Effect of the temperature of sodium hypochlorite on the cyclic fatigue resistance of ProTaper Gold rotary files.

Background: Instrument fracture is one of major challenges during root canal treatment. In order to reduce such errors, it seems necessary to investigate the effects of potentially impactful factors. One of such factors could be the temperature of an agitator.

Objectives: This study examined the effects of different temperature of the sodium hypochlorite solution on the cyclic fatigue resistance of ProTaper Gold (PTG) rotary files.

Material And Methods: Forty-five PTG S1 rotary files were tested in a metal block that simulated a canal curvature angle of 60° and a curvature radius of 5 mm. They were randomly divided into 3 groups of 15 according to sodium hypochlorite temperatures of 22°C (group 1), 4°C (group 2) and 37°C (group 3). Files from each group were rotated at 300 rpm in the block at each temperature. The number of cycles to fracture was calculated and the fragment length was measured. The fractured surfaces were examined by means of scanning electron microscopy (SEM). The statistical analysis was completed using the Kolmogorov-Smirnov and Kruskal-Wallis tests, and the IBM SPSS Statistics for Windows software, v. 22.0, at a significance level of 5%.

Results: The cyclic fatigue resistance of the PTG rotary files was not significantly affected by the temperature of sodium hypochlorite (p > 0.05).

Conclusions: Increasing the temperature of sodium hypochlorite to 37°C or decreasing it to 4°C did not significantly affect the cyclic fatigue resistance of PTG rotary files.