LAUSR

INTRODUCTION The present study compared the effect of the number of pecking motions at working length (WL) on the shaping ability of single-file systems in long oval-shaped curved root canals. METHODS Single-rooted mandibular premolars with long oval-shaped curved canals (25-35°) were pre-scanned using micro-computed tomography (micro-CT), anatomically-paired and randomly divided into 3 groups (n=15): XP-endo Shaper (XPS), Reciproc Blue (RB) and WaveOne Gold (WOG). After preparation to the WL, each specimen underwent 1, 2, 4, 10 or 20 pecking motions to WL and was re-scanned. Morphological parameters were measured and analyzed using a two-factor repeated-measures analysis of variance and Scheirer-Ray-Hare test. RESULTS The minor apical diameter and percentage increase in canal volume increased with the number of pecking motions, while the percentage of unprepared canal surface area decreased (P<0.05). The mean minor diameters (in mm) at D0 varied between 0.29 and 0.35 after four pecking motions with the RB and WOG systems, and between 0.35 and 0.36 after 10 pecking motions with the XPS system. No significant differences in canal transportation or centering ratio were observed among the 3 groups at the levels of canal curvature and canal-thirds (P>0.05). CONCLUSIONS Increasing the number of pecking motions improves the cutting efficacy of single-file systems without adversely altering the anatomical characteristics of oval-shaped curved canals. No more than four pecking motions for the RB and WOG systems and 10 pecking motions for the XPS system appear to be acceptable for the shaping of these difficult-to-clean root canals.