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Article

Mechanical Properties and Torque/Force Generation of XP-Endo Shaper, Trunatomy, Spring Endo File, and Spring Endo Heated Finish File, Part 1

by
Soram Oh
1,†,
Bong-Ki Jeon
2,† and
Seok Woo Chang
1,*
1
Department of Conservative Dentistry, Kyung Hee University College of Dentistry, Kyung Hee University Medical Center, Seoul 02447, Korea
2
Ilsanstar 28 Dental Clinic, Goyang 10401, Korea
*
Author to whom correspondence should be addressed.
†
These authors contributed equally to this work.
Appl. Sci. 2022, 12(20), 10393; https://doi.org/10.3390/app122010393
Submission received: 20 September 2022 / Revised: 7 October 2022 / Accepted: 12 October 2022 / Published: 15 October 2022
(This article belongs to the Section Applied Dentistry and Oral Sciences)
Browse Figures
Review Reports Versions Notes

Abstract

:
We evaluated the mechanical properties and torque/force generated during canal shaping by four NiTi files with innovative designs. Each of the 52 TruNatomy Prime, XP-endo Shaper, Spring Endo files with unheated finish (Spring Endo), and Spring Endo files with heated finish (Spring H) were subjected to bending, buckling, cyclic fatigue, and torsional resistance tests (n = 10 per NiTi file type). Canal shaping was simulated with J-shaped resin blocks (n = 10). Phase transformation behavior was investigated using differential scanning calorimetry (n = 2). Statistical analysis was performed by one-way ANOVA and the Games-Howell test. Spring Endo and Spring H files showed higher bending and buckling resistances, ultimate torsional strength, and elastic modulus than TruNatomy and XP-endo Shaper (p < 0.05). XP-endo Shaper demonstrated the highest cyclic fatigue resistance and angle of rotation to fracture (p < 0.05). The elastic modulus increased in the order of XP-endo Shaper, TruNatomy Prime, Spring H, and Spring Endo. During simulated canal shaping, XP-endo Shaper generated greater clockwise torque and less screw-in force compared to Spring Endo files, with superior cutting ability. TruNatomy Prime generated the least clockwise torque and screw-in force. At room temperature, TruNatomy and XP-endo Shaper files consisted of mixed phases of austenite, martensite, and R-phase; Spring H files consisted of martensite; and Spring Endo files consisted of austenite.

1. Introduction

NiTi rotary instruments have enabled efficient and faster canal shaping with less transportation than hand instruments [1]. However, the separation of NiTi rotary files remains a concern for clinicians. Manufacturers have developed new NiTi files with heat treatment and variations in design to reduce the risk of file fracture [2,3].
The controlled memory (CM) wire, introduced in 2010, was the first thermomechanically treated NiTi endodontic alloy with reduced super-elasticity [4]. NiTi files with CM wire contain martensite, whereas conventional NiTi files contain austenite at body temperature [5]. CM wire instruments have a lower tendency to straighten curved root canals during preparation, thereby resulting in less transportation [6]. In 2015, another proprietary thermomechanically treated NiTi alloy, martensite–austenite–electropolish-file X (Max-Wire), was introduced [7]. Max-Wire NiTi files exist in a martensitic state at room temperature; at body temperature, phase transformation to an austenitic state occurs, and these wires acquire a memorized curved shape [7].
Recently, many developments and advances have been made, not only in terms of heat treatment but also geometric designs. NiTi files with a small taper and slim wire allowed sufficient enlargement of the apical portion of the canal without undue file stress or compression of debris [8,9]. The XP-endo Shaper (FKG Dentaire, La Chaux-de-Fonds, Switzerland) and TruNatomy (Dentsply Sirona, Maillefer, Ballaigues, Switzerland) systems were recently introduced as a new generation of NiTi file systems designed to respect the original canal anatomy and preserve the peri-cervical dentin [9,10]. These files are shape-conforming and can easily take the original shape of a canal [11]. The XP-endo Shaper is a single-file system made of Max-Wire with a 1% taper [7]. Due to the geometric design, the XP-endo Shaper offers minimal stress to the dentine wall, excellent debris removal, remarkable flexibility, and cyclic fatigue resistance [8,12,13]. The TruNatomy file system is produced via special heat treatment using a 0.8 mm wire, which has an off-centered parallelogram cross-section [9,14]. TruNatomy has been reported to have enhanced cyclic fatigue resistance and cause less extrusion of debris [9,14].
Another novel file is the Spring Endo file (Denflex, Seoul, Republic of Korea), which has an elastic spring on the shaft of the NiTi rotary instrument [15]. According to its manufacturer, the elastic spring on the shaft of the NiTi instrument can make its insertion in the root canals of posterior teeth easy and reduce the risk of fracture [16]. The manufacturer also suggests that the spring structure buffers the overload applied to the instrument, resulting in an improved resistance to cyclic fatigue. Previous studies showed that the spring part of the shaft of NiTi rotary instruments improved the torsional resistance, bending flexibility, and cyclic fatigue resistance [3,15]. Two types of Spring Endo Files are produced: unheated and heated.
To the best of our knowledge, few studies have compared the mechanical properties of the newly introduced NiTi rotary systems, which have been fabricated using novel designs and heat treatments. Therefore, the purpose of this study was to evaluate the mechanical properties and phase transformation behavior of the following systems: TruNatomy Prime, XP-endo Shaper, Spring Endo file with an unheated finish, and Spring Endo file with a heated finish. Additionally, their cutting ability and the maximum torque and screw-in force generated during canal shaping were compared by simulating canal shaping in resin blocks.

