Ni-Ti rotary instruments surface alterations caused by heat sterilization

Objectives: Defects on of nickeltitanium endodontic file surface can play a role in instrument fracture. Aim of our study was to evaluate the effect of repeated dry heat sterilization on surface characteristics of NiTi rotary instruments by using scanning electrical microscopy (SEM), Energy dispersive x-ray spectroscopy (EDS) and Atomic Force Microscopy (AFM). Methods: ProTaper (Dentsply Maillefer, Switzerland) and AlphaKite (Komet, Italy) files were tested. The instruments were exposed to 1, 5 and 10 cycles of sterilization. Each groups included four Protaper and four AlphaKite. After sterilization the samples were observed by SEM (FEI, Netherlands), and surface analysis was performed on each instrument by EDS. Moreover, twenty areas of the surface the files were analyzed by AFM (Perception, Assing, Italy). Three-dimensional images were processed by Gwiddion software and the roughness average (Ra) and the root-mean-square value (Rms) of the scanned surface profiles were recorded. Data were statistically analyzed by Student t Test (p