The main drawback of several studies is the limited analysis performed for the comparison of nickel-titanium (NiTi) rotary systems. Most often, research articles in this area are focalized on the static characteristics such as static cyclic fatigue, torsional loads, and flexibility, not considering their reciprocal interaction and all dynamic factors.1 Recent evidence in the literature defines the reciprocal interaction between these parameters as a fundamental element in the study of their mechanical characteristics.2 However, static mechanical behavior is fundamental to assess the basic performance of NiTi instruments, but its interpretation during clinical practice is pointless as it does not resemble the real clinical scenario.1,3,4 Results arising from static tests, certainly valid as a first approach to the evaluation of an instrument recently introduced on the market, and comparative evaluations, should be considered in a general and more complete view, considering their reciprocal relationships.3-6 For these reasons, different types of researches that investigate both static and dynamic performance of NiTi instruments should be strongly recommended in order to give to original research and in vitro study an actual clinical significance, certainly much more indicative in view of a subsequent clinical application of NiTi rotary instruments.7-9.