Management of file separation in young permanent molar: A report of two cases

Laresh Mistry, Sahili Mungekar-Markandey^*, Vatsala Srivastava and Ashwin Jawdekar

^*Correspondence: Sahili Mungekar-Markandey, Pediatric and Preventive Dentistry, Bharti Vidyapeeth Deemed to be university Dental College and Hospital, Navi, Mumbai, India, Email:

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Introduction

Endodontic mishaps are the unintentional outcomes during the endodontic management of teeth. These can be accidents such as iatrogenic perforations, instrument fractures in the root canals or ledge formations that increase the risk of endodontic failure [1]. Endodontic instrument fracture also known as instrument separation is a well-known mishap [2]. Separated root canal instruments may include endodontic files, spreaders, lentulo spirals, and Gates-Glidden burs, and can be made of stainless steel, nickel-titanium (NiTi), or carbon steel. A review of the literature reported that the mean prevalence of retained fractured endodontic hand instruments (mostly stainless-steel files) is approximately 1.6%, with a range of 0.7 to 7.4%.3 The fracture of rotary NiTi files, has been shown to lie in the range 0.4 to 5%; the higher fractures only in molar teeth. NiTi rotary files fracture because of excessive cyclic fatigue, torsional failure or a combination of both while most of SS instruments fracture due to excessive torque [3-6].

For the fracture of instrument is encountered in permanent teeth, two treatment options need to be considered [7]:

To remove the broken segment.

To retain the broken segment.

Various techniques exist to manage the broken segment in the canal which have been explained in dental literature, such as the use of Stieglitz pliers to remove the silver points [8]. Grossman suggested that chloroform or xylol can be used to soften the gutta-percha which is then easily removed with a file or broach [9]. Riog Green demonstrated the use of a simple device consisting of a disposable 25-gauze dental needle, a segment of thin steel wire and a small mosquito hemostat to remove silver cones from the root canals. Williams and Vjirndal described the Masserann technique to remove the fractured post [9]. Ultrasonic scaler has been used to remove solid objects from the root canal. Meidinger and Kahes successfully used the Cavi-Endo ultrasonic instruments to remove a broken bur tip and amalgam particles from the intracanal spaces [10].

The file separation in children can be related to child factors: co-operation and anatomical differences, operator factors, instrument related factors, limited mouth opening, inadvertent closure while making radiograph of working length and lack of co-operation [7].

The aim of the present case report is to describe the management of separated intracanal instrument in first permanent molar and to highlight its successful outcome.

Case Report 1

A 12-year-old boy reported to the department of pediatric and preventive dentistry with a chief complaint of pain in lower right back region of the jaw for 1 week. The pain was intermittent and non-progressive in nature. The medical history was non-contributory and there was past dental history of the tooth receiving an endodontic treatment six months earlier. On clinical examination, tooth number 46 presented with a non-aesthetic restoration (Miracle mix) (Figure 1). On radiographic examination, it was observed that the obturation was inadequate in all four canals of right first permanent molar (Figure 2 and Table 1).

Figure 1: 46–Pre-operative view of the tooth with nonaesthetic restoration.

Figure 2: 2A: Pre-operative radiograph of 46. 2B: Removal of radicular GP. 2C: Removal of GP from distal canal. 2D: Fractured of file fragment in mesio-buccal canals. 2E: Bypassing of the fragment 2f- Obturation and POR done with 46.

Table 1: Examination of tooth 46.

After discussing with the parent and obtaining their consent, the treatment for 46 was decided as re-RCT followed by preformed stainless steel crown. The access was gained for 46 after removing restoration using a large round bur (BR 31). Multiple attempts were made for the removal of the pre-obturatred gutta percha cones from the root canals of the same tooth. While removing the GP cones, there was a separation of endodontic instrument (20- K file) in the mesio-lingual canal (Figure 2). Since the file fragment was in the apical third it was decided to by-pass the fragment and complete the biomechanical preparation (BMP). This was done with hand instruments using copious irrigation 0.9% saline solution and the use of EDTA to bypass the broken file fragment. The successful bypass was confirmed using intra oral periapical radiographs. In the next visit gutta percha cones were removed from the distal canals. Another file separation was encountered in mesiobuccal canal. This was also dealt with the similar way as for the previous file separation (Figure 2).

