Multimethod analysis of three rotary instruments produced by electric discharge machining technology

摘要

Abstract Aim This study aimed to compare three rotary instruments produced by the EDM process with the heat‐treated ProTaper Gold system regarding design, metallurgy, mechanical properties and shaping ability. Methodology HyFlex EDM (25/~), Neoniti (25/.06), EDMax (25/.06) and ProTaper Gold (25/.08v) instruments (n?=?58 per group) were compared regarding design, metallurgy and mechanical performance. Unprepared canal areas were calculated for each system after preparation of mesiobuccal, mesiolingual and distal canals of mandibular molars (15 canals per group) using micro‐CT technology. Statistical analyses were performed using One‐way anova post‐hoc Tukey and Kruskal–Wallis post‐hoc Dunn's tests (α?=?5%). Results All instruments had asymmetrical blades, no radial lands, no major defects and almost equiatomic nickel/titanium ratios, but different cross‐section designs, tip geometries and surface appearances. Although instruments had distinct transformation temperature curves, they showed crystallographic martensitic arrangement at 21°C and mixed austenite plus R‐phase at body temperature. Neoniti and HyFlex EDM showed similar results in all mechanical tests (p?>?.05), while EDMax and ProTaper Gold had similar time to fracture (p?=?.841), maximum bending load (p?=?.729), and cutting ability (p?=?.985). ProTaper Gold showed the highest torque to failure (p??.05). Conclusions Instruments' geometry and phase transformation temperatures influenced the results of the mechanical tests, but not their shaping ability.