the used instruments that did not suffer a fracture, as well as for new, unused instruments of all examined groups. Additionally, there was a coincidence of peak intensities for new and fractured instruments in all groups. The specific treatment of electropolishing of the active surface of BioRace instruments caused a completely different electromagnetic response compared to conventional NiTi sets of tested instruments. New, unused BioRace instruments had the most pronounced positive (5.6078 n.a.u. x1000) and negative (-8.5218 n.a.u. x1000) intensity values. The analysis of NiTi instruments using opto-magnetic imaging spectroscopy indicated changes in the magnetic properties after their instrumentation.

Impact of a Retained Instrument on Treatment Outcome: A Systematic Review

Instrument separation during endodontic therapy is a frequent accident with rotary instruments being more likely to separate than manual ones. There are various treatment options when the instrument separates in a canal depending on the location, complexity of the canal anatomy, and the operators' ability. The success of the tooth that has a retained fragment of instrument in the canal has been assessed in various studies but no clear conclusion has been drawn. The goal of this systematic review is to answer as many questions as possible. Does the retention of a separated instrument, compared with no retained separated instrument, result in a worse clinical outcome in adult patients who have received nonsurgical root canal treatment?

Materials and Methodology The search was conducted with the boolean terms in various database following the PRISMA guidelines. The inclusion and exclusion criteria were set for the inclusion of the study for the systematic review.

Results Out of the 330 articles that were obtained, 28 were duplicates. After screening for eligibility, only 7 articles were retrieved for full text. When inclusion and exclusion criteria were applied, none of the studies could be included.

Conclusion There is still a lack of consensus on the treatment option for a separated instrument and there is no clear evidence to suggest whether the prognosis of the tooth with retained instrument is reduced or not.

A single-file endodontic treatment: A promising endodontic concept

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Comparison of three irrigation methods: SWEEPS, Ultrasonic, and Traditional irrigation, in smear layer and debris removal abilities in the root canal, beyond the fractured instrument

BACKGROUND

This study compared the effectiveness of three irrigation methods in removing smear layer and debris in the presence of the fractured instrument. The three compared irrigation methods were conventional syringe irrigation, passive ultrasonic irrigation, and SWEEPS (Shock wave enhanced emission photoacoustic streaming) irrigation.

METHODS AND MATERIALS

Sixty-three permanent mandibular molars with moderate curvature were included in this experimental study. Mesiobuccal root canals were prepared with Race files (FKG Dentaire. Switzerland) up to #25, 4%. A #30, 6% Race file was used to simulate file fracture 3 mm short of working length. The prepared samples, randomly divided into three groups, and final irrigation was separately done in each group. Group 1 conventional syringe irrigation (CSI) as the control group, Group 2 passive ultrasonic irrigation (PUI), and Group 3 Shock wave enhanced emission photoacoustic streaming or SWEEPS Irrigation (SI). Smear layer and debris removal beyond separated file scored with scanning electron microscope(SEM) images. Data were analyzed using the nonparametric tests to compare the smear layer and debris scores.

RESULT

SWEEPS and passive ultrasonic irrigation significantly removed smear layer and debris, better than conventional syringe irrigation (p<0.001). The smear layer and debris removal efficiency between passive ultrasonic Irrigation and SWEEPS were not significantly different (p=0.629).

CONCLUSION

In the face of the irretrievably broken instrument in the root canal, passive ultrasonic irrigation and the SWEEPS method can enhance smear layer and debris removal compared to conventional syringe irrigation.

Sealer penetration: effect of separated file's cross-section, taper and motion characteristics

OBJECTIVES

The separated root canal instruments may affect the quality of root canal filling, hence the success of endodontic treatment. The aim of this study was to evaluate the effects of separated file fragments of nickel-titanium rotary systems with different cross-section, taper and motion characteristics on the apical sealer penetration in oval-shaped root canals via confocal laser scanning microscope (CLSM).

MATERIALS AND METHODS

Distal roots of 60 mandibular molars with oval-shaped root canals were randomly divided into 4 groups as follows: group 1, FlexMaster Nickel Titanium Rotary File System (NTRFS) (separated instrument: 30/.06); group 2, ProTaper Next NTRFS (X3); group 3, ProTaper Universal NTRFS (F3); group 4, Revo-S NTRFS (AS30/.06). Root canals were filled with gutta-percha and AH plus labelled with 0.1% rhodamine B using a warm vertical compaction technique. Each specimen was horizontally sectioned at 1st, 3rd and 5th mm from apical foramen. Amount of maximum and average penetration depths, penetration percentage and sealer penetrated area were measured and analysed with one-way repeated measures of ANOVA and the Bonferroni post hoc tests. p < 0.05 was considered significant.

RESULTS

The penetration depth, percentage and penetrated area of the sealer increased from apical to coronal in all systems. The maximum and average penetration depths and penetration areas were higher in FlexMaster and Revo-S groups at the 3rd mm (p < 0.05). At the 5th mm, the Revo-S group had a higher penetration percentage, when compared with ProTaper Next and ProTaper Universal groups (p < 0.05).

CONCLUSIONS

In the 1st mm, separated fragments of any system did not allow the penetration of the sealer, while it was observed that the files with constant taper showed more positive results in terms of sealer penetration at apical 3rd and 5th mm.

CLINICAL RELEVANCE

In the presence of a separated file, the taper of the file might significantly affect the amount of penetrated sealer into the dentinal tubules as compared with the cross-section and motion characteristics of the file.