Abstract : Recently, Ni-Ti files are used in endodontic therapy, and many investigators have reported that characterization of Ni-Ti files. However, many clinicians are perplexed to select proper various newly Ni-Ti files. In this study, we examined the accidents when using Ni-Ti files : Quantec and ProFile, on root canal enlargement. The perforation of canal wall occurred using＃9 Quantec, 2 canals per 20 root canals, however, no perforation was observed using ProFile. The broken instruments were observed 2 cases on using Quantec and 1 case on using ProFile, respectively. The dentin muds at apical area were produced in using both Ni-Ti files, 3 canals in Quantec and 1 canal in ProFile, respectively. When using Ni-Ti files, we have to know the characterization and prevention of those accidents.
