2.1. Case 1: Removal of a Broken Instrument Using an Ultrasonic Instrument

A systemically healthy 30-year-old female patient was referred to an endodontist complaining of pain in her maxillary right first premolar while chewing. Clinical examination revealed that the tooth was sensitive to percussion and palpation, and had no mobility. The probing depth was within the normal range. Periapical radiograph revealed a broken instrument in the palatal canal and a radiolucency in the periradicular area of the palatal root (Figure 1(b)). Informed consent was taken from the patient. The amalgam restoration was removed, and endodontic retreatment was commenced by gutta-percha removal using rotary NiTi instruments and chloroform (Merck, Darmstadt, Germany) as gutta-percha solvent. The coronal portion of the broken instrument was visualized under a dental operating microscope (DOM; Magna Labomed, Labo America Inc., CA, USA) at ×4 magnification (Figure 1(c)). The tip of a #2 Gates-Glidden drill was cut by a carbide bur at high speed to prepare a staging platform (Figure 1(d)) in order to establish a straight-line access to the coronal part of the broken instrument with minimal dentin removal. Then, the dentinal walls around the coronal 2 mm of the broken instrument were removed using a size 25 U-file on a U-tip (NSK, Nakanishi, Japan) at ×15 magnification. The U-file moved around the broken instrument in a counterclockwise direction. After about 10 minutes, the broken file was successfully removed (Figure 1(e)). The canals were prepared with rotary NiTi instruments (DENCO Super Files III; Longhua, Shenzhen, China), irrigated with 5.25% hypochlorite solution and its activation with ultrasonic, and finally, rinsed with 17% EDTA. Subsequently, canals were obturated with gutta-percha points and AH 26 resin sealer (Dentsply-Tulsa Dental, Johnson City, TN, USA) using the cold lateral compaction technique (Figures 1(f) and 1(g)). The patient was then referred for coronal restoration. At the 2-year follow-up, the patient was completely symptom-free, and the healing of the apical radiolucency was evident in the periapical radiograph (Figure 1(j)).

2.2. Case 2: Removal of a Broken Instrument Using the Tube-and-Glue Technique

A 62-year-old male patient was referred to an endodontist due to an instrument fracture during root canal treatment of his maxillary left lateral incisor. The tooth was asymptomatic, with normal periodontal and periradicular status. Periapical radiograph showed a broken instrument in the middle third of the canal.

Enlargement of the coronal third of the canal revealed previous attempts to retrieve the instrument (Figure 2(a)). After taking the informed consent, the temporary restoration was removed, and the access cavity was corrected under magnification such that a straight-line access to the coronal portion of the fragment was provided. The dentinal walls around the coronal 2 mm of the broken file were removed by a size 25 U-file on a U-tip (NSK, Nakanishi, Japan) using an ultrasonic instrument (Varios 970; NSK, Japan) under a DOM (Magna Labomed, Labo America Inc., CA, USA) at ×10 magnification. The U-file moved around the broken instrument in a counterclockwise direction. Several unsuccessful attempts were made to remove the broken instrument using the ultrasonic tip. Therefore, the tube-and-glue technique was used to remove the broken instrument. The blunt tip of a 24-gauge needle (Supa, Tehran, Iran) which could encircle the coronal 2 mm of the broken fragment was used as a tube, along with cyanoacrylate glue (Rever Glue, Tehran, Iran). One drop of cyanoacrylate glue was carefully poured on the tip of the tube. The tube was inserted into the canal and held still for 3 minutes to ensure the setting of the glue. With the outward movement of the tube, the broken instrument was successfully removed while entrapped in the tube (Figures 2(c), 2(d), and 2(e)). Then, the canals were cleaned with5.25% hypochlorite solution and 17% EDTA, shaped, and obturated with gutta-percha points and AH 26 resin sealer (Dentsply-Tulsa Dental, Johnson City, TN, USA) using the cold lateral compaction technique (Figures 2(f) and 2(g)). The patient was then referred for coronal restoration (Figures 2(h) and 2(i)).

