Prevalence of Separated Instruments in Routine Endodontic Practice and its Overall Impact on the Procedure: A Questionnaire Study

Introduction

The primary objectives of root canal treatment are proper cleaning, shaping, and three-dimensional fluid-tight sealing of the root canal system. Fracture of instruments inside the root canal is one of the many obstacles any clinician can face in a routine endodontic procedure. Endodontic files or reamers are the commonly separated instruments, but other instruments such as gates-glidden or peeso drills, lentulospirals, thermomechanical gutta-percha compactors, or tips of hand instruments such as explores and spreaders can get separated too.^1,2 This mishap is frustrating for the clinician as it prevents access to the apex, and increases the treatment time. The reasons for separation could be many, such as internal curvature, design of the access, number of times the instrument has been used.

Dental operating microscope, dental loops, and CBCT (Cone Beam Computed Tomography) which plays an important role in diagnosis can aid in the retrieval process. The retrieval process can lead to procedural errors like root perforations and fractures which in turn affects the prognosis of the tooth. The success of the treatment depends on the management of these errors. The benefits of retrieval should be weighed against the risks, such as other complications that could occur during the retrieval process. The retrieval is not always possible and in such situations, bypassing the fragment to clean and shape the canal till the apical third with subsequent follow-ups is a good option.³ This paper includes a survey conducted among dental undergraduate students, postgraduate students, dental practitioners, endodontists, and other practicing specialists to assess the prevalence, diagnosis and management of separated instruments.

Materials and Methods

Study design

Survey

Sample size estimation

n = Z2 (1-α) ×PQ

∆2

Z1-α = 1.96 for 95% confidence interval

P = 0.5 (based on the probability that 50% of the dentist are practising)

Q = 1-P

∆ (Margin of error) = 0.05

After replacing the above values,

n = 384

Keeping additional 10% to compensate for any loss to follow up,

n = 384+39 = 423

Rounded off to 450

Inclusion criteria

Bachelor of Dental Surgery (BDS) students, practicing dental surgeons, postgraduate students of various departments of dentistry and practicing specialists.

Exclusion criteria

Anyone other than those mentioned in the inclusion criteria.

Methodology

A questionnaire containing 30 questions was designed, and was validated by seven subject experts. Based on CVR (Content Validity Ratio) scores obtained from validation, a total of 12 questions were retained, 14 were modified and four questions were eliminated. A pilot study was conducted among 45 subjects.

An online form comprising of 26 questions was circulated to all the known BDS students, practicing dentists, postgraduate students of various departments and specialists via E-mail, WhatsApp and other social media from 17/02/2022 till 16/03/2022 to fill the form and circulate among known practitioners. A total of 507 responses were received, and the first 75 responses from each of the six groups were included in the study for standardization, with a total of 450 participants.

Statistical analysis

The data was compiled systematically and a master table was prepared in Microsoft Excel. Epi info version 7 statistical software by Centre for Disease Control and Prevention (CDC, Atlanta, GA) was used to perform statistical analysis. Descriptive analysis of all variables was done using frequency and proportion for categorical variables and Chi-square test was used to compare the proportions. The level of significance was set at p <0.05.

Discussion

Only 341 out of 450 participants either had separated or diagnosed an instrument separation; 100% of endodontists and postgraduates of Endodontics department had diagnosed this mishap. Out of 109 participants who were unable to diagnose a separated instrument, 69 were BDS students (Table 2). Around 78% of the participants diagnosed the separation in routine diagnostic radiographs in asymptomatic patients. Majority of the separations were observed in the apical third (73.6%), followed by middle third (20.2%), and this finding is similar to that reported by Tzanetakis and co-workers.⁴

The study conducted by Di Fiore and associates attributed increase in complexity of canal morphology in the posterior teeth for a higher incidence of separation with about 39.5% of fractured instruments located in the mesiobuccal canals of molars.5 Similar findings were observed in the present study with 48.1% incidence of separation noted in the mesial roots of mandibular molars (Table 1).

Around 46.3% of the participants reported fractured rotary instruments and 34% reported fractured stainless steel (SS) hand instruments (Table 1). Plotino and coworkers attributed the fracture of Nickel-titanium (NiTi) rotary instruments to cyclic flexural fatigue or torsional failure, or a combination. The torsional resistance of SS files was certified to be higher than NiTi instruments. But, any instrument may fracture in the root canals if the curvatures are severe, regardless of the torsional or fatigue resistance.⁶

SS instruments show visual signs of deformation before fracture, while NiTi instruments do not, which could lead to over usage of the file without warning. This could be one of the reasons for 59.3% of the participants mentioning over usage as the reason for fracture.

