Cyclic and spontaneous movement of a fractured and extruded instrument back into the root canal: A rare case report.

Retreatment of endodontically involved teeth may require the removal of obstruction from root canal space. Instrument fracture is an undesirable and stressful incident which can negatively affect the prognosis of the tooth. Any corrective step taken should be performed with utmost care to prevent extrusion of the fragment into periapex. This case report describes a rare occurrence of movement of a fractured instrument during inter-appointment period. A previously treated left mandibular first molar with a fractured instrument was taken up for retreatment. During the course of treatment, the fractured fragment which was previously located in the apical third of the distal canal was dislodged into the periapical region. However, it was found that fragment moved back inside the canal after the inter-appointment period. The same sequence of events repeated before the instrument could be retrieved. Hydrostatic and vascular pressure build due to periapical inflammation could be cited reasons for such a movement. Copyright:

INTRODUCTION

Retreatment of endodontically treated teeth may require the removal of an obstruction from the root canal space. Instrument fracture is an undesirable and stressful incident that leads to psychological distress to practitioners as well as patients.[1] It can happen even to experienced clinicians if appropriate preventive measures are not followed.

The reported prevalence of retained fractured instruments ranges between 0.7% to 7.4% in teeth undergoing root canal treatment.[234] Instrument separation can occur at different levels along the length of the canal, but the incidence in the apical third beyond the curvature is 33 times greater compared to the coronal third and almost six times when compared to the middle third of the root canal.[5]

The separated file fragment is often engaged and firmly held inside the root canal wall. However, it is not uncommon to encounter a loose fragment, especially after gutta-percha (GP) removal or use of ultrasonics in a canal with a fractured instrument. In rare cases, it can get displaced into sinus or nerve canals during vigorous attempts to remove the same.[5] However, the reverse migration of a fractured instrument from the periapical region into the root canal has never been reported.

This case report describes a rare case of migration of separated instrument. During the course of treatment, the broken fragment oscillated twice between the canal and the periapex during inter-appointment periods.

CASE REPORT

A 37-year-old female patient presented to the department of conservative dentistry and endodontics with pain on mastication in the lower left back tooth region for the past 2 months.

The patient reported with a history of root canal treatment performed 6 months earlier. Extraoral examination showed no remarkable findings. Intraoral examination revealed tooth no. 36 had a temporary restoration and it was tender on percussion. Intraoral periapical (IOPA) radiograph revealed under-obturated both canals [Figure 1a and b].

Figure 1

(a) Preoperative clinical picture (b) Preoperative intraoral periapical radiograph irt 36 showing under-obturated canals with separated instrument at the apical third; (c) Displaced broken file extending 3 mm beyond apex; (d) CBCT depicting fractured file fragment in the coronal section; (e) Fractured fragment 2.14 mm beyond apex; (f) Broken file fragment back within the root canal

Furthermore, the distal canal showed separated instrument extending 1 mm beyond the apex with diffuse periapical radiolucency around it. Based on clinical and radiographic findings, a diagnosis of previously treated tooth with chronic apical periodontitis in relation to 36 was formulated. It was planned to retrieve the instrument considering it as one of the etiological factors for persisting disease. The patient was informed about the treatment procedure and informed consent form from the patient was taken. Local anesthesia (LA) (Lignox, Indoco Remedies Ltd., Warren Pharma, Mumbai, Maharashtra, India) was administered as the patient reported with pain, the tooth was tender to percussion and even the rubber dam application occasionally leads to discomfort due to impingement of the prongs. Hence, to avoid any pain to the patient during instrumentation and alleviate the patient anxiety, LA was administered. As a part of emergency treatment, old restoration was removed, three orifices were located, and GP was removed from all the canals using H-files (Mani, INC., Japan) in the same appointment. Extreme care was taken not to disturb the broken file. IOPA was taken to confirm the removal of GP. It was observed that GP was removed but the separated instrument was displaced further, around 3 mm beyond the apex [Figure 1c]. No further attempt was made to remove the file and the patient was prescribed anti-inflammatory drugs and was recalled after 2–3 days.

