UNIVERSIDADE ESTADUAL PAULISTA
“JÚLIO DE MESQUITA FILHO”
Instituto de Ciência e Tecnologia
Campus de São José dos Campos
ORIGINAL ARTICLE DOI: https://doi.org/10.4322/bds.2025.e4638
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Braz Dent Sci 2025 Apr/Jun;28 (2): e4638
This is an Open Access article distributed under the terms of the Creative Commons Attribution license (https://creativecommons.org/licenses/by/4.0/), which permits
unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Influence of gold and blue heat treatments on mechanical
properties and phase transformation behavior of flat-designed
rotary instruments
Influência dos tratamentos térmicos gold e blue nas propriedades mecânicas e no comportamento de transformação de fase
de instrumentos rotatórios com design flat
Anne Rafaella Tenório VIEIRA1 , Guilherme Ferreira da SILVA1 , Pablo Andrés AMOROSO-SILVA2 , Rodrigo Ricci VIVAN1 ,
Thaine Oliveira LIMA1 , Maria Carolina Guiotti de OLIVEIRA1 , Marco Antonio Hungaro DUARTE1 , Murilo Priori ALCALDE1
1 - Universidade de São Paulo, Faculdade de Odontologia de Bauru, Departamento de Dentística, Endodontia e Materiais Odontológicos.
Bauru, SP, Brazil.
2 - Universidade Estadual de Londrina, Departamento de Odontologia Restauradora. Londrina, PR, Brazil.
How to cite: Vieira ART, Silva GF, Amoroso-Silva PA, Vivan RR, Lima TO, Oliveira MCG et al. Inuence of Gold and Blue heat treatments
on mechanical properties and phase transformation behavior of at-designed rotary instruments. Braz Dent Sci. 2025;28(2):e4638.
https://doi.org/10.4322/bds.2025.e4638
ABSTRACT
Objective: To evaluate the mechanical properties and austenite phase transformation temperature of at-designed
rotary instruments manufactured with gold and blue heat treatments. Material and Methods: A total of 60
rotary instruments with a at design 25.04 with gold (Flat File 25.04 – MK Life, Brazil) and blue (Prototype
25.04 - MK Life, Brazil) heat treatments were used for cyclic fatigue, torsional fatigue, and bending tests (n=30).
The cyclic fatigue test was conducted in an articial canal with a curvature of 60° and a radius of 5 mm (n=10).
The torsion test was conducted to evaluate the torque (N.cm) and angular deection (°) required for fracture
(n=10). Finally, the 60° bending test evaluated the force (g.f) required to exion the instruments at the 5 mm
tip (n=10). Differential Scanning Calorimetry (DSC) analysis was performed to establish the initial (Ai) and
nal (Af) austenitic transformation temperatures. The data were statistically analyzed using the Kolmogorov-
Smirnov test for normality and the unpaired t-test, with a signicance level of 5%. Results: The cyclic fatigue test
showed that Flat 25.04 gold instruments had signicantly greater cyclic fatigue resistance (p<0.05). The torsion
test revealed that Flat 25.04 gold instruments exhibited lower maximum torque (N.cm) and greater angular
deection (°) (P<0.05). The bending test showed that the gold instrument required less force (P<0.05). DSC
analysis demonstrated that the gold heat treatment had a higher Af temperature (42.8 °C) compared to the blue
treatment (32.2 °C). Conclusion: The different heat treatments impacted in phase transformation temperatures
and on the mechanical properties of the instruments.
KEYWORDS
Cyclic fatigue; Endodontics; Flat design; Nickel-Titanium; Torsional fatigue.
RESUMO
Objetivo: Avaliar as propriedades mecânicas e a temperatura de transformação de fase austenita em instrumentos
com design at confeccionados com tratamento térmico gold e blue. Material e Métodos: Foram utilizados 60
instrumentos rotatórios com design at 25.04 com tratamento térmico gold (Flat File 25.04 – Mk Life, Brasil) e
blue (Protótipo 25.04 – Mk Life Brasil) para avaliar a resistência a fadiga cíclica, torcional e exional (n=30). O
teste de fadiga cíclica foi realizado em um canal articial com 60° de curvatura e 5 mm de raio (n=10). O teste
de torção avaliou o torque máximo (N.cm) e deexão angular (°) (n=10). O teste de exão foi realizado para
avaliar a força necessária para exionar os instrumentos a uma curvatura de 60° (n=10). O teste de Escaneamento
Diferencial de Calorimetria (EDC) avaliou a temperatura de transformação austenita inicial (Ai) e nal (Af).
