INTRODUCTION
Root canal treatment entails the removal of infected pulpal tissue and cleaning the root canal system to minimize bacterial load and prevent root canal reinfection while preserving the tooth with a good apical seal in the dental arch.[1] Thorough cleaning and shaping of the complex root canal system are undeniably essential in root canal treatment to provide a more predictable result which is best accomplished by a combination of mechanical instrumentation and chemical irrigating solution. In the past two decades, endodontic research has advanced significantly, and the invention of nickel-titanium (NiTi) rotary instruments has revolutionized the way root canal shaping is performed.[2] Since the introduction of NiTi rotary instruments, much attention has drifted to the use of NiTi files, and the success of root canal treatment performed around the globe has gradually increased.[3]
Shape memory, superelasticity, anatomically predictable root canal preparation, shortened preparation time, and less operator fatigue are advantages of using NiTi rotary instruments.[4,5] Although NiTi rotary files performed better in terms of canal preparation with a lower risk of procedural errors than stainless steel files, instrument separation is still considered one of the NiTi system’s significant drawbacks, which accounts for 1.3%–10%.[6] Instrument separation restricts proper debridement by obstructing mechanical instruments and irrigating solutions to reach the apical parts of the root canals. As a result, root canal procedures will be hampered and eventually jeopardize the treatment outcome.
Orthograde retreatment with or without instrument removal, endodontic surgery, and extraction are the options to treat instrument separation.[6,7] In most cases, the separated instruments need to be retrieved or bypassed to achieve a complete debridement and sealing of the root canals. However, removing separated instruments can be difficult and challenging for clinicians, with a reported success rate of 55%–79%.[7] This has heightened interest in removing intracanal separated NiTi rotary instruments, prompting new research to remove separated instruments. Various instrument retrieval kits, such as the Masserann kit, Meitrac Endo Safety System, Instrument Removal System Kit, Cancellier Extractor kit, and the Endo Extractor System, are currently available in the market. Some practitioners have used chairside methods for retrieving fractured instruments, including the braided technique, loop technique, hypodermic needle technique, mini forceps, and glue technique.[6–9]
To the best of the authors’ knowledge, there is no universal guideline or consensus in the literature regarding the management of separated files in the root canal. Hence, this case series emphasizes the successful retrieval of separated instruments using a simple customized chairside syringe and loop technique under a dental operating microscope (DOM).
CASE REPORTS
Case report 1
A 65-year-old male patient with a noncontributory medical history reported to the specialist dental clinic, MAHSA University, Selangor, Malaysia, with a chief complaint of pain in the lower left front teeth region that lasted for 1 month. The pain was mild in intensity, intermittent in nature, aggravated on chewing food, and relieved on taking medication. The patient gave a past dental history of tooth-colored restoration done at a private dental clinic on the mandibular left canine (tooth #33) 1 year ago.
On clinical examination, a large resin composite restoration was noted on tooth #33, and the tooth was tender on horizontal and vertical percussion. Besides, a deep periodontal pocket measuring 5 mm and above was explicitly detected on the distal aspect of the tooth. The tooth showed no response to the electric pulp testing (Digitest, Parkell Inc, USA) and cold test (Endo-Frost, Coltene Whaledent, Switzerland). On radiographic examination [Figure 1a], radiopacity was seen involving the pulp, and secondary caries was noted beneath the restoration. Based on the clinical and radiographic observations, a diagnosis of pulp necrosis with symptomatic apical periodontitis was made with respect to the mandibular left canine (tooth #33), and root canal treatment was initiated after obtaining the patient’s consent for treatment procedures and photographs purposes.