2. Materials and Methods

Each of the 52 TruNatomy Prime instruments (tip size #26, variable 4% taper), XP-endo Shaper files (tip size #30, 1% taper), Spring Endo files with an unheated finish #25 (Spring Endo), and Spring Endo files with a heated finish #25 (Spring H) were studied (Table 1). Unlike Spring Endo, TruNatomy Prime, XP-endo Shaper, and Spring H files are manufactured using heat treatment. The instrument lengths of TruNatomy Prime and XP-endo Shaper files are 21 mm, and Spring Endo and Spring H files have a length of 23 mm and have elastic spring shafts.

2.1. Mechanical Tests

Ten specimens of each NiTi file type were subjected to the following four mechanical tests: bending, buckling, cyclic fatigue, and torsional resistance. All mechanical tests and canal shaping were performed using a universal testing machine (UTM; Universal Mechanics Analyzer, IB Systems, Seoul, Republic of Korea).
The cantilever bending test was conducted based on ISO 3630-1:2019 [17,18], using the UTM to evaluate the bending resistance of the instruments. An apical 3 mm length from the tip of the NiTi file was tightly clamped into a chuck connected to the load cell of the UTM. The file tip was bent clockwise at 2 rpm. The bending resistance (Ncm) was recorded as the torque value when the instrument was rotated at 45°.
The buckling resistance test was performed using a lithium disilicate block (IPS e.max CAD; Ivoclar Vivadent, Schaan, Liechtenstein) having a small dimple. The shaft of the NiTi file handle was fixed to the UTM, and the instrument tip was in contact with a cube block. The small dimple helped restrain the file tip on the block. The file was moved downward at a crosshead speed of 1.2 mm/s. The buckling resistance (gf) was recorded as the maximum load during a 1-mm axial movement of the file.
The cyclic fatigue resistance was evaluated using a customized jig with a curved canal made of stainless steel, which was connected to the load cell of the UTM. The artificial canal had a 1.5-mm diameter, and the curvature had a radius of 2 mm and an angle of 45°, according to Pruett’s method [19]. A file was inserted into the artificial curved canal of the jig to a depth of 19 mm. The instruments were operated using an X-Smart motor (Dentsply Sirona), and the handpiece of the motor was firmly fixed to the UTM. The instrument was rotated according to the manufacturers’ recommended rotational speed: 500, 800, 200, and 200 rpm for TruNatomy Prime, XP-endo Shaper, Spring Endo, and Spring H instruments, respectively. The time at which a file separated was recorded. The number of cycles to fracture (NCF) was calculated by multiplying the speed of each instrument in rpm with the fracture time.
The torsional resistance test was performed based on ISO 3630-1:2019 [17,18]. An apical 3 mm length from the tip of the NiTi file was tightly clamped into a chuck connected to the load cell of the UTM. The shaft of the instrument was fastened to an opposing chuck, which was rotated clockwise at 2 rpm until the file fractured. The ultimate torsional strength (UTS) and angle of rotation to fracture (ARF) were recorded as the clockwise torque and angle of rotation, respectively, when the instrument fractured. The clockwise torque and angle of rotation recorded in real time were plotted. In the graph, the slope of the elastic deformation section which occurred at the beginning of the torsional resistance test was determined as the elastic modulus (EM).
After the cyclic fatigue and torsional resistance tests, the fractured instruments were cleaned with 70% alcohol and subjected to fractographic analysis using field-emission scanning electron microscopy (FE-SEM) (JSM-7800F Prime; JEOL Ltd., Akishima, Tokyo, Japan). Different magnifications (×180, ×200, ×250, and ×1000) were used for FE-SEM analysis.
The data of the mechanical test results (bending and buckling resistances, NCF, UTS, ARF, and EM) were normally distributed according to the Shapiro-Wilk test, while the homogeneity of the variances was not satisfied by Levene’s test. One-way ANOVA was performed to compare the mechanical test results between different file types; intergroup comparison was performed with the Games-Howell test. Pearson’s correlation analysis was conducted among the six variables of the mechanical test results, i.e., bending and buckling resistances, NCF, UTS, ARF, and EM. Statistical analysis was performed using SPSS 25 (IBM, Armonk, NY, USA) at a 95% significance level.