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Braz Dent Sci 2025 Apr/Jun;28 (2): e4638
Vieira ART et al.
Influence of Gold and Blue heat treatments on mechanical properties and phase transformation behavior of flat-designed rotary instruments
Vieira ART et al. Influence of Gold and Blue heat treatments on mechanical
properties and phase transformation behavior of flat-designed
rotary instruments
INTRODUCTION
Nickel-Titanium (NiTi) mechanized
instruments have been widely used for preparing
curved root canals due to their high exibility,
providing safety and low risk of instrumentation
errors or instrument fracture [1,2]. However,
instrument fracture continues to be a concern
for clinicians [2].
The instruments separation during use can occur
due to two causes: cyclic and torsional fatigue [3,4].
Cyclic fatigue occurs when instruments are rotating
inside the curved root canal and are subjected to
tensile and contraction forces at their maximum
flexion point, which can lead to rupture of the
metallic alloy [3,4]. Torsional fatigue occurs when
the instrument’s tip becomes trapped in the dentin
walls while the instrument continues its rotational
movement, which can lead to plastic deformation
and/or instrument rupture [3,4]. Therefore,
manufacturers have developed several modications
to optimize their mechanical properties, such as: new
instrument designs, manufacturing processes, new
kinematics, and different thermal treatments of the
NiTi alloy [1,2,4-7].
The thermal treatment of NiTi provides a
better arrangement of the crystalline structure of the
metallic alloy, which favors the appearance of the
R or martensitic phase, phases responsible for the
super exibility of the alloy and, consequently, better
mechanical properties of the instruments [1,2,7]
Aditionally, these treatments tend to modify the
alloy transformation temperature, altering the
presence of these different phases in response to
the temperature of the root canal [1,7]. Therefore,
it is essential that the endodontist knows the
characteristics of the instruments and select
them according to the anatomy to be prepared,
enabling safety and effectiveness during root canal
preparation [1,8,9].
Gambarini et al. [10] proposed a new design
concept for instruments known as “flat”. This
design involves an instrument with one of its sides
at and without a cutting surface, aiming to reduce
friction with the canal walls, reduce the volume
of metal and decrease debris accumulation inside
the root canals. According to the authors, this
characteristic provides a signicant improvement
in resistance to cyclic fatigue.
Some rotary systems were launched on the
world market driven by this innovative design,
even without any other robust scientic evidence at
that time, varying with the preparation sequence,
types of heat treatments, etc. Silva et al. [11] and
Jeong et al. [12] demonstrated that the at design
did not provide improvements in resistance to
cyclic and torsional fatigue compared to S cross-
section instruments. Additionally, Silva et al. [11]
demonstrated that the flat design provides
similar efciency in removing debris. Therefore,
although there are few studies regarding the
impact of the flat design on the mechanical
properties and preparation of root canals, it is
possible to state that the at design does not
provide improvements in mechanical properties
compared to the conventional S cross-section.
Although the flat design cross-section
does not present advantages in the mechanical
properties of NiTi rotary instruments, the use of
different types of heat treatments is an industrial
option widely used for this purpose [7,8]. There
is no study that has evaluated the mechanical
properties of instruments with a at design made
with different heat treatments. The objective of this
study was to compare the mechanical properties
of two at-design instruments made with gold
and blue heat treatments and the NiTi alloy
transformation temperatures using Differential
Calorimetry Scanning. The null hypotheses of
this study were was: thermal treatments do not
Os dados obtidos foram analisados estatisticamente empregando o teste de Kolmogorov-smirnov e teste t não
pareado, com nível de signicância de 5%. Resultados: O teste de fadiga cíclica demonstrou que o instrumento
at 25.04 gold apresentou maior resistência à fadiga cíclica (P<0,05). O teste de torção demonstrou que o
instrumento at 25.04 gold apresentou menor torque e maior deexão angular (P<0,05). O teste de exão
demonstrou que o instrumento at 25.04 gold apresentou menor força à exão de 60° (P<0,05). O teste de
EDC demonstrou que o tratamento gold (42,8 °C) apresentou uma temperatura Af maior que o tratamento blue
(32,2 °C). Conclusão: Os tratamentos térmicos impactaram na temperatura de transformação e nas propriedades
mecânicas dos instrumentos avaliados.
