Cyclic fatigue and Structural Analysis of Three Rotary Nickel Titanium Files

Nickel-titanium (NiTi) rotary shaping techniques were devised as a solution to the drawbacks associated with manual filing systems.The study was conducted to evaluate the cyclic fatigue resistance and martensitic/austenitic phase at body and room temperatures for HyFlex CM, Fanta (AH wire), Soco files. Twenty files of each system were used. Ten of them were used at room temperature and ten were used at body temperature. Dynamic cyclic fatigue testing was performed with a specific device, which allowed the instruments to rotate freely inside a Stainless-Steel artificial canal while providing an axial movement with amplitude of 3mm up and down movement. The time was calculated until instrument fracture occurred. A Sample with weight 10 to 15 grams of each instrument was evaluated using Differential Scanning Calorimetry (DSC).The DSC analyses were conducted over a temperature range from 0°C to 60°C . The results showed that HyFlex CM exhibited higher cyclic fatigue, followed by Fanta(AH wire), while soco showed the lowest values for both room and body temperatures. Temperature showed an effect (between body and room temperature) on cyclic fatigue resistance of some of CM wire type of instruments (Fanta and soco files).The differential scanning calorimetry confirmed the presence of the martensitic R-phase in Hyflex CM in both body and room temperatures which improved the cyclic fatigue resistance of this file, while presence of the martensitic phase only in room temperature for Fanta and Soco files not in body temperature which significantly decreases their cyclic fatigue resistance.