Methods: Simulated canals with a 30-degree curvature in resin blocks were divided into 4 groups (n = 8, each) and prepared using the following instruments: Group 1, Reciproc R25 (25/.08); Group 2, RaCe (10/.04) followed by Reciproc R25; Group 3, RaCe (10/.06) followed by Reciproc R25; and Group 4, TF (25/.08). The time required for instrumentation was recorded. After the preparation, canal width increases at the inner and outer sides of the curvature were measured with digital image analysis at 1- to 12-mm levels from the apical foramen. Canal centering ratios were then calculated. Data were analyzed by one-way analysis of variance and Bonferroni-Dunn test at the significance level of 5%.
Results: The Group 4 exhibited significantly smaller canal width increases at 1- to 4-mm levels of the inner side and larger increases at 7- to 12-mm levels of the outer side, compared with the other groups (P < 0.05). The Group 4 also showed significantly smaller centering ratios at 1-, 2-, 7-, and 9-mm levels, compared with either or all of the other groups (P < 0.05). Total instrumentation time in the Group 1 was significantly longer than that in the other groups. The time taken for Reciproc instrumentation was significantly shorter in the Groups 2 and 3 compared with that in the Group 1.
Conclusions: Under the present experimental condition, Reciproc instruments produced less canal deviation compared with TF instruments. Prior glide path preparation reduced the instrumentation time of Reciproc.