The effect of rotational speed and the curvature of root canals on the breakage of rotary endodontic instruments.

One of the biggest concerns when working with rotary endodontic instruments is that the instrument might break in the root canal thus compromising the treatment. This study evaluated the effect of rotational speed and the curvature of root canals on the breakage of ProFile rotary instruments to determine whether either causes an increase in instrument breakage. One hundred twenty root canals of extracted molars were divided into two groups according to whether the curvature of the canal was greater or lesser than 30 degrees. Three different rotational speeds (150, 250, and 350 rpm) were then used to carry out the instrumentation of the canals. The curvature of the canals would seem to be the most important factor that increases the risk of instrument breakage.