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rev port estomatol med dent cir maxilofac . 2021;62(1):1-8 7

mechanical performance. Therefore, the null hypothesis the internal validity of the methodologies. 10-12 Another
was rejected. strength is the use of replica -like coronal shaping instruments
Although some design differences could be noted between that are already being marketed and used in clinics, but with
PTG and Premium Taper Gold instruments, the most relevant no available reported data in the literature regarding their per-
was observed in the Go -Taper Flex instrument: a flat tip, mim- formance and safety, making the present study relevant to
icking the fracture pattern of an instrument subjected to a both the scientific and clinical points of view.
torsion test, but without any visible plastic deformation of the With regards to the study’s limitations, it should be men-
blades. The inspected instruments were picked from sealed tioned that other replica -like orifice shapers exist in the
packages and placed directly into the SEM sample holder to market and were not tested herein. Besides, some addition-
minimize the operator handling, therefore excluding any han- al characteristics, such as cutting efficiency, shaping ability,
dling damage. Although this flat tip feature was observed in and certain instrument geometries, like dimensions, were
the several SX instruments inspected, it could not be conclud- not considered in the present methodology, as was not the
ed whether it was a defect or a geometric characteristic. More- influence of temperature. Further studies should focus on
over, this feature was not observed in other Go -Taper Flex other replica -like instruments available in the market and
instruments (S1, S2, F1, F2, and F3) (unpublished data), which understanding the similarities regarding instruments’ pitch,
presented a conventional tip design (non -flat tip). Therefore, core volume, and dimensions, using a reliable 3 -dimensional
the impact of that difference in these instruments’ shaping analysis.
ability and safety is still unclear.
Differences in the instruments’ mechanical performance
must be analyzed considering multiple factors that may be Conclusions
more or less relevant depending on the test. Torsional strength
refers to the ability to sustain torsional stress before fracture Overall, both replica -like SX instruments were similar to the
and is a highly advisable characteristic for coronal shaper in- PTG premium brand regarding the number of blades, helix
struments whose goal is to widen a narrow root canal en- angles, design symmetry, cross -sectional geometry, and Ti/
trance into a large size. 17,18 The angle of rotation is related to Ni atomic proportions. Geometric differences were noted re-
the capacity to sustain deformation before rupture under a garding the instruments’ tip. Premium Taper Gold showed
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torsional load, and the maximum bending load required to the smoothest surface finishing, while the Go -Taper Flex
perform a predefined displacement represents a flexibility presented a surface with more irregularities. Distinct phase
score in which lower loads reflect superior flexibility. It is also transformation temperatures were observed among sys-
a recommended characteristic for coronal shaper instruments tems. Go -Taper Flex had the lowest maximum torque and
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to prevent pathway deviation or cervical -third straightening, less flexibility when compared to PTG. No significant differ-
preserving the pericervical dentin, as advocated in minimally- ences were noted between Premium Taper Gold and PTG SX
-invasive procedures. instruments in the mechanical tests.
The maximum torque to fracture was lower in the Go-
-Taper Flex than the PTG SX instrument, which might be par-
tially explained by its worst surface finishing leading to a more Acknowledgements
20
rapid microfracture development and propagation. The sim-
ilarities of maximum torque, angle of rotation, and bending The authors thank to Francisco Manuel Braz Fernandes (CE-
load results observed between PTG SX and Premium Taper NIMAT/I3N, Department of Materials Science, NOVA School of
Gold instruments may be explained by the non -full austenitic Science and Technology, Universidade NOVA de Lisboa, Capa-
characteristics observed at the test temperature, the similari- rica, Portugal) who is acknowledged for running the DSC tests
ties in the instruments’ design at the maximum stress level, of the instruments.
and their Ti/Ni proportions. The lowest flexibility was observed
in the Go -Taper instruments and, although this result cannot
be explained based only on the assessed characteristics, it Ethical disclosures
could be influenced by other aspects such as the dimensions
of the instrument submitted to the bending test, which were Protection of human and animal subjects. The authors
not measured in the present study. To the best of the authors’ declare that no experiments were performed on humans or
knowledge, no previous studies have reported torsional and animals for this study.

bending strength for PTG SX instruments or the tested replica- Confidentiality of data. The authors declare that no patient
-like ones; therefore, the present results cannot be compared
with previous literature. However, a previous study comparing data appear in this article.

ProTaper Universal instruments and six replica -likes revealed Right to privacy and informed consent. The authors declare
differences in mechanical performance despite the design that no patient data appear in this article.
similarities. 15
The multimethod approach was one of the strengths of the
present investigation, as it allowed a more comprehensive un- Conflict of interest
derstanding of the tested instruments. Accordingly, well-
16
-established international protocols were followed, enhancing The authors have no conflicts of interest to declare.