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Figure 1: (a) Preoperative intraoral periapical radiograph (IOPA) of mandibular left canine (tooth #33). (b) A separated instrument has been seen from the radiograph where the coronal portion of the instrument is 2–3 mm below the orifice and 1 mm short of the apex. (c) A 22-gauge composite dispensing syringe. (d) A small vent was created on the outer portions of the syringe using a tapered fissure bur. (e) Dispensing syringe below the vent, bent to a right angle using an orthodontic plier. (f) The free ends of the ligature wire are passed into the prepared vent. (g) The free ends of the ligature wire are pulled to form a loop at the tip, which can grab the separated instrument. (h) Separated instrument retrieved using customized syringe and loop technique. (i) Radiograph shows the proper fit of the master cone and removal of the separated instrument. (j) Postobturation periapical radiograph. (k) Nine-month follow-up of tooth #33
Local anesthesia was given, followed by rubber dam isolation and cavity accessed using a no. 6 large round bur (Prime Dental Pvt. Ltd., Mumbai, Maharashtra, India). Next, the cavity was refined using a safe end bur/EZ Bur (Dentsply Maillefer, Switzerland). Copious irrigation of 3% sodium hypochlorite (NaOCl) (Prime Dental Pvt. Ltd., Mumbai, India) was used to clean the pulp chamber and remove the debris. The working length was estimated using an apex locator (Reypex 6, VDW, Germany) with a size 15 K-file and confirmed using a periapical radiograph. The coronal flaring was done using ProTaper SX (Dentsply Maillefer, Switzerland) rotary instrument, and the Aurum Blue (Meta Biomed, Korea) rotary files were used for the cleaning and shaping procedure.
During the cleaning and shaping procedure, the patient bit on the handpiece accidentally, which resulted in the separation of the size 35, tapered. 04 rotary file in the root canal. Upon taking a periapical radiograph, the coronal portion of the instrument was observed to be 2–3 mm below the canal orifice, with an approximate 14–15 mm of the instrument being separated in the root canal [Figure 1b]. The access cavity was modified to obtain better visibility of the fractured instrument. The fractured fragment was visible, but it was well past the orifice to be removed using a Stieglitz forceps. The Ultrasonics (Ultra X, Eighteeth Medical, China) were used to loosen the instrument, which permitted the easy removal of the fragment but was not successful, as the fragment was tightly locked within the canal. Since the instrument retrieval kit was not available in the clinic, an alternate technique was used to remove the separated instruments.
To retrieve the separated instrument, a 22-gauge composite dispensing syringe (Ivoclar Vivadent, United States of America) and an orthodontic ligature wire were customized accordingly to enable the removal of the instrument. A small vent was created on the outer tube portion of the dispensing syringe with a tapered fissure bur using a high-speed handpiece. The portion of the dispensing syringe below the vent was carefully bent to a right angle using an orthodontic plier without breaking. An orthodontic ligature wire (size 0.20 mm) of sufficient length was used and passed into the hole of the dispensing tip and pulled from the other side to form a small loop at the end of the tip, which was capable enough to grab the tip of the separated instrument. Using a DOM (Zumax private limited, China), at a magnification of 10x, careful troughing of the dentin around the separated instrument was done using an ultrasonic instrument. The step-by-step procedure to prepare the customized syringe and loop equipment is illustrated [Figure 1c-g]. Sufficient space was created around the coronal portion of the separated instrument. The loop was secured into the exposed part of the instrument and engaged by pulling the ligature wire. The separated instrument was successfully retrieved by carefully removing the syringe and ligature wire together from the root canal [Figure 1h].
The working length was reconfirmed using an apex locator, and the canals were prepared using ProTaper Next rotary files till X4 (Dentsply Maillefer, Switzerland). The master gutta-percha (Dentsply Maillefer, Switzerland) was confirmed with a radiograph [Figure 1i]. The canal was irrigated with 3% NaOCl and dried using paper points (Dentsply Maillefer, Switzerland). The obturation was done using the master gutta-percha with AH Plus sealer (Dentsply Maillefer, Switzerland) using the lateral condensation technique. The tooth was temporized with zinc oxide-based filling material (Kalzinol, Dentsply Maillefer, Switzerland) for 2 weeks. Subsequently, the temporary filling material was removed, and the tooth was filled with Filtek Z350 resin composite (3M, ESPE, Minnesota, US) to provide a coronal seal [Figure 1j]. After 9 months of follow-up, the tooth was clinically asymptomatic and the pocket had reduced or almost disappeared [Figure 1k].