PALAVRAS-CHAVE
Fadiga cíclica; Endodontia; Design at; Níquel-Titânio; Fadiga torcional.
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Vieira ART et al.
Influence of Gold and Blue heat treatments on mechanical properties and phase transformation behavior of flat-designed rotary instruments
Vieira ART et al. Influence of Gold and Blue heat treatments on mechanical
properties and phase transformation behavior of flat-designed
rotary instruments
impact the mechanical properties and the phase
transformation behavior of instruments with a
at design.
MATERIAL AND METHODS
To perform mechanical tests, a sample size
calculation was conducted using the G*Power
v3.1 for Mac software (Heinrich Heine University
Düsseldorf (HHU)) by selecting the Wilcoxon-
Mann-Whitney test from the t-test family. An
alpha type error of 0.05, a beta power of 0.95,
and an N2/N1 ratio of 1 were also stipulated.
The effect size of the sample was 1.65, and the
actual power was 0.965. A total of 10 specimens
per group was indicated as the ideal sample size,
based on the article by Alcalde et al. [13]. Prior
to the mechanical tests, all instruments were
inspected for possible defects or deformities
under a stereomicroscope (Stemi 2000C; Carls
Zeiss, Jena, Germany) with 16X magnication.
For the mechanical tests in this study, a
total of 60 rotary instruments 25.04 with a
at design, manufactured with blue and gold
thermal treatment (n=30 each), were used. The
instruments used in the gold treatment group
are commercially available in Brazil from the
company MK Life (Porto Alegre, Rio Grande do
Sul, Brazil), under the brand name Flat File.
Conversely, the instruments with blue thermal
treatment are prototypes that differ from the Flat
File instruments solely in the thermal treatment
applied (Figure 1).
Cyclic fatigue test
A total of 20 rotary instruments 25.04 with
a at design, gold and blue (n=10) were used.
The cyclic fatigue test was conducted using an
apparatus with an articial stainless-steel canal
with a 60° curvature and a 5 mm radius under
conditions simulating body temperature (36° ±
1 °C), as described by Klymus et al. [14]. The
instruments were activated using a VDW Silver
Reciproc electric motor (VDW, Munich, Germany)
and operated in a rotary motion at 500 rotations
per minute (RPM) and 2 N.cm of torque. During
the test, the time until instrument fracture was
measured using a digital stopwatch and conrmed
by video recording simultaneously with the test.
After measuring the time to fracture, the number of
cycles was calculated using the following formula:
( )
( )
/ 60
time to fracture in seconds
speed rotations per minute
×
(1)
Torsion and bending test
For torsion test, 20 rotary instruments 25.04
with a flat design, manufactured with blue and
gold thermal treatment (n=10 each), were used.
The torsion tests were performed according to ISO
3630-1 specification [15] and under conditions
simulating body temperature (36° ± 1 °C), as
previously described by Osaki et al. [16]. The
torsion test evaluated the torque (N.cm) and angular
deection (°) required to fracture the instruments.
Prior to the tests, all instruments had their
shafts removed to allow xation in the torsion
machine. The ends of the instruments were then
xed in screwable mandrels, with the rst 3 mm
of the instrument tip xed in a mandrel coupled to
a torque cell and the other end xed in a mandrel
connected to a reversible gear motor. A clockwise
rotation at a speed of 2 rotations per minute
(RPM) was applied to all groups. Simultaneously
with the motor rotation, the software provided
the torque (N.cm) and angular deection values
required for instrument fracture.
The bending test was performed using the same
torsion equipment under conditions simulating
body temperature (36° ± 1 °C), following an
adaptation employed by Alcalde et al. [13]. A total
of 20 instruments (n=10 each) were used, with
5 mm of the instrument tips xed in a force cell
and bent to 60°. The software then provided the
necessary force in gram-force (g.f).
