2019 Volume 40 Issue 3 Pages 179-185
Abstract : This study aimed to evaluate the canal-centering ability and instrumentation time of different nickel-titanium (NiTi) rotary preparation techniques performed by undergraduate students. Simulated J-shaped resin canals were instrumented by undergraduate students with no clinical experience of NiTi rotary instrumentation, using (1) the single-length technique with Optimal Torque Reverse (OTR) motion ; (2) the crown-down technique with rotary motion ; or (3) the step-back technique with manual stainless-steel K-files (Zipperer). The rotary instrumentation was done using EndoWave instruments (FKG) and TriAuto ZX2 motor (J. Morita). Canal-centering ratios were determined after superimposition of pre- and post-instrumentation images. Instrumentation time was measured and ledge formation was recorded. At ≥ 1 mm from the apex, the single-length and crown-down groups showed significantly lower canal-centering ratio (i. e., less deviation) than the step-back group (p<0.05). The length of instrumentation time was single-length group=crown-down group<step-back group (p<0.05). Ledge formation occurred in 2, 1 and 10 canals in the single-length, crown-down, and step-back groups, respectively. Within the limitation of this study, EndoWave rotary instrumentation with the single-length technique (in OTR motion) and crown-down technique exhibited superior canal-shaping ability compared with the manual step-back technique with K-files, when the instrumentation was performed by novice undergraduate students.
