Influence of heat treatment on color and flexibility of nickel-titanium endodontic instruments

ABSTRACT Objective The aim of this study was to evaluate and compare the effect of heat treatment at different temperatures on the color and flexibility of nickel-titanium endodontic instruments. Methods Thirty-six nickel-titanium K-file endodontic instruments were divided into six groups and submitted to heat treatment at several temperatures between 450ºC and 750ºC. The color was visually observed. Cantilever-bending tests were performed to measure the flexibility of the instruments. The data were statistically evaluated by one-way analysis of variance and Tukey post hoc comparisons. Results It was observed that the color becomes darker as the heating temperature increases. The flexibility is significantly higher after the heat treatment (P