Prevention and management of fractured instruments in endodontic treatment

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.

Perception of Dental House Officers regarding Endodontic File Separation during Endodontic Treatment

Background

Despite of having improved endodontic file designs as well as the reinforced metal alloy file structure, intracanal endodontic file separation (EFS) is still a very problematic and worrisome dental incident, which usually occurs without any visible signs of permanent deformation. Further, there have been conflicting reports regarding the clinical significance of leaving separated files within root canals.

Aims

The aim of this study was to look into the current perceptions and awareness about file separation during endodontic treatment among the dental house officers (DHOs).

Materials and Methods

A novel validated questionnaire comprising of 15 close-ended questions was distributed anonymously via Google Forms through email to 1100 DHOs across Pakistan. The questionnaire consisted of two parts: the first component (Section I) collected demographic data and the second component (Section II) investigated the causes of EFS during root canal treatment. Following the completion of socioeconomic information, including age and gender, the DHOs were asked to answer a few questions about the various reasons for endodontic instrument fracture.

Results

A total of 800 responses were recorded, with an effective rate of 72.8%. The majority of the DHOs (p value < 0.001) perceived that endodontic instrument fracture occurred in the posterior (61.5%) and apical third of the canal (50.5%) and in older permanent dentition (67.3%), possibly due to patient anxiety (62%). Better choice of instrument (61.15%), operators' experience (95.3%), knowledge (87.5%), and proper root canal cleaning (91.1%) are believed to be the vital steps in reducing endodontic file separation/fracture. Furthermore, majority of them (p value < 0.001) perceived that stainless steel was a superior alloy for filing instruments. Manual files tend to be more prone to fractures due to repeated use than rotary files.

Conclusion

This study demonstrated that young DHOs had adequate knowledge and awareness regarding the potential predisposing factors and handling techniques for EFS. This study thereby provides an evaluating tool to access the insights of the current perceptions and awareness of DHOs concerning EFS.

Defects and Safety of NiTi Root Canal Instruments: A Systematic Review and Meta-Analysis

Aim: To review the reported defect and fracture rates of various NiTi instrumentation systems and identify factors that may influence the chance of NiTi file separation clinically.

Data Sources: PubMed, EMBASE, and SCOPUS with controlled vocabulary and keywords in various combinations to identify articles that reported on the defects and/or fracture of NiTi instrument used clinically (Jan 1980 till Aug 2021), with additional search manually by going through the list of references of the initially screened articles. Those satisfying the inclusion and exclusion criteria were entered into the analysis.

Study Eligibility Criteria, Participants, and Interventions: All studies from the said databases reporting on NiTi root canal instruments that were deformed or separated during normal clinical use.

Study Appraisal and Synthesis Methods: Studies with data available and suitable for meta-analysis were grouped according to the general design of the NiTi instruments for comparison. Safety quotient value was calculated based on the rate of instrument distortion and fracture.

Results: Various instrument designs exhibited different incidences of distortion and fracture, hence a different “safety quotient” (ratio of the amount of deformed instruments to that of fractures in use). Heat-treated files showed the highest safety quotient value. All brands of NiTi file demonstrated a statistically significantly lower incidence of fracture, if treated as disposable instruments after clinical use in a patient.

Limitations: Inclusion of articles written in English only, and grouping of file systems into general design types in the analysis.

Conclusions and Implications of Key Findings: NiTi endodontic files should be scrutinized for defects before being used in the root canal. Disposing the NiTi instruments after clinical use in a patient (so-called “single use”) is recommended for minimizing fracture clinically. Certain instrument designs tend to show discernible deformation before they should fracture in the next use.

Fractographic analysis of separated endodontic file designs

Endodontic rotary files are cutting instruments used to perform root canal procedures within a tooth interior. Focusing on quantitative fractographic analysis increases necessary, clinical performance understanding of file separation failure. This research employed controlled, dynamic testing to failure of commercial rotary files, analyzing the fractographic, forensic characteristics in relation to Weibull reliability determination, considering: (1) design analysis; (2) stress concentrations; (3) times to failure; (4) number of cycles to failure (NCF). Ex vivo testing included three file designs, each having constant tip size (0.035 mm), taper (0.06 mm/mm), and length (25 mm). Files were individually tested using an electric, torque-controlled handpiece, rotating within a standardized, simulated canal until fracture separation occurred. Fractographic analysis, including critical measurements, was conducted using the scanning electron microscope (SEM) (PhenomProX, PhenomWorld, NL). Weibull statistical analysis established reliability factors per design group. Fractographic analysis identified separation fractures, processing inclusions, flexural-fatigue striations, and stress concentrations at flute pitches. Calculated NCF median values (1277-EE; 899-VB; 713-PI) demonstrated significant statistical differences among groups (p < 0.001). Separated apical fragments yielded statistically significant differences (p ≤ 0.05) for varying file design groups. Weibull moduli among groups were statistically equivalent. Fractographic analysis exposed a presence of multiple failure factors in addition to defect distribution, governing cyclic fatigue failure originating at stress concentration points irrespective of file design. Fractographic analysis indicated that a change in file design, specifically at the working edges, in addition to improved surface finish, has the potential of reducing failures by lowering points of stress concentration and reducing fracture initiating surface cracks.