Evaluation of Instrument Surfaces Using
Scanning Electron Microscopy (SEM)
This step aimed to evaluate the topographical
characteristics of the fractured surfaces of the
instruments subjected to torsion and cyclic
fatigue tests. All instruments were examined
using a scanning electron microscope (SEM)
(JSM-T220A, Jeol, Tokyo, Japan) to assess the
Figure 1 - Representative images of Flat 25.04 instruments with
gold and blue thermal treatments.
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Influence of Gold and Blue heat treatments on mechanical properties and phase transformation behavior of flat-designed rotary instruments
Vieira ART et al. Influence of Gold and Blue heat treatments on mechanical
properties and phase transformation behavior of flat-designed
rotary instruments
topographical characteristics of the fractured
surfaces with a magnication of 35x and 500x.
Differential Scanning Calorimetry (DSC)
Differential scanning calorimetry was
employed to determine the initial austenite
transformation temperature (Ai) and final
austenite transformation temperature (Af) of the
different thermal treatments applied. The DSC
analysis was conducted according to the 2004
ASTM [17] guidelines, using ve new instruments.
A fragment of 3 to 5 mm, weighing 7 to 12 mg, was
extracted from the active part of the instrument
and treated with a mixture of 25% hydrouoric
acid, 45% nitric acid, and 30% distilled water for
two minutes. The specimens were subsequently
cleaned with distilled water and mounted on an
aluminum support, with an empty support serving
as the control. All analyses were performed using
the Differential Scanning Calorimetry Equipment
(Mettler Toledo, Tamboré - Barueri - SP, Brazil),
connected to a Samsung desktop computer
(Samsung Digital City, Maetan-dong, Yeongtong).
The STARe software (Mettler Toledo) was used,
and the DSC graphs were extracted.
The thermal cycles lasted 45 minutes and
included the following steps: isothermal retention
at 25 °C for 5 minutes, heating to 150 °C (at a rate
of 10 °C/min), an isothermal hold for 2 minutes,
cooling to -30 °C (at a rate of 10 °C/min), an
isothermal hold for 2 minutes, heating to 150 °C
(at a rate of 10 °C/min), and nally, an isothermal
hold for 2 minutes, followed by cooling to 25 °C.
The phase transformation temperature results
were analyzed using the Netzsch Proteus Thermal
Analysis software (Netzsch-Garatebau GmbH).
The test was performed twice for each group to
conrm the results.
Statistical analysis
The data obtained from the cyclic fatigue,
torsional, and bending tests were analyzed
using the Kolmogorov-Smirnov test to evaluate
the normal distribution. The data were then
assessed using the unpaired Student’s t-test, with
a signicance level of 5%.
RESULTS
Cyclic fatigue, torsional, and bending tests
The mean values and standard deviations for
the cyclic fatigue, torsional, and bending tests are
shown in Table I. The results demonstrated that
the Flat 25.04 gold instruments had signicantly
greater time and NCF compared to the Flat
25.04 blue instruments (P<0.05). The torsion
test showed that the Flat 25.04 gold instruments
exhibited lower maximum torque (N.cm) and
greater angular deection (°) compared to the
Flat 25.04 blue instruments (P<0.05). Finally,
the bending test demonstrated that the gold
instrument required less force compared to the
blue instrument (P>0.05).
Scanning Electron Microscopy (SEM)
The SEM analysis of the fractured surfaces
of all instruments subjected to cyclic fatigue
and torsional tests demonstrated typical
characteristics of cyclic fatigue and torsional
failure. After the cyclic fatigue test, typical
patterns of microcavities and topographical
features of ductile fracture were observed
(Figure 2). Regarding the torsional test, the
instruments exhibited concentric abrasion marks
indicative of stress and torsional failure. Fibrous
marks were observed at the center of rotation,
conrming torsional failure (Figure 3).
DSC analysis
The DSC graphs demonstrated different
phase transformation temperatures for the gold
and blue 25.04 instruments. The initial (Ai) and
nal (Af) austenite transformation temperatures
are presented in the heating curve (left to right).
