Evaluation of surface characteristics of M-two rotary files before and after autoclaving with scanning electron microscopy

Nowadays Ni-Ti rotary files have many advantages and are totally accepted in endodontic treatment. Sterilization of Ni-Ti rotary files is essential due to their frequent clinical use. The aim of this study was to evaluate the surface characteristics of M-two rotary files before and after autoclaving with scanning electron microscopy (SEM).

Ten #25 new M-two Ni-Ti rotary files (VDW, Munich, Germany) with 0.06 taper were analyzed with scanning electron microscopy under two magnifications of ×200 and ×1000 before and after 1, 5 and 10 autoclave cycles in this experimental prospective study. Scanning electron microscopic images were inspected in relation to surface changes, including the presence of millings, debris and surface irregularities. Paired-sample t-test was used for data analysis with SPSS 22 (α=0.05).

Scanning electron microscopy measurements showed cavities, debris and surface irregularities on specimens of both file groups, in the as-received condition and after sterilization. Surface irregularities and corrosion increased significantly after 10 autoclave cycles (p value = 0.001).

The results showed that after multiple autoclave cycles, debris, holes and surface corrosion increased significantly. These surface imperfections were proportional to the number of autoclave cycles and single autoclave cycle seemed to have a less detrimental effect on rotary files. However, multiple autoclave cycles increased surface irregularities progressively. The results showed inherent Ni-Ti rotary file limitations in clinical usee and after multiple sterilization cycles.