2.2. Simulated Canal Shaping

Ten new instruments were used for shaping of J-shaped canals prepared in resin blocks. The canal had a curvature with a 5-mm radius, 45° angle, and a length of 15 mm. The cross-section was elliptical, with a long diameter of 0.6 mm and a short diameter of 0.2 mm at a point 5 mm from the apex, and its size gradually increased toward the orifice. The NiTi file was instrumented for three cycles of pecking motions of 6 mm depth until the file touched the apex. The vertical movement was performed at 1.17 mm/s. During pecking motions, the NiTi files were rotated according to the manufacturer’s instructions. TruNatomy Prime and XP-endo Shaper files were rotated at 500 rpm and 800 rpm, respectively. Spring Endo and Spring H files were rotated at 200 rpm. The torque and load generated during canal shaping were recorded. The screw-in force was determined by the negative domain of the load. The maximum clockwise torque and screw-in force were recorded for statistical analysis. After the canal-shaping debris was removed by blowing the orifice of canal with an air syringe and the resin blocks were dried, their mass was measured. The normality of the data was verified by the Shapiro-Wilk test, while the homogeneity of the variances was not satisfactory. The maximum clockwise torque, maximum screw-in force, and mass of resin blocks were compared between NiTi files using one-way ANOVA; intergroup comparison was performed with the Games-Howell test.

2.3. Differential Scanning Calorimetry (DSC)

The DSC of the apical 3 mm of unused instruments was performed (two samples per each of the four-file type) with DSC250 (TA Instruments, New Castle, DE, USA). Each specimen was heated from 25 °C to 90 °C, cooled to −90 °C, and then heated again to 90 °C at 10 °C/min. Based on the DSC curve, the starting and finishing temperatures of martensitic transformation (Ms and Mf, respectively), austenitic transformation (As and Af, respectively), and R-phase transformation (Rs and Rf, respectively) and the peak temperatures for phase transformation were determined.

3. Results

3.1. Mechanical Test Results

The means and standard deviations of the mechanical test results are presented in Table 2 and Figure 1. Spring H had the greatest bending resistance, followed by Spring Endo (p < 0.05). The buckling resistance of Spring Endo and Spring H files was the highest (p < 0.05). XP-endo Shaper showed the highest NCF, followed by TruNatomy Prime (p < 0.05). The UTS of the Spring Endo and Spring H files was more than that of the TruNatomy Prime and XP-endo Shaper files. The ARF of the XP-endo Shaper was the highest, followed by TruNatomy Prime. Representative graphs of torsional strength and angle of rotation during the torsional resistance test are shown in Figure 2. EM was obtained from the slope of the initial linear portion of the graph. Spring Endo had the highest EM, followed by Spring H. XP-endo Shaper demonstrated the lowest bending and buckling resistances, UTS, and EM, along with the highest NCF and ARF.
The FE-SEM images of fractured instruments from the cyclic fatigue resistance test presented typical patterns of fatigue fracture, such as multiple fatigue striations located near the cracks (Figure 3). The FE-SEM images of the fractured instruments from the torsional resistance test showed a torn-off appearance at the center of the fractured surfaces (Figure 4). The cyclic fatigue and torsional resistance tests revealed brittle and ductile fracture patterns on lateral view, respectively (Figure 3 and Figure 4).