Case report 2
A 60-year-old female patient with a noncontributory medical history reported to the endodontic specialist private dental clinic, Baroda, Gujarat, India, with a chief complaint of pain in the lower left mandibular first molar (tooth #36) following a separated rotary file. The pain was mild in intensity, intermittent in nature, aggravated on chewing food, and was relieved on taking medication. The patient gave a past dental history of attempted root canal treatment at a private dental clinic 6 months back and has had pain since then.
Upon clinical examination, the access cavity was not filled with any filling material and was wide-open to the oral environment. The tooth was tender to vertical percussion and showed no response to the electric pulp testing (Digitest, Parkell Inc, USA) and cold test (Endo-Frost, Coltene Whaledent, Switzerland). A separated instrument was noted on radiographic examination at the apical portion of the distal root associated with a large periapical radiolucency, while the mesial canals were not obturated [Figure 2a]. Based on the clinical and radiographic observations, a diagnosis of previously initiated root canal treatment with symptomatic apical periodontitis was made, and retreatment was planned to retrieve the separated instrument. Informed consent was obtained from the patient after explaining the treatment plan.
Figure 2: (a) Separated instrument at the apical portion of the distal root of tooth #36 associated with a large periapical radiolucency. (b) The coronal part of the broken instrument was exposed. (c) Root canal after the instrument was successfully retrieved using the customized syringe and loop. (d) Canals were shaped until size 25 tapered 0.06. (e) Canals were obturated using the warm vertical condensation technique
Local anesthesia was given, followed by rubber dam isolation and cavity accessed using a no. 6 large round bur (Prime Dental Pvt. Ltd., Mumbai, India). The cavity was then refined using a safe end bur/EZ Bur (Dentsply Maillefer, Switzerland) with copious irrigation of 3% of NaOCl (Prime Dental Pvt. Ltd., Mumbai, India). Gates-Glidden (GG) drills no. 2 and 3 (Dentsply Maillefer, Ballaigues, Switzerland) were modified by cutting the drill perpendicular to the long axis at the greatest cross-sectional diameter. Modified GG drills were used to prepare a staging platform, and the coronal part of the broken instrument was exposed by removing the surrounding dentinal tissue [Figure 2b]. Acteon Satelec P5 Newtron Ultrasonic Generator with ultrasonic tips ET25 (Satelec Acteon, France) was used to trephine around the fragment. The procedure was carried out under a DOM (Global Corporation, USA) with a magnification of ×10 and ×16. The ultrasonic tip ET25 was activated at a power setting of 6 to trephine dentin around the broken fragment, and about 2–3 mm of the fragment was exposed. A customized loop (Similar to Yoshi’s loop) was used to retrieve the separated instrument by engaging the head of the exposed fragment and tightening with the stylus pulled downward. The loop used in this case was 27 gauge and was created using a ligature wire with a diameter of 0.1 mm. The entire assembly of the loop and the broken fragment are removed in toto, and an image of the canal after instrument retrieval was taken [Figure 2c].
The canal was re-negotiated with a size 10 K-file (Dentsply Maillefer, Ballaigues, Switzerland). The working length was estimated using an apex locator (Root ZX mini, J. Morita Corp., Japan) and confirmed using a radiograph. The coronal flaring was done using ProTaper SX (Dentsply Maillefer, Switzerland) rotary instrument, and the cleaning and shaping procedure were carried out up to size 25 tapered. 06 using ProTaper Next rotary files (Dentsply Sirona) [Figure 2d]. The canals were then obturated with master gutta-percha cones (Dentsply Maillefer, Ballaigues, Switzerland) and AH Plus sealer (Dentsply Maillefer, Ballaigues, Switzerland) using a warm vertical condensation technique [Figure 2e]. The postendodontic restoration was done using Filtek Z350 resin composite (3M, ESPE). A 6-month follow-up revealed that the tooth was asymptomatic with a significant reduction in the periapical radiolucency associated with the distal root.