As the patient reported back with persistent pain, cone-beam computed tomography (CBCT) scan and mandatory blood investigations were advised for the patient to plan the removal of the fractured file surgically. Fractured fragment measured 2.14 mm in length in the sagittal view of CBCT [Figure 1d and e]. A day before surgery, IOPA was taken as per the protocol. To our surprise, separated instrument's radio-opacity was observed within the confines of the canal in the middle third [Figure 1f]. Two angulated radiographs at different horizontal angulation were taken to rule out any error in position.

Considering the position of the file, it was deemed necessary to attempt its removal nonsurgically. Build-up of the missing distal wall was done using composite resin (Tokuyama Dental Deutschland, GmbH, Altenberge, Germany). After bypassing the fragment with #10 and #15 K file (Mani, INC., Japan), attempt was made to dislodge it out of the canal using vigorous irrigation with saline, H file (Mani, INC. Japan) and the use of ultrasonics under magnification (Labomed Prima DNT, Labomed India, Bangaluru). Unfortunately, within the recommended time frame of 45 min, none of techniques worked and we could only manage to loosen the fragment.[67] Further attempt led to the displacement of the file back into the periapical region [Figure 2a].

Figure 2

(a) Displacement of the file again into the periapical region; (b) Broken file back inside the canal again; (c) Retrieved instrument; (d) Confirmatory IOPA after file retrieval; (e) Post-obturation IOPA; (f) Follow up IOPA at 2 years

Assuming that the instrument was mobile in a rare interconnection between the root canal and the periapical region, the patient was recalled after a week again with the hope that it would migrate back like it did before. IOPA revealed the surprising movement of the file fragment back up to the middle third of root canal [Figure 2b].

As a final attempt, extreme precautions were taken this time to retrieve the instrument. Coronal flaring of the distal canal was done using GG drills no. 1 and 2 (Mani, INC., Japan) for improved visibility, thereby creating space for the fragment to move coronally. Vigorous saline irrigation was performed initially using #30-gauge side vented needle (Neo-Endo, Orikam Dental Pvt. Ltd., India) with its end placed apical to the fragment end.

Ultrasonic tips (IR2; IR3 Retrieval tips, Cric Dental, Mumbai) were then used to remove any interfering coronal root dentin and loosen the fragment on a power setting of 3. The fractured file fragment popped out on when the canal was irrigated again with saline. Periapical radiograph was taken postoperatively for confirmation of file retrieval [Figure 2c and d]. Biomechanical preparation was completed in the same visit and calcium hydroxide dressing (Prime Dental RC Cal, Prime Dental Products, Mumbai, Maharashtra, India) was placed for 2 weeks.

In the subsequent visit, obturation was done with GP and AH plus sealer (Dentsply Maiellefer, Tulsa, Oklahoma, USA) using cold lateral compaction technique [Figure 2e]. Post-endodontic restoration was done using packable composite (Tokuyama Dental Deutschland, GmbH, Altenberge, Germany) after sealing the orifices using flowable composite. After the removal of rubber dam, final occlusion was checked and adjusted. Finishing and polishing of restoration were done using composite finishing and polishing kit (Shofu, Super-Snap Rainbow Kit, Shofu Dental Corporation, USA). The patient did not report for prosthetic rehabilitation further and was not available for follow-up due to COVID restrictions. The patient reported no complaints with regard to the same tooth telephonically. The patient came for follow-up directly after 2 years. Radiograph shows complete periapical healing is seen in relation to both the roots [Figure 2f].

