Cleaning of used rotary nickel-titanium ﬁles in an
ultrasonic bath by locally intensiﬁed acoustic
L. M. Bryson
, D. Fernandez Rivas
& C. Boutsioukis
Department of Endodontology, Academic Centre for Dentistry Amsterdam (ACTA), Amsterdam; and
Systems Group, Faculty of Science and Technology, University of Twente, Enschede, The Netherlands
Bryson LM, Fernandez Rivas D, Boutsioukis C.
Cleaning of used rotary nickel-titanium ﬁles in an ultrasonic
bath by locally intensiﬁed acoustic cavitation. International
Endodontic Journal, 51, 457–468, 2018.
Aim To compare the pre-sterilization cleaning of
rotary Ni-Ti ﬁles of different sizes previously used a.
ex vivo and b. clinically by a washer–disinfector, a
regular ultrasonic bath, and the same ultrasonic bath
in combination with a recently developed cavitation
Methodology Two sets of two hundred rotary Ni-Ti
ﬁles, one previously used ex vivo and another one used
clinically, were collected from the undergraduate and
postgraduate clinics of the Academic Centre for Den-
tistry Amsterdam (ACTA). The instruments were
immersed in an enzymatic solution and subsequently
cleaned either by a washer–disinfector, a regular ultra-
sonic bath combined with a glass beaker, the same
bath combined with a beaker lined with two cavitation
intensifying sheets or with two standard plastic sheets.
The positive control consisted of used ﬁles that did not
undergo any cleaning and the negative control
included new unused ﬁles. The instruments were then
stained to reveal remaining protein material and scored
under a stereoscopic microscope. The results were anal-
ysed by nonparametric statistical tests (a = 0.05).
Results No signiﬁcant difference was found between
the combination of the ultrasonic bath and the regu-
lar glass beaker and the same ultrasonic bath with
the beaker lined with the cavitation intensifying
sheets. The washer–disinfector left signiﬁcantly more
debris compared to the latter group when clinically
used ﬁles were evaluated (P ≤ 0.001). The effect of
instrument size on cleaning was not consistent.
Conclusion None of the tested methods was able to
remove all residual protein material from the ﬁles; how-
ever, it could be noted that this study did not follow the
reprocessing protocol provided by the manufacturer.
Keywords: cavitation, cleaning, rotary instruments,
ultrasonic bath, washer–disinfector.
Received 9 July 2017; accepted 6 October 2017
Rotary Nickel-Titanium (Ni-Ti) instruments are widely
used for root canal preparation by both endodontists
and general dentists (Parashos & Messer 2005, Bird
et al. 2009, Locke et al. 2013). Owing primarily to
their cost (Eggert et al. 1999), there is an interest in
reusing these instruments on different patients to
make treatments more affordable (Messer et al. 2003)
provided that the instruments are not labelled as sin-
gle use by the manufacturer. Reuse does not seem to
Correspondence: Dr. Christos Boutsioukis, Department of
Endodontology, Academic Centre for Dentistry Amsterdam
(ACTA), Gustav Mahlerlaan 3004, 1081 LA, Amsterdam, The
Netherlands (Tel.: +31 20 59 80140; e-mail: c.boutsioukis@
This is an open access article under the terms of the Creative
Commons Attribution-NonCommercial-NoDerivs License,
which permits use and distribution in any medium, provided
the original work is properly cited, the use is non-
commercial and no modiﬁcations or adaptations are made.
International Endodontic Journal
, 51, 457–468, 2018
© 2017 The Authors. International Endodontic Journal published by John Wiley & Sons Ltd
on behalf of British Endodontic Society