Bending resistance and cyclic fatigue resistance of WaveOne Gold, Reciproc Blue, and HyFlex EDM instruments

Abstract

Background/purpose Several single-file systems manufactured using different heat treatment and operated by different kinematics have been released. This study compared the bending resistance and cyclic fatigue resistance of three NiTi files, and examined their phase-transformation behavior. Materials and methods WaveOne Gold Primary (WOG), Reciproc Blue R25 (RPB), and HyFlex EDM OneFile (HDM) were tested (N = 40/instrument). A vertical load was applied to a point 3 mm from the tip, and the stress was measured until a displacement of 3 mm. Tests were conducted at either room temperature (RT: 22 °C) or body temperature (BT: 37 °C) (n = 10). Cyclic fatigue resistance tests were performed in an artificial canal, which had a curvature angle of 40° and a 5-mm radius. Tests were conducted at either RT or BT (n = 10). Instruments were operated according to the manufacturers' instructions. Test results were analyzed using the Kruskal–Wallis and the Mann–Whitney tests. Additional three instruments of each brand were subjected to differential scanning calorimetry (DSC). Results At RT the bending resistance of three files were not significantly different. However, at BT the bending resistance of RPB was highest, followed by WOG, and HDM ( P < 0.05). At RT, RPB demonstrated the longest fracture time, followed by HDM, and WOG ( P < 0.05). At BT, HDM had the longest fracture time, followed by RPB, and WOG ( P < 0.05). The WOG, RPB consisted of austenite in a considerable proportion, whereas HDM was mainly martensite state at BT. Conclusion HDM presented superior flexibility and cyclic fatigue resistance at BT.

Physical Properties of Modern Reciprocal Endodontic Systems and Fatigue Failure Testing in Simulated Clinical Conditions

“…It is clear that the Unicone made of M-wire was significantly less resistant to cyclic fatigue in comparison to Reciproc Blue, WaveOne Gold and Unicon Plus, all made of CM-wire; this agrees with other studies comparing effect of phase composition on NiTi-based alloys [14,[20][21][22]. Our study also shows that Reciproc Blue is more resistant to cyclic fatigue than WaveOne Gold, similar to previous studies [16,20]. The higher fatigue resistance of Reciproc Blue compared to WaveOne Gold is mainly attributed to different thermomechanical treatment.…”

“…Due to the possible existence/co-existence of different crystallographic phases, the mechanical and fatigue properties of nitinol instruments strongly depend on a particular phase composition [9] predetermined by the thermal treatment during manufacturing. Alloy phase and chemical composition together with surface roughness, shape, and crosssectional area [13] are generally noted as intrinsic parameters with a crucial impact on overall instrument performance [14][15][16][17][18][19][20][21][22]. Additionally, there are multiple ambient factors governing the cyclic fatigue of endodontic instruments, such as type of motion (continuous, various reciprocating), ambient temperature, and artificial root canal geometry [13].…”

“…Nowadays, cyclic fatigue tests are performed mainly using an artificial canal, usually grooved in a stainless steel block [14,20,23]. Canal curvature is usually between 30 • and 90 • with a variable curvature radius [14,16,24,25].…”

“…Former studies of fatigue resistance and torque fatigue resistance were accomplished either mainly at room temperature [26][27][28] or at body temperature, 37 • C [16,23], even though a temperature inside the root canal system of 35 • C is reported [14,29]. There are several studies showing that higher ambient temperature reduces cyclic fatigue resistance [14,[30][31][32] by affecting the internal crystallographic structure (switching martensite to austenite ratio), which leads to lowering the cyclic fatigue resistance in intracanal temperature compared to room temperature [33,34].…”

Evaluation of Cyclic Fatigue and Bending Resistance of Coronal Preflaring NiTi File Manufactured with Different Heat Treatments

“…The cyclic fatigue resistance of the instruments was evaluated using a customized device with a static model [27]. Twenty instruments of each brand (EDM, CM, OF) were tested within a curved artificial canal made of lithium disilicate CAD/CAM block (E. max HT A2 shade, Dentsply Sirona), which provided a reproducible curved path to the NiTi files with a 50 • angle and 6.4 mm-radius according to Pruetts's method (Figure 1A).…”