DISCUSSION

Separation of endodontic instruments within the root canal is an unfortunate occurrence that may hinder root canal procedures and affect the outcome.[8] With the increased use of rotary Nickel − Titanium rotary files, there has been an increased prevalence (0.4%–5%) of fractured instruments due to their low yield strength and tensile strength as compared to stainless steel files.[34]

The decision on the management of fractured instruments is generally based on the constraints of the root canal accommodating the fragment, the stage of root canal instrumentation, the expertise of the clinician, armamentarium available, the strategic importance of the tooth involved, the presence or absence of periapical pathosis, and associated complications.[28] In the present case, the decision to retrieve the instrument was taken as the instrument was interfering in complete debridement of the apical part of the distal canal which had a periapical lesion.

Majority of instrument fracture occurs in the apical third of the root canal as was seen in this case.[9]

Retreatment was justified in the present case as the patient was symptomatic, temporary restoration was fractured, microleakage around the restoration was evident, and a fractured instrument was seen radiographically in the distal root which also had a periapical lesion. In the emergency visit, GP was removed with the aim of relieving the patient of the pain. H-files were used to remove the GP as they are rigid and their flutes easily engage the GP allowing effortless removal with slight clockwise motion.[8]

In the present case, even after taking precautions to avoid disturbing the fractured file, it moved into the periapex. The broken file was probably loose and only held by GP. Removal of GP with H-file would have let the file free. Furthermore, the contact of the fractured fragment with the H-file would have pushed it beyond the apex.

Any instrument which is pushed beyond the apex needs to be removed if the symptoms of disease and pain persist.[10] In the above case, the patient was symptomatic and the success with nonsurgical technique for the removal of fractured instrument from the periapical region was unlikely without extensive dentin loss and weakening of tooth.[5] Hence, surgical removal of the instrument was planned.

A CBCT was required to plan for the surgical removal of the instrument.[11] In the present case, it helped in surgical treatment planning by assessing the exact dimensions and location of fractured file segment with respect to the root end and to determine the dimensions of the drill site. It also helped in the evaluation of the tooth morphology and proximity of the root end to the mandibular canal.

Coronal enlargement of distal canal was carried out for enhanced visibility, accessibility, and creating space for the fragment to move coronally.[1] Ultrasonic agitation with retrieval tips was done under 16 X magnification at a lower power setting. It is a less invasive procedure that delivers controlled vibrational motion at the interface of file and tooth and loosens file fragment leading to outward displacement or popping out of the separated file from the canal.[12]

Copious irrigation was performed with normal saline to remove root dentin debris and dentin chips to enhance visibility and facilitate the removal of loosened file from the canal.[13]

The above case is the first report of such an incident where a separated file fragment got dislodged twice into the periapex and moved back inside the canal up to the middle third, travelling distance of 4 mm against gravity. There are various assumptions for intra-appointment movement of the instrument in and out of the tooth. Irrigation and negative aspiration alone can move the fragment because of fluid dynamics.[14] Intracanal medicaments can lead to inadvertent movement of the file, especially in Vertucci type 2 canal configuration.

Inter-appointment movement of fractured instrument can be attributed only to gravity or force exerted by any inflammatory products. In the present case, the coronal movement of the fragment was observed twice in a short span of time. The gravitational pull can only lead to apical movement for a mandibular tooth, so the only practical explanation to the movement of the file could be a large communication between the periapex and the root canal and pressure generated by inflammatory products in the periapical region leading to movement of the file. Inflammation can lead to hydrostatic and vascular pressure build-up which can displace the file.[15]

CONCLUSION

Instrument fracture is a complication in itself and any corrective steps taken should be performed with utmost care to prevent extrusion of the fragment into the periapex. Unexpected, spontaneous and favorable movement of the fractured fragment can occur rarely as was seen in the above case where periapical inflammation possibly proved to be a boon.

Declaration of patient consent

The authors certify that they had obtained all appropriate patient consent forms. In the form, the patient has given her consent for her images and other clinical information to be reported in the journal. The patient understands that her name and initial will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.