2.3. Case 3: Removal of a Broken Instrument Using the Tube-and-Wire Technique

A systemically healthy 35-year-old female patient was referred to a private endodontic office for assessment of the prognosis of nonsurgical root canal retreatment of the left mandibular first molar. The patient complained of pain on chewing in the aforementioned tooth. Upon clinical examinations, the tooth was slightly sensitive to percussion. The periodontal status of the tooth was normal. A periapical radiograph of the tooth revealed a perforation in the furcation area and a broken instrument in the middle and apical third of the mesiolingual root canal, which was beyond the root apex (Figure 3(a)). There was a periapical radiolucency associated with the corresponding root and the furcation area. The patient was informed about the compromised tooth structure and the fair to poor overall prognosis. Following this, informed consent was obtained from the patient. In the first appointment, the porcelain-fused-to-metal crown was cut using a high-speed carbide fissure bur (Dentsply Sirona, Germany). The intracanal post was then removed using a G21 ultrasonic tip (NSK, Nakanishi, Japan) with counterclockwise movement (Figure 3(c)). The access cavity was cleaned and irrigated with 5.25% NaOCl. The perforation site was detected under magnification (×10) using a DOM (Magna Labomed, Labo America Inc., CA, USA) and was sealed with RetroMTA (BioMTA, Deajon, Seoul, Korea) (Figures 3(d), 3(e), and 3(f)).

Since the quality of the root filling of the distal canals was acceptable, there was no evidence of coronal leakage and apical radiolucency, the previous root canal treatment was done by an endodontist, and selective retreatment of mesial root canals was scheduled. A moist cotton pellet was placed over the RetroMTA to facilitate the proper setting of the cement; the gutta-percha was removed from the mesial canals using ProTaper Universal retreatment file (Dentsply-Maillefer, Ballaigues, Švicarska) with 1200 rpm speed, without using solvent. These files feature end-cutting tips designed to enhance penetration and facilitate the removal of root filling material, thus boosting their efficiency. Additionally, the combination of flute design and recommended usage techniques may also help reduce the risk of file separation. When the coronal portion of the broken file was visualized under the DOM, the dentinal walls surrounding the coronal 2 mm of the broken instrument were circumferentially removed using a size 25 U-file on a U-tip. In the second treatment session, after the temporary filling removal, the setting of RetroMTA was evaluated. A blunt-tip 21-gauge needle (Supa, Tehran, Iran) and a 0.15 mm wire of Tar (string musical instrument) were used. Both ends of the wire were passed through the tube in a way that a lasso was formed (Figure 3(g)). Next, the tube was inserted into the canal, and the lasso entrapped the coronal part of the broken instrument. On the other side, the wire was twisted using a needle holder to lock the loop around the fragment. The broken file was successfully removed with some lateral movements and, finally, outward force after three attempts. The canals were then prepared with Neoniti rotary instrument (Neolix, Châtres-la-Forêt, France), irrigated with 5.25% hypochlorite solution and its activation with ultrasonic, and finally, rinsed with 17% EDTA. Subsequently, canals were obturated with gutta-percha points and AH26 resin sealer (Dentsply-Tulsa Dental, Johnson City, TN, USA) using a cold lateral compaction technique (Figures 3(i) and 3(j)). The patient was subsequently referred for coronal restoration. At the 2-year recall, the tooth was symptom-free, and the radiolucencies in apical and furcal areas were resolved on periapical radiograph (Figures 3(k) and 3(l)).

2.4. Case 4: Removal of a Broken Instrument Using BTEX PEN

A 29-year-old healthy female patient was referred to a private endodontic office complaining of pain on chewing on the maxillary right second premolar tooth. The patient reported a history of root canal treatment approximately 4 months earlier. During intraoral examinations, it was observed that the tooth had a faulty restoration and exhibited sensitivity to percussion. However, radiographic examinations revealed that the tooth had a normal periodontal status. Periapical radiograph revealed a broken instrument in the palatal canal, transportation and perforation in the buccal canal, and overextension of an MTA-like material in her previous root canal treatment. Furthermore, there was a separated instrument in the periradicular area (Figure 4(a)). The buccal canal seemed to be filled with an MTA-like material that fortunately was not set and was easily removed by irrigation and ultrasonic agitation. After the removal of guttapercha from the palatal canal, the coronal portion of the broken file was visualized under a DOM (Magna Labomed, Labo America Inc., CA, USA). The coronal 2 mm of the broken file was exposed by a size 25 Ufile on a U-tip using an ultrasonic instrument (Varios 970; NSK, Japan) at ×15 magnification. The U-file moved around the broken instrument with a counterclockwise movement. Since the broken file could not be removed from the canal and further efforts would lead to excessive dentin removal, BTEX PEN (Dimotech, Daya Tajhiz Teb Shomal, Iran), an extractor device, was applied (Figure 4(c)). The broken file was successfully removed after 3 attempts (Figures 4(d), 4(e), 4(f), and 4(g)). A perforation was detected in the buccal canal under a DOM and was sealed with RetroMTA (BioMTA, Deajon, Seoul, Korea) (Figure 4(h)). The canals were then prepared with NiTi rotary instruments (DENCO Super Files III, Longhua, Shenzhen, China), irrigated with 5.25% hypochlorite solution and its activation with ultrasonic, and finally, rinsed with 17% EDTA. Subsequently, canals were filled with EndoSeal MTA (Maruchi, Wonju, Korea) using the single-cone technique (Figure 4(i)). Finally, the patient was referred for coronal restoration. At the 3-year follow-up, the tooth was restored by a metal-ceramic crown. The patient reported no sign or symptom. On the periapical radiograph, the periradicular area seemed to be healthy with no changes in the surrounding bone.