After removal of all the gutta percha from the four canals, bio-mechanical preparation was completed till 40 size K-file. The canals were obturated using Endoflas and 2% gutta-percha cones with lateral condensation technique and post obturation restoration was done with composite resin (Figure 2).

Two weeks later after the obturation, a coronal seal was achieved with a preformed stainless-steel crown (SSC) (Figure 2). Summary of treatment of Case Report 1 is mentioned in Table 2.

Table 2: Treatment plan /Summary of treatment of Case Report 1

Case Report 2

A 10-year-old girl reported to the department of pediatric and preventive dentistry with a chief complaint of pain in the lower left back region of jaw for 1 week. The pain was sudden in onset and intermittent in nature. It was aggravated by mastication. The medical history was non-contributory and there was past dental history of the tooth receiving a restoration. On clinical examination, tooth number 36 presented with a toothcoloured restoration. IOPA radiograph showed occlusal radiopacity and peri-apical radiolucency (Figure 3). (Figure 4a-Pre-operative radiograph 4b- Working length radiograph of 36 4c- IOPA displaying fracture fragment in mesiolingual canal 4d-IOPA displaying bypass of the fragment in mesiolingual canal 4e-IOPA displaying master cone 4f-IOPA displaying obturation) (Table 3).

Figure 3: 46-IOPA displaying SSC crown and intra-oral picture post crown cementation.

Table 3: Examination of tooth 36.

Based on clinical and radiographic examination the diagnosis of tooth 36, was made as symptomatic irreversible pulpitis with apical periodontitis. After discussing with the parent, the treatment plan for 36 was endodontic management followed by preformed SSC. After obtaining a written parental consent, local While doing the biomechanical preparation, 20 K-file got separated in mesio-lingual canal (Figure 4c).

Figure 4: Endodontic treatment of 36.

Since, the separated fragment was near to the apical end, it was decided to by-pass the fragment and completes the treatment. Attempts were made to bypass the fragment with size 6 K-file followed by size 8 K-file and size 10 K-file with copious irrigation of 0.9% saline and EDTA. Sequential filing with smaller files helped achieve by-passing of the fragment (Figure 4d). Once, the canal was bypassed, the same was prepared with 40 K-file in all canals with circumferential preparation with 30 H-file followed by copious irrigation with 2.5% sodium hypochlorite solution.

In the next appointment, obturation was completed with 2% 40 Gutta percha cones and zinc oxide eugenol sealer, followed by post-obturation restoration with composite resin (Figure 4e and 4f). Two weeks after obturation, a definitive coronal seal was achieved with a preformed SSC (Figure 5). Summary of treatment of Case Report 2 is given in Table 4.

Figure 5: 36-IOPA radiograph displaying SSC.

Table 4: Treatment plan /Summary of treatment of Case Report 2

Follow-up

The follow-up over next one week after SSC placement on 36 was uneventful. Radiographic examination at 3 months revealed, evidence of bone healing and establishment of trabecular pattern (Figure 6).

Figure 6:36-3 months follow-up.

Discussion

Procedural errors in endodontics which occur during the process of root canal treatment can be a result of various factors over which the operator may or may not have control. Stainless steel instruments usually fail by excessive amounts of torque and NiTi instruments break due to combined action of torsional stress and cyclic loading [11,12]. Various factors have been implicated in the fracture of endodontic instruments including operator skill/experience, instrumentation technique, dynamics of instrument use, number of uses, instrument design, anatomic configuration of the canals, metallurgy and number of sterilization cycles [13,14].

Operated related fracture could be related to incorrect instrumentation technique due to lack of professional mastery. A crown-down instrumentation technique (enlarging the coronal aspect of the canal before apical preparation) and creation of a manual glide path (preparing the canals manually with a SS file to working length before rotary NiTi instrumentation) has been proposed to reduce the frequency of instrument fracture [14]. An instrument can fracture if its ultimate strength is exceeded, or when a crack has propagated to such a degree that the remaining cross section of the instrument is unable to bear the operating load.