Pearson Correlation Analysis

The results of the Pearson correlation analysis are shown in Table 3. The bending and buckling resistances, UTS, and EM had strong positive correlations with each other (p < 0.001, Pearson’s r = 0.848–0.932). A strong positive correlation was observed between the NCF and ARF (p < 0.001, Pearson’s r = 0.961). A strong negative correlation was identified between the buckling resistance and NCF (p < 0.001, Pearson’s r = −0.723) and between the buckling resistance and ARF (p < 0.001, Pearson’s r = −0.774). A moderate negative correlation was observed between ARF and UTS (p < 0.001, Pearson’s r = −0.656).

3.2. Simulated Canal Shaping Results

XP-endo Shaper and Spring H files generated a higher maximum clockwise torque than other files (Table 4). Spring Endo and Spring H files demonstrated higher maximum screw-in forces than the other files (Table 4). TruNatomy Prime files generated the least clockwise torque and screw-in force. The mean mass of resin blocks after shaping with the XP-endo Shaper files was less compared to other files, while the other files had no significant difference from each other (Table 4). Namely, XP-endo Shaper files removed more resin than the other files during shaping.

3.3. DSC

The DSC curves for each NiTi rotary instrument are presented in Figure 5. Table 5 summarizes the phase transformation temperatures and associated energies. The DSC curves of TruNatomy Prime and XP-endo Shaper files showed a peak on the heating curve and two separate peaks on the cooling curve (Figure 5A,B). The DSC curves of Spring Endo and Spring H files exhibited single peaks on the heating and cooling curves, respectively (Figure 5C,D). While the peaks for Spring Endo files were present at below room temperature, those for Spring H were observed above room temperature (Figure 5C,D).

