Cyclic Fatigue and Torsional Strength of a New Thermally Treated Reciprocating System.

OBJECTIVE: This study evaluated the resistance to cyclic fatigue and the torsional strength of Prima One Gold® and WaveOne Gold® reciprocating systems. METHODS: Cyclic fatigue was tested in an artificial canal with 60º curvature, a 5 mm radius of curvature at 22°C (n=10) and 36.5°C (n=10). The torsional strength test followed ISO 3630-1, measuring torque and deflection angle until fracture (n=10). The t-test was used to compare the two groups, and the significance level was set at 5%. RESULTS: The Prima One Gold group presented greater resistance to cyclic fatigue at room temperature (P=0.001) and body temperature (P<0.001). For the torsional resistance test, the Prima One Gold group had a lower maximum torque value (P=0.029), despite having a greater deflection angle (P<0.001). CONCLUSION: The Prima One Gold group showed greater resistance to cyclic fatigue regardless of temperature and a greater deflection angle. The WaveOne Gold group showed a greater maximum torque value than the Prima One Gold group.

Effect of A Clinical-Replicable Cooling Protocol on the Cyclic Fatigue Resistance of Heat-Treated Nickel-Titanium Instruments.

Introduction: The aim of this study was to evaluate the bending and cyclic fatigue resistance of Wave One Gold (WOG) and X1 Blue (X1B) instruments when tested at body temperature (36°C ± 1°C) with and without subjected to an alloy cooling protocol. Materials and Methods: A total of sixty instruments (n=30) were tested. Forty instruments (n=20) were randomly selected and divided into two groups: body temperature (BT; n=20) and body temperature with cooling protocol (CP; n=20). Cyclic fatigue test was performed until fracture in a conventional stainless-steel device with water bath equipment to simulate body temperature. CP group instruments were subjected to 5 seconds of spray cooling every 30 seconds. Time to fracture was recorded in seconds. Resistance to bending at an angle of 45 degrees was evaluated using twenty instruments (n=10). Fractured surfaces were examined under scanning electron microscopy (SEM). Statistical analysis was performed at a 5% significance level. Results: There was no difference in the cyclic fatigue resistance between instruments in BT groups (P>0.05). Cooling protocol significantly increased the cyclic fatigue resistance of X1B instruments (P=0.0003) and WOG instruments (P=0.0003). Results: WOG instruments had a significantly lower cyclic fatigue resistance compared to X1B instruments in CP group (P=0.0001). There were no significant differences between the values of resistance increase presented by the instruments after cooling (P>0.05). Bending test presented no statistically significant differences between the tested instruments (P>0.05). Both instruments in both groups showed typical features of cyclic fatigue behavior under SEM. Conclusions: X1 Blue #25.06 and WaveOne Gold #25.07 instruments presented similar cyclic fatigue resistance. The investigated clinical-replicable cooling protocol improved the cyclic fatigue resistance of the tested instruments, with X1 Blue #25.06 presenting a greater cyclic fatigue resistance after cooling. Both instruments presented a similar bending capacity.

Mechanical Properties of ProTaper Gold, EdgeTaper Platinum, Flex Gold and Pro-T Rotary Systems.

OBJECTIVE: The aim of this study was to evaluate the cyclic fatigue, torsional behavior and bending resistance of EdgeTaper Platinum [ETP (tip 25, taper 0.06)], Flex Gold [FG (tip 25, taper 0.08)], Pro-T [PT (tip 25, taper 0.08)] and ProTaper Gold [PTG (tip 25, taper 0.08)] systems. METHODS: Rotary instruments of ETP, PT, FG, and PTG were used (n=30). Cyclic fatigue tests were performed using an artificial stainless-steel canal with a 60o angle and a 5-mm radius of curvature at body temperature (35°±1°C). The time and number of cycles to fracture (NCF) was recorded. The torsional test evaluated the torque and angle of rotation to failure at 3 mm from the tip according to ISO 3630-1. The fractured surface of each fragment was observed by using scanning electron microscopy (SEM). The bending test evaluated the torque required to bend the instruments at an angular deflection of 60°. Data were analyzed using one-way ANOVA and Tukey tests, and the level of significance was set at 5%. RESULTS: The ETP had highest time until fracture and NCF than all the groups (P<0.05). The PTG had the highest torsional strength, followed by FG (P<0.05). The ETP had the highest angular rotation, followed by PT and PTG (P<0.05). The FG showed the highest bending resistance, followed by the PTG (P<0.05). CONCLUSION: In conclusion, the ETP and PT exhibited higher cyclic fatigue resistance, higher angular deflection values and lower bending force than FG and PTG. The PTG instruments showed the highest torsional strength and the lowest cyclic fatigue resistance.