Iranian Endodontic Journal

Abstract

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° ± 1°C) subjected or not to an alloy cooling protocol.

Methods and Materials: Twenty instruments of each system (n=40) were selected and divided into two groups: body temperature (BT); body temperature with cooling protocol (CP). Cyclic fatigue test was performed until fracture in a custom stainless-steel device with water bath equipment to simulate body temperature. CP group instruments were subjected to 5 seconds of spray cooling at every 30 seconds. Time to fracture was recorded. Resistance to bending at 45^o was evaluated using ten instruments of each system. Fractured surfaces were examined under scanning electron microscopy (SEM). Statistical analysis was performed using Student t test at 5% significance level.

Results: WOG instruments had significantly less cyclic fatigue resistance compared to X1B instruments in BT (P=0.00001) and CP (P=0.0001) groups. Significantly increased resistance was observed in X1B instruments (P=0.0003) and in WOG (P=0.0003) when cooling protocol was applied. 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: Cooling protocol extended the cyclic fatigue resistance of both instruments.