Remocion de limas

Basic Research—Technology

Dissolution of Nickel-Titanium Endodontic Files via an
Electrochemical Process: A New Concept for Future
Retrieval of Fractured Files in Root Canals
´
ˆ
Fabiola Ormiga, MSc,*,† Jose Antonio da Cunha Ponciano Gomes, DSc,*
´
and Marcos Cesar Pimenta de Araujo, DSc†
Abstract
Introduction: The retrieval of fractured instruments
from root canals has been largelyreported in the literature. However, a less complex retrieval method that
causes minimum damage to the dental structures is
needed. The aim of this article is to introduce a new
concept of retrieval of fractured instruments from root
canals based on an electrochemical process. Methods:
Current register tests were used to evaluate the dissolution process of 25.04 nickel-titanium (NiTi) K3rotary
files. A constant anodic potential was applied to the
NiTi files, whereas the Potentiostat registered the
anodic current. After the tests, all files were observed
by using an optical microscope. Results: The current attained initial values of approximately 55 mA that
declined during the entire test. A good reproducibility
of results was observed. The optical microscopy analysis
evidenced aprogressive consumption of the files with
increasing polarization time. Conclusions: The results
presented here show that the concept of fractured file
retrieval by an electrochemical process is feasible. This
concept resulted in a consistent basis for the development of a method to remove fractured instruments
from root canals. (J Endod 2010;36:717–720)

Key Words
Endodontic instrument,fracture, micro-electrodes,
nickel-titanium, retrieval of fractured instrument

From the *Department of Metallurgy and Materials and
Department of Endodontics, Federal University of Rio de
Janeiro, Rio de Janeiro, Brazil.
´
ˆ
Address requests for reprints to Dr Jose Antonio da Cunha
´
Ponciano Gomes, Av. Ipiranga, 910/02. Petropolis, RJ, CEP:
25610-150, Brazil. E-mail address:ponciano@metalmat.ufrj.br.
0099-2399/$0 - see front matter
Copyright ª 2010 American Association of Endodontists.
doi:10.1016/j.joen.2009.11.024
†

T

he presence of a fractured instrument in the root canal represents an obstacle to
routine endodontic therapy (1). The retrieval of fractured instruments from root
canals has been largely reported in the literature, and many devices and methods
havebeen proposed to accomplish that (2–14). However, those mechanical methods
present some limitations related to canal morphology, reduction of root strength, and
operator ability. According to Alomairy (15), less curved canals and longer radius of
curvature are favorable factors for removal of fractured nickel-titanium (NiTi) fragments. In many cases a straight-line access to the fracturedinstrument is not obtained
(16, 17), thus making its visualization and access to the adjacent dentin with straight
instruments impossible. Consequently, it is not recommended to attempt to remove
a fragment situated beyond the curve of the canal (18–21). Such attempts might
lead to ledge formation and perforation, and they might also promote a reduction of
the root strength (18–21). Madarati et al(22) observed that removal of fractured files
located deeper in the root canal resulted in significant tooth structure loss. However,
excessive removal of dentin tissue and significant loss of mechanical resistance of
the root were observed even in cases of removal of fractured instruments situated in
straight canals or in the medium third of curved canals (21, 23). Another point to
beconsidered is that mechanical methods to remove fractured instruments are strongly
dependent on professional ability (23), and most of the time the use of an operating
microscope is necessary (10, 13, 17).
In this context, a less complex retrieval method that causes minimum damage to
the dental structures is necessary. Dissolution of a fractured instrument might represent
an actual possibility to...