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The use of Ni-Ti alloys in the practice of endodontic comes from their important properties such
as: shape memory and superelasticity phenomena, good corrosion resistance and high compatibility with
biological tissues. In the last twenty years a great variety of nickel-titanium rotary instruments, with various
sections and taper, have been developed and marketed. Although they have many advantages and despite their
increasing popularity, a major concern with the use of Ni-Ti rotary instruments is the possibility of unexpected
failure in use due to several reasons: cyclic fatigue, novice operator handling, presence manufacturing defects,
etc. Recently the use of an aqueous gel during experimental tests shown a longer duration of the instruments.
The aim of the present work is to contribute to the study of the fracture behavior of these endodontic rotary
instruments particularly assessing whether the use of the aqueous lubricant gel can extend the their operative life
stating its reasons. A finite element model (FE) has been developed to support the experimental results. The
results were quite contradictory, also because the Perspex (Poly-methyl methacrylate, PMMA) cannot simulate
completely the dentin mechanical behavior; however the results highlight some interesting points which are
discussed in the paper.