after instrumentation, the root canal acquires the necessary shape for a perfect adaptation of filling material. during this phase cutting end and lx type an interaction between instrument and root canal is necessary in order to reduce alterations that could occur at this point. this study evaluated the action of two mechanical-rotatory endodontic instruments, quantec files 2000 serie type sc with blunt end, during the instrumentation of simulated canals curved between 20 and 35 degrees, using quantec graduating tapers. results showed that the mean curvature alteration of group i canals that were instrumented with sc files, was 2,15%, and for group ii instrumented with lx files, was 2,61%. furthermore group i canals showed lower percentage of curvature alteration. mann-whitney tests showed no significant statistical difference at 5% between experimental groups.