This study aims to compare the cyclic fatigue resistance of nickel-titanium (NiTi) endodontic instruments, focusing on the impact of various alloy treatments and manufacturing processes across different generations of these instruments; Twenty instrumentation systems from different generations, comprising both continuous and reciprocating motion designs, were tested. Four hundred instruments underwent cyclic fatigue testing using an INSTRON machine, with the time and number of cycles to fracture (NCF) recorded for each instrument. Statistical analyses were performed to compare the fatigue resistance between systems, generations, and motion types; Instruments treated with advanced thermal processing, such as Excalibur, Reciproc Blue, and TruNatomy, demonstrated superior resistance to fracture, whereas systems like Protaper Universal, K3XF, and 2Shape showed the lowest resistance. Reciprocating instruments generally exhibited higher cyclic fatigue resistance than continuously rotating instruments; Technological advancements in NiTi instrument design, especially the implementation of heat-treated alloys, have improved cyclic fatigue resistance, enhancing the safety and efficiency of endodontic treatments. Reciprocating systems, in particular, exhibit superior fracture resistance, suggesting their greater utility in challenging clinical conditions.
Keywords: cyclic fatigue resistance; endodontic file systems; nickel–titanium instruments; root canal instrumentation.