4. Discussion

In the present study, there was a significant difference in the mechanical properties of the NiTi rotary instruments according to their design. The XP-endo Shaper showed the lowest bending and buckling resistances, UTS, and EM. Spring Endo and Spring H files exhibited higher bending and buckling resistances, UTS, and EM than TruNatomy Prime and XP-endo Shaper files. Although the tip sizes of TruNatomy Prime (#26) and XP-endo Shaper files are larger than those of Spring Endo (#25) and Spring H (#25) files, the overall mass of the instrument was the lowest for XP-endo Shaper files, followed by TruNatomy Prime files, due to a smaller taper. SEM images of the fractured instruments from the torsional and cyclic fatigue resistance tests showed cross-sectional images at 3 and 5 mm from the apex, respectively (Figure 3 and Figure 4). The cross-sectional areas of Spring Endo and Spring H files were larger than those of TruNatomy Prime and XP-endo Shaper files. Among the mechanical test results, bending and buckling resistances, UTS, and EM had strong positive correlations with each other (Table 3) because they are all strongly affected by the cross-sectional area [19]. Our results are in agreement with those of previous studies, according to which NiTi files with larger cross-sectional areas had higher bending and buckling resistances and UTS [19,20,21].
The XP-endo Shaper presented the highest cyclic fatigue resistance, followed by TruNatomy Prime (Table 2, Figure 1). In this study, the cyclic fatigue resistance test of NiTi files were performed at 22 °C. According to DSC curves, the XP-endo Shaper and TruNatomy Prime files consisted of austenite, martensite, and R-phase at 22 °C (Figure 5A,B), whereas Spring Endo consisted of austenite and Spring H was composed of martensite at 22 °C (Figure 5C,D). The R-phase is a transitional phase between martensite and austenite [7]. The EM of R-phase is lower than those of martensite or austenite phases, and the transformation strain of the R-phase is less than 10% of martensitic transformation [22]. Therefore, the presence of the R-phase can explain the higher NCF of TruNatomy Prime and XP-endo Shaper files. The NCF of XP-endo Shaper was significantly higher than that of the other instruments. It was presumed that geometric designs, such as taper and cross-sectional configurations, as well as the Max-Wire property, influenced the NCF. XP-endo Shaper had the smallest cross-sectional area at D3. Our results are consistent with those of previous studies showing that NiTi files with smaller cross-sectional areas presented superior resistance to cyclic fatigue [23,24]. Further, XP-endo Shaper has a unique design, with a curved shape, booster tip, and six cutting edges [11]. The contact time between the surface of the instrument and the artificial root canal during rotation was less with XP-endo Shaper than with other instruments. This may have lowered the stress developing due to repetitive bending during the cyclic fatigue resistance test. TruNatomy Prime had the second highest NCF among all the instruments tested. This could be attributed to several factors, including thermomechanical processing, special heat treatment, off-centered parallelogram cross-sectional design, and slim NiTi wire (0.8 mm) [11,14].
Spring Endo and Spring H files have identical designs; however, unlike Spring Endo, Spring H is heat-treated. The bending resistance and ARF of Spring H were higher than those of Spring Endo, whereas the EM was higher for Spring Endo (Table 2, Figure 1). Spring H consisted of martensite at body temperature (Figure 5D), although the type of heat treatment has not been revealed. The increased ARF and decreased EM after heat treatment are consistent with the findings of previous studies [25,26].
Buckling is a sudden sideways deflection that occurs during vertical compressive loading [27]. Lopes et al. measured the buckling resistance as the force generated by a 1-mm lateral elastic displacement of the NiTi file [27]. In the present study, we measured the buckling resistance as the maximum load during a 1-mm axial movement of the file because lateral displacement could not be measured. Sufficient buckling resistance can enable exploration of canal orifices and negotiation of narrow canals [28]. Instruments with low buckling resistances, such as the XP-endo Shaper, require the prior use of glide path instruments. Spring Endo and Spring H files demonstrated a higher buckling resistance, suggesting that instruments with larger diameters have a higher buckling resistance, which agrees with the findings of a previous study [29].
