Electrochemical dissolution of nickel‐titanium instrument fragments in root canals of extracted human maxillary molars using a small reservoir of electrolyte

• Published in: International endodontic journal Vol. 53; no. 11; pp. 1559 - 1568
• Main Authors: Amaral, C. C. F., Ormiga, F., Araújo, O. M. O., Lopes, R. T., Gomes, J. A. C. P.
• Format: Journal Article
• Language: English
• Published: England Wiley Subscription Services, Inc 01-11-2020
• Subjects: Dental Alloys; Dental pulp; Dental Pulp Cavity; Dentistry; Dissolution; electrochemical dissolution; Electrodes; Electrolytes; endodontic instruments; Endodontics; fracture; Fractures; Humans; Maxilla; micro‐computed tomography; Molar - diagnostic imaging; Molars; Nickel; nickel‐titanium; Porosity; Root Canal Preparation; Root canals; Solubility; Teeth; Titanium; micro-computed tomography; endodontic instruments; electrochemical dissolution; nickel-titanium; fracture
• ISSN: 0143-2885; 1365-2591
• DOI: 10.1111/iej.13381

Aim
To evaluate the viability of the electrochemical dissolution of fragments of fractured NiTi instruments in root canals of extracted human maxillary molars, using two electrodes and the solution restricted to a small reservoir coupled to the pulp chamber. The primary hypothesis was that this method enables the reduction of fragment volume and re‐establishment of the root canal path with a size 08 K‐file, both in simulated canals and in extracted human maxillary molars.
Methodology
Fragments of F1 ProTaper instruments were polarized in simulated root canals and in distobuccal root canals of extracted maxillary molars using a new method, with the solution restricted to a small acrylic microcell coupled to each resin block or pulp chamber. Two electrodes were used, where one was kept in contact with the intracanal fragment and another was positioned in the solution present in the acrylic microcell. After the tests, a size 08 K‐file was used passively to verify the possibility of bypassing the fragment, which was also confirmed by radiographic analysis. Micro‐CT analysis of the teeth was used before and after fragment dissolution to evaluate the volume, length and porosity of the fragments. The D'Agostino–Pearson normality test was used to verify the distribution of the data. A paired t‐test (P < 0.05) was used to compare the volume, length and porosity of the fragments before and after the dissolution tests.
Results
After dissolution, all fragments could be bypassed with a size 08 K‐file in both simulated canals and in extracted teeth. The dissolution process did not result in significant reduction of neither the fragment length nor the fragment porosity. However, it resulted in a significant reduction of fragment volume (paired t‐test, P < 0.05).
Conclusion
The electrochemical dissolution of fragments of NiTi files in root canals of extracted human maxillary molars using two electrodes, and the solution restricted to a small reservoir coupled to the pulp chamber resulted in a significant reduction of fragment volume. The re‐establishment of the root canal path with the passive insertion of size 08 K‐files was possible in all samples after the tests, both in simulated canals and in extracted teeth.
The electrochemical dissolution using two electrodes immersed in the solution contained in the acrylic microcell, allowed the recovery of the original canal path with a size 08 K‐file. (WE) working electrode in contact with the fragment; (CE + RE) counter‐electrode and reference electrode.