Treatment outcome of young molars obstructed by fractured endodontic instruments : two case reports

Ultrasonic tips and anatomic finishing files have been used as strategies to improve the cleaning and disinfection of root canals, especially in complex anatomies. These instruments are also subjected to fractures, which can hinder the endodontic treatment and negatively affect the outcome. This article presents two cases of successful management of intracanalfractured instruments with unfavourable prognosis, emphasizing on treatment protocols and outcomes. Two 14-year-old female patients underwent root canal treatment of teeth 37 (case 1) and 47 (case 2). During the final irrigation protocols, case 1 presented a fractured XPResearch, Society and Development, v. 9, n. 10, e3149108537, 2020 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v9i10.8537 2 Clean file within the mesiobuccal canal and within the distal canal in case 2, which also showed fractured E1-Irrisonic tips within the mesiobuccal and distal canals. Non-surgical management and bypassing retained instrument fragments were successful in both cases and they may be considered adequate approaches.


Methodology
This case report followed the CARE 2013 guidelines (Gagnier et al., 2013). All procedures performed in this case report were in accordance with the Helsinki Declaration.
The parents of the patients signed an informed consent form authorizing the publication of the case and any accompanying images.
Two 14-year-old female patients were referred to endodontic treatment in the left (tooth 37, case 1) and right (tooth 47, case 2) mandibular second molars. A detailed review of the patient's medical and dental histories revealed no systemic disease and contributory oral conditions. Intraoral examinations showed negative responses to pulp sensitivity tests and palpation in the apical region and the absence of pathological mobility, but both patients reported positive responses to percussion, with the presence of caries. The radiographic examination revealed periapical radiolucent lesions (Figures 1a and 2a) and the pulp and periradicular status were diagnosed as pulp necrosis and asymptomatic apical periodontitis, respectively.
A single and experienced operator performed the root canal treatments of cases 1 and 2 using local anaesthesia and absolute isolation with a rubber dam. First, manual glide path preparations were performed with #08, #10, and #15 K-files (Dentsply Maillefer, Ballaigues, Switzerland) and 2.5% NaOCl (Rioquímica Ltda., São José do Rio Preto, SP, Brazil). The working lengths (WL) were determined with a RomiApex A-15 apex locator (Romidan Ltd., Kyriat Ono, Israel) and #15 K-file in all root canals. Biomechanical instrumentations were performed 1 mm short of the root canal length using the Twisted File (TF) Adaptive system up to the SM3 (#35/.04) file (SybronEndo, Orange, CA) adapted to the Elements motor (SybronEndo, Glendora, CA) in adaptive motion, according to the manufacturer's protocol, under abundant irrigation with 2.5% NaOCl.
The final irrigation of all canals was carried out with 5 mL of 17% ethylenediaminetetraacetic acid (EDTA) for 3 minutes followed by 5 mL of 2.5% NaOCl agitated by XP-Clean instruments (MK Life, Porto Alegre, RS, Brazil) in continuous rotation, according to the manufacturer´s recommendations (900 rpm and 1 Ncm-1 torque). However, during the agitation technique, the XP-Clean instruments fractured within the mesiobuccal (Figure 1b) and distal ( Figure 2b) canals of teeth 37 (case 1) and 47 (case 2), respectively.
The patients were informed about the fractured instruments and attempts were made to bypass and remove the fragments from the root canals with the help of the E5 ultrasonic insert (Helse Dental Technology, São Paulo, SP, Brazil) coupled to the EMS Piezon Master 200 Ultrasound Research, Society and Development, v. 9, n. 10, e3149108537, 2020 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v9i10.8537 5 (EMS, São Bernardo do Campo, SP, Brazil) at a power setting of 20%. In both cases, the fragment was only bypassed and not removed, but in tooth 37 (case 1) it moved apically beyond the apical foramen ( Figure 1c). Final irrigation was performed again in each canal using the E1-Irrisonic tip (Helse Dental Technology) at a power of 10% to activate ultrasonically the solutions for 30 seconds. During this procedure, new fractures occurred in the apical third of the ultrasonic insert within the mesiobuccal and distal canals (Figure 2b) of tooth 47 (case 2), and only the fragment within the distal canal was removed.
In both cases, the fragments within the canals were maintained and surgical removal was not indicated due to the proximity of the roots to the mandibular canal. Intracanal medication with calcium hydroxide paste (UltraCal™ XS, Ultradent Products Inc., South Jordan, UT, USA) was used for 14 days. In a second visit, as the teeth were asymptomatic, the roots were obturated with the lateral condensation technique using gutta-percha cones