Case report 3
A 27-year-old male patient with a noncontributory medical history was referred by a general dentist to the endodontic specialist private dental clinic, Baroda, Gujarat, India, for endodontic management with a chief complaint of pain in the lower left mandibular second premolar (tooth #35). The dentist gave a history of attempted root canal treatment and a separated ProTaper F2 (Dentsply Maillefer, Switzerland) rotary instrument during the cleaning and shaping procedure.
On the periapical radiograph, the separated instrument (approximately 7–8 mm in length) was located in the apical third of the root canal and separated below the middle third of the root canal system [Figure 3a]. After the administration of local anesthesia, rubber dam isolation was placed, and the access opening was modified by creating a staging platform using a GG bur no. 3 (Dentsply, Ballaigues, Switzerland) to access the coronal portion of the separated instrument under a DOM. The coronal portion of the separated instrument was visible at 16x, where the instrument was threaded into the dentin [Figure 3b].
Figure 3: (a) The separated instrument was located in the apical third of the root canal of tooth #35. (b) The coronal portion of the separated instrument was visible at ×16. (c) Customized syringe and loop device. (d) Separated instrument successfully retrieved. (e) The periapical radiograph confirmed the complete removal of the separated instrument. (f) Obturation of tooth #35. (g) Two-year-follow-up of tooth #35
The dentin surrounding the fractured instrument was carefully troughed using an ultrasonically activated ET25 tip mounted on handpiece (ACTEON, Satelec) at a power setting three-under coolant. Since the file was tightly screwed-in, a retrieval attempt was failed. Therefore, an alternative method using a customized syringe and loop device was chosen, as mentioned previously [Figure 3c]. The loop was secured around the exposed part of the separated instrument and pulled out the instrument carefully [Figure 3d].
A periapical radiograph was taken to confirm that the separated instrument was successfully retrieved [Figure 3e]. After confirming the working length with the periapical radiograph, the canal was re-negotiated and shaped to size F3 (ProTaper Universal, Dentsply Maillefer, Ballaigues, Switzerland). The canals were then obturated with master gutta-percha cones (Dentsply Maillefer, Ballaigues, Switzerland) and AH Plus sealer (Dentsply Maillefer, Ballaigues, Switzerland) using a warm vertical condensation technique [Figure 3f]. The postendodontic restoration was completed using Filtek Z350 resin composite (3M, ESPE). Subsequently, a porcelain crown was placed on the tooth. A 2-year follow-up showed no sign of periapical pathology, and the tooth was asymptomatic with an excellent coronal seal [Figure 3g].
DISCUSSION
Endodontic instrument fracture is an unfortunate condition that occurs commonly in the dental clinic. It is often challenging to remove fractured instruments from the root canal system, and if they are not retrieved, the success of retreatment will be significantly decreased.[9] The location of the broken instrument in the root canal, the stage of endodontic treatment at the time of the fracture, and the existence of preoperative periapical radiolucency may influence the prognosis. Endodontic NiTi rotary instrument fractures are often caused by incorrectly applied forces on instruments or the use of defective instruments, all of which increase the likelihood of fracturing due to torsional stress and cyclic fatigue.[7] When rotary files are used in curved canals, the separation of instruments due to cyclic fatigue is most often found in the smaller size instruments. The area of compression tension at a particular point on the instrument is created by the constant rotation of the file, which gradually results in separation.
However, if the tip of the rotating file becomes entangled in the root canal while the shaft continues to rotate, the file will eventually fracture due to torsional stresses. Instrument separations of this nature are common when using larger instruments, mainly when used in calcified or narrow canals.[4,10] Various thermal and surface treatments are used to improve the fracture resistance of NiTi rotary files, rendering them more resistant to cyclic fatigue and torsional stresses, decreasing the possibility of instrument breakup.[4] The clinician may experience stress and anxiety due to the instruments being separated during root canal preparation.[7] The best approach with a separated instrument is to prevent it from occurring in the first place. Conservative and surgical procedures are used to treat the separated instrument.[11] Still, the conservative way is favored the surgical method, which implies a) bypassing the separated instrument, b) removing the separated instrument, and c) instrumenting and obturating till the coronal portion of the separated instrument.[10] In the present case series, the root canals were straight and wide, making them possible to be retrieved with a conservative approach.