There is no expiry date presented by any manufacturer for the use of files. The Department of Health’ in the United Kingdom in 2007 has dictated that all endodontic files to be used as “single use” for reasons relating to cross infection and theoretical prion transmission.18 File manufacturers have recently advocated that files should be single use only and have introduced features into new files which distort when autoclaving, hence preventing their reuse (WaveOne™, Dentsply Maillefer, Ballaigues, Switzerland).

When an instrument fractures in the root canal system, a decision has to be made to leave, bypass or remove the fragment, the choice being based on an assessment of the potential benefit of removal compared with the risk of complication. The interests of the patient are paramount in this decision as they may opt to have the tooth extracted for reasons such as anxiety, time and finance.

In the earlier times, it was advised to leave the fractured instrument in situ and root canal treatment could be completed coronal to the fragment. It was proposed that the fractured instrument generally did not affect prognosis and could therefore be retained, as the risk of removal was high [13]. However, that these publications predate the use of the operating microscope and ultrasonic tips, which would reduce the risk of complication. Although it was suggested that the retention of the fractured instrument did not affect prognosis but the patient’s perspective, retaining in the root canal can be a source of anxiety as it can be viewed as a treatment failure or even clinical negligence and may be perceived as a source of problem in the future. Furthermore, it is difficult for the patient to further invest in a ‘compromised’ tooth (eg. coronal restoration) where the prognosis seems uncertain [14]. However in the reported cases here, the parents understood the mishap and agreed to the suggested management.

Recently, it has been stated that removal of fractured instrument should always be attempted and the fragment only being retained when nonsurgical removal has been unsuccessful. The rationale is that unless the obstruction in the canal is removed – allowing complete chemo-mechanical disinfection of the root canal system will be compromised [15]. The major challenge in the biomechanical preparation is the dead space which exist between the bypassed fragment and the gutta percha so the sealer should flow adequately in that space preferably calcium hydroxide based during the withdrawal of instrument used for sealer placement in the canal (Figure 7). It is very important to know the stage at which file fragment is separated because during initial separation it is more difficult to disinfect the canal than the separation at later stages during shaping.

Figure 7:Diagrammatic representation of by-passed broken fragment in the root canal.

In cases where access to the fragment is difficult and/ or visibility is limited, removal may lead to further iatrogenic complications such as ledge formation, perforation or excessive enlargement of the canal; this may result in a weakened root structure which may predispose the tooth to vertical fracture [16].

Saunders, et al. suggests that it is more conservative to bypass the fractured instrument, particularly where access to the fragment is restricted (apical one-third of canal or beyond the canal curvature) and its removal may lead to excessive removal of dentine with associated sequelae. It has been reported that if the file is bypassed, the retained fragment does not compromise obturation quality [17,18]. Fractured instruments can be removed by a variety of methods such as fine ultrasonic tips, micro-tubule devices and pliers/haemostatic forceps, although many of these techniques have been described as successful, they require skilled use of the operating microscope and practice the removal of a fractured file is associated with considerable risk and is expensive, therefore a cost-benefit analysis of the treatment should be considered before selecting a definitive treatment for the patient in terms of time and equipment [14].

Conclusion

Based on the present report of two cases, it can be concluded that bypassing the separated instrument and thorough cleaning and shaping, and obturation with coronal seal can provide satisfactory results.

The success rate of an endodontic treatment is can be achieved by combining the best strategies and making use of safe techniques during root canal preparation procedures. Separation of instrument can be prevented if the instruments used for negotiating and cleaning and shaping the root canal are disposed well in time. Discarding worn down instruments will reduce breakage and prevent loss of clinical time failures caused by procedural accidents. However rare, instrument breakage might happen in spite of the best existing technologies and techniques, and retrieval may not always be feasible and successful. In these instances, and in the presence of clinical symptoms and/or radiographic pathology, bypassing the fragment should be considered as a safer alternative as the retained fragment does not compromise obturation quality and may present as the best treatment option.

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