RELATIONSHIP BETWEEN FILE SIZE AND STIFFNESS OF NICKEL-TITANIUM INSTRUMENTS

The purpose of this study was to evaluate the relationship existing be tween file size and stiffness for 3 endodontic files made of nickel ti tanium. Three groups of instruments with different cross-sections were tested: a triangular cross-section, a square cross-section and a modi fied triangular cross-section. The instruments were tested from size 1 5 to size 40 or 60 according to ANSI/ADA specification n degrees 28 fo r binding moment evaluation. There was a statistically significant dif ference between the 3 groups: the square cross-section K files present ed a larger bending moment than the triangular cross-section K files, which presented a larger bending moment than the modified cross-sectio n K files. Like the stainless steel instrumens, there was an exponenti al relationship between file size and bending moment for triangular an d square cross-section K files, but a linear relationship between file size and bending moment for the files with a modified triangular cros s-section.