ARF represents the ability to sustain deformation under a twisting force before fracture and is related to ductility. In the present study, ARF and NCF had a strong positive correlation (Table 3) because both were affected by the flexibility of the NiTi file. In the present study, NiTi files with a small cross-sectional diameter around D3 (XP-endo Shaper, TruNatomy Prime) demonstrated a higher ARF. The bending resistances of the XP-endo Shaper and TruNatomy Prime files were the lowest, indicating that they were the most flexible. In this study, the Spring Endo was not compared to spring-free controls with the same cross-sectional shape, tip size, and taper. According to a finite element study by Kim et al., a lower torque is required to axially rotate NiTi files with spring shafts compared with NiTi file with identical design without spring [15].
According to the FE-SEM results, only TruNatomy Prime had a parallelogram cross-section, whereas the other instruments had a triangular cross-section (Figure 4). In this study, there was no significant difference in the UTS of TruNatomy Prime with a parallelogram cross-section and XP-endo Shaper with a triangular cross-section. There has been no study to compare torsional fracture resistances of TruNatomy Prime and XP-endo Shaper. XP-endo Shaper demonstrated lower torsional resistance compared to TRUShape #30/06, ProFile Vortex #30/04, and FlexMaster #30/04 with modified triangular cross-sectional designs [8,30], which were conducted at 37 °C. Conversely, the torsional resistance test was performed at 22 °C in this study. Experimental temperature and alloy characteristics seem to collectively affect the torsional resistance.
During canal shaping, XP-endo Shaper removed more of the artificial canal wall from the resin block (Table 4). These files can expand and reach areas that conventional files cannot access [31]; therefore, the cutting efficiency of XP-endo Shaper files was superior. The maximum clockwise torque generated by XP-endo Shaper files was greater than that generated by TruNatomy Prime and Spring Endo files, and was comparable to that of Spring H files. A previous study reported that NiTi files with a larger taper caused a higher torque and screw-in force [32]. Although XP-Shaper files have a minimal taper, abundant cutting of the resin canal wall during instrumentation generated greater clockwise torque.
Spring Endo and Spring H files had the highest maximum screw-in forces, followed by XP-endo Shaper and TruNatomy Prime files, respectively. Kyaw et al. found that the maximum upward force (screw-in force) and clockwise torque were significantly smaller in the 500 rpm group than in the 300 rpm groups [33]. In Kyaw et al.’s study, the handpiece was moved up and down for 2 and 1 s at 0.83 mm/s, whereas, in our study, 6 mm up-and-down motions were performed at 1.17 mm/s. The rotating speeds were 800, 500, 200, and 200 rpm for XP-endo Shaper, TruNatomy Prime, Spring Endo, and Spring H files, respectively. The screw-in forces generated by NiTi files operating at higher speeds (TruNatomy Prime and XP-endo Shaper files) were lower than those of other NiTi files, which is consistent with the findings of Kyaw et al.
TruNatomy Prime generated the least clockwise torque and screw-in force. The cutting ability of TruNatomy Prime was similar to those of Spring Endo and Spring H files (Table 4). A parallelogram cross-section with an off-centered design, as well as a regressive taper and small radius, contributed to the reduced torque and stress.
The limitation of this study was that the mechanical tests and simulated canal shaping were performed at 22 °C. The main phase of XP-endo Shaper changes from martensite to austenite on heating from room temperature to body temperature. XP-endo Shaper, which is composed of Max-Wire NiTi alloy, display optimal properties only at higher temperatures (37 °C) [34]. Therefore, experiments at body temperature are necessary to observe the mechanical properties of the XP-endo Shaper files used in clinical practice.