The blue-treated instrument exhibited Ai and Af
Table I - Mean and standard deviation of cyclic fatigue, torsional fatigue, and flexural fatigue tests for Flat 25.04 gold and blue instruments
Cyclic Fatigue Torsional Fatigue Bending 60°
Time Cycles to fracture (NCF) Torque (N.cm) Angular deflection (°) Force (g.f)
Flat 25.04 gold 255.3 ± 30.73a2119 ± 210.1a0.81 ± 0.183a398.1 ± 30.2a139.6 ± 17.8a
Flat 25.04 blue 199.9 ± 18.28b1659 ± 151.7b1.2 ± 0.125b338.8 ± 34.9b178.1 ± 21.1b
Different lowercase letter in columns indicate significant difference among the instruments (P<0.05).
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Influence of Gold and Blue heat treatments on mechanical properties and phase transformation behavior of flat-designed rotary instruments
Vieira ART et al. Influence of Gold and Blue heat treatments on mechanical
properties and phase transformation behavior of flat-designed
rotary instruments
temperatures of 23.1 °C and 32.2 °C, respectively,
while the gold-treated instrument showed Ai and
Af temperatures of 22.4 °C and 42.8 °C, respectively
(Figure 4). Considering the temperature at which
the mechanical tests were conducted (36 °C), the
blue-treated instrument would undergo complete
austenitic transformation, while the gold-treated
instrument would exhibit a combination of
austenite with R-phase.
DISCUSSION
Comparing the mechanical properties
of NiTi rotary instruments available on the
market is crucial for understanding the initial
behavior of these instruments during root
canal preparation [2]. However, the various
design characteristics (taper, cross-section,
core diameter), surface treatments, and
thermal treatments of NiTi make this process
challenging, as they directly influence the
mechanical properties and must be considered
in studies [9,13].
Previous studies have evaluated the cyclic
fatigue and torsional resistance of rotary and
reciprocating instruments with identical designs
and different thermal treatments [18-22]. The
authors demonstrated that thermal treatments
have a significant impact on mechanical
properties, as they alter the amount of R-phase
and martensite in the NiTi alloy structure,
making it more flexible compared to alloys
Figure 2 - Representative Scanning Electron Microscopy (SEM) images of Flat instruments with gold and blue treatments after cyclic fatigue.
Images A and C show the gold and blue instruments with 35x magnification, respectively. Images B and D show representative images of the
fractured surfaces with 500x magnification for gold and blue, respectively. The red circle highlights the area selected for 500x magnification.
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Influence of Gold and Blue heat treatments on mechanical properties and phase transformation behavior of flat-designed rotary instruments
Vieira ART et al. Influence of Gold and Blue heat treatments on mechanical
properties and phase transformation behavior of flat-designed
rotary instruments
with predominant austenite phase [7,19].
Furthermore, this increased exibility tends to
provide more centered canal preparations in
canals with sharp curvatures [1,7,23].
There is no consensus in the literature
regarding which thermal treatment is
considered ideal, as this characteristic should
be evaluated according to the type of root canal
anatomy [23,24]. Furthermore, no studies
have assessed the mechanical properties of at-
designed instruments with different thermal
treatments. The results of this study demonstrated
that the Flat 25.04 gold instruments exhibited
a greater time and higher number of cycles
to fracture compared to the Flat 25.04 blue
instruments. Additionally, the gold treatment
provided lower maximum torque and greater
angular deection to fracture compared to the
blue treatment. Moreover, it required less force
for bending compared to the blue treatment.
Therefore, the initial hypothesis was rejected.
Considering that the instruments have
identical designs, the likely and sole explanation for
the differences observed in this study is the varying
percentage of R-phase and martensite between
the gold and blue treatments. Moreira et al. [21]
evaluated the mechanical properties of Prole
25.06 instruments made from conventional NiTi
alloy, with blue and gold thermal treatments.
The authors demonstrated that both gold and
blue thermal treatments provided greater cyclic
fatigue resistance compared to instruments made
from conventional NiTi. Additionally, the gold
treatment exhibited signicantly higher cyclic
fatigue resistance (both in terms of time and
number of cycles) and lower bending resistance
compared to the blue treatment. These ndings
support the results of our study.
Figure 3 - Representative Scanning Electron Microscopy (SEM) images of Flat instruments with gold and blue treatments after torsional fatigue.
