One of the iatrogenic errors that every practitioner might face is instruments separated during the root canal treatment. The rate of separated instruments is estimated from 1.83% to 8.2%.^[1] The separated instruments might negatively affect the prognosis by impeding the cleaning and shaping of the root canal system and reducing the sealing of the apical foramen.^[2,3]

When an instrument is separated, the practitioner has to appraise the treatment options, considering the pulpal and periradicular status, the root canal infection, the root canal anatomy, the position and type of separated instrument, and the amount of dentin loss. The preferred methods include orthograde removal of the separated instrument, surgical retrieval, bypassing the fragment, sealing it within the root canal space, or establishing complete blockage.^[4-6]

One approach for managing a separated instrument is orthograde retrieval. For this purpose, special instruments and techniques such as ultrasonic instruments, hollow tubes combined with cyanoacrylate adhesive, trephining methods utilizing an ultrasonic tip or trepan bur, endo extractors, and neodymium-doped yttrium aluminum garnet laser welding have been implemented. Nevertheless, the use of a dental operating microscope (DOM) combined with an ultrasonic device has consistently been identified as a method with high success and safety in many studies.^[7]

One of the approaches for orthograde retrieval is loop techniques that enhance retrieval efficiency when grasping separated instruments.^[8] The present case series describes the management of separated instruments by removing them using DOM, an ultrasonic device, and the loop technique.

This case report has been ethically approved by the Ethics Committee of Isfahan University of Medical Sciences (IR.MUI.DHMT.REC.1403.175).

When dealing with a separated instrument, the primary objective is to thoroughly clean the root canal system. Retrieval of the separated instrument should be attempted whenever feasible. If retrieval is not possible, alternative strategies include bypassing the fragment or obturating the canal up to the level of the instrument. In cases previously treated without any signs or symptoms, opting for no further treatment may also be considered.^[9] If the retrieval file was selected, the predictive factors affecting instrument retrieval are: the location, visibility, dimensions, length, and classification of the separated instrument; the curvature of the root canal; the radius of curvature; as well as the operator’s experience and level of fatigue.^[10-15]

One commonly cited method for retrieving separated instruments in the literature is the technique detailed by Ward et al.,^[15] which modifies the protocol originally described by Ruddle.^[16] This approach involves the use of thin ultrasonic tips, typically after creating a “staging platform” with a Gates Glidden (GG) bur. Ward et al. suggest using a size 3 bur for the coronal portion and a size 2 for the apical third, as recommended by Cujé et al.^[11] The procedure is performed under a DOM to either vibrate and dislodge the instrument or bypass it. This technique has proven effective for removing separated instrument when they are partially located in the straight section of the root canal. However, its success decreases significantly when separated instruments are entirely within the curved portion of the canal, as this increases the risk of root perforation. According to Cujé et al.,^[11] the lowest success rates are observed in root canals with curvature angles between 41° and 50°.

The retrieval loop is employed for the extraction of separated instruments longer than 4.5 mm in length or in instances where retrieval via ultrasonics proves unsuccessful after a duration exceeding 10 s. In contrast to ultrasonics, which are utilized under wet conditions, the retrieval loop necessitates dry conditions to ensure visibility. Furthermore, loop systems, such as EndoCowboy (Köhrer Medical Engineering), BTR Pen (CERKAMED), and Yoshi Loop (DELabs), are designed to engage and extract elongated, loosened, separated instruments by applying forces in a coronal direction. To use these systems effectively, the canal must have a minimum diameter of 0.4 mm, and the coronal portion of the separated instrument should be exposed to a depth of at least 0.7 mm to allow the loop system to grasp it securely. A #40 plugger is inserted into the canal to assess the space adjacent to the separated instrument. The loop dimensions are then adjusted to match the coronal diameter of the instrument using an endodontic explorer or calibrator. The loop is bent at a 45° angle initially to minimize space requirements for placement over the separated instrument. Once positioned, the loop is inserted into the canal and adjusted to a 90° angle upon contact with the instrument. The loop is tightened around the separated piece and smoothly pulled to extract it. If resistance occurs, the loop should be gently maneuvered in various directions with a swaying motion until the instrument is successfully removed. It is crucial to avoid forcing the loop vertically, as this could cause breakage. The pulling motion and direction are key factors in ensuring successful retrieval.^[17]

A literature search showed the promise of the loop technique for file retrieval [Tables 1 and 2]. Barakat and Attia. found a significant difference in the changes in root canal space volume before and after instrument retrieval in the BTR Pen and Zumax kit, with the difference being higher in the Zumax kit. However, no significant difference was found for mean fracture resistance. Therefore, retrieving separated instruments from the coronal third of the root canal is considered safe and does not impact tooth fracture resistance.^[22] Dulundu and Helvacioglu-Yigit concluded that the BTR-Pen and ultrasonic techniques had similar success rates (86.7% and 83.3%, respectively) and similar procedural times (23.97 and 24.1 min, respectively). However, the roots treated with the BTR-Pen system exhibited less fracture resistance.^[8] Pruthi found that Terauchi File Retrieval Kit (TFRK) and ProUltra tips were deemed acceptable clinical tools for instrument retrieval, but the loop system required slightly more dexterity.^[26] The loop technique is generally a reliable, efficient, and safe method for file retrieval in certain clinical situations

By leveraging cutting-edge technologies and refined techniques such as DOM, ultrasonic tools, and loop techniques, dental professionals can effectively identify and remove separated instruments. Although no single approach ensures consistent outcomes, the success rate of retrieving separated instruments significantly depends on operator expertise, careful case selection, and the application of magnification tools and advanced retrieval systems.