Cyclic Fatigue Resistance of Blue Heat-Treated Instruments at Different Temperatures.

The main aim is to evaluate the cyclic fatigue resistance of blue heat-treated instruments with different kinematics. Twenty-four endodontic instruments of the same brand were used for each of three experimental groups: VB (Vortex Blue 40/0.04), RB (RECIPROC Blue 40/0.06), and XB (X1 Blue 40/0.06). The instruments were randomly distributed and subjected to temperatures of 20°C and 37°C. The fatigue test was performed using a stainless steel device. Data were analysed using the Shapiro-Wilk test, Student's t-test, the F test, and Tukey's and Tamhane tests at significance level P=0.05. The instruments' cyclic fatigue resistance at both temperatures differed significantly for each instrument type (P < 0.001). The RB instruments displayed greater cyclic fatigue resistance at the tested temperatures compared with the VB and XB instruments (P < 0.001). Reciprocating kinematics positively influenced cyclic fatigue resistance. Blue heat-treated instruments showed decreased cyclic fatigue resistance as the temperature increased (P < 0.001).

Influence of Temperature on the Cyclic Fatigue of Nickel-Titanium Instruments with Different Heat Treatments on Severely Curved Canals.

AIM: This study aims to investigate the influence of temperatures of 20 °C and 37 °C on the resistance to cyclic fatigue of NiTi instruments with different heat treatments, as tested in severely curved simulated canals. MATERIALS AND METHODS: Seventy-two instruments were distributed according to the temperature used (20 °C and 37 °C): XP-endo Shaper (30/0.01), ProDesign Logic (30/0.05), and iRaCe (30/0.04). The instruments were rotated freely until the occurrence of fracture inside an artificial severely curved stainless steel canal, which had a 90° angle of curvature and a curvature radius of 5 mm. Kolmogorov-Smirnov, Wilcoxon, ANOVA, and Kruskal-Wallis tests were performed. A p value of <0.05 was considered statistically significant. RESULTS: XP-endo Shaper instruments presented higher NCF values and time to failure compared with ProDesign Logic and iRaCe instruments at 20 °C and 37 °C (p < 0.001). CONCLUSION: Within the limitations of this study, the results show that the body temperature (37 °C) significantly lowers the resistance to cyclic fatigue of all instruments compared with 20 °C. CLINICAL SIGNIFICANCE: Body temperature is an important factor in the results of cyclic fatigue tests.