Choosing the Right File for the Canal: Clinical Applications of Two Different Single-File Reciprocating Systems

Reciprocating single-file nickel-titanium (NiTi) systems have simplified root canal shaping while offering improved resistance to cyclic fatigue, the predominant mode of instrument failure. This article presents two cases treated with two different reciprocating systems built on different heat-treated NiTi alloys with distinct mechanical profiles. In the first case, the reciprocating system's patented heat treatment provided the added cutting efficacy and stiffness needed to enable confident management of a four-canal maxillary first molar (tooth No. 14), including complete location and shaping of the second mesiobuccal canal. The second case features a different reciprocating NiTi system that employs an original heat treatment and prioritizes flexibility and resistance to cyclic stress and was applied in a mandibular second molar (tooth No. 18) with curved canal morphology. The article demonstrates how selecting between the two systems based on canal anatomy-rather than defaulting to one system for every case-supports complete, predictable shaping in different cases despite meaningfully varied anatomical challenges.