Evaluation of Cyclic Fatigue of Hyflex EDM, Twisted Files, and ProTaper Gold Manufactured with Different Processes: An In Vitro Study

A Comparative Evaluation of the Efficiencies of Different Rotary File Systems in Terms of Remaining Dentin Thickness Using Cone Beam Computed Tomography: An In Vitro Study

AIM

The aim of this study was to evaluate and compare the dentin thickness of the mesio-buccal canal of the lower first molar after canal preparation with three different rotary file systems using cone beam computed tomography (CBCT).

METHODOLOGY

TruNatomy (Dentsply Sirona, USA), 2Shape (Micro-Mega, France), and One Curve (Micro-Mega, France) were the three different rotary files that were employed. A total of 45 excised human permanent first mandibular molars were divided into Groups A (TruNatomy), B (2Shape), and C (One Curve) at random. To measure the residual dentin thickness at 3 mm, 5 mm, and 7 mm from the radiographic apex, the mesial root of the tooth was removed from the tooth, and a mesio-buccal canal was taken. Samples were mounted in clear acrylic resin and were subjected to a pre-instrumentation CBCT scan. The mesio-buccal canal was cleaned and shaped while maintaining the final mesio-buccal canal preparation of Group A - 26/0.04, Group B - 25/0.04, and Group C - 25/0.04. The samples were extensively irrigated with 3% sodium hypochlorite and 17% EDTA, and a post-instrumentation scan was performed on them. Statistics were used to determine the values from CBCT scans that were recorded for pre- and post-instrumentations.

RESULTS

The results showed that Group A had the greatest drop in dentin thickness, followed by Group B and Group C. The change in dentin thickness was greatest at 3 mm and 7 mm.

CONCLUSION

In contrast to TruNatomy and 2Shape rotary file systems, One Curve has the advantage of maintaining a tooth's thickness at 3 and 7 millimeters from the radiological apex. Since the TruNatomy file system removes more dentin than the other two combined, it should be used cautiously. Choosing the right instrument is crucial for cleaning and shaping during root canal preparation.

Evaluation of cyclic fatigue behavior of RACE EVO rotary Files: In-vitro comparative study

Introduction

Comparative evaluation of the newly introduced; RACE EVO file system to the currently well-performing file systems like HyFlex EDM OneFile, Vortex Blue, ProTaper Gold (PTG) with regards to the cyclic fatigue resistance.

Materials

&Methods.The endodontic rotary files under evaluation were segregated into four groups as follows:; RACE EVO, PTG, Vortex Blue, and HyFlex EDM OneFile. A detailed physical analysis of the cyclic fatigue resistance was performed in 15 files of each type (n = 60). Under the test conditions of 37 °C the test samples were subjected to continuous motion at the manufacturer recommended speed within an artificial curved canal until it fractured. For all the test samples, with the recording of time of fracture, calculation was done for number of cycles to fracture (NCF). In addition, the length of the fractured segment was determined. The fractured surface was further evaluated with scanning electron microscopic (SEM) images.

Results

Highest significance for NCF was seen in HyFlex EDM OneFile followed by the Vortex Blue, PTG, and; RACE EVO (p < 0.05) by analyzing the data statistically. Significant differences among the lengths of the fractured segments were evident among tested files, ranging between 4.73 and 6.3 mm (p < 0.05) with HyFlex EDM OneFile uniquely differentiating from the others showing the fracture at 6.3 mm. The common features of cyclic fatigue failure was further substantiated by SEM images.

Conclusions

Compared to the HyFlex EDM OneFile, Vortex Blue, and PTG files; RACE EVO demonstrated significantly lower resistance to cyclic fatigue.

Effect of NaOCl on cyclic fatigue resistance

The impact of 5.25 percent NaOCL on the resistance offered by TruNatomy, Hero Gold and ProtaperGold against cyclic fracture as against the treatment of NiTi rotary files with distilled water is of interest to dentists. Inside the stainless steel blocks, man-made canals were created for the purpose of testing the cyclic fatigue. 60 endodontic files were taken as study specimens. It was observed that values of number of cycles to fracture in NaOCl among three file systems were in the order of TruNatomy (1053.50 ± 134.81)>Hero Gold (652.66 ± 58.66) > ProtaperGold (494.50 ± 47.69). The TruNatomy file system reflected greatest cyclic fatigue resistance. It was also found that cyclic fatigue resistance in NiTi rotary files studied here is not hampered by 5.25% NaOCl.

Comparative evaluation of pericervical dentin preservation and fracture resistance of root canal-treated teeth with rotary endodontic file systems of different types of taper - An in vitro study

Aims

The aim of this study was to evaluate and compare the pericervical dentin preservation and fracture resistance of root canal-treated teeth with rotary endodontic file systems of different types of taper.

Subjects and Methods

Thirty-two single-rooted human-extracted premolars were used. They were mounted in wax, and preoperative cone-beam computed tomography (CBCT) scans were taken with 11 × 8 Field of view (FOV). The evaluation of the pericervical dentin thickness was done at the cementoenamel junction level. After pre-CBCT, the 32 samples were divided into four groups (n = 8) - Group A: fixed tapered hand files, Group B: variable regressive tapered TruNatomy, Group C: progressive tapered ProTaper Gold, and Group D: fixed tapered HyFlex EDM. Following instrumentation, postoperative CBCT scans were taken to evaluate pericervical dentin thickness. Obturation was done and access cavity was restored with composite. Fracture strength was checked for all the samples using "universal testing machine" until fracture, and calculated in newtons (N).

Statistical Analysis Used

Student's t-test and ANOVA test, along with Tukey's post hoc analysis, were used for comparing mean values between the groups, and P < 0.05 was considered statistically significant.

Results

The results of this study showed that there is no statistically significant difference in preserving pericervical dentin with file system of different types of taper and fracture resistance between the groups.

Conclusions

Within the limitations of the study, it was concluded that different types of file taper systems used for root canal preparation have no significant effect on the preservation of pericervical dentin and fracture resistance of teeth.

Shaping ability of ProTaper Gold and WaveOne Gold nickel-titanium rotary instruments in simulated S-shaped root canals

Background/purpose

Gold metal technology improves flexibility and the resistance to cyclic fatigue of the endodontic mechanical files. This study compared the performance of ProTaper Gold (PTG) multiple file system and WaveOne Gold (WOG) single file system in simulated S-shaped root canals, which represents one of the most challenging root canal morphology.

Materials and methods

Forty S-shaped canals (n = 20 canals/per group) in resin blocks were instrumented to an apical size of 0.25 mm using PTG and WOG Primary, respectively. The total amount of resin removal, canal transportation, centering ratio, and the degree of canal straightening were measured in Photoshop CS6 software. Statistical analysis was performed by using Mann–Whitney U-test (α = .05).

Results

None of the files fractured during the instrumentation. The WOG group removed significantly less amount of resin at 0, 3, 6, 7 and 9 mm from the apex (P < .05). The WOG group remained more centered in canals at 0 mm from the apex (P < .05). The PTG group showed a better centering ability and less canal transportation at 4, 5 and 6 mm from the apex (P < .05). In the coronal curvature portion, the use of WOG Primary significantly decreased curvature angle and increased radius compared with PTG instruments (P < .05). There was no significant difference between the two groups in terms of the apical curvature angle and radius change (P > .05).

Conclusion

The WOG Primary file has a less aggressive dentin cutting and more centered apical preparation. The PTG system is more advantageous in shaping the coronal curvature of S-shaped canal.