Comparison of Surface Characteristics of Apical Third of Rotary NiTi Files Manufactured from Different Phases of NiTi before and after Use : an SEM Analysis

Clinically, there is a real potential for rotary NiTi instruments to separate in the canal; hence increasing the resistance to fracture has been a focus in the designing of new NiTi rotary systems. NiTi alloys go through various transitional phases and these have been utilized by manufacturers in different file systems. Aim : To evaluate and compare the surface changes of rotary nickel-titanium instruments manufactured from the Austenite phase, M-wire technology and R-phase before and after multiple uses. Materials and Methodology : 60 freshly extracted human mandibular premolars with a single, straight canal were selected. They were divided into 3 groups of 20 teeth each. Cleaning and Shaping was carried out using the crown down technique. All instruments were evaluated for defects under Scanning Electron Microscope (SEM) before and after multiple uses and scored for the defects. Results were statistically analyzed using KruskalWallis and Mann Whitney U test. Results : The p-value was <0.0001, indicating a statistically significant difference between the three groups in terms of resistance to surface defects. Conclusion : R-phase technology had superior resistance to surface defects, followed by M-wire and the austenitic phase.