Around 61.3% of participants could bypass the instrument successfully (Table 1). 84% of the Endodontists and 68% of the postgraduate students from the department of Conservative Dentistry and Endodontics could bypass the separated instrument, while this could be achieved only by 3% to 54.4% of participants from other groups (Table 3). It has been reported by Saunders and associates that if the file is bypassed, the retained fragment does not compromise obturation quality.⁷ Bypassing the separated instrument is a relatively conservative approach than the instrument retrieval.¹

More than 80% of the participants used magnification either a dental operating microscope (DOM) or loops during retrieval. Around 54.2% participants used ultrasonics to remove the instrument (Table 1). The use of ultrasonic tips in combination with DOM is very effective for removing separated instruments from the root canals. Success rates for fragment removal using ultrasonics reported in various clinical trials range from 67% as reported by Nagai et al., to 88% and 95% as reported recently by Cuje et al., and Fu et al., respectively.^8-10

Only 144 (42.2%) participants could remove the separated instruments, out of which 40 were Endodontists, 33 were postgraduate students from Conservative Dentistry, while 71 were from other groups (Table 4).

In our study, 57.8% of the participants failed to remove the fragments (Table 1). It could be because the groups included were very diverse, including the least experienced undergraduate students to the experienced Endodontists. Among them, 32% attempted to bypass, failed and continued with obturation. Around 26.6% of the respondents obturated as the patients were asymptomatic. About 25% of respondents attempted to remove, failed and continued with obturation of the canal. Retained, fractured endodontic instruments did not reduce the prognosis of endodontically treated teeth when the apical infection was absent.^11,12

In our study, 60% of the participants used a combination of NaOCl, EDTA and saline as irrigants (Table 1). It has been suggested that the use of EDTA can help in removal of debris and smear layer from the grooves of the instrument and thus facilitates fragment removal from the root canal.¹³ NaOCl, considered a gold standard is the most commonly used irrigant due to its high antimicrobial activity, antibiofilm activity, and soft tissue dissolving capabilities. However, prolonged use could corrode the instrument and increase the probability of fracture of instrument.¹⁴

Around 36.1% of the respondents used lateral compaction technique and 48.4% used ZnOE as the sealer (Table 1). Jisna and co-workers showed that ZnOE is associated with higher apical leakage compared to resin and bioceramic sealers due to the lack of chemical adhesion to dentin. But the clinicians prefer it over other sealers as it is economical and easily available.¹⁵

In our study, 68.9% of the participants performed the removal and retreatment in multiple visits (Table 1). A study conducted by Suter and associates reported an increase in failure rate when treatment time exceeded 45–60 min. It could be due to increased operator fatigue and stress.¹⁶

The most common procedural errors that occurred while attempting an instrument removal were ledge formation (47%), and perforations (18%) (Table 1). This could be due to the additional removal of dentin from the canals while attempting to produce straight-line access and trying to loosen the separated fragment.^17,18

Around 63% of the respondents preferred calcium hydroxide (Table 1) which is the most common intracanal medicament used while attempting the removal of separated instrument in multiple visits because of its high pH, antimicrobial properties and low chance of flare-ups.¹⁹

Patients were commonly followed up for a period of three months using conventional radiographs. This study did not consider the experience of the participants and the stage of the root canal procedure at which the instrument separated, which plays a critical role in prognosis after separation.

Conclusion

In the present study, majority of the participants could diagnose the instrument separation in routine diagnostic radiographs because most of the patients were asymptomatic. The prevalence of instrument separation was higher with NiTi rotary instruments. Incidence was highest in the mesial roots of mandibular molars compared to other roots and in the apical third of the canals. Most of them informed patients about the separation and its management. They reasoned that the separation was mainly due to overuse of files and anatomic variations. Most of them preferred a conservative approach of bypass over the removal. Ultrasonics was the most preferred technique used for instrument removal. A combination of NaOCl, EDTA and normal saline was the most common irrigation protocol used, zinc oxide eugenol was the commonly used sealer and single cone technique was most commonly followed for obturation. Ledge formation seemed to be the most prevalent procedural mishap during bypassing or removal process. Endodontists and postgraduates from Department of Conservative Dentistry and Endodontics showed higher success in diagnosis, bypassing and removal of separated instrument.

Conflict of interest

Nil

Acknowledgement

I would like to thank all the subject experts Dr. Archana Krishna Murthy, Dr. Bharati SB, Dr. Ravi Kumar N, Dr. Archana S and Dr. Shilpa from Oxford Dental College for spending their valuable time in validating the questionnaire.