Efficiency of rotary nickel-titanium K3 instruments compared with stainless steel hand K-Flexofile.: Part 1.: Shaping ability in simulated curved canals

Aim To compare the shaping ability of K3 rotary nickel-titanium instruments with stainless steel K-Flexofiles manipulated by hand. Part 1 of this two-part report describes the efficiency of these two instruments in simulated curved root canals. Methodology Simulated canals with 28degrees and 35degrees curves in resin blocks were prepared by K3 instruments with a rotational speed of 250 r.p.m. using a crown-down preparation technique, or by K-Flexofiles using a reaming motion (n = 24 canals in each case). All canals were prepared up to size 35 at the end-point of preparation. Pre- and postinstrumentation images were recorded, and assessment of canal shape was completed with a computer image analysis program. Material removal was measured at 20 measuring points, beginning 1 mm from the apex. Incidence of canal aberrations, preparation time, changes of working length and instrument failures were also recorded. Results In comparison with stainless steel K-Flexofiles, rotary K3 instruments achieved better canal geometry and showed significantly less canal transportation (P < 0.05). Eleven K3 instruments and none of the K-Flexofiles fractured during preparation (P < 0.05). Between both the canal types, K3 was significantly faster (P < 0.001) than K-Flexofiles. Both instruments maintained a good working distance. Conclusions K3 instruments prepared curved canals rapidly and with minimal transportation towards the outer aspect of the curve. Fractures occurred significantly more often with K3.