Endodontology

CASE REPORT
Year
: 2017  |  Volume : 29  |  Issue : 1  |  Page : 65--68

Retrieval of fractured Ni-Ti rotary instrument using ultrasonics and file braiding technique under surgical operating microscope


Velmurugan Natanasabapathy, Sathish Sundar, Vishnupriya Koteeswaran 
 Department of Conservative Dentistry and Endodontics, Meenakshi Ammal Dental College, Chennai, Tamil Nadu, India

Correspondence Address:
Velmurugan Natanasabapathy
Room No. 9 and 10, Department of Conservative Dentistry and Endodontics, Meenakshi Ammal Dental College, Alapakkam Main Road, Maduravoyal, Chennai - 600 095, Tamil Nadu
India

Abstract

During routine endodontic therapy, a clinician may encounter many procedural errors and obstacles which may alter the course of treatment; one such error is instrument separation. A separated instrument prevents complete cleaning and shaping of the root canal and this might potentially influence the course of the treatment. Hence, every attempt must be made to retrieve the broken instrument. There are various instrument retrieval kits and chairside techniques available for this purpose. The present case report is about the successful retrieval of separated nickel-titanium rotary instrument with the help of ultrasonics and file braiding technique under surgical operating microscope.



How to cite this article:
Natanasabapathy V, Sundar S, Koteeswaran V. Retrieval of fractured Ni-Ti rotary instrument using ultrasonics and file braiding technique under surgical operating microscope.Endodontology 2017;29:65-68


How to cite this URL:
Natanasabapathy V, Sundar S, Koteeswaran V. Retrieval of fractured Ni-Ti rotary instrument using ultrasonics and file braiding technique under surgical operating microscope. Endodontology [serial online] 2017 [cited 2021 Feb 28 ];29:65-68
Available from: https://www.endodontologyonweb.org/text.asp?2017/29/1/65/206997


Full Text

 Introduction



The introduction of nickel-titanium (Ni-Ti) alloy by Walia in 1988 revolutionized the way root canals were instrumented.[1] Despite its wide acceptance, these files tend to fracture without warning. The separation rates of stainless steel instruments have been reported to range between 0.25% and 6% compared to that of Ni-Ti rotary instruments, which are between 1.3% and 10.0%.[2]

A separated instrument prevents complete debridement and sealing of the root canal system. Hence, every attempt must be made to retrieve the broken instrument. There are various specialized instruments retrieval kits such as the Masserann Kit, IRS Kit, and Canal Finder system. Some of the authors have used chairside techniques such as wire-and-loop method, file braiding technique, hypodermic needle, and glue technique for retrieving broken instruments.[3]

The present case report is about the successful retrieval of separated Ni-Ti rotary instrument with the help of ultrasonics and canal braiding technique under a dental operating microscope.

 Case Report



A 27-year-old female patient referred by a general dentist to our department for the endodontic management of maxillary right canine (13). The dentist gave a history of fracture of S1 Ni-Ti rotary file (Protaper Universal system, Dentsply, USA) during cleaning and shaping.

An intraoral periapical radiograph revealed the separated instrument (approximately 11 mm length) at the junction of the coronal and middle third of the canal [Figure 1].{Figure 1}

After the administration of local anesthesia (2% lignocaine hydrochloride with adrenaline 1:80,000) under rubber dam isolation, the access cavity was modified and the lingual shoulder was removed using Gates Glidden (GG) drill-3, -2, -1 (Dentsply, Ballaigues, Switzerland) to ensure a straight line access to the coronal end of the fragment.

When viewed under the dental operating microscope (Labomed, Operating microscope) at ×3.5 magnification, the coronal part of the separated instrument was visible and the fragment was oriented toward the buccal aspect of the canal and was threaded into the dentin [Figure 2].{Figure 2}

The dentin surrounding the fractured fragment was troughed using ultrasonically activated ET25 tip mounted on handpiece (ACTEON, Satelec) at a power setting 3 under coolant. Troughing was initially performed on the palatal aspect to free the coronal end of the fragment. The fractured fragment was gently bypassed using K-file ISO size 15 and with the use of 17% ethylenediaminetetraacetic acid to the full working length (25 mm) and enlarged up to size 30.