Images A and C show the gold and blue instruments with 35x magnification, respectively. Images B and D show representative images of the
fractured surfaces with 500x magnification for gold and blue, respectively. The red circle highlights the area selected for 500x magnification.
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Vieira ART et al.
Influence of Gold and Blue heat treatments on mechanical properties and phase transformation behavior of flat-designed rotary instruments
Vieira ART et al. Influence of Gold and Blue heat treatments on mechanical
properties and phase transformation behavior of flat-designed
rotary instruments
Although no studies have assessed the
torsional resistance of instruments with identical
designs and blue and gold thermal treatments,
several previous studies have shown differences in
the presence of R-phase and martensite between
the two treatments [1,7,22]. Therefore, the
torsional results presented by the Flat 25.04 gold
instrument indicate greater exibility compared
to the blue, corroborating the results obtained in
the cyclic fatigue and bending tests of this study.
The SEM analysis showed the typical features
of cyclic and torsional fatigue for both thermal
treatments. After the cyclic fatigue test, the
instruments showed areas of crack initiation and
overload zones, with numerous dimples spread
across the fractured surface. After the torsional
test, the fragments showed concentric abrasion
marks and fibrous dimples at the center of
rotation, as previously reported [8,13].
Differential Scanning Calorimetry (DSC)
is a fundamental analysis for understanding
the transformation temperature of NiTi alloy
thermal treatments and has been previously
explored in various studies [1,7,23]. Knowledge
of the transformation temperature allows for
understanding whether the NiTi alloy will
exhibit an austenitic or martensitic behavior
during root canal preparation. Additionally, it
is a complementary analysis to the mechanical
test results. In this study, the DSC analysis
demonstrated that the final transformation
temperature (Af) for the gold treatment is higher
than that for the blue treatment, thus, the second
hypothesis of this study was rejected.
The different Af transformation temperatures
between the gold (42.8 °C) and blue (32.2 °C)
treatments significantly impacted the results
of this study, as all tests were conducted in
an environment simulating body temperature.
Therefore, the blue treatment exhibited complete
austenitic transformation at 36 °C, making it less
exible compared to the gold treatment. These
results complement and justify those found in
the mechanical tests. Furthermore, the ndings
of this study are consistent with the results of
Moreira et al. [21].
Laboratory mechanical tests of cyclic fatigue,
torsion, and bending are used to estimate how the
instruments would behave during the preparation
of curved and/or constricted canals. Additionally,
the bending test provides an estimate of which type
of instrument is likely to exert greater force against
the walls of the root canals and, consequently, a
higher chance of deviations [21,23]. However,
mechanical tests do not necessarily directly
translate into greater safety or efficacy during
root canal treatments, which requires additional
studies, such as evaluations in ex vivo models or
clinical studies to conrm our results.
CONCLUSION
Different thermal treatments signicantly
impact the resistance to cyclic fatigue, torsion,
and bending of the instruments, with the gold
treatment exhibiting greater exibility. The DSC
analysis demonstrated that the gold treatment
had a higher nal transformation temperature
(Af) compared to blue.
Acknowledgements
The authors would like to thank all
contributors to the article for their content
contributions, critical review of the manuscript,
and support during the development and writing
of this manuscript.
Figure 4 - Representative image of the Differential Scanning Calorimetry (DSC) graph showing the transformation temperatures of initial
austenite (Ai) and final austenite (Af). The lines represent the heating curves identifying Ai and Af (left to right).
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Vieira ART et al.
Influence of Gold and Blue heat treatments on mechanical properties and phase transformation behavior of flat-designed rotary instruments
Vieira ART et al. Influence of Gold and Blue heat treatments on mechanical
properties and phase transformation behavior of flat-designed
rotary instruments
Author’s Contributions
ARTV: Writing – Original Draft Preparation.
GFS: Writing – Review & Editing. PAAS:
Investigation. RRV: Investigation. MAHD: Writing
– Review & Editing. TOL: Writing – Original Draft
Preparation. MCGO: Writing – Original Draft
Preparation. MPA: Supervision.
Conict of Interest
No conicts of interest declared concerning
the publication of this article.