5. Conclusions

In conclusion, the mechanical properties of NiTi rotary instruments were significantly affected by the instrument design. XP-endo Shaper files demonstrated superior flexibility and cyclic fatigue resistance with higher cutting ability and less screw-in force, while their buckling resistance and UTS were the lowest.

Author Contributions

Conceptualization, B.-K.J. and S.W.C.; methodology, S.O. and B.-K.J.; software, S.O.; validation, B.-K.J. and S.W.C.; formal analysis, S.O. and B.-K.J.; investigation, S.O. and B.-K.J.; resources, S.W.C.; data curation, S.O. and B.-K.J.; writing—original draft preparation, S.O. and B.-K.J.; writing—review and editing, S.W.C.; supervision, S.W.C.; project administration, S.O. and B.-K.J.; funding acquisition, S.O. All authors have read and agreed to the published version of the manuscript.

Funding

This study was funded by the National Research Foundation of the Republic of Korea (grant number, NRF-2021R1G1A1006751) and by Kyung Hee University in 2021 (KHU-20210146).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The data presented in this study are available on request from the corresponding author.

Conflicts of Interest

The authors declare no conflict of interest.

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Applsci 12 10393 g001 550
Figure 1. Mechanical test results of TruNatomy Prime, XP-endo Shaper, Spring Endo, and Spring H files. Different lowercase letter indicates statistically significant differences between files. Bending resistance (A), buckling resistance (B), NCF from cyclic fatigue resistance test (C), UTS (D), ARF (E) and EM (F) from torsional resistance test.
Figure 1. Mechanical test results of TruNatomy Prime, XP-endo Shaper, Spring Endo, and Spring H files. Different lowercase letter indicates statistically significant differences between files. Bending resistance (A), buckling resistance (B), NCF from cyclic fatigue resistance test (C), UTS (D), ARF (E) and EM (F) from torsional resistance test.
Applsci 12 10393 g001
Applsci 12 10393 g002 550
Figure 2. Representative torque–angle of rotation curves of the tested files based on the torsional resistance test results.
Figure 2. Representative torque–angle of rotation curves of the tested files based on the torsional resistance test results.
Applsci 12 10393 g002
Applsci 12 10393 g003 550
Figure 3. Scanning electron microscopic photographs of TruNatomy Prime (A1–A4), XP-endo Shaper (B1–B4), Spring Endo (C1–C4), and Spring H (D1–D4) files after the cyclic fatigue resistance test. (A1,B1,C1,D1) (×180) fractured surface; (A2,B2,C2,D2) (×1000) magnified view of sections indicated by arrows in A1, B1, C1, and D1, respectively; (A3,B3,C3,D3) (×200) lateral surface; (A4,B4,C4,D4) (×1000) magnified view of sections indicated by arrows in A3, B3, C3, and D3, respectively. The asterisk indicates fatigue striation.
Figure 3. Scanning electron microscopic photographs of TruNatomy Prime (A1–A4), XP-endo Shaper (B1–B4), Spring Endo (C1–C4), and Spring H (D1–D4) files after the cyclic fatigue resistance test. (A1,B1,C1,D1) (×180) fractured surface; (A2,B2,C2,D2) (×1000) magnified view of sections indicated by arrows in A1, B1, C1, and D1, respectively; (A3,B3,C3,D3) (×200) lateral surface; (A4,B4,C4,D4) (×1000) magnified view of sections indicated by arrows in A3, B3, C3, and D3, respectively. The asterisk indicates fatigue striation.
Applsci 12 10393 g003
Applsci 12 10393 g004 550
Figure 4. Scanning electron microscopic photographs of TruNatomy Prime (A1–A4), XP-endo Shaper (B1–B4), Spring Endo (C1–C4), and Spring H (D1–D4) files after the torsional resistance test. (A1,B1,C1,D1) (×250) fractured surface; (A2,B2,C2,D2) (×1000) magnified view of sections indicated by arrows in A1, B1, C1, and D1, respectively; (A3,B3,C3,D3) (×250) lateral surface; (A4,B4,C4,D4) (×1000) magnified view of sections indicated by arrows in A3, B3, C3, and D3, respectively.
Figure 4. Scanning electron microscopic photographs of TruNatomy Prime (A1–A4), XP-endo Shaper (B1–B4), Spring Endo (C1–C4), and Spring H (D1–D4) files after the torsional resistance test. (A1,B1,C1,D1) (×250) fractured surface; (A2,B2,C2,D2) (×1000) magnified view of sections indicated by arrows in A1, B1, C1, and D1, respectively; (A3,B3,C3,D3) (×250) lateral surface; (A4,B4,C4,D4) (×1000) magnified view of sections indicated by arrows in A3, B3, C3, and D3, respectively.
Applsci 12 10393 g004
Applsci 12 10393 g005a 550Applsci 12 10393 g005b 550
Figure 5. Differential scanning calorimetry curves for TruNatomy Prime (A), XP-endo Shaper (B), Spring Endo (C), and Spring H files (D). The upper and lower curves represent the cooling and heating curves, respectively.