Ultrasonic vibrations (direct and indirect) failed to deliver the instrument out of the canal. Hence, additional troughing was performed on the buccal aspect of the canal to free the instrument from dentin. This caused the loosening of the fractured instrument from the dentin. The IRS Kit microtube was used to grasp the freed portion of the fragment, but it was not possible. Hence, the file braiding technique was employed wherein the fractured instrument was engaged as deep as possible with the help of three new H-files of ISO sizes 15, 25, and 30 (Maillefer, Dentsply, USA). Braiding of these files and a short outward pull resulted in the instrument being removed from the canal [Figure 3] and [Figure 4].[4]{Figure 3}{Figure 4}

Cleaning and shaping was performed manually (K files, Maillefer, Dentsply, USA) and the canal was enlarged up to ISO size 45 and irrigated with 2.5% sodium hypochlorite during instrumentation. The final irrigation was performed using 17% EDTA and 2.5% sodium hypochlorite. The canal was dried with absorbent paper points and obturation was performed using cold lateral compaction technique using Gutta-percha and AH plus sealer (Dentsply Ballaigues, Switzerland) [Figure 5]. The access cavity was restored with resin composite Filtek Z250 (3M Dental Products, St Paul, MN, USA). The patient was asymptomatic during the 4-week follow-up period.{Figure 5}

 Discussion



A Ni-Ti rotary file may fracture inside the root canal due to cyclic or torsional fatigue.[5] A variety of strategies such as heat treatment, ion implantation, electropolishing, twisting of files, altering the metallurgy,[6] and newer design features [7] are being employed during the manufacturing process to improve the fracture resistance.

Various factors have been associated with the fracture of Ni-Ti rotary instruments: operator experience, rotational speed, canal curvature, instrument design and technique, torque, manufacturing process, and absence of glide path. Restricted access, improper angulation of the file during usage, canal anatomy, and over usage of files could have contributed to file separation in this case.

Intracanal instrument separation can be effectively managed by either bypassing it or retrieving.[3] However, retrieval was attempted in the present case; as the file separated at the early stage of cleaning and shaping, the tooth was strategically important and accessibility that was enhanced with document object model (DOM).

There are various specialized instrument-retrieval kits such as the Masserann Kit, Cancellier Kit, IRS Kit, Canal Finder, Endo rescue, and Mini forceps that works by freeing the fragment from surrounding dentin and use of microtube to grasp the fragment. Recently, Terauchi developed a new file retrieval kit that claims to remove minimal dentin. It consists of a modified GG drill # 3, FRK-T microtrephine bur that is used to create a staging platform down to the separated fragment and concave spoon-shaped ultrasonic tip FRK-6 and a microlasso for grasping the fragment that makes it unique from other retrieval kits.[3]

However, these devices are not readily available, very expensive and usually involve removal of a considerable amount of dentin which could weaken the roots. Few authors suggest the use of specialized ultrasonic tips under DOM to overcome the problem of excessive removal of dentin. Operating under high power magnification enables precise use of ultrasonic, avoiding unnecessary dentin removal thereby increasing the success rate by 67%–95%.[8]

In this particular case, the fractured instrument was bypassed and ultrasonic vibrations were delivered, but this approach failed to disengage the fragment. Hence, further ultrasonic troughing was performed on the buccal aspect of the fragment using the ET25 tip to free the dentin surrounding the fragment. Then, the instrument retrieval system was used to grasp the freed coronal portion of the separated fragment, but it was not possible as the tip diameter of the microtube was smaller than the coronal end of the separated fragment. Hence, file braiding technique was employed in the present case with different sizes of three new H-files that were braided and a short outward stroke that retrieved the fragment.[4]

There are other innovative methods tested in vitro for this purpose. Ormiga et al. introduced and tested a new concept that is based on electrochemical-induced dissolution of metal.[9] Two electrodes are immersed in the electrolyte; one acts as a cathode and the other as an anode. The contact between the separated file and the anode as well as an adequate electrochemical potential difference between the anode and cathode electrodes results in the release of metallic ions to the solution, consequently causing progressive dissolution of the fragment inside the root canal. Recently, Wohlgemuth et al. studied the effectiveness of novel gentle wave irrigation system that works by multisonic ultracleaning principle in retrieval of fractured instrument.[10]

It would be wiser to prevent separation of instruments from occurring as attempting its retrieval is time-consuming, involves potential complications, and increases the anxiety level of the patient. Instrument seperation can be avoided by following proper straight line access, use Ni-Ti rotary files at settings suggested by the manufacturer, single usage of Ni-Ti rotary files and having adequate glide path prior to Ni-Ti instrumentation.

 Conclusion



The Ni-Ti rotary file was successfully retrieved in the maxillary right canine using ultrasonic tips and canal braiding technique under the surgical operating microscope.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

References

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