• The Journal of the Korean dental association
• /
• v.47 no.7
• /
• pp.435-443
• /
• 2009

The purpose of this study was to compare the centering ratio and reduction of canal curvature according to the preparation sizes of #30, #40 and #50 using three rotary NiTi instruments which have different shaft tapers. Seventy-two simulated root canals in clear resin blocks (Endo Training Bloc; Dentsply Maillefer, Ballaigues, Switzerland) were divided as following 3 groups according to the file system; the 24 canal blocks prepared with each of ProTaper Universal system (Group P), LightSpeed eXtra system (Group L), and K3 (Group K). The pre- and post-instrumented root canals were scanned and superimposed to evaluate and calculate the centering ratio and reduction of canal curvature. Mean scores of each group were statistically analyzed using one-way ANOV A and Duncan's multiple range test for post-hoc comparison. The results were as followings: 1. Group L showed better centering ratio, followed by K and P. And all experimental groups generally showed increasing tendency of centering ratio as the apical size was increasing from #30 to #50, except at 1 mm level of group P where showed reducing tendency of centering ratio. The smaller the ratio, the better the instrument remained centered in the canal. 2. Group P showed more decrease of canal curvature at all apical shaping size (p < 0.05). Under the conditions of this study, the shaft design could affect the quality of canal shaping and the smooth taperless flexible (LightSpeed) shaft design was capable of preparing canals with good morphological characteristics in curved canals.