Results and Discussion
Case reports are still a great contribution to the endodontic literature, especially when involving techniques and instruments used extensively today, in which potential usage complications have not yet been reported, as in the two cases presented. This is the first Research, Society and Development, v. 9, n. 10, e3149108537, 2020 (CC BY 4 Considering this complication, potential solutions would be trying to remove the XP-Clean fragment or bypass the fragments retained within the canal. Both alternatives may be difficult and time-consuming, with an overall clinical success rate ranging from 53% to 87% (Shen et al., 2004;Suter et al., 2005). The success of the non-surgical removal of fractured instruments from root canals depends on factors such as length and location of the fragment in the canal, instrument cross-sectional design, and diameter and degree of curvature of the root and the canal (Shen et al., 2004). When the position of the fragment prevents its conventional removal, with evidence of a negative impact on the treatment outcome due to its maintenance within the canal, a surgical approach may be considered the best option. However, in cases in which the surgical area is near vital anatomical structures at risk of damaging them, surgical removal is not indicated (Madarati et al., 2013;Wang et al., 2010). Ultrasonics under the visualization of an operating microscope has been considered the most effective method of Development, v. 9, n. 10, e3149108537, 2020 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v9i10.8537 9 removing intracanal instrument fragments (Gencoglu & Helvacioglu, 2009). However, the use of ultrasound for removing broken rotary nickel-titanium files may result in some procedural errors such as transportation, perforation, and root fracture (Shahabinejad et al., 2013) or create a secondary fracture of separated file fragments (Arslan et al., 2020;Terauchi et al., 2013). In the two cases reported, the attempt to remove the fragments with ultrasonic tips was partially unsuccessful, which led to their maintenance within the root canals due to the proximity to the mandibular canal, rendering surgical removal impossible. A very undesirable event observed after the removal attempt was the displacement of the fractured fragment beyond the apex, in proximity to the alveolar nerve (Gandevivala et al., 2014;Singh et al., 2017;Wang et al., 2016).
Unfortunately, in case 2, in addition to the primary file fracture, there was also a fracture of the E1-Irrisonic tip during the final irrigation of the root canal. Studies have shown that the acoustic flow and cavitation produced by ultrasound contribute to the cleaning capacity of the root canal irrigation (Jiang et al., 2010). This also makes them effective in several applications including root canal preparation, removal of pulp nodules and fractured instruments, and condensation of endodontic filling materials (Wan et al., 2014). However, regardless of the technique used, endodontic instruments might fracture within the root canal by improper use or pre-existing factors such as anatomical complications and weak points of the instrument itself related to the manufacturing process (Lopes et al., 2016). The fracture of ultrasonic inserts during endodontic procedures is rarely reported in the literature, but some studies correlate it with weak points such as the angle and the diameter of the tips (Walmsley et al., 1996). The acoustic streaming generated by ultrasound varies according to the tip size, in which instruments with smaller diameters have greater displacement amplitude (Ahmad et al., 1987;Lin et al., 2006). This may have favoured the fracture of the ultrasonic inserts in the roots of case 2. Additionally, the previous use of ultrasonic tips without controlling the number of times used and associated with the potential damage caused by the endodontic autoclave sterilization process may have contributed to the fracture (Dioguardi et al., 2019).
Further studies evaluating the number of times ultrasonic inserts for endodontics can be used and sterilized are required to bring more safety to clinicians (Kirsch et al., 2019).
Overall, the occurrence of retained instrument fragment may affect the outcome of the endodontic treatment, transforming a common endodontic procedure into a complication that could result in tooth extraction (Madarati et al., 2013;McGuigan et al., 2013). The degree of canal infection should be considered when determining the potential effect of instrument fracture on the treatment outcome, as the healing rates of teeth with periapical lesions and Research, Society and Development, v. 9, n. 10, e3149108537, 2020 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v9i10.8537 retained instrument fragment are around 86.7% compared with 92.9% for cases without retained fragment, after a 1-year follow-up (Spili et al., 2005). In both cases reported, the evidence of tissue repair characterized by bone neoformation and absence of clinical symptoms show the success of endodontic therapy although the maintenance of intracanal fragments has limited the access to the apical third of root canals. The stage and degree of root canal preparation and disinfection at the time of instrument fracture, fragment position, use of sterile instruments and antimicrobial solutions, and intracanal medication may have favoured the treatment prognosis (McGuigan et al., 2013). Generally, the cases presented reinforce the assumption that the success rate of endodontic treatment is related to the efficiency in disinfecting the root canal system, even in the presence of a fractured instrument (Nevares et al., 2012;Parashos & Messer, 2006;Simon et al., 2008). It is also necessary to be aware of the use of XP-Endo files, which even in single use seem to have a high potential for fractures.

Conclusions
Non-surgical management and bypassing retained fragments of anatomic finishing files (XP-Clean) and ultrasonic inserts (E1-Irrisonic) were successful in both cases and they may be considered adequate approaches. Clinical investigations are required to validate our results and to investigate the effectiveness of different protocols for the removal of fractured endodontic instruments from root canal systems.