The odds of retrieving the separated instruments are determined by considerations such as the type of teeth, the degree of instrument fracture in the root canal, instruments separated above or below the curvature, straight or curved canals, type of files used for preparation, clinician skills, and the patient’s mouth opening.[12] In addition, the size and irregularities of the canals may influence the effectiveness of the fractured instrument removal, with a lower success rate in cases where the fragment is removed from the apical third than that in the middle or coronal third.[13] Undeniably, instrument retrieval kits and a combination of ultrasonics and a DOM are the most popular methods for retrieving intracanal separated instruments.[7,9] Ultrasonic retrieval of fragmented instruments was also previously reported to be effective in 67%–88% of cases.[14] However, this would not be the case if the fragment was tightly screwed into the root canal. Improper use of ultrasonics may cause the instrument to crack by absorbing the heat emitted from the ultrasonics. The excessive removal of the tooth surface results in procedural errors such as perforation and ledge formation.[10]
Since ultrasonic retrieval of the fractured instrument is not always successful, other strategies to remove the broken segment should be sought and attempted. In the current case presentation, the separated instruments were intended to be retrieved using a simple and low-cost customized chairside syringe and loop technique. In case report 1, the instrument was retrieved from the permanent mandibular left canine with a single straight canal. Moreover, the coronal portion of the instrument was visible 2–3 mm below the orifices under the DOM, and the long-separated fragment clinically made bypassing difficult or impossible. The second case report is considered challenging, too, as the separated instrument was located at the apical portion of the root canal, which is difficult to retrieve. Although these cases can be managed using endodontic retrieval kits such as the Masserann Kit or the Canal Finder System. These expensive devices still display unnecessary dentin wear, undermining the tooth’s long-term prognosis due to excessive enlargement, and they are seldom used in difficult-to-access canals.[9]
The current customized technique is simple to use and produces minimal dental wear, resulting in minimal tooth structure deterioration and a substantial reduction in the incidence of tooth fracture. On the contrary, securing the loop to the coronary part of the separated fragment is challenging for this procedure, as it could result in perforations or deviations from the canals’ original path.[7,8] Clinicians must be knowledgeable about the various procedures and techniques used to retrieve a separated fragment. Instrument separation can be avoided by adopting general recommendations that reduce the possibility of instrument separation in clinical settings.
- Read the manufacturer instructions before using the rotary files
- A preoperative radiograph is necessary to evaluate the root and canal morphology
- A proper rubber dam placement and stabilization with mouth prop to prevent accidental closure of the mouth
- A proper decision on whether to use the 4% or 6% taper files to prevent the chances of separation
- Straight-line access to the apex or the initial curvature should be established
- The coronal flaring should be done, and the crown-down technique may be adapted
- Establishing canal patency throughout the procedure with a proper glide path
- Rotary files should be used after preparing the canal with a minimum size of 15 K-file
- Finger rest to stabilize the head of the endomotor
- Files should never be used in dry conditions (fill the pulp chamber with NaOCl)
- Never force the instruments, but with a light touch in brushing or pecking motion
- Keep a count on the usage of the rotary instruments
- Do not hurry instrumentation and avoid rapid jerking movements
- Do not skip the sequence of instrumentations and avoid large instruments in narrow and curved canals
- The torque and speed settings for the rotary file systems should follow the manufacturer’s recommendations
- Wipe the surface of the file after each stroke with a gauge to remove the accumulated debris
- Examine the files regularly before use for any possible distortions under magnification
- Turn on the rotary file before entering the root canal (insert a rotating instrument into the root canal)
- Files should always be kept moving in the canal rather than placed at one spot. Coat the surface of the file with ethylenediaminetetraacetic acid gel for lubrication
- If the clinician plans to adopt a new file system in their practice, it is always better to try the files once on a simulated tooth model for better understanding.
CONCLUSION
In the present case series, an alternate technique for instrument retrieval was successfully performed using a simple and cost-effective, customized chairside syringe and loop technique. This modified approach can be considered an alternative for general dental practitioners and endodontists who do not have access to instrument retrieval systems in their daily clinical practice.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient (s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials 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.
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