A Comparison of Dentin Cutting Efficiency of 4 Round-tipped Ultrasonic Instruments

Introduction: Ultrasonic instruments are available for a variety of endodontic uses. Few published evaluations exist that compare the dentin cutting efficiency of endodontic ultrasonic tips. Furthermore, previous comparison studies often did not take into account 2 critical factors: clinically relevant downward forces and linear movement during use. Methods: Four different round-tipped ultrasonic tips were compared (n = 5 per tip group): BUC-1 (Obtura Spartan, Fenton, MO), BL-2 (B&L Biotech, Bala Cynwyd, PA), BL-3 (B&L Biotech), and START-X #2 (Dentsply Maillefer, Ballaigues, Switzerland). The tips were attached to a testing apparatus that applied a 15-g axial force and a linear movement during instrumentation of a human dentin specimen. Instrumentation was completed at the manufacturers' recommended power settings, and 3 of the tips were also compared at an equal power setting. Instrumentation consisted of 20-second cycles for a total of 6 minutes. Dentin specimens were weighed at baseline and after 2, 4, and 6 minutes of instrumentation. The dentin cutting efficiency was measured by the change in weight of dentin specimens to the nearest 0.1 mg. Results: A 1-factor analysis of variance and Tukey post hoc analysis of cumulative dentin removal (after 6 minutes of instrumentation) revealed a statistically significant difference among the 4 ultrasonic tips (P <= .0001) at the recommended PS, with the BUC-1 tip removing significantly more dentin across time. At an equal power setting, the BUC-1 was significantly more efficient than the BL-3; no difference was found between the BUC-1 and the BL-2. Conclusions: Within the limits of this study, the BUC-1 showed the greatest dentin removal. Adding a linear movement and a clinically relevant axial force allows better generalization to clinical applications.