Aim: A new manufacturing method aimed at producing more flexible and resistant nickel titanium (NiTi) root canal instruments has been recently developed (CM-wire). The purpose of the study was to determine whether this new manufacturing method produces NiTi instruments (Hyflex) of superior flexibility, when compared with instruments produced by a traditional or thermally treated NiTi alloy.
Materials and methods: Ten 0.06 size 25 Hyflex instruments (Coltène Whaledent, Langenau, Germany), ten 06.25 Vortex instruments (Dentsply-Tulsa, Tulsa, OK, USA) and ten 06.25 RaCe instruments (FKG, La Chaux-de-Fonds, Switzerland) were evaluated for stiffness on bending. Test procedures strictly followed recommendations from ISO specification 3630-1. Bending moments were measured when the instruments attained a 45-degree bend. All data obtained were recorded and statistically analysed using an ANOVA test, followed by a post-hoc Tukey (HSD) test. The level of significance was set at α = 0.05.
Results: Statistical analysis showed that bending moments were significantly greater (P < 0.05) for Vortex (mean value 57.58 g/cm) and RaCe (mean value 52.11 g/cm) instruments, compared to the Hyflex instruments (mean value 14.46 g/cm), thereby confirming the increased flexibility of the instruments produced with CM-wire alloy.
Conclusion: Results of the present study demonstrate the ability of the new CM-wire manufacturing process to produce more flexible NiTi rotary instruments.
Keywords: endodontic rotary instruments, mechanical properties, nickel titanium