Bending properties of nickel-titanium instruments: a comparative study.

Aim: The aim of the present study was to evaluate the bending properties of twisted file instruments, and compare them with other commercially available nickel-titanium (NiTi) instruments (Mtwo and Hero) manufactured with traditional methods.

Methods: Despite NiTi superelastic properties, flexibility of NiTi instruments is limited by size and taper. A new manufacturing process involving twisting of a ground blank combined with heat treatment has been developed by SybronEndo, aiming to produce a NiTI rotary file with superior flexibility: the Twisted File (TF). Experimental procedures strictly followed the testing methodology described in ISO 3630-1. Bending moment was measured when the instrument attained a 45 degrees bend. Data were collected and statistically analyzed.

Results: Results showed that TF were the most flexible instruments, with a significant improvement in flexibility (P< 0.05). ranging from 100% to 250% over the other tested instruments. Even if flexibility is also influenced by instruments design, such a great improvement is mainly related to the new TF manufacturing process.

Conclusion: The flexibility is influenced by instruments design, such a great improvement is mainly related to the new manufacturing process developed by SybronEndo, which seems to play a major role in increasing the flexibility of TF instruments.