Figure 5. Differential scanning calorimetry curves for TruNatomy Prime (A), XP-endo Shaper (B), Spring Endo (C), and Spring H files (D). The upper and lower curves represent the cooling and heating curves, respectively.
Applsci 12 10393 g005aApplsci 12 10393 g005b
Table
Table 1. Specifications of NiTi rotary instruments used in this study.
Table 1. Specifications of NiTi rotary instruments used in this study.
ProductSizeTaperLengthAlloy TypeManufacturer
TruNatomy Prime#264%, variable21 mmUnknown heat treatmentDenstply Sirona, Ballaigues, Switzerland
XP-endo Shaper#301%21 mmMax-WireFKG Dentaire, La Chaux-de-Fonds, Switzerland
Spring Endo file unheated finish (Spring Endo)#25Variable23 mmConventionalDenflex, Seoul, Republic of Korea
Spring Endo file heated finish (Spring H)#25Variable23 mmGold wireDenflex, Seoul, Republic of Korea
Table
Table 2. Mechanical test results (mean ± standard deviation).
Table 2. Mechanical test results (mean ± standard deviation).
TruNatomy PrimeXP-Endo ShaperSpring Endo Spring H
Bending resistance (Ncm)0.125 ± 0.026 a0.106 ± 0.016 a0.544 ± 0.063 b0.643 ± 0.074 c
Buckling resistance (gf)226.34 ± 23.69 b103.99 ± 17.64 a599.28 ± 86.16 c614.35 ± 97.51 c
NCF712.81 ± 54.49 b5344.46 ± 665.86 c376.04 ± 60.11 a433.20 ± 52.34 a
UTS (Ncm)0.540 ± 0.090 a0.471 ± 0.037 a1.019 ± 0.135 b1.217 ± 0.192 b
ARF (degrees)654.71 ± 83.14 c1834.09 ± 176.82 d417.41 ± 42.94 a515.33 ± 62.85 b
EM (Ncm/degrees)0.00149 ± 0.00022 b0.00056 ± 0.00006 a0.00961 ± 0.00089 d0.00597 ± 0.00048 c
Different superscript letters in the same row indicate significant differences between NiTi files (p < 0.05). NCF, number of cycles to fracture; UTS, ultimate torsional strength; ARF, angle of rotation to fracture; EM, elastic modulus.
Table
Table 3. Pearson correlation analysis.
Table 3. Pearson correlation analysis.
Pearson Correlation Analysis
Coefficientp-Value
Bending resistanceBuckling resistance0.930 *<0.001
NCF–0.621 *<0.001
UTS0.932<0.001
ARF–0.664 *<0.001
EM0.848 *<0.001
Buckling resistanceNCF–0.723 *<0.001
UTS0.907<0.001
ARF–0.774 *0.001
EM0.897 *<0.001
NCFUTS–0.616 *<0.001
ARF0.961<0.001
EM–0.642 *<0.001
ARFUTS–0.656 *<0.001
The asterisk means significant correlation between two variables (p < 0.05).
Table
Table 4. Maximum clockwise torque and screw-in force generated during simulated canal shaping and mass of resin blocks after shaping (mean ± standard deviation).
Table 4. Maximum clockwise torque and screw-in force generated during simulated canal shaping and mass of resin blocks after shaping (mean ± standard deviation).
TruNatomy PrimeXP-Endo ShaperSpring Endo Spring H
Maximum clockwise torque (Ncm)0.171 ± 0.044 a1.543 ± 0.129 c 0.978 ± 0.295 b 1.773 ± 0.728 c
Maximum screw-in force (gf)66.42 ± 30.10 a157.30 ± 12.90 b 499.65 ± 185.48 c 661.32 ± 199.82 c
Mass of resin blocks after shaping (gm)3.4188 ± 0.0050 b 3.4118 ± 0.0052 a 3.4201 ± 0.0036 b 3.4202 ± 0.0052 b
Different superscript letters in the same row indicate significant differences between files (p < 0.05).
Table
Table 5. Transformation temperatures and associated energy from the differential scanning calorimetry curves.
Table 5. Transformation temperatures and associated energy from the differential scanning calorimetry curves.
CoolingHeating
Rs (°C)Rf (°C)ΔH (J/g)Ms (°C)Mf (°C)ΔH (J/g)As (°C)Af (°C)ΔH (J/g)
TruNatomy Prime25.5217.863.83–37.84–59.6213.6416.7330.7717.19
XP-endo Shaper29.5121.534.28–38.76–77.7010.3230.0238.4615.98
Spring Endo 17.61–5.171.580.7129.332.95
Spring H 43.1528.133.0534.6152.133.51
Rs and Rf, starting and finishing temperatures, respectively, of R-phase transformation; Ms and Mf, starting and finishing temperatures, respectively, of martensitic transformation; As and Af, starting and finishing temperatures, respectively, of austenitic transformation.
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Oh, S.; Jeon, B.-K.; Chang, S.W. Mechanical Properties and Torque/Force Generation of XP-Endo Shaper, Trunatomy, Spring Endo File, and Spring Endo Heated Finish File, Part 1. Appl. Sci. 2022, 12, 10393. https://doi.org/10.3390/app122010393

AMA Style

Oh S, Jeon B-K, Chang SW. Mechanical Properties and Torque/Force Generation of XP-Endo Shaper, Trunatomy, Spring Endo File, and Spring Endo Heated Finish File, Part 1. Applied Sciences. 2022; 12(20):10393. https://doi.org/10.3390/app122010393

Chicago/Turabian Style

Oh, Soram, Bong-Ki Jeon, and Seok Woo Chang. 2022. "Mechanical Properties and Torque/Force Generation of XP-Endo Shaper, Trunatomy, Spring Endo File, and Spring Endo Heated Finish File, Part 1" Applied Sciences 12, no. 20: 10393. https://doi.org/10.3390/app122010393

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