Comparative analysis of reciprocating and flat‐side heat‐treated rotary single‐file systems: Design, metallurgical characteristics, and mechanical performance

Aim To compare two flat‐side single‐file rotary instruments with three single‐file reciprocating systems through a multimethod assessment. Methodology A total of 290 new NiTi single‐file rotary (AF F One Blue 25/0.06 and Platinum V.EU 25/0.06) and reciprocating (One Files Blue R25, Reciproc Blue R25, Reciproc R25) instruments were selected, carefully examined for any major deformations, and evaluated regarding their macroscopic and microscopic design, nickel and titanium elements ratio, phase transformation temperatures, and mechanical performance (time/rotation to fracture, maximum torque, angle of rotation, microhardness, maximum bending, and buckling strengths). One‐way anova post hoc Tukey, T‐test, and nonparametric Mood's median tests were used for statistical comparisons (α = 5%). Results Tested instruments had identical blade counts and near‐identical helical angles of approximately 24° (rotary instruments) and 151° (reciprocating instruments). The flat‐side analysis revealed a few inconsistencies, such as discontinuity segments, different orientations, and gaps in the homogeneity of the bluish colour. Microscopically, flat‐side instruments exhibited blade discontinuity and an incomplete S‐shaped cross‐section. The surface finish was smoother for One Files Blue and more irregular for both rotary instruments. There were distinct phase transformation temperatures amongst all instruments. All heat‐treated instruments were in R‐phase arrangement, and Reciproc was in R‐phase plus austenite at test temperature (20°C). Compared with the reciprocating instruments, both flat‐side instruments exhibited lower results in the cyclic fatigue tests using two different clockwise kinematics, maximum torque, angle of rotation, and maximum buckling strength (p