An analysis of breakage of ultrasonic files during root canal instrumentation.

The incidence of fracture of Cavi-Endo ultrasonic K-files during ultrasonic root canal preparation was evaluated. In addition, the appearance and the sites of fractures were examined in relation to the nodal points on the file. The displacement amplitudes and the hardness of the files were quantified to determine their relationship to fracture. It was observed that the files exhibited a low incidence of fracture, which was of the brittle type and occurred at the apical ends. The displacement amplitude and the hardness of the files did not appear to influence the incidence of fracture.