Funding
This research did not receive any specic
grant from funding agencies in the public,
commercial, or not-for-prot sectors.
Regulatory Statement
Ethics approval was not required.
REFERENCES
1. Shen Y, Zhou HM, Zheng YF, Peng B, Haapasalo M. Current
challenges and concepts of the thermomechanical treatment of
nickel-titanium instruments. J Endod. 2013;39(2):163-72. http://
doi.org/10.1016/j.joen.2012.11.005. PMid:23321225.
2. Kaval ME, Capar ID, Ertas H. Evaluation of the cyclic fatigue and
torsional resistance of novel nickel-titanium rotary files with
various alloy properties. J Endod. 2016;42(12):1840-3. http://
doi.org/10.1016/j.joen.2016.07.015. PMid:27776878.
3. Sattapan B, Nervo GJ, Palamara JE, Messer HH. Defects in rotary
nickel-titanium files after clinical use. J Endod. 2000;26(3):161-
5. http://doi.org/10.1097/00004770-200003000-00008.
PMid:11199711.
4. Pedullà E, Lo Savio F, Boninelli S, Plotino G, Grande NM, La
Rosa G,etal. Torsional and cyclic fatigue resistance of a new
nickel-titanium instrument manufactured by electrical discharge
machining. J Endod. 2016;42(1):156-9. http://doi.org/10.1016/j.
joen.2015.10.004. PMid:26586518.
5. Karataş E, Arslan H, Buker M, Seckin F, Capar ID. Effect of
movement kinematics on the cyclic fatigue resistance of nickel-
titanium instruments. Int Endod J. 2016;49(4):361-4. http://doi.
org/10.1111/iej.12453. PMid:25816834.
6. Özyürek T. Cyclic fatigue resistance of reciproc, waveone,
and waveone gold nickel-titanium instruments. J Endod.
2016;42(10):1536-9. http://doi.org/10.1016/j.joen.2016.06.019.
PMid:27520406.
7. Zupanc J, Vahdat-Pajouh N, Schafer E. New thermomechanically
treated NiTi alloys: a review. Int Endod J. 2018;51(10):1088-103.
http://doi.org/10.1111/iej.12924. PMid:29574784.
8. Alcalde MP, Duarte MAH, Bramante CM, Vasconselos BC,
Tanomaru-Filho M, Guerreiro-Tanomaru JM,etal. Cyclic fatigue
and torsional strength of three different thermally treated
reciprocating nickel-titanium instruments. Clin Oral Investig.
2018;22(4):1865-71. http://doi.org/10.1007/s00784-017-2295-
8. PMid:29224061.
9. Bürklein S, Zupanc L, Donnermeyer D, Tegtmeyer K, Schäfer E.
Effect of core mass and alloy on cyclic fatigue resistance of
different nickel-titanium endodontic instruments in matching
artificial canals. Materials. 2021;14(19):5734. http://doi.
org/10.3390/ma14195734. PMid:34640131.
10. Gambarini G, Miccoli G, Seracchiani M, Khrenova T, Donfrancesco
O, D’Angelo M, et al. Role of the flat-designed surface in
improving the cyclic fatigue resistance of endodontic NiTi
rotary instruments. Materials. 2019;12(16):2523. http://doi.
org/10.3390/ma12162523. PMid:31398814.
11. Silva EJNL, Alcalde MP, Martins JNR, Vieira VTL, Vivan RR,
Duarte MAH,etal. To flat or not to flat? Exploring the impact
of flat-side design on rotary instruments using a comprehensive
multimethod investigation. Int Endod J. 2023;56(10):1301-15.
http://doi.org/10.1111/iej.13960. PMid:37594701.
12. Jeong HY, Ha JH, Sigurdsson A, Peters OA, Kim HC, Kwak
SW. Effects of side flattening on torsional and cyclic fracture
resistance of Nickel-Titanium file. J Endod. 2024;50(7):1011-6.
http://doi.org/10.1016/j.joen.2024.04.008. PMid:38642733.
13. Alcalde M, Duarte MAH, Amoroso Silva PA, Souza Calefi PH,
Silva E, Duque J,et al. Mechanical properties of ProTaper
Gold, EdgeTaper Platinum, Flex Gold and Pro-T rotary systems.