2.5. Case 5: Removal of a Broken Instrument Using the Tube-and-Internal Shaft Technique

A 44-year-old healthy female patient was referred to a private endodontic office with a chief complaint of pain while chewing on the maxillary left first premolar. In clinical examination, the maxillary left first premolar had a composite restoration and coronal discoloration (Figure 5(b)). The tooth had a normal periodontal condition. A preoperative periapical radiograph revealed a broken file in the apical third of the palatal canal with no evidence of periapical radiolucency (Figure 5(a)). After the removal of gutta-percha from the canals by NiTi rotary instruments without a solvent, the coronal portion of the broken file was visualized under a DOM (Magna Labomed, Labo America Inc., CA, USA) (Figure 5(c)). The dentinal walls surrounding the coronal 2 mm of the broken fragment were removed by a size 25 U-file on a U-tip using an ultrasonic instrument (Varios 970; NSK, Japan). The sharp tip of a 21-gauge spinal tap needle (Dr. J, Japan) was polished, and a window with a diameter of 1 mm was created 1 mm away from the tip by a fissure diamond bur with a high-speed handpiece without water spray (Figure 5(d)). The coronal 2 mm of the fragment was surrounded by the hollow tube of the spinal tap needle at ×20 magnification. Then, the internal shaft was inserted into the tube in a proper direction in order to push the coronal end of the broken file into the window such that the file would be fixed within the tube. The broken file was successfully removed after two attempts (Figure 5(f)). The canals were prepared with NiTi rotary instruments (DENCO Super Files III, Longhua, Shenzhen, China), irrigated with 5.25% hypochlorite solution and its activation with ultrasonic, and finally, rinsed with 17% EDTA.

Subsequently, canals were obturated with gutta-percha points and AH 26 resin sealer (Dentsply-Tulsa Dental, Johnson City, TN, USA) by the cold lateral compaction technique (Figures 5(g) and 5(h)). The patient was then referred for final restoration.

2.6. Case 6: Removal of a Broken Instrument with Stieglitz Forceps

A 27-year-old healthy female patient was referred to an endodontist with the chief complaint of pain in her maxillary left second molar. Clinical examination revealed pain on percussion and a normal periodontal status. There was no evidence of periapical radiolucency on the periapical radiograph; however, a broken instrument in the coronal third of the second mesiobuccal canal was detected (Figures 6(a) and 6(b)). After the removal of temporary restoration, the broken file in the mesiobuccal canal was visualized under a DOM (Magna Labomed, Labo America Inc., CA, USA). The dentinal walls surrounding the coronal 2 mm of the broken file were removed using an E8D ultrasonic tip (Varios 970; NSK, Japan) at ×10 magnification. Next, the broken file was gripped with Stieglitz forceps (Falcon Medical Italia) and successfully removed from the canal on the first attempt (Figures 6(c), 6(d), and 6(e)). The canals were prepared with NiTi rotary instrument (DENCO Super Files III, Longhua, Shenzhen, China), irrigated with 5.25% hypochlorite solution and its activation with ultrasonic, and finally, rinsed with 17% EDTA. Subsequently, canals were obturated with gutta-percha points and AH 26 resin sealer (Dentsply Tulsa Dental, Johnson City, TN, USA) using the cold lateral compaction technique (Figures 6(f), 6(g), and 6(h)). The patient was then referred for coronal restoration.