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

Influência do tratamento térmico na cor e flexibilidade de instrumentos endodônticos de níquel-titânio

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 < 0.05). Instruments treated at 650ºC and 750ºC had higher flexibility than those treated at lower temperatures (450ºC, 500ºC and 550ºC) (P < 0.05).

Conclusion  Heat treatment has a significant effect on the surface color and flexibility of nickel-titanium endodontic instruments. The highest flexibility was observed in instruments heated at 650ºC and 750ºC.

Indexing terms
Dental instruments; Heat treatment; Pliability