Eur Endod J. 2020;5(3):205-11. http://doi.org/10.14744/
eej.2020.48658. PMid:33353917.
14. Klymus ME, Alcalde MP, Vivan RR, Só MVR, de Vasconselos
BC, Duarte MAH. Effect of temperature on the cyclic fatigue
resistance of thermally treated reciprocating instruments. Clin
Oral Investig. 2019;23(7):3047-52. http://doi.org/10.1007/
s00784-018-2718-1. PMid:30397733.
15. International Organization for Standardization – ISO. ISO 3630-1:
dentistry: endodontic instruments. Geneva: ISO; 1992.
16. Osaki RB, Bramante CM, Vivan RR, Alcalde MP, Calefi PHS, Duarte
MAH. Influence of temperature on the torsional properties of two
thermally treated NiTi rotary instruments. Braz Dent J. 2023;34(1):12-
8. http://doi.org/10.1590/0103-6440202305094. PMid:36888838.
17. American Society for Testing and Materials – ASTM.
ASTM F2004-17: standard test method for transformation
temperatureof nickel- titanium alloys by thermal analysis. West
Conshohocken: ASTM; 2004. p. 1-5.
18. Topçuoğlu HS, Topçuoğlu G. Cyclic fatigue resistance of
reciproc blue and reciproc files in an S-shaped canal. J Endod.
2017;43(10):1679-82. http://doi.org/10.1016/j.joen.2017.04.009.
PMid:28733080.
19. De-Deus G, Silva EJ, Vieira VT, Belladonna FG, Elias CN,
Plotino G, etal. Blue thermomechanical treatment optimizes
fatigue resistance and flexibility of the reciproc files. J Endod.
2017;43(3):462-6. http://doi.org/10.1016/j.joen.2016.10.039.
PMid:28131415.
20. Özyürek T, Yılmaz K, Uslu G. The effects of autoclave sterilization
on the cyclic fatigue resistance of ProTaper Universal, ProTaper
Next, and ProTaper Gold nickel-titanium instruments. Restor
Dent Endod. 2017;42(4):301-8. http://doi.org/10.5395/
rde.2017.42.4.301. PMid:29142878.
21. Moreira EJL, Silva EJNL, Belladonna FG, Maciel AC, Vieira VTL,
De-Deus G. Mechanical performance of original; yellowish
and blueish ProFile instruments: isolating heat-treatment
as a variable. Braz Dent J. 2022;33(4):47-53. http://doi.
org/10.1590/0103-6440202204978. PMid:36043568.
22. Hiran-us S, Morakul S. Effect of temperatures on cyclic
fatigue resistance of 3 different Ni-Ti alloy files. Int Dent J.
2023;73(6):904-9. http://doi.org/10.1016/j.identj.2023.06.008.
PMid:37423864.
23. Martins JNR, Silva EJNL, Marques D, Arantes-Oliveira S,
Ginjeira A, Caramês J,etal. Multimethod assessment of design,
metallurgical, and mechanical characteristics of original and
Counterfeit ProGlider instruments. Materials. 2022;15(11):3971.
http://doi.org/10.3390/ma15113971. PMid:35683270.
24. Zhang EW, Cheung GS, Zheng YF. Influence of cross-sectional
design and dimension on mechanical behavior of nickel-
titanium instruments under torsion and bending: a numerical
analysis. J Endod. 2010;36(8):1394-8. http://doi.org/10.1016/j.
joen.2010.04.017. PMid:20647104.
9
Braz Dent Sci 2025 Apr/Jun;28 (2): e4638
Vieira ART et al.
Influence of Gold and Blue heat treatments on mechanical properties and phase transformation behavior of flat-designed rotary instruments
Vieira ART et al. Influence of Gold and Blue heat treatments on mechanical
properties and phase transformation behavior of flat-designed
rotary instruments
Date submitted: 2025 Jan 05
Accept submission: 2025 May 08
Anne Rafaella Tenório Vieira
(Corresponding address)
Universidade de São Paulo, Faculdade de Odontologia de Bauru, Departamento de
Dentística, Endodontia e Materiais Odontológicos, Bauru, SP, Brazil.
